IMX Colloquium - Radiation damage of high temperature superconductors for fusion magnets

High temperature superconductors (HTS) in the form of coated conductors are an enabling technology for the next generation of compact nuclear fusion reactors that require higher magnetic fields than Nb3Sn can provide. However, in operation, the superconducting magnet windings will be exposed to a flux of fast neutrons which will introduce structural damage at cryogenic temperatures. Many previous studies using both fission spectrum neutrons and ions at room temperature (or slightly elevated temperatures) have shown that an initial increase in the superconducting current carrying performance upon irradiation is followed at higher fluences by a severe degradation of the properties and eventually complete loss of superconductivity. The superconducting transition temperature is found to decrease monotonically with fluence, strongly suggesting that radiation-induced defects occur throughout the entire crystal lattice, even at relatively low fluence. This talk will outline the research being carried out by the Oxford Superconducting Materials group to improve understanding of radiation damage in HTS materials. This includes innovative in situ ion irradiation experiments to assess radiation damage of HTS at cryogenic temperatures, superconducting property measurements at ultra-high magnetic fields, and studies aimed at elucidating the nature of irradiation induced lattice defects using state-of-the-art microscopy and spectroscopy techniques.

Bio: Susie Speller is a Professor of Materials Science at the University of Oxford where she leads the Superconducting Materials research group and co-directs the Oxford Centre for Applied Superconductivity. Over the last 20 years, she has worked on a wide variety of superconducting materials, ranging from superconducting solders for persistent mode joints to high temperature superconducting cuprates and iron-based materials. Her research focuses on correlating processing with microstructure and superconducting properties using advanced microscopy and spectroscopy techniques. She is currently undertaking a 5 year EPSRC Fellowship to study irradiation damage of coated conductors for compact fusion applications. Her group has carried out pioneering in situ experiments to measure the effects of cryogenic irradiation on superconducting properties, as well as investigating the nature of irradiation-induced defects using the combination of atomic-resolution electron microscopy, synchrotron x-ray absorption spectroscopy and density functional theory. She enjoys working closely with industrial collaborators and national laboratories, including Tokamak Energy, United Kingdom Atomic Energy Authority (UKAEA), Oxford Instruments and Siemens Healthineers, on industrially-relevant projects. Susie is currently the Letters Editor for Superconductor Science and Technology and has published a book for the general audience: “A materials science guide to superconductors: and how to make them super”.