Advanced modeling for the HIT-SI Experiment

Abstract

A two-temperature magnetohydrodynamic (MHD) model, which evolves the electron\nand ion temperatures separately, is implemented in the PSI-Tet code and used to\nmodel plasma dynamics in the HIT-SI experiment. When compared with\nsingle-temperature Hall-MHD, the two-temperature Hall-MHD model demonstrates\nimproved qualitative agreement with experimental measurements, including:\nfar-infrared interferometry, ion Doppler spectroscopy, Thomson scattering, and\nmagnetic probe measurements. The two-temperature model is utilized for HIT-SI\nsimulations in both the PSI-Tet and NIMROD codes at a number of different\ninjector frequencies in the 14.5-68.5 kHz range. At all frequencies the\ntwo-temperature models result in increased toroidal current, lower\nchord-averaged density, and symmetrization of the current centroid, relative to\nsingle-temperature simulations. Both codes produce higher average temperatures\nand toroidal currents as the injector frequency is increased. Power balance and\nheat fluxes to the wall are calculated for the two-temperature PSI-Tet model\nand indicate considerable viscous and compressive heating, particularly at high\ninjector frequency. Parameter scans are also presented for the artificial\ndiffusivity, and Dirichlet wall temperature and density. Artificial diffusivity\nand the density boundary condition both significantly modify the plasma density\nprofiles, leading to larger average temperatures, higher toroidal current, and\nincreased relative density fluctuations at low diffusivity and low wall\ndensity. High power, low density simulations at 14.5 kHz achieve sufficiently\nhigh gain (G = 5) to generate significant volumes of closed flux lasting 1-2\ninjector periods.\n