Hot plasma and nonlinear effects in inductive discharges

Abstract

Recent advances in the physics of low pressure inductively coupled plasma (ICP) are reviewed where the interaction of an electromagnetic field with electrons is governed by electron thermal motion rather than electron-atom collisions. Direct measurement of the radio-frequency (rf) electric field and rf current density in the plasma made it possible to distinguish between collisional and stochastic (collisionless) electron heating. Several new phenomena such as a wave phase bifurcation, phase velocity reversal, a second current layer, and negative power absorption have been found and interpreted in terms of nonlocal electrodynamics. Nonlinear effects induced by the rf Lorentz force as well as modification of the spatial distribution of the plasma caused by ponderomotive forces have been demonstrated in ICP under discharge conditions typical for industrial applications. Classical works on the anomalous skin effect have been revived and successfully applied to describe these phenomena. The effects observed in these experiments with weakly ionized cold plasma are intrinsic to fusion and space plasmas.