A non-self-consistent electron-beam controlled discharge in methane

The use of methane in a non-self-consistent discharge controlled by an electron beam permits obtaining high discharge currents for relatively low electric fields. The current gain is 10³for 500 V/cm fields and a 14 mA/cm² injection current density. For fields greater than 7–8 kV/cm and atmospheric pressure, punch-through of the gas discharge gap occurs. It is shown that a breakpoint in the CVC in the area of low currents is associated with the appearance of spots on the cathode. A domain Instability, related to the nonmonotonic dependence of the drift velocity on the reduced field in methane, is detected.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 65–68, April, 1982.     

High-current plasma opening switch fed by a magnetic explosion generator

A plasma opening switch fed by a helical magnetic explosion generator is developed. A plasma sheath with an axial length of ≈4 cm and an electron density of ～10¹⁷ cm^?3 is produced in the electrode gap of the switch by six coaxial gaseous-plasma injectors. A series of explosion experiments shows that the system developed allows one to study the switch at currents of about 2 MA.     

Production of high-energy electron beams in moderate and high-pressure gases

The feasibility of producing high-current, high-energy electron beams was studied for the application of nanosecond voltage pulses with amplitudes to 300 kV in accelerating gaps. The pressures of the gap gases (helium and nitrogen) measured from 10^–1 torr to atmospheric. Experiments showed that the placement of two barriers in the accelerating gap significantly increased the electron beam current due to an increase in the burn time of the volume discharge under conditions involving significant over-voltage in the electrical field. Electron beams with energies of up to 250 keV and currents up to 260 A were obtained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 7–9, February, 1992.     

Influence of the axial magnetic field on the current instability and on the collective acceleration of ions in plasma diodes

It is shown that, while suppressing transverse electron motion, the axial magnetic field with an induction of up to 6.8 × 10⁻² T in the gap of a plasma diode has no significant effect on the current instability and on the acceleration of ions at electron beam currents of ≤40 A. The increase in both the critical current and the period of current oscillations is related to an increase in the plasma density after applying the magnetic field. The maximum energy of the accelerated magnesium ions decreases by ≈25% at an induction of 1.7 × 10⁻² T and does not depend on the magnetic field in the range (1.7–6.8) × 10⁻² T.     

Photoconductive properties of HgGa2S4

Mercury thiogallate, HgGa₂S₄ is a defect chalcopyrite semiconductor with the space group S₄² which offers a combination of attractive properties for applications.In order to obtain information about the electron states in the energy gap, photoconductivity measurements are performed in the 80–300 K range. Photoconductivity spectra show two peaks related to intrinsic and extrinsic excitation at about 410 and 500 nm, respectively; these maxima show a temperature dependence similar to the linear coefficient of the energy gap. Thermally stimulated currents have been studied by exciting the samples with intrinsic light at different temperatures. For all excitation temperatures a single TSC peaks were obtained. The analysis of TSC curves allowed one to estimate the kinetics of the trap emptying, trap energy distribution and thermal activation energy.A model for the level distribution in the semiconductor energy gap is suggested which in good agreement with the results of a previous photoluminescence study.     

Microtopography and field emission properties of carbon films grown in a microwave gas discharge plasma

Graphite-like carbon films are grown in an ethanol vapor plasma in a microwave gas discharge. The electrical parameters controlling the microtopography and electronic properties of carbon films are determined. It is shown that electron bombardment affects the fine structure of graphite-like nanocrystallites and their emissive power with characteristics close to those of carbon nanotubes. The emission properties of layered graphite-like films can be improved by metal (cadmium) impurity doping. For nanocrystalline graphite-like films, emission currents with a density of 0.3 A/cm² are induced at an electric field strength of less than 7 V/μ m in the gap. __________ Translated from Fizika Tverdogo Tela, Vol. 46, No. 2, 2004, pp. 367–371. Original Russian Text Copyright ? 2004 by Suzdal’tsev, Yafarov.     

Tests of the space-time properties of neutral currents in electron-positron annihilation

Electron-positron processes are very valuable for investigating neutral currents. Interference between neutral currents and the electromagnetic current provides unambiguous tests of the space-time properties of neutral currents. We discuss the structure of this interference with particular reference to the process e⁺e^? → hadron + anything.     

Designing of a lead ion model source for plasma separation of spent nuclear fuel

Plasma sources of model substances are required for solving problems associated with the development of a plasma separation method for spent nuclear fuel (SNF). Lead is chosen as the substance simulating the kinetics and dynamics of the heavy SNF component. We report on the results of analysis of the discharge in lead vapor with a concentration of 10¹²–10¹³ cm^–3. Ionization is produced by an electron beam (with electron energy up to 500 eV) in the centimeter gap between planar electrodes. The discharge is simulated using the hydrodynamic and one-particle approximations. The current–voltage characteristics and efficiencies of single ionization depending on the vapor concentrations and thermoelectron current are obtained. The experimentally determined ion currents on the order of 100 μA for an ionization efficiency on the order of 0.1% are in conformity with the result of simulation.     

Über den zeitlichen Verlauf des Stromes einer Gasentladung in Wasserstoff

The transient growth of currents in a Townsend gas discharge system under uniform dc field conditions in Hydrogen is examined. The discharge is started by 10³ to 10⁶ electrons released from the cathode by an UV light pulse within some 10^?7 seconds. Observed oscillations of the current are found to be due to the motion of the electrons through the gap creating new electrons by photoelectron emission at the cathode due to photons generated in the gap. At sparking threshold conditions (Μ ₀=1) the electron current becomes self-sustaining after a few electron transit times. The positive ion current soon exceeds the electron current and grows linearly with time (Μ ₀=1) until the positive ions of the first generation enter the cathode. For times greater than a positive-ion transit time the current becomes self-sustaining. Neglecting space-charge effects one would not expect a spark to occur. The space-charge of the positive ions, however, causes a distortion of the field changing the ionization efficiency of the electrons. It is shown that an observed rapid growth of current leading to breakdown after some positive-ion transit times is in agreement to this conception.     

Pion exchange currents in elastic electron deuteron scattering

The effects of pion-exchange pari and recoil currents on the electromagnetic form factors of the deuteron are calculated. Both exchange currents give significant contributions to the charge form factor and, despite some cancellation, their net effect is appreciable for q² ? 10 fm^?2.     

流体静压力对高简并砷化镓P-N结某些参数的影响

本文报导了在流体静压力18000kg/cm²范围内,高简并砷化镓P-N结峯值电流l_p,谷值电流l_v,峯值电压V_p,谷值电压V_v,指数过剩电流I_x等参数随压力变化的实验结果。分析了峯值电压V_p随压力P的增加按指数规律显著减小,以及指数过剩电流I_x的斜率S=(dlnI_x)/dV随压力P的增加而增加等实验结果。分析的     

Zur Modulation des Wandstromes in der geschichteten positiven Säule der Neon-Glimmentladung

It is shown, that the wall current of the striated positive column in a neon low pressure glow discharge is modulated with the frequency of the moving striations. There is a phase shift between wall currents of electrons and ions (～π/2–3/4π), A mass-spectrometric analysis of the ion currents shows Ne⁺ and Ne₂⁺ ions, both currents are modulated. The modulation factor of the electron and ion current reaches values near 100% and 50%, repectively. The behaviour of the modulated wall currents may by explained by the potential oscillations in the Langmuir sheath near the wall.     

Semi-leptonic weak and electromagnetic interactions in nuclei:: Parity violations in electron scattering and weak neutral currents

A general result for the difference in differential cross sections for electron scattering between any two nuclear levels with incident longitudinally polarized right- and left-handed electrons is derived. This difference must involve the parity-violating weak interaction at least linearly and can be used to study weak neutral currents as pointed out by Feinberg. A V — A structure for the weak neutral currents is assumed with a semi-leptonic current-current interaction, and the electromagnetic interaction is treated in the one-photon-exchange approximation. The result is expressed in terms of the same set of reduced matrix elements of the multipoles of the nuclear currents which govern all electromagnetic and weak transitions between these levels. A previously developed unified analysis of semi-leptonic weak and electromagnetic interactions in nuclei which determines one-body transition densities, including their spin and spatial dependences, through electron scattering provides nuclear transitions to serve as known analyzers in testing the structure of this part of the weak interaction. Examples are given using Weinberg's model of the weak neutral currents. Feinberg's result for elastic scattering from spin-0 nuclei is rederived and two new examples using previously determined one-body densities are discussed : the 1⁺0 → 0⁺1 (3.56 MeV) transition in ⁶Li and the 0⁺0 → 1⁺ 1(15.1 MeV) transition in ¹²C.     

Radiative decays as a test for right-handed currents

It is shown that the purity violating amplitude for the decays Σ⁺ → pγ and Ξ^? → Σ^?γ vanish in the SU(3) symmetry limit if the charged weak currents possess a U spin symmetry for strangeness changing processes. This applies to Cabibbo currents and their SU (4) generalization. Assuming an asymptotically free model for the strong interactions this result applies to all models with only left-handed charged currents. Observation of a large parity violating amplitude would indicate right-handed charged weak currents. Tests involving other radiative decays are also considered.     

Amiloride-sensitive channels in type I fungiform taste cells in mouse

Background  

Taste buds are the sensory organs of taste perception. Three types of taste cells have been described. Type I cells have voltage-gated outward currents, but lack voltage-gated inward currents. These cells have been presumed to play only a support role in the taste bud. Type II cells have voltage-gated Na⁺ and K⁺ current, and the receptors and transduction machinery for bitter, sweet, and umami taste stimuli. Type III cells have voltage-gated Na⁺, K⁺, and Ca²⁺ currents, and make prominent synapses with afferent nerve fibers. Na⁺ salt transduction in part involves amiloride-sensitive epithelial sodium channels (ENaCs). In rodents, these channels are located in taste cells of fungiform papillae on the anterior part of the tongue innervated by the chorda tympani nerve. However, the taste cell type that expresses ENaCs is not known. This study used whole cell recordings of single fungiform taste cells of transgenic mice expressing GFP in Type II taste cells to identify the taste cells responding to amiloride. We also used immunocytochemistry to further define and compare cell types in fungiform and circumvallate taste buds of these mice.     

Exchange currents in electron scattering from light nuclei

Effects of meson exchange currents on elastic and inelastic electron scattering from nuclei are considered with specific applications to ³He, ⁶Li, ⁷Li, ⁹Be and ¹⁰B. The one-pion exchange approximation is employed (with “pair” and “pionic” graphs) in the non-relativistic limit, where only transverse isovector multipoles are allowed. This approach is shown to be consistent with current conservation. Form factors are calculated with and without exchange currents for a wide range of momentum transfers (up to 1 GeV/c) and for a variety of nuclear transitions to determine where exchange-current effects are large. The relevance of these calculations to experiment is discussed.     

Josephson current in ferromagnetic d-wave superconductor/ferromagnetic d-wave superconductor junction

We solve a self-consistent equation for the d-wave superconducting gap and the effective exchange field in the mean-field approximation, study the Zeeman effects on the d-wave superconducting gap and thermodynamic potential. The Josephson currents in the d-wave superconductor (S)/insulating layer (I)/d-wave S junction are calculated as a function of the temperature, exchange field, and insulating barrier strength under a Zeeman magnetic field on the two d-wave Ss. It is found that the Josephson critical currents in d-wave S/d-wave S junction depend to a great extent on the relative orientation of the effective exchange field of the two S electrodes, and the crystal orientation of the d-wave S. The exchange field can under certain conditions enhance the Josephson critical current in a d-wave S/I/d-wave S junction.     

Local charge-carrier trapping centers in C60 single crystals

The energy spectrum of local charge-carrier trapping centers in C₆₀ single crystals is studied in terms of the theory of space-charge-limited currents in the Gaussian approximation. The energy distribution of these centers in the energy gap is found, and the type and parameters of this distribution are determined.     

Parity violation correlations in light muonic atoms

The 2S-1S transition in light muonic atoms is very sensitive to parity violation correlations induced via neutral currents. Observables depending on these transitions such as the photon polarization and the angular correlation between the emitted radiation and the atom polarization are a clear signal of weak neutral currents in atoms. We find the relation between the lepton and quark couplings and these observables emphasizing the effect of the nuclear spin. The results expected in muonic, atoms μ-⁴He and μ-³He are given.     

Meson exchange current effects in the electroexcitation of magnetic states in closed shell nuclei

A microscopic approach to evaluate the contributions of one-pion exchange currents to the inelastic (e,e') scattering form factor of closed shell nuclei is developed. Both seagull and pionic parts of the two-body term are treated on the same footing and their final expressions are simple, clear and physically transparent. Application to the magnetic stretched states 4^?(18.98 MeV) of ¹⁶O and 14^?(6.74 MeV) of ²⁰⁸Pb is done. Agreement with the available experimental data is discussed. It is found that the effect of the meson exchange currents is a smooth but non-negligible enhancement ?15% at the first scattering maximum) at small momentum transfers and an increase by a factor bigger than 1.5 in the region of the second maximum.