Evaluation of Interface and Cohesion Shear Strength of Mechanical Lap-Joint Between HTS Coated Conductors Intended for Segmented HTS Magnet

Abstract

This study evaluates the mechanical strength, failure mechanism and change in electrical resistance under shear stress of a mechanical lap joint of Rare-Earth Barium Copper Oxide high-temperature superconducting (HTS) tapes using indium as bonding material, which has been proposed for “remountable” (demountable) or segmented HTS magnet in future fusion reactors. Results from tensile shear tests using reinforced REBCO tapes along with an analysis on the failure mode demonstrated that contact conductivity is the critical parameter that defines joint’s shear strength rather than joint pressure. Additionally, it was concluded that change in joint resistance when failure occur is not abrupt and its behavior as joint displaces depends on the failure mode of the joint.

Keywords:

• Superconducting magnet
• high-temperature superconductor
• segmented magnet
• mechanical lap joint

Acknowledgments

This work was supported in part by the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research (C) under Grant 26420849; and by the National Institute for Fusion Science (NIFS) Collaboration Research Program under Grant NIFS16KECF016.