Kinetic study of low-pressure H2 multipole discharge

Abstract

This paper is devoted to the study of kinetic equilibrium among electrons, H2 molecules, H atoms, and positive H+, H 2 + , and H 3 + ions in a multipole discharge working under low-pressure (1- to 15-m Torr) and moderated current conditions. In such a discharge used either as a H+ or a H− ion source or for plasma-surface interactions, the dependence of the densities of these species versus experimental parameters is of a great interest. In the present situation, the electron energy distribution function (e.e.d.f.) is largely nonmaxwellian. The kinetic model that determines the densities of the plasma species is self-consistently coupled to the e.e.d.f. calculated through the use of the Boltzmann equation. The influence of the main processes, volume ones, and those involving plasma walls is emphasized. An attempt is made to use the profiles of Balmer lines obtained experimentally in order to determine absolute concentrations of H atoms and H 2 + ions. Results derived from the experiment are compared to results of the model. Such an analysis of Balmer line shapes appears to be an interesting way to determine, by anin situ nonintrusive method, the absolute concentration of H atoms.