Browsing by Author "Smith, ML"

Now showing 1 - 12 of 12
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    Characterisation of a well-type NaI(T1) detector by means of a Monte Carlo simulation for radionuclide metrology application
    (Elsevier B. V., 2021-10) Heranudin, H; Smith, ML; van Wyngaardt, WM; Guatelli, S; Li, E; Rosenfeld, AB
    A well-type NaI(Tl) detector was modelled and characterised by means of a Monte Carlo simulation, as part of a project to develop a 4πβ (Plastic Scintillator)-4πγ instrument to be used for the primary standardisation of radionuclides at ANSTO. The simulation based on GEANT4 was used to characterise the 4πγ detector in terms of potential dead layer/inactive materials, full energy peak efficiency, coincidence-summing correction, and energy resolution. An excellent agreement was obtained between the simulation results and the experimental measurements. © 2021 Elsevier Ltd.
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    Comparison of LaBr3 : Ce and LaCl3 : Ce with NaI(Tl) and cadmium zinc telluride (CZT) detectors
    (Institute of Electrical and Electronics Engineers (IEEE), 2008-06) Alexiev, D; Mo, L; Prokopovich, DA; Smith, ML; Matuchova, M
    Energy resolution and detection efficiency were compared between new scintillators, lanthanum bromide (LaBr3:Ce) and lanthanum chloride (LaCl3:Ce) with conventional detectors, sodium iodide NaI(Tl) and cadmium zinc telluride (CdZnTe or CZT). The study has shown that LaBr3:Ce and LaCl3:Ce scintillator detectors provided by Saint-Gobain offer better resolution than NaI(Tl) detector. LaBr3:Ce and LaCl3:Ce detectors could resolve some closely spaced peaks from 133Ba and 152Eu, which Na(I) could not. LaBr3:Ce has slightly better resolution and higher efficiency than LaCl3:Ce. An overall advantage of LaBr3:Ce and LaCl3:Ce detectors over NaI(Tl) and CZT has been discussed. The intrinsic activity of LaBr3:Ce is also demonstrated in this study. © 2008, Institute of Electrical and Electronics Engineers (IEEE)
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    Comparison of photoexcited p-InAs THz radiation source with conventional thermal radiation sources
    (American Institute of Physics, 2009-03-15) Smith, ML; Mendis, R; Vickers, REM; Lewis, RA
    P-type InAs excited by ultrashort optical pulses has been shown to be a strong emitter of terahertz radiation. In a direct comparison between a p-InAs emitter and conventional thermal radiation sources, we demonstrate that under typical excitation conditions p-InAs produces more radiation below 1.2 THz than a globar. By treating the globar as a blackbody emitter we calibrate a silicon bolometer which is used to determine the power of the p-InAs emitter. The emitted terahertz power was found to be 98 +/- 10 nW in this experiment. © 2009, American Institute of Physics
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    Development of the Australian standard for germanium-68 by two liquid scintillation counting methods
    (Elsevier B. V., 2018-04) van Wyngaardt, WM; Smith, ML; Jackson, TW; Howe, B; Tobin, SM; Reinhard, MI
    In response to the increasing application of 68Ge/68Ga and 68Ga in nuclear medicine, an international comparison of activity measurement of 68Ge in equilibrium with 68Ga was organised. ANSTO standardised the comparison solution by the 4π(LS)β+-γ coincidence extrapolation and TDCR efficiency calculation methods, with excellent agreement between the two results. The primary standard was transferred to the ANSTO Secondary Standard Ionisation Chamber. Internationally traceable Australian Certified Reference Materials (ACRMs) of 68Ge/68Ga can now be prepared in various measurement geometries applied in nuclear medicine. © 2017 Crown Copyright, Published by Elsevier Ltd. All
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    Evaluation of lead shielding for a gamma-spectroscopy system
    (Elsevier, 2008-05-01) Smith, ML; Bignell, LJ; Alexiev, D; Mo, L; Harrison, JJ
    Three types of lead shielding assemblies were investigated to establish which provides the lowest background as preliminary work for determining the efficiency of a High Purity Germanium (HPGe) detector. The background continuum and peaks were examined using gamma spectroscopy with a coaxial and a planar HPGe detector. The Pb-210 concentration in each lead sample taken from the assemblies was quantitatively determined. A French lead sample was found to have the lowest background in this relative comparison with a Pb-210 concentration of 29.1 +/- 1.3 Bq kg(-1). © 2008, Elsevier Ltd.
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    Monte Carlo simulation of a Au-198 thin foil: the response of a 4πβ-γ detector
    (Institute of Electrical and Electronics Engineers (IEEE), 2008-12) Bignell, LJ; Mo, L; Smith, ML; Alexiev, D; Hashemi-Nezhad, SR
    Monte Carlo simulations have been performed of the decay of a(198) Au solid source within a 4πβ-γ coincidence detector. Calculations of the proportional counter efficiency to both β and γ emissions are simulated. A comparison of results obtained using the MCNP-5 and Geant4 simulation packages indicates that Geant4 better evaluates the K correction to the coincidence equation than MCNP-5 predictions. This difference can be accounted for in terms of how the codes handle the physical interactions occurring in the foil and surrounds. © 2008, Institute of Electrical and Electronics Engineers (IEEE)
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    Post-LGM evolution of the lower Ord River, WA, constrained by luminescence and cosmogenic radionuclide dating
    (Australiasian Quaternary Association Inc., 2018-12-10) Smith, ML; McPherson, AA; Cupper, ML; Fuijoka, T; Wilcken, KM
    The landscape history of northern Australia is significant for understanding both environmental and human history. In this region the Upper Pleistocene to Holocene represents a period of major flux in response to external drivers such as climate variation and sea-level change. The influence of these drivers has been profound, and they have exerted significant controls on landscape form and composition along Australia’s northern margin. This also has implications for groundwater resources and quality. This study investigates the lower Ord River system, a bedrock-dominated catchment in the East Kimberley region of northwest Western Australia. Geochronological and geomorphological investigations of landforms of the lower Ord plain, and its paleo-floodplain within the central Ord River valley, highlight the significance of the terminal stages of the Last Glacial Maximum (LGM) as a control on regional base level and consequently on landscape change. The timing of capture of the Ord River from its northeast-draining paleo-valley to its present westerly course is constrained by cosmogenic radionuclide bedrock exposure ages from Tarrara Bar - the likely location of capture by westward flowing drainage at ca. 15 ka. Optically-stimulated luminescence ages from scroll plains on the lower Ord River downstream of Tarrara Bar are younger than 7 ka, suggesting that their evolution is tied to regional climatic variation affecting sediment supply to these lower reaches of the system post-LGM sea-level stabilisation. This landscape history is significant in that it controls the distribution and nature of alluvial materials within both the current and paleo-valley systems, and has implications for the properties of depositional units that may influence the distribution and quality of groundwater. © Author(s)
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    Primary standardisation of technetium-99m by liquid scintillation coincidence counting
    (Elsevier B. V., 2020-02) van Wyngaardt, WM; Tobin, SM; Lee, S; Smith, ML; Jackson, TW; Ilter, J; Howe, B; Sarbutt, A
    Technetium-99m was standardised by the 4π(LS)ce-γ coincidence extrapolation method. Sensitivity of the 4π(LS) channel to two types of radiation, namely conversion electrons and γ-rays, resulted in incorrect activity values being obtained when this was not adequately accounted for. Measurements were more robust when the LS detection efficiency was optimised, and when a γ-window setting was used that monitored the combined LS efficiency for conversion electrons and γ-rays. The primary standard was internationally compared through participation in the BIPM.RI(II)-K4.Tc99m key comparison. © 2019 Elsevier Ltd
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    Results of an international comparison of activity measurements of 68Ge
    (Elsevier B. V., 2018-04) Cessna, JT; Fitzgerald, R; Zimmerman, BE; Laureano-Pérez, L; Bergeron, DE; van Wyngaardt, WM; Smith, ML; Jackson, TW; Howe, B; da Silva, CJ; Iwahara, A; da Cruz, PAL; Zhang, M; Liu, H; Liang, JC; Fréchou, C; Bobin, C; Cassette, P; Kossert, K; Nähle, O; Marganiec-Gałązka, J; Joseph, L; Ravindra, A; Kulkarni, DN; Yunoki, A; Sato, Y; Lee, KB; Lee, JM; Agusbudiman, A; Dziel, T; Listkowska, A; Tymiński, Z; Sahagia, M; Antohe, A; Ioan, MR; Luca, A; Krivosek, M; Ometakova, J; Javornik, A; Zalesakova, M; García-Toraño Martinez, E; Roteta, M; Mejuto, M; Nedjadi, Y; Juget, F; Yuan, MC; Yeh, CY; Yeltepe, E; Dirican, A; Keightley, JD; Pearce, AK
    An international key comparison, identifier CCRI(II)-K2.Ge-68, has been performed. The National Institute of Standards and Technology (NIST) served as the pilot laboratory, distributing aliquots of a 68Ge/68Ga solution. Results for the activity concentration, CA, of 68Ge at a reference date of 12h00 UTC 14 November 2014 were submitted by 17 laboratories, encompassing many variants of coincidence methods and liquid-scintillation counting methods. The first use of 4π(Cherenkov)β-γ coincidence and anticoincidence methods in an international comparison is reported. One participant reported results by secondary methods only. Two results, both utilizing pure liquid-scintillation methods, were identified as outliers. Evaluation using the Power-Moderated Mean method results in a proposed Comparison Reference Value (CRV) of 621.7(11) kBq g−1, based on 14 results. The degrees of equivalence and their associated uncertainties are evaluated for each participant. Several participants submitted 3.6 mL ampoules to the BIPM to link the comparison to the International Reference System (SIR) which may lead to the evaluation of a Key Comparison Reference Value and associated degrees of equivalence. An international key comparison, identifier CCRI(II)-K2.Ge-68, has been performed. The National Institute of Standards and Technology (NIST) served as the pilot laboratory, distributing aliquots of a 68Ge/68Ga solution. Results for the activity concentration, CA, of 68Ge at a reference date of 12h00 UTC 14 November 2014 were submitted by 17 laboratories, encompassing many variants of coincidence methods and liquid-scintillation counting methods. The first use of 4π(Cherenkov)β-γ coincidence and anticoincidence methods in an international comparison is reported. One participant reported results by secondary methods only. Two results, both utilizing pure liquid-scintillation methods, were identified as outliers. Evaluation using the Power-Moderated Mean method results in a proposed Comparison Reference Value (CRV) of 621.7(11) kBq g−1, based on 14 results. The degrees of equivalence and their associated uncertainties are evaluated for each participant. Several participants submitted 3.6 mL ampoules to the BIPM to link the comparison to the International Reference System (SIR) which may lead to the evaluation of a Key Comparison Reference Value and associated degrees of equivalence. An international key comparison, identifier CCRI(II)-K2.Ge-68, has been performed. The National Institute of Standards and Technology (NIST) served as the pilot laboratory, distributing aliquots of a 68Ge/68Ga solution. Results for the activity concentration, CA, of 68Ge at a reference date of 12h00 UTC 14 November 2014 were submitted by 17 laboratories, encompassing many variants of coincidence methods and liquid-scintillation counting methods. The first use of 4π(Cherenkov)β-γ coincidence and anticoincidence methods in an international comparison is reported. One participant reported results by secondary methods only. Two results, both utilizing pure liquid-scintillation methods, were identified as outliers. Evaluation using the Power-Moderated Mean method results in a proposed Comparison Reference Value (CRV) of 621.7(11) kBq g−1, based on 14 results. The degrees of equivalence and their associated uncertainties are evaluated for each participant. Several participants submitted 3.6 mL ampoules to the BIPM to link the comparison to the International Reference System (SIR) which may lead to the evaluation of a Key Comparison Reference Value and associated degrees of equivalence. © 2021 Elsevier Ltd.
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    Review of Ge detectors for gamma spectroscopy
    (Springer, 2002-09) Alexiev, D; Reinhard, MI; Mo, L; Rosenfeld, AB; Smith, ML
    A review is given of the use of germanium detectors for gamma spectroscopy. The advantages, principles of operation, and fabrication processes of semiconductor radiation detectors are described. © 2002, Springer.
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    Sensitivity and uncertainty analysis of the simulation of 123I and 54Mn decay in liquid scintillation vials
    (Elsevier, 2009-09-10) Bignell, LJ; Mo, L; Smith, ML; Steele, T; Alexiev, D; Hashemi-Nezhad, SR
    General purpose, widely distributed Monte Carlo simulations for radiation transport have found many applications in the fields of radionuclide metrology, detector research and nuclear medicine. A full evaluation of the uncertainties due to the simulation of physical quantities and correction factors is required for model validation, uncertainty analysis and quality assurance, yet this evaluation is rarely explicitly carried out. The decay of the most important gamma and x-ray emissions of 123I and 54Mn in the ANSTO Triple-to-Double Coincidence Ratio (TDCR) liquid scintillation detector have been simulated using the radiation transport code Geant4. The energy deposition spectrum in the scintillant and the interaction probability for each emission has been determined. Both of these calculated quantities are required for an absolute activity measurement of these nuclides using the TDCR method. A sensitivity and uncertainty analysis of the simulation model with respect to these output parameters has been carried out and is presented here. The uncertainty in the simulation results due to the input parameter uncertainties was found to be several times larger than the statistical uncertainty component for a typical number of simulated decay events. The scintillant volume was the most sensitive input parameter to produce changes in the output quantities studied, indicating that the minimization of the uncertainty of this parameter would be most beneficial for reducing the uncertainty of the simulation outputs. The scintillant density and composition were also important, which is significant as the uncertainties associated with these input parameters are generally not well known. Estimates of the relative uncertainty associated with the simulation outputs due to the combined stochastic and input uncertainties are provided.
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    Sipping test: checking for failure of fuel elements at the OPAL Reactor
    (Korean Nuclear Society, 2010-02) Smith, ML; Bignell, LJ; Alexiev, D; Mo, L
    Sipping measurements were implemented at the Open Pool Australian Light water reactor (OPAL) to test for failure in reactor fuel elements. Fission product released by the fuel element into the pool water was measured using both High Purity Germanium (HPGe) detection via samples and a NaI(Tl) detection in-situ with the sipping device. Results from two fuel elements are presented. © 2010, Korean Nuclear Society