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Magnet coils added

After the successful lift of tokamak sector module #1 at the end of July, focus has shifted to the next-in-line: sector module #9. 

Each of the tokamak’s nine modules has three main elements—a vacuum vessel sector, two toroidal field coils, and a set of vacuum vessel thermal shield panels. With sector #9 and its thermal shield already in the sector sub-assembly tool, the addition of two toroidal field coils in August means sub-assembly can now be completed. Thermal shield pipes and intercoil structures are now being connected, with the aim of finishing work by the end of November and carrying out the transfer to the tokamak pit at the beginning of December. 

“The work on sector module #9 is particularly important because it is on the critical path,” says Jens Reich, ���ߺ���’s Machine Assembly Program Manager. “We need to move the completed module to the tokamak pit so the next and last sector can take its place in the sector sub-assembly tool. We’re dealing with tight sequences but at this point we are happy with the progress.”

Vacuum vessel thermal shield repairs completed

The program to repair the vacuum vessel thermal shield after microscopic stress-corrosion cracking was discovered in sections of the cooling pipes came to a close this summer. The repair program, launched in 2023 and completed in July 2026, involved removing approximately 11 kilometres of cooling pipework and grinding away one tonne of silver coating to eliminate any remaining risk from chlorine residues. New piping was then manufactured and bent and welded to the shield panels, whose surfaces were polished to mirror-like perfection to restore their ability to reflect thermal radiation.

“It is a remarkable achievement because these repairs represented a first-of-its-kind technical challenge and they were completed by INOX-CVA ahead of schedule,” says Donato Lioce, Tokamak Program Manager. “This is a testament to the excellent teamwork between ���ߺ��� and the Indian industrial ecosystem.”

Bellows system takes shape

During operation, ���ߺ���’s vacuum vessel chamber will undergo vertical and horizontal movement of up to 2.5 centimetres due to thermal expansion and contraction or to relative displacements induced by structural loads. This motion will be accommodated by a system of 93 bellows connecting the vacuum vessel to the cryostat and the cryostat to the Tokamak Building that will allow the machine to “breathe.” The installation began this summer for the rectangular port cell bellows. Five sets are now in place with welding underway on several of them. The welding project that includes the bellows is scheduled to last five years.

“It’s been a long path and a lot of work to get to this stage,” says Elena Rodilla, ���ߺ���’s Technical Responsible Officer for bellows assembly. “The bellows are part of an enormous welding project so starting work now gives us an advantage, as we can take the lessons learned and apply them to optimize the activities that come later.”

Another successful load transfer

Once installed in the pit, a vacuum vessel sector is temporarily supported beneath a radial beam that distributes its weight between the concrete walls and the central column tool. Then, the bracing tools are removed and the load is transferred to a dedicated gravity support—a delicate operation that requires stabilization with rods and struts before the support is raised into position and gradually assumes the component’s weight. Following the first successful operation in May 2026, two more sectors were transferred this summer, including sector #5 in August. With three sectors now resting on their gravity supports, teams have confirmed the configuration is sufficiently stable to begin preparations for vacuum vessel welding.

“What is important is that after the August load transfer of sector #5, the sector just beside it, sector #6, had limited relative movement while the next one, sector #7, remained stable. This shows the process is working as hoped and we can begin to look ahead to the welding phase,” says Sébastien Koczorowski, ���ߺ���’s Deputy Program Manager for machine assembly.

Repaired and prepared for assembly

Vacuum vessel sector #3 has been handed over to assembly teams after a summer of intensive work to complete bevel repairs and other preparatory activities. The component arrived onsite in May and was subsequently rotated into the position required to repair its bevels—the edges that will eventually be welded to neighbouring sectors. 

Alongside the repairs, teams installed instrumentation on the outer shell and welded bosses on the inner shell. Sector #3 is one of the most heavily instrumented vacuum vessel sectors, carrying 120 sensors that will be used to measure magnetic field during machine operation. Its handover also marks the completion of a three-year campaign to repair sector bevels. The component is now destined for the Assembly Hall, where it will be combined with thermal shield panels and toroidal field coils to form a tokamak sector module.

“This is a very good ending to a project that began with a great deal of uncertainty,” said ���ߺ��� project leader Nicolas Sapet. “Thanks to the excellent work of our teams and industrial partners, we have completed repairs that are essential for the project to move forward.”