The production of superconducting cables for ITER’s large and powerful Toroidal Field (TF) coils is making remarkable progress: as of today, 330 tons of strands made out of Nb_SUBSCRIPT_3_/SUBSCRIPT_Sn, a special alloy made of niobium and tin, have been produced in factories in China, Europe, Japan, Korea, Russia and the United States. In the pre-ITER world, global production was 15 tons a year. „The current production status represents 75% of the total required TF strands”, reports Arnaud Devred, Section Leader for ITER’s Superconducting Systems. "Out of these strands, conductors for six out of the machine’s 18 TF coils have been produced."
The 18 TF coils will produce a magnetic field around the ITER torus helping to confine and control the plasma inside. The coils are designed to achieve operation at magnetic fields up to 13 Tesla. They are made of cable-in-conduit superconductors, in which a bundle of superconducting strands is cabled together and contained in a structural jacket. Unit lengths of theses cables — measuring 760 metres or 415 metres depending on their position within the coil – are then spooled into a D-shaped double spiral called a „double pancake” giving the structure the characteristic shape of ITER’s TF coils.
As of today, a total of 30 760-m Unit Lengths and 13 415-m Unit Lengths have been manufactured by the procuring agencies in Japan, Korea, Russia and Europe which adds up to the material required for six of the 18 TF coils.
„Quality tests”, says Devred, „are currently underway to confirm that these unit lengths can be accepted for coil winding”.