The effect of high pressure on prebreakdown phenomena in n-hexane

The effect of pressure on initiation of prebreakdown streamers in n-hexane in a nonuniform field is investigated. Using a high-magnification (100*) high-resolution (1 mu m) optical system and a high-speed camera, the initial growth of low-density streamers propagating from a needle cathode is examined at pressures ranging from 0.1 to 1.1 MPa. The initial streamer is a single filament which grows to approximately 4 mu m in diameter and 8 mu m in length before the appearance of a dense bushy structure at its tip. Oscillatory behavior of the initial streamer is observed in which the diameter of the initial streamer expands and contracts as the streamer grows. The pressure dependence of the streamer initiation voltage is shown.<>