A high-energy resolution observed from a YAP : Ce scintillator

An energy resolution of 4.38 +/- 0.11% was obtained for 662 keV gamma-rays with a 3 x 3 x 20 mm(3) YAP : Ce crystal with its long face coupled to an X P2020Q photomultiplier. The measured number of photoelectrons of 5290 +/- 8 0 phe/MeV implies a photoelectron statistical contribution of 4.18 +/- 0.04 % and hence a YAP intrinsic energy resolution of 1.3 +/- 0.5%, the lowest v alue ever observed for scintillators. The relative light output of the YAP crystal measured for energies between 14.4 keV and 1.275 MeV was constant w ithin +/-2%. These observations are consistent with the assumption that the re is a direct correlation between the energy resolution of scintillators a nd nonproportionality of their light output versus energy. (C) 1999 Elsevie r Science B.V. All rights reserved.