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Zhang W.,Radiation Protection Bureau of Health Canada | Yi J.,Radiation Protection Bureau of Health Canada | Mekarski P.,Radiation Protection Bureau of Health Canada | Hoffman I.,Radiation Protection Bureau of Health Canada | And 2 more authors.
Journal of Radioanalytical and Nuclear Chemistry | Year: 2011

In this study, a gamma-gamma coincidence spectrometry was developed and examined for environmental low-level cosmogenic 22Na monitoring purposes. The spectrometry consists of two bismuth germanate scintillators (BGO) and XIA LLC Digital Gamma Finder (DGF)/Pixie-4 software and card package. The developed spectrometry was optimized according to the considerations of output count rate and gamma peak energy resolution. This spectrometry provides a more sensitive and effective way to quantify even trace amounts of 22Na with critical detection limit of 9 mBq. A sophisticated computer simulation was also created with the goal of obtaining a better understanding of the experimental results and gamma-gamma coincidence efficiencies at different sample geometries. © 2010 Akadémiai Kiadó, Budapest, Hungary. Source


Zhang W.,Radiation Protection Bureau of Health Canada | Mekarski P.,Radiation Protection Bureau of Health Canada | Ungar K.,Radiation Protection Bureau of Health Canada
Applied Radiation and Isotopes | Year: 2010

A single-channel phoswich well detector has been assessed and analysed in order to improve beta-gamma coincidence measurement sensitivity of 131mXe and 133mXe. This newly designed phoswich well detector consists of a plastic cell (BC-404) embedded in a CsI(Tl) crystal coupled to a photomultiplier tube (PMT). It can be used to distinguish 30.0-keV X-ray signals of 131mXe and 133mXe using their unique coincidence signatures between the conversion electrons (CEs) and the 30.0-keV X-rays. The optimum coincidence efficiency signal depends on the energy resolutions of the two CE peaks, which could be affected by relative positions of the plastic cell to the CsI(Tl) because the embedded plastic cell would interrupt scintillation light path from the CsI(Tl) crystal to the PMT. In this study, several relative positions between the embedded plastic cell and the CsI(Tl) crystal have been evaluated using Monte Carlo modeling for its effects on coincidence detection efficiency and X-ray and CE energy resolutions. The results indicate that the energy resolution and beta-gamma coincidence counting efficiency of X-ray and CE depend significantly on the plastic cell locations inside the CsI(Tl). The degraded X-ray and CE peak energy resolutions due to light collection efficiency deterioration by the embedded cell can be minimised. The optimum of CE and X-ray energy resolution, beta-gamma coincidence efficiency as well as the ease of manufacturing could be achieved by varying the embedded plastic cell positions inside the CsI(Tl) and consequently setting the most efficient geometry. © 2010. Source


Zhang W.,Radiation Protection Bureau of Health Canada | Mekarski P.,Radiation Protection Bureau of Health Canada | Lam J.,Radiation Protection Bureau of Health Canada | Ungar K.,Radiation Protection Bureau of Health Canada
Journal of Radioanalytical and Nuclear Chemistry | Year: 2010

This paper describes a Monte Carlo (MC) simulation method for calculating radioxenon beta-gamma coincidence spectral information. These spectral components include detector response simulations by Geant4 modeling, detector energy and resolution calibrations using the histograms of detector response, beta-gamma coincidence efficiency values and spectral interference ratios. The work presented in this paper demonstrates the feasibility of using the spectral information to create beta-gamma coincidence spectra at various radioxenon activity concentrations. The analysis of these synthetic spectra by XECON software shows an excellent correlation between the analysed radioxenon activity concentration and number of MC samplings. © 2010 Akadémiai Kiadó, Budapest, Hungary. Source


Zhang W.,Radiation Protection Bureau of Health Canada | Ungar K.,Radiation Protection Bureau of Health Canada | Liu C.,Radiation Protection Bureau of Health Canada | Mailhot M.,Radiation Protection Bureau of Health Canada
Journal of Environmental Radioactivity | Year: 2016

A series of measurements have been recently conducted to determine the cosmic-muon intensities and attenuation factors at various indoor and underground locations for a gamma spectrometer. For this purpose, a digital coincidence spectrometer was developed by using two BC408 plastic scintillation detectors and an XIA LLC Digital Gamma Finder (DGF)/Pixie-4 software and card package. The results indicate that the overburden in the building at surface level absorbs a large part of cosmic ray protons while attenuating the cosmic-muon intensity by 20-50%. The underground facility has the largest overburden of 39 m water equivalent, where the cosmic-muon intensity is reduced by a factor of 6. The study provides a cosmic-muon intensity measurement and overburden assessment, which are important parameters for analysing the background of an HPGe counting system, or for comparing the background of similar systems. © 2016 Elsevier Ltd. Source


Zhang W.,Radiation Protection Bureau of Health Canada | Ungar K.,Radiation Protection Bureau of Health Canada | Stukel M.,Radiation Protection Bureau of Health Canada | Mekarski P.,Radiation Protection Bureau of Health Canada
Journal of Environmental Radioactivity | Year: 2014

In this study, a digital gamma-gamma coincidence/anticoincidence spectrometer was developed and examined for low-level cosmogenic 22Na and 7Be in air-filter sample monitoring. The spectrometer consists of two bismuth germanate scintillators (BGO) and an XIA LLC Digital Gamma Finder (DGF)/Pixie-4 software and card package. The spectrometer design allows a more selective measurement of 22Na with a significant background reduction by gamma-gamma coincidence events processing. Hence, the system provides a more sensitive way to quantify trace amounts of 22Na than normal high resolution gamma spectrometry providing a critical limit of 3mBq within a 20h count. The use of a list-mode data acquisition technique enabled simultaneous determination of 22Na and 7Be activity concentrations using a single measurement by coincidence and anticoincidence mode respectively. © 2014 Elsevier Ltd. Source

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