ITER’s superhot plasma is expected to reach 150 million ˚C and thanks to powerful superconducting magnets it will be confined. Toroidal Field (TF) coils will entrap the plasma and keep it away from the walls of the vacuum vessel. Poloidal Field (PF) coils will embrace the TF coils from top to bottom to maintain the plasma’s shape and stability.
The ITER machine will have six PF coils in total. Europe is responsible for five of them and Russia for one. Due to their impressive diameter and weight, four of the European PF coils will be manufactured in a facility located on the ITER site. The remaining one, known as PF 6 in the ITER jargon because it will be the sixth coil, is being manufactured through a collaboration agreement signed in 2013 between Europe’s F4E and China’s ASIPP laboratory. We travelled to the province of Hefei to see how the tooling and testing are coming along.
The sixth PF coil will have a diameter of 10 metres and will weigh approximately 350 tonnes. It will consist of nine pairs of conductors that will form nine double pancakes or 18 individual layers. The nine double pancakes will be stacked to form the PF6 superconducting coil. The ICAS consortium is responsible for the production of the conductors to be used; six conductors have already been delivered to ASIPP together with two copper dummy conductors. It is expected that by the end of the year the rest of the conductors will travel from Europe to China in order to carry on with manufacturing. This idea of working together around the globe is entirely congruent with spirit of the ITER project where teams collaborate in a seamless manner to manufacture components.
ASIPP has already been conducting several trials to qualify the tooling where the conductor will be wound and tested in different conditions. Currently, the engineers are working on the winding of a two by two dummy conductor. In parallel, vacuum chamber leak tests, welding and insulation qualification tests are being carried out. Electrical insulation testing will be conducted on a 2 metre 3x3 (three by three) dummy coil mock-up and a full size joint sample will travel to the Sultan facility for testing at the Swiss Plasma Centre, the only installation worldwide capable of testing the superconductors used in fusion devices like ITER.