The electrode which is usually used as the carrier of the high-voltage insulator is very important for the vacuum electronic devices.The reasonable design of the electrode geometry can considerably improve the surface flashover hold-off voltage of the insulator.In this paper

the influence of several geometries on the electric field distribution at the triple junction was simulated and experimentally studied.The single pulsed flashover hold-off voltage tests of cylindrical alumina insulators in vacuum were conducted.The results indicate that these geometries weaken the electric field at the triple junction

and the average hold-off voltage limit of the alumina ceramics is increased by 55% with the concave electrode compared to the plate electrode.