Breakdown Charge Dependence for Saturation of Spark Conditioning under Non-uniform Electric Field in Vacuum

Spark conditioning is one of the effective measures to improve the dielectric strength in vacuum. In this paper, we discuss breakdown charge dependence and a saturation condition of spark conditioning in vacuum under various non-uniform electric field and circuit condition. We used a rod-plane electrode system, and the gap distance and the tip radius of the rod electrode were varied. Negative lightning impulse voltage was applied to the rod electrode for the spark conditioning of electrodes. We changed the discharge current at breakdown by the circuit condition, i.e. the limiting resistance. As a result, as the breakdown charge increased, the dielectric strength was improved. However, when the breakdown charge was too large, the dielectric strength decreased due to the damaging effect of…