UK scientists achieve record plasma pressure, tackling key fusion instability

At the UKAEA’s Culham Campus in Oxfordshire, scientists completed a fifth experimental campaign on the MAST Upgrade device, producing more than 1,100 fusion plasmas and attaining a record pressure level without plasma destabilisation. By employing quasi-continuous exhaust and resonant magnetic perturbations, they mitigated edge-localised modes that previously threatened the tokamak’s inner wall. The experiments also demonstrated four high-performance regimes—Quiescent H-mode, I-mode, and two others—while introducing a light-based system to track and correct plasma position in real time.

Additional studies explored negative triangularity shapes that avoid ELMs, a concept watched by the global fusion community. Planned upgrades this year will add new neutral beam injectors and an Electron Bernstein Wave system, paving the way for a sixth campaign in 2028 and supporting the STEP project in Nottinghamshire. James Harrison, head of MAST Upgrade science, said the findings move practical fusion energy closer to reality.