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23 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3 [Next/Last]

Instruments / Technical Area	Publication Details	Published
B16-Test Beamline Optics	Two-dimensional wavefront characterization of adaptable corrective optics and Kirkpatrick–Baez mirror system using ptychography Thomas E. J. Moxham , Vishal Dhamgaye , David Laundy , Oliver J. L. Fox , Hossein Khosroabadi , Kawal Sawhney , Alexander Korsunsky Optics Express 30 DOI: 10.1364/OE.453239 Open Access Show Abstract ▼ Abstract: Aberrations introduced during fabrication degrade the performance of X-ray optics and their ability to achieve diffraction limited focusing. Corrective optics can counteract these errors by introducing wavefront perturbations prior to the optic which cancel out the distortions. Here we demonstrate two-dimensional wavefront correction of an aberrated Kirkpatrick-Baez mirror pair using adaptable refractive structures. The resulting two-dimensional wavefront is measured using hard X-ray ptychography to recover the complex probe wavefield with high spatial resolution and model the optical performance under coherent conditions. The optical performance including the beam caustic, focal profile and wavefront error is examined before and after correction with both mirrors found to be diffraction limited after correcting. The results will be applicable to a wide variety of high numerical aperture X-ray optics aiming to achieve diffraction limited focussing using low emittance sources.	May 2022
Optics	Refractive optics for modifying X-ray wavefronts David Laundy , Thomas Moxham , Vishal Dhamgaye , Hossein Khosroabadi , Oliver Fox , Kawal Sawhney Synchrotron Radiation News DOI: 10.1080/08940886.2021.2022400 Open Access	Feb 2022
B16-Test Beamline I15-Extreme Conditions	First observation of radiolytic bubble formation in unstirred nano-powder sludges and a consistent model thereof Mel O'Leary , Aliaksandr Baidak , Martyn Barnes , Thomas Donoclift , Christopher Emerson , Catarina Figueira , Oliver Fox , Annette Kleppe , Aaron Mcculloch , Darryl Messer , Robin Orr , Fred Currell Scientific Reports 11 DOI: 10.1038/s41598-021-01868-1 Diamond Proposal Number(s): [21977, 20531, 20469, 19017, 17524, 17519, 16218] Open Access Show Abstract ▼ Abstract: Experiments involving the irradiation of water contained within magnesium hydroxide and alumina nanoparticle sludges were conducted and culminated in observations of an increased yield of molecular hydrogen when compared to the yield from the irradiation of bulk water. We show that there is a relationship linking this increased yield to the direct nanoscale ionization mechanism in the nanoparticles, indicating that electron emission from the nanoparticles drives new radiative pathways in the water. Because the chemical changes in these sludges are introduced by irradiation only, we have a genuinely unstirred system. This feature allows us to determine the diffusivity of the dissolved gas. Using the measured gas production rate, we have developed a method for modelling when hydrogen bubble formation will occur within the nanoparticle sludges. This model facilitates the determination of a consistent radiolytic consumption rate coinciding with the observations of bubble formation. Thus, we demonstrate a nanoscale radiation effect directly influencing the formation of molecular hydrogen.	Nov 2021
B16-Test Beamline Detectors Optics	Improved spatial resolution in X-ray microscopy using a tilted angle detector Polad Shikhaliev , Oliver Fox , Nicola Tartoni 2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) DOI: 10.1109/NSS/MIC42677.2020.9507906 Show Abstract ▼ Abstract: We performed simulations and experimental tests of a new method for improving the spatial resolution of x-ray imaging detectors using tilted angle irradiation. In this method, the x-ray beam arrives at the detector surface at an angle of <90° so that the beam footprint is expanded and the spatial resolution is increased. The proposed method is applicable for imaging with x-rays in the energy range of E = 0.2-15 keV, which is widely used for x-ray microscopy. The tilted angle irradiation technique can be applied to different types of x-ray microscopy detectors, including indirect conversion detectors (which consist of a scintillator optically coupled to the imaging camera), direct conversion detectors (such as CCD- and CMOS-based soft x-ray cameras) and some other semiconductor detectors. The experimental study described here employed an indirect detector configuration where a thin scintillator was optically coupled to an imaging camera via microscope optics. The spatial resolution was improved by a factor of 2.5 by using a tilt angle of 12° for 13.5 keV x-rays. This study will be continued using different xray energies and detector configurations.	Aug 2021
B16-Test Beamline	X-ray microbeam characterisation of crystalline defects in small pixel GaAs:Cr detectors R. M. Wheater , L. Jowitt , S. Richards , M. C. Veale , M. D. Wilson , O. J. L. Fox , K. J. S. Sawhney , A. D. Lozinskaya , A. Shemeryankina , O. P. Tolbanov , A. Tyazhev , A. N. Zarubin Nuclear Instruments And Methods In Physics Research Section A: Accelerators, Spectrometers, Detectors And Associated Equipment DOI: 10.1016/j.nima.2021.165207 Diamond Proposal Number(s): [23500] Show Abstract ▼ Abstract: A newly supplied 80 × 80 chromium compensated GaAs sensor with a matrix of 80 × 80 pixels on a 250 m pixel pitch has been characterised utilising microbeam mapping techniques at the Diamond Light Source. The GaAs:Cr sensor was mounted to a HEXITEC DAQ system before raster scanning an x-ray beam with area 25 × 25 m in steps of 25 m, providing sub-pixel resolution spectroscopic imaging. Scans were performed with incident x-ray energies ranging from 12 to 45 keV. Following processing of the data in MatLab 2019b an analysis of defects previously observed in etched GaAs wafers occured. Findings indicate the presence of regions with reduced charge collection efficiency where up to 88 % of incident events show significant charge loss, and changing charge carrier lifetimes across the sensor.	Mar 2021
B16-Test Beamline Optics	Aberration characterization of x-ray optics using multi-modal ptychography and a partially coherent source Thomas E. J. Moxham , David Laundy , Vishal Dhamgaye , Oliver J. L. Fox , Kawal Sawhney , Alexander M. Korsunsky Applied Physics Letters 118 DOI: 10.1063/5.0041341 Show Abstract ▼ Abstract: Ptychography is a scanning coherent diffraction imaging technique that provides high-resolution imaging and complete spatial information of the complex probe and object transmission function. The wavefront error caused by aberrated optics has previously been recovered using ptychography when a highly coherent source is used, but has not been demonstrated with partial coherence due to the multi-modal probe required. Here, we demonstrate that partial coherence can be accounted for in ptychographic reconstructions using the multi-modal approach and assuming that decoherence arises from either the probe or the object. This equivalence recovers coherent (or single state) reconstructions of both the probe and the object even in the presence of partial coherence. We demonstrate this experimentally by using hard x-ray ptychography with a partially coherent source to image a Siemens star test object and to also recover the wavefront error from an aberrated beryllium compound refractive lens. The source properties and resolving capabilities are analyzed, and the wavefront error results are compared with another at-wavelength metrology technique. Our work demonstrates the capability of ptychography to provide high-resolution imaging and optics characterization even in the presence of partial coherence.	Mar 2021
B16-Test Beamline	Characterisation of Ge micro-strip sensors with a micro-focused X-ray beam M. Borri , C. Cohen , O. Fox , J. Groves , W. Helsby , O. Mathon , L. Mcnicholl , S. Pascarelli , K. Sawhney , R. Torchio , M. Zuvic Nuclear Instruments And Methods In Physics Research Section A: Accelerators, Spectrometers, Detectors And Associated Equipment DOI: 10.1016/j.nima.2020.164932 Diamond Proposal Number(s): [24637] Open Access Show Abstract ▼ Abstract: Germanium micro-strip sensors were selected as the sensor technology to take data in energy dispersive X-ray spectroscopy experiments at the Extremely Brilliant Source (EBS) in Grenoble (FR). It is important for this experimental technique to use sensors with a large uniform area and a fine pitch. The former determines the range of energy detectable with a single sensor. The latter improves spectral resolution. A high stopping power is also important to perform studies with hard X-rays. The device under test in this measurement was a germanium micro-strip sensor made of 1024 strips with pitch. The bulk was 1.5 mm thick. The sensor was assembled into a prototype cryostat part of the XH detector system. The device was tested at the B16 beamline at the Diamond Light Source (DLS) in Didcot (UK). The objective of the test-beam was to characterise charge-sharing between strips. In fact, this effect limits the spectral resolution of the device. To carry out this test, the sensor was scanned over a subset of strips with micro-focused X-rays under different settings. These were beam energy and intensity, sensor temperature and bias voltage. Results are presented in this paper. It was measured that the full width half maximum of the charge-sharing profile across different strips was for settings which were indicative of the experimental conditions at the EBS. This was a signal current per unit area on the sensor of 10−8 A/ , a bias voltage of -180 V and a temperature of -159 C.	Dec 2020
B16-Test Beamline Optics	Hard X-ray ptychography for optics characterization using a partially coherent synchrotron source Thomas E. J. Moxham , Aaron Parsons , Tunhe Zhou , Lucia Alianelli , Hongchang Wang , David Laundy , Vishal Dhamgaye , Oliver J. L. Fox , Kawal Sawhney , Alexander M. Korsunsky Journal Of Synchrotron Radiation 27 DOI: 10.1107/S1600577520012151 Open Access Show Abstract ▼ Abstract: Ptychography is a scanning coherent diffraction imaging technique which provides high resolution imaging and complete spatial information of the complex electric field probe and sample transmission function. Its ability to accurately determine the illumination probe has led to its use at modern synchrotrons and free-electron lasers as a wavefront-sensing technique for optics alignment, monitoring and correction. Recent developments in the ptychography reconstruction process now incorporate a modal decomposition of the illuminating probe and relax the restriction of using sources with high spatial coherence. In this article a practical implementation of hard X-ray ptychography from a partially coherent X-ray source with a large number of modes is demonstrated experimentally. A strongly diffracting Siemens star test sample is imaged using the focused beam produced by either a Fresnel zone plate or beryllium compound refractive lens. The recovered probe from each optic is back propagated in order to plot the beam caustic and determine the precise focal size and position. The power distribution of the reconstructed probe modes also allows the quantification of the beams coherence and is compared with the values predicted by a Gaussian–Schell model and the optics exit intensity.	Nov 2020
B16-Test Beamline	Room-temperature performance of 3 mm-thick cadmium–zinc–telluride pixel detectors with sub-millimetre pixelization Antonino Buttacavoli , Fabio Principato , Gaetano Gerardi , Manuele Bettelli , Nicola Sarzi Amade , Andrea Zappettini , Paul Seller , Matthew C. Veale , Oliver Fox , Kawal Sawhney , Leonardo Abbene Journal Of Synchrotron Radiation 27 DOI: 10.1107/S1600577520008942 Diamond Proposal Number(s): [20545] Show Abstract ▼ Abstract: Cadmium–zinc–telluride (CZT) pixel detectors represent a consolidated choice for the development of room-temperature spectroscopic X-ray imagers, finding important applications in medical imaging, often as detection modules of a variety of new SPECT and CT systems. Detectors with 3–5 mm thicknesses are able to efficiently detect X-rays up to 140 keV giving reasonable room-temperature energy resolution. In this work, the room-temperature performance of 3 mm-thick CZT pixel detectors, recently developed at IMEM/CNR of Parma (Italy), is presented. Sub-millimetre detector arrays with pixel pitch less than 500 µm were fabricated. The detectors are characterized by good room-temperature performance even at high bias voltage operation (6000 V cm−1), with energy resolutions (FWHM) of 3% (1.8 keV) and 1.6% (2 keV) at 59.5 keV and 122.1 keV, respectively. Charge-sharing investigations were performed with both uncollimated and collimated synchrotron X-ray beams with particular attention to recovering the charge losses at the inter-pixel gap region. High rate measurements demonstrated the absence of high-flux radiation-induced polarization phenomena up to 25 × 106 photons mm−2 s−1.	Sep 2020
B16-Test Beamline	Detection and imaging of gadolinium accumulation in human bone tissue by micro- and submicro-XRF Anna Turyanskaya , Mirjam Rauwolf , Vanessa Pichler , Rolf Simon , Manfred Burghammer , Oliver J. L. Fox , Kawal Sawhney , Jochen G. Hofstaetter , Andreas Roschger , Paul Roschger , Peter Wobrauschek , Christina Streli Scientific Reports 10 DOI: 10.1038/s41598-020-63325-9 Diamond Proposal Number(s): [16260] Open Access Show Abstract ▼ Abstract: Gadolinium-based contrast agents (GBCAs) are frequently used in patients undergoing magnetic resonance imaging. In GBCAs gadolinium (Gd) is present in a bound chelated form. Gadolinium is a rare-earth element, which is normally not present in human body. Though the blood elimination half-life of contrast agents is about 90 minutes, recent studies demonstrated that some tissues retain gadolinium, which might further pose a health threat due to toxic effects of free gadolinium. It is known that the bone tissue can serve as a gadolinium depot, but so far only bulk measurements were performed. Here we present a summary of experiments in which for the first time we mapped gadolinium in bone biopsy from a male patient with idiopathic osteoporosis (without indication of renal impairment), who received MRI 8 months prior to biopsy. In our studies performed by means of synchrotron radiation induced micro- and submicro-X-ray fluorescence spectroscopy (SR-XRF), gadolinium was detected in human cortical bone tissue. The distribution of gadolinium displays a specific accumulation pattern. Correlation of elemental maps obtained at ANKA synchrotron with qBEI images (quantitative backscattered electron imaging) allowed assignment of Gd structures to the histological bone structures. Follow-up beamtimes at ESRF and Diamond Light Source using submicro-SR-XRF allowed resolving thin Gd structures in cortical bone, as well as correlating them with calcium and zinc.	Apr 2020

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