Sample records for electrical breakdown characteristics

  1. Electrical breakdown of gases

    Microsoft Academic Search

    J. M. Meek; J. D. Craggs

    1978-01-01

    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)

  2. Influence of magnetic field on the electrical breakdown characteristics in cylindrical diode

    Microsoft Academic Search

    Shou-Zhe Li; Han S. Uhm

    2004-01-01

    The influence of magnetic field on the electrical breakdown properties is investigated by applying a magnetic field along the longitudinal direction in a cylindrical diode for two electrical polarities. Breakdown characteristics in a crossed magnetic field are analyzed with the equivalentreduced-electric-field concept and Townsend criterion. The discharge experiment at reduced pressure is carried out in the moderate magnetic field. Experimental

  3. The electrical breakdown characteristics of oil-paper insulation under steep front impulse voltages

    SciTech Connect

    Vandermaar, A.J.; Wang, M.; Neilson, J.B. (Powertech Labs Inc., Surrey, British Columbia (Canada)); Srivastava, K.D. (Univ. of British Columbia, Vancouver (Canada))

    1994-10-01

    Disconnecting switch operations in gas insulated equipment cause transient voltages with rise times as steep as 5 to 20 nanoseconds and magnitudes as high as 2.5 pu. There is very little information on the effect of these transients on oil-paper insulated equipment. There have been reports, however of transformer and bushing failures caused by these transients. The electrical breakdown characteristics of oil-paper insulation under steep front impulse were studied in this project, which was co-sponsored by the Canadian Electrical Association and B.C. Hydro. V[sub 50] (50% breakdown probability voltage) breakdown data was obtained with steep front (10 ns/2500 [mu]s), lightning and switching impulse waveforms. Insulation breakdown voltage vs breakdown time (V-t) data and multiple impulse breakdown data were obtained with the steep front impulse waveform. The V[sub 50] results showed that the breakdown strengths were lower for steep front impulses than for lightning impulses. The multiple impulse breakdown results showed that oil-paper insulation breakdown strength can be lower than 100 kV/mm. These results are alarming, since they suggest that oil-paper insulated equipment subjected to steep front transients will fail at voltages below the lightning impulse design level (BIL). The Volt-time data had a discontinuity. The breakdown process at risetime below about 50 ns was different from the breakdown process at rise times above 50 ns.

  4. Breakdown characteristics of MV distribution and electric traction lines insulators stressed by standard and short tail lightning impulses

    Microsoft Academic Search

    A. Ancajima; I. Baran; M. Costea; A. Carrus; E. Cinieri; G. Dragan; C. Mazzetti

    2005-01-01

    The paper presents the results of experimental tests performed with impulse voltage with short tail (STLI: 1.2\\/4 mus) on composite insulators in use in the MV distribution lines and electric traction lines. The voltage-time to breakdown characteristics under 1.2\\/4 mus waves are presented and compared with the characteristics under standard lightning impulse (LI: 1.2\\/50 mus). Models based on the disruptive

  5. Breakdown characteristics of an isolated conducting object in a uniform electric field

    NASA Technical Reports Server (NTRS)

    Grothaus, M. G.; Trost, T. F.

    1986-01-01

    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.

  6. Laser-induced electric breakdown in solids

    NASA Technical Reports Server (NTRS)

    Bloembergen, N.

    1974-01-01

    A review is given of recent experimental results on laser-induced electric breakdown in transparent optical solid materials. A fundamental breakdown threshold exists characteristic for each material. The threshold is determined by the same physical process as dc breakdown, namely, avalanche ionization. The dependence of the threshold on laser pulse duration and frequency is consistent with this process. The implication of this breakdown mechanism for laser bulk and surface damage to optical components is discussed. It also determines physical properties of self-focused filaments.

  7. Electrical Breakdown in Water Vapor

    SciTech Connect

    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)

    2011-11-15

    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.

  8. Electrical Breakdown Properties in Spherical Electrodes

    NASA Astrophysics Data System (ADS)

    Uhm, Han S.

    2000-10-01

    Most of the previous studies of the electrical breakdown have been carried out for a uniform electric field. Reduction of breakdown voltage in non-uniform field is needed for various practical applications. We therefore investigate properties of electrical breakdown in spherical diodes, by making use of Paschen's law. The sparking criterion indicates that discharge properties are insensitive to the electrical field polarity inside a spherical diode, if the second ionization-coefficient is constant. The minimum breakdown-voltage for spherical system increases continuously to a finite value, as the curvature aspect ratio b/a increases to infinity, where a and b are radii of the inner and outer conductors, respectively. Due to a finite value of the minimum breakdown-voltage, the corresponding pressure may not be zero even for the infinite aspect ratio. This means that an electrical breakdown with a minimum voltage may occur at surface of a spherical conductor immersed in a gas with an appropriate pressure.

  9. Electrical breakdown gas detector featuring carbon nanotube array electrodes.

    PubMed

    Kim, Seongyul; Pal, Sunil; Ajayan, Pulickel M; Borca-Tasciuc, Theodorian; Koratkar, Nikhil

    2008-01-01

    We demonstrate here detection of dichloro-difluoro-methane and oxygen in mixtures with helium using a carbon nanotube electrical breakdown sensor device. The sensor is comprised of an aligned array of multiwalled carbon nanotubes deposited on a nickel based super-alloy (Inconel 600) as the anode; the counter electrode is a planar nickel sheet. By monitoring the electrical breakdown characteristics of oxygen and dichloro-difluoro-methane in a background of helium, we find that the detection limit for dichloro-difluoro-methane is approximately 0.1% and the corresponding limit for oxygen is approximately 1%. A phenomenologigal model is proposed to describe the trends observed in detection of the two mixtures. These results indicate that carbon nanotube based electrical breakdown sensors show potential as end detectors in gas-chromatography devices. PMID:18468093

  10. Planned waveguide electric field breakdown studies

    SciTech Connect

    Wang Faya; Li Zenghai [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)

    2012-12-21

    This paper presents an experimental setup for X-band rf breakdown studies. The setup is composed of a section of WR90 waveguide with a tapered pin located at the middle of the waveguide E-plane. Another pin is used to rf match the waveguide so it operates in a travelling wave mode. By adjusting the penetration depth of the tapered pin, different surface electric field enhancements can be obtained. The setup will be used to study the rf breakdown rate dependence on power flow in the waveguide for a constant maximum surface electric field on the pin. Two groups of pins have been designed. The Q of one group is different and very low. The other has a similar Q. With the test of the two groups of pins, we should be able to discern how the net power flow and Q affect the breakdown. Furthermore, we will apply an electron beam treatment to the pins to study its effect on breakdown. Overall, these experiments should be very helpful in understanding rf breakdown phenomena and could significantly benefit the design of high gradient accelerator structures.

  11. A study on the breakdown characteristics of the fluorocarbon

    SciTech Connect

    Huh, C.S. [Inha Univ., Inchon (Korea, Republic of). Dept. of Electrical Engineering; Lee, J.B. [Korea Electrotechnology Research Inst., Changwon (Korea, Republic of)

    1996-12-31

    In this paper, the authors investigated physical properties and electrical characteristics of the fluorocarbon that used as coolants for large power gas-insulated transformer. Volume resistivity of the fluorocarbon is {rho} = 1.87 {times} 10{sup 15} [Q{center_dot}cm] at 1 atm, 27 C. Dielectric constant is 1.86 and decreases as temperature increases. The breakdown voltage at 1 atm is higher than that of transformer oil. The breakdown voltage of fluorocarbon vapor is about 18 kV when pressure in a test chamber increases over 1 kg/cm{sup 2}. When fluorocarbon is mixed with SF{sub 6} gas, breakdown voltage of the mixed is higher than that of fluorocarbon. Then fluorocarbon leads to increase over 4 kg/cm{sup 2} in pressure as temperature increase. Therefore, when a gas-insulated transformer is manufactured, the design must be taken into consideration at high-pressure.

  12. Nanocomposites-a review of electrical treeing and breakdown

    Microsoft Academic Search

    Michael G. Danikas; Toshikatsu Tanaka

    2009-01-01

    In this short review, we discussed some aspects of nanocomposites regarding electrical tree growth and breakdown. It appears that nanoparticles, properly mixed and dispersed in the polymer matrix, increase the breakdown strength and hinder the growth of electrical trees in the nanocomposite. Nanoparticles act as barriers obstructing electrical tree growth and delaying dielectric breakdown. This article also put forward a

  13. Abnormal breakdown characteristic in a two-phase mixture

    NASA Astrophysics Data System (ADS)

    Qizheng, Ye; Jin, Li; Fei, Lu

    2006-05-01

    A two-phase mixture (TPM) is a mixture of gas and macroparticles of high concentration. Based on Townsend's theory, a new cell-iterative model in analytical form for the breakdown mechanism in TPM is presented. Compared with the original cell-iterative model in our previous paper, the obstructive factor of the macroparticles that influences the electron avalanche propagation is considered, except for the macroparticles distorting the electrical field and capture of the electrons. The cell attractive parameter k is presented according to the classical continuum theory for field charging. The modified Paschen law for a TPM is presented to calculate the breakdown voltage. The breakdown voltage of the TPM, UTPM, increases gradually with an increase in the macroparticle number density (m). The voltage UTPM is lower than that of the pure gas at low m values and larger at high m values. With a decrease of the macroparticle volume fraction and the dielectric mismatch, the voltage UTPM increases gradually at low m values and decreases gradually at high m values. The voltage UTPM at pd = 200 cm Torr is lower than that at pd = 760 cm Torr for low m values and larger for high m values. This kind of abnormal breakdown characteristic in the TPM occurs in the case of high macroparticle volume fraction. On the other hand, the minimum of the TPM's Paschen curve increases with increase in m. It provides the possibility and the conditions of greatly increasing the breakdown voltage in a nearly uniform field.

  14. Electrical breakdown studies with Mycalex insulators

    SciTech Connect

    Waldron, W.; Greenway, W.; Eylon, S.; Henestroza, E.; Yu, S.

    2003-05-01

    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.

  15. Vacuum emission and breakdown characteristics of a planar He-Xe microdischarge

    Microsoft Academic Search

    Olivier B. Postel; Mark A. Cappelli

    2000-01-01

    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

  16. Vacuum emission and breakdown characteristics of a planar He–Xe microdischarge

    Microsoft Academic Search

    Olivier B. Postel; Mark A. Cappelli

    2000-01-01

    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

  17. Breakdown voltage characteristic of a pseudospark device

    SciTech Connect

    Rhee, M.J.; Ding, B.N. (Laboratory for Plasma Research and Electrical Engineering Department, University of Maryland at College Park, College Park, Maryland 20742 (United States))

    1992-03-01

    The breakdown voltage of a pseudospark device is measured for a wide range of gas pressure and anode--cathode gap distance. The data are analyzed by least-squares-fit methods, and the breakdown voltage is expressed by an empirical function of the gas pressure and the anode--cathode gap distance. It is found that the breakdown voltage is a function of {ital p}{sup 2}{ital d}, the product of the pressure squared and anode--cathode gap distance. This is in contrast to that of a parallel-plate system that is described by Paschen's curve, where the breakdown voltage is a function of {ital pd}.

  18. Electrical conduction mechanism in bulk ceramic insulators at high voltages until dielectric breakdown

    NASA Astrophysics Data System (ADS)

    Neusel, C.; Jelitto, H.; Schneider, G. A.

    2015-04-01

    In order to develop and verify a dielectric breakdown model for bulk insulators thicker than 100 ?m, the knowledge of the dominating conduction mechanism at high electric fields, or respectively voltages, is necessary. The dielectric breakdown is the electrical failure of an insulator. In some existing breakdown models, ohmic conduction is assumed as dominating conduction mechanism. For verification, the dominating dc conduction mechanism of bulk insulators at room temperature was investigated by applying high voltages up to 70 kV to the insulator until dielectric breakdown occurs. Four conduction models, namely, ohmic, space charge limited, Schottky, and Poole-Frenkel conduction, were employed to identify the dominating conduction mechanism. Comparing the calculated permittivities from the Schottky and Poole-Frenkel coefficients with experimentally measured permittivity, Schottky and Poole-Frenkel conduction can be excluded as dominating conduction mechanism. Based on the current density voltage characteristics (J-V-curve) and the thickness-dependence of the current density, space charge limited conduction (SCLC) was identified to be the dominating conduction mechanism at high voltages leading to dielectric breakdown. As a consequence, breakdown models based on ohmic conduction are not appropriate to explain the breakdown of the investigated bulk insulators. Furthermore, the electrical failure of the examined bulk insulators can only be described correctly by a breakdown model which includes SCLC as conduction mechanism.

  19. The intrinsic electrical breakdown strength of insulators from first principles

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Boggs, S. A.; Ramprasad, R.

    2012-09-01

    A first principles quantum-mechanical method for estimating intrinsic breakdown strength of insulating materials has been implemented based on an average electron model which assumes that the breakdown occurs when the average electron energy gain from the electric field exceeds the average energy loss to phonons. The approach is based on density functional perturbation theory and on the direct integration of electronic scattering probabilities over all possible final states, with no adjustable parameters. The computed intrinsic breakdown field for several prototypical materials compares favorably with available experimental data. This model also provides physical insight into the material properties that affect breakdown.

  20. Electrical Breakdown in High-temperature Gases

    Microsoft Academic Search

    D. W. George; H. K. Messerle

    1963-01-01

    RELATIVELY few experimental results are available for the breakdown of high-temperature gases at atmospheric pressure and above. Alston1 has confirmed Paschen's law for air up to 1,100° C and obtained flashover voltages which were independent of electrode material. On the other hand, it is well known from investigations of the decaying properties of freely recovering arcs2 that `thermal' breakdown can

  1. Breakdown characteristics and conditioning of carbon and refractory metal electrodes

    NASA Technical Reports Server (NTRS)

    Goebel, Dan M.

    2004-01-01

    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.

  2. Investigation of electrical breakdown properties in curved electrodes

    NASA Astrophysics Data System (ADS)

    Uhm, Han S.

    2000-11-01

    Properties of electrical breakdown in curved electrodes are investigated by making use of Paschen's law. Simple analytical expressions for minimum breakdown voltage and its corresponding values of physical parameters are obtained for cylindrical and spherical geometries. The sparking criterion indicates that discharge properties are insensitive to the electrical field polarity inside a diode for both cylindrical and spherical systems, if the second ionization coefficient ? is constant. Due to the curvature effects, the minimum breakdown voltage in cylindrical and spherical geometries increases significantly from its planar value for a large aspect ratio of b/a, where a and b are radii of the inner and outer conductors, respectively. However, the optimum pressure parameter for minimum breakdown voltage in cylindrical geometry is identical to that in planar electrodes. The minimum breakdown voltage for spherical system increases continuously to a finite value, as the curvature aspect ratio b/a increases to infinity. Therefore, pressure for the minimum breakdown voltage may not be zero, even for the infinite aspect ratio. This means that an electrical breakdown with a minimum voltage may occur at surface of a spherical conductor immersed in a gas with an appropriate pressure.

  3. Gas Temperature Effects on Electrical Breakdown in Cylindrical Electrodes

    NASA Astrophysics Data System (ADS)

    Uhm, Han; Jung, She

    2002-11-01

    One of the most important applications of atmospheric pressure plasma is in the corona discharge system, for the potential reduction of NOx and SOx gas emissions from diesel engines. However, the conventional corona discharge system for the emission control application requires a high electrical voltage (typically 45 kV or higher), making its high voltage modulator heavy and bulky with insulating material. We, therefore, investigate the influence of the gas temperature on the electrical breakdown properties in the cylindrical electrode system. A theoretical model of the electrical breakdown in a cylindrical electrode system is briefly summarized, by making use of Paschen¡¯s law. The breakdown voltage increases, reaches its peak and decreases, as the aspect ratio a/b increases from 0.01 to unity, where a and b are radii of the inner and outer electrodes, respectively. The experimental data agree remarkably well with the theoretical predictions. The breakdown voltage V in a high gas temperature Tg is given by V = (Tr/Tg)V0, where V0 is the breakdown voltage at the room temperature Tr. Obviously, the breakdown voltage decreases as the gas temperature Tg increases. The experimental data agree well with the theoretical values. It is, therefore, concluded that the breakdown voltage is inversely proportional to the gas temperature Tg as predicted from the theoretical analysis.

  4. Electric breakdown in deuterium and hydrogen at low pressures

    SciTech Connect

    Armstrong, R.J.; Bennett, T.K. [Princeton Plasma Physics Laboratory, P. O. Box 451, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, P. O. Box 451, Princeton, New Jersey 08543 (United States)

    1997-09-01

    The electrical breakdown of plane parallel steel electrodes (10 cm diam) is studied in a Pyrex-walled vacuum chamber (minimum pressure less than 8{times}10{sup {minus}6} Torr). For clean gases, H{sub 2} and D{sub 2}, and with electrode gaps from 0.5 to 8 cm, the breakdown at pressures from 0.3 to 0.5 Torr is consistent with a secondary process of electron release by ion bombardment. The breakdown curves for the two gases, when scaled on both axes, overlap to a considerable extent. {copyright} {ital 1997 American Institute of Physics.}

  5. Electrical breakdown and ultrahigh electrical energy density in poly,,vinylidene fluoride-hexafluoropropylene... copolymer

    E-print Network

    Zhao, Xuanhe

    are of great importance for the power electronics in hybrid electric vehicles, medical devices, and electrical the film pro- cessing conditions and consequently the film quality, a higher electrical breakdown field can- tromechanical breakdown strength of the new model agrees quite well with the experimental data. P VDF-HFP 95

  6. Electrical Breakdown and Dielectric Recovery of Propylene Carbonate

    Microsoft Academic Search

    Shu Xiao; J. F. Kolb; Muhammad Arif Malik; Xinpei Lu; Mounir Laroussi; Ravindra P. Joshi; Edl Schamiloglu; Karl H. Schoenbach

    2006-01-01

    Polar liquids are characterized by high permittivity and high dielectric strength. These properties make them appealing dielectrics for use in high-energy storage systems and as high-power switching media. Most of the studies on electrical breakdown and recovery have focused on water as a switch medium in pulsed-power systems. As an alternative to water, the authors have studied the breakdown and

  7. Electrical breakdown of soil under nonlinear pulsed current spreading

    NASA Astrophysics Data System (ADS)

    Vasilyak, L. M.; Pecherkin, V. Ya; Vetchinin, S. P.; Panov, V. A.; Son, E. E.; Efimov, B. V.; Danilin, A. N.; Kolobov, V. V.; Selivanov, V. N.; Ivonin, V. V.

    2015-07-01

    Laboratory investigations on pulsed current spreading from spherical electrodes and evolution of electrical breakdown of silica sand with different water contents under a 15–20?kV voltage pulse were carried out. A sharp nonlinear decrease in the pulsed resistance of soil was observed when the current density exceeded a certain threshold value. Then ionization-overheating instability develops and leads to current contraction and plasma channel formation in the soil. The method for determination of the threshold electric field for ionization is proposed. Electrical discharge in wet sand was found to develop with a significant delay time for long discharge gaps similar to thermal breakdown.

  8. Electric properties and carrier multiplication in breakdown sites in multi-crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Schneemann, Matthias; Kirchartz, Thomas; Carius, Reinhard; Rau, Uwe

    2015-05-01

    This paper studies the effective electrical size and carrier multiplication of breakdown sites in multi-crystalline silicon solar cells. The local series resistance limits the current of each breakdown site and is thereby linearizing the current-voltage characteristic. This fact allows the estimation of the effective electrical diameters to be as low as 100 nm. Using a laser beam induced current (LBIC) measurement with a high spatial resolution, we find carrier multiplication factors on the order of 30 (Zener-type breakdown) and 100 (avalanche breakdown) as new lower limits. Hence, we prove that also the so-called Zener-type breakdown is followed by avalanche multiplication. We explain that previous measurements of the carrier multiplication using thermography yield results higher than unity, only if the spatial defect density is high enough, and the illumination intensity is lower than what was used for the LBIC method. The individual series resistances of the breakdown sites limit the current through these breakdown sites. Therefore, the measured multiplication factors depend on the applied voltage as well as on the injected photocurrent. Both dependencies are successfully simulated using a series-resistance-limited diode model.

  9. Electrical breakdown phenomena for devices with micron separations

    Microsoft Academic Search

    Ching-Heng Chen; J. Andrew Yeh; Pei-Jen Wang

    2006-01-01

    The electric breakdown of gaseous dielectrics predicted by Paschen's law has been successfully employed for the design of insulation among metallic conductors separated by millimeter scale gaps or larger. However, today most electrostatic actuated MEMS devices have been designed and fabricated with micron-scale gaps that lead to a high risk of failure. Paschen's curves measured under macro or meso gaps

  10. Theory of optically-triggered electrical breakdown of semiconductors

    Microsoft Academic Search

    Kenneth E. Kambour; Harold P. Hjalmarson; Charles W. Myles

    2003-01-01

    In this paper, we describe a rate equation approach that leads to new insights about electrical breakdown in insulating and semiconducting materials. In this approach, the competition between carrier generation by impact ionization and carrier recombination by Auger and defect recombination leads to steady state solutions for the carrier generation rate, and it is the accessibility of these steady state

  11. Reducing bubbles in glass coatings improves electrical breakdown strength

    NASA Technical Reports Server (NTRS)

    Banks, B.

    1968-01-01

    Helium reduces bubbles in glass coatings of accelerator grids for ion thrustors. Fusing the coating in a helium atmosphere creates helium bubbles in the glass. In an argon atmosphere, entrapped helium diffuses out of the glass and the bubbles collapse. The resultant coating has a substantially enhanced electrical breakdown strength.

  12. Ionizing gas breakdown waves in strong electric fields.

    NASA Technical Reports Server (NTRS)

    Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.

    1972-01-01

    A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.

  13. Reduce of Threshold of Laser Inducing Breakdown in Atmosphere by Introducing an Electric Spark

    Microsoft Academic Search

    Xian-Bin Zhang; Wei Shi; Hua Li

    2005-01-01

    We report laser-generated plasmas in atmosphere with electrical spark generated by a synchronization circuit. The breakdown thresholds under the conditions that the electrical spark is used and not used are compared. The breakdown threshold has a distinct decrease after the electrical spark is used. Breakdown thresholds as a function of atmosphere pressure have also been measured at laser wavelengths 532

  14. Breakdown characteristics of RTO 10 nm SiO2 films grown at different temperatures

    Microsoft Academic Search

    L. Fonseca; F. Campabadal

    1994-01-01

    Metal-oxide-semiconductor capacitors with 10 nm gate oxides grown by rapid thermal oxidation at temperatures of 1000, 1100 and 1150°C have been electrically characterized by means of C-V techniques, time-zero and time-dependent breakdown experiments. The oxides grown at higher temperatures show superior interfacial and oxide integrity characteristics, which is consistent with a lower level of intrinsic stress in such layers. The

  15. Electric breakdown effect in the current-voltage characteristics of amorphous indium oxide thin films near the superconductor-insulator transition

    Microsoft Academic Search

    O. Cohen; M. Ovadia; D. Shahar

    2011-01-01

    Current-voltage characteristics in the insulator bordering superconductivity in disordered thin films exhibit current jumps of several orders of magnitude due to the development of a thermally bistable electronic state at very low temperatures. In this high-resolution study we find that the jumps can be composed of many (up to 100) smaller jumps that appear to be random. This indicates that

  16. Lightning Impulse Breakdown Characteristics and Electrodynamic Process of Insulating Vegetable Oil-Based Nanofluid

    NASA Astrophysics Data System (ADS)

    Li, Jian; Zhang, Zhao-Tao; Zou, Ping; Du, Bin; Liao, Rui-Jin

    2012-06-01

    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.

  17. Ion manipulation device with electrical breakdown protection

    DOEpatents

    Chen, Tsung-Chi; Tang, Keqi; Ibrahim, Yehia M; Smith, Richard D; Anderson, Gordon A; Baker, Erin M

    2014-12-02

    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.

  18. Dissociation dynamics of CH3I in electric spark induced breakdown revealed by time-resolved laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Liu, Wei-long; Song, Yun-fei; Duo, Li-ping; Liu, Yu-qiang; Yang, Yan-qiang

    2015-02-01

    The electric discharge spark dissociation of gas CH3I is found to be similar to its femtosecond laser photodissociation. The almost identical spectra of the two processes show that their initial ionization conditions are very similar. The initial ionization followed by molecular fragmentation is proposed as the dissociation mechanism, in which the characteristic emissions of I+, CH3, CH2, CH, H, and I2 are identified as the dissociation products. The emission band of 505 nm I2 is clearly observed in the time-resolved laser induced breakdown spectroscopy (LIBS). The dynamic curve indicates that I2? molecules are formed after the delay time of ?4.7 ns. The formation of I2? molecule results from the bimolecular collision of the highly excited iodine atom I?(4P) and CH3I molecule. This dynamical information can help understand the process of electric discharge spark dissociation of CH3I.

  19. Electrical breakdown phenomena for devices with micron separations

    NASA Astrophysics Data System (ADS)

    Chen, Ching-Heng; Yeh, J. Andrew; Wang, Pei-Jen

    2006-07-01

    The electric breakdown of gaseous dielectrics predicted by Paschen's law has been successfully employed for the design of insulation among metallic conductors separated by millimeter scale gaps or larger. However, today most electrostatic actuated MEMS devices have been designed and fabricated with micron-scale gaps that lead to a high risk of failure. Paschen's curves measured under macro or meso gaps hereby must be re-examined and carefully evaluated for providing the guidelines of insulation design in MEMS devices. In this paper, geometric configurations commonly employed for MEMS electrodes, typically planar and inter-digitated combs, have been designed and analyzed with commercial software packages. For verification purposes, breakdown voltages were measured on test samples fabricated with metallic, p-type and n-type silicon substrates in standard MEMS processes. The samples were prepared by etching insulation gaps measured from 2 to 21 µm. In conclusion, Paschen's curves for describing the electric breakdown phenomena of gaseous dielectrics were revisited and compared to the published data so that design guidelines of electrical insulation in MEMS actuators are established.

  20. Mass spectra of neutral particles released during electrical breakdown of thin polymer films

    NASA Technical Reports Server (NTRS)

    Kendall, B. R. F.

    1985-01-01

    A special type of time-of-flight mass spectrometer triggered from the breakdown event was developed to study the composition of the neutral particle flux released during the electrical breakdown of polymer films problem. Charge is fed onto a metal-backed polymer surface by a movable smooth platinum contact. A slowly increasing potential from a high-impedance source is applied to the contact until breakdown occurs. The breakdown characteristics is made similar to those produced by an electron beam charging system operating at similar potentials. The apparatus showed that intense instantaneous fluxes of neutral particles are released from the sites of breakdown events. For Teflon FEP films of 50 and 75 microns thickness the material released consists almost entirely of fluorocarbon fragments, some of them having masses greater than 350 atomic mass units amu, while the material released from a 50 micron Kapton film consists mainly of light hydrocarbons with masses at or below 44 amu, with additional carbon monoxide and carbon dioxide. The apparatus is modified to allow electron beam charging of the samples.

  1. Pressure dependence of electrical breakdown in water vapour

    NASA Astrophysics Data System (ADS)

    Kelsey, Colin; Graham, Bill; Stalder, Ken; Field, Tom; Patton, David; Gilmore, Tom

    2013-09-01

    The relationship of breakdown voltage to the electric field strength and number density of a gas is a fundamental part of plasma physics. It is well studied and understood for parallel plate geometries where the relationship is described by Paschen's Law and thousands of experiments have been performed to measure such curves under a wide variety of conditions. Here we produce a plasma by applying a voltage in a point to plane geometry in a conducting liquid. Shadowgraph images show a vapour layer forming on the point and subsequent light emission indicates plasma creation within the vapour. However the processes are not spatially or temporally reproducible. In order to gain further understanding of the underlying physics of the plasma formation we are determining the electric field strength with at the aid of simulations, experimentally determining the breakdown voltage and varying the gas density by performing the experiments and simulations at different pressures. Preliminary results indicate electric field strengths of about 107V/m and that the plasma persists throughout voltage pulses of up to 2 ms. The relationship of breakdown voltage to the electric field strength and number density of a gas is a fundamental part of plasma physics. It is well studied and understood for parallel plate geometries where the relationship is described by Paschen's Law and thousands of experiments have been performed to measure such curves under a wide variety of conditions. Here we produce a plasma by applying a voltage in a point to plane geometry in a conducting liquid. Shadowgraph images show a vapour layer forming on the point and subsequent light emission indicates plasma creation within the vapour. However the processes are not spatially or temporally reproducible. In order to gain further understanding of the underlying physics of the plasma formation we are determining the electric field strength with at the aid of simulations, experimentally determining the breakdown voltage and varying the gas density by performing the experiments and simulations at different pressures. Preliminary results indicate electric field strengths of about 107V/m and that the plasma persists throughout voltage pulses of up to 2 ms. L. Schaper PSST. 20 (2011) 034003.

  2. Onset of electrical breakdown in dust layers: I. Microsparking described by Paschen's Law

    SciTech Connect

    Young, R.P.; DuBard, J.L.; Sparks, L.E.

    1988-11-01

    The onset of electrical breakdown in dust layers has been studied 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's Law. The size of voids where breakdown occurs was in the range of 10 to 20 ..mu..M for the layers used. The distribution of particle sizes in a sample influences its breakdown through changes in the average void dimension where breakdown takes place. Water vapor in the test environment, which affects the electrical conduction mechanism prior to breakdown, lowered the average electric field required to initiate breakdown. Moderate compaction of the sample had little or no effect on its breakdown behavior. Three dust species were chosen for this investigation: two pulverized coal fly ashes and a Portland cement dust.

  3. Electrical Breakdown in Lightning Arrestor Connector (LAC) Devices

    NASA Astrophysics Data System (ADS)

    Hjalmarson, Harold P.; Kambour, Kenneth; Pineda, Andrew C.

    2011-03-01

    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.

  4. Experimental and theoretical studies of the breakdown voltage characteristics at micrometre separations in air

    Microsoft Academic Search

    M. Klas; S. Matejcík; B. Radjenovic; M. Radmilovic-Radjenovic

    2011-01-01

    This paper presents experimental results and computer simulation for the direct current (DC) breakdown voltages in dry, synthetic and ambient air and discharge gaps ranging from 1 to 100 mum. The measured breakdown voltage curves were systematically analyzed and the effective electron yields from cathode for dry and synthetic air as a function of the reduced electric field have been

  5. Visual and Electrical Evidence Supporting a Two-Plasma Mechanism of Vacuum Breakdown Initiation

    SciTech Connect

    Castano-Giraldo, C. [University of Illinois, Urbana-Champaign; Aghazarian, Maro [ORNL; Caughman, John B [ORNL; Ruzic, D. N. [University of Illinois, Urbana-Champaign

    2012-01-01

    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.

  6. Radiation-induced electrical breakdown of helium in fusion reactor superconducting magnet systems

    SciTech Connect

    Perkins, L.J.

    1983-12-02

    A comprehensive theoretical study has been performed on the reduction of the electrical breakdown potential of liquid and gaseous helium under neutron and gamma radiation. Extension of the conventional Townsend breakdown theory indicates that radiation fields at the superconducting magnets of a typical fusion reactor are potentially capable of significantly reducing currently established (i.e., unirradiated) helium breakdown voltages. Emphasis is given to the implications of these results including future deployment choices of magnet cryogenic methods (e.g., pool-boiling versus forced-flow), the possible impact on magnet shielding requirements and the analogous situation for radiation-induced electrical breakdown in fusion RF transmission systems.

  7. Stretch dependence of the electrical breakdown strength and dielectric constant of dielectric elastomers

    NASA Astrophysics Data System (ADS)

    Tröls, Andreas; Kogler, Alexander; Baumgartner, Richard; Kaltseis, Rainer; Keplinger, Christoph; Schwödiauer, Reinhard; Graz, Ingrid; Bauer, Siegfried

    2013-10-01

    Dielectric elastomers are used for electromechanical energy conversion in actuators and in harvesting mechanical energy from renewable sources. The electrical breakdown strength determines the limit of a dielectric elastomer for its use in actuators and energy harvesters. We report two experimental configurations for the measurement of the stretch dependence of the electrical breakdown strength of dielectric elastomers, and compare the electrical breakdown fields for compliant and rigid electrodes on the elastomer. We show that the electrode configuration strongly influences the electrical breakdown field strength. Further, we compare the stretch dependent dielectric function and breakdown of the acrylic elastomer VHB 4910™ from 3M™, and of the natural rubber ZruElast™ A1040™ from Zrunek rubber technology. While the dielectric permittivity of VHB decreases with increasing stretch ratio, the dielectric constant of rubber is insensitive to stretch. Our results suggest natural rubber as a versatile material for dielectric elastomer energy harvesting.

  8. Breakdown characteristics in air gaps with artificial floating metals under DC voltage

    Microsoft Academic Search

    Mamoru Kubuki; Ryuichi Yoshimoto; Kazuki Tanoue; Masanori Hara

    1995-01-01

    The DC breakdown characteristics of a sphere-to-sphere gap with conducting objects supported by an insulator rod in atmospheric air are investigated experimentally to provide fundamental parameters determining the breakdown voltage in the presence of floating objects around DC power apparatus by an air insulation. The shape of tested floating objects made of metal is plate, needle or sphere. Experimental results

  9. The influence of defects on the short-term breakdown characteristics and long-term dc performance of LDPE insulation

    Microsoft Academic Search

    G. Chen; A. E. Davies

    2000-01-01

    Extruded polyethylene is used as the bulk insulation for ac HV cables because of its high electric resistivity and breakdown strength. Although the material at present has limited use in dc power cables, it is used extensively in submarine optical communication cable systems. This paper reports on the study of the short-term characteristics and long-term performance of low-density polyethylene (LDPE)

  10. Electrical breakdown and nanogap formation of indium oxide core/shell heterostructure nanowires.

    PubMed

    Jung, Minkyung; Song, Woon; Sung Lee, Joon; Kim, Nam; Kim, Jinhee; Park, Jeunghee; Lee, Hyoyoung; Hirakawa, Kazuhiko

    2008-12-10

    We report the electrical breakdown behavior and subsequent nanogap formation of In(2)O(3)/InO(x) core/shell heterostructure nanowires with substrate-supported and suspended structures. The radial heterostructure nanowires, composed of crystalline In(2)O(3) cores and amorphous In-rich shells, are grown by chemical vapor deposition. As the nanowires broke down, they exhibited two distinct current drops in the current-voltage characteristics. The tips of the broken nanowires were found to have a cone or a volcano shape depending on the width of the nanowire. The shape, the size, and the position of the nanogap depend strongly on the device structure and the nanowire dimensions. The substrate-supported and the suspended devices exhibit distinct breakdown behavior which can be explained by the diffusive thermal transport model. The breakdown temperature of the nanowire is estimated to be about 450 K, close to the melting temperature of indium. We demonstrated the usefulness of this technique by successful fabrication of working pentacene field-effect transistors. PMID:21730682

  11. Laser initiation and early stages of electrical breakdown in charge glasses

    SciTech Connect

    Akishin, A.I.; Zelikin, N.V.; Kornienko, L.S.; Radchenko, V.V.; Trukhanova, L.P.; Tyutrin, Yu.I.

    1989-01-01

    A single pulse from a neodymium laser is used to initiate electrical breakdown in glasses which accumulate and preserve a space charge induced by a beam of rapid monoenergetic electrons. Laser initiation permits use of high-speed recording apparatus and study of the initial stage of electrical breakdown in the charged glasses. A time delay in electrical breakdown relative to the initiating optical radiation was observed and measured, corresponding to the time of formation of a conductive channel between the region of space-charge localization and the specimen surface. Growth rates of the conductive channel are determined for surface and volume initiation, and possible mechanisms of laser initiation are considered.

  12. THE ONSET OF ELECTRICAL BREAKDOWN IN DUST LAYERS: I. MICROSPARKING DESCRIBED BY PASCHEN'S LAW

    EPA Science Inventory

    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...

  13. Modeling of electric field distribution and its corelation with breakdown strength in diphasic dielectrics

    Microsoft Academic Search

    S. K. Patil; M. Y. Koledintseva; R. W. Schwartz; W. Huebner

    2008-01-01

    An electric field distribution in a 3D diphasic dielectric structure with inclusions randomly dispersed in a host phase is simulated using a boundary element method (BEM) to mimic real-world system. A dielectric composite is assumed to undergo the intrinsic breakdown, and a percolation model is used to define the initiation of breakdown process. The simulations comprehensively identify the impact of

  14. Locating initial breakdown pulses using electric field change network

    NASA Astrophysics Data System (ADS)

    Karunarathne, Sumedhe; Marshall, Thomas C.; Stolzenburg, Maribeth; Karunarathna, Nadeeka; Vickers, Lauren E.; Warner, Tom A.; Orville, Richard E.

    2013-07-01

    Initial breakdown pulses (IBPs) observed in the fast electric field change (E-change) at the beginning of intracloud (IC) and cloud-to-ground (CG) lightning flashes are located using a time-of-arrival technique called Position By Fast Antenna (PBFA) with data from a network of 10 E-change sensors located at Kennedy Space Center. Location errors, estimated using a Monte Carlo method, are usually less than 100 m for horizontal coordinates and several hundreds of meters for altitude, depending on distance to the sensors and altitude of the source. Comparison of PBFA source locations to locations from a VHF lightning mapping system (Lightning Detection and Ranging II (LDAR2)) shows that PBFA locates most of the "classic" IBPs while LDAR2 locates only a few percent of them. As the flash develops during the IB stage, PBFA and LDAR2 obtain similar locations when they detect the same IBPs. The overall vertical motion indicated by the PBFA positions of IBPs was downward with time for CG flashes and upward with time for IC flashes. Location of the fast pulses due to return strokes of CG flashes is also determined using PBFA. Comparison to locations from the Cloud-to-Ground Lightning Surveillance System (CGLSS) shows that PBFA reliably locates ground strokes. These results are verified using ground truth data acquired with a high-speed video camera. After cross calibration with the CGLSS data set, peak currents of return strokes are also determined.

  15. Breakdown characteristics in pulsed-driven dielectric barrier discharges: influence of the pre-breakdown phase due to volume memory effects

    NASA Astrophysics Data System (ADS)

    Höft, H.; Kettlitz, M.; Becker, M. M.; Hoder, T.; Loffhagen, D.; Brandenburg, R.; Weltmann, K.-D.

    2014-11-01

    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.

  16. Decrease in the static electric gas breakdown voltage in the presence of free electrons in a discharge gap

    Microsoft Academic Search

    U. Yusupaliev; V. G. Elenskii

    2008-01-01

    The dependence of the gas breakdown voltage U\\u000a \\u000a B\\u000a on the anode-cathode spacing d, pressure p, and other gas characteristics in the presence of a steady external ionizer in the discharge gap was determined within the\\u000a avalanche discharge theory. The case was considered where the spatial charge created by the external ionizer did not distort\\u000a the electric field in the

  17. Pre-breakdown cavitation development in the dielectric fluid in the inhomogeneous, pulsed electric fields

    E-print Network

    Mikhail N. Shneider; Mikhail Pekker

    2014-12-01

    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.

  18. Pre-breakdown processes in a dielectric fluid in inhomogeneous pulsed electric fields

    NASA Astrophysics Data System (ADS)

    Shneider, Mikhail N.; Pekker, Mikhail

    2015-06-01

    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.

  19. Investigation of the statistical nature and structure of the electrical breakdown time delay in gas diodes filled with neon

    SciTech Connect

    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)

    2006-12-01

    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.

  20. Experimental investigation of breakdown voltage characteristics of single-gap and multigap pseudosparks

    SciTech Connect

    Liu, C.J. [China Academy of Engineering Physics, Chengdu, Sichuan (China)] [China Academy of Engineering Physics, Chengdu, Sichuan (China); Rhee, M.J. [Univ. of Maryland, College Park, MD (United States)] [Univ. of Maryland, College Park, MD (United States)

    1995-06-01

    Simple empirical scaling laws that can be applied universally are determined for breakdown voltage characteristics of single-gap and multigap pseudosparks. For the single-gap pseudospark, the breakdown voltage is found to be a function of the product of the gas pressure squared, the anode-cathode gap distance, and the hollow cavity diameter, p{sup 2}dD, and a function of the product pd for a gap distance less than and greater than three times the cavity diameter, respectively. For the multigap pseudospark, however, the breakdown voltage is found to be only a function of the product p{sup 2}dD.

  1. Abnormal breakdown characteristic in a two-phase mixture

    Microsoft Academic Search

    Ye Qizheng; Li Jin; Lu Fei

    2006-01-01

    A two-phase mixture (TPM) is a mixture of gas and macroparticles of high concentration. Based on Townsend's theory, a new cell-iterative model in analytical form for the breakdown mechanism in TPM is presented. Compared with the original cell-iterative model in our previous paper, the obstructive factor of the macroparticles that influences the electron avalanche propagation is considered, except for the

  2. Characteristics of Gas Breakdown in Hollow-Core Fibers

    Microsoft Academic Search

    X. Shi; X. B. Wang; W. Jin; M. S. Demokan

    2008-01-01

    We succeeded in obtaining gas discharge in 250-, 150-, and 50-mum inner-diameter (i.d.) hollow-core fibers (HCFs) by using longitudinal direct current excitation. Stable glow discharges of at least several minutes were observed for these HCFs. A flash glow was also observed for an HCF with an i.d. of ~20 mum. Breakdown of helium and argon gases in a 26.2-cm-long 250-mum-i.d.

  3. Modeling characteristics of nonequilibrium processes during breakdown of capacitive rf argon glow discharge

    SciTech Connect

    Deng Yongfeng [State Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams, School of Physics and Optoelectronic Technology, and College of Advanced Science and Technology, Dalian University of Technology, Dalian 116085 (China); OXi'an Space Power Institute, Xi'an 710100 (China); Han Xianwei [OXi'an Space Power Institute, Xi'an 710100 (China); Shafiq-ur-Rehman; Liu Yue [State Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams, School of Physics and Optoelectronic Technology, and College of Advanced Science and Technology, Dalian University of Technology, Dalian 116085 (China)

    2008-05-15

    A self-consistent, diffusion-drift approximated fluid model including ion and electron continuity equations and an electron energy equation is presented for simulating the nonequilibrium characteristics during breakdown of argon rf glow discharge. The nonlinear partial differential equations of the model are solved numerically by using a so-called finite volume method. The numerical results indicate that there exist two different phases on the breakdown curves, i.e., the low p{center_dot}d phase and high p{center_dot}d phase. The breakdown voltage, analyzed for three different gaps, varies little in low p{center_dot}d phase while in the high p{center_dot}d phase, it increases linearly with pressure increase. Time evolution of Ohmic heating and energy loss during breakdown are presented in detail. Analysis yields that the heating mechanisms are the dominant factors in breakdown. Moreover, the steady discharge characteristics are also studied specifically under breakdown voltage of 10 Torr. The charged particle densities are on the order of 10{sup 15}/m{sup 3} and the electron energy has two characteristic values at different rf phases.

  4. Electrical environmental characteristics for automotive electric systems

    Microsoft Academic Search

    Shin Yamamoto; OSAMU OZEKI; TERUO YAMANAKA; HIROSHI KONDO

    1983-01-01

    The electrical environment is one of the most important factors in the design of high reliability electronic systems mounted on automobiles. Studies were made of the generation mechanisms and characteristics of both transients and high-frequency conducted noise generated in automotive electrical components. The high-frequency conducted noise data were obtained in terms of amplitude-frequency through real-time statistical treatment of the acquired

  5. The Short-Time Electric Breakdown Behavior of Polyethylene

    Microsoft Academic Search

    Peter H. Fischer; Kurt Nissen

    1976-01-01

    The measurement of dielectric strengths is generally beset with numerous difficulties, and results depend to a large extent upon experimental conditions and sample geometry. The development of so-called cylindrical samples, in which spherical electrodes are almost completely embedded in the dielectric to be measured, and observation of stringent cleanliness, have resulted in distributions of the measured breakdown field strengths which

  6. PART I. THERMAL BREAKDOWN CHARACTERISTICS OF MUNICIPAL SOLID WASTE COMPONENTS IN

    E-print Network

    Columbia University

    teraphthalate (PETE), low density polyethylene (LDPE) and food waste. Samples of these materials were heatedPART I. THERMAL BREAKDOWN CHARACTERISTICS OF MUNICIPAL SOLID WASTE COMPONENTS IN VARYING OXYGEN ENVIRONMENTS AND PART II. MUNICIPAL SOLID WASTE MANAGEMENT IN CHINA Alexander P. Whitworth Advisor: Prof. Marco

  7. Study on breakdown characteristics of a low-pressure dielectric barrier discharge

    Microsoft Academic Search

    Yi-Ming Ling

    2007-01-01

    The breakdown characteristics of a low-frequency dielectric barrier discharge (DBD) at low pressure are investigated experimentally in He, Ne and Ar. The current waveform of this DBD, a series of pulses, is caused by the results of the electron avalanches under the action of the applied field and the quenching effect of the wall-charge field on the avalanches. Taking into

  8. Noise characteristics of radiation-induced soft breakdown current in ultrathin gate oxides

    Microsoft Academic Search

    Andrea Cester; Leonardo Bandiera; Marco Ceschia; Gabriella Ghidini; Alessandro Paccagnella

    2001-01-01

    We have investigated new aspects of the gate leakage current due to radiation-induced soft breakdown (RSB) of thin oxides subjected to heavy-ion irradiation. Temperature and noise characteristics of RSB on MOS capacitors with 3- and 4- nm MOS oxides have been experimentally investigated. We have developed an empirical law to describe quantitatively the temperature dependence of the RSB current. A

  9. High frequency breakdown characteristics of various electrode geometries in air

    Microsoft Academic Search

    W. G. Dunbar; D. L. Schweickart; J. C. Horwath; L. C. Walko

    1998-01-01

    In airborne and spacecraft electronic applications, minimum weight and volume constraints have always influenced electrical component and cabling designs. Insulation system specifications must include the total operating environment, voltage excursions, current capacity, mechanical integrity and aging. This is true for both power source equipment as well as special purpose electronics such as radar or high power transmitters, where bare or

  10. Statistical analysis of the electrical breakdown time delay distributions in krypton

    SciTech Connect

    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)

    2006-08-15

    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.

  11. Microcontroller based system for electrical breakdown time delay measurement in gas-filled devices

    NASA Astrophysics Data System (ADS)

    Pejovi?, Mili? M.; Deni?, Dragan B.; Pejovi?, Mom?ilo M.; Neši?, Nikola T.; Vasovi?, Nikola

    2010-10-01

    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.

  12. Microcontroller based system for electrical breakdown time delay measurement in gas-filled devices.

    PubMed

    Pejovi?, Mili? M; Deni?, Dragan B; Pejovi?, Mom?ilo M; Neši?, Nikola T; Vasovi?, Nikola

    2010-10-01

    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. PMID:21034116

  13. Effects of load voltage on voltage breakdown modes of electrical exploding aluminum wires in air

    NASA Astrophysics Data System (ADS)

    Wu, Jian; Li, Xingwen; Yang, Zefeng; Wang, Kun; Chao, Youchuang; Shi, Zongqian; Jia, Shenli; Qiu, Aici

    2015-06-01

    The effects of the load voltage on the breakdown modes are investigated in exploding aluminum wires driven by a 1 kA, 0.1 kA/ns pulsed current in air. From laser probing images taken by laser shadowgraphy, schlieren imaging, and interferometry, the position of the shockwave front, the plasma channel, and the wire core edge of the exploding product can be determined. The breakdown mode makes a transition from the internal mode, which involves breakdown inside the wire core, to the shunting mode, which involves breakdown in the compressed air, with decreasing charging voltage. The breakdown electrical field for a gaseous aluminum wire core of nearly solid density is estimated to be more than 20 kV/cm, while the value for gaseous aluminum of approximately 0.2% solid density decreases to 15-20 kV/cm. The breakdown field in shunting mode is less than 20 kV/cm and is strongly affected by the vaporized aluminum, the desorbed gas, and the electrons emitted from the wire core during the current pause. Ohmic heating during voltage collapses will induce further energy deposition in the current channel and thus will result in different expansion speeds for both the wire core and the shockwave front in the different modes.

  14. Electrical and thermal testing and modelling of breakdown in space solar cells and generators

    Microsoft Academic Search

    J. P. David; J. Duveau; J. Guerin; A. Michel

    1993-01-01

    The paper presents a summing up of experimental results relative to electrical and thermal testing of destroying breakdown apt to occur in a space solar array when a cell may be reverse biased due for instance to accidental shadowing. The results give time during which the cell can withstand the power corresponding to reverse biasing without destruction. Infrared observations of

  15. Study of oxide breakdown under very low electric field

    Microsoft Academic Search

    A. Teramoto; H. Umeda; K. Azamawari; K. Kobayashi; K. Shiga; J. Komori; Y. Ohno; H. Miyoshi

    1999-01-01

    We have performed TDDB measurements at temperatures lower than 125°C in an electric field (Eox) range of 7-13.5 MV\\/cm and have evaluated the intrinsic lifetime in a wide electric field range, using both area and temperature dependences of oxide lifetime. For positive gate bias, log(tBD) of 7.1 and 9.6 nm oxides is not proportional to the electric field but is

  16. Mass spectrometric studies of the electrical breakdown of thin polymer films

    NASA Technical Reports Server (NTRS)

    Kendall, B. R. F.; Rohrer, V. S.; Bojan, V. J.

    1986-01-01

    The composition of the neutral particles released during the electrical breakdown of 50-micron and 75-micron insulating films of the type used on spacecraft exteriors investigated experimentally using a time-of-flight mass spectrometer triggered by the breakdown event. The experimental apparatus is described in detail, and the results are presented in photographs. It is found that the particle flux from Teflon FEP and PFA films comprise mainly fluorocarbon fragments, some with mass 350 amu or greater, but the flux from Kapton oxygen-ion-beam treated Kapton, Tefzel, and Mylar comprises mainly molecules of mass 44 amu or less.

  17. 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)

    Seo, In-jin; Choi, Won; Seong, Jae-gyu; Lee, Bang-wook; Koo, Ja-yoon

    2014-08-01

    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.

  18. Model for the current-voltage characteristics of ultrathin gate oxides after soft breakdown

    Microsoft Academic Search

    M. Houssa; T. Nigam; P. W. Mertens; M. M. Heyns

    1998-01-01

    The current-voltage characteristics of metal-oxide-semiconductor capacitors with a 4.2 nm SiO2 gate oxide are investigated. After the occurrence of soft breakdown, which is observed during constant current stress of the devices, the gate current is shown to behave like a power law of the applied gate voltage. We propose that this power law behavior is due to the formation of

  19. Time-dependent dielectric breakdown of SiO2 films in a wide electric field range

    Microsoft Academic Search

    A. Teramoto; H. Umeda; K. Azamawari; K. Kobayashi; K. Shiga; J. Komori; Y. Ohno; A. Shigetomi

    2001-01-01

    We have performed time dependent dielectric breakdown measurement of SiO2 films in the electric field (EOX) range 7–13.5 MV\\/cm and evaluated the electric field dependence of intrinsic lifetime, using both area and temperature dependences of oxide lifetime. We have evaluated the electric field dependence of time to breakdown (tBD) below 125°C, because the activation energy of intrinsic lifetime changes at

  20. Mass analysis of neutral particles and ions released during electrical breakdowns on spacecraft surfaces

    NASA Technical Reports Server (NTRS)

    Kendall, B. R. F.

    1985-01-01

    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.

  1. Radiation polarization of silicon carbide p-n-structures, operating in electrical breakdown regime

    NASA Astrophysics Data System (ADS)

    Genkin, Aleksey M.; Genkina, Vera K.; Zubkova, Svetlana M.

    2015-05-01

    The spectral dependence of the linear polarization degree of the electroluminescence that accompanies the electrical breakdown of the alloyed p-n-structures prepared on the basis of 4H-, 6H-, 15R-, and 3C-SiC polytypes in the region of 1.4-3.8 eV has been obtained. The structures were located on the crystal faces parallel and perpendicular to the crystallographic C-axis. The radiation was extracted from a thin p-region at an acute angle and also perpendicular to a working face of a crystal. The radiation components which were linearly polarized in the planes parallel and perpendicular to the crystallographic C-axis (E?C, E?C) and parallel to the vector F of the electric field intensity (E?F) in a p-n-junction have been revealed. It turned out that the spectrum position and the intensity of the components associated with the C-axis direction differ essentially depending on the polytypes. It has been revealed that the presence of the radiation polarization with the degree of 0.3-0.4 in the plane E?C in the fundamental absorption region and in the adjacent region is common for all polytypes. Only in 6H- and 15R-SiC polytypes did the optical absorption data correspond to the radiation polarization characteristics. The polarization E?F achieved the degree of 0.5 and had a tendency to increase towards the higher photon energies.

  2. Electric arc radius and characteristics

    SciTech Connect

    Fang, T.M.

    1980-09-30

    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.

  3. Experimental and theoretical studies of the breakdown voltage characteristics at micrometre separations in air

    NASA Astrophysics Data System (ADS)

    Klas, M.; Matej?ík, Š.; Radjenovi?, B.; Radmilovi?-Radjenovi?, M.

    2011-08-01

    This paper presents experimental results and computer simulation for the direct current (DC) breakdown voltages in dry, synthetic and ambient air and discharge gaps ranging from 1 to 100 ?m. The measured breakdown voltage curves were systematically analyzed and the effective electron yields from cathode for dry and synthetic air as a function of the reduced electric field have been estimated. As complement to the experimental results, simulations have been performed using a kinetic particle-in-cell (PIC) code. For the electrode gaps less than 20 ?m, both experimental and simulation results revealed an interesting departures from the Paschen law on the left-hand side of the Paschen curve. The present results should be useful for the determination of minimum ignition voltages in microplasma sources as well as the maximum safe operating voltages and critical dimensions in other microdevices, high-power switches and circuit breakers.

  4. Effect of static magnetic fields on the base conductance and electric breakdown of bilayer lipid membranes

    SciTech Connect

    Simonov, A.N.; Kuznetsov, A.N.; Livshits, V.A.

    1986-07-01

    Static magnetic fields (MF) having inductions of 0.85 to 1.1 T were found to have an effect on the base conductance and electric breakdown of bilayer lipid membranes (BLM) formed from egg lecithin in decane. In membranes with a low specific resistance (R /SUB SP/ < 10/sup 7/ ..cap omega.. X cm/sup 2/ and membranes in a state of ''stress,'' MF parallel to the BLM plane will increase the conductance, current fluctuations, and probability of rupture. Magnetic fields perpendicular to the membranes have no effect on their conductance. In electric breakdown, MF parallel to the membranes prolong the stage of steady-state currents and shorten that of the prebreakdown fluctuations, while MF perpendicular to the membranes shorten the stage of steady-state currents and have no effect on that of the prebreakdown fluctuations. These effects appear to be due to the influence of MF on the formation probability and diameter of ''hydrophilic'' pores.

  5. Field Emission Current and Electrical Breakdown by a Pointed Cathode Coated with Carbon-Nano-Tube

    Microsoft Academic Search

    Yoshinori Hirata; Masayoshi Teramoto; Mizue Mizoshiri; Ukyo Ikeda; Takayoshi Ohji; Kimihiro Ozaki

    2007-01-01

    Feature of field emission current and electrical breakdown was experimentally investigated for very short gap in the range of 0.1mum to 3mum between a pointed cathode coated with Carbon-Nano-Tube (CNT) and a plane anode in vacuum environment. The experimental setup, which consists of the CNT coated cathode, the stainless steel anode and the precise positioning mechanisms actuated by piezoelectric devices,

  6. Effects of thermal and electrical stressing on the breakdown behavior of space wiring

    NASA Technical Reports Server (NTRS)

    Hammoud, Ahmad; Stavnes, Mark; Suthar, Jayant; Laghari, Javaid

    1995-01-01

    Several failures in the electrical wiring systems of many aircraft and space vehicles have been attributed to arc tracking and damaged insulation. In some instances, these failures proved to be very costly as they have led to the loss of many aircraft and imperilment of space missions. Efforts are currently underway to develop lightweight, reliable, and arc track resistant wiring for aerospace applications. In this work, six wiring constructions were evaluated in terms of their breakdown behavior as a function of temperature. These hybrid constructions employed insulation consisting of Kapton, Teflon, and cross-linked Tefzel. The properties investigated included the 400 Hz AC dielectric strength at ambient and 200 C, and the lifetime at high temperature with an applied bias of 40, 60, and 80% of breakdown voltage level. The results obtained are discussed, and conclusions are made concerning the suitability of the wiring constructions investigated for aerospace applications.

  7. Application of dynamic displacement current for diagnostics of subnanosecond breakdowns in an inhomogeneous electric field

    SciTech Connect

    Shao Tao; Zhang Cheng; Yan Ping [Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Key Laboratory of Power Electronics and Electric Drive, Chinese Academy of Sciences, Beijing 100190 (China); Tarasenko, Victor F.; Burachenko, Alexandr G.; Rybka, Dmitry V.; Kostyrya, Igor' D.; Lomaev, Mikhail I.; Baksht, Evgeni Kh. [Institute of High Current Electronics, Russian Academy of Sciences, Tomsk 634055 (Russian Federation)

    2013-05-15

    The breakdown of different air gaps at high overvoltages in an inhomogeneous electric field was investigated with a time resolution of up to 100 ps. Dynamic displacement current was used for diagnostics of ionization processes between the ionization wave front and a plane anode. It is demonstrated that during the generation of a supershort avalanche electron beam (SAEB) with amplitudes of {approx}10 A and more, conductivity in the air gaps at the breakdown stage is ensured by the ionization wave, whose front propagates from the electrode of small curvature radius, and by the dynamic displacement current between the ionization wave front and the plane electrode. The amplitude of the dynamic displacement current measured by a current shunt is 100 times greater than the SAEB. It is shown that with small gaps and with a large cathode diameter, the amplitude of the dynamic displacement current during a subnanosecond rise time of applied pulse voltage can be higher than 4 kA.

  8. Experimental study of electric breakdowns in liquid argon at centimeter scale

    NASA Astrophysics Data System (ADS)

    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.

    2014-04-01

    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).

  9. Protein Preconcentration Using Nanofractures Generated by Nanoparticle-Assisted Electric Breakdown at Junction Gaps

    PubMed Central

    Jen, Chun-Ping; Amstislavskaya, Tamara G.; Kuo, Chen-Chi; Chen, Yu-Hung

    2014-01-01

    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

  10. Breakdown, scaling and volt ampere characteristics of low current micro-discharges

    NASA Astrophysics Data System (ADS)

    Petrovi?, Z. Lj; Škoro, N.; Mari?, D.; Mahony, C. M. O.; Maguire, P. D.; Radmilovi?-Ra?enovi?, M.; Malovi?, G.

    2008-10-01

    We give preliminary results on the breakdown and low current limit of volt-ampere characteristics of simple parallel plate non-equilibrium dc discharges at standard (centimetre size) and micro-discharge conditions. Experiments with micro-discharges are reported attempting to establish the maintenance of E/N, pd and j/p2 scalings at small dimensions down to 20 µm. It was found that it may not be possible to obtain properly the left-hand side of the Paschen curve. The possible causes are numerous but we believe that it is possible that long path prevention techniques do not work at high pressures. Nevertheless, the standard scaling laws seem to be maintained down to these dimensions which are consistent with simulations that predict violation of scaling below 10 µm. Volt-ampere characteristics are also presented and compared with those of the standard size discharges.

  11. Dielectric breakdown via emergent nonequilibrium steady states of the electric-field-driven Mott insulator

    NASA Astrophysics Data System (ADS)

    Lee, Woo-Ram; Park, Kwon

    2014-05-01

    In this work, we explore the possibility of emergent nonequilibrium steady states arising from the electric-field-driven Mott insulator via the Keldysh-Floquet dynamical mean-field theory (DMFT), which can determine the fully interacting, nonequilibrium steady-state Green's functions with the noninteracting counterparts as an input to the DMFT self-consistency loop. Unlike the retarded component, obtaining the lesser Green's function for the noninteracting system presents an important obstacle since the thermalization of the noninteracting system still requires a precise understanding of the dissipation mechanism. A crucial breakthrough in this work is that the noninteracting lesser Green's function can be determined in terms of the Wannier-Stark ladder (WSL) eigenstates, which are thermalized via the standard canonical ensemble according to the Markovian quantum master equation. As a result, it is shown that the intricate interplay between strong correlation and large electric field can generate a sequence of two dielectric breakdowns with the first induced by a coherent reconstruction of the midgap state within the Mott gap and the second by an incoherent tunneling through the biased Hubbard bands. It is predicted that the reconstructed midgap state generates its own emergent WSL structure with a reduced effective electric field. The two dielectric breakdowns are mediated by a reentrant insulating phase, which is characterized by the population inversion, causing instability toward inhomogeneous current density states at weak electron-impurity scattering.

  12. Characterizing Electrical and Thermal Breakdown of Metamaterial Structures for HPM Applications

    NASA Astrophysics Data System (ADS)

    Wynkoop, T.; Gilmore, M.; Lynn, A. G.; Prasad, S.; Schamiloglu, E.

    2013-10-01

    The use of metamaterials (MTMs) has been proposed to increase the performance and efficiency of high power microwave (HPM) sources. However, by nature, MTMs are composed of subwavelength structures and are prone to electrical breakdown. In order to investigate the survivability of potential MTM structures in an HPM environment, two test stands are being constructed to characterize MTM electrical and thermal response. First, the SINUS-6 electron beam accelerator with maximum deliverable power of 4.2 GW(700 kV, 6 kA) , and pulse duration of 12 ns will be utilized. MTM's will be placed in close proximity to the beam, and breakdown will be characterized via fast imaging, and survey and high resolution spectroscopy. Secondly, a low current electron gun with Vbeam <= 50 kV, that can operate from ns pulsed to steady state, will investigate thermal loading and charging. Ultimately, results of this characterization will be used to develop robust MTM resonant/slow wave structures for HPM applications. The use of metamaterials (MTMs) has been proposed to increase the performance and efficiency of high power microwave (HPM) sources. However, by nature, MTMs are composed of subwavelength structures and are prone to electrical breakdown. In order to investigate the survivability of potential MTM structures in an HPM environment, two test stands are being constructed to characterize MTM electrical and thermal response. First, the SINUS-6 electron beam accelerator with maximum deliverable power of 4.2 GW(700 kV, 6 kA) , and pulse duration of 12 ns will be utilized. MTM's will be placed in close proximity to the beam, and breakdown will be characterized via fast imaging, and survey and high resolution spectroscopy. Secondly, a low current electron gun with Vbeam <= 50 kV, that can operate from ns pulsed to steady state, will investigate thermal loading and charging. Ultimately, results of this characterization will be used to develop robust MTM resonant/slow wave structures for HPM applications. Work supported by US AFOSR MURI Grant FA9550-12-1-0489.

  13. Electric breakdowns of the "plasma capacitors" occurs on insulation coating of the ISS surface

    NASA Astrophysics Data System (ADS)

    Homin, Taras; Korsun, Anatolii

    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).

  14. Effects of void size and gas content on electrical breakdown in lightweight, mechanically compliant, void-filled dielectrics

    Microsoft Academic Search

    R. A. Anderson; R. R. Lagasse; E. M. Russick; J. L. Schroeder

    2002-01-01

    Dielectric potting materials (encapsulants) are used to prevent air breakdown in high-voltage electrical devices. We report breakdown strengths in void-filled encapsulants, stressed with unipolar voltage pulses of the order of 10 mus duration. High strengths, on the order of 100 kV mm-1, are measured under these test conditions. The materials studied include low-density open celled gel-derived foams with cell sizes

  15. Effects of void size and gas content on electrical breakdown in lightweight, mechanically compliant, void-filled dielectrics

    Microsoft Academic Search

    R. A. Anderson; R. R. Lagasse; E. M. Russick; J. L. Schroeder

    2002-01-01

    Dielectric potting materials (encapsulants) are used to prevent air breakdown in high-voltage electrical devices. We report breakdown strengths in void-filled encapsulants, stressed with unipolar voltage pulses of the order of 10 ?s duration. High strengths, on the order of 100 kV mm?1, are measured under these test conditions. The materials studied include low-density open celled gel-derived foams with cell sizes

  16. Electric-induced oxide breakdown of a charge-coupled device under femtosecond laser irradiation.

    PubMed

    Gao, Liuzheng; Zhu, Zhiwu; Shao, Zhengzheng; Cheng, Xiang'ai; Chang, Shengli

    2013-11-01

    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

  17. Electrical measurements at the microscale: Air breakdown and silicon Coulomb blockade devices

    NASA Astrophysics Data System (ADS)

    Hourdakis, Emmanouel Spyros

    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.

  18. Estimating the energy of electric breakdown in air gap between electrolyte and metal electrode

    NASA Astrophysics Data System (ADS)

    Orlov, A. M.; Yavtushenko, I. O.; Churilov, M. V.

    2010-07-01

    The influence of induced electric charge (localized on the surface of a suspended copper rod) on the formation of a protrusion (Taylor cone) on the inducing liquid (aqueous solution) surface is considered. At an applied voltage of U ? 12 kV, the protrusion height in the interval of pre-breakdown voltages ( U < U P) is limited by the electric field strength. At U > U P, the growth of protrusion is terminated by an electric discharge, which drives the liquid to oscillate in a broad range of applied voltages U at almost constant multiple frequencies f = f 0 n, which are resonantly switched at certain fixed U values. By measuring the amount of evaporated liquid, the energy (27.8 × 10-3 J) and current (64.9 A) of single discharge were evaluated and the electric capacitance (7.6 × 10-10 F) of a system comprising the water surface and suspended copper electrode was estimated. Serial connection of an additional capacitor (100 ?F) to the copper electrode with induced electric charge leads to a threefold increase in these parameters.

  19. The influence of mechanical properties in the electrical breakdown in poly-styrene-ethylene-butadiene-styrene thermoplastic elastomer

    NASA Astrophysics Data System (ADS)

    Kollosche, Matthias; Melzer, Michael; Becker, Andre; Stoyanov, Hristian; McCarthy, Denis N.; Ragusch, Hülya; Kofod, Guggi

    2009-03-01

    Dielectric elastomer actuators (DEA) are a class of eletro-active polymers with promising properties for a number of applications, however, such actuators are prone to failure. One of the leading failure mechanisms is the electrical breakdown. It is already well-known that the electro-mechanical actuation properties of DEA are strongly influenced by the mechanical properties of the elastomer and compliant electrodes. It was recently suggested that also the electrical breakdown in such soft materials is influenced by the mechanical properties of the elastomer. Here, we present stress-strain measurements obtained on two tri-block thermoplastic elastomers (SEBS 500040 and SEBS 500120, poly-styrene-ethylene-butadiene-styrene), with resulting large differences in mechanical properties, and compare them to measurements on the commonly used VHB 4910. Materials were prepared by either direct heat-pressing of the raw material, or by dissolving in toluene, centrifuging and drop-casting. Experiments showed that materials prepared with identical processing steps showed a difference in stiffness of about 20%, where centrifuged and drop-casted films were seen to be softer than heat-pressed films. Electric breakdown measurements showed that for identically processed materials, the stiffness seemed to be a strong indicator of the electrical breakdown strength. It was therefore found that processing leads to differences in both stiffness and electrical breakdown strength. However, unexpectedly, the softer drop-cast films had a much higher breakdown strength than the heatpressed films. We attribute this effect to impurities still present in the heat-pressed films, since these were not purified by centrifuging.

  20. Generalized criterion for thermo-field emission driven electrical breakdown of gases

    NASA Astrophysics Data System (ADS)

    Venkattraman, Ayyaswamy

    2014-05-01

    Microdischarges operating in an ambient gas with both thermionic and field emission from the cathode are considered theoretically to predict pre-breakdown current density vs voltage as well as breakdown voltages. The integrals in the thermo-field current density expression lead to a breakdown criterion that does not have a simple closed-form and requires the use of optimization techniques to obtain the breakdown voltage. The breakdown voltage is shown to be a non-monotonic function of both cathode temperature and gap size. The proposed framework can be applied with no additional effort to gas breakdown driven by other cathode emission mechanisms.

  1. Investigations of the electrical breakdown properties of insulator materials used in high voltage vacuum diodes

    SciTech Connect

    Shurter, R.P.; Carlson, R.L.; Melton, J.G.

    1993-08-01

    The Injector for the proposed Dual-Axis Radiographic Hydrodynamic Testing (DARHT) Facility at Los Alamos utilizes a monolithic insulator deployed in a radial configuration. The 1.83-m-diam {times} 25.4-cm-thick insulator with embedded grading rings separates the output oil transmission line from the vacuum vessel that contains the re-entrant anode and cathode assemblies. Although much work has been done by the pulse power community in studying surface flash-over of insulating materials used in both axial and radial configurations, dendrite growth at the roots of grading rings embedded in materials suitable for very large insulators is less well characterized. Degradation of several acrylic insulators has been observed in the form of dendrites growing at the roots of the grading rings for large numbers (100`s) of pulses on the prototype DARHT Injector and other machines using similar radial geometries. In a few cases, these dendrites have led to catastrophic bulk breakdown of the acrylic between two grading rings making the insulator a costly loss. Insulating materials under investigation are acrylic (Lucite), epoxy (Furane), and cross-linked polystyrene (Rexolite); each of these materials has its own particular mechanical and electrical merits. All of these materials have been cast and machined into the required large size for the Injector. Test methods and the results of investigations into the breakdown strength of various interface geometries and the susceptibility of these materials to dendrite growth are reported.

  2. Electrical characteristics of simulated tornadoes

    NASA Astrophysics Data System (ADS)

    Zimmerman, M. I.; Farrell, W. M.; Barth, E. L.; Lewellen, D. C.; Lewellen, W. S.; Perlongo, N. J.; Jackson, T.

    2012-12-01

    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.

  3. Ignition characteristics of methane/air premixed mixture by microwave-enhanced laser-induced breakdown plasma.

    PubMed

    Nishiyama, Atsushi; Moon, Ahsa; Ikeda, Yuji; Hayashi, Jun; Akamatsu, Fumiteru

    2013-11-01

    A microwave-enhanced plasma generation technique was combined with laser-induced ignition to improve ignition characteristics. A locally intensified microwave field was formed near the laser-induced breakdown plasma. As the plasma absorbed the microwaves, the plasma emission intensity increased. The plasma lifetime could be controlled by changing the microwave oscillation duration. Furthermore, the microwave-enhanced laser-induced breakdown plasma improved the minimum ignition energy of the methane/air pre-mixture with just a small amount of absorbed microwave energy. PMID:24514928

  4. Investigation of vibration characteristics of electric motors

    NASA Technical Reports Server (NTRS)

    Bakshis, A. K.; Tamoshyunas, Y. K.

    1973-01-01

    The vibration characteristics of electric motors were analyzed using mathematical statistics methods. The equipment used and the method of conducting the test are described. Curves are developed to show the visualization of the electric motor vibrations in the vertical direction. Additional curves are included to show the amplitude-phase frequency characteristic of dynamic rotor-housing vibrations at the first lug and the same data for the second lug of the electric motor. Mathematical models were created to show the transmission function of the dynamic rotor housing system.

  5. Characteristics of primary electric propulsion systems. [conferences

    NASA Technical Reports Server (NTRS)

    Byers, D. C.

    1979-01-01

    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.

  6. Dielectric breakdown of MXB-71 phenolic and Sylgard 184/GMB silicone at high temperature

    SciTech Connect

    Johnson, R.T. Jr.; Beeson, P.M.

    1983-07-01

    High temperature electrical breakdown characteristics have been determined for MXB-71 phenolic and Sylgard 184/GMB silicone in air and nitrogen environments. The phenolic material is used for electronic case housings whereas the silicone is an encapsulant. The experiments were performed with constant electric fields (values ranging from 3 x 10/sup 3/ to 2.5 x 10/sup 4/ V/cm) applied to the samples while the temperature was increased at a rate of 10/sup 0/C/minute. The sample current until breakdown was determined. Results showed that breakdown occurred between 470 to 725/sup 0/C, and was principally dependent upon the material conductivity at time breakdown and the electric field. The breakdown temperature decreased with increasing electric field and decreased in an oxygen-containing environment. Materials postcured at 580 to 600/sup 0/C prior to electrical testing exhibited considerably lower breakdown temperatures at higher electric fields. Results suggest that breakdown occurred via thermal runaway.

  7. Effects of void size and gas content on electrical breakdown in lightweight, mechanically compliant, void-filled dielectrics

    NASA Astrophysics Data System (ADS)

    Anderson, R. A.; Lagasse, R. R.; Russick, E. M.; Schroeder, J. L.

    2002-03-01

    Dielectric potting materials (encapsulants) are used to prevent air breakdown in high-voltage electrical devices. We report breakdown strengths in void-filled encapsulants, stressed with unipolar voltage pulses of the order of 10 ?s duration. High strengths, on the order of 100 kV mm-1, are measured under these test conditions. The materials studied include low-density open celled gel-derived foams with cell sizes of 4 ?m or less, closed celled CO2-blown polystyrene and urethane foams, and epoxies containing 48 vol % of hollow glass microballoon (GMB) fillers. These last specimens varied the void gas (N2 or SO2) and also the void diameters (tens to hundreds of ?m). Our measurements are thought to be directly sensitive to the rate of field-induced ionization events in the void gas; however, the breakdown strengths of the materials tested appeared to vary in direct proportion with the conventional Paschen-law gas-discharge inception threshold, the electric stress at which gas-ionization avalanches become possible. The GMB-epoxy specimens displayed this type of dependence of breakdown strength on the void-gas density and void size, but the measurements were an order of magnitude above the conventional predictions. Small-celled foams also showed increased breakdown strengths with decreased cell size, although their irregular void geometry prevented a direct comparison with the more uniformly structured microballoon-filled encapsulants. The experimental observations are consistent with a breakdown mechanism in which the discharge of a few voids can launch a full breakdown in the composite material.

  8. Electrical Breakdown of Aliphatic and Aromatic Self-Assembled Monolayers Used as Nanometer-Thick Organic Dielectrics

    E-print Network

    Prentiss, Mara

    Electrical Breakdown of Aliphatic and Aromatic Self-Assembled Monolayers Used as Nanometer by a nanometer-thick dielectric.1 The procedure used in the preparation and characterization of this system recently, silver, copper, and mercury have received focused attention as the supporting metal.6

  9. Transport parameters and breakdown voltage characteristics of the dry air and its constituents

    Microsoft Academic Search

    M. Klas; M. Radmilovi?-Radjenovi?; B. Radjenovi?; M. Stano; Š. Matej?ik

    2012-01-01

    This paper contains measured breakdown voltage curves and calculated transport parameters for the dry air and gases included in the air composition. The breakdown voltage curves exhibit U-shaped form for the interelectrode separation of 100 ?m and departure from the standard Paschen law for a few micrometers gap sizes. The results of calculations provide an insight into similarities and differences

  10. The influence of HBr additives on breakdown characteristics of Ne-H2-Cu laser mixture

    NASA Astrophysics Data System (ADS)

    Petrash, Gueorgii G.; Rybkin, Vladimir V.

    2004-05-01

    Stationary criterion of the Ne-H2-Cu-HBr laser mixture breakdown has been calculated using solutions of Boltzmann kinetic equation for electron energy distribution function (EEDF). It was found that increase of HBr molar fraction in the mixture leads to increase of breakdown voltage and, as a consequence, to more favorable ratio of rate constants of electron excitation of 2P (upper laser) and 2D (lower laser) atomic copper levels. Increase of Cu molar fraction in the mixture also can lead to increase of breakdown voltage due to an influence of electron collisions with copper atoms on the process of EEDF formation.

  11. Effect of silane coupling agent chemistry on electrical breakdown across hybrid organic-inorganic insulating films.

    PubMed

    Diebold, Roger M; Gordon, Michael J; Clarke, David R

    2014-08-13

    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

  12. Electrical Characteristics of an Alternating Current Plasma Igniter in Airflow

    NASA Astrophysics Data System (ADS)

    Zhao, Bingbing; He, Liming; Du, Hongliang; Zhang, Hualei

    2014-04-01

    The electrical characteristics of an alternating current (AC) plasma igniter were investigated for a working gas of air at atmospheric pressure. The discharge voltage and current were measured in air in both breakdown and stable combustion processes, respectively, and the current-zero phenomena, voltage-current (V-I) characteristics were studied for different working gas flow rates. The results indicated that the working gas between anode and cathode could be ionized to generate gas discharge when the voltage reached 8 kV, and the maximum current was 33.36 A. When the current came to zero, current-zero phenomena appeared with duration of 2 ?s. At the current-zero moment, dynamic resistance between electrodes became extremely high, and the maximum value could reach 445 k?, which was the main factor to restrain the current. With increasing working gas flow rates, the gradient of V-I characteristic curves was increased, as was the dynamic resistance. At a constant driven power, the discharge voltage increased.

  13. Transport parameters and breakdown voltage characteristics of the dry air and its constituents

    NASA Astrophysics Data System (ADS)

    Klas, M.; Radmilovi?-Radjenovi?, M.; Radjenovi?, B.; Stano, M.; Matej?ik, Š.

    2012-05-01

    This paper contains measured breakdown voltage curves and calculated transport parameters for the dry air and gases included in the air composition. The breakdown voltage curves exhibit U-shaped form for the interelectrode separation of 100 ?m and departure from the standard Paschen law for a few micrometers gap sizes. The results of calculations provide an insight into similarities and differences between the transport parameters for individual gases and the gas mixture.

  14. Wind tunnel investigation of the interaction and breakdown characteristics of slender wing vortices at subsonic, transonic, and supersonic speeds

    NASA Technical Reports Server (NTRS)

    Erickson, Gary E.

    1991-01-01

    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.

  15. Operational characteristics of microfabricated electric motors

    Microsoft Academic Search

    Lee S. Tavrow; Stephen F. Bart; Jeffrey H. Lang

    1991-01-01

    The authors report on the operational characteristics of LOGOS-based microfabricated radial-gap electric motors through lifetime tests, transient measurements, modeling, and parameter extraction. It is found that the reduction of static friction (stiction) in the bearings by the incorporation of a silicon nitride film permits these micromotors to spin in normal air ambients. Frictional drag from the bearing, which results from

  16. The validity of the one-dimensional fluid model of electrical breakdown in synthetic air at low pressure

    NASA Astrophysics Data System (ADS)

    Jovanovi?, A. P.; Stankov, M. N.; Markovi?, V. Lj.; Stamenkovi?, S. N.

    2013-12-01

    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.

  17. Electrical characteristics of a dc superconducting cable

    NASA Astrophysics Data System (ADS)

    Chowdhuri, P.

    A dc superconducting cable is ideal for transmitting large blocks of electrical power over a long distance. However, it must be designed to operate reliably within the constraints of the electrical system. Therefore, system analysis must be performed for each application. The conductor losses caused by the harmonics on the dc must be within the design goals; a system fault should not drive the cable normal with eventual damage to the cable and interruption of power flow; and, the dielectric system of the cable must be designed to be compatible with the expected transient voltages by proper insulation coordination. Transient overvoltages are of concern to electrical power systems; these are especially critical to cryogenic cables because of the susceptibility of the cryogenic enclosures to these transients. This paper discusses the electrical system constraints which are particularly applicable to a dc superconducting cable and shows how such a cable can be designed to be compatible with the electrical system. This paper also summarizes the work on low temperature dielectrics performed at Los Alamos. It shows the variation of break down voltage of dielectric materials, in sheet form and cable configuration, with temperature and pressure under dc and impulse voltage. The surface flashover characteristics with large creepage distance as well as electrical conductivity of dielectric materials at cryogenic temperatures are discussed. These studies are essential for the design of high voltage apparatus operating in cryogenic environments.

  18. Simulating fuse electrical characteristics during faults

    NASA Astrophysics Data System (ADS)

    Liffring, Mark E.

    Various types of SPICE (Simulation Program with Integrated Circuits Emphasis) fuse models for predicting the characteristics of faulted fuses are presented and compared. The SPICE computer program is used to simulate electrical circuits containing both linear and nonlinear elements. The need for an improved fuse model in which resistance is controlled is discussed. A new fuse model that accurately predicts fuse resistance is described, and a diagram of the model is provided.

  19. Electric field enhancement due to a saw-tooth asperity in a channel and implications on microscale gas breakdown

    NASA Astrophysics Data System (ADS)

    Venkattraman, Ayyaswamy

    2014-10-01

    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.

  20. Micrometer-scale electrical breakdown in high-density fluids with large density fluctuations: Numerical model and experimental assessment

    NASA Astrophysics Data System (ADS)

    Muneoka, Hitoshi; Urabe, Keiichiro; Stauss, Sven; Terashima, Kazuo

    2015-04-01

    Experimentally observed electrical breakdown voltages (UB) in high-pressure gases and supercritical fluids deviate from classical theories for low-pressure gas discharges, and the underlying breakdown mechanisms for the high-density fluids making the UB differ from those in the classical discharges are not yet well understood. In this study, we developed an electrical breakdown model for the high-density fluids taking into account the effects of density fluctuations and ion-enhanced field emission (IEFE). The model is based on the concept that a critical anomaly of the UB (local minimum near the critical point) is caused by long mean free electron path leading to a large first Townsend coefficient in locally low-density spatial domains generated by the density fluctuations. Also, a modified Paschen's curve considering the effect of the IEFE on the second Townsend coefficient was used to reproduce the UB curve in the high-density fluids. Calculations based on the novel model showed good agreements with the experimentally measured UB even near the critical point and it also suggested that the critical anomaly of the UB depends on the gap distance. These results indicate that both the density fluctuations and the IEFE have to be considered to comprehend the plasmas in high-density and density-fluctuating fluids.

  1. Enhanced electric breakdown field of CaCu3Ti4O12 ceramics: tuning of grain boundary by a secondary phase

    NASA Astrophysics Data System (ADS)

    Li, Jianying; Jia, Ran; Tang, Xian; Zhao, Xuetong; Li, Shengtao

    2013-08-01

    The electric breakdown field of CaCu3Ti4O12 ceramics has been enhanced by one order, i.e. from the conventional 1.0-2.0 kV cm-1 to 21 kV cm-1. Such great enhancement, associated with lower and relatively flat dielectric loss at low frequency, has arisen from optimum Al2O3 addition and sintering process. It is indicated that the addition of Al2O3 can affect the grain growth and the grain boundary characteristics via the distribution of a secondary phase of CuAl2O4, which is confirmed by x-ray diffraction and electron dispersive spectroscopy. The performance of grain boundary can be described well by the Schottky barrier model. It is found that the activation energy of hopping conduction at grain boundary is increased from 0.60 to 0.81 eV due to the secondary phase, which consequently leads to enhanced breakdown field.

  2. Electric breakdown in ultrathin MgO tunnel barrier junctions for spin-transfer torque switching

    SciTech Connect

    Schaefers, M.; Drewello, V.; Reiss, G.; Thomas, A. [Department of Physics, Thin Films and Physics of Nanostructures, Bielefeld University, 33501 Bielefeld (Germany); Thiel, K. [Fraunhofer Institut fuer Fertigungstechnik und Angewandte Materialforschung, Wiener Str. 12, 28359 Bremen (Germany); Eilers, G.; Muenzenberg, M.; Schuhmann, H.; Seibt, M. [I. and IV. Physikalisches Institut and Sonderforschungsbereich 602, Friedrich-Hund-Platz 1, Georg-August-Universitaet Goettingen, 37077 Goettingen (Germany)

    2009-12-07

    Magnetic tunnel junctions for spin-transfer torque (STT) switching are prepared to investigate the dielectric breakdown. Intact and broken tunnel junctions are characterized by transport measurements prior to transmission electron microscopy analysis. The comparison to our previous model for thicker MgO tunnel barriers reveals a different breakdown mechanism arising from the high current densities in a STT device: instead of local pinhole formation at a constant rate, massive electromigration and heating leads to displacement of the junction material and voids are appearing. This is determined by element resolved energy dispersive x-ray spectroscopy and three dimensional tomographic reconstruction.

  3. The correlation between electric field emission phenomenon and Schottky contact reverse bias characteristics in nanostructured systems

    NASA Astrophysics Data System (ADS)

    Yu, J.; Liu, J.; Breedon, M.; Shafiei, M.; Wen, H.; Li, Y. X.; Wlodarski, W.; Zhang, G.; Kalantar-zadeh, K.

    2011-06-01

    Two different morphologies of nanotextured molybdenum oxide were deposited by thermal evaporation. By measuring their field emission (FE) properties, an enhancement factor was extracted. Subsequently, these films were coated with a thin layer of Pt to form Schottky contacts. The current-voltage (I-V) characteristics showed low magnitude reverse breakdown voltages, which we attributed to the localized electric field enhancement. An enhancement factor was obtained from the I-V curves. We will show that the enhancement factor extracted from the I-V curves is in good agreement with the enhancement factor extracted from the FE measurements.

  4. Chemical Implications due to the low Electrical Breakdown in the Martian Atmosphere

    Microsoft Academic Search

    Charles R. Buhler; Carlos I. Calle

    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

  5. Progress on Tests of Electric Breakdown of Superfluid Liquid Helium-4 in High Electric Field for the SNS nEDM Experiment

    NASA Astrophysics Data System (ADS)

    Wei, Wanchun; Beck, Douglas; Cianciolo, Vince; Clayton, Steven; Crawford, Christopher; Currie, Scott; Griffith, William; Ito, Takeyasu; Ramsey, John; Roberts, Amy; Schmid, Richardo; Seidel, George; Wagner, Daniel; Williamson, Steven; Yao, Weijun; SNS nEDM Collaboration

    2015-04-01

    The SNS nEDM experiment is a collaborative project under development, which aims to search for the neutron electric dipole moment (EDM) with ultracold neutrons (UCNs) stored in superfluid liquid helium-4 at the Spallation Neutron Source (SNS) in Oak Ridge National Laboratory. In general, the ultimate sensitivity of the EDM searches linearly depends on the strength of the applied electric field across the volume of superfluid liquid helium-4 in the UCN storage space. Our goal is to achieve an electric field with strength of 75 kV/cm. However, the phenomenon of electric breakdown in liquid helium-4 is poorly understood in the available literatures. We, therefore, have developed an apparatus to study it at temperatures as low as 0.4 K and pressures between saturated vapor pressure (SVP) of liquid helium and 1 atm. In this talk, we will present the latest progress on the tests of the electric breakdown of superfluid liquid helium-4 and its implications of findings that affect the design of the SNS nEDM experiment.

  6. Measurements of the volt-ampere characteristics and the breakdown voltages of direct-current helium and hydrogen discharges in microgaps

    NASA Astrophysics Data System (ADS)

    Klas, M.; Matej?ik, Š.; Radjenovi?, B.; Radmilovi?-Radjenovi?, M.

    2014-10-01

    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.

  7. Measurements of the volt-ampere characteristics and the breakdown voltages of direct-current helium and hydrogen discharges in microgaps

    SciTech Connect

    Klas, M.; Matej?ik, Š. [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)

    2014-10-15

    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.

  8. On the calculation of breakdown voltages for uniform electric fields in compressed air and SF6

    Microsoft Academic Search

    MAZEN ABDEL-SALAM; E. KEITH STANEK

    1988-01-01

    A novel method is described for calculating the breakdown voltage of uniform field gaps in compressed air and SF6 without the need for experiments. This method is based on the criterion of self-recurring single-electron avalanches developed in the gap. It is shown that the results computed by this method for pd values to the right of Paschen's minimum (up to

  9. Non-Gated Laser Induced Breakdown Spectroscopy Provides a Powerful Segmentation Tool on Concomitant Treatment of Characteristic and Continuum Emission

    PubMed Central

    Dasari, Ramachandra Rao; Barman, Ishan; Gundawar, Manoj Kumar

    2014-01-01

    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

  10. Weibull Statistical Analysis of Pulsed Breakdown Voltages in High-Pressure Carbon Dioxide Including Supercritical Phase

    Microsoft Academic Search

    Tsuyoshi Kiyan; Takeshi Ihara; Suguru Kameda; Tomohiro Furusato; Masanori Hara; Hidenori Akiyama

    2011-01-01

    Pulsed discharge plasma in supercritical fluids (SCFs) has attracted a great deal of attention in the field of plasma application for chemical processing. Characteristics of electrical breakdown are one of the important concerns for dielectric reli- ability of a plasma reactor with SCFs. In this paper, the pulsed breakdown voltages of quasi-uniform gaps were measured by changing the CO2 medium

  11. Characteristics of ac capillary discharge produced in electrically conductive water solution

    NASA Astrophysics Data System (ADS)

    DeBaerdemaeker, F.; Simek, M.; Schmidt, J.; Leys, C.

    2007-05-01

    Basic electrical, optical and calorimetric characteristics of an ac (50 Hz) driven capillary discharge produced in a water solution were studied for initial water solution conductivity in the range 50-1000 µS cm-1. Typical current and voltage waveforms and emission intensities produced by several electronically excited species were recorded with high time resolution. The evolution of the electrical current, power and capillary resistance was inspected during positive ac half-cycle for various operational regimes. A fast relaxation of the discharge following a breakdown event was observed. Optical measurements indicate that radiative species are mostly generated during the first few hundreds of nanoseconds of plasma generation and that the average duration of plasma emission induced by a discharge pulse is of the order of a few microseconds. Results of calorimetric measurements are in good agreement with average electrical measurements and support the assumption that the discharge is a constant source of heat delivered to the liquid. Assuming that only a fraction of the heat released inside the capillary can be transported by conduction through the capillary wall and via its orifices, the processes of bubble formation, expulsion and re-filling the capillary with 'fresh' water must play a key role in maintaining a thermal balance during long-time steady-state operation of the device. Furthermore, a simplified numerical model and a first order energy deposition calculation prove the plausibility of the bubble breakdown mechanism.

  12. Electric current characteristic of anodic bonding

    NASA Astrophysics Data System (ADS)

    He, Jun; Yang, Fang; Wang, Wei; Zhang, Li; Huang, Xian; Zhang, Dacheng

    2015-06-01

    In this paper, a novel current–time model of anodic bonding is proposed and verified experimentally in order to investigate underlying mechanisms of anodic bonding and to achieve real-time monitoring of bonding procedure. The proposed model provides a thorough explanation for the electric current characteristic of anodic bonding. More significantly, it explains two issues which other models cannot explain. One is the sharp rise in current when a voltage is initially applied during anodic bonding. The other is the unexpected large width of depletion layers. In addition, enlargement of the intimately contacted area during anodic bonding can be obtained from the proposed model, which can be utilized to monitor the bonding process. To verify the proposed model, Borofloat33 glass and silicon wafers were adopted in bonding experiments in SUSS SB6 with five different bonding conditions (350?°C 1200?V 370?°C 1200?V 380?°C 1200?V 380?°C 1000?V and 380?°C 1400?V). The results indicate that the observed current data highly coincide with the proposed current-time model. For widths of depletion layers, depth profiling using secondary ion mass spectrometry demonstrates that the calculated values by the model are basically consistent with the experimental values as well.

  13. Polarization of the terahertz radiation of uniaxially compressed p germanium at the electrical breakdown of a shallow acceptor impurity

    SciTech Connect

    Andrianov, A. V., E-mail: alex.andrianov@mail.ioffe.ru; Zakhar'in, A. O.; Alekseev, P. S., E-mail: pavel.alekseev@mail.ioffe.ru [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)

    2012-12-15

    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.

  14. Relationship between the structure and electrical characteristics of diamond-like carbon films

    SciTech Connect

    Takabayashi, Susumu, E-mail: stak@riec.tohoku.ac.jp; 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; Ješko, Radek; Takakuwa, Yuji [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2014-09-07

    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.

  15. Mechanical and Electrical Characteristics of Poly-Lactic Acid which Added Plasticizer

    NASA Astrophysics Data System (ADS)

    Shinyama, Katsuyoshi; Fujita, Shigetaka

    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.

  16. Mass analysis of neutral particles and ions released during electrical breakdowns on spacecraft surfaces

    NASA Technical Reports Server (NTRS)

    Kendall, B. R. F.

    1983-01-01

    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.

  17. Partial discharge and breakdown characteristics on needle\\/dielectrics composite electrode systems under pulse voltage

    Microsoft Academic Search

    N. Sakamoto; Y. Kuninaka; H. Ueno; H. Nakayama

    2001-01-01

    Studied the discharge characteristics on the composite electrode under a pulse voltage in N2. The configuration is a needle-plane one, in which the needle is in contact with solid dielectrics, with a narrow gap. The configuration has a plurality of places of the local high field, namely a needle tip and another a triple junction. To examine a local corona

  18. Comparison of the Detection Characteristics of Trace Species Using Laser-Induced Breakdown Spectroscopy and Laser Breakdown Time-of-Flight Mass Spectrometry

    PubMed Central

    Wang, Zhenzhen; Deguchi, Yoshihiro; Yan, Junjie; Liu, Jiping

    2015-01-01

    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

  19. Simple models for electric gun operating characteristics

    Microsoft Academic Search

    1988-01-01

    The electric gun, sometimes called a foil gun, uses the energy initially stored in a capacitor to electrically heat a thin conducting bridge in a transmission line connected to the capacitor. The deposited energy, typically several times the cohesive energy of the bridge material, is deposited in a time much less than the thermal time constant of the bridge, causing

  20. Power system characteristics for more electric aircraft

    NASA Technical Reports Server (NTRS)

    Hansen, Irving G.

    1993-01-01

    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.

  1. VERY LOW FREQUENCY BREAKDOWN PROPERTIES OF ELECTRICAL INSULATION MATERIALS AT CRYOGENIC TEMPERATURES

    SciTech Connect

    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)

    2010-04-08

    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.

  2. Effect of tree channel conductivity on electrical tree shape and breakdown in XLPE cable insulation samples

    Microsoft Academic Search

    Xiangrong Chen; Yang Xu; Xiaolong Cao; S. J. Dodd; L. A. Dissado

    2011-01-01

    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

  3. Layer-by-layer dielectric breakdown of hexagonal boron nitride.

    PubMed

    Hattori, Yoshiaki; Taniguchi, Takashi; Watanabe, Kenji; Nagashio, Kosuke

    2015-01-27

    Hexagonal boron nitride (BN) is widely used as a substrate and gate insulator for two-dimensional (2D) electronic devices. The studies on insulating properties and electrical reliability of BN itself, however, are quite limited. Here, we report a systematic investigation of the dielectric breakdown characteristics of BN using conductive atomic force microscopy. The electric field strength was found to be ? 12 MV/cm, which is comparable to that of conventional SiO2 oxides because of the covalent bonding nature of BN. After the hard dielectric breakdown, the BN fractured like a flower into equilateral triangle fragments. However, when the applied voltage was terminated precisely in the middle of the dielectric breakdown, the formation of a hole that did not penetrate to the bottom metal electrode was clearly observed. Subsequent I-V measurements of the hole indicated that the BN layer remaining in the hole was still electrically inactive. On the basis of these observations, layer-by-layer breakdown was confirmed for BN with regard to both physical fracture and electrical breakdown. Moreover, statistical analysis of the breakdown voltages using a Weibull plot suggested the anisotropic formation of defects. These results are unique to layered materials and unlike the behavior observed for conventional 3D amorphous oxides. PMID:25549251

  4. Non-Gated Laser Induced Breakdown Spectroscopy Provides a Powerful Segmentation Tool on Concomitant Treatment of Characteristic and Continuum Emission

    E-print Network

    Myakalwar, Ashwin Kumar

    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 ...

  5. Confusion and its dynamics during device comprehension with breakdown scenarios.

    PubMed

    D'Mello, Sidney; Graesser, Art

    2014-09-01

    The incidence and dynamics of confusion during complex learning and problem solving were investigated in an experiment where participants first read illustrated texts on everyday devices (e.g., an electric bell) followed by breakdown scenarios reflecting device malfunctions (e.g., "When a person rang the bell there was a short ding and then no sound was heard"). The breakdown scenarios were expected to trigger impasses and put participants in a state of cognitive disequilibrium where they would experience confusion and engage in effortful confusion resolution activities in order to restore equilibrium. The results confirmed that participants reported more confusion when presented with the breakdown scenarios compared to control scenarios that involved focusing on important device components in the absence of malfunctions. A second-by-second analysis of the dynamics of confusion yielded two characteristic trajectories that distinguished participants who partially resolved their confusion from those who remained confused. Participants who were successful in partial confusion resolution while processing the breakdowns outperformed their counterparts on knowledge assessments after controlling for scholastic aptitude, engagement, and frustration. This effect was amplified for those who were highly confused by the breakdowns. There was no direct breakdown vs. control effect on learning, but being actively engaged and partially resolving confusion during breakdown processing were positive predictors of increased learning with the breakdown compared to control scenarios. Implications of our findings for theories that highlight the role of impasses, cognitive disequilibrium, and confusion to learning are discussed. PMID:24973629

  6. Opposite carrier dynamics and optical absorption characteristics under external electric

    E-print Network

    Demir, Hilmi Volkan

    external electric field in nonpolar InGaN/GaN heterostructure epitaxy, whereas exactly the opposite occurs field as a result of reversed quantum confined Stark effect in these polar structures, while we observeOpposite carrier dynamics and optical absorption characteristics under external electric field

  7. Electric propulsion - characteristics, applications, and status

    NASA Technical Reports Server (NTRS)

    Maloy, J. E.; Dulgeroff, C. R.; Poeschel, R. L.

    1981-01-01

    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.

  8. Electrical Discharge Machining (EDM) Characteristics Associated with Electrical Discharge Energy on Machining of Cemented Tungsten Carbide

    Microsoft Academic Search

    Yan-Cherng Lin; Yuan-Feng Chen; Ching-Tien Lin; Hsinn-Jyh Tzeng

    2008-01-01

    In this investigation, cemented tungsten carbides graded K10 and P10 were machined by electrical discharge machining (EDM) using an electrolytic copper electrode. The machining parameters of EDM were varied to explore the effects of electrical discharge energy on the machining characteristics, such as material removal rate (MRR), electrode wear rate (EWR), and surface roughness. Moreover, the effects of the electrical

  9. Electrical Characteristic Study of a Hybrid PEMFC and Ultracapacitor System

    Microsoft Academic Search

    Junbo Jia; Gucheng Wang; Yew Thean Cham; Youyi Wang; Ming Han

    2010-01-01

    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

  10. Temperature and Gas-Environment Dependent Electron and Phonon Transport in Suspended Carbon Nanotubes Up to Electrical Breakdown

    Microsoft Academic Search

    David Mann; Eric Pop; Jien Cao; Qian Wang; Kenneth Goodson; Hongjie Dai

    2005-01-01

    High bias electrical transport characteristics of freely suspended metallic single-walled carbon nanotubes (SWNTs) are investigated at 250-400K in vacuum and various gases. Self-heating is exploited to examine the temperature dependence of phonon transport and optical phonon decay in SWNTs. The acoustic phonon thermal conductivity of a SWNT follows ~1\\/T at high temperatures. Non-equilibrium optical phonon effects in suspended nanotubes decrease

  11. Drying Characteristics of Pulsed Electric Field-Treated Carrot

    Microsoft Academic Search

    T. K. Gachovska; A. A. Adedeji; M. Ngadi; G. V. S. Raghavan

    2008-01-01

    This study was designed to establish the interaction effect of various components of pulsed electric field (PEF) system on drying characteristics of carrot, a vegetable rich in carotenoid. Carrots were treated in PEF system of 0.5, 1, and 1.5 kV\\/cm electric field strength, 0.5 and 1 ?F capacitance, and pulse numbers of 10, 30, and 50. The samples were subsequently dried at

  12. A relationship between statistical time to breakdown distributions and pre-breakdown negative differential resistance at nanometric scale

    SciTech Connect

    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)

    2014-07-14

    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.

  13. High field breakdown of narrow quasi uniform field gaps in vacuum

    NASA Astrophysics Data System (ADS)

    Muzykov, P. G.; Ma, Xianyun; Cherednichenko, D. I.; Sudarshan, T. S.

    1999-06-01

    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.

  14. Characterization of the dielectric breakdown field strength of PDMS thin films: thickness dependence and electrode shape

    NASA Astrophysics Data System (ADS)

    Förster-Zügel, Florentine; Grotepaß, Tanja; Schlaak, Helmut F.

    2015-04-01

    During the operation of a dielectric elastomer generator (DEG) the energy harvested should be maximized. A higher electrical field strength in the DEG leads to a higher energy gain. However, the applied electrical field strength is restricted due to the dielectric breakdown field strength of the dielectric elastomer in the generator. For appropriate operation of the generator the dielectric breakdown field strength of the elastomer has to be known. From literature it is known that the breakdown strength of polymers depends on several parameters like the thickness of the material and the electrode shape. In this work, the dielectric breakdown strength of a novel PDMS thin film material for the fabrication of dielectric elastomer transducers developed by Wacker Chemie AG is investigated. Several PDMS film thicknesses are compared to determine the influence of the film thickness on the breakdown strength. The results show that the expected inverse thickness dependence of the breakdown strength is not valid for the new film material. In fact, no significant thickness dependence of the dielectric breakdown field strength is existent. The electrical characteristics of the measurement setup used for characterization of the dielectric breakdown field strength of the PDMS thin films are investigated using numerical simulations to determine the influence of the electrode shape.

  15. On the electrical characteristics of complementary metamaterial resonators

    Microsoft Academic Search

    Jordi Bonache; Marta Gil; Ignacio Gil; Joan García-García; Ferran Martín

    2006-01-01

    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.

  16. Probabilistic description of traffic breakdowns

    Microsoft Academic Search

    Reinhart Kühne; Reinhard Mahnke; Ihor Lubashevsky; Jevgenijs Kaupuzs

    2002-01-01

    We analyze the characteristic features of traffic breakdown. To describe this phenomenon we apply the probabilistic model regarding the jam emergence as the formation of a large car cluster on a highway. In these terms, the breakdown occurs through the formation of a certain critical nucleus in the metastable vehicle flow, which enables us to confine ourselves to one cluster

  17. Electrical reliability of tunneling magnetoresistive read heads

    NASA Astrophysics Data System (ADS)

    Bae, Seongtae; Judy, Jack H.; Tsu, I.-Fei; Davis, Marshall

    2003-12-01

    The electrical reliability of tunneling magnetoresistive (TMR) read heads has been studied in terms of dielectric breakdown characteristics of tunnel barrier and electrical failures under constant biasing current. The TMR read heads showed both "intrinsic breakdown" characteristics, which is caused by the high electric field, and "extrinsic breakdown" characteristics, which is caused by defects or pinhole-induced breakdown especially in a very thin dielectric layer. The dielectric breakdown voltage (Vbd) of real TMR read head is revealed to be strongly dependent on the duration of the applied voltage step (or applied voltage ramping speed), the initial junction resistance (R×A, A: Junction area) related to pinholes in a dielectric tunnel barrier, the tunnel barrier thickness, the ambient substrate temperature during breakdown test, and the applied voltage polarities. Different from typical metallic giant magnetoresistive spin-valve read heads, TMR read heads have a weaker reliability on sensing current density and exhibit two types of electrical failures: (1) Electrical short induced by tunnel barrier breakdown, and (2) electrical open induced by possible void formation in the metallic layers, which are used for free and pinned layers in exchange biased TMR read heads. The quasi-static transfer curves of head gimble assemble TMR read head was measured under various biasing currents. Transfer curve exhibited a strong dependence on the number of measurements above the threshold bias current, which is considered to be due to the current-induced voltage breakdown in the tunnel barrier.

  18. Dielectric breakdown model for composite materials.

    PubMed

    Peruani, F; Solovey, G; Irurzun, I M; Mola, E E; Marzocca, A; Vicente, J L

    2003-06-01

    This paper addresses the problem of dielectric breakdown in composite materials. The dielectric breakdown model was generalized to describe dielectric breakdown patterns in conductor-loaded composites. Conducting particles are distributed at random in the insulating matrix, and the dielectric breakdown propagates according to new rules to take into account electrical properties and particle size. Dielectric breakdown patterns are characterized by their fractal dimension D and the parameters of the Weibull distribution. Studies are carried out as a function of the fraction of conducting inhomogeneities, p. The fractal dimension D of electrical trees approaches the fractal dimension of a percolation cluster when the fraction of conducting particles approximates the percolation limit. PMID:16241318

  19. Rapid field screening of soils for heavy metals with spark-induced breakdown spectroscopy

    Microsoft Academic Search

    Amy J. R. Hunter; Richard T. Wainner; Lawrence G. Piper; Steven J. Davis

    2003-01-01

    Spark-induced breakdown spectroscopy (SIBS) is a recently developed atomic-fluorescence-based analytical technique that is analogous to laser-induced breakdown spectroscopy. SIBS, however, uses an electrical plasma generation method on nonconductive samples instead of a focused laser beam. Here we describe the basic characteristics of SIBS and its application to the field-screening analysis of soil, using a standard addition analytical approach. Detection limits

  20. Electric discharge in the water: physics of formation and radiative characteristics.

    NASA Astrophysics Data System (ADS)

    Anpilov, Andrei; Barkhudarov, Eduard; Kozlov, Yurii; Kossyi, Igor; Silakov, Valerii; Temchin, Savelii

    2004-09-01

    ELECTRIC DISCHARGE IN THE WATER: PHYSICS OF FORMATION AND RADIATIVE CHARACTERISTICS 2.10. Lighting plasmas. 2.26. Other plasma topics. A.M.Anpilov, E.M.Barkhudarov, Yu.N.Kozlov, I.A.Kossyi, V.P.Silakov and S.M.Temchin Two types of electric discharge in the water have been investigated: discharge between two electrodes and multielectrode gliding surface discharge. Results are presented from experimental studies of the prebreakdown phase of an electric discharge between the point (anode) and plane (cathode) electrodes immersed in the water with different initial conductivity. When a high-voltage pulse is applied, the induced conductivity is detected in the discharge gap. Its value is one order of magnitude higher than the initial one. It is shown that the induced conductivity increases almost linearly with initial conductivity. The induced conductivity correlates with the UV emission from the cathode surface. A qualitative analysis of the experimental results is performed. Investigations of a spectrum of radiation of discharge in water have been carried out. On the base of broadening and shifting of atomic hydrogen and oxygen lines electron density in a prebreakdown as well as breakdown stages has been determined. Results are presented from investigations of multispark electric discharge in water excited along multielectrode metal-dielectric systems with gas supply into the interelectrode gaps. The intensity distribution of discharge radiation in the region covering the biologically active soft UV (190 £l£430 nm) has been determined and the absolute number of quanta in this wavelength interval has been measured. The potentiality of the gliding surface discharge in water for its disinfection is analysed.

  1. Effect of oxygen plasma on the electrical characteristics of GaAs MESFETs

    Microsoft Academic Search

    Vipan Kumar; Aji Baby; C Dhanavantri; J. K Singh; B. R Singh

    2000-01-01

    Plasma induced damage often degrades the electrical and optical performance of the compound semiconductor based microwave\\/photonics devices and circuits. We have investigated the effect of oxygen plasma on the performance degradation of GaAs MESFETs, as measured by changes in breakdown voltage, saturation current, channel resistance, drift mobility etc. The performance degradation of the device is attributed to reduction of carrier

  2. Electrical characteristics of interconnections for high-performance systems

    Microsoft Academic Search

    ALINA DEUTSCH

    1998-01-01

    A review is presented of the electrical characteristics of high-density, high-performance interconnections used in digital and communication applications. These interconnections behave as lossy transmission lines for the frequency range of interest. A brief theoretical explanation of the key properties of lossy, coupled transmission lines is given. A new short-pulse propagation technique used for characterizing a large category of wiring is

  3. Breakdown of organic insulators

    NASA Technical Reports Server (NTRS)

    Cuddihy, E. F.

    1983-01-01

    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.

  4. Dielectric breakdown weathering of the Moon's polar regolith

    NASA Astrophysics Data System (ADS)

    Jordan, A. P.; Stubbs, T. J.; Wilson, J. K.; Schwadron, N. A.; Spence, H. E.

    2015-02-01

    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.

  5. Electrical characteristics of mammalian cells on porous supports

    NASA Astrophysics Data System (ADS)

    Chen, Guo

    2003-10-01

    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.

  6. 49 CFR 236.8 - Operating characteristics of electromagnetic, electronic, or electrical apparatus.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 2012-10-01 false Operating characteristics of electromagnetic, electronic, or electrical apparatus. 236.8 Section...Systems General § 236.8 Operating characteristics of electromagnetic, electronic, or electrical apparatus. Signal...

  7. 49 CFR 236.8 - Operating characteristics of electromagnetic, electronic, or electrical apparatus.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 2014-10-01 false Operating characteristics of electromagnetic, electronic, or electrical apparatus. 236.8 Section...Systems General § 236.8 Operating characteristics of electromagnetic, electronic, or electrical apparatus. Signal...

  8. 49 CFR 236.8 - Operating characteristics of electromagnetic, electronic, or electrical apparatus.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 2013-10-01 false Operating characteristics of electromagnetic, electronic, or electrical apparatus. 236.8 Section...Systems General § 236.8 Operating characteristics of electromagnetic, electronic, or electrical apparatus. Signal...

  9. 49 CFR 236.8 - Operating characteristics of electromagnetic, electronic, or electrical apparatus.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 2010-10-01 false Operating characteristics of electromagnetic, electronic, or electrical apparatus. 236.8 Section...Systems General § 236.8 Operating characteristics of electromagnetic, electronic, or electrical apparatus. Signal...

  10. 49 CFR 236.8 - Operating characteristics of electromagnetic, electronic, or electrical apparatus.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 2011-10-01 false Operating characteristics of electromagnetic, electronic, or electrical apparatus. 236.8 Section...Systems General § 236.8 Operating characteristics of electromagnetic, electronic, or electrical apparatus. Signal...

  11. Low-temperature (77-300 K) current-voltage characteristics of 4H-SiC p{sup +}-p-n{sup +} diodes: Effect of impurity breakdown in the p-type base

    SciTech Connect

    Ivanov, P. A., E-mail: Pavel.Ivanov@mail.ioffe.ru; Potapov, A. S.; Samsonova, T. P. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

    2012-04-15

    The effect of impurity breakdown on the low-temperature (77-300 K) current-voltage (I-V) characteristics of 4H-SiC diodes with a p-type base has been studied. Experimental samples were fabricated from CVD-grown (chemical vapor deposition) commercial p{sup +}-p-n{sup +} 4H-SiC structures. A high electric field in the p-type base was created by applying a forward bias to the diodes. It was found that, at temperatures of 136, 89, and 81 K, the commonly observed 'diode' portion of the I-V characteristics is followed by a portion in which the current grows more rapidly due to the impact ionization of frozen-out Al acceptor atoms in the ground (unexcited) state. At temperatures of 81 and 77 K, this portion is followed by one with a negative differential resistance due to the regenerative dynistor-like switching of the diode, caused by impact ionization of aluminum atoms in the excited state.

  12. Prediction of Treeing Breakdown from Pulse Height of Partial Discharge on Voltage-Phase Angle

    Microsoft Academic Search

    Tatsuki Okamoto; Toshikatsu Tanaka

    1985-01-01

    This paper describes the change in the partial discharge (PD) characteristics due to the growth of electrical trees in insulating materials under the application of an AC voltage. An electrical tree consists of branch-like dielectric breakdown paths. Investigation of a number of characteristic PD parameters shows that the phi-q distribution profile has a good correlation with tree growth. The phi-q

  13. The plasma arc torch -- its electrical and thermal characteristics

    SciTech Connect

    Camacho, S.L. [Plasma Technology Corp., Raleigh, NC (United States)

    1995-12-31

    The plasma arc torch is a very effective heating device. Plasma arc heating technology is very appropriate and essential for product manufacture and for remediating and protecting the environment. The plasma torch initiates and maintains a length of arc column, similar to a lightning bolt, and the electrically-conducting column is used in the conversion of electricity into heat energy. The format of the heat energy delivery is a low-mass, high-enthalpy gas. Heat energy is delivered by the plasma torch with a minimum of mass -- only about 2--3% of the mass delivery from a combustion heater that is delivering the same heat enthalpy. This virtually mass-less heat is ideal for promoting very rapid physical changes and chemical changes in the material being heated. It is ideal for the pyrolysis (or gasification) of organic materials and for the vitrification (or melting) of inorganic materials -- processes that are desirable for new product manufacture and for environmental remediation and protection. Plasma arc heating technology has been perfected by industry during the last 20--30 years, and the industrial sector today is employing this unique heating source in product manufacture and, lately, in environmental remediation and protection processes. It is a cost-effective industrial heat source. The primary objective of this paper is to familiarize one with plasma heaters and their operating characteristics. The essential elements of the plasma arc torch: electrodes, insulators, gas injectors, water-cooling, electrical connectors, etc., are described and the electrical and thermal characteristics of this novel heating device are highlighted. An overview of today`s employment of plasma heating technology and a sample of some of today`s applications of the technology in the industrial sector in the United States and around the world are presented.

  14. Full-range electrical characteristics of WS2 transistors

    NASA Astrophysics Data System (ADS)

    Kumar, Jatinder; Kuroda, Marcelo A.; Bellus, Matthew Z.; Han, Shu-Jen; Chiu, Hsin-Ying

    2015-03-01

    We fabricated transistors formed by few layers to bulk single crystal WS2 to quantify the factors governing charge transport. We established a capacitor network to analyze the full-range electrical characteristics of the channel, highlighting the role of quantum capacitance and interface trap density. We find that the transfer characteristics are mainly determined by the interplay between quantum and oxide capacitances. In the OFF-state, the interface trap density (<1012 cm-2) is a limiting factor for the subthreshold swing. Furthermore, the superior crystalline quality and the low interface trap density enabled the subthreshold swing to approach the theoretical limit on a back-gated device on SiO2/Si substrate.

  15. A new protection system against high voltage vacuum breakdowns

    NASA Astrophysics Data System (ADS)

    Fumelli, M.; Jequier, F.; Paméla, J.

    1989-12-01

    A passive, electrical fast-switch-off/on system for protecting electrodes subject to fortuitous high voltage vacuum breakdown has been developed. This system is based on the principle of oscillatory discharges in an RLC network coupled with the use of a diode. When a breakdown occurs, the current is automatically and rapidly switched off, preventing the damaging of electrodes and power supply by the electrical arc. The interruption lasts as long as required to stop the short-circuit metal vapor arc: a couple of milliseconds are generally sufficient. Then the current is automatically restored, allowing a rapid recovery of the normal electrical operating conditions. Besides the economical advantages of this circuit, one should note that its operating characteristics are very useful for electrode conditioning. The study of this protection circuit has been made for protecting some elements of the neutral beam injectors in the Tore Supra Tokamak experiment, but its field of application should be quite large.

  16. Proposed RF Breakdown Studies at the AWA

    SciTech Connect

    Antipov, S.; Conde, M.; Gai, W.; Power, J.G.; Spentzouris, L.; Yusof, Z.; /Argonne /IIT, Chicago; Dolgashev, V.; /SLAC

    2007-03-21

    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.

  17. Dielectric breakdown of cell membranes.

    PubMed

    Zimmermann, U; Pilwat, G; Riemann, F

    1974-11-01

    With human and bovine red blood cells and Escherichia coli B, dielectric breakdown of cell membranes could be demonstrated using a Coulter Counter (AEG-Telefunken, Ulm, West Germany) with a hydrodynamic focusing orifice. In making measurements of the size distributions of red blood cells and bacteria versus increasing electric field strength and plotting the pulse heights versus the electric field strength, a sharp bend in the otherwise linear curve is observed due to the dielectric breakdown of the membranes. Solution of Laplace's equation for the electric field generated yields a value of about 1.6 V for the membrane potential at which dielectric breakdown occurs with modal volumes of red blood cells and bacteria. The same value is also calculated for red blood cells by applying the capacitor spring model of Crowley (1973. Biophys. J. 13:711). The corresponding electric field strength generated in the membrane at breakdown is of the order of 4 . 10(6) V/cm and, therefore, comparable with the breakdown voltages for bilayers of most oils. The critical detector voltage for breakdown depends on the volume of the cells. The volume-dependence predicted by Laplace theory with the assumption that the potential generated across the membrane is independent of volume, could be verified experimentally. Due to dielectric breakdown the red blood cells lose hemoglobin completely. This phenomenon was used to study dielectric breakdown of red blood cells in a homogeneous electric field between two flat platinum electrodes. The electric field was applied by discharging a high voltage storage capacitor via a spark gap. The calculated value of the membrane potential generated to produce dielectric breakdown in the homogeneous field is of the same order as found by means of the Coulter Counter. This indicates that mechanical rupture of the red blood cells by the hydrodynamic forces in the orifice of the Coulter Counter could also be excluded as a hemolysing mechanism. The detector voltage (or the electric field strength in the orifice) depends on the membrane composition (or the intrinsic membrane potential) as revealed by measuring the critical voltage in E. coli B harvested from the logarithmic and stationary growth phases. The critical detector voltage increased by about 30% for a given volume on reaching the stationary growth phase. PMID:4611517

  18. On electric stresses at wedge-shaped oil gaps in power transformers with application to surface discharge and breakdown

    Microsoft Academic Search

    H.-Z. Ding; Z. D. Wang; P. Jarman

    2008-01-01

    The problem of a high-voltage applied to a wedge-shaped oil gap in power transformers is considered as far as induced distortions and tangential electric stresses are concerned. Near-tip distortions and electric stress concentration occur due to the essentially difference in the relative permittivity between the insulating oil and the pressboard. When the magnitude of tangential electric stress intensity reaches a

  19. Electrical characteristics of low temperature polysilicon TFT with a novel TEOS\\/oxynitride stack gate dielectric

    Microsoft Academic Search

    Kow-Ming Chang; Wen-Chih Yang; Chiu-Pao Tsai

    2003-01-01

    This investigation is the first to demonstrate a novel tetraethylorthosilicate (TEOS)\\/oxynitride stack gate dielectric for low-temperature poly-Si (LTPS) thin film transistors (TFTs), composed of a plasma-enhanced chemical vapor deposition (PECVD) thick TEOS oxide\\/ultrathin oxynitride grown by PECVD N2O-plasma. The stack oxide shows a very high electrical breakdown field of 8.4 MV\\/cm, which is approximately 3 MV\\/cm larger than traditional PECVD

  20. Basic study of transient breakdown voltage in solid dielectric cables

    NASA Astrophysics Data System (ADS)

    Bahder, G.; Sosnowski, M.; Katz, C.

    1980-09-01

    A comprehensive review of the technical and scientific publications relating to crosslinked polyethylene (XLPE) and ethylene propylene rubber (EPR) insulated cables revealed that there is very little known with respect to the life expectancy, the final factory voltage test background and the mechanism of voltage breakdown of these cables. A new methodology for the investigation of breakdown voltages of XLPE and EPR insulated cables was developed which is based on the investigation of breakdown voltages at various voltage transients such as unipolarity pulses and dual-polarity pulses, and a.c. voltage at power and high frequency. Also, a new approach to statistical testing was developed which allows one to establish a correlation among the breakdown voltages obtained with various voltage transients. Finally, a method for the determination of threshold voltage regardless of the magnitude of apparent charge was developed. A model of breakdown and electrical aging of XLPE and EPR insulated cables was developed as well as life expectancy characteristics for high voltage stress XLPE insulated cables operated in a dry environment at room temperature and at 900 C.

  1. Locating Initial Breakdown Pulses of Lightning Flashes

    NASA Astrophysics Data System (ADS)

    Karunarathne, S.; Marshall, T.; Stolzenburg, M.; Betz, H.; Wieczorek, G.

    2010-12-01

    Lightning flashes often begin with a series of bipolar pulses, 1-5 us in width, called initial breakdown pulses or characteristic pulses. In this presentation we show electric field change data of initial breakdown pulses collected with a network of 5 flat-plate antennas with a bandwidth of 0 - 5 MHz. These pulses were obtained at the NASA/Kennedy Space Center (KSC) during the summer of 2010. The (x, y, z, t) positions of these pulses have been determined using a time of arrival technique [Koshak and Solakiewicz, JGR, 1996] for several lightning flashes. In addition, we also collected magnetic field change data with a LINET system [e.g., Betz et al., GRL, 2004], which consisted of 7 crossed-loop sensors having a bandwidth of 5 - 200 kHz; the pulse locations detected by this system were also determined by time of arrival. The locations of the initial breakdown pulses from both systems will be compared to locations of VHF lightning sources made with the KSC LDAR2 system (with a center frequency of 63 MHz and a bandwidth of 6 MHz). Possible implications of the pulse locations derived from the three different sets of sensors on lightning initiation and propagation will be discussed.

  2. Time dependent breakdown in silicon dioxide films

    NASA Technical Reports Server (NTRS)

    Svensson, C.; Shumka, A.

    1975-01-01

    An investigation was conducted regarding the possible existence of a time-dependent breakdown mechanism in thermal oxides of the type used as gate oxide in MOS circuits. Questions of device fabrication are discussed along with details concerning breakdown measurements and the determination of C-V characteristics. A relatively large prebreakdown current observed in one of the cases is related to the time-dependent breakdown.

  3. Minimum Breakdown Voltage in Cylindrical Diode

    NASA Astrophysics Data System (ADS)

    Uhm, Han S.

    2000-10-01

    The discharge plasma is generated by the electrical breakdown. Reduction of the discharge voltage is therefore the key element in enhancing the electrical efficiency for plasma generation. The electrical efficiency enhancement of plasma generation also prolongs system's lifetime, eliminating unnecessary heat and stress generations in the system. Properties of electrical breakdown in cylindrical diode are investigated by making use of Paschen's law. The sparking criterion indicates that discharge properties are insensitive to the electrical field polarity inside cylindrical diode, if the second ionization-coefficient is constant. Due to the curvature effects, the minimum breakdown-voltage in cylindrical geometry increases significantly from its planar value for a large aspect ratio of b/a, where a and b are radii of the inner and outer conductors, respectively. However, the optimum pressure parameter for minimum breakdown-voltage in cylindrical geometry is identical to that in planar electrodes.

  4. Probabilistic description of traffic breakdowns

    NASA Astrophysics Data System (ADS)

    Kühne, Reinhart; Mahnke, Reinhard; Lubashevsky, Ihor; Kaupužs, Jevgenijs

    2002-06-01

    We analyze the characteristic features of traffic breakdown. To describe this phenomenon we apply the probabilistic model regarding the jam emergence as the formation of a large car cluster on a highway. In these terms, the breakdown occurs through the formation of a certain critical nucleus in the metastable vehicle flow, which enables us to confine ourselves to one cluster model. We assume that, first, the growth of the car cluster is governed by attachment of cars to the cluster whose rate is mainly determined by the mean headway distance between the car in the vehicle flow and, maybe, also by the headway distance in the cluster. Second, the cluster dissolution is determined by the car escape from the cluster whose rate depends on the cluster size directly. The latter is justified using the available experimental data for the correlation properties of the synchronized mode. We write the appropriate master equation converted then into the Fokker-Planck equation for the cluster distribution function and analyze the formation of the critical car cluster due to the climb over a certain potential barrier. The further cluster growth irreversibly causes jam formation. Numerical estimates of the obtained characteristics and the experimental data of the traffic breakdown are compared. In particular, we draw a conclusion that the characteristic intrinsic time scale of the breakdown phenomenon should be about 1 min and explain the case why the traffic volume interval inside which traffic breakdown is observed is sufficiently wide.

  5. Electrical and Sensing Properties of Single-Walled Carbon Nanotubes Network: Effect of Alignment and Selective Breakdown

    E-print Network

    with a limited number of nano- tubes aligned across the electrodes as a consequence of mechanical flowFull Paper Electrical and Sensing Properties of Single-Walled Carbon Nanotubes Network: Effect DOI: 10.1002/elan.200900314 1. Introduction Carbon nanotubes have many potential applications

  6. Breakdown voltage of zinc and magnesium vapours

    NASA Astrophysics Data System (ADS)

    Zoestbergen, E.; Commandeur, C.; Maalman, T.

    2014-06-01

    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.

  7. Dielectric Breakdown of Polymer Films

    Microsoft Academic Search

    J. Blok; D. G. Legrand

    1969-01-01

    Strong electric fields have been applied to dielectric polymer films to study field-induced mechanical stresses. For voltages near breakdown the mechanical forces are sufficient to cause localized deformation in some polymer films. Considerable field enhancement can occur at the deformation sites, leading to reduced nominal dielectric strength for the samples. Experimental evidence for electromechanical deformation is presented as a possible

  8. Departure from Paschen's Law of Breakdown in Gases

    Microsoft Academic Search

    W. S. Boyle; P. Kisliuk

    1955-01-01

    The failure of Paschen's law of electrical breakdown in gases at both high pressures and extremely small electrode separations is explained by a single breakdown mechanism. The breakdown field in each of these cases is sufficiently great to draw measurable field-emission current from the cathode, which produces a relatively small number of ions. The space-charge field of these ions is

  9. Effects of excess charge density on dielectric breakdown

    Microsoft Academic Search

    J. M. Lloyd Jr.

    1977-01-01

    From consideration of the available experimental evidence and an examination of the previously proposed models of electric breakdown in solid dielectrics, it appears that the model, proposed by Budenstein, for the formation of a hot, high pressure gas channel within the dielectric prior to breakdown conduction best describes the conditions occurring during breakdown. This paper considers the manner in which

  10. Effects of excess charge density on dielectric breakdown in solids

    Microsoft Academic Search

    J. M. Lloyd Jr.; P. P. Budenstein

    1977-01-01

    After consideration of the available experimental evidence and an examination of the previously proposed models of electric breakdown in solid dielectrics, it appears that the model (proposed by Budenstein) for the formation of a hot, high pressure gas channel within the dielectric prior to breakdown conduction more nearly describes the conditions occurring during breakdown. This paper considers the formation of

  11. Threshold criteria for undervoltage breakdown James E. Cooleya

    E-print Network

    Choueiri, Edgar

    Threshold criteria for undervoltage breakdown James E. Cooleya and Edgar Y. Choueirib Electric an externally supplied pulse of electrons will induce breakdown in an undervoltaged, low-gain discharge gap Undervoltage breakdown is the phenomenon in which a burst of electrons at the cathode of a discharge gap

  12. Ageing and breakdown of thin insulating polymer films

    NASA Astrophysics Data System (ADS)

    Zakrevskii, V. A.; Pakhotin, V. A.; Sudar, N. T.

    2014-06-01

    A mechanism of ageing and breakdown of thin insulating polymer films in an electric field is described. Ageing and breakdown are attributed to the field ionization of macromolecules which is regarded as a self-accelerating process that takes place during the entire electric lifetime and results in an abrupt current increase in the breakdown channel. Calculations are compared with experimental dependences of polymer film lifetimes on electric field intensity.

  13. Analysis of Electrical Characteristics of Thin Film Photovoltaic Cells

    NASA Technical Reports Server (NTRS)

    Kasick, Michael P.

    2004-01-01

    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

  14. Tin Whisker Electrical Short Circuit Characteristics—Part II

    Microsoft Academic Search

    Karim J. Courey; Shihab S. Asfour; Arzu Onar; Jon A. Bayliss; Lawrence L. Ludwig; Maria C. Wright

    2009-01-01

    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

  15. Characteristics of thermoplastics containing electrically conducting asymmetric particles - anisotropic electrical conductivity of injection molded parts and extrusion behavior

    Microsoft Academic Search

    Jan Martinsson; James L. White

    1986-01-01

    The characteristics of compounds of acrylonitrile-butadiene-styrene and high impact polystyrene resins filled with carbon fibers, steel fibers, carbon black, and aluminum flakes have been investigated with special emphasis on electrical conductivity and flow behavior in a capillary rheometer. Compression- and injection-molded compounds were found to be highly electrically anisotropic. The components of the electrical conductivity tensor, were measured. Generally, kappa-11,

  16. Characteristics of parallel electric fields in the downward current region of the aurora

    E-print Network

    California at Berkeley, University of

    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

  17. Performance Characteristics of the First, State-of-the-art Electric Vehicle Implemented in Chile

    E-print Network

    Catholic University of Chile (Universidad Católica de Chile)

    Performance Characteristics of the First, State-of-the-art Electric Vehicle Implemented in Chile@ing.puc.cl *University of Concepción Abstract The first, state-of-the-art electric vehicle implemented in Chile to transform a conventional ICE truck to an electric vehicle. The vehicle used for this transformation

  18. A theoretical approach to electric breakdown behaviour and effective secondary emission coefficient in gas discharge process between two parallel-plane disk electrodes

    SciTech Connect

    Noori, H.; Ranjbar, A. H. [Faculty of Physics, Shahid Bahonar University of Kerman, Kerman (Iran, Islamic Republic of)

    2012-07-15

    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.

  19. Rapid field screening of soils for heavy metals with spark-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Hunter, Amy J. R.; Wainner, Richard T.; Piper, Lawrence G.; Davis, Steven J.

    2003-04-01

    Spark-induced breakdown spectroscopy (SIBS) is a recently developed atomic-fluorescence-based analytical technique that is analogous to laser-induced breakdown spectroscopy. SIBS, however, uses an electrical plasma generation method on nonconductive samples instead of a focused laser beam. Here we describe the basic characteristics of SIBS and its application to the field-screening analysis of soil, using a standard addition analytical approach. Detection limits of ~25 mg/kg have been seen for lead, chromium, barium, mercury, and cadmium. A variety of soils have been tested, some cocontaminated with organic material and uranium (238U).

  20. Electrical properties of biodegradable polylactic acid film

    Microsoft Academic Search

    Takashi Nakagawa; Takuo Nakiri; Ryuichi Hosoya; Yoshiro Tajitsu

    2004-01-01

    We measured the basic electrical insulation characteristic of biodegradable polylactic acid (PLA), and the following results were obtained. The volume resistivity, dielectric constant, and dielectric loss tangent measured at room temperature were almost the same as those of crosslinked polyethylene (XLPE) currently used as insulating material for cables and electric wires. The mean impulse breakdown strength of PLA was about

  1. Basic study of transient breakdown voltage in solid dielectric cables

    SciTech Connect

    Not Available

    1982-02-01

    A comprehensive review of publications relating to cross linked polyethylene (XLPE) and ethylene propylene rubber (EPR) insulated cables revealed that there is very little known with respect to the life expectancy, the final factory voltage test background and the mechanism of voltage breakdown of these cables. In this study a new methodology was developed which depends on the investigation of breakdown voltages at various voltage transients such as unipolarity pulses and dual-polarity pulses, and ac voltage at power and high frequency. Also, a new approach to statistical testing was developed which allows one to establish a correlation among the breakdown voltages obtained with various voltage transients. Finally, a method for the determination of threshold voltage (true partial discharge inception voltage) regardless of the magnitude of apparent charge was developed. Extensive statistical testing of breakdown voltages was conducted using: impulses with front durations from approximately 1.5 to 1000 ..mu..s and times to half-values from 40 to 3000 ..mu..s; dual-polarity pulses consisting of dc voltage and standard impulse of opposite polarity; combined ac and dc voltages; and ac voltages at power and high frequencies. Based on the results of this testing, a model of breakdown and electrical aging of XLPE and EPR insulated cables was developed as well as life expectancy characteristics for high voltage stress XLPE insulated cables operated in a dry environment at room temperature and at 90/sup 0/C. Life expectancy characteristics for EPR insulated cables are approximated. A test procedure including requirements for full-reel factory voltage withstand and partial discharge testing of finished XLPE and EPR insulated cables is proposed. Cables that pass the proposed tests will exhibit a smaller rate of failure in service than cables tested in accordance with present practices.

  2. High-frequency breakdown and paschen law

    Microsoft Academic Search

    J. C. Biswas; Ved Mitra

    1979-01-01

    In the present paper an attempt has been made to draw theoretically a correlation between the well-known Paschen curve and\\u000a the high-frequency breakdown characteristic of a gas device by interpreting electron mean free path in terms of the frequency\\u000a of the applied field. The analytical high-frequency breakdown characteristic, so obtained, agree fairly well with the experimental\\u000a results.

  3. Electrical characteristics of specific grain boundaries in polycrystalline Si

    Microsoft Academic Search

    O. E. Valassiades; C. A. Dimitriades; L. Papadimitriou; Ph. Komninou; Th. Karakostas; K. J. Chrissafis; N. A. Economou

    1984-01-01

    Specific grain boundaries were characterized by back reflection Laue X-ray patterns and electron diffraction patterns as Sigma = 3 coherent type twin with a boundary (111) and Sigma = 37 incoherent twin with boundaries composed of matching planes (115)\\/(011). The Sigma = 3 boundary was proved electrically inactive. The Sigma = 37 boundary was electrically active and asymmetrical. From the

  4. Characteristics of electrically driven two-dimensional photonic crystal lasers

    Microsoft Academic Search

    Hong-Gyu Park; Se-Heon Kim; Min-Kyo Seo; Young-Gu Ju; Sung-Bock Kim; Yong-Hee Lee

    2005-01-01

    We demonstrate room-temperature low-threshold- current lasing action from electrically driven wavelength-scale high-quality photonic crystal lasers having large spontaneous emission factors by solving the theoretical and technical con- straints laid upon by the additional requirement of the current injection. The ultrasmall cavity is electrically pulse pumped through a submicron-size semiconductor \\

  5. Partial Discharge Characteristics of Polymer Nanocomposite Materials in Electrical Insulation: A Review of Sample Preparation Techniques, Analysis Methods, Potential Applications, and Future Trends

    PubMed Central

    Izzati, Wan Akmal; Adzis, Zuraimy; Shafanizam, Mohd

    2014-01-01

    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

  6. Modelling of battery temperature effect on electrical characteristics of Li-ion battery in hybrid electric vehicle

    Microsoft Academic Search

    Yen Kheng Tan; J. C. Mao; King Jet Tseng

    2011-01-01

    This paper presents an enhanced modelling method for the commonly used energy storage device i.e. lithium-ion (Li-ion) battery of a hybrid electrical vehicle (HEV). In this enhanced modelling method, the thermal effect, an important part of the battery electrical model, is considered to generate a holistic understanding, hence the characteristic of the Li-ion battery. Because of the high temperature sensitivity

  7. Undervoltage Breakdown Threshold Criteria

    Microsoft Academic Search

    James Cooley; Edgar Choueiri

    2006-01-01

    Undervoltage breakdown, the process by which a pulse of electrons induces a discharge gap to break down when it is near but has not achieved its self-breakdown conditions, is discussed. Specifically, threshold criteria that determine the number of electrons required to induce breakdown both to glow and arc discharges are presented. Numerical and theoretical predictions of these criteria are compared

  8. An Investigation of the Electrical Short Circuit Characteristics of Tin Whiskers

    NASA Technical Reports Server (NTRS)

    Courey, Karim J.

    2008-01-01

    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.

  9. Electrical response characteristics of soil-electrolyte systems (10kHz-10MHz) 

    E-print Network

    Bachu, Umesh Kumar

    1997-01-01

    The electrical response characteristics of saturated soils depend on soil structure, particle orientation, effective particle size and size distribution, fluid type, fluid conductivity, volume fractions, etc. The use of ...

  10. Microwave air breakdown enhanced with metallic initiators

    SciTech Connect

    Herring, G. C. [NASA Langley Research Center, Hampton, Virginia 23681 (United States); Popovic, S. [Department of Physics, Old Dominion University, Norfolk, Virginia 23529 (United States)

    2008-03-31

    We have determined X-band (9.4 GHz) electric field strengths required to obtain air breakdown at atmospheric pressure in the presence of metallic initiators, which are irradiated with repetitive (30 pulses/s) microwave pulses of 3 {mu}s duration and 200 kW peak power. Using a half-wavelength initiator, a factor of 40 reduction (compared to no initiator) was observed in the electric field required to achieve breakdown. The present measurements are compared to a previously published model for air breakdown, which was originally validated with S-band (3 GHz) frequencies and single 40 {mu}s pulses. We find good agreement between this previous model and our present measurements of breakdown with X-band frequencies and repetitive 3 {mu}s pulses.

  11. Microwave gas breakdown in elliptical waveguides

    NASA Astrophysics Data System (ADS)

    Koufogiannis, I. D.; Sorolla, E.; Mattes, M.

    2014-01-01

    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.

  12. Driving characteristics of electric-powered wheelchair users: How far, fast, and often do people drive?

    Microsoft Academic Search

    Rory A. Cooper; Tricia Thorman; Rosemarie Cooper; Michael J. Dvorznak; Shirley G. Fitzgerald; William Ammer; Guo Song-Feng; Michael L. Boninger

    2002-01-01

    Cooper RA, Thorman T, Cooper R, Dvorznak MJ, Fitzgerald SG, Ammer W, Song-Feng G, Boninger ML. Driving characteristics of electric-powered wheelchair users: how far, fast, and often do people drive? Arch Phys Med Rehabil 2002;83:250-5. Objectives: To determine the driving characteristics of electric-powered wheelchair users during unrestricted community activities and to compare the activity levels among an active group and

  13. The effects of plasticizer on the mechanical and electrical characteristics of PLA

    Microsoft Academic Search

    Katsuyoshi Shinyama; Shigetaka Fujita

    2008-01-01

    Polylactic 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

  14. Structural and electrical characteristics of R.F. magnetron sputtered ZnO films

    E-print Network

    Boo, Jin-Hyo

    Structural and electrical characteristics of R.F. magnetron sputtered ZnO films D.J. Kanga , J on the physical and electrical properties of ZnO films deposited by R.F. magnetron sputtering. We found that the preferential c-axis growth of deposited ZnO films depends on the type of bottom electrode: Both Al and Au

  15. Investigation of Mechanical and Electrical Characteristics for Cracked Conductive Particle in Anisotropic Conductive Adhesive (ACA) Assembly

    Microsoft Academic Search

    Bin Xie; X. Q. Shi; Han Ding

    2008-01-01

    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

  16. Optical and Electrical Characteristics of AC Glow-Discharge Plasma in

    Microsoft Academic Search

    Horacio Martínez Valencia; Farouk Bashir Yousif; Arturo Robledo-Martínez; Fermin Castillo Mejia

    2006-01-01

    This paper considers the optical and electrical characterization of an ac glow-discharge plasma in the abnormal glow mode used for optical emission spectroscopy. The total discharge current and applied voltage are measured using conventional techniques. The electrical characteristics of the planer-cathode glow discharge confirmed that the plasma is operating at an abnormal discharge mode characterized by the increases in the

  17. Characteristics of low frequency electic and magnetic fields in the vicinity of electric power lines

    Microsoft Academic Search

    R. G. Olsen; P. S. K. Wong

    1992-01-01

    Power engineers are often asked questions about the characteristics of low frequency electric and magnetic fields in the vicinity of power lines. Is it reasonable to use a quasi-static theory to calculate these fields Is it or is it not correct to describe these fields as radiation How can Poyntings theorem be used to address this question Why are electric

  18. Electrical Characteristics of Simulated Tornadoes and Dust Devils

    NASA Technical Reports Server (NTRS)

    Zimmerman, Michael I.; Farrell, William M.; Barth, E. L.; Lewellen, W. S.; Perlongo, N. J.; Jackson, T. L.

    2012-01-01

    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.

  19. Statistic Characteristic Estimations of Harmonic And Flicker on Electric Arc Furnace Feeders

    Microsoft Academic Search

    Ming-Tang Chen; Chen-Wen Lu

    2006-01-01

    This paper proposes the estimation results of the stochastic characteristics of harmonic and flicker for an AC and a DC electric arc furnace feeders. These characteristics include stationarity, normality and correlation. Besides, the statistic probability was assessed, too. The estimation and the assessment are implemented by a PC-based virtual instrumentation system. The results show that (1) most harmonic and flicker

  20. IMPACT OF UNIAXIAL STRAIN ON THE ELECTRICAL CHARACTERISTICS OF MOSFETS AND ESAKI TUNNEL DIODES

    E-print Network

    IMPACT OF UNIAXIAL STRAIN ON THE ELECTRICAL CHARACTERISTICS OF MOSFETS AND ESAKI TUNNEL DIODES CHARACTERISITCS OF MOSFETS AND ESAKI TUNNEL DIODES Abstract by Wei Zhao Process-induced uniaxial strain is widely on the influence of stress on the current-voltage characteristics of Esaki tunnel diode and the strain effects

  1. Starting Characteristics of Electric Submergible Oil Well Pumps

    Microsoft Academic Search

    Robert L. Hyde; Thomas R. Brinner

    1986-01-01

    The electric submergible pump (ESP) consists of a centrifugal pump powered by a medium-voltage three-phase induction motor. Being constrained to operate within common well casings, the ESP is rather unique; for example, a 500-hp motor may be less than 6 in in diameter and more than 100 ft long. As such, its mechanical rotational behavior under starting conditions can be

  2. Electrically silent Kv subunits: their molecular and functional characteristics.

    PubMed

    Bocksteins, Elke; Snyders, Dirk J

    2012-04-01

    Electrically silent voltage-gated potassium (KvS) ?-subunits do not form homotetramers but heterotetramerize with Kv2 subunits, generating functional Kv2/KvS channel complexes in which the KvS subunits modulate the Kv2 current. This poses intriguing questions into the molecular mechanisms by which these KvS subunits cannot form functional homotetramers, why they only interact with Kv2 subunits, and how they modulate the Kv2 current. PMID:22505664

  3. Effect of Electrical Stress on Josephson Tunneling Characteristics of Junctions

    Microsoft Academic Search

    Denis Amparo; Sergey K. Tolpygo

    2009-01-01

    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

  4. Evaluating thermal aging characteristics of electric power transmission lines

    Microsoft Academic Search

    M. M. I. Bhuiyan; P. Musilek; J. Heckenbergerova; D. Koval

    2010-01-01

    Assessment of aging characteristics of conductors and other components of power transmission networks plays an important role in asset management systems. Due to adverse effects of conductor aging caused by annealing, the conductors lose their tensile strength. Although the loss of strength is gradual, it accumulates over time and increases the probability of outages and blackouts. Therefore, the most important

  5. Breakdown phenomena in high power klystrons

    SciTech Connect

    Vlieks, A.E.; Allen, M.A.; Callin, R.S.; Fowkes, W.R.; Hoyt, E.W.; Lebacqz, J.V.; Lee, T.G.

    1988-03-01

    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.

  6. Effect of the Mesh Transparency on the Electrical Characteristics of DC Pseudo Discharge

    NASA Astrophysics Data System (ADS)

    A. Abd Al-Halim, M.; Abu-Hashem, A.; I. Moubarak, D.

    2015-06-01

    A DC pseudo discharge for air has been studied. Air pressure is used in the range between 0.7 Torr and 12 Torr. The breakdown occurs between a plane cathode and a mesh anode at transparencies of 19%, 46%, and 65%. The current-voltage characteristic curves of the discharge, which are measured at different pressures, distances, and mesh transparences, take effect in the region of abnormal glow. The discharge voltage decreases as the air pressure increases, while more voltage is needed to maintain the discharge when either the mesh transparency or the inter-electrode distance is increased. An increment of mesh transparency causes high negative potential behind the mesh due to the high concentration of electrons, which accumulate and collide with neutral atoms. Paschen curves deviate from the expected regular one. The left side of Paschen curves appears at inter-electrode distance of 1 mm, whereas the right side appears at inter-electrode distance of 5 mm. The intermediate region is observed only at 3 mm distance between the two electrodes. For the transparency range used in this work, it is found that the decrement of the breakdown voltage, on the right side, depends on the mesh transparency. For different electrode separations, the measured Paschen curves are coincident and deviate from the standard ones of Paschen's law.

  7. Optical and electrical characteristics of ZnO/Si heterojunction

    NASA Astrophysics Data System (ADS)

    Urgessa, Z. N.; Dobson, S. R.; Talla, K.; Murape, D. M.; Venter, A.; Botha, J. R.

    2014-04-01

    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.

  8. Research on Electrical Characteristics of Dielectric Barrier Discharge and Dielectric Barrier Corona Discharge

    NASA Astrophysics Data System (ADS)

    Sun, Yanzhou; Zeng, Mi; Cui, Zhiyong

    2012-09-01

    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.

  9. Electrical characteristics of highly reliable ultrathin hafnium oxide gate dielectric

    Microsoft Academic Search

    Laegu Kang; Byoung Hun Lee; Wen-Jie Qi; Yongjoo Jeon; Renee Nieh; Sundar Gopalan; Katsunori Onishi; Jack C. Lee

    2000-01-01

    Electrical and reliability properties of ultrathin HfO2 have been investigated. Pt electroded MOS capacitors with HfO2 gate dielectric (physical thickness ~45-135 Å and equivalent oxide thickness ~13.5-25 Å) were fabricated. HfO2 was deposited using reactive sputtering of a Hf target with O2 modulation technique. The leakage current of the 45 Å HfO2 sample was about 1×10-4 A\\/cm 2 at +1.0

  10. Characteristics of thermoplastics containing electrically conducting asymmetric particles - anisotropic electrical conductivity of injection molded parts and extrusion behavior

    SciTech Connect

    Martinsson, J.; White, J.L.

    1986-10-01

    The characteristics of compounds of acrylonitrile-butadiene-styrene and high impact polystyrene resins filled with carbon fibers, steel fibers, carbon black, and aluminum flakes have been investigated with special emphasis on electrical conductivity and flow behavior in a capillary rheometer. Compression- and injection-molded compounds were found to be highly electrically anisotropic. The components of the electrical conductivity tensor, were measured. Generally, kappa-11, the flow direction conductivity, has the highest value and the thickness direction, and kappa-33 has the lowest. The injection-molded parts were usually electrically heterogeneous, with the conductivities highest at the greatest distances from the gate. The flow of these compounds through dies was investigated. Examination of material from the die entrance indicated streamline flow without entrance vortices. Extrudates were found to contain oriented particles. 25 references.

  11. Aerodynamic characteristics of sixteen electric, hybrid, and subcompact vehicles

    NASA Technical Reports Server (NTRS)

    Kurtz, D. W.

    1979-01-01

    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.

  12. An investigation of breakdown voltage in AMTECs

    NASA Astrophysics Data System (ADS)

    Momozaki, Yoichi; El-Genk, Mohamed S.

    2002-01-01

    Experiments are conducted to investigate the DC electrical breakdown voltage in cesium vapor between two planner molybdenum electrodes, 1.6 cm in diameter, separated by a 0.5 mm gap, and relate the results to the potential electrical breakdown on the cathode side of Alkali Metal Thermal-to-Electric Converters (AMTECs). In the first set of experiments, in which the electrodes are kept at 560 and 650 K, while varying the cesium pressure from 0.71 to 29 Pa, when the cooler electrode is positively biased, breakdown occurs at ~500 V, but at 700 V when the cooler electrode is negatively biased. In the second set of experiments, in which the electrodes are held at 625 and 1100 K and the cesium pressure varied from 1.7 to 235 Pa, when the cooler electrode is positively biased, breakdown voltage is <4 V, but in excess of 400 V when the cooler electrode is negatively biased. Since the first ionization potential and the ionization rate constant of cesium are lower and higher, respectively, than for the sodium (5.14 V) and potassium (4.34 V) vapors in AMTECs, the DC electrical breakdown voltage in an AMTEC is expected to be higher than measured in this work for cesium vapor. .

  13. Influence of Defects on the Electrical Characteristics of Mercury-Drop Junctions: Self-Assembled Monolayers of

    E-print Network

    Prentiss, Mara

    : This paper compares the structural and electrical characteristics of self-assembled monolayers (SAMs) of n the structural and electrical character- istics of self-assembled monolayers (SAMs) of n-alkanethiolates on twoInfluence of Defects on the Electrical Characteristics of Mercury-Drop Junctions: Self-Assembled

  14. Modeling of Electro Optic Polymer Electrical Characteristics in a 3 layer Optical Waveguide Modulator

    NASA Technical Reports Server (NTRS)

    Watson, Michael D.; Ashley, Paul R.; Guenthner, Andrew J.; Abushagur, Mustafa

    2004-01-01

    The electrical characteristics of electro optic polymer waveguide modulators are often described by the bulk reactance of the individual layers. However, the resistance and capacitance between the layers can significantly alter the electrical performance of a waveguide modulator. These interface characteristics are related to the boundary charge density and are strongly affected by the adhesion of the layers in the waveguide stack. An electrical reactance model has been derived to investigate this phenomenon at low frequencies. The model shows the waveguide stack frequency response has no limiting effects below the microwave range and that a true DC response requires a stable voltage for over 1000 hours. Thus, reactance of the layers is the key characteristic of optimizing the voltage across the core layer, even at very low frequencies (> 10(exp -6) Hz). The results of the model are compared with experimental data for two polymer systems and show quite good correlation.

  15. The electrical characteristics of a 4H—silicon carbide metal—insulator—semiconductor structure with Al2O3 as the gate dielectric

    NASA Astrophysics Data System (ADS)

    Liu, Li; Yang, Yin-Tang; Ma, Xiao-Hua

    2011-12-01

    A 4H—silicon carbide metal—insulator—semiconductor structure with ultra-thin Al2O3 as the gate dielectric, deposited by atomic layer deposition on the epitaxial layer of a 4H—SiC (0001) 80N-/N+ substrate, has been fabricated. The experimental results indicate that the prepared ultra-thin Al2O3 gate dielectric exhibits good physical and electrical characteristics, including a high breakdown electrical field of 25 MV/cm, excellent interface properties (1×1014 cm-2) and low gate-leakage current (IG = 1 × 10-3 A/cm-2@Eox = 8 MV/cm). Analysis of the current conduction mechanism on the deposited Al2O3 gate dielectric was also systematically performed. The confirmed conduction mechanisms consisted of Fowler—Nordheim (FN) tunneling, the Frenkel—Poole mechanism, direct tunneling and Schottky emission, and the dominant current conduction mechanism depends on the applied electrical field. When the gate leakage current mechanism is dominated by FN tunneling, the barrier height of SiC/Al2O3 is 1.4 eV, which can meet the requirements of silicon carbide metal—insulator—semiconductor transistor devices.

  16. Determination of the characteristics of an electric arc plasma contaminated by vapors from insulators

    SciTech Connect

    Abbaoui, M.; Cheminat, B. (Lab. de Physique des Materiaux, Univ. Blaise Pascal (Clermont II), 24 Avenue des Landais, F-63177 Aubiere Cedex (FR))

    1991-02-01

    An experimental study at atmospheric pressure carried out on plasma penetrated by vapors from different industrial insulators allowed the showing of the influence of the nature of the insulator upon the characteristics of the electric arc plasma; i.e., an increase of the temperature, electron density, electric field, and extinction velocity of the arc. Measurements have been made spectrometrically and by means of probes.

  17. Studies on the Electrical Characteristics of Ni and NiPt-alloy Silicided

    Microsoft Academic Search

    Schottky Diodes; R. Das; A. R. Saha; L. J. Jin; W. K. Choi; D. A. Antoniadis; E. A. Fitzgerald; S. Chattopadhyay; S. Saha; C. Bose; C. K. Maiti

    Ni(Pt) alloy-silicided\\/Si1-xGex Schottky barrier diodes have been fabricated by annealing the co-deposited NiPt alloy film on Si1-xGex layers and characterized electrically in the temperature range of 100 K-300 K to investigate the effect of Pt co-deposition (with Ni) on the electrical characteristics of alloy-silicided Schottky diodes. The Schottky barrier height (?b) and ideality factor (?) have been determined from the

  18. Electrical characteristics of a seawater MHD thruster. Final report

    SciTech Connect

    Tempelmeyer, K.E.

    1990-06-01

    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.

  19. Effects of passivation on breakdown voltage and leakage current of normally-off InAlN/GaN MISHFETs—a simulation study

    NASA Astrophysics Data System (ADS)

    Tang, Chenjie; Shi, Junxia

    2014-12-01

    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).

  20. Material Characteristics of Molten-metal Bridges at Electrical Contacts

    NASA Astrophysics Data System (ADS)

    Mori, Masami; Kohno, Akio

    Steel and copper are widely used as current collecting material for power supply in electric railways. In this field experimental studies on material wear and friction phenomena are important for improving stability and reliability of current collection in service operation. However few are reported to the effect of contact bridge formation, which is caused by separation of electrodes, in the material wear and friction phenomena, especially for different materials, such as, steel and copper. In this paper, anode and cathode materials, which are made of same metal (either steel or copper), are separated with very low constant speed. to observe the bridge formation and contact surface after the bridge separation in detail. As a result, melting bridge formation of 0.5mm height was observed while steel electrodes separating. In the similar test of the identical condition of the copper electrode, the observation of the bridge formation was difficult. However, the copper bridge that grew at 0.2mm height was observed, where test was conducted with separating speed slowed down to 1/10. The molten bridge was formed at the boundary on the anode side with high brightness, and this effect was seen for both steel and copper. Although this phenomena appears for both cases of steel and copper, the anode made of steel material is damaged more seriously. Also in this paper, special strips of steel and copper, simulating the contact bridge, are studied for contact drop, contact resistance and temperature increase at contact point to melt down by increasing current slowly from zero ampere. As the result, the resistance of the copper which is a diamagnetic material rose in a smooth quadratic curve for the increase in current (temperature), and the steel which is ferromagnetic showed the rapid increase above magnetic transformation and allotropic transformation temperature. The increase of heat quantity by decreasing of specific heat due to magnetic transformation and the consequent resistance increase are the cause of the formation of large melting bridge in the steel And Thomson effect is considered as the cause of damage of anode.

  1. Grammatical Errors Communication Breakdown.

    ERIC Educational Resources Information Center

    Tomiyana, Machiko

    1980-01-01

    Investigates to what extent ESL learners' syntactic errors in written communication cause comprehension breakdown. The variables considered are the omission, insertion, and wrong choice of articles and connectors. Results indicated that errors concerning connectors cause communication breakdown more often than do errors in article usage. (PMJ)

  2. Physical characteristics of GE (General Electric) BWR (boiling-water reactor) fuel assemblies

    SciTech Connect

    Moore, R.S.; Notz, K.J.

    1989-06-01

    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.

  3. Development and optimization of breakdown strength measurements on polyethylene insulants

    Microsoft Academic Search

    R. Clavreul; J. Berdala

    1995-01-01

    In order to study the ageing phenomena of polyethylene insulants in high voltage cables, we carried out electrical measurements, for example the short time dielectric breakdown field in polyethylene. The decrease of the intrinsic dielectric rigidity of polyethylene may be correlated with ageing. That is why we optimized the short time breakdown field measurements on polyethylene samples between plane surface

  4. Relativistic breakdown in planetary atmospheres

    SciTech Connect

    Dwyer, J. R. [Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, Florida 32901 (United States)

    2007-04-15

    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.

  5. Pre-breakdown evaluation of gas discharge mechanisms in microgaps

    SciTech Connect

    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)

    2013-04-29

    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.

  6. Structural properties and electrical characteristics of electron-beam gun evaporated erbium oxide films

    E-print Network

    Eisenstein, Gadi

    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

  7. Electrical characteristics of Ta2O5 thin films deposited by electron beam gun evaporation

    E-print Network

    Eisenstein, Gadi

    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

  8. Noise and Electrical Characteristics below 10 K of small CHFET Circuits and Discrete Devices

    NASA Technical Reports Server (NTRS)

    Cunningham, Thomas J.; Gee, Russell; Fossum, Eric R.; Baier, Steven M.

    1993-01-01

    This paper discusses the lates results of a continuing study of the properties of the complementary heterojunction field-effect transistor (CHFET) at 4K. The electrical characteristics, including the gate leakage current and the subthreshold transconductance, and the input-referred noise voltage for a new lot of discrete CHFETs is presented and discussed.

  9. Electrical Characteristics and Testing Considerations for Gate Oxide Shorts in CMOS ICs

    Microsoft Academic Search

    Jerry M. Soden; Charles F. Hawkins

    1985-01-01

    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

  10. Frequency-dependent electrical characteristics of DNA using molecular dynamics simulation

    Microsoft Academic Search

    Makoto Ikeda; Kazuo Nakazato; Hiroshi Mizuta; Martin Green; David Hasko; Haroon Ahmed

    2003-01-01

    Research on DNA has been widely carried out as a promising material for nanoelectronics, medicine development and disease diagnosis, using experiment, simulation and theory. We have carried out molecular dynamics simulation coupled with the linear response theory, based on the time-correlation function of an observable, in order to extract the frequency-dependent electrical characteristics of DNA. We observe a dielectric relaxation

  11. Kinetic theory of runaway air breakdown

    Microsoft Academic Search

    R. A. Roussel-Dupre; A. V. Gurevich; T. Tunnell; G. M. Milikh

    1994-01-01

    The kinetic theory for an air breakdown mechanism advanced in a previous paper [Phys. Lett. A 165, 463 (1992)] is developed. The relevant form of the Boltzmann equation is derived and the particle orbits in both velocity space and configuration space are computed. A numerical solution of the Boltzmann equation, assuming a spatially uniform electric field, is obtained and the

  12. Inherent time delay for dielectric breakdown in shock-loaded x-cut quartz

    NASA Technical Reports Server (NTRS)

    Graham, R. A.; Yang, L. C.

    1975-01-01

    Dielectric breakdown in shock-loaded x-cut quartz is examined under conditions of both impact loading and Q-switched laser-irradiation loading. It is observed that breakdown is characterized by an inherent time delay which depends on the magnitude of the electric field. For pulse duration less than about 30 ns, dielectric breakdown is not observed.

  13. Second Discharge Characteristics of Aluminum Wire Electrical Explosion Under Various Argon Pressures

    NASA Astrophysics Data System (ADS)

    Yan, Wenyu; Zhang, Qiaogen; Zhao, Junping; Chen, Gangliang; Liu, Longchen

    2014-10-01

    Electrical wire explosion is a promising method for the preparation of metal nanopowder, but the properties of metal nanopowder are affected by the second discharge process of electrical wire explosion. The second discharge characteristics of aluminum wire electrical explosion under variant argon pressures were studied in a RLC discharge circuit. The results show that the curve of the second discharge voltages versus the pressure presents a U-shape. To clarify the roles of aluminum vapor and argon in the process of the second discharge, a spectrograph and a high speed framing camera were used to study the radiation spectrum and spatial distribution of the electrical explosion plasma. It is observed that argon participates in the second discharge process under low pressure. A discharge channel develops along the surface of the aluminum vapor. Under higher pressure, a second discharge takes place in the aluminum vapor and the discharge channel is inside the aluminum vapor.

  14. Steam-zone electrical characteristics for geodiagnostic evaluation of steamflood performance

    SciTech Connect

    Mansure, A.J. (Sandia National Labs., Albuquerque, NM (USA)); Meldau, R.F. (Dolphin Petroleum Consultants (US))

    1990-09-01

    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.

  15. Characteristics of the calibration curves of copper for the rapid sorting of steel scrap by means of laser-induced breakdown spectroscopy under ambient air atmospheres.

    PubMed

    Kashiwakura, Shunsuke; Wagatsuma, Kazuaki

    2013-01-01

    For the rapid and precise sorting of steel scrap with relatively high contents of copper, laser-induced breakdown spectroscopy (LIBS) is a promising method. It has several advantages such that it can work under ambient air atmospheres, and specimens can be tested without any pretreatment, such as acid digestion, polishing of the surface of the specimens, etc. For the application of LIBS for actual steel scrap, we obtained emission spectra by an LIBS system, which was mainly comprised of an Nd:YAG laser, an Echelle-type spectrometer, and an ICCD detector. The standard reference materials (SRMs) of JISF FXS 350-352, which are Fe-Cu binary alloy and have certified concentrations of copper, were employed for making calibration lines. Considering spectral interferences from the emission lines of the iron matrix in the alloys, Cu I lines having wavelengths of 324.754 and 327.396 nm could be chosen. In five replicate measurements of each SRM, shorter delay times after laser irradiation and longer gate widths for detecting the transient emission signal are suggested to be the optimal experiment parameters. In the determination process, utilizing the calibration line from Cu I 327.396 nm was better because of less spectral interference. By using 200 pulsed laser shots for the measurement sequence, a limit of detection of 0.004 Cu at% could be obtained. PMID:24334981

  16. Microwave air breakdown enhanced with metallic initiators

    Microsoft Academic Search

    G. C. Herring; S. Popovic

    2008-01-01

    We have determined X-band (9.4 GHz) electric field strengths required to obtain air breakdown at atmospheric pressure in the presence of metallic initiators, which are irradiated with repetitive (30 pulses\\/s) microwave pulses of 3 mus duration and 200 kW peak power. Using a half-wavelength initiator, a factor of 40 reduction (compared to no initiator) was observed in the electric field

  17. Ionizing potential waves and high-voltage breakdown streamers.

    NASA Technical Reports Server (NTRS)

    Albright, N. W.; Tidman, D. A.

    1972-01-01

    The structure of ionizing potential waves driven by a strong electric field in a dense gas is discussed. Negative breakdown waves are found to propagate with a velocity proportional to the electric field normal to the wavefront. This causes a curved ionizing potential wavefront to focus down into a filamentary structure, and may provide the reason why breakdown in dense gases propagates in the form of a narrow leader streamer instead of a broad wavefront.

  18. Review of electric discharge microplasmas generated in highly fluctuating fluids: Characteristics and application to nanomaterials synthesisa)

    NASA Astrophysics Data System (ADS)

    Stauss, Sven; Muneoka, Hitoshi; Urabe, Keiichiro; Terashima, Kazuo

    2015-05-01

    Plasma-based fabrication of novel nanomaterials and nanostructures is indispensible for the development of next-generation electronic devices and for green energy applications. In particular, controlling the interactions between plasmas and materials interfaces, and the plasma fluctuations, is crucial for further development of plasma-based processes and bottom-up growth of nanomaterials. Electric discharge microplasmas generated in supercritical fluids represent a special class of high-pressure plasmas, where fluctuations on the molecular scale influence the discharge properties and the possible bottom-up growth of nanomaterials. This review discusses an anomaly observed for direct current microplasmas generated near the critical point, a local decrease in the breakdown voltage. This anomalous behavior is suggested to be caused by the concomitant decrease of the ionization potential due to the formation of clusters near the critical point, and the formation of extended electron mean free paths caused by the high-density fluctuation near the critical point. It is also shown that in the case of dielectric barrier microdischarges generated close to the critical point, the high-density fluctuation of the supercritical fluid persists. The final part of the review discusses the application of discharges generated in supercritical fluids to synthesis of nanomaterials, in particular, molecular diamond—so-called diamondoids—by microplasmas generated inside conventional batch-type and continuous flow microreactors.

  19. Electrical characteristics of Ni Ohmic contact on n-type GeSn

    SciTech Connect

    Li, H.; Cheng, H. H., E-mail: hhcheng@ntu.edu.tw [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)

    2014-06-16

    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.

  20. Electrical characteristics of Ni Ohmic contact on n-type GeSn

    NASA Astrophysics Data System (ADS)

    Li, H.; Cheng, H. H.; Lee, L. C.; Lee, C. P.; Su, L. H.; Suen, Y. W.

    2014-06-01

    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.

  1. Universal low cost controller for electric motors with programmable characteristic curves

    Microsoft Academic Search

    J. Oehm; M. Grafe; T. Kettner; K. Schumacher

    1996-01-01

    The realization of a universal low-cost controller for electric motors in CMOS technology with programmable characteristic curves is presented. With regard to the required chip area of 2.7 mm2 in a 1.6 ?m, 40 nm technology, the general advantage in comparison to microcontroller-based solutions lies in the low factory costs. The analog dc power supply is generated directly from the

  2. Charge Accumulation Effects on Breakdown Condition of Capacitive Discharges in DC-biased RF Field

    NASA Astrophysics Data System (ADS)

    Shoji, M.; Sato, M.

    1998-10-01

    Breakdown characteristics of capacitively coupled argon dc-biased rf (13.56 MHz) discharges are measured using an insulated electrode (IE) system made from glass-covered aluminum disk plates. In the IE system under the influence of a dc-biased rf field, charged particles generated in the discharge space will accumulate at the glass surface without leakage, which may weaken the dc electric field strength. After the dc-biased rf voltage is applied, a time lag Tl until breakdown is observed and the rf breakdown voltage V_rf is considerably lowered. For example, V_rf decreases by more than 10 % at Tl = 1000 sec. The values of V_rf which cause breakdown within Tl = 20 sec. in the IE system are compared with those for the bare metal electrode (BME) system for which no charge accumulation takes place. At low dc biases, they are almost the same for both systems. As the dc bias is increased, V_rf of the BME system becomes much smaller than that of the IE system. The decrease in V_rf can be explained by the occurring of secondary electron emission from the metal surface.

  3. Understanding junction breakdown in multicrystalline solar cells

    NASA Astrophysics Data System (ADS)

    Breitenstein, Otwin; Bauer, Jan; Bothe, Karsten; Kwapil, Wolfram; Lausch, Dominik; Rau, Uwe; Schmidt, Jan; Schneemann, Matthias; Schubert, Martin C.; Wagner, Jan-Martin; Warta, Wilhelm

    2011-04-01

    Extensive investigations on industrial multicrystalline silicon solar cells have shown that, for standard 1 ? cm material, acid-etched texturization, and in absence of strong ohmic shunts, there are three different types of breakdown appearing in different reverse bias ranges. Between -4 and -9 V there is early breakdown (type 1), which is due to Al contamination of the surface. Between -9 and -13 V defect-induced breakdown (type 2) dominates, which is due to metal-containing precipitates lying within recombination-active grain boundaries. Beyond -13 V we may find in addition avalanche breakdown (type 3) at etch pits, which is characterized by a steep slope of the I-V characteristic, avalanche carrier multiplication by impact ionization, and a negative temperature coefficient of the reverse current. If instead of acid-etching alkaline-etching is used, all these breakdown classes also appear, but their onset voltage is enlarged by several volts. Also for cells made from upgraded metallurgical grade material these classes can be distinguished. However, due to the higher net doping concentration of this material, their onset voltage is considerably reduced here.

  4. Effect of SnO2 Addition on Electrical Degradation Characteristics of ZnO Varistors

    NASA Astrophysics Data System (ADS)

    Takada, Masayuki; Yosikado, Sinzo

    The effects of SnO2 additon on the electrical degradation characteristics of Bi2O3-MnO2-Co3O4-added ZnO varistors were investigated by field-emission scanning electron microscopy (FE-SEM), energy dispersion X-ray spectroscopy (EDX), X-ray diffraction (XRD), voltage-current (V-I) characteristics, and capacitance-voltage (C-V) characteristics. The microstructure containing both twins of ZnO and Zn2SnO4-type spinel particles was observed at the grain boundary similar to Bi-Mn-Co-Sb2O3-added ZnO varistors. Spinel particles began to appear by the addition of SnO2 over approximately 0.5mol%. Before electrical degradation, value of nonlinearity index ? of V-I characteristic for Bi-Mn-Co-SnO2-added samples was approximately 50 and varistor voltage was 120?140V/mm. Varistor voltage increased with increasing the amount of SnO2. Value of ? after the electrical degradation showed local maximum at approximately 0.1mol% with the increase of the amount of SnO2 and then showed local minimum at approximately 0.5mol% similar to the relative integral intensity of XRD diffraction peak for (004) plane at small amount of SnO2. It is suggested that the diffusion of oxygen ions through the grain boundary is affected by the change of crystal orientation of ZnO grains at the grain boundary by addition of small amount of SnO2. It is found that the increase of the varistor voltage by addition of SnO2 is due to the increase of the barrier height of Schottky barriers.

  5. Mechanical constraints enhance electrical energy densities of soft dielectrics

    E-print Network

    Ferrari, Silvia

    Mechanical constraints enhance electrical energy densities of soft dielectrics Lin Zhang, Qiming, the dielectric will breakdown electrically. The breakdown limits the electrical energy density of the dielectric including high dielectric strength, fast charging rate, and mechanical flexibility and conformability. Soft

  6. Beauty in the Breakdown

    ERIC Educational Resources Information Center

    Brisco, Nicole

    2008-01-01

    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…

  7. Multipactor breakdown - Lessons unlearned

    Microsoft Academic Search

    1984-01-01

    Multipactor breakdown in satellites continues to reappear as a problem every few years, even through there is adequate knowledge to avoid it. The failures occur most often in transmission lines, filters, connectors, and switches. Multipactor and gas discharge problems have occurred for many reasons: including RF analyses and inadequate testing. Usually the multipactor problems were not discovered until the satellites

  8. An estimation of the electrical characteristics of planetary shallow subsurfaces with TAPIR antennas

    NASA Astrophysics Data System (ADS)

    Le Gall, A.; Reineix, A.; Ciarletti, V.; Berthelier, J. J.; Ney, R.; Dolon, F.; Corbel, C.

    2006-06-01

    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.

  9. Dc breakdown of low pressure gas in long tubes

    NASA Astrophysics Data System (ADS)

    Lisovskiy, V. A.; Koval, V. A.; Yegorenkov, V. D.

    2011-05-01

    The gas breakdown was experimentally investigated in dc electrical field in long discharge tubes. The measurements were performed in the tube of radius R=4 mm, whereas the inter-electrode gap values varied in the range L=2-230 mm. The conventional Paschen law was shown to hold in short discharge tubes for which L/R?1. At L/R>1 the breakdown curves U(p) are shifted not only to lower pressure p values but also to higher dc voltage U values with the gap value increasing, i.e., one must employ the modified law of gas breakdown U(pL,L/R). However in long tubes the breakdown curve pattern experiences qualitative changes. At L/R>20 increasing L makes the dc breakdown curves to shift to higher U values, their minima being observed almost at the same gas pressure value. That is, for small gaps with increasing distance between the electrodes, the breakdown curves shift to the left on the scale of the gas pressure at a constant voltage at the minimum, and for long tubes with increasing distance between the electrodes, the breakdown curves shift upward on the scale of the voltage with the same gas pressure at the minimum. Theoretical treatment reveals that for gas breakdown in a long tube the rates of ionization via electron impact and diffusion loss to the tube wall must be equal.

  10. The Effect of Isopropyl Alcohol Adsorption on the Electrical Characteristics of Thin Oxide

    NASA Astrophysics Data System (ADS)

    Motai, Kumi; Itoga, Toshihiko; Irie, Takashi

    1998-03-01

    The effect of isopropyl alcohol (IPA) adsorption on the electrical characteristics of thin oxide has been investigated. Metal-oxide-semiconductor (MOS) capacitors were fabricated on Si substrates after IPA was intentionally adsorbed on the substrate surfaces. The leakage current was raised in the low electric field region for the 5-nm-thick thin oxide due to increased IPA adsorption, but the leakage current was not affected in the 8- and 10-nm-thick oxides. Using X-ray photoelectron spectroscopy, we found that the heat treatment creates C-Si bonds in the oxide due to organic adsorbates including IPA. These bonds appear likely to cause weak points or prevent uniform oxidation. A pre-annealing treatment was found to be effective in suppressing the formation of the C-Si bonds.

  11. Electrical characteristics of metal oxide based multi-layer vertical resistive switching memories.

    PubMed

    Jang, Sung Hwan; Kim, Dong Hun; Yoon, Dong Yoel; Kim, Tae Whan

    2014-11-01

    The electrical properties of vertical resistive switching random access memories (VRRAMs) were investigated to enhance their device performance by using a stochastic method based on the generation and the rupture probability of the conductive filaments (CFs) together with a tunneling model. The carrier transport mechanisms were dominantly attributed to the tunneling current between the CFs and the electrode. Carrier transport mechanisms of the high resistance state current were dominantly attributed to the direct tunneling current between the electrode and the CFs locating at nearest the electrode. The simulated forming voltages of the VRRAMs were in reasonable agreement with the experimental data. The low resistance/high resistance state current ratio of the VRRAMs was improved due to an increase in the distance between the CFs and the electrode of the VRRAMs with a barrier material after a reset operation. These results can help understanding electrical characteristics and optimal structures of the VRRAMs. PMID:25958500

  12. Neutron, gamma ray, and temperature effects on the electrical characteristics of thyristors

    NASA Technical Reports Server (NTRS)

    Frasca, A. J.; Schwarze, G. E.

    1992-01-01

    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.

  13. Effect of Electrostatic Discharge on Electrical Characteristics of Discrete Electronic Components

    NASA Technical Reports Server (NTRS)

    Wysocki, Phil; Vashchenko, Vladislav; Celaya, Jose; Saha, Sankalita; Goebel, Kai

    2009-01-01

    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.

  14. VORTEX BREAKDOWN INCIPIENCE: THEORETICAL CONSIDERATIONS

    E-print Network

    Erlebacher, Gordon

    or momentum or heat exchange; or destructive, as in degradation of aerodynamic performance. Vortex breakdown interest, vortex breakdown has important technological applications, both aerodynamic and non­ aerodynamic. There is a tendency for the breakdown to migrate back and forth in the test section or on the aerodynamic surface

  15. Threshold Criteria for Undervoltag Breakdown

    Microsoft Academic Search

    J. E. Cooley; E. Y. Choueiri

    2005-01-01

    Summary form only given. Undervoltage breakdown, the process by which a pulse of electrons induces a discharge gap to break down when it is near but has not achieved its self-breakdown conditions, is discussed. Specifically, threshold criteria that determine the number of electrons required to induce breakdown both to glow and arc discharges are presented. Numerical and theoretical predictions of

  16. Electric Characteristics of Rotational States positive parity in isotopes 170,172,174Yb

    E-print Network

    Usmanov, P N; Kassim, H Abu; Salikhbaev, U S

    2015-01-01

    Accounting for Coriolis mixing of experimentally known rotational bands with $K^{\\pi}< 3^+$, non-adiabatic effects in energy and electric characteristics of excited states are investigated, within phenomenological model. The energy and wave function structure of excited states are calculated. The finding reveals that the bands mixing has been found to have considerable impact on the wave function of low-lying states $0^+$ and $2^+$ bands. In addition, the probabilities of $E2$-- transitions have been calculated. The values from calculations of $B(E2)$-- transitions from $0_2^+$, $0_3^+$, $2_1^+$, and $2_2^+$ bands are compared with the experimental data.

  17. Multivariable robust controller for linear and angular velocities of Electrically-Powered Wheelchair using characteristic loci method

    Microsoft Academic Search

    Mohammad Nasser Saadatzi; Javad Poshtan

    2010-01-01

    A MIMO description of an Electrically-Powered Wheelchair (EPW) is developed using kinematics of non-holonomic mobile robots in addition to DC electric motors dynamics. The dynamics is augmented with an innovative static matrix in order to achieve diagonal dominance and to obtain a reliable estimation of the plant. Characteristic loci method is exploited to design a MIMO controller for the augmented

  18. Electrical Characteristics of Air-Bridge-Structured Silicon Nanowire Fabricated by Micromachining a Silicon-on-Insulator Substrate

    Microsoft Academic Search

    Hideo Fujii; Seigo Kanemaru; Takashi Matsukawa; Junji Itoh

    1999-01-01

    A new air-bridge-structured silicon nanowire was fabricated by micromachining a silicon-on-insulator (SOI) substrate and was then electrically characterized. The nanowire, which is isolated from the substrate by an air gap, is 15 100 nm in diameter and 300 600 nm in length. Electrical characteristics of p-type silicon nanowires under vacuum showed ambient dependency of conductance and anomalous electric conductivity such

  19. Dc breakdown of low pressure gas in long tubes

    Microsoft Academic Search

    V. A. Lisovskiy; V. A. Koval; V. D. Yegorenkov

    2011-01-01

    The gas breakdown was experimentally investigated in dc electrical field in long discharge tubes. The measurements were performed in the tube of radius R=4 mm, whereas the inter-electrode gap values varied in the range L=2-230 mm. The conventional Paschen law was shown to hold in short discharge tubes for which L\\/R1 the breakdown curves U(p) are shifted not only to

  20. Dc breakdown of low pressure gas in long tubes

    Microsoft Academic Search

    V. A. Lisovskiy; V. A. Koval; V. D. Yegorenkov

    2011-01-01

    The gas breakdown was experimentally investigated in dc electrical field in long discharge tubes. The measurements were performed in the tube of radius R=4 mm, whereas the inter-electrode gap values varied in the range L=2–230 mm. The conventional Paschen law was shown to hold in short discharge tubes for which L\\/R?1. At L\\/R>1 the breakdown curves Udc(p) are shifted not

  1. Electrical Characteristics of Air-Bridge-Structured Silicon Nanowire Fabricated by Micromachining a Silicon-on-Insulator Substrate

    NASA Astrophysics Data System (ADS)

    Fujii, Hideo; Kanemaru, Seigo; Matsukawa, Takashi; Itoh, Junji

    1999-12-01

    A new air-bridge-structured silicon nanowire was fabricated by micromachining a silicon-on-insulator (SOI) substrate and was then electrically characterized. The nanowire, which is isolated from the substrate by an air gap, is 15 100 nm in diameter and 300 600 nm in length. Electrical characteristics of p-type silicon nanowires under vacuum showed ambient dependency of conductance and anomalous electric conductivity such as negative resistance and hysteresis at room temperature. The change in the effective channel width resulting from the surface depletion of p-type silicon nanowire is considered to be a dominant characteristic.

  2. Probability characteristics of electrical noise in heterojunction light-emitting diodes

    SciTech Connect

    Sergeev, V. A., E-mail: sva@ulstu.ru; Frolov, I. V.; Shirokov, A. A.; Shcherbatyuk, Yu. N. [Ul'yanovsk State Technical University (Russian Federation)

    2011-12-15

    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.

  3. Enhancement of the electrical characteristics of metal-free phthalocyanine films using cold isostatic pressing

    NASA Astrophysics Data System (ADS)

    Matsushima, Toshinori; Esaki, Yu; Adachi, Chihaya

    2014-12-01

    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.

  4. Optical and electrical characteristics of air dielectric barrier discharges in mode transition at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Wang, Weiwei; Liu, Feng; Wang, Xue; Han, Haiyan; Huang, Yanbin; Liang, Rongqing

    2015-04-01

    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.

  5. Factors affecting foster care breakdown in Spain.

    PubMed

    López López, Mónica; del Valle, Jorge F; Montserrat, Carme; Bravo, Amaia

    2011-05-01

    Breakdown of foster care has been defined as the situation in which one of the involved parties terminates the intervention before having achieved the goals established for the case plan. This work presents a study carried out with a Spanish sample of 318 closed cases of children who were placed in foster homes and kinship care. The data were collected through the exhaustive review of the child protection and foster placement files, complemented with interviews of the welfare workers in charge of each case. The rate of breakdown of the entire sample was 26.1%, although it was significantly different in kinship care (19.7%) and foster care (31.2%). The results of this study indicate that the variables related to breakdown depend on the placement modality, either in foster care or kinship care. In the first case, the variables related to the child's characteristics are noteworthy, especially behavior and academic problems, with special relevance in the 9-12-year-old group, and in children who were previously in residential care. In contrast, in kinship care, the parents' problems (prison, mental health) and having some measure of guardianship are the most important. The fact of undergoing foster placement after having lived in various residential homes is transcendental. Lastly, the availability of economic resources and even the foster carers' studies seem to be related to foster breakdown. PMID:21568169

  6. Effect of molecular weight on the dielectric breakdown strength of ferroelectric poly(vinylidene fluoride-chlorotrifluoroethylene)s

    NASA Astrophysics Data System (ADS)

    Claude, Jason; Lu, Yingying; Wang, Qing

    2007-11-01

    The dielectric strengths of poly(vinylidene fluoride-chlorotrifluoroethylene) copolymers have been investigated as a function of molecular weights (MW) at different temperatures. We have shown that the electrical breakdown strength increases with increasing MW and decreasing temperature. Experimental measurements of the electrical breakdown field at 25°C agree fairly well with an electromechanical breakdown model. The dielectric breakdown at lower temperatures near and below the glass transition is attributed to the existence of thermal breakdown process, which is supported by numerical calculations and experimental measurements.

  7. Simulating and modeling the breakdown voltage in a semi-insulating GaAs P+N junction diode

    NASA Astrophysics Data System (ADS)

    Resfa, A.; Menezla, Brahimi. R.; Benchhima, M.

    2014-08-01

    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.

  8. Modelling of time-dependent dielectric barrier breakdown mechanisms in MgO-based magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Amara-Dababi, S.; Bea, H.; Sousa, R.; Mackay, K.; Dieny, B.

    2012-07-01

    An investigation of barrier endurance till electrical breakdown in MgO-based magnetic tunnel junctions (MTJs) is presented. Samples were tested under pulsed electrical stress. By studying the effect of delay between successive pulses, an optimum endurance of MTJs is observed for an intermediate value of delay between pulses corresponding to an optimum trade-off between the average density of charge trapped in the barrier and the amplitude of its time-modulation at each voltage pulse. A charge trapping-detrapping model was developed which shows good coherence with experimental results. The influence of the delay between pulses on the trapped charge density in the tunnel barrier and on its time-modulation is discussed. The average density of trapped charges and its time-modulation are, respectively, responsible for a static and dynamic stress within the tunnel barrier, both leading to breakdown. The probability of breakdown of the MTJ for different applied pulse conditions has been evaluated. The expected endurance of the MTJs was deduced depending on the characteristics of the electrical stress in terms of delay, and unipolarity versus bipolarity. The study emphasizes the role of electron trapping/detrapping mechanisms on the tunnel barrier reliability. It also shows that extremely long endurance could be obtained in MTJs by reducing the density of electron trapping sites in the tunnel barrier.

  9. Solar PV electricity and market characteristics: two Canadian case-studies

    Microsoft Academic Search

    Ian H. Rowlands

    2005-01-01

    To determine whether solar electricity (that is, electricity generated by photovoltaics) is, on an average, more valuable—in market terms—than the electricity generated in power systems as a whole, this article investigates the extent to which solar resource availability in two Canadian locations is associated with peak electricity market demand and peak electricity market price. More specifically, solar radiation and electricity

  10. Influence of contaminants on partial discharge characteristics for model XLPE transmission cable joints

    Microsoft Academic Search

    Z. Nadolny; J. M. Braun; R. J. Densley

    1998-01-01

    This paper describes the influence on partial discharge (PD) characteristics of contaminants at the EPR-epoxy interfaces of transmission-class cable joints. The contaminants used included paper fibers and metallic whiskers which could inadvertently be present at the joint interfaces. The contaminants considered increase the local electric field at the interface, leading to PD activity and breakdown. This paper presents the results

  11. Kerr electro-optic measurements for electric field and space charge distributions using similar and dissimilar electrode pairs

    E-print Network

    Nowocin, John Kendall

    2013-01-01

    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 ...

  12. Effects of nuclear radiation on a high-reliability silicon power diode. 4: Analysis of reverse bias characteristics

    NASA Technical Reports Server (NTRS)

    Been, J. F.

    1973-01-01

    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.

  13. Electric transport of a single-crystal iron chalcogenide FeSe superconductor: Evidence of symmetry-breakdown nematicity and additional ultrafast Dirac cone-like carriers

    NASA Astrophysics Data System (ADS)

    Huynh, K. K.; Tanabe, Y.; Urata, T.; Oguro, H.; Heguri, S.; Watanabe, K.; Tanigaki, K.

    2014-10-01

    An SDW antiferromagnetic (SDW-AF) low-temperature phase transition is generally observed and the AF spin fluctuations are considered to play an important role for the superconductivity pairing mechanism in FeAs superconductors. However, a similar magnetic phase transition is not observed in FeSe superconductors, which has caused considerable discussion. We report on the intrinsic electronic states of FeSe as elucidated by electric transport measurements under magnetic fields using a high quality single crystal. A mobility spectrum analysis, an ab initio method that does not make assumptions on the transport parameters in a multicarrier system, provides very important and clear evidence that another hidden order, most likely the symmetry broken from the tetragonal C4 symmetry to the C2 symmetry nematicity associated with the selective d -orbital splitting, exists in the case of superconducting FeSe other than the AF magnetic order spin fluctuations. The intrinsic low-temperature phase in FeSe is in the almost compensated semimetallic states but is additionally accompanied by Dirac cone-like ultrafast electrons ˜104cm2(VS) -1 as minority carriers.

  14. High-Power Microwave Breakdown of Dielectric Interfaces.

    NASA Astrophysics Data System (ADS)

    Calico, Steve Eugene

    A project to study the electrical breakdown of microwave windows due to high-power pulsed microwave fields was undertaken at Texas Tech University. The pulsed power equipment was acquired from the Air Force Weapons Laboratory in Albuquerque, NM, refurbished and redesigned as necessary, and serves as the high-power microwave source. The microwaves are used to test various vacuum to atmosphere interfaces (windows) in an attempt to isolate the mechanisms governing the electrical breakdown at the window. Windows made of three different materials and of three basic geometrical designs were tested in this experiment. Additionally, the surfaces of two windows were sanded with different grit sandpapers to determine the effect the surface texture has on the breakdown. The windows were tested in atmospheric pressure air, argon, helium, and to a lesser extent sulfur-hexafluoride. Estimates of the breakdown threshold in air and argon on a Lexan window were obtained as a consequence of these tests and were found to be considerably lower than that reported for pulsed microwave breakdown in gases. A hypothesis is presented in an attempt to explain the lower breakdown phenomena. A discussion of the comparative performance of the windows and an explanation as to the enhanced performance of some windows is given.

  15. Thickness and temperature dependences of the degradation and the breakdown for MgO-based magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Min; Song, Yun-Heub

    2015-03-01

    The reliability of a magnetic tunnel junction (MTJ) with an MgO tunnel barrier was evaluated. In particular, various voltage tests were used to investigate the effects of the barrier thickness and the temperature on the resistance drift. We compared the resistance change during a constant voltage stress (CVS) test and confirmed a trap/detrap phenomenon during the interval stress for different barrier thicknesses and temperatures. The resistance drift representing degradation and the time to breakdown (T BD ) representing the breakdown characteristic were better for a thicker barrier and lower temperature, but were worse for a thinner barrier and a higher temperature. The results suggest that breakdown and degradation due to trap generation strongly depend on both the barrier thickness and the temperature. Furthermore, as the TBD varies at steady rates with changing barrier thickness, temperature, and electric field, we assume that a MTJ with an adnormal thin layer of MgO can be screened effectively based on the predicted T BD . As a result, the barrier thickness and the temperature are very important in determining the reliability of a MTJ, and this study is expected to be helpful in understanding the degradation and the breakdown of a MTJ.

  16. The characteristics of Au:VO2 nanocomposite thin film for photo-electricity applications

    NASA Astrophysics Data System (ADS)

    Zhu, Yabin; Na, Jie; He, Fan; Zhou, Yueliang

    2013-08-01

    Au nanoparticles have been fabricated on normal glass substrates using nanosphere lithography (NSL) method. Vanadium dioxide has been deposited on Au/glass by reactive radio frequency (rf) magnetron sputtering. The structure and composition were determined by X-ray diffraction and X-ray photoelectron spectroscope. Electrical and optical properties of bare VO2 and Au:VO2 nanocomposite thin films were measured. Typical hysteresis behavior and sharp phase transition were observed. Nanopartical Au could effectively reduce the transition temperature to 40 °C. The transmittance spectrum for both Au:VO2 nanocomposite thin film shows high transmittance under transition temperature and low transmittance above transition temperature. The characteristics present the Au:VO2 nanocomposite thin film can be used for applications, such as “smart window” or “laser protector”.

  17. Ambient air effects on electrical characteristics of GaP nanowire transistors

    NASA Astrophysics Data System (ADS)

    Kang, Donghun; Ko, Ju-Hue; Bae, Eunju; Hyun, Jaewoong; Park, Wanjun; Kim, Byoung-Kye; Kim, Ju-Jin; Lee, Cheoljin

    2004-12-01

    Gallium phosphide (GaP) nanowire transistors were fabricated in back-gated structure, and their electrical characteristics were measured systematically in both air and vacuum. The transistors turn on typically between -5 and -7V in ambient air. However, a large threshold voltage (Vth) shift, ˜10V, toward negative gate bias was observed in vacuum. After the transistors were exposed to air for 48h, Vth returned to the similar value in ambient air, implying a reversible process. The rate of Vth shift slows down when they were exposed to N2 in comparison with that of air. The shift of Vth is believed to be related to the charge transfer from the surface of GaP nanowire to the physically adsorbed OH or oxygen. In addition, the observed Vth shift from the GaP nanowire transistors can be explained by the conventional n-channel depletion mode metal-oxide-semiconductor field-effect transistor.

  18. Hybrid nanocomposite based on cellulose and tin oxide: growth, structure, tensile and electrical characteristics

    NASA Astrophysics Data System (ADS)

    Mahadeva, Suresha K.; Kim, Jaehwan

    2011-10-01

    A highly flexible nanocomposite was developed by coating a regenerated cellulose film with a thin layer of tin oxide (SnO2) by liquid-phase deposition. Tin oxide was crystallized in solution and formed nanocrystal coatings on regenerated cellulose. The nanocrystalline layers did not exfoliate from cellulose. Transmission electron microscopy and energy dispersive x-ray spectroscopy suggest that SnO2 was not only deposited over the cellulose surface, but also nucleated and grew inside the cellulose film. Current-voltage characteristics of the nanocomposite revealed that its electrical resistivity decreases with deposition time, with the lowest value obtained for 24 h of deposition. The cellulose-SnO2 hybrid nanocomposite can be used for biodegradable and disposable chemical, humidity and biosensors.

  19. Electrical characteristics and interface structure of magnetic tunnel junctions with hafnium oxyfluoride barrier

    SciTech Connect

    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)

    2004-12-01

    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.

  20. Structural and electrical characteristics of Er{sub 2}TiO{sub 5} gate dielectrics

    SciTech Connect

    Pan, T.-M.; Shu, W.-H.; Hong, J.-L. [Department of Electronics Engineering, Chang Gung University, Taoyuan 333, Taiwan (China)

    2007-05-28

    The authors report on the structural and electrical characteristics of high-k erbium titanium oxide (Er{sub 2}TiO{sub 5}) gate dielectrics deposited on Si (100) substrates by reactive rf sputtering. They find that the capacitance value of Er{sub 2}TiO{sub 5} gate dielectric annealed at 700 deg. C is higher compared to other annealing temperatures and exhibits a lower hysteresis voltage as well as interface trap density in C-V curves. This dielectric also shows almost negligible charge trapping under high constant voltage stress. This phenomenon is attributed to an amorphous Er{sub 2}TiO{sub 5} structure and the suppression of the interfacial layer and Er silicate observed from x-ray diffraction and x-ray photoelectron spectroscopy, respectively.

  1. Size-dependence of the dielectric breakdown strength from nano- to millimeter scale

    NASA Astrophysics Data System (ADS)

    Neusel, Claudia; Schneider, Gerold A.

    2014-02-01

    Dielectric breakdown decisively determines the reliability of nano- to centimeter sized electronic devices and components. Nevertheless, a systematic investigation of this phenomenon over the relevant lengths scales and materials classes is still missing. Here, the thickness and permittivity-dependence of the dielectric breakdown strength of insulating crystalline and polymer materials from the millimeter down to the nanometer scale is investigated. While the dependence of breakdown strength on permittivity was found to be thickness-independent for materials in the nm-mm range, the magnitude of the breakdown strength was found to change from a thickness-independent, intrinsic regime, to a thickness-dependent, extrinsic regime. The transition-thickness is interpreted as the characteristic length of a breakdown-initiating conducting filament. The results are in agreement with a model, where the dielectric breakdown strength is defined in terms of breakdown toughness and length of a conducting filament.

  2. Multiple performance characteristics optimization for Al 7075 on electric discharge drilling by Taguchi grey relational theory

    NASA Astrophysics Data System (ADS)

    Khanna, Rajesh; Kumar, Anish; Garg, Mohinder Pal; Singh, Ajit; Sharma, Neeraj

    2015-05-01

    Electric discharge drill machine (EDDM) is a spark erosion process to produce micro-holes in conductive materials. This process is widely used in aerospace, medical, dental and automobile industries. As for the performance evaluation of the electric discharge drilling machine, it is very necessary to study the process parameters of machine tool. In this research paper, a brass rod 2 mm diameter was selected as a tool electrode. The experiments generate output responses such as tool wear rate (TWR). The best parameters such as pulse on-time, pulse off-time and water pressure were studied for best machining characteristics. This investigation presents the use of Taguchi approach for better TWR in drilling of Al-7075. A plan of experiments, based on L27 Taguchi design method, was selected for drilling of material. Analysis of variance (ANOVA) shows the percentage contribution of the control factor in the machining of Al-7075 in EDDM. The optimal combination levels and the significant drilling parameters on TWR were obtained. The optimization results showed that the combination of maximum pulse on-time and minimum pulse off-time gives maximum MRR.

  3. An integrated measurement system for LED thermal, optical and electrical characteristics

    NASA Astrophysics Data System (ADS)

    Zou, Xiyong; Zheng, Xiaoming; Jin, Shangzhong; Ni, Kai; Zhou, Huaming; He, Xianqi

    2008-03-01

    Thermal, optical and electrical parameters are main characterization of light-emitting diodes (LEDs). Consumers are often concerned about the explicit properties such as luminous intensity, luminous flux and color. But Manufacturers may pay more attention to the thermal characteristic. Excess heat at the junction directly affects the LED performance in terms of color shit, light output and life. To measure all these parameters of LED accurately and simultaneously, we designed an integrated system, product number SSP8112, which was based on a new developed thermal, optical and electrical measurement instrument and a specially-made integrating sphere with temperature controller. The thermal measurement segment of the instrument was developed in accordance with JESD51-1 standard; it can automatically record the transient response curve of heat with a 50?s time resolution and a 0.5mV voltage resolution. And the integrating sphere, which has high light reflectivity, good thermal insulation and tolerance to high temperature, was used to achieve the optical response during the experiment. The principle and structure of this system were introduced and discussed, and at the end an application example was presented.

  4. Deep-level dominated electrical characteristics of Au contacts on beta-SiC

    NASA Technical Reports Server (NTRS)

    Das, K.; Kong, H. S.; Petit, J. B.; Bumgarner, J. W.; Davis, R. F.; Matus, L. G.

    1990-01-01

    Electrical characteristics of Au contacts on beta-SiC films, grown epitaxially on both nominal and off-axis (100) silicon substrates, are reported. An analysis of the logarithmic I-V plots of the Au/beta-SiC diodes revealed information pertaining to the deep states present in the materials. It was found that while the beta-SiC films grown on nominally (100) oriented substrates show the presence of two deep levels located between 0.26 and 0.38 eV below the conduction bandedge, the beta-SiC films deposited on off-axis substrates have only one deep level, located about 0.49 eV below the conduction bandedge for the 2-deg off (100) substrates and 0.57 eV for the 4-deg off (100) substrates. The presence of the shallower deep states in the beta-SiC films grown on nominal (100) substrates is attributed to the electrical activity of antiphase domain boundaries.

  5. Nanocrystalline non-stoichiometric SBT: Effect of milling duration on structural and electrical characteristics

    SciTech Connect

    Sugandha, E-mail: miglani.sugandha@gmail.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: Prof.akjha@gmail.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)

    2012-03-15

    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.

  6. An analysis of electrical and optical characteristics of a type II superlattice for optical switching applications

    NASA Astrophysics Data System (ADS)

    Rahman, M.; Rouf, A. S. M. S.; Mohammedy, F. M.

    2015-06-01

    The present work demonstrates an analysis of electronic and optical characteristics of InAs/GaSbType II superlattice based photodetectors. The electronic characteristics are analyzed by developing a model of the Type II superlattice. The 8 band k.p method is implemented to deduce the wavefunctions. The effects of temperature on zero-bias resistance- area product (R0A) are also included in the model. The newly proposed M-Structure design method is also implemented for our model. Electrical and optical properties of the material such as dark current density and absorption coefficient are calculated. At 50mV reverse bias, the dark current density is found equal to 1.5×10-4 A/cm2. These calculations are done based on the approximation based models of reflectivity. These results were used to demonstrate the variation of optical properties with applied bias voltage to be used as a novel optical switching technique in WDM based communication networks.

  7. The Effect of Risk Characteristics on the Willingness to Pay for Mortality Risk Reductions from Electric Power Generation

    Microsoft Academic Search

    Kenshi Itaoka; Aya Saito; Alan Krupnick; Wiktor Adamowicz; Taketoshi Taniguchi

    2006-01-01

    The objective of this study is to estimate willingness to pay (WTP) for the reduction of mortality risks caused by fossil\\u000a fuel (natural gas, coal and oil) versus nuclear electric power generation systems and to examine the influence of risk characteristics\\u000a involved with electric power generation on WTP. A choice experiment was conducted to achieve these objectives. The attributes\\u000a for

  8. Multipactor breakdown - Lessons unlearned

    NASA Astrophysics Data System (ADS)

    August, G.

    1984-03-01

    Multipactor breakdown in satellites continues to reappear as a problem every few years, even through there is adequate knowledge to avoid it. The failures occur most often in transmission lines, filters, connectors, and switches. Multipactor and gas discharge problems have occurred for many reasons: including RF analyses and inadequate testing. Usually the multipactor problems were not discovered until the satellites were in thermal-vacuum qualification tests, or in orbit. Even where corrective steps were possible, they frequently were expensive and time-consuming and had undesireable side-effects. The occurrence of multipactor problems on satellites, despite the large body of knowledge about the multipactor breakdown process, shows that lessons from previous satellite programs were not learned or have been forgotten. Satellite project managers need to provide adequate manuals suitable for both design and testing; insist on complete RF system analyses; and ensure that adequate testing occurs sufficiently early in the development program. The payoff will be avoidance of very costly and time-consuming program delays to correct problems that should not have occurred at this present state of knowledge.

  9. Study of Bulk and Elementary Screw Dislocation Assisted Reverse Breakdown in Low-Voltage (<250 V) 4H-SiC p+n Junction Diodes - Part 1: DC Properties

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Huang, Wei; Dudley, Michael

    1999-01-01

    Given the high density (approx. 10(exp 4)/sq cm) of elementary screw dislocations (Burgers vector = lc 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.

  10. Electric Field Statistics and Modulation Characteristics of Bursty Langmuir Waves Observed in the Cusp

    NASA Astrophysics Data System (ADS)

    Labelle, J.; Cairns, I. H.; Kletzing, C. A.

    2008-12-01

    The Twin Rockets to Investigate Cusp Electrodynamics (TRICE) were launched Dec. 10, 2007, from Andoya into the active cusp over Svalbard. The high-frequency electric field waveform receiver on the higher flying payload detected Langmuir waves concentrated at 900-1145 km on the downleg. The waves occurred in bursts having durations between tens of ms and a few hundred ms. From analysis of selected sample intervals, it is estimated that the rocket encountered more than 1000 such bursts ranging in amplitude from about 1 mV/m, near the detection threshold, to nearly 1000 mV/m, though only a few bursts approached this upper bound. Waveform analysis showed that the waves were modulated at kHz to tens of kHz frequencies. The modulation was not monochromatic but consisted of many nonstationary frequency components giving rise to a complex envelope waveform. The modulated waves were sufficiently oversampled to clearly observe 180-degree phase shifts when the envelopes of the modulations passed through zero, as expected if a superposition of modulating waves is responsible. Dynamic spectra of the bursts showed that the bandwidth of each event was related to the modulation frequencies. The dynamic spectra also revealed a repeatable pattern whereby the highest Langmuir wave frequency and largest bandwidth occurred in the center of each burst, with frequency and bandwidth decreasing toward either side of each burst. For the conditions of the observations (fpe ? fce/2), Langmuir waves convert to whistler mode waves, and the observed pattern may be explained by trapping of the Langmuir/whistler waves in density enhancements. The observed wave electric fields were statistically analyzed in two ways: First, the distribution of the absolute values of all of the electric field measurements was determined, hereafter referred to as the "waveform distribution"; second, the envelope of the Langmuir waves was extracted and the distribution of this field was determined, hereafter referred to as the "envelope distribution". The waveform distribution showed a characteristic E+1 dependence at low electric fields. Bandpass-filtering the waves with progressively narrower passbands preserved the E+1 dependence but with a sharper cutoff at the high-electric field end, approaching the analytical expectation for a rectified sine wave. The envelope distribution showed a steeper power-law index at low electric fields. Averaging the waveforms by factors of 10-300 produced waveform distributions with a power index comparable to that of the envelope distribution, as expected since averaging by 10 corresponded to half the wave period so that the resulting statistics were dominated by the envelope. Averaging by factors greater than about 300, corresponding to averaging times exceeding about half of the modulation period, led to waveform distributions that appeared Gaussian although they were not well defined due to the small number of points. The relation between the waveform and envelope distributions appeared to be well explained by recent analytical predictions confirmed by numerical calculations [Cairns et al., Statistics of Waveform and Envelope Fields: Theory, Simulations and Initial Applications to TRICE Data, EOS Trans. Am. Geophys. Union, 2008, this issue]. The observed envelope distributions also appear consistent with theory [Kletzing et al., Determination of the Envelope Distribution for Langmuir Waves in the Topside Ionosphere, EOS Trans. Am. Geophys. Union, 2008, this issue].

  11. Phase-field model for dielectric breakdown in solids Krishna Chaitanya Pitike and Wei Hong*

    E-print Network

    Hong, Wei

    are often several orders of magnitude lower than the intrinsic strengths predicted by microscopic models1 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

  12. A quantitative physical model for time-dependent breakdown in SiO2

    Microsoft Academic Search

    I. C. Chen; S. Holland; C. Hut

    1985-01-01

    A quantitative physical breakdown model for thin SiO2 is developed. The physical mechanism responsible fcor oxide breakdown has been reexamined and found to be hole trapping at localized areas. A quantitative model is built on this physical understanding of the wearout mechanism. Using this model, which considers electron injection, hole generation and charge trapping during electrical stresses and their effects

  13. Electrical properties of epoxy resin based nano-composites

    SciTech Connect

    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

    2007-01-01

    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.

  14. Electron irradiation effect on minority carrier lifetime and other electrical characteristics in silicon power devices

    NASA Astrophysics Data System (ADS)

    Fuochi, P. G.; Di Marco, P. G.; Monti, A.; Bisio, G. M.; Di Zitti, E.; Passerini, B.; Tenconi, S.

    Irradiation of silicon power rectifiers with electrons of 12 MeV energy has been carried out. Minority carrier lifetime ?, forward voltage V F, reverse recovered charge Q RR, reverse recovery time t RR for the diodes, circuit commutated turn-off time t q, and on-state voltage V T for the thyristors are measured as a function of dose. Power diodes and thyristors obtained from <111> neutron transutation or phosphorus doped float-zone silicon slices having 120?cm and 65?cm starting resistivity respectively and Ga-diffused are irradiated at room temperature. A linear relationship between carrier lifetime of irradiated diodes and electron dose is found and the calculated damage coefficients are k ? = 1.1x10 -8 cm 2/s and 7.2x10 -9 cm 2/s for the low-level and high-level lifetimes respectively at 25°C. For irradiated thyristors the linear relationship between turn-off time and dose yields k tq = 3x10 -9 cm 2/s at 125°C. Electron irradiation also affects the resistivity of the starting n-type silicon, increasing it of ? 15?cm for radiation doses > 1×10 4 Gy. A dose rate effect on the electrical characteristics of the devices using pulses of different duration is analyzed. Annealing studies are carried out at 150 °C, 200°C and 360°C to assess the stability of the defects produced by the electron bombardment by monitoring the variation of the electrical characteristics of the irradiated devices in the temperature range of interest. DLTS measurements performed on electron irradiated power rectifiers have revealed a complex defect pattern. The E 1 defect level (E c-0.17 ev) is the principal recombination center that controls lifetime following room temperature irradiation. The energy levels and capture cross sections of these irradiation induced-defects are reported. This study confirms that lifetime control in silicon power devices is feasible by high energy electrons. The major advantages of this technique over metallic diffusion or 60Co ?-irradiation methods are: better quality, lower processing cost and higher device yields. Annealing after irradiation is important to ensure long-term device stability.

  15. Optical breakdown threshold investigation of 1064 nm laser induced air plasmas

    SciTech Connect

    Thiyagarajan, Magesh; Thompson, Shane [Plasma Engineering Research Lab (PERL), College of Science and Engineering, Texas A and M University-Corpus Christi, Texas 78412 (United States)

    2012-04-01

    We present the theoretical and experimental measurements and analysis of the optical breakdown threshold for dry air by 1064 nm infrared laser radiation and the significance of the multiphoton and collisional cascade ionization process on the breakdown threshold measurements over pressures range from 10 to 2000 Torr. Theoretical estimates of the breakdown threshold laser intensities and electric fields are obtained using two distinct theories namely multiphoton and collisional cascade ionization theories. The theoretical estimates are validated by experimental measurements and analysis of laser induced breakdown processes in dry air at a wavelength of 1064 nm by focusing 450 mJ max, 6 ns, 75 MW max high-power 1064 nm IR laser radiation onto a 20 {mu}m radius spot size that produces laser intensities up to 3 - 6 TW/cm{sup 2}, sufficient for air ionization over the pressures of interest ranging from 10 to 2000 Torr. Analysis of the measured breakdown threshold laser intensities and electric fields are carried out in relation with classical and quantum theoretical ionization processes, operating pressures. Comparative analysis of the laser air breakdown results at 1064 nm with corresponding results of a shorter laser wavelength (193 nm) [M. Thiyagarajan and J. E. Scharer, IEEE Trans. Plasma Sci. 36, 2512 (2008)] and a longer microwave wavelength (10{sup 8} nm) [A. D. MacDonald, Microwave Breakdown in Gases (Wiley, New York, 1966)]. A universal scaling analysis of the breakdown threshold measurements provided a direct comparison of breakdown threshold values over a wide range of frequencies ranging from microwave to ultraviolet frequencies. Comparison of 1064 nm laser induced effective field intensities for air breakdown measurements with data calculated based on the collisional cascade and multiphoton breakdown theories is used successfully to determine the scaled collisional microwave portion. The measured breakdown threshold of 1064 nm laser intensities are then scaled to classical microwave breakdown theory after correcting for the multiphoton ionization process for different pressures and good agreement, regarding both pressure dependence and breakdown threshold electric fields, is obtained. The effect of the presence of submicron particles on the 1064 nm breakdown threshold was also investigated. The measurements show that higher breakdown field is required, especially at lower pressures, and in close agreement with classical microwave breakdown theory and measurements in air.

  16. Multiscale mechanisms of SRF breakdown A. Gurevich *

    E-print Network

    Multiscale mechanisms of SRF breakdown A. Gurevich * Applied Superconductivity Center, University of Wisconsin, 1500 Johnson Drive, ERB, Madison, WI 53706, USA Abstract Multiscale mechanisms of SRF breakdown

  17. Electrical and noise characteristics of graphene field-effect transistors: ambient effects, noise sources and physical mechanisms

    E-print Network

    . Special attention was given to determining the dominant noise sources in these devices and the effect.1088/0953-8984/22/39/395302 Electrical and noise characteristics of graphene field-effect transistors: ambient effects, noise sources-frequency electronic noise come from the graphene layer itself rather than from the contacts. Aging of graphene

  18. Effects of illumination and 60Co ?-ray irradiation on the electrical characteristics of porous silicon solar cells

    Microsoft Academic Search

    Ö. Tüzün; ?. Alt?ndal; ?. Oktik

    2008-01-01

    A new approach for hybrid metal–insulator–semiconductor (MIS) Si solar cells is adopted by Institute of Fundamental Problems for High Technology, Ukrainian Academy of Sciences. In order to interpret the effect of illumination and 60Co ?-ray radiation dose on the electrical characteristics of solar cells are studied at room temperature. Before the solar cells are subjected to stressed irradiation six different

  19. Fabrication, characteristics and electrical model of an ionic polymer metal-carbon nanotube composite

    NASA Astrophysics Data System (ADS)

    He, Qingsong; Song, Linlin; Yu, Min; Dai, ZhenDong

    2015-07-01

    We develop an ionic polymer metal-carbon nanotube composite (IPMCC) actuator composed of a multiwalled carbon nanotube (MWCNT)/Nafion membrane sandwiched between two hybrid electrodes, composed of palladium, platinum and MWCNTs. The surface morphology and cross-sectional structure of the metal-carbon nanotube hybrid electrode were observed using scanning electron microscopy (SEM). SEM investigation indicated that the MWCNT layer can adhere very well with the platinum–palladium metal electrode, fill the cracks in the metal surface, and prevent the oxidation of nanoscale platinum particles. These observations show that the surface resistance of the total electrode is retained and the stability of electrode property is maintained. The displacement, blocking force and nonlinear current versus voltage (V–I) characteristics were measured. Compared with an ionic polymer metal composite (IPMC), the IPMCC shows a more stable displacement and blocking force under 1, 1.2 and 2 V at 0.1 Hz, and 2.34–3.29 times higher effective air-operating time under 3 V at 0.1 Hz. It can be observed from the V–I characteristics that the change in shape becomes significant at amplitudes higher than 1.2 V. An equivalent circuit is used to model the nonlinear behavior of the IPMCC, in which the leakage current was taken into account and analyzed. The values of the components in the circuit are estimated and electrical behavior is simulated by using the Pspice software. Compared with the model with no consideration of the leakage current, the simulations obtained by the model considering leakage current showed better agreement with the experimental results. The impressive leakage current (20 mA), which is successfully simulated by the proposed model with the nonlinear circuit, is shown to play an important role in the total current.

  20. DC Breakdown of Low Pressure Gas in Long Tubes

    NASA Astrophysics Data System (ADS)

    Lisovskiy, Valeriy; Koval, Veronika; Yegorenkov, Vladimir

    2009-10-01

    We studied the dc breakdown of low pressure nitrogen in the pressure range p = 0.1 -- 2 Torr. The measurements were performed in the tube of radius R = 4 mm, whereas the inter-electrode gap values varied in the range L = 2 -- 250 mm. The conventional Paschen law was shown to hold in short discharge tubes for which L/R <= 1. At L/R > 1 the increase of the inter-electrode distance shifts the breakdown curves U(p) to higher breakdown voltage values U and lower gas pressure ones (larger products of gas pressure and inter-electrode distance pL). The breakdown curve minima lie on the same straight line. At L/R > 10 increasing L makes the dc breakdown curves to shift to higher U values, their minima being observed almost at the same gas pressure value. Perhaps the electrons escaping to the tube walls due to diffusion perturb the electric field distribution and affect the development of the gas breakdown.

  1. Dielectric breakdown induced by picosecond laser pulses

    NASA Technical Reports Server (NTRS)

    Smith, W. L.; Bechtel, J. H.; Bloembergen, N.

    1976-01-01

    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.

  2. Metastable electrical characteristics of polycrystalline thin-film photovoltaic modules upon exposure and stabilization

    NASA Astrophysics Data System (ADS)

    Deline, Chris A.; del Cueto, Joseph A.; Albin, David S.; Rummel, Steve R.

    2011-09-01

    The significant features of a series of stabilization experiments conducted at the National Renewable Energy Laboratory (NREL) between May 2009 and the present are reported. These experiments evaluated a procedure to stabilize the measured performance of thin-film polycrystalline cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) thin-film photovoltaic (PV) modules. The current-voltage (I-V) characteristics of CdTe and CIGS thin-film PV devices and modules exhibit transitory changes in electrical performance after thermal exposure in the dark and/or bias and light exposures. We present the results of our case studies of module performance versus exposure: light-soaked at 65°C exposed in the dark under forward bias at 65°C and, finally, longer-term outdoor exposure. We find that stabilization can be achieved to varying degrees using either light-soaking or dark bias methods and that the existing IEC 61646 light-soaking interval may be appropriate for CdTe and CIGS modules with one caveat: it is likely that at least three exposure intervals are required for stabilization.

  3. Electrospraying in a complex electrical field: jet formation and characteristics of final product

    NASA Astrophysics Data System (ADS)

    Khodadadi, Sheila; Rovers, Kirsten; Meesters, Gabriel; TUDelft-Delft project managment Team

    2015-03-01

    The electrohydrodynamic atomization (EDHA) of liquid solutions is a technique developed to produce micro and nanometer size droplets. It consists of breaking a liquid jet by applying electrical forces. EHDA is one of the most suitable techniques for drug delivery and bio-nanotechnology, when precise (nm- ?m) particle size and narrow size distribution is needed. However there are some challenges facing application of this technique such as limitation in flow rate, characteristics of liquids (surface tension, conductivity,...), and the possible droplet size reduction due to evaporation of the liquid and Coulomb fission. To tackle these challenges in an EHDA-based inhalation device, we explored different possibilities to reach a stable mode in terms of jet formations, droplet-particle size and size distribution. In this contribution, we demonstrate how device configuration and operational conditions influence the electrosprayed liquid and final product. We will also discuss how our approach can be used to tailor morphological properties of nanostructured materials with identical chemical compositions.

  4. Mechanical and electric characteristics of vacuum impregnated no-insulation HTS coil

    NASA Astrophysics Data System (ADS)

    Park, Heecheol; Kim, A.-rong; Kim, Seokho; Park, Minwon; Kim, Kwangmin; Park, Taejun

    2014-09-01

    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.

  5. Metastable Electrical Characteristics of Polycrystalline Thin-Film Photovoltaic Modules upon Exposure and Stabilization: Preprint

    SciTech Connect

    Deline, C. A.; del Cueto, J. A.; Albin, D. S.; Rummel, S. R.

    2011-09-01

    The significant features of a series of stabilization experiments conducted at the National Renewable Energy Laboratory (NREL) between May 2009 and the present are reported. These experiments evaluated a procedure to stabilize the measured performance of thin-film polycrystalline cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) thin-film photovoltaic (PV) modules. The current-voltage (I-V) characteristics of CdTe and CIGS thin-film PV devices and modules exhibit transitory changes in electrical performance after thermal exposure in the dark and/or bias and light exposures. We present the results of our case studies of module performance versus exposure: light-soaked at 65 degrees C; exposed in the dark under forward bias at 65 degrees C; and, finally, longer-term outdoor exposure. We find that stabilization can be achieved to varying degrees using either light-soaking or dark bias methods and that the existing IEC 61646 light-soaking interval may be appropriate for CdTe and CIGS modules with one caveat: it is likely that at least three exposure intervals are required for stabilization.

  6. Electrical percolation characteristics of metallic single-walled carbon nanotube networks by vacancy evolution.

    PubMed

    Kim, Do-Hyun; Jin, Jun Eon; Piao, Mingxing; Choi, Jun Hee; Kim, Gyu Tae

    2014-09-14

    In the present study, we demonstrate the effect of vacancy evolution on high-pure metallic single-walled carbon nanotube (m-SWCNT) networks by observing the electrical characteristics of the networks on the field-effect transistor (FET). By catalytic oxidation using Co catalyst, vacancy evolution was gradually realized in high-pure m-SWCNT formed as networks between source-drain electrodes of FET. The evolution of vacancy defects in the m-SWCNT networks gradually proceeded by heating FET several times at 250 °C in air. Atomic force microscopic images showed the presence of the Co catalyst nanoparticles, which were evenly formed in the m-SWCNT networks between the electrodes of FET. Vacancy evolution was confirmed by monitoring the D- and G-bands in the Raman spectra measured from the networks after every step of the catalytic oxidation. With vacancy evolution in the networks, the D-band gradually increased, and the transconductance of m-SWCNT networks drastically decreased. In addition, the metallic behaviour of the m-SWCNT networks was converted into a semiconducting one with an on/off ratio of 2.7. PMID:25069594

  7. Improving the electrical characteristics of graphene field effect transistors by hexamethyldisilazane interaction

    NASA Astrophysics Data System (ADS)

    Chowdhury, Sk.; Rahimi, Somayyeh; Sonde, Sushant; Tao, Li; Banerjee, Sanjay; Akinwande, Deji

    2014-03-01

    We report the improvement of the electrical characteristics of graphene field effect transistors (FET) by hexamethyldisilazane (HMDS) passivation. Sample is left in liquid HMDS after complete back gated FET fabrication. Both electron and hole field effect mobilities are improved by 1.5X - 2X, accompanied by effective residual carrier concentration reduction. Dirac voltage also moves closer to zero. Various techniques for HMDS application are investigated. Time evolution of mobility data shows that mobility improvement saturates after a few hours of HMDS dosing. Temperature-dependent transport measurements show small mobility variation between 77K and room temperature (295K) before HMDS application. But mobility at 77K is almost 2 times higher than mobility at 295K after HMDS application. The best CVD devices achieve a mobility of ~ 20,000 cm2/V-s at 77K. Performance improvement is observed for FETs made with exfoliated graphene and for FETs made on hydrophobic substrate- an HMDS-graphene-HMDS sandwich structure. Raman spectroscopic analysis shows that G peak width is increased, G peak position is down shifted and intensity ratios between 2D and G peak is increased after HMDS application. AFM data shows increased RMS roughness after HMDS application.

  8. Electricity

    NSDL National Science Digital Library

    Miss Lerdahl

    2010-02-23

    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. ...

  9. Threshold energy effect on avalanche breakdown voltage in semiconductor junctions

    Microsoft Academic Search

    Y. Okuto; C. R. Crowell

    1975-01-01

    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

  10. High-Power Microwave Breakdown of Dielectric Interfaces

    Microsoft Academic Search

    Steve Eugene Calico

    1991-01-01

    A project to study the electrical breakdown of microwave windows due to high-power pulsed microwave fields was undertaken at Texas Tech University. The pulsed power equipment was acquired from the Air Force Weapons Laboratory in Albuquerque, NM, refurbished and redesigned as necessary, and serves as the high-power microwave source. The microwaves are used to test various vacuum to atmosphere interfaces

  11. The Relationship Between Continuing Current and Positive Breakdown

    NASA Astrophysics Data System (ADS)

    Lapierre, J. L.; Sonnenfeld, R. G.; Stock, M.; Edens, H. E.; Hager, W. W.; Thomas, R. J.

    2013-12-01

    Continuing currents (CCs) during negative cloud to ground discharges have long been theorized to be dependent on the associated positive breakdown activity, yet direct evidence has remained elusive. Data from the Langmuir Electric Field Array (LEFA, 0.3 Hz-50 kHz electric field change), Lightning Mapping Array (LMA, 66 MHz narrowband RF), and Continuous Digital Interferometer (Continuous DITF, 20-80 MHz broadband RF), obtained at Langmuir Laboratory, are being used to analyze the dependence of CCs on positive breakdown branching and growth. The primary flash analyzed was a bolt-from-the-blue that occurred on August 14, 2012 and had 6 return strokes (RSs), 3 of which produced CCs. We used the high time resolution of the Continuous DITF to determine when each RS ended, and the LMA data to detect positive breakdown growth subsequent to the RSs, including any CC. We found that CCs occurred only after the positive breakdown started developing multiple branches. The branches appeared to be continually developing during the CCs, hence providing the source of charge for the CC. We also found that longer CCs were associated with more positive leader channel branching and growth, implying that CC duration depends on the activity of the positive breakdown. These analyses are continuing to be applied to other flashes, yielding similar results. Ultimately, the study of CCs will improve our understanding of negative RSs, the most common form of cloud-to-ground lightning.

  12. Propagation characteristics of a focused laser beam in a strontium barium niobate photorefractive crystal under reverse external electric field.

    PubMed

    Guo, Q L; Liang, B L; Wang, Y; Deng, G Y; Jiang, Y H; Zhang, S H; Fu, G S; Simmonds, P J

    2014-10-01

    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

  13. Scalable Methods for the Analysis and Optimization of Gate Oxide Breakdown Jianxin Fang, Sachin S. Sapatnekar

    E-print Network

    Sapatnekar, Sachin

    Scalable Methods for the Analysis and Optimization of Gate Oxide Breakdown Jianxin Fang, Sachin S- nomenon. The time-to-breakdown characteristic for a MOS transistor is typically modeled as a Weibull. Precise analysis or measured results on very small circuits, such as op amps, nor gates, ring oscillators

  14. High field breakdown of narrow quasi uniform field gaps in vacuum

    Microsoft Academic Search

    P. G. Muzykov; Xianyun Ma; D. I. Cherednichenko; T. S. Sudarshan

    1999-01-01

    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

  15. Probabilistic Description of Traffic Breakdowns Caused by On-ramp Flow

    Microsoft Academic Search

    Reinhart Kuhne; Ihor Lubashevsky; Reinhard Mahnke; Jevgenijs Kaupush

    2004-01-01

    The characteristic features of traffic breakdown near on-ramp are analyzed. To describe this phenomenon the probabilistic description regarding the jam emergence as the formation of a large car cluster on highway inside the synchronized traffic is constructed. In these terms the breakdown occurs through the formation of a certain critical nucleus in the metastable vehicle flow, which is located near

  16. An experimental study on vortex breakdown in a differentially-rotating cylindrical container

    Microsoft Academic Search

    Kazuyuki Fujimura; Hide S. Koyama; JaeMin Hyun

    2004-01-01

    The vortex breakdown phenomenon in a closed cylindrical container with a rotating endwall disk was reproduced. Visualizations were performed to capture the prominent flow characteristics. The locations of the stagnation points of breakdown bubbles and the attendant global flow features were in excellent agreement with the preceding observations. Experiments were also carried out in a differentially-rotating cylindrical container in which

  17. Unseen emitter-base breakdown in RF power amplifiers- a possible hazard

    Microsoft Academic Search

    N. O. Sokal

    1977-01-01

    RF power amplifier circuits other than Class A have a previously unreported operating characteristic which can cause emitter-base reverse breakdown once each RF cycle. The breakdown is not necessarily observable at the external terminals of the transistor; it can be deduced from the observed emitter-base terminal voltage and base current and the transistor internal lead inductances and junction capacitances. Certain

  18. Charge transport and breakdown physics in liquid/solid insulation systems

    E-print Network

    Jadidian, Jouya

    2013-01-01

    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 ...

  19. Driving force characteristics of 40kW switched reluctance motor for electric vehicle

    Microsoft Academic Search

    K. Watanabe; S. Aida; A. Komatsuzaki; I. Miki

    2007-01-01

    There is a growing interest in an electric vehicle (EV), a hybrid-electric vehicle and a fuel-cell vehicle due to air pollution and exhaustion of fossil fuels. These vehicles use motors to obtain the driving force. Switched reluctance motors (SRMs) have a simple structure, high reliability and low cost. Furthermore, these are desirable features for electric vehicle. Our purpose is conversion

  20. Microwave breakdown of air initiated by a short electromagnetic vibrator

    Microsoft Academic Search

    K. V. Aleksandrov; L. P. Grachev; I. I. Esakov

    2007-01-01

    The electrical breakdown of air (under a pressure from several tens of Torr to several hundreds of Torr) is initiated in a\\u000a linearly polarized quasi-optical microwave beam using a rounded-end cylindrical metallic electromagnetic vibrator placed parallel\\u000a to the electric component of the microwave field. The vibrator is much shorter than the wavelength of the field. The field\\u000a strength at the

  1. Fractal Dimension of Dielectric Breakdown

    Microsoft Academic Search

    L. Niemeyer; L. Pietronero; H. J. Wiesmann

    1984-01-01

    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.

  2. An electromagnetic vibrator fixed on a screen initiates gas breakdown in the subcritical field of a microwave beam

    NASA Astrophysics Data System (ADS)

    Aleksandrov, K. V.; Grachev, L. P.; Esakov, I. I.; Severinov, L. G.

    2014-03-01

    Results of experimental investigation of the electric breakdown of air in a quasi-optical microwave beam with a deep subcritical field level are presented. The breakdown was initiated by a linear or ?-shaped electromagnetic (EM) vibrator fixed on a screen. It is established that a vibrator positioned above the screen at a distance shorter than quarter-wavelength of the EM field can induce the electric breakdown of air at high pressures and relatively low field level. Using a ?-shaped EM vibrator, it is possible to preset the spatial region of breakdown.

  3. Threshold criteria for undervoltage breakdown

    Microsoft Academic Search

    James E. Cooley; Edgar Y. Choueiri

    2008-01-01

    The conditions under which an externally supplied pulse of electrons will induce breakdown in an undervoltaged, low-gain discharge gap are experimentally and theoretically explored. The minimum number of injected electrons required to achieve breakdown in a parallel-plate gap is measured in argon at pd values of 3–10 Torr m using ultraviolet laser pulses to photoelectrically release electrons from the cathode.

  4. Threshold criteria for undervoltage breakdown

    Microsoft Academic Search

    James E. Cooley; Edgar Y. Choueiri

    2008-01-01

    The conditions under which an externally supplied pulse of electrons will induce breakdown in an undervoltaged, low-gain discharge gap are experimentally and theoretically explored. The minimum number of injected electrons required to achieve breakdown in a parallel-plate gap is measured in argon at pd values of 3-10 Torr m using ultraviolet laser pulses to photoelectrically release electrons from the cathode.

  5. Lifetime modeling of intrinsic gate oxide breakdown at high temperature

    Microsoft Academic Search

    R. Moonen; P. Vanmeerbeek; G. Lekens; Ward De Ceuninck; P. Moens; J. Boutsen

    2007-01-01

    High resolution time-dependent dielectric breakdown tests are carried out on 7.2nm gate oxide capacitors (n-type) in the electric field range 8.3–13.2MV\\/cm at high temperatures (160–240°C). It is proven that even at these high temperatures log(tBD) is proportional to 1\\/EOX and the time-to-breakdown mechanism matches the anode hole injection (AHI) model (1\\/EOX model). In addition it is presented that the TDDB

  6. Electrical performance characteristics of high power converters for space power applications

    NASA Technical Reports Server (NTRS)

    Stuart, Thomas A.; King, Roger J.

    1989-01-01

    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.

  7. Electrical characteristics of AlGaN\\/GaN metal-insulator semiconductor heterostructure field-effect transistors on sapphire substrates

    Microsoft Academic Search

    W. S. Tan; P. A. Houston; G. Hill; R. J. Airey; P. J. Parbook

    2003-01-01

    The electrical performance of AlGaN\\/GaN metal-insulator semiconductor, heterostructure field-effect transistors (MISHFETs)\\u000a were studied and compared to passivated and unpassivated HFETs. Record MISHFET current densities up to 1,010 mA\\/mm were achieved,\\u000a and the devices exhibited stable operation at elevated temperatures up to 200C. Higher maximum-drain current, breakdown voltage,\\u000a and a lower gate-leakage current were obtained in the MISHFETs compared to unpassivated

  8. Laser induced breakdown spectroscopy in paintings and sculptures research

    Microsoft Academic Search

    A. Sarzynski; W. Skrzeczanowski; J. Marczak

    2007-01-01

    Application of Laser Induced Breakdown Spectroscopy (LIBS) for investigation of chemical constitution and stratigraphy of artworks, and metallic objects with multilayer structures is described in the paper. Physical phenomena accompanying LIBS investigations, especially temporal evolution and spectral lines broadening are described. Operational characteristics of experimental equipment are shown. Results obtained with use of two different echelle spectrometers are compared. Pigments

  9. Electrical and physical characteristics of PrTixOy for metal-oxide-semiconductor gate dielectric applications

    NASA Astrophysics Data System (ADS)

    Jeon, Sanghun; Hwang, Hyunsang

    2002-12-01

    The electrical and physical characteristics of PrTixOy, for use in metal-oxide-semiconductor gate dielectric applications were investigated. An amorphous layer of PrTixOy with an equivalent oxide thickness of 1 nm and a dielectric constant of 23 was formed by means of e-beam evaporation. Compared to Pr2O3, PrTixOy was found to exhibit excellent characteristics such as a high accumulation capacitance, a low leakage current density, a thin interfacial layer, and a lower reactivity to water. The superiority of PrTixOy can be attributed to the addition of TiO2 to the praseodymium oxide matrix.

  10. Optical and electrical characteristics of pyrite films prepared by a new spray method using PVDF as a polymeric binder

    NASA Astrophysics Data System (ADS)

    Javad Zanganeh, Mohammad; Ziarati, Mahmoud; Khandan, Nahid; Goudarzi, Ali Reza

    2015-06-01

    Pyrite thin films were deposited on glass substrates by a new and simple spray method using polyvinylidene fluoride as polymeric binder. Prepared pyrite films were characterized by field emission scanning electron microscopy, ultraviolet-visible spectroscopy and Hall auto-measuring instrument. Hall measurements showed p-type conduction of all the prepared thin films. The film prepared by using binder concentration of 2 wt.% showed the best results. Its band gap was estimated 1.55 eV. Also, electrical characteristics of the deposited film were obtained by I-V characteristic curve.

  11. Investigating the Characteristics of Cobalt-Substituted MnZn Ferrites by Equivalent Electrical Elements

    Microsoft Academic Search

    Tsorng-Juu Liang; Hsiau-Hsian Nien; Jiann-Fuh Chen

    2007-01-01

    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

  12. The Criterion of Intrinsic Safe Circuit Characteristic Based on Electric Arc Power

    Microsoft Academic Search

    Ligong Wang

    \\u000a Intrinsic safety electric equipments are commonly used in coal wells . Because intrinsic safety electric equipments have not\\u000a the flameproof shell, the determinacy whether the electric arcs can ignite gas becomes the important investigated subject\\u000a . The energy criterion takes the minimum burning energy as standard. However, it can be known that discharge power must be\\u000a considered except discharge energy

  13. The impact of moisture absorption on the electrical characteristics of organic dielectric materials

    Microsoft Academic Search

    Brian Curran; Ivan Ndip; Jorg Bauer; Stephan Guttowskil; Klaus Dieter Langl; Herbert Reichl

    2011-01-01

    Organic dielectric materials will absorb moisture when in direct contact with a liquid or a humid environment. The dielectric then becomes a two­ phase dielectric composite with new dielectric characteristics. Using the Lichtenecker Equation, the composite dielectric permittivity and loss characteristics are modeled. The loss modeling includes the polymer dielectric loss characteristics, as well as the conductive loss of the

  14. High-voltage atmospheric breakdown across intervening rutile dielectrics.

    SciTech Connect

    Williamson, Kenneth Martin; Simpson, Sean; Coats, Rebecca Sue; Jorgenson, Roy Eberhardt; Hjalmarson, Harold Paul; Pasik, Michael Francis

    2013-09-01

    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.

  15. Force- and light-controlled electrical transport characteristics of carbon nanotube 1D/2D bulk junctions

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Li, Chunyan; Li, Xinming; Zhu, Hongwei; Wei, Jinquan; Wang, Kunlin; Wu, Dehai

    2009-10-01

    Pure carbon bulk junctions are fabricated based on carbon nanotube (CNT) macrostructures and their electrical transport characteristics are investigated. The planar 1D/2D strand-on-film (SOF) junctions show interesting force- and light-controlled transport behaviors. Considering the excellent chemical stability and good mechanical properties (strength, hardness and elasticity) of CNTs, the SOF junctions could find practical and wide applications in electromechanical and optoelectronic devices.

  16. Optical and Electrical Characteristics of CO2-Laser-Treated Mg-Doped GaN Film

    Microsoft Academic Search

    Wei-Chih Lai; Meiso Yokoyama; Shoou-Jinn Chang; Jan-Dar Guo; Chia-Hon Sheu; Tsung-Yu Chen; Wen-Chung Tsai; Jian-Shihn Tsang; Shih-Hsiung Chan; Simon M. Sze

    2000-01-01

    This work investigates the optical and electrical characteristics of CO2-laser annealed Mg-doped GaN films to activate Mg-doped p-type GaN films. Results obtained from the CO2 laser annealing investigation were similar to those of thermal annealing or low energy electron beam irradiation (LEEBI) treatment to activate the Mg-doped p-GaN films. The room-temperature photoluminescence (PL) intensity of the blue emission of the

  17. Structural, electrical and magnetic characteristics of nickel substituted cobalt ferrite nano particles, synthesized by self combustion method

    NASA Astrophysics Data System (ADS)

    Sontu, Uday Bhasker; Yelasani, Vijayakumar; Musugu, Venkata Ramana Reddy

    2015-01-01

    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.

  18. Impact of Process-Effect Correction Strategies on Variability of Critical Dimension and Electrical Characteristics in Extreme Ultraviolet Lithography

    NASA Astrophysics Data System (ADS)

    Ng, Philip C. W.; Chien, Sheng-Wei; Chang, Bo-Sen; Tsai, Kuen-Yu; Lu, Yi-Chang; Li, Jia-Han; Chen, Alek C.

    2011-06-01

    The conventional correction strategy used to compensate for imaging errors in extreme ultraviolet (EUV) lithography is accomplished by incorporating independent corrections in which rule-based corrections are used to compensate for EUV-specific imaging effects such as mask shadowing, and a model-based correction is used to compensate for proximity effects. Because most rule-based corrections are empirically developed by using simple Manhattan patterns, some of the simplified approximation approaches would not be applicable in a circuit layout with complicated geometric patterns. These kinds of approximation approaches can lead to ineffective corrections of EUV-specific imaging effects, resulting in inaccurate patterns printed on a wafer which will significantly alter the electrical characteristics of fabricated circuits. In order to prevent the problems due to rule-based corrections, a promising correction strategy has been proposed to simultaneously deal with EUV-specific imaging effects and proximity effects. In this study, the impact of two different correction strategies on the critical dimension (CD) variation caused by defocus and the deviation of electrical characteristics from the design intent is explored. Numerical experiments indicate that the variability of CD and electrical characteristics is significantly improved by the proposed correction strategy.

  19. Dielectric breakdown of polycrystalline alumina: A weakest-link failure analysis

    NASA Astrophysics Data System (ADS)

    Block, Benjamin

    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.

  20. RF BREAKDOWN STUDIES USING PRESSURIZED CAVITIES

    SciTech Connect

    Johnson, Rolland

    2014-09-21

    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.

  1. Scaling law for direct current field emission-driven microscale gas breakdown

    NASA Astrophysics Data System (ADS)

    Venkattraman, A.; Alexeenko, A. A.

    2012-12-01

    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.

  2. Scaling law for direct current field emission-driven microscale gas breakdown

    SciTech Connect

    Venkattraman, A.; Alexeenko, A. A. [School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana 47907 (United States)

    2012-12-15

    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.

  3. Collision and diffusion in microwave breakdown of nitrogen gas in and around microgaps

    SciTech Connect

    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: remillard@hope.edu [Hope College, Holland, MI 49423 (United States)

    2014-01-15

    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.

  4. Effects of a parallel resistor on electrical characteristics of a piezoelectric transformer in open-circuit transient state.

    PubMed

    Chang, Kuo-Tsai

    2007-01-01

    This paper investigates electrical transient characteristics of a Rosen-type piezoelectric transformer (PT), including maximum voltages, time constants, energy losses and average powers, and their improvements immediately after turning OFF. A parallel resistor connected to both input terminals of the PT is needed to improve the transient characteristics. An equivalent circuit for the PT is first given. Then, an open-circuit voltage, involving a direct current (DC) component and an alternating current (AC) component, and its related energy losses are derived from the equivalent circuit with initial conditions. Moreover, an AC power control system, including a DC-to-AC resonant inverter, a control switch and electronic instruments, is constructed to determine the electrical characteristics of the OFF transient state. Furthermore, the effects of the parallel resistor on the transient characteristics at different parallel resistances are measured. The advantages of adding the parallel resistor also are discussed. From the measured results, the DC time constant is greatly decreased from 9 to 0.04 ms by a 10 k(omega) parallel resistance under open output. PMID:17225805

  5. Statistical analysis of lightning electric field measured under Malaysian condition

    NASA Astrophysics Data System (ADS)

    Salimi, Behnam; Mehranzamir, Kamyar; Abdul-Malek, Zulkurnain

    2014-02-01

    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.

  6. Exploration of Underwater Laser Breakdown Using Two Synchronized Gated Cameras

    NASA Astrophysics Data System (ADS)

    Huwel, Lutz; Baumgart, Clayton; Betts, Susannah; Morgan, Thomas J.; Graham, William G.

    2014-10-01

    Using two synchronized intensified CCD cameras, we have studied spatial and temporal characteristics of optical breakdown in water created by a focused 10 ns pulsed Nd:YAG laser operating at 1064 nm. For three water samples with different impurity content (ultrapure, distilled, and tap water), the plasma evolution was monitored up to 1 ms after breakdown. Images taken by the two cameras, systematically delayed relative to each other, reveal that the center of emission intensity does not remain at a fixed location. In single plasma events, the center first moves, on average, toward the incoming laser beam. Then, at about 100 to 200 ns, the apparent direction of motion reverses and the center returns towards the focal point. On the other hand, in repetitive breakdown the time averaged center moves steadily downstream with each subsequent pulse. Details of this behavior depend on repetition frequency. We will also present shadowgraphy results revealing time resolved speeds of both shockwave and bubble expansion.

  7. Performance characteristics of an electric-vehicle lead-acid battery pack at elevated temperatures

    SciTech Connect

    Chapman, P.

    1982-04-01

    Data are presented for discharge testing of an 18-Exide IV electric car battery pack over initial electrolyte temperature variations between 27 and 55/sup 0/C. The tests were conducted under laboratory conditions and then compared to detailed electric vehicle simulation models. Results showed that battery discharge capacity increased with temperature for constant current discharges, and that battery energy capacity increased with temperature for constant power discharges. Dynamometer test of the GE Electric Test Vehicle showed an increase in range of 25% for the highest electrolyte temperature.

  8. Optical, structural, and electrical characteristics of high dielectric constant zirconium oxide thin films deposited by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Aguilar-Frutis, M.; Reyna-Garcia, G.; Garcia-Hipolito, M.; Guzman-Mendoza, J.; Falcony, C.

    2004-07-01

    The spray pyrolysis technique was used to obtain high dielectric constant zirconium oxide films. These films were deposited on silicon substrates, and quartz slides from two different solution concentrations (0.033 and 0.066 M) of zirconium acetylacetonate dissolved in N,N-dimethylformamide at substrate temperatures in the range of 400-600 °C. The films are transparent with a surface roughness lower than 40 Å and with the ZrO2 stoichiometry. The refractive index of the films was up to 2.12 at 630 nm. Infrared spectroscopy measurements show a dominant absorption band associated to ZrO2 at 420 cm-1 and the presence of silicon oxide (SiO2) peaks as well. Cross-section transmission electron microscopy (TEM) images of these films reveal the existence of a thin layer at the silicon substrate interface with the deposited ZrO2 film. It is also found from both cross-section and plan-view TEM observations that the deposited layers consist of tetragonal ZrO2 nano-crystallites embedded in an amorphous zirconium oxide matrix. Spectroscopic ellipsometry measurements were fitted assuming the existence of a thin interface layer on top of the Si substrate, composed of SiO2, ZrO2, and crystalline silicon. The as-deposited films have a dielectric constant in the range from 10.9 to 17.5 when they are deposited at different substrate temperatures for the two spraying solution concentrations studied. The films withstand electric fields up to 3 MV/cm, without observing destructive dielectric breakdown. .

  9. Numerical Simulation of Electrical and Optical Characteristics of Multilayer Organic Light-Emitting Devices

    Microsoft Academic Search

    Chih-Chien Lee; Mei-Ying Chang; Yeung-Dong Jong; Tain-Wang Huang; Chrong-Shyua Chu; Yih Chang

    2004-01-01

    A numerical model for the quantitative simulation of multilayer organic light-emitting devices is presented in this article. Unlike most studies published in the literature, both electrical and optical modeling are incorporated into one. The electrical modeling is based on the drift-diffusion equations that contain charge carrier drift along with field-dependent mobility, charge carrier trapping, the heterojunction interface and the recombination

  10. The characteristics of chromized 1020 steel with electrical discharge machining and Ni electroplating pretreatments

    Microsoft Academic Search

    Ching-Yuan Bai; Jeou-Long Lee; Tse-Min Wen; Kung-Hsu Hou; Min-Sheng Wu; Ming-Der Ger

    2011-01-01

    A uniform and continuous chromized coating on AISI 1020 steel is produced by low-temperature pack chromization (LTPC) with electrical discharge machining and Ni electroplating pretreatments. The anticorrosive performance of the chromized steels is investigated in a 0.5M H2SO4 solution at room temperature. The testing results indicate that the chromized specimen with electrical discharge machining and Ni electroplating pretreatments exhibits the

  11. Synthesis and Structural and Electrical Characteristics of Polypyrrole Nanotube\\/TiO2 Hybrid Composites

    Microsoft Academic Search

    Meifang Luo; Ying He; Qilin Cheng; Chunzhong Li

    2010-01-01

    Hybrid composites of conducting polypyrrole nanotubes with TiO2 nanoparticles were synthesized in the presence of ?-naphthalenesulfonic acid by chemical oxidative polymerization. The morphology, structure, and electrical properties were investigated by several experimental techniques. The results indicated that the structural and electrical properties of the composites were influenced by the content of TiO2 nanoparticles. The DC conductivity of the composites increased

  12. Electrical, structural and etching characteristics of ZnO:Al films prepared by rf magnetron

    Microsoft Academic Search

    Yong Hyun Kim; Kyung Seok Lee; Taek Sung Lee; Byung-ki Cheong; Tae-Yeon Seong; Won Mok Kim

    2010-01-01

    Al doped ZnO (AZO) films were prepared by radio frequency (rf) magnetron sputtering with varying substrate temperature, working Ar gas pressure and rf power imposed on 2-inch ZnO–Al2O3 (2wt%) target, and their electrical and structural properties together with the corresponding etching behavior in 0.5% HCl solution were examined. The effect of rf power on the electrical and structural properties of

  13. Electrical characteristics of Au/n-GaAs structures with thin and thick SiO{sub 2} dielectric layer

    SciTech Connect

    Altuntas, H., E-mail: altunhalit@gmail.edu.tr [Cankiri Karatekin University, Department of Physics, Faculty of Sciences (Turkey); Altindal, S. [Gazi University, Department of Physics, Faculty of Arts and Sciences (Turkey); Corekci, S. [Kirklareli University, Department of Physics, Faculty of Arts and Sciences (Turkey); Ozturk, M. K.; Ozcelik, S. [Gazi University, Department of Physics, Faculty of Arts and Sciences (Turkey)

    2011-10-15

    The aim of this study, to explain effects of the SiO{sub 2} insulator layer thickness on the electrical properties of Au/n-GaAs Shottky barrier diodes (SBDs). Thin (60 A) and thick (250 A) SiO{sub 2} insulator layers were deposited on n-type GaAs substrates using the plasma enganced chemical vapour deposition technique. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics have been carried out at room temperature. The main electrical parameters, such as ideality factor (n), zero-bias barrier height ({phi}{sub Bo}), series resistance (R{sub s}), leakage current, and interface states (N{sub ss}) for Au/SiO{sub 2}/n-GaAs SBDs have been investigated. Surface morphologies of the SiO{sub 2} dielectric layer was analyzed using atomic force microscopy. The results show that SiO{sub 2} insulator layer thickness very affects the main electrical parameters. Au/n-GaAs SBDs with thick SiO{sub 2} insulator layer have low leakage current level, small ideality factor, and low interface states. Thus, Au/n-GaAs SBDs with thick SiO{sub 2} insulator layer shows better diode characteristics than other.

  14. Laser spark ignition and combustion characteristics of methane-air mixtures

    SciTech Connect

    Ma, J.X.; Alexander, D.R.; Poulain, D.E. [Univ. of Nebraska, Lincoln, NE (United States)] [Univ. of Nebraska, Lincoln, NE (United States)

    1998-03-01

    Ignition breakdown kernels of methane-air mixtures initiated by laser-induced sparks and by conventional electric sparks are compared during initial stages. Experiments were conducted using a four-stroke (Otto-cycle) single-cylinder typical high-pressure combustion chamber. The piston is cycled in the cylinder by using an electric motor driven hydraulic ram. An excimer laser beam, either produced from krypton fluoride gas ({lambda} = 248 nm) or argon fluoride gas ({lambda} = 193 nm), or a Nd:YAG laser beam ({lambda} = 1,064 nm) is focused into a combustion chamber to initiate ignition. Conventional electric spark ignition is used as a basis for comparison between the two different ignition methods and the resultant early breakdown kernel characteristics. A streak camera is used to investigate and record the initial stages of kernel formation. Both a breakdown and a radial expansion wave of the ignition plasma are observed for certain laser ignition conditions of methane-air mixtures under typical internal combustion (IC) engine conditions. Results indicate that only certain wavelengths used for producing laser ignition produce a radial expansion wave. Laser ignition kernel size is calculated and laser-supported breakdown velocity is calculated by using Raizer`s theory and is compared with measured results. Laser ignition results in a 4--6 ms decrease in the time for combustion to reach peak pressure than is obtained when using electric spark ignition in the same combustion chamber and under the same ignition conditions.

  15. Monte Carlo simulation of initial breakdown phase for magnetised toroidal ICRF discharges

    NASA Astrophysics Data System (ADS)

    Tripský, M.; Wauters, T.; Lyssoivan, A.; Koch, R.; Bobkov, V.; Vervier, M.; van Oost, G.; van Schoor, M.; ASDEX Upgrade Team, Textor Team

    2014-02-01

    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.

  16. Characterization of solar cells for space applications. Volume 13: Electrical characteristics of Hughes LPE gallium arsenide solar cells as a function of intensity and temperature

    NASA Technical Reports Server (NTRS)

    Anspaugh, B. E.; Beckert, D. M.; Downing, R. G.; Miyahira, T. F.; Weiss, R. S.

    1980-01-01

    Electrical characteristics of Hughes Liquid phase epitaxy, P/N gallium aluminum arsenide solar cells are presented in graphical and tabular format as a function of solar illumination intensity and temperature.

  17. Influence of ITO, Graphene Thickness and Electrodes Buried Depth on LED Thermal-Electrical Characteristics Using Numerical Simulation

    NASA Astrophysics Data System (ADS)

    Xue, Sheng-Jie; Fang, Liang; Long, Xing-Ming; Lu, Yi; Wu, Fang; Li, Wan-Jun; Zuo, Jia-Qi; Zhang, Shu-Fang

    2014-02-01

    Finite elements methods are used to investigate the thermal-electrical characteristics of gallium-nitride (GaN) light-emitting diodes (LEDs) with different transparent conductive layers (TCLs) and buried depths of electrodes, where the transparent conductive layers include indium tin oxide (ITO), graphene (Gr) and the combination of them (ITO/Gr). The optimal material parameters and the precision and accuracy of the simulation model are validated. Moreover, the parameters' sensitivity analysis is carried out as well. The results indicate that the LED with the TCL of a 100-nm ITO or 4-layer Gr has a good thermal-electrical performance from the viewpoint of the maximum temperature and the current density deviation of multiple quantum well (MQW), where the maximum temperature occurs at the n-Pad rather than p-Pad. The compound TCL with a 20-nm ITO and 3-layer Gr reaches a thermal-electrical performance better than that of a 100-nm ITO or 4-layer Gr. Moreover, their maximum temperatures decrease about -0.43% and 1.21%, and the current density uniformities increase up to -6.09% and 17.41%, respectively. Furthermore, when the electrode buried depth is 0.51 ?m, the thermal-electrical performance of the GaN LEDs can be further improved.

  18. Charged dendrimers under the action of AC electric fields: Breathing characteristics of molecular size, polarizations, and ion distributions

    NASA Astrophysics Data System (ADS)

    Das, Ashok K.; Hsiao, Pai-Yi

    2015-02-01

    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.

  19. Influence on electrical characteristics of the design of 4H-SiC ultraviolet photodetectors: Theoretical analysis and simulations

    NASA Astrophysics Data System (ADS)

    Biondo, Stéphane; Vervisch, Wilfried; Ottaviani, Laurent; Palais, Olivier

    2012-01-01

    This paper deals with the simulation of the reverse current density of 4H-SiC ultraviolet- (UV) photodetector devices based on p-i-n diodes. Simulations using the finite-element method presented in this paper lead to an understanding of the photodetector current density levels in dark field, as well as under UV exposure. The theoretical study coming from these simulations allows us to propose some UV-photodetector performance enhancements. A way to improve the UV-photodetector performance is to increase the current density at reverse bias. This study demonstrates the improvement in electrical characteristics achievable by either optical or electrical means. Optical simulations prove that an increase in photon harvesting is possible by using a specific patterned surface, a surface grating which behaves as a photonic crystal. In addition to the absorption enhancement achieved caused by this kind of surface, we point out wavelength selectivity. Nevertheless, the electrical simulation confirms that the electric field placement is of primary importance. To ensure that the photon absorption is carried out inside the space-charge region, the simulation study leads us to propose a UV-photodetector comprising a "flat-top pyramid" surface.

  20. Investigation of exploding cylindrical foils in air. I - Electrical characteristics of foil explosion

    Microsoft Academic Search

    V. A. Burtsev; V. A. Dubianskii; N. P. Egorov; M. P. Kasatkina; A. B. Produvnov; I. V. Shestakov

    1978-01-01

    The characteristics of exploding foils in air and the properties of high-current shunt discharges were studied experimentally. Results obtained with cylindrical aluminum foils are diagrammed and analyzed.

  1. Dynamic response characteristics of thermoelectric generator predicted by a three-dimensional heat-electricity coupled model

    NASA Astrophysics Data System (ADS)

    Meng, Jing-Hui; Zhang, Xin-Xin; Wang, Xiao-Dong

    2014-01-01

    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.

  2. Modeling of electrical characteristics of midwave type II InAs /GaSb strain layer superlattice diodes

    NASA Astrophysics Data System (ADS)

    Gopal, V.; Plis, E.; Rodriguez, J.-B.; Jones, C. E.; Faraone, L.; Krishna, S.

    2008-12-01

    This paper reports the results of modeling of electrical characteristics of midinfrared type II InAs /GaSb strain layer superlattice (SLS) diode with p-on-n polarity. Bulk based model with the effective band gap of SLS material has been used in modeling of the experimental data. Temperature dependence of zero-bias resistance area product (R0A) and bias dependent dynamic resistance of the diode have been analyzed in detail to investigate dark current contributing mechanisms that are limiting the electrical performance of the diode. R0A of the diode is found to be limited by thermal diffusion currents at higher temperatures and Ohmic shunt resistance contribution limits it at low temperatures ˜82K.

  3. Electricity

    NSDL National Science Digital Library

    Iowa Public Television. Explore More Project

    2004-01-01

    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

  4. Swelling characteristics of acrylic acid polyelectrolyte hydrogel in a dc electric field

    NASA Astrophysics Data System (ADS)

    Jabbari, Esmaiel; Tavakoli, Javad; Sarvestani, Alireza S.

    2007-10-01

    A novel application of environmentally sensitive polyelectrolytes is in the fabrication of BioMEMS devices as sensors and actuators. Poly(acrylic acid) (PAA) gels are anionic polyelectrolyte networks that exhibit volume expansion in aqueous physiological environments. When an electric field is applied to PAA polyelectrolyte gels, the fixed anionic polyelectrolyte charges and the requirement of electro-neutrality in the network generate an osmotic pressure, above that in the absence of the electric field, to expand the network. The objective of this research was to investigate the effect of an externally applied dc electric field on the volume expansion of the PAA polyelectrolyte gel in a simulated physiological solution of phosphate buffer saline (PBS). For swelling studies in the electric field, two platinum-coated plates, as electrodes, were wrapped in a polyethylene sheet to protect the plates from corrosion and placed vertically in a vessel filled with PBS. The plates were placed on a rail such that the distance between the two plates could be adjusted. The PAA gel was synthesized by free radical crosslinking of acrylic acid monomer with ethylene glycol dimethacrylate (EGDMA) crosslinker. Our results demonstrate that volume expansion depends on the intensity of the electric field, the PAA network density, network homogeneity, and the position of the gel in the field relative to positive/negative electrodes. Our model predictions for PAA volume expansion, based on the dilute electrolyte concentration in the gel network, is in excellent agreement with the experimental findings in the high-electric-field regime (250-300 Newton/Coulomb).

  5. Joining characteristics of titanium-based orthodontic wires connected by laser and electrical welding methods.

    PubMed

    Matsunaga, Junko; Watanabe, Ikuya; Nakao, Noriko; Watanabe, Etsuko; Elshahawy, Waleed; Yoshida, Noriaki

    2015-01-01

    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

  6. EXPENSE BREAKDOWN SHEET BUSINESS MEALS

    E-print Network

    Mohri, Mehryar

    . Meal expenses incurred by an individual during business travel should be reported on Form EXP2000TEXPENSE BREAKDOWN SHEET BUSINESS MEALS (WHEN NEEDED PLEASE ATTACH TO FORM EXP2000) Form EXP2000M) when requesting reimbursement for expenses related to meals taken during business meetings or events

  7. The structure of vortex breakdown

    NASA Technical Reports Server (NTRS)

    Leibovich, S.

    1978-01-01

    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.

  8. Predicting Flow Breakdown Probability and Duration in Stochastic Network Models: Impact on Travel Time Reliability

    SciTech Connect

    Dong, Jing [ORNL; Mahmassani, Hani S. [Northwestern University, Evanston

    2011-01-01

    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.

  9. Electrical characteristics of schottky barriers on 4H-SiC: The effects of barrier height nonuniformity

    Microsoft Academic Search

    B. J. Skromme; E. Luckowski; K. Moore; M. Bhatnagar; C. E. Weitzel; T. Gehoski; D. Ganser

    2000-01-01

    Electrical properties, including current-voltage (I-V) and capacitance-voltage (C-V) characteristics, have been measured on\\u000a a large number of Ti, Ni, and Pt-based Schottky barrier diodes on 4H-SiC epilayers. Various nonideal behaviors are frequently\\u000a observed, including ideality factors greater than one, anomalously low I-V barrier heights, and excess leakage currents at\\u000a low forward bias and in reverse bias. The nonidealities are highly

  10. Nanoscale Probing of Local Electrical Characteristics on MBE-Grown Bi2Te3 Surfaces under Ambient Conditions.

    PubMed

    Macedo, Rita J; Harrison, Sara E; Dorofeeva, Tatiana S; Harris, James S; Kiehl, Richard A

    2015-07-01

    The local electrical characteristics on the surface of MBE-grown Bi2Te3 are probed under ambient conditions by conductive atomic force microscopy. Nanoscale mapping reveals a 10-100× enhancement in current at step-edges compared to that on terraces. Analysis of the local current-voltage characteristics indicates that the transport mechanism is similar for step-edges and terraces. Comparison of the results with those for control samples shows that the current enhancement is not a measurement artifact but instead is due to local differences in electronic properties. The likelihood of various possible mechanisms is discussed. The absence of enhancement at the step-edges for graphite terraces is consistent with the intriguing possibility that spin-orbit coupling and topological effects play a significant role in the step-edge current enhancement in Bi2Te3. PMID:26030139

  11. CHARACTERISTICS OF TRANSVERSE ELECTRIC AND MAGNETIC FIELD TRANSMISSION CELLS AT EXTREMELY LOW FREQUENCIES

    EPA Science Inventory

    Transverse electric and magnetic field cells are often designed to subject samples to electromagnetic radiation of intrinsic impedance (E/H) that is the same as in free space, 377 ohms. Earlier work has shown this value to be correct for the RF region. In the study, measurements ...

  12. Electrical, electromagnetic and structural characteristics of carbon nanotube-polymer nanocomposites

    E-print Network

    Park, Sung-Hoon

    2009-01-01

    terephthalate, PVA – polyvinylalcohol Composite PreparationPVA – polyvinylalcohol…………………………………………………………………11 Table 4-2 Mechanical and electrical properties of functionalized SWCNT/RET composites…………………………………………………………………. …..PVA Solution mixing 0.055 wt% Figure 1-8 SEM of fractured cross-section of CNTs/polymer composites: (

  13. Electrical characteristics of arc-free high-power pulsed sputtering glow plasma

    Microsoft Academic Search

    K. Yukimura; R. Mieda; H. Tamagaki; T. Okimoto

    2008-01-01

    A high power pulsed sputtering (HPPS) plasma is generated using a Penning discharge, and is featured to be highly ionized in a glow discharge mode. An electric field and a magnetic field are parallel to each other. Argon ions are initially produced in the plasma and are accelerated towards the cathode as a sputtering target. An arc-free plasma can be

  14. Characteristics of Electromagnetic Radiation from Gap-Type Spark Discharges on Electric Power Distribution Lines

    Microsoft Academic Search

    John German

    1969-01-01

    This paper describes the measured properties of the electromagnetic radiation from gap-type electrical discharges which occur on distribution lines and discusses some of the factors which affect these emissions. A discussion is given of the methods by which these waves are generated, of the measurement techniques, and the findings of this investigation.

  15. Computation of Corona Space Charge, Electric Field, and VI Characteristic Using Equipotential Charge Shells

    Microsoft Academic Search

    Mark N. Horenstein

    1984-01-01

    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,

  16. Characterization of solar cells for space applications. Volume 11: Electrical characteristics of 2 ohm-cm, 228 micron wraparound solar cells as a function of intensity, temperature, and irradiation. [for solar electric propulsion

    NASA Technical Reports Server (NTRS)

    Anspaugh, B. E.; Beckert, D. M.; Downing, R. G.; Weiss, R. S.

    1980-01-01

    Parametric characterization data on Spectrolab 2 by 4 cm, 2 ohm/cm, 228 micron thick wraparound cell, a candidate for the Solar Electric Propulsion Mission, are presented. These data consist of the electrical characteristics of the solar cell under a wide range of temperature and illumination intensity combinations of the type encountered in space applications.

  17. A numerical model of avalanche breakdown in MOSFET's

    Microsoft Academic Search

    T. Toyabe; K. Yamaguchi; S. Asai; M. S. Mock

    1978-01-01

    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

  18. The role of tip leakage vortex breakdown in compressor rotor aerodynamics

    SciTech Connect

    Furukawa, M.; Inoue, M.; Saiki, K.; Yamada, K. [Kyushu Univ. Fukuoka (Japan). Dept. of Mechanical Science and Engineering

    1999-07-01

    The breakdown of tip leakage vortex has been investigated on low-speed axial compressor rotor with moderate blade loadings. Effects of the breakdown on the rotor aerodynamics are elucidated by Navier-Stokes flow simulations and visualization techniques for identifying the breakdown. The simulations show that the leakage vortex breakdown occurs inside the rotor at a lower flow rate than the peak pressure rise operating condition. The breakdown is characterized by the existence of the stagnation point followed by a bubblelike recirculation region. The onset of breakdown causes significant changes in the nature of the tip leakage vortex: large expansion of the vortex and disappearance of the streamwise vorticity concentrated in the vortex. The expansion has an extremely large blockage effect extending upstream of the leading edge. The disappearance of the concentrated vorticity results in no rolling-up of the vortex downstream of the rotor and the disappearance of the pressure through on the casing. The leakage flow field downstream of the rotor is dominated by the outward radial flow, resulting from the contraction of the bubblelike structure of the breakdown region. It is found that the leakage vortex breakdown plays a major role in characteristic of rotor performance at near-stall conditions. As the flow rate is decreased from the peak pressure rise operating condition, the breakdown region grows rapidly in the streamwise, spanwise, and pitchwise directions. The growth of the breakdown causes the blockage and the loss to increase drastically. Then, the interaction of the breakdown region with the blade suction surface gives rise to the tree-dimensional separation of the suction surface boundary layer, thus leading to a sudden drop in the total pressure rise across the rotor.

  19. Simulation of the formation of a runaway electron beam in an overvolted gas gap breakdown

    NASA Astrophysics Data System (ADS)

    Shklyaev, V. A.; Belomyttsev, S. Ya.; Ryzhov, V. V.

    2012-12-01

    The paper reports on numerical simulation to inquire into the breakdown of a gas-filled diode in a highly inhomogeneous electric field. It is shown that early in the breakdown a runaway electron beam (RAEB) is formed in the diode and this strongly affects the rate of breakdown development. The energy gained by RAEB electrons corresponds to the electron energy gained under the same conditions in vacuum. The properties of the emission surface of the cathode determine the instant at which the beam is formed during subnanosecond voltage pulse rise time and hence the beam current and the energy spectrum of runaway electrons.

  20. Electrical characteristics of TMAH-surface treated Ni/Au/Al2O3/GaN MIS Schottky structures

    NASA Astrophysics Data System (ADS)

    Reddy, M. Siva Pratap; Lee, Jung-Hee; Jang, Ja-Soon

    2014-03-01

    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.

  1. High voltage characteristics of junctionless poly-silicon thin film transistors

    NASA Astrophysics Data System (ADS)

    Cheng, Ya-Chi; Wu, Yung-Chun; Chen, Hung-Bin; Han, Ming-Hung; Lu, Nan-Heng; Su, Jun-Ji; Chang, Chun-Yen

    2013-09-01

    The breakdown voltage (VBD) and breakdown mechanism of junctionless (JL) poly-Si thin film transistor (TFT) were compared to the conventional inversion-mode (IM) TFT using fabricated devices and 3D quantum-corrected hydrodynamic transport device simulation. The simulated results are correspondent with experimental ones. The analyses of electric field distributions in on-state show that the channel of JL devices can equally share the voltage like a resistor, because there are no junctions formed between channel and source/drain. The JL TFT shows excellent breakdown characteristics; the off-state VBD of 53.4 V is several times larger than VBD of 9.5 V in IM TFT with same device size. JL devices have large potential for high voltage power metal-oxide-semiconductor devices and circuit applications.

  2. Oxide breakdown mechanism and quantum physical chemistry for time-dependent dielectric breakdown

    Microsoft Academic Search

    M. Kimura

    1997-01-01

    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

  3. Structural and electrical characteristics of dysprosium-doped barium stannate titanate ceramics

    SciTech Connect

    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: luli@nus.edu.sg [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)

    2010-03-15

    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.

  4. Comparison between in situ and remotely-sensed storm microphysics and electrical characteristics

    NASA Astrophysics Data System (ADS)

    Detwiler, A. G.

    2012-12-01

    During the Severe Thunderstorm Electrification/Precipitation Study (STEPS) in 2000 the armored T-28 research aircraft carried a modified High Volume Precipitation Spectrometer capable of both imaging and observing charge on hydrometeors. Published studies have used polarimetric radar and lightning mapping array (LMA) data to compare aggregate microphysical properties of STEPS storms to lightning activity and charge structure inferred from LMA observations. We present here detailed airborne in situ microphysical, thermodynamic, electric field, and hydrometeor charge data for representative thunderstorm passes. There is general agreement between in situ microphysical properties and those deduced from polarimetric radar, and in situ electric field and hydrometeor charge observations and charge distribution inferred from the LMA. The quantitative airborne data is compared to results from laboratory charge separation experiments and supports the importance of non-inductive charging processes in these storms following the Manchester/Cordoba laboratory results.

  5. Electricity end-use characteristics of air-cooled chillers in hotels in Hong Kong

    Microsoft Academic Search

    F. W. Yu; K. T. Chan

    2005-01-01

    This paper presents the operating efficiency of air-cooled chillers in three existing hotels and investigates the extent to which the annual electricity consumption can decrease by improving their efficiency. Chillers in these hotels tend to be improperly staged, causing their seasonal efficiency to rise by 0.05–0.12kW\\/kW from a full load efficiency of 0.32kW\\/kW. When chiller sequencing is restored, their seasonal

  6. Characteristics of penetration electric fields to the equatorial ionosphere during southward and northward IMF turnings

    NASA Astrophysics Data System (ADS)

    Bhaskar, Ankush; Vichare, Geeta

    2013-07-01

    The signatures of abrupt turnings of the vertical component of the interplanetary magnetic field (IMF), Bz, can be seen at equatorial latitudes through the prompt transmission of high-latitude electric fields to the lower latitudes, called as prompt penetration electric field (PPE). The present work studies the signatures of PPE in daytime equatorial electrojet (EEJ) index derived in the Indian sector during 2001-2005. The signatures are observed in polar (PCN index) and equatorial (EEJ index) ionosphere almost instantaneously (<1 min). The communication time of 12±6 min is observed between bow shock nose and the equatorial ionosphere, and it is found to have inverse relationship with radial component of solar wind velocity during southward and northward Bz turnings which might indicate magnetosphere crossing time scale by solar wind. Ionospheric reconfiguration time during southward turnings shows inverse relationship with solar wind flow in contrast to northward turnings with "no relationship," indicating differences in underlying physical mechanisms during both turnings. We observe no local time dependence (within 06-18 h) in conductivity-corrected EEJ signatures associated with Bz turnings. Regression analysis between conductivity-corrected EEJ and interplanetary electric field shows higher efficiency during northward turnings. However, further analysis investigating the effect of actual orientation of Bz indicates that the magnitude of northward Bz does not have influence on the ionospheric signatures. It is noticed that the response signatures are mainly controlled by the magnitudes of southward Bz. Thus, the present study signifies the role of inner magnetospheric shielding electric field in addition to ceasing of convection during northward turnings.

  7. Characteristics for Small Capacity Electric Energy Storage System with Batteries by Current Source Inverter

    Microsoft Academic Search

    Yasuhiro Ogura; Shigeo Masukawa; Shoji Iida

    2008-01-01

    We propose an electric energy storage system with batteries by a current source inverter. It is interconnected to the single-phase three-wire distribution system. In order to reduce the dc reactor capacity and change the discharging and the charging operations by signals, a set of DC-DC converters is added between the inverter and the batteries. In this paper, the proposed circuit

  8. Magnetic field-aligned electric field acceleration and the characteristics of the optical aurora

    Microsoft Academic Search

    A. B. Christensen; L. R. Lyons; J. H. Hecht; G. G. Sivjee; R. R. Meier; D. G. Strickland

    1987-01-01

    The long-recognized association of brighter aurora with more deeply penetrating, and hence more energetic electrons is examined. Using the Knight (1973) relation between the magnetic field aligned current density j{sub parallel} and potential drop V{sub parallel}, derived from the theory of single particle motion in the presence of a magnetic field-aligned electric field, an approximate expression relating the energy flux

  9. Magnetic field-aligned electric field acceleration and the characteristics of the optical aurora

    Microsoft Academic Search

    A. B. Christensen; L. R. Lyons; J. H. Hecht; G. G. Sivjee; R. R. Meier

    1987-01-01

    The long-recognized association of brighter aurora with more deeply penetrating, and hence more energetic, electrons is examined. Using the Knight (1973) relation between the magnetic-field-aligned current density and potential drop (derived from the theory of single-particle motion in the presence of a magnetic-field-aligned electric field), an approximate expression relating the energy flux of the precipitating electrons over discrete aurora and

  10. Experimental research on machining characteristics of SiC ceramic with end electric discharge milling

    Microsoft Academic Search

    Renjie Ji; Yonghong Liu; Yanzhen Zhang; Xin Dong; Zhili Chen; Baoping Cai

    2011-01-01

    Silicon carbide (SiC) ceramic has been widely used in modern industry. However, the beneficial properties of SiC ceramic make\\u000a machining difficult and costly by conventional machining methods. This paper proposes a new process of machining SiC ceramic\\u000a using end electric discharge (ED) milling. The process is able to effectively machine a large surface area on SiC ceramic\\u000a at low cost

  11. Asymmetric surface dielectric barrier discharge in air at atmospheric pressure: electrical properties and induced airflow characteristics

    Microsoft Academic Search

    Jérôme Pons; Eric Moreau; Gérard Touchard

    2005-01-01

    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

  12. The influence of electric field and mobility profile on GaAs MESFET characteristics

    Microsoft Academic Search

    Chung-Hsu Chen; David K. Arch

    1989-01-01

    Analytical approximations for the drain I-V relationship, including the mobility profile and field distribution in the channel from the drain to the source, of GaAs MESFETs are derived. The model includes the extended depletion from the gate to the drain for nonself-aligned devices. The calculation of the electric field along the channel is in very good agreement with existing analytical

  13. Characteristics of electrical properties of wide temperature range TGB phases in liquid crystal dimers

    Microsoft Academic Search

    R. Dhar; M. B. Pandey; V. S. Pandey; A. S. Pandey; I. M. L. Das; A. S. Achalkumar; C. V. Yelamaggad

    2009-01-01

    4-n-decyloxy-4?-(cholesteryloxycarbonyl-1-butyloxy) chalcone and its two successive homologous are optically active dimeric\\u000a compound derived from cholesterol. They possess wide temperature ranges of two twist grain boundary (TGB) phases namely TGBA\\u000a and TGBC*. Comprehensive dielectric studies have been carried out for these compounds in the frequency range of 1 Hz to 10\\u000a MHz for different conditions of molecular anchoring. Various electrical parameter

  14. Electrical transport characteristics of single-layer organic devices from theory and experiment

    Microsoft Academic Search

    S. J. Martin; Alison B. Walker; A. J. Campbell; D. D. C. Bradley

    2005-01-01

    An electrical model based on drift diffusion is described. We have explored systematically how the shape of the current density-voltage (J-V) curves is determined by the input parameters, information that isessential when deducing values of these parameters by fitting to experimental data for an ITO\\/PPV\\/Al organic light-emitting device (OLED), where ITO is shorthand for indium tin oxide and PPV is

  15. An Investigation of the Electrical Short Circuit Characteristics of Tin Whiskers

    NASA Technical Reports Server (NTRS)

    Courey, Karim J.

    2008-01-01

    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.

  16. EFFECT OF LOW FREQUENCY ELECTRIC FIELD ON GROWTH CHARACTERISTICS AND PROTEIN MOLECULAR STRUCTURE OF WHEAT PLANT

    Microsoft Academic Search

    MAGDA S. HANAFY; HANAN A. MOHAMED; ELHAM A. ABD EL-HADY

    Two exposure systems of an extremely low frequency electric field were used, the first was an experimental model (50 Hz, 6 kV\\/m strength) and the second was the high voltage transmission lines passing through an open agricult ural field (50 Hz, 66 kV\\/11 m = 6 kV\\/m). The effects of the two exposure systems were investigat ed on mitosis, meiosis

  17. Electric characteristics of a surface barrier discharge with a plasma induction electrode

    SciTech Connect

    Alemskii, I. N.; Lelevkin, V. M.; Tokarev, A. V.; Yudanov, V. A. [Kyrgyz-Russian Slavic University (Kyrgyzstan)

    2006-07-15

    Static and dynamic current-voltage and charge-voltage characteristics of a surface barrier discharge with a plasma induction electrode have been investigated experimentally. The dependences of the discharge current on both the gas pressure in the induction electrode tube and the winding pitch of the corona electrode, as well as of the discharge power efficiency on the applied voltage, have been measured.

  18. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Noise Characteristics of Optocouplers on Neutron Radiation

    Microsoft Academic Search

    Ying-Hui Li; Chun-Xia Chen; Yong-Zhi Liu; Cheng Jiang; Ze-Ya Zou; Yi Ou; Zu-An Li

    2008-01-01

    Neutron dose radiation experiment is designed to study the optocoupler's displacement effects and the noise characteristics. The burst noise is introduced in optocouplers on neutron radiation, which is indicated from experiments. With the increasing neutron radiation the displacement defects in space-charge region increase, the scattering enhances and the noise signal mutations increase. All these represent the noise time series mutations,

  19. Effect of COOH-functionalized SWCNT addition on the electrical and photovoltaic characteristics of Malachite Green dye based photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Chakraborty, S.; Manik, N. B.

    2014-12-01

    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.

  20. Joining characteristics of beta-titanium wires with electrical resistance welding.

    PubMed

    Iijima, Masahiro; Brantley, William A; Yuasa, Toshihiro; Kawashima, Isao; Mizoguchi, Itaru

    2008-05-01

    The goal of this research was to investigate the effects of different conditions for electrical resistance welding of beta-titanium orthodontic wires. Three electrode types were used with a range of power settings on an electrical resistance welding machine to join beta-titanium wires (Resolve, GAC International). Forces that caused bond failures for joined specimens were obtained with tensile loading, and the values were compared using one-way ANOVA and the Tukey test (alpha = 0.05). Metallurgical phases in the joint region were determined by micro-X-ray diffraction. Mean tensile forces for bond failure ranged from 5 to 20 kgf for the eight specimen groups and were dependent on electrode type and power setting. All X-ray diffraction peaks in the joint region were indexed to beta-titanium. Superior bond strength was achieved with the use of wide electrodes. The absence of phases other than beta-titanium in the joint area suggests that the electrical resistance welding may not adversely affect clinically important mechanical properties. Scanning microscope observations indicated that the localized permanent deformation and the formation of an undesirable equiaxed grain structure occurred with the use of narrow electrodes. PMID:17937410

  1. Lightning initiation by simultaneous effect of runaway breakdown and cosmic ray showers

    Microsoft Academic Search

    A. V. Gurevich; K. P. Zybin; R. A. Roussel-Dupre

    1999-01-01

    The combined action of cosmic ray showers (CRS) and runaway breakdown (RB) on thunderstorm atmosphere is studied. The ionization of atmosphere produced by CRS core being strongly amplified in RB conditions is shown to be sufficient to generate a highly ionized plasma region. Electric polarization of this plasma region is manifested in a significant local amplification of a thunderstorm electric

  2. Initiation of breakdown in slender compressible vortices

    NASA Technical Reports Server (NTRS)

    Krause, E.; Menne, S.; Liu, C. H.

    1986-01-01

    The initiation of the breakdown process for axially symmetric compressible flows is investigated using a numerical solution of the conservation equations for mass, momentum, and energy. The vortex is isolated, with its axis parallel to the direction of the main stream, and the core radius is small compared to the breakdown length. Computations for several flowfields indicate that the breakdown of the solution is shifted further downstream with increasing Mach number until breakdown is no longer observed. In the subsonic case, the influence of the initial temperature distribution on the breakdown length of the solution is more pronounced than in the supersonic case, with heating of the core enhancing breakdown, and cooling delaying it. The breakdown of the solution is seen to always occur for nonvanishing axial velocity components.

  3. 1D PIC-DSMC simulations of breakdown in microscale gaps

    NASA Astrophysics Data System (ADS)

    Moore, Chris H.; Hopkins, Matthew M.; Crozier, Paul S.; Boerner, Jeremiah J.; Musson, Lawrence C.; Hooper, Russell W.; Bettencourt, Matthew T.

    2012-11-01

    An explicit electrostatic particle-in-cell (PIC) code with complex boundary conditions and direct simulation Monte Carlo (DSMC) particle collisions is utilized to investigate one dimensional direct current breakdown between two electrodes separated by air at STP. The simulation model includes Auger neutralization and cold field electron emission from the cathode as well as electron-neutral elastic, ionization, and excitation interactions. The simulated breakdown voltages at various electrode gap sizes are compared to experimental data and the Paschen curve. It is found that cold field electron emission can explain the breakdown voltage deviation from the Paschen curve measured for small gaps. Breakdown in large gaps proceeds over multiple ion transit timescales as electrons created via Auger neutralization of ions at the cathode quickly stream across the gap, creating new ions which accelerate towards the cathode and release another "pulse" of electrons. If the resultant pulse of electrons is larger than the initial pulse, then this process can build up a significant quasi-neutral plasma in the gap and the voltage drop across the gap will occur primarily across the (thin) sheath. Breakdown is accelerated if the electric field at the cathode surface is large enough for significant cold field emission flux, which increases the plasma density and decreases the Debye length and thus the sheath size, further increasing the electric field and cold field emission flux from the cathode surface. Breakdown in air pressure gaps was found to be sensitive to the differential scattering cross section for electron-neutral interactions. Isotropic scattering of elastic collisions results in lower breakdown voltages at moderate gaps (several mean free paths) and higher breakdown voltages for large gap sizes compared to when more accurate forward-biased scattering distributions are used. The dependence of breakdown voltage on the scattering distribution is due to a competition between increased backscattering resulting in a larger effective path length across the gap versus changes in the electron energy distribution function.

  4. Electrical characteristic signatures for non-uniformity analysis in HgCdTe photodiode arrays

    NASA Astrophysics Data System (ADS)

    Saxena, Raghvendra Sahai; Nokhwal, Radheshyam; Bhan, R. K.; Sharma, R. K.

    2013-01-01

    In this paper we present a method of analyzing the performance non-uniformity of HgCdTe photodiode arrays for infrared imaging applications. For quantifying the characteristic behavior of various photodiodes, we have parametrized the dynamic resistance verses voltage signatures in such a way that the obtained signature parameters have some relevance with different physical parameters. We also estimated the sensitivity of the proposed signatures on physical parameters using statistical technique. These characteristics signatures may be used to quantify the non-uniformity of the HgCdTe photodiodes in IR imaging arrays and its analysis. The method presented here is based on theoretical calculation of MWIR HgCdTe photodiodes. However, the method is generic and may be implemented on any other type of diode arrays for theoretical or experimental analysis of their non-uniformity.

  5. Metastable Electrical Characteristics of Polycrystalline Thin-Film Photovoltaic Modules upon Exposure and Stabilization: Preprint

    Microsoft Academic Search

    C. A. Deline; J. A. del Cueto; D. S. Albin; S. R. Rummel

    2011-01-01

    The significant features of a series of stabilization experiments conducted at the National Renewable Energy Laboratory (NREL) between May 2009 and the present are reported. These experiments evaluated a procedure to stabilize the measured performance of thin-film polycrystalline cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) thin-film photovoltaic (PV) modules. The current-voltage (I-V) characteristics of CdTe and CIGS thin-film

  6. Electrical and Noise Characteristics of Graphene Field-Effect Transistors: Ambient Effects and Noise Sources

    Microsoft Academic Search

    S. Rumyantsev; G. Liu; W. Stillman; M. Shur; A. A. Balandin

    2010-01-01

    We fabricated a large number of single and bilayer graphene transistors and\\u000acarried out a systematic experimental study of their low-frequency noise\\u000acharacteristics. A special attention was given to determining the dominant\\u000anoise sources in these devices and the effect of aging on the current-voltage\\u000aand noise characteristics. The analysis of the noise spectral density\\u000adependence on the area of

  7. Leakage currrent characteristics and dielectric breakdown of antiferroelectric Pb{sub 0.92}La{sub 0.08}Zr{sub 0.95}Ti{sub 0.05}O{sub 3} film capacitors grown on metal foils.

    SciTech Connect

    Ma, B.; Kwon, D.-K.; Narayanan, M.; Balachandran, U.; Energy Systems

    2008-01-01

    We have grown crack-free antiferroelectric (AFE) Pb{sub 0.92}La{sub 0.08}Zr{sub 0.95}Ti{sub 0.05}O{sub 3} (PLZT) films on nickel foils by chemical solution deposition. To eliminate the parasitic effect caused by the formation of a low-permittivity interfacial oxide, we applied a conductive buffer layer of lanthanum nickel oxide (LNO) on the nickel foil by chemical solution deposition prior to the PLZT deposition. Use of the LNO buffer allowed high-quality film-on-foil capacitors to be prepared at high temperatures in air. With the AFE PLZT deposited on LNO-buffered Ni foils, we observed field-induced phase transformations of AFE to ferroelectric (FE). The AFE-to-FE phase transition field, E{sub AF} = 260 kV cm{sup -1}, and the reverse phase transition field, E{sub FA} = 220 kV cm{sup -1}, were measured at room temperature on a {approx}1.15 {micro}m thick PLZT film grown on LNO-buffered Ni foils. The relative permittivities of the AFE and FE states were {approx}530 and {approx}740, respectively, with dielectric loss <0.05 at room temperature. P-E hysteresis loop measured at room temperature confirmed the field-induced phase transition. The time-relaxation current density was investigated under various applied electric fields. The leakage current density of a 1.15 {micro}m thick AFE PLZT film-on-foil capacitor was 5 x 10{sup -9} A cm{sup -2} at room temperature under 87 kV cm{sup -1} applied field. The breakdown behavior of the AFE PLZT film-on-foil capacitors was studied by Weibull analysis. The mean breakdown time decreased exponentially with increasing applied field. The mean breakdown time was over 610 s when a field of 1.26 MV cm{sup -1} was applied to a 1.15 {micro}m thick AFE PLZT film-on-foil capacitor.

  8. Electricity

    NSDL National Science Digital Library

    Brieske, Joel A.

    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.

  9. IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. III. BREAKDOWN CONDITIONS FOR MINERAL CLOUDS

    SciTech Connect

    Helling, Ch.; Jardine, M.; Stark, C. [SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS (United Kingdom); Diver, D., E-mail: ch@leap2010.eu [SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

    2013-04-20

    Electric discharges were detected directly in the cloudy atmospheres of Earth, Jupiter, and Saturn, are debatable for Venus, and indirectly inferred for Neptune and Uranus in our solar system. Sprites (and other types of transient luminous events) have been detected only on Earth, and are theoretically predicted for Jupiter, Saturn, and Venus. Cloud formation is a common phenomenon in ultra-cool atmospheres such as in brown dwarf and extrasolar planetary atmospheres. Cloud particles can be expected to carry considerable charges which may trigger discharge events via small-scale processes between individual cloud particles (intra-cloud discharges) or large-scale processes between clouds (inter-cloud discharges). We investigate electrostatic breakdown characteristics, like critical field strengths and critical charge densities per surface, to demonstrate under which conditions mineral clouds undergo electric discharge events which may trigger or be responsible for sporadic X-ray emission. We apply results from our kinetic dust cloud formation model that is part of the DRIFT-PHOENIX model atmosphere simulations. We present a first investigation of the dependence of the breakdown conditions in brown dwarf and giant gas exoplanets on the local gas-phase chemistry, the effective temperature, and primordial gas-phase metallicity. Our results suggest that different intra-cloud discharge processes dominate at different heights inside mineral clouds: local coronal (point discharges) and small-scale sparks at the bottom region of the cloud where the gas density is high, and flow discharges and large-scale sparks near, and maybe above, the cloud top. The comparison of the thermal degree of ionization and the number density of cloud particles allows us to suggest the efficiency with which discharges will occur in planetary atmospheres.

  10. Recovery characteristics of the electrically stimulated auditory nerve in deafened guinea pigs: relation to neuronal status.

    PubMed

    Ramekers, Dyan; Versnel, Huib; Strahl, Stefan B; Klis, Sjaak F L; Grolman, Wilko

    2015-03-01

    Successful cochlear implant performance requires adequate responsiveness of the auditory nerve to prolonged pulsatile electrical stimulation. Degeneration of the auditory nerve as a result of severe hair cell loss could considerably compromise this ability. The main objective of this study was to characterize the recovery of the electrically stimulated auditory nerve, as well as to evaluate possible changes caused by deafness-induced degeneration. To this end we studied temporal responsiveness of the auditory nerve in a guinea pig model of sensorineural hearing loss. Using masker-probe and pulse train paradigms we compared electrically evoked compound action potentials (eCAPs) in normal-hearing animals with those in animals with moderate (two weeks after ototoxic treatment) and severe (six weeks after ototoxic treatment) loss of spiral ganglion cells (SGCs). Masker-probe interval and pulse train inter-pulse interval was varied from 0.3 to 16 ms. Whereas recovery assessed with masker-probe was roughly similar for normal-hearing and both groups of deafened animals, it was considerably faster for six weeks deaf animals (? ? 1.2 ms) than for two weeks deaf or normal-hearing animals (? ? 3-4 ms) when 100-ms pulse trains were applied. Latency increased with decreasing inter-pulse intervals, and this was more pronounced with pulse trains than with masker-probe stimulation. With high frequency pulse train stimulation eCAP amplitudes were modulated for deafened animals, meaning that amplitudes for odd pulse numbers were larger than for even pulses. The relative refractory period (?) and the modulation depth of the eCAP amplitude for pulse trains, as well as the latency increase for both paradigms significantly correlated with quantified measures of auditory nerve degeneration (size and packing density of SGCs). In addition to these findings, separate masker-probe recovery functions for the eCAP N1 and N2 peaks displayed a robust non-monotonic or shoulder-shaped course in all animals. The time interval between the N1 and N2 correlated with neuronal refractoriness, suggesting that the N2 peak reflects a second firing of part of the SGC population. We conclude that - compared to the commonly used masker-probe recovery functions - recovery functions obtained with pulse train stimulation may provide a means to augment differences and, by doing so, to more potently discriminate between auditory nerve conditions. PMID:25582354

  11. Magnetic field-aligned electric field acceleration and the characteristics of the optical aurora

    NASA Technical Reports Server (NTRS)

    Christensen, A. B.; Lyons, L. R.; Hecht, J. H.; Sivjee, G. G.; Meier, R. R.

    1987-01-01

    The long-recognized association of brighter aurora with more deeply penetrating, and hence more energetic, electrons is examined. Using the Knight (1973) relation between the magnetic-field-aligned current density and potential drop (derived from the theory of single-particle motion in the presence of a magnetic-field-aligned electric field), an approximate expression relating the energy flux of the precipitating electrons over discrete aurora and the mean particle energy is derived. This expression is used in conjunction with an auroral optical excitation and emission model to specify the dependence of the red/blue ratio of auroral optical emissions on the brightness of the aurora. It is shown that the quantitative predictions of the discrete auroral theory are in accord with observations of the aurora.

  12. Temperature-dependent electrical characteristics of c-Si and CIGS solar cells.

    PubMed

    Choi, Pyung Ho; Baek, Do Hyun; Park, Hyoung Sun; Kim, Sang Soo; Yi, Jun Sin; Kim, Sang Soo; Choi, Byoung Deog

    2014-12-01

    We characterized the electrical behavior of crystalline silicon (c-Si) and Cu(In(1-x)Ga(x))Se2 (CIGS) solar cells by current-voltage (I-V) and capacitance-voltage (C-V) methods. We investigated the temperature-dependent carrier transport mechanism by determining the parameters of ideality factor (n) and activation energy (E(a)) deduced from I-V measurements. CLGS solar cells, as a function of temperature, showed drastic changes in n and E(a) in the space charge region (SCR) that forms near the ZnS/CIGS interface. Furthermore, by using a C-V measured substrate doping profiling method, we confirmed that the CIGS absorption layer had a graded band-gap structure from the end point of the SCR to the CIGS/Mo back contacts, while c-Si solar cells had a uniformly doped carrier concentration. PMID:25971038

  13. Effects of the roughness characteristics on the wire tool surface for the electrical discharge machining properties

    SciTech Connect

    Fukuzawa, Yasushi; Yamashita, Masahide; Mamuro, Hiroaki; Yamashita, Ken [Nagaoka University of Technology, Department of Mechanical Engineering, 1603-1 Kamitomioka-machi, Nagaoka, Niigata, 940-2188 (Japan); Ogata, Masayoshi [Macoho Co., Ltd. 525 Kanawa, Isurugi-machi, Nagaoka, Niigata 940-2032 JAPAN (Japan)

    2011-01-17

    Wire electrical discharge machining (WEDM) has been investigated to obtain the better discharge machining properties of the removal rate and the surface roughness in a few decades. Recently, it revealed that the rough tool electrodes can improve the WEDM properties for some sort of materials. In this study, the rough wire electrodes using a wet blasting method was developed and evaluated the machining performance for the insulated Si{sub 3}N{sub 4} in the WEDM processes. As the results, it could not recognize the advantage of roughness wire electrode under the high-energy condition, but it found that the electro-conductive layer thickness became thinner in comparison with those of normal wires. On the contrary, it could be obtained the better surface roughness in the low energy condition. It was supposed that the roughed wire surface generates the homogeneous dispersion discharges on the workpiece.

  14. Effects of interface reactions on electrical characteristics of metal-GaAs contacts

    SciTech Connect

    Yu, K.M.; Walukiewicz, W.; Jaklevic, J.M.; Haller, E.E.; Sands, T.

    1987-07-20

    Solid-state interface reactions between metal thin films and (100) GaAs substrates at elevated temperatures are studied by conventional and heavy-ion Rutherford backscattering spectrometry, x-ray diffraction, and transmission electron microscopy. Metals investigated in this study include Pt, Pd, Ni, Co, Rh, and W. Electrical properties of the metal/n-GaAs diodes undergoing annealing treatments at various temperatures were also measured with the current-voltage dependence. Optimum diodes with maximum barrier heights as well as minimum leakage currents are obtained for diodes annealed at temperatures at which a uniform thin layer of reacted phase is observable at the interface. The barrier heights of the optimum diodes show a linear dependence on the work functions of the various metals. The range of these barrier heights is limited by nonstoichiometry related defects as suggested by a recently proposed amphoteric native defect model.

  15. Change of electrical characteristics of radio-frequency cables under thermal effect

    NASA Astrophysics Data System (ADS)

    Lobanov, A. V.; Pavlov, P. P.; Khrenkov, N. N.

    1985-01-01

    Four basic temperature dependent electrical parameters of r-f cables are described by expressions which facilitate an analysis of their sensitivity to temperature effects, these parameters being capacitance, wave impedance, attenuation factor and phase shift factor. Calculations for coaxial cables are based on an equivalent dielectric permittivity of the insulation system, including air gap between dielectric and outer conductor produced in the manufacturing process as well as the air gap between dielectric and inner conductor produced by variation of the radius of the latter. Mechanical strains affecting the system geometry are found from the solution to Lame's problem for thin walled cylinders and Hooke's law extended to a three dimensional state of stress. For illustration, numerical results are given for RK-3-28-Pr high precision cables with monolithic Teflon-4D insulation (dielectric constant epsilon = 2.03 at 20 C).

  16. Clinical characteristics and outcome of children with electrical status epilepticus during slow wave sleep

    PubMed Central

    Yilmaz, Sanem; Serdaroglu, Gul; Akcay, Ayfer; Gokben, Sarenur

    2014-01-01

    Background: Electrical status epilepticus in slow wave sleep (ESES) is a rare, age-related, self-limited disorder characterized as epilepsy with different seizure types, neuropsychological impairment in the form of global or selective regression of cognitive functions, motor impairment, and typical electroencephalographic (EEG) findings of continuous epileptic activity occupying 85% of nonrapid eye movement sleep. Aims: The aim is to examine the clinical and electrophysiological findings and treatment modalities of children with ESES and to evaluate the outcome of the disorder. Materials and Methods: Fourteen patients with a diagnosis of electrical status epilepticus during slow wave sleep and followed-up at least 2 years were included. Statistical Analysis: Pearson correlation test was used in the study. Results: Among the 14 patients, eight of them had normal mental development before ESES. Twelve of the patients mentioned cognitive impairment and decline in school performance during ESES. After ESES, seven patients had mental retardation in different severity. One of these patients was diagnosed with benign partial epilepsy of childhood with centrotemporal spikes and had normal intelligence quotient level prior to ESES. The diagnosis of ESES was made after newly occurred different seizure types in four of the patients while two of the previously known epileptic patients presented with only severe psychiatric impairment. Valproic acid and carbamazepine were the mostly frequently used drugs before the onset of ESES. After at least 2 years of follow-up, seven patients were seizure free, but still taking antiepileptic treatment. Five patients were seizure free, while two of them had ongoing seizures despite antiepileptic therapy. Conclusion: ESES should be kept in mind in children with unexplained regression or stagnation of development associated with seizures or not. Sleep EEGs should be performed for timely diagnosis, proper treatment and prevention of permanent cognitive impairment. PMID:25250061

  17. Electrical and photovoltaic characteristics of Ni/(n)Bi2S3 Schottky barrier junction

    NASA Astrophysics Data System (ADS)

    Hussain, Amir; Rahman, Atowar

    2015-04-01

    Ni doped nanocrystalline Bi2S3 thin films are chemically deposited on Fluorine Doped Tin Oxide (FTO) substrate from the solution containing Ni(NO3)2, Bi(NO3)3.5H2O, C6H15NO3 and CH2CS.NH2 at deposition temperature 318 K. The Current-voltage (I-V) characteristics of the junctions are measured in the temperature range 300-340 K and junction parameters are calculated. The ideality factor (n) and barrier height (?b) at different temperature are found to vary from 4.7 to 3.8 and 0.74 to 0.79 respectively. It is observed that the ideality factor decreases while the barrier height increases with increase of temperature. The calculated junction parameters are strongly temperature dependent. The discrepancy between the barrier height obtained from capacitance-voltage (C-V) and current-voltage (I-V) characteristics is analyzed. The carrier concentration determined from the C-V plot is found to be of the order 1017/cm3.

  18. On the electrical characteristics of latent finger mark corrosion of brass

    NASA Astrophysics Data System (ADS)

    Bond, J. W.

    2008-06-01

    Apparatus constructed to measure the variation (?V) in applied potential (V) over the surface of brass discs subject to corrosion by latent finger mark deposits is described. Results show values of ?V of up to 14 V for V = 1400 V on regions of disc coincident with the location of finger mark corrosion. Measurement of ?V for 0 V <= V <= 1400 V has revealed a non-linear relationship, which is very similar to that measured for a commercial metal-semiconductor Schottky rectifier. Further experiments have shown the corrosion product on the brass to be a p-type semiconductor with current/voltage characteristics for the brass-corrosion contact consistent with the characteristics expected for a rectifying metal-semiconductor contact. The composition of the semiconductor is discussed in terms of metal oxide corrosion products with p-type copper (I) and copper (II) oxides thought most likely to be responsible for the semiconductor behaviour of the corrosion product. A simple model is described for the galvanic corrosion of brass by finger mark deposits that is consistent with the experimental results.

  19. Modification of graphene/SiO2 interface by UV-irradiation: effect on electrical characteristics.

    PubMed

    Imamura, Gaku; Saiki, Koichiro

    2015-02-01

    Graphene is a promising material for next-generation electronic devices. The effect of UV-irradiation on the graphene devices, however, has not been fully explored yet. Here we investigate the UV-induced change of the field effect transistor (FET) characteristics of graphene/SiO2. UV-irradiation in a vacuum gives rise to the decrease in carrier mobility and a hysteresis in the transfer characteristics. Annealing at 160 °C in a vacuum eliminates the hysteresis, recovers the mobility partially, and moves the charge neutrality point to the negative direction. Corresponding Raman spectra indicated that UV-irradiation induced D band relating with defects and the annealing at 160 °C in a vacuum removed the D band. We propose a phenomenological model for the UV-irradiated graphene, in which photochemical reaction produces dangling bonds and the weak sp(3)-like bonds at the graphene/SiO2 interface, and the annealing restores the intrinsic graphene/SiO2 interface by removal of such bonds. Our results shed light to the nature of defect formation by UV-light, which is important for the practical performance of graphene based electronics. PMID:25569142

  20. Frequency characteristics of a nuclear spin maser for the search for the electric dipole moment of 129Xe atom

    NASA Astrophysics Data System (ADS)

    Inoue, T.; Tsuchiya, M.; Furukawa, T.; Hayashi, H.; Nanao, T.; Yoshimi, A.; Uchida, M.; Matsuo, Y.; Asahi, K.

    2011-01-01

    Frequency characteristics of a 129Xe nuclear spin maser was studied, which is under development at Tokyo Institute of Technology for the search for a permanent electric dipole moment in diamagnetic 129Xe atom. Drifts in the solenoid current and cell temperature were found to be the most influential factors on the maser frequency. From correlation coefficient analysis, there seem to exist other origins of frequency fluctuation, such as phase drifts in the maser oscillation. In order to improve the stability of the maser frequency, the intensity of the pumping laser required to fully polarize 129Xe nuclei was evaluated. Construction of a polarization assessment system for 129Xe gas cells and development of a new scheme of current stabilization are also remarked.

  1. Temperature dependence of electrical characteristics of Pt/GaN Schottky diode fabricated by UHV e-beam evaporation

    PubMed Central

    2013-01-01

    Temperature-dependent electrical characterization of Pt/n-GaN Schottky barrier diodes prepared by ultra high vacuum evaporation has been done. Analysis has been made to determine the origin of the anomalous temperature dependence of the Schottky barrier height, the ideality factor, and the Richardson constant calculated from the I-V-T characteristics. Variable-temperature Hall effect measurements have been carried out to understand charge transport at low temperature. The modified activation energy plot from the barrier inhomogeneity model has given the value of 32.2 A/(cm2 K2) for the Richardson constant A** in the temperature range 200 to 380 K which is close to the known value of 26.4A/(cm2 K2) for n-type GaN. PMID:24229424

  2. Room temperature-synthesized vertically aligned InSb nanowires: electrical transport and field emission characteristics

    PubMed Central

    2013-01-01

    Vertically aligned single-crystal InSb nanowires were synthesized via the electrochemical method at room temperature. The characteristics of Fourier transform infrared spectrum revealed that in the syntheses of InSb nanowires, energy bandgap shifts towards the short wavelength with the occurrence of an electron accumulation layer. The current–voltage curve, based on the metal–semiconductor–metal model, showed a high electron carrier concentration of 2.0?×?1017?cm?3 and a high electron mobility of 446.42?cm2?V?1?s?1. Additionally, the high carrier concentration of the InSb semiconductor with the surface accumulation layer induced a downward band bending effect that reduces the electron tunneling barrier. Consequently, the InSb nanowires exhibit significant field emission properties with an extremely low turn-on field of 1.84?V??m?1 and an estimative threshold field of 3.36?V??m?1. PMID:23399075

  3. Electric-field-induced current-voltage characteristics in electronic conducting perovskite thin films

    NASA Astrophysics Data System (ADS)

    Rupp, Jennifer L. M.; Reinhard, Patrick; Pergolesi, Daniele; Ryll, Thomas; Tölke, Rene; Traversa, Enrico

    2012-01-01

    Mixed ionic-electronic conductors (MIECs) such as the (La,Sr)(Co,Fe)O3-d perovskite family are well described in their charge transport through their high temperature applications, i.e., as solid-oxide fuel cell electrodes (600-1000 °C). In this study, the current-voltage (I-V) profiles of these well-known MIEC perovskites are studied between room temperature and 150 °C under bias of ±15 V for potential applications in resistance random access memories. The impact of the metal-oxide interface on the I-V characteristics ranging from ohmic to non-linear hysteretic is discussed for metals of varying work functions and redox potentials, as well as changes in metal electrode distances and areas.

  4. Breakdown voltage calculations using PIC-DSMC

    NASA Astrophysics Data System (ADS)

    Crozier, Paul; Boerner, Jeremiah; Hopkins, Matthew; Moore, Christopher; Musson, Lawrence

    2012-10-01

    In general, modeling and simulation provide physical insight and enable extrapolative predictions beyond theory and experimental data. In the specific case of electrostatic discharges, modeling and simulation may enable extrapolative predictions of breakdown voltages and a better physical understanding of breakdown phenomena. Using our PIC-DSMC software, we compute breakdown voltages for molecular nitrogen gas and compare our results against Bolsig+ for simple 1D geometries. We further verify our breakdown voltage calculations for a simple 3D geometry. In these calculations, 25 different N2 -- electron interactions are included and good agreement with Bolsig+ is observed. Our approach to computing breakdown voltages using PIC-DSMC software can be extended to the prediction of breakdown voltages in more difficult cases where experimental data may be unavailable and the Paschen equation assumptions are no longer valid, as in the cases of complex 3D geometries and microscale discharges.

  5. Particle-in-cell simulation of gas breakdown in microgaps

    NASA Astrophysics Data System (ADS)

    Radmilovic-Radjenovic, M.; Lee, J. K.; Iza, F.; Park, G. Y.

    2005-03-01

    Gas breakdown in large scale systems has been widely studied and is reasonably well understood. Deviations from the well-known Paschen law, however, have been reported in microgaps. One possible mechanism responsible for these deviations is the increase of the secondary electron emission yield due to the quantum tunnelling of electrons from the metal electrodes to the gas phase. The high electric fields obtained in small gaps combined with the lowering of the potential barrier seen by the electrons in the cathode as an ion approaches lead to the onset of ion-enhanced field emissions. Particle-in-cell/Monte Carlo simulations including ion-enhanced field emission have been performed to evaluate the importance of these mechanisms in the discharge breakdown. Deviations from the Paschen curve in gaps smaller than 5 µm can be explained based on this mechanism.

  6. The effects of ion gun beam voltage on the electrical characteristics of NbCN/PbBi edge junctions

    NASA Technical Reports Server (NTRS)

    Lichtenberger, A. W.; Feldman, M. J.; Mattauch, R. J.; Cukauskas, E. J.

    1989-01-01

    The authors have succeeded in fabricating high-quality submicron NbCN edge junctions using a technique which is commonly used to make Nb edge junctions. A modified commercial ion gun was used to cut an edge in SiO2/NbCN films partially covered with photoresist. An insulating barrier was then formed on the exposed edge by reactive ion beam oxidation, and a counterelectrode of PbBi was deposited. The electrical quality of the resulting junctions was found to be strongly influenced by the ion beam acceleration voltages used to cut the edge and to oxidize it. For low ion beam voltages, the junction quality parameter was as high as Vm = 55 mV (measured at 3 mV), but higher ion beam voltages yielded strikingly poorer quality junctions. In light of the small coherence length of NbN, the dependence of the electrical characteristics on ion beam voltage is presumably due to mechanical damage of the NbCN surface. In contrast, for similar ion beam voltages, no such dependence was found for Nb edge junctions.

  7. Low-temperature electrical characteristics of the Au/Si interface

    NASA Astrophysics Data System (ADS)

    Tran, A.; Yang, C. Y.; Gao, M.; Kim, N.; Cooley, R. F.

    1987-05-01

    An investigation has been conducted on the irregular electrical behavior of eutectic and polyimide die-attached NMOS devices at low temperatures. The nature of the Au/Si interface on the back side of each die is the focus of this study. A test structure consisting of alloyed gold films on both sides of the wafer was fabricated. Models of the structure were proposed to explain the observed low-temperature behavior. The Au/Si interface was assumed to be a Schottky junction. This assumption was confirmed in conjunction with measurements on another test structure which consists of Au on the back side and Al on the front side. It had been suspected that contamination introduced from the eutectic die-attach materials was solely responsible for the observed behavior. However, tests conducted on heat-treated polyimide die-attached NMOS devices produced similar observation. Solutions to the problem were discussed and a simple technique to eliminate the rectifying behavior of Au/p-Si contacts was described.

  8. Experiment for measurements of the gas breakdown statistics by ramp voltage pulses

    SciTech Connect

    Markovic, V. Lj.; Stamenkovic, S. N.; Gocic, S. R.; Petrovic, Z. Lj. [Department of Physics, University of Nis, P.O. Box 224, 18001 Nis (Serbia and Montenegro); Institute of Physics, P.O. Box 68, 11080 Belgrade (Serbia and Montenegro)

    2006-09-15

    In the first part of this article the electronic automatic system for the measurements of dynamic breakdown voltages U{sub b} with linearly rising (ramp) pulses is presented. It generates the sequence of ramp pulses with subvoltage level U{sub sub}{approx_equal}0 during the relaxation time {tau} of the tube, and the ramp pulses start from the static breakdown voltage U{sub s}, thus enabling the correct study of electrical breakdowns and relaxation in gases. In the second part the measurements in argon with and without a voltage during the off period of the pulse are analyzed. The influence of the subvoltage on the mean value of the breakdown voltage U{sub b} as a function of the rise rate k, on the statistical U{sub b} distributions and on the afterglow kinetics is also discussed.

  9. Fine properties of trains of unusually strong preliminary breakdown pulses observed at different distances

    NASA Astrophysics Data System (ADS)

    Kolmasova, Ivana; Santolik, Ondrej; Farges, Thomas; Diendorfer, Gerhard; Lan, Radek; Uhlir, Ludek

    2015-04-01

    We analyze fine characteristics of trains of unusually strong preliminary breakdown pulses (PBPs) measured at different distances by two different receivers. Each of the observed trains of PBPs preceded a follow-up pulse (FP) which arrived with a time delay corresponding to a usually occurring return stroke (RS). However, most of the observed FPs can be identified as non-RS bipolar pulses; only in one case we observe a very weak return stroke. The amplitudes of the largest PBPs reach, on average, four times the amplitudes of the following return strokes or non-RS bipolar pulses. This could indicate an abnormally electrified storm and a high occurrence of attempted cloud-to-ground leaders. High-resolution magnetic-field waveforms were measured at distances between 69 and 176 km from the source lightning, as it was identified by lightning detection network EUCLID. The time derivative of the magnetic field was detected with a newly designed Shielded Loop Antenna with a Versatile Integrated Amplifier (SLAVIA) and sampled at 80 MHz using a ground-based version of a broadband receiver which is being prepared for the TARANIS spacecraft. . . Electric-field waveforms were measured at distances between 258 and 377 km using a receiver sampling at 12 MHz. We use these electric field waveforms and numerically integrated magnetic field waveform records to analyze properties of the PBP trains. Our dataset consists of 10 trains of preliminary breakdown pulses measured during one thunderstorm which occurred in Southern France in June 2013 and lasted about four hours. The lightning detection network EUCLID misclassified 4 strong preliminary breakdown pulses as cloud-to-ground RSs, in 6 other cases they were classified as intra-cloud (IC) discharges. Follow-up pulses were absent in the list provided by EUCLID (6 cases) or classified as negative cloud-to-ground (2 cases) or IC discharges (2 cases). We estimate the duration of the trains and the time between the first pulse in the train and the FP peak. We estimate the amplitude ratios of the largest PBP and the FP peaks in each individual train at different distances. We also investigate the variability in the pulse shapes belonging to the PBP trains and the fine structure of the FP waveforms. Finally, we compare the properties of the trains of unusually strong PBPs with the regular trains of PBPs preceding usual negative cloud-to-ground flashes.

  10. Evaluation of breakdown characteristics of gas insulated switchgears for non-standard lightning impulse waveforms - analysis and generation circuit of non-standard lightning impulse waveforms in actual field

    Microsoft Academic Search

    Shigemitsu Okabe; Sadayuki Yuasa; Shuhei Kaneko

    2007-01-01

    To lower the insulation specifications (specifically, the lightning impulse withstand voltage) of a gas insulated switchgear (GIS) and thus cut the equipment cost while maintaining the high reliability of its insulation performance, it is necessary to define in an organized way the insulation characteristics for non-standard lightning impulse voltage waveforms that represent actual surge waveforms in the field and compare

  11. Thermal breakdown of gypsum crystals

    SciTech Connect

    Kuznetsova, L.F.; Lomovskii, O.I.

    1986-03-01

    This paper reports which gypsum dehydration step is responsible, and to what degree, for developing the morphology of the reaction product and whether it is possible to affect it by changing the reaction conditions. The authors show that the thermal breakdown (200 D) of gypsum single crystals in a 1.33 Pa vacuum changed the original monoclinic structure to a hexagonal and then to a orthorhombic configuration. Conversion of the monoclinic to the hexagonal structure was accompanied by the formation of parallel cracks on the plane. The cracks were oriented along the c axis of the original single crystal.

  12. Electrical transport and contact characteristics of single layer MoS2 devices

    NASA Astrophysics Data System (ADS)

    Chen, Jen-Ru; Odenthal, Patrick; Kawakami, Roland

    2013-03-01

    MoS2 and related metal dichalcogenides (MoSe2, WS2, WSe2) are layered two dimensional materials with analogous structure to graphene. The monolayer MoS2, where the Mo layer is sandwiched between two sulfur layers, is a semiconductor with a direct band gap (1.8 eV) at valley K and K' points. These materials are of significant technological interest for nanoscale electronic devices with high on off ratio, opto-electronics, and gas sensing. Also, due to giant spin-orbit coupling and spin splitting (~ 150 meV) in the valence band of monolayer MoS2, monolayer MoS2 has great potential for fascinating spin behavior, including the intrinsic spin Hall effect. Towards investigating spin transport in monolayer MoS2, we have investigated ferromagnetic metal contacts on monolayer MoS2. Through transport measurements, we are able to determine the Schottky barrier height between the Co contact electrodes and monolayer MoS2 with characteristic temperature dependence.

  13. A study of the characteristics and limitations of various platings on cylindrical electrical conductors

    NASA Astrophysics Data System (ADS)

    Scully, Robert C.

    This work explores the impedance characteristics of copper wires plated with tin, silver, or nickel, the most common type of wiring used in the computer, communications, and aerospace industries. The background of plated wires and a brief review of related research is provided. This is followed by a detailed development of the theory of plated wires, accompanied by a MAPLE code in the appendix that can be used for the numerical analysis of plated wires having two or more plating layers. The code was used to generate a series of curves predicting the impedance behavior of both solid, "pure" metals, as well as copper wire plated with silver, tin, and nickel. Additional curves are provided highlighting the very interesting impedance behavior of nickel plated copper wire. All of these curves are accompanied by a number of observations to point out the more interesting aspects of the behavior. Several impedance measurements of commonly available military specification plated wire stranded conductors are then discussed. A number of the attempted measurements were unable to resolve the very small impedances. Even so, a last attempt worked very well to demonstrate the predicted impedance behavior, as evidenced by the measured raw data curves shown in contrast to the same curves with fixture parasitics removed. Insertion loss measurements were then made of commonly available military specification plated wire twisted shielded pair that provided further confirming evidence for the predictions made from the numerical analysis. In all cases, observations and comments are provided to explain why some measurements were superior to others, and why certain steps were taken to defeat interference from clouding the results. The document closes with recommendations for future efforts and concluding remarks.

  14. Electrical characteristics of frog atrial trabeculae in the double sucrose gap.

    PubMed Central

    Connor, J; Barr, L; Jakobsson, E

    1975-01-01

    The electrical behavior of small single frog atrial trabeculae in the double sucrose gap has been investigated. The currents injected during voltage clamp experiments did not behave as predicted from the assumption of spatial uniformity of the voltage across a Hodgkin-Huxley membrane. Much of the difference is due to the geometrical complexities of this tissue. Nonetheless, two transient inward currents have been identified, the faster of which is blocked by tetrodotoxin (TTX). The magnitude of the slower transient varies markedly between preparations but always increases in a given preparation with increase of external calcium. The fast transient current traces, at small to intermediate depolarizations, are often marred by the presence of notches and secondary peaks due most probably to the loss of space clamp conditions. In many preparations these could be removed by reducing the current magnitude through application of a partially-blocking dose of TTX. Conversely, in the preparations whose fast transient was fully blocked by TTX, notches and secondary peaks in the slow transient could by induced through increasing calcium concentration and thereby the slow current magnitude. Previously used techniques for the measurement of the reversal potential of the fast inward transient have been shown to be invalid. In so far as they can be measured, the reversal potentials of the fast and slow inward transient are in the same neighborhood, i.e. around 120 mV from rest. The true values may be quite a bit apart. The total charge flow in the capacitive transient was measured for different sized nodes and preparations. From these data and estimates of plasma membrane area per unit trabecular volume, specific membrane capacitances of around 3 muF/cm2 were calculated for small bundles. The apparent ion current densities on this basis are approximately 1/10 of those measured in axons. The capacitive current occurring in small bundles decayed as the sum of at least three exponential functions of time. On the basis of these data and the anomalously large stable node widths, we suggest a coaxial core model of the preparation with the inner elements in series with an additional large extracellular resistance. PMID:1081889

  15. Cell separation using electric fields

    NASA Technical Reports Server (NTRS)

    Mangano, Joseph A. (Inventor); Eppich, Henry M. (Inventor)

    2003-01-01

    The present invention involves methods and devices which enable discrete objects having a conducting inner core, surrounded by a dielectric membrane to be selectively inactivated by electric fields via irreversible breakdown of their dielectric membrane. One important application of the invention is in the selection, purification, and/or purging of desired or undesired biological cells from cell suspensions. According to the invention, electric fields can be utilized to selectively inactivate and render non-viable particular subpopulations of cells in a suspension, while not adversely affecting other desired subpopulations. According to the inventive methods, the cells can be selected on the basis of intrinsic or induced differences in a characteristic electroporation threshold, which can depend, for example, on a difference in cell size and/or critical dielectric membrane breakdown voltage. The invention enables effective cell separation without the need to employ undesirable exogenous agents, such as toxins or antibodies. The inventive method also enables relatively rapid cell separation involving a relatively low degree of trauma or modification to the selected, desired cells. The inventive method has a variety of potential applications in clinical medicine, research, etc., with two of the more important foreseeable applications being stem cell enrichment/isolation, and cancer cell purging.

  16. Cell separation using electric fields

    NASA Technical Reports Server (NTRS)

    Mangano, Joseph (Inventor); Eppich, Henry (Inventor)

    2009-01-01

    The present invention involves methods and devices which enable discrete objects having a conducting inner core, surrounded by a dielectric membrane to be selectively inactivated by electric fields via irreversible breakdown of their dielectric membrane. One important application of the invention is in the selection, purification, and/or purging of desired or undesired biological cells from cell suspensions. According to the invention, electric fields can be utilized to selectively inactivate and render non-viable particular subpopulations of cells in a suspension, while not adversely affecting other desired subpopulations. According to the inventive methods, the cells can be selected on the basis of intrinsic or induced differences in a characteristic electroporation threshold, which can depend, for example, on a difference in cell size and/or critical dielectric membrane breakdown voltage. The invention enables effective cell separation without the need to employ undesirable exogenous agents, such as toxins or antibodies. The inventive method also enables relatively rapid cell separation involving a relatively low degree of trauma or modification to the selected, desired cells. The inventive method has a variety of potential applications in clinical medicine, research, etc., with two of the more important foreseeable applications being stem cell enrichment/isolation, and cancer cell purging.

  17. Effect of Interface Microrelief on Optical, Electrical and Photoelectric Characteristics of Heteroepitaxial AlxGa1-xAs\\/GaAs Structures

    Microsoft Academic Search

    N. L. Dmitruk; O. Yu. Borkovskaya; R. V. Konakova; A. V. Korovin; I. B. Mamontova; O. S. Kondratenko

    2006-01-01

    We have investigated the dependence of optical, photoelectric and electrical characteristics of heteroepitaxial AlxGa1-x As\\/GaAs structures on active interface microrelief morphology. Experimental study of heterostructures included analysis of surface microrelief parameters by AFM techniques, measurements of specular and diffuse reflection spectra, the dark and light current-voltage (I-V) characteristics and spectra of the short-circuit photocurrent. Investigation showed that advantages of optical

  18. Hybrid Breakdown in Cichlid Fish

    PubMed Central

    Stelkens, Rike Bahati; Schmid, Corinne; Seehausen, Ole

    2015-01-01

    Studies from a wide diversity of taxa have shown a negative relationship between genetic compatibility and the divergence time of hybridizing genomes. Theory predicts the main breakdown of fitness to happen after the F1 hybrid generation, when heterosis subsides and recessive allelic (Dobzhansky-Muller) incompatibilities are increasingly unmasked. We measured the fitness of F2 hybrids of African haplochromine cichlid fish bred from species pairs spanning several thousand to several million years divergence time. F2 hybrids consistently showed the lowest viability compared to F1 hybrids and non-hybrid crosses (crosses within the grandparental species), in agreement with hybrid breakdown. Especially the short- and long-term survival (2 weeks to 6 months) of F2 hybrids was significantly reduced. Overall, F2 hybrids showed a fitness reduction of 21% compared to F1 hybrids, and a reduction of 43% compared to the grandparental, non-hybrid crosses. We further observed a decrease of F2 hybrid viability with the genetic distance between grandparental lineages, suggesting an important role for negative epistatic interactions in cichlid fish postzygotic isolation. The estimated time window for successful production of F2 hybrids resulting from our data is consistent with the estimated divergence time between the multiple ancestral lineages that presumably hybridized in three major adaptive radiations of African cichlids. PMID:25996870

  19. Work Breakdown Structure (WBS) Handbook

    NASA Technical Reports Server (NTRS)

    2010-01-01

    The purpose of this document is to provide program/project teams necessary instruction and guidance in the best practices for Work Breakdown Structure (WBS) and WBS dictionary development and use for project implementation and management control. This handbook can be used for all types of NASA projects and work activities including research, development, construction, test and evaluation, and operations. The products of these work efforts may be hardware, software, data, or service elements (alone or in combination). The aim of this document is to assist project teams in the development of effective work breakdown structures that provide a framework of common reference for all project elements. The WBS and WBS dictionary are effective management processes for planning, organizing, and administering NASA programs and projects. The guidance contained in this document is applicable to both in-house, NASA-led effort and contracted effort. It assists management teams from both entities in fulfilling necessary responsibilities for successful accomplishment of project cost, schedule, and technical goals. Benefits resulting from the use of an effective WBS include, but are not limited to: providing a basis for assigned project responsibilities, providing a basis for project schedule development, simplifying a project by dividing the total work scope into manageable units, and providing a common reference for all project communication.

  20. Production Lot Sizing with Machine Breakdowns

    Microsoft Academic Search

    Harry Groenevelt; Liliane Pintelon; Abraham Seidmann

    1992-01-01

    Economic lot sizing and batching models often assume reliable manufacturing facilities. In this research, we focus on the effects of machine breakdowns and corrective maintenance on the economic lot sizing decisions. Two production control policies are proposed for coping with these stochastic interferences. The first policy assumes that production of the interrupted lots is not resumed after a breakdown. Instead,

  1. Telecommunication BreakdownConcepts of Communication

    E-print Network

    Sethares, William A.

    Telecommunication BreakdownConcepts of Communication Transmitted via Software-Defined Radio C. Richard Johnson Jr. · William A.Sethares #12;TELECOMMUNICATION BREAKDOWN or How I Learned to Stop Worrying before the industry went and did it. Our editor wanted a subtitle mentioning the book's actual content

  2. Simulation of vortex breakdown in tubes

    NASA Technical Reports Server (NTRS)

    Menne, Stefan

    1988-01-01

    The breakdown of a vortex flow in a tube is studied for a slightly diverging tube by means of a numerical solution of the Navier-Stokes equations for a quasi-stationary, incompressible, laminar flow. Numerical results are compared to experiments of Faler and Leibovich. The numerical data display features similar to the experimental results concerning breakdown conditions, location, and structure.

  3. Physical mechanism of initial breakdown pulses and narrow bipolar events in lightning discharges

    NASA Astrophysics Data System (ADS)

    Silva, Caitano L.; Pasko, Victor P.

    2015-05-01

    To date the true nature of initial breakdown pulses (IBPs) and narrow bipolar events (NBEs) in lightning discharges remains a mystery. Recent experimental evidence has correlated IBPs to the initial development of lightning leaders inside the thundercloud. NBE wideband waveforms resemble classic IBPs in both amplitude and duration. Most NBEs are quite peculiar in the sense that very frequently they occur in isolation from other lightning processes. The remaining fraction, 16% of positive polarity NBEs, according to Wu et al. (2014), happens as the first event in an otherwise regular intracloud lightning discharge. These authors point out that the initiator type of NBEs has no difference with other NBEs that did not start lightning, except for the fact that they occur deeper inside the thunderstorm (i.e., at lower altitudes). In this paper, we propose a new physical mechanism to explain the source of both IBPs and NBEs. We propose that IBPs and NBEs are the electromagnetic transients associated with the sudden (i.e., stepwise) elongation of the initial negative leader extremity in the thunderstorm electric field. To demonstrate our hypothesis a novel computational/numerical model of the bidirectional lightning leader tree is developed, consisting of a generalization of electrostatic and transmission line approximations found in the literature. Finally, we show how the IBP and NBE waveform characteristics directly reflect the properties of the bidirectional lightning leader (such as step length, for example) and amplitude of the thunderstorm electric field.

  4. Characterization of solar cells for space applications. Volume 14: Electrical characteristics of Hughes liquid phase epitaxy gallium arsenide solar cells as a function of intensity, temperature and irradiation

    NASA Technical Reports Server (NTRS)

    Anspaugh, B. E.; Downing, R. G.; Miyahira, T. F.; Weiss, R. S.

    1981-01-01

    Electrical characteristics of liquid phase epitaxy, P/N gallium aluminum arsenide solar cells are presented in graphical and tabular format as a function of solar illumination intensity and temperature. The solar cells were exposed to 1 MeV electron fluences of, respectively, 0, one hundred trillion, one quadrillion, and ten quadrillion e/sq cm.

  5. Characterization of terrestrial solar cells for space applications: Electrical characteristics of thin Westinghouse dendritic web cells as a function of solar intensity, temperature, and incidence angle

    NASA Technical Reports Server (NTRS)

    Stella, P. M.; Anspaugh, B. E.

    1985-01-01

    Electrical characteristics of thin (100- and 140-micron) Westinghouse dendritic-web N/P silicon solar cells are presented in graphical and tabular format as a function of solar illumination intensity and temperature. Performance is also shown as a function of solar illlumination angle of incidence for AMO.

  6. Improvement of adhesion of electric vehicles using series motors. Readhesion characteristics in line with those of separately excited motor and promotion of recovery of tractive effort after readhesion

    SciTech Connect

    Sone, S.; Yokota, T.; Kakizoe, H.

    1982-01-01

    Historically, the unit power of electric vehicles has been small in Japan, and full effort for the improvement of adhesion has not been given. As a result, the adhesion characteristics are significantly inferior to the typical European vehicles. It is well known that the best way to materialize a high adhesion vehicle is to use external excitation motors with independent control of each axle. However, the independently controlled external excitation motor is neither necessarily economical with the scale of vehicles in Japan, nor is the technical background sufficient. This paper attempts to improve the adhesion characteristics, which have been used widely in the extension of serial motor technology. The possibility of good adhesion characteristics in line with external excitation motors with serial motors controlled by fast response power electronics with choppers and controlled rectifiers is shown and a practical proposal for realistic conditions is made. This paper discusses the adhesion characteristics only with regard to the readhesion and traction recovery characteristics.

  7. Surface analysis of oxygen free electrolytic-copper X-band accelerating structures and possible correlation to radio frequency breakdown events

    NASA Astrophysics Data System (ADS)

    Harvey, S. E.; Le Pimpec, F.; Kirby, R. E.; Marcelja, F.; Adamson, K.; Garwin, E. L.

    2004-07-01

    X-band accelerator structures meeting the next linear collider design requirements have been found to suffer vacuum surface damage caused by rf breakdown, when processed to high electric-field gradients. Improved understanding of these breakdown events is desirable for the development of structure designs, fabrication procedures, and processing techniques that minimize structure damage. rf reflected wave analysis and acoustic sensor pickup have provided breakdowns localization in rf structures. Particle contaminations found following clean autopsy of four rf-processed traveling wave structures have been catalogued and analyzed. Their influence on rf breakdown, as well as that of several other material-based properties, are discussed. .

  8. Kinetic modeling of the Townsend breakdown in argon

    NASA Astrophysics Data System (ADS)

    Macheret, S. O.; Shneider, M. N.

    2013-10-01

    Kinetic modeling of the Townsend breakdown in argon was performed in the "forward-back" approximation. The kinetic model was found to adequately describe the left branch of the Paschen curve, and the important role of ionization by fast ions and atoms near the cathode, as well as the increase in secondary emission coefficient in strong electric fields described in the literature, was confirmed. The modeling also showed that the electron energy distribution function develops a beam of high-energy electrons and that the runaway effect, i.e., the monotonic increase of the mean electron energy with the distance from the cathode, occurs at the left branch of the Paschen curve.

  9. Breakdown of the dipole approximation in strong-field ionization.

    PubMed

    Ludwig, A; Maurer, J; Mayer, B W; Phillips, C R; Gallmann, L; Keller, U

    2014-12-12

    We report the breakdown of the electric dipole approximation in the long-wavelength limit in strong-field ionization with linearly polarized few-cycle mid-infrared laser pulses at intensities on the order of 10¹³ W/cm². Photoelectron momentum distributions were recorded by velocity map imaging and projected onto the beam propagation axis. We observe an increasing shift of the peak of this projection opposite to the beam propagation direction with increasing laser intensities. From a comparison with semiclassical simulations, we identify the combined action of the magnetic field of the laser pulse and the Coulomb potential as the origin of our observations. PMID:25541770

  10. Mechanical vibrations induced resonant breakdown of the Coulomb blockade

    SciTech Connect

    Pogosov, A. G.; Budantsev, M. V.; Shevyrin, A. A. [Institute of Semiconductor Physics, SB RAS, Novosibirsk (Russian Federation); Novosibirsk State University, Novosibirsk (Russian Federation); Plotnikov, A. E.; Bakarov, A. K.; Toropov, A. I. [Institute of Semiconductor Physics, SB RAS, Novosibirsk (Russian Federation)

    2011-12-23

    Influence of forced mechanical vibrations of a suspended single-electron transistor on electron tunneling through the quantum dot limited by the Coulomb blockade is investigated. It is shown that mechanical oscillations of the quantum dot lead to the Coulomb blockade breakdown, shown in sharp resonant peaks in the transistor conductance dependence on the excitation frequency at values corresponding to the mechanical oscillations eigen modes. The observed effect is presumably connected with oscillations of the mutual electrical capacitances between the quantum dot and surrounding electrodes.

  11. Analysis of low-pressure dc breakdown in nitrogen between two spherical iron electrodes

    NASA Astrophysics Data System (ADS)

    Pejovic, Momcilo M.; Nesic, Nikola T.; Pejovic, Milic M.

    2006-02-01

    The influence of afterglow period ?, voltage increase rate k, and electrode gap d on breakdown voltage Ub for a nitrogen-filled tube with spherical electrodes of diameter D ?d and p =6.5mbar has been investigated. The data for the breakdown voltage were obtained for the case when there is a presence of N(S4) atoms, which release secondary electrons via recombination on the cathode. By fitting the experimental data of breakdown voltage mean values as a function of the voltage increase rate, the static breakdown voltages for afterglow periods of 15 and 100 s were estimated. The electrical field as a function of the electrode gap using breakdown voltage mean values was also determined. It is shown that experimental results of the breakdown voltage mean value as a function of pd in the interval of d from 0.82 to 1.62 mm can be very well described with Paschen's law, valid for the case of parallel-plate electrodes.

  12. Analysis of low-pressure dc breakdown in nitrogen between two spherical iron electrodes

    SciTech Connect

    Pejovic, Momcilo M.; Nesic, Nikola T.; Pejovic, Milic M. [Faculty of Electronic Engineering, University of Nis, P.O. Box 73, 18001 (Serbia and Montenegro)

    2006-02-15

    The influence of afterglow period {tau}, voltage increase rate k, and electrode gap d on breakdown voltage U{sub b} for a nitrogen-filled tube with spherical electrodes of diameter D>>d and p=6.5 mbar has been investigated. The data for the breakdown voltage were obtained for the case when there is a presence of N({sup 4}S) atoms, which release secondary electrons via recombination on the cathode. By fitting the experimental data of breakdown voltage mean values as a function of the voltage increase rate, the static breakdown voltages for afterglow periods of 15 and 100 s were estimated. The electrical field as a function of the electrode gap using breakdown voltage mean values was also determined. It is shown that experimental results of the breakdown voltage mean value as a function of pd in the interval of d from 0.82 to 1.62 mm can be very well described with Paschen's law, valid for the case of parallel-plate electrodes.

  13. Analytical model of the breakdown mechanism in a two-phase mixture

    NASA Astrophysics Data System (ADS)

    Qizheng, Ye; Jin, Li; Zhihui, Xie

    2004-12-01

    A two-phase mixture (TPM) is a mixture of gas and macroparticles of high concentration. It is of interest in many different areas, such as in macroparticle-contaminated insulated systems, gas-liquid discharges, dusty plasmas and processing plasmas. Based on Townsend's theory, a physical model in analytical form for the breakdown mechanism in TPM is presented. In this model, two factors that influence the electron avalanche propagation are considered: macroparticles distorting the electric field and capture of the electrons. According to this breakdown mechanism and the dipole-enhanced model for calculating the maximum local field strength in TPM, the modified Paschen' law for TPM is presented to calculate the breakdown voltage. When the number of series of macroparticles (m) between two plate electrodes is very small, such as when m = 1, the breakdown voltage of the TPM is always lower than that of gas. With an increase in m or a decrease in the radius of macroparticles, the breakdown voltage tends to increase gradually for the same volume fraction of macroparticles. When m Gt 1, the breakdown voltage of TPM may be lower or higher than that of gas, depending on the ratio of the number of saturation electrons captured by a macroparticle to the cell primary electrons generated at the cathode. Some other relevant factors, such as the volume fraction of macroparticles, the dielectric mismatch, the charging rate and the product of gas pressure and the gas length, are also discussed.

  14. A study on the electrical characteristic of n-ZnO/p-Si heterojunction diode prepared by vacuum coating technique

    NASA Astrophysics Data System (ADS)

    Sharma, Shashikant; Periasamy, C.

    2014-09-01

    This article reports fabrication and characterization of n-ZnO/p-Si heterojunction diode using vacuum coating technique. Structural properties, surface morphology and quality of thin film have been studied using XRD, AFM and EDX measurements. The temperature dependent electrical junction properties were investigated by Current-Voltage-Temperature (I-V-T) measurement. Barrier height and ideality factor obtained from I-V measurement has shown the variations of 0.66-0.79 eV and 3.50-3.14 respectively for the temperature range of 25-120 °C. The temperature dependence of series resistance for n-ZnO/p-Si heterojunction diode has also been studied. Temperature dependent I-V measurement gives mean barrier height of 194 meV and Richardson constant of 6.61 × 10-7 A cm-2 K-2, which has shown significant deviation from standard theoretical values for these parameters. Consideration of Gaussian distribution with a standard deviation of ?0 = 0.176 gives modified barrier height and Richardson constant of 1.25 eV and 39.18 A cm-2 K-2 respectively. Value obtained for Richardson constant from modified Richardson plot has shown close relevance with its theoretical value (i.e., 32 A cm-2 K-2) for ZnO. Results confirm that the temperature dependent I-V characteristics of n-ZnO/p-Si heterojunction obey the theory of thermionic emission with Gaussian distribution.

  15. Technical Development on Partial Discharge Measurement and Electrical Insulation Techniques for Low Voltage Motors Driven by Voltage Inverters

    Microsoft Academic Search

    Hitoshi Okubo; Naoki Hayakawa; Gian Carlo Montanari

    2007-01-01

    This paper reviews the up-to-date research activities on electrical insulation techniques under repetitive surge voltages with steep wavefront for low voltage inverter-fed motors. Partial discharge (PD) inception, propagation, ageing and breakdown characteristics of magnet wires, including recently developed PD-resistant wires such as nanocomposite enameled wires, are described. PD measurement techniques under the steep-front voltages and IEC activity toward their standardization

  16. Electrical and Mechanical Characterizations of Nanocomposite Insulation for HTS Systems

    SciTech Connect

    Walsh, J K [Composite Technology Development, Inc., Lafayette, CO; Fabian, Paul E [Composite Technology Development, Inc., Lafayette, CO; Hooker, M W [Composite Technology Development, Inc., Lafayette, CO; Lizotte, M J [Composite Technology Development, Inc., Lafayette, CO; Tuncer, Enis [ORNL; Sauers, Isidor [ORNL

    2011-01-01

    As HTS wire technology continues to advance, a critical need has emerged for dielectric materials that can be used in superconducting components such as terminations, fault current limiters, transformers, and motors. To address this need, CTD is developing nanocomposite insulations based on epoxy and benzoxazine chemistries. Depending on part geometry, some processing methods are more efficient than others. For this reason, CTD is investigating both fiber-reinforced and filled resin systems for use in these applications. A thorough set of electrical testing including AC breakdown, breakdown as a function of thickness, and flashover shows promising performance characteristics. In addition, mechanical testing (short beam shear and compression) indicate that these new materials to have as good or better performance than G10.

  17. Breakdown voltage determination of gaseous and near cryogenic fluids with application to rocket engine ignition

    Microsoft Academic Search

    Nicholas Jeremy Nugent

    2009-01-01

    Liquid rocket engines extensively use spark-initiated torch igniters for ignition. As the focus shifts to longer missions that require multiple starts of the main engines, there exists a need to solve the significant problems associated with using spark-initiated devices. Improving the fundamental understanding of predicting the required breakdown voltage in rocket environments along with reducing electrical noise is necessary to

  18. A novel technique for partial discharge and breakdown investigation based on current pulse waveform analysis

    Microsoft Academic Search

    Hitoshi Okubo; Naoki Hayakawa

    2005-01-01

    A novel technique for partial discharge (PD) measurement and analysis (PD-CPWA; PD current pulse waveform analysis) is developed and introduced in this paper. PD-CPWA is expected to be utilized to discuss PD mechanisms and physics in electrical insulating materials, focusing on the PD current pulse waveform and its time transition from PD inception to breakdown (BD). In this paper, the

  19. Laser-induced breakdown in air and behind droplets: A detailed Monte-Carlo simulation

    Microsoft Academic Search

    A. Müsing; U. Riedel; J. Warnatz; W. Herden; H. Ridderbusch

    2007-01-01

    Laser ignition has become an active research topic recently, due to the fact that it has the potential to replace the conventional electric spark plug in engines. In this work, a model for simulating the laser-induced breakdown in air and behind droplets is developed. The model is based on laser energy absorption by inverse bremsstrahlung and multiphoton ionization. A direct

  20. Electrical properties of commercial sheet insulation materials for cryogenic applications

    SciTech Connect

    Tuncer, Enis [ORNL; Sauers, Isidor [ORNL; James, David Randy [ORNL; Ellis, Alvin R [ORNL; Pace, Marshall O [ORNL

    2008-01-01

    Dielectric properties of electrical insulation materials are needed for low-temperature power applications. Performance of materials and their compatibility determine the size of the electrical insulation in power equipment. In this work we report the dielectric properties of some commercially available materials in sheet form. The selected materials are polypropylene laminated paper from Sumitomo Electric U.S.A., Inc., porous polyethylene (Tyvek\\texttrademark) from Dupont, and polyamide paper (Nomex\\texttrademark) from Dupont. The dielectric properties are characterized with an electrical impedance analyzer in the frequency domain. The impedances are recorded in a cryocooler in the temperature range from 50 to 300 K. The dielectric breakdown characteristics of the materials are measured in a liquid nitrogen bath at atmospheric pressure.

  1. Influence of VUV illumination on breakdown mechanics: pre-ionization, direct photoionization, and discharge initiation

    NASA Astrophysics Data System (ADS)

    Stephens, J.; Fierro, A.; Dickens, J.; Neuber, A.

    2014-08-01

    A microdischarge (MD) vacuum ultraviolet (VUV) light source is fired onto a N2-NO (99.92?:?0.08%) target gas. The minor gas constituent, NO, was chosen for its ionization potential (9.23 eV) and photoionization cross-section (1.4 × 10-18 cm2) at the wavelength of interest (121.6 nm, 10.2 eV). The result is a plasma generated entirely by volume photoionization in a N2-NO background. Using a very low electric field amplitude, charge carriers are drifted though the photoplasma at picoampere levels, serving as a non-invasive diagnostic. Using a simple one-dimensional fluid approximation for the low electric field condition, theoretical predictions of photoplasma current were found to be in meaningful agreement with experimental data. The impact of direct photoionization and pre-ionization on nanosecond timescale high voltage breakdown yielded two primary observations: (1) a significant reduction in the formative delay time necessary for spark formation, and (2) almost complete elimination of the statistical delay time. Again utilizing one-dimensional fluid approximations, reasonable agreement between experimental and simulated breakdown voltage was observed. Utilizing the same VUV source to illuminate a HV spark gap biased to about 95% self-breakdown voltage revealed that direct volume photoionization alone was insufficient to trigger breakdown of the high voltage gap. However, permitting electrode illumination, the same source was found to be capable of triggering breakdown in the undervoltaged gap, albeit with a large temporal jitter.

  2. Electrical characterization of interfacial defects

    NASA Astrophysics Data System (ADS)

    Bersuker, Gennadi

    2012-02-01

    Aggressive transistor scaling to achieve better chip functionality calls for the introduction of new dielectric and metal materials into traditional device gate stacks. The advanced gate stacks represent multilayer structures, the materials of which may strongly interact (primarily during high temperature processing), generating structural defects in these layers. These complex structures pose new challenges in interpreting electrical measurements, which are sensitive to even extremely small concentrations of electrically active defects. The critical task is, thus, to link the structural and electrical characteristics of these multicomponent gate stacks in order to identify and control defects affecting device performance. In this presentation, we focus on analyzing interfacial defects affecting electrical characteristics of the metal/high-k (HK) gate stacks, which are of major interest to the semiconductor industry. We first developed models of the physical processes governing the measurements of the electrical techniques we used that allowed us to extract the structural parameters of the defects from the electrical data. By comparing the extracted parameters to those obtained by ab initio calculations of the material structures, we identified the nature of the contributing defects. A recently proposed model for random telegraph noise (RTN) and frequency-dependent charge pumping (CP) measurements that takes into consideration the multi-phonon lattice relaxation induced by charge trapping/detrapping at the defect sites was employed to extract characteristics of the traps in the interfacial SiO2 layer in HfO2-based HK devices. Our results indicate that the electron capture/emission times are controlled by the lattice re-arrangement (caused by the trapped electrons) rather than by electron tunneling to/from the trap as generally assumed. The strong dependency of the measured values on defect relaxation and ionization energies allows these values to be extracted; the values can then be used as a defect identifier. Complementary modeling of the gate leakage current in HK devices during electrical stress using the same approach yields characteristics of the traps in the interfacial SiO2 layer contributing to trap-assisted tunneling (TAT). Based on the values obtained by RTN, CP, and TAT measurements, the electrically active defects were tentatively assigned to oxygen vacancies in various charged states. In all cases, stress-induced traps were generated exclusively in the interfacial layer of the HK stacks, consistent with earlier findings that HK dielectrics are more resistant to defect generation than SiO2. Based on these findings, as well as an earlier TEM/EELS study of the elemental composition of the breakdown path, we proposed that the breakdown path formation/evolution in the interfacial layer is associated with the growth of an oxygen-deficient filament facilitated by the grain boundaries in the overlaying high-k film. This model successfully describes the temperature-dependent evolution of interfacial layer degradation through various breakdown phases.

  3. Acoustic effects at interaction of laser radiation with a liquid accompanied by optical breakdown

    NASA Astrophysics Data System (ADS)

    Bulanov, A. V.; Nagorny, I. G.

    2012-09-01

    The experimental researches of acoustic emission from optical breakdown in liquids are presented. Spectral characteristics and power of the acoustic waves generated in a liquid by optical breakdown at interaction of laser radiation with the wavelength of 532 nanometers were studied. It is shown, that two spectral maxima characterizing acoustic emission are observed. The shift of low-frequency maximum depending on the laser energy pulse is observed. As a whole, the linear dependence of acoustic pressure on the energy of laser pulse is observed. It is shown, that using acoustic data it is possible to reproduce function R(t) which will be in accord with characteristic dependences R(t), obtained from optical data. The last is especially important for breakdown studying in opaque environments.

  4. Laser induced breakdown spectroscopy in paintings and sculptures research

    NASA Astrophysics Data System (ADS)

    Sarzy?ski, A.; Skrzeczanowski, W.; Marczak, J.

    2007-07-01

    Application of Laser Induced Breakdown Spectroscopy (LIBS) for investigation of chemical constitution and stratigraphy of artworks, and metallic objects with multilayer structures is described in the paper. Physical phenomena accompanying LIBS investigations, especially temporal evolution and spectral lines broadening are described. Operational characteristics of experimental equipment are shown. Results obtained with use of two different echelle spectrometers are compared. Pigments used in oil paintings are analyzed and analysis results are presented. Experimental results of measurements of various objects like paintings, sculptures and artifacts are shown. Works on dating of investigated paintings are described.

  5. Breakdown tests of glass fibre reinforced polymers (GFRP) as part of improved lightning protection of wind turbine blades

    Microsoft Academic Search

    S. F. Madsen; J. Holboell; M. Henriksen; F. M. Larsen; L. B. Hansen; K. Bertelsen

    2004-01-01

    This paper addresses a need for analysing the interaction between electrical discharges and GFRP. A test method for evaluating the breakdown and withstand voltages for materials used in wind turbine blades has been developed. The method is based on IEC 243-3, methods of test for electrical strength of solid insulating materials, and simulates the situation in a wind turbine blade,

  6. Breakdown Voltage for Superjunction Power Devices With Charge Imbalance: An Analytical Model Valid for Both Punch Through and Non Punch Through Devices

    E-print Network

    Udrea, Florin

    An analytical model for the electric field and the breakdown voltage (BV) of an unbalanced superjunction (SJ) device is presented in this paper. The analytical technique uses a superposition approach treating the asymmetric ...

  7. Kerr electro-optic field mapping study of the effect of charge injection on the impulse breakdown strength of transformer oil

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Zahn, M.

    2013-10-01

    The smart use of charge injection to improve breakdown strength in transformer oil is demonstrated in this paper. Hypothetically, bipolar homo-charge injection with reduced electric field at both electrodes may allow higher voltage operation without insulation failure, since electrical breakdown usually initiates at the electrode-dielectric interfaces. To find experimental evidence, the applicability and limitation of the hypothesis is first analyzed. Impulse breakdown tests and Kerr electro-optic field mapping measurements are then conducted with different combinations of parallel-plate aluminum and brass electrodes stressed by millisecond duration impulse. It is found that the breakdown voltage of brass anode and aluminum cathode is ˜50% higher than that of aluminum anode and brass cathode. This can be explained by charge injection patterns from Kerr measurements under a lower voltage, where aluminum and brass electrodes inject negative and positive charges, respectively. This work provides a feasible approach to investigating the effect of electrode material on breakdown strength.

  8. X-Band Photonic Band-Gap Accelerator Structure Breakdown Experiment

    SciTech Connect

    Marsh, Roark A.; /MIT /MIT /NIFS, Gifu /JAERI, Kyoto /LLNL, Livermore; Shapiro, Michael A.; Temkin, Richard J.; /MIT; Dolgashev, Valery A.; Laurent, Lisa L.; Lewandowski, James R.; Yeremian, A.Dian; Tantawi, Sami G.; /SLAC

    2012-06-11

    In order to understand the performance of photonic band-gap (PBG) structures under realistic high gradient, high power, high repetition rate operation, a PBG accelerator structure was designed and tested at X band (11.424 GHz). The structure consisted of a single test cell with matching cells before and after the structure. The design followed principles previously established in testing a series of conventional pillbox structures. The PBG structure was tested at an accelerating gradient of 65 MV/m yielding a breakdown rate of two breakdowns per hour at 60 Hz. An accelerating gradient above 110 MV/m was demonstrated at a higher breakdown rate. Significant pulsed heating occurred on the surface of the inner rods of the PBG structure, with a temperature rise of 85 K estimated when operating in 100 ns pulses at a gradient of 100 MV/m and a surface magnetic field of 890 kA/m. A temperature rise of up to 250 K was estimated for some shots. The iris surfaces, the location of peak electric field, surprisingly had no damage, but the inner rods, the location of the peak magnetic fields and a large temperature rise, had significant damage. Breakdown in accelerator structures is generally understood in terms of electric field effects. These PBG structure results highlight the unexpected role of magnetic fields in breakdown. The hypothesis is presented that the moderate level electric field on the inner rods, about 14 MV/m, is enhanced at small tips and projections caused by pulsed heating, leading to breakdown. Future PBG structures should be built to minimize pulsed surface heating and temperature rise.

  9. Magnetic and Electrical Characteristics of Cobalt-Based Amorphous Materials and Comparison to a Permalloy Type Polycrystalline Material

    NASA Technical Reports Server (NTRS)

    Wieserman, William R.; Schwarze, Gene E.; Niedra, Janis M.

    2005-01-01

    Magnetic component designers are always looking for improved soft magnetic core materials to increase the efficiency, temperature rating and power density of transformers, motors, generators and alternators, and energy density of inductors. In this paper, we report on the experimental investigation of commercially available cobalt-based amorphous alloys which, in their processing, were subjected to two different types of magnetic field anneals: A longitudinal magnetic field anneal or a transverse magnetic field anneal. The longitudinal field annealed material investigated was Metglas 2714A. The electrical and magnetic characteristics of this material were investigated over the frequency range of 1 to 200 kHz and temperature range of 23 to 150 C for both sine and square wave voltage excitation. The specific core loss was lower for the square than the sine wave voltage excitation for the same maximum flux density, frequency and temperature. The transverse magnetic field annealed core materials include Metglas 2714AF and Vacuumschmelze 6025F. These two materials were experimentally characterized over the frequency range of 10 to 200 kHz for sine wave voltage excitation and 23 C only. A comparison of the 2174A to 2714AF found that 2714AF always had lower specific core loss than 2714A for any given magnetic flux density and frequency and the ratio of specific core loss of 2714A to 2714AF was dependent on both magnetic flux density and frequency. A comparison was also made of the 2714A, 2714AF, and 6025F materials to two different tape thicknesses of the polycrystalline Supermalloy material and the results show that 2714AF and 6025F have the lowest specific core loss at 100 kHz over the magnetic flux density range of 0.1 to 0.4 Tesla.

  10. Simulations of avalanche breakdown statistics: probability and timing

    Microsoft Academic Search

    Jo Shien Ng; Chee Hing Tan; John P. R. David

    2010-01-01

    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

  11. Initiation of breakdown in slender compressible vortices

    NASA Technical Reports Server (NTRS)

    Krause, E.; Menne, S.; Liu, C. H.

    1986-01-01

    The onset of vortex breakdown in compressible flows is investigated analytically for the case in which the flow is axially symmetric, the vortex is isolated, its axis is parallel to the main flow, and the vortex radius is small compared to the breakdown length. The conservation equations for mass, momentum, and energy are formulated and solved numerically using a finite-difference scheme, as described by Krause (1985); numerical results are presented in graphs and briefly characterized.

  12. Avalanche injection and second breakdown in transistors

    Microsoft Academic Search

    P. L. Hower; V. G. Krishna Reddi

    1970-01-01

    A rapid type of second breakdown observed in silicon n+-p-n-n+transistors is shown to be due to avalanche injection at the collector n-n+junction. Localized thermal effects, which are usually associated With second breakdown, are shown to play a minor role in the initiation of the transition to the low voltage state. A useful tool in the analysis of avalanche injection is

  13. Aquatic macrophyte breakdown in an Appalachian river

    Microsoft Academic Search

    B. H. Hill; J. R. Webster

    1982-01-01

    Weight loss from Podostemum ceratophyllum, Elodea canadensis, Potamogeton crispus, Justicia americana, and Typha latifolia was measured by exposing air dried leaf material in 15 cm2 nylon mesh bags (3 mm octagonal openings). Breakdown rates for these species were 0.037, 0.026, 0.02l, 0.016, and 0.007 day-1, respectively. In general, these rates are much faster than reported rates of tree leaf breakdown

  14. Spark gap with low breakdown voltage jitter

    SciTech Connect

    Rohwein, Gerald J. (Albuquerque, NM); Roose, Lars D. (Albuquerque, NM)

    1996-01-01

    Novel spark gap devices and electrodes are disclosed. The novel spark gap devices and electrodes are suitable for use in a variety of spark gap device applications. The shape of the electrodes gives rise to local field enhancements and reduces breakdown voltage jitter. Breakdown voltage jitter of approximately 5% has been measured in spark gaps according the invention. Novel electrode geometries and materials are disclosed.

  15. Spark gap with low breakdown voltage jitter

    DOEpatents

    Rohwein, G.J.; Roose, L.D.

    1996-04-23

    Novel spark gap devices and electrodes are disclosed. The novel spark gap devices and electrodes are suitable for use in a variety of spark gap device applications. The shape of the electrodes gives rise to local field enhancements and reduces breakdown voltage jitter. Breakdown voltage jitter of approximately 5% has been measured in spark gaps according the invention. Novel electrode geometries and materials are disclosed. 13 figs.

  16. Luminosity of initial breakdown in lightning

    NASA Astrophysics Data System (ADS)

    Stolzenburg, M.; Marshall, T. C.; Karunarathne, S.; Karunarathna, N.; Vickers, L. E.; Warner, T. A.; Orville, R. E.; Betz, H.-D.

    2013-04-01

    Time correlated high-speed video and electromagnetic data for 15 cloud-to-ground and intracloud lightning flashes reveal bursts of light, bright enough to be seen through intervening cloud, during the initial breakdown (IB) stage and within the first 3 ms after flash initiation. Each sudden increase in luminosity is coincident with a CG type (12 cases) or an IC type (3 cases) IB pulse in fast electric field change records. The E-change data for 217 flashes indicate that all CG and IC flashes have IB pulses. The luminosity bursts of 14 negative CG flashes occur 11-340 ms before the first return stroke, at altitudes of 4-8 km, and at 4-41 km range from the camera. In seven cases, linear segments visibly advance away from the first light burst for 55-200 µs, then the entire length dims, then the luminosity sequence repeats along the same path. These visible initial leaders or streamers lengthen intermittently to about 300-1500 m. Their estimated 2-D speeds are 4-18 × 105 m s-1 over the first few hundred microseconds and decrease by about 50% over the first 2 ms. In other cases, only a bright spot or a broad area of diffuse light, presumably scattered by intervening cloud, is visible. The bright area grows larger over 20-60 µs before the luminosity fades in about 100 µs, then this sequence may repeat several times. In several flashes, a 1-2 ms period of little or no luminosity and small E-change is observed following the IB stage prior to stepped leader development.

  17. Influence of near-surface graded-gap layers on electrical characteristics of MIS-structures based on MBE grown HgCdTe

    Microsoft Academic Search

    A. V. Voitsekhovskii; S. N. Nesmelov; S. M. Dzyadukh; V. S. Varavin; S. A. Dvoretskii; N. N. Mikhailov; Yu. G. Sidorov; M. V. Yakushev

    2010-01-01

    The paper examines influence of near-surface graded-gap layers on electrical characteristics of MIS-structures fabricated\\u000a on heteroepitaxial Hg1?xCdxTe films grown by molecular beam epitaxy (MBE). Two types of insulators, i.e., two-layer SiO2\\/Si3N4 and anodic oxide films were used. As it is seen from the depth and width of the valley on the C-V characteristics, the capacitance\\u000a is found to vary in

  18. Electrical properties of PET films with semiconducting\\/interface layer

    Microsoft Academic Search

    Dae-H. Park; Dong-S. Kim

    2000-01-01

    In this paper, PET (polyethylene terephthalate) films with semiconducting and interface layers were investigated. The electrical properties, such as volume resistivity, tan? (dissipation factor), and breakdown strength at various temperatures were measured. It is found that the volume resistivity of him (dependence on semiconducting\\/interface layers) and electrical properties of PET films are changed. Breakdown strength and dissipation factor of PET

  19. Humidity effects on wire insulation breakdown strength.

    SciTech Connect

    Appelhans, Leah

    2013-08-01

    Methods for the testing of the dielectric breakdown strength of insulation on metal wires under variable humidity conditions were developed. Two methods, an ASTM method and the twisted pair method, were compared to determine if the twisted pair method could be used for determination of breakdown strength under variable humidity conditions. It was concluded that, although there were small differences in outcomes between the two testing methods, the non-standard method (twisted pair) would be appropriate to use for further testing of the effects of humidity on breakdown performance. The dielectric breakdown strength of 34G copper wire insulated with double layer Poly-Thermaleze/Polyamide-imide insulation was measured using the twisted pair method under a variety of relative humidity (RH) conditions and exposure times. Humidity at 50% RH and below was not found to affect the dielectric breakdown strength. At 80% RH the dielectric breakdown strength was significantly diminished. No effect for exposure time up to 140 hours was observed at 50 or 80%RH.

  20. The Gate-Bias Dependency of Breakdown Location in GaAs Metal Semiconductor Field Effect Transistors (MESFETs)

    Microsoft Academic Search

    Jayne M. Ashworth; Norbert Arnold

    1991-01-01

    The breakdown behaviour of refractory metal self-aligned GaAs metal semiconductor field effect transistors (MESFETs) has been studied by two-dimensional simulation using a drift-diffusion transport model and emission microscopy. Exact quantitative simulation of the device characteristics has been achieved for a device with a four fold implant scheme. The location of breakdown, as defined as the area of high avalanche generation