The first of the six Poloidal Field (PF) coils has been transported to the Tokamak pit at the International Thermonuclear Experimental Reactor (Iter) under construction in France, Iter said on 26 April. The 350-tonne coil, 11.2 metres in diameter, is being transported by a crane that can carry a load of 750 tonnes. Once all the Toroidal Field (TF) coils are inserted, this PF coil will be installed in its final position.

The PF6 coil is the second smallest of the six ring-shaped magnets (11.5 metres in diameter) but by far the heaviest. The coil was delivered to ITER in June 2020 after completing its long journey from China and was the first to be cold-tested on site. It comprises nine double-pancake-shaped coils and a series of supporting accessories, and winds up 13.5 kilometres of a niobium–titanium cable. It is the bottom-most of the six circular magnets surrounding the vacuum chamber and the first to be inserted in the tokamak pit.

It took roughly 30 minutes to lift the component to a height of 25 metres and approximately eight hours to complete the operation to move it from the Assembly Hall into the pit, placing it on its temporary support structures. For a few years, the coil will sit at the bottom of the pit on temporary supports before being raised to its final position towards the end of the assembly process when all 18 toroidal field coils and nine vacuum vessel sectors have been installed.

More than 130 people were involved in producing the magnet during the last eight years. Europe and China worked side-by-side to manufacture this first-of-a-kind superconductive magnet, which will control the shape and stability of the Iter plasma. Its production took place in ASIPP (Institute of Plasma Physics of the Chinese Academy of Sciences), while the cold tests and final checks were performed by F4E, and its contractors, on-site at the Poloidal Fields coil factory built and run by Europe.

Alessandro Bonito-Oliva, F4E Magnets Programme Manager, said: “It’s a milestone of symbolic importance for the parties involved in this magnet because it paves the way for the assembly and insertion of the rest of the Iter coils.”

The International Thermonuclear Experimental Reactor (ITER) agreement was signed in 2006 by Euratom, the USA, Russia, Japan, China, South Korea and India. Construction of the international experimental tokamak nuclear fusion reactor is funded mainly by the European Union (45.6%) with the remainder shared equally by China, India, Japan, Korea, Russia and the USA (9.1% each). However, in practice, the members deliver little monetary contribution to the project, instead providing ‘in-kind’ contributions of components, systems or buildings. First plasma is scheduled for December 2025, with the full operation estimated for 2035.