Modeling of Townsend discharges at high E/N and low pressure

Abstract

This report presents the results of an investigation of complex behavior of electrons and ions in Townsend discharge by a Monte Carlo simulation (MCS) technique. Although recognized as a relatively simple for implementation and at the same time difficult to test and verify, this technique is revealed as a right choice for modelling Townsend discharges. This work begins with selection of input data and benchmarking of codes. We have included description of effects of ions and fast neutrals to kinetics of excitation, description of nonhydrodynamic effects in the vicinity of electrodes and at the high E/N the runaway of electrons and ions. We also present description of impulse discharges and time resolved current impulses under similar conditions. Main presented results were electron energy distribution functions (EEDF), spatial excitation coefficients and arrival time spectra (ATS) obtained for the conditions of Townsend discharges in nitrogen and argon at low pressures and very high E/N. In addition we have compiled cross section sets that may serve for discharge modelling in argon and nitrogen in broad range of conditions and discussed numerous approximations that were recently used in modelling of plasmas.