Transient current and light emission associated to the propagation of pre-breakdown phenomena in water

This paper presents a study of pre-breakdown phenomena in water. Streamer propagation is studied by the simultaneous recording of transient currents, and fast photographs. The light emitted by streamers is intense compared to hydrocarbons, and this allows us to visualize on the same photograph both the emitted fight and the shadow of gaseous channels. This allows us to observe the spatial and temporal development of streamers: fast luminous discharge first propagate (velocity about 30 km/s), and gaseous filaments develop afterwards in the hot track left by the discharge. The succession of fast discharges produces a stepped propagation. At very high voltage, a single fast discharge can lead to breakdown in a unique step. The initiation and propagation are both favored when the conductivity of water is increased.