The clock has been ticking from the moment ITER’s sixth Poloidal Field coil (PF) sailed on 22 March from Hefei (China) to arrive in Cadarache (France). The first of the six magnets that will embrace from top to bottom the super-hot plasma, and manage its shape and stability, was finally heading home.
In June, a delegation headed by Dr. Bernard Bigot, ITER Organization Director-General, welcomed the component on-site marking the start of the final manufacturing tests. The 10-metre magnet, weighing approximately 350 t, was transported to the PF coils factory. In this facility, financed by Europe, F4E and its industrial partners are producing another four of these magnets. Last, but not least, Russia is manufacturing an additional one.
Naturally being the first of the PF coils, the team of engineers was both enthusiastic and extremely cautious because the operations ahead had to be carried out for the first time. After inspecting the coil and receiving the go-ahead for the cold tests, they inserted it in the cryostat, an airtight metallic container connected to equipment cooling down the magnet to extremely low temperatures. Each cryogenic test lasts roughly one month and needs to be repeated. The aim is to test how the magnet responds to some of the ITER operational conditions and conduct global leak tests, electrical and high voltage tests.
From room temperature, the magnet is cooled down to -188 °C (85K) during 15 days. When at this temperature, engineers perform the necessary tests. Once these are over, they bring the component back to room temperature to carry out the final acceptance tests. This process is performed twice to make sure the component withstands the low temperature with no technical issues.
Towards the end of November, the European team announced the successful completion of the final tests. They did it! The story of the magnet, resulting from a collaboration agreement signed in 2013 between Europe’s F4E and China’s ASIPP laboratory, had come to end.
Alessandro Bonito-Oliva, F4E Magnets Programme Manager, shares with us the importance of this significant milestone: “First of all, this is a collective achievement of Europe and China working together side by side to manufacture such a magnet. The team in ASIPP carried out the actual production of the coil, in partnership with F4E, and in close collaboration with PF coils team in ITER Organization. For me, the completion of this component has been an enriching experience. I would like to thank all colleagues who have spent a good part of the last four years following up the work in China. Also, the people who have supervised the final steps in Cadarache— a team of extremely dedicated people who made this important achievement possible. Finally, I would like to conclude by thanking Criotec for supplying the cold test equipment and ASG Superconductors for carrying out the cold and final acceptance tests.”
In case you are wondering where we stand with the remaining European PF coils, there is more good news in the picture. PF 5 is ready to undergo cryotests (nearing the end of manufacturing), PF2 is already impregnated (an advanced stage in the production cycle), and for the biggest coil of all, PF4, measuring 24 m in diameter, the winding process of two of its layers (double pancakes) is already completed.