Modeling a collision-dominated space-charge sheath in high-pressure arc discharges

A model of collision-dominated space-charge sheaths is developed using the approximation of mobility-controlled ion motion. Results of numerical and a symptotic solutions are given. The asymptotic solution has exponential accu racy with respect to the ratio sheath voltage/electron temperature and prov ides for near-cathode sheaths results which can be considered as practicall y exact. On the basis of the asymptotic analysis, a simple exponential-accu racy analytical model of the ion layer is given. Voltage drops in different zones (the ionization layer, the ion-electron layer, and the ion layer) ar e identified. The voltage drop in the ion-electron layer is found to be qui te close to kT(e)/e. Results of numerical integration for conditions typica l for high-intensity discharge lamps are presented. (C) 2001 American Insti tute of Physics.