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Mechanical and electromagnetic transverse load effects on superconducting niobium-tin performance

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dc.contributor.advisor Joseph V. Minervini and Jeffrey P. Freidberg. en_US Chiesa, Luisa en_US
dc.contributor.other Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering. en_US 2010-03-25T15:22:36Z 2010-03-25T15:22:36Z 2009 en_US 2009 en_US
dc.description Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2009. en_US
dc.description Cataloged from PDF version of thesis. en_US
dc.description Includes bibliographical references (p. 233-238). en_US
dc.description.abstract Cable-in-Conduit Conductor is the typical geometry for the conductor employed in superconducting magnets for fusion applications. Once energized, the magnets produce an enormous electromagnetic force and very large transverse loads are applied against the strands. This large force results in a degradation of the performance of the superconducting magnets. In this thesis work transverse load experiments on sub-sized cables, have been designed to study the mechanical and electrical transverse load effects on superconducting cables. Two devices to apply external mechanical loads to a cable have been developed and several different size cables have been tested simulating the International Thermonuclear Experimental Reactor (ITER) Lorentz stress conditions. The first device was designed to use a circular turn sample of a 36-strand cable. Four samples were successfully tested with this device and significant degradations of the critical current due to the external transverse loads have been measured. However, all samples showed unexpectedly large initial degradations that made an analysis of transverse load effects of the samples difficult. The second device was developed for a hairpin configuration. Three different size cables of a single strand, a triplet and a 45-strand cable were systematically tested using this method. This hairpin sample device has successfully operated and provided very reliable experimental data. The experimental results were difficult to explain by existing theories. en_US
dc.description.abstract (cont.) A new model based on contact mechanics concepts has been developed to determine the number of contacts and the effective contact pressure among the strands in a cable. The model was used to analyze and accurately calculate the displacements of a cable under transverse mechanical load, and it has evaluated the effective contact pressures between strands for the first time. The new model can explain the Lorentz force and contact pressure distribution effect on the critical current degradation of the tested samples. The 3-strand data and their critical current behavior as a function of the effective contact pressure were used to predict the test behavior of a 45-strand cable. It was also used to simulate the critical current degradations of various cables including ITER full size cables. The model has predicted an initial degradation of 20% for an ITER TF cable of 1152 strands at 68 kA operational current caused by the transverse Lorentz load effect only. Parametric studies of the model have indicated that the initial degradation could be reduced by shortening the twist pitch length of the initial stages of a full size cable or by mechanically supporting the last stage bundles of the cable. This thesis work shows for the first time, that the transverse Lorentz load effect, which is inherent in the CICC design, contributes a significant fraction of the degradation of a large Nb3Sn superconducting cable. The model quantifies the degradation and this information could be used in better estimating the appropriate margin requirements in magnet design. en_US
dc.description.statementofresponsibility by Luisa Chiesa. en_US
dc.format.extent 238 p. en_US
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
dc.rights M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. en_US
dc.rights.uri en_US
dc.subject Nuclear Science and Engineering. en_US
dc.title Mechanical and electromagnetic transverse load effects on superconducting niobium-tin performance en_US
dc.type Thesis en_US Ph.D. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering. en_US
dc.identifier.oclc 540814158 en_US

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