SPARC is 📝Commonwealth Fusion Systems' demonstration fusion machine — a compact, high-field 📝tokamak under construction at the company's Devens, Massachusetts campus, designed to be the world's first commercially relevant fusion device to produce more energy from fusion than it needs to power the process (Q>1).
SPARC's design grew out of design courses at the 📝MIT Plasma Science and Fusion Center and was set out in a series of peer-reviewed physics papers published in the Journal of Plasma Physics in 2020, before construction began in December 2021. The machine is designed to reach net-energy conditions in a device a fraction of the size of the international ITER project by using 📝high-temperature superconducting (HTS) magnets — the 20-tesla class demonstrated in a full-scale model coil in 2021. Entering 2026 the build was roughly 75 percent complete; the first of its 18 toroidal field magnets was installed in January 2026, with full magnet installation targeted by the end of summer 2026 and net energy gain targeted for 2027. SPARC is the testbed for the technology and operating experience that carry directly into 📝ARC, the commercial plant that follows it.
SPARC is where we intend to prove it — the machine designed to show fusion can produce more power than it consumes, on a timeline fast enough to matter.
Key Features
- High-field HTS magnets — 18 toroidal field coils in the 20-tesla class, the technology that makes a compact net-energy tokamak possible.
- Net energy goal (Q>1) — designed to produce more fusion power than the plasma requires, targeted for 2027.
- Peer-reviewed physics basis — performance predictions published in the Journal of Plasma Physics before construction.
- Compact scale — designed to reach commercially relevant conditions in a machine far smaller than ITER, cutting cost and build time.
- ARC testbed — every system is built to prove out technology bound for the follow-on commercial power plant.