Light emission characteristics before flashover along surface of polymer under AC voltage in vacuum

The initiation mechanism of flashover along the surface of polytetrafluoroethylene (PTFE) under AC voltage in vacuum was examined. Two distinct phases of light emission were observed, i.e., a stable low-level optical process under low voltage, so-called phase A, and an irregularly intense process called phase B for a light higher voltage. The results suggest that phase A is due to electroluminescence (EL) produced by the recombination of electrons and holes injected from electrodes. A new model has been proposed to explain the optical phenomena in phase B and the developing process of surface flashover.