The relation of trap distribution of alumina with surface flashover performance in vacuum

The alumina ceramic samples prepared under different sintering temperature and varied additives were measured to indicate the trap density and trap energy located in the alumina materials by using thermally stimulated current (TSC). The surface charges on the alumina materials in vacuum after applying a pulse voltage (0.7/4mus), and flashover performances of the materials in vacuum also were measured. We found that the trap distribution in alumina material has a correlation with surface charges and flashover performances of the alumina in vacuum. It is shown that the higher is the trap density in the material, the higher is the surface charge density, and the lower is the flashover voltage on alumina surface. It is believed that the trapping and de-trapping mechanism of trap carriers could play an important role during the developing discharge processes, together with the secondary electron emission mechanism.