Design & Modeling of a Non-Planar REBCO Coil for Stellarators

The long understood benefits of operating fusion devices, such as tokamaks and stellarators, at high fields make superconducting magnets necessary to realize a compact fusion power system. Superconducting stellarators, such as W7-X, have used standard low-temperature superconductor technology (NbTi). ARPA-E has recently funded a 2-year project led by the startup Type One Energy and involving the Fusion Technology Institute at the University of Wisconsin–Madison and the Plasma Science and Fusion Center at MIT, to design and manufacture the first non-planar HTS (REBCO) coil based on the SPARC tokamak’s VIPER cable concept for a high-field stellarator. The design consists of a two-turn non-planar HTS coil supported by a pair of 3D printed stainless steel radial plates. The ultimate goals of the project are to determine if commercial REBCO tapes and additive manufacturing can be used to fabricate high field (>10 T) non-planar coils with tight bending radii (100 mm) and without degradation of the superconducting performance. In this presentation we will report on the fabrication of a two-turn non-planar HTS coil with tight-radius bends that will be supported by a pair of 3D printed stainless steel radial plates. A critical risk that is still to be retired is the accurate 3D bending of a multi-turn coil so that it mates properly with the radial plates, and produces the desired 3D B-field structure. Testing of the completed coil at 77 K will characterize the Ic, the 3D B-field structure, and the quench robustness, and will be compared to detailed electromagnetic, mechanical, and thermal modeling.