Absolute light output of scintillators

The absolute light outputs of EGO, CsI(Tl) and some new Ce-doped crystals have been measured to an accuracy of about +/-5 % using calibrated XP2020Q photomultipliers and standard S3590-03 and S2740-03 photodiodes. The use of small crystals, 9 mm in diameter and 1 mm thick, reduces the corrections for imperfections in the light collection process and in the photoelectron collection by the photomultipliers. The measured Light output of 8500+/-350 ph/MeV (photons/MeV) for the EGO crystals agrees well with the earlier measurement done by Hell et al. The carried out study highlighted the importance of die spread in the published emission spectra of the crystals which seems to limit measurement accuracy. Finally, a simple comparative method of measuring light output to an accuracy of +/-10 %, is proposed using an uncalibrated XP2020 photomultiplier and a 1 mm thick EGO crystal as a standard.