Dynamic response of liquid metal free surfaces to localized pulsed current

We present results from an experimental campaign to examine the MHD response of a liquid metal free surface to localized pulsed currents (10—100 kA) and the resulting magnetic fields parallel to the free surface (2—20 T). An LC pulse forming network (PFN) delivers a current pulse through a suspended wire (3.175 mm diameter) into a pool of liquid tin-bismuth (42/58% composition by mass). An estimation of the skin depth suggests that the current is conducted radially along the liquid surface to the walls of the vacuum chamber and returned to ground. The PFN current and liquid metal surface behavior are recorded and compared to MHD simulations, theoretical approximations, and circuit models. The current pulse is shown to produce an annular jet of liquid metal near the suspended wire followed by radially-propagating waves in the pool thereafter. Experiments have characterized the sensitivity of jet velocity and current pulse amplitude to the liquid metal depth and charge transfer from the PFN.