Interaction between the electromagnetic fields and the plasma in a microwave plasma reactor

Abstract

We investigate the interaction between electromagnetic (EM) fields and a hydrogen plasma in a resonance-type microwave plasma reactor, by combining an elementary theoretical analysis and a self-consistent two-dimensional numerical model. We show that the EM fields in the reactor are strongly modified by the presence of plasma; due to absorption the standing wave patterns of the field intensity are less pronounced. In turn, the electric field controls the electron temperature and the plasma formation. For typical conditions (field frequency 2.45GHz, gas pressure 10–200mbar, gas temperature 2000–3000K) it is not just the electric field that controls the plasma, but rather the reduced electric field, i.e., the ratio of electric field strength to gas particle density. We show that the dependence of the reduced field on the gas temperature has a reinforcing effect on plasma formation and may cause jumps in the spatial plasma configuration as a function of power or pressure. We also show that the plasma size is limited by the skin effect.