High-voltage multichannel rail gap switch triggered by corona discharges

A simple trigger assembly designed to promote multichannel breakdown in a high-voltage low-inductance rail gap switch operating in a dc voltage hold-off mode is described. The switch is formed by two extended (rail) cylindrical electrodes, separated by spacing of 10 mm and pressurized with nitrogen or air up to about 0.5 bar. The gas breakdown in multiple sites of the interelectrode volume is initiated by preionization with ultraviolet radiation pulses simultaneously emitted from an array of circular orifices and is performed along one generatrix of the surface of a tabular electrode (cathode) which are generated in its interior by capacitively coupled (pulsed corona) discharges. The switch has been tested by discharging capacitors of 40 and 100 nF in an underdamped condition at voltages and peak currents up to 15 kV and 14 kA, respectively. The maximum energy transferred per shot was about 11 J. The trigger assembly allows one to arbitrarily select the number of channels to be formed just by varying the number of preionization sources (orifices) distributed in the cathode and as a result they are unaffected by the discharges. (C) 2003 American Institute of Physics.