A visualization of the damage in Lead Tungstate calorimeter crystals after exposure to high-energy hadrons


The anticipated performance of calorimeter crystals in the environment
expected after the planned High-Luminosity upgrade of the Large Hadron Collider
(HL-LHC) at CERN has to be well understood, before informed decisions can be
made on the need for detector upgrades. Throughout the years of running at the
HL-LHC, the detectors will be exposed to considerable fluences of fast hadrons,
that have been shown to cause cumulative transparency losses in Lead Tungstate
scintillating crystals. In this study, we present direct evidence of the main
underlying damage mechanism. Results are shown from a test that yields a direct
insight into the nature of the hadron-specific damage in Lead Tungstate
calorimeter crystals exposed to 24 GeV/c protons.

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    ABSTRACT: Lutetium-Yttrium Orthosilicate doped with Cerium (LYSO:Ce), as a bright scintillating crystal, is a candidate for calorimetry applications in strong ionizing-radiation fields and large high-energy hadron fluences as are expected at the CERN Large Hadron Collider after the planned High-Luminosity upgrade. There, proton-proton collisions will produce fast hadron fluences up to ~5E14/cm^2 in the large-rapidity regions of the calorimeters. The performance of LYSO:Ce has been investigated, after exposure to different fluences of 24 GeV/c protons. Measured changes in optical transmission as a function of proton fluence are presented, and the evolution over time due to spontaneous recovery at room temperature is studied. The activation of materials will also be an issue in the described environment. Studies of the ambient dose induced by LYSO and its evolution with time, in comparison with other scintillating crystals, have also been performed through measurements and FLUKA simulations.
    Preview · Article · Sep 2013 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
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    ABSTRACT: Ce3+:Lu3Al5O12 (Ce:LuAG) scintillator ceramics were fabricated using solid state reaction method. High transparency (∼80% at 550 nm) was obtained, the grain boundary was clean and no secondary phase was observed. After further optimized by an air-annealing process, Ce:LuAG ceramic shows a much higher steady state scintillation efficiency than that of BGO single crystal under X-ray excitation, and the light yield (137Cs, 662KeV) improved around double compared with that of the before one. The radiation hardness of Ce:LuAG ceramic was investigated under 60Co gamma radiation with dose of 2 × 105 Gy and a dose rate of about 1 × 104 Gy/h. The radiation induced absorption appears in ∼380 nm and 610 nm (away from the emission band of Ce:LuAG) demonstrating its perspective for application in High Energy Physics.
    Full-text · Article · Oct 2014 · Optical Materials