Characteristics of interelectrode flashover in air with the existence of a weakly ionized plasma channel induced by a KrF laser (248 nm)

The irradiation of a KrF laser (248 nm) into the interelectrode space affects the electric flashover characteristics there. The results obtained show that negative oxygen ions dominate formation of the interelectrode arc in air. A laser beam is introduced parallel to the interelectrode axis and the equipment is arranged to prevent the occurrence of photoelectric effects on the electrode surfaces. The time separation between laser firing and application of the interelectrode voltage is varied from 10 ns to 10 ms. The interelectrode spacing is set in the range 2–12 cm. The arc formation time and the flashover probability are measured. The initial ion number density is estimated experimentally to be on the order of 1011 cm−3 throughout the channel.