The JT-60SA experiment, built by Europe and Japan, relies on a mix of advanced technologies to bring plasma to extremely high temperatures. The machine will combine Electron Cyclotron heating and Neutral Beam heating, installed in stages to provide up to 41 MW of power. Technicians in Naka (Japan) are currently adding more of these systems, as JT-60SA gears up for its next operations starting 2026.
Europe is providing parts of the transmission lines of the new Electron Cyclotron systems. They consist of a set of waveguides, metal ducts designed to channel powerful radiofrequency waves in vacuum conditions. The microwaves will travel through them from the gyrotrons, in an adjacent room, to the launchers that inject them into the tokamak. Along the way, they must cross into the hermetically sealed vacuum vessel. Diamond windows, placed within the waveguides, will act as the gateway, letting the waves through while keeping the boundary leak-tight.
Fusion for Energy (F4E) is responsible for providing four window units for JT-60SA. These components have two main parts: a thick synthetic diamond disk and a cooled vacuum casing made of a copper alloy. Buying them separately would have been the conventional approach. Instead, F4E sought a supplier capable of delivering the integrated units. “Providing full systems, rather than isolated hardware, is an opportunity for industry to get more involved and learn a lot about the requirements of fusion reactors,” explains Mario Cavinato, Project Manager at F4E.
In 2023, F4E signed a contract with SAES Rial Vacuum, a subsidiary of SAES. The Italian company worked closely with F4E to refine the design and manufactured the four units in its workshop in the outskirts of Parma. The project was recently completed as the windows arrived in Japan and passed acceptance tests on-site. The bolder procurement strategy proved successful in only two years.
“Our high-quality engineering and production, plus the collaboration with F4E were key to this achievement. The component required expertise in advanced materials, vacuum-compatible mechanical systems and custom solutions, areas in which our company has long-standing experience,” says Enrico Maccallini, Business Manager at SAES.
In the coming months, the QST team, host of the experiment, will test the transmission lines using one of Japan’s megawatt-class gyrotrons. It will be a decisive performance check for the diamond windows, a technology also used in ITER. “Diamond is an irreplaceable material for fusion reactors, as it can transmit up to 1MW of power with very limited losses. Being at the crossroads of vacuum and heating systems, they must offer extraordinary durability and reliability. Therefore, it’s vital to have European suppliers experienced in fabricating the discs, and even the entire components,” describes Luca Novello, Project Manager at F4E.
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