Fabrication of 1 m long multi layered superconducting coated conductor with high engineering critical current density

Abstract

Cable conductors fabricated by bundling coated conductors to increase the transport current have been developed for large-scale electric applications such as highly magnetic field magnets, large accelerators and fusion reactors. Various types of cable conductors (CORC cables, Roebel cables, TSTC and round wires) have been fabricated using coated conductors; however, these cable conductors do not have a high engineering critical current density (Je) required high performance in large-scale applications. In this study, new high temperature superconducting (HTS) multilayered conductors have been fabricated to increase the critical current and Je of coated conductors as cable conductors. The property of easy exfoliation owing to the weak c-axis strength of coated conductors is used to fabricate multi layered HTS conductors. In order to stack and bond multiple-HTS layers on one substrate (MHOS), a silver diffusion bonding technique using only a silver plated coated conductor is adopted. The MHOS conductor consists of multiple, biaxial-, textured, superconducting layers without any intermediate epitaxial grown buffer layer or solder layer between them. A 1 m long 4-MHOS conductor was successfully fabricated to proposed fabrication process; it exhibited a high critical current (2484 A/12 mm-w) and high engineering critical current density (Je = 0.12 MA cm−2). The critical current of the fabricated MHOS conductor at liquid nitrogen temperature (65–77 K) with a magnetic field ranging from 0 to 6 T increased proportionally with the number of superconducting layers.