Hall Magnetohydrodynamics Simulations of Hall-Physics-Driven Effects in Low-Density Plasmas Surrounding Dense Z-Pinch Liners

Abstract

Presented in this dissertation is a new Hall physics driven mechanism for describing the seeding and formation of helical instability structures in axially premagnetized thin-foil liner z-pinch implosions driven by the 1-MA, 100-ns MAIZE pulsed power generator at the University of Michigan. This mechanism involves several effects within a low-density coronal plasma layer around the thin-foil liner that forms when the driving current pulse is applied. This low-density coronal layer is then subject to Hall physics, specifically a Hall interchange instability, which leads to several effects including current advection, current vortices, magnetic field advection, axial flux amplification, and other phenomena that all contribute to a helical seeding of the magneto-Rayleigh-Taylor instability (MRTI). These Hall physics effects are studied numerically using the 3D Hall magnetohydrodynamics code, PERSEUS [C.E. Seyler and M.R. Martin, Phys. Plasmas 18, 012703 (2011)]. This study has important implications for the magnetized liner inertial fusion (MagLIF) program at Sandia National Laboratories, where similar helical instability structures have been observed in axially premagnetized thick-walled liner implosions on the 18-30 MA Z facility.

This dissertation also used PERSEUS to explore the late time effects of the on-axis support rod used to hold the thin-foil liners upright in the MAIZE facility as well as make a comparison of MRTI behavior between simulation and experiment. The simulation results [J.M. Woolstrum, et. al., Phys. Plasmas 27, 092705 (2020)] show that by limiting the maximum implosion convergence obtainable, the on-axis support rod plays a key role in preserving the integrity of the helical MRTI structures beyond the implosion phase, into the stagnation and explosion phases of the experiments (as observed on MAIZE [D.A. Yager-Elorriaga, et. al., Phys. Plasmas 25, 056307 (2018)]). The simulation results also show that if the support rod were removed, the morphology of the stagnation column during the explosion phase would be determined by the morphology of the precursor plasma column that establishes itself on axis prior to the arrival of the bulk of the imploding liner material.