Effects of Supersonic Flow Channel Configuration on Pulse Discharge for Excimer Laser Excitation

Abstract

Several supersonic flow channel configurations chosen from the viewpoints of electric field and aerodynamics are constructed to evaluate their effects on the stability of a single pulse discharge for excimer laser excitation. First, two types of electrode with a flat or curved top are experimentally investigated in still gas and the electrode with a curved top is selected for discharge experiments in a supersonic flow. A Ludwieg tube with a two-dimensional shock-free nozzle is used to generate a supersonic flow with a Mach number of 2 in a discharge cavity. A shadowgraph technique is applied to visualize the gas density disturbance inside the discharge cavity due to shock waves and boundary layers. It is shown that discharge stability strongly depends on the flow channel configuration. Within the scope of this investigation, a channel configuration with an upstream cover and a downstream channel widened by 2 mm is the most suitable configuration for the excitation discharge preionized by UV pin spark in a supersonic flow.