Advancing ReBCO-CORC wire and cable-in-conduit conductor technology for superconducting magnets

Abstract

ReBCO Coated Conductors are ceramic flat tape High Temperature Superconductors (HTS) capable of carrying large currents in a broad temperature and magnetic field range. ReBCO tapes significantly exceed the performance reach of NbTi and Nb3Sn Low Temperature Superconductors (LTS), which allows the creation of large-scale magnets capable of generating a magnetic field far beyond 20 T at 4.5 K and of magnets operating in the temperature range of 30 to 60 K, a range served uniquely by ReBCO material. Large-scale magnets require currents far beyond the capacity of a single ReBCO tape and therefore multiple ReBCO tapes must be combined into a multi-tape, high-current ReBCO cable. The three main cabling concepts today are the Roebel, Twisted Stack Tape and Conductor On Round Core (CORC) cable. The focus of the work presented in this thesis is on the development of CORC technology. CORC type conductors can be grouped in three categories: CORC cable, which is a standalone general purpose HTS cable; thin CORC wire, that aims at a high-current density for application in accelerator magnets and insert coils; and CORC Cable-In-Conduit Conductor designed for enabling stable, high-current magnets and their bus lines. The aim of this thesis work is to pioneer the development of ReBCO CORC conductors for application in large-scale magnet systems. This includes both the development of thin flexible CORC wires with high current density, as well as the design, preparation and testing of CORC multi-strand Cable-In-Conduit Conductors. A key aspect of this work is the development of joint terminals for CORC conductors that allow low-resistive and homogeneous current injection and extraction.