Magnetic Design and Optimization of Large Encircling Toroidal Coils with REBCO Conductors for all Planar Coil Stellarators

Thea Energy is at the forefront of stellarator development with novel magnetic confinement design for future pilot fusion plants. Unique to Thea Energy, the stellarator magnet systems are designed to be entirely planar coils consisting of two groups of HTS magnets: small surface-shaping coils and large, encircling toroidal coils. This division of confinement improves simplicity for modularity and minimizes complex, twisting coil geometries. Essential to this is the magnetic design of the large encircling coils which includes benchmarking between simulations, initial magnetic design optimization, and physics software. A scripted automation process developed during benchmarking will be used in peak magnetic field (Bmax) optimization in coil winding packs. The coil cross-section is the product of radial thickness and axial height, the two main parameters being scanned to search for minimum Bmax and optimal field angle relative to coil axis. REBCO conductors and their field and angle dependence will be considered in optimization. Large current cables other than single tape may be employed in coil winding due to large Ampere-turns. An initial design of encircling coils will be achieved to reach an average 6T along the stellarator axis, but with minimal REBCO conductors/cables.