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

Instruments / Technical Area	Publication Details	Published
Detectors	Arc-Detector: Design of a CdTe photon-counting detector for the X-ray Pair Distribution Function beamline at Diamond Light Source E. N. Gimenez , P. A. Chater , G. Crevatin , G. Dennis , A. Fairley , I. Horswell , D. Omar , J. Spiers , N. Tartoni 2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) DOI: 10.1109/NSS/MIC42101.2019.9060070 Show Abstract ▼ 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.	Apr 2020
B16-Test Beamline	Timepix3 as X-ray detector for time resolved synchrotron experiments Hazem Yousef , Giulio Crevatin , Eva Gimenez-Navarro , Ian Horswell , David Omar , Nicola Tartoni Nuclear Instruments And Methods In Physics Research Section A: Accelerators, Spectrometers, Detectors And Associated Equipment DOI: 10.1016/j.nima.2016.04.075 Show Abstract ▼ Abstract: The Timepix3 ASIC can be used very effectively for time resolved experiments at synchrotron facilities. We have carried out characterizations with the synchrotron beam in order to determine the time resolution and other characteristics such as the energy resolution, charge sharing and signals overlapping. The best time resolution achieved is 19 ns FWHM for 12 keV photons and 350 V bias voltage. The time resolution shows dependency on the photon energy as well as on the chip and acquisition parameters.	Apr 2016
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
Detectors	Development of a Schottky CdTe Medipix3RX hybrid photon counting detector with spatial and energy resolving capabilities Eva Gimenez-Navarro , Vytautas Astromskas , Ian Horswell , David Omar , J. Spiers , Nicola Tartoni Nuclear Instruments And Methods In Physics Research Section A: Accelerators, Spectrometers, Detectors And Associated Equipment DOI: 10.1016/j.nima.2015.10.092 Show Abstract ▼ Abstract: A multichip CdTe-Medipix3RX detector system was developed in order to bring the advantages of photon-counting detectors to applications in the hard X-ray range of energies. The detector head consisted of 2×2 Medipix3RX ASICs bump-bonded to a 28 mm×28 mm e− collection Schottky contact CdTe sensor. Schottky CdTe sensors undergo performance degrading polarization which increases with temperature, flux and the longer the HV is applied. Keeping the temperature stable and periodically refreshing the high voltage bias supply was used to minimize the polarization and achieve a stable and reproducible detector response. This leads to good quality images and successful results on the energy resolving capabilities of the system.	Nov 2015
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	Edge pixel response studies of edgeless silicon sensor technology for pixellated imaging detectors Dzmitry Maneuski , Richard Bates , Andrew Blue , C. Buttar , Kate Doonan , Lars Eklund , Eva Gimenez-Navarro , D. Hynds , Slava Kachkanov , J. Kalliopuska , Thomas Mcmullen , V. O'Shea , Nicola Tartoni , Richard Plackett , S. Vahanen , Kennenth Wraight Journal Of Instrumentation 10, P03018 - P03018 DOI: 10.1088/1748-0221/10/03/P03018 Diamond Proposal Number(s): [9405, 10390] Open Access Show Abstract ▼ Abstract: Silicon sensor technologies with reduced dead area at the sensor's perimeter are under development at a number of institutes. Several fabrication methods for sensors which are sensitive close to the physical edge of the device are under investigation utilising techniques such as active-edges, passivated edges and current-terminating rings. Such technologies offer the goal of a seamlessly tiled detection surface with minimum dead space between the individual modules. In order to quantify the performance of different geometries and different bulk and implant types, characterisation of several sensors fabricated using active-edge technology were performed at the B16 beam line of the Diamond Light Source. The sensors were fabricated by VTT and bump-bonded to Timepix ROICs. They were 100 and 200 μm thick sensors, with the last pixel-to-edge distance of either 50 or 100 μm. The sensors were fabricated as either n-on-n or n-on-p type devices. Using 15 keV monochromatic X-rays with a beam spot of 2.5 μm, the performance at the outer edge and corners pixels of the sensors was evaluated at three bias voltages. The results indicate a significant change in the charge collection properties between the edge and 5th (up to 275 μm) from edge pixel for the 200 μ m thick n-on-n sensor. The edge pixel performance of the 100 μm thick n-on-p sensors is affected only for the last two pixels (up to 110 μm) subject to biasing conditions. Imaging characteristics of all sensor types investigated are stable over time and the non-uniformities can be minimised by flat-field corrections. The results from the synchrotron tests combined with lab measurements are presented along with an explanation of the observed effects.	Mar 2015
I13-1-Coherence	X-ray Bragg magnifier microscope as a linear shift invariant imaging system: image formation and phase retrieval P. Vagovic , L. Sveda , A. Cecilia , E. Hamann , D. Pelliccia , E. N. Gimenez-Navarro , D. Korytar , K. M. Pavlov , Zdenko Zaprazny , M. Zuber , T. Koenig , M. Olbinado , W. Yashiro , A. Momose , M. Fiederle , T. Baumbach Optics Express 22 (18) DOI: 10.1364/OE.22.021508 PMID: 25321529 Open Access Show Abstract ▼ Abstract: We present the theoretical description of the image formation with the in-line germanium Bragg Magnifier Microscope (BMM) and the first successful phase retrieval of X-ray holograms recorded with this imaging system. The conditions under which the BMM acts as a linear shift invariant system are theoretically explained and supported by the experiment. Such an approach simplifies the mathematical treatment of the image formation and reconstruction as complicated propagation of the wavefront onto inclined planes can be avoided. Quantitative phase retrieval is demonstrated using a test sample and a proof of concept phase imaging of a spider leg is also presented.	Aug 2014
Detectors	Comparisons between simulation and measurements taken with the Medipix3RX detector John Mcgrath , Julien Marchal , Richard Plackett , Ian Horswell , David Omar , Eva Gimenez-Navarro , Nicola Tartoni 15th international workshop on radiation imaging detectors (iworid2013) DOI: 10.1088/1748-0221/9/05/C05007 Show Abstract ▼ Abstract: A simulation toolkit developed for use at Diamond Light Source is presented, accompanied with experimental validation using a silicon pixel-array sensor coupled to a Medipix3RX chip controlled via the Merlin Readout System. The simulation makes use of Geant4, where photons are tracked in order to determine their position of interaction and energy deposition. Further to this, a Finite Element Methods package, Comsol, is used to model the Charge Induction Efficiencies of various sensors. Results are coupled to Geant4 simulations to provide an accurate method for computing the signals generated on each pixel within the sensor and then an algorithm to model the front-end electronics of the device. The validity of the simulation toolkit is tested by investigating charge-sharing effects using a Medipix3RX chip bump-bonded to a silicon pixel-array sensor. The dependence of the imaging parameters, on the energy threshold, is presented from both simulation and experiment for the Medipix3RX chip operated with and without the charge sharing compensation circuitry enabled. This simulation toolkit can be used to calculate image quality parameters for the next generation of detectors, including CdTe, as well as to improve data corrections on existing detectors on synchrotron beamlines.	May 2014
I15-Extreme Conditions	Comparison of energy resolution spectra of CdTe TIMEPIX detector working in photon counting and time-over-threshold mode David Krapohl , Chrsiter Frojdh , Goran Thungstrom , Erik Frojdh , Eva Gimenez-Navarro , Heribert Wilhelm , Nicola Tartoni , Dzmitry Maneuski , Val O'Shea , Kennenth Wraight Nuclear Science Symposium and Medical Imaging Conference DOI: 10.1109/NSSMIC.2013.6829825 Show Abstract ▼ Abstract: Hybrid pixel detectors like the Medipix and TIMEPIX developed by the Medipix collaboration combined with high-z materials are of growing interest. In particular the TIMEPIX detector can be operated in photon counting mode and time-over-threshold mode (ToT) to obtain spectral information. Previous studies showed that 110ìm pixel sizes obtain a better energy resolution than 55ìm pixel sizes. Furthermore, threshold scans obtained a better spectral resolution than operation in ToT mode. In this work the influence of noise sources in different measurement approaches on the spectral response of a TIMEPIX chip bump-bonded to CdTe sensor are presented. Two 1mm thick CdTe sensors with pixel sizes of 55ìm and 110 ìm, bump-bonded to a TIMEPIX readout chip, were evaluated at the Diamond Light Source synchrotron. A finely collimated, perpendicular pencil beam with x-ray energies of 25 keV and 79 keV was used to investigate single pixels. A small area of 10x10 pixels was investigated in ToT-mode and compared to a threshold scan of the same pixels on both detectors. The measurements are compared to an analytical SPICE/Python simulation	Nov 2013
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

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