Necessary Conditions for the Homogeneous Formation of a Volume Avalanche Discharge with Specific Applications to Rare Gas-Halide Excimer Laser Discharges.

The phenomena involved in high E/n (electric field to gas number density ratio) breakdown and its relationship to the formation of spatially homogeneous discharges is considered. Assuming uniform field electrodes with no edge effects, the minimum preionization density required for homogeneous discharge initiation is found to depend on the voltage rise time across the electrodes as well as on the total gas pressure and various electrochemical properties of the gas mixture. A large volume avalanche dicharge laser was constructed which employs an 1 X-ray preionization scheme to obtain the required spatially uniform volume preionization. Using X-rays as an ionizing agent, spatially homogeneous pulsed avalanche discharges of several liter volume at several atmosphere pressure for up to 100-nesec duration were successfully generated. In concurrent laser generation experiments, high-optical-quality pulsed UV laser output up to 2.5 J/liter from such discharges in rare gas/halogen mixtures, and ir laser output of up to 12.5 J/liter from a He/N2/CO2 mixture were observed.