Uncertainties in TDCR measurement revisited: contribution of optical effects

Philippe Cassette (1) , Vladislav Todorov (1) , Benoit Sabot (2) , Krasimir Mitev (1) , Strahil Georgiev (1)

1 Sofia University "St. Kliment Ohridski"
2 LNHB (CEA, LIST) - Laboratoire National Henri Becquerel (CEA, LIST)

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: metrology; instrumentation; nuclear instrumentation; Triple to Double Coincidence Ratio (TDCR); Liquid Scintillation; radioactivity; ionizing radiation; detection efficiency; Poisson distribution; statistical analysis

Domains: Instrumentation and Detectors [physics.ins-det]

Philippe Cassette, Vladislav Todorov, Benoit Sabot, Krasimir Mitev, Strahil Georgiev. Uncertainties in TDCR measurement revisited: contribution of optical effects. Applied Radiation and Isotopes, 2023, 201, pp.110992. ⟨10.1016/j.apradiso.2023.110992⟩. ⟨cea-04191073⟩