Verification of positive streamer mechanism for negative corona Trichel pulses in O2/H2 mixtures

•The first negative corona pulses in O2 + H2 at sub atmospheric pressures were studied.•The results confirm the positive-streamer mechanism for Trichel pulse formation.•The role of secondary photoemission processes from cathode was confirmed.•The hydrogen in oxygen causes the decrease of attachment coefficient.

Current waveforms of the first negative corona pulses have been measured in O2 + H2 mixtures at a pressure range from 27 kPa to 50 kPa. It was observed that the hydrogen admixtures less than 4% do not change significantly the pulse current waveforms. Effects of changing cathode secondary electron emission were studied using a copper cathode coated by CuI and graphite. The results obtained support the theory of the cathode-directed streamer formation during the negative corona pulse rise.