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The ITER In-Vessel Coils (IVCs) are crucial components of the Tokamak fusion reactor. They are located within the vacuum vessel (VV) behind the blanket shield modules and are responsible for compensating for fast perturbations of the plasma. There are a total of 176 joints used to connect the IVCs, feeders and feedthrough. The joint structure consists of a central copper conductor, a mineral (MgO) insulation layer, and an outer stainless-steel jacket. Given the inaccessibility of the IVCs once the blanket modules are installed, the highest level of quality is required for the joints. One key item is the welding of the copper conductor which has to be done inside the VV. To address the high thermal conductivity of copper conductor and the challenging constraints working inside the VV, a preheating method by the arc of the welding head has been developed. Macro- and micro-structure examination were performed on the welding cross sections, and tensile tests were carried out to check the strength of the copper joint, which demonstrated that arc preheating does not have a significant impact on the heat-affected zone. After more than 40 welding attempts and several design updates, the copper joint has been successfully developed and can be repeatedly and successfully welded.

Four samples of full size ITER toroidal field (TF) conductor are manufactured according to the conductor layout defined by ITER. The manufacturing procedures and the dc test under relevant load conditions are described.

Two European ITER toroidal field (TF) prototype samples are prepared, assembled and tested in SULTAN. The ITER specifications are fulfilled by both samples, with outstanding results for the conductor with longer twist pitches.

High-energy physics (HEP) type [Nb.sub.3]Sn strands with a [J.sub.c] ~ 2400 A/[mm.sup.2] are applied to a steel Cable-in-Conduit Conductors (CICC). The high-field (HF) conductor qualification process, the design modifications and the analysis of the test results are discussed.

An alternative solution is described by using a relatively thin walled rectangular conductor without an additional reinforcing structure. The conductor and the layout of the winding, the magnetic, thermo-hydraulic and mechanical behavior of the ITER toroidal field (TF) coils are analyzed.

A 12.5 T superconducting dipole magnet (European DIPOle, EDIPO) is designed by EFDA, which is procured within the framework of the European Fusion Programme in order to be installed in CRPP-PSI. The magnet parameters are described together with the key supporting electromagnetic, mechanical and thermal analyses.

The Poloidal Field Coil 6 (PF6) coil design based on [Nb.sub.3]Sn superconductor, which has delivered the required temperature margin as well as the higher performance capability, is examined. The design analysis has discussed the performance parameters of the coil including the hot spot temperature and quench propagation.

The test results of the new generation of ITER TF conductor samples in SULTAN are discussed. The homogenization of performance toward the upper range has provided an effective margin for the operation of the ITER coil system.

The effect of strain on the critical current of [Nb.sub.3]Sn cable-in-conduit-conductors (CICC) is examined. Findings reveal the impact of transversal stresses to a current carrying cable exposed to an external magnetic field.

Two conductor short samples were tested for examining the use of high current [Nb.sub.3]Sn strands in International Thermonuclear Experimental Reactor (ITER) cable-in-conduit conductors (CICC). Findings revealed the strong degradation of the CICC performance in comparison to the strand for all conductors.

The study explains various pure bending strain experiments conducted on several jacketed [Nb.sub.3]Sn strands for International Thermonuclear Experimental Reactor (ITER).

The tests of the Toroidal Field Model Coil (TFMC) are completed in the TOSKA facility of Forschungszentrun Karlsruhe. The TFMC isolated strand is characterized at different applied uniaxial strain, and preliminary results indicate a stronger reduction of carrying capacity compared to the extrapolation from summers scaling used in the analysis.

Reporting on the angular and field dependence of the critical transport current densities at various temperatures of Y-123 coated conductors deposited by PLD on a newly developed Ni-alloy with improved mechanical properties is discussed. It shows that the irreversible properties of the specimens are not limited by the pinning structure of the super conducting film, but mainly by substrate impurities.

Coated conductors were deposited using high rate pulsed laser deposition methods on ion beam assisted deposition layers of yttria-stabilized zirconia on steel substrates, to study superconducting layers.

Studying the transport properties of a-axis oriented YBCO films grown by a self-template layer procedure is strongly improved by using a YCaBCO cap layer is discussed. In contrast, when the magnetic field is oriented perpendicular to the plane of the substrate, strong pinning takes place due to the presence of 90 degree grain boundaries.

The ITER vertical stabilization coil system is designed to provide fast plasma stabilization in all scenarios with elongated plasma cross-section. It consists of two water-cooled coils located in upper and lower portions of the vacuum vessel (VV), with feedthroughs responsible for the transfer of electricity and cooling water across the vacuum boundary of VV. Depending on location, the feedthroughs can be divided into upper port feedthroughs (UPR feedthroughs) and lower port feedthroughs (LWR feedthroughs), each family sharing the same design. Both designs are subject to demanding operation scheme, a severe working environment and the presence of interfacing components, which impose important thermal, electromagnetic and seismic loads on the components. In particular, the LWR feedthrough, object of present paper, is more impacted by seismic loads due to the more flexible structure compared to the UPR feedthrough. During the worst seismic event, it is subjected to a vertical acceleration of 28.8 m s−2, acting on an effective mass of 249.9 kg at its first order modal mode. Furthermore, the current circulating in the conductor of the LWR feedthrough, impose significant linear forces, up to 27.7 kN m−1 during normal operation and 30.3 kN m−1 during categories I & II abnormal plasma events, respectively. Finally, the effect of differential thermal expansions of interfacing structures imposes a relative displacement between the supports up to 32.9 mm in X (radial) direction and up to 14.67 mm in Z (vertical) direction, during baking. Being part of the vacuum boundary, the feedthrough must assure confinement function under all normal and accidental loading conditions, with proper structural integrity assessment by applying analysis approach and design criteria foreseen by the applicable nuclear codes. The paper details the load types and categories, the analysis methodologies, the structural design criteria, and the assessment results in views of static stress and fatigue for the LWR feedthrough. This study could be a comprehensive reference for the structural integrity assessment of other similar components in fusion devices. [ABSTRACT FROM AUTHOR]

The inter- and intra-granular critical current densities were determined for different types of coated conductors as well as mono- and multi-filamentary (BiPb)[sub 2]Sr[sub 2]Ca[sub 2]Cu[sub 3]Ox tapes. Either the inter- or the intra-granular critical current density was changed systematically by bending the tapes or by neutron irradiation, respectively. Thus, we are able to assess these two critical current densities, even in samples with very good grain connectivity. [ABSTRACT FROM AUTHOR]

Inter- and intragranular critical current densities in high temperature super conducting tapes and coated conductors were determined. Two critical current densities could be assessed even in samples with very good grain connectivity as either inter- or intragranular critical current density was changed by bending the tapes or by neutron irradiation.

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 nondestructivemethod 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. [ABSTRACT FROM AUTHOR]

This paper summarizes the work on the manufacturing and testing of conductor samples for ITER poloidal field 1&6 coils. The work was carried out by the IO and multiple institutions in the EU, Switzerland and Russia. Five samples were manufactured and tested in the SULTAN test facility. Analyses of dc performances, ac, and mechanical losses test results have been performed. All measurements were carried out before and after cyclic mechanical load created by the electromagnetic forces. DC test results of all samples tested demonstrated that the conductor performances are not affected by cycling mechanical load and meet the required value of current-sharing temperature $T_{{\rm{cs}}}\geq $ 5.8 K at magnetic field $B_{{{\max}}}\,= $ 6.4 T and operating current $I_{{\rm{op}}}\,= $ 48 kA. Measurements of the ac and mechanical losses were performed by gas flow calorimetric method. AC loss measurements were carried out at different operating currents and background magnetic fields. AC loss of tested samples showed no change under cycling mechanical load, but showed a correlation of ac loss versus background magnetic field. Mechanical loss, as had been expected, decreased significantly after first ten cycles then reaches a stabile value. The value of mechanical loss even in virgin condition does not affect workability of a magnet. [ABSTRACT FROM PUBLISHER]

Taking the relay of the large Hadron collider (LHC) at CERN, ITER has become the largest project in applied superconductivity. In addition to its technical complexity, ITER is also a management challenge as it relies on an unprecedented collaboration of seven partners, representing more than half of the world population, who provide 90% of the components as in-kind contributions. The ITER magnet system is one of the most sophisticated superconducting magnet systems ever designed, with an enormous stored energy of 51 GJ. It involves six of the ITER partners. The coils are wound from cable-in-conduit conductors (CICCs) made up of superconducting and copper strands assembled into a multistage cable, inserted into a conduit of butt-welded austenitic steel tubes. The conductors for the toroidal field (TF) and central solenoid (CS) coils require about 600 t of Nb3Sn strands while the poloidal field (PF) and correction coil (CC) and busbar conductors need around 275 t of Nb–Ti strands. The required amount of Nb3Sn strands far exceeds pre-existing industrial capacity and has called for a significant worldwide production scale up. The TF conductors are the first ITER components to be mass produced and are more than 50% complete. During its life time, the CS coil will have to sustain several tens of thousands of electromagnetic (EM) cycles to high current and field conditions, way beyond anything a large Nb3Sn coil has ever experienced. Following a comprehensive R&D program, a technical solution has been found for the CS conductor, which ensures stable performance versus EM and thermal cycling. Productions of PF, CC and busbar conductors are also underway. After an introduction to the ITER project and magnet system, we describe the ITER conductor procurements and the quality assurance/quality control programs that have been implemented to ensure production uniformity across numerous suppliers. Then, we provide examples of technical challenges that have been encountered and we present the status of ITER conductor production worldwide. [ABSTRACT FROM AUTHOR]

Construction of the ITER magnet systems has been started at the end of 2007 following the signature of the first procurement arrangements (PA) for the toroidal field (TF) conductors. Six ITER members are involved in the share of the ITER magnet components and, to date, eighteen PA between the ITER Organization and six domestic agencies have been signed. Substantial progress towards full-scale construction has been achieved with the placement of the first large manufacturing contracts, the production of several tens of tons of advanced Nb3Sn and NbTi strand, and the set-up of large cabling and jacketing facilities. The detailed design of the coils and support structures has also been finalized. The qualification of the fabrication processes for the TF coils and poloidal field (PF) coils has been initiated. The detailed design of the central solenoid (CS) coils is being developed. The design of the correction coils (CCs) with their support structures has been finalized, as well as for the TF gravity supports and clamps of the PF coils. The manufacture of prototypes of the feeder lines and current leads has been started, while ITER is in charge of the procurement of the required magnet instrumentation. This paper provides a progress report on the ITER magnet construction as per December 2010. [ABSTRACT FROM AUTHOR]

The differences in thermal contraction of the composite materials in a cable in conduit conductor (CICC) for the International Thermonuclear Experimental Reactor (ITER), in combination with electromagnetic charging, cause axial, transverse contact and bending strains in the Nb3Sn filaments. These local loads cause distributed strain alterations, reducing the superconducting transport properties. The sensitivity of ITER strands to different strain loads is experimentally explored with dedicated probes. The starting point of the characterization is measurement of the critical current under axial compressive and tensile strain, determining the strain sensitivity and the irreversibility limit corresponding to the initiation of cracks in the Nb3Sn filaments for axial strain. The influence of spatial periodic bending and contact load is evaluated by using a wavelength of 5 mm. The strand axial tensile stress-strain characteristic is measured for comparison of the axial stiffness of the strands. Cyclic loading is applied for transverse loads following the evolution of the critical current, n-value and deformation. This involves a component representing a permanent (plastic) change and as well as a factor revealing reversible (elastic) behavior as a function of the applied load. The experimental results enable discrimination in performance reduction per specific load type and per strand type, which is in general different for each manufacturer involved. Metallographic filament fracture studies are compared to electromagnetic and mechanical load test results. A detailed multifilament strand model is applied to analyze the quantitative impact of strain sensitivity, intrastrand resistances and filament crack density on the performance reduction of strands and full-size ITER CICCs. Although a full-size conductor test is used for qualification of a strand manufacturer, the results presented here are part of the ITER strand verification program. In this paper, we present an overview of the results and comparisons. [ABSTRACT FROM AUTHOR]

The performance of the toroidal field (TF) magnet conductors for the ITER machine are qualified by a short full-size sample (4 m) current sharing temperature (Tcs) test in the SULTAN facility at CRPP in Villigen, Switzerland, using the operating current of 68 kA and the design peak field of 11.8 T. Several samples, including at least one from each of the six ITER Domestic Agencies participating in TF conductor fabrication (China, European Union, Japan, Russia, South Korea and the United States), have been qualified by the ITER Organization after achieving Tcs values of 6.0-6.9 K, after 700-1000 electromagnetic cycles. These Tcs values exceed the ITER specification and enabled the industrial production of these long-lead items for the ITER tokamak to begin in each Domestic Agency. Some of these samples did not pass the qualification test. In this paper, we summarize the performance of the qualified samples, analyze the effect of strand performance on conductor performance, and discuss the details of the test results. [ABSTRACT FROM AUTHOR]

We analyzed the ITER TFEU5 cable-in-conduit conductor (CICC) after the full SULTAN conductor qualification test in order to explore whether Lorentz force induced strand movement inside the CICC produces any fracture of the brittle Nb3Sn filaments. Metallographic image analysis was used to quantify the change in void fraction of each sub-cable (petal); strands move in the direction of the Lorentz force, increasing the void space on the low force side of the CICC and producing a densification on the high force side. Adjacent strand counting shows that local increases in void space result in lower local strand-strand support. Extensive metallographic sampling unambiguously confirms that Nb3Sn filament fracture occurred in the TFEU5 CICC, but the filament fracture was highly localized to strand sections with high local curvature (likely produced during cabling, where strands are pivoted around each other). More than 95% of the straighter strand sections were free of filament cracks, while less than 60% of the bent strand sections were crack free. The high concentration of filament fractures on the tensile side of the strand-strand pivot points indicates that these pivot points are responsible for the vast majority of filament fracture. Much lower crack densities were observed in CICC sections extracted from a lower, gradient-field region of the SULTAN-tested cable. We conclude that localized filament fracture is induced by high Lorentz forces during SULTAN testing of this prototype toroidal field CICC and that the strand sections with the most damage are located at the petal corners of the high field zone. [ABSTRACT FROM AUTHOR]

The ITER magnet coils are wound from Cable-In-Conduit Conductors (CICC) made up of superconducting and copper strands assembled into a multistage, rope-type cable inserted into a conduit of butt-welded austenitic steel tubes. The conductors for the Toroidal Field (TF) and Central Solenoid (CS) coils require about 500 tons of Nb3Sn strands while the Poloidal Field (PF) and Correction Coil (CC) conductors need around 250 tons of Nb-Ti strands. The required amount of Nb3Sn strands far exceeds pre-existing industrial capacity and calls for a significant worldwide production scale up. [ABSTRACT FROM PUBLISHER]

The influence of the expected Lorentz loading and time dependent operating conditions of a magnet on the conductor AC loss is experimentally simulated by a cryogenic cable press that applies cyclic mechanical loading. A series of ITER conductor tests with the press have commenced and we report on the results from the first set of two TF conductors, which have the option-II cabling scheme but consist of Nb3Sn strands from different manufacturers. With the press, we apply a transverse load of 578 kN/m and the load cycle is repeated up to 30,000 times. As a function of load cycles, we measure the cable mechanical stiffness, interstrand contact resistances, and the coupling loss. When compared with a previously measured option-II type conductor, the present conductors have higher initial losses. However, they showed greater cable displacement and larger increase in contact resistance with load cycles. This is due to the lower cable stiffness thought to be related to the lower axial strand stiffness, resulting in greater cable displacement than the previous cable. Consequently, the two conductors tested here have lower losses already within the first few cycles. [ABSTRACT FROM PUBLISHER]