High-Temperature Superconducting Non-Planar Coil Development: From Design to Cryogenic Testing

The Columbia Stellarator eXperiment’s (CSX) objective is to upgrade the Columbia Non-neutral Torus to a quasi-symmetric stellarator incorporating high-temperature superconducting (HTS) magnet technology. Stellarators are a favorable path toward sustainable fusion energy due to their steady-state operation. This presentation focuses on the design, fabrication, and testing of the HTS magnets. The design process incorporates quasi-symmetric field shaping while minimizing torsion and strain on the HTS tape, recently achieving a calculated strain of 0.22%. The design is used to produce a non-planar bobbin following the shape of the HTS. CSX’s third coil prototype has recently transitioned from a two-channel double-pancake design to a four-channel design to test windability and achieve higher fields.

Furthermore, new retention clamps are redesigned and machined in-house for improved retention during winding and powering of the HTS tape. The magnet test stand features a cryogenic system comprising a cold head, a two-stage magnet interface, copper feedthroughs, HTS-110 leads, and aluminum support structures. Recent engineering upgrades include sapphire spacers between the coil and bracket to provide both thermal and electrical insulation, and the addition of copper braid connections between the first stage and thermal shields to enhance cooling. The current system achieves a minimum operational temperature of 25 K. Additionally, the soldering technique for connecting HTS tapes to copper current leads is under active development.