Monte Carlo based approach to the LS–NaI 4πβ–γ anticoincidence extrapolation and uncertainty. (March 2016)

• Record Type: Journal Article
• Authors: Fitzgerald, R.
• Is Part Of: Applied radiation and isotopes. Volume 109(2016:Mar.)
• Page Start: 308
• Page End: 313
• Publication Date: 2016-03
• Subjects: Beta–gamma method -- Anticoincidence -- Coincidence -- Monte Carlo simulations; Radiology -- Periodicals; Radiation -- Industrial applications -- Periodicals; Nuclear chemistry -- Periodicals; Internet resource; Periodical; 660.298
• DOI: 10.1016/j.apradiso.2015.11.107
• Languages: English
• ISSNs: 0969-8043

Abstract

Abstract: The 4 πβ – γ anticoincidence method is used for the primary standardization of β −, β +, electron capture (EC), α, and mixed-mode radionuclides. Efficiency extrapolation using one or more γ ray coincidence gates is typically carried out by a low-order polynomial fit. The approach presented here is to use a Geant4-based Monte Carlo simulation of the detector system to analyze the efficiency extrapolation. New code was developed to account for detector resolution, direct γ ray interaction with the PMT, and implementation of experimental β -decay shape factors. The simulation was tuned to 57 Co and 60 Co data, then tested with 99m Tc data, and used in measurements of 18 F, 129 I, and 124 I. The analysis method described here offers a more realistic activity value and uncertainty than those indicated from a least-squares fit alone. Highlights: Monte Carlo approach to 4 πβ – γ anticoincidence counting extrapolation. Geant4 simulations of the detector systems employed. Demonstrates more realistic estimates of activity values and uncertainties.