Waveforms of prebreakdown primary streamers in a short positive point-plane gap in air

Current pulses of single and repetitive prebreakdown streamers have been measured in a positive point-plane gap in dry air at pressures of 3.33-26.7 kPa and at various overvoltages. The pulses of the single streamers exhibited a complex double-peaked form and, in contrast to the commonly held belief, differed significantly from those of the repetitive streamers. To explain the complex waveforms observed, a qualitative physical picture of the processes occurring during the streamer-cathode contact is outlined.