Stellarator Simplification using Permanent Magnets*

We report the status of the permanent magnet stellarator project. Non-planar coils are the most complicated and expensive part of a stellarator. Permanent magnets provide a novel method to produce optimized stellarator configurations using very simple coils. The new concept for generating 3D fields using permanent magnets has led to the world's first project examining the use of permanent magnets for stellarators, which has been funded by ARPA-E and FES and will be located at Princeton Plasma Physics Laboratory. The project will design and construct a half-period of the magnet structure for a possible stellarator concept that would use components from NCSX, including the toroidal field coils and vacuum vessel, together with an array of neodymium magnets. Two new codes, MAGPIE and FAMUS, have been developed to design the magnets. MAGPIE provides the geometry information and FAMUS optimizes the magnet arrangements. By using the two codes, the target quasi-axisymmetric equilibrium with improved energetic particle confinement can be realized by uniform cuboidal magnets in a limited number of discrete polarizations together with planar toroidal field coils. A post-office-box structure will be used to mount the magnets. An automated system has been developed within the Virtual Engineering framework of the ANSYS suite of codes to integrate the MAGPIE-FAMUS code set with engineering analysis codes. The magnet positions will be adjusted iteratively and an array of correction magnets will be installed to minimize error fields with tolerance. The methods used and the results from the design effort will be described in detail and the status of the construction activity will be summarized. A table-top PM stellarator project (MUSE) has also been designed for basic experiments, and construction is underway.