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Comparison of propagation-based phase-contrast CT and absorption-based CT for breast imaging using synchrotron radiation
(Society of Photo-Optical Instrumentation Engineers (SPIE), 2020-05-22) Taba, ST; Lewis, S; Baran, PM; Arhatari, BD; Nesterets, YI; Mayo, SC; Thompson, D; Fox, J; Kumar, B; Prodanovic, Z; Häusermann, D; Masimenko, A; Hall, CJ; Dimmock, M; Pavlov, KM; Peele, AG; Quiney, HM; Lockie, D; Tromba, G; Gureyev, TE; Brennan, PC
Propagation-based phase-contrast CT (PB-CT) is a novel imaging technique that visualises variations in both X-ray attenuation and refraction. This study aimed to compare the clinical image quality of breast PB-CT using synchrotron radiation with conventional absorption-based CT (AB-CT), at the same radiation dose. Seven breast mastectomy specimens were scanned and evaluated by a group of 14 radiologists and medical imaging experts who assessed the images based on seven radiological image quality criteria. Visual grading characteristics (VGC) were used to analyse the results and the area under the VGC curve was obtained to measure the differences between the two techniques. For six image quality criteria (overall quality, perceptible contrast, lesion sharpness, normal tissue interfaces, calcification visibility and image noise), PB-CT images were superior to AB-CT images of the same dose (AUCVGC: 0.704 to 0.914, P≤.05). For the seventh criteria (artefacts), PB-CT images were also rated better than AB-CT images (AUCVGC: 0.647) but the difference was not significant. The results of this study provide a solid basis for future experimental and clinical protocols of breast PB-CT. © 2020 Society of Photo-Optical Instrumentation Engineers (SPIE).
Complex atomic fine structure in the phase domain: exciting opportunities and challenges
(International Union of Crystallography, 2021-08-14) Tran, CQ; Chantler, CT; Kirk, T; Dao, MH; Di Pasquale, P; Ceddia, J; Barnea, Z; de Jonge, MD; Kewish, CM
X-ray Absorption Spectroscopy has been one of the most powerful tools for probing atomic and molecular structures of materials. However, the measured fine structures in the absorption domain do not have adequate dimensionalities to extract three-dimensional structural information of the material of interest. A technique that allows accurate measurements of atomic fine structure in both the absorption and phase domains will open exciting opportunities in a wide range of fundamental and applied research. In this presentation, we will describe a new technique for determining simultaneously the real and imaginary components of the complex atomic form factor. The technique used Fourier Transform Holography with an extended reference and applicable to both crystalline and amorphous samples. Details of an application of the technique in spectroscopy mode to obtain the X-ray Complex Fine Structure across the copper K-edge will be discussed. © The Authors
Effect of welding thermal cycle on the microstructure of Zircaloy-4
(International Institute of Welding, 2009-07-16) Thorogood, KJ; Li, HJ; Carr, DG; Harrison, RP; Nolan, D
Zirconium and its alloys are important materials commonly utilised in the nuclear industry, primarily due to their low neutron absorption cross-section and excellent corrosion resistant properties. Zircaloy-4 is one of the most widely used nuclear grade zirconium alloys and contains primary alloying elements of tin, iron, chromium and oxygen. Typical applications include structural core components and fuel cladding. Fully welded structures such as heavy water reflector vessels have been fabricated from Zircaloy-4. Although the structure-property relationships of Zircaloy-4 parent metal and weld metal is well understood, there is limited understanding of the same relationship for the narrow weld heat-affected zone. The work reported in this paper is an investigation of the influence of the weld thermal cycles on the microstructure and texture of Zircaloy-4 heat-affected zone material. Discrete regions within the heat-affected zone were simulated using a thermo-mechanical simulator (Gleeble 3500). Peak temperatures of the thermal cycles studied were 1000,1200, 1400 and 1600°C. Weld simulation has been shown to produce a volume of material sufficient for analysis and which represents the individual sub-zones. © 2010, International Institute of Welding
Estimating dielectric parameters by reflecting evanescent waves at THz frequencies
(Society of Photo-Optical Instrumentation Engineers (SPIE), 2021-04-20) Vilagosh, Z; Foroughimehr, N; Lajevardipour, A; Appadoo, D; Juodkazis, S; Wood, AW
The THz/Far-IR Beamline at the Australian Synchrotron was used to demonstrate a novel method of estimating the dielectric properties of homogenous substances in the 1.0 THz to 4.0 THz region. Attenuated total reflection (ATR) coupled with synchrotron sources allow rapid evaluation of samples. The source is incoherent, thus normally only reflectance can be derived, as phase shift data cannot be obtained with this arrangement. A method is presented of deriving the full complex dielectric parameters by a modified frustrated internal reflection technique which reflects the evanescent wave using a gold plated mirror. Oil and alcohol samples were used in the study. With the mirror in situ, the reflectance changed from being enhanced at some frequencies to undergoing a frequency dependent destructive interference at other frequencies. The change in different samples was noted to vary according to the refractive index (but not the absorption coefficient) of the sample. © (2022) Society of Photo-Optical Instrumentation Engineers (SPIE)
The HIFAR oscillator
(Melbourne University Press on behalf of The Australian Atomic Energy Commission, 1958-06-02) Nicholson. KP; Pryor, AW
A description is given of a pile oscillator which will enable thermal absorption cross-section measurements to be made on HIFAR. The apparatus is in course of construction. The principal design factors are discussed, with particular reference to the effects of scattering by the sample, and the extension of the range of cross-section measurements to include moderators such as graphite and beryllium.
High-pressure single-crystal neutron diffraction
(Australian Institute of Physics, 2017-02-03) McIntyre, GJ; Binns, J; Parsons, S
High-pressure neutron diffraction is always challenging, but it can offer several advantages over high-pressure X-ray diffraction to make meeting those challenges worthwhile. In addition to the usual higher sensitivity to low-X elements, notably hydrogen, and to magnetic moments, the low absorption by many pressure cell materials can yield greater reciprocal space coverage for single crystals. The low scattering power usually requires considerably larger sample volumes than with X-rays, but for the same reason the cell-wall materials can be quite thick. Common cell designs include He-gas cells and simple clamp cells, opposed piston cells (e.g. Bloch, McWhan), opposed-anvil cells (e.g. diamond anvil cell, Paris-Edinburgh cell), and multi-anvil cells, each adapted to sample volume, accessibility, pressure, and other external parameters, especially temperature, that suit the scientific question of interest. State-of-the-art experiments using each cell type will be described. A special challenge in high-pressure diffraction is to perform neutron and X-ray experiments on the same material under the same conditions. Previously, this meant using different cells and samples with achieving identical pressures largely a hit-or-miss affair. This has all changed with the recent demonstration on KOALA on the OPAL research reactor that modern neutron Laue diffraction can be performed on the same sample in the same diamond-anvil cell as used for laboratory X-ray experiments [1].
Imaging the molecular orientation at the disperse-continuous interface of a PP-PA6 blend by the Four-Polarization FTIR Method
(POLY-CHAR, 2023-01-24) Bertin, M; Nguyen, D; Verbeek, CJR; Vongsvivut, JP
Fourier-transform infrared spectroscopy (FTIR) is a well-known technique used to analyze the chemical composition of polymeric materials by measuring the absorption of infrared light over a range of wavelengths, where each absorption peak corresponds to a specific chemical bond. A chemical map image can be constructed by acquiring multiple IR spectra with a specified step distance over an area. Furthermore, it is possible to extract information about the molecular orientation by utilizing linearly polarized light, as the absorption intensity varies with the polarization angle of the incident radiation. Recently, a mathematical method was introduced which makes it possible to create a complete vector map of the dipole orientation of a selected vibrational mode by utilizing measurements of IR spectra in four different polarized orientation. In this work, we seek to gain insight into the molecular orientation near the interface between the disperse phase and the continuous matrix of a polypropylene-polyamide 6 (PP-PA6) blend by comparing an uncompatibilized blend with a blend compatibilized with the addition of maleic anhydride grafted polypropylene (PP-g-MA) [4] and another with the application of a novel in-situ plasma treatment. The goal of plasma treatment is to introduce polar oxygen groups such as C−O, C=O, and O−C=O, promoting stronger interactions between phases. Plasma treatment is widely used as a surface treatment to increase wettability and adhesion, but its use as a compatibilization method of blends is relatively new and has already provided positive results. However, the mechanisms behind the improvements in this context are mostly unknown so the current research will provide valuable data for further development of this novel polymer modification method. © 2023 The Authors.
Magneto-structural study of La0.57-x,,CexCa0.33Mn03 (X = 0, 0.05, 0.10, 0.20)
(The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Alejandro, G; Morales, L; Steren, L; James, M
A comparative study of the nuclear and magnetic structure of La0.57-x,,CexCa0.33Mn03 (X = 0, 0.05, 0.10, 0.20) perovskite (x =0, 0.05, 0.10, and 0.20) is reported. When the lanthanum is partially substituted by yttrium or a rare earth such as Pr or Tb, the structural cation disorder has been shown to lead to different and interesting phenomena, depending on the nature of the substitute cation (in general isovalent one in Ce-doped manganites, Ce3+ and Ce4+ species are able to coexist adding an extra source of disorder. This statement is supported by previous x-ray absorption (XAS) experiments[1]. Magnetic measurements made on these compounds have shown that Ce-doping introduces strong magnetic frustration in the spin system[2]. Furthermore, the magnetic behavior of La0.47CeO.2OCa0.33Mn03.OO observed[2] has been to be closely correlated with the electronic transport properties. To achieve a better understanding the nature of the magnetic phase in these Ce-doped manganites, we have carried out systematic neutron of powder diffraction experiments. Both nuclear and magnetic structure are studied as a function of temperature and cerium content. © 2005 The Authors
Materials for the control of nuclear reactors
(Melbourne University Press on behalf of The Australian Atomic Energy Commission, 1958-06-02) Wright, WJ; Nicholson, KP
The desirable properties of neutron absorbers are discussed, and the investments for the equivalent absorption in various materials are calculated. Physical and metallurgical limitations exist in the use of boron and cadmium, and the investment for blackness compared to burn-up in hafnium is unattractive. The rare earths, gadolinium, samarium and europium are discussed; dispersions of the oxides in steel are suggested for use as control elements in future high temperature reactors.
Measurement of concentration of tungsten suspensions and density of liquid sodium by gamma ray absorption
(Melbourne University Press on behalf of The Australian Atomic Energy Commission, 1958-06-02) Watt, JS; Lawther, JS
Gamma ray absorption techniques have been applied to measure the density of various media, and the theory of selecting the appropriate energy gamma ray to give optimum sensitivity of density determination for a homogeneous system is outlined. A gauge to determine the concentration of tungsten powder suspended in water in a concentration range of O to 8 gm. tungsten/c.c. suspension, has been developed. In this apparatus the mean tungsten concentration, 0.08 gm./c.c., can be measured to an accuracy of approximately +-0.0015gm./c.c. In the case of liquid sodium contained in o stainless steel vessel, preliminary experiments indicate that the density may be measured to an accuracy of +-0.01gm./ c.c. and that 0.01gm./c.c. transient changes in density occurring in a few seconds can be resolved.
Neutron diffraction and in situ gas-loading investigations of functional MOFs for energy-relevant gas separations
(Australian Institute of Nuclear Science and Engineering (AINSE), 2012-11-08) Duyker, SG; Peterson, VK; Ogilvie, SH; Turner, DR; Hill, MR; D'Alessandro, DM; Kepert, CJ
Intense research is currently directed towards realising metal-organic frameworks (MOFs) for industrially-applied gas separation and storage due to their unique structural properties, including: robustness; thermal and chemical stability; unprecedented internal surface area; and high void volume. A particular focus of current research is the development of MOFs for the separation of CO, from the other components of flue gas in fossil-fuelled power plants. The use of NPD to study gas adsorption in framework materials is a relatively new but growing field. Structural measurements, which show the arrangement of both the host and guest, allow derivation of the nature of the host-guest interaction, and the host's response to the guest. The capability to perform these measurements, with accurate gas dosing and temperature control, has recently been realised at ANSTO's Bragg Institute. Using these techniques, we have investigated the adsorption mechanisms of a number of gases in selected new and established MOFs that display impressive selectivity for specific gases. The location and orientation of industrially-relevant gases including D2, 02, CO2, and CD4, within their crystal structures provide insights into the modes of binding, which will help to tune the materials' performance and benefit the design and development process for the next generation of materials.
Oxidation state of uranium in mantle melts
(Elsevier; Cambridge Publications, 2008-07) Berry, AJ; O'Neill, HSC; Foran, GJ
The oxidation state of U exerts a first order control on its partitioning during partial mantle melting. An understanding of U partitioning, and its abundance relative to other members of the U decay series, is important for interpreting U series disequilibrium, with implications for the rate of melt transport at mid-ocean ridges. U LIII-edge X-ray absorption near edge structure (XANES) spectra were recorded for a synthetic mid-ocean ridge basalt (MORB), and a number of CMAS (CaO-MgOAl2O3-SiO2) compositions, containing 0.5 wt % U3O8, equilibrated at 1400 ˚C and controlled oxygen fugacities (fO2)at one-atmosphere. Spectra were obtained for both quenched glasses, and in situ at magmatic temperatures (Berry et al. 2003). In situ measurements allowed changes in the spectra in response to the imposed fO2 to be followed in real time. The spectra were recorded in fluorescence mode at the Australian National Beamline Facility (beamline 20B), Photon Factory, Japan. The spectra exhibit systematic variations in absorption edge energy and crest intensity with fO2. These changes occur between -4 and +6 log units of the nickel-nickel oxide (NNO) fO2 buffer. The fO2 range of the spectral variation indicates that U4+ must oxidise to U6+ through two stepwise one-electron reactions, involving a U5+ intermediate, rather than a direct two-electron process. The results also suggest that U5+ may be the dominant oxidation state at the fO2 conditions of MORB generation. © 2008 Elsevier Ltd
Plutonium and neptunium incorporation in zirconolite
(Materials Research Society, 1997) Begg, BD; Vance, ER; Day, RA; Hambley, M; Conradson, SD
The incorporation of Pu and Np in zirconolite (CaZrTi2O7) has been investigated over a range of redox conditions. Zirconolite formulations designed to favour either trivalent or tetravalent Pu and Np were prepared by limiting the amount of charge compensating additives available to maintain electroneutrality. From near-edge X-ray absorption spectroscopy the Pu valence state was found to vary with the processing atmosphere, from completely tetravalent when fired in air, and located on either the Ca or Zr sites, to trivalent, when substituted on the Ca site after annealing in 3.5% H2/N2. Np was predominantly tetravalent over the range of redox conditions examined and was readily incorporated on either of zirconolite's Ca or Zr sites. The charge compensation mechanisms at work in different zirconolites are also discussed. © Materials Research Society 1997
Rigid unit modes dynamics in the molecular sieve material AlPO4-5
(Australian Institute of Nuclear Science and Engineering, 2016-11-29) Cortie, DL; McBride, BR; Mole, RA; Withers, RL; Yu, DH; McIntyre, GJ; Liu, Y
The web-like ring structure composed of corner-sharing tetrahedra in AlPO4-5 has received considerable attention over the years because its unusual topology enables entrapment and diffusion of guest molecules within the extended micropores1. Recent work on this molecular sieve reported clear evidence for strong sub-picosecond tetrahedral dynamics attributed to rigid-unit modes (RUMS). In order to preserve the bond-lengths during these motions, some chemical species undergo restricted rotational diffusion within relatively large volumes around their average lattice positions. These motions drive fluctuations in the effective pore-window sizes, potentially acting to filter absorption and diffusion of guest species. Here we report a quasi-elastic neutron scattering investigation of the dynamics over the temperature range 1.5 – 300 K using the PELICAN instrument. This is compared with ab initio molecular dynamics to gain a clear microscopic picture of the timescales of the entangled motions within the tetrahedra network.
Simultaneous reconstruction and structural fitting of the complex atomic fine structure of copper and iron
(Australian Institute of Physics, 2022-12-11) Di Pasquale, P; Tran, CQ; Chantler, CT; Barnea, Z; Kirk, T; Dao, MN; Balaur, E; van Riessen, GA; Hinsley, GN; Jallandhra, A; Ceddia, J; Rogers, J; Kewish, CM; Paterson, DJ; Reinhardt, J; Kirby, N; Mudie, ST
A novel technique for determining complex atomic fine structure will be described. Exciting applications of the technique such as a phase analogue to x-ray absorption fine structure applications will also be discussed.
Total scattering measurements at the Australian Synchrotron Powder Diffraction beamline: capabilities and limitations
(Australian Nuclear Science and Technology Organisation, 2021-11-24) D'Angelo, AM; Gu, QF; Brand, HEA; Mitchell, VD; Hamilton, JL; Liu, ACY; Oldfield, DT
The PD beamline at the Australian Synchrotron (ANSTO) consistently receives requests to carry out total scattering experiments for various materials including battery electrodes, piezoelectrics and coordination frameworks. In this study we describe the capabilities and limitations of carrying out total scattering experiments on the Powder Diffraction beamline. A maximum instrument momentum transfer of 19 Å-1 can be achieved. Our results detail how the pair distribution function is affected by Qmax, absorption, and counting time duration at the PD beamline. We also trial a variable counting time strategy using the Mythen II detector. Refined structural parameters exemplify how the PDF is affected by these parameters. Total scattering experiments can be carried out at PD although there are limitations. These are: (1) only measurements on stable systems and at non-ambient conditions is possible if the temperature is held during data collection, (2) it is essential to dilute highly absorbing samples (μR>1), and (3) only correlation lengths >0.35 Å may be resolved. A case study comparing the PDF atom-atom correlation lengths with EXAFS derived radial distances of Ni and Pt nanoparticles is also presented, which shows good agreement between the two techniques. The results here can be used as a guide for researchers considering total scattering experiments at the PD beamline. © The Authors

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