Water flows and phase transitions generated by strip line sub-microsecond time-scale discharges

We present results of an experimental study of underwater strip line configurations with exploding or non-exploding foil electrodes, using a sub-microsecond generator delivering a ∼100 kA current pulse rising in 290 ns. For thin (≤15-μm) exploding copper and aluminum foils, the onset of visible and infrared light emissions, obtained by fast photomultiplier tubes, was found to coincide with the onset of melting and boiling, respectively. This suggests that this method can be applied for studies of phase transitions in conductors. For thick (>100-μm) non-exploding foils, streak shadow imaging and photonic Doppler velocimetry reveal that foil vibrations are synchronous with current oscillations, driven by a restoring compressed water pressure of ∼90 MPa. A water flow propagating at the speed of sound is observed ∼100 ns after the onset of the current. Current distribution simulations confirm that mechanical deformations, rather than magnetic or thermal diffusion, are responsible for this effect. This finding provides a means to probe the elastic behavior of conductors under extreme pulsed-current loading.