Laser-triggered water switching

Summary form only given. We are studying the use of lasers to command trigger high-voltage water switches. The jitter in self-breaking water switches currently; limits the peak power and timing accuracy in a number of high-voltage accelerators. We have previously demonstrated water breakdown using focused laser beams at 1064, 532, and 355 nm (1). The lowest breakdown threshold of 110 J/cm/sup 2/ or 14 GW/cm/sup 2/ occurred at 532 nm. In initial experiments, we demonstrated laser triggering of a 3.5-mm water gap that was pulse-charged to 170 kV in 300 ns using 70 mJ of focused laser energy at 532 nm. The laser was focused through a hole in one electrode to break down the water in the middle of the gap. The, repeatability of these initial experiments appeared to be degraded by small bubbles on the electrodes and by material in the water that was blasted off the electrodes by the laser. New experiments using a debubbled, flowing water system are in progress.