Modeling of the Influence of the Thickness of an Insulating Film on a Cathode Surface on its Effective Secondary-Electron Emission Yield in Low-Current Gas Discharge

Abstract

A model of low-current (Townsend) gas discharge in the presence of a thin insulating film on the surface of a cathode is formulated. It takes into account, along with ion-induced secondary-electron emission from the cathode, also the field emission of electrons from the cathode metal substrate into the film under a strong electric field, which is generated in the insulator when the current flows in the discharge. The emission efficiency of the film and the discharge characteristics are calculated as functions of its thickness. It is shown that the experimentally observed nonmonotonic dependences of the effective secondary-electron emission yield of the cathode and discharge ignition voltage on the film thickness can be explained by the nonuniformity of the electric-field distribution across the film.