Investigations of pulsed surface flashovers for the triggering of pseudospark high-power switches

Surface discharges over insulators in vacuum under rectangular high-voltage pulses are investigated. These discharges are among the methods used to trigger pseudospark switches. Low breakdown voltage and long lifetime are the requirements these insulators have to meet to be used as trigger materials. For this purpose the breakdown behavior of certain ceramics stressed by high-voltage pulses was investigated in an oil-free vacuum of 10^-5 Pa. The erosion of the insulator by the discharge plasma was investigated with a scanning electron microscope. An evaluation of the measurement and a comparison of the properties of the investigated insulators show that SiN, Al₂O ₃, and CaTiO₃ have low breakdown voltages and exhibit the lowest erosion rates. First results obtained with these materials as trigger insulators in pseudospark switches are promising with regard to the achieved lifetimes. A lifetime of four million triggered discharges under 90% switch current reversal was reached at a peak switch current of 25 kA without a serious reduction in trigger performance