Continuous Formation of Ta Barrier and Cu Sheath of Nb3Sn Subelements

70576 The Nb3Sn superconductor is an enabling technology that will determine the future of high-energy hadron colliders for high energy physics research. Unfortunately, the cost of the Nb3Sn superconductor is ten times that of other superconductors. The high cost comes not from materials, but from the necessity to fabricate the multi-filament wire in small batches. Batch size is limited by the process for wrapping a Ta diffusion barrier and a copper sheath around the wire subelement, which must be completed before the subelement is drawn to its finished dimension. This project will develop a continuous process for forming the Ta barrier and the Cu sheath onto the wire subelement after drawing, thereby enabling the preparation of large restack billets (twenty times present size) for final wire drawing. In Phase I, three approaches to the formation of the Ta barrier will be developed and evaluated: spiral wrap with lap, formation of continuous tube and TIG welding the butt seam, and formation of continuous tube and laser welding the butt seam. The Cu sheath will be applied in the same continuous tube forming process. All formations will be evaluated for weld integrity, strain and embrittlement, and survival after subsequent drawing operations. Commercial Applications and Other Benefits as described by the awardee: Although, Nb3Sn is the only superconducting alloy that can be used to produce very high magnetic field strength, its current cost (~$1,000/kg) is prohibitive. This technology could reduce the cost by a factor of ~2, making it practical for the high-field magnets used in high-energy particle accelerators, magnetic confinement fusion, NMR spectroscopy in structural biology, MRI imaging systems, and magnetic levitation transportation.