[WB1] Nb₃Sn, MgB₂, Bi-system

9:45 AM - 10:15 AM JST(12:45 AM - 1:15 AM UTC)

[WB1-01-INV] High-Jc Nb₃Sn ultrafine superconducting wire fabricated by the Jelly-Roll process

*Akihiro Kikuchi¹ (1. National Institute for Materials Science (Japan))

Keywords:

ultrafine wire,Nb3Sn,Jelly roll process,critical current density

We are strongly 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, such as Nb₃Sn, superconducting wire becomes flexible through the wire diameter reduction. This is a large advantage that can apply 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 successfully fabricated a kilometer-scale Nb₃Sn ultrafine wire through the bronze process [1]. To increase the critical current density of Nb₃Sn ultrafine wires, we tried to fabricate the precursor wires through the Jelly-roll process in this study. Nb and Cu thin foils are overlapped on the pure Sn rod, and then this laminated composite is inserted into the Cu tube with the Nb foil diffusion barrier. The rotary swaging was applied at the beginning of area reduction, and then conventional die-drawing was applied. Eventually, we fabricated the ultrafine Nb₃Sn wires with 50 microns in diameter through the Jelly-roll process. It could be confirmed that a relatively high non-Cu critical current density of 1,000 A/mm² at 4.2 K and 14 T could be obtained after the heat treatment at 650^oC-700^oC.