text:
Shock wave generated by high-energy electric spark discharge
NASA Astrophysics Data System (ADS)
Liu, Qingming; Zhang, Yunming
Shock wave generated by electric spark discharge was studied experimentally and the shock wave energy was evaluated in this paper. A pressure measurement system was established to study the pressure field of the electric spark discharge process. A series of electric spark discharge experiments were carried out and the energy of the electric spark used in present study was in the range of 10 J, 100 J, and 1000 J, respectively. The shock wave energy released from the electric spark discharge process was calculated by using the overpressure values at different measurement points near the electric spark discharge center. The good consistency of shock wave energies calculated by pressure histories at different measuring points in the same electric spark discharge experiment illustrates the applicability of the weak shock wave theory in calculating the energy of shock wave induced by electric spark discharge process. The result showed that shock wave formed at the initial stage of electric spark discharge process, and the shock wave energy is only a little part of electric spark energy. From the analysis of the shock wave energy and electric spark energy, a good linear relationship between shock wave energy and electric spark energy was established, which make it possible to calculate shock wave energy by measuring characteristic parameters of electric spark discharge process instead of shock wave. So, the initiation energy of direct initiation of detonation can be determined easily by measuring the parameters of electric spark discharge process.
A time-resolved imaging and electrical study on a high current atmospheric pressure spark discharge
NASA Astrophysics Data System (ADS)
Palomares, J. M.; Kohut, A.; Galbács, G.; Engeln, R.; Geretovszky, Zs.
We present a time-resolved imaging and electrical study of an atmospheric pressure spark discharge. The conditions of the present study are those used for nanoparticle generation in spark discharge generator setups. The oscillatory bipolar spark discharge was generated between two identical Cu electrodes in different configurations (cylindrical flat-end or tipped-end geometries, electrode gap from 0.5 to 4 mm), in a controlled co-axial N2 flow, and was supplied by a high voltage capacitor. Imaging data with nanosecond time resolution were collected using an intensified CCD camera. This data were used to study the time evolution of plasma morphology, total light emission intensity, and the rate of plasma expansion. High voltage and high current probes were employed to collect electrical data about the discharge. The electrical data recorded allowed, among others, the calculation of the equivalent resistance and inductance of the circuit, estimations for the energy dissipated in the spark gap. By combining imaging and electrical data, observations could be made about the correlation of the evolution of total emitted light and the dissipated power. It was also observed that the distribution of light emission of the plasma in the spark gap is uneven, as it exhibits a "hot spot" with an oscillating position in the axial direction, in correlation with the high voltage waveform. The initial expansion rate of the cylindrical plasma front was found to be supersonic; thus, the discharge releases a strong shockwave. Finally, the results on equivalent resistance and channel expansion are comparable to those of unipolar arcs. This shows the spark discharge has a similar behavior to the arc regime during the conductive phase and until the current oscillations stop.
Method and apparatus for electrical cable testing by pulse-arrested spark discharge
Barnum, John R.; Warne, Larry K.; Jorgenson, Roy E.; Schneider, Larry X.
A method for electrical cable testing by Pulse-Arrested Spark Discharge (PASD) uses the cable response to a short-duration high-voltage incident pulse to determine the location of an electrical breakdown that occurs at a defect site in the cable. The apparatus for cable testing by PASD includes a pulser for generating the short-duration high-voltage incident pulse, at least one diagnostic sensor to detect the incident pulse and the breakdown-induced reflected and/or transmitted pulses propagating from the electrical breakdown at the defect site, and a transient recorder to record the cable response. The method and apparatus are particularly useful to determine the location of defect sites in critical but inaccessible electrical cabling systems in aging aircraft, ships, nuclear power plants, and industrial complexes.
Quantitative infrared spectroscopic analysis of SF 6 decomposition products obtained by electrical partial discharges and sparks using PLS-calibrations
NASA Astrophysics Data System (ADS)
Kurte, R.; Heise, H. M.; Klockow, D.
Infrared spectroscopy is a powerful tool for the analysis of gaseous by-products in sulfur hexafluoride gas used as an insulator in high-voltage equipment. Sparks and electrical partial discharges were generated between different point-plane configurations within a custom-made discharge chamber constructed from stainless steel and Teflon ®. Various electrode materials were used such as stainless steel, copper, aluminium, silver, tungsten and tungsten/copper alloy. Owing to the different electrical conditions, a wide concentration range of the decomposition products existed. The main-products found were the sulfuroxyfluorides SOF 4 and SOF 2, as well as HF following experiments with partial discharges and sparking with energies around 1.0 J/spark. All infrared spectra were recorded using an FTIR-spectrometer equipped with a 10 cm gas cell. Quantification was carried out using classical least-squares and partial least-squares (PLS) with multivariate spectral data from selected intervals. PLS calibration models were also optimised under the constraint of a minimum number of spectral variables with a view to developing simple photometers based on a restricted number of laser wavelengths. Standard errors of prediction obtained by cross-validation of different PLS calibration models are reported for the compounds mentioned, as well as for SF 4, SO 2F 2 and SiF 4.
Power Measurements of Spark Discharge Experiments
NASA Astrophysics Data System (ADS)
Navarro-González, Rafael; Romero, Alfredo; Honda, Yasuhiro
An accurate and precise knowledge of the amount of energy introduced into prebiotic discharge experiments is important to understand the relative roles of different energy sources in the synthesis of organic compounds in the primitive Earth's atmosphere and other planetary atmospheres. Two methods widely used to determine the power of spark discharges were evaluated, namely calorimetric and oscilloscopic, using a chemically inert gas. The power dissipated by the spark in argon at 500 Torr was determined to be 2.4 (^+12%/_-17%) J s^-1 by calorimetry and 5.3 +/- 15%) J s^-1 by the oscilloscope. The difference between the two methods was attributed to (1) an incomplete conversion of the electric energy into heat, and (2) heat loss from the spark channel to the connecting cables through the electrodes. The latter contribution leads to an unwanted effect in the spark channel by lowering the spark product yields as the spark channel cools by mixing with surrounding air and by losing heat to the electrodes. Once the concentrations of the spark products have frozen at the freeze-out temperature, any additional loss of heat from the spark channel to the electrodes has no consequence in product yields. Therefore, neither methods accurately determines the net energy transferred to the system. With a lack of a quantitative knowledge of the amount of heat loss from the spark channel during the interval from ignition of the spark to when the freeze-out temperature is reached, it is recommended to derive the energy yields of the spark products from the mean value of the two methods with the uncertainty being their standard deviation. For the case of argon at 500 Torr, this would be 3.8 (+/-50%) J s^-1.
Large discharge-volume, silent discharge spark plug
Kang, Michael
A large discharge-volume spark plug for providing self-limiting microdischarges. The apparatus includes a generally spark plug-shaped arrangement of a pair of electrodes, where either of the two coaxial electrodes is substantially shielded by a dielectric barrier from a direct discharge from the other electrode, the unshielded electrode and the dielectric barrier forming an annular volume in which self-terminating microdischarges occur when alternating high voltage is applied to the center electrode. The large area over which the discharges occur, and the large number of possible discharges within the period of an engine cycle, make the present silent discharge plasma spark plug suitable for use as an ignition source for engines. In the situation, where a single discharge is effective in causing ignition of the combustible gases, a conventional single-polarity, single-pulse, spark plug voltage supply may be used.
Spark discharge trace element detection system
Adler-Golden, Steven; Bernstein, Lawrence S.; Bien, Fritz
A spark discharge trace element detection system is provided which includes a spark chamber including a pair of electrodes for receiving a sample of gas to be analyzed at no greater than atmospheric pressure. A voltage is provided across the electrodes for generating a spark in the sample. The intensity of the emitted radiation in at least one primary selected narrow band of the radiation is detected. Each primary band corresponds to an element to be detected in the gas. The intensity of the emission in each detected primary band is integrated during the afterglow time interval of the spark emission and a signal representative of the integrated intensity of the emission in each selected primary bond is utilized to determine the concentration of the corresponding element in the gas.
Spark discharge trace element detection system
Adler-Golden, S.; Bernstein, L.S.; Bien, F.
A spark discharge trace element detection system is provided which includes a spark chamber including a pair of electrodes for receiving a sample of gas to be analyzed at no greater than atmospheric pressure. A voltage is provided across the electrodes for generating a spark in the sample. The intensity of the emitted radiation in at least one primary selected narrow band of the radiation is detected. Each primary band corresponds to an element to be detected in the gas. The intensity of the emission in each detected primary band is integrated during the afterglow time interval of the spark emission and a signal representative of the integrated intensity of the emission in each selected primary bond is utilized to determine the concentration of the corresponding element in the gas. 12 figs.
Suprathermal electrons in a vacuum spark discharge
NASA Astrophysics Data System (ADS)
Bashutin, O. A.; Savjolov, A. S.
Results of experiments on the detection of suprathermal electron beams in the plasma of a highcurrent low-inductance vacuum spark by means of space-resolved spectral X-ray polarimetry are presented. It is shown that the observed polarization of bremsstrahlung may be caused by an ~100-keV electron beam propagating along the discharge axis from the pinching region toward the anode. The influence of the discharge initiation conditions on the parameters of the generated electron beams is analyzed.
Possible Influences of Spark Discharges on Cardiac Pacemakers.
Korpinen, Leena; Kuisti, Harri; Tarao, Hiroo; Virtanen, Vesa; Pääkkönen, Rauno; Dovan, Thanh; Kavet, Robert
Exposure to spark discharges may occur beneath high voltage transmission lines when contact is initiated with a conductive object (such as a motor vehicle) with the spark discharge mediated by the ambient electric field from the line. The objective of this study was to assess whether such exposures could interfere with the normal functioning of implanted cardiac pacemakers (PMs). The experiment consisted of PMs implanted in a human-sized phantom and then exposed to spark discharge through an upper extremity. A circuit was designed that produced spark discharges between two spherical electrodes fed to the phantom's left hand. The circuit was set to deliver a single discharge per half cycle (every 10 ms) about 10 μs in duration with a peak current of 1.2-1.3 A, thus simulating conditions under a 400-kV power line operating at 50 Hz. Of 29 PMs acquired, all were tested in unipolar configuration and 20 in bipolar configuration with exposure consisting of 2 min of continuous exposure (one unit was exposed for 1 min). No interference was observed in bipolar configuration. One unit in unipolar configuration incorrectly identified ventricular extra systoles (more than 400 beats min(-1)) for 2 s. The use of unipolar configuration in new implants is extremely rare, thus further minimizing the risk of interference with the passage of time. Replication of this study and, if safety for human subjects can be assured, future testing of human subjects is also advisable. PMID:26606060
Observations and Modeling of Long Negative Laboratory Discharges: Identifying the Physics Important to an Electrical Spark in Air
Biagi, C J; Uman, M A
There are relatively few reports in the literature focusing on negative laboratory leaders. Most of the reports focus exclusively on the simpler positive laboratory leader that is more commonly encountered in high voltage engineering [Gorin et al., 1976; Les Renardieres Group, 1977; Gallimberti, 1979; Domens et al., 1994; Bazelyan and Raizer 1998]. The physics of the long, negative leader and its positive counterpart are similar; the two differ primarily in their extension mechanisms [Bazelyan and Raizer, 1998]. Long negative sparks extend primarily by an intermittent process termed a 'step' that requires the development of secondary leader channels separated in space from the primary leader channel. Long positive sparks typically extend continuously, although, under proper conditions, their extension can be temporarily halted and begun again, and this is sometimes viewed as a stepping process. However, it is emphasized that the nature of positive leader stepping is not like that of negative leader stepping. There are several key observational studies of the propagation of long, negative-polarity laboratory sparks in air that have aided in the understanding of the stepping mechanisms exhibited by such sparks [e.g., Gorin et al., 1976; Les Renardieres Group, 1981; Ortega et al., 1994; Reess et al., 1995; Bazelyan and Raizer, 1998; Gallimberti et al., 2002]. These reports are reviewed below in Section 2, with emphasis placed on the stepping mechanism (the space stem, pilot, and space leader). Then, in Section 3, reports pertaining to modeling of long negative leaders are summarized.
Measurement of the electron density in Transient Spark discharge
NASA Astrophysics Data System (ADS)
Janda, Mário; Martišovitš, Viktor; Hensel, Karol; Dvonč, Lukáš; Machala, Zdenko
This paper presents our measurements of the electron density in a streamer-to-spark transition discharge, which is named transient spark (TS), in atmospheric pressure air. Despite the dc applied voltage, TS has a pulsed character with short (˜10-100 ns) high current (>1 A) pulses, with a repetition frequency on the order of kHz. The electron density ne ˜ 1017 cm-3 at maximum is reached in TS with repetition frequencies below ˜3 kHz, using relatively low power delivered to the plasma (0.2-3 W). The temporal evolution of ne was estimated from the resistance of the plasma discharge, which was obtained by a detailed analysis of the electric circuit representing the TS and the discharge diameter measurements using a fast intensified charge-coupled device (iCCD) camera. This estimate was compared with ne calculated from the measured Stark broadening of several atomic lines: Hα, N at 746 nm, and O triplet at 777 nm. Good agreement was obtained, although the method based on the plasma resistance is sensitive to an accurate determination of the discharge diameter. We have found that this method is also limited for strongly ionized plasmas. On the other hand, a lower ne detection limit can be obtained by this method than from the Stark broadening of atomic lines.
Coupling discharge and gas dynamics in streamer-less spark formation in supercritical N2
NASA Astrophysics Data System (ADS)
Agnihotri, Ashutosh; Hundsdorfer, Willem; Ebert, Ute
A two-dimensional cylindrically symmetric model is developed to study the streamer-less spark formation in a short gap on the timescale of ion motion. It incorporates the coupling between the electric discharge and the gas through the heat generated by the discharge and the consecutive gas expansion. The model is employed to study electrical breakdown in supercritical N2. We present the simulation results of gas heating by the electrical discharge and the effect of gas expansion on the electrical discharge.
The Optical Diagnosis of Underwater Positive Sparks and Corona Discharges
NASA Astrophysics Data System (ADS)
Chen, Dan; Zeng, Xinwu; Wang, Yibo
In this paper, two types of underwater discharges, spark discharge and corona discharge, are investigated by optical diagnosis using a high speed framing camera (HSFC) with the framing time within nanoseconds under the same experimental conditions. In order to capture the photographs of streamer propagation, the influence of the randomicity of the pre-breakdown duration is taken into consideration. By increasing the conductivity of water, the randomicity reduces effectively. Experimental results show that, for a spark discharge, the process can be separated into three stages: the generation and propagation of a streamer, the generation and expansion of the discharge channel, and the development and annihilation of the plasma. The streamers do not directly move to the opposite electrode, but form a bush-like figure. With the increase of the number of branches, the velocity of streamer propagation slows down. The trajectory of the initial channel between electrodes is not straight. However, with the channel expanding, its shape transforms into a straight column. For a corona discharge, there are two stages: the generation and propagation of a streamer, and the stagnation and annihilation of the streamer. The initial streamer in a corona discharge is generated later than in a spark discharge. The forms of streamers for both kinds of discharge are similar; however, streamers generated by a corona discharge propagate with a slower velocity and the number of branches is less compared with a spark discharge. When the energy injection stops, the luminescence of plasma inside the discharge channel (spark discharge) or streamers (corona discharge) becomes weaker and weaker, and finally disappears.
The Miller volcanic spark discharge experiment.
Johnson, Adam P; Cleaves, H James; Dworkin, Jason P; Glavin, Daniel P; Lazcano, Antonio; Bada, Jeffrey L
Miller's 1950s experiments used, besides the apparatus known in textbooks, one that generated a hot water mist in the spark flask, simulating a water vapor-rich volcanic eruption. We found the original extracts of this experiment in Miller's material and reanalyzed them. The volcanic apparatus produced a wider variety of amino acids than the classic one. Release of reduced gases in volcanic eruptions accompanied by lightning could have been common on the early Earth. Prebiotic compounds synthesized in these environments could have locally accumulated, where they could have undergone further processing. PMID:18927386
The streamer-to-spark transition in a transient spark: a dc-driven nanosecond-pulsed discharge in atmospheric air
NASA Astrophysics Data System (ADS)
Janda, Mário; Machala, Zdenko; Niklová, Adriana; Martišovitš, Viktor
We present a study of the streamer-to-spark transition in a self-pulsing dc-driven discharge called a transient spark (TS). The TS is a streamer-to-spark transition discharge with short spark duration (˜10-100 ns), based on charging and discharging of the internal capacity of the electric circuit with repetition frequency 1-10 kHz. The TS can be maintained under relatively low energy conditions (0.1-1 mJ pulse-1). It generates a very reactive non-equilibrium air plasma applicable for flue gas cleaning or bio-decontamination. Thanks to the short spark current pulse duration, the steady-state gas temperature, measured at the beginning of the streamers initiating the TS, increases from an initial value of ˜300 K only up to ˜550 K at 10 kHz. The streamer-to-spark transition is governed by the subsequent increase in the gas temperature in the plasma channel up to ˜1000 K. This breakdown temperature does not change with increasing repetition frequency f. The heating after the streamer accelerates with increasing f, leading to a decrease in the average streamer-to-spark transition time from a few µs to less than 100 ns.
Focused shock spark discharge drill using multiple electrodes
Moeny, William M.; Small, James G.
A spark discharge focused drill provided with one pulse forming line or a number of pulse forming lines. The pulse forming line is connected to an array of electrodes which would form a spark array. One of the electrodes of each of the array is connected to the high voltage side of the pulse forming line and the other electrodes are at ground potential. When discharged in a liquid, these electrodes produce intense focused shock waves that can pulverize or fracture rock. By delaying the firing of each group of electrodes, the drill can be steered within the earth. Power can be fed to the pulse forming line either downhole or from the surface area. A high voltage source, such as a Marx generator, is suitable for pulse charging the lines.
Carbon and hydrogen isotopic composition of methane and C2+ alkanes in electrical spark discharge: implications for identifying sources of hydrocarbons in terrestrial and extraterrestrial settings.
Telling, Jon; Lacrampe-Couloume, Georges; Sherwood Lollar, Barbara
The low-molecular-weight alkanes--methane, ethane, propane, and butane--are found in a wide range of terrestrial and extraterrestrial settings. The development of robust criteria for distinguishing abiogenic from biogenic alkanes is essential for current investigations of Mars' atmosphere and for future exobiology missions to other planets and moons. Here, we show that alkanes synthesized during gas-phase radical recombination reactions in electrical discharge experiments have values of δ(2)H(methane)>δ(2)H(ethane)>δ(2)H(propane), similar to those of the carbon isotopes. The distribution of hydrogen isotopes in gas-phase radical reactions is likely due to kinetic fractionations either (i) from the preferential incorporation of (1)H into longer-chain alkanes due to the more rapid rate of collisions of the smaller (1)H-containing molecules or (ii) by secondary ion effects. Similar δ(13)C(C1-C2+) and δ(2)H(C1-C2+) patterns may be expected in a range of extraterrestrial environments where gas-phase radical reactions dominate, including interstellar space, the atmosphere and liquid hydrocarbon lakes of Saturn's moon Titan, and the outer atmospheres of Jupiter, Saturn, Neptune, and Uranus. Radical recombination reactions at high temperatures and pressures may provide an explanation for the combined reversed δ(13)C(C1-C2+) and δ(2)H(C1-C2+) patterns of terrestrial alkanes documented at a number of high-temperature/pressure crustal sites. PMID:23683048
The spark discharge synthesis of amino acids from various hydrocarbons
NASA Technical Reports Server (NTRS)
Ring, D.; Miller, S. L.
The spark discharge synthesis of amino acids using an atmosphere of CH4+N2+H2O+NH3 has been investigated with variable pNH3. The amino acids produced using higher hydrocarbons (ethane, ethylene, acetylene, propane, butane, and isobutane) instead of CH4 were also investigated. There was considerable range in the absolute yields of amino acids, but the yields relative to glycine (or alpha-amino-n-butyric acid) were more uniform. The relative yields of the C3 to C6 aliphatic alpha-amino acids are nearly the same (with a few exceptions) with all the hydrocarbons. The glycine yields are more variable. The precursors to the C3-C6 aliphatic amino acids seem to be produced in the same process, which is separate from the synthesis of glycine precursors. It may be possible to use these relative yields as a signature for a spark discharge synthesis provided corrections can be made for subsequent decomposition events (e.g. in the Murchison meteorite).
NASA Astrophysics Data System (ADS)
Antanasijević, R.; Banjanac, R.; Dragić, A.; Joković, D.; Joksimović, D.; Marić, Z.; Panić, B.; Udovičić, V.; Vigier, J. P.
An experiment on electrical discharges in air under normal atmospheric conditions has been performed. The ratio between output and input energy is greater than 1, which confirms the results already reported by Graneau et al.
FTIR Analysis of Flowing Afterglow from a High-Frequency Spark Discharge
NASA Astrophysics Data System (ADS)
White, Allen; Hieftje, Gary M.; Ray, Steve; Pfeuffer, Kevin
Plasmas are often used as ionization sources for ambient mass spectrometry (AMS). Here, the flowing afterglow of a novel high-energy spark discharge system, operated in nitrogen at high repetition rates, is investigated as a source for AMS. The spark discharge here is the same as that of an automobile ignition circuit.Combustion in automobile engines is initiated by a spark ignition system that is designed to deliver short-duration,high-voltage sparks to multiple engine cylinders. The arrangement utilized in this study is a modified discharge configuration designed to produce similarly short-duration, high-voltage discharges. It consists of an automotive ignition coil that is activated by a spark initiation circuit that discharges in turn into a cell with neutral gas input flow and ultimately into the collection orifice of a mass spectrometer. The discharge voltage is approximately 40kV at 800 Hz. High-frequency spark discharges in a nitrogen flow produce reagent ions such as NO+. In order to better evaluate the effectiveness of the discharge in producing reagent ions, an FTIR is utilized to measure IR active species such as nitric oxide, hydroxide, ozone, and water in the afterglow of the spark discharge during variation of discharge parameters. Time-resolved IR emission spectra provide additional insight into the reagent ion production mechanisms.
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
Electrical Discharge Machining.
ERIC Educational Resources Information Center
Montgomery, C. M.
The manual is for use by students learning electrical discharge machining (EDM). It consists of eight units divided into several lessons, each designed to meet one of the stated objectives for the unit. The units deal with: introduction to and advantages of EDM, the EDM process, basic components of EDM, reaction between forming tool and workpiece,…
Bent paths of a positive streamer and a cathode-directed spark leader in diffuse discharges preionized by runaway electrons
NASA Astrophysics Data System (ADS)
Zhang, Cheng; Tarasenko, Viktor F.; Shao, Tao; Beloplotov, Dmitry V.; Lomaev, Mikhail I.; Wang, Ruixue; Sorokin, Dmitry A.; Yan, Ping
Diffuse discharges preionized by runaway electrons can produce large-area homogeneous discharges at elevated pressures, which is an intriguing phenomenon in the physics of pulsed discharges. In this paper, runaway-electron-preionized diffuse discharge (REP DD) was obtained in a wide pressure range (0.05-0.25 MPa), and under certain conditions a positive streamer and a cathode-directed spark leader could be observed to propagate at some angles to the applied (background) electric field lines. For a 16-mm gap at an air pressure of 0.08-0.1 MPa, the percentage of pulses in which such propagation is observed is about 5%-50% of their total number, and in the other pulses such bent paths could not be observed because there is even no streamer or cathode-directed spark leader in diffuse discharges. In our opinion, such propagation of the positive streamer and the cathode-directed spark leader at some angle to the background electric field lines owes to different increase rates of the electron density in different regions of the discharge volume under REP DD conditions. Therefore, during the formation of a REP DD, the increase of the electron density is inhomogeneous and nonsimultaneous, resulting in an electron density gradient at the ionization wave front.
Bent paths of a positive streamer and a cathode-directed spark leader in diffuse discharges preionized by runaway electrons
Zhang, Cheng; Shao, Tao Wang, Ruixue; Yan, Ping; Tarasenko, Viktor F.; Beloplotov, Dmitry V.; Lomaev, Mikhail I.; Sorokin, Dmitry A.
Diffuse discharges preionized by runaway electrons can produce large-area homogeneous discharges at elevated pressures, which is an intriguing phenomenon in the physics of pulsed discharges. In this paper, runaway-electron-preionized diffuse discharge (REP DD) was obtained in a wide pressure range (0.05–0.25 MPa), and under certain conditions a positive streamer and a cathode-directed spark leader could be observed to propagate at some angles to the applied (background) electric field lines. For a 16-mm gap at an air pressure of 0.08–0.1 MPa, the percentage of pulses in which such propagation is observed is about 5%–50% of their total number, and in the other pulses such bent paths could not be observed because there is even no streamer or cathode-directed spark leader in diffuse discharges. In our opinion, such propagation of the positive streamer and the cathode-directed spark leader at some angle to the background electric field lines owes to different increase rates of the electron density in different regions of the discharge volume under REP DD conditions. Therefore, during the formation of a REP DD, the increase of the electron density is inhomogeneous and nonsimultaneous, resulting in an electron density gradient at the ionization wave front.
Influence of the capillary on the ignition of the transient spark discharge
NASA Astrophysics Data System (ADS)
Gerling, T.; Hoder, T.; Brandenburg, R.; Bussiahn, R.; Weltmann, K.-D.
A self-pulsing negative dc discharge in argon generated in a needle-to-plane geometry at open atmosphere is investigated. Additionally, the needle electrode can be surrounded by a quartz capillary. It is shown that the relative position of the capillary end to the needle tip strongly influences the discharge inception and its spatio-temporal dynamics. Without the capillary for the selected working parameters a streamer corona is ignited, but when the capillary surrounds the needle, the transient spark (TS) discharge is ignited after a pre-streamer (PS) occurs. The time between PS and TS discharge depends on the relative capillary end position. The existence of the PS is confirmed by electro-optical characterization. Furthermore, spectrally and spatio-temporally resolved cross-correlation spectroscopy is applied to show the most active region of pre-phase emission activity as indicators for high local electric field strength. The results indicate that with a capillary in place, the necessary energy input of the pre-phase into the system is mainly reduced by additional electrical fields at the capillary edge. Even such a small change as a shift of dielectric surface close to the plasma largely changes the energy balance in the system.
Detection of S2F10 produced by a single-spark discharge in SF6
NASA Astrophysics Data System (ADS)
Sauers, I.; Mahajan, S. M.
Improvement in detection sensitivity of S2F10 in SF6 down to concentrations below 10 parts per billion, using a cryogenic enrichment-gas chromatography technique, has permitted the detection of S2F10 produced by a single-spark discharge in SF6. The spark yield of S2F10 was found to fall in the range of yields found in earlier work on more highly decomposed SF6. Based on preliminary data the spark discharge may provide a suitable and reproducible reference source of S2F10.
Spark discharge method of liquid rare-gas purification
NASA Astrophysics Data System (ADS)
Pokachalov, S. G.; Kirsanov, M. A.; Kruglov, A. A.; Obodovski, I. M.
The spark disharge method of liquid rare-gas purification is describe. The method is sufficiently more simple than those widely used. Physical aspects of the method are discussed, and examples of its application are presented.
Primordial synthesis of amines and amino acids in a 1958 Miller H2S-rich spark discharge experiment.
Parker, Eric T; Cleaves, Henderson J; Dworkin, Jason P; Glavin, Daniel P; Callahan, Michael; Aubrey, Andrew; Lazcano, Antonio; Bada, Jeffrey L
Archived samples from a previously unreported 1958 Stanley Miller electric discharge experiment containing hydrogen sulfide (H(2)S) were recently discovered and analyzed using high-performance liquid chromatography and time-of-flight mass spectrometry. We report here the detection and quantification of primary amine-containing compounds in the original sample residues, which were produced via spark discharge using a gaseous mixture of H(2)S, CH(4), NH(3), and CO(2). A total of 23 amino acids and 4 amines, including 7 organosulfur compounds, were detected in these samples. The major amino acids with chiral centers are racemic within the accuracy of the measurements, indicating that they are not contaminants introduced during sample storage. This experiment marks the first synthesis of sulfur amino acids from spark discharge experiments designed to imitate primordial environments. The relative yield of some amino acids, in particular the isomers of aminobutyric acid, are the highest ever found in a spark discharge experiment. The simulated primordial conditions used by Miller may serve as a model for early volcanic plume chemistry and provide insight to the possible roles such plumes may have played in abiotic organic synthesis. Additionally, the overall abundances of the synthesized amino acids in the presence of H(2)S are very similar to the abundances found in some carbonaceous meteorites, suggesting that H(2)S may have played an important role in prebiotic reactions in early solar system environments. PMID:21422282
Primordial Synthesis of Amines and Amino Acids in a 1958 Miller H2S-Rich Spark Discharge Experiment
NASA Technical Reports Server (NTRS)
Parker, Eric T.; Cleaves, Henderson J.; Dworkin, Jason P.; Glavin, Daniel P.; Callahan, Michael; Aubrey, Andrew; Lazcano, Antonio; Bada, Jeffrey L.
Archived samples from a previously unreported 1958 Stanley Miller electric discharge experiment containing hydrogen sulfide (H2S) were recently discovered and analyzed using high-performance liquid chromatography and time-of-flight mass spectrometry. We report here the detection and quantification of primary amine-containing compounds in the original sample residues, which were produced via spark discharge using a gaseous mixture of H2S, CH4, NH3, and CO2. A total of 23 amino acids and 4 amines, including 7 organosulfur compounds, were detected in these samples. The major amino acids with chiral centers are racemic within the accuracy of the measurements, indicating that they are not contaminants introduced during sample storage. This experiment marks the first synthesis of sulfur amino acids from spark discharge experiments designed to imitate primordia! environments. The relative yield of some amino acids, in particular the isomers of aminobutyric acid, are the highest ever found in a spark discharge experiment. The simulated primordial conditions used by Miller may serve as a model for early volcanic plume chemistry and provide insight to the possible roles such plumes may have played in abiotic organic synthesis. Additionally, the overall abundances of the synthesized amino acids in the presence of H2S are very similar to the abundances found in some carbonaceous meteorites, suggesting that H2S may have played an important role in prebiotic reactions in early solar system environments.
Experimental study of micro electrical discharge machining discharges
Braganca, I. M. F.; Rosa, P. A. R.; Martins, P. A. F.; Dias, F. M.; Alves, L. L.
Micro electrical discharge machining ({mu}EDM) is an atmospheric-pressure plasma-assisted technology that uses point-to-plane discharges in liquid dielectrics to remove microscopic quantities of electrically conductive materials. In this work, an innovative {mu}EDM prototype machine was specifically designed and fabricated to produce and control single spark discharges, thus, resolving the typical limitations of (multi-discharge) commercial machines. The work analyses the type of discharge and the micro-plasma electron-density values obtained for 0.5-38 {mu}m gap sizes, 3-10 000 {mu}s pulse durations, 75-250 V low breakdown voltages, and 1-20 A discharge currents, using different combinations of metallic electrodes in oil and in water. Results allow fitting, for micro-scale and low voltages, an empirical law between the maximum gap-size for breakdown, the breakdown voltage, and the effective stress-time. The electron density n{sub e} is obtained by optical emission spectroscopy diagnostics of the H{sub {alpha}}-line Stark broadening (yielding n{sub e}{approx}10{sup 16}-10{sup 17} cm{sup -3}, i.e., ionization degrees of {approx}2 Multiplication-Sign 10{sup -5}-10{sup -4}) and by a semi-empirical resistive plasma model. The model uses the experimental values of several electrical and geometrical quantities, and of the gas pressure estimated as {approx}60 bar-2 kbar from measurements of the plasma mechanical action, obtained using a force sensor. The quantitative information of this phenomenological study can assist the optimization of this micro-fabrication technique.
Experimental study of micro electrical discharge machining discharges
NASA Astrophysics Data System (ADS)
Bragança, I. M. F.; Rosa, P. A. R.; Dias, F. M.; Martins, P. A. F.; Alves, L. L.
Micro electrical discharge machining (μEDM) is an atmospheric-pressure plasma-assisted technology that uses point-to-plane discharges in liquid dielectrics to remove microscopic quantities of electrically conductive materials. In this work, an innovative μEDM prototype machine was specifically designed and fabricated to produce and control single spark discharges, thus, resolving the typical limitations of (multi-discharge) commercial machines. The work analyses the type of discharge and the micro-plasma electron-density values obtained for 0.5-38 μm gap sizes, 3-10 000 μs pulse durations, 75-250 V low breakdown voltages, and 1-20 A discharge currents, using different combinations of metallic electrodes in oil and in water. Results allow fitting, for micro-scale and low voltages, an empirical law between the maximum gap-size for breakdown, the breakdown voltage, and the effective stress-time. The electron density ne is obtained by optical emission spectroscopy diagnostics of the Hα-line Stark broadening (yielding ne˜1016-1017 cm-3, i.e., ionization degrees of ˜2×10-5-10-4) and by a semi-empirical resistive plasma model. The model uses the experimental values of several electrical and geometrical quantities, and of the gas pressure estimated as ˜60 bar-2 kbar from measurements of the plasma mechanical action, obtained using a force sensor. The quantitative information of this phenomenological study can assist the optimization of this micro-fabrication technique.
Nanosecond repetitively pulsed discharges in air at atmospheric pressure—the spark regime
NASA Astrophysics Data System (ADS)
Pai, David Z.; Lacoste, Deanna A.; Laux, Christophe O.
Nanosecond repetitively pulsed (NRP) spark discharges have been studied in atmospheric pressure air preheated to 1000 K. Measurements of spark initiation and stability, plasma dynamics, gas temperature and current-voltage characteristics of the spark regime are presented. Using 10 ns pulses applied repetitively at 30 kHz, we find that 2-400 pulses are required to initiate the spark, depending on the applied voltage. Furthermore, about 30-50 pulses are required for the spark discharge to reach steady state, following initiation. Based on space- and time-resolved optical emission spectroscopy, the spark discharge in steady state is found to ignite homogeneously in the discharge gap, without evidence of an initial streamer. Using measured emission from the N2 (C-B) 0-0 band, it is found that the gas temperature rises by several thousand Kelvin in the span of about 30 ns following the application of the high-voltage pulse. Current-voltage measurements show that up to 20-40 A of conduction current is generated, which corresponds to an electron number density of up to 1015 cm-3 towards the end of the high-voltage pulse. The discharge dynamics, gas temperature and electron number density are consistent with a streamer-less spark that develops homogeneously through avalanche ionization in volume. This occurs because the pre-ionization electron number density of about 1011 cm-3 produced by the high frequency train of pulses is above the critical density for streamer-less discharge development, which is shown to be about 108 cm-3.
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.
Comparison between the discharge development in the two- and three-electrode spark gap switches
NASA Astrophysics Data System (ADS)
Golnabi, Hossein
Results of numerical simulation of two- and three-electrode spark gaps operating with pure nitrogen gas are compared. Our result show that in both cases the discharge process evolves via two stages very similar to that was reported in nitrogen glow discharge studies. First, the primary electrons produce positive nitrogen ions; second, the produced ions can disturb the applied field, and can create the space charge region. The undulations observed are because of the secondary effects, in particular, the cathode-directed streamers. The delay time for the three-electrode spark gap is more than that of the two-electrode discharge. Current growth is faster for the two-electrode spark gap in comparison with the three-electrode one. The oscillations are more enhanced for the case of the three-electrode spark gap. Our simulation method provides both temporal and spatial information concerning the operation of such switches. The reported results are helpful in design and optimization of both the two- and three-electrode spark gaps.
Electrostatic Discharge Sensitivity and Electrical Conductivity of Composite Energetic Materials
Michael A. Daniels; Daniel J. Prentice; Chelsea Weir; Michelle L. Pantoya; Gautham Ramachandran; Tim Dallas
Composite energetic material response to electrical stimuli was investigated and a correlation between electrical conductivity and ignition sensitivity was examined. The composites consisted of micrometer particle aluminum combined with another metal, metal oxide, or fluoropolymer. Of the nine tested mixtures, aluminum with copper oxide was the only mixture to ignite by electrostatic discharge with minimum ignition energy (MIE) of 25 mJ and an electrical conductivity of 1246.25 nS; two orders of magnitude higher than the next composite. This study showed a similar trend in MIE for ignition triggered by a discharged spark compared with a thermal hot wire source.
Application of pulsed spark discharge for calcium carbonate precipitation in hard water.
Yang, Yong; Kim, Hyoungsup; Starikovskiy, Andrey; Fridman, Alexander; Cho, Young I
The effect of underwater pulsed spark discharge on the precipitation of dissolved calcium ions was investigated in the present study. Water samples with different calcium hardness were prepared by continuous evaporation of tap water using a laboratory cooling tower. It was shown that the concentration of calcium ions dropped by 20-26% after 10-min plasma treatment, comparing with no drop for untreated cases. A laser particle counting method demonstrated that the total number of solid particles suspended in water increased by over 100% after the plasma treatment. The morphology and the crystal form of the particles were identified by both scanning electron microscopy and X-ray diffraction. Calcite with rhombohedron morphology was observed for plasma treated cases, comparing with the round structure observed for no-treatment cases. It was hypothesized that the main mechanisms for the plasma-assisted calcium carbonate precipitation might include electrolysis, local heating in the vicinity of plasma channel and a high electric field at the tip of plasma streamers, inducing structural changes in the electric double layer of hydrated ions. PMID:20494397
High-altitude electrical discharges associated with thunderstorms and lightning
NASA Astrophysics Data System (ADS)
Liu, Ningyu; McHarg, Matthew G.; Stenbaek-Nielsen, Hans C.
The purpose of this paper is to introduce electrical discharge phenomena known as transient luminous events above thunderstorms to the lightning protection community. Transient luminous events include the upward electrical discharges from thunderstorms known as starters, jets, and gigantic jets, and electrical discharges initiated in the lower ionosphere such as sprites, halos, and elves. We give an overview of these phenomena with a focus on starters, jets, gigantic jets, and sprites, because similar to ordinary lightning, streamers and leaders are basic components of these four types of transient luminous events. We present a few recent observations to illustrate their main properties and briefly review the theories. The research in transient luminous events has not only advanced our understanding of the effects of thunderstorms and lightning in the middle and upper atmosphere, but also improved our knowledge of basic electrical discharge processes critical for sparks and lightning.
Measurement of Temporally and Spatially Resolved Electron Density in the Filament of a Pulsed Spark Discharge in Water
NASA Astrophysics Data System (ADS)
Niu, Zhiwen; Wen, Xiaoqiong; Ren, Chunsheng; Qiu, Yuliang
The temporally and spatially resolved optical emission spectrum of Hα of a pulsed spark discharge in water was experimentally measured. The temporally and spatially resolved electron densities, along the radial direction of the spark filament, for a pulsed spark discharge in water with a conductivity of 100 μS/cm were investigated. The electron density in the spark filament was found to be in the 1018/cm3 order of magnitude. The highest electron density was measured at the primary stage of the spark filament, and it decreased with time. The radial distribution of electron density increased from the center to the edge of the spark filament. supported in part by National Natural Science Foundation of China (Nos. 11275040 and 51437002)
Optoelectronical Measurements Of The Electric Field Distribution At Pseudo Spark Chambers
NASA Astrophysics Data System (ADS)
Ehrler, Horst
A fiberoptic sensor for electric fieldstrength measurements was developed. This sensor allows to measure even high electric fields in a contactless way, therefore nearly undisturbing the phenomenon to be measured. The basic idea is to rotate the polarization plane of linearly polarized light in an optically active medium (linear electrooptic effect). Further advantages of this method are: high bandwidth near the GHz-region, high local resolution because of small size, no electromagnetic pulse disturbance, useable in high field regions, where electrical methods fail, even in rigid environments. The fiberoptic sensor together with the detector system, which comprises a streakcamera with an image processing system, allows the analog data aquisition and -transmission of about 40 time synchronised signals at one shot using fiberoptics. The application and results of the new diagnostic in the case of the Pseudo Spark Chamber, where classical electric measurements fail, will be presented. The Pseudo Spark1 is a hollow cathode, low pressure gas discharge system, in a special rotational symmetric geometrie. It is situated on the left hand side of the Paschen curve by about 20 Pa hydrogen. During the dicharge there is observed a well pinched electron beam as well as an ion beam; also various kinds of X-ray emission can be detected. The applications of this systems are in Pulse Power technology, lithography, as well as high power switching and material processing.
The lattice distortion of nickel particles generated by spark discharge in hydrocarbon dielectric mediums
NASA Astrophysics Data System (ADS)
Liu, Yifan; Li, Xianglong; Li, Yan; Zhao, Zhankui; Bai, Fushi
Nickel particles were prepared by the ultrasound-aided spark discharge in pure water and hydrocarbons (kerosene and EDM fluid). The element composition and lattice structure were analyzed by EDS and XRD, respectively. The EDS indicated a high-purity powder was generated in pure water. For hydrocarbons, the carbon was detected as the majority impurity dissolved into the Ni interstitial sites, and the quantitative XRD revealed that the peak positions are lower than those of the corresponding perfect Ni crystal. The d-spacing deviation increases with the effect of ultrasound in hydrocarbons, while the distortion is negligible for pure water. We reported the composition, interatomic distances, and distortion of the Ni particles resulting from C doping. These findings revealed a new method to synthesize the solid solution via the spark discharge.
Nanoparticle formation by laser ablation in air and by spark discharges at atmospheric pressure
NASA Astrophysics Data System (ADS)
Itina, T. E.; Voloshko, A.
Recent promising methods of nanoparticle fabrication include laser ablation and spark discharge. Despite different experimental conditions, a striking similarity is often observed in the sizes of the obtained particles. To explain this result, we elucidate physical mechanisms involved in the formation of metallic nanoparticles. In particular, we compare supersaturation degree and sizes of critical nucleus obtained under laser ablation conditions with that obtained for spark discharge in air. For this, the dynamics of the expansion of either ablated or eroded products is described by using a three-dimensional blast wave model. Firstly, we consider nanosecond laser ablation in air. In the presence of a background gas, the plume expansion is limited by the gas pressure. Nanoparticles are mostly formed by nucleation and condensation taking place in the supersaturated vapor. Secondly, we investigate nanoparticles formation by spark discharge at atmospheric pressure. After efficient photoionization and streamer expansion, the cathode material suffers erosion and NPs appear. The calculation results allow us to examine the sizes of critical nuclei as function of the experimental parameters and to reveal the conditions favorable for the size reduction and for the increase in the nanoparticle yield.
Water purification by electrical discharges
NASA Astrophysics Data System (ADS)
Arif Malik, Muhammad; Ghaffar, Abdul; Akbar Malik, Salman
There is a continuing need for the development of effective, cheap and environmentally friendly processes for the disinfection and degradation of organic pollutants from water. Ozonation processes are now replacing conventional chlorination processes because ozone is a stronger oxidizing agent and a more effective disinfectant without any side effects. However, the fact that the cost of ozonation processes is higher than chlorination processes is their main disadvantage. In this paper recent developments targeted to make ozonation processes cheaper by improving the efficiency of ozone generation, for example, by incorporation of catalytic packing in the ozone generator, better dispersion of ozone in water and faster conversion of dissolved ozone to free radicals are described. The synthesis of ozone in electrical discharges is discussed. Furthermore, the generation and plasma chemical reactions of several chemically active species, such as H2O2, Obullet, OHbullet, HO2bullet, O3*, N2*, e-, O2-, O-, O2+, etc, which are produced in the electrical discharges are described. Most of these species are stronger oxidizers than ozone. Therefore, water treatment by direct electrical discharges may provide a means to utilize these species in addition to ozone. Much research and development activity has been devoted to achieve these targets in the recent past. An overview of these techniques and important developments that have taken place in this area are discussed. In particular, pulsed corona discharge, dielectric barrier discharge and contact glow discharge electrolysis techniques are being studied for the purpose of cleaning water. The units based on electrical discharges in water or close to the water level are being tested at industrial-scale water treatment plants.}
Internal dynamics of electrical discharges
Kadish, A.; Maier, W.B. II ); Robiscoe, R.T. )
The existence of thresholds for electrical discharge onset suggests a functional relation between macroscopic resistivity and current. At low current, the resistivity should be inversely proportional to the magnitude of the current. Macroscopic models which employ this scaling predict many empirically observed properties of transient electrical discharges, such as (1) thresholds for onset of current, (2) abrupt termination of current in active regions of a current channel, (3) current restart in passive regions of current channels, (4) leaders, and (5) residual charge, both in channels and at sources when current terminates. We present an overview of research with these models and use examples to illustrate the results that have been obtained. We also show how these models predict current channel formation and describe results of efforts to benchmark theory with experimental data. 12 refs., 9 figs.
Effect of electrode geometry on high energy spark discharges in air
NASA Astrophysics Data System (ADS)
Belmouss, Mounia
The government, aerospace, and transportation industries are deeply invested in developing new technologies to improve the performance and maneuverability of current and future aircraft while reducing aerodynamic noise and environmental impact. One of the key pathways to meet these goals is through aerodynamic flow control, which can involve suppressing or inducing separation, transition and management of turbulence in boundary layers, increasing the lift and reducing the drag of airfoils, and gas mixing to control fluctuating forces and aerodynamic noise [1]. In this dissertation, the complex flow field following a spark discharge is studied for a range of geometries and discharge characteristics, and the possibilities for using the induced flow for aerodynamic control are assessed. This work shows the influence of the electrode configuration on the fluid dynamics following the spark discharge and how the hot gas evolution gives rise to various physical phenomena (i.e. generation of turbulence, inducing vorticity, and gas mixing) that can be used to modify the flow-field structure near the boundary layer on an aerodynamic surface.
Quantification of monocarboxylic acids from a spark discharge synthesis. [in meteorites
NASA Technical Reports Server (NTRS)
Yuen, G. U.; Lawless, J. G.; Edelson, E. H.
A suite of sixteen monocarboxylic acids having carbon numbers 2 to 7, formed by the Miller-Urey spark discharge process, was identified and quantified by gas chromatography and mass fragmentography using a deuterium spiking technique. The molar concentration and isomeric distribution of these laboratory synthesized monocarboxylic acids are compared to those previously reported for the Murchison meteorite. They show similar trends, namely, decreasing molar concentration with increasing molecular weight, and a ratio of normal/branched isomers tending toward smaller values with increasing carbon numbers.
Flame Speed and Spark Intensity
NASA Technical Reports Server (NTRS)
Randolph, D W; Silsbee, F B
This report describes a series of experiments undertaken to determine whether or not the electrical characteristics of the igniting spark have any effect on the rapidity of flame spread in the explosive gas mixtures which it ignites. The results show very clearly that no such effect exists. The flame velocity in carbon-monoxide oxygen, acetylene oxygen, and gasoline-air mixtures was found to be unaffected by changes in spark intensity from sparks which were barely able to ignite the mixture up to intense condenser discharge sparks having fifty time this energy. (author)
Classification of electrical discharges in DC Accelerators
NASA Astrophysics Data System (ADS)
Banerjee, Srutarshi; Deb, A. K.; Rajan, Rehim N.; Kishore, N. K.
Controlled electrical discharge aids in conditioning of the system while uncontrolled discharges damage its electronic components. DC Accelerator being a high voltage system is no exception. It is useful to classify electrical discharges according to the severity. Experimental prototypes of the accelerator discharges are developed. Photomultiplier Tubes (PMTs) are used to detect the signals from these discharges. Time and Frequency domain characteristics of the detected discharges are used to extract features. Machine Learning approaches like Fuzzy Logic, Neural Network and Least Squares Support Vector Machine (LSSVM) are employed to classify the discharges. This aids in detecting the severity of the discharges.
A focused electric spark source for non-contact stress wave excitation in solids.
Dai, Xiaowei; Zhu, Jinying; Haberman, Michael R
A focused electric spark is used as a non-contact acoustic source to excite stress waves in solids. The source consists of an electric spark source located at the near focus of an ellipsoidal reflector that focuses the acoustic disturbance generated by the spark source to the far focal point. Experimental studies using both contact and non-contact sensors indicate that the source has the capability to excite the Rayleigh surface wave and impact-echo mode (S1-zero-group-velocity Lamb mode) in a 250 mm thick concrete slab and to enable fully air-coupled testing of concrete specimens. PMID:25669297
Measurement of effective blast energy for direct initiation of spherical gaseous detonations from high-voltage spark discharge
NASA Astrophysics Data System (ADS)
Zhang, B.; Ng, H. D.; Lee, J. H. S.
In this study, effective energy from spark discharge for direct blast initiation of spherical gaseous detonations is investigated. In the experiment, direct initiation of detonation is achieved via a spark discharge from a high-voltage and low-inductance capacitor bank and the spark energy is estimated from the analysis of the current output. To determine the blast wave energy from the powerful spark, the time-of-arrival of the blast wave in air is measured at different radii using a piezoelectric pressure transducer. Good agreement is found in the scaled blast trajectories, i.e., scaled time c o· t/ R o where c o is the ambient sound speed, as a function of blast radius R s/ R o between the numerical simulation of a spherical blast wave from a point energy source and the experimental results where the explosion length scale R o is computed using the equivalent spark energy from the first 1/4 current discharge cycle. Alternatively, by fitting the experimental trajectories data, the blast energy estimated from the numerical simulation appears also in good agreement with that obtained experimentally using the 1/4 cycle criterion. Using the 1/4 cycle of spark discharge for the effective energy, direct initiation experiments of spherical gaseous detonations are carried out to determine the critical initiation energy in C2H2-2.5O2 mixtures with 70 and 0% argon dilution. The experimental results obtained from the 1/4 cycle of spark discharge agree well with the prediction from two initiation models, namely, the Lee's surface energy model and a simplified work done model. The main source of discrepancy in the comparison can be explained by the uncertainty of cell size measurement which is needed for both the semi-empirical models.
Effects of solution volume on hydrogen production by pulsed spark discharge in ethanol solution
NASA Astrophysics Data System (ADS)
Xin, Y. B.; Sun, B.; Zhu, X. M.; Yan, Z. Y.; Liu, H.; Liu, Y. J.
Hydrogen production from ethanol solution (ethanol/water) by pulsed spark discharge was optimized by varying the volume of ethanol solution (liquid volume). Hydrogen yield was initially increased and then decreased with the increase in solution volume, which achieved 1.5 l/min with a solution volume of 500 ml. The characteristics of pulsed spark discharge were studied in this work; the results showed that the intensity of peak current, the rate of current rise, and energy efficiency of hydrogen production can be changed by varying the volume of ethanol solution. Meanwhile, the mechanism analysis of hydrogen production was accomplished by monitoring the process of hydrogen production and the state of free radicals. The analysis showed that decreasing the retention time of gas production and properly increasing the volume of ethanol solution can enhance the hydrogen yield. Through this research, a high-yield and large-scale method of hydrogen production can be achieved, which is more suitable for industrial application.
Final report on development of Pulse Arrested Spark Discharge (PASD) for aging aircraft wiring application
Lockner, Thomas Ramsbeck; Howard, R. Kevin; Pena, Gary Edward; Schneider, Larry X.; Higgins, Matthew B.; Glover, Steven Frank
Pulsed Arrested Spark Discharge (PASD) is a Sandia National Laboratories Patented, non-destructive wiring system diagnostic that has been developed to detect defects in aging wiring systems in the commercial aircraft fleet. PASD was previously demonstrated on relatively controlled geometry wiring such as coaxial cables and shielded twisted-pair wiring through a contract with the U.S. navy and is discussed in a Sandia National Laboratories report, SAND2001-3225 ''Pulsed Arrested Spark Discharge (PASD) Diagnostic Technique for the Location of Defects in Aging Wiring Systems''. This report describes an expansion of earlier work by applying the PASD technique to unshielded twisted-pair and discrete wire configurations commonly found in commercial aircraft. This wiring is characterized by higher impedances as well as relatively non-uniform impedance profiles that have been found to be challenging for existing aircraft wiring diagnostics. Under a three year contract let by the Federal Aviation Administration, Interagency Agreement DTFA-03-00X90019, this technology was further developed for application on aging commercial aircraft wiring systems. This report describes results of the FAA program with discussion of previous work conducted under U.S. Department of Defense funding.
Spark ignition of flowing gases
NASA Technical Reports Server (NTRS)
Swett, Clyde C , Jr
Research conducted at the NACA Lewis Laboratory on ignition of flowing gases by means of long-duration discharges is summarized and analyzed. Data showing the effect of a flowing combustible mixture on the physical and electrical characteristics of spark discharges and data showing the effects of variables on the spark energy required for ignition that has been developed to predict the effect of many of the gas-stream and spark variables is described and applied to a limited amount of experimental data.
Surface-spark discharges compared with exploding wires/films as high temperature uv sources. [40,000/sup 0/K
Ware, K.D.; Johnson, T.M.; Jones, C.R.
Extensive experimental studies of electrically exploded 0.05- to 0.25-mm-diameter metal wires and film thicknesses from 0.1 to 10 ..mu..m (coated on 0.6- to 10.0-cm diameter substrates) were made for lengths from 3.0 to 100 cm. These exploded metal-conductor-initiated discharges proved to be excellent sources for intense radiation in the near-ultraviolet range, 200 to 300 nm, with brightness temperatures measured over 40,000 K. The impedance-matching characteristics and scaling laws developed through these studies will be presented and used as a basis to compare more recent results on surface-spark discharges. These latter discharges do not appear to be as nearly blackbody as the conductor-initiated discharges, but through selected insulator surfaces, intense emission in the spectral range of interest can be obtained.
Effects of air transient spark discharge and helium plasma jet on water, bacteria, cells, and biomolecules.
Hensel, Karol; Kučerová, Katarína; Tarabová, Barbora; Janda, Mário; Machala, Zdenko; Sano, Kaori; Mihai, Cosmin Teodor; Ciorpac, Mitică; Gorgan, Lucian Dragos; Jijie, Roxana; Pohoata, Valentin; Topala, Ionut
Atmospheric pressure DC-driven self-pulsing transient spark (TS) discharge operated in air and pulse-driven dielectric barrier discharge plasma jet (PJ) operated in helium in contact with water solutions were used for inducing chemical effects in water solutions, and the treatment of bacteria (Escherichia coli), mammalian cells (Vero line normal cells, HeLa line cancerous cells), deoxyribonucleic acid (dsDNA), and protein (bovine serum albumin). Two different methods of water solution supply were used in the TS: water electrode system and water spray system. The effects of both TS systems and the PJ were compared, as well as a direct exposure of the solution to the discharge with an indirect exposure to the discharge activated gas flow. The chemical analysis of water solutions was performed by using colorimetric methods of UV-VIS absorption spectrophotometry. The bactericidal effects of the discharges on bacteria were evaluated by standard microbiological plate count method. Viability, apoptosis and cell cycle were assessed in normal and cancerous cells. Viability of cells was evaluated by trypan blue exclusion test, apoptosis by Annexin V-FITC/propidium iodide assay, and cell cycle progression by propidium iodide/RNase test. The effect of the discharges on deoxyribonucleic acid and protein were evaluated by fluorescence and UV absorption spectroscopy. The results of bacterial and mammalian cell viability, apoptosis, and cell cycle clearly show that cold plasma can inactivate bacteria and selectively target cancerous cells, which is very important for possible future development of new plasma therapeutic strategies in biomedicine. The authors found that all investigated bio-effects were stronger with the air TS discharge than with the He PJ, even in indirect exposure. PMID:25947389
A modified resistance equation for modeling underwater spark discharge with salinity and high pressure conditions
Zhao, Pengfei; Roy, Subrata
This work investigates the performance of underwater spark discharge relating to bubble growth and decay under high pressure and with salinity conditions by introducing a modified form of the resistance equation. Here, we study salinity influence on circuit parameters by fitting the experimental data for which gap resistance is much larger in conductive water than in dielectric water. Accordingly, the resistance equation is modified by considering the influence of both plasma and its surrounding liquid. Thermal radiation effect of the bubble is also studied by comparing two different radiation models. Numerical results predict a larger bubble pressure for saline water but a reduced size and a smaller bubble cycle at a greater water depth. Such study may be useful in many saltwater applications, including that for deep sea conditions.
Growth and Collapse of a Single Bubble near a Plate by Spark Discharge in Water
NASA Astrophysics Data System (ADS)
Akcam, I.; Inaba, K.; Takahashi, K.; Kishimoto, K.
Single bubble dynamics in the vicinity of a solid boundary submerged in water were studied experimentally. Single bubble inside a water tank was generated by a spark discharge of capacitor into a couple of copper wires closing a simple circuit. A circular polycarbonate plate was placed horizontally above the bubble creation site. Polycarbonate plates with two different thicknesses were tested by changing the distance between the plate and the creation site. The effects of distance to the wall and wall thickness on the bubble motion is observed by considering the fluid-structure interaction. It is shown that motion of the two boundaries during the bubble generation differ from each other. Jetting behavior of two cases is also different.
Investigation of Luna-20 soil samples, using a mass spectrometer with a spark-discharge ion source
NASA Technical Reports Server (NTRS)
Hubbard, N. J.; Ramendik, G. I.; Gronskaia, S. I.; Gubina, I. IA.; Gushchin, V. N.
A method of analyzing soil samples with a mass spectrometer employing a spark-discharge ion source is described, and the effectiveness of the method is demonstrated by applying it to the determination of impurities, in amounts of less than 10 mg, in lunar samples. It is shown that four parts of the Luna-20 lunar highland sample differ in their chemical composition.
Reliable prediction of electric spark sensitivity of nitramines: a general correlation with detonation pressure.
Keshavarz, Mohammad Hossein; Pouretedal, Hamid Reza; Semnani, Abolfazl
For nitramines, a general correlation has been introduced to predict electric spark sensitivity through detonation pressure. New method uses maximum obtainable detonation pressure as a fundamental relation so that it can be corrected for some nitramines which have some specific molecular structure. There is no need to use crystal density and heat of formation of nitramine explosives for predicting detonation pressure and electric spark sensitivity. The predicted electric spark sensitivities are compared with calculated results on the basis of quantum mechanical computations for some nitramines that latter can be applied. The root mean square (rms) deviations from experiment for new method and the predicted results of complicated quantum mechanical method are 1.18 and 3.49J, respectively. PMID:19188021
Electrical discharges in the atmosphere of Venus
NASA Technical Reports Server (NTRS)
Ksanfomaliti, L. V.; Vasilchikov, N. M.; Ganpantserova, O. F.; Petrova, Y. V.; Suvorov, A. P.; Filippov, G. F.; Yablonskaya, O. V.; Yabrova, L. V.
Data received from Venera 11 and 12 experiments involving the electrical activity of the atmosphere of Venus show that the electrical discharges occur in the cloud layer. Their energy is roughly the same as in terrestrial lightning, but with a pulse repetition frequency of the discharges which is much greater.
CNC electrical discharge machining centers
Jaggars, S.R.
Computer numerical control (CNC) electrical discharge machining (EDM) centers were investigated to evaluate the application and cost effectiveness of establishing this capability at Allied-Signal Inc., Kansas City Division (KCD). In line with this investigation, metal samples were designed, prepared, and machined on an existing 15-year-old EDM machine and on two current technology CNC EDM machining centers at outside vendors. The results were recorded and evaluated. The study revealed that CNC EDM centers are a capability that should be established at KCD. From the information gained, a machine specification was written and a shop was purchased and installed in the Engineering Shop. The older machine was exchanged for a new model. Additional machines were installed in the Tool Design and Fabrication and Precision Microfinishing departments. The Engineering Shop machine will be principally used for the following purposes: producing deep cavities in small corner radii, machining simulated casting models, machining difficult-to-machine materials, and polishing difficult-to-hand polish mold cavities. 2 refs., 18 figs., 3 tabs.
Fluid jet electric discharge source
Bender, Howard A.
A fluid jet or filament source and a pair of coaxial high voltage electrodes, in combination, comprise an electrical discharge system to produce radiation and, in particular, EUV radiation. The fluid jet source is composed of at least two serially connected reservoirs, a first reservoir into which a fluid, that can be either a liquid or a gas, can be fed at some pressure higher than atmospheric and a second reservoir maintained at a lower pressure than the first. The fluid is allowed to expand through an aperture into a high vacuum region between a pair of coaxial electrodes. This second expansion produces a narrow well-directed fluid jet whose size is dependent on the size and configuration of the apertures and the pressure used in the reservoir. At some time during the flow of the fluid filament, a high voltage pulse is applied to the electrodes to excite the fluid to form a plasma which provides the desired radiation; the wavelength of the radiation being determined by the composition of the fluid.
Physicochemical Characterization of Simulated Welding Fume from a Spark Discharge System
Park, Jae Hong; Mudunkotuwa, Imali A.; Kim, Jong Sung; Stanam, Aditya; Thorne, Peter S.; Grassian, Vicki H.; Peters, Thomas M.
This study introduces spark discharge system (SDS) as a way to simulate welding fumes. The SDS was developed using welding rods as electrodes with an optional coagulation chamber. The size, morphology, composition, and concentration of the fume produced and the concentration of ozone (O3) and nitrogen oxides (NOX) were characterized. The number median diameter (NMD) and total number concentration (TNC) of fresh fume particles were ranged 10–23 nm and 3.1×107–6×107 particles/cm3, respectively. For fresh fume particles, the total mass concentration (TMC) measured gravimetrically ranged 85–760 μg/m3. The size distribution was stable over a period of 12 h. The NMD and TNC of aged fume particles were ranged 81–154 nm and 1.5×106–2.7×106 particles/cm3, respectively. The composition of the aged fume particles was dominated by Fe and O with an estimated stoichiometry between that of Fe2O3 and Fe3O4. Concentrations of O3 and NOX were ranged 0.07–2.2 ppm and 1–20 ppm, respectively. These results indicate that the SDS is capable of producing stable fumes over a long-period that are similar to actual welding fumes. This system may be useful in toxicological studies and evaluation of instrumentation. PMID:25097299
Comparison of Nitrogen Incorporation in Tholins Produced by FUV Irradiation and Spark Discharge
NASA Technical Reports Server (NTRS)
Horst, S. M.; DeWitt, H. L.; Trainer, M. G.; Tolbert, M. A.
The discovery of very heavy ions (Coates et al., 2007) in Titan's thermosphere has dramatically altered our understanding of the processes involved in the formation of the complex organic aerosols that comprise Titan's characteristic haze. Before Cassini's arrival, it was believed that aerosol production began in the stratosphere where the chemical processes were predominantly initiated by FUV radiation. This understanding guided the design of Titan atmosphere simulation experiments. However, the energy environment of the thermosphere is significantly different than the stratosphere; in particular there is a greater flux of EUV photons and energetic particles available to initiate chemical reactions, including the destruction of N2. in the upper atmosphere. Using a High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS), we have obtained in situ composition measurements of aerosol particles (so'called "tholins") produced in CH4/N2 gas mixtures subjected to either FUV radiation (deuterium lamp, 115-400 nm) (Trainer et al., 2012) or a spark discharge. A comparison of the composition of tholins produced using the two different energy sources will be presented, in particular with regard to the variation in nitrogen content of the two types of tholin. Titan's aerosols are known to contain significant amounts of nitrogen (Israel et al., 2005) and therefore understanding the role of nitrogen in the aerosol chemistry is important to further our knowledge of the formation and evolution of aerosols in Titan's atmosphere.
Setup Aid for Electrical-Discharge Machining
NASA Technical Reports Server (NTRS)
Lines, G.; Duca, J.
Interlock assures that workpiece is correctly assembled in machining fixture. A Plunger in a Hollow Shaft actuates a switch, allowing a power supply to produce current for electrical-discharge machining. Plunger operates only when necessary parts are position.
Electrical-Discharge Machining Of Perpendicular Passages
NASA Technical Reports Server (NTRS)
Malinzak, R. Michael; Booth, Gary N.
Perpendicular telescoping electrode used to perform electrical-discharge machining (EDM) of internal passage through previously inaccessible depth of metal workpiece. More specifically, used to make internal passage perpendicular to passage entering from outer surface.
Electroformed Electrodes for Electrical-Discharge Machining
NASA Technical Reports Server (NTRS)
Werner, A.; Cassidenti, M.
Copper electrodes replace graphite electrodes in many instances of electrical-discharge machining (EDM) of complex shapes. Copper electrodes wear longer and cause less contamination of EDM dielectric fluid than do graphite electrodes.
Contamination-Free Electrical-Discharge Machining
NASA Technical Reports Server (NTRS)
Schmidt, Mark G.
Contamination of parts by electrical-discharge machining (EDM) almost completely eliminated by reversing flow of coolant. Flow reversed from usual direction so coolant carries contaminants out through passage in electrode. Coolant for reverse flow is pressurized dichlorodifluoromethane vapor.
Nonprotein Amino Acids from Spark Discharges and Their Comparison with the Murchison Meteorite Amino Acids
Wolman, Yecheskel; Haverland, William J.; Miller, Stanley L.
All the nonprotein amino acids found in the Murchison meteorite are products of the action of electric discharge on a mixture of methane, nitrogen, and water with traces of ammonia. These amino acids include α-amino-n-butyric acid, α-aminoisobutyric acid, norvaline, isovaline, pipecolic acid, β-alanine, β-amino-n-butyric acid, β-aminoisobutyric acid, γ-aminobutyric acid, sarcosine, N-ethylglycine, and N-methylalanine. In addition, norleucine, alloisoleucine, N-propylglycine, N-isopropylglycine, N-methyl-β-alanine, N-ethyl-β-alanine α,β-diaminopropionic acid, isoserine, α,γ-diaminobutyric acid, and α-hydroxy-γ-aminobutyric acid are produced by the electric discharge, but have not been found in the meteorite. PMID:16591973
Nonprotein amino acids from spark discharges and their comparison with the murchison meteorite amino acids.
Wolman, Y; Haverland, W J; Miller, S L
All the nonprotein amino acids found in the Murchison meteorite are products of the action of electric discharge on a mixture of methane, nitrogen, and water with traces of ammonia. These amino acids include alpha-amino-n-butyric acid, alpha-aminoisobutyric acid, norvaline, isovaline, pipecolic acid, beta-alanine, beta-amino-n-butyric acid, beta-aminoisobutyric acid, gamma-aminobutyric acid, sarcosine, N-ethylglycine, and N-methylalanine. In addition, norleucine, alloisoleucine, N-propylglycine, N-isopropylglycine, N-methyl-beta-alanine, N-ethyl-beta-alanine alpha,beta-diaminopropionic acid, isoserine, alpha,gamma-diaminobutyric acid, and alpha-hydroxy-gamma-aminobutyric acid are produced by the electric discharge, but have not been found in the meteorite. PMID:16591973
Contour dynamics model for electric discharges.
Arrayás, M; Fontelos, M A; Jiménez, C
We present an effective contour model for electrical discharges deduced as the asymptotic limit of the minimal streamer model for the propagation of electric discharges, in the limit of small electron diffusion. The incorporation of curvature effects to the velocity propagation and not to the boundary conditions is a feature and makes it different from the classical Laplacian growth models. The dispersion relation for a nonplanar two-dimensional discharge is calculated. The development and propagation of fingerlike patterns are studied and their main features quantified. PMID:20365808
Evolution of electrical discharge channel in isopropyl alcohol solution
NASA Astrophysics Data System (ADS)
Panov, V. A.; Vasilyak, L. M.; Pecherkin, V. Ya; Vetchinin, S. P.; Kulikov, Yu M.; Son, E. E.
Evolution of the spark channel created by the high voltage pulse generator in 15% isopropyl alcohol solution in tap water was investigated experimentally. Fast camera images show the start of spark discharge channel with the anode region glowing, which is due to ionization-overheating instability near the surface of anode electrode. Measured propagation velocity is about 4 m/s and points to thermal process of channel evolution. Partial discharges in gas bubbles near the spark channel were observed. When the channel bridges the gap the cathode flash of lightning occurs which is much brighter than anode glowing and channel one. After destruction of the spark channel the cathode glowing stays for a longer period than anode one.
Discharge Characteristics of SF6 in a Non-Uniform Electric Field Under Repetitive Nanosecond Pulses
NASA Astrophysics Data System (ADS)
Ran, Huijuan; Wang, Lei; Wang, Jue; Wang, Tao; Yan, Ping
The characteristics of high pressure sulphur hexafluoride (SF6) discharges in a highly non-uniform electric field under repetitive nanosecond pulses are investigated in this paper. The influencing factors on discharge process, such as gas pressure, pulse repetition frequency (PRF), and number of applied pulses, are analyzed. Experimental results show that the corona intensity weakens with the increase of gas pressure and strengthens with the increase of PRF or number of applied pulses. Spark discharge images suggest that a shorter and thicker discharge plasma channel will lead to a larger discharge current. The number of applied pulses to breakdown descends with the increase of PRF and ascends with the rise of gas pressure. The reduced electric field (E/p) decreases with the increase of PRF in all circumstances. The experimental results provide significant supplements to the dielectric characteristics of strongly electronegative gases under repetitive nanosecond pulses.
Electrical characteristics of spark generators for automotive ignition
NASA Technical Reports Server (NTRS)
Brode, R B; Randolph, D W; Silsbee, F B
This paper reports the results of an extensive program of measurements on 11 ignition systems differing widely in type. The results serve primarily to give representative data on the electric and magnetic constants of such systems, and on the secondary voltage produced by them under various conditions of speed, timing, shunting resistance, etc. They also serve to confirm certain of the theoretical formulas which have been proposed to connect the performance of such systems with their electrical constants, and to indicate the extent to which certain simplified model circuits duplicate the performance of the actual apparatus.
Electric Dipole Moment Experiment Systematic from Electric Field Discharge Current
NASA Astrophysics Data System (ADS)
Feinberg, B.; Gould, Harvey
A magnetic field, in the direction of the electric field and synchronous with the electric field reversal, will mimic an EDM signal. One might expect a discharge across the electric field plates to produce magnetic fields with only small or vanishing components parallel to the electric field, minimizing its systematic effect. Our experimental model, using simulated discharge currents, found otherwise: the discharge current may be at an angle to the normal, and thus generate a normal magnetic field. Comparison of data from the experimental model with the results from calculations will be presented, along with estimates of the time-averaged normal magnetic field seen by atoms in an electron EDM experiment using a fountain of laser-cooled francium, as a function of discharge current.
Fast and stable electrical discharge machining (EDM)
NASA Astrophysics Data System (ADS)
Wu, Jianyang; Zhou, Ming; Xu, Xiaoyi; Yang, Jianwei; Zeng, Xiangwei; Xu, Donghui
In order to improve EDM performances, the most important issue is to develop a highly stable control system. As a serious defect in EDM adaptive control system by minimum-variance control law, the occasional instability deterred its full applications in industries. This paper focuses on stabilizing EDM process by establishing a new minimum-variance and pole-placement coupled control law. Based on real-time estimation of EDM process model parameters, this adaptive control system directly controls electrode discharging cycle not only to follow a specified gap state for fast machining but also to track the dynamical response of a reference model for stabilizing EDM process. Confirmation experiment demonstrates that this control system can timely adjust electrode discharging cycle in terms of different machining situations quantified as a series of varied gap states to maintain a stable and fast fabrication. The adaptive control system by this newly developed control law exhibits its superior machining ability and capability of stabilizing sparking process to those of the adaptive control system by minimum-variance control law. The adaptive system has actually theoretically and technically solved the stability issue puzzled EDM circle for decades.
Electric field profiles in obstructed helium discharge
NASA Astrophysics Data System (ADS)
Fendel, Peter; Ganguly, Biswa; Bletzinger, Peter
Axial and radial variations of electric field have been measured in dielectric shielded 25 mm diameter parallel plate electrode for 2 mA, 2250 V helium dc discharge at 1.75 Torr with 6.5 mm gap. The axial and radial electric field profiles have been measured from the polarization dependent Stark splitting of 21S --> 11 1P transition through collision induced fluorescence from 43D --> 23P. The electric field values showed a strong radial variation peaking up to 5 kV/cm near the cathode radial boundary, and decreasing to about 1 kV/cm near the anode, suggesting the formation of an obstructed discharge for this low Pd condition. Also, the on-axis electric field was nearly constant across the gap indicating a radially non-uniform current density. In order to obtain information about the space charge distribution in this obstructed discharge, it was modeled using the 2-d axisymmetric Poisson solver with COMSOL finite element modeling program. The model discharge dimensions were selected to match the experimental dimensions. The best fit to the measured electric field distribution was obtained with a space charge variation of ρ(r) =ρ0 (r/r0)3 , where ρ(r) is the local space charge density, ρ0 is the maximum space-charge density, r the local radial value and r0 the radius of the electrode.
Application of Pulse Spark Discharges for Scale Prevention and Continuous Filtration Methods in Coal-Fired Power Plant
Cho, Young; Fridman, Alexander
The overall objective of the present work was to develop a new scale-prevention technology by continuously precipitating and removing dissolved mineral ions (such as calcium and magnesium) in cooling water while the COC could be doubled from the present standard value of 3.5. The hypothesis of the present study was that if we could successfully precipitate and remove the excess calcium ions in cooling water, we could prevent condenser-tube fouling and at the same time double the COC. The approach in the study was to utilize pulse spark discharges directly in water to precipitate dissolved mineral ions in recirculating cooling water into relatively large suspended particles, which could be removed by a self-cleaning filter. The present study began with a basic scientific research to better understand the mechanism of pulse spark discharges in water and conducted a series of validation experiments using hard water in a laboratory cooling tower. Task 1 of the present work was to demonstrate if the spark discharge could precipitate the mineral ions in water. Task 2 was to demonstrate if the selfcleaning filter could continuously remove these precipitated calcium particles such that the blowdown could be eliminated or significantly reduced. Task 3 was to demonstrate if the scale could be prevented or minimized at condenser tubes with a COC of 8 or (almost) zero blowdown. In Task 1, we successfully completed the validation study that confirmed the precipitation of dissolved calcium ions in cooling water with the supporting data of calcium hardness over time as measured by a calcium ion probe. In Task 2, we confirmed through experimental tests that the self-cleaning filter could continuously remove precipitated calcium particles in a simulated laboratory cooling tower such that the blowdown could be eliminated or significantly reduced. In addition, chemical water analysis data were obtained which were used to confirm the COC calculation. In Task 3, we conducted a series
Sb/O nano-composites produced via Spark Discharge Generation for Li-ion battery anodes
NASA Astrophysics Data System (ADS)
Simonin, L.; Lafont, U.; Tabrizi, N.; Schmidt-Ott, A.; Kelder, E. M.
Spark Discharge Generation (SDG) was used to produce powders of 10-20 nm of Sb and antimony oxides. Different composite materials with different textures were obtained either with an amorphous passive layer of antimony oxide or with crystalline cubic Sb 2O 3. The composition and shape of the different mixtures, depending on the production and collection conditions, were analysed via XRD and HRTEM coupled with EDX. The effect of the nature and the content of the oxides on the electrode performances were studied using Swagelok cells, cycled galvanostatically with a MACCOR cycler.
Multiplex electric discharge gas laser system
NASA Technical Reports Server (NTRS)
Laudenslager, James B. (Inventor); Pacala, Thomas J. (Inventor)
A multiple pulse electric discharge gas laser system is described in which a plurality of pulsed electric discharge gas lasers are supported in a common housing. Each laser is supplied with excitation pulses from a separate power supply. A controller, which may be a microprocessor, is connected to each power supply for controlling the application of excitation pulses to each laser so that the lasers can be fired simultaneously or in any desired sequence. The output light beams from the individual lasers may be combined or utilized independently, depending on the desired application. The individual lasers may include multiple pairs of discharge electrodes with a separate power supply connected across each electrode pair so that multiple light output beams can be generated from a single laser tube and combined or utilized separately.
Monitor For Electrical-Discharge Machining
NASA Technical Reports Server (NTRS)
Burley, Richard K.
Circuit monitors electrical-discharge-machining (EDM) process to detect and prevent abnormal arcing, which can produce unacceptable "burn" marks on workpiece. When voltage between EDM electrode and workpiece behaves in manner indicative of abnormal arcing, relay made to switch off EDM power, which remains off until operator attends to EDM setup and resets monitor.
Electrical-Discharge Machining Of Curved Passages
NASA Technical Reports Server (NTRS)
Guirguis, Kamal S.
Electrical-discharge machining (EDM) used to cut deep hole with bends. EDM process done with articulating segmented electrode. Originally straight, electrode curved as it penetrates part, forming long, smoothly curving hole. After hole cut, honed with slurry to remove thin layer of recast metal created by EDM. Breakage of tools, hand deburring, and drilling debris eliminated.
Six-Axis Electrical-Discharge Machine
NASA Technical Reports Server (NTRS)
Werner, A. R.
Electrical discharge machine (EDM) of unusual versitility made by conversion of radial drill. Drilling head is replaced by ram that holds and positions electrode. Tank and recirculation system for coolant are added. EDM has six independent motions and drastically reduced cost of manufacturing. New applications are constantly being found.
Electric-discharge-pumped nitrogen ion laser
NASA Technical Reports Server (NTRS)
Laudenslager, J. B.; Pacala, T. J.; Wittig, C.
The routine operation is described of an N2(+) laser oscillating on the first negative band system of N2(+) which is produced in a preionized transverse discharge device. The discharge design incorporates features which favor the efficient production of the excitation transfer reaction of He2(+) with N2. A capacitive discharge switched by means of a high-current grounded grid thyratron is used to meet the design requirement of a volumetric discharge in high-pressure gas mixtures where the electric discharge need not have an ultrafast rise time (greater than 10 nsec) but should be capable of transferring large quantities of stored electric energy to the gas. A peak power of 180 kW in an 8-nsec laser pulse was obtained with a 0.1% mixture of N2 in helium at a total pressure of 3 atm. The most intense laser oscillations were observed on the (0,1) vibrational transition at 427.8 microns.
Spark plasma sintering of alumina nanopowders produced by electrical explosion of wires.
An, Vladimir; Khasanov, Alexey; de Izarra, Charles
Alumina nanopowders produced by electrical explosion of wires were sintered using the spark plasma sintering technique. The results of XRD analysis show that the main phase in the compacted nanopowders is α-Al2O3. According to the SEM observations, the sintered alumina nanopowder consists of micron-sized faceted grains and nano-sized necked grains. The increase in sintering temperature resulted in a higher density of the sintered powders: from 78.44 to 98.21 % of theoretical density. PMID:26543716
Electrical-Discharge Machining With Additional Axis
NASA Technical Reports Server (NTRS)
Malinzak, Roger M.; Booth, Gary N.
Proposed electrical-discharge-machining (EDM) apparatus uses moveable vertical wire as electrode. Wire positionable horizontally along one axis as it slides vertically past workpiece. Workpiece indexed in rotation about horizontal axis. Because of symmetry of parts, process used to make two such parts at a time by defining boundary between them. Advantages: cost of material reduced, imparts less residual stress to workpiece, and less time spent machining each part when parts produced in such symmetrical pairs.
Preset Electrodes for Electrical-Discharge Machining
NASA Technical Reports Server (NTRS)
Coker, Bill E.
New electrode holder for electrical-discharge machining (EDM) provides for repeatable loading and setting of many electrodes. New holder is rotating-index tool carrying six, eight, or more electrodes. Before use, all electrodes set with aid of ring surrounding tool, and locked in position with screws. When electrode replaced, EDM operator pulls spring-loaded pin on tool so it rotates about center pin. Fresh electrode then rotated into position against workpiece.
Investigation of Wire Electrical Discharge Machining of Thin Cross-Sections and Compliant Mechanisms
Miller, Scott F.; Kao, Chen C.; Shih, Albert J.; Qu, Jun
The wire electrical discharge machining (EDM) of cross-section with minimum thickness and compliant mechanisms is studied. Effects of EDM process parameters, particularly the spark cycle time and spark on-time on thin cross-section cutting of Nd-Fe-B magnetic material, carbon bipolar plate, and titanium are investigated. An envelope of feasible wire EDM process parameters is generated for the commercially pure titanium. The application of such envelope to select suitable EDM process parameters for micro feature generation is demonstrated. Scanning electron microscopy (SEM) analysis of EDM surface, subsurface, and debris are presented. SEM observations lead to a hypothesis based on the thermal and electrostatic stress induced fracture to explain the limiting factor for wire EDM cutting of thin-sections. Applications of the thin cross-section EDM cutting for manufacture of compliant mechanisms are discussed.
Site-specific growth and density control of carbon nanotubes by direct deposition of catalytic nanoparticles generated by spark discharge
Catalytic iron nanoparticles generated by spark discharge were used to site-selectively grow carbon nanotubes (CNTs) and control their density. The generated aerosol nanoparticles were deposited on a cooled substrate by thermophoresis. The shadow mask on top of the cooled substrate enabled patterning of the catalytic nanoparticles and, thereby, patterning of CNTs synthesized by chemical vapor deposition. The density of CNTs could be controlled by varying the catalytic nanoparticle deposition time. It was also demonstrated that the density could be adjusted by changing the gap between the shadow mask and the substrate, taking advantage of the blurring effect of the deposited nanoparticles, for an identical deposition time. As all the processing steps for the patterned growth and density control of CNTs can be performed under dry conditions, we also demonstrated the integration of CNTs on fully processed, movable silicon microelectromechanical system (MEMS) structures. PMID:24090218
Formation of chondrules by electrical discharge heating
NASA Technical Reports Server (NTRS)
Love, S. G.; Keil, K.; Scott, E. R. D.
A possible mechanism for making chondrules in the solar nebula is electrical discharge ('lightning') heating, which can create high-temperature (greater than 1600 K), short-duration (approximately 10 s) thermal events as indicated by the chondritic record. Lightning occurs in many diverse terrestrial and planetary settings, and may have occurred in the solar nebula; it is thus worthwhile to investigate its implications for chondrule formation. Nebular discharges do not appear a viable source of heat for melting chondrule precursors, regardless of the uncertainty in the details of the mode. Nonetheless, we believe nebular lightning worthy of further investigation than what is presented here. Experiments analogous to those currently underway to investigate terrestrial thunderstorm lightning could be fruitful in refining nebular lightning models, and would be double interesting in application to nonthunderstorm and planetary lightnings.
Characterization of Microwave-Induced Electric Discharge Phenomena in Metal–Solvent Mixtures
Chen, Wen; Gutmann, Bernhard; Kappe, C Oliver
Electric discharge phenomena in metal–solvent mixtures are investigated utilizing a high field density, sealed-vessel, single-mode 2.45 GHz microwave reactor with a built-in camera. Particular emphasis is placed on studying the discharges exhibited by different metals (Mg, Zn, Cu, Fe, Ni) of varying particle sizes and morphologies in organic solvents (e.g., benzene) at different electric field strengths. Discharge phenomena for diamagnetic and paramagnetic metals (Mg, Zn, Cu) depend strongly on the size of the used particles. With small particles, short-lived corona discharges are observed that do not lead to a complete breakdown. Under high microwave power conditions or with large particles, however, bright sparks and arcs are experienced, often accompanied by solvent decomposition and formation of considerable amounts of graphitized material. Small ferromagnetic Fe and Ni powders (<40 μm) are heated very rapidly in benzene suspensions and start to glow in the microwave field, whereas larger particles exhibit extremely strong discharges. Electric discharges were also observed when Cu metal or other conductive materials such as silicon carbide were exposed to the microwave field in the absence of a solvent in an argon or nitrogen atmosphere. PMID:24551491
Characterization of microwave-induced electric discharge phenomena in metal-solvent mixtures.
Chen, Wen; Gutmann, Bernhard; Kappe, C Oliver
Electric discharge phenomena in metal-solvent mixtures are investigated utilizing a high field density, sealed-vessel, single-mode 2.45 GHz microwave reactor with a built-in camera. Particular emphasis is placed on studying the discharges exhibited by different metals (Mg, Zn, Cu, Fe, Ni) of varying particle sizes and morphologies in organic solvents (e.g., benzene) at different electric field strengths. Discharge phenomena for diamagnetic and paramagnetic metals (Mg, Zn, Cu) depend strongly on the size of the used particles. With small particles, short-lived corona discharges are observed that do not lead to a complete breakdown. Under high microwave power conditions or with large particles, however, bright sparks and arcs are experienced, often accompanied by solvent decomposition and formation of considerable amounts of graphitized material. Small ferromagnetic Fe and Ni powders (<40 μm) are heated very rapidly in benzene suspensions and start to glow in the microwave field, whereas larger particles exhibit extremely strong discharges. Electric discharges were also observed when Cu metal or other conductive materials such as silicon carbide were exposed to the microwave field in the absence of a solvent in an argon or nitrogen atmosphere. PMID:24551491
Effect of water vapor on the production of S{sub 2}F{sub 10} and S{sub 2}OF{sub 10} by spark discharges in SF{sub 6}
Sauers, I.
Because of its toxicity, S{sub 2}F{sub 10} is of concern to users of SF{sub 6}-filled electrical equipment. While no significantly high concentrations of S{sub 2}F{sub 10} has been found in high voltage power equipment, thus far, it is important to understand the mechanism of and the influence of SF{sub 6} impurities on the formation of S{sub 2}F{sub 10} in order to assess the potential buildup of this byproduct in high voltage equipment under a wide range of discharge conditions. Production rates of the compounds disulfur decafluoride (S{sub 2}F{sub 10}) and bis(pentafuorosulfur) oxide (S{sub 2}OF{sub 10}) have been measured following spark discharges in SF{sub 6} as a function of water content for water concentrations in the range 600--3,400 ppm (parts-per-million). Sparks were produced by capacitive discharge (80 J per spark) into SF{sub 6} at a pressure of 100 kPa. Absolute yields were determined from the spark energy from direct measurements of the voltage and current waveforms. In dry SF{sub 6} the spark yield of S{sub 2}F{sub 10} is 2.2 {times} 10{sup {minus}11} mol J{sup {minus}1}. Adding water to SF{sub 6} the spark yield of S{sub 2}F{sub 10} is 2.2 {times} 10{sup {minus}11} mol J{sup {minus}1}. Adding water to SF{sub 6} results in a decrease in the yield of S{sub 2}F{sub 10} and an increase in the S{sub 2}OF{sub 10} yields. Production of both S{sub 2}F{sub 10} and S{sub 2}OF{sub 10} are believed to be formed via the precursor SF{sub 5}. Mechanism for production of these two disulfur compounds will be discussed.
Extreme-UV electrical discharge source
Fornaciari, Neal R.; Nygren, Richard E.; Ulrickson, Michael A.
An extreme ultraviolet and soft x-ray radiation electric capillary discharge source that includes a boron nitride housing defining a capillary bore that is positioned between two electrodes one of which is connected to a source of electric potential can generate a high EUV and soft x-ray radiation flux from the capillary bore outlet with minimal debris. The electrode that is positioned adjacent the capillary bore outlet is typically grounded. Pyrolytic boron nitride, highly oriented pyrolytic boron nitride, and cubic boron nitride are particularly suited. The boron nitride capillary bore can be configured as an insert that is encased in an exterior housing that is constructed of a thermally conductive material. Positioning the ground electrode sufficiently close to the capillary bore outlet also reduces bore erosion.
Closed cycle electric discharge laser design investigation
NASA Technical Reports Server (NTRS)
Baily, P. K.; Smith, R. C.
Closed cycle CO2 and CO electric discharge lasers were studied. An analytical investigation assessed scale-up parameters and design features for CO2, closed cycle, continuous wave, unstable resonator, electric discharge lasing systems operating in space and airborne environments. A space based CO system was also examined. The program objectives were the conceptual designs of six CO2 systems and one CO system. Three airborne CO2 designs, with one, five, and ten megawatt outputs, were produced. These designs were based upon five minute run times. Three space based CO2 designs, with the same output levels, were also produced, but based upon one year run times. In addition, a conceptual design for a one megawatt space based CO laser system was also produced. These designs include the flow loop, compressor, and heat exchanger, as well as the laser cavity itself. The designs resulted in a laser loop weight for the space based five megawatt system that is within the space shuttle capacity. For the one megawatt systems, the estimated weight of the entire system including laser loop, solar power generator, and heat radiator is less than the shuttle capacity.
The electrical asymmetry effect in capacitive discharges
NASA Astrophysics Data System (ADS)
Czarnetzki, Uwe
One of the major demands in plasma processing has always been the independent control of ion energy and ion flux. Dual-frequency capacitive discharges with one low and one typically an order of magnitude higher frequency are one of the concepts presently applied in industry. However, recent investigations have shown that there is in fact a coupling between the two frequency components that limits independent control by the two RF powers. Here, a novel concept is introduced based on the electrical asymmetry effect (EAE) that provides simple and stable control of ion energy and flux in an almost ideally independent way [1]. Also here two RF frequencies are applied but with the second frequency being exactly the second harmonic of the first and with a fixed but controllable phase. This phase is the control parameter for the ion energy that changes approximately linearly with the phase. Geometrically symmetric discharges can be made effectively asymmetric with one electrode showing a higher sheath potential than the other. Choosing the proper phase allows then to reverse the situation or to make the discharge symmetric. In geometrically asymmetric discharges the wall potential can be raised or lowered. When tuning the phase, the flux stays approximately constant and its absolute value can be set with the RF amplitudes. The concept of the EAE is developed and analyzed by 1) an analytical model, 2) a hydrodynamic and Monte-Carlo (MC) simulation, 3) a self consistent PIC/MC simulation, and 4) an experimental verification in a laboratory experiment. All four approaches show excellent agreement and confirm the above advantages. The technique has found successful application already in an industrial reactor for large area solar cell production (Leybold Optics). Compared to the standard single frequency case at 13.56 MHz the silicon deposition rate was easily more than doubled and the homogeneity improved. [4pt] [1] Brian G. Heil, U. Czarnetzki, R. P. Brinkmann, T
Development of an Eco-Friendly Electrical Discharge Machine (E-EDM) Using TRIZ Approach
NASA Astrophysics Data System (ADS)
Sreebalaji, V. S.; Saravanan, R.
Electrical Discharge Machine (EDM) is one of the non-traditional machining processes. EDM process is based on thermoelectric energy between the work and an electrode. A pulse discharge occurs in a small gap between the work piece and the electrode and removes the unwanted material from the parent metal through melting and vaporization. The electrode and the work piece must have an electrical conductivity in order to generate the spark. Dielectric fluid acts as a spark conductor, concentrating the energy to a very narrow region. There are various types of products can be produced and finished using EDM such as Moulds, Dies, Parts of Aerodynamics, Automotives and Surgical components. This research work reveals how an Eco friendly EDM (E-EDM) can be modeled to replace die electric fluid and introducing ozonised oxygen in to EDM to eliminate harmful effects generated while machining by using dielectric, to make pollution free machining environment through a new design of EEDM using TRIZ (a Russian acronym for Theory of Inventive Problem Solving) approach, since Eco friendly design is the need of the hour.
Electric organ discharges and electric images during electrolocation
NASA Technical Reports Server (NTRS)
Assad, C.; Rasnow, B.; Stoddard, P. K.
Weakly electric fish use active electrolocation - the generation and detection of electric currents - to explore their surroundings. Although electrosensory systems include some of the most extensively understood circuits in the vertebrate central nervous system, relatively little is known quantitatively about how fish electrolocate objects. We believe a prerequisite to understanding electrolocation and its underlying neural substrates is to quantify and visualize the peripheral electrosensory information measured by the electroreceptors. We have therefore focused on reconstructing both the electric organ discharges (EODs) and the electric images resulting from nearby objects and the fish's exploratory behaviors. Here, we review results from a combination of techniques, including field measurements, numerical and semi-analytical simulations, and video imaging of behaviors. EOD maps are presented and interpreted for six gymnotiform species. They reveal diverse electric field patterns that have significant implications for both the electrosensory and electromotor systems. Our simulations generated predictions of the electric images from nearby objects as well as sequences of electric images during exploratory behaviors. These methods are leading to the identification of image features and computational algorithms that could reliably encode electrosensory information and may help guide electrophysiological experiments exploring the neural basis of electrolocation.
ICPP: Transient Electrical Discharges in Small Devices
NASA Astrophysics Data System (ADS)
Soto, Leopoldo
Small devices of low energy and high power are used to study the basic physics and applications of transient electrical discharges. Three experiments are discussed: a) ionization processes and early stage of a Z-pinch under various initial conditions driven by a small generator (10^12 A/s current derivative) (1, 2) , b) high brightness VUV to soft X-ray emission from a fast capillary discharge (5ns rise time, 5kA peak current and 10^12 A/s current derivative) (3), c) neutron pulses (10^4 -10^5 neutrons per pulse) from a small plasma focus (160 nF capacitor bank, 100 - 200 J energy storage) (4). The last device is oriented to repetitive neutron pulses for substance detection. Numerical simulations of the MHD equations have been carried out to assist the experimental design and diagnostics. The diagnostics developed include current and voltage monitors, multipinhole camera with a multichannel plate (four frames, one frame every 4 ns), in order to obtain the plasma dynamics. Also, 1 ns pulse interferometry was implemented to observe the evolution of the electron density profiles. In addition, VUV spectroscopy was applied to characterize the capillary discharge. Electrical characterization of the plasma focus was established. A comprehensive picture of the plasma dynamics and radiation emission behavior is obtained. This work has been funded by FONDECYT grant 1980187 and a Presidential Chair in Science granted by Chilean government. Part of this work, in collaboration with PLADEMA, Argentina (Bilateral agreement CNEA-CCHEN) and in collaboration with Institute of Spectroscopy, ISAN, Troitsk, Russia. 1.- L. Soto, H. Chuaqui, M. Favre, R. Saavedra. E. Wyndham, M. Skowronek, P. Romeas, R. Aliaga-Rossel, and I. Mitchell, IEEE Trans. Plasma Sci. 26, 1179 (1998) 2.- A. Esaulov, P. Sasorov, L. Soto and M. Zambra, ``MHD Simulation of Gas Embedded Plasma Discharge'', submitted for publication. 3.- P. Choi and M. Favre, Rev. Sci. Instrum. 69, 3118, (1998) 4.- C. Moreno, H
Development of Extreme Ultraviolet Radiation Source using Laser Triggered Vacuum Spark Discharge Plasma
Watanabe, Masato; Yamada, Junzaburo; Zhu Qiushi; Hotta, Eiki
A laser triggerd discharge produced Sn plasma light source has been developed. Experimental parameters such as electrode separation and laser irradiation power are varied to optimize EUV emission power. It is clear that the maximum EUV radiation was occurred in the position where the pinch was observed.
Flow processes in electric discharge drivers
NASA Technical Reports Server (NTRS)
Baganoff, D.
The performance of an electric discharge shock tube is discussed from the point of view that the conditions at the sonic station are the primary controlling variables (likewise in comparing designs), and that the analysis of the flow on either side of the sonic station should be done separately. The importance of considering mass-flow rate in matching a given driver design to the downstream flow required for a particular shock-wave speed is stressed. It is shown that a driver based on the principle of liquid injection (of H2) is superior to one based on the Ludwieg tube, because of the greater mass-flow rate and the absence of a massive diaphragm.
Auroral substorms as an electrical discharge phenomenon
NASA Astrophysics Data System (ADS)
Akasofu, Syun-Ichi
During the last 50 years, we have made much progress in studying auroral substorms (consisting of the growth phase, the expansion phase, and the recovery phase). In particular, we have quantitatively learned about auroral substorms in terms of the global energy input-output relationship. (i) What powers auroral substorms? (ii) Why is there a long delay (1 h) of auroral activities after the magnetosphere is powered (growth phase)? (iii) How much energy is accumulated and unloaded during substorms? (iv) Why is the lifetime of the expansion phase so short (1h)? (v) How is the total energy input-output relationship? (vi) Where is the magnetic energy accumulated during the growth phase? On the basis of the results obtained in (i)-(vi), we have reached the following crucial question: (vii) how can the unloaded energy produce a secondary dynamo, which powers the expansion phase? Or more specifically, how can the accumulated magnetic energy get unloaded such that it generates the earthward electric fields needed to produce the expansion phase of auroral substorms? It is this dynamo and the resulting current circuit that drive a variety of explosive auroral displays as electrical discharge phenomena during the expansion phase, including the poleward advance of auroral arcs and the electrojet. This chain of processes is summarized in Section 4.2. This is the full version of work published by Akasofu (2015).
The Effects of Ferrous and other Ions on the Abiotic Formation of Biomolecules using Aqueous Aerosols and Spark Discharges
NASA Astrophysics Data System (ADS)
Ruiz-Bermejo, M.; Menor-Salván, C.; Osuna-Esteban, S.; Veintemillas-Verdaguer, S.
It has been postulated that the oceans on early Earth had a salinity of 1.5 to 2 times the modern value and a pH between 4 and 10. Moreover, the presence of the banded iron formations shows that Fe+2 was present in significant concentrations in the primitive oceans. Assuming the hypotheses above, in this work we explore the effects of Fe+2 and other ions in the generation of biomolecules in prebiotic simulation experiments using spark discharges and aqueous aerosols. These aerosols have been prepared using different sources of Fe+2, such as FeS, FeCl2 and FeCO3, and other salts (alkaline and alkaline earth chlorides and sodium bicarbonate at pH = 5.8). In all these experiments, we observed the formation of some amino acids, carboxylic acids and heterocycles, involved in biological processes. An interesting consequence of the presence of soluble Fe+2 was the formation of Prussian Blue, Fe4[Fe(CN)6]3, which has been suggested as a possible reservoir of HCN in the initial prebiotic conditions on the Earth.
Electric-discharge gas laser based on a multisectional discharge gap
Lazhintsev, B V; Nor-Arevyan, V A
An electric discharge laser with an electrode unit of novel design was developed. An electric discharge system was based on multisectional plate-like electrodes and an automatic UV preionisation that makes it possible to form a highly stable volume discharge. High-efficiency lasing in N{sub 2} and XeF lasers was achieved. A pulse repetition rate up to 200 Hz was realised in the N{sub 2} laser without recourse to gas circulation. (lasers)
Discharge processes of UV pre-ionized electric-discharge pulsed DF laser
NASA Astrophysics Data System (ADS)
Pan, Qikun; Xie, Jijiang; Shao, Chunlei; Wang, Chunrui; Shao, Mingzhen; Guo, Jin
The discharge processes of ultraviolet (UV) pre-ionized electric-discharge pulsed DF laser operating with a SF6-D2 gas mixture are studied. A mathematical model based on continuity equation of electrons and Kirchhoff equations for discharge circuit is established to describe the discharge processes. Voltage and current waveforms of main discharge and voltage waveforms of pre-ionization are solved numerically utilizing the model. The calculations correctly display some physical processes, such as the delay time between pre-ionization and main discharge, breakdown of the main electrode and self-sustained volume discharge (SSVD). The results of theory are consistent with the experiments, which are performed in our non-chain pulsed DF laser. Then the delay inductance and peak capacitance are researched to analyze their influences on discharge processes, and the circuit parameters of DF laser are given which is useful to improve the discharge stability.
Discharge analysis and electrical modeling for the development of efficient dielectric barrier discharge
NASA Astrophysics Data System (ADS)
Pal, U. N.; Kumar, M.; Tyagi, M. S.; Meena, B. L.; Khatun, H.; Sharma, A. K.
Dielectric-barrier discharges (DBDs) are characterized by the presence of at least one insulating layer in contact with the discharge between two planar or cylindrical electrodes connected to an AC/pulse power supply. The dielectric layers covering the electrodes act as current limiters and prevent the transition to an arc discharge. DBDs exist usually in filamentary mode, based on the streamer nature of the discharges. The main advantage of this type of electrical discharges is that nonequilibrium and non-thermal plasma conditions can be established at atmospheric pressure. VUV/UV sources based on DBDs are considered as promising alternatives of conventional mercury-based discharge plasmas, producing highly efficient VUV/UV radiation. The experiments have been performed using two coaxial quartz double barrier DBD tubes, which are filled with Xe/Ar at different pressures. A sinusoidal voltage up to 2.4 kV peak with frequencies from 20 to 100 kHz has been applied to the discharge electrodes for the generation of microdischarges. A stable and uniform discharge is produced in the gas gap between the dielectric barrier electrodes. By comparisons of visual images and electrical waveforms, the filamentary discharges for Ar tube while homogeneous discharge for Xe tube at the same conditions have been confirmed. The electrical modeling has been carried out to understand DBD phenomenon in variation of applied voltage waveforms. The simulated discharge characteristics have been validated by the experimental results.
NASA Technical Reports Server (NTRS)
Golbabaei-Asl, Mona; Knight, Doyle; Anderson, Kellie; Wilkinson, Stephen
A novel method for determining the thermal efficiency of the SparkJet is proposed. A SparkJet is attached to the end of a pendulum. The motion of the pendulum subsequent to a single spark discharge is measured using a laser displacement sensor. The measured displacement vs time is compared with the predictions of a theoretical perfect gas model to estimate the fraction of the spark discharge energy which results in heating the gas (i.e., increasing the translational-rotational temperature). The results from multiple runs for different capacitances of c = 3, 5, 10, 20, and 40 micro-F show that the thermal efficiency decreases with higher capacitive discharges.
Testing of the J-2X Augmented Spark Igniter (ASI) and Its Electronics
NASA Technical Reports Server (NTRS)
Osborne, Robin
Reliable operation of the spark ignition system electronics in the J-2X Augmented Spark Igniter (ASI) is imperative in assuring ASI ignition and subsequent Main Combustion Chamber (MCC) ignition events are reliable in the J-2X Engine. Similar to the man-rated J-2 and RS-25 engines, the J-2X ignition system electronics are equipped with spark monitor outputs intended to indicate that the spark igniters are properly energized and sparking. To better understand anomalous spark monitor data collected on the J-2X development engines at NASA Stennis Space Center (SSC), a comprehensive subsystem study of the engine's low- and high-tension spark ignition system electronics was conducted at NASA Marshall Space Flight Center (MSFC). Spark monitor output data were compared to more detailed spark diagnostics to determine if the spark monitor was an accurate indication of actual sparking events. In addition, ignition system electronics data were closely scrutinized for any indication of an electrical discharge in some location other than the firing tip of the spark igniter - a problem not uncommon in the development of high voltage ignition systems.
Supersonic CO electric-discharge lasers
NASA Technical Reports Server (NTRS)
Hason, R. K.; Mitchner, M.; Stanton, A.
Laser modeling activity is described which involved addition of an option allowing N2 as a second diatomic gas. This option is now operational and a few test cases involving N2/CO mixtures were run. Results from these initial test cases are summarized. In the laboratory, a CW double-discharge test facility was constructed and tested. Features include: water-cooled removable electrodes, O-ring construction to facilitate cleaning and design modifications, increased discharge length, and addition of a post-discharge observation section. Preliminary tests with this facility using N2 yielded higher power loadings than obtained in the first-generation facility. Another test-section modification, recently made and as yet untested, will permit injection of secondary gases into the cathode boundary layer. The objective will be to vary and enhance the UV emission spectrum from the auxiliary discharge, thereby influencing the level of photoionization in the main discharge region.
The Electrical Characteristics of a Filamentary Dielectric Barrier Discharge
Tay, W. H.; Yap, S. L.; Wong, C. S.
The electrical characteristics of a filamentary dielectric barrier discharge using parallel-plate electrodes geometry were statistically studied. The DBD's system was powered by a 50 Hz power supply and operated at atmospheric pressure. The influence of the air gap and position of dielectric on the discharge had been investigated. It was found that the air gap distance and position of dielectric had significant influence on the discharge current pulse. The results showed that discharge with large distance between the high voltage electrode and the dielectric would generate higher current pulses during the positive cycle. The discharge energy of single pulse was also determined.
Wire electric-discharge machining and other fabrication techniques
NASA Technical Reports Server (NTRS)
Morgan, W. H.
Wire electric discharge machining and extrude honing were used to fabricate a two dimensional wing for cryogenic wind tunnel testing. Electric-discharge cutting is done with a moving wire electrode. The cut track is controlled by means of a punched-tape program and the cutting feed is regulated according to the progress of the work. Electric-discharge machining involves no contact with the work piece, and no mechanical force is exerted. Extrude hone is a process for honing finish-machined surfaces by the extrusion of an abrasive material (silly putty), which is forced through a restrictive fixture. The fabrication steps are described and production times are given.
Electric field in an AC dielectric barrier discharge overlapped with a nanosecond pulse discharge
NASA Astrophysics Data System (ADS)
Goldberg, Benjamin M.; Shkurenkov, Ivan; Adamovich, Igor V.; Lempert, Walter R.
The effect of ns discharge pulses on the AC barrier discharge in hydrogen in plane-to-plane geometry is studied using time-resolved measurements of the electric field in the plasma. The AC discharge was operated at a pressure of 300 Torr at frequencies of 500 and 1750 Hz, with ns pulses generated when the AC voltage was near zero. The electric field vector is measured by ps four-wave mixing technique, which generates coherent IR signal proportional to the square of electric field. Absolute calibration was done using an electrostatic (sub-breakdown) field applied to the discharge electrodes, when no plasma was generated. The results are compared with one-dimensional kinetic modeling of the AC discharge and the nanosecond pulse discharge, predicting behavior of both individual micro-discharges and their cumulative effect on the electric field distribution in the electrode gap, using stochastic averaging based on the experimental micro-discharge temporal probability distribution during the AC period. Time evolution of the electric field in the AC discharge without ns pulses, controlled by a superposition of random micro-discharges, exhibits a nearly 'flat top' distribution with the maximum near breakdown threshold, reproduced quite well by kinetic modeling. Adding ns pulse discharges on top of the AC voltage waveform changes the AC discharge behavior in a dramatic way, inducing transition from random micro-discharges to a more regular, near-1D discharge. In this case, reproducible volumetric AC breakdown is produced at a well-defined moment after each ns pulse discharge. During the reproducible AC breakdown, the electric field in the plasma exhibits a sudden drop, which coincides in time with a well-defined current pulse. This trend is also predicted by the kinetic model. Analysis of kinetic modeling predictions shows that this effect is caused by large-volume ionization and neutralization of surface charges on the dielectrics by ns discharge pulses. The present
Electrical discharge heating of chondrules in the solar nebula
NASA Technical Reports Server (NTRS)
Love, Stanley G.; Keil, Klaus; Scott, Edward R. D.
We present a rudimentary theoretical assessment of electrical discharge heating as a candidate mechanism for the formation of chondrules in the solar nebula. The discharge model combines estimates of the properties of the nebula, a mechanism for terrestrial thunderstorm electrification, and some fundamental electrical properties of gases. Large uncertainties in the model inputs limit these calculations to order-or-magnitude accuracy. Despite the uncertainty, it is possible to estimate an upper limit to the efficiency of nebular discharges at melting millimeter-sized stony objects. We find that electrical arcs analogous to terrestrial lightning could have occurred in the nebula, but that under most conditions these discharges probably could not have melted chondrules. Despite our difficulties, we believe the topic worthy of further investigation and suggest some experiments which could improve our understanding of nebular discharges.
A distributed parameter wire model for transient electrical discharges
NASA Astrophysics Data System (ADS)
Maier, William B., II; Kadish, A.; Sutherland, C. D.; Robiscoe, R. T.
This paper presents a three-dimensional model developed for freely propagating electrical discharges, such as lightning and punch-through arcs. In this model, charge transport is described by a nonlinear differential equation containing two phenomenological parameters characteristic of the medium and the arc; the electromagnetic field is described by Maxwell's equations. Using this model, a cylindrically symmetric small-diameter discharge is analyzed. It is shown that the model predicts discharge properties consistent with experimentally known phenomena.
Development of the electric discharge oxygen-iodine laser
NASA Astrophysics Data System (ADS)
Carroll, David L.; Verdeyen, Joseph T.; King, Darren M.; Palla, Andrew D.; Laystrom, Julia K.; Benavides, Gabriel F.; Zimmerman, Joseph W.; Woodard, Brian S.; Solomon, Wayne C.
In the hybrid electric discharge Oxygen-Iodine laser (ElectricOIL), the desired O II(a1Δ) is produced using a low-to-medium pressure electric discharge. The discharge production of atomic oxygen, ozone, and other excited species adds higher levels of complexity to the post-discharge kinetics which are not encountered in a classic purely chemical O II(a1Δ) generation system. Experimental studies over the past six years using electric discharges have demonstrated O II(a) yields greater than 20%, gain, and cw laser power. Several modeling studies have also been performed for ElectricOIL and similar systems. As the development of this type of iodine laser continues, the roles of oxygen atoms and NO/NO II are found to be very significant in both the discharge region and downstream of the discharge region. A series of O II(1Δ) emission, I* emission, O-atom titrations, gain, and O II(1Δ) yield, NO II* emission, and laser power measurements have been taken to explore the complex phenomena that are being observed. As the overall system is better understood improvements are being made in laser power and efficiency.
Electric winds driven by time oscillating corona discharges
NASA Astrophysics Data System (ADS)
Drews, Aaron M.; Cademartiri, Ludovico; Whitesides, George M.; Bishop, Kyle J. M.
We investigate the formation of steady gas flows—so-called electric winds—created by point-plane corona discharges driven by time oscillating (ac) electric fields. By varying the magnitude and frequency of the applied field, we identify two distinct scaling regimes: (i) a low frequency (dc) regime and (ii) a high frequency (ac) regime. These experimental observations are reproduced and explained by a theoretical model describing the transport and recombination of ions surrounding the discharge and their contribution to the measured wind velocity. The two regimes differ in the spatial distribution of ions and in the process by which ions are consumed. Interestingly, we find that ac corona discharges generate strong electric forces localized near the tip of the point electrode, while dc corona discharges generate weaker forces distributed throughout the interelectrode region. Consequently, the velocity of the electric winds (>1 m/s) generated by ac discharges is largely independent of the position of the counter electrode. The unified theoretical description of dc and ac electric winds presented here reconciles previous observations of winds driven by dc corona and ac dielectric barrier discharges; insights from the model should also prove useful in the design of other plasma actuators.
Spark decomposition studies of dielectric gas mixtures
NASA Astrophysics Data System (ADS)
Sauers, I.; Christophorou, L. G.
The ultimate usefulness of a high voltage insulating gas depends not only on the ability of the gas to withstand high voltages, but also on the degradation of the gas resulting from spark discharges, corona or prolonged electrical stress and the effect(s) of the by-products on the equipment and, possibly, the environment. In view of these considerations, the study of long-range spark decomposition was undertaken in an effort to improve the decomposition characteristics of dielectric gases through proper tailoring of gas mixtures while maintaining high breakdown strengths. The data reported are on the analyses of gases sparked by capactive (0.1 micro F) discharge into a 0.5-mm gap, resulting in an energy input of approximately 5 J per spark. The nature of the decomposition products of SF6 formed by high voltage discharges observed is found to be critically dependent on impurities (particularly H2O), electrode material and insulating materials present in the system.
Electric discharge for treatment of trace contaminants
NASA Technical Reports Server (NTRS)
Flamm, D. L.; Wydeven, T. J. (Inventor)
A radio frequency glow discharge reactor is described for removing trace oxidizable contaminants from an oxygen bearing atmosphere. The reaction chamber is defined by an inner metal electrode facing a dielectric backed by an outer conductive electrode. In one embodiment, a conductive liquid forms the conductor of an outer electrode and cools the dielectric. A resonator coupled to a variable radio frequency source generates the high voltages for creating a glow discharge in the chamber at a predetermined pressure whereby the trace contaminants are oxidized into a few simple non-toxic products that may be easily recovered. The corresponding process for removal of trace contaminants from an oxygen-bearing atmosphere with high efficiency independent of the concentration level is also disclosed.
Laser-assisted guiding of electric discharges around objects
Clerici, Matteo; Hu, Yi; Lassonde, Philippe; Milián, Carles; Couairon, Arnaud; Christodoulides, Demetrios N.; Chen, Zhigang; Razzari, Luca; Vidal, François; Légaré, François; Faccio, Daniele; Morandotti, Roberto
Electric breakdown in air occurs for electric fields exceeding 34 kV/cm and results in a large current surge that propagates along unpredictable trajectories. Guiding such currents across specific paths in a controllable manner could allow protection against lightning strikes and high-voltage capacitor discharges. Such capabilities can be used for delivering charge to specific targets, for electronic jamming, or for applications associated with electric welding and machining. We show that judiciously shaped laser radiation can be effectively used to manipulate the discharge along a complex path and to produce electric discharges that unfold along a predefined trajectory. Remarkably, such laser-induced arcing can even circumvent an object that completely occludes the line of sight. PMID:26601188
Laser-assisted guiding of electric discharges around objects.
Clerici, Matteo; Hu, Yi; Lassonde, Philippe; Milián, Carles; Couairon, Arnaud; Christodoulides, Demetrios N; Chen, Zhigang; Razzari, Luca; Vidal, François; Légaré, François; Faccio, Daniele; Morandotti, Roberto
Electric breakdown in air occurs for electric fields exceeding 34 kV/cm and results in a large current surge that propagates along unpredictable trajectories. Guiding such currents across specific paths in a controllable manner could allow protection against lightning strikes and high-voltage capacitor discharges. Such capabilities can be used for delivering charge to specific targets, for electronic jamming, or for applications associated with electric welding and machining. We show that judiciously shaped laser radiation can be effectively used to manipulate the discharge along a complex path and to produce electric discharges that unfold along a predefined trajectory. Remarkably, such laser-induced arcing can even circumvent an object that completely occludes the line of sight. PMID:26601188
TOPICAL REVIEW: Nucleation and aerosol processing in atmospheric pressure electrical discharges: powders production, coatings and filtration
NASA Astrophysics Data System (ADS)
Borra, Jean-Pascal
This review addresses the production of nano-particles and the processing of particles injected in atmospheric pressure electrical discharges (APED). The mechanisms of formation and the evolution of particles suspended in gases are first presented, with numerical and experimental facilities. Different APED and related properties are then introduced for dc corona, streamer and spark filamentary discharges (FD), as well as for ac filamentary and homogeneous dielectric barrier discharges (DBD). Two mechanisms of particle production are depicted in APED: when FD interact with the surface of electrodes or dielectrics and when filamentary and homogeneous DBD induce reactions with gaseous precursors in volume. In both cases, condensable gaseous species are produced, leading to nano-sized particles by physical and chemical routes of nucleation. The evolution of the so-formed nano-particles, i.e. the growth by coagulation/condensation, the charging and the collection are detailed for each APED, with respect to fine powders production and thin films deposition. Finally, when particles are injected in APED, they undergo interfacial processes. Non-thermal plasmas charge particles for electro-collection and trigger heterogeneous chemical reactions for organic and inorganic films deposition. Heat exchanges in thermal plasmas enable powder purification, shaping, melting for hard coatings and fine powders production by reactive evaporation.
Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Lehr, Jane Marie
The later time phase of electrical breakdown in water is investigated for the purpose of improving understanding of the discharge characteristics. One dimensional simulations in addition to a zero dimensional lumped model are used to study the spark discharge. The goal is to provide better electrical models for water switches used in the pulse compression section of pulsed power systems. It is found that temperatures in the discharge channel under representative drive conditions, and assuming small initial radii from earlier phases of development, reach levels that are as much as an order of magnitude larger than those used to model discharges in atmospheric gases. This increased temperature coupled with a more rapidly rising conductivity with temperature than in air result in a decreased resistance characteristic compared to preceding models. A simple modification is proposed for the existing model to enable the approximate calculation of channel temperature and incorporate the resulting conductivity increase into the electrical circuit for the discharge channel. Comparisons are made between the theoretical predictions and recent experiments at Sandia. Although present and past experiments indicated that preceding late time channel models overestimated channel resistance, the calculations in this report seem to underestimate the resistance relative to recent experiments. Some possible reasons for this discrepancy are discussed.
Pulsed electrical discharge in gas bubbles in water
NASA Astrophysics Data System (ADS)
Gershman, Sophia
A phenomenological picture of pulsed electrical discharge in gas bubbles in water is produced by combining electrical, spectroscopic, and imaging methods. The discharge is generated by applying one microsecond long 5 to 20 kilovolt pulses between the needle and disk electrodes submerged in water. A gas bubble is generated at the tip of the needle electrode. The study includes detailed experimental investigation of the discharge in argon bubbles and a brief look at the discharge in oxygen bubbles. Imaging, electrical characteristics, and time-resolved optical emission data point to a fast streamer propagation mechanism and formation of a plasma channel in the bubble. Spectroscopic methods based on line intensity ratios and Boltzmann plots of line intensities of argon, atomic hydrogen, and argon ions and the examination of molecular emission bands from molecular nitrogen and hydroxyl radicals provide evidence of both fast beam-like electrons and slow thermalized ones with temperatures of 0.6 -- 0.8 electron-volts. The collisional nature of plasma at atmospheric pressure affects the decay rates of optical emission. Spectroscopic study of rotational-vibrational bands of hydroxyl radical and molecular nitrogen gives vibrational and rotational excitation temperatures of the discharge of about 0.9 and 0.1 electron-volt, respectively. Imaging and electrical evidence show that discharge charge is deposited on the bubble wall and water serves as a dielectric barrier for the field strength and time scales of this experiment. Comparing the electrical and imaging information for consecutive pulses applied at a frequency of 1 Hz indicates that each discharge proceeds as an entirely new process with no memory of the previous discharge aside from long-lived chemical species, such as ozone and oxygen. Intermediate values for the discharge gap and pulse duration, low repetition rate, and unidirectional character of the applied voltage pulses make the discharge process here unique
Multiple performance characteristics optimization for Al 7075 on electric discharge drilling by Taguchi grey relational theory
NASA Astrophysics Data System (ADS)
Khanna, Rajesh; Kumar, Anish; Garg, Mohinder Pal; Singh, Ajit; Sharma, Neeraj
Electric discharge drill machine (EDDM) is a spark erosion process to produce micro-holes in conductive materials. This process is widely used in aerospace, medical, dental and automobile industries. As for the performance evaluation of the electric discharge drilling machine, it is very necessary to study the process parameters of machine tool. In this research paper, a brass rod 2 mm diameter was selected as a tool electrode. The experiments generate output responses such as tool wear rate (TWR). The best parameters such as pulse on-time, pulse off-time and water pressure were studied for best machining characteristics. This investigation presents the use of Taguchi approach for better TWR in drilling of Al-7075. A plan of experiments, based on L27 Taguchi design method, was selected for drilling of material. Analysis of variance (ANOVA) shows the percentage contribution of the control factor in the machining of Al-7075 in EDDM. The optimal combination levels and the significant drilling parameters on TWR were obtained. The optimization results showed that the combination of maximum pulse on-time and minimum pulse off-time gives maximum MRR.
Discharging a DC bus capacitor of an electrical converter system
Kajouke, Lateef A; Perisic, Milun; Ransom, Ray M
A system and method of discharging a bus capacitor of a bidirectional matrix converter of a vehicle are presented here. The method begins by electrically shorting the AC interface of the converter after an AC energy source is disconnected from the AC interface. The method continues by arranging a plurality of switching elements of a second energy conversion module into a discharge configuration to establish an electrical current path from a first terminal of an isolation module, through an inductive element, and to a second terminal of the isolation module. The method also modulates a plurality of switching elements of a first energy conversion module, while maintaining the discharge configuration of the second energy conversion module, to at least partially discharge a DC bus capacitor.
Polymerization of adamantane vapors during electrical discharge
Fedoseev, D.V.; Lavrent'ev, A.V.; Barshavskaya, I.G.
The authors describe the polymerization and deposition of adamantane films on quartz and molybdenum substrates under arc spraying conditions and use infrared spectroscopy, electron diffraction, and transmission electron microscopy to determine the crystal and molecular structure of the resulting film. Film microhardness and electrical conductivity were also determined as was the temperature dependence of these properties.
Biological and Agricultural Studies on Application of Discharge Plasma and Electromagnetic Fields 2.Sterilization by Electrical Discharges and Plasmas
NASA Astrophysics Data System (ADS)
Watanabe, Takayuki
The use of electrical discharges and plasmas for sterilization is reviewed. Plasmas generated by a silent discharge, a pulse discharge, and a radio frequency discharge under atmospheric pressure have been used for sterilization. Furthermore, a microwave plasma, a radio frequency plasma, and a low temperature plasma with hydrogen peroxide under low pressure conditions have been also used for sterilization. Sterilization results from injury caused by the discharge current, and from the reaction of species affected by the discharge. A silent discharge with air or oxygen is most effective for the sterilization. Nitrogen discharge also has a significant effect, however, argon discharge does not have a significant effect.
Comparative study of INPIStron and spark gap
NASA Technical Reports Server (NTRS)
Han, Kwang S.; Lee, Ja H.
An inverse pinch plasma switch, INPIStron, was studied in comparison to a conventional spark gap. The INPIStron is under development for high power switching applications. The INPIStron has an inverse pinch dynamics, opposed to Z-pinch dynamics in the spark gap. The electrical, plasma dynamics and radiative properties of the closing plasmas have been studied. Recently the high-voltage pulse transfer capabilities or both the INPIStron and the spark gap were also compared. The INPIStron with a low impedance Z = 9 ohms transfers 87 percent of an input pulse with a halfwidth of 2 mu s. For the same input pulse the spark gap of Z = 100 ohms transfers 68 percent. Fast framing and streak photography, taken with an TRW image converter camera, was used to observe the discharge uniformity and closing plasma speed in both switches. In order to assess the effects of closing plasmas on erosion of electrode material, emission spectra of two switches were studied with a spectrometer-optical multi channel analyzer (OMA) system. The typical emission spectra of the closing plasmas in the INPIStron and the spark gap showed that there were comparatively weak carbon line emission in 658.7 nm and copper (electrode material) line emissions in the INPIStron, indicating low erosion of materials in the INPIStron.
A direct search for energetic electrons produced by laboratory sparks
NASA Astrophysics Data System (ADS)
Carlson, B. E.; Kochkin, P.; van Deursen, A. P. J.; Hansen, R.; Gjesteland, T.; Ostgaard, N.
High-voltage sparks in the lab unexpectedly emit x-rays with energies up to several hundred keV. These x-rays have been observed repeatedly and can only be produced by bremsstrahlung, impling the presence of a population of energetic electrons. Such energetic electron and x-ray production may be important for the physics of streamers, spark discharges, and lightning, and has been suggested as directly related to the production of terrestrial gamma-ray flashes. We present the results of the first direct search for energetic electrons produced by a lab spark. Small electrically-isolated scintillators are placed at various locations near the spark gap of a 2 MV Marx generator and the resulting signals are recorded. We present results on the spatial, temporal, and statistical variability of signals produced by energetic electrons and compare our results to predictions of energetic electron production from the literature.
Runaway breakdown and electrical discharges in thunderstorms
NASA Astrophysics Data System (ADS)
Milikh, Gennady; Roussel-Dupré, Robert
This review considers the precise role played by runaway breakdown (RB) in the initiation and development of lightning discharges. RB remains a fundamental research topic under intense investigation. The question of how lightning is initiated and subsequently evolves in the thunderstorm environment rests in part on a fundamental understanding of RB and cosmic rays and the potential coupling to thermal runaway (as a seed to RB) and conventional breakdown (as a source of thermal runaways). In this paper, we describe the basic mechanism of RB and the conditions required to initiate an observable avalanche. Feedback processes that fundamentally enhance RB are discussed, as are both conventional breakdown and thermal runaway. Observations that provide clear evidence for the presence of energetic particles in thunderstorms/lightning include γ-ray and X-ray flux intensifications over thunderstorms, γ-ray and X-ray bursts in conjunction with stepped leaders, terrestrial γ-ray flashes, and neutron production by lightning. Intense radio impulses termed narrow bipolar pulses (or NBPs) provide indirect evidence for RB particularly when measured in association with cosmic ray showers. Our present understanding of these phenomena and their enduring enigmatic character are touched upon briefly.
Electrical isolation of RF plasma discharges
Miller, P.A.; Anderson, H.; Splichal, M.P.
Plasmas excited by radio-frequency (rf) power have nonlinear impedance characteristics. This causes the plasma state to depend on the nature of the circuitry that supplies electrical power to the plasma. This dependency occurs because the harmonics of the drive frequency, which are generated by the plasma nonlinearity, interact with the impedance of the external circuitry at the harmonic frequencies. The authors describe the use of a low-pass rf filter in the power feed to the plasma in the GEC RF Reference Cell. The filter successfully isolates the plasma and eliminates its sensitivity to changes in the rf generator, cable plant, and matching network.
Neal, R.B.
An improved triggered spark gap switch is described, capable of precisely controllable firing time while switching very large amounts of power. The invention in general comprises three electrodes adjustably spaced and adapted to have a large potential impressed between the outer electrodes. The central electrode includes two separate elements electrically connected togetaer and spaced apart to define a pair of spark gaps between the end electrodes. Means are provided to cause the gas flow in the switch to pass towards the central electrode, through a passage in each separate element, and out an exit disposed between the two separate central electrode elements in order to withdraw ions from the spark gap.
On the Propagation of Streamers in Electrical Discharges
NASA Astrophysics Data System (ADS)
Qin, J.; Pasko, V. P.
Streamers are non-thermal filamentary plasmas developing in insulating mediums under influence of strong external electric fields. Decades of extensive research have been dedicated to the understanding of streamer physics and their related applications. It is now well known that streamers are fundamental components in many types of gas discharges in laboratory and in the Earth's atmosphere, such as the dielectric-barrier discharges, the lightning discharges in thunderstorms, and the sprite discharges in the upper atmosphere. Recent studies also suggest that streamers might play an essential role in the production of terrestrial gamma ray flashes in thunderstorms. In industry, streamers have a long history of being used for various applications such as ozone production, plasma-assisted combustion, and pollution control. Moreover, benefiting from their non-thermal property, streamers have recently shown a great medical potential, for example, in wound healing and treatment of skin diseases. Understanding of the streamer propagation mechanism is of essential importance for the studies of the above-mentioned electrical discharge phenomena, as well as the industrial and medical applications of streamers. According to the present knowledge on the streamer physics, the applied electric field plays a decisive role in controlling the streamer dynamics. In this study, we propose a new understanding of the streamer propagation mechanism, in which we refine some fundamental concepts in the streamer physics. We will discuss possible ways to flexibly control the streamer parameters in applications, and also implications of this new mechanism for understanding of fundamental sprite physics.
Consumption of the electric power inside silent discharge reactors
Yehia, Ashraf
An experimental study was made in this paper to investigate the relation between the places of the dielectric barriers, which cover the surfaces of the electrodes in the coaxial cylindrical reactors, and the rate of change of the electric power that is consumed in forming silent discharges. Therefore, silent discharges have been formed inside three coaxial cylindrical reactors. The dielectric barriers in these reactors were pasted on both the internal surface of the outer electrode in the first reactor and the external surface of the inner electrode in the second reactor as well as the surfaces of the two electrodes in the third reactor. The reactor under study has been fed by atmospheric air that flowed inside it with a constant rate at normal temperature and pressure, in parallel with the application of a sinusoidal ac voltage between the electrodes of the reactor. The electric power consumed in forming the silent discharges inside the three reactors was measured as a function of the ac peak voltage. The validity of the experimental results was investigated by applying Manley's equation on the same discharge conditions. The results have shown that the rate of consumption of the electric power relative to the ac peak voltage per unit width of the discharge gap improves by a ratio of either 26.8% or 80% or 128% depending on the places of the dielectric barriers that cover the surfaces of the electrodes inside the three reactors.
Vehicle exhaust treatment using electrical discharge and materials chemistry
Tonkyn, R.G.; Balmer, M.L.; Barlow, S.E.; Orlando, T.M.; Goulette, D.; Hoard, J.
Current 3-way catalytic converters have proven quite effective at removing NO{sub x} from the exhaust of spark ignition vehicles operating near stoichiometric air-to-fuel ratios. However, diesel engines typically operate at very high air-to-fuel ratios. Under such lean burn conditions current catalytic converters are ineffective for NO{sub x} removal. As a result, considerable effort has been made to develop a viable lean NO{sub x} catalyst. Although some materials have been shown to reduce NO{sub x} under lean burn conditions, none exhibit the necessary activity and stability at the high temperatures and humidities found in typical engine exhaust,. As a result, alternative technologies are being explored in an effort to solve the so-called lean NO{sub x} problem. Packed-bed barrier discharge systems are well suited to take advantage of plasma-surface interactions due to the large number of contaminant surface collisions in the bed. The close proximity of the active surface to transient species produced by the plasma may lead to favorable chemistry at considerably lower temperatures than required by thermal catalysts. The authors present data in this paper illustrating that the identity and surface properties of the packing material can alter the discharge-driven chemistry in synthetic leanburn exhaust mixtures. Results using non-porous glass beads as the packing material suggest the limits of NO{sub x} reduction using purely gas phase discharge chemistry. By comparison, encouraging results are reported for several alternative packing materials.
Effect of fine bubbles on electric discharge in water
NASA Astrophysics Data System (ADS)
Hayashi, Yui; Takada, Noriharu; Kanda, Hideki; Goto, Motonobu
Ar or O2 fine bubbles of diameter <80 μm were introduced in water and a pulsed discharge plasma was generated between cylinder electrodes in water. Fine bubbles in water affected discharge ignition and caused low inception voltage and suppression of rising temperature. The contamination from electrodes was suppressed in the case of fine bubbles addition because fine bubbles assisted plasma generation. In addition, discharge with fine bubbles enhanced plasma emission with high electron density compared to the no-bubbling case. Discharge with fine bubbles at low-pH conditions generated intense plasma emission compared to neutral and high-pH conditions owing to the electric charge of the fine bubbles.
Clean Electrical-Discharge Machining Of Delicate Honeycomb
NASA Technical Reports Server (NTRS)
Johnson, Clarence S.
Precise recesses in fragile metal honeycomb blocks formed in special electrical-discharge machining process. Special tooling used, and recesses bored with workpiece in nonstandard alignment. Cutting electrode advances into workpiece along x axis to form pocket of rectangular cross section. Deionized water flows from fitting, along honeycomb tubes of workpiece, to electrode/workpiece interface.
Discharging Static Electricity From Inside A Glass Tube
NASA Technical Reports Server (NTRS)
Ellsbury, Walter L.
Device that contains emitter of alpha particles discharges static electricity from inside wall of glass tube of volumetric-flow calibrator. Includes cylinder that has wall thickness of 1/16 in., diameter about 1/2 in. smaller than inside diameter of tube, and height that extends about 1/2 in. above piston that moves along tube and is part of calibrator.
Degradation of Synthetic Dyeing Wastewater by Underwater Electrical Discharge Processes
NASA Astrophysics Data System (ADS)
D. Kim, S.; I. Jang, D.; J. Lim, B.; B. Lee, S.; S. Mok, Y.
Electrical discharge treatments of synthetic dyeing wastewater were carried out with two different systems: underwater pulsed electrical discharge (UPED) and underwater dielectric barrier discharge (UDBD). Reactive Blue 4 (RB4) and Acid Red 4 (AR4) were used as model contaminants for the synthetic wastewater. The performance of the aforementioned systems was compared with respect to the chromaticity removal and the energy requirement. The results showed that the present electrical discharge systems were very effective for degradation of the dyes. The dependences of the dye degradation rate on treatment time, initial dye concentration, electrical energy, and the type of working gas including air, O2, and N2 were examined. The change in the initial dye concentration did not largely affect the degradation of either RB4 or AR4. The energy delivered to the UPED system was only partially utilized for generating reactive species capable of degrading the dyes, leading to higher energy requirement than the UDBD system. Among the working gases, the best performance was observed with O2. As the degradation proceeded, the concentration of total dissolved solids and the solution conductivity kept increasing while pH showed a decreasing trend, revealing that the dyes were effectively mineralized.
Upward electrical discharges observed above Tropical Depression Dorian
Liu, Ningyu; Spiva, Nicholas; Dwyer, Joseph R.; Rassoul, Hamid K.; Free, Dwayne; Cummer, Steven A.
Observation of upward electrical discharges from thunderstorms has been sporadically reported in the scientific literature. According to their terminal altitudes, they are classified as starters (20–30 km), jets (40–50 km) and gigantic jets (70–90 km). They not only have a significant impact on the occupied atmospheric volumes but also electrically couple different atmospheric regions. However, as they are rare and unpredictable, our knowledge of them has been built on observations that typically record only one type of such discharges. Here we report a close-distance observation of seven upward discharges including one starter, two jets and four gigantic jets above Tropical Depression Dorian. Our optical and electromagnetic data indicate that all events are of negative polarity, suggesting they are initiated in the same thundercloud charge region. The data also indicate that the lightning-like discharge channel can extend above thunderclouds by about 30 km, but the discharge does not emit low-frequency electromagnetic radiation as normal lightning. PMID:25607345
Upward electrical discharges observed above Tropical Depression Dorian.
Liu, Ningyu; Spiva, Nicholas; Dwyer, Joseph R; Rassoul, Hamid K; Free, Dwayne; Cummer, Steven A
Observation of upward electrical discharges from thunderstorms has been sporadically reported in the scientific literature. According to their terminal altitudes, they are classified as starters (20-30 km), jets (40-50 km) and gigantic jets (70-90 km). They not only have a significant impact on the occupied atmospheric volumes but also electrically couple different atmospheric regions. However, as they are rare and unpredictable, our knowledge of them has been built on observations that typically record only one type of such discharges. Here we report a close-distance observation of seven upward discharges including one starter, two jets and four gigantic jets above Tropical Depression Dorian. Our optical and electromagnetic data indicate that all events are of negative polarity, suggesting they are initiated in the same thundercloud charge region. The data also indicate that the lightning-like discharge channel can extend above thunderclouds by about 30 km, but the discharge does not emit low-frequency electromagnetic radiation as normal lightning. PMID:25607345
Electric field vector measurements in a surface ionization wave discharge
NASA Astrophysics Data System (ADS)
Goldberg, Benjamin M.; Böhm, Patrick S.; Czarnetzki, Uwe; Adamovich, Igor V.; Lempert, Walter R.
This work presents the results of time-resolved electric field vector measurements in a short pulse duration (60 ns full width at half maximum), surface ionization wave discharge in hydrogen using a picosecond four-wave mixing technique. Electric field vector components are measured separately, using pump and Stokes beams linearly polarized in the horizontal and vertical planes, and a polarizer placed in front of the infrared detector. The time-resolved electric field vector is measured at three different locations across the discharge gap, and for three different heights above the alumina ceramic dielectric surface, ~100, 600, and 1100 μm (total of nine different locations). The results show that after breakdown, the discharge develops as an ionization wave propagating along the dielectric surface at an average speed of 1 mm ns-1. The surface ionization wave forms near the high voltage electrode, close to the dielectric surface (~100 μm). The wave front is characterized by significant overshoot of both vertical and horizontal electric field vector components. Behind the wave front, the vertical field component is rapidly reduced. As the wave propagates along the dielectric surface, it also extends further away from the dielectric surface, up to ~1 mm near the grounded electrode. The horizontal field component behind the wave front remains quite significant, to sustain the electron current toward the high voltage electrode. After the wave reaches the grounded electrode, the horizontal field component experiences a secondary rise in the quasi-dc discharge, where it sustains the current along the near-surface plasma sheet. The measurement results indicate presence of a cathode layer formed near the grounded electrode with significant cathode voltage fall, ≈3 kV, due to high current density in the discharge. The peak reduced electric field in the surface ionization wave is 85-95 Td, consistent with dc breakdown field estimated from the Paschen curve for
The Early Phase of Spark Ignition
NASA Astrophysics Data System (ADS)
Pitt, Philip Lawrence
In this dissertation, some practical ignition techniques are presented that show how some problems of lean-burn combustion can be overcome. Then, to shed light on the effects of the ignition techniques described, the focus shifts to the more specific problem of the early phase of spark ignition. Thermal models of ignition are reviewed. These models treat the energy provided by the electrical discharge as a point source, delivered infinitely fast and creating a spherically symmetric ignition kernel. The thesis challenges the basis of these thermal models by reviewing the work of many investigators who have clearly shown that the temporal characteristics of the discharge have a profound effect upon ignition. Photographic evidence of the early phase of ignition, as well as other evidence from the literature, is also presented. The evidence clearly demonstrates that the morphology of spark kernels in the early phase of development is toroidal, not spherical as suggested by thermal models. A new perspective for ignition, a fluid dynamic point of view, is described. The common ignition devices are then classified according to fluid dynamics. A model describing the behaviour of spark kernels is presented, which extends a previously established mixing model for plasma jets, to the realm of conventional axial discharges. Comparison of the model behaviour to some limited data is made. The model is modified by including the effect of heat addition from combustion, and ignition criteria are discussed.
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.
Microsecond-scale electric field pulses in cloud lightning discharges
NASA Technical Reports Server (NTRS)
Villanueva, Y.; Rakov, V. A.; Uman, M. A.; Brook, M.
From wideband electric field records acquired using a 12-bit digitizing system with a 500-ns sampling interval, microsecond-scale pulses in different stages of cloud flashes in Florida and New Mexico are analyzed. Pulse occurrence statistics and waveshape characteristics are presented. The larger pulses tend to occur early in the flash, confirming the results of Bils et al. (1988) and in contrast with the three-stage representation of cloud-discharge electric fields suggested by Kitagawa and Brook (1960). Possible explanations for the discrepancy are discussed. The tendency for the larger pulses to occur early in the cloud flash suggests that they are related to the initial in-cloud channel formation processes and contradicts the common view found in the atmospheric radio-noise literature that the main sources of VLF/LF electromagnetic radiation in cloud flashes are the K processes which occur in the final, or J type, part of the cloud discharge.
ElectricOIL discharge and post-discharge kinetics experiments and modeling
NASA Astrophysics Data System (ADS)
Palla, A. D.; Zimmerman, J. W.; Woodard, B. S.; Carroll, D. L.; Verdeyen, J. T.; Lim, T. C.; Rawlins, W. T.; Lee, S.; Davis, S. J.; Solomon, W. C.
Laser oscillation at 1315 nm on the I(2P 1/2) --> I(2P 3/2) transition of atomic iodine has been obtained by a near resonant energy transfer from O II(a1Δ) produced using a low-pressure oxygen/helium/nitric-oxide discharge. In the electric discharge oxygen-iodine laser (ElectricOIL) the discharge production of atomic oxygen, ozone, and other excited species adds levels of complexity to the singlet oxygen generator (SOG) kinetics which are not encountered in a classic purely chemical O II(a1Δ) generation system. The advanced model BLAZE-IV has been introduced in order to study the energy-transfer laser system dynamics and kinetics. Levels of singlet oxygen, oxygen atoms and ozone are measured experimentally and compared with calculations. The new BLAZE-IV model is in reasonable agreement with O 3, O II(b1Σ), and O atom, and gas temperature measurements, but is under-predicting the increase in O II(a1Δ) concentration resulting from the presence of NO in the discharge. A key conclusion is that the removal of oxygen atoms by NOX species leads to a significant increase in O II(a1Δ) concentrations downstream of the discharge in part via a recycling process, however there are still some important processes related to the NO X discharge kinetics that are missing from the present modeling. Further, the removal of oxygen atoms dramatically inhibits the production of ozone in the downstream kinetics.
Aluminum-Enhanced Underwater Electrical Discharges for Steam Explosion Triggering
For a number of years, we have been initiating steam explosions of single drops of molten materials with pressure and flow (bubble growth) transients generated by discharging a capacitor bank through gold bridgewires placed underwater. Recent experimental and theoretical advances in the field of steam explosions, however, have made it important to substantially increase these relatively mild transients in water without using high explosives, if possible. To do this with the same capacitor bank, we have discharged similar energies through tiny strips of aluminum foil submerged in water. By replacing the gold wires with the aluminum strips, we were able to add the energy of the aluminum-water combustion to that normally deposited electrically by the bridgewire explosion in water. The chemical enhancement of the explosive characteristics of the discharges was substantial: when the same electrical energies were discharged through the aluminum strips, peak pressures increased as much as 12-fold and maximum bubble volumes as much as 5-fold above those generated with the gold wires. For given weights of aluminum, the magnitudes of both parameters appeared to exceed those produced by the underwater explosion of equivalent weights of high explosives.
PIC simulations of electrically asymmetric dual frequency capacitive RF discharges
NASA Astrophysics Data System (ADS)
Donko, Zoltan; Schulze, Julian; Schuengel, Edmund; Czarnetzki, Uwe
A geometrically symmetric dual frequency capacitively coupled RF discharge operated in argon at 13.56 MHz and 27.12 MHz with variable phase shift between the driving voltage waveforms is investigated by a 1d PIC simulation. Due to the Electrical Asymmetry Effect (EAE) a variable DC self bias is generated as a function of the phase shift, that allows efficient separate control of ion energy and flux at the electrodes. An analytical model demonstrates why the ion flux does not depend on the phase shift. The quality of this separate control is found to be better compared to conventional dual frequency discharges operated at substantially different frequencies, where limitations due to frequency coupling occur. The EAE is optimized by choosing optimum amplitudes of the low and high frequency voltage waveforms. For the first time non-linear self excited plasma series resonance (PSR) oscillations are observed in geometrically symmetric discharges. The PSR oscillations and non-linear electron resonance heating (NERH) are turned on and off depending on the electrical discharge asymmetry controlled by the phase shift between the driving frequencies.
High energy XeBr electric discharge laser
Sze, R.C.; Scott, P.B.
A high energy XeBr laser for producing coherent radiation at 282 nm is disclosed. The XeBr laser utilizes an electric discharge as the excitation source to minimize formation of molecular ions thereby minimizing absorption of laser radiation by the active medium. Additionally, HBr, is used as the halogen donor which undergoes harpooning reactions with Xe/sub M/ to form XeBr.
High energy XeBr electric discharge laser
Sze, Robert C.; Scott, Peter B.
A high energy XeBr laser for producing coherent radiation at 282 nm. The XeBr laser utilizes an electric discharge as the excitation source to minimize formation of molecular ions thereby minimizing absorption of laser radiation by the active medium. Additionally, HBr is used as the halogen donor which undergoes harpooning reactions with Xe.sub.M * to form XeBr*.
Properties of UN Sintered by High Voltage Electric Discharge Consolidation
NASA Astrophysics Data System (ADS)
Yurlova, M.; Tarasov, B.; Shornikov, D.; Grigoryev, E.; Olevsky, E.
In the present work, the opportunity of the consolidation of uranium nitride tablets by high voltage electric discharge consolidation (HVEDC) is considered. It is shown that the consolidation by HVEDC allows the prevention of the expansion of uranium nitride powders and renders pellets with relative density of up to 97%. The thermal stability of the obtained samples has been investigated. The analysis of the microstructure of the processed samples indicates the retention of the initial powder structure
The electrical characteristics of the dielectric barrier discharges
NASA Astrophysics Data System (ADS)
Yehia, Ashraf
The electrical characteristics of the dielectric barrier discharges have been studied in this paper under different operating conditions. The dielectric barrier discharges were formed inside two reactors composed of electrodes in the shape of two parallel plates. The dielectric layers inside these reactors were pasted on the surface of one electrode only in the first reactor and on the surfaces of the two electrodes in the second reactor. The reactor under study has been fed by atmospheric air that flowed inside it with a constant rate at the normal temperature and pressure, in parallel with applying a sinusoidal ac voltage between the electrodes of the reactor. The amount of the electric charge that flows from the reactors to the external circuit has been studied experimentally versus the ac peak voltage applied to them. An analytical model has been obtained for calculating the electrical characteristics of the dielectric barrier discharges that were formed inside the reactors during a complete cycle of the ac voltage. The results that were calculated by using this model have agreed well with the experimental results under the different operating conditions.
Producing nitric oxide by pulsed electrical discharge in air for portable inhalation therapy.
Yu, Binglan; Muenster, Stefan; Blaesi, Aron H; Bloch, Donald B; Zapol, Warren M
Inhalation of nitric oxide (NO) produces selective pulmonary vasodilation and is an effective therapy for treating pulmonary hypertension in adults and children. In the United States, the average cost of 5 days of inhaled NO for persistent pulmonary hypertension of the newborn is about $14,000. NO therapy involves gas cylinders and distribution, a complex delivery device, gas monitoring and calibration equipment, and a trained respiratory therapy staff. The objective of this study was to develop a lightweight, portable device to serve as a simple and economical method of producing pure NO from air for bedside or portable use. Two NO generators were designed and tested: an offline NO generator and an inline NO generator placed directly within the inspiratory line. Both generators use pulsed electrical discharges to produce therapeutic range NO (5 to 80 parts per million) at gas flow rates of 0.5 to 5 liters/min. NO was produced from air, as well as gas mixtures containing up to 90% O2 and 10% N2. Potentially toxic gases produced in the plasma, including nitrogen dioxide (NO2) and ozone (O3), were removed using a calcium hydroxide scavenger. An iridium spark electrode produced the lowest ratio of NO2/NO. In lambs with acute pulmonary hypertension, breathing electrically generated NO produced pulmonary vasodilation and reduced pulmonary arterial pressure and pulmonary vascular resistance index. In conclusion, electrical plasma NO generation produces therapeutic levels of NO from air. After scavenging to remove NO2 and O3 and filtration to remove particles, electrically produced NO can provide safe and effective treatment of pulmonary hypertension. PMID:26136478
NASA Technical Reports Server (NTRS)
Eichenberg, Dennis J.; Lindamood, Glenn R.; Weiland, Karen J.; VanderWal, Randall L.
The Mars Spark Source Prototype (MSSP) hardware has been developed as part of a proof of concept system for the detection of trace metals such as lead, cadmium, and arsenic in Martian dusts and soils. A spark discharge produces plasma from a soil sample and detectors measure the optical emission from metals in the plasma that will allow their identification and quantification. Trace metal measurements are vital for the assessment of the potential toxicity of the Martian environment for human exploration. The current method of X-ray fluorescence can yield concentrations only of major species. Other instruments are incompatible with the volume, weight, and power constraints for a Mars mission. The instrument will be developed primarily for use in the Martian environment, but would be adaptable for terrestrial use in environmental monitoring. This paper describes the Mars Spark Source Prototype hardware, the results of the characterization tests, and future plans for hardware development.
Schofield, A.E.
A multiple spark gap switch of unique construction is described which will permit controlled, simultaneous discharge of several capacitors into a load. The switch construction includes a disc electrode with a plurality of protuberances of generally convex shape on one surface. A firing electrode is insulatingly supponted In each of the electrode protuberances and extends substantially to the apex thereof. Individual electrodes are disposed on an insulating plate parallel with the disc electrode to form a number of spark gaps with the protuberances. These electrodes are each connected to a separate charged capacitor and when a voltage ls applied simultaneously between the trigger electrodes and the dlsc electrode, each spark gap fires to connect its capacitor to the disc electrode and a subsequent load.
State Waste Discharge Permit Application: Electric resistance tomography testing
Not Available
This permit application documentation is for a State Waste Discharge Permit issued in accordance with requirements of Washington Administrative Code 173-216. The activity being permitted is a technology test using electrical resistance tomography. The electrical resistance tomography technology was developed at Lawrence Livermore National Laboratory and has been used at other waste sites to track underground contamination plumes. The electrical resistance tomography technology measures soil electrical resistance between two electrodes. If a fluid contaminated with electrolytes is introduced into the soil, the soil resistance is expected to drop. By using an array of measurement electrodes in several boreholes, the areal extent of contamination can be estimated. At the Hanford Site, the purpose of the testing is to determine if the electrical resistance tomography technology can be used in the vicinity of large underground metal tanks without the metal tank interfering with the test. It is anticipated that the electrical resistance tomography technology will provide a method for accurately detecting leaks from the bottom of underground tanks, such as the Hanford Site single-shell tanks.
Preparation of nanocomposite fluid by electrical arc discharge technique.
Chang, Ho
This study proposes a new method, the electrical arc discharge system, for preparing a nanocomposite fluid with the basic ingredients of Cu, Fe and O. The proposed system has the advantages of a high-power electric arc heating system, excellent stability of the electric arc, and well-developed control technology. In the fabrication process, the positive electrode uses a copper rod and the negative electrode an iron rod, and the two electrodes are processed in the insulating processing liquid. The nanocomposite fluid generated by the synthesis system is analyzed by morphological analysis, heat transfer analysis, magnetism analysis, and rheological testing. The experiment generates satisfactory results for nanocomposite fluid with an average particle diameter of 25 nm by process conditions of vacuum pressure of 30 torr, peak current of 7 A for arc discharge, breakdown voltage of 250 V and duration time of 10 micros. The experimental results showed that the nanocomposite fluid is composed of Fe, FeO, Cu, and Cu2O. SEM images show that Fe and Cu are spherical, FeO is square, and Cu2O is ovoid. For the heat transfer experiment, the experimental temperature was set at ambient temperature of 30 degrees C, the average heat transfer coefficient is 0.708 W/m oC, which is 16.3% higher than that of deionized water. The magnetism test shows that the magnetic retentivity of the fluid is 47.27 (Oe), which makes it a soft magnetic fluid. PMID:18464430
Numerical simulation of nanosecond-pulse electrical discharges
NASA Astrophysics Data System (ADS)
Poggie, J.; Adamovich, I.; Bisek, N.; Nishihara, M.
Recent experiments with a nanosecond-pulse, dielectric barrier discharge at the stagnation point of a Mach 5 cylinder flow have demonstrated the formation of weak shock waves near the electrode edge, which propagate upstream and perturb the bow shock. This is a promising means of flow control, and understanding the detailed physics of the conversion of electrical energy into gas motion will aid in the design of efficient actuators based on the concept. In this work, a simplified configuration with planar symmetry was chosen as a vehicle to develop a physics-based model of nanosecond-pulse discharges, including realistic air kinetics, electron energy transport, and compressible bulk gas flow. A reduced plasma kinetic model (23 species and 50 processes) was developed to capture the dominant species and reactions for energy storage and thermalization in the discharge. The kinetic model included electronically and vibrationally excited species, and several species of ions and ground state neutrals. The governing equations included the Poisson equation for the electric potential, diffusion equations for each neutral species, conservation equations for each charged species, and mass-averaged conservation equations for the bulk gas flow. The results of calculations with this model highlighted the path of energy transfer in the discharge. At breakdown, the input electrical energy was transformed over a time scale on the order of 1 ns into chemical energy of ions, dissociation products, and vibrationally and electronically excited particles. About 30% of this energy was subsequently thermalized over a time scale of 10 µs. Since the thermalization time scale was faster than the acoustic time scale, the heat release led to the formation of weak shock waves originating near the sheath edge, consistent with experimental observations. The computed translational temperature rise (40 K) and nitrogen vibrational temperature rise (370 K) were of the same order of magnitude as
Electrode configuration for extreme-UV electrical discharge source
Spence, Paul Andrew; Fornaciari, Neal Robert; Chang, Jim Jihchyun
It has been demonstrated that debris generation within an electric capillary discharge source, for generating extreme ultraviolet and soft x-ray, is dependent on the magnitude and profile of the electric field that is established along the surfaces of the electrodes. An electrode shape that results in uniform electric field strength along its surface has been developed to minimize sputtering and debris generation. The electric discharge plasma source includes: (a) a body that defines a circular capillary bore that has a proximal end and a distal end; (b) a back electrode positioned around and adjacent to the distal end of the capillary bore wherein the back electrode has a channel that is in communication with the distal end and that is defined by a non-uniform inner surface which exhibits a first region which is convex, a second region which is concave, and a third region which is convex wherein the regions are viewed outwardly from the inner surface of the channel that is adjacent the distal end of the capillary bore so that the first region is closest to the distal end; (c) a front electrode positioned around and adjacent to the proximal end of the capillary bore wherein the front electrode has an opening that is communication with the proximal end and that is defined by a non-uniform inner surface which exhibits a first region which is convex, a second region which is substantially linear, and third region which is convex wherein the regions are viewed outwardly from the inner surface of the opening that is adjacent the proximal end of the capillary bore so that the first region is closest to the proximal end; and (d) a source of electric potential that is connected across the front and back electrodes.
NASA Technical Reports Server (NTRS)
Golbabaei-Asl, M.; Knight, D.; Wilkinson, S.
The thermal efficiency of a SparkJet is evaluated by measuring the impulse response of a pendulum subject to a single spark discharge. The SparkJet is attached to the end of a pendulum. A laser displacement sensor is used to measure the displacement of the pendulum upon discharge. The pendulum motion is a function of the fraction of the discharge energy that is channeled into the heating of the gas (i.e., increasing the translational-rotational temperature). A theoretical perfect gas model is used to estimate the portion of the energy from the heated gas that results in equivalent pendulum displacement as in the experiment. The earlier results from multiple runs for different capacitances of C = 3, 5, 10, 20, and 40(micro)F demonstrate that the thermal efficiency decreases with higher capacitive discharges.1 In the current paper, results from additional run cases have been included and confirm the previous results
Vertical EDM (electric discharge machining) using modular programming
Fuller, J.E.
The usual function of computer numerically controlled (CNC) machining programs is to specify a sequence of machining operations. When CNC is applied to electric discharge machining (EDM), the possibilities and needs are much greater. This paper describes a modular system of programming in which various functions are carried out by subroutines contained in the controller memory. The subroutines are made more versatile by using variables. Such functions as orbiting, cavity inspection, electrode wear measurement and compensation, and multiple cavities are possible. 3 refs., 9 figs.
Electrical discharge machining of type-N(f) microwave connectors
Haushalter, R.J.
A particular out-of-specification mechanical dimension on Type-N(f) [Type-N(female)] microwave connectors sometimes disqualifies otherwise perfectly acceptable microwave devices from being used in calibration systems. The Miniature Machining Group at Sandia National Laboratories applied a technique called Electrical Discharge Machining (EDM) to quickly and economically machine these devices without disassembly. In so doing, they facilitated the use of existing components without the need to purchase new devices. The technique also improves an uncertainty of calibration known as Mismatch Uncertainty by optimizing the reflection coefficient of the calibration test port. This effects a reduction in overall calibration uncertainties.
Sample preparation of metal alloys by electric discharge machining
NASA Technical Reports Server (NTRS)
Chapman, G. B., II; Gordon, W. A.
Electric discharge machining was investigated as a noncontaminating method of comminuting alloys for subsequent chemical analysis. Particulate dispersions in water were produced from bulk alloys at a rate of about 5 mg/min by using a commercially available machining instrument. The utility of this approach was demonstrated by results obtained when acidified dispersions were substituted for true acid solutions in an established spectrochemical method. The analysis results were not significantly different for the two sample forms. Particle size measurements and preliminary results from other spectrochemical methods which require direct aspiration of liquid into flame or plasma sources are reported.
Large-area assembly of three-dimensional nanoparticle structures via ion assisted aerosol lithography with a multi-pin spark discharge generator
NASA Astrophysics Data System (ADS)
Ha, Kyungyeon; Choi, Hoseop; Jung, Kinam; Han, Kyuhee; Lee, Jong-Kwon; Ahn, KwangJun; Choi, Mansoo
We present an approach utilizing ion assisted aerosol lithography (IAAL) with a newly designed multi-pin spark discharge generator (SDG) for fabricating large-area three-dimensional (3D) nanoparticle-structure (NPS) arrays. The design of the multi-pin SDG allows us to uniformly construct 3D NPSs on a large area of 50 mm × 50 mm in a parallel fashion at atmospheric pressure. The ion-induced focusing capability of IAAL significantly reduces the feature size of 3D NPSs compared to that of the original pre-patterns formed on a substrate. The spatial uniformity of 3D NPSs is above 95% using the present multi-pin SDG, which is far superior to that of the previous single-pin SDG with less than 32% uniformity. The effect of size distributions of nanoparticles generated via the multi-pin SDG on the 3D NPSs also has been studied. In addition, we measured spectral reflectance for the present 3D NPSs coated with Ag, demonstrating enhanced diffuse reflectance.
Second Discharge Characteristics of Aluminum Wire Electrical Explosion Under Various Argon Pressures
NASA Astrophysics Data System (ADS)
Yan, Wenyu; Zhang, Qiaogen; Zhao, Junping; Chen, Gangliang; Liu, Longchen
Electrical wire explosion is a promising method for the preparation of metal nanopowder, but the properties of metal nanopowder are affected by the second discharge process of electrical wire explosion. The second discharge characteristics of aluminum wire electrical explosion under variant argon pressures were studied in a RLC discharge circuit. The results show that the curve of the second discharge voltages versus the pressure presents a U-shape. To clarify the roles of aluminum vapor and argon in the process of the second discharge, a spectrograph and a high speed framing camera were used to study the radiation spectrum and spatial distribution of the electrical explosion plasma. It is observed that argon participates in the second discharge process under low pressure. A discharge channel develops along the surface of the aluminum vapor. Under higher pressure, a second discharge takes place in the aluminum vapor and the discharge channel is inside the aluminum vapor.
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.
Morphological processing of ultraviolet emissions of electrical corona discharge for analysis and diagnostic use.
Schubert, Matthew; Moore, Andrew J
Electron cascades from electrical discharge produce secondary emissions from atmospheric plasma in the ultraviolet band. For a single point of discharge, these emissions exhibit a stereotypical discharge morphology, with latent information about the discharge location. Morphological processing can uncover the location and therefore have diagnostic utility. PMID:26974615
Morphological Processing of Ultraviolet Emissions of Electrical Corona Discharge for Analysis and Diagnostic Use
NASA Technical Reports Server (NTRS)
Schubert, Matthew R.; Moore, Andrew J.
Electron cascades from electrical discharge produce secondary emissions from atmospheric plasma in the ultraviolet band. For a single point of discharge, these emissions exhibit a stereotypical discharge morphology, with latent information about the discharge location. Morphological processing can uncover the location and therefore can have diagnostic utility.
Micro electrical discharge drilling of tungsten carbide using deionized water
NASA Astrophysics Data System (ADS)
Song, Ki Young; Chung, Do Kwan; Park, Min Soo; Chu, Chong Nam
Micro electrical discharge machining (micro EDM) is an effective machining method for cobalt-bonded tungsten carbide (WC-Co); however, this material is susceptible to electrolytic corrosion when deionized water is used as the working fluid with a dc power source for the RC circuit. In this study, a bipolar pulse power source and a triangular electrode were used in order to reduce the electrolytic corrosion phenomenon during micro EDM using an RC discharge circuit. A bipolar pulse power source reduces the positive polarity period of the workpiece by periodically alternating the polarity of the workpiece and electrode and decreases the average gap voltage at the machining gap. Therefore, electrolytic corrosion, which is a type of electrochemical reaction on the positively charged workpiece, is reduced by these electrical conditions. The triangular electrode has a smaller side area as compared with the cylindrical electrode. Since the electrolytic corrosion is an electrochemical reaction between the side of the electrode and the surface of the workpiece, the small side area of the triangular electrode could reduce these reactions. With the aid of the bipolar pulse power source and the triangular electrode, an electrolytic-corrosion-free hole could be machined on the WC-Co workpiece using deionized water.
Electrical discharge from a thundercloud top to the lower ionosphere.
Pasko, Victor P; Stanley, Mark A; Mathews, John D; Inan, Umran S; Wood, Troy G
For over a century, numerous undocumented reports have appeared about unusual large-scale luminous phenomena above thunderclouds and, more than 80 years ago, it was suggested that an electrical discharge could bridge the gap between a thundercloud and the upper atmosphere. Since then, two classes of vertically extensive optical flashes above thunderclouds have been identified-sprites and blue jets. Sprites initiate near the base of the ionosphere, develop very rapidly downwards at speeds which can exceed 107 m s-1 (ref. 15), and assume many different geometrical forms. In contrast, blue jets develop upwards from cloud tops at speeds of the order of 105 m s-1 and are characterized by a blue conical shape. But no experimental data related to sprites or blue jets have been reported which conclusively indicate that they establish a direct path of electrical contact between a thundercloud and the lower ionosphere. Here we report a video recording of a blue jet propagating upwards from a thundercloud to an altitude of about 70 km, taken at the Arecibo Observatory, Puerto Rico. Above an altitude of 42 km-normally the upper limit for blue jets and the lower terminal altitude for sprites-the flash exhibited some features normally observed in sprites. As we observed this phenomenon above a relatively small thunderstorm cell, we speculate that it may be common and therefore represent an unaccounted for component of the global electric circuit. PMID:11894087
Electric plasma discharge combustion synthesis of chlorine dioxide
Dotson, R. L.; Geren, G. W.
A process for the production of chlorine dioxide comprises feeding an inert gas to a reaction zone and applying an electrical discharge to the inert gas to produce a high temperature plasma. Chlorine gas and oxygen gas are supplied simultaneously to the reaction zone and reacted in the plasma to produce a gaseous mixture comprised of chlorine dioxide, chlorine, oxygen and inert gas, the molar ratio of oxygen to chlorine in the reaction zone being at least about 2.5;1. The gaseous mixture is recovered from the reaction zone. Chlorine dioxide, which may be recovered as a gas or reacted to produce an alkali metal chlorite, is employed as a bleaching agent and a water treatment agent.
PREFACE: Diagnostics for electrical discharge light sources: pushing the limits Diagnostics for electrical discharge light sources: pushing the limits
NASA Astrophysics Data System (ADS)
Zissis, Georges; Haverlag, Marco
Light sources play an indispensable role in the daily life of any human being. Quality of life, health and urban security related to traffic and crime prevention depend on light and on its quality. In fact, every day approximately 30 billion electric light sources operate worldwide. These electric light sources consume almost 19% of worldwide electricity production. Finding new ways to light lamps is a challenge where the stakes are scientific, technological, economic and environmental. The production of more efficient light sources is a sustainable solution for humanity. There are many opportunities for not only enhancing the efficiency and reliability of lighting systems but also for improving the quality of light as seen by the end user. This is possible through intelligent use of new technologies, deep scientific understanding of the operating principles of light sources and knowledge of the varied human requirements for different types of lighting in different settings. A revolution in the domain of light source technology is on the way: high brightness light emitting diodes arriving in the general lighting market, together with organic LEDs (OLEDs), are producing spectacular advances. However, unlike incandescence, electrical discharge lamps are far from disappearing from the market. In addition, new generations of discharge lamps based on molecular radiators are becoming a reality. There are still many scientific and technological challenges to be raised in this direction. Diagnostics are important for understanding the fundamental mechanisms taking place in the discharge plasma. This understanding is an absolute necessity for system optimization leading to more efficient and high quality light sources. The studied medium is rather complex, but new diagnostic techniques coupled to innovative ideas and powerful tools have been developed in recent years. This cluster issue of seven papers illustrates these efforts. The selected papers cover all domains, from
Micro Electro Discharge Machining of Electrically Nonconductive Ceramics
NASA Astrophysics Data System (ADS)
Schubert, A.; Zeidler, H.; Wolf, N.; Hackert, M.
EDM is a known process for machining of hard and brittle materials. Due to its noncontact and nearly forceless behaviour, it has been introduced into micro manufacturing and through constant development it is now an important means for producing high-precision micro geometries. One restriction of EDM is its limitation to electrically conducting materials. Today many applications, especially in the biomedical field, make use of the benefits of ceramic materials, such as high strength, very low wear and biocompatibility. Common ceramic materials such as Zirconium dioxide are, due to their hardness in the sintered state, difficult to machine with conventional cutting techniques. A demand for the introduction of EDM to these materials could so far not be satisfied because of their nonconductive nature. At the Chemnitz University of Technology and the Fraunhofer IWU, investigations in the applicability of micro-EDM for the machining of nonconductive ceramics are being conducted. Tests are undertaken using micro-EDM drilling with Tungsten carbide tool electrodes and ZrO2 ceramic workpieces. A starting layer, in literature often referred to as `assisting electrode' is used to set up a closed electric circuit to start the EDM process. Combining carbon hydride based dielectric and a specially designed low-frequency vibration setup to excite the workpiece, the process environment can be held within parameters to allow for a constant EDM process even after the starting layer is machined. In the experiments a cylindrical 120 μm diameter Tungsten carbide tool electrode and Y2O3- and MgO- stabilized ZrO2 worpieces are used. The current and voltage signals of the discharges within the different stages of the process (machining of the starting layer, machining of the base material, transition stage) are recorded and their characteristics compared to discharges in metallic material. Additionally, the electrode feed is monitored. The influences of the process parameters are
Micro Electro Discharge Machining of Electrically Nonconductive Ceramics
Schubert, A.; Zeidler, H.; Hackert, M.; Wolf, N.
EDM is a known process for machining of hard and brittle materials. Due to its noncontact and nearly forceless behaviour, it has been introduced into micro manufacturing and through constant development it is now an important means for producing high-precision micro geometries. One restriction of EDM is its limitation to electrically conducting materials.Today many applications, especially in the biomedical field, make use of the benefits of ceramic materials, such as high strength, very low wear and biocompatibility. Common ceramic materials such as Zirconium dioxide are, due to their hardness in the sintered state, difficult to machine with conventional cutting techniques. A demand for the introduction of EDM to these materials could so far not be satisfied because of their nonconductive nature.At the Chemnitz University of Technology and the Fraunhofer IWU, investigations in the applicability of micro-EDM for the machining of nonconductive ceramics are being conducted. Tests are undertaken using micro-EDM drilling with Tungsten carbide tool electrodes and ZrO{sub 2} ceramic workpieces. A starting layer, in literature often referred to as 'assisting electrode' is used to set up a closed electric circuit to start the EDM process. Combining carbon hydride based dielectric and a specially designed low-frequency vibration setup to excite the workpiece, the process environment can be held within parameters to allow for a constant EDM process even after the starting layer is machined. In the experiments a cylindrical 120 {mu}m diameter Tungsten carbide tool electrode and Y{sub 2}O{sub 3}- and MgO- stabilized ZrO{sub 2} worpieces are used. The current and voltage signals of the discharges within the different stages of the process (machining of the starting layer, machining of the base material, transition stage) are recorded and their characteristics compared to discharges in metallic material. Additionally, the electrode feed is monitored. The influences of the
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.
Production of organic compounds in plasmas - A comparison among electric sparks, laser-induced plasmas, and UV light
NASA Astrophysics Data System (ADS)
Scattergood, T. W.; McKay, C. P.; Borucki, W. J.; Giver, L. P.; van Ghyseghem, H.; Parris, J. E.; Miller, S. L.
In order to ascertain the features of organic compound-production in planetary atmospheres under the effects of plasmas and shocks, various mixtures of N2, CH4, and H2 modeling the atmosphere of Titan were subjected to discrete sparks, laser-induced plasmas, and UV radiation. The experimental results obtained suggest that UV photolysis from the plasma is an important organic compound synthesis process, as confirmed by the photolysis of gas samples that were exposed to the light but not to the shock waves emitted by the sparks. The thermodynamic equilibrium theory is therefore incomplete in the absence of photolysis.
Production of organic compounds in plasmas - A comparison among electric sparks, laser-induced plasmas, and UV light
NASA Technical Reports Server (NTRS)
Scattergood, Thomas W.; Mckay, Christopher P.; Borucki, William J.; Giver, Lawrence P.; Van Ghyseghem, Hilde
In order to ascertain the features of organic compound-production in planetary atmospheres under the effects of plasmas and shocks, various mixtures of N2, CH4, and H2 modeling the atmosphere of Titan were subjected to discrete sparks, laser-induced plasmas, and UV radiation. The experimental results obtained suggest that UV photolysis from the plasma is an important organic compound synthesis process, as confirmed by the photolysis of gas samples that were exposed to the light but not to the shock waves emitted by the sparks. The thermodynamic equilibrium theory is therefore incomplete in the absence of photolysis.
NASA Technical Reports Server (NTRS)
Silsbee, F B; Loeb, L B; Sawyer, L G; Fonseca, E L; Dickinson, H C; Agnew, P G
The successful operation of the spark plug depends to a large extent on the gas tightness of the plug. Part 1 of this report describes the method used for measuring the gas tightness of aviation spark plugs. Part 2 describes the methods used in testing the electrical conductivity of the insulation material when hot. Part 3 describes the testing of the cold dielectric strength of the insulation material, the resistance to mechanical shock, and the final engine test.
Influence of Electrical Resistivity and Machining Parameters on Electrical Discharge Machining Performance of Engineering Ceramics
Ji, Renjie; Liu, Yonghong; Diao, Ruiqiang; Xu, Chenchen; Li, Xiaopeng; Cai, Baoping; Zhang, Yanzhen
Engineering ceramics have been widely used in modern industry for their excellent physical and mechanical properties, and they are difficult to machine owing to their high hardness and brittleness. Electrical discharge machining (EDM) is the appropriate process for machining engineering ceramics provided they are electrically conducting. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics. This paper investigates the effects of the electrical resistivity and EDM parameters such as tool polarity, pulse interval, and electrode material, on the ZnO/Al2O3 ceramic's EDM performance, in terms of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The results show that the electrical resistivity and the EDM parameters have the great influence on the EDM performance. The ZnO/Al2O3 ceramic with the electrical resistivity up to 3410 Ω·cm can be effectively machined by EDM with the copper electrode, the negative tool polarity, and the shorter pulse interval. Under most machining conditions, the MRR increases, and the SR decreases with the decrease of electrical resistivity. Moreover, the tool polarity, and pulse interval affect the EWR, respectively, and the electrical resistivity and electrode material have a combined effect on the EWR. Furthermore, the EDM performance of ZnO/Al2O3 ceramic with the electrical resistivity higher than 687 Ω·cm is obviously different from that with the electrical resistivity lower than 687 Ω·cm, when the electrode material changes. The microstructure character analysis of the machined ZnO/Al2O3 ceramic surface shows that the ZnO/Al2O3 ceramic is removed by melting, evaporation and thermal spalling, and the material from the working fluid and the graphite electrode can transfer to the workpiece surface during electrical discharge
Influence of electrical resistivity and machining parameters on electrical discharge machining performance of engineering ceramics.
Ji, Renjie; Liu, Yonghong; Diao, Ruiqiang; Xu, Chenchen; Li, Xiaopeng; Cai, Baoping; Zhang, Yanzhen
Engineering ceramics have been widely used in modern industry for their excellent physical and mechanical properties, and they are difficult to machine owing to their high hardness and brittleness. Electrical discharge machining (EDM) is the appropriate process for machining engineering ceramics provided they are electrically conducting. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics. This paper investigates the effects of the electrical resistivity and EDM parameters such as tool polarity, pulse interval, and electrode material, on the ZnO/Al2O3 ceramic's EDM performance, in terms of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The results show that the electrical resistivity and the EDM parameters have the great influence on the EDM performance. The ZnO/Al2O3 ceramic with the electrical resistivity up to 3410 Ω·cm can be effectively machined by EDM with the copper electrode, the negative tool polarity, and the shorter pulse interval. Under most machining conditions, the MRR increases, and the SR decreases with the decrease of electrical resistivity. Moreover, the tool polarity, and pulse interval affect the EWR, respectively, and the electrical resistivity and electrode material have a combined effect on the EWR. Furthermore, the EDM performance of ZnO/Al2O3 ceramic with the electrical resistivity higher than 687 Ω·cm is obviously different from that with the electrical resistivity lower than 687 Ω·cm, when the electrode material changes. The microstructure character analysis of the machined ZnO/Al2O3 ceramic surface shows that the ZnO/Al2O3 ceramic is removed by melting, evaporation and thermal spalling, and the material from the working fluid and the graphite electrode can transfer to the workpiece surface during electrical discharge
The use of electrical discharge for ignition and control of combustion of solid propellants
NASA Technical Reports Server (NTRS)
Tachibana, Takeshi; Kobayashi, Tsuruo; Matsuda, Takashi; Kimura, Itsuro
As the first step of the study of the combustion control of solid propellants by electrical discharges, the effects of an arc discharge, which flows along the burning surface, on the burning rate and on the increase of enthalpy of the combustion product were investigated. For specially devised composite propellants, which are composed of Al and Teflon powders, it was shown that the combination can be controlled by an arc discharge; the combustion continues when the arc discharge is applied and is interrupted when the arc discharge breaks. In the present investigation, it was also shown that an arc discharge coupled with a high-frequency electrical discharge has potential as an effective ignition method for solid propellants. For the application of this type of combustion control to an ignitor for a solid propellant rocket motor or to a control rocket motor, this method lacks flexibility in the configuration scale and needs relatively high electric power at the present stage.
Low Pressure Experimental Simulation of Electrical Discharges Above and Inside a Cloud
NASA Technical Reports Server (NTRS)
Jarzembski, Maurice A.; Srivastava, Vandana
A low pressure laboratory experiment to generate sporadic electrical discharges in either a particulate dielectric or air, representing a competing path of preferred electrical breakdown, was investigated. At high pressures, discharges occurred inside the dielectric particulate; at low pressures, discharges occurred outside the dielectric particulate; at a transition pressure regime, which depends on conductivity of the dielectric particulate, discharges were simultaneously generated in both particulate dielectric and air. Unique use of a particulate dielectric was critical for sporadic discharges at lower pressures which were not identical in character to discharges without the particulate dielectric. Application of these experimental results to the field of atmospheric electricity and simulation of the above-cloud type discharges that have recently been documented, called jets and sprites, are discussed.
Electric Field Measurements in Non-Equilibrium Electric Discharge Plasmas Using Picosecond Four-Wave Mixing
NASA Astrophysics Data System (ADS)
Goldberg, Benjamin M.
This dissertation presents the results of development of a picosecond four wave mixing technique and its use for electric field measurements in nanosecond pulse discharges. This technique is similar to coherent anti-Stokes Raman spectroscopy and is well suited for electric field measurements in high pressure plasmas with high spatial and temporal resolution. The results show that the signal intensity scales proportionally to the square of the electric field, the signal is emitted as a coherent beam, and is polarized parallel to the electric field vector, making possible electric field vector component measurements. The signal is generated when a collinear pair of pump and Stokes beams, which are generated in a stimulated Raman shifting cell (SRS), generate coherent excitation of molecules into a higher energy level, hydrogen for the present work. The coherent excitation mixes with a dipole moment induced by an external electric field. The mixing of these three "waves'" allows the molecules to radiate at their Raman frequency, producing a fourth, signal, wave which is proportional to the square of the electric field. The time resolution of this technique is limited by the coherence decay time of the molecules, which is a few hundred picoseconds.
Dynamic Reduction Effect of CO2 Gas Discharge in Introducing Electric Vehicles
NASA Astrophysics Data System (ADS)
Liu, Bin; Inaba, Tsuginori
For this study, the dynamic reduction effect of CO2 gas discharge for change from internal combustion engines to electric vehicles, EVs, was investigated quantitatively. The Japanese power generation status, which shows characteristics of electricity generation, and optimized adjustment to electricity demand, load and environment was examined. Based on a CO2 gas discharge basic unit, the estimated reduction quantity of CO2 gas discharge from EVs was calculated. The reduction effect of CO2 gas discharge is expected to be 52% by changing gas-fuelled vehicles to EVs. However, the dynamic differential is only 19% reduction by using the thermal power and -2% if only the coal thermal power is used.
Obtaining electricity by direct transfer of charge generated in corona discharge
NASA Astrophysics Data System (ADS)
Berezkina, T. E.; Masyukevich, S. V.; Gall, N. R.
We have studied the possibility of generating electricity directly by using the charge that is created in a corona discharge and transferred by airflow in the direction perpendicular to the discharge axis. Results of experimental measurements and theoretical estimations confirm this possibility. The electric power output from corona discharge in experiment was on the order of 10-3 W, which is about one-tenth of the theoretical limit. It is proposed to use this effect for creating wind-driven generators.
Power spectrum of electrical discharges seen on earth and at Saturn
NASA Astrophysics Data System (ADS)
Warwick, J. W.
A technique is described for deriving the radio spectrum of electrical discharges by using the properties of the time series of charges crossing the discharge gap. The method was applied to the spectrum of lightning and to the Saturn's electrical discharges (SEDs). It is shown that the occurrence and the power density of SEDs have subtle, but important, differences from these observables described in the last five years. The reasons for these differences are discussed.
Enhanced osteoblast response to electrical discharge machining surface.
Otsuka, Fukunaga; Kataoka, Yu; Miyazaki, Takashi
The purpose of this study is to investigate the surface characteristics and biocompatibility of titanium (Ti) surfaces modified by wire electrical discharge machining (EDM). EDM surface characteristics were evaluated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), thin-film X-ray diffractometry (XRD) and contact angle measurements. MC3T3-E1 cell morphology, attachment and proliferation, as well as analysis of osteoblastic gene expressions, on machined surfaces and EDM surfaces were also evaluated. EDM surfaces exhibited high super hydrophilicity, due to high surface energy. XPS and XRD revealed that a passive oxide layer with certain developing thickness onto. EDM surfaces promoted cell attachment, but restrained proliferation. Counted cell numbers increased significantly on the machined surfaces as compared to the EDM surfaces. Real-time PCR analyses showed significantly higher relative mRNA expression levels of osteoblastic genes (ALP, osteocalcin, Runx2, Osterix) in cells cultured on the EDM surfaces as compared to cells cultured on the machined surfaces. PMID:22447066
Development of the Cylindrical Wire Electrical Discharge Machining Process.
McSpadden, SB
Results of applying the wire Electrical Discharge Machining (EDM) process to generate precise cylindrical forms on hard, difficult-to-machine materials are presented. A precise, flexible, and corrosion-resistant underwater rotary spindle was designed and added to a conventional two-axis wire EDM machine to enable the generation of free-form cylindrical geometries. A detailed spindle error analysis identifies the major source of error at different frequency. The mathematical model for the material removal of cylindrical wire EDM process is derived. Experiments were conducted to explore the maximum material removal rate for cylindrical and 2D wire EDM of carbide and brass work-materials. Compared to the 2D wire EDM, higher maximum material removal rates may be achieved in the cylindrical wire EDM. This study also investigates the surface integrity and roundness of parts created by the cylindrical wire EDM process. For carbide parts, an arithmetic average surface roughness and roundness as low as 0.68 and 1.7 {micro}m, respectively, can be achieved. Surfaces of the cylindrical EDM parts were examined using Scanning Electron Microscopy (SEM) to identify the craters, sub-surface recast layers and heat-affected zones under various process parameters. This study has demonstrated that the cylindrical wire EDM process parameters can be adjusted to achieve either high material removal rate or good surface integrity.
Low-pressure spark gap triggered by an ion diode
Prono, D.S.
Spark gap apparatus for use as an electric switch operating at high voltage, high current and high repetition rate. Mounted inside a housing are an anode, cathode and ion plate. An ionizable fluid is pumped through the chamber of the housing. A pulse of current to the ion plate causes ions to be emitted by the ion plate, which ions move into and ionize the fluid. Electric current supplied to the anode discharges through the ionized fluid and flows to the cathode. Current stops flowing when the current source has been drained. The ionized fluid recombines into its initial dielectric ionizable state. The switch is now open and ready for another cycle.
Low pressure spark gap triggered by an ion diode
Prono, Daniel S.
Spark gap apparatus for use as an electric switch operating at high voltage, high current and high repetition rate. Mounted inside a housing are an anode, cathode and ion plate. An ionizable fluid is pumped through the chamber of the housing. A pulse of current to the ion plate causes ions to be emitted by the ion plate, which ions move into and ionize the fluid. Electric current supplied to the anode discharges through the ionized fluid and flows to the cathode. Current stops flowing when the current source has been drained. The ionized fluid recombines into its initial dielectric ionizable state. The switch is now open and ready for another cycle.
Discharge processes and an electrical model of atmospheric pressure plasma jets in argon
NASA Astrophysics Data System (ADS)
Fang, Zhi; Shao, Tao; Yang, Jing; Zhang, Cheng
In this paper, an atmospheric pressure plasma discharge in argon was generated using a needle-to-ring electrode configuration driven by a sinusoidal excitation voltage. The electric discharge processes and discharge characteristics were investigated by inspecting the voltage-current waveforms, Lissajous curves and lighting emission images. The change in discharge mode with applied voltage amplitude was studied and characterised, and three modes of corona discharge, dielectric barrier discharge (DBD) and jet discharge were identified, which appeared in turn with increasing applied voltage and can be distinguished clearly from the measured voltage-current waveforms, light-emission images and the changing gradient of discharge power with applied voltage. Based on the experimental results and discharge mechanism analysis, an equivalent electrical model and the corresponding equivalent circuit for characterising the whole discharge processes accurately was proposed, and the three discharge stages were characterised separately. A voltage-controlled current source (VCCS) associated with a resistance and a capacitance were used to represent the DBD stage, and the plasma plume and corona discharge were modelled by a variable capacitor in series with a variable resistor. Other factors that can influence the discharge, such as lead and stray capacitance values of the circuit, were also considered in the proposed model. Contribution to the Topical Issue "Recent Breakthroughs in Microplasma Science and Technology", edited by Kurt Becker, Jose Lopez, David Staack, Klaus-Dieter Weltmann and Wei Dong Zhu.
Production of organic compounds in plasmas: a comparison among electric sparks, laser-induced plasmas, and UV light.
Scattergood, T W; McKay, C P; Borucki, W J; Giver, L P; Van Ghyseghem, H; Parris, J E; Miller, S L
The chemistry in planetary atmospheres that is induced by processes associated with high-temperature plasmas is of broad interest because such processes may explain many of the chemical species observed. There are at least two important phenomena that are known to generate plasmas (and shocks) in planetary atmospheres: lightning and meteor impacts. For both phenomena, rapid heating of atmospheric gases leads to formation of a high-temperature plasma which emits radiation and produces shock waves that propagate through the surrounding atmosphere. These processes initiate chemical reactions that can transform simple gases into more complex compounds. In order to study the production of organic compounds in plasmas (shocks), various mixtures of N2, CH4, and H2, modeling the atmosphere of Titan, were exposed to discrete sparks, laser-induced plasmas (LIP), an ultraviolet radiation. The yields of HCN and several simple hydrocarbons were measured by gas chromatography and compared to those calculated from a simple quenched thermodynamic equilibrium model. The agreement between experiment and theory was fair for HCN and C2H2. However, the agreement for C2H6 and the other hydrocarbons was poor, indicating that a more comprehensive theory is needed. Our experiments suggest that photolysis by ultraviolet light from the plasma is an important process in the synthesis. This was confirmed by the photolysis of gas samples exposed to the light but not to the shock waves emitted by the sparks. Hence, the results of these experiments demonstrate that the thermodynamic equilibrium theory does not adequately model lightning and meteor impacts and that photolysis must be included. Finally, the similarity in yields between the spark and the LIP experiments suggest that LIP provide valid and clean simulations of lightning and meteor impacts and that photolysis must be included. Finally, the similarity in yields between the spark and the LIP experiments suggests that LIP provide valid
Predictive spark timing method
Tang, D.L.; Chang, M.F.; Sultan, M.C.
This patent describes a method of determining spark time in a spark timing system of an internal combustion engine having a plurality of cylinders and a spark period for each cylinder in which a spark occurs. It comprises: generating at least one crankshaft position reference pulse for each spark firing event, the reference pulse nearest the next spark being set to occur within a same cylinder event as the next spark; measuring at least two reference periods between recent reference pulses; calculating the spark timing synchronously with crankshaft position by performing the calculation upon receipt of the reference pulse nearest the next spark; predicting the engine speed for the next spark period from at least two reference periods including the most recent reference period; and based on the predicted speed, calculating a spark time measured from the the reference pulse nearest the next spark.
2-dimensional simulations of electrically asymmetric capacitively coupled RF-discharges
NASA Astrophysics Data System (ADS)
Mohr, Sebastian; Schulze, Julian; Schuengel, Edmund; Czarnetzki, Uwe
Capactively coupled RF-discharges are widely used for surface treatment like the deposition of thin films. For industrial applications, the independent control of the ion flux to and the mean energy of the electrons impinging on the surfaces is desired. Experiments and 1D3v-PIC/MCC-simulations have shown that this independent control is possible by applying a fundamental frequency and its second harmonic to the powered electrode. This way, even in geometrically symmetric discharges, as they are often used in industrial reactors, a discharge asymmetry can be induced electrically, hence the name Electrical Asymmetry Effect (EAE). We performed 2D-simulations of electrically asymmetric discharges using HPEM by the group of Mark Kushner, a simulation tool suitable for simulating industrial reactors. First results are presented and compared to previously obtained experimental and simulation data. The comparison shows that for the first time, we succeeded in simulating electrically asymmetric discharges with a 2-dimensional simulation. Capactively coupled RF-discharges are widely used for surface treatment like the deposition of thin films. For industrial applications, the independent control of the ion flux to and the mean energy of the electrons impinging on the surfaces is desired. Experiments and 1D3v-PIC/MCC-simulations have shown that this independent control is possible by applying a fundamental frequency and its second harmonic to the powered electrode. This way, even in geometrically symmetric discharges, as they are often used in industrial reactors, a discharge asymmetry can be induced electrically, hence the name Electrical Asymmetry Effect (EAE). We performed 2D-simulations of electrically asymmetric discharges using HPEM by the group of Mark Kushner, a simulation tool suitable for simulating industrial reactors. First results are presented and compared to previously obtained experimental and simulation data. The comparison shows that for the first time, we
An Research on Electrical Vehicle'S Charge-Discharge Behavior Based on Logit Model
NASA Astrophysics Data System (ADS)
Xiaoyin, Wang; Junyong, Liu
Electric Vehicle is the future trend of the automobile industry, and the energy exchanging between the electrical vehicles and the grid through the vehicle-to-grid (V2G) technology becomes possiable. V2G leads to a rapid load growth effecting the benefit of the grid, which wasn't discussed. The charge and discharge model of the electrical vehicles is discussed using the multinomial logit model based on the discrete choice theory, then preliminarily evaluates the effects of economic benefit both on the motorist and the grid. Finally, suggestions on period division and electricity pricing for charge and discharge of the electrical vehicle are given.
Temporal characteristics of the pulsed electric discharges in small gaps filled with hydrocarbon oil
NASA Astrophysics Data System (ADS)
Maradia, U.; Hollenstein, Ch; Wegener, K.
In order to understand the role of electrode materials in electrical discharges with micro gaps (<200 µm) filled with a liquid hydrocarbon dielectric, the post-breakdown phase of low ignition voltage (100 V) and low current (<20 A) pulsed electric discharges is experimentally investigated. The electric discharge energies are selected in the range from 1 to 150 mJ. Due to the non-repetitive and transient nature of the micro-discharges, time-resolved imaging, spectroscopy and electrical analysis of single discharges are performed. The plasma-material interaction is investigated by analysing the erosion craters on anode and cathode. It is found that the electrode materials in these multiphase discharges affect the gas bubble dynamics, the transport properties of the discharge plasmas and the transition from the gaseous to metallic vapour plasma. The change in the energy fractions dissipated in the electrodes in function of the discharge time is influenced by the thermo-physical properties of the electrode materials. The simulation of craters in multiple discharge process requires consideration of the gas bubble dynamics due to different energy fractions and plasma flushing efficiencies.
Application of Microsecond Voltage Pulses for Water Disinfection by Diaphragm Electric Discharge
NASA Astrophysics Data System (ADS)
Kakaurov, S. V.; Suvorov, I. F.; Yudin, A. S.; Solovyova, T. L.; Kuznetsova, N. S.
The paper presents the dependence of copper and silver ions formation on the duration of voltage pulses of diaphragm electric discharge and on the pH of treated liquid medium. Knowing it allows one to create an automatic control system to control bactericidal agent's parameters obtained in diaphragm electric discharge reactor. The current-voltage characteristic of the reactor with a horizontal to the diaphragm membrane water flow powered from the author's custom pulse voltage source is also presented. The results of studies of the power consumption of diaphragm electric discharge depending on temperature of the treated liquid medium are given.
Ultraviolet radiation induced discharge laser
Gilson, Verle A.; Schriever, Richard L.; Shearer, James W.
An ultraviolet radiation source associated with a suitable cathode-anode electrode structure, disposed in a gas-filled cavity of a high pressure pulsed laser, such as a transverse electric atmosphere (TEA) laser, to achieve free electron production in the gas by photoelectric interaction between ultraviolet radiation and the cathode prior to the gas-exciting cathode-to-anode electrical discharge, thereby providing volume ionization of the gas. The ultraviolet radiation is produced by a light source or by a spark discharge.
Phase and amplitude maps of the electric organ discharge of the weakly electric fish, Apteronotus leptorhynchus.
Rasnow, B; Assad, C; Bower, J M
The electric organ discharge (EOD) potential was mapped on the skin and midplane of several Apteronotus leptorhynchus. The frequency components of the EOD on the surface of the fish have extremely stable amplitude and phase. However, the waveform varies considerably with different positions on the body surface. Peaks and zero crossings of the potential propagate along the fish's body, and there is no point where the potential is always zero. The EOD differs significantly from a sinusoid over at least one third of the body and tail. A qualitative comparison between fish showed that each individual had a unique spatiotemporal pattern of the EOD potential on its body. The potential waveforms have been assembled into high temporal and spatial resolution maps which show the dynamics of the EOD. Animation sequences and Macintosh software are available by anonymous ftp (mordor.cns.caltech.edu; cd/pub/ElectricFish). We interpret the EOD maps in terms of ramifications on electric organ control and electroreception. The electrocytes comprising the electric organ do not all fire in unison, indicating that the command pathway is not synchronized overall. The maps suggest that electroreceptors in different regions fulfill different computational roles in electroreception. Receptor mechanisms may exist to make use of the phase information or harmonic content of the EOD, so that both spatial and temporal patterns could contribute information useful for electrolocation and communication. PMID:8315610
Electric discharge synthesis of HCN in simulated Jovian atmospheres
NASA Astrophysics Data System (ADS)
Stribling, R.; Miller, S. L.
HCN energy yields (moles J-1) were measured using corona discharge for gas mixtures containing H2, CH4, NH3, with H2/CH4 ratios from 4.4 to 1585. The yields are approximately proportional to the mole fraction of methane in the gas mixture. Assuming that the 3/1 ratio of corona discharge to lightning energy on the Earth applies to Jupiter, HCN column densities from corona discharge could account for approximately 10% of the observed HCN. These estimates are very dependent on the values used for the energy available as lightning on Jupiter and the eddy diffusion coefficients in the region of synthesis.
Gann, R.A.
This patent describes a direct spark ignition system having a gas burner, an electrically operable valve connected to the burner to admit fuel thereto, a gated oscillator having a timing circuit for timing a trial ignition, a spark generator responsive to the oscillator for igniting fuel emanating from the burner, and a flame sensor for sustaining oscillations of the oscillator while a flame exists at the burner. The spark generator has an inverter connected to a low voltage dc source and responsive to the oscillator for converting the dc voltage to a high ac voltage, a means for rectifying the high ac voltage, a capacitor connected to the rectifying means for storing the rectified high voltage, an ignition coil in series between the storage capacitor and a switch, and a means for periodically turning on the switch to produce ignition pulses through the coil. The ignition system is powered from the dc source but controlled by the oscillator. An improvement described here is wherein the inverter is comprised of a step-up transformer having its primary winding connected in series with the dc source and a common emitter transistor having its collector connected to the primary winding. The transistor has its base connected to be controlled by the oscillator to chop the dc into ac in the primary winding, and a diode connected between the storage capacitor and the collector of the transistor, the diode being poled to couple into the capacitor back EMF energy when the transistor is turned off.
Electric Organ Discharges of Mormyrid Fish as a Possible Cue for Predatory Catfish
NASA Astrophysics Data System (ADS)
Hanika, S.; Kramer, B.
During reproductive migration the electroreceptive African sharptooth catfish, Clarias gariepinus (Siluriformes), preys mainly on a weakly electric fish, the bulldog Marcusenius macrolepidotus (Mormyridae; Merron 1993). This is puzzling because the electric organ discharges of known Marcusenius species are pulses of a duration (<1ms) too short for being detected by the catfishes' low-frequency electroreceptive system (optimum sensitivity, 10-30Hz Peters and Bretschneider 1981). On the recent discovery that M. macrolepidotus males emit discharges lasting approximately ten times longer than those of females (Kramer 1997a) we determined behavioral thresholds for discharges of both sexes, using synthetic playbacks of field-recorded discharges. C. gariepinus detected M. macrolepidotus male discharges down to a field gradient of 103μVpeak-peak/cm and up to a distance of 1.5m at natural field conditions. In contrast, thresholds for female discharges were not reached with our setup, and we presume the bulldogs eaten by catfish are predominantly male.
High-voltage spark atomic emission detector for gas chromatography
NASA Technical Reports Server (NTRS)
Calkin, C. L.; Koeplin, S. M.; Crouch, S. R.
A dc-powered, double-gap, miniature nanosecond spark source for emission spectrochemical analysis of gas chromatographic effluents is described. The spark is formed between two thoriated tungsten electrodes by the discharge of a coaxial capacitor. The spark detector is coupled to the gas chromatograph by a heated transfer line. The gas chromatographic effluent is introduced into the heated spark chamber where atomization and excitation of the effluent occurs upon breakdown of the analytical gap. A microcomputer-controlled data acquisition system allows the implementation of time-resolution techniques to distinguish between the analyte emission and the background continuum produced by the spark discharge. Multiple sparks are computer averaged to improve the signal-to-noise ratio. The application of the spark detector for element-selective detection of metals and nonmetals is reported.
Development of a web application for estimate the total charge in an electric discharge
NASA Astrophysics Data System (ADS)
Vera-Rivera, F. H.; Dugar-Zhabon, V. D.; Dulce-Moreno, H. J.; V-Niño, E. D.
This research seeks to implement a web application to estimate the total charge in an electric discharge from the experimental parameters established in reactors such as the JUPITER-MOSMET [1-5], used to perform surface modifications of metallic and nonmetallic species in solids substrates by hybrid discharges pulsed of high voltage and electric arc at low pressures [6-13]. Estimate the total charge generated in an electric discharge will allow to know the approximate value of the dose of ions implanted in the material surface [14-15], which are of great importance in each one of the experiments performed in the plasma laboratory of the Universidad Industrial de Santander (UIS), where the reactor is installed. Currently there are no applications developed to ease the process optimization and estimate the total charge generated in a pulsed electric discharge.
The electrical asymmetry effect in capacitively coupled radio-frequency discharges
NASA Astrophysics Data System (ADS)
Czarnetzki, U.; Schulze, J.; Schüngel, E.; Donkó, Z.
We present an analytical model to describe capacitively coupled radio-frequency (CCRF) discharges and the electrical asymmetry effect (EAE) based on the non-linearity of the boundary sheaths. The model describes various discharge types, e.g. single and multi-frequency as well as geometrically symmetric and asymmetric discharges. It yields simple analytical expressions for important plasma parameters such as the dc self-bias, the uncompensated charge in both sheaths, the discharge current and the power dissipated to electrons. Based on the model results the EAE is understood. This effect allows control of the symmetry of CCRF discharges driven by multiple consecutive harmonics of a fundamental frequency electrically by tuning the individual phase shifts between the driving frequencies. This novel class of capacitive radio-frequency (RF) discharges has various advantages: (i) A variable dc self-bias can be generated as a function of the phase shifts between the driving frequencies. In this way, the symmetry of the sheaths in geometrically symmetric discharges can be broken and controlled for the first time. (ii) Almost ideal separate control of ion energy and flux at the electrodes can be realized in contrast to classical dual-frequency discharges driven by two substantially different frequencies. (iii) Non-linear self-excited plasma series resonance oscillations of the RF current can be switched on and off electrically even in geometrically symmetric discharges. Here, the basics of the EAE are introduced and its main applications are discussed based on experimental, simulation, and modeling results.
Evaluation of plasma pressure of high current low inductance vacuum spark on cathode surface
NASA Astrophysics Data System (ADS)
Sarantsev, S. A.
This paper presents evaluation of the plasma pressure in a high current, low inductance vacuum spark on the cathode surface (the electrode material is steel). Calculations are provided for the first half period of the discharge, wherein the cathode surface is subjected to the most severe impacts (micropinches are created resulting in high-energy plasma beams). The evaluations were made using the experimental data obtained on the Pion device. The data of electrical measurements of the discharge current, the average plasma flow values obtained with the multi-grid probe and the data from a cathode macrostructure study were used. The results are given for different values of the discharge current.
Signal enhancement of lead and arsenic in soil using laser ablation combined with fast electric discharge
NASA Astrophysics Data System (ADS)
Kexue, L. I.; Zhou, Weidong; Shen, Qinmei; Shao, Jie; Qian, Huiguo
In comparison to the traditional single pulse laser induced breakdown spectroscopy (SP-LIBS), a significant enhancement of atomic emission of lead and arsenic from laser plasma of soil has been demonstrated by the use of a laser ablation and fast pulse discharge plasma spectroscopy technique (LA-FPDPS). In this technique, a specifically designed high voltage and rapid discharge circuit was used to reheat the laser plasma and to enhance the plasma emission. A rapid and time damped alternating discharge current was observed with a short oscillating period ˜ 0.6 μs and sustained for about 6 μs. The peak intensities of Pb (283.31 nm) and As (286.04 nm) lines from soil plasma emission were greatly enhanced when compare to the traditional single pulse (SP) LIBS system. In addition, the precision of measurements in terms of the relative standard deviation (RSD) and the signal to noise ( S/ N) ratios were also improved. Scanning electron microscopy (SEM) images of the laser ablation regions indicated that the plasma reheating by the discharge spark was presumably the main mechanism for observed signal enhancement in the LA-FPDPS technique.
Oxygen discharge and post-discharge kinetics experiments and modeling for the electric oxygen-iodine laser system.
Palla, A D; Zimmerman, J W; Woodard, B S; Carroll, D L; Verdeyen, J T; Lim, T C; Solomon, W C
Laser oscillation at 1315 nm on the I(2P1/2)-->I(2P3/2) transition of atomic iodine has been obtained by a near resonant energy transfer from O2(a1Delta) produced using a low-pressure oxygen/helium/nitric oxide discharge. In the electric discharge oxygen-iodine laser (ElectricOIL) the discharge production of atomic oxygen, ozone, and other excited species adds levels of complexity to the singlet oxygen generator (SOG) kinetics which are not encountered in a classic purely chemical O2(a1Delta) generation system. The advanced model BLAZE-IV has been introduced to study the energy-transfer laser system dynamics and kinetics. Levels of singlet oxygen, oxygen atoms, and ozone are measured experimentally and compared with calculations. The new BLAZE-IV model is in reasonable agreement with O3, O atom, and gas temperature measurements but is under-predicting the increase in O2(a1Delta) concentration resulting from the presence of NO in the discharge and under-predicting the O2(b1Sigma) concentrations. A key conclusion is that the removal of oxygen atoms by NOX species leads to a significant increase in O2(a1Delta) concentrations downstream of the discharge in part via a recycling process; however, there are still some important processes related to the NOX discharge kinetics that are missing from the present modeling. Further, the removal of oxygen atoms dramatically inhibits the production of ozone in the downstream kinetics. PMID:17461557
Response of nickel to zinc cells to electric vehicle chopper discharge waveforms
NASA Technical Reports Server (NTRS)
Cataldo, R. L.
The preliminary results of simulated electric vehicle chopper controlled discharge of a Nickel/Zinc battery shows delivered energy increases of 5 to 25 percent compared to constant current discharges of the same average current. The percentage increase was a function of chopper frequency, the ratio of peak to average current, and the magnitude of the discharge current. Because the chopper effects are of a complex nature, electric vehicle battery/speed controller interaction must be carefully considered in vehicle design to optimize battery performance.
Laser electric field measurement in open-air dielectric barrier discharges
NASA Astrophysics Data System (ADS)
Ito, Tsuyohito; Kanazawa, Tatsuya; Hamaguchi, Satoshi
Electric field induced coherent Raman scattering (E-CRS) measurement is a promising technique for measuring electric field in high-pressure environments. In this study, the discharge initiation mechanism of nanosecond dielectric barrier discharges (DBDs) in open air has been examined with time dependent measurement of the discharge electric field by E-CRS. Two pulsed ns laser beams (532 nm and 607 nm) are employed. In the presence of nitrogen molecules the two laser beams together with the electric field induce a coherent IR signal at a wavelength of 4.29 μm and the normal coherent anti-Stokes Raman scattering (CARS) signal at 473 nm. The ratio of these two signals (IR and CARS) is a function of the electric field strength, so that the magnitude of the electric field can be estimated. Our experimental observations have revealed that, in the pre-breakdown phase of a nanosecond DBD discharge, the externally applied fast-rising electric field is strongly enhanced near the cathode due to large accumulation of space charge, which then strongly enhances ionization near the cathode. This process is essentially different from the well-known Townsend mechanism for slower discharges.
Photo-triggering and secondary electron produced ionization in electric discharge ArF* excimer lasers
NASA Astrophysics Data System (ADS)
Xiong, Zhongmin; Kushner, Mark J.
Electric discharge excimer lasers are sustained in multi-atmosphere attaching gas mixtures that are typically preionized to enable a reproducible, uniform glow, which maximizes optical quality and gain. This preionization is often accomplished using UV light produced by a corona discharge within the plasma cavity. To quantify the relationship between corona discharge properties and those of the laser discharge, the triggering of electron avalanche by preionizing UV light in an electric discharge-pumped ArF* excimer laser was numerically investigated using a two-dimensional model. The preionizing UV fluxes were generated by a corona-bar discharge driven by the same voltage pulse as the main discharge sustained in a multi-atmospheric Ne/Ar/Xe/F2 gas mixture. The resulting peak photo-electron density in the inter-electrode spacing is around 108 cm-3, and its distribution is biased toward the UV source. The preionization density increases with increasing dielectric constant and capacitance of the corona bar. The symmetry and uniformity of the discharge are, however, improved significantly once the main avalanche develops. In addition to bulk electron impact ionization, the ionization generated by sheath accelerated secondary electrons was found to be important in sustaining the discharge current at experimentally observed values. At peak current, the magnitude of the ionization by sheath accelerated electrons is comparable to that from bulk electron impact in the vicinity of the cathode.
Field reversals in electrically asymmetric capacitively coupled radio-frequency discharges in hydrogen
NASA Astrophysics Data System (ADS)
Mohr, Sebastian; Schüngel, Edmund; Schulze, Julian; Czarnetzki, Uwe
In this paper, we present a simulation study of electrically asymmetric capacitively coupled radio-frequency hydrogen discharges using the hybrid plasma equipment model operated at the combined frequencies of 10 and 20 MHz. We find that, in such discharges, field reversals cause ionization near the electrodes during the sheath collapse. In the case of the investigated asymmetric voltage waveforms, the field reversals are asymmetrically distributed over the sheaths, which causes asymmetric ionization and density profiles. The asymmetry of these profiles can be controlled by the phase angle between the two frequencies. As a result, the possibility to control the ion energy independently from the ion flux via the electrical asymmetry effect (EAE) is reduced in discharges displaying strong field reversals, as the asymmetric field reversals compensate the electrically induced asymmetry. The reason for this is understood by an analytical model. Furthermore, we demonstrate, that the EAE can be restored by the addition of specific gases to a pure hydrogen discharge.
Plasma synthetic jet actuator: electrical and optical analysis of the discharge
NASA Astrophysics Data System (ADS)
Belinger, A.; Naudé, N.; Cambronne, J. P.; Caruana, D.
Active flow control is based on the development of robust actuators which are reliable, small and easy to integrate. A promising actuator referred to as plasma synthetic jet actuator produces a synthetic jet with high exhaust velocities and holds the promise of enabling high-speed flows. With this high velocity jet, it is possible to reduce fluid phenomena such as transition and turbulence, thus making it possible to increase an aircraft's performance whilst at the same time reducing its environmental impact. This high velocity jet is produced by a pulsed discharge in a microcavity. In this paper, we focus on the properties of the discharge in order to understand the functioning of the actuator. In the first part an electrical description of the discharge in presented. Afterwards, optical measurements (optical emission spectroscopy and ICCD photograph) enable the determination of temperature, volume and duration of the discharge. At the end of the paper we present an electrical model of the discharge, which can be obtained both from electrical measurements and from macroscopic properties of the discharge (temperature, volume). This electrical model can easily be included in electrical simulation software.
Electric discharge in the water: physics of formation and radiative characteristics.
NASA Astrophysics Data System (ADS)
Anpilov, Andrei; Barkhudarov, Eduard; Kozlov, Yurii; Kossyi, Igor; Silakov, Valerii; Temchin, Savelii
ELECTRIC DISCHARGE IN THE WATER: PHYSICS OF FORMATION AND RADIATIVE CHARACTERISTICS 2.10. Lighting plasmas. 2.26. Other plasma topics. A.M.Anpilov, E.M.Barkhudarov, Yu.N.Kozlov, I.A.Kossyi, V.P.Silakov and S.M.Temchin Two types of electric discharge in the water have been investigated: discharge between two electrodes and multielectrode gliding surface discharge. Results are presented from experimental studies of the prebreakdown phase of an electric discharge between the point (anode) and plane (cathode) electrodes immersed in the water with different initial conductivity. When a high-voltage pulse is applied, the induced conductivity is detected in the discharge gap. Its value is one order of magnitude higher than the initial one. It is shown that the induced conductivity increases almost linearly with initial conductivity. The induced conductivity correlates with the UV emission from the cathode surface. A qualitative analysis of the experimental results is performed. Investigations of a spectrum of radiation of discharge in water have been carried out. On the base of broadening and shifting of atomic hydrogen and oxygen lines electron density in a prebreakdown as well as breakdown stages has been determined. Results are presented from investigations of multispark electric discharge in water excited along multielectrode metal-dielectric systems with gas supply into the interelectrode gaps. The intensity distribution of discharge radiation in the region covering the biologically active soft UV (190 £l£430 nm) has been determined and the absolute number of quanta in this wavelength interval has been measured. The potentiality of the gliding surface discharge in water for its disinfection is analysed.
Relativistic electrons from sparks in the laboratory
NASA Astrophysics Data System (ADS)
Østgaard, N.; Carlson, B. E.; Nisi, R. S.; Gjesteland, T.; Grøndahl, Ø.; Skeltved, A.; Lehtinen, N. G.; Mezentsev, A.; Marisaldi, M.; Kochkin, P.
Discharge experiments were carried out at the Eindhoven University of Technology in 2013. The experimental setup was designed to search for electrons produced in meter-scale sparks using a 1 MV Marx generator. Negative voltage was applied to the high voltage (HV) electrode. Five thin (1 mm) plastic detectors (5 cm2 each) were distributed in various configurations close to the spark gap. Earlier studies have shown (for HV negative) that X-rays are produced when a cloud of streamers is developed 30-60 cm from the negative electrode. This indicates that the electrons producing the X-rays are also accelerated at this location, that could be in the strong electric field from counterstreamers of opposite polarity. Comparing our measurements with modeling results, we find that ˜300 keV electrons produced about 30-60 cm from the negative electrode are the most likely source of our measurements. A statistical analysis of expected detection of photon bursts by these fiber detectors indicates that only 20%-45% of the detected bursts could be from soft (˜10 keV) photons, which further supports that the majority of detected bursts are produced by relativistic electrons.
Spark ignition systems for internal combustion engines
Gol, G.; Hill, W.F.
An internal combustion engine spark ignition system is provided which ensures that sparks are inhibited if the engine temperature exceeds a maximum safe level. The ignition circuit includes an input transistor which is switched on and off by an engine shaft transducer. The input transistor controls charging and discharging of a capacitor the voltage on which determines whether switching of the input transistor causes a spark to be produced via an output amplifier and ignition coil. A temperature sensing element determines both the rate at which the capacitor can charge and the final voltage to which it can be charged.
Vibrator improves spark erosion cutting process
NASA Technical Reports Server (NTRS)
Thrall, L. R.
Variable frequency mechanical vibrator improves spark erosion cutting process. The vibration of the cutting tip permits continual flushing away of residue around the cut area with nondestructive electric transformer oil during the cutting process.
Response of lead-acid batteries to chopper-controlled discharge. [for electric vehicles
NASA Technical Reports Server (NTRS)
Cataldo, R. L.
The results of tests on an electric vehicle battery, using a simulated electric vehicle chopper-speed controller, show energy output losses up to 25 percent compared to constant current discharges at the same average current of 100 A. However, an energy output increase of 22 percent is noticed at the 200 A average level and 44 percent increase at the 300 A level using pulse discharging. Because of these complex results, electric vehicle battery/speed controller interactions must be considered in vehicle design.
Method and apparatus for debris mitigation for an electrical discharge source
Klebanoff, Leonard E.; Rader, Daniel J.; Silfvast, William T.
Method and apparatus for mitigating the transport of debris generated and dispersed from electric discharge sources by thermophoretic and electrostatic deposition. A member is positioned adjacent the front electrode of an electric discharge source and used to establish a temperature difference between it and the front electrode. By flowing a gas between the member and the front electrode a temperature gradient is established that can be used for thermophoretic deposition of particulate debris on either the member or front electrode depending upon the direction of the thermal gradient. Establishing an electric field between the member and front electrode can aid in particle deposition by electrostatic deposition.
Metod And Apparatus For Debris Mitigation For An Electrical Discharge Source
Klebanoff, Leonard E.; Silfvast, William T.; Rader, Daniel J.
Method and apparatus for mitigating the transport of debris generated and dispersed from electric discharge sources by thermophoretic and electrostatic deposition. A member is positioned adjacent the front electrode of an electric discharge source and used to establish a temperature difference between it and the front electrode. By flowing a gas between the member and the front electrode a temperature gradient is established that can be used for thermophoretic deposition of particulate debris on either the member or front electrode depending upon the direction of the thermal gradient. Establishing an electric field between the member and front electrode can aid in particle deposition by electrostatic deposition.
High energy KrCl electric discharge laser
Sze, R.C.; Scott, P.B.
A high energy KrCl laser is presented for producing coherent radiation at 222 nm. Output energies on the order of 100 mJ per pulse are produced utilizing a discharge excitation source to minimize formation of molecular ions, thereby minimizing absorption of laser radiation by the active medium. Additionally, HCl is used as a halogen donor which undergoes a harpooning reaction with metastable Kr/sub M/ to form KrCl.
High energy KrCl electric discharge laser
Sze, Robert C.; Scott, Peter B.
A high energy KrCl laser for producing coherent radiation at 222 nm. Output energies on the order of 100 mJ per pulse are produced utilizing a discharge excitation source to minimize formation of molecular ions, thereby minimizing absorption of laser radiation by the active medium. Additionally, HCl is used as a halogen donor which undergoes a harpooning reaction with metastable Kr.sub.M * to form KrCl.
Initiation of a discharge channel in water by means of electrical explosion of aluminum foil
NASA Astrophysics Data System (ADS)
Sil'nikov, M. V.; Krivosheev, S. I.; Kulakov, K. S.; Kulakov, S. L.
This paper reports the results of an experimental investigation into initiation of the electric discharge in service water by means of explosion of aluminum foil having various mass and dimensions. The electric discharge was formed in a chamber with a movable wall (the piston). As an electric energy storage, the capacitor bank having the capacity C = 200-600 μF with charging voltage U 0 = 2-5 kV (stored energy Q 0 = 0.4-7.5 kJ) and the rate of rise of the discharging current dI/ dt = (3-4) × 109 A/s. The results of experiments showed that destruction (loss of conductivity) of foil occurs at the value of the integral of the current density h j = (0.3-0.65) × 109 (A2/cm4)/s. The stage of the repeated breakdown in the electric discharge occurs when the value of the intensity of the electric field along the discharge channel is of E rb ≥ 50 V/mm. Geometric dimensions and mass of the initiating conductor that provide the maximum efficiency of conversion of the value of Q 0 into kinetic energy of the piston have been determined.
Electric discharge in the Martian atmosphere, Paschen curves and implications for future missions
NASA Astrophysics Data System (ADS)
Manning, H. L. K.; ten Kate, I. L.; Battel, S. J.; Mahaffy, P. R.
Electric discharge between two electrically charged surfaces occurs at a well-defined, gas-dependent combination of atmospheric pressure and the distance between those two surfaces, as described by Paschen's law. The understanding of when the discharge will occur in the conditions present on Mars is essential for designing space-flight hardware that will operate on the Martian surface as well as understanding electrical discharge processes occurring in the Martian atmosphere. Here, we present experimentally measured Paschen curves for a gas mixture representative of the Martian atmosphere and compare our results to breakdown voltages of carbon dioxide, nitrogen, and helium as measured with our system and from the literature. We will discuss possible implications for instrument development as well as implications for processes in the Martian atmosphere. The DC voltage at which electric discharge occurred between two stainless steel spheres was measured at pressures from 10 -2 to 100 torr in all gases. We measured a minimum voltage for discharge in the Mars ambient atmosphere of 410 ± 10 V at 0.3 torr cm. As an application, the breakdown properties of space-qualified, electrical wires to be used in the Sample Analysis at Mars (SAM) instrument suite on the Mars Science Laboratory (MSL) were studied.
Electric Discharge in the Martian Atmosphere, Paschen Curves and Implications for Future Missions
NASA Astrophysics Data System (ADS)
Manning, Heidi L. K.; ten Kate, I. L.; Battel, S. J.; Mahaffy, P. R.
Electric discharge between two electrically charged surfaces occurs at a well-defined, gas-dependent combination of atmospheric pressure and the distance between those two surfaces, as described by Paschen's law. The understanding of when the discharge will occur in the conditions present on Mars is essential for designing space flight hardware that will operate on the Martian surface as well as understanding electrical discharge processes occurring in the Martian atmosphere. We present experimentally measured Paschen curves for a gas mixture representative of the Martian atmosphere and compare our results to breakdown voltages of carbon dioxide, nitrogen, and helium as measured with our system and from the literature. We will discuss possible implications for instrument development as well as implications for processes in the Martian atmosphere. The DC voltage at which electric discharge occurred between two stainless steel spheres was measured at pressures from 10-2 to 100 torr in all gases. We measured a minimum voltage for discharge in the Mars ambient atmosphere of 410±10 volts at 0.3 torr cm. As an application, the breakdown properties of space-qualified, electrical wires to be used in the Sample Analysis at Mars (SAM) instrument suite on the Mars Science Laboratory (MSL) were studied. H. Manning was funded in the framework of the Sample Analysis at Mars development; I. ten Kate was funded by the Goddard Center for Astrobiology.
Production of organic compounds in plasmas: A comparison among electric sparks, laser-induced plasmas and UV light
NASA Technical Reports Server (NTRS)
Scattergood, T. W.; Mckay, C. P.; Borucki, W. J.; Giver, L. P.; Vanghyseghem, H.; Parris, J. E.; Miller, S. L.
In order to study the production of organic compounds in plasmas (and shocks), various mixtures of N2, CH4, and H2, modeling the atmosphere of Titan, were exposed to discrete sparks, laser-induced plasmas (LIP) and ultraviolet light. The yields of HCN and simple hydrocarbons were measured and compared to those calculated from a simple quenched thermodynamic equilibrium model. The agreement between experiment and theory was fair for HCN and C2H2. However, the yields of C2H6 and other hydrocarbons were much higher than those predicted by the model. Our experiments suggest that photolysis by ultraviolet light from the plasma is an important process in the synthesis. This was confirmed by the photolysis of gas samples exposed to the light, but not to the plasma or shock waves. The results of these experiments demonstrate that, in addition to the well-known efficient synthesis of organic compounds in plasmas, the yields of saturated species, e.g., ethane, may be higher than predicted by theory and that LIP provide a convenient and clean way of simulating planetary lightning and impact plasmas in the laboratory.
Pulsed electric breakdown in adipose tissue
NASA Astrophysics Data System (ADS)
Kolb, Juergen F.; Scully, Noah; Paithankar, Dilip
High voltage pulses of sub-microsecond duration can instigate electrical breakdown in adipose tissue, which is followed by a spark discharge. Breakdown voltages are generally lower than observed for purified lipids but higher than for air. Development of breakdown for the repetitive application of pulses resembles a gradual and stochastic process as reported for partial discharges in solid dielectrics. The inflicted tissue damage itself is confined to the gap between electrodes, providing a method to use spark discharges as a precise surgical technique.
Fractal dynamics of electric discharges in a thundercloud.
Iudin, D I; Trakhtengerts, V Y; Hayakawa, M
We have investigated the fractal dynamics of intracloud microdischarges responsible for the formation of a so-called drainage system of electric charge transport inside a cloud volume. Microdischarges are related to the nonlinear stage of multiflow instability development, which leads to the generation of a small-scale intracloud electric structure. The latter is modeled by using a two-dimensional lattice of finite-state automata. The results of numerical simulations show that the developed drainage system belongs to the percolation-cluster family. We then point out the parameter region relevant to the proposed model, in which the thundercloud exhibits behavior corresponding to a regime of self-organized criticality. The initial development and statistical properties of dynamic conductive clusters are investigated, and a kinetic equation is introduced, which permits us to find state probabilities of electric cells and to estimate macroscopic parameters of the system. PMID:12935264
Television image of a large upward electrical discharge above a thunderstorm system
NASA Technical Reports Server (NTRS)
Franz, R. C.; Nemzek, R. J.; Winckler, J. R.
A low light-level TV camera is used to obtain an unusual image of luminous electrical discharge over a thunderstorm 250 km from the observation site. The image is presented and the discharge in the image is described. It is suggested that the image is probably due to two localized electric charge concentrations at the cloud tops. The hazard of these discharges for aircraft and rocket launches is examined. Consideration is given to the possibility that these discharges may account for unexplained photometric observations of distant lightning events that show a low rise rate of the luminous pulse and no electromagnetic sferic pulse like that in cloud-to-earth lightning strokes. The photometric events of this type that occurred on September 22-23, 1989 during hurricane Hugo are noted.
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.
NASA Technical Reports Server (NTRS)
Hoop, J. M.
Nondestructive testing by spark transducer induces ultrasonic pulses in materials without physical contact. High power pulse generator connected to step up transformer produces sparking between two tungsten rods and ultrasonic energy pulses in test samples placed between rods.
Electric field measurement in microwave discharge ion thruster with electro-optic probe.
Ise, Toshiyuki; Tsukizaki, Ryudo; Togo, Hiroyoshi; Koizumi, Hiroyuki; Kuninaka, Hitoshi
In order to understand the internal phenomena in a microwave discharge ion thruster, it is important to measure the distribution of the microwave electric field inside the discharge chamber, which is directly related to the plasma production. In this study, we proposed a novel method of measuring a microwave electric field with an electro-optic (EO) probe based on the Pockels effect. The probe, including a cooling system, contains no metal and can be accessed in the discharge chamber with less disruption to the microwave distribution. This method enables measurement of the electric field profile under ion beam acceleration. We first verified the measurement with the EO probe by a comparison with a finite-difference time domain numerical simulation of the microwave electric field in atmosphere. Second, we showed that the deviations of the reflected microwave power and the beam current were less than 8% due to inserting the EO probe into the ion thruster under ion beam acceleration. Finally, we successfully demonstrated the measurement of the electric-field profile in the ion thruster under ion beam acceleration. These measurements show that the electric field distribution in the thruster dramatically changes in the ion thruster under ion beam acceleration as the propellant mass flow rate increases. These results indicate that this new method using an EO probe can provide a useful guide for improving the propulsion of microwave discharge ion thrusters. PMID:23278009
Electric field measurement in microwave discharge ion thruster with electro-optic probe
Ise, Toshiyuki; Tsukizaki, Ryudo; Koizumi, Hiroyuki; Togo, Hiroyoshi; Kuninaka, Hitoshi
In order to understand the internal phenomena in a microwave discharge ion thruster, it is important to measure the distribution of the microwave electric field inside the discharge chamber, which is directly related to the plasma production. In this study, we proposed a novel method of measuring a microwave electric field with an electro-optic (EO) probe based on the Pockels effect. The probe, including a cooling system, contains no metal and can be accessed in the discharge chamber with less disruption to the microwave distribution. This method enables measurement of the electric field profile under ion beam acceleration. We first verified the measurement with the EO probe by a comparison with a finite-difference time domain numerical simulation of the microwave electric field in atmosphere. Second, we showed that the deviations of the reflected microwave power and the beam current were less than 8% due to inserting the EO probe into the ion thruster under ion beam acceleration. Finally, we successfully demonstrated the measurement of the electric-field profile in the ion thruster under ion beam acceleration. These measurements show that the electric field distribution in the thruster dramatically changes in the ion thruster under ion beam acceleration as the propellant mass flow rate increases. These results indicate that this new method using an EO probe can provide a useful guide for improving the propulsion of microwave discharge ion thrusters.
Low-pressure electrical discharge experiment to simulate high-altitude lightning above thunderclouds
NASA Technical Reports Server (NTRS)
Jarzembski, M. A.; Srivastava, V.
Recently, extremely interesting high-altitude cloud-ionosphere electrical discharges, like lightning above thunderstorms, have been observed from NASA's space shuttle missions and during airborne and ground-based experiments. To understand these discharges, a new experiment was conceived to simulate a thundercloud in a vacuum chamber using a dielectric in particulate form into which electrodes were inserted to create charge centers analogous to those in an electrified cloud. To represent the ionosphere, a conducting medium (metallic plate) was introduced at the top of the chamber. It was found that for different pressures between approximately 1 and 300 mb, corresponding to various upper atmospheric altitudes, different discharges occurred above the simulated thundercloud, and these bore a remarkable similarity to the observed atmospheric phenomena. At pressures greater than 300 mb, these discharges were rare and only discharges within the simulated thundercloud were observed. Use of a particulate dielectric was critical for the successful simulation of the high-altitude lightning.
Whealton, John H.; Tsai, Chin-Chi
A spark plug device includes a structure for modification of an arc, the modification including arc rotation. The spark plug can be used in a combustion engine to reduce emissions and/or improve fuel economy. A method for operating a spark plug and a combustion engine having the spark plug device includes the step of modifying an arc, the modifying including rotating the arc.
Apparatus and method for tuned unsteady flow purging of high pulse rate spark gaps
Thayer, III, William J.
A spark gap switch apparatus is disclosed which is capable of operating at a high pulse rate which comprises an insulated housing; a pair of spaced apart electrodes each having one end thereof within a first bore formed in the housing and defining a spark gap therebetween; a pressure wave reflector in the first bore in the housing and spaced from the spark gap and capable of admitting purge flow; and a second enlarged bore contiguous with the first bore and spaced from the opposite side of the spark gap; whereby pressure waves generated during discharge of a spark across the spark gap will reflect off the wave reflector and back from the enlarged bore to the spark gap to clear from the spark gap hot gases residues generated during the discharge and simultaneously restore the gas density and pressure in the spark gap to its initial value.
A tomographic visualization of electric discharge sound fields in atmospheric pressure plasma using laser diffraction
NASA Astrophysics Data System (ADS)
Nakamiya, Toshiyuki; Mitsugi, Fumiaki; Iwasaki, Yoichiro; Ikegami, Tomoaki; Tsuda, Ryoichi; Sonoda, Yoshito; Danuta Stryczewska, Henryka
The phase modulation of transparent gas can be detected using Fraunhofer diffraction technique, which we call optical wave microphone (OWM). The OWM is suitable for the detection of sonic wave from audible sound to ultrasonic wave. Because this technique has no influence on sound field or electric field during the measurement, we have applied it to the sound detection for the electric discharges. There is almost no research paper that uses the discharge sound to examine the electrical discharge phenomenon. Two-dimensional visualization of the sound field using the OWM is also possible when the computerized tomography (CT) is combined. In this work, coplanar dielectric barrier discharge sin different gases of Ar, N2, He were characterized via the OWM as well as applied voltage and discharge current. This is the first report to investigate the influence of the type of the atmospheric gas on the two-dimensional sound field distribution for the coplanar dielectric barrier discharge using the OWM with CT. Contribution to the Topical Issue "13th International Symposium on High Pressure Low Temperature Plasma Chemistry (Hakone XIII)", Edited by Nicolas Gherardi, Henryca Danuta Stryczewska and Yvan Ségui.
Locating groundwater discharge in large lakes using bottom sediment electrical conductivity mapping
NASA Astrophysics Data System (ADS)
Harvey, F. Edwin; Lee, David R.; Rudolph, David L.; Frape, Shaun K.
Groundwater-surface water studies that use conventional near-shore piezometers and /or seepage meters are impractical in larger, areal extensive lakes, as they require exorbitant numbers of instruments to quantify groundwater discharge zones. In smaller lakes an electrical conductivity mapping method has proven useful in mapping groundwater discharge zones. The technique identifies groundwater discharge by measuring variations in sediment pore water electrical conductivity and reduces the number of instruments necessary to quantify inflow, thereby lowering instrumentation costs and increasing a study's efficiency. This study sought to determine the technique's applicability in larger lakes. Thus the method was tested within the Hamilton Harbour, at the western end of Lake Ontario. This study found systematic variations between nearshore and offshore sediments and identified three anomalous zones that were thought to represent groundwater inflow. Onshore and offshore piezometers were used to verify the presence of upward gradients and elevated electrical conductivities. The sediment probe survey provided qualitative maps of areas of elevated electrical conductivity indicative of groundwater discharge and allowed a fairly extensive shoreline to be mapped quickly and economically. Survey results guided the installation of nearshore piezometers to discharge zones, eliminating the inefficiency of more conventional "hit or miss" point source installation approaches. This research demonstrated that the sediment probe was a valuable tool for studying groundwater inputs into large lakes.
Investigation of properties of coal-water slurries produced by electric discharge methods
NASA Astrophysics Data System (ADS)
Buyantuev, S.; Khmelev, A.; Kondratenko, A.; Baldynova, F.
The purpose of research is to obtain high quality coal-water slurry with minimum energy consumption. The paper presents the characteristics of coal-water slurries produced by electric discharge methods. The raw material is coal from different mines (Tugnuisky, Aduun- Chulunsky, etc.). Micrographs of the surface of the coal particles in the slurry and its chemical composition are obtained by scanning electron microscopy. Micrographs showed that the electric discharge treatment resulted in a significant dispersion of the coal particles. Elemental analysis showed a significant reduction of oxides of sulfur and nitrogen. Viscosity of slurries was determined by Brookfield rotational viscometer and corresponds to the standard of GB / T18856.4.
Transverse-type laser assembly using induced electrical discharge excitation and method
Ault, Earl R.
A transverse-type laser assembly is disclosed herein. This assembly defines a laser cavity containing a vapor or gaseous substance which lases when subjected to specific electrical discharge excitation between a pair of spaced-apart electrodes located within the cavity in order to produce a source of light. An arrangement located entirely outside the laser cavity is provided for inducing a voltage across the electrodes within the cavity sufficient to provide the necessary electrical discharge excitation to cause a vapor substance between the electrodes to lase.
Transverse-type laser assembly using induced electrical discharge excitation and method
Ault, E.R.
A transverse-type laser assembly is disclosed herein. This assembly defines a laser cavity containing a vapor or gaseous substance which lases when subjected to specific electrical discharge excitation between a pair of spaced-apart electrodes located within the cavity in order to produce a source of light. An arrangement located entirely outside the laser cavity is provided for inducing a voltage across the electrodes within the cavity sufficient to provide the necessary electrical discharge excitation to cause a vapor substance between the electrodes to lase. 3 figures.
Method for visualizing gas temperature distributions around hypersonic vehicles by using electric discharge
NASA Astrophysics Data System (ADS)
Nishio, Masatomi
A method for visualizing qualitative gas temperature distributions around hypersonic vehicles by taking a photograph of the electric discharge is proposed. A gas temperature distribution over a slightly blunted wedge is visualized using the electric discharge generated by a pair of point-line electrodes. A hypersonic tunnel used for the experiment is characterized by Mach 10, a freestream duration of 10 ms, and a stagnation temperature of the tunnel barrel of 1000 K. It is concluded that the photograph shows a radiation spectrum contrast near the model surface, from which a temperature layer is seen.
Discharge current and current of supershort avalanche E-beam at volume nanosecond discharge in non-uniform electric field
NASA Astrophysics Data System (ADS)
Tarasenko, Victor F.; Rybka, Dmitrii V.; Baksht, Evgenii H.; Kostyrya, Igor'D.; Lomaev, Mikhail I.
The gas diode current-voltage characteristics at the voltage pulses applied from the RADAN and SM-3NS pulsers, and generation of an supershort avalanche electron beam (SAEB) have been studied experimentally in an inhomogeneous electric field upon a nanosecond breakdown in an air gap at atmospheric pressure. Displacement currents with amplitude over 1 kA have been observed and monitored. It is shown that the displacement current amplitude gets increased due to movement of the dense plasma front and charging of a "capacitor" formed between plasma and anode. The SAEB generation time relatively to the discharge current pulses and the gap voltage were determined in the experiments. It is shown that the SAEB current maximum at the pulser voltages of hundreds kV is registered on the discharge current pulse front, before the discharge current peak of the gas diode capacitance, and the delay time of these peaks is determined by the value of an interelectrode spacing. The delay time in case of a gap of 16 mm and air breakdown at atmospheric pressure was ~100 ps, and in case of 10 mm it was less than 50 ps.
Plasma rotation by electric and magnetic fields in a discharge cylinder
NASA Technical Reports Server (NTRS)
Wilhelm, H. E.; Hong, S. H.
A theoretical model for an electric discharge consisting of a spatially diverging plasma sustained electrically between a small ring cathode and a larger ring anode in a cylindrical chamber with an axial magnetic field is developed to study the rotation of the discharge plasma in the crossed electric and magnetic fields. The associated boundary-value problem for the coupled partial differential equations which describe the electric potential and the plasma velocity fields is solved in closed form. The electric field, current density, and velocity distributions are discussed in terms of the Hartmann number and the Hall coefficient. As a result of Lorentz forces, the plasma rotates with speeds as high as 1 million cm/sec around its axis of symmetry at typical conditions. As an application, it is noted that rotating discharges of this type could be used to develop a high-density plasma-ultracentrifuge driven by j x B forces, in which the lighter (heavier) ion and atom components would be enriched in (off) the center of the discharge cylinder.
Electron heating and the Electrical Asymmetry Effect in capacitively coupled RF discharges
NASA Astrophysics Data System (ADS)
Schulze, Julian
For applications of capacitive radio frequency discharges, the control of particle distribution functions at the substrate surface is essential. Their spatio-temporal shape is the result of complex heating mechanisms of the respective species. Enhanced process control, therefore, requires a detailed understanding of the heating dynamics. There are two known modes of discharge operation: α- and γ-mode. In α-mode, most ionization is caused by electron beams generated by the expanding sheaths and field reversals during sheath collapse, while in γ-mode secondary electrons dominate the ionisation. In strongly electronegative discharges, a third heating mode is observed. Due to the low electron density in the discharge center the bulk conductivity is reduced and a high electric field is generated to drive the RF current through the discharge center. In this field, electrons are accelerated and cause significant ionisation in the bulk. This bulk heating mode is observed experimentally and by PIC simulations in CF4 discharges. The electron dynamics and mode transitions as a function of driving voltage and pressure are discussed. Based on a detailed understanding of the heating dynamics, the concept of separate control of the ion mean energy and flux in classical dual-frequency discharges is demonstrated to fail under process relevant conditions. To overcome these limitations of process control, the Electrical Asymmetry Effect (EAE) is proposed in discharges driven at multiple consecutive harmonics with adjustable phase shifts between the driving frequencies. Its concept and a recipe to optimize the driving voltage waveform are introduced. The functionality of the EAE in different gases and first applications to large area solar cell manufacturing are discussed. Finally, limitations caused by the bulk heating in strongly electronegative discharges are outlined.
The electrical asymmetry effect in multi-frequency capacitively coupled radio frequency discharges
NASA Astrophysics Data System (ADS)
Schulze, J.; Schüngel, E.; Donkó, Z.; Czarnetzki, U.
The electrical asymmetry effect (EAE) in geometrically symmetric capacitively coupled radio frequency discharges operated at multiple consecutive harmonics is investigated by a particle-in-cell (PIC) simulation and an analytical model. The model is based on the original EAE model, which is extended by taking into account the floating potentials, the voltage drop across the plasma bulk, and the symmetry parameter resulting from the PIC simulation. Compared with electrically asymmetric dual-frequency discharges we find that (i) a significantly stronger dc self-bias can be generated electrically and that (ii) the mean ion energies at the electrodes can be controlled separately from the ion flux over a broader range by tuning the phase shifts between the individual voltage harmonics. A recipe for the optimization of the applied voltage waveform to generate the strongest possible dc self-bias electrically and to obtain maximum control of the ion energy via the EAE is presented.
Bibliography and author index for electrical discharges in vacuum (1897 to 1980)
Miller, H.C.
This bibliography covers the field of electrical discharges in vacuum, comprising both electrical breakdown in vacuum and vacuum arcs. A brief review section lists some review papers which would be helpful to the novice in this field. The bulk of the paper consists of bibliographic listings, arranged by year of publication and within each year, alphabetically by first author. An author index refers one to all papers authored or coauthored by a particular person. There are 2450 papers listed through December 1980.
Solid-state laser-pumped high-power electric-discharge HF laser
Velikanov, S D; Garanin, Sergey G; Kodola, B E; Komarov, Yu N; Shchurov, V V; Efanov, V M; Efanov, M V; Yarin, P M; Kazantsev, S Yu; Kononov, I G; Firsov, K N; Domazhirov, A P; Podlesnykh, S V; Sivachev, A A
We report the possibility of creating high-power nonchain electric-discharge HF lasers with an all-solid-state pump source. The maximum energy stored in the pump source capacitors based on solid-state FID-switches is 990 J for the open-circuit voltage of 240 kV. The pulse energy of 30 J is obtained in the hydrogen-containing SF{sub 6} mixture at the electric efficiency of the order of 3%. (lasers)
The aurora - An electrical discharge phenomenon surrounding the earth
NASA Technical Reports Server (NTRS)
Akasofu, S.-I.
An attempt to model the processes underlying the appearance of auroral phenomena as a chain of events beginning with power production and resulting in auroral light emissions is presented. Power is produced by the interaction of the solar wind with the earth magnetosphere, creating a dynamo effect which is a function of the solar wind speed and the magnitude and orientation of the solar wind magnetic field. The dynamo power generates the convective motion of magnetospheric plasma, and subsequent magnetic-field aligned currents communicate the dynamo power to the polar ionosphere. The currents close as Pederson currents, and the associated Lorentz force accelerates the ionosphere in the direction of the convective motion. An electric potential structure develops at a few thousand km height, forcing current-carrying electrons to flow down the field lines to the ionosphere, where interactions with atmospheric constituents create auroral displays.
Wire Electrical Discharge Truing of Metal Bond Diamond Grinding Wheels
McSpadden, SB
Cylindrical wire EDM profile truing of the metal bond diamond wheel for precision form grinding of ceramics is presented in this report. First a corrosion-resistant, precise spindle with the high-electrical current capability for wire EDM truing of grinding wheel was fabricated. An arc profile was adopted in order to determine form tolerances capabilities of this process. Results show the wire EDM process can generate {micro}m-scale precision form on the diamond wheel efficiently. The wheel, after truing, was used to grind silicon nitride. Grinding forces, surface finish of ground components, and wheel wear were measured. The EDM trued wheel showed a reduction in grinding force from that of the stick dressed wheel. Surface finishes between the two truing methods were similar. In the beginning of the grinding, significant wheel wear rate was identified. The subsequent wheel wear rate stabilized and became considerably lower.
Electric-discharge contour-dynamics model: the effects of curvature and finite conductivity.
Arrayás, M; Fontelos, M A
In this paper we present the complete derivation of the effective contour model for electrical discharges which appears as the asymptotic limit of the minimal streamer model for the propagation of electric discharges, when the electron diffusion is small. It consists of two integro-differential equations defined at the boundary of the plasma region: one for the motion and a second equation for the net charge density at the interface. We have computed explicit solutions with cylindrical symmetry and found the dispersion relation for small symmetry-breaking perturbations in the case of finite resistivity. We implement a numerical procedure to solve our model in general situations. As a result we compute the dispersion relation for the cylindrical case and compare it with the analytical predictions. Comparisons with experimental data for a 2D positive streamers discharge are provided and predictions confirmed. PMID:21929117
Mechanism of singlet oxygen deactivation in an electric discharge oxygen – iodine laser
Azyazov, V N; Mikheyev, P A; Torbin, A P; Pershin, A A; Heaven, M C
We have determined the influence of the reaction of molecular singlet oxygen with a vibrationally excited ozone molecule O{sub 2}(a {sup 1}Δ) + O{sub 3}(ν) → 2O{sub 2} + O on the removal rate of O{sub 2}(a {sup 1}Δ) in an electric-discharge-driven oxygen – iodine laser. This reaction has been shown to be a major channel of O{sub 2}(a {sup 1}Δ) loss at the output of an electric-discharge singlet oxygen generator. In addition, it can also contribute significantly to the loss of O{sub 2}(a {sup 1}Δ) in the discharge region of the generator. (lasers)
Traveling wire electrode increases productivity of Electrical Discharge Machining /EDM/ equipment
NASA Technical Reports Server (NTRS)
Kotora, J., Jr.; Smith, S. V.
Traveling wire electrode on electrical discharge machining /EDM/ equipment reduces the time requirements for precision cutting. This device enables cutting with a minimum of lost material and without inducing stress beyond that inherent in the material. The use of wire increases accuracy and enables tighter tolerances to be maintained.
Erroneous discharge of an implantable cardioverter defibrillator caused by an electric razor.
Seifert, T; Block, M; Borggrefe, M; Breithardt, G
We report an unusual case of the erroneous discharge of a third-generation multiprogrammable implantable cardioverter defibrillator in a 64-year-old patient with a history of recurrent ventricular tachycardias caused by electromagnetic interference while shaving with an electric razor. Electromagnetic interference was related to a defect in the electrode's insulation and could not be provoked in an intact electrode. PMID:7479183
Electric discharge effects on a XeCl pumped S2 heat-pipe laser
NASA Technical Reports Server (NTRS)
Killeen, K.; Greenberg, K.; Verdeyen, J. T.
It is shown that an electrical discharge can dissociate the higher-order sulfur molecules S(3-8) into dimers S2 and thus create the proper environment for efficient conversion of XeCl radiation at 308 nm to the blue-green. The use of a heat-pipe configuration greatly alleviates the technological problems.
Recovery of electrical stability in the gaps after a sliding discharge on a dielectric surface
NASA Astrophysics Data System (ADS)
Belkov, E. P.; Dashuk, P. N.
Experimental results are presented on the recovery of electrical stability in gaps of air, argon, xenon, SF6, and argon-SF6 mixtures after a sliding discharge on a dielectric surface; pressure was in the range of 2500-9500, discharge current was in the range 2-4000 A, and current pulse duration was in the range 10-20 microsec. It is shown that after the discharge the breakdown voltage of the discharge gaps decreases to 0.1-0.4 U sub 0 (where U sub 0 is the breakdown voltage in the absence of a preliminary discharge) at current pulses of 150-4000 A and 10 microsec, and to 0.2-0.5 U sub 0 at 2-5 A and 10-20 microsec. After a streamer discharge, the breakdown voltage of the gaps decreases to 0.85-0.9 U sub 0; after the leader discharge it decreases to 0.6-0.8 U sub 0 in air, rare gases and the rare gas/SF6 mixture, and to 0.8-0.9 U sub 0 in pure SF6.
Numerical simulations of electrical asymmetry effect on electronegative plasmas in capacitively coupled rf discharge
NASA Astrophysics Data System (ADS)
Zhang, Quan-Zhi; Jiang, Wei; Hou, Lu-Jing; Wang, You-Nian
Recently a so-called electrical asymmetry effect (EAE), which could achieve high-degree separate control of ion flux and energy in dual-frequency capacitively coupled radio-frequency (CCRF) discharges, was discovered theoretically by Heil et al. [J. Phys. D: Appl. Phys. 41, 165202 (2008)] and was confirmed by experiments and theory/numerical simulations later on for electropositive argon discharges. In this work simulations based on particle-in-cell/Monte Carlo collision are performed to study the EAE on electronegative oxygen plasmas in geometrically symmetric CCRF discharges. Dual frequency discharges operating at 13.56 and 27.12 MHz are simulated for different pressures and the results are compared with those of electropositive argon discharges at the same conditions. It is found that in general the EAE on oxygen discharges has similar behavior as on argon discharge: The self-bias voltage η increases monotonically and almost linearly with the increase in the phase angle θ between the two driving voltages in the range 0<θ<90°, and the maximum ion energy varies by a factor of 3 by adjusting θ. However, the ion flux varies with θ by ±12% for low pressure and by ±15% for higher pressure, due primarily to an enhanced plasma series resonance, which then leads to dramatic changes in plasma density, power absorption and consequently the electronegativity. This may place a limitation for achieving separate control of ion energy and flux for electronegative plasma via the EAE.
Numerical simulations of electrical asymmetry effect on electronegative plasmas in capacitively coupled rf discharge
Zhang Quanzhi; Jiang Wei; Wang Younian; Hou Lujing
Recently a so-called electrical asymmetry effect (EAE), which could achieve high-degree separate control of ion flux and energy in dual-frequency capacitively coupled radio-frequency (CCRF) discharges, was discovered theoretically by Heil et al. [J. Phys. D: Appl. Phys. 41, 165202 (2008)] and was confirmed by experiments and theory/numerical simulations later on for electropositive argon discharges. In this work simulations based on particle-in-cell/Monte Carlo collision are performed to study the EAE on electronegative oxygen plasmas in geometrically symmetric CCRF discharges. Dual frequency discharges operating at 13.56 and 27.12 MHz are simulated for different pressures and the results are compared with those of electropositive argon discharges at the same conditions. It is found that in general the EAE on oxygen discharges has similar behavior as on argon discharge: The self-bias voltage {eta} increases monotonically and almost linearly with the increase in the phase angle {theta} between the two driving voltages in the range 0<{theta}<90 deg. , and the maximum ion energy varies by a factor of 3 by adjusting {theta}. However, the ion flux varies with {theta} by {+-}12% for low pressure and by {+-}15% for higher pressure, due primarily to an enhanced plasma series resonance, which then leads to dramatic changes in plasma density, power absorption and consequently the electronegativity. This may place a limitation for achieving separate control of ion energy and flux for electronegative plasma via the EAE.
Erosion of electrode metal in the electric discharge under the exposure of the electrolyte stream
NASA Astrophysics Data System (ADS)
Shakirov, Yu I.; Valiev, R. I.; Khafizov, A. A.; Valiev, R. A.; Khakimov, R. G.
The discharge between solid and liquid electrodes under the normal atmospheric conditions (SATP) was investigated. As electrodes, the metal materials and unsaturated salts solutions are used. Such discharge takes place in the range of voltage from 510 V to 525 V, a current from 0.2 A to 6 A, a electrolyte liquid flow rate from 2 cm3/s to 14 cm3/s, an electrolyte stream length from 5 mm to 40 mm. Increasing the flow rate of electrolyte liquid increases the discharge current. There are minimum and maximum critical values of the electrolyte flow rate of beyond which the existence of discharge is impossible. Specific values of the critical flow rate of the electrolyte depend on the nature, composition and stream length of the electrolyte. The electrical discharge between the electrolyte stream and a metal electrode is followed by erosion of the electrode material. The technique for local removal of metal by means of such a discharge is developed and the optimal values of erosion treatment parameters are determined. By using the discharge, technical processes of cleaning surface, deburring, drilling and cutting of metal materials were implemented.
Numerical modeling of the electrical breakdown and discharge properties of laser-generated plasma channels.
Petrova, Tz B; Ladouceur, H D; Baronavski, A P
An extensive nonequilibrium steady-state kinetics model incorporating collisional and radiative processes is developed to study the electrical breakdown and discharge maintenance of laser-induced atmospheric plasma channels formed in externally applied electric fields. The model is based upon a self-consistent numerical solution of the Boltzmann equation for the electron energy distribution function coupled with the electron energy balance equation and the population balance equations for electrons and air species. Using the electron energy distribution function, the ionization and electron attachment rates as a function of the reduced applied electric field at different degrees of ionization are calculated. We find that the ionization rate as a function of applied electric field in a laser-induced plasma channel is orders of magnitude larger than that obtained for a natural atmospheric air discharge. Therefore, the electrical breakdown of these plasma channels may occur at significantly lower applied electric fields. The present model predicts a breakdown electric field of 10kVcm , while the experimentally determined breakdown field strength is approximately 5.7kVcm [A. P. Baronavski, NRL Memorandum Report No. NRL/MR/6110-02-8642, 2002 (unpublished)], a reduction of about a factor of 5 from the natural Paschen electrical breakdown field of approximately 30kVcm . PMID:18233930
An investigation of the reduction of carbon dioxide in a silent electric discharge
NASA Technical Reports Server (NTRS)
Luce, R. S.; Greenough, B. (Editor)
The reduction of CO2 to O2 and CO in a silent electric discharge was studied. It was found that current alone (in the ionized plasma induced by the silent electric discharge) was reponsible for the CO2 reduction process. Voltage and frequency were important only in so far as they induced current in the plasma. Pressure and temperature were of minimum influence in the process. The large power consumption in the process was recognized as resulting from the low power factor of the reactor vessel which electrically behaved like a capacitor. The power factor was subsequently improved by adding an inductive element to make the reactor vessel capacitance part of a resonant circuit. It was found that the CO2 reduction process was most efficient in terms of power vs reduction rate when a voltage was employed that was only slightly higher than that needed to induce the plasma.
Prevention of ion flux inhomogeneities in large area capacitively coupled discharges via the Electrical Asymmetry Effect
NASA Astrophysics Data System (ADS)
Schuengel, Edmund; Schulze, Julian; Mohr, Sebastian; Czarnetzki, Uwe
For large area processing applications of capacitively coupled radio frequency (CCRF) discharges, the lateral uniformity of the plasma surface interaction is crucially important. The benefit of an increase in the plasma density and, therefore, in the overall deposition rate by driving the discharge at higher frequencies is accompanied with inhomogeneities caused by the presence of electromagnetic effects. Here, we propose a method based on the Electrical Asymmetry Effect (EAE) to prevent such inhomogeneities. Spatially resolved measurements of the ion flux onto the grounded electrode of a CCRF discharge operated in hydrogen show a standing wave pattern in a 81.36 MHz single-frequency discharge, strongly reducing the ion flux uniformity. However, applying a dual-frequency voltage waveform consisting of 40.68 MHz + 81.36 MHz, the lateral distribution of the ion flux can be controlled via the phase angle between the two applied harmonics. Using the EAE, a phase angle dependent DC self-bias develops in the geometrically symmetric discharge. Tuning the phase angle allows for the compensation of ion flux inhomogeneities due to the standing wave effect. Thus, a high and laterally uniform ion flux can be generated in electrically asymmetric high frequency plasmas. Funding by the German Federal Ministry for the Environment, Nature conservation, and Nuclear Safety (0325210B) is gratefully acknowledged.
Measurement and simulation of partial discharge in oil impregnated pressboard with an electrical aging process
NASA Astrophysics Data System (ADS)
Li, Junhao; Si, Wenrong; Yao, Xiu; Li, Yanming
The continuous test on oil impregnated pressboard insulation with internal void defect was developed and the phase resolved partial discharge (PRPD) pattern of partial discharge (PD) signals during the electrical aging process was measured. Two different void structures which have different void volume were used in this experiment. It shows that the PD pattern could be classified into five stages and a great diversity in the first four stages is observed. The larger void volume leads to larger PD magnitude. The computer numerical simulation model which is based on a physical discharge process was used and the causes of PD pattern change were interpreted by comparison with computer numerical simulation results. The initial values and change tendency of gas pressure and surface conductivity were determined through experiment. The model parameters in different stages have been studied as well as the insight into the physical changes in the void during electrical aging. The results provide rules for the identification of the electrical aging stage through the partial discharge measurements.
Electron heating and the electrical asymmetry effect in dual-frequency capacitive CF4 discharges
NASA Astrophysics Data System (ADS)
Schulze, J.; Derzsi, A.; Donkó, Z.
The electron heating and the electrical asymmetry effect (EAE) in electronegative dual-frequency capacitive CF4 discharges are investigated by particle-in-cell simulations and analytical modeling. One electrode is driven at 13.56 and 27.12 MHz with fixed but adjustable phase shift, θ, between the driving harmonics. First, the electron heating and ionization rates are studied, space and time resolved, for different phase shifts and pressures. The results are compared with those obtained for an electropositive gas (argon). In contrast to classical α- or γ-mode operation, we observe the electron heating and ionization rates to be high inside the bulk. This bulk heating mode is a consequence of the high electronegativity of CF4 discharges, where the conductivity in the bulk is low due to the low density of electrons. Thus, a high electric field builds up to drive the RF current through the bulk causing a high electron mean energy and ionization rate in the discharge center. Second, we investigate the consequences of the bulk heating on the EAE. We focus on the electrical generation of a dc self-bias as a function of θ and the quality of the separate control of the ion mean energy and flux at the electrodes by tuning θ. Compared with argon discharges the high voltage drop across the plasma bulk and the specific ionization dynamics affect the bias generation and the separate control of ion properties. These effects are described and explained by an analytical model.
Self-Consolidation Mechanism of Nanostructured Ti5Si3 Compact Induced by Electrical Discharge
Lee, W. H.; Cheon, Y. W.; Jo, Y. H.; Seong, J. G.; Jo, Y. J.; Kim, Y. H.; Noh, M. S.; Jeong, H. G.; Van Tyne, C. J.; Chang, S. Y.
Electrical discharge using a capacitance of 450 μF at 7.0 and 8.0 kJ input energies was applied to mechanical alloyed Ti5Si3 powder without applying any external pressure. A solid bulk of nanostructured Ti5Si3 with no compositional deviation was obtained in times as short as 159 μsec by the discharge. During an electrical discharge, the heat generated is the required parameter possibly to melt the Ti5Si3 particles and the pinch force can pressurize the melted powder without allowing the formation of pores. Followed rapid cooling preserved the nanostructure of consolidated Ti5Si3 compact. Three stepped processes during an electrical discharge for the formation of nanostructured Ti5Si3 compact are proposed: (a) a physical breakdown of the surface oxide of Ti5Si3 powder particles, (b) melting and condensation of Ti5Si3 powder by the heat and pinch pressure, respectively, and (c) rapid cooling for the preservation of nanostructure. Complete conversion yielding a single phase Ti5Si3 is primarily dominated by the solid-liquid mechanism. PMID:25884039
High voltage spark carbon fiber detection system
NASA Technical Reports Server (NTRS)
Yang, L. C.
The pulse discharge technique was used to determine the length and density of carbon fibers released from fiber composite materials during a fire or aircraft accident. Specifications are given for the system which uses the ability of a carbon fiber to initiate spark discharge across a high voltage biased grid to achieve accurate counting and sizing of fibers. The design of the system was optimized, and prototype hardware proved satisfactory in laboratory and field tests.
Ring-shaped electric discharge as an igniter of gas mixtures
NASA Astrophysics Data System (ADS)
Barkhudarov, E. M.; Berezhetskaya, N. K.; Kop'ev, V. A.; Kossyi, I. A.; Popov, N. A.; Taktakishvili, M. I.; Temchin, S. M.
Results are presented from experimental studies of ignition of a stoichiometric methane-oxygen mixture in a closed chamber by a ring electric discharge. It is shown that the process of fast (explosive) ignition of the reactor volume starts on the axis of the ring, near its centre, i.e. at a distance from the annular region of power deposition. Experimental evidence suggests that the ignition of a combustible gas mixture near the axis is triggered by strong gas-dynamic perturbations converging to the axis, radially propagating from the ring discharger.
Studies of oxygen-helium discharges for use in electric oxygen-iodine lasers
NASA Astrophysics Data System (ADS)
Zimmerman, Joseph William
In recent work, the performance of the Electric Oxygen-Iodine Laser (ElectricOIL), developed in partnership by researchers at the University of Illinois and CU Aerospace, has been greatly improved through systematic study of various components of this new laser technology. One major contribution to the advancement of ElectricOIL technology has been the development of electric discharges capable of producing significant flow rates of the precursor electronically-excited molecular oxygen, O2(a1Delta). O2(a 1Delta) serves as an energy reservoir in the laser system, pumping atomic iodine by near-resonant energy transfer producing gain and laser on the I(2P1/2) → I(2P3/2 ) transition at 1315 nm. Initial experimental work with radio-frequency discharges showed the importance of controlling O-atom flow rates to reduce quenching losses of energy stored in O2(a1Delta), and determined proper selection of the helium diluent ratio and specific power deposition (power per O2 flow rate). Further experimental investigations with transverse capacitive radio-frequency discharges in O2/He/NO mixtures in the pressure range of 1-100 Torr and power range of 0.1-1.2 kW have indicated that O2(a1Delta) production is a strong function of geometry (transverse gap), excitation frequency, and pressure. These parameters along with gas flow mixture dictate the current density at which the discharge operates, and its modal characteristics (normal vs. abnormal, homogeneous vs. inhomogeneous). A key result is that to encourage efficient O2(a1Delta) production these parameters should be selected in order to promote a homogeneous (low current density) discharge. The discharge behavior is characterized using terminal current-voltage-characteristics, microwave interferometer measurements, and plasma emission intensity measurements. Numerous spectroscopic measurements of O2(a1Delta), oxygen atoms, and discharge excited states are made in order to describe the discharge performance dependent on
Discharger Using Cascaded Switched Capacitor Converters and Selectable Intermediate Taps for Electric Double-Layer Capacitors
NASA Astrophysics Data System (ADS)
Uno, Masatoshi; Tanaka, Koji
Electric double-layer capacitors (EDLCs) offer several advantages over traditional batteries, such as long cycle life, high power capability, good low-temperature performance, etc. However, their major drawbacks, such as low specific energy and large voltage variation due to charge/discharge cycling, necessitate the use of high-efficiency power conversion electronics that can be used to efficiently discharge EDLCs and thus completely utilize the precious stored energy. In this study, we propose a novel discharger for EDLCs; this discharger uses cascaded switched capacitor converters (SCCs) and selectable intermediate taps. Although the voltage conversion ratio of SCCs is fixed, the load voltage can be maintained within a desired voltage range by the selectable intermediate taps. The circuit configuration, operating principle, and procedure for designing SCCs and selectable intermediate taps are presented. Experimental tests were performed using an EDLC module and a 200W prototype of the discharger. The obtained results showed that the 60V EDLC could be discharged to 30V with an average efficiency of 96% when the load voltage was maintained within the range 30-40V.
Electrical and optical characteristics of the radio frequency surface dielectric barrier discharge plasma actuation
NASA Astrophysics Data System (ADS)
Wei-Long, Wang; Hui-Min, Song; Jun, Li; Min, Jia; Yun, Wu; Di, Jin
Electrical characteristics and optical emission spectrum of the radio frequency (RF) surface dielectric barrier discharge (SDBD) plasma actuation are investigated experimentally in this paper. Influences of operating pressure, duty cycle and load power on the discharge are analyzed. When the operating pressure reaches 30 kPa, the discharge energy calculated from the Charge–Voltage (Q–V) Lissajous figure increases significantly, while the effective capacitance decreases remarkably. As the duty cycle of the applied voltage increases, the voltage–current waveforms, the area of Q–V loop and the capacity show no distinct changes. Below 40 W, effective capacitance increases with the increase of load power, but it almost remains unchanged when load power is between 40 W and 95 W. The relative intensity changes little as the operating pressure varies from 4 kPa to 100 kPa, while it rises evidently with the pressure below 4 kPa, which indicates that the RF discharge mode shifts from filamentary discharge to glow discharge at around 4 kPa. With the increase of load power, the relative intensity rises evidently. Additionally, the relative intensity is insensitive to the pressure, the duty cycle, and the load power. Project supported by the National Natural Science Foundation of China (Grant Nos. 11472306, 51276197, and 51336011).
Indirect determination of the electric field in plasma discharges using laser-induced fluorescence spectroscopy
Vaudolon, J. Mazouffre, S.
The evaluation of electric fields is of prime interest for the description of plasma characteristics. In this work, different methods for determining the electric field profile in low-pressure discharges using one- and two-dimensional Laser-Induced Fluorescence (LIF) measurements are presented and discussed. The energy conservation, fluid, and kinetic approaches appear to be well-suited for the electric field evaluation in this region of the plasma flow. However, the numerical complexity of a two-dimensional kinetic model is penalizing due to the limited signal-to-noise ratio that can be achieved, making the computation of the electric field subject to large error bars. The ionization contribution which appears in the fluid model makes it unattractive on an experimental viewpoint. The energy conservation and 1D1V kinetic approaches should therefore be preferred for the determination of the electric field when LIF data are used.
Mars Spark Source Prototype Developed
NASA Technical Reports Server (NTRS)
Eichenberg, Dennis J.; Lindamood, Glenn R.; VanderWal, Randall L.; Weiland, Karen J.
The Mars Spark Source Prototype (MSSP) hardware was developed as part of a proof of concept system for the detection of trace metals such as lead, cadmium, and arsenic in Martian dusts and soils. A spark discharge produces plasma from a soil sample, and detectors measure the optical emission from metals in the plasma to identify and quantify them. Trace metal measurements are vital in assessing whether or not the Martian environment will be toxic to human explorers. The current method of x-ray fluorescence can yield concentrations of major species only. Other instruments are incompatible with the volume, weight, and power constraints for a Mars mission. The new instrument will be developed primarily for use in the Martian environment, but it would be adaptable for terrestrial use in environmental monitoring. The NASA Glenn Research Center at Lewis Field initiated the development of the MSSP as part of Glenn's Director's Discretionary Fund project for the Spark Analysis Detection of Trace Metal Species in Martian Dusts and Soils. The objective of this project is to develop and demonstrate a compact, sensitive optical instrument for the detection of trace hazardous metals in Martian dusts and soils.
Sub-nanosecond dynamics of atmospheric air discharge under highly inhomogeneous and transient electric field
NASA Astrophysics Data System (ADS)
Tardiveau, Pierre; Magne, Lionel; Pasquiers, Stephane; Jeanney, Pascal; Bournonville, Blandine
The effects of the application of extreme overvoltages (>500%) in air gaps over less than a few nanoseconds bring us to reconsider the classical physics of streamer used to describe air discharges at atmospheric pressure. Non equilibrium discharges created by extremely transient and intense electric fields in standard conditions of pressure and temperature exhibit unusual diffuse and large structure. In point-to-plane electrode configurations, a plasma cloud is observed which properties depend on voltage pulses features (amplitude, rise time, length, and frequency) and electrodes properties (material, shape, and gap length). Our parametric experimental study is based on fast electrical characterization and sub-nanosecond imaging and shows the different stages of propagation of the cloud. This work details the conditions to maximize the cloud size without moving towards a multi-channel streamer regime. Based on the analysis and the Abel transform processing of the emission of excited states of nitrogen from the discharge, a focus is made on the structuration of the plasma cloud while it is propagating. It shows how much, according to the experimental conditions, the external electric field can be screened by the plasma and, inversely, how deep and how long a high electric field can be sustained in the gap, that is challenging for pulsed atmospheric plasmas applications. This work benefits from the financial support of the National Agency of Research within the framework of the project ANR-13-BS09-0014.
Measurement and modeling of electric field and space-charge distributions in obstructed helium discharge
Fendel, Peter; Ganguly, Biswa N.; Bletzinger, Peter
Axial and radial variations of electric field have been measured in dielectric shielded 0.025 m diameter parallel plate electrode with 0.0065 m gap for 1.6 mA, 2260 V helium dc discharge at 1.75 Torr. The axial and radial electric field profiles have been measured from the Stark splitting of 2{sup 1}S→11 {sup 1}P transition through collision induced fluorescence from 4{sup 3}D→2{sup 3}P. The electric field values showed a strong radial variation peaking to 500 kV/m near the cathode radial boundary, and decreasing to about 100 kV/m near the anode edge, suggesting the formation of an obstructed discharge for this low nd condition, where n is the gas density and d is the gap distance. The off-axis Stark spectra showed that the electric field vector deviates from normal to the cathode surface which permits longer path electron trajectories in the inter-electrode gap. Also, the on-axis electric field gradient was very small and off-axis electric field gradient was large indicating a radially non-uniform current density. In order to obtain information about the space charge distribution in this obstructed discharge, it was modeled using the 2-d axisymmetric Poisson solver with the COMSOL finite element modeling program. The best fit to the measured electric field distribution was obtained with a space charge variation of ρ(r) = ρ{sub 0}(r/r{sub 0}){sup 3}, where ρ(r) is the local space charge density, ρ{sub 0} = 6 × 10{sup −3} Coulomb/m{sup 3}, r is the local radial value, and r{sub 0} is the radius of the electrode.
Sparking rates measured on the CRITS RFQ
Balleyguier, P.
During the test of the LEDA injector on the CRITS RFQ, an automatic data acquisition system has been implemented. The purpose was to measure the sparking rate of this CW RFQ. The RF level has some influences on vacuum, but there is no evidence of any reciprocal effect. The raw sparking rate is very difficult to interpret, since burst of sparks bias the statistics. A more convenient and useful interpretation is the number of sparking seconds. At the nominal field level (1.75 Kilp), the sparking-second rate is 0.5 per minute without beam. It strongly depends on the field, with a logarithmic law: 4.5 decade/Kilp. With beam, the sparking rate jumps to 3.0 per minute. As far as tested, it depends neither on the beam current (20 to 80 mA) nor on the field (1.5 to 1.7 Kilp tested). With sparking rates as measured here, one could not hope to build an RFQ that would be free of sparks over a several months continuous operation. Such a requirement, based on an extrapolation of the curves presented here, would lead to a maximal electric field much lower than the Kilpatrick value, an unreasonable requirement for a functional RFQ. A conclusion is that a sparkless RFQ is hopeless, even with a very carefully conditioned cavity. It will probably be necessary to deal with a few sparks per day, and the linac must be able to restart automatically after a short beam interruption.
Waveform generation in the weakly electric fish Gymnotus coropinae (Hoedeman): the electric organ and the electric organ discharge.
Castelló, María E; Rodríguez-Cattáneo, Alejo; Aguilera, Pedro A; Iribarne, Leticia; Pereira, Ana Carolina; Caputi, Angel A
This article deals with the electric organ and its discharge in Gymnotus coropinae, a representative species of one of the three main clades of the genus. Three regions with bilateral symmetry are described: (1) subopercular (medial and lateral columns of complex shaped electrocytes); (2) abdominal (medial and lateral columns of cuboidal and fusiform electrocytes); and (3) main [four columns, one dorso-lateral (containing fusiform electrocytes) and three medial (containing cuboidal electrocytes)]. Subopercular electrocytes are all caudally innervated whereas two of the medial subopercular ones are also rostrally innervated. Fusiform electrocytes are medially innervated at the abdominal portion, and at their rostral and caudal poles at the main portion. Cuboidal electrocytes are always caudally innervated. The subopercular portion generates a slow head-negative wave (V(1r)) followed by a head-positive spike (V(3r)). The abdominal and main portions generate a fast tetra-phasic complex (V(2345ct)). Since subopercular components prevail in the near field and the rest in the far field, time coincidence of V(3r) with V(2) leads to different waveforms depending on the position of the receiver. This confirms the splitting hypothesis of communication and exploration channels based on the different timing, frequency band and reach of the regional waveforms. The following hypothesis is compatible with the observed anatomo-functional organization: V(1r) corresponds to the rostral activation of medial subopercular electrocytes and V(3r) to the caudal activation of all subopercular electrocytes; V(2), and part of V(3ct), corresponds to the successive activation of the rostral and caudal poles of dorso-lateral fusiform electrocytes; and V(345ct) is initiated in the caudal face of cuboidal electrocytes by synaptic activation (V(3ct)) and it is completed (V(45ct)) by the successive activation of rostral and caudal faces by the action currents evoked in the opposite face. PMID
Optical and electrical investigation of a cylindrical diffuse-discharge chamber
Teng, Yun; Li, Lee Cheng, Yong; Ma, Ning; Peng, Ming-yang; Liu, Ming-hai
More and more attention has been attached to atmospheric-pressure air diffuse plasma due to its enormous potential applications. In this paper, we designed a large-scale, cylindrical diffuse-plasma chamber using wire electrodes and a repetitive nanosecond pulse generator. The plasma chamber can be completely exposed in the open air without any barrier dielectric, and the length of cylindrical plasma chamber was extensible. Using optical and electrical measurements, we investigated the effects of electrode distance, electrode length, pulse repetition frequency, and electrode angle on the uniformity of discharge space. Four discharge regions were distinguished based on different spectral characteristics. Additionally, it was found that the discharge uniformity was improved as the electrode distance decreases, but remained almost constant with the variations of electrode length and pulse repetition frequency. Both of the plasma uniformity and the power density increased significantly as the electrode angle reduced.
Effects of the roughness characteristics on the wire tool surface for the electrical discharge machining properties
Fukuzawa, Yasushi; Yamashita, Masahide; Mamuro, Hiroaki; Yamashita, Ken; Ogata, Masayoshi
Wire electrical discharge machining (WEDM) has been investigated to obtain the better discharge machining properties of the removal rate and the surface roughness in a few decades. Recently, it revealed that the rough tool electrodes can improve the WEDM properties for some sort of materials. In this study, the rough wire electrodes using a wet blasting method was developed and evaluated the machining performance for the insulated Si{sub 3}N{sub 4} in the WEDM processes. As the results, it could not recognize the advantage of roughness wire electrode under the high-energy condition, but it found that the electro-conductive layer thickness became thinner in comparison with those of normal wires. On the contrary, it could be obtained the better surface roughness in the low energy condition. It was supposed that the roughed wire surface generates the homogeneous dispersion discharges on the workpiece.
Experimental characterization of plasma formation and shockwave propagation induced by high power pulsed underwater electrical discharge.
Claverie, A; Deroy, J; Boustie, M; Avrillaud, G; Chuvatin, A; Mazanchenko, E; Demol, G; Dramane, B
High power pulsed electrical discharges into liquids are investigated for new industrial applications based on the efficiency of controlled shock waves. We present here new experimental data obtained by combination of detailed high speed imaging equipments. It allows the visualization of the very first instants of plasma discharge formation, and then the pulsations of the gaseous bubble with an accurate timing of events. The time history of the expansion/compression of this bubble leads to an estimation of the energy effectively transferred to water during the discharge. Finally, the consecutive shock generation driven by this pulsating bubble is optically monitored by shadowgraphs and schlieren setup. These data provide essential information about the geometrical pattern and chronometry associated with the shock wave generation and propagation. PMID:24985821
Effects of the roughness characteristics on the wire tool surface for the electrical discharge machining properties
NASA Astrophysics Data System (ADS)
Fukuzawa, Yasushi; Yamashita, Masahide; Mamuro, Hiroaki; Yamashita, Ken; Ogata, Masayoshi
Wire electrical discharge machining (WEDM) has been investigated to obtain the better discharge machining properties of the removal rate and the surface roughness in a few decades. Recently, it revealed that the rough tool electrodes can improve the WEDM properties for some sort of materials. In this study, the rough wire electrodes using a wet blasting method was developed and evaluated the machining performance for the insulated Si3N4 in the WEDM processes. As the results, it could not recognize the advantage of roughness wire electrode under the high-energy condition, but it found that the electro-conductive layer thickness became thinner in comparison with those of normal wires. On the contrary, it could be obtained the better surface roughness in the low energy condition. It was supposed that the roughed wire surface generates the homogeneous dispersion discharges on the workpiece.
Self-pulsing discharges in pre-heated air at atmospheric pressure
NASA Astrophysics Data System (ADS)
Janda, Mário; Machala, Zdenko; Dvonč, Lukáš; Lacoste, Deanna; Laux, Christophe O.
The paper presents investigations of self-pulsing discharges in atmospheric pressure air pre-heated to 300-1000 K. Despite using a direct-current power supply, two self-pulsing discharge regimes, a repetitive transient spark (TS) and a repetitive streamer (RS) were generated. The pulse repetition frequency, on the order of a few kHz, can be controlled by adjusting the generator voltage. The TS is a discharge initiated by a streamer, followed by a short (tens of ns) spark current pulse (˜ 1 A), associated with the total discharging of the internal capacity of the electric circuit. The TS is suitable for the study of 'memory' effects (pre-heating, pre-ionization) on the mechanisms of streamer-to-spark transition and electrical breakdown in atmospheric pressure air. The TS regime was stable below ˜600 K. Above ˜600 K, a stable repetitive streamer (RS) regime was observed. In this regime, the breakdown and spark did not occur. After the initial streamer, the internal capacity of the electrical circuit discharged partially. With further pre-heating of the gas, the stable TS appeared again at ˜1000 K.
Extending lean operating limit and reducing emissions of methane spark-ignited engines using a microwave-assisted spark plug
Rapp, Vi H.; DeFilippo, Anthony; Saxena, Samveg; Chen, Jyh-Yuan; Dibble, Robert W.; Nishiyama, Atsushi; Moon, Ahsa; Ikeda, Yuji
Amore » microwave-assisted spark plug was used to extend the lean operating limit (lean limit) and reduce emissions of an engine burning methane-air. In-cylinder pressure data were collected at normalized air-fuel ratios of λ = 1.46, λ = 1.51, λ = 1.57, λ = 1.68, and λ = 1.75. For each λ, microwave energy (power supplied to the magnetron per engine cycle) was varied from 0 mJ (spark discharge alone) to 1600 mJ. At lean conditions, the results showed adding microwave energy to a standard spark plug discharge increased the number of complete combustion cycles, improving engine stability as compared to spark-only operation. Addition of microwave energy also increased the indicated thermal efficiency by 4% at λ = 1.68. At λ = 1.75, the spark discharge alone was unable to consistently ignite the air-fuel mixture, resulting in frequent misfires. Although microwave energy produced more consistent ignition than spark discharge alone at λ = 1.75, 59% of the cycles only partially burned. Overall, the microwave-assisted spark plug increased engine performance under lean operating conditions (λ = 1.68) but did not affect operation at conditions closer to stoichiometric.« less
Non-stationary corona around multi-point system in atmospheric electric field: I. Onset electric field and discharge current
NASA Astrophysics Data System (ADS)
Bazelyan, E. M.; Raizer, Yu. P.; Aleksandrov, N. L.
The properties of a non-stationary glow corona maintained near the tips of a multi-point ground system in a time-varying thundercloud electric field have been studied numerically and analytically. Computer and analytical models were developed to simulate the corona discharge initiated from a system of identical vertical conductive electrodes distributed uniformly over a grounded plane surface. The simulation was based on a solution of the electrostatic equation for electric field and continuity equations for light and aerosol ions. The development of individual corona space charge layers from different points and the formation of a united plane layer were considered. The effect of system dimensions and that of the distance between electrodes on the external electric field corresponding to corona onset near the rod tips was investigated. The evolution in time of the corona current was calculated for systems with various numbers of coronating rods in time-varying atmospheric electric field. In the limit of infinite number of coronating rods, reasonable agreement was obtained between numerical calculations and analytical theory considering the effect of surrounding rods on the corona discharge from a given rod in a simplified integral way. Conditions were determined under which the corona properties of a multi-point system are similar to the properties of a plane surface emitting ions into the atmosphere. In this case, the corona current density is governed by the time derivative of the thundercloud electric field and is independent of the ion mobility and of the coronating system dimensions. The total corona space charge injected into the atmosphere per unit area by a given instant is controlled by the thundercloud electric field at this instant and depends on the geometrical parameters of the system only indirectly, through the corona onset atmospheric electric field. This simple model could be used to simulate a corona discharge during thunderstorms at the earth�
Electric discharges produced by clouds of charged water droplets in the presence of moving conducting object
NASA Astrophysics Data System (ADS)
Kostinskiy, Alexander Y.; Syssoev, Vladimir S.; Mareev, Eugene A.; Rakov, Vladimir A.; Andreev, Mikhail G.; Bogatov, Nikolai A.; Makal'sky, Leonid M.; Sukharevsky, Dmitry I.; Aleshchenko, Alexander S.; Kuznetsov, Vladimir E.; Shatalina, Maria V.
The possibility of initiation of electric discharges by a crossbow bolt (projectile) moving in the electric field of a cloud of negatively charged water droplets has been demonstrated for the first time. Over one hundred of discharges have been produced. For each event, a high-speed video camera recorded the images of upward positive leaders developing from both the nearby grounded sphere and the projectile, followed by the return-stroke-like process. Corresponding currents were measured and integrated photos of the events were obtained. The results can help to improve our understanding of lightning initiation by airborne vehicles and by a vertical conductor rapidly extended below the thundercloud in order to trigger lightning with the rocket-and-wire technique.
Electron beam method and apparatus for obtaining uniform discharges in electrically pumped gas lasers
Fenstermacher, Charles A.; Boyer, Keith
A method and apparatus for obtaining uniform, high-energy, large-volume electrical discharges in the lasing medium of a gas laser whereby a high-energy electron beam is used as an external ionization source to ionize substantially the entire volume of the lasing medium which is then readily pumped by means of an applied potential less than the breakdown voltage of the medium. The method and apparatus are particularly useful in CO.sub.2 laser systems.
VUV generation by adiabatically expanded and excited by a DC electrical discharge Argon gas
Pipergias, K.; Yasemidis, D.; Reppa, E.; Pentaris, D.; Efthimiopoulos, T.; Merlemis, N.; Giannetas, V.
We investigate the emission of Argon (Ar) gas which is adiabatically expanded through a nozzle and excited using a DC electrical discharge. Because of the expansion and the electronic excitation, Ar dimers and clusters are formed, which give radiation in the second (2nd) and in the third (3rd) continua of Ar, centered at about 126 and 254 nm respectively. We particularly focus our study on the 2nd continuum, in order to develop a laser at this wavelength.
Production of ball-lightning-like luminous balls by electrical discharges in silicon.
Paiva, Gerson Silva; Pavão, Antonio Carlos; Alpes de Vasconcelos, Elder; Mendes, Odim; da Silva, Eronides Felisberto
We performed electric arc discharges in pure Si to generate luminous balls with lifetime in the order of seconds and several properties usually reported for natural ball lightning. This simple experiment does not rely on energy sources and excitation mechanisms that are improbable in the natural phenomenon and clearly demonstrates the role of vaporization and oxidation of Si, as proposed by the Abrahamson-Dinniss theory for ball-lightning formation. PMID:17358820
Production of Ball-Lightning-Like Luminous Balls by Electrical Discharges in Silicon
NASA Astrophysics Data System (ADS)
Paiva, Gerson Silva; Pavão, Antonio Carlos; Alpes de Vasconcelos, Elder; Mendes, Odim, Jr.; Felisberto da Silva, Eronides, Jr.
We performed electric arc discharges in pure Si to generate luminous balls with lifetime in the order of seconds and several properties usually reported for natural ball lightning. This simple experiment does not rely on energy sources and excitation mechanisms that are improbable in the natural phenomenon and clearly demonstrates the role of vaporization and oxidation of Si, as proposed by the Abrahamson-Dinniss theory for ball-lightning formation.
Investigation of the breakdown products produced from electrical discharge in selected CFC replacement fluids
Hawley-Fedder, R.; Goerz, D.; Koester, C.; Wilson, M.
LLNL personnel have designed and constructed a special purpose electrical test stand to evaluate CFCs and CFC replacement fluids under simulated AC, DC, and pulsed breakdown conditions. The test stand includes an electrical diagnostic system which allows the measurement of breakdown voltage, discharge current, arc power, and energy associated with each pulse. The appropriate data that is collected in order to correlate the quantity of by-products produced with the pertinent control variables, such as voltage, current, pulse width, pulse repetition frequency, and energy. Along with the electrical test stand, LLNL has extensive chemical analysis facilities that enable us to perform gas chromatographic and gas chromatographic-mass spectrometric analysis of various fluids to identify and quantify the breakdown products formed under various scenarios of electrical energy deposition.
The sparking voltage of spark plugs
NASA Technical Reports Server (NTRS)
Silsbee, F B
This report has been prepared in order to collect and correlate into convenient and useful form the available data on this subject. The importance of the subject lies in the fact that it forms the common meeting ground for studies of the performance of spark generators and spark plugs on the one hand and of the internal combustion engines on the other hand. While much of the data presented was obtained from various earlier publications, numerous places were found where necessary data were lacking, and these have been provided by experiments in gasoline engines at the Bureau of Standards.
Control of plasma properties in capacitively coupled oxygen discharges via the electrical asymmetry effect
NASA Astrophysics Data System (ADS)
Schüngel, E.; Zhang, Q.-Z.; Iwashita, S.; Schulze, J.; Hou, L.-J.; Wang, Y.-N.; Czarnetzki, U.
Using a combined experimental, numerical and analytical approach, we investigate the control of plasma properties via the electrical asymmetry effect (EAE) in a capacitively coupled oxygen discharge. In particular, we present the first experimental investigation of the EAE in electronegative discharges. A dual-frequency voltage source of 13.56 MHz and 27.12 MHz is applied to the powered electrode and the discharge symmetry is controlled by adjusting the phase angle θ between the two harmonics. It is found that the bulk position and density profiles of positive ions, negative ions, and electrons have a clear dependence on θ, while the peak densities and the electronegativity stay rather constant, largely due to the fact that the time-averaged power absorption by electrons is almost independent of θ. This indicates that the ion flux towards the powered electrode remains almost constant. Meanwhile, the dc self-bias and, consequently, the sheath widths and potential profile can be effectively tuned by varying θ. This enables a flexible control of the ion bombarding energy at the electrode. Therefore, our work proves the effectiveness of the EAE to realize separate control of ion flux and ion energy in electronegative discharges. At low pressure, the strength of resonance oscillations, which are found in the current of asymmetric discharges, can be controlled with θ.
Electrical behavior and vacuum ultraviolet radiation efficiency of monofilamentary xenon dielectric barrier discharges
Merbahi, N.; Ledru, G.; Sewraj, N.; Marchal, F.
In this paper we report the experimental investigation of a pure xenon monofilamentary dielectric barrier discharge (DBD), using a high voltage power supply. Stable microdischarges were achieved and studied in the pressure range of 100-400 Torr, at frequencies between 10 and 40 kHz. Successive 3 ns exposure time snapshots of the discharge clearly show how it built up. Its diameter was about 0.26 mm. The discharge voltage and current were determined from the measurement of the supply voltage and current. Compared to those in argon, the current pulses were shorter (less than 30 ns, above 200 Torr) and had much higher peak values. Ignition voltages were also higher in the heavier gas. Electrical energy and vacuum ultraviolet radiation energy of the second continuum of xenon were both independent of frequency. They both varied almost linearly with pressure. The measured DBD vuv efficiency of a single xenon microdischarge reported here was between 55% and 60%, and the maximum value was reached for 200 Torr. These values were twice those reported for multifilamentary discharges working with a sinusoidal supply. They were similar to those obtained for multifilamentary dielectric barrier discharges excited with short voltage pulses.
Basic energy efficiency of plasma production in electrical discharge and electron beam reactors
Penetrante, B.M.; Hsiao, M.C.; Bardsley, J.N.; Merritt, B.T.; Vogtlin, G.E.; Kuthi, A.; Burkhart, C.P.; Bayless, J.R.
Non-thermal plasma processing is an emerging technology for the abatement of volatile organic compounds (VOCs) and nitrogen oxides (NO{sub x}) in atmospheric pressure gas streams. Either electrical discharge of electron beam methods can produce these plasmas. This paper presents a comparative assessment of various non-thermal plasma reactors. The goal of our project is two-fold: (1) to understand the feasibility and scalability of various non-thermal plasma reactors by focusing on the energy efficiency of the electron and chemical kinetics, and (2) to optimize process parameters and provide performance and economic data. Experimental results using a compact electron beam reactor, pulsed corona reactor and dielectric-barrier discharge will be presented. These reactors have been used to study the removal of NO{sub x} and a wide variety of VOCs. The effects of background gas decomposition and gas temperature on the decomposition chemistry have been studied. The decomposition mechanisms are discussed to illustrate how the chemistry could strongly affect the economics of the process. An analysis of the electron kinetics show that electrical discharge reactors are the most suitable only for processes requiring O radicals. For pollution control applications requiring copious amounts of electrons, ions, N atoms or OH radicals, the sue of electron beam reactors is generally the best way of minimizing the electrical power consumption.
Power consumption and byproducts in electron beam and electrical discharge processing of volatile organic compounds
Penetrante, B.M.; Hsiao, M.C.; Bardsley, J.N.
Among the new methods being investigated for the post-process reduction of volatile organic compounds (VOCs) in atmospheric-pressure air streams are based on non-thermal plasmas. Electron beam, pulsed corona and dielectric-barrier discharge methods are among the more extensively investigated techniques for producing non-thermal plasmas. In order to apply non-thermal plasmas in an industrial scale, it is important to establish the electrical power requirements and byproducts of the process. In this paper the authors present experimental results using a compact electron beam reactor, a pulsed corona and a dielectric-barrier discharge reactor. They have used these reactors to study the removal of a wide variety of VOCs. The effects of background gas composition and gas temperature on the decomposition chemistry have been studied. They present a description of the reactions that control the efficiency of the plasma process. They have found that pulsed corona and other types of electrical discharge reactors are most suitable only for processes requiring O radicals. For VOCs requiring copious amounts of electrons, ions, N atoms or OH radicals, the use of electron beam reactors is generally the best way of minimizing the electrical power consumption. Electron beam processing is remarkably more effective for all of the VOCs tested. For control of VOC emissions from dilute, large volume sources such as paint spray booths, cost analysis shows that the electron beam method is cost-competitive to thermal and catalytic methods that employ heat recovery or hybrid techniques.
Effects of Electric Discharge Plasma Treatment on the Thermal Conductivity of Polymer-Metal Nitride/Carbide Composites
NASA Astrophysics Data System (ADS)
Parali, Levent; Kurbanov, Mirza A.; Bayramov, Azad A.; Tatardar, Farida N.; Sultanakhmedova, Ramazanova I.; Xanlar, Huseynova Gulnara
High-density polymer composites with semiconductor or dielectric fillers such as aluminum nitride (AIN), aluminum oxide (Al2O3), titanium carbide (TiC), titanium nitride (TiN), boron nitride (BN), silicon nitride (Si3N4), and titanium carbonitride (TiCN) were prepared by the hot pressing method. Each powder phase of the composites was exposed to an electric discharge plasma process before composite formation. The effects of the electric discharge plasma process and the filler content (volume fraction) on the thermal conductivity, volt-ampere characteristics, thermally stimulated depolarization current, as well as electrical and mechanical strength were investigated. The results of the study indicate that, with increasing filler volume fraction, the thermal conductivity of the samples also increased. Furthermore, the thermal conductivity, and electrophysical and mechanical properties of the high-density polyethylene + 70% BN composite modified using the electric discharge plasma showed improvement when compared with that without electric discharge plasma treatment.
Relationship between Exploding Bridgewire & Spark Initiation of Low Density PETN
NASA Astrophysics Data System (ADS)
Lee, Elizabeth; Drake, Rod
Recent work has shown that the energy delivered after bridgewire burst affects the function time of an EBW detonator. The spark which is formed post bridgewire burst is the means by which the remaining fireset energy is delivered into the detonator. Therefore, by studying the characteristics of spark-gap detonators insight into the contribution of spark initiation to the functioning of EBW detonators may be achieved. Spark initiation of low density explosives consists of; (i) spark formation, (ii) spark interaction with the bed, and (iii) ignition and growth of reaction. Experiments were performed in which beds of an inert simulant were used to study the formation and propagation of sparks. The effect of the spark on inert porous beds was studied over a limited delivered energy range. The disruption of the bed was found to be dependent on the particle size / pore structure of the bed. The effect of spark initiation on a low density PETN bed was then examined, the relationship between delivered energy and function time was found to be the same as for EBW detonators. This necessitated the development of electrical diagnostic techniques to measure the energy delivered to the spark.
Sound production to electric discharge: sonic muscle evolution in progress in Synodontis spp. catfishes (Mochokidae)
Boyle, Kelly S.; Colleye, Orphal; Parmentier, Eric
Elucidating the origins of complex biological structures has been one of the major challenges of evolutionary studies. Within vertebrates, the capacity to produce regular coordinated electric organ discharges (EODs) has evolved independently in different fish lineages. Intermediate stages, however, are not known. We show that, within a single catfish genus, some species are able to produce sounds, electric discharges or both signals (though not simultaneously). We highlight that both acoustic and electric communication result from actions of the same muscle. In parallel to their abilities, the studied species show different degrees of myofibril development in the sonic and electric muscle. The lowest myofibril density was observed in Synodontis nigriventris, which produced EODs but no swim bladder sounds, whereas the greatest myofibril density was observed in Synodontis grandiops, the species that produced the longest sound trains but did not emit EODs. Additionally, S. grandiops exhibited the lowest auditory thresholds. Swim bladder sounds were similar among species, while EODs were distinctive at the species level. We hypothesize that communication with conspecifics favoured the development of species-specific EOD signals and suggest an evolutionary explanation for the transition from a fast sonic muscle to electrocytes. PMID:25080341
Cylindrical Wire Electrical Discharge Machining of Metal Bond Diamond Wheels- Part II: Wheel Wear Mechanism
McSpadden, SB
The use of stereo scanning Electron Microscopy (SEM) to investigate the wear mechanism of the wire EDM true metal bond diamond wheel for ceramic grinding is presented. On the grinding wheel, a wedge-shape removal part was machined to enable the examination and measurement of the worn wheel surfaces using the stereo SEM. The stereo SEM was calibrated by comparing results of depth profile of a wear groove with the profilometer measurements. On the surface of the grinding wheel after wire EDM truing and before grinding, the diamond protruding heights were measured in the level of 35 {micro}m, comparing to the 54 {micro}m average size of the diamond in the grinding wheel. The gap between the EDM wire and rotating grinding wheel is estimated to be about 35 to 40 {micro}m. This observation indicates that, during the wire EDM, electrical sparks occur between the metal bond and EDM wire, which leaves the diamond protruding in the gap between the wire and wheel. The protruding diamond is immediately fractured at the start of the grinding process, even under a light grinding condition. After heavy grinding, the grinding wheel surface and the diamond protrusion heights are also investigated using the stereo SEM. The height of diamond protrusion was estimated in the 5 to 15 {micro}m range. This study has demonstrated the use of stereo SEM as a metrology tool to study the grinding wheel surface.
Ng, Henry K.; Novick, Vincent J.; Sekar, Ramanujam R.
A NO.sub.X control system for an internal combustion engine includes an oxygen enrichment device that produces oxygen and nitrogen enriched air. The nitrogen enriched air contains molecular nitrogen that is provided to a spark plug that is mounted in an exhaust outlet of an internal combustion engine. As the nitrogen enriched air is expelled at the spark gap of the spark plug, the nitrogen enriched air is exposed to a pulsating spark that is generated across the spark gap of the spark plug. The spark gap is elongated so that a sufficient amount of atomic nitrogen is produced and is injected into the exhaust of the internal combustion engine. The injection of the atomic nitrogen into the exhaust of the internal combustion engine causes the oxides of nitrogen to be reduced into nitrogen and oxygen such that the emissions from the engine will have acceptable levels of NO.sub.X. The oxygen enrichment device that produces both the oxygen and nitrogen enriched air can include a selectively permeable membrane.
An advanced energy management system for controlling the ultracapacitor discharge and improving the electric vehicle range
NASA Astrophysics Data System (ADS)
Armenta, Jesús; Núñez, Ciro; Visairo, Nancy; Lázaro, Isabel
Over the last years issues regarding both the use and the improvement of energy management in electric vehicles have been highlighted by industry and academic fields. Some of the research has been focused on exploiting the ultracapacitor characteristics and on protecting the battery life. From this standpoint, this paper proposes an advanced energy management system based on the adequate discharge of the ultracapacitor bank in order to utilize all the energy available from the regenerative breaking. In this way, the energy consumption is reduced and the electric vehicle range is increased. This strategy, based on simple rules, takes advantage of the high power density of the ultracapacitor and prevents an overstress of the battery. The benefits are featured using three standard drive cycles for a 1550 kg electric vehicle via simulations.
Neuron discharges in the rat auditory cortex during electrical intracortical stimulation.
Maldonado, P E; Altman, J A; Gerstein, G L
Studies were carried out in rats anesthetized with ketamine or nembutal, with recording of multicellular activity (with separate identification of responses from individual neurons) in the primary auditory cortex before and after electrical intracortical microstimulation. These experiments showed that about half of the set of neurons studied produced responses to short tonal bursts, these responses having two components-initial discharges arising in response to the sound, and afterdischarge occurring after pauses of 50-100 msec. Afterdischarges lasted at least several seconds, and were generally characterized by a rhythmic structure (with a frequency of 8-12 Hz). After electrical microstimulation, the level of spike activity increased, especially in afterdischarges, and this increase could last up to 4 h. Combined peristimulus histograms, cross-correlations, and gravitational analyses were used to demonstrate interactions of neurons, which increased after electrical stimulation and were especially pronounced in the response afterdischarges. PMID:9513978
Comparative Analysis of Thermography Studies and Electrical Measurement of Partial Discharges in Underground Power Cables
NASA Astrophysics Data System (ADS)
Gonzalez-Parada, A.; Guzman-Cabrera, R.; Torres-Cisneros, M.; Guzman-Sepulveda, J. R.
The principal cause of damage in underground power cable installations is partial discharge (PD) activity. PD is a localized non-linear phenomenon of electrical breakdown that occurs in the insulating medium sitting between two conducting materials, which are at different potentials. The damage to the insulating material is induced by the AC voltage to which the insulator is subjected during the discharge process, and it can be directly or indirectly measured by the charge displacement across the insulation and the cavity defect. Non-invasive detection techniques that help in identifying the onset of the discharge process are required as PD is a major issue in terms of maintenance and performance of underground power installations. The main locations of failure are the accessories at points of connection such as terminals or splices. In this article, a study of electrical detection of PD and image processing of thermal pictures is presented. The study was carried out by controllably inducing specific failures in the accessories of the installation. The temporal evolution of the PD signals was supported with thermal images taken during the test in order to compare the PD activity and thermal increase due to failure. The analysis of thermographic images allows location of the failure by means of intensity-based texture segmentation algorithms. This novel technique was found to be suitable for non-invasive detection of the PD activity in underground power cable accessories.
Electrical and kinetical aspects of homogeneous dielectric-barrier discharge in xenon for excimer lamps
Belasri, A.; Harrache, Z.
A pulsed dielectric-barrier discharge in xenon has been simulated for operating conditions typical to excimer lamps, in which the discharge is considered spatially homogeneous. The computer model developed is based on the xenon plasma chemistry, the circuit, and the Boltzmann equations. First, the validity of the physical model was checked and compared to experimental and theoretical works, and then the model is applied in the case of a sinusoidal voltage at period frequencies in the range of 50 kHz-2 MHz. The results obtained with the present description are in good agreement with experimental measurements and one-dimensional fluid prediction in terms of electrical characteristics and vacuum ultraviolet (vuv) emission. The effect of operation voltage, power source frequency, dielectric capacitance, as well as gas pressure on the discharge efficiency and the 172, 150, and 147 nm photon generation, under the typical experimental operating conditions and for the case of a sinusoidal applied voltage, have been investigated and discussed. Calculations suggest that the overall conversion efficiency from electrical energy to vuv emission in the lamp is greater than 38%, and it will be very affected at high power source frequency and high gas pressure with a significant dependence on the dielectric capacitance.
[Experience with ablation of the bundle of His using electrical discharge].
Lukl, J; Cernosek, B; Heinc, P
Ablation of the bundle of His by an electric discharge was made in 10 patients (average age 64 years, range 48-80) unsuccessfully treated with 3-14 antiarrhythmic drugs or their combinations (average 8.7) on account of supraventricular tachycardia occurring repeatedly for 3-44 years (average 12.5 years). By means of a bipolar electrode inserted into the area of the bundle of His a nonsynchronized defibrillation discharge with a mean energy of 323 J (40-380) was administered. On average 2.9 discharges were used (1-9) per patient, in 1-3 sessions. The patients were followed up for a period of 15.3 months (10-19). Permanent complete a-v block was achieved in 6 patients, the remaining 4 patients are also free from complaints with have antiarrhythmic treatment. To all patients a pacemaker was implanted, four times "physiological" stimulation was used. One month after the operation the authors observed once the development of a transient phatic disorder and once the slow development of cardiac tamponade in conjunction with anticoagulant treatment, resolved by pericardial puncture. Ablation of the bundle of His by a defibrillation discharge is thus in carefully selected patients a highly effective method of treatment of stubborn supraventricular tachycardias. PMID:2327082
Ultrafast traveling wave dominates the electric organ discharge of Apteronotus leptorhynchus: an inverse modelling study
Shifman, Aaron R.; Longtin, André; Lewis, John E.
Identifying and understanding the current sources that give rise to bioelectric fields is a fundamental problem in the biological sciences. It is very difficult, for example, to attribute the time-varying features of an electroencephalogram recorded from the head surface to the neural activity of specific brain areas; model systems can provide important insight into such problems. Some species of fish actively generate an oscillating (c. 1000 Hz) quasi-dipole electric field to communicate and sense their environment in the dark. A specialized electric organ comprises neuron-like cells whose collective signal underlies this electric field. As a step towards understanding the detailed biophysics of signal generation in these fish, we use an anatomically-detailed finite-element modelling approach to reverse-engineer the electric organ signal over one oscillation cycle. We find that the spatiotemporal profile of current along the electric organ constitutes a travelling wave that is well-described by two spatial Fourier components varying in time. The conduction velocity of this wave is faster than action potential conduction in any known neuronal axon (>200 m/s), suggesting that the spatiotemporal features of high-frequency electric organ discharges are not constrained by the conduction velocities of spinal neuron pathways. PMID:26514932
Ultrafast traveling wave dominates the electric organ discharge of Apteronotus leptorhynchus: an inverse modelling study
NASA Astrophysics Data System (ADS)
Shifman, Aaron R.; Longtin, André; Lewis, John E.
Identifying and understanding the current sources that give rise to bioelectric fields is a fundamental problem in the biological sciences. It is very difficult, for example, to attribute the time-varying features of an electroencephalogram recorded from the head surface to the neural activity of specific brain areas; model systems can provide important insight into such problems. Some species of fish actively generate an oscillating (c. 1000 Hz) quasi-dipole electric field to communicate and sense their environment in the dark. A specialized electric organ comprises neuron-like cells whose collective signal underlies this electric field. As a step towards understanding the detailed biophysics of signal generation in these fish, we use an anatomically-detailed finite-element modelling approach to reverse-engineer the electric organ signal over one oscillation cycle. We find that the spatiotemporal profile of current along the electric organ constitutes a travelling wave that is well-described by two spatial Fourier components varying in time. The conduction velocity of this wave is faster than action potential conduction in any known neuronal axon (>200 m/s), suggesting that the spatiotemporal features of high-frequency electric organ discharges are not constrained by the conduction velocities of spinal neuron pathways.
Ultrafast traveling wave dominates the electric organ discharge of Apteronotus leptorhynchus: an inverse modelling study.
Shifman, Aaron R; Longtin, André; Lewis, John E
Identifying and understanding the current sources that give rise to bioelectric fields is a fundamental problem in the biological sciences. It is very difficult, for example, to attribute the time-varying features of an electroencephalogram recorded from the head surface to the neural activity of specific brain areas; model systems can provide important insight into such problems. Some species of fish actively generate an oscillating (c. 1000 Hz) quasi-dipole electric field to communicate and sense their environment in the dark. A specialized electric organ comprises neuron-like cells whose collective signal underlies this electric field. As a step towards understanding the detailed biophysics of signal generation in these fish, we use an anatomically-detailed finite-element modelling approach to reverse-engineer the electric organ signal over one oscillation cycle. We find that the spatiotemporal profile of current along the electric organ constitutes a travelling wave that is well-described by two spatial Fourier components varying in time. The conduction velocity of this wave is faster than action potential conduction in any known neuronal axon (>200 m/s), suggesting that the spatiotemporal features of high-frequency electric organ discharges are not constrained by the conduction velocities of spinal neuron pathways. PMID:26514932
Intracellular electric fields produced by dielectric barrier discharge treatment of skin
NASA Astrophysics Data System (ADS)
Babaeva, Natalia Yu; Kushner, Mark J.
The application of atmospheric pressure plasmas to human tissue has been shown to have therapeutic effects for wound healing and in treatment of skin diseases. These effects are attributed to both production of beneficial radicals which intersect with biological reaction chains and to the surface and intracellular generation of electric fields. In this paper, we report on computational studies of the intersection of plasma streamers in atmospheric pressure dielectric barrier discharges (DBDs) sustained in air with human skin tissue, with emphasis on the intracellular generation of electric fields. Intracellular structures and their electrical properties were incorporated into the computational mesh in order to self-consistently couple gas phase plasma transport with the charging of the surface of the skin and the intracellular production of electrical currents. The short duration of a single plasma filament in DBDs and its intersection with skin enables the intracellular penetration of electric fields. The magnitude of these electric fields can reach 100 kV cm-1 which may exceed the threshold for electroporation.
[Mechanism of the organic pollutant degradation in water by hybrid gas-liquid electrical discharge].
Zhu, Li-nan; Ma, Jun; Yang, Shi-dong
The method of hybrid gas-liquid electrical discharge was investigated for the removal of phenol. The results indicate that this new method can remove phenol in water effectively. The removal rate increases with increasing voltage and air aeration. The production quantity of H2O2 and O3 is measured respectively in the discharge region and the production quantity increases with increasing of voltage and air aeration. The energy consumption analysis indicates that with increasing the voltage, the increase extent of the phenol removal rate is smaller than the energy's, so the increase of energy efficiency is very small. Air aeration increases the energy consumption. At the same time, a considerable part of energy in the overall input energy makes the temperature of the solution increase, and more energy is transformed into heat, which leads to the waste of energy. PMID:17990549
Specific features of an electric discharge operating between an electrolytic anode and a metal cathode
NASA Astrophysics Data System (ADS)
Gaisin, A. F.; Sarimov, L. R.
Results are presented from experimental studies of a high-current electric discharge operating between an St45 steel cathode and a service water anode in a wide range of air pressures. Peculiarities of discharge ignition and specific features of cathode and anode spots were revealed. The behavior of the current density on a service water anode was investigated for the first time. Comparison of the current densities j on the steel cathode and service water anode shows that, in the parameter range under study, Hehl's law is not satisfied on the water anode. The two-dimensional distribution of the potential inside and on the surface of the service water anode was measured.
Organic synthesis from reducing models of the atmosphere of the primitive earth with UV light and electric discharges.
Bossard, A R; Raulin, F; Mourey, D; Toupance, G
The purpose of this paper is to compare the role of UV light and of electric discharges, the two most important sources of energy on the primitive earth, in the synthesis of organic compounds out of a reducing model of that atmosphere. Since Miller's experiments in 1953, most of the experimental simulations have been performed with electric discharges, and it has been assumed that UV radiations would give similar results. In order to check this assumption we have performed both experimental simulations in our laboratory. Experimental results indicate that this assumption was wrong in a large extent. Our four main conclusions are: 1. Unlike electric discharges, UV light is not an efficient source for producing unsaturated carbon chains. 2. UV light is efficient for producing nitriles in CH4--NH3 mixtures when the mole fraction of NH3 is very low while electric discharges need a higher mole fraction of NH3. 3. UV light is not able to produce nitriles from CH4--N2 mixtures while electric discharges produce important quantities of diversified nitriles from these mixtures. 4. UV light is not very efficient for producing aldehydes from CH4--H2O model atmosphere, electric discharges seem to be able to produce them more efficiently. PMID:7097776
Evaluating the electrical discharge machining (EDM) parameters with using carbon nanotubes
NASA Astrophysics Data System (ADS)
Sari, M. M.; Noordin, M. Y.; Brusa, E.
Electrical discharge machining (EDM) is one of the most accurate non traditional manufacturing processes available for creating tiny apertures, complex or simple shapes and geometries within parts and assemblies. Performance of the EDM process is usually evaluated in terms of surface roughness, existence of cracks, voids and recast layer on the surface of product, after machining. Unfortunately, the high heat generated on the electrically discharged material during the EDM process decreases the quality of products. Carbon nanotubes display unexpected strength and unique electrical and thermal properties. Multi-wall carbon nanotubes are therefore on purpose added to the dielectric used in the EDM process to improve its performance when machining the AISI H13 tool steel, by means of copper electrodes. Some EDM parameters such as material removal rate, electrode wear rate, surface roughness and recast layer are here first evaluated, then compared to the outcome of EDM performed without using nanotubes mixed to the dielectric. Independent variables investigated are pulse on time, peak current and interval time. Experimental evidences show that EDM process operated by mixing multi-wall carbon nanotubes within the dielectric looks more efficient, particularly if machining parameters are set at low pulse of energy.
Electric field induced needle-pulsed arc discharge carbon nanotube production apparatus: Circuitry and mechanical design
Kia, Kaveh Kazemi; Bonabi, Fahimeh
A simple and low cost apparatus is reported to produce multiwall carbon nanotubes and carbon nano-onions by a low power short pulsed arc discharge reactor. The electric circuitry and the mechanical design details and a micro-filtering assembly are described. The pulsed-plasma is generated and applied between two graphite electrodes. The pulse width is 0.3 {mu}s. A strong dc electric field is established along side the electrodes. The repetitive discharges occur in less than 1 mm distance between a sharp tip graphite rod as anode, and a tubular graphite as cathode. A hydrocarbon vapor, as carbon source, is introduced through the graphite nozzle in the cathode assembly. The pressure of the chamber is controlled by a vacuum pump. A magnetic field, perpendicular to the plasma path, is provided. The results show that the synergetic use of a pulsed-current and a dc power supply enables us to synthesize carbon nanoparticles with short pulsed plasma. The simplicity and inexpensiveness of this plan is noticeable. Pulsed nature of plasma provides some extra degrees of freedom that make the production more controllable. Effects of some design parameters such as electric field, pulse frequency, and cathode shape are discussed. The products are examined using scanning probe microscopy techniques.
Electric field induced needle-pulsed arc discharge carbon nanotube production apparatus: Circuitry and mechanical design
NASA Astrophysics Data System (ADS)
Kia, Kaveh Kazemi; Bonabi, Fahimeh
A simple and low cost apparatus is reported to produce multiwall carbon nanotubes and carbon nano-onions by a low power short pulsed arc discharge reactor. The electric circuitry and the mechanical design details and a micro-filtering assembly are described. The pulsed-plasma is generated and applied between two graphite electrodes. The pulse width is 0.3 μs. A strong dc electric field is established along side the electrodes. The repetitive discharges occur in less than 1 mm distance between a sharp tip graphite rod as anode, and a tubular graphite as cathode. A hydrocarbon vapor, as carbon source, is introduced through the graphite nozzle in the cathode assembly. The pressure of the chamber is controlled by a vacuum pump. A magnetic field, perpendicular to the plasma path, is provided. The results show that the synergetic use of a pulsed-current and a dc power supply enables us to synthesize carbon nanoparticles with short pulsed plasma. The simplicity and inexpensiveness of this plan is noticeable. Pulsed nature of plasma provides some extra degrees of freedom that make the production more controllable. Effects of some design parameters such as electric field, pulse frequency, and cathode shape are discussed. The products are examined using scanning probe microscopy techniques.
A Study of Electromagnetic Radiation of Corona Discharge Near 500-Kv Electric Installations
Korzhov, A. V.; Okrainskaya, I. S.; Sidorov, A. I.; Kufel'd, V. D.
Data on the spectral composition and intensity of electromagnetic radiation of corona discharge are obtained in an experimental study performed on the outdoor switchgear of the Shagol 500-kV substation of the Chelyabinsk Enterprise of Trunk Transmission Grids and under a 500-kV Shagol - Kozyrevo overhead transmission line. The electromagnetic environment on the territory of the 500-kV outdoor switchgear is shown to be determined by narrow-band radiations (harmonics of the frequency of electric supply) and wide-band radiations due to corona discharges of high-voltage sources. This means that the personnel experience the action of a commercial-frequency electric field and electromagnetic radiation of a quite wide range, which is not allowed for by the existing guidelines. It is recommended to continue the study in cooperation with medical institutions in order to create guidelines that would allow for the joint action of commercial-frequency electric field and electromagnetic radiation and for the voltage in the line, the current load, the meteorological situation, and other factors.
The study on the atomic force microscopy base nanoscale electrical discharge machining.
Huang, Jen-Ching; Chen, Chung-Ming
This study proposes an innovative atomic force microscopy (AFM) based nanoscale electrical discharge machining (AFM-based nanoEDM) system which combines an AFM with a self-produced metallic probe and a high-voltage generator to create an atmospheric environment AFM-based nanoEDM system and a deionized water (DI water) environment AFM-based nanoEDM system. This study combines wire-cut processing and electrochemical tip sharpening techniques on a 40-µm thick stainless steel sheet to produce a high conductive AFM probes, the production can withstand high voltage and large current. The tip radius of these probes is approximately 40 nm. A probe test was executed on the AFM using probes to obtain nanoscales morphology of Si wafer surface. The silicon wafer was as a specimen to carry out AFM-base nanoEDM process in atmospheric and DI water environments by AFM-based nanoEDM system. After experiments, the results show that the atmospheric and DI water environment AFM-based nanoEDM systems operate smoothly. From experimental results, it can be found that the electric discharge depth of the silicon wafer at atmospheric environments is a mere 14.54 nm. In a DI water environment, the depth of electric discharge of the silicon wafer can reach 25.4 nm. This indicates that the EDM ability of DI water environment AFM-based nanoEDM system is higher than that of atmospheric environment AFM-based nanoEDM system. After multiple nanoEDM process, the tips become blunt. After applying electrochemical tip sharpening techniques, the tip radius can return to approximately 40 nm. Therefore, AFM probes produced in this study can be reused. PMID:21898457
Analysis on the spectra and synchronous radiated electric field observation of cloud-to-ground lightning discharge plasma
Cen Jianyong; Yuan Ping; Qu Haiyan; Zhang Tinglong
According to the spectra of cloud-to-ground (CG) lightning discharge plasma captured by a slit-less spectrograph and the information of synchronous radiated electric field, the temperatures, the total intensity of spectra, the peak value of current and its action integral of discharge plasma channel have been calculated. Furthermore, the correlativity of these parameters has been analyzed for the first time. The results indicate that the total intensity of spectra has a positive correlation to the discharge current in different strokes of one CG lightning, and the temperature of discharge plasma is direct proportion to the action integral in the first return strokes of different lightning.
Comments on "Evaluation of interactions of electric fields due to electrostatic discharge with human tissue".
Seaman, Ronald L; Comeaux, James A
Attention is drawn to recent paper by Rogers et al. (Aug., 2004) in which ultra-wideband pulses are applied to an isolated muscle as part of deriving a strength-duration curve for threshold stimulation. The paper extends the strength-duration threshold curve for unipolar pulses down to a pulse duration of about 1 ns, on the order of 1000 times shorter than previously studied. Results of the work justify use of traditional mathematical models of the strength-duration curve for nanosecond pulses, as done recently for the electric field resulting from electrostatic discharge through the body (Dawson, et al., 2004). PMID:16761853
Electric-discharge XeCl laser emitting 10-J, 300-ns pulses
Konovalov, I N; Losev, V F; Panchenko, Yu N; Ivanov, N G; Sukhov, M Yu
The development of a long-pulse electric-discharge XeCl laser with the 9 x 6 x 100 cm active volume is reported. Laser is excited by using a double circuit with a pulsed charged storage capacitor consisting of paper-oil capacitors forming the pulse-shaping line. The storage capacitor is switched by a multichannel extended gap. The laser mixture was preionised by X-rays. The laser generated the 10-J output pulses with the FWHM of 300 ns, and a uniform intensity distribution over the exit aperture. (lasers)
Organic solids produced by electrical discharges in reducing atmospheres: Molecular analysis
NASA Technical Reports Server (NTRS)
Khare, B. N.; Sagan, C.; Zumberge, J. E.; Sklarew, D.; Nagy, B.
The complex brown polymer produced on passage of an electrical discharge through a mixture of methane, ammonia, and water, is analyzed by pyrolytic GC/MS. Pyrolyzates include a wide range of alkanes, alkenes, aromatic hydrocarbons, aliphatic and aromatic nitriles, pyrroles, and pyridine. Similar pyrolyzates are obtained from polypeptides and polynucleotides with hydrocarbon moieties. This polymer is remarkably stable up to 950 C; its degradation products are candidate constituents of planetary aerosols in the outer solar system and the grains and gas in the interstellar medium.
Shaping of steel mold surface of lens array by electrical discharge machining with single rod electrode.
Takino, Hideo; Hosaka, Takahiro
We propose a method for fabricating a lens array mold by electrical discharge machining (EDM). In this method, the tips of rods are machined individually to form a specific surface, and then a number of the machined rods are arranged to construct an electrode for EDM. The repetition of the EDM process using the electrode enables a number of lens elements to be produced on the mold surface. The effectiveness of our proposed method is demonstrated by shaping a lens array mold made of stainless steel with 16 spherical elements, in which the EDM process with a single rod electrode is repeatedly conducted. PMID:25607880
Organic solids produced by electrical discharge in reducing atmospheres - Tholin molecular analysis
NASA Technical Reports Server (NTRS)
Khare, B. N.; Sagan, C.; Zumberge, J. E.; Sklarew, D. S.; Nagy, B.
The complex dark brown solid of a class called tholins, produced on passage of an electrical discharge through a roughly equimolar mixture of methane and ammonia with 2.6% water vapor, is analyzed by vacuum pyrolysis followed by gas chromatography and mass spectrometry. Pyrolyzates include a wide range of aliphatic and aromatic nitriles, alkanes, alkenes, aromatic hydrocarbons, pyrrole, and pyridine. This tholin is remarkably stable to 950 C. It and its degradation products are candidate constituents of planetary aerosols in the outer solar system and of the grains in the interstellar medium.
A new visibly-excited fluorescent component in latent fingerprint residue induced by gaseous electrical discharge.
Davies, L M; Jones, N E; Brennan, J S; Bramble, S K
A technique that exposes fingerprint residue to a gaseous electrical discharge in nitrogen followed by treatment with ammonium hydrogen carbonate vapors to produce fluorescence is investigated. Particular attention is made to fluorescence observed via laser illumination at 514 nm. Insight into the nature of the fluorescent components is achieved through the use of thin-layer chromatography (TLC) of fingerprint residue. Results reported indicate the fluorescence observed is from previously non-fluorescent fractions of the fingerprint residue, and TLC results point towards lipid derivatives as a possible source of the fluorescence. PMID:11110185
Electric Discharge Sintering and Joining of Tungsten Carbide--Cobalt Composite with High-Speed Steel Substrate
Grigoryev, Evgeny G.
Simultaneous electro discharge sintering of high strength structure of tungsten carbide-cobalt composite and connection it with high-speed steel substrate is investigated and suitable operating parameters are defined. Tungsten carbide-cobalt and high-speed steel joining was produced by the method of high voltage electrical discharge together with application of mechanical pressure to powder compact. It was found that the density and hardness of composite material reach its maximum values at certain magnitudes of applied pressure and high voltage electrical discharge parameters. We show that there is an upper level for the discharge voltage beyond which the powder of composite material disintegrates like an exploding wire. Due to our results it is possible to determine optimal parameters for simultaneous electro discharge sintering of WC-Co and bonding it with high-speed steel substrate.
Effect of Electrostatic Discharge on Electrical Characteristics of Discrete Electronic Components
NASA Technical Reports Server (NTRS)
Wysocki, Phil; Vashchenko, Vladislav; Celaya, Jose; Saha, Sankalita; Goebel, Kai
This article reports on preliminary results of a study conducted to examine how temporary electrical overstress seed fault conditions in discrete power electronic components that cannot be detected with reliability tests but impact longevity of the device. These defects do not result in formal parametric failures per datasheet specifications, but result in substantial change in the electrical characteristics when compared with pristine device parameters. Tests were carried out on commercially available 600V IGBT devices using transmission line pulse (TLP) and system level ESD stress. It was hypothesized that the ESD causes local damage during the ESD discharge which may greatly accelerate degradation mechanisms and thus reduce the life of the components. This hypothesis was explored in simulation studies where different types of damage were imposed to different parts of the device. Experimental results agree qualitatively with the simulation for a number of tests which will motivate more in-depth modeling of the damage.
Heat energy of various ignition sparks
NASA Technical Reports Server (NTRS)
Silsbee, F B; Loeb, L B; Fonseca, E L
This report describes a method developed at the Bureau of Standards for measuring the total energy liberated as heat in a spark gap by an ignition system. Since this heat energy is obtained from the electromagnetic energy stored in the windings of the magneto or coil, it is a measure of the effectiveness of the device as an electric generator. Part 2 gives the results of measurements in absolute units of the total heat supplied to a spark gap by ignition systems of different types operating at various speeds, under conditions substantially equivalent to those in the cylinder of a high-compression aviation engine.
Simulation of electrical discharge in a 3.6 Joule miniature plasma focus device using SIMULINK
NASA Astrophysics Data System (ADS)
Jafari, Hossein; Habibi, Morteza
A novel technique has been developed and studied in this paper to simulate the electrical discharge circuit of a 3.6 J miniature plasma focus device (PFD) and investigate the effect of inductance variation on voltage spike and current dip. The technique is based on a correlation between the electrical discharge circuit and plasma dynamics in a very small PFD that operates at the energy of 3.6 J. The simulation inputs include the charging voltage, capacitor bank capacitance, current limiter resistance, by-pass resistance as well as the time-dependent inductance and resistance of the plasma sheath which are calculated by assuming the plasma dynamics as transit times in going from one phase to the next. The variations of the most important elements in the circuit (i.e. the constant and breakdown inductances) and their effects on the current dip are studied in PFDs with low and high constant inductance. The model demonstrated for achieving a good pinch in the PFD, although the total inductance of the system should be low; however there is always an optimum inductance which causes an appropriate pinch. Furthermore, the electrical power produced by the pulsed power supply, the mechanical energy as well as the magnetic energy which are transferred into the plasma tube were obtained from simulation. The graph of electrical power demonstrated a high instantaneous increment in the power transferred into the plasma as one of the greatest advantages of the pulsed power supply. The simulation was performed using software tools within the MATLAB/SIMULINK simulation environment.
Effect of electric discharge machining on the fatigue life of Inconel 718
NASA Technical Reports Server (NTRS)
Jeelani, S.; Collins, M. R.
The effect of electric discharge machining on the fatigue life of Inconel 718 alloy at room temperature was investigated. Data were generated in the uniaxial tension fatigue mode at ambient temperature using flat 3.175 mm thick specimens. The specimens were machined on a wire-cut electric discharge machine at cutting speeds ranging from 0.5 to 2 mm per minute. The specimens were fatigued at a selected stress, and the resulting fatigue lives compared with that of the virgin material. The surfaces of the fatigued specimens were examined under optical and scanning electron microscopes, and the roughness of the surfaces was measured using a standard profilometer. From the results of the investigation, it was concluded that the fatigue life of the specimens machined using EDM decreased slightly as compared with that of the virgin material, but remained unchanged as the cutting speed was changed. The results are explained using data produced employing microhardness measurements, profilometry, and optical and scanning microscopy.
Amino Acids Generated from Hydrated Titan Tholins: Comparison with Miller-Urey Electric Discharge Products
NASA Technical Reports Server (NTRS)
Cleaves, H. James, II; Neish, Catherine; Callahan, Michael P.; Parker, Eric; Fernandez, Facundo M.; Dworkin, Jason P.
Various analogues of Titan haze particles (termed tholins) have been made in the laboratory. In certain geologic environments on Titan, these haze particles may come into contact with aqueous ammonia (NH3) solutions, hydrolyzing them into molecules of astrobiological interest. A Titan tholin analogue hydrolyzed in aqueous NH3 at room temperature for 2.5 years was analyzed for amino acids using highly sensitive ultra-high performance liquid chromatography coupled with fluorescence detection and time-of-flight mass spectrometry (UHPLC-FDToF-MS) analysis after derivatization with a fluorescent tag. We compare here the amino acids produced from this reaction sequence with those generated from room temperature Miller-Urey (MU) type electric discharge reactions. We find that most of the amino acids detected in low temperature MU CH4N2H2O electric discharge reactions are generated in Titan simulation reactions, as well as in previous simulations of Triton chemistry. This argues that many processes provide very similar mixtures of amino acids, and possibly other types of organic compounds, in disparate environments, regardless of the order of hydration. Although it is unknown how life began, it is likely that given reducing conditions, similar materials were available throughout the early Solar System and throughout the universe to facilitate chemical evolution.
Electrical Discharge Machining Techniques for Evaluating the Effects of Tritium on Materials
In this investigation, new ways to evaluate the long-term effects of tritium on the structural properties of components were developed. Electric discharge machining (EDM) techniques for cutting tensile and fracture toughness samples from the tritium-exposed regions of returned reservoirs were demonstrated. An existing electric discharge machine was used to cut sub-size tensile and fracture toughness samples from the inside walls of reservoir mock-ups. Tensile properties from the EDM tensile samples were similar to those measured using full-size samples cut from similar stock. Although the existing equipment could not be used for machining tritium-exposed hardware, off-the-shelf EDM units are available that could. With the right equipment and the required radiological controls in place, similar machining and testing techniques could be used to directly measure the effects of tritium on the properties of material cut from reservoir returns. Stress-strain property data from tritium-exposed reservoirs would improve finite-element modeling of reservoir performance because the data are representative of the true state of the reservoir material in the field. Tensile data from samples cut directly from reservoirs complement existing shelf storage and burst test data of the Life Storage Program and help answer questions about a specific reservoir's processing history and properties.
Electric-Discharge Machining Techniques for Evaluating Tritium Effects on Materials
Morgan, M.J.
In this investigation, new ways to evaluate the long-term effects of tritium on the structural properties of components were developed. Electric-discharge machining (EDM) techniques for cutting tensile and fracture toughness samples from tritium exposed regions of returned reservoirs were demonstrated. An existing electric discharge machine was used to cut sub-size tensile and fracture toughness samples from the inside surfaces of reservoir mockups. Tensile properties from the EDM tensile samples were similar to those measured using full-size samples cut from similar stock. Although the existing equipment could not be used for machining tritium-exposed hardware, off-the shelf EDM units are available that could. With the right equipment and the required radiological controls in place, similar machining and testing techniques could be used to directly measure the effects of tritium on the properties of material cut from reservoir returns. Stress-strain properties from tritium-exposed reservoirs would improve finite element modeling of reservoir performance because the data would be representative of the true state of the reservoir material in the field. Tensile data from samples cut directly from reservoirs would also complement existing shelf storage and burst test data of the Life Storage Program and help answer questions about a specific reservoir's processing history and properties.
Amino acids generated from hydrated Titan tholins: Comparison with Miller-Urey electric discharge products
NASA Astrophysics Data System (ADS)
Cleaves, H. James; Neish, Catherine; Callahan, Michael P.; Parker, Eric; Fernández, Facundo M.; Dworkin, Jason P.
Various analogues of Titan haze particles (termed 'tholins') have been made in the laboratory. In certain geologic environments on Titan, these haze particles may come into contact with aqueous ammonia (NH3) solutions, hydrolyzing them into molecules of astrobiological interest. A Titan tholin analogue hydrolyzed in aqueous NH3 at room temperature for 2.5 years was analyzed for amino acids using highly sensitive ultra-high performance liquid chromatography coupled with fluorescence detection and time-of-flight mass spectrometry (UHPLC-FD/ToF-MS) analysis after derivatization with a fluorescent tag. We compare here the amino acids produced from this reaction sequence with those generated from room temperature Miller-Urey (MU) type electric discharge reactions. We find that most of the amino acids detected in low temperature MU CH4/N2/H2O electric discharge reactions are generated in Titan simulation reactions, as well as in previous simulations of Triton chemistry. This argues that many processes provide very similar mixtures of amino acids, and possibly other types of organic compounds, in disparate environments, regardless of the order of hydration. Although it is unknown how life began, it is likely that given reducing conditions, similar materials were available throughout the early Solar System and throughout the universe to facilitate chemical evolution.
SI Engine with repetitive NS spark plug
NASA Astrophysics Data System (ADS)
Pancheshniy, Sergey; Nikipelov, Andrey; Anokhin, Eugeny; Starikovskiy, Andrey; Laplase Team; Mipt Team; Pu Team
Now de-facto the only technology for fuel-air mixtures ignition in IC engines exists. It is a spark discharge of millisecond duration in a short discharge gap. The reason for such a small variety of methods of ignition initiation is very specific conditions of the engine operation. First, it is very high-pressure of fuel-air mixture - from 5-7 atmospheres in old-type engines and up to 40-50 atmospheres on the operating mode of HCCI. Second, it is a very wide range of variation of the oxidizer/fuel ratio in the mixture - from almost stoichiometric (0.8-0.9) at full load to very lean (φ = 0.3-0.5) mixtures at idle and/or economical cruising mode. Third, the high velocity of the gas in the combustion chamber (up to 30-50 m/s) resulting in a rapid compression of swirling inlet flow. The paper presents the results of tests of distributed spark ignition system powered by repetitive pulse nanosecond discharge. Dynamic pressure measurements show the increased pressure and frequency stability for nanosecond excitation in comparison with the standard spark plug. Excitation by single nanosecond high-voltage pulse and short train of pulses was examined. In all regimes the nanosecond pulsed excitation demonstrate a better performance.
Characteristics of a plasma production and a laser-induced discharge by a CO2 laser on DC electric field
Ihara, S.; Maiguma, T.; Satoh, S.; Ishimine, M.; Yamabe, C.
The experiments of a laser-induced discharge were carried out with a CO{sub 2} laser radiation in the atmospheric ambient gases under a DC electric field applied. In these experiments, both of the laser-induced discharge and the plasma production by the CO{sub 2} laser were suppressed with an increasing DC electric field strength. Although the laser-produced plasma was generated between the electrodes without DC electric field, both the probability of induced-discharge and plasma production decreased with the applied voltage across the electrodes. In this paper, the mechanisms of the phenomena for the suppression of the plasma production under applying the electric field between electrodes were discussed. It was found that the attachment processes of electrons most likely played an important role in this phenomena. {copyright} {ital 1996 American Institute of Physics.}
Active medium gain study of electric-discharge oxygen-iodine laser
NASA Astrophysics Data System (ADS)
Kolobyanin, Yuriy; Adamenkov, Yuriy; Vyskubenko, Boris; Goryachev, Leonid; Ilyin, Sergey; Kalashnik, Anatoliy; Rakhimova, Tatiana; Rogozhnikov, Georgiy
The paper reports on experimental studies of the active medium gain in supersonic electric-discharge oxygen-iodine laser (DOIL) based on traveling mw discharge. The measurements have included: absolute concentration, yield, and energy efficiency of production of SO in pure oxygen and oxygen-helium mixes at an oxygen partial pressure 3 to 15 Torr. For the gas flow to get rid of atomic oxygen, both heterogeneous mercury oxide coatings of the tube walls and homogeneous additives to the work mix, such as nitrogen oxide, have been used. The active medium of DOIL was formed using a nozzle array of the type of ejector sized as 10*50 mm2. The singlet oxygen-helium mix was supplied through three rows of sonic cylindrical nozzles, while the iodine-carrier gas mix - through two rows of supersonic conical nozzles with a half-opening angle of 10°(arc). The gas-phase iodine was produced in a quartz cell filled with iodine crystals. Room-temperature iodine vapors were picked up with a carrier gas (nitrogen or helium) and thus delivered into the nozzle array. The active medium was investigated by the high-resolution laser diode spectroscopy approach that used the laser type Vortex 6025 purchased from New Focus, Inc. The laser medium gain factor was determined by the intra-cavity approach having a sensitivity about 1*10 -6 cm -1. The static temperature of the medium was determined from the measurements of gain half-width. The gain of the active medium of electric-discharge OIL has been investigated. The DOIL in use was operating on a mix composed as O II:He=1:1 at a total pressure of 6 Torr and flowrate - about 1 mmol/s. With helium as an iodine carrier gas at a flowrate ~3 mmol/s, we have recorded a positive gain in the DOIL medium.
Electrical Resistivity and Seismic Characterization of Submarine Groundwater Discharge in Long Bay, SC
NASA Astrophysics Data System (ADS)
Viso, R. F.; McCoy, C.; Quafisi, D.; Gayes, P. T.
Submarine groundwater discharge (SGD) has been identified as a significant contributor of dissolved nutrients and contaminants to near-shore waters. Little is known, however, about geologic controls on the spatial distribution of SGD seeps. Discharge estimates are typically derived from geochemical tracers such as Rn-222. Such estimates of total fluxes over a given area do not consider the potential for spatial variability in discharge rates. Higher fluxes of chemically distinct SGD over smaller areas could have complex effects on localized water masses, ecosystems, and geological features. In an effort to assess the distribution of SGD, electrical resistivity and seismic surveys were conducted along the inner shelf of Long Bay, South Carolina during a series of cruises between October, 2005 and November 2006. In addition, basic bottom water quality parameters including dissolved oxygen, temperature, salinity, and pH were measured. Preliminary submarine groundwater flux estimates for northern Long Bay were also generated from measurements of Rn-222. The resistivity signal is highly variable along shore with several instances of elevated values suggesting presence of relatively fresher pore waters. In some cases, elevated resistivity measurements were spatially co-registered with seismically defined paleochannels extending across the shelf. Other areas of elevated resistivity values correlate with smaller discontinuities in seismic reflectors. A third category of resistivity anomalies does not correlate with seismically defined features. Overall, anomaly frequency and intensity decrease rapidly with increasing distance from shore. At distances > 1 km from shore, the resistivity signal is uniform in space and low in magnitude, implying less of a fresh water contribution. Water quality parameters are variable along shore and may reflect the influence of SGD. Rn-derived fluxes suggest SGD equivalent to as much as 50% of riverine discharge into Long Bay. Ongoing work is
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.
Species-Specific Diversity of a Fixed Motor Pattern: The Electric Organ Discharge of Gymnotus
Rodríguez-Cattaneo, Alejo; Pereira, Ana Carolina; Aguilera, Pedro A.; Crampton, William G. R.; Caputi, Angel A.
Understanding fixed motor pattern diversity across related species provides a window for exploring the evolution of their underlying neural mechanisms. The electric organ discharges of weakly electric fishes offer several advantages as paradigmatic models for investigating how a neural decision is transformed into a spatiotemporal pattern of action. Here, we compared the far fields, the near fields and the electromotive force patterns generated by three species of the pulse generating New World gymnotiform genus Gymnotus. We found a common pattern in electromotive force, with the far field and near field diversity determined by variations in amplitude, duration, and the degree of synchronization of the different components of the electric organ discharges. While the rostral regions of the three species generate similar profiles of electromotive force and local fields, most of the species-specific differences are generated in the main body and tail regions of the fish. This causes that the waveform of the field is highly site dependant in all the studied species. These findings support a hypothesis of the relative separation of the electrolocation and communication carriers. The presence of early head negative waves in the rostral region, a species-dependent early positive wave at the caudal region, and the different relationship between the late negative peak and the main positive peak suggest three points of lability in the evolution of the electrogenic system: a) the variously timed neuronal inputs to different groups of electrocytes; b) the appearance of both rostrally and caudally innervated electrocytes, and c) changes in the responsiveness of the electrocyte membrane. PMID:18461122
NASA Astrophysics Data System (ADS)
Krompholz, H.; Kristiansen, M.
The results of a one-year contract on electrode erosion phenomena are summarized. The arc voltage drop in a spark gap was measured for various electrode, gas, and pressure combinations. A previously developed model of self breakdown voltage distribution was extended. A jet model for electrode erosion was proposed and an experimental arrangement for testing the model was constructed. The effects of inhomogeneities and impurities in the electrodes were investigated. Some of the work described here is scheduled for completion in 1985 under a current grant (AFOSR 84-0032). The areas of investigation described here include: (1) Self breakdown voltage distributions; (2) Electrode erosion; (3) Spark gap voltage recovery.
Spark gap device for precise switching
Boettcher, G.E.
A spark gap device for precise switching of an energy storage capacitor into an exploding bridge wire load is disclosed. Niobium electrodes having a melting point of 2,415 degrees centigrade are spaced apart by an insulating cylinder to define a spark gap. The electrodes are supported by conductive end caps which, together with the insulating cylinder, form a hermetically sealed chamber filled with an inert, ionizable gas, such as pure xenon. A quantity of solid radioactive carbon-14 within the chamber adjacent the spark gap serves as a radiation stabilizer. The sides of the electrodes and the inner wall of the insulating cylinder are spaced apart a sufficient distance to prevent unwanted breakdown initiation. A conductive sleeve may envelop the outside of the insulating member from the midpoint of the spark gap to the cap adjacent the cathode. The outer metallic surfaces of the device may be coated with a hydrogen-impermeable coating to lengthen the shelf life and operating life of the device. The device breaks down at about 1,700 volts for input voltage rates up to 570 volts/millisecond and allows peak discharge currents of up to 3,000 amperes from a 0.3 microfarad energy storage capacitor for more than 1,000 operations. 3 figs.
Spark gap device for precise switching
Boettcher, Gordon E.
A spark gap device for precise switching of an energy storage capacitor into an exploding bridge wire load is disclosed. Niobium electrodes having a melting point of 2,415 degrees centrigrade are spaced apart by an insulating cylinder to define a spark gap. The electrodes are supported by conductive end caps which, together with the insulating cylinder, form a hermetically sealed chamber filled with an inert, ionizable gas, such as pure xenon. A quantity of solid radioactive carbon-14 within the chamber adjacent the spark gap serves as a radiation stabilizer. The sides of the electrodes and the inner wall of the insulating cylinder are spaced apart a sufficient distance to prevent unwanted breakdown initiation. A conductive sleeve may envelop the outside of the insulating member from the midpoint of the spark gap to the cap adjacent the cathode. The outer metallic surfaces of the device may be coated with a hydrogen-impermeable coating to lengthen the shelf life and operating life of the device. The device breaks down at about 1,700 volts for input voltage rates up to 570 volts/millisecond and allows peak discharge currents of up to 3,000 amperes from a 0.3 microfarad energy storage capacitor for more than 1,000 operations.
Electric organ discharge patterns during group hunting by a mormyrid fish
Arnegard, Matthew E; Carlson, Bruce A
Weakly electric fish emit and receive low-voltage electric organ discharges (EODs) for electrolocation and communication. Since the discovery of the electric sense, their behaviours in the wild have remained elusive owing to their nocturnal habits and the inaccessible environments in which they live. The transparency of Lake Malawi provided the first opportunity to simultaneously observe freely behaving mormyrid fish and record their EODs. We observed a piscivorous mormyrid, Mormyrops anguilloides, hunting in small groups in Lake Malawi while feeding on rock-frequenting cichlids of the largest known vertebrate species flock. Video recordings yielded the novel and unexpected finding that these groups resembled hunting packs by being largely composed of the same individuals across days. We show that EOD accelerations accompany prey probing and size estimation by M. anguilloides. In addition, group members occasionally synchronize bursts of EODs with an extraordinary degree of precision afforded by the mormyrid echo response. The characteristics and context of burst synchronization suggest that it may function as a pack cohesion signal. Our observations highlight the potential richness of social behaviours in a basal vertebrate lineage, and provide a framework for future investigations of the neural mechanisms, behavioural rules and ecological significance of social predation in M. anguilloides. PMID:16006329
Study on Miniaturized UHF Antennas for Partial Discharge Detection in High-Voltage Electrical Equipment.
Liu, Jingcun; Zhang, Guogang; Dong, Jinlong; Wang, Jianhua
Detecting partial discharge (PD) is an effective way to evaluate the condition of high-voltage electrical equipment insulation. The UHF detection method has attracted attention due to its high sensitivity, strong interference resistance, and ability to locate PDs. In this paper, a miniaturized equiangular spiral antenna (ESA) for UHF detection that uses a printed circuit board is proposed. I-shaped, L-shaped, and C-shaped microstrip baluns were designed to match the impedance between the ESA and coaxial cable and were verified by a vector network analyzer. For comparison, three other types of UHF antenna were also designed: A microstrip patch antenna, a microstrip slot antenna, and a printed dipole antenna. Their antenna factors were calibrated in a uniform electric field of different frequencies modulated in a gigahertz transverse electromagnetic cell. We performed comparison experiments on PD signal detection using an artificial defect model based on the international IEC 60270 standard. We also conducted time-delay test experiments on the ESA sensor to locate a PD source. It was found that the proposed ESA sensor meets PD signal detection requirements. The sensor's compact size makes it suitable for internal installation in high-voltage electrical equipment. PMID:26610506
Study on Miniaturized UHF Antennas for Partial Discharge Detection in High-Voltage Electrical Equipment
Liu, Jingcun; Zhang, Guogang; Dong, Jinlong; Wang, Jianhua
Detecting partial discharge (PD) is an effective way to evaluate the condition of high-voltage electrical equipment insulation. The UHF detection method has attracted attention due to its high sensitivity, strong interference resistance, and ability to locate PDs. In this paper, a miniaturized equiangular spiral antenna (ESA) for UHF detection that uses a printed circuit board is proposed. I-shaped, L-shaped, and C-shaped microstrip baluns were designed to match the impedance between the ESA and coaxial cable and were verified by a vector network analyzer. For comparison, three other types of UHF antenna were also designed: A microstrip patch antenna, a microstrip slot antenna, and a printed dipole antenna. Their antenna factors were calibrated in a uniform electric field of different frequencies modulated in a gigahertz transverse electromagnetic cell. We performed comparison experiments on PD signal detection using an artificial defect model based on the international IEC 60270 standard. We also conducted time-delay test experiments on the ESA sensor to locate a PD source. It was found that the proposed ESA sensor meets PD signal detection requirements. The sensor's compact size makes it suitable for internal installation in high-voltage electrical equipment. PMID:26610506
Streamer development in barrier discharge in air: spectral signatures and electric field
NASA Astrophysics Data System (ADS)
Hoder, Tomas; Simek, Milan; Bonaventura, Zdenek; Prukner, Vaclav
Electrical breakdown in the upper atmosphere takes form of so called Transient Luminous Events (TLE). Down to the certain pressure limit, the first phases of the TLE-phenomena are controlled by the streamer mechanism. In order to understand the development of these events, streamers in 10 torr air were generated in volume barrier discharge. Stability and reproducibility of generated streamers were secured by proper electrode geometry and specific applied voltage waveform. In this work, spectrally resolved measurements of the streamer head emission with high spatial and temporal resolution are presented. Precise recordings of the emission of the second positive and first negative systems of molecular nitrogen allowed the determination of the spatio-temporal development of the reduced electric field in the streamer head. This unique experimental result reveals in more details the early stages of the streamer development and gives, besides values for streamer velocity and its diameter, quantitative information on the magnitude of the electric field. T.H. was financed through the ESF Programme TEA-IS (Grant No. 4219), M.S. and V.P. by the AVCR under collaborative project M100431201 and Z.B. acknowledges the support of grant of Czech Science Foundation GA15-04023S.
Waveform diversity of electric organ discharges: the role of electric organ auto-excitability in Gymnotus spp.
Rodríguez-Cattáneo, Alejo; Caputi, Angel Ariel
This article shows that differences in the waveforms of the electric organ discharges (EODs) from two taxa are due to the different responsiveness of their electric organs (EOs) to their previous activity (auto-excitability). We compared Gymnotus omarorum endemic to Uruguay (35 degrees South, near a big estuary), which has four components in the head to tail electric field (V(1) to V(4)), with Gymnotus sp. endemic to the south of Brazil, Paraguay and Argentinean Mesopotamia (25 degrees South, inland), which shows a fifth component in addition to the others (V(5)). We found that: (a) the innervation pattern of the electrocytes, (b) the three earlier, neurally driven, EOD components (V(1) to V(3)), and (c) their remnants after curarisation were almost identical in the two taxa. The equivalent electromotive forces of late components (V(4) and V(5)) increased consistently as a function of the external current associated with the preceding component and were abolished by partial curarisation in both taxa. Taken together these data suggest that these components are originated in the responses of the electrocytes to longitudinal currents through the EO. By using a differential load procedure we showed that V(4) in G. omarorum responded to experimental changes in its excitation current with larger amplitude variations than V(4) in Gymnotus sp. We conclude that the differences in the EOD phenotype of the two studied taxa are due to the different EO auto-excitability. This, in turn, is caused either by the different expression of a genetic repertoire of conductance in the electrocyte membrane or in the wall of the tubes forming the EO. PMID:19837890
Obtaining molecular hydrogen in electric discharge of the tornado type in air mixture with ethanol and water vapors
NASA Astrophysics Data System (ADS)
Levko, D. S.; Shchedrin, A. I.; Chernyak, V. Ya.; Ol'Shevskiĭ, S. V.; Nedybalyuk, O. A.
A new plasmachemical reactor is proposed that provides a high yield of hydrogen from electric discharge in a mixture of air with ethanol and water vapors. It is shown that intense electron-molecule reactions and high temperature in the discharge region favor an increase in the degree of H2O and C2H5OH conversion into molecular hydrogen. A mechanism of the initiation of chain reactions leading to H2 formation is determined. It is established that H2 concentration reaches saturation in the region of discharge currents above 200 mA.
Optical diagnostic and electrical analysis in dusty RF discharges containing plasmoids
Lagrange, J. F.; Géraud-Grenier, I.; Massereau-Guilbaud, V.
The presence of hydrogenated carbon nitride a-CN{sub x}:H particles confined in an argon dusty discharge induces the appearance of instabilities. Those instabilities, also called plasmoids, are luminous regions which move through the plasma and rotate around the biased electrode circumference. Electrical characteristics of the plasma have been used to evidence the presence of dust particles and to demonstrate that plasmoid appearance is triggered by particles. The light emitted by the plasma is analysed by optical emission spectroscopy. This paper presents the spatial distribution of excited species, such as CN, Ar I… between electrodes both inside plasmoids and in the surrounding dusty plasma. Obtained results allow to get information for the electron energy distribution function. Moreover, the interplay between plasmoid behaviour and particle presence in the plasma is shown.
Experimental study of the water jet induced by underwater electrical discharge in a narrow rectangular tube
NASA Astrophysics Data System (ADS)
Koita, T.; Zhu, Y.; Sun, M.
This paper reports an experimental investigation on the effects of explosion depth and tube width on the water jet induced by an underwater electrical discharge in a narrow rectangular tube. The water jet formation and bubble structure were evaluated from the images recorded by a high-speed video camera. Two typical patterns of jet formation and four general patterns of bubble implosion were observed, depending on the explosion depth and tube width. The velocity of the water jet was calculated from the recorded images. The jet velocity was observed to depend on not only the explosion depth and energy, but also on the tube width. We proposed an empirical formula defining the water jet velocity in the tube as a function of the tube width and explosion depth and energy.
Amino acids on the rampant primordial Earth: electric discharges and the hot salty ocean.
Plankensteiner, Kristof; Reiner, Hannes; Rode, Bernd M
For more than 50 years scientists who study prebiotic chemistry have been dealing with chemical evolution as it could have possibly taken place on the primordial Earth. Since we will never know what processes have really taken place around 3.8 to 4 billion years ago we can only come up with plausible reaction pathways that work well in an early Earth scenario as indicated by geochemists. In our work we have investigated the plausibility of one particularly important branch of prebiotic chemistry, the formation of amino acids, by electric discharge in a neutral atmosphere composed of carbon dioxide, nitrogen, and water vapour above liquid water. We have found yields of various amino acids under different temperature conditions, with and without sodium chloride in a simulated primordial lake or ocean within extremely short reaction times compared to the timespan available for prebiotic evolution. PMID:16404523
Stable transformation of Populus and incorporation of pest resistance by electric discharge particle acceleration.
McCown, B H; McCabe, D E; Russell, D R; Robison, D J; Barton, K A; Raffa, K F
Three different target tissues (protoplast-derived cells, nodules, and stems) and two unrelated hybrid genotypes of Populus (P. alba x P. grandidentata 'Crandon' and P. nigra 'Betulifolia' x P. trichocarpa) have been stably transformed by electric discharge particle acceleration using a 18.7 kb plasmid containing NOS-NPT, CaMV 35S-GUS, and CaMV 35S-BT. Four transformed plants of one hybrid genotype, NC5339, containing all 3 genes were recovered and analyzed. Two expressed GUS and one was highly resistant to feeding by 2 lepidopteran pests (the forest tent caterpillar, Malacosoma disstria, and the gypsy moth, Lymantria dispar.) Pretreatment of the target tissues, fine-tuning of the bombardment parameters, and the use of a selection technique employing flooding of the target tissues were important for reliable recovery of transformed plants. PMID:24220719
Dynamic nuclear polarization in solid samples by electrical-discharge-induced radicals
NASA Astrophysics Data System (ADS)
Katz, Itai; Blank, Aharon
Dynamic nuclear polarization (DNP) is a method for enhancing nuclear magnetic resonance (NMR) signals that has many potential applications in chemistry and medicine. Traditionally, DNP signal enhancement is achieved through the use of exogenous radicals mixed in a solution with the molecules of interest. Here we show that proton DNP signal enhancements can be obtained for solid samples without the use of solvent and exogenous radicals. Radicals are generated primarily on the surface of a solid sample using electrical discharges. These radicals are found suitable for DNP. They are stable under moderate vacuum conditions, yet readily annihilate upon compound dissolution or air exposure. This feature makes them attractive for use in medical applications, where the current variety of radicals used for DNP faces regulatory problems. In addition, this solvent-free method may be found useful for analytical NMR of solid samples which cannot tolerate solvents, such as certain pharmaceutical products.
Possibility of nonexistence of hot and superhot hydrogen atoms in electrical discharges
Loureiro, J.; Amorim, J.
Recently, the existence of extremely energetic hydrogen atoms in electrical discharges has been proposed in the literature with large controversy, from the analysis of the anomalous broadening of hydrogen Balmer lines. In this paper, the velocity distribution of H atoms and the profiles of the emitting atom lines created by the exothermic reaction H{sub 2}{sup +}+H{sub 2}{yields}H{sub 3}{sup +}+H+{Delta}E are calculated, as a function of the internal energy defect {Delta}E. The shapes found for the non-Maxwell-Boltzmann distributions resulting in non-Gaussian line profiles raise serious arguments against the existence of hot and superhot H atoms as it has been proposed, at least with those temperatures.
An on-line monitoring system for a micro electrical discharge machining (micro-EDM) process
NASA Astrophysics Data System (ADS)
Liao, Y. S.; Chang, T. Y.; Chuang, T. J.
A pulse-type discriminating system to monitor the process of micro electrical discharge machining (micro-EDM) is developed and implemented. The specific features are extracted and the pulses from a RC-type power source are classified into normal, effective arc, transient short circuit and complex types. An approach to discriminate the pulse type according to three durations measured at three pre-determined voltage levels of a pulse is proposed. The developed system is verified by using simulated signals. Discrimination of the pulse trains in actual machining processes shows that the pulses are mainly the normal type for micro wire-EDM and micro-EDM milling. The pulse-type distribution varies during the micro-EDM drilling process. The percentage of complex-type pulse increases monotonically with the drilling depth. It starts to drop when the gap condition is seriously deteriorated. Accordingly, an on-line monitoring strategy for the micro-EDM drilling process is proposed.
A fatigue study of electrical discharge machine (EDM) strain-gage balance materials
NASA Technical Reports Server (NTRS)
Rhew, Ray D.
A fatigue study was undertaken to determine how much electrical-discharge-machine (EDM) processing affected the fatigue life of balance materials: EDM and regular milling-machine (MM) samples were compared. Simulation of a typical balance stress configuration was devised for the fatigue testing in order to obtain results more closely related to balance situations. The fatigue testing of the EDM and MM specimens has indicated that the EDM technique does indeed reduce the fatigue life of 15-5PH steel, the first balance material tested. This conclusion was based on comparisons of the specimen fatigue lives with theoretical and manufacturer's data. Hence the EDM surface effects are detrimental to the fatigue life of this balance material.
Optical diagnostic and electrical analysis in dusty RF discharges containing plasmoids
NASA Astrophysics Data System (ADS)
Lagrange, J. F.; Géraud-Grenier, I.; Faubert, F.; Massereau-Guilbaud, V.
The presence of hydrogenated carbon nitride a-CNx:H particles confined in an argon dusty discharge induces the appearance of instabilities. Those instabilities, also called plasmoids, are luminous regions which move through the plasma and rotate around the biased electrode circumference. Electrical characteristics of the plasma have been used to evidence the presence of dust particles and to demonstrate that plasmoid appearance is triggered by particles. The light emitted by the plasma is analysed by optical emission spectroscopy. This paper presents the spatial distribution of excited species, such as CN, Ar I… between electrodes both inside plasmoids and in the surrounding dusty plasma. Obtained results allow to get information for the electron energy distribution function. Moreover, the interplay between plasmoid behaviour and particle presence in the plasma is shown.
Characterisation of TiC layers deposited using an electrical discharge coating process
NASA Astrophysics Data System (ADS)
Algodi, S. J.; Murray, J. W.; Clare, A. T.; Brown, P. D.
Electrical discharge machining (EDM) is a non-conventional, high-accuracy machining process for the manufacture of complex shapes, regardless of hardness of the workpiece. There is interest to develop the EDM technique for coating or surface modification by using a powder metallurgy (PM) tool electrode and/or added powder suspended within the dielectric fluid. We report on the EDM deposition of TiC coatings onto stainless steel, using either Cu or TiC electrodes, with and without Ti powder in the working oil. EDM processed layers exhibited hardness values ∼ 3-4 times higher than the substrate, emphasising the ability of EDM to impart improved mechanical performance to the surface of austenitic stainless steel.
Shaping of steel mold surface of lens array by electrical discharge machining with spherical ball electrode.
Takino, Hideo; Hosaka, Takahiro
We propose a method for fabricating a spherical lens array mold by electrical discharge machining (EDM) with a ball-type electrode. The electrode is constructed by arranging conductive spherical balls in an array. To fundamentally examine the applicability of the proposed EDM method to the fabrication of lens array molds, we use an electrode having a single ball to shape a lens array mold made of stainless steel with 16 spherical elements, each having a maximum depth of 0.5 mm. As a result, a mold surface is successfully shaped with a peak-to-valley shape accuracy of approximately 10 μm, and an average surface roughness of 0.85 μm. PMID:27409126
Study of Flowfield around a Hypersonic Model of HOPE-X Utilizing the Electric Discharge Method
NASA Astrophysics Data System (ADS)
Nishio, Masatomi; Kotake, Mutsuo; Sezaki, Shinji; Nakamura, Hiroaki
The shock shapes, boundary layers, and temperature layers around a model of HOPE-X traveling at a hypersonic speed were visualized utilizing the electric discharge method. The experiments were carried out under the condition that the angles of attack were 0°, 15°, 30°, and 45°. To visualize 3-D shock shapes around the model, the observation of shock shapes were conducted from the side and back of the model. From the experimental results, it was confirmed that the two kinds of shock shapes interacted with each other. The various kinds of shock shapes according to the model angles of attack were also obtained. Subsequently, the visualized results of temperature layer around the model were described. Furthermore, the boundary layers generated around the model were visualized and compared with the temperature layers. A hypersonic gun tunnel was used in these experiments. The main characteristics of the tunnel were the Mach number was 10 and the duration was 10ms.
Tracing explosive in solvent using quantum cascade laser with pulsed electric discharge system
Park, Seong-Wook; Tian, Chao; Martini, Rainer; Chen, Gang; Chen, I-chun Anderson
We demonstrated highly sensitive detection of explosive dissolved in solvent with a portable spectroscopy system (Q-MACS) by tracing the explosive byproduct, N{sub 2}O, in combination with a pulsed electric discharge system for safe explosive decomposition. Using Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), the gas was monitored and analyzed by Q-MACS and the presence of the dissolved explosive clearly detected. While HMX presence could be identified directly in the air above the solutions even without plasma, much better results were achieved under the decomposition. The experiment results give an estimated detection limit of 10 ppb, which corresponds to a 15 pg of HMX.
Development of CAD/CAM System for Cross Section's Changing Hole Electrical Discharge Machining
NASA Astrophysics Data System (ADS)
Ishida, Tohru; Ishiguro, Eiki; Kita, Masahiko; Nakamoto, Keiichi; Takeuchi, Yoshimi
This study deals with the development of a new CAD/CAM system for fabricating holes whose cross sections change variously. The cross sections of machined holes are generally constant. The limitations in the shapes of holes that can be machined make obstacles in the design stage of industrial products. A new device that utilizes electrical discharge machining has been developed that can create holes with various cross sections to solve this problem. However, it has been impossible to put the device into practical use since there has been no software that has enabled the designed shapes to be easily machined. Therefore, we aimed at developing a new CAD/CAM system for machining the beforehand designed holes with changing cross sections by using the device. As the first step in developing the CAD/CAM system, the post processor in the CAM system is formulated in this paper.
Dynamic nuclear polarization in solid samples by electrical-discharge-induced radicals.
Katz, Itai; Blank, Aharon
Dynamic nuclear polarization (DNP) is a method for enhancing nuclear magnetic resonance (NMR) signals that has many potential applications in chemistry and medicine. Traditionally, DNP signal enhancement is achieved through the use of exogenous radicals mixed in a solution with the molecules of interest. Here we show that proton DNP signal enhancements can be obtained for solid samples without the use of solvent and exogenous radicals. Radicals are generated primarily on the surface of a solid sample using electrical discharges. These radicals are found suitable for DNP. They are stable under moderate vacuum conditions, yet readily annihilate upon compound dissolution or air exposure. This feature makes them attractive for use in medical applications, where the current variety of radicals used for DNP faces regulatory problems. In addition, this solvent-free method may be found useful for analytical NMR of solid samples which cannot tolerate solvents, such as certain pharmaceutical products. PMID:26547016
Can carbon fibres work as tool electrodes in micro electrical discharge machining?
NASA Astrophysics Data System (ADS)
Trych-Wildner, Anna; Kudla, Leszek
This paper presents a basic study of the possible application of carbon fibres as tool electrodes in micro electrical discharge machining. The purpose of the experiments with this novel material was to gain knowledge about the operation of the new tool electrode. In the paper, the procedure for adapting a single fibre to such a function is described, with detailed steps on preparing the shanks essential for the mounting operation in the experimental setup. The design setup is also presented and the experimental conditions of each test are shown. Furthermore, tests with the prepared electrodes concerning the general observations of the process and the results on the machined surface and on the tool are presented. The shape cavity fabrication and tests with the reverse polarity of the electrodes are also introduced. Next, the influence of single discharge energy is considered and the geometry of the obtained microholes is discussed. Detailed data about the wear of the tool, which can be up to 90% of the entire eroded material, in comparison with the material removal rate from the workpiece, which can be at a level of 10%, is gathered. Then, the geometrical analysis of the cavities is described showing that their depths are in the range of a few micrometres.
Development of an on-board charge and discharge management system for electric-vehicle batteries
NASA Astrophysics Data System (ADS)
Alzieu, J.; Gagnol, P.; Smimite, H.
To improve the service quality of its electric-vehicle (EV) fleet (≈500 vehicles) and master the behaviour of the valve-regulated lead/acid (VRLA) batteries, which power the major part of it, Electricité de France (EDF) has developed an on-board battery-management system. Information on the operating battery behaviour is given to the driver. Overdischarges can then be avoided. Rapid charging of VRLA batteries is monitored. The main available functions of this device are: (i) battery life recording, short- and long-term information storage is available; (ii) charge monitoring, communication with a 23 kW charger is established through an ISO 9141 interface; a fast-charging algorithm for VRLA batteries has been developed and up to 50% of the range can be returned to the EV in 20 min; (iii) battery management during driving, 'orange' and 'red' alarms related to the depth-of-discharge help the driver to manage the driving; cell overdischarges can then be avoided; (iv) maintenance, the faulty groups of cells are identified; (v) gauge (state-of-charge indicator), this function requires mid-term R and D; for the moment, only charged and discharged Ah are indicated but when more accurate state-of-charge prediction algorithms are available, the software will be up-graded.
Effects of water vapor on flue gas conditioning in the electric fields with corona discharge.
Liqiang, Qi; Yajuan, Zhang
Sulfur dioxide (SO2) removal via pulsed discharge nonthermal plasma in the absence of ammonia was investigated to determine how electrostatic precipitators (ESPs) can effectively collect particulate matter less than 2.5μm in diameter from flue gas. SO2 removal increased as water vapor concentration increased. In a wet-type plasma reactor, directing a gas-phase discharge plasma toward the water film surface significantly enhanced the liquid-phase oxidation of HSO3(-) to SO4(2-). Comparisons of various absorbents revealed that the hydroxyl radical is a key factor in plasma-induced liquid-phase reactions. The resistivity, size distribution, and cohesive force of fly ash at different water vapor contents were measured using a Bahco centrifuge, which is a dust electrical resistivity test instrument, as well as a cohesive force test apparatus developed by the researchers. When water vapor content increased by 5%, fly ash resistivity in flue gas decreased by approximately two orders of magnitude, adhesive force and size increased, and specific surface area decreased. Therefore, ESP efficiency increased. PMID:23669785
ERIC Educational Resources Information Center
Crow, Sherry R.
Many of the children in the early grades who marveled at the plethora of beautiful resources just did not seem that interested by the time they reached upper elementary school. While some children sustained their spark of curiosity, others did not. The force that keeps children (or people of any age) excited about anything is called "intrinsic…
Dust particles under the influence of crossed electric and magnetic fields in the sheath of an rf discharge
Puttscher, M. Melzer, A.
Experimental studies on the interaction of micron-sized dust particles in plasmas with external magnetic fields are presented. The particles are levitated in the sheath region of an rf discharge by gravity and electric field force under the presence of a horizontal magnetic field of up to 50 mT. It is observed that the dust particles are pushed either in the E{sup →}×B{sup →}- or in the opposite direction depending on magnetic field strength, particle properties, and discharge conditions. This transport behavior is described by a competition between horizontal ambipolar electric field force and ion and neutral drag.
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.
Observation of a new class of electric discharges within artificial clouds of charged water droplets and its implication for lightning initiation within thunderclouds
NASA Astrophysics Data System (ADS)
Kostinskiy, Alexander Yu.; Syssoev, Vladimir S.; Bogatov, Nikolay A.; Mareev, Evgeny A.; Andreev, Mikhail G.; Makalsky, Leonid M.; Sukharevsky, Dmitry I.; Rakov, Vladimir A.
We have observed unusual plasma formations (UPFs) in artificial clouds of charged water droplets using a high-speed infrared camera operating in conjunction with a high-speed visible-range camera. Inferred plasma parameters were close to those of long-spark leaders observed in the same experiments, while the channel morphology was distinctly different from that of leaders, so that UPFs can be viewed as a new type of in-cloud discharge. These formations can occur in the absence of spark leaders and appear to be manifestations of collective processes building, essentially from scratch, a complex hierarchical network of interacting channels at different stages of development (some of which are hot and live for milliseconds). We believe that the phenomenon should commonly occur in thunderclouds and might give insights on the missing link in the still poorly understood lightning initiation process.
Field emission driven direct current argon discharges and electrical breakdown mechanism across micron scale gaps
NASA Astrophysics Data System (ADS)
Matejčik, Štefan; Radjenović, Branislav; Klas, Matej; Radmilović-Radjenović, Marija
In this paper results of the experimental and theoretical studies of the field emission driven direct current argon microdischarges for the gaps between 1 μm and 100 μm are presented and discussed. The breakdown voltage curves and Volt-Ampere characteristics proved to be a fertile basis providing better understanding of the breakdown phenomena in microgaps. Based on the measured breakdown voltage curves, the effective yields have been estimated confirming that the secondary electron emission due to high electric field generated in microgaps depends primarily on the electric field leading directly to the violation of the Paschen's law. Experimental data are supported by the theoretical predictions that suggest departure from the scaling law and a flattening of the Paschen curves at higher pressures confirming that Townsend phenomenology breaks down when field emission becomes the key mechanism leading to the breakdown. Field emission of electrons from the cathode, the space charge effects in the breakdown and distinction between the Fowler-Nordheim field emission and the space charge limited current density are also analyzed. Images and Volt-Ampere characteristics recorded at the electrode gap size of 20 μm indicate the existence of a discharge region similar to arc at the pressure of around 200 Torr has been observed. Contribution to the Topical Issue "Recent Breakthroughs in Microplasma Science and Technology", edited by Kurt Becker, Jose Lopez, David Staack, Klaus-Dieter Weltmann and Wei Dong Zhu.
Small-size controlled vacuum spark-gap in an external magnetic field
Asyunin, V. I. Davydov, S. G.; Dolgov, A. N. Pshenichnyi, A. A.; Yakubov, R. Kh.
It is demonstrated that the operation of a small-size controlled spark-gap can be controlled by applying a uniform external magnetic field. It is shown that the magnetic field of such a simple configuration efficiently suppresses the effect of localization of the discharge current after multiple actuations of the spark-gap.
Comparative complexity of emission spectra from ICP, dc, Arc, and spark excitation sources
Winge, R.K.; DeKalb, E.L.; Fassel, V.A.
A comparison of atomic emission spectra excited in high voltage spark and dc are discharges and in an inductively coupled plasma revealed that the most complex spectra were emitted by the high voltage spark. The dc arc and the inductively coupled plasma yielded spectra of approximately equivalent complexity. These observations are not in accord with the impressions conveyed in the literature.
Synchronised electrical monitoring and high speed video of bubble growth associated with individual discharges during plasma electrolytic oxidation
NASA Astrophysics Data System (ADS)
Troughton, S. C.; Nominé, A.; Nominé, A. V.; Henrion, G.; Clyne, T. W.
Synchronised electrical current and high speed video information are presented from individual discharges on Al substrates during PEO processing. Exposure time was 8 μs and linear spatial resolution 9 μm. Image sequences were captured for periods of 2 s, during which the sample surface was illuminated with short duration flashes (revealing bubbles formed where the discharge reached the surface of the coating). Correlations were thus established between discharge current, light emission from the discharge channel and (externally-illuminated) dimensions of the bubble as it expanded and contracted. Bubbles reached radii of 500 μm, within periods of 100 μs, with peak growth velocity about 10 m/s. It is deduced that bubble growth occurs as a consequence of the progressive volatilisation of water (electrolyte), without substantial increases in either pressure or temperature within the bubble. Current continues to flow through the discharge as the bubble expands, and this growth (and the related increase in electrical resistance) is thought to be responsible for the current being cut off (soon after the point of maximum radius). A semi-quantitative audit is presented of the transformations between different forms of energy that take place during the lifetime of a discharge.
Boundary-value problem for a counterrotating electrical discharge in an axial magnetic field. [plasma centrifuge for isotope separation
NASA Technical Reports Server (NTRS)
Hong, S. H.; Wilhelm, H. E.
An electrical discharge between two ring electrodes embedded in the mantle of a cylindrical chamber is considered, in which the plasma in the anode and cathode regions rotates in opposite directions under the influence of an external axial magnetic field. The associated boundary-value problem for the coupled partial differential equations describing the azimuthal velocity and radial current-density fields is solved in closed form. The velocity, current density, induced magnetic induction, and electric fields are presented for typical Hartmann numbers, magnetic Reynolds numbers, and geometry parameters. The discharge is shown to produce anodic and cathodic plasma sections rotating at speeds of the order 1,000,000 cm/sec for conventional magnetic field intensities. Possible application of the magnetoactive discharge as a plasma centrifuge for isotope separation is discussed.
Distribution of E/N and N/e/ in a cross-flow electric discharge laser. [electric field to neutral gas density and electron number density
NASA Technical Reports Server (NTRS)
Dunning, J. W., Jr.; Lancashire, R. B.; Manista, E. J.
Measurements have been conducted of the effect of the convection of ions and electrons on the discharge characteristics in a large scale laser. The results are presented for one particular distribution of ballast resistance. Values of electric field, current density, input power density, ratio of electric field to neutral gas density (E/N), and electron number density were calculated on the basis of measurements of the discharge properties. In a number of graphs, the E/N ratio, current density, power density, and electron density are plotted as a function of row number (downstream position) with total discharge current and gas velocity as parameters. From the dependence of the current distribution on the total current, it appears that the electron production in the first two rows significantly affects the current flowing in the succeeding rows.
The synthesis of higher oxides of alkali and alkaline earth metals in an electric discharge: Theoretical and experimental studies
NASA Technical Reports Server (NTRS)
Bell, A. T.; Sadhukhan, P.
Potassium hydroxide was subjected to the products of an electrical discharge sustained in oxygen and produced both potassium peroxide and superoxide. The conversion to higher oxides was shown to strongly depend upon the particle size of KOH, the position of KOH in the discharge zone, and the operating conditions of the discharge. Similar experiments were performed with hydroxides of lithium and calcium which do not form superoxides, but are converted to peroxides. The yields of peroxides were shown to strongly depend upon the operating conditions of the discharge. The absence of superoxides and the presence of peroxides of lithium and calcium was explained from the consideration of relative thermodynamic stability of the oxides of lithium and calcium. Thermogravimetric analysis was shown to provide a more accurate means for determining the amount of KO2 than previous methods.
46 CFR 108.437 - Pipe sizes and discharge rates for enclosed ventilation systems for rotating electrical equipment.
Code of Federal Regulations, 2012 CFR
... 46 Shipping 4 2012-10-01 2012-10-01 false Pipe sizes and discharge rates for enclosed ventilation systems for rotating electrical equipment. 108.437 Section 108.437 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Fire Extinguishing Systems Fixed Carbon Dioxide...
46 CFR 108.437 - Pipe sizes and discharge rates for enclosed ventilation systems for rotating electrical equipment.
Code of Federal Regulations, 2011 CFR
... 46 Shipping 4 2011-10-01 2011-10-01 false Pipe sizes and discharge rates for enclosed ventilation systems for rotating electrical equipment. 108.437 Section 108.437 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Fire Extinguishing Systems Fixed Carbon Dioxide...
46 CFR 108.437 - Pipe sizes and discharge rates for enclosed ventilation systems for rotating electrical equipment.
Code of Federal Regulations, 2010 CFR
... 46 Shipping 4 2010-10-01 2010-10-01 false Pipe sizes and discharge rates for enclosed ventilation systems for rotating electrical equipment. 108.437 Section 108.437 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Fire Extinguishing Systems Fixed Carbon Dioxide...
Study on electrical characteristics of barrier-free atmospheric air diffuse discharge generated by nanosecond pulses and long wire electrodes
Li, Lee Liu, Yun-Long; Teng, Yun; Liu, Lun; Pan, Yuan
In room-temperature atmospheric air, the large-scale diffuse plasmas can be generated via high-voltage nanosecond pulses with short rise-time and wire electrodes. Diffuse discharge with the wire electrode length up to 110.0 cm and the discharge spacing of several centimeters has been investigated in this paper. Electrical characteristics of diffuse discharge have been analyzed by their optical photographs and measuring of the voltage and current waveforms. Experimental results show the electrode spacing, and the length of wire electrodes can influence the intensity and mode transition of diffuse discharge. The characteristic of current waveforms is that there are several current oscillation peaks at the time of applied pulsed voltage peak, and at the tail of applied pulse, the conduction current component will compensate the displacement one so that the measured current is unidirectional in diffuse discharge mode. The transition from diffuse discharge to arc discharge is always with the increasing of conduction current density. As for nanosecond pulses with long tail, the long wire electrodes are help for generating non-equilibrium diffuse plasmas.
Extended plasma channels created by UV laser in air and their application to control electric discharges
Zvorykin, V. D. Ionin, A. A.; Levchenko, A. O.; Seleznev, L. V.; Sinitsyn, D. V.; Smetanin, I. V.; Ustinovskii, N. N.; Shutov, A. V.
Results are presented from a series of experimental and theoretical studies on creating weakly ionized extended plasma channels in atmospheric air by 248-nm UV laser radiation and their application to control long high-voltage discharges. The main mechanisms of air ionization by UV laser pulses with durations from 100 fs to 25 ns and intensities in the ranges of 3×10{sup 11}–1.5×10{sup 13} and 3×10{sup 6}–3×10{sup 11} W/cm{sup 2}, respectively, which are below the threshold for optical gas breakdown, as well as the main relaxation processes in plasma with a density of 10{sup 9}–10{sup 17} cm{sup −3}, are considered. It is shown that plasma channels in air can be efficiently created by amplitude-modulated UV pulses consisting of a train of subpicosecond pulses producing primary photoelectrons and a long UV pulse suppressing electron attachment and sustaining the density of free electrons in plasma. Different modes of the generation and amplification of trains of subterawatt subpicosecond pulses and amplitude-modulated UV pulses with an energy of several tens of joules were implemented on the GARPUN-MTW hybrid Ti:sapphire-KrF laser facility. The filamentation of such UV laser beams during their propagation in air over distances of up to 100 m and the parameters of the corresponding plasma channels were studied experimentally and theoretically. Laser initiation of high-voltage electric discharges and control of their trajectories by means of amplitude-modulated UV pulses, as well as the spatiotemporal structure of breakdowns in air gaps with length of up to 80 cm, were studied.
Digital optical spark chambers
NASA Technical Reports Server (NTRS)
Evenson, Paul; Tuska, Evelyn
The authors constructed and tested a prototype digital readout system for optical spark chambers using a linear, solid-state charge-coupled-device detector array. Position resolution of 0.013 mm (sigma) over a 25-cm field of view has been demonstrated. It is concluded that this technique should permit the construction of economical, lightweight and low-power trajectory hodoscopes for use in cosmic-ray instrumentation on balloons and in spacecraft.
Production of S{sub 2}F{sub 10}, S{sub 2}OF{sub 10} and S{sub 2}O{sub 2}F{sub 10} by spark discharges in SF{sub 6}*
Sauers, I.; Mahajan, S.M.; Cacheiro, R.A.
Measurements have been made of the spark yield of S{sub 2}F{sub 10} and S{sub 2}OF{sub 10} as a function of O{sub 2} and H{sub 2}O concentration. In addition the formation of S{sub 2}O{sub 2}F{sub 10} is reported. The spark yield of S{sub 2}F{sub 10} is reduced when either oxygen or water is added to SF{sub 6}. On the other hand the yield of S{sub 2}OF{sub 10} is increased when either oxygen or water is added, oxygen having the greater effect. A simple model is presented based on a common SF{sub 5} precursor to S{sub 2}F{sub 10} and S{sub 2}OF{sub 10} showing good agreement with the yields of both byproducts in O{sub 2}/SF{sub 6} and H{sub 2}O/SF{sub 6} mixtures. The yield of S{sub 2}F{sub 10} is found to be greatest when the spark chambers is very dry and the electrodes are well conditioned.
Unraveling the Image of Commutation Spark Generated in Universal Motors
NASA Astrophysics Data System (ADS)
Hanazawa, Tamio; Almazroui, Ali; Egashira, Torao
A universal motor, which is mainly used in vacuum cleaners, generates commutation sparks at the moment when the brush and the commutator segment are separated from each other during rotation. This study investigates the mechanism of commutation spark generation by analyzing high-speed camera images and its electrical aspect. We invented a new external trigger method that used laser light as the trigger signal for the shuttering a high-speed camera. This method enabled us to photograph sparks on any desired commutator segments during high-speed rotation, and that made the analysis after photographing easier. This paper shows that commutation sparks in universal motors are generated on every other commutator segment and at the peak of pulses in the voltage between the brush and commutator segment. Other aspects are also clarified, such as the generation of the singular and plural number of sparks on one commutator segment at a time, the time from the moment of spark generation to extinction, and spark generation during a single rotation.
Role of electrical resistance of electrodes in modeling of discharging and charging of flooded lead-acid batteries
NASA Astrophysics Data System (ADS)
Gandhi, K. S.
Electrical resistance of both the electrodes of a lead-acid battery increases during discharge due to formation of lead sulfate, an insulator. Work of Metzendorf [1] shows that resistance increases sharply at about 65% conversion of active materials, and battery stops discharging once this critical conversion is reached. However, these aspects are not incorporated into existing mathematical models. Present work uses the results of Metzendorf [1], and develops a model that includes the effect of variable resistance. Further, it uses a reasonable expression to account for the decrease in active area during discharge instead of the empirical equations of previous work. The model's predictions are compared with observations of Cugnet et al. [2]. The model is as successful as the non-mechanistic models existing in literature. Inclusion of variation in resistance of electrodes in the model is important if one of the electrodes is a limiting reactant. If active materials are stoichiometrically balanced, resistance of electrodes can be very large at the end of discharge but has only a minor effect on charging of batteries. The model points to the significance of electrical conductivity of electrodes in the charging of deep discharged batteries.
Plasma-Surface Interactions in Hollow Cathode Discharges for Electric Propulsion
NASA Astrophysics Data System (ADS)
Capece, Angela Maria
Electric thrusters generate high exhaust velocities and can achieve specific impulses in excess of 1000 s. The low thrust generation and high specific impulse make electric propulsion ideal for interplanetary missions, spacecraft station keeping, and orbit raising maneuvers. Consequently, these devices have been used on a variety of space missions including Deep Space 1, Dawn, and hundreds of commercial spacecraft in Earth orbit. In order to provide the required total impulses, thruster burn time can often exceed 10,000 hours, making thruster lifetime essential. One of the main life-limiting components on ion engines is the hollow cathode, which serves as the electron source for ionization of the xenon propellant gas. Reactive contaminants such as oxygen can modify the cathode surface morphology and degrade the electron emission properties. Hollow cathodes that operate with reactive impurities in the propellant will experience higher operating temperatures, which increase evaporation of the emission materials and reduce cathode life. A deeper understanding of the mechanisms initiating cathode failure will improve thruster operation, increase lifetime, and ultimately reduce cost. A significant amount of work has been done previously to understand the effects of oxygen poisoning on vacuum cathodes; however, the xenon plasma adds complexity, and its role during cathode poisoning is not completely understood. The work presented here represents the first attempt at understanding how oxygen impurities in the xenon discharge plasma alter the emitter surface and affect operation of a 4:1:1 BaO-CaO-Al2O3 hollow cathode. A combination of experimentation and modeling was used to investigate how oxygen impurities in the discharge plasma alter the emitter surface and reduce the electron emission capability. The experimental effort involved operating a 4:1:1 hollow cathode at various conditions with oxygen impurities in the xenon flow. Since direct measurements of the emitter
PIC simulations of the separate control of ion flux and energy in CCRF discharges via the electrical asymmetry effect
NASA Astrophysics Data System (ADS)
Donkó, Z.; Schulze, J.; Heil, B. G.; Czarnetzki, U.
Recently a novel approach for achieving separate control of ion flux and energy in capacitively coupled radio frequency (CCRF) discharges based on the electrical asymmetry effect (EAE) was proposed (Heil et al 2008 J. Phys. D: Appl. Phys. 41 165202). If the applied, temporally symmetric voltage waveform contains an even harmonic of the fundamental frequency, the sheaths in front of the two electrodes are necessarily asymmetric. A dc self-bias develops and is a function of the phase angle between the driving voltages. By tuning the phase, precise and convenient control of the ion energy can be achieved while the ion flux stays constant. This effect works even in geometrically symmetric discharges and the role of the two electrodes can be reversed electrically. In this work the EAE is verified using a particle in cell simulation of a geometrically symmetric dual-frequency CCRF discharge operated at 13.56 and 27.12 MHz. The self-bias is a nearly linear function of the phase angle. It is shown explicitly that the ion flux stays constant within ±5%, while the self-bias reaches values of up to 80% of the applied voltage amplitude and the maximum ion energy is changed by a factor of 3 for a set of low pressure discharge conditions investigated. The EAE is investigated at different pressures and electrode gaps. As geometrically symmetric discharges can be made electrically asymmetric via the EAE, the plasma series resonance effect is observed for the first time in simulations of a geometrically symmetric discharge.
Computer modeling and experimental study of non-chain pulsed electric-discharge DF laser.
Ruan, Peng; Xie, Jijiang; Zhang, Laiming; Guo, Jin; Xie, Jingjiang; Yang, Guilong; Li, Dianjun; Pan, Qikun; Tan, Gaijuan; Meng, Fanjiang; Li, Shiming
Computer simulation and experimental study of a pulsed electrical-discharge DF laser pumped by the SF(6)-D(2) non-chain reaction are presented. The computer model encompassing 28 reactions is based on laser rate equations theory, and applied to approximately describe the chemical processes of non-chain DF laser. A comprehensive study of the dependence of number density on time for all particles in the gain area is conducted by numerical calculation adopting Runge-Kutta method. The output performance of non-chain pulsed DF laser as a function of the output mirror reflectivity and the mixture ratio are analyzed. The calculation results are compared with experimental data, showing good agreement with each other. Both the theoretical analysis and experimental results present that the laser output performance can be improved by optimizing the mixture ratio and output mirror reflectivity. The optimum values of mixture ratio and output mirror reflectivity are respectively 10:1 and 30%. The single pulse energy of 4.95J, pulse duration of 148.8ns and peak power of 33.27 MW are achieved under the optimum conditions. PMID:23263131
Elution of zinc in dust discharged from electric arc furnace in carbonic acid solution
NASA Astrophysics Data System (ADS)
Yokoyama, S.; Sasaki, T.; Sasano, J.; Izaki, M.
The dust discharged from an electric arc furnace (EAF) is a valuable resource of zinc. As a fundamental study of extraction of zinc, iron and chlorine in the EAF dust, the elution behavior of them in carbonic acid solution was studied. The influence of the weight of the EAF dust on the elution behavior was examined in this study. Experiment was carried out putting the EAF dust from 1 g to 200 g in weight into 1 L of water that was introduced by CO2. Generally, the pH in the aqueous solution increased with an increase in weight of the additive EAF dust. Maximums of the eluted concentrations of zinc and chloride ion increased with an increase in the weight of the additive EAF dust whereas the extraction ratios of both of them decreased with an increase in the weight of the additive EAF dust. Iron in the EAF dust remained in the dust without elution. The limit of extraction of zinc from the EAF dust to water was given by the solubilities of ZnFe2O4 and ZnO expressed by eq. (6) and eq. (9) respectively.
Surface Preparation of Powder Metallurgical Tool Steels by Means of Wire Electrical Discharge Machining
NASA Astrophysics Data System (ADS)
Hatami, Sepehr; Shahabi-Navid, Mehrdad; Nyborg, Lars
The surface of two types of powder metallurgical (PM) tool steels ( i.e., with and without nitrogen) was prepared using wire electrical discharge machining (WEDM). From each grade of tool steel, seven surfaces corresponding to one to seven passes of WEDM were prepared. The WEDM process was carried out using a brass wire as electrode and deionized water as dielectric. After each WEDM pass the surface of the tool steels was thoroughly examined. Surface residual stresses were measured by the X-ray diffraction (XRD) technique. The measured stresses were found to be of tensile nature. The surface roughness of the WEDM specimens was measured using interference microscopy. The surface roughness as well as the residual stress measurements indicated an insignificant improvement of these parameters after four passes of WEDM. In addition, the formed recast layer was characterized by means of scanning electron microscopy (SEM), XRD, and X-ray photoelectron spectroscopy (XPS). The characterization investigation clearly shows diffusion of copper and zinc from the wire electrode into the work material, even after the final WEDM step. Finally, the importance of eliminating excessive WEDM steps is thoroughly discussed.
Hydrophobic and oleophobic re-entrant steel microstructures fabricated using micro electrical discharge machining
NASA Astrophysics Data System (ADS)
Weisensee, Patricia B.; Torrealba, Eduardo J.; Raleigh, Mark; Jacobi, Anthony M.; King, William P.
This paper presents the fabrication of metallic micro-mushroom re-entrant structures and the characterization of their hydrophobicity and oleophobicity. Five different microstructure geometries are introduced, with typical feature sizes in the range of 10-100 μm. These microstructures are realized in steel, and are fabricated over the cm-scale using micro electrical discharge machining (mEDM). The liquid repellency of these surfaces is characterized using droplets of either water (surface energy γlg = 72.4 mN m-1), RL-68H oil (γlg = 28.6 mN m-1), or Isopropanol (IPA) (γlg = 21.7 mN m-1). The water droplets form nearly perfect spheres, with contact angles in the range 146-162°, and contact angle hysteresis of 19-35°. The oil droplet contact angles are in the range 106-152° and the IPA contact angles are in the range 75-123°. Strong re-entrant features and close spacing are necessary to support a fully non-wetting state for use with oil and IPA. Water forms the highest contact angles with narrow, post-like, and widely spaced micro-mushroom geometries.
Particle simulation of femtosecond laser stimulation of electrical discharges in small gaps
Chen, J.; He, L. N.; Farson, D. F.; Rokhlin, S. I.
A particle-in-cell/Monte Carlo collision simulation study of femtosecond laser stimulation of electrical discharges in submicron gaps between platinum scanning tunneling microscope cathode tips and gold film anodes in atmospheric pressure argon gas is described. The breakdown potential of gaps containing either preloaded electrons or preloaded neutral and ionized platinum atoms and electrons at various densities were compared to the breakdown potential of gaps with background argon gas alone. It was found that gaps preloaded with sufficient densities of either electrons or partially ionized electrode materials broke down at cathode potential of -80 V while gaps with background argon gas alone required applied cathode potentials between -200 to -250 V to cause a breakdown. Also, partially ionized material was much more effective at stimulating breakdown than electrons alone. The density of preloaded partially ionized platinum required to lower breakdown cathode potential to -80 V was approximately 12.5 times smaller than that required for the preloaded electrons alone in the same size gap. Analysis of the mechanism by which the preloaded partially ionized material promoted breakdown showed that laser ablated ions located near the cathode tip increased the local field at the cathode surface and the field-emitted electron flux from the cathode. This higher electron flux ionized background argon gas and preloaded platinum which resulted in gap breakdown. The threshold density of partially ionized platinum for gap breakdown varied approximately linearly with applied cathode potential.
Mathematical modeling and multi-criteria optimization of rotary electrical discharge machining process
NASA Astrophysics Data System (ADS)
Shrinivas Balraj, U.
In this paper, mathematical modeling of three performance characteristics namely material removal rate, surface roughness and electrode wear rate in rotary electrical discharge machining RENE80 nickel super alloy is done using regression approach. The parameters considered are peak current, pulse on time, pulse off time and electrode rotational speed. The regression approach is very much effective in mathematical modeling when the performance characteristic is influenced by many variables. The modeling of these characteristics is helpful in predicting the performance under a given set of combination of input process parameters. The adequacy of developed models is tested by correlation coefficient and Analysis of Variance. It is observed that the developed models are adequate in establishing the relationship between input parameters and performance characteristics. Further, multi-criteria optimization of process parameter levels is carried using grey based Taguchi method. The experiments are planned based on Taguchi's L9 orthogonal array. The proposed method employs single grey relational grade as a performance index to obtain optimum levels of parameters. It is found that peak current and electrode rotational speed are influential on these characteristics. Confirmation experiments are conducted to validate optimal parameters and it reveals the improvements in material removal rate, surface roughness and electrode wear rate as 13.84%, 12.91% and 19.42% respectively.
Electrical characterization and an equivalent circuit model of a microhollow cathode discharge reactor
Taylan, O.; Berberoglu, H.
This paper reports the electrical characterization and an equivalent circuit of a microhollow cathode discharge (MHCD) reactor in the self-pulsing regime. A MHCD reactor was prototyped for air plasma generation, and its current-voltage characteristics were measured experimentally in the self-pulsing regime for applied voltages from 2000 to 3000 V. The reactor was modeled as a capacitor in parallel with a variable resistor. A stray capacitance was also introduced to the circuit model to represent the capacitance of the circuit elements in the experimental setup. The values of the resistor and capacitors were recovered from experimental data, and the proposed circuit model was validated with independent experiments. Experimental data showed that increasing the applied voltage increased the current, self-pulsing frequency and average power consumption of the reactor, while it decreased the peak voltage. The maximum and the minimum voltages obtained using the model were in agreement with the experimental data within 2.5%, whereas the differences between peak current values were less than 1%. At all applied voltages, the equivalent circuit model was able to accurately represent the peak and average power consumption as well as the self-pulsing frequency within the experimental uncertainty. Although the results shown in this paper was for atmospheric air pressures, the proposed equivalent circuit model of the MHCD reactor could be generalized for other gases at different pressures.
TiO2 Nanoparticles Produced by Electric-Discharge-Nanofluid-Process as Photoelectrode of DSSC
NASA Astrophysics Data System (ADS)
Chen, Sih-li; Su, Hung-ting; Chang, Ho; Jwo, Ching-song; Feng, Hsiao Ju
Self-made TiO2 nanoparticles were used as photoelectrode material of dye sensitized solar cell. The TiO2 thin film coats through spreading nanoparticles evenly onto the ITO glass via self-made spin-heat platform, and then TiO2 thin film is soaked in the dye N-719 more than 12 h to prepare the photoelectrode device. The TiO2 nanoparticles produced by electric-discharge-nanofluid-process have premium anatase crystal property, and its diameter can be controlled within a range of 20-50 nm. The surface energy zeta potential of nanofluid is from -22 mV to -28.8 mV, it is a stable particle suspension in the deionized water. A trace of surfactant Triton X-100 put upon the surface of ITO glass can produce a uniform and dense TiO2 thin film and heating up the spin platform to 200 °C is able to eliminate mixed surfactant. Self-made TiO2 film presents excellent dye absorption performance and even doesn't need heat treatment procedure to enhance essential property. Results of energy analysis show the thicker film structure will increase the short-circuit current density that causes higher conversion efficiency. But, as the film structure is large and thick, both the open-circuit voltage and fill factor will decline gradually to lead bad efficiency of dye-sensitized solar cell.
Long period gratings written in fluorine-doped fibers by electric arc discharge technique
NASA Astrophysics Data System (ADS)
Ranjan, Rajeev; Esposito, Flavio; Iadicicco, Agostino; Stǎncǎlie, Andrei; Sporea, Dan; Campopiano, Stefania
In this work, we present long period gratings (LPGs) in two different Fluorine-doped fibers realized by electric arc discharge (EAD) technique. Firstly, we optimized the EAD fabrication procedure for standard Ge-doped fibers where we are able to fabricate relatively short LPGs with deep attenuation bands (up to 32 dB) and trivial power losses. Successively, for the first time to the best of our knowledge, we produced LPGs in F-doped fibers with maximum attenuation band depths in range 25-30 dB and trivial power losses. We also investigated the sensitivity of LPGs fabricated in such F-doped fibers, with surrounding refractive index (SRI) and temperature changes, and compared the results with those of LPGs fabricated in standard fiber. We found that SRI response of LPGs in F-doped fibers is significantly higher than in standard fiber and it strongly depends on the type of F-doped fiber considered, whereas they exhibit a slightly lower sensitivity to temperature compared to LPGs in standard fiber.
Characterization of nanoparticles from abrasive waterjet machining and electrical discharge machining processes.
Ling, Tsz Yan; Pui, David Y H
Abrasive Waterjet Machining (AWM) and Electrical Discharge Machining (EDM) processes are found to produce nanoparticles during operation. Impacts of engineered nanoparticles released to the environment and biological system have caused much concern. Similarly, the nanoparticles unintentionally produced by the AWM and EDM can lead to comparable effects. By application of the Nanoparticle Tracking Analysis (NTA) technique, the size distribution and concentration of nanoparticles in the water used in AWM and EDM were measured. The particles generally have a peak size of 100-200 nm. The filtration systems of the AWM and EDM processes were found to remove 70% and 90% the nanoparticles present, respectively. However, the particle concentration of the filtered water from the AWM was still four times higher than that found in regular tap water. These nanoparticles are mostly agglomerated, according to the microscopy analysis. Using the electron dispersive spectroscopy (EDS) technique, the particles are confirmed to come from the debris of the materials cut with the equipment. Since AWM and EDM are widely used, the handling and disposal of used filters collected with nanoparticles, release of nanoparticles to the sewer, and potential use of higher performance filters for these processes will deserve further consideration. PMID:24144041
A nanosecond surface dielectric barrier discharge at elevated pressures: time-resolved electric field and efficiency of initiation of combustion
NASA Astrophysics Data System (ADS)
Kosarev, I. N.; Khorunzhenko, V. I.; Mintoussov, E. I.; Sagulenko, P. N.; Popov, N. A.; Starikovskaia, S. M.
We study a nanosecond surface dielectric barrier discharge (SDBD) initiated by negative or positive polarity pulses 10-15 kV in amplitude in a cable, 25-30 ns FWHM, 5 ns rise time, in the regime of a single shot or 3 Hz repetitive frequency. Discharge parameters, namely spatial structure of the discharge and time- and space-resolved electric field are studied in a N2 : O2 = 4 : 1 mixture for P = 1-5 atm. The possibility of igniting a combustible mixture with the help of an SDBD is demonstrated using the example of a stoichiometric C2H6 : O2 mixture at ambient initial temperature and at 1 atm pressure. Flame propagation and ignited volume as a function of time are compared experimentally for two discharge geometries: SDBD and pin-to-pin configurations at the same shape and amplitude of the incident pulse. It is shown that the SDBD can be considered as a multi-point ignition system with maximum energy release near the high-voltage electrode. Numerical modeling of the discharge and subsequent combustion kinetics for the SDBD conditions is performed. The discharge action leads to the production of atoms and radicals as well as to fast gas heating, due to the relaxation of electronic and vibrational degrees of freedom. The calculated ignition delay time is in reasonable agreement with the experimental results.
Study on Reduction of Time Lag for Laser-Induced Electrical Discharge in Atmospheric Air with Non-Uniform Electric Field
NASA Astrophysics Data System (ADS)
Okano, Daisuke
Study on Reduction of Time Lag for Laser-Induced Electrical Discharge in Atmospheric Air with Non-Uniform Electric Field* , Daisuke Okano, Kyushu Tokai University, 9-1-1 Toroku, Kumamoto, Japan. -----As an electrical discharge can be inductively occurred [1] by a pulsed laser-produced plasma (PLPP) in a rod-to-plate air gap stressed by a DC high voltage(Va), the starting point of laser-induced electrical discharge (LIED) is almost delayed more than few microseconds from focusing the laser beam. It is expected that the LIED by a PLPP is effectively occurred by reducing the time lag. The aim of our research focuses on the reduction for the time lag of LIED using CO2- and YAG pulsed lasers. The typical results are summarized as follows.The time lag of LIED in an atmospheric air gap (30mm) stressed at Va=30 kV is strongly reduced to 33 using CO2- and YAG pulsed lasers. The mechanism for the time lag of LIED is due to the electron attachment and detachment. [1] M.Inoue, T.Takashima, D.Okano et.al., Bull. of Inst. of Industrial Sci. & technical res.in Kyushu Tokai University, No.11 (1995)165 in Japanese. . *This work was supported by Grant-in-Aid for Scientific Research (C)-no.10650295 of The Ministry of education, Science Sports and Culture in japan.
Uniform and non-uniform modes of nanosecond-pulsed dielectric barrier discharge in atmospheric air: fast imaging and spectroscopic measurements of electric field
Liu, Chong; Dobrynin, Danil; Fridman, Alexander
In this study, we report experimental results on fast ICCD imaging of development of nanosecond-pulsed dielectric barrier discharge (DBD) in atmospheric air and spectroscopic measurements of electric field in the discharge. Uniformity of the discharge images obtained with nanosecond exposure times were analyzed using chi-square test. The results indicate that DBD uniformity strongly depends on applied (global) electric field in the discharge gap, and is a threshold phenomenon. We show that in the case of strong overvoltage on the discharge gap (provided by fast rise times), there is transition from filamentary to uniform DBD mode which correlates to the corresponding decrease of maximum local electric field in the discharge. PMID:25071294
Application of surface electrical discharges to the study of lightning strikes on aircraft
NASA Technical Reports Server (NTRS)
Boulay, J. L.; Larigaldie, S.
Considered here is the characterization of surface discharges which provide a facility complementary to that of artificially triggered lightning. General characteristics of a simplified surface discharge, including current waveforms and the constitution of a surface discharge are outlined, and the application of this approach to the study of aircraft lightning strikes is considered. Representations of leader-streamer and return-stroke phases are discussed, and the application to the two-dimensional discharge phase is covered. It is noted that the fact that the initiation times of surface discharges could be controlled, and the path followed by the discharge channels could be predetermined, indicates that it is possible to produce a highly dedicated high performance instrumentation system.
Distribution of E/N and N sub e in a cross-flow electric discharge laser
NASA Technical Reports Server (NTRS)
Dunning, J. W., Jr.; Lancashire, R. B.; Manista, E. J.
The spatial distribution of the ratio of electric field to neutral gas density on a flowing gas, multiple pin-to-plane discharge was measured in a high-power, closed loop laser. The laser was operated at a pressure of 140 torr (1:7:20, CO2, N2, He) with typically a 100 meter/second velocity in the 5 x 8 x 135 centimeter discharge volume. E/N ratios ranged from 2.7 x 10 to the minus 16th power to 1.4 x 10 to the minus 16th power volts/cu cm along the discharge while the electron density ranged from 2.8 x 10 to the 10th power to 1.2 x 10 to the 10th power cm/3.
Comparison of electrical and optical characteristics in gas-phase and gas-liquid phase discharges
NASA Astrophysics Data System (ADS)
Qazi, H. I. A.; Nie, Qiu-Yue; Li, He-Ping; Zhang, Xiao-Fei; Bao, Cheng-Yu
This paper presents an AC-excited argon discharge generated using a gas-liquid (two-phase) hybrid plasma reactor, which mainly consists of a powered needle electrode enclosed in a conical quartz tube and grounded deionized water electrode. The discharges in the gas-phase, as well as in the two-phase, exhibit two discharge modes, i.e., the low current glow-like diffuse mode and the high current streamer-like constrict mode, with a mode transition, which exhibits a negative resistance of the discharges. The optical emission spectral analysis shows that the stronger diffusion of the water vapor into the discharge region in the two-phase discharges boosts up the generation of OH (A-X) radicals, and consequently, leads to a higher rotational temperature in the water-phase plasma plume than that of the gas-phase discharges. Both the increase of the power input and the decrease of the argon flow rate result in the increase of the rotational temperature in the plasma plume of the water-phase discharge. The stable two-phase discharges with a long plasma plume in the water-phase under a low power input and gas flow rate may show a promising prospect for the degradation of organic pollutants, e.g., printing and dyeing wastewater, in the field of environmental protection.
Comparison of electrical and optical characteristics in gas-phase and gas-liquid phase discharges
Qazi, H. I. A.; Li, He-Ping Zhang, Xiao-Fei; Bao, Cheng-Yu; Nie, Qiu-Yue
This paper presents an AC-excited argon discharge generated using a gas-liquid (two-phase) hybrid plasma reactor, which mainly consists of a powered needle electrode enclosed in a conical quartz tube and grounded deionized water electrode. The discharges in the gas-phase, as well as in the two-phase, exhibit two discharge modes, i.e., the low current glow-like diffuse mode and the high current streamer-like constrict mode, with a mode transition, which exhibits a negative resistance of the discharges. The optical emission spectral analysis shows that the stronger diffusion of the water vapor into the discharge region in the two-phase discharges boosts up the generation of OH (A–X) radicals, and consequently, leads to a higher rotational temperature in the water-phase plasma plume than that of the gas-phase discharges. Both the increase of the power input and the decrease of the argon flow rate result in the increase of the rotational temperature in the plasma plume of the water-phase discharge. The stable two-phase discharges with a long plasma plume in the water-phase under a low power input and gas flow rate may show a promising prospect for the degradation of organic pollutants, e.g., printing and dyeing wastewater, in the field of environmental protection.
Analysis of Effects of Cutting Parameters of Wire Electrical Discharge Machining on Material Removal Rate and Surface Integrity
NASA Astrophysics Data System (ADS)
Tonday, H. R.; Tigga, A. M.
As wire electrical discharge machining is pioneered as a vigorous, efficient and precise and complex nontraditional machining technique, research is needed in this area for efficient machining. In this paper, the influence of various input factors of wire electrical discharge machining (WEDM) on output variable has been analyzed by using Taguchi technique and analysis of variance. The design of experiments has been done and by applying L8 orthogonal arrays method and experiments have been conducted and collected required data. The objectives of the research are to maximize the material removal rate and to minimize the surface roughness value (Ra). Surface morphology of machined workpiece has been obtained and examined by employing scanning electron microscopy (SEM) technique.
Failure modes of valve-regulated lead-acid batteries for electric bicycle applications in deep discharge
NASA Astrophysics Data System (ADS)
Guo, Yonglang; Tang, Shengqun; Meng, Gang; Yang, Shijun
The 36 or 48 V valve-regulated lead-acid (VRLA) battery packs have been widely applied to the power sources of electric bicycles or light electric scooters in China. The failure modes of the 12 V/10 Ah VRLA batteries have been studied by the cycle life test at C 2 discharge rate and 100% depth of discharge (DOD). It indicates that the main cause of the battery failure in this cycle duty is the softening and shedding of positive active mass (PAM) rather than individual water loss, recombination efficiency or sulfation, etc. When the electrolyte saturation falls to a certain extent, the high oxygen recombination current leads to the depolarization of the negative plate and the shift of the positive plate to a higher potential. The violent oxygen evolution accelerates the softening of PAM and the end of cycle life.
Laboratory studies of spacecraft response to transient discharge pulses
NASA Technical Reports Server (NTRS)
Nanevicz, J. E.; Adamo, R. C.
The in-orbit measurement of spacecraft discharge properties was investigated. The experiments include design and fabrication of appropriate sensors and effects of spacecraft electromagnetic responses on the interpretation of the discharge data. Electric field sensors especially designed to response to high-speed transient signals were installed on a mock-up of a satellite. The simple mock-up was basically a sheet of aluminum rolled to form a cylinder. A movable spark-discharge noise source designed to be electromagnetically isolated from its power supply system was used to induce transient signals at various locations on the spacecraft's outer surface. The measurements and their implications are described. It is concluded that practical orbital measurements to define discharge noise source properties should be possible, and that simple mock-ups of the type described below are useful in sensor system design and data interpretation.
Electrical Resistivity Tomography to characterize localized freshwater discharge in coastal environment
NASA Astrophysics Data System (ADS)
Kumm, Max; Scheuermann, Alexander; Hauck, Christian; Welti, Nina
North Stradbroke Island, located in the Pacific Ocean about 40 km east of Brisbane in Queensland, Australia, is formed by massive sand dunes of heights up to 229 m. The Island represents a reservoir for vast amounts of groundwater and plays an important role for the regional water supply. Therefore a detailed understanding of its hydrogeological features is of particular interest. In the intertidal zone on the western shores of the island, two localized freshwater springs with 4 m and 6 m in diameter were found. Hydrochemical investigations could not unequivocally identify the source of the freshwater by comparing its chemical properties to adjacent surface water and groundwater features. This case study presents the application of electrical resistivity tomography (ERT) in order to identify the source of the discharged freshwater and to delineate preferential flow paths in the saturated sand sediments. Several measurements with in-line arrays switching 48 electrodes as well as square arrays with 96 electrodes were conducted. The results of two- and three-dimensional data inversion were refined and verified implementing additional information. In-lab resistivity measurements on undisturbed samples of the sand sediments from the area under investigation as well as data from drill cores were considered for the refinement of the inversion model. The field work was impeded by the tides and allowed only for short periods for set up and measurement. A semi-confined aquifer formed by a layer of cemented sand at 7 m to 8 m depth perforated at the location of the springs could be identified. The interpretation of ERT data without considering additional geological and in lab resistivity data did not unambiguously indicate the real geological structure of the subsurface. High conductivities in the saturated sandy sediments lead to low investigation depths. Porosity-conductivity relationships for the loose sediments as well as for the cemented sand layer had to be modified to
Time-Lapse Electrical Resistivity Surveys of the Intertidal Zone: Implications for Submarine Groundwater Discharge
NASA Astrophysics Data System (ADS)
Durand, J. M.; Wong, T.
Submarine groundwater discharge (SGD) is now widely recognized as a crucial contributor to surface water as it provides a pathway for nutrients and contaminants that can significantly impact coastal ecosystems. Field measurements in the vicinity of the freshwater/seawater interface (FSI) have shown that the spatio-temporal distribution of SGD can be highly heterogeneous. Some numerical models have identified 3 regions (a density-driven circulation cell offshore, an upper saline plume and a freshwater tube in the intertidal zone) which seem to persist over time, such that the distinct regions can be recognized in simulations that average the numerically predicted salinity profiles over the tidal phases. The size and shape of each region are influenced by factors such as the tidal and wave loading, inland hydraulic gradient, beach geometry and aquifer properties. There is a paucity of field data at the FSI on the evolution of the salinity profile during a tidal cycle. To characterize the spatio-temporal heterogeneities of the FSI and compare with numerical predictions, we used electrical resistivity as a proxy for salinity. Electrical resistivity surveys were acquired during a 12-hour cycle in a tidally dominated environment. On September 12 2012, at West Neck Bay (Shelter Island, NY), a 33.4 m long stationary cable with 56 electrodes was extended over land and sea to image the intertidal zone. Hourly measurements were conducted over a full tidal cycle. Our measurements indicate fundamentally different scenarios during high and low tide. At low tide, our resistivity data suggest a strong influx of freshwater from land, forming a plume that rises up and contributes significantly to SGD in the intertidal zone. We also observed the occurrence of 3 regions somewhat analogous to the numerical predictions. However, at high tide, instead of these distinct regions, we observed a diffuse mixing zone that extended along the water/sediment interface and overlaid the freshwater
The influence of Kr, CO2, and iso-C4H8 admixtures on the time of the formation of a stable flame front in mixtures of natural gas and isobutylene with oxygen and hydrogen with air under initiation with a spark discharge
NASA Astrophysics Data System (ADS)
Rubtsov, N. M.; Seplyarskii, B. S.; Chernysh, V. I.; Tsvetkov, G. I.
High-speed color filming was used to study laminar spherical flame propagation at the initial stage in preliminarily mixed stoichiometric mixtures of natural gas and isobutylene with oxygen containing krypton and carbon dioxide and in hydrogen-air mixtures at atmospheric pressure in a bomb with a constant volume. Under experimental conditions ( T 0 = 298 K, p 0 = 100 torr, spark discharge energy E 0 = 0.91 J), the dilution of mixtures with Kr and CO2 increased the time of formation of a stable flame front by more than 10 times. The introduction of a small chemically active admixture (1.2% isobutylene) into a stoichiometric mixture of hydrogen and air sharply increased the time of formation of a stable flame front, which was evidence of an important role played by the chemical mechanism of the reaction in the formation of the combustion field.
Composition analyzer for microparticles using a spark ion source
NASA Technical Reports Server (NTRS)
Auer, S.; Berg, O. E.
Iron microparticles were fired onto a capacitor-type microparticle detector which responded to an impact with a spark discharge. Ion currents were extracted from the spark and analyzed in a time-of-flight mass spectrometer. The mass spectra showed the elements of both detector and particle materials. The total extracted ion current was typically 10 A within a period of 100 nsec, indicating very efficient vaporization of the particle and ionization of the vapor. Potential applications include research on cosmic dust, atmospheric aerosols and cloud droplets, particles ejected by rocket or jet engines, by machining processes or by nuclear bomb explosions.
Tool grinding and spark testing
NASA Technical Reports Server (NTRS)
Widener, Edward L.
The objectives were the following: (1) to revive the neglected art of metal-sparking; (2) to promote quality-assurance in the workplace; (3) to avoid spark-ignited explosions of dusts or volatiles; (4) to facilitate the salvage of scrap metals; and (5) to summarize important references.
Evaluation of R. Paul Smith Steam Electric Station thermal discharge effects on benthic communities; Spring 1980. Final report
Not Available
A study of thermal effluent effects on benthic invertebrates was conducted near the R.P. Smith Steam Electric Station. Samples were collected during May 1980 with a dome suction sampler and an aquatic drift net. Samples were collected on upstream and downstream control transects and on transects in the thermally influenced area. The objective of this survey was to assess effects of thermal discharge on the abundance and biomass macroinvertebrates in the Potomac River.
Effect of electric field configuration on streamer and partial discharge phenomena in a hydrocarbon insulating liquid under AC stress
NASA Astrophysics Data System (ADS)
Liu, Z.; Liu, Q.; Wang, Z. D.
This paper concerns pre-breakdown phenomena, including streamer characteristics from a fundamental perspective and partial discharge (PD) measurements from an industrial perspective, in a hydrocarbon insulating liquid. The aim was to investigate the possible changes of the liquid's streamer and PD characteristics and their correlations when the uniformity of the AC electric field varies. In the experiments, a plane-to-plane electrode system incorporating a needle protrusion was used in addition to a needle-to-plane electrode system. When the applied electric field became more uniform, fewer radial branches occurred and streamer propagation towards the ground electrode was enhanced. The transition from streamer propagation dominated breakdown in divergent fields to streamer initiation dominated breakdown in uniform fields was evidenced. Relationships between streamer and PD characteristics were established, which were found to be electric field dependent. PD of the same apparent charge would indicate longer streamers if the electric field is more uniform.
Study on AC-DC Electrical Conductivities in Warm Dense Matter Generated by Pulsed-power Discharge with Isochoric Vessel
NASA Astrophysics Data System (ADS)
Sasaki, Toru; Ohuchi, Takumi; Takahashi, Takuya; Kawaguchi, Yoshinari; Saito, Hirotaka; Miki, Yasutoshi; Takahashi, Kazumasa; Kikuchi, Takashi; Aso, Tsukasa; Harada, Nob.
To observe AC and DC electrical conductivity in warm dense matter (WDM), we have demonstrated to apply the spectroscopic ellipsometry for a pulsed-power discharge with isochoric vessel. At 10 μs from the beginning of discharge, the generated parameters by using pulsed-power discharge with isochoric vessel are 0.1 ρ s (ρ s: solid density) of density and 4000 K of temperature, respectively. The DC electrical conductivity for above parameters is estimated to be 104 S/m. In order to measure the AC electrical conductivity, we have developed a four-detector spectroscopic ellipsometer with a multichannel spectrometer. The multichannel spectrometer, in which consists of a 16-channel photodiode array, a two-stages voltage adder, and a flat diffraction grating, has 10 MHz of the frequency response with covered visible spectrum. For applying the four-detector spectroscopic ellipsometer, we observe the each observation signal evolves the polarized behavior compared to the ratio as I 1/I 2.
Development and Experimental Study of Surface-Electrical Discharge Diamond Grinding of Al-10 wt%SiC Composite
NASA Astrophysics Data System (ADS)
Agrawal, Shyam Sunder; Yadava, Vinod
As silicon carbide possesses small fracture toughness, it is difficult to grind because it leads to cracking. Metal matrix composites can be machined using electrical discharge machining (EDM) but the process is slow. Electrical discharge diamond grinding (EDDG), which consists of diamond grinding and EDM with a rotating disk which enhanced material removal rate (MRR) and produce better surface finish. This paper describes the machining characteristic of Al-SiC composite using EDDG in surface grinding configuration which is called as surface-electrical discharge diamond grinding (S-EDDG). A chain of experiments were performed on S-EDDG set up by mounting newly self designed and fabricated set up on conventional die sinking EDM machine using the approach of one parameter-at-a-time concept. Surface roughness (Ra) and MRR are taken as output parameters as both are important outcome in the manufacturing process and they materialize a major division in the manufacturing system. The effects of current, wheel speed and depth of cut is analyzed on MRR and Ra. Finally, optimization have been done through weighted principal component analysis.
Electrical Grain Boundary Characteristics of Dense Cubic Li 7-3xAlxLa3Zr2O7 (x = 0.05 - 0.3) Prepared by Spark Plasma Sintering
NASA Astrophysics Data System (ADS)
Ibbotson, Matthew Gianni Equi
In an effort to measure the electrical grain boundary characteristics of fully dense (˜99%) cubic Li 7-3xAlxLa3Zr 2O12 (x = 0.05 - 0.3), small grain size samples of 1 - 2mum were made using the Spark Plasma Sintering (SPS) method. The large internal interfacial area of SPS samples increased the grain boundary contribution to the total resistance to separate typically overlapping bulk and grain boundary impedance responses, supporting grain boundary conductivity (sigma GB) measurements. sigmaGBwas on average two orders of magnitude lower than the bulk conductivity (sigmabulk), indicating the grain boundaries of this material are resistive to Li+ transport, despite literature reports of low grain boundary resistance. sigmaGB = 3.8x10-7 +/- 11%, 7.9x10-7 +/- 11%, and 4.8x10-7 +/- 27% S/cm at 250C with corresponding EaGB = 0.44 +/- 3%, 0.49 +/- 4%, 0.46 +/- 2% eV, for 5, 20, and 30mol%Al 3+ LLZO, respectively. The electrical grain boundary thickness (delta GB) calculated using the Brick Layer Model decreased monotonically with aluminum concentration (CAl3+) to indicate a possible space-charge effect on sigmaGB, and was deltaGB = 10.2 +/- 18% , 9.9 +/- 12% , 6.0 +/- 20% nm for 5, 20, and 30mol%Al LLZO, respectively. Non-linear behavior of sigmaGB with CAl3+ was discussed in terms of competing space-charge and impurity segregation effects that simultaneously influence lithium conduction in the electrical GB. Optimum sigmaGB and sigmabulk of 7.9x10-7 +/- 11% and 4.6x10-4 +/- 4% S/cm at 250C, respectively, were found to coincide at CAl3+ = 20mol%, the critical aluminum dopant concentration for cubic LLZO phase stability.
Runaway electrons from laboratory discharges in air
NASA Astrophysics Data System (ADS)
Montanya, J.; March, V.
The role of runaway electrons in the lightning discharge it is still unknown. High energy electrons are associated with lightning discharges and occur with electric field variations associated with leader lightning advancement. On the other hand, Terrestrial Gamma-ray Flashes (TGF) are bursts of high energetic particles from the earth. TGF have been associated with lightning, but its origin is still under debate. In 2005 it was demonstrated that runaway electrons appear during high voltage impulses in the laboratory. These results opened the research of high energy particles in the laboratory and some researchers have focused its research in this field. From 2010 we have conducted different experiments using a Marx generator. We created impulse voltages up to 1 MV for air gaps between 30 and 100 cm. Shielded NaI(Tl) detectors were used to measure high energy particles from the discharge. We have designed experiments in order to discover the properties of these runaway electrons. From more than 2000 sparks, we showed that runaway electrons are affected by the rise time of the impulse, presented the role of each electrode in the acceleration of electrons and the role of the electric field in the process. In this presentation, we focus on the results of laboratory discharges and the possible implications in lightning discharges and TGF. The controlled impulse voltages in the laboratory can constitute an indirect way for study this phenomenon.
Conditions for uniform impact of the plasma of a runaway-electron-induced pulsed diffuse discharge on an anode
NASA Astrophysics Data System (ADS)
Erofeev, M. V.; Baksht, E. Kh.; Burachenko, A. G.; Tarasenko, V. F.
The subject matters in this work are (i) the spatial structure of a volume (diffuse) discharge initiated in atmospheric-pressure air in a heavily nonuniform electric field by nanosecond voltage pulses and (ii) the influence of its plasma on the surface of a plane aluminum anode. It is shown that a diffuse discharge initiated by nanosecond voltage pulses makes it possible to uniformly process the anode's surface in atmospheric-pressure air in contrast to a spark discharge, which results in microcracking, locally changes the surface properties, and thereby degrades the surface.
Two-color interferometer for the study of laser filamentation triggered electric discharges in air
Point, Guillaume Brelet, Yohann; Arantchouk, Leonid; Carbonnel, Jérôme; Prade, Bernard; Mysyrowicz, André; Houard, Aurélien
We present a space and time resolved interferometric plasma diagnostic for use on plasmas where neutral-bound electron contribution to the refractive index cannot be neglected. By recording simultaneously the plasma optical index at 532 and 1064 nm, we are able to extract independently the neutral and free electron density profiles. We report a phase resolution of 30 mrad, corresponding to a maximum resolution on the order of 4×10{sup 22} m{sup −3} for the electron density, and of 10{sup 24} m{sup −3} for the neutral density. The interferometer is demonstrated on centimeter-scale sparks triggered by laser filamentation in air with typical currents of a few tens of A.
Dual spark plug ignition system for motorcycle internal combustion engine
Hoeptner, H.W.
This patent describes an ignition system for a motorcycle two cylinder internal combustion engine, the system including magnetically coupled primary and secondary coil means, two spark plugs at each of the cylinders, a source of electrical current, and a single set of contacts controlling electrical current flow to the primary coil means for producing high voltage outputs from the secondary coil means to be delivered to all four of the spark plugs, the secondary coil means including certain secondary coil means operatively connected via the primary coil means with both the of spark plugs at one cylinder, a single cam controlling only the contacts, and a single magnetic core between the primary coil means and both the secondary coil means, and wherein the spark plugs include: two plugs at one cylinder and connected with the certain secondary coil means, two plugs at the second cylinder and connected with the other secondary coil means, the primary coil means including certain primary coil means magnetically coupled to the certain secondary coil means, and other primary coil means magnetically coupled to the other secondary coil means, the certain and other primary coil means being connected in series, electrically, the two spark plugs at one cylinder being electrically connected to opposite ends of the certain secondary coil means, and the two spark plugs at the other cylinder are electrically connected to opposite ends of the other secondary coil means. It comprises the cam driven by the engine for controlling opening of the contacts, the cam rotatable about a first axis, carrier means carrying the contacts, and adjustably rotatable about the axis.
Benefits and applications of laser-induced sparks in real scale model measurements.
Gómez-Bolaños, Javier; Delikaris-Manias, Symeon; Pulkki, Ville; Eskelinen, Joona; Hæggström, Edward; Jeong, Cheol-Ho
The characteristics of using a laser-induced spark as a monopole source in scale model measurements were assessed by comparison with an electric spark and a miniature spherical loudspeaker. Room impulse responses of first order directivity sources were synthesized off-line using six spatially distributed sparks. The source steering direction was scanned across the horizontal and vertical plane to assess the origin of early reflections. The results confirm that the characteristics of the laser-induced spark outperform those of typical sources. Its monopole characteristics enable the authors to synthesize room responses of directional sources, e.g., to obtain directional information about reflections inside scale models. PMID:26428809
Observation of a spark channel generated in water with shock wave assistance in plate-to-plate electrode configuration
NASA Astrophysics Data System (ADS)
Stelmashuk, V.
When a high voltage pulse with an amplitude of 30 kV is applied to a pair of disk electrodes at a time when a shock wave is passing between them, an electrical spark is generated. The dynamic changes in the spark morphology are studied here using a high-speed framing camera. The primary result of this work is the provision of experimental evidence of plasma instability that was observed in the channel of the electric spark.
The Chlorella killed by pulsed electrical discharge in liquid with two different reactors
NASA Astrophysics Data System (ADS)
Gao, Z. Y.; Sun, B.; Yan, Z. Y.; Zhu, X. M.; Liu, H.; Song, Y. J.; Sato, M.
The application of pulsed high-voltage discharge in liquid has attracted wide attention as an effective water treatment. In this paper, two different liquid high-voltage discharge systems were constructed with plate-hole-plate and needle-plate electrode structures, and the inactivation behaviors of Chlorella were studied in the two reactors. The results show that the killing rates of algae in both reactors all increased significantly with increasing discharge voltage and the killing rates were intensely related to discharge power, instantaneous power and single pulse input energy. Furthermore, the inactivation effect in needle-plate reactor was superior to that in plate-hole-plate reactor under the same experimental conditions.
Electro-spark deposition technology
Johnson, R.N.
Electro-Spark Deposition (ESD) is a micro-welding process that uses short duration, high-current electrical pulses to deposit or alloy a consumable electrode material onto a metallic substrate. The ESD process was developed to produce coatings for use in severe environments where most other coatings fail. Because of the exceptional damage resistance of these coatings, and the versatility of the process to apply a wide variety of alloys, intermetallics, and cermets to metal surfaces, the ESD process has been designated critical to the life and economy of the advanced fossil energy systems as the higher temperatures and corrosive environments exceed the limits of known structural materials to accommodate the service conditions. Developments include producing iron aluminide-based coatings with triple the corrosion resistance of the best previous Fe{sub 3}Al coatings, coatings with refractory metal diffusion barriers and multi layer coatings for achieving functionally gradient properties between the substrate and the surface. A new development is the demonstration of advanced aluminide-based ESD coatings for erosion and wear applications. One of the most significant breakthroughs to occur in the last dozen years is the discovery of a process regime that yields an order of magnitude increase in deposition rates and achievable coating thicknesses. Achieving this regime has required the development of advanced ESD electronic capabilities. Development is now focused on further improvements in deposition rates, system reliability when operating at process extremes, and economic competitiveness.
Comparison of the AWA lumped-circuit model of electrical discharges with empirical data
Maier, W.B. II; Kadish, A. ); Robiscoe, R.T. . Dept. of Physics)
The authors compare experimental data for three 1.7-m-long transient discharges with an AWA lumped- circuit discharge model in which the arc resistance is taken from the Arc Welder's Ansatz, R{sub a} = V*/{vert bar}I {vert bar}, where V* is a positive constant and I is the discharge current. In addition to the arc resistance, there is a small series resistance R present in the external circuit. A single value for each of R and V* is deduced from the data, and these values are used to characterize all three discharges. Adequate agreement with the experimental data is obtained; for example, the authors predict the proper number of current reversals for each discharge and abrupt termination of current flow after a finite time. The authors suggest that the AWA lumped circuit provides a better representation of the data than a standard lumped-circuit RLC model and hence is more useful as a tool for prediction and interpretation of discharges.
Search for relativistic electrons in laboratory discharge experiments
NASA Astrophysics Data System (ADS)
Ostgaard, Nikolai; Carlson, Brant E.; Grøndahl, Øystein; Kochkin, Pavlo; Nisi, Ragnhild S.; Gjesteland, Thomas
Discharge experiments were carried out at the Technical University of Eindhoven in 2013. The experimental set-up was designed to search for electrons produced in meter-scale sparks using a 1 MV Marx generator. Negative voltage was applied to the HV electrode. Five thin (1 mm) plastic detectors (5 cm2 each) were distributed in various configurations close to the spark gap. Earlier studies have shown (for HV negative) that X-rays are produced when a cloud of streamers has developed 30-60 cm from the negative electrode. This indicates that the electrons producing the X-rays are also accelerated in this location, probably in the strong electric field from countestreaming streamers of opposite polarity. Comparing our measurements with modeling results we find that 200-400 keV electrons produced about 30-60 cm from the negative electrode is the most likely source of our measurements.
Separate control of ion flux and energy in capacitively coupled RF discharges via the Electrical Asymmetry Effect
NASA Astrophysics Data System (ADS)
Schulze, Julian; Donko, Zoltan; Heil, Brian; Czarnetzki, Uwe
Recently a novel approach towards achieving separate control of ion flux and energy in capacitively coupled RF discharges based on the Electrical Asymmetry Effect (EAE) was proposed using fluid models. If the applied voltage waveform contains an even harmonic of its fundamental frequency, the sheaths will not be electrically symmetric. In order to balance electron and ion fluxes at each electrode a DC self bias develops. The self bias and, consequently, the ion energy can be controlled by tuning the phase between the two applied voltages. This technique works in geometrically symmetric and asymmetric discharges. Here the EAE is verified using a PIC simulation of a geometrically symmetric discharge. The self bias is found to be a nearly linear function of the phase angle. If the phase is changed, the ion flux stays constant within 5%, while the self bias reaches values of up to 80% of the applied voltage amplitude and the ion energy is changed by a factor of three. The EAE is investigated at different pressures and electrode gaps with focus on separate control of ion flux and energy.
Sparking protection for MFTF-B neutral beam power supplies
Cummings, D.B.
This paper describes the upgrade of MFTF-B Neutral Beam Power Supplies for sparking protection. High performance ion sources spark repeatedly so ion source power supplies must be insensitive to sparking. The hot deck houses the series tetrode, arc and filament supplies, and controls. Hot deck shielding has been upgraded and a continuous shield around the arc, filament, gradient grid, and control cables now extends from the hot deck, through the core snubber, to the source. The shield carries accelerating current and connects only to the source. Shielded source cables go through an outer duct which now connects to a ground plane under the hot deck. This hybrid transmission line is a low inductance path for sparks discharging the stray capacitance of the hot deck and isolation transformers, reducing coupling to building steel. Parallel dc current return cables inside the duct lower inductance to reduce inductive turn-off transients. MOVs to ground further limit surges in the remote power supply return. Single point grounding is at the source. No control or rectifier components have been damaged nor are there any known malfunctions due to sparking up to 80 kV output.
Responses of selected aquatic biota to thermal discharges from Cumberland Steam-Electric Plant: Barkley Reservoir, Tennessee, 1978 and 1979
Craven, T.M.; Dycus, D.L.; Wade, D.C.
The extent and degree of exposure of aquatic biota to the thermal plume from Cumberland Steam-Electric Plant (CUF) depends upon several factors, including temperature and volume of water discharged from the plant into the Cumberland River and river flow rates. During periods of discharging large volumes of heated water (maximum plant operation) to the Cumberland River under low flow conditions, maximum exposure would occur, influencing aquatic biota both up- and downstream of the plant. Results of this study, made during periods of maximum potential thermal stress (July to September) under varying flow and reservoir conditions, show thermal discharges from TVA's Cumberland Plant are not adversely impacting local aquatic communities studied. Differences in population structures and standing crops of plankton and macroinvertebrates were more related to reservoir conditions (i.e., suspended solids) than to operation of the plant. Community numbers and indices of health (as measured) downstream of the plant were usually as high as or higher than in upstream (unaffected) areas. Although several isolated effects occurred immediately downstream of the thermal discharge, no permanent alterations were documented on the local Cumberland River floral and faunal communities. 101 references, 25 figures, 24 tables.
Saffman-Taylor streamers: mutual finger interaction in spark formation.
Luque, Alejandro; Brau, Fabian; Ebert, Ute
Bunches of streamers form the early stages of sparks and lightning but theory presently concentrates on single streamers or on coarse approximations of whole breakdown trees. Here a periodic array of interacting streamer discharges in a strong homogeneous electric field is studied in density or fluid approximation in two dimensions. If the period of the streamer array is small enough, the streamers do not branch, but approach uniform translation. When the streamers are close to the branching regime, the enhanced field at the tip of the streamer is close to 2Einfinity, where Einfinity is the homogeneous field applied between the electrodes. We discuss a moving boundary approximation to the density model. This moving boundary model turns out to be essentially the same as the one for two-fluid Hele-Shaw flows. In two dimensions, this model possesses a known analytical solution. The shape of the two-dimensional interacting streamers in uniform motion obtained from the PDE simulations is actually well fitted by the analytically known "selected Saffman-Taylor finger." This finding helps to understand streamer interactions and raises new questions on the general theory of finger selection in moving boundary problems. PMID:18764034
Parameters of an electric-discharge generator of iodine atoms for a chemical oxygen-iodine laser
Azyazov, V N; Vorob'ev, M V; Voronov, A I; Kupryaev, Nikolai V; Mikheev, P A; Ufimtsev, N I
Laser-induced fluorescence is used for measuring the concentration of iodine molecules at the output of an electric-discharge generator of atomic iodine. Methyl iodide CH{sub 3}I is used as the donor of atomic iodine. The fraction of iodine extracted from CH{sub 3}I in the generator is {approx}50%. The optimal operation regimes are found in which 80%-90% of iodine contained in the output flow of the generator was in the atomic state. This fraction decreased during the iodine transport due to recombination and was 20%-30% at the place where iodine was injected into the oxygen flow. The fraction of the discharge power spent for dissociation was {approx}3%. (elements of laser setups)
On the origin of hard X-rays in the growth of meter long sparks
NASA Astrophysics Data System (ADS)
van Deursen, A. P.; Kochkin, P.; Nguyen, V.; Ebert, U.
Meter-long laboratory sparks generate high-energetic radiation in a similar way as lightning: Bremsstrahlung generated in collisions between high-energy electrons and air molecules. This study aims to localize and characterize the X-ray source and to visualize the relevant processes. A Marx generator delivers a standardized lightning impulse voltage pulse of 1.2/50~ μ s rise/fall time of positive or negative polarity. The generator was loaded by a spark gap formed by two conical electrodes at about 1~m distance; one of the electrodes was grounded. Applied voltages were 1~MV, which lead to breakdown of the gap. The voltage was measured by a high-voltage divider. Both electrodes were equipped with current probes to determine the electrical characteristics of the discharge. Two LaBr 3 (Ce + ) scintillation detectors measured the X-rays; different distances and angles gave information on the spatial distribution around the spark gap. Lead collimators limited the field of view. Lead attenuators of different thicknesses helped to determine the energy distribution. An intensified CCD camera allows us to capture images of pre-breakdown phenomena with ten-ns resolution. All diagnostics was synchronized to better than 1~ns. Many hundreds of discharges allowed statistical analysis. The X-ray emission area is concentrated in the vicinity of the cathode. The variation with detector position shows a 1/r 2 dependence of the detection rate, characteristic of a point-like source of constant luminosity. The reduction with attenuators of variable thickness agrees with a characteristic X-ray energy of 200~keV. The X-rays never occur before there is any cathode current. The nanosecond-fast photography allowed us to follow all pre-breakdown stages of the discharge, from the formation of a first inception cloud, to the formation and propagation of streamers crossing the gap. At a later stage, some cold streamer channels developed into hot leaders which then lead to breakdown. For the X
Double-ended metal halide arc discharge lamp with electrically isolated containment shroud
NASA Technical Reports Server (NTRS)
Muzeroll, Martin M. (Inventor)
A double-ended arc discharge lamp includes a sealed, light-transmissive outer jacket, a light-transmissive shroud mounted within the outer jacket and directly supported by the outer jacket, and an arc discharge tube mounted within the shroud. The arc tube is typically a metal halide arc discharge tube. In a preferred embodiment, the shroud includes an outwardly flared portion at each end. The outwardly flared portions space the shroud from the outer jacket and support the shroud within the outer jacket. The outwardly flared portions of the shroud can be affixed to the outer jacket by fusing. The outer jacket can be provided with inwardly extending dimples for locating the shroud with respect to the outer jacket. In another embodiment, the outer jacket includes reduced diameter portions near each end which are attached to the shroud.
A Simulation of Pre-Arcing Plasma Discharge Processes in Water Purification
Rodriguez-Mendez, B. G.; 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.
The simulation of a water purification system within a coaxial cylinder reactor operated by 1 kHz frequency plasma discharges in pre-arcing regimes is presented. In contrast with precedent works, this computational model considers three mechanisms of the system operation: (a) the relevant physical characteristics of water (b) the ionisation and expansion processes in the spark channel including the near-breakdown electric current generated by the rate of change of the effective capacitance and resistance in the discharge, and (c) the energy associated with this initial spark in the water. The outcome of the model seems to meet all main requirements to allow the design and construction of specific water purification technology devices.
Optimization of the electrical asymmetry effect in dual-frequency capacitively coupled radio frequency discharges: Experiment, simulation, and model
NASA Astrophysics Data System (ADS)
Schulze, J.; Schüngel, E.; Czarnetzki, U.; Donkó, Z.
An electrical asymmetry in capacitive rf discharges with a symmetrical electrode configuration can be induced by driving the discharge with a fundamental frequency and its second harmonic. For equal amplitudes of the applied voltage waveforms, it has been demonstrated by modeling, simulation, and experiments that this electrical asymmetry effect (EAE) leads to the generation of a variable dc self-bias that depends almost linearly on the phase angle between the driving voltage signals. Here, the dependence of the dc self-bias generated by the EAE on the choice of the voltage amplitudes, i.e., the ratio A of high to low frequency amplitude, is investigated experimentally as well as by using an analytical model and a particle-in-cell simulation. It is found that (i) the strongest electrical asymmetry is induced for A <1 at pressures ranging from 6 to 100 Pa and that (ii) around this optimum voltage ratio the dc self-bias normalized to the sum of both voltage amplitudes is fairly insensitive to changes of A. Thus, by choosing the optimum voltage ratio, the EAE is optimized: The ion energy can be changed over a broader energy range and a high degree of process stability with respect to small changes in the applied voltages is expected.
Optimization of the electrical asymmetry effect in dual-frequency capacitively coupled radio frequency discharges: Experiment, simulation, and model
Schulze, J.; Schuengel, E.; Czarnetzki, U.; Donko, Z.
An electrical asymmetry in capacitive rf discharges with a symmetrical electrode configuration can be induced by driving the discharge with a fundamental frequency and its second harmonic. For equal amplitudes of the applied voltage waveforms, it has been demonstrated by modeling, simulation, and experiments that this electrical asymmetry effect (EAE) leads to the generation of a variable dc self-bias that depends almost linearly on the phase angle between the driving voltage signals. Here, the dependence of the dc self-bias generated by the EAE on the choice of the voltage amplitudes, i.e., the ratio A of high to low frequency amplitude, is investigated experimentally as well as by using an analytical model and a particle-in-cell simulation. It is found that (i) the strongest electrical asymmetry is induced for A<1 at pressures ranging from 6 to 100 Pa and that (ii) around this optimum voltage ratio the dc self-bias normalized to the sum of both voltage amplitudes is fairly insensitive to changes of A. Thus, by choosing the optimum voltage ratio, the EAE is optimized: The ion energy can be changed over a broader energy range and a high degree of process stability with respect to small changes in the applied voltages is expected.
Machining Performance and Surface Integrity of AISI D2 Die Steel Machined Using Electrical Discharge Surface Grinding Process
NASA Astrophysics Data System (ADS)
Choudhary, Rajesh; Kumar, Harmesh; Singh, Shankar
The aim of this study is to establish optimum machining conditions for EDSG of AISI D2 die steel through an experimental investigation using Taguchi Methodology. To achieve combined grinding and electrical discharge machining, metal matrix composite electrodes (Cu-SiCp) were processed through powder metallurgy route. A rotary spindle attachment was developed to perform the EDSG experimental runs on EDM machine. Relationships were developed between various input parameters such as peak current, speed, pulse-on time, pulse-off time, abrasive particle size, and abrasive particle concentration, and output characteristics such as material removal rate and surface roughness. The optimized parameters were further validated by conducting confirmation experiments.
Economics of electron beam and electrical discharge processing for post-combustion NO(x) control in internal combustion engines
NASA Astrophysics Data System (ADS)
Penetrante, B. M.
The physics and chemistry of non-thermal plasma processing for post-combustion NO(x) control in internal combustion engines are discussed. A comparison of electron beam and electrical discharge processing is made regarding their power consumption, radical production, NO(x) removal mechanisms, and by-product formation. Pollution control applications present a good opportunity for transferring pulsed power techniques to the commercial sector. However, unless advances are made to drastically reduce the price and power consumption of electron beam sources and pulsed power systems, these plasma techniques will not become commercially competitive with conventional thermal or surface-catalytic methods.
Pulsed oxygen-iodine chemical laser initiated by an electrical discharge
Zhang Rongyao; Chen Fang; Song Xueqin; Xu Qingzhou; Huan Changqing; Zhuang Qi; Zhang Cunhao
This paper demonstrates for the first time the feasibility of an electrically initiated, pulsed oxygen-iodine laser which can be initiated efficiently by low energy electrons. By electrical initiation, an O/sub 2/(/sup 1/..delta..)--CH/sub 3/I--N/sub 2/ mixture has been made to lase with an output energy of 130 mJ. The efficiency of the electrical initiation is 350 times higher than that obtained with photo-initiation.
Electrical generators driving microhollow and dielectric barrier discharges applied for analytical chemistry.
Heming, R; Michels, A; Olenici, S B; Tombrink, S; Franzke, J
Scaling down the size of plasma discharges would reduce the amount of gases, liquids, and consumables required, which in turn would decrease the operating costs. Nevertheless, the application of a specialized plasma generator for microhollow cathode discharges (MHCD) and dielectric barrier discharges are driven with commercially available power sources. Those generators are bulky and expensive and their overall efficiency is poor. This work develops and explains several circuit topologies and design hints to excite MHCD and dielectric barrier discharge (DBD) plasmas with respect to its system with as low as possible input power in a very efficient way. Benefits in sensitivity and life expectancy are shown. The generator for the MHCD needs voltages up to 7 V and consumes up to 5 W. The DBD generator has an input power of 3 W and produces a fast rising output pulse up to 9 kV, which has a time duration of 2 micros. These low-power circuits offer the operation with batteries. PMID:19333583
Review of the methods to form hydrogen peroxide in electrical discharge plasma with liquid water
NASA Astrophysics Data System (ADS)
Locke, Bruce R.; Shih, Kai-Yuan
This paper presents a review of the literature dealing with the formation of hydrogen peroxide from plasma processes. Energy yields for hydrogen peroxide generation by plasma from water span approximately three orders of magnitude from 4 × 10-2 to 80 g kWh-1. A wide range of plasma processes from rf to pulsed, ac, and dc discharges directly in the liquid phase have similar energy yields and may thus be limited by radical quenching processes at the plasma-liquid interface. Reactor modification using discharges in bubbles and discharges over the liquid phase can provide modest improvements in energy yield over direct discharge in the liquid, but the interpretation is complicated by additional chemical reactions of gas phase components such as ozone and nitrogen oxides. The highest efficiency plasma process utilizes liquid water droplets that may enhance efficiency by sequestering hydrogen peroxide in the liquid and by suppressing decomposition reactions by radicals from the gas and at the interface. Kinetic simulations of water vapor reported in the literature suggest that plasma generation of hydrogen peroxide should approach 45% of the thermodynamics limit, and this fact coupled with experimental studies demonstrating improvements with the presence of the condensed liquid phase suggest that further improvements in energy yield may be possible. Plasma generation of hydrogen peroxide directly from water compares favorably with a number of other methods including electron beam, ultrasound, electrochemical and photochemical methods, and other chemical processes.
Experimental study of hard-X ray emission from laboratory sparks
NASA Astrophysics Data System (ADS)
Marisaldi, Martino; Rizzi, Rolando; Levi, Giuseppe; Malgesini, Roberto; Villa, Andrea; Mazza, Paolo; Labanti, Claudio; Fuschino, Fabio; Campana, Riccardo; Bianchini, David; Brancaccio, Rossella; Montanari, Alessandro; Patrizii, Laura
We present the characterization of hard-X rays produced by meter-long laboratory sparks carried out at the high-voltage laboratory of RSE, Milano, Italy. Sparks are known to emit X-rays when positive and negative streamers connect, before breakdown. Numerical simulations suggest that X-rays are produced by Bremsstrahlung in air by electrons accelerated to the runaway regime in the high electric field at the streamers tip. Positive meter-long discharges are produced by a Marx generator loaded by a meter-long air gap formed by a spherical anode and a conical-shaped cathode. Maximum voltage at breakdown is about 1 MV. We investigate the production of X-rays by means of an array of scintillation detectors deployed around the cathode. Each detector is a 2'' NaI(Tl) scintillating crystal coupled to a photomultiplier tube (PMT). Each detector is battery-powered and enclosed in a metallic housing for EM shielding. Analog signal output is trasmitted to a shielded control room by means of optical fibre tranceivers, and then collected by a fast digitizer. We present the experimental setup and first results concerning detection efficiency, energy spectra, and geometrical distribution of the emission.
Electrical and chemical properties of XeCl*(308 nm) exciplex lamp created by a dielectric barrier discharge
Baadj, S.; Harrache, Z. Belasri, A.
The aim of this work is to highlight, through numerical modeling, the chemical and the electrical characteristics of xenon chloride mixture in XeCl* (308 nm) excimer lamp created by a dielectric barrier discharge. A temporal model, based on the Xe/Cl{sub 2} mixture chemistry, the circuit and the Boltzmann equations, is constructed. The effects of operating voltage, Cl{sub 2} percentage in the Xe/Cl{sub 2} gas mixture, dielectric capacitance, as well as gas pressure on the 308-nm photon generation, under typical experimental operating conditions, have been investigated and discussed. The importance of charged and excited species, including the major electronic and ionic processes, is also demonstrated. The present calculations show clearly that the model predicts the optimal operating conditions and describes the electrical and chemical properties of the XeCl* exciplex lamp.
Numerical study on the hydrodynamic behavior of the dielectric fluid around an electrical discharge generated bubble in EDM
NASA Astrophysics Data System (ADS)
Shervani-Tabar, Mohammad T.; Mobadersany, Nima
In the process of EDM, due to the electrical current, very small bubbles are created within the gap. These bubbles are connected to each other and generate a single bubble. The vapor bubble continues to grow until it finally collapses to small bubbles. The bubble behavior can be ascertained on the distribution of the pressure in the dielectric fluid around the bubble. In this paper, velocity fields and pressure distribution in the dielectric fluid around the bubble that is generated in the process of EDM are investigated numerically. The tool and the workpiece are assumed as two parallel rigid boundaries with dielectric liquid between them. The boundary integral equation method is applied for the numerical solution of the problem. This study can lead to better understanding of the bubble importance in the performance of the electrical discharge machining process.
Statistical analysis of storm electrical discharges reconstituted from a lightning mapping system, a lightning location system, and an acoustic array
NASA Astrophysics Data System (ADS)
Gallin, Louis-Jonardan; Farges, Thomas; Marchiano, Régis; Coulouvrat, François; Defer, Eric; Rison, William; Schulz, Wolfgang; Nuret, Mathieu
In the framework of the European Hydrological Cycle in the Mediterranean Experiment project, a field campaign devoted to the study of electrical activity during storms took place in the south of France in 2012. An acoustic station composed of four microphones and four microbarometers was deployed within the coverage of a Lightning Mapping Array network. On the 26 October 2012, a thunderstorm passed just over the acoustic station. Fifty-six natural thunder events, due to cloud-to-ground and intracloud flashes, were recorded. This paper studies the acoustic reconstruction, in the low frequency range from 1 to 40 Hz, of the recorded flashes and their comparison with detections from electromagnetic networks. Concurrent detections from the European Cooperation for Lightning Detection lightning location system were also used. Some case studies show clearly that acoustic signal from thunder comes from the return stroke but also from the horizontal discharges which occur inside the clouds. The huge amount of observation data leads to a statistical analysis of lightning discharges acoustically recorded. Especially, the distributions of altitudes of reconstructed acoustic detections are explored in detail. The impact of the distance to the source on these distributions is established. The capacity of the acoustic method to describe precisely the lower part of nearby cloud-to-ground discharges, where the Lightning Mapping Array network is not effective, is also highlighted.
Control of extended high-voltage electric discharges in atmospheric air by UV KrF-laser radiation
Zvorykin, V D; Levchenko, A O; Ustinovskii, N N
Experiments in the commutation of extended ({approx}1-m long) high-voltage (up to 390 kV) electric discharges were carried out with the aid of 100-ns long UV pulses of the GARPUN KrF laser, in which we demonstrated a one-and-a-half-fold lengthening of the discharge gap broken down in the presence of laser illumination. Total control of discharge trajectory along the direction of the laser beam was observed for a radiation energy of {approx}300 mJ (the corresponding intensity I = 5x10{sup 8} W cm{sup -2} and its attendant initial electron density Ne {approx} 10{sup 11} cm{sup -3}) and partial control for an energy of 40 mJ (I = 7x10{sup 7} W cm{sup -2}, Ne {approx} 8x10{sup 9} cm{sup -3}) with a 100% probability of breakdown. We discuss the advantages of employing a UV laser for active lightning protection in comparison with IR lasers and ultrashort-pulse laser systems. (interaction of laser radiation with matter)
Electro-spark deposition technology
Johnson, R.N.
Electro-Spark Deposition (ESD) is a micro-welding process that uses short duration, high-current electrical pulses to deposit or alloy a consumable electrode material onto a metallic substrate. The ESD process was developed to produce coatings for use in severe environments where most other coatings fail. Because of the exceptional damage resistance of these coatings, and the versatility of the process to apply a wide variety of alloys, intermetallics, and cermets to metal surfaces, the ESD process has been designated as one of the enabling technologies for advanced energy systems. Developments include producing iron aluminide-based coatings with triple the corrosion resistance of the best previous Fe{sub 3}Al coatings, coatings with refractory metal diffusion barriers and multi layer coatings for achieving functionally gradient properties between the substrate and the surface. One of the most significant breakthroughs to occur in the last dozen years is the discovery of a process regime that promises an order of magnitude increase in deposition rates and achievable coating thicknesses. Since this regime borders on and exceeds the normal operating limits of existing ESD electronic equipment, development is in progress to produce equipment that can consistently and reliably achieve these conditions for a broad range of materials. Progress so far has resulted in a consistent 500% increase in deposition rates, and greater rates still are anticipated. Technology transfer activities are a significant portion of the ESD program effort. Notable successes now include the start-up of a new business to commercialize the ESD technology, the incorporation of the process into the operations of a major gas turbine manufacturer, major new applications in gas turbine blade and steam turbine blade protection and repair, and in military, medical, metal-working, and recreational equipment applications.
Time-resolved imaging of electrical discharge development in underwater bubbles
NASA Astrophysics Data System (ADS)
Tu, Yalong; Xia, Hualei; Yang, Yong; Lu, Xinpei
The formation and development of plasma in single air bubbles submerged in water were investigated. The difference in the discharge dynamics and the after-effects on the bubble were investigated using a 900 000 frame per second high-speed charge-coupled device camera. It was observed that depending on the position of the electrodes, the breakdown could be categorized into two modes: (1) direct discharge mode, where the high voltage and ground electrodes were in contact with the bubble, and the streamer would follow the shortest path and propagate along the axis of the bubble and (2) dielectric barrier mode, where the ground electrode was not in touch with the bubble surface, and the streamer would form along the inner surface of the bubble. The oscillation of the bubble and the development of instabilities on the bubble surface were also discussed.
Fiber Optic Sensor for Acoustic Detection of Partial Discharges in Oil-Paper Insulated Electrical Systems
Posada-Roman, Julio; Garcia-Souto, Jose A.; Rubio-Serrano, Jesus
A fiber optic interferometric sensor with an intrinsic transducer along a length of the fiber is presented for ultrasound measurements of the acoustic emission from partial discharges inside oil-filled power apparatus. The sensor is designed for high sensitivity measurements in a harsh electromagnetic field environment, with wide temperature changes and immersion in oil. It allows enough sensitivity for the application, for which the acoustic pressure is in the range of units of Pa at a frequency of 150 kHz. In addition, the accessibility to the sensing region is guaranteed by immune fiber-optic cables and the optical phase sensor output. The sensor design is a compact and rugged coil of fiber. In addition to a complete calibration, the in-situ results show that two types of partial discharges are measured through their acoustic emissions with the sensor immersed in oil. PMID:22666058
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.
Particle model analyses of N2O dilution with He on electrical characteristics of radio-frequency discharges
NASA Astrophysics Data System (ADS)
Younis, G.; Yousfi, M.; Despax, B.
The electrical characteristics (voltage, electric field, charged particle densities, dissipated power, particle energy, etc.) are analyzed in the case of low pressure (0.5 and 1 Torr) radio-frequency (rf) discharges in nitrous oxide (N2O)/Helium (He) mixtures. An optimized and validated particle model has been used for these analyses in the case of gradual dilutions of N2O with He buffer gas. A specific care is carried on the power density evolution and variation which show a complex behavior as a function of He proportion (up to 85%). These analyses are based on a microscopic approach enabling one to show the contribution of the different inelastic processes mainly between electrons and respectively N2O and He gases. This approach enables also one to show the discharge region (the positive column or the plasma region) where the power is preferentially dissipated. The power density variation is found to be mainly proportional to the electron density variation. The latter is dependent on the different processes occurring between the charged particles [i.e., electrons, negative ions (O- and NO-), and positive ions (N2O+ and He+)] and the neutral gas mixture (N2O and He). Furthermore, the particle model shows the role of the electron-He collisions on the variation in the electron energy and distribution. This allows more particularly explaining the effects of N2O dilution with He on the dissipated power variation in terms of creation and loss of electrons through collision processes.
Micro electrical discharge milling of WC-Co using a deionized water spray and a bipolar pulse
NASA Astrophysics Data System (ADS)
Song, Ki Young; Chung, Do Kwan; Park, Min Soo; Chu, Chong Nam
Micro electrical discharge milling (ED-milling) is an effective machining process for manufacturing micro structures on hard metals. This method of machining generally uses kerosene or deionized water as the working fluid, both of which are associated with some problems. Kerosene results in considerable electrode wear and deionized water causes electrolytic corrosion in workpieces. In particular, when cemented tungsten carbide (WC-Co), which has superior strength, hardness and wear resistance, is machined by electrical discharge machining (EDM), the problem of electrolytic corrosion arises as a matter of course since the material is very susceptible to electrolyzation. In this study, spray ED-milling with a bipolar pulsed power source and deionized water was conducted to solve the above problems. This method uses a water spray, which is a mixture of compressed air and deionized water. The spray is injected into the machining gap between the electrode and the workpiece. WC-Co was used for the workpiece and micro grooves were machined on the workpiece. As a result, using the spray ED-milling method, high-quality micro grooves were manufactured on the WC-Co workpiece with no electrolytic corrosion and almost-zero electrode wear.
Phospholipid turnover in Torpedo marmorata electric organ during discharge in vivo.
Bleasdale, J E; Hawthorne, J N; Widlund, L; Heilbronn, E
One electric organ of anaesthetized Torpedo marmorata was stimulated through electrodes placed on the electric lobe of the brain. Nerves to the other electric organ were cut to provide an unstimulated control. Glucose 6-[32P]phosphate was injected into each organ 16h before electrical stimulation. After stimulation for 10 min at 5 Hz, the organs were removed homogenized and centrifuged on a density gradient for the preparation of subcellular fractions. Stimulation increased the incorporation of 32P into phosphatidate, phosphatidylinositol and phosphatidylcholine. The increased phosphatidate labelling, but not that of the other two lipids, was seen in fractions rich in synaptic vesicles. Stimulation had no effect on ATP labelling. The phosphatidate content of most fractions fell slightly after stimulation, but amounts of other phospholipids were not affected. Images PLATE 1 PLATE 2 PMID:825114
Effect of a solid insulator on the spark yield of S2F10 in SF6(*)
NASA Astrophysics Data System (ADS)
Sauers, I.; Mahajan, S. M.; Cacheiro, R. A.
Because of its toxicity S2F10 production in SF6 discharges has been the focus of intensive study in recent years. In previous work we have examined the yield of S 2F10 for corona, spark and arc discharges and, in sparks, the effects of water and oxygen have been studied systematically. Here we report the influence of an insulating solid spacer on the production of S2F10 in SF6 when subjected to spark discharges in the energy range 1.6-43 J/spark at a gas pressure of 1 atm. Analyses of the sparked gases were performed using a cryogenic enrichment gas chromatography technique with a sensitivity of less than 10 ppb (parts-per-billion) or 1 in 10(exp 8). With this sensitivity S2F10 can be detected after one or just a few spark(s), minimizing secondary effects of gas contamination, electrode erosion and insulator damage that can influence S2F10 production and make quantitative yield determinations difficult to establish. For these studies Teflon was used as the spacer sandwiched between two stainless steel electrodes. Energy measurements were made after recording the voltage and current waveforms. The amount of S2F10 produced per unit energy deposited into the discharge was found to be greater in the presence of the spacer than for a purely gas gap. Factors which influence S2F10 stability such as surfaces and water will also b e discussed.
On the origin of hard X-rays in the growth of meter long sparks
NASA Astrophysics Data System (ADS)
Kochkin, Pavlo; van Deursen, A. P. J.; Ebert, Ute
Meter-long laboratory sparks generate high-energetic radiation in a similar way as lightning: Bremsstrahlung generated in collisions between high-energy electrons and air molecules. This study aims to localize and characterize the X-ray source and to visualize the relevant processes. A Marx generator delivers a standardized lightning impulse voltage pulse of 1.2/50 microsec rise/fall time of positive or negative polarity. The generator was loaded by a spark gap formed by two conical electrodes at about 1 m distance; one of the electrodes was grounded. Applied voltages were 1 MV, which lead to breakdown of the gap. The voltage was measured by a high-voltage divider. Both electrodes were equipped with current probes to determine the electrical characteristics of the discharge. Two La(Ce)Br3 scintillation detectors measured the X-rays; different distances and angles gave information on the spatial distribution around the spark gap. Lead collimators limited the field of view. Lead attenuators of different thicknesses helped to determine the energy distribution. An intensified CCD camera allows us to capture images of pre-breakdown phenomena with ten-ns resolution. All diagnostics was synchronized to better than 1 ns. Many hundreds of discharges allowed statistical analysis. The X-ray emission area is concentrated in the vicinity of the cathode. The variation with detector position shows a 1/r2 dependence of the detection rate, characteristic of a point-like source of constant luminosity. The reduction with attenuators of variable thickness agrees with a characteristic X-ray energy of 200 keV. The X-rays never occur before there is any cathode current. The nanosecond-fast photography allowed us to follow all pre-breakdown stages of the discharge, from the formation of a first inception cloud, to the formation and propagation of streamers crossing the gap. At a later stage, some cold streamer channels developed into hot leaders which then lead to breakdown. For the X
Are Crab nanoshots Schwinger sparks?
Stebbins, Albert; Yoo, Hojin
The highest brightness temperature ever observed are from "nanoshots" from the Crab pulsar which we argue could be the signature of bursts of vacuum e± pair production. If so this would be the first time the astronomical Schwinger effect has been observed. These "Schwinger sparks" would be an intermittent but extremely powerful, ~103 L⊙, 10 PeV e± accelerator in the heart of the Crab. These nanosecond duration sparks are generated in a volume less than 1 m3 and the existence of such sparks has implications for the small scale structure of the magnetic field of young pulsars such as the Crab. As a result, this mechanism may also play a role in producing other enigmatic bright short radio transients such as fast radio bursts.
NASA Astrophysics Data System (ADS)
Riordan, Naoimh
My name is Naoimh Riordan and I am the Vice Principal of Rockboro Primary School in Cork City, South of Ireland. I am a full time class primary teacher and I teach 4th class, my students are aged between 9-10 years. My passion for education has developed over the years and grown towards STEM (Science, Technology, Engineering and Mathematics) subjects. I believe these subjects are the way forward for our future. My passion and beliefs are driven by the unique after school programme that I have developed. It is titled "Sparks" coming from the term Bright Sparks. "Sparks" is an after school programme with a difference where the STEM subjects are concentrated on through lessons such as Science, Veterinary Science Computer Animation /Coding, Eco engineering, Robotics, Magical Maths, Chess and Creative Writing. All these subjects are taught through activity based learning and are one-hour long each week for a ten-week term. "Sparks" is fully inclusive and non-selective which gives all students of any level of ability an opportunity to engage into these subjects. "Sparks" is open to all primary students in County Cork. The "Sparks" after school programme is taught by tutors from the different Universities and Colleges in Cork City. It works very well because the tutor brings their knowledge, skills and specialised equipment from their respective universities and in turn the tutor gains invaluable teaching practise, can trial a pilot programme in a chosen STEM subject and gain an insight into what works in the physical classroom.
Nitric Oxide Studies in Low Temperature Plasmas Generated with a Nanosecond Pulse Sphere Gap Electrical Discharge
NASA Astrophysics Data System (ADS)
Burnette, David Dean
This dissertation presents studies of NO kinetics in a plasma afterglow using various nanosecond pulse discharges across a sphere gap. The discharge platform is developed to produce a diffuse plasma volume large enough to allow for laser diagnostics in a plasma that is rich in vibrationally-excited molecules. This plasma is characterized by current and voltage traces as well as ICCD and NO PLIF images that are used to monitor the plasma dimensions and uniformity. Temperature and vibrational loading measurements are performed via coherent anti-Stokes Raman spectroscopy (CARS). Absolute NO concentrations are obtained by laser-induce fluorescence (LIF) measurements, and N and O densities are found using two photon absorption laser-induced fluorescence (TALIF). For all dry air conditions studied, the NO behavior is characterized by a rapid rate of formation consistent with an enhanced Zeldovich process involving electronically-excited nitrogen species that are generated within the plasma. After several microseconds, the NO evolution is entirely controlled by the reverse Zeldovich process. These results show that under the chosen range of conditions and even in extreme instances of vibrational loading, there is no formation channel beyond ~2 musec. Both the NO formation and consumption mechanisms are strongly affected by the addition of fuel species, producing much greater NO concentrations in the afterglow.
Fiber laser coupled optical spark delivery system
Yalin, Azer; Willson, Bryan; Defoort, Morgan; Joshi, Sachin; Reynolds, Adam
A spark delivery system for generating a spark using a laser beam is provided, and includes a laser light source and a laser delivery assembly. The laser delivery assembly includes a hollow fiber and a launch assembly comprising launch focusing optics to input the laser beam in the hollow fiber. The laser delivery assembly further includes exit focusing optics that demagnify an exit beam of laser light from the hollow fiber, thereby increasing the intensity of the laser beam and creating a spark. Other embodiments use a fiber laser to generate a spark. Embodiments of the present invention may be used to create a spark in an engine. Yet other embodiments include collecting light from the spark or a flame resulting from the spark and conveying the light for diagnostics. Methods of using the spark delivery systems and diagnostic systems are provided.
Spark gap with low breakdown voltage jitter
Rohwein, G.J.; Roose, L.D.
Novel spark gap devices and electrodes are disclosed. The novel spark gap devices and electrodes are suitable for use in a variety of spark gap device applications. The shape of the electrodes gives rise to local field enhancements and reduces breakdown voltage jitter. Breakdown voltage jitter of approximately 5% has been measured in spark gaps according the invention. Novel electrode geometries and materials are disclosed. 13 figs.
Spark gap with low breakdown voltage jitter
Rohwein, Gerald J.; Roose, Lars D.
Novel spark gap devices and electrodes are disclosed. The novel spark gap devices and electrodes are suitable for use in a variety of spark gap device applications. The shape of the electrodes gives rise to local field enhancements and reduces breakdown voltage jitter. Breakdown voltage jitter of approximately 5% has been measured in spark gaps according the invention. Novel electrode geometries and materials are disclosed.
Electric Field in a Plasma Channel in a High-Pressure Nanosecond Discharge in Hydrogen: A Coherent Anti-Stokes Raman Scattering Study
NASA Astrophysics Data System (ADS)
Yatom, S.; Tskhai, S.; Krasik, Ya. E.
Experimental results of a study of the electric field in a plasma channel produced during nanosecond discharge at a H2 gas pressure of (2-3)×105 Pa by the coherent anti-Stokes scattering method are reported. The discharge was ignited by applying a voltage pulse with an amplitude of ˜100 kV and a duration of ˜5 ns to a blade cathode placed at a distance of 10 and 20 mm from the anode. It was shown that this type of gas discharge is characterized by the presence of an electric field in the plasma channel with root-mean-square intensities of up to 30 kV/cm. Using polarization measurements, it was found that the direction of the electric field is along the cathode-anode axis.
Search for a ''3.5-eV isomer'' in {sup 229}Th in a hollow-cathode electric discharge
Inamura, T. T.; Haba, H.
A hollow-cathode electric discharge, a well-established source in optical spectroscopy, was used to populate the ''3.5-eV isomer'' in {sup 229}Th with use of nuclear excitation by electron transition (NEET). The radiochemically purest {sup 229}Th sample was loaded into the hollow cathode in which the electric discharge excited the {sup 229}Th to atomic states some of which could be expected to lie close to the excitation energy of the sought isomer. Although there remain some uncertainties, our experiments indicate that the isomer was populated by NEET and its {alpha} decay observed after switching off the electric discharge with a corresponding isomer half-life 1 min < or approx. T{sub 1/2}{sup m} < or approx. 3 min. From the present NEET condition, the isomer appears to lie between 3 eV and 7 eV. The probability of the isomer population by NEET is discussed.
New Technology Sparks Smoother Engines and Cleaner Air
NASA Technical Reports Server (NTRS)
Automotive Resources, Inc. (ARI) has developed a new device for igniting fuel in engines-the SmartPlug.TM SmartPlug is a self-contained ignition system that may be retrofitted to existing spark-ignition and compression-ignition engines. The SmartPlug needs as little as six watts of power for warm-up, and requires no electricity at all when the engine is running. Unlike traditional spark plugs, once the SmartPlug ignites the engine, and the engine heats up, the power supply for the plug is no longer necessary. In the utility industry, SmartPlugs can be used in tractors, portable generators, compressors, and pumps. In addition to general-purpose applications, such as lawn mowers and chainsaws, SmartPlugs can also be used in the recreational, marine, aviation, and automotive industries. Unlike traditional ignition systems, the SmartPlug system requires no distributor, coil points, or moving parts. SmartPlugs are non-fouling, with a faster and cleaner burn than traditional spark plugs. They prevent detonation and are not sensitive to moisture, allowing them to be used on a variety of engines. Other advantages include no electrical noise, no high voltage, exceptionally high altitude capabilities, and better cold-start statistics than those of standard spark ignition systems. Future applications for the SmartPlug are being evaluated by manufacturers in the snowmobile industry.
Electric-pulse discharge as a novel technique to synthesize {beta}-SiC nano-crystallites from liquid-phase organic precursors
Du Kai; Yang Haibin Wei Ronghui; Li Minghui; Yu Qingjiang; Fu Wuyou; Yang Nan; Zhu Hongyang; Zeng Yi
{beta}-SiC nano-crystallites have been prepared by electric pulses discharged in liquid-phase organic precursors. The composition and crystal structure of the products were characterized by X-ray diffraction, Raman spectroscopy, field emission scanning electronic and transmission electron microscopy. Transmission electron microscopy showed that the sample synthesized from the precursor (hexamethyl disilane) is composed of uniform grains with only 8 nm, while the one synthesize from the other precursor (dimethyl silicone oil) is of better crystalline structure with average grain size 22 nm, which may be attributed to discharge in liquid-phase source and short discharge intervals.
Development of a Discharge Channel upon Electric Explosion of a Wire in Interrupted- and Uninterrupted-Current Regimes
Romanova, Vera; Tkachenko, Svetlana; Mingaleev, Albert; Agafonov, Alexey; Ter-Oganesyan, Alexey; Shelkovenko, Tatiana; Pikuz, Sergey
Experimental results on the electrical explosion of thin W, Cu and Ni wires with a current density of {approx}10{sup 12} A/m{sup 2}, a current rise rate (dI/dt){approx}40 A/ns and a current pulse with amplitude 9 kA are presented. The structures of the discharge channels developed in single wire explosions in air and vacuum using laser shadow and schlieren imaging have been studied under the condition that the current in the circuit was interrupted. A difference in the shock wave propagation in air and the expansion of the exploded wire dense core in interrupted- and uninterrupted-current regimes has been observed. Analysis of the optical images has been performed in a shunting breakdown scenario.
Microstructure investigation of 13Cr-2Mo ODS steel components obtained by high voltage electric discharge compaction technique
Bogachev, Igor; Yudin, Artem; Grigoryev, Evgeniy; Chernov, Ivan; Staltsov, Maxim; Khasanov, Oleg; Olevsky, Eugene
Refractory oxide dispersion strengthened 13Cr-2Mo steel powder was successfully consolidated to near theoretical density using high voltage electric discharge compaction. Cylindrical samples with relative density from 90% to 97% and dimensions of 10 mm in diameter and 10–15 mm in height were obtained. Consolidation conditions such as pressure and voltage were varied in some ranges to determine the optimal compaction regime. Three different concentrations of yttria were used to identify its effect on the properties of the samples. It is shown that the utilized ultra-rapid consolidation process in combination with high transmitted energy allows obtaining high density compacts, retaining the initial structure with minimal grain growth. The experimental results indicate some heterogeneity of the structure which may occur in the external layers of the tested samples due to various thermal and electromagnetic in-processing effects. As a result, the choice of the optimal parameters of the consolidation enables obtaining samples of acceptable quality.
Characterization of electric discharge machining, subsequent etching and shot-peening as a surface treatment for orthopedic implants
NASA Astrophysics Data System (ADS)
Stráský, Josef; Havlíková, Jana; Bačáková, Lucie; Harcuba, Petr; Mhaede, Mansour; Janeček, Miloš
Presented work aims at multi-method characterization of combined surface treatment of Ti-6Al-4V alloy for biomedical use. Surface treatment consists of consequent use of electric discharge machining (EDM), acid etching and shot peening. Surface layers are analyzed employing scanning electron microscopy and energy dispersive X-ray spectroscopy. Acid etching by strong Kroll's reagent is capable of removing surface layer of transformed material created by EDM. Acid etching also creates partly nanostructured surface and significantly contributes to the enhanced proliferation of the bone cells. The cell growth could be positively affected by the superimposed bone-inspired structure of the surface with the morphological features in macro-, micro- and nano-range. Shot peening significantly improves poor fatigue performance after EDM. Final fatigue performance is comparable to benchmark electropolished material without any adverse surface effect. The proposed three-step surface treatment is a low-cost process capable of producing material that is applicable in orthopedics.
Fe{sup 2+} : ZnSe laser pumped by a nonchain electric-discharge HF laser at room temperature
Velikanov, S D; Zakharov, N G; Shchurov, V V; Danilov, V P; Il'ichev, N N; Kazantsev, S Yu; Kalinushkin, V P; Kononov, I G; Studenikin, M I; Pashinin, P P; Firsov, K N; Nasibov, A S; Shapkin, P V
The characteristics of a Fe{sup 2+} : ZnSe laser in a scheme with transverse pumping by a nonchain electric-discharge HF laser at room temperature are studied. Doping of ZnSe crystals with Fe{sup 2+} ions was performed by diffusion simultaneously through two surfaces under the conditions of thermodynamic equilibrium. It is found that the Fe{sup 2+} : ZnSe laser pulses are modulated by short spikes (3 – 7 ns at half maximum at low pump energies), whose number decreases and modulation depth increases as the pump energy decreases to a threshold value. A laser pulse energy of 30.6 mJ is achieved at a pulse duration at half maximum of ∼125 ns (at high pump energies); the possibility of a further increase in the energy of Fe{sup 2+} : ZnSe lasers pumped by nonchain HF lasers is discussed. (lasers)
Employing Ti nano-powder dielectric to enhance surface characteristics in electrical discharge machining of AISI D2 steel
NASA Astrophysics Data System (ADS)
Marashi, Houriyeh; Sarhan, Ahmed A. D.; Hamdi, Mohd
Manufacturing components with superior surface characteristics is challenging when electrical discharge machining (EDM) is employed for mass production. The aim of this research is to enhance the characteristics of AISI D2 steel surface machined with EDM through adding Ti nano-powder to dielectric under various machining parameters, including discharge duration (Ton) and peak current (I). Surface roughness profilometer, FESEM and AFM analysis were utilized to reveal the machined surface characteristics in terms of surface roughness, surface morphology and surface micro-defects. Moreover, EDX analysis was performed in order to evaluate the atomic deposition of Ti nano-powder on the surface. The concentration of Ti nano-powder in dielectric was also examined using ESEM and EDX. According to the results, the addition of Ti nano-powder to dielectric notably enhanced the surface morphology and surface roughness at all machining parameters except Ton = 340 μs. Of these parameters, maximum enhancement was observed at Ton = 210 μs, where the material removal rate and average surface roughness improved by ∼69 and ∼35% for peak current of 6 and 12 A, respectively. Elemental analysis signified negligible Ti deposition on the machined surface while the atomic concentration of Ti was increased around the crack areas.
Spectroscopy peculiarities of thermal plasma of electric arc discharge between electrodes with Zn admixtures
NASA Astrophysics Data System (ADS)
Semenyshyn, R. V.; Veklich, A. N.; Babich, I. L.; Boretskij, V. F.
Plasma of the free burning electric arc between Ag-SnO2-ZnO composite electrodes as well as brass electrodes were investigated. The plasma temperature distributions were obtained by Boltzmann plot method involving Cu I, Ag I or Zn I spectral line emissions. The electron density distributions were obtained from the width and from absolute intensity of spectral lines. The laser absorption spectroscopy was used for measurement of copper atom concentration in plasma. Plasma equilibrium composition was calculated using two independent groups of experimental values (temperature and copper atom concentration, temperature and electron density). It was found that plasma of the free burning electric arc between brass electrodes is in local thermodynamical equilibrium. The experimental verification of the spectroscopic data of Zn I spectral lines was carried out.
Baker, W.R.
A protective system for high-energy resonant cavities is described. It is particularly directed to the discharging of resonant cavities for preventing energy back flow through associated equipment as a result of faults. The invention in general provides means defining a spark gap communicating with the interior of a cavity or waveguide adapted for high-power energization or an evacuated chamber containing an electrode having a large power differential from the wall or other electrode. A control or trigger circuit is connected between a power supply energizing the cavity and the spark gap whereby reverse current flow in the power supply circuit instantaneously triggers the spark gap to initiate discharge within the cavity, whereupon cavity energy discharges across the gap, or with an electrode present the electrode discharges to one of the spark gap elements.
Low partial discharge vacuum feedthrough
NASA Technical Reports Server (NTRS)
Benham, J. W.; Peck, S. R.
Relatively discharge free vacuum feedthrough uses silver-plated copper conductor jacketed by carbon filled silicon semiconductor to reduce concentrated electric fields and minimize occurrence of partial discharge.
Optical visualization of electric and magnetic field perturbations in tokamak discharges by hydrogen pellet injection
NASA Astrophysics Data System (ADS)
Drawin, H.-W.; Dubois, M. A.
Two-dimensional intensity distribution mappings of photographs of pellet ablation cloud trajectories in TFR and TORE SUPRA reveal irregular shapes of the luminous striations. The observed features are not well understood, but a likely interpretation is that these features are caused by pre-existing electric and/or magnetic field perturbations in the hot core of tokamak plasmas. It is suggested to further investigate pellet injection as a diagnostic tool for the study of plasma structures and transport phenomena
Changes in electrode microstructure and charge efficiency produced by pulsed discharge of electric vehicle lead acid batteries
Caulder, S.; Dowgiallo, E.; Simon, A.
Comparison of battery plates with invariant vs. pulsed current discharges showed greater electrolyte stratification and a more rapid detrimental change in active material microstructure for the batteries receiving the pulsed discharges. This microstructural change could not be reversed by subsequent invariant current discharges. No significant differences in grid corrosion rate were noted in the two discharge modes.
Electrical and optical characterization of a pulsed discharge in an inverted cylindrical magnetron
NASA Astrophysics Data System (ADS)
Vozniy, O. V.; Duday, D.; Luciu, I.; Wirtz, T.
An inverted cylindrical magnetron operating in pulsed mode was developed, with a rotating unbalanced system of magnets. The magnetic field was calculated using the finite integration technique in order to determine the optimal anode-to-cathode distance inside the reactor. A cylindrical titanium target was used for our experiments. The average power input was varied between 500 and 1300 W leading to low power densities varying between 0.9 and 2.4 W cm-2. The frequency was fixed at a low value of 250 Hz, suitable for depositing Ti and TiO2 at low temperatures on polymer substrates. Long on-time pulses (400 µs) were used in order to reach interesting deposition rates (>1 µm h-1). A transition from metallic to oxide mode was observed for all power inputs. Time-resolved optical emission spectroscopy was used for the investigation of plasma dynamics during the on-time pulse in both metallic and reactive regimes. Three phases of discharge evolution were identified in the metallic mode: the Ar-dominated phase, followed by a transition zone and a Ti-dominated phase. The emission of Ti species completely disappeared in the reactive mode, associated with the fact that titanium atoms left the target surface as TiOx molecular fragments. In conclusion, the deposition system and conditions used resulted in a new mode of TiO2 deposition.
Nonisothermal theory of the positive column of an electric discharge in the axial magnetic field
Ul'yanov, D. K. Ul'yanov, K. N.
A nonisothermal model of the positive column allowing for electron energy balance is analyzed. The influence of the axial magnetic field on the characteristics of the cylindrical positive column of a low-pressure discharge is investigated in the hydrodynamic approximation. It is shown that the magnetic field affects the plasma density distribution, plasma velocity, and electron energies. The radial dependences of the plasma density, electron energy, and plasma velocity, as well as the azimuthal velocities of electrons and ions, are calculated for helium at different values of the magnetic field strength. It is established that inertia should be taken into account in the equations for the azimuthal motion of electrons and ions. The results obtained in the hydrodynamic approximation differ significantly from those obtained in the framework of the common diffusion model of the positive column in the axial magnetic field. It is shown that the distributions of the plasma density and radial plasma velocity in the greater part of the positive column tend to those obtained in the diffusion approximation at higher values of the axial magnetic field and gas density, although substantial differences remain in the near-wall region.
Process for Ignition of Gaseous Electrical Discharge Between Electrodes of a Hollow Cathode Assembly
NASA Technical Reports Server (NTRS)
Patterson, Michael J. (Inventor); Verhey, Timothy R. R. (Inventor); Soulas, George C. (Inventor)
The design and manufacturing processes for Hollow Cathode Assemblies (HCA's) that operate over a broad range of emission currents up to 30 Amperes, at low potentials, with lifetimes in excess of 17,500 hours. The processes include contamination control procedures which cover hollow cathode component cleaning procedures, gas feed system designs and specifications, and hollow cathode activation and operating procedures to thereby produce cathode assemblies that have demonstrated stable and repeatable operating conditions, for both the discharge current and voltage. The HCA of this invention provides lifetimes of greater than 10,000 hours, and expected lifetimes of greater than 17,500 hours, whereas the present state-of-the-art is less than 500 hours at emission currents in excess of 1 Ampere. Stable operation is provided over a large range of operating emission currents, up to a 6:1 ratio, and this HCA can emit electron currents of up to 30 Amperes in magnitude to an external anode that simulates the current drawn to a space plasma, at voltages of less than 20 Volts.
Hard-facing with electro-spark deposition. Final report
Kees, K.P.
A common method to improve wear resistance of metals in rubbing contact is to increase their surface hardness. Electro-Spark Deposition is a process which uses capacitive discharge pulses of high current passing through a hard carbide electrode in contact with and scanning the metal surface to be hardened. The result is a thin, hard, adherent coating of carbide deposited with a minimum of heat influence on the substrate and a significant increase in wear life of the coated metal. Electro-Spark Deposition is similar to a micro-welding process. It is a simple, portable and inexpensive coating method, which has great potential for commercial utilization. This thesis is an in depth study of the parameters associated with the ESD process and the wear resistance of the coatings.
By-product Generation through Electrical Discharge in CF3I Gas and its Effect to Insulation Characteristics
NASA Astrophysics Data System (ADS)
Takeda, Toshinobu; Matsuoka, Shigeyasu; Kumada, Akiko; Hidaka, Kunihiko
CF3I gas, which is one of promising SF6 substitutions, is investigated from the view point of by-product generated in gas discharge, since its global warming potential (GWP) is quite low and its insulation performance is equivalent or superior to SF6 gas. The insulation performance of CF3I gas is examined through measuring sparkover voltage in various electric fields and flashover voltage on the surface of insulating material together with analyzing by-products of CF3I gas. Gas chromatography analysis shows that C2F6, C2F4, CHF3, C3F8, C3F6, and C2F5I are generated by the sparkover and the flashover. The sparkover voltage after 1300 times sparkover in uniform electric field is decreased by 11%. The flashover voltage for a virgin insulator in CF3I gas is almost equal to that in SF6 gas. The flashover voltage in CF3I gas is, however, 0.6 times lower than that in SF6 gas, when the number of surface flashover is increased.
Fiber coupled optical spark delivery system
Yalin, Azer; Willson, Bryan; Defoort, Morgan
A spark delivery system for generating a spark using a laser beam is provided, the spark delivery system including a laser light source and a laser delivery assembly. The laser delivery assembly includes a hollow fiber and a launch assembly comprising launch focusing optics to input the laser beam in the hollow fiber. In addition, the laser delivery assembly includes exit focusing optics that demagnify an exit beam of laser light from the hollow fiber, thereby increasing the intensity of the laser beam and creating a spark. In accordance with embodiments of the present invention, the assembly may be used to create a spark in a combustion engine. In accordance with other embodiments of the present invention, a method of using the spark delivery system is provided. In addition, a method of choosing an appropriate fiber for creating a spark using a laser beam is also presented.
Spark bubble interaction with a suspended particle
NASA Astrophysics Data System (ADS)
Ohl, Siew-Wan; Wu, Di Wei; Klaseboer, Evert; Cheong Khoo, Boo
Cavitation bubble collapse is influenced by nearby surfaces or objects. A bubble near a rigid surface will move towards the surface and collapse with a high speed jet. When a hard particle is suspended near a bubble generated by electric spark, the bubble expands and collapses moving the particle. We found that within a limit of stand-off distance, the particle is propelled away from the bubble as it collapses. At a slightly larger stand-off distance, the bubble collapse causes the particle to move towards the bubble initially before moving away. The bubble does not move the particle if it is placed far away. This conclusion is important for applications such as drug delivery in which the particle is to be propelled away from the collapsing bubble.
Discharge processes, electric field, and electron energy in ISUAL-recorded gigantic jets
NASA Astrophysics Data System (ADS)
Kuo, Cheng-Ling; Chou, J. K.; Tsai, L. Y.; Chen, A. B.; Su, H. T.; Hsu, R. R.; Cummer, S. A.; Frey, H. U.; Mende, S. B.; Takahashi, Y.; Lee, L. C.
This article reports the first high time resolution measurements of gigantic jets from the Imager of Sprites and Upper Atmospheric Lightning (ISUAL) experiment. The velocity of the upward propagating fully developed jet stage of the gigantic jets was ˜107 m s-1, which is similar to that observed for downward sprite streamers. Analysis of spectral ratios for the fully developed jet emissions gives a reduced E field of 400-655 Td and average electron energy of 8.5-12.3 eV. These values are higher than those in the sprites but are similar to those predicted by streamer models, which implies the existence of streamer tips in fully developed jets. The gigantic jets studied here all contained two distinct photometric peaks. The first peak is from the fully developed jet, which steadily propagates from the cloud top (˜20 km) to the lower ionosphere at ˜90 km. We suggest that the second photometric peak, which occurs ˜1 ms after the first peak, is from a current wave or potential wave-enhanced emissions that originate at an altitude of ˜50 km and extend toward the cloud top. We propose that the fully developed jet serves as an extension of the local ionosphere and produces a lowered ionosphere boundary. As the attachment processes remove the charges, the boundary of the local ionosphere moves up. The current in the channel persists and its contact point with the ionosphere moves upward, which produces the upward surging trailing jets. Imager and photometer data indicate that the lightning activity associated with the gigantic jets likely is in-cloud, and thus the initiation of the gigantic jets is not directly associated with cloud-to-ground discharges.
Spectroscopy of Benzyl-Type Radicals Generated by Electric Discharge : Jet-Cooled Dichlorobenzyl Radicals
NASA Astrophysics Data System (ADS)
Yoon, Young Wook; Lee, Sang Kuk
The technique of corona excited supersonic expansion coupled with a pinhole-type glass nozzle has been proved a useful laser-free spectroscopic tool for observation of vibronic emission spectra of large aromatic molecules, especially for molecular radicals which are long believed to play an important role as a reaction intermediate in aromatic chemical reactions. The vibronic emission spectra recorded with a long-path monochromator exhibit the electronic transition energy in the D_1 → D_0 transition and vibrational mode frequencies at the D_0 state. In this laboratory, all six isomeric dichlorobenzyl radicals have been produced from the corona discharge of corresponding dichlorotoluenes seeded in a large amount of inert carrier gas He. The vibronic emission spectra show very weak intensity due to the existence of Cl atoms in the precursor molecules and possible breakdown of benzene ring by free Cl atoms. Nevertheless, we clearly identified the origin band and a few well-known vibrational modes for each isomer. From an analysis of the spectra observed, we determined the energy of electronic transition and several vibrational modes in the ground electronic state. Also, the red-shift of the origin band from the parental benzyl radical clearly shows the substituent effect of Cl atoms on electronic energy, for which we satisfactorily explain in terms of the shape of the molecular planes and position of the nodal points at a given electronic state, recently developed in this laboratory for identification of isomeric multi-substituted benzyl-type radicals. Y. W. Yoon, C. S. Huh, and S. K. Lee, Chem. Phys. Lett. {550}, 58 (2012). S. K. Lee and S. J. Kim, Chem. Phys. Lett. {412}, 88 (2005).
Double-discharge copper-vapor laser
NASA Technical Reports Server (NTRS)
Chen, C. J.; Merheim, N. M.; Russell, G. R.
Power supply for discharge pulses consists of two capacitors that are made to discharge synchronously with adjustable time intervals. First pulse is switched with hydrogen thyratron, and second by spark gap. Lasing action peaks for appropriate combination of these two parameters.
Spark ignited turbulent flame kernel growth. Annual report, January--December 1991
Santavicca, D.A.
An experimental study of the effect of spark power on the growth rate of spark-ignited flame kernels was conducted in a turbulent flow system at 1 atm, 300 K conditions. All measurements were made with premixed, propane-air at a fuel/air equivalence ratio of 0.93, with 0%, 8% or 14% dilution. Two flow conditions were studied: a low turbulence intensity case with a mean velocity of 1.25 m/sec and a turbulence intensity of 0.33 m/sec, and a high turbulence intensity case with a mean velocity of 1.04 m/sec and a turbulence intensity of 0.88 m/sec. The growth of the spark-ignited flame kernel was recorded over a time interval from 83 {mu}sec to 20 msec following the start of ignition using high speed laser shadowgraphy. In order to evaluate the effect of ignition spark power, tests were conducted with a long duration (ca 4 msec) inductive discharge ignition system with an average spark power of ca 14 watts and two short duration (ca 100 nsec) breakdown ignition systems with average spark powers of ca 6 {times} 10{sup 4} and ca 6 {times} 10{sup 5} watts. The results showed that increased spark power resulted in an increased growth rate, where the effect of short duration breakdown sparks was found to persist for times of the order of milliseconds. The effectiveness of increased spark power was found to be less at high turbulence and high dilution conditions. Increased spark power had a greater effect on the 0--5 mm burn time than on the 5--13 mm burn time, in part because of the effect of breakdown energy on the initial size of the flame kernel. And finally, when spark power was increased by shortening the spark duration while keeping the effective energy the same there was a significant increase in the misfire rate, however when the spark power was further increased by increasing the breakdown energy the misfire rate dropped to zero.
2D gasdynamic simulation of the kinetics of an oxygen-iodine laser with electric-discharge generation of singlet oxygen
Chukalovsky, A. A.; Rakhimova, T. V.; Klopovsky, K. S.; Mankelevich, Yu. A.; Proshina, O. V.
The kinetic processes occurring in an electric-discharge oxygen-iodine laser are analyzed with the help of a 2D (r, z) gasdynamic model taking into account transport of excited oxygen, singlet oxygen, and radicals from the electric discharge and their mixing with the iodine-containing gas. The main processes affecting the dynamics of the gas temperature and gain are revealed. The simulation results obtained using the 2D model agree well with the experimental data on the mixture gain. A subsonic oxygen-iodine laser in which singlet oxygen is generated by a 350 W transverse RF discharge excited in an oxygen flow at a pressure P = 10 Torr and the discharge tube wall is covered with mercury oxide is simulated. The simulated mixing system is optimized in terms of the flow rate and the degree of preliminary dissociation of the iodine flow. The optimal regime of continuous operation of a subsonic electric-discharge oxygen-iodine laser is found.
Spectroscopic investigation of the spatiotemporal dynamics of an electric field in plasma of a beam-type high-voltage discharge in helium
Demkin, V. P.; Mel'nichuk, S. V.
In the present work, a method of determining the spatiotemporal characteristics of the electric field strength in an accelerating gap and a plasma flare of a beam-type high-voltage pulsed discharge in He at moderate pressure is presented. The method is based on spectroscopic data on the Stark splitting of π-components of He 2P–4Q transitions; Q = D(4921.93 Å), F(4920.35 Å) in the near-cathode region of the discharge and on the spatiotemporal characteristics of intensities of He(2s{sup 1}S–3p{sup 1}P{sup 0}) spectral lines with λ = 5015 Å and He{sup +}(3d–4f) spectral lines with λ = 4685 Å measured experimentally and calculated from the data of statistical simulation of the electron kinetics by the Monte Carlo method. The shape and strength of the electric field of the space charge in the interelectrode gap and the drift region of the discharge are estimated. It is demonstrated that the electric field created by the current pulse of uncompensated space charge in the near-anode region changes the discharge regime and causes degradation of the electron beam in the plasma flare. It is established that the flux of secondary electrons from the drift region to the anode has significant effect on the radiation intensity distribution in this region of the discharge.
Conversion of NO to NO(2) in air by a micro electric NO(x) converter based on a corona discharge process.
Yoon, Seung-Il; Heo, Sungmoo; Song, Soonho; Kim, Yong-Jun
A micro-electric-NO(x)-converter based on volume treatment is proposed for the evaluation of NO(x) concentrations in air. It can electrically convert NO(x) mixture from variable mixing rates into a fixed-mixing rate of 25% NO(2) and 75% NO using the corona discharge process with stable conversion efficiency and high throughput (space velocity = 6.3 x 10(4) h(-1)). The micro-electric-NO(x)-converter is based on a volume process. Applying high voltage to the electrodes of the micro-electric-NO(x)-converter generates a corona discharge. This discharge creates high-energy electrons, which collide with gas molecules. After these collisions, NO and O(2) are broken into single atoms, and they are re-combined as a balanced form, NO(2) in this case. The fabricated micro-electric-NO(x)-converter converted NO into NO(2) at conversion efficiency of 25.63%, when 5.5 kV (the applied corona power = 0.196 W) was applied to the micro-electric-NO(x)-converter. PMID:20498882
Partial Discharge Characteristics of Polymer Nanocomposite Materials in Electrical Insulation: A Review of Sample Preparation Techniques, Analysis Methods, Potential Applications, and Future Trends
Izzati, Wan Akmal; Adzis, Zuraimy; Shafanizam, Mohd
Polymer nanocomposites have recently been attracting attention among researchers in electrical insulating applications from energy storage to power delivery. However, partial discharge has always been a predecessor to major faults and problems in this field. In addition, there is a lot more to explore, as neither the partial discharge characteristic in nanocomposites nor their electrical properties are clearly understood. By adding a small amount of weight percentage (wt%) of nanofillers, the physical, mechanical, and electrical properties of polymers can be greatly enhanced. For instance, nanofillers in nanocomposites such as silica (SiO2), alumina (Al2O3) and titania (TiO2) play a big role in providing a good approach to increasing the dielectric breakdown strength and partial discharge resistance of nanocomposites. Such polymer nanocomposites will be reviewed thoroughly in this paper, with the different experimental and analytical techniques used in previous studies. This paper also provides an academic review about partial discharge in polymer nanocomposites used as electrical insulating material from previous research, covering aspects of preparation, characteristics of the nanocomposite based on experimental works, application in power systems, methods and techniques of experiment and analysis, and future trends. PMID:24558326
Partial discharge characteristics of polymer nanocomposite materials in electrical insulation: a review of sample preparation techniques, analysis methods, potential applications, and future trends.
Izzati, Wan Akmal; Arief, Yanuar Z; Adzis, Zuraimy; Shafanizam, Mohd
Polymer nanocomposites have recently been attracting attention among researchers in electrical insulating applications from energy storage to power delivery. However, partial discharge has always been a predecessor to major faults and problems in this field. In addition, there is a lot more to explore, as neither the partial discharge characteristic in nanocomposites nor their electrical properties are clearly understood. By adding a small amount of weight percentage (wt%) of nanofillers, the physical, mechanical, and electrical properties of polymers can be greatly enhanced. For instance, nanofillers in nanocomposites such as silica (SiO2), alumina (Al2O3) and titania (TiO2) play a big role in providing a good approach to increasing the dielectric breakdown strength and partial discharge resistance of nanocomposites. Such polymer nanocomposites will be reviewed thoroughly in this paper, with the different experimental and analytical techniques used in previous studies. This paper also provides an academic review about partial discharge in polymer nanocomposites used as electrical insulating material from previous research, covering aspects of preparation, characteristics of the nanocomposite based on experimental works, application in power systems, methods and techniques of experiment and analysis, and future trends. PMID:24558326
Arrol, W.J.; Jefferson, S.
The construction of gas discharge devices where the object is to provide a gas discharge device having a high dark current and stabilized striking voltage is described. The inventors have discovered that the introduction of tritium gas into a discharge device with a subsequent electrical discharge in the device will deposit tritium on the inside of the chamber. The tritium acts to emit beta rays amd is an effective and non-hazardous way of improving the abovementioned discharge tube characteristics
Lifecycle of laser-produced air sparks
NASA Astrophysics Data System (ADS)
Harilal, S. S.; Brumfield, B. E.; Phillips, M. C.
We investigated the lifecycle of laser-generated air sparks or plasmas using multiple plasma diagnostic tools. The sparks were generated by focusing the fundamental radiation from an Nd:YAG laser in air, and studies included early and late time spark dynamics, decoupling of the shock wave from the plasma core, emission from the spark kernel, cold gas excitation by UV radiation, shock waves produced by the air spark, and the spark's final decay and turbulence formation. The shadowgraphic and self-emission images showed similar spark morphology at earlier and late times of its lifecycle; however, significant differences are seen in the midlife images. Spectroscopic studies in the visible region showed intense blackbody-type radiation at early times followed by clearly resolved ionic, atomic, and molecular emission. The detected spectrum at late times clearly contained emission from both CN and N2+. Additional spectral features have been identified at late times due to emission from O and N atoms, indicating some degree of molecular dissociation and excitation. Detailed spatially and temporally resolved emission analysis provides insight about various physical mechanisms leading to molecular and atomic emission by air sparks, including spark plasma excitation, heating of cold air by UV radiation emitted by the spark, and shock-heating.
Lifecycle of laser-produced air sparks
Harilal, S. S. Brumfield, B. E.; Phillips, M. C.
We investigated the lifecycle of laser-generated air sparks or plasmas using multiple plasma diagnostic tools. The sparks were generated by focusing the fundamental radiation from an Nd:YAG laser in air, and studies included early and late time spark dynamics, decoupling of the shock wave from the plasma core, emission from the spark kernel, cold gas excitation by UV radiation, shock waves produced by the air spark, and the spark's final decay and turbulence formation. The shadowgraphic and self-emission images showed similar spark morphology at earlier and late times of its lifecycle; however, significant differences are seen in the midlife images. Spectroscopic studies in the visible region showed intense blackbody-type radiation at early times followed by clearly resolved ionic, atomic, and molecular emission. The detected spectrum at late times clearly contained emission from both CN and N{sub 2}{sup +}. Additional spectral features have been identified at late times due to emission from O and N atoms, indicating some degree of molecular dissociation and excitation. Detailed spatially and temporally resolved emission analysis provides insight about various physical mechanisms leading to molecular and atomic emission by air sparks, including spark plasma excitation, heating of cold air by UV radiation emitted by the spark, and shock-heating.
Experimental Characterization of a Laser-Triggered, Gas-Insulated, Spark-Gap Switch
NASA Astrophysics Data System (ADS)
Camacho, J. F.; Brown, D. J.; Domonkos, M. T.; Ruden, E. L.; Schmitt-Sody, A.; Lucero, A. P.; Canright, J. P.; Miner, R. L.
We have developed an experimental test bed to characterize the performance of a laser-triggered spark-gap switch as it transitions from photoionization to current conduction. The discharge of current through the switch is triggered by a focused 532-nm wavelength beam from a Q-switched Nd:YAG laser with a pulse duration of about 10 ns. The trigger pulse is delivered along the longitudinal axis of the switch, and the focal spot can be placed anywhere along the axis of the 5-mm, gas-insulated gap between the switch electrodes. The test bed is designed to support a variety of working gases (e.g., Ar, N2, He, H2) over a range of pressures. Electrical and optical diagnostics are used to measure switch performance as a function of parameters such as charge voltage, trigger pulse energy, insulating gas pressure, and gas species. Data from our experiments will be used to determine the minimum conditions necessary to induce the breakdown and conduction of a gas-insulated electrode gap in the presence of laser-induced photoionization. The electromagnetic particle-in-cell code ICEPIC will be used to produce numerical simulations of the laser-initiated arc discharge, and the experimental data will be used to validate the calculations.
Influence of specific energy expenditures in electric-discharge sintering on the structure and properties of a copper-tin-abrasive composite
Baidenko, A.A.; Istomina, T.I.; Popov, V.P.; Raichenko, A.I.; Gol'dberg, M.Sh.; Svechkov, A.V.
The purpose of this work is a study of the influence of the energy consumptions in electric-discharge sintering on the sintering temperature, phase composition, porosity, hardness, and specific electric resistance of a copper-tin-abrasive sintered composite. The investigations were made on specimens in the form of 50 x 6 x 4 mm parallelepipeds sintered from an electrocorundum composite. The structural transformations were studied by x-ray diffraction on a DRON-2.0 instrument in CuK/sub gamma/-radiation and metallographic analysis. It is established that by changing the specific energy consumption, parts with different structures and properties are obtained from this composite by electric discharge sintering.
Electrode system for electric-discharge generation of atomic iodine in a repetitively pulsed oxygen - iodine laser with a large active volume
Kazantsev, S Yu; Kononov, I G; Podlesnykh, S V; Firsov, K N
Possibilities for increasing the active medium volume of a chemical oxygen - iodine laser (CCOIL) with a pulsed electric-discharge generation of atomic iodine are studied. The reasons are analysed of the low stability of the transverse self-sustained volume discharge in electrode systems with metal cathodes under the conditions of the electric energy input into gas-discharge plasma that are typical for CCOILs: low pressure of mixtures containing a strongly electronegative component, low voltage of discharge burning, low specific energy depositions, and long duration of the current pulse. An efficient electrode system is elaborated with the cathode based on an anisotropically-resistive material, which resulted in a stable discharge in the mixtures of iodide (CH{sub 3}I, n-C{sub 3}H{sub 7}I, C{sub 2}H{sub 5}I) with oxygen and nitrogen at the specific energy depositions of {approx}5 J L{sup -1}, pressures of 10 - 25 Torr, and mixture volume of 2.5 L. (lasers)
The Changes in Electrical and Interfacial Properties of Polyimide Exposed to Dielectric Barrier Discharge in SF6 Medium
Alisoy, Hafiz Z.; Koseoglu, Murat
The formation mechanism of space charges in polyimide (PI) which was exposed to dielectric barrier discharge (DBD) in SF6 medium and the effects of the space charges on interfacial and electrical properties of PI were investigated. The variation of normalized surface charge density on PI sample was calculated and illustrated for different DBD exposure times. The surface potential was measured to determine the effect of the space charges on the sample. Then, the contact angle values were measured to obtain the relation between the surface energy and the surface charge density. The expressions for the total charge and the concentration of trapped electrons were derived by using Poisson and continuity equations at stationary state. The space charges were determined experimentally by using thermally stimulated depolarization current (TSDC) method. Also, SEM image and FTIR spectrum of virgin and treated samples were presented to observe the structural variations. It was seen that the approach for the formation mechanism of the space charges agreed with the experimental data. However, it was concluded particularly for the short-time DBD treatments that the space charges accumulated in the sample should be considered besides the effects of surface functionalization in the determination of the surface energy. PMID:23844414
Full multi grid method for electric field computation in point-to-plane streamer discharge in air at atmospheric pressure
NASA Astrophysics Data System (ADS)
Kacem, S.; Eichwald, O.; Ducasse, O.; Renon, N.; Yousfi, M.; Charrada, K.
Streamers dynamics are characterized by the fast propagation of ionized shock waves at the nanosecond scale under very sharp space charge variations. The streamer dynamics modelling needs the solution of charged particle transport equations coupled to the elliptic Poisson's equation. The latter has to be solved at each time step of the streamers evolution in order to follow the propagation of the resulting space charge electric field. In the present paper, a full multi grid (FMG) and a multi grid (MG) methods have been adapted to solve Poisson's equation for streamer discharge simulations between asymmetric electrodes. The validity of the FMG method for the computation of the potential field is first shown by performing direct comparisons with analytic solution of the Laplacian potential in the case of a point-to-plane geometry. The efficiency of the method is also compared with the classical successive over relaxation method (SOR) and MUltifrontal massively parallel solver (MUMPS). MG method is then applied in the case of the simulation of positive streamer propagation and its efficiency is evaluated from comparisons to SOR and MUMPS methods in the chosen point-to-plane configuration. Very good agreements are obtained between the three methods for all electro-hydrodynamics characteristics of the streamer during its propagation in the inter-electrode gap. However in the case of MG method, the computational time to solve the Poisson's equation is at least 2 times faster in our simulation conditions.