Theory of stepped pulses in negative corona discharges

Theoretical calculations are presented which account for the development of the step observed on the leading edge of the current pulse in a negative point-plane corona (Trichel pulse). The theory explains the step in terms of independent photon and ion secondary processes at the cathode. It is applied specifically to describe the shape of an experimentally determined corona current pulse from a 2-mm-diam negative point located 20 mm from a positive plane in oxygen at 6.67 kPa. The secondary-emission coefficients are determined to be ${\gamma }_p$=2×${10}^{\mathrm{-}4}$ (photon secondaries) and ${\gamma }_i$=0.12 (ion secondaries).