High speed and high resolution diagnostics for the early phase of dielectric surface flashover

With a novel experimental setup, emphasizing high-speed and high-resolution electrical and optical diagnostic methods, the authors attempted to elucidate the physical mechanisms leading to surface flashover in vacuum. The device used a cable discharge into an impedance matched, coaxial, surface flashover test chamber in a micro-torr vacuum, operated in self-breakdown mode with a DC charging voltage. Preflashover current, breakdown voltage, luminosity, and soft X-rays were measured for different dielectric materials. In addition, DC magnetic fields were applied. Preliminary results indicated the existence of a secondary electron avalanche above the surface and electron stimulated outgassing before flashover occurred