Formation and Growth of Plasma Channels Generated by Discharge of High Voltage Nanosecond Pulse in Water: A Simulation Study

The formation and growth of plasma channel(s),generated by discharge of high voltage nanosecond pulse in water,was empirically approximated,mathematically modeled,theoretically analyzed,numerically simulated with COMSOL and experimentally evaluated with the lab-built setup.The influence of the properties of voltage pulse and water conductivity on the time evolution of the plasma characteristics,including the distributions of ion/electron densities,shape of plasma channels,was investigated.The results show that depending on the voltage,the field ionization zone,above the tip-apex where the strongest field exists,has a major impact.For example,at a less high voltage,single ion-beam,forming in ionization zone,moves forward increasingly faster,accompanied by strong collision ionization of water molecules,consequently,a plasma channel appeared;at a high voltage,splitting of plasma channel occurs and the possible mechanism were tentatively discussed.De-ionized water increased the e-density of plasma channel and field at its front.