A trigger power supply for vacuum arc ion sources

Arc initiation plays a key role in the operation of pulsed metal vapor vacuum arc (MEVVA) ion sources. The favored triggering method in most sources is a surface discharge across an insulator inserted between an auxiliary trigger electrode and the main gap cathode. The trigger power supply must be capable of meeting specific requirements. As part of an ongoing program to develop such a power supply the authors have designed, constructed, and tested several simple units. The most successful of these is a design employing a resonant 1/2-cycle capacitor discharge which generates peak voltages to 10 kV. The maximum current and duration of the output pulse in the present configuration are 40 A and 50 μs, respectively. The trigger unit has been tested on a MEVVA II ion source equipped with a tungsten cathode. For the trigger pulse parameters given, a misfire rate of <0.1% is obtained. The effect of changing the magnitude of the output pulse is investigated and described. Some preliminary results obtained with a silicon cathode are presented