ELECTRO-OPTICAL MEASUREMENTS OF INSULATOR SURFACE FLASHOVER IN VACUUM

Abstract

Electro-optical measurements of the electric field along insulator surfaces in vacuum during the few nanoseconds prior to insulator flashover have been made. The Pockels and the Kerr effect are used in conjunction with a polarization interferometer to measure the interfacial fields which have a risetime of a few ns. Insulator surface charging and cathode field enchancement occurs, followed by plasma formation near the cathode which propagates toward the anode at approximately one tenth the speed of light. Voltage collapse across the insulator occurs after the plasma formation has reached the anode.