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Author: Torrin A Bechtel
Requested Type: Poster
Submitted: 2018-02-28 10:00:01

Co-authors: C. C. Hegna, C. R. Sovinec

Contact Info:
University of Wisconsin - Madison
1415 Engineering Drive
Madison,   53706
United States of Ame

Abstract Text:
The nonlinear, extended MHD code NIMROD is employed to simulate high beta stellarator physics. This work concentrates on the dependency of the resulting MHD equilibrium configuration on finite parallel transport processes. In particular, the numerical simulations show that anisotropic heat conduction has a significant effect on the pressure profile in regions with stochastic magnetic fields. As a consequence, the attained stored energy is sensitive to the size of the anisotropy in this region, underscoring that equilibrium beta limits are sensitive to anisotropic transport properties.

The configuration under investigation is an l=2, M=10 torsatron with vacuum rotational transform near unity. Finite-beta plasmas are created using a volumetric heating source and temperature dependent resistivity; modelled with 22 stellarator symmetric (integer multiples of M) toroidal modes. Extended MHD simulations are then performed to generate steady state solutions that represent 3D equilibria. With increased heating, Shafranov shifts occur, and the associated break up of edge magnetic surfaces limits the achievable beta. Due to the presence of finite parallel heat conduction, pressure profiles can exist in regions of magnetic stochasticity. Here, we present results of independently varying the parallel and perpendicular thermal anisotropy. Preliminary studies with temperature dependent Braginskii conduction closures and MHD stability with non-stellarator symmetric modes are also presented.

*Research supported by US DOE under grant no. DE-FG02-99ER54546.