In a significant construction step at its Devens, Massachusetts facility, Commonwealth Fusion Systems (CFS) has lowered the first of 18 high-temperature superconducting (HTS) magnets into the SPARC tokamak. The 20-ton toroidal field (TF) coil was placed into its stainless-steel vacuum vessel housing this spring, initiating the final assembly phase of the compact, high-field fusion device. This event transitions the project from component manufacturing to machine integration, a complex process requiring micrometer precision to align the powerful magnetic coils. The successful placement of the first magnet is a key validator of the project's manufacturing and installation logistics ahead of completing the full toroidal array. Source: MIT PSFC

The SPARC experiment is designed to be the first magnetic confinement device to achieve a net energy gain, or a plasma energy gain factor (Q) greater than one. Projections based on established plasma physics principles suggest SPARC will achieve Q > 2, and potentially as high as Q ≈ 11, producing between 50 MW and 140 MW of fusion power. The project's foundation is its use of HTS magnets, which can generate significantly stronger magnetic fields (targeting 12.2 T on-axis) than the low-temperature superconducting magnets used in devices like ITER. This high field strength allows for a much more compact device to achieve the plasma pressure and confinement necessary for net energy production, a core tenet of the high-field pathway to fusion energy. Source: MIT PSFC

Projections based on established plasma physics principles suggest SPARC will achieve Q > 2, and potentially as high as Q ≈ 11, producing between 50 MW and 140 MW of fusion power.

The installation follows the successful 2021 demonstration of a full-scale prototype TF magnet, which achieved a peak field of 20 T. That test validated the core technology and manufacturing processes for the HTS magnets, which are wound with rare-earth barium copper oxide (REBCO) tape. Each of the 18 D-shaped production magnets for SPARC is a precision-engineered component designed to withstand immense magnetic forces and cryogenic operating temperatures. The assembly of the full magnet set, along with the central solenoid and poloidal field coils, will form the magnetic cage that confines and shapes the deuterium-tritium plasma. The work by Commonwealth Fusion Systems represents a major private-sector effort in the fusion industry. Source: MIT PSFC

With the first magnet in place, the project team will proceed with installing the remaining 17 TF coils over the coming months. Following the completion of the magnet assembly, the vacuum vessel will be sealed, and the cryostat will be closed around it. The subsequent phase will involve commissioning the extensive support systems, including cryogenics, power supplies, and diagnostics. According to the project timeline, CFS is targeting the achievement of first plasma in 2027. The experimental campaign on SPARC is intended to directly inform the design of ARC, a commercial-scale fusion power plant that would follow. Source: MIT PSFC