Browsing by Author "Kirkwood, HJ"

Now showing 1 - 5 of 5
  • No Thumbnail Available
    Item
    Application and validity of the Radon transform applied to axisymmetric neutron strain imaging
    (Elsevier B. V., 2019-12-15) Kirkwood, HJ; Wensrich, CM; Paradowska, AM; Abbey, B
    Next generation pulsed neutron sources and wavelength dispersive imaging detectors are creating new opportunities for strain analysis. One such technique is Bragg edge transmission analysis in which projected measurements of the crystallographic properties of bulk polycrystalline samples are recorded on a time-of-flight area detector. The ability to measure the elastic strain field poses the question of whether it is possible to reconstruct a three-dimensional map of the elastic strain tensor from a set of lower order projection data. Here we present a fundamental exploration of the validity of axisymmetric strain reconstruction algorithms available for inverting Bragg edge data. The results demonstrate that the compatibility of the elastic strain field under investigation is critical in determining which algorithm may be successfully applied. Finally, a more robust approach to Radon transform strain tomography is presented based on the condition of zero total strain. ©2019 Elsevier Ltd.
  • No Thumbnail Available
    Item
    Energy-resolved neutron imaging options at a small angle neutron scattering instrument at the Australian Center for Neutron Scattering
    (AIP Publishing, 2019-03-26) Tremsin, AS; Sokolova, AV; Salvemini, F; Luzin, V; Paradowska, AM; Muránsky, O; Kirkwood, HJ; Abbey, B; Wensrich, CM; Kisi, EH
    Energy-resolved neutron imaging experiments conducted on the Small Angle Neutron Scattering (SANS) instrument, Bilby, demonstrate how the capabilities of this instrument can be enhanced by a relatively simple addition of a compact neutron counting detector. Together with possible SANS sample surveying and location of the region of interest, this instrument is attractive for many imaging applications. In particular, the combination of the cold spectrum of the neutron beam and its pulsed nature enables unique non-destructive studies of the internal structure for samples that are opaque to other more traditional techniques. In addition to conventional white beam neutron radiography, we conducted energy-resolved imaging experiments capable of resolving features related to microstructure in crystalline materials with a spatial resolution down to ∼0.1 mm. The optimized settings for the beamline configuration were determined for the imaging modality, where the compromise between the beam intensity and the achievable spatial resolution is of key concern. © 2020 AIP Publishing LLC
  • Thumbnail Image
    Item
    Polycrystalline materials analysis using the Maia pixelated energy-dispersive x-ray area detector
    (Cambridge University Press, 2017-09-26) Kirkwood, HJ; De Jonge, MD; Howard, DL; Ryan, CG; van Riessen, GA; Hofmann, F; Rowles, MR; Paradowska, AM; Abbey, B
    Elemental, chemical, and structural analysis of polycrystalline materials at the micron scale is frequently carried out using microfocused synchrotron X-ray beams, sometimes on multiple instruments. The Maia pixelated energy-dispersive X-ray area detector enables the simultaneous collection of X-ray fluorescence (XRF) and diffraction because of the relatively large solid angle and number of pixels when compared with other systems. The large solid angle also permits extraction of surface topography because of changes in self-absorption. This work demonstrates the capability of the Maia detector for simultaneous measurement of XRF and diffraction for mapping the short- and long-range order across the grain structure in a Ni polycrystalline foil. Copyright © International Centre for Diffraction Data 2017
  • No Thumbnail Available
    Item
    Simultaneous X-ray diffraction, crystallography and fluorescence mapping using the Maia detector
    (Elsevier, 2018-02-01) Kirkwood, HJ; de Jonge, MD; Muránsky, O; Hofmann, F; Howard, DL; Ryan, CG; van Riessen, GA; Rowles, MR; Paradowska, AM; Abbey, B
    Interactions between neighboring grains influence the macroscale behavior of polycrystalline materials, particularly their deformation behavior, damage initiation and propagation mechanisms. However, mapping all of the critical material properties normally requires that several independent measurements are performed. Here we report the first grain mapping of a polycrystalline foil using a pixelated energy-dispersive X-ray area detector, simultaneously measuring X-ray fluorescence and diffraction with the Maia detector in order to determine grain orientation and estimate lattice strain. These results demonstrate the potential of the next generation of X-ray area detectors for materials characterization. By scanning the incident X-ray energy we investigate these detectors as a complete solution for simultaneously mapping the crystallographic and chemical properties of the sample. The extension of these techniques to broadband X-ray sources is also discussed. © 2017 Acta Materialia Inc. Published by Elsevier Ltd.
  • Thumbnail Image
    Item
    Towards real-time analysis of liquid jet alignment in serial femtosecond crystallography
    (International Union of Crystallography, 2022-06-02) Patel, J; Round, A; Bielecki, J; Doerner, K; Kirkwood, HJ; Letrun, R; Schulz, J; Sikorski, M; Valiki, M; de Wijn, R; Peele, AG; Mancuso, AP; Abbey, B
    Liquid sample delivery systems are used extensively for serial femtosecond crystallography at X-ray free-electron lasers (XFELs). However, misalignment of the liquid jet and the XFEL beam leads to the X-rays either partially or completely missing the sample, resulting in sample wastage and a loss of experiment time. Implemented here is an algorithm to analyse optical images using machine vision to determine whether there is overlap of the X-ray beam and liquid jet. The long-term goal is to use the output from this algorithm to implement an automated feedback mechanism to maintain constant alignment of the X-ray beam and liquid jet. The key elements of this jet alignment algorithm are discussed and its performance is characterized by comparing the results with a manual analysis of the optical image data. The success rate of the algorithm for correctly identifying hits is quantified via a similarity metric, the Dice coefficient. In total four different nozzle designs were used in this study, yielding an overall Dice coefficient of 0.98. © 2022 The Authors, CC BY 4.0 licence