TRANSIENT EFFECTS IN BURST-MODE OPERATION OF PULSED BARIUM VAPOR LASERS

An externally heated barium laser has been operated in burst mode in o rder to investigate the approach of the medium to steady-state operati on in a continuously pulsed self-heated mode. Studies of the temporal evolution of discharge-current and cathode-voltage waveforms and laser output throughout a burst of pulses reveal short-term (first few puls es) and long-term (tens of pulses) transient effects. The former are a ttributed to changing prepulse conditions early in the burst. and the latter to the build up of radial thermal gradients in the laser medium due to gas heating. Simple models enabling the calculation of time-av eraged radial gas temperature profiles in the steady-state limit and t emporal evolution of spatially averaged gas temperatures are presented to elucidate the effects of gas heating.