On the scintillation response of NaI(Tl)-Crystals

Several articles are reviewed on the scintillation response of NaI(Tl). Those publications which report on results obtained with radioactive sources either dispersed throughout the NaI(Tl)-lattice or located inside the wells of NaI(Tl)-crystals, match within ± 0.9 % standard deviation a linear scintillation response between 3 MeV and 3 keV. Several authors who placed their sources outside the crystals, measured non linear responses of NaI(Tl) with up to ± 5.3 % standard deviations between 700 keV and 4.5 keV. The presented analysis suggests that the observed non-linearity is not an intrinsic effect of NaI(Tl), but could be caused, at least partly, by effects occuring at the radiation entrance surfaces of the crystals.