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An ultrafine A15 composite wires with a diameter of 30 to 50 mm were developed by the National Institute for Materials Science (NIMS) to enable the use of R&W technology for the fabrication of superconducting magnets. Nb3Al wires were fabricated using the Jelly-rolled method, and Nb/Al composite monofilament Nb3Al superconducting wires and Nb3Al multi-stranded wires were successfully fabricated. In this Jelly-roll process, pure Nb and Al foils were prepared as starting materials, and those foils were tightly overlapped around a pure core material. On the other hand, ultrafine Nb3Sn wires were fabricated by the bronze process. The starting billet of Nb3Sn wire was 19 Nb rods. Furthermore, it was composed of a bronze alloy matrix containing Cu, Sn, and Ti, and a Nb diffusion barrier. A Cu stabilizer was placed on the outermost layer. Our goal is to develop flexible, ultrafine Nb3Sn and Nb3Al wires that can be used in the react & wind method, and we plan to use these high-performance ultrafine wires to develop superconducting applications operated in cryocoolers. We have in mind not only DC but also AC applications for superconducting applications. In this paper, single and multi-stranded ultrafine Nb3Al and Nb3Sn superconducting sample wires with different diameters were prepared to evaluate the critical properties and AC loss characteristics. The critical current and n value of sample wires are measured by current sweep, constant current, and pulse current methods using conduction cooling by a 4K cryocooler. The measured temperature (4.5 K -14 K) dependence of the critical current and the AC loss characteristics of fabricated ultrafine Nb3Al and Nb3Sn superconducting sample wires will be presented.

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Keyword: AC transport current losses, critical properties, cryocooler system, ultrafine Nb3Al wire, ultrafine Nb3Sn wire

Date published: 2024-12-09

Publisher: Institute of Electrical and Electronics Engineers (IEEE)

Journal:

• IEEE Transactions on Applied Superconductivity (ISSN: 10518223) vol. 35 issue. 5 p. 1-4

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Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.5588

First published URL: https://doi.org/10.1109/tasc.2024.3513936

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Updated at: 2025-07-15 12:30:25 +0900

Published on MDR: 2025-07-15 12:17:06 +0900