Spatial distributions of electron temperature and density in electron cyclotron resonance discharges

Abstract

Spatial profiles of electron density and temperature of electron cyclotron resonance discharge plasmas have been successfully measured using laser Thomson scattering. The results, thus obtained, were valuable for quantitative comparison with results of a computer simulation. Measurements were performed for two cases with different locations of the electron cyclotron resonance zones. Simulation results obtained from a hybrid code, which treats ions and neutral particles as discrete particles and electrons as a fluid, were fitted to the experimental profiles of the electron density and temperature by adjusting the microwave power deposition profiles. From these comparisons and an analysis of other simulation data, it was found that the large difference of radial electron density profiles for two discharge conditions was caused by the difference of radial space-charge electric-field distributions. The radial electron temperature distribution determined the radial electric field that drove the ions radially and also resulted in a peaked electron density profile for one case and a more uniform profile for the other case. It is also shown that Coulomb collisions of electrons with ions as well as electron–neutral collisions are important for the analysis of electron behavior along the magnetic field lines.