MAST Upgrade is UKAEA's spherical tokamak at Culham, the main UK physics testbed feeding the STEP prototype plant. Its fifth experimental campaign (2025-26, 1,100+ plasmas) reached the machine's highest stable plasma pressure and tested exhaust and instability-control techniques.
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Current state
| Status | Operating |
| Country | United Kingdom |
| Location | Culham Campus, Oxfordshire |
| Developer | UK Atomic Energy Authority (UKAEA) |
| Developer type | Public |
| Concept | Spherical tokamak |
| Fuel | D-D |
| Purpose | Research |
| Public funding | UK government (DESNZ) via UKAEA |
Notes
First plasma of MAST Upgrade (2020) not verified in the sources reviewed; not recorded.
Timeline
- 2025 — MAST Upgrade began its fifth experimental campaign with new enhancements. (source)
- 2026-08-06 — UKAEA reported its fifth campaign produced more than 1,100 plasmas and the highest plasma pressure on the machine without destabilising events. (source)
The timeline is append-only: corrections are added as new entries. Stated targets appear in the current-state table, never as milestones.
Related projects
- CTRFR-1 / Startorus No.1 (Startorus Fusion) Design · China
- JET (Joint European Torus) Shut down · United Kingdom
- Machine 4 (First Light Fusion) Cancelled · United Kingdom
- ST40 (Tokamak Energy) Operating · United Kingdom
- ST80-HTS (Tokamak Energy) Design · United Kingdom
- STEP Fusion (West Burton) Design · United Kingdom
See all 51 projects in the Fusion Energy Companies & Projects Tracker →
Sources
- Under Pressure: Record plasma for UK flagship machine — UK Atomic Energy Authority (GOV.UK) (primary), checked 2026-10-11
- MAST Upgrade: the world's largest operational spherical tokamak — UKAEA (primary), checked 2026-10-11