The ITER magnet procurement is now well underway. The magnet systems consist of 4 superconducting coil sets (toroidal field (TF), poloidal field (PF), central solenoid (CS) and correction coils (CC)) which use both NbTi and -based conductors. The magnets sit at the core of the ITER machine and are tightly integrated with each other and the main vacuum vessel. The total weight of the system is about 10000 t, of which about 500 t are strands and 250 t, NbTi. The reaction of the magnetic forces is a delicate balance that requires tight control of tolerances and the use of high-strength, fatigue-resistance steel forgings. Integration and support of the coils and their supplies, while maintaining the necessary tolerances and clearance gaps, have been completed in steps, the last being the inclusion of the feeder systems. Twenty-one procurement agreements have now been signed with 6 of the ITER Domestic Agencies for all of the magnets together with the supporting feeder subsystems. All of them except one (for the CS coils) are so-called Build to Print agreements where the IO provides the detailed design including full three-dimensional CAD models. The production of the first components is underway (about 175 t of strand was finished by July 2011) and manufacturing prototypes of TF coil components are being completed. The paper will present a design overview and the manufacturing status.
A new kind of superconductor, using the cable-in-conduit concept, is emerging, mainly in the context of fusion activity. At present no large Nb3Sn magnet in the world is operating using this concept. The difficulty of this technology, which has now been studied for 20 years, is that it requires major advances in several interconnected new fields, such as handling a large number (1000) of superconducting strands, high current conductors (50 kA), forced flow cryogenics, Nb3Sn technology, low loss conductors in pulsed operation, high current connections and high voltage insulation (10 kV), as well as demonstration of its economical and industrial feasibility. CEA has been very much involved, during the past ten years, in this development, which took place in the framework of the NET and ITER technological programmes. One major milestone was reached in 1998-1999 with the successful tests by Euratom-CEA of three full size conductor and connection samples in the SULTAN facility in Switzerland.
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