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AbstractAbstract
[en] Localization of gamma ray emitters is currently a major issue for nuclear industry and for Homeland Security applications. The GAMPIX coded-mask gamma camera developed by the CEA is able to carry out this localization. Its main limitation is the lack of spectrometric information preventing the identification of detected radionuclides and consequently the assessment of radiation dangerousness. Based on this observation, the aim of the PhD was to design a coded-mask gamma imaging-spectrometer for simultaneous localization and identification of gamma ray emitters. In a first time, we implemented a detection system, optimized for spectrometry, based on the system currently integrated in GAMPIX which is composed of a Timepix readout chip (designed by the CERN) hybridized with a cadmium telluride semiconductor substrate. After setting the electronic parameters of the chip, we determined the optimal bias voltage for the substrate and achieved energy calibration of the detection system. A second research path dealt with the integration of the spectrometric information coming from the detector into data treatment. Two trails were considered respectively based on an energy windowing of the data and on the use of MLEM algorithms. A last part was finally dedicated to the assessment of detectors providing an added value compared to Timepix in terms of spectrometric performances. Two detectors were considered: the Medipix3 detector designed by the CERN and the Caliste HD detector developed by the IRFU Institute (CEA). The latter was integrated into a prototype of gamma camera and tests proved the relevance of its use in such a system. (author)
[fr]
La localisation des radioelements emetteurs gamma constitue un enjeu majeur pour l'industrie nucleaire et pour les applications de securite interieure. La camera gamma a masque code GAMPIX, developpee par le CEA LIST, est apte a realiser cette localisation. Sa principale limitation est l'absence d'information spectrometrique empechant l'identification des elements detectes. De la, l'objectif de la these a ete le developpement d'un spectro-imageur gamma a masque code permettant d'assurer conjointement la localisation et l'identification des radioelements emetteurs. Dans un premier temps, nous avons mis en place un systeme de detection optimise du point de vue de la spectrometrie en partant du systeme actuellement integre a GAMPIX, compose de la puce de lecture Timepix hybridee a un substrat de tellurure de cadmium. Apres reglage des parametres de la puce, nous avons determine la tension de polarisation optimale du substrat puis realise la calibration du systeme de detection. Un deuxieme axe de recherche a ete dedie a l'integration de l'information spectrometrique issue du systeme de detection dans le traitement des donnees. Deux approches ont ete mises en oeuvre et testees, reposant respectivement sur un fenetrage en energie des donnees et sur l'utilisation d'algorithmes MLEM. Une derniere partie a enfin ete consacree a l'evaluation de detecteurs apportant une plus-value par rapport a Timepix en termes de performances spectrometriques. Deux detecteurs ont ete testes: le detecteur Medipix3 developpe par le CERN et le detecteur Caliste HD concu par l'IRFU (CEA). Ce dernier a ete integre a un prototype de camera gamma et des tests ont prouve la pertinence de son utilisation dans un tel systemeOriginal Title
Developpement d'une camera gamma de troisieme generation
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25 Sep 2015; 216 p; 119 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses; Constituants Elementaires
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Report
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Thesis/Dissertation
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