Effect of surface shallow traps on flashover characteristics across machinable ceramic in vacuum

The electrical strength of the surface of low-temperature melting machinable glass ceramic, prepared by using several different methods, is investigated before and after treatment with diluted hydrofluoric acid (HF). Using the surface potential decay method, the surface trap density and the energy of each sample are measured. The influence of acid treatment on the trap distribution is analyzed. Concurrent optical and electrical measurements allow surface flashover phenomena in vacuum under impulse voltage to be investigated, along with the influence of surface trapping parameters on flashover performance. It is shown that the glass phase on the surface of machinable ceramic greatly influences the shallow traps, which in turn degrade the flashover characteristics. Removing the glass phase with HF treatment reduces the concentration of shallow traps and stabilizes the flashover voltage.