Characteristics and time resolutions of two CeBr3 gamma-ray spectrometers

Abstract

The purpose of this work is to study the pulse shape, energy resolution, non-proportionality of energy response for gamma-rays, and time characteristics of CeBr3 detector. The time and energy responses of two CeBr3 detectors were characterized by an analog method and a digital method using a set of standard γ-ray sources. The pulse shape, energy resolution and non-proportionality (nPR) of energy response for γ-rays were characterized using the analog method. For the analog method, the high voltage applied to PMTs, parameters of walk and external delay of constant fraction discriminator were optimized. For the digital method, a CEAN 1729A digitizer with sampling frequency of 2 GS/s and resolution of 11 bit, and a digital constant fraction discrimination technique were used to study the time performance of the two CeBr3 detectors. Then, the coincidence time resolutions of the CeBr3 detectors for the gamma peaks of 22Na and 60Co were measured using the two methods. The trise, lifetime τ, tfall for CeBr3 21# and 22# are 11.2 ns, 23.8 ns, 50.2 ns, and 10.4 ns, 26.5 ns, 58.6 ns, respectively. The measured non-proportionality of CeBr3 21# and 22# are 1.08% and 2.22%, respectively. The time resolutions of the two CeBr3 detectors are 244 ± 2 ps and 248 ± 3 ps at the energy peaks of 60Co source, and 336 ± 2 ps and 335 ± 3 ps at 511 keV for the analog and the digital methods. The time resolutions obtained by the analog method and the digital method are almost identical. The CeBr3 detector is a good option in the applications such as half-life measurements, ToF-PET and high counting rate conditions. Furthermore, it is a good γ-ray spectrometer owing to the preferable energy resolution and non-internal activity.