Start Counter Simulations

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Geant4 Simulations

Geometry and Setup

  • Scintillator: Imported AutoCAD drawing into GEANT4 using CADMESH utility
  • SiPM: 12x12x10 mm volume
  • Surrounded by Air
  • Spacing between scintillator and SiPM: 0.1 mm
  • Generated 10K optical photons at every 2.5 cm spacing inside the scintillator (-300, 300) mm or (0, 60) cm

Material Properties

  • Scintillator: ELJAN 212 material composition properties
    • Density: 1.023 g/cm3
    • Scintillation yield: 10000 photons/MeV
    • Optical photon energy range: 0.5 eV - 3.76 eV
    • Index of refraction: 1.58
    • Absorption length: 400cm (not correct!)
  • SiPM: Silicon
    • Efficiency: 100%
    • Used just to track optical photon hits

Optical Surface

  • The actual scintillators under microscope: [4] [5]
  • An optical surface between air and scintillator is set
  • Properties of optical surface are defined by
    • Material of surfaces: dielectric_dielectric
    • Physics model: unified Levin and Moisan, 1996
    • Transmission efficiency and reflection
    • Finish of the surface: polished or ground
      • polished: Fresnel reflection, Total Internal Reflection, Fresnel Refraction
      • ground: Spike reflection, lobe reflection, backscatter, Lambertian reflection, Fresnel refraction
Spike reflection: the photon is reflected like a perfect mirror or about the average surface normal
Lambertian reflection: the photon is reflected with a Lambertian distribution
Back scatter: the photon is reflected in the direction of incidence
Lobe reflection: based on the orientation of the micro-facet on the surface. The sigma_alpha parameter defines the standard deviation of the distribution of the micro-facets orientation
  • Measurement of Scintillator 1 (at FIU): [6]
  • Variation of transmission efficiency with polished finish: [7]
  • Variation of sigma_alpha with ground finish: [8]
  • Variation of lobe reflectivity with ground finish: [9]