EXPERIMENTAL CONFIRMATION OF POSITIVE-STREAMER-LIKE MECHANISM FOR NEGATIVE CORONA CURRENT PULSE RISE

Current growth waveforms corresponding to initial phases of negative corona current pulses were measured in nitrogenous gas mixtures at pressures of 6.67-40 kPa. The measurements showed that the steep pulse rise is not dependent on cathode secondary emission processes for pressures above 30 kPa. This, together with a discontinuous transition in the current waveforms observed with increasing gap voltage in N2 at pressures of 20-26.6 kPa, implies that the feedback-to-cathode Townsend ionization mechanism was supplanted by a faster streamer-like mechanism. At pressures below 20 kPa a positive-streamer-like wave results in complex Trichel pulse shapes with a step on the pulse leading edge and a hump on the pulse trailing part.