Investigations of glow discharge formation with volume preionization

Abstract

The discharge formation process has been studied experimentally for CO2 planar TEA laser discharges. Theoretical models are presented which predict the preionization electron and ion densities, the spatiotemporal development of the discharge plasma, discharge voltage, and current waveforms, and the quasisteady operating characteristics of the discharge. The preionization is provided in the experiments by a pulse of ultraviolet radiation. The discharge formation model accounts for cathode photoemission and anode collection of electrons, discharge−circuit interactions, and gaseous ionization processes. The model predicts that photoemission and anode collection can be neglected when strong preionization and moderate overvoltages are used. When photoemission and anode collection are neglected, the discharge formative time is independent of the discharge volume. Calculated and experimental voltage and current waveforms are in very good agreement. The results of the calculations show that the discharge formative time is determined primarily by the characteristics of the external circuit in the experiments. Formation calculations for a large−volume discharge show that a uniform glow discharge will develop even when the preionization is nonuniform along the electric field, and confirm that the formative time is approximately independent of the discharge volume.