THE INFLUENCE OF MAGNETIC-FIELDS ON DIELECTRIC SURFACE FLASHOVER

The influence of low-amplitude magnetic fields, in a variety of configurations, on pulsed dielectric surface flashover has been investigated. These variations include dc magnetic fields; pulsed magnetic fields simulating conditions for magnetic self-insulation; and different environments (vacuum, ambient gas, plasma), geometries, dielectric materials, and orientations of the magnetic field. For field amplitudes of 0.3 T, typically a doubling of the flashover voltage is observed, if the E x B drift is away from the surface. For flashover in vacuum, it is sufficient to place permanent magnets in the cathode vicinity to increase the flashover voltage. The observations are consistent with the "saturated surface secondary avalanche model" and electron-induced gas desorption. The pulse shape of light emission during the prebreakdown phase depends on the orientation and amplitude of the magnetic field and shows the electron trajectories above the surface are altered by magnetic fields.