The influence of instrumental factors at uncertainty evaluation of scintillators technical light output measurements

Abstract

This article complements the cycle of previous works that were devoted to the evaluation of uncertainty of measurement results of cylindrical scintillators on the base of NaI(Tl), CsI(Tl), CWO, BGO, p-terphenyl, anthracene, stilbene and long length strips based on polystyrene (PS strip) technical light output in photons/MeV (ph/MeV). The comparison method with the working sample was used. The investigated scintillators were manufactured at the Institute for Scintillation Materials of the National Academy of Sciences of Ukraine (ISMA NASU). Technical light output of the scintillators was in the range from 38 ph/MeV for strips to 55000 ph/MeV for CsI(Tl).In this work, we compared the estimates of instrumental uncertainty of type B of the measurement results of the technical light output of scintillators using pulse and current measurement modes. Factors influencing the magnitude of instrumental measurement uncertainty are determined. The contributions of these factors to the instrumental uncertainty for specified measurement modes are evaluated. It is established that the value of instrumental measurement uncertainty is related to the limited sensitivity of the scale of analyzing instrument and depends on the number of divisions of the used scale and the location of the measured parameter on this scale. The calculated values of contributions’ estimates to the uncertainty of the measurement results of the technical light output of scintillators are in the range from 0.05 to 0.18 % for CsI(Tl) and from 0.95 to 2.45 % for strip No. 1.Based on the results of the instrumental uncertainty estimates received in this work and taking into account the results of previous studies, the measurement uncertainty budgets for the technical light output of scintillators based on CsI(Tl) (pulse mode) and strip No. 3 (current mode) are compiled.