Understanding Properties and Fabrication Processes of Superconducting Nb3Sn Wires

Abstract

The fabrication of multifilamentary Nb 3 Sn wires was started by the discovery of the bronze process, a solid-state diffusion process, to form filamentary A15 structure compounds in 1969-1970. Through a number of improvements and modifications of the original process in the ensuing years, these wires are now indispensable components for the construction of magnets, producing very high magnetic fields for nuclear magnetic resonance spectroscopy, magnetic fusion experiments, and future high-energy particle accelerators. A comprehensive review article summarizes the state of the knowledge up to 1980 on the formation mechanisms and the super-conducting properties of the A15 compounds that were fabricated by this process. Since 1980, significant advances have been made in the basic understanding of the factors controlling the growth processes, and basic superconducting properties of the bronze-processed Nb 3 Sn. In particular, significant progress has been made in understanding the effects of alloying on these properties and mechanisms for flux-line pinning in the compound. Furthermore, for the practical usage of these wires, tremendous progress in the critical-current densities of multifilamentary Nb 3 Sn wires has been made over the last several years. This chapter reviews these new findings about Nb 3 Sn by the solid-state diffusion process and the critical-current densities of the state-of-the-art multifilamentary Nb 3 Sn wires.