Measurements on Insulator-Surface Breakdown in Vacuum Under dc Voltage

Abstract

The breakdown voltage over insulator surfaces in vacuum between plane electrodes has been investigated for different insulator materials and geometries using dc voltage. The spark current as a function of time was measured showing a current rim of 1–2 A/nsec and a slower decay. The spark is followed within a millisecond by weak discharge pulses. The time delay of these pulses indicates that they originate at the cathode.