Method of simplified kinetic equation for simulating the electron kinetics in dense gases in strong electric fields

A method for calculating the electron kinetics in dense gases in strong electric fields is developed. The method differs from the forward-backward approximation proposed by Ra?zer and Shne?der for “high-energy” electrons in that it introduces the effective cosines of the scattering angles with respect to the electric force, μ⁺(?, E) and μ^?(?, E), which are different from +1 and ?1, as in the forward-backward approximation. The method was implemented numerically for atmospheric-pressure helium and molecular nitrogen for fields in the ranges 10–200 and 50–800 kV/cm, respectively. The cosines μ⁺(?, E) and μ^?(?, E), the frequency of “fatal” collisions making high-energy electrons to pass from an acceleration regime to a deceleration one, and the rate at which the electrons leave the low-energy reservoir with energies of ≤15 eV for nitrogen and of ≤20 eV for helium are calculated.     

Influence of the Hall effect on the plasma dynamics in an MTF/MAGO chamber

The role of the Hall effect in experiments on the magnetic implosion of a D-T plasma in a cylindrical MTF/MAGO chamber fed from a helical explosive magnetic generator is investigated. The plasma dynamics is simulated numerically by a 2D code developed for solving the set of MHD equations with account of the Hall effect. In simulations, the generator, the break switch, and other units were replaced with LR circuits. It is shown that taking into account the Hall effect provides better agreement between numerical simulations and experimental data.     

Fundamental parameters of a relativistic runaway electron avalanche in air

A relativistic runaway electron avalanche in air is simulated numerically by the Monte Carlo method with allowance for a large number of elementary processes involving electrons, positrons, and photons. The characteristic time scale of the avalanche amplification is calculated as a function of the overvoltage δ relative to the minimum value of the drag force between the electrons and the atomic particles of the medium. The dynamics of the formation of the electron energy distribution is investigated. The steady-state mean electron energy depends weakly on δ. Over a wide range of δ values, there exists a universal electron energy distribution, which is essentially independent of δ. The angular distributions of electrons integrated over energies, as well as the angular distributions for different energy groups, are calculated. Analytic approximations for the energy and angular distributions are obtained.     

Heating of a Local Region of a Branching Streamer as a Starting Point of a Space Leader and a Negative-Leader Step

Plasma Physics Reports - Localized plasma formations called space leaders are observed in streamer coronas of negative leaders of long laboratory sparks. The main leader completes a step when the...     

Dependence of the Generation Rate of High-Energy Electrons in Helium on the Electron Angular Scattering Model

Plasma Physics Reports - It is known that in dense gases in sufficiently strong electric fields, electrons can be continuously accelerated, when they receive more energy from the field than is lost...     

Analysis of the results of a laboratory experiment on the observation of a runaway electron avalanche in air under high overvoltages

Analytic estimates and numerical computations are carried out to test the concept of a laboratory experiment on the demonstration of a runaway electron (RE) avalanche and RE-induced air breakdown under high overvoltages. It is shown that the development of an RE avalanche is impossible under the conditions of the given laboratory experiment. The experimentally observed distinct tail of the picosecond RE pulse, which was interpreted as the RE avalanche induced by the primary RE peak, is very weakly pronounced in the numerical experiment. Only the initial stage of the RE avalanche could be observed in the laboratory experiment; however, according to the numerical results, the fraction of REs in it is too small (as compared to the number of electrons in the primary peak) for the secondary REs to appreciably affect the breakdown process.