A theory for the cathode mechanism in lowcurrent vacuum arcs, with application to the calculation of erosion rate

Articles you may be interested inEnhanced surface flashover strength in vacuum of polymethylmethacrylate by surface modification using atmospheric-pressure dielectric barrier discharge A simple highpressure reaction chamber connected to an ultrahigh vacuum system for surface studies J. Vac. Sci. Technol. A 5, 234 (1987); 10.1116/1.574110 Surface flashover of conical insulators in vacuum J. Appl. Phys. 56, 1374 (1984); 10.1063/1.334128 Surface flashover of solid dielectric in vacuumDesorbed gases from insulator surfaces may be much more important in flashover initiation than properties of the dielectric surface. Ambient neutral densities, immediately above the insulator surface, in the initial stages of flashover have been calculated to lie in the range from 2 X 1OI7/cm3 to 2 X 1021/cm 3 with a mean of about 1 X 10 19 / cm3, whether flashover occurred on surfaces in air at atmospheric pressure or in vacuum as low as 10-6 Torr. The evidence presented indicates that, for dc and microsecond pulse voltages, surface flashover is a local, relatively high-pressure phenomenon. Comparison of field strengths of surface flashover for various insulating materials perpendicular to the electrodes, operating pressures, and voltage waveforms appears to indicate that flashover values range well within an order ofrnagnitude . A filamentary nature of the flashover discharge is shown and is consistent with gas breakdown phenomena. Ionization wave front velocities are examined and these compare favorably with those obtained from gaseous breakdown studies.gap of -1.3 X 10-2 cm, with a 10 7 n series resistance, on the 132

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