Study of streamers point-plane gap

The main focus of the research program is primarily an empirical study of the streamer formation and propagation in a moderate-length, atmospheric-pressure gap. There has been a long history of electrical breakdown of gases, and this report starts with a brief review of this work. The design and operation of a high voltage, fast risetime generator is described. This high voltage generator produces pulse of amplitude up to 150 kV, with fast risetime of about 20 ns. Empirical results include shutter and streak photographs of streamers propagating in non-uniform field gap of approximately 14 cm. Data is available for both cathode-directed and anode-directed streamers for pressure range from about 100 to 760 Torr and the applied voltage range from 100 kV to 150 kV. Filling gases are pure N$\sb2$ and consisting of mixtures of N$\sb2$ and O$\sb2.$ Significantly different results in pure N$\sb2$ and in mixture containing a small amount of O$\sb2$ for both polarities are obtained. The velocity increase with voltage has a stronger dependence on voltage for the cathode-directed streamer and the velocity increase with voltage weaker dependence on voltage for the anode-directed streamer. The delay increase with O$\sb2$ for cathode-directed streamer, but there are consistent delay for anode-directed streamer. The electrical breakdown process is described in this moderate-length, atmospheric-pressure gap. The breakdown process of our gap has two phases, one is the streamer propagation (fast phase) and the other is highly conductive filamentary channel propagation (slow phase)