The measurements of streamer initiation in cyclohexane under high magnification

Streamer initiation process was observed in cyclohexane under impulse voltage conditions. The streamer inception and growth under non-uniform field was photographed using a high magnification (100 /spl mu/m/spl times/), high speed shadowgraph system (20 ns/F). The minimum streamer inception voltages for both polarities were determined to be -5.18 kV and +7.7 kV, respectively. The initial structure of the streamer was filamentary just after the initiation for both polarities and then changed into bush-like structure within 40 ns. For a negative streamer, the size of the bush increased with the crest of an applied voltage until a secondary system appeared and the process appeared to repeat itself. The growth of a positive streamer was branched and successive while it was step-wise for a negative one. After their expansion process stopped, they started to contract and then broke up into small bubbles through damped oscillation. In conjunction with the optical study, current pulses were also measured simultaneously using a LED current pulse measurement system. The inception of the current pulse occurred prior to the streamer inception for both polarities. >