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Author(s):
A. Shimizu, S. Okamura, M. Isobe, C. Suzuki, S. Nishimura, T. Watari, K. Matsuoka
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Title:
Design of Modular Coils for a Quasi-axisymmetric Stellarator with a Flexible Control of the Magnetic Field Configuration
Date of publication:
Aug. 2002
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Key words:
quasi-axisymmetric stellarator, modular coil system, engineering design, poloidal coil, CHS-qa
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Abstract:
A design of the modular coil system for CHS-qa has been made for the plasma configuration Ŗb32" with the aspect ratio 3.2. The magnetic field strength and the major radius are 1.5 T and 1.5 m, respectively. The normal component of magnetic field produced by the modular coils is minimized on the plasma boundary to obtain the optimum coil design. We put engineering constraint on the distance between adjacent modular coils and the radius of coil curvature. The dependence of the residual normal component of the field on these conditions is examined, and the realistic values for them are selected. Additional coils to control various properties of the magnetic field configuration (the rotational transform, the magnetic well depth, etc.) have been designed and a flexibility of the magnetic field configuration is realized. For the case that the rotational transform crosses the low-order rational value resulting in magnetic islands, the residues of islands are evaluated with which a further improvement of coil design can be made to eliminate magnetic islands.
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