React-and-Wind Nb₃Sn Superconducting Wires for Practical Use

― Progress and prospects on the development of elemental technologies ―

Abstract

The development of elemental technologies is required for the practical use of React-and-Wind (R&W)-processed Nb₃Sn coil applications. The critical currents (I_c) of a Nb₃Sn strand under several common strains are able to be estimated using both characteristics of the I_c-magnetic field-temperature-axial strain (I_c-B-T-ε) property and considerations of the bending strain effects. However, designing the I_c of a large-scale Nb₃Sn conductor becomes much more difficult because the Nb₃Sn wires are under extremely complicated strains. Recently, Nb-rod-method Cu-Nb reinforced Nb₃Sn wires were successfully developed using the bronze process. The performance of the Cu-Nb/Nb₃Sn Rutherford cables was improved by utilizing the pre-bending process. It is expected that pre-bent Cu-Nb/Nb₃Sn wires will be very useful for R&W-processed Nb₃Sn coil. This paper describes the progress and prospects for developing elemental technologies used in R&W Nb₃Sn wires.