Simulation Study of Energy Absorption of X- and $\gamma$-Rays in Plastic Scintillating Fiber Arrays

X- and gamma-rays' energy deposition in plastic scintillation fibers and fiber arrays in an energy range from 10 keV to 20 MeV has been studied using Monte Carlo simulations. The results show that the characteristics of the energy deposition in fibers are similar to that observed in bulk scintillation materials. The deposition efficiency increases with the fiber length, but the rate of increase drops as the length of the fibers is beyond 8 cm, suggesting such a length might be the optimum thickness of an imaging plate constructed using the scintillation fiber arrays. The results suggest that plastic scintillation fibers are useful for X- and gamma-ray imaging below about 1 MeV. For incident photons above that energy, the energy leakages from a fiber and crosstalk between fibers in an array become severe, which results in significant deteriorations in spatial resolution of the fiber arrays used for imaging.