Abstract
This paper deals with factors affecting the charging characteristics of insulators exposed to high voltages in vacuum. We examined the influence of voltage shape on charging. The charging was studied by using an electrostatic probe that measured electric field on the cathode. A ramped dc and an impulse voltage were tested in a low pressure and found that the electric field due to surface charging was larger for the impulse voltage than that for dc voltage. We also examined the influence of pressure that varied from 10-5 Pa to 0.5 Pa and found that an insulator acquired more charge in a high pressure range than that acquired in a low pressure range. These results suggest that the charging may be assisted by electrons produced by ionization of gas molecules desorbed from the insulator surface.
