Influence of the Electric Field Enhanced Thermal Electron Emission on Temperature of the Cathode with a Thin Insulating Film in the Arc Gas Discharge

A model of the electric field enhanced thermal (thermo-field) emission of electrons from the metal cathode substrate into a thin insulating film on its surface is developed. A system of equations for the cathode surface temperature in the arc discharge and the electric field strength in the film, providing the required discharge current density, is formulated. It is shown that existence of the insulating film can result in a considerable reduction of the cathode temperature in the discharge due to lower potential barrier height at the metal-insulator boundary than at the metal-discharge boundary in case of the cathode without the film. It is found that due to an enhancement of the thermal emission of electrons into the film by the electric field generated in it, an additional decrease in the cathode temperature by about 100 K takes place.