Commonwealth Fusion Systems broke ground on SPARC — the first compact, high-field tokamak designed to demonstrate net energy gain from fusion — marking the transition from magnet R&D to integrated device construction.
In 2024, Commonwealth Fusion Systems (CFS) began construction of SPARC at its facility in Devens, Massachusetts. SPARC is designed to be the first privately funded fusion device to produce a burning plasma and achieve a fusion gain factor (Q) greater than 2, with a design target of Q ≥ 11. The device leverages high-temperature superconducting (HTS) magnets to achieve high magnetic fields in a compact form factor.[1]
SPARC is a compact tokamak with a major radius of approximately 1.85 meters and a toroidal field of roughly 12.2 tesla on axis. By operating at high field, SPARC achieves reactor-relevant plasma conditions in a device substantially smaller than ITER. The machine is designed to produce approximately 140 MW of fusion power from 25 MW of auxiliary heating, demonstrating that compact high-field approaches can achieve net energy.[2]
The construction of SPARC is significant beyond its technical objectives. It demonstrates that private capital can fund and execute major fusion hardware programs on timelines shorter than traditional government-funded projects. CFS raised over $2 billion in private investment to support SPARC and the subsequent ARC power plant design, making it one of the most well-funded private fusion ventures in history.[3]
SPARC is explicitly designed as the scientific precursor to ARC, a compact fusion pilot plant that CFS intends to connect to the grid in the early 2030s. Data from SPARC operations will validate the physics models and engineering approaches needed for ARC, including burning plasma behavior, HTS magnet performance under neutron irradiation, and plasma control systems.[1]