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P: Plasmaphysik

P VIII: HV VIII

P VIII.1: Invited Talk

Thursday, April 5, 2001, 15:30–16:00, 2053

Application and theory of surface wave produced discharges — •J. Berndt — Institut für Experimentalphysik II , Ruhr-Universität Bochum, D-44780 Bochum

Electromagnetic surface waves which are propagating along a boundary formed by the discontinuity of refractive indices has found a wide use in sustaining gas discharges. Stimulated by the growing number of applications theoretical and experimental efforts have been made to get a better understanding of such kind of discharges. Due to the development of suitable coupling structures (Moisan, Beerwald) surface wave produced discharges can be operated over a wide pressure and frequency range (100 kHz to 10 GHz ; a few Pa up to atmospheric pressure).

The lecture will first give a survey of the basic properties of surface waves (i.e. dispersion relation, field configuration) as well as some examples of coupling structures (Surfatron) for the generation of surface wave produced discharges. The properties of such kind of discharges are treated afterwards. Their spatial structure (i.e. electron density profiles) which results from the interaction between wave propagation and wave generation will be discussed in particular. Surface wave produced discharges always exhibit electron density gradients both in radial and axial direction. Consequently one of the most important questions in this field is related to the problem of wave propagation in inhomogeneous cylindrical plasma columns.

The application of surface wave produced discharges in the field of plasma technology will be illustrated by means of two examples: The production of atomic nitrogen using the afterglow of a surface wave produced discharge and the deposition of thin a-C:H films using an expanding surface wave plasma.