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Time-delayed transition of normal-to-abnormal glow in pin-to-water discharge
NASA Astrophysics Data System (ADS)
Yoon, S.-Y.; Byeon, Y.-S.; Yoo, S.; Hong, E. J.; Kim, S. B.; Yoo, S. J.; Ryu, S.
Time-delayed transition of normal-to-abnormal glow was investigated in discharge between spoke-like pins and ultrapure water by applying AC-driven power at a frequency of 14.3 kHz at atmospheric pressure. The normal-to-abnormal transition can be recognized from the slope changes of current density, gas temperature, electrode temperature, and OH density. The slope changes took place in tens of minutes rather than just after discharge, in other words, the transition was delayed. The time-delay of the transition was caused by the interaction between the plasma and water. The plasma affected water properties, and then the water affected plasma properties.
Development of a sintering methodology through abnormal glow discharge for manufacturing metal matrix composites
NASA Astrophysics Data System (ADS)
Pérez, S.; Pineda, Y.; Sarmiento, A.; López, A.
In this study, a sintering methodology is presented by using abnormal glow discharge to metal matrix composites (MMC), consisting of 316 steel, reinforced with titanium carbide (TiC). The wear behaviour of these compounds was evaluated according to the standard ASTM G 99 in a tribometer pin-on-disk. The effect of the percentage of reinforcement (3, 6, and 9%), with 40 minutes of mixing in the planetary mill is analysed, using compaction pressure of 700MPa and sintering temperature of 1,100°C±5°C, gaseous atmosphere of H2 - N2, and sintering time of 30 minutes. As a result of the research, it shows that the best behaviour against wear is obtained when the MMC contains 6% TiC. Under this parameter the lowest percentage of pores and the lowest coefficient of friction are achieved, ensuring that the incorporation of ceramic particles (TiC) in 316 austenitic steel matrix significantly improves the wear resistance. Also, it is shown that it is possible to sinter such materials using the abnormal glow discharge, being a novel and effective method in which the working temperature is reached in a short time.
Synthesis of Polycrystalline Diamond Films in Abnormal Glow Discharge and their Properties
NASA Astrophysics Data System (ADS)
Gaydaychuk, A. V.; Linnik, S. A.; Kabyshev, A. V.; Konusov, F. V.; Remnev, G. E.
The optical and electrophysical properties of polycrystalline diamond films (PDF) deposited from the abnormal glow discharge have been studied. The dominating mechanisms of absorption and charge carrier transfer and the energy spectrum of the localized states (LS) of defects which determine the properties of the films have been specified. The parameters of the interband absorption and electrical conductivity are determined by the continuous energy distribution in the band gap (BG) of the states of defects of different nature. The absorption edge of the crystalline phase of the films is separated from the absorption zone determined by the electron transitions between LS defects. The width of BG is narrowed to 0.2-0.5 eV from the quantity typical to the diamond. An additional film absorption edge is formed in the energy interval 1.2-3.3 eV, where Urbach rule is fulfilled and the interband absorption is realized at direct transitions through the optical gap 1.1-1.5 eV. The average width of BG is 2.6-3.24 eV estimated within semiclassical interband model. The interaction of the parameters of the interband and exponential absorption is determined by the crystal lattice static disorder. The dominating n-type of the activation component of the electrical conductivity is complemented by the hopping mechanism with the participation of the localized states of the defects distributed near the Fermi level with a density 5.6T017-2.1·1021 eV-1-cm-3.
Cathode fall thickness of abnormal glow discharges between parallel-plane electrodes in different radii at low pressure
Fu, Yangyang; Luo, Haiyun; Zou, Xiaobing; Wang, Xinxin
In order to investigate the influence of electrode radius on the characteristics of cathode fall thickness, experiments of low-pressure (20 Pa ≤ p ≤ 30 Pa) abnormal glow discharge were carried out between parallel-plane electrodes in different radii keeping gap distance unchanged. Axial distributions of light intensity were obtained from the discharge images captured using a Charge Coupled Device camera. The assumption that the position of the negative glow peak coincides with the edge of cathode fall layer was verified based on a two-dimensional model, and the cathode fall thicknesses, d{sub c}, were calculated from the axial distributions of light intensity. It was observed that the position of peak emission shifts closer to the cathode as current or pressure grows. The dependence of cathode fall thickness on the gas pressure and normalized current J/p{sup 2} was presented, and it was found that for discharges between electrodes in large radius the curves of pd{sub c} against J/p{sup 2} were superimposed on each other, however, this phenomenon will not hold for discharges between the smaller electrodes. The reason for this phenomenon is that the transverse diffusions of charged particles are not the same in two gaps between electrodes with different radii.
Powerful glow discharge excilamp
Tarasenko, Victor F.; Panchenko, Aleksey N.; Skakun, Victor S.; Sosnin, Edward A.; Wang, Francis T.; Myers, Booth R.; Adamson, Martyn G.
A powerful glow discharge lamp comprising two coaxial tubes, the outer tube being optically transparent, with a cathode and anode placed at opposite ends of the tubes, the space between the tubes being filled with working gas. The electrodes are made as cylindrical tumblers placed in line to one other in such a way that one end of the cathode is inserted into the inner tube, one end of the anode coaxially covers the end of the outer tube, the inner tube penetrating and extending through the anode. The increased electrodes' surface area increases glow discharge electron current and, correspondingly, average radiation power of discharge plasma. The inner tube contains at least one cooling liquid tube placed along the axis of the inner tube along the entire lamp length to provide cathode cooling. The anode has a circumferential heat extracting radiator which removes heat from the anode. The invention is related to lighting engineering and can be applied for realization of photostimulated processes under the action of powerful radiation in required spectral range.
Constricted glow discharge plasma source
Anders, Andre; Anders, Simone; Dickinson, Michael; Rubin, Michael; Newman, Nathan
A constricted glow discharge chamber and method are disclosed. The polarity and geometry of the constricted glow discharge plasma source is set so that the contamination and energy of the ions discharged from the source are minimized. The several sources can be mounted in parallel and in series to provide a sustained ultra low source of ions in a plasma with contamination below practical detection limits. The source is suitable for applying films of nitrides such as gallium nitride and oxides such as tungsten oxide and for enriching other substances in material surfaces such as oxygen and water vapor, which are difficult process as plasma in any known devices and methods. The source can also be used to assist the deposition of films such as metal films by providing low-energy ions such as argon ions.
Atmospheric sampling glow discharge ionization source
McLuckey, Scott A.; Glish, Gary L.
An atmospheric sampling glow discharge ionization source that can be used in combination with an analytical instrument which operates at high vacuum, such as a mass spectrometer. The atmospheric sampling glow discharge ionization source comprises a chamber with at least one pair of electrodes disposed therein, an inlet for a gaseous sample to be analyzed and an outlet communicating with an analyzer which operates at subatmospheric pressure. The ionization chamber is maintained at a pressure below atmospheric pressure, and a voltage difference is applied across the electrodes to induce a glow discharge between the electrodes, so that molecules passing through the inlet are ionized by the glow discharge and directed into the analyzer. The ionization source accepts the sample under atmospheric pressure conditions and processes it directly into the high vacuum instrument, bridging the pressure gap and drawing off unwanted atmospheric gases. The invention also includes a method for analyzing a gaseous sample using the glow discharge ionization source described above.
Atmospheric sampling glow discharge ionization source
McLuckey, S.A.; Glish, G.L.
An atmospheric sampling glow discharge ionization source that can be used in combination with an analytical instrument which operates at high vacuum, such as a mass spectrometer. The atmospheric sampling glow discharge ionization source comprises a chamber with at least one pair of electrodes disposed therein, an inlet for a gaseous sample to be analyzed and an outlet communicating with an analyzer which operates at subatmospheric pressure. The ionization chamber is maintained at a pressure below atmospheric pressure, and a voltage difference is applied across the electrodes to induce a glow discharge between the electrodes, so that molecules passing through the inlet are ionized by the glow discharge and directed into the analyzer. The ionization source accepts the sample under atmospheric pressure conditions and processes it directly into the high vacuum instrument, bridging the pressure gap and drawing off unwanted atmospheric gases. The invention also includes a method for analyzing a gaseous sample using the glow discharge ionization source described above. 3 figs.
Glow discharge plasma deposition of thin films
Weakliem, Herbert A.; Vossen, Jr., John L.
A glow discharge plasma reactor for deposition of thin films from a reactive RF glow discharge is provided with a screen positioned between the walls of the chamber and the cathode to confine the glow discharge region to within the region defined by the screen and the cathode. A substrate for receiving deposition material from a reactive gas is positioned outside the screened region. The screen is electrically connected to the system ground to thereby serve as the anode of the system. The energy of the reactive gas species is reduced as they diffuse through the screen to the substrate. Reactive gas is conducted directly into the glow discharge region through a centrally positioned distribution head to reduce contamination effects otherwise caused by secondary reaction products and impurities deposited on the reactor walls.
Normal glow discharge in axial magnetic field
NASA Astrophysics Data System (ADS)
Surzhikov, S.; Shang, J.
Theory and results of mathematical modeling of a glow discharge in a parallel-plate configuration with axial magnetic field is presented. The model consists of continuity equations for electron and ion fluids, the Poisson equation for the self-consistent electric field. Numerical simulation results are presented for two-dimensional glow discharge at various initial conditions. The results are obtained for molecular nitrogen at pressure 1-5 Torr, emf of power supply 1-2 kV, and magnetic field induction B = 0-0.5 T. It is shown that in the presence of the axial magnetic field the glow discharge is rotated around its axis of symmetry. Nevertheless it is shown that in the investigated range of discharge parameters in an axial magnetic field the law of the normal current density is retained.
Striations in an ethyl alcohol glow discharge
NASA Astrophysics Data System (ADS)
Reyes, P. G.; Gómez, A.; Torres, C.; Martínez, H.; Castillo, F.; Vergara, J.
This research shows the behavior of striations in glow discharge generated with high purity ethyl alcohol at a pressure of 0.6 Torr. This paper present the number of striations as a function of the of current and voltage discharge.
Evolution of Striation in Pulsed Glow Discharges
NASA Astrophysics Data System (ADS)
Liu, Yuanye; He, Feng; Zhao, Xiaofei; Ouyang, Jiting
In this work, striations in pulsed glow discharges are studied by experiments and Particle-In-Cell/Monte Carlo Collision (PIC/MCC) simulation. The spatio-temporal evolution of the potential and the electron energy during the discharge are analyzed. The processes of striation formation in pulsed glow discharges and dielectric barrier discharges (DBD) are compared. The results show that the mechanisms of striation in pulsed DC discharge and DBD are similar to each other. The evolution of electron energy distribution function before and after the striation formation indicates that the striation results from the potential well of the space charge. During a pulsed breakdown, the striations are formed one by one towards the anode in a weak field channel. This indicates that the formation of striations in a pulsed discharge depends on the flow of modulated electrons. supported by National Natural Science Foundation of China (Nos. 10875010 and 11175017)
Use of glow discharge in fluidized beds
NASA Technical Reports Server (NTRS)
Wydeven, T.; Wood, P. C.; Ballou, E. V.; Spitze, L. A. (Inventor)
Static charges and agglomerization of particles in a fluidized bed systems are minimized by maintaining in at least part of the bed a radio frequency glow discharge. This approach is eminently suitable for processes in which the conventional charge removing agents, i.e., moisture or conductive particle coatings, cannot be used. The technique is applied here to the disproportionation of calcium peroxide diperoxyhydrate to yield calcium superoxide, an exceptionally water and heat sensitive reaction.
Is the negative glow plasma of a direct current glow discharge negatively charged?
NASA Astrophysics Data System (ADS)
Bogdanov, E. A.; Demidov, V. I.; Kudryavtsev, A. A.; Saifutdinov, A. I.
A classic problem in gas discharge physics is discussed: what is the sign of charge density in the negative glow region of a glow discharge? It is shown that traditional interpretations in text-books on gas discharge physics that states a negative charge of the negative glow plasma are based on analogies with a simple one-dimensional model of discharge. Because the real glow discharges with a positive column are always two-dimensional, the transversal (radial) term in divergence with the electric field can provide a non-monotonic axial profile of charge density in the plasma, while maintaining a positive sign. The numerical calculation of glow discharge is presented, showing a positive space charge in the negative glow under conditions, where a one-dimensional model of the discharge would predict a negative space charge.
Is the negative glow plasma of a direct current glow discharge negatively charged?
Bogdanov, E. A.; Saifutdinov, A. I.; Demidov, V. I.; Kudryavtsev, A. A.
A classic problem in gas discharge physics is discussed: what is the sign of charge density in the negative glow region of a glow discharge? It is shown that traditional interpretations in text-books on gas discharge physics that states a negative charge of the negative glow plasma are based on analogies with a simple one-dimensional model of discharge. Because the real glow discharges with a positive column are always two-dimensional, the transversal (radial) term in divergence with the electric field can provide a non-monotonic axial profile of charge density in the plasma, while maintaining a positive sign. The numerical calculation of glow discharge is presented, showing a positive space charge in the negative glow under conditions, where a one-dimensional model of the discharge would predict a negative space charge.
Glow discharge based device for solving mazes
Dubinov, Alexander E. Mironenko, Maxim S.; Selemir, Victor D.; Maksimov, Artem N.; Pylayev, Nikolay A.
A glow discharge based device for solving mazes has been designed and tested. The device consists of a gas discharge chamber and maze-transformer of radial-azimuth type. It allows changing of the maze pattern in a short period of time (within several minutes). The device has been tested with low pressure air. Once switched on, a glow discharge has been shown to find the shortest way through the maze from the very first attempt, even if there is a section with potential barrier for electrons on the way. It has been found that ionization waves (striations) can be excited in the maze along the length of the plasma channel. The dependancy of discharge voltage on the length of the optimal path through the maze has been measured. A reduction in discharge voltage with one or two potential barriers present has been found and explained. The dependency of the magnitude of discharge ignition voltage on the length of the optimal path through the maze has been measured. The reduction of the ignition voltage with the presence of one or two potential barriers has been observed and explained.
Shock wave propagation in glow discharges
NASA Astrophysics Data System (ADS)
Ganguly, B. N.
The modification of acoustic shock wave propagation characteristics in a 25 cm long positive column low pressure (10 to 50 Torr), low current density (2 to 10 mA/cm^2) argon and N2 dc discharges have been measured by laser beam deflection technique. The simultaneous multi point shock velocity, dispersion and damping have been measured both inside and outside the glow discharge region. The local shock velocity is found to increase with the increased propagation path length through the discharge; for Mach number greater than 1.7 the upstream velocity exceeded the downstream velocity in contrast to the opposite behavior in neutral gas. The damping and dispersion are also dependent on the propagation distance. The recovery of the shock dispersion and damping in the post discharge region, for a given discharge condition, are functions of the initial Mach number. The optical measurement of the wall and the gas (rotational) temperatures suggest the observed shock features can not be solely explained by the gas heating in a self sustained discharge. The results are similar for both Ar and N2 discharges showing that vibrational excitation and relaxation are not essential^1. The explanation of the observed weak shock propagation properties in a glow discharge appears to require long range cooperative interactions that enhance heavy particle collisional energy transfer rates for the measured discharge conditions. Unlike collisional shock wave propagation in highly ionized plasmas^2,3, the exact energy coupling mechanism between the nonequilibrium weakly ionized plasma and shock is not understood. 1. A.I. Osipov and A.V. Uvarov, Sov. Phys. Usp. 35, 903 (1992) and other references there in. 2. M. Casanova, O. Larroche and J-P Matte, Phys. Rev. Lett. 67, 2143 (1991). 3. M.C.M. van de Sanden, R. van den Bercken and D.C. Schram, Plasma Sources Sci.Technol. 3, 511 (1994).
Power balance at cathode in glow discharges
Suraj, K.S.; Mukherjee, S.
When an electrode is biased negatively ({approx} few hundred volts) with respect to a metallic chamber, maintained at a subatmospheric pressure ({approx} few millibars), glow discharge plasma is formed around the electrode (cathode). The plasma supplies ions and other species to the cathode, along with other events at the cathode, and its temperature also rises. From the measurement of temporal temperature profile, in the pressure range of 0.5-5 mbars, the thermal influx at the cathode has been determined. Various modes of power input to the cathode are estimated from the discharge parameters. The contribution of ions and neutrals to the total input power is obtained theoretically from respective velocity distributions at the cathode considering charge exchange as the dominant collision mechanism inside the sheath region. The comparison of experimental and theoretical results suggests that in the pressure range being considered, which is typical of glow discharges, the major contribution to the energy input at the cathode comes from energetic neutrals generated by the charge-exchange collision inside the collisional ion sheath.
Phenomena of oscillations in atmospheric pressure direct current glow discharges
Liu, Fu-cheng; Yan, Wen; Wang, De-zhen
Self-sustained oscillations in a dc glow discharge with a semiconductor layer at atmospheric pressure were investigated by means of a one-dimensional fluid model. It is found that the dc glow discharge initially becomes unstable in the subnormal glow region and gives rise to oscillations of plasma parameters. A variety of oscillations with one or more frequencies have been observed under different conditions. The discharge oscillates between the glow discharge mode and the Townsend discharge mode in the oscillations with large amplitude while operates in the subnormal glow discharge mode all the while in the oscillations with small amplitude. Fourier Transform spectra of oscillations reveal the transition mechanism between different oscillations. The effects of semiconductor conductivity on the oscillation frequency of the dominant mode, gas voltage, as well as the discharge current have also been analyzed.
Advances in the Remote Glow Discharge Experiment
NASA Astrophysics Data System (ADS)
Dominguez, Arturo; Zwicker, A.; Rusaits, L.; McNulty, M.; Sosa, Carl
The Remote Glow Discharge Experiment (RGDX) is a DC discharge plasma with variable pressure, end-plate voltage and externally applied axial magnetic field. While the experiment is located at PPPL, a webcam displays the live video online. The parameters (voltage, magnetic field and pressure) can be controlled remotely in real-time by opening a URL which shows the streaming video, as well as a set of Labview controls. The RGDX is designed as an outreach tool that uses the attractive nature of a plasma in order to reach a wide audience and extend the presence of plasma physics and fusion around the world. In March 2014, the RGDX was made publically available and, as of early July, it has had approximately 3500 unique visits from 107 countries and almost all 50 US states. We present recent upgrades, including the ability to remotely control the distance between the electrodes. These changes give users the capability of measuring Paschen's Law remotely and provides a comprehensive introduction to plasma physics to those that do not have access to the necessary equipment.
Coaxial (tubular) glow discharge in electronegative gases
NASA Astrophysics Data System (ADS)
Golovitskii, A. P.
The positive-column plasma of a low- and medium-pressure electronegative glow discharge initiated in the gap between two coaxial cylindrical tubes has been considered (the current is directed along the tube axis). It is assumed that the gas mixture contains halogens, and ion diffusion is not negligibly weak. It is found that the coaxial discharge is characterized by plasma separation into three coaxial regions with different compositions in the direction transverse to the current. It has been shown that the ionization and excitation frequencies of atoms are higher than in the purely cylindrical case, even for a small (0.05-0.15) ratio of the radii of the inner and outer walls. An asymptotic analysis of the continuity equations yields analytic expressions that make it possible to rapidly and easily estimate the geometrical parameters of the spatial distributions of charge particle concentrations, as well as energy parameters of the plasma for the radii ratio that exceed 0.3. The conditions for the applicability of analytic relations and their accuracy are established from a comparison of the results of analytic and numerical calculations.
Glow Discharge Characteristics in Transverse Supersonic Air Flow
NASA Astrophysics Data System (ADS)
Timerkaev, B. A.; Zalyaliev, B. R.; Saifutdinov, A. I.
A low pressure glow discharge in a transverse supersonic gas flow of air at pressures of the order 1 torr has been experimentally studied for the case where the flow only partially fills the inter electrode gap. It is shown that the space region with supersonic gas flow has a higher concentration of gas particles and, therefore, works as a charged particle generator. The near electrode regions of glow discharge are concentrated specifically in this region. This structure of glow discharge is promising for plasma deposition of coatings under ultralow pressures
Glow discharge techniques for conditioning high vacuum systems
Dylla, H.F.
A review is given of glow discharge techniques which are useful for conditioning vacuum vessels for high vacuum applications. Substantial development of glow discharge techniques has been done for the purpose of in-situ conditioning of the large ultrahigh vacuum systems for particle accelerators and magnetic fusion devices. In these applications the glow discharge treatments remove impurities from vessel surfaces in order to minimize particle-induced desorption coefficients. Cleaning mechanisms involve a mixture of sputtering and ion- (or neutral) induced desorption effects depending on the gas mixture (ArO/sub 2/ vs. H/sub 2/) and excitation method (DC, RF, and ECR). The author will review the methodology of glow discharge conditioning, diagnostic measurements provided by residual gas and surface composition analysis, and applications to vessel conditioning and materials processing. 76 refs., 16 figs.
Enhanced Glow Discharge Production of Oxygen
NASA Technical Reports Server (NTRS)
Ash, Robert; Zhong, Shi
Studies starting in late seventies have shown Mars atmosphere can be used as a feedstock for oxygen production using simple chemical processing systems during early phases of the Mars exploration program. This approach has been recognized as one of the most important in-situ resource utilization (ISRU) concepts for enabling future round trip Mars missions. It was determined a decade ago that separation of oxygen can be accomplished efficiently by permeation through a silver membrane at temperatures well below 1000 K. This process involves adsorption of atomic oxygen on the surface and its subsequent diffusion through a silver lattice via an oxygen concentration gradient. We have determined recently that glow discharge can be used to liberate atomic oxygen from Mars atmosphere and that the oxygen can be collected through a silver permeation membrane. Recently, we demonstrated a substantial increase in energy efficiency of the process by applying a radio frequency discharge in combination with a silver permeation membrane. The experiments were performed using pure carbon dioxide in the pressure range equal to Mars surface conditions. Energy efficiency was defined as the ratio of the energy required to dissociate a unit mass of oxygen from carbon dioxide to the (electrical) energy consumed by the overall system during the dissociation and collection process. The research effort, started at NASA Langley Research Center, continued with this project. Oxygen production apparatus, built and operated under the research grant NAG1-1140 was relocated to the Atomic Beams Laboratory at ODU in July 1996, being since then in fall operation.
Simulation of nonstationary phenomena in atmospheric-pressure glow discharge
NASA Astrophysics Data System (ADS)
Korolev, Yu. D.; Frants, O. B.; Nekhoroshev, V. O.; Suslov, A. I.; Kas'yanov, V. S.; Shemyakin, I. A.; Bolotov, A. V.
Nonstationary processes in atmospheric-pressure glow discharge manifest themselves in spontaneous transitions from the normal glow discharge into a spark. In the experiments, both so-called completed transitions in which a highly conductive constricted channel arises and incomplete transitions accompanied by the formation of a diffuse channel are observed. A model of the positive column of a discharge in air is elaborated that allows one to interpret specific features of the discharge both in the stationary stage and during its transition into a spark and makes it possible to calculate the characteristic oscillatory current waveforms for completed transitions into a spark and aperiodic ones for incomplete transitions. The calculated parameters of the positive column in the glow discharge mode agree well with experiment. Data on the densities of the most abundant species generated in the discharge (such as atomic oxygen, metastable nitrogen molecules, ozone, nitrogen oxides, and negative oxygen ions) are presented.
Glow discharge conditioning of the PDX vacuum vessel
Dylla, H.F.; Cohen, S.A.; Rossnagel, S.M.; McCracken, G.M.; Staib, P.
A glow discharge technique has been developed and applied to the conditioning of the large (38 m/sup 3/) Poloidal Divertor Experiment (PDX) vacuum vessel. The discharge parameters and working gas (H/sub 2/) were chosen to maximize C and O removal and minimize metal sputtering. The glow discharge was produced by biasing one or two internal anodes at 400 V to sustain a discharge current of 2 to 4 A per anode. Purified H/sub 2/ at a pressure of 3 x 10/sup -2/ torr was flowed through PDX at approx. 10 t-l/s. The effectiveness of the glow discharge conditioning was monitored by measuring impurity gas (CH/sub 4/, C/sub 2/H/sub 4/, and CO) exhaust rates by mass spectrometry and C and O surface removal rates by in-situ AES and XPS.
Examination of interior surfaces using glow-discharge illumination
Lord, David E.; Petrini, Richard R.; Carter, Gary W.
Endoscopic examination of the interior of a hollow structure through a light pipe that is inserted into the structure, the interior being illuminated by means of a glow discharge that is established with a high voltage applied between the structure wall as one electrode and a second electrode that is inserted into the structure, or establishing the glow with two electrodes inserted into the structure.
Dust-void formation in a dc glow discharge.
Fedoseev, A V; Sukhinin, G I; Dosbolayev, M K; Ramazanov, T S
Experimental investigations of dusty plasma parameters of a dc glow discharge were performed in a vertically oriented discharge tube. Under certain conditions, dust-free regions (voids) were formed in the center of the dust particle clouds that levitated in the strong electric field of a stratified positive column. A model for radial distribution of dusty plasma parameters of a dc glow discharge in inert gases was developed. The behavior of void formation was investigated for different discharge conditions (type of gas, discharge pressure, and discharge current) and dust particle parameters (particle radii and particle total number). It was shown that it is the ion drag force radial component that leads to the formation of voids. Both experimental and calculated results show that the higher the discharge current the wider dust-free region (void). The calculations also show that more pronounced voids are formed for dust particles with larger radii and under lower gas pressures. PMID:26382534
Sensitive glow discharge ion source for aerosol and gas analysis
Reilly, Peter T. A.
A high sensitivity glow discharge ion source system for analyzing particles includes an aerodynamic lens having a plurality of constrictions for receiving an aerosol including at least one analyte particle in a carrier gas and focusing the analyte particles into a collimated particle beam. A separator separates the carrier gas from the analyte particle beam, wherein the analyte particle beam or vapors derived from the analyte particle beam are selectively transmitted out of from the separator. A glow discharge ionization source includes a discharge chamber having an entrance orifice for receiving the analyte particle beam or analyte vapors, and a target electrode and discharge electrode therein. An electric field applied between the target electrode and discharge electrode generates an analyte ion stream from the analyte vapors, which is directed out of the discharge chamber through an exit orifice, such as to a mass spectrometer. High analyte sensitivity is obtained by pumping the discharge chamber exclusively through the exit orifice and the entrance orifice.
Extension of spatiotemporal chaos in glow discharge-semiconductor systems
Akhmet, Marat Fen, Mehmet Onur; Rafatov, Ismail
Generation of chaos in response systems is discovered numerically through specially designed unidirectional coupling of two glow discharge-semiconductor systems. By utilizing the auxiliary system approach, [H. D. I. Abarbanel, N. F. Rulkov, and M. M. Sushchik, Phys. Rev. E 53, 4528–4535 (1996)] it is verified that the phenomenon is not a chaos synchronization. Simulations demonstrate various aspects of the chaos appearance in both drive and response systems. Chaotic control is through the external circuit equation and governs the electrical potential on the boundary. The expandability of the theory to collectives of glow discharge systems is discussed, and this increases the potential of applications of the results. Moreover, the research completes the previous discussion of the chaos appearance in a glow discharge-semiconductor system [D. D. Šijačić U. Ebert, and I. Rafatov, Phys. Rev. E 70, 056220 (2004).].
Mechanism of boriding from pastes in a glow discharge
Isakov, S.A.; Al'tshuler, S.A.
The authors investigate the boridation of steel 45 from the standpoint of the glow-discharge dissociation of a borax paste and the plasma arc spraying of the resulting boron into the steel. The effects of process parameters on the impregnation of boron into the steel and its phase behavior in the boridation process are discussed.
Metal Mesh Smear Sampling for Glow Discharge Analytical Spectroscopy
Shaw, R.W.; Barshick, C.M.; Ramsey, J.M.; Smith, D.H.
Metal mesh smear sampling is being developed and evaluated for use in a number of glow discharge and other optical and mass spectrometric techniques. Sensitive elemental and isotopic analyses thus will be coupled with a convenient sampling scheme similar to one that is common for radiological surveys.
Degradation of Organics in a Glow Discharge Under Martian Conditions
NASA Technical Reports Server (NTRS)
Hintze, P. E.; Calle, L. M.; Calle, C. I.; Buhler, C. R.; Trigwell, S.; Starnes, J. W.; Schuerger, A. C.
The primary objective of this project is to understand the consequences of glow electrical discharges on the chemistry and biology of Mars. The possibility was raised some time ago that the absence of organic material and carbonaceous matter in the Martian soil samples studied by the VikinG Landers might be due in part to an intrinsic atmospheric mechanism such as glow discharge. The high probability for dust interactions during Martian dust storms and dust devils, combined with the cold, dry climate of Mars most likely results in airborne dust that is highly charged. Such high electrostatic potentials generated during dust storms on Earth are not permitted in the low-pressure CO2 environment on Mars; therefore electrostatic energy released in the form of glow discharges is a highly likely phenomenon. Since glow discharge methods are used for cleaning and sterilizing surfaces throughout industry, the idea that dust in the Martian atmosphere undergoes a cleaning action many times over geologic time scales appears to be a plausible one.
Synchronization between two coupled direct current glow discharge plasma sources
Chaubey, Neeraj; Mukherjee, S.; Sen, A.; Sekar Iyengar, A. N.
Experimental results on the nonlinear dynamics of two coupled glow discharge plasma sources are presented. A variety of nonlinear phenomena including frequency synchronization and frequency pulling are observed as the coupling strength is varied. Numerical solutions of a model representation of the experiment consisting of two coupled asymmetric Van der Pol type equations are found to be in good agreement with the observed results.
Immobilization of proteins on glow discharge treated polymers
NASA Astrophysics Data System (ADS)
Kiaei, D.; Safranj, A.; Chen, J. P.; Johnston, A. B.; Zavala, F.; Deelder, A.; Castelino, J. B.; Markovic, V.; Hoffman, A. S.
Certain glow discharge-treated surfaces have been shown to enhance retention of adsorbed proteins. On the basis of this phenomenon, we have investigated the possibility of immobilizing (a) albumin for developing thromboresistant and non-fouling surfaces, (b) antibodies for immuno-diagnostic assays and (c) enzymes for various biosensors and industrial bioprocesses. Albumin retention was highest on surfaces treated with tetrafluoroethylene (TFE) compared to untreated surfaces or other glow discharge treatments studied. Preadsorption of albumin on TFE-treated surfaces resulted in low fibrinogen adsorption and platelet adhesion. IgG retention was also highest on TFE-treated surfaces. The lower detection limits of both malaria antigen and circulating anodic antigen of the schistosomiasis worm were enhanced following glow discharge treatment of the assay plates with TFE. Both TFE and tetrachloroethylene (TCE) glow discharge treated surfaces showed high retention of adsorbed horseradish peroxidase (HRP). However, the retained specific activity of HRP after adsorption on TCE-treated surfaces was remarkably higher than on TFE-treated surfaces.
Effect of glow discharge air plasma on grain crops seed
Dubinov, A.E.; Lazarenko, E.M.; Selemir, V.D.
Oat and barley seeds have been exposed to both continuous and pulsed glow discharge plasmas in air to investigate the effects on germination and sprout growth. Statistical analysis was used to evaluate the effect of plasma exposure on the percentage germination and length of sprout growth. A stimulating effect of plasma exposure was found together with a strong dependence on whether continuous or pulsed discharges were used.
Electron concentration distribution in a glow discharge in air flow
NASA Astrophysics Data System (ADS)
Mukhamedzianov, R. B.; Gaisin, F. M.; Sabitov, R. A.
Electron concentration distributions in a glow discharge in longitudinal and vortex air flows are determined from the attenuation of the electromagnetic wave passing through the plasma using microwave probes. An analysis of the distribution curves obtained indicates that electron concentration decreases in the direction of the anode. This can be explained by charge diffusion toward the chamber walls and electron recombination and sticking within the discharge.
Dual-frequency glow discharges in atmospheric helium
Huang, Xiaojiang; Guo, Ying; Dai, Lu; Zhang, Jing; Shi, J. J.
In this paper, the dual-frequency (DF) glow discharges in atmospheric helium were experimented by electrical and optical measurements in terms of current voltage characteristics and optical emission intensity. It is shown that the waveforms of applied voltages or discharge currents are the results of low frequency (LF) waveforms added to high frequency (HF) waveforms. The HF mainly influences discharge currents, and the LF mainly influences applied voltages. The gas temperatures of DF discharges are mainly affected by HF power rather than LF power.
Glow discharge electron impact ionization source for miniature mass spectrometers.
Gao, Liang; Song, Qingyu; Noll, Robert J; Duncan, Jason; Cooks, R Graham; Ouyang, Zheng
A glow discharge electron impact ionization (GDEI) source was developed for operation using air as the support gas. An alternative to the use of thermoemission from a resistively heated filament electron source for miniature mass spectrometers, the GDEI source is shown to have advantages of long lifetime under high-pressure operation and low power consumption. The GDEI source was characterized using our laboratory's handheld mass spectrometer, the Mini 10. The effects of the discharge voltage and pressure were investigated. Design considerations are illustrated with calculations. Performance is demonstrated in a set of experimental tests. The results show that the low power requirements, mechanical ruggedness, and quality of the data produced using the small glow discharge ion source make it well-suited for use with a portable handheld mass spectrometer. PMID:17441220
Radiation effects on ETFE polymer exposed to glow discharge
NASA Astrophysics Data System (ADS)
Minamisawa, Renato Amaral; Abidzina, Volha; de Almeida, Adelaide; Budak, Satilmis; Tereshko, I.; Elkin, I.; Ila, Daryush
The polymer ethylenetetrafluoroethylene (ETFE) is composed of alternating ethylene and tetrafluoroethylene segments. Because it has applications in areas such as medical physics and industrial coatings, there is a great interest in surface modification studies of ETFE polymer. When this material is exposed to ionizing radiation it suffers damage that depends on the type, energy and intensity of the irradiation. In order to determine the radiation damage mechanism from exposure to low voltage plasma, ETFE films were exposed to residual gas plasma in glow discharge regime to a fluence of 2 × 1017 ions/cm2. Irradiated films were analyzed with optical absorption photospectrometry, Fourier transform infrared (FTIR) and Raman spectroscopy to determine the chemical nature of the structural changes caused by low energy glow discharge.
Glow Discharge Induced Hydroxyl Radical Degradation of 2-Naphthylamine
NASA Astrophysics Data System (ADS)
Lu, Quanfang; Yu, Jie; Gao, Jinzhang; Yang, Wu
In an aqueous solution, normal electrolysis at high voltages switches over spontaneously to glow discharge electrolysis and gives rise to hydroxyl radical, hydrogen peroxide, and aqueous electron, as well as several other active species. Hydroxyl radical directly attacks organic contaminants to make them oxidized. In the present paper, 2-naphthylamine is eventually degraded into hydrogen carbonate and carbon dioxide. The degradation process is analyzed by using an Ultraviolet (UV) absorption spectrum, high-performance liquid chromatography (HPLC) and chemical oxygen demand (COD). It is demonstrated that 2-naphthylamine (c0 =30 mg·l-1) is completely converted within 2h at 30°C and 600 V by glow discharge electrolysis, and the degradation is strongly dependent upon the presence of ferrous ions. COD is ascended in the absence of ferrous ions and descended in the presence of them.
The Use of DC Glow Discharges as Undergraduate Educational Tools
Stephanie A. Wissel and Andrew Zwicker, Jerry Ross, and Sophia Gershman
Plasmas have a beguiling way of getting students excited and interested in physics. We argue that plasmas can and should be incorporated into the undergraduate curriculum as both demonstrations and advanced investigations of electromagnetism and quantum effects. Our device, based on a direct current (DC) glow discharge tube, allows for a number of experiments into topics such as electrical breakdown, spectroscopy, magnetism, and electron temperature.
Plasma kinetics of ethanol conversion in a glow discharge
NASA Astrophysics Data System (ADS)
Levko, D. S.; Tsymbalyuk, A. N.; Shchedrin, A. I.
The mechanism of ethanol conversion in a nonequilibrium glow discharge has been studied. It is shown that molecular hydrogen is produced in reactions between ethanol molecules and hydrogen atoms in the initial stage and in reactions involving active H, CH2OH, CH3CHOH, and formaldehyde in the final stage. Comparison with experimental data shows that the kinetic mechanism used in these calculations correctly predicts the concentrations of the main components of the gas mixture.
Physics and chemistry in glow dielectric barrier discharges
NASA Astrophysics Data System (ADS)
Massines, Françoise
Atmospheric pressure glow discharge (APGD) are of great interest for application in gas chemistry, sterilization, surface activation or thin film deposition. But the development of a new process based on this discharge needs a clear understanding of the discharge physics and chemistry. The aim of this work is to contribute to that goal. One difficulty is the large variety of discharges called APGD. Then the first point of this talk will consist on a quick description of the different APGD families. This overview will be limited to dielectric barrier glow discharges. Then, we will focussed on those due to a Townsend breakdown. The analysis of their working domain in helium and in nitrogen shows that a lot of seed electrons are necessary to turn on the discharge through a Townsend breakdown. The main mechanism leading to these seed electrons depends (i) on the life time of the gas metastables compared to the delay between two consecutive discharges (ii) on the maximum ionisation level which can be reached without transition to FD. In helium, the origin of the seed electrons is mainly the electrons created by direct ionisation and Penning ionisation during a discharge or at the end of it, trapped in the positive column and still present in the gas when the following discharge is turned on. In nitrogen, the seed electrons are created by Penning ionisation just before the breakdown. Then in helium, the time between two discharges has to be short enough and a positive column is necessary as well as the presence of helium metastables. In N2, metastable density just before the breakdown is a dominant parameter. Moreover, the density of N2 molecules and then the gas temperature, is also important in order to maintain a large contribution of Penning ionisation compared to direct electronic ionisation. In all the gases, the metastables control the discharge development and then play an important role in the gas chemistry.
Development of blood compatible materials by glow discharge-treatment
NASA Astrophysics Data System (ADS)
Ishikawa, Y.; Sasakawa, S.
Glow discharge-treatment was applied to preparation of blood compatible materials. Plasticized polyvinylchloride (PVC) which is used for blood bags was treated in the presence of various gases or monomers. Wettability of PVC was modified by the treatment over a wide range. And leakage of plasticizer, di-(2-ethylhexyl)phthalate (DEHP), was prevented. When platelet concentrates were stored in the treated PVC bags, impairment of platelet functions was suppressed by the prevention of DEHP leakage. But platelet adhesion to the surfaces increased by the treatments. Aldehyde groups were grafted on polyethylene film (PE) by glow discharge-treatment in the presence of formaldehyde gas. Although the aldehyde-grafted PE (HCHO-PE) had higher reactivity with platelet than PE after albumin coating, it exhibited excellent antithrombogenicity after blood plasma coating. HCHO-PE adsorbed proteins with almost the same composition as blood plasma, although non-treated PE adsorbed proteins with higher fibinogen/albumin ratio. Segmented-polyurethane which is well known to exhibit good antithrombogenicity, also formed the adsorption layer having composition like that of blood plasma. These results suggest that protein layer adsorbed with blood plasma composition is hardly recognized by platelets. Glow discharge-treatment is a simple and effective method for surface modification of medical polymers.
Glow discharge optical emission of plutonium and plutonium waste
Marcus, R.K.; Spencer, W.A.
The application of glow discharges to the analysis of nonconducting materials such as glasses and ceramics is of great interest due to the number of advantages afforded by their direct solids capabilities. These types of samples, by their chemical nature, pose difficulties in dissolution for their subsequent analysis by common spectroscopic instrumental methods such as inductively coupled plasma atomic emission (ICP-AES). The ability of the glow discharge to sputter-atomize and excite solid nonconducting materials greatly reduces sample preparation time, cost, and complexity of an analysis. In comparison with x-ray spectroscopies, GD also provides the advantage of a relatively uniform sample atomization rate, resulting in a lowering of matrix effects. In a traditional direct current glow discharge (dc-GD), the material to be analyzed must first be ground and thoroughly mixed with a conductive host matrix and pressed into a solid pellet. Additionally, atmospheric gases which are often trapped in the sample upon pressing can degrade the quality of the plasma and obscure analytical results by reducing sputtering rates and affecting excitation conditions. Internal standardization has been carried out in both atomic absorption and emission dc-GD analyses in order to improve precision and accuracy which are affected by these problems.
Interaction of a surface glow discharge with a gas flow
Aleksandrov, A. L. Schweigert, I. V.
A surface glow discharge in a gas flow is of particular interest as a possible tool for controlling the flow past hypersonic aircrafts. Using a hydrodynamic model of glow discharge, two-dimensional calculations for a kilovolt surface discharge in nitrogen at a pressure of 0.5 Torr are carried out in a stationary gas, as well as in a flow with a velocity of 1000 m/s. The discharge structure and plasma parameters are investigated near a charged electrode. It is shown that the electron energy in a cathode layer reaches 250-300 eV. Discharge is sustained by secondary electron emission. The influence of a high-speed gas flow on the discharge is considered. It is shown that the cathode layer configuration is flow-resistant. The distributions of the electric field and electron energy, as well as the ionization rate profile in the cathode layer, do not change qualitatively under the action of the flow. The basic effect of the flow's influence is a sharp decrease in the region of the quasineutral plasma surrounding the cathode layer due to fast convective transport of ions.
Similarities and differences between gliding glow and gliding arc discharges
NASA Astrophysics Data System (ADS)
Kolev, St.; Bogaerts, A.
In this work we have analyzed the properties of a gliding dc discharge in argon at atmospheric pressure. Despite the usual designation of these discharges as 'gliding arc discharges', it was found previously that they operate in two different regimes—glow and arc. Here we analyze the differences in both regimes by means of two dimensional fluid modeling. In order to address different aspects of the discharge operation, we use two models—Cartesian and axisymmetric in a cylindrical coordinate system. The obtained results show that the two types of discharges produce a similar plasma column for a similar discharge current. However, the different mechanisms of plasma channel attachment to the cathode could produce certain differences in the plasma parameters (i.e. arc elongation), and this can affect gas treatments applications.
Nitrogen Glow Discharge by a DC Virtual Cathode
NASA Astrophysics Data System (ADS)
Shager, Azza M.; Sroor, Amany T.; Tayeb, Hoda A. El; Gamal, Hoda A. El; Masoud, Mohamed M.
A DC glow discharge operating with a virtual cathode is studied. The system consists of a solid disc cathode and mesh anode. The discharge occurs in nitrogen gas at the left-hand side of Paschen's curve. The plasma electron density in the axial direction has been found to be 0.2 · 108 cm-3 at 2 cm from the mesh. The electron temperature peak value has been found to be 3.5 eV at 6 cm from the mesh. The radial distribution of the plasma electron density and temperature are discussed. The variation of the plasma parameters are in good agreement with the experimental results.
The One Atmosphere Glow Discharge in Air: Phenomenology and Applications
NASA Astrophysics Data System (ADS)
Ben Gadri, Rami; Sherman, Daniel M.; Chen, Zhiyu; Karakaya, Fuat; Reece Roth, J.
The existence of an atmospheric pressure RF glow plasma with the characteristics of a classical low pressure DC glow discharge has been experimentally and theoretically demonstrated [1, 2]. At the UTK Plasma Sciences Laboratory, the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP) in air has been applied to a wide range of plasma processing applications. The technology is simple, technically attractive, and suitable for online treatment of webs and 3-dimensional workpieces. A parallel plate reactor and a Remote Exposure Reactor (RER) have been developed for direct plasma immersion and remote exposure, respectively. The RER is based on generating active species capable of sterilization and surface treatment in a uniform surface layer of the OAUGDP on planar panels [3], and convecting the active species to a remote chamber where the workpiece is located. A related surface plasma has been developed for indoor air filtration systems. In addition, the surface plasma on flat panels modified the boundary layer in wind tunnel tests to produce electrohydrodynamic (EHD) flow effects that can be used to increase or decrease aerodynamic drag [3]. [1] Massines et al., J. Appl. Phys., Vol. 83, N 6, pp 2950-2957, Mar. 1998. [2] J. R. Roth, "Industrial Plasma Engineering" Vol. I: Principles. Inst. Phys. Pub., Bristol and philadelphia, ISBN 0-7503-0318-2, 1995. [3] Roth et al., AIAA Paper 98-0328, 36th AIAA Meeting, Reno NV, 1998, Jan. 12-15.
Ozone generation using atmospheric pressure glow discharge in air
NASA Astrophysics Data System (ADS)
Buntat, Z.; Smith, I. R.; Razali, N. A. M.
This paper presents results from a study into the generation of ozone by a stable atmospheric glow discharge, using dry air as the feeding gas for ozone generation. The power supply is 50 Hz ac, with the use of a perforated aluminium sheet for the electrodes and soda lime glass as a dielectric layer in a parallel-plate configuration, stabilizing the generation process and enabling ozone to be produced. The stable glow discharge spreads uniformly at a gas breakdown voltage below 4.8 kV and requires only 330 mW discharge power, with a limitation of 3 mm on the maximum gap spacing for the dry air. With the technique providing a high collision rate between the electrons and gas molecules during the discharge process, a high ozone yield is obtained. An analysis of the effect on the production rate of parameters such as the input voltage, gas flow rate and reaction chamber dimensions resulted in a highest efficiency of production of almost 350 g kWh-1 and confirms its potential as an important ozone generation technology.
On electron bunching and stratification of glow discharges
Golubovskii, Yuri B.; Kolobov, Vladimir I.; Nekuchaev, Vladimir O.
Plasma stratification and excitation of ionization waves is one of the fundamental problems in gas discharge physics. Significant progress in this field is associated with the name of Lev Tsendin. He advocated the need for the kinetic approach to this problem contrary to the traditional hydrodynamic approach, introduced the idea of electron bunching in spatially periodic electric fields, and developed a theory of kinetic resonances for analysis of moving striations in rare gases. The present paper shows how Tsendin's ideas have been further developed and applied for understanding the nature of the well-known S-, P-, and R-striations observed in glow discharges of inert gases at low pressures and currents. We review numerical solutions of a Fokker-Planck kinetic equation in spatially periodic electric fields under the effects of elastic and inelastic collisions of electrons with atoms. We illustrate the formation of kinetic resonances at specific field periods for different shapes of injected Electron Distribution Functions (EDF). Computer simulations illustrate how self-organization of the EDFs occurs under nonlocal conditions and how Gaussian-like peaks moving along resonance trajectories are formed in a certain range of discharge conditions. The calculated EDFs agree well with the experimentally measured EDFs for the S, P, and R striations in noble gases. We discuss how kinetic resonances affect dispersion characteristics of moving striations and mention some non-linear effects associated with glow discharge stratification. We propose further studies of stratification phenomena combining physical kinetics and non-linear physics.
Characteristics of a glow discharge maintained in the vapors of a liquid
NASA Astrophysics Data System (ADS)
Ramazanov, A. N.; Kostrin, D. K.; Goncharov, V. D.; Lisenkov, A. A.
Glow discharge in atmospheric pressure air in the discharge cell with a liquid cathode is considered. Current-voltage characteristic of such a system at different distances between the electrodes and various electrode placements, different thickness of the liquid layer and the cathode surface area are shown. Spectral emission of the glow discharge plasma in the vapors of a liquid is demonstrated.
Electrical properties of pulsed glow discharge Two new aspects
NASA Astrophysics Data System (ADS)
Efimova, V. V.; Voronov, M. V.; Hoffmann, V.; Eckert, J.
At the application of pulsed glow discharge (PGD) a transient power of several kW can be reached. This leads to a significant increase of the excitation and ionization efficiency of the sputtered sample atoms. Moreover, with pulsed mode temporally resolved optical emission spectrometry (OES) and mass spectrometry (MS) deliver additional information about the chemical bonds (Harrison 1998, Bengtson et al. 2000, Hang et al. 1996, Klingler et al. 1990, Lewis et al. 2001, Jackson and King 2003). However, the practical application of pulsed glow discharge (PGD) requires an understanding of the processes taking place in the pulsed system. There are some publications, where attention was paid on the voltage current characteristics and the current signal shape of PGD (King and Pan 1993, Lewis et al. 2003). Nevertheless more attention should be paid on the electrical properties of the PGD. In this work the shapes of current, voltage and emission intensity signals, obtained with two different pulse generators are compared. For better understanding of processes, taking place in the discharge the knowledge of the gas temperature is very important. Several authors have mentioned that heating of the cathode leads to changes of the voltage current curve, mainly a decrease of the current at the same voltage. This can be explained by a lower gas density at the same pressure but at higher temperatures (Chenlong et al. 1999, Tian and Chu 2001, Kasik et al. 2002). This phenomenon gives an approach to estimate the gas temperature of the plasma.
Diode laser excited optogalvanic spectroscopy of glow discharges
Barshick, C.M.; Shaw, R.W.; Post-Zwicker, A., Young, J.P.; Ramsey, J.M.
The development of diode-laser-excited isotopically-selective optogalvanic spectroscopy (OGS) of uranium metal, oxide and fluoride in a glow discharge (GD) is presented. The technique is useful for determining isotopic ratios of {sup 235}U/({sup 235}U + {sup 238}U) in the above samples. The precision and accuracy of this determination is evaluated, and a study of experimental parameters pertaining to optimization of he measurement is discussed. Application of the GD-OGS to other f-transition elements is also described.
Reproducing continuous radio blackout using glow discharge plasma
Xie, Kai; Li, Xiaoping; Liu, Donglin; Shao, Mingxu; Zhang, Hanlu
A novel plasma generator is described that offers large-scale, continuous, non-magnetized plasma with a 30-cm-diameter hollow structure, which provides a path for an electromagnetic wave. The plasma is excited by a low-pressure glow discharge, with varying electron densities ranging from 10{sup 9} to 2.5 × 10{sup 11} cm{sup −3}. An electromagnetic wave propagation experiment reproduced a continuous radio blackout in UHF-, L-, and S-bands. The results are consistent with theoretical expectations. The proposed method is suitable in simulating a plasma sheath, and in researching communications, navigation, electromagnetic mitigations, and antenna compensation in plasma sheaths.
Glow discharge assisted oxynitriding process of titanium for medical application
NASA Astrophysics Data System (ADS)
Wierzchoń, Tadeusz; Czarnowska, Elżbieta; Grzonka, Justyna; Sowińska, Agnieszka; Tarnowski, Michał; Kamiński, Janusz; Kulikowski, Krzysztof; Borowski, Tomasz; Kurzydłowski, Krzysztof J.
The plasma oxynitriding process is a prospective method of producing titanium oxides as an integral part of a diffusive nitrided surface layer on titanium implants. This hybrid process, which combines glow discharge assisted nitriding and oxidizing, permits producing TiO2 + Ti2N + αTi(N)-type diffusive surface layers. The oxynitrided surface layers improve the corrosion and wear resistance of the substrate material. Additionally, the nanocrystalline titanium oxide TiO2 (rutile) improves the biological properties of titanium and its alloys when in contact with blood, whereas the TiN + Ti2N + αTi(N) zone eliminates the effect of metalosis.
Glow discharge lamp: A light source for optical emission spectroscopy
NASA Astrophysics Data System (ADS)
Vishwanathan, K. S.; Srinivasan, V.; Nalini, S.; Mahalingam, T. R.
A glow discharge lamp based on a modified version of the Grimm design has been fabricated. Its utility as a radiation source for optical emission spectrography by standardizing a method for the analysis of low alloy steels using a set of certified standards from DMRL, Hyderabad, has been demonstrated. A model has been proposed where the sputtering rates of different metals have been correlated with their heats of sublimation, metallic radii, and densities. Sputtering rates of ten different metals obtained from literature have been used to test this model, and the correlation appears to be excellent.
Radial Distributions of Dusty Plasma Parameters in a Glow Discharge
Fedoseev, A. V.; Sukhinin, G. I.
A self-consistent model for radial distributions of dusty plasma parameters in a DC glow discharge based on the non-local Boltzmann equation for EEDF, the drift-diffusion equation for ions, and the Poisson equation for self-consistent electric field is presented. The results show that for the case of high dust particles density when the recombination of electrons and ions exceeds the ionization near the tube axis, radial electron and ion fluxes change their direction toward the center of the tube, and the radial electric field is reversed.
Comparative Spectroscopic Temperature Measurements In Hydrogen Hollow Cathode Glow Discharge
NASA Astrophysics Data System (ADS)
Majstorovic, G. Lj.; Šišovic, N. M.; Konjevic, N.
We report results of optical emission spectroscopy measurements of rotational Trot and translational temperature Ttr of hydrogen molecules. The light source was hollow cathode glow discharge with titanium cathode operated in hydrogen at low pressure. The rotational temperature of excited electronic states of H2 was determined either from relative line intensities of the R branch of the GK ? B band or from the Q branch of the Fulcher-a diagonal band. The population of excited energy levels, determined from relative line intensities, was used to derive ro-vibronic temperature of the ground state of hydrogen molecule.
Inception of Snapover and Gas Induced Glow Discharges
NASA Technical Reports Server (NTRS)
Galofaro, J. T.; Vayner, B. V.; Degroot, W. A.; Ferguson, D. C.; Thomson, C. D.; Dennison, J. R.; Davies, R. E.
Ground based experiments of the snapover phenomenon were conducted in the large vertical simulation chamber at the Glenn Research Center (GRC) Plasma Interaction Facility (PIF). Two Penning sources provided both argon and xenon plasmas for the experiments. The sources were used to simulate a variety of ionospheric densities pertaining to a spacecraft in a Low Earth Orbital (LEO) environment. Secondary electron emission is believed responsible for dielectric surface charging, and all subsequent snapover phenomena observed. Voltage sweeps of conductor potentials versus collected current were recorded in order to examine the specific charging history of each sample. The average time constant for sample charging was estimated between 25 and 50 seconds for all samples. It appears that current drops off by approximately a factor of 3 over the charging time of the sample. All samples charged in the forward and reverse bias directions, demonstrated hysteresis. Current jumps were only observed in the forward or positive swept voltage direction. There is large dispersion in tile critical snapover potential when repeating sweeps on any one sample. The current ratio for the first snapover region jumps between 2 and 4.6 times, with a standard deviation less than 1.6. Two of the samples showed even larger current ratios. It is believed the second large snapover region is due to sample outgassing. Under certain preset conditions, namely at the higher neutral gas background pressures, a perceptible blue-green glow was observed around the conductor. The glow is believed to be a result of secondary electrons undergoing collisions with an expelled tenuous cloud of gas, that is outgassed from the sample. Spectroscopic measurements of the glow discharge were made in an attempt to identify specific lines contributing to the observed glow.
Demonstration of Separation Control Using Glow-Discharge Plasma Actuators
NASA Technical Reports Server (NTRS)
Hultgren, Lennart S.; Ashpis, David E.
Active flow control of boundary-layer separation using glow-discharge plasma actuators is studied experimentally. Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modem low-pressure-turbine airfoil. The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2%) and high (2.5%) free-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface-flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control.
Demonstration of Separation Delay with Glow-Discharge Plasma Actuators
NASA Technical Reports Server (NTRS)
Hultgren, Lennart S.; Ashpis, David E.
Active flow control of boundary-layer separation using glow-discharge plasma actuators is studied experimentally. Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modern low-pressure-turbine airfoil. The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2 percent) and high (2.5 percent) free-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface-flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control.
Flush-mounted probe diagnostics for argon glow discharge plasma
Xu, Liang Cao, Jinxiang; Liu, Yu; Wang, Jian; Du, Yinchang; Zheng, Zhe; Zhang, Xiao; Wang, Pi; Zhang, Jin; Li, Xiao; Qin, Yongqiang; Zhao, Liang
A comparison is made between plasma parameters measured by a flush-mounted probe (FP) and a cylindrical probe (CP) in argon glow discharge plasma. Parameters compared include the space potential, the plasma density, and the effective electron temperature. It is found that the ion density determined by the FP agrees well with the electron density determined by the CP in the quasi-neutral plasma to better than 10%. Moreover, the space potential and effective electron temperature calculated from electron energy distribution function measured by the FP is consistent with that measured by the CP over the operated discharge current and pressure ranges. These results present the FP can be used as a reliable diagnostic tool in the stable laboratory plasma and also be anticipated to be applied in other complicated plasmas, such as tokamaks, the region of boundary-layer, and so on.
Glow discharge deposition at high rates using disilane
Rajeswaran, G.; Corderman, R.R.; Kampas, F.J.; Vanier, P.E.
The research program reported makes use of the fact that amorphous silicon films can be grown faster from disilane in a glow discharge than from the traditional silane. The goal is to find a method to grow films at a high rate and with sufficiently high quality to be used in an efficient solar cell. It must also be demonstrated that the appropriate device structure can be successfully fabricated under conditions which give high deposition rates. High quality intrinsic films have been deposited at 20 A/s. Efficiency of 5.6% on steel substrates and 5.3% on glass substrates were achieved using disilane i-layers deposited at 15 A/s in a basic structure, without wide-gap doped layers or light trapping. Wide gap p-layers were deposited using disilane. Results were compared with those obtained at Vactronic using high power discharges of silane-hydrogen mixtures. (LEW)
Evolution of a vortex in glow discharge plasma
Soukhomlinov, V.S.; Sheverev, V.A.; Oetuegen, M.V.
The evolution of a vortex in glow discharge plasma is studied analytically. Specifically, the mechanism of local energy deposition into the flow by the plasma is considered and its effect on the structure of an inviscid vortex is analyzed. The vortex is modeled by a set of Euler's equations while the energy transferred by the plasma into the gas is represented by Rayleigh mechanism. In this mechanism, the amount of heat addition is a function of local gas density. The analysis indicates that the plasma can have a considerable effect on the structure of a vortex. The inviscid calculations show that in a uniform discharge, a 1 cm vortex dies out in a fraction of a second.
Study on Glow Discharge Plasma Used in Polyester Surface Modification
NASA Astrophysics Data System (ADS)
Liu, Wenzheng; Lei, Xiao; Zhao, Qiang
To achieve an atmospheric pressure glow discharge (APGD) in air and modify the surface of polyester thread using plasma, the electric field distribution and discharge characteristics under different conditions were studied. We found that the region with a strong electric field, which was formed in a tiny gap between two electrodes constituting a line-line contact electrode structure, provided the initial electron for the entire discharge process. Thus, the discharge voltage was reduced. The dielectric barrier of the line-line contact electrodes can inhibit the generation of secondary electrons. Thus, the transient current pulse discharge was reduced significantly, and an APGD in air was achieved. We designed double layer line-line contact electrodes, which can generate the APGD on the surface of a material under treatment directly. A noticeable change in the surface morphology of polyester fiber was visualized with the aid of a scanning electron microscope (SEM). Two electrode structures - the multi-row line-line and double-helix line-line contact electrodes - were designed. A large area of the APGD plasma with flat and curved surfaces can be formed in air using these contact electrodes. This can improve the efficiency of surface treatment and is significant for the application of the APGD plasma in industries.
Ion bombardment glow-discharge furnaces for atomic emission spectroscopy
Tanguay, S.L.
Two glow discharge plasma devices for the atomic emission analysis of aqueous samples were investigated. The devices use thermal vaporization of samples from a graphite cathode coupled with glow-discharge excitation. Furnace heating of the cathode is accomplished by the positive ion bombardment of the cathode during plasma operation. The dc plasma operates in Ar at 0.5-5.0 torr, with currents up to 250 mA. A cw, axial magnetic field of up to 1.25 kG is applied to the cylindrical-post cathode system to reduce electron losses, thereby increasing plasma excitation and ionization efficiency. At higher currents, the cathodes heat to temperatures as high as 2,500{degree}C in the case of the cylindrical-post cathode. Hollow-cathode heating temperatures are lower under comparable conditions, due to the larger cathode surface area, greater cathode mass, and lower power dissipation. The peak furnace temperature using this configuration is approximately 2100{degree}C. The role of the emission of thermionic electrons from the hot cathodes in limiting the cathode heating and in regulating the cathode temperature are considered. Sample residues of up to 50 ng of the analyte are vaporized from the cylindrical-post cathode within a few seconds of the initiation of the discharge, resulting in a transient emission intensity profile. With the hollow-cathode furnace, vaporization may take several seconds. Although a lower rate of cathode heating and a lower sample vapor residence time results in limits of detection which are one to two orders of magnitude lower than those achieved using the cylindrical-post cathode system. For the hollow cathode, limits of detection are on the order of 10 pg to 1 ng.
Xe isotopic fractionation in a cathodeless glow discharge
NASA Astrophysics Data System (ADS)
Bernatowicz, T. J.; Fahey, A. J.
Results are reported on the isotopic composition of Xe processed in cathodeless glow discharges in rarefied air at pressures of 20-40 microns Hg, in the presence of activated charcoal and in empty pyrex containers. Residual gas phase Xe and trapped Xe were found to be fractionated, with the trapped Xe fractionated up to 1 percent per amu. A model is presented for the fractionating process in which Xe ions are simultaneously implanted and sputtered from substrate material, with a mass dependence favoring retention of the heavy isotopes in the substrate. Results of the investigation show that plasma synthesis of carbonaceous material is unnecessary for producing Xe fractionations, and that the fractionations observed in previous synthesis experiments are probably due to implantation of ions into the synthesized material.
Mass dependency of turbulent parameters in stationary glow discharge plasmas
Titus, J. B.; Alexander, A. B.; Wiggins, D. L.; Johnson, J. A. III
A direct current glow discharge tube is used to determine how mass changes the effects of certain turbulence characteristics in a weakly ionized gas. Helium, neon, argon, and krypton plasmas were created, and an axial magnetic field, varied from 0.0 to 550.0 Gauss, was used to enhance mass dependent properties of turbulence. From the power spectra of light emission variations associated with velocity fluctuations, determination of mass dependency on turbulent characteristic unstable modes, energy associated with turbulence, and the rate at which energy is transferred from scale to scale are measured. The magnetic field strength is found to be too weak to overcome particle diffusion to the walls to affect the turbulence in all four types of plasmas, though mass dependency is still detected. Though the total energy and the rate at which the energy moves between scales are mass invariant, the amplitude of the instability modes that characterize each plasma are dependent on mass.
Glow discharge cleaning of carbon fiber composite and stainless steel
NASA Astrophysics Data System (ADS)
Airapetov, A.; Begrambekov, L.; Brémond, S.; Douai, D.; Kuzmin, A.; Sadovsky, Ya.; Shigin, P.; Vergasov, S.
The paper experimentally investigates and analyses the features and mechanisms of both of oxygen removal by deuterium glow discharge from CFC, pyrolytic graphite and stainless steel subjected to irradiation in oxygen contaminated plasma. It is shown that oxygen implanted in pyrolytic graphite (PG) perpendicular to basal plates is removed after sputtering the layer slightly thicker than oxygen stopping zone (≈2 nm). Fast deuterium ions penetrating into CFC during GDC transfer the trapped oxygen atoms into the bulk. Thus, much thicker surface layer has to be removed (500-1000 nm) for oxygen release. Irradiation of stainless steel in plasma leads to formation of a barrier layer with thickness (2-4 nm) equal, or slightly higher than stopping range of oxygen ions. The layer accumulates the main fraction of implanted oxygen and prevents its penetration into the bulk. After barrier layer sputtering oxygen spreads into the bulk. Parameters and conditions of optimum GDC are discussed.
High-pressure dc glow discharges in hollow diamond cathodes
NASA Astrophysics Data System (ADS)
Truscott, B. S.; Turner, C.; May, P. W.
We report the generation and characterization of dc helium microdischarges at several times atmospheric pressure in monolithic diamond hollow-cathode devices having cavity diameters on the order of 100 μm. I-V characteristics indicated operation in the glow discharge regime even at nearly 10 atm, while spectroscopic measurements of the N2 C3Πu → B3Πg emission returned rotational temperatures always around 420 K, with a pressure-dependent vibrational population distribution. The variation of breakdown voltage with pressure closely followed Paschen's law, but with offsets in both axes that we tentatively ascribe to strong diffusive loss and a partial thermalization of electron energies under the high pressures considered here.
Fluorination of polymethylmethaacrylate with tetrafluoroethane using DC glow discharge plasma
NASA Astrophysics Data System (ADS)
Guruvenket, S.; Iyer, Ganjigunte R. S.; Shestakova, Larisa; Morgen, Per; Larsen, N. B.; Mohan Rao, G.
Fluorination of polymer surfaces has technological applications in various fields such as microelectronics, biomaterials, textile, packing, etc. In this study PMMA surfaces were fluorinated using DC glow discharge plasma. Tetrafluoroethane was used as the fluorinating agent. On the fluorinated PMMA surface, static water contact angle, surface energy, optical transmittance (UV-vis), XPS and AFM analyses were carried out. After the fluorination PMMA surface becomes hydrophobic with water contact angle of 107° without losing optical transparency. Surface energy of fluorine plasma-treated PMMA decreased from 35 mJ/cm 2 to 21.2 mJ/cm 2. RMS roughness of the fluorinated surface was 4.01 nm and XPS studies revealed the formation of C-CF x and CF 3 groups on the PMMA surface.
Use of Atmospheric Glow Discharge Plasma to Modify Spaceport Materials
NASA Technical Reports Server (NTRS)
Trigwell, S.; Shuerger, A. C.; Buhler, C. R.; Calle, C. J.
Numerous materials used in spaceport operations require stringent evaluation before they can be utilized. It is critical for insulative polymeric materials that any surface charge be dissipated as rapidly as possible to avoid Electrostatic Discharges (ESD) that could present a danger. All materials must pass the Kennedy Space Center (KSC) standard electrostatic test [1]; however several materials that are considered favorable for Space Shuttle and International Space Station use have failed. Moreover, to minimize contamination of Mars spacecraft, spacecraft are assembled under cleanroom conditions and specific cleaning and sterilizing procedures are required for all materials. However, surface characteristics of these materials may allow microbes to survive by protecting them from sterilization and cleaning techniques. In this study, an Atmospheric Pressure Glow Discharge Plasma (APGD) [2] was used to modify the surface of several materials. This allowed the materials surface to be modified in terms of hydrophilicity, roughness, and conductivity without affecting the bulk properties. The objectives of this study were to alter the surface properties of polymers for improved electrostatic dissipation characteristics, and to determine whether the consequent surface modification on spaceport materials enhanced or diminished microbial survival.
Killing Microorganisms with the One Atmosphere Uniform Glow Discharge Plasma
NASA Astrophysics Data System (ADS)
South, Suzanne; Kelly-Wintenberg, Kimberly; Montie, T. C.; Reece Roth, J.; Sherman, Daniel; Morrison, Jim; Chen, Zhiyu; Karakaya, Fuat
There is an urgent need for the development of new technologies for sterilization and decontamination in the fields of healthcare and industrial and food processing that are safe, cost-effective, broad-spectrum, and not deleterious to samples. One technology that meets these criteria is the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP). The OAUGDP operates in air and produces uniform plasma without filamentary discharges at room temperature, making this technology advantageous for sterilization of heat sensitive materials. The OAUGDP operates in a frequency band determined by the ion trapping mechanisms provided that, for air, the electric field is above 8.5kV/cm. The OAUGDP efficiently generates plasma reactive oxygen species (ROS) including atomic oxygen and oxygen free radicals without the requirement of a vacuum system. We have demonstrated the efficacy of the OAUGDP in killing microorganisms including bacteria, yeast, viruses, and spores in seconds to minutes on a variety of surfaces such as glass, films and fabrics, stainless steel, paper, and agar.
Borax as flux on sintering of iron Ancor Steel 1000® under glow discharge
NASA Astrophysics Data System (ADS)
Ariza Suarez, H. G.; Sarmiento Santos, A.; Ortiz Otálora, C. A.
This work studies the flux effect of borax (di sodium tetraborate decahydrate) on sintering of iron Ancor Steel 1000® in abnormal glow discharge. The incidence of the percentage by weight of borax and the sintering temperature in the process were observed. Samples of powder metallurgical iron were prepared with proportions of 0.50%, 2.0%, 4.0% and 6.0% by weight of borax using the procedures of powder metallurgy. The samples were sintered at 800 and 1100°C for 30min, by glow discharge at low pressure in a reducing atmosphere composed of 20% H2+80% Ar. The samples in compact green-state were analyzed by TGA-DSC to determine the fusion process and mass loss during sintering. The analysis of microhardness and density, shows that at a sintering temperature of 800°C the sample density decreases and the sample microhardness increases with respect to sintered samples without borax. Sintered samples were analysed by DRX showing the absence of precipitates.
Low pressure glow discharge in a system with hollow electrode at floating potential
NASA Astrophysics Data System (ADS)
Babinov, N. A.
This article describes the research of the low pressure gas discharge in a system with hollow electrode at the floating potential. The main characteristic features of the discharge distinguishing it from the glow discharge with hollow cathode are described. The studied type of discharge has good perspective to use in the plasma emission systems allowing to reach high current efficiency of the ion sources.
Efficiency of surface cleaning by a glow discharge for plasma spraying coating
NASA Astrophysics Data System (ADS)
Kadyrmetov, A. M.; Kashapov, N. F.; Sharifullin, S. N.; Saifutdinov, A. I.; Fadeev, S. A.
The article presents the results of experimental studies of the quality of cleaning steel surfaces by a glow discharge for plasma spraying. Shows the results of measurements of the angle of surface wetting and bond strength of the plasma coating to the surface treated. The dependence of the influence of the glow discharge power, chamber pressure, distance between the electrodes and the processing time of the surface on cleaning efficiency. Optimal fields of factors is found. It is shown increase joint strength coating and base by 30-80% as a result of cleaning the substrate surface by a glow discharge plasma spraying.
Influence of annular magnet on discharge characteristics in enhanced glow discharge plasma immersion ion implantation
Li Liuhe; Wang Zhuo; Lu Qiuyuan; Fu, Ricky K. Y.; Chu, Paul K.; Pang Enjing; Dun Dandan; He Fushun; Li Fen
A permanent annular magnet positioned at the grounded anode alters the discharge characteristics in enhanced glow discharge plasma immersion ion implantation (EGD-PIII). The nonuniform magnetic field increases the electron path length and confines electron motion due to the magnetic mirror effect and electron-neutral collisions thus occur more frequently. The plasma potential and ion density measured by a Langmuir probe corroborate that ionization is improved near the grounded anode. This hybrid magnetic field EGD-PIII method is suitable for implantation of gases with low ionization rates.
Radio frequency glow discharge-induced acidification of fluoropolymers.
Krawczyk, Benjamin M; Baltrusaitis, Jonas; Yoder, Colin M; Vargo, Terrence G; Bowden, Ned B; Kader, Khalid N
Fluoropolymer surfaces are unique in view of the fact that they are quite inert, have low surface energies, and possess high thermal stabilities. Attempts to modify fluoropolymer surfaces have met with difficulties in that it is difficult to control the modification to maintain bulk characteristics of the polymer. In a previously described method, the replacement of a small fraction of surface fluorine by acid groups through radio frequency glow discharge created a surface with unexpected reactivity allowing for attachment of proteins in their active states. The present study demonstrates that 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride (EDC) reacts with the acid groups on fluoropolymer surfaces in a novel reaction not previously described. This reaction yields an excellent leaving group in which a primary amine on proteins can substitute to form a covalent bond between a protein and these surfaces. In an earlier study, we demonstrated that collagen IV could be deposited on a modified PTFE surface using EDC as a linker. Once collagen IV is attached to the surface, it assembles to form a functional stratum resembling collagen IV in native basement membrane. In this study, we show data suggesting that the fluorine to carbon ratio determines the acidity of the fluoropolymer surfaces and how well collagen IV attaches to and assembles on four different fluoropolymer surfaces. PMID:21887736
Glow-Discharge Production of Oxygen from the Martian Atmosphere
NASA Astrophysics Data System (ADS)
Hughes, Caleb; Outlaw, Ronald
One of the most crucial aspects of any mission to Mars is a continual supply of oxygen for astronaut respiration on site. The most popular approach to this problem favors in-situ oxygen production on Mars, utilizing the CO2 Martian atmosphere. However, this requires a large energy budget. NASA's current plans for Mars include sending a system called MOXIE, which produces oxygen through solid oxide electrolysis at high temperatures. An alternative approach utilizes the 6 Torr Martian atmosphere to provide a continual source of oxygen by breaking down the molecule into CO and O using a glow-discharge. After dissociation, a thin film Agmembrane uniquely permeates the atomic oxygen which then recombines to O2 on the downstream side, where it is subsequently stored. By taking advantage of recent advances in thin film technology to reduce the thickness of the film to many orders of magnitude less than used in the initial study, a corresponding increase in O2 flux can be realized. The Ag thin film requires the support of a porous ceramic substructure. With this system, it is shown that this method produces a viable energy efficient alternative to MOXIE.
Experimental investigations of dust levitation in a DC glow discharge
NASA Astrophysics Data System (ADS)
Sheth, Niraj; Behrend, Christina; Jiang, Feng; Post-Zwicker, Andrew
Dusty plasmas continue to be of considerable interest to both the astrophysical and plasma processing communities. We recently constructed a DC glow discharge source to investigate dust behavior and its effect on the plasma parameters. The system, roughly based upon one reported elsewhere(1) consists of a 4" stainless steel cross with two planar stainless steel electrodes. Both the anode and cathode are biased with respect to the chamber ground. Typical values are 100 V and -410 V, respectively with argon as the working gas and 1.5 cm electrode distance. The silica dust particles are 3 - 5 microns in diameter and rested on a stainless tray that could be electrically isolated, biased, or grounded. Clouds were observed by scattering light from a He-Ne laser into a CCD camera and the plasma diagnosed by a Langmuir probe. A variety of dust modes are observed, including dust acoustic and dust lattice modes. We report on our initial results investigating the charging of the dust grains and the sheath structure surrounding the dust cloud. (1)Thomas, E., Watson, M., Phys. Plasmas, 7, 3194 (2000)
Synthesis of Single-Walled Carbon Nanotubes in a Glow Discharge Fine Particle Plasma
Imazato, N.; Imano, M.; Hayashi, Y.
Carbon fine particles were synthesized being negatively charged and confined in a glow discharge plasma. The deposited fine particles were analyzed by Raman spectroscopy and transmission electron microscopy (TEM) and were confirmed to include single-walled carbon nanotubes.
Effect of glow discharge sintering in the properties of a composite material fabricated by powder metallurgy
NASA Astrophysics Data System (ADS)
Cardenas, A.; Pineda, Y.; Sarmiento Santos, A.; Vera, E.
Composite samples of 316 stainless steel and SiC were produced by powder metallurgy. Starting materials were mixed in different proportions and compacted to 700MPa. Sintering stage was performed by abnormal glow discharge plasma with direct current in an inert atmosphere of argon. The process was conducted at a temperature of 1200°C±5°C with a heating rate of 100°C/min. This work shows, the effectiveness of plasma sintering process to generate the first contacts between particles and to reduce vacancies. This fact is confirmed by comparing green and sintered density of the material. The results of porosity show a decrease after plasma sintering. Wear tests showed the wear mechanisms, noting that at higher SiC contents, the wear resistance decreases due to poor matrix-reinforcement interaction and by the porosity presence which causes matrix-reinforcement sliding.
Influence of cathode material on generation of energetic hydrogen atoms in a glow discharge
Cvetanovic, N.; Obradovic, B. M.; Kuraica, M. M.
In this paper influence of cathode material on formation of fast hydrogen atoms in an abnormal glow discharge is investigated using Balmer alpha emission spectroscopy. Energetic H atoms are generated in charge exchange reactions of hydrogen ions that are accelerated in the electric field, and also formed in the backscattering process at the cathode surface. Copper and graphite cathodes were used. Investigation was performed in two orthogonal directions of observation in pure hydrogen and argon-hydrogen mixture. The shapes of the profiles are examined together with the space intensity distribution of Balmer alpha line. Reduced atom reflection from graphite was manifested in the spectroscopic result, in accordance to the field acceleration model. The effect was evident only at high ion energies. This is explained by energy dependence of reflection coefficient for H atoms.
Effect of volume and surface charges on discharge structure of glow dielectric barrier discharge
Xu, Shao-Wei; He, Feng; Wang, Yu; Li, Lulu; Ouyang, Ji-Ting
The effect of volume and surface charges on the structure of glow dielectric barrier discharge (DBD) has been investigated numerically by using two-dimensional (2D) fluid modeling. The local increase of volume or surface charges induces a kind of activation-inhibition effect, which enhances the local volume discharge and inhibits the discharge in neighborhoods, resulting in non-uniform discharge. The activation-inhibition effect due to the non-uniform volume and/or surface charges depends on the non-uniformity itself and the applied voltage. The activation-inhibition of non-uniform charges has different effects on the volume charges and the accumulated surface charges. The distribution of remaining free charges (seed electrons) in volume at the beginning of voltage pulse plays a key role for the glow DBD structure, resulting in a patterned DBD, when the seed electrons are non-uniform at higher frequency and moderate voltage or uniform DBD, when the seed electrons are uniform at lower frequency or high voltage. The distribution of surface charges is not the determining factor but a result of the formed DBD structure.
"Decoking" of a "coked" zeolite catalyst in a glow discharge.
Khan, M A; Al-Jalal, A A; Bakhtiari, I A
"Decoking" of a "coked" zeolite catalyst in a glow discharge in oxygen is investigated. The "decoking" process involves reactions of atomic oxygen (O atoms) with "coke" and yields gases such as CO, CO(2) as well as other gaseous products that could be easily pumped out. Three different modes of discharge were investigated including a static mode, a flowing-gas mode, and a periodic-purge mode where the oxygen and other gaseous products of the discharge were replaced by fresh O(2)gas after short but regular intervals of time. In some cases, additional heating was also used to provide base temperatures of the order of 100 degrees C to facilitate penetration of oxygen atoms into the inner layers and cages of the zeolite catalyst. This paper presents some results of spectroscopic analytical techniques used to monitor the atomization of oxygen, oxidation of "coke", and to confirm the process of "decoking". More specifically, radiation emission on the 3 s (5)S- 3p (5)P transitions of O around 777.2-777.5 nm were selected for monitoring the atomization of O(2). On the other hand, X-ray photo-electron spectroscopy (XPS) was used to determine the amount of residual carbon and extent of "decoking". Furthermore, evolution of CO and CO(2) gases as a function of time was systematically monitored in real time. For CO, the 451.1 nm band head belonging to the B(1) Sigma - A(1) Pi bands of the Angstrom system of the CO spectrum was used, while for CO(2), the band head at 353.4 nm belonging to the CO(2)(+) spectrum was used. The rates of evolution of CO and CO(2) were related to the rate of "decoking" of the catalyst. It is noted that in the periodic-purge mode, about 63% of the total yield of CO from a given sample of the catalyst appears in the first 3-min exposure to discharge whereas it takes up to 15 min to remove nearly 94% of the removable carbon under our experimental conditions. PMID:12861433
Binary and ternary gas mixtures for use in glow discharge closing switches
Hunter, Scott R.; Christophorou, Loucas G.
Highly efficient binary and ternary gas mixtures for use in diffuse glow discharge closing switches are disclosed. The binary mixtures are combinations of helium or neon and selected perfluorides. The ternary mixtures are combinations of helium, neon, or argon, a selected perfluoride, and a small amount of gas that exhibits enhanced ionization characteristics. These mixtures are shown to be the optimum choices for use in diffuse glow discharge closing switches by virtue of the combined physio-electric properties of the mixture components.
Note: Rapid reduction of graphene oxide paper by glow discharge plasma
Bo, Zheng; Qian, Jiajing; Duan, Liangping; Qiu, Kunzan Yan, Jianhua; Cen, Kefa; Han, Zhao Jun; Ostrikov, Kostya
This note reports on a novel method for the rapid reduction of graphene oxide (GO) paper using a glow discharge plasma reactor. Glow discharge is produced and sustained between two parallel-plate graphite electrodes at a pressure of 240 mTorr. By exposing GO paper at the junction of negative-glow and Faraday-dark area for 4 min, the oxygen-containing groups can be effectively removed (C/O ratio increases from 2.6 to 7.9), while the material integrality and flexibility are kept well. Electrochemical measurements demonstrate that the as-obtained reduced GO paper can be potentially used for supercapacitor application.
Dynamics of multiple double layers in high pressure glow discharge in a simple torus
Kumar Paul, Manash; Sharma, P. K.; Thakur, A.; Kulkarni, S. V.; Bora, D.
Parametric characterization of multiple double layers is done during high pressure glow discharge in a toroidal vessel of small aspect ratio. Although glow discharge (without magnetic field) is known to be independent of device geometry, but the toroidal boundary conditions are conducive to plasma growth and eventually the plasma occupy the toroidal volume partially. At higher anode potential, the visibly glowing spots on the body of spatially extended anode transform into multiple intensely luminous spherical plasma blob structures attached to the tip of the positive electrode. Dynamics of multiple double layers are observed in argon glow discharge plasma in presence of toroidal magnetic field. The radial profiles of plasma parameters measured at various toroidal locations show signatures of double layer formation in our system. Parametric dependence of double layer dynamics in presence of toroidal magnetic field is presented here.
Long range temporal correlation in the chaotic oscillations of a dc glow discharge plasma
Lahiri, S.; Roychowdhury, D.
Long range temporal correlations in the fluctuations of the plasma floating potentials (measured using a Langmuir probe) are investigated in a dc glow discharge plasma. Keeping the neutral pressure constant, the discharge voltage was varied and at the formation of the plasma, quasi periodic oscillations were excited and on further increase of the discharge voltage they became chaotic (irregular) beyond a threshold voltage. We compared the Lyapunov exponent with the Hurst exponent obtained from R/S statistics which showed an opposite behaviour at the transition point. These results are perhaps new since we have not come across such comparative analysis for chaotic oscillations in a glow discharge plasma before.
Array of surface-confined glow discharges in atmospheric pressure helium: Modes and dynamics
Li, D.; Liu, D. X. E-mail: email@example.com; Nie, Q. Y.; Li, H. P.; Chen, H. L.; Kong, M. G. E-mail: firstname.lastname@example.com
Array of atmospheric pressure surface discharges confined by a two-dimensional hexagon electrode mesh is studied for its discharge modes and temporal evolution so as to a theoretical underpinning to their growing applications in medicine, aerodynamic control, and environmental remediation. Helium plasma surface-confined by one hexagon-shaped rim electrode is shown to evolve from a Townsend mode to a normal and abnormal glow mode, and its evolution develops from the rim electrodes as six individual microdischarges merging in the middle of the hexagon mesh element. Within one hexagon element, microdischarges remain largely static with the mesh electrode being the instantaneous cathode, but move towards the hexagon center when the electrode is the instantaneous anode. On the entire array electrode surface, plasma ignition is found to beat an unspecific hexagon element and then spreads to ignite surrounding hexagon elements. The spreading of microdischarges is in the form of an expanding circle at a speed of about 3 × 10{sup 4} m/s, and their quenching starts in the location of the initial plasma ignition. Plasma modes influence how input electrical power is used to generate and accelerate electrons and as such the reaction chemistry, whereas plasma dynamics are central to understand and control plasma instabilities. The present study provides an important aspect of plasma physics of the atmospheric surface-confined discharge array and a theoretical underpinning to its future technological innovation.
An example of abnormal glow curves identification in personnel thermoluminescent dosimetry.
Osorio Piniella, V; Stadtmann, H; Lankmayr, E
The personal Dosimetry Service Seibersdorf analyses monthly a large number of thermoluminescent dosimeters (TLD). The dosimeters consist of LiF chips, and the readout is carried out with an automated Harshaw 8800 reader system. In some cases, the luminescent glow curves of the routine analysis do not have the expected form as a result of external chemical contamination, hardware problems, poor heat transfer, etc. It is therefore necessary to investigate the reasons for the irregularity of these curves. An algorithm for the investigation of the routine curves was developed. It is based on the fact that the shape of an abnormal glow curve differs from the shape of a normal one. An interesting type of abnormal glow curves in the routine service was found. Some dosimeters of a certain client, a steel industry, exhibit glow curves with an atypical shape and very high signals. In those dosimeters, a possible chemical contamination in the form of a powder was discovered, which interferes with the dosimetric signal. A quantitative analysis of that powder was made by means of inductively coupled plasma emission spectroscopy (ICP-OES) after microwave dissolution. Elements like aluminium, barium, calcium and others were found. Such elements are used in different combinations as thermoluminescent materials. PMID:12406593
Influence of longitudinal argon flow on DC glow discharge at atmospheric pressure
NASA Astrophysics Data System (ADS)
Zhu, Sha; Jiang, Weiman; Tang, Jie; Xu, Yonggang; Wang, Yishan; Zhao, Wei; Duan, Yixiang
A one-dimensional self-consistent fluid model was employed to investigate the influence of longitudinal argon flow on the DC glow discharge at atmospheric pressure. It is found that the charges exhibit distinct dynamic behaviors at different argon flow velocities, accompanied by a considerable change in the discharge structure. The positive argon flow allows for the reduction of charge densities in the positive column and negative glow regions, and even leads to the disappearance of negative glow. The negative argon flow gives rise to the enhancement of charge densities in the positive column and negative glow regions. These observations are attributed to the fact that the gas flow convection influences the transport of charges through different manners by comparing the argon flow velocity with the ion drift velocity. The findings are important for improving the chemical activity and work efficiency of the plasma source by controlling the gas flow in practical applications.
Decomposition Characteristics of an Artificial Biogas in a Low-Pressure DC Glow Discharge
NASA Astrophysics Data System (ADS)
Itoh, Yasuhiro; Oshita, Takamasa; Satoh, Kohki; Itoh, Hidenori
The decomposition characteristics of an artificial biogas, which is a mixture of CH4, CO2 and H2S, using a low pressure DC glow discharge have been investigated. It is found that H2, CO, C2H2, H2O, CS2 and COS are produced from the artificial biogas in the glow discharge. About 65 % of hydrogen atoms in CH4 are converted into H2 at the input energy of 800 J, at which CH4 is completely decomposed, and the decomposition characteristics of the artificial biogas has little dependency on H2S additive. Farther, H2S has a tendency to be decomposed earlier than the other components of the artificial biogas. When the glow discharge is generated in the artificial biogas with H2S, some of carbon atoms are found to deposit on electrodes and the wall of a discharge chamber.
Gas Breakdown of Radio Frequency Glow Discharges in Helium at near Atmospheric Pressure
NASA Astrophysics Data System (ADS)
Liu, Xinkun; Xu, Jinzhou; Cui, Tongfei; Guo, Ying; Zhang, Jing; Shi, Jianjun
A one-dimensional self-consistent fluid model was developed for radio frequency glow discharge in helium at near atmospheric pressure, and was employed to study the gas breakdown characteristics in terms of breakdown voltage. The effective secondary electron emission coefficient and the effective electric field for ions were demonstrated to be important for determining the breakdown voltage of radio frequency glow discharge at near atmospheric pressure. The constant of A was estimated to be 64±4 cm-1Torr-1, which was proportional to the first Townsend coefficient and could be employed to evaluate the gas breakdown voltage. The reduction in the breakdown voltage of radio frequency glow discharge with excitation frequency was studied and attributed to the electron trapping effect in the discharge gap.
Detrapping of tungsten nanoparticles in a direct-current argon glow discharge
NASA Astrophysics Data System (ADS)
Couëdel, L.; Kumar K., Kishor; Arnas, C.
Nanoparticles are grown from the sputtering of a tungsten cathode in a direct current argon glow discharge. Laser light scattering of a vertical laser sheet going through the plasma reveals that the dust particle cloud is compressed and pushed towards the anode during the discharge. Scanning electron microscopy images of substrates exposed to the plasma for given durations show that dust particles are continuously falling down on the anode during the discharge. These observations are explained by the fact that the electrostatic force at the negative glow-anode sheath boundary cannot balance the ion drag, gravity, and thermophoresis forces for particles of more than a few tens of nanometres in diameter.
Detrapping of tungsten nanoparticles in a direct-current argon glow discharge
Couëdel, L. Kumar, K. Kishor; Arnas, C.
Nanoparticles are grown from the sputtering of a tungsten cathode in a direct current argon glow discharge. Laser light scattering of a vertical laser sheet going through the plasma reveals that the dust particle cloud is compressed and pushed towards the anode during the discharge. Scanning electron microscopy images of substrates exposed to the plasma for given durations show that dust particles are continuously falling down on the anode during the discharge. These observations are explained by the fact that the electrostatic force at the negative glow-anode sheath boundary cannot balance the ion drag, gravity, and thermophoresis forces for particles of more than a few tens of nanometres in diameter.
Requirements of the glow discharge techniques to the fundamentals - an exemplary approach.
Broekaert, J A
The importance of gaining knowledge on the fundamental processes in glow discharges in the field of the signal generation, the sputtering phenomena taking place in the case of solids and the analyte breakdown in the excitation of gases is treated. For gaining more knowledge on the plasma processes diagnostics including temperature and electron number density as well as gas and analyte atom and ion densities are required. For the sputtering process, it is shown at the hand of measurements with gas-jet enhanced sputtering and magnetically enhanced sputtering that selective sputtering may occur and that the influence of the analyte loading of the glow discharge plasma needs further study. For the case of the introduction of gaseous samples, the analyte distribution as well as the break-down mechanisms and kinetics in the case of molecular species ask for further study as shown by experiments with gas-sampling glow discharges. PMID:15045277
Non-Thermal Equilibrium Atmospheric Pressure Glow-Like Discharge Plasma Jet
NASA Astrophysics Data System (ADS)
Chang, Zhengshi; Yao, Congwei; Zhang, Guanjun
Non-thermal equilibrium atmospheric pressure plasma jet (APPJ) is a cold plasma source that promises various innovative applications, and the uniform APPJ is more favored. Glow discharge is one of the most effective methods to obtain the uniform discharge. Compared with the glow dielectric barrier discharge (DBD) in atmospheric pressure, pure helium APPJ shows partial characteristics of both the glow discharge and the streamer. In this paper, considering the influence of the Penning effect, the electrical and optical properties of He APPJ and Ar/NH3 APPJ were researched. A word "Glow-like APPJ" is used to characterize the uniformity of APPJ, and it was obtained that the basic characteristics of the glow-like APPJ are driven by the kHz AC high voltage. The results can provide a support for generating uniform APPJ, and lay a foundation for its applications. supported by National Natural Science Foundation of China (Nos. 51307133, 51125029, 51221005) and the Fundamental Research Funds for the Central Universities of China (Nos. xjj2012132, xkjc2013004)
Observation and interpretation of energy efficient, diffuse direct current glow discharge at atmospheric pressure
Tang, Jie Jiang, Weiman; Wang, Yishan; Zhao, Wei; Li, Jing; Duan, Yixiang
A diffuse direct-current glow discharge was realized with low energy consumption and high energy utilization efficiency at atmospheric pressure. The formation of diffuse discharge was demonstrated by examining and comparing the electrical properties and optical emissions of plasmas. In combination with theoretical derivation and calculation, we draw guidelines that appearance of nitrogen ions at low electron density is crucial to enhance the ambipolar diffusion for the expansion of discharge channel and the increasing ambipolar diffusion near the cathode plays a key role in the onset of diffuse discharge. An individual-discharge-channel expansion model is proposed to explain the diffuse discharge formation.
Observation and interpretation of energy efficient, diffuse direct current glow discharge at atmospheric pressure
NASA Astrophysics Data System (ADS)
Tang, Jie; Jiang, Weiman; Li, Jing; Wang, Yishan; Zhao, Wei; Duan, Yixiang
A diffuse direct-current glow discharge was realized with low energy consumption and high energy utilization efficiency at atmospheric pressure. The formation of diffuse discharge was demonstrated by examining and comparing the electrical properties and optical emissions of plasmas. In combination with theoretical derivation and calculation, we draw guidelines that appearance of nitrogen ions at low electron density is crucial to enhance the ambipolar diffusion for the expansion of discharge channel and the increasing ambipolar diffusion near the cathode plays a key role in the onset of diffuse discharge. An individual-discharge-channel expansion model is proposed to explain the diffuse discharge formation.
Producing a Radioactive Source in a Deuterated Palladium Electrode Under Direct-Current Glow Discharge
Yamada, Hiroshi; Uchiyama, Kazuyoshi; Kawata, Nobuhiko; Kurisawa, Yoshiyuki; Nakamura, Mitsuru
Anomalous gamma emission was rarely observed during direct-current glow discharge in {approx}3 Torrs of deuterium gas using a deuterated palladium foil cathode. Autoradiography after the discharge experiment showed that isotopes with low- and high-energy radiation components were produced before or during the discharge. The palladium foil after the anomalous gamma-ray emission was analyzed by secondary ion mass spectroscopy, which revealed a considerable increase in the content of iron and copper on the surface.
Endotoxin removal by radio frequency gas plasma (glow discharge)
NASA Astrophysics Data System (ADS)
Poon, Angela
Contaminants remaining on implantable medical devices, even following sterilization, include dangerous fever-causing residues of the outer lipopolysaccharide-rich membranes of Gram-negative bacteria such as the common gut microorganism E. coli. The conventional method for endotoxin removal is by Food & Drug Administration (FDA)-recommended dry-heat depyrogenation at 250°C for at least 45 minutes, an excessively time-consuming high-temperature technique not suitable for low-melting or heat-distortable biomaterials. This investigation evaluated the mechanism by which E. coli endotoxin contamination can be eliminated from surfaces during ambient temperature single 3-minute to cumulative 15-minute exposures to radio-frequency glow discharge (RFGD)-generated residual room air plasmas activated at 0.1-0.2 torr in a 35MHz electrodeless chamber. The main analytical technique for retained pyrogenic bio-activity was the Kinetic Chromogenic Limulus Amebocyte Lysate (LAL) Assay, sufficiently sensitive to document compliance with FDA-required Endotoxin Unit (EU) titers less than 20 EU per medical device by optical detection of enzymatic color development corresponding to < 0.5 EU/ml in sterile water extracts of each device. The main analytical technique for identification of chemical compositions, amounts, and changes during sequential reference Endotoxin additions and subsequent RFGD-treatment removals from infrared (IR)-transparent germanium (Ge) prisms was Multiple Attenuated Internal Reflection (MAIR) infrared spectroscopy sensitive to even monolayer amounts of retained bio-contaminant. KimaxRTM 60 mm x 15 mm and 50mm x 15mm laboratory glass dishes and germanium internal reflection prisms were inoculated with E. coli bacterial endotoxin water suspensions at increments of 0.005, 0.05, 0.5, and 5 EU, and characterized by MAIR-IR spectroscopy of the dried residues on the Ge prisms and LAL Assay of sterile water extracts from both glass and Ge specimens. The Ge prism MAIR
An XPS study of the KCl surface oxidation in oxygen glow discharge
NASA Astrophysics Data System (ADS)
Stoch, J.; Ladecka, M.
The reaction between the surface of KCl and oxygen in a glow discharge has been studied by X-ray photoemission spectroscopy (XPS). Oxygen glow discharge treatment resulted in the formation of a superoxide, which decomposed under vacuum at room temperature to KO 2 and finally to K 2O. No evidence of KClO 3 or KClO 4 formation has been found. Binding energies of some oxygen species in potassium oxides were determined. The possible role of potassium in K-doped silver catalysts of ethylene epoxidation is discussed.
Binary and ternary gas mixtures for use in glow discharge closing switches
Hunter, S.R.; Christophorou, L.G.
Highly efficient binary and ternary gas mixtures for use in diffuse glow discharge closing switches are disclosed. The binary mixtures are combinations of helium or neon and selected perfluorides. The ternary mixtures are combinations of helium, neon, or argon, a selected perfluoride, and a small amount of gas that exhibits enhanced ionization characteristics. These mixtures are shown to be the optimum choices for use in diffuse glow discharge closing switches by virtue if the combines physio-electric properties of the mixture components. 9 figs.
Binary and ternary gas mixtures with temperature enhanced diffuse glow discharge characteristics for use in closing switches
Christophorou, Loucas G.; Hunter, Scott R.
An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc.
Binary and ternary gas mixtures with temperature enhanced diffuse glow discharge characteristics for use in closing switches
Christophorou, L.G.; Hunter, S.R.
An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc. 11 figs.
Binary and ternary gas mixtures with temperature enhanced diffuse glow discharge characteristics for use in closing switches
Christophorou, L.G.; Hunter, S.R.
An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc. 11 figs.
Parametric Investigations of an Atmospheric pressure Uniform Glow Discharge in helium
NASA Astrophysics Data System (ADS)
Ben Gadri, Rami
In the cold plasma processing field, applications of the atmospheric pressure uniform glow discharge are numerous. Among them one can mention the increase of the surface energy of materials, the cleaning and etching of surfaces, and the decontamination and sterilization. The development of the glow regime at atmospheric pressure permits to avoid the technical and economical drawbacks of low pressure glow discharge systems. It also increases the efficiency of the surface treatment as compared to the corona discharge. In these conditions, a glow regime is obtained and studied in particular experimental conditions. The working gas is helium, the frequency in the range 1-20 kHz, the gap distance of some mm and the metallic electrodes are covered by a dielectric layer. The current is characterized by one peak per half cycle and is typically in the range of a few tens of mA. Since this discharge involves complex nonlinear processes and is sensitive to the variation of its parameters, detailed experimental (Ph. Decomps (1996), PhD thesis, Universite Paul Sabatier Toulouse France, No d'ordre 2538.) and numerical studies, covering wide ranges of system parameters, were required. These investigations allowed the determination of the optimal operating conditions for which the discharge remains of the glow type, and therefore induces a better surface treatment. In this paper the detailed theory ( Ben Gadri R., Rabehi A., Massines F. and Segur P. (1994), XIIth Eur. Sect. Conf. on the At. & Mol. Phy. of Ionized Gases, The Netherlands, 23-26 August, pp. 228-229.) of the one dimensional f luid model and a parametric study of the discharge characteristics are presented. A particular attention will be given to the influence of the different system parameters on the operational mode of the discharge.
Simulation of stationary glow patterns in dielectric barrier discharges at atmospheric pressure
Liu, Fucheng He, Yafeng; Dong, Lifang
Self-organized stationary patterns in dielectric barrier discharges operating in glow regime at atmospheric pressure are investigated by a self-consistent two-dimensional fluid model. The simulation results show that two different modes, namely, the diffuse mode and the static patterned mode, can be formed in different ranges of the driving frequency. The discharge operates in Townsend regime in the diffuse mode, while it operates in a glow regime inside the filaments and in a Townsend regime outside the filaments in the stable pattered mode. The forming process of the stationary filaments can be divided into three stages, namely, destabilizing stage, self-assembling stage, and stable stage. The space charge associated with residual electron density and surface charge is responsible for the formation of these stationary glow patterns.
Chemical equilibria of rare earth oxides in glow-discharge mass spectrometry
Mei, Y.
This research centers around method development and fundamental exploration of the rare earth elements (REE) in glow discharge mass spectrometry (GDMS). The capability of GDMS to analyze directly solids materials eliminates the sample dissolution and preconcentration steps required by many other methods. The simplicity of sample preparation and instrumental operation makes GDMS a promising analytical technique for the field of earth science. Initial studies were dedicated to improving the detection sensitivity of GDMS in analyzing the REE. This was accomplished by eliminating water contamination, a factor that was found to prevent the conversion of the rare earth oxidized to their atomic form in the glow discharge plasma. Methods experimented for water elimination included the uses of both a cryogenic cooling device and getter reagents. When used to determine the REE concentrations in a standard rock sample, the chemical elimination approach yielded comparable results to that obtained by other analytical methods. Further studies focused on probing the chemical reactions involving the REE and other plasma constituents in the glow discharge. It is proposed that the availability of the atomic REE in the glow discharge is strongly influenced by the oxidant and reductant contents in the plasma. Species that contain oxygen tend to shift the redox equilibria of REE toward the formation of their oxides, whereas species that compete for oxygen help reduce the oxidant content in the plasma, and shift the REE redox equilibria toward the formation of the REE atoms. Factors that govern the reaction processes of the REE equilibria were investigated by means of plasma reagent introduction and time-resolved discharge operation. Results indicate that while redox equilibria between the elemental REE and their monoxides exist on the cathode surface and in the gas phase, interactions occurring in the gas phase are probably the main paths for this equilibration in the glow discharge.
Radio frequency atmospheric pressure glow discharge in α and γ modes between two coaxial electrodes
NASA Astrophysics Data System (ADS)
Shang, Wanli; Wang, Dezhen; Zhang, Yuantao
The discharge in pure helium and the influence of small nitrogen impurities at atmospheric pressure are investigated based on a one-dimensional self-consistent fluid model controlled by a dielectric barrier between two coaxial electrodes. The simulation of the radiofrequency (rf) discharge is based on the one-dimensional continuity equations for electrons, ions, metastable atoms, and molecules, with the much simpler current conservation law replacing the Poisson equation for electric field. Through a computational study of rf atmospheric glow discharges over a wide range of current density, this paper presents evidence of at least two glow discharge modes, namely the α mode and the γ mode. The simulation results show the asymmetry of the discharge set exercises great influence on the discharge mechanisms compared to that with parallel-plane electrodes. It is shown that the particle densities are not uniform in the discharge region but increase gradually from the outer to the inner electrode in both modes. The contrasting dynamic behaviors of the two glow modes are studied. Secondary electron emission strongly influences gas ionization in the γ mode yet matters little in the α mode.
High explosives vapor detection by atmospheric sampling glow discharge ionization/tandem mass spectrometry
McLuckey, S.A.; Goeringer, D.E.; Asano, K.G.
The combination of atmospheric sampling glow discharge ionization with tandem mass spectrometry for the detection of traces of high explosives is described. Particular emphasis is placed on use of the quadrupole ion trap as the type of tandem mass spectrometer. Atmospheric sampling glow discharge provides a simple, rugged, and efficient means for anion formation while the quadrupole ion trap provides for efficient tandem mass spectrometry. Mass selective ion accumulation and non-specific ion activation methods can be used to overcome deleterious effects arising from ion/ion interactions. Such interactions constitute the major potential technical barrier to the use of the ion trap for real-time monitoring of targeted compounds in uncontrolled and highly variable matrices. Tailored waveforms can be used to effect both mass selective ion accumulation and ion activation. Concatenated tailored waveforms allow for both functions in a single experiment thereby providing the capability for monitoring several targeted species simultaneously. The combination of atmospheric sampling glow discharge ionization with a state-of-the-art analytical quadrupole ion trap is a highly sensitive and specific detector for traces of high explosives. The combination is also small and inexpensive relative to virtually any other form of tandem mass spectrometry. The science and technology underlying the glow discharge/ion trap combination is sufficiently mature to form the basis for an engineering effort to make the detector portable. 85 refs.
Plasma Processing with a One Atmosphere Uniform Glow Discharge Plasma (OAUGDP)
NASA Astrophysics Data System (ADS)
Reece Roth, J.
The vast majority of all industrial plasma processing is conducted with glow discharges at pressures below 10 torr. This has limited applications to high value workpieces as a result of the large capital cost of vacuum systems and the production constraints of batch processing. It has long been recognized that glow discharges would play a much larger industrial role if they could be operated at one atmosphere. The One Atmosphere Uniform Glow Discharge Plasma (OAUGDP) has been developed at the University of Tennessee Plasma Sciences Laboratory. The OAUGDP is non-thermal RF plasma with the time-resolved characteristics of a classical low pressure DC normal glow discharge. An interdisciplinary team was formed to conduct exploratory investigations of the physics and applications of the OAUGDP. This team includes collaborators from the UTK Textiles and Nonwovens Development Center (TANDEC) and the Departments of Electrical and Computer Engineering, Microbiology, Food Science and Technology, and Mechanical and Aerospace Engineering and Engineering Science. Exploratory tests were conducted on a variety of potential plasma processing and other applications. These include the use of OAUGDP to sterilize medical and dental equipment and air filters; diesel soot removal; plasma aerodynamic effects; electrohydrodynamic (EDH) flow control of the neutral working gas; increasing the surface energy of materials; increasing the wettability and wickability of fabrics; and plasma deposition and directional etching. A general overview of these topics will be presented.
Atomic iodine production in a gas flow by decomposing methyl iodide in a dc glow discharge
Mikheyev, P A; Shepelenko, A A; Voronov, A I; Kupryaev, Nikolai V
The production of atomic iodine for an oxygen - iodine laser is studied by decomposing methyl iodide in a dc glow discharge in a vortex gas flow. The concentration of iodine atoms in discharge products was measured from the atomic iodine absorption of the radiation of a single-frequency tunable diode laser at a wavelength of 1.315 {mu}m. Atomic iodine concentrations sufficient for the operation of an oxygen - iodine laser were obtained. The concentration of atomic iodine amounted to 3.6 x 10{sup 15} cm{sup -3} for a pressure of the carrying argon gas of 15 Torr. The discharge stabilisation by a vortex gas flow allowed the glow discharge to be sustained in a strongly electronegative halogen-containing gas mixture for pressures up to 20 Torr. (active media)
Self-Organization of a Laminar Structure of a Normal Glow Discharge
NASA Astrophysics Data System (ADS)
Timerkaev, B. A.; Petrova, O. A.; Saifutdinov, A. I.
The behavior of a glow discharge at low pressures is considered. A combined experimental and theoretical method for determining the distributions of electron and ion concentrations in the discharge chamber is proposed. It is shown that the concentrations of charged particles in the negative glow rise not due to the intense ionization by fast electrons from the cathode regions, but instead due to the slowing down of their drift motion. The use of an experimental curve of the potential distribution along a discharge chamber and account of the nonlocal dependence of the Townsend coefficient on the electric field strength have allowed obtaining the distribution of the electric field strength and determining the exact character of variation in the concentration of charged particles along the discharge axis.
Investigation of complexity dynamics of inverse and normal homoclinic bifurcation in a glow discharge plasma
Saha, Debajyoti Kumar Shaw, Pankaj; Janaki, M. S.; Sekar Iyengar, A. N.; Ghosh, Sabuj; Mitra, Vramori Michael Wharton, Alpha
Order-chaos-order was observed in the relaxation oscillations of a glow discharge plasma with variation in the discharge voltage. The first transition exhibits an inverse homoclinic bifurcation followed by a homoclinic bifurcation in the second transition. For the two regimes of observations, a detailed analysis of correlation dimension, Lyapunov exponent, and Renyi entropy was carried out to explore the complex dynamics of the system.
Nonlocal control of electron temperature in short direct current glow discharge plasma
Demidov, V. I.; Kudryavtsev, A. A.; Stepanova, O. M.; Kurlyandskaya, I. P.
To demonstrate controlling the electron temperature in nonlocal plasma, experiments have been performed on a short (without positive column) dc glow discharge with a cold cathode by applying different voltages to the conducting discharge wall. The experiments have been performed for low-pressure noble gas discharges. The applied voltage can modify trapping the energetic electrons emitted from the cathode sheath and arising from the atomic and molecular processes in the plasma within the device volume. This phenomenon results in the energetic electrons heating the slow plasma electrons, which consequently modifies the electron temperature. Furthermore, a numerical model of the discharge has demonstrated the electron temperature modification for the above case.
Diagnostics of a nonlocal plasma of a short glow discharge with active boundaries
NASA Astrophysics Data System (ADS)
Demidov, Vladimir; Astafiev, Alexander; Gutsev, Sergie; Kudryavtsev, Anatoly; Zamchiy, Roman
Short glow discharges have attracted interest of researchers. In such discharges, the gap is chosen such a way that the positive column with direct electron heating by electric field could not be formed. However, in contrast to the positive column, the properties of the plasmas of NG and FDS are poorly understood. In this work, experimental study of the short glow discharge in helium at different gas pressures and distances between the electrodes are performed. The short discharge has a positive differential characteristic. As a result the discharge is stable even without ballast resistance, which may be important for applications. Experiments confirm that the plasma of the short glow discharge is characterized by a low electron temperature and weak electric field. Since the dimensions of the NG are determined by energy of fast electrons produced in the cathode sheath, in atomic gases, the electron distribution function is nonlocal, i.e. different groups of electrons behave independently of each other (did not have time ``to mix due to collisions''). As the EDF is nonlocal, it allows measurement of the fast part of the EDF by application of measuring wall electrode. The results of measurements by Langmuir and wall probes are in good agreement. This work has been supported by SPbSU and FZP.
Generation and Control of Electrolyte Cathode Atmospheric Glow Discharges using Miniature Gas Flow
NASA Astrophysics Data System (ADS)
Shirai, Naoki; Nakazawa, Masato; Ibuka, Shinji; Ishii, Shozo
Stable electrolyte cathode atmospheric dc glow microdischarges were generated by using a miniature helium gas flow from a nozzle electrode in air. We developed two schemes to control the temporal evolution of the discharge and the interaction between the discharge column and the ambient air. The vaporization of electrolyte solutions takes place and affects the discharge characteristics. It takes time from the start of the discharge. Therefore the discharge was controlled by applying pulse modulated dc voltages. If the voltage was dropped down to zero before the vaporization, the gas discharge developed without the ionization of the components of solution. The helium gas discharge without air developed when the nozzle electrode was placed in a glass capillary. This was confirmed by examining the change in pH of the solution, which usually decreased owing to the generation of nitrogen oxides in the discharge in air.
Plasma mixing glow discharge device for analytical applications
Pinnaduwage, L.A.
An instrument for analyzing a sample has an enclosure that forms a chamber containing an anode which divides the chamber into a discharge region and an analysis region. A gas inlet and outlet are provided to introduce and exhaust a rare gas into the discharge region. A cathode within the discharge region has a plurality of pins projecting in a geometric pattern toward the anode for exciting the gas and producing a plasma discharge between the cathode and the anode. Low energy electrons (e.g. <0.5 eV) pass into the analysis region through an aperture. The sample to be analyzed is placed into the analysis region and bombarded by the metastable rare gas atoms and the low energy electrons extracted into from the discharge region. A mass or optical spectrometer can be coupled to a port of the analysis region to analyze the resulting ions and light emission. 3 figs.
Plasma mixing glow discharge device for analytical applications
Pinnaduwage, Lal A.
An instrument for analyzing a sample has an enclosure that forms a chamber containing an anode which divides the chamber into a discharge region and an analysis region. A gas inlet and outlet are provided to introduce and exhaust a rare gas into the discharge region. A cathode within the discharge region has a plurality of pins projecting in a geometric pattern toward the anode for exciting the gas and producing a plasma discharge between the cathode and the anode. Low energy electrons (e.g. <0.5 eV) pass into the analysis region through an aperture. The sample to be analyzed is placed into the analysis region and bombarded by the metastable rare gas atoms and the low energy electrons extracted into from the discharge region. A mass or optical spectrometer can be coupled to a port of the analysis region to analyze the resulting ions and light emission.
Controlled growth of aligned carbon nanotube using pulsed glow barrier discharge
NASA Astrophysics Data System (ADS)
Nozaki, Tomohiro; Kimura, Yoshihito; Okazaki, Ken
We first achieved a catalytic growth of aligned carbon nanotube (CNT) using atmospheric pressure pulsed glow barrier discharge combined with DC bias (1000 V). Aligned CNT can grow with the directional electric field, and this is a big challenge in barrier discharges since dielectric barrier does not allow DC bias and forces to use AC voltage to maintain stable plasma conditions. To overcome this, we developed a power source generating Gaussian-shape pulses at 20 kpps with 4% duty, and DC bias was applied to the GND electrode where Ni-, Fe-coated substrate existed. With positive pulse, i.e. substrate was the cathode, random growth of CNT was observed at about 10^9 cm-2. Growth rate significantly reduced when applied negative pulse; Negative glow formation near substrate is essential for sufficient supply of radical species to the catalyst. If -DC was biased, aligned CNT with 20 nm was synthesized because negative bias enhanced negative glow formation. Interestingly, 2 to 3 CNTs stuck each other with +DC bias, resulting in 50-70 nm and non-aligned CNT. Atmospheric pressure glow barrier discharges can be highly controlled and be a potential alternative to vacuum plasmas for CVD, micro-scale, nano-scale fabrication.
Growth of arc in high-pressure, pulsed glow discharge by gas density depletion
NASA Astrophysics Data System (ADS)
Imada, Go; Yatsui, Kiyoshi; Masuda, Wataru
Effects of gas density depletion on arc formation of high-pressure, pulsed glow discharge have been investigated by eliminating the other factors which may affect the discharge stability, such as shock waves, residual ions, electrode heating, and discharge products. The gas density depletion has been simulated by utilizing a subsonic gas flow between the curved electrodes combined with a convergent nozzle and a divergent diffuser. A comparison has been made on the discharge in the aerodynamically created gas density depletion with the second discharge in the double-pulse discharge within a stable gas. We have found that the large gas density depletion, Δρ/ρ0˜-3.6% corresponding to a pulse repetition rate (PRR) of ˜50 Hz, tends to cause an arc-like filament or an arc without the shocks, ions, electrode heating, and products. However, the second discharge in the double-pulse discharge becomes an arc in much smaller gas density depletion (Δρ/ρ0˜-1.2% corresponding to PRR ˜3 Hz). Therefore, the collapse of high-pressure, pulsed glow discharge is most likely caused by some factor other than the gas density depletion.
Signature of fast H atoms from cathode glow region of a dc discharge
Bharathi, P.; Suraj, K. S.; Prahlad, V.; Mukherjee, S.; Vasu, P.
Asymmetric broadening of H{sub {alpha}} line from cathode glow region has been studied. In the cathode glow, mean energy and fractional population of very fast hydrogen atoms were found to be {approx}130 eV and {approx}55%, respectively. These values reduced to {approx}90 eV and {approx}20% when measured at negative glow region. The observed asymmetry was attributed to the presence of the fast hydrogen atoms near the cathode surface. The mean energy and number density of excited fast hydrogen atoms were estimated from the velocity distribution of H{sup +}, H{sub 2}{sup +}, and H{sub 3}{sup +} considering collisions inside the cathode sheath. The reduction in the mean energy and number density of the excited fast hydrogen atoms, at the other locations of the discharge, was explained by energy relaxation and thermalization of the neutrals with the background gas.
A self-consistent particle model for the simulation of RF glow discharges
Trombley, H.W.; Terry, F.L. Jr.; Elta, M.E. . Dept. of Electrical Engineering and Computer Science)
This paper reports on a self-consistent particle model of an argon RF glow discharge that has been developed. Electric field and charged-particle density profiles determined from simulations with the RF glow discharge model are consistent with results obtained from continuum models. The average ion energy is found to vary greatly between the bulk of the discharge and sheaths, contrary to the assumption that the ion energy is uniform, as is assumed in some continuum models. The accuracy of the particle cross sections and collision representation used in the model is verified with a simplified dc model which calculates swarm parameters. Electron swarm parameters determined with this model are in excellent agreement with experimental data taken from the literature.
Hydrogen absorption behavior into boron films by glow discharges in hydrogen and helium
NASA Astrophysics Data System (ADS)
Tsuzuki, K.; Natsir, M.; Inoue, N.; Sagara, A.; Noda, N.; Motojima, O.; Mochizuki, T.; Hino, T.; Yamashina, T.
Hydrogen absorption behavior into boron films deposited on graphite and stainless steel (SS) has been studied. Hydrogen absorption into a H-depleted boron film was investigated during a hydrogen glow discharge with pressure drop measured by a diaphragm gauge. It was found that, after strong but short time absorption at initial phase, hydrogen atoms were slowly (a few percents of injected H atoms) but continuously absorbed without saturation up to 3 h, which was not observed with SS liner without boron coating. Hydrogen atoms were not only desorbed but also implanted into the film during a helium glow discharge and thus, hydrogen atoms were accumulated in the film when H 2 and He discharges were repeated alternately. These accumulation effects enhanced by ions from the glow discharge were investigated quantitatively and the effect of bombarding ion species (H + or He +) was discussed. Depth profile of H atoms was measured by elastic recoil detection (ERD). The density of only near surface region was increased when the hydrogen atoms were injected. Longer time exposure to H 2 discharge resulted in increase in surface density and shift of the peak position to deeper into the film. These results were explained by diffusion of H atoms due to ion impact into the films with keeping its saturation level if we consider resolution of ERD method of 25 nm. From the results, applicability of boron film as protection layer of tritium permeation is discussed.
Atmospheric pressure glow discharge deposition of thermo-sensitive poly (N-isopropylacrylamide)
NASA Astrophysics Data System (ADS)
Shao, M.; Tang, X. L.; Wen, D.; Chen, Y.; Qiu, G.
In this paper, a self-made atmospheric pressure dielectric barrier discharge reactor on intermediate frequency is brought forward and developed, which is equipped with power supply of 1-20 KHz, and the working gas is argon. The experimental results show that is a very stable and uniform atmospheric pressure glow discharge (APGD). Through a series of experiments, the waveforms of single pulse and multi-pulse glow discharge were both obtained. The voltage amplitude, discharge gap and dielectric material are studied, and the conditions of multi-pulse glow discharge are discussed as well. The novel methods of depositing poly (N-isopropylacrylamide) (PNIPAAm) coatings on the surface of glass slides and PS petri dish are provided by atmospheric pressure plasma polymerization. PNIPAAm can be obtained by plasma polymerization of N-isopropylacrylamide using the self-made equipment of atmospheric pressure plasma vapor treatment. The samples were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle. SEM analysis has revealed that the PNIPAAm coatings were formed on the surface of the smooth glass slides. Further evaluation by using XPS, it has shown the presence of PNIPAAm. The wettability can be significantly modified by changing of the temperatures at above and below of the lower critical solution temperature (LCST) from the data of the contact angle test. These results have advantage for further application on the thermo-sensitive textile materials.
A study of the glow discharge characteristics of contact electrodes at atmospheric pressure in air
Liu, Wenzheng Sun, Guangliang Li, Chuanhui; Zhang, Rongrong
Electric field distributions and discharge properties of rod-rod contact electrodes were studied under the condition of DBD for the steady generation of atmospheric pressure glow discharge plasma (APGD) in air. We found that under the effect of the initial electrons generated in a nanometer-scale gap, the rod-rod cross-contact electrodes yielded APGD plasma in air. Regarding the rod-rod cross-contact electrodes, increasing the working voltage expanded the strong electric field area of the gas gap so that both discharge area and discharge power increased, and the increase in the number of contact points kept the initial discharge voltage unchanged and caused an increase in the plasma discharge area and discharge power. A mesh-like structure of cross-contact electrodes was designed and used to generate more APGD plasma, suggesting high applicability.
Ultrasonic nebulization atmospheric pressure glow discharge - Preliminary study
NASA Astrophysics Data System (ADS)
Greda, Krzysztof; Jamroz, Piotr; Pohl, Pawel
Atmospheric pressure glow microdischarge (μAPGD) generated between a small-sized He nozzle jet anode and a flowing liquid cathode was coupled with ultrasonic nebulization (USN) for analytical optical emission spectrometry (OES). The spatial distributions of the emitted spectra from the novel coupled USN-μAPGD system and the conventional μAPGD system were compared. In the μAPGD, the maxima of the intensity distribution profiles of the atomic emission lines Ca, Cd, In, K, Li, Mg, Mn, Na and Sr were observed in the near cathode region, whereas, in the case of the USN-μAPGD, they were shifted towards the anode. In the novel system, the intensities of the analytical lines of the studied metals were boosted from several to 35 times. As compared to the conventional μAPGD-OES with the introduction of analytes through the sputtering and/or the electrospray-like nebulization of the flowing liquid cathode solution, the proposed method with the USN introduction of analytes in the form of a dry aerosol provides improved detectability of the studied metals. The detection limits of metals achieved with the USN-μAPGD-OES method were in the range from 0.08 μg L- 1 for Li to 52 μg L- 1 for Mn.
Prediction of atmospheric pressure glow discharge in dielectric-barrier system
NASA Astrophysics Data System (ADS)
Duan, Xiaoxi; He, Feng; Ouyang, Jiting
A one-dimensional fluid model was used to investigate the breakdown mechanism and discharge mode in dielectric-barrier system. The results show that the dielectric barrier discharge mode depends strongly on the gas property (i.e., the electron multiplication). The atmospheric pressure dielectric barrier glow discharge could only be achieved in a gas (e.g., noble gas) in which the first Townsend ionization coefficient is sufficiently small and the electron multiplication does not rise up rapidly with the electric field, while could not be sustained in the gas (e.g., N2 and O2) in which the electron multiplication is sensitive to the field.
The Influence of Polymer Film on an Atmospheric Pressure Glow Discharge in Helium*
NASA Astrophysics Data System (ADS)
Nersisyan, Gagik; Graham, William
Atmospheric pressure glow discharges (APGD) have potential in polymer surface modification. Here the affect of low density polyethylene (LDPE) film, placed on the electrodes and in the inter-electrode gap, on the development and the uniformity of pulsed APGDs in helium has been studied using short exposure time images and emission spectroscopy of the gap. The APGD was generated between two parallel, glass-ceramic plates, covering metallic mesh electrodes driven by a sinusoidal (5 kV peak to peak) voltage at a frequency of 30 kHz. The build-up of the APGD started from a weak luminous region near the anode followed by the formation of a bright negative glow. When the film was tightly pressed to one of the dielectric plates the intensity of the negative glow decreased and after about 5 minutes the discharge became spatially non-uniform. When the film was stretched through the middle of the gap, it behaved like a dielectric barrier splitting the gap into two APGD regions i.e. with a negative glow on both sides. The affect of the film on the emission spectroscopy and on the electric characteristics will be discussed.
Spectral Evidence for Ionization in Air-Filled Glow Discharge Tubes: Application to Sprites
NASA Astrophysics Data System (ADS)
Armstrong, R. A.; Williams, E. R.; Golka, R. K.; Williams, D. R.
The question of ionization in sprites and the evidence for VLF backscatter from sprites has motivated a quantitative spectral analysis of the various (classical) regions of the glow discharge tube under DC excitation and at air densities appropriate for sprites in the mesosphere. A PR-650 colorimeter (Photo Research, Inc.) has enabled calibrated irradiance measurements for localized zones along the axis of the discharge tube--in the dominantly blue negative glow, in the Faraday dark space and in the red/pink positive column. Consistent with historical nomenclature, nitrogen first and second positive emission is dominant in the positive column (associated with neutral N2), and nitrogen first negative emission, with a prominent peak at 4278 A, is dominant in the blue negative glow (associated with ionized N2+). Whereas nitrogen first and second positive emission are also detected in the negative glow, no spectral evidence for ionization (no 4279, no 3914, no Meinel) is found in the red/pink positive column. This negative result is attributed not to an absence of ionization in the positive column, but rather to a sparse population of N2+ relative to neutral nitrogen in this region, and to the prominent emission in the blue part of the spectrum due to nitrogen second positive. A similar interpretation may be appropriate for the time-integrated spectra from the red body of sprites, also lacking direct evidence for ionization.
Features of plasma glow in low pressure terahertz gas discharge
Bratman, V. L.; Golubev, S. V.; Izotov, I. V.; Kalynov, Yu. K.; Koldanov, V. A.; Razin, S. V.; Litvak, A. G.; Sidorov, A. V.; Skalyga, V. A.; Zorin, V. G.
Investigations of the low pressure (1–100 Torr) gas discharge in the powerful (1 kW) quasi-optical terahertz (0.55 THz) wave beams were made. An intense afterglow was observed after the end of gyrotron terahertz radiation pulse. Afterglow duration significantly exceeded radiation pulse length (8 μs). This phenomenon could be explained by the strong dependence of the collisional-radiative recombination rate (that is supposed to be the most likely mechanism of electron losses from the low pressure terahertz gas discharge) on electron temperature.
Features of plasma glow in low pressure terahertz gas discharge
NASA Astrophysics Data System (ADS)
Bratman, V. L.; Golubev, S. V.; Izotov, I. V.; Kalynov, Yu. K.; Koldanov, V. A.; Litvak, A. G.; Razin, S. V.; Sidorov, A. V.; Skalyga, V. A.; Zorin, V. G.
Investigations of the low pressure (1-100 Torr) gas discharge in the powerful (1 kW) quasi-optical terahertz (0.55 THz) wave beams were made. An intense afterglow was observed after the end of gyrotron terahertz radiation pulse. Afterglow duration significantly exceeded radiation pulse length (8 μs). This phenomenon could be explained by the strong dependence of the collisional-radiative recombination rate (that is supposed to be the most likely mechanism of electron losses from the low pressure terahertz gas discharge) on electron temperature.
Effect of a floating circular aperture on a dc glow discharge dusty plasma
NASA Astrophysics Data System (ADS)
Heinrich, Jonathon R.; Kim, Su-Hyun; Merlino, Robert L.
We have investigated novel effects observed when a floating aperture, either 6 mm or 8 mm in diameter, is placed 1-2 cm in front of an anode disk (4 cm diameter) that is used to form a dc glow discharge dusty plasma. Dust is incorporated into the anode glow plasma from a tray located below the anode which contained kaolin powder. The glow discharge traps particles with an average size of 1 micron. When the aperture is placed in front of the disk, well-defined pear-shaped or spherical dust clouds are formed, depending on the diameter of the aperture and its distance from the anode. The dust interacts with the aperture through the potential structure associated with the floating (negative) plate in which the aperture is located. The dust cloud is imaged using a CCD camera and a thin sheet of 532 nm laser light. Some of the effects observed include: outwardly expanding spherical dust acoustic waves and shocks, dust rotation around a void formed at the aperture, and a dust/discharge instability in which the discharge is periodically quenched and reignited while the dust cloud expands and contracts, with the dust retaining a residual charge.
Comparative Study of Electric Field Measurement in Glow Discharges using Laser Optogalvanic Spectroscopy
Hussain, Shahid; Saleem, M.; Baig, M. A.
The net electric field inside low-pressure glow discharges has been measured using laser optogalvanic spectroscopy of 1s2s {sup 1}S{sub 0}{yields}np{sup 1}P{sub 1} Rydberg series of atomic helium. Three different types of discharges, an inductively coupled RF discharge cell operating at 4 MHz, a homemade DC discharge cell and a commercial see-through hollow cathode lamp have been used for these studies. The Rydberg series terminates earlier in the high electric field discharge as compared to that in the low electric field discharge. The net electric field also produces shift and broadens the observed spectral lines especially in the high lying Rydberg transitions. The electric field has been determined from the series termination and also from the energy shift of the observed transitions.
Surface modification of PDMS using atmospheric glow discharge polymerization of tetrafluoroethane for immobilization of biomolecules
NASA Astrophysics Data System (ADS)
Anand, V.; Ghosh, S.; Ghosh, M.; Rao, G. M.; Railkar, R.; Dighe, R. R.
In this study an atmospheric glow discharge with a fluorocarbon gas as precursor was used to modify the surface of polydimethyl siloxane (PDMS -[(CH 3) 2SiO] n-). The variation in protein immobilizing capability of PDMS was studied for different times of exposure. It was observed that the concentration of proteins adsorbed on the surface varied in an irregular manner with treatment time. The fluorination results in the formation of a thin film of fluorocarbon on the PDMS surface. The AFM and XPS data suggest that the film cracks due to stress and regains its uniformity thereafter. This Stranski-Krastanov growth model of the film was due to the high growth rate offered by atmospheric glow discharge.
Plasma Treatment of Polyethylene Powder Particles in Hollow Cathode Glow Discharge
Wolter, Matthias; Quitzau, Meike; Bornholdt, Sven; Kersten, Holger
Polyethylen (PE) is widely used in the production of foils, insulators, packaging materials, plastic bottles etc. Untreated PE is hydrophobic due to its unpolar surface. Therefore, it is hard to print or glue PE and the surface has to be modified before converting.In the present experiments a hollow cathode glow discharge is used as plasma source which is mounted in a spiral conveyor in order to ensure a combines transport of PE powder particles. With this set-up a homogeneous surface treatment of the powder is possible while passing the glow discharge. The plasma treatment causes a remarkable enhancement of the hydrophilicity of the PE powder which can be verified by contact angle measurements and X-ray photoelectron spectroscopy.
Isotope effects on desorption kinetics of hydrogen isotopes implanted into stainless steel by glow discharge
Matsuyama, M.; Kondo, M.; Noda, N.; Tanaka, M.; Nishimura, K.
In a fusion device the control of fuel particles implies to know the desorption rate of hydrogen isotopes by the plasma-facing materials. In this paper desorption kinetics of hydrogen isotopes implanted into type 316L stainless steel by glow discharge have been studied by experiment and numerical calculation. The temperature of a maximum desorption rate depends on glow discharge time and heating rate. Desorption spectra observed under various experimental conditions have been successfully reproduced by numerical simulations that are based on a diffusion-limited process. It is suggested, therefore, that desorption rate of a hydrogen isotope implanted into the stainless steel is limited by a diffusion process of hydrogen isotope atoms in bulk. Furthermore, small isotope effects were observed for the diffusion process of hydrogen isotope atoms. (authors)
Boundary Layer Flow Control with a One Atmosphere Uniform Glow Discharge Surface Plasma
NASA Technical Reports Server (NTRS)
Roth, J. Reece; Sherman, Daniel M.; Wilkinson, Stephen P.
Low speed wind tunnel data have been acquired for planar panels covered by a uniform, glow-discharge surface plasma in atmospheric pressure air known as the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP). Streamwise and spanwise arrays of flush, plasma-generating surface electrodes have been studied in laminar, transitional, and fully turbulent boundary layer flow. Plasma between symmetric streamwise electrode strips caused large increases in panel drag, whereas asymmetric spanwise electrode configurations produced a significant thrust. Smoke wire flow visualization and mean velocity diagnostics show the primary cause of the phenomena to be a combination of mass transport and vortical structures induced by strong paraelectric ElectroHydroDynamic (EHD) body forces on the flow.
OAK A271 COATING AND MANDREL EFFECTS ON FABRICATION OF GLOW DISCHARGE POLYMER NIF SCALE INDIRECT DRIVE CAPSULES. Targets for the National Ignition Facility (NIF) need to be about 200 {micro}m thick and 2 mm in diameter. These dimensions are well beyond those currently fabricated on a routine basis. They have investigated fabrication of near NIF scale targets using the depolymerizable mandrel technique. Poly-alpha-methylstyrene (PAMS) mandrels, about 2 mm in diameter, of varying qualities were coated with as much as 125 {micro}m of glow discharge polymer (GDP). The surface finish of the final shells was examined using a variety of techniques. A clear dependence of the modal spectrum of final GDP shell on the quality of the initial PAMS mandrels was observed. isolated features were found to be the greatest cause for a shell not meeting the NIF standard.
Analysis Of The Different Zones Of Glow Discharge Of Ethyl Alcohol (C2H6O)
NASA Astrophysics Data System (ADS)
Torres, C.; Reyes, P. G.; Mulia, J.; Castillo, F.; Martínez, H.
The aim of this work is to explore the emission spectroscopy of ethyl alcohol in some regions, also is determine the result elements of the glow discharge, the spectrums were observed in a range of 200 at 1100 nm in the different zones inside of the tube at different distances of 20 and 30 cm. The elements are: in anode region C6H5 (483.02nm), CHO (519.56nm) and H2 (560.47nm), in the positive column CO2+ (315.52 y 337.00nm), O+ (357.48nm), CH+ (380.61nm) and CO+ (399.73nm); in the cathode region we observed O+ (391.19nm), CHOCHO (428.00nm), CO+ (471.12nm) and H2 (656.52nm). C6H5, CHO y H2 species occurring in all regions analyzed varying the glow discharge emission intensity.
Dust structurization observed in a dc glow discharge dusty plasma
NASA Astrophysics Data System (ADS)
Heinrich, Jonathon R.; Kim, Su-Hyun; Merlino, Robert L.
Dusty plasmas, which are inherently open systems which require an ionization source to replenish the plasma absorbed on the grains, tend to exhibit self-organization. Various structures have been observed in dusty plasmas such as dust crystals, voids, and vortices. Due to the presence of drifting ions in dc discharge plasmas, spontaneously excited dust acoustic waves are also a common occurrence. By adjusting the discharge parameters we have observed a new phenomenon in dusty plasmas -- the spontaneous formation of three-dimensional stationary dust density structures. These structures appear as an ordered pattern consisting of alternating regions of high and low dust density arranged in a nested bowl-type configuration The stationary structure evolves from dust density waves that slow down as their wavelength decreases and eventually stop moving when the wavelength reaches some minimum size.
Electrical Characterization of an RF Glow Discharge at Room Pressure
Perez-Martinez, J. A.; Piedad-Beneitez, A. de la; Pena-Eguiluz, R.; Mercado-Cabrera, A.; Valencia A, R.; Barocio, S. R.; Lopez-Callejas, R.; Godoy-Cabrera, O. G.; Benitez-Read, J. S.; Pacheco-Sotelo, J. O.
A non-thermal atmospheric-like plasma source able to operate at room temperature represents, by its physical nature, a considerable potential for biological applications, given its highly accurate action and extremely controllable penetration on the surface of biological tissue. As we start up a research line into this technology, we report the electrical characterization of a room pressure plasma discharge by means of a coupling network model. The discharge is produced by a 13.56MHz commercial generator. As it is impossible to measure directly its state variables (voltage and current intensity) due to the considerable perturbation created by introducing a low impedance at the system output, then an indirect estimation of such variables is achieved from experimental diagnostics at the input, so to validate the proposed electrical model.
Positive column of the glow discharge in argon
NASA Astrophysics Data System (ADS)
Lisovskiy, Valeriy; Artushenko, Ekaterina; Yegorenkov, Vladimir
We report the measurements we performed of the reduced electric field strength E / p in the positive column in the range of the gas pressure and tube radius product of 0.01
Dynamic of the Dust Structures under Magnetic Field Effect in DC Glow Discharges
Vasiliev, M. M.; D'yachkov, L. G.; Antipov, S. N.; Petrov, O. F.; Fortov, V. E.
In this work, we investigate dust structures in the striation of DC glow discharges under magnetic field actions. The dependence of rotation frequency of dusty plasma structures as a function of the magnetic field was investigated. For various magnetic fields kinetic temperatures of the dust particles, diffusion coefficients, and effective coupling coefficient {gamma}* have been determined. Obtained results are analyzed and compared with theoretical predictions.
Microstructure and biocompatibility of titanium oxides produced on nitrided surface layer under glow discharge conditions.
Czarnowska, E; Morgiel, J; Ossowski, M; Major, R; Sowinska, A; Wierzchon, T
The disadvantages of titanium implants are their low wear resistance and the release of titanium elements into surrounding tissue. These can be eliminated by modifying the surface by surface engineering methods, among them nitriding under glow discharge conditions which allow to produce diffusive surface layers. Their combining with an oxide layer might be valuable for biological events occurring at the bone implant interface. The aim of this study was to enhance the titanium biomaterial performance via combining nitriding and oxidizing treatments in one process under glow discharge conditions. The oxynitrided surface layers were produced at 680 degrees C. The obtained layer was TiO + TiN + Ti2N + alphaTi(N) type and about 4-microm thick and was of diffusive character. This layer significantly increased wear resistance and slightly corrosion resistance compared to that of the reference titanium alloy. The produced titanium oxide was about 400-nm thick and built from fine crystallites. This oxide exhibits bioactivity in SBF (simulated body fluid). Osteoblasts of Saos-2 line incubated on this surface exhibited good adhesion and proliferation and ALP release comparable with cells cultured on the reference titanium alloy and TiN + Ti2N + alphaTi(N) surface layers. A quantitative analysis of blood platelets adhering to this layer revealed their highest amount in comparison to that on both the nitrided surface layer and titanium alloy. The presented study provided a simple and reproducible method of combining oxidizing and nitriding under glow discharge in one process. Experimental data in vitro suggests that titanium alloy oxynitriding under low temperatures at glow discharge conditions improves titanium alloy properties and biocompatibility and tissue healing. Therefore, the layer of TiO + TiN +Ti2N + alphaTi(N) type could be valuable for long-term bone implants. PMID:22400281
Accumulation and evolution of the spatial distribution of radicals in vitreous propanol in a glow discharge
Kurshev, V.V.; Raitsimring, A.M.
Analysis of the dipole broadening of an EPR line is used to explain the change in the spatial distribution of radicals formed in the plasma of a high-frequency glow discharge on the surface of vitreous propanol, which contains an electron acceptor. The contributions of various mechanisms for radical formation are evaluated. A model is proposed to describe both the accumulation and the evolution of the stabilization region of radicals in the plasmolysis process. 13 refs., 4 figs.
Non-linear macro evolution of a dc driven micro atmospheric glow discharge
Xu, S. F.; Zhong, X. X.
We studied the macro evolution of the micro atmospheric glow discharge generated between a micro argon jet into ambient air and static water. The micro discharge behaves similarly to a complex ecosystem. Non-linear behaviors are found for the micro discharge when the water acts as a cathode, different from the discharge when water behaves as an anode. Groups of snapshots of the micro discharge formed at different discharge currents are captured by an intensified charge-coupled device with controlled exposure time, and each group consisted of 256 images taken in succession. Edge detection methods are used to identify the water surface and then the total brightness is defined by adding up the signal counts over the area of the micro discharge. Motions of the water surface at different discharge currents show that the water surface lowers increasingly rapidly when the water acts as a cathode. In contrast, the water surface lowers at a constant speed when the water behaves as an anode. The light curves are similar to logistic growth curves, suggesting that a self-inhibition process occurs in the micro discharge. Meanwhile, the total brightness increases linearly during the same time when the water acts as an anode. Discharge-water interactions cause the micro discharge to evolve. The charged particle bomb process is probably responsible for the different behaviors of the micro discharges when the water acts as cathode and anode.
Non-linear macro evolution of a dc driven micro atmospheric glow discharge
NASA Astrophysics Data System (ADS)
Xu, S. F.; Zhong, X. X.
We studied the macro evolution of the micro atmospheric glow discharge generated between a micro argon jet into ambient air and static water. The micro discharge behaves similarly to a complex ecosystem. Non-linear behaviors are found for the micro discharge when the water acts as a cathode, different from the discharge when water behaves as an anode. Groups of snapshots of the micro discharge formed at different discharge currents are captured by an intensified charge-coupled device with controlled exposure time, and each group consisted of 256 images taken in succession. Edge detection methods are used to identify the water surface and then the total brightness is defined by adding up the signal counts over the area of the micro discharge. Motions of the water surface at different discharge currents show that the water surface lowers increasingly rapidly when the water acts as a cathode. In contrast, the water surface lowers at a constant speed when the water behaves as an anode. The light curves are similar to logistic growth curves, suggesting that a self-inhibition process occurs in the micro discharge. Meanwhile, the total brightness increases linearly during the same time when the water acts as an anode. Discharge-water interactions cause the micro discharge to evolve. The charged particle bomb process is probably responsible for the different behaviors of the micro discharges when the water acts as cathode and anode.
Modelling of tokamak glow discharge cleaning II: comparison with experiment and application to ITER
NASA Astrophysics Data System (ADS)
Kogut, D.; Douai, D.; Hagelaar, G.; Pitts, R. A.
The primary function of the ITER glow discharge cleaning (GDC) system will be the preparation of in-vessel component surfaces prior to the machine start-up. It may also contribute to tritium removal in the nuclear phase. In GDC, conditioning efficiency is strongly dependent on the homogeneity of the flux of ions impinging onto wall surfaces. In order to assess the wall particle flux distribution in ITER, a novel 2D multi-fluid model, described in a companion paper, has recently been developed and is benchmarked here against both experimental glow discharge data obtained in a small laboratory chamber with cylindrical geometry and from two large toroidal devices: the JET tokamak and the RFX reverse field pinch. In the laboratory plasma, simulated and measured plasma electron density and temperature are in a good agreement in the negative glow region, while discrepancies exist in the anode glow, where the fluid description of the model is inaccurate due to long mean free paths of electrons. Calculated and measured ion flux distribution profiles in RFX are found in good agreement, whereas in JET comparison it is more difficult, due to the complex geometry of the first wall which leads to local inhomogeneities in the measured flux. Simulations of H2-GDC for ITER with one or two anodes indicate fairly homogeneous plasma parameters and wall ion flux in the negative glow at 0.5 Pa, a commonly used gas pressure for GDC in existing fusion devices. Although the axisymmetric geometry in the model does not allow all seven ITER anodes to be powered simultaneously in the simulations, the results can be extrapolated to the full system and predict ion current densities on wall surfaces close to the simple expectation of total anode current divided by wall surface area (0.21 A m-2), which is relevant to GDC in JET and other machines.
Atmospheric sampling glow discharge ionizataion and triple quadrupole tandem mass spectrometry for explosives vapor detection
McLuckey, S.A.; Goeringer, D.E.; Asano, K.G.; Hart, K.J.; Glish, G.L.; Grant, B.C.; Chambers, D.M.
The detection and identification of trace vapors of hidden high explosives is an excellent example of a targeted analysis problem. It is desirable to push to ever lower levels the quantity or concentration of explosives material that provides an analytical signal, while at the same time discriminating against all other uninteresting material. The detection system must therefore combine high sensitivity with high specificity. This report describes the philosophy behind the use of atmospheric sampling glow discharge ionization, which is a sensitive, rugged, and convenient means for forming anions from explosives molecules, with tandem mass spectrometry, which provides unparalleled specificity in the identification of explosives-related ions. Forms of tandem mass spectrometry are compared and contrasted to provide a summary of the characteristics to be expected from an explosives detector employing mass spectrometry/mass spectrometry. The instrument developed for the FAA, an atmospheric sampling glow discharge/triple quadrupole mass spectrometer, is described in detail with particular emphasis on the ion source/spectrometer interface and on the capabilities of the spectrometer. Performance characteristics of the system are also described as they pertain to explosives of interest including a description of an automated procedure for the detection and identification of specific explosives. A comparison of various tandem mass spectrometers mated with atmospheric sampling glow discharge is then described and preliminary studies with a vapor preconcentration system provided by the FAA will be described.
Mechanism behind self-sustained oscillations in direct current glow discharges and dusty plasmas
Cho, Sung Nae
An alternative explanation to the mechanism behind self-sustained oscillations of ions in direct current (DC) glow discharges is provided. Such description is distinguished from the one provided by the fluid models, where oscillations are attributed to the positive feedback mechanism associated with photoionization of particles and photoemission of electrons from the cathode. Here, oscillations arise as consequence of interaction between an ion and the surface charges induced by it at the bounding electrodes. Such mechanism provides an elegant explanation to why self-sustained oscillations occur only in the negative resistance region of the voltage-current characteristic curve in the DC glow discharges. Furthermore, this alternative description provides an elegant explanation to the formation of plasma fireballs in the laboratory plasma. It has been found that oscillation frequencies increase with ion's surface charge density, but at the rate which is significantly slower than it does with the electric field. The presented mechanism also describes self-sustained oscillations of ions in dusty plasmas, which demonstrates that self-sustained oscillations in dusty plasmas and DC glow discharges involve common physical processes.
Elimination of stick-slip of elastomeric sutures by radiofrequency glow discharge deposited coatings.
Griesser, H J; Chatelier, R C; Martin, C; Vasic, Z R; Gengenbach, T R; Jessup, G
Fine elastomeric sutures intended for cardiovascular surgery can exhibit "stick-slip" behavior as they are pulled through tissue; the resulting oscillatory force can damage delicate tissue or cause sutures to snap. To eliminate this undesirable effect, sutures were surface-modified using a radiofrequency glow discharge in a vapor of either hexamethyldisiloxane or hexamethyldisilazane, to produce a thin polymeric coating on the suture. The same coatings were also deposited onto aluminized tape to facilitate their characterization by measurement of air/water contact angles and by X-ray photoelectron spectroscopy. Coatings from both monomers were found to be very hydrophobic. The hexamethyldisiloxane glow discharge coatings underwent negligible oxidation when stored in air, and thus remained stable over a shelf-life period akin to what may be required of sutures. The hexamethyldisilazane glow discharge coatings, in contrast, incorporated substantial amounts of oxygen over a 3-month period. The coatings did not measurably alter the tensile properties of the sutures. The frictional properties of coated sutures were assessed by measuring the dynamic friction between the suture and ovine myocardium. Both coatings were effective in removing the inherent stick-slip behavior of polybutester sutures in this model. The coatings remained intact after several passes and proved to be robust and efficacious under various strain regimes. PMID:10813763
Dusty Plasma in He-Ar Glow Discharge
Maiorov, S. A.; Ramazanov, T. S.; Dzhumagulova, K. N.; Dosbolayev, M. K.; Jumabekov, A. N.
The paper reports on the first experiments with plasma-dust formations in dc gas discharge plasma for He-Ar mixture. It is shown that under the conventional conditions of the experiments with dusty structures in plasma, the choice of light and heavy gases for the mixture suppresses electron heating in electric field and results in a supersonic jet with high Mach numbers. Distribution functions for drifting ions in the gas mixture are calculated for various mixture concentrations, electric field strengths and gas pressures.
Dynamic model based on voltage transfer curve for pattern formation in dielectric barrier glow discharge
Li, Ben; He, Feng; Ouyang, Jiting; Duan, Xiaoxi
Simulation work is very important for understanding the formation of self-organized discharge patterns. Previous works have witnessed different models derived from other systems for simulation of discharge pattern, but most of these models are complicated and time-consuming. In this paper, we introduce a convenient phenomenological dynamic model based on the basic dynamic process of glow discharge and the voltage transfer curve (VTC) to study the dielectric barrier glow discharge (DBGD) pattern. VTC is an important characteristic of DBGD, which plots the change of wall voltage after a discharge as a function of the initial total gap voltage. In the modeling, the combined effect of the discharge conditions is included in VTC, and the activation-inhibition effect is expressed by a spatial interaction term. Besides, the model reduces the dimensionality of the system by just considering the integration effect of current flow. All these greatly facilitate the construction of this model. Numerical simulations turn out to be in good accordance with our previous fluid modeling and experimental result.
Influence of Forbidden Processes on Similarity Law in Argon Glow Discharge at Low Pressure
NASA Astrophysics Data System (ADS)
Fu, Yang-Yang; Luo, Hai-Yun; Zou, Xiao-Bing; Wang, Xin-Xin
The similarity law of gas discharge is not always valid due to the occurrence of some elementary processes, such as the stepwise ionization process, which are defined as the forbidden processes. To research the influence of forbidden processes on the similarity law, physical parameters (i.e., the electric field, electron density, electron temperature) in similar gaps are investigated based on the fluid model of gas discharge. The products of gas pressure p and dimensions are kept to be constant in similar gaps and the discharge model is solved with and without the forbidden processes, respectively. Discharges in similar gaps are identified as glow discharges and the typical similarity relations all are investigated. The results show that the forbidden processes cause significant deviations of similarity relations from the theoretical ones and the deviations are enlarged as the scaled-down factor k increases. If the forbidden processes are excluded from the model, the similarity law will be valid in argon glow discharge at low pressure.
Dynamic model based on voltage transfer curve for pattern formation in dielectric barrier glow discharge
NASA Astrophysics Data System (ADS)
Li, Ben; He, Feng; Duan, Xiaoxi; Ouyang, Jiting
Simulation work is very important for understanding the formation of self-organized discharge patterns. Previous works have witnessed different models derived from other systems for simulation of discharge pattern, but most of these models are complicated and time-consuming. In this paper, we introduce a convenient phenomenological dynamic model based on the basic dynamic process of glow discharge and the voltage transfer curve (VTC) to study the dielectric barrier glow discharge (DBGD) pattern. VTC is an important characteristic of DBGD, which plots the change of wall voltage after a discharge as a function of the initial total gap voltage. In the modeling, the combined effect of the discharge conditions is included in VTC, and the activation-inhibition effect is expressed by a spatial interaction term. Besides, the model reduces the dimensionality of the system by just considering the integration effect of current flow. All these greatly facilitate the construction of this model. Numerical simulations turn out to be in good accordance with our previous fluid modeling and experimental result.
On the mechanism of pattern formation in glow dielectric barrier discharge
NASA Astrophysics Data System (ADS)
Qiao, Yajun; Li, Ben; Ouyang, Jiting
The formation mechanism of pattern in glow dielectric barrier discharge is investigated by two-dimensional fluid modeling. Experimental results are shown for comparison. The simulation results show that the non-uniform distribution of space charges makes the discharge be enhanced in the high-density region but weakened in its neighborhood, which is considered as an activation-inhibition effect. This effect shows through during a current pulse (one discharge event) but also in a certain period of time after discharge that determines a driving frequency range for the non-uniformity of space charges to be enhanced. The effects of applied voltage, surface charge, electrode boundary, and external field are also discussed. All these factors affect the formation of dielectric-barrier-discharge pattern by changing the distribution or the dynamics of space charges and hence the activation-inhibition effect of non-uniform space charges.
A study of the glow discharge plasma jet of the novel Hamburger-electrode
NASA Astrophysics Data System (ADS)
Liu, Wenzheng; Ma, Chuanlong; Yang, Xiao; Cui, Weisheng; Chen, Xiuyang
To generate atmospheric pressure glow discharge plasma jets (APGDPJs), a novel Hamburger-electrode was proposed. Through the study on electric field distributions, flow field distributions, and characteristics of the discharge and jet, we found that adopting the mode of dielectric barrier discharge with non-uniform thickness of dielectric, it was easy to form the strong electric field areas which were conducive to generate discharge and electric field distributions with large electric field intensity in the narrow gap and weak electric field intensity in the wide gap that were not inclined to form a filament discharge. Using the structure of evenly distributed inner electrodes, it was easy to weaken the pressure of strong electric field areas and form flow field distributions which is beneficial for taking out the high density charged particles and generating APGDPJs. Stable APGDPJs in nitrogen with 3.5 mm in diameter and 9 mm in length were formed by using the novel Hamburger-electrode.
Potential Industrial Applications of the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP) Operating in Ambient Air
NASA Astrophysics Data System (ADS)
Reece Roth, J.
The majority of industrial plasma processing with glow discharges has been conducted at pressures below 10 torr. This tends to limit applications to high value workpieces as a result of the high capital cost of vacuum systems and the production constraints of batch processing. It has long been recognized that glow discharge plasmas would play a much larger industrial role if they could be generated at one atmosphere. The One Atmosphere Uniform Glow Discharge Plasma (OAUGDP), developed at the University of Tennessee's Plasma Sciences Laboratory, is a non-thermal RF plasma operating on displacement currents with the time-resolved characteristics of a classical low pressure DC normal glow discharge. As a glow discharge, the OAUGDP operates with maximum electrical efficiency at the Stoletow point, where the energy input per ion-electron pair is a minimum [1, 2]. Several interdisciplinary teams have investigated potential applications of the OAUGDP. These teams included collaborators from the UTK Textiles and Nonwovens Development Center (TANDEC), and the Departments of Electrical and Computer Engineering, Microbiology, and Food Science and Technology, as well as the NASA Langley Research Center. The potential applications of the OAUGDP have all been at one atmosphere and room temperature, using air as the working gas. These applications include sterilizing medical and dental equipment; sterilizable air filters to deal with the "sick building syndrome"; removal of soot from Diesel engine exhaust; subsonic plasma aerodynamic effects, including flow re-attachment to airfoils and boundary layer modification; electrohydrodynamic (EDH) flow control of working gases; increasing the surface energy of materials; improving the adhesion of paints and electroplated layers: improving the wettability and wickability of fabrics; stripping of photoresist; and plasma deposition and directional etching of potential microelectronic relevance. [1] J. R. Roth, Industrial Plasma Engineering
Charge mitigation techniques using glow and corona discharges for advanced gravitational wave detectors
NASA Astrophysics Data System (ADS)
Campsie, P.; Cunningham, L.; Hendry, M.; Hough, J.; Reid, S.; Rowan, S.; Hammond, G. D.
Charging of silica test masses in gravitational wave detectors could potentially become a significant low-frequency noise source for advanced detectors. Charging noise has already been observed and confirmed in the GEO600 detector and is thought to have been observed in one of the LIGO detectors. In this paper, two charge mitigation techniques using glow and corona discharges were investigated to create repeatable and robust procedures. The glow discharge procedure was used to mitigate charge under vacuum and would be intended to be used in the instance where an optic has become charged while the detector is in operation. The corona discharge procedure was used to discharge samples at atmospheric pressure and would be intended to be used to discharge the detector optics during the cleaning of the optics. Both techniques were shown to reduce both polarities of surface charge on fused silica to a level that would not limit advanced LIGO. Measurements of the transmission of samples that had undergone the charge mitigation procedures showed no significant variation in transmission, at a sensitivity of ~ 200 ppm, in TiO2-doped Ta2O5/SiO2 multi-layer coated fused silica.
An investigation of short glow discharge in helium and the development of its applications for the analysis of gases
NASA Astrophysics Data System (ADS)
Sisoev, Sergey; Saifutdinov, Almaz; Kudryavtsev, Anatoly
DC glow discharge is the subject of constant attention, because it is widely used in practical applications. However, the main object of study remained positive column, the negative glow area has not been fully studied. The main objective of this work was to investigate the short glow discharge in helium. In this work current-voltage characteristics of short glow discharge and probe were obtained. Plasma parameters in the negative glow at different discharge currents and gas pressures were measured. It is shown that the temperature of the core group of electrons in negative glow is low and amounts to a few tenths electronvolts. The concentration of the main groups of electrons is typical for this discharge. Electron energy distribution function was calculated by the method of double numerical differentiation. Features in the form of peaks were found in the ion part of EEDF. These peaks correspond to the electrons which were born as a result of Penning ionization. These peaks may be used for identification of gas mixture. This work was supported by Russian Science Foundation (project #14-19-00311).
Transitions between corona, glow, and spark regimes of nanosecond repetitively pulsed discharges in air at atmospheric pressure
NASA Astrophysics Data System (ADS)
Pai, David Z.; Lacoste, Deanna A.; Laux, Christophe O.
In atmospheric pressure air preheated from 300 to 1000 K, the nanosecond repetitively pulsed (NRP) method has been used to generate corona, glow, and spark discharges. Experiments have been performed to determine the parameter space (applied voltage, pulse repetition frequency, ambient gas temperature, and interelectrode gap distance) of each discharge regime. In particular, the experimental conditions necessary for the glow regime of NRP discharges have been determined, with the notable result that there exists a minimum and maximum gap distance for its existence at a given ambient gas temperature. The minimum gap distance increases with decreasing gas temperature, whereas the maximum does not vary appreciably. To explain the experimental results, an analytical model is developed to explain the corona-to-glow (C-G) and glow-to-spark (G-S) transitions. The C-G transition is analyzed in terms of the avalanche-to-streamer transition and the breakdown field during the conduction phase following the establishment of a conducting channel across the discharge gap. The G-S transition is determined by the thermal ionization instability, and we show analytically that this transition occurs at a certain reduced electric field for the NRP discharges studied here. This model shows that the electrode geometry plays an important role in the existence of the NRP glow regime at a given gas temperature. We derive a criterion for the existence of the NRP glow regime as a function of the ambient gas temperature, pulse repetition frequency, electrode radius of curvature, and interelectrode gap distance.
A brush-shaped air plasma jet operated in glow discharge mode at atmospheric pressure
NASA Astrophysics Data System (ADS)
Li, Xuechen; Bao, Wenting; Jia, Pengying; Di, Cong
Using ambient air as working gas, a direct-current plasma jet is developed to generate a brush-shaped plasma plume with fairly large volume. Although a direct-current power supply is used, the discharge shows a pulsed characteristic. Based on the voltage-current curve and fast photography, the brush-shaped plume, like the gliding arc plasma, is in fact a temporal superposition of a moving discharge filament in an arched shape. During it moves away from the nozzle, the discharge evolves from a low-current arc into a normal glow in one discharge cycle. The emission profile is explained qualitatively based on the dynamics of the plasma brush.
On the physical processes ruling an atmospheric pressure air glow discharge operating in an intermediate current regime
Prevosto, L. Mancinelli, B.; Chamorro, J. C.; Cejas, E.; Kelly, H.
Low-frequency (100 Hz), intermediate-current (50 to 200 mA) glow discharges were experimentally investigated in atmospheric pressure air between blunt copper electrodes. Voltage–current characteristics and images of the discharge for different inter-electrode distances are reported. A cathode-fall voltage close to 360 V and a current density at the cathode surface of about 11 A/cm{sup 2}, both independent of the discharge current, were found. The visible emissive structure of the discharge resembles to that of a typical low-pressure glow, thus suggesting a glow-like electric field distribution in the discharge. A kinetic model for the discharge ionization processes is also presented with the aim of identifying the main physical processes ruling the discharge behavior. The numerical results indicate the presence of a non-equilibrium plasma with rather high gas temperature (above 4000 K) leading to the production of components such as NO, O, and N which are usually absent in low-current glows. Hence, the ionization by electron-impact is replaced by associative ionization, which is independent of the reduced electric field. This leads to a negative current-voltage characteristic curve, in spite of the glow-like features of the discharge. On the other hand, several estimations show that the discharge seems to be stabilized by heat conduction; being thermally stable due to its reduced size. All the quoted results indicate that although this discharge regime might be considered to be close to an arc, it is still a glow discharge as demonstrated by its overall properties, supported also by the presence of thermal non-equilibrium.
A Study on Helium Glow Discharge Cleaning in the HL-1M Tokamak
NASA Astrophysics Data System (ADS)
Wang, Zhi-wen; Yan, Dong-hai; Wang, En-yao
Based on the principle of ion-bombarded reemission and sputtering desorption, the Glow Discharge Cleaning with helium (GDC(He)) is an effective method for controlling the recycle of H on the chamber wall, Carbon (C), Oxygen (O) impurity and improving the wall conditioning in HL-1M tokamak. It is characterized by simplicity without magnet and safety, compared with Taylor Discharge Cleaning (TDC), Alternating current glow discharge Cleaning (AC), Electron Cyclotron Resonance-Discharge Cleaning (ECR-DC). Compared with bake-out degassing, the wall has a higher degassing rate during GDC(He) and a lower impurity concentration in vacuum chambers after GDC(He). Cleaning patterns have been developed dominantly for de-oxidization, decarbonization and de-hydrogenization. The cleaning parameters for H recycle on the wall are also presented. This paper mainly describes the GDC system along with its parameters, breakdown voltage, volt-ampere characteristic, the range of operation safe and suitable cleaning patterns in the HL-1M tokamak, finally concluding with some suggestions on HL-2A GDC.
Stability of atmospheric pressure glow discharge and application to carbon nanotube deposition
NASA Astrophysics Data System (ADS)
Nozaki, Tomohiro; Okazaki, Ken; Kortshagen, Uwe; Heberlein, Joachim
This paper describes carbon nanotube deposition using helium-based glow barrier discharge. Two important issues will be discussed: The stability of glow discharge and aligned growth of nanotube. Silicone substrate having 20 nm nickel film was secured on metallic bottom electrode where the temperature was elevated by 600C. In addition to CH4 or C2H2, the process gas also include hydrogen ( ˜10vol%) in order to etch out excess carbon deposited on Ni particle. Highly contaminated helium tends to form filamentary discharges, and then severely deteriorates deposited materials. It also limits operating conditions such as gap separation, voltage amplitude, and so on. The stability issue will be extensively discussed in terms of emission spectroscopy which also makes clear chemical processes. Nanotubes vertically grow in the presence of directional electric field, and this is a big challenge in barrier discharges because dielectric barrier forces to use AC voltage to maintain stable plasma conditions. Alignment of nanotube also depends on carbon sources. C2H2 generally provides curly nanotubes, whereas rather straight nanotubes likely grow with methane. Control growth of nanotube will be discussed based on voltage waveform (Sin/Pulse) and carbon source.
Atmospheric Pressure Glow Discharge Plasma and Surface Modification of PET Textile by APGDP
NASA Astrophysics Data System (ADS)
Gu, Biao; Chen, Ru; Xu, Yin; Deng, Xiang; Shi, Qingjun
Comparing with traditional chemistry method, surface modification of Polyethylene terephthalate (PET) fabrics by using of Atmospheric Pressure Glow Discharge Plasma (APGDP) has many advantages, such as low cost, low pollution and low energy consumption. So it has huge application in textile industry due to no requirement for vacuum system. In this paper, the generation and the characteristics of APGDP on a homemade device were investigated experimentally. The volt-ampere characteristic and the Lissajous figure demonstrated that, different from dielectric barrier discharge (DBD), there is no filaments appeared between electrodes. It is a glow discharge in one atmospheric pressure. Furthermore we investigated the surface modification of PET by APGDP. The relationship between PET characteristics (wettability, critical surface tension, timing-effect, dyeablity etc.) and various discharge parameters are discussed. At last, the measurements of ATR-FTIR (Attenuated Total Refraction-Fourier Transform Infarared Spectroscopy) and dyeing properties are demonstrated, and the mechanism of modification is analyzed basically. Key words: APGDP£¬Surface modification , PET
A low-power magnetic-field-assisted plasma jet generated by dielectric-barrier discharge enhanced direct-current glow discharge at atmospheric pressure
Jiang, Weiman; Tang, Jie Wang, Yishan; Zhao, Wei; Duan, Yixiang
A magnetic field is introduced to the dielectric-barrier discharge enhanced direct-current glow discharge for efficient plasma generation, with the discharge power of 2.7 W and total energy consumption reduced to 34% of the original. By spatially examining the emission spectra and plasma temperature, it is found that their peaks shift from edges to the center and the negative and anode glows merge into the positive column and disappear, accompanied by improvement of uniformity and chemical activity of the enlarged plasma. This lies in the enhancement of ionization in the curved and lengthened electron path and the dispersion of discharge domains.
Non-local Effects in a Stratified Glow Discharge With Dusty Particles
Sukhinin, G. I.; Fedoseev, A. V.; Ramazanov, T. S.; Amangaliyeva, R. Zh.; Dosbolayev, M. K.; Jumabekov, A. N.
The work is aimed to describe non-local effects in the positive column of a low pressure stratified DC glow discharge in argon with dusty particles in a vertical cylindrical discharge tube. The numerical calculations of plasma parameters in the axis of the discharge tube were performed with the help of hybrid model based on the solution of non-local Boltzmann equation for EEDF. Distributions of optical emission from striations were measured experimentally. It is shown that in a stratified positive column the EEDF is not Maxwellian and even non-monotonous. Also, the effect of displacing of optical emission distribution relative to the electric field is shown both by numerical simulation and experimental measurements.
Characteristics of atmospheric-pressure, radio-frequency glow discharges operated with argon added ethanol
Sun Wenting; Li Guo; Li Heping; Bao Chengyu; Wang Huabo; Zeng Shi; Gao Xing; Luo Huiying
Rf, atmospheric-pressure glow discharge (APGD) plasmas with bare metal electrodes have promising prospects in the fields of plasma-aided etching, thin film deposition, disinfection and sterilization, etc. In this paper, the discharge characteristics are presented for the rf APGD plasmas generated with pure argon or argon-ethanol mixture as the plasma-forming gas and using water-cooled, bare copper electrodes. The experimental results show that the breakdown voltage can be reduced significantly when a small amount of ethanol is added into argon, probably due to the fact that the Penning ionization process is involved, and a pure {alpha}-mode discharge can be produced more easily with the help of ethanol. The uniformity of the rf APGDs of pure argon or argon-ethanol mixtures using bare metallic electrodes is identified with the aid of the intensified charge coupled device images.
Characteristics of atmospheric-pressure, radio-frequency glow discharges operated with argon added ethanol
NASA Astrophysics Data System (ADS)
Sun, Wen-Ting; Li, Guo; Li, He-Ping; Bao, Cheng-Yu; Wang, Hua-Bo; Zeng, Shi; Gao, Xing; Luo, Hui-Ying
Rf, atmospheric-pressure glow discharge (APGD) plasmas with bare metal electrodes have promising prospects in the fields of plasma-aided etching, thin film deposition, disinfection and sterilization, etc. In this paper, the discharge characteristics are presented for the rf APGD plasmas generated with pure argon or argon-ethanol mixture as the plasma-forming gas and using water-cooled, bare copper electrodes. The experimental results show that the breakdown voltage can be reduced significantly when a small amount of ethanol is added into argon, probably due to the fact that the Penning ionization process is involved, and a pure α-mode discharge can be produced more easily with the help of ethanol. The uniformity of the rf APGDs of pure argon or argon-ethanol mixtures using bare metallic electrodes is identified with the aid of the intensified charge coupled device images.
Spectroscopic study of hydrogen rotational, vibrational and translational temperatures in a hollow cathode glow discharge
NASA Astrophysics Data System (ADS)
Majstorovic, G. Lj.
Hydrogen hollow cathode glow discharges (HCGD) have been extensively used for study of fundamental discharge processes as well as for wide variety of applications. For instance, recently, this type of discharge was utilized for producing hydrogen by reforming natural gas (da Silva et al. 2006). The translational or gas kinetic temperature in gas discharges is a parameter of utmost importance in the field of plasma chemistry while vibrationally excited neutral hydrogen molecules play significant role in the chemistry of weakly ionized hydrogen plasmas. This is why the modeling of cold, reactive hydrogen plasma includes rotational and vibrational energy of the hydrogen molecule. This is the reason why we study HC discharge parameters like rotational, translational and vibrational temperature. Several diagnostic techniques are developed to determine gas kinetic temperature T_g like coherent anti-stokes Raman scattering (CARS), laser-induced fluorescence (LIF) and optical emission spectroscopy (OES). Here we selected OES. This diagnostic technique provides information about atom, molecule and ion density in excited and ground state, as well as rotational, vibrational, and gas temperature including the excitation temperature of certain group of excited levels. The technique is applied for measurements of the rotational T_rot, vibrational T_vib and determines translational temperatures in a hollow cathode glow discharge in hydrogen. The rotational temperature of excited electron energy levels is determined from the Boltzmann plot of intensities of rotational moleculelar hydrogen lines belonging to Fulcher-alpha diagonal bands. Following procedure described elsewhere (Astashkevich et al. 2006) the temperature of ground state rovibronic levels is evaluated. The constrains of rotational temperature are discussed in detail. The vibrational temperature is also determined, but from the relative intensities of the H_2 Fulcher-alpha diagonal bands. The dependence of these
Influence of the transverse dimension on the structure and properties of dc glow discharges
Bogdanov, E. A.; Adams, S. F.; Demidov, V. I.; Kudryavtsev, A. A.; Williamson, J. M.
Two-dimensional (2D) simulations of a dc glow discharge with a cold cathode in argon have been performed for various radii of the discharge tube. It is shown that the loss of the charged particles to the walls can significantly affect plasma parameters as well as properties of the cathode sheath. The longitude dimensions of the negative glow and Faraday dark space depend on the transverse loss of the charge particles and are not consistently predicted with a 1D model. The common assumption that the cathode sheath can be analyzed independently of the plasma also may not be valid. The transverse inhomogeneity of the plasma leads to a change in the current density distribution over the cathode surface. The thickness of the cathode sheath can vary with radial distance from the discharge axis, even for the case of negligible radial loss of the charge particles. The 2D model results provide an analysis of the conditions of applicability of the 1D model.
Characteristics of Liquid Flow Induced by Atmospheric Pressure DC Glow Discharge with Liquid Electrode
NASA Astrophysics Data System (ADS)
Tochikubo, Fumiyoshi; Aoki, Takuya; Shirai, Naoki; Uchida, Satoshi
In the application of atmospheric-pressure discharges in contact with liquid, primary reactions are initiated between radicals and liquid molecules at plasma-liquid interface. Since the diffusion in the liquid is very slow, some convective flow is necessary to exchange the chemicals at the plasma-liquid interface for the efficient reactions. In our previous work, we found the appearance of specific downward flow in the liquid just below the dc glow discharge in contact with liquid. This downflow will be effective for exchanging the chemicals at plasma-liquid interface. In this work, we investigated the characteristics of liquid flow induced by atmospheric-pressure dc glow discharge with liquid electrode in detail; the influence of voltage polarity, current amplitude, liquid conductivity, the electrode arrangement, and so on. The spatiotemporal development of liquid flow was visualized by schlieren method, and the temperature distribution was measured using temperature-sensitive liquid crystal particles dispersed in the liquid. The liquid-flow characteristics was reproduced by a fluid simulation considering a downward driving force at liquid surface from plasma. The candidate of the driving force will be the momentum transfer of charged species at the liquid surface. This work is partly supported by JSPS KAKENHI Grant Number 15H03584.
Novel approach to produce polymerized hydrocarbon coatings using dielectric barrier controlled atmospheric pressure glow discharge plasma
NASA Astrophysics Data System (ADS)
Mishra, K. K.; Khardekar, R. K.; Singh, Rashmi; Pant, H. C.
Conventionally, low-pressure (<1 Torr) electrical discharges are used for material processing and thin-film deposition. These schemes suffer mainly due to the high cost of equipment and the complexity of operations. The atmospheric pressure glow discharge plasma is developed using a threaded styled electrode in different configurations, and these reactors are used to produce plasma polymerized coatings, required on plane substrates as self-supporting films to obtain membranes for blocking holes in cavities, and on microballoon targets, which are used as fuel containers for inertial confinement fusion, to avoid DT gas permeation. Helium gas is used as the supporting gas for formation and stabilization of atmospheric pressure glow discharge plasma reactors. Ethylene and acetylene gases are used as monomers to produce plasma polymerized hydrocarbon films. These films are characterized using scanning electron microscopy. Plasma polymerized coatings of thickness 100 nm-10 μm with a smooth surface finish (rms<100 nm) are deposited successfully. The surface finish is further improved using a postdischarge configuration. Preliminary results are very encouraging but further progress is to be made in this area. We are also planning to extend this technique for C:H coating of microballoons, which are used as fuel containers in inertial confinement fusion.
Radio-frequency powered glow discharge device and method with high voltage interface
Duckworth, Douglas C.; Marcus, R. Kenneth; Donohue, David L.; Lewis, Trousdale A.
A high voltage accelerating potential, which is supplied by a high voltage direct current power supply, is applied to the electrically conducting interior wall of an RF powered glow discharge cell. The RF power supply desirably is electrically grounded, and the conductor carrying the RF power to the sample held by the probe is desirably shielded completely excepting only the conductor's terminal point of contact with the sample. The high voltage DC accelerating potential is not supplied to the sample. A high voltage capacitance is electrically connected in series between the sample on the one hand and the RF power supply and an impedance matching network on the other hand. The high voltage capacitance isolates the high DC voltage from the RF electronics, while the RF potential is passed across the high voltage capacitance to the plasma. An inductor protects at least the RF power supply, and desirably the impedance matching network as well, from a short that might occur across the high voltage capacitance. The discharge cell and the probe which holds the sample are configured and disposed to prevent the probe's components, which are maintained at ground potential, from bridging between the relatively low vacuum region in communication with the glow discharge maintained within the cell on the one hand, and the relatively high vacuum region surrounding the probe and cell on the other hand. The probe and cell also are configured and disposed to prevent the probe's components from electrically shorting the cell's components.
Radio-frequency powered glow discharge device and method with high voltage interface
Duckworth, D.C.; Marcus, R.K.; Donohue, D.L.; Lewis, T.A.
A high voltage accelerating potential, which is supplied by a high voltage direct current power supply, is applied to the electrically conducting interior wall of an RF powered glow discharge cell. The RF power supply desirably is electrically grounded, and the conductor carrying the RF power to the sample held by the probe is desirably shielded completely excepting only the conductor's terminal point of contact with the sample. The high voltage DC accelerating potential is not supplied to the sample. A high voltage capacitance is electrically connected in series between the sample on the one hand and the RF power supply and an impedance matching network on the other hand. The high voltage capacitance isolates the high DC voltage from the RF electronics, while the RF potential is passed across the high voltage capacitance to the plasma. An inductor protects at least the RF power supply, and desirably the impedance matching network as well, from a short that might occur across the high voltage capacitance. The discharge cell and the probe which holds the sample are configured and disposed to prevent the probe's components, which are maintained at ground potential, from bridging between the relatively low vacuum region in communication with the glow discharge maintained within the cell on the one hand, and the relatively high vacuum region surrounding the probe and cell on the other hand. The probe and cell also are configured and disposed to prevent the probe's components from electrically shorting the cell's components. 11 figures.
Methodology to analyse small silicon samples by glow discharge mass spectrometry using a thin wafer mask
Modanese, C.; Arnberg, L.; Di Sabatino, M.
Glow discharge mass spectrometry (GDMS) is widely used for trace element analysis of bulk solid samples. The geometry of the GD source limits the minimum size of the sample, which for the instrument used in this work (ThermoElementGD) is 20 mm in diameter. From time to time, there is the need to analyse smaller samples with this technique, and we present here a methodology to analyse samples of 9–20 mm diameter through the use of thin masks. Thin masks have been previously used mostly as secondary cathode for the analysis of non-conducting materials, with hole size smaller than the area of the glow discharge. The use of masks in this work includes the following customization:•The choice of highly-pure Si as mask material, to decrease the chance of interferences with the Si samples.•The use of a hole in the mask of the same size as the discharge area. This implies that the mask material is not sputtered, thus decreasing chances for contamination from the mask itself. PMID:26649274
A comparison of polypropylene-surface treatment by filamentary, homogeneous and glow discharges in helium at atmospheric pressure
NASA Astrophysics Data System (ADS)
Massines, F.; Gouda, G.
Three different dielectric barrier-controlled discharge regimes in helium at atmospheric pressure under sinusoidal excitation have been obtained by varying the excitation frequency or the gas chemical composition: the filamentary discharge, which is the discharge that is usually obtained; the glow discharge, which is controlled by cathode secondary emission; and the homogeneous discharge, which is of a nature in between those of the filamentary and the glow discharges. All the characteristics that have been studied, such as the discharge current, the emission spectrum, the wettability and the chemical transformations of a polypropylene film, are related to the discharge-regime variation. The glow discharge is clearly more efficient than the others as a means of increasing the polypropylene-surface energy. Values as high as 62 mJ 0022-3727/31/24/003/img1 are obtained with this discharge whereas the maximum value after interaction with the filamentary one is 45 mJ 0022-3727/31/24/003/img1. This improvement in wettability is due to there being more O atoms implanted at the surface as well as to the addition of N atoms. The differences among in surface transformations have been correlated to the characteristics of these different discharges and more specifically to the localization of the electrical energy transfer into the gas and to the nature of the ions created during the discharge.
Efficient methane conversion to hydrogen and hydrocarbons by combination of corona and glow discharge
NASA Astrophysics Data System (ADS)
Ghorbanzadeh, A. M.; Matin, N. S.
In this study we offer a new type of plasma which consists of double, corona and glow, discharge to convert natural gas, the main part of which is methane. The most important future of this type of plasma is the steady increase of overall chemical energy efficiency by enhancement of repetition rate. At repetition rate of R=80 Hz, the energy efficiency of 5.5% was increased to 10% at R=330 Hz and more improvement was yet expected at higher repetition rates. Easy control of selectivity of products that were hydrogen, acetylene, ethylene, ethane and hydrocarbons with up to 5 carbons, was also possible by repetition rate.
Numerical simulation of atomic nitrogen formation in plasma of glow discharge in nitrogen-argon mixture
NASA Astrophysics Data System (ADS)
Khomich, V. A.; Ryabtsev, A. V.; Didyk, E. G.; Zhovtyansky, V. A.; Nazarenko, V. G.
We consider the problem of determining the content of atomic nitrogen as an active component responsible for the efficiency of metal surface modification in plasma of stationary low-pressure glow discharge in nitrogen-argon mixture (widely used in this technology). The influence of the gas mixture composition on the rate constant of molecular nitrogen dissociation, which determines the atomic nitrogen production, has been calculated, The parameters of plasma have been experimentally determined using the method of double probes. The electron energy distribution function is found by numerically integrating the Boltzmann equation in a two-term approximation for the molecular nitrogen-argon mixture.
Genetic effects of radio-frequency, atmospheric-pressure glow discharges with helium
NASA Astrophysics Data System (ADS)
Li, Guo; Li, He-Ping; Wang, Li-Yan; Wang, Sen; Zhao, Hong-Xin; Sun, Wen-Ting; Xing, Xin-Hui; Bao, Cheng-Yu
Due to low gas temperatures and high densities of active species, atmospheric-pressure glow discharges (APGDs) would have potential applications in the fields of plasma-based sterilization, gene mutation, etc. In this letter, the genetic effects of helium radio-frequency APGD plasmas with the plasmid DNA and oligonucleotide as the treated biomaterials are presented. The experimental results show that it is the chemically active species, instead of heat, ultraviolet radiation, intense electric field, and/or charged particles, that break the double chains of the plasmid DNA. The genetic effects depend on the plasma operating parameters, e.g., power input, helium flow rate, processing distance, time, etc.
Genetic effects of radio-frequency, atmospheric-pressure glow discharges with helium
Li Guo; Li Heping; Wang Sen; Sun Wenting; Bao Chengyu; Wang Liyan; Zhao Hongxin; Xing Xinhui
Due to low gas temperatures and high densities of active species, atmospheric-pressure glow discharges (APGDs) would have potential applications in the fields of plasma-based sterilization, gene mutation, etc. In this letter, the genetic effects of helium radio-frequency APGD plasmas with the plasmid DNA and oligonucleotide as the treated biomaterials are presented. The experimental results show that it is the chemically active species, instead of heat, ultraviolet radiation, intense electric field, and/or charged particles, that break the double chains of the plasmid DNA. The genetic effects depend on the plasma operating parameters, e.g., power input, helium flow rate, processing distance, time, etc.
Hydrogen in carbon foils made by DC glow discharge in ethylene
NASA Astrophysics Data System (ADS)
Bailey, P.; Armour, D. G.; England, J. B. A.; Tait, N. R. S.; Tolfree, D. W. L.
Thermal desorption has been studied from thin films of carbon prepared by dc glow discharge in ethylene. The only gases released in significant quantities are hydrogen and methane. Both releases can be characterised by a continuum of activation energies but the methane release peaks at a lower temperature than that from hydrogen. The estimated total hydrogen release is compared with the hydrogen content determined by nuclear scattering experiments. Infra red studies suggest that the majority of CH 2 and CH 3 bonds can be ruptured by annealing at 300°C, a temperature well below the hydrogen and methane release rate maxima. Possible hydrogen bonding modes and desorption mechanisms are discussed.
Child–Langmuir law applicability for a cathode sheath description of glow discharge in hydrogen
NASA Astrophysics Data System (ADS)
Lisovskiy, V. A.; Artushenko, K. P.; Yegorenkov, V. D.
The present paper reveals that the Child-Langmuir law version with the constant ion mobility has to be applied for the cathode sheath description of the glow discharge in hydrogen. Using the analytical model we demonstrate that even in a high electric field the constant mobility law version rather than that for the constant ion mean free path has to hold in the case of impeded charge exchange and the dominant effect of polarization forces on the ion motion through the cathode sheath.
Degradation of Chloroanilines in Aqueous Solution by Contact Glow Discharge Electrolysis
NASA Astrophysics Data System (ADS)
Gao, Jin-zhang; Hu, Zhong-ai; Lu, Quan-fang; Na, Peng-jun; Chen, Ping; Liu, Yong-jun; Yu, Jie
Contact glow discharge electrolysis of some chloroanilines in sodium sulfate was investigated in different initial concentrations. Each of them underwent the dechlorination, deamination through oxidative degradation, and were eventually decomposed into hydrogen carbonate and carbon dioxide. It was testified that the chlorine atom and amidogen could be transformed into chloride ion and nitrite ion, respectively. Fe2+ has a remarkable catalytic effect on the degradation of them. On the basis of the detailed analysis of the intermediate products and kinetic behaviors, the reaction pathway was proposed, in which the attack of hydroxyl radical on the benzene ring of starting material might be a key step.
Surface oxygen micropatterns on glow discharge polymer targets by photo irradiation
Reynolds, Hannah; Baxamusa, Salmaan; Haan, Steven W.; Fitzsimmons, Paul; Carlson, Lane; Farrell, Mike; Nikroo, Abbas; Watson, Brian J.
Recent simulations predict surface oxygen may be a significant source of disruptive perturbations in the implosion process of glow-discharge polymers (GDP) ablators at the National Ignition Facility. GDP material held in ambient atmospheric conditions showed an increase in mass when stored in light transparent containers, which suggests that photo exposure is a driving force for oxygen absorption. To investigate if surface oxygen is a contributing factor of disruptive perturbations during implosion, we developed a method to imprint a periodic micropattern of oxygen on the surface of GDP and used it to fabricate a flat sample for empirical testing.
Formation of carbonic nanostructures using PECVD and glow-discharge plasma at direct current
NASA Astrophysics Data System (ADS)
Gromov, D. G.; Gavrilov, S. A.; Dubkov, S. V.
In this research the process of formation carbonic nanostructures using low temperatures was studied. Nanostructures were formed using PECVD and glow-discharge plasma. The research was carried out at temperature range between 300°C - 700°C. The influence of Ni catalyst thickness and concentration of carbon-containing component in vapour phase on the structure of carbonic deposit was studied. Consequently we attained productive growth of both the homogeneous vertical nanotubes and graphene flakes array at low temperature (350°C). Electrophysical features of obtained structures were examined.
Formation of carbonic nanostructures using PECVD and glow-discharge plasma at direct current
NASA Astrophysics Data System (ADS)
Gromov, D. G.; Gavrilov, S. A.; Dubkov, S. V.
In this research the process of formation carbonic nanostructures using low temperatures was studied. Nanostructures were formed using PECVD and glow-discharge plasma. The research was carried out at temperature range between 300°C - 700°C. The influence of Ni catalyst thickness and concentration of carbon-containing component in vapour phase on the structure of carbonic deposit was studied. Consequently we attained productive growth of both the homogeneous vertical nanotubes and graphene flakes array at low temperature (350°C). Electrophysical features of obtained structures were examined.
Generation of O2 From CO2 by Glow Discharge And Permeation
NASA Technical Reports Server (NTRS)
Outlaw, R. A.
Technique for generating supply of highly pure O2 from CO2 developed. First, atomic oxygen at useful partial pressure generated by glow-discharge dissociation of CO2. Atomic oxygen formed in vicinity of hot silver membrane and permeates through membrane to downstream region, where thermally recombined into O2 and pumped away to storage tank. Pure oxygen stored suitable for human consumption and other uses. Originally developed to convert Martian atmosphere of CO2 to O2 for astronaut consumption. Other potential applications include purification of atmospheres in Space Shuttle and Space Station Freedom. Byproduct CO must be handled by other techniques.
Analysis of green fluorescent protein bioluminescence in vivo and in vitro using a glow discharge
NASA Astrophysics Data System (ADS)
Hernández, L.; Mandujano, L. A.; Cuevas, J.; Reyes, P. G.; Osorio-González, D.
The discovery of fluorescent proteins has been a revolution in cell biology and related sciences because of their many applications, mainly emphasizing their use as cellular markers. The green fluorescent protein (GFP) is one of the most used as it requires no cofactors to generate fluorescence and retains this property into any organism when it is expressed by recombinant DNA techniques, which is a great advantage. In this work, we analyze the emission spectra of recombinant green fluorescent protein in vivo and in vitro exposed to a glow discharge plasma of nitrogen in order to relate electron temperature to fluorescence intensity.
Irregular-regular-irregular mixed mode oscillations in a glow discharge plasma
Ghosh, Sabuj Shaw, Pankaj Kumar Saha, Debajyoti Janaki, M. S. Iyengar, A. N. Sekar
Floating potential fluctuations of a glow discharge plasma are found to exhibit different kinds of mixed mode oscillations. Power spectrum analysis reveals that with change in the nature of the mixed mode oscillation (MMO), there occurs a transfer of power between the different harmonics and subharmonics. The variation in the chaoticity of different types of mmo was observed with the study of Lyapunov exponents. Estimates of correlation dimension and the Hurst exponent suggest that these MMOs are of low dimensional nature with an anti persistent character. Numerical modeling also reflects the experimentally found transitions between the different MMOs.
Laser-induced optogalvanic signal oscillations in miniature neon glow discharge plasma.
Saini, V K
Laser-induced optogalvanic (OG) signal oscillations detected in miniature neon glow discharge plasma are investigated using a discharge equivalent-circuit model. The damped oscillations in OG signal are generated when a pulsed dye laser is tuned to a specific neon transition (1s5→2p2) at 588.2 nm under the discharge conditions where dynamic resistance changes its sign. Penning ionization via quasi-resonant energy transfer collisions between neon gas atoms in metastable state and sputtered electrode atoms in ground state is discussed to explain the negative differential resistance properties of discharge plasma that are attributed to oscillations in the OG signal. The experimentally observed results are simulated by analyzing the behavior of an equivalent discharge-OG circuit. Good agreement between theoretically calculated and experimental results is observed. It is found that discharge plasma is more sensitive and less stable in close vicinity to dynamic resistance sign inversion, which can be useful for weak-optical-transition OG detection. PMID:23842186
Effects of traces of molecular gases (hydrogen, nitrogen) in glow discharges in noble gases
NASA Astrophysics Data System (ADS)
Steers, E. B. M.; Smid, P.; Hoffmann, V.
The "Grimm" type of low pressure glow discharge source, introduced some forty years ago, has proved to be a versatile analytical source. A flat sample is used as the cathode and placed about 0.2mm away from the end of a hollow tubular anode leading to an obstructed discharge. When the source was first developed, it was used for the direct analysis of solid metallic samples by optical emission spectroscopy (OES), normally with argon as the plasma gas; it was soon found that, using suitable electrical parameters, the cathode material was sputtered uniformly from a circular crater of diameter equal to that of the tubular anode, so that the technique could be used for compositional depth profile analysis (CDPA). Over the years the capability and applications of the technique have steadily increased. The use of rf powered discharges now permits the analysis of non-conducting layers and samples; improved instrumental design now allows CDPA of ever thinner layers (e.g. resolution of layers 5 nm thick in multilayer stacks is possible). For the original bulk material application, pre-sputtering could be used to remove any surface contamination but for CDPA, analysis must start immediately the discharge is ignited, so that any surface contamination can introduce molecular gases into the plasma gas and have significant analytical consequences, especially for very thin layers; in addition, many types of samples now analysed contain molecular gases as components (either as occluded gas, or e.g. as a nitride or oxide), and this gas enters the discharge when the sample is sputtered. It is therefore important to investigate the effect of such foreign gases on the discharge, in particular on the spectral intensities and hence the analytical results. The presentation will concentrate mainly on the effect of hydrogen in argon discharges, in the concentration range 0-2 % v/v but other gas mixtures (e.g. Ar/N_2, Ne/H_2) will be considered for comparison. In general, the introduction of
Irradiation of silver and agar/silver nanoparticles with argon, oxygen glow discharge plasma, and mercury lamp.
Ahmad, Mahmoud M; Abdel-Wahab, Essam A; El-Maaref, A A; Rawway, Mohammed; Shaaban, Essam R
The irradiation effect of argon, oxygen glow discharge plasma, and mercury lamp on silver and agar/silver nanoparticle samples is studied. The irradiation time dependence of the synthesized silver and agar/silver nanoparticle absorption spectra and their antibacterial effect are studied and compared. In the agar/silver nanoparticle sample, as the irradiation time of argon glow discharge plasma or mercury lamp increases, the peak intensity and the full width at half maximum, FWHM, of the surface plasmon resonance absorption band is increased, however a decrease of the peak intensity with oxygen glow plasma has been observed. In the silver nanoparticle sample, as the irradiation time of argon, oxygen glow discharge plasma or mercury lamp increases, the peak intensity of the surface plasmon resonance absorption band is increased, however, there is no significant change in the FWHM of the surface plasmon resonance absorption band. The SEM results for both samples showed nanoparticle formation with mean size about 50 nm and 40 nm respectively. Throughout the irradiation time with the argon, oxygen glow discharge plasma or mercury lamp, the antibacterial activity of several kinds of Gram-positive and Gram-negative bacteria has been examined. PMID:25184109
Decomposition of toluene in a steady-state atmospheric-pressure glow discharge
NASA Astrophysics Data System (ADS)
Trushkin, A. N.; Grushin, M. E.; Kochetov, I. V.; Trushkin, N. I.; Akishev, Yu. S.
Results are presented from experimental studies of decomposition of toluene (C6H5CH3) in a polluted air flow by means of a steady-state atmospheric pressure glow discharge at different water vapor contents in the working gas. The experimental results on the degree of C6H5CH3 removal are compared with the results of computer simulations conducted in the framework of the developed kinetic model of plasma chemical decomposition of toluene in the N2: O2: H2O gas mixture. A substantial influence of the gas flow humidity on toluene decomposition in the atmospheric pressure glow discharge is demonstrated. The main mechanisms of the influence of humidity on C6H5CH3 decomposition are determined. The existence of two stages in the process of toluene removal, which differ in their duration and the intensity of plasma chemical decomposition of C6H5CH3 is established. Based on the results of computer simulations, the composition of the products of plasma chemical reactions at the output of the reactor is analyzed as a function of the specific energy deposition and gas flow humidity. The existence of a catalytic cycle in which hydroxyl radical OH acts a catalyst and which substantially accelerates the recombination of oxygen atoms and suppression of ozone generation when the plasma-forming gas contains water vapor is established.
Effect of hydrogen ratio on plasma parameters of N2-H2 gas mixture glow discharge
NASA Astrophysics Data System (ADS)
El-Brulsy, R. A.; Abd Al-Halim, M. A.; Abu-Hashem, A.; Rashed, U. M.; Hassouba, M. A.
A dc plane glow discharge in a nitrogen-hydrogen (N2-H2) gas mixture has been operated at discharge currents of 10 and 20 mA. The electron energy distribution function (EEDF) at different hydrogen concentrations is measured. A Maxwellian EEDF is found in the positive column region, while in both cathode fall and negative glow regions, a non-Maxwellian one is observed. Langmuir electric probes are used at different axial positions, gas pressures, and hydrogen concentrations to measure the electron temperature and plasma density. The electron temperature is found to increase with increasing H2 concentration and decrease with increasing both the axial distance from the cathode and the mixture pressure. At first, with increasing distance from the cathode, the ion density decreases, while the electron density increases; then, as the anode is further approached, they remain nearly constant. At different H2 concentrations, the electron and ion densities decrease with increasing the mixture pressure. Both the electron and ion densities slightly decrease with increasing H2 concentration.
Glow Discharge Plasma Active Control of Separation at Low Pressure Turbine Conditions.
NASA Astrophysics Data System (ADS)
Hultgren, Lennart S.; Ashpis, David E.
Active flow control of boundary-layer separation using glow-discharge plasma actuators is studied experimentally. Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modern low-pressure-turbine airfoil. The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2%) and high (2.5%) free-stream turbulence intensities are set using passive grids. The base flow includes closed separation bubbles and non-reattaching separated flow, and is thoroughly documented using single-wire constant-temperature anemometry and static surface pressure measurements. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface-flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the controlled flow are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control.
Improvement of titanium alloy for biomedical applications by nitriding and carbonitriding processes under glow discharge conditions.
Czarnowska, E; Wierzchoń, T; Maranda-Niedbała, A; Karczmarewicz, E
Although titanium alloys are used in medicine, they present low wear resistance. In this paper we present the results of studies on surface layers produced by nitriding at three different temperatures, and by carbonitriding under glow discharge conditions in order to improve wear resistance, hardness, and to modulate microstructure and chemical composition of surface layers. A cell culture model using human fibroblasts was chosen to study the effect of such treatments on the cytocompatibility of these materials. The results showed that nitrided and carbonitrided surface layers were cytocompatible. Modulation of surface microstructure by temperature in the nitriding process and chemical composition of surface layers by carbonitriding led to differences in cellular behaviour. Cell proliferation appeared to be slightly reduced from the 6th day of culture on nitrided surfaces produced at 730 degrees C and 1000 degrees C, however after 12 days of culture, the best growth was on surface layers produced at 850 degrees C. The best viability was observed on the carbonitrided layer. The orientation and shape of the cells corresponded to surface topography. Nitriding and carbonitriding under glow discharge conditions may constitute interesting techniques allowing the formation of surface layers on parts with sophisticated shapes. They may also permit modulating surface topography in a way improving the features of titanium alloys for various applications in medicine. PMID:15348050
OAK A271 PRODUCTION OF HIGHER STRENGTH THIN WALLED GLOW DISCHARGE POLYMER SHELLS FOR CRYOGENIC EXPERIMENTS AT OMEGA. Thin walled polymer shells are needed for OMEGA cryogenic laser experiments. These capsules need to be about 900 {micro}m in diameter and as thin as possible (approx 1-2 {micro}m), while having enough strength to be filled with DT as fast as possible to about 1000 atm. The authors have found that by optimizing the coating parameters in the glow discharge polymer (GDP) deposition system, traditionally used for making ICF targets, they can routinely make robust, {approx} 1.5 {micro}m thick, 900 {micro}m diameter GDP shells with buckle strengths of over 0.3 atm. This is twice the strength of shells made prior to the optimization and is comparable to values quoted for polyimide shells. In addition, these shells were found to be approximately three times more permeable and over 20% denser than previously made GDP shells. The combination of higher strength and permeability is ideal for direct drive cryogenic targets at OMEGA. Shells as thin as 0.5 {micro}m have been made. In this paper, the authors discuss the shell fabrication process, effects of modifying various GDP deposition parameters on shell properties and chemical composition.
Transmission characteristics of microwave in a glow-discharge dusty plasma
NASA Astrophysics Data System (ADS)
Jia, Jieshu; Yuan, Chengxun; Gao, Ruilin; Liu, Sha; Yue, Feng; Wang, Ying; Zhou, Zhong-Xiang; Wu, Jian; Li, Hui
In this study, the propagation characteristics of electromagnetic wave in a glow discharge plasma with dust particles are experimentally investigated. A helium alternating current glow discharge plasmas have been successfully generated. Measurements of the plasma parameters using Langmuir probes, in the absence of dust particles, provide plasma densities (ne) of 1017 m-3 and electron temperatures (Te) ranging from 2 to 4 eV. Dusty plasmas are made by adding 30 nm radius aluminum oxide (Al2O3) particles into the helium plasma. The density of the dust particle (nd) in the device is about 1011-1012 m-3. The propagation characteristics of electromagnetic waves are determined by a vector network analyzer with 4-6 GHz antennas. An apparent attenuation by the dust is observed, and the measured attenuation data are approximately in accordance with the theoretical calculations. The effects of gas pressure and input power on the propagation are also investigated. Results show that the transmission attenuation increases with the gas pressure and input power, the charged dust particles play a significant role in the microwave attenuation.
DC negative corona discharge in atmospheric pressure helium: transition from the corona to the 'normal' glow regime
NASA Astrophysics Data System (ADS)
Hasan, Nusair; Antao, Dion S.; Farouk, Bakhtier
Direct current (dc) negative corona discharges in atmospheric pressure helium are simulated via detailed numerical modeling. Simulations are conducted to characterize the discharges in atmospheric helium for a pin plate electrode configuration. A self-consistent two-dimensional hybrid model is developed to simulate the discharges and the model predictions are validated with experimental measurements. The discharge model considered consists of momentum and energy conservation equations for a multi-component (electrons, ions, excited species and neutrals) gas mixture, conservation equations for each component of the mixture and state relations. A drift-diffusion approximation for the electron and the ion fluxes is used. A model for the external circuit driving the discharge is also considered and solved along with the discharge model. Many of the key features of a negative corona discharge, namely non-linear current-voltage characteristics, spatially flat cathode current density and glow-like discharge in the high current regime are displayed in the predictions. A transition to the 'normal' glow discharge from the corona discharge regime is also observed. The transition is identified from the calculated current-voltage characteristic curve and is characterized by the radial growth of the negative glow and the engulfment of the cathode wire.
UV-VUV excimer emitter pumped by a subnormal glow discharge
Shuaibov, Aleksandr K; Dashchenko, Arkadii I; Shevera, Igor' V
Characteristics of a small-size excimer emitter operating on an Ar - Cl{sub 2} mixture excited by a subnormal glow discharge are studied. It is shown that this discharge is a source of multiwavelength emission in a range of 175 - 258 nm. The optimum pressures lie in ranges of 0.3 - 0.5 kPa for chlorine and 2 - 4 kPa for argon. The average power of UV- VUV emission reaches 0.7 W, with the emission efficiency equal to 3 %. The emitter can be used in microelectronics, high-energy chemistry, short-wavelength photometry, biophysics, and medicine. (laser applications and other topics in quantum electronics)
Investigation and quantification of nonlinearity using surrogate data in a glow discharge plasma
Saha, Debajyoti Shaw, Pankaj Kumar; Ghosh, Sabuj; Janaki, M. S.; Sekar Iyengar, A. N.
Detection of nonlinearity has been carried out in periodic and aperiodic floating potential fluctuations of DC glow discharge plasma by generating surrogate data using iterative amplitude adjusted Fourier transform method. We introduce "delay vector variance" analysis (DVV) for the first time, which allows reliable detection of nonlinearity and provides some easy to interpret diagram conveying information about the nature of the experimental floating potential fluctuations (FPF). The method of false nearest neighbourhood is deployed on the FPF's to find a good embedding so as to be acquainted with the precise knowledge of m, which is desirable for carrying out DVV analysis. The emergence of nonlinearity with increase in discharge voltage has been ensured by taking into consideration the total energy present in different band of frequencies excited due to nonlinear processes. Rejection of null hypothesis has been verified by performing the rank test method that confirms the presence of nonlinearity quantitatively.
Investigation and quantification of nonlinearity using surrogate data in a glow discharge plasma
NASA Astrophysics Data System (ADS)
Saha, Debajyoti; Shaw, Pankaj Kumar; Ghosh, Sabuj; Janaki, M. S.; Sekar Iyengar, A. N.
Detection of nonlinearity has been carried out in periodic and aperiodic floating potential fluctuations of DC glow discharge plasma by generating surrogate data using iterative amplitude adjusted Fourier transform method. We introduce "delay vector variance" analysis (DVV) for the first time, which allows reliable detection of nonlinearity and provides some easy to interpret diagram conveying information about the nature of the experimental floating potential fluctuations (FPF). The method of false nearest neighbourhood is deployed on the FPF's to find a good embedding so as to be acquainted with the precise knowledge of m, which is desirable for carrying out DVV analysis. The emergence of nonlinearity with increase in discharge voltage has been ensured by taking into consideration the total energy present in different band of frequencies excited due to nonlinear processes. Rejection of null hypothesis has been verified by performing the rank test method that confirms the presence of nonlinearity quantitatively.
Size-dependent capacitance of NiO nanoparticles synthesized with cathodic contact glow discharge electrolysis
NASA Astrophysics Data System (ADS)
Allagui, Anis; Alami, Abdul Hai; Baranova, Elena A.; Wüthrich, Rolf
NiO nanoparticles of 70, 91 and 107 nm average diameter are synthesized by cathodic contact glow discharge electrolysis at 30, 36 and 42 VDC respectively, in 2 M H2SO4 + 0.5 M ethanol + 2.5 mg ml-1 of PVP, and are investigated for electrochemical energy storage. From the cyclic voltammetry and galvanostatic charge-discharge measurements in 1 M KOH, it was found that a maximum specific capacitance of 218 F g-1 is achieved with the 70 nm NiO nanoparticles at 2.7 A g-1. Larger nanoparticles of 91 and 107 nm diameter exhibit specific capacitances of 106 and 63 F g-1, respectively, suggesting a size-dependent capacitive performance enhanced with decreasing particles size.
High frequency glow discharges at atmospheric pressure with micro-structured electrode arrays
NASA Astrophysics Data System (ADS)
Baars-Hibbe, L.; Sichler, P.; Schrader, C.; Lucas, N.; Gericke, K.-H.; Büttgenbach, S.
Micro-structured electrode (MSE) arrays allow the generation of large-area uniform glow discharges over a wide pressure range up to atmospheric pressure. The electrode widths, thicknesses and distances in the micrometre range are realized by means of modern micro-machining and galvanic techniques. The electrode distance, the gap width d, is small enough to generate sufficiently high electric field strengths to ignite gas discharges by applying only moderate radio frequency (RF, 13.56 MHz) voltages (80-390 V in Ne, He, Ar, N2 and air). The non-thermal plasma system is characterized by a special probe measuring the electric parameters. We tested MSE arrays with d = 70, 25 and 15 µm. The MSE driven plasmas show a different behaviour from conventional RF discharge plasmas. Due to the very small electrode gap width we can describe the behaviour of the charged particles in the RF field of our system with the dc Townsend breakdown theory, depending on the pressure range and gas. With decreasing pressure, the gas discharges, especially in Ne and He, are increasingly dominated by field electron emission. With the MSE arrays as plasma sources several applications were developed and successfully tested, e.g. decomposition of waste gases and sterilization of food packaging materials at atmospheric pressure.
Study of a contracted glow in low-frequency plasma-jet discharges operating with argon
Minotti, F.; Giuliani, L.; Xaubet, M.; Grondona, D.
In this work, we present an experimental and theoretical study of a low frequency, atmospheric plasma-jet discharge in argon. The discharge has the characteristics of a contracted glow with a current channel of submillimeter diameter and a relatively high voltage cathode layer. In order to interpret the measurements, we consider the separate modeling of each region of the discharge: main channel and cathode layer, which must then be properly matched together. The main current channel was modeled, extending a previous work, as similar to an arc in which joule heating is balanced by lateral heat conduction, without thermal equilibrium between electrons and heavy species. The cathode layer model, on the other hand, includes the emission of secondary electrons by ion impact and by additional mechanisms, of which we considered emission due to collision of atoms excited at metastable levels, and field-enhanced thermionic emission (Schottky effect). The comparison of model and experiment indicates that the discharge can be effectively sustained in its contracted form by the secondary electrons emitted by collision of excited argon atoms, whereas thermionic emission is by far insufficient to provide the necessary electrons.
Study of a contracted glow in low-frequency plasma-jet discharges operating with argon
NASA Astrophysics Data System (ADS)
Minotti, F.; Giuliani, L.; Xaubet, M.; Grondona, D.
In this work, we present an experimental and theoretical study of a low frequency, atmospheric plasma-jet discharge in argon. The discharge has the characteristics of a contracted glow with a current channel of submillimeter diameter and a relatively high voltage cathode layer. In order to interpret the measurements, we consider the separate modeling of each region of the discharge: main channel and cathode layer, which must then be properly matched together. The main current channel was modeled, extending a previous work, as similar to an arc in which joule heating is balanced by lateral heat conduction, without thermal equilibrium between electrons and heavy species. The cathode layer model, on the other hand, includes the emission of secondary electrons by ion impact and by additional mechanisms, of which we considered emission due to collision of atoms excited at metastable levels, and field-enhanced thermionic emission (Schottky effect). The comparison of model and experiment indicates that the discharge can be effectively sustained in its contracted form by the secondary electrons emitted by collision of excited argon atoms, whereas thermionic emission is by far insufficient to provide the necessary electrons.
Hybrid modelling of open glow discharge with account of nonlocal ionization by fast electrons
NASA Astrophysics Data System (ADS)
Eliseev, Stepan; Eremin, Denis; Kudryavtsev, Anatoly
Cage and open discharges as well as hollow cathode devices are used for creating negative glow plasma. In order to perform numerical simulations of such kind of plasma object properly it is necessary to account for nonlocal excitation and ionization induced by fast electrons emitted from cathode and accelerated up to energies 102-103eV in cathode voltage drop. In this work a numerical study of open discharge in argon is presented. Simulations were performed using simple hybrid model that incorporates nonlocal ionization by fast electrons into ``extended'' fluid framework. Electron energy balance is written with account of electron heating due to coulomb interaction between ``bulks'' (with energies less than 1eV) and ``intermediate'' electrons (with energies up to inelastic collisions energy threshold). Distributions of main discharge parameters, such charged particle densities, electron temperature, electric potential, current-voltage characteristics of the discharge were obtained. Comparison with experimental results showed good agreement and suggests good applicability of the model. This work was supported by Russian Science Foundation (project #14-19-00311).
The influence of resonance radiation transport on the contraction of a glow discharge in argon
NASA Astrophysics Data System (ADS)
Golubovskii, Yu B.; Maiorov, V. A.
The role of resonance radiation transport in the contraction of a positive column in an argon glow discharge is studied numerically. The theory is based on the self-consistent solution of the ambipolar diffusion equation for electrons, the diffusion equation for metastable atoms and the Biberman-Holstein equation for resonance atoms. To calculate the ionization and excitation rates, the Boltzmann equation is solved in a local approximation taking into account elastic, inelastic and electron-electron collisions. A solution method for a boundary problem is developed which allows one to obtain a hysteresis of the parameters during a continuous transition from a diffuse mode to a contracted mode through an unstable branch. At small currents there is a diffuse discharge where the role of radiation transport is inessential because the radial distributions of electrons and excited atoms are close to the fundamental modes of the corresponding equations. Under these conditions, the traditional approximation of 'effective lifetime' is accurate enough. For a contracted discharge, this approximation is not applicable because the higher diffusion and radiation modes play a notable role and a more strict description of radiation transport is required. It is shown that, when radiation transport is taken into account, the width of a filament in a contracted discharge significantly exceeds that obtained in the traditional 'effective lifetime' approximation. The critical current, when the discharge abruptly turns into a contracted mode, is shifted towards higher current values. The results obtained in this paper can also relate to a discharge in other inert gases.
Modelling the interaction between the plasma and the neutral gas in a pulsed glow discharge in nitrogen
Guiberteau, E.; Bonhomme, G.; Zoheir, C.
We present here the first results obtained from the modelling of a pulsed glow discharge in nitrogen, taking into account the heat transfer to the neutral gas. The aim of modelling is to optimize the plasma process in a nitriding reactor. The iron sample to be nitrided forms the cathode of the glow discharge at low pressure (100 to 200 Pa). The reactor uses two disks of diameter 50 mm as electrodes with a 40 mm gap. It works in a pulsed regime (cycle period varies from 10 to 100 ms) with a discharge duration which can be varied from 0.5 to 10 ms. Experimental studies have been carried out using emission spectroscopy resolved in space (1 mm) and time (1 {mu}s), under various discharge and post-discharge durations. These studies have shown the important effect of energy transfer from the discharge to the neutral gas. In fact this transfer produces an expansion of the negative glow observed when the post-discharge duration is decreased. A realistic modelling should thus be performed bearing in mind that the neutral gas behaves not as a thermostat. Consequently the thermal and hydrodynamic evolution of the neutral gas must be considered in the whole modelling.
Design and construction of uniform glow discharge plasma system operating under atmospheric condition
Kocum, C.; Ayhan, H.
The design of a uniform glow discharge plasma system operating without vacuum is presented. A full-bridge switching circuit was used to switch the transformers. The primary windings of transformers were connected in parallel, but in opposite phase to double the output voltage. Theoretically, 20 000 V{sub pp} was obtained. Rectangle copper electrodes were used, and placed parallel to each other. To prevent the spark production that is, to obtain uniformity, two 2 mm Teflon sheets were glued to the electrodes. However, it was observed that the operating frequency also affected the uniformity. For the system presented here, the frequency at which more uniformity was obtained was found to be 14 kHz.
Analysis of glow discharges for understanding the process of film formation
NASA Technical Reports Server (NTRS)
Venugopalan, M.; Avni, R.
The physical and chemical processes which occur during the formation of different types of films in a variety of glow discharge plasmas are discussed. Emphasis is placed on plasma diagnostic experiments using spectroscopic methods, probe analysis, mass spectrometric sampling and magnetic resonance techniques which are well suited to investigate the neutral and ionized gas phase species as well as some aspects of plasma surface interactions. The results on metallic, semi-conducting and insulating films are reviewed in conjunction with proposed models and the problem encountered under film deposition conditions. It is concluded that the understanding of film deposition process requires additional experimental information on plasma surface interactions of free radicals and the synergetic effects where photon, electron and ion bombardment change the reactivity of the incident radical with the surface.
Improved ion implant fluence uniformity in hydrogen enhanced glow discharge plasma immersion ion implantation into silicon.
Luo, J; Li, L H; Liu, H T; Yu, K M; Xu, Y; Zuo, X J; Zhu, P Z; Ma, Y F; Fu, Ricky K Y; Chu, Paul K
Enhanced glow discharge plasma immersion ion implantation does not require an external plasma source but ion focusing affects the lateral ion fluence uniformity, thereby hampering its use in high-fluence hydrogen ion implantation for thin film transfer and fabrication of silicon-on-insulator. Insertion of a metal ring between the sample stage and glass chamber improves the ion uniformity and reduces the ion fluence non-uniformity as the cathode voltage is raised. Two-dimensional multiple-grid particle-in-cell simulation confirms that the variation of electric field inside the chamber leads to mitigation of the ion focusing phenomenon and the results are corroborated experimentally by hydrogen forward scattering. PMID:24985818
Improved ion implant fluence uniformity in hydrogen enhanced glow discharge plasma immersion ion implantation into silicon
NASA Astrophysics Data System (ADS)
Luo, J.; Li, L. H.; Liu, H. T.; Yu, K. M.; Xu, Y.; Zuo, X. J.; Zhu, P. Z.; Ma, Y. F.; Fu, Ricky K. Y.; Chu, Paul K.
Enhanced glow discharge plasma immersion ion implantation does not require an external plasma source but ion focusing affects the lateral ion fluence uniformity, thereby hampering its use in high-fluence hydrogen ion implantation for thin film transfer and fabrication of silicon-on-insulator. Insertion of a metal ring between the sample stage and glass chamber improves the ion uniformity and reduces the ion fluence non-uniformity as the cathode voltage is raised. Two-dimensional multiple-grid particle-in-cell simulation confirms that the variation of electric field inside the chamber leads to mitigation of the ion focusing phenomenon and the results are corroborated experimentally by hydrogen forward scattering.
A glow discharge ion source with fourier transform ion cyclotron resonance mass spectrometric detection.
Barhick, C M; Eyler, J R
A glow discharge (CD) ion source has been coupled to a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer using a four-element electrostatic lens to accelerate and focus ions generated external to the instrument's high magnetic field into its analyzer cell. Like other CD mass spectrometers, GD-FT-ICR can provide a quantitative measure of bulk analyte concentration with good precision and accuracy. Although detection limits currently attainable are several orders of magnitude higher than the commercially available magnetic sector-based instrument, CD-FT-ICR holds promise for ultrahigh resolving power elemental mass analysis. Several schemes are proposed to lower the detection limits of the technique while still providing high enough resolution to resolve isobaric interferences. PMID:24242880
Heterodyne detection at 300 GHz using neon indicator lamp glow discharge detector.
Aharon Akram, Avihai; Rozban, Daniel; Kopeika, Natan S; Abramovich, Amir
A miniature neon indicator lamp, also known as a glow discharge detector (GDD), costing about 50 cents, was found to be an excellent room temperature terahertz radiation detector. Proof-of-concept 300 GHz heterodyne detection using GDD is demonstrated in this paper. Furthermore, a comparison to direct detection was carried out as well. Previous results with the GDD at 10 GHz showed 40 times better sensitivity using heterodyne detection compared to direct detection. Preliminary results at 300 GHz showed better sensitivity by a factor of 20 with only 56 μW local-oscillator power using heterodyne compared to direct detection. The higher the local-oscillator power (P(lo)), the better the sensitivity of the detector. Further improvement can be achieved by employing better quasi-optical design. PMID:23759859
Observation of dust torus with poloidal rotation in direct current glow discharge plasma
Kaur, Manjit Bose, Sayak; Chattopadhyay, P. K. Sharma, Devendra; Ghosh, J.; Saxena, Y. C.
Observation of dust cloud rotation in parallel-plate DC glow discharge plasma is reported here. The experiments are carried out at high pressures (∼130 Pa) with a metallic ring placed on the lower electrode (cathode). The dust cloud rotates poloidally in the vertical plane near the cathode surface. This structure is continuous toroidally. Absence of magnetic field rules out the possibility of E × B induced ion flow as the cause of dust rotation. The dust rotational structures exist even with water cooled cathode. Therefore, temperature gradient driven mechanisms, such as thermophoretic force, thermal creep flow, and free convection cannot be causing the observed dust rotation. Langmuir probe measurement reveals the existence of a sharp density gradient near the location of the rotating dust cloud. The gradient in the density, giving rise to a gradient in the ion drag force, has been identified as the principal cause behind the rotation of dust particles.
A novel Y-type reactor for selective excitation of atmospheric pressure glow discharge plasma
NASA Astrophysics Data System (ADS)
Xia, Guan-Guang; Wang, Jin-Yun; Huang, Aimin; Suib, Steven L.; Hayashi, Yuji; Matsumoto, Hiroshige
A novel Y-type atmospheric pressure ac glow discharge plasma reactor has been designed and tested in CO reduction with hydrogen and the reverse water-gas shift reaction. The reactor consists of a Y-type quartz tube with an angle of 120°-180° between the two long arms, two metal rod electrodes serving as high voltage terminals and two pieces of aluminum foil which were wrapped outside of the quartz tubes as a ground electrode. Different combinations of input power applied on this three- electrode system can lead to selective plasmas on one side, two sides, or can also generate a stable arc between the two high voltage terminal electrodes. The ability to selectively activate different species with this type of apparatus can help to minimize side reactions in plasmas to obtain desirable products. The Y-type reactor may provide a novel means to study fundamental problems regarding radical reactions.
In-situ reactive of x-ray optics by glow discharge
Johnson, E.D.; Garrett, R.F.
We have developed a method of in-situ reactive glow discharge cleaning of x-ray optical surfaces which is capable of complete removal of carbon contamination. Our work is the first to successfully clean an entire optical system in-situ and characterize its performance at short wavelengths (as low as 10 /angstrom/). The apparatus required is quite simple and can easily be fitted to most existing UHV (ultra high vacuum) mirror boxes of monochromators. The advantages of this technique over previously available methods include dramatic improvements in instrument performance and reductions in down time since the whole process typically takes a few days. This paper will briefly describe our results and detail the experimental considerations for application of the technique on different monochromator geometries. Possible improvements and extensions of the technique are also discussed.
PROGRESS IN 2 mm GLOW DISCHARGE POLYMER MANDREL DEVELOPMENT FOR NIF
NIKROO,A; BOUSQUET,J; COOK,R; McQUILLAN,B.W; PAGUIO,R; TAKAGI,M
OAK-B135 All planned National Ignition Facility (NIF) capsule targets except machined beryllium require a glow discharge polymer (GDP) mandrel upon which the albator is applied. This mandrel, {approx} 2 mm in diameter, must at least meet if not exceed the symmetry and surface finish requirements of the final capsule. Such mandrels are currently produced by the three-step depolymerizable mandrel technique. The quality of the final mandrel depends upon precise optimization and execution of each of the three steps. They had shown previously that fabrication of a mandrel which met the symmetry and surface finish requirements was feasible using this technique. In this paper they will discuss recent progress towards converting this process into a high yield, production scale process.
Xe isotopic fractionation in a cathodeless glow discharge. [for carbonaceous meteoritic composition studies
NASA Technical Reports Server (NTRS)
Bernatowicz, T. J.; Fahey, A. J.
Results are reported on the isotopic composition of Xe processed in cathodeless glow discharges in rarefied air at pressures of 20-40 microns Hg, in the presence of activated charcoal and in empty pyrex containers. Residual gas phase Xe and trapped Xe were found to be fractionated, with the trapped Xe fractionated up to 1 percent per amu. A model is presented for the fractionating process in which Xe ions are simultaneously implanted and sputtered from substrate material, with a mass dependence favoring retention of the heavy isotopes in the substrate. Results of the investigation show that plasma synthesis of carbonaceous material is unnecessary for producing Xe fractionations, and that the fractionations observed in previous synthesis experiments are probably due to implantation of ions into the synthesized material.
Degradation of m-dihydroxybenzene by contact glow discharge electrolysis in aqueous
NASA Astrophysics Data System (ADS)
Gai, Ke; Qi, Huili; Ma, Dongping; Wang, Chunlin
This paper reported the degradation of m-dihydroxybenzene aqueous solution with contact Glow Discharge Electrolysis. The rate of degradation in different conditions such as pH, H2O2, Fe2+, methanol, and other affecting factors were studied. The results showed that there is faster removal rate when the solution is in a relatively higher acidity; H2O2 can improve the efficiency rate. Fe2+ can promote reaction, but radical elimination agent of methanol will decrease the rate of the reaction. On the basis of analyzing the ultraviolet (UV) spectra of the solution and the intermediate products from High Performance Liquid Chromatography-Mass Spectrum (HPLC-MS), reaction pathway was proposed.
Improved ion implant fluence uniformity in hydrogen enhanced glow discharge plasma immersion ion implantation into silicon
Luo, J.; Li, L. H. E-mail: email@example.com; Liu, H. T.; Xu, Y.; Zuo, X. J.; Zhu, P. Z.; Ma, Y. F.; Yu, K. M.; Fu, Ricky K. Y.; Chu, Paul K. E-mail: email@example.com
Enhanced glow discharge plasma immersion ion implantation does not require an external plasma source but ion focusing affects the lateral ion fluence uniformity, thereby hampering its use in high-fluence hydrogen ion implantation for thin film transfer and fabrication of silicon-on-insulator. Insertion of a metal ring between the sample stage and glass chamber improves the ion uniformity and reduces the ion fluence non-uniformity as the cathode voltage is raised. Two-dimensional multiple-grid particle-in-cell simulation confirms that the variation of electric field inside the chamber leads to mitigation of the ion focusing phenomenon and the results are corroborated experimentally by hydrogen forward scattering.
High deposition rate preparation of amorphous silicon solar cells by rf glow discharge decomposition of disilane
Kenne, J.; Ohashi, Y.; Matsushita, T.; Konagai, M.; Takahashi, K.
The optical and electrical properties of hydrogenated amorphous silicon films produced by rf glow discharge decomposition of disilane diluted in helium (Si/sub 2/H/sub 6//He = 1/9) have been studied while systematically varying the film deposition rate. The properties and composition of the films were monitored by measuring the optical band gap, IR vibrational spectrum, dark conductivity, and the photoconductivity as a function of the deposition rate. The photoluminescence of the high deposition rate films gave a peak at 1.33 eV. These films, whose properties are rather similar to those of the conventional a-Si:H films prepared from monosilane, have been used to fabricate nip-type a-Si:H solar cells. At a deposition rate of 11 A/sec, a conversion efficiency of 6.86% was obtained. This high efficiency shows that disilane is applicable for mass production fabrication of a-Si:H solar cells.
Plasma sheath physics and dose uniformity in enhanced glow discharge plasma immersion ion implantation and deposition
Li Liuhe; Li Jianhui; Kwok, Dixon T. K.; Chu, Paul K.; Wang Zhuo
Based on the multiple-grid particle-in-cell code, an advanced simulation model is established to study the sheath physics and dose uniformity along the sample stage in order to provide the theoretical basis for further improvement of enhanced glow discharge plasma immersion ion implantation and deposition. At t=7.0 mus, the expansion of the sheath in the horizontal direction is hindered by the dielectric cage. The electron focusing effect is demonstrated by this model. Most of the ions at the inside wall of the cage are implanted into the edge of the sample stage and a relatively uniform ion fluence distribution with a large peak is observed at the end. Compared to the results obtained from the previous model, a higher implant fluence and larger area of uniformity are disclosed.
Account of nonlocal ionization by fast electrons in the fluid models of a direct current glow discharge
Rafatov, I.; Bogdanov, E. A.; Kudryavtsev, A. A.
We developed and tested a simple hybrid model for a glow discharge, which incorporates nonlocal ionization by fast electrons into the 'simple' and 'extended' fluid frameworks. Calculations have been performed for an argon gas. Comparison with the experimental data as well as with the hybrid (particle) and fluid modelling results demonstated good applicability of the proposed model.
Effect of discharge parameters on emission yields in a radio-frequency glow-discharge atomic-emission source
NASA Astrophysics Data System (ADS)
Parker, Mark; Hartenstein, Matthew L.; Marcus, R. Kenneth
A study is performed on a radio-frequency glow-discharge atomic-emission (rf-GD-AES) source to determine the factors effecting the emission yields for both metallic and nonconductive sample types. Specifically, these studies focus on determining how the operating parameters (power and pressure) influence emission yields. The results follow predicted patterns as determined by Langmuir probe diagnostic studies of a similar source. In particular, discharge gas pressure is the key operating parameter as slight changes in pressure may significantly affect the emission yield of the analyte species. RF power is less important and is shown to produce only relatively small changes in the emission yield over the ranges typically used in rf-GD analyses. These studies indicate that the quantitative analysis of layered materials, depth-profiling, may be adversely affected if the data collection scheme, i.e. the quantitative algorithm, requires changing the pressure during an analysis to keep the operating current and voltage constant. A direct relationship is shown to exist between the Ar (discharge gas) emission intensity and that of sputtered species for nonconductors. This observance is used to compensate for differences in emission intensities observed in the analysis of various thickness nonconductive samples. The sputtered element emission signals are corrected based on the emission intensity of an Ar (1) transition, implying that quantitative analysis of nonconductive samples is not severely limited by the availability of matrix matched standards.
Properties of dust-plasma structures formed in a glow discharge above the lower wall of the discharge chamber
NASA Astrophysics Data System (ADS)
Dzlieva, E. S.; Ermolenko, M. A.; Karasev, V. Yu.
The properties are studied of dusty plasma structures formed in a glow discharge in a dust trap above the lower wall of the side branch of the discharge tube, near the turn of the discharge channel. The dust structure is three-dimensional with a characteristic size of up to 3 cm and contains about 30000 dust grains. Depending on the experimental conditions, dust-acoustic, dissipative, and charge-gradient instabilities can develop in such a structure. When using highly polydisperse dust grains of arbitrary shape, the effect of selection of dust grains by the plasma with respect to their mean size and shape was discovered. This effect was studied quantitatively in two gases by using the method of gathering and extraction of the dust grains levitating in the trap. The morphology of the dust structures was determined from the pair correlation functions of the horizontal cross sections containing long-range order peaks and elements of a hexagonal lattice. Stratification of a uniform structure accompanied by convective rotation caused by the grain charge gradient was observed. Applications of the dusty plasma created in this type of device are discussed.
Nonlinear time-series analysis of current signal in cathodic contact glow discharge electrolysis
NASA Astrophysics Data System (ADS)
Allagui, Anis; Rojas, Andrea Espinel; Bonny, Talal; Elwakil, Ahmed S.; Abdelkareem, Mohammad Ali
In the standard two-electrode configuration employed in electrolytic process, when the control dc voltage is brought to a critical value, the system undergoes a transition from conventional electrolysis to contact glow discharge electrolysis (CGDE), which has also been referred to as liquid-submerged micro-plasma, glow discharge plasma electrolysis, electrode effect, electrolytic plasma, etc. The light-emitting process is associated with the development of an irregular and erratic current time-series which has been arbitrarily labelled as "random," and thus dissuaded further research in this direction. Here, we examine the current time-series signals measured in cathodic CGDE configuration in a concentrated KOH solution at different dc bias voltages greater than the critical voltage. We show that the signals are, in fact, not random according to the NIST SP. 800-22 test suite definition. We also demonstrate that post-processing low-pass filtered sequences requires less time than the native as-measured sequences, suggesting a superposition of low frequency chaotic fluctuations and high frequency behaviors (which may be produced by more than one possible source of entropy). Using an array of nonlinear time-series analyses for dynamical systems, i.e., the computation of largest Lyapunov exponents and correlation dimensions, and re-construction of phase portraits, we found that low-pass filtered datasets undergo a transition from quasi-periodic to chaotic to quasi-hyper-chaotic behavior, and back again to chaos when the voltage controlling-parameter is increased. The high frequency part of the signals is discussed in terms of highly nonlinear turbulent motion developed around the working electrode.
O2 and CO2 glow-discharge-assisted oxygen transport through Ag
NASA Astrophysics Data System (ADS)
Outlaw, R. A.
The permeation of oxygen through Ag normally occurs by a sequence of steps which include the initial dissociative adsorption of molecular oxygen at the upstream surface, the dissolution of the atoms into the bulk, and the subsequent migration of the atoms between octahedral sites of the lattice until they arrive at the vacuum interface downstream. The dissociative adsorption step, however, proceeds slowly, as indicated by the low sticking coefficient of O2 on Ag(10-6-10-3). The application of a dc field in 0.5 Torr of O2 (E/n˜10-14 V cm2) on the upstream side of a Ag membrane generated gas phase atomic oxygen that substantially enhanced the transport. The transport flux was observed to increase from a value of 4.4×1013 cm-2 s-1 to a glow discharge value of 2.83×1014 cm-2 s-1 at a membrane temperature of 650 °C. This suggests that the dissociative adsorption step limits the supply of oxygen atoms to the upstream side of the membrane. When the upstream O2 was replaced by an equal pressure of CO2, only a small permeation signal was observed, but the application of the glow discharge substantially increased the transport flux from 3.25×1012 cm-2 s-1 to 1.74×1014 cm-2 s-1. This method of separating O2 from a CO2 environment may be a possible mechanism for providing a supply of oxygen for astronauts in a manned mission to Mars.
Room temperature sterilization of surfaces and fabrics with a one atmosphere uniform glow discharge plasma.
Kelly-Wintenberg, K; Montie, T C; Brickman, C; Roth, J R; Carr, A K; Sorge, K; Wadsworth, L C; Tsai, P P
We report the results of an interdisciplinary collaboration formed to assess the sterilizing capabilities of the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP). This newly-invented source of glow discharge plasma (the fourth state of matter) is capable of operating at atmospheric pressure in air and other gases, and of providing antimicrobial active species to surfaces and workpieces at room temperature as judged by viable plate counts. OAUGDP exposures have reduced log numbers of bacteria, Staphylococcus aureus and Escherichia coli, and endospores from Bacillus stearothermophilus and Bacillus subtilis on seeded solid surfaces, fabrics, filter paper, and powdered culture media at room temperature. Initial experimental data showed a two-log10 CFU reduction of bacteria when 2 x 10(2) cells were seeded on filter paper. Results showed > or = 3 log10 CFU reduction when polypropylene samples seeded with E. coli (5 x 10(4)) were exposed, while a 30 s exposure time was required for similar killing with S. aureus-seeded polypropylene samples. The exposure times required to effect > or = 6 log10 CFU reduction of E. coli and S. aureus on polypropylene samples were no longer than 30 s. Experiments with seeded samples in sealed commercial sterilization bags showed little or no differences in exposure times compared to unwrapped samples. Plasma exposure times of less than 5 min generated > or = 5 log10 CFU reduction of commercially prepared Bacillus subtilis spores (1 x 10(5)); 7 min OAUGDP exposures were required to generate a > or = 3 log10 CFU reduction for Bacillus stearothermophilus spores. For all microorganisms tested, a biphasic curve was generated when the number of survivors vs time was plotted in dose-response cures. Several proposed mechanisms of killing at room temperature by the OAUGDP are discussed. PMID:9523458
Modeling of RF glow discharges by direct numerical procedure of the Boltzmann equation
Nakano, N.; Makabe, T.
In the previous papers, the authors performed a direct numerical procedure (DNP) of the Boltzmann equation with an algorithm of their own without any expansion of the velocity distribution in spatial homogeneity, in order to study and radio frequency (rf) electron transport. They further developed ;and applied the DNP to the modeling of an rf glow discharge with space and time variation of the electron velocity distribution. It has a great advantage in that the nonequilibrium characteristics of electrons in transport can be exactly expressed without statistical error. Only collision cross sections of the electron with the molecular are required for calculation without swarm parameters as for electrons, when the governing equation system is numerically simulated. It is of practical advantage to a gas mixture which results from the dissociation of an initial gas after discharge initiation. Capacitively couples parallel plate discharge with 20mm spacing is considered in the present modeling in order to simplify the model and to compare the plasma structure with the previous result using relaxation continuum model. Non reactive Ar with simple cross sections is employed as the source gas.
Plasma characteristics of argon glow discharge produced by AC power supply operating at low frequencies
Kongpiboolkid, Watcharapon; Mongkolnavin, Rattachat
Non-thermal properties of Argon glow discharge operating with various operating pressures were measured and presented in this work. The Argon plasma is produced by a parallel conducting electrodes coupling with a high voltage AC power supply. The power supply can generate high AC voltage at various frequencies. The frequencies for the operation are in the range of a few kHz. The system is capable of generating electric field between the two metal electrodes discharge system. The characteristics of plasma produced were measured by optical emission spectroscopy (OES) technique where electron temperature (T{sub e}) and electron number density (n{sub e}) can be determined by line intensity ratio method. The value of electron number density was then determined from the Saha-Eggert equation. Our results show that the electron number density of the discharge obtained is of the order of 10{sup −17} − 10{sup −18} m{sup −3} where the electron temperature is between 1.00−2.00 eV for various operating frequencies used which are in good agreement with similar results published earlier.
Radiofrequency gas plasma (glow discharge) disinfection of dental operative instruments, including handpieces.
Baier, R E; Carter, J M; Sorensen, S E; Meyer, A E; McGowan, B D; Kasprzak, S A
The radiofrequency-stimulated argon gas plasma (glow discharge) technique, already well-known for surface cleaning and activation of adhesion, was investigated for determination of its separate potential for rapid disinfection of dental operative instruments. Disinfection effectiveness was judged from diminished post-treatment recovery of viable organisms from the instruments agitated in saline. Streptococcus salivarius, Bacillus stearothermophilus, and Escherichia coli were used as primary contaminant organisms, dried from gelatin-thickened laboratory cultures onto the instruments and not subjected to any preliminary cleaning steps. Significant disinfection was obtained, with no sensible temperature increases, in under 10 minutes in laboratory apparatus consuming fewer than 5 Watts of power per cycle. Also, clinically used and deliberately-saliva-contaminated high-speed handpieces were gas-discharge-treated, with their resultant rapid disinfection noted by complete suppression of the viability of any transferred natural contaminant organisms within two minutes. With regard to preservation of instrument quality, it was also shown that this low-temperature gas-discharge method provides the noted substantial disinfection without deterioration of sharp edges. Work now in progress suggests that the method can provide cool, rapid, and complete sterilization when hydrogen peroxide vapors are present in the gas plasma used for treatment of instruments first given the normally recommended thorough pre-cleaning. PMID:1289559
Two-dimensional extended fluid model for a dc glow discharge with nonlocal ionization source term
NASA Astrophysics Data System (ADS)
Rafatov, Ismail; Bogdanov, Eugeny; Kudryavtsev, Anatoliy
Numerical techniques applied to the gas discharge plasma modelling are generally grouped into fluid and kinetic (particle) methods, and their combinations which lead to the hybrid models. Hybrid models usually employ Monte Carlo method to simulate fast electron dynamics, while slow plasma species are described as fluids. However, since fast electrons contribution to these models is limited to deriving the ionization rate distribution, their effect can be expressed by the analytical approximation of the ionization source function, and then integrating it into the fluid model. In the context of this approach, we incorporated effect of fast electrons into the ``extended fluid model'' of glow discharge, using two spatial dimensions. Slow electrons, ions and excited neutral species are described by the fluid plasma equations. Slow electron transport (diffusion and mobility) coefficients as well as electron induced reaction rates are determined from the solutions of the electron Boltzmann equation. The self-consistent electric field is calculated using the Poisson equation. We carried out test calculations for the discharge in argon gas. Comparison with the experimental data as well as with the hybrid model results exhibits good applicability of the proposed model. The work was supported by the joint research grant from the Scientific and Technical Research Council of Turkey (TUBITAK) 212T164 and Russian Foundation for Basic Research (RFBR).
Spatial distribution and accumulation of radicals arising in organic solids under the action of glow discharge
NASA Astrophysics Data System (ADS)
Raitsimring, A. M.; Kurshev, V. V.
The method, based on analyzing the dipolar broadening of EPR spectra was applied for investigation of the spatial distribution of radicals generated by high-frequency glow discharge in organic molecular crystals (powders of malonic and dimethylmalonic acids) and glassy isopropanol contained electron scavenger. It was shown that in the first case the radical distribution does not depend on time of discharge. The radicals are generated in layer of size ˜.05-0.1 μm at a concentration of ˜2 10 20 cm -3. For the second case the distribution function was changed in the course of plasma treatment and the depth of radical generation was varied from 0.25 to 1.5 μm during the discharge action. Contribution of the various mechanisms of radical formation were evaluated and it was shown that ionic mechanism predominated. A kinetic model is proposed to describe both the radical accumulation and evolution of spatial distribution function in plasmolysis. The use of the model, method and obtained data for general and practical applications is discussed.
Phenol degradation by a nonpulsed diaphragm glow discharge in an aqueous solution.
Liu, Yong Jun; Jiang, Xuan Zhen
In the present study, a nonpulsed direct current diaphragm glow discharge process was developed for the first time for phenol degradation in an aqueous solution. The discharge was generated in a small hole in a dielectric diaphragm interposed between two submersed graphite electrodes. The experimental results revealed that supplied voltage, initial pH, iron salts, and radical scavengers impact the phenol degradation significantly. Enhancing the applied voltage, lowering the solution pH, and adding appropriate amounts of Fe2+ or Fe3+ to the solution were found to be favorable for phenol degradation. Carbonate ions or n-butanol in the solution can decelerate the phenol removal. When the treatment time is increased, the pH value of the solution decreased, leading to an increase in the phenol decomposition. It was revealed by high performance liquid chromatography and ionic chromatography that the main intermediates of phenol decomposition are hydroquinone, pyrocatechol, p-benzoquinone and organic acids. In comparison with the high-voltage corona discharge plasma in distilled water, this process offers simple technology, higher energy efficiency, easier scaleup, and easier applicability to salt-containing wastewater with no electrode erosion and electromagnetic radiation. PMID:16294895
Carbon nanotubes formation in the decomposition of heavy hydrocarbons creeping along the surface of the glow discharge
NASA Astrophysics Data System (ADS)
Timerkaev, B. A.; Sofronitskiy, A. O.; Andreeva, A. A.
The possibility of heavy hydrocarbons decomposition in the plasma of the creeping glow discharge in a magnetic field is investigated. An electron microscopic analysis of carbon deposit on the electrodes and the walls of the discharge chamber, and gas chromatographic analysis formed in the course of the experiment is carried out. The grown carbon nanotubes have a length of about 6,17µm and a diameter of about 18nm.
Laser-induced fluorescence monitoring of the gas phase in a glow discharge during reactive sputtering of vanadium
NASA Astrophysics Data System (ADS)
Khvostikov, V. A.; Grazhulene, S. S.; Burmii, Zh. P.; Marchenko, V. A.
Processes in the gas phase of a glow discharge during diode and magnetron reactive sputtering of vanadium in an Ar-O2 atmosphere have been investigated by laser-induced fluorescence (LIF) as a function of the parameters of the glow discharge and the composition of the atmosphere. The intensity of the fluorescence spectra increased by 1.5-2.0 orders of magnitude in the magnetron sputtering process compared with that of diode sputtering. Under continuous sputtering conditions, the dependences of the intensities and relative compositions of the fluorescence spectra on the discharge parameters (discharge voltage and current) have been investigated. In pulsed mode of the glow discharge, the dynamics of changes in the spectra have been studied versus variations in the discharge duration and the lag time for recording the fluorescence signal. The dependence of the spectral line intensities on the partial pressure of oxygen has been found for vanadium and its oxide. The cathode surface at pressures of 0.03-0.04 Pa was shown to convert to the oxidized state.
Study of nonlinear oscillations in a glow discharge plasma using empirical mode decomposition and Hilbert Huang transform
Wharton, A. M.; Sekar Iyengar, A. N.; Janaki, M. S.
Hilbert Huang transform (HHT) based time series analysis was carried out on nonlinear floating potential fluctuations obtained from hollow cathode glow discharge plasma in the presence of anode glow. HHT was used to obtain contour plots and the presence of nonlinearity was studied. Frequency shift with time, which is a typical nonlinear behaviour, was detected from the contour plots. Various plasma parameters were measured and the concepts of correlation coefficients and the physical contribution of each intrinsic mode function have been discussed. Physically important quantities such as instantaneous energy and their uses in studying physical phenomena such as intermittency and non-stationary data have also been discussed.
Arsenic and antimony determination by on-line flow hydride generation glow discharge optical emission detection
NASA Astrophysics Data System (ADS)
Guillermo Orellana-Velado, Néstor; Fernández, Matilde; Pereiro, Rosario; Sanz-Medel, Alfredo
Hollow cathode (HC) and conventional flat cathode (FC) glow discharge (GD) optical emission spectrometry (OES) were used as detectors for the determination of arsenic and antimony by on-line hydride generation (HG) in a flow system. Both radiofrequency (rf) and direct current (dc) sources were investigated to produce the discharge. The design of the HC and FC and also the parameters governing the discharge (pressure, He flow rate, voltage, current and delivered power) and the HG (sodium borohydride concentration and reagent flow rates) were investigated using both cathodes. The analytical performance characteristics of HG-GD-OES with HC and FC were evaluated for some emission lines of arsenic (193.7, 200.3, 228.8 and 234.9 nm). The best detection limit (0.2 μg l -1) was obtained when the emission line of 228.8 nm was used with FC. Under the same arsenic optimized experimental conditions, the system was evaluated to determine antimony at 259.7, 252.7 and 231.1 nm, 252.7 nm being the emission line which produced the best detection limit (0.7 μg l -1). The rf-HC-GD-OES system was applied successfully to the determination of arsenic in freeze-dried urine in the standard reference material 2670 from NIST. Finally, a flow injection system was assayed to determine arsenic at 228.8 nm, using a dc-GD with both FC and HC. The results indicated that for low volumes of sample, the HC discharge allows better analytical signals than the FC.
Role of cathode identity in liquid chromatography particle beam glow discharge mass spectrometry
NASA Astrophysics Data System (ADS)
Krishna, M. V. Balarama; Marcus, R. K.
A detailed evaluation of the role of cathode identity on the analytical and spectral characteristics of various organic, organometallic and metal analytes using liquid chromatography-particle beam/glow discharge mass spectrometry (LC-PB/GDMS) has been carried out. A d.c. discharge, operating with argon as the support gas, was used throughout this work. In this study, Cu which has a relatively high sputtering rate, Ni which has moderate sputtering rate and Ta which has very low sputtering rate, are taken as cathode materials to study the ionization, fragmentation, and analytical characteristics of organic (caffeine, epigallocatechin gallate, peptide as representative compounds), organometallic (selenomethionine, triethyl lead chloride as representative compounds) and metal (Fe, La, Cs and Pb) species. A range of discharge gas pressures (26.6-106.4 Pa) and currents (0.2-1.5 mA) were investigated with the test cathodes to determine their influence on the spectral composition and overall analytical response for the various test species. Calibration plots were obtained for all of the species for each of the three cathodes to determine the respective limits of detection. Relative detection limits in the range of 0.02 to 15 ng mL - 1 (0.002-1.5 ng, absolute) for the test species were found to be in the order of Cu > Ni > Ta; which follows the order of the sputtering characteristics of the respective cathodes. These studies rendered information about the respective discharge parameters' role in choosing the most appropriate cathode identity in PB-GDMS for application in the areas of organic, organometallic and inorganic species analysis.
Studies on gas breakdown in pulsed radio frequency atmospheric pressure glow discharges
Huo, W. G.; Jian, S. J.; Yao, J.; Ding, Z. F.
In pulsed RF atmospheric pressure glow discharges, the gas breakdown judged by the rapid drop in the amplitude of the pulsed RF voltage is no longer universally true. The steep increment of the plasma-absorbed RF power is proposed to determine the gas breakdown. The averaged plasma-absorbed RF power over a pulse period is used to evaluate effects of the preceding pulsed RF discharge on the breakdown voltage of the following one, finding that the breakdown voltage decreases with the increment in the averaged plasma-absorbed RF power under constant pulse duty ratio. Effects of the pulse off-time on the breakdown voltage and the breakdown delay time are also studied. The obtained dependence of the breakdown voltage on the pulse off-time is indicative of the transitional plasma diffusion processes in the afterglow. The breakdown voltage varies rapidly as the plasma diffuses fast in the region of moderate pulse off-time. The contribution of nitrogen atom recombination at the alumina surface is demonstrated in the prolonged memory effect on the breakdown delay time vs. the pulse off-time and experimentally validated by introducing a trace amount of nitrogen into argon at short and long pulse off-times.
Control of plasma properties in a short direct current glow discharge with active boundaries
NASA Astrophysics Data System (ADS)
Demidov, Vladimir; Adams, Steven; Bogdanov, Yevgeny; Koepke, Mark; Kudryavtsev, Anatoly; Kurlyandskaya, Iya
To demonstrate controlling electron and metastable density ratio and electron temperature by applying negative voltages to the active (conducting) discharge wall in a low-pressure plasma with nonlocal electron energy distribution function, modeling has been performed in a short (without positive column) dc glow discharge with a cold cathode. The applied negative voltage can modify trapping the low-energy part of the energetic electrons emitted from the cathode sheath and arising from the atomic and molecular processes in the plasma within the device volume. Those electrons are responsible for heating the slow, thermal electrons, while production of slow electrons (ions) and metastable atoms is mostly due to energetic electrons with higher energies. Increasing electron temperature results in increasing decay rate of slow, thermal electrons, while decay rate of metastable atoms and production rates of slow electrons and metastable atoms practically are unchanged. The result is in variation of electron and metastable density ratio and electron temperature with variation of the wall negative voltage. A part of this research was performed, while one of the authors (VID) held a National Research Council Research Associateship Award at AFRL. The work was also partially supported by SPbGU (Grant No. 11.38.658.2013) and ITMO University (Grant No. 713577).
Junction silicon solar cells made with molecular beam glow discharge bombardment
Caine, E.J.
The fabrication of silicon PN junction solar cells with molecular implanted emitter regions is described. A simple, economical high current (0.5 mA/cm/sup 2/), low voltage (4-6 kV) glow discharge apparatus without any ion mass separation is used for implantation. The discharge beam is characterized with a current-voltage conduction curve, radial profile of target sheet resistance and operating temperature of implant target. Molecular implantation compounds discussed include: boron trifluoride, trimethyl borate, boron trichloride, trimethyl phosphite, arsenic trifluoride, phosphorus trichloride, phosphorus oxychloride and arsenic trichloride. Annealing is accomplished with a Q-switched ruby laser and with a standard diffusion furnace. Solar cell performance parameters (conversion efficiency, quantum efficiency and junction ideality) are compared with cells conventionally implanted at 30 keV with /sup 11/B and /sup 31/P and cells made with a standard open tube phosphorus oxychloride diffusion. Cell substrate thickness was found to limit short circuit current. Total area simulated AM1 power conversion efficiencies of molecular cells without antireflection coatings or backsurface fields are at best 8.2% as compared to 9.0% for conventional implanted or diffused devices. To achieve optimum performance, laser light had to be incorporated in the molecular implant annealing procedure.
Control of plasma properties in a short direct-current glow discharge with active boundaries
NASA Astrophysics Data System (ADS)
Adams, S. F.; Demidov, V. I.; Bogdanov, E. A.; Koepke, M. E.; Kudryavtsev, A. A.; Kurlyandskaya, I. P.
To demonstrate controlling electron/metastable density ratio and electron temperature by applying negative voltages to the active (conducting) discharge wall in a low-pressure plasma with nonlocal electron energy distribution function, modeling has been performed in a short (lacking the positive-column region) direct-current glow discharge with a cold cathode. The applied negative voltage can modify the trapping of the low-energy part of the energetic electrons that are emitted from the cathode sheath and that arise from the atomic and molecular processes in the plasma within the device volume. These electrons are responsible for heating the slow, thermal electrons, while production of slow electrons (ions) and metastable atoms is mostly due to the energetic electrons with higher energies. Increasing electron temperature results in increasing decay rate of slow, thermal electrons (ions), while decay rate of metastable atoms and production rates of slow electrons (ions) and metastable atoms practically are unchanged. The result is in the variation of electron/metastable density ratio and electron temperature with the variation of the wall negative voltage.
Spectroscopic study of high energy excited deuterium atoms in a hollow cathode glow discharge
Majstorovic, G. Lj.; Sisovic, N. M.; Konjevic, N.
The presented results are concerned with the shape of the Balmer alpha line emitted from a low pressure dc glow discharge with stainless steel (SS) and titanium (Ti) hollow cathode (HC) with D{sub 2} or Ar/D{sub 2}/H{sub 2} gas mixture. The analysis indicates that the line profile represents a convolution of three Gaussian profiles resulting from different collision excitation processes. The average energy of excited deuterium atoms determined from the width of the broadest Gaussian is about 86 eV in both HCs. In Ar/D{sub 2}/H{sub 2} gas mixtures, the energies are in the range from 33 eV to 47 eV, but with much larger contribution of this Gaussian to the Balmer alpha profile. In discharges with hydrogen isotopes, the energy derived from the medium-width Gaussian is in the range from 4 eV to 6 eV, while in gas mixtures it is between 1 eV and 2 eV. The width of the narrowest Gaussian slightly exceeds the instrumental broadening and it is always below 0.5 eV.
Microfabricated glow discharge plasma (MFGDP) for ambient desorption/ionization mass spectrometry.
Ding, Xuelu; Zhan, Xuefang; Yuan, Xin; Zhao, Zhongjun; Duan, Yixiang
A novel ambient ionization technique for mass spectrometry, microfabricated glow discharge plasma (MFGDP), is reported. This device is made of a millimeter-sized ceramic cavity with two platinum electrodes positioned face-to-face. He or Ar plasma can be generated by a direct current voltage of several hundreds of volts requiring a total power below 4 W. The thermal plume temperature of the He plasma was measured and found to be between 25 and 80 °C at a normal discharge current. Gaseous, liquid, creamy, and solid samples with molecular weights up to 1.5 kDa could be examined in both positive and negative mode, giving limits of detection (LOD) at or below the fg/mm(2) level. The relative standard deviation (RSD) of manual sampling ranged from 10% to ~20%, while correlation coefficients of the working curve (R(2)) are all above 0.98 with the addition of internal standards. The ionization mechanisms are examed via both optical and mass spectrometry. Due to the low temperature characteristics of the microplasma, nonthermal momentum desorption is considered to dominate the desorption process. PMID:24000803
Experimental study of a glow discharge of CH2-C12
NASA Astrophysics Data System (ADS)
Gomez, A.; Salazar-Flores, L.; Martinez, H.; Reyes, P. G.; Castillo, F.
Low-pressure DC plasma discharges sustained in a glow discharge of CH2-Cl2 are studied. This plasma was generated at a pressure of 1.0 Torr, power of 20 W and a flow of 12 l/min. The diagnostic has been made by optical emission spectroscopy (OES) using a spectrometer. The principal species observed were: were at 339.61, 358.60 and 377.96 nm for C2(c'1Πg-b1Πu) at 392.50 nm for C3('Πu-'Σ+g) at 431.42 nm for CH(A2Δ-X2Π) at 778.28 nm for Cl; at 657.80 nm for C+; at 471.90 and 487.30 nm for H2; at 380.61 nm for CH+A'Π-X'Σ) and at 317.73 nm for HCL+(A2ΣI-X2Π). In the study, special attention was given to the behavior of material deposition in the electrodes. The time dependence of material deposition in the electrodes was also investigated. When the discharge time of CH2CL2 plasma was increased, the mass deposition was increased. It can observe that the mass deposition display an increased behavior until 30 min, and then shows an saturation behavior. Fourier Transform Infrared (FTIR) spectroscopy was applied for the surface analysis. The variations of the size of the thin film may change the subsequent chemical reactions in the gas phase significantly. As the reaction time was increased signal from structural fragment containing chlorine atom were loosed, which can explain the behavior observed in the chlorine signal using emission spectroscopy measurements.
Dynamics of Metal Etching and Oxidation in Fluorocarbon/oxygen RF Glow Discharges
NASA Astrophysics Data System (ADS)
Martz, Joseph Christopher
A variety of in situ diagnostics have been used to determine the dynamic behavior of both the etching and oxidation reactions of tantalum and plutonium in RF glow discharges (plasmas). Numerous aspects of the concerted, heterogeneous reactions involved have been studied with quadrupole mass spectroscopy, emission spectroscopy (actinometry), and fluoroptic thermometry. In addition, direct in situ measurement of reaction rates has been performed with a quartz-crystal microbalance. The chemistry of the CF_4/O _2 discharge and its use in etching both tantalum and plutonium has been studied. Major products from the reaction of CF_4 with O _2 within the plasma include CO _2, CO, COF_2, F _2, and F. Chemical mechanisms are suggested to account for the formation of these products. Measurement of Ta etch rates in CF_4 /O_2 and C_2 F_6/O_2 plasmas as functions of reactor pressure, applied power, temperature, and system residence time reveal numerous chemical effects. The large heat of reaction in the Ta/F etching system, in conjunction with the moderate activation energy and thermally isolated nature of the plasma environment, leads to significant autothermic effects. Fluorocarbon polymer deposition at pressures above 400 mtorr leads to a quenching of the etch reaction in CF_4 /O_2 plasmas. Similarly, the etch behavior of Ta in C_2F _6/O_2 discharges at all pressures mirrors that of Ta in CF_4 /O_2 plasmas at pressures above 400 mtorr. Plutonium etching has also been demonstrated in CF_4/O_2 plasmas. Plutonium oxides etch at rates 5 to 10 times faster than pure Pu metal. The reaction of Pu in the discharge proceeds at least 200 times faster than the reaction of Pu with purely thermal sources of F atoms such as O _2F_2. Such results suggest significant enhancement of the Pu/F reaction by the plasma environment. Lastly, oxidation of Ta in O_2 discharges has been studied as a potential means of low-temperature Ta_2O _5 thin film fabrication. Plasma oxidation proceeds readily at
Enhancing DC Glow Discharge Tube Museuum Displays using a Theremin Controlled Helmholtz Coil to Demonstrate Magnetic Confinement
NASA Astrophysics Data System (ADS)
Siu, Theodore; Wissel, Stephanie; Guttadora, Larry; Liao, Susan; Zwicker, Andrew
Since their discovery in the mid 1800's, DC glow discharge apparatuses have commonly been used for spectral analysis, the demonstration of the Frank-Hertz experiment, and to study plasma breakdown voltages following from the Paschen Curve. A DC glow discharge tube museum display was outfitted with a Helmholtz Coil electromagnet in order to demonstrate magnetic confinement for a science museum display. A device commonly known as a ``theremin'' was designed and built in order to externally control the Helmholtz Coil current and the plasma current. Originally a musical instrument, a theremin has two variable capacitors connected to two radio frequency oscillators which determine pitch and volume. Using a theremin to control current and ``play'' the plasma adds appeal and durability by providing a new innovative means of interacting with a museum exhibit. Educationally, students can use the display to not only learn about plasma properties but also electronic properties of the human body.
OAK A271 RECENT PROGRESS IN FABRICATION OF HIGH-STRENGTH GLOW DISCHARGE POLYMER SHELLS BY OPTIMIZATION OF COATING PARAMETERS. In this paper, the authors report the progress they have made in fabrication of high-strength thin-walled glow discharge polymer (GDP) shells for cryogenic experiments at OMEGA. They have investigated a number of different parameters involved in making such shells. Optimization of hydrogen to hydrocarbon precursor flow has been observed to be critical in obtaining strong shells. They can routinely make high-strength shells of OMEGA size (900 {micro}m in diameter) with thicknesses in the range of 1.0 to 1.5 {micro}m. The permeabilities of these shells to various gases have been found to be as much as three times higher than those of lower strength shells. Run to run variability and other batch statistics are discussed.
Terahertz measurements of the hot hydronium ion with an extended negative glow discharge
Yu, Shanshan; Pearson, John C.
Terahertz absorption spectroscopy was employed to detect the ground-state inversion transitions of the hydronium ion (H{sub 3}O{sup +}). The highly excited ions were created with an extended negative glow discharge through a gas mixture of 1 mtorr of H{sub 2}O, 2 mtorr of H{sub 2}, and 12 mtorr of Ar, which allowed observation of transitions with J and K up to 12. In total, 47 transitions were measured in the 0.9-2.0 THz region and 22 of these were observed for the first time. The experimental uncertainties range from 100 to 300 kHz, which are much better than the range 0.3-1.2 MHz reported in previous work. Differences of up to 25.6 MHz were found between the observed positions and the catalog values that have been used for Herschel data analysis of observations of Sagittarius B2(N), NGC 4418, and Arp 220. The new and improved measurements were fit to experimental accuracies with an updated Hamiltonian, and better H{sub 3}O{sup +} predictions are reported to support the proper analysis of astronomical observations by high-resolution spectroscopy telescopes, such as Herschel, SOFIA, and ALMA.
Pulsed laser ablation of borax target in vacuum and hydrogen DC glow discharges
NASA Astrophysics Data System (ADS)
Kale, A. N.; Miotello, A.; Mosaner, P.
The aim of our experiment was to produce a material with B sbnd H bonds for applications in hydrogen storage and generation. By using KrF excimer laser ( λ = 248 nm) ablation of borax (Na 2B 4O 7) target, thin films were deposited on KBr and silicon substrates. Ablation was performed both in vacuum and in hydrogen atmosphere. DC glow discharge technique was utilized to enhance hydrogen gas ionization. Experiments were performed using laser fluence from 5 to 20 J/cm 2. Films were deposited under gas pressure of 1 × 10 -5 to 5 × 10 -2 mbar and substrate temperatures of 130-450 °C. Scanning electron microscopy analysis of films showed presence of circular particulates. Film thickness, roughness and particulates number increased with increase in laser fluence. Energy dispersive X-ray spectroscopy analysis shows that sodium content in the particulates is higher than in the target. This effect is discussed in terms of atomic arrangements (both at surface and bulk) in systems where ionic and covalent bonds are present and by looking at the increased surface/bulk ratio of the particulates with respect to the deposited films. The Fourier transform infrared spectroscopy measurements showed presence of B sbnd O stretching and B sbnd O sbnd B bending bonds. Possible reasons for absence of B sbnd H bonds are attributed to binding enthalpy of the competing molecules.
Electric field development in γ-mode radiofrequency atmospheric pressure glow discharge in helium
NASA Astrophysics Data System (ADS)
Navrátil, Zdeněk; Josepson, Raavo; Cvetanović, Nikola; Obradović, Bratislav; Dvořák, Pavel
Time development of electric field strength during radio-frequency sheath formation was measured using Stark polarization spectroscopy in a helium γ-mode radio-frequency (RF, 13.56 MHz) atmospheric pressure glow discharge at high current density (3 A cm-2). A method of time-correlated single photon counting was applied to record the temporal development of spectral profile of He I 492.2 nm line with a sub-nanosecond temporal resolution. By fitting the measured profile of the line with a combination of pseudo-Voigt profiles for forbidden (2 1P-4 1F) and allowed (2 1P-4 1D) helium lines, instantaneous electric fields up to 32 kV cm-1 were measured in the RF sheath. The measured electric field is in agreement with the spatially averaged value of 40 kV cm-1 estimated from homogeneous charge density RF sheath model. The observed rectangular waveform of the electric field time development is attributed to increased sheath conductivity by the strong electron avalanches occurring in the γ-mode sheath at high current densities.
Surface modification of polyimide (PI) film using water cathode atmospheric pressure glow discharge plasma
NASA Astrophysics Data System (ADS)
Zheng, Peichao; Liu, Keming; Wang, Jinmei; Dai, Yu; Yu, Bin; Zhou, Xianju; Hao, Honggang; Luo, Yuan
The industrial use of polyimide film is limited because of undesirable properties such as poor wettability. In the present paper, a new kind of equipment called water cathode atmospheric pressure glow discharge was used to improve the surface properties of polyimide films and made them useful to technical applications. The changes in hydrophilicity of modified polyimide film surfaces were investigated by contact angle, surface energy and water content measurements as a function of treatment time. The results obtained show good treatment homogeneity and that the variation trends of contact angles are different for polar and non-polar testing liquids, while surface energy and water content are significantly enhanced with the increase of treatment time until they achieve saturated values after 60 s plasma treatment. Also, the thickness of liquid layer plays an important role in plasma processing and directly affects the treatment effect. Changes in morphology of polyimide films were analyzed by atomic force microscope and the results indicate that surface hydrophilicity after plasma treatment are improved partly due to the increase in the roughness. In addition, polyimide films treated by plasma are subjected to an ageing process to determine the durability of plasma treatment. It is found that the hydrophilicity is still better than untreated ones though the hydrophobic character partly recovers after long-term storage in ambient air.
Dechlorination and decomposition of chloroform induced by glow discharge plasma in an aqueous solution.
Liu, Yongjun; Crittenden, John C; Wang, Lei; Liu, Panliang
In this study, efficient dechlorination and decomposition of chloroform (CF) induced by glow discharge plasma (GDP) in contact with a sodium sulfate solution was investigated. Intermediate byproducts were determined by ionic chromatography and headspace gas chromatography, respectively. Results showed that CF can be effectively dechlorinated and decomposed under the action of GDP. Both removal and dechlorination of CF increased with increasing pH and with addition of hydroxyl radical scavengers to the solution. Addition of H2O2 to the solution slightly decreased the CF removal. Formic acid, oxalic acid and dichloromethane were determined as the major intermediate byproducts. Final products were carbon dioxide and hydrochloric acid. Hydrated electrons were the most likely active species responsible for initiation of the dechlorination, and hydroxyl radicals may be the ones for the oxidation of the organic intermediate byproducts. Hydrolyses of the chloromethyl radicals contributed much in the mineralization of the organic chlorine. Reaction mechanism was proposed based on the dechlorination kinetics and the distribution of intermediate byproducts. PMID:26808246
Contact glow discharge electrolysis: its origin, plasma diagnostics and non-faradaic chemical effects
NASA Astrophysics Data System (ADS)
Gupta, Susanta K. Sen
Contact glow discharge electrolysis (CGDE) also termed plasma electrolysis is a novel electrolysis where a stable sheath of light emitting plasma develops around an electrode immersed well inside a relatively high-conductivity liquid electrolyte during normal electrolysis (NE) at several hundred volts. The phenomenon may develop in dc-, pulsed dc-, ac- as well as RF-driven electrolyses. The chemical effects of CGDE are remarkably non-faradaic in respect to the nature of the products as well as their yields. The article traces comprehensively the progress made in studies of CGDE in aqueous and non-aqueous solutions since 1844 and reviews the developments in the understanding of its origin, light emission, plasma state and non-faradaic effects leading to the elucidation of detailed mechanism of the origin of CGDE on the basis of the onset of hydrodynamic instabilities in local vaporization of the solvent near the working electrode during NE, and that of highly non-faradaic effects of CGDE based on a model of two reaction zones located within the electrode plasma and at the plasma-liquid interface producing solvent derived radicals at high local concentrations. Keeping in view the recent surge of interest in varied applications of CGDE, the article is appended with highlights of these applications across synthetic chemistry, waste water treatment, electrosurgical devices, nanoparticle fabrications, surface engineering and micro-machining.
Femtosecond laser ablation particle introduction to a liquid sampling-atmospheric pressure glow discharge ionization source
Carado, Anthony J.; Quarles, C. Derrick; Duffin, Andrew M.; Barinaga, Charles J.; Russo, Richard E.; Marcus, R. Kenneth; Eiden, Gregory C.; Koppenaal, David W.
This work describes the use of a compact, liquid sampling – atmospheric pressure glow discharge (LS-APGD) ionization source to ionize metal particles within a laser ablation aerosol. Mass analysis was performed with a Thermo Scientific Exactive Mass Spectrometer which utilizes an orbitrap mass analyzer capable of producing mass resolution exceeding M/ΔM > 160,000. The LS-APGD source generates a low-power plasma between the surface of an electrolytic solution flowing at several µl min-1 through a fused silica capillary and a counter electrode consisting of a stainless steel capillary employed to deliver the laser ablation particles into the plasma. Sample particles of approximately 100 nm were generated with an Applied Spectra femtosecond laser located remotely and transported through 25 meters of polyurethane tubing by means of argon carrier gas. Samples consisted of an oxygen free copper shard, a disk of solder, and a one-cent U.S. coin. Analyte signal onset was readily detectable relative to the background signal produced by the carrier gas alone. The high mass resolution capability of the orbitrap mass spectrometer was demonstrated on the solder sample with resolution exceeding 90,000 for Pb and 160,000 for Cu. In addition, results from a laser ablation depth-profiling experiment of a one cent coin revealed retention of the relative locations of the ~10 µm copper cladding and zinc rich bulk layers.
Stimulated Electromagnetic Emission Indicator of Glow Plasma Discharges from Ionospheric HF Wave Transmissions with HAARP
NASA Astrophysics Data System (ADS)
Bernhardt, P. A.; Scales, W.; Briczinski, S. J.; Fu, H.; Mahmoudian, A.; Samimi, A.
High power radio waves resonantly interact with to accelerate electrons for production of artificial aurora and plasma clouds. These plasma clouds are formed when the HF frequency is tuned near a harmonic of the electron cyclotron frequency. At a narrow band resonance, large electrostatic fields are produced below the F-layer and the neutral atmosphere breaks down with a glow plasma discharge. The conditions for this resonance are given by matching the pump wave frequency and wave-number with the sum of daughter frequencies and wave-numbers for several plasma modes. The most likely plasma mode that accelerates the electrons is the electron Bernstein wave in conjunction with an ion acoustic wave. Both upper hybrid and whistler mode waves are also possible sources of electron acceleration. To determine the plasma process for electron acceleration, stimulated electromagnetic emissions are measured using ground receivers in a north-south chain from the HAARP site. Recent observations have shown that broad band spectral lines downshifted from the HF pump frequency are observed when artificial plasma clouds are formed. For HF transmissions are the 2nd, 3rd, and 4th gyro harmonic, the downshifted indicators are found 500 Hz, 20 kHz, and 140 kHz, respectively, from the pump frequency. This Indicator Mode (IM) anticipates that a plasma layer will be formed before it is recorded with an ionosonde or optical imager.
Possible Mechanism of ``Additional'' Production of H^- in a Glow Discharge
NASA Astrophysics Data System (ADS)
Belostotskiy, S.; Economou, D.; Lopaev, D.; Rakhimova, T.
Based on measurements of H^- and H densities a DC glow discharge in H2 (P=0.1-3 Torr) the rate coefficient of H^- production as a function of E/N was determined. To analyze the mechanisms of H^- production, a simple model of H2 vibrational excitation was developed. Estimations of vibrational level densities (v=3-5) obtained from VUV absorption measurements were in reasonable agreement with the calculated data. The analysis revealed that standard mechanisms of H^- production (dissociative attachment to vibrationally excited molecules H2(v) and molecules in Rydberg states H2(Ry)) were not enough to explain the experimental results. In order to describe both the shape (vs E/N) and the magnitude of the measured H^- production rate coefficient, an ``additional'' source of H^-, having a strong resonant electron attachment CS in the range of ˜5-9 eV, should be invoked. Although H2 has no resonances in the 5-9 eV range, water is known to strongly dissociatively attach in this range. Thus, even small amounts (0.1-1%) of water vapor in the apparatus can explain the origin of the ``additional'' H^- production. This result is corroborated by the work of Cadez et. al. in Proc. of XXVII ICPIG, 2005. This work was supported by the RFBR (No.05-02-17649a), Scientific School - 171113.2003.2 and NATO Collaborative Linkage Grant (No.980097).
Destruction of 4-phenolsulfonic acid in water by anodic contact glow discharge electrolysis.
Yang, Haiming; An, Baigang; Wang, Shaoyan; Li, Lixiang; Jin, Wenjie; Li, Lihua
Destruction of 4-phenolsulfonic acid (4-PSA) in water was carried out using anodic contact glow discharge electrolysis. Accompanying the decay of 4-PSA, the amount of total organic carbon (TOC) in water correspondingly decreased, while the sulfonate group of 4-PSA was released as sulfate ion. Oxalate and formate were obtained as minor by-products. Additionally, phenol, 1,4-hydroquinone, hydroxyquinol and 1,4-benzoquinone were detected as primary intermediates in the initial stages of decomposition of 4-PSA. A reaction pathway involving successive attacks of hydroxyl and hydrogen radicals was assumed on the basis of the observed products and kinetics. It was revealed that the decay of both 4-PSA and TOC obeyed a first-order rate law. The effects of different Fe ions and initial concentrations of 4-PSA on the degradation rate were investigated. It was found that the presence of Fe ions could increase the degradation rate of 4-PSA, while initial concentrations lower than 80 mmol/L had no significant effect on kinetic behaviour. The disappearance rate of 4-PSA was significantly affected by pH. PMID:24191593
Surface characterization of radio-frequency glow discharged and autoclaved titanium surfaces.
Kawahara, D; Ong, J L; Raikar, G N; Lucas, L C; Lemons, J E; Nakamura, M
To characterize titanium surfaces treated with radio-frequency glow discharge (RFGD) after media exposure, surface chemical analyses were performed using x-ray photoelectron spectroscopy. Auger electron spectroscopy, and Fourier transform infrared-reflection absorption spectroscopy (FTIR-RAS). The RFGD treatments resulted in a cleaner surface as compared to as-sputtered or as-autoclaved titanium specimens. The oxide thickness of RFGD-treated titanium specimens was not statistically different from the as-autoclaved and as-sputter cleaned titanium specimens. Exposure to a phosphate-buffered saline solution revealed a greater deposition of calcium and phosphorous on the RFGD-treated surfaces. Auger electron spectroscopy depth profiles showed that calcium and phosphorous ions diffused into the titanium oxide layer. The calcium and phosphorous deposits were identified as amorphous calcium phosphate compounds using FTIR-RAS. These results suggest that RFGD treatments of titanium enhance calcium and/or phosphate affinity because of an increase in elemental interactions at the surface, thereby resulting in the formation of amorphous calcium phosphate compounds. PMID:8803338
Impurity reduction in a plasma by using the deuterium and helium glow discharge method
NASA Astrophysics Data System (ADS)
Lee, Sangyong; Kim, Jaeyong
To reduce the levels of impurities such as water, oxygen and nitrogen in a plasma chamber, we evaporated and deposited carborane (C2B10H12) powders on a silicon substrate by using a glow discharge method, and investigated the effects of boronization as functions of the carborane temperature and the rates of the flowing gases between deuterium and helium. The reduced amount of impurities after boronization was estimated by measuring the partial pressures of the corresponding gases in the chamber and the concentrations of nitrogen and oxygen in a deposited carborane film. The ratio of deuterium to hydrogen in the deposited film was analyzed by using secondary ion mass spectrometry (SIMS). When carborane powders were evaporated under a deuterium atmosphere, the residual gas analyzer showed a significant decrease in the partial pressure of water while less change was noted from the partial pressures of nitrogen and oxygen. The most efficient removal rate for water was obtained when carborane powder was flown under deuterium atmosphere at 150 °C. The SIMS data showed higher concentrations of nitrogen and oxygen in the carborane films deposited on Si substrates under a deuterium atmosphere, demonstrating that boronization under a deuterium atmosphere is an effective method to remove impurities.
Effects of rf power on chemical composition and surface roughness of glow discharge polymer films
NASA Astrophysics Data System (ADS)
Zhang, Ling; He, Xiaoshan; Chen, Guo; Wang, Tao; Tang, Yongjian; He, Zhibing
The glow discharge polymer (GDP) films for laser fusion targets were successfully fabricated by plasma enhanced chemical vapor deposition (PECVD) at different radio frequency (rf) powers. The films were deposited using trans-2-butene (T2B) mixed with hydrogen as gas sources. The composition and state of plasma were diagnosed by quadrupole mass spectrometer (QMS) and Langmuir probe during the deposition process. The composition, surface morphology and roughness were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and white-light interferometer (WLI), respectively. Based on these observation and analyses, the growth mechanism of defects in GDP films were studied. The results show that, at low rf power, there is a larger probability for secondary polymerization and formation of multi-carbon C-H species in the plasma. In this case, the surface of GDP film turns to be cauliflower-like. With the increase of rf power, the degree of ionization is high, the relative concentration of smaller-mass hydrocarbon species increases, while the relative concentration of larger-mass hydrocarbon species decreases. At higher rf power, the energy of smaller-mass species are high and the etching effects are strong correspondingly. The GDP film's surface roughness shows a trend of decrease firstly and then increase with the increasing rf power. At rf power of 30 W, the surface root-mean-square roughness (Rq) drops to the lowest value of 12.8 nm, and no "void" defect was observed.
Fast polymer fingerprinting using flowing afterglow atmospheric pressure glow discharge mass spectrometry.
Jecklin, Matthias C; Gamez, Gerardo; Zenobi, Renato
Flowing afterglow atmospheric pressure glow discharge mass spectrometry (FA-APGD-MS) was used to interrogate different polymer species such as biopolymers, synthetic homo- and co-polymers. The main advantages of FA-APGD-MS for polymer samples include speed (<30 s per sample) and analysis at atmospheric pressures. Moreover, there are essentially no restrictions as to the kind of polymer sample that can be analyzed because FA-APGD-MS can deal with liquid and solid (soluble or insoluble) bulk polymers and granulates, irrespective of their conductivity, without requiring any sample preparation prior to analysis. We will discuss the mechanism of ion formation as well as the limitation of the accessible mass range (m/z < 500) in view of what type of information can be gained from the mass spectra obtained. Monomer units and some fragments were detected for homopolymers, e.g.cis-polyisoprene (IR), poly(ethylene glycol) (PEG), poly(ethylene terephthalate) (PET), which allowed identification of the polymer composition. The mass spectra obtained were further processed using principal component analysis (PCA) for a better visualization and assessing of mass-spectral reproducibility. Combination with PCA even allowed differentiation of pectin, amylopectin, and cellulose, chemically very similar polysaccharides whose characteristic differences lie in the nature of the glycosidic linkage. Finally, we were able to detect and identify phthalate plasticizers, bis(2-ethylhexyl) phthalate (BEHP) and dibutyl phthalate (DBP), present in poly(vinyl chloride)-based food wraps. PMID:20448931
Sterilization of Materials with a One Atmosphere Uniform Glow Discharge Plasma.*
NASA Astrophysics Data System (ADS)
Ku, Yongmin; Brickman, C.; Tosh, K.; Kelly-Wintenberg, K.; Montie, T. C.; Tsai, P.; Wadsworth, L.; Roth, J. Reece
The relatively recent development of the One Atmosphere Uniform Glow Discharge Plasma sterilization technique at the UTK Plasma Science Laboratory has produced initial results which indicate that the technique may have commercial potential. We have shown that active species in a OAUGDP can be applied to the sterilization of fabrics, films, solid materials, and microbiological culture media. With a OAUGDP, we can eliminate the vacuum system which enforces batch processing and requires a continuous input of electrical power. With a OAUGDP, the exposure time is as little as 15 seconds. Sterilization of microorganisms with a kill ratio of 10E6 or higher, can be achieved with minimal unwanted byproducts and at less expense, compared to such conventional sterilization methods as autoclaving, ethylene oxide, or low pressure plasma treatment. This paper discusses the sterilization mechanisms of this new technique, and compares its advantages and disadvantages with other widely used techniques. ^1 Department of Microbiology, UTK ^2 UTK Textiles and Nonwovens Development Center (TANDEC) Research supported in part by the UTK Textiles and Nonwovens Development Center and UTK Center for Materials Processing.
Rapid oxidation and immobilization of arsenic by contact glow discharge plasma in acidic solution.
Jiang, Bo; Hu, Ping; Zheng, Xing; Zheng, Jingtang; Tan, Minghui; Wu, Mingbo; Xue, Qinzhong
Arsenic is a priority pollutant in aquatic ecosystem and therefore the remediation of arsenic-bearing wastewater is an important environmental issue. This study unprecedentedly reported simultaneous oxidation of As(III) and immobilization of arsenic can be achieved using contact glow discharge process (CGDP). CGDP with thinner anodic wire and higher energy input were beneficial for higher As(V) production efficiency. Adding Fe(II) in CGDP system significantly enhanced the oxidation rate of As(III) due to the generations of additional OH and Fe(IV) species, accompanied with which arsenic can be simultaneously immobilized in one process. Arsenic immobilization can be favorably obtained at solution pH in the range of 4.0-6.0 and Fe(II) concentration from 250 to 1000 μM. The presence of organics (i.e., oxalic acid, ethanol and phenol) retarded the arsenic immobilization by scavenging OH or complexing Fe(III) in aqueous solution. On the basis of these results, a mechanism was proposed that the formed ionic As(V) rapidly coprecipitated with Fe(III) ions or was adsorbed on the ferric oxyhydroxides with the formation of amorphous ferric arsenate-bearing ferric oxyhydroxides. This CGDP-Fenton system was of great interest for engineered systems concerned with the remediation of arsenic containing wastewater. PMID:25600320
Application of Glow Discharge Plasma to Alter Surface Properties of Materials
NASA Technical Reports Server (NTRS)
Trigwell, Steve; Buhler, Charles R.; Calle, Carlos I.
Some polymer materials that are considered important for spaceport operations are rendered noncompliant when subjected to the Kennedy Space Center (KSC) Standard electrostatic testing. These materials operate in stringent environmental conditions, such as high humidity. Treating materials that fail electrostatic testing and altering their surface properties so that they become compliant would result in considerable cost savings. Significant improvement in electrostatic dissipation of Saf-T-Vu PVC after treatment with air Atmospheric Plasma Glow Discharge (APGD) was observed and the material now passed the KSC electrostatic test. The O:C ratio on the surface, as monitored by X-ray Photoelectron Spectroscopy, increased from 0.165 tO 0.275 indicating enhanced oxidation, and surface contact angle measurements decreased from 107.5 to 72.6 showing increased hydrophilicity that accounted for the increased conductivity. Monitoring of the aging showed that the materials hydrophobic recovery resulted in it failing the electrostatic test 30 hours after treatment. This was probably due to the out-diffusion of the added Zn, Ba, and Cd salt stabilizers detected on the surface and/or diffusion of low molecular weight oligomers. On going work includes improving the long term hydrophilicity by optimizing the APGD process with different gas mixtures. Treatment of other spaceport materials is also presented.
Nitrogen Plasma Ion Implantation of Al and Ti alloys in the High Voltage Glow Discharge Mode
NASA Astrophysics Data System (ADS)
Oliveira, R. M.; Ueda, M.; Rossi, J. O.; Reuther, H.; Lepienski, C. M.; Beloto, A. F.
Enhanced surface properties can be attained for aluminum and its alloys (mechanical and tribological) and Ti6Al4V (mainly tribological) by Plasma Immersion Ion Implantation (PIII) technique. The main problem here, more severe for Al case, is the rapid oxygen contamination even in low O partial pressure. High energy nitrogen ions during PIII are demanded for this situation, in order to enable the ions to pass through the formed oxide layer. We have developed a PIII system that can operate at energies in excess of 50keV, using a Stacked Blumlein (SB) pulser which can nominally provide up to 100 kV pulses. Initially, we are using this system in the High Voltage Glow Discharge (HVGD) mode, to implant nitrogen ions into Al5052 alloy with energies in the range of 30 to 50keV, with 1.5μs duration pulses at a repetition rate of 100Hz. AES, pin-on-disc, nanoindentation measurements are under way but x-ray diffraction results already indicated abundant formation of AlN in the surface for Al5052 treated with this HVGD mode. Our major aim in this PIII experiment is to achieve this difficult to produce stable and highly reliable AlN rich surface layer with high hardness, high corrosion resistance and very low wear rate.
Gas-phase free radical reactions in the glow-discharge deposition of hydrogenated amorphous silicon from silane and disilane
Kampas, F.J.
An analysis of a measurement by Matsuda and co-workers of the lifetimes of the free radicals involved in the glow-discharge deposition of amorphous hydrogenated silicon from silane and disilane at 20-mTorr pressure is consistent with the hypothesis that SiH or SiH/sub 2/, but not SiH/sub 3/, is the dominant radical in the deposition from silane at that pressure.
Grafting of synthetic polyelectrolyte onto polymer surfaces--comparison of glow discharge and sup 60 Co-gamma-irradiation method
Hari, P.R.; Sharma, C.P. )
Water soluble polyelectrolyte synthesized from natural rubber contains sulfamate and carboxylate groups similar to that of heparin. It is observed that synthetic heparinoid polyelectrolyte is capable of inhibiting blood coagulation. In the present study, we attempted to graft the same onto polystyrene and polymethylmethacrylate surfaces using glow discharge technique and {sup 60}Co-gamma-irradiation method, and the surfaces were compared with respect to water contact angle and platelet adhesion parameters. Heparinized surfaces are also evaluated for relative comparison.
Use of Helium Production to Screen Glow Discharges for Low Energy Nuclear Reactions (LENR)
NASA Astrophysics Data System (ADS)
Passell, Thomas O.
My working hypothesis of the conditions required to observe low energy nuclear reactions (LENR) follows: 1) High fluxes of deuterium atoms through interfaces of grains of metals that readily accommodate movement of hydrogen atoms interstitially is the driving variable that produces the widely observed episodes of excess heat above the total of all input energy. 2) This deuterium atom flux has been most often achieved at high electrochemical current densities on highly deuterium-loaded palladium cathodes but is clearly possible in other experimental arrangements in which the metal is interfacing gaseous deuterium, as in an electrical glow discharge. 3) Since the excess heat episodes must be producing the product(s) of some nuclear fusion reaction(s) screening of options may be easier with measurement of those ``ashes'' than the observance of the excess heat. 4) All but a few of the exothermic fusion reactions known among the first 5 elements produce He-4. Hence helium-4 appearance in an experiment may be the most efficient indicator of some fusion reaction without commitment on which reaction is occurring. This set of hypotheses led me to produce a series of sealed tubes of wire electrodes of metals known to absorb hydrogen and operate them for 100 days at the 1 watt power level using deuterium gas pressures of ~ 100 torr powered by 40 Khz AC power supplies. Observation of helium will be by measurement of helium optical emission lines through the glass envelope surrounding the discharge. The results of the first 18 months of this effort will be described.
Effects of easily ionizable elements on the liquid sampling atmospheric pressure glow discharge
NASA Astrophysics Data System (ADS)
Venzie, Jacob L.; Marcus, R. Kenneth
A series of studies has been undertaken to determine the susceptibility of the liquid sampling-atmospheric pressure glow discharge (LS-APGD) atomic emission source to easily ionizable element (EIE) effects. The initial portions of the study involved monitoring the voltage drop across the plasma as a function of the pH to ascertain whether or not the conductivity of the liquid eluent alters the plasma energetics and subsequently the analyte signal strength. It was found that altering the pH (0.0 to 2.0) in the sample matrix did not significantly change the discharge voltage. The emission signal intensities for Cu(I) 327.4 nm, Mo(I) 344.7 nm, Sc(I) 326.9 nm and Hg(I) 253.6 nm were measured as a function of the easily ionizable element (sodium and calcium) concentration in the injection matrix. A range of 0.0 to 0.1% (w/v) EIE in the sample matrix did not cause a significant change in the Cu, Sc, and Mo signal-to-background ratios, with only a slight change noted for Hg. In addition to this test of analyte response, the plasma energetics as a function of EIE concentration are assessed using the ratio of Mg(II) to Mg(I) (280.2 nm and 285.2 nm, respectively) intensities. The Mg(II)/Mg(I) ratio showed that the plasma energetics did not change significantly over the same range of EIE addition. These results are best explained by the electrolytic nature of the eluent acting as an ionic (and perhaps spectrochemical) buffer.
Improved voltage transfer coefficients for nonconductive materials in radiofrequency glow discharge optical emission spectrometry.
Therese, L; Ghalem, Z; Guillot, P; Belenguer, P
In radiofrequency glow discharge emission spectrometry (RF-GDOES), the excitation voltage used to create the plasma is applied to the back or front end of the sample to be analyzed. In this paper we focus on back-applied voltage systems (a configuration that represents about half of the instruments available on the market), and on applied voltage problems (the power coupling efficiency and materials analysis are beyond the scope of this study). In the RF-GDOES of nonconductive samples, a voltage drop develops inside the material. The voltage transfer coefficient is defined as the ratio between the peak voltage in front of the sample (facing the plasma) and the peak voltage applied to the back of the sample. In this work, we show that it is possible to increase the voltage transfer coefficient by increasing the capacitance of the sample. The capacitance of a given nonconductive material depends on its surface, its thickness and its permittivity. Increasing the voltage transfer coefficient permits higher power deposition in the plasma. This study is based on an electrical equivalent circuit for the discharge device, which takes into account the sample and reactor capacitances as well as the voltage probes used for the measurements. This circuit, when modeled by a commercial electrical circuit simulator, gives the voltage transfer coefficient as a function of the sample capacitance. Different approaches to increasing the sample capacitance and their influence on the voltage transfer coefficient are presented and related to the 750.4 nm argon line intensity, which is correlated to the electron density. PMID:16724217
Glow discharge with electrostatic confinement of electrons in a chamber bombarded by fast electrons
NASA Astrophysics Data System (ADS)
Metel, A. S.; Grigoriev, S. N.; Melnik, Yu. A.; Prudnikov, V. V.
A metal substrate is immersed in plasma of glow discharge with electrostatic confinement of electrons inside the vacuum chamber volume V ≈ 0.12 m3 filled with argon or nitrogen at pressures 0.005-5 Pa, and dependence of discharge characteristics on negative substrate potential is studied. Emitted by the substrate secondary electrons bombard the chamber walls and it results in electron emission growth of the chamber walls and rise of gas ionization intensity inside the chamber. Increase of voltage U between the chamber and the substrate up to 10 kV at a constant discharge current I d in the anode circuit results in a manifold rise of current I in the substrate circuit and decrease of discharge voltage U d between the anode and the chamber from hundreds to tens of volts. At pressure p < 0.05 Pa nonuniformity of plasma density does not exceed ˜10%. Using the Child-Langmuir law, as well as measurement results of sheath width d between homogeneous plasma and a lengthy flat substrate dependent on voltage U ion current density j i on the substrate surface and ion-electron emission coefficient γ i are calculated. After the current in circuit of a substrate made of the same material is measured, the γ i values may be used to evaluate the average dose of ion implantation. The rate of dose rise at a constant high voltage U is by an order of magnitude higher than in known systems equipped with generators of square-wave high-voltage pulses. Application to the substrate of 10-ms-wide sinusoidal high-voltage pulses, which follow each other with 100-Hz frequency, results in synchronous oscillations of voltage U and ion current I i in the substrate circuit. In this case variation of the sheath width d due to oscillations of U and Ii is insignificant and d does not exceed several centimeters thus enabling substrate treatment in a comparatively small vacuum chamber.
Physical mechanisms of self-organization and formation of current patterns in gas discharges of the Townsend and glow types
Raizer, Yu. P.; Mokrov, M. S.
The paper discusses current filamentation and formation of current structures (in particular, hexagonal current patterns) in discharges of the Townsend and glow types. The aim of the paper, which is in part a review, is to reveal basic reasons for formation of current patterns in different cases, namely, in dielectric barrier discharge, discharge with semiconductor cathode, and micro-discharge between metallic electrodes. Pursuing this goal, we give a very brief review of observations and discuss only those theoretical, computational, and experimental papers that shed light on the physical mechanisms involved. The mechanisms are under weak currents—the thermal expansion of the gas as a result of Joule heating; under enhanced currents—the electric field and ionization rate redistribution induced by space charge. Both mechanisms lead to instability of the homogeneous discharges. In addition, we present new results of numerical simulations of observed short-living current filaments which are chaotic in space and time.
Transport Equations Resolution By N-BEE Anti-Dissipative Scheme In 2D Model Of Low Pressure Glow Discharge
Kraloua, B.; Hennad, A.
The aim of this paper is to determine electric and physical properties by 2D modelling of glow discharge low pressure in continuous regime maintained by term constant source. This electric discharge is confined in reactor plan-parallel geometry. This reactor is filled by Argon monatomic gas. Our continuum model the order two is composed the first three moments the Boltzmann's equations coupled with Poisson's equation by self consistent method. These transport equations are discretized by the finite volumes method. The equations system is resolved by a new technique, it is about the N-BEE explicit scheme using the time splitting method.
Enhanced tissue integration of implantable electrodes for sensing, and stimulation, via radio frequency glow discharge
NASA Astrophysics Data System (ADS)
O'Connor, Laurie M.
Biopotential electrodes are conductive materials that convert electronic currents to or from ionic currents for sensing, and stimulating specific tissue sites for medical applications. Implanted electrodes become "walled off" by the foreign body tissue reactions producing poorly attached scar capsules dominated by surrounding dense collagenous lamellae and source fibroblasts which are electrically resistive. The conductive interstitial fluid that is typical between an electrode and the resistive capsule allows spurious current paths. The insulating layer increases the distance between the electrode and the target sites and poor attachment often results in electrode migration within the host tissue. This investigation tested the hypothesis that surface-energy modulation of electrodes, via Radio Frequency Glow Discharge Treatment (RFGDT), can improve the performance of tissue-implantable electrodes by reducing the foreign body tissue reaction and enhancing interfacial bonding between the tissue and electrode material. Previously published findings were reproduced in a pilot study of explanted reference grade medical-grade methyl silicone (PDMS) and commercially pure titanium (cpTi) materials and their tissue capsules from 30-day subcutaneous exposures in Balb/C mice. The low-critical surface tension PDMS produced thick, dense, poorly attached scar capsules while the higher-surface-energy commercially pure titanium (cpTi) produced more cellular and strongly attached tissue layers difficult to delaminate from the biomaterial. For the main body of work, cpTi, capacitor-grade Tantalum (Ta), and synthetic heart valve-quality Pyrolytic Carbon (PyC) were evaluated, representative of potential high-surface-energy implant electrode materials. Their surface characteristics were determined as-manufactured and after Radio Frequency Glow Discharge Treatment (RFGDT) by Critical Surface Tension (CST) measurement, Scanning Electron Microscopy (SEM), Energy Dispersive X
Liquid sampling-atmospheric pressure glow discharge as a secondary excitation source: Assessment of plasma characteristics
NASA Astrophysics Data System (ADS)
Manard, Benjamin T.; Gonzalez, Jhanis J.; Sarkar, Arnab; Dong, Meirong; Chirinos, Jose; Mao, Xianglei; Russo, Richard E.; Marcus, R. Kenneth
The liquid sampling-atmospheric pressure glow discharge (LS-APGD) has been assessed as a secondary excitation source with a parametric evaluation regarding carrier gas flow rate, applied current, and electrode distance. With this parametric evaluation, plasma optical emission was monitored in order to obtain a fundamental understanding with regards to rotational temperature (Trot), excitation temperature (Texc), electron number density (ne), and plasma robustness. Incentive for these studies is not only for a greater overall fundamental knowledge of the APGD, but also in instrumenting a secondary excitation/ionization source following laser ablation (LA). Rotational temperatures were determined through experimentally fitting of the N2 and OH molecular emission bands while atomic excitation temperatures were calculated using a Boltzmann distribution of He and Mg atomic lines. The rotational and excitation temperatures were determined to be ~ 1000 K and ~ 2700 K respectively. Electron number density was calculated to be on the order of ~ 3 × 1015 cm- 3 utilizing Stark broadening effects of the Hα line of the Balmer series and a He I transition. In addition, those diagnostics were performed introducing magnesium (by solution feed and laser ablation) into the plasma in order to determine any perturbation under heavy matrix sampling. The so-called plasma robustness factor, derived by monitoring Mg II/Mg I emission ratios, is also employed as a reflection of potential perturbations in microplasma energetics across the various operation conditions and sample loadings. While truly a miniaturized source (< 1 mm3 volume), the LS-APGD is shown to be quite robust with plasma characteristics and temperatures being unaffected upon introduction of metal species, whether by liquid or laser ablation sample introduction.
Heat and Radiofrequency Plasma Glow Discharge Pretreatment of a Titanium Alloy Promote Bone Formation and Osseointegration
MacDonald, Daniel E.; Rapuano, Bruce E.; Vyas, Parth; Lane, Joseph M.; Meyers, Kathleen; Wright, Timothy
Orthopedic and dental implants manifest increased failure rates when inserted into low density bone. We determined whether chemical pretreatments of a titanium alloy implant material stimulated new bone formation to increase osseointegration in vivo in trabecular bone using a rat model. Titanium alloy rods were untreated or pretreated with heat (600°C) or radiofrequency plasma glow discharge (RFGD). The rods were then coated with the extracellular matrix protein fibronectin (1 nM) or left uncoated and surgically implanted into the rat femoral medullary cavity. Animals were euthanized 3 or 6 weeks later, and femurs were removed for analysis. The number of trabeculae in contact with the implant surface, surface contact between trabeculae and the implant, and the length and area of bone attached to the implant were measured by histomorphometry. Implant shear strength was measured by a pull-out test. Both pretreatments and fibronectin enhanced the number of trabeculae bonding with the implant and trabeculae-to-implant surface contact, with greater effects of fibronectin observed with pretreated compared to untreated implants. RFGD pretreatment modestly increased implant shear strength, which was highly correlated (r2 = 0.87 – 0.99) with measures of trabecular bonding for untreated and RFGD-pretreated implants. In contrast, heat pretreatment increased shear strength 3 to 5-fold for both uncoated and fibronectin-coated implants at 3 and 6 weeks, suggesting a more rapid increase in implant-femur bonding compared to the other groups. In summary, our findings suggest that the heat and RFGD pretreatments can promote the osseointegration of a titanium alloy implant material. PMID:23649564
Investigation of spectrochemical matrix effects in the liquid sampling-atmospheric pressure glow discharge source
NASA Astrophysics Data System (ADS)
Manard, Benjamin T.; Gonzalez, Jhanis J.; Sarkar, Arnab; Mao, Xianglei; Zhang, Lynn X.; Konegger-Kappel, Stefanie; Marcus, R. Kenneth; Russo, Richard E.
The liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma was evaluated with regard to its spectrochemical robustness in its application as a miniaturized optical emission spectroscopy (OES) source for liquid samples. The susceptibility to perturbations in excitation/ionization conditions was probed across a wide range test species, including transition metals, easily ionized elements (group I), and elements with low second ionization potentials (group II). Spectrochemical metrics included the plasma excitation temperature (Texc), ionization temperatures (Tion), and magnesium (Mg) ionic:atomic (Mg II:Mg I) ratios. The introduction of the 11 different matrix elements into the LS-APGD at concentrations of 500 μg mL- 1 yielded no significant changes in the optically-determined plasma characteristics, indicating a relative immunity to spectrochemical matrix effects. Texe values for the plasma, using He I as the spectrometric species averaged 2769 ± 79 K across the test matrix, with Mg-based ionization temperature values centered at 6665 ± 151 K. Typical Mg II:Mg I ratios (the so-called robustness parameter) were 0.95 ± 0.3. The lack of appreciable perturbation in excitation/ionization conditions observed here is also manifested in virtually no changes in the probe Mg II and I species' intensities, even at matrix loadings of up to 1000 μg mL- 1 of Ba. These observations indicate that the LS-APGD could serve as an OES source for the analysis of diverse aqueous samples without appreciable spectroscopic matrix effects, though potential physical matrix effects including vaporization effects must be evaluated.
Protein destruction by a helium atmospheric pressure glow discharge: Capability and mechanisms
NASA Astrophysics Data System (ADS)
Deng, X. T.; Shi, J. J.; Kong, M. G.
Biological sterilization represents one of the most exciting applications of atmospheric pressure glow discharges (APGD). Despite the fact that surgical instruments are contaminated by both microorganisms and proteinaceous matters, sterilization effects of APGD have so far been studied almost exclusively for microbial inactivation. This work presents the results of a detailed investigation of the capability of a helium-oxygen APGD to inactivate proteins deposited on stainless-steel surfaces. Using a laser-induced fluorescence technique for surface protein measurement, a maximum protein reduction of 4.5 logs is achieved by varying the amount of the oxygen admixture into the background helium gas. This corresponds to a minimum surface protein of 0.36 femtomole/mm2. It is found that plasma reduction of surface-borne protein is through protein destruction and degradation, and that its typically biphasic reduction kinetics is influenced largely by the thickness profile of the surface protein. Also presented is a complementary study of possible APGD protein inactivation mechanisms. By interplaying the protein inactivation kinetics with optical emission spectroscopy, it is shown that the main protein-destructing agents are excited atomic oxygen (via the 777 and 844 nm emission channels) and excited nitride oxide (via the 226, 236, and 246 nm emission channels). It is also demonstrated that the most effective protein reduction is achieved possibly through a synergistic effect between atomic oxygen and nitride oxide. This study is a useful step toward a full confirmation of the efficacy of APGD as a sterilization technology for surgical instruments contaminated by prion proteins.
Terahertz Measurements of Hot Hydronium Ions (H_3O^+) with AN Extended Negative Glow Discharge
NASA Astrophysics Data System (ADS)
Yu, Shanshan; Pearson, John
Terahertz absorption spectroscopy was employed to detect the ground-state inversion transitions of the hydronium ion. The highly excited ions were created with an extended negative glow discharge through a gas mixture of 1 mtorr of H_2O, 2 mtorr of H_2, and 12 mtorr of Ar, which allowed observation of transitions with J and K up to 12. In total forty seven transitions were measured in the 0.9--2.0 THz region and twenty two of them were observed for the first time. The experimental uncertainties range from 100 to 300 kHz, which are much better than those of 0.3--1.2 MHz reported in previous work. Differences up to 25.6 MHz were found between the observed positions and the catalog values that have been used for Herschel data analysis of observations towards Sagittarius B2(N), NGC 4418 and Arp 220. The new and improved measurements were fit to experimental accuracies with an updated Hamiltonian; and better H_3O^+ predictions are reported to support the proper analysis of astronomical observations by high-resolution spectroscopy telescopes, such as Herschel, SOFIA, and ALMA. Lis et al., '' Hot, metastable hydronium ion in the Galactic center: formation pumping in X-ray-irradiated gas?'', Phil. Trans. R. Soc. A 370, 5162 (2012). González-Alfonso et al., '' Excited OH^+, H_2O^+ and H_3O^+ in NGC 4418 and Arp 220'', Astrophys. Astronom 550, A25 (2013). Lis et al., '' Widespread rotaional-hot hydronium in the Galactic Interstellar Medium'', Astrophys. J., submitted (2014).
Hvasta, M.G.; and Zwicker, A.
Dusty plasmas consist of electrons, ions, neutrals and nm-μm sized particles commonly referred to as dust. In man-made plasmas this dust may represent impurities in a tokamak or plasma etching processing. In astrophysical plasmas this dust forms structures such as planetary rings and comet tails. To study dusty plasma dynamics an experiment was designed in which a 3:1 silica (<5 μm diameter) and fl uorescent dust mixture was added to an argon DC glow discharge plasma and exposed to UV radiation. This fl uorescent lighting technique offers an advantage over laser scattering (which only allows two-dimensional slices of the cloud to be observed) and is simpler than scanning mirror techniques or particle image velocimetry. Under typical parameters (P=150 mTorr, V anode= 100 V, Vcathode= -400 V, Itotal < 2mA) when the cloud is exposed to the UV light (100W, λ = 365 nm) the mixture fl uoresces, moves ~2mm towards the light source and begins rotating in a clockwise manner (as seen from the cathode). By calibrating a UV lamp and adjusting the relative intensity of the UV with a variable transformer it was found that both translational and rotational velocities are a function of UV intensity. Additionally, it was determined that bulk cloud rotation is not seen when the dust tray is not grounded while bulk translation is. This ongoing experiment represents a novel way to control contamination in man-made plasmas and a path to a better understanding of UV-bathed plasma systems in space..
Etching of UO{sub 2} in NF{sub 3} RF Plasma Glow Discharge
John M. Veilleux
A series of room temperature, low pressure (10.8 to 40 Pa), low power (25 to 210 W) RF plasma glow discharge experiments with UO{sub 2} were conducted to demonstrate that plasma treatment is a viable method for decontaminating UO{sub 2} from stainless steel substrates. Experiments were conducted using NF{sub 3} gas to decontaminate depleted uranium dioxide from stainless-steel substrates. Depleted UO{sub 2} samples each containing 129.4 Bq were prepared from 100 microliter solutions of uranyl nitrate hexahydrate solution. The amorphous UO{sub 2} in the samples had a relatively low density of 4.8 gm/cm{sub 3}. Counting of the depleted UO{sub 2} on the substrate following plasma immersion was performed using liquid scintillation counting with alpha/beta discrimination due to the presence of confounding beta emitting daughter products, {sup 234}Th and {sup 234}Pa. The alpha emission peak from each sample was integrated using a gaussian and first order polynomial fit to improve quantification. The uncertainties in the experimental measurement of the etched material were estimated at about {+-} 2%. Results demonstrated that UO{sub 2} can be completely removed from stainless-steel substrates after several minutes processing at under 200 W. At 180 W and 32.7 Pa gas pressure, over 99% of all UO{sub 2} in the samples was removed in just 17 minutes. The initial etch rate in the experiments ranged from 0.2 to 7.4 {micro}m/min. Etching increased with the plasma absorbed power and feed gas pressure in the range of 10.8 to 40 Pa. A different pressure effect on UO{sub 2} etching was also noted below 50 W in which etching increased up to a maximum pressure, {approximately}23 Pa, then decreased with further increases in pressure.
Surface oxygen micropatterns on glow discharge polymer targets by photo irradiation
NASA Astrophysics Data System (ADS)
Reynolds, Hannah; Baxamusa, Salmaan; Haan, Steven W.; Fitzsimmons, Paul; Carlson, Lane; Farrell, Mike; Nikroo, Abbas; Watson, Brian J.
Recent simulations predict surface oxygen may be a significant source of disruptive perturbations in the implosion process of glow-discharge polymers (GDP) ablators at the National Ignition Facility. GDP material held in ambient atmospheric conditions showed an increase in mass when stored in light transparent containers, which suggests that photo exposure is a driving force for oxygen absorption. To investigate if surface oxygen is a contributing factor of disruptive perturbations during implosion, a method to imprint a periodic micropattern of oxygen on the surface of GDP was developed and used to fabricate a flat sample for empirical testing. Photo exposure using collimated blue light was used to generate micropatterns of surface oxygen on the GDP material. The periodic oxygen micropattern was confirmed by secondary ion mass spectrometry (SIMS) and energy dispersive spectroscopy. A SIMS depth profile showed the atomic percent of oxygen ranged from 8 at. % near the surface to 1 at. % at a depth of 2 μm in a sample exposed for 4 min. The molecular interactions formed between the GDP and oxygen molecules were characterized using Fourier transform infrared resonance (FTIR), which showed the formation of hydroxyl (O-H) and carbonyl (C=O) bonds. The FTIR enabled the oxygen mass uptake as a function of photo exposure time to be quantified (resolved to typically 0.05 at. % oxygen). This experimental protocol was then applied to produce a GDP flat part with a periodic 75 μm wavelength micropattern of photo exposed (oxygen rich) and masked (oxygen deficient) regions. The micropatterned GDP ablators developed in this work are being used to assess the effect of surface oxygen on disruptive perturbations during the inertial confinement fusion implosion process.
Protein destruction by a helium atmospheric pressure glow discharge: Capability and mechanisms
Deng, X. T.; Shi, J. J.; Kong, M. G.
Biological sterilization represents one of the most exciting applications of atmospheric pressure glow discharges (APGD). Despite the fact that surgical instruments are contaminated by both microorganisms and proteinaceous matters, sterilization effects of APGD have so far been studied almost exclusively for microbial inactivation. This work presents the results of a detailed investigation of the capability of a helium-oxygen APGD to inactivate proteins deposited on stainless-steel surfaces. Using a laser-induced fluorescence technique for surface protein measurement, a maximum protein reduction of 4.5 logs is achieved by varying the amount of the oxygen admixture into the background helium gas. This corresponds to a minimum surface protein of 0.36 femtomole/mm{sup 2}. It is found that plasma reduction of surface-borne protein is through protein destruction and degradation, and that its typically biphasic reduction kinetics is influenced largely by the thickness profile of the surface protein. Also presented is a complementary study of possible APGD protein inactivation mechanisms. By interplaying the protein inactivation kinetics with optical emission spectroscopy, it is shown that the main protein-destructing agents are excited atomic oxygen (via the 777 and 844 nm emission channels) and excited nitride oxide (via the 226, 236, and 246 nm emission channels). It is also demonstrated that the most effective protein reduction is achieved possibly through a synergistic effect between atomic oxygen and nitride oxide. This study is a useful step toward a full confirmation of the efficacy of APGD as a sterilization technology for surgical instruments contaminated by prion proteins.
Heat and Radiofrequency Plasma Glow Discharge Pretreatment of a Titanium Alloy: Eveidence for Enhanced Osteoinductive Properties
Rapuano, Bruce E.; Singh, Herman; Boskey, Adele L.; Doty, Stephen B.; MacDonald, Daniel E.
It is believed that orthopedic and implant longevity can be improved by optimizing fixation, or direct bone-implant contact, through the stimulation of new bone formation around the implant. The purpose of this study was to determine whether heat (600°C) or radiofrequency plasma glow discharge (RFGD) pretreatment of Ti6Al4V stimulated calcium-phosphate mineral formation in cultures of attached MC3T3 osteoprogenitor cells with or without a fibronectin coating. Calcium-phosphate mineral was analyzed by flame atomic absorption spectrophotometry, scanning electron microscopy (SEM)/electron dispersive X-ray microanalysis (EDAX) and Fourier transformed infrared spectroscopy (FTIR). RFGD and heat pretreatments produced a general pattern of increased total soluble calcium levels, although the effect of heat pretreatment was greater than that of RFGD. SEM/EDAX showed the presence of calcium-and phosphorus-containing particles on untreated and treated disks that were more numerous on fibronectin-coated disks. These particles were observed earliest (1 week) on RFGD-pretreated surfaces. FTIR analyses showed that the heat pretreatment produced a general pattern of increased levels of apatite mineral at 2–4 weeks; a greater effect was observed for fibronectin-coated disks compared to uncoated disks. The observed findings suggest that heat pretreatment of Ti6Al4V increased the total mass of the mineral formed in MC3T3 osteoprogenitor cell cultures more than RFGD while the latter pretreatment hastened the early deposition of mineral. These findings help to support the hypothesis that the pretreatments enhance the osteoinductive properties of the alloy. PMID:23494951
Atmospheric pressure glow discharge desorption mass spectrometry for rapid screening of pesticides in food.
Jecklin, Matthias Conradin; Gamez, Gerardo; Touboul, David; Zenobi, Renato
Flowing afterglow atmospheric pressure glow discharge tandem mass spectrometry (APGD-MS/MS) is used for the analysis of trace amounts of pesticides in fruit juices and on fruit peel. The APGD source was rebuilt after Andrade et al. (Andrade et al., Anal. Chem. 2008; 80: 2646-2653; 2654-2663) and mounted onto a hybrid quadrupole time-of-flight mass spectrometer. Apple, cranberry, grape and orange juices as well as fruit peel and salad leaves were spiked with aqueous solutions containing trace amounts of the pesticides alachlor, atrazine, carbendazim, carbofuran, dinoseb, isoproturon, metolachlor, metolcarb, propoxur and simazine. Best limits of determination (LODs) of pesticides in the fruit juices were achieved for metolcarb (1 microg/L in apple juice), carbofuran and dinoseb (2 microg/L in apple juice); for the analysis of apple skin best LODs were 10 pg/cm(2) of atrazine, metolcarb and propoxur which corresponds to an estimated concentration of 0.01 microg/kg apple, taking into account the surface area and the weight of the apple. The measured LODs were within or below the allowed maximum residue levels (MRLs) decreed by the European Union (1-500 microg/kg for pesticides in fruit juice and 0.01-5 microg/kg for apple skin). No sample pretreatment (extraction, pre-concentration, chromatographic separation) was necessary to analyze these pesticides by direct desorption/ionization using APGD-MS and to identify them using MS/MS. This makes APGD-MS a powerful high-throughput tool for the investigation of very low amounts of pesticides in fruit juices and on fruit peel/vegetable skin. PMID:18697232
Glow Discharge Plasma Demonstrated for Separation Control in the Low-Pressure Turbine
NASA Technical Reports Server (NTRS)
Ashpis, David e.; Hultgren, Lennart S.
Flow separation in the low-pressure turbine (LPT) is a major barrier that limits further improvements of aerodynamic designs of turbine airfoils. The separation is responsible for performance degradation, and it prevents the design of highly loaded airfoils. The separation can be delayed, reduced, or eliminated completely if flow control techniques are used. Successful flow control technology will enable breakthrough improvements in gas turbine performance and design. The focus of this research project was the development and experimental demonstration of active separation control using glow discharge plasma (GDP) actuators in flow conditions simulating the LPT. The separation delay was shown to be successful, laying the foundation for further development of the technologies to practical application in the LPT. In a fluid mechanics context, the term "flow control" means a technology by which a very small input results in a very large effect on the flow. In this project, the interest is to eliminate or delay flow separation on LPT airfoils by using an active flow control approach, in which disturbances are dynamically inserted into the flow, they interact with the flow, and they delay separation. The disturbances can be inserted using a localized, externally powered, actuating device, examples are acoustic, pneumatic, or mechanical devices that generate vibrations, flow oscillations, or pulses. A variety of flow control devices have been demonstrated in recent years in the context of the external aerodynamics of aircraft wings and airframes, where the incoming flow is quiescent or of a very low turbulence level. However, the flow conditions in the LPT are significantly different because there are high levels of disturbances in the incoming flow that are characterized by high free-stream turbulence intensity. In addition, the Reynolds number, which characterizes the viscous forces in the flow and is related to the flow speed, is very low in the LPT passages.
Enhancement of intensities in glow discharge mass spectrometry by using mixtures of argon and helium as plasma gases.
Lange, Britta; Matschat, Ralf; Kipphardt, Heinrich
Glow discharge mass spectrometry (GD-MS) is an excellent technique for fast multi-element analysis of pure metals. In addition to metallic impurities, non-metals also can be determined. However, the sensitivity for these elements can be limited due to their high first ionization potentials. Elements with a first ionization potential close to or higher than that of argon, which is commonly used as discharge gas in GD-MS analysis, are ionized with small efficiency only. To improve the sensitivity of GD-MS for such elements, the influence of different glow-discharge parameters on the peak intensity of carbon, chlorine, fluorine, nitrogen, phosphorus, oxygen, and sulfur in pure copper samples was investigated with an Element GD (Thermo Fisher Scientific) GD-MS. Discharge current, discharge gas flow, and discharge gas composition, the last of which turned out to have the greatest effect on the measured intensities, were varied. Argon-helium mixtures were used because of the very high potential of He to ionize other elements, especially in terms of the high energy level of its metastable states. The effect of different Ar-He compositions on the peak intensity of various impurities in pure copper was studied. With Ar-He mixtures, excellent signal enhancements were achieved in comparison with use of pure Ar as discharge gas. In this way, traceable linear calibration curves for phosphorus and sulfur down to the microg kg(-1) range could be established with high sensitivity and very good linearity using pressed powder samples for calibration. This was not possible when pure argon alone was used as discharge gas. PMID:17940753
Characteristics in the jet region of helium radio-frequency atmospheric-pressure glow discharge with array generators
NASA Astrophysics Data System (ADS)
Wang, Zhi-Bin; Nie, Qiu-Yue
The two-dimensional spatially extended atmospheric plasma arrays by many parallel radio-frequency glow discharge plasma jets packed densely, represent a feature option of large-scale low-temperature atmospheric plasma technologies with distinct capability of directed delivery of reactive species and good insusceptibility to sample variations. However, it is still a challenge to form plasma jet with large area of uniform active species on a downstream substrate due to the complex interactions between individual jets. This paper proposes to numerically study the strategy and mechanism of control/modulation for the array discharge to produce two-dimensional plasma uniformity in the downstream working area. In this work, a two dimensional fluid model is employed to investigate the characteristics in the jet region of helium radio-frequency atmospheric-pressure glow discharge (RF APGD) with array generators. The influences of upstream discharge characteristics, gas flow and their cooperative effects on the distribution of species densities, gas temperatures and the uniformity of active species in the material treating area is studied, and the essential strategy for the modulation method is acquired. The results will be significant for deep understanding of coupling behaviors of multiple plasma plumes in the RF APGD array and applications of the technology.
Linear and Nonlinear Dust Acoustic Waves, Shocks and Stationary Structures in a dc-Glow-Discharge Dusty Plasma
NASA Astrophysics Data System (ADS)
Merlino, Robert
In 1990, Rao, Shukla, and Yu (Planet. Space Sci. 38, 543) predicted the existence of the dust acoustic (DA) wave, a low-frequency (~ few Hz), compressional dust density wave that propagates through a dusty plasma at a phase speed ~ several cm/s. The DA wave was first observed by Chu et. al., (J. Phys. D: Appl. Phys. 27, 296, 1994) in an rf-produced dusty plasma, and by Barkan et. al., (Barkan et. al. Phys. Plasmas 2, 2161, 1995) who obtained video images of the DA wave trains using light scattering from a dust suspension confined in an anodic glow discharge plasma formed within a Q machine plasma. The dispersion relation for DAWs was measured by Thompson et. al., (Phys. Plasmas 4, 2331, 1997) in a dc glow discharge dusty plasma by modulating the discharge current at a set frequency. DAWs have been investigated by many groups both in weakly-coupled and strongly-coupled dusty plasmas (E. Thomas, Jr., Contrib. Plasma Phys. 49, 316, 2009). In most experiments where DA waves are present, the wave amplitude is relatively high, indicating that they are nonlinear. In this talk, results of our recent experiments on DAWs will be presented. The following experiments, performed in a dc glow-discharge dusty plasma will be described: (1) Observations of spontaneously excited nonlinear, cylindrical DAWs, which exhibit confluence of waves propagating at different speeds. (2) Investigations of self-steepening DAWs that develop into DA shocks with thicknesses comparable to the interparticle separation (Heinrich et. al., Phys. Rev. Lett. 103, 115001, 2009). (3) Measurements of the linear growth rates of DAWs excited in merging dust clouds. (4) The formation of stationary, stable dust density structures appearing as non-propagating DAWs (Heinrich et. al., Phys. Rev. E, in press, 2011). This work was performed in collaboration with S. H. Kim, J. R. Heinrich, and J. K. Meyer. Work supported by DOE Grant No. DE-FG01-04ER54795
Hysteresis in amplitudes of self-excited oscillations for co-axial electrode-geometry DC glow discharge plasma
Kumar, R.; Narayanan, R.; Prasad, Awadhesh
Hysteresis in amplitudes of the self-excited oscillations of the floating potential and discharge current is observed in an unmagnetized co-axial electrode-geometry DC glow discharge plasma system. The nonlinearities of these oscillations are studied using standard dynamical analysis tools. The characterization revealed the transition of low-amplitude high-frequency period-n oscillations to a large amplitude low frequency period-1 oscillations through a chaotic intermediate route. The transition of the low amplitude, high frequency period-n oscillations to chaotic type is observed to be linked to the dynamical change in the plasma system, i.e., after a negative differential resistance (NDR) region, whereas the transition from chaotic to period-1 is observed to be linked to a discharge current threshold.
Investigation of Meltblown Microfiber and Electrospun Nanofiber Fabrics Treated with a One Atmosphere Uniform Glow Discharge Plasma (OAUGDP)
NASA Astrophysics Data System (ADS)
Chen, Weiwei; Reece Roth, J.; Tsai, Peter P.-Y.
Nanofiber webs are made by the electrospinning (ES) process [1], which uses the repulsive electrostatic force to spin fibers from a polymer solution or melt at room temperature and low energy input. We have developed apparatus at the UT Textiles and Nonwovens Development Center (TANDEC) to produce fabrics with fiber diameters of tens of nanometers. This paper will report data on the distribution function of nanofiber diameters that were taken from digitized SEM images of the electrospun materials. It is also found in the tensile tests that the strength of the electrospun nanofiber fabrics is up to ten times that of the coarser meltblown material. The one atmosphere uniform glow discharge plasma (OAUGDP) developed at the UT Plasma Sciences Laboratory generates a normal glow electrical discharge at one atmosphere. This plasma has been used to treat meltblown and electrospun fabrics, with a resulting increase in surface energy [1]. We recently found that the surface energy of meltblown Nylon could be increased to 70 dynes/cm by five seconds of OAUGDP exposure, and was durable at this level for six months. Our results also show that Nylon and PU nanofiber fabrics can be exposed to the OAUGDP for treatment without significant damage for up to 10 seconds [1], a duration sufficient to produce important effects, including durable wettability. We will describe our progress in improving the properties of nanofiber fabrics using a variety of latest developments in OAUGDP reactor technology, including a new porous electrode that injects gases other than air to generate different active species for plasma treatment. [1] Tsai P. P.-Y., Chen W., Li X. and Roth J.R.: "Improving the Properties of Protective Clothing by Exposing Nanofiber Webs to a One Atmospheric Uniform Glow Discharge Plasma (OAUGDP)", National Science Foundation (NSF) Grantee¡¯s Workshop and Conference, Birmingham, Alabama, Jan. 6-9, 2003.
Two-dimensional hybrid Monte Carlo–fluid modelling of dc glow discharges: Comparison with fluid models, reliability, and accuracy
Eylenceoğlu, E.; Rafatov, I.; Kudryavtsev, A. A.
Two-dimensional hybrid Monte Carlo–fluid numerical code is developed and applied to model the dc glow discharge. The model is based on the separation of electrons into two parts: the low energetic (slow) and high energetic (fast) electron groups. Ions and slow electrons are described within the fluid model using the drift-diffusion approximation for particle fluxes. Fast electrons, represented by suitable number of super particles emitted from the cathode, are responsible for ionization processes in the discharge volume, which are simulated by the Monte Carlo collision method. Electrostatic field is obtained from the solution of Poisson equation. The test calculations were carried out for an argon plasma. Main properties of the glow discharge are considered. Current-voltage curves, electric field reversal phenomenon, and the vortex current formation are developed and discussed. The results are compared to those obtained from the simple and extended fluid models. Contrary to reports in the literature, the analysis does not reveal significant advantages of existing hybrid methods over the extended fluid model.
Glow discharge plasma treatment for surface cleaning and modification of metallic biomaterials.
Aronsson, B O; Lausmaa, J; Kasemo, B
Glow discharge plasma treatment is a frequently used method for cleaning, preparation, and modification of biomaterial and implant surfaces. The merits of such treatments are, however, strongly dependent on the process parameters. In the present work the possibilities, limitations, and risks of plasma treatment for surface preparation of metallic materials are investigated experimentally using titanium as a model system, and also discussed in more general terms. Samples were treated by different low-pressure direct current plasmas and analyzed using Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), atomic force microscopy, scanning electron microscopy, and light microscopy. The plasma system is a home-built, ultra-high vacuum-compatible system that allows sample introduction via a load-lock, and precise control of pressure, gas composition and flow rate, etc. This system allows uniform treatment of cylindrical and screw-shaped samples. With appropriate plasma parameters, argon plasma remove all chemical traces from former treatments (adsorbed contaminants and other impurities, and native oxide layers), in effect producing cleaner and more well-controlled surfaces than with conventional preparation methods. Removal (sputtering) rates up to 30 nm/min are possible. However, when inappropriate plasma parameters are used, the result may be increased contamination and formation of unintentional or undesired surface layers (e.g., carbides and nitrides). Plasma-cleaned surfaces provide a clean and reproducible starting condition for further plasma treatments to form well-controlled surface layers. Oxidation in pure O2 (thermally or in oxygen plasmas) results in uniform and stoichiometric TiO2 surface oxide layers of reproducible composition and thicknesses in the range 0.5-150 nm, as revealed by AES and XPS analyses. Titanium nitride layers were prepared by using N2 plasmas. While mild plasma treatments leave the surface microstructure unaffected
Argon gas concentration effects on nanostructured molybdenum nitride layer growth using 100 Hz pulsed dc glow discharge
NASA Astrophysics Data System (ADS)
Ikhlaq, U.; Ahmad, R.; Saleem, S.; Shah, M. S.; Umm-i-Kalsoom; Khan, N.; Khalid, N.
The effect of argon concentration (10%-40%) on the surface properties of molybdenum is studied in nitrogen-argon mixture using 100 Hz pulsed dc glow discharge. The analysis is carried out by using X-ray diffractometer (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and Vickers microhardness tester to investigate surface properties of the nitrided samples. XRD results exhibit the formation of molybdenum nitrides. Crystallite size analysis and SEM morphology confirm the growth of nanostructured molybdenum nitride layers. Moreover, significant increase in surface hardness (by a factor of about two times) is found when the sample is treated for 30% argon in nitrogen-argon mixed plasma.
Effect of the electric field of the anode sheath on the growth of aligned carbon nanotubes in a glow discharge
Pal', A. F.; Rakhimova, T. V.; Suetin, N. V.; Timofeev, M. A.; Filippov, A. V.
Arrays of aligned carbon nanotubes on silicon substrates were grown in the anode sheath of a dc glow discharge. In order to clarify the role of the electric field in the growth of nanotubes, numerical simulations of charged particle transport in the anode sheath were carried out in the drift-diffusion approximation. The distributions of the charged particle density and electric field are obtained. Possible mechanisms whereby the electric field influences the growth of aligned carbon nanotubes are analyzed. It is found that the nanotubes grow in the region in which the electric field is enhanced due to the depletion of positive ions in the anode sheath.
Ab initio and experimental studies of glow-discharge polymer used in Laser MégaJoule capsules
NASA Astrophysics Data System (ADS)
Colin-Lalu, Pierre; Huser, Gaël; Recoules, Vanina; Salin, Gwenael; CEA DAM DIF Team
Equations of state tables used in Initial Confinement Fusion capsule design tools are highly dependent on the cold curve in the multimegabar range. Original ab-initio molecular dynamic simulations were performed to get accurate cold curves of glow-discharge polymer (GDP) plastics. Furthermore the effect of oxygen absorption by GDP structure is studied on the cold curve, as well as its impact on the Hugoniot curves. Results are compared with Hugoniot experimental data obtained in a recent experiment at the LULI2000 laser facility in France. This study leads to improve equation of states knowledge of ablator materials, which is of primary importance for NIF and LMJ experiments.
Multi-scale dynamics of glow discharge plasma through wavelets: self-similar behavior to neutral turbulence and dissipation.
Giri, Bapun K; Mitra, Chiranjit; Panigrahi, Prasanta K; Iyengar, A N Sekar
The multiscale dynamics of glow discharge plasma is analysed through wavelet transform, whose scale dependent variable window size aptly captures both transients and non-stationary periodic behavior. The optimal time-frequency localization ability of the continuous Morlet wavelet is found to identify the scale dependent periodic modulations efficiently, as also the emergence of neutral turbulence and dissipation, whereas the discrete Daubechies basis set has been used for detrending the temporal behavior to reveal the multi-fractality of the underlying dynamics. The scaling exponents and the Hurst exponent have been estimated through wavelet based detrended fluctuation analysis, and also Fourier methods and rescale range analysis. PMID:25554055
Pulsed-gas glow discharge for ultrahigh mass resolution measurements with Fourier transform ion cyclotron resonance mass spectrometry
Watson, C.H.; Eyler, J.R.; Barshick, C.M.; Wronka, J.; Laukien, F.H.
A new pulsed-gas glow discharge (GD) source has been developed for use with an external ion source Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. With pulsed argon gas introduction into the GD source, the gas load and pressure in the mass analyzer region were greatly reduced; this resulted in improved mass resolution. Mass resolution of greater than 145000 (fwhm) has been achieved for Cu{sup +} ions from a brass sample, the highest reported for any type of GD mass spectrometer. The pulsed-gas GD source promises analytical usefulness for ultrahigh resolution measurements in GD mass spectrometry. 16 refs., 3 figs.
Disilane versus monosilane: a comparison of the properties of glow-discharge a-Si:H Films and solar cells
Delahoy, A.E.; Corderman, R.R.; Griffith, R.W.; Kampas, F.J.; Vanier, P.E.
The consequences of using disilane instead of silane for the glow-discharge deposition of a-Si:H solar cells have been studied. Deposition rates were increased fivefold by the use of disilane. The a-Si:H films have a higher hydrogen content, but otherwise are quite similar to silane produced films and possess the same type of gap states. Chlorosilanes, HCl, and oxysilanes were detected in the disilane by mass spectrometry and their influence on film and solar cell properties assessed. The problem of inadvertent dopant tails resulting from the higher deposition rate of the solar cells is identified.
High performance hydrogenated amorphous silicon solar cells made at a high deposition rate by glow discharge of disilane
Ohashi, Y.; Kenne, J.; Konagai, M.; Takahashi, K.
The deposition rate, electronic and optical properties of hydrogenated amorphous silicon films prepared from rf glow discharge decomposition of disilane (Si/sub 2/H/sub 6/) diluted in helium have been measured. These films show excellent electrical and optical properties and, most importantly, a high deposition rate coupled with satisfactory solar cell application was realized for the first time. At a deposition rate of 11 A/s, 5.47% and 6.5% conversion efficiencies were obtained with a first trial of n-i-p type solar cells deposited on SnO/sub 2//ITO glass and metal substrates, respectively.
Disilane versus monosilane: a comparison of the properties of glow-discharge a-Si:H films and solar cells
Delahoy, A.E.; Kampas, F.J.; Corderman, R.R.; Vanier, P.E.; Griffith, R.W.
The consequences of using disilane instead of silane for the glow-discharge deposition of a-Si:H solar cells have been studied. Deposition rates were increased fivefold by the use of disilane. The a-Si:H films have a higher hydrogen content, but otherwise are quite similar to silane produced films and possess the same type of gap states. Chlorosilanes, HCl, and oxysilanes were detected in the disilane by mass spectrometry and their influence on film and solar cell properties assessed. The problem of inadvertent dopant tails resulting from the higher deposition rate of the solar cells is identified.
Research Into Characteristics of X-Ray Emission Laser Beams from Solid-State Cathode Medium of High-Current Glow Discharge
NASA Astrophysics Data System (ADS)
Karabut, Alexander B.
X-ray emissions ranging 1.2-3.0 keV with dose rate up to 1.0 Gy/s have been registered in experiments with high-current Glow Discharge. The emissions energy and intensity depend on the cathode material, the kind of plasma-forming gas, and the discharge parameters. The experiments were carried out on the high-current glow discharge device using D2, H2, Kr, and Xe at pressure up to 10 Torr, as well as cathode samples made from Al, Sc, Ti, Ni, Nb, Zr, Mo, Pd, Ta, W, Pt, at current up to 500 mA, and discharge voltage of 500-2500 V. Two emission modes were revealed under the experiments: (1) Diffusion X-rays was observed as separate X-ray bursts (up to 5 × 105 bursts a second and up to 106 X-ray quanta in a burst), (2) X-rays in the form of laser microbeams (up to 104 beams a second and up to 1010 X-ray of quanta in a beam, angular divergence was up to 10-4, the duration of the separate laser beams must be τ = 3 × 10-13-3 × 10-14 s, the separate beam power must be 107-108 W). The emission of the X-ray laser beams occurred when the discharge occurred and within 100 ms after turning off the current. The results of experimental research into the characteristics of secondary penetrating radiation occurring when interacting primary X-ray beams from a solid-state cathode medium with targets made of various materials are reported. It was shown that the secondary radiation consisted of fast electrons. Secondary radiation of two types was observed: (1) The emission with a continuous temporal spectrum in the form of separate bursts with intensity up to 106 fast electrons a burst. (2) The emission with a discrete temporal spectrum and emission rate up to 1010 fast electrons a burst. A third type of the penetrating radiation was observed as well. This type was recorded directly by the photomultiplier placed behind of the target without the scintillator. The abnormal high penetrating ability of this radiation type requires additional research to explain. The obtained results
A lithium-fluoride flashover ion source cleaned with a glow discharge and irradiated with vacuum-ultraviolet radiation
NASA Astrophysics Data System (ADS)
Burns, E. J. T.; Woodworth, J. R.; Bieg, K. W.; Mehlhorn, T. A.; Stygar, W. A.; Sweeney, M. A.
We have studied methods of varying the ion species generated by a lithium-fluoride overcoated anode in a 0.5-MV magnetically insulated ion diode. We found that cleaning the anode surface with a 13.6-MHz rf glow discharge or illuminating the anode with a pulsed soft x-ray, vacuum-ultraviolet (XUV) radiation source just before the accelerator pulse significantly altered the ion species of the ion beam produced by the diode. The glow-discharge plasma removed adsorbates (carbon, hydrogen, and oxygen) from the surface of the LiF flashover source. The ions seen were lithium and hydrogen. Unfortunately, the diode impedance with a lithium-fluoride anode was high and the ion efficiency was low; however, XUV irradiation of the surface dramatically lowered the impedance by desorbing neutrals from the ion source via photon-stimulated desorption. Current densities of ten times the Child-Langmuir space-charge limit were achieved under XUV irradiation. In particular, ion currents increased by over a factor of 3 when 12 mJ/cm2 of XUV radiation was used. However, with XUV irradiation the largest fraction of ions were fluorine, oxygen, carbon, and hydrogen, not lithium.
Effect of hydrogen ratio on plasma parameters of N{sub 2}-H{sub 2} gas mixture glow discharge
El-Brulsy, R. A.; Abd Al-Halim, M. A.; Abu-Hashem, A.; Rashed, U. M.; Hassouba, M. A.
A dc plane glow discharge in a nitrogen-hydrogen (N{sub 2}-H{sub 2}) gas mixture has been operated at discharge currents of 10 and 20 mA. The electron energy distribution function (EEDF) at different hydrogen concentrations is measured. A Maxwellian EEDF is found in the positive column region, while in both cathode fall and negative glow regions, a non-Maxwellian one is observed. Langmuir electric probes are used at different axial positions, gas pressures, and hydrogen concentrations to measure the electron temperature and plasma density. The electron temperature is found to increase with increasing H{sub 2} concentration and decrease with increasing both the axial distance from the cathode and the mixture pressure. At first, with increasing distance from the cathode, the ion density decreases, while the electron density increases; then, as the anode is further approached, they remain nearly constant. At different H{sub 2} concentrations, the electron and ion densities decrease with increasing the mixture pressure. Both the electron and ion densities slightly decrease with increasing H{sub 2} concentration.
Development of a DC Glow Discharge Exhibit for the Demonstration of Plasma Behavior in a Magnetic Field
NASA Astrophysics Data System (ADS)
Bruder, Daniel
The DC Glow Discharge Exhibit is intended to demonstrate the effects a magnetic field produces on a plasma in a vacuum chamber. The display, which will be featured as a part of The Liberty Science Center's ``Energy Quest Exhibition,'' consists of a DC glow discharge tube and information panels to educate the general public on plasma and its relation to fusion energy. Wall posters and an information booklet will offer brief descriptions of fusion-based science and technology, and will portray plasma's role in the development of fusion as a viable source of energy. The display features a horse-shoe magnet on a movable track, allowing viewers to witness the effects of a magnetic field upon a plasma. The plasma is created from air within a vacuum averaging between 100-200 mTorr. Signage within the casing describes the hardware components. The display is pending delivery to The Liberty Science Center, and will replace a similar, older exhibit presently at the museum.
Determination of trace elements in high purity alumina powder by helium enhanced direct current glow discharge mass spectrometry
NASA Astrophysics Data System (ADS)
Jung, Sehoon; Kim, Sunhye; Hinrichs, Joachim
Trace impurities in high purity alumina powder were determined by fast flow direct current glow discharge mass spectrometry (GD-MS). The non-conductive samples were prepared with high purity graphite powder and used as a sample binder and as a secondary cathode. To improve the sensitivity of the GD-MS analysis, helium was introduced as an additional glow discharge gas to argon plasma. The quantification results of the GD-MS measurement were calculated by external calibration with matrix matched certified reference materials. The GD-MS results for the determination of Na, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn and Ga in the alumina samples agreed well with the certified values of a reference material and the results of chemical analysis using wet sample digestion with inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The GD-MS analysis is a rapid analysis technique to determine trace elements in non-conductive alumina to below mg·kg- 1 levels.
Sampling modulation technique in radio-frequency helium glow discharge emission source by use of pulsed laser ablation.
Naeem, Tariq Mahmood; Matsuta, Hideyuki; Wagatsuma, Kazuaki
An emission excitation source comprising a high-frequency diode-pumped Q-switched Nd:YAG laser and a radio-frequency powered glow discharge lamp is proposed. In this system sample atoms ablated by the laser irradiation are introduced into the lamp chamber and subsequently excited by the helium glow discharge plasma. The pulsed operation of the laser can produce a cyclic variation in the emission intensities of the sample atoms whereas the plasma gas species emit the radiation continuously. The salient feature of the proposed technique is the selective detection of the laser modulation signal from the rest of the continuous background emissions, which can be achieved with the phase sensitive detection of the lock-in amplifier. The arrangement may be used to estimate the emission intensity of the laser ablated atom, free from the interference of other species present in the plasma. The experiments were conducted with a 13.56 MHz radio-frequency (rf) generator operated at 80 W power to produce plasma and the laser at a wavelength of 1064 nm (pulse duration:34 ns, repetition rate:7 kHz and average pulse energy of about 0.36 mJ) was employed for sample ablation. The measurements resulted in almost complete removal of nitrogen molecular bands (N(2)(+) 391.44 nm). Considerable reduction (about 75%) in the emission intensity of a carbon atomic line (C I 193.03 nm) was also observed. PMID:15034707
Tritium Generation from the Interaction of a Glow Discharge Plasma with Metals and with a Magnetic Field
NASA Astrophysics Data System (ADS)
Romodanov, V. A.
We present results of our research on tritium generation through the bombardment of the surface of various metals by accelerated ions of hydrogen isotopes from a glow discharge plasma, with and without a magnetic field. The introduction of a magnetic field perpendicular to the sample surface results in an increase in the tritium activity, and in the tritium generation rate, of almost two orders of magnitude as compared to similar experiments run with no magnetic field. The largest tritium generation rates observed were obtained with the glow discharge operating in a magnetic field, and were in the range 109-1010 atom/s. This is higher than our background by three to four orders of magnitude. The use of a magnetic field has resulted in good reproducibility, and the development of a reliable tritium generation rate of about 1010 atom/s for tantalum, tungsten, and platinum. A new technique for the generation and measurement of excess heat is presented based on the transfusion of hydrogen isotopes through the metal wall of a hollow sample electrode toward the glow discharge. In the case of a vanadium cathode, the maximum excess thermal power is about 30% of the absorbed power. The generation of excess power is found to be maximized in the temperature 600-700 K for relative power, and 800-1000K for absolute power. The results of measurements support a nuclear origin for the tritium generation, as opposed to a conventional thermal activation explanation. Mass spectroscopic measurements show an increase in species with deuterium in discharge experiments with hydrogen gas and with deuterium gas. The tritium generation rate is found to increase with the addition of deuterium, but by an amount not commensurate with the amount of deuterium added. Measurements of the gamma spectrum indicate that positrons are not generated in the course of tritium generation. These observations allow us to assert that modified versions of p+p and p+d reactions are responsible for the
Numerical simulation of an oxygen-fed wire-to-cylinder negative corona discharge in the glow regime
NASA Astrophysics Data System (ADS)
Yanallah, K.; Pontiga, F.; Castellanos, A.
Negative glow corona discharge in flowing oxygen has been numerically simulated for a wire-to-cylinder electrode geometry. The corona discharge is modelled using a fluid approximation. The radial and axial distributions of charged and neutral species are obtained by solving the corresponding continuity equations, which include the relevant plasma-chemical kinetics. Continuity equations are coupled with Poisson's equation and the energy conservation equation, since the reaction rate constants may depend on the electric field and temperature. The experimental values of the current-voltage characteristic are used as input data into the numerical calculations. The role played by different reactions and chemical species is analysed, and the effect of electrical and geometrical parameters on ozone generation is investigated. The reliability of the numerical model is verified by the reasonable agreement between the numerical predictions of ozone concentration and the experimental measurements.
[Determination of aqueous potassium and sodium ions with liquid-phase diaphragm glow discharge-atomic emission spectrometry].
Liu, Yong-jun; Wang, Lei
The present paper described the determination of potassium and sodium ions with a liquid-phase diaphragm glow discharge emission spectroscopy (LDGD-AES) in aqueous solution. The discharge was formed in a pin hole on a dielectric diaphragm interposed between two submerged graphite electrodes. Effects of applied voltage and the addition of organic additive methanol on the determination were examined. It was found that increasing the applied voltage and adding of methanol can increase the detection sensitivity and decrease the detection limit. Limits of detection for K and Na were 0. 007 and 0. 001 mg x L(-1) under the applied voltage of 850 V and addition of 0.6%-0.8% methanol, respectively. It was demonstrated that the LDGD-AES is a promising technique in measurements of metal ions in aqueous solution, because no optical interferences from the electrodes and the background molecular bands from air were found. PMID:24369674
Erosion of a-C:H films deposited on W, Mo, and stainless steel under interaction with air glow discharge
NASA Astrophysics Data System (ADS)
Zalavutdinov, R. Kh.; Gorodetsky, A. E.; Bukhovets, V. L.; Zakharov, A. P.; Mazul, I. V.
An air direct current glow discharge with a hollow cathode was used as source of chemically active oxygen for selective removal of amorphous hydrogenated (a-C:H) films deposited on W, Mo, and stainless steel. The films were removed both directly in the discharge and afterglow region. The film erosion rates depend on the sample position relatively to plasma and decrease in the order: hollow cathode, positive column, afterglow region. It was shown that primary (1-3 nm) continuous amorphous and secondary (1-30 nm) island-like oxide films were formed on the metal surfaces after removal of the a-C:H films. Polycrystalline island-like oxide films were generated due to recrystallization of the primary films. Material oxidation suppression was caused by reactions of oxygen ion neutralization and atomic oxygen recombination on metals.
Characteristics of sheath-driven tangential flow produced by a low-current DC surface glow discharge plasma actuator
NASA Astrophysics Data System (ADS)
Shin, Jichul; Shajid Rahman, Mohammad
An experimental investigation of low-speed flow actuation at near-atmospheric pressure is presented. The flow actuation is achieved via low-current ( \\lesssim 1.0 mA) continuous or pulsed DC surface glow discharge plasma. The plasma actuator, consisting of two sharp-edged nickel electrodes, produces a tangential flow in a direction from anode to cathode, and is visualized using high-speed schlieren photography. The induced flow velocity estimated via the schlieren images reaches up to 5 m/s in test cases. The actuation capability increases with pressure and electrode gap distances, and the induced flow velocity increases logarithmically with the discharge power. Pulsed DC exhibits slightly improved actuation capability with better directionality. An analytic estimation of induced flow velocity obtained based on ion momentum in the cathode sheath and gas dynamics in one-dimensional flow yields values similar to those measured.
Grassroots Advancement Plasma Physics: The Creation of a Dc Glow Discharge Tube for a high school classroom
NASA Astrophysics Data System (ADS)
Onumah, Henrietta; Sheth, Niraj; Gershman, Sophia; Post Zwicker, Andrew
The objective of the project is to create a safe, affordable, portable, computer interactive, and multifunctional DC glow discharge tube for use in a typical high school physics classroom. Our goal is to use this device not only to capture and cerate interest in plasma physics but as a tool to engage students in an active exploration of a variety of physics topics. We present the design, operation and labs created with our discharge tube. We are creating a selection of labs ranging from current/voltage relationships to spectroscopy that can be done on our setup. We have evaluated the vacuum chamber material- glass vs. plastic, our electrode spacing- a fixed vs. variable, external electronics with an emphasis on the power supply, safety and ease of use. Our design is an accessible 6 inch long tube with an inner diameter of 2 inches, which attains low pressure of about 20- 40 mTorr and is computer interactive.
On line vapor generation of osmium based on solution cathode glow discharge for the determination by ICP-OES.
Zhu, Zhenli; Huang, Chunying; He, Qian; Xiao, Qing; Liu, Zhifu; Zhang, Suicheng; Hu, Shenghong
A novel plasma induced vapor generation method is proposed to determine osmium in solutions. Without any chemical oxidizing agents, osmium ion can be readily converted to volatile osmium tetraoxide vapor in the solution cathode glow discharge (SCGD) system. The generated osmium vapor is then transported to inductively coupled plasma for determination by optical emission spectrometry. The influences of background electrolyte, carrier gas flow rate, sample flow rate, ICP power and discharge current were investigated. The analytical performances of this proposed technique were evaluated under optimized conditions. The detection limit of Os was calculated to be 0.51 ng mL(-1). The reproducibility, expressed as the relative standard deviation (n=11) of a 2.0 μg mL(-1) standard solution, was 1.9%. This SCGD induced vapor generation is sensitive and simple, oxidation reagents free, providing an alternative analytical method for measuring Os in geological or environmental water samples. PMID:23598105
Etching of uranium dioxide in nitrogen trifluoride RF plasma glow discharge
NASA Astrophysics Data System (ADS)
Veilleux, John Mark
A series of room temperature, low pressure (10.8 to 40 Pa), low power (25 to 210 W) RF plasma glow discharge experiments with UO2 were conducted to demonstrate that plasma treatment is a viable method for decontaminating UO2 from stainless steel substrates. Experiments were conducted using NF3 gas to decontaminate depleted uranium dioxide from stainless-steel substrates. Results demonstrated that UO2 can be completely removed from stainless-steel substrates after several minutes processing at under 200 W. At 180 W and 32.7 Pa gas pressure, over 99% of all UO2 in the samples was removed in just 17 minutes. The initial etch rate in the experiments ranged from 0.2 to 7.4 mum/min. Etching increased with the plasma absorbed power and feed gas pressure in the range of 10.8 to 40 Pa. A different pressure effect on UO2 etching was also noted below 50 W in which etching increased up to a maximum pressure, ˜23 Pa, then decreased with further increases in pressure. A computer simulation, CHEMKIN, was applied to predict the NF3 plasma species in the experiments. The code was validated first by comparing its predictions of the NF3 plasma species with mass spectroscopy etching experiments of silicon. The code predictions were within +/-5% of the measured species concentrations. The F atom radicals were identified as the primary etchant species, diffusing from the bulk plasma to the UO2 surface and reacting to form a volatile UF6, which desorbed into the gas phase to be pumped away. Ions created in the plasma were too low in concentration to have a major effect on etching, but can enhance the etch rate by removing non-volatile reaction products blocking the reaction of F with UO2. The composition of these non-volatile products were determined based on thermodynamic analysis and the electronic structure of uranium. Analysis identified possible non-volatile products as the uranium fluorides, UF2-5, and certain uranium oxyfluorides UO2F, UO2F2, UOF3, and UOF 4 which form over the
Improved performance of the pulsed copper-vapor-laser CuCl-vapor-laser with a compact device by applying an ac continuous-glow-discharge
NASA Astrophysics Data System (ADS)
Saito, H.; Taniguchi, H.; Ohgami, K.
An additional continuous-glow-discharge was applied to the aperiodic pulsed CuCl-vapor laser. The experimental results exhibited an increase of up to 60 percent the laser-output average power at the maximum point, an increase of 1.5 times the peak power and pulse repetition frequency, and twice the pulse width in the laser oscillation against the laser without the continuous-glow discharge. Further, the additional technique led the CuCl-vapor-laser to operate in the higher operating-temperature region.
Influence of Parameters of the Glow Discharge on Change of Structure and the Isotope Composition of the Cathode Materials
NASA Astrophysics Data System (ADS)
Savvatimova, I. B.; Gavritenkov, D. V.
Results of examinations of changes in structure, element, and isotope composition of cathodes after the glow discharge exposure in hydrogen, deuterium, argon, and xenon are submitted. The voltage of the discharge was less than 1000 V and the current was 5-150 mA. Samples before and after ions bombardment in the glow discharge were explored by the methods of mass spectrometry: the secondary ions (SIMS), the secondary ions with additional ionization of neutral sprayed particles (SNMS), spark (SMS), and thermo-ionization (TIMS), and also methods of energy dispersion X-ray spectral analysis (EDX). The alpha-, beta-, gamma- emission, and gamma- spectrometry for radioactive uranium specimens were also carried out before and after experiments in the glow discharge. Changes in structure, isotope, and element composition of the cathode samples depend on current density, integrated ions flow (fluence of ions), kind of irradiating ions and other experimental conditions. Attempts are made to estimate qualitatively and quantitatively the role of each of the parameters on intensity of the observed changes in cathode composition. It is shown that the maximum changes in structure, chemical and isotope composition of the cathode material occur in "hot points," such as craters from microexplosions, phase segregations, blisters and other new formations. Various methods of the analysis revealed that the basic elements Mg, O, Si, Al, and Ca with quantities up to per cents and more were prevailing in these zones and not found out before experiment. The greatest changes of the isotope relations were observed for iron, calcium, silicon, chromium after experiments with pulsing current. EDX method finds out the elements missing in the samples before experiment such as cadmium, strontium, tin. The isotopes with mass number 59 (Co 100%), 55 (Mn 100%), 45 (Sc 100%) are also not found in initial samples and background measurement by TIMS method. Results of changes in the element and isotope
The back-diffusion effect of air on the discharge characteristics of atmospheric-pressure radio-frequency glow discharges using bare metal electrodes
NASA Astrophysics Data System (ADS)
Sun, Wen-Ting; Liang, Tian-Ran; Wang, Hua-Bo; Li, He-Ping; Bao, Cheng-Yu
Radio-frequency (RF), atmospheric-pressure glow discharge (APGD) plasmas using bare metal electrodes have promising prospects in the fields of plasma-aided etching, deposition, surface treatment, disinfection, sterilization, etc. In this paper, the discharge characteristics, including the breakdown voltage and the discharge voltage for sustaining a stable and uniform α mode discharge of the RF APGD plasmas are presented. The experiments are conducted by placing the home-made planar-type plasma generator in ambient and in a vacuum chamber, respectively, with helium as the primary plasma-forming gas. When the discharge processes occur in ambient, particularly for the lower plasma-working gas flow rates, the experimental measurements show that it is the back-diffusion effect of air in atmosphere, instead of the flow rate of the gas, that results in the obvious decrease in the breakdown voltage with increasing plasma-working gas flow rate. Further studies on the discharge characteristics, e.g. the luminous structures, the concentrations and distributions of chemically active species in plasmas, with different plasma-working gases or gas mixtures need to be conducted in future work.
Diagnostics of glow discharges used to produce hydrogenated amorphous silicon films. Subcontract report, 15 April 1984-14 April 1985
Gallagher, A; Scott, J
Measurements of monosilane and disilane radicals were made at the surface of dc glow discharges (GD) in pure silane and silane-argon mixtures. These observations were interpreted as discharge kinetic models. It was inferred that the dominant radical, SiH/sub 3/, is produced in the gas and is primarily responsible for film growth. The heavier radicals observed in the gas appear to be a consequence of surface reactions, as is the disilane, a major product of the monosilane decomposition. A detailed model of the ion chemistry in the discharge was formulated to derive theoretical distributions of ions at the cathodes of low-pressure dc discharges. Chemical vapor deposition (CVD) rates of silane and disilane, measured previously in the laboratory, have now also been interpreted in detail to yield a self-consistent model for the CVD process. This model identifies and quantifies the role of H/sub 2/ as an inhibitor of silane GD and CVD deposition. Implications of these discoveries to deposition rates and film properties are discussed.
The effect of frequency on atmospheric pressure glow discharge in a pin-to-plate gap sustained by a resonant power supply
NASA Astrophysics Data System (ADS)
Wang, Yong Sheng; Ding, Wei Dong; Wang, Ya Nan; Wang, Jia Chen; Li, Fang; Fan, Chuan
More and more researchers have been attracted to the research of atmospheric pressure glow discharge (APGD) because of its great prospect in numerous industrial applications. Nevertheless, almost all of the industrial applications are based on achievement of stable, large-volume, and uniform APGD. In a previous study, stable filamentary APGD was obtained by applying a resonant power supply between pin-to-plate electrodes which could limit the peak value of discharge current to supress the glow-to-arc transition through a series-wound resonance principle. The filamentary APGD is centimeter-level in the length but only several millimeters in diameter. Therefore, in order to obtain large-volume and uniform APGD, it is significant to study how to diffuse filamentary APGD in radial direction. With the increasing resonant frequency of alternating current discharge, excited particles (mainly including energetic electrons and trapped ions left from the previous half-cycle discharge) in the electrodes gap increase, which benefits obtaining stable self-sustaining APGD. In this paper, mechanism and law of the influence of resonant frequency on the diffusion of filamentary APGD in ambient air were studied. By comparing the photos of discharge plasma and waveforms of the discharge voltage and current, it is found that the volume of the glow discharge plasma enlarges as the resonant frequency of the power supply increases. It is very significant and anticipating to study how to obtain stable, large-volume, and uniform APGD in ambient air by the resonant power supply.
Evaluation of the stiffness and friction of Ti6Al4V ELI treated by glow discharge nitriding
NASA Astrophysics Data System (ADS)
Tavera, J. R.; Peña Ballesteros, D. Y.; Estupiñán Duran, H. A.
In this study, an evaluation of the elastic-plastic surface hardening on Ti6Al4V ELI titanium nitride films obtained by glow discharge method was carried out by nanoindentation tests according to the standard ISO 14577. The nanotribological properties (metal-metal) were also evaluated using the pin-on-disc system Ti6Al4V surface deposition ELI with nitrogen, obtaining a correlation between the coefficient of friction of Ti6Al4V ELI treated by PVD and the Young's modulus of the respective substrate modified by PVD. To characterize the substrate for the characterization tests, scanning electron microscopy, atomic force microscopy and X-ray diffraction and contact angle were carried out. The results demonstrated that the substrates nitrided improved mechanical and tribological properties, hardness, Young's modulus and coefficient of friction, making the alloy Ti6Al4V ELI support axial loads in tension and compression.
Impurity Studies of Cd(0.8)Zn(0.2)Te Crystals Using Photoluminescence and Glow Discharge Mass Spectroscopy
NASA Technical Reports Server (NTRS)
Su, Ching-Hua; Lehoczky, Sandor L.; Scripa, Rosalie N.
Cd(1-x)Zn(x)Te semiconductor crystal is a highly promising material for room temperature x- and gamma-ray detector applications because of its high resistivity, long carrier lifetime, and relatively high hole and electron mobilities. This paper reports the investigation of the impurities in several Cd(1-x)Zn(x)Te (x = 0.20) crystals grown using the vertical Bridgman method under a Cd overpressure. The impurity concentrations were measured using glow discharge mass spectroscopy (GDMS). The energy states of the impurities were studied using photoluminescence (PL) spectroscopy at liquid helium temperature. The PL spectra showed a series of sharp high energy lines which are associated with free excitons and excitons bound to impurities as donors and acceptors in the crystals. The impurities also contributed to donor-acceptor pair recombination. The correlation between the GDMS and PL results will be reported.
Canard and mixed mode oscillations in an excitable glow discharge plasma in the presence of inhomogeneous magnetic field
NASA Astrophysics Data System (ADS)
Shaw, Pankaj Kumar; Sekar Iyengar, A. N.; Nurujjaman, Md.
We report on the experimental observation of canard orbit and mixed mode oscillations (MMOs) in an excitable glow discharge plasma induced by an external magnetic field perturbation using a bar magnet. At a small value of magnetic field, small amplitude quasiperiodic oscillations were excited, and with the increase in the magnetic field, large amplitude oscillations were excited. Analyzing the experimental results, it seems that the magnetic field could be playing the role of noise for such nonlinear phenomena. It is observed that the noise level increases with the increase in magnetic field strength. The experimental results have also been corroborated by a numerical simulation using a FitzHugh-Nagumo like macroscopic model derived from the basic plasma equations and phenomenology, where the noise has been included to represent the internal plasma noise. This macroscopic model shows MMO in the vicinity of the canard point when an external noise is added.
Canard and mixed mode oscillations in an excitable glow discharge plasma in the presence of inhomogeneous magnetic field
Shaw, Pankaj Kumar Sekar Iyengar, A. N.
We report on the experimental observation of canard orbit and mixed mode oscillations (MMOs) in an excitable glow discharge plasma induced by an external magnetic field perturbation using a bar magnet. At a small value of magnetic field, small amplitude quasiperiodic oscillations were excited, and with the increase in the magnetic field, large amplitude oscillations were excited. Analyzing the experimental results, it seems that the magnetic field could be playing the role of noise for such nonlinear phenomena. It is observed that the noise level increases with the increase in magnetic field strength. The experimental results have also been corroborated by a numerical simulation using a FitzHugh-Nagumo like macroscopic model derived from the basic plasma equations and phenomenology, where the noise has been included to represent the internal plasma noise. This macroscopic model shows MMO in the vicinity of the canard point when an external noise is added.
Influence of Operating Parameters on Surface Properties of RF Glow Discharge Oxygen Plasma Treated TiO2/PET Film for Biomedical Application
Thin transparent titania (TiO2) films were coated on the surface of flexible poly (ethylene terephthalate) (PET) surface using standard sol gel techniques. The TiO2/PET thin film surfaces were further modified by exposing the films to a RF glow discharge oxygen plasma. The exposu...
Final Report DE-FG02-00ER54583: "Physics of Atmospheric Pressure Glow Discharges" and "Nanoparticle Nucleation and Dynamics in Low-Pressure Plasmas"
Uwe Kortshagen; Joachim Heberlein; Steven L. Girshick
This project was funded over two periods of three years each, with an additional year of no-cost extension. Research in the first funding period focused on the physics of uniform atmospheric pressure glow discharges, the second funding period was devoted to the study of the dynamics of nanometer-sized particles in plasmas.
A Study of a Striated Positive Column after Ethanol Impurity Injection in an Air DC Glow Discharge
NASA Astrophysics Data System (ADS)
Berzak, Laura; Post Zwicker, Andrew
In a glow discharge when ethanol (CH3CH2OH) was injected, a series of atypical striations formed through the positive column. When the pressure decreased as the ethanol evaporated and was evacuated by the vacuum pump, this behavior decayed away until only an anode glow or normal discharge remained. Varying interelectrode spacings and quantities of ethanol yielded similar patterns. The typical evolution as the pressure decreased consisted of a visible traveling wave traveling from the anode to the cathode followed by numerous, thin ( 1.6 mm) striations evenly spaced down the entire length of the positive column. These, shifted back toward the anode and transformed into bent striations with the tip of the 'V' pointing toward the cathode, and finally, the 'V' striations grouped into fours and took on the appearance of beats. The unusual 'V' striations may be due in part to a contraction of the column, causing the equipotential surfaces to shift from smooth convex to the observed striation shape. The conditions for this contraction effect include a nonlinearly increasing dependence of electron production rate on electron density and a bulk recombination rate higher than that at the tube walls. Visible emission spectra indicated the presence of carbon monoxide (CO), signifying that the striations are due to not only vibrational excitation of the ethanol molecule but also to decomposition and subsequent excitation of the decomposition products as well. One possible mechanism of decomposition is the formation of a radical cation from the ethanol molecule and the ensuing loss of a proton to yield formaldehyde; this then would follow an analogous decomposition to produce carbon monoxide. Thus, there may exist additional charged species which can then contribute to the unique observations. Further analysis, if possible, will include higher temporal resolution spectroscopy and a detailed model of the positive column under these specific conditions.
The micro-discharge family (dark, corona, and glow-discharge) for analytical applications realized by dielectric barriers.
Franzke, J
The similarity principles of electric plasmas, and the current-voltage characteristics of the most prominent kinds of discharges used for analytical applications, are discussed. Most of the discharges can be miniaturized, and some of the analytical applications of different discharges can be realized by use of dielectric barriers for analytical applications, for example element spectrometry, as an ionization source for ion-mobility spectrometry or organic mass spectrometry, and as an electrospray ionization source. PMID:19434400
FAST TRACK COMMUNICATION: Contrasting characteristics of sub-microsecond pulsed atmospheric air and atmospheric pressure helium-oxygen glow discharges
NASA Astrophysics Data System (ADS)
Walsh, J. L.; Liu, D. X.; Iza, F.; Rong, M. Z.; Kong, M. G.
Glow discharges in air are often considered to be the ultimate low-temperature atmospheric pressure plasmas for numerous chamber-free applications. This is due to the ubiquitous presence of air and the perceived abundance of reactive oxygen and nitrogen species in air plasmas. In this paper, sub-microsecond pulsed atmospheric air plasmas are shown to produce a low concentration of excited oxygen atoms but an abundance of excited nitrogen species, UV photons and ozone molecules. This contrasts sharply with the efficient production of excited oxygen atoms in comparable helium-oxygen discharges. Relevant reaction chemistry analysed with a global model suggests that collisional excitation of O2 by helium metastables is significantly more efficient than electron dissociative excitation of O2, electron excitation of O and ion-ion recombination. These results suggest different practical uses of the two oxygen-containing atmospheric discharges, with air plasmas being well suited for nitrogen and UV based chemistry and He-O2 plasmas for excited atomic oxygen based chemistry.
Degradation of bisphenol A and formation of hydrogen peroxide induced by glow discharge plasma in aqueous solutions.
Wang, Lei; Jiang, Xuanzhen; Liu, Yongjun
Degradation of bisphenol A (BPA) and simultaneous formation of hydrogen peroxide induced by glow discharge plasma in contact with aqueous solution were investigated. Experimental results indicated that the BPA degradation rate was higher in sodium chloride solution than that in sodium sulfate or phosphate solutions. However, the formation rates of hydrogen peroxide were on the opposite case. Both the BPA removal and the hydrogen peroxide production rates decreased in the presence of hydroxyl radical scavengers, indicating that hydroxyl radicals are the most probable oxidants responsible for BPA degradation and the precursors of hydrogen peroxide. Ferric ion showed better catalytic effect than that of ferrous ion, suggesting that the ferric ion was reduced by the intermediates formed during BPA degradation, which was confirmed by following the production of ferrous ion in the system. TOC of the solution gradually reduced with discharge time; however, without catalysts, the solution COD increased with discharge time and sharply decreased in the presence of iron salts. The major intermediate products were identified by LC/MS and the possible degradation mechanism was discussed. PMID:18082947
Doppler spectroscopy of hydrogen Balmer lines in a hollow cathode glow discharge in ammonia and argon-ammonia mixture
Sisovic, N. M.; Konjevic, N.
The results of Doppler spectroscopy of hydrogen Balmer lines from a stainless steel (SS) and copper (Cu) hollow cathode (HC) glow discharge in ammonia and argon-ammonia mixture are reported. The experimental profiles in ammonia discharge are fitted well by superposing three Gaussian profiles. The half widths, in energy units, of narrow and medium Gaussians are in the ranges 0.3-0.4 eV and 3-4 eV, respectively, for both hollow cathodes what is expected on the basis of earlier electron beam{yields}NH{sub 3} experiments. The half widths of the largest Gaussian in ammonia are 46 and 55 eV for SS and Cu HC, respectively. In argon-ammonia discharge, three Gaussians are also required to fit experimental profiles. While half widths of narrow and medium Gaussians are similar to those in ammonia, the half widths of the largest Gaussians are 35 and 42 eV for SS and Cu HC, respectively. The half widths of the largest Gaussians in ammonia and in argon-ammonia mixture indicate the presence of excessive Doppler broadening.
Experimental evidence of intermittent chaos in a glow discharge plasma without external forcing and its numerical modelling
Ghosh, S. Kumar Shaw, Pankaj; Sekar Iyengar, A. N.; Janaki, M. S.; Saha, Debajyoti; Michael Wharton, Alpha
Intermittent chaos was observed in a glow discharge plasma as the system evolved from regular type of relaxation oscillations (of larger amplitude) to an irregular type of oscillations (of smaller amplitude) as the discharge voltage was increased. Floating potential fluctuations were analyzed by different statistical and spectral methods. Features like a gradual change in the normal variance of the interpeak time intervals, a dip in the skewness, and a hump in the kurtosis with variation in the control parameter have been seen, which are strongly indicative of intermittent behavior in the system. Detailed analysis also suggests that the intrinsic noise level in the experiment increases with the increasing discharge voltage. An attempt has been made to model the experimental observations by a second order nonlinear ordinary differential equation derived from the fluid equations for an unmagnetized plasma. Though the experiment had no external forcing, it was conjectured that the intrinsic noise in the experiment could be playing a vital role in the dynamics of the system. Hence, a constant bias and noise as forcing terms were included in the model. Results from the theoretical model are in close qualitative agreement with the experimental results.
The glow discharge inception and post-discharge relaxation of charged and neutral active particles in synthetic air at low pressure
NASA Astrophysics Data System (ADS)
Jovanović, A. P.; Marković, V. Lj; Stamenković, S. N.; Stankov, M. N.
The study of dc glow discharge inception and post-discharge relaxation of charged and neutral active particles in synthetic air at low pressure is presented. The breakdown time delay dependence as a function of relaxation time \\overline{{{t}\\text{d}}}(τ ) (the memory curve) is measured and modelled from milliseconds to the saturation region determined by the cosmic rays and natural radioactivity level. Due to fast conversion \\text{N}2++{{\\text{O}}2}\\to {{\\text{N}}2}+\\text{O}2+ , relaxation of dc discharge in synthetic air in the time interval from one to about ninety milliseconds is dominated by the diffusion decay of molecular oxygen {{O}}_2^ + ions. The change of regimes, from ambipolar to the free diffusion limit, is investigated and the variation of effective diffusion coefficients is determined. The late relaxation is explained by the kinetics of nitrogen atoms, recombining on the surfaces of gas discharge tube and stainless steel electrodes and relevant surface recombination coefficients are determined.
Diagnostics of a glow discharge used to produce hydrogenated amorphous silicon films. Final subcontract report
Gallagher, A.
This report and recent publications cited summarize our measurements of the neutral radicals produced in pure silane discharges, our measurements of the interaction of silane with a growing amorphous silicon surface, qualitative models of discharge neutral radical chemistry, and quantitative models of dc discharge ion chemistry. All radicals of the monosilane and disilane groups have been measured and are reported as a function of discharge parameters, but not yet for the full range of parameters that must be investigated for detailed analysis. Observations of the reaction of SiH/sub 4/ with a hot amorphous silicon surface are given. These are closely related to the dominant discharge film deposition mechanism of SiH/sub 3/ reacting with a hydrogen covered amorphous silicon surface and a surface reaction model is suggested that explains some but not all of our data. The dc discharge model is used to obtain quantitative predictions of the ion species at the cathode surface of a dc discharge. This is compared to observations and used to explain the observations at our laboratory and other laboratories. We conclude that most but not all features of the ion chemistry in dc discharges of pure silane can be relatively well understood from this model.
Multiple solutions in the theory of direct current glow discharges: Effect of plasma chemistry and nonlocality, different plasma-producing gases, and 3D modelling
Almeida, P. G. C.; Benilov, M. S.
The work is aimed at advancing the multiple steady-state solutions that have been found recently in the theory of direct current (DC) glow discharges. It is shown that an account of detailed plasma chemistry and non-locality of electron transport and kinetic coefficients results in an increase of the number of multiple solutions but does not change their pattern. Multiple solutions are shown to exist for discharges in argon and helium provided that discharge pressure is high enough. This result indicates that self-organization in DC glow microdischarges can be observed not only in xenon, which has been the case until recently, but also in other plasma-producing gases; a conclusion that has been confirmed by recent experiments. Existence of secondary bifurcations can explain why patterns of spots grouped in concentric rings, observed in the experiment, possess in many cases higher number of spots in outer rings than in inner ones.
Improved hydrogen ionization rate in enhanced glow discharge plasma immersion ion implantation by enlarging the interaction path using an insulating tube
Wang Zhuo; Zhu Ying; Li Liuhe; He Fushun; Dun Dandan; Li Fen; Lu Qiuyuan; Fu, Ricky K. Y.; Chu, Paul K.
A small pointed hollow anode and large tabular cathode are used in enhanced glow discharge plasma immersion ion implantation (EGD-PIII). Electrons are repelled from the substrate by the electric field formed by the negative voltage pulses and concentrate in the vicinity of the anode to enhance the self-glow discharge process. To extend the application of EGD-PIII to plasma gases with low ionization rates, an insulating tube is used to increase the interaction path for electrons and neutrals in order to enhance the discharge near the anode. Results obtained from numerical simulation based on the particle-in-cell code, finite element method, and experiments show that this configuration enhances the ionization rate and subsequent ion implant fluence. The process is especially suitable for gases that have low ionization rates such as hydrogen and helium.
Complex dynamics of a dc glow discharge tube: Experimental modeling and stability diagrams
Pugliese, Eugenio; Meucci, Riccardo; Euzzor, Stefano; Freire, Joana G.; Gallas, Jason A. C.
We report a detailed experimental study of the complex behavior of a dc low-pressure plasma discharge tube of the type commonly used in commercial illuminated signs, in a microfluidic chip recently proposed for visible analog computing, and other practical devices. Our experiments reveal a clear quasiperiodicity route to chaos, the two competing frequencies being the relaxation frequency and the plasma eigenfrequency. Based on an experimental volt-ampere characterization of the discharge, we propose a macroscopic model of the current flowing in the plasma. The model, governed by four autonomous ordinary differential equations, is used to compute stability diagrams for periodic oscillations of arbitrary period in the control parameter space of the discharge. Such diagrams show self-pulsations to emerge remarkably organized into intricate mosaics of stability phases with extended regions of multistability (overlap). Specific mosaics are predicted for the four dynamical variables of the discharge. Their experimental observation is an open challenge. PMID:25677058
Dissociation and product formation in NF sub 3 radio-frequency glow discharges
Hargis, P.J. Jr.; Greenberg, K.E. )
Laser Raman spectroscopy was used to measure NF{sub 3} dissociation and N{sub 2} formation in the active volume of 13.56-MHz NF{sub 3} radio-frequency (rf) discharges. Gating the rf discharge suppressed optical emission, allowing NF{sub 3} and N{sub 2} Raman measurements at rf powers where N{sub 2} production was expected to be significant. Greater than 90% dissociation of the NF{sub 3} was observed in a 750 mTorr discharge at rf power densities on the order of 1 W/cm{sup 2} , yet less than 50 mTorr of N{sub 2} was produced. NF was the only other nitrogen containing species detected in the active volume of the discharge.
Multiple solutions in the theory of dc glow discharges and cathodic part of arc discharges. Application of these solutions to the modeling of cathode spots and patterns: a review
NASA Astrophysics Data System (ADS)
Benilov, M. S.
A new class of stationary solutions in the theory of glow discharges and plasma-cathode interaction in ambient-gas arc discharges has been found over the past 15 years. These solutions exist simultaneously with the solution given in textbooks, which describes a discharge mode with a uniform or smooth distribution of current over the cathode surface, and describes modes with various configurations of cathode spots: normal spots on glow cathodes, patterns of multiple spots recently observed on cathodes of glow microdischarges and spots on arc cathodes. In particular, these solutions show that cathode spots represent a manifestation of self-organization caused by basic mechanisms of the near-cathode space-charge sheath; another illustration of the richness of the gas discharge science. As far as arc cathodes are concerned, the new solutions have proved relevant for industrial applications. This work is dedicated to reviewing the multiple solutions obtained to date, their systematization, and analysis of their properties and physical meaning. The treatment is performed in the context of general trends of self-organization in bistable nonlinear dissipative systems, which allows one to consider glow discharges or arc-cathode interaction within a single physically transparent framework without going into mathematical details and offers a possibility of systematic computation of the multiple solutions. Relevant computational aspects and experimental data are discussed.
Plasma Diagnostics For The Investigation of Silane Based Glow Discharge Deposition Processes
NASA Astrophysics Data System (ADS)
Mataras, Dimitrios
In this work is presented the study of microcrystalline silicon PECVD process through highly diluted silane in hydrogen discharges. The investigation is performed by applying different non intrusive plasma diagnostics (electrical, optical, mass spectrometric and laser interferometric measurements). Each of these measurements is related to different plasma sub-processes (gas physics, plasma chemistry and plasma surface interaction) and compose a complete set, proper for the investigation of the effect of external discharge parameters on the deposition processes. In the specific case these plasma diagnostics are applied for prospecting the optimal experimental conditions from the ic-Si:H deposition rate point of view. Namely, the main characteristics of the effect of frequency, discharge geometry, power consumption and total gas pressure on the deposition process are presented successively. Special attention is given to the study of the frequency effect (13.56 MHz 50 MHz) indicating that the correct way to compare results of different driving frequency discharges is by maintaining constant the total power dissipation in the discharge. The important role of frequency in the achievement of high deposition rates and on the optimization of all other parameters is underlined. Finally, the proper combination of experimental conditions that result from the optimal choice of each of the above-mentioned discharge parameters and lead to high microcrystalline silicon deposition rates (7.5 Å/sec) is presented. The increase of silane dissociation rate towards neutral radicals (frequency effect), the contribution of highly sticking to the surface radicals (discharge geometry optimum) and the controlled production of higher radicals through secondary gas phase reactions (total gas pressure), are presented as prerequisites for the achievement of high deposition rates.
Ion Current Rectification in Nano/Micro-Fluidic Interfaces and Pulsed Glow Discharge Time-of-Flight Mass Spectrometric Chemical Speciation
NASA Astrophysics Data System (ADS)
Wang, Han
Microfluidics continues to be of interest for analyzing chemical and biological samples because of the disposability, portability, low sample consumption, fast analysis time, and parallel analysis potential for multiple samples in a single device. To improve microfluidic device functionality, integrated systems-nanofluidic/microfluidic interfaces (NMIs) have been fabricated for concentrating samples and performing as molecular gates. Ion current rectification has been confirmed in NMI with an asymmetric system. In chapter 2, the asymmetry of the NMI is systematically altered by varying the inner diameter of the nanocapillary membrane (NCM) reservoir, and the current rectification factor is observed to increase as the inner diameter of NCM reservoir increases. The data provide a new approach to tune the ion current rectification of NMIs and strengthen the fundamental knowledge of how these devices function. Glow discharge mass spectrometry (GDMS) is a well-established technique for the direct analysis of elements in solid samples. The introduction of pulsed glow discharge makes the internal energy of GD plasma tunable so that the specific desired ion signal profiles can be obtained and used for chemical speciation. For example, the elemental, structural, and molecular information of organic molecules have been obtained nearly simultaneously using glow discharge time-of-flight mass spectrometry (GDToFMS) coupled with gas chromatography. With careful control of operating parameters of GDToFMS, specific cluster ions or ion abundance ratios can be used for speciation of chromium oxides, manganese oxides, and iron oxides. Chapters 3 and 4 focus on extending the application of pulsed glow discharge time-of-flight mass spectrometry for chemical speciation. Chapter 3 is the analysis of cysteine using pulsed glow discharge time-of-flight mass spectrometry. The characteristic fragment ion at m/z 76 is used for the quantitative analysis for cysteine. The calibration curve for
Role of electrostatic and magnetic electron confinement in a hollow-cathode glow discharge in a nonuniform magnetic field
Metel, A. S. Grigoriev, S. N.; Volosova, M. A.; Bolbukov, V. P.; Melnik, Yu. A.
Glow discharge with electron confinement in an electrostatic trap has been studied. The trap is formed by a cylindrical hollow cathode, as well as by a flat target on its bottom and a grid covering its output aperture, both being negatively biased relative to the cathode. At a gas pressure of 0.2–0.4 Pa, the fraction of ions sputtering the target (δ = 0.13) in the entire number of ions emitted by the uniform discharge plasma corresponds to the ratio of the target surface area to the total surface area of the cathode, grid, and target. When a nonuniform magnetic field with force lines passing through the target center (where the magnetic induction reaches 35 mT), as well as through the grid, hollow cathode, and target periphery (where the field lines are arc-shaped), is applied to the trap, its influence on the discharge depends on the magnetic induction B{sub 0} at the target edge. At B{sub 0} = 1 mT, the electrons emitted from the target periphery and drifting azimuthally in the arc-shaped field insignificantly contribute to gas ionization. Nevertheless, since fast electrons that are emitted from the cathode and oscillate inside it are forced by the magnetic field to come more frequently to the target, thereby intensifying gas ionization near the latter, the fraction δ doubles and the plasma density near the target becomes more than twice as high as that near the grid. At B{sub 0} = 6 mT, the contribution of electrons emitted from the target surface to gas ionization near the target grows up and δ increases two more times. At cathode-target voltages in the range of 0–3 kV, the current in the target circuit vanishes as the voltage between the anode and the cathode decreases to zero.
Role of electrostatic and magnetic electron confinement in a hollow-cathode glow discharge in a nonuniform magnetic field
NASA Astrophysics Data System (ADS)
Metel, A. S.; Grigoriev, S. N.; Volosova, M. A.; Bolbukov, V. P.; Melnik, Yu. A.
Glow discharge with electron confinement in an electrostatic trap has been studied. The trap is formed by a cylindrical hollow cathode, as well as by a flat target on its bottom and a grid covering its output aperture, both being negatively biased relative to the cathode. At a gas pressure of 0.2-0.4 Pa, the fraction of ions sputtering the target (δ = 0.13) in the entire number of ions emitted by the uniform discharge plasma corresponds to the ratio of the target surface area to the total surface area of the cathode, grid, and target. When a nonuniform magnetic field with force lines passing through the target center (where the magnetic induction reaches 35 mT), as well as through the grid, hollow cathode, and target periphery (where the field lines are arc-shaped), is applied to the trap, its influence on the discharge depends on the magnetic induction B 0 at the target edge. At B 0 = 1 mT, the electrons emitted from the target periphery and drifting azimuthally in the arc-shaped field insignificantly contribute to gas ionization. Nevertheless, since fast electrons that are emitted from the cathode and oscillate inside it are forced by the magnetic field to come more frequently to the target, thereby intensifying gas ionization near the latter, the fraction δ doubles and the plasma density near the target becomes more than twice as high as that near the grid. At B 0 = 6 mT, the contribution of electrons emitted from the target surface to gas ionization near the target grows up and δ increases two more times. At cathode-target voltages in the range of 0-3 kV, the current in the target circuit vanishes as the voltage between the anode and the cathode decreases to zero.
CW 20 kW SAGE CO[sub 2] laser for industrial use. [Silent-discharge Assisted Glow discharge Excitation
Nagai, Haruhiko ); Hishii, Masao ); Tanaka, Masaaki; Myoi, Yasuhito; Yagi, Toshinori . Manufacturing Development Lab.); Wakata, Hitoshi . Central Research Lab.); Tabata, Norikazu . Industrial Electronics and Systems Lab.)
A new type of high-power CW CO[sub 2] laser with power output of more than 20 kW is described. The laser consists of a discharge excitation system named SAGE (Silent-discharge (SD) Assisted Glow discharge Excitation) and a ZnSe or a KCl transmissive window to extract high quality beams with axisymmetric intensity profile from a confocal positive-branch unstable resonator. The SAGE is effective to form a uniformly distributed and stable discharge in a large-volume and high-pressure gas excitation medium. Together with appropriate high-pressure gas conditions leading to low dissociation rate of CO[sub 2] and with using the properly selected zeolite to adsorb water vapor in the laser chamber, the transmissive windows have enabled gas-sealed operations. Prior to the design of the 20-kW SAGE laser, small-scaled experiments of the SAGE and stress analyses of the window were studied. The structure of the 20-kW SAGE laser and its performance characteristics such as SD power, magnification factor of the unstable resonator and gas pressure dependences of the power output, long-term gas-sealed operation, and beam quality are described in detail. The maximum CW power of 26.5 kW with an efficiency of 16.5 percent is attained through the ZnSe window, and a 20.3 kW power output is extracted through the KCl window. A long-term gas-sealed operation at a CW power level of 20 kW is demonstrated during a period of 65 hours.
Evaluation of a pulsed glow discharge time-of-flight mass spectrometer as a detector for gas chromatography and the influence of the glow discharge source parameters on the information volume in chemical speciation analysis.
Fliegel, Daniel; Fuhrer, Katrin; Gonin, Marc; Günther, Detlef
The figures of merit of a pulsed glow discharge time-of-flight mass spectrometer (GD-TOFMS) as a detector for gas chromatography (GC) analysis were evaluated. The mass resolution for the GD-TOFMS was determined on FWHM in the high mass range (208Pb+) as high as 5,500. Precision of 400 subsequent analyses was calculated on 63Cu+ to be better than 1% RSD with no significant drift over the time of the analysis. Isotope precision based on the 63Cu+/65Cu+ ratio over 400 analyses was 1.5% RSD. The limits of detection for gaseous analytes (toluene in methanol as solvent) were determined to be as low as several hundred ppb or several hundred pg absolute without using any pre-concentration technique. Furthermore, the different GD source parameters like capillary distance, cathode-anode spacing, and GD source pressure with regards to the accessible elemental, structural, and molecular information were evaluated. It was demonstrated that each of these parameters has severe influence on the ratio of elemental, structural, and parent molecular information in chemical speciation analysis. PMID:16773303
Evidence of homoclinic chaos in the plasma of a glow discharge
Braun, T.; Lisboa, J.A.; Gallas, J.A.C. Departamento de Engenharia Eletrica da Universidad Federal do Rio Grande do Sul, 90000 Porto Alegre, Rio Grande do Sul Laboratorio de Optica Quantica da Universidade Federal de Santa Catarina, Departamento de Fisica, 88049 Florianopolis, Santa Catarina Hoechstleistungsrechenzentrum , Kernforschungsanlage Juelich, W-5170 Juelich )
Homoclinic chaos is shown to occur in the electric current measured on an electrical discharge in argon. We report a clear sequence of four hesitations followed by a reverse period doubling. The experimental signals are used to construct {ital return}-{ital time} and {ital time}-{ital of}-{ital flight} maps that evidence a Shilnikov scenario in the system.
A dc glow discharge as a source of electrons for a portable mass spectrometer: characterization of the electron current intensity and electron kinetic energy distribution
NASA Astrophysics Data System (ADS)
Chalkha, A.; Despenes, C.; Janulyte, A.; Zerega, Y.; Andre, J.; Brkic, B.; Taylor, S.
A dc glow discharge cell with planar electrodes operating at about 1 Torr has been characterized with an inlet flow from ambient air. It will be used as a source of electrons to further ionize molecules by electron impact in a portable mass spectrometer. The Paschen curve has been measured for six values of the pressure around the minimum of the curve. The voltage-current characteristic, observed until 7 mA for different values of the pressure, increases with current in the normal glow regime. The temporal evolution of the discharge current has been recorded over long periods greater than one day for different insulator materials. The best stability has been obtained with Macor and Nylon. The available electron current for ionization has been measured at about 0.6 µA and the electron kinetic energy distribution has been found to be between 0 and a few tens of eV.
Characteristics of N2 and N2/O2 atmospheric pressure glow discharges
NASA Astrophysics Data System (ADS)
Klas, Matej; Ptasinska, Sylwia
Due to its richness in various active species a nitrogen plasma discharge is a promising tool for many applications. However, owing to the difficulties in igniting and sustaining this type of discharge, the construction of plasma sources operating in nitrogen gas is still very challenging. In this work we describe and characterize two home-built plasma sources with two different electrode configurations able to work in a nitrogen atmosphere. For this purpose, the jets of plasma species formed are studied by emission spectroscopy, and thermal and electrical measurements. It is noted that the addition of a small amount of oxygen to the nitrogen flow changes the optical and thermal properties of the jet and these results are also discussed.
Force interaction of high pressure glow discharge with fluid flow for active separation control
Roy, Subrata; Gaitonde, Datta V.
Radio frequency based discharges at atmospheric pressures are the focus of increased interest in aerodynamics because of the wide range of potential applications including, specifically, actuation in flows at moderate speeds. Recent literature describing promising experimental observations, especially on separation control, has spurred efforts in the development of parallel theoretical modeling to lift limitations in the current understanding of the actuation mechanism. The present effort demonstrates higher fidelity first-principle models in a multidimensional finite-element framework to predict surface discharge-induced momentum exchange. The complete problem of a dielectric barrier discharge at high pressure with axially displaced electrodes is simulated in a self-consistent manner. Model predictions for charge densities, the electric field, and gas velocity distributions are shown to mimic trends reported in the experimental literature. Results show that a residual of electrons remains deposited on the dielectric surface downstream of the exposed powered electrode for the entire duration of the cycle and causes a net electric force in the direction from the electrode to the downstream surface. For the first time, results document the mitigation process of a separation bubble formed due to flow past a flat plate inclined at 12 degree sign angle of attack. This effort sets the basis for extending the formulation further to include polyphase power input in multidimensional settings, and to apply the simulation method to flows past common aerodynamic configurations.
Generation of multiple toroidal dust vortices by a non-monotonic density gradient in a direct current glow discharge plasma
Kaur, Manjit Bose, Sayak; Chattopadhyay, P. K.; Sharma, D.; Ghosh, J.; Saxena, Y. C.; Thomas, Edward
Observation of two well-separated dust vortices in an unmagnetized parallel plate DC glow discharge plasma is reported in this paper. A non-monotonic radial density profile, achieved by an especially designed cathode structure using a concentric metallic disk and ring of different radii, is observed to produce double dust tori between cathode and anode. PIV analysis of the still images of the double tori shows oppositely rotating dust structures between the central disk and the ring. Langmuir probe measurements of background plasma shows a non-uniform plasma density profile between the disk and the ring. Location and sense of rotation of the dust vortices coincides with the location and direction of the radial gradient in the ion drag force caused by the radial density gradient. The experimentally observed dust vorticity matches well with the calculated one using hydrodynamic formulations with shear in ion drag dominating over the dust charge gradient. These results corroborate that a radial gradient in the ion drag force directed towards cathode is the principal cause of dust rotation.
The effect of glow discharge plasma surface modification of polymers on the osteogenic differentiation of committed human mesenchymal stem cells.
Mwale, Fackson; Wang, Hong Tian; Nelea, Valentin; Luo, Li; Antoniou, John; Wertheimer, Michael R
Little is known of the effect of material surfaces on stem cell differentiation. The present study has addressed the hypothesis that the interaction of mesenchymal stem cells (MSCs) with material surfaces modified by glow discharge plasma is a major regulator of osteogenic differentiation. We found that biaxially oriented polypropylene (BOPP) plasma treated in ammonia significantly reduced up-regulation of expression of osteogenic marker genes, such as alkaline phosphatase (ALP), bone sialoprotein (BSP) and osteocalcin (OC). In contrast, ALP expression was up-regulated when cultured on treated Nylon-6 polyamide (Ny-t) but was substantially reduced when cultured on its pristine counterpart (Ny-p) on day 3. On day 7, ALP expression was down-regulated with MSCs cultured on Ny-t although its expression level was up again on day 14. BSP was expressed weakly on day 3, but was up-regulated when cultured on Ny-t and Ny-p. Its expression reached its maximum on day 14 when cultured on a polystyrene control, while it was cyclically up-regulated on Ny-t. Similarly, there was a slight increase in OC expression when MSCs were cultured on Ny-t and Ny-p on day 3, when compared to control. Thus, the nature of the surface can directly influence MSCs differentiation, ultimately affecting the quality of new tissue formation with BOPP-t suppressing osteogenic differentiation. PMID:16313952
Conceptual Demonstration of Ambient Desorption-Optical Emission Spectroscopy Using a Liquid Sampling-Atmospheric Pressure Glow Discharge Microplasma Source.
Marcus, R Kenneth; Paing, Htoo W; Zhang, Lynn X
The concept of ambient desorption-optical emission spectroscopy (AD-OES) is demonstrated using a liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma as the desorption/excitation source. The LS-APGD has previously been employed for elemental analysis of solution samples and particulates introduced via laser ablation in both the optical emission and mass spectrometries (OES, MS) modes. In addition, the device has been shown to be effective for the analysis of elemental and molecular species operating in an ambient desorption/ionization mass spectrometry (ADI-MS) mode. Proof-of-concept is presented here in the use of the LS-APGD to volatilize three very diverse sample forms (metallic thin films, dry solution residues, and bulk materials), with the liberated material excited within the microplasma and detected via OES, i.e., AD-OES. While the demonstration is principally qualitative at this point, it is believed that the basic approach may find application across a broad spectrum of analytical challenges requiring elemental analysis, including metals, soils, and volume-limited solutions, analogous to what has been seen in the development of the field of ADI-MS for molecular species determinations. PMID:27175512
Grafting of lactose-carrying styrene onto polystrene dishes using plasma glow discharge and their interaction with hepatocytes.
Kang, Inn-Kyu; Lee, Dong Woo; Lee, Seung Kyung; Akaike, Toshihiro
Lactose-carrying styrene (VLA)-grafted polystyrene (PS) dish (PS-VLA) was prepared by treatment of PS dish with oxygen plasma glow discharge followed by the graft polymerization of VLA. The surface topology and hepatocytes behavior on PS-VLA were examined by comparison with those on a PVLA-coated PS dish (PS-PVLA). According to the results of surface topologies obtained by a phase mode of atomic force microscope (AFM), it was found that PS-VLA exhibits a pointed texture image similar to forest while PS-PVLA exhibits a phase-separated, cloud-like image. In an experiment involving hepatocytes adhesion, the cells more slowly adhered to PS-VLA than to PS-PVLA during the first 2 h incubation. According to topological data, it may be suggested that lactose density on the air side surface of PS-VLA is lower than that of PS-PVLA, thus leading to the slow adhesion of hepatocytes to PS-VLA. PMID:15348423
Shock compression of glow discharge polymer (GDP): density functional theory (DFT) simulations and experiments on Sandia's Z-machine
NASA Astrophysics Data System (ADS)
Cochrane, K. R.; Ao, T.; Hamel, S.; Lemke, R. W.; Schoff, M. E.; Blue, B. E.; Herrmann, M. C.; Mattsson, T. R.
Glow discharge polymer (GDP) is used extensively in inertial confinement fusion (ICF) capsules. Accurate knowledge of the equation of state (EOS) under shock and release is particularly important for high-fidelity design and analysis of ICF experiments since the capsule material is subject to several converging shocks as well as release towards the cryogenic fuel. We performed Density Functional Theory (DFT) based molecular dynamics simulations, to gain knowledge of the behavior of GDP - for example regarding the role of chemical dissociation during shock compression, we find that the dissociation regime along the Hugoniot extends from 50 GPa to 250 GPa. The shock pressures calculated from DFT are compared to experimental data taken on magnetically launched flyer plate impact experiments at Sandia's Z-machine. Large GDP samples were grown in a planar geometry to improve the sample quality and maintained in a nitrogen atmosphere following manufacturing, thus allowing for a direct comparison to the simulations. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's NNSA under Contract DE-AC04-94AL85000
Fluorine and boron co-doped diamond-like carbon films deposited by pulsed glow discharge plasma immersion ion processing
NASA Astrophysics Data System (ADS)
He, Xiao-Ming; Hakovirta, M.; Peters, A. M.; Taylor, B.; Nastasi, M.
Fluorine (F) and boron (B) co-doped diamond-like carbon (FB-DLC) films were prepared on different substrates by the plasma immersion ion processing (PIIP) technique. A pulse glow discharge plasma was used for the PIIP deposition and was produced at a pressure of 1.33 Pa from acetylene (C2H2), diborane (B2H6), and hexafluoroethane (C2F6) gas. Films of FB-DLC were deposited with different chemical compositions by varying the flow ratios of the C2H2, B2H6, and C2F6 source gases. The incorporation of B2H6 and C2F6 into PIIP deposited DLC resulted in the formation of F-C and B-C hybridized bonding structures. The levels of the F and B concentrations effected the chemical bonding and the physical properties as was evident from the changes observed in density, hardness, stress, friction coefficient, and contact angle of water on films. Compared to B-doped or F-doped DLC films, the F and B co-doping of DLC during PIIP deposition resulted in the formation of films that possessed a reduced hydrogen concentration and stress, while maintaining a high hardness, low friction coefficient, and high wetting contact angle.
Non-linear optical diagnostic of a-Si:H thin films deposited by RF-glow discharge
NASA Astrophysics Data System (ADS)
Ebothé, J.; Plucinski, K. J.; Roca i Cabarrocas, P.; Kityk, I. V.
We have evidenced the high sensitivity of infra red-induced second harmonic generation (IR-ISHG) to the structural changes that occurred in amorphous hydrogenated silicon films (a-Si:H) prepared by Rf-glow discharge technique at different substrate temperatures and doping types. In every case, a maximal signal of the IR-induced SHG is achieved at a temperature of about 110 K and pump-probe delaying time about 22-38 ps. This one indicates a marked effect of doped subsystems in the observed non-linear optical effects. A tremendous effect of doping is established from a drastic change of the IR-induced SHG behavior presenting an anomaly at about 400 MW/cm 2 for a pumping power with wavelength 3.7 μm. A minimum of the SHG is observed in that case for standard non-doped films. Note here that the doping type does not markedly affect the behavior of the second-order non-linear optical susceptibility. The thermo-annealing leads to a slight decrease of the effective second-order susceptibilities. More drastic changes are observed with doped samples for the pump-probe delaying time from about 39 till 24 ps.
Depth profile characterization of Zn-TiO2 nanocomposite films by pulsed radiofrequency glow discharge-optical emission spectrometry.
Alberts, Deborah; Fernández, Beatriz; Frade, Tania; Gomes, Anabela; Pereira, Maria Isabel da Silva; Pereiro, Rosario; Sanz-Medel, Alfredo
In recent years particular effort is being devoted towards the development of radiofrequency (rf) pulsed glow discharges (GDs) coupled to optical emission spectrometry (OES) for depth profile analysis of materials with technological interest. In this work, pulsed rf-GD-OES is investigated for the fast and sensitive depth characterization of Zn-TiO(2) nanocomposite films deposited on conductive substrates (Ti and steel). The first part of this work focuses on assessing the advantages of pulsed GDs, in comparison with the continuous GD, in terms of analytical emission intensities and emission yields. Next, the capability of pulsed rf-GD-OES for determination of thickness and compositional depth profiles is demonstrated by resorting to a simple multi-matrix calibration procedure. A rf forward power of 75 W, a pressure of 600 Pa, 10 kHz pulse frequency and 50% duty cycle were selected as GD operation parameters.Quantitative depth profiles obtained with the GD proposed methodology for Zn-TiO(2) nanocomposite films, prepared by the occlusion electrodeposition method using pulsed reverse current electrolysis, have proved to be in good agreement with results achieved by complementary techniques, including scanning electron microscopy and inductively coupled plasma-mass spectrometry. The work carried out demonstrates that pulsed rf-GD-OES is a promising tool for the fast analytical characterization of nanocomposite films. PMID:21376989
Tailoring surface properties of polyethylene separator by low pressure 13.56 MHz RF oxygen plasma glow discharge
NASA Astrophysics Data System (ADS)
Li, Chun; Liang, Chia-Han; Huang, Chun
Low-pressure plasma surface modification in a radio-frequency capacitively coupled glow discharge of oxygen gas was carried out to induce polar functional groups onto polyethylene membrane separator surfaces to enhance its hydrophilicity. The surface changes in surface free energy were monitored by static contact angle measurement. A significant increase in the surface energy of polyethylene membrane separators caused by the oxygen gas plasma modifications was observed. The static water contact angle of the plasma-modified membrane separator significantly decreased with the increase in treatment duration and plasma power. An obvious increase in the surface energy of the membrane separators owing to the oxidative effect of oxygen-gas-plasma modifications was also observed. Optical emission spectroscopy was carried out to analyze the chemical species generated by oxygen gas plasma surface modification. The variations in the surface morphology and chemical structure of the separators were confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). XPS showed significantly higher surface concentrations of oxygen functional groups in the oxygen-gas-plasma-modified polymeric separator surfaces than in the unmodified polymeric separator surface. The experimental results show the important role of chemical species in the interaction between oxygen gas plasmas and the separator surface, which can be controlled by surface modification to tailor the hydrophilicity of the separator.
Evolution of Self-organized Poloidal Dust Rotation with Neutral Pressure in a Direct Current Glow Discharge
NASA Astrophysics Data System (ADS)
Kaur, Manjit; Bose, Sayak; Chattopadhyay, P. K.; Ghosh, J.; Sharma, D.; Saxena, Y. C.
Poloidal rotation of mono-dispersed dust particles in toroidally symmetric structures is obtained experimentally in an unmagnetized parallel plate dc glow discharge at high pressures, using a concentric metallic ring placed over surface of cathode. The poloidal rotation of dust particles is observed to be localized above the ring. A radial gradient in the ion drag force arising due to a radial density gradient above the ring is identified as the principal cause of dust rotation. The evolution of this poloidal dust rotation with background gas pressure is studied. A transition from a filled-vortex (poloidal cross-section of the toroidal structure) to a vortex with void at the centre is observed with increase in fill-in gas pressure accompanied by a decrease in vortex height from cathode surface. The velocity of the dust particles is observed to increase with an increase in neutral gas pressure. This observation contradicts the obvious interpretation of slowing down of dust rotation due to an increase in neutral frictional force which increases with pressure. These experimental results with probable causes will be presented in details.
Production Of Multi-magnetron Plasma By Using Polyphase Ac Glow Discharge In An Improved Multi-pole Magnetic Field
NASA Astrophysics Data System (ADS)
Matsumoto, Kazunori; Motoki, Kentaro; Miyamoto, Masahiro; Uetani, Yasuhiro
Effects of an improved multi-pole magnetic field on a plasma production generated by a polyphase ac glow discharge with multiple electrodes have been investigated. Conventional configuration of the multi-pole magnetic filed has been modified to suppress plasma losses at both ends of the chamber due to ExB drift motion. The modified multi-pole magnetic field has enabled us to produce a multiple magnetron-plasma at a considerably low pressure less than mTorr. The low temperature plasma has been widely used as the fine processing technology of a dry etching and as the thin film formation technology of a sputtering coating. Large-scale plasmas which can be generated at a low gas-pressure have been desired for more wider dry etching and greater sputter coating. The purpose of this study is to develop a large-scale and low-cost plasma generator by using a polyphase ac power source with the low frequency. In this session, we will present the experimental result as to a multiple magnetron-plasma generated in the modified twenty-four poles magnetic field by using the twenty-four-phase ac power source with the commercial electric power frequency of 60Hz. The ac power is supplied to twenty-four electrodes which are fixed to the water-cooled chamber-wall through sheet insulators so that the electrodes can be cooled indirectly.
Automatable on-line generation of calibration curves and standard additions in solution-cathode glow discharge optical emission spectrometry
NASA Astrophysics Data System (ADS)
Schwartz, Andrew J.; Ray, Steven J.; Hieftje, Gary M.
Two methods are described that enable on-line generation of calibration standards and standard additions in solution-cathode glow discharge optical emission spectrometry (SCGD-OES). The first method employs a gradient high-performance liquid chromatography pump to perform on-line mixing and delivery of a stock standard, sample solution, and diluent to achieve a desired solution composition. The second method makes use of a simpler system of three peristaltic pumps to perform the same function of on-line solution mixing. Both methods can be computer-controlled and automated, and thereby enable both simple and standard-addition calibrations to be rapidly performed on-line. Performance of the on-line approaches is shown to be comparable to that of traditional methods of sample preparation, in terms of calibration curves, signal stability, accuracy, and limits of detection. Potential drawbacks to the on-line procedures include signal lag between changes in solution composition and pump-induced multiplicative noise. Though the new on-line methods were applied here to SCGD-OES to improve sample throughput, they are not limited in application to only SCGD-OES-any instrument that samples from flowing solution streams (flame atomic absorption spectrometry, ICP-OES, ICP-mass spectrometry, etc.) could benefit from them.
Rf glow discharge optical emission spectrometry for the analysis of arrays of Ni nanowires in nanoporous alumina and titania membranes
NASA Astrophysics Data System (ADS)
Prida, V. M.; Navas, D.; Pirota, K. R.; Hernandez-Velez, M.; Menéndez, A.; Bordel, N.; Pereiro, R.; Sanz-Medel, A.; Hernando, B.; Vazquez, M.
Anodic alumina (Al2O3) and titania (TiO2) nanoporous oxide membranes are among the most widely studied self-organized nanopore templates, formed by uniform and well aligned arrays of synthetized nanometric pores or tubes. Here, we perform a comparative study of the depth profiling analysis in self-ordered alumina and titania nanoporous membrane templates by means of the radiofrequency glow discharge coupled to optical emission spectrometry (rf-GD-OES) technique. The densely packed columnar arrays of hexagonally self-ordered nanoporous alumina membranes investigated, with an average inner pore diameter of 35 nm and 105 nm interspacing, give an uniform thickness pore length about more than 5 μm, depending on the anodization time. Meanwhile, the analysis of the anodized titania nanotubes, with an average inner pore diameter of 100 nm and 40 nm wall thickness, shown to be about 300 nm in length. Each type of membranes were also studied in both cases, when the nanopores were empty and after filling with electrodeposited Ni. The direct analysis by rf-GD-OES reveals the ability of this technique to control the quality of these so synthesized nanocomposites formed by electrodeposited Ni nanowires into the alumina and titania nanoporous templates.
Modification of polyethylene powder with an organic precursor in a spiral conveyor by hollow cathode glow discharge
NASA Astrophysics Data System (ADS)
Quitzau, M.; Wolter, M.; Zaporojtchenko, V.; Kersten, H.; Faupel, F.
Hexamethyldisiloxane (HMDSO) films were deposited on polyethylene (PE, (C2H4)n) powder by hollow cathode glow discharge. The reactive species in different HMDSO/Ar plasmas were studied by optical emission spectroscopy (OES). Increasing the HMDSO fraction in the gas mixture additional compounds like CHx, OH, SiC and SiO can be identified. After deposition the formed silicon and carbon containing groups (C-O, C=O, SiC and SiO) on the PE powder surface have been analyzed by X-ray photoemission spectroscopy (XPS). Changes in wettability depending on the HMDSO fraction were investigated by contact angle measurements (CAM). The free surface energy of the PE powder decreases with increasing HMDSO fraction in the process gas and encapsulation of the powder particles occurs. An aging effect of the plasma treated PE surface was observed depending on the process gas composition. The higher the HMDSO fraction the less is the aging effect of the plasma treated PE surface.
Atmospheric pressure glow discharge generated in nitrogen-methane gas mixture: PTR-MS analyzes of the exhaust gas
NASA Astrophysics Data System (ADS)
Torokova, Lucie; Mazankova, Vera; Krcma, Frantisek; Mason, Nigel J.; Matejcik, Stefan
This paper reports the results of an extensive study of with the in situ mass spectrometry analysis of gaseous phase species produced by an atmospheric plasma glow discharge in N2-CH4 gas mixtures (with methane concentrations ranging from 1% to 4%). The products are studied using proton-transfer-reaction mass spectrometry (PTR-MS). HCN and CH3CN are identified as the main gaseous products. Hydrazine, methanimine, methyldiazene, ethylamine, cyclohexadiene, pyrazineacetylene, ethylene, propyne and propene are identified as minor compounds. All the detected compounds and their relative abundances are determined with respect to the experimental conditions (gas composition and applied power). The same molecules were observed by the Cassini-Huygens probe in Titan's atmosphere (which has same N2-CH4 gas mixtures). Such, experiments show that the formation of such complex organics in atmospheres containing C, N and H, like that of Titan, could be a source of prebiotic molecules. Contribution to the topical issue "The 14th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XIV)", edited by Nicolas Gherardi, Ronny Brandenburg and Lars Stollenwark
Shock compression of glow discharge polymer (GDP): density functional theory (DFT) simulations and experiments on Sandia's Z-machine
NASA Astrophysics Data System (ADS)
Mattsson, Thomas R.; Cochrane, K. R.; Ao, T.; Lemke, R. W.; Flicker, D. G.; Schoff, M. E.; Blue, B. E.; Hamel, S.; Herrmann, M. C.
Glow discharge polymer (GDP) is used extensively as capsule/ablation material in inertial confinement fusion (ICF) capsules. Accurate knowledge of the equation of state (EOS) under shock and release is particularly important for high-fidelity design, analysis, and optimization of ICF experiments since the capsule material is subject to several converging shocks as well as release towards the cryogenic fuel. We performed Density Functional Theory (DFT) based quantum molecular dynamics (QMD) simulations, to gain knowledge of the behavior of GDP - including the effect of changes in chemical composition. The shock pressures calculated from DFT are compared experimental data taken on magnetically launched flyer plate impact experiments on at Sandia's Z-machine. Large GDP samples were grown in a planar geometry to improve the sample quality and maintained in a nitrogen atmosphere following manufacturing, thus allowing for a direct comparison to the DFT/QMD simulations. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's NNSA under contract DE-AC04-94AL85000.
Comparison in the analytical performance between krypton and argon glow discharge plasmas as the excitation source for atomic emission spectrometry.
Wagatsuma, Kazuaki
The emission characteristics of ionic lines of nickel, cobalt, and vanadium were investigated when argon or krypton was employed as the plasma gas in glow discharge optical emission spectrometry. A dc Grimm-style lamp was employed as the excitation source. Detection limits of the ionic lines in each iron-matrix alloy sample were compared between the krypton and the argon plasmas. Particular intense ionic lines were observed in the emission spectra as a function of the discharge gas (krypton or argon), such as the Co II 258.033 nm for krypton and the Co II 231.707 nm for argon. The explanation for this is that collisions with the plasma gases dominantly populate particular excited levels of cobalt ion, which can receive the internal energy from each gas ion selectively, for example, the 3d(7)4p (3)G(5) (6.0201 eV) for krypton and the 3d(7)4p (3)G(4) (8.0779 eV) for argon. In the determination of nickel as well as cobalt in iron-matrix samples, more sensitive ionic lines could be found in the krypton plasma rather than the argon plasma. Detection limits in the krypton plasma were 0.0039 mass% Ni for the Ni II 230.299-nm line and 0.002 mass% Co for the Co II 258.033-nm line. However, in the determination of vanadium, the argon plasma had better analytical performance, giving a detection limit of 0.0023 mass% V for the V II 309.310-nm line. PMID:19277614
A spectroscopic study of the initial stages of pulsed glow discharges in noble gases
NASA Astrophysics Data System (ADS)
Demidov, V. I.; Adams, S. F.; Bogdanov, E. A.; Kudryavtsev, A. A.; Williamson, J. M.
The dynamics of the rapid growth of electron and metastable atom densities at the beginning of a pulsed dc discharge in argon was explored by investigating the relationship between the strength of the applied electric field and the measured emission line intensities at 419.8 and 420.1 nm. Data showed that when the electric field strength was low, the growth of the metastable atom density began before the growth of the electron density. The opposite relationship was observed when a higher strength electric field was applied. This observed dependence can be confirmed by modeling the argon dc discharge. Furthermore, similar measurements for the 345.4 and 347.3 nm spectral lines in neon and the 480.7 and 467.2 nm spectral lines in xenon suggest analogous behaviors in these noble gases. Thus, spectral measurements of the above lines could be a sensitive indicator of the presence of noble gas metastable atoms in plasmas. This relationship could be used to control plasma properties, a tool that would be useful for many technological applications. This work was supported by the DOE (DE-SC0001939), NSF CBET-0903635, GK 14.740.11.0893 and AFOSR.
Penning Ionization Electron Spectroscopy in Glow Discharge: A New Dimension for Gas Chromatography Detectors
NASA Technical Reports Server (NTRS)
Sheverev, V. A.; Khromov, N. A.; Kojiro, D. R.; Fonda, Mark (Technical Monitor)
Admixtures to helium of 100 ppm and 5 ppm of nitrogen, and 100 ppm and 10 ppm of carbon monoxide were identified and measured in the helium discharge afterglow using an electrical probe placed into the plasma. For nitrogen and carbon monoxide gases, the measured electron energy spectra display distinct characteristic peaks (fingerprints). Location of the peaks on the energy scale is determined by the ionization energies of the analyte molecules. Nitrogen and carbon monoxide fingerprints were also observed in a binary mixture of these gases in helium, and the relative concentration analytes has been predicted. The technically simple and durable method is considered a good candidate for a number of analytical applications, and in particular, in GC and for analytical flight instrumentation.
Chemistry in glow discharges of H2 / O2 mixtures. Diagnostics and modelling
Jiménez-Redondo, M; Carrasco, E; Herrero, V J; Tanarro, I
The chemistry of low pressure H2 + O2 discharges with different mixture ratios has been studied in a hollow cathode DC reactor. Neutral and positive ion distributions have been measured by mass spectrometry, and Langmuir probes have been used to provide charge densities and electron temperatures. A simple zero order kinetic model including neutral species and positive and negative ions, which takes into account gas-phase and heterogeneous chemistry, has been used to reproduce the global composition of the plasmas over the whole range of mixtures experimentally studied, and allows for the identification of the main physicochemical mechanisms that may explain the experimental results. To our knowledge, no combined experimental and modelling studies of the heavy species kinetics of low pressure H2 + O2 plasmas including ions has been reported before. As expected, apart from the precursors, H2O is detected in considerable amounts. The model also predicts appreciable concentrations of H and O atoms and the OH radical. The relevance of the metastable species O(1D) and O2(a1Δg) is analysed. Concerning the charged species, positive ion distributions are dominated by H3O+ for a wide range of intermediate mixtures, while H3+ and O2+ are the major ions for the higher and lower H2/O2 ratios, respectively. The mixed ions OH+, H2O+ and HO2+ are also observed in small amounts. Negative ions are shown to have a limited relevance in the global chemistry; their main contribution is the reduction of the electron density available for electron impact processes. PMID:26702195
Factors influencing the analytical performance of an atmospheric sampling glow discharge ionization source as revealed via ionization dynamics modeling.
Goeringer, Douglas E
A kinetic model is developed for the dynamic events occurring within an atmospheric sampling glow discharge that affect its performance as an ion source for analytical mass spectrometry. The differential equations incorporate secondary electron generation and thermalization, reagent and analyte ion formation via electron capture and ion-molecule reactions, ion loss via recombination processes, diffusion, and ion-molecule reactions with matrix components, and the sampling and pumping parameters of the source. Because the ion source has a flow-through configuration, the number densities of selected species can be estimated by applying the steady-state assumption. However, understanding of its operation is aided by knowledge of the dynamic behavior, so numerical methods are applied to examine the time dependence of those species as well. As in other plasma ionization sources, the ionization efficiency is essentially determined by the ratio of the relevant ion formation and recombination rates. Although thermal electron and positive reagent ion number densities are comparable, the electron capture/ion-molecule reaction rate coefficient ratio is normally quite large and the ion-electron recombination rate coefficient is about an order of magnitude greater than that for ion-ion recombination. Consequently, the efficiency for negative analyte ion formation via electron capture is generally superior to that for positive analyte ion generation via ion-molecule reaction. However, the efficiency for positive analyte ion formation should be equal to or better than that for negative analyte ions when both ionization processes occur via ion-molecule reaction processes (with comparable rate coefficients), since the negative reagent ion density is considerably less than that for positive reagent ions. Furthermore, the particularly high number densities of thermal electrons and reagent ions leads to a large dynamic range of linear response for the source. Simulation results also
Surface oxide net charge of a titanium alloy: comparison between effects of treatment with heat or radiofrequency plasma glow discharge.
MacDonald, Daniel E; Rapuano, Bruce E; Schniepp, Hannes C
In the current study, we have compared the effects of heat and radiofrequency plasma glow discharge (RFGD) treatment of a Ti6Al4V alloy on the physico-chemical properties of the alloy's surface oxide. Titanium alloy (Ti6Al4V) disks were passivated alone, heated to 600 °C, or RFGD plasma treated in pure oxygen. RFGD treatment did not alter the roughness, topography, elemental composition or thickness of the alloy's surface oxide layer. In contrast, heat treatment altered oxide topography by creating a pattern of oxide elevations approximately 50-100 nm in diameter. These nanostructures exhibited a three-fold increase in roughness compared to untreated surfaces when RMS roughness was calculated after applying a spatial high-pass filter with a 200 nm-cutoff wavelength. Heat treatment also produced a surface enrichment in aluminum and vanadium oxides. Both RFGD and heat treatment produced similar increases in oxide wettability. Atomic force microscopy (AFM) measurements of metal surface oxide net charge signified by a long-range force of attraction to or repulsion from a (negatively charged) silicon nitride AFM probe were also obtained for all three experimental groups. Force measurements showed that the RFGD-treated Ti6Al4V samples demonstrated a higher net positive surface charge at pH values below 6 and a higher net negative surface charge at physiological pH (pH values between 7 and 8) compared to control and heat-treated samples. These findings suggest that RFGD treatment of metallic implant materials can be used to study the role of negatively charged surface oxide functional groups in protein bioactivity, osteogenic cell behavior and osseointegration independently of oxide topography. PMID:20880672
Production of a biofunctional titanium surface using plasma electrolytic oxidation and glow-discharge plasma for biomedical applications.
Beline, Thamara; Marques, Isabella da Silva Vieira; Matos, Adaias O; Ogawa, Erika S; Ricomini-Filho, Antônio P; Rangel, Elidiane C; da Cruz, Nilson Cristino; Sukotjo, Cortino; Mathew, Mathew T; Landers, Richard; Consani, Rafael L X; Mesquita, Marcelo Ferraz; Barão, Valentim Adelino Ricardo
In this study, the authors tested the hypotheses that plasma electrolytic oxidation (PEO) and glow-discharge plasma (GDP) would improve the electrochemical, physical, chemical, and mechanical properties of commercially pure titanium (cpTi), and that blood protein adsorption on plasma-treated surfaces would increase. Machined and sandblasted surfaces were used as controls. Standard electrochemical tests were conducted in artificial saliva (pHs of 3.0, 6.5, and 9.0) and simulated body fluid. Surfaces were characterized by scanning electron microscopy, energy-dispersive spectroscopy, x-ray photoelectron spectroscopy, atomic force microscopy, x-ray diffraction, profilometry, Vickers microhardness, and surface energy. For biological assay, the adsorption of blood serum proteins (i.e., albumin, fibrinogen, and fibronectin) was tested. Higher values of polarization resistance and lower values of capacitance were noted for the PEO and GDP groups (p < 0.05). Acidic artificial saliva reduced the corrosion resistance of cpTi (p < 0.05). PEO and GDP treatments improved the surface properties by enrichment of the surface chemistry with bioactive elements and increased surface energy. PEO produced a porous oxide layer (5-μm thickness), while GDP created a very thin oxide layer (0.76-μm thickness). For the PEO group, the authors noted rutile and anatase crystalline structures that may be responsible for the corrosion barrier improvement and increased microhardness values. Plasma treatments were able to enhance the surface properties and electrochemical stability of titanium, while increasing protein adsorption levels. PMID:26984234
Reactive sputter deposition of alumina films on magnesium alloy by double cathode glow-discharge plasma technique
Zhou Chenghou; Xu Jiang; Jiang Shuyun
In order to overcome the problem of the corrosion resistance of AZ31 magnesium alloy, the nanocrystalline Al{sub 2}O{sub 3} film was deposited on AZ31 magnesium alloy by double cathode glow-discharge plasma technique. The microstructure, chemical composition and elemental chemical state of the sputter-deposited nanocrystalline Al{sub 2}O{sub 3} film were analyzed by means of scanning electron microscopy equipped with an energy dispersive spectroscope, X-ray diffraction), transmission electron microscope and X-ray photoelectron spectroscopy. The results indicated that the sputter-deposited nanocrystalline Al{sub 2}O{sub 3} film consisted of single {theta}-Al{sub 2}O{sub 3} phase with average grain size about 60 nm. The hardness and the elastic modulus of the as-deposited nanocrystalline Al{sub 2}O{sub 3} film were about 17.21 GPa and 217 GPa measured by nanoindentation instrument, respectively. The corrosion behavior of the sputter-deposited nanocrystalline Al{sub 2}O{sub 3} film in 3.5%NaCl solution was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy. The amount of porosity for the sputter-deposited nanocrystalline Al{sub 2}O{sub 3} film calculated by two electrochemical methods was equal to 0.0086% and 0.168%, respectively. The sputter-deposited nanocrystalline Al{sub 2}O{sub 3} film exhibited excellent corrosion resistance, which was attributed to its dense enough structure to prevent magnesium alloy from corrosion in aggressive solutions.
Surface Oxide Net Charge of a Titanium Alloy; Comparison Between Effects of Treatment With Heat or Radiofrequency Plasma Glow Discharge
MacDonald, Daniel E.; Rapuano, Bruce E.; Schniepp, Hannes C.
In the current study, we have compared the effects of heat and radiofrequency plasma glow discharge (RFGD) treatment of a Ti6Al4V alloy on the physico-chemical properties of the alloy's surface oxide. Titanium alloy (Ti6Al4V) disks were passivated alone, heated to 600 °C, or RFGD plasma treated in pure oxygen. RFGD treatment did not alter the roughness, topography, elemental composition or thickness of the alloy's surface oxide layer. In contrast, heat treatment altered oxide topography by creating a pattern of oxide elevations approximately 50–100 nm in diameter. These nanostructures exhibited a three-fold increase in roughness compared to untreated surfaces when RMS roughness was calculated after applying a spatial high-pass filter with a 200 nm cutoff wavelength. Heat treatment also produced a surface enrichment in aluminum and vanadium oxides. Both RFGD and heat treatment produced similar increases in oxide wettability. Atomic force microscopy (AFM) measurements of metal surface oxide net charge signified by a long range force of attraction to or repulsion from a (negatively charged) silicon nitride AFM probe were also obtained for all three experimental groups. Force measurements showed that the RFGD-treated Ti6Al4V samples demonstrated a higher net positive surface charge at pH values below 6 and a higher net negative surface charge at physiological pH (pH values between 7 and 8) compared to control and heat-treated samples These findings suggest that RFGD treatment of metallic implant materials can be used to study the role of negatively charged surface oxide functional groups in protein bioactivity, osteogenic cell behavior and osseointegration independently of oxide topography. PMID:20880672
[Evaluation of potentiality of combined SHF- and glow discharge in intensification of carbon dioxide and hydrogen processing within life support system].
Klimarev, S I
The article reports an experimental carbon dioxide hydration process in combined SHF- and glow discharge, and describes a design of SHF plasmatrones for CO2 processing at air pressure and in an integrated unit. Maximal transformation of 80% CO2 per a run was reached with the total input power of no more than 0.9 kW. Thermal zero lag of plasma forming, essentially instant and timely engagement and disengagement of thermal action on CO2-H2 mixture renders SHF-energy applicable to intensification of next generation life support technologies, processing of these gases within atmosphere regeneration system specifically. PMID:21970045
Synergism between low-energy neutral particles and energetic ions in the pulsed glow discharge deposition of diamond-like carbon films
NASA Astrophysics Data System (ADS)
Afanasyev-Charkin, I. V.; Nastasi, M.
Diamond-like carbon films were deposited using pulsed glow discharge deposition at 4kV. The duty factor was varied and all other parameters were kept constant. It was shown that the contribution of neutral particles to the total number of deposition atoms is much larger than that of energetic ions. At the same time, there is a relationship between the deposition of neutral particles and ion bombardment. The sticking coefficient of the neutral particles in proportional to the flux of energetic ions and does not exceed 5×10-4 for the deposition parameters used in our experiment.
Plasma in a Pulsed Discharge Environment
NASA Technical Reports Server (NTRS)
Remy, J.; Bienier, L.; Salama, F.
The plasma generated in a pulsed slit discharge nozzle is used to form molecular ions in an astrophysically relevant environment. The plasma has been characterized as a glow discharge in the abnormal regime. Laboratory studies help understand the formation processes of polycyclic aromatic hydrocarbon (PAH) ions that are thought to be the source of the ubiquitous unidentified infrared bands.
Single drop solution electrode glow discharge for plasma assisted-chemical vapor generation: sensitive detection of zinc and cadmium in limited amounts of samples.
Li, Zhi-ang; Tan, Qing; Hou, Xiandeng; Xu, Kailai; Zheng, Chengbin
A simple and sensitive approach is proposed and evaluated for determination of ultratrace Zn and Cd in limited amounts of samples or tens of cells based on a novel single drop (5-20 μL) solution electrode glow discharge assisted-chemical vapor generation technique. Volatile species of Zn and Cd were immediately generated and separated from the liquid phase for transporting to atomic fluorescence or atomic mass spectrometric detectors for their determination only using hydrogen when the glow discharge was ignited between the surface of a liquid drop and the tip of a tungsten electrode. Limits of detection are better than 0.01 μg L(-1) (0.2 pg) for Cd and 0.1 μg L(-1) (2 pg) for Zn, respectively, and comparable or better than the previously reported results due to only a 20 μL sampling volume required, which makes the proposed technique convenient for the determination of Zn and Cd in limited amounts of samples or even only tens of cells. The proposed method not only retains the advantages of conventional chemical vapor generation but also provides several unique advantages, including better sensitivity, lower sample and power consumption, higher chemical vapor generation efficiencies and simpler setup, as well as greener analytical chemistry. The utility of this technique was demonstrated by the determination of ultratrace Cd and Zn in several single human hair samples, Certified Reference Materials GBW07601a (human hair powder) and paramecium cells. PMID:25409265
In-situ characterisation of the dynamics of a growing dust particle cloud in a direct-current argon glow discharge
NASA Astrophysics Data System (ADS)
Barbosa, S.; Couëdel, L.; Arnas, C.; Kishor Kumar, K.; Pardanaud, C.; Onofri, F. R. A.
The growth and the dynamics of a tungsten nanoparticle cloud were investigated in a direct-current low pressure argon glow discharge. Real-time analyses of the dust particle size and number concentration were performed in-situ by light extinction spectrometry, while spatial dynamics of the cloud was investigated with the laser light-sheet scattering method. Additional off-line electron microscopy and Raman spectroscopy measurements were also performed for comparison purpose. This experimental work reveals the existence of an agglomeration phase followed by the appearance of a new dust particle generation. While growing, the dust cloud is pushed towards the anode and the discharge edge. Afterwards, a new dust particle generation can grow in the space freed by the first generation of nanoparticles. The continuous growth, below the light extinction spectrometry scanning positions, explains the apparent dissimilarities observed between the in-line optical and the off-line electron microscopy analyses.
Ion and neutral energy flux distributions to the cathode in glow discharges in Ar/Ne and Xe/Ne mixtures
NASA Astrophysics Data System (ADS)
Capdeville, H.; Pédoussat, C.; Pitchford, L. C.
The work presented in the article is a study of the heavy particle (ion and neutral) energy flux distributions to the cathode in conditions typical of discharges used for luminous signs for advertising ("neon" signs). The purpose of this work is to evaluate the effect of the gas mixture on the sputtering of the cathode. We have combined two models for this study: a hybrid model of the electrical properties of the cathode region of a glow discharge and a Monte Carlo simulation of the heavy particle trajectories. Using known sputtering yields for Ne, Ar, and Xe on iron cathodes, we estimate the sputtered atom flux for mixtures of Ar/Ne and Xe/Ne as a function of the percent neon in the mixture.
Does asymmetric charge transfer play an important role as an ionization mode in low power-low pressure glow discharge mass spectrometry?
NASA Astrophysics Data System (ADS)
Mushtaq, S.; Steers, E. B. M.; Churchill, G.; Barnhart, D.; Hoffmann, V.; Pickering, J. C.; Putyera, K.
We report results of comprehensive studies using the Nu Instruments Astrum high-resolution glow discharge mass spectrometer (GD-MS) and optical emission spectrometry (OES) to investigate the relative importance of discharge mechanisms, such as Penning ionization (PI) and asymmetric charge transfer (ACT), at low-power/low-pressure discharge conditions. Comparison of the ratios of the ion signals of each constituent element to that of the plasma gas shows that for oxygen, the ratio in krypton is more than ten times higher than in argon (oxygen ground state ions are produced by Kr-ACT). For many elements, the ratios are very similar but that for tungsten is higher with krypton, while for iron, the reverse holds. These effects are linked to the arrangement of ionic energy levels of the elements concerned and the resulting relative importance of ACT and PI. The GD-MS and GD-OES results have shown that the ACT process can play an important role as the ionization mode in low-power/low-pressure discharges. However, OES results have shown that the magnitude of change in spectral intensities of elements studied are dependent on the discharge conditions.
The abnormal electrostatic discharge of a no-connect metal cover in a ceramic packaging device
NASA Astrophysics Data System (ADS)
Song, Li; Chuanbin, Zeng; Jiajun, Luo; Zhengsheng, Han
The human body model (HBM) stress of a no-connect metal cover is tested to obtain the characteristics of abnormal electrostatic discharge, including current waveforms and peak current under varied stress voltage and device failure voltage. A new discharge model called the "sparkover-induced model" is proposed based on the results. Then, failure mechanism analysis and model simulation are performed to prove that the transient peak current caused by a sparkover of low arc impedance will result in the devices' premature damage when the potential difference between the no-connect metal cover and the chip exceeds the threshold voltage of sparkover.
Whether abnormal energy electrons are being produced in electric discharges in dense gases?
NASA Astrophysics Data System (ADS)
Babich, L. P.; Loiko, T. V.
Reviewing results of experimental research of picosecond pulses of runaway electrons (REs) generated by discharges in dense gases at multiple overvoltages, including, along with routine measurements of voltage pulses and RE current, direct measurements of RE energy distributions, pressure dependence of RE numbers and experiment with retarding voltage similar to the accelerating voltage, a reality of the effect of "abnormal energy" REs is being substantiated. With this goal we emphasize non-conventional qualitative RE characteristics rather than quantitative.
ERIC Educational Resources Information Center
Scharlin, Pirketta; And Others
Extends the work of Weimer and Battino in electrical conductivity demonstrations creating "glowing" vegetables (see article this issue) to other vegetables and the spectra generated by other elements other than the sodium in pickle brines. Describes a study on the effect of concentration and voltage on glow intensity. (MKR)
Study on the effect of hydrogen addition on the variation of plasma parameters of argon-oxygen magnetron glow discharge for synthesis of TiO2 films
NASA Astrophysics Data System (ADS)
Saikia, Partha; Saikia, Bipul Kumar; Bhuyan, Heman
We report the effect of hydrogen addition on plasma parameters of argon-oxygen magnetron glow discharge plasma in the synthesis of H-doped TiO2 films. The parameters of the hydrogen-added Ar/O2 plasma influence the properties and the structural phases of the deposited TiO2 film. Therefore, the variation of plasma parameters such as electron temperature (Te), electron density (ne), ion density (ni), degree of ionization of Ar and degree of dissociation of H2 as a function of hydrogen content in the discharge is studied. Langmuir probe and Optical emission spectroscopy are used to characterize the plasma. On the basis of the different reactions in the gas phase of the magnetron discharge, the variation of plasma parameters and sputtering rate are explained. It is observed that the electron and heavy ion density decline with gradual addition of hydrogen in the discharge. Hydrogen addition significantly changes the degree of ionization of Ar which influences the structural phases of the TiO2 film.
Modeling of Hydrogenated Amorphous Silicon (a-Si:H) Thin Films Prepared by the Saddle Field Glow Discharge Method for Photovoltaic Applications
NASA Astrophysics Data System (ADS)
Sachenko, A. V.; Shkrebtii, A. I.; Gaspari, F.; Kherani, N.; Kazakevitch, A.
We present results of combined theoretical and experimental study of the thin hydrogenated amorphous silicon (a-Si:H) films based solar cells. The films for efficient and inexpensive solar cells were grown by the Saddle Field Glow Discharge Method. An analytical model to optimize photo-conversion efficiency a-Si:H based solar cells with contact grid has been developed. This two-dimensional model allows an optimization of the p+-i-n sandwich in terms of carrier mobilities, layers thickness, doping levels and others. The geometry of the grid fingers that conduct the photo-current to the bus bars and ITO/SiO2 layers has been optimizes as well as the effect of non-zero sun incidence angles. We demonstrate the optimization method to the typical a-Si:H solar cells.
Comparative nonempirical analysis of emission properties of the Ar-MeIn glow discharge (Me = Ga, Zn, Sn, In, Bi, Tl)
NASA Astrophysics Data System (ADS)
Deminsky, M.; Adamson, S.; Chernysheva, I.; Dyatko, N.; Eletzkii, A.; Kochetov, I.; Napartovich, A.; Rykova, E.; Sukhanov, L.; Umanskii, S.; Zaitsevskii, A.; Smith, D. J.; Sommerer, T. J.; Costas, J.; Potapkin, B.
A screening procedure is applied for several candidates (GaI3, ZnI2, SnI2, InI, BiI3, TlI) in respect of their light emission properties in a Ar-MeIn glow discharge. Candidates are compared in terms of emission efficiency for a wide range of external conditions: temperature, matrix gas pressure, and MeIn vapor pressure. The differences among the systems are explained by analyzing the kinetic mechanisms of formation, excitation, and loss of the emitting atoms. Analysis of the trends in the electronic structures of emitters (atoms) and precursors (molecules), as well as the stoichiometry and endothermicity of the plasma-chemical reactions, was made, and matched with selection rules.
Structure and properties of the surface of a laminate polyimide-fluoropolymer film modified in a low-frequency glow discharge plasma
Gil`man, A.B.; Kuznetsov, A.A.; Vengerskaya, L.E.
Variations in the wettability of a PMR-351 laminate (polyimide and tetrafluoroethylene-hexafluoropropylene copolymer) film under the action of a low-frequency glow discharge plasma depending on the duration and conditions of the treatment was studied. For the modified films, the stability of contact angles {theta} upon film storage in air was studied. Experimental values of {theta} were used for calculations of the total free energy of the surface and its polar and dispersion components. Chemical and structural changes on the polyimide and the fluoropolymer surface of the film under the action of plasma were studied using the technique of multiple internal-reflection IR spectroscopy. A possible mechanism of these changes is suggested.
Evaluation of the temporal profiles and the analytical features of a laser ablation - Pulsed glow discharge coupling for optical emission spectrometry
NASA Astrophysics Data System (ADS)
González de Vega, Claudia; Bordel, Nerea; Pereiro, Rosario; Sanz-Medel, Alfredo
The coupling of a glow discharge (GD) in pulsed mode (PGD) as secondary source for excitation/ionization of the material provided by laser ablation (LA) has been investigated using optical emission spectrometry (OES). The variation of the laser pulse delay with respect to the GD pulse allows to producing the ablation process during prepeak, plateau or afterglow GD regions. Emission properties of the LA-PGD plasma in each temporal region of the GD pulse have been evaluated for analytical lines of different elements. Resonant atomic lines have shown higher emission intensity in the prepeak region compared to non-resonant lines. Non-resonant lines showed higher enhancement of the emission intensity in the afterglow region. Moreover, the coupled LA-PGD system offered better linear correlation coefficients using a set of glass standards for calibration as well as lower detection limits (by at least a factor of two) when compared to laser induced breakdown spectroscopy.
Amorphous silicon nitride films of different composition deposited at room temperature by pulsed glow discharge plasma immersion ion implantation and deposition
Afanasyev-Charkin, I.V.; Jacobsohn, L.G.; Averitt, R.D.; Nastasi, M.
Amorphous hydrogenated silicon nitride (a-SiN{sub x}:H) films of different compositions (0{<=}x{<=}1.18) were prepared by pulsed glow discharge plasma immersion ion implantation and deposition. The processing gases were silane and nitrogen at a substrate temperature {<=}50 deg. C. The properties of the films were investigated using Rutherford backscattering, elastic recoil detection analysis, UV-visible optical absorption, Fourier transform infrared, and Raman spectroscopies, and nanoindentation. Depending on the value of x, the band gap of the films changes from 1.54 to 4.42 eV, and hardness changes from 11.2 to 15.3 GPa. Changes in the film properties are caused by formation of Si-N bonds and by reducing disorder in the films. It is shown that hard and transparent silicon nitride films can be obtained at room temperature.
Amorphous silicon nitride films of different composition deposited at room temperature by pulsed glow discharge plasma immersion ion implantation and deposition
NASA Astrophysics Data System (ADS)
Afanasyev-Charkin, I. V.; Jacobsohn, L. G.; Averitt, R. D.; Nastasi, M.
Amorphous hydrogenated silicon nitride (a-SiNx:H) films of different compositions (0<=x<=1.18) were prepared by pulsed glow discharge plasma immersion ion implantation and deposition. The processing gases were silane and nitrogen at a substrate temperature <=50 °C. The properties of the films were investigated using Rutherford backscattering, elastic recoil detection analysis, UV-visible optical absorption, Fourier transform infrared, and Raman spectroscopies, and nanoindentation. Depending on the value of x, the band gap of the films changes from 1.54 to 4.42 eV, and hardness changes from 11.2 to 15.3 GPa. Changes in the film properties are caused by formation of Si-N bonds and by reducing disorder in the films. It is shown that hard and transparent silicon nitride films can be obtained at room temperature.
Characterization of argon direct-current glow discharge with a longitudinal electric field applied at ambient air
Jiang, Weiman; Tang, Jie; Wang, Yishan; Zhao, Wei; Duan, Yixiang
A direct-current-driven plasma jet is developed by applying a longitudinal electric field on the flowing argon at ambient air. This plasma shows a torch shape with its cross-section increased from the anode to the cathode. Comparison with its counterparts indicates that the gas flow plays a key role in variation of the plasma structure and contributes much to enlarging the plasma volume. It is also found that the circular hollow metal base promotes generation of plasma with a high-power volume density in a limited space. The optical emission spectroscopy (OES) diagnosis indicates that the plasma comprises many reactive species, such as OH, O, excited N2, and Ar metastables. Examination of the rotational and vibrational temperature indicates that the plasma is under nonequilibrium condition and the excited species OH(A 2Σ+), O(5P), and N2(C 3Πu) are partly generated by energy transfer from argon metastables. The spatially resolved OES of plasma reveals that the negative glow, Faraday dark space, and positive column are distributed across the gas gap. The absence of the anode glow is attributed to the fact that many electrons in the vicinity of the anode follow ions into the positive column due to the ambipolar diffusion in the flowing gas. PMID:25205176
Characterization of argon direct-current glow discharge with a longitudinal electric field applied at ambient air.
Jiang, Weiman; Tang, Jie; Wang, Yishan; Zhao, Wei; Duan, Yixiang
A direct-current-driven plasma jet is developed by applying a longitudinal electric field on the flowing argon at ambient air. This plasma shows a torch shape with its cross-section increased from the anode to the cathode. Comparison with its counterparts indicates that the gas flow plays a key role in variation of the plasma structure and contributes much to enlarging the plasma volume. It is also found that the circular hollow metal base promotes generation of plasma with a high-power volume density in a limited space. The optical emission spectroscopy (OES) diagnosis indicates that the plasma comprises many reactive species, such as OH, O, excited N2, and Ar metastables. Examination of the rotational and vibrational temperature indicates that the plasma is under nonequilibrium condition and the excited species OH(A (2)Σ(+)), O((5)P), and N2(C (3)Πu) are partly generated by energy transfer from argon metastables. The spatially resolved OES of plasma reveals that the negative glow, Faraday dark space, and positive column are distributed across the gas gap. The absence of the anode glow is attributed to the fact that many electrons in the vicinity of the anode follow ions into the positive column due to the ambipolar diffusion in the flowing gas. PMID:25205176
Poly (Acrylamide-co-Acrylic Acid) Hydrogel Induced by Glow-Discharge Electrolysis Plasma and Its Adsorption Properties for Cationic Dyes
NASA Astrophysics Data System (ADS)
Yu, Jie; Yang, Gege; Pan, Yuanpei; Lu, Quanfang; Yang, Wu; Gao, Jinzhang
In this paper, poly (acrylamide-co-acrylic acid) (P(AM-co-AA)) hydrogel was prepared in an aqueous solution by using glow-discharge electrolysis plasma (GDEP) induced copolymerization of acrylamide (AM) and acrylic acid (AA), in which N,N'-methylenebisacrylamide (MBA) was used as a crosslinker. A mechanism for the synthesis of P(AM-co-AA) hydrogel was proposed. To optimize the synthesis condition, the following parameters were examined in detail: the discharge voltage, discharge time, the content of the crosslinker, and the mass ratio of AM to AA. The results showed that the optimum pH range for cationic dyes removal was found to be 5.0-10.0. The P(AM-co-AA) hydrogel exhibits a very high adsorption potential and the experimental adsorption capacities for Crystal violet (CV) and Methylene blue (MB) were 2974.3 mg/g and 2303.6 mg/g, respectively. The adsorption process follows a pseudo-second-order kinetic model. In addition, the adsorption mechanism of P(AM-co-AA) hydrogel for cationic dyes was also discussed.
Liquid Sampling-Atmospheric Pressure Glow Discharge (LS-APGD) Ionization Source for Elemental Mass Spectrometry: Preliminary Parametric Evaluation and Figures of Merit
Quarles, C. Derrick; Carado, Anthony J.; Barinaga, Charles J.; Koppenaal, David W.; Marcus, R. Kenneth
A new, low power ionization source for the elemental analysis of aqueous solutions has recently been described. The liquid sampling-atmospheric pressure glow discharge (LS-APGD) source operates at relatively low currents (<20 mA) and solution flow rates (<50 μL min-1), yielding a relatively simple alternative for atomic mass spectrometry applications. The LS-APGD has been interfaced to what is otherwise an organic, LC-MS mass analyzer, the Thermo Scientific Exactive Orbitrap without any modifications; other than removing the electrospray ionization (ESI) source supplied with that instrument. A glow discharge is initiated between the surface of the test solution exiting a glass capillary and a metallic counter electrode mounted at a 90° angle and separated by a distance of ~5 mm. As with any plasma-based ionization source, there are key discharge operation and ion sampling parameters that affect the intensity and composition of the derived mass spectra; including signal-to-background ratios. We describe here a preliminary parametric evaluation of the roles of discharge current, solution flow rate, argon sheath gas flow rate, and ion sampling distance as they apply on this mass analyzer system. A cursive evaluation of potential matrix effects due to the presence of easily ionized elements (EIEs) indicate that sodium concentrations of up to 500 μg mL-1 generally cause suppressions of less than 50%, dependant upon the analyte species. Based on the results of this series of studies, preliminary limits of detection (LOD) have been established through the generation of calibration functions. Whilst solution-based concentrations LOD levels of 0.02 – 2 μg mL-1 3 are not impressive on the surface, the fact that they are determined via discrete 5 μL injections leads to mass-based detection limits at picogram to singlenanogram levels. The overhead costs associated with source operation (10 W d.c. power, solution flow rates of <50 μL min-1, and gas flow rates <10 mL min
Liquid sampling-atmospheric pressure glow discharge (LS-APGD) ionization source for elemental mass spectrometry: preliminary parametric evaluation and figures of merit.
Quarles, C Derrick; Carado, Anthony J; Barinaga, Charles J; Koppenaal, David W; Marcus, R Kenneth
A new, low-power ionization source for the elemental analysis of aqueous solutions has recently been described. The liquid sampling-atmospheric pressure glow discharge (LS-APGD) source operates at relatively low currents (<20 mA) and solution flow rates (<50 μL min(-1)), yielding a relatively simple alternative for atomic mass spectrometry applications. The LS-APGD has been interfaced to what is otherwise an organic, LC-MS mass analyzer, the Thermo Scientific Exactive Orbitrap without any modifications, other than removing the electrospray ionization source supplied with that instrument. A glow discharge is initiated between the surface of the test solution exiting a glass capillary and a metallic counter electrode mounted at a 90° angle and separated by a distance of ~5 mm. As with any plasma-based ionization source, there are key discharge operation and ion sampling parameters that affect the intensity and composition of the derived mass spectra, including signal-to-background ratios. We describe here a preliminary parametric evaluation of the roles of discharge current, solution flow rate, argon sheath gas flow rate, and ion sampling distance as they apply on this mass analyzer system. A cursive evaluation of potential matrix effects due to the presence of easily ionized elements indicate that sodium concentrations of up to 50 μg mL(-1) generally cause suppressions of less than 50%, dependant upon the analyte species. Based on the results of this series of studies, preliminary limits of detection (LOD) have been established through the generation of calibration functions. While solution-based concentration LOD levels of 0.02-2 μg mL(-1) are not impressive on the surface, the fact that they are determined via discrete 5 μL injections leads to mass-based detection limits at picogram to single-nanogram levels. The overhead costs associated with source operation (10 W d.c. power, solution flow rates of <50 μL min(-1), and gas flow rates <10 mL min(-1)) are
Diagnostics of a glow discharge used to produce hydrogenated amorphous silicon films. Final report, April 15, 1982-April 14, 1983
Gallagher, A.; Scott, J.
The amount of silane reacted in a discharge is studied. The dependence of the fraction of reacted silane and the product forms on discharge conditions is studied. Results indicate the criteria for rapid, efficient film deposition, and the discharge and flow conditions that induce major modifications of the gas and probably of the depositing species. The discharge energy efficiency is also obtained as well as silane-use efficiency in pure silane and silane-noble gas mixtures. In-situ film-deposition rate monitors have been developed and used to study deposition as a function of discharge conditions. Further study has concentrated on the discharge ion species and the collisional processes which control the mixture of ion species. It is confirmed that the ion deposition is a relatively small fraction of all silicon deposition in dc discharges. Total electron collisional ionization of silane and disilane were measured, as well as the partial cross sections for producing various product ions. Ion-molecule reactions are also measured. (LEW)
Effects of the shielding cylinder and substrate on the characteristics of an argon radio-frequency atmospheric glow discharge plasma jet
Li Guo; Le Peisi; Li Heping; Bao Chengyu
With unique features of low breakdown voltages, large and uniform discharge areas and high concentrations of chemically reactive species, radio-frequency, atmospheric-pressure glow discharge (rf APGD) plasma sources produced with bare-metallic electrodes have shown promising prospects in the field of materials processing. In this paper, the spatial distributions (i.e., the directly measured integrated axial distribution and the radial distribution by using the inverse Abel transform) of the emission intensities of the Ar I 696.5 nm line are studied for the argon rf APGD plasma jet under different operation conditions, including variations of the rf power input or the argon flow rate, the existence of the solid shielding cylinder or the substrate. The experimental results show that, with other parameters being unchanged, the emission intensities of the Ar I 696.5 nm line increase with increasing the rf power input or the argon flow rate; and the solid shielding cylinder has more significant influences on the characteristics of the plasma impinging jet by reducing the mass flow rate of the ambient air entrained into the plasma jet region than those for the cases without the existence of the substrate at the downstream of the plasma torch nozzle exit.
Solution cathode glow discharge induced vapor generation of mercury and its application to mercury speciation by high performance liquid chromatography-atomic fluorescence spectrometry.
He, Qian; Zhu, Zhenli; Hu, Shenghong; Jin, Lanlan
A novel solution cathode glow discharge (SCGD) induced vapor generation was developed as interface to on-line couple high-performance liquid chromatography (HPLC) with atomic fluorescence spectrometry (AFS) for the speciation of inorganic mercury (Hg(2+)), methyl-mercury (MeHg) and ethyl-mercury (EtHg). The decomposition of organic mercury species and the reduction of Hg(2+) could be completed in one step with this proposed SCGD induced vapor generation system. The vapor generation is extremely rapid and therefore is easy to couple with flow injection (FI) and HPLC. Compared with the conventional HPLC-CV-AFS hyphenated systems, the proposed HPLC-SCGD-AFS system is very simple in operation and eliminates auxiliary redox reagents. Parameters influencing mercury determination were optimized, such as concentration of formic acid, discharge current and argon flow rate. The method detection limits for HPLC-SCGD-AFS system were 0.67 μg L(-1) for Hg(2+), 0.55 μg L(-1) for MeHg and 1.19 μg L(-1) for EtHg, respectively. The developed method was validated by determination of certified reference material (GBW 10029, tuna fish) and was further applied for the determination of mercury in biological samples. PMID:21641599
Effects of the shielding cylinder and substrate on the characteristics of an argon radio-frequency atmospheric glow discharge plasma jet
NASA Astrophysics Data System (ADS)
Li, Guo; Le, Pei-Si; Li, He-Ping; Bao, Cheng-Yu
With unique features of low breakdown voltages, large and uniform discharge areas and high concentrations of chemically reactive species, radio-frequency, atmospheric-pressure glow discharge (rf APGD) plasma sources produced with bare-metallic electrodes have shown promising prospects in the field of materials processing. In this paper, the spatial distributions (i.e., the directly measured integrated axial distribution and the radial distribution by using the inverse Abel transform) of the emission intensities of the Ar I 696.5 nm line are studied for the argon rf APGD plasma jet under different operation conditions, including variations of the rf power input or the argon flow rate, the existence of the solid shielding cylinder or the substrate. The experimental results show that, with other parameters being unchanged, the emission intensities of the Ar I 696.5 nm line increase with increasing the rf power input or the argon flow rate; and the solid shielding cylinder has more significant influences on the characteristics of the plasma impinging jet by reducing the mass flow rate of the ambient air entrained into the plasma jet region than those for the cases without the existence of the substrate at the downstream of the plasma torch nozzle exit.
Influence of thin porous Al{sub 2}O{sub 3} layer on aluminum cathode to the H{sub a}lpha line shape in glow discharge
Steflekova, V.; Sisovic, N. M.; Konjevic, N.
The results of the Balmer alfa line shape study in a plane cathode-hollow anode Grimm discharge with aluminum (Al) cathode covered with thin layer of porous Al{sub 2}O{sub 3} are presented. The comparison with same line profile recorded with pure Al cathode shows lack of excessive Doppler broadened line wings, which are always detected in glow discharge with metal cathode. The effect is explained by the lack of strong electric field in the cathode sheath region, which is missing in the presence of thin oxide layer in, so called, spray discharge.
Development of High Quality 1.36 eV Amorphous SiGe:H Alloy by RF Glow Discharge under Helium Dilution
NASA Astrophysics Data System (ADS)
Hazra, Sukti; Middya, Abdul; Rath, Jatindra; Basak, Subhashis; Ray, Swati
The use of 1.35 eV amorphous silicon-germanium (a-SiGe:H) alloy as the second/third intrinsic layer along with 1.85 eV front layer in double/triple tandem solar cells is believed to be the best combination for the maximum power output for multijunction cells. In this study high quality low-band-gap (1.36 eV) a-SiGe:H alloy has been developed by RF glow discharge optimizing the deposition parameters and helium dilution of source gases. It has been observed that the structural, electronic properties and defect densities of alloy films developed under the deposition condition which is the transition from low-discharge-power to high-discharge-power regime, become optimum. In the present case this deposition condition is a combination of chamber pressure 0.8 Torr and RF power 60 mW/cm2. The properties of the alloy films developed under helium dilution improve and defect density decreases with the increase of deposition rate up to 120 Å/min. The 1.36 eV alloy film prepared under this condition has very low defect density ( 3.2×1016 cm-3 eV-1). The analysis of spectral response of Pd/a-SiGe:H Schottky barrier solar cells reveals that the hole transport properties improve due to increase of RF power from 15 to 60 mW/cm2 and also due to increase of growth rate from 51 to 120 Å/min.
The Influence of CO2 Admixtures on the Product Composition in a Nitrogen-Methane Atmospheric Glow Discharge Used as a Prebiotic Atmosphere Mimic
NASA Astrophysics Data System (ADS)
Mazankova, V.; Torokova, L.; Krcma, F.; Mason, N. J.; Matejcik, S.
This work extends our previous experimental studies of the chemistry of Titan's atmosphere by atmospheric glow discharge. The Titan's atmosphere seems to be similarly to early Earth atmospheric composition. The exploration of Titan atmosphere was initiated by the exciting results of the Cassini-Huygens mission and obtained results increased the interest about prebiotic atmospheres. Present work is devoted to the role of CO2 in the prebiotic atmosphere chemistry. Most of the laboratory studies of such atmosphere were focused on the chemistry of N2 + CH4 mixtures. The present work is devoted to the study of the oxygenated volatile species in prebiotic atmosphere, specifically CO2 reactivity. CO2 was introduced to the standard N2 + CH4 mixture at different mixing ratio up to 5 % CH4 and 3 % CO2. The reaction products were characterized by FTIR spectroscopy. This work shows that CO2 modifies the composition of the gas phase with the detection of oxygenated compounds: CO and others oxides. There is a strong influence of CO2 on increasing concentration other products as cyanide (HCN) and ammonia (NH3).
Atmospheric identification of active ingredients in over-the-counter pharmaceuticals and drugs of abuse by atmospheric pressure glow discharge mass spectrometry (APGD-MS).
Brewer, Tim M; Verkouteren, Jennifer R
Atmospheric pressure glow discharge mass spectrometry was used to characterize the active ingredients in pharmaceutical over-the-counter (OTC) drug formulations (Tylenol Allergy, Alka-Seltzer Plus Nighttime, Sudafed, Aleve and Mucinex DM) and drugs of abuse (crack cocaine, methamphetamine, MDMA (ecstasy) and hydrocodone). Material was desorbed and directly ionized under atmospheric conditions by allowing the substance to come in direct contact with the plasma followed by mass spectrometric detection. With this technique, controlled substances and OTC medications were readily distinguished from one another. Characteristic mass spectra were identified for the active ingredients in the OTC and drugs of abuse. Importantly, all drug compounds studied here, both OTC and illicit, demonstrated signals for either molecular ions or protonated molecules as well as fragmentation patterns that are readily identified in the National Institute of Standards and Technology (NIST) electron ionization (EI) mass spectral library. It is believed that this technique holds promise for forensic and law enforcement communities for real-time atmospheric analysis of drugs with database-searchable spectra of controlled substances. PMID:21818799
Oxynitrided Surface Layer Produced On Ti6Al4V Titanium Alloy Under Low Temperature Glow Discharge Conditions For Medical Applications
NASA Astrophysics Data System (ADS)
Wierzchon, T.; Ossowski, M.; Borowski, T.; Morgiel, J.; Czarnowska, E.
In spite that titanium oxides increase biocompatibility of titanium implants but their functional life is limited due to the problems arising from brittles and metalosis. Therefore technology, that allow to produce composite surface layer with controlled microstructure, chemical and phase composition and surface morphology on titanium alloy and eliminates the oxides disadvantages has been existing till now is searched. The requirements of titanium and its alloys implants can be fulfill by the low—temperature glow discharge assisted oxynitriding. The paper describes the surface layer of TiO2+TiN+Ti2N+αTi(N) type produced at temperature 680° C that preserves mechanical properties of titanium alloy Ti6Al4V. Characteristics of produced diffusion multi-phase surface layers in range of phase composition, microstructure (SEM, TEM, XRD) and its properties, such as frictional wear resistance are presented. The biological properties in dependency to the applied sterilization method are also analyzed. Properties of produced surface layers are discussed with reference to titanium alloy. The obtained data show that produced surface layers improves titanium alloy properties both frictional wear and biological. Preliminary in vitro examinations show good biocompatibility and antithrombogenic properties.
Characterization of Doped Amorphous Silicon Thin Films through the Investigation of Dopant Elements by Glow Discharge Spectrometry. A Correlation of Conductivity and Bandgap Energy Measurements
Sánchez, Pascal; Lorenzo, Olaya; Menéndez, Armando; Menéndez, Jose Luis; Gomez, David; Pereiro, Rosario; Fernández, Beatriz
The determination of optical parameters, such as absorption and extinction coefficients, refractive index and the bandgap energy, is crucial to understand the behavior and final efficiency of thin film solar cells based on hydrogenated amorphous silicon (a-Si:H). The influence of small variations of the gas flow rates used for the preparation of the p-a-SiC:H layer on the bandgap energy, as well as on the dopant elements concentration, thickness and conductivity of the p-layer, is investigated in this work using several complementary techniques. UV-NIR spectrophotometry and ellipsometry were used for the determination of bandgap energies of four p-a-SiC:H thin films, prepared by using different B2H6 and SiH4 fluxes (B2H6 from 12 sccm to 20 sccm and SiH4 from 6 sccm to 10 sccm). Moreover, radiofrequency glow discharge optical emission spectrometry technique was used for depth profiling characterization of p-a-SiC:H thin films and valuable information about dopant elements concentration and distribution throughout the coating was found. Finally, a direct relationship between the conductivity of p-a-SiC:H thin films and the dopant elements concentration, particularly boron and carbon, was observed for the four selected samples. PMID:21731436
Oxynitrided Surface Layer Produced On Ti6Al4V Titanium Alloy Under Low Temperature Glow Discharge Conditions For Medical Applications
Wierzchon, T.; Ossowski, M.; Borowski, T.; Morgiel, J.; Czarnowska, E.
In spite that titanium oxides increase biocompatibility of titanium implants but their functional life is limited due to the problems arising from brittles and metalosis. Therefore technology, that allow to produce composite surface layer with controlled microstructure, chemical and phase composition and surface morphology on titanium alloy and eliminates the oxides disadvantages has been existing till now is searched. The requirements of titanium and its alloys implants can be fulfill by the low-temperature glow discharge assisted oxynitriding.The paper describes the surface layer of TiO{sub 2}+TiN+Ti{sub 2}N+{alpha}Ti(N) type produced at temperature 680 deg. C that preserves mechanical properties of titanium alloy Ti6Al4V. Characteristics of produced diffusion multi-phase surface layers in range of phase composition, microstructure (SEM, TEM, XRD) and its properties, such as frictional wear resistance are presented. The biological properties in dependency to the applied sterilization method are also analyzed.Properties of produced surface layers are discussed with reference to titanium alloy. The obtained data show that produced surface layers improves titanium alloy properties both frictional wear and biological. Preliminary in vitro examinations show good biocompatibility and antithrombogenic properties.
Evaluation of flow injection-solution cathode glow discharge-atomic emission spectrometry for the determination of major elements in brines.
Yang, Chun; Wang, Lin; Zhu, Zhenli; Jin, Lanlan; Zheng, Hongtao; Belshaw, Nicholas Stanley; Hu, Shenghong
A new method for the determination of major metal elements in high salinity brines was developed by solution cathode glow discharge (SCGD) with flow injection analysis (FIA). The matrix interferences of major cations and anions in brines have been evaluated. It was found that high concentration of Na(+) and K(+) could interfere each other, K(+) at a concentration of 400mgL(-1) enhanced the signal intensity of Na(+) more than 20%. The effect of the anions was observed and it was noted that the signal intensity of both Ca(2+) and Mg(2+) were suppressed significantly when the SO4(2-) reached 100mgL(-1). It was demonstrated that some low molecular weight organic substances such as formic acid, glycerol and ascorbic acid could eliminate interference of SO4(2-) even with volume percentages of 0.5%. Under the optimized condition, the proposed FIA-SCGD can determine K, Na, Ca and Mg with the limits of detection of 0.49 (K), 0.14 (Na), 11 (Ca) and 5.5 (Mg) ngmL(-1). The proposed method has been successfully applied to the analysis of 5 salt lake samples and compared with those obtained with inductively coupled plasma atomic emission spectrometry (ICP-AES). The advantages of small size, low energy consumption, good stability and repeatability indicated that the SCGD is promising for the determination of major ions in brine samples. PMID:27216688
Characterization of doped amorphous silicon thin films through the investigation of dopant elements by glow discharge spectrometry: a correlation of conductivity and bandgap energy measurements.
Sánchez, Pascal; Lorenzo, Olaya; Menéndez, Armando; Menéndez, Jose Luis; Gomez, David; Pereiro, Rosario; Fernández, Beatriz
The determination of optical parameters, such as absorption and extinction coefficients, refractive index and the bandgap energy, is crucial to understand the behavior and final efficiency of thin film solar cells based on hydrogenated amorphous silicon (a-Si:H). The influence of small variations of the gas flow rates used for the preparation of the p-a-SiC:H layer on the bandgap energy, as well as on the dopant elements concentration, thickness and conductivity of the p-layer, is investigated in this work using several complementary techniques. UV-NIR spectrophotometry and ellipsometry were used for the determination of bandgap energies of four p-a-SiC:H thin films, prepared by using different B(2)H(6) and SiH(4) fluxes (B(2)H(6) from 12 sccm to 20 sccm and SiH(4) from 6 sccm to 10 sccm). Moreover, radiofrequency glow discharge optical emission spectrometry technique was used for depth profiling characterization of p-a-SiC:H thin films and valuable information about dopant elements concentration and distribution throughout the coating was found. Finally, a direct relationship between the conductivity of p-a-SiC:H thin films and the dopant elements concentration, particularly boron and carbon, was observed for the four selected samples. PMID:21731436
Tuneable microsecond-pulsed glow discharge design for the simultaneous acquisition of elemental and molecular chemical information using a time-of-flight mass spectrometer.
Solà-Vázquez, Auristela; Martín, Antonio; Costa-Fernández, José M; Pereiro, Rosario; Sanz-Medel, Alfredo
A microsecond-pulsed direct current glow discharge (GD) was interfaced and synchronized to a time-of-flight mass spectrometer MS(TOF) for time-gated generation and detection of elemental, structural, and molecular ions. In this way, sequential collection of the mass spectra at different temporal regimes occurring during the GD pulse cycle is allowed. The capabilities of this setup were explored using bromochloromethane as model analyte. A simple GD chamber, developed in our laboratory and characterized by a low plasma volume minimizing dilution of the sample but showing great robustness to the entrance of organic compounds in the microsecond-pulsed plasma, has been used. An exhaustive analytical characterization of the GD-MS(TOF) prototype has been performed. Calibration curves for bromochloromethane observed at the different time regimes of the GD pulse cycle (that is, for elemental, fragment, and molecular ions from the analyte) showed very good linearity for the measurement of the different involved ions, with precisions in the range of 7-13% (relative standard deviation). Actual detection limits obtained for bromochloromethane were in the range of 1-3 microg/L for elements monitoring in the GD pulse "prepeak", in the range of 11-13 microg/L when monitoring analyte fragments in the plateau, and about 238 microg/L when measuring the molecular peak in the afterpeak regime. PMID:19256521
Investigation on the erosion/deposition processes in the ITER-like wall divertor at JET using glow discharge optical emission spectrometry technique
NASA Astrophysics Data System (ADS)
Ruset, C.; Grigore, E.; Luculescu, C.; Tiseanu, I.; Likonen, J.; Mayer, M.; Rubel, M.; Matthews, G. F.; contributors, JET
As a complementary method to Rutherford back scattering (RBS), glow discharge optical emission spectrometry (GDOES) was used to investigate the depth profiles of W, Mo, Be, O and C concentrations into marker coatings (CFC/Mo/W/Mo/W) and the substrate of divertor tiles up to a depth of about 100 μm. A number of 10 samples cored from particular areas of the divertor tiles were analyzed. The results presented in this paper are valid only for those areas and they cannot be extrapolated to the entire tile. Significant deposition of Be was measured on Tile 3 (near to the top), Tile 6 (at about 40 mm from the innermost edge) and especially on Tile 0 (HFGC). Preliminary experiments seem to indicate a penetration of Be through the pores and imperfections of CFC material up to a depth of 100 μm in some cases. No erosion and a thin layer of Be (<1 μm) was detected on Tiles 4, 7 and 8. On Tile 1 no erosion was found at about 1/3 from bottom.
Effects of pulse voltage and deposition time on the adhesion strength of graded metal/carbon films deposited on bendable stainless steel foils by hybrid cathodic arc - glow discharge plasma assisted chemical vapor deposition
NASA Astrophysics Data System (ADS)
Jamesh, Mohammed Ibrahim; Boxman, R. L.; Bilek, Marcela M. M.; Kocer, Cenk; Hu, Tingwei; Zhang, Xuming; McKenzie, David R.; Chu, Paul K.
Graded Ti/C composite films with carbon topcoats are prepared on bendable stainless steel foils by hybrid cathodic arc / glow discharge plasma-assisted chemical vapor deposition to simulate cardiovascular stents. Strong adhesion between the stainless steel substrate and carbon topcoat is achieved due to the graded Ti/C interface and it is further improved by increasing the pulse voltage. Moreover, the graded coating is more hydrophilic than the stainless steel substrate.
Mercury speciation by HPLC--cold-vapour radiofrequency glow-discharge optical-emission spectrometry with on-line microwave oxidation.
Martínez, R; Pereiro, R; Sanz-Medel, A; Bordel, N
Hollow-cathode (HC) radiofrequency glow-discharge (rf-GD) optical-emission spectrometry (OES) has been used as detector for the determination of inorganic mercury by cold-vapour (CV) generation in a flow-injection (FI) system. Both NaBH4 and SnCl2 were evaluated as reducing reagents for production of mercury CV. The conditions governing the discharge (pressure, He flow rate, and delivered power) and Hg CV generation (NaBH4 or SnCl2 concentration and reagent flow rate) were optimized using both reducing agents. The analytical performance characteristics of FI-CV-rf-GD-OES for mercury detection were evaluated at the 253.6 nm emission mercury line. Detection limits (DL) of 0.2 ng mL(-1) using SnCl2 and 1.8 ng mL(-1) using NaBH4 were obtained (100 microliter sample injections were used). When the optimized experimental conditions using SnCl2 had been determined, the analytical potential of this CV-rf-GD-OES method was investigated as on-line detector for high-performance liquid chromatographic (HPLC) speciation of mercury (Hg(II) and methylmercury). The HPLC-CV-rf-GD-OES detection limits for 100 microliter sample injections were found to be 1.2 and 1.8 ng mL(-1) (as mercury) of inorganic mercury and methylmercury, respectively. The reproducibility observed was below +/- 8% for both species. Finally, the HPLC-CV-rf-GD-OES system developed was successfully applied to the determination of methylmercury (speciation) in two certified reference materials, Dorm-2 and Dolt-2. PMID:11768461
Influence of operating parameters on surface properties of RF glow discharge oxygen plasma treated TiO₂/PET film for biomedical application.
Pandiyaraj, K Navaneetha; Deshmukh, R R; Mahendiran, R; Su, Pi-G; Yassitepe, Emre; Shah, Ismat; Perni, Stefano; Prokopovich, Polina; Nadagouda, Mallikarjuna N
In this paper, a thin transparent titania (TiO2) film was coated on the surface of flexible poly(ethylene terephthalate) (PET) film using the sol-gel method. The surface properties of the obtained TiO2/PET film were further improved by RF glow discharge oxygen plasma as a function of exposure time and discharge power. The changes in hydrophilicity of TiO2/PET films were analyzed by contact angle measurements and surface energy. The influence of plasma on the surface of the TiO2/PET films was analyzed by atomic force microscopy (AFM) as well as the change in chemical state and composition that were investigated by X-ray photo electron spectroscopy (XPS). The cytotoxicity of the TiO2/PET films was analyzed using human osteoblast cells and the bacterial eradication behaviors of TiO2/PET films were also evaluated against Staphylococcus bacteria. It was found that the surface roughness and incorporation of oxygen containing polar functional groups of the plasma treated TiO2/PET films increased substantially as compared to the untreated one. Moreover the increased concentration of Ti(3+) on the surface of plasma treated TiO2/PET films was due to the transformation of chemical states (Ti(4+)→Ti(3+)). These morphological and chemical changes are responsible for enhanced hydrophilicity of the TiO2/PET films. Furthermore, the plasma treated TiO2/PET film exhibited no citotoxicity against osteoblast cells and antibacterial activity against Staphylococcus bacteria which can find application in manufacturing of biomedical devices. PMID:24433917
Use of a solution cathode glow discharge for cold vapor generation of mercury with determination by ICP-atomic emission spectrometry.
Zhu, Zhenli; Chan, George C-Y; Ray, Steven J; Zhang, Xinrong; Hieftje, Gary M
A novel vapor-generation technique is described for mercury determination in aqueous solutions. Without need for a chemical reducing agent, dissolved mercury species are converted to volatile Hg vapor in a solution cathode glow discharge. The generated Hg vapor is then transported to an inductively coupled plasma for determination by atomic emission spectrometry. Mercury vapor is readily generated from a background electrolyte containing 0.1 M HNO 3. Vapor generation efficiency was found to be higher by a factor of 2-3 in the presence of low molecular weight organic acids (formic or acetic acids) or alcohols (ethanol). Optimal conditions for discharge-induced vapor generation and reduced interference from concomitant inorganic ions were also identified. However, the presence of chloride ion reduces the efficiency of Hg-vapor generation. In the continuous sample introduction mode, the detection limit was found to be 0.7 microg L (-1), and repeatability was 1.2% RSD ( n = 11) for a 20 microg L (-1) standard. In comparison with other vapor generation methods, it offers several advantages: First, it is applicable to both inorganic and organic Hg determination; organic mercury (thiomersal) can be directly transformed into volatile Hg species without the need for prior oxidation. Second, the vapor-generation efficiency is high; the efficiency (with formic acid as a promoter) is superior to that of conventional SnCl 2-HCl reduction. Third, the vapor generation is extremely rapid and therefore is easy to couple with flow injection. The method is sensitive and simple in operation, requires no auxiliary reagents, and serves as a useful alternative to conventional vapor generation for ultratrace Hg determination. PMID:18710258
Common Gamma-ray Glows above Thunderclouds
NASA Astrophysics Data System (ADS)
Kelley, Nicole; Smith, David; Dwyer, Joseph; Hazelton, Bryna; Grefenstette, Brian; Lowell, Alex; Splitt, Michael; Lazarus, Steven; Rassoul, Hamid
Gamma-ray glows are continuous, long duration gamma- and x-ray emission seen coming from thunderclouds. The Airborne for Energetic Lightning Emissions (ADELE) observed 12 gamma-ray glows during its summer 2009 flight campaign over the areas of Colorado and Florida in the United States. For these glows we shall present their spectra, relationship to lightning activity and how their duration and size changes as a function of distance. Gamma-ray glows follow the relativistic runaway electron avalanche (RREA) spectrum and have been previously measured from the ground and inside the cloud. ADELE measured most glows as it flew above the screening layer of the cloud. During the brightest glow on August 21, 2009, we can show that we are flying directly into a downward facing relativistic runaway avalanche, indicative of flying between the upper positive and negative screening layer of the cloud. In order to explain the brightness of this glow, RREA with an electric field approaching the limit for relativistic feedback must be occurring. Using all 12 glows, we show that lightning activity diminishes during the onset of the glow. Using this along with the fact that glows occur as the field approaches the level necessary for feedback, we attempt to distinguish between two possibilities: that glows are evidence that RREA with feedback, rather than lightning, is sometimes the primary channel for discharging the cloud, or else that the overall discharging is still controlled by lightning, with glows simply appearing during times when a subsidence of lightning allows the field to rise above the threshold for RREA.
Preliminary Figures of Merit for Isotope Ratio Measurements: The Liquid Sampling-Atmospheric Pressure Glow Discharge Microplasma Ionization Source Coupled to an Orbitrap Mass Analyzer
NASA Astrophysics Data System (ADS)
Hoegg, Edward D.; Barinaga, Charles J.; Hager, George J.; Hart, Garret L.; Koppenaal, David W.; Marcus, R. Kenneth
In order to meet a growing need for fieldable mass spectrometer systems for precise elemental and isotopic analyses, the liquid sampling-atmospheric pressure glow discharge (LS-APGD) has a number of very promising characteristics. One key set of attributes that await validation deals with the performance characteristics relative to isotope ratio precision and accuracy. Owing to its availability and prior experience with this research team, the initial evaluation of isotope ratio (IR) performance was performed on a Thermo Scientific Exactive Orbitrap instrument. While the mass accuracy and resolution performance for Orbitrap analyzers are well-documented, no detailed evaluations of the IR performance have been published. Efforts described here involve two variables: the inherent IR precision and accuracy delivered by the LS-APGD microplasma and the inherent IR measurement qualities of Orbitrap analyzers. Important to the IR performance, the various operating parameters of the Orbitrap sampling interface, high-energy collisional dissociation (HCD) stage, and ion injection/data acquisition have been evaluated. The IR performance for a range of other elements, including natural, depleted, and enriched uranium isotopes was determined. In all cases, the precision and accuracy are degraded when measuring low abundance (<0.1% isotope fractions). In the best case, IR precision on the order of 0.1% RSD can be achieved, with values of 1%-3% RSD observed for low-abundance species. The results suggest that the LS-APGD is a promising candidate for field deployable MS analysis and that the high resolving powers of the Orbitrap may be complemented with a here-to-fore unknown capacity to deliver high-precision IRs.
Preliminary Figures of Merit for Isotope Ratio Measurements: The Liquid Sampling-Atmospheric Pressure Glow Discharge Microplasma Ionization Source Coupled to an Orbitrap Mass Analyzer.
Hoegg, Edward D; Barinaga, Charles J; Hager, George J; Hart, Garret L; Koppenaal, David W; Marcus, R Kenneth
In order to meet a growing need for fieldable mass spectrometer systems for precise elemental and isotopic analyses, the liquid sampling-atmospheric pressure glow discharge (LS-APGD) has a number of very promising characteristics. One key set of attributes that await validation deals with the performance characteristics relative to isotope ratio precision and accuracy. Owing to its availability and prior experience with this research team, the initial evaluation of isotope ratio (IR) performance was performed on a Thermo Scientific Exactive Orbitrap instrument. While the mass accuracy and resolution performance for Orbitrap analyzers are well-documented, no detailed evaluations of the IR performance have been published. Efforts described here involve two variables: the inherent IR precision and accuracy delivered by the LS-APGD microplasma and the inherent IR measurement qualities of Orbitrap analyzers. Important to the IR performance, the various operating parameters of the Orbitrap sampling interface, high-energy collisional dissociation (HCD) stage, and ion injection/data acquisition have been evaluated. The IR performance for a range of other elements, including natural, depleted, and enriched uranium isotopes was determined. In all cases, the precision and accuracy are degraded when measuring low abundance (<0.1% isotope fractions). In the best case, IR precision on the order of 0.1% RSD can be achieved, with values of 1%-3% RSD observed for low-abundance species. The results suggest that the LS-APGD is a promising candidate for field deployable MS analysis and that the high resolving powers of the Orbitrap may be complemented with a here-to-fore unknown capacity to deliver high-precision IRs. Graphical Abstract . PMID:27080006
Preliminary Figures of Merit for Isotope Ratio Measurements: The Liquid Sampling-Atmospheric Pressure Glow Discharge Microplasma Ionization Source Coupled to an Orbitrap Mass Analyzer
NASA Astrophysics Data System (ADS)
Hoegg, Edward D.; Barinaga, Charles J.; Hager, George J.; Hart, Garret L.; Koppenaal, David W.; Marcus, R. Kenneth
In order to meet a growing need for fieldable mass spectrometer systems for precise elemental and isotopic analyses, the liquid sampling-atmospheric pressure glow discharge (LS-APGD) has a number of very promising characteristics. One key set of attributes that await validation deals with the performance characteristics relative to isotope ratio precision and accuracy. Owing to its availability and prior experience with this research team, the initial evaluation of isotope ratio (IR) performance was performed on a Thermo Scientific Exactive Orbitrap instrument. While the mass accuracy and resolution performance for Orbitrap analyzers are well-documented, no detailed evaluations of the IR performance have been published. Efforts described here involve two variables: the inherent IR precision and accuracy delivered by the LS-APGD microplasma and the inherent IR measurement qualities of Orbitrap analyzers. Important to the IR performance, the various operating parameters of the Orbitrap sampling interface, high-energy collisional dissociation (HCD) stage, and ion injection/data acquisition have been evaluated. The IR performance for a range of other elements, including natural, depleted, and enriched uranium isotopes was determined. In all cases, the precision and accuracy are degraded when measuring low abundance (<0.1% isotope fractions). In the best case, IR precision on the order of 0.1% RSD can be achieved, with values of 1%-3% RSD observed for low-abundance species. The results suggest that the LS-APGD is a promising candidate for field deployable MS analysis and that the high resolving powers of the Orbitrap may be complemented with a here-to-fore unknown capacity to deliver high-precision IRs.
Isotope dilution mass spectrometry for quantitative elemental analysis of powdered samples by radiofrequency pulsed glow discharge time of flight mass spectrometry.
Alvarez-Toral, Aitor; Fernandez, Beatriz; Malherbe, Julien; Claverie, Fanny; Molloy, John L; Pereiro, Rosario; Sanz-Medel, Alfredo
In recent years particular effort is being devoted to the development of pulsed glow discharges (PGDs) for mass spectrometry because this powering operation mode could offer important ionization analytical advantages. However, the capabilities of radiofrequency (RF) PGD coupled to a time of flight mass spectrometry (ToFMS) for accurate isotope ratio measurements have not been demonstrated yet. This work is focused on investigating different time positions along the pulse profile for the accurate measurement of isotope ratios. As a result, a method has been developed for the direct and simultaneous multielement determination of trace elements in powdered geological samples by RF-PGD-ToFMS in combination with isotope dilution mass spectrometry (IDMS) as an absolute measurement method directly traceable to the International System of Units. Optimized operating conditions were 70 W of applied radiofrequency power, 250 Pa of pressure, 2 ms of pulse width and 4 ms of pulse period, being argon the plasma gas used. To homogeneously distribute the added isotopically-enriched standards, lithium borate fusion of powdered solid samples was used as sample preparation approach. In this way, Cu, Zn, Ba and Pb were successfully determined by RF-PGD-ToF(IDMS) in two NIST Standard Reference Materials (SRM 2586 and SRM 2780) representing two different matrices of geological interest (soil and rock samples). Cu, Zn, Ba and Pb concentrations determined by RF-PGD-ToF(IDMS) were well in agreement with the certified values at 95% confidence interval and precisions below 12% relative standard deviation were observed for three independent analyses. Elemental concentrations investigated were in the range of 81-5770 mg/kg, demonstrating the potential of RF-PGD-ToF(IDMS) for a sensitive, accurate and robust analysis of powdered samples. PMID:24054645
Characterization of helium/argon working gas systems in a radiofrequency glow discharge atomic emission source. Part I: Optical emission, sputtering and electrical characteristics
NASA Astrophysics Data System (ADS)
Christopher, Steven J.; Hartenstein, Matthew L.; Marcus, R. Kenneth; Belkin, Mikhail; Caruso, Joseph A.
Studies are performed to determine the influence of discharge gas composition (helium/argon working gas mixtures) on the analyte emission signal intensities, sputtering rates, and DC-bias characteristics of an analytical radiofrequency glow discharge atomic emission spectroscopy (RF-GD-AES) source. As the partial pressure of He is increased from 0 to 15 torr, increased emission intensity is observed for a range of bulk and trace elements in NIST 1250 SRM (low alloy steel), regardless of the base pressure of Ar in the source (5 and 9 torr). In contrast to increases in analyte emission intensity of up to 300%, counterindicative decreases in the sputtering rates on the order of about 30-50% are observed. The magnitude of these effects depends on both the partial pressure of helium introduced to the source and the total pressure of the He and Ar gases. Use of relative emission yield (REY) to normalize changes in emission intensity to sputtering rates indicates that excitation efficiencies increase under these conditions. Increases in average electron energy and temperature appear to control this response. Decreases in both analyte emission intensities and sputter rates occur with increasing He partial pressure when the total pressure in the cell remains fixed (11 torr in these studies). Emission yields for the fixed pressure, mixed gas plasmas decrease as the partial pressure of He (He/Ar ratio) in the RF-GD source increases. In this case, decreases in electron number densities appear to dictate the lower REYs. Measurement of DC-bias values at the sample surface provide understanding with respect to the observed changes in sputtering rates as well as suggest the origins of changes in plasma electron energetics. Use of a diamond stylus profilometer provides both the quantitative sputter rate information as well as qualitative insights into the use of mixed gas plasmas for enhanced depth profiling capabilities. The analyte emission characteristics of these mixed gas
Flowing Liquid Anode Atmospheric Pressure Glow Discharge as an Excitation Source for Optical Emission Spectrometry with the Improved Detectability of Ag, Cd, Hg, Pb, Tl, and Zn.
Greda, Krzysztof; Swiderski, Krzysztof; Jamroz, Piotr; Pohl, Pawel
A novel atmospheric pressure glow discharge generated in contact with a flowing liquid anode (FLA-APGD) was developed as the efficient excitation source for the optical emission spectrometry (OES) detection. Differences in the appearance and the electrical characteristic of the FLA-APGD and a conventional system operated with a flowing liquid cathode (FLC-APGD) were studied in detail and discussed. Under the optimal operating conditions for the FLA-APGD, the emission from the analytes (Ag, Cd, Hg, Pb, Tl, and Zn) was from 20 to 120 times higher as compared to the FLC-APGD. Limits of detections (LODs) established with a novel FLA-APGD system were on average 20 times better than those obtained for the FLC-APGD. A further improvement of the LODs was achieved by reducing the background shift interferences and, as a result, the LODs for Ag, Cd, Hg, Pb, Tl, and Zn were 0.004, 0.040, 0.70, 1.7, 0.035, and 0.45 μg L(-1), respectively. The precision of the FLA-APGD-OES method was evaluated to be within 2-5% (as the relative standard deviation of the repeated measurements). The method found its application in the determination of the content of Ag, Cd, Hg, Pb, Tl, and Zn in a certified reference material (CRM) of Lobster hepatopancreas (TORT-2), four brass samples as well as mineral water and tea leaves samples spiked with the analytes. In the case of brass samples, a reference method, i.e., inductively coupled plasma optical emission spectrometry (ICP-OES) was used. A good agreement between the results obtained with FLA-APGD-OES and the certified values for the CRM TORT-2 as well as the reference values obtained with ICP-OES for the brass samples was revealed, indicating the good accuracy of the proposed method. The recoveries obtained for the spiked samples of mineral water and tea leaves were within the range of 97.5-102%. PMID:27476678
A study of plasma reaction mechanisms and kinetics in glow discharges of methyl methacrylate and related precursors using in situ FTIR spectroscopy
NASA Astrophysics Data System (ADS)
Pan, Yu-Chi Vickie
In order to understand plasma deposition processes, it is important to have a knowledge of the plasma gas-phase reactions. In this project, in situ Fourier Transform Infrared Spectroscopy (FTIR) was utilized to study the plasma gas-phase chemistry in a capacitively coupled glow discharge. Gas-phase measurements of a number of organic plasmas were performed. The precursors include methyl methacrylate (MMA), methyl crotonate, methyl isobutyrate, ethyl methacrylate, vinyl acetate, isopropanol, methanol, tetramethyl cyclobutanedione and formaldehyde. However, MMA was studied most extensively. In addition to the gas-phase study, plasma polymerized films were also characterized. A number of dissociation products were detected by FTIR in the plasmas. Calibration curves of these products and some monomers were prepared to determine the species concentrations and gas-phase composition. Plasma reaction kinetics were studied in closed systems to determine parameters such as dissociation pathway efficiencies, monomer decomposition rate coefficients, and intermediate species decomposition rate coefficients. The study shows that there are two major electron-impact induced dissociation pathways in MMA plasmas: the C-O bond cleavage reaction and decarboxylations. The C-O bond cleavage reaction accounts for approximately half of the MMA dissociation, and neutral formaldehyde and dimethyl ketene (DMK) molecules are produced via intramolecular rearrangement. Decarboxylation reactions produce CO, COsb2 and a number of radicals that subsequently stabilize to form neutral molecules, such as propylene, allene and methanol. These intermediate species then further dissociate in the plasma to small hydrocarbons (methane, acetylene and ethylene), CO, COsb2 and Hsb2. The reaction mechanisms in the plasmas of other alpha ,beta-unsaturated esters and vinyl acetate were found to be similar to the MMA mechanisms. However, the saturated ester (methyl isobutyrate) and isopropanol plasmas were found
Optical magnetic resonances induced by the interference of reactive components in the near radiation-field zone of atoms in a glow discharge of a mixture of even neon isotopes
NASA Astrophysics Data System (ADS)
Saprykin, E. G.
Four types of anomalous optical magnetic resonances shifted with respect to the zero magnetic field and with different shapes are found in radiation of a glow discharge in a mixture of even neon isotopes placed in a swept longitudinal magnetic field. This testifies to the manifestation of collective processes of synchronous light emission by oscillators belonging to isotopically different spatially separated atoms in discharge plasma. The origin of resonances is associated with nonstationary interference of reactive fields in the near radiation-field zones of emission of atoms, averaged over the lifetime of the fields (interference), while different types of resonances are associated with different methods of synchronization of the phases of the fields.
Chronic compression of the posterior longitudinal ligament of the cervical spine is associated with abnormal discharge of middle cervical ganglion
Gu, Qingguo; Jiang, Dongjie; Wang, Xinwei; Chen, Deyu; Yuan, Wen
There are abundant sympathetic nerve fibers in cervical posterior longitudinal ligament (PLL). The aim of this study was to investigate the role of PLL in the occurrence of sympathetic symptoms. Ten healthy adult beagles were selected and anesthetized to establish a PLL compression model by C4/5 discectomy, nucleus pulposus tissue replantation, and plate internal fixation. The middle cervical ganglia (MCG) activities were recorded before modeling, shortly after modeling, and two months after modeling. The waveform parameters and spectral densities of autonomic discharge of MCG among the three periods were compared. There was significant difference only in terms of the area of waveform per unit time between before and shortly after modeling. Abnormal discharge waveforms of MCG were detected in two months after modeling. The wave amplitude and waveform area per unit time in two months after modeling were increased significantly compared with those in shortly after modeling. Functional spectral decomposition found a significant increase in 100-250 Hz in two months after modeling. In conclusion, abnormal discharge of MCG caused by chronic compression of PLL may be one of the pathological basis of sympathetic nervous symptoms. PMID:25550947
... medlineplus.gov/news/fullstory_159698.html Beware Broken Glow Sticks Contents can irritate skin, eyes, mouth, poison-control ... 2016 (HealthDay News) -- Letting kids chew or cut glow sticks is a bad idea, health experts say. While ...
[Discharge of incompetent mentally abnormal criminals: experience from the Austrian central treatment institution].
Knecht, G; Morawitz, I; Schanda, H
Based on the data of 66 male patients not guilty for reason of insanity, who were treated in Justizanstalt Göllersdorf, Austria's central institution for mentally ill offenders, we examined the influence of age, duration of detention, diagnosis, and offence on discharge. Law provides a yearly, compulsory examination of the necessity of further inpatient-treatment. We also tried to describe a concept of further dangerousness (considered to be the essential basis for the decision of possible discharge) in a four-factor-model including the criteria psychopathology, insight, conflict behaviour, and social competence. Concerning the various levels of decision finding (institution, expert, court) different interpretations of these criteria could be demonstrated. Independent of diagnostic and prognostic considerations the court stressed mainly kind of offence as the most important factor for the possibility of discharge. PMID:8248443
The use of radiative transition rates to study the changes in the excitation of Cu ions in a Ne glow discharge caused by small additions of H2, O2 and N2
NASA Astrophysics Data System (ADS)
Weiss, Z.; Steers, E. B. M.; Mushtaq, S.; Hoffmann, V.; Pickering, J. C.
The excitation of Cu+ ions in a Ne glow discharge with small additions of H2, O2 and N2 was studied. Ratios of radiative transition rates between different Cu II levels in a discharge in neon, with and without the molecular gas added, were calculated, and the formalism of transition rate ratio (TRR) diagrams was developed and used to study the changing excitation conditions. Virtually no changes in the excitation of Cu+ ions occur in a neon discharge if nitrogen is added. Additions of hydrogen and oxygen to neon as the discharge gas affect excitation of the 4d, 5s and some other Cu II levels in the vicinity of the ionization energy of neon (21.56 eV). Also some lower Cu II levels, excited by radiative decay of those higher energy levels, are affected. The 4p 3P2 level at 15.96 eV is enhanced by additions of hydrogen. It was suggested that this enhancement is caused by the asymmetric charge transfer reaction between neutral copper atoms and the H2+ molecular ions.
Diagnostics of a glow discharge used to produce hydrogenated amorphous-silicon films. Quarterly progress report, July 15, 1981-October 14, 1981
Gallagher, A.; Scott, J.
Several aspects have been studied of the modification of silane gas by discharges in pure silane and in Ar-SiH/sub 4/ and He-SiH/sub 4/ mixtures. Results are given relating to the efficiency for modifying SiH/sub 4/, the ions, and the neutrals produced from SiH/sub 4/. Emphasis is on dc proximity discharges. It is found that a major portion of the Si atoms depleted from SiH/sub 4/ by the discharge go into other stable molecules, the disilane Si/sub 2/H/sub 6/ being the most prominant. Also discussed is the role of unstable radicals. (LEW)
Diagnostics of glow discharges used to produce hydrogenated amorphous silicon films: Annual subcontract report, 15 April 1986-14 June 1987
Gallagher, A.; Doyle, J.; He, M.; Lin, G.H.; Scott, J.
This report presents results of research done to measure the neutral species produced in silane, silane-hydrogen, disilane, disilane-hydrogen, germane, germane-hydrogen, and silane-germane discharges. Interpretation and modeling of the data in terms of discharge chemistry are also desirable. Mass-spectrometric measurements were made of the stable gases flow through and produced in silane, disilane, and silane-germane discharges. From these observations, the discharge stoichiometry was determined and the reaction pathways that lead to film deposition clarified. The importance of one processing parameter (powerflow) is explained, and a high ratio of germanesilane depletion in mixed-gas discharges is identified. A calculation of radical deposition in pure silane discharges shows the dominance of SiH/sub 3/ deposition at low powers and suggests the reason (surface mobility) why this produced good-quality films. Measurements of postdeposition sputtering of a-Si:H films were important in understanding and modeling the deposition reactions as well as the high-rate deposition method was also developed and studied.
Excitation Energy Transfer of Metastable Krypton Atoms in Kr-He-Xe Low Pressure Glow Discharge for Mercury-Free Lighting
NASA Astrophysics Data System (ADS)
Hwang, Hyeon Seok; Baik, Hong Koo; Park, Ki Wan; Song, Kie Moon; Jong Lee, Se
The discharge of the gas mixture Kr-He-Xe was investigated as a source of vacuum ultraviolet for lighting purposes. The discharge characteristics of the Xe-He-Kr gas mixture were enhanced in comparison to those of Xe and a Xe-He gas mixture. The experimental results were evaluated by the infrared radiation from the positive column. The amount of infrared radiation under optimum conditions displayed higher efficiency than that of the He-Xe gas mixture, which results in the improved efficacy of lamp. This result was due to the emission properties that were improved by the potential energy transferred from the excited Kr to the Xe.
Changes in the IR internal reflection and absorption spectra of AK 60/40 polyamide films after the action of a glow discharge plasma
NASA Astrophysics Data System (ADS)
Lunin, V. V.; Rode, S. V.; Samoilovich, V. G.
The modification of surface layers of AK 60/40 polyamide under the action of a gas discharge plasma was studied. Measurements were performed by infrared internal reflection spectroscopy. The results were analyzed to establish possible mechanisms of the interaction of a plasma with the polymer and structural changes in the polymer.
Coupling of multi-walled carbon nanotubes/polydimethylsiloxane coated stir bar sorptive extraction with pulse glow discharge-ion mobility spectrometry for analysis of triazine herbicides in water and soil samples.
Zou, Nan; Yuan, Chunhao; Liu, Shaowen; Han, Yongtao; Li, Yanjie; Zhang, Jialei; Xu, Xiang; Li, Xuesheng; Pan, Canping
An analytical method based on stir bar sorptive extraction (SBSE) coupled with pulse glow discharge-ion mobility spectrometry (PGD-IMS) was developed for analysis of three triazine pesticide residues in water and soil samples. An injection port with sealing device and stir bars hold device were designed and constructed to directly position the SBSE fiber including the extracted samples into the heating device, making desorption and detection of analytes proceeded simultaneously. The extraction conditions such as SBSE solid phase material, extraction time, extraction temperature, pH value and salt concentration were optimized. Mixture of MWCNTs-COOH and PDMS were shown to be effective in enriching the triazines. The LODs and LOQs of three triazines were found to be 0.006-0.015μgkg(-1) and 0.02-0.05μgkg(-1), and the linear range was 0.05-10μgL(-1) with determination coefficients from 0.9987 to 0.9993. The SBSE-PGD-IMS method was environmentally friendly without organic solvent consumption in the entire experimental procedures, and it was demonstrated to be a commendable rapid analysis technique for analysis of triazine pesticide residues in environmental samples on site. The proposed method was applied for the analysis of real ground water, surface water and soil samples. PMID:27371024
Passivation of GaAs(001) surface by the growth of high quality c-GaN ultra-thin film using low power glow discharge nitrogen plasma source
NASA Astrophysics Data System (ADS)
Monier, G.; Bideux, L.; Robert-Goumet, C.; Gruzza, B.; Petit, M.; Lábár, J. L.; Menyhárd, M.
The benefits of using a low power glow discharge nitrogen plasma source to create high quality GaN layers on GaAs(001) surface are first highlighted. This uncommon type of plasma source has the particularity of working at a low power (3-10 W) and a low pressure (10- 1 Pa) which induce creation of a small quantity of active nitrogen species. We put in evidence that this distinctiveness allows the growth of a stoichiometric and As-free GaN ultra-thin film on a GaAs(001) substrate by the mean of the inter-diffusion of As and N atoms. XPS, EELS, AFM are used to monitor surface composition and structure changes and to estimate the GaN thickness. A near saturation of the nitride layer thickness versus plasma exposure time is found. Furthermore, the possibility to crystallize the amorphous GaN layer by an annealing at 620 °C in a cubic structure with a lattice parameter close to that of c-GaN is put in evidence by means of TEM and LEED measurements. These measurements also show the homogeneity of the GaN thickness. In addition, the passivating effect of the GaN ultra-thin film to protect the GaAs surface is proved with the monitoring by XPS of the surface oxidation during several days of air exposure.
Determination of elemental constituents in different matrix materials and flow injection studies by the electrolyte cathode glow discharge technique with a new design
Shekhar, R.; Karunasagar, D.; Ranjit, M.; Arunachalam, J.
An open-to-air type electrolyte cathode discharge (ELCAD) has been developed with a new design. The present configuration leads to a stable plasma even at low flow rates (0.96 mL/min). Plasma fluctuations arising from the variations in the gap between solid anode and liquid cathode were eliminated by providing a V-groove to the liquid glass-capillary. Cathode (ground) connection is given to the solution at the V-groove itself. Interfaced to atomic emission spectrometry (AES), its analytical performance is evaluated. The optimized molarity of the solution is 0.2 M. The analytical response curves for Ca, Cu, Cd, Pb, Hg, Fe, and Zn demonstrated good linearity. The limit of detections of Ca, Cu, Cd, Pb, Hg, Fe, and Zn are determined to be 17, 11, 5, 45, 15, 28, and 3 ng mL{sup -1}. At an integration time of 0.3 s, the relative standard deviation (RSD) values of the acid blank solutions are found to be less than 10% for the elements Ca, Cu, Cd, Hg, Fe, and Zn and 18% for Pb. The method is applied for the determination of the elemental constituents in different matrix materials such as tuna fish (IAEA-350), oyster tissue (NIST SRM 1566a), and coal fly ash (CFA SRM 1633b). The obtained results are in good agreement with the certified values. The accuracy is found to be between 7% and 0.6% for major to trace levels of constituent elements and the precision between 11% and 0.6%. For the injection of 100 {mu} L of 200 ng mL{sup -1} mercury solution at the flow rate of 0.8 mL/min, the flow injection studies resulted in the relative standard deviation (RSD) of 8%, concentration detection limit of 10 ng/mL, and mass detection limit of 1 ng for mercury.
Determination of elemental constituents in different matrix materials and flow injection studies by the electrolyte cathode glow discharge technique with a new design.
Shekhar, R; Karunasagar, D; Ranjit, Manjusha; Arunachalam, J
An open-to-air type electrolyte cathode discharge (ELCAD) has been developed with a new design. The present configuration leads to a stable plasma even at low flow rates (0.96 mL/min). Plasma fluctuations arising from the variations in the gap between solid anode and liquid cathode were eliminated by providing a V-groove to the liquid glass-capillary. Cathode (ground) connection is given to the solution at the V-groove itself. Interfaced to atomic emission spectrometry (AES), its analytical performance is evaluated. The optimized molarity of the solution is 0.2 M. The analytical response curves for Ca, Cu, Cd, Pb, Hg, Fe, and Zn demonstrated good linearity. The limit of detections of Ca, Cu, Cd, Pb, Hg, Fe, and Zn are determined to be 17, 11, 5, 45, 15, 28, and 3 ng mL(-1). At an integration time of 0.3 s, the relative standard deviation (RSD) values of the acid blank solutions are found to be less than 10% for the elements Ca, Cu, Cd, Hg, Fe, and Zn and 18% for Pb. The method is applied for the determination of the elemental constituents in different matrix materials such as tuna fish (IAEA-350), oyster tissue (NIST SRM 1566a), and coal fly ash (CFA SRM 1633b). The obtained results are in good agreement with the certified values. The accuracy is found to be between 7% and 0.6% for major to trace levels of constituent elements and the precision between 11% and 0.6%. For the injection of 100 microL of 200 ng mL(-1) mercury solution at the flow rate of 0.8 mL/min, the flow injection studies resulted in the relative standard deviation (RSD) of 8%, concentration detection limit of 10 ng/mL, and mass detection limit of 1 ng for mercury. PMID:19715301
On the transition from stable positive glow corona to streamers
NASA Astrophysics Data System (ADS)
Liu, Lipeng; Becerra, Marley
A 2D numerical simulation of the transition from stable positive glow corona to streamers in coaxial cylindrical configuration is presented. The hydrodynamic model with several convection-dominated continuity equations together with Poisson equation are solved with consideration of the ionization layer. The transition from a stable positive glow corona produced under a DC voltage to streamers is investigated under a sudden change of the applied voltage. The critical rate of rise of voltage required for the transition from positive glow to streamer corona is evaluated with a voltage ramp. By introducing either physical or numerical instabilities into the model, streamers with filamentary structures are observed, which produce a sudden increase of the discharge current by more than two orders of magnitude. It is also found that the surface electric field of the corona-generating conductor deviates from the onset electric field, casting doubts about the validity of Kaptzov's approximation to evaluate the transition from stable glow to streamers.
[Effect of radio frequency discharge plasma on surface properties and biocompatibility of polycaprolactone matrices].
Bolbasov, E N; Antonova, L V; Matveeva, V G; Novikov, V A; Shesterikov, E V; Bogomolova, N L; Golovkin, A S; Tverdohlebov, S I; Barbarash, O L; Barbarash, L S
Surface modification of bioresorbable polymer material (polycaprolactone, PCL) with abnormal glow discharge, initiated during radio-frequency magnetron sputtering of a hydroxyapatite target was investigated. Plasma treatment resulted in an increase of surface roughness of PCL, crystallite size, the surface free energy and hydrophilicity. Increased treatment time (30, 60, 150 seconds) provoked the polymer surface saturation with the sputtering target ions (calcium, phosphorus). The assessment of plasma exposure of PCL surface on bone marrow multipotent mesenchymal stromal cells behavior (BM MSCs) has been performed. Modification of the polymer surface with the abnormal glow discharge stimulated adhesion and subsequent proliferation of BM MSCs; thus, maximum values were achieved with the surface treatment for 60 s. This type of plasma modification did not affect cell viability (apoptosis, necrosis). Thus, the surface modification with abnormal glow discharge, initiated during radio-frequency magnetron sputtering of a hydroxyapatite target, appear to be a promising method of surface modification of bioresorbable polymer material (PCL) for tissue engineering. PMID:26973188
Study of short atmospheric pressure dc glow microdischarge in air
NASA Astrophysics Data System (ADS)
Kudryavtsev, Anatoly; Bogdanov, Eugene; Chirtsov, Alexander; Emelin, Sergey
The results of experiments and simulations of short (without positive column) atmospheric pressure dc glow discharge in air are presented. We used metal steel electrodes with a gap of 5-100 microns. The experimental voltage-current characteristic's (VAC) have a constant or slightly increasing form at low gap. The most stable microdischarges were burning with a flat cathode and rounded anode, when the length of the discharge is automatically established near the minimum of the Paschen curve by changing their binding on the anode. In this case microdischarge was stable and it had growing VAC. For simulations we used 2D fluid model with kinetic description of electrons. We solved the balance equations for the vibrationally- and the electronically-excited states of a nitrogen and oxygen molecules; nitrogen and oxygen atoms; ozone molecule; and different nitrogen and oxygen ions with different plasmochemical reactions between them. Simulations predicted the main regions of the dc glow discharges including cathode and anode sheath and plasma of negative glow, Faraday dark space and transition region. Gas heating plays an important role in shaping the discharge profiles. The results of experiments and simulations of short (without positive column) atmospheric pressure dc glow discharge in air are presented. We used metal steel electrodes with a gap of 5-100 microns. The experimental voltage-current characteristic's (VAC) have a constant or slightly increasing form at low gap. The most stable microdischarges were burning with a flat cathode and rounded anode, when the length of the discharge is automatically established near the minimum of the Paschen curve by changing their binding on the anode. In this case microdischarge was stable and it had growing VAC. For simulations we used 2D fluid model with kinetic description of electrons. We solved the balance equations for the vibrationally- and the electronically-excited states of a nitrogen and oxygen molecules; nitrogen
Detection of surface glow related to spacecraft glow phenomena
NASA Technical Reports Server (NTRS)
Langer, W. D.; Cohen, S. A.; Manos, D. M.; Motley, R. W.; Ono, M.
A source of low energy neutral atoms and molecules has been developed by using a biased limiter to scrape off and reflect neutralized ions from a toroidal plasma. Beams of nitrogen and nitrogen-oxygen mixtures with energies of 1 to 15 eV and fluxes greater than about 10 to the 14 per centimeter per second were directed onto target surfaces consisting of Z-302 and Z-306 paints. With the nitrogen beams, a glow due to beam-surface interactions was successfully detected. In addition, a volume glow effect due to beam-gas interactions was observed which may play a role in spacecraft glow.
Detection of surface glow related to spacecraft glow phenomenon
Langer, W.D.; Cohen, S.A.; Manos, D.M.; Motley, R.W.; Ono, M.; Paul, S.; Roberts, D.; Selberg, H.
We have developed a high flux source of low energy neutral beams to study the spacecraft glow phenomena by using a biased limiter to neutralize plasma in ACT-1. Beams of nitrogen and nitrogen-oxygen mixtures with energies of 1 to 15 eV and fluxes greater than or equal to 10/sup 14//cm/sup 2//s were directed on target surfaces consisting of Z-302 and Z-306 paints. With the nitrogen beams we successfully detected a glow due to beam-surface interactions. In addition, we discovered a volume glow effect due to beam-gas interactions which may also play a role in spacecraft glow. 11 refs., 14 figs.
Observation of the glow-to-arc transitions
NASA Astrophysics Data System (ADS)
Watanabe, Shigeru; Saito, Shigeki; Takahashi, Kunio; Onzawa, Tadao
Researches of the glow-to-arc transitions have been required for a new development of the welding technology in low current. It is important to clarify the characteristics of plasma in the transitions because there have been few reports investigated the transitions in detail. The glow-to-arc transitions were observed in argon at atmospheric pressure. The Th-W electrodes of 1 mm in a diameter are used. Both of the electrodes are needle-shaped and set in a quartz tube coaxially. Plasma is generated between the electrodes with the gap spacing of 1 mm. A DC power supply has been applying constant voltage of 600 V during the discharge. A high-speed camera is used to record the images of plasma in the transitions with the measurement of voltage and current between the electrodes. As a result, two things were confirmed for the behavior of the glow-to-arc transition. First, plasma extended over the cathode surface in the transition from the glow to the arc. Second, temperature in the tip of the cathode would increase gradually during the glow and decrease during the arc.
The theory of positive glow corona
NASA Astrophysics Data System (ADS)
Morrow, R.
A theory for the current and light pulses of positive glow corona from a point in air is presented; this phenomenon was first observed as an apparently continuous glow by Michael Faraday. Results are obtained, in concentric sphere geometry, for air at atmospheric pressure, by solving the continuity equations for electrons, positive ions, negative ions and metastable oxygen molecules, coupled with Poisson's equation. A series of `saw-toothed' current pulses of period about 0022-3727/30/22/008/img1 is predicted with a DC current level. Accompanying the current peaks are discrete pulses of light 30 ns wide. Successive `shells' of positive ions, from successive current pulses, carry 96% of the mean current. The mean current - voltage relationship has the classic square-law form. The seed electrons required for successive pulses are detached from negative ions by metastable oxygen molecules. Photo-ionization is crucial for the discharge at the anode and for the formation of negative ions throughout the gap. The pulse frequency varies with applied voltage and is found to be approximately proportional to the positive-ion mobility. The surface electric field at the central electrode remains close to Peek's onset field. The origin of onset streamers is explained and sub-microsecond voltage pulses are found to produce streamers. The results for concentric-cylinder electrodes are described briefly.
Mechanistic investigations of shuttle glow
NASA Technical Reports Server (NTRS)
Caledonia, G. E.; Holtzclaw, K. W.; Krech, R. H.; Sonnenfroh, D. M.; Leone, A.; Blumberg, W. A. M.
A series of laboratory measurements have been performed in order to provide a mechanistic interpretation for the visible shuttle glow. These studies involved interactions of an 8 km/s oxygen atom beam with both contaminant dosed surfaces and gaseous targets. We conclude that visible shuttle glow arises from surface mediated O + NO recombination via a Langmuir-Hinshelwood mechanism and that the gas-phase exchange reaction O + N2 - NO + N provides a viable source of precursor NO above surfaces oriented in the ram direction.
Mechanistic investigations of shuttle glow
Caledonia, G.E.; Holtzclaw, K.W.; Krech, R.H.; Sonnenfroh, D.M. ); Leone, A. ); Blumber, W.A.M. )
A series of laboratory measurements have been performed in order to provide a mechanistic interpretation for the visible shuttle glow. These studies involved interactions in an 8 km/s oxygen atom beam with both contaminant dosed surfaces and gaseous targets. The authors conclude that visible shuttle glow arises from surface mediated O + NO recombination via a Langmuir-Hinshelwood mechanism and that the gas-phase exchange reaction O + N[sub 2] [r arrow] NO + N provides a viable source of precursor NO above surfaces oriented in the ram direction. 35 refs., 4 figs.
Second Workshop on Spacecraft Glow
NASA Technical Reports Server (NTRS)
Waite, J. H., Jr. (Editor); Moorehead, T. W. (Editor)
Various aspects of space glow were considered. Results of a workshop held on May 6 to 7, 1985, at the Space Science Laboratory of NASA/Marshall Space Flight Center, Huntsville, Alabama are presented. The topics of discussion are divided as follows: (1) in situ observations; (2) theoretical calculations; (3) laboratory measurements; and (4) future experiments.
BABE - a brush cathode discharge for thermal fluctuation measurements
NASA Astrophysics Data System (ADS)
Ratynskaia, S.; Dilecce, G.; Tolias, P.
For experimental tests of fluctuation theory in ideal plasmas and plasmas seeded with dust, the ideal environment would be that of stable quiescent plasma. In most laboratory plasmas the homogeneous state of the positive column is often unstable, rare exceptions are the so-called brush cathode discharges, proposed in the 60s, where a specially manufactured cathode allows stable operation in the abnormal glow regime and the only fluctuations present are those due the thermal motion of the particles. Such a device, the BAri Brush Electrode (BABE), has recently been built in a novel configuration that combines the advantages of the inverse design with those of the reflex geometry. The region between the two anodes is essentially field-free and extremely stable in wide range of plasma densities and collisionalities. Unprecedented low fluctuation levels of δn/n <= 10-5 in He and δn/n <= 5 × 10-6 in Ar discharges have been achieved.
Emission spectroscopy of a microhollow cathode discharge plasma in helium-water gas mixtures
Namba, S.; Yamasaki, T.; Hane, Y.; Fukuhara, D.; Kozue, K.; Takiyama, K.
A dc microhollow cathode discharge (MHCD) plasma was generated inflowing helium gas containing water vapor. The cathode hole diameters were 0.3, 0.7, 1.0, and 2.0 mm, each with a length of 2.0 mm. Emission spectroscopy was carried out to investigate the discharge mode and to determine the plasma parameters. For the 0.3-mm cathode, stable MHCDs in an abnormal glow mode existed at pressures up to 100 kPa, whereas for larger diameters, a plasma was not generated at atmospheric pressure. An analysis of the lineshapes relevant to He at 667.8 nm and to H{alpha} at 656.3 nm implied an electron density and gas temperature of 2 x 10{sup 14} cm{sup -3} and 1100 K, respectively, for a 100-kPa discharge in the negative glow region. The dependence of the OH band, and H{alpha} intensities on the discharge current exhibited different behaviors. Specifically, the OH spectrum had a maximum intensity at a certain current, while the H atom intensity kept increasing with the discharge current. This observation implies that a high concentration of OH radicals results in quenching, leading to the production of H atoms via the reaction OH + e{sup -}{yields} O + H + e{sup -}.
Positive Streamers and Glows in Air and Exhaust Gases
NASA Astrophysics Data System (ADS)
Morrow, R.
Theoretical and experimental studies have been made of the effects of sub-microsecond voltage pulses on the plasma chemistry of real flue gases in a test cell. Chemical analysis shows that, for real flue gases, the pulsed system can remove up to 90 % of NO, and 30 % of SO_2, if a residence time of ~ 30s is used. We also find that (i) water vapour is essential to the removal of SO_2, but not for the removal of NO or NO_2; and (ii) that small quantities of N_2O are produced. The removal of SO2 is primarily due to reactions with OH radicals from water vapour, producing sulphuric acid, whereas nitrogen oxides are reduced by N atoms. When a positive voltage is abruptly applied to a point in air at atmospheric pressure, positive streamers are produced. A theory is presented for the development of the first such streamer by solving the continuity equations for electrons, positive ions and negative ions, including the effects of ionisation, attachment, recombination, electron diffusion, and photoionisation, simultaneously with Poisson's equation. With an applied voltage of 20 kV across a 50 mm gap, the streamer does not reach the cathode. When the voltage is sustained in the presence of free electrons, the electric field at the anode starts to recover until positive glow pulses develop at the anode. The presence of the positive glow corona precludes any further streamer formation; this limits the number of chemical reactions stimulated by the discharge because the positive glow is confined close to the anode. Thus, a limit is set for the voltage pulse width. A theory is also presented for the current and light pulses of positive glow corona from a point in air; results are obtained by solving the continuity equations, described above, in concentric sphere geometry. A series of ``saw--toothed'' current pulses of period ~ 1 μs are predicted with a dc current level. Accompanying the current peaks are discrete 30 ns wide pulses of light. It is found that if, in the presence
Deodato, G; Consoli, A; Riggi, M; Longo, G; Finocchiaro, G B
The Authors examine the various types of breast discharge concentrating in particular on the secretions due to inherent pathology. After having studied origin, they concentrate on the diagnostic significance and the limits of exfoliative cytology and contrast mammography. The Authors conclude by presenting an original protocol of treatment of the afflicted breast illustrating in addition, the various surgical techniques proposed for the cure of the sicknesses of intramammary origin that cause abnormal discharge. PMID:7261200
Glow Sticks: Spectra and Color Mixing
NASA Astrophysics Data System (ADS)
Birriel, Jennifer; Birriel, Ignacio
Glow sticks are a popular Halloween staple familiar to most of our students. The production of light via a chemical reaction is called "chemiluminescence," and glow sticks are often used as demonstrations and experiments in the chemistry classroom to study reaction rates as a function of temperature.1-3 A black light can be used to illuminate glow sticks that have not been cracked or those that are "dead" in order to demonstrate fluorescence in liquid chemicals.4 In this article, we present the use of glow sticks as an inexpensive demonstration of spectra and color addition.
Spacecraft ram glow and surface temperature
NASA Technical Reports Server (NTRS)
Swenson, G. R.; Mende, S. B.; Llewellyn, E. J.
Space shuttle glow intensity measurements show large differences when the data from different missions are compared. In particular, on the 41-G mission the space shuttle ram glow was observed to display an unusually low intensity. Subsequent investigation of this measurement and earlier measurements suggest that there was a significant difference in temperature of the glow producing ram surfaces. The highly insulating properties coupled with the high emissivity of the shuttle tile results in surfaces that cool quickly when exposed to deep space on the night side of the orbit. The increased glow intensity is consistent with the hypothesis that the glow is emitted from excited NO2. The excited NO2 is likely formed through three body recombination (OI + NO + M = NO2*) where ramming of OI interacts with weakly surface bound NO. The NO is formed from atmospheric OI and NI which is scavenged by the spacecraft moving through the atmosphere. It is postulated that the colder surfaces retain a thicker layer of NO thereby increasing the probability of the reaction. It has been found from the glow intensity/temperature data that the bond energy of the surface bound precursor, leading to the chemical recombination producing the glow, is approximately 0.14 eV. A thermal analysis of material samples of STS-8 was made and the postulated temperature change of individual material samples prior to the time of glow measurements above respective samples are consistent with the thermal effect on glow found for the orbiter surface.
ADELE's Common Gamma-Ray Glows
NASA Astrophysics Data System (ADS)
Kelley, N. A.; Smith, D. M.; Dwyer, J. R.; Hazelton, B. J.; Grefenstette, B. W.; Lowell, A.; Splitt, M. E.; Lazarus, S. M.; Rassoul, H. K.
Gamma-ray glows have been observed for the first time as a common, long duration phenomenon from the tops of thunderclouds. The Airborne Detector for Energetic Lightning Emissions (ADELE) observed 12 gamma-ray glows during its Summer 2009 flight campaign. We present their spectra, their relationship to lightning activity and show how the duration and size of a glow changes with distance from the glow. Since glows have a very hard spectrum, with many counts above 5 MeV, they may be evidence of a continual relativistic runaway process with positron feedback. We compare our spectra with simulations of relativistic runaway in the atmosphere with all effects of feedback included. We show that the lightning activity diminishes during the onset of a glow. From our simulations we attempt to distinguish between the two possibilities for this decrease: the mechanism responsible for glows is only able to become significant when lightning activity subsides or glows are actually stifling the lightning activity and considerably limiting the charging of the cloud. Comparison of the data with our simulations will determine if runaway or feedback are necessary to explain the glow brightness and if these mechanisms have significant effects on the total charging of the cloud.
Simulation Study of an Extended Density DC Glow Toroidal Plasma Source
Granda-Gutierrez, E. E.; Piedad-Beneitez, A. de la; Lopez-Callejas, R.; Godoy-Cabrera, O. G.; Benitez-Read, J. S.; Pacheco-Sotelo, J. O.; Pena-Eguiluz, R.; Mercado-Cabrera, A.; Valencia A, R.; Barocio, S. R.
Conventional wisdom assigns the DC glow discharge regime to plasma currents below {approx}500 mA values, beyond which the discharge falls into the anomalous glow and the turbulent arc regimes. However, we have found evidence that, during toroidal discharges, this barrier can be ostensibly extended up to 800 mA. Thus, a computer simulation has been applied to the evolution of the main electrical characteristics of such a glow discharge plasma in a toroidal vessel in order to design and construct a respective voltage/current controlled source. This should be able to generate a DC plasma in the glow regime with which currents in the range 10-3-100 A can be experimented and 109-1010 cm-3 plasma densities can be achieved to PIII optimization purposes. The plasma is modelled as a voltage-controlled current source able to be turned on whenever the breakdown voltage is reached across the gap between the anode and the vessel wall. The simulation outcome fits well our experimental measurements showing that the plasma current obeys power laws that are dependent on the power current and other control variables such as the gas pressure.
APEX reveals glowing stellar nurseries
NASA Astrophysics Data System (ADS)
Illustrating the power of submillimetre-wavelength astronomy, an APEX image reveals how an expanding bubble of ionised gas about ten light-years across is causing the surrounding material to collapse into dense clumps that are the birthplaces of new stars. Submillimetre light is the key to revealing some of the coldest material in the Universe, such as these cold, dense clouds. Glowing Stellar Nurseries ESO PR Photo 40/08 Glowing Stellar Nurseries The region, called RCW120, is about 4200 light years from Earth, towards the constellation of Scorpius. A hot, massive star in its centre is emitting huge amounts of ultraviolet radiation, which ionises the surrounding gas, stripping the electrons from hydrogen atoms and producing the characteristic red glow of so-called H-alpha emission. As this ionised region expands into space, the associated shock wave sweeps up a layer of the surrounding cold interstellar gas and cosmic dust. This layer becomes unstable and collapses under its own gravity into dense clumps, forming cold, dense clouds of hydrogen where new stars are born. However, as the clouds are still very cold, with temperatures of around -250˚ Celsius, their faint heat glow can only be seen at submillimetre wavelengths. Submillimetre light is therefore vital in studying the earliest stages of the birth and life of stars. The submillimetre-wavelength data were taken with the LABOCA camera on the 12-m Atacama Pathfinder Experiment (APEX) telescope, located on the 5000 m high plateau of Chajnantor in the Chilean Atacama desert. Thanks to LABOCA's high sensitivity, astronomers were able to detect clumps of cold gas four times fainter than previously possible. Since the brightness of the clumps is a measure of their mass, this also means that astronomers can now study the formation of less massive stars than they could before. The plateau of Chajnantor is also where ESO, together with international partners, is building a next generation submillimetre telescope, ALMA
Glow Sticks: Spectra and Color Mixing
ERIC Educational Resources Information Center
Birriel, Jennifer; Birriel, Ignacio
Glow sticks are a popular Halloween staple familiar to most of our students. The production of light via a chemical reaction is called "chemiluminescence," and glow sticks are often used as demonstrations and experiments in the chemistry classroom to study reaction rates as a function of temperature. A black light can be used to…
Numerical investigation on operation mode influenced by external frequency in atmospheric pressure barrier discharge
Wang Qi; Sun Jizhong; Wang Dezhen
The influence of external driving frequency on the discharge mode in the dielectric barrier discharge was investigated with a two-dimensional, self-consistent fluid model. The simulation results show that the helium discharge exhibits three operation modes: Townsend, homogeneous glow, and local glow discharges from the lower frequency (1 kHz) to the higher frequency (100 kHz) under discharge parameters specified in this work. The discharge operates in a Townsend mode when the driving frequency varies from 1 to about 7 kHz; while it exhibits homogenous glow characteristics in an approximate range from 7 to 65 kHz; when the external frequency exceeds 65 kHz, it turns into a local glow discharge. The effects of external driving frequency on the discharge mode were revealed and the physical reasons were discussed.
Combination of physico-chemical analysis, Allium cepa test system and Oreochromis niloticus erythrocyte based comet assay/nuclear abnormalities tests for cyto-genotoxicity assessments of treated effluents discharged from textile industries.
Hemachandra, Chamini K; Pathiratne, Asoka
Bioassays for cyto-genotoxicity assessments are generally not required in current textile industry effluent discharge management regulations. The present study applied in vivo plant and fish based toxicity tests viz. Allium cepa test system and Oreochromis niloticus erythrocyte based comet assay and nuclear abnormalities tests in combination with physico-chemical analysis for assessing potential cytotoxic/genotoxic impacts of treated textile industry effluents reaching a major river (Kelani River) in Sri Lanka. Of the treated effluents tested from two textile industries, color in the Textile industry 1 effluents occasionally and color, biochemical oxygen demand and chemical oxygen demand in the Textile industry 2 effluents frequently exceeded the specified Sri Lankan tolerance limits for discharge of industrial effluents into inland surface waters. Exposure of A. cepa bulbs to 100% and 12.5% treated effluents from both industries resulted in statistically significant root growth retardation, mito-depression, and induction of chromosomal abnormalities in root meristematic cells in comparison to the dilution water in all cases demonstrating cyto-genotoxicity associated with the treated effluents. Exposure of O. niloticus to the 100% and 12.5% effluents, resulted in erythrocytic genetic damage as shown by elevated total comet scores and induction of nuclear abnormalities confirming the genotoxicity of the treated effluents even with 1:8 dilution. The results provide strong scientific evidence for the crucial necessity of incorporating cyto-genotoxicity impact assessment tools in textile industry effluent management regulations considering human health and ecological health of the receiving water course under chronic exposure. PMID:27209118
Glow plasma trigger for electron cyclotron resonance ion sources.
Vodopianov, A V; Golubev, S V; Izotov, I V; Nikolaev, A G; Oks, E M; Savkin, K P; Yushkov, G Yu
Electron cyclotron resonance ion sources (ECRISs) are particularly useful for nuclear, atomic, and high energy physics, as unique high current generators of multicharged ion beams. Plasmas of gas discharges in an open magnetic trap heated by pulsed (100 micros and longer) high power (100 kW and higher) high-frequency (greater than 37.5 GHz) microwaves of gyrotrons is promising in the field of research in the development of electron cyclotron resonance sources for high charge state ion beams. Reaching high ion charge states requires a decrease in gas pressure in the magnetic trap, but this method leads to increases in time, in which the microwave discharge develops. The gas breakdown and microwave discharge duration becomes greater than or equal to the microwave pulse duration when the pressure is decreased. This makes reaching the critical plasma density initiate an electron cyclotron resonance (ECR) discharge during pulse of microwave gyrotron radiation with gas pressure lower than a certain threshold. In order to reduce losses of microwave power, it is necessary to shorten the time of development of the ECR discharge. For fast triggering of ECR discharge under low pressure in an ECRIS, we initially propose to fill the magnetic trap with the plasmas of auxiliary pulsed discharges in crossed ExB fields. The glow plasma trigger of ECR based on a Penning or magnetron discharge has made it possible not only to fill the trap with plasma with density of 10(12) cm(-3), required for a rapid increase in plasma density and finally for ECR discharge ignition, but also to initially heat the plasma electrons to T(e) approximately = 20 eV. PMID:20192326
Glow plasma trigger for electron cyclotron resonance ion sources
Vodopianov, A. V.; Golubev, S. V.; Izotov, I. V.; Nikolaev, A. G.; Oks, E. M.; Savkin, K. P.; Yushkov, G. Yu.
Electron cyclotron resonance ion sources (ECRISs) are particularly useful for nuclear, atomic, and high energy physics, as unique high current generators of multicharged ion beams. Plasmas of gas discharges in an open magnetic trap heated by pulsed (100 {mu}s and longer) high power (100 kW and higher) high-frequency (greater than 37.5 GHz) microwaves of gyrotrons is promising in the field of research in the development of electron cyclotron resonance sources for high charge state ion beams. Reaching high ion charge states requires a decrease in gas pressure in the magnetic trap, but this method leads to increases in time, in which the microwave discharge develops. The gas breakdown and microwave discharge duration becomes greater than or equal to the microwave pulse duration when the pressure is decreased. This makes reaching the critical plasma density initiate an electron cyclotron resonance (ECR) discharge during pulse of microwave gyrotron radiation with gas pressure lower than a certain threshold. In order to reduce losses of microwave power, it is necessary to shorten the time of development of the ECR discharge. For fast triggering of ECR discharge under low pressure in an ECRIS, we initially propose to fill the magnetic trap with the plasmas of auxiliary pulsed discharges in crossed ExB fields. The glow plasma trigger of ECR based on a Penning or magnetron discharge has made it possible not only to fill the trap with plasma with density of 10{sup 12} cm{sup -3}, required for a rapid increase in plasma density and finally for ECR discharge ignition, but also to initially heat the plasma electrons to T{sub e}{approx_equal}20 eV.
Characteristics of thermoluminescence glow curves for materials exhibiting more than one glow peak
Levy, P.W.
The properties of thermoluminescence glow curves, containing one or more glow peaks, have been determined for situations where the assumptions invoked to obtain the usual first and second order kinetics do not apply. First order kinetics occurs only when retrapping is negligible. If more than one glow peak is present and retrapping occurs between different types of traps the glow peaks can be approximated, except in the wings, by the usual first and second order expressions; but often physically unrealistic parameters are obtained. These studies indicate that dating is best accomplished with minerals exhibiting first order kinetics. 6 figures, 1 table.
Orbiter glow observations at high spectral resolution
NASA Technical Reports Server (NTRS)
Kendall, D. J. W.; Mende, S. B.; Yn, E. J. ADMCDADE, I. C. AEMENDE, S. B.
An experiment flow on mission STS 41-G as part of the Canadian complement of experiments was designed to obtain relatively high resolution spectra of the Orbiter glow phenomenon over limited spectral regions centered on prominent upper atmospheric emissions. Observations were carried out successfully at altitudes of 360 km and 230 km although those at the lower altitude were limited by degradation of the image intensifier. Definitive glow results were obtained at the end of a thruster firing which showed the spectrum to be a continuum at a resolution of approximately 0.4 nm centered at a wavelength of 360 nm. Results at other wavelengths in the absence of any firings strongly suggest that the Orbiter glow is a continuum throughout the spectral region 550 nm to 760 nm. A discussion is presented that considers the reaction NO + O2 as being a possible candidate for the mechanism producing the shuttle glow.
Electric discharge during electrosurgery.
Shashurin, Alexey; Scott, David; Zhuang, Taisen; Canady, Jerome; Beilis, Isak I; Keidar, Michael
Electric discharge utilized for electrosurgery is studied by means of a recently developed method for the diagnostics of small-size atmospheric plasma objects based on Rayleigh scattering of microwaves on the plasma volume. Evolution of the plasma parameters in the near-electrode sheaths and in the positive column is measured and analyzed. It is found that the electrosurgical system produces a glow discharge of alternating current with strongly contracted positive column with current densities reaching 10(3) A/cm(2). The plasma electron density and electrical conductivities in the channel were found be 10(16) cm(-3) and (1-2) Ohm(-1) cm(-1), respectively. The discharge interrupts every instance when the discharge-driving AC voltage crosses zero and re-ignites again every next half-wave at the moment when the instant voltage exceeds the breakdown threshold. PMID:25880721
Relativistic feedback models of terrestrial gamma-ray flashes and gamma-ray glows
NASA Astrophysics Data System (ADS)
Dwyer, J. R.
Relativistic feedback discharges, also known as dark lightning, are capable of explaining many of the observed properties of terrestrial gamma-ray flashes (TGFs) and gamma-ray glows, both created within thunderstorms. During relativistic feedback discharges, the generation of energetic electrons is self-sustained via the production of backward propagating positrons and back-scattered x-rays, resulting in very larges fluxes of energetic radiation. In addition, ionization produces large electric currents that generate LF/VLF radio emissions and eventually discharge the electric field, terminating the gamma-ray production. In this presentation, new relativistic feedback model results will be presented and compared to recent observations.
Infrared spectral measurement of space shuttle glow
Ahmadijian, M.
Infrared spectral measurements of the space shuttle glow were successfully conducted during the STS-39 space shuttle mission. Analysis indicates that NO, NO[sup +], OH, and CO are among the molecules associated with the infrared glow phenomenon. During orbiter thruster firings the glow intensities in the infrared are enhanced by factors of 10x to 100x with significant changes in spectral distribution. These measurements were obtained with the Spacecraft Kinetic Infrared Test (SKIRT) payload which included a cryogenic infrared circular variable filter (CVF) spectrometer (0.6 [mu]m to 5.4 [mu]) and a number of infrared, visible, and ultraviolet radiometers (0.2 [mu]m to 5.4 [mu]m and 9.9 [mu]m to 10.4 [mu]m). In addition, glow measurements were unsuccessfully attempted with the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS-1A) with its 2.5 [mu]m to 25 [mu]m Fourier transform interferometer. SKIRT CVF obtained over 14,000 spectra of quiescent shuttle glow, thruster enhanced shuttle glow, upper atmosphere airglow, aurora, orbiter environment, and deep space non-glow backgrounds during its eight day mission. The SKIRT radiometers operated almost continuously throughout the mission to provide a detailed history of the IR/VIS/UV optical environment associated with the operation of large spacecraft structures in low earth orbit. This dissertation will primarily address those measurements conducted by the SKIRT spectrometer as they relate to space shuttle glow in the infrared. The STS-39 Space Shuttle Discovery was launched from the NASA Kennedy Space Center on 28 April 1991 into a 57 degree inclination circular orbit at an altitude of 260 km.
Laboratory investigation of shuttle glow mechanisms
NASA Astrophysics Data System (ADS)
Caledonia, G. E.; Holtzclaw, K. W.; Green, B. D.; Krech, R. H.; Leone, A.; Swenson, G.
A fast oxygen atom source was used to investigate the Shuttle glow phenomena in the laboratory. Both room temperature and cooled targets were dosed with NO and then irradiated by 8 km/s oxygen atoms. The observed fluorescence is spectrally similar to that seen on the Shuttle supporting previous suggestions that recombination of O with surface bound NO is the responsible mechanism for the visible Shuttle glow.
Vehicle glow measurements on the space shuttle
NASA Technical Reports Server (NTRS)
Mende, S. B.; Swenson, G. R.
From the combined data set of glow observations on shuttle flight STS-3, STS-4, STS-5, STS-8, STS-9, 41-E, and 41-G some of the properties of the shuttle glow are discussed. Comparison of the STS-3 and STS-5 (240 and 305 km altitude, respectively) photographs shows that the intensity of the glow is about a factor of 3.5 brighter on the low-altitude (STS-3) flight. In an experiment to observe the dependence of the intensity on the ram angle, the angle of incidence between the spacecraft surface normal and the velocity vector, the Orbiter was purposely rotated about the x axis on the STS-5 mission. For a relatively large angle between the velocity vector and the surface normal there is an appreciable glow, provided the surface is not shadowed by some other spacecraft structure. As the angle becomes less the glow intensifies. Material samples were also exposed in the ram direction during nightside orbits and the glow surrounding the samples was photographed.
Decomposition of hydrazine by high frequency glow electrical discharges
NASA Technical Reports Server (NTRS)
Suzuki, M.; Miyazaki, M.; Takahashi, S.
Originally, de Groot et al. examined electrical conductivity phenomena in terms of the thermodynamics of irreversible processes. They considered the system to be discontinuous and calculated only the differences between the opposing ends of the process. Thus these theories are phenomenological. In the present work, thermodynamics is developed as a continuous system based on hydrodynamics and the entropy production for a thin capillary. It is shown that electroconductivity can be interpreted without difficulty. For the electric double layer, the effects of electrolytes and surface conductivity and the gap width were calculated for the Gouy model.
Hydrogenated amorphous silicon films prepared by glow discharge of disilane
Wiesmann, H.J. )
This report describes the results of an investigation of the properties of hydrogenated amorphous silicon films and the efficiency of amorphous silicon solar cells deposited from disilane at rates of 1.5 nanometers/second or greater. The study was divided into two parts, investigation of basic materials properties of hydrogenated amorphous silicon thin films and the fabrication of glass-P-I-N-metal solar cells. The thin film materials properties investigated included the dark conductivity, photoconductivity, dihydride/monohydride concentration ratio, activation energy, and mobility-lifetime product. Hydrogenated amorphous silicon solar cells were fabricated with an intrinsic layer which was deposited at 1.5 nanometers/second. The absolute and reverse bias quantum yields were measured and solar cell efficiencies of 5% were achieved. Attempts to increase the efficiency by reverse bias annealing are also reported. 7 refs., 27 figs.
Survey of ultraviolet shuttle glow
NASA Technical Reports Server (NTRS)
Spear, K. A.; Uckler, G. J.; Tobiska, K.
The University of Colorado Get Away Special (GAS) project utilizes the efforts of its students to place experiments on the shuttle. The objective of one experiment, the shuttle glow study, is to conduct a general survey of emissions in the ultraviolet near vehicle surfaces. An approximate wavelength range of 1900 to 3000 A will be scanned to observe predominant features. Special emphasis will be placed on studying the band structure of NO near 2000 A and the Mg+ line at 2800 A. The spectrometer, of Ebert-Faste 1/8-meter design, will perform the experiment during spacecraft night. It will be oriented such that the optical axis points to the cargo bay zenith. In order to direct the field-of-view of the instrument onto the shuttle vertical stabilizer (tail), a mirror assembly is employed. The mirror system has been designed to rotate through 7.5 degrees of arc using 10 positions resulting in a spatial resolution of 30 x 3 cm, with the larger dimension corresponding to the horizontal direction. Such a configuration can be attained from the forwardmost position in the cargo bay. Each spatial position will be subjected to a full spectral scan with a resolution on the order of 10 A.
Chapter 19, describes meiotic abnormalities. These include nondisjunction of autosomes and sex chromosomes, genetic and environmental causes of nondisjunction, misdivision of the centromere, chromosomally abnormal human sperm, male infertility, parental age, and origin of diploid gametes. 57 refs., 2 figs., 1 tab.
Sprite beads and glows arising from the attachment instability in streamer channels
NASA Astrophysics Data System (ADS)
Luque, A.; Stenbaek-Nielsen, H. C.; McHarg, M. G.; Haaland, R. K.
The complex dynamics of a sprite discharge are not limited to the propagation of streamers. After the passage of a streamer head, the ionized channel established in its wake develops intricate luminous patterns that evolve on timescales from 1 up to 100 ms. To investigate these patterns, conventionally called beads and glows, we present high-speed recordings of their onset and decay; our main observation here is that in many cases distant points within a channel decay at the same rate despite considerable differences in the underlying air density. We then show that the properties of beads and glows, including this synchronized decay, are explained by the tendency of electric current within a streamer channel to converge to an uniform value and by an attachment instability of electric discharges in air. However, we also discuss the uncertainty about the chemical reactions that affect the electron density during the sprite decay.
Influence of driving frequency on discharge modes in a dielectric-barrier discharge with multiple current pulses
Jiang, Weiman; Tang, Jie; Wang, Yishan; Zhao, Wei; Duan, Yixiang
A one-dimensional self-consistent fluid model was employed to investigate the effect of the driving frequency on the discharge modes in atmospheric-pressure argon discharge with multiple current pulses. The discharge mode was discussed in detail not only at current peaks but also between two adjacent peaks. The simulation results show that different transitions between the Townsend and glow modes during the discharge take place with the driving frequency increased. A complicated transition from the Townsend mode, through glow, Townsend, and glow, and finally back to the Townsend one is found in the discharge with the driving frequency of 8 kHz. There is a tendency of transition from the Townsend to glow mode for the discharge both at the current peaks and troughs with the increasing frequency. The discharge in the half period can all along operate in the glow mode with the driving frequency high enough. This is resulted from the preservation of more electrons in the gas gap and acquisition of more electron energy from the swiftly varying electric field with the increase in driving frequency. Comparison of the spatial and temporal evolutions of the electron density at different driving frequencies indicates that the increment of the driving frequency allows the plasma chemistry to be enhanced. This electrical characteristic is important for the applications, such as surface treatment and biomedical sterilization.
NASA Technical Reports Server (NTRS)
Volcanic hot spots and auroral emissions glow on the darkside of Jupiter's moon Io in the image at left. The image was taken by the camera onboard NASA's Galileo spacecraft on 29 June, 1996 UT while Io was in Jupiter's shadow. It is the best and highest-resolution image ever acquired of hot spots or auroral features on Io. The mosaic at right of 1979 Voyager images is shown with an identical scale and projection to identify the locations of the hot spots seen in the Galileo image. The grid marks are at 30 degree intervals of latitude and longitude. North is to the top.In the nighttime Galileo image, small red ovals and perhaps some small green areas are from volcanic hot spots with temperatures of more than about 700 kelvin (about 1000 degrees Fahrenheit). Greenish areas seen near the limb, or edge of the moon, are probably the result of auroral or airglow emissions of neutral oxygen or sulfur atoms in volcanic plumes and in Io's patchy atmosphere. The image was taken from a range of 1,035,000 kilometers (about 643,000 miles).The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo
Oxygen glow treating of ZnO electrode for thin film silicon solar cell
Elias, E.; Knapp, K.E.
This patent describes an improvement in a process for production of a photoconductive device wherein a first conductive layer comprising ZnO is applied to a substrate, and a thin film silicon hydrogen alloy is applied to the first conductive layer. The improvement comprising: after applying the first conductive layer comprising ZnO to the substrate, treating the first conductive layer with a glow discharge in a gas containing a source of oxygen.
Columnar discharge mode between parallel dielectric barrier electrodes in atmospheric pressure helium
Hao, Yanpeng; Zheng, Bin; Liu, Yaoge
Using a fast-gated intensified charge-coupled device, end- and side-view photographs were taken of columnar discharge between parallel dielectric barrier electrodes in atmospheric pressure helium. Based on three-dimensional images generated from end-view photographs, the number of discharge columns increased, whereas the diameter of each column decreased as the applied voltage was increased. Side-view photographs indicate that columnar discharges exhibited a mode transition ranging from Townsend to glow discharges generated by the same discharge physics as atmospheric pressure glow discharge.
... serious health problems (e.g. Down syndrome ). Single-Gene Abnormalities Sometimes the chromosomes are normal in number, ... blood flow to the fetus impair fetal growth. Alcohol consumption and certain drugs during pregnancy significantly increase ...
... of the skull and face. Craniofacial abnormalities are birth defects of the face or head. Some, like cleft ... palate, are among the most common of all birth defects. Others are very rare. Most of them affect ...
... include: Arthritis of the leg or foot joints Conversion disorder (a psychological disorder) Foot problems (such as a ... injuries. For an abnormal gait that occurs with conversion disorder, counseling and support from family members are strongly ...
... decade, newer techniques have been developed that allow scientists and doctors to screen for chromosomal abnormalities without using a microscope. These newer methods compare the patient's DNA to a normal DNA ...
Nail abnormalities are problems with the color, shape, texture, or thickness of the fingernails or toenails. ... Fungus or yeast cause changes in the color, texture, and shape of the nails. Bacterial infection may ...
NASA Technical Reports Server (NTRS)
NGC 3132 is a striking example of a planetary nebula. This expanding cloud of gas, surrounding a dying star, is known to amateur astronomers in the southern hemisphere as the 'Eight-Burst' or the 'Southern Ring' Nebula. The name 'planetary nebula' refers only to the round shape that many of these objects show when examined through a small visual telescope. In reality, these nebulae have little or nothing to do with planets, but are instead huge shells of gas ejected by stars as they near the ends of their lifetimes. NGC 3132 is nearly half a light year in diameter, and at a distance of about 2000 light years is one of the nearer known planetary nebulae. The gases are expanding away from the central star at a speed of 9 miles per second. This image, captured by NASA's Hubble Space Telescope, clearly shows two stars near the center of the nebula, a bright white one, and an adjacent, fainter companion to its upper right. (A third, unrelated star lies near the edge of the nebula.) The faint partner is actually the star that has ejected the nebula. This star is now smaller than our own Sun, but extremely hot. The flood of ultraviolet radiation from its surface makes the surrounding gases glow through fluorescence. The brighter star is in an earlier stage of stellar evolution, but in the future it will probably eject its own planetary nebula. In the Heritage Team's rendition of the Hubble image, the colors were chosen to represent the temperature of the gases. Blue represents the hottest gas, which is confined to the inner region of the nebula. Red represents the coolest gas, at the outer edge. The Hubble image also reveals a host of filaments, including one long one that resembles a waistband, made out of dust particles which have condensed out of the expanding gases. The dust particles are rich in elements such as carbon. Eons from now, these particles may be incorporated into new stars and planets when they form from interstellar gas and dust. Our own Sun may eject a
A dielectric barrier discharge in neon at atmospheric pressure
NASA Astrophysics Data System (ADS)
Ran, Junxia; Luo, Haiyun; Wang, Xinxin
A dielectric barrier discharge in neon at atmospheric pressure is investigated with electrical measurement and fast photography. It is found that a stable diffuse discharge can be easily generated in a gap with a gap space of 0.5-6 mm and is identified with a glow discharge. The first breakdown voltage of the gap is considerably higher than that of the same gap working in a stable diffuse discharge mode, which indicates that Penning ionization of neon metastables from the previous discharge with inevitable gas impurities plays an important role in the decrease in the breakdown voltage. Discharge patterns are observed in a gap shorter than 1 mm. From the experiments with a wedge-like gap, it is found that the discharge patterns are formed in the area with a higher applied electric field, which suggests that a higher applied electric field may cause a transition from a diffuse glow to discharge patterns.
Interaction between pulsed discharge and radio frequency discharge burst at atmospheric pressure
Zhang, Jie; Guo, Ying; Shi, Yuncheng; Zhang, Jing; Shi, J. J.
The atmospheric pressure glow discharges (APGD) with dual excitations in terms of pulsed voltage and pulse-modulation radio frequency (rf) power are studied experimentally between two parallel plates electrodes. Pulse-modulation applied in rf APGD temporally separates the discharge into repetitive discharge bursts, between which the high voltage pulses are introduced to ignite sub-microsecond pulsed discharge. The discharge characteristics and spatio-temporal evolution are investigated by means of current voltage characteristics and time resolved imaging, which suggests that the introduced pulsed discharge assists the ignition of rf discharge burst and reduces the maintain voltage of rf discharge burst. Furtherly, the time instant of pulsed discharge between rf discharge bursts is manipulated to study the ignition dynamics of rf discharge burst.
Interaction between pulsed discharge and radio frequency discharge burst at atmospheric pressure
NASA Astrophysics Data System (ADS)
Zhang, Jie; Guo, Ying; Shi, Yuncheng; Zhang, Jing; Shi, J. J.
The atmospheric pressure glow discharges (APGD) with dual excitations in terms of pulsed voltage and pulse-modulation radio frequency (rf) power are studied experimentally between two parallel plates electrodes. Pulse-modulation applied in rf APGD temporally separates the discharge into repetitive discharge bursts, between which the high voltage pulses are introduced to ignite sub-microsecond pulsed discharge. The discharge characteristics and spatio-temporal evolution are investigated by means of current voltage characteristics and time resolved imaging, which suggests that the introduced pulsed discharge assists the ignition of rf discharge burst and reduces the maintain voltage of rf discharge burst. Furtherly, the time instant of pulsed discharge between rf discharge bursts is manipulated to study the ignition dynamics of rf discharge burst.
Rare TGFs and common glows: a systematic survey of data from the first flights of ADELE
NASA Astrophysics Data System (ADS)
Kelley, N.; Lowell, A.; Smith, D. M.; Dwyer, J. R.; Cummer, S. A.; Lu, G.; Blakeslee, R.
The Airborne Detector for Energetic Lightning Emission (ADELE) is a mobile array of gamma and x-ray detectors meant to study radiation associated with thunderstorms. ADELE flew aboard a Gulfstream V jet near the tops of Florida thunderstorms in summer of 2009, performing the first systematic search for Terrestrial Gamma-ray Flashes (TGFs) at aircraft altitudes. We use GEANT3 simulations of electron and gamma-ray propagation in Earth's atmosphere and our instrument to show that ADELE was within the range of detection for TGFs from numerous lightning flashes but only saw one TGF event (see the companion presentation by Lowell et al.). This allows us to place strong upper limits on TGF emission from IC, +CG, and -CG lightning, demonstrating that TGFs are a rare phenomenon in lightning in this region, and cannot be the primary triggering mechanism for most lightning. The ADELE campaign also observed "glows" of high-energy radiation over several clouds. We shall also report the frequency of the occurrence of glows during our Florida 2009 campaign. On one occasion, the glow lasted through two passes of the aircraft over the same cell. This glow may represent the relativistic runaway feedback process continuously limiting the total charging of the cell, showing that this mechanism may compete with discrete lightning discharges as the main charge-limiting process in storms.
Effects of self-erasing discharges on the uniformity of the dielectric barrier discharge
NASA Astrophysics Data System (ADS)
Somekawa, T.; Shirafuji, T.; Sakai, O.; Tachibana, K.; Matsunaga, K.
Atmospheric pressure discharges in Ne, N2 and N2/O2 gases have been investigated with a novel high-voltage pulse power supply. Three characteristic types of discharge modes were observed: (1) diffuse glow discharge seen in Ne gas both with the eye and high-speed camera; (2) diffuse glow-like discharge in N2 gas observed with the eye, but seen as a vague filamentary discharge with a high-speed camera; and (3) clear filamentary discharge in N2/O2 gas mixture both with the eye and high-speed camera. Characteristics in the current and voltage waveforms revealed that the existence of the second voltage with opposite polarity following the first impulse voltage was important to have a diffuse glow-like discharge. This suggests that elimination of the memory effect by non-uniformly distributed charges on the surface is important for obtaining the diffuse mode because the non-uniformity triggers a positive feedback to the current constriction at the points with higher charge density, and results in filamentation of the discharge.
Numerical study on rectangular microhollow cathode discharge
He Shoujie; Ouyang Jiting; He Feng; Li Shang
Rectangular microhollow cathode discharge in argon is investigated by using two-dimensional time-dependent self-consistent fluid model. The electric potential, electric field, particle density, and mean electron energy are calculated. The results show that hollow cathode effect can be onset in the present configuration, with strong electric field and high mean electron energy in the cathode fall while high density and quasineutral plasma in the negative glow. The potential well and electric filed reversal are formed in the negative glow region. It is suggested that the presence of large electron diffusion flux necessitates the field reversal and potential well.
NASA CONNECT: 'Glow with the Flow'
NASA Technical Reports Server (NTRS)
'Geometry and Algebra: Glow with the Flow' is the second of five programs in the 2000-2001 NASA CONNECT series. Produced by NASA Langley Research Center's Office of Education, NASA CONNECT is an award-winning series of instructional programs designed to enhance the teaching of math, science and technology in grades 5-8. NASA CONNECT establishes teh 'connection' between the mathematics, science, and tehcnology concepts taught in the classroom and NASA research. NASA CONNECT is FREE and the programs in the series are in the public domain. Visit our web site adn register http://connect.larc.nasa.gov In 'Geometry and Algebra: Glow with the Flow', students will learn about the force of drag and how NASA engineers use models and glowing paints to see how air flows over vehicles in a wind tunnel. Students will also discover how the blended wing body(BWB), a concept super jumbo jet that resembles a flying wing, will affect air travelers of the future. Students will observe NASA engineers using geometry and algebra when they measure and design models to be tested in wind tunnels. By conducting classroom and on-line activities, students will make connections between NASA research and the mathematics, science and technology they learn in their classroom.

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