Gas desorption induced discharge in vacuum and its polarity effect

The objective of this paper is to propose mechanisms of gas desorption induced discharge and their polarity effect. Three electrode pair types were combined in the in-situ experimental apparatus with high vacuum; air-exposed cathode and anode, airexposed cathode and conditioned anode, conditioned cathode and air-exposed anode. Electrode pairs were subjected to repetitive impulse voltage breakdowns till conditioning saturation. The results showed two gas desorption induced discharge mechanisms; namely, pulsed current discharge (PCD) and pulsed current induced breakdown (PB). Many gas desorption induced discharge (PCD and PB) occurred in air-exposed cathode and anode pair and air-exposed cathode and conditioned anode pairs. While only a few discharges occurred in the conditioned cathode and air-exposed anode pair. The gas desorption induced discharge in vacuum showed a polarity effect; Only when the cathode electrode of the pair was the original air-exposed electrode, no matter the anode electrode was or not, gas desorption induced discharge (PCD and PB) could occur in the beginning stage of the conditioning. The physical evolution of gas desorption induced discharge is explained.