Self-consistent modelling of overdense plasmas in ECR discharges

A two-dimensional self-consistent model of a large-volume ECR discharge is presented. The set-up of the plasma source is introduced briefly. The model treats electrons as a fluid assuming a Maxwellian velocity distribution and determines electron density and temperature from a particle and energy balance. Wave propagation in the plasma is calculated from a wave equation derived from Maxwell's equations in matter. The self-consistent coupling of the equations is achieved by determining the material properties of the plasma from the dispersion relation of right-hand circularly polarized waves propagating parallel to the external magnetic field. We do not adopt the cold plasma approximation so that thermal effects like Doppler broadening of the resonance zone and collisionless electron cyclotron heating of the plasma are included. The neutral temperature is estimated from a global balance of energy. Results of the simulation for different operating conditions are discussed and compared with theoretical predictions and experimental data of other authors.