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Journal ArticleDOI

Influence of Wire Parameters on Critical Current Versus Strain Characteristics of Bronze Processed ${\hbox {Nb}}_{3}{\hbox {Sn}}$ Superconducting Wires

TL;DR: In this article, the influence of various parameters of wires such as filament diameter, barrier materials, barrier thickness, heat treatment pattern and Ti addition on critical current (Ic) versus intrinsic strain eν(-1.0% <; eν <; +0.1%) characteristics was investigated.
Abstract: In order to develop bronze processed Nb3Sn wire for the ITER CS coil operating under higher compressive strain, the influence of various parameters of wires such as filament diameter, barrier materials, barrier thickness, heat treatment pattern and Ti addition on critical current (Ic) versus intrinsic strain eν(-1.0% <; eν <; +0.1%) characteristics was investigated. The change of these parameters brought significant changes to superconducting properties such as Ic and n-value. In spite of different wire parameters, the strain dependency of normalized Ic was almost the same, except that a Ti addition affects the upper critical field Bc2. This result suggests that assuming the same Ti-addition level, Nb3Sn wire with higher performance at a certain eν would exhibit higher performance at any eν in the compressive regime. Based on the result, bronze processed Nb3Sn wires with non-Cu critical current density more than 1100 A/mm2 at 12 T, 4.2 K, zero applied strain have been successfully developed for the CS coil.
Citations
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Journal ArticleDOI
TL;DR: The ITER project is one of the most sophisticated superconducting magnet systems ever designed, with an enormous stored energy of 51?GJ as mentioned in this paper, taking the relay of the large Hadron collider (LHC) at CERN.
Abstract: 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.

160 citations

Journal ArticleDOI
TL;DR: 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 as discussed by the authors.
Abstract: 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. After explaining the in-kind procurement sharing of the various conductor types among the six ITER Domestic Agencies (DA) involved: China, Europe, Japan, South Korea, Russia, and the United States, we detail the technical requirements defined by the ITER International Fusion Energy Organization (IO), and we present a brief status of ongoing productions. The most advanced production is that for the TF conductors, where all six DAs have qualified suppliers and about 50% of the required strands have been produced and registered into the web-based conductor database developed by the IO.

158 citations


Cites background from "Influence of Wire Parameters on Cri..."

  • ...2 K and 12 T [50], [51], exhibit high current sharing temperatures, , but does not achieve stabilization after 10000 cycles to high Lorentz loads....

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Journal ArticleDOI
TL;DR: In this article, the authors report the results of the on-going ITER central solenoid conductor performance qualification and present the options under consideration for the different modules constituting the CS coil.
Abstract: The ITER central solenoid (CS) must be capable of driving inductively 30 000 15 MA plasma pulses with a burn duration of 400 s. This implies that during the lifetime of the machine, the CS, comprised of six independently powered coil modules, will have to sustain severe and repeated electromagnetic cycles to high current and field conditions. The design of the CS calls for the use of cable-in-conduit conductors made up of and pure copper strands, assembled in a five-stage, rope-type cable around a central cooling spiral that is inserted into a circle-in-square jacket made up of a special grade of high manganese stainless steel. Since cable-in-conduit conductors are known to exhibit electromagnetic cycling degradation, prior to the launch of production, the conductor design and potential suppliers must be qualified through the successful testing of full-size conductor samples. These tests are carried out at the SULTAN test facility. In this paper, we report the results of the on-going CS conductor performance qualification and we present the options under consideration for the different modules constituting the CS coil.

53 citations


Cites background from "Influence of Wire Parameters on Cri..."

  • ...2 K and 12 T on ITER barrel [20], exhibits much higher TCS (the best leg [solid green] stays above 6....

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Journal ArticleDOI
TL;DR: In this article, a post-mortem metallographic analysis of two Nb3Sn-based superconductor-based CS CICC prototypes is presented, which exhibited some rate of irreversible performance degradation during cycling.
Abstract: Cables made with Nb3Sn-based superconductor strands will provide the 13 T maximum peak magnetic field of the ITER central solenoid (CS) coils and they must survive up to 60 000 electromagnetic cycles. Accordingly, prototype designs of CS cable-in-conduit-conductors (CICC) were electromagnetically tested over multiple magnetic field cycles and warm-up-cool-down scenarios in the SULTAN facility at CRPP. We report here a post-mortem metallographic analysis of two CS CICC prototypes which exhibited some rate of irreversible performance degradation during cycling. The standard ITER CS CICC cable design uses a combination of superconducting and Cu strands, and because the Lorentz force on the strand is proportional to the transport current in the strand, removing the copper strands (while increasing the Cu:SC ratio of the superconducting strands) was proposed as one way of reducing the strand load. In this study we compare the two alternative CICCs, with and without Cu strands, keeping in mind that the degradation after the SULTAN test was lower for the CICC without Cu strands. The post-mortem metallographic evaluation revealed that the overall strand transverse movement was 20% lower in the CICC without Cu strands and that the tensile filament fractures found were less, both indications of an overall reduction in high tensile strain regions. It was interesting to see that the Cu strands in the mixed cable design (with higher degradation) helped reduce the contact stresses on the high pressure side of the CICC, but in either case, the strain reduction mechanisms were not enough to suppress cyclic degradation. Advantages and disadvantages of each conductor design are discussed here aimed to understand the sources of the degradation.

22 citations

Journal ArticleDOI
TL;DR: In this article, a distributed tin (DT) method was used to improve the performance of a high performance Nb� 3�sn wire via a distributed diffusion condition and the ternary additive elements.
Abstract: We have developed a high-performance (high-J C ) Nb 3 Sn wire via a distributed tin (DT) method. Non-Cu J C of 1100 A/mm 2 at 16 T, 4.2 K has been achieved by improving the Sn diffusion and optimizing the Ti content. With the future circular collider magnet planned by European Organization for Nuclear Research (CERN), the target of non-Cu J C is set to 1500 A/mm 2 at 4.2 K, 16 T. For this target, we have chosen the DT method, which is a type of internal Sn method, and because it has no limitation of Sn solubility, higher J C can be expected. This paper finds that further improvement of J C can be realized by controlling the Sn diffusion condition and the ternary additive elements. By setting the Sn diffusion distance to lower than 48 μm, the Nb 3 Sn composition in multi-Nb modules becomes uniform and fine. In addition, by controlling the ternary element content (Ti) for improving the characteristics of the middle magnetic field, it is possible to achieve high J C at 16 T.

12 citations


Cites background or methods from "Influence of Wire Parameters on Cri..."

  • ...2915307 Among these, the bronze-route method has been developed for many years in our group [2]....

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  • ...nance magnet [1], fusion magnets [2], and accelerator magnets [3]....

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References
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Journal ArticleDOI
TL;DR: In this paper, it was shown that the peak in Fp scales as [Hc2(T)]2.5 if the temperature is changed; the maximum value of Fp occurred at the same value of reduced field regardless of temperature.
Abstract: For all hard high‐field superconductors examined to date, there is a maximum in the pinning force density Fp as a function of the reduced magnetic field h. Fietz and Webb first demonstrated in dilute Nb alloys that the peak in Fp scales as [Hc2(T)]2.5 if the temperature is changed; the maximum value of Fp occurred at the same value of reduced field regardless of temperature. Recent data on the temperature dependence of pinning in Nb3Sn, Nb–25% Zr and a Nb–Ti alloy, which exhibits the ``peak effect'', are analyzed to show that similar scaling laws are obeyed by these materials. All presently available evidence indicates however that the reduced field hp at which the maximum Fp occurs, as well as the height and shape of this maximum, can be altered by metallurgical treatment. Apparently weak pinning defects, or widely spaced ones, produce a small peak in Fp(h) at high h whereas strong closely spaced pins produce a large peak in Fp(h) at low h without producing much change in Fp(h) at high h. A model which p...

1,104 citations


"Influence of Wire Parameters on Cri..." refers background in this paper

  • ...The pinning force density in Nb Sn wires can be described by the scaling relation [4]...

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Journal ArticleDOI
TL;DR: In this paper, a technique for deriving the critical current distribution from the resistive critical current transition has been described, which has been applied to NbTi and Nb 3 Sn composites of different types.

149 citations


"Influence of Wire Parameters on Cri..." refers background in this paper

  • ...The -value in multifilamentary superconducting wire is generally considered to originate from local critical current distribution arising from combination of the inhomogeneous cross-sectional area of filaments (extrinsic factor) and local flux pinning properties (intrinsic factor) [13], [14]....

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Journal ArticleDOI
TL;DR: In this article, an improved model for the strain dependence of the superconducting properties of Nb{sub 3}Sn was proposed, based on the three dimensional strain tensor and derived in terms of the first, second and third invariants, and improved an existing model that only included the second invariant.
Abstract: We propose an improved model for the strain dependence of the superconducting properties of Nb{sub 3}Sn. The model is based on the three dimensional strain tensor and derived in terms of the first, second and third invariants, and improves an existing model that only includes the second invariant. The axial form of the new model accurately accounts for the experimentally observed dependence of the effective upper critical magnetic field (H*{sub c2}) on axial strain, i.e. a quasi-parabolic strain dependence, asymmetry, and an upturn at large compressive axial strain. An accurate model that accounts for the three dimensional nature of strain is important for scaling relations for the critical current that are used to model magnet performance based on wire measurements.

50 citations


"Influence of Wire Parameters on Cri..." refers methods in this paper

  • ...7 shows the strain dependences of for GTSM-I measured at 12 T and 14 T, and calculated from the scaling model [8]....

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  • ...The strain dependence of for GTSM-I was analysed by using a recent scaling formalism [8] that includes an upward curvature in for high compressive strains....

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  • ...Strain dependence of critical current for GTSM-I measured at 12 T/14 T, and calculated from the model [8] using parameters in Table III....

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Journal ArticleDOI
TL;DR: In this paper, the relationship between the n-value and critical current (IC) was investigated for six different ITER-candidate Nb3Sn wires characterized as a function of magnetic field (B≤28 T), temperature (4.2 K ≤T≤12 K), and intrinsic axial strain (−1%≤eI≤+0.4%).
Abstract: The relationship between the n-value and critical current (IC) is investigated for six different ITER-candidate Nb3Sn wires characterized as a function of magnetic field (B≤28 T), temperature (4.2 K ≤T≤12 K) and intrinsic axial strain (−1%≤eI≤+0.4%). For the five wires exhibiting intrinsic behaviour, n(IC) can be parameterized by a modified power law of the form n = 1+rICs, where s is a constant with a value of 0.41 ± 0.03. The parameter r decreases as the magnitude of the intrinsic strain increases and is a relatively weak function of temperature. For one of the wires, the n-value saturates at high critical currents (low magnetic fields), characteristic of extrinsic filament nonuniformities.

50 citations

Journal ArticleDOI
TL;DR: In this paper, the resistive transition of a superconductor with a Gaussian distribution of critical currents is analyzed and exact relations for the voltage-current characteristic and the resistor transition index (n value) are developed.
Abstract: The resistive transition of a superconductor with a Gaussian distribution of critical currents is analyzed and exact relations for the voltage‐current characteristic and the resistive transition index (n value) in such a superconductor are developed. Excellent fits are found to the experimental transitions in two very different types of superconductor; a Nb‐Ti monofilament and a Bi2Sr2Ca2Cu3O10 tape.

48 citations


"Influence of Wire Parameters on Cri..." refers background in this paper

  • ...The -value in multifilamentary superconducting wire is generally considered to originate from local critical current distribution arising from combination of the inhomogeneous cross-sectional area of filaments (extrinsic factor) and local flux pinning properties (intrinsic factor) [13], [14]....

    [...]