Probing active-edge silicon sensors using a high precision telescope Akiba, K.; Artuso, M.; van Beveren, V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2015, Letnik:
777
Journal Article
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The performance of prototype active-edge VTT sensors bump-bonded to the Timepix ASIC is presented. Non-irradiated sensors of thicknesses 100–200μm and pixel-to-edge distances of 50μm and 100μm were ...probed with a beam of charged hadrons with sub-pixel precision using the Timepix telescope assembled at the SPS at CERN. The sensors are shown to be highly efficient up to a few micrometers from the physical edge of the sensor. The distortion of the electric field lines at the edge of the sensors is studied by reconstructing the streamlines of the electric field using two-pixel clusters. These results are supported by TCAD simulations. The reconstructed streamlines are used to study the field distortion as a function of the bias voltage and to apply corrections to the cluster positions at the edge.
The Timepix Telescope for high performance particle tracking Akiba, K.; Ronning, P.; van Beuzekom, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2013, Letnik:
723
Journal Article
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The Timepix particle tracking telescope has been developed as part of the LHCb VELO Upgrade project, supported by the Medipix Collaboration and the AIDA framework. It is a primary piece of ...infrastructure for the VELO Upgrade project and is being used for the development of new sensors and front end technologies for several upcoming LHC trackers and vertexing systems. The telescope is designed around the dual capability of the Timepix ASICs to provide information about either the deposited charge or the timing information from tracks traversing the 14×14mm matrix of 55×55μm pixels. The rate of reconstructed tracks available is optimised by taking advantage of the shutter driver readout architecture of the Timepix chip, operated with existing readout systems. Results of tests conducted in the SPS North Area beam facility at CERN show that the telescope typically provides reconstructed track rates during the beam spills of between 3.5 and 7.5kHz, depending on beam conditions. The tracks are time stamped with 1ns resolution with an efficiency of above 98% and provide a pointing resolution at the centre of the telescope of ∼1.6μm. By dropping the time stamping requirement the rate can be increased to ∼15kHz, at the expense of a small increase in background. The telescope infrastructure provides CO2 cooling and a flexible mechanical interface to the device under test, and has been used for a wide range of measurements during the 2011–2012 data taking campaigns.
•We provide a technical description of the Timepix Telescope for particle tracking applications.•We demonstrate the spatial and timing resolution to be 2μm and 1ns respectively.•The maximum particle rate is 7.5kHz with highly resolved timing and spacing.•The maximum particle rate is 15kHz with only highly resolved spacing.•We briefly describe the software and tracking algorithms used to achieve this.
While designed primarily for X-ray imaging applications, the Medipix3 ASIC can also be used for charged-particle tracking. In this work, results from a beam test at the CERN SPS with irradiated and ...non-irradiated sensors are presented and shown to be in agreement with simulation, demonstrating the suitability of the Medipix3 ASIC as a tool for characterising pixel sensors.
Reported matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) identification rates of Gram-positive rods (GPR) are low compared to identification rates of ...Gram-positive cocci. In this study, three sample preparation methods were compared for MALDI-TOF MS identification of 190 well-characterized GPR strains: direct transfer, direct transfer-formic acid preparation, and ethanol-formic acid extraction. Using the interpretation criteria recommended by the manufacturer, identification rates were significantly higher for direct transfer-formic acid preparation and ethanol-formic acid extraction than for direct transfer. Reducing the species cutoff from 2.0 to 1.7 significantly increased species identification rates. In a subsequent prospective study, 215 clinical GPR isolates were analyzed by MALDI-TOF MS, and the results were compared to those for identification using conventional methods, with discrepancies being resolved by 16S rRNA and rpoB gene analysis. Using the direct transfer-formic acid preparation and a species cutoff of 1.7, congruencies on the genus and species levels of 87.4% and 79.1%, respectively, were achieved. In addition, the rate of nonidentified isolates dropped from 12.1% to 5.6% when using an extended database, i.e., the Bruker database amended by reference spectra of the 190 GPR of the retrospective study. Our data demonstrate three ways to improve GPR identification by the Bruker MALDI Biotyper, (i) optimize sample preparation using formic acid, (ii) reduce cutoff scores for species identification, and (iii) expand the database. Based on our results, we suggest an identification algorithm for the clinical laboratory combining MALDI-TOF MS with nucleic acid sequencing.
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