(TH/6-2) Constructing Integrable Full-Pressure Full-Current Free-Boundary Stellarator Magnetohydrodynamic Equilibrium Solutions.

**Abstract.** For stellarators to be feasible candidates for fusion power
stations it is essential that the magnetic field lines lie on nested flux
surfaces; however, the lack of a continuous symmetry implies that magnetic
islands, caused by Pfirsch-Schlüter currents, diamagnetic currents and
resonant coil fields, are guaranteed to exist. The challenge is to design
the plasma and coils such that these effects cancel. Magnetic islands in
free-boundary full-pressure full-current stellarator magnetohydrodynamic
equilibria are suppressed using a procedure based on the PIES code
[Comp. Phys. Comm., 43:157, 1986] which iterates the equilibrium equations
to obtain the plasma equilibrium. At each iteration, changes to a Fourier
representation of the coil geometry are made to cancel resonant fields
produced by the plasma. The changes are constrained to lie in the nullspace
of certain measures of engineering acceptability and kink stability. As the
iterations continue, the coil geometry and the plasma simultaneously
converge to an equilibrium in which the island content is negligible. The
method is applied to a candidate plasma and coil design for NCSX
[Phys. Plas., 7:1911, 2000].

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*IAEA 2003*