Innovative X-Ray Fluorescence Techniques Enabled by the Development of Advanced X-Ray Optics

<p dir="ltr">X-ray fluorescence (XRF) analysis is a powerful technique for elemental analysis that is widely used in a variety of fields. Traditionally, XRF has been limited to elemental analysis and is unable to distinguish between different compounds of the same element. It is typically only able to measure elements at concentrations above 1 part per million. In this thesis, two XRF analysers were developed with different capabilities and purposes. The first analyser was designed to measure toxic elements such as arsenic, lead, mercury, cadmium, and bromine at concentrations down to the parts per billion level in soil and water. The analyser utilises two X-ray focusing optics and a 150W molybdenum target X-ray tube to enable the high sensitivity needed for these measurements. Monte Carlo simulations were used to optimise the design of the X-ray optics. The limits of detection for the analyser were determined by measuring a variety of water and soil samples each with known concentrations of the toxic elements. The analyser achieved limits of detection between 20��100 ppb in soil and water, except for cadmium, which could not be measured due to a manufacturing error in the X-ray focusing optic. The ability to accurately measure toxic elements at the parts per billion level has the potential to inform the development of remediation strategies and protect public health. The second analyser was a high-resolution XRF analyser capable of chemical state analysis. Using a low-powered X-ray tube, a poly-capillary X-ray focusing optics, a flat analysing crystal, and a silicon strip detector, vanadium and copper X-ray fluorescence spectra were measured at resolutions of 3:14 eV and 8:94 eV, respectively. The oxide and sulphide variants of these elements were also measured and their XRF spectra were analysed to observe changes to the XRF spectrum due to the oxidation state of compound. At these high energy resolutions, the valence electron transition lines can be resolved from the diagram lines, which can be used to probe the fundamental atomic physics of materials. Both analysers utilised non-linear least squares fitting to analyse the XRF spectra and deconvolute the contributions from the various elements and compounds in the sample.</p><p dir="ltr">This thesis demonstrates the potential of XRF analysis for trace element analysis and chemical state analysis and presents opportunities for further development and application of XRF analysers. X-ray optics played a crucial role in the development and performance of both analysers described in this thesis. The use of X-ray optics allowed for the focusing and manipulation of X-ray beams, enabling the high sensitivity and resolution needed for trace element analysis and chemical state analysis. The versatility of X-ray optics makes them useful in a variety of different cases, and further research on the development and optimisation of X-ray optics has the potential to enhance the capabilities of XRF analysers and other X-ray-based techniques.</p>