Study On The Flashover Characteristics Of Dielectric Vortex Along The Burst Of High Voltage Pulse

Vacuum flashover is a peculiar gas discharge phenomenon which occur in the interface of Vacuum and solid insulated dielectric. Intensive experimental studies and meticulous theoretic analyses have been taking since its discovery in1950s, as the restriction to the development of highvoltage technology and pulsepower technology. The vacuum flashover theory is still unconsummated while so much investigation have been taking so many years, as it is so complicated a process. More and more experimental phenomenons and truth have been coming to light by the development of experimental technology.The vacuum falshover characters of insulated dielectric under MHz bursted highvoltage pulse were investigated by the bursted multipulse power source. First of all, optical diagnoses of the flashover process of two type insulators, high gradient insulators and conventional insulators, under submicrosecond pluse highvoltage were taked by ICCD cameras. The discharge process of vacuum flashover in the even electric field under submicrosecond pluse were explained by the streamer discharge theory, according to the phenomenons observed by ICCD cameras combine with the discharge mark on the surface of insulators and electrodes.It was reported that accumulated charges were gathered on the surface of insulators after preflahover or flashover, and the flashover process would been affected by the electric field abnormality which was induced by the accumulated charges. The multipulse power source pulse interval was transformed from invariable,500ns, to alterable. The flashover voltages of the insulator samples under monopulse and multipulse highvoltage were measured. It was foud that the average flashover voltage under multipulse was a little lower than that under monopulse. It was presumed that the difference of flashover voltage was conduced by the accumulated charges gathered during anterior pulse, which increased the flashover probability during posterior pulse.It was infered that the flashover vlotages under different pulse interval multipulse would be different if the flashover vlotages difference under monopulse and multipulse was caused by the surface accumulated charges, which would eliminating after its appearance. This conclusion was substantiated by the determination of flashover voltages of insulators under the loading of different pulse interval multipulse, including300ns、500ns and1μs. It was found that the difference of flashover voltage under different pulse interval had something to do with the material and shape of the insulators and the reason was analysed. The reason,why the insulators in the cavities of the linear induction accelerator would breakdown when the electron beam passthrough the cavities, was analysed. It was found that the vacuum flashover performance of the insulated material declined by the surface accumulated charges, which was aroused by the electron beam. It was indicated that surface accumulated charges not only increased the flashover probability during posterior pulse in the same loading experiment, but also declined the vacuum flashover performance of the insulated material in the posterior loading experiment.