1. Introduction
A high energy resolution of 3.3% for 662 keV ?rays of the recently developed LaCl3:Ce crystal [1], reported for small samples below 1 cm3 [1-3], prompted the present comparison of a larger sample of ∅25×25 mm size to NaI(Tl) in ?-ray spectrometry. LaCl3:Ce has an aemission maximum at 335 nm, a
density of 3.86 g/cm3 and is hygroscopic. Its effective Z is 59.5, as compared to 50.0 for NaI(Tl). The latter characteristics suggest that the detection efficiency of ?-rays and the photofraction of LaCl3:Ce should be comparable to that of NaI(Tl). The reported high light output of 49000 ph/MeV and a short decay time of the main component of the light pulse of 25 ns allowed getting a time resolution comparable to that of BaF2, as reported in [3]. The study of nonproportionality of the light yield versus energy showed a good proportionality down to 20 keV [4].