Magnetization measurements on ITER Nb3Sn CICC and strands subjected to irreversible degradation

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Abstract

We investigated the impact of irreversible strain changes and filament cracking on the AC losses of several Nb3Sn strands and a full-size ITER cable-in-conduit-conductor (CICC). The aim is to evaluate whether the presence of filament cracks in full-size ITER Nb3Sn CICC (after cyclic loading) can be detected without extracting strands from the cable for microscopic observation. The strand AC loss was measured in a magnetometer in virgin condition and after an applied periodic and cyclic bending strain. The filament fracture pattern was determined afterwards by SEM analysis. We found a significant decrease of the hysteresis loss in ITER bronze and internal-tin type strands with increasing filament fracture density. However, in the experimental comparison between a highly degraded section of a full-size ITER TF CICC sample subjected to high electromagnetic load and a section taken from the low magnetic field zone, no clear difference is observed in hysteresis loss but only in coupling loss. The first measurement on a full-size ITER CICC sample indicates that the amount of cracks is at least restricted to an average crack density of 0.05 cracks/filament/mm but a higher accuracy of the CICC AC loss measurement is required for better precision. Further work is required to evaluate whether the observed degradation of the current sharing temperature and n-value is essentially attributed to strand deformation and associated periodic strain variations or filament cracks.
Original languageEnglish
Article number075004
Number of pages9
JournalSuperconductor science and technology
Volume25
Issue number7
DOIs
Publication statusPublished - 2012

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strands
cables
Magnetization
filaments
Cables
conductors
degradation
cracks
Degradation
magnetization
Cracks
alternating current
Hysteresis
hysteresis
Bending (deformation)
Tin
Bronze
bronzes
Magnetometers
magnetometers

Cite this

@article{a6dd848e5d8447e895e435bed65662e5,
title = "Magnetization measurements on ITER Nb3Sn CICC and strands subjected to irreversible degradation",
abstract = "We investigated the impact of irreversible strain changes and filament cracking on the AC losses of several Nb3Sn strands and a full-size ITER cable-in-conduit-conductor (CICC). The aim is to evaluate whether the presence of filament cracks in full-size ITER Nb3Sn CICC (after cyclic loading) can be detected without extracting strands from the cable for microscopic observation. The strand AC loss was measured in a magnetometer in virgin condition and after an applied periodic and cyclic bending strain. The filament fracture pattern was determined afterwards by SEM analysis. We found a significant decrease of the hysteresis loss in ITER bronze and internal-tin type strands with increasing filament fracture density. However, in the experimental comparison between a highly degraded section of a full-size ITER TF CICC sample subjected to high electromagnetic load and a section taken from the low magnetic field zone, no clear difference is observed in hysteresis loss but only in coupling loss. The first measurement on a full-size ITER CICC sample indicates that the amount of cracks is at least restricted to an average crack density of 0.05 cracks/filament/mm but a higher accuracy of the CICC AC loss measurement is required for better precision. Further work is required to evaluate whether the observed degradation of the current sharing temperature and n-value is essentially attributed to strand deformation and associated periodic strain variations or filament cracks.",
author = "Chao Zhou and D.S. Bink and Bo Liu and Y. Miyoshi and Wessel, {Wilhelm A.J.} and Krooshoop, {Hendrikus J.G.} and Arend Nijhuis",
year = "2012",
doi = "10.1088/0953-2048/25/7/075004",
language = "English",
volume = "25",
journal = "Superconductor science and technology",
issn = "0953-2048",
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}

Magnetization measurements on ITER Nb3Sn CICC and strands subjected to irreversible degradation. / Zhou, Chao; Bink, D.S.; Liu, Bo; Miyoshi, Y.; Wessel, Wilhelm A.J.; Krooshoop, Hendrikus J.G.; Nijhuis, Arend.

In: Superconductor science and technology, Vol. 25, No. 7, 075004, 2012.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Magnetization measurements on ITER Nb3Sn CICC and strands subjected to irreversible degradation

AU - Zhou, Chao

AU - Bink, D.S.

AU - Liu, Bo

AU - Miyoshi, Y.

AU - Wessel, Wilhelm A.J.

AU - Krooshoop, Hendrikus J.G.

AU - Nijhuis, Arend

PY - 2012

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N2 - We investigated the impact of irreversible strain changes and filament cracking on the AC losses of several Nb3Sn strands and a full-size ITER cable-in-conduit-conductor (CICC). The aim is to evaluate whether the presence of filament cracks in full-size ITER Nb3Sn CICC (after cyclic loading) can be detected without extracting strands from the cable for microscopic observation. The strand AC loss was measured in a magnetometer in virgin condition and after an applied periodic and cyclic bending strain. The filament fracture pattern was determined afterwards by SEM analysis. We found a significant decrease of the hysteresis loss in ITER bronze and internal-tin type strands with increasing filament fracture density. However, in the experimental comparison between a highly degraded section of a full-size ITER TF CICC sample subjected to high electromagnetic load and a section taken from the low magnetic field zone, no clear difference is observed in hysteresis loss but only in coupling loss. The first measurement on a full-size ITER CICC sample indicates that the amount of cracks is at least restricted to an average crack density of 0.05 cracks/filament/mm but a higher accuracy of the CICC AC loss measurement is required for better precision. Further work is required to evaluate whether the observed degradation of the current sharing temperature and n-value is essentially attributed to strand deformation and associated periodic strain variations or filament cracks.

AB - We investigated the impact of irreversible strain changes and filament cracking on the AC losses of several Nb3Sn strands and a full-size ITER cable-in-conduit-conductor (CICC). The aim is to evaluate whether the presence of filament cracks in full-size ITER Nb3Sn CICC (after cyclic loading) can be detected without extracting strands from the cable for microscopic observation. The strand AC loss was measured in a magnetometer in virgin condition and after an applied periodic and cyclic bending strain. The filament fracture pattern was determined afterwards by SEM analysis. We found a significant decrease of the hysteresis loss in ITER bronze and internal-tin type strands with increasing filament fracture density. However, in the experimental comparison between a highly degraded section of a full-size ITER TF CICC sample subjected to high electromagnetic load and a section taken from the low magnetic field zone, no clear difference is observed in hysteresis loss but only in coupling loss. The first measurement on a full-size ITER CICC sample indicates that the amount of cracks is at least restricted to an average crack density of 0.05 cracks/filament/mm but a higher accuracy of the CICC AC loss measurement is required for better precision. Further work is required to evaluate whether the observed degradation of the current sharing temperature and n-value is essentially attributed to strand deformation and associated periodic strain variations or filament cracks.

U2 - 10.1088/0953-2048/25/7/075004

DO - 10.1088/0953-2048/25/7/075004

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JO - Superconductor science and technology

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