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The Central Solenoid (CS), a key component of the ITER Magnet system, using a 45 kA Nb3Sn conductor, includes six identical coils, called modules, to form a solenoid, enclosed inside a structure providing vertical pre-compression and mechanical support. Procurement of the components of the ITER CS is the responsibility of US ITER, the US Domestic Agency (USDA), while the assembly of these components will be carried out by the ITER Organization (IO). Procurement of all the coil modules was awarded in 2011 to General Atomics, while procurement of the structure is split among several manufacturers, using existing equipment, sometimes among the largest ones in the world. Assembly of the ITER CS will require a dedicated area in the ITER Assembly Hall, conventional tooling and special tooling. US ITER is in charge of the procurement of special tooling, while IO is responsible for the procurement of the conventional ones. A detailed assembly procedure is under development at US ITER, in close collaboration with IO and with the support of CEA. Procurement of the special Assembly Tooling is carried out by US ITER and the main part of the first item, the Assembly Platform, was delivered to IO in 2017.

The correction coils (CCs) are a system of 18 superconducting coils composed of top CCs, side CCs, and bottom CCs, and are required to correct asymmetries and reduce magnetic error fields detrimental to the plasma performance of the ITER machine. The CC terminals will be connected with those of the superconducting busbars with twin-box joints. Qualification of the manufacturing procedure of the coil terminals is achieved by performing electrical tests of prototype joints in relevant conditions of current, temperature, and background field (4.5 K, 10 kA, and 2.5 T). In order to control the dc resistance and ac loss in series production, special tooling and manufacturing processes were developed. The main technological steps are conductor dejacketing, nickel removal, and silvering of the cable in the terminal, followed by cable compaction and tungsten inert gas welding of the termination box. To this end, two joint samples were manufactured in 2015 and 2016. The performance of the joint samples was verified before and after 1000 electromagnetic cycles. The qualification tests were carried out in the SULTAN facility and ASIPP facility. The test results show the dc resistance below 5- $\text{n}\Omega $ criterion and ac losses below 7 J/cycle.

The superconducting coils of the ITER magnet system have hundreds of electrical lap joints interconnecting superconducting cables. The joints operate in a magnetic field of up to 4 T, field derivatives of 0.5 T/s, and currents up to 70 kA. The acceptance tests for the toroidal field (TF), poloidal field (PF), and correction coil (CC) coils will be performed at 77 K, before they are assembled in the pit. Hence there will be no possibility to measure the resistance of the joints in the superconducting state before the whole magnet system is enclosed in the Tokamak cryostat. In addition, no reliable nondestructive method has been found to spot the joints with a failure at room temperature. Therefore, the production of the joints relies on the strict adhesion to established robust manufacturing procedures during the qualification phase. As additional quality monitoring, a periodic test of the joint samples manufactured in parallel with a coil fabrication is foreseen to control the reproducibility of the joint electrical performance. In order to qualify the manufacturing procedures, to establish a series production tools and worker teams, a comprehensive qualification program has been set up for manufacturers of the coils in Russia (Poloidal Coil 1, PF1), China (PF6, feeders, CC), Japan (TF), Europe (TF and PF), and USA (Central Solenoid, CS). This program includes a set of mockups manufactured according to the process to be used for the coils and submitted to different tests. They include mechanical testing of materials, electrical tests of full size joint samples, destructive microscopic examination of the joint mockups, and mechanical testing of the full size joint mockups. All tests are carried out in specialized laboratories qualified for this type of work. This paper describes the main items of the qualification program, the tests performed, and the acceptance criteria. The test results are reported and compared to the criteria.

The ITER central solenoid (CS) components are currently being manufactured. This Nb3Sn superconducting magnet will provide the magnetic flux swing required to induce up to 15 MA as plasma current. It includes six identical coils, called modules, stacked on top of each other to form a solenoid, enclosed inside a structure split into nine subsets, to provide vertical precompression and mechanical support. High mechanical stresses in materials and high voltages call for the use of structural materials with high strength and toughness and high dielectric strength insulating materials, respectively. The pulsed operation imposes materials with high fatigue strength at cryogenic temperatures. Unlike for the structure, where large existing manufacturing tools were usable, the modules required the construction of a dedicated manufacturing line. A comprehensive qualification programme is performed at the manufacturers before applying procedures for the production of the CS components. The main characteristics of the CS components, their manufacturing routes and the different elements of the qualification programme are described. The overall plan for the manufacture is reported. The status of the first series production components manufactured is presented as well as the planned delivery schedule to the ITER site.

The system of correction coils (CC) is a component of the ITER magnet system, required to correct toroidal asymmetries and reduce error magnetic fields detrimental for physical processes in the plasma. It includes 18 coils, inserted in between toroidal field coils and poloidal field coils and split into 3 sets of 6 coils each: bottom correction coils (BCC), side correction coils (SCC), and top correction coils (TCC). BCC and TCC are planar coils, whereas SCC are wound on a cylinder. All CC coils are wound using a 10 kA NbTi cable-in-conduit conductor and are manufactured by ASIPP laboratory (Institute of Plasma Physics, Chinese Academy of Sciences), under the responsibility of ITER China. A manufacturing line was installed in 2013 at ASIPP in a dedicated workshop for the construction of the CC. In order to qualify the manufacturing procedures, a comprehensive qualification program has been set up. This program includes a set of mock-ups, manufactured according to the process to be used for the coils and submitted to different tests. These qualification items are winding, insulation and vacuum pressure impregnation, helium inlet/outlet, terminal joints, case material, filler material between winding-pack and case, case assembly, and terminal service box. Qualification of conductor winding, He inlet/outlet manufacture, winding-pack turn and ground insulation installation and impregnation, case material, winding-pack-case filler material is achieved. This included mechanical testing of materials at room and cryogenic temperature in specialized testing laboratories and high-voltage tests performed at the CC workshop. Joint qualification, relying on electrical tests of joints in a dedicated test facility, is nearly complete. Remaining qualification items are case assembly, winding-pack insertion into case, and case closure welding. Manufacture of the first coil started in 2015 and its winding-pack is near completion.

The central solenoid (CS) is a key component of the ITER magnet system to provide the magnetic flux swing required to drive induced plasma current up to 15 MA. The manufacture of its different subcomponents has now started, following completion of the design analyses and achievement of the qualification of the manufacturing procedures. A comprehensive set of analyses has been produced to demonstrate that the CS final design meets all requirements. This includes in particular structural analyses carried out with different finite-element models and addressing normal and fault conditions. Following the Final Design Review, held in November 2013, and the subsequent design modifications, the analyses were updated for consistency with the final design details and provide evidence that the Magnet Structural Design Criteria are fully met. Before starting any manufacturing activity of a CS component, a corresponding dedicated qualification program has been carried out. This includes manufacture of mockups using the real manufacturing tools to be tested in relevant conditions. Acceptance criteria have been established for materials and components, winding including joints, cooling inlets and outlets, insulation, precompression, and support structure elements.

The manufacturing line of the ITER Correction Coils (CC) at ASIPP in Hefei (China) was completed in 2013 and the manufacturing line of the ITER Central Solenoid (CS) modules is under installation at General Atomic premises in Poway (USA). In both cases, before starting production of the first coils, qualification of the manufacturing procedures is achieved by the construction of a set of mock-ups and prototypes to demonstrate that design requirements defined by the ITER Organization are effectively met. For each qualification item, the corresponding mock-ups are presented with the tests to be performed and the related acceptance criteria. The first qualification results are discussed.

The ITER correction coil (CC) case reinforces the winding packs against the electromagnetic loads, minimizes stresses and deformations to the winding pack. The cases are made of high strength and high toughness austenitic stainless steel (316LN) hot rolled heavy plate and have a thickness of 20 mm. Considering the small cross-section and large dimensions of the case, deformation of the case when welding becomes a challenge in the case manufacturing. Therefore, laser welding was developed as the main welding technology for manufacturing. In this paper, multi-pass laser welding technology is used, the laser weldability of a 20 mm thick 316LN austenitic stainless steel plate is studied and the microstructure of the welded joint is analyzed. The welding experiment used an YLS-6000 fiber laser (IPG) and weld filler of 316LMn to match the base metal was used. The result shows that the welded joint has no obvious surface and internal defects based on the optimized welding parameters. The weld joint have a fine austenite microstructure and display columnar dendrites and cellular grains with strong directional characteristics. No apparent heat affected zone is observed and approximately 2 μm an austenite microstructure of the fusion line is clearly presented.

The Final Design of the Central Solenoid (CS) of the ITER Magnet system is currently being completed by the US ITER Domestic Agency (USDA) and the manufacturing line of the coil under installation at the supplier's premises in the USA. The Central Solenoid includes 6 identical Nb3Sn coil modules independently powered and enclosed inside a precompression structure preventing their separation. The CS structure includes 9 subsets, made of Nitronic 50 high strength austenitic stainless steel, evenly distributed around the stack of the 6 modules.