Influence of the radial electron density profile on the determination of the characteristics of surface-wave-produced discharges

Abstract

Until recently, surface wave discharges have been studied, both experimentally and theoretically, using the wave propagation constant calculated in the assumption of a flat electron density profile. This paper deals with determination of wave characteristics (wavenumber, attenuation and fields) taking into account a radial profile of the electron density. The consequences for the experimental diagnostics are presented. In the range of low electron densities, the authors show that some results deduced from experimental measurements are spoilt if the radial electron density profile is not taken into account. They present an argon surface wave discharge (390 MHz) at low pressure (about 1 Torr) in a 76 mm diameter tube. The influence of the radial electron density profile is studied on the following experimental results: electron density, effective electron-neutral collision frequency and the mean power needed to maintain an electron in the discharge.