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Advances in NIMROD Modeling of the HIT-SI Experiment

Author: Kyle D Morgan
Requested Type: Consider for Invited
Submitted: 2014-05-29 18:40:35

Co-authors: C. Akcay, T.R. Jarboe, B.S. Victor

Contact Info:
University of Washington
AERB 120 Box 352250
Seattle, WA   98195
United States

Abstract Text:
Validated results from zero beta and initial results from finite beta NIMROD simulations of the HIT-SI experiment using a two-fluid MHD model are presented. The Steady Inductive Helicity Injectors are modeled via a time dependent boundary condition on the normal magnetic and tangential electric field of the simulation domain. The zero beta results, which assume a uniform temperature and density, have been shown to achieve agreement with experimental observations at low injector frequencies (f=14.5kHz), by achieving similar current amplification Itor/Iinj and spheromak formation time with similar magnetic field fluctuations, though with differences in the internal magnetic profile. Biorthogonal Decomposition is employed to quantify the agreement with a global array of surface magnetic probes. Recent experimental results from operations at high injector frequencies (f>50kHz) has justified the inclusion of dynamic density and temperature in the model. The zero beta model fails to show agreement as the drive frequency is increased, evidenced in reduced current amplifications and differences from the magnetic field profile, while initial calculations using a Braginskii anisotropic thermal conduction model improves quantitative agreement of bulk plasma current and captures some qualitative features of the experiment, most notably being a Shafranov shift in the location of the magnetic axis. This work is funded by the DOE.

Characterization: 2.0

Comments:

Workshop on Exploratory Topics in Plasma and Fusion Research (EPR) and US-Japan Compact Torus (CT) Workshop
August 5-8, 2014
Madison, Wisconsin

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