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36 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4 [Next/Last]

Instruments / Technical Area	Publication Details	Published
Detectors	Performance of the lancelot beam position monitor at the Diamond Light Source H. Chagani , T. B. Garcia-Nathan , C. Jiang , A. Kachatkou , J. Marchal , D. Omar , N. Tartoni , Roelof Van Silfhout , S. Williams Journal Of Instrumentation 12, C12044 - C12044 11th International Conference on Position Sensitive Detectors (PSD11) DOI: 10.1088/1748-0221/12/12/C12044 Open Access Show Abstract ▼ Abstract: The Lancelot beam position and profile monitor records the scattered radiation off a thin, low-density foil, which passes through a pinhole perpendicular to the path of the beam and is detected by a Medipix3RX sensor. This arrangement does not expose the detector to the direct beam at synchrotrons and results in a negligible drop in flux downstream of the module. It allows for magnified images of the beam to be acquired in real time with high signal-to-noise ratios, enabling measurements of tiny displacements in the position of the centroid of approximately 1 μm. It also provides a means for independently measuring the photon energy of the incident monoenergetic photon beam. A constant frame rate of up to 245 Hz is achieved. The results of measurements with two Lancelot detectors installed in different environments at the Diamond Light Source are presented and their performance is discussed.	Dec 2017
	Review of hybrid pixel detector readout ASICs for spectroscopic X-ray imaging R. Ballabriga , J. Alozy , M. Campbell , E. Frojdh , E. H. M. Heijne , T. Koenig , X. Llopart , J. Marchal , D Pennicard , T. Poikela , L. Tlustos , P. Valerio , W. Wong , M. Zuber Journal Of Instrumentation 11, P01007 - P01007 DOI: 10.1088/1748-0221/11/01/P01007 Open Access Show Abstract ▼ Abstract: Semiconductor detector readout chips with pulse processing electronics have made possible spectroscopic X-ray imaging, bringing an improvement in the overall image quality and, in the case of medical imaging, a reduction in the X-ray dose delivered to the patient. In this contribution we review the state of the art in semiconductor-detector readout ASICs for spectroscopic X-ray imaging with emphasis on hybrid pixel detector technology. We discuss how some of the key challenges of the technology (such as dealing with high fluxes, maintaining spectral fidelity, power consumption density) are addressed by the various ASICs. In order to understand the fundamental limits of the technology, the physics of the interaction of radiation with the semiconductor detector and the process of signal induction in the input electrodes of the readout circuit are described. Simulations of the process of signal induction are presented that reveal the importance of making use of the small pixel effect to minimize the impact of the slow motion of holes and hole trapping in the induced signal in high-Z sensor materials. This can contribute to preserve fidelity in the measured spectrum with relatively short values of the shaper peaking time. Simulations also show, on the other hand, the distortion in the energy spectrum due to charge sharing and fluorescence photons when the pixel pitch is decreased. However, using recent measurements from the Medipix3 ASIC, we demonstrate that the spectroscopic information contained in the incoming photon beam can be recovered by the implementation in hardware of an algorithm whereby the signal from a single photon is reconstructed and allocated to the pixel with the largest deposition.	Jan 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 Detectors Diagnostics	A compact and portable X-ray beam position monitor using Medipix3 Octavio Rico Alvarez , Anton Kachatkou , Julien Marchal , Brian Willis , Kawal Sawhney , Nicola Tartoni , Roelof Van Silfhout Journal Of Instrumentation 9, C12036 - C12036 DOI: 10.1088/1748-0221/9/12/C12036 Show Abstract ▼ Abstract: The present work reports on the design and implementation of a novel portable X-ray beam diagnostics (XBPM) device. The device is transparent to the X-ray beam and provides real-time measurements of beam position, intensity, and size. The measurement principle is based on a pinhole camera which records scattered radiation from a Kapton foil which is placed in the beam path. The use of hybrid detectors (Medipix3) that feature a virtually noiseless readout system with capability of single photon detection and energy resolving power enables the diagnostics with a better resolution and higher sensitivity compared to the use of traditional indirect X-ray detection schemes. We describe the detailed system design, which consists of a vacuum compatible focal plane sensor array, a sensor conditioning and readout board and a heterogeneous data processing unit, which also acts as a network server that handles network communications with clients. The readout protocol for the Medipix3 sensor is implemented using field programmable gate array (FPGA) logic resulting in a versatile and scalable system that is capable of performing advanced functions such as data compression techniques and feature extraction. For the system performance measurements, we equipped the instrument with a single Medipix3 die, bump bonded to a Si sensor, rather than four for which it was designed. Without data compression, it is capable of acquiring magnified images and profiles of synchrotron X-ray beams at a transfer rate through Ethernet of 27 frames/s for one Medipix3 die.	Dec 2014
I19-Small Molecule Single Crystal Diffraction	Time-resolved crystallographic developments utilising detector gating techniques Mark Warren , Dave Allan , Paul Raithby , J Christensen , J Trincao , M Hamilton , Lauren Hatcher , L Thomas , Arwen Pearson , Julien Marchal Show Abstract ▼ Abstract: The X-ray scattering process occurs on the time scale of about 10-18 seconds; the complete data collection is in the order of hours at synchrotron sources and consequently gives a time-averaged structure of the crystalline material. Previously on beamline I19 at Diamond Light Source we have used a method which involves mechanically chopping the X-ray beam to produce a pulsed source. The pulsed X-ray beam can then be used to probe the crystal a short period after the sample has been photo-activated by a laser beam. This method can be repeated changing the period between the laser (pump) and X-ray pulse (probe) until the entire time series is obtained. Beamline I19 in collaboration with the Dynamic Structural Sciences Consortium at the Research Complex at Harwell have designed a novel strategy to collect an entire time-series (zero to 100 ms) in one data collection utilising the fast image collection time of the Pilatus detector. The 300K Pilatus detector has a readout out time of 2.7 ms and can be gated down to 200 ns. This means that we can use this gating (instead of the mechanical chopper) to obtain single crystal time-resolved structures. This technique shortens the data collection time and as the entire series is obtained from one crystal during the same data collection, this reduces decay and scaling issues.	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
B16-Test Beamline Detectors	In situ micro-focused X-ray beam characterization with a lensless camera using a hybrid pixel detector Anton Kachatkou , Julien Marchal , Roelof Van Silfhout Journal Of Synchrotron Radiation 21, 333 - 339 DOI: 10.1107/S1600577513034759 PMID: 24562554 Diamond Proposal Number(s): [517427] Open Access Show Abstract ▼ Abstract: Results of studies on micro-focused X-ray beam diagnostics using an X-ray beam imaging (XBI) instrument based on the idea of recording radiation scattered from a thin foil of a low-Z material with a lensless camera are reported. The XBI instrument captures magnified images of the scattering region within the foil as illuminated by the incident beam. These images contain information about beam size, beam position and beam intensity that is extracted during dedicated signal processing steps. In this work the use of the device with beams for which the beam size is significantly smaller than that of a single detector pixel is explored. The performance of the XBI device equipped with a state-of-the-art hybrid pixel X-ray imaging sensor is analysed. Compared with traditional methods such as slit edge or wire scanners, the XBI micro-focused beam characterization is significantly faster and does not interfere with on-going experiments. The challenges associated with measuring micrometre-sized beams are described and ways of optimizing the resolution of beam position and size measurements of the XBI instrument are discussed.	Mar 2014
B18-Core EXAFS I11-High Resolution Powder Diffraction Detectors	Analytical model of single-X-ray photon counting pixel-array detectors J. Marchal , J. Mcgrath , K. Medjoubi Journal Of Instrumentation 9, C03006 - C03006 15th International Workshop on Radiation Imaging Detectors (IWORID2013) DOI: 10.1088/1748-0221/9/03/C03006 Show Abstract ▼ Abstract: Single-X-ray-photon counting pixel array detectors are now widely used on synchrotron beamlines for X-ray diffraction and imaging experiments. Efforts have been carried out in the recent years to extend X-ray detector system analysis to include charge-sharing effects and characteristic X-ray re-absorption on image quality parameters such as MTF, NPS and DQE. These efforts led to the formulation of an analytical model of single-X-ray-photon counting pixel array detectors which is presented in this contribution to the IWORID-2013 conference. This model links together imaging and spectroscopic performance of pixel array detectors. It provides a framework for optimising the design of single-energy threshold, multiple-energy thresholds and energy-sensitive pixel array detectors. This analytical model is applied to typical silicon- and CdTe-based pixel sensor geometries associated to single-X-ray processing read-out electronics	Mar 2014
Detectors	Sampling function of single-X-ray-photon counting hybrid pixel detectors: combining an analytical approach to Monte-Carlo simulations and Finite-Element-Modeling J. Mcgrath , J. Marchal , K. Medjoubi Journal Of Instrumentation 8, P10008 - P10008 DOI: 10.1088/1748-0221/8/10/P10008 Show Abstract ▼ Abstract: Spectroscopic and imaging performance parameters of hybrid pixel detectors operated in single-X-ray photon-counting mode can be inferred from the dependence of their sampling function (or aperture function) on the detection energy threshold. In a previous paper, it was shown that this dependence could be modelled using a simple analytical method. Measurements were performed on typical synchrotron X-ray detectors and fitted to the analytical formulas in order to obtain detector parameters such as charge-sharing width, energy dispersion and fill-factor at 50% threshold. In the present paper, we use Monte-Carlo (MC) and Finite-Element-Modeling (FEM) software tools to perform a more detailed simulation of image formation processes taking place in photon-counting hybrid pixel detectors of various pixel sizes associated to standard silicon sensor thickness and exposed to 15 keV monochromatic X-rays. We show that the MC/FEM simulation results can be used to produce detector parameters required in the analytical expressions of the sampling function of these detectors.	Oct 2013
Detectors	EXCALIBUR: a small-pixel photon counting area detector for coherent X-ray diffraction - Front-end design, fabrication and characterisation J. Marchal , I. Horswell , B. Willis , R. Plackett , E. N. Gimenez-Navarro , J. Spiers , D. Ballard , P. Booker , J. A. Thompson , P. Gibbons , S. R. Burge , T. Nicholls , J. Lipp , N. Tartoni Journal Of Physics: Conference Series 425 11th International Conference on Synchrotron Radiation Instrumentation (SRI 2012) DOI: 10.1088/1742-6596/425/6/062003 Show Abstract ▼ Abstract: Coherent X-ray diffraction experiments on synchrotron X-ray beamlines require detectors with high spatial resolution and large detection area. The read-out chip developed by the MEDIPIX3 collaboration offers a small pixel size of 55 microns resulting in a very high spatial resolution when coupled to a direct X-ray conversion segmented silicon sensor. MEDIPIX3 assemblies present also the advantages of hybrid pixel detectors working in single photon counting mode: noiseless imaging, large dynamic range, extremely high frame rate. The EXCALIBUR detector is under development for the X-ray Coherence and Imaging Beamline I13 of the Diamond Light Source. This new detector consists of three modules, each with 16 MEDIPIX3 chips which can be read-out at 100 frames per second in continuous mode or 1000 frames per second in burst mode. In each module, the sensor is a large single silicon die covering 2 rows of 8 individual MEDIPIX3 read-out chips and provides a continuous active detection region within a module. Each module includes 1 million solder bumps connecting the 55 microns pixels of the silicon sensor to the 55 microns pixels of the 16 MEDIPIX3 read-out chips. The detection area of the 3-module EXCALIBUR detector is 115 mm × 100 mm with a small 6.8 mm wide inactive region between modules. Each detector module is connected to 2 FPGA read-out boards via a flexi-rigid circuit to allow a fully parallel read-out of the 16 MEDIPIX3 chips. The 6 FPGA read-out boards used in the EXCALIBUR detector are interfaced to 6 computing nodes via 10Gbit/s fibre-optic links to maintain the very high frame-rate capability. The standard suite of EPICS control software is used to operate the detector and to integrate it with the Diamond Light Source beamline software environment. This article describes the design, fabrication and characterisation of the MEDIPIX3-based modules composing the EXCALIBUR detector.	Mar 2013

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