Development of a bespoke hybrid electron paramagnetic resonance (EPR) spectrometer for simultaneous neutron diffraction studies

Silver, Kai 2025. Development of a bespoke hybrid electron paramagnetic resonance (EPR) spectrometer for simultaneous neutron diffraction studies. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

This thesis presents the design, development, and commissioning of the world’s first integrated instrument capable of performing simultaneous Electron Paramagnetic Resonance (EPR) spectroscopy and Neutron Powder Diffraction (NPD). The work addresses a critical gap in experimental materials science by enabling real-time, multimodal measurements of both electronic and structural properties within a single sample environment. The project focuses on the engineering challenges involved in adapting EPR instrumentation for operation within the spatial constraints of a Neutron diffractometer. A bespoke, neutron-transparent microwave cavity was therefore developed, capable of supporting X-band EPR measurements with a loaded cavity quality factor exceeding 2500. The custom electromagnet, modulation system, and precision supporting rig were all designed to function without interfering with neutron beam paths or detector geometry and supports in-situ measurements. These innovations were implemented and tested on the Polaris diffractometer at the ISIS Neutron and Muon Source, Rutherford and Appleton Laboratory. Complementary to the hardware design, the thesis explores new methodologies for direct detec�tion of EPR signals, including spectrum analyzer and software-defined radio (SDR) approaches. These were validated using common reference standards employed in EPR spectroscopy, such as DPPH, where spectra were successfully obtained with high signal-to-noise ratios for both architectures, respectively. Furthermore, the implementation of a phase-sensitive detector based system also demonstrated good EPR detection on common samples such as DPPH and copper complexes (i.e., Cu(acac)2). The integrated system was applied to a standard paramagnetic reference sample, DPPH. The simultaneous collection of EPR spectra and neutron diffraction patterns confirmed the viability of the platform. Furthermore, neutron diffraction measurements (in the absence of simultaneous EPR detection) were also made successfully on a technologically relevant battery cathode material; LiNi0.8Mn0.1Co0.1O2 (NMC811) with clear detection of lithium and oxygen ordering. This thesis lays the groundwork for future operando studies in energy materials and quantum systems by establishing a robust experimental platform for probing coupled paramagnetic and structural phenomena. The ability to track both ionic and electronic (paramagnetic) evolution in real time marks a major step forward in the development of next-generation integrating characterisation tools for functional materials.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Engineering
Uncontrolled Keywords:	1. Electron Paramagnetic Resonance (EPR) 2. Neutron Powder Diffraction (NPD) 3. Microwave cavities, 4. RF Systems 5. Instrumentation.
Date of First Compliant Deposit:	2 March 2026
Last Modified:	02 Mar 2026 13:13
URI:	https://orca.cardiff.ac.uk/id/eprint/185262

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