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13 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 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
B16-Test Beamline	Characterization of a submicro-X-ray fluorescence setup on the B16 beamline at Diamond Light Source M. Rauwolf , Anna Turyanskaya , D. Ingerle , N. Szoboszlai , I. Pape , A. W. Malandain , O. J. L. Fox , L. Hahn , K. J. S. Sawhney , C. Streli Journal Of Synchrotron Radiation 25 DOI: 10.1107/S1600577518006203 Diamond Proposal Number(s): [12705, 12869, 15267, 16260] Open Access Show Abstract ▼ Abstract: An X-ray fluorescence setup has been tested on the B16 beamline at the Diamond Light Source synchrotron with two different excitation energies (12.7 and 17 keV). This setup allows the scanning of thin samples (thicknesses up to several micrometers) with a sub-micrometer resolution (beam size of 500 nm × 600 nm determined with a 50 µm Au wire). Sensitivities and detection limits reaching values of 249 counts s−1 fg−1 and 4 ag in 1000 s, respectively (for As Kα excited with 17 keV), are presented in order to demonstrate the capabilities of this setup. Sample measurements of a human bone and a single cell performed at B16 are presented in order to illustrate the suitability of the setup in biological applications.	Jul 2018
B16-Test Beamline	Dual-polarity pulse processing and analysis for charge-loss correction in cadmium–zinc–telluride pixel detectors Leonardo Abbene , Gaetano Gerardi , Fabio Principato , Manuele Bettelli , Paul Seller , Matthew C\|. Veale , Oliver Fox , Kawal Sawhney , Nicola Zambelli , Giacomo Benassi , Andrea Zappettini Journal Of Synchrotron Radiation 25 DOI: 10.1107/S1600577518006422 Diamond Proposal Number(s): [15047] Show Abstract ▼ Abstract: Charge losses at the inter-pixel gap are typical drawbacks in cadmium–zinc–telluride (CZT) pixel detectors. In this work, an original technique able to correct charge losses occurring after the application of charge-sharing addition (CSA) is presented. The method, exploiting the strong relation between the energy after CSA and the beam position at the inter-pixel gap, allows the recovery of charge losses and improvements in energy resolution. Sub-millimetre CZT pixel detectors were investigated with both uncollimated radiation sources and collimated synchrotron X-rays, at energies below and above the K-shell absorption energy of the CZT material. The detectors are DC coupled to fast and low-noise charge-sensitive preamplifiers (PIXIE ASIC) and followed by a 16-channel digital readout electronics, performing multi-parameter analysis (event arrival time, pulse shape, pulse height). Induced-charge pulses with negative polarity were also observed in the waveforms from the charge-sensitive preamplifiers (CSPs) at energies >60 keV. The shape and the height of these pulses were analysed, and their role in the mitigation of charge losses in CZT pixel detectors. These activities are in the framework of an international collaboration on the development of energy-resolved photon-counting systems for spectroscopic X-ray imaging (5–140 keV).	Jul 2018
B16-Test Beamline I15-Extreme Conditions	Observation of dose-rate dependence in a Fricke dosimeter irradiated at low dose rates with monoenergetic X-rays Mel O'leary , Daria Boscolo , Nicole Breslin , Jeremy M. C. Brown , Igor P. Dolbnya , Chris Emerson , Catarina Figueira , Oliver J. L. Fox , David Robert Grimes , Vladimir Ivosev , Annette K. Kleppe , Aaron Mcculloch , Ian Pape , Chris Polin , Nathan Wardlow , Fred J. Currell Scientific Reports 8 DOI: 10.1038/s41598-018-21813-z Diamond Proposal Number(s): [11529, 10228] Open Access Show Abstract ▼ Abstract: Absolute measurements of the radiolytic yield of Fe3+ in a ferrous sulphate dosimeter formulation (6 mM Fe2+), with a 20 keV x-ray monoenergetic beam, are reported. Dose-rate suppression of the radiolytic yield was observed at dose rates lower than and different in nature to those previously reported with x-rays. We present evidence that this effect is most likely to be due to recombination of free radicals radiolytically produced from water. The method used to make these measurements is also new and it provides radiolytic yields which are directly traceable to the SI standards system. The data presented provides new and exacting tests of radiation chemistry codes.	Mar 2018
	Direct observation of electron emission from CVD diamond grain boundaries by tunnelling atomic force microscopy independent of surface morphology Robert Harniman , Paul W. May , Oliver J. L. Fox Diamond And Related Materials DOI: 10.1016/j.diamond.2017.09.009 Show Abstract ▼ Abstract: We present direct observation of the electron field emission sites over a large area of polycrystalline diamond using tunnelling atomic force microscopy. Any effects of surface topography have been reduced by measuring polycrystalline samples which have surface roughness values < 5 nm. Measurements show that emission arises preferentially from the grain boundaries independent of the surrounding surface morphology.	Sep 2017
I13-1-Coherence Optics	Aberration-free x-ray lenses made of silicon L. Alianelli , I. Pape , J. P. Sutter , O. J. L. Fox , K. J. S. Sawhney , K. Korwin-mikke Spie Proceedings DOI: 10.1117/12.2240005 Diamond Proposal Number(s): [9980] Open Access Show Abstract ▼ Abstract: Brilliant beams of hard x-rays, with geometrical cross-sections below 50×50 nm2, are a standard research tool for synchrotron users. With the advent of lower emittance sources, such as NSLSII, Petra III and Max IV, and planned upgraded lattices, such as APS-2, SPING8-II, ESRF II and DLS II, nanofocusing optics operating in transmission mode will become more competitive than they are currently. In general, they suffer from lower efficiency than reflective optics, however they often have easier set-up and alignment, combined with a smaller footprint. Fabrication and exploitation of ultra-short focal refractive lenses has not witnessed the same progress in the last decade as other optics, such as multilayer mirrors and multilayer Laue lenses. This paper reports on current status of high-resolution lithography for fabricating silicon lenses and on proposed designs for a new class of refractive lenses with zero aberrations and good efficiency. The new designs are created with geometrical parameters matching the spatial resolution achieved by modern lithography and silicon etch technology.	Sep 2016
Optics	Aberration-free short focal length x-ray lenses Lucia Alianelli , Manuel Sánchez Del Rio , Oliver J . L. Fox , Katarzyna Korwin-mikke Optics Letters 40 (23), 5586-5589 DOI: 10.1364/OL.40.005586 PMID: 26625057 Open Access Show Abstract ▼ Abstract: We treat the problem of defining the ideal x-ray refractive lens design for point focusing of low emittance x-ray beams at third- and fourth-generation synchrotron sources. The task is accomplished by using Fermat’s principle to define a lens shape that is completely free from geometrical aberrations. Current microfabrication resolution limits are identified, and a design that tolerates the inherent fabrication imperfections is proposed. The refractive lens design delivers nanometer-sized focused x-ray beams and is compatible with current microfabrication techniques.	Nov 2015

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