Experimental research on methods to improve lifetime of insulators in multi-stage gas switches

Abstract

We report on research into methods to improve the lifetime of insulators in multi-stage gas switches exposed to microsecond kV pulses at 20 Hz repetition rate. Two sets of experiments are reported; first on a comparison of polyetheretherketone (PEEK) and polyimide (PI) insulation. The results shows that the lifetime of PI far exceeds that of PEEK, which is attributed to the softening temperature of PI being higher than that of PEEK. In the second experiment, two methods are used to enhance the lifetime of PI; the first is to gild the surface of PI insulators, and the second is to insert PI films between the insulators and the electrodes. Both methods significantly increase the PI lifetime, but the film method leads to a longer lifetime than the gilding method. Imaging the insulator surfaces at the microscopic level reveals that local regions are not smooth, which results in greater electron emission from the cathode. The gilding method lowers electron emission and ejection and the film method blocks electron emission and ejection and thus they enhance the lifetime of PI insulators in multi-stage gas switches.