The potential for using superconducting materials to generate high magnetic fields was realised by Kamerlingh Onnes very soon after his initial discovery of superconductivity in mercury in 1911. However, disappointment shortly followed as superconductivity in the early elemental superconductors was found to be completely destroyed in relatively low magnetic fields. It was not until the early 1960s that Kunzler and colleagues at Bell Laboratories discovered that a type II alloy superconductor, Nb₃Sn, could sustain a superconducting current density over 1000 A mm^-2 in a magnetic field of 8.8 T, paving the way for practical superconducting high field magnets. Nowadays, superconducting magnets have found widespread applications, from the magnetic resonant imaging machines found in hospitals all over the world to the magnets that bend the proton beams in the Large Hadron Collider at CERN. However, there is a constant drive towards generating higher and higher magnetic fields for research magnets, nuclear magnetic resonance (NMR) instruments, particle accelerators and fusion applications that will require the shift to using high temperature superconductors.

In this plenary lecture, I will introduce the key materials developments that have led to the manufacture of technological superconducting wires and tapes for high field magnets, as well as exploring what developments are needed to meet future high field magnet requirements. In particular, I will focus on some of the materials challenges to deploying high temperature superconductors in practical applications, including radiation damage in fusion magnets and persistent jointing for NMR.

Figure caption: Structural damage in REBCO coated conductor as a result of irradiation with O²⁺ ions. High angle annular dark field (HAADF) image taken by Dr Mohsen Danaie using the JEOL ARM300CF scanning transmission electron microscope at the ePSIC facility, Harwell Science and Innovation Campus, UK.

Keywords: High temperature superconductor, wires and tapes, high field magnets, fusion