Europe and Japan upgrade JT-60SA with new components

View of the JT-60SA tokamak, surrounded by auxiliary systems. December 2024. ©F4E

The JT-60SA experiment has already made its mark in the fusion books. The machine, a flagship EU-Japan collaboration under the Broader Approach, had its first plasma operations towards the end of 2023. Reaching a plasma volume of up to 160 m3, it was crowned as the world’s largest tokamak – a title it will hold until ITER is up and running. But that was only the beginning. The device was switched off shortly after, with sights set on a powerful return in 2026.

Hosted in Naka, Japan, JT-60SA aims to advance fusion research by providing know-how to ITER, exploring key physics and technology challenges for future fusion reactors. Assembling it was like putting together a huge puzzle of components, procured by F4E and QST from over 70 suppliers in Europe and Japan.

Sam Davis, Project Leader of JT-60SA, was at the control room to witness the first plasma operations. “The work is far from over, as we only completed the basic configuration before. We are currently adding many key components, including powerful diagnostic and heating systems to unleash the tokamak’s full potential,” he explains. The technical upgrades will lead to the next commissioning phase by mid-2026, paving the way for experiments later in the year.  

Lifting of a perpendicular neutral beam tank in the JT-60SA tokamak hall.
Lifting of a perpendicular neutral beam unit, a component inherited from the former JT-60U tokamak. December 2024. ©F4E

Things are indeed moving fast around the tokamak hall. Since last year, the teams have been busy installing the remaining 18 ports – the entryways to the vacuum vessel for the supporting systems. They also placed 8 Neutral Beam tanks, an operation combining heavy lifting and accurate positioning. Further components are arriving from Europe, including the cryopumps and diagnostics like the Thomson scattering or the VUV divertor spectrometer.

In parallel, technicians are doing meticulous handiwork inside the vessel. What was an almost bare inner wall is becoming a shell equipped with numerous components. The teams have installed 18 correction coils and are now winding the fast plasma position control directly inside the chamber.

Technicians install a lower oblique port onto the vacuum vessel of JT-60SA.
Technicians install a lower oblique port onto the vacuum vessel of JT-60SA. April 2024. ©QST

As new operations draw closer, the experiment team, which brings together over 280 European and Japanese scientists, is devising a detailed course of action. Experts are analysing the data from the initial plasma shots and reviewing the physics models for the next.

“JT-60SA is emerging as a unique global facility and will have a critical role in preparing the next generation of fusion operators and researchers,” asserts Sam Davis. This autumn, the project will issue a first call for proposals, inviting researchers to use the tokamak for their experiments. Additionally, the project will help train young experts through a third edition of the JT-60SA International Fusion School in August.

Do you want to step inside the world’s largest tokamak?

Watch our new video and discover JT-60SA with the help of Sam Davis!

You can also check out our new pictures of the device.