Browsing by Author "Stevenson, AW"
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- ItemThe Australian diffractometer at the Photon Factory(American Institute of Physics, 1992-01) Barnea, Z; Creagh, GC; Davis, TJ; Garrett, RF; Janky, S; Stevenson, AW; Wilkins, SWOutlined are design features of a versatile high‐resolution two‐axis diffractometer that is being constructed for operation at the Photon Factory as an Australian national facility. The instrument features optional use of multiple‐imaging plates on a translating cassette to allow rapid recording of an almost complete range of data covering both the high‐angle and small‐angle scattering regime or alternatively the use of electronic detectors. The instrument will be capable of operation in various modes including the following: (i) high‐resolution powder diffraction with single‐channel counter and crystal analyzer, (ii) high‐resolution, high‐speed powder diffraction in the Debye–Scherrer mode with imaging plates as recording medium, either stationary or translating (for time‐dependent studies), (iii) small‐angle x‐ray scattering with imaging plates as recording medium, (iv) protein crystallography in screenless Weissenberg mode, and (v) two‐ or three‐axis single‐crystal diffractometry. The salient features of the instrument are the use of a double‐crystal sagittal focusing monochromator as primary monochromator together with the optional use of a condensing–collimating channel‐cut (CCCC) monochromator or other channel‐cut monochromator as secondary monochromator. The use of a CCCC monochromator enables fine tuning of beam position on sample, harmonic suppression, beam‐condensation, and variation of wavelength bandpass. Further features include the use of high‐precision incremental encoders on both axes, together with the capability of operating the whole diffractometer, including secondary monochromator and detectors, in vacuum of order 10−3 Torr in order to reduce absorption and parasitic scattering, and the use of a large camera radius (approximately 0.57 m) for the imaging plate cassette in order to increase angular resolution and signal to noise. © 1992 American Institute of Physics.
- ItemFirst experiments on the Australian Synchrotron imaging and medical beamline, including investigations of the effective source size in respect of x-ray imaging(International Union of Crystallography, 2010-01) Stevenson, AW; Mayo, SC; Häusermann, D; Maksimenko, A; Garrett, RF; Hall, CJ; Wilkins, SW; Lewis, RA; Myers, DEThe Imaging and Medical beamline at the Australian Synchrotron achieved 'first light' in December 2008. Here, the first experiments performed on the beamline are reported, which involved both X-ray imaging and tomography studies for a range of samples. The use of a plastic-edge phantom for quantitative measurements of contrast and resolution proved to be very instructive and helped to confirm certain parameter values such as the effective horizontal source size, detector resolution and average X-ray energy for the polychromatic beam. © 2010, International Union of Crystallography
- ItemHigh‐resolution triple‐crystal x‐ray‐diffraction experiments performed at the Australian National Beamline Facility in Japan(American Institute of Physics, 1994-07-18) Nikulin, AY; Stevenson, AW; Hashizume, H; Wilkins. SW; Cookson, DJ; Foran, G; Garrett, RFThe x‐ray‐diffraction results reported here are from the first high‐resolution triple‐crystal experiments to be performed at the Australian National Beamline Facility at the Photon Factory. The heart of the facility is a multipurpose two‐axis high‐resolution vacuum diffractometer (BIGDIFF) Z. Barnea et al., Rev. Sci. Instrum. 63, 1069 (1992) capable of use for high‐resolution powder diffraction (using both conventional scintillation detectors and imaging plates), protein crystallography, reflectometry, as well as single‐crystal diffractometry. The present experiments were conducted on BIGDIFF in triple‐crystal diffraction mode with a monolithic channel‐cut Si monochromator (supplied by Professor M. Hart), a single‐crystal Si sample, and a four‐reflection monolithic channel‐cut Si analyzer crystal. The Si(111) sample is a part of a wafer which had been implanted with 100 keV B+ ions (doses 1×1015 and 5×1015 cm−2) through a one‐dimensional 0.5 μm thick oxide strip pattern with a 5.83 μm period and 4 μm open region. The triple‐crystal data were collected in the form of two‐dimensional intensity maps in the vicinity of the 111 Bragg peak, varying the sample rotation (ω) and the analyzer/scintillation detector rotation (2θ). The first results were collected in air both with the as‐described sample and after the oxide layer had been removed. Certain slice scans (one‐dimensional sections of the two‐dimensional intensity maps) were also collected with a vacuum of 1 Torr and reveal considerable improvement in signal to background. The data will be compared with a recent similar study A. Yu. Nikulin et al., J. Appl. Cryst. 27, 338 (1994) performed on BL‐14B at the Photon Factory. The new data collected in air indicate that lattice distortion may be mapped with a resolution of approximately 160 Å, to a depth of approximately 1.0 μm, providing valuable quantitative information on ion diffusion in such implanted materials. The slice scans collected in vacuum indicate that a depth resolution of 50 Å is certainly achievable using BIGDIFF. The data show the excellent potential of BIGDIFF for extremely good signal to noise and very high resolution in such experiments, and the advantages of working entirely in vacuum. © 1995 American Institute of Physics.
- ItemMCT beamline at ANSTO/Australian Synchrotron: commissioning & first user operations(Australian Nuclear Science and Technology Organisation, 2022-12-01) Stevenson, AWThe Micro-Computed Tomography (MCT) beamline is one of the first new beamlines to be constructed at the Australian Synchrotron as part of the BRIGHT program. MCT complements the X-ray imaging/tomography capability provided by the Imaging & Medical Beamline (IMBL), and targets applications requiring higher (sub-micron) spatial resolution and involving commensurately smaller samples. MCT is a bending-magnet beamline, operating in the 8 to 40 keV range, based on a novel double-multilayer monochromator. Filtered white and pink beams are also available, the latter utilising a single-bounce mirror. MCT will benefit from X-ray phase-contrast modalities (such as propagation-based, grating-based and speckle) in addition to conventional absorption contrast, and is equipped with a robotic stage for rapid sample exchange. A higher-resolution CT configuration based on the use of a Fresnel zone plate system will also be available soon. Anticipated application areas for non-destructive 3D sample characterisation include biomedical/ health science, food, materials science, and palaeontology. This presentation will provide a description of the commissioning activities undertaken thus far, leading to the first user operations taking place in the current cycle (2022/3). Future developments on the beamline will also be discussed.
- ItemMicro-Computed Tomography (MCT) beamline at ANSTO/Australian Synchrotron: a progress report(Australian Nuclear Science and Technology Organisation, 2021-11-24) Stevenson, AW; Arhatari, BD; Banerjee, R; Bosworth, R; Fiala, T; Graham, B; Griffin, E; Lee, J; McKinlay, J; Michalczyk, A; Millen, C; Oelofse, S; Ozbilgen, S; Rakman, A; Sarris, N; Tabar, E; Tissa, P; Walsh, A; Wirthensohn, J; Harvey, EThe Micro-Computed Tomography (MCT) beamline is one of the first new beamlines to be constructed at the Australian Synchrotron as part of the BRIGHT program. MCT will complement the existing X-ray imaging/tomography capability provided by the Imaging and Medical Beamline (IMBL), and will target applications requiring higher (sub-micron) spatial resolution and involving smaller samples. MCT will be a bendingmagnet beamline, operating in the 8 to 40 keV range, based on a double-multilayer monochromator. Filtered white and pink beams will also be available, the latter utilising a single-(vertical)bounce mirror. MCT will benefit from X-ray phase-contrast modalities (such as propagation-based, grating-based and speckle) in addition to conventional absorption contrast, and be equipped with a robotic stage for rapid sample exchange. A higher-resolution CT configuration based on the use of a Fresnel zone plate system will also be available. A number of sample environmental stages, such as for high temperature and the application of loads, are planned in collaboration with certain groups in the user community. Anticipated application areas for non-destructive 3D sample characterisation include biomedical/ health science, food, materials science, and palaeontology. This presentation will provide an update on the progress of the MCT project, including the procurement of three state-of-the-art X-ray detector systems, and the significant scientific-computing effort required to meet the demands of this high-performance imaging beamline. © The Authors
- ItemMicro-computed tomography beamline of the Australian synchrotron: micron-size spatial resolution X-ray imaging(MDPI, 2023-01-18) Arhatari, BD; Stevenson, AW; Thompson, D; Walsh, A; Fiala, T; Ruben, G; Afshar, N; Ozbilgen, S; Feng, TT; Mudie, ST; Tissa, PThe first new beamline of the BRIGHT project—involving the construction of eight new beamlines at the Australian Synchrotron—is the Micro-Computed Tomography (MCT) beamline. MCT will extend the facility’s capability for higher spatial resolution X-ray-computed tomographic imaging allowing for commensurately smaller samples in comparison with the existing Imaging and Medical Beamline (IMBL). The source is a bending-magnet and it is operating in the X-ray energy range from 8 to 40 keV. The beamline provides important new capability for a range of biological and material-science applications. Several imaging modes will be offered such as various X-ray phase-contrast modalities (propagation-based, grating-based, and speckle-based), in addition to conventional absorption contrast. The unique properties of synchrotron radiation sources (high coherence, energy tunability, and high brightness) are predominantly well-suited for producing phase contrast data. An update on the progress of the MCT project in delivering high-spatial-resolution imaging (in the order of micron size) of mm-scale objects will be presented in detail with some imaging results from the hot-commissioning stage. © 2023 The Authors.
- ItemMicrotomography applications at the Imaging and Medical Beamline of the Australioan Synchrotron (sic)(Australian Microscopy and Microanalysis Society, 2016-02-04) Maksimenko, A; Acres, RG; Hall, C; Häusermann, D; Stevenson, AW; Livingston, J; Pearson, JThe Imaging and Medical Beamline (IMBL) of the Australian Synchrotron (AS) is now becoming one of the most advanced instruments of this type in the world. It is designed to provide a wide variety of imaging techniques including but not limited to the in-line and analyzed phase contrasts, monochromatic and pink beam imaging. Three beamline’s enclosures at various distances, when combined with the 25kW superconducting multipole wiggler and double Laue bent monochromator provide the end user a good choice of beam characteristics ranging from the hi-flux for high resolution and size up to huge 48x5cm beam at 134m from the source with the allowed energy range 17-120kEv. The wide range of the area detectors allows the computed tomography (CT) and tomosynthesis methods to be applied to almost any known X-ray imaging modality. The beamline’s data acquisition system is directly linked to the high performance computing facilities tuned for the on-the-fly real-time reconstruction and 3D rendering. Deep integration of the acquisition, reconstruction and rendering facilities allows one to think of the their combination as of a single system with modular architecture. The system is designed for the fully automated experiments with minimal user interaction. This report summarizes implemented, designed and planned features of the beamline as applied to the microtomography experiments. Some latest outcomes of the CT system are presented with the samples coming of different fields of science: Biology, Geology, Paleontology, Medicine and others.
- ItemSpeckle-based x-ray dark-field tomography of an attenuating object(Society of Photo-Optical Instrumentation Engineers (SPIE), 2021-08-01) Alloo, SJ; Paganin, DM; Morgan, KS; Kitchen, MJ; Stevenson, AW; Mayo, SC; Li, HT; Kennedy, BM; Maksimenko, A; Bowden, J; Pavlov, KMSpatial resolution in standard phase-contrast X-ray imaging is limited by the finite number and size of detector pixels. As a result, this limits the size of features that can be seen directly in projection images or tomographic reconstructions. Dark-field imaging allows information regarding such features to be obtained, as the reconstructed image is a measure of the position-dependent small-angle X-ray scattering of incident rays from the unresolved microstructure. In this paper we utilize an intrinsic speckle-tracking-based X-ray imaging technique to obtain the effective dark-field signal from a wood sample. This effective dark-field signal is extracted using a Fokker-Planck type formalism, which models the deformations of illuminating reference-beam speckles due to both coherent and diffusive scatter from the sample. We here assume that (a) small-angle scattering fans at the exit surface of the sample are rotationally symmetric, and (b) the object has both attenuating and refractive properties. The associated inverse problem, of extracting the effective dark-field signal, is numerically stabilised using a “weighted determinants” approach. Effective dark-field projection images are presented, as well as the dark-field tomographic reconstructions obtained using Fokker-Planck implicit speckle-tracking. © SPIE
- ItemSynchrotron CT dosimetry at the IMBL for low wiggler magnetic field strength and spatial modulation with bow tie filters(Australian Nuclear Science and Technology Organisation, 2021-11-26) Midgley, S; Schleich, N; Stevenson, AW; Merchant, ASynchrotron CT dose reduction was investigated for the IMBL wiggler source operated at lower magnetic field strength and for beam modulation with spatial filters placed upstream from the sample. Beam quality at 25-30 KeV for 1.4-3.0 T was assessed using transmission measurements with copper to quantify the influence of third harmonic radiation. The low energy operational limit is 24-28 KeV for 0.1-1% transmission by added filters, 2 mm path length through silicon and 25 m of air. The upper limit is near 80 KeV for wiggler field 1.4 T, approximately 100 keV for 2.0 T and extend beyond 100 keV for 3.0-4.2 T. The harmonic radiation contribution is reduced for lower field strengths. Measured dose rates suggest the influence of harmonics is insignificant above approximately 26 keV at 1.4 T and above 33 keV at 2.0 T. Relative to 3 T operation, the mean dose rate in air is reduced to approximately 12% at 2 T and 4% at 1.4 T. Spatial filters were constructed from blocks of perspex with circular voids of diameter matching the CT dosimetry test objects. A calibrated ion chamber integrated absorbed dose to the phantom during 360o rotation. CT dose indices (CTDI) were measured at 25-100 KeV for 3.0T only, at the centre and periphery for 35-160 mm diameter perspex phantoms. Beam shaping filters offer protection to the sample by reducing the peripheral and volumetric CTDI by about 10% for small objects and 20-30% for the larger samples. © 2021 The Authors
- ItemSystemic effects of synchrotron radiation(Institute of Physics Publishing, 2018-02-06) Ventura, J; Sprung, CN; Forrester, HB; Palazzolo, JS; Ivashkevich, A; Stevenson, AW; Hall, CJ; Georgakilas, AG; Lobachevsky, PN; Martin, OAA change in an organ or tissue distant from the irradiated region was termed the radiation-induced abscopal effect (RIAE). It is not known how radiation settings affect non-targeted normal tissues and therefore the risk of radiation-related adverse abscopal effects. In a recent study, we examined abscopal effects of microbeam radiotherapy (MRT) and broad beam (BB) configurations, in mice that were locally exposed to a very short pulse of a high dose-rate synchrotron beam utilizing the Imaging and Medical Beamline (IMBL) at the Australian Synchrotron. Here we summarise this study. Oxidative DNA damage was elevated in a wide variety of unirradiated normal tissues. Out-of-field duodenum showed a trend for elevated apoptotic cell death under most irradiation conditions, however, double-strand breaks (DSBs) elevated only after exposure to lower doses. These genotoxic events were accompanied by changes in concentrations of several plasma cytokines and in frequencies of macrophages, neutrophils and T-lymphocytes in duodenum. Overall, systemic radiation responses were independent of dose, time post-irradiation, and radiation modality. These findings have implications for the planning of therapeutic and diagnostic radiation treatment to reduce the risk of radiation-related adverse systemic effects. ©2019 The Authors. Open Access CC-BY.
- ItemX-ray phase-contrast computed tomography for full breast mastectomy imaging at the Australian Synchrotron(Society of Photo-Optical Instrumentation Engineers (SPIE), 2021-08-01) Arhatari, BD; Nesterets, YI; Taba, ST; Maksimenko, A; Hall, CJ; Stevenson, AW; Häsermann, D; Lewis, SJ; Dimmock, M; Thompson, D; Mayo, SC; Quiney, HM; Gureyev, TE; Brennan, PCOne of the imaging modalities offered by the Imaging and Medical Beamline (IMBL) at the Australian Synchrotron is Xray phase-contrast propagation-based computed tomography (PB-CT). The unique combination of high coherence and high brightness of radiation produced by synchrotron X-ray sources enables phase contrast imaging with excellent sensitivity to small density differences in soft tissues and tumors. The PB-CT images using spatially coherent radiation show high signal-to-noise ratio (SNR) without reducing the spatial resolution. This is due to the combined effect of forward free-space propagation and the advanced step of phase retrieval in the reconstruction processes that allows to accommodate noisier recorded images. This gives an advantage of potentially reducing the radiation dose delivered to the sample whilst preserving the reconstructed image quality. It is expected that the PB-CT technique will be well suited for diagnostic breast imaging in the near future with the advantage that it could provide better tumor detection and characterization/grading than mammography and other breast imaging modalities/techniques in general. The PB-CT technique is expected to reduce false negative and false positive cancer diagnoses that result from overlapping regions of tissue in 2D mammography and avoid patient pain and discomfort that results from breast compression. The present paper demonstrates that PB-CT produces superior results for imaging low-density materials such as breast mastectomy samples, when compared to the conventional absorption-based CT collected at the same radiation dose. The performance was quantified in terms of both the measured objective image characteristics and the subjective scores from radiological assessments. This work is part of the ongoing research project aimed at the introduction of 3D X-ray medical imaging at the IMBL as innovative tomographic methods to improve the detection and diagnosis of breast cancer. Major progress of this project includes the characterization of a large number of mastectomy samples, both normal and cancerous. © (2021) Society of Photo-Optical Instrumentation Engineers (SPIE).
- ItemX-ray phase-contrast computed tomography for soft tissue Imaging at the Imaging and Medical Beamline (IMBL) of the Australian Synchrotron(MDPI, 2021-04-30) Arhatari, BD; Stevenson, AW; Abbey, B; Nesterets, YI; Maksimenko, A; Hall, CJ; Thompson, D; Mayo, SC; Fiala, T; Quiney, HM; Taba, ST; Lewis, SJ; Brennan, PC; Dimmock, MR; Häusermann, D; Gureyev, TEThe Imaging and Medical Beamline (IMBL) is a superconducting multipole wiggler-based beamline at the 3 GeV Australian Synchrotron operated by the Australian Nuclear Science and Technology Organisation (ANSTO). The beamline delivers hard X-rays in the 25–120 keV energy range and offers the potential for a range of biomedical X-ray applications, including radiotherapy and medical imaging experiments. One of the imaging modalities available at IMBL is propagation-based X-ray phase-contrast computed tomography (PCT). PCT produces superior results when imaging low-density materials such as soft tissue (e.g., breast mastectomies) and has the potential to be developed into a valuable medical imaging tool. We anticipate that PCT will be utilized for medical breast imaging in the near future with the advantage that it could provide better contrast than conventional X-ray absorption imaging. The unique properties of synchrotron X-ray sources such as high coherence, energy tunability, and high brightness are particularly well-suited for generating PCT data using very short exposure times on the order of less than 1 min. The coherence of synchrotron radiation allows for phase-contrast imaging with superior sensitivity to small differences in soft-tissue density. Here we also compare the results of PCT using two different detectors, as these unique source characteristics need to be complemented with a highly efficient detector. Moreover, the application of phase retrieval for PCT image reconstruction enables the use of noisier images, potentially significantly reducing the total dose received by patients during acquisition. This work is part of ongoing research into innovative tomographic methods aimed at the introduction of 3D X-ray medical imaging at the IMBL to improve the detection and diagnosis of breast cancer. Major progress in this area at the IMBL includes the characterization of a large number of mastectomy samples, both normal and cancerous, which have been scanned at clinically acceptable radiation dose levels and evaluated by expert radiologists with respect to both image quality and cancer diagnosis. © 2021 The Authors, Licensee MDPI, Basel, Switzerland. Open Access Creative Commons Attribution (CC BY).