Optimum breakdown charge for spark conditioning in vacuum under non-uniform electric field

Spark conditioning is one of the effective measures to improve the dielectric strength in vacuum. In this paper, we obtained the breakdown (BD) charge dependence for spark conditioning in vacuum under various non-uniform electric field and anode materials, and discussed the BD mechanism in terms of BD based on anode heating or cathode heating. Experimental results revealed that, in the case of BD based on anode heating, the longer the gap distance was, the larger the BD charge to obtain maximum dielectric strength was. On the other hand, in the case of BD based on cathode heating, the BD charge for maximum dielectric strength was smaller than that in the case of BD based on anode heating. From these results, we can estimate the optimal BD charge for the spark conditioning in vacuum.