A numerical study of plasma-neutral interaction in a coaxial electrode configuration

The flow Z-pinch concept magnetically confines a high-temperature, high-density plasma, while using sheared axial flows to provide stability. The Z-pinch has a simple, linear configuration in which the self-field generated by the axial current compresses plasma up to 1000 eV and confines it for 20-60 microseconds. Interactions between plasma and neutral species can have a large effect on the dynamic behavior both during plasma acceleration and when the Z-pinch plasma is magnetically confined. In this research, a reacting plasma-neutral model [Meier \& Shumlak, POP 19 (2012)] is incorporated into the NIMROD plasma simulation code to explore the effects of neutral gas in the acceleration phase of a z-pinch device. This combines a magnetohydrodynamic (MHD) plasma model with a gas dynamic neutral fluid model allowing for the study of electron-impact ionization, radiative recombination, and resonant charge-exchange in plasma-neutral systems. The acceleration section of the flow Z-pinch is modeled as a coaxial electrode accelerator, and neutral gas effects on current sheet propagation and spreading are investigated. Simulations with experimentally relevant current injection lead to current sheet propagation at about 40 km/s.