Heavy-particle hybrid modeling of transients in a direct-current argon discharge

A hybrid model incorporating heavy-particle processes was developed to describe the transient behavior of a low-pressure, cold-cathode, direct-current-excited argon discharge, recently studied experimentally by Jelenkovic and Phelps [J. Appl. Phys. 85, 7089 (1999)]. The transients were initiated by applying a high-voltage pulse to the discharge, which induced a transition from the Townsend state to the abnormal glow mode. The model made it possible to calculate the transient electrical characteristics, as well as the spatiotemporal changes of the light intensity distribution of the discharge. While in the initial state of the discharge most of the light emission occurs near the anode, with the development of the cathode sheath (taking place on the mu s time scale), intensity peaks corresponding to the negative glow (created by electron-impact excitation) and the cathode glow (created by heavy-particle excitation) could be identified. The results of the simulations are in good agreement with the experimental observations, both in terms of electrical signals and light intensity distributions. It was also found that hybrid models not taking into account heavy-particle processes (and assuming that the secondary electron emission coefficient depends on the reduced electric field at the cathode surface) do not give satisfactory agreement with the experimental data. (C) 2000 American Institute of Physics. [S0021-8979(00)01418-3].