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CFS-MIT High-Field Magnet Technology for Commercial Fusion Experimentally Validated

Today’s most mature approach to commercial fusion power uses magnetic fields to contain a high-temperature plasma inside a fusion device called a tokamak. In 2015, researchers at MIT published a paper predicting that tokamaks can be made smaller, easier to build, and more cost effective through the use of higher magnetic fields. However, at the time of that publication, the magnetic technology required to produce those fields had not been demonstrated.

Now, a series of six peer-reviewed papers published in the journal IEEE Transactions on Applied Superconductivity have demonstrated the required magnet technology, marking  a pivotal moment in the high-field pathway to commercial fusion. These papers describe work that culminated in a 2021 test of the world’s strongest high-temperature superconducting (HTS) magnet for fusion, carried out by MIT’s Plasma Science and Fusion Center (PSFC) in collaboration with Commonwealth Fusion Systems (CFS). The magnet, called the Toroidal Field Model Coil or TFMC, was able to achieve a field of 20 T and a stored energy of 110 MJ, approaching the performance metrics required for the SPARC net-energy tokamak currently under construction outside of Boston.  

Crucially, the magnet exceeded the mechanical loading required by SPARC’s magnets, directly addressing a key risk category. To extract the maximum information on its physics and engineering constraints, the magnet was then destructively tested, confirming predictive models and increasing confidence around its operational capabilities in a fusion power plant.

The lessons learned from these tests have informed the design, manufacturing, and operation of SPARC’s full-scale TF magnets, which are currently being produced by CFS on a newly constructed high-throughput manufacturing line. This same magnet and manufacturing technology will be used for ARC, a commercial power plant that CFS will deploy by the mid-2030’s.

The papers also reflect the commitment of CFS to transparency and scientific rigor, which is a key feature of its partnership with MIT and other institutions around the world.