3,137 research outputs found

    Preliminary Results for LP VPE X-Ray Detectors

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    Thick epitaxial layers have been grown using Low Pressure Vapour Phase Epitaxy techniques with low free carrier concentrations . This type of material is attractive as a medium for X-ray detection, because of its high conversion efficiency for X-rays in the medically interesting energy range.Comment: 4 pages. PS file only - original in WORD. Also available at http://ppewww.ph.gla.ac.uk/preprints/97/07

    Recent results on GaAs detectors - 137

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    The present understanding of the charge collection in GaAs detectors with respect to the materials used and its processing are discussed. The radiation induced degradation of the charge collection efficiency and the leakage current of the detectors are summarised. The status of strip and pixel detectors for the ATLAS experiment are reported along with the latest results from GaAs X-ray detectors for non-high energy physics applications.Comment: 7 pages. 4 postscript figures + 1 postscript preprint logo + 1 LaTeX file + 1 style file. Also available at http://ppewww.ph.gla.ac.uk/preprints/97/05

    Test beam Characterizations of 3D Silicon Pixel detectors

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    3D silicon detectors are characterized by cylindrical electrodes perpendicular to the surface and penetrating into the bulk material in contrast to standard Si detectors with planar electrodes on its top and bottom. This geometry renders them particularly interesting to be used in environments where standard silicon detectors have limitations, such as for example the radiation environment expected in an LHC upgrade. For the first time, several 3D sensors were assembled as hybrid pixel detectors using the ATLAS-pixel front-end chip and readout electronics. Devices with different electrode configurations have been characterized in a 100 GeV pion beam at the CERN SPS. Here we report results on unirradiated devices with three 3D electrodes per 50 x 400 um2 pixel area. Full charge collection is obtained already with comparatively low bias voltages around 10 V. Spatial resolution with binary readout is obtained as expected from the cell dimensions. Efficiencies of 95.9% +- 0.1 % for tracks parallel to the electrodes and of 99.9% +- 0.1 % at 15 degrees are measured. The homogeneity of the efficiency over the pixel area and charge sharing are characterized.Comment: 5 pages, 7 figure

    Ecological genomics: steps towards unraveling the genetic basis of inducible defenses in Daphnia

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    Little is known about the genetic mechanisms underlying inducible defenses. Recently, the genome of Daphnia pulex, a model organism for defense studies, has been sequenced. Building on the genome information, recent preliminary studies in BMC Developmental Biology and BMC Molecular Biology have assessed gene response profiles in Daphnia under predation pressure. We review the significance of the findings and highlight future research perspectives

    Active-edge planar radiation sensors

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    Abstract Many systems in medicine, biology, high-energy physics, and astrophysics require large area radiation sensors. In most of these applications, minimizing the amount of dead area or dead material is crucial. We have developed a new type of silicon radiation sensor in which the device is active to within a few microns of the mechanical edge. Their perimeter is made by a plasma etcher rather than a diamond saw. Their edges can be defined and also passivated by growing, in an intermediate step, a field oxide on the side surfaces. In this paper, the basic architecture and results from a synchrotron beam test are presented. r 2006 Published by Elsevier B.V

    Plasticity of the Mycobacterium tuberculosis respiratory chain and its impact on tuberculosis drug development.

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    The viability of Mycobacterium tuberculosis (Mtb) depends on energy generated by its respiratory chain. Cytochrome bc1-aa3 oxidase and type-2 NADH dehydrogenase (NDH-2) are respiratory chain components predicted to be essential, and are currently targeted for drug development. Here we demonstrate that an Mtb cytochrome bc1-aa3 oxidase deletion mutant is viable and only partially attenuated in mice. Moreover, treatment of Mtb-infected marmosets with a cytochrome bc1-aa3 oxidase inhibitor controls disease progression and reduces lesion-associated inflammation, but most lesions become cavitary. Deletion of both NDH-2 encoding genes (Δndh-2 mutant) reveals that the essentiality of NDH-2 as shown in standard growth media is due to the presence of fatty acids. The Δndh-2 mutant is only mildly attenuated in mice and not differently susceptible to clofazimine, a drug in clinical use proposed to engage NDH-2. These results demonstrate the intrinsic plasticity of Mtb's respiratory chain, and highlight the challenges associated with targeting the pathogen's respiratory enzymes for tuberculosis drug development

    Optoelectronic analogue signal transfer for LHC detectors, 1991

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    We propose to study and develop opto-electronic analogue front-ends based on electro-optic intensity modulators. These devices translate the detector electrical analogue signals into optical signals which are then transferred via optical fibres to photodetector receivers at the remote readout. In comparison with conventional solutions based on copper cables, this technique offers the advantages of high speed, very low power dissipation and transmission losses, compactness and immunity to electromagnetic interference. The linearity and dynamic range that can be obtained are more than adequate for central tracking detectors, and the proposed devices have considerable radiation- hardness capabilities. The large bandwidth and short transit times offer possibilities for improved triggering schemes. The proposed R&D programme is aimed at producing multi-channel "demonstrator" units for evaluation both in laboratory and beam tests. This will allow the choice of the most effective technology. A detailed study will also be carried out on packaging and interconnection to large arrays of fibres, as well as on the optimization of the processes for the production of large quantities

    Preliminary results of 3D-DDTC pixel detectors for the ATLAS upgrade

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    3D Silicon sensors fabricated at FBK-irst with the Double-side Double Type Column (DDTC) approach and columnar electrodes only partially etched through p-type substrates were tested in laboratory and in a 1.35 Tesla magnetic field with a 180GeV pion beam at CERN SPS. The substrate thickness of the sensors is about 200um, and different column depths are available, with overlaps between junction columns (etched from the front side) and ohmic columns (etched from the back side) in the range from 110um to 150um. The devices under test were bump bonded to the ATLAS Pixel readout chip (FEI3) at SELEX SI (Rome, Italy). We report leakage current and noise measurements, results of functional tests with Am241 gamma-ray sources, charge collection tests with Sr90 beta-source and an overview of preliminary results from the CERN beam test.Comment: 8 pages, 8 figures, presented at RD09 - 9th International Conference on Large Scale Applications and Radiation Hardness of Semiconductor Detectors, 30 September - 2 October 2009, Florence, Ital