Development of Cu-Nb Reinforced Nb3Sn Wires Appropriate for Large Multi-Stage Stranded Cables With Short-Pitch Twisting and Low-Void Ratio

Abstract

The strength of the conventional Cu/Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires may be too low to be applied to much larger cable-in-conduit (CIC) conductors with the multi-stranded cable structure of short-pitch twisting and low-void ratio applied for ITER-CS conductors. In this study, the Nb-rod-method Cu-Nb reinforced ITER-type Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wire was developed by using a bronze-process not only to realize superior superconducting properties under high electromagnetic stresses but also to mitigate damage to the superconducting wires during the cable manufacturing process. The critical current properties of the Cu-Nb/Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wire were significantly higher performance under both tensile stress and transverse compression stress compared to a conventional non-reinforced Cu/Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wire. The Cu-Nb reinforcement had no detrimental effect on the AC losses of the wire. The trial production of short-pitch sub-cables was conducted, and it was confirmed that the Cu-Nb/Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires can improve the manufacturability of multi-stage stranded cables co-twisted with copper wires.