Characterizing Solid-to-Plasma Evolution of Metals Driven by Megaampere Current Pulses Using Computational Magnetohydrodynamics (MHD) Simulations

The evolution of a conductor driven by multi-megaampere current pulses from solid metal to thermal plasma is of great interest when designing imploding liner inertial confinement fusion (ICF) experiments, magnetically driven flyer plate material science tests, and electrical initiators for high explosives. The MHD code FLAG is used to model electrically thick rods driven by the ~1 MA, ~100 ns Mykonos current driver to interpret experimental results and develop an analytical description of deforming conductors. The local balance of magnetic and internal forces at the metal-vacuum/insulator interface drives the metal along a specific trajectory in density/temperature phase space that dictates the expansion velocity of the rod. Moreover, equation of state (EOS) models used to close the MHD system of equations differ by a factor of two or more in temperature and/or density in the region of interest-leading to a similar factor of two difference in expansion velocity. Experimental velocimetry of exploding rod experiments is leveraged to distinguish between simulations using various SEASAME EOS models and validate them for metals in expansion.