We are promoting the R&D of ultrafine superconducting wires with a much smaller diameter than human hair. In principle, the bending strain decreases with decreasing the wire diameter, therefore, we may expect that the brittle compound or brittle oxide superconducting wires become flexible through the wire diameter reduction. This is a big advantage of applying the React and Wind method for magnet fabrication, and it would minimize the fabrication cost and improve the magnetic field quality. So far, we have already reported for the bronze-processed Nb3Sn wire with 20-50 microns in diameter [1], the Jelly roll processed Nb3Al wires with 17-50 microns in diameter [2], and the powder-in-tube processed MgB2 wire with 15-50 microns in diameter [3]. Recently, we demonstrated a fabrication of the Silver sheathed Bi2212 mono-core wire with 50 microns in diameter. SC filament size is about 10 microns. In addition, we have fabricated a 50-micron Nb47Ti multifilamentary wire that had 55 Nb47Ti filaments as well. A filament size is about 4 microns. NbTi is well known as a ductile alloy, but NbTi wire is still generally a little hard. However, the present fine NbTi multifilamentary wire shows an extremely flexible and very easy to handle compared to general ones. In this paper, recent progress of the development of NbTi, Nb3Sn, Nb3Al, MgB2, and Bi2212 ultrafine superconducting wires and some of those flexible cables will be reported.
[1] Akihiro Kikuchi, Yasuo Iijima, Masaru Yamamoto, Masatoshi Kawano and Masato Otsubo, “The Bronze Processed Nb3Sn Ultra-Thin Superconducting Wires”, IEEE Transaction on Applied Superconductivity, Vol. 32, No. 4, 6000104 (2022) DOI: 10.1109/TASC.2022.3145286.
[2] Akihiro Kikuchi, Yasuo Iijima, Shigeki Nimori, Masaru Yamamoto, Masahiko Kawano, Motoyoshi Kimura, Jun Nagamatsu, Masato Otsubo, Ataru Ichinose and Kiyosumi Tsuchiya, “Ultra-Fine Nb3Al Mono-Core Wires and Cables”, IEEE Transaction on Applied Superconductivity, Vol. 31, No. 5, 6000105 (2021) DOI: 10.1109/TASC.2021.3057323.
[3] Akihiro Kikuchi, Yasuo Iijima, Hiroaki Kumakura, Masaru Yamamoto, Masatoshi Kawano, and Masato Otsubo, “Development of the Ultrafine MgB2 Superconducting Wires and Flexible Cables”, IEEE Transaction on Applied Superconductivity, Vol. 34, No. 3 6200104 (2024) DOI: 10.1109/TASC.2023.3335881
A part of this study was financially supported by the mid-term research project at NIMS, JSPS KAKENHI Grant Number 19K05088, 21H04477, 23K25130, 24H00234, a project, JPNP16006, commissioned by the New Energy and Industrial Technology Development Organization (NEDO), and U.S.-Japan Science and Technology Cooperation Program in High Energy Physics operated by KEK in Japan and DOE in U.S.
Keywords:fine superconducting wire, flexible cable, Nb3Al, Nb3Sn, MgB2, Bi2212, NbTi