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A collection of individual works on electrical discharges is presented. Topics covered include: fundamental processes in the electrical breakdown of gases; vacuum breakdown; spark breakdown in uniform fields; corona discharge; spark breakdown in non-uniform fields; breakdown voltage characteristics; irradiation and time lags; high-frequency breakdown of gases; laser-induced electrical breakdown of gases; spark channels; and electrode phenomena. (GHT)
J. M. Meek; J. D. Craggs
The Breakdown Characteristics of the Silicone Oil for Electric Power Apparatus
NASA Astrophysics Data System (ADS)
The basic breakdown characteristics of the silicone oil as an insulating medium was studied with aim of realization of electric power apparatus which may be considered to be SF6 free and flame-retarding. As the first step, the impulse breakdown characteristics was measured with three kinds of electrodes whose electric field distributions differed. The breakdown characteristics in silicone oil was explained in relation to stressed oil volume (SOV) and the breakdown stress. At the second step the surface breakdown characteristic for impulse voltage was measured with two kinds of insulators which was set to between plane electrodes. The surface breakdown characteristic for impulse voltage was explained in relation to the ratio of the relative permittivity of oil and insulator. And on the third step, the breakdown characteristics of oil gap after interrupting small capacitive current was studied. In this experiment, the disconnecting switch to interrupt capacitive current was simulated by oil gap after interrupting impulse current, and to measure breakdown characteristics the high impulse voltage was subsequently applied. The breakdown stress in silicone oil after application of impulse current was discussed for insulation recovery characteristics.
Yoshida, Hisashi; Yanabu, Satoru
Breakdown characteristics in transformer oil under the controlled effect of thermal and electric strength
Summary form only given. This paper deals with the breakdown characteristics in commercial transformer oils effected by both controlled thermal and electric strength (controlling the field efficiency factor) under DC voltage. The experiments are done under the normal practical operation condition in Thailand. The results are compared with the manufacture's specification. The commercial transformer oil from a main transformer plant
C. Lorthongkam; K. Masarat; K. Petcharaks
Experimental Study on the Electrical Breakdown Characteristics of Sub-Cooled Liquid Nitrogen for Designing a High Voltage Superconducting Machine
The electrical breakdown characteristics of liquid nitrogen should be investigated for developing of a high voltage superconducting machine. This paper deals with the experimental study for the verification of dielectric characteristics of sub-cooled in accordance with utilization factors. AC dielectric experiments were carried out by using sphere-plane electrode systems. The utilization factors of simulated electrode systems were controlled by gap
Jin Bae Na; Hyoungku Kang; Young Jin Hwang; Seong Eun Yang; Dong Keun Park; Duck Kweon Bae; Tae Kuk Ko
Experimental study on simulated lunar soil. High voltage breakdown and electrical insulation characteristics
A low-mass solution to electrical insulation in the lunar environment may be possible by embedding bare HV conductors within the lunar soil itself. In the paper, a `standard' NASA soil (lunar simulant) representing chemical and physical conditions found in some lunar samples was used in laboratory experiments, and its HV electrical breakdown data were presented for the first time. Insulation
Hulya Kirkici; M. Frank Rose; Todd Chaloupka
Characteristics of edge breakdowns on Teflon samples
NASA Technical Reports Server (NTRS)
The characteristics of electrical discharges induced on silverbacked Teflon samples irradiated by a monoenergetic electron beam have been studied under controlled laboratory conditions. Measurements of breakdown threshold voltages indicate a marked anisotropy in the electrical breakdown properties of Teflon: differences of up to 10 kV in breakdown threshold voltage are observed depending on the sample orientation. The material anisotropy can be utilized in spacecraft construction to reduce the magnitude of discharge currents.
Yadlowsky, E. J.; Hazelton, R. C.; Churchill, R. J.
Breakdown characteristics of an isolated conducting object in a uniform electric field
NASA Technical Reports Server (NTRS)
A laboratory experiment was conducted to determine the physical processes involved in the electrical breakdown of a particular spark gap arrangement. The gap consists of an isolated conducting ellipsoid located midway between two large flat electrodes. Gradual increase of the applied electric field, E, in the gap produces corona on the ellipsoid tips followed by flashover in a leader-arc sequence. The leader phase consists of the abrupt formation of ionized channels which partially bridge the gap and then decay prior to the arc. Measurements of dE/dt and of current were made, and photographs were taken with an image converter. Experimental parameters are listed.
Grothaus, M. G.; Trost, T. F.
Electrical Breakdown Characteristics of Superconducting Magnet System in Sub-Cooled Liquid Nitrogen
Dielectric characteristics of gaseous helium (GHe) injected into the cooling system to make sub-cooled nitrogen condition with constant pressure is found to be extraordinarily weak in dielectric strength by H. Mitsuii (1998). In high voltage superconducting machines using the sub-cooled nitrogen cooling system, the current lead part in GHe environment could be electrical weak points rather than the superconducting magnet
Hyoungku Kang; Chanjoo Lee; Tae Kuk Ko; Bok-Yeol Seok
Electrical Breakdown in Water Vapor
In this paper investigations of the voltage required to break down water vapor are reported for the region around the Paschen minimum and to the left of it. In spite of numerous applications of discharges in biomedicine, and recent studies of discharges in water and vapor bubbles and discharges with liquid water electrodes, studies of the basic parameters of breakdown are lacking. Paschen curves have been measured by recording voltages and currents in the low-current Townsend regime and extrapolating them to zero current. The minimum electrical breakdown voltage for water vapor was found to be 480 V at a pressure times electrode distance (pd) value of around 0.6 Torr cm ({approx}0.8 Pa m). The present measurements are also interpreted using (and add additional insight into) the developing understanding of relevant atomic and particularly surface processes associated with electrical breakdown.
Skoro, N.; Maric, D.; Malovic, G.; Petrovic, Z. Lj. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Graham, W. G. [Centre for Plasma Physics, School of Mathematics and Physics, Queens University Belfast, BT7 1NN (United Kingdom)
Temperature and electric field characteristics of time-dependent dielectric breakdown for silicon dioxide and reoxidized-nitrided oxides
TDDB characteristics of 150 � reoxidized nitrided oxide (ONO) gate dielectrics were examined at temperatures from 77 K to 400 K. These ONO films were processed with different conditions of rapid thermal nitridation (RTN) and rapid thermal re-oxidation (RTO). Optimized ONO films show better Qbd performance while maintaining a similar temperature and electric field dependence compared to SiO2. The low
Chi-Hung Lin; James Cable; C. S. Woo
Differentiation between electric breakdowns and dielectric breakdown in thin silicon oxides
It has been known for some time that non-destructive electric breakdowns precede destructive thermal dielectric breakdown. We have been studying both processes in oxides between 5 nm and 80 nm in thickness. We have shown that the electric breakdowns can trigger dielectric breakdown under certain conditions. This triggering of dielectric breakdown causes TDDB distributions to be non-unique. The TDDB distributions
J. C. Jackson; T. Robinson; O. Oralkan; D. J. Dumin; G. A. Brown
Breakdown Characteristics of Moving Transformer Oil
As a result of investigating breakdown characteristics of moving oil, it has become clear that the breakdown voltage of ac and dc for moving oil is higher than that for stationary oil by 10-15 % at a moving velocity of 5 cm\\/s region; the former voltage becomes almost equal to the latter voltage in the region of 25 cm\\/s, and
M. Ikeda; T. Teranishi; M. Honda; T. Yanari
Electrical breakdown studies with Mycalex insulators
Insulating materials such as alumina and glass-bonded mica (Mycalex) are used in accelerator systems for high voltage feedthroughs, structural supports, and barriers between high voltage insulating oil and the vacuum beam pipe in induction accelerator cells. Electric fields in the triple points should be minimized to prevent voltage breakdown. Mechanical stress can compromise seals and result in oil contamination of the insulator surface. We have tested various insulator cleaning procedures including ultrasonic cleaning with a variety of aqueous-based detergents, and manual scrubbing with various detergents. Water sheeting tests were used to determine the initial results of the cleaning methods. Ultimately, voltage breakdown tests will be used to quantify the benefits of these cleaning procedures.
Waldron, W.; Greenway, W.; Eylon, S.; Henestroza, E.; Yu, S.
Strip electric�magnetic breakdown model in a magnetoelectroelastic medium
Extending the polarization saturation model [Gao et al., 1997. Local and global energy release rates for an electrically yielded crack in a piezoelectric ceramic. J. Mech. Phys. Solids 45, 491�510] and the dielectric breakdown (DB) model [Zhang et al., 2005. The strip dielectric breakdown model. Int. J. Fract. 132, 311�327] in piezoelectric materials, the Strip Electric�Magnetic Breakdown (SEMB) model is
Ming-Hao Zhao; Cui-Ying Fan
Electrical breakdown in thin oxides during bias-temperature ramps
Electrical breakdown in thin oxides is assessed by a new bias-temperature ramp technique. No significant effect of radiation exposure on breakdown is observed for high quality thermal and nitrided oxides, up to 20 Mrad(SiO{sub 2}).
Influence of electrode configuration upon electric breakdown in electronegative gases
This paper represents an effort to derive a theoretical expression which will predict the influence of electrode configuration upon the electric breakdown voltage in electronegative gases. The initial portion of the paper is involved with a presentation and discussion of the generalized condition for breakdown in all gases for an unspecified electrode configuration or structure. The equation is then applied
Robert W. Crowe
Electric field breakdown in single molecule junctions.
Here we study the stability and rupture of molecular junctions under high voltage bias at the single molecule/single bond level using the scanning tunneling microscope-based break-junction technique. We synthesize carbon-, silicon-, and germanium-based molecular wires terminated by aurophilic linker groups and study how the molecular backbone and linker group affect the probability of voltage-induced junction rupture. First, we find that junctions formed with covalent S-Au bonds are robust under high voltage and their rupture does not demonstrate bias dependence within our bias range. In contrast, junctions formed through donor-acceptor bonds rupture more frequently, and their rupture probability demonstrates a strong bias dependence. Moreover, we find that the junction rupture probability increases significantly above ?1 V in junctions formed from methylthiol-terminated disilanes and digermanes, indicating a voltage-induced rupture of individual Si-Si and Ge-Ge bonds. Finally, we compare the rupture probabilities of the thiol-terminated silane derivatives containing Si-Si, Si-C, and Si-O bonds and find that Si-C backbones have higher probabilities of sustaining the highest voltage. These results establish a new method for studying electric field breakdown phenomena at the single molecule level. PMID:25675085
Li, Haixing; Su, Timothy A; Zhang, Vivian; Steigerwald, Michael L; Nuckolls, Colin; Venkataraman, Latha
Humidity Effects and Breakdown Characteristics of Class II Insulating Gloves
The paper discusses how humidity and other atmospheric conditions affect the electrical testing of insulating gloves used for live line maintenance. Results of humidity effects upon the AC and DC in-service testing of new gloves and gloves used in service between 0.5 to 11 years are presented. The paper also gives, results of Class II electrical breakdown tests made on
Nestor Kolcio; Richard Peszlen
Breakdown characteristics and conditioning of carbon and refractory metal electrodes
NASA Technical Reports Server (NTRS)
High voltage carbon and refractory metal electrodes employed in devices used in space, such as ion thrusters and traveling wave tubes, can be easily damaged by electrical breakdown and arcing events. Modification of the electrode surfaces due to these events can impact the voltage hold off capability of the surfaces, which could lead to additional arcing, further damage, and the potential for device failure. On the cathode-potential surface, the arc energy is deposited by all of the processes at the surface ultimately responsible for net electron emission, such as melting, vapor and particulate formation, sputtering, ion bombardment, etc. On the anode-potential surface, the energy is deposited from the plasma or electron stream that crosses the gap, which causes surface damage by local heating. In spite of this energy dependence on the damage, many systems that use arc discharges characterize the amount of material removed from the surfaces and the lifetime of the device for voltage hold-off by the amount of current that passes through the arc, or the 'Coulomb-rating'. The results of a series of tests that were preformed on the boltage hold off capability and damage to carbon-carbon composite surfaces and molybdenum surfaces due to induced arcing will be presented and discussed. Damage to the surfaces was characterized by the field emission performance after the arc initiation and SEM photographs for the different energy and coulomb-transfer arc conditions. Both conditioning and damage to the surfaces were observed, and will be related to the characteristics of the electrical breakdown.
Goebel, Dan M.
Experimental Study on Electrical Breakdown for Devices with Micrometer Gaps
NASA Astrophysics Data System (ADS)
The understanding of electrical breakdown in atmospheric air across micrometer gaps is critically important for the insulation design of micro & nano electronic devices. In this paper, planar aluminum electrodes with gaps ranging from 2 ?m to 40 ?m were fabricated by microelectromechanical system technology. The influence factors including gap width and surface dielectric states were experimentally investigated using the home-built test and measurement system. Results showed that for SiO2 layers the current sustained at 2�3 nA during most of the pre-breakdown period, and then rose rapidly to 10�30 nA just before breakdown due to field electron emission, followed by the breakdown. The breakdown voltage curves demonstrated three stages: (1) a constantly decreasing region (the gap width d < 5 ?m), where the field emission effect played an important role just near breakdown, supplying enough initial electrons for the breakdown process; (2) a plateau region with a near constant breakdown potential (5 ?m < d < 10 ?m) (3) a region for large gaps that adhered to Paschen's curve (d > 10 ?m). And the surface dielectric states including the surface resistivity and secondary electron yield were verified to be related to the propagation of discharge due to the interaction between initial electrons and dielectrics.
Meng, Guodong; Cheng, Yonghong; Dong, Chengye; Wu, Kai
Runaway breakdown and electrical discharges in thunderstorms
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
Gennady Milikh; Robert Roussel-Dupr�
Electrical breakdown of water using porous ceramic-coated electrode
Electrical breakdown of water using porous ceramic- coated rod electrodes were investigated for two types of ceramics, oxide (corundum) and silicates (almandine). Properties of the ceramic layer and its interaction with the electrolyte, i.e., surface chemistry at the electrolyte\\/ceramic surface interface, were found as important factors in generating electrical discharges in water. The buildup of surface charge, which was determined
Petr Lukes; Martin Clupek; Vaclav Babicky; Pavel Sunka
Experimental Study on High Electrical Breakdown of Water Dielectric
NASA Astrophysics Data System (ADS)
By means of a coaxial apparatus, pressurized water breakdown experiments with microsecond charging have been carried out with different surface roughness of electrodes and different ethylene glycol concentrations of ethylene glycol/water mixture. The experimental results about the breakdown stress and the effective time are presented. The breakdown stress is normalized to the situation that the effective time is transformed to 1 ?s and analyzed. The conclusions are as follows: (1) the breakdown stress formula is modified to E = 0.561M A-1/10teff-1/N P1/8; (2) the coefficient M is significantly increased by surface polishing and ethylene glycol additive; (3) it is accumulative for the capacity of improving electrical breakdown strength for surface polishing, ethylene glycol additive, and pressurization, of which pressurization is the most effective method; (4) the highest stress of 235.5 kV/cm is observed in ethylene glycol/water mixture with an ethylene glycol concentration of 80% at a hydrostatic pressure of 1215.9 kPa and is about one time greater than that in pure water at constant pressure; (5) for pressurization and surface polishing, the primary mechanism to improve the breakdown strength of water dielectric is the increase in the breakdown time delay. Research results indicate great potential in the application of the high power pulse conditioning system of water dielectric.
Zhang, Zicheng; Zhang, Jiande; Yang, Jianhua
A theory of lock-on and electrical breakdown
NASA Astrophysics Data System (ADS)
In this dissertation, a collective impact ionization approach is used to develop a generalized theory of electrical breakdown in insulators, which includes both the electric field dependence and the carrier density dependence of impact ionization. This theory is applied to photoconductive semiconductor switches (PCSS's) and is used to explain the lock-on effect, an optically triggered breakdown that occurs in GaAs PCSS's. The basic principle of collective impact ionization theory is that, at high carrier densities, carrier-carrier scattering will enhance the impact ionization rate. This generalized breakdown theory uses a rate equation approach to find the carrier densities which, at a given electric field, result in a steady state. In this approach, the competition between carrier generation (by impact ionization) and carrier recombination (by Auger and defect mechanisms) governs whether or not electrical breakdown occurs. This approach leads to a definition of the bulk breakdown field as the lowest field for which the injection of an infinitesimally small carrier density will result in a steady state with a large carrier density. It also leads to the definition of the lock-on field as the lowest field for which a stable, non-zero steady state carrier density is possible. To implement this theory, the Ensemble Monte Carlo (EMC) method is used to calculate the carrier distribution function, including the effects of carrier-carrier scattering. Since the EMC calculations are computationally intense, this theory also uses both low and high density approximations for the distribution function. The low density limit is obtained using an EMC method without including the effects of carrier-carrier scattering. The high density limit is obtained by approximating the distribution function as a Maxwellian. Using this theory, predictions are made for both the lock-on field and the bulk breakdown field in several materials. In this theory, the lock-on effect is a type of carrier-density dependent electrical breakdown which occurs in all insulating materials. Further, it is the difference between the predicted lock-on and the breakdown fields which determines whether or not the lock-on effect will observable as a phenomenon distinct from ordinary breakdown.
Kambour, Kenneth Eugene
The electrical breakdown of thin dielectric elastomers: thermal effects
NASA Astrophysics Data System (ADS)
Dielectric elastomers are being developed for use in actuators, sensors and generators to be used in various applications, such as artificial eye lids, pressure sensors and human motion energy generators. In order to obtain maximum efficiency, the devices are operated at high electrical fields. This increases the likelihood for electrical breakdown significantly. Hence, for many applications the performance of the dielectric elastomers is limited by this risk of failure, which is triggered by several factors. Amongst others thermal effects may strongly influence the electrical breakdown strength. In this study, we model the electrothermal breakdown in thin PDMS based dielectric elastomers in order to evaluate the thermal mechanisms behind the electrical failures. The objective is to predict the operation range of PDMS based dielectric elastomers with respect to the temperature at given electric field. We performed numerical analysis with a quasi-steady state approximation to predict thermal runaway of dielectric elastomer films. We also studied experimentally the effect of temperature on dielectric properties of different PDMS dielectric elastomers. Different films with different percentages of silica and permittivity enhancing filler were selected for the measurements. From the modeling based on the fitting of experimental data, it is found that the electrothermal breakdown of the materials is strongly influenced by the increase in both dielectric permittivity and conductivity.
Zakaria, Shamsul; Morshuis, Peter H. F.; Benslimane, Mohamed Y.; Gernaey, Krist V.; Skov, Anne L.
Electrical breakdown at low pressure for planar microelectromechanical systems with
2008, San Jose, California. The paper presented there appears unrefereed in SPIE Proceedings Vol. 6884Electrical breakdown at low pressure for planar microelectromechanical systems with 10- to 500- m, leading to the de- scription of the "modified" Paschen curve.4 The general conclusion has been
Dalang, Robert C.
Experimental bench modeling of a plasma environment and solar batteries influence on ISS surface electric breakdowns
NASA Astrophysics Data System (ADS)
Most of the surface of all International Space Station segments are coated with thin dielectric films. The cathode potential drop collects a surface charge on the coatings. The coated parts of the ISS frame are electric capacities that accumulate high charge and energy. These surfaces is plasma capacitors. The plasma capacitors breakdowns generate powerful impulsive discharges that is a threat to space-suit and ISS systems. It is necessary to know all breakdown characteristics to forecast the disturbance and damaging effects on space-suit and ISS systems. We examine their characteristics in bench experiments. The spectrum of the electromagnetic emission arising at a plasma capacitor breakdown is determined. There are peaks of the high-frequency oscillations in spectrum caused by interactions of an electron beam and plasma. Low-frequency oscillations are generated by oscillations in the virtual contour consisting of plasma capacities and inductances.
Homin, Taras; Tverdokhlebova, Ekaterina; Korsun, Anatolii; Borisov, Broris; Garkusha, Valerii; Rusakov, Anatolii; Sizov, Aleksandr; Jurchenko, Nikolai
Influence of impulse breakdown delay of soil on lightning protection characteristics of transmission line
The impulse breakdown characteristic of soil is significant for evaluating the lightning trip-out rate of transmission lines. Firstly, this paper examined the impulse breakdown delay characteristics of soil through considerable experiments. Then the influence of the impulse breakdown delay phenomenon of soil on the lightning protection characteristics of transmission lines with different rated voltages is analyzed through the numerical calculation.
Jinliang He; Xi Wang; Rong Zeng; Xiangyang Peng
Ion manipulation device with electrical breakdown protection
An ion manipulation method and device is disclosed. The device includes a pair of substantially parallel surfaces. An array of inner electrodes is contained within, and extends substantially along the length of, each parallel surface. The device includes a first outer array of electrodes and a second outer array of electrodes. Each outer array of electrodes is positioned on either side of the inner electrodes, and is contained within and extends substantially along the length of each parallel surface. A DC voltage is applied to the first and second outer array of electrodes. A RF voltage, with a superimposed electric field, is applied to the inner electrodes by applying the DC voltages to each electrode. Ions either move between the parallel surfaces within an ion confinement area or along paths in the direction of the electric field, or can be trapped in the ion confinement area. The surfaces are housed in a chamber, and at least one electrically insulative shield is coupled to an inner surface of the chamber for increasing a mean-free-path between two adjacent electrodes in the chamber.
Chen, Tsung-Chi; Tang, Keqi; Ibrahim, Yehia M; Smith, Richard D; Anderson, Gordon A; Baker, Erin M
Kinetic theory of runaway breakdown in inhomogeneous thundercloud electric field
NASA Astrophysics Data System (ADS)
Kinetic theory of runaway breakdown in inhomogeneous thunderstorm electric field is developed. The kinetic equation, boundary and initial conditions are formulated. Spectrum of X-ray emission generated by runaway electrons is calculated. It has quite a specific form: a sharp maximum at energies 50-60 keV and a rapid fall both to the smaller and higher energies. The intensity of the emission is growing effectively with the relation Em/ Ec (of maximal electric field Em to critical field Ec) and falling down sharply with the distance near the point z where electric field E( z) is equal to critical field Ec.
Gurevich, A. V.; Carlson, H. C.; Medvedev, Yu. V.; Zybin, K. P.
Electrical Breakdown in a V2O3 device at the Insulator to Metal Transition
NASA Astrophysics Data System (ADS)
We have measured the electrical properties of a V2O3 thin film micro bridge at the insulator metal transition (IMT). Discontinuous jumps to lower voltages in the current voltage characteristic (IV) followed by an approximately constant voltage progression for high currents indicate an electrical breakdown of the device. In addition, the IV curves show hysteresis and a training effect, i.e. the subsequent IV loops are different from the first IV loop after thermal cycling. Low temperature scanning electron microscopy (LTSEM) reveals that the electrical breakdown over the whole device is caused by the formation of electro-thermal domains (ETDs), i.e. the current and temperature redistribution in the device. On the contrary, at the nanoscale, the electrical breakdown causes the IMT of individual domains. In a numerical model we considered these domains as a network of resistors and we were able to reproduce the electro-thermal breakdown as well as the hysteresis and the training effect in the IVs. This work was supported by AFOSR grant number FA9550-12-1-0381.
Gu�non, S.; Wang, Siming; Ram�rez, J. G.; Schuller, Ivan K.; Scharinger, S.; D; Koelle; Kleiner, R.
Fast Diagnostic For Electrical Breakdowns In Vacuum
The design of an inexpensive, small, high bandwidth diagnostic for the study of vacuum insulator flashover is described. The diagnostic is based on the principle of capacitive coupling and is commonly referred to as a D-dot probe due to its sensitivity to the changing of the electric displacement field. The principle challenge for the design proved to be meeting the required mechanical size for the application rather than bandwidth. An array of these probes was fabricated and used in an insulator test stand. Data from the test stand with detailed analysis is presented. A highlight of the application of the probes to the test stand was the ability to detect the charging of the insulator surface by UV illumination as a prelude to the insulator flashover. The abrupt change in the insulator's surface charge during the flashover was also detected.
Houck, T L; Javedani, J B; Lahowe, D A
Lightning Impulse Breakdown Characteristics and Electrodynamic Process of Insulating Vegetable Oil-Based Nanofluid
NASA Astrophysics Data System (ADS)
Insulating vegetable oils are considered environment-friendly and fire-resistant substitutes for insulating mineral oils. This paper presents the lightning impulse breakdown characteristic of insulating vegetable oil and insulating vegetable oil-based nanofluids. It indicates that Fe3O4 nanoparticles can increase the negative lightning impulse breakdown voltages of insulating vegetable oil by 11.8% and positive lightning impulse breakdown voltages by 37.4%. The propagation velocity of streamer is reduced by the presence of nanoparticles. The propagation velocities of streamer to positive and negative lightning impulse breakdown in the insulating vegetable oil-based nanofluids are 21.2% and 14.4% lesser than those in insulating vegetable oils, respectively. The higher electrical breakdown strength and lower streamer velocity is explained by the charging dynamics of nanoparticles in insulating vegetable oil. Space charge build-up and space charge distorted filed in point-sphere gap is also described. The field strength is reduced at the streamer tip due to the low mobility of negative nanoparticles.
Li, Jian; Zhang, Zhao-Tao; Zou, Ping; Du, Bin; Liao, Rui-Jin
Vacuum emission and breakdown characteristics of a planar He-Xe microdischarge
NASA Astrophysics Data System (ADS)
Vacuum emission, breakdown, and current-voltage characteristics of a large surface area-to-volume ratio planar dc microdischarge have been measured for different He-Xe mixtures in the range of 10%-100% Xe and pressures in the range of 60-500 Torr. The electrical measurements show that the Paschen breakdown curves and the current-voltage characteristics are primarily controlled by the xenon concentration in the mixture. A study of the vacuum ultraviolet emission of xenon atoms at 147 nm and of xenon dimers at 150 nm normalized to the discharge power reveals the presence of local maxima in the emitted intensity as a function of discharge pressure and xenon concentration, indicative of complex excited-state atomic and excimer kinetic processes.
Postel, Olivier B.; Cappelli, Mark A.
Detection of pre-electrical breakdown of IZO/?-NPD/Alq3/Al light-emitting diodes by electric-field-induced optical second-harmonic generation measurement
NASA Astrophysics Data System (ADS)
By using the electric-field-induced optical second-harmonic generation (EFISHG), we measured the EFISHG-time (EFISHG-t) characteristics to study pre-electrical breakdown of indium-zinc-oxide (IZO)/N,N?-di[(1-naphthyl)-N,N?-diphenyl]-(1,1?-biphenyl)-4,4?-diamine (?-NPD)/tris(8-hydroxy-quinolinato)aluminum(III) (Alq3)/Al organic light-emitting diodes (OLEDs). A series of EFISHG pulses were identified as a pre-electrical breakdown phenomenon, before OLEDs were electrically broken. Analyzing the results revealed the additional negative charge accumulation at the ?-NPD/Alq3 interface which caused by the generation of EFISHG pulses. We concluded that the EFISHG-t measurement is available as a method for detecting pre-electrical breakdown phenomena of OLEDs.
Taguchi, Dai; Nakamoto, Ryo; Manaka, Takaaki; Iwamoto, Mitsumasa
Enhanced electric breakdown strength and high energy density of barium titanate filled polymer nanocomposites
NASA Astrophysics Data System (ADS)
We report improved electric breakdown strength, high energy density, and low dielectric loss of nanocomposites using surface modified BaTiO3 (BT) nanoparticles filling in poly(vinylidene fluoride) polymer matrix. Dielectric and electric breakdown properties of the nanocomposites have been investigated as a function of BT content. The electric breakdown strength of 285 MV/m has been achieved at the nanocomposite with 10 vol. % BT nanoparticles. The results indicate that functionalized and produced passivation layers on the surface of ceramic fillers can improve the homogeneity of the nanocomposites, promote space charge and interface effects, and significantly enhance electric breakdown strength of the nanocomposites.
Yu, Ke; Niu, Yujuan; Xiang, Feng; Zhou, Yongcun; Bai, Yuanyuan; Wang, Hong
A NEW FAILURE MECHANISM BY SCANNING ELECTRON MICROSCOPE INDUCED ELECTRICAL BREAKDOWN OF TUNGSTEN..................................................................15 2.1.3 Mechanics of CVD Tungsten 2.2.2 Tungsten Corrosion
Pearton, Stephen J.
Electrical Breakdown in Lightning Arrestor Connector (LAC) Devices
NASA Astrophysics Data System (ADS)
Lightning arrestor connector (LAC) devices protect electronic devices by providing a conductive path to ground for electrical power surges caused by lightning. Such devices consist of an insulating material between electrodes. This insulation region is composed of an air gap and a high permittivity dielectric. In this presentation, the physics of the phenomena active in the early stages of the flow of transient electrical current will be described. The conditions that lead to thermal breakdown of the dielectric will also be discussed.--Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Hjalmarson, Harold P.; Kambour, Kenneth; Pineda, Andrew C.
Electrical breakdown and ultrahigh electrical energy density in poly,,vinylidene fluoride-hexafluoropropylene... copolymer
investigates the electrical breakdown of a polar fluoropolymer, poly vinylidene fluoride, and graceful failure nature.3,4 Recently, we reported that in polar fluoropolymers, by properly tuning be achieved in another polar fluoropolymer, poly vinylidene fluoride- hexafluoropropylene P VDF-HFP , which
Zhao, Xuanhe
The thickness and stretch dependence of the electrical breakdown strength of an acrylic dielectric elastomer
The thickness and stretch dependence of the electrical breakdown strength of an acrylic dielectric. Phys. 112, 054106 (2012) Modeling of dielectric and piezoelectric response of 1-3 type piezocomposites and stretch dependence of the electrical breakdown strength of an acrylic dielectric elastomer Jiangshui Huang
Suo, Zhigang
Experimental Study on High Electrical Breakdown of Water Dielectric
By means of a coaxial apparatus, pressurized water breakdown experiments with microsecond charging have been carried out with different surface roughness of electrodes and different ethylene glycol concentrations of ethylene glycol\\/water mixture. The experimental results about the breakdown stress and the effective time are presented. The breakdown stress is normalized to the situation that the effective time is transformed to
Zicheng Zhang; Jiande Zhang; Jianhua Yang
Visual and Electrical Evidence Supporting a Two-Plasma Mechanism of Vacuum Breakdown Initiation
The energy available during vacuum breakdown between copper electrodes at high vacuum was limited using resistors in series with the vacuum gap and arresting diodes. Surviving features observed with SEM in postmortem samples were tentatively correlated with electrical signals captured during breakdown using a Rogowski coil and a high-voltage probe. The visual and electrical evidence is consistent with the qualitative model of vacuum breakdown by unipolar arc formation by Schwirzke [1, 2]. The evidence paints a picture of two plasmas of different composition and scale being created during vacuum breakdown: an initial plasma made of degassed material from the metal surface, ignites a plasma made up of the electrode material.
Castano-Giraldo, C. [University of Illinois, Urbana-Champaign; Aghazarian, Maro [ORNL; Caughman, John B [ORNL; Ruzic, D. N. [University of Illinois, Urbana-Champaign
Effect of temperature on the electric breakdown strength of dielectric elastomer
NASA Astrophysics Data System (ADS)
DE (dielectric elastomer) is one of the most promising artificial muscle materials for its large strain over 100% under driving voltage. However, to date, dielectric elastomer actuators (DEAs) are prone to failure due to the temperature-dependent electric breakdown. Previously studies had shown that the electrical breakdown strength was mainly related to the temperature-dependent elasticity modulus and the permittivity of dielectric substances. This paper investigated the influence of ambient temperature on the electric breakdown strength of DE membranes (VHB4910 3M). The electric breakdown experiment of the DE membrane was conducted at different ambient temperatures and pre-stretch levels. The real breakdown strength was obtained by measuring the deformation and the breakdown voltage simultaneously. Then, we found that with the increase of the environment temperature, the electric breakdown strength decreased obviously. Contrarily, the high pre-stretch level led to the large electric breakdown strength. What is more, we found that the deformations of DEs were strongly dependent on the ambient temperature.
Liu, Lei; Chen, Hualing; Sheng, Junjie; Zhang, Junshi; Wang, Yongquan; Jia, Shuhai
Partial breakdown characteristics in the simulated electrode system of high temperature superconducting coils
In this study, partial breakdown phenomena in a composite insulation system of GFRP and liquid nitrogen are investigated to understand the breakdown mechanism and characteristics in high temperature superconducting (HTS) coils at quench. The electrode system consists of concentric coil-to-cylindrical electrode with an insulation barrier and spacers and is immersed in liquid nitrogen. A heater is mounted inside the coil
Bok-Yeol Seok; H. Komatsu; M. Hara
The effect of polymer type on electric breakdown strength on a nanosecond time scale
NASA Astrophysics Data System (ADS)
Based on the concepts of fast polarization, effective electric field and electron impact ionization criterion, the effect of polymer type on electric breakdown strength (EBD) on a nanosecond time scale is investigated, and a formula that qualitatively characterizes the relation between the electric breakdown strength and the polymer type is derived. According to this formula, it is found that the electric breakdown strength decreases with an increase in the effective relative dielectric constants of the polymers. By calculating the effective relative dielectric constants for different types of polymers, the theoretical relation for the electric breakdown strengths of common polymers is predicted. To verify the prediction, the polymers of PE (polyethylene), PTFE (polytetrafluoroethelene), PMMA (organic glass) and Nylon are tested with a nanosecond-pulse generator. The experimental result shows EBD (PTFE) > EBD (PMMA) > EBD (Nylon) > EBD (PE). This result is consistent with the theoretical prediction.
Zhao, Liang; Su, Jian-Cang; Pan, Ya-Feng; Zhang, Xi-Bo
This paper describes a study of the onset of electrical breakdown in dust layers, for hand-deposited dust layers in a parallel-plate geometry. It was found that the breakdown was an ordinary electron-avalanche process originating in voids within the dust layer and obeying Paschen...
Breakdown characteristics in pulsed-driven dielectric barrier discharges: influence of the pre-breakdown phase due to volume memory effects
NASA Astrophysics Data System (ADS)
The pre-phase of the breakdown of pulsed-driven dielectric barrier discharges (DBDs) was investigated by fast optical and electrical measurements on double-sided DBDs with a 1 mm gap in a gas mixture of 0.1 vol% O2 in N2 at atmospheric pressure. Depending on the pulse width (the pause time between subsequent DBDs), four different breakdown regimes of the following discharge were observed. By systematically reducing the pulse width, the breakdown characteristics could be changed from a single cathode-directed propagation (positive streamer) to simultaneous cathode- and anode-directed propagations (positive and negative streamer) and no propagation at all for sub-?s pulse times. For all cases, different spatio-temporal emission structures in the pre-phase were observed. The experimental results were compared with time-dependent, spatially one-dimensional fluid model calculations. The modelling results confirmed that different pre-ionisation conditions, i.e. considerably high space charges in the volume created by the residual electrons and ions from the previous discharge, are the reason for the observed phenomena.
H�ft, H.; Kettlitz, M.; Becker, M. M.; Hoder, T.; Loffhagen, D.; Brandenburg, R.; Weltmann, K.-D.
Partial and complete electrical breakdown in simulated high temperature superconducting coils
The partial breakdown (PBD) and complete breakdown (BD) phenomena in a composite insulation system of glass fiber reinforced plastic (GFRP) and liquid nitrogen are investigated to find the PBD and BD characteristics in high temperature superconducting (HTS) coils at quench. The electrode system used is made from a coaxial spiral coil-to-cylindrical electrode with an insulation barrier and spacers, and is
B. Y. Seok; H. Komatsu; J. Suehiro; M. Hara; H. Okamoto
Pre-breakdown cavitation development in the dielectric fluid in the inhomogeneous, pulsed electric fields
We consider the development of pre-breakdown cavitation nanopores appearing in the dielectric fluid under the influence of the electrostrictive stresses in the inhomogeneous pulsed electric field. It is shown that three characteristic regions can be distinguished near the needle electrode. In the first region, where the electric field gradient is greatest, the cavitation nanopores, occurring during the voltage nanosecond pulse, may grow to the size at which an electron accelerated by the field inside the pores can acquire enough energy for excitation and ionization of the liquid on the opposite pore wall, i.e., the breakdown conditions are satisfied. In the second region, the negative pressure caused by the electrostriction is large enough for the cavitation initiation (which can be registered by optical methods), but, during the voltage pulse, the pores do not reach the size at which the potential difference across their borders becomes sufficient for ionization or excitation of water molecules. And, in the third, the development of cavitation is impossible, due to an insufficient level of the negative pressure: in this area, the spontaneously occurring micropores do not grow and collapse under the influence of surface tension forces. This paper discusses the expansion dynamics of the cavitation pores and their most probable shape.
Mikhail N. Shneider; Mikhail Pekker
Contribution of interface capacitance to the electric-field breakdown in thin-film AlAlOx Al capacitors
) of the true breakdown electric field Eb across the dielectric. By modeling this interface contribution the dielectric, this cor- responds to a surface charge density on the aluminum elec- trodes at breakdown givenContribution of interface capacitance to the electric-field breakdown in thin-film AlAlOx Al
Hebard, Arthur F.
Investigation of the statistical nature and structure of the electrical breakdown time delay in gas diodes filled with neon
The electrical breakdown time delay in gas diodes filled by neon at the low pressures is investigated experimentally and theoretically. Experimental results are obtained measuring the characteristics of gas diodes filled by spectroscopically pure neon. In order to discard any systematic trend during the measurement procedure, checking of the measured values randomness preceded the statistical analysis of the experimental results. Novel theoretical model is established for interpretation of obtained experimental results on the breakdown time delay. The model is based on the assumptions of the exponential distribution of the statistical time delay and Gaussian distribution of the formative discharge time. Therefore, the density distribution of the breakdown time delay is assumed to be convolution of the statistical and formative time delay distributions. Parameters of the statistical and formative time delay, as stochastic variables, are modeled by the numerical Monte Carlo method. Numerical distributions are tested to the corresponding experimental distributions of the breakdown time delay by varying the distribution parameters. In addition, the asymmetry coefficient and skewness coefficient of the breakdown time delay distribution, and coefficients of the statistical and formative time delay distributions are analyzed. Numerically calculated time delay distributions fit well to the corresponding experimental distributions in gas diodes filled with neon at low pressures.
Maluckov, Cedomir A. [Technical Faculty in Bor, University of Belgrade, Vojske Jugoslavije 24, 19210 Bor (Serbia and Montenegro); Karamarkovic, Jugoslav P. [Faculty of Civil Eng. and Architecture, University of Nis, Beogradska 14, 18000 Nis (Serbia); Radovic, Miodrag K. [Faculty of Sciences and Mathematics, University of Nis, P.O.B.224, 18001 Nis (Serbia)
A novel method for investigating electrical breakdown enhancement by nm-sized features.
Electrical transport studies across nm-thick dielectric films can be complicated, and datasets compromised, by local electrical breakdown enhanced by nm-sized features. To avoid this problem we need to know the minimal voltage that causes the enhanced electrical breakdown, a task that usually requires numerous measurements and simulation of which is not trivial. Here we describe and use a model system, using a "floating" gold pad to contact Au nanoparticles, NPs, to simultaneously measure numerous junctions with high aspect ratio NP contacts, with a dielectric film, thus revealing the lowest electrical breakdown voltage of a specific dielectric-nanocontact combination. For a 48 � 1.5 � SiO(2) layer and a ?7 � monolayer of organic molecules (to link the Au NPs) we show how the breakdown voltage decreases from 4.5 � 0.4 V for a flat contact, to 2.4 � 0.4 V if 5 nm Au NPs are introduced on the surface. The fact that larger Au NPs on the surface do not necessarily result in significantly higher breakdown voltages illustrates the need for combining experiments with model calculations. This combination shows two opposite effects of increasing the particle size, i.e., increase in defect density in the insulator and decrease in electric field strength. Understanding the process then explains why these systems are vulnerable to electrical breakdown as a result of spikes in regular electrical grids. Finally we use XPS-based chemically resolved electrical measurements to confirm that breakdown occurs indeed right below the nm-sized features. PMID:22517579
Shpaisman, Hagay; Cohen, Hagai; Har-Lavan, Rotem; Azulai, Daniel; Stein, Nir; Cahen, David
Breakdown characteristics of InP\\/InGaAs composite-collector double heterojunction bipolar transistor
This investigation proposes an InP\\/InGaAs composite-collector double heterojunction bipolar transistor (CC-DHBT) grown by metalorganic chemical vapor deposition. The improved structure exhibits the advantages of no knee-shaped characteristics, no switching effect, low output conductance, a high two-terminal base-collector breakdown voltage (BV) that exceeds 20 V, and high three-terminal breakdown voltages (BVCEO>15 V, BVCBO>20 V). The current gain is over unity at
Y. S. Lin
Breakdown characteristics of InP\\/InGaAs composite-collector double heterojunction bipolar transistor
This investigation proposes an InP\\/InGaAs composite-collector double heterojunction bipolar transistor (CC-DHBT) grown by metalorganic chemical vapor deposition. The improved structure exhibits the advantages of no knee-shaped characteristics, no switching effect, low output conductance, a high two-terminal base�collector breakdown voltage (BV) that exceeds 20 V, and high three-terminal breakdown voltages (BVCEO>15 V,BVCBO>20 V). The current gain is over unity at ultralow
Y. S. Lin
Pulse trains that are characteristic of preliminary breakdown in cloud-to-ground lightning but are not followed by return stroke pulses
In this study, we identify and examine electric field pulse trains that are characteristic of preliminary breakdown in negative cloud-to-ground discharges but are not followed by return stroke waveforms. We assume that such trains are manifestations of the initiation of downward negative stepped leaders that fail to propagate all the way to the ground and refer to these events as
Amitabh Nag; Vladimir A. Rakov
Effect of pulsed electric fields on dielectric breakdown in Cu damascene interconnects
NASA Astrophysics Data System (ADS)
We investigated the effects of pulsed electric fields on dielectric breakdown in Cu damascene interconnects. Among the DC, unipolar, and bipolar pulse conditions that were examined, the dielectric lifetime was longest under the bipolar condition because Cu contamination was suppressed due to backward Cu migration. Under the unipolar pulse condition, the dielectric lifetime was enhanced over that under the DC condition, as the pulse frequency increased. These results suggest that the intrinsic breakdown of dielectrics, in addition to Cu contamination, significantly contributes to their reliability. The bond breakdown probability decreased as the unipolar pulse width decreased below the threshold value.
Yeon, Han-Wool; Song, Jun-Young; Lim, Seung-Min; Bae, Jang-Yong; Hwang, Yuchul; Joo, Young-Chang
Investigation of the breakdown products produced from electrical discharge in selected CFC replacement fluids
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.
Hawley-Fedder, R.; Goerz, D.; Koester, C.; Wilson, M.
Influence of magnetic field on the electric breakdown in penning ion source
A cold-cathode penning-type ion source has been developed in our laboratory to study the electric breakdown in this type of sources. The breakdown voltage was measured as a function of axial magnetic field, in the range of 440�600 G, and anode length, in steps of 14, 20, and 24 mm. The measurement was performed with stainless steel cathodes in argon
M. Mahjour-Shafiei; H. Noori; A. H. Ranjbar
Aromatic polythiourea dielectrics with ultrahigh breakdown field strength, low dielectric loss, and high electric energy density.
The promise of aromatic, amorphous, polar polymers containing high dipolar moments with very low defect levels is demonstrated for future dielectric materials with ultrahigh electric-energy density, low loss at high applied fields, and ultrahigh breakdown strengths. Specifically, aromatic polythiourea films exhibit an ultrahigh breakdown field (>1 GV m(-1)), which results in an energy density of ?22 J cm(-3), as well as a low loss. PMID:23315675
Wu, Shan; Li, Weiping; Lin, Minren; Burlingame, Quinn; Chen, Qin; Payzant, Andrew; Xiao, Kai; Zhang, Q M
Studies of electrical breakdown processes across vacuum gaps between metallic electrodes
NASA Astrophysics Data System (ADS)
An experimental program to elucidate the physical causes of electrical breakdown across vacuum gaps, such as those that occur in charged particle accelerators, is discussed. Magnetic insulation is explored as a technique to differentiate between field emission of electrons and clump acceleration as possible causative mechanisms for the onset of breakdown. The results and limitations of an exploratory experiment are described, along with plans for a more comprehensive experimental and theoretical campaign.
Grisham, L. R.; Von Halle, A.; Carpe, A. F.; Rossi, Guy; Gilton, K. R.; McBride, E. D.; Gilson, E. P.; Stepanov, A.; Stevenson, T. N.
Study of electric breakdown of liquid dielectrics using Schlieren optical techniques
The work is a contribution to the understanding of the mechanism of electric breakdown in liquid dielectrics. The liquid dielectric chosen throughout the experiments was n-hexane, because an extensive literature exists on the breakdown of this material. The applied voltage was a rectangular pulse of different durations supplied from a 125 kv, five-stage Marx-Goodlet impulse generator. A novel rotary multiple
B. Farazmand
Measurements of electric-field strengths in ionization fronts during breakdown.
Using laser-induced fluorescence-dip Stark spectroscopy, we performed time-resolved, direct measurements of electric-field strengths during the breakdown phase of a low-pressure, pulsed discharge in xenon. With this experimental technique we could for the first time quantitatively measure the time evolution of the driving force of the plasma breakdown process: the electric field. Moving ionization fronts were measured with submicrosecond resolution. These ionization fronts were sustained by a spatially narrow, rapidly moving region of strong electric field. PMID:17359030
Wagenaars, E; Bowden, M D; Kroesen, G M W
Measurements of Electric-Field Strengths in Ionization Fronts during Breakdown
NASA Astrophysics Data System (ADS)
Using laser-induced fluorescence-dip Stark spectroscopy, we performed time-resolved, direct measurements of electric-field strengths during the breakdown phase of a low-pressure, pulsed discharge in xenon. With this experimental technique we could for the first time quantitatively measure the time evolution of the driving force of the plasma breakdown process: the electric field. Moving ionization fronts were measured with submicrosecond resolution. These ionization fronts were sustained by a spatially narrow, rapidly moving region of strong electric field.
Wagenaars, E.; Bowden, M. D.; Kroesen, G. M. W.
The contribution of field-induced morphological change to the electrical aging and breakdown of polyethylene
A brief review of the early literature is given which provides evidence that electrically-induced mechanical stresses make an important contribution to the electrical breakdown of solid dielectrics. Special attention is given to polyethylene and the manner in which this semi-crystalline polymer yields under mechanical stress by microvoid, crack and craze development in the amorphous phase between the lamellar crystallites. The
J. P. Jones; J. P. Llewellyn; T. J. Lewis
Studies of electrical breakdown processes across vacuum gaps between metallic electrodes
Studies of electrical breakdown processes across vacuum gaps between metallic electrodes L concen- tration, and reducing the use of materials in, for instance, accelerator insulator columns, which or electric field. They also had in common that no matter which combination of techniques was used, new
Gilson, Erik
The surface discharge and breakdown characteristics of HTS DC cable and stop joint box
NASA Astrophysics Data System (ADS)
A high temperature superconducting (HTS) DC cable system consists of a HTS cable and cable joint. The HTS DC cable should be electrically connected in joint boxes because of the unit length of HTS cable is limited to several-hundred meters. In particular, the stop joint box (SJB) must be developed for a compact cooling system. Polypropylene laminated paper (PPLP) and epoxy maybe used as insulating materials for HTS DC cable and SJB. To develop a HTS DC cable, it is necessary to develop the cryogenic insulation technology, materials and the joint methods. In this paper, we will mainly discuss on the DC and impulse characteristics of epoxy and PPLP in liquid nitrogen (LN2). The surface discharge characteristics of epoxy included fillers, PPLP and epoxy with PPLP composite (epoxy + PPLP) were measured under 0.4 MPa. Also, the PPLP-insulated mini-model cable was fabricated and then DC, impulse and DC polarity reversal breakdown strength of mini-model cable under 0.4 MPa were investigated.
Kim, W. J.; Kim, H. J.; Cho, J. W.; Kim, S. H.
Statistical analysis of the electrical breakdown time delay distributions in krypton
The statistical analysis of the experimentally observed electrical breakdown time delay distributions in the krypton-filled diode tube at 2.6 mbar is presented. The experimental distributions are obtained on the basis of 1000 successive and independent measurements. The theoretical electrical breakdown time delay distribution is evaluated as the convolution of the statistical time delay with exponential, and discharge formative time with Gaussian distribution. The distribution parameters are estimated by the stochastic modelling of the time delay distributions, and by comparing them with the experimental distributions for different relaxation times, voltages, and intensities of UV radiation. The transition of distribution shapes, from Gaussian-type to the exponential-like, is investigated by calculating the corresponding skewness and excess kurtosis parameters. It is shown that the mathematical model based on the convolution of two random variable distributions describes experimentally obtained time delay distributions and the separation of the total breakdown time delay to the statistical and formative time delay.
Maluckov, Cedomir A.; Karamarkovic, Jugoslav P.; Radovic, Miodrag K.; Pejovic, Momcilo M. [Technical Faculty in Bor, University of Belgrade, Vojske Jugoslavije 24, 19210 Bor (Serbia and Montenegro); Faculty of Civil Engineering and Architecture, University of Nis, Beogradska 14, 18000 Nis (Serbia and Montenegro); Faculty of Sciences and Mathematics, University of Nis, P.O. Box 224, 18001 Nis (Serbia and Montenegro); Faculty of Electronic Engineering, University of Nis, P.O. Box 73, 18001 Nis (Serbia and Montenegro)
Microcontroller based system for electrical breakdown time delay measurement in gas-filled devices
NASA Astrophysics Data System (ADS)
This paper presents realization of a digital embedded system for measuring electrical breakdown time delay. The proposed system consists of three major parts: dc voltage supply, analog subsystem, and a digital subsystem. Any dc power source with the range from 100 to 1000 V can be used in this application. The analog subsystem should provide fast and accurate voltage switching on the testing device as well as transform the signals that represent the voltage pulse on the device and the device breakdown into the form suitable for detection by a digital subsystem. The insulated gate bipolar transistor IRG4PH40KD driven by TC429 MOSFET driver is used for high voltage switching on the device. The aim of a digital subsystem is to detect the signals from the analog subsystem and to measure the elapsed time between their occurrences. Moreover, the digital subsystem controls various parameters that influence time delay and provides fast data storage for a large number of measured data. For this propose, we used the PIC18F4550 microcontroller with a full-speed compatible universal serial bus (USB) engine. Operation of this system is verified on different commercial and custom made gas devices with different structure and breakdown mechanisms. The electrical breakdown time delay measurements have been carried out as a function of several parameters, which dominantly influence electrical breakdown time delay. The obtained results have been verified using statistical methods, and they show good agreement with the theory. The proposed system shows good repeatability, sensitivity, and stability for measuring the electrical breakdown time delay.
Pejovi?, Mili? M.; Deni?, Dragan B.; Pejovi?, Mom?ilo M.; Ne�i?, Nikola T.; Vasovi?, Nikola
Microcontroller based system for electrical breakdown time delay measurement in gas-filled devices
This paper presents realization of a digital embedded system for measuring electrical breakdown time delay. The proposed system consists of three major parts: dc voltage supply, analog subsystem, and a digital subsystem. Any dc power source with the range from 100 to 1000 V can be used in this application. The analog subsystem should provide fast and accurate voltage switching on the testing device as well as transform the signals that represent the voltage pulse on the device and the device breakdown into the form suitable for detection by a digital subsystem. The insulated gate bipolar transistor IRG4PH40KD driven by TC429 MOSFET driver is used for high voltage switching on the device. The aim of a digital subsystem is to detect the signals from the analog subsystem and to measure the elapsed time between their occurrences. Moreover, the digital subsystem controls various parameters that influence time delay and provides fast data storage for a large number of measured data. For this propose, we used the PIC18F4550 microcontroller with a full-speed compatible universal serial bus (USB) engine. Operation of this system is verified on different commercial and custom made gas devices with different structure and breakdown mechanisms. The electrical breakdown time delay measurements have been carried out as a function of several parameters, which dominantly influence electrical breakdown time delay. The obtained results have been verified using statistical methods, and they show good agreement with the theory. The proposed system shows good repeatability, sensitivity, and stability for measuring the electrical breakdown time delay.
Pejovic, Milic M.; Denic, Dragan B.; Pejovic, Momcilo M.; Nesic, Nikola T.; Vasovic, Nikola [Faculty of Electronic Engineering, University of Nis, Aleksandra Medvedeva 14, 18000 Nis (Serbia)
The Effect of Wave Shape on the Electric Breakdown of Nitrogen Gas
The electric breakdown of nitrogen gas is determined using direct and 60-Hz voltage and impulse waves of both positive and negative polarity over the range of � ?? 10 to 550 ?? 9000 microseconds. The electrode system is composed of a 1-inch diameter brass sphere and a 1�-inch-diameter square-edged brass plane with a spacing between them of � inch. The
Keith Crouch; Lawrence Whitman
High Speed Laser Schlieren Studies of Electrical Breakdown in Liquid Hydrocarbons
The events occurring just prior, during, and after electrical break-down in liquid hydrocarbons have been photographed using 15 ns laser pulses produced with a ruby laser, to illuminate the space between two parallel plate electrodes, and schlieren optics. In this manner it was possible to obtain experimental evidence of the density gradients produced by the movement of charge carriers during
E. O. Forster; P. Wong
Electrical conduction and dielectric breakdown in sputter-deposited silicon dioxide films on silicon
Silicon dioxide films, 8�100 nm thick, are sputter deposited in an oxygen-argon atmosphere onto a silicon substrate at 200 �C. Electrical conduction and dielectric breakdown in oxygen-argon sputter-deposited film are measured using metal-oxide-semiconductor capacitors and compared with those in thermal dioxide film. Moreover, their mechanisms are investigated. Thin oxygen-argon sputter-deposited film is found to have the same low electrical conduction
S. Suyama; A. Okamoto; T. Serikawa; H. Tanigawa
Experimental and analytical study of the DC breakdown characteristics of polypropylene laminated paper with a butt gap condition considering the insulation design of superconducting cable
NASA Astrophysics Data System (ADS)
It has been reported that the insulation design under DC stress is considered as one of the critical factors in determining the performance of high-voltage direct current (HVDC) superconducting cable. Therefore, it is fundamentally necessary to investigate the DC breakdown characteristics of the composite insulation system consisting of liquid nitrogen (LN2)/polypropylene-laminated-paper (PPLP). In particular, the insulation characteristics under DC polarity reversal condition should be verified to understand the polarity effect of the DC voltage considering the unexpected incidents taking place at line-commutated-converters (LCC) under service at a DC power grid. In this study, to examine the variation of DC electric field strength, the step voltage and polarity reversal breakdown tests are performed under DC stress. Also, we investigate the electric field distributions in a butt gap of the LN2/PPLP condition considering the DC polarity reversal by using simulation software.
Seo, In-jin; Choi, Won; Seong, Jae-gyu; Lee, Bang-wook; Koo, Ja-yoon
An analysis of strake vortex breakdown characteristics in relation to design features
NASA Technical Reports Server (NTRS)
This paper describes a water tunnel study of the vortex breakdown characteristics of a large number of analytically designed vortex strakes tested in combination with a moderate aspect ratio trapezoidal wing. A wide range of strake sizes and slenderness ratios are covered, and examples of the effects of the primary design parameters of size, span, and slenderness on the vortex breakdown characteristics are presented and analyzed in relation to the leading-edge suction distributions. Several examples of detailed planform shaping on strakes of the same general size and slenderness are shown from which it can be concluded that, consistent with the design criterion, those with leading-edge suction distributions which increase more rapidly near, and have a higher value at, the spanwise tip of the strake produce a more stable vortex.
Frink, N. T.; Lamar, J. E.
Mass analysis of neutral particles and ions released during electrical breakdowns on spacecraft surfaces
NASA Technical Reports Server (NTRS)
Charged-particle fluxes from breakdown events were studied. Methods to measure mass spectra and total emitted flux of neutral particles were developed. The design and construction of the specialized mass spectrometer was completed. Electrical breakdowns were initiated by a movable blunt contact touching the insulating surface. The contact discharge apparatus was used for final development of two different high-speed recording systems and for measurements of the composition of the materials given off by the discharge. It was shown that intense instantaneous fluxes of neutral particles were released from the sites of electrical breakdown events. A laser micropulse mass analyzer showed that visible discoloration at breakdown sites were correllated with the presence of iron on the polymer side of the film, presumably caused by punch-through to the Inconel backing. Kapton samples irradiated by an oxygen ion beam were tested. The irradiated samples were free of surface hydrocarbon contamination but otherwise behaved in the same way as the Kapton samples tested earlier. Only the two samples exposed to oxygen ion bombardment were relatively clean. This indicates an additional variable that should be considered when testing spacecraft materials in the laboratory.
Kendall, B. R. F.
Electrical breakdown strength results from the EU testing program for potential ITER insulation
Insulation systems will be a key element in the future construction and impregnation of the coils for the ITER device. Electrical barrier layers have been specified to improve the electrical reliability, and this program includes ceramic plasma sprayed coatings, Kapton, Nomex and Mica in conjunction with various Epoxy resins. The electrical breakdown strengths in liquid nitrogen of twenty-two different insulation systems are reported. The final results of this program are presented and compared with the results from a benchmark testing program (insulation system based on anhydride cured DGEBA resin and S2 glass).
Broadbent, A.J.; Crozier, J.; Smith, K.D. [Oxford Instruments, Oxon (United Kingdom)] [and others
Electric arc radius and characteristics
The heat transfer equation of an arc discharge has been solved. The arc is assumed to be a cylinder with negligible axial variation and the dominant heat transfer process is conduction radially inside the column and radiation/convection at the outside edge. The symmetric consideration allows a simple one-dimensional formulation. By taking into account proper variation of the electrical conductivity as function of temperature, the heat balance equation has been solved analytically. The radius of the arc and its current-field characteristics have also been obtained. The conventional results that E approx. I/sup 0/ /sup 5385/ and R approx. I/sup 0/ /sup 7693/ with E being the applied field, I the current, and R the radius of the cylindrical arc, have been proved to be simply limiting cases of our more general characteristics. The results can be applied quite widely including, among others, the neutral beam injection project in nuclear fusion and MHD energy conversion.
Fang, T.M.
Model Analysis of Self and Laser-Triggered Electrical Breakdown of Liquid Water for Pulsed-Power Applications
Electrical breakdown simulations for liquids, in response to a submicrosecond (~100-200 ns) voltage pulse, are carried out. It is shown that breakdown is initiated by field emission at the interface of preexisting microbubbles. Impact ionization within the microbubble gas then contributes to plasma development, with cathode injection having a delayed and secondary role. The model used in this paper adequately
Jun Qian; Ravindra P. Joshi; Karl H. Schoenbach; J. R. Woodworth; G. S. Sarkisov
Explosive Electric Breakdown due to Conducting-Particle Deposition on an Insulating Substrate
NASA Astrophysics Data System (ADS)
We introduce a theoretical model to investigate the electric breakdown of a substrate on which highly conducting particles are adsorbed and desorbed with a probability that depends on the local electric field. We find that, by tuning the relative strength q of this dependence, the breakdown can change from continuous to explosive. Precisely, in the limit in which the adsorption probability is the same for any finite voltage drop, we can map our model exactly onto the q-state Potts model and thus the transition to a jump occurs at q=4. In another limit, where the adsorption probability becomes independent of the local field strength, the traditional bond percolation model is recovered. Our model is thus an example of a possible experimental realization exhibiting a truly discontinuous percolation transition.
Oliveira, Cl�udio L. N.; Ara�jo, Nuno A. M.; Andrade, Jos� S.; Herrmann, Hans J.
Excess thermal-noise in the electrical breakdown of random resistor networks
: ��We discuss a new type of excess noise strongly sensitive to non-homogeneous Joule heating of random resistor network and associated\\u000a with local sources of thermal noise. The evolution of the network towards an electrical breakdown of conductor-insulator type\\u000a is then studied by using a biased percolation model and it is analysed in terms of an excess-noise temperature. Monte Carlo
C. Pennetta; L. B. Kiss; Z. Gingl; L. Reggiani
Imaging the Effect of Electrical Breakdown in Multilayer Polymer Capacitor Films
NASA Astrophysics Data System (ADS)
Multilayer polymer films show great promise as the dielectric material in high energy density capacitors. Such films show enhancement in both dielectric strength (EB) and energy density (Ud) relative to monolithic films of either source polymer. Composites are typically comprised of alternating layers of a high EB polymer and a high permittivity polymer. Here, we discuss a multilayer system based on polycarbonate (PC) interleaved with polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). The dielectric properties of the PC/PVDF-HFP films are influenced by both composition and individual layer thickness. Optimized films show EB=750 kV/mm and Ud=13 J/cm^3. Further enhancements in EB and Ud are expected through optimization of the component polymers, composition, and layer structure. To guide next generation design, it is important to understand the breakdown mechanism, as it directly influences EB. To elucidate the role of the layer structure during electrical breakdown, we use a tandem focused ion beam (FIB) / scanning electron microscope (SEM) imaging technique. The technique allows us to image the internal layer structure of both `as fabricated' control films, and those subjected to high electric fields. It is therefore a powerful tool to assess film quality and analyze failure mechanisms. Specifically, the FIB is used to mill site-specific holes in a film and the resulting cross-sections are imaged via SEM. Individual layers are easily resolved down to 50 nm. For films subjected to electrical breakdown, the location and propagation of damage is tracked with sequential FIB milling and SEM imaging. Spatially resolved FIB/SEM imaging allows preparation of quasi-3D maps displaying the evolution of internal voids in areas adjacent to the breakdown location (pinhole of d = 30-80 microns). A majority of the voids are localized at the interfaces between layers and may propagate as far as 30-50 microns from the pinhole. The data suggest that the enhancement in dielectric strength arises from a barrier effect, whereby the propagation of an electrical breakdown in the direction of the applied field is impeded by the layer interfaces. We will also discuss recent TEM imaging results that are used to characterize the interfacial length scale and chemical makeup, factors that may influence breakdown.
Wolak, Mason
DOE Task Force meeting on Electrical Breakdown of Insulating Ceramics in a High Radiation Field
This volume contains the abstracts and presentation material from the Research Assistance Task Force Meeting Electrical Breakdown of Insulating Ceramics in a High-Radiation Field.'' The meeting was jointly sponsored by the Office of Basic Energy Sciences and the Office of Fusion Energy of the US Department of Energy in Vail, Colorado, May 28--June 1, 1991. The 26 participants represented expertise in fusion, radiation damage, electrical breakdown, ceramics, and semiconductor and electronic structures. These participants came from universities, industries, national laboratories, and government. The attendees represented eight nations. The Task Force meeting was organized in response to the recent discovery that a combination of temperature, electric field, and radiation for an extended period of time has an unexplained adverse effect in ceramics, termed radiation-enhanced electrical degradation (REED). REED occurs after an incubation period and continues to accelerate with irradiation until the ceramics can no longer be regarded as insulators. It appears that REED is irreversible and the ceramic insulators cannot be readily annealed or otherwise repaired for future services. This effect poses a serious threat for fusion reactors, which require electrical insulators in diagnostic devices, in radio frequency and neutral beam systems, and in magnetic assemblies. The problem of selecting suitable electrical insulating materials in thus far more serious than previously anticipated.
Green, P.H. (comp.) [comp.
Ion-induced electrical breakdown in metal-oxide-silicon capacitors
NASA Astrophysics Data System (ADS)
Physical effects related to radiation-induced intrinsic electrical breakdown in metal-oxide-silicon capacitors used for the detection of Cf-252 fission fragments were investigated, with special attention given to the effect of the oxide annealing temperature between 100 and 400 K, the oxide thickness, the differing metal electrodes, and the material interaction due to the spark discharge breakdown. It was found that the current emission into the SiO2 was significantly enhanced by means of both Si-ion and Cs-ion implants near the metal-SiO2 interface of the capacitors. However, the enhanced emission had no effect on increasing the sensitivity to lower specific ionization radiation as seen by fission-fragment detection, indicating that the radiation-induced breakdown mechanism occurs within the bulk of the SiO2 film and is not influenced by conditions at the dielectric interfaces. It was also found that thin films of HfO2 or ZrO2 placed between the oxide film and a top electrode prevented the Al-SiO2 interaction during the discharge and made it possible to operate the capacitor at higher electric fields.
Milgram, Alvin A.
Experimental study of electric breakdowns in liquid argon at centimeter scale
NASA Astrophysics Data System (ADS)
In this paper we present results on measurements of the dielectric strength of liquid argon near its boiling point and cathode-anode distances in the range of 0.1 mm to 40 mm with spherical cathode and plane anode. We show that at such distances the applied electric field at which breakdowns occur is as low as 40 kV/cm. Flash-overs across the ribbed dielectric of the high voltage feed-through are observed for a length of 300 mm starting from a voltage of 55 kV. These results contribute to set reference for the breakdown-free design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).
Blatter, A.; Ereditato, A.; Hsu, C.-C.; Janos, S.; Kreslo, I.; Luethi, M.; von Rohr, C. Rudolf; Schenk, M.; Strauss, T.; Weber, M. S.; Zeller, M.
Protein Preconcentration Using Nanofractures Generated by Nanoparticle-Assisted Electric Breakdown at Junction Gaps
Sample preconcentration is an important step that increases the accuracy of subsequent detection, especially for samples with extremely low concentrations. Due to the overlapping of electrical double layers in the nanofluidic channel, the concentration polarization effect can be generated by applying an electric field. Therefore, a nonlinear electrokinetic flow is induced, which results in the fast accumulation of proteins in front of the induced ionic depletion zone, the so-called exclusion-enrichment effect. Nanofractures were created in this work to preconcentrate proteins via the exclusion-enrichment effect. The protein sample was driven by electroosmotic flow and accumulated at a specific location. The preconcentration chip for proteins was fabricated using simple standard soft lithography with a polydimethylsiloxane replica. Nanofractures were formed by utilizing nanoparticle-assisted electric breakdown. The proposed method for nanofracture formation that utilizes nanoparticle deposition at the junction gap between microchannels greatly decreases the required electric breakdown voltage. The experimental results indicate that a protein sample with an extremely low concentration of 1 nM was concentrated to 1.5�104-fold in 60 min using the proposed chip. PMID:25025205
Jen, Chun-Ping; Amstislavskaya, Tamara G.; Kuo, Chen-Chi; Chen, Yu-Hung
Electrical Breakdown of Anodized Structures in a Low Earth Orbital Environmental
NASA Technical Reports Server (NTRS)
A comprehensive set of investigations involving arcing on a negatively biased anodized aluminum plate immersed in a low density argon plasma at low pressures (P(sub O), 7.5 x 10(exp -5) Torr) have been performed. These arcing experiments were designed to simulate electrical breakdown of anodized coatings in a Low Earth Orbital (LEO) environment. When electrical breakdown of an anodized layer occurs, an arc strikes, and there is a sudden flux of electrons accelerated into the ambient plasma. This event is directly followed by ejection of a quasi-neutral plasma cloud consisting of ejected material blown out of the anodized layer. Statistical analysis of plasma cloud expansion velocities have yielded a mean propagation velocity, v = (19.4 +/- 3.5) km/s. As the plasma cloud expands into the ambient plasma, energy in the form of electrical noise is generated. The radiated electromagnetic noise is detected by means of an insulated antenna immersed in the ambient plasma. The purpose of the investigations is (1) to observe and record the electromagnetic radiation spectrum resulting from the arcing process. (2) Make estimates of the travel time of the quasi-neutral plasma cloud based on fluctuations to several Langmuir probes mounted in the ambient plasma. (3) To study induced arcing between two anodized aluminum structures in close proximity.
Galofaro, J. T.; Doreswamy, C. V.; Vayner, B. V.; Snyder, D. B.; Ferguson, D. C.
Electric breakdowns of the "plasma capacitors" occurs on insulation coating of the ISS surface
NASA Astrophysics Data System (ADS)
High electric fields and currents are occurred in the spacecrafts plasma environment by onboard electric generators. Thus the high voltage solar array (SA) of the American segment of International Space Station (ISS) generates potential 160 V. Its negative pole is shorted to the frames of all the ISS segments. There is electric current between the SA and the frame through the plasma environment, i.e. electric discharge occurs. As a result a potential drop exists between the frames of all the ISS segments and the environmental plasma [1], which is cathode drop potential varphi _{c} defined. When ISS orbiting, the ?c varies greatly in the range 0-100 V. A large area of the ISS frames and SA surface is coated with a thin dielectric film. Because of cathode drop potential the frame surfaces accumulate ion charges and the SA surfaces accumulate electron charges. These surfaces become plasma capacitors, which accumulate much charge and energy. Micrometeorite impacts or buildup of potential drop in excess of breakdown threshold varphi_{b} (varphi _{c} > varphi _{b} = 60 V) may cause breakdowns of these capacitors. Following a breakdown, the charge collected at the surfaces disperses and transforms into a layer of dense plasma [2]. This plasma environment of the spacecraft produces great pulsed electric fields E at the frame surfaces as well as heavy currents between construction elements which in turn induce great magnetic fields H. Therefore the conductive frame and the environmental plasma is plasma inductors. We have calculated that the densities of these pulsing and high-frequency fields E and H generated in the plasma environment of the spacecraft may exceed values hazardous to human. Besides, these fields must induce large electromagnetic impulses in the space-suit and in the power supply and control circuits of onboard systems. During astronaut�s space-suit activity, these fields will penetrate the space-suit and the human body with possible hazardous effects. These effects need to be studied, and appropriate remedies are to be developed. References 1. Mikatarian, R., et al., �Electrical Charging of the International Space Station�, AIAA Paper No. 2003-1079, 41th. Aerospace Sciences Meeting and Exhibit, January 2003. 2. A.G. Korsun, �Electric discharge processes intensification mechanisms on International Space Station surface�. Astronautics and rocket production, ?1, 2011 (in Russian).
Homin, Taras; Korsun, Anatolii
Tether electrical characteristics design report
The design of a tether system for use in electric and magnetic fields requires an analysis of the equivalent electrical circuit of the baboon and tether. The response of this equivalent circuit to an electric or magnetic field is dependent on the connection of the tether system to the baboon. The tether will be designed so that the currents induced in the tethered baboon are approximately the same as those induce in an untethered baboon. 6 figs., 3 tabs.
Lucas, J.H.
Electrical measurements at the microscale: Air breakdown and silicon Coulomb blockade devices
NASA Astrophysics Data System (ADS)
In this thesis I describe the work performed in two different areas of research, electrical breakdown of air for small electrode separations and measurements of silicon (Si)-based tunable-barrier single electron transistors (SETs). In this work, I describe a new method for measuring the breakdown of air for the range of electrode separation of interest. This method has several advantages compared to ones found in the literature, namely it allows for a measurement of electrode separation before each breakdown measurement; it has a parallel plate geometry and the surface roughness of the electrodes used is very small. Using the results obtained with this method I have made a quantitative comparison between the predictions of the standard theory of the field (field emission of electrons) and our data, something that has not been done before. In this thesis I describe analytically both the theory and the analysis of our data. I conclude that the standard theory used in this field fails for the range of electrode separations of interest (400 nm to 45 mum). Also, I describe electrical measurements performed on a Si-based tunable-barrier device fabricated in the group of Neil Zimmerman at the National Institute of Standards and Technology (NIST) using the fabrication facilities of Cornell University. I demonstrate that this device can be operated as an SET. I continue by describing measurements of the charge offset drift (Q 0(t)) for this device and show that it is almost 3 orders of magnitude smaller than in metal devices, and comparable to previously measured Si devices of this type. All of the previously measured devices originated from the same fabrication source, NTT, Japan. Our ability to demonstrate the same low drift in devices fabricated at Cornell, USA, indicates that the small values of Q0(t) is a robust property of Si-based devices, and not sensitive to the details of fabrication.
Hourdakis, Emmanouel Spyros
Electric-induced oxide breakdown of a charge-coupled device under femtosecond laser irradiation.
A femtosecond laser provides an ideal source to investigate the laser-induced damage of a charge-coupled device (CCD) owing to its thermal-free and localized damage properties. For conventional damage mechanisms in the nanosecond laser regime, a leakage current and degradation of a point spread function or modulation transfer function of the CCD are caused by the thermal damages to the oxide and adjacent electrodes. However, the damage mechanisms are quite different for a femtosecond laser. In this paper, an area CCD was subjected to Ti: sapphire laser irradiation at 800 nm by 100 fs single pulses. Electric-induced oxide breakdown is considered to be the primary mechanism to cause a leakage current, and the injured oxide is between the gate and source in the metal-oxide semiconductor field-effect transistor (MOSFET) structure for one CCD pixel. Optical microscopy and scanning electron microscopy are used to investigate the damaged areas and the results show that the electrodes and the oxide underneath are not directly affected by the femtosecond laser, which helps to get rid of the conventional damage mechanisms. For the primary damage mechanism, direct damage by hot carriers, anode hole injection, and an enlarged electric field in the insulating layer are three possible ways to cause oxide breakdown. The leakage current is proved by the decrease of the resistance of electrodes to the substrate. The output saturated images and the dynamics of an area CCD indicate that the leakage current is from an electrode to a light sensing area (or gate to source for a MOSFET), which proves the oxide breakdown mechanism. PMID:24216654
Gao, Liuzheng; Zhu, Zhiwu; Shao, Zhengzheng; Cheng, Xiang'ai; Chang, Shengli
Breakdown characteristics of AlGaN/GaN Schottky barrier diodes fabricated on a silicon substrate
NASA Astrophysics Data System (ADS)
In this work, the breakdown characteristics of AlGaN/GaN planar Schottky barrier diodes (SBDs) fabricated on the silicon substrate are investigated. The breakdown voltage (BV) of the SBDs first increases as a function of the anode-to-cathode distance and then tends to saturate at larger inter-electrode spacing. The saturation behavior of the BV is likely caused by the vertical breakdown through the intrinsic GaN buffer layer on silicon, which is supported by the post-breakdown primary leakage path analysis with the emission microscopy. Surface passivation and field plate termination are found effective to suppress the leakage current and enhance the BV of the SBDs. A high BV of 601 V is obtained with a low on-resistance of 3.15 m?�cm2.
Jiang, Chao; Lu, Hai; Chen, Dun-Jun; Ren, Fang-Fang; Zhang, Rong; Zheng, You-Dou
Impact of the layout on the electrical characteristics of double-sided silicon 3D sensors fabricated at FBK
NASA Astrophysics Data System (ADS)
We report on experimental results and TCAD simulations addressing the impact of layout on the electrical characteristics of double-sided 3D diodes fabricated at Fondazione Bruno Kessler (FBK), Trento, Italy. Simulations are found to accurately reproduce the device characteristics, thus explaining the basic mechanisms governing the breakdown behavior and capacitance of different devices and providing useful hints for layout optimization.
Povoli, M.; Bagolini, A.; Boscardin, M.; Dalla Betta, G.-F.; Giacomini, G.; Mattedi, F.; Vianello, E.; Zorzi, N.
Breakdown Probability Distribution and Equi-Probabilistic VT Characteristics of Transformer Oil
Breakdown probability distributions of transformer oil are investigated by applying repeatedly ac voltages with various durations. It is suggested from the test results that the Weibull distribution defined by the shape parameter of ca. 8 fits the breakdown probability distribution of oil. The breakdown probability distributions of oil do not seem to depend on the stressing time.
M. Ikeda; S. Menju
Strongly Dipolar Polythiourea and Polyurea Dielectrics with High Electrical Breakdown, Low Loss, and High Electrical Energy Density
NASA Astrophysics Data System (ADS)
Dielectric materials with high electric energy density and low loss are of great importance for applications in modern electronics and electrical systems. Strongly dipolar materials have the potential to reach relatively higher dielectric constants than the widely used non-polar or weakly dipolar polymers, as well as a much lower loss than that of nonlinear high K polymer dielectrics or polymer-ceramic composites. To realize the high energy density while maintaining the low dielectric loss, aromatic polythioureas and polyureas with high dipole moments, high dipole densities, tunable molecular structures and dielectric properties were investigated. High energy density (>24 J/cm3), high breakdown strength (>800 MV/m), and high charge-discharge efficiency (>90%) can be achieved in the new polymers. The molecular structure and film surface morphology were also studied; it is of great importance to optimize the fabrication process to make high-quality thin films.
Wu, Shan; Burlingame, Quinn; Cheng, Zhao-Xi; Lin, Minren; Zhang, Q. M.
Strongly Dipolar Polythiourea and Polyurea Dielectrics with High Electrical Breakdown, Low Loss, and High Electrical Energy Density
NASA Astrophysics Data System (ADS)
Dielectric materials with high electric energy density and low loss are of great importance for applications in modern electronics and electrical systems. Strongly dipolar materials have the potential to reach relatively higher dielectric constants than the widely used non-polar or weakly dipolar polymers, as well as a much lower loss than that of nonlinear high K polymer dielectrics or polymer-ceramic composites. To realize the high energy density while maintaining the low dielectric loss, aromatic polythioureas and polyureas with high dipole moments, high dipole densities, tunable molecular structures and dielectric properties were investigated. High energy density (>24 J/cm3), high breakdown strength (>800 MV/m), and high charge-discharge efficiency (>90%) can be achieved in the new polymers. The molecular structure and film surface morphology were also studied; it is of great importance to optimize the fabrication process to make high-quality thin films.
Wu, Shan; Burlingame, Quinn; Cheng, Zhao-Xi; Lin, Minren; Zhang, Q. M.
The Applicability of Fluid Model to Electrical Breakdown and Glow Discharge Modeling in Argon
NASA Astrophysics Data System (ADS)
The simple fluid model, an extended fluid model, and the fluid model with nonlocal ionization are applied for the calculations of static breakdown voltages, Paschen curves and current-voltage characteristics. The best agreement with the experimental data for the Paschen curve modeling is achieved by using the model with variable secondary electron yield. The modeling of current-voltage characteristics is performed for different inter-electrode distances and the results are compared with the experimental data. The fluid model with nonlocal ionization shows an excellent agreement for all inter-electrode distances, while the extended fluid model with variable electron transport coefficients agrees well with measurements at short inter-electrode distances when ionization by fast electrons can be neglected.
N. Stankov, M.; D. Petkovi?, M.; Lj. Markovi?, V.; N. Stamenkovi?, S.; P. Jovanovi?, A.
Electrical characteristics of simulated tornadoes
NASA Astrophysics Data System (ADS)
It is well known that tornadoes and dust devils have the ability to accumulate significant, visible clouds of debris. Collisions between sand-like debris species produce different electric charges on different types of grains, which convect along different trajectories around the vortex. Thus, significant charge separations and electric currents are possible, which as the vortex fluctuates over time are thought to produce ULF radiation signatures that have been measured in the field. These electric and magnetic fields may contain valuable information about tornado structure and genesis, and may be critical in driving electrochemical processes within dust devils on Mars. In the present work, existing large eddy simulations of debris-laden tornadoes performed at West Virginia University are coupled with a new debris-charging and advection code developed at Goddard Space Flight Center to investigate the detailed (meter-resolution) fluid-dynamic origins of electromagnetic fields within terrestrial vortices. First results are presented, including simulations of the electric and magnetic fields that would be observed by a near-surface, instrument-laden probe during a direct encounter with a tornado. This research was supported by an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by Oak Ridge Associated Universities through a contract with NASA. The generous allocation of computing resources by Dr. Timothy J. Stubbs is gratefully acknowledged.
Zimmerman, M. I.; Farrell, W. M.; Barth, E. L.; Lewellen, D. C.; Lewellen, W. S.; Perlongo, N. J.; Jackson, T.
Characteristics of primary electric propulsion systems. [conferences
NASA Technical Reports Server (NTRS)
The use of advanced electric propulsion systems is expected to provide cost and performance benefits for future energetic space missions. A methodology to predict the characteristics of advanced electric propulsion systems was developed and programmed for computer calculations to allow evaluation of a broad set of technology and mission assumptions. The impact on overall thrust system characteristics was assessed for variations of propellant type, total accelerating voltage, thruster area, specific impulse, and power system approach. The data may be used both to provide direction to technology emphasis and allow for preliminary estimates of electric propulsion system properties for a wide variety of applications.
Byers, D. C.
Effect of silane coupling agent chemistry on electrical breakdown across hybrid organic-inorganic insulating films.
Dielectric breakdown measurements were conducted on self-assembled monolayer (SAM)/native silicon oxide hybrid dielectrics using conductive atomic force microscopy (C-AFM). By depositing silane coupling agents (SCAs) through a diffusional barrier layer, SAM roughness was decoupled from chemistry to compare the chemical effects of exposed R-group functionality on dielectric breakdown. Using Weibull and current-voltage (I-V) analysis, the breakdown strength was observed to be independent of SCA R-group length, and the addition of a SAM was seen to improve the breakdown strength relative to native silicon oxide by up to 158%. Fluorinated SCAs were observed to suppress tunneling leakage and exhibited increased breakdown strength relative to their hydrocarbon analogs. Electron trapping, scattering, or attachment processes inherent to the fluorinated moieties are thought to be the origin of the improved breakdown properties. PMID:25010384
Diebold, Roger M; Gordon, Michael J; Clarke, David R
Applications of LIBS for determination of ionic species (NaCl) in electrical cables for investigation of electrical breakdown
NASA Astrophysics Data System (ADS)
The formation of water trees in high-voltage cables can wreak havoc to power systems. The water tree is produced within the high voltage cable insulator when impurities like sodium and magnesium present in the insulating material react with moist soil to form chlorides. This water tree causes electrical breakdown by short circuiting the metallic conductor and the earth. In this paper we use laser-induced breakdown spectroscopy (LIBS) to detect the potentially dangerous elements that form the water tree in the insulating cable. The LIBS system used for this work consists of the fundamental (1064 nm) of a Nd:YAG laser, four spectrometer modules that cover the visible and near-UV spectral ranges and an ICCD camera with proper delay and gating sequence. With this arrangement we were able to measure the elemental concentrations of trace metals present in the insulating cable. The concentrations measured with our LIBS system were counter checked by a standard technique like inductively coupled plasma (ICP) emission spectrometry. The maximum concentrations for ionic species such as Ba (455.40 nm), Ca (393.36 nm), Cr (267.71 nm), Fe (259.94 nm), Cl (542.3 nm), Mg (516.7 nm), Mn (257.61 nm), Na (589.59 nm) and Ti (334.18 nm) are 20.6, 43.2, 1.6, 148.4, 24.2, 22.1, 4.2, 39.56 and 4.35 ppm, respectively. The relative accuracy of our LIBS system for various elements as compared with the ICP method is in the range of 0.03-0.6 at 2.5% error confidence.
Gondal, M. A.; Shwehdi, M. H.; Khalil, A. A. I.
Investigation on critical breakdown electric field of hot carbon dioxide for gas circuit breaker applications
NASA Astrophysics Data System (ADS)
Sulfur hexafluoride (SF6) gas is widely used in high-voltage circuit breakers, but due to its high global warming potential, substitutes are being sought. CO2 has been investigated as a candidate based on its arc interruption performance. The hot gas in the circuit breaker after current zero, with a complicated species composition caused by the dissociation and many other reactions, will lead to the electrical breakdown, which is one of the major concerns in assessing the arc interruption performance. Despite this, little research has been reported on the dielectric strength of hot CO2. In this paper, the dielectric properties of hot CO2 related to the dielectric recovery phase of the circuit breaker were investigated in the temperature range from 300 to 4000?K and in the pressure range from 0.01 to 1.0?MPa. Under the assumptions of local thermodynamic equilibrium (LTE) and local chemical equilibrium (LCE), the equilibrium compositions of hot CO2 were obtained based on Gibbs free energy minimization. The cross sections for interactions between electrons and the species are presented. The critical reduced electric field strength of CO2 was determined by balancing electron generation and loss. These were evaluated using the electron energy distribution function (EEDF) derived from the two-term Boltzmann transport equation. The result indicates that unlike SF6 or air, in hot CO2 the reduced critical electric field strength does not change monotonically with increasing heavy-particle temperature from 300 to 4000?K. CO2 has a superior dielectric strength to pure SF6 above 2500?K at 0.5?MPa, which means it has the potential to improve the interruption performance of the circuit breakers, while reducing the global warming effect. Good agreement was found with published experimental results and calculations for CO2 at room temperature, and with previous calculations for hot CO2.
Sun, Hao; Rong, Mingzhe; Wu, Yi; Chen, Zhexin; Yang, Fei; Murphy, Anthony B.; Zhang, Hantian
Water-tunnel and analytical investigation of the effect of strake design variables on strake vortex breakdown characteristics
NASA Technical Reports Server (NTRS)
A systematic water-tunnel study was made to determine the vortex breakdown characteristics of 43 strakes. The strakes were mounted on a 1/2-scale model of a Langley Research Center general research fighter fuselage model with a 44deg leading-edge-sweep trapezoidal wing. The analytically designed strake shapes provided examples of the effects of the primary design parameters (size, span, and slenderness) on vortex breakdown characteristics. These effects were analyzed in relation to the respective strake leading-edge suction distributions. Included were examples of the effects of detailed strake planform shaping. It was concluded that, consistent with the design criterion, those strakes with leading-edge suction distributions which increase more rapidly near, and have a higher value at, the spanwise tip of the strake produce a more stable vortex.
Frink, N. T.; Lamar, J. E.
NASA Astrophysics Data System (ADS)
In the context of the CLIC (Compact Linear Collider) project investigations of DC breakdown in ultra high vacuum are carried out in parallel with high power RF tests. From the point of view of saturation breakdown field the best material tested so far is stainless steel, followed by titanium. Copper shows a four times weaker breakdown field than stainless steel. The results indicate clearly that the breakdown events are initiated by field emission current and that the breakdown field is limited by the cathode. In analogy to RF, the breakdown probability has been measured in DC and the data show similar behaviour as a function of electric field.
Calatroni, S.; Descoeudres, A.; Levinsen, Y.; Taborelli, M.; Wuensch, W.
The Electrical Characteristics of Fixed Charge Membranes
A theoretical analysis is made of the electrical characteristics of a membrane containing two fixed charge regions, of opposite sign, in contact. Profiles of ion concentrations, electrostatic potential, space charge density, as well as the voltage-current characteristics were obtained by numerical integration of the field equations on a computer. Comparison with the predictions of an earlier analysis of this system (Coster, 1965) shows that the latter is valid to a good approximation for membranes > 70 A in thickness. In particular the form of the electrical characteristics, including the punch-through effect, have been verified by the computer analysis. The range of useful validity of the earlier analysis, the use of Boltzmann statistics when currents are present, and variation of membrane capacitance with applied potential, are discussed in the light of the results obtained. PMID:5786315
Coster, H. G. L.; George, E. P.; Simons, R.
Wind tunnel investigation of the interaction and breakdown characteristics of slender wing vortices at subsonic, transonic, and supersonic speeds
NASA Technical Reports Server (NTRS)
The vortex dominated aerodynamic characteristics of a generic 65 degree cropped delta wing model were studied in a wind tunnel at subsonic through supersonic speeds. The lee-side flow fields over the wing-alone configuration and the wing with leading edge extension (LEX) added were observed at M (infinity) equals 0.40 to 1.60 using a laser vapor screen technique. These results were correlated with surface streamline patterns, upper surface static pressure distributions, and six-component forces and moments. The wing-alone exhibited vortex breakdown and asymmetry of the breakdown location at the subsonic and transonic speeds. An earlier onset of vortex breakdown over the wing occurred at transonic speeds due to the interaction of the leading edge vortex with the normal shock wave. The development of a shock wave between the vortex and wing surface caused an early separation of the secondary boundary layer. With the LEX installed, wing vortex breakdown asymmetry did not occur up to the maximum angle of attack in the present test of 24 degrees. The favorable interaction of the LEX vortex with the wing flow field reduced the effects of shock waves on the wing primary and secondary vortical flows. The direct interaction of the wing and LEX vortex cores diminished with increasing Mach number. The maximum attainable vortex-induced pressure signatures were constrained by the vacuum pressure limit at the transonic and supersonic speeds.
Erickson, Gary E.
A New Lateral Trench Electrode Insulated Gate Bipolar Transistor with p+ Diverter for Superior Electrical Characteristics
NASA Astrophysics Data System (ADS)
A new lateral trench electrode insulated gate bipolar transistor (LTEIGBT) with a p+ diverter was proposed and fabricated to improve the electrical characteristics of the conventional LTIGBT. The p+ diverter was placed between anode and cathode electrodes. Because the p+ diverter region of the proposed device was an enclosed trench oxide layer, the electric field centered on the trench oxide layer and the punch-through breakdown of the LTEIGBT with a p+ diverter was occurred at a high. Therefore, the p+ diverter of the proposed LTIGBT was not related to the breakdown voltage in contrast to that of the conventional LTIGBT. As a result of device simulation, the electrical characteristics of the proposed LTEIGBT including latching current density, breakdown voltage and switching speed were superior to those of the conventional LIGBTs. After simulation, we fabricated and analyzed the proposed LTEIGBT with a p+ diverter. The maximum currents of the proposed and conventional LTIGBTs were 90 mA and 70 mA, respectively. Therefore, the proposed LTEIGBT with a p+ diverter is an effective device for a smart power IC.
Sung, Man Young; Kang, Ey Goo; Kim, Dae Jong; Kim, Sang sig
The validity of the one-dimensional fluid model of electrical breakdown in synthetic air at low pressure
NASA Astrophysics Data System (ADS)
In this letter the validity of the fluid model used to simulate the electrical breakdown in air at low pressure is discussed. The new method for the determination of the ionization source term for the mixed gases is proposed. Paschen's curve obtained by the fluid model is compared to the available experimental data. The electron and ions density profiles calculated by the fluid model are presented. Based on Ohm's law, the current and voltage waveforms are calculated and compared to the ones measured by the oscilloscope in the synthetic-air filled tube with stainless-steel electrodes. It is shown that the one-dimensional fluid model can be used for modeling the electrical breakdown at pd values higher than Paschen's minimum and to determine stationary values of electron and ions densities.
Jovanovi?, A. P.; Stankov, M. N.; Markovi?, V. Lj.; Stamenkovi?, S. N.
Changes in electrical characteristics associated with degradation of InGaN blue light-emitting diodes
Because of the high concentration of threading dislocations, the reverse current-voltage (I�V) characteristics for either\\u000a homo- or heterojunctions made on GaN-based materials grown on sapphire often show a strong electric field dependence (called\\u000a a soft breakdown characteristic), which can be described by a power law I=Vn, with n between 4 to 5. We find a significant increase of reverse currents
Z.-Q. Fang; D. C. Reynolds; D. C. Look
Measurement of the electric breakdown strength of transformer oil in the sub-nanosecond regime
The dielectric strength of highly purified insulating transformer oil has been measured in the sub-nanosecond regime under single pulse and repetitive burst conditions. Single pulse breakdown fields have been measured to be 11 MV\\/cm. Repetitive bursts to 1 kHz reduce the threshold field value by a factor of two, with lower breakdown fields recorded at a 1.2 kHz repetition rate.
J. M. Lehr; F. J. Agee; R. Copeland; W. D. Prather
Electric field enhancement due to a saw-tooth asperity in a channel and implications on microscale gas breakdown
NASA Astrophysics Data System (ADS)
The electric field enhancement due to an isolated saw-tooth asperity in an infinite channel is considered with the goal of providing some inputs to the choice of field enhancement factors used to describe microscale gas breakdown. The Schwarz�Christoffel transformation is used to map the interior of the channel to the upper half of the transformed plane. The expression for the electric field in the transformed plane is then used to determine the electric field distribution in the channel as well as field enhancement near the asperity. The effective field enhancement factor is determined and its dependence on operating and geometrical parameters is studied. While the effective field enhancement factor depends only weakly on the height of the asperity in comparison to the channel, it is influenced significantly by the base angles of the asperity. Due to the strong dependence of field emission current density on electric field, the effective field enhancement factor (?eff) is shown to vary rapidly with the applied electric field irrespective of the geometrical parameters. This variation is included in the analysis of microscale gas breakdown and compared with results obtained using a constant ?eff as is done traditionally. Even though results for a varying ?eff may be approximately reproduced using an equivalent constant ?eff independent of E-field, it might be important for a range of operating conditions. This is confirmed by extracting ?eff from experimental data for breakdown in argon microgaps with plane-parallel cathodes and comparing its dependence on the E-field. While the use of two-dimensional asperities is shown to be a minor disadvantage of the proposed approach in its current form, it can potentially help in developing predictive capabilities as opposed to treating ?eff as a curve-fitting parameter.
Venkattraman, Ayyaswamy
Influence of transverse magnetic field on breakdown characteristics of vacuum, gaseous helium at low temperature and liquid helium
NASA Astrophysics Data System (ADS)
The dielectric strength of coaxial cylindrical gaps in vacuum, gaseous helium at low temperature or liquid helium has been investigated under d.c. stresses in the presence of transverse magnetic field. Experimental results show that the dielectric strength in vacuum is lowered drastically by the application of transverse magnetic field. Therefore, a high voltage test under full load current is recommended to ensure the safe drive of superconducting devices with vacuum electrical insulation. A method for improvement of vacuum insulation performance is proposed on the basis of discussion on breakdown mechanism.
Hara, M.; Shigematsu, H.; Yano, S.; Yamafuji, K.; Takeo, M.; Funaki, K.
Electric field changes generated by the preliminary breakdown for the negative cloud-to-ground lightning flashes in Malaysia and Sweden
NASA Astrophysics Data System (ADS)
We present the study of the electric field changes generated by the preliminary breakdown for negative cloud-to-ground lightning flashes in Malaysia and Sweden concerning the association of slow field changes associated in preliminary breakdown process. We examined the total of 1685 negative cloud-to-ground lightning flashes from the total of 39 thunderstorms by recording the slow electric field, fast electric field and narrowband radiation field at 3 and 30 MHz signals simultaneously. Our results show that there is a pre-starting time, i.e. the duration between the first preliminary breakdown pulse and slow field changes starting point, which is found to be after the first preliminary breakdown pulse. The pre-starting time has the arithmetic and geometric mean range from 1.4-6.47 and 1-3.36 ms, respectively. The mean values of pre-starting time in Malaysia are greater than the values observed in Sweden by more than a factor of 3. From the two data sets it shows that the slow field changes never start before the preliminary breakdown. Furthermore, the use of single-station electric fields measurement with high resolutions of 12 bits transient recorder with several nanosecond accuracy allow one to distinguish the slow field changes generated by preliminary breakdown, which preceded the negative first return stroke, between tens to hundreds of milliseconds of pre-return stroke duration.
Baharudin, Z. A.; Fernando, M.; Ahmad, Noor Azlinda; M�kel�, J. S.; Rahman, Mahbubur; Cooray, Vernon
The influence of the breakdown electric field in the configuration of lightning corona sheath on charge distribution in the channel
NASA Astrophysics Data System (ADS)
A model of corona sheath that surrounds the thin core of the lightning channel has been investigated by using a generalized traveling current source return stroke model. The lightning channel is modeled by a charged corona sheath that stretches around a highly conductive central core through which the main current flows. The channel core with the negatively charged outer channel sheath forms a strong electric field, with an overall radial orientation. The return stroke process is modeled as the negative leader charge in the corona sheath being discharged by the positive charge coming from the channel core. Expressions that describe how the corona sheath radius evolves during the return stroke are obtained from the corona sheath model, which predicts charge motion within the sheath. The corona sheath model, set forth by Maslowski and Rakov (2006), Tausanovic et al. (2010), Marjanovic and Cvetic (2009), Cvetic et al. (2011) and Cvetic et al. (2012), divides the sheath onto three zones: zone 1 (surrounding the channel core with net positive charge), zone 2 (surrounding zone 1 with negative charge) and zone 3 (the outer zone, representing uncharged virgin air). In the present study, we have assumed a constant electric field inside zone 1, as suggested by experimental research of corona discharges in coaxial geometry conducted by Cooray (2000). The present investigation builds upon previous studies by Tausanovic et al. (2010) and Cvetic et al. (2012) in several ways. The value of the breakdown electric field has been varied for probing its effect on channel charge distribution prior and during the return stroke. With the aim of investigating initial space charge distribution along the channel, total electric field at the outer surface of the channel corona sheath, just before the return stroke, is calculated and compared for various return stroke models. A self-consistent algorithm is applied to the generalized traveling current source return stroke model, so that the boundary condition for total electric field is fulfilled. The new density of space charge and the new radius of channel corona envelope, immediately before the return stroke stage, are calculated. The obtained results indicate a strong dependence of channel charge distribution on the breakdown electric field value. Among the compared return stroke models, transmission-line-type models have exhibited a good agreement with the predictions of the Gauss' law regarding total breakdown electric field on the corona sheath's outer surface. The generalized lightning traveling current source return stroke model gives similar results if the adjustment of the space charge density inside the corona sheath is performed.
Ignjatovic, Milan; Cvetic, Jovan; Heidler, Fridolin; Markovic, Slavoljub; Djuric, Radivoje
THE TIME LAGS OF ELECTRICAL BREAKDOWN IN THE MAGNETIC FIELD. Technical Report No. 5
Using coaxial geometry and a pulsed transverse magnetic field, formative ; time lags were measured in air, argon, and helium at pressures varying from 0.2 ; mm Hg to atmospheric. The magnetic field intensities for the measurements varied ; from 0 to 90 kGauss with a pulse duration up to 140 microseconds. Static ; breakdown potentials as a function of
S. T. Nolan; H. W. Kendall; J. W. Flowers
Electromechanical modeling and characterization of the electrical breakdown for the capacitive microarrayed ultrasonic transducers
This paper presents two numerical evaluation schemes to simulate the dielectric breakdown phenomena for the capacitive micro-arrayed ultrasonic transducers (CMUT). The performance of dielectric strength was investigated using a commercial finite element method (FEM) software package of ANSYS. The electro-mechanical model was established using the ANSYS parametric design language (APDL) technique. A built in Multiphysics solver of ANSYS was employed
Te-I Chiu; Shi-Bing Luo; Tsai-Chu Hsiao
Chemical Implications due to the low Electrical Breakdown in the Martian Atmosphere
Abstract�This paper addresses the possibility that the chemical reactions ob- served by the Viking landers on Mars may be a consequence of chemically reactive species on the surface of particles as a result of glow discharge. Triboelectrically charged particles due to the presence of daily dust devils and planetary- encompassing dust storms coupled with the low-pressure atmospheric breakdown in the
Charles R. Buhler; Carlos I. Calle
DC conduction and breakdown characteristics of Al2O3/cross-linked polyethylene nanocomposites for high voltage direct current transmission cable insulation
NASA Astrophysics Data System (ADS)
We have discussed a cross-linked polyethylene (XLPE) nanocomposite insulating material that is able to DC voltage applications. Nanocomposites, which are composed in polymer matrix mixed with nano-fillers, have received considerable attention because of their potential benefits as dielectrics. The nano-sized alumina oxide (Al2O3)/XLPE nanocomposite was prepared, and three kinds of test, such as DC breakdown, DC polarity reversal breakdown, and volume resistivity were performed. By the addition of nano-sized Al2O3 filler, both the DC breakdown strength and the volume resistivity of XLPE were increased. A little homogeneous space charge was observed in Al2O3/XLPE nanocomposite material in the vicinity of electrode through the polarity reversal breakdown test. From these results, it is thought that the addition of Al2O3 nano-filler is effective for the improvement of DC electrical insulating properties of XLPE.
Park, Yong-Jun; Kwon, Jung-Hun; Sim, Jae-Yong; Hwang, Ju-Na; Seo, Cheong-Won; Kim, Ji-Ho; Lim, Kee-Joe
Electric breakdown and ionization detection in normal liquid and superfluid 4He for the SNA nEDM experiment
NASA Astrophysics Data System (ADS)
A new experiment to search for the neutron electric dipole moment (nEDM) is under construction at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. The SNS nEDM experiment is a national collaboration spanning over 20 universities and laboratories with more than 100 physicists and engineers contributing to the research and development. The search for a nEDM is a precision test of time reversal symmetry in particle physics, in the absence of a discovery, the SNS nEDM experiment seeks to improve the present limit on the nEDM value by two orders of magnitude. A non-zero value of the nEDM would help to explain the asym- metry between matter and anti-matter in the universe by providing an additional source of charge conjugation and parity symmetry violation, a necessary ingredient in the theory of baryogenesis in the early universe. The nEDM experiment will measure the Larmor precession frequency of neutrons by detecting scintillation from neutron capture by a dilute concentration of 3He inside a bath of superfluid 4He. Neutron capture by 3He is spin-dependent and the magnetic moments of the neutron and the 3He nucleus are comparable. A direct measurement of the precession frequency of polarized 3He and scintillation from neutron capture allows for the relative precession frequencies of 3He and the neutron to be determined. The experiment will then look for changes in the relative precession of 3He and neutrons under the influence of strong electric fields. 3He has negligible EDM and therefore any deviation due to an applied electric field would be from a nEDM. The nEDM experiment will need to apply strong electric fields inside superfluid (SF) 4He and it was necessary to investigate the ability of SF 4He to sustain electric fields. An experiment to study electric breakdown in superfluid 4He was constructed at the Indiana University Center for Exploration of Energy and Matter (CEEM). The experiment studied the electric breakdown behavior of liquid Helium throughout the pressure-temperature phase space, between 1 bar and the saturation curve and between 4.2 K and 1.7 K. A new breakdown hysteresis in liquid helium was discovered and is attributed to the suppression of heterogeneous nucleation sites inside the liquid. A phenomenological model involving the Townsend breakdown mechanism and Paschen's Law in liquid helium is proposed. In addition, the many challenges faced by efficient scintillation detection in the cryogenic environment of the nEDM experiment motivated additional studies at CEEM. To test the effect of an electric field on scintillation in superfluid, a SF test cell was constructed inside a dilution refrigerator and it was found that the scintil- lation intensity from a 241Am source in the cell, is reduced at high electric fields. Alternatives to scintillation detection for the nEDM experiment were also explored and the test cell was reconfigured to operate as a superfluid ionization chamber. The superfluid ionization chamber was tested with 241Am in pulse mode and current mode configurations. While the pulse mode in superfluid, which relies on the drift velocity of charges, is hindered by quasi-particle excitations in superfluid, results of current mode measurements appear promising. To further explore the prospect of cryogenic ionization detection, a detector cryo-stat capable of detecting neutrons using a 10B converter was also constructed at CEEM and tested at the Indiana University Low Energy Neutron Source (LENS). The neutron detector cryostat has the benefit of being able to modulate the ioniza- tion source which was not possible with the superfluid ionization chamber. Tests with argon gas led to the development of more efficient boron targets. The cryogenic test of ionization detection in current mode will be discussed.
Karcz, Maciej
Note: Tesla based pulse generator for electrical breakdown study of liquid dielectrics.
In the process of studying charge holding capability and delay time for breakdown in liquids under nanosecond (ns) time scales, a Tesla based pulse generator has been developed. Pulse generator is a combination of Tesla transformer, pulse forming line, a fast closing switch, and test chamber. Use of Tesla transformer over conventional Marx generators makes the pulse generator very compact, cost effective, and requires less maintenance. The system has been designed and developed to deliver maximum output voltage of 300 kV and rise time of the order of tens of nanoseconds. The paper deals with the system design parameters, breakdown test procedure, and various experimental results. To validate the pulse generator performance, experimental results have been compared with PSPICE simulation software and are in good agreement with simulation results. PMID:24387484
Veda Prakash, G; Kumar, R; Patel, J; Saurabh, K; Shyam, A
Note: Tesla based pulse generator for electrical breakdown study of liquid dielectrics
NASA Astrophysics Data System (ADS)
In the process of studying charge holding capability and delay time for breakdown in liquids under nanosecond (ns) time scales, a Tesla based pulse generator has been developed. Pulse generator is a combination of Tesla transformer, pulse forming line, a fast closing switch, and test chamber. Use of Tesla transformer over conventional Marx generators makes the pulse generator very compact, cost effective, and requires less maintenance. The system has been designed and developed to deliver maximum output voltage of 300 kV and rise time of the order of tens of nanoseconds. The paper deals with the system design parameters, breakdown test procedure, and various experimental results. To validate the pulse generator performance, experimental results have been compared with PSPICE simulation software and are in good agreement with simulation results.
Veda Prakash, G.; Kumar, R.; Patel, J.; Saurabh, K.; Shyam, A.
Measurements of the volt-ampere characteristics and the breakdown voltages of direct-current helium and hydrogen discharges in microgaps
The discharge phenomena for micro meter gap sizes include many interesting problems from engineering and physical perspectives. In this paper, the authors deal with the experimental and theoretical results of the breakdown voltage and current-voltage characteristics of the direct-current helium and hydrogen discharges. The measurements were performed at a constant pressure of around one atmosphere, while varying the gap size between two parallel plane tungsten electrodes between 1??m and 100??m. From the measured breakdown voltage curves, the effective yields and the ionization coefficients were derived for both gases. Present data for the ionization coefficients correlate with the data obtained for the breakdown voltage curves measured for fixed 100??m interelectrode separation. The current-voltage characteristics were plotted for the various gap sizes illustrating the role of the field emission effects in the microgaps. Based on the Fowler-Nordheim theory, the enhancement factors were determined. The gap spacing dependence of the field emission current can be explained by the introduction of two ideas, the first being a space charge effect by emitted electrons, and the second a change in the breakdown mechanism. Experimental results, presented here, demonstrate that Townsend phenomenology breaks down when field emission becomes the key mechanism affecting the breakdown and deforming the left hand side of the breakdown voltage curves.
Klas, M.; Matej?ik, �. [Department of Experimental Physics, Comenius University, Mlynskadolina F2, 84248 Bratislava (Slovakia); Radjenovi?, B.; Radmilovi?-Radjenovi?, M. [Institute of Physics, University of Belgrade, P.O. Box 57, 11080 Belgrade (Serbia)
Measurements of the volt-ampere characteristics and the breakdown voltages of direct-current helium and hydrogen discharges in microgaps
NASA Astrophysics Data System (ADS)
The discharge phenomena for micro meter gap sizes include many interesting problems from engineering and physical perspectives. In this paper, the authors deal with the experimental and theoretical results of the breakdown voltage and current-voltage characteristics of the direct-current helium and hydrogen discharges. The measurements were performed at a constant pressure of around one atmosphere, while varying the gap size between two parallel plane tungsten electrodes between 1 ?m and 100 ?m. From the measured breakdown voltage curves, the effective yields and the ionization coefficients were derived for both gases. Present data for the ionization coefficients correlate with the data obtained for the breakdown voltage curves measured for fixed 100 ?m interelectrode separation. The current-voltage characteristics were plotted for the various gap sizes illustrating the role of the field emission effects in the microgaps. Based on the Fowler-Nordheim theory, the enhancement factors were determined. The gap spacing dependence of the field emission current can be explained by the introduction of two ideas, the first being a space charge effect by emitted electrons, and the second a change in the breakdown mechanism. Experimental results, presented here, demonstrate that Townsend phenomenology breaks down when field emission becomes the key mechanism affecting the breakdown and deforming the left hand side of the breakdown voltage curves.
Klas, M.; Matej?ik, �.; Radjenovi?, B.; Radmilovi?-Radjenovi?, M.
Tin Whisker Electrical Short Circuit Characteristics Part 2
NASA Technical Reports Server (NTRS)
Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that has a currently unknown probability associated with it. Due to contact resistance electrical shorts may not occur at lower voltage levels. In this experiment, we study the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From this data we can estimate the probability of an electrical short, as a function of voltage, given that a free tin whisker has bridged two adjacent exposed electrical conductors. In addition, three tin whiskers grown from the same Space Shuttle Orbiter card guide used in the aforementioned experiment were cross-sectioned and studied using a focused ion beam (FIB).
Courey, Karim J.; Asfour, Shihab S.; Bayliss, Jon A.; Ludwib, Lawrence L.; Zapata, Maria C.
Graded electrical breakdown method for obtaining excellent ohmic contact on nonpolar (11\\bar{2}0) p-GaN
NASA Astrophysics Data System (ADS)
The graded electrical breakdown (EBD) method was introduced to obtain ohmic contact on nonpolar (11\\bar{2}0) a-plane p-GaN surfaces. The graded EBD method, by which the electrical stress voltage could be increased up to 50 V in the Ni/SiO2/p-GaN structure, produced an ohmic contact with a specific resistance of 1.47 � 10?3 ? cm2 without any sudden degradation in the contact. Secondary ion mass spectroscopy measurements revealed that the ohmic contact was due to gallium vacancies generated near the SiO2/p-GaN interface. Current�voltage-temperature measurements exhibited an insensitive temperature dependence of the contact resistance, indicating predominant tunneling transport at the contact.
Gil, Youngun; Choi, Yunju; Song, Keun Man; Kim, Hyunsoo
CHARACTERISTICS OF IMPULSIVE NOISE IN ELECTRICITY SUBSTATIONS Qingshan Shan1
CHARACTERISTICS OF IMPULSIVE NOISE IN ELECTRICITY SUBSTATIONS Qingshan Shan1 , Shahzad firstname.lastname@example.com, website: www.strath.ac.uk ABSTRACT Measurements of noise in an electricity substation are re- ported-voltage electricity substations, has discouraged electricity utility companies from deploying wireless technologies
Atkinson, Robert C
We outline a model of breakdown in RF cavities. In this model, the breakdown trigger is the injection of ions, atoms and clusters into cavities by either of two mechanisms. One mechanism is some combination of fracture and field evaporation of ions from solid surfaces caused by locally high electric fields. The second mechanism, driven by high local current densities,
J. Norem; Z. Insepov; I. Konkashbaev
Parametric study of the vacuum ultraviolet emission and electrical characteristics of a He-Xe microdischarge
NASA Astrophysics Data System (ADS)
Vacuum ultraviolet emission and electrical characteristics of a simple discharge configuration consisting of two planar cylindrical electrodes operated with a dc voltage have been measured over a wide range of He/Xe mixtures and discharge pressures. Breakdown characteristics are consistent with those found in the literature, however current-voltage characteristics and the inferred discharge resistivity suggest the presence of a complex process controlling electron emission at the cathode. Ultraviolet vacuum emission maps of atomic and molecular xenon at 147, 150, and 173 nm, respectively, have been measured as a function of pressure, from 60 to 500 Torr, and gas mixture, from pure Xe to 5% Xe in He. The calibrated ratios of each emission map help to visualize the zones of strongest ultraviolet emission over a wide range of operating conditions. One-dimensional simulations of the breakdown voltage and current discharge have been performed using the commercially available discharge-modeling package SIGLO. Good agreement with experimental results is found in the case of pure helium and xenon, however, in the case of pure xenon, the gas temperature was adjusted (elevated) in order to reproduce the measured current-voltage characteristics. Modeling of the electron number density distribution indicates that the discharge is principally composed of a thick ion sheath near the cathode.
Postel, Olivier B.; Cappelli, Mark A.
Non-Gated Laser Induced Breakdown Spectroscopy Provides a Powerful Segmentation Tool on Concomitant Treatment of Characteristic and Continuum Emission
We demonstrate the application of non-gated laser induced breakdown spectroscopy (LIBS) for characterization and classification of organic materials with similar chemical composition. While use of such a system introduces substantive continuum background in the spectral dataset, we show that appropriate treatment of the continuum and characteristic emission results in accurate discrimination of pharmaceutical formulations of similar stoichiometry. Specifically, our results suggest that near-perfect classification can be obtained by employing suitable multivariate analysis on the acquired spectra, without prior removal of the continuum background. Indeed, we conjecture that pre-processing in the form of background removal may introduce spurious features in the signal. Our findings in this report significantly advance the prior results in time-integrated LIBS application and suggest the possibility of a portable, non-gated LIBS system as a process analytical tool, given its simple instrumentation needs, real-time capability and lack of sample preparation requirements. PMID:25084522
Dasari, Ramachandra Rao; Barman, Ishan; Gundawar, Manoj Kumar
Projected characteristics of hybrid-electric cars
Performance and costs are projected for future hybrid-electric cars in which a small internal-combustion engine (ICE) is added to the basic electric propulsion system to permit unlimited highway range. In most driving these hybrids would be operated in the all-electric mode without use of the ICE, thus providing most of the benefits of electric cars without their range limitation. The
W. F. Hamilton; R. L. Curtis
Analysis of waste electrical and electronic equipment (WEEE) using laser induced breakdown spectroscopy (LIBS) and multivariate analysis.
This study shows the application of laser induced breakdown spectroscopy (LIBS) for waste electrical and electronic equipment (WEEE) investigation. Several emission spectra were obtained for 7 different mobiles from 4 different manufacturers. Using the emission spectra of the black components it was possible to see some differences among the manufacturers and some emission lines from organic elements and molecules (N, O, CN and C2) led to the highest contribution for this differentiation. Some polymeric internal parts in contact with the inner pieces of the mobiles and covered with a special paint presented a strong emission signal for Cr. The white pieces presented mainly Al, Ba and Ti in their composition. Finally, this study developed a procedure for LIBS emission spectra using chemometric strategies and suitable information can be obtained for identification of manufacturer and counterfeit products. In addition, the results obtained can improve the classification for establishing recycling strategies of e-waste. PMID:24209362
�ngel Aguirre, Miguel; Hidalgo, Montserrat; Canals, Antonio; N�brega, Joaquim A; Pereira-Filho, Edenir R
Polarization of the terahertz radiation of uniaxially compressed p germanium at the electrical breakdown of a shallow acceptor impurity
The spectral and polarization investigations of spontaneous terahertz radiation under the conditions of the electrical breakdown of shallow acceptors (gallium) in germanium crystals have been reported. The radiation spectra of crystals uniaxially compressed in the [111] direction at a pressure of about 3 kbar, as well as undeformed crystals, have been measured at T = 5 K using a Fourier spectrometer with step scanning. The polarization of radiation has been estimated for transitions of holes between various states of a shallow acceptor in uniaxially compressed germanium. To identify the observed radiation lines, their experimental energies and polarizations have been compared to the respective calculated values. The spectral lines corresponding to the transitions of holes from the resonance state to the excited states of acceptors have been identified.
Andrianov, A. V., E-mail: email@example.com; Zakhar'in, A. O.; Alekseev, P. S., E-mail: email@example.com [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Kagan, M. S. [Russian Academy of Sciences, Kotel'nikov Institute of Radio Engineering and Electronics (Russian Federation)
Mass analysis of neutral particles and ions released during electrical breakdowns on spacecraft surfaces
NASA Technical Reports Server (NTRS)
A specialized spectrometer was designed and developed to measure the mass and velocity distributions of neutral particles (molecules and molecular clusters) released from metal-backed Teflon and Kapton films. Promising results were obtained with an insulation breakdown initiation system based on a moveable contact touching the insulated surfaces. A variable energy, high voltage pulse is applied to the contact. The resulting surface damage sites can be made similar in size and shape to those produced by a high voltage electron beam system operating at similar discharge energies. The point discharge apparatus was used for final development of several high speed recording systems and for measurements of the composition of the materials given off by the discharge. Results with this apparatus show evolution of large amounts of fluorocarbon fragments from discharge through Teflon FEP, while discharges through Kapton produce mainly very light hydrocarbon fragments at masses below about 80 a.m.u.
Kendall, B. R. F.
Mechanical and Electrical Characteristics of Poly-Lactic Acid which Added Plasticizer
NASA Astrophysics Data System (ADS)
Poly-lactic acid (PLA), a biodegradable plastic, has excellent electrical insulation properties. Being a hard resin, however, PLA is difficult to apply to coated cable. In this study, we blended a plasticizer with PLA to soften it, and examined the effects of the plasticizer on the mechanical and electrical characteristics of PLA. The glass transition temperature (Tg) and the melting point (Tm) had a tendency to decrease with an increase in the amount of plasticizer. With an increase in the amount of plasticizer, the tensile strength had a tendency to decrease and the breaking elongation to increase. As described above, PLA became softer with an increase in the amount of plasticizer. At 25�C, dielectric breakdown strength (EB) was about 5 MV/cm, irrespective of the presence of the plasticizer; the plasticizer showed almost no effect on EB. At 80�C, however, EB had a tendency to increase with an increase in the amount of plasticizer.
Shinyama, Katsuyoshi; Fujita, Shigetaka
Relationship between the structure and electrical characteristics of diamond-like carbon films
To elucidate the relationship between the structure and the electrical characteristics of diamond-like carbon (DLC) films, DLC films were synthesized in a well-controlled glow discharge with the aid of photoelectrons in an argon/methane atmosphere. The dielectric constant and breakdown strength of the films exhibited opposite behaviors, depending on the total pressure during the synthesis. The product of these two values decreased monotonically as the pressure increased. The Raman spectra were analyzed with a Voigt-type formula. Based on the results, the authors propose the �sp{sup 2} cluster model� for the DLC structure. This model consists of conductive clusters of sp{sup 2} carbons surrounded by a dielectric matrix sea of sp{sup 2} carbon, sp{sup 3} carbon, and hydrogen, and indicates that the dielectric constant of the whole DLC film is determined by the balance between the dielectric constant of the matrix and the total size of the clusters, while the breakdown strength is determined by the reciprocal of the cluster size. The model suggests that a high-? DLC film can be synthesized at a middle pressure and consists of well-grown sp{sup 2} clusters and a dense matrix. A low-? DLC film can be synthesized both at low and high pressures. The sp{sup 2} cluster model explains that a low-? DLC film synthesized at low pressure consists of a dense matrix and a low density of sp{sup 2} clusters, and exhibits a high breakdown strength. On the other hand, a low-? film synthesized at high pressure consists of a coarse matrix and a high density of clusters and exhibits a low breakdown strength.
Takabayashi, Susumu, E-mail: email@example.com; Otsuji, Taiichi [Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Yang, Meng; Ogawa, Shuichi; Hayashi, Hiroyuki; Je�ko, Radek; Takakuwa, Yuji [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)
Comparison of the Detection Characteristics of Trace Species Using Laser-Induced Breakdown Spectroscopy and Laser Breakdown Time-of-Flight Mass Spectrometry.
The rapid and precise element measurement of trace species, such as mercury, iodine, strontium, cesium, etc. is imperative for various applications, especially for industrial needs. The elements mercury and iodine were measured by two detection methods for comparison of the corresponding detection features. A laser beam was focused to induce plasma. Emission and ion signals were detected using laser-induced breakdown spectroscopy (LIBS) and laser breakdown time-of-flight mass spectrometry (LB-TOFMS). Multi-photon ionization and electron impact ionization in the plasma generation process can be controlled by the pressure and pulse width. The effect of electron impact ionization on continuum emission, coexisting molecular and atomic emissions became weakened in low pressure condition. When the pressure was less than 1 Pa, the plasma was induced by laser dissociation and multi-photon ionization in LB-TOFMS. According to the experimental results, the detection limits of mercury and iodine in N2 were 3.5 ppb and 60 ppb using low pressure LIBS. The mercury and iodine detection limits using LB-TOFMS were 1.2 ppb and 9.0 ppb, which were enhanced due to different detection features. The detection systems of LIBS and LB-TOFMS can be selected depending on the condition of each application. PMID:25769051
Wang, Zhenzhen; Deguchi, Yoshihiro; Yan, Junjie; Liu, Jiping
Power system characteristics for more electric aircraft
NASA Technical Reports Server (NTRS)
It should not be suprising that more electric aircraft must meet significantly more difficult electrical power system requirements than were considereed when today's power distribution systems were being developed. Electric power, no longer a secondary system, will become a critical element of the primary control system. Functional reliability requiirements will be extremely stringent and can only be met by controlling element redundancy within a distributed power system. Existing electrical systems were not developed to have both the power system and the control/sensing elements distributed and yet meet the requirements of lighting tolerance and high intensity radio frequency (HIRF). In addition, the operation of electric actuators involves high transient loading and reverse energy flows. Such phenomena were also not anticipated when power quality was specified for either 270 vdc or 400 Hertz ac power systems. This paper will expand upon the issues and discuss some of the technologies involved in their resolution.
Hansen, Irving G.
For long cables or equipment with large capacitance it is not always possible to conduct high voltage withstand at tests at 60 Hz due to limitations in charging currents of the power supply. Very low frequency (typically at a frequency of 0.1 Hz) has been used for conventional cables as a way of getting around the charging current limitation. For superconducting grid applications the same issues apply. However there is very little data at cryogenic temperatures on how materials perform at low frequency compared to 60 Hz and whether higher voltages should be applied when performing a high voltage acceptability test. Various materials including G10 (fiberglass reinforced plastic or FRP), Cryoflex (a tape insulation used in some high temperature superconducting cables), kapton (commonly used polyimide), polycarbonate, and polyetherimide, and in liquid nitrogen alone have been tested using a step method for frequencies of 60 Hz, 0.1 Hz, and dc. The dwell time at each step was chosen so that the aging factor would be the same in both the 60 Hz and 0.1 Hz tests. The data indicated that, while there is a small frequency dependence for liquid nitrogen, there are significant differences for the solid materials studied. Breakdown data for these materials and for model cables will be shown and discussed.
Sauers, Isidor [ORNL; Tuncer, Enis [ORNL; Polyzos, Georgios [ORNL; James, David Randy [ORNL; Ellis, Alvin R [ORNL; Pace, Marshall O [ORNL
For long cables or equipment with large capacitance it is not always possible to conduct high voltage withstand tests at 60 Hz due to limitations in charging currents of the power supply. Very low frequency (typically at a frequency of 0.1 Hz) has been used for conventional cables as a way of getting around the charging current limitation. For superconducting grid applications the same issues apply. However there is very little data at cryogenic temperatures on how materials perform at low frequency compared to 60 Hz and whether higher voltages should be applied when performing a high voltage acceptability test. Various materials including G10 (fiberglass reinforced plastic or FRP), Cryoflex (a tape insulation used in some high temperature superconducting cables), kapton (commonly used polyimide), polycarbonate, and polyetherimide, and in liquid nitrogen alone have been tested using a step method for frequencies of 60 Hz, 0.1 Hz, and dc. The dwell time at each step was chosen so that the aging factor would be the same in both the 60 Hz and 0.1 Hz tests. The data indicated that, while there is a small frequency dependence for liquid nitrogen, there are significant differences for the solid materials studied. Breakdown data for these materials and for model cables will be shown and discussed.
Sauers, I.; Tuncer, E.; Polizos, G.; James, D. R.; Ellis, A. R.; Pace, M. O. [Applied Superconductivity Group, Fusion Energy Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)
For long cables or equipment with large capacitance it is not always possible to conduct high voltage withstand tests at 60 Hz due to limitations in charging currents of the power supply. Very low frequency (typically at a frequency of 0 1 Hz) has been used for conventional cables as a way of getting around the charging current limitation For superconducting grid applications the same issues apply. However there is very little data at cryogenic temperatures on how materials perform at low frequency compared to 60 Hz and whether higher voltages should be applied when performing a high voltage acceptability test. Various materials including G 10 (fiberglass reinforced plastic or FRP), Cryoflex (TM) (a tape insulation used in some high temperature superconducting cables), kapton (commonly used polyimide), polycarbonate, and polyetherimide, and in liquid nitrogen alone have been tested using a step method for frequencies of 60 Hz, 0.1 Hz, and dc The dwell time at each step was chosen so that the aging factor would be the same in both the 60 Hz and 0 I Hz tests. The data indicated that, while there is a small frequency dependence for liquid nitrogen, there are significant differences for the solid materials studied. Breakdown data for these materials and for model cables will be shown and discussed.
Sauers, I. [Oak Ridge National Laboratory (ORNL); Tuncer, E. [Oak Ridge National Laboratory (ORNL); Polizos, G. [Oak Ridge National Laboratory (ORNL); James, D. R. [Oak Ridge National Laboratory (ORNL); Ellis, A. R. [Oak Ridge National Laboratory (ORNL); Pace, M. O. [Oak Ridge National Laboratory (ORNL)
Electric field mediated breakdown of thin liquid films separating microscopic emulsion droplets
NASA Astrophysics Data System (ADS)
The authors present a microfluidic technique for electrically induced breakup of thin films formed between microscopic emulsion droplets. The method involves creating a stationary film at the intersection of two microchannels etched onto a glass substrate. After stabilizing the film, a ramped potential is applied across it. The electrical stresses developed at the film interfaces lead to its rupture above a threshold potential. The potential difference at which the film ruptures assesses the film stability. This approach is employed to demonstrate how surfactant (lecithin) adsorption imparts stability to an ultrathin oil film formed between two water droplets.
Mostowfi, Farshid; Khristov, Khristo; Czarnecki, Jan; Masliyah, Jacob; Bhattacharjee, Subir
Effect of tree channel conductivity on electrical tree shape and breakdown in XLPE cable insulation samples
The results of an investigation into electrical tree growth in XLPE cable insulation using an embedded needle electrode are reported for a range of voltages from 9 kV rms to 27 kV rms. The partial discharge (PD) activity and tree structures were measured simultaneously throughout the tree growth and the trees were recorded from initiation up to and including the
Xiangrong Chen; Yang Xu; Xiaolong Cao; S. J. Dodd; L. A. Dissado
The strip dielectric breakdown model
This paper reports on the analysis of the strip dielectric breakdown (DB) model for an electrically impermeable crack in a piezoelectric medium based on the general linear constitutive equations. The DB model assumes that the electric field in a strip ahead of the crack tip is equal to the dielectric breakdown strength, which is in analogy with the classical Dugdale
Electric propulsion - characteristics, applications, and status
NASA Technical Reports Server (NTRS)
A comparative review of the principles of ion thruster and chemical rocket operations is presented. The 30cm mercury ion thruster development and the specifications imposed on it by the Solar Electric propulsion System program are discussed. The 30cm thruster operating range, efficiency, wear out lifetime, and interface requirements are described.
Maloy, J. E.; Dulgeroff, C. R.; Poeschel, R. L.
Non-Gated Laser Induced Breakdown Spectroscopy Provides a Powerful Segmentation Tool on Concomitant Treatment of Characteristic and Continuum Emission
We demonstrate the application of non-gated laser induced breakdown spectroscopy (LIBS) for characterization and classification of organic materials with similar chemical composition. While use of such a system introduces ...
Myakalwar, Ashwin Kumar
REVIEWS OF TOPICAL PROBLEMS: Fast ionisation waves under electrical breakdown conditions
An analysis of experimental and theoretical investigations is the basis of this state-of-art review of models of fast ionisation waves (FIWs) and of characteristics and properties of these waves. The attention is concentrated on waves with the maximum possible velocities of 109-2�1010 cm s-1 when the amplitudes of voltage pulses are 20-300 kV. At low and moderate pressures the reduced
L. M. Vasilyak; S. V. Kostyuchenko; N. N. Kudryavtsev; I. V. Filyugin
The impact of different alkali ion concentrated hollow glass microspheres on the electrical breakdown mechanism of syntactic foam
This paper deals with the experimental investigation on syntactic foam, a new composite insulation material consisting of an epoxy resin matrix filled with hollow glass microspheres. The investigations carried out focus on the impact of the glass composition of the microspheres on the dc breakdown field strength of syntactic foam. Two different breakdown test procedures are used to analyze the
Andrey Mashkin; Anja Strauchs; Armin Schnettler; Arne Lunding
Understanding the thermal, mechanical and electrical properties of epoxy nanocomposites
In the present work, the electrical, mechanical and thermal properties of epoxy nanocomposite materials were studied. The electrical insulation characteristics were analyzed through short time breakdown voltage test, accelerated electrical ageing test, and by tracking test. The breakdown voltage increases with increase in nano-clay content up to 5wt%, under AC and DC voltages. The volume resistivity, permittivity and tan(?) of
R. Sarathi; R. K. Sahu; P. Rajeshkumar
The Effect of an Fe-doped GaN Buffer on off-State Breakdown Characteristics in AlGaN\\/GaN HEMTs on Si Substrate
An Fe-doped GaN buffer layer was employed in the growth of AlGaN\\/GaN high-electron mobility transistors (HEMTs) on Si substrates. In order to investigate the effects of an Fe-doped GaN buffer on OFF-state breakdown characteristics, HEMT devices with an Fe-doped GaN buffer on Si substrates were fabricated along with conventional devices utilizing an unintentionally doped GaN buffer on Si substrates. The
Young Chul Choi; Milan Pophristic; Ho-Young Cha; Boris Peres; Michael G. Spencer; Lester F. Eastman
Electrical Characteristic Study of a Hybrid PEMFC and Ultracapacitor System
This paper presents the characteristic study of a clean hybrid power supply system combining proton exchange membrane fuel cell (PEMFC) as the main power source and ultracapacitor (UC) as the energy storage unit. Unlike the conventional fuel-cell hybrid system with power conditioning unit, the study investigated the electrical characteristic of the PEMFC and UC hybrid system without dc\\/dc converter. As
Junbo Jia; Gucheng Wang; Yew Thean Cham; Youyi Wang; Ming Han
Tin Whisker Electrical Short Circuit Characteristics. Part 2
NASA Technical Reports Server (NTRS)
Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that has an unknown probability associated with it. Note however that due to contact resistance electrical shorts may not occur at lower voltage levels. In our first article we developed an empirical probability model for tin whisker shorting. In this paper, we develop a more comprehensive empirical model using a refined experiment with a larger sample size, in which we studied the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From the resulting data we estimated the probability distribution of an electrical short, as a function of voltage. In addition, the unexpected polycrystalline structure seen in the focused ion beam (FIB) cross section in the first experiment was confirmed in this experiment using transmission electron microscopy (TEM). The FIB was also used to cross section two card guides to facilitate the measurement of the grain size of each card guide's tin plating to determine its finish.
Courey, Karim J.; Asfour, Shihab S.; Onar, Arzu; Bayliss, Jon A.; Ludwig, Lawrence L.; Wright, Maria C.
Filamentary model of dielectric breakdown
A dielectric breakdown model based on the phenomenological description of the nucleation and growth of filaments is proposed. This description involves different characteristic times according to the interfacial or bulk nature of the growth processes. The resulting time to breakdown distribution presents Weibull or bimodal shape according to the relative values of those characteristic times. In particular, the variation in
S. Blonkowski
Electrical properties and humidity sensor characteristics of lead hydroxyapatite material
NASA Astrophysics Data System (ADS)
Crystalline lead hydroxyapatite is obtained by direct precipitation from aqueous solution, the method being easy, fast and reproducible. The synthesis route which does not involve sodium salts or sulfates makes the material suitable for applications in catalysis. The electrical characteristics of lead hydroxyapatite material treated at different temperatures, made us focus on the analysis of the influence of water vapors upon the electrical characteristics. Thus, the electrical response to humidity adsorptive processes of lead hydroxyapatite material suggested us to analyze the material characteristics in terms of its use as a humidity sensor. The hydrophilic properties of lead hydroxyapatite material are reflected especially in high sensitivity and reduced time of response of the humidity sensors but also in long time of recovery, which suggests that Pb10(PO4)6(OH)2 material can be used for humidity sensors specialized in monitoring fluctuating humidity environments.
Tudorache, Florin; Petrila, Iulian; Popa, Karin; Catargiu, Ana Maria
Influence of oxygen content on the structural and electrical characteristics of thin neodymium oxide gate dielectrics
NASA Astrophysics Data System (ADS)
The structural properties and electrical characteristics of thin Nd2O3 gate oxides were deposited on silicon substrates by reactive rf sputtering. The structural and morphological features of these films were studied, as a function of the growth conditions (three various argon-to-oxygen flow ratios: 20/5, 15/10, and 12.5/12.5 and temperature from 600to800�C), by x-ray diffraction, atomic force microscopy, and x-ray photoelectron spectroscopy. It is found that Nd2O3 dielectrics with a 12.5/12.5 ratio condition annealed at 700�C exhibit a thinner capacitance equivalent thickness and excellent electrical properties, including the electric breakdown field, the interface trap density, the hysteresis, and frequency dispersion in the capacitance-voltage curves. This condition is suggested to the reduction of the interfacial SiO2 and silicate formation, and the small of surface roughness due to the optimization of oxygen in the metal oxide film.
Pan, Tung-Ming; Lee, Jian-Der; Yeh, Wen-Wei
Improvement of breakdown and current collapse characteristics of GaN HEMT with a polarization-graded AlGaN buffer
NASA Astrophysics Data System (ADS)
A GaN HEMT with a polarization-graded AlGaN buffer is performed by two-dimensional analysis of drift-diffusion simulations. The bulk trap-induced current collapse of the proposed structure is effectively restrained in contrast to that of conventional HEMTs with a GaN or AlGaN buffer, resulting from the fact that the high and flat back-barrier altitude in the proposed structure prevents the two-dimensional electron gas (2DEG) from spilling over from the channel, with the reduction of hot carriers injecting into the buffer followed by trapping in deep acceptor-like levels. Simultaneously, the off-state breakdown voltage is remarkably enhanced, due to the strong electric breakdown field of the polarization-graded AlGaN buffer and the restraint of the buffer leakage current. In addition, the relationship between the off-state breakdown voltage and the thickness of the polarization-graded AlGaN buffer is analyzed.
Li, Chuanhao; Li, Zhonghui; Peng, Daqing; Ni, Jinyu; Pan, Lei; Zhang, Dongguo; Dong, Xun; Kong, Yuechan
Material dependent dielectric breakdown model
Dielectric breakdown in ceramics and composites has previously been determined by the dielectric breakdown model, dependent only on the electric field strength at a certain point and intermolecular distance in a lattice. This does not take into account quantum aspects of the lattice structure into account. The present model takes into account quantum variations of particles in conjunction with different
Khalil Arshak; Ivor Guiney; Edward Forde
Gas breakdown driven by L band short-pulse high-power microwave
High power microwave (HPM) driven gas breakdown is a major factor in limiting the radiation and transmission of HPM. A method that HPM driven gas breakdown could be obtained by changing the aperture of horn antenna is studied in this paper. Changing the effective aperture of horn antenna can adjust the electric field in near field zone, leading to gas breakdown. With this method, measurements of air and SF{sub 6} breakdowns are carried out on a magnetically insulated transmission-line oscillators, which is capable of generating HPM with pulse duration of 30 ns, and frequency of 1.74 GHz. The typical breakdown waveforms of air and SF{sub 6} are presented. Besides, the breakdown field strengths of the two gases are derived at different pressures. It is found that the effects of air and SF{sub 6} breakdown on the transmission of HPM are different: air breakdown mainly shortens the pulse width of HPM while SF{sub 6} breakdown mainly reduces the peak output power of HPM. The electric field threshold of SF{sub 6} is about 2.4 times larger than that of air. These differences suggest that gas properties have a great effect on the transmission characteristic of HPM in gases.
Yang Yiming; Yuan Chengwei; Qian Baoliang [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)
Gas breakdown driven by L band short-pulse high-power microwave
NASA Astrophysics Data System (ADS)
High power microwave (HPM) driven gas breakdown is a major factor in limiting the radiation and transmission of HPM. A method that HPM driven gas breakdown could be obtained by changing the aperture of horn antenna is studied in this paper. Changing the effective aperture of horn antenna can adjust the electric field in near field zone, leading to gas breakdown. With this method, measurements of air and SF6 breakdowns are carried out on a magnetically insulated transmission-line oscillators, which is capable of generating HPM with pulse duration of 30 ns, and frequency of 1.74 GHz. The typical breakdown waveforms of air and SF6 are presented. Besides, the breakdown field strengths of the two gases are derived at different pressures. It is found that the effects of air and SF6 breakdown on the transmission of HPM are different: air breakdown mainly shortens the pulse width of HPM while SF6 breakdown mainly reduces the peak output power of HPM. The electric field threshold of SF6 is about 2.4 times larger than that of air. These differences suggest that gas properties have a great effect on the transmission characteristic of HPM in gases.
Yang, Yi-Ming; Yuan, Cheng-Wei; Qian, Bao-Liang
A relationship between statistical time to breakdown distributions and pre-breakdown negative differential resistance at nanometric scale
Using an ultra-high vacuum Conductive atomic force microscopy (C-AFM) current voltage, pre-breakdown negative differential resistance (NDR) characteristics are measured together with the time dependent dielectric breakdown (TDDB) distributions of Si/SiON (1.4 and 2.6?nm thick). Those experimental characteristics are systematically compared. The NDR effect is modelled by a conductive filament growth. It is showed that the Weibull TDDB statistic distribution scale factor is proportional to the growth rate of an individual filament and then has the same dependence on the electric field. The proportionality factor is a power law of the ratio between the surfaces of the CAFM tip and the filament's top. Moreover, it was found that, for the high fields used in those experiments, the TDDB acceleration factor as the growth rate characteristic is proportional to the Zener tunnelling probability. Those observations are discussed in the framework of possible breakdown or forming mechanism.
Foissac, R. [STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles Cedex (France); Univ. Grenoble Alpes, LTM, F-38000 Grenoble, France and CNRS, LTM, F-38000 Grenoble (France); Blonkowski, S.; Delcroix, P. [STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles Cedex (France); Kogelschatz, M. [Univ. Grenoble Alpes, LTM, F-38000 Grenoble, France and CNRS, LTM, F-38000 Grenoble (France)
A relationship between statistical time to breakdown distributions and pre-breakdown negative differential resistance at nanometric scale
NASA Astrophysics Data System (ADS)
Using an ultra-high vacuum Conductive atomic force microscopy (C-AFM) current voltage, pre-breakdown negative differential resistance (NDR) characteristics are measured together with the time dependent dielectric breakdown (TDDB) distributions of Si/SiON (1.4 and 2.6 nm thick). Those experimental characteristics are systematically compared. The NDR effect is modelled by a conductive filament growth. It is showed that the Weibull TDDB statistic distribution scale factor is proportional to the growth rate of an individual filament and then has the same dependence on the electric field. The proportionality factor is a power law of the ratio between the surfaces of the CAFM tip and the filament's top. Moreover, it was found that, for the high fields used in those experiments, the TDDB acceleration factor as the growth rate characteristic is proportional to the Zener tunnelling probability. Those observations are discussed in the framework of possible breakdown or forming mechanism.
Foissac, R.; Blonkowski, S.; Kogelschatz, M.; Delcroix, P.
Characteristics of electric parameters in aluminium alloy MAO coating process
Characteristics of electric parameters in the microarc oxidation (MAO) process of aluminium alloy at constant voltage were studied by a homemade data collecting system. The experimental results show that (1) the variations of the cathodic and anodic current amplitudes and the effective working current reflect obviously five different stages in the course of treatment and (2) variations of the dynamic
B H Long; H H Wu; B Y Long; J B Wang; N D Wang; X Y L�; Z S Jin; Y Z Bai
On the electrical characteristics of complementary metamaterial resonators
In this letter, a method to obtain the electrical characteristics of complementary split ring resonators (CSRRs) coupled to planar transmission lines is presented. CSRRs have been recently proposed by some of the authors as new constitutive elements for the synthesis of metamaterials with negative effective permittivity, and they have been applied to the fabrication of metamaterial-based circuits in planar technology.
Jordi Bonache; Marta Gil; Ignacio Gil; Joan Garc�a-Garc�a; Ferran Mart�n
Electrical and gas-dynamic characteristics of an electric-arc gas heater
An investigation and generalization are made of the volt ampere characteristics and thermal efficiency of a dc electric arc heater in a vortex layout with a power of 300 kW with a mixing chamber and lateral discharge of the untwisted jet. The heater operates in the area of ascending volt ampere characteristics. The installation which was developed was used for
A. B. Ambrazevicius; P. Yu. Valatkevicius; R. M. Kezelis; R. A. Juskevicius
We outline a model of breakdown in RF cavities. In this model, the breakdown trigger is the injection of ions, atoms and clusters into cavities by either of two mechanisms. One mechanism is some combination of fracture and field evaporation of ions from solid surfaces caused by locally high electric fields. The second mechanism, driven by high local current densities, is localized Ohmic heating at grain boundaries and defects. Field evaporation and fracturing are similar processes, both driven by the high tensile stresses in the electric field that occur at local electric fields of {approx}10{sup 10} V/m, which have been measured in a number of experimental environments. We also outline how ions can be injected into cavities in the presence of large RF electric fields. The model can explain most of the behavior seen in a variety of cavities at different frequencies without assuming that melting or gas emission occurs at breakdown sites. This model may also be relevant to DC vacuum breakdown.
Norem, J.; Insepov, Z.; Konkashbaev, I.
NASA Astrophysics Data System (ADS)
We outline a model of breakdown in RF cavities. In this model, the breakdown trigger is the injection of ions, atoms and clusters into cavities by either of two mechanisms. One mechanism is some combination of fracture and field evaporation of ions from solid surfaces caused by locally high electric fields. The second mechanism, driven by high local current densities, is localized Ohmic heating at grain boundaries and defects. Field evaporation and fracturing are similar processes, both driven by the high tensile stresses in the electric field that occur at local electric fields of �10 10 V/m, which have been measured in a number of experimental environments. We also outline how ions can be injected into cavities in the presence of large RF electric fields. The model can explain most of the behavior seen in a variety of cavities at different frequencies without assuming that melting or gas emission occurs at breakdown sites. This model may also be relevant to DC vacuum breakdown.
Norem, J.; Insepov, Z.; Konkashbaev, I.
High field breakdown of narrow quasi uniform field gaps in vacuum
NASA Astrophysics Data System (ADS)
The challenge in vacuum microelectronic device design is to be able to stress a given micrometric gap to relatively high voltages without threat of a breakdown, which, in effect could destroy the device. In order to obtain basic vacuum insulation data related to the regime of vacuum microelectronics, the prebreakdown and breakdown characteristics of narrow gaps in the range of 3-25 ?m were extensively investigated. The observed prebreakdown current was related to field emission from atomic scale microprotrusions or planar emission sites; the emission from these sites eventually produces breakdown. A single spark breakdown caused damage to both the anode and cathode. The dc glow discharge conditioning in air improved the insulation capability of narrow gaps (3-25 ?m) significantly. The breakdown strength of a 5 ?m gap after conditioning was as high as 5�108 V/m, which is the highest value reported in literature for broad area electrodes. It is shown that the electric field evaporation of metal ions from the electrode surface at an electric field E?1010 V/m is able to instigate breakdown of the gap even under high vacuum conditions. Electric field evaporation can occur both at the cathode and anode surfaces to create the breakdown conditions. The breakdown data obtained in the micrometric gap regime is very valuable in the design of field emission displays and other vacuum microelectronic devices.
Muzykov, P. G.; Ma, Xianyun; Cherednichenko, D. I.; Sudarshan, T. S.
Basic Studies on Chaotic Characteristics of Electric Power Market Price
NASA Astrophysics Data System (ADS)
Recently, deregulation and reform of electric power utilities have been progressing in many parts of the world. In Japan, partial deregulation has been started from generation sector since 1995 and partial deregulation of retail sector is executed through twice law revisions. Through the deregulation, because electric power is traded in the market and its price is always fluctuated, it is important for the electric power business to analyze and predict the price. Although the price data of the electric power market is time series data, it is not always proper to analyze by the linear model such as ARMA because the price sometimes changes suddenly. Therefore, in this paper, we apply the methods of chaotic time series analysis, one of non-linear analysis methods, and investigate the chaotic characteristics of the system price of JEPX.
Takeuchi, Yuya; Miyauchi, Hajime; Kita, Toshihiro
We outline a model of rf breakdown. Breakdown can be triggered by two mechanisms, one is fracture of the surface produced by tensile stress produced by the electric field, the second is Ohmic heating at grain boundaries and defects at very high current densities. We show how this model follows from measurements of local electronic fields using electron field emission, and show how the model applies to the operating conditions of a variety of rf structures. This model may have some relevance to superconducting rf and DC structures.
Norem, J.; Insepov, Z.; High Energy Physics
Probing and modeling voltage breakdown in vacuum
NASA Astrophysics Data System (ADS)
Voltage breakdown limits many technologies that rely on strong electric fields. Although many kinds of voltage breakdown have been well-explained, voltage breakdown in vacuum---the sudden transition from vacuum insulation to vacuum arc---remains relatively poorly understood. Despite the importance of vacuum insulation, technology has hardly improved breakdown voltages in the last ninety years. This work describes experiments in vacuum breakdown, as well as computer simulations of the initial stages of breakdown. A better understanding of voltage breakdown could particularly benefit particle accelerators used for high energy physics experiments and radiation sources, which require the highest attainable electric fields in the microwave resonators that accelerate particles. Despite some differences, voltage breakdown in microwave resonators shares some features with breakdown in DC vacuum gaps (diodes). In both cases, the localized adsorption of gas around an electron emission-source (e.g., field emission) could lead to breakdown. Analytical calculation shows that breakdown occurs when the product of the gas density and emission current exceed a critical value. Voltage breakdown in vacuum results from the interaction of the electric field and the electrodes. Using a scanning electron microscope, with energy dispersive x-ray spectroscopy (EDX) and Auger electron spectroscopy (AES) to identify surface constituents, we found that breakdown occurs often at the site of foreign particles on the cathode, usually leaving only a very small trace of the original material. At the breakdown site we frequently find small craters, surrounded by a large starburst-shaped pattern; surface analysis suggests that during breakdown, ions bombard the surface within the starburst region and sputter away surface contaminants and oxides. In general, particulate contamination on the cathode determines the breakdown voltage, independent of the cathode material or the thickness of the insulating surface oxide; however, the oxide thickness does change the nature of the starburst and the damage done to the surface during breakdown.
Werner, Gregory Richard
Effects of activation by proton irradiation on silicon particle detector electric characteristics
After irradiation with 7 and 9 MeV protons, activation-induced effects were encountered in measurements of current-voltage (IV) and capacitance-voltage (CV) characteristics for Czochralski and float-zone grown silicon particle detectors prepared on printed circuit boards with copper electrodes. With the present detector construction, the {sup 30}Si(p,n){sup 30}P and {sup 63}Cu(p,n){sup 63}Zn reactions induce dominant interference in such measurements. The daughter nuclides are positron emitters with half-lives of 2.5 and 38.5 min, respectively, and the slowing down of the emitted positrons generates a significantly large concentration of electron-hole pairs in the detector volume increasing the leakage current level and decreasing the breakdown voltage. The observed time-dependent characteristics were verified by modeling the activation of the detector structure and the resulting leakage current. As a result, the electrical measurements cannot be performed immediately after irradiation due to silicon activation, and, generally, materials becoming easily activated should be avoided in the detector concept.
Vaeyrynen, S.; Raeisaenen, J.; Tikkanen, P. [Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 University of Helsinki (Finland); Kassamakov, I. [Department of Micro and Nanosciences, Helsinki University of Technology, P.O. Box 3000, FI-02015 TKK (Finland); Tuominen, E. [Helsinki Institute of Physics, University of Helsinki, P.O. Box 64, FI-00014 University of Helsinki (Finland)
Obtaining DC and AC isothermal electrical characteristics for RF MOSFET
NASA Astrophysics Data System (ADS)
In this paper we demonstrate a new and simple approach to obtain isothermal electrical characteristics of metal oxide field effect transistor (MOSFET) from conventional non-isothermal measurements. DC and continuous wave (CW) S-parameter measurements are performed at different chuck temperatures (Tchuck). Knowing the thermal resistance (RTH) of the device the variation of DC and AC characteristic due to self-heating can be de-embedded and all the isothermal DC data and AC data above isothermal frequency can be determined. The method is validated by comparing the results with pulsed DC and pulsed RF measurements and found to be in good agreements.
Sahoo, A. K.; Fregonese, S.; Scheer, P.; Celi, D.; Juge, A.; Zimmer, T.
Breakdown of organic insulators
NASA Technical Reports Server (NTRS)
Solar cells and their associated electrical interconnects and leads were encapsulated in transparent elastomeric materials. Their purpose in a photovoltaic module, one of the most important for these elastomeric encapsulation materials, is to function as electrical insulation. This includes internal insulation between adjacent solar cells, between other encapsulated electrical parts, and between the total internal electrical circuitry and external metal frames, grounded areas, and module surfaces. Catastrophic electrical breakdown of the encapsulant insulation materials or electrical current through these materials or module edges to external locations can lead to module failure and can create hazards to humans. Electrical insulation stability, advanced elastomeric encapsulation materials are developed which are intended to be intrinsically free of in-situ ionic impurities, have ultralow water absorption, be weather-stable (UV, oxygen), and have high mechanical flexibility. Efforts to develop a method of assessing the life potential of organic insulation materials in photovoltaic modules are described.
Cuddihy, E. F.
Electrical characteristics of mammalian cells on porous supports
NASA Astrophysics Data System (ADS)
The quantification of epithelial barrier functions by measuring the trans-epithelial electrical resistance (TER) and using the Electric Cell-substrate Impedance Sensing (ECIS) has been complicated by the current flowing inside the narrow space underneath cells. This thesis work, by examining the electrical characteristics of epithelial cells on porous supports, is aimed to tackle this problem. A mathematical model has been constructed to quantify the impedance from the various sources within a cell/electrode system. This model presents three cell-related parameters, alpha, Rb and Cm: alpha stands for the impedance contribution from the above-mentioned current underneath cells, Rb is an equivalent representation of epithelial barrier functions and Cm denotes the capacitive impedance of cell membranes. Analysis of the three parameters as well as the electrode impedance (Z e) has revealed two experimental approaches to reduce or eliminate the complication of alpha to the deduction of Rb: lowering alpha down to zero or lowering both Ze and alpha. The experimental realization of the first approach has been studied by examining the electrical characteristics of the African green monkey kidney (BS-C-1) and Madin-Darby canine kidney (MDCK-II) cells on porous filters of mixed esters of cellulose or nitrocellulose. A unique setup featuring a plastic/filter/plastic triple-layer structure was constructed to measure the impedance of cells on filters. With the extremely low alpha, all the electrical characteristics can be explained by using an equivalent circuit and Rb can be directly obtained from the resistance difference in the low frequency range. The second approach has been experimentally investigated by examining the electrical characteristics of BS-C-1 cells on porous/rough electrodes, i.e. the gold ECIS electrodes electrochemically coated with conducting polypyrrole/heparin composites or platinum black. Ze and alpha, especially the former, were found to be significantly lowered, which greatly reduces the effect of alpha and yields many new impedance features. Rb can be also directly obtained in a different way from that for the solely lowered alpha on the non-conducting porous filters.
Chen, Guo
Dielectric breakdown weathering of the Moon's polar regolith
NASA Astrophysics Data System (ADS)
Galactic cosmic rays and solar energetic particles (SEPs) can charge the Moon's subsurface, a process expected to be particularly important in the polar regions. Experiments have shown that sufficient fluences (i.e., time-integrated fluxes) of energetic charged particles can cause dielectric breakdown, in which the electric field rapidly vaporizes small, filamentary channels within a dielectric. Lunar regolith has both the characteristics and, in some polar locations, the environment needed to make breakdown likely. We combine the Jet Propulsion Laboratory proton fluence model with temperature measurements from the Lunar Reconnaissance Orbiter's (LRO's) Diviner instrument and related temperature modeling to estimate how often breakdown occurs in the polar regions. We find that all gardened regolith within permanently shadowed regions (PSRs) has likely experienced up to 2�106 SEP events capable of causing breakdown, while the warmest polar regions have experienced about 2 orders of magnitude fewer events. We also use measurements from the Cosmic Ray Telescope for the Effects of Radiation on LRO to show that at least two breakdown-inducing events may have occurred since LRO arrived at the Moon in 2009. Finally, we discuss how such "breakdown weathering" may increase the percentage of fine and monomineralic grains within PSRs; explain the presence of so-called "fairy castle" regolith structures; and contribute to other low-albedo features detected by LRO's Lyman Alpha Mapping Project, possibly establishing a correlation between these features and the average temperatures within craters that are only partly in permanent shadow.
Jordan, A. P.; Stubbs, T. J.; Wilson, J. K.; Schwadron, N. A.; Spence, H. E.
NASA Technical Reports Server (NTRS)
The topics concerning the Center for Space Construction (CSC) space construction breakdown structure are presented in viewgraph form. It is concluded that four components describe a task -- effecting, information gathering, analysis, and regulation; uncertainties effect the relative amount of information gathering and analysis that occurs; and that task timing requirements drive the 'location in time' of cognition.
Pavlich, Jane
Electrical power generation characteristics of PZT piezoelectric ceramics.
The electrical power generation characteristics of Mn-doped PZT ceramics responding to slow mechanical stress as well as to impact stress have been investigated. Although both the slow and impact stresses induce a reversible electrical response, the generation properties are distinctly different. Slow stress releases two output current peaks with opposite directions, responding to the increasing and decreasing part of the stress, respectively. However, impact stress produces a nearly one-directional signal. The output charge and energy by slow stress are found to be two orders of magnitude higher than that produced by impact stress. This work shows that the energy conversion efficiency of piezoelectric ceramics strongly depends on the method of stress application. PMID:18244261
Xu, C N; Akiyama, M; Nonaka, K; Watanabe, T
Post-breakdown secondary discharges at the electrode/dielectric interface of a cylindrical barrier discharge
NASA Astrophysics Data System (ADS)
The electrical breakdown characteristics of a double-walled cylindrical dielectric barrier discharge (DBD) lamp with a neon buffer gas under pulsed voltage excitation have been investigated. Following the formation of plasma in the main discharge gap, we have observed secondary breakdown phenomena at the inner and outer mesh electrode/dielectric interfaces under specific operating conditions. Plasma formation at these interfaces is investigated by monitoring the Ozone production rate in controlled flows of ultra high purity oxygen together with the overall electrical voltage-charge characteristics of the lamp. The results show that this secondary breakdown only occurs after the main discharge plasma has been established, and that significant electrical power may be dissipated in generating these spurious secondary plasmas. The results are important with regards to optimising the design and identifying efficient operating regimes of DBD based devices that employ mesh-type or wire/strip electrodes.
Carman, Robert; Ward, Barry; Kane, Deborah
Electrical characteristics of amorphous iron-tungsten contacts on silicon
NASA Technical Reports Server (NTRS)
The electrical characteristics of amorphous Fe-W contacts have been determined on both p-type and n-type silicon. The amorphous films were obtained by cosputtering from a composite target. Contact resistivities of 1 x 10 to the -7th and 2.8 x 10 to the -6th were measured on n(+) and p(+) silicon, respectively. These values remain constant after thermal treatment up to at least 500 C. A barrier height of 0.61 V was measured on n-type silicon.
Finetti, M.; Pan, E. T.-S.; Nicolet, M.-A.; Suni, I.
Phase formation, sintering behavior, and electrical characteristics of NASICON compounds
The dependence of phase formation, sintering behavior, and electrical characteristics of Sodium Superionic Conductor (NASICON) compounds on sintering temperature, time, and cooling process was investigated. In the von Alpen-type composition Na3.2Zr1.3Si2.2P0.8O10.5, ZrO2 second phase is in thermal equilibrium with crystalline NASICON and liquid phase above 1320�C, and when cooled through 1260�1320�C, the crystalline NASICON was formed by reaction between the
Hee-Bog Kang; N.-H. Cho
Electrical discharge machining characteristics of metal matrix composites
This paper reports experimental investigations of the effect of machining parameters (discharge current, pulse-on time, pulse-off time, voltage) on the machining feed rate and surface roughness during wire electrical discharge machining (WEDM) of metal matrix composite AlSi7Mg\\/SiC and AlSi7Mg\\/Al2O3. Generally, the machining characteristics of WEDM metal matrix composites are similar to those which occur in the base material (AlSi7Mg aluminium
M. Rozenek; J. Kozak; L. D; K. ?ubkowski
A modified berman model for the prediction of time-dependent dielectric breakdown (TDDB) characteristics of low-k\\/ULK interconnect dielectrics from dual-voltage ramp dielectric breakdown (DVRDB) test
We present a modified Berman model that relates breakdown voltage distributions, from dual voltage ramp dielectric breakdown (DVRDB) test, to the distribution of time-to-fail (TTF) during constant voltage stress (CVS) conditions, assuming that dielectric failure behavior under a constant voltage stress follows the square-root E-model. The methodology presented in this work demonstrates a fast and very effective way of extracting
Tae-Young Jeong; Seunghee Oh; Miji Lee; Seungman Choi; A. T. Kim
Numerical analysis of dielectric breakdown in polypropylene film based on thermal and electronic composite breakdown model
DC electrical breakdown of polypropylene film was studied experimentally and theoretically. The temperature region was divided into two regions, and qualitative analysis of experimental results suggested an electronic breakdown in the low-temperature region and a thermal process in the high-temperature region. A novel breakdown model was proposed by introducing the electronic-breakdown criterion with thickness dependence in the bulk into the
M. Fukuma; M. Nagao; M. Kosaki
Linear dielectric-breakdown electrostatics
The dielectric breakdown of solids is a problem of great practical and theoretical interest. It is the electrical analog of the fracture of solids under applied loads. In the case of fracture, the reigning theory for linear elastic materials is linear elastic fracture mechanics. This paper develops the analogous theory, linear dielectric-breakdown electrostatics, based on a Griffith-like energy-balance calculation applied
E. J. Garboczi
High-resolution measurements of the electric field at the streamer arrival to the cathode: a unification of the streamer-initiated gas-breakdown mechanism.
A time-correlated single-photon counting technique was used to verify the formation of a cathode-directed streamer inside the narrow cathode region following the interpulse phase of regular negative corona Trichel pulses in ambient air. A purely experimental approach was used to determine the spatiotemporal development of the electric field during the Trichel pulse rise with an extremely high resolution of 10 ?m and tens of picoseconds. The results confirm the positive-streamer mechanism for Trichel pulse formation and provide supportive evidence for the hypothesis that the formation of a primary cathode-directed streamer occurs always in any streamer-initiated breakdown and prebreakdown phenomena associated with cathode spot formation. PMID:23214836
Hoder, Tom�; Cern�k, Mirko; Paillol, Jean; Loffhagen, Detlef; Brandenburg, Ronny
High-resolution measurements of the electric field at the streamer arrival to the cathode: A unification of the streamer-initiated gas-breakdown mechanism
NASA Astrophysics Data System (ADS)
A time-correlated single-photon counting technique was used to verify the formation of a cathode-directed streamer inside the narrow cathode region following the interpulse phase of regular negative corona Trichel pulses in ambient air. A purely experimental approach was used to determine the spatiotemporal development of the electric field during the Trichel pulse rise with an extremely high resolution of 10 ?m and tens of picoseconds. The results confirm the positive-streamer mechanism for Trichel pulse formation and provide supportive evidence for the hypothesis that the formation of a primary cathode-directed streamer occurs always in any streamer-initiated breakdown and prebreakdown phenomena associated with cathode spot formation.
Hoder, Tom�; ?ern�k, Mirko; Paillol, Jean; Loffhagen, Detlef; Brandenburg, Ronny
Characteristics of ecto-ATPase of Xenopus oocytes and the inhibitory actions of suramin on ATP breakdown.
Ecto-ATPase activity of Xenopus oocytes was studied by measuring the production of inorganic phosphate (Pi) from the breakdown of extracellular ATP. Enzyme activity involved Ca2+/Mg(2+)-dependent and Ca2+/Mg(2+)-independent dephosphorylation of ATP. Ca2+/Mg(2+)-dependent ecto-ATPase was active over a limited range of 0.01-1.0 mM ATP, while Ca2+/Mg(2+)-independent ATPase activity was active over a range of 0.1-30 mM ATP. Total enzyme activity was insensitive to changes in buffer pH (pH 7.0-9.0), but increased in a relatively linear manner with: (1) time of reaction (0-90 min), (2) number of cells (1-20 oocytes), and (3) temperature (10-37 degrees C). Ecto-ATPase activity was unaffected by ouabain (100 microM), sodium azide (100 microM), and oligomycin (5 micrograms/ml) (as inhibitors of endo-ATPases) and beta-glycerophosphate (10 mM) and p-nitrophenyl phosphate (10 mM) (as inhibitors of non-specific alkaline phosphatase). Total ecto-ATPase activity was reduced significantly in defolliculated oocytes, suggesting that the enzyme was located mainly on the enveloping follicle cell layer. The range order of preferential substrates was: ATP>GTP, ITP, UTP, CTP, TTP, 2-methylthioATP>ADP, 2-methylthioADP, AMP>alpha, beta-methylene ATP, beta, gamma-methylene ATP, in the presence of divalent ions (where G is guanosine, I is inosine, U is uridine, C is cytidine and T is ribosylthymine). The P2-purinoceptor antagonist suramin [8-(3-benzamido-4-methylbenzamido)napthalene-1,3,5-trisul phonic acid), 100 microM] significantly inhibited total ecto-ATPase activity; this inhibition was competitive for the Ca2+/Mg(2+)-dependent enzyme.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7761265
Ziganshin, A U; Ziganshina, L E; King, B E; Burnstock, G
Electrical Characteristics of Top-Down ZnO Nanowire Transistors Using Remote Plasma ALD
Top-down fabrication is used to produce ZnO nanowires by remote plasma atomic layer deposition over a $\\\\hbox{SiO}_{2}$ pillar and anisotropic dry etching. Nanowire field-effect transistors (FETs), with channel lengths in the range of 1.3�18.6 $\\\\mu\\\\hbox{m}$, are then fabricated using these 80 nm $ \\\\times$ 40 nm nanowires. Measured electrical results show n-type enhancement behavior and a breakdown voltage $\\\\geq$75 V
S. M. Sultan; K. Sun; O. D. Clark; T. B. Masaud; Q. Fang; R. Gunn; J. Partridge; M. W. Allen; P. Ashburn; H. M. H. Chong
Proposed RF Breakdown Studies at the AWA
A study of breakdown mechanism has been initiated at the Argonne Wakefield Accelerator (AWA). Breakdown may include several factors such as local field enhancement, explosive electron emission, Ohmic heating, tensile stress produced by electric field, and others. The AWA is building a dedicated facility to test various models for breakdown mechanisms and to determine the roles of different factors in the breakdown. We plan to trigger breakdown events with a high-powered laser at various wavelengths (IR to UV) to determine the role of explosive electron emission in the breakdown process. Another experimental idea follows from the recent work on a Schottky-enabled photoemission in an RF photoinjector [1] that allows us to determine in situ the field enhancement factor on a cathode surface. Monitoring the field enhancement factor before and after the breakdown can shed some light on a number of observations such as the crater formation process.
Antipov, S.; Conde, M.; Gai, W.; Power, J.G.; Spentzouris, L.; Yusof, Z.; /Argonne /IIT, Chicago; Dolgashev, V.; /SLAC
We describe breakdown in 805 MHz rf accelerator cavities in terms of a number of mechanisms. We devide the breakdown process into three stages: (1) we model surface failure using molecular dynamics of fracture caused by electrostatic tensile stress, (2) we model the ionization of neutrals responsible for plasma initiation and plasma growth using a particle in cell code, and (3) we model surface damage by assuming a process similar to unipolar arcing. Although unipolar arcs are strictly defined with equipotential boundaries, we find that the cold, dense plasma in contact with the surface produces very small Debye lengths and very high electric fields over a large area. These high fields produce strong erosion mechanisms, primarily self sputtering, compatible with the crater formation that we see. Results from the plasma simulation are included as a guide to experimental verification of this model.
Insepov, Zeke; Huang, Dazhang; Mahalingam, Sudhakar; Veitzer, Seth
AC and Impulse Breakdown of Liquid Nitrogen at 77 K for Quasi-Uniform Field Gaps
Liquid nitrogen (LN2) is commonly used both as a coolant and electrical insulation in high temperature superconductor (HTS) equipment for power applications. Hence it is necessary to know the electrical breakdown characteristics of LN2 under a variety of conditions which are likely to be encountered in practice. The ac breakdown and positive and negative polarity breakdown results for lightning impulse (1.2 microsecond rise time/50 microsecond fall time) are presented for LN2 using sphere to plane electrode geometry for sphere diameters of 50.8 and 101.6 mm over a gap range of 1 to 15 mm. Voltages up to 110 kVrms were studied for ac breakdown and up to 500-kV peak for impulse. In this work both the ac and impulse breakdown voltages scale approximately with distance over the limited gaps studied which is indicative of a quasi-uniform (near- uniform) electric field between sphere and plane. These measurements were conducted in a dewar which could be pressurized from 1 to 2 bar absolute which greatly reduces the spontaneous formation of bubbles that can occur in open LN2 bath experiments and thus potentially reduce the breakdown strength. Results from the pressurized system and near atmospheric pressure similar to an open bath are compared.
James, David Randy [ORNL; Sauers, Isidor [ORNL; Ellis, Alvin R [ORNL; Schwenterly, S W [ORNL; Tuncer, Enis [ORNL; Pleva, Ed [Waukesha Electric Systems, Waukesha, WI
Plasma breakdown and combustion ignition
NASA Astrophysics Data System (ADS)
Ignition in chemically reactive media and electrical breakdown are among the most widely used transient processes. The two phenomena operate together during electrical (and laser) spark ignition of combustible gases. Analogs between them show up in Semenov's early (1920's) work on chemical chain reactions and on thermal breakdown of dielectrics. Both breakdown and ignition are under active study today. The energy source for breakdown is an applied electric field, and that for ignition, an applied flux of heat or radicals. Electrons and intermediate reactants are the corresponding driver particles, with a velocity difference that implies a vast difference in the growth rates for the two processes. Combustion takes place in a fuel-oxidant mixture, and an ignited reaction can proceed until the fuel or oxidant is depleted, while a (non-afterglow, non-fusion) plasma is sustained by an external power supply. The energy balance, propagation behavior, and time evolution of some specific forms of plasma breakdown and chemical ignition are further compared in order to illustrate their physical nature.
McNeill, Donald H.; Tran, Phuoc
The effect of the inversion channel at the AlN/Si interface on the vertical breakdown characteristics of GaN-based devices
NASA Astrophysics Data System (ADS)
GaN-on-Si transistors attract increasing interest for power applications. However, the breakdown behavior of such devices remains below theoretical expectations, for which the Si substrate is typically made responsible. In this work, the effect of the thickness of an aluminum nitride buffer layer on the vertical breakdown voltage, measured relative to a grounded silicon substrate, has been investigated. A voltage-polarity-dependent breakdown mechanism has been observed. It has been found that the breakdown in the positive bias voltage regime is initiated by carrier injection, for which the carriers originate from an inversion channel formed between the epitaxial layers and the p-silicon substrate. TCAD simulations have confirmed the proposed explanations, and suggest that appropriate modification of the electronic structure at the AlN/silicon interface could significantly improve the vertical breakdown voltage.
Yacoub, H.; Fahle, D.; Finken, M.; Hahn, H.; Blumberg, C.; Prost, W.; Kalisch, H.; Heuken, M.; Vescan, A.
Conduction and breakdown mechanismsin transformer oil
With a fast coaxial test setup using high speed electrical and optical diagnostics, prebreakdown current pulses and shadowgraphy images are measured for direct current (dc) breakdown in Univolt 61 transformer oil. Also, dc currents across the gap are measured using a high sensitivity electrometer. The conduction and breakdown mechanisms in transformer oil as function of applied hydrostatic pressures are quantified.
Michael Butcher; Andreas A. Neuber; Michael D. Cevallos; James C. Dickens; Hermann Krompholz
Dielectric breakdown patterns and active walker model
Simulations based on the active walker model are used successfully to reconstruct the dielectric breakdown patterns observed in a cell with parallel-plate electrodes. Different types of patterns can be obtained with suitable parameters. These parameters correspond to the electrical and environmental conditions during the breakdown.
Chia-Rong Sheu; Ching-Yen Cheng; Ru-Pin Pan
Thermal dielectric breakdown with cylindrical electrodes
NASA Technical Reports Server (NTRS)
Solutions to the equations of thermal breakdown are computed for cylindrial electrodes with different boundary conditions. The development of the electric field and the temperature distributions are followed as functions of time, consequent on the application of a constant interelectrode voltage. The implications for possible breakdown by modes other than thermal are briefly discussed.
Beers, B. L.; Odwyer, J. J.
Electrical characteristics of amorphous molybdenum-nickel contacts to silicon
NASA Technical Reports Server (NTRS)
The electrical characteristics of sputtered, amorphous Mo-Ni contacts have been measured on both p- and n-type Si, as functions of composition (30, 54, and 58 at. percent Mo). The contact resistivity on both p(+) and n(+) Si is in the 0.00000 ohm sq cm range. The barrier height for as-deposited samples varies between phi-bp = 0.47-0.42 V on p-type Si and between phi-bn = 0.63-0.68 V on n-type Si, as the composition of the amorphous layer goes from Ni-rich to Mo-rich. The sum phi-bp + phi-bn always equals 1.12 V, within experimental error. After thermal treatment at 500 C for 1/2 h, the contact resistivity changes by a factor of two or less, while the barrier height changes by at most approximately 0.05 V. In light of these results, the amorphous Mo-Ni film makes good ohmic contacts to silicon.
Kung, K. T.-Y.; Nicolet, M.-A.; Suni, I.
Improved breakdown voltage and RF characteristics in AlGaN/GaN high-electron-mobility transistors achieved by slant field plates
NASA Astrophysics Data System (ADS)
We experimentally demonstrate the efficacy of using slant field plates (field plates with the plate-to-channel gap gradually increasing away from the gate edge) on the breakdown voltage. We develop a new fabrication process using a multi-step SiCN film such that both slant and conventional field plates are fabricated simultaneously. Consequently, we fabricate 230-nm-gate AlGaN/GaN HEMTs with several types of field plates. The slant field plate increases the breakdown voltage by 66% more than that of the conventional field plate. The advantages of using slant field plates to increase the breakdown voltage are experimentally confirmed for the first time.
Kobayashi, Kengo; Hatakeyama, Shinya; Yoshida, Tomohiro; Yabe, Yuhei; Piedra, Daniel; Palacios, Tom�s; Otsuji, Taiichi; Suemitsu, Tetsuya
Breakdown voltage of zinc and magnesium vapours
NASA Astrophysics Data System (ADS)
In this paper the findings of a study into the electrical breakdown of zinc and magnesium metal vapours are reported. The interest in the breakdown of these vapours lies in the fact that there is a growing interest in producing zinc-magnesium coated articles using physical vapour deposition. For commercial scale operations which require a high power input, a disturbance by electrical breakdown of the metal vapour is unacceptable. Hence, knowledge of the breakdown voltage and pressure relation of these elements is essential in the engineering of a set-up. To determine the breakdown of these metal vapours, a Knudsen effusion cell is built. It is proven that the flow through the Knudsen cell does not change the minimum breakdown voltage or location of this minimum, and is a reliable apparatus for determining the zinc and magnesium vapour data. The outcome of the experiments show that the minimum breakdown for zinc is in agreement with the reported data in the literature, around 350 V. Magnesium has a much lower minimum breakdown voltage than that found for zinc, around 110 V. Furthermore, the locations of the minimum breakdown voltages of both zinc and magnesium are found at around 4-7 Pa m and 1.5 Pa m respectively.
Zoestbergen, E.; Commandeur, C.; Maalman, T.
Analysis of Electrical Characteristics of Thin Film Photovoltaic Cells
NASA Technical Reports Server (NTRS)
Solar energy is the most abundant form of energy in many terrestrial and extraterrestrial environments. Often in extraterrestrial environments sunlight is the only readily available form of energy. Thus the ability to efficiently harness solar energy is one of the ultimate goals in the design of space power systems. The essential component that converts solar energy into electrical energy in a solar energy based power system is the photovoltaic cell. Traditionally, photovoltaic cells are based on a single crystal silicon absorber. While silicon is a well understood technology and yields high efficiency, there are inherent disadvantages to using single crystal materials. The requirements of weight, large planar surfaces, and high manufacturing costs make large silicon cells prohibitively expensive for use in certain applications. Because of silicon s disadvantages, there is considerable ongoing research into alternative photovoltaic technologies. In particular, thin film photovoltaic technologies exhibit a promising future in space power systems. While they are less mature than silicon, the better radiation hardness, reduced weight, ease of manufacturing, low material cost, and the ability to use virtually any exposed surface as a substrate makes thin film technologies very attractive for space applications. The research group lead by Dr. Hepp has spent several years researching copper indium disulfide as an absorber material for use in thin film photovoltaic cells. While the group has succeeded in developing a single source precursor for CuInS2 as well as a unique method of aerosol assisted chemical vapor deposition, the resulting cells have not achieved adequate efficiencies. While efficiencies of 11 % have been demonstrated with CuInS2 based cells, the cells produced by this group have shown efficiencies of approximately 1 %. Thus, current research efforts are turning towards the analysis of the individual layers of these cells, as well as the junctions between them, to determine the cause of the poor yields. As a student of electrical engineering with some material science background, my role in this research is to develop techniques for analyzing the electrical characteristics of the CuInS2 cells. My first task was to design a shadow mask to be used to place molybdenum contacts under a layer of CuInS;! in order to analyze the contact resistance between the materials. In addition, I have also analyzed evaporated aluminum top contacts and have tested various methods of increasing their thicknesses in order to decrease series resistance. More recently I have worked with other members of the research group in reviving a vertical cold-wall reactor for experimentation with CuInS2 quantum dots. As part of that project, I have improved the design for a variable frequency and pulse width square wave generator to be used in driving the precursor injection process. My task throughout the remainder of my tenure is to continue to analyze and develop tools for the analysis of electrical properties of the CuInS2 cells with the ultimate goal of discovering ways to improve the efficiency of our photovoltaic cells. Traditionally, photovoltaic cells are based on a single crystal silicon absorber. While The research group lead by Dr. Hepp has spent several years researching copper indium
Kasick, Michael P.
A new approach to analyze the degradation and breakdown of thin SiO 2 films under static and dynamic electrical stress
A test procedure, which provokes the oxide breakdown in two stages, is proposed to analyze the degradation and breakdown of thin SiO 2 films. This procedure can partially overcome the problems associated with dynamic tests and allows a direct comparison of static and dynamic stresses. The analysis of the data obtained using the proposed method has allowed us to conclude
R. Rodriguez; M. Nafria; E. Miranda; J. Sune; X. Aymerich
Nanolaminates: increasing dielectric breakdown strength of composites.
Processable, low-cost, high-performance hybrid dielectrics are enablers for a vast array of green technologies, including high-temperature electrical insulation and pulsed power capacitors for all-electric transportation vehicles. Maximizing the dielectric breakdown field (E(BD)), in conjunction with minimization of leakage current, directly impacts system performance because of the field's quadratic relationship with electrostatic energy storage density. On the basis of the extreme internal interfacial area and ultrafine morphology, polymer-inorganic nanocomposites (PNCs) have demonstrated modest increases in E(BD) at very low inorganic loadings, but because of insufficient control of the hierarchal morphology of the blend, have yielded a precipitous decline in E(BD) at intermediate and high inorganic volume fractions. Here in, we demonstrate that E(BD) can be increased up to these intermediate inorganic volume fractions by creating uniform one-dimensional nanocomposites (nanolaminates) rather than blends of spherical inorganic nanoparticles and polymers. Free standing nanolaminates of highly aligned and dispersed montmorillonite in polyvinyl butyral exhibited enhancements in E(BD) up to 30 vol % inorganic (70 wt % organically modified montmorillonite). These relative enhancements extend up to five times the inorganic fraction observed for random nanoparticle dispersions, and are anywhere from two to four times greater than observed at comparable volume fraction of nanoparticles. The breakdown characteristics of this model system suggested a trade-off between increased path tortuosity and polymer-deficient structural defects. This implies that an idealized PNC morphology to retard the breakdown cascade perpendicular to the electrodes will occur at intermediate volume fractions and resemble a discotic nematic phase where highly aligned, high-aspect ratio nanometer thick plates are uniformly surrounded by nanoscopic regions of polymer. PMID:22301841
Fillery, Scott P; Koerner, Hilmar; Drummy, Lawrence; Dunkerley, Erik; Durstock, Michael F; Schmidt, Daniel F; Vaia, Richard A
A theoretical approach to electric breakdown behaviour and effective secondary emission coefficient in gas discharge process between two parallel-plane disk electrodes
The gas discharge characteristics are seriously influenced by the effective secondary electron-emission coefficient ({gamma}{sub eff}) originally defined by Townsend. A theoretical approach has been proposed for the determination of variation of this coefficient as a function of the geometrical parameter d/R (the ratio of inter-electrode distance to electrode radius) in the most practical range of 0.08{<=}d/R{<=}1.90. Two geometrical factors g{sub i} and g{sub p}, which are attributed to ion-induced and photon-induced terms, respectively, were introduced to the effective gamma in parallel-plane arrangement. The factors were theoretically derived and hence the effective gamma and the breakdown voltage for a specified geometrical parameter, such as d/R=0.16, were obtained. Then, the effective gamma and the Paschen curves for various geometrical parameters such as d/R=0.32, 0.63, 1.27, and 1.90 were theoretically reproduced. The obtained results showed quite a good agreement with those reported by other researchers and verified that the proposed g{sub i} and g{sub p} have properly been introduced and derived.
Noori, H.; Ranjbar, A. H. [Faculty of Physics, Shahid Bahonar University of Kerman, Kerman (Iran, Islamic Republic of)
Characteristics of parallel electric fields in the downward current region of the aurora
Characteristics of parallel electric fields in the downward current region of the aurora L downward current region. The observed parallel electric fields have amplitudes reaching nearly 1 V, Colorado 80309 Received 19 December 2001; accepted 7 May 2002 Direct measurements of parallel electric
California at Berkeley, University of
Dielectric breakdown in continuous models of metal-loaded dielectrics
We develop two- and three-dimensional models for breakdown of metal-loaded dielectrics based on the breakdown of random arrays of perfectly conducting cylinders and spheres embedded in a uniform dielectric and placed in a uniform external electric field. We determine the breakdown field, breakdown-path geometry, and dielectric constant as a function of metal packing fraction. The computer solution of Laplace's equation
Mark F. Gyure; Paul D. Beale
Bulk charging and breakdown in electron-irradiated polymers
NASA Technical Reports Server (NTRS)
High energy electron irradiations were performed in an experimental and theoretical study of ten common polymers. Breakdowns were monitored by measuring currents between the electrodes on each side of the planar samples. Sample currents as a function of time during irradiation are compared with theory. Breakdowns are correlated with space charge electric field strength and polarity. Major findings include evidence that all polymers tested broke down, breakdowns remove negligible bulk charge and no breakdowns are seen below 20 million V/m.
Frederickson, A. R.
Linear dielectric-breakdown electrostatics
NASA Astrophysics Data System (ADS)
The dielectric breakdown of solids is a problem of great practical and theoretical interest. It is the electrical analog of the fracture of solids under applied loads. In the case of fracture, the reigning theory for linear elastic materials is linear elastic fracture mechanics. This paper develops the analogous theory, linear dielectric-breakdown electrostatics, based on a Griffith-like energy-balance calculation applied to a single conducting crack in an isotropic dielectric medium. Results include the development of the critical field-intensity factor, Kec, and the introduction of a contour-independent line integral, Je, which is analogous to the J integral of linear and nonlinear elastic fracture mechanics. Some discussion of the relation between these results and recent lattice models of dielectric breakdown is given.
Garboczi, E. J.
Electrical Characteristics of Contacts Contaminated with Silver Sulfide Film
Frequently the electrical performance of silver contacts is impaired by the unavoidable growth of a sulfide film on the mating contact surfaces. In the case where one or both of the electrodes are silver, or partly silver, and a silver sulfide film is formed on one or both of the electrodes, the electrical performance is greatly deteriorated and is among
Vortex breakdown incipience: Theoretical considerations
NASA Technical Reports Server (NTRS)
The sensitivity of the onset and the location of vortex breakdowns in concentrated vortex cores, and the pronounced tendency of the breakdowns to migrate upstream have been characteristic observations of experimental investigations; they have also been features of numerical simulations and led to questions about the validity of these simulations. This behavior seems to be inconsistent with the strong time-like axial evolution of the flow, as expressed explicitly, for example, by the quasi-cylindrical approximate equations for this flow. An order-of-magnitude analysis of the equations of motion near breakdown leads to a modified set of governing equations, analysis of which demonstrates that the interplay between radial inertial, pressure, and viscous forces gives an elliptic character to these concentrated swirling flows. Analytical, asymptotic, and numerical solutions of a simplified non-linear equation are presented; these qualitatively exhibit the features of vortex onset and location noted above.
Berger, Stanley A.; Erlebacher, Gordon
Partial Discharge Characteristics of Polymer Nanocomposite Materials in Electrical Insulation: A Review of Sample Preparation Techniques, Analysis Methods, Potential Applications, and Future Trends
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
Izzati, Wan Akmal; Adzis, Zuraimy; Shafanizam, Mohd
Partial discharge characteristics of polymer nanocomposite materials in electrical insulation: a review of sample preparation techniques, analysis methods, potential applications, and future trends.
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
Izzati, Wan Akmal; Arief, Yanuar Z; Adzis, Zuraimy; Shafanizam, Mohd
An Investigation of the Electrical Short Circuit Characteristics of Tin Whiskers
NASA Technical Reports Server (NTRS)
Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that has a currently unknown probability associated with it. Due to contact resistance electrical shorts may not occur at lower voltage levels. In this experiment, we study the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From this data we can estimate the probability of an electrical short, as a function of voltage, given that a free tin whisker has bridged two adjacent exposed electrical conductors. Also, three tin whiskers grown from the same Space Shuttle Orbiter card guide used in the aforementioned experiment were cross-sectioned and studied using a focused ion beam (FIB). The rare polycrystalline structure seen in the FIB cross section was confirmed using transmission electron microscopy (TEM). The FIB was also used to cross section two card guides to facilitate the measurement of the grain size to determine that the tin plating on the card guides had a bright finish.
Courey, Karim J.
Electrical characteristics of Ta2O5 thin films deposited by electron beam gun evaporation
NASA Astrophysics Data System (ADS)
We report electrical characteristics of Ta2O5 films deposited by a simple electron beam gun evaporator. We describe thickness-dependent characteristics for films with thicknesses of 7-130 nm. An equivalent SiO2 thickness of 3.5-4.5 nm for films whose leakage current density at an electric field of 106V/cm is lower than 10-7 A/cm2 is demonstrated.
Mikhelashvili, V.; Eisenstein, G.
Electrical Characteristics of Simulated Tornadoes and Dust Devils
NASA Technical Reports Server (NTRS)
It is well known that tornadoes and dust devils have the ability to accumulate significant, visible clouds of debris. Collisions between sand-like debris species produce different electric charges on different types of grains, which convect along different trajectories around the vortex. Thus, significant charge separations and electric currents are possible, which as the vortex fluctuates over time are thought to produce ULF radiation signatures that have been measured in the field. These electric and magnetic fields may contain valuable information about tornado structure and genesis, and may be critical in driving electrochemical processes within dust devils on Mars. In the present work, existing large eddy simulations of debris-laden tornadoes performed at West Virginia University are coupled with a new debris-charging and advection code developed at Goddard Space Flight Center to investigate the detailed (meter-resolution) fluid-dynamic origins of electromagnetic fields within terrestrial vortices. First results are presented, including simulations of the electric and magnetic fields that would be observed by a near-surface, instrument-laden probe during a direct encounter with a tornado.
Zimmerman, Michael I.; Farrell, William M.; Barth, E. L.; Lewellen, W. S.; Perlongo, N. J.; Jackson, T. L.
~stivity and power The use of electric fields is presently being investigated as a possible method of diverting fish A major problem of this investigatIon is the evaluation of an electric fi~ld as a motivating stimulus characteristics. Appli- cation of pulsed voltaaes to the cell demonstrated a minimum power density below which
Impact of electrical degradation on trapping characteristics of GaN high electron mobility transistors
One of the most deleterious effects of electrical degradation of GaN HEMTs is an increase in carrier trapping and subsequent current collapse. In this work, we have investigated the trapping and detrapping characteristics of GaN HEMTs before and after device degradation through a new current transient analysis methodology. We have found that electrical stress beyond a critical voltage significantly enhances
Jungwoo Joh; Jes�s A. del Alamo
Investigation of Mechanical and Electrical Characteristics for Cracked Conductive Particle in Anisotropic Conductive Adhesive (ACA) Assembly
In an anisotropic conductive adhesive (ACA) assembly, the electrical conduction is usually achieved with the conductive particles between the bumps of integrated circuit (IC) and corresponding conductive tracks on the glass substrate. Fully understanding of the mechanical and electrical characteristics of ACA particles can help to optimize the assembly process and improve the reliability of ACA interconnection. Most conductive particles
Bin Xie; X. Q. Shi; Han Ding
Electrical noise characteristics of a doped silicon microcantilever heater-thermometer
Electrical noise characteristics of a doped silicon microcantilever heater-thermometer Elise A with resistive heater-thermometers,1013 there is a lack of published reports on the electrical noise silicon heater- thermometer cantilevers.12 However, a key difference is that doped silicon heater-thermometers
King, William P.
Measurement of space charge in XLPE insulation under 50 Hz ac electric stresses using the LIPP method
Space charge is believed to play an important role in ac electrical ageing of polymeric insulation, particularly where electrical treeing is the dominant cause of premature failure. The majority of work to date has been on the space charge characteristics under dc electric stresses, whereas work on the dynamics and the role of space charge on electrical breakdown under 50
Y. F. F. Ho; G. Chen; A. E. Davies; S. G. Swingler; S. J. Sutton; R. N. Hampton; S. Hobdell
Microwave gas breakdown in elliptical waveguides
This paper analyzes the microwave gas discharge within elliptical waveguides excited by the fundamental mode. The Rayleigh-Ritz method has been applied to solve the continuity equation. The eigenvalue problem defined by the breakdown condition has been solved and the effective diffusion length of the elliptical waveguide has been calculated, what is used to find the corona threshold. This paper extends the microwave breakdown model developed for circular waveguides and shows the better corona withstanding capabilities of elliptical waveguides. The corona breakdown electric field threshold obtained with the variational method has been compared with the one calculated with the Finite Elements Method, showing excellent agreement.
Koufogiannis, I. D.; Sorolla, E., E-mail: firstname.lastname@example.com; Mattes, M. [�cole Polytechnique F�d�rale de Lausanne, Laboratoire d��lectromagn�tisme et d'Acoustique (LEMA), Station 11, CH-1015 Lausanne (Switzerland)] [�cole Polytechnique F�d�rale de Lausanne, Laboratoire d��lectromagn�tisme et d'Acoustique (LEMA), Station 11, CH-1015 Lausanne (Switzerland)
Electrical and Mechanical Characteristics of Epoxy-Nanoclay Composite
NASA Astrophysics Data System (ADS)
In this study, we investigated the effects of nanoclay additives on the electrical and mechanical properties of diglycidyl ether of bisphenol A (DGEBA) epoxy resin. Epoxy-clay nanocomposites were synthesized using organically modified two montmorillonite clays (MMT) with different interlamellar spacing (31.5 � and 18.5 �). The electrical and mechanical properties of epoxy-clay nanocopomosites were measured with variation of the amount and type of clay. The nanocomposites were found to be homogenous materials although the nanocomposites still have clay aggregates with increasing nanoclay contents. The dielectric constant showed between 3.2 ~ 3.5 and the dielectric loss showed between 3.2 ~ 5.7% in all nanocoposites. The dielectric strength and tensile strength of the 5 wt% Cloisite 15A added epoxy-oclay nanocomposite were 23.9 kV/mm and 86.7 MPa, respectively.
Noh, Hyun-Ji; Nam, Sung-Pill; Lee, Sung-Gap; Ahn, Byeong-Lib; Won, Woo-Sik; Woo, Hyoung-Gwan; Park, Sang-Man
Effect of Electrical Stress on Josephson Tunneling Characteristics of Junctions
Fabrication-induced variations in the critical currents of Josephson junctions significantly affect the performance and yield of complex superconducting integrated circuits. Electrical stress that may develop during plasma processing steps in the fabrication process was initially suggested as a possible cause of these variations. The effect on the Josephson and quasiparticle tunneling properties of Nb\\/Al\\/AlOx\\/Nb junctions with ultrathin AlOx barriers by
Denis Amparo; Sergey K. Tolpygo
Physical characteristics of GE (General Electric) BWR (boiling-water reactor) fuel assemblies
The physical characteristics of fuel assemblies manufactured by the General Electric Company for boiling-water reactors are classified and described. The classification into assembly types is based on the GE reactor product line, the Characteristics Data Base (CDB) assembly class, and the GE fuel design. Thirty production assembly types are identified. Detailed physical data are presented for each assembly type in
R. S. Moore; K. J. Notz
Electrical conductivity and current-voltage characteristics of alumina with or without neutron and electron irradiation
Electrical conductivity and current-voltage characteristics of alumina with or without neutron±voltage (I±V) characteristics of single- and poly- crystal alumina have been carried out both in HFIR (high for non-ohmic behavior is discussed on the basis of the dierence of work function between electrode
Howlader, Matiar R
Temporal characteristics of the pulsed electric discharges in small gaps filled with hydrocarbon oil
NASA Astrophysics Data System (ADS)
In order to understand the role of electrode materials in electrical discharges with micro gaps (<200?�m) 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.
Maradia, U.; Hollenstein, Ch; Wegener, K.
dc breakdown conditioning and breakdown rate of metals and metallic alloys under ultrahigh vacuum
NASA Astrophysics Data System (ADS)
The rf accelerating structures of the Compact Linear Collider (CLIC) require a material capable of sustaining high electric field with a low breakdown rate and low induced damage. Because of the similarity of many aspects of dc and rf breakdown, a dc breakdown study is underway at CERN in order to test candidate materials and surface preparations, and have a better understanding of the breakdown mechanism under ultrahigh vacuum in a simple setup. Conditioning speeds and breakdown fields of several metals and alloys have been measured. The average breakdown field after conditioning ranges from 100MV/m for Al to 850MV/m for stainless steel, and is around 170MV/m for Cu which is the present base-line material for CLIC structures. The results indicate clearly that the breakdown field is limited by the cathode. The presence of a thin cuprous oxide film at the surface of copper electrodes significantly increases the breakdown field. On the other hand, the conditioning speed of Mo is improved by removing oxides at the surface with a vacuum heat treatment, typically at 875�C for 2 hours. Surface finishing treatments of Cu samples only affect the very first breakdowns. More generally, surface treatments have an effect on the conditioning process itself, but not on the average breakdown field reached after the conditioning phase. In analogy to rf, the breakdown probability has been measured in dc with Cu and Mo electrodes. The dc data show similar behavior as rf as a function of the applied electric field.
Descoeudres, A.; Ramsvik, T.; Calatroni, S.; Taborelli, M.; Wuensch, W.
Optical and electrical characteristics of ZnO/Si heterojunction
NASA Astrophysics Data System (ADS)
Self-assembled ZnO nanorods have been synthesized on a seeded Si substrate by a simple chemical bath deposition method at a temperature of 80 �C. Room-temperature photoluminescence analysis revealed material of high optical quality with a low density of defects that can be reduced by post growth annealing. Current-voltage measurements on these devices showed excellent rectification. Junction characteristics were also studied using capacitance-voltage measurements and showed that the junction characteristics are mainly determined by the properties of the p-Si substrate. Based on the energy band diagram and possible interface states at the junction, it was suggested that the current transport in the device is predominantly determined by hopping of charge carriers between localized states through a multi-step tunneling process.
Urgessa, Z. N.; Dobson, S. R.; Talla, K.; Murape, D. M.; Venter, A.; Botha, J. R.
Factors affecting the electrical characteristics of cadmium mercury telluride crystals
NASA Astrophysics Data System (ADS)
The electrical properties of cadmium mercury telluride crystals grown by both a cast-recrystallise and a normal freeze melt growth process have been investigated. Material equilibrated at high temperatures is found to be p-type and the carrier concentration is believed to be determined by native defects. Two models have been considered to explain the carrier concentrations found after low temperature heat treatment of slices in the presence of mercury vapour. These are based on native defects and on residual impurities respectively. It is concluded that for material grown by both growth processes the level of residual impurities is the dominant factor controlling carrier concentration.
Bartlett, B. E.; Capper, P.; Harris, J. E.; Quelch, M. J. T.
Aerodynamic characteristics of sixteen electric, hybrid, and subcompact vehicles
NASA Technical Reports Server (NTRS)
An elementary electric and hybrid vehicle aerodynamic data base was developed using data obtained on sixteen electric, hybrid, and sub-compact production vehicles tested in the Lockheed-Georgia low-speed wind tunnel. Zero-yaw drag coefficients ranged from a high of 0.58 for a boxey delivery van and an open roadster to a low of about 0.34 for a current four-passenger proto-type automobile which was designed with aerodynamics as an integrated parameter. Vehicles were tested at yaw angles up to 40 degrees and a wing weighting analysis is presented which yields a vehicle's effective drag coefficient as a function of wing velocity and driving cycle. Other parameters investigated included the effects of windows open and closed, radiators open and sealed, and pop-up headlights. Complete six-component force and moment data are presented in both tabular and graphical formats. Only limited commentary is offered since, by its very nature, a data base should consist of unrefined reference material. A justification for pursuing efficient aerodynamic design of EHVs is presented.
Kurtz, D. W.
Role of the substrate in the electrical transport characteristics of focused ion beam fabricated nanogap electrode
Precise metallic nanogap structure is fabricated on a glass substrate by using a 30 keV focused Ga ion beam. While investigating the I-V behavior of the nanogap structure, tunneling through the substrate has been found to play a vital role in the electrical transportation process. Substrate breakdown occurs at a certain applied voltage and a metal vapor state is initiated through intense heat generation at the nanogap region. The experimental observation confirms the role of the substrate in the explosion process. Metallic spherical particles are formed during cooling/condensation of the metal vapors or splashing of the liquid droplets showing a wide distribution of size from few tens of nanometers to few microns.
Rajput, Nitul S.; Verma, H. C. [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016 (India); Singh, Abhishek K. [Materials Science Programme, Indian Institute of Technology Kanpur, Kanpur 208016 (India)
Research on Electrical Characteristics of Dielectric Barrier Discharge and Dielectric Barrier Corona Discharge
NASA Astrophysics Data System (ADS)
The dielectric barrier corona discharge (DBCD) in a wire-cylinder configuration and the dielectric barrier discharge (DBD) in a coaxial cylinder configuration are studied. The discharge current in DBD has higher pulse amplitude than in DBCD. The dissipated power and the gas gap voltage are calculated by analyzing the measured Lissajous figure. DBCD has lower gas gap breakdown voltage. The average electric field is about 10-20 kV/cm in gas gap during DBCD, and is 30-40 kV/cm during DBD. In the positive half cycle the DBCD appears as continuous discharge current mode and in negative half cycle it appears as Trichel pulse mode. Under some conditions DBCD can show homogeneous diffuse discharges mode.
Sun, Yanzhou; Zeng, Mi; Cui, Zhiyong
Breakdown phenomena in high power klystrons
In the course of developing new high peak power klystrons at SLAC, high electric fields in several regions of these devices have become an important source of vacuum breakdown phenomena. In addition, a renewed interest in breakdown phenomena for nanosecond pulse, multi-megavolt per centimeter fields has been sparked by recent R and D work in the area of gigawatt RF sources. The most important regions of electrical breakdown are in the output cavity gap area, the RF ceramic windows, and the gun ceramic insulator. The details of the observed breakdown in these regions, experiments performed to understand the phenomena and solutions found to alleviate the problems will be discussed. Recently experiments have been performed on a new prototype R and D klystron. Peak electric fields across the output cavity gaps of this klystron exceed 2 MV/cm. The effect of peak field duration (i.e. pulse width) on the onset of breakdown have been measured. The pulse widths varied from tens of nanoseconds to microseconds. Results from these experiments will be presented. The failure of ceramic RF windows due to multipactor and puncturing was an important problem to overcome in order that our high power klystrons would have a useful life expectancy. Consequently many studies and tests were made to understand and alleviate window breakdown phenomena. Some of the results in this area, especially the effects of surface coatings, window materials and processing techniques and their effects on breakdown will be discussed. Another important source of klystron failure in the recent past at SLAC has been the puncturing of the high voltage ceramic insulator in the gun region. A way of alleviating this problem has been found although the actual cause of the puncturing is not yet clear. The ''practical'' solution to this breakdown process will be described and a possible mechanism for the puncturing will be presented. 9 refs., 5 figs., 3 tabs.
Vlieks, A.E.; Allen, M.A.; Callin, R.S.; Fowkes, W.R.; Hoyt, E.W.; Lebacqz, J.V.; Lee, T.G.
Magnetic control of breakdown: Toward energy-efficient hollow-cathode magnetron discharges
Characteristics of electrical breakdown of a planar magnetron enhanced with an electromagnet and a hollow-cathode structure, are studied experimentally and numerically. At lower pressures the breakdown voltage shows a dependence on the applied magnetic field, and the voltage necessary to achieve the self-sustained discharge regime can be significantly reduced. At higher pressures, the dependence is less sensitive to the magnetic field magnitude and shows a tendency of increased breakdown voltage at the stronger magnetic fields. A model of the magnetron discharge breakdown is developed with the background gas pressure and the magnetic field used as parameters. The model describes the motion of electrons, which gain energy by passing the electric field across the magnetic field and undergo collisions with neutrals, thus generating new bulk electrons. The electrons are in turn accelerated in the electric field and effectively ionize a sufficient amount of neutrals to enable the discharge self-sustainment regime. The model is based on the assumption about the combined classical and near-wall mechanisms of electron conductivity across the magnetic field, and is consistent with the experimental results. The obtained results represent a significant advance toward energy-efficient multipurpose magnetron discharges.
Baranov, O.; Romanov, M. [National Aerospace University 'KhAI', Kharkov, 61070 (Ukraine); Kumar, S. [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield NSW 2070 (Australia); Zong, X. X. [Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China); Ostrikov, K. [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield NSW 2070 (Australia); Plasma Nanoscience - Complex Systems, School of Physics, University of Sydney, Sydney NSW 2006 (Australia)
Structural, optical and electrical characteristics of a new NLO crystal
NASA Astrophysics Data System (ADS)
A new nonlinear optical (NLO) organic crystal 1-[4-({(E)-[4-(methylsulfanyl)phenyl]methylidene}amino)phenyl]ethanone (MMP) has been grown by slow evaporation technique at ambient temperature. The crystal structure of MMP was determined by single crystal X-ray diffraction. MMP crystallizes in non-centrosymmetric monoclinic system with space group P21. The FT-IR spectrum recorded for new crystal confirmed the presence of various functional groups in the material. MMP was found to be thermally stable up to 300 �C. The grown crystal was optically transparent in the wavelength range of 400-1100 nm. The second harmonic generation (SHG) efficiency of the crystal was measured by the classical powder technique using Nd:YAG laser and was found to be 4.13 times more efficient than reference material, urea. Third order nonlinear parameters were measured by employing the Z-scan technique. The laser damage threshold for MMP crystal was determined to be 4.26 GW/cm2. The Brewster angle technique was employed to measure the refractive index of the crystal and the values for green and red wavelengths were found to be 1.35 and 1.33, respectively. The dielectric and electrical measurements were carried out to study the different polarization mechanisms and conductivity of the crystal.
D'silva, E. D.; Krishna Podagatlapalli, G.; Venugopal Rao, S.; Dharmaprakash, S. M.
Ionising radiation and electrical stress on nanocrystal memory cell array
In this work, we have investigated the effects of irradiation and electrical stress of nanocrystal memory cell arrays. Heavy ion irradiation has no or negligible immediate effects on the nanocrystal MOSFET characteristics, and on the programming window of the cells. By electrically stressing irradiated device, we see accelerated oxide breakdown similar to that previously observed on conventional thin gate oxide
A. Cester; A. Gasperin; N. Wrachien; Alessandro Paccagnella; V. Ancarani; Cosimo Gerardi
Electrical characteristics of a seawater MHD thruster. Final report
There is renewed interest in the application of the magnetohydrodynamic (MHD) propulsion concept to marine propulsion. However, there is almost no experimental information concerning the major physical processes which will occur in a seawater MHD propulsion unit, such as (1) the seawater electrolysis process at operational conditions needed for ship propulsion, (2) the effects of bubble formation on the performance of a seawater thruster and (3) the effectiveness of the MHD interaction in seawater. Small scale tests of an MHD type channel but without an applied magnetic field have been carried out to provide information about the first two of these areas (1) seawater electrolysis and (2) the effect of the H2 bubbles generated during the electrolysis of seawater. Current/voltage characteristics were obtained with different electrode materials for current densities up to 0.3 amp/sq cm. The effect of bubble formation on the channel current has been assessed over a range of operating conditions. Long-duration tests to 100 hrs have been made to provide information on electrode durability and long-term operational problems.
Tempelmeyer, K.E.
High breakdown GaN HEMT with overlapping gate structure
GaN high electron mobility transistors (HEMTs) were fabricated using an overlapping-gate technique in which the drain-side edge of the metal gate overlaps on a high breakdown and high dielectric constant dielectric. The overlapping structure reduces the electric field at the drain-side gate edge, thus increasing the breakdown of the device. A record-high three-terminal breakdown figure of 570 V was achieved
N.-Q. Zhang; S. Keller; G. Parish; S. Heikman; S. P. DenBaars; U. K. Mishra
Physical characteristics of GE (General Electric) BWR (boiling-water reactor) fuel assemblies
The physical characteristics of fuel assemblies manufactured by the General Electric Company for boiling-water reactors are classified and described. The classification into assembly types is based on the GE reactor product line, the Characteristics Data Base (CDB) assembly class, and the GE fuel design. Thirty production assembly types are identified. Detailed physical data are presented for each assembly type in an appendix. Descriptions of special (nonstandard) fuels are also reported. 52 refs., 1 fig., 6 tabs.
Moore, R.S.; Notz, K.J.
A mesh reflecting surface with electrical characteristics independent on direction of electric field of incident wave
For large deployable antennas on board satellites, a knitted wire mesh is used as reflecting surface because it is lightweight and elastic due to its knitted structure. The mesh reflecting surface has high reflectivity for the electric field parallel to the wire running direction (Takano, T. et al., 1992). This nature of the mesh, the dependence of reflectivity on the
Amane Miura; Masato Tanaka
Breakdown of transformer oil is affected not only by electrostatic field configurations, but also by many other factors. The latters make it difficult to predict break- down voltage from electrostatic field, as made for air and S F6 gaps. Alternatively, many experimenters tried to express the breakdown stress of oil as a function of stressed oil volume. But, results are
Y. Kawaguchi; H. Murata; M. Ikeda
On dielectric breakdown statistics
In this paper, we investigate the dielectric breakdown data of some insulating materials and focus on the applicability of the two- and three-parameter Weibull distributions. A new distribution function is also proposed. In order to assess the model distribution's trustworthiness, we employ the Monte Carlo technique and, randomly selecting data-subsets from the whole dielectric breakdown data, determine whether the selected
Enis Tuncer; D Randy James; Isidor Sauers; Alvin R Ellis; Marshall O Pace
Generalized dielectric breakdown model
We propose a generalized version of the dielectric breakdown model (DBM) for generic breakdown processes. It interpolates between the standard DBM and its analog with quenched disorder (QDBM), as a temperaturelike parameter is varied. The physics of other well-known fractal growth phenomena such as invasion percolation and the Eden model are also recovered for some particular parameter values. Competition between
R. Cafiero; A. Gabrielli; M. Marsili; M. A. Mu�oz; L. Pietronero
We describe breakdown in 805 MHz rf accelerator cavities in terms of a number of self consistent mechanisms. We divide the breakdown process into three stages: 1) we model surface failure using molecular dynamics of fracture caused by electrostatic tensile stress, 2) we model the ionization of neutrals responsible for plasma initiation and plasma growth using a particle in cell
Zeke Insepov; Jim Norem; Thomas Proslier; Dazhang Huang; Sudhakar Mahalingam; Seth Veitzer
Effects of passivation on breakdown voltage and leakage current of normally-off InAlN/GaN MISHFETs�a simulation study
NASA Astrophysics Data System (ADS)
Effects of passivation on breakdown characteristics of normally-off InAlN/GaN MISHFETs have been investigated via physics based simulations. The product of passivation layer permittivity and thickness is found to dramatically affect breakdown voltage, due to alleviation of peak electric field at the gate edge on the drain side, leading to a much smoother field distribution in the channel. A proposed structure with a 985 nm TiO2 top and 15 nm HfO2 bottom passivation stack exhibits a breakdown at �750 V with leakage current �4 ?A mm?1, showing �15� increase in breakdown voltage compared to the structure without the TiO2 top layer (50 V).
Tang, Chenjie; Shi, Junxia
From physical dielectric breakdown to the stochastic fractal model
We show how the stochastic growth model we have formulated for dielectric breakdown is related to microscopic mechanisms. Beginning with gas discharges we focus on the origin of the stochastic features and the dependence of growth probability on the local electric field. For dielectric breakdown in solid insulators we argue that quenched disorder does not appreciably modify the patterns which
L. Pietronero; H. J. Wiesmann
Relativistic breakdown in planetary atmospheres
In 2003, a new electrical breakdown mechanism involving the production of runaway avalanches by positive feedback from runaway positrons and energetic photons was introduced. This mechanism, which shall be referred to as 'relativistic feedback', allows runaway discharges in gases to become self-sustaining, dramatically increasing the flux of runaway electrons, the accompanying high-energy radiation, and resulting ionization. Using detailed Monte Carlo calculations, properties of relativistic feedback are investigated. It is found that once relativistic feedback fully commences, electrical breakdown will occur and the ambient electric field, extending over cubic kilometers, will be discharged in as little as 2x10{sup -5} s. Furthermore, it is found that the flux of energetic electrons and x rays generated by this mechanism can exceed the flux generated by the standard relativistic runaway electron model by a factor of 10{sup 13}, making relativistic feedback a good candidate for explaining terrestrial gamma-ray flashes and other high-energy phenomena observed in the Earth's atmosphere.
Dwyer, J. R. [Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, Florida 32901 (United States)
Radiation-Induced Modifications of the Electrical Characteristics of Nanocrystal Memory Cells and Arrays
Proton irradiation of nanocrystals memories produces peculiar radiation effects on the electrical characteristics of these devices, owing to their thin tunnel oxide and to the presence of nanocrystals replacing the conventional flash memory floating gate. In this work, we show that the data retention capability is compromised only after high fluences and that irradiated devices do not show accelerated degradation
Alberto Gasperin; Andrea Cester; Nicola Wrachien; Alessandro Paccagnella; Valentina Ancarani; Cosimo Gerardi
Structural properties and electrical characteristics of electron-beam gun evaporated erbium oxide films
Structural properties and electrical characteristics of electron-beam gun evaporated erbium oxide for publication 3 January 2002 We report properties of Er2O3 films deposited on silicon using electron-beam gun to 700 °C.6 The Er2O3 films we describe were deposited by an electron-beam gun EBG evaporation system
Eisenstein, Gadi
Electrical characteristics of Ta2O5 thin films deposited by electron beam gun evaporation
Electrical characteristics of Ta2O5 thin films deposited by electron beam gun evaporation V films deposited by a simple electron beam gun evaporator. We describe thicknessO5 thin films deposited by a simple electron beam gun evaporator which enables versatility
Eisenstein, Gadi
Evaluation of motor characteristics for hybrid electric vehicles using the hardware-in-the-loop concept
If the concept of Hardware-in-the-Loop (HIL) is applied to component testing, characteristic of component of hybrid electric vehicle in real vehicle environment can be evaluated without actually installing that component in real vehicle. In this paper, when commercially available test motor is adopted as a drivetrain of hybrid vehicle, we need to figure out which drive train configuration would be
Sung Chul Oh
Statistical Analysis of the Disturbance Sources characteristics on Hybrid Electric Vehicle
With the wide application of the power electronic devices in hybrid electric vehicle, the electromagnetic environment of the car is getting more and more complex. After analyzing a large amount of real vehicle experimental data, the typical waveforms of the voltage and the frequency-domain characteristics of the common-mode current can be got by the statistical method. In this paper, the
Li Yulong; Wu Zhenjun; Wang Lifang
Electrical Characteristics and Testing Considerations for Gate Oxide Shorts in CMOS ICs
This paper examines the electrical characteristics and testing considerations of gate oxide shorts. Gate oxide shorts will cause increased IDD and in the majority of cases will degrade logic voltage levels and propagation delay times, but may not affect functionality. Stuck-at and functional models are therefore inadequate for testing gate oxide shorts in CMOS ICs unless they are used in
Jerry M. Soden; Charles F. Hawkins
Nonlinear electric field tuning characteristics of yttrium iron garnetlead zirconate titanate microwave resonators
crystals of barium ferrite that have high uniaxial magnetic anisotropy. Lead zirconium titanate PZT or leadNonlinear electric field tuning characteristics of yttrium iron garnetlead zirconate titanate in a bilayer of yttrium iron garnet YIG -lead zirconate titanate PZT . The tuning is facilitated
Srinivasan, Gopalan
Simulation study of electrical dynamic characteristics of lithium-ion battery
The electrical dynamic characteristics of a lithium-ion battery have been simulated by an equivalent circuit, which is derived from the measured impedance. The transient voltage response to the various kinds of applied current waves such as single pulse, single rectangular, triangle, and sawtooth waves is experimentally examined and calculated by using the numerical Laplace transform with the equivalent circuit. The
Kiyonami Takano; Ken Nozaki; Yoshiyasu Saito; Akira Negishi; Ken Kato; Yoshio Yamaguchi
Vortex breakdown over delta wing and its induced turbulent flow
Vortex breakdown over delta wing is simulated by solving Navier-Stokes equations. Iso-surfaces of total pressure and flow parameters along vortex core axis are employed to depict this phenomena. To have an insight into the turbulence characteristics induced by vortex breakdown, iso-surfaces of turbulent kinetic energy and turbulence dissipation rate are employed. The results indicated that, vortex breakdown location moves upstream
Dang Huixue; Yang Zhichun
Electric Characteristics of Hybrid Polymer Membranes Composed of Two Lipid Species
NASA Astrophysics Data System (ADS)
Electric characteristics of hybrid polymer membranes composed of two lipid species were studied, where one lipid species is positively charged in aqueous solution and the other is negatively charged. As a result, it was found that the hybrid membranes responded to taste substances in different ways according to the molar mixing ratio of these two kinds of lipids, and also showed different response characteristics from those of the single-lipid membranes. The membranes with the mixing ratio around 50% exhibited the largest responses to HCl (sourness) and monosodium glutamate (umami). Moreover, good quantitative agreements with the observed data on the response electric potential were obtained using a theory describing both the changes in surface electric potential and surface charge density with taste substances.
Oohira, Koji; Toko, Kiyoshi; Akiyama, Hideyuki; Yoshihara, Hiroshi; Yamafuji, Kaoru
Modelling of the electric characteristic of type II superconductors by means of Ligurian minimization
The electrical behavior of type II superconductors can be characterized--in a first approximation--by a strongly nonlinear (even not univocal) e-j relationship. Numerical modelling is necessary to accede to the local characteristic e-j starting from experimental data; the global characteristic U-I of the sample. Classical methods such as Newton-Raphson might fail in dealing with materials having such a characteristic as superconductors have. The authors thus use an absolutely convergent method based on convex optimization, with the Ligurian as objective function. Numerical modelling shows that the smooth U-I characteristic might be generated by a simple e-j characteristic with a well-defined critical current density. It is shown how this technique may be extended to solve complete Maxwell equations in the most general case.
Vasiliu, S.; Bouillault, F.; Degardin, A.; Kreisler, A. [ESE, Gif sur Yvette (France). Lab. de Genie Electrique de Paris] [ESE, Gif sur Yvette (France). Lab. de Genie Electrique de Paris
Pre-breakdown evaluation of gas discharge mechanisms in microgaps
The individual contributions of various gas discharge mechanisms to total pre-breakdown current in microgaps are quantified numerically. The variation of contributions of field emission and secondary electron emission with increasing electric field shows contrasting behavior even for a given gap size. The total current near breakdown decreases rapidly with gap size indicating that microscale discharges operate in a high-current, low-voltage regime. This study provides the first such analysis of breakdown mechanisms and aids in the formulation of physics-based theories for microscale breakdown.
Semnani, Abbas; Peroulis, Dimitrios [School of Electrical and Computer Engineering, Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States)] [School of Electrical and Computer Engineering, Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Venkattraman, Ayyaswamy; Alexeenko, Alina A. [School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana 47907 (United States)] [School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana 47907 (United States)
Dielectric breakdown mechanism of thin-SiO2 studied by the post-breakdown resistance statistics
The dielectric breakdown mechanism of SiO2 has been discussed on the basis of the experimental results of the post-breakdown resistance (Rbd) distribution. We have noticed for the first time that Rbd of SiO2 in MOS devices is strongly related to the SiO2 breakdown characteristics such as the polarity dependence or the oxide field dependence of Qbd. In this paper, we
Hideki Satake; Akira Toriumi
Steam-zone electrical characteristics for geodiagnostic evaluation of steamflood performance
An essential part of the development of electrical geodiagnostic techniques for mapping thermal recovery processes is understanding the relationship of formation resistivity to the thermal recovery process. As a result of laboratory measurements of a ID steamflood, a preliminary understanding of some of the mechanisms of the electrical resistivity change has been gained. The theory of electrical resistivity of a steamflood is reviewed and used to evaluate the resistivity changes expected. A conceptual electrical model of a steamflood porous reservoir, based on a qualitative description of the fluid zones of an ideal heavy-oil steamflood, is presented. The model assumes that salinity, temperature, and saturation are the important factors controlling resistivity changes and that Archie's law applies. The authors found that the characteristics of each individual reservoir must be considered before the in-situ resistivity changes are predicted and that in-situ resistivity can either increase as a result of steamflooding.
Mansure, A.J. (Sandia National Labs., Albuquerque, NM (USA)); Meldau, R.F. (Dolphin Petroleum Consultants (US))
Electrical characteristics and thermal shock properties of Cu-filled TSV prepared by laser drilling
NASA Astrophysics Data System (ADS)
The electrical characteristics and thermal shock properties of a Through Silicon Via (TSV) for the three dimensional (3D) stacking of a Si wafer were investigated. The TSVs were fabricated on a Si wafer by a laser drilling process. The via had a diameter of 75 �m at the via opening and a depth of 150 �m. A daisy chain was made for testing electrical characteristics, such as R sh (sheet resistance), R c (contact resistance) and Z 0 (characteristic impedance). After Cu filling, a cross section of the via was observed by Field Emission-Scanning Electron Microscopy. The electrical characteristics were measured using a commercial impedance analyzer and probe station, which revealed the values of R sh , R c and Z 0 as 35.5 m?/sq, 25.4 m? and 48.5 ?, respectively. After a thermal shock test of 500 cycles, no cracks were observed between the TSV and Si wafer. This study confirms that the laser drilling process is an effective method for via formation on a Si wafer for 3D integration technology.
Jeong, Il Ho; Jung, Do Hyun; Shin, Kyu Sik; Shin, Dong Sik; Jung, Jae Pil
Electrode surface roughness initiated breakdown in compressed SF6 gas
The effect of electrode roughness on the behaviour of a SF6 gaseous gap is studied analytically in this paper by introducing an elongated protrusion in the form of a fixed small conducting needle on an ideally smooth electrode surface. This effect is discussed by applying the streamer theory of breakdown. The breakdown characteristics for elongated protrusions on the coaxial electrode
S. M. El-Makkawy
Phase-field model for dielectric breakdown in solids Krishna Chaitanya Pitike and Wei Hong*
1 Phase-field model for dielectric breakdown in solids Krishna Chaitanya Pitike and Wei Hong dielectric breakdown and fracture of solids, this paper develops a phase field model for the electric damage of a conductive crack is derived and used to model dielectric breakdown [11]. Considering the one
Hong, Wei
Breakdown of gaseous dielectrics at non-isothermic heating up to 3600 K
Quantitative data on breakdown voltages of non-isothermically heated inert gases at temperatures up to 3600 K are obtained. Existence of polarity effect of breakdown voltages Ubr in uniform electric field at temperatures more than ~1700 K is established. At cathode heating up to specified temperatures breakdown voltages sharply decrease comparing with Ubr at positive polarity of a heating electrode up
Ju. V. Serdjuk; I. V. Bozhko; N. I. Falkovsky
Models for breakdown-resistant dielectric and ferroelectric ceramics
NASA Astrophysics Data System (ADS)
MODELSFOR dielectric breakdown are proposed and analysed, with emphasis on concepts leading to breakdown-resistant materials. The Griffith energy balance is extended to cracks under combined electrical and mechanical loading, and to conductive tubular channels. Breakdown strength for a perfect crystal is estimated by an analogue of the Frenkel model. In a crystal subjected to an electric field the equilibrium displacement of the electron clouds is described by a curve with periodicity of the lattice constant. A theory of breakdown-resistant laminates is proposed on the basis of charge relocation, facilitated by breakdown of the weak layers and the interfaces. A process by which a conducting path grows like a crack in ferroelectric ceramics is discussed, followed by an outline of fields around conducting cracks in piezoelectric ceramics.
Suo, Z.
Ragone characteristics of aqueous mobile batteries and their application in projecting ranges of electric vehicles
NASA Astrophysics Data System (ADS)
A Ragone characteristic is defined as the specific energy available from a battery as a function of the specific power level at which it is discharged. Ragone plots obtained are given for the following electric vehicle propulsion batteries: NiZn, Ni/Fe, improved state of the art lead-acid, a lead-acid designed for hybrid vehicle application, and a standard golf cart battery. It is found that the ragone plots can be used to project the range of an electric vehicle with a particular battery.
Hornstra, F.; Christianson, C. C.; Corp, D. O.; Fredrickson, D.; Gay, E.; Hayes, E. R.; Webster, C. E.; Yao, N. P.
Simulations of avalanche breakdown statistics: probability and timing
NASA Astrophysics Data System (ADS)
Important avalanche breakdown statistics for Single Photon Avalanche Diodes (SPADs), such as avalanche breakdown probability, dark count rate, and the distribution of time taken to reach breakdown (providing mean time to breakdown and jitter), were simulated. These simulations enable unambiguous studies on effects of avalanche region width, ionization coefficient ratio and carrier dead space on the avalanche statistics, which are the fundamental limits of the SPADs. The effects of quenching resistor/circuit have been ignored. Due to competing effects between dead spaces, which are significant in modern SPADs with narrow avalanche regions, and converging ionization coefficients, the breakdown probability versus overbias characteristics from different avalanche region widths are fairly close to each other. Concerning avalanche breakdown timing at given value of breakdown probability, using avalanche material with similar ionization coefficients yields fast avalanche breakdowns with small timing jitter (albeit higher operating field), compared to material with dissimilar ionization coefficients. This is the opposite requirement for abrupt breakdown probability versus overbias characteristics. In addition, by taking band-to-band tunneling current (dark carriers) into account, minimum avalanche region width for practical SPADs was found to be 0.3 and 0.2 ?m, for InP and InAlAs, respectively.
Ng, Jo Shien; Tan, Chee Hing; David, John P. R.
Electrical characteristics of Ni Ohmic contact on n-type GeSn
We report an investigation of the electrical and material characteristics of Ni on an n-type GeSn film under thermal annealing. The current-voltage traces measured with the transmission line method are linear for a wide range of annealing temperatures. The specific contact resistivity was found to decrease with increasing annealing temperature, followed by an increase as the annealing temperature further increased, with a minimum value at an annealing temperature of 350?�C. The material characteristics at the interface layer were measured by energy-dispersive spectrometer, showing that an atomic ratio of (Ni)/(GeSn)?=?1:1 yields the lowest specific contact resistivity.
Li, H.; Cheng, H. H., E-mail: email@example.com [Center for Condensed Matter Sciences and Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 106, Taiwan (China); Lee, L. C.; Lee, C. P. [Center for Nano Science and Technology, National Chiao Tung University, Hsinchu 300, Taiwan (China); Su, L. H.; Suen, Y. W. [Department of Physics and Institute of Nano Science, National Chung Hsing University, Taichung 402, Taiwan (China)
Electrical characteristics of Ni Ohmic contact on n-type GeSn
NASA Astrophysics Data System (ADS)
We report an investigation of the electrical and material characteristics of Ni on an n-type GeSn film under thermal annealing. The current-voltage traces measured with the transmission line method are linear for a wide range of annealing temperatures. The specific contact resistivity was found to decrease with increasing annealing temperature, followed by an increase as the annealing temperature further increased, with a minimum value at an annealing temperature of 350 �C. The material characteristics at the interface layer were measured by energy-dispersive spectrometer, showing that an atomic ratio of (Ni)/(GeSn) = 1:1 yields the lowest specific contact resistivity.
Li, H.; Cheng, H. H.; Lee, L. C.; Lee, C. P.; Su, L. H.; Suen, Y. W.
Sensitivity of electricity cost to heavy-ion fusion target characteristics
The systems model for a commercial electric power facility produced by the Heavy-Ion Fusion System Assessment is used to study the sensitivity of electricity cost to various inertial confinement fusion target characteristics including gain, peak power, ion range, and target fabrication cost. Net electric power from the plant was fixed at 1000 MW(electric) to eliminate large effects caused by economies of scale. An improved target cost model is used and compared with earlier results. Although specific quantitative results changed, the earlier general conclusions remain valid. The system is moderately insensitive to target gain. A factor of 2.5 change in gain causes <10% change in electricity cost. Increased peak power needed to drive targets poses only a small cost risk but requires many more beamlets be transported to the target. Shortening the required ion range causes both cost and beamlet difficulties. A factor of 4 decrease in the required range at a fixed driver energy increases electricity cost by 43% and raises the number of beamlets from 34 to 330. Finally, the heavy-ion fusion system can accommodate large increases in target costs.
Wilson, D.C.; Dudziak, D.J.; Magelssen, G.R.; Zuckerman, D.S.; Driemeyer, D.E.
Sensitivity of electricity cost to heavy-ion fusion target characteristics
The systems model for a commercial electric power facility produced by the Heavy-Ion Fusion Sshytem Assessment is used to study the sensitivity of electricity cost to various inertial confinement fusion target characteristics including gain, peak power, ion range, and target fabrication cost. Net electric power from the plant was fixed at 1000 MW(electric) to eliminate large effects caused by economies of scale. An improved target cost model is used and compared with earlier results. Although specific quantitative results changed, the earlier general conclusions remain valid. The system is moderately insensitive to target gain. A factor of 2.5 change in gain causes <10% change in electricity cost. Increased peak power needed to drive targets poses only a small cost risk but requires many more beamlets be transported to the target. Shortening the required ion range causes both cost and beamlet difficulties. A factor of 4 decrease in the required range at a fixed driver energy increases electricity cost by 43% and raises the number of beamlets from 34 to 330. Finally, the heavy-ion fusion system can accommodate large increases in target costs. While moderate target gain is required, to address the other major uncertainties target design should concentrate on understanding requirements for ion range and peak driver power.
Wilson, D.C.; Dudziak, D.J.; Magelssen, G.R.; Zuckerman, D.S.; Driemeyer, D.E.
Field and temperature acceleration model for time-dependent dielectric breakdown
Electric-field and temperature acceleration models, such as the thermochemical breakdown (linear field dependence) model, the hole-induced breakdown (reciprocal field dependence) model, and the modified hole-induced breakdown model, are discussed. These models are examined; based on the results of long-term time-dependent dielectric breakdown (TDDB) tests over wide ranges of negative gate bias stress (8-13 MV\\/cm), test temperature (25, 75, and 125�C),
Mikihiro Kimura
The fabrication and electrical characteristics of ZnO twinned nanowires
Zinc oxide (ZnO) twinned nanowires (TNWs) were synthesized by self-catalyzed chemical vapor deposition (CVD) method. The microstructures and growth mechanism of the TNWs were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). In order to study the electrical characteristics of ZnO TNWs, ZnO TNW-based devices were realized with the help of high-resolution optical microscope and the scanning tunneling
L. Cao; M. K. Li; M. Lu; W. Zhang; Q. Wei; Z. B. Liu
Electrical characteristics of silicon-rare-earth fluoride layered switching structures
Switching and memory effects in the electrical conductance of layered structures based on rare-earth fluorides are investigated.\\u000a These investigations reveal the existence of high-and low-resistance states in structures of metal-insulator-semiconductor\\u000a type. It is shown that the characteristics of the low-resistance state of such structures are described by a metal-tunneling\\u000a insulator-semiconductor model.
V. A. Rozhkov; M. B. Shalimova
Processability and electrical characteristics of glass substrates for RF wafer-level chip-scale packages
Various types of glass substrates have been compared with respect to their suitability as a low-loss substrate in waferlevel chipscale packaging for RF applications. Processability has been evaluated by fabrication of shallow and deep recesses using wet etching in HF (iHjP04) solutions. Electrical characteristics (dielectric constant and attenuation) have been extracted from measurements on coplanar wave guides (CPWs) up to
A. Polyakov; P. M. Mendes; S. M. Sinaga; M. Bartek; B. Rejaci; J. H. Correia; J. N. Burghartz
A cardiac sound characteristic waveform method for in-home heart disorder monitoring with electric stethoscope
An analytical model based on a single-DOF is proposed for extracting the characteristic waveforms (CSCW) from the cardiac sounds recorded by an electric stethoscope. Also, the diagnostic parameters [T1, T2, T11, T12], the time intervals between the crossed points of the CSCW and an adaptive threshold line (THV), were verified useful for identification of heart disorders. The easy-understanding graphical representation
Zhongwei Jiang; Samjin Choi
Electrical machine having controlled characteristics and its application to a wind-driven machine
The invention provides an electrical machine having an inductor and an armature, one of which has at least two independent winding assemblies. The switching into and out of circuit of each winding assembly is controlled by a processor which receives monitoring parameters of the machine and desired value parameters, thereby controlling in real time the operating characteristics of the machine. The machine may be a winddriven generator.
Berna, M.; Kant, M.; Seger, R.; Vilain, J.P.
Analysis of the electrical characteristics and structure of Cu-Filled TSV with thermal shock test
NASA Astrophysics Data System (ADS)
The electrical characteristics and failure of a Through-Silicon Via (TSV) were investigated using a thermal shock test. The electrical characteristics, such as resistance ( R), self-inductance ( L s ), self-capacitance ( C s ), and mutual capacitance ( C m ), were extracted using a T-equivalent circuit. A cross section of the Cu-filled via was observed by field emission-scanning electron microscopy and the electrical characteristics were measured using a commercial Agilent E4980A LCR Meter. The experimental results revealed R, L s , C s , and C m values of 3.2 m?, 29.3 pH, 12 fF, and 0.42 pF, respectively. C m occurred between the charge-holding TSVs, which changed from 0.42 pF to 0.26 pF due to a permittivity transition of the Cu ion drift. After 1,000 cycles of a thermal shock test, cracks were observed between the opening and around the side of the TSV and Si wafer due to mismatch of the coefficient of thermal expansion between the Cu-plug and Si substrate.
Jeong, Il Ho; Roh, Myong Hoon; Jung, Flora; Song, Wan Ho; Mayer, Michael; Jung, Jae Pil
Electrical characteristics of an electrostatic valve used for bulk transport of agricultural seeds
In an electrostatic valve used for bulk transport of agricultural seeds, the interparticulate electroclamping forces can be established by applying electric potential gradient between a separated pair of conducting electrode grids placed perpendicularly across the flow. The flow control of particulate material is thus achieved using no moving parts. When an electric field is applied, several types of electric field forces are generated, depending on the bulk and surface resistivities of the particles, the geometry of the electrodes, the applied field, and the geometry and the conductivity of the materials used for the transport channel. In this study the current-voltage characteristics of the valve were experimentally investigated for different flow control parameters. The triboelectrification of turnip seeds caused by the frictional contact on the channel walls was investigated and compared with the valve current. A range of wall liner materials with different electrical properties conductive to insulating were tested. The materials used for the wall liner did not significantly influence the current characteristics of the electrostatic valve. The effect of pulse duration of the applied potential on charge-to-mass ratio of the level of net charge acquired by the particles could be controlled by controlling the duty cycle of the electroclamping field.
Balachandran, W.; Machowski, W. [Brunel Univ., Uxbridge (United Kingdom). Dept. of Mfg. and Engineering Systems] [Brunel Univ., Uxbridge (United Kingdom). Dept. of Mfg. and Engineering Systems; Thompson, S.A.; Law, S.E. [Univ. of Georgia, Athens, GA (United States). Dept. of Biological and Agricultural Engineering] [Univ. of Georgia, Athens, GA (United States). Dept. of Biological and Agricultural Engineering
Breakdown and partial discharges in magnetic liquids.
The dielectric properties (permittivity, loss factor, dielectric breakdown strength) of magnetic liquids were investigated. The magnetic liquids were composed of magnetite particles coated with oleic acid as surfactant and dispersed in transformer oil. To determine their dielectric properties they were subjected to a uniform magnetic field at high alternating electric fields up�to 14�MV�m(-1). Nearly constant permittivity of magnetic liquid with particle volume concentration ? = 0.0019 as a function of electric field was observed. Magnetic liquids with concentrations ? = 0.019 and 0.032 showed significant changes of permittivity and loss factor dependent on electric and magnetic fields. The best concentration of magnetic fluid was found at which partial current impulse magnitudes were the lowest. The breakdown strength distribution of the magnetic liquid with ? = 0.0025 was fitted with the Duxbury-Leath, Weibull and Gauss distribution functions. PMID:21694240
Herchl, F; Marton, K; Tom?o, L; Kop?ansk�, P; Timko, M; Konerack�, M; Kolcunov�, I
Electrical characteristics of thin Ta2O5 films deposited by reactive pulsed direct-current magnetron sputtering
NASA Astrophysics Data System (ADS)
Room temperature deposition of tantalum oxide films on metallized silicon substrates was investigated by reactive pulsed magnetron sputtering of Ta in an Ar/O2 ambient. The dielectric constant of the tantalum oxide ranged from 19 to 31 depending on the oxygen percentage [P(%)=PO2/(PO2+PAr)] used during sputtering. The leakage current density was less than 10 nA/cm2 at 0.5 MV/cm electric field and the dielectric breakdown field was greater than 3.8 MV/cm for P=60%. A charge storage as high as 3.3 ?F/cm2 was achieved for 70-�-thick film. Pulse frequency variation (from 20 to 200 kHz) did not give a significant effect in the electrical properties (dielectric constant or leakage current density) of the Ta2O5 films.
Kim, J.-Y.; Nielsen, M. C.; Rymaszewski, E. J.; Lu, T.-M.
Breakdown processes in metal halide lamps
NASA Astrophysics Data System (ADS)
Metal halide lamps typically have cold fills of tens to a few hundred Torr of a rare gas and the vapour from the dosing of a metal halide solid and mercury. Breakdown and starting of the lamp occurs following application of multi-kV pulses across electrodes separated by a few centimetres. Restarting of warm lamps is often problematic as the available voltage is insufficient to break down the higher pressure (>many atm) of metal halide vapour. In this paper, fundamental processes during breakdown in cold and warm, idealized metal halide lamps in mixtures of Ar and Hg are investigated using a two-dimensional fluid model for plasma transport. We find that the capacitances of the walls of the discharge tube and adjacent ground planes are important in determining the breakdown voltage and avalanche characteristics. The prompt capacitance represented by, for example, external trigger wires provides a larger E/N to sustain ionization early in the avalanche. This effect is lost as the walls charge and shield the plasma from the ground planes. More rapid breakdown occurs in slightly warm lamps having small vapour pressures of Hg due to the resulting Penning mixture. Warmer lamps, having larger mole fractions of Hg, have less efficient breakdown as the increase in momentum transfer of the electrons is not offset by the additional ionization sources of the Penning mixture.
Lay, Brian; Moss, Richard S.; Rauf, Shahid; Kushner, Mark J.
Time-Dependent Dielectric Breakdown of -Doped High \\/Metal Gate Stacked NMOSFETs
Time-dependent dielectric breakdown (TDDB) characteristics of La2O3-doped high-k dielectric in Hf-based high-k\\/TaN metal gate stack were studied. Unlike the abrupt breakdown in the conventional SiO2 , dielectric breakdown behaviors of La-incorporated HfON and HfSiON dielectrics show progressive breakdown characteristics. Moreover, the extracted Weibull slope beta of breakdown distribution is in the range of 0.87-1.19, and it is independent on capacitor
In-Shik Han; Won-Ho Choi; Hyuk-Min Kwon; Min-Ki Na; Ying-Ying Zhang; Yong-Goo Kim; Jin-Suk Wang; Chang Yong Kang; Gennadi Bersuker; Byoung Hun Lee; Yoon Ha Jeong; Hi-Deok Lee; Raj Jammy
Electrical Characteristics of Al/Poly(methyl methacrylate)/ p-Si Schottky Device
NASA Astrophysics Data System (ADS)
Al/Poly(methyl methacrylate)(PMMA)/ p-Si organic Schottky devices were fabricated on a p-Si semiconductor wafer by spin coating of PMMA solution. The capacitance-voltage ( C- V) and conductance-voltage ( G- V) characteristics of Al/PMMA/ p-Si structures have been investigated in the frequency range of 1 kHz-10 MHz at room temperature. The diode parameters such as ideality factor, series resistance and barrier height were calculated from the forward bias current-voltage ( I- V) characteristics. In order to explain the electrical characteristics of metal-polymer-semiconductor (MPS) with a PMMA interface, the investigation of interface states density and series resistance from C- V and G- V characteristics in the MPS structures with thin interfacial insulator layer have been reported. The measurements of capacitance (C) and conductance (G) were found to be strongly dependent on bias voltage and frequency for Al/PMMA/ p-Si structures. The values of interface state density ( D it) were calculated. These values of D it and series resistance ( R s) were responsible for the non-ideal behavior of I- V and C- V characteristics.
Sel�uk, A. B.; Bilge Ocak, S.; Aras, F. G.; Oz Orhan, E.
The prevention of electrical breakdown and electrostatic voltage problems in the space shuttle and its payloads. Part 1: Theory and phenomena
NASA Technical Reports Server (NTRS)
An introduction to the theory of corona discharge and electrostatic phenomena is presented. The theory is mainly qualitative so that workers in the field should not have to go outside this manual for an understanding of the relevant phenomena. Some of the problems that may occur with the space shuttle in regard to electrical discharge are discussed.
Whitson, D. W.
Transformation of the electrical characteristics of graphene field-effect transistors with fluoropolymer.
We report on the improvement of the electronic characteristics of monolayer graphene field-effect transistors (FETs) by an interacting capping layer of a suitable fluoropolymer. Capping of monolayer graphene FETs with CYTOP improved the on-off current ratio from 5 to 10 as well as increased the field-effect mobility by as much as a factor of 2 compared to plain graphene FETs. Favorable shifts in the Dirac voltage toward zero with shift magnitudes in excess of 60 V are observed. The residual carrier concentration is reduced to ~2.8 � 10(11) cm(-2). Removal of the fluoropolymer from graphene FETs results in a return to the initial electronic properties before depositing CYTOP. This suggests that weak, reversible electronic perturbation of graphene by the fluoropolymer favorably tune the electrical characteristics of graphene, and we hypothesize that the origin of this improvement is in the strongly polar nature of the C-F chemical bonds that self-organize upon heat treatment. We demonstrate a general method to favorably restore or transform the electrical characteristics of graphene FETs, which will open up new applications. PMID:23252452
Ha, Tae-Jun; Lee, Jongho; Chowdhury, Sk Fahad; Akinwande, Deji; Rossky, Peter J; Dodabalapur, Ananth
Adaptive femtosecond laser-induced breakdown spectroscopy of uranium
NASA Astrophysics Data System (ADS)
Laser-induced breakdown spectroscopy (LIBS) is an established technique for material characterization applicable to a variety of problems in research, industry, environmental studies, and security. LIBS conducted with femtosecond laser pulses exhibits unique properties, arising from the characteristics of laser-matter interactions in this pulse width regime. The time evolution of the electric field of the pulse determines its interaction with sample materials. We present the design and performance of a femtosecond LIBS system developed to systematically optimize the technique for detection of uranium. Sample analysis can be performed in vacuum environment, and the spectral and temporal diagnostics are coupled through an adaptive feedback loop, which facilitates optimization of the signal-to-noise ratio by pulse shaping. Initial experimental results of LIBS on natural uranium are presented.
Ko, P.; Hartig, K. C.; McNutt, J. P.; Schur, R. B. D.; Jacomb-Hood, T. W.; Jovanovic, I.
An estimation of the electrical characteristics of planetary shallow subsurfaces with TAPIR antennas
NASA Astrophysics Data System (ADS)
In the frame of the NETLANDER program, we have developed the Terrestrial And Planetary Investigation by Radar (TAPIR) imaging ground-penetrating radar to explore the Martian subsurface at kilometric depths and search for potential water reservoirs. This instrument which is to operate from a fixed lander is based on a new concept which allows one to image the various underground reflectors by determining the direction of propagation of the reflected waves. The electrical parameters of the shallow subsurface (permittivity and conductivity) need to be known to correctly determine the propagation vector. In addition, these electrical parameters can bring valuable information on the nature of the materials close to the surface. The electric antennas of the radar are 35 m long resistively loaded monopoles that are laid on the ground. Their impedance, measured during a dedicated mode of operation of the radar, depends on the electrical parameters of soil and is used to infer the permittivity and conductivity of the upper layer of the subsurface. This paper presents an experimental and theoretical study of the antenna impedance and shows that the frequency profile of the antenna complex impedance can be used to retrieve the geoelectrical characteristics of the soil. Comparisons between a numerical modeling and in situ measurements have been successfully carried over various soils, showing a very good agreement.
Le Gall, A.; Reineix, A.; Ciarletti, V.; Berthelier, J. J.; Ney, R.; Dolon, F.; Corbel, C.
Neutron, gamma ray, and temperature effects on the electrical characteristics of thyristors
NASA Technical Reports Server (NTRS)
Experimental data showing the effects of neutrons, gamma rays, and temperature on the electrical and switching characteristics of phase-control and inverter-type SCR's are presented. The special test fixture built for mounting, heating, and instrumenting the test devices is described. Four SCR's were neutron irradiated at 300 K and four at 365 K for fluences up to 3.2 x 10 exp 13 n/sq. cm, and eight were gamma irradiated at 300 K only for gamma doses up to 5.1 Mrads. The electrical measurements were made during irradiation and the switching measurements were made only before and after irradiation. Radiation induced crystal defects, resulting primarily from fast neutrons, caused the reduction of minority carrier lifetime through the generation of R-G centers. The reduction in lifetime caused increases in the on-state voltage drop and in the reverse and forward leakage currents, and decreases in the turn-off time.
Frasca, A. J.; Schwarze, G. E.
Neutron, gamma ray, and temperature effects on the electrical characteristics of thyristors
NASA Technical Reports Server (NTRS)
Experimental data showing the effects of neutrons, gamma rays, and temperature on the electrical and switching characteristics of phase-control and inverter-type SCR's are presented. The special test fixture built for mounting, heating, and instrumenting the test devices is described. Four SCR's were neutron irradiated at 300 K and four at 365 K for fluences up to 3.2 x 10 exp 13 pn/sq. cm, and eight were gamma irradiated at 300 K only for gamma doses up to 5.1 Mrads. The electrical measurements were made during irradiation and the switching measurements were made only before and after irradiation. Radiation induced crystal defects, resulting primarily from fast neutrons, caused the reduction of minority carrier lifetime through the generation of R-G centers. The reduction in lifetime caused increases in the on-state voltage drop and in the reverse and forward leakage currents, and decreases in the turn-off time.
Frasca, A. J.; Schwarze, G. E.
Electrical and Electrochemical Performance Characteristics of Large Capacity Li-Ion Cells
We are currently evaluating large capacity (20 - 40 Ah) Bluestar (cylindrical) and Yardney (prismatic) Li-ion cells for their electrical and electrochemical performance characteristics at different temperatures. The cell resistance was nearly constant from room temperature to -20{degrees}C but increased by over 10 times at -40{degrees}C. The specific energy and power as well as the energy density and power density are high and didn't reach a plateau even at the highest discharge rates tested. For example, the prismatic Li-ion cells gave close to 280 Wh l{sup -1} at 4-amp discharge and 249 Wh l{sup -1} at 20-amp discharge at room temperature. For the same current range the specific power values are 102 Wh kg{sup -1} and 91 Wh kg{sup -1}. Cycle life and other electrical and electrochemical properties of the cells will be presented.
Doughty, I.D.; Hill, C.; Ingersoll, D.; Marsh, C.; Nagasubramanian, G.; Radzykewycz, D
Effect of Electrostatic Discharge on Electrical Characteristics of Discrete Electronic Components
NASA Technical Reports Server (NTRS)
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.
Wysocki, Phil; Vashchenko, Vladislav; Celaya, Jose; Saha, Sankalita; Goebel, Kai
We present a simple model of breakdown in rf cavities. For most events this involves tensile stress and tensile strength, however other effects can also contribute. We discuss the effects of different materials, fatigue, high pressure gas, primary and secondary emission sites, local field enhancements, dark currents, secondary emission, work functions, magnetic fields, macro and microscopic fracture mechanisms high current
J. Norem; A. Hassanein; Z. Insepov; I. Konkashbaev
ERIC Educational Resources Information Center
Most human beings look at erosion as the destruction of a surface, but artists can see that erosion often creates indefinable beauty. Where do you see beauty in the breakdown? In this article, the author presents an innovative lesson that would allow students to observe both human and physical nature. In this activity students will create a work�
Brisco, Nicole
This paper reviews the studies undertaken on vortex breakdown over the past 45 years. The paper is structured such that the area is considered in three sections � experimental, numerical and finally theoretical, and provides a �guide� to the literature and where necessary directs the reader to more indepth reviews in the specific areas.
O Lucca-Negro; T O'Doherty
Thick-film PTC thermistors and LTCC structures: The dependence of the electrical and microstructural characteristics on the firing temperature
The electrical and microstructural characteristics of 1k?\\/sq thick-film thermistors with high positive temperature coefficients of resistivity, i.e., PTC 5093 (Du Pont) fired either on �green� LTCC (low-temperature co-fired ceramics) substrates or buried within LTCC structures, were evaluated. The thermistors were fired at different temperatures to study the influence of firing temperature on the electrical characteristics. The noise indices of the
Marko Hrovat; Darko Belavi?; Jaroslaw Kita; Janez Holc; Jena Cilen�ek; Leszek Golonka; Andrzej Dziedzic
Effect of configuration and dimensions of reactor electrodes on electrical and optical corona discharge characteristics
An experimental parametric study is made to investigate how the electrical corona discharge characteristics are influenced by the geometrical configuration and dimensions of the reactor and the electrode polarity of the applied voltage. Furthermore, features of the corona discharge plasma formed around the stressed electrode in some different gases are recorded photographically to provide more information on the physical mechanisms of the corona discharge in the investigated gases. The obtained results have been discussed in the light of gas discharge physics and its applications.
El-Koramy, Reda Ahmed; Yehia, Ashraf; Omer, Mohamed [Department of Physics, Faculty of Science, Assiut University, 71516 Assiut (Egypt)
Experimental study on the dielectric characteristics of liquid nitrogen with respect to various pressures
NASA Astrophysics Data System (ADS)
The electrical breakdown characteristics of liquid nitrogen (LN 2) are required to design of high voltage superconducting machines which should have high reliability. This paper deals with the investigation to verify the relationships between the electrical breakdown characteristics of LN 2 its pressure condition. The electrical breakdown characteristics of LN 2 were measured by using sphere-plane electrode systems. The diameter of sphere electrode had five different values. The gaseous nitrogen was injected into a cryostat which contained the sphere-plane electrode system to control the pressure of LN 2 from 50 to 200 kPa. The AC dielectric tests in LN 2 were repeated 10 times in each pressure condition. The AC breakdown voltage at sparkover with 50% probability was calculated by commercialized statics tools. From finite element method simulation results, the field utilization factor which means the field uniformity was calculated between sphere and plane electrode and its relations with AC breakdown voltage with 50% probability were analyzed. Finally, these results provided a suitable design parameter of electrical insulation for high voltage superconducting machines such as superconducting fault current limiters, superconducting cables, and superconducting transformers.
Na, J. B.; Kang, H.; Chang, K. S.; Kim, Y. J.; Kim, K. J.; Lee, H. G.; Ko, T. K.
Land-ocean contrast on electrical characteristics of lightning discharge derived from satellite optical measurements
NASA Astrophysics Data System (ADS)
Comparative studies on the electrical properties of oceanic and continental lightning are crucial to elucidate air discharge processes occurring under different conditions. Past studies however have primarily focused on continental lightning because of the limited coverage of ground-based instruments. Recent satellite measurements by FORMOSAT-2/ISUAL provided a new way to survey the global characteristics of lightning and transient luminous events regardless of land and ocean. In this study, we analyze ISUAL/spectrophotometer data to clarify the electrical properties of lightning on a global level. Based on the results obtained by Cummer et al. [2006] and Adachi et al. [2009], the OI-777.4nm emission intensity is used to infer lightning electrical parameters. Results show a clear land-ocean contrast on the parameters of lightning discharge: in oceanic lightning, peak luminosity is 60 % higher and the time scale of return stroke is 30 % shorter. These results suggest higher peak current in oceanic lightning, which is consistent with the fact that elves, EMP-driven phenomena, also tend to occur over the ocean [Chen et al., 2008]. Further analysis of lightning events occurring around the Caribbean Sea shows that the transition-line of lightning electrical properties is precisely located along the coastline. We suggest that the differences in these electrical properties may be due to the boundary conditions (conductivity, surface terrain, etc). In this talk, based on the calibration with NLDN and Duke magnetometer data, current moment change and charge moment change will be globally evaluated using a complete set of the ISUAL-observed lightning events.
Adachi, T.; Said, R.; Cummer, S. A.; Li, J.; Takahashi, Y.; Hsu, R.; Su, H.; Chen, A. B.; Mende, S. B.; Frey, H. U.
GPR-based evaluation of strength properties of unbound pavement material from electrical characteristics
NASA Astrophysics Data System (ADS)
It is well known that inter-particle friction and cohesion of soil particles and aggregates deeply affect the strength and deformation properties of soils, exerting critical effects on the bearing capacity of unbound pavement materials. In that respect, considering that strength characteristics of soil are highly dependent on particle interactions, and assuming a relationship between electric properties (e.g. electric permittivity) and bulk density of materials, a good correlation between mechanical and electric characteristics of soil is expected. In this work, Ground Penetrating Radar (GPR) techniques are used to investigate this topic. Two GPR equipment with same electronic characteristics and different survey configurations are used. Each radar operates with two ground-coupled antennae at 600 MHz and 1600 MHz central frequencies. Measurements are developed using 4 channels, 2 mono-static and 2 bi-static. The received signal is sampled in the time domain at dt = 7.8125 � 10-2 ns, and in the space domain every 2.4 � 10-2 m. A semi-empirical model is proposed for predicting the resilient modulus of sub-asphalt layers from GPR-derived data. Basically, the method requires to follow two steps. Firstly, laboratory tests are carried out for calibration, with the main focus to provide consistent empirical relationships between physical (e.g. bulk density) and electric properties. The second step is focused on the in-situ validation of results through soil strength measurements retrieved by CBR tests and Light Falling Weight Deflectometer (LFWD). On the basis of traditional empirical equations used for flexible pavement design, the following expression is proposed: -m Ei = ?j?hj,i j=1 where Ei [MPa] is the ith expected resilient modulus of the surveyed soil under the line of scan, hj,i [m] is the ith thickness referred to the jth layer, and ?j is a dielectric parameter calibrated as a function of the relative electric permittivity. The experimental setting requires the use of road material, typically employed for subgrade and subbase courses. Different types of soil ranging from group A1 to A4 by AASHTO soil classification system, are analyzed. As regards the laboratory experiments, material is gradually compacted in electrically and hydraulically isolated test boxes. A large metal sheet supports the experimental boxes, so that the transmitted GPR signal is totally reflected. GPR inspections are carried out for any compaction step up to the maximum density value available. Moreover, in-situ tests are carried out on targeted types of soil, with grain size distribution and texture comparable to those analyzed in laboratory environment. The results of this study confirm a promising correlation between the electric permittivities and the strength and deformation properties of the surveyed soils. Laboratory analyses show that the relationship between the relative permittivity and the bulk density is positive: the higher the density of the compacted soil sample, the higher the electric permittivity of the medium. Analogously, in-situ validation presents a good comparison between measured and predicted data. Percentage errors less than 20% demonstrate that a reliable prediction of Young Modulus using this GPR-based approach can be achieved.
Benedetto, Andrea; D'Amico, Fabrizio; Tosti, Fabio
Probability characteristics of electrical noise in heterojunction light-emitting diodes
A hardware-software complex for measurements of the characteristics of electrical and optical noise in light-emitting diodes (LEDs) in the frequency range from 1 to 40 kHz is described. The electrical noise of several types of heterojunction-based LEDs are studied; these types include red-emission LEDs with AlInGaP/GaAs quantum wells and the green- and blue-emission LEDs with AlInGaN/SiC quantum wells are studied by the method of discrete samples. The spectra of all studied LEDs in the frequency range from 1 to 10 kHz have the form 1/f{sup {gamma}}. It is noteworthy that, for red-emission LEDs, the exponent {gamma} is significantly smaller than unity; this index is close to unity for the green- and blue-emission LEDs. The characteristic time of correlation of the noise of red-emission LEDs by several times exceeds the correlation times for the blue- and green-emission LEDs. It is shown that reduced functions of the amplitude distribution of the noise voltage are close to Gaussian functions with almost the same dispersion for all LED types.
Sergeev, V. A., E-mail: firstname.lastname@example.com; Frolov, I. V.; Shirokov, A. A.; Shcherbatyuk, Yu. N. [Ul'yanovsk State Technical University (Russian Federation)
Optical and electrical characteristics of air dielectric barrier discharges in mode transition at atmospheric pressure
NASA Astrophysics Data System (ADS)
Atmospheric pressure dielectric barrier discharges (DBDs) have a wide range of industrial applications, generally exhibiting either filamentary or diffuse (i.e. glow) discharges. The focus of this investigation is on the formation mechanisms of the discharge current pulse width, on the order of tens of microseconds, accompanied by a light source formation, which is called a light source (LS) mode in air DBDs at atmospheric pressure. From a macroscopic point of view, the characteristics of the discharge current in the LS mode are similar with those of the glow mode. The optical and electrical characteristics of air DBDs at atmospheric pressure are investigated in the transition from the filamentary mode to the LS mode by measuring the optical emission spectroscopy and electrical signals. It is shown that in the manual increasing voltage stage, the vibrational temperature almost never changes and the gas temperature, electron temperature, dielectric capacitance, gas voltage (Vg) and discharge power (P) increase with an increase in the applied voltage. In the automatic decreasing voltage stage, all of these parameters, except Vg and P, increase with a decrease in the voltage. But, when the voltage decreases to a minimum value corresponding to the LS mode, P reaches a maximum value. In this paper, the variations of these parameters are analyzed and discussed in detail. The formation of the LS mode originates from the secondary electrons. The formation mechanisms of the secondary electrons are also discussed.
Wang, Weiwei; Liu, Feng; Wang, Xue; Han, Haiyan; Huang, Yanbin; Liang, Rongqing
Enhancement of the electrical characteristics of metal-free phthalocyanine films using cold isostatic pressing
NASA Astrophysics Data System (ADS)
Spatial gaps between grains and other grains, substrates, or electrodes in organic electronic devices are one of the causes of the reduction in the electrical characteristics. In this study, we demonstrate that cold isostatic pressing (CIP) is an effective method to crush the gaps and enhance the electrical characteristics. CIP of metal-free phthalocyanine (H2PC) films induced a decrease in the film thickness by 34%-40% because of the gap crush. The connection of smaller grains into a larger grain and planarization of the film surface were also observed in the CIP film. The crystal axes of the H2PC crystallites were rearranged from the a-axis to the c-axis of the ?-phase crystal structure in a direction perpendicular to the substrate by CIP, indicating favorable hole injection and transport in this direction because of a better overlap of ? orbitals. Thermally stimulated current measurements showed that deep hole traps disappeared and the total hole-trap density decreased after CIP. These CIP-induced changes of the film thicknesses, crystal axes and the hole traps lead to a marked increase in the hole mobility of the H2PC films from 2.0 � 10-7 to 4.0 � 10-4 cm2/V s by 2000 times in the perpendicular direction. We believe that these findings are important for unveiling the underlying carrier injection and transport mechanisms of organic films and for enhancing the performance of future organic electronic devices.
Matsushima, Toshinori; Esaki, Yu; Adachi, Chihaya
Electric Field Waveform Characteristics of Positive and Negative Lightning Return Strokes in Florida
NASA Astrophysics Data System (ADS)
In 2007-2008, 52 positive cloud-to-ground flashes containing 63 return strokes (52 first, 10 second, and 1 third) were recorded at the Lightning Observatory in Gainesville (LOG), Florida. NLDN-reported distances from the LOG for 48 (40 first and 8 second) strokes ranged from 7.8 to 157 km. In this study, various microsecond-scale features of electric field waveforms of these positive return strokes including risetimes, characteristics of the slow-front and fast transition, zero-crossing time, opposite-polarity overshoot, and characteristics of the electric field derivative (dE/dt) pulse are examined and compared with the characteristics of negative return strokes in Florida found in the literature. Parameters of electric field waveforms produced by positive and negative first return strokes are summarized in Table 1. The AM zero-to-peak risetime and 10-90% risetime for 51 positive first return strokes were 7.9 ?s and 4.0 ?s, respectively, which are longer than the corresponding values of 4.4 ?s and 2.6 ?s for 105 first strokes in negative cloud-to-ground flashes in Florida reported by Master et al. (1984). The AM slow front duration for 51 positive first strokes was 6.1 ?s which is about a factor of two greater than that found for negative first return strokes by Master et al. For positive first return strokes examined here, the AM zero-crossing time was 58 ?s and the opposite polarity overshoot was, on average, 14% of the peak. These values are not much different from those (50 ?s and 19%) reported by Pavlick et al. (2002) for negative first return strokes in Florida. On the other hand, Haddad et al. (2012) reported the AM zero-crossing time of 96 ?s and the average opposite polarity overshoot of 23% for 48 negative first strokes recorded at the LOG at distances of 50 to 100 km. References: Haddad, M. A., V. A. Rakov et al. (2012), J. Geophys. Res., 117, D10101, doi:10.1029/2011JD017196. Krider, E. P., C. Leteinturier et al. (1996), J. Geophys. Res., 101(D1), 1589-1597. Master, M. J., M. A. Uman et al. (1984), IEEE Trans. PAS, PAS-103, pp. 2519-2529. Pavlick, A., D. E. Crawford et al. (2002), 7th International Conference on Probabilistic Methods Applied to Power Systems, Naples, Italy.Table 1. Parameters of electric field waveforms produced by positive and negative first return strokes in Floridat;
Nag, A.; Rakov, V. A.
Electrical and mechanical characteristics of surface AC dielectric barrier discharge plasma actuators applied to airflow control
NASA Astrophysics Data System (ADS)
The present paper is a wide review on AC surface dielectric barrier discharge (DBD) actuators applied to airflow control. Both electrical and mechanical characteristics of surface DBD are presented and discussed. The first half of the present paper gives the last results concerning typical single plate-to-plate surface DBDs supplied by a sine high voltage. The discharge current, the plasma extension and its morphology are firstly analyzed. Then, time-averaged and time-resolved measurements of the produced electrohydrodynamic force and of the resulting electric wind are commented. The second half of the paper concerns a partial list of approaches having demonstrated a significant modification in the discharge behavior and an increasing of its mechanical performances. Typically, single DBDs can produce mean force and electric wind velocity up to 1 mN/W and 7 m/s, respectively. With multi-DBD designs, velocity up to 11 m/s has been measured and force up to 350 mN/m.
Benard, Nicolas; Moreau, Eric
Near-field characteristics of electric dipole antennas in the inner magnetosphere
NASA Astrophysics Data System (ADS)
Electric dipole antennas are commonly used in space plasmas with applications that range from radio frequency probing of the magnetosphere to plasma diagnostics. With the recent interest in the in-situ injection of ELF/VLF waves for the study of magnetospheric wave-particle interactions, the characterization of the antenna-plasma coupling behavior in this regime is of primary importance. The coupling considered in this dissertation occurs in an operating environment that corresponds to magnetospheric conditions found between L=2 and L=3 in the geomagnetic equatorial plane. The near field of the antenna consists of a plasma sheath which directly affects the terminal impedance properties. Inside the sheath region, the plasma dynamics are highly nonlinear and must be solved numerically. In order to optimally inject VLF waves and thereby maximize the antenna-plasma coupling response, it is necessary to determine the characteristics of electric dipole antennas operating within this region of space. This dissertation addresses the efficacy of using electric dipole antennas as in-situ wave injection instruments and focuses on the near-field coupling of these antennas to the environment in which they are immersed. A two-tiered hydrodynamic approach has been developed to solve for the plasma dynamics in the region surrounding the antenna. First, a three-dimensional full wave solution of Maxwell's equations is implemented to simulate the current distribution and input impedance of an electric dipole antenna operating in a cold magnetoplasma at VLF. It is shown that the current distribution for antennas with length <100 m is approximately triangular for magnetospheric conditions considered herein. Calculated variations of input impedance as a function of drive frequency are presented for two case studies and compared with predictions of existing analytical work. This model is then extended to include finite temperature effects allowing for the determination of the sheath characteristics as a function of drive frequency and voltage. The primary assumptions underlying the closure mechanisms for the infinite set of fluid moments are examined through theoretical observations and simulated comparisons of the various truncation schemes. Results from these two models allow for the complete characterization of the near-field properties of electric dipole antennas operating in this highly anisotropic environment.
Chevalier, Timothy W.
Breakdown During High-Field Bias-Temperature Stress
Measurements of dielectric breakdown during high-field electrical stress are typically performed at or near room temperature via constant voltage or current stress methods. In this summary they explore whether useful information might also be obtained by performing current measurements during a temperature ramp at high electric field.
Fleetwood, D.M.; Krisch, K.S.; Sexton, F.W.
Electrical and photovoltaic characteristics of MoS2/Si p-n junctions
NASA Astrophysics Data System (ADS)
Bulk-like molybdenum disulfide (MoS2) thin films were deposited on the surface of p-type Si substrates using dc magnetron sputtering technique and MoS2/Si p-n junctions were formed. The vibrating modes of E12g and A1g were observed from the Raman spectrum of the MoS2 films. The current density versus voltage (J-V) characteristics of the junction were investigated. A typical J-V rectifying effect with a turn-on voltage of 0.2 V was shown. In different voltage range, the electrical transporting of the junction was dominated by diffusion current and recombination current, respectively. Under the light illumination of 15 mW cm-2, the p-n junction exhibited obvious photovoltaic characteristics with a short-circuit current density of 3.2 mA cm-2 and open-circuit voltage of 0.14 V. The fill factor and energy conversion efficiency were 42.4% and 1.3%, respectively. According to the determination of the Fermi-energy level (�4.65 eV) and energy-band gap (�1.45 eV) of the MoS2 films by capacitance-voltage curve and ultraviolet-visible transmission spectra, the mechanisms of the electrical and photovoltaic characteristics were discussed in terms of the energy-band structure of the MoS2/Si p-n junctions. The results hold the promise for the integration of MoS2 thin films with commercially available Si-based electronics in high-efficient photovoltaic devices.
Hao, Lanzhong; Liu, Yunjie; Gao, Wei; Han, Zhide; Xue, Qingzhong; Zeng, Huizhong; Wu, Zhipeng; Zhu, Jun; Zhang, Wanli
Growth characteristics of different heart cells on novel nanopatch substrate during electrical stimulation.
During a heart attack, the heart's oxygen supply is cut off, and cardiomyocytes perish. Unfortunately, once these tissues are lost, they cannot be replaced and results in cardiovascular disease-the leading cause of deaths worldwide. Advancements in medical research have been targeted to understand and combat the death of these cardiomyocytes. For example, new research (in vitro) has demonstrated that one can expand cardiomyocyte adhesion and proliferation using polylactic-co-glycolic acid (PLGA) (50:50 (weight percent)) supplemented with carbon nanofibers (CNFs) to create a cardiovascular patch. However, the examination of other cardiovascular cell types has not been investigated. Therefore, the purpose of this present in vitro study was to determine cell growth characteristics of three different important cardiovascular cell types (aortic endothelial, fibroblast and cardiomyocyte) onto the substrate. Cells were seeded onto different PLGA:CNF ratio composites to determine if CNF density has an effect on cell growth, both in static and electrically stimulated environments. During continuous electrical stimulation (rectangle, 2 nm, 5 V/cm, 1 Hz), cardiomyocyte cell density increased in comparison to its static counterparts after 24, 72 and 120 hours. A minor rise in Troponin I excretion in electrical stimulation compared to static conditions indicated nominal cardiomyocyte cell function during cell experiments. Endothelial and fibroblast cell growth experiments indicated the material hindered or stalled proliferation during both static and electrical stimulation experiments, thus supporting the growth of cardiomyocytes onto the dead tissue zone. Furthermore, the results specified that CNF density did have an effect on PLGA:CNF composite cytocompatibility properties with the best results coming from the 50:50 [PLGA:CNF (weight percent:weight percent)] composite. Therefore, this study provides further evidence that a conductive scaffold using nanotechnology should be further research for various cardiovascular applications. PMID:25226907
Stout, David A; Raimondo, Emilia; Marostica, Giuliano; Webster, Thomas J
Breakdown of the continuum limit approximation to the discrete scattering events and its influence on the electric field autocorrelation functions of transmitted light
NASA Astrophysics Data System (ADS)
The complexity of modeling light propagation in turbid media can be significantly simplified if one assumes it to be diffusive. This is, however, only valid after the light has traveled a sufficient distance so that the diffusion equation can be employed. So far, there has been no reliable way to determine this distance, despite the fact that the assumption is often applied in optics. The discrete nature of scattering events plays an important role in modeling propagation of weakly scattered light, so a continuum equation such as the diffusion equation cannot be used to describe this process. Electric field autocorrelation functions g1(? ) of light transmitted through turbid colloidal samples are measured using diffusing wave spectroscopy and compared to Monte Carlo simulations in order to obtain a better estimation of the continuum limit. The two methods to calculate g1(? ) from the simulated photon trajectories are compared; the first assumes the continuum limit by using the path-length distributions of photon trajectories, while the second considers the square momentum transfers and therefore accurately calculates g1(? ) even if the detected signal is composed of weakly scattered light. The results of the two methods are used to determine the lengths of the shortest diffuse photon trajectories; they grow with the sample thickness and scattering anisotropy.
�ormaz, Milo�; Reufer, Mathias; V�lker, Andreas C.; Simon, Klaus
Study and modeling of the breakdown voltage in semi insulating GaAs P+N, PN+, P+N+ junctions diodes presenting deep centers traps
NASA Astrophysics Data System (ADS)
This work aims at determining the characteristic I (Breakdown voltage) of the inverse current in GaAs PN junction diode, subject to an reverse polarization while specifying the parameters that influence the Breakdown voltage of the diodes. In this work, we simulated the behavior of the ionization phenomenon by impact Breakdown by avalanche of the PN junctions, subject to an inverse polarization. Will be taken into account both the trapping model in a stationary regime in the P+N, PN+, and P+N+ structures using like material of basis the III-V compounds and mainly the GaAs semi-insulating in which the deep centers have in important densities. The study of the physical and electric behavior of the semiconductors, and notably is based on the influence of the deep center presence on the characteristic I(V) current-tension, that requires calculation the electrostatic potential, the electric field, the integral of ionization, the density of the states traps, the diffusion current of minority in the regions (1) and (3), the current thermal generation in the region (2), the leakage current in surface, and the breakdown voltage.
Resfa, A.; Menezla, Brahimi R.; Bougueneya, Mustapha
Breakdown studies of helium and nitrogen in partial vacuum subject to non-uniform, unipolar fields in the 20--220 kHz range
NASA Astrophysics Data System (ADS)
Partial discharges and corona are considered as unwanted processes in electrical power systems since they are constant source of power loss and electrical noise (EMI). These effects can further develop into a major problem at the component level, causing solid insulation deterioration and component failure leading to possible bulk electrical breakdown. The problems are well documented for traditional ground-based (i.e. utility) electrical power systems, and there exists a considerable knowledge base on the subject. However, this knowledge base does not readily extend to on-board electrical power systems in aerospace vehicles because such systems are required to operate at very low atmospheric pressure (i.e. in partial vacuum) and frequencies in the tens of kHz range. Also, much of what is known for aerospace systems is limited to standard 28 V dc systems, whereas the next generation of aerospace systems is expected to operate at higher voltages. Thus, there is an incentive to conduct basic research into corona, partial discharge and gaseous breakdown in gases at partial vacuum conditions, voltages, and frequencies, and for geometries corresponding to the environment encountered in current and future aerospace power systems. This work presents studies on the breakdown characteristics of helium, nitrogen and zero air under unipolar sinusoidal and pulsed voltages at frequencies varying from 20 kHz to 220 kHz in partial vacuum, for a point-to-point and point-to-plane electrode configurations. These voltages are compared to the dc data obtained under similar conditions. Also, breakdown voltage versus pressure curves similar to Pashcen plots are presented. Breakdown voltages of these gases as a function of signal frequency are also presented.
Koppisetty, Kalyan
Simulating and modeling the breakdown voltage in a semi-insulating GaAs P+N junction diode
NASA Astrophysics Data System (ADS)
This work aims to determine the characteristic I (breakdown voltage) of the inverse current in a GaAs PN junction diode, subject to a reverse polarization, while specifying the parameters that influence the breakdown voltage of the diode. In this work, we simulated the behavior of the ionization phenomenon by impact breakdown by avalanche of the PN junctions, subject to an inverse polarization. We will take into account both the trapping model in a stationary regime in the P+N structure using like material of basis the III-V compounds and mainly the GaAs semi-insulating in which the deep centers have in important densities. We are talking about the model of trapping in the space charge region (SCR) and that is the trap density donor and acceptor states. The carrier crossing the space charge region (SCR) of W thickness creates N electron�hole pairs: for every created pair, the electron and the hole are swept quickly by the electric field, each in an opposite direction, which comes back, according to an already accepted reasoning, to the crossing of the space charge region (SCR) by an electron or a hole. So the even N pair created by the initial particle provoke N2 ionizations and so forth. The study of the physical and electrical behaviour of semiconductors is based on the influence of the presence of deep centers on the characteristic I(V) current-tension, which requires the calculation of the electrostatic potential, the electric field, the integral of ionization, the density of the states traps, the diffusion current of minority in the regions (1) and (3), the current thermal generation in the region (2), the leakage current in the surface, and the breakdown voltage.
Resfa, A.; Menezla, Brahimi. R.; Benchhima, M.
Simplified fabrication of back surface electric field silicon cells and novel characteristics of such cells
NASA Technical Reports Server (NTRS)
An investigation of the characteristics and behavior of 10 ohm-cm silicon cells having abnormally high open-circuit voltages was made. The cells studied were made by a new, highly simplified, contact fabrication process which creates both a contact and a thin electric field region at the cell back surface without the need for phosphorus layer removal. These cells had open-circuit voltages of about 0.58 V and their performance as a function of thickness, temperature, and 1 MeV electron irradiation is detailed. The study showed that 10 ohm-cm back-surface-field cells can have the high initial efficiencies and desirable temperature behavior of low resistivity cells. Thin back-surface-field cells were made and showed, in addition, much greater radiation damage resistance. A mechanism is proposed to explain the results.
Mandelkorn, J.; Lamneck, J. H., Jr.
Some characteristics of polymers in composite materials and as electrical conductors
NASA Technical Reports Server (NTRS)
The characteristics of carbon fibers (CF) made from polyacrylonitrile (PAN) materials are discussed, together with research on conducting polymers. CF materials have better mechanical properties, chemical inertness, and higher stiffness than metallic materials but are subject to environmental instability, flammability, and delamination fatigue. Polymerization procedures for the monopolymer PAN are described, noting the use of SEM and X-ray diffraction techniques for studying the fiber structure. High modulus and strength of CF are caused by covalent sp(2) bonds in hexagonal carbon rings, which are stronger than the same links in diamonds. Details of the molecular chain structures and macroformations, stress-strain as a function of temperature, and thermosetting and glass transition temperatures of polymers are provided. Computational quantum chemistry techniques are being applied to studying electrical conductance in polymers, mainly to discover ways to stabilize the materials. Doped CH(x) has exhibited photovoltaic properties and other polymers have become superconductors at cryogenic temperatures.
Hansen, C. F.
GeTe sequences in superlattice phase change memories and their electrical characteristics
We studied GeTe structures in superlattice phase change memories (superlattice PCMs) with a [GeTe/Sb{sub 2}Te{sub 3}] stacked structure by X-ray diffraction (XRD) analysis. We examined the electrical characteristics of superlattice PCMs with films deposited at different temperatures. It was found that XRD spectra differed between the films deposited at 200?�C and 240?�C; the differences corresponded to the differences in the GeTe sequences in the films. We applied first-principles calculations to calculate the total energy of three different GeTe sequences. The results showed the Ge-Te-Ge-Te sequence had the lowest total energy of the three and it was found that with this sequence the superlattice PCMs did not run.
Ohyanagi, T., E-mail: firstname.lastname@example.com; Kitamura, M.; Takaura, N. [Low-Power Electronics Association and Projects (LEAP), Onogawa 16-1, Tsukuba, Ibaraki 305-8569 (Japan); Araidai, M. [Department of Computational Science and Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Kato, S. [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571 (Japan); Shiraishi, K. [Department of Computational Science and Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571 (Japan)
Electrical characteristics and interface structure of magnetic tunnel junctions with hafnium oxyfluoride barrier
We have studied the effects of fluorine inclusion on the electrical transport characteristics and interface structure of the hafnium oxide barrier in a magnetic tunnel junction. The tunneling magnetoresistance (TMR) and resistance-area (RA) as a function of oxidation time show that the TMR ratio of the hafnium oxyfluoride barrier is higher (8.3%) than that of the hafnium oxide barrier (5.7%) at their optimum conditions, and the oxyfluoride barrier junctions maintain a high TMR ratio even when the RA product increases by three orders of magnitude. X-ray photoelectron spectroscopy analysis shows that the fluorine atoms in the oxyfluoride barrier play an important role in the formation of a barrier with uniform composition. We believe that the initial fluoride layer is causing the subsequent oxygen diffusion to slow down, resulting in the formation of a defect-free hafnium oxide layer. These results are consistent with what we have found for aluminum oxyfluoride barriers.
Yu, Y.Y.; Kim, D.S.; Char, K. [Center for Strongly Correlated Materials Research and School of Physics, Seoul National University, Seoul 151-742 (Korea, Republic of)
Two-dimensional Effects in High Power Microwave Breakdown
NASA Astrophysics Data System (ADS)
A major limiting factor in transmission of high power microwave radiation is dielectric window breakdown. A one-dimensional particle-in-cell/Monte Carlo collision (PIC/MCC) model was used to study dielectric window breakdown from vacuum multipactor to collisional microwave discharge for noble gases [1]. It showed that multipactor on the dielectric window drives breakdown at low pressure, and volumetric collisional ionization is the main mechanism for breakdown at high pressure. A Monte Carlo (MC) model was also used to investigate dielectric window breakdown in two-dimensionals, including spatial variation of the microwave electric field in transverse direction [2]. The breakdown times were consistent with their experiment data and also showed the interesting feature of electron clusters above the window. MC, however, is not self-consistent and neglects the space charge effect resulting from the charge build-up. In this work, two-dimensional PIC/MCC was employed to investigate the breakdown in oxygen including the space charge effect. [1] H.C. Kim, and J.P. Verboncoeur, Phys. Plasmas, 13, 123506(2006). [2] J.T. Krile, A.A. Neuber, and H. G. Krompholz, Appl. Phys. Lett., 89, 201501(2006).
Nam, Sang Ki; Lim, Chul-Hyun; Verboncoeur, John
Electrical characteristics of rf-magnetron sputtered BaTa 2O 6 thin film
NASA Astrophysics Data System (ADS)
The characteristics of radio-frequency magnetron sputtered BaTa 2O 6 thin films with aluminum (Al) top and indium tin oxide (ITO) bottom electrodes have been investigated as a function of applied field and temperature. The optical transmittance in the visible range was in range of 80-90% regardless of the substrate temperature. The dielectric constant increased from 20 to 30 with increasing the substrate temperature and nearly independent of the frequency in the range of 0.3-100 kHz but the loss factors increased with increasing the substrate temperature at high frequency. The leakage currents of BaTa 2O 6 thin film are in the order of 10 -6-10 -7A/cm 2 at the applied field of 1 MV/cm and the charge storage capacitance ( ?Ebreakdown) are 5.64 (100�C), 10.6 (200�C) and 11.8 (300�C) ?C/cm 2. From the deposition temperature, voltage polarity and thickness dependence of leakage current, we can conclude that the dominant conduction mechanism is ascribed to Schottky emission at high electric field (>1 MV/cm) and hopping conduction at low electric field (<1 MV/cm). The Schottky barrier heights measured are 1.14 eV at Al(+) and 0.8 eV at Al(-).
Kim, Y. S.; Lee, Y. H.; Sung, M. Y.
Water film motor driven by alternating electric fields: its dynamical characteristics.
The "liquid film motor," a novel device with important implications for basic research and technology, is analyzed. It works perfectly with both direct current (dc) and alternating current (ac) fields. We develop a mathematical model describing electrohydrodynamical (EHD) motions induced by ac fields, which are more complex and have wider technological applications than those produced by dc fields. The main characteristics of these motions, derived in our paper and in full agreement with the experimental ones, are as follows: (i) Rotation of the film requires that the frequencies of the ac fields are exactly the same and their magnitudes surpass a threshold, which depends on their phase difference. (ii) Vibrations may be induced by fields with different frequencies. (iii) The EHD motions strongly depend on the polarization induced by the external electric field. However, these motions are little affected by the liquid's electrical conductivity, viscosity, dielectric constant, and density. Our model also predicts several features, which have yet to be experimentally verified. PMID:22587187
Liu, Zhong-Qiang; Zhang, Guang-Cai; Li, Ying-Jun; Jiang, Su-Rong
Optical measurements for interfacial conduction and breakdown
NASA Astrophysics Data System (ADS)
Measurements and calculations contributing to the understanding of space and surface charges in practical insulation systems are given. Calculations are presented which indicate the size of charge densities necessary to appreciably modify the electric field from what would be calculated from geometrical considerations alone. Experimental data is also presented which locates the breakdown in an electrode system with a paper sample bridging the gap between the electrodes. It is found that with careful handling, the breakdown does not necessarily occur along the interface even if heavily contaminated oil is used. The effects of space charge in the bulk liquid are electro-optically examined in nitrobenzene and transformer oil. Several levels of contamination in transformer oil are investigated. Whereas much space charge can be observed in nitrobenzene, very little space charge, if any, can be observed in the transformer oil samples even at temperatures near 100 degrees C.
Hebner, R. E., Jr.; Kelley, E. F.; Hagler, J. N.
Kerr electro-optic measurements for electric field and space charge distributions using similar and dissimilar electrode pairs
The electrical breakdown strength of insulating materials is a major limiting factor of reliability in electric power, medical devices, and other high electric field applications. Electrical breakdown strength increase ...
Nowocin, John Kendall
We present a simple model of breakdown in rf cavities. For most events this involves tensile stress and tensile strength, however other effects can also contribute. We discuss the effects of different materials, fatigue, high pressure gas, primary and secondary emission sites, local field enhancements, dark currents, secondary emission, work functions, magnetic fields, macro and microscopic fracture mechanisms high current densities, surface and subsurface defects, and astronomical power densities. While primarily devoted to normal conductors, this work also has consequences for superconducting rf surfaces.
Norem, J.; Hassanein, A.; Insepov, Z.; Konkashbaev, I.
Soluble N-Type organic thin-film transistors with enhanced electrical characteristics
NASA Astrophysics Data System (ADS)
We fabricated and investigated soluble, organic, thin-film transistors (OTFTs) containing `[6, 6]-phenyl-C61-butyric acid methyl ester (PCBM)' as a semiconducting layer, and an organic dielectric buffer (cross-linked poly-4-vinylphenol) as a dielectric buffer-layer to improve electrical characteristics. The semiconducting layer of the devices was fabricated by the drop-casting method where PCBM was dissolved in three different solvents (odichlorobenzene, chloroform, and chlorobenzene). From the transfer and output characteristics of the PCBM OTFTs, a threshold voltage of 10 V, sub-threshold slope of 10 V/dec, on/off current ratio of 7.305 � 103, and field-effect mobility of 1.53 � 10-2 cm2/Vs were obtained; for PCBM using o-dichlorobenzene solvent and an organic dielectric buffer layer. It was also found that the hysteresis for the same device was improved conspicuously compared to the other devices, by the above-mentioned condition.
Lee, Ho Won; Lee, Seok Jae; Koo, Ja Ryong; Cho, Eou Sik; Kwon, Sang Jik; Kim, Woo Young; Park, Jaehoon; Kim, Young Kwan
Nanocrystalline non-stoichiometric SBT: Effect of milling duration on structural and electrical characteristics
In the present work, nanocrystalline specimens of non-stoichiometric Strontium Bismuth Tantalate (SBT) ferroelectric ceramics were synthesized by mechanical activation process using a high energy planetary ball mill. The powders were milled for different milling durations (5, 10, 20 h) keeping the milling speed fixed at 300 rpm. Microstructural characterizations have been performed using X-ray diffraction, scanning electron microscopy, electron diffraction and transmission electron microscopy. Nanocrystallites with average grain size in the range of 30-50 nm are observed to be formed. Grain size is observed to decrease with increasing milling duration. Detailed dielectric study as a function of temperature has been carried out. It is observed that dielectric constant increases and dielectric loss decreases with increasing milling duration. The observed characteristics have been explained in terms of increased number of grain boundaries due to the reduction of granular size. - Highlights: Black-Right-Pointing-Pointer In the present work nano crystalline non-stoichiometric SBT has been synthesized. Black-Right-Pointing-Pointer The technique involved is mechanical activation (high energy ball milling). Black-Right-Pointing-Pointer The milling duration has been optimized. Black-Right-Pointing-Pointer Sr0.8Bi2.2Ta2O9 milled for 20 hours exhibit enhanced electrical characteristics.
Sugandha, E-mail: email@example.com [Thin Film and Material Science Laboratory, Department of Applied Physics, Delhi Technological University (Formerly Delhi College of Engineering), Delhi-110042 (India); Jha, A.K., E-mail: email@example.com [Thin Film and Material Science Laboratory, Department of Applied Physics, Delhi Technological University (Formerly Delhi College of Engineering), Delhi-110042 (India); Department of Applied Sciences, Ambedkar Institute of Technology, GGSIPU, Geeta Colony, Delhi-110092 (India)
Effects of nuclear radiation on a high-reliability silicon power diode. 4: Analysis of reverse bias characteristics
NASA Technical Reports Server (NTRS)
The effects of nuclear radiation on the reverse bias electrical characteristics of one hundred silicon power diodes were investigated. On a percentage basis, the changes in reverse currents were large but, due to very low initial values, this electrical characteristic was not the limiting factor in use of these diodes. These changes were interpreted in terms of decreasing minority carrier lifetimes as related to generation-recombination currents. The magnitudes of reverse voltage breakdown were unaffected by irradiation.
Been, J. F.
Investigating changes of electrical characteristics of the saturated zone affected by hazardous organic waste
NASA Astrophysics Data System (ADS)
The Picillo Farm, EPA Superfund Site, in western Rhode Island was an unauthorized disposal site of hazardous organic chemicals. Predominantly organic contaminants have entered an aquifer comprised of layered glacial deposits and fractured bedrock and spread past the site boundaries with groundwater flow. Hydraulic conductivities in the glacial deposits range over two orders of magnitude and fractures and faults in the granitic bedrock further complicate the spreading of contaminants. Monitoring wells delineate two plumes that extend towards a fault-controlled valley with lakes and wetlands; one to the northwest and the other to the southwest. In this investigation we studied the electrical characteristics of both plumes. One dimensional Schlumberger depth soundings were conducted along several profile lines over the plumes and compared to those over non-contaminated sections of the site. With regard to the southwestern plume, high formation factors (ratio of bulk layer to pore water resistivity) between 12 and 45 were observed compared to values between 2.5 and 7.7 measured over the non-contaminated sections. Also, high values (> 5) of vertical electrical anisotropy (ratio of geoelectrically determined depth to high resistivity bedrock to drilled depth to bedrock) were measured over the contaminated part of the site. These values are extremely high compared to other non-contaminated sites (range: 2 to 3) in glacial stream channels of southern Rhode Island. Geoelectric measurements were affected by lateral effects. However, the consistency of high formation factors (11 to 35) and high vertical anisotropies (3 to 5) over the southwestern plume in comparison to low formation factors (3 to 8) and vertical anisotropies (1 to 1.5) over non-contaminated sites represents a marked difference between both sites. Overall, the Schlumberger depth soundings are less susceptible to near-surface lateral inhomogeneities than expected from other geoelectrical methods. Also, the disadvantage of a 1D interpretation was compensated by estimating resistivity and thickness ranges within the concept of non-uniqueness using the Dar Zarrouk parameters (Maillet, R., 1947. The fundamental equations of electrical prospecting. Geophysics, 12(4): 529-556.). The results over the northwestern plume, i.e. an area with higher contaminant concentration than the southwestern plume, were mixed and showed no consistent trends. Predominantly reducing conditions, as indicated by the presence of soluble ferric (FeII) iron hydroxides in ground water samples, increased the electrical conductivity. This is believed to have compensated the effect of high formation factors on the bulk saturated layer resistivity within the affected area.
Frohlich, Reinhard K.; Barosh, Patrick J.; Boving, Thomas
Aspects of dielectric breakdown in a model for disordered non-linear composites
We study dielectric breakdown in a semi-classical bond percolation model for non-linear composite materials introduced by us and the related breakdown exponent near the percolation threshold in two dimensions. The breakdown exponent after doing finite size scaling analysis is found to be tB ⋍ 1.42. We discuss in detail the differences in our model from the traditional models for electric
A. K. Gupta; A. K. Sen
A method to investigate the electron scattering characteristics of ultrathin metallic films by in situ electrical resistance measurements
In this article, a method to measure the electrical resistivity/conductivity of metallic thin films during layer growth on specific underlayers is described. The in situ monitoring of an underlayer electrical resistance, its change upon the incoming of new material atoms/molecules, and the growth of a new layer are presented. The method is easy to implement and allows obtaining in situ experimental curves of electrical resistivity dependence upon film thickness with a subatomic resolution, providing insight in film growth microstructure characteristics, specular/diffuse electron scattering surfaces, and optimum film thicknesses.
Trindade, I. G.; Sousa, J. B. [IFIMUP and IN, Rua do campo Alegre, 687, 4169-007 Porto (Portugal); Department of Physics, FCUP, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Fermento, R. [Instituto de Microelectronica de Madrid, Isaac Newton 8, 28760 Tres Cantos, Madrid (Spain); Leitao, D. [IFIMUP and IN, Rua do campo Alegre, 687, 4169-007 Porto (Portugal)
Study of bulk and elementary screw dislocations assisted reverse breakdown in low-voltage (<250 V) 4H-SiC p{sup +}n junction diodes. Part 1: DC properties
Given the high-density ({approximately}10{sup 4} cm{sup {minus}2}) of elementary screw dislocations (Burgers vector = 1c with no hollow core) in commercial SiC wafers and epilayers, all large current (>1 A) SiC power devices will likely contain elementary screw dislocations for the foreseeable future. It is therefore important to ascertain the electrical impact of these defects, particularly in high-field vertical power device topologies where SiC is expected to enable large performance improvements in solid-state high-power systems. This paper compares the dc-measured reverse-breakdown characteristics of low-voltage (<250 V) small-area (<5 {times} 10{sup {minus}4} cm{sup 2}) 4H-SiC p{sup +}n diodes with and without elementary screw dislocations. Diodes containing elementary screw dislocations exhibited higher pre-breakdown reverse leakage currents, softer reverse breakdown current-voltage (I-V) knees, and highly localized microplasmic breakdown current filaments compared to screw dislocation-free devices. The observed localized 4H-SiC breakdown parallels microplasmic breakdown observed in silicon and other semiconductors, in which space-charge effects limit current conduction through the local microplasma as reverse bias is increased.
Neudeck, P.G. [NASA Lewis Research Center, Cleveland, OH (United States)] [NASA Lewis Research Center, Cleveland, OH (United States); Huang, W.; Dudley, M. [State Univ. of New York, Stony Brook, NY (United States). Dept. of Materials Science and Engineering] [State Univ. of New York, Stony Brook, NY (United States). Dept. of Materials Science and Engineering
Study of Bulk and Elementary Screw Dislocation Assisted Reverse Breakdown in Low-Voltage (less than 250 V) 4H-SiC p(+)n Junction diodes. Part 1; DC Properties
NASA Technical Reports Server (NTRS)
Given the high density (approx. 10(exp 4)/sq cm) of elementary screw dislocations (Burgers vector = 1c with no hollow core) in commercial SiC wafers and epilayers, all appreciable current (greater than 1 A) SiC power devices will likely contain elementary screw dislocations for the foreseeable future. It is therefore important to ascertain the electrical impact of these defects, particularly in high-field vertical power device topologies where SiC is expected to enable large performance improvements in solid-state high-power systems. This paper compares the DC-measured reverse-breakdown characteristics of low-voltage (less than 250 V) small-area (less than 5 x 10(exp -4)/sq cm) 4H-SiC p(+)n diodes with and without elementary screw dislocations. Compared to screw dislocation-free devices, diodes containing elementary screw dislocations exhibited higher pre-breakdown reverse leakage currents, softer reverse breakdown I-V knees, and highly localized microplasmic breakdown current filaments. The observed localized 4H-SiC breakdown parallels microplasmic breakdowns observed in silicon and other semiconductors, in which space-charge effects limit current conduction through the local microplasma as reverse bias is increased.
Neudeck, Philip G.; Huang, Wei; Dudley, Michael
NSDL National Science Digital Library
5th Grade Electricity Try this Using Electricity Activity. Don't forget to follow the directions! Use this to learn more about electricity: Blobz Guide to Electricity Follow the directions closely! Learn more about Electricity with Electricity Tech-Topics. ...
Miss Lerdahl
Study of the effect of machining parameters on the machining characteristics in electrical discharge machining of tungsten carbide
Electrical discharge machining (EDM) is a process for shaping hard metals and forming deep and complex-shaped holes by arc erosion in all kinds of electro-conductive materials. The objective of this research is to study the influence of operating parameters of EDM of tungsten carbide on the machining characteristics. The effectiveness of the EDM process with tungsten carbide is evaluated in
S. H. Lee; X. P. Li
Effect of electrical discharge machining on surface characteristics and machining damage of AISI D2 tool steel
In this work the electrical discharge machining (EDM) of AISI D2 tool steel was investigated. The surface characteristics and machining damage caused by EDM were studied in terms of machining parameters. Based on the experimental data, an empirical model of the tool steel was also proposed. A new damage variable was used to study the EDM damage. The workpiece surface
Y. H. Guu; H. Hocheng; C. Y. Chou; C. S. Deng
Influence of ambient gases on the dc saturated breakdown field of molybdenum, tungsten, and copper during intense breakdown conditioning
NASA Astrophysics Data System (ADS)
A comprehensive investigation of the effect of Ar, H2, air, and CO on the saturated breakdown field (Esat) of molybdenum, tungsten, and copper has been performed at intensive breakdown conditioning. A significant decrease in Esat is observed for molybdenum and tungsten when exposed to air. Specifically, at air pressures of �10-5mbar, the decrease in Esat is found to be up to 50% and �30% compared to UHV conditions for molybdenum and tungsten, respectively. In addition, a �30% decrease is found when molybdenum is conditioned with a �10-5mbar CO pressure. Surface analysis measurements and breakdown conditioning in O2 ambience imply that the origin of the decrease in Esat is closely linked to oxide formation on the electrode surfaces. Ex situ heat treatment of molybdenum is shown to improve the breakdown characteristics drastically.
Ramsvik, T.; Calatroni, S.; Reginelli, A.; Taborelli, M.
Influence of ambient gases on the dc saturated breakdown field of molybdenum, tungsten, and copper during intense breakdown conditioning
A comprehensive investigation of the effect of Ar, H2, air, and CO on the saturated breakdown field (Esat) of molybdenum, tungsten, and copper has been performed at intensive breakdown conditioning. A significant decrease in Esat is observed for molybdenum and tungsten when exposed to air. Specifically, at air pressures of ?10-5???mbar, the decrease in Esat is found to be up to 50% and ?30% compared to UHV conditions for molybdenum and tungsten, respectively. In addition, a ?30% decrease is found when molybdenum is conditioned with a ?10-5???mbar CO pressure. Surface analysis measurements and breakdown conditioning in O2 ambience imply that the origin of the decrease in Esat is closely linked to oxide formation on the electrode surfaces. Ex situ heat treatment of molybdenum is shown to improve the breakdown characteristics drastically.
Ramsvik, T; Reginelli, A; Taborelli, M
Space charge behavior in low density polyethylene at pre-breakdown
It has been known that the electrical breakdown of insulating materials is strongly affected by the formation of space charge in the bulk of the materials. Many researchers have attempted to study the relationship between the space charge and the breakdown; however, it has not been clarified yet. Although the pulsed electroacoustic (PEA) method has been widely used to observe
Kohei Matsui; Yasuhiro Tanaka; Tatsuo Takada; Tadashi Fukao; Kaori Fukunaga; Takashi Maeno; John M. Alison
Effects of defects on dielectric breakdown phenomena and life time of polymeric insulation
Effects of defects on dielectric breakdown phenomena and life time of PE insulation were investigated. Volatile impurity was observed by FT-IR spectrum and oxidation reaction was faster on Cu than Al open pan. From the artificial impurities such as carbon fiber, nylon, Cu and Al particles, electrical tree started and dielectric breakdown was occurred finally. Space charge formed by the
Young-Shin Cho; Jang-Ho Park; Mi-Ja Shim; Sang-Wook Kim
Effect of hydrogen impurity on the electrical characteristics of neon-argon gas mixtures. I. Measurement of ionization coefficients
The effect of H2 on the breakdown potential and Townsend ionization coefficients for Ne-A mixtures were measured by the luminous-flux method. Both argon and hydrogen form Penning mixtures with neon. The breakdown potentials for Ne-A gas mixtures are determined by the Penning reaction, Nem+A?Ne+e+A+, between metastable neon (Nem) and ground state A atoms. At low H2 concentrations (<0.1%) the breakdown
A. K. Bhattacharya
Study of space-charge effects on dielectric breakdown of polymers by direct probing
Direct and quantitative probing of space charge was carried out to study effects of space charge on dielectric breakdown of polymeric insulating materials. In poly-p-phenylene sulfide, in which dielectric-breakdown characteristics were explained in terms of space-charge formation, positive homo space charge was observed. The amount and the depth of space charge detected could explain the dependence of impulse breakdown strength
Yasuo Suzuoki; Yohji Matsukawa; Sang-Ok Han; Akihiro Fujii; Jong-Seok Kim; Teruyoshi Mizutani; M. Ieda; N. Yoshifuji
Electrical properties of epoxy resin based nano-composites
We investigate the electrical properties of composite materials prepared as nano and sub-micro scale metal-oxide particles embedded in a commercial resin. The filler particles are barium titanate and calcium copper titanate. The physical and structural characteristics of constituents and the fabricated composites are reported. The electrical characterization of the composite samples are performed with the time- and frequency-domain dielectric spectroscopy techniques. The electrical breakdown strength of samples with nano and sub-micron size particles have better electrical insulation properties than the unfilled resin.
Tuncer, Enis [ORNL; Sauers, Isidor [ORNL; James, David Randy [ORNL; Ellis, Alvin R [ORNL; Paranthaman, Mariappan Parans [ORNL; Aytug, Tolga [ORNL; Sathyamurthy, Srivatsan [ORNL; More, Karren Leslie [ORNL; Li, Jing [ORNL; Goyal, Amit [ORNL
Electrical switching dynamics and broadband microwave characteristics of VO2 radio frequency devices
NASA Astrophysics Data System (ADS)
Vanadium dioxide (VO2) is a correlated electron system that features a metal-insulator phase transition (MIT) above room temperature and is of interest in high speed switching devices. Here, we integrate VO2 into two-terminal coplanar waveguides and demonstrate a large resistance modulation of the same magnitude (>103) in both electrically (i.e., by bias voltage, referred to as E-MIT) and thermally (T-MIT) driven transitions. We examine transient switching characteristics of the E-MIT and observe two distinguishable time scales for switching. We find an abrupt jump in conductivity with a rise time of the order of 10 ns followed by an oscillatory damping to steady state on the order of several ?s. We characterize the RF power response in the On state and find that high RF input power drives VO2 further into the metallic phase, indicating that electromagnetic radiation-switching of the phase transition may be possible. We measure S-parameter RF properties up to 13.5 GHz. Insertion loss is markedly flat at 2.95 dB across the frequency range in the On state, and sufficient isolation of over 25 dB is observed in the Off state. We are able to simulate the RF response accurately using both lumped element and 3D electromagnetic models. Extrapolation of our results suggests that optimizing device geometry can reduce insertion loss further and maintain broadband flatness up to 40 GHz.
Ha, Sieu D.; Zhou, You; Fisher, Christopher J.; Ramanathan, Shriram; Treadway, Jacob P.
Mechanical and electric characteristics of vacuum impregnated no-insulation HTS coil
NASA Astrophysics Data System (ADS)
For the conduction cooling application, epoxy impregnation is inevitable to enhance the thermal conduction. However, there have been several research results on the delamination problem with coated conductor and the main cause of the delamination is related with the different thermal contraction between epoxy, the insulation layer and the weak conductor. To avoid this problem, the amount of epoxy and insulation layer between conductors should be minimized or removed. Therefore, no insulation (NI) winding method and impregnation after dry winding can be considered to solve the problem. The NI coil winding method is very attractive due to high mechanical/thermal stability for the special purpose of DC magnets by removing the insulation layer. In this paper, the NI coil winding method and vacuum impregnation are applied to a HTS coil to avoid the delamination problem and enhance the mechanical/thermal stability for the conduction cooling application. Through the charging/discharging operation, electric/thermal characteristics are investigated at 77 K and 30 K.
Park, Heecheol; Kim, A.-rong; Kim, Seokho; Park, Minwon; Kim, Kwangmin; Park, Taejun
Propagation characteristics of a focused laser beam in a strontium barium niobate photorefractive crystal under reverse external electric field.
The propagation characteristics of a focused laser beam in a SBN:75 photorefractive crystal strongly depend on the signal-to-background intensity ratio (R=Is/Ib) under reverse external electric field. In the range 20>R>0.05, the laser beam shows enhanced self-defocusing behavior with increasing external electric field, while it shows self-focusing in the range 0.03>R>0.01. Spatial solitons are observed under a suitable reverse external electric field for R=0.025. A theoretical model is proposed to explain the experimental observations, which suggest a new type of soliton formation due to "enhancement" not "screening" of the external electrical field. PMID:25322227
Guo, Q L; Liang, B L; Wang, Y; Deng, G Y; Jiang, Y H; Zhang, S H; Fu, G S; Simmonds, P J
Dielectric breakdown induced by picosecond laser pulses
NASA Technical Reports Server (NTRS)
The damage thresholds of transparent optical materials were investigated. Single picosecond pulses at 1.06 microns, 0.53 microns and 0.35 microns were obtained from a mode locked Nd-YAG oscillator-amplifier-frequency multiplier system. The pulses were Gaussian in space and time and permitted the determination of breakdown thresholds with a reproducibility of 15%. It was shown that the breakdown thresholds are characteristic of the bulk material, which included nine alkali halides, five different laser host materials, KDP, quartz, sapphire and calcium fluoride. The extension of the damage data to the ultraviolet is significant, because some indication was obtained that two- and three-photon absorption processes begin to play a role in determining the threshold. Throughout the visible region of the spectrum the threshold is still an increasing function of frequency, indicating that avalanche ionization is the dominant factor in determining the breakdown threshold. This was confirmed by a detailed study of the damage morphology with a high resolution microscope just above the threshold. The influence of self focusing is discussed, and evidence for beam distortion below the power threshold for complete self focusing is presented, confirming the theory of Marburger.
Smith, W. L.; Bechtel, J. H.; Bloembergen, N.
NSDL National Science Digital Library
William J. Beaty, an Electrical Engineer at the University of Washington, has posted this website about electricity. He offers a simple answer to the question, What Is "Electricity?," identifies twenty misconceptions he has found to be barriers to understanding electricity, and then proceeds to explain various aspects of electricity. Beaty's debunking articles address common misconceptions about circuitry, doorknob sparks, voltage, and more.
Beaty, William J.
Ion Solid Interaction And Surface Modification At RF Breakdown In High-Gradient Linacs
Ion solid interactions have been shown to be an important new mechanism of unipolar arc formation in high-gradient rf linear accelerators through surface self-sputtering by plasma ions, in addition to an intense surface field evaporation. We believe a non-Debye plasma is formed in close vicinity to the surface and strongly affects surface atomic migration via intense bombardment by ions, strong electric field, and high surface temperature. Scanning electron microscope studies of copper surface of an rf cavity were conducted that show craters, arc pits, and both irregular and regular ripple structures with a characteristic length of 2 microns on the surface. Strong field enhancements are characteristic of the edges, corners, and crack systems at surfaces subjected to rf breakdown.
Insepov, Zeke; Norem, Jim [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Veitzer, Seth [Tech-X Corp., 5621 Arapahoe Ave., Suite A, Boulder CO 80303 (United States)
Dielectric breakdown in solids modeled by DBM and DLA
Using numerical simulation, two stochastic models of electrical treeing in solid dielectrics are compared. These are the diffusion-limited aggregation (DLA) model and the dielectric breakdown model (DBM or ?-model). On a linear two-dimensional geometry, the relationship between both models, when the size of the structures is of the order of the experimental samples (the electrode gap is 100 times the
I. M Irurzun; P. Bergero; V. Mola; M. C Cordero; J. L Vicente; E. E. Mola
Simulation of root development based on the dielectric breakdown model
Knowing the root distribution in soil is essential for estimating water uptake by plant roots. It is difficult, however, to characterize and model undisturbed root systems. Root development in a two-dimensional potential field is simulated with the dielectric breakdown model (DBM), which implies a similarity between electric discharge and root distribution. A weighted potential gradient with an exponent rj was
Simulation of root development based on the dielectric breakdown model
Knowing the root distribution in soil is essential for estimating water uptake by plant roots. It is difficult, however, to characterize and model undisturbed root systems. Root development in a two-dimensional potential field is simulated with the dielectric breakdown model (DBM), which implies a similarity between electric discharge and root distribution. A weighted potential gradient with an exponent ? was
Silicon dioxide breakdown lifetime enhancement under bipolar bias conditions
The authors point out that time to breakdown (tBD) of silicon dioxide has a pronounced frequency dependence when it is measured under bipolar bias conditions. At high frequencies, bipolar t BD, can be enhanced by two orders of magnitude over the tBD, obtained using DC or unipolar pulse bias of the same frequency and electric field. The lifetime improvement is
Elyse Rosenbaum; Zhihong Liu; Chenming Hu
Threshold energy effect on avalanche breakdown voltage in semiconductor junctions
The band bending for avalanche breakdown in semiconductor junctions and its temperature dependence are predicted taking account of threshold energy effects on the ionization process in semiconductors. Where experimental results exist, the theoretical predictions and experimental results are in excellent agreement. In the high electric field region inclusion of both bulk and boundary threshold energy effects is essential. The predictions
Y. Okuto; C. R. Crowell
Direct current breakdown in gases for complex geometries from high vacuum to atmospheric pressure
NASA Astrophysics Data System (ADS)
The demand for improved performances of power transmission devices requires ever smaller dimensions and higher working voltages which lead to increased risk of breakdown, for example, in satellite slip rings. Previous works are mostly limited to breakdown in simple geometries such as parallel plates or pin to plate. Here we discuss the effect of more complex geometries for dc breakdown in gases over a large pressure range (2 � 10-5 to 103 mbar). Experimental measurements of dc gas discharge breakdown in a ring assembly geometry are compared with a numerical simulation model for gas breakdown using a fluid model. Starting with parallel plates (1 and 100 mm gap width representing approximately the shortest and longest electric field path lengths in the ring assembly geometry) and extending to double gap and multi-gap geometries, an understanding of the overall shape of the breakdown voltage versus pressure curve is established. The high (low) pressure thresholds of gas discharge are determined by the shortest (longest) electric field path length in a complex geometry. Moreover, the availability of multiple path lengths leads to a breakdown voltage minimum over a wide range of intermediate pressure because breakdown can occur in the most favourable gap. Finally, the numerical simulation in the ring assembly shows the importance of parameters such as the secondary electron emission coefficient which play a major role in determining the breakdown voltage value.
Schnyder, R.; Howling, A. A.; Bommottet, D.; Hollenstein, Ch
Breakdown in the pretext tokamak
Data are presented on the application of ion cyclotron resonance RF power to preionization in tokamaks. We applied 0.3-3 kW at 12 MHz to hydrogen and obtained a visible discharge, but found no scaling of breakdown voltage with any parameter we were able to vary. A possible explanation for this, which implies that higher RF power would have been much more effective, is discussed. Finally, we present our investigation of the dV/dt dependence of breakdown voltage in PRETEXT, a phenomenon also seen in JFT-2. The breakdown is discussed in terms of the physics of Townsend discharges.
Benesch, J.F.
Electrical performance characteristics of high power converters for space power applications
NASA Technical Reports Server (NTRS)
The first goal of this project was to investigate various converters that would be suitable for processing electric power derived from a nuclear reactor. The implementation is indicated of a 20 kHz system that includes a source converter, a ballast converter, and a fixed frequency converter for generating the 20 kHz output. This system can be converted to dc simply by removing the fixed frequency converter. This present study emphasized the design and testing of the source and ballast converters. A push-pull current-fed (PPCF) design was selected for the source converter, and a 2.7 kW version of this was implemented using three 900 watt modules in parallel. The characteristic equation for two converters in parallel was derived, but this analysis did not yield any experimental methods for measuring relative stability. The three source modules were first tested individually and then in parallel as a 2.7 kW system. All tests proved to be satisfactory; the system was stable; efficiency and regulation were acceptable; and the system was fault tolerant. The design of a ballast-load converter, which was operated as a shunt regulator, was investigated. The proposed power circuit is suitable for use with BJTs because proportional base drive is easily implemented. A control circuit which minimizes switching frequency ripple and automatically bypasses a faulty shunt section was developed. A nonlinear state-space-averaged model of the shunt regulator was developed and shown to produce an accurate incremental (small-signal) dynamic model, even though the usual state-space-averaging assumptions were not met. The nonlinear model was also shown to be useful for large-signal dynamic simulation using PSpice.
Stuart, Thomas A.; King, Roger J.
Dynamic characteristics and electromechanical fields of 1-3 piezoelectric/polymer composites under AC electric fields
NASA Astrophysics Data System (ADS)
This paper studies the dynamic electromechanical response of 1-3 piezoelectric/polymer composites under alternating current (AC) electric fields. The piezocomposites contain square or circular piezoelectric rods in an epoxy matrix. Experiments were conducted to measure the electrical impedance and phase angle at various frequencies, using the device specimen of the 1-3 piezocomposites. Three dimensional finite element analysis was also employed to calculate the frequency characteristics, and a comparison is made between simulation and experiment. The dynamic electromechanical fields in the 1-3 piezocomposites are then discussed in detail.
Narita, Fumio; Shindo, Yasuhide; Watanabe, Taiki
P. J. Antsaklis, "Polynomial Matrix Characterization Using Characteristic Values and Vectors," Publication No. 80/18, Dept. of Electrical Engineering, Imperial College, July 1980.
," Publication No. 80/18, Dept. of Electrical Engineering, Imperial College, July 1980. #12;P. J. Antsaklis. of Electrical Engineering, Imperial College, July 1980. #12;P. J. Antsaklis, "Polynomial Matrix Characterization Using Characteristic Values and Vectors," Publication No. 80/18, Dept. of Electrical Engineering
Antsaklis, Panos
Integrating nanopore sensors within microfluidic channel arrays using controlled breakdown.
Nanopore arrays are fabricated by controlled dielectric breakdown (CBD) in solid-state membranes integrated within polydimethylsiloxane (PDMS) microfluidic devices. This technique enables the scalable production of independently addressable nanopores. By confining the electric field within the microfluidic architecture, nanopore fabrication is precisely localized and electrical noise is significantly reduced. Both DNA and protein molecules are detected to validate the performance of this sensing platform. PMID:25631885
Tahvildari, Radin; Beamish, Eric; Tabard-Cossa, Vincent; Godin, Michel
Fractal Dimension of Dielectric Breakdown
It is shown that the simplest nontrivial stochastic model for dielectric breakdown naturally leads to fractal structures for the discharge pattern. Planar discharges are studied in detail and the results are compared with properly designed experiments.
L. Niemeyer; L. Pietronero; H. J. Wiesmann
Marine chemistry: Marine mercury breakdown
The neurotoxin methylmercury accumulates in marine biota and their predators. An analysis of seabird egg shells suggests that sea-ice cover reduces the breakdown of this highly toxic compound in sea water.
Joel D. Blum
Marine chemistry: Marine mercury breakdown
NASA Astrophysics Data System (ADS)
The neurotoxin methylmercury accumulates in marine biota and their predators. An analysis of seabird egg shells suggests that sea-ice cover reduces the breakdown of this highly toxic compound in sea water.
Blum, Joel D.
Charge transport and breakdown physics in liquid/solid insulation systems
Liquid dielectrics provide superior electrical breakdown strength and heat transfer capability, especially when used in combination with liquid-immersed solid dielectrics. Over the past half-century, there has been extensive ...
Jadidian, Jouya
Elucidating the mechanisms behind pre-breakdown phenomena in transformer oil systems
The widespread use of dielectric liquids for high voltage insulation and power apparatus cooling is due to their greater electrical breakdown strength and thermal conductivity than gaseous insulators. In addition, their ...
Hwang, Jae-Won George, 1980-
Experimental and theoretical study of an improved breakdown voltage SOI LDMOS with a reduced cell pitch
NASA Astrophysics Data System (ADS)
An improved breakdown voltage (BV) SOI power MOSFET with a reduced cell pitch is proposed and fabricated. Its breakdown characteristics are investigated numerically and experimentally. The MOSFET features dual trenches (DTMOS), an oxide trench between the source and drain regions, and a trench gate extended to the buried oxide (BOX). The proposed device has three merits. First, the oxide trench increases the electric field strength in the x-direction due to the lower permittivity of oxide (?ox) than that of Si (?Si). Furthermore, the trench gate, the oxide trench, and the BOX cause multi-directional depletion, improving the electric field distribution and enhancing the RESURF (reduced surface field) effect. Both increase the BV. Second, the oxide trench folds the drift region along the y-direction and thus reduces the cell pitch. Third, the trench gate not only reduces the on-resistance, but also acts as a field plate to improve the BV. Additionally, the trench gate achieves the isolation between high-voltage devices and the low voltage CMOS devices in a high-voltage integrated circuit (HVIC), effectively saving the chip area and simplifying the isolation process. An 180 V prototype DTMOS with its applied drive IC is fabricated to verify the mechanism.
Xiaorong, Luo; Xiaowei, Wang; Gangyi, Hu; Yuanhang, Fan; Kun, Zhou; Yinchun, Luo; Ye, Fan; Zhengyuan, Zhang; Yong, Mei; Bo, Zhang
Effect of annealing on magnetostrictive characteristics of a grain-oriented electrical steel with ordinary and refined domain structure
NASA Astrophysics Data System (ADS)
We present the results of investigating the effect of annealing on the magnetostrictive characteristics of a grain-oriented electrical steel (GOES) with ordinary and refined domain structure. Not infrequently, the annealing of sheet samples leads to an increase in the electromagnetic induction B 100 and, simultaneously, to an enhancement in the specific electromagnetic losses P 1.7/50. In a GOES with a refined domain structure, the minimum absolute values of ?0-peak and ?peak-peak are observed before annealing. For these samples, after annealing, the magnetostrictive characteristics are impaired most severely. The mechanism for explaining this experimental fact has been suggested.
Redikul'tsev, A. A.; Korzunin, G. S.; Lobanov, M. L.; Rusakov, G. M.; Lobanova, L. V.
Direct spectroscopic determination of breakdown field in microwave discharges
The breakdown electric field E at microwave frequencies is usually determined as the result of a sequence of measurements of power, frequency, standing wave ratios, etc. Breakdown measurements are further complicated by impurity, plasma, and boundary effects. In contrast, the polarization-dependent Stark shift offers the possibility of direct measurement of E in microwave discharges. The magnitude of the shift depends on whether the light is viewed parallel or perpendicular to an applied electric field, as opposed to the isotropic collisional Stark broadening in dense plasmas. This technique has been used to measure electric fields in the cathode sheath of dc glow discharges. Kamp and Himmel report Stark splitting of Balmer series lines in low-pressure microwave (2.45 GHz) discharges irradiated by a supplementary microwave field (34.8 GHz) above the cutoff frequency to create a high electric field in the plasma. A similar method has been proposed for measuring electric fields near RF antennas in plasmas. Here we report low-resolution observations of the Stark shift of H alpha light (wavelength 656.3 nm) during breakdown from hydrogenic impurities in microwave discharges in argon at pressures p{ge}200 Torr. Fields of 2-5 kV/cm were measured. Our work differs from that of Kamp and Himmel in that it concerns the intrinsic, plasma-producing electric field in pulsed microwave discharges.
McNeill, D.H.; Efthimion, P.C. [EEI, Pluckemin, NJ (United States)
Performance characteristics of an electric vehicle lead-acid battery pack at elevated temperatures
NASA Technical Reports Server (NTRS)
Discharge testing data electric car battery pack over initial electrolyte temperature variations between 27 and 55 C are presented. The tests were conducted under laboratory conditions and then compared to detailed electric vehicle simulation models. Battery discharge capacity increased with temperature for constant current discharges, and battery energy capacity increased with temperature for constant power discharges. Dynamometer tests of the electric test vehicle showed an increase in range of 25% for the higher electrolyte temperature.
Chapman, P.
Investigating the Characteristics of Cobalt-Substituted MnZn Ferrites by Equivalent Electrical Elements
We investigated the electrical and magnetic properties of cobalt-substituted manganese-zinc soft ferrite by using the equivalent lumped elements acquired from the appropriate equivalent electrical circuit of polycrystalline ferrite. We applied the equivalent lumped circuit, combined with equivalent lumped resistances and capacitance, to determine the effect of microstructure on electrical and magnetic properties of cobalt-substituted manganese-zinc ferrites. Both the hysteresis loss
Tsorng-Juu Liang; Hsiau-Hsian Nien; Jiann-Fuh Chen
Fundamentals of undervoltage breakdown through the Townsend mechanism
NASA Astrophysics Data System (ADS)
The conditions under which an externally supplied pulse of electrons will induce breakdown in an undervoltaged, low-gain, DC discharge gap are experimentally and theoretically explored. The phenomenon is relevant to fundamental understanding of breakdown physics, to switching applications such as triggered spark gaps and discharge initiation in pulsed-plasma thrusters, and to gas-avalanche particle counters. A dimensionless theoretical description of the phenomenon is formulated and solved numerically. It is found that a significant fraction of the charge on the plates must be injected for breakdown to be achieved at low avalanche-ionization gain, when an electron undergoes fewer than approximately 10 ionizing collisions during one gap transit. It is also found that fewer injected electrons are required as the gain due to electron-impact ionization (alpha process) is increased, or as the sensitivity of the alpha process to electric field is enhanced by decreasing the reduced electric field (electric field divided by pressure, E/p). A predicted insensitivity to ion mobility implies that breakdown is determined during the first electron avalanche when space charge distortion is greatest. A dimensionless, theoretical study of the development of this avalanche reveals a critical value of the reduced electric field to be the value at the Paschen curve minimum divided by 1.6. Below this value, the net result of the electric field distortion is to increase ionization for subsequent avalanches, making undervoltage breakdown possible. Above this value, ionization for subsequent avalanches will be suppressed and undervoltage breakdown is not possible. Using an experimental apparatus in which ultraviolet laser pulses are directed onto a photo-emissive cathode of a parallel-plate discharge gap, it is found that undervoltage breakdown can occur through a Townsend-like mechanism through the buildup of successively larger avalanche generations. The minimum number of injected electrons required to achieve breakdown is measured in argon at pd values of 3-10 Torr-m. The required electron pulse magnitude was found to scale inversely with pressure and voltage in this parameter range. When higher-power infrared laser pulses were used to heat the cathode surface, a faster, streamer-like breakdown mechanism was occasionally observed. As an example application, an investigation into the requirements for initiating discharges in Gas-fed Pulsed Plasma Thrusters (GFPPTs) is conducted. Theoretical investigations based on order-of-magnitude characterizations of previous GFPPT designs reveal that high-conductivity arc discharges are required for critically-damped matching of circuit components, and that relatively fast streamer breakdown is preferable to minimize delay between triggering and current sheet formation. The faster breakdown mechanism observed in the experiments demonstrates that such a discharge process can occur. However, in the parameter space occupied by most thrusters, achieving the phenomenon by way of a space charge distortion caused purely by an electron pulse should not be possible. Either a transient change in the distribution of gas density, through ablation or desorption, or a thruster design that occupies a different parameter space, such as one that uses higher mass bits, higher voltages, or smaller electrode spacing, is required for undervoltage breakdown to occur.
Cooley, James E.
Critical exponent of dielectric breakdown strength of composites made with polyethylene and fillers
Electrical properties at high electric fields of composites have not been investigated based on the percolation theory in depth. Works on numerical modeling of dielectric breakdown have been done for a random resistor-capacitor network. The aim of this paper is to discuss the dielectric breakdown phenomena of the composites made with polyethylene and fillers such as carbon black, Fe3O4 and
T. Tomimural; N. Tanimoto; M. Hishida; S. Nakamura; T. Okamoto
Pulsed electron-beam-sustained discharge in oxygen-containing gas mixtures: electrical characteristics, spectroscopy,and singlet oxygen yield
The electrical and spectroscopic characteristics of electron-beam-sustained discharge (EBSD) in oxygen and oxygen-containing gas mixtures are studied experimentally under gas pressures up to 100 Torr in a large excitation volume (�18 L). It is shown that the EBSD in pure oxygen and its mixtures with inert gases is unstable and is characterised by a small specific energy contribution. The addition
Nikolai P Vagin; Andrei A Ionin; Yu M Klimachev; A A Kotkov; Yu P Podmarkov; L V Seleznev; D V Sinitsyn; M P Frolov; Nikolai N Yuryshev; Igor V Kochetov; A P Napartovich; G D Hager
Effects of Electroless Ni\\/Sn Bump Formation using Hydrogen-Plasma Reflow on the Electrical Characteristics of MOSFETs
Fine size Ni\\/Sn bumps were formed by electroless Ni\\/Sn plating and hydrogen plasma reflow, and then electrical characteristics of nMOSFETs and pMOSFETs were evaluated on the bumped chips. After the hydrogen plasma reflow, threshold voltages and carrier mobilities were not changed from those of the nMOSFETs and pMOSFETs as fabricated, before Ni\\/Sn plating. Also, gate leak currents were not increased
Akihiro Ikeda; Yashuhiro Kimiya; Yoshiaki Fukunaga; Hiroshi Ogi; Reiji Hattori; Hisao Kuriyaki; Yashuhide Ohno; Yukinori Kuroki
Effect of a pulsed power supply on the ultraviolet radiation and electrical characteristics of a low-pressure mercury discharge
The influence of a pulsed-current power supply on the electrical properties and the spectral radiant flux emitted by a germicidal ultraviolet (UV) lamp has been investigated, both experimentally and theoretically. A self-consistent collisional�radiative model has been developed and used to model the temporal behaviour of the plasma characteristics of the lamp operated in the pulsed mode. The model includes elastic
B. Mrabet; H. Elloumi; A. Chammam; M. Stambouli; G. Zissis
Effects of turn-to-turn compactness in the straight sections of HTS racetrack coils on thermal and electrical characteristics
NASA Astrophysics Data System (ADS)
The thermal and electrical characteristics of two GdBCO-coated conductor racetrack coils, one insulated with Kapton insulation and the other without turn-to-turn insulation, were investigated by typical voltage-current measurement, charge-discharge, sudden discharge, and over-current tests with respect to external pressures applied to the straight sections of the coils. The test results show that the thermal and electrical stabilities of the racetrack coil without insulation were enhanced considerably with increasing external pressure up to 0.5 MPa, whereas those of the insulated coil were not affected by the pressure. The non-insulated HTS racetrack-type coil with improved turn-to-turn thermal contact in the straight sections may have the potential to be manufactured into field coils for HTS wind turbine generators with highly enhanced thermal and electrical stabilities.
Kwon, O. J.; Kim, K. L.; Choi, Y. H.; Shin, H. J.; Hahn, S.; Iwasa, Y.; Lee, H. G.
Structural, electrical and magnetic characteristics of nickel substituted cobalt ferrite nano particles, synthesized by self combustion method
NASA Astrophysics Data System (ADS)
Nickel-substituted cobalt ferrite nano-particles are synthesized using a self-combustion method. Aqueous metal nitrates and citric acid form the precursors. No external oxidizing agents are used to change the pH of the precursors; this resulted in a more environment friendly synthesis. Structural, magnetic and electrical characteristics of the nano ferrites are verified using X-ray diffractometer (XRD), VSM and impedance analyzer respectively. Phase formation, particle size, lattice parameter, X-ray density, saturation magnetization, coercivity, dielectric constant and electrical activation energy as function of nickel substitution in cobalt ferrite are studied. It is shown here that the magnetic and electrical properties can be tuned by varying the nickel concentration.
Sontu, Uday Bhasker; Yelasani, Vijayakumar; Musugu, Venkata Ramana Reddy
[Spatiotemporal characteristics, of the heart electrical field at the period of ventricular depolarization in athletes training endurance and strength].
As a result of haemodynamic and structural changes occurring in athletes' heart under the influence of systematic physical loads, myocardial electrical activity changes that is reflected on the electric field being formed on the body surface. The heart electrical activity during ventricular depolarization at rest has been investigated in the highly skilled athletes who train to develop physical characteristics--endurance and strength by a method of electrocardiotopography. In the investigated sportsmen under uniformity of the character of the movement of positive and negative cardioelectric potential zones and localization of extrema, and general depolarization duration, the significant distinctions of: 1) amplitude of the maximum negative extremum, 2) the time of the beginning and end of the first inversion, 3) duration of the second inversion, the initial stage and the stability period between inversions, 4) the relative location of the zones of positive and negative cardiopotentials were revealed. PMID:25711099
Strel'nikova, S V; Panteleeva, N I; Roshchevskaia, I M
Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor
Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14??m. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7??m gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.
Saheed, M. Shuaib M.; Muti Mohamed, Norani; Arif Burhanudin, Zainal, E-mail: email@example.com [Centre of Innovative Nanostructures and Nanodevices, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)
DC Treeing Breakdown Associated with Space Charge Formation in Polyethylene
It is well known that space charge accumulation has a great influence on both the short-time and long-time breakdown strengths of plastic insulation systems operating under direct voltages. In this paper, dc treeing phenomena initiated from the tip of a needle electrode inserted into a polyethylene specimen have been investigated under various conions. The characteristics of four kinds of trees,
Ieda; Nawata
Bulk Electricity Generating Technologies This appendix describes the technical characteristics and cost and performance
of other issues where generic information concerning power plants is needed. PROJECT FINANCING Project PRICES The price forecasts for coal, fuel oil and natural gas are described in Appendix B. COAL-FIRED STEAM-ELECTRIC PLANTS Coal-fired steam-electric power plants are a mature technology, in use for over
The characteristics of electrical trees in the inner and outer layers of different voltage rating XLPE cable insulation
NASA Astrophysics Data System (ADS)
The statistical initiation and propagation characteristics of electrical trees in cross-linked polyethylene (XLPE) cables with different voltage ratings from 66 to 500 kV were investigated under a constant test voltage of 50 Hz/7 kV (the 66 kV rating cable is from UK, the others from China). It was found that the characteristics of electrical trees in the inner region of 66 kV cable insulation differed considerably from those in the outer region under the same test conditions; however, no significant differences appeared in the 110 kV rating cable and above. The initiation time of electrical trees in both the inner and the outer regions of the 66 kV cable is much shorter than that in higher voltage rating cables; in addition the growth rate of electrical trees in the 66 kV cable is much larger than that in the higher voltage rating cables. By using x-ray diffraction, differential scanning calorimetry and thermogravimetry methods, it was revealed that besides the extrusion process, the molecular weight of base polymer material and its distribution are the prime factors deciding the crystallization state. The crystallization state and the impurity content are responsible for the resistance to electrical trees. Furthermore, it was proposed that big spherulites will cooperate with high impurity content in enhancing the initiation and growth processes of electrical trees via the 'synergetic effect'. Finally, dense and small spherulites, high crystallinity, high purity level of base polymer material and super-clean production processes are desirable for higher voltage rating cables.
Xie, Ansheng; Li, Shengtao; Zheng, Xiaoquan; Chen, George
Poly(Vinyl Alcohol)/Poly(Acrylic Acid) Hydrogel in a dc Electric Field: Swelling, Shape Change, and Actuation Characteristics
Poly(vinyl alcohol) (PVA)/Poly(acrylic acid) (PAA) hydrogel can be utilized as a biomimetic actuator and coating material for tissue-implant interface, when employing an electrical stimulus. The swelling, shape change, and actuation characteristics of PVA/PAA hydrogel in a range of dc electrical fields were determined to find the optimal electric field for the hydrogel application as biomimetic actuator and coating materials. The hydrogel samples were prepared by dissolving PVA and PAA in deionized water at 4 wt% and mixed together at 1:1 ratio. Two custom made experimental setups were fabricated; one used for the measurement of swelling ratio of the hydrogels; and the other used for the shape changes or actuation characteristics of the hydrogels. Swelling experiments show increased swelling ratios of the hydrogel due to 10 V, 20 V, and 30 V electric fields. The rate of increment of the swelling ratio of hydrogel samples under 10V was higher compare to those samples under 20 V and 30 V. The width and height changes of rectangular shapes and maximum deflection along the length of hydrogel sample due to a range of electric fields (0-30V) were measured using an optical microscope. Incremental shape change up to a specific threshold value (around 10V) was observed due to electric stimulus. Electrostatic actuation pressure of hydrogel samples under 10V was higher compare to those samples under 20 V and 30 V. These results suggested that optimal performance of PVA/PAA hydrogel can be achieved around 10V. PMID:25478321
Investigation of the dc vacuum breakdown mechanism
NASA Astrophysics Data System (ADS)
Breakdowns occurring in rf accelerating structures will limit the ultimate performance of future linear colliders such as the Compact Linear Collider (CLIC). Because of the similarity of many aspects of dc and rf breakdown, a dc breakdown study is underway at CERN to better understand the vacuum breakdown mechanism in a simple setup. Measurements of the field enhancement factor ? show that the local breakdown field is constant and depends only on the electrode material. With copper electrodes, the local breakdown field is around 10.8GV/m, independent of the gap distance. The ? value characterizes the electrode surface state, and the next macroscopic breakdown field can be well predicted. In breakdown rate experiments, where a constant field is applied to the electrodes, clusters of consecutive breakdowns alternate with quiet periods. The occurrence and lengths of these clusters and quiet periods depend on the evolution of ?. The application of a high field can even modify the electrode surface in the absence of breakdown. Measurements of time delays to breakdown show two distinct populations, immediate and delayed breakdowns, indicating that two different mechanisms could exist. The ratio of these two populations depends on the conditioning state of the electrodes and on material. Gas release during breakdown is dominated by H2 and CO. This degassing is mainly due to electron-stimulated desorption. During the quiet periods without breakdown, gases are also released but the quantities are much smaller. All the measurements presented here emphasize the crucial role of field emission in the breakdown triggering.
Descoeudres, A.; Levinsen, Y.; Calatroni, S.; Taborelli, M.; Wuensch, W.
High-voltage atmospheric breakdown across intervening rutile dielectrics.
This report documents work conducted in FY13 on electrical discharge experiments performed to develop predictive computational models of the fundamental processes of surface breakdown in the vicinity of high-permittivity material interfaces. Further, experiments were conducted to determine if free carrier electrons could be excited into the conduction band thus lowering the effective breakdown voltage when UV photons (4.66 eV) from a high energy pulsed laser were incident on the rutile sample. This report documents the numerical approach, the experimental setup, and summarizes the data and simulations. Lastly, it describes the path forward and challenges that must be overcome in order to improve future experiments for characterizing the breakdown behavior for rutile.
Williamson, Kenneth Martin; Simpson, Sean; Coats, Rebecca Sue; Jorgenson, Roy Eberhardt; Hjalmarson, Harold Paul; Pasik, Michael Francis
Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Part of the problem is that RF breakdown in an evacuated cavity involves a complex mixture of effects, which include the geometry, metallurgy, and surface preparation of the accelerating structures and the make-up and pressure of the residual gas in which plasmas form. Studies showed that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas, as needed for muon cooling channels, without the need for long conditioning times, even in the presence of strong external magnetic fields. This positive result was expected because the dense gas can practically eliminate dark currents and multipacting. In this project we used this high pressure technique to suppress effects of residual vacuum and geometry that are found in evacuated cavities in order to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. One of the interesting and useful outcomes of this project was the unanticipated collaborations with LANL and Fermilab that led to new insights as to the operation of evacuated normal-conducting RF cavities in high external magnetic fields. Other accomplishments included: (1) RF breakdown experiments to test the effects of SF6 dopant in H2 and He gases with Sn, Al, and Cu electrodes were carried out in an 805 MHz cavity and compared to calculations and computer simulations. The heavy corrosion caused by the SF6 components led to the suggestion that a small admixture of oxygen, instead of SF6, to the hydrogen would allow the same advantages without the corrosion in a practical muon beam line. (2) A 1.3 GHz RF test cell capable of operating both at high pressure and in vacuum with replaceable electrodes was designed, built, and power tested in preparation for testing the frequency and geometry effects of RF breakdown at Argonne National Lab. At the time of this report this cavity is still waiting for the 1.3 GHz klystron to be available at the Wakefield Test Facility. (3) Under a contract with Los Alamos National Lab, an 805 MHz RF test cavity, known as the All-Seasons Cavity (ASC), was designed and built by Muons, Inc. to operate either at high pressure or under vacuum. The LANL project to use the (ASC) was cancelled and the testing of the cavity has been continued under the grant reported on here using the Fermilab Mucool Test Area (MTA). The ASC is a true pillbox cavity that has performed under vacuum in high external magnetic field better than any other and has demonstrated that the high required accelerating gradients for many muon cooling beam line designs are possible. (4) Under ongoing support from the Muon Acceleration Program, microscopic surface analysis and computer simulations have been used to develop models of RF breakdown that apply to both pressurized and vacuum cavities. The understanding of RF breakdown will lead to better designs of RF cavities for many applications. An increase in the operating accelerating gradient, improved reliability and shorter conditioning times can generate very significant cost savings in many accelerator projects.
Johnson, Rolland
Uncertainty versus Risk Model Efficiency Breakdown Market Breakdown and Indeterminacy under
Efficiency Breakdown Uncertainty versus Risk Roulette versus Horse Races objective probability versus probability P #12;Uncertainty versus Risk Model Efficiency Breakdown Uncertainty versus Risk Roulette versus Efficiency Breakdown Uncertainty versus Risk Roulette versus Horse Races objective probability versus
Sadeh, Norman M.
Gain characteristics of THz surface plasmons in electrically pumped monolayer graphene
NASA Astrophysics Data System (ADS)
Considering the electrically pumped monolayer graphene structures with split gates, we calculated propagation index and the imaginary part of ac conductivity, and numerically simulated the surface plasmons (SPs) frequency dependence on the absorption coefficient and the real part of the propagation index. From the simulations, the SPs gain is larger at low temperature, small gate voltage, long momentum relaxation time and high bias voltage. We compared SPs absorption coefficient and the real part of the propagation index between electrically pumped and optically pumped monolayer graphene. SPs stimulated in electrically pumped monolayer graphene have a large gain with higher bias voltage.
Zhang, Yu-Ping; Liu, Ya-Qing; Cao, Yan-Yan; Lv, Huan-Huan; Li, Tong-Tong; Huang, Xiaoyan; Zhang, Hui-Yun; Ren, Guang-Jun
Dielectric breakdown of polycrystalline alumina: A weakest-link failure analysis
NASA Astrophysics Data System (ADS)
The effects of varying electrode geometry (ball and ring) and size (radius), dielectric media (castor oil and DialaRTM oil), specimen thickness, and concentration of defects on the dielectric breakdown strength of commercial-grade alumina and high-purity fine-grained (HPFG) alumina were investigated. The breakdown strength was expressed in terms of the maximum electric field in the ceramic at the breakdown voltage calculated by finite element analysis (FEA). The breakdown strength decreased systematically with increasing electrode radius and specimen thickness. The breakdown strength increased with decreasing concentration of defects. The breakdown strength was higher in the Diala RTM oil (dielectric constant, epsilonr = 2.3 +/- 0.12) as compared to the castor oil (epsilonr = 4.59 +/- 0.06). The breakdown strength was higher for the HPFG alumina as compared to the commercial- grade alumina. These effects of the electrode geometry, specimen thickness, concentration of defects, and of the dielectric media were analyzed with a weakest-link failure model employing the Laplace and Weibull distributions for a population of defects in the material. The measured size or scaling effects of the electrodes, specimen thickness, concentration of defects, and of the liquid media on breakdown strength were in better agreement with the Laplace distribution for the population. The measured concentration of surface defects was in good agreement with the concentration of surface defects estimated from the surface area scaling of the breakdown field with the Laplace distribution.
Block, Benjamin
Scaling law for direct current field emission-driven microscale gas breakdown
The effects of field emission on direct current breakdown in microscale gaps filled with an ambient neutral gas are studied numerically and analytically. Fundamental numerical experiments using the particle-in-cell/Monte Carlo collisions method are used to systematically quantify microscale ionization and space-charge enhancement of field emission. The numerical experiments are then used to validate a scaling law for the modified Paschen curve that bridges field emission-driven breakdown with the macroscale Paschen law. Analytical expressions are derived for the increase in cathode electric field, total steady state current density, and the ion-enhancement coefficient including a new breakdown criterion. It also includes the effect of all key parameters such as pressure, operating gas, and field-enhancement factor providing a better predictive capability than existing microscale breakdown models. The field-enhancement factor is shown to be the most sensitive parameter with its increase leading to a significant drop in the threshold breakdown electric field and also to a gradual merging with the Paschen law. The proposed scaling law is also shown to agree well with two independent sets of experimental data for microscale breakdown in air. The ability to accurately describe not just the breakdown voltage but the entire pre-breakdown process for given operating conditions makes the proposed model a suitable candidate for the design and analysis of electrostatic microscale devices.
Venkattraman, A.; Alexeenko, A. A. [School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana 47907 (United States)
Phase-field model for dielectric breakdown in solids
NASA Astrophysics Data System (ADS)
Using an analogy between dielectric breakdown and fracture of solids, this paper develops a phase field model for the electric damage initiation and propagation in dielectric solids during breakdown. Instead of explicitly tracing the growth of a conductive channel, the model introduces a continuous phase field to characterize the degree of damage, and the conductive channel is represented by a localized region of fully damaged material. Similar as in the classic theory of fracture mechanics, an energetic criterion is taken: The conductive channel will grow only if the electrostatic energy released per unit length of the channel is greater than that dissipated through damage. Such an approach circumvents the detailed analysis on the complex microscopic processes near the tip of a conductive channel and provides a means of quantitatively predicting breakdown phenomena in materials, composites, and devices. This model is implemented into a finite-element code, and several numerical examples are solved. With randomly distributed defects, the model recovers the inverse power relation between breakdown strength and sample thickness. Finally, the effect of the layered structure in a breakdown-resistant laminate is demonstrated through a numerical example.
Chaitanya Pitike, Krishna; Hong, Wei
Effect of anatomical variability on electric field characteristics of electroconvulsive therapy and magnetic seizure therapy: a parametric modeling study.
Electroconvulsive therapy (ECT) and magnetic seizure therapy (MST) are conventionally applied with a fixed stimulus current amplitude, which may result in differences in the neural stimulation strength and focality across patients due to interindividual anatomical variability. The objective of this study is to quantify the effect of head anatomical variability associated with age, sex, and individual differences on the induced electric field characteristics in ECT and MST. Six stimulation modalities were modeled including bilateral and right unilateral ECT, focal electrically administered seizure therapy (FEAST), and MST with circular, cap, and double-cone coils. The electric field was computed using the finite element method in a parameterized spherical head model representing the variability in the general population. Head tissue layer thicknesses and conductivities were varied to examine the impact of interindividual anatomical differences on the stimulation strength, depth, and focality. Skull conductivity most strongly affects the ECT electric field, whereas the MST electric field is independent of tissue conductivity variation in this model but is markedly affected by differences in head diameter. Focal ECT electrode configurations such as FEAST is more sensitive to anatomical variability than that of less focal paradigms such as BL ECT. In MST, anatomical variability has stronger influence on the electric field of the cap and circular coils compared to the double-cone coil, possibly due to the more superficial field of the former. The variability of the ECT and MST electric fields due to anatomical differences should be considered in the interpretation of existing studies and in efforts to improve dosing approaches for better control of stimulation strength and focality across patients, such as individualization of the current amplitude. The conventional approach to individualizing dosage by titrating the number of pulses cannot compensate for differences in the spatial extent of stimulation that result from anatomical variability. PMID:25055384
Deng, Zhi-De; Lisanby, Sarah H; Peterchev, Angel V
Effect of anatomical variability on electric field characteristics of electroconvulsive therapy and magnetic seizure therapy: a parametric modeling study
Electroconvulsive therapy (ECT) and magnetic seizure therapy (MST) are conventionally applied with a fixed stimulus current amplitude, which may result in differences in the neural stimulation strength and focality across patients due to interindividual anatomical variability. The objective of this study is to quantify the effect of head anatomical variability associated with age, sex, and individual differences on the induced electric field characteristics in ECT and MST. Six stimulation modalities were modeled including bilateral and right unilateral ECT, focal electrically administered seizure therapy (FEAST), and MST with circular, cap, and double-cone coils. The electric field was computed using the finite element method in a parameterized spherical head model representing the variability in the general population. Head tissue layer thicknesses and conductivities were varied to examine the impact of interindividual anatomical differences on the stimulation strength, depth, and focality. Skull conductivity most strongly affects the ECT electric field, whereas the MST electric field is independent of tissue conductivity variation in this model but is markedly affected by differences in head diameter. Focal ECT electrode configurations such as FEAST is more sensitive to anatomical variability than that of less focal paradigms such as BL ECT. In MST, anatomical variability has stronger influence on the electric field of the cap and circular coils compared to the double-cone coil, possibly due to the more superficial field of the former. The variability of the ECT and MST electric field due to anatomical differences should be considered in the interpretation of existing studies and in efforts to improve dosing approaches for better control of stimulation strength and focality across patients, such as individualization of the current amplitude. The conventional approach to individualizing dosage by titrating the number of pulses cannot compensate for differences in the spatial extent of stimulation that result from anatomical variability. PMID:25055384
Deng, Zhi-De; Lisanby, Sarah H.; Peterchev, Angel V.
Historical aspects of electricity are reviewed with individual articles on hydroelectric dams, coal-burning power plants, nuclear power plants, electricity distribution, and the energy future. A glossary is included. (PSB)
Sims, B. (ed.)
Dynamics and characteristics of electric-field structures in the auroral return current region observed by Cluster
NASA Astrophysics Data System (ADS)
The temporal evolution and other characteristics of intense quasi-static electric fields in the return current region are discussed using Cluster observations. A narrow-scale, divergent electric field, the high-altitude signature of a positive U-shaped potential structure, was observed at the poleward edge of the central plasma sheet, close to magnetic midnight at a geocentric distance of about 4.2 Earth radii. Its acceleration potential increased from less than 1 to 3 kV on a 100 s timescale, similar to the formation time for ionospheric plasma density holes, and consistent with previous results for this kind of structure. In the adjacent upward current region, an energy decrease in inverted-V ions was observed some minutes prior to this. The inverted-V potential decrease was roughly equal to the subsequent perpendicular potential increase in the return current region, suggesting that a potential redistribution took place between the two adjacent current branches. Other characteristics of this and three other return current structures are summarized, to illustrate both common and different features of these. The structures are characterized by (all values have been mapped to the ionospheric level) peak electric-field magnitudes of ap1 V m-1, bipolar or unipolar profiles, occurrence at plasma boundaries associated with plasma density gradients, perpendicular scale sizes of ap10 km, downward field-aligned currents of ap10 ?A m-2, and upward electron beams with characteristic energies of a few hundred to a few thousand eV. The bipolar and unipolar electric-field profiles are proposed to reflect whether plasma populations, dense enough to support upward field-aligned currents (by which the return current can close) exist on both sides, or on one side only of the boundary.
Marklund, G. T.; Karlsson, T.; Figueiredo, S.; Johansson, T.; Lindqvist, P.-A.; Andr�, M.; Buchert, S.; Kistler, L. M.
Characteristic Analysis of DC Electric Railway Systems with Superconducting Power Cables Connecting Power Substations
NASA Astrophysics Data System (ADS)
The application of superconducting power cables to DC electric railway systems has been studied. It could leads to an effective use of regenerative brake, improved energy efficiency, effective load sharing among the substations, etc. In this study, an electric circuit model of a DC feeding system is built and numerical simulation is carried out using MATLAB-Simulink software. A modified electric circuit model with an AC power grid connection taken into account is also created to simulate the influence of the grid connection. The analyses have proved that a certain amount of energy can be conserved by introducing superconducting cables, and that electric load distribution and concentration among the substations depend on the substation output voltage distribution.
Ohsaki, H.; Matsushita, N.; Koseki, T.; Tomita, M.
Collision and diffusion in microwave breakdown of nitrogen gas in and around microgaps
The microwave induced breakdown of N{sub 2} gas in microgaps was modeled using the collision frequency between electrons and neutral molecules and the effective electric field concept. Low pressure breakdown at the threshold electric field occurs outside the gap, but at high pressures it is found to occur inside the microgap with a large threshold breakdown electric field corresponding to a very large electron oscillation amplitude. Three distinct pressure regimes are apparent in the microgap breakdown: a low pressure multipactor branch, a mid-pressure Paschen branch, both of which occur in the space outside the microgap, and a high pressure diffusion-drift branch, which occurs inside the microgap. The Paschen and diffusion-drift branches are divided by a sharp transition and each separately fits the collision frequency model. There is evidence that considerable electron loss to the microgap faces accompanies the diffusion-drift branch in microgaps.
Campbell, J. D.; Lenters, G. T. [Grand Valley State University, Allendale, MI 49401 (United States)] [Grand Valley State University, Allendale, MI 49401 (United States); Bowman, A.; Remillard, S. K., E-mail: firstname.lastname@example.com [Hope College, Holland, MI 49423 (United States)
Embedded Electrical and Computer Engineering MASTER ORAL DEFENSE
the circuit performance. Models for predicting the Time to Dielectric Breakdown (TDDB) are valuableEmbedded Electrical and Computer Engineering MASTER ORAL DEFENSE TITLE: Time dependent Breakdown breakdown caused by excessive electric field in the gate oxide causes increased gate leakage degrading
Mahmoodi, Hamid
Statistical analysis of lightning electric field measured under Malaysian condition
NASA Astrophysics Data System (ADS)
Lightning is an electrical discharge during thunderstorms that can be either within clouds (Inter-Cloud), or between clouds and ground (Cloud-Ground). The Lightning characteristics and their statistical information are the foundation for the design of lightning protection system as well as for the calculation of lightning radiated fields. Nowadays, there are various techniques to detect lightning signals and to determine various parameters produced by a lightning flash. Each technique provides its own claimed performances. In this paper, the characteristics of captured broadband electric fields generated by cloud-to-ground lightning discharges in South of Malaysia are analyzed. A total of 130 cloud-to-ground lightning flashes from 3 separate thunderstorm events (each event lasts for about 4-5 hours) were examined. Statistical analyses of the following signal parameters were presented: preliminary breakdown pulse train time duration, time interval between preliminary breakdowns and return stroke, multiplicity of stroke, and percentages of single stroke only. The BIL model is also introduced to characterize the lightning signature patterns. Observations on the statistical analyses show that about 79% of lightning signals fit well with the BIL model. The maximum and minimum of preliminary breakdown time duration of the observed lightning signals are 84 ms and 560 us, respectively. The findings of the statistical results show that 7.6% of the flashes were single stroke flashes, and the maximum number of strokes recorded was 14 multiple strokes per flash. A preliminary breakdown signature in more than 95% of the flashes can be identified.
Salimi, Behnam; Mehranzamir, Kamyar; Abdul-Malek, Zulkurnain
NSDL National Science Digital Library
Electricity is very important to our lives. This reading, part of a series about the future of energy, introduces students to the need and uses for electricity. Students review sources of electricity generation and investigate the evaluation of energy production resources. Here students review information on the generation of electric power and the infrastructure needed to transmit and distribute electricity. Thought-provoking questions afford students chances to reflect on what they've read. Web links to two PBS NewsHour energy-related articles are provided, along with a link to information on the benefits of small-scale wind projects. Copyright 2005 Eisenhower National Clearinghouse
Iowa Public Television. Explore More Project
Investigation of structural properties, electrical and dielectrical characteristics of Al/Dy2O3/porous Si heterostructure
NASA Astrophysics Data System (ADS)
This paper describes the structural properties, electrical and dielectric characteristics for the first time of the high-k Dy2O3 oxide film deposited on the porous Si substrate by electron beam deposition under ultra vacuum. Structural and morphological characterizations are investigated by a scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and X-ray diffraction measurements (XRD). The electrical and dielectric characteristics of the Al/Dy2O3/porous Si heterostructure are studied through current- voltage I (V), capacitance-voltage C (V), conductance- and capacitance-frequency dependencies (G (f) and C (f)). Therefore, the dominant conduction mechanisms for the Al/Dy2O3/porous Si heterostructure are extracted from the determining of Schottky coefficient (?SC) and Poole-Frenkel coefficient (?PF). The experimental values of ?SC and ?PF coefficients are calculated from I (V) characteristics and compared with theoretical values, thus, the appropriate model has been proposed. The C (V) characteristics at different frequencies revealed a large frequency-dispersion, indicative of a significant density of interface states. Furthermore, the G (f) characteristics were well fitted by the modified law GAC(f)=A1f+A2f and the results showed frequency dependent and evidence of two different behaviors in ac conductance i.e. the low-frequency conductivity is due to long-range ordering (frequency-independent) and high frequency conduction due to the localized orientation hopping mechanism. The Nyquist diagrams are used to identify the equivalent circuit, so, the Al/Dy2O3/porous Si heterostructure is accurately modeled at frequency ranges from 10 Hz to 1000 kHz, as a two parallel elements (RC) network placed in series.
Cherif, A.; Jomni, S.; Belgacem, W.; Hannachi, R.; Mliki, N.; Beji, L.
Joining characteristics of titanium-based orthodontic wires connected by laser and electrical welding methods.
This study investigated the possibility of electrical and laser welding to connect titanium-based alloy (beta-titanium and nickel-titanium) wires and stainless-steel or cobalt-chromium alloy wires for fabrication of combination arch-wires. Four kinds of straight orthodontic rectangular wires (0.017 � 0.025 inch) were used: stainless-steel (S-S), cobalt-chromium (Co-Cr), beta-titanium alloy (?-Ti), and nickel-titanium (Ni-Ti). Homogeneous and heterogeneous end-to-end joints (15 mm long each) were made by electrical welding and laser welding. Non-welded wires (30 mm long) were also used as a control. Maximum loads at fracture (N) and elongation (%) were measured by conducting tensile test. The data (n = 10) were statistically analyzed using analysis of variance/Tukey test (P < 0.05).The S-S/S-S and Co-Cr/Co-Cr specimens showed significantly higher values of the maximum load (ML) at fracture and elongation (EL) than those of the Ni-Ti/Ni-Ti and ?-Ti/?-Ti specimens for electrical welding and those of the S-S/S-S and Co-Cr/Co-Cr specimens welded by laser. On the other hand, the laser-welded Ni-Ti/Ni-Ti and ?-Ti/?-Ti specimens exhibited higher values of the ML and EL compared to those of the corresponding specimens welded by electrical method. In the heterogeneously welded combinations, the electrically welded Ni-Ti/S-S, ?-Ti/S-S and ?-Ti/Co-Cr specimens showed significantly (P < 0.05) higher ML and EL than those of the corresponding specimens welded by laser. Electrical welding exhibited the higher values of maximum load at fracture and elongation for heterogeneously welded combinations than laser-welding. PMID:25595723
Matsunaga, Junko; Watanabe, Ikuya; Nakao, Noriko; Watanabe, Etsuko; Elshahawy, Waleed; Yoshida, Noriaki
Partial discharge characteristics of oil-immersed insulation systems under DC, combined AC-DC and DC reversed polarity voltage
Breakdown characteristics of insulating oil, under combined ac-dc voltage and dc reversed polarity voltage, and partial discharge characteristics of oil-immersed insulation, under combined ac-dc voltage and polarity revesal of dc voltage Were made clear by elementary experiments. After that, a numerical dc field mapping method for electric field analysis of two-dimensional configurations which consist of composite insulation and field mapping
E. Takahashi; Y. Tsutsumi; K. Okuyama; F. Ogata
Charged dendrimers under the action of AC electric fields: Breathing characteristics of molecular size, polarizations, and ion distributions
NASA Astrophysics Data System (ADS)
Langevin dynamics simulations are performed to study the response of charged dendrimers in alternating current electric fields in 3:1 salt solutions. Time evolutions of molecular size show breathing characteristics which take saw-tooth-like patterns in square-wave electric fields and undulated sine-function ones in sine-wave fields. Detailed study reveals how the dendrimer and condensed ions oscillate in the electric fields, which result in polarization of the molecule. To effect a significant deformation of the dendrimer, the applied field amplitude must be larger than some critical strength Ecrit and the field frequency smaller than a threshold fcrit. The response behavior is characterized by two relaxation times in square-wave fields, both of which decrease linearly with the strong field strength larger than Ecrit. In sine-wave fields, the molecular size exhibits interesting hysteretic behavior in plotting the curves with the field variation. A Maxwell-Wagner type polarization theory is derived and proved by simulations, which connects fcrit with the strength of the applied electric field.
Das, Ashok K.; Hsiao, Pai-Yi
Electrical characteristics of a novel gate structure 4H-SiC power static induction transistor
A power SIT with a novel gate structure was conceived, in which high blocking gain and low on-state voltage have been simultaneously achieved and the characteristics of silicon carbide (SiC) have been effectively employed. Simulation studies on characteristics of the SIT have been conducted. When a forward bias that was less than the built-in voltage was applied to the gate,
T. Iwasaki; T. Oono; K. Asano; Y. Sugawara; T. Yatsuo
Dynamic response characteristics of thermoelectric generator predicted by a three-dimensional heat-electricity coupled model
NASA Astrophysics Data System (ADS)
The practical application environments of thermoelectric generators (TEGs) always change, which make�a requirement for studying the dynamic response characteristics of TEGs. This work develops a complete, three-dimensional and transient model to investigate this issue. The model couples the energy and electric potential equations. Seebeck effect, Peltier effect, Thomson effect, Joule heating and Fourier heat conduction are taken into account in this model. Dynamic output power and conversion efficiency of the TEG, which are caused by variations of the hot end temperature, cold end temperature and load current, are studied. The response hysteresis of the output power to the hot end and cold end temperatures, the overshoot or undershoot of the conversion efficiency are found and attributed to the delay of thermal diffusion. However, the output power is synchronous with the load current due to much faster electric response than thermal response.
Meng, Jing-Hui; Zhang, Xin-Xin; Wang, Xiao-Dong
Computer Data Bank of the Current�Voltage Characteristics of Electricity Generating Channels
A great deal of experimental data has now been accumulated from investigations and reactor tests of electricity-generating channels (EGCs) in loop systems. More than 100 channels with different structures were tested under a wide range of operating conditions only at the Physics and Power Engineering Institute. The results of the lifetime tests of EGCs are stored on paper carriers filled
E. G. Vinogradov; V. S. Mironov; V. G. Petrovskii; V. P. Rezvykh; G. I. Smol'nikova; A. G. Yuferov; V. I. Yarygin
Characteristics of Raindrop Charge and Associated Electric Field in Different Types of Rain
Simultaneous measurements of raindrop charge, atmospheric electric field and rain intensity were made at Poona using fast response, continuous recording surface instruments during four types of rain: pre-monsoon (thunderstorm rain), monsoon rain type I (tight intermittent rain), monsoon rain type II (heavy continuous rain) and post-monsoon (thunderstorm rain). Measurements were also made of the conductivity of rainwater samples collected during
A. Mary Selvam; G. K. Manohar; L. T. Khemani; Bh. V. Ramana Murty
Performance Characteristics of the First, State-of-the-art Electric Vehicle Implemented in Chile
, Alejandro Amaro and Eduardo Wiechmann*, Department of Electrical Engineering Catholic University of Chile for the large amount of Diesel and gasoline propelled ICE. In Santiago there are more than 12,000 buses parts are cheap and easy to find; and d) it has lot of room in the engine compartment, which allowed
Catholic University of Chile (Universidad Católica de Chile)
Electrical characteristics of carbon nanotube network fabricated by a simple transfer method
We demonstrated a simple transfer method enables to fabricate the single-walled carbon nanotube (SWCNT) film on the plastic substrate. SWCNT network was separated from the initial substrate and transferred onto another substrate using the nitric acid. We also found that electrical conductivity of transferred film was improved. The sheet resistance of SWCNT films was changed from a 150~300 �\\/sq to
Sun Kug Kim; Sang Min Park; Doo Hee Hwang; Dong Kyu Jang; R. Koizhaiganova; S. Roth; Cheol Jin Lee
Test and simulation of axial flux-motor characteristics for hybrid electric vehicles
High power density is the main advantage of the axial flux motors compared to the conventional radial flux motors. Therefore, they are suitable candidates for the power train of hybrid electric vehicles. In addition, operating speed range and efficiency of axial flux motors can be improved by changing the air gap of the machine. In this paper, for each operating
Sung Chul Oh; Ali Emadi
Computation of Corona Space Charge, Electric Field, and VI Characteristic Using Equipotential Charge Shells
A charge simulation technique incorporating discretized equipotential charge shells in the volume is used to approximate the electric field and space charge around a single conductor in corona and to compute the voltage-current relationship for the discharge. No iteration is required in the solution method. Results are compared to corona in coaxial geometry, for which analytical treatment is also possible,
Mark N. Horenstein
The structure of vortex breakdown
NASA Technical Reports Server (NTRS)
The term 'vortex breakdown', as used in the reported investigation, refers to a disturbance characterized by the formation of an internal stagnation point on the vortex axis, followed by reversed flow in a region of limited axial extent. Two forms of vortex breakdown, which predominate, are shown in photographs. One form is called 'near-axisymmetric' (sometimes 'axisymmetric'), and the other is called 'spiral'. A survey is presented of work published since the 1972 review by Hall. Most experimental data taken since Hall's review have been in tubes, and the survey deals primarily with such cases. It is found that the assumption of axial-symmetry has produced useful results. The classification of flows as supercritical or subcritical, a step that assumes symmetry, has proved universally useful. Experiments show that vortex breakdown is always preceded by an upstream supercritical flow and followed by a subcritical wake. However, a comparison between experiments and attempts at prediction is less than encouraging. For a satisfactory understanding of the structure of vortex breakdown it is apparently necessary to take into account also aspects of asymmetry.
Leibovich, S.
Effects of Annealing Temperature on Electrical Characteristics of Solution-Processed Zinc Tin Oxide Thin-Film Transistors
NASA Astrophysics Data System (ADS)
We investigated the effects of annealing temperature on the electrical characteristics of solution-processed zinc tin oxide (ZTO) thin-film transistors (TFTs). When the annealing temperature increased from 300 to 500 �C, the threshold voltage of solution-processed ZTO TFTs decreased from 16.89 to -0.23 V owing to the increase in electron concentration in the active layer. The increase in electron concentration is caused by the decrease in Cl atomic concentration. When the annealing temperature increased to 500 �C, the saturation mobility increased from 0.18 to 4.75 cm2�V-1�s-1 and the threshold voltage shift for positive gate bias stress as a reliability characteristic decreased from 5.34 to 2.6 V, because of the decomposition of halide residues such as Cl and the nanocrystallization.
Lee, Jeong-Soo; Kim, Yong-Jin; Lee, Yong-Uk; Kim, Yong-Hoon; Kwon, Jang-Yeon; Han, Min-Koo
Modeling of electrical and optical characteristics of near room-temperature CdS/ZnSe based NIR photodetectors
NASA Astrophysics Data System (ADS)
Results of modeled photodetector characteristics in (CdS/ZnSe)/BeTe multi-well diode with p-i-n polarity are reported. The dark current density (J-V) characteristics, the temperature dependence of zero-bias resistance area product (R0A), the dynamic resistance as well as bias dependent dynamic resistance (Rd) and have been analyzed to investigate the mechanisms limiting the electrical performance of the modeled photodetectors. The quantum efficiency, the responsivity and the detectivity have been also studied as function of the operating wavelength. The suitability of the modeled photodetector is demonstrated by its feasibility of achieving good device performance near room temperature operating at 1.55 ?m wavelength required for photodetection in optical communication. Quantum efficiency of �95%, responsivity �0.6 A/W and D* � 5.7 � 1010 cm Hz1/2/W have been achieved at 300 K in X BeTe conduction band minimum.
Zeiri, N.; Abdi-Ben Nasrallah, S.; Sfina, N.; Said, M.
Monte Carlo simulation of initial breakdown phase for magnetised toroidal ICRF discharges
The radio-frequency (RF) plasma production technique in the ion cyclotron range of frequency (ICRF) attracts growing attention among fusion experts because of its high potential for solving several basic problems of reactor-oriented superconducting fusion machines, such as ICRF wall conditioning in tokamaks and stellarators (T{sub e}?=?3?5eV, n{sub e}<10{sup 12}cm{sup ?3}), ICRF-assisted tokamak start-up and target plasma production (n{sub e}?=?10{sup 13}cm{sup ?3}) in stellarators. Plasma initiation by ICRF has been studied intensively using single particle descriptions and basic analytic models. To further improve the present understanding on plasma production employing the vacuum RF field of ICRF antennas in toroidal devices in presence of the toroidal magnetic field, and its parametric dependencies a Monte Carlo code has been developed. The 1D code RFdinity1D describes the motion of electrons, accelerated by the RF field in front of the ICRF antenna, along one toroidal magnetic field line. Dependent on their individual energies and the related electron collision cross sections (ionisation, excitation and dissociation) weighted by a Monte Carlo procedure, an electron avalanche may occur. Breakdown conditions are discussed as function of RF discharge parameters (i) RF vacuum electric field strength, (ii) RF frequency and (iii) neutral pressure (H2). The slope of the exponential density increase, taken as measure for the breakdown speed, shows qualitative agreement to experimental breakdown times as found in literature and experimental data of the ASDEX upgrade and TEXTOR tokamak, and is interpreted by studying the characteristic electron velocity distribution functions.
Tripsk�, M. [Association Euratom-Belgian State, LPP-ERM/KMS, 1000 Brussels, Belgium and Ghent University, Department of Applied Physics, 9000 Ghent (Belgium); Wauters, T.; Lyssoivan, A.; Koch, R.; Vervier, M.; Van Schoor, M. [Association Euratom-Belgian State, LPP-ERM/KMS, 1000 Brussels (Belgium); Bobkov, V. [Association Euratom-IPP, Max-Planck Institut f�r Plasmaphysik, 85748 Garching (Germany); Van Oost, G. [Ghent University, Department of Applied Physics, 9000 Ghent (Belgium); Collaboration: ASDEX Upgrade Team; TEXTOR Team
Monte Carlo simulation of initial breakdown phase for magnetised toroidal ICRF discharges
NASA Astrophysics Data System (ADS)
The radio-frequency (RF) plasma production technique in the ion cyclotron range of frequency (ICRF) attracts growing attention among fusion experts because of its high potential for solving several basic problems of reactor-oriented superconducting fusion machines, such as ICRF wall conditioning in tokamaks and stellarators (Te = 3-5eV, ne<1012cm-3), ICRF-assisted tokamak start-up and target plasma production (ne = 1013cm-3) in stellarators. Plasma initiation by ICRF has been studied intensively using single particle descriptions and basic analytic models. To further improve the present understanding on plasma production employing the vacuum RF field of ICRF antennas in toroidal devices in presence of the toroidal magnetic field, and its parametric dependencies a Monte Carlo code has been developed. The 1D code RFdinity1D describes the motion of electrons, accelerated by the RF field in front of the ICRF antenna, along one toroidal magnetic field line. Dependent on their individual energies and the related electron collision cross sections (ionisation, excitation and dissociation) weighted by a Monte Carlo procedure, an electron avalanche may occur. Breakdown conditions are discussed as function of RF discharge parameters (i) RF vacuum electric field strength, (ii) RF frequency and (iii) neutral pressure (H2). The slope of the exponential density increase, taken as measure for the breakdown speed, shows qualitative agreement to experimental breakdown times as found in literature and experimental data of the ASDEX upgrade and TEXTOR tokamak, and is interpreted by studying the characteristic electron velocity distribution functions.
Tripsk�, M.; Wauters, T.; Lyssoivan, A.; Koch, R.; Bobkov, V.; Vervier, M.; van Oost, G.; van Schoor, M.; ASDEX Upgrade Team, Textor Team
Relation between stimulation characteristics and clinical outcome in studies using electrical stimulation to improve motor control of the upper extremity in stroke
OBJECTIVE: Electrical stimulation can be applied in a variety of ways to the hemiparetic upper extremity following stroke. The aim of this review is to explore the relationship between characteristics of stimulation and the effect of electrical stimulation on the recovery of upper limb motor control following stroke. METHODS: A systematic literature search was performed to identify clinical trials evaluating
Kroon de Joke R; Maarten J. IJzerman; John Chae; Gustaaf J. Lankhorst; Gerrit Zilvold
A study of dielectric breakdown mechanism in CoFeB\\/MgO\\/CoFeB magnetic tunnel junction
We examined the breakdown characteristics of a 1-nm-thick MgO barrier by measuring the time dependent dielectric breakdown (TDDB) and conducting atomic force microscopy (C-AFM) observation. We found that two different local conduction modes, the percolation path and Fowler-Nordheim (F-N) tunneling, contribute to dielectric breakdown. Furthermore, the operating voltage of magnetic tunnel junctions (MTJs) for maintaining reliability over ten years against
Chikako Yoshida; Masaki Kurasawa; Young Min Lee; Koji Tsunoda; Masaki Aoki; Yoshihiro Sugiyama
Percolation path and dielectric-breakdown-induced-epitaxy evolution during ultrathin gate dielectric breakdown transient
A physical model has been developed which complies with the experimental observation on the failure mechanism of ultrathin gate oxide breakdown during constant voltage stress. Dynamic equilibrium needs to be established between the percolation conductive path and the dielectric breakdown induced epitaxy (DBIE) formation during gate dielectric breakdown transient. The model is capable of linking the percolation model, soft breakdown,
Chih Hang Tung; Kin Leong Pey; Lei Jun Tang; M. K. Radhakrishnan; Wen He Lin; Felix Palumbo; Salvatore Lombardo
Electrical characteristics of TMAH-surface treated Ni/Au/Al2O3/GaN MIS Schottky structures
NASA Astrophysics Data System (ADS)
The electrical characteristics and reverse leakage mechanisms of tetramethylammonium hydroxide (TMAH) surface-treated Ni/Au/Al2O3/GaN metal-insulator-semiconductor (MIS) diodes were investigated by using the current-voltage ( I-V) and capacitance-voltage ( C-V) characteristics. The MIS diode was formed on n-GaN after etching the AlGaN in the AlGaN/GaN heterostructures. The TMAH-treated MIS diode showed better Schottky characteristics with a lower ideality factor, higher barrier height and lower reverse leakage current compared to the TMAH-free MIS diode. In addition, the TMAH-free MIS diodes exhibited a transition from Poole-Frenkel emission at low voltages to Schottky emission at high voltages, whereas the TMAH-treated MIS diodes showed Schottky emission over the entire voltage range. Reasonable mechanisms for the improved device-performance characteristics in the TMAH-treated MIS diode are discussed in terms of the decreased interface state density or traps associated with an oxide material and the reduced tunneling probability.
Reddy, M. Siva Pratap; Lee, Jung-Hee; Jang, Ja-Soon
Electrical and physical characteristics of ultrathin hafnium silicate films with polycrystalline silicon and TaN gates
NASA Astrophysics Data System (ADS)
Metal-oxide-semiconductor transistors of ultrathin hafnium silicate films (equivalent oxide thickness (EOT) of 12.5-14 A) with polycrystalline silicon and metal (TaN) gates have been demonstrated. Well-behaved transistor characteristics and EOT stability of Hf silicate with n+ polysilicon indicates good compatibility with polysilicon gate process without use of barrier layer. Transmission electron microscopy analysis indicates that the films have no top interfacial layer with both TaN and polysilicon gates. The films also remain amorphous and show no indication of phase separation even after a 950 degC dopant activation anneal. Hf silicate films also show excellent transistor characteristics with TaN gate. NH3 pretreatment results in degraded transistor characteristics for TaN and poly gate samples. Good capacitance-voltage characteristics and negligible hysteresis (<10 mV) was observed in the capacitors after a 1000 degC activation indicating good electrical stability at high temperatures and minimal charge trapping.
Gopalan, S.; Onishi, K.; Nieh, R.; Kang, C. S.; Choi, R.; Cho, H.-J.; Krishnan, S.; Lee, J. C.
Assessing the effects of multiple stressors on the functioning of Mediterranean rivers using poplar wood breakdown.
Mediterranean rivers in the Iberian Peninsula are being increasingly affected by human activities, which threaten their ecological status. A clear picture of how do these multiple stressors affect river ecosystem functioning is still lacking. We addressed this question by measuring a key ecosystem process, namely breakdown of organic matter, at 66 sites distributed across Mediterranean Spain. We performed breakdown experiments by measuring the mass lost by wood sticks for 54 to 106 days. Additionally, we gathered data on physico-chemical, biological and geomorphological characteristics of study sites. Study sites spanned a broad range of environmental characteristics and breakdown rates varied fiftyfold across sites. No clear geographic patterns were found between or within basins. 90th quantile regressions performed to link breakdown rates with environmental characteristics included the following 7 variables in the model, in decreasing order of importance: altitude, water content in phosphorus, catchment area, toxicity, invertebrate-based biotic index, riparian buffer width, and diatom-based quality index. Breakdown rate was systematically low in high-altitude rivers with few human impacts, but showed a high variability in areas affected by human activity. This increase in variability is the result of the influence of multiple stressors acting simultaneously, as some of these can promote whereas others slow down the breakdown of organic matter. Therefore, stick breakdown gives information on the intensity of a key ecosystem process, which would otherwise be very difficult to predict based on environmental variables. PMID:22781304
Aristi, Ibon; D�ez, Jose Ramon; Larra�aga, Aitor; Navarro-Ortega, Al�cia; Barcel�, Dami�; Elosegi, Arturo
Dielectric breakdown: optimal bounds A. Garroni
of convex duality. 1 Introduction We study a model of (first failure) dielectric breakdown in Rn . We and then the body begins to conduct. This is a reasonable way to model the first failure in dielectric breakdown. Dielectric breakdown is one of the many nonlinear models which are used in the physicist's literature (see
Garroni, Adriana
Bounds for the rth characteristic frequency of a beaded string or of an electrical filter
The fundamental mode of vibration of a beaded string has a shape without change of sign. The rth higher normal mode of vibration has r changes of sign. Given any virtual shape of the string with r changes of sign, an algorithm is found that gives upper and lower bounds for the rth characteristic frequency as a function of the virtual shape. By making a certain transformation it is found that this algorithm holds for the characteristic frequencies of an inductor-capacitor network. Other transformations show that it applies to the rth eigenvalue of a Hermitian matrix. PMID:16592835
Barnsley, Michael F.; Duffin, Richard J.
Study of RF Breakdown Mechanisms Relevant to an ICH Antenna Environment
The mechanisms that contribute to RF breakdown/arcing in an antenna environment are being studied. RF breakdown/arcing is a major power-limiting factor in antenna systems used for RF heating and current drive in fusion experiments. The factors that contribute to breakdown include gas pressure, gas type, magnetic field, materials, ultraviolet light, and local plasma density. The effects of these factors on RF breakdown are being studied in a resonant 1/4-wavelength section of vacuum transmission line terminated with an open circuit electrode structure. The electrode structure is designed to determine the role of the RF electric field strength and magnetic field orientation on the breakdown process. Changes in the electrical parameters, such as input impedance and the voltage at the electrodes, are being monitored to detect the breakdown events. Measurements of the light emission prior to and during an arc are also being made. For high vacuum conditions using copper electrodes, bright spots appear on the electrode surfaces prior to a breakdown event. An increase in the RF field results in an arc and a flash of light corresponding to copper line emission (578.2 or 521.8 nm). Analysis of the electrode surfaces show large areas of melting and formation of micron-sized rounded protrusions, especially along the sharp edges of small scratches. An increase in the chamber pressure results in a decrease in the maximum RF electric field that can be sustained without breakdown as the pressure approaches a few mTorr. The breakdown event leads to formation of a plasma in the structure, with light emission corresponding to the particular gas being used. The addition of an external magnetic field causes the formation of a plasma at lower pressures, thus limiting the amount of coupled RF power. The presence of UV light has been found to initiate multipactor under some operating conditions.
Caughman, J. B. O.; Baity, F. W.; Rasmussen, D. A. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Castano-Giraldo, C.; Aghazarian, M.; Ruzic, D. N. [University of Illinois, Urbana-Champaign, IL (United States)
Structural and electrical characteristics of dysprosium-doped barium stannate titanate ceramics
Effects of dysprosium (Dy) amphoteric doping on the structural, dielectric and electric properties of barium stannate titanate (BTS) ceramics have been studied. X-ray diffraction analyses reveal that all Dy-doped BTS ceramics exhibit cubic perovskite structure until to 1 mol%. Dy doping at the A site shows lower solubility than that at the B site. SEM surface morphologies display that the Dy B site doping is beneficial for the compact and homogeneous grain distribution. The dielectric constant and loss tangent are reduced with increase of the doping levels. Impedance spectroscopy investigation demonstrates that all samples are insulating at room temperature. Doping alters the full resistive regions of pure BTS ceramics to Doped BTS with insulating grain boundaries and semiconducting bulk regions, but the doping contents has little effect on changing the electric structures.
Wang, Shijie; Tan, Tai Aik; Lai, Man On [Department of Mechanical Engineering, National University of Singapore, 9, Engineering Drive 1, Singapore 117576 (Singapore)] [Department of Mechanical Engineering, National University of Singapore, 9, Engineering Drive 1, Singapore 117576 (Singapore); Lu, Li, E-mail: firstname.lastname@example.com [Department of Mechanical Engineering, National University of Singapore, 9, Engineering Drive 1, Singapore 117576 (Singapore)] [Department of Mechanical Engineering, National University of Singapore, 9, Engineering Drive 1, Singapore 117576 (Singapore)
Recent experiments on vacuum breakdown of oxygen-free copper electrodes
The effects of the gas content, in situ sputter cleaning, annealing and a mirror finish of oxygen-free copper (OFC) electrodes on the electrical breakdown in a vacuum were investigated. The grade of the OFC meets the ASTM-F-68 Class I standard. Electrochemical buffing (ECB) or diamond turning was employed for obtaining a mirror finish. It was found that every one of the parameters investigated, namely, low gas content, in situ sputter cleaning and annealing, increases the breakdown fields after conditioning due to repetitive breakdowns. In addition, a higher annealing temperature produced higher breakdown fields. The mirror finish reduced the required number of breakdowns conditioning procedure by repetitive breakdowns to improve the insulating capability of the vacuum gap. A breakdown field of about 250 MV/m was obtained by a combination of annealing at 700{degrees} C and a mirror finish by diamond turning. It has been pointed out that the combination of these treatments is necessary for obtaining higher breakdown fields. The effect of annealing and diamond turning is discussed on the basis of the recrystallization of copper and residual stresses on the surface.
Kobayashi, S. [Saitama Univ. (Japan)
Asymmetric surface dielectric barrier discharge in air at atmospheric pressure: electrical properties and induced airflow characteristics
The electrical properties of an asymmetric surface dielectric barrier discharge in atmospheric air have been investigated experimentally. The discharge is used for airflow production close to the dielectric surface, and the time-averaged flow velocity spatial profiles have been measured. Velocities of up to 3.5 m s-1 at heights of 1-2 mm are reached when filamentary discharges with current peaks up
J�r�me Pons; Eric Moreau; G�rard Touchard
An Investigation of the Electrical Short Circuit Characteristics of Tin Whiskers
NASA Technical Reports Server (NTRS)
In this experiment, an empirical model to quantify the probability of occurrence of an electrical short circuit from tin whiskers as a function of voltage was developed. This model can be used to improve existing risk simulation models FIB and TEM images of a tin whisker confirm the rare polycrystalline structure on one of the three whiskers studied. FIB cross-section of the card guides verified that the tin finish was bright tin.
Courey, Karim J.
Strong correlation between capacitance and breakdown voltage of GaInN/GaN light-emitting diodes
NASA Astrophysics Data System (ADS)
Investigating the relationship between the breakdown voltage and the capacitance of GaInN light-emitting diodes (LEDs), we find that a lower capacitance due to weaker internal electric field in depletion region or wider depletion width at the pn junction results in lower reverse leakage current and thus larger breakdown voltage. The measured breakdown voltage and capacitance of LEDs show a strong correlation, opening a nondestructive and non-intrusive way to estimate the breakdown voltage of an LED based on the capacitance-voltage measurement.
Cho, Jaehee; Schubert, E. F.; Son, Joong Kon; Kim, Dong Yeong; Kim, Jong Kyu
Backside optimization for improving avalanche breakdown behavior of 4.5 kV IGBT
NASA Astrophysics Data System (ADS)
The static avalanche breakdown behavior of 4.5 kV high-voltage IGBT is studied by theory analysis and experiment. The avalanche breakdown behaviors of the 4.5 kV IGBTs with different backside structures are investigated and compared by using the curve tracer. The results show that the snap back behavior of the breakdown waveform is related to the bipolar PNP gain, which leads to the deterioration of the breakdown voltage. There are two ways to optimize the backside structure, one is increasing the implant dose of the N+ buffer layer, the other is decreasing the implant dose of the P+ collector layer. It is found that the optimized structure is effective in suppressing the snap back behavior and improving the breakdown characteristic of high voltage IGBT. Project supported by the National Major Science and Technology Special Project of China (No. 2011ZX02503-003).
Xiaoli, Tian; Jiang, Lu; Yuan, Teng; Wenliang, Zhang; Shuojin, Lu; Yangjun, Zhu
Predicting Flow Breakdown Probability and Duration in Stochastic Network Models: Impact on Travel Time Reliability
This paper proposes a methodology to produce random flow breakdown endogenously in a mesoscopic operational model, by capturing breakdown probability and duration. Based on previous research findings that probability of flow breakdown can be represented as a function of flow rate and the duration can be characterized by a hazard model. By generating random flow breakdown at various levels and capturing the traffic characteristics at the onset of the breakdown, the stochastic network simulation model provides a tool for evaluating travel time variability. The proposed model can be used for (1) providing reliability related traveler information; (2) designing ITS (intelligent transportation systems) strategies to improve reliability; and (3) evaluating reliability-related performance measures of the system.
Dong, Jing [ORNL; Mahmassani, Hani S. [Northwestern University, Evanston
Impacts of Various Characteristics of Electricity and Heat Demand on the Optimal Configuration of a Microgrid
NASA Astrophysics Data System (ADS)
A methodology was developed to design the number and capacity for each piece of equipment (e.g. gas engines, batteries, thermal storage tanks) in microgrids with combined heat and power systems. We analyzed three types of microgrids; the first one consists of an office building and an apartment, the second one consists of a hospital and an apartment, the third one consists of a hotel, office and retails. In the methodology, annual cost is minimized by considering the partial load efficiency of a gas engine and its scale economy, and the optimal number and capacity of each piece of equipment and the annual operational schedule are determined by using the optimal planning method. Based on calculations using this design methodology, it is found that the optimal number of gas engines is determined by the ratio of bottom to peak of the electricity demand and the ratio of heat to electricity demand. The optimal capacity of a battery required to supply electricity for a limited time during a peak demand period is auxiliary. The thermal storage tank for space cooling and space heating is selected to minimize the use of auxiliary equipment such as a gas absorption chiller.
Bando, Shigeru; Watanabe, Hiroki; Asano, Hiroshi; Tsujita, Shinsuke
Structural Evolving Sequence and Porous Ba6Zr2Nb8O30 Ferroelectric Ceramics with Ultrahigh Breakdown Field and Zero Strain
dielectric constant, highest electric field breakdown strength, and nearly zero macroscopic electric field Breakdown Field and Zero Strain Shan-Tao Zhang,, Guoliang Yuan,§, Jun Chen,¶ Zheng-Bin Gu, Bin Yang,k Jiang counterparts and can be well understood by using brick-wall model. Our results may provide useful information
Cao, Wenwu
A numerical model of avalanche breakdown in MOSFET's
An accurate numerical model of avalanche breakdown in MOSFET's is presented. Features of this model are a) use of an accurate electric-field distribution calculated by a two-dimensional numerical analysis, b) introduction of multiplication factors for a high-field path and the channel current path, and c) incorporation of the feedback effect of the excess substrate current induced by impact ionization into
T. Toyabe; K. Yamaguchi; S. Asai; M. S. Mock
Mechanical characteristics of automotive hybrid drives using electric power splitting generator
Paper deals with automotive hybrid and power splitting drive. Well-tried DC power splitting drive used on Express Czechoslovak Units is described. These units were in operation between 1936-1951 years. New idea to use a similar drive with AC machinery and power electronic converters is studied in Research Centre of Combustion Motors and Automobiles Josef Bozek. Mechanical characteristics and power flow
Z. Cerovsky; P. Mindl
Characteristics of future Vertical Axis Wind Turbines (VAWTs). [to generate utility grid electric power
NASA Technical Reports Server (NTRS)
The developing Darrieus VAWT technology whose ultimate objective is economically feasible, industry-produced, commercially marketed wind energy systems is reviewed. First-level aerodynamic, structural, and system analyses capabilities which support and evaluate the system designs are discussed. The characteristics of current technology designs are presented and their cost effectiveness is assessed. Potential improvements identified are also presented along with their cost benefits.
Kadlec, E. G.
NSDL National Science Digital Library
This Topic In Depth explores some of what the Web has to offer on the subject of electricity.The first site from Thinkquest.org called Electricity Online (1) gives an excellent overview, with topics ranging from circuits and transformers to electricity's discovery and history. The site even contains games, activities, and quizzes. The second site, Edison's Miracle of Light (2) from PBS.org, is a companion site to a PBS special of the same name. The site explores the life and accomplishments of one of the 19th century's greatest inventors, offering a timeline, recordings, and more. From Clark Public Utilities of Clark County Washington, the next site is called Electricity (3). This Web site offers information from a public utilities perspective, with subjects like electrical safety, how electricity gets to your home, what it costs to run appliances, and so on. Next, from the US Department of Energy, is a site that offers an Overview of the Electric Power Industry (4). Here, visitors can find information, data, publications, statistics, and more relating to electric power in the US. The fifth site from ExploreScience.com is called Multimedia Activities (5) and contains just that. Geared towards students, the four interactive lessons include an introduction to electricity and magnetism, an introduction to plasma, coulomb force, and lissajous figures. The next site, provided by the BBC, is another interactive learning site, called Activity Electricity (6). Users click through a lesson about circuits and current, answering questions along the way. The site also contains a fact sheet and quiz. From NASA, the Dataset Information site (7) contains data archived and cataloged by the Global Hydrology Resource Center relating to lighting. Several datasets from varying sources are available for free and include such things as Long Range Cloud to Ground Data. The last site is offered by the Canada Science and Technology Museum and is called Background Information for Electricity (8). This Web site for kids offers simple descriptions and illustrations about electricity, who discovered it, conductors and insulators, fuses, and more. The electricity workshop link also contains lesson plans and additional student activities.
Brieske, Joel A.
The use of the orthogonal array with grey relational analysis to optimize the electrical discharge machining process with multiple performance characteristics
In this paper a new approach for the optimization of the electrical discharge machining (EDM) process with multiple performance characteristics based on the orthogonal array with the grey relational analysis has been studied. A grey relational grade obtained from the grey relational analysis is used to solve the EDM process with the multiple performance characteristics. Optimal machining parameters can then
J. L Lin; C. L Lin
Effect of COOH-functionalized SWCNT addition on the electrical and photovoltaic characteristics of Malachite Green dye based photovoltaic cells
NASA Astrophysics Data System (ADS)
We report the effect of COOH-functionalized single walled carbon nanotubes (COOH-SWCNT) on the electrical and photovoltaic characteristics of Malachite Green (MG) dye based photovoltaic cells. Two different types of photovoltaic cells were prepared, one with MG dye and another by incorporating COOH-SWCNT with this dye. Cells were characterized through different electrical and photovoltaic measurements including photocurrent measurements with pulsed radiation. From the dark current�voltage (I�V) characteristic results, we observed a certain transition voltage (Vth) for both the cells beyond which the conduction mechanism of the cells change sharply. For the MG dye, Vth is 3.9 V whereas for COOH-SWCNT mixed with this dye, Vth drops to 2.7 V. The device performance improves due to the incorporation of COOH-SWCNT. The open circuit voltage and short circuit current density change from 4.2 to 97 mV and from 108 to 965 ?A/cm2 respectively. Observations from photocurrent measurements show that the rate of growth and decay of the photocurrent are quite faster in the presence of COOH-SWCNT. This observation indicates a faster charge separation processes due to the incorporation of COOH-SWCNT in the MG dye cells. The high aspect ratio of COOH-SWCNT allows efficient conduction pathways for the generated charge carriers.
Chakraborty, S.; Manik, N. B.
Electrical characteristics of nanoscale NAND silicon-oxide-nitride-oxide-silicon flash memory devices fabricated on SOI substrates.
NAND silicon-oxide-nitride-oxide-silicon (SONOS) flash memory devices with double gates fabricated on silicon-on-insulator (SOI) substrates were proposed. The current-voltage characteristics related to the programming operation of the designed nanoscale NAND SONOS flash memory devices on a SOI substrate and on the conventional bulk-Si substrate were simulated and compared in order to investigate device characteristics of the scaled-down memory devices. The simulation results showed that the short channel effect and the subthreshod leakage current for the memory device with a large spacer length were lower than that of the memory device with a small spacer length due to increase of the effective channel length. The device performance of the memory device utilizing the SOI substrate exhibited a smaller subthreshold swing and a larger drain current level in comparison with those on the bulk-Si substrate. These improved electrical characteristices for the SOI devices could be explained by comparing the electric field distribution in a channel region for both devices. PMID:22103232
Ryu, Ju Tae; You, Joo Hyung; Yoo, Keon-Ho; Kim, Tae Whan
Oxide breakdown mechanism and quantum physical chemistry for time-dependent dielectric breakdown
Thermochemical-breakdown and hole-induced-breakdown models are theoretically formulated to explain the field-acceleration of TDDB phenomenon. Long-term TDDB test results proved to support the thermochemical-breakdown model. The time-dependent oxide breakdown mechanism is further studied on the basis of quantum physical chemistry. The structural transformations of a-SiO2 up to breakdown are simulated by the semiempirical molecular orbital calculation method (PM3 method) using Si5O16H12
M. Kimura
New phenomenology of gas breakdown in DC and RF fields
NASA Astrophysics Data System (ADS)
This paper follows a review lecture on the new developments in the field of gas breakdown and low current discharges, usually covered by a form of Townsend's theory and phenomenology. It gives an overview of a new approach to identifying which feedback agents provide breakdown, how to model gas discharge conditions and reconcile the results with binary experiments and how to employ that knowledge in modelling gas discharges. The next step is an illustration on how to record volt-ampere characteristics and use them on one hand to obtain the breakdown voltage and, on the other, to identify the regime of operation and model the secondary electron yields. The second aspect of this section concerns understanding the different regimes, their anatomy, how those are generated and how free running oscillations occur. While temporal development is the most useful and interesting part of the new developments, the difficulty of presenting the data in a written form precludes an easy publication and discussion. Thus, we shall only mention some of the results that stem from these measurements. Most micro discharges operate in DC albeit with complex geometries. Thus, parallel plate micro discharge measurements were needed to establish that Townsend's theory, with all its recent extensions, is still valid until some very small gaps. We have shown, for example, how a long-path breakdown puts in jeopardy many experimental observations and why a flat left-hand side of the Paschen curve often does not represent good physics. We will also summarize a kinetic representation of the RF breakdown revealing a somewhat more complex picture than the standard model. Finally, we will address briefly the breakdown in radially inhomogeneous conditions and how that affects the measured properties of the discharge. This review has the goal of summarizing (rather than developing details of) the current status of the low-current DC discharges formation and operation as a discipline which, in spite of its very long history, is developing rapidly.
Petrovi?, Zoran Lj; Sivo�, Jelena; Savi?, Marija; �koro, Nikola; Radmilovi? Radenovi?, Marija; Malovi?, Gordana; Goci?, Sa�a; Mari?, Dragana
Adaptive Simulation of Electrical Discharges Bernd Bickel Martin Wicke Markus Gross
-to-ground lightning. The breakdown pattern is computed iteratively using the dielectric breakdown model. Electric discharges can be simu- lated using the dielectric breakdown model. Reg- ular discretization breakdown model (DBM). In Section 4, our adaptive space discretiza- tion is described. Section 5 introduces
Martin, Sebastian
Influence of sand granulometry on electrical characteristics, temperature and electron density during high-voltage fuse arc extinction
NASA Astrophysics Data System (ADS)
Emission spectroscopy and the recording of electrical characteristics are used to study the influence of the granulometric composition of arc-quenching material. Six adjacent intervals of grain size are studied: each of them is 50 �m wide, and the upper limit of the global interval is lower than 1000 �m. The final dimensions of the fulgurite are found to be proportional to the granulometry. Concerning the electrical parameters, two groups are considered: the extinction time constant, the dissipated energy and the I2t value decrease with the granulometry, whereas the maximum value of the arc voltage increases with the granulometry. The rate of decrease of the temperature depends on the time interval observed: at the beginning of the arcing period, the decrease is fastest for the smallest granulometric parameters; and during the last part of the arcing period the trend is reversed. At the beginning of the arcing period, the electron number density increase varies between 1019 and 1020 cm-3 ms-1. When the electric current decreases, the electron number density decreases exponentially with a time constant value ranging from 0.40 ms to 0.25 ms.
Bussi�re, W.
A percolation based dielectric breakdown model with randomic changes in the dielectric constant
We describe a percolation based model for the dielectric breakdown of metal-oxide-semiconductor capacitors where the dielectric constant varies randomly throughout the oxide layer. We consider the SiO2 oxide within a rectangular lattice framework, and the breakdown is simulated as a cluster growth depending process where the local electric field is a function of the randomly varying permissivity. The effects of
Sergio S. Sombra; Uriel M. S. Costa; Valder N. Freire; E. A. de Vasconcelos; Eronildes F. da Silva
Structural and electrical characteristics of SiGeC and GeC alloys and their application to optical detectors
NASA Astrophysics Data System (ADS)
The formation of ternary alloy Sisb{1-x-y}Gesb{x}Csb{y} by adding C to the SiGe system makes it possible to control the strain within the SiGeC system about the lattice matching condition for Si substrates. This work studies the structural and electrical properties of the Sisb{1-x-y}Gesb{x}Csb{y}/Si and the Gesb{1-x}Csb{x}/Si systems and their applications to photodetectors which can be operated in the infrared wavelength region. The strain modification in Sisb{1-x-y}Gesb{x}Csb{y} 3D islanded growth was studied for self-organized quantum dot growth. Strain shifts island size and distribution of both coherent islands and misfit dislocation relaxed islands in different ways. The optimum growth condition for small coherent islands with a large density and a narrow size distribution is determined by the strain, surface free energy, as well as the substrate temperature and growth rate. Also, the temperature effects on the growth of the binary alloy Gesb{1-x}Csb{x}/Si was studied for optimal growth conditions. Contact resistance of Al, Au, W, and Ti/Au metalizations to p-type epitaxial GeC on Si were measured. Values of specific ohmic contact resistance of these metals range from 10sp{-5}\\ Omega*cmsp2 to 10sp{-7}\\ Omega*cmsp2. No clear dependence of specific contact resistance and barrier height on carbon composition was found. p-Gesb{1-x}Csb{x}/n-Si photodiodes were fabricated and characterized in this study. The p-Gesb{1-x}Csb{x}/n-Si diodes show a high reverse breakdown voltage in excess of -40 volts and some up to -80 volts. The p-Ge/n-Si diode exhibits a much larger reverse saturation current than comparable p-Gesb{1-x}Csb{x}/n-Si diodes, suggesting carbon could improve the performance of the heterojunction diode. Despite the large number of dislocations and defects at the heterojunction interface, photoresponsivity from the GeC/Si diodes was observed at a wavelength of 1.3 mum. External quantum efficiency of the normal incidence photodetector was measured between 1.3 and 2.2%, in spite of its thin active region. Some dependence of external quantum efficiency on the carbon concentration was observed in this study. These initial results are promising, and indicate that the addition of carbon to the Sisb{1-x}Gesb{x} material system may provide an avenue for building Si-based electronic and optoelectronic circuits.
Shao, Xiaoping
Electrical Characteristics of Ultraviolet Photodetector based on ZnO Nanostructures
NASA Astrophysics Data System (ADS)
ZnO nanostructures were grown on p- type Si substrate by spray pyrolysis technic. A UV light was used as an illuminating source at 365 nm. The current-voltage characteristics of the device under UV illumination showed an enhancement that dark current. The dark current is about 58 ?A, and the photocurrent is about 97 ?A under a reverse bias voltage of 6 V. The photocurrent characteristic of photodetector is measured under 3 V forward biases and after 18 min it saturated. Continuous measurements indicate the reproducibility and stability of this UV photodetector. The Schottky diode parameters as the barrier height, the ideality factor, and the series resistance as calculated using a method developed by Cheung's method. It was found that ideality factor was greater than unity and barrier height was larger than 0,8 eV.
Bedia, A.; Bedia, F. Z.; Benyoucef, B.; Hamzaoui, S.
Performance characteristics of a microwave plasma disk ion source. [time varying electric propulsion concept
NASA Technical Reports Server (NTRS)
The development, design, and preliminary performance characteristics of a microwave plasma disk ion source are presented. Several important design concepts indigenous to microwave plasmas have been utilized in the development of this ion source: generation of a resonantly sustained microwave discharge inside a microwave/plasma coupler, probe and length tuning of the microwave/plasma coupler, and minimization of plasma volume. The experimental results for a 2.45 GHz, eight cm ion source excited in the TE(211) and TM(011) modes are described. Results are presented for electromagnetic mode excitation, electron density, coupling efficiency and loaded cavity Q, and I-V characteristics and efficiencies. It is preliminarily shown that a microwave disk-like plasma can be sustained adjacent to the grids with either TE or TM cavity modes at pressures below 2 x 10 to the -4th torr. Over 80% of the power absorbed in the cavity is coupled into the plasma.
Asmussen, J.; Root, J.; Nakanishi, S.
Characteristics of high-temperature solid-electrolyte oxygen pumps specific electrical energy consumption
In order to select the optimal operating conditions for oxygen pumps with low energy consumption it is necessary to calculate the relation between the specific electrical energy requirements for the production of pure oxygen and the working parameters of the oxygen pump. A schematic illustrates an electrochemical cell with ceramic solid electrolyte and the porous electrodes applied to the electrolyte from both sides. The amount of pure oxygen obtained was determined algebraically according to Faraday's law. The way of combining the electrochemical cells was found to have no effect on the specific energy requirements and these requirements can be determined numerical expressions.
Voloshchenko, G.N.; Korovin, N.V.; Slavnov, Yu.A.
Effect of a pulsed power supply on the spectral and electrical characteristics of HID lamps
NASA Astrophysics Data System (ADS)
Results of spectral and photometric measurements are presented for pulsed power operated high intensity discharges (HIDs). This investigation is related to the application of a pulsed power supply for pile driving of HID lamps. Specifically, we are interested in controlling the spectral response radiation of visible and ultraviolet (UV) lines for tertiary treatment of water using UV radiation. Simulations based on a physical model of the lamps were conducted. These results relate to the radial temperature, line intensity and electrical properties (voltage, power and conductivity). Good agreement has been found between the results of the simulations and the experimental findings.
Chammam, Abdeljelil; Elloumi, Hatem; Mrabet, Brahim; Charrada, Kamel; Stambouli, Mongi; Damelincourt, Jean Jacques