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Guests at JT60-SA’s first component ceremony are dwarfed by the huge circular cryostat base. (Credit: EFDA)

Clutching 2.5 metre long spanners, three teams of dignitaries from Europe and Japan simultaneously tighten bolts on the cryostat base of JT60 Super-Advanced, thereby marking a significant milestone—this major component for the Japanese tokamak was designed and manufactured in Spain.

The base is a 250-ton structure made of low-cobalt stainless steel that will support the complete tokamak. Together with an upper section the base will form a vacuum enclosure around the vacuum vessel and coils, allowing them to be cooled to low temperatures required by JT60-SA’s superconducting coils.

“Every project brings to you some new challenges.” says Joaquin Sanchez, head of research unit at CIEMAT (the Spanish signatory to the European Fusion Development Agreement). “On the one side, the need adapt the structure to the existing support basis at the JT60 building, which consists of two concentric rings. On the other side we have to guarantee the geometric stability of the upper part in order to preserve the vacuum tightness of the cryostat. This second requirement was a problem due to the fact that the upper ring of the base has to be in contact with elements at different  temperatures: the TF coil supports, and the vacuum vessel supports.”  However CIEMAT’s team of mechanical engineers was equal to the task, says Dr Sanchez: “We have been working on mechanical analysis & design problems for ITER and DEMO for a long time.”

The cryostat base was completed under the Broader Approach agreement between Japan and Europe. It was constructed by the company IDESA, located in Aviles, in the North of Spain, taking approximately 20 months.