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The energy resolution of LaCl3:Ce and NaI(Tl) measured with the same photomultiplier versus energy is shown in Fig. 6. The curve for NaI(Tl) has a known step-like shape [8], while the energy resolution of LaCl3:Ce is approximately inversely proportional to the square root of the energy as reported recently in [4]. The curves confirm observations presented in Fig. 1 – Fig. 3 . The energy resolution of LaCl3:Ce above 122 keV is superior, while below 122 keV is poorer as compared to those measured with NaI(Tl) crystals.