Picosecond discharge development in water and dodecane and liquid plasma formation*

In most cases, the electric breakdown of liquids is initiated by the application of high electric field on the electrode, followed by rapid propagation and branching of plasma channels. Typically, plasmas are only considered to exist through the ionization of gases and typical production of plasmas in liquids has generated bubbles through heating or via cavitations and sustains the plasmas within those bubbles. The question appears: Is it possible to ionize the liquid without cracking and voids formation? High-voltage pulses with durations of 320 ps and amplitudes of 100 kV were used for discharge initiation. Discharge cell had point-to-plate geometry with a tungsten high-voltage electrode diameter of D ~ 1 mm. Inter-electrode distance was 10 mm. The PicoStar HR12 LaVision camera with a spectral response range of 200÷800 nm and a temporal resolution of down to 80 ps was used to measure the spatial and temporal characteristics of the streamer flash. The ICCD camera was focused on the needle of the low voltage electrode. We have demonstrated possibility of formation of nonequilibrium plasma in liquid phase and investigated the dynamics of excitation and quenching of plasma in water and dodecane without voids formation.