Coil Optimization for a High-Beta Stellarator-Tokamak Hybrid

Magnetic coil configurations are developed for a drift-optimized, tokamak-stellarator hybrid that is stable to both pressure- and current-driven modes for high values of b. Previous work on this configuration [A. S. Ware, et al., Phys. Rev. Lett, 89, 125003 (2002)] was carried out using a fixed-boundary equilibrium (i.e., with no set of external coils) and prior attempts to develop an initial coil set using the COILOPT code were not successful. In this work, the recently developed SIMSOPT code [M. Landreman, et. al., J. Open Source Software 6, 3525 (2021)] is used to optimize coils for this configuration. Since this is a hybrid device, the goal is to develop a modular coil set that is simpler than modular coils for stellarators such as W7-X and NCSX. Ballooning stability is analyzed using the COBRAVMEC code and transport properties are analyzed using the NEO code. The SIMPLE code [C. Albert, et al., J. Plasma Physics 86, 815860201 (2020)] will then be used to analyze the confinement of fusion alpha particles in a reactor-sized version of this configuration. Further optimization including targeting quasi-symmetry and minimization of the radial drift velocity will be conducted.