Europe and Japan restart JT-60SA

JT-60SA, the world's largest tokamak, is getting ready to resume plasma operations. The European and Japanese teams have kicked off integrated commissioning, a gradual start-up to test the main systems of the upgraded machine. This process will lead to a new round of experiments, expected to start at the end of 2026 and run for around six months.

The device was built by Europe and Japan under the Broader Approach agreement. It is hosted by QST in the Japanese city of Naka. The goal of JT-60SA is to offer the scientific community an opportunity to explore advanced fusion technologies and plasma physics, providing valuable knowledge for ITER and future reactors.

The machine was first started in late 2023 for low-power plasma operations and was switched off shortly after. The shutdown has lasted roughly two years, but this was far from a break period. Around the tokamak hall, assembly teams worked intensively to install and assemble a wide range of new components provided by F4E and QST. "We included diagnostics and cryopumps from Europe, as well as additional heating systems, key to achieving hotter, more powerful plasmas," explains Jerónimo García, JT-60SA Project Leader.

The inside of JT-60SA has also changed, with a new first wall and divertor made with a carbon-based armour. Japanese technicians also mounted a set of in-vessel coils. Among them are two ring-shaped coils, designed to control the plasma position at high speed. They are 8 meters in diameter and were wound directly inside the machine, in a display of high-precision skills.

In fact, the in-vessel coils, connected to Europe's power supplies, are among the first components to be commissioned. The plan starts with the systems that can be operated at room temperature and non-vacuum conditions. The next phase will involve pumping the cryostat and vacuum vessel to create high-vacuum conditions. Finally, the teams will cool down and energise the large magnets, a decisive stage to validate the integration of all new components. The process will also be a chance to test new AI and high-performance computing tools, which could enhance plasma simulations and speed up operations.

F4E will follow the campaign closely, with a team stationed in Naka alongside QST. Their expertise will help operate the advanced technologies now coming online. "The start of commissioning is a big accomplishment for the European and Japanese teams. Our enormous efforts to deliver all components on schedule are coming to fruition," says Valerio Tomarchio, Project Manager for F4E.

The next experimental campaign is attracting wide interest from the international fusion community. The operations will push the machine to unprecedented levels of current, advancing towards long-pulse and steady-state plasma scenarios. Currently, the experiment team is defining the strategy and reviewing over 150 proposals by scientists from Europe, Japan and ITER Organization. In fact, experts from EUROfusion laboratories as well as ITER Organization will be able to take part in the campaign from Naka. F4E's Valerio Tomarchio attended the last meeting of the group: "the expectations from all the community are high, and our motivation to deliver results is just as strong," he concludes.