Simultaneous measurement of light emission, current pulses and growth of prebreakdown streamers in hexane

Extensive studies of events leading to electrical breakdown in liquids [1] and in solids [2] show that streamers are formed in the dielectric before breakdown. The streamers are believed to be low density regions in which charge carriers can move more freely than in the surrounding dense medium [1]. For a needle — sphere electrode system, when the streamer emanates from the cathode needle a pulsed current is produced. The light emitted by the cathode streamer is also in the form of pulses which temporally correlate with the current pulses. When the needle is the anode, the current is in the form of a pulse train superimposed upon a continuous background current. These are familiar results which have received recent attention [3].