Understanding radiation damage mechanisms in high temperature superconductors for fusion applications

Rare-earth barium copper oxides (REBCO) are the only class of high-temperature superconducting (HTS) materials that have been developed into commercial wires with an engineering performance good enough for use in the high field magnet for small fusion tokamaks like the one being designed in the STEP programme (https://ccfe.ukaea.uk/research/step/). One of the critical aspects we must understand before deciding to deploy these expensive materials in a fusion reactor is how they respond to ionising radiation to ensure that they can retain adequate performance for the lifetime of the reactor (or planned lifetime of the magnet at least) when exposed to high energy neutrons and a significant flux of gamma rays. 

The manufactured microstructure, local oxygen stoichiometry and the distribution of lattice defects that act as flux pinning centres in REBCO play crucial roles in determining the superconducting properties, but the exact mechanisms by which radiation alters these microstructural features are unclear. Different types of radiation can cause point defects and larger damage cascades, or stimulate radiolysis effects, but the quantitative relationships between initial structure, radiation type, energy and flux, specific damage processes and the final engineering properties are poorly understood. The overall aim of the project is to contribute to the development of a mechanistic understanding of how the defect structure in REBCO is affected by radiation, and how these changes control the superconducting properties over the lifetime of a magnet in service. The student will introduce careful doses of damage using unique ion beam and neutron sources in Surrey, Manchester and Birmingham universities, and measure superconducting properties with new facilities at the Culham Center for Fusion Energy. (Dr Holly Campbell will be the UKAEA supervisor) In order to understand the details of the lattice damage processes, there will also be the opportunity to join the team designing spectroscopy experiments on irradiated materials using the Diamond Light Source.