Geant4 Simulations of the Responses of the GdI_3:Ce Scintillator Detector to Thermal Neutrons and Gamma-rays

摘要

A simulation model based on the Geant4 packages was developed for the GdI3:Ce scintillator detector in order to investigate its responses to thermal neutrons and gamma-rays, and explore the appreciate parameters to improve its performance for thermal neutron detection. The characteristic gamma-ray and internal conversion (IC) electron yields of GdI3:Ce induced by a thermal neutron beam were obtained by simulation, and were used to analyze the IC electron detecting capability versus the scintillator thickness. Results show that the performance for detecting IC electrons is hardly improved when the scintillator thickness is more than 250 μm whilst the detection efficiency to gamma-rays keeps increasing. The detection performances of 250 μm thickness GdI3:Ce scintillator to thermal neutrons and gamma-rays in an energy range from 20 keV to 1000 keV showed that the scintillator achieved a 65.3% detection efficiency to thermal neutrons and a high detection efficiency to gamma-rays below 200 keV. That means the detector is need to be shielded to reject low-energy gamma background while detecting thermal neutrons. The thermal neutron peaks are located mainly at 30, 40, 70 and 80 keV, thus the energy discrimination method can be used to effectively discriminate thermal neutron signals from gamma background.