UV-laser triggering of multi-megavolt gas switches

The use of uv lasers to trigger multimegavolt gas switches found in many large pulsed power systems is discussed. Using 77 mJ from a low divergence (100 micro rad) KrF laser system to trigger a 2.8-MV switch, a 1 sigma jitter of 0.5 ns for a series of applied voltages ranging from 65% to 90% of the self break voltage was demonstrated (Jitter is defined as deviation of the data points from a best fit line through the data). In this sequence of measurements, the triggering delay was relatively insensitive to voltage variations, changing by only approximately 2 ns for a 10% change in voltage. The low divergence KrF beam is focused through a hole in one switch electrode, forming a breakdown arc in the high pressure SF6 between the electrodes. Breakdown arcs were demonstrated which stretch all the way across the 11 cm electrode gap in the 2.8-MV switch. The sudden appearance of this conductive breakdown arc triggers the switch. Techniques, applications and results are discussed.