Charging process of a solid insulator in vacuum under a.c. voltage excitation

This paper describes charging process of a glass or polymeric insulator exposed to A.C. voltage in vacuum. The charging characteristics of the insulator were investigated by using an electrostatic probe that allowed online measurement of the charging process. The insulator specimen was made of fused quartz, borosilicate or PMMA, and was in the shape of a right cylinder with 10 mm in thickness. It has been clarified that the charging process is characterized by three States; initiation, the quasi-stable and stable states.