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3D IDEAL MHD EQUILIBRIA IN HIT-SI

Author: Chris J Hansen
Requested Type: Consider for Invited
Submitted: 2012-12-07 15:13:05

Co-authors: G. J. Marklin, T. R. Jarboe

Contact Info:
University of Washington
AERB Rm 120 Box 352250 Univers
Seattle, Wa   98105
United States

Abstract Text:
An equilibrium code, PSI‐TET, has been developed to solve for solutions to the Ideal MHD equilibrium equation μ_0J=λB in arbitrary 3D geometry. The code employs a novel method, based on thermal diffusion, for the identification of flux surfaces from general 3D magnetic fields. No constraints are imposed on the flux surface geometry, which may have nested surfaces, islands, and/or stochastic regions. In Ideal MHD lambda is allowed to vary across flux surfaces but must be constant along a flux surface and in stochastic regions. A scalar flux surface variable is computed by solving an artificial diffusion problem with a large ratio of parallel to perpendicular thermal conductivity. A fixed lambda profile, specified as a function of this flux surface variable, is defined. Equilibria in HIT‐SI have been computed for the homogenous (Spheromak) and inhomogeneous (injector) fields separately for experimental comparison. Combined equilibria of interest with injector driving have also been computed for various lambda profiles. In HIT-SI the ratio of Spheromak to injector flux is used to constrain the current profile as the spatial current profile is not well known. In equilibrium solutions Spheromak flux is controlled through coupling to the applied injector vacuum fields. Capturing fine scale field structure such as islands requires high accuracy in the diffusion solve. A mimetic finite element discretization on a tetrahedral mesh is employed, with up to 4th order spatial representation. Geometric and polynomial multigrid preconditioning is used to provide solver scalability. Results will be presented demonstrating the general nature and viability of this method for highly 3D magnetic configurations. Work supported by DOE.

Characterization: 1.4

Comments:
Please group with other HIT-SI posters if not accepted for talk