Stellarator Magnets using High Temperature Superconductors and Advanced Manufacturing

The stellarator is second only to the tokamak in triple product achieved and has many positive attributes as a fusion reactor. High magnetic field operation is advantageous due to observed gyro-bohm confinement scaling. High-temperature superconducting tapes (HTS) can produce significantly higher magnetic fields than conventional superconductors. The 3D shape of the coils necessitates bending in many directions with torsion. Performance of the tapes is sensitive to local field values and tape strains. ARPA-E has funded Type One Energy Group, in collaboration with the MIT Plasma Science and Fusion Center, UW-Madison, and CFS, to develop and fabricate a demonstration HTS stellarator coil building upon a modified VIPER cable technology. Tests have shown a single cable length can be formed in multiple orthogonal directions with radii as small as 10 cm without any degradation in the superconducting properties compared to virgin tapes. A 2-turn coil will be formed using this cable and supported in 3D stainless steel plates printed with additive manufacturing. Tests of this coil will demonstrate the ability to fabricate a 3D coil using HTS and provide data to incorporate into simulations and models.