Surface flashover performance of alumina insulators at high voltage microsecond pulses in vacuum

The surface flashover performance of insulators is the critical factor strongly influencing the voltage hold-off capability of high voltage vacuum devices. Based upon the simulations of electric fields, the influences of residual gas pressure, alumina insulator materials and cathode electrode geometries on the pulsed flashover performances of the hollowly cylindrical alumina insulators are experimentally studied under the condition of the single high-voltage microsecond pulses. The results indicate that the flashover voltage of the alumina insulators is independent on the residual gas pressure below 10^-1Pa. The flashover voltage of the 94% Al₂O₃ insulators doped with Cr₂O₃ is almost 30% higher than that of the 95% Al₂O₃ insulators. The pulsed flashover voltage of alumina insulators can be raised significantly because the reasonable metal electrode geometry can reduce the cathode-triple-junction fields of the ceramics insulators.