The JT-60SA tokamak is the largest nuclear fusion facility in operation. This research reactor was inaugurated on December 1st 2023 in Naka, Japan. Designed and funded by the European Union and Japan to study hydrogen fusion, the research will run in parallel with the ITER project in France. Magnetic confinement of the plasma is provided by superconducting magnets cooled by a helium cryogenic plant capable to extract 9 kW at 4.5 K.

To ensure that the magnets are maintained at a temperature of 4.5 K, teams from the IRIG designed a cryogenic plant, manufactured by the French company Air Liquide and installed in Japan. Following the successful commissioning of the cryogenic system, the scientists contributed to the testing of the superconducting magnets during the first fusion experiments, which led to the creation of a plasma current with an intensity of 1 MA.
During these tests, rapid discharges of the current circulating in the magnets were carried out to test the magnet system’s ability to trip. Rapid discharge of the current dissipates heat, which increases the pressure in the cryogenic loop that cools the magnets and risks causing helium to escape into warm storage. Beforehand, the researchers used the Simcryogenics simulation tool to model the loop, to ensure that the rise in pressure would remain below a safety threshold and thus prevent the helium exhaust.

The simulation tools designed by the IRIG were used to test the behaviour of the cooling loop for the superconducting magnets in the JT-60SA tokamak. These calculations ensured the safe commissioning of the fusion reactor.