Will the SPARC tokamak reach first plasma before 31 December 2026?
deadline 2026-12-31
confidence medium
tier 4 evidence
16%Asturna 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) officially maintained a 2026 target for first plasma as of January 2026 [1].
- CFS has a strong track record of meeting technical milestones, such as the successful 2021 test of their 20-Tesla high-temperature superconducting magnet [1].
What pushes it down
- As of January 2026, 17 of the 18 toroidal field magnets still required installation, a process that typically takes most of a year [1].
- With only 82 days remaining in 2026, there have been no official announcements regarding the completion of magnet installation or the start of the vacuum vessel sealing [1].
- The cryogenic cooldown process required for superconducting magnets usually takes several weeks to a month, leaving almost no margin for error if it has not yet begun [1].
- The project has already experienced a schedule slip from its original 2025 target, suggesting a trend of delays [1].
What would move this number most
The current status of the vacuum vessel assembly and whether the cryogenic cooldown phase has commenced.
How this number is built
| Deadline | 2026-12-31 |
| Base rate | 20% |
| Best evidence | tier 4 · 1 article(s) used |
| Independent runs | 15 · 17 (spread 2 pts) |
| Confidence | medium |
| Evidence cap | not triggered |
| Last revised | 2026-10-10 09:12 |
| Model | gemini-3-flash-preview |
Sources consulted
Probability history
2026-10-10 09:12 16% 1 article(s) on file · gemini-3-flash-preview
- What pushes it up. Commonwealth Fusion Systems (CFS) officially maintained a 2026 target for first plasma as of January 2026 [1].
- What pushes it up. CFS has a strong track record of meeting technical milestones, such as the successful 2021 test of their 20-Tesla high-temperature superconducting magnet [1].
- What pushes it down. As of January 2026, 17 of the 18 toroidal field magnets still required installation, a process that typically takes most of a year [1].
- What pushes it down. With only 82 days remaining in 2026, there have been no official announcements regarding the completion of magnet installation or the start of the vacuum vessel sealing [1].
- What pushes it down. The cryogenic cooldown process required for superconducting magnets usually takes several weeks to a month, leaving almost no margin for error if it has not yet begun [1].
- What pushes it down. The project has already experienced a schedule slip from its original 2025 target, suggesting a trend of delays [1].
- What would move this number most. The current status of the vacuum vessel assembly and whether the cryogenic cooldown phase has commenced.
2026-10-06 09:19 16% 1 article(s) on file · qwen/qwen3.8-27b (Groq)
- What pushes it up. CFS officially maintains a 'later this year' (2026) target for first plasma [1]
- What pushes it up. The installation of the first of 18 toroidal superconducting magnets was confirmed in January 2026, indicating active progress [1]
- What pushes it down. Seventeen magnets remain to be installed and the cryostat must be closed, a process that typically takes many months [1]
- What pushes it down. The initial 2025 target had already slipped, suggesting a pattern of optimistic scheduling [1]
- What pushes it down. The only recent press article is tier 4 and provides no new technical milestones or confirmation of the 2026 timeline [4]
- What would move this number most. Whether the remaining 17 magnets can be installed and the cryostat closed within the remaining ~2.5 months of 2026.
2026-09-22 00:33 14% 13 article(s) on file · gemini-3-flash-preview
Reasons not recorded for this revision (detailed history has only been kept since recently).