Commonwealth Fusion Systems (CFS), a spin-off from MIT's Plasma Science and Fusion Center, announced the successful high-field magnet test on February 15, 2024. This electromagnet, utilizing high-temperature superconducting (HTS) tape, achieved a field strength of 20 tesla (T), a record for fusion magnets. The test validates the core technology intended for the SPARC tokamak, which aims to achieve net energy gain.

The magnet's performance is crucial for SPARC's design, which requires a magnetic field strength of 12 T to confine the plasma at the temperatures necessary for fusion. Conventional superconducting magnets, typically using niobium-tin or niobium-titanium alloys, struggle to reach such high fields without becoming prohibitively large and complex. The HTS material, specifically a rare-earth barium copper oxide (REBCO) tape, enables significantly stronger magnetic fields in a more compact form factor.

The magnet's performance is crucial for SPARC's design, which requires a magnetic field strength of 12 T to confine the plasma at the temperatures necessary for fusion.

This achievement builds upon years of research at MIT and represents a significant step towards the commercialization of fusion energy. The SPARC device is designed to be a net-energy-producing fusion experiment, with a target Q_plasma of 10, meaning it will produce ten times more fusion power than is injected into the plasma. The successful magnet test indicates that the magnetic confinement required for this level of performance is achievable.

The 20 T magnet test is a key milestone in CFS's roadmap, which includes the subsequent construction of the ARC power plant, intended to be a net-electricity-producing fusion power plant. The successful development and testing of these HTS magnets are foundational to both SPARC and ARC, demonstrating the viability of this advanced magnet technology for future fusion power generation. The company has stated its goal to deliver net energy from fusion by 2025.

Future work will focus on integrating this magnet technology into the full SPARC device, which is currently under construction. The successful operation of SPARC will be the next critical validation point for the entire approach to fusion power generation being pursued by CFS and its partners. The performance data from this magnet test will inform the engineering and construction of the full tokamak.