I18-Microfocus Spectroscopy
Detectors
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Open Access
Abstract: A new type of transmissive pixel detector has been developed for synchrotron radiation diagnostics at Diamond Light Source. A thin single-crystal CVD diamond plate is used as the detector material, and a pulsed-laser technique has been used to write conductive graphitic electrodes inside the diamond plate. Instead of using traditional electrodes formed from a layer of surface metallisation, the graphitic electrodes are buried under the surface of the diamond and result in an all-carbon imaging detector. Within the instrument’s transmissive aperture there are no surface structures that could be damaged by exposure to radiation beams, and no surface metallization that could introduce unwanted absorption edges. The instrument has successfully been used to image the X-ray beam profile and measure the beam position to sub-micron accuracy at 100 Hz at Diamond Light Source. A novel modulation lock-in technique is used to read out all pixels simultaneously. Presented in this work are measurements of the detector’s beam position resolution and intensity resolution. Initial measurements of the instrument’s spread-function are also presented. Numerical simulations are used to identify potential improvements to the electrode geometry to improve the spatial resolution of similar future detectors. The instrument has applications in both synchrotron radiation instrumentation, where real-time monitoring of the beam profile is useful for beam diagnostics and fault-finding, and particle tracking at colliders, where the electrode geometries that buried graphitic tracks can provide increased the charge collection efficiency of the detector.
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Oct 2021
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B16-Test Beamline
Detectors
Optics
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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.
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Aug 2021
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Detectors
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Abstract: Annular-dark field imaging is one of the most readily interpretable techniques in scanning transmission electron microscopy (STEM). The ADF detector integrates the intensity of incoherent, high-angle scattered electrons providing images with strong atomic number sensitivity that can be directly interpreted in terms of the sample’s atomic structure. The ADF contrast increases monotonically with the number of atoms in projection. This allows direct atomic counting to solve three-dimensional (3D) structures or determine composition at a given thickness. However, ADF STEM is not efficient for light elements detection because they scatter less strongly at high scattering angles. More suitable methods to image both light and heavy atoms are based on bright-field or phase-contrast techniques that collect low-angle scattered electrons. However, because these electrons scatter coherently, image quantification, in this case, is non-trivial.
This talk will discuss quantification methods for two main (quasi-)coherent STEM imaging modes: annular- bright field (ABF) imaging and 4D STEM electron ptychography.
In the case of ABF, image quantification is applied to the characterisation of the oxygen framework in lithium- rich Li1.2Ni0.2Mn0.6O2 (LNMO) layered cathodes. In this material, short-range oxygen sublattice distortions are evidence for oxygen participation in charge compensation mechanisms. These movements are of the order of picometres and, to be measured, require well-designed quantification methods. However, achieving picometre accuracy and precision is challenging in these materials because of the limited signal-to-noise ratio of the images imposed by the electron dose. The first part of this talk discusses how to achieve high-quality ABF quantification using a combination of experimental design and computational data processing including simultaneous ADF atom counting and multi-slice image simulations.
The second part of the talk shows how these methods can be extended to the quantification of 4D STEM electron ptychography data using fast electron detectors. A four-dimensional dataset consist of a two- dimensional (2D) convergent beam electron diffraction pattern (CBED) recorded at every pixel of a 2D scan array. The exit wave resulting from the electron-specimen interaction can be restored from this dataset using electron ptychography. In analogy with the contrast in ADF, the exit wave phase is fully quantitative and is highly sensitive to the number of atoms in the sample and their position along the column. Here, phase and ADF quantification are used to count the number of light and heavy elements simultaneously. The technique is applied to determine the composition in a reduced CeO2-x nanoparticle by simultaneous counting the number of Ce and O atoms.
Experimental design is fundamental for any quantification technique. The last part of this talk discusses design strategies for comparing ptychographic techniques at low dose and imaging of light biological materials. Also, it examines how to efficiently compare restored data based on the effect of the contrast transfer function for the recovered spatial frequencies.
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Jul 2021
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Detectors
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Alessandro
Marras
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Jonathan
Correa
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Sabine
Lange
,
Vahagn
Vardanyan
,
Tim
Gerhardt
,
Manuela
Kuhn
,
Frantisek
Krivan
,
Igor
Shevyakov
,
Manfred
Zimmer
,
Moritz
Hoesch
,
Kai
Bagschik
,
Frank
Scholz
,
Niccolo
Guerrini
,
Ben
Marsh
,
Iain
Sedgwick
,
Giuseppe
Cautero
,
Dario
Giuressi
,
Gregori
Iztok
,
Ralf H.
Menk
,
Martin
Scarcia
,
Luigi
Stebel
,
Tim
Nicholls
,
William
Nichols
,
Ulrik K.
Pedersen
,
Polad
Shikhaliev
,
Nicola
Tartoni
,
Hyojung
Hyun
,
Seonghan
Kim
,
Kyungsook
Kim
,
Seungyu
Rah
,
Arkadiusz
Dawiec
,
Fabienne
Orsini
,
Giovanni
Pinaroli
,
Alan
Greer
,
Steve
Aplin
,
April D.
Jewell
,
Todd J.
Jones
,
Shouleh
Nikzad
,
Michael E.
Hoenk
,
Frank
Okrent
,
Heinz
Graafsma
,
Cornelia B.
Wunderer
Open Access
Abstract: In this paper the back-side-illuminated Percival 2-Megapixel (P2M) detector is presented, along with its characterization by means of optical and X-ray photons. For the first time, the response of the system to soft X-rays (250 eV to 1 keV) is presented. The main performance parameters of the first detector are measured, assessing the capabilities in terms of noise, dynamic range and single-photon discrimination capability. Present limitations and coming improvements are discussed.
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Jan 2021
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Detectors
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Abstract: At synchrotron facilities, many X-ray imaging and diffraction experiments require pixel detectors with minimal noise, high speed and reasonably small pixel size, all of which can be achieved with the Medipix ASIC family. So, ESRF, Diamond Light Source and DESY have developed detector systems based on Medipix. In this paper, we report on these developments, with an emphasis on the challenges involved building readout systems and the potential of the Medipix family ASICs in this field of research.
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Oct 2020
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B16-Test Beamline
Detectors
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K.
Metodiev
,
M.
Mironova
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D.
Bortoletto
,
R.
Plackett
,
P.
Allport
,
I.
Asensi Tortajada
,
R.
Cardella
,
F.
Dachs
,
V.
Dao
,
M.
Dyndal
,
L.
Flores Sanz De Acedo
,
P.
Freeman
,
A.
Gabrielli
,
L.
Gonella
,
M.
Munker
,
H.
Pernegger
,
F.
Piro
,
P.
Riedler
,
A.
Sharma
,
E. J.
Schioppa
,
I.
Shipsey
,
W.
Snoeys
,
C.
Solans Sanchez
,
H.
Wennloef
,
D. P.
Weatherill
,
D.
Wood
,
S.
Worm
Diamond Proposal Number(s):
[2206]
Abstract: Detector prototypes are commonly characterised in testbeams, either using charged particles or X-rays. Charged particles are used to quantify detector performance in terms of absolute efficiency, while X-rays can provide additional information about the detector structure. This paper presents an alternative approach to calculating charged particle efficiencies, using the results of an X-ray testbeam of the mini-MALTA CMOS prototype at Diamond Light Source, and additional laboratory measurements. Results are presented for an unirradiated and an irradiated sample and compared to the results of charged particle testbeams at SPS and ELSA. The extrapolated efficiencies are in agreement with the measured values. Additionally, the extrapolated efficiency maps provide more insight about the location of the pixel inefficiencies, due to the better spatial resolution of the X-ray testbeam.
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Aug 2020
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B16-Test Beamline
Detectors
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Abstract: One of the major limitations of XAS experiment at synchrotron facilities is the performance of the detectors. In order to be able to measure more challenging samples and to cope with the very high photon flux of the current and future (diffraction limited) sources technological developments of detectors are necessary. This paper reports on the construction and characterization of a monolithic nineteen channel germanium detector demonstrator fitted with CMOS preamplifiers. The detector was characterized in the lab with radioactive sources and with the X-ray synchrotron beam. Characteristics such as energy resolution, linearity, counting rate capabilities, and stability of the detector were thoroughly evaluated. In addition, it was proved that by using an advanced pulse processor such as Xspress4 it was possible to improve the performance of the detector system by eliminating the cross talk among channels and by suppressing the charge shared events. This work could pave the way to enhanced germanium fluorescence detectors for high throughput X-ray spectroscopy.
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Jun 2020
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Detectors
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Abstract: This work presents the design and development of a CdTe sensor, Medipix3RXv2 readout ASICs photocounting detector of 55 pm pixel size arranged in an arc modular distribution for its use in X-ray Pair Distribution Function (PDF) applications at the Diamond Light Source (DLS) synchrotron. This contribution highlights the concept and technical solutions adopted for this new detector which include the development of a fibre optic link between the detector head and the readout FPGA cards. This solution enables a considerable reduction in the weight and size of the detector head.
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Apr 2020
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B16-Test Beamline
Detectors
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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
Diamond Proposal Number(s):
[20545]
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.
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Mar 2020
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Detectors
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I.
Sedgwick
,
F.
Krivan
,
I.
Shevyakov
,
M.
Zimmer
,
H.
Graafsma
,
G.
Cautero
,
D.
Giuressi
,
R.
Menk
,
G.
Pinaroli
,
L.
Stebel
,
A.
Greer
,
N.
Guerrini
,
U.
Pedersen
,
N.
Tartoni
,
S. Y.
Rah
,
H. J.
Hyun
,
K. S.
Kim
,
S. H.
Kim
,
B.
Boitrelle
,
F
Orsini
,
B.
Marsh
,
T.
Nicholls
,
A.
Marras
,
C. B.
Wunderer
,
J.
Correa
,
S.
Lange
,
M.
Kuhn
Abstract: High brilliance synchrotrons and Free Electron Lasers (FELs) require high performing detector systems to realise their full potential. High dynamic range, low noise and high frame rate are all of great importance. In this paper we describe the P2M CMOS sensor, designed for soft X-ray detection at such facilities. We refer to previous work on test devices demonstrating a noise of <16e-, a full well capacity of >5Me- and quantum efficiency of >80% at 400eV (and with good sensitivity even below this value). Initial test results on the first Front Side Illuminated (FSI) 2 Megapixel device are also presented, and an outline of future work is described.
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Nov 2019
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