High current two-electrode gas switch

High current and high-charge transfer spark gap switches are required for a range of capacitor bank applications such as electromagnetic rail,power conditioning system that power the flashlamps for laser fusion drivers.A compact long-lived spark gap and a matched series-injection trigger generator have been developed.The switch has two electrodes made of alloy Cu-W and a spark gap located in the centre of metal chamber.This kind of structure can prevent arc form approaching the insulated bracket.Elimination of the trigger electrode,used in many other switches,combined with an integral, coaxial current-return housing,allows the switch to handle very high current and charge transfer.Recently,the peak current of the switch is near 150 kA with a transfer-charge of 50 C.The two-electrode spark gap is triggered by directly overstressing the gap by a high-voltage,low-energy trigger generator such as Marx generator with an output voltage of 80 kV,a risetime of 30 ns,and a pulse duration of 130 ns.The spark gap can be triggered reliably when the operating voltage is 40% of the self-breakdown voltage,assuring low pre-fire rates. The design approach,and application of the switch and trigger system in pulse forming circuits are discussed.