Fast electron effects in helicon discharges

Abstract

Summary form given only, as follows. The mechanisms responsible for fast and thermal electron heating are examined for the WOMBAT and UW helicon experiments. RF phase-correlated ArII optical emission, Bdot,Langmuir probe and antenna impedance measurements are used to evaluate near and far antenna wave field damping, fast electron (>20 eV) acceleration mechanisms and their fraction for a range of neutral pressures from 2-10 milliTorr and power levels from 0.6-3.4 kW producing densities in the 10/sup 11-13/ range. Analysis of the experimental data and computer models show that significant fractions of the electron distribution are accelerated to high energies at lower pressures and that the fast electron component is reduced at higher pressures. The correlation of Bdot phase and optical emission peak phase data show corresponding fast electon velocities. Computer models show the wave character and ionization fraction arising from electron acceleration over the range of pressures and wave powers.