Experimental study of streamers in pure N₂and N₂/O₂mixtures and a ≈13 cm gap

Empirical data on streamer formation and propagation in near-atmospheric pressure N 2 and N 2 /O 2 mixtures are presented. The data were obtained primarily from high-speed, high-sensitivity shutter and streak photography of streamers produced in a ≈13 cm gap. The streamer propagation velocity as a function of applied voltage, polarity, total pressure, and O 2 concentration are provided. In addition, information on streamer bifurcation, and streamer shape and size is included. The breakdown process has two phases: a fast phase featuring the propagation of streamers, and much slower phase involving the heating of the gas to form the spark channel. Also we found that the addition of O 2 significantly alters the streamer characteristics and behaviour, indicating that photoionization processes play an important role.