Investigation of Effect of Needle Electrode Configuration on Microplasma Discharge Process in Sea Water

Microplasma discharge in sea water was investigated using a needle-to-plane electrode system with various types of needle insulation. A platinum plane electrode and a palladium needle electrode were placed with a gap of 20 μm in the artificial sea water. A pulse current source, consisting of a MOSFET switch, a capacitance, and inductance, was used. The sea water between the electrodes performed as resistance for the current source circuit. Using the microgap configuration, microplasma discharges were reproducibly ignited under low breakdown voltages in the highly conductive sea water. In order to significantly diminish the current dispersing into the surrounding water, the needle electrode was insulated, enabling more accurate investigation of the preheating and bubble formation processes before the microplasma discharge. It was established that the microplasma discharge was ignited after formation of the bubble of size, sufficient to cover entire discharge gap between the electrodes. Influence of the needle electrode insulation on microplasma parameters was investigated.