STRUCTURE AND HIGH‐FIELD PERFORMANCE OF JELLY ROLL PROCESSED Nb3Sn WIRES USING Sn‐Ta AND Sn‐Ti BASED ALLOY SHEET

Sn‐Ta based alloy buttons of different compositions were prepared by the melt diffusion process among constituent metal powders, and then pressed into plates. Meanwhile Sn‐Ti based alloy plates were sliced from the melt and cast ingot. Resulting Sn‐based alloy plates were rolled into thin sheets. The Sn‐based alloy sheet was laminated with a Nb sheet, and wound into a Jelly Roll (JR) composite. The composite was encased in a sheath, and fabricated into a thin wire followed by the heat treatment. The application of hydrostatic extrusion is useful at the initial stage of the fabrication. The JR wires using Sn‐Ta and Sn‐Ti based alloy sheets show a non‐Cu Jc of ∼250 A/mm2 and ∼150 A/mm2 at 20 T and 22 T, respectively, at 4.2 K. It has been found that the Nb impregnates into the Sn‐based alloy layers during the reaction, and Nb3Sn layers are synthesized by the mutual diffusion between the Nb sheet and the Sn‐based alloy sheet without formation of voids. Sn‐Ti based alloy sheets are attractive due to their eas...