Electrically Triggered Water Switches

We have developed an electrically triggered water switch as a low-cost, compact alternative to laser switching. The trigger electrode of the trigatron-type switch consists of a tungsten wire with a diameter of 50 mum, enclosed in glass tubing. The high electric fields at the triple-point (metal, glass, water) allow the generation of plasma streamers for a trigger voltage of approximately +16 kV at a pulse duration of 100 ns. The luminous streamers propagate with a speed on the order of 20 km/s to the two main electrodes. The applied main gap voltage and the trigger voltage, and the distances between electrodes, can be adjusted such that the filaments reach the opposite electrodes at approximately the same time. The streamers then serve as preionized channels for the breakdown between the main electrodes. Preliminary experiments with this trigger system have demonstrated the feasibility of this concept. We were able to consistently trigger breakdown of the main gap for voltages in the range of 18 to 30 kV. The delay time of the main breakdown to the trigger pulse was approximately 150 ns, and the minimum jitter was less than plusmn10 ns. Better positioning of the trigger electrode promises to reduce the jitter to values on the order of nanoseconds