MHD simulation of preionization dynamics in FRC formation

Summary form only given. In experiments at the Air Force Research Laboratory to form, translate, and compress a field reversed plasma configuration (FRC), the initial plasma is formed by driving the main theta coil with a one-quarter MHz current pulse. In our magnetohydrodynamic (MHD) simulations of the full experiment to date we have assumed an initially uniform density, 1 eV plasma with an embedded bias field. In order to refine this assumption, we are performing MHD simulations of the heating and ionization of cold deuterium gas with MACH2. Our breakdown model assumes a possibly non-equilibrium background ionization level that might reasonably result from the applied voltage pulse and follows the subsequent Ohmic heating due to electron-neutral and electron-ion collisions. By following the post-breakdown dynamics we hope to determine density, energy, and field distributions to assess the optimal relative timing for field reversal. Results will be shown from simulations performed for the 0.025 eV initial temperature at a variety of deuterium chamber fill pressures near the design value of 50 mTorr driven with a specified current waveform that matches the experimental magnetic field probe on the outer surface of the quartz tube. The line integrals and spatial distributions of electron number density vs. time from the MACH2 simulations are comparable with the interferometric measurements from the experiment and match many features including time and amplitude of peaks in the data.