Development mechanism of impulse surface flashover on alumina dielectrics in vacuum

We investigated the development mechanism of impulse surface flashover on alumina ceramic insulator in vacuum. We measured the still image and framing image of fast developing surface flashover in synchronous with applied impulse voltage and current waveforms. The light emission transition in initiation of surface flashover was clarified. We found the dark area is formed around the cathode and conducting channel is formed from the anode in developing process of surface flashover in vacuum.