European and Japanese teams have begun the integrated commissioning of the JT-60SA tokamak to test its systems before a six-month round of plasma experiments scheduled for the end of 2026. The JT-60SA is currently the largest operational tokamak in the world. 

The upcoming experimental campaign will push the machine to higher current levels to study long-pulse and steady-state plasma scenarios. To prepare for these operations, the experiment team is reviewing over 150 research proposals submitted by scientists from Europe, Japan, and the ITER Organization.

This commissioning phase follows a two-year shutdown that began shortly after the machine’s initial low-power plasma startup in late 2023. During this period, assembly teams installed new components, including in-vessel coils. 

“Among them are two ring-shaped coils, designed to control the plasma position at high speed,” said Fusion for Energy (F4E). “They are 8 meters in diameter and were wound directly inside the machine, in a display of high-precision skills.”

These coils were wound directly inside the machine to control the plasma position at high speeds. The device was built under the Broader Approach agreement and is hosted by the National Institutes for Quantum Science and Technology (QST) in Japan.

Modifications focused on necessary components

The recent modifications focused on components necessary for achieving higher plasma temperatures and managing increased thermal loads. Teams installed new diagnostics and cryopumps provided by Europe, alongside additional heating systems. 

The interior of the JT-60SA was also updated with a new first wall and a divertor utilizing a carbon-based armour.

“We included diagnostics and cryopumps from Europe, as well as additional heating systems, key to achieving hotter, more powerful plasmas,” stated Jerónimo García, JT-60SA Project Leader.

The integrated commissioning serves as a gradual start-up to verify the main systems of the upgraded machine. Operations began at room temperature and under non-vacuum conditions, focusing on the newly installed in-vessel coils connected to European power supplies.

The next phase requires pumping the cryostat and vacuum vessel to create high-vacuum conditions. Finally, teams will cool down and energize the large superconducting magnets to validate the integration of all new components. 

This process will also test new artificial intelligence and high-performance computing tools designed to improve plasma simulations and operational efficiency.

International collaboration for future objectives

Personnel from F4E are stationed in Naka to work alongside QST, providing technical expertise to help operate the technologies now coming online.

Scientists from EUROfusion laboratories and the ITER Organization will also participate on-site during the campaign to gather data for ITER and future fusion reactors.

Valerio Tomarchio, Project Manager for F4E, stated that the start of commissioning represents the completion of the component delivery schedule. He noted that expectations across the fusion community are high as the teams prepare to deliver the experimental results.

“JT‑60SA will conduct high‑temperature high pressure plasma experiments ahead of ITER, currently under construction in France, and in support of the development of DEMO reactor aimed at demonstrating fusion power generation,” concluded QST.