Enhancement of DC positive streamer corona in a point-plane gap in air due to addition of a small amount of an electronegative gas

When the potential across a positive-point-plane gap in air is increased, discharges proceed in order as follows: intermittent streamer corona, glow corona and spark. The streamer is markedly enhanced by adding a small amount of an electronegative gas e.g. Cl 2 , NO 2 NO etc. This is because the streamer can be initiated at a higher potential than is corona onset potential due to extinction of the glow corona. This effect becomes more marked with increased concentration of the additive. For a gap system mounted in an enclosed chamber (air), the streamer formation is enhanced by successive discharges and a pronounced fall of the sparking potential is expected to occur. This is due to NO 2 formation resulting from successive discharges.