Home  About us  Contact
 

Electrical Breakdown (electrical + breakdown)

Distribution by Scientific Domains
Physics and Astronomy75%

Selected Abstracts

Stochastic and Relaxation Processes in Argon by Measurements of Dynamic Breakdown Voltages

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 7 2005
V. Lj.
Abstract Statistically based measurements of breakdown voltages Ub and breakdown delay times td and their variations in transient regimes of establishment and relaxation of discharges are a convenient method to study stochastic processes of electrical breakdown of gases, as well as relaxation kinetics in afterglow. In this paper the measurements and statistical analysis of the dynamic breakdown voltages Ub for linearly rising (ramp) pulses in argon at 1.33 mbar and the rates of voltage rise k up to 800 V s,1 are presented. It was found that electrical breakdowns by linearly rising (ramp) pulses is an inhomogeneous Poisson process caused by primary and secondary ionization coefficients , , , and electron yield Y variations on the voltage (time). The experimental breakdown voltage distributions were fitted by theoretical distributions by applying approximate analytical and numerical models. The afterglow kinetics in argon was studied based on the dependence of the initial electron yield on the relaxation time Y0 (, ) derived from fitting of distributions. The space charge decay was explained by the surface recombination of nitrogen atoms present as impurities. The afterglow kinetics and the surface recombination coefficients on the gas tube and cathode were determined from a gas-phase model. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Extraction Using Moderate Electric Fields

JOURNAL OF FOOD SCIENCE, Issue 1 2004
I. SENSOY
ABSTRACT: During moderate electric field (MEF) processing, a voltage applied across a food material may affect the permeability of cell membranes. It is known that high electric fields can cause either reversible or irreversible rupture of cell membranes. In this research, the effect of MEF processing on permeability was studied. Effects of frequency and electric field strength were investigated. Cellular structure was investigated by transmission electron microscopy (TEM). Fermented black tea leaves and fresh or dry mint leaves were placed in tea bags or cut in 1 cm2 squares, depending on the experiment, and immersed in an aqueous fluid medium. Control samples were heated on a hot plate. MEF treatments were conducted by applying a voltage across electrodes immersed in opposite sides of the beaker. Control and MEF-treated fresh mint leaf samples heated to 50°C were analyzed by TEM. MEF processing significantly increased the extraction yield for fresh mint leaves because of additional electric field effects during heating. Dried mint leaves and fermented black tea leaves were not affected by the treatment type. Low frequency resulted in higher extraction rates for fresh mint leaves. The electric field strength study showed that electrical breakdown is achieved even at low electric field strengths. MEF treatment shows potential to be used as an alternative to conventional heating for extraction from cellular materials. [source]

ta-C/Si heterojunction diodes with apparently giant ideality factors

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2010
Marc Brötzmann
Abstract A common feature of many wide band gap heterojunction diodes is an unexplained large ideality factor n > 2. In this context we investigate the diode characteristics of heterojunction diodes consisting of a crystalline semiconductor material such as Si covered with a thin semiconducting film of amorphous or disordered material. As thin amorphous film we use tetrahedral amorphous carbon (ta-C). These heterojunctions exhibit a pronounced rectifying behavior, low saturation current and low parasitic currents. Moreover, we observe an apparently giant ideality factor reaching values of n > 75. As a consequence, the turn on voltage is around 3 , 10 V and the I-V curves can be measured for bias up to 40 V without reaching saturation or electrical breakdown. We present a quantitative model for the unusual diode characteristics of these Metal , Amorphous Semiconductor , Semiconductor diodes (MASS-diodes). We demonstrate that the I-V characteristics of the heterojunctions are well described by a serial arrangement of an ideal Schottky-diode, a Frenkel-Poole type resistance and an Ohmic contact resistance, emulating a p-n- or Schottky diode characteristic with giant ideality factor and referred to as the FPID-model. We propose that heterojunctions exhibiting apparently large ideality factors n , 2 may possess an interfacial disordered or amorphous layer with Frenkel-Poole conduction properties. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Stochastic and Relaxation Processes in Argon by Measurements of Dynamic Breakdown Voltages

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 7 2005
V. Lj.
Abstract Statistically based measurements of breakdown voltages Ub and breakdown delay times td and their variations in transient regimes of establishment and relaxation of discharges are a convenient method to study stochastic processes of electrical breakdown of gases, as well as relaxation kinetics in afterglow. In this paper the measurements and statistical analysis of the dynamic breakdown voltages Ub for linearly rising (ramp) pulses in argon at 1.33 mbar and the rates of voltage rise k up to 800 V s,1 are presented. It was found that electrical breakdowns by linearly rising (ramp) pulses is an inhomogeneous Poisson process caused by primary and secondary ionization coefficients , , , and electron yield Y variations on the voltage (time). The experimental breakdown voltage distributions were fitted by theoretical distributions by applying approximate analytical and numerical models. The afterglow kinetics in argon was studied based on the dependence of the initial electron yield on the relaxation time Y0 (, ) derived from fitting of distributions. The space charge decay was explained by the surface recombination of nitrogen atoms present as impurities. The afterglow kinetics and the surface recombination coefficients on the gas tube and cathode were determined from a gas-phase model. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]