Browsing by Author "Flynn, A"

Now showing 1 - 6 of 6
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    A condensed overview of sub-geV hadronic physics in GEANT4
    (Australian Nuclear Science and Technology Organisation, 2022-08-11) Brown, JMC; Boardman, DA; Flynn, A
    This technical report provides a condensed overview of the underlying physics processes of transport, interaction, and production of sub-GeV hadronic particles in Geant4. The report was developed and funded under Project Arrangement 10256 in collaboration with the Defence Science and Technology Group of the Australian Department of Defence. The material contained in this report provides a complementing resource to the Geant4 Physics Reference Manual (G4PRM) for novice to intermediate user of the Monte Carlo toolkit. The authors acknowledge that this condensed overview draws heavily on the past work of the Geant4 Collaboration (G4Collab) and publications outlined in Section 9 (References).
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    Evaluation of novel gamma ray imaging technology
    (Australasian Radiation Protection Society, 2017-08-09) Guenette, MC; Boardman, DA; Sarbutt, A; Flynn, A; Prokopovich, DA
    We present the imaging results from a novel single pixel gamma-ray imaging system, developed at ANSTO, which is capable of providing quantitative, spectroscopic gamma images using a fast and efficient imaging methodology. Gamma ray imaging can assist in surveying active areas by providing information of the radiation environment in areas which are hard to reach (e.g. in enclosed spaces or at height) and by gaining valuable information about the radiation environment whist limiting exposure to personnel in high dose rate environments. The system design provides a large field of view (360° × 70°) and covers a wide energy range of 40 keV to 1.5 MeV. The gamma ray image is overlaid on a 360° panoramic optical image of the scene, which allows for easy location of the gamma emitting radionuclides that are present. By selecting different regions of interest in the recorded gamma spectrum, separate radionuclide specific images, of the area being surveyed, can be visualised. Calibration of the detector allows for quantitative mapping of where each component of the dose rate at the detector originates. This can be converted into activity with a priori knowledge of the scene geometry. Gamma-ray images have been experimentally obtained for both point sources and extended sources in controlled testing environments and these results will be presented. The imaging results from a range of real world operational environments, around the ANSTO site, will be presented and demonstrate the systems capability for locating sources of radiation in nuclear industry applications.
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    A gamma-ray identification algorithm based on fisher linear discriminant analysis
    (Institute of Electrical and Electronics Engineers (IEEE), 2015-12-25) Boardman, DA; Flynn, A
    An algorithm for gamma-ray identification applications has been developed and evaluated. The algorithm is based on a Fisher Linear Discriminant Analysis (FLDA) technique that generates loading coefficients that maximize the separation of a particular radionuclide from all the other radionuclides in a training library. Separate experimental data sets were obtained for the algorithms training data and for the performance evaluation. The algorithm was evaluated against a range of radionuclides and acquisitions times. An inverse square root relationship between the cluster standard deviation and its gross mean counts enabled the production of an adaptable threshold. The inverse square relationship between the Mahalanobis distance metric and the Cs-137 standoff distance demonstrated a means to quantify the measured number of counts. The FLDA identification performance, for a number of threat radionuclides (including special nuclear materials), exceeded that of a commercially available peak search algorithm. The high sensitivity and specificity, of the FLDA algorithm, was maintained in low count situations. The poor performance for some radionuclides was attributed to the measured number of counts being below the minimal detectable limit. The FLDA algorithm has the potential to be used in gamma-ray identification applications and, in particular, count starved situations. © 2012, Institute of Electrical and Electronics Engineers (IEEE).
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    Performance of a fisher linear discriminant analysis gamma-ray identification algorithm
    (Institute of Electrical and Electronics Engineers (IEEE), 2013-04-11) Boardman, DA; Flynn, A
    The development of a gamma-ray identification algorithm based on a Fisher Linear Discriminant Analysis (FLDA) approach has previously shown high potential in count starved situations. This work uses 48,000 semi-empirical synthetic spectra to evaluate the algorithm performance over a broad range of dose rates and acquisition times. True positive identifications of 100% were typically seen for dose rates ≥ 0.05 μSv/h and acquisition times ≥10 s. For in air and shielded radionuclide spectra, no false alarms were observed for dose rates ≥ 0.01 μSv/h and acquisition times ≥10 s. The single radionuclide identification performance typically exceeded the ANSI 42.34 standard by a factor of 10 for dose rate and a factor of 10 for acquisition time. The evaluated shielded signatures had no detrimental effects to the identification performance. The correct identification of HEU masked by a 0.5 μSv/h 40K or 60Co source could typically be made for a masking ratio of 10:1 for acquisition times ≥ 1 s. For masking with a 0.5 μSv/h 137Cs source, HEU could be identified at 7:1 ratios for times ≥10 s. The excellent results were obtained for a non-optimal identification threshold. Optimization of the threshold would lead to further performance improvements. © 2013, Institute of Electrical and Electronics Engineers (IEEE).
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    Single pixel compressive gamma-ray imaging with randomly encoded masks
    (IOP Publishing, 2020-04-15) Boardman, DA; Sarbutt, A; Flynn, A; Guenette, MC
    We report on the development and demonstration of a single pixel spectroscopic gamma-ray imaging concept based on the principles of compressed sensing. Compressive gamma-ray images were obtained for both point sources and complex extended sources. The reconstruction of images at different photon energies allowed the spatial mapping of different radionuclides. When compared to traditional aperture based gamma-ray imaging techniques, the point source images were generated with ten times fewer measurements. More complex extended source images were generated with up to three times fewer measurements. Gamma-ray imaging techniques designed around the principles of compressed sensing have the potential to exploit the sparsity typically found in gamma-ray images, leading to a new class of fast and low cost imaging systems. © Copyright 2020 IOP Publishing
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    The validation of synthetic spectra used in the performance evaluation of radionuclide identifiers
    (Elsevier, 2013-07-01) Flynn, A; Boardman, DA; Reinhard, MI
    This work has evaluated synthetic gamma-ray spectra created by the RASE sampler using experimental data. The RASE sampler resamples experimental data to create large data libraries which are subsequently available for use in evaluation of radionuclide identification algorithms. A statistical evaluation of the synthetic energy bins has shown the variation to follow a Poisson distribution identical to experimental data. The minimum amount of statistics required in each base spectrum to ensure the subsequent use of the base spectrum in the generation of statistically robust synthetic data was determined. A requirement that the simulated acquisition time of the synthetic spectra was not more than 4% of the acquisition time of the base spectrum was also determined. Further validation of RASE was undertaken using two different radionuclide identification algorithms. © 2013, Elsevier Ltd.