Pulsed electrical discharge propagation along the surface of liquid dielectricts

Chemical and physical processes accompanying the propagation of electrical discharges along liquid surfaces are important for wide range of applications from electrical switching to liquid disinfection. 1-μs, 10-15 kV, 800 ns flat-top pulses are applied in a pin-to-plane electrode geometry. The discharge above and along a water surface is investigated in an Ar/Air mixture. The distilled water with conductivity of 5 μS/cm serves as a dielectric surface on the time scales of this experiment. The path of the streamer discharge from the needle to the flat (disk) electrode depends on the proximity of the water surface. The results of ICCD imaging with gate widths of 5-10 ns show the discharge path transition from a straight horizontal path directly from the needle to plane to a curved path along the water surface. A 10 nm width bandpass filter selecting an Ar+ emission region is used to image the propagation of the ionization front and the build-up of plasma density. The time of the increase in plasma density corresponds to a sharp increase in the discharge current. The imaging results show distinct differences in the discharge development in the positive and negative polarity of the needle electrode. The novel aspect of this study is in combining a variety of time-resolved methods to study the dynamics of the streamer propagation along the surface of a liquid dielectric.