Modelling of a self-sustained discharge-excited ArF excimer laser

A one-dimensional model including Poisson's equation to consider the space-charge for a discharge-excited ArF excimer laser has been developed. Behaviour of the field distortion by the space-charge and its effect on discharge evolution in the cathode sheath region have been studied. It was shown that the electric field near the cathode was extremely distorted due to the positive space-charge and became approximately 300 kV cm^-1 at the period of laser oscillation, though the maximum of the external field was approximately 20 kV cm^-1. This high field may suggest that a local filamentation starts from the cathode by field emission, if a microscopic protuberance is on the cathode surface. The photoelectron emission from the cathode was shown to be essential to moderate the field distortion in the cathode region and to sustain high-power-large-volume discharges. The decrease in the preionization density caused an increase in the electric field in the cathode at the final stage of the discharge, and an increase in the maximum values of the ArF* and electron number densities.