Two-dimensional MHD simulations of a neon Z pinch on Hawk

Two-dimensional magnetohydrodynamic (MHD) simulations using MACH2 are benchmarked against laser shearing interferometer (LSI) images of the evolving electron-density sheath during 250-ns neon gas-puff Z pinch implosions on the Naval Research Laboratory Hawk generator. The initial density distribution for the MHD simulations is calculated using a ballistic-flow-model fit to the measured initial gas-density distributions. The implosion is modeled using an applied current profile, single-temperature energy equations, and black-body-limited optically thin radiation. For consistency with the radiation model, neon ionization and equation-of-state models have been added to MACH2. Computed MHD ion-density distributions compare well with LSI images as the snowplowed plasma channel evolves during implosion. The MHD results also show features that may be helpful for understanding early and weak K-shell radiation observed near the nozzle in Double-Eagle gas-puff experiments. Current-channel evolution derived from one-dimensional snowplow calculations compare well to the MHD results for the same current history and initial density distribution, indicating that axial mass flow does not strongly impact the implosion dynamics.