Energy technical light output of scintillators – problems of assessment and an alternative method for their solution

The paper analyzes the problems that arise when assessing the energy technical light output by existing methods. A modern alternative method for assessing the energy technical light output of various scintillators produced by the Institute of Scintillation Materials of the National Academy of Sciences of Ukraine is described. The possibility of evaluating the technical light output of any scintillator by relative comparison with a reference stilbene-based scintillator with a known technical light output is shown. The resulting ratio of responses is recalculated in ph/MeV by taking into account the technical light output of the reference scintillator, equal to 0.023, and the photon formation energy of a particular scintillator. The estimation procedure is described. Expressions are given for calculating the values of the technical light yield of scintillators in stilbene units and in ph/MeV. The radioluminescence spectra of the tested scintillators are compared with the sensitivity spectra of the normalized and laboratory photodetectors. The technical light yield of scintillators based on single crystals of NaI(Tl), CsI(Tl), CWO, BGO, p-terphenyl, anthracene, stilbene, and a plastic scintillator has been estimated. The values of the responses amplitudes ratio, the spectral normalization coefficients and the tested scintillators technical light output were obtained in stilbene units and in ph/MeV. To check the adequacy of the method the calculation of the tested inorganic scintillators absolute light output was carried out using the light collection coefficients values given in the literature. It is shown that with an increase in the scintillators technical light output, in stilbene units, from 0.26 for BGO to 4.3 for NaI(Tl), their technical light output increases from 2500 ph/MeV to 33100 ph/MeV. A decrease in the scintillation photon energy from 2.988 (l = 415 nm) for NaI(Tl) to 2.214 (l = 560 nm) for CsI(Tl) also increases the technical light output of the latter to 35300 ph/MeV. The performed estimates accuracy of scintillators technical light output was 8%.