Dark current measurements in pressurized air, N2, and SF6

Dark current measurements in pressurized gases at high electric field are performed in a coaxial electrode geometry. Three main parameters are investigated: the influence of electrode surface roughness, the nature and pressure of gas, the presence of water. Currents are measured in both negative and positive polarities. A large influence of electrode surface roughness and of the gas water content is observed. Most of results suggest that charge injection from the electrode constitute the basic mechanism of high field conduction through pressurized gases, and this mechanism is considerably enhanced when water is present.