The SPARC Toroidal Field Model Coil Program
Zachary Hartwig, R. Vieira, Darby Dunn, T. Golfinopoulos, B. LaBombard, Christopher J. Lammi, Philip C. Michael, Susan Agabian, David Arsenault, Raheem Barnett, Mike Barry, L. Bartoszek, W. Beck, David Bellofatto, D. Brunner, W. Burke, Jason Burrows, William Byford, C. Cauley, Sarah Chamberlain, David Chavarria, JL Cheng, James Chicarello, Van Diep, Eric Dombrowski, J. Doody, Raouf Doos, Brian Eberlin, J. Estrada, Vincent Fry, Matthew Fulton, Sarah Garberg, R. Granetz, A. S. Greenberg, M. Greenwald, S. R. HELLER, A. Hubbard, Ernest Ihloff, J. Irby, M. V. Iverson, Peter Jardin, Daniel Korsun, Sergey Kuznetsov, Stephen Lane-Walsh, Richard G. Landry, Richard Lations, Rick Leccacorvi, Matthew Levine, G M Mackay, K. Metcalfe, Kevin Moazeni, John Mota, Theodore Mouratidis, R. Mumgaard, JP Muncks, Richard A. Murray, Daniel A. Nash, Ben Nottingham, Colin O’Shea, A. Pfeiffer, Samuel Z. Pierson, Clayton Purdy, Alexi Radovinsky, Dhananjay K. Ravikumar, Verónica Rivera Reyes, Nicolò Riva, Ron Rosati, Michael W. Rowell, Erica Salazar, Fernando Santoro, Akhdiyor Sattarov, Wayne R. Saunders, Patrick Schweiger, Shane Schweiger, M. L. Shepard, S. Shiraiwa, Maria Silveira, FT Snowman, Brandon Sorbom, Peter W. Stahle, Ken Stevens, J. Stillerman, Deepthi Tammana, Thomas Toland, David Tracey, R.P. Turcotte, Kiran Uppalapati, Matthew T. Vernacchia, Christopher Vidal, E. Voirin, A. J. Warner, Amy Watterson, D.G. Whyte, S. Wilcox, Michael J. Wolf, Bruce Wood, Lihua Zhou, A. Zhukovsky
Abstract
The SPARC Toroidal Field Model Coil (TFMC) Program was a three-year effort between 2018 and 2021 that developed novel Rare Earth Barium Copper Oxide (REBCO) superconductor technologies and then successfully utilized these technologies to design, build, and test a first-in-class, high-field (∼20 T), representative-scale (∼3 m) superconducting toroidal field (TF) coil. The program was executed jointly by the MIT Plasma Science and Fusion Center (PSFC) and Commonwealth Fusion Systems (CFS) as a technology enabler of the superconducting high-field pathway to fusion energy, and, in particular, as a risk retirement program for the no insulation (NI) TF magnet in the SPARC net-energy fusion tokamak. The TFMC achieved its programmatic goal of experimentally demonstrating a large-scale high-field REBCO magnet, achieving 20.1 T peak field-on-conductor with 40.5 kA of terminal current, 815 kN/m of Lorentz loading on the REBCO stacks, and almost 1 GPa of mechanical stress accommodated by the structural case. Fifteen internal demountable pancake-to-pancake joints operated in the 0.5 to 2.0 nΩ range at 20 K and in magnetic fields up to 12 T. The DC and AC electromagnetic performance of the magnet predicted by new advances in high-fidelity computational models was confirmed in two test campaigns while the parallel, single-pass, pressure-vessel style coolant scheme capable of large heat removal was validated. In the test facility, a feeder system composed of REBCO current leads and cables was experimentally qualified up to 50 kA, and a liquid-free cryocooler-based helium cryogenic system provided 600 W of cooling power at 20 K with mass flow rates up to 70 g/s at a maximum design pressure of 2 MPa for the test campaigns. Finally, the feasibility of using passive, self-protection against a quench in a fusion-scale NI TF coil was experimentally assessed. While the TFMC was intentionally not optimized for quench resiliency – and suffered localized thermal damage in response to an intentional open-circuit quench at 31.5 kA terminal current – the extensive data and validated models that it produced represent a critical step towards this important objective.