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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. [ABSTRACT FROM AUTHOR]

The ITER poloidal field (PF) magnet system is composed of six circular coils, consisting of winding packs (WP) made up from a stack of double pancakes (DP) wound of NbTi cable-inconduit superconductor. The largest coil has a diameter of 24 m, the heaviest weighs 400 ton, and they are designed to produce a total magnetic energy of 4 Giga Joules at a maximum magnetic field of 6 T for 30 000 inductively driven plasma pulses. The ends of the conductors (in the outer-most coil turns) of the top and bottom DP are coil terminations, which are connected to the superconducting bus bars of the feeders, these conductors exit being one of the weakest structural points of the coils. The main function of the tail is to reinforce this region by linking the outer-most termination to the last-but-one turn, thus guaranteeing the transfer of longitudinal tensile force, through an electrically insulated mechanical connection featuring a fiberglass strap. The PF coils are subject to electromagnetic forces induced from their own magnetic field and the magnetic field generated from the rest of the ITER magnet system, the thermal stresses during cooldown and warmup cycles and dc/ac high-voltage levels. Therefore, the tail components shall withstand these conditions while staying within the geometrical boundaries imposed by the conductor dimensions, in order to avoid any protrusion on the WP surface. This paper aims to describe the adopted solution throughout its lifecycle, from the design validation, by the electromagnetic and mechanical analyses, to the design qualification of the set of imposed requirements through the manufacture, and testing of a set of full-size mock-ups. [ABSTRACT FROM AUTHOR]

The ITER poloidal field magnet system consists of 6 pulsed coils with a diameter ranging from 8 m to 24 m and a weight of up to 400 t. The coils are made of independent modules connected to each other by joints. [ABSTRACT FROM PUBLISHER]

Since it is practically impossible to remove the Poloidal Field (PF) coils from the assembled ITER (International Thermonuclear Experimental Reactor) tokamak without major interruption in operation, the design of these coils shall provide their high reliability under high voltage operation. The design of the coil insulation relies on a separation of functions: mechanical function of the load transmission, performed by glass-fiber impregnated with epoxy resin on one side, and the independent electrical barrier made of polyimide tapes on the other side. Numerical simulation has shown that the maximum electrical field in the coil is lower than 4 kV/mm, which is taken as the design criterion for the PF insulator system. In case of a single insulation failure in a coil, its functionality can be recovered by installing a so-called jumper to by-pass the faulty double pancake. The design of the jumpers and their installation procedure are described. [ABSTRACT FROM AUTHOR]

Recent design changes to the ITER Poloidal Field (PF) coils and PF conductor layout have been implemented to give a greater operational window for low li (self-inductance) plasmas during burn, extend the operating window for plasmas with currents above 15 MA, and improve the plasma vertical stability control. In addition, the PF and CS (Central Solenoid) operating window has been updated leading to higher currents and peak fields in some of the PF coils. Altogether, this results in higher heat generation in the PF conductors due to AC losses. To confirm that the range of heat loads is acceptable for the PF conductors, a time-dependent thermo-hydraulic analysis of the PF coils has been performed with a model based on the GANDALF code. The deposited heat due to AC losses in the conductors, thermal radiation, thermal conduction, and nuclear heating are given as input data. The results show a moderate impact on minimum temperature margin of the PF conductors during the baseline scenario, stemming from the design modifications. [ABSTRACT FROM AUTHOR]

IRFU/SACM at CEA/Saclay has undertaken an R&D program on Nb3Sn aimed at designing, building and testing a 1-m-long, 56-mm-single-aperture quadrupole magnet model. Model design is based on the design of LHC arc quadrupole magnets, without iron yoke. It is expected to reach a nominal field gradient of 211 T/m at 11,870 A. The main goal of the program is to learn about Nb3Sn technology and evaluate fabrication techniques relative to the use of this superconductor. Coils are manufactured by the so called "wind, react and impregnate" technique. Laminated, austenitic steel collars are locked around the coil assembly by means of keys in order to restrain Lorentz forces. Coil manufacturing and magnet assembly have been achieved in 2007. Cold mass assembly is under work. Warm field measurements are carried out at each step of magnet and cold mass assembly. After a brief recall of the conceptual design, the paper reviews the manufacturing of the coils and of the magnet assembly and presents the results of warm magnetic field measurements. [ABSTRACT FROM AUTHOR]