Improvement of Time Resolution of BaF $_{2}$ Scintillator for Low-Energy Gamma Rays by Digital Pulse-Shape Method

A digital pulse-shape method (DPSM) is proposed to improve the time resolution of a BaF₂ scintillation detector for low-energy gamma rays. By using chi-square fitting of digitally measured pulse shapes with calculated shapes, the proposed DPSM determined the pulse height and the start time corresponding to the deposited energy and the interaction moment, respectively, of gamma rays incident on the BaF₂ scintillator. We calculated theoretical pulse shapes by considering light output, light-attenuation length, and light path within the scintillator. In particular, we calculated the light path inside the scintillator by using a Monte Carlo method. We performed coincidence measurements for gamma rays emitted from ²²Na and ¹³³Ba standard sources with two cylindrical BaF₂ scintillation detectors and then we obtained a time resolution of around 6 ns for 81-keV and 511-keV gamma rays by using the DPSM. Although time resolution obtained using the DPSM was inferior to that obtained using a conventional analog signal process, it had a consistent value irrespective of gamma-ray energy.