Gas heating and streamer-to-leader transition of impulse surface discharge on quartz glass in atmospheric air

The mechanism for the streamer-to-leader transition of a positive surface discharge in atmospheric air was studied from the viewpoint of gas heating in a discharge channel. In the experiment, a quartz glass having a conductive indium tin oxide (ITO) coated back-surface was used as an insulation material having a back electrode. The gas temperature change of an impulse surface discharge ranging from streamer-to-leader was measured by spectroscopic method in atmospheric air. The gas temperature in a surface discharge was assumed to be equivalent with the rotational temperature determined by (0-0) band emission spectrum of N₂ second positive system. The ITO coat is thin enough for the light emission spectrum to penetrate. As a result, the drastic increase of gas temperature in a discharge channel was confirmed when the discharge phase transformed to leader.