Located at UKAEA’s Culham Campus, MAST (Mega Amp Spherical Tokamak) Upgrade is the UK’s flagship fusion machine, creating plasmas reaching 10 million degrees Celsius. MAST Upgrade has three key aims:
- To investigate novel exhaust concepts
- To de-risk / advance the spherical tokamak design, as a future power plant
- To extend physics knowledge in support of the broader fusion programme
MAST Upgrade is studying some key physics challenges which remain. To do this, the MAST Upgrade tokamak builds on the original MAST machine which ran from 2000 to 2013. MAST was reengineered to create MAST Upgrade which has enabled higher performance, such as longer plasma pulses, increased heating power and a stronger magnetic field, plus an innovative new plasma exhaust system.
Culham’s MAST Upgrade is keeping the UK at the forefront of global research in our quest for a sustainable and low carbon energy.
Plasma exhaust
One of the key challenges MAST Upgrade focuses on is understanding and reducing the heat coming out of a super-hot plasma. The tokamak exhaust system (known as the ‘divertor’) takes the particles and heat ejected from the plasma and directs it onto surfaces within the tokamak. Tackling the plasma exhaust is a key issue that must be solved to achieve commercial fusion power.
The intense power loads that will be created in the large fusion machines in future power plants have the potential to damage the divertor components. The result of this would be that divertor components would require replacement every few years, making it difficult for fusion to become an economically competitive energy source. The challenge is to develop a divertor which can reduce the power loads to a manageable level; about the same as in a car engine. Experiments in MAST Upgrade are providing UKAEA with valuable information on how to cool the plasma enough, where it meets surfaces in the divertor, to ensure that any damage is minimal.
What makes MAST Upgrade particularly unique is that it is the first tokamak in the world to use a highly optimised Super-X divertor. This is a unique exhaust system which should mean divertor components will last much longer. Previous experiments on MAST Upgrade using the Super-X divertor have shown to be successful, reducing the heat load on the parts of the divertor by a factor of ten.
MAST Upgrade can also operate with a variety of other divertor configurations to compare their effectiveness and inform design choices for future fusion machines.
Advancing the spherical tokamak design
MAST Upgrade continues UKAEA’s pioneering research into spherical tokamaks. The spherical tokamak design has benefits which mean it can achieve more efficient performance. This has excellent potential for building a more compact power plant, such as the UK’s prototype fusion power plant – STEP (Spherical Tokamak for Energy Production).
A facility to extend physics knowledge in support of the broader fusion programme
Fusion scientists from around the UK and the rest of the world utilise MAST Upgrade to study many areas of plasma physics. Researchers from UKAEA and from our partners at universities and other fusion laboratories carry out a wide range of experiments to better understand plasma physics. MAST Upgrade’s excellent diagnostics and plasma viewing capabilities make it one of the best tokamaks for novel experiments and allow it to capture extensive data.
MAST Upgrade is funded by the Department for Energy Security and Net Zero (DESNZ) and is part of the EUROfusion European Medium-Sized Tokamak programme.
MAST Upgrade’s Fourth Scientific Campaign
MAST Upgrade is currently performing experiments as part of the fourth scientific campaign. The fourth set of experiments brings together more than 100 scientists from 37 institutions helping to answer the big questions in fusion physics. Experiments started in October 2024 and will continue running throughout 2025.
