Designing a Permanent Magnet Stellarator

Models show that optimized stellarator plasma boundaries can be achieved with permanent magnets and circular planar coils. MUSE, a tabletop stellarator being assembled at PPPL, promises to show excellent quasi-symmetry and achieve very low effective ripple, through the use of 16 planar coils and about 10,000 neodymium magnets. MUSE is designed to be as simple as possible. MUSE has a vacuum vessel with a circular cross-section, a major radius of 30cm, and a constant minor radius of 7.5 cm. It also has a toroidal field of .15T, andrectangular prism magnets with discrete sizes that are both physically and magnetically oriented normal to a circular cross-section torus. These features make it as simple as possible. Allowing for a more complex design increases the engineering difficulty, but it also increases the design space of the types of equilibria that are achievable. This poster will discusses MUSE's approach to the iterative process of finding an arrangement of permanent magnets that meet their plasma and engineering constraints, it will discuss the lessons learned from the physical assembly of MUSE, as well as next-step stellarator designs and approaches, including Landreman and Paul's recent "PreciseQA".