共查询到20条相似文献,搜索用时 15 毫秒
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U. Yusupaliev 《Moscow University Physics Bulletin》2008,63(3):224-225
In terms of the Townsend model of a static electrical gas discharge, the ratio of breakdown voltage U B to its minimal value U min is expressed as a function of generalized variable Ξ B ? f(Ξ b ), such that the function depends on neither the gas type nor the cathode material. 相似文献
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This work has been devoted to a numerical and analytical calculus of the voltage breakdown in electrical discharge for several rare gases such as argon, krypton, neon, xenon and helium. It was performed using a fluid model 2D, which is based on the numerical solution of the two Boltzmann equations (equation of continuity and momentum), coupled to Poisson's equation to measure the breakdown voltage according to the product of the electrode spacing and the pressure. This study allowed a better comprehension of the physical phenomena occurring in the discharges. We, thus, developed a calculation, based on the empirically Paschen's law, allowing the determination of the breakdown voltage, which describes the transition from insulating gas to the conductive state. Paschen's curves of the different gases are plotted and a comparison between numerical and experimental as well as analytical results is also presented and analyzed. 相似文献
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The breakdown characteristics of a gas in the presence of crossed electric and magnetic fields are discussed in terms of the Townsend ionization coefficients. The “equivalent pressure” concept is used to assess the effect of a transverse magnetic field on the first Townsend coefficient and the objections which have been raised to the application of this approach to breakdown potentials are shown to be removed by a consideration of the dependence of the second Townsend coefficient upon electric and magnetic field strengths. 相似文献
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This Letter addresses the counterintuitive behavior of electrons injected into dense cryogenic media with negative scattering length L. Instead of strongly reduced mobility at all but the lowest densities due to the polaronic effect involving the formation of density enhancement clusters (expected in the theory with a simple gas-electron interaction successfully applied earlier to electrons in helium where L>0) which should substantially decrease the electron mobility, an opposite picture is observed: with increasing |L| (the trend taking place for inert gases with the growth of atomic number) and the gas density, the electrons remain practically free. An explanation of this behavior is provided based on consistent accounting for the nonlinearity of the electron interaction with the gaseous medium in the gas atom number density. 相似文献
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B. M. Smirnov 《Journal of Experimental and Theoretical Physics》1997,85(5):1010-1018
The melting of a macroscopic system of bound atoms with a pairwise interaction is examined as a vacancy formation process.
It is found that the existence of a liquid state is related to a double-humped dependence of the partition function on the
number of vacancies, where the peaks correspond to the solid and liquid states and the heights of the peaks are equal at the
melting point. In order for the liquid state to form, the derivative of the vacancy interaction with respect to energy must
have a maximum. The vacancies are compressed as a result of the interaction. In the condensed inert gases, the specific energy
of vacancy formation is proportional to the resulting empty space per atom.
Zh. éksp. Teor. Fiz. 112, 1847–1862 (November 1997) 相似文献
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The statistics of dielectric breakdown at fields 8 MV/cm has been studied under both static (constant voltage) and dynamic (ramped voltage) conditions. MOS capacitors of the same size and from the same wafer were used for all measurements. Data from both types of test conformed to a Weibull distribution. The Weibull parameters a and b, which determine the time and field dependence of breakdown, were calculated from static tests at various applied fields and independently from dynamic tests at various ramp-rates. The values of a and b were: a 0.24; b 6.89 and a 0.34; b 6.55, from static and dynamic tests respectively. The similarity of the values for the two pairs of Weibull parameters suggests that breakdown proceeds by the same mechanism in both types of test. 相似文献
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The behavior of excess and intrinsic free electrons inside compressed inert gases is described as a function of pressure by
using a pairwise approximation for the electron interaction with atomic surroundings. The change of sign from negative to
positive for the xenon atom electric potential inside condensed xenon is predicted to occur at a pressure around 3 GPa, preventing
slow electron embedding into solid xenon from the gas phase at higher pressure. To overcome this difficulty, the electrons
should be injected into a solid sample just before its pulsed shock loading. The ionization of xenon by pressure and its further
metallization are described by decreasing the forbidden gap at the expense of increasing the xenon ground electronic term
and simultaneous splitting of the upper ionized electronic state. A good coincidence between the calculated and measured pressure
of the dielectric-metal transition in xenon is demonstrated.
The text was submitted by the authors in English. 相似文献
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The dependence of the gas breakdown voltage U B 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 avalanche discharge theory. The case was considered where the spatial charge created by the external ionizer did not distort the electric field in the discharge gap. In the absence of external ionizer the obtained dependence comes down to the well-known expression for the gas breakdown voltage (the Paschen law). 相似文献
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We report on the use of high resolution electron microscopy and optical processing techniques to study defects in solid inert gas precipitates (bubbles) formed by ion implantation into aluminium. Faceted precipitates, of the order of 5 run in length and epitaxial with the aluminium, in some cases exhibit a high degree of crystalline perfection but in others departure from the regular atomic arrangement is evident in the lattice images. Optical processing techniques have been applied to enhance the lattice images and in some cases to colour encode the aluminium and inert gas spacings present in the micrograph, with the aim of indentifying specific defect structures in the inert gas solid. We demonstrate that the solid “bubble”, formed in a metal by ion implantation, provides a means of studying defects in a simple insulator, the rare gas solid. 相似文献
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It is found experimentally that the critical Reynolds numbers for the transition to turbulence are different for He, Ar, and
Kr flows.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 7, 557–559 (10 October 1998) 相似文献
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A. S. Mustafaev 《Technical Physics》2004,49(9):1224-1226
The paper considers the conditions under which the development of beam instabilities of the after-glow plasma in inert gases
is possible. The validity of assumptions has been experimentally confirmed. 相似文献
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M.C. Gower 《Optics Communications》1981,36(1):43-45
Measurements have been made of the threshold intensities for gas breakdown at the KrF 248 nm laser wavelength. The threshold intensities were measured as a function of pressure for air, H2, CH4 and the rare gases. 相似文献
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A method of measuring the sodium diffusion coefficient in neon and argon is presented. It is based on recording the concentration change of sodium in a sodium discharge as it diffuses along a discharge tube. A diagram of the apparatus is given and the technique of measurements is described. It is pointed out that the proposed method can also be used for measuring the diffusion coefficient of other alkaline metals in inert gases and their mixtures.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 57–62, August, 1987. 相似文献
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M. N. Magomedov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2013,7(4):697-706
The dependences of the specific surface energy (σ) and its isochoric temperature derivative (?σ/?T) V on the degree of compression (V/V 0) of the crystal are calculated on the basis of the Mie-Lennard-Jones pair potential of interatomic interaction. The calculations are performed for all face-centered cubic crystals of inert gases (from Ne to Rn) to the degree of compression V/V 0 = 0.016 along three isotherms: 1K, T m and 300 K, where T m is the melting temperature at zero pressure (V/V 0 = 1). The activation processes such as the creation of vacancies and self-diffusion are taken into account in the calculations. It is shown that the isotherm σ(V/V 0) reaching its maximum at (V/V 0)max sharply decreases upon further compression. The surface energy becomes negative (σ(V/V 0) fr =0) at V/V 0 ≤ (V/V 0) fr < (V/V 0)max which should stimulate the process of crystal fragmentation, i.e., an increase in the specific (per atom) intercrystallite surface. It is shown that at high temperatures the condition of fragmentation holds in the crystal in the case of uniform tension, but it is already in the region of the liquid phase. The values of σ, (?σ/?T) V , the vacancy concentration and the fraction of the diffusion atoms are estimated at the points: V/V 0 = 1, (V/V 0)max and (V/V 0) fr at 1 K, Tm and 300 K. The size evolution of the surface and activation parameters is studied using neon as an example. 相似文献
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Drift of an excess electron in dense and condensed inert gases in external electric field and excitation of atoms by electron impact in these systems are analyzed. The effective potential energy surface for an excess electron at a given electric field strength consists of wells and hills, and the actions of neighboring atoms are therefore separated by saddles of the potential energy. At such atomic densities that the difference of interaction potentials for an excess electron between neighboring wells and hills of the potential energy surface becomes small, the electron mobility is large. This is realized for heavy inert gases (Ar, Kr, Xe) with a negative scattering length of an electron on individual atoms. In these cases, the average potential energy of the electron interaction with atoms corresponds to attraction at low atomic densities and to repulsion at high densities. The transition from attraction to repulsion at moderate atomic densities leads to a maximum of the electron mobility. A gas model for electron drift in condensed inert gases is constructed on the basis of this character of interaction. Due to high electron mobility, condensed inert gases provide high efficiency of transformation of the electric field energy into the energy of emitting photons through drifting electrons. It is shown that, although the role of formation of autodetaching states in the course of electron drift is more important for condensed inert gases than for rare gases, this effect acts weakly on exciton production at optimal atomic densities. The parameters of a self-maintained electric discharge in condensed inert gases as a source of ultraviolet radiation are discussed from the standpoint of electron drift processes. 相似文献
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Precise measurements show that the microwave resonance frequencies of ground-state Rb or Cs atoms have a nonlinear dependence on the pressure of the buffer gases Ar and Kr. No nonlinearities were observed in the gases He or N(2). These observations strongly suggest that the nonlinearities are due to the van der Waals molecules that form in Ar and Kr, but not in He or N(2). The nonlinear part of the shifts is largest in the pressure range of a few tens of torr, similar to the operating pressures of gas-cell atomic clocks. The observed shifts are very well described by a simple function, parametrized by the effective three-body formation rate of molecules and by the effective product of the collisionally limited lifetime times the shift of the hyperfine coupling coefficient in the molecule. 相似文献