DC-Induced Prebreakdown Events in N-Hexane

A dc source was applied to a point/plane gap in n-hexane, at a level just below that required to cause breakdown. Detailed shadowgraph images of the gap were obtained by using a pulse laser for illumination. When the laser was synchronized with a conduction current pulse, a distinct prebreakdown event could be recorded. It is shown that disturbance inception occurs at the onset of a conduction current pulse, then the event develops as a streamer and grows into the gap and, finally, fragmentation occurs during the current tail. Provided that the applied voltage is maintained, repetitive events may be observed with a waiting period of as little as 100 μs.