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AbstractAbstract
[en] Gamma imaging is a technique that allows the spatial localization of radioactive sources. The various applications of this technique cover decommissioning phases of nuclear facilities, nuclear waste management applications, but also radiation protection or Homeland Security. Using gamma camera reduces the dose received by operators and consequently contributes to the respect of the ALARA principle. There are two imaging techniques for the localization of gamma ray emitters: coded aperture imaging and Compton imaging. Coded aperture imaging relies on the spatial modulation of the incident gamma-ray flux by a multi-hole collimator placed between the detector and the radioactive source. It has the advantage of being extremely efficient for 'low energy' gamma-ray emitters in terms of sensitivity and angular resolution. On the other hand, Compton imaging is based of the Compton scattering kinematic. The energy deposited during the scattering process will determine the scattering angle, and the positions of the interactions will determine the direction of the incoming gamma-ray. The position of the radioactive source can thus be limited to a cone. If several cones are used, then, the position where the greatest number of cones overlap corresponds to the position of the radioactive source. One limitations of this technique concerns the location of 'low energy' gamma-ray emitters, for which the angular resolution is strongly degraded until it is completely not localizable. The objective of this work is to develop a prototype of hybrid imager that combines coded aperture and Compton imaging techniques in order to take advantage of each type of imaging. The different studies carried out, around the Timepix3 pixel detector, but also in the development of mathematical algorithms, have led to propose two prototypes of hybrid imager. The results obtained from this research work made it possible to validate experimentally the performance of one of the imager prototypes, and to illustrate the interest of a hybrid system. (author)
[fr]
L'imagerie gamma est une technique qui permet la localisation spatiale de sources radioactives. Les differentes applications de cette technique couvrent les phases de demantelement des installations nucleaires ou de gestion des dechets nucleaires, mais aussi la radioprotection ou la securite interieure. L'utilisation de cameras gamma permet de reduire la dose recue par les operateurs, et, par consequent, de respecter le principe ALARA. Il existe deux techniques d'imagerie permettant la localisation de radioelements emetteurs gamma: l'imagerie a masque code et l'imagerie Compton. L'imagerie a masque code utilise la modulation spatiale du flux de photons gamma incidents par collimateur multi-trous place entre la source et le detecteur. Elle presente l'avantage d'etre extremement performante pour des emetteurs gamma 'basses energies', aussi bien en matiere de sensibilite, qu'en matiere de resolution angulaire. L'imagerie Compton, quant a elle, repose sur l'utilisation de la mecanique de diffusion Compton. L'energie deposee pendant le processus de diffusion determinera l'angle de diffusion, et les positions des interactions determineront la direction des rayons gamma entrants. La position de la source radioactive peut ainsi etre limitee a un cone. Si plusieurs cones sont utilises, alors la position ou le plus grand nombre de cones se chevauchent correspond a la position de la source radioactive. Une des limitations de cette technique concerne la localisation des emetteurs gamma 'basses energies', pour lesquels la resolution angulaire est fortement degradee allant jusqu'a l'impossibilite complete de trouver la position. L'objectif de ces travaux est de developper un prototype d'imageur hybride associant les techniques d'imagerie a masque code et d'imagerie Compton, afin de tirer profit des avantages de chacun des types d'imagerie. Les differents travaux menes, autour du detecteur pixellise Timepix3, mais aussi en matiere de developpement d'algorithmes mathematiques, ont permis de proposer deux prototypes d'imageurs hybrides. Les resultats obtenus a l'issue de ces travaux de recherche ont permis de valider experimentalement les performances d'un des prototypes d'imageurs et d'illustrer l'interet d'un systeme hybrideOriginal Title
Developpement d'un imageur gamma hybride pour les applications de l'industrie nucleaire
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27 Sep 2019; 195 p; 66 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses; Physique
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Report
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Thesis/Dissertation
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