Characterisation of a small volume (1′′ × 1′′) CeBr₃ crystal for γ-ray measurements up to 4.4 MeV

Abstract

A: This paper reports about complete characterization of a small volume, cylindrical (1 × 1 ) CeBr 3 crystal. The measurements include determination of energy and timing resolutions, absolute photo-peak detection efficiency, internal activity and linearity of response up to 4.43 MeV gamma-ray energy. The results, so obtained, have been compared with the performance of NaI(Tl) and LaBr 3 :Ce crystals of similar volume. Realistic Monte Carlo simulations were carried out using GEANT4 package to reproduce the experimental spectra and photo-peak detection efficiency. We have obtained best energy resolution of 4.7% at 662 keV for −800 V using a 2 ET9266B tube. A somewhat better value of 4.3% is obtained using Hamamatsu R10233 tube. On the timing front we have obtained a resolution of 310 ps at Co energy. We have determined the absolute photopeak efficiency of the crystal for 662 keV to be 13.2%, in very close conformity with our Geant4 simulated value of 13.8%. We have estimated from the measurements the actual internal activity of the crystal to be less than 0.045 counts cm −3 s −1 . It has been concluded that while CeBr 3 is just marginally inferior to LaBr 3 :Ce in terms of energy and timing resolutions, it scores over LaBr 3 :Ce in terms of internal activity. Unlike LaBr 3 :Ce, CeBr 3 is much purer and has no significant gamma and beta activity.