Will the SPARC tokamak reach first plasma before 31 December 2026?
deadline 2026-12-31
confidence medium
tier 4 evidence
14%PolySignal estimate
Resolution criterion
Yes if Commonwealth Fusion Systems officially announces SPARC's first plasma with an occurrence date before 1 January 2027.
Verified starting state
At CES in January 2026, CFS announced the installation of the first of 18 toroidal superconducting magnets and publicly maintains a first plasma "later this year" (2026), with net energy targeted for 2027. The initial 2025 target had already slipped. Seventeen magnets remain to be installed and the cryostat to be closed.
What pushes it up
- Commonwealth Fusion Systems (CFS) is a well-funded private entity that has successfully met previous high-stakes technical milestones, such as the 20 Tesla magnet test [1].
- As of January 2026, the organization publicly maintained its commitment to a 2026 first plasma target [1].
What pushes it down
- As of January 2026, 17 of the 18 toroidal field magnets still required installation, representing a massive assembly and alignment task [1].
- The process of closing the cryostat, achieving a vacuum seal, and cooling the superconducting magnets to cryogenic temperatures typically takes several months, leaving a very narrow window for a December 2026 deadline [1].
- The provided press articles [0, 1, 2, 3, 4] are entirely irrelevant to the SPARC tokamak, referring instead to AI stocks, electronics companies, and theater groups, meaning there is no recent Tier 1 or Tier 2 evidence of progress [4].
- The lack of any Tier 1 announcement regarding the completion of magnet installation or the start of the cooling phase by late September 2026 strongly suggests the project has fallen behind the January 2026 schedule [1].
What would move this number most
The current status of magnet installation and cryostat sealing, which has not been updated in Tier 1 or Tier 2 sources since January 2026.
How this number is built
| Deadline | 2026-12-31 |
| Base rate | 20% |
| Best evidence | tier 4 · 0 article(s) used |
| Independent runs | 12 · 15 (spread 3 pts) |
| Confidence | medium |
| Evidence cap | not triggered |
| Last revised | 2026-09-22 00:33 |
| Model | gemini-3-flash-preview |