Measurements and simulations of Cherenkov light in lead fluoride crystals

Institut für Kernphysik, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment (Impact Factor: 1.22). 09/2001; 465(2-3):318-328. DOI: 10.1016/S0168-9002(01)00668-4
Source: arXiv


The anticipated use of more than 1000 lead fluoride (PbF2) crystals as a fast and compact Cherenkov calorimeter material in a parity violation experiment at MAMI stimulated the investigation of the light yield (LY) of these crystals. The number of photoelectrons (p.e.) per MeV deposited energy has been determined with a hybrid photomultiplier tube (HPMT). In response to radioactive sources a LY between 1.7 and was measured with 4% statistical and 5% systematic error. The LY optimization with appropriate wrappings and couplings was investigated by means of the HPMT. Furthermore, a fast Monte Carlo simulation based on the GEANT code was employed to calculate the characteristics of Cherenkov light in the PbF2 crystals. The computing time was reduced by a factor of 50 compared to the regular photon tracking method by implementing detection probabilities as a three-dimensional look-up table. For a single crystal a LY of was calculated. The corresponding detector response to electrons between 10 and was highly linear with a variation smaller than 1%.

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Available from: E. Schilling, Sep 02, 2015
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    • "Their compact nature provides freedom in the mechanical design of the calorimeter housing so they can be mounted in tight geometries. They operate in high magnetic fields without degradation 5 The A4 Collaboration published a number of important technical papers; see [4] [5] Wavelength [nm] "
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    ABSTRACT: The electromagnetic calorimeter for the new muon (g-2) experiment at Fermilab will consist of arrays of PbF2 Cherenkov crystals read out by large-area silicon photo-multiplier (SiPM) sensors. We report here on measurements and simulations using 2.0 -- 4.5 GeV electrons with a 28-element prototype array. All data were obtained using fast waveform digitizers to accurately capture signal pulse shapes versus energy, impact position, angle, and crystal wrapping. The SiPMs were gain matched using a laser-based calibration system, which also provided a stabilization procedure that allowed gain correction to a level of 1e-4 per hour. After accounting for longitudinal fluctuation losses, those crystals wrapped in a white, diffusive wrapping exhibited an energy resolution sigma/E of (3.4 +- 0.1) % per sqrt(E/GeV), while those wrapped in a black, absorptive wrapping had (4.6 +- 0.3) % per sqrt(E/GeV). The white-wrapped crystals---having nearly twice the total light collection---display a generally wider and impact-position-dependent pulse shape owing to the dynamics of the light propagation, in comparison to the black-wrapped crystals, which have a narrower pulse shape that is insensitive to impact position.
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    • "A large calorimeter with 1022 crystals to handle a total of 100 MHz counting rate has been developed. An innovative feature of this detector is a use of new, high resolution and very fast PbF 2 Cerenkov radiators [11]. The 10 cm liquid hydrogen target provides a luminosity of 5 × 10 37 cm −2 s −1 at 20 µA electron beam current. "
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    ABSTRACT: We present a new powerful liquid hydrogen target developed for the precise study of parity violating electron scattering on hydrogen and deuterium. This target has been designed to have minimal target density fluctuations under the heat load of a CW 854.3 MeV electron beam without rastering the electron beam. The target cell has a wide aperture for scattered electrons and is axially symmetric around the beam axis. The construction is optimized to intensify heat exchange by a transverse turbulent mixing in the hydrogen stream, which is directed along the electron beam. The target is constructed as a closed loop circulating system cooled by a helium refrigerator. It is operated by a tangential mechanical pump with an optional natural convection mode. The cooling system supports removal of up to 250 W of beam heating removal. Deeply subcooled liquid hydrogen is used to keep the in-beam temperature below the boiling point. The target density fluctuations are found to be at the level of 10-3 at a beam current of .
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 04/2005; 564(1-564):13-25. DOI:10.1016/j.nima.2006.03.022 · 1.22 Impact Factor
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    • "level. The PbF 2 material employed in the A4 calorimeter is an intrinsically fast Cherenkov radiator with no slow scintillation components [8]. The PbF 2 detector electronics measures the energy within a 20 ns integration gate, which is the largest dead time in the system. "
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    ABSTRACT: A water Cherenkov luminosity monitor system with associated electronics has been developed for the A4 parity violation experiment at MAMI. The detector system measures the luminosity of the hydrogen target hit by the MAMI electron beam and monitors the stability of the liquid hydrogen target. Both are required for the precise study of the count rate asymmetries in the scattering of longitudinally polarized electrons on unpolarized protons. Any helicity correlated fluctuation of the target density leads to false asymmetries. The performance of the luminosity monitor, investigated in about 2000 h with electron beam, and the results of its application in the A4 experiment are presented.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 04/2005; 564(1-564):1-12. DOI:10.1016/j.nima.2006.03.028 · 1.22 Impact Factor
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