Manufacturing and Testing HTS Coils for Magnetic Mirror

Commonwealth Fusion Systems (CFS) completed the design, construction, assembly, and full field dual magnet factory acceptance testing of two identical compact (< 2 ton), high-field (20 T on tape, 17 T in warm bore) HTS REBCO magnets for a magnetic mirror in an axial fusion device. The CFS magnets will serve as the high field end coils for the ARPA-E funded project, “An HTS Axisymmetric Magnetic Mirror on a Faster Path to Lower Cost Fusion Energy.” CFS is a subrecipient of the ARPA-E BETHE Fusion Grant with the University of Wisconsin-Madison.The CFS magnets are DC magnets which will operate in the presence of other magnetic coils. The magnets use partial insulation pancake design. They are conduction cooled by cryocoolers to a nominal design operating temperature of 20 K. Field-induced mechanical stresses in the winding pack are managed such that the tape is constrained within allowable stress and strain during magnet operation. The winding pack is mechanically supported and thermally isolated in the cryostat by a set of high strength, low thermal conductivity supports. The cold mass supports are designed to sustain over 60 tons of axial loading during peak operating conditions. Results of the magnet tests and commissioning are presented below.