Experimental study on gas desorption in surface flashover of solids in vacuum

The relation of desorbed gases and surface discharge in vacuum is a complex problem without reliable theory. The vacuum experimental platform of direct current and nanosecond pulse source was built, and the quadrupole mass spectrometer connected to vacuum cavity was used to analysis the out-gassing characteristics of insulation materials. Then the vacuum surface discharge experiments were done and the desorbed gases were measured in the process. By comparing the mass spectrum before discharges with ones after discharges, we obtained the out-gassing composition of several insulation materials. Meanwhile we analyzed the probable sources of different gases. Main gas components generated by vacuum surface flashover included H₂O, N₂, H₂, O₂, hydrocarbon fragment, CO, CO₂ and sometimes high polymer fragment. C₂H₂ appeared in gas components when the filamentary discharge channel was formed between two electrodes. The results show that the high polymer surface may decompose and the dissolved gases may be extracted besides gas desorption in discharges. The discharge pattern has direct effect on their out-gassing characteristics. We´ll thoroughly research their relation in subsequent work.