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

Instruments / Technical Area	Publication Details	Published
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	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	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
B16-Test Beamline Detectors	Room-temperature X-ray response of cadmium–zinc–telluride pixel detectors grown by the vertical Bridgman technique Leonardo Abbene , Fabio Principato , Gaetano Gerardi , Antonino Buttacavoli , Donato Cascio , Manuele Bettelli , Nicola Sarzi Amade , Paul Seller , Matthew C. Veale , Oliver Fox , Kawal Sawhney , Silvia Zanettini , Elio Tomarchio , Andrea Zappettini Journal Of Synchrotron Radiation 27 DOI: 10.1107/S1600577519015996 Diamond Proposal Number(s): [20545] Show Abstract ▼ Abstract: In this work, the spectroscopic performances of new cadmium–zinc–telluride (CZT) pixel detectors recently developed at IMEM-CNR of Parma (Italy) are presented. Sub-millimetre arrays with pixel pitch less than 500 µm, based on boron oxide encapsulated vertical Bridgman grown CZT crystals, were fabricated. Excellent room-temperature performance characterizes the detectors even at high-bias-voltage operation (9000 V cm−1), with energy resolutions (FWHM) of 4% (0.9 keV), 1.7% (1 keV) and 1.3% (1.6 keV) at 22.1, 59.5 and 122.1 keV, respectively. Charge-sharing investigations were performed with both uncollimated and collimated synchrotron X-ray beams with particular attention to the mitigation of the charge losses at the inter-pixel gap region. High-rate measurements demonstrated the absence of high-flux radiation-induced polarization phenomena up to 2 × 106 photons mm−2 s−1. These activities are in the framework of an international collaboration on the development of energy-resolved photon-counting systems for high-flux energy-resolved X-ray imaging.	Mar 2020
B16-Test Beamline Metrology Optics	Optimized alignment of X-ray mirrors with an automated speckle-based metrology tool T. Zhou , H. Wang , O. J. L. Fox , K. J. S. Sawhney Review Of Scientific Instruments 90 DOI: 10.1063/1.5057712 Diamond Proposal Number(s): [16534] Open Access Show Abstract ▼ Abstract: X-ray mirrors are widely used in beamlines and laboratories as focusing or collimating optics. As well as the highly accurate processes used to fabricate them, optimized alignment of X-ray mirrors also plays an important role in achieving an ideal X-ray beam. Currently, knife-edge scans are the most often used method for aligning X-ray mirrors, which can characterize the focal size and tune the alignment iteratively. However, knife-edge scanning provides only one-dimensional information and this method suffers from being time-consuming and requiring a high-resolution piezo translation stage. Here we describe a straightforward and non-iterative method for mirror alignment by measuring the relationship between the tilt aberration and the misaligned pitch angle, which is retrieved by an at-wavelength metrology technique using a randomly shaped wavefront modulator. Software and a graphical user interface have been developed to automate the alignment process. Combining the user-friendly interface and the flexibility of the at-wavelength metrology technique, we believe the proposed method and software can benefit researchers working at synchrotron facilities and on laboratory sources.	Feb 2019
B16-Test Beamline Optics	Development of pseudo-perfect x-ray optics using refractive compensators Kawal Sawhney , David Laundy , Tom Moxham , Oliver Fox , Vishal Dhamgaye Proceedings of the 13th International Conference on Synchrotron Radiation Instrumentation – SRI2018 DOI: 10.1063/1.5084634 Open Access Show Abstract ▼ Abstract: With progress towards diffraction limited focusing at third synchrotron sources, obtaining a distortion free wavefront for the X-rays following focusing optics becomes important to enable the exploitation of the high X-ray coherence. We describe a practical method for determining and applying a correction to the wavefront to compensate for distortions caused by fabrication errors in the optics. The method uses custom designed refractive correctors inserted in-line with the optical element. We describe a method for characterising the optics and determining the profile of the refractive corrector and show results from measurements made on real beamline optics.	Jan 2019
B16-Test Beamline Metrology Optics	Auto-alignment of X-ray focusing mirrors with speckle-based at-wavelength metrology Tunhe Zhou , Hongchang Wang , Oliver Fox , Kawal Sawhney Optics Express 26 DOI: 10.1364/OE.26.026961 Show Abstract ▼ Abstract: Significant improvements have been made in the fabrication of diffraction-limited X-ray optics used to pursue an aberration-free wavefront. Alignment of these optics plays a crucial role in the resultant beam quality. Here, we present a simple and fast alignment method based on imaging X-ray near-field speckle patterns, with experimental demonstration using a pair of Kirkpatrick-Baez mirrors. The proposed technique has the potential to be an alternative to conventional methods. It loosens the stringent demand for high-resolution scanning stages compared to conventional knife-edge scan and, hence, can be applied to nano-focusing optics. The flexibility and straightforward implementation of the method allow it to be applied to a wide range of experiments at synchrotron facilities and laboratory-based sources.	Oct 2018

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