Evaluation of Bending Properties of REBCO Spiral Conductors

Large scale superconducting coil applications, such as nuclear fusion devices and particle accelerators, require large current capacity conductors consisting of multiple superconducting strands, and various structures of conductors using REBCO tapes have been proposed, including stacked tapes type, Roebel type, and spirally wound tapes around a round core. Especially, a conductor with spirally wound REBCO tapes around a circular core (hereinafter called as a spiral conductor) is characterized by their flexibility. In this study, we carried out a basic study on spiral conductors using Fujikura's REBCO tapes with a 50 μm thick substrate. First, the core diameter that could be wound without degradation was investigated. Based on the results, spiral conductors with several hundred millimeters long were manually fabricated. The fabricated conductors were evaluated the bending properties at room temperature, and it was confirmed that they could be bent up to approximately 20 mm in diameter without degradation.