Energy resolution of scintillation detectors with large area avalanche photodiodes and photomultipliers light readout

The energy resolution of small NaI:Tl, CsI:Tl, BGO, GSO, YAP and LSO crystals was studied using 16 mm diameter large area avalanche photodiodes (LAAPD) and a 52 mm diameter photomultiplier. The best result of 4.8% for the 662 keV γ-rays from a ¹³⁷Cs source was obtained for a 9 mm in diameter by 9 mm high CsI(Tl) scintillator coupled to an LAAPD. Measured number of primary electron-hole pairs produced in the LAAPD and photoelectrons in the photomultiplier, as well as the noise contribution of the LAAPD, allow for quantitative discussion of the results. It has been shown that the energy resolutions measured with LAAPDs are comparable, or significantly better (at certain emission wavelengths), than those obtained with the photomultiplier. We observed that at energies, above 100 keV, the energy resolution measured with majority of crystals and the LAAPDs was weakly affected by photodiode noise contribution. The advantages and limitations of the LAAPDs in energy spectrometry with scintillation detectors are also discussed here