The successful 2021 test of a large-scale high-temperature superconducting (HTS) magnet, achieving a 20-tesla field, underpins the strategy for developing compact, high-field fusion devices. Developed by Commonwealth Fusion Systems in collaboration with MIT’s Plasma Science and Fusion Center, the magnet utilizes rare-earth barium copper oxide (REBCO) superconducting tape. This material enables significantly stronger magnetic fields compared to the low-temperature superconductors used in larger experimental reactors like ITER. The demonstration confirmed the viability of HTS magnets for the demanding operational conditions of a tokamak, paving the way for the construction of the SPARC experiment. The test was a critical validation step for the entire high-field pathway to commercial fusion energy. Source: Cfs

The physics of magnetic confinement fusion dictates that fusion power output scales with the magnetic field strength to the fourth power (B⁴). This relationship means that doubling the magnetic field strength increases the potential fusion power by a factor of 16 within the same plasma volume. By leveraging HTS magnets to achieve fields of 20 T, CFS and MIT project that their SPARC device can achieve a net energy gain (Q_plasma > 1) in a device substantially smaller and less costly than predecessors. This approach contrasts with lower-field designs that must compensate by increasing the plasma volume and, consequently, the overall machine size and capital cost. The HTS technology is therefore not an incremental improvement but a fundamental enabler of the compact reactor design. Source: Cfs

The physics of magnetic confinement fusion dictates that fusion power output scales with the magnetic field strength to the fourth power (B⁴).

SPARC is the planned successor to this magnet development program, designed to be the first magnetic confinement fusion device to produce net energy. It is projected to be approximately 1/40th the size of the ITER tokamak while producing a similar level of fusion power. Following the successful magnet demonstration, CFS is proceeding with SPARC's construction, which will serve as the final integrated proof-of-concept before a commercial power plant. The data and operational experience from SPARC are intended to directly inform the design and engineering of ARC, the company's concept for a first-of-its-kind commercial fusion power plant capable of delivering electricity to the grid. Source: Cfs

To support these projects, CFS has established a manufacturing facility and corporate campus in Devens, Massachusetts. This site is dedicated to the production of the HTS magnets required for SPARC and future ARC power plants. The ability to manufacture hundreds of kilometers of REBCO tape into robust, high-performance magnets at scale is a critical industrial challenge being addressed in parallel with the scientific development. The successful operation of this supply chain and manufacturing process is as vital to the commercialization timeline as the physics performance of the devices themselves. The next major inflection point will be the integrated commissioning of all SPARC systems and the subsequent experimental campaigns aiming for net energy gain. Source: Cfs