Conditioning process of multi-gap electrode system with Cu-Cr rod electrode in vacuum

In order to clarify the characteristics of spark conditioning carried out in parallel at several parts of electrodes, we studied conditioning process in a multi-gap electrode system with two rod-plane electrodes in vacuum. The rod material and gap distance of one gap was kept to Cu-Cr (d=5 mm) in some multi-gap electrodes. On the other hand, the rod material and gap distance of the other gap were varied. As a result, the number of breakdowns till conditioning saturation of Cu-Cr rod in the multi-gap electrode system was less than that in the single-gap electrode system. These results suggest that charge activity occurs between electrodes even at the gap without breakdown, which can also contribute to the conditioning effect.