SPARC is Commonwealth Fusion Systems' compact high-field HTS-magnet tokamak, built to show net fusion energy (Q>1). Assembly began in 2025 and the machine was about three-quarters built by April 2026, with first plasma now targeted for 2027.
New to fusion? Nuclear fusion, explained: three ways to bottle a star
Current state
| Status | Under construction |
| Country | United States |
| Location | Devens, Massachusetts |
| Developer | Commonwealth Fusion Systems |
| Developer type | Private |
| Concept | Tokamak |
| Fuel | D-T |
| Purpose | Demonstration |
| First plasma target | 2027 |
| Net energy target | 2027 |
| Site | Built on CFS's own Devens campus |
| Private funding raised | USD 3bn (as of 2025-08-28) |
| Public funding | DOE Milestone-Based Fusion Development Program awardee |
| Regulation | Licensed under Massachusetts radiation-control (Agreement State) rules for fusion machines, not as a reactor. |
Notes
private funding raised is the company-wide figure ('close to $3 billion') per CFS's Aug 2025 release; the $863M B2 was the latest disclosed round. Net-energy target is Q_sci>1 (fusion power > plasma heating power), not Q_eng; CFS projects Q~10 potential. First plasma target slipped from 2025 to 2026 to 2027.
Timeline
- 2023-09-05 — CFS reported Tokamak Hall weather-tight and ready for SPARC assembly. (source)
- 2025-04 — CFS installed the 75-tonne cryostat base, marking the start of SPARC tokamak assembly. (source)
- 2025-08-28 — CFS raised an $863 million Series B2, bringing total capital raised to close to $3 billion. (source)
- 2026-01 — CFS announced installation of the first of SPARC's 18 toroidal field magnets and an AI digital-twin partnership with Nvidia and Siemens. (source)
- 2026-04-09 — CFS said about three-quarters of SPARC construction was complete, with both vacuum-vessel halves and two TF magnets in Tokamak Hall. (source)
The timeline is append-only: corrections are added as new entries. Stated targets appear in the current-state table, never as milestones.
NNN coverage
About SPARC
About Commonwealth Fusion Systems
Related projects
- ARC (Commonwealth Fusion Systems) Design · United States
- Athena (Xcimer Energy) Concept · United States
- BEST (Burning Plasma Experimental Superconducting Tokamak) Under construction · China
- Century (Zap Energy) Operating · United States
- CFEDR / China Fusion Energy Co. demo reactor (successor to CFETR) Design · China
- Copernicus (TAE Technologies) Under construction · United States
- Da Vinci / first utility-scale plant (TAE Technologies) Concept · United States
- Demonstration System (Pacific Fusion) Under construction · United States
See all 51 projects in the Fusion Energy Companies & Projects Tracker →
Sources
- Commonwealth Fusion Systems Raises $863 Million Series B2 Round — Commonwealth Fusion Systems (primary), checked 2026-10-11
- Devens Events & Updates — Commonwealth Fusion Systems (primary), checked 2026-10-11
- Our SPARC fusion facility is now about 75% done — Commonwealth Fusion Systems (primary), checked 2026-10-11
- Assembly starts of SPARC, as ITER cryopumps completed — World Nuclear News, checked 2026-10-11
- CFS, Nvidia and Siemens SPARC digital twin; first magnets installed — Gigazine, checked 2026-10-11
- SPARC (tokamak) — Wikipedia, checked 2026-10-11