Regime transitions in liquid metal response to pulsed Lorentz forces

The Liquid Electrode eXperiment (LEX) at Virginia Tech is configured to pulse current through a solid wire intersecting the surface of a liquid metal (LM). This design was chosen as a surrogate scenario to study the effect of large current densities present in the liquid first wall of future fusion reactor concepts. The self-generated magnetic fields and resulting Lorentz forces produce an annular jet of LM originating at the free surface and rising to significant heights; in some cases reaching the top of the containing vessel (≈0.25 m). Along with this feature, a void is created below the wire which appears to expand before obscuration by the upwards-traveling jet. As the LM is subjected to a range of driving current amplitudes from 50–200 kA and wire radii from 1.59 mm to 2.38 mm, transitions are observed in the qualitative behavior of the LM wave as the Lorentz force increases. Hydrodynamic simulations of the LM response to electromagnetic forces and Ohmic heating are employed to interpret experimental results. Evidence also indicates that the vertical velocity of the jet is proportional to the Lorentz force, and that other parameters such as void formation and initial phase velocity may be similarly proportional.