A Modek for the Production of Initial Electrons by Detachment of SF-6-IONS

Experiments with positive pulses in a sphere-to-plane gap give evidence of the fact that initial electrons are provided by collisional detachment of SF6 ions. The position-dependent density of negative ions prior to a pulse application is calculated numerically for different geometries. The results are then included in a quantitative model for the electron production rate which is based on physical assumptions about the detachment coefficient. From a comparison with the measurement, ¿/n is obtained as a function of E/Ecr.