22 research outputs found

    Qualification of a 40 Ka Nb3sn Superconducting Conductor for Net/Iter Coils

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    A 40 kA Nb3Sn conductor, designed to operate with forced helium flow at 4.5 K was tested in the SULTAN III facility, (I(max) = 50kA, B(max) (background) = 11T). The test sample and the operating conditions of the test facility are described. Two measurement procedures were used to investigate the conductor behaviour near the critical value : Sample current or temperature are increased up to the quench with background field and temperature or current reciprocally kept at steady state. The critical current of the conductor could be measured with the same criterion as for the basic strand (0.1muV/cm). The obtained results are discussed and compared with the basic strand performances. In addition some results on the thermohydraulic behaviour of the CIC conductor are presented

    Using the HELIOS facility for assessment of bundle-jacket thermal coupling in a CICC

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    CHATS on Applied Superconductivity Workshop (CHAT-AS), Dept Elect, Elect & Informat Engn, Bologna, ITALY, SEP 14-16, 2015International audienceIn a Cable In Conduit Conductor (CICC) cooled by forced circulation of supercritical helium, the heat exchange in the bundle region can play a significant role for conductor safe operation, while remaining a quite uncertain parameter. Heat exchange between bundle and jacket depends on the relative contributions of convective heat transfer due to the helium flow inside the bundle and of thermal resistance due to the wrappings between the cable and the conduit. In order to qualify this thermal coupling at realistic operating conditions, a dedicated experiment on a 1.2 m sample of ITER Toroidal Field (TF) dummy conductor was designed and performed in the HELIOS test facility at CEA Grenoble. Several methods were envisaged, and the choice was made to assess bundle jacket heat transfer coefficient by measuring the temperature of a solid copper cylinder inserted over the conductor jacket and submitted to heat deposition on its outer surface. The mock-up was manufactured and tested in spring 2015. Bundle jacket heat transfer coefficient was found in the range 300-500 W m(-2) K-1. Results analysis suggests that the order of magnitude of convective heat transfer coefficient inside bundle is closer to Colburn-Reynolds analogy than to Dittus-Boelter correlation, and that bundle jacket thermal coupling is mainly limited by thermal resistance due to wrappings. A model based on an equivalent layer of stagnant helium between wraps and jacket was proposed and showed a good consistency with the experiment, with relevant values for the helium layer thickness. (C) 2016 Elsevier Ltd. All rights reserved