Evaluation of the Ionization and Recombination Processes in Low-Density Plasma Based on the Statistical Model of Atom

Abstract

Summary form only given. The issue of plasma irradiation on impurities is very important for the MAGO/MTF approach as it provides considerable contribution to plasma cooling. The density of the MACK VMTF plasma is rather low, therefore the radiation processes can be considered in the coronal limit. If we are interested in radiation on heavy impurities with big number of electrons, the statistical approach can be used for the plasma-electron interaction kinetics description (and, accordingly, the radiation occurring at such interaction). The discrete transitions and lines in this approach are taken into account statistically and on the average. In this paper, the ionization and recombination processes proceeding in plasma in free electrons-ions collisions are considered basing on the atom statistical model. The ionization and recombination processes can be presented in this approximation as the process of binary collisions of electrons in the atomic electron gas. The expression for the ionization rate depending on the ionization potential / and temperature T is obtained. This formula shows that at 1>> T the ionization rate is proportional to exp(-I/T). In the proposed approach, the recombination rate is calculated for an ion with high nuclear charge Z, and at arbitrary Z the recombination rate is estimated. The obtained values of the ionization and recombination rates are in reasonable agreement with available experimental data. The considered model explains low coronal model values of I/T , as compared with the Saha equation, and the reduction of these values with the growth of Z. The values I/T and the mean ion charge obtained from the balance equation for multi-electron ions using one fitting coefficient agree with the tabular data obtained in the multi-level coronal model. The obtained results can be applied not only to the MAGO/MTF plasma but also to the systems with magnetic plasma confinement and to low densitv cosmic plasma.