Variety of coil sets for the compact stellarator-tokamak hybrid

Abstract

Abstract A first of-its-kind quasi-axisymmetric stellarator-tokamak hybrid design concept has recently been presented (Henneberg and Plunk 2024 Phys. Rev. Res. 6 L022052). Here we will provide an overview of various coil configurations that can be employed in this hybrid design, showcasing the versatility of possible topologies. A device based on this design method could be operated either as a tokamak or as a low-aspect-ratio, quasi-axisymmetric stellarator. The volumes and aspect ratios of the two distinct modes of operation are kept approximately constant, thereby ensuring that no volume is lost due to the shaping of the stellarator coils. It is notable that the number of coils required for this optimized stellarator can be reduced to a single additional type of unlinked modular coil (‘banana coil’), as compared to the tokamak scenario (Henneberg and Plunk 2024 Phys. Rev. Res. 6 L022052). However, the use of multiple, smaller banana coils is also a viable option, as demonstrated in this study.