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A number of models for the critical surface of Nb3 Sn, and in general A15 superconductors, have been developed in the past years. This paper compares the most common parameterizations using consistent notation. Although the parameterizations appear dissimilar at first sight, they are in reality all based on a fit of the normalized pinning force vs. the reduced field, and have similar scalings for the critical field and critical temperature based on a Unified Scaling Law. In this paper we take the various parameterizations as a basis for a generic scaling proposed for the characterization and production follow-up of the ITER Nb3 Sn strands. The accuracy of the scaling is estimated using the fitting residuals on various sets of Ic (B, T, ϵ) data available in literature. We discuss the results, and give our view of the work towards a unified, practical parameterization. [ABSTRACT FROM AUTHOR]

For the superconducting magnet system of the International Thermonuclear Experimental Reactor, ITER, 60 current leads for a total current of more than 2500 kA are needed. The use of High Temperature Superconductor current leads (HTS-CL) will reduce the resultant large refrigerator load considerably. Within the EU Fusion Technology Programme, the Forschungszentrum Karlsruhe and CRPP have developed and built a 70 kA HTS-CL demonstrator optimized for 50 K Helium operation. In 2004-2005, the CL was successfully tested with 50 K as well as 80 K Helium, and finally with LN2. In the meantime, ITER has decided to use HTS-CLs for the magnet system and China has taken the responsibility to provide the sc feeders for ITER including the current leads. In this paper, the performance of a 70 kA HTS-CL in fault conditions will be analysed using the FZK-CRPP demonstrator as a model. In particular, the quench performance and the safety behavior in case of a loss-of-flow accident (LOFA) will be described and an extrapolation of the leads performance in real ITER conditions will be given. Finally the effect of different shunt materials is discussed. [ABSTRACT FROM AUTHOR]

Numerous manufacturers and different strand processing techniques are involved with the production of the Nb3 Sn strand material required for ITER. The superconducting transport properties of brittle Nb3 Sn layers strongly depend on their strain state. Hence, the thermal compression and the substantial transverse load in combination with the key choice for the cabling pattern of the CICCs, will determine their performance. Knowledge of the influence of axial strain, periodic bending, and contact stress on the critical current (Ic) of the used Nb3 Sn strands is inevitable to gain sufficient confidence in an economic design and a stable operation of ITER. We have measured the Ic and n-value of Nb3 Sn strands from various manufacturers in the TARSIS facility, when subjected to spatial periodic bending and contact stress. The Ic and n-values have been determined for applied axial compressive and tensile strain varying from -0.8% up to +0.5%, between T = 4.2 K and 10 K and B = 6 T to 14 T. The strain sensitivity varies appreciably for different strand types. We present a selection of the results obtained so far. [ABSTRACT FROM AUTHOR]