The ITER magnet system will be the largest and most integrated superconducting magnet system ever built.
Ten thousand tonnes of magnets, with a combined stored magnetic energy of 51 Gigajoules (GJ), will produce the magnetic fields that will initiate, confine, shape and control the ITER plasma. Manufactured from niobium-tin (Nb3Sn) or niobium-titanium (Nb-Ti), the magnets become superconducting when cooled with supercritical helium in the range of 4 Kelvin (-269 °C).
Superconducting magnets are able to carry higher current and produce stronger magnetic field than conventional counterparts. They also consume less power and are cheaper to operate ... making superconducting magnet technology the only option for ITER's huge magnet systems.
ITER uses high-performance, internally cooled superconductors called "cable-in-conduit conductors," in which bundled superconducting strands—mixed with copper—are cabled together and contained in a structural steel jacket.
For the most technically challenging raw material—the niobium-tin (Nb3Sn) superconducting strands used in ITER's toroidal field and central solenoid magnet systems—500 metric tons of strand (more than 100,000 km) were produced by nine suppliers in a procurement effort that lasted from 2008 to 2015. This large-scale industrial effort demanded a ramp-up of global production capacity from 15 metric tons/year to 100 metric tons/year, as well as the introduction of three new strand suppliers.