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  • 51.
    Thungström, Göran
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Dubaric, Ervin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Svensson, B.G.
    Royal Institute of Technology, Dept. Electronics, Electrum 229, S., Stockholm.
    Processing of silicon UV-photodetectors2001In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 460, no 1, p. 165-184Article in journal (Refereed)
    Abstract [en]

    UV-enhanced photodetectors of both n+-p and p+-n type have been processed in silicon. Photodetectors of the p+-n type display a responsivity close to the theoretical limit with an antireflective coating of either thermally grown dry silicon dioxide or deposited oxide (TEOS), followed by a short wet oxidizing step. This holds, irrespective of whether the detector window is doped by boron through ion implantation or diffusion from a solid source. However, for p+-n photodiodes with a TEOS-oxide in the as-deposited state the responsivity decreases substantially for wavelenghts below 500 nm compared to the theoretical predictions. This is attributed to a high recombination velocity at the silicon dioxide/silicon interface, as supported by computer simulations of the detector performance. In contrast, n+-p photodiodes are found to be rather insensitive with respect to the properties of the silicon dioxide/silicon interface. These results provide the first experimental demonstration that high built in electric fields, caused by abrupt dopant profiles, can suppress the influence of a high interface carrier recombination velocity.

  • 52.
    Thungström, Göran
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Mattsson, Claes
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Rönnqvist, Camilla
    Fabrication and Characterization of Silicon Detectors for use in Radiotherapy Dosimetry, Pre-irradiated by High Energy Electrons2007In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 576, no 1, p. 209-214Article in journal (Refereed)
    Abstract [en]

    Fabricated silicon detectors for use in radiotherapy dosimetry have been pre-irradiated by means of 10 MeV electrons. The purpose of this irradiation is to saturate the diffusion carrier length in order to achieve linear dose rate dependence. A characterized n+p-detector has a relatively flat sensitivity slope after pre-irradiation and the detector exhibits a low leakage current and high shunt-resistance. The int. E-detector has a constant sensitivity slope for all doses and consequently requires no pre-irradiation. Due to a larger generation carrier volume, the leakage current and shunt-resistance are respectively higher and lower in comparison to the n+p-detector. After the annealing of the detectors has taken place, the n+p has the lowest leakage current and there is already significant recovery at 200 ˚C. The int. E detector has a constant sensitivity response to all the applied doses and performed annealing. The leakage current for the int. E detector improved to acceptable values after a FGA step was performed. An unacceptably high leakage current and low shunt-resistance means that the E-detectors are not considered to be useful for this application.

  • 53.
    Thungström, Göran
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Westerberg, Lars
    Spohr, Reimar
    Petersson, Sture
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Fabrication and Characterization of thin delta E-Detectors for Spectroscopic Application2005In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 546, no 1-2, p. 312-318Article in journal (Refereed)
    Abstract [en]

    Ultra thin delta E-detectors for spectroscopic applications have been fabricated and characterized down to a thickness of 4.5 μm. A common one-side mask aligner was in use to fabricate the detectors. The detectors display low leakage current and the resulting capacitance is close to the detector window capacitance below a threshold voltage. The detector telescope should be slightly tilted to reduce the probability for channeling. However, even better control of the thickness uniformity is needed to improve the resolution in the E-E detector telescope

  • 54.
    Tlustos, Lukas
    et al.
    CERN.
    Campbell, Michael
    CERN.
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Kostamo, Pasi
    Helsinku University of Technology.
    Nenonen, Seppo
    Oxford Instruments Analythical Oy.
    Characterisation of an epitaxial GaAs/Medipix2 detctor using fluorescence photons2008In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 591, no 1, p. 42-45Article in journal (Refereed)
    Abstract [en]

    A high-purity GaAs sensor of 110 μm thickness has been bump bonded to a Medipix2 readout chip. The room temperature spectroscopic response of this device to fluorescence photons in the energy range from 8 to 28 keV is presented and compared to the response of a 300 μm thick Si sensor, also bonded to a Medipix2 chip. The measured photopeak responses are used to calibrate both detectors. The depth of depletion of the GaAs sensor is estimated to be 50 μm at 140 V sensor bias voltage from measurements made using the 8 keV Kα line of a Cu target X-ray tube.

  • 55.
    Uher, J.
    et al.
    Czech Technical University in Prague, Czech Republic.
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Jakubek, J.
    Czech Technical University in Prague, Czech Republic.
    Kenney, C.
    Stanford University, United States.
    Kohout, Z.
    Czech Technical University in Prague, Czech Republic.
    Linhart, V.
    Czech Technical University in Prague, Czech Republic.
    Parker, S.
    University of Hawaii, United States.
    Petersson, Sture
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Pospisil, S.
    Czech Technical University in Prague, Czech Republic.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Characterization of 3D thermal neutron semiconductor detectors2007In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 576, no 1, p. 32-37Article in journal (Refereed)
    Abstract [en]

    Neutron semiconductor detectors for neutron counting and neutron radiography have an increasing importance. Simple silicon neutron detectors are combination of a planar diode with a layer of an appropriate neutron converter such as (LiF)-Li-6. These devices have limited detection efficiency of not more than 5%. The detection efficiency can be increased by creating a 3D microstructure of dips, trenches or pores in the detector and filling it with a neutron converter. The first results related to the development of such devices are presented. Silicon detectors were fabricated with pyramidal dips on the surface covered with (LiF)-Li-6 and then irradiated by thermal neutrons. Pulse height spectra of the energy deposited in the sensitive volume were compared with simulations. The detection efficiency of these devices was about 6.3%. Samples with different column sizes were fabricated to study the electrical properties of 3D structures. Charge collection efficiencies in silicon columns from 10 to 800 mu m wide and 80-200 mu m high were measured with alpha particles.

    The neutron detection efficiency of a full 3D structure was simulated. The results indicate an increase in detection efficiency by a factor of 6 in comparison with a standard planar neutron detector.

  • 56.
    Ulyanov, A.
    et al.
    School of Physics, University College Dublin, Ireland.
    Morris, O.
    School of Physics, University College Dublin, Ireland; Galway-Mayo Institute of Technology, Galway, Ireland.
    Hanlon, L
    School of Physics, University College Dublin, Ireland.
    Mc Breen, S
    School of Physics, University College Dublin, Ireland.
    Foley, S
    School of Physics, University College Dublin, Ireland.
    Roberts, O
    School of Physics, University College Dublin, Ireland.
    Tobin, I
    School of Physics, University College Dublin, Ireland.
    Murphy, D
    School of Physics, University College Dublin, Ireland.
    Wade, C
    School of Physics, University College Dublin, Ireland.
    Nelms, N
    European Space Agency, ESTEC.
    Shortt, B
    European Space Agency, ESTEC.
    Slavicek, Tomas
    Czech Technical University in Prague.
    Granja, C.
    Czech Technical University in Prague.
    Solar, M.
    Czech Technical University in Prague.
    Performance of a monolithic LaBr3: Ce crystal coupled to an array of silicon photomultipliers2016In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 810, no 810, p. 107-119Article in journal (Refereed)
    Abstract [en]

    A gamma-ray detector composed of a single 28×28×20 mm3 LaBr3:Ce crystal coupled to a custom built 4×4 array of silicon photomultipliers was tested over an energy range of 30 keV to 9.3 MeV. The silicon photomultipliers were initially calibrated using 20 ns light pulses generated by a light emitting diode. The photodetector responses measured as a function of the number of incident photons were found to be non-linear and consistent with model predictions. Using corrections for the non-linearity of the silicon photomultipliers, the detector showed a linear response to gamma-rays with energies from 100 keV to the maximum available energy of 9.3 MeV. The energy resolution was found to be 4% FWHM at 662 keV. Despite the large thickness of the scintillator (20 mm) and a 5 mm thick optical window, the detector was capable of measuring the positions of the gamma-ray interaction points. The position resolution was measured at 356 keV and was found to be 8 mm FWHM in the detector plane and 11 mm FWHM for the depth of interaction. The detector can be used as a building block of a larger calorimeter system that is capable of measuring gamma-ray energies up to tens of MeV.

12 51 - 56 of 56
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