Study on the residual gaseous filament of microsecond pulsed positive streamer discharge in water

Abstract

The residual gaseous filament soon after a streamer discharge in water contains a wealth of information closely related to the streamer propagation. We have investigated the residual gaseous filament of microsecond pulsed positive streamer discharge in water by using a shadowgraph imaging technique. Based on the obtained shadow images, we measured the average gas density, the average radius, and the average length of the residual gaseous filament. We found that the average gas density has no significant dependence on the applied voltage, but decreases from 883 to 610 kg/m3 as the water conductivity increases from 20 to 476 μS/cm. The amount of gas produced in a unit length of the streamer filament and the energy consumed for producing a unit mass of gas in the streamer filament also have no dependence on the applied voltage, but increase as the water conductivity increases. In our experiments, the energy consumed for producing a unit mass of gas in the streamer filament is far smaller than the latent heat of vaporization of liquid water, indicating that the gas produced in the streamer filament during the discharge is unlikely produced through a heating process.