Cathode: the Key Factor in Vacuum Breakdown

The objective of this paper is to prove that the cathode is the key factor in vacuum breakdown. Three identical groups (I, II and III) of electrodes were prepared. Each group contained two pairs of plane-plane copper electrodes, pair A and B. In each group, the two pairs of electrodes were firstly applied the conditioning process of impulse voltage. Afterward, pair C was arranged by a combination of cathode of pair A and B, pair A cathode- pair B cathode. Pair D was arranged by a combination of anode of pair A and B, pair A anode- pair B anode. The arrangement was under the vacuum condition without exposure of air condition. Surface-analysis of the electrode surfaces were done before and after the vacuum breakdown test for pair A and B by X-ray photoelectron spectroscopy (XPS). The breakdown test and surface analysis were repeated to new combined electrode pairs, pair C and D, again to check the breakdown characteristic of the two new pairs of electrodes. All the three group results showed that after the conditioning saturation, no XPS result difference existed among pair A, B C and D. The breakdown electric fields of pair B and C (sharing the same cathode) were nearly the same, suggesting the cathode influence the breakdown electric field. The breakdown electric field of pair D was obvious higher than that of pair A. The only difference between pair A and D is the cathode. The results may provide a further understanding about the factor of the anode and cathode in the vacuum breakdown test.