Uncertainties in TDCR measurement revisited: Contribution of optical effects

Philippe Cassette; Vladislav Todorov; Benoit Sabot; Strahil Georgiev; Krasimir Mitev

doi:10.1016/j.apradiso.2023.110992

Uncertainties in TDCR measurement revisited: Contribution of optical effects

Appl Radiat Isot. 2023 Nov:201:110992. doi: 10.1016/j.apradiso.2023.110992. Epub 2023 Aug 20.

Authors

Philippe Cassette¹, Vladislav Todorov², Benoit Sabot³, Strahil Georgiev², Krasimir Mitev²

Affiliations

¹ Sofia University "St. Kliment Ohridski", Faculty of Physics, 1164, Sofia, Bulgaria. Electronic address: philippe.cassette@phys.uni-sofia.bg.
² Sofia University "St. Kliment Ohridski", Faculty of Physics, 1164, Sofia, Bulgaria.
³ Université Paris-Saclay, CEA, LIST, Laboratoire National Henri Becquerel (LNE-LNHB), 91120, Palaiseau, France.

PMID: 37657226
DOI: 10.1016/j.apradiso.2023.110992

Abstract

In the Triple to Double Coincidence Ratio method in Liquid Scintillation Counting, the detection efficiency is calculated from the value of a free parameter describing the intrinsic light yield of the counting system. This model is generally based on a Poisson distribution of the number of photoelectrons detected and the detection efficiency is obtained from the complement of the non-detection efficiency. In the classical free parameter model, the mean of the Poisson distribution, m, is a constant but some variability of this mean could be expected from optical effects due to internal reflections inside the LS source or from non-homogeneity of the detection efficiency of the photomultiplier tubes. Then, m becomes a random variable and the distribution of the photoelectrons becomes a compound Poisson distribution, with a random variable as mean value. This paper explores the implications of the variance of m, which were, to our knowledge, never considered previously in the uncertainty budget of TDCR measurements.

Keywords: LSC; LSC vials; PMT non-uniformity; TDCR.