Theory of positive onset corona pulses in SF/sub 6/

The mechanism of formation of positive corona onset pulses in SF/sub 6/ at 100 kPa is examined. A constant positive voltage of 50 kV is applied to an 0.5-cm diameter sphere located 6.5 cm from a grounded plane. The calculated current pulse has a width at half maximum amplitude of approximately 0.3 ns, thus explaining the origin of subnanosecond current pulses in SF/sub 6/. During the current pulse a streamer moves out into the gap along a 100- mu m channel, with the electric field in the streamer trail E>E*, where E* is the critical field for which ionization equals attachment.>