  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 $\mu$S/cm) 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 $\mu$S and 1 ms is applied between two 100 $\mu$m diameter platinum
tips separated by 2 mm and immersed in the aqueous solution. This work, which
provides valuable complementary results of paper [1], 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 $\mu$S/cm) 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 $\mu$S/cm results have highlighted
cathode regime for low applied voltage but a mixed regime (anode and cathode)
for high applied voltage.
