Metallographic autopsies of full-scale ITER prototype cable-in-conduit conductors after full testing in SULTAN: 1. The mechanical role of copper strands in a CICC
Carlos Sanabria,Peter J. Lee,William L. Starch,Timothy Blum,Arnaud Devred,M. C. Jewell,I. Pong,Nicolai Martovetsky,David C. Larbalestier +8 more
TLDR
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.read more
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ITER Central Solenoid Insert Test Results
Nicolai Martovetsky,Takaaki Isono,Denis Bessette,Yoshikazu Takahashi,Yoshihiko Nunoya,Yoshihiro Nabara,Hidemasa Ozeki,Katsumi Kawano,Toru Saito,Tomone Suwa,Kiyoshi Okuno,Arnaud Devred,Florent Gauthier,Neil Mitchell,Roberto Zanino,Laura Savoldi,Roberto Bonifetto,Marco Breschi,Daniel Ciazynski,W. Reiersen,Alexandre Smirnov,Andrei Khodak,Pierluigi Bruzzone,Igor Rodin,V. Tronza,Alexandre Torre,Sylvie Nicollet,Louis Zani,Alexandre Louzguiti,Jean Luc Duchateau +29 more
TL;DR: In this paper, the ITER central solenoid (CS) was tested in the aperture of the CSMC facility in Naka, Japan, during the first half of 2015.
Journal ArticleDOI
Performance analysis of the toroidal field ITER production conductors
TL;DR: In this article, the results of the tests of the production conductor samples were reported and a detailed comparison is also presented between the performance of the conductors and that of their constituting strands.
Journal ArticleDOI
Metallographic autopsies of full-scale ITER prototype cable-in-conduit conductors after full cyclic testing in SULTAN: II. Significant reduction of strand movement and strand damage in short twist pitch CICCs
TL;DR: In this paper, a detailed strand-to-cable analysis of short and longer 'baseline' twist pitch CICCs was performed and it was found that the use of internal tin (IT) strands in the longer ''baseline'' CICCICC can be beneficial possibly because of their superior stiffness, which better resist strand movement.
Journal ArticleDOI
Metallographic autopsies of full-scale ITER prototype cable-in-conduit conductors after full cyclic testing in SULTAN: III. The importance of strand surface roughness in long twist pitch conductors
TL;DR: In this article, it was shown that the high surface roughness of the VNIINM strand may be responsible for the suppression of the compressive strain enhancement (characteristic of long twist pitch conductors).
Journal ArticleDOI
Strain distributions in superconducting strands with twisted filaments
TL;DR: In this article, a multistage micromechanical model is adopted to characterize the mechanical behavior of the superconducting strand with twisted filaments, and the results for two different structures are compared.
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