Browsing by Author "Streli, Christina"

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    Charge transfer properties through graphene for applications in gaseous detectors
    (Elsevier, 2016-07-11) Franchino, S.; Gonzalez-Diaz, Diego; Hall-Wilton, Richard; Jackman, Richard; Muller, H.; Nguyen, T. T.; de Oliveira, R.; Oliveri, Eraldo; Pfeiffer, Dorothea; Resnati, F.; Ropelewski, L.; Smith, Joe; van Stenis, M.; Streli, Christina; Thuiner, P.; Veenhof, Robert J.; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 6603742499
    Graphene is a single layer of carbon atoms arranged in a honeycomb lattice with remarkable mechanical and electrical properties. Regarded as the thinnest and narrowest conductive mesh, it has drastically different transmission behaviours when bombarded with electrons and ions in vacuum. This property, if confirmed in gas, may be a definitive solution for the ion back-flow problem in gaseous detectors. In order to ascertain this aspect, graphene layers of dimensions of about 2 x 2 cm(2), grown on a copper substrate, are transferred onto a flat metal surface with holes, so that the graphene layer is freely suspended. The graphene and the support are installed into a gaseous detector equipped with a triple Gaseous Electron Multiplier (GEM), and the transparency properties to electrons and ions are studied in gas as a function of the electric fields. The techniques to produce the graphene samples are described, and we report on preliminary tests of graphene-coated GEMs.
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    Live event reconstruction in an optically read out GEM-based TPC
    (Elsevier, 2017-12-27) Brunbauer, Florian Maximilian; Galgóczi, Gábor; Oliveri, Eraldo; Resnati, Filippo; Ropelewski, Leszek; Streli, Christina; Thuiner, Patrik; Van Stenis, Miranda; Díaz, Diego González; Uludağ Üniversitesi.; 0000-0002-6809-5996; K-7265-2014; 6507842627
    Combining strong signal amplification made possible by Gaseous Electron Multipliers (GEMs) with the high spatial resolution provided by optical readout, highly performing radiation detectors can be realized. An optically read out GEM-based Time Projection Chamber (TPC) is presented. The device permits 3D track reconstruction by combining the 2D projections obtained with a CCD camera with timing information from a photomultiplier tube. Owing to the intuitive 2D representation of the tracks in the images and to automated control, data acquisition and event reconstruction algorithms, the optically read out TPC permits live display of reconstructed tracks in three dimensions. An Ar/CF4 (80/20%) gas mixture was used to maximize scintillation yield in the visible wavelength region matching the quantum efficiency of the camera. The device is integrated in a UHV-grade vessel allowing for precise control of the gas composition and purity. Long term studies in sealed mode operation revealed a minor decrease in the scintillation light intensity.