Breakdown Charge Dependence of Counter Electrode Material Adhesion and Dielectric Strength After Spark Conditioning in Vacuum

Spark conditioning is an effective method of increasing the dielectric strength in vacuum. In this article, we discuss the breakdown (BD) charge dependence of counter electrode material adhesion and dielectric strength after spark conditioning. We have applied a negative impulse voltage to a rod-plane electrode configuration with a cathode and an anode made of stainless steel (SUS) that is defined as SUS304 by JIS G 4303 or oxygen-free high-conductivity copper (Cu). The electrode system of cathode SUS and anode Cu is called SUS–Cu electrode system, and the electrode system of cathode Cu and anode SUS is called Cu–SUS electrode system. We have changed BD charge (QBD) in conditioning by changing the limiting resistance in the experimental circuit. As a result, in both cases of SUS–Cu and Cu–SUS electrode systems, the larger theQBD, the smaller the amount of the anode material adhered to the cathode surface. WhenQBDis large, the dielectric strength increases in SUS–Cu electrode system and decreases in Cu–SUS electrode system. From these results, whenQBDis large, we consider that the conditioning characteristics are less likely to be dominated by the anode material, i.e., Cu in the case of SUS–Cu electrode system and SUS in the case of Cu–SUS electrode system. In other words, the decisive parameters, such asQBDto maximize the dielectric strength, may depend on the combination of electrode materials.