A Study of Charge Transport in a High-Pressure rf Discharge

The purpose of this theoretical analysis is to show that certain properties of high-pressure rf gas discharges can be largely accounted for by a relatively simple model. An experimental investigation of rf glow discharges in air at atmospheric pressure in the frequency range 1–25 MHz has been made and a summary of the measurement results pertaining to this paper is presented. An analysis is made of the processes in an rf glow discharge which take place during approximately the first quarter of each half-cycle, while a cathode fall is built up in front of the negative electrode. The computations are based on a model plasma between two electrodes to which an external voltage is applied. This voltage is assumed to increase linearly with time, starting at zero. Thus it approximates the voltage increase in an rf discharge at the beginning of each half-cycle. The application of this voltage results in a current which can be both experimentally observed and computed. A numerical method to perform these computations on a digital computer is presented. The results of the computations are plotted and compared to the experimental values. It turns out that both the amplitude and the frequency behavior of the current through the plasma are in good agreement with experimental values, which the time dependence is not. Experiment shows the current to be constant while the computation yields a decrease with time. This decrease, however, is less than 1/t1/2.