Dark current measurements in humid SF6 at high uniform electric field

Measurements of “dark currents” in pressurized SF
6
in high uniform electric field are carried out. To identify the mechanism involved, the influences of electric field, gas pressure and relative humidity are investigated. The experimental results support the hypothesis of emission of charged water clusters from electrodes. A simple model describing the above mechanism is developed, which allows accounting for the complex equilibrium of water between the gas volume and the electrode surface.