A. V. Davies

Characterisation of cascade summing effects in gamma spectroscopy using Monte Carlo simulations

A GEANT4 based Monte Carlo simulation has been successfully utilised to calculate peak efficiency characterisations and cascade summing (true coincidence summing) corrections in two source geometries commonly used for environmental monitoring. The cascade summing corrections are compared with values generated using an existing (validated) system, and found to be in excellent agreement for all radionuclides simulated. The calculated correction factors and peak efficiencies were also tested by analysing well defined sources used in the operation of the International Monitoring System, which undertakes radionuclide monitoring for verification of the Comprehensive Nuclear-Test-Ban Treaty. All abundances of the radionuclides measured matched the values that were previously determined using proprietary software. Using GEANT4 in this way, cascade summing corrections can now be extended to complex detector models and source matrices, such as Compton Suppression systems.

International inter-comparison exercise on \({}^{153}\hbox {Sm}\)

Samarium-153 (153Sm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}

Development of a cosmic veto gamma-spectrometer

{}^{153}\hbox {Sm}

Preliminary simulations of NaI(Tl) detectors, and coincidence analysis using event stamping

\end{document}) is a short-lived radionuclide that decays to stable europium-153 via beta emission, with subsequent de-excitation via gamma emission and internal conversion. Historical measurements of 153Sm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}

Compton suppressed gamma-spectrometry for Comprehensive Nuclear-Test-Ban Treaty samples

{}^{153}\hbox {Sm}

Coincidence corrections for a multi-detector gamma spectrometer

\end{document} by gamma spectrometry and beta liquid scintillation counting have shown a low bias compared to beta proportional counting. In order to investigate this, four national laboratories jointly conducted an experimental inter-comparison exercise on a certified 153Sm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}