Performance of a corona-stabilised switch activated by fast-rising trigger pulses

Plasma closing switches used in pulsed-power applications have traditionally been insulated with sulphur hexafluoride (SF₆) due to its high dielectric strength. The global warming potential of SF₆, however, is estimated to be 23900 times greater than that of CO₂. The present study details tests conducted in order to replace SF₆ with air as the switching medium within an existing corona-stabilised switch, the main goal being to extend the triggering range by deploying a fast-rising (~40 ns) trigger pulse. Delay times were measured and jitter calculated at a range of pressures, for different triggering regimes. The most stable performance was found with a negative-polarity dc voltage across the main electrodes, and a positive-polarity trigger voltage. With this triggering regime, the average delay time to breakdown was ~300 ns over a 2-bar pressure range. The minimum calculated jitter was 5 ns. When the switch was charged with a positive dc voltage and the trigger pulse was of negative polarity, the triggering range was extended by up to 7 kV compared to the triggering regime previously used (μs pulse).