Abstract
A continuous photograph of a streamer propagation process in water was successfully observed using a nano-pulse discharge system, an ultra high speed camera system with a microscope lens and a phase shift type Mach-Zehnder interferometer. After the initiation process of 600 ns - 800 ns from the applying voltage of 16 kV0p-17.5 kV0p, a primary streamer was occurred. It accompanied with a shock wave and the period of the propagation was several hundred ns. The propagation velocity of the primary streamer was around 1.5 km/s.
