Under Pressure: Record plasma for UK flagship machine
UKAEA’s MAST Upgrade fusion experiments achieved record plasma pressure while addressing key stability challenges, advancing practical fusion energy research.
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The UK Atomic Energy Authority (UKAEA) completed its fifth experimental series on the MAST Upgrade fusion machine, running from 2025 to 2026. The team produced over 1,100 fusion plasmas, achieving the highest pressure recorded on the device without destabilisation. These results align with UKAEA’s 2026–2030 strategy to develop fusion as a low-carbon energy source.
The central focus was suppressing Edge Localised Modes (ELMs), which can damage reactor components by ejecting stored energy. Researchers used Quasi-Continuous Exhaust and Resonant Magnetic Perturbations to stabilise the plasma edge. They also accessed stable operating regimes like Quiescent H-mode and I-mode, which reduce damaging bursts while improving energy confinement.
A novel technique was developed to control plasma position in real time by detecting light emissions from deuterium. This advance supports the development of automated control systems for future fusion power plants. The team also tested impurity injection, such as nitrogen, to dissipate excess heat volumetrically, reducing wear on internal components.
The findings were presented at the European Physical Society’s Plasma Physics Conference 2026 and are being shared with international projects like STEP and ITER. UKAEA states these results mark a significant step toward practical fusion energy by demonstrating stable, high-performance plasma regimes.