Influence of various geometries on detection efficiency of polystyrene, polyvinyl-toluene, and sodium iodide detectors using Geant4

Abstract

In this work, comparative study on energy dependence of absorbed, intrinsic, photo-peak and absolute total efficiency of polystyrene plastic scintillation fiber and polyvinyl-toluene detectors with NaI(Tl) scintillation detectors has been performed using Geant4 version 9.6 toolkit. The effects of geometry parameters on various efficiencies were investigated by varying detector radii, thickness and various source-to-detector configurations. These studies were carried out for both cylindrical and slab geometries for photon energy range of 10 keV-20 MeV using point isotropic sources and parallel beams of photons. Comparisons of the Geant4.9.6 based simulations for polystyrene scintillation fiber intrinsic efficiency as a function of photon energy and corresponding results obtained by earlier versions Geant4 (version 5.1) and Geant4 (version 8.1) show good agreements. The variation of the intrinsic efficiency with energy for polyvinyltoluene is also found to match very well with respective earlier results. This work confirms that the plastic scintillator based fibers and slab detectors are suitable for X-ray and low energy g-ray applications with energies typically below 50 keV with the optimum length of polystyrene scintillation fiber equal to 10 cm. For high energy range, cross talk remains an issue for polystyrene scintillation fiber and it is prominent in fibers having longer lengths and small diameters. Also, until the fiber radius is smaller than the incident photon beam, the fiber intrinsic efficiency increases with an increase in the radius.

Keywords

• plastic scintillator fiber
• polyvinyl-toluene scintillator
• detection efficiency
• Geant4