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Optimizing Spheromak Geometry for Maximum Beta Limit

Author: George J. Marklin
Requested Type: Poster Only
Submitted: 2014-05-30 16:21:12

Co-authors: T. R. Jarboe, C. J. Hansen

Contact Info:
University of Washington
Rm 120 AERB
Seattle, WA   98195
USA

Abstract Text:
The next generation of inductively driven spheromak experiments to follow HIT-SI will investigate energy confinement in a larger device with higher temperature to test for compatibility with Imposed Dynamo Current Drive (IDCD). Optimizing the design for maximum beta limit is crucial. Previous optimization studies [U. Shumlak and T. R. Jarboe, Phys. Plasmas 7, 2959 (2000)] identified the bow tie configuration currently used in HIT-SI. Recent development of the PSI-TRI code makes a much more elaborate optimization study now possible. PSI-TRI is a 2D Grad-Shafranov equilibrium code that uses a triangular mesh which can be generated automatically for any complex geometry from a standard CAD description. Beta limits were determined for a wide variety of cross section shapes for an equilibrium with a Taylor state current profile but a pressure profile that is everywhere marginally stable to the Mercier criterion. This study finds the optimum shape to be a low aspect ratio (1.5) circular cross section torus with a peak engineering beta over 20%, significantly higher than the bow tie. The PSI-TRI code is also being upgraded to perform 2D ideal MHD stability calculations and different current profiles will be examined to determine how far they can deviate from the Taylor profile before they become unstable to current driven modes, and the effect they have on the beta limit.

Characterization: 1.2

Comments:
Please place with other PSI Center computational posters.

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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