Modeling of the effect of temperature and field-induced electron emission from the cathode with a thin insulating film on the Townsend discharge ignition voltage in argon–mercury mixture

•Components of argon–mercury mixture ionization coefficient are calculated.•Insulating film on cathode surface facilitates low-current discharge ignition.•Effect of field electron emission is determined by film electron emission efficiency.

A model of the low-current (Townsend) discharge in argon–mercury mixture in the presence of a thin insulating oxide film on the cathode is developed. It takes into account the cathode ion-electron emission and the electron emission from the cathode metal substrate under the strong electric field generated in the film by the ion surface charge. An influence of the mixture temperature and the oxide film on the discharge ignition voltage is estimated and it is shown that formation of a thin insulating film on the cathode surface can facilitate the discharge ignition in mercury-containing gas discharge devices at low temperatures.