Pulsed Glow Discharges in Laser Excitation and Breakdown

The spatiotemporal development of discharges in uniform field gaps has been studied for many years in order to understand the physical mechanisms of breakdown. These studies have shown that a glow discharge structure is produced as an intermediate stage in the breakdown process which finally leads to the formation of a filamentary arc. Recently these pulsed or transient glow discharges have been used to pump a wide variety of gas lasers including CO2 lasers and rare gas-halide excimer lasers. Preionization of the gas volume is usually used to ¿stabilize¿ these laser glow discharges, i.e. to increase the duration and/or energy density of the pulsed glow discharge and delay the onset of arc formation. Recent experimental work also has shown that the corona discharges which are observed in point-plane gaps have a glow discharge-like structure. These two types of discharges are compared and some speculations are offered about the ¿corona stabilization¿ process in point-plane gaps and its relationship to arc formation in uniform field gaps.