A compact high-field superconducting tokamak under construction by Commonwealth Fusion Systems, designed to achieve Q > 2 (predicted Q ~ 11) using high-temperature superconducting magnets — the fastest private-sector path to demonstrating fusion energy gain.
SPARC is a compact deuterium–tritium tokamak being built by Commonwealth Fusion Systems (CFS) in Devens, Massachusetts, in collaboration with MIT’s Plasma Science and Fusion Center. It uses high-temperature superconducting (HTS) magnets made from REBCO tape to achieve extremely high magnetic fields in a compact device.[1]
On 5 September 2021, CFS and MIT demonstrated a large-bore HTS magnet reaching 20 T — the strongest magnetic field of its kind at that time. The magnet used 16 stacked REBCO plates. This test validated the core enabling technology for SPARC. Peer-reviewed results were published in IEEE Transactions on Applied Superconductivity in March 2024.[2]
As of mid-2026, SPARC is approximately 75% complete. Both halves of the vacuum vessel (~48 tons each) have been joined. The first of 18 D-shaped toroidal field magnets was completed in January 2026; multiple TF magnets are now installed. First plasma is targeted for late 2026 or 2027.[3]
SPARC is the demonstration device; ARC is the follow-on commercial fusion power plant designed for ~1.1 GW fusion power and 400 MW net electricity. ARC is planned near Richmond, Virginia, with operations targeted for the early 2030s.[4]