Prototype Multifilamentary Nb3Sn Superconductor for the High Field Test Facility at Lawrence Livermore Laboratory

Abstract

Earlier work in fabricating [1–3] and testing [4–6] monolithic copper-stabilized multifllamentary Nb3Sn superconductors and in soldering embossed stabilizing copper to superconductors [7] has led to the current design [8] for a superconductor for the High Field Test Facility at Lawrence Livermore Laboratory (see Fig. 1 and Table I). This cryostable conductor is designed for an operating current of 5 kA at 12 T and 4.2 K. It consists of a superconducting core sandwiched between and soldered to stabilizing copper strips. The superconducting core is manufactured by a two-stage extrusion process and consists of a bronze-niobium-Nb3Sn region surrounded by 65 vol.% OFHC copper; the bronze and the copper regions are separated by a tantalum barrier. Transverse grooves embossed in the stabilizing copper strips provide internal cooling channels and additional surface area in contact with liquid helium to improve the cryostability of the assembled conductor. Approximately 75 vol.% of the completed conductor consists of stabilized OFHC copper.