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Abstract

The tests analysis of the ITER model coils put in evidence a performances reduction higher than expected from those of the Nb3Sn strand. For that, a specific program has been recently launched in Europe for investigating the influence of bending strain on the superconducting transport properties of high-performance Nb3Sn strands inside cable-in-conduit conductors subjected to significant Lorentz forces. To this purpose, a dedicated experimental campaign has been initiated on single Nb3Sn strands jacketed inside a 0.2 mm thick stainless-steel (SS) tube in order to be tested in mechanical ITER TF Coils relevant conditions. In this article we describe the procedures investigated at CEA to impose a controlled pure bending strain upon jacketed stands and we present the results of the qualification tests carried out in the ENEA facility to assess the reliability of the chosen method. In practice, the maximum possible bending strain (evaluated at 0.5%) is imposed by transferring the strands from the heat treatment mandrel to a different diameter measuring mandrel. Two solutions are considered: a reduction and an increase in diameter. As well, two options are possible for the jacket removal at strand ends: before or after heat treatment. Each of those options provides benefits or disadvantages regarding easiness, time, cost or damaging risk. In fact the four options are tested to provide an investigation area as large as possible. Specific supports and tooling have been designed and manufactured (SS mandrels, intermediate pieces for bending, external tooling and Cu current leads). Eighteen samples have been characterized through measurement of their critical current in He bath at a magnetic induction from 10 to 14 T. Performances have then been compared between bent and unbent samples for the choice of the best bending method, as well as for the assessment of the dependence of the critical properties of specific Nb3Sn strands on bending strain.

Additional information

Authors: ZANI L, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);CLOEZ H, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);TENA M, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);DELLA CORTE A, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);MUZZI L, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);BESI VETRELLA U, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);CHIARELLI S, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);VOSTNER A, EFDA Close Support Unit, Garching (DE);SALPIETRO E, EFDA Close Support Unit, Garching (DE)
Bibliographic Reference: An oral paper given at: 7th European Conference on Applied Superconductivity Organised by: Vienna University of Technology, Vienna (AT) Held at: Vienna University of Technology, Vienna (AT)
Availability: Available from Association EURATOM-CEA, Département de Recherches sur la Fusion Contrôlée, CEA Cadarache, F-13108 St Paul-Lez-Durance, France Tel: (+33) 4 42 25 70 01; Fax: (+33) 4 42 25 64 21 E-mail: dirdrfc@drfc.cad.cea.fr
Record Number: 200518353 / Last updated on: 2005-10-04
Category: PUBLICATION
Original language: en
Available languages: en
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