ISSN:
1089-7674
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The control of magnetic islands is a crucial issue in designing stellarators. Islands are associated with resonant radial magnetic fields at rational rotational-transform surfaces and can lead to chaos and poor plasma confinement. In this article it is shown that variations in the resonant fields of a full pressure stellarator equilibrium can be related to variations in the boundary via a coupling matrix, and that inversion of this matrix determines a boundary modification for which the island content is significantly reduced. The numerical procedure is described and the results of island optimization are presented. Equilibria with islands are computed using the Princeton Iterative Equilibrium Solver, and resonant radial fields are calculated via construction of quadratic-flux-minimizing surfaces. A design candidate for the National Compact Stellarator Experiment [A. Reimann, L. Ku, D. Monticello et al., Phys. Plasmas 8, 2083 (2001)], which has a large island, is used to illustrate the technique. Small variations in the boundary shape are used to reduce island size and to reverse the phase of a major island chain. © 2001 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1377614
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