Electro-optical measurements of solid insulator surface fields and surface charging in vacuum

Electro optical measurements of the electric field along insulator surfaces and in the bulk of insulator materials was made to determine the mechanisms associated with insulator surface flashover. The Pockels effect in KDP was used in conjunction with a polarization interferometer and a pulsed laser to measure interfacial and bulk fields for KDP/vacuum interfaces. The results show that the solid insulator surface and bulk electric field distributions are spatially nonuniform. The electric field at the cathode is considerably enhanced while the field at the anode is reduced. The time evolution and steady state behavior of the insulator electric field distributions for DC, 60 Hz AC, and pulsed excitations are presented.