Influence of embedded electrode structure and sputtering gold coating on surface flashover characteristics of PMMA in vacuum

The surface flashover phenomena of insulating materials in vacuum greatly weakens the overall performance of vacuum-dielectric system. The improvement of surface flashover characteristics of insulators in vacuum becomes a significant challenge for the development of high voltage electrical equipment. In this paper, we propose a convenient avenue to achieve the high surface flashover performance of polymethyl methacrylate (PMMA) in vacuum based on adopting two kinds of electrode dielectric contacts, one is to insert electrodes into samples, and the other is to sputter gold coating on the samples surface. Furthermore, the surface electric field distribution of PMMA samples under different embedded electrode structures were simulated in the COMSOL software. The results show that all the two kinds of electrode dielectric contacts treatment can apparently improve the flashover voltage of PMMA in vacuum. For the embedded electrode structure, when the electrode height is higher or lower than the embedding depth, flashover voltage is lower than the structure that electrode height is as high as the embedding depth. And the bigger difference between the electrode height and the embedding depth is, the lower its flashover voltage is and the smaller its dispersion is. Besides, sputtering gold coating on dielectric surface can effectively improve the contact between electrodes and dielectrics. But comparing with the situation of sputtering both bottom side and flank side, the flashover voltage of only sputtering bottom side is much higher and its dispersion is much smaller. This research provides two methods for improving the dielectric surface flashover characteristics in vacuum.