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

Instruments / Technical Area	Publication Details	Published
Detectors	Tristan - a 10 million pixel large area time resolved detector for synchrotron use David Omar , Giulio Crevatin , Alan Greer , Ian Horswell , Jonathan Spiers , Richard Plackett , Paul Booker , Gale Lockwood , Dan Beckett , Emily Galvin , John Lipp , Michelangelo Di Palo , Mark Warren , Scott Williams , Nicola Tartoni Ieee Transactions On Nuclear Science DOI: 10.1109/TNS.2022.3204064 Open Access Show Abstract ▼ Abstract: This paper describes the development of the Tristan 10M detector for time resolved synchrotron experiments. Tristan 10M has an unprecedented time resolution (ns time scale) over long duration continuous acquisition (days). The detector is constructed from an array of 160 Timepix3 readout ASIC (about 10 million pixels) flip chip bonded to 10 monolithic silicon sensors which enable it to cover an area large enough to effectively carry out crystallography experiments. The large array of ASICs resulted in a number of severe technical challenges that had to be overcome during the development of the detector. The minimization of the dead area between sensors required the development of a very challenging mechanical and electronic packaging. Such a packaging had to be able to route the large number of data and power lines within the footprint of a sensor, had to effectively sink the heat generated by the ASICs, and had to be able to position the sensors accurately. In addition, the packaging of the detector was designed to be scalable in consideration of possible future larger versions of this detector which added a further challenge. The data driven nature of Timepix3 and the sheer data volume produced by the array of ASICs required us to devise a dedicated hardware, firmware, and software data acquisition architecture. This architecture proved very effective during the commissioning of Tristan10M when time resolved crystallography experiments were carried out.	Sep 2022
Accelerator Physics	Symmetry exploitation in orbit feedback systems of synchrotrons for computational efficiency Idris Kempf , Paul J. Goulart , Stephen R. Duncan , Guenther Rehm Ieee Transactions On Nuclear Science DOI: 10.1109/TNS.2021.3052553 Show Abstract ▼ Abstract: Structural symmetries in the storage ring of synchrotrons are intentionally created during the design phase of the magnetic lattices, but they are rarely considered in the design of control algorithms that stabilize the beam of accelerated particles. The choice of control algorithm, however, is limited by the high actuation frequency and the large number of inputs and outputs. Standard control algorithms for synchrotrons are based on a singular value decomposition (SVD) of the orbit response matrix. SVD controllers exploit neither the structural symmetries nor exhibit any speed advantages. By considering the periodicity and the reflection properties of the betatron function, we show that these structural symmetries are inherited by the orbit response matrix. We then show that the resulting block-circulant and centrosymmetric properties of the matrix can be used for different computationally efficient decompositions of the controller. We also address the case of broken symmetry caused by odd placements of individual magnets and monitors. Our efficient decomposition enables the use of more advanced control techniques for synchrotrons, such as control algorithms that require real-time optimization. These advanced control techniques can in turn increase the stability of photon beams in synchrotron light sources.	Jan 2021
B16-Test Beamline Detectors	Hexagonal pad multichannel Ge X-ray spectroscopy detector demonstrator: comprehensive characterization N. Tartoni , S. Chatterji , R. Crook , T. Krings , L. Bombelli , A. Alborini Ieee Transactions On Nuclear Science DOI: 10.1109/TNS.2020.3004923 Show Abstract ▼ 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.	Jun 2020
Detectors	Evaluation of polarization effects of e− collection Schottky CdTe Medipix3RX hybrid pixel detector Vytautas Astromskas , Eva N. Gimenez , Annika Lohstroh , Nicola Tartoni Ieee Transactions On Nuclear Science 63, 252 - 258 DOI: 10.1109/TNS.2016.2516827 Show Abstract ▼ Abstract: This paper focuses on the evaluation of operational conditions such as temperature, exposure time and flux on the polarization of a Schottky electron collection CdTe detector. A Schottky e- collection CdTe Medipix3RX hybrid pixel detector was developed as a part of the CALIPSO-HIZPAD2 EU project. The 128 ×128 pixel matrix and 0.75 mm thick CdTe sensor bump-bonded to Medipix3RX readout chips enabled the study of the polarization effects. Single and quad module Medipix3RX chips were used which had 128 ×128 and 256 ×256 pixel matrices, respectively. This study reports the sensor-level and pixel-level polarization effects of the detector obtained from a laboratory X-ray source. We report that the sensor-level polarization is highly dependent on temperature, flux and exposure time. Furthermore, the study of pixel-level polarization effects led to identification of a new type of pixel behaviour that is characterised by three distinct phases and, thus, named “tri-phase” (3-P) pixels. The 3-P pixels were the dominant cause of degradation of the flat-field image uniformity under high flux operation. A new method of identifying the optimum operational conditions that utilises a criterion related to the 3-P pixels is proposed. A generated optimum operational conditions chart under the new method is reported. The criterion is used for bias voltage reset depolarization of the detector. The method successfully represented the dependency of polarization on temperature, flux and exposure time and was reproducible for multiple sensors. Operating the detector under the 3-P pixel criterion resulted in the total efficiency not falling below 95%.	Feb 2016
B16-Test Beamline Detectors	Medipix3RX: characterizing the Medipix3 redesign with synchrotron radiation Eva Gimenez-Navarro , Rafael Ballabriga , Gabriel Blaj , Michael Campbell , Igor Dolbnya , Erik Frodjh , Ian Horswell , Xavier Llopart-Cudie , Julien Marchal , John Mcgrath , David Omar , Richard Plackett , Kawal Sawhney , Nicola Tartoni Ieee Transactions On Nuclear Science 62 (3), 1413 - 1421 DOI: 10.1109/TNS.2015.2425227 Show Abstract ▼ Abstract: The Medipix3RX is the latest version of the Medipix3 photon counting ASICs, which implements two new operational modes, with respect to the Medipix2 ASIC, aimed at eliminating charge shared events (referred to as Charge Summing Mode (CSM)) and at providing spectroscopic information (referred to as Colour Mode (CM)). The Medipix3RX is a redesign of the Medipix3v0 ASIC and corrects for the underperformance of CSM features observed in the previous version. This paper presents the results from synchrotron X-rays tests to evaluate the Medipix3RX ASIC performance. The newly implemented CSM algorithm eliminates the charge sharing effect at the same time as allocating the event to the readout pixel corresponding to the sensor pixel where the X-ray photon impinged. The new pixel trimming circuit led to a reduced dispersion between pixels. Further results of the linearity for all the gain modes, energy resolution and pixel uniformity are also presented.	Jun 2015
B16-Test Beamline	Monolithic multi-element HPGe detector equipped with CMOS preamplifiers: construction and characterization of a demonstrator Nicola Tartoni , R. Crook , T. Krings , D. Protic , C. Ross , L. Bombelli , R. Alberti , T. Frizzi , Vytautas Astromskas Ieee Transactions On Nuclear Science 62 (1), 387 - 394 DOI: 10.1109/TNS.2014.2381492 Diamond Proposal Number(s): [4007] Open Access Show Abstract ▼ Abstract: Multi-element germanium detectors for X-ray fluorescence are widely used in synchrotron experiments and in particular in XAFS experiments. This paper presents the construction and characterization of a demonstrator built to investigate the viability of multi-element monolithic germanium detectors equipped with CMOS front-end electronics. Semikon Detector GmbH fabricated a germanium sensor segmented with a pad pattern with pad size 1×1 mm2. 16 channels were instrumented with the CUBE preamplifiers developed at XGLab Srl. The detector was tested with radioactive sources and with the synchrotron X-ray beam of Diamond. The results showed spectra with energy resolution satisfactory for XAFS experiments but with a considerable tail. The low energy tail was proved to be due to charge sharing. In addition the spectra showed the peak stability as a function of counting rate better than 1% for rate up to 838 kcps. The non-linearity of the peak position vs. energy was estimated to be a maximum of 0.13% No evidence of charge loss in the crystal was identified. This work proved that this technology is a viable option to improve the throughput of germanium fluorescence detectors as long as methods to reduce events leading to charge sharing are in place.	Feb 2015
I15-Extreme Conditions Detectors	Probing defects in a small pixellated CdTe sensor using an inclined mono energetic X-ray micro beam E. Frojdh , C. Frojdh , E. Gimenez-Navarro , D. Krapohl , D. Maneuski , B. Norlin , V. O'Shea , H. Wilhelm , N. Tartoni , G. Thungstrom , R. M. Zain Ieee Transactions On Nuclear Science 60 (4), 2864 - 2869 DOI: 10.1109/TNS.2013.2257851 Show Abstract ▼ Abstract: High quantum efficiency is important in X-ray imaging applications. This means using high-Z sensor materials. Unfortunately many of these materials suffer from defects that cause non-ideal charge transport. In order to increase the understanding of these defects, we have mapped the 3D response of a number of defects in two 1 mm thick CdTe sensors with ifferent pixel sizes (55 m and 110 m) using a monoenergetic microbeam at 79 keV. The sensors were bump bonded to Timepix read out chips. Data was collected in photon counting as well as time-over-thresholdmode. The time-over-thresholdmode is a very powerful tool to investigate charge transport properties and fluorescence in pixellated detectors since the signal from the charge that each photon deposits in each pixel can be analyzed. Results show distorted electrical field around the defects, indications of excess leakage current and large differences in behavior between electron collection and hole collection mode. The experiments were carried out on the Extreme onditions Beamline I15 at Diamond Light Source.	Apr 2013
B16-Test Beamline	Evaluation of a second-generation ultra-fast energy-resolved ASIC for photon-counting spectral CT Cheng Xu , Mats Persson , Moa Yveborg , Han Cheng , Staffan Karlsson , Mats Danielsson , Christer Svensson , Hans Bornefalk Ieee Transactions On Nuclear Science 60 (1), 437-445 DOI: 10.1109/TNS.2012.2228276 Diamond Proposal Number(s): [5676] Show Abstract ▼ Abstract: A second-generation ultra-fast energy-resolved application specific integrated circuit (ASIC) has been developed for photon-counting spectral computed tomography (CT). The energy resolution, threshold dispersion and gain of the ASIC were characterized with synchrotron radiation at Diamond Light Source. The standard deviation of threshold offsets at zero keV is 0.89 keV. An RMS energy resolution of 1.09 keV has been demonstrated for 15 keV photon energy at a count rate of 40 kcps, and it deteriorates at a rate of 0.29 keV/Mcps with the increase of output cout rate. The count rate performance of the ASIC has also been evaluated with 120 kV polychromatic x-rays produced by a tungsten anode tube and the results are presented.	Feb 2013
B16-Test Beamline	Characterization of edgeless CdTe detectors for use in hard X-ray imaging applications Matthew C. Veale , Steven J. Bell , Lawrence L. Jones , Paul Seller , Matthew D. Wilson , Robert C. Cernik , Juha Kalliopuska , Harri Pohjonen , Hans Andersson , Seppo Nenonen , Vyacheslav Kachkanov Ieee Transactions On Nuclear Science 59 (4), 1-8 DOI: 10.1109/TNS.2012.2197025 Diamond Proposal Number(s): [5614] Show Abstract ▼ Abstract: Hfq is a bacterial RNA binding protein that facilitates small RNA-mediated posttranscriptional gene regulation. In Vibrio cholerae, Hfq and four Hfq-dependent small RNAs are essential for the expression of virulence genes, but little is known about this mechanism at the molecular level. To better understand V. cholerae Hfq structure and mechanism, we characterized the protein, alongside Escherichia coli Hfq for comparison, using biochemical and biophysical techniques. The N-terminal domain (NTD) of the two proteins is highly conserved, but the C-terminal regions (CTRs) vary in both sequence and length. Small-angle X-ray scattering studies showed that both proteins adopt a star-shaped hexameric structure in which the conserved NTD adopts the expected Sm fold while the variable CTR is disordered and extends radially outwards from the folded core. Despite their structural similarity, SDS-PAGE stability assays and collision-induced dissociation mass spectrometry revealed that the V. cholerae hexamer is less stable than that of E. coli. We propose that this is due to minor differences between the intersubunit interface formed by the NTDs and the ability of the E. coli CTR to stabilize this interface. However, based on electrophoretic mobility shift assays, the divergent CTRs do appear to perform a common function with regard to RNA-binding specificity. Overall, the similarities and differences in the fundamental properties of V. cholerae and E. coli Hfq provide insight into their assembly and molecular mechanisms.	Aug 2012
I15-Extreme Conditions	X-Ray beam studies of charge sharing in small pixel, spectroscopic, CdZnTe detectors Christopher Allwork , Dimitris Kitou , Sandeep Chaudhuri , Paul J. Sellin , Paul Seller , Matthew C. Veale , Nicola Tartoni , Perumal Veeramani Ieee Transactions On Nuclear Science 59 (4), 1563-1568 DOI: 10.1109/TNS.2012.2195678 Show Abstract ▼ Abstract: Recent advances in the growth of CdZnTe material have allowed the development of small pixel, spectroscopic, X-ray imaging detectors. These detectors have applications in a diverse range of fields such as medical, security and industrial sectors. As the size of the pixels decreases relative to the detector thickness, the probability that charge is shared between multiple pixels increases due to the non zero width of the charge clouds drifting through the detector. These charge sharing events will result in a degradation of the spectroscopic performance of detectors and must be considered when analyzing the detector response. In this paper charge sharing and charge loss in a 250 mu m pitch CdZnTe pixel detector has been investigated using a mono-chromatic X-ray beam at the Diamond Light Source, U. K. Using a 20 mu m beam diameter the detector response has been mapped for X-ray energies both above (40 keV) and below (26 keV) the material K-shell absorption energies to study charge sharing and the role of fluorescence X-rays in these events.	Aug 2012

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