Time resolved imaging of pulsed streamer discharge in water

Pulsed positive streamers in water were investigated in the needle-to-plate electrode configuration with an electrode gap of 20 mm. The characteristics of streamer and its propagation in water were observed with the use of an ICCD camera. The ICCD camera images showed clearly streamers with a few streamer branches having their channel diameters of ~250 mum. The images also showed that the streamers in water did not reach the plate electrode at the stable operation voltage range, i.e. below the transition to spark. Under the present experimental condition, the propagation velocity of the streamer head was 3 times 10⁴ m/s, which is one order of magnitude lower than that of the streamer in air.