Influence of applied voltage and electrical conductivity on underwater pin-to-pin pulsed discharge

A parametric study of an underwater pulsed plasma discharge in pin-to-pin electrode configuration has been performed. The influence of two parameters has been reported, the water conductivity (from 50 to 500 µS cm⁻¹) and the applied voltage (from 6 to 16 kV). Two complementary diagnostics, time resolved refractive index-based techniques and electrical measurements have been performed in order to study the discharge propagation and breakdown phenomena in water according to the two parameters. A single high voltage of duration between 100 µs and 1 ms is applied between two 100 µm diameter platinum tips separated by 2 mm and immersed in the aqueous solution. This work, which provides valuable new results, is of great interest to better understand the mechanisms of initiation and propagation of pin-to-pin discharge in water. For low conductivity (from 50 to 100 µS cm⁻¹) results have confirmed two regimes of discharge (cathode and anode) and the increase of the applied voltage first makes the breakdown more achievable and then favors the apparition of the anode regime. For 500 µS cm⁻¹ results have highlighted cathode regime for low applied voltage but a mixed regime (anode and cathode) for high applied voltage. (paper)