A detailed study of electron kinetics involved in modelling discharge pumped excimer laser plasmas

Abstract

A detailed analysis of the nonstationary behaviour of the electron kinetics for the preionized, discharge pumped excimer laser plasma has been performed solving the nonstationary electron Boltzmann equation. The nonstationary treatment of this equation is based on the conventional two-term approximation of the velocity distribution and on the quasi-stationary description of the anisotropic part of the distribution. The validity of both has been analysed. Using the atomic data of the relevant electron-heavy particle collision processes and the temporal course of the electric field in the laser discharge, the degree of nonstationarity of the energy distribution and of the consistent particle and power balance of the electrons has been critically evaluated. By applying a new and very efficient solution technique of the nonstationary kinetic equation to the typical excimer laser mixture Ne/Xe/HCl, the temporal behaviour of the energy distribution and of the corresponding particle and energy budget has been comprehensively studied. The results confirm the conclusions of the mentioned evaluation. In addition, some results concerning the impact of electron-electron interaction and the replacement of the nonstationary treatment by a quasi-stationary approximation are reported; these indicate the limitations enforced by different simplified treatments. The technique developed in this paper and applied to the particular laser plasma mentioned can be used in the modelling of other excimer laser plasmas.