Influence of surface ion exchange on pulsed flashover characteristics of machinable ceramics in vacuum

For pulsed power devices, the surface flashover across their solid insulation becomes a serious problem. Investigators have paid much attention on improving the surface electric withstanding strength of insulator. It is found that surface treatment is very useful to increase the surface flashover voltage. The flashover phenomena along machinable ceramics (MCs) are investigated under pulsed voltage in vacuum. The ion exchange method is used to adjust the surface components of MCs for improving its surface electric strength. CuSO₄ is used for ion exchanging with the MC. It is found that ion exchange treatment greatly changes the surface components and microstructure of MCs, which has obvious influence on flashover characteristics of MCs. The MCs with 10 h ion-exchange time show a much improved flashover holdoff. Based on the secondary electron emission avalanche (SEEA) theory, the improvement of flashover withstanding ability can be reasonably explained by electron impact and transport behaviors.