Focal construct geometry for spatially resolved high-energy x-ray diffraction

Hogg, A, 2024. Focal construct geometry for spatially resolved high-energy x-ray diffraction. PhD, Nottingham Trent University.

Text Alex Hogg Thesis 2024.pdf - Published version Full-text access embargoed until 15 May 2026. Download (47MB)

Abstract

While X-ray diffraction (XRD) is perhaps the most specific method of material phase identification, its use is typically restricted to low energy, ∼8 keV, laboratory instrumentation. However, there are many screening and imaging applications that would benefit from a high energy XRD probe capable of inspecting dense or cluttered materials at unknown positions along the beam.

This thesis investigates a novel focal construct geometry (FCG) application incorporating a conical shell or hollow X-ray beam combined with a multi-parallel channel collimator configured within the central region encompassed by the beam. The primary purpose is to establish an instrumental d-spacing range that is invariant to the sample position along the beam by collecting scattered photons at a fixed diffraction angle, 2θ. Theoretical analysis of previous FCG implementations, computer simulation, and error propagation studies supported and informed the proof-of-concept laboratory demonstration of the new FCG instrument.

The experimental instrument produced a conical shell beam with a half-angle (or 2θ) of (3.87 ± 0.05)°, formed by collimating the emission produced by a thermionic 100 kV, 200 µA, W-target X-ray source. Scattered photons from an extended sample placed in the beam were received by an array of collimator channels of aspect ratio 1 : 246. The resultant collimated photons were measured with a pixelated energy-resolving detector, where calibration of these detectors was accomplished using an existing machine learning algorithm for spectral clustering. A comparative analysis of the instrumental combined d-spacing uncertainty using a HEXITEC detector recorded approximately 0.05 Å (2 Å), 0.10 Å (4 Å), and 0.24 Å(8 Å); while an IDEAS Gamma-Spect 5×5 detector, recorded approximately 0.08 Å (2 Å), 0.24 Å (4 Å), and 0.92 Å (8 Å). The combined uncertainties were dependent on the d-spacing value under consideration and the concatenated effects of both angular and energy uncertainties.

The resultant XRD patterns enabled discrimination between a preliminary series of 14 different powdered samples. Thus, by hypothesis, the new probe shows great promise for time sensitive volumetric inspection of applications such as the detection and identification of explosives and narcotics concealed in goods or luggage.

Item Type:	Thesis
Creators:	Hogg, A.
Contributors:	Name Role NTU ID ORCID Evans, J.P.O. Thesis supervisor EEE3EVANSJP https://orcid.org/0000-0001-9831-1461 Downes, D. Thesis supervisor EEE3DOWNEDJ https://orcid.org/0000-0002-4886-5260
Date:	20 March 2024
Rights:	This work is the intellectual property of the author. You may copy up to 5% of this work for private study, or personal, non-commercial research. Any re-use of the information contained within this document should be fully referenced, quoting the author, title, university, degree level and pagination. Queries or requests for any other use, or if a more substantial copy is required, should be directed in the owner(s) of the Intellectual Property Rights.
Divisions:	Schools > School of Science and Technology
Record created by:	Jonathan Gallacher
Date Added:	14 May 2025 08:54
Last Modified:	14 May 2025 08:54
URI:	https://irep.ntu.ac.uk/id/eprint/53573

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