1. Fusion Research Infrastructure
This chapter examines the United Kingdom's fusion research infrastructure, which spans government laboratories, private commercial ventures, and international collaborations. The UK's fusion ecosystem is one of the most diverse in the world, encompassing the UKAEA's STEP program and MAST Upgrade, Tokamak Energy's private FRC/stellarator development with a DARPA PUMP submarine MHD drive contract, and General Fusion UK's magnetized target fusion (MTF) program. All of these activities are civilian in nature, with no evidence of plasma orb weapons development.
1.1 UKAEA and the Culham Centre for Fusion Energy
UKAEA (UK Atomic Energy Authority, est. 1954) operates the Culham Centre for Fusion Energy (CCFE) in Oxfordshire, the UK's primary fusion research campus. UKAEA has been at the forefront of fusion research for over six decades, having operated the Joint European Torus (JET), the Mega Amp Spherical Tokamak (MAST), and now leading the STEP (Spherical Tokamak for Energy Production) program. With 7 documented connections, UKAEA is a central node in the UK's plasma physics network.
Culham/CCFE (est. 1960) is UKAEA's fusion research campus in Oxfordshire, hosting JET, MAST Upgrade, and historical devices including ZETA, HBTX1, and SPHEX. With 9 documented connections, Culham is the second most connected entity in the network, serving as the physical and institutional hub of UK fusion research.
Key relationships:
- UK Government funds UKAEA (1991)
- UKAEA operates Culham/CCFE (1960)
- UKAEA operates JET (1983)
- UKAEA operates MAST-U (2020)
- UKAEA parent of UKFE (2021)
1.2 JET: The World's Most Successful Fusion Facility
JET (Joint European Torus, est. 1983) was the world's most successful fusion facility, operated by UKAEA at Culham from 1983 to 2023. JET set the world record for fusion energy output with 69.26 megajoules (MJ) in October 2023, the final major experiment before decommissioning. JET was a European collaboration under the EUROfusion program, with the UK hosting and operating the device on behalf of the European fusion community.
JET's contributions to fusion science are foundational. The device validated physics scenarios for ITER, demonstrated sustained high-power fusion operation, and provided the experimental basis for the ITER design. JET's deuterium-tritium experiments in 1997 and 2023 produced the highest fusion power outputs ever achieved in a laboratory, establishing benchmarks that ITER is designed to exceed.
Key relationships:
- UKAEA operates JET (1983)
- Culham/CCFE hosts JET (1983)
- JET validates ITER (1988)
- JET validates STEP (2019)
1.3 MAST Upgrade: Spherical Tokamak Innovation
MAST-U (Mega Amp Spherical Tokamak Upgrade, est. 2020) is the world's largest operational spherical tokamak, located at Culham. MAST-U achieved the Super-X Divertor breakthrough — a novel exhaust system that reduces heat loads on plasma-facing components by spreading the exhaust plasma over a larger area. MAST-U also achieved a world-first in ELM (Edge-Localized Mode) suppression using resonant magnetic perturbations in a spherical tokamak.
MAST-U is funded by DESNZ (Department for Energy Security and Net Zero) and is included in the EUROfusion research program. The device validates physics for the STEP program, providing the experimental foundation for the UK's prototype fusion power plant design.
Key relationships:
- UKAEA operates MAST-U (2020)
- DESNZ funds MAST-U (2023)
- MAST-U validates STEP (2020)
- EUROfusion includes MAST-U (2020)
1.4 STEP: The UK's Prototype Fusion Power Plant
STEP (Spherical Tokamak for Energy Production, est. 2019) is the UK's program to build a prototype fusion power plant at West Burton, Nottinghamshire — the site of a former coal power station. STEP targets first operations in the early 2040s and represents one of the most ambitious national fusion energy programs in the world. The program is led by UKFE (UK Fusion Energy Ltd), a UKAEA subsidiary established in 2021 to manage the STEP public-private partnership.
STEP is based on spherical tokamak technology validated by MAST-U and JET. The spherical tokamak configuration offers advantages over conventional tokamaks — including higher plasma beta (the ratio of plasma pressure to magnetic pressure) and more compact size — making it attractive for a prototype power plant. The UK Government has committed record funding to fusion research, with 2.6 billion pounds allocated for 2025/26.
Key relationships:
- UK Government funds STEP (2019)
- UKFE leads STEP (2021)
- West Burton hosts STEP (2022)
- JET validates STEP (2019)
- MAST-U validates STEP (2020)
1.5 Tokamak Energy: Private FRC and Stellarator Development
Tokamak Energy is one of the world's leading private fusion companies, based in Oxfordshire, UK. The company pursues a combined FRC/stellarator approach to fusion energy development, representing a distinctive technology pathway that differs from both the conventional tokamak approach (UKAEA/STEP) and the pure FRC approach (TAE Technologies in the US). Tokamak Energy has secured multiple significant contracts and funding rounds that establish it as a major player in the global commercial fusion sector.
In October 2025, Tokamak Energy was awarded a DARPA PUMP (Portable Utilization of Magnetic Power) contract for submarine magnetohydrodynamic (MHD) drive development. This DARPA contract represents a significant US-UK technology link and demonstrates the dual-use potential of MHD technology — the same plasma physics that enables fusion energy can potentially enable underwater propulsion systems. The MHD drive concept uses magnetic fields to accelerate conductive plasma or seawater, producing thrust without moving parts.
In April 2026, Tokamak Energy secured a 70 million pound STEP contract, integrating the company's private fusion development with the UK Government's STEP program. In January 2025, the company received 200 million pounds in LIBRTI (Long-term Investment in British Research and Technology for Innovation) funding, further establishing its financial foundation.
1.6 General Fusion UK: Magnetized Target Fusion
General Fusion UK is the UK subsidiary of General Fusion, a Canadian company pursuing magnetized target fusion (MTF) — a hybrid approach that combines elements of magnetic confinement and inertial confinement fusion. In MTF, a plasma target (typically an FRC or spheromak) is formed inside a liquid metal vortex, and the liquid metal is then rapidly compressed by mechanical pistons, compressing the plasma to fusion conditions.
General Fusion UK's presence in the UK fusion ecosystem adds further diversity to the country's fusion technology portfolio. The MTF approach is distinct from both the spherical tokamak (UKAEA/STEP) and the FRC/stellarator (Tokamak Energy) approaches, providing a third pathway toward fusion energy development. General Fusion's UK operations benefit from the country's fusion research infrastructure and skilled workforce.
1.7 AWE and the Orion Laser Facility
AWE (Atomic Weapons Establishment, est. 1950) at Aldermaston operates the Orion laser facility for nuclear weapons stewardship under the Comprehensive Test Ban Treaty (CTBT). Orion is a large neodymium-glass laser system used for high-energy-density physics experiments that support the UK's nuclear weapons stockpile — ensuring the safety and reliability of the Trident warhead without underground nuclear testing.
AWE collaborates with the US National Ignition Facility (NIF) at Lawrence Livermore National Laboratory and with France under the TEUTATES Treaty for joint hydrodynamics experiments. These collaborations are focused on nuclear weapons stewardship — the science of maintaining an existing nuclear stockpile — not on plasma weapons development.
Key relationships:
- UK Government funds AWE (1991)
- AWE operates Orion Laser (1985)
- AWE collaborates with NIF (1997)
- AWE collaborates with France (1995)
- AWE supports CASD (1969)
1.8 Historical Devices: ZETA, HBTX1, SPHEX
The UK has a long history of plasma physics research, with several historical devices at Culham contributing to the field:
- ZETA (Zero Energy Thermonuclear Assembly, est. 1957): An early UK fusion experiment that was foundational for reversed field pinch (RFP) research. ZETA was one of the first large-scale fusion devices built in the UK.
- HBTX1 (High Beta Toroidal Experiment, est. 1976): A UK RFP experiment at Culham that demonstrated spontaneous field reversal, contributing to the understanding of self-organized magnetic field configurations.
- SPHEX (Spheromak Experiment, est. 1989): A UK spheromak device at universities (Imperial College London and University of York) that demonstrated steady-state current drive via helicity injection — a technique relevant to both spheromak and FRC sustainment.
These historical devices demonstrate the UK's long-standing expertise in alternative magnetic confinement concepts — RFP, spheromak, and compact toroid physics — that are relevant to the broader plasma weapons investigation. However, all of these devices were civilian research installations, and their research was published in the open literature.