(SATURN CDT) New directions in radiation tolerant superconducting magnets

About the Project

Magnetic confinement of fusion plasma is a central requirement of Tokamak and spherical reactors. The proposed rare earth- barium copper oxide (ReBCO) materials have been heavily studied since their discovery in the late 1980s, however their specific application to a fusion environment still presents a number of significant challenges. These include stability in the extreme operational environment (temperature, field, strain and neutron fluence), and wider issues around supply chain and manufacture, which is mainly focussed on slow and costly chemical vapour deposition techniques, for which there is currently no UK-based supplier. UKAEA recently tested some ReBCO tapes under neutron bombardment, and while they showed no detriment to the material performance, the tests were conducted at much higher temperatures than would be used operationally in a reactor. ReBCO performance close to the transition temperature is known to be quite different to that measured at low/operational temperatures and is therefore likely to be unrepresentative of fusion-relevant conditions (this set of experiments will have been constrained by practicalities). Under higher fields and lower temperatures, this is likely to be unrepresentative of performance. Additionally, there are currently no UK-based manufacturers of superconducting tape, and current manufacturing processes are neither optimised for the quantities required by reactors, nor producing materials designed specific to the fusion environment. As such, there is scope for development of high temperature superconducting materials which meet these requirements, however this will require fundamental research into structure-function relationships in ReBCO materials. We will achieve this by combining modelling with emergent synthesis and sintering techniques, which enable access to high levels of grain engineering, and seek to understand potential radiation tolerance using AC flux creep properties as a proxy.

The objectives of the project would therefore be to:

• Synthesis ReBCO materials with controlled morphologies
• Use these powders in conjunction with novel cold sintering techniques to make solid ceramics with bespoke microstructures
• Use the full range of characterisation techniques available to understand phase and grain structure (XRD, SEM, TEM etc)
• Develop structural models to understand how damage might accumulate and impact properties
• Use SQUID magnetometry to measure transition temperature, and effect of grain structure on critical current density and AC flux creep susceptibility.

This will lead to a better understanding of the links between grain structure and superconducting properties, with a view to enhancing the intrinsic radiation tolerance. It is envisaged that this will lead to irradiation and modelling studies using down-selected grain structures. Additionally, the scalability of these methods means that the work could lead to addressing a critical bottleneck in reactor production and position the UK as a leader in manufacturing. Finally, this project will produce a fusion magnet engineer, an area identified by the Fusion Roadmap as in critical need of population.