Small-radius planar-coil driven inductive discharge as a source of negative hydrogen ions

Abstract

A two-dimensional (2D) model of a low-pressure hydrogen discharge is presented in the study. Gas-discharge description based on the fluid-plasma theory is self-consistently coupled to electrodynamics of a planar-coil driven inductive discharge, with the coil included in the modeling domain. A discharge with a small radius is considered regarding development of the concept for a source of negative hydrogen ions completed as a matrix of small-radius discharges. Confirming previous results for the spatial distribution of the plasma parameters and, in particular, the result for a strong accumulation of the negative ions in the region around the maximum of the potential of the dc electric filed in the discharge, the model specifies the behavior of the TE-mode sustaining the discharge as well as of the rf current density and of the rf power input to the plasma. Comparison with results for the plasma parameters obtained by simulating the rf power deposition via a half of a super-Gaussian profile shows that the latter is a good approximation. Analytical estimations and comparison with numerical results from a model, in which the accounting for the coil is via a surface current applied as a boundary condition, are involved in discussion on the role of the finite – small – radius of the discharge in determining the skin depth of the TE-mode producing the plasma.