Influence of the Thermo-Field Electron Emission from the Cathode with a Thin Insulating Film on the Film Emission Efficiency and Ignition Voltage of the Townsend Gas Discharge

A model of the thermo-field electron emission from the metal cathode with a thin insulating surface film at temperatures of 200-400 K is developed. An expression for the film emission efficiency in the gas discharge is obtained. The efficiency is equal to the fraction of electrons emitted into the film from the metal substrate, which enter the discharge volume and increase the effective secondary-electron emission yield of the cathode. It is shown that the thermo-field mechanism of electron emission influences noticeably the ignition voltage of the low-current discharge with such cathode at rather low temperatures exceeding the room temperature by less than 100 K.