Will Commonwealth Fusion Systems announce first plasma in its SPARC tokamak by June 30, 2027?

CFS says SPARC, its compact fusion machine in Massachusetts, is about 80% built and will start operating in coming months, with net energy targeted for 2027. First plasma would be the first real switch-on, and the original target of 2025 has already slipped.

How this question entered the record and how it will be resolved.

Resolution criteria

Resolves Yes if Commonwealth Fusion Systems announces, on cfs.energy or its official blog or channels, that SPARC achieved first plasma on or before June 30, 2027. Resolves No otherwise.

Expected resolution

Jun 30, 2027

• CFS blog, August 28, 2026: SPARC to start operating in coming months; first plasma comes before Q>1 attempts
• Utility Dive, August 24, 2026: CEO says SPARC is about 80% complete after a $1 billion raise

Many toroidal field magnets still had to be installed this autumn, and the dry run of the full system has not been dated. Big first of a kind machines usually slip.

• Installation of the remaining magnets
• The dry dress rehearsal
• Supply chain or funding news