Computational Modeling of Pulsed Power Experiments

A variety of pulsed power applications and experiments have been modeled with a magnetohydrodynamics code. The smallest scale devices are exploding wires and foils (I_peak ~ 1 kA, t_rise ~ 100 ns). Here, Joule heating dominates and there is strong coupling to the circuit. In density/temperature phase space, the material uniformly follows liquid/vapor coexistence line. The integral action is shown to compare with historic experiments. When, the material expansion is included, a well-defined asymptotic value is observed at burst. Opening switches are typically used in pulse shaping to decrease the risetime. They operate similarly to wires and foils, but typically at larger spatial and current scales (I_peak > 1 MA, t_rise > 2 ms). Small, fast generators such as the Mykonos driver at Sandia (I_peak ~ 1 MA, t_rise ~ 100 ns) provide a testbed for fundamental physics. One series of experiments investigated a machined sine wave surface on a current carrying rod with and without a dielectric coating. In simulation, trough overheating is quantitively compared to theory and qualitatively compared to experiments. Variations in the initial peak-to-peak amplitude and wavelength are consistent with experiments. The Sandia Z-machine is currently the largest pulsed power driver (I_peak ~ 25 MAmps, t_rise ~ 100 ns). The modeling of fundamental science experiments investigating the magnetic Rayleigh-Taylor instability has shown good agreement with data.