Vacuum flashover of Dragon-Ⅱ accelerator insulator ring

Two types of flashover phenomenons were discovered during the high voltage test of Dragon-Ⅱ linear induction accelerator insulator ring, which was made by cross-linked polystyrene. One type of the flashover was initialized from cathode and the other one was initialized from anode. The mechanism of the phenomenon was analyzed by comparing breakdown voltage waveform and discharge trace，and calculating electric field combination with flashover experiment on little insulator samples. It is assumed that the cooperating problem of the insulator and cathode caused the difference between accelerator and injector insulator ring flashover.