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Dissertations / Theses on the topic 'Radiations physics'
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Dodd, Ian Martin. "Applications of synchrotron and conventional radiations in crystal structure analyses." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260358.
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Maccaferri, Francesco. "Organic thin-film transistors fabricated via pneumatic nozzle printing as direct detectors for ionizing radiations." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23204/.
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Organic semiconducting materials have recently proved to be a suitable candidate for the direct detection of X-ray radiation. Despite the low atomic number Z, organic materials can respond to ionizing radiation through the photoconductive gain mechanism. The response is governed by trap states: majority carrier traps directly impact the mobility, reducing the collection of charges at the electrodes; minority carrier traps, on the other hand, increase the output current by inducing the injection of extra majority carriers from the contacts in order to preserve charge neutrality. Employing organic semiconductors allows to take advantage of the electrical properties typical of their inorganic counterpart with additional features pertaining to low-Z materials like organic ones: flexibility, radiation hardness, human-tissue equivalence. In this thesis, organic field-effect transistors based on 6,13-bis-(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) fabricated with the novel Pneumatic Nozzle Printing technique have been characterized with the aim to correlate the sensitivity of the devices to the morphology of the semiconducting layer. In particular, the effect of the substitution of Silicon atoms with Germanium ones in the molecular structure has been investigated through many experimental techniques, including photocurrent spectroscopy. The fabricated devices exhibit sensitivities up to (7.4±0.4)×10^2µC/Gy cm^2, with mobilities reaching 0.25 cm^2/V s. Devices with Ge-substituted molecules exhibit higher sensitivities than their Silicon counterpart, but not as much as theoretically predicted based only on the higher absorption coefficient of Germanium atoms: this contrast has been attributed to a less efficient photoconductive gain mechanism.
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Coupier, B. "Studies towards the understanding of the effects of ionizing radiations at the molecular scales (20 to 150 keV H+/H + He Collisions; Dissociative Electron Attachment to Water)." Phd thesis, Université Claude Bernard - Lyon I, 2005. http://tel.archives-ouvertes.fr/tel-00012069.
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Ce travail s'inscrit dans le cadre d'études récentes pour la compréhension à l'échelle moléculaire des effets des rayonnements ionisants sur les systèmes biologiques, mises en oeuvre par le groupe IPM de l'IPNL en collaboration avec l'Institut für Ionenphysik de l'Université d'Innsbruck. Il est composé de deux parties. La première présente un nouvel ensemble de mesures des sections efficaces d'ionisation de l'hélium par impact de protons ou d'atomes d'hydrogène dans la gamme d'énergie d'intérêt pour la radiobiologie (20 à 150keV). Il s'agit de systèmes modèles d'intérêt pour la compréhension des phénomènes de base, et les collisions H + He ont fait l'objet, jusqu'à présent, de peu d'études utilisant les techniques de coïncidences. En outre, cette étude avec l'hélium a été faite dans l'intention de réaliser un test général de fonctionnement de l'appareillage avant d'aller vers des systèmes plus complexes. Des études similaires ont été ensuite réalisées en remplaçant la cible d'hélium par l'eau ou par des molécules d'intérêt biologique (Uracil, Thymine ...). La seconde partie de la thèse traite d'un autre type de radiations ionisantes que l'on peut voir comme une des conséquences secondaires des radiations étudiées dans la première partie. Des électrons de faible énergie (1 à 16eV) sont émis lors du bombardement de la matière par des protons ou des atomes d'hydrogène rapides; ces électrons ayant à leur tour des effets ionisants sur l'environnement. Une étude de l'attachement dissociatif des électrons sur l'eau a été entreprise à l'université d'Innsbruck, motivée par l'existence d'importants désaccords entre les précédentes études sur le même sujet. Le problème de la discrimination des ions à grande énergie cinétique dans le monochromateur trochoïdal utilisé pour cette étude a fait l'objet d'une attention particulière.
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Stonell, G. P. "The track structure of protons and other radiations in pure water vapour measured in a low pressure cloud chamber." Thesis, University of Westminster, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373002.
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Tortech, Blandine. "Effets des radiations sur des fibres optiques dopées erbium : influence de la composition." Phd thesis, Université Jean Monnet - Saint-Etienne, 2008. http://tel.archives-ouvertes.fr/tel-00366057.
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Nous avons étudié la sensibilité des fibres dopées erbium (EDF) sous irradiation et les défauts induits par celle-ci. Le premier chapitre présente l'état de l'art sur les EDF sous irradiations ainsi que des défauts générés dans la silice par les radiations. Le deuxième chapitre précise les types de radiations utilisés et les moyens expérimentaux mis en oeuvre pour caractériser les réponses des fibres sous irradiation ainsi que les défauts à l'origine des pertes. Dans le troisième chapitre, nous présentons la réponse de plusieurs fibres dopées erbium irradiées aux rayons γ, protons et rayons X pulsés. Les fibres dopées erbium et aluminium présentent des pertes induites par radiation plus élevées que les fibres classiques de transmission des télécommunications (SMF28) ou celles dopées erbium avec peu d'aluminium. La présence de l'aluminium dans la composition du coeur des fibres dopées erbium est en grande partie responsable des pertes induites. Quelque soit le type d'irradiation, les défauts créés par l'irradiation sont liés à la matrice hôte. Nos études montrent aussi que l'erbium n'est affecté qu'à travers son interaction avec les défauts créés. Le quatrième chapitre traite des EDF sous insolation UV et montre que les UV conduisent aux mêmes effets que les rayons γ. Le dernier chapitre présente, quant à lui, l'étude des amplificateurs optiques sous irradiation γ.
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Medeiros, Rogério Fachel de. "Elaboração de um material de apoio didático e paradidático para o ensino de física das radiações no ensino médio e técnico." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/39078.
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Este trabalho apresenta a implementação de um material de apoio para o ensino de Física das Radiações, e os resultados obtidos com sua aplicação em sala de aula para alunos do curso técnico em radiologia. Essa proposta tem como marco teórico a Aprendizagem Significativa apresentada por Ausubel. A aplicação do material de apoio em sala de aula fez uso sistemático de recursos computacionais, com destaque à utilização de um CD para promover o aprendizado significativo de conceitos básicos de Física das Radiações. Considerando que o assunto faz parte do curso técnico de radiologia a aplicação e avaliação do referido material de apoio foi realizada como parte do conteúdo básico de Física das Radiações, já prevista na ementa do curso. Como este material foi produzido vislumbrando a possibilidade de sua utilização também no Ensino Médio, a proposta contempla as recomendações dos Parâmetros Curriculares Nacionais no sentido de uma progressiva inserção da Física do Século XX no Ensino Médio. Na expectativa real de que, em um futuro próximo, a Física das Radiações passe a constar de maneira mais efetiva nos programas e conteúdos das escolas, o material de apoio produzido por esta dissertação poderá ser utilizado por professores do Ensino Médio que queiram abordar o assunto em suas aulas regulares em escolas que disponham de recursos de informática. A metodologia utilizada para produção do material de apoio estava focada, inicialmente, em um levantamento preliminar de dados em livros didáticos utilizados no Ensino Médio e Técnico e em artigos publicados em revistas especializadas. Posteriormente, utilizamos os resultados levantados pela aplicação dos questionários (Anexos 2 e 3) para direcionamento e definir os tópicos desenvolvidos no material onde finalizamos a produção do mesmo com um estudo detalhado em 8 bibliografias especializadas. Com o objetivo de analisar e avaliar a aplicação do material de apoio de um ponto de vista geral realizamos o cálculo da porcentagem média geral de acertos e erros obtidos na avaliação prévia e comparamos com a porcentagem média geral de acertos e erros obtidos na avaliação final. A porcentagem média geral de acertos verificado nas 45 questões objetivas aplicadas durante o desenvolvimento da atividade aumentou de 17,0% para 82,3 % e a porcentagem média geral de erros diminuiu de 83,0% para 17,7%. Sendo assim, podemos concluir que, durante a implementação do curso, nosso objetivo foi alcançado onde os resultados indicam que assuntos atuais (que fazem parte da vida cotidiana dos alunos) são bem recebidos por eles e a utilização de um material direcionado para esta realidade produz bom resultado em termos de aprendizagem significativa.This study presents not only the implementation of support material for teaching Physics of Radiations, but also the results obtained through its application in the classroom with students of the course technician in radiology. This proposal has as its theoretical framework the meaningful learning theory presented by Ausubel, and the application of support material in the classroom has used computational resources systematically, highlighting the utilization of an interactive CD in order to promote meaningful learning of basic concepts of radiations. Considering that the subject makes part of the course technician in radiology, the application and assessment of the referred support material was carried out as part of the basic content of Physics of Radiations already predicted in the course program. In addition, as this material was produced glimpsing the possibility of its utilization in the high school, this work proposal has contemplated the recommendations of National Curricular Parameters with the direction of a progressive insertion of physics of the twentieth century in high school teaching. Whit the real expectation that, in the near future, the Physics of Radiations will appear in a more effective way, in programs and contents of the schools, the support material produced by this dissertation will be available for high school teachers who want to approach the subject in their regular classrooms, which have provided informatics resources. The methodology utilized for the production of support material has been focused, initially, on a preliminary survey of data collected from textbooks utilized in high/technical school teaching and articles published in specialized magazines. Subsequently, the results obtained with the application of the questionnaires (Annexes 2 and 3) were utilized for directing and defining the topics developed in the material, where the production of it was completed within a detailed study in 8 specialized literatures. Then, with the objective of analyzing and assessing the application of this support material, we have carried out, from a general point of view, the calculus of the general mean percentage of accuracy and errors obtained in the previous assessment, and we have compared it with the general mean percentage of accuracy and errors obtained in the final assessment. The general mean percentage of accuracy verified in the 45 objective questions, applied during the development of the activity, increased from 17.0% to 82.3 %, and, the general mean percentage of errors decreased from 83.0% to 17.7%. Therefore, we may conclude that, during the course implementation, our objective was achieved and the results suggest that current physics topics can make part of the routine life of students, as well as that they were well received by them; the utilization of support material, directed for this reality, has produced a good result in terms of meaningful learning.
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Sousa, Wellington Batista de. "Física das radiações: uma proposta para o Ensino Médio." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/81/81131/tde-17092012-141621/.
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A sociedade vem questionando os conteúdos presentes no currículo de ciências, quanto ao \"por que\" e \"para que\" ensiná-los. Isso ocorre também dentro do ambiente escolar. Atualmente, o ensino de ciências tem acontecido de maneira bastante desconexa da realidade de nossos alunos, afinal, este ensino não tem apresentado inovações ou trazido temas atualizados para as discussões que ocorrem no ambiente da sala de aula. Apresentamos neste trabalho uma proposta de atualização curricular do ensino de ciências através da inserção de tópicos de Física Moderna e Contemporânea, com base na proposta curricular inserida nos PCNEM e PCNEM+ para a disciplina de Física. Nossa proposta consiste em uma seqüência didática de um curso de Física das Radiações voltado ao Ensino Médio, onde se utilizam as noções de \"marcadores\" e \"marcadores-estruturantes\", desenvolvidas no contexto da teoria da Transposição Didática, para delinear as atividades que acreditamos serem essenciais para que esta nova seqüência de ensino seja exeqüível.The society has questioned what should be taught in science learning, including both \"why\" and \"what for\" some subjects should be taught. This kind of discussion occurs also inside the educational environment. Presently the science teaching is not connected to the reality of the student, because teaching has not related to scientific innovations, no updated themes are discussed in the classroom. In this work the curricular updating is inserted through the inclusion of Modern and Contemporary Physics topics, as suggested in the PCNEM and PCNEM+. This proposal consists of a didactic sequence of a course on Radiations Physics appropriated to the high school teaching. The concept of \"markers\" and \"structurating-markers\" is discussed within the Didactic Transposition Theory. \"Markers\" are established through the proposed activities, which are supposed to be the essential ones to the learning sequence.
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Raine, Melanie. "Etude de l' effet de l'énergie des ions lourds sur la sensibilité des composants électroniques." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00647328.
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Ce mémoire de thèse traite de l'étude de la sensibilité des composants électroniques avancés en milieu radiatif. Le travail porte sur la modélisation détaillée du dépôt d'énergie induit par un ion lourd dans la matière, et sur l'influence de la prise en compte de cette trace d'ion dans les outils de simulation de la réponse de composants irradiés. Dans ce but, nous avons développé une chaîne de simulation, combinant différents codes de calcul à des échelles variées. Dans une première étape, le code d'interactions particule-matière Geant4 est ainsi utilisé pour modéliser la trace d'ion. Ces traces sont ensuite implémentées dans un code de simulation TCAD, afin d'étudier la réponse de transistors élémentaires à ces dépôts d'énergies détaillés. Cette étape est complétée par des mesures expérimentales. Enfin, l'étude est étendue au niveau circuit, en interfaçant les traces d'ions avec un outil de prédiction des SEE. Ces différentes étapes mettent en évidence la nécessité de prendre en compte la dimension radiale de la trace d'ion à tous les niveaux de simulation, pour modéliser de façon adéquate la réponse de composants avancés sous irradiation par des ions lourds.
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Benoit, Mathieu. "Étude des détecteurs planaires pixels durcis aux radiations pour la mise à jour du détecteur de vertex d'ATLAS." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00610015.
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Le Large Hadron Collider (LHC), située au CERN, Genève, produit des collisions de protons accélérés à une énergie de 3.5 TeV depuis le 23 Novembre 2009. L'expérience ATLAS enregistre depuis des données et poursuit sa recherche de nouvelle physique à travers l'analyse de la cinématique des événements issues des collisions. L'augmentation prévue de la luminosité sur la période s'étalant de 2011 2020 apportera de nouveaux défis pour le détecteur qui doivent être considérés pour maintenir les bonnes performance de la configuration actuelle. Le détecteur interne sera le sous-détecteur le plus affecté par l'augmentation de la luminosité qui se traduira par une augmentation des dommages occasionnés par la forte radiation et par la multiplication du nombre de traces associées à chaque croisement de faisceau. Les dommages causés par l'irradiation intense entrainera une perte d'efficacité de détection et une réduction du nombre de canaux actifs. Un intense effort de Recherche et Développement (R&D) est présentement en cours pour concevoir un nouveau détecteur pixel plus tolérant aux radiations et au cumul des événements générant un grand nombre de traces à reconstruire. Un premier projet de mise-à-jour du détecteur interne, nommé Insertable B-Layer (IBL) consiste à ajouter un couche de détection entre le tube à vide du faisceau et la première couche de silicium. Le projet SLHC prévoit de remplacer l'ensemble du détecteur interne par une version améliorée plus tolérante aux radiations et aux cumuls des événements. Dans cet ouvrage, je présente une étude utilisant la simulation technologique assisté par ordinateur (TCAD) portant sur les méthodes de conception des détecteurs pixels planaires permettant de réduire les zones inactives des détecteurs et d'augmenter leurs tolérances aux radiations. Les différents modèles physiques disponible ont étés étudiés pour développer un modèle cohérent capablede prédire le fonctionnement des détecteurs pixels planaires après irradiation. La structure d'anneaux de gardes utilisée dans le détecteur interne actuel a été étudié pour obtenir de l'information sur les possible méthodes permettant de réduire l'étendu de la surface occupée par cette structure tout en conservant un fonctionnement stable tout au long de la vie du détecteur dans l'expérience ATLAS. Une campagne de mesures sur des structures pixels fut organisée pour comparer les résultats obtenue grâce à la simulation avec le comportement des structures réelles. Les paramètres de fabrication ainsi que le comportement électrique ont été mesurés et comparés aux simulations pour valider et calibrer le modèle de simulation TCAD. Un modèle a été développé pour expliquer la collection de charge excessive observée dans les détecteurs planaires en silicium lors de leur exposition a une dose extrême de radiations. Finalement, un modèle simple de digitalisation à utiliser pour la simulation de performances détecteurs pixels individuels exposés à des faisceau de haute énergie ou bien de l'ensemble du détecteur interne est présenté. Ce modèle simple permets la comparaison entre les données obtenue en faisceau test aux modèle de transport de charge inclut dans ladigitalisation. Le dommage dû à la radiation , l'amincissement et l'utilisation de structures à bords minces sont autant de structures dont les effets sur la collecte de charges affectent les performance du détecteur. Le modèle de digititalisation fut validé pour un détecteur non-irradié en comparant les résultats obtenues avec les données acquises en test faisceau de haut énergie. Le modèle validé sera utilisé pour produire la première simulation de l'IBL incluant les effets d'amincissement du substrat, de dommages dûes aux radiations et de structure dotés de bords fins.
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Elf, Patric. "Radiation effects on wide bandgap semiconductor devices." Thesis, KTH, Tillämpad fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-283320.
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Gallium nitride (GaN) based high-electron-mobility transistors (HEMTs) are used in a wide variety of areas, such as 5G, automotive, aeronautics/astronautics and sensing elds ranging from chemical, mechanical, biological to optical applications. Owing superior material properties, the GaN based HEMTs are especially useful in harsh operation environments e.g. in the combustion engine, exhaust, space, and medical instruments where the reliability and resilience are highly demanded. In this thesis the e ect of proton irradiation on the GaN HEMTs as well as the possible incorporation of them in biomedicine and diagnostics are investigated. The thesis includes mainly two parts: one is on theoretic background of GaN HEMTs, and another presents the experiment/simulation details of the devices before and after proton radiation. In the background section, the HEMTs function, manufacture technique and defect formation mechanism in the device under di erent proton radiation conditions are introduced. Then, the characterizations of the HEMT devices and related test structures before and after the proton radiation with dose range from 1011 to 1015 protons=cm2 are emphasized, as well as the comparison with simulation results obtained using SRIM/TRIM program. In addition, the biocompatibility of GaN devices and their biomedicine applications in proton radiation scenarios are also described and discussed in this thesis.Gallium Nitrid (GaN) baserade high electron mobility transistors (HEMTs) används inom många olika områden, såsom 5G, bil-industrin, yg/rymd och i sensorer fö kemiska, mekaniska, biologiska och optiska applikationer. Tack vare dess goda materialegenskaper GaN baserade HEMTs särskilt användbara i harda miljöer, som till exempel i förbränningsmotorer, avgaser, i rymden, samt till medicinska instrument där pålitlighet och tålighet är eftersträvat. I det här examensarbetet sa undersöks e ekten av protonbestrålning pa GaN HEMTs samt möjligheten till användning av dem inom biomedicin och diagnostik. Arbetet är uppdelat i två delar: den ena behandlar den teoretiska bakgrunden av GaN HEMTs och den andra presenterar de experiment/simuleringar som utförts för att se efekterna på komponenterna före och efter protonbestrålning. I bakgrunds-sektionen så beskrivs hur HEMTs fungerar, tillverkningstekniker och mekanismerna för hur defekter uppkommer under olika former av protonbestrålning. Därefter sa karaktäriseras HEMT komponenterna och relaterade teststrukturer före och efter protonbestralning, med ett fokus på doser mellan 1011 to 1015 protoner=cm2, samt en jämförelse med resultat som fatts fran simuleringar med SRIM/TRIM-program. Utöver detta sa beskrivs och diskuteras även biokompatibiliteten och applikationer inom biomedicin av GaN komponenter vid protonbestralnings-scenarion i arbetet.
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ALVES, RODRIGO M. "Segurança alimentar através da determinação de 2-alcilciclobutanonas em alimentos processados por radiação ionizante." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26942.
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A irradiação de alimentos é um meio de preservação de alimentos onde se utiliza uma técnica de processamento que expõe os alimentos a uma radiação ionizante controlada de alta energia. O tratamento realizado com o uso das radiações ionizantes em alimentos tem muitas aplicações tecnologicamente e tecnicamente viáveis incluindo a capacidade de melhorar a segurança microbiológica, reduzir os níveis de bactérias patogénicas, inibir a germinação de tubérculos, aplicação fitossanitária, conservar alimentos armazenados ou a estabilidade de armazenamento e também é utilizada para aumentar a vida de prateleira de determinados produtos devido à redução da contaminação por microrganismos. Em função do aumento do comércio internacional de alimentos e das crescentes exigências regulatórias dos mercados consumidores, cada vez mais países importadores e exportadores têm demonstrando interesse na irradiação de alimentos e desenvolvido pesquisas na aplicação prática desta tecnologia e de métodos de detecção do tratamento. Inúmeras pesquisas foram realizadas mundialmente, resultando em eficientes protocolos para identificar quais alimentos foram ou não irradiados. Até então, o \"mito\" que alimentos irradiados não poderiam ser detectados e que não eram formados quaisquer produtos únicos da radiação foi substituído pelo conhecimento que muitas mudanças podem ocorrer nos alimentos irradiados e essas mudanças poderiam ser utilizadas como ferramentas para identificar essa tecnologia. O processamento por radiação resulta em formações de padrões característicos de hidrocarbonetos saturados, aldeídos, metil e etil ésteres e 2-alcilciclobutanonas, dependendo da composição do ácido graxo do lipídio que compõe o alimento. Com isso a proposta do trabalho foi levantar dados para comparar os efeitos das diferentes doses de radiação gama e de elétrons em alimentos que possuem gordura para verificar as possíveis alterações decorrentes do uso da irradiação, como a presença de 2-Alcilciclobutanonas e também, mostrar os principais equipamentos utilizados para a irradiação de alimentos e suas categorias, com o objetivo de informar o publico em geral.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Wagner, A., C. Schneidereit, B. Kämpfer, K. Fahmy, and E. Grosse. "Annual Report 2006 - Institute of Radiation Physics." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-28211.
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Jabor, Abbas. "Novelty and change detection radiation physics experiments." Licentiate thesis, Stockholm : Fysiska institutionen, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4410.
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Wagner, A., C. Schneidereit, B. Kämpfer, K. Fahmy, and E. Grosse. "Annual Report 2006 - Institute of Radiation Physics." Forschungszentrum Dresden-Rossendorf, 2007. https://hzdr.qucosa.de/id/qucosa%3A21648.
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Gray, Derrick. "Applications of radiation physics in civil engineering." Thesis, University of Surrey, 1999. http://epubs.surrey.ac.uk/842854/.
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This thesis presents two separate applications of ionising radiation in Civil Engineering. The first is an investigation to determine the cement content of concrete using gamma-rays from the naturally occurring isotopes 238U, 232Th and their decay chains as well as 40K. Two sets of equations are derived and discussed. Spectra from cement, aggregate and concrete samples were made and the useful full energy peaks from the above sources identified. Two concrete samples were prepared using the same cement, but, containing two different aggregates: a granite based aggregate and a flint based aggregate. A third concrete sample was then prepared where the cement content was not initially known. Data from the first two tests was then used to determine the mass of cement used in the blind test. A great deal of valuable information has also been accrued concerning the interaction of statistical errors in the equations for the prediction of cement content. Spectra from four different cements were collected at regular intervals over a 24 month period and the variation in the activity of each cement over this period is discussed. The second section of this work presents an imaging technique that uses pair production annihilation photons to examine the state of steel reinforcement in concrete structures. Computer simulations along with experimental work have been used. The experimental work used a 226Ra needle as a photon source as it provided a range of gamma-rays with energies over the pair production threshold of 1022keV. A 31mm rebar with 30mm of concrete cover was successfully located during the experimental work. The data collected from the computer simulations has shown that the geometry and the material between the photon source, rebar and detector is of great importance.
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TEIXEIRA, CHRISTIAN A. H. M. "Efeito da radiação ionizante em diferentes tipos de farinhas utilizadas em tecnologia de panificação." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9960.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Sabes, David. "Reconstruction des électrons et recherche de couplages anormaux dans le canal pp->ZZ->4l avec le détecteur CMS auprès du LHC." Phd thesis, Ecole Polytechnique X, 2012. http://pastel.archives-ouvertes.fr/pastel-00764836.
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La thèse en physique des particules que j'ai effectuée au sein de l'équipe CMS (Compact Muon Solenoid) du Laboratoire Leprince-Ringuet de l'École Polytechnique porte sur l'analyse de la production de di-bosons pp→ZZ+X et la recherche de couplages anormaux et ce, dans le cadre de l'expérience CMS et des données accumulées à l'aide du grand collisionneur de hadrons du CERN, le LHC. Elle débute avec le démarrage du LHC en fin 2009 et l'étude et l'optimisation de la reconstruction des électrons via la combinaison de deux algorithmes afin d'améliorer les performances à bas moment transverse. Les critères de sélection des événements caractéristiques des désintégrations de bosons Z, assurant une sélection pure d'électrons, ont été étudiés. Les efficacités de reconstruction des électrons pour les données 2010 et 2011 ainsi que leurs erreurs statistiques et systématiques ont été mesurées et ces mesures ont ensuite été utilisées par la collaboration CMS pour les analyses 2010 et 2011. Une étude des caractéristiques des radiations dans l'état final (Final State Radiation) affectant les leptons issus de la désintégration du Z a été menée. Un algorithme en vue de récupérer les photons FSR et reconstruire pleinement la masse du Z a été développé et optimisé. Il corrige 4.2% des cas ZZ→4μ tout en assurant une pureté de sélection des photons FSR de 95.6%. L'analyse physique développée dans cette thèse porte sur la recherche et l'extraction de limites sur les couplages trilinéaires neutres. L'existence de ces couplages est interdite dans le formalisme du Modèle Standard mais peut cependant être introduite dans un Lagrangien effectif par l'ajout de deux termes de couplages f4Z et f5Z dans le cas du couplage ZZZ, en vue de la recherche d'une nouvelle physique. La présence de ces couplages anormaux se traduit généralement par une augmentation de la section efficace de production des di-bosons ZZ ainsi que par les déformations des distributions cinématiques des Z ou encore de la masse des 4 leptons par rapport à l'attendu Modèle Standard. Dans le cadre de l'analyse du canal pp→ZZ→4l, une sélection pure des événements a été établie et les distributions différentielles du moment transverse et de la rapidité des bosons Z sont également présentées. Une recherche des couplages anormaux est effectuée en utilisant une méthode de repondération des distributions simulées et des limites sont extraites par la technique CLs. Les limites obtenues avec un niveau de confiance de 95% sont: -0.0116< f4Z <0.0116 et -0.0119< f5Z <0.0119.
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Chmill, Valery. "Radiation tests of semiconductor detectors." Doctoral thesis, Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4026.
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Schnittman, Jeremy David. "Radiation transport around Kerr black holes." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/30362.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 201-212).
This Thesis describes the basic framework of a relativistic ray-tracing code for analyzing accretion processes around Kerr black holes. We begin in Chapter 1 with a brief historical summary of the major advances in black hole astrophysics over the past few decades. In Chapter 2 we present a detailed description of the ray-tracing code, which can be used to calculate the transfer function between the plane of the accretion disk and the detector plane, an important tool for modeling relativistically broadened emission lines. Observations from the Rossi X-Ray Timing Explorer have shown the existence of high frequency quasi-periodic oscillations (HFQPOs) in a number of black hole binary systems. In Chapter 3, we employ a simple \hot spot" model to explain the position and amplitude of these HFQPO peaks. The power spectrum of the periodic X-ray light curve consists of multiple peaks located at integral combinations of the black hole coordinate frequencies, with the relative amplitude of each peak determined by the orbital inclination, eccentricity, and hot spot arc length. In Chapter 4, we introduce additional features to the model to explain the broadening of the QPO peaks as well as the damping of higher frequency harmonics in the power spectrum. The complete model is used to fit the power spectra observed in XTE J1550-564, giving confidence limits on each of the model parameters. In Chapter 5 we present a description of the structure of a relativistic alpha-disk around a Kerr black hole. Given the surface temperature of the disk, the observed spectrum is calculated using the transfer function mentioned above.
(cont.) The features of this modified thermal spectrum may be used to infer the physical properties of the accretion disk and the central black hole. In Chapter 6 we develop a Monte Carlo code to calculate the detailed propagation of photons from a hot spot emitter scattering through a corona surrounding the black hole. The coronal scattering has two major observable effects: the inverse-Compton process alters the photon spectrum by adding a high energy power-law tail, and the random scattering of each photon effectively damps out the highest frequency modulations in the X-ray light curve.
by Jeremy David Schnittman.
Ph.D.
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Podgorsak, Matthew B. "Fricke radiation dosimetry using nuclear magnetic resonance." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59290.
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The spin-lattice relaxation rate R$ sb1$ of irradiated Fricke solution was studied as a function of the absorbed dose D. The R$ sb1$ increases linearly with D up to a dose of $ sim$250 Gy after which the response saturates. A model describing the R$ sb1$ of a solution of either ferrous (Fe$ sp{2+})$ or ferric (Fe$ sp{3+})$ ions is presented; it is based on fast exchange between protons on water molecules in the bulk and protons on water molecules in the coordination shell of the ions. All inherent relaxation parameters of the different proton groups are determined. An extension of the model is made to describe the spin-lattice relaxation behaviour of irradiated Fricke solution. Good agreement between model predictions and experimental results is observed. The model relates the spin-lattice relaxation rate of a Fricke dosimeter to the chemical yield of ferric ion, thus creating an absolute dosimetry technique. Various practical aspects of the NMR-Fricke system are described.
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Moncet, Jean-Luc. "Narrowband models of radiation in inhomogeneous atmospheres." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61924.
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Turbide, Simon. "Electromagnetic radiation from matter under extreme conditions." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102221.
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The subject of this thesis is the production of electromagnetic radiations during relativistic heavy ions collisions. Since they constitute one of the major ways to probe the presence of a quark-gluon plasma (QGP), their evaluation through theoretical models is very important. The photon production at low-to intermediate transverse momentum (pT) is first studied. The photon production rate in a mesonic gas is evaluated within a massive Yang-Mills (MYM) approach. Earlier calculations are reexamined with additional constraints, including new production channels and with the inclusion of form-factors. Adding primordial N-N contribution and existing baryonic and QGP production rates, we can reproduce the photon spectra observed at the Super Proton Synchrotron (SPS). The intermediate to high-p T region is dominated by the physics of jets. A treatment, complete to leading-order in the strong coupling, is used to calculate energy loss in the strongly interacting medium. This approach is convolved with a physical description of the initial spatial distribution of jets and with an expansion of the emission zone. The role played by jet-plasma interactions is highlighted, showing that they dominate in the range 2 < p T < 4 GeV, at the Relativistic Heavy Ion Collider (RHIC). This mechanism has an important impact on both the total photon yield and the photon azimuthal asymmetry, turning the coefficient v 2 negative. Finally, the dilepton production at high p T is calculated with hard-thermal loops (HTL) effects, showing, that in perfect analogy with real photons, jet-plasma interactions also dominate the dilepton yield around pT = 4 GeV.
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Davis, Andrew. "Radiation Shielding of Fusion Systems." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/918/.
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This thesis discusses the development, benchmarking and applications of activation dose analysis methods for fusion devices. The development and code logic of the Mesh Coupled Rigorous 2 Step (MCR2S) system is discussed. Following the development of the code, appropriate benchmarking studies were performed on the Frascati neutron generator, and revealed that the code was able to predict shutdown gamma ray doserates to within ±3% of experimentally determined values, for decay times between 3×105 and 107 seconds. The development of the Ion Cyclotron Resonance Heater (ICRH) with regards to neutronics was discussed. The ICRH went through a number of design stages and shutdown gamma ray dose rates were determined for each stage. It was determined that of all the designs analysed only one of them, the first concept design for the internally matched design did not meet the shutdown dose criteria. This was due to a flaw in the system design, brought about by a lack of consideration towards nuclear design. The ITER Light Imaging Detection and Ranging (LIDAR) system was subjected to a full shutdown nuclear analysis. It was found that the design of the LIDAR system supplied did not meet the ITER required shutdown gamma ray dose rate limit of 100 µSvhr−1, however use of the MCR2S system highlighted the components that contributed most to the shutdown gamma ray dose rate and were shown to be the mirror holder and the laser beam pipe. Future designs should include additional shielding around the beam pipe.
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Mohd, Zain Rasif. "CdTe/CdZnTe pixellated radiation detector." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/5799/.
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The work in this thesis is focused on the study of CdTe/CdZnTe pixellated detectors. During this research, three main aspects have been covered in the development and application of these detectors. These broadly describe the fabrication process, characterisation of energy spectrum and imaging performance, and application of these detectors in industrial X-ray tomography. The first topic to be discussed in detail is the fabrication process of CZT pixellated detectors. This is a process that involves many steps, such as cutting the sample, cleaning the substrate, writing a masking pattern with e-beam lithography, photolithography, cleaning the surface using oxygen ash, metallisation and removing the resin in the development stage. However, these stages were grouped into three major steps to give a clearer image on what was going on throughout the fabrication process. They are grouped as sample preparation, pixellated structure deposition and sample passivation. The dry ash processing had been carried out in the James Watt Nano Fabrication Centre at Glasgow University. The motivation for the development of the dry ash process was to reduce the level of leakage current on the surface of the device so that a good energy spectrum resolution could be obtained. The research showed that a passivation technique using a layer of SiN as well as an oxygen plasma oxidation layer provided low leakage current in the pixel and lower interpixel leakage current. A good performance in energy spectrum was achieved after performing passivation. The FWHM of Co-57 is 10.78 keV where energy resolution is 8.8%. The second area covered in this thesis is the energy spectrum and imaging performance of pixellated CdTe Timepix detector. Two pitches of pixel have been studied namely, 110 µm pitch and 55 µm pitch. The work on characterisations has been performed with polychromatic and monoenergetic beams of X-rays. In both the Counting mode and ToT (Time over Threshold) mode it was discovered that there were large effects on performance due to charge sharing and fluorescence. In terms of image quality the result of MTF was found to be as expected, around half the contrast transfer (30%) recorded for 110 µm compared to 55 µm pixel detector at 4 lp/mm. Another field of interest explored was the defect factor. For this to be achieved studies had been performed in positive and negative bias of CdTe Timepix detector. The results showed that the presence of defects in the material affects the performance of the energy resolution of CdTe Timepix detector. The third area covered in this thesis was the study of CdTe Timepix detector for use in Industrial X-ray tomography. To give the sensor the best performance it could offer in capturing images for industrial use, work had been carried to optimise the technique for producing good quality images. The hardware setup involved the careful alignment all of the components of the system and the introduction of a collimator. In addition the sofware software it dealt with the flat field correction, noise filter and data projection algorithm. The results show that the CdTe Timepix detector can be used as a good detector for X-ray tomography. Here, the 3D of volume rendering studies had been performed to a pencil as a sample and voltage regulator. The result of the pencil image in volume rendering showed that CdTe Timepix detector had successfully provided good image for different density profile of material (paint coating, wooden and carbon). Not only that, another important finding besides the excellent image produced was that the effect of beam hardening, ring artifact and metal shrank artifact in tomogram of voltage regulator had been eliminated successfully.
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Korbly, Stephen E. "Smith Purcell radiation from femtosecond electron bunches." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32419.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Includes bibliographical references (p. 125-131).
We present theoretical and experimental results from a Smith-Purcell radiation experiment using the electron beam from a 17 GHz high gradient accelerator. Smith- Purcell radiation occurs when a charged particle travels above a periodic grating structure. The electron beam consists of a train of 15 MeV, 9 pC bunches of bunch lengths varying from 600 fs to 1 ps. The radiated energy for one electron travelling above a periodic grating is solved. The effects of multiple electrons in a bunch and multiple bunches in a train are introduced. The Smith-Purcell resonance condition and the dependence of the radiated energy upon beam current and beam height above the grating are presented. Measurement of the angular distribution of the Smith- Purcell radiation resulted in bunch length measurements of 0.60 ± 0.1 ps and 1 ± 0.1 ps under different accelerator operating conditions. This demonstrates the use of Smith-Purcell radiation as a non-destructive bunch length diagnostic with 100 fs resolution. Smith-Purcell radiation is comparable to other sources of radiation, such as transistion radiation, synchrotron radiation, etc. except that it has an inherent enhancement by a factor of Ng, the number of grating periods. Additional enhancement occurs when the electron bunch length is short compared with the radiation wavelength, resulting in coherent emission with an enhancement by a factor of Ne the number of electrons in the bunch. Finally, the electron beam consists of a regular train of Nb bunches, resulting in an energy density spectrum that is restricted in frequency space to harmonics of the bunch train frequency, with an increase in the energy density at these frequencies by a factor of Nb.
(cont.) We report the first observation of Smith-Purcell radiation displaying all three of these enhancements, that is, with a total enhancement of Ng.Ne.Nb. This total enhancement provides a simple method of generating powerful THz radiation at specific frequencies, which can be detected with a high signal to noise ratio by a heterodyne receiver.
by Stephen E. Krobly.
Ph.D.
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Shi, Yue S. B. Massachusetts Institute of Technology. "Performance of drift tubes under high radiation." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32976.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Includes bibliographical references (p. 63-67).
In this thesis, the aging and the rejuvenation of an ATLAS proportional drift tube are described. Firstly, the Diethorn model of gain is tested using pressure and sense-wire voltage measurements. The drift tube was then aged using P10 gas (Ar:CH₄ 90:10) and a small amount of Si oil vapor, with a tube section of radius [approx.] 1 cm being subjected to UV radiation. An aging current of 30[mu]A was maintained and after the accumulation of 21 coulombs on the wire, the tube gain decreased to less than 70%. Subsequently, the tube was rejuvenated by the treatment with Ar:0₂ 99:1 gas, at reverse wire potential and an reverse "rejuvenation" current of 30[mu]A. Rejuvenation was successful after the accumulation of the equivalent of 3C from this current.
by Yue Shi.
S.B.
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Lu, Jie Ph D. Massachusetts Institute of Technology. "Novel electromagnetic radiation in Left-Handed materials." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/39566.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.Includes bibliographical references (leaves 137-141).
In this thesis, Cerenkov radiation of a moving charged particle inside a Left-Handed material (LHM) is studied through both theory and numerical simulations. A LHM is a material whose permittivity and permeability have negative real parts. In the analysis of this thesis, the general theory of Cerenkov radiation was first studied for the unbounded regions filled with LHM. The physical meanings of different Green's functions are discussed, and finally the second kind of Hankel function is determined to represent the special properties of Cerenkov radiation: forward incoming phase and backward outgoing power, which satisfies both momentum and energy conservation. The effects of the dispersion and dissipation of both permittivity and permeability are also investigated. The results show that both forward and backward radiated waves can co-exist at different frequencies. When the dissipation is reduced, the directions of forward and backward radiation are close to 900 with respect to the particle's moving direction. When the LHM is bounded, a waveguide can be formed. Depending upon the configuration and the relative dielectric constants of the surrounding normal material (we call them RHM in comparison with LHM), a surface wave can be formed.
(cont.) When a LHM is used as the filling material of a metallic waveguide, the radiation at some frequencies can be enhanced when a surface wave is excited. This enhancement can make the total radiated power in the waveguide larger than the radiation when the LHM is unbounded. Furthermore, using the same surface wave property, the decay of the radiation by a free space channel can be compensated when the channel is surrounded by a LHM. The wave of Cerenkov radiation is a TM wave. In order to have a homogeneous response, the LHM structure should have at least two dimensional isotropic negative permittivity and one dimensional negative permeability. A new LHM design was proposed in this thesis. We have demonstrated that this design shows several advantages in comparison with present published designs through reflection and transmission simulations, and TM (TE) prism simulations. For the unit cell's dimension of 5mm, a LHM band is observed between 6GHz and 7GHz for TM wave incidence. We use an antenna array to model a traveling current source, which can represent a single frequency component of a particle motion. The simulations show that our design can bend the radiation inside the structure.
(cont.) In order to observe the signal in the far field, we propose to use prism shaped LHM structures around the antenna array, by which, the difference between the angles of the forward radiation and backward radiation can be further amplified. These results can be a basis for a future experimental verification of backward radiation of the antenna arrays in a LHM. Besides, two effects of the surface wave for the effective LHM slab are also investigated. The results show that the surface wave actually determines the focusing ability of a LHM slab. When the mismatch between the slab and the surrounding area becomes small, those evanescent waves, whose wave number is less than that of the surface wave, can be amplified by the slab, and contribute to the focusing at the image plane. This property can help us easily estimate the resolution of a LHM slab when it is used as a flat lens. A unique guided wave can also exist when a LHM slab is surrounded by two RHMs, where the two RHMs can be different or the same. This guided wave has a linear function for the transverse profile of the field inside the LHM slab, which can never exist in either a RHM or a plasma dielectric waveguide.
by Jie Lu.
Ph.D.
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Rasoanaivo, Andriniaina Narindra. "Gluon radiation beyond Poisson using MHV techniques." Doctoral thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/28160.
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For the first time, MHV techniques are applied to radiative energy loss processes in QCD. First, we provide a pedagogical introduction to MHV techniques with explicit computational example on qq → ɡɡ cross section and splitting functions which reproduces known results. Next, we derive the multiple photon emissions current to reproduce the Poisson distribution of photon radiated from a high energetic quark. Then we derive the equivalent current for the case of multiple gluon emissions in vacuum. We then use the previous result to compute the two gluon correlation. We also study the radiation current induced from a change in the color state of an energetic quark: we start with the case of 1, 2, and 3 gluon induced radiations and then conjecture the analytic expression for n gluon emissions. We then prove this conjecture for the case where the emitted gluons are symmetric and antisymmetric under gluon permutations.
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Redd, Randall Alex. "Radiation dosimetry and medical physics calculations using MCNP 5." Texas A&M University, 2004. http://hdl.handle.net/1969.1/467.
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Six radiation dosimetry and medical physics problems were analyzed using a beta version of MCNP 5 as part of an international intercomparison of radiation dosimetry computer codes, sponsored by the European Commission committee on the quality assurance of computational tools in radiation dosimetry. Results have been submitted to the committee, which will perform the inter-code comparison and publish the results independently. A comparison of the beta version of MCNP 5 with MCNP 4C2 is made, as well as a comparison of the new Doppler broadening feature. Comparisons are also made between the *F8 and F6 tallies, neutron tally results with and without the use of the S(a,b) cross sections, and analytically derived peak positions with pulse height distributions of a Ge detector obtained using the beta version of MCNP 5.
The following problems from the study were examined:
Problem 1 was modeled to determine the near-field angular anisotropy and dose distribution from a high dose rate 192Ir brachytherapy source in a surrounding spherical water phantom.
Problem 2 was modeled to find radial and axial dose in an artery wall from an intravascular brachytherapy 32P source.
Problem 4 was modeled to investigate the response of a four-element TLD-albedo personal dosimeter from neutrons and/or photons. Significant differences in neutron response with S(a,b) cross sections compared to results without these cross sections were found.
Problem 5 was modeled to obtain air kerma backscatter profiles for 150 and 200 kVp X-rays upon a water phantom. Air kerma backscatter profiles were determined along the apothem and diagonal of the front face of the phantom. A comparison of experimental results is also made.
Problem 6 was modeled to determine indirect spectral and energy fluences upon two neutron detectors within a calibration bunker. The largest indirect contribution was found to come from low energy neutrons with an average angle of 47o where 0o is a plane parallel to the floor.
Problem 7 was modeled to obtain pulse height distributions for a germanium detector. Comparison of analytically derived peaks with peak positions in the spectra are made. An examination of the Doppler broadening feature is also included.
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Grant, James Paul. "GaN radiation detectors for particle physics and synchrotron applications." Thesis, University of Glasgow, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443418.
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VILLAVICENCIO, ANNA L. C. H. "Avaliacao dos efeitos da radiacao ionizante de sup60Co em propriedades fisicas , quimicas e nutricionais dos feijoes PHASEOLUS VULGARIS L. e VIGNA UNGUICULATA (L.) WALP." reponame:Repositório Institucional do IPEN, 1998. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10785.
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Made available in DSpace on 2014-10-09T12:43:58Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:07:39Z (GMT). No. of bitstreams: 1 06166.pdf: 3240531 bytes, checksum: 4104476275b9d0bf7a27427ff116d1ee (MD5)
Tese (Doutoramento)
IPEN/T
Faculdade de Ciencias Farmaceuticas, Universidade de Sao Paulo - CF/USP
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Damet, Jerome. "Physics and Detector Simulation Studies of B-Meson Decays in ATLAS." Doctoral thesis, Uppsala University, Department of Nuclear and Particle Physics, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1284.
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Stoner, Richard Earl. "Radiation from relativistic electron beams in periodic structures." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/33526.
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Schulz, Michael B. (Michael Brian). "Theory of accelerated detectors and black hole radiation." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/105016.
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Maneuski, Dzmitry. "Pixellated radiation detectors for scientific applications." Thesis, University of Glasgow, 2009. http://theses.gla.ac.uk/1219/.
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The work in this thesis is focused on characterisation and evaluation of two classes of science grade imaging radiation detectors. The first class is Monolithic Active Pixel Sensors (MAPS). The advances in CMOS fabrication technologies over the last four decades allowed MAPS to compete with Charge-Coupled Devices (CCD) in many applications. The technology also provides relatively inexpensive ways to tailor design to suit specific application needs. It is important to understand performance capabilities of new sensor designs through characterisation and optimisation of readout parameters. In this work three MAPSs were characterised. The first one - HEPAPS4 - designed for charged particle detection, with the potential technology application in the vertex detector for the International Linear Collider. The noise of the sensor was measured to be 35±5 e, which agrees well with simulated data. The dark current was found to be 175 pA/cm2. The SNR performance for minimum ionising particles detection was demonstrated to be 40. The sensor was also evaluated for indirect detection of thermal and fast neutrons using lithium and polyethylene converters. The technology performed well in such an application with an estimated fast neutron detection efficiency of ~0.01%. The second sensor characterised – Vanilla MAPS – was designed to evaluate new techniques for fast readout, small noise and reduced image lag. The system was capable to readout 150 full frames (520x520 pixels) per second; the sensor showed 14±4 e noise and decreased image lag. The dark current was found to be ~50 pA/cm2. The back-thinned version of the sensor demonstrated dramatic improvement in quantum efficiency from 0% to 20% at 220 nm. The third device is parametric sensor eLeNA. It features 14 test structure designed to evaluated noise reduction architectures. The most promising structures showed temporal noise values as low as 6 e and 20 e fixed pattern noise. Medipix as an example of the second class of imaging detectors - hybrid pixel detectors - was evaluated in two applications. It was used as the core element of the ATLAS radiation background monitoring system. The sensors were covered with neutron converters, which extended the number of radiation types that can be detected. X-ray calibration was performed, showing excellent tolerance of all 18 devices characterised. Detection efficiencies were estimated to be ~1% for thermal and ~0.1% for fast neutrons. The second application of Medipix was mass spectrometry. The detector was place in the focal plane of a prototype mass spectrometer. 2D representation of data allowed focusing correction of the ion beam. The system was capable to detect ions in the range of 5-25 keV. The detector characterisation with broad range of ions (from Cu to Pb) showed very good abundance agreement with table data.
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O'Donnell, N. "Electromagnetic radiation reaction in general relativity." Thesis, Bucks New University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384632.
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Davis, Anthony. "Radiation transport in scale invariant optical media." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39357.
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We focus primarily on the bulk response to external illumination of conservatively scattering thick inhomogeneous media (or simply "clouds") which are exactly or statistically scale invariant; these radiative properties are compared to those of homogeneous media with the same shapes and masses. Also considered are the ensemble-average responses of multifractal distributions of optical thicknesses and the closely related spatially averaged responses obtained within the "independent pixel" approximation to inhomogeneous transfer. In all cases, the nonlinearity of the radiation/density field coupling induces systematic and specific variability effects. Generally speaking, the details of the scattering process and of the boundary shape affect only prefactors whereas "anomalous" scaling exponents are found for extreme forms of internal variability which, moreover, are different for different physical transport models (e.g., kinetic versus diffusion approaches). Finally, detailed numerical computations of radiation flows inside a log-normal multifractal illustrate the basic inhomogeneous transport mechanism of "channeling."
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Williams, Stephen Alexander. "Half-brightness measurements of candidate radiation sensors." Thesis, University of Louisiana at Lafayette, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10163329.
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Ionizing radiation poses a significant challenge for human and robotic space missions. Practical luminescent sensors will depend heavily upon research investigating the resistance of these materials to ionizing radiation and the ability to anneal or self-heal the damage caused by such radiation. In 1951, Birks and Black experimentally showed that the luminescent efficiency of anthracene bombarded by alpha particles varies with total fluence. From 1990 to the present, we found that the Birks and Black relation describes the reduction in light emission yield for every tested luminescent material except lead phosphate glass due to proton irradiation. These results indicate that radiation produced quenching centers compete with emission for absorbed energy. The purpose of this thesis is to present new results from related luminescent materials by exposing them to a 1-3 MeV proton beam. Particular emphasis will be placed on recent measurements made with bright luminescent materials, such as zinc sulfide doped with manganese (ZnS:Mn), europium tetrakis dibenzoylmethide triethylammonium (EuD4TEA), an magnesium tetrakis dibenzoylmethide triethylammonium (MgD4TEA). This research can be used to help determine if luminescent materials can be used as a real-time sensor to detect ionizing radiation.
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Angus, Stephen Andrew. "Phenomenology of dark radiation and string compactifications." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:739ffcb2-bf9d-4fd3-8d6c-911d2d599f5e.
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In this Thesis I explore aspects of dark radiation and its role in String Phenomenology. Dark radiation is any additional hidden type of relativistic matter present in the Universe today, conventionally labelled as an "excess effective number of neutrino species", Δ Neff. It provides a powerful test of hitherto untested theoretical models based on fundamental theories such as String Theory. I begin by considering dark radiation in the LARGE Volume Scenario, a phenomenologically viable class of string compactifications. First I review how the minimal setup slightly overproduces axionic dark radiation via modulus decay. I then demonstrate that loop corrections to the main competing visible-sector decay process have a negligible effect and are unable to alleviate the tension with observations. In the following chapter I explore fibred extensions of the LARGE Volume Scenario. The predictions for Δ Neff are qualitatively different: in particular, models with a sequestered visible sector on D3 branes at a singularity are swamped by massless axions and decisively ruled out. I then consider TeV-scale supersymmetry in a model with anisotropic modulus stabilisation. If the Standard Model is realised on D7 branes wrapping the small volume cycle a hierarchy of soft terms is generated, which may have applications to natural supersymmetry. The final chapter takes a different approach and investigates the proposition that dark radiation, in the form of a Cosmic Axion Background, could explain the long-standing soft X-ray excess from galaxy clusters. I show for the Coma cluster that the morphology of the excess can be reproduced by axion-photon conversion in the intracluster magnetic field, provided the field is allowed to have more structure on smaller scales than typically assumed based on Faraday rotation data. This explanation requires an inverse axion-photon coupling M ∼ 1011 - 1012 GeV and a mean axion energy (ECAB) ∼ 50 - 250 eV.
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Minerskjöld, Maxim. "Sensors, signals and systems for electromagnetic radiation experiments in physics /." Stockholm, 1998. http://www.lib.kth.se/abs98/mine0528.pdf.
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Takane, Mpeli Alice. "Context dependence of Physics students' responses to the term "radiation"." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13299.
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Includes bibliographical references.For the public to be able to participate meaningfully in debates regarding issues that are related to science and technology it is important that they are properly informed and that their sources of information are reliable. One source of such information are university science students and it is therefore interesting to find out what their views are regarding various scientific concepts. For example such an area of interest is that of using nuclear power for electricity generation, in particular the dangers associated with radiation. A reasonably correct view of radiation would be seen as an important part of having a meaningful debate. The present study aims to find out the views that a group of university students who are studying physics hold about radiation, in particular their immediate response to being asked to clarify what the term radiation means. However, the notion that students simply have conceptions that are unitary and static has been challenged by several Physics Education Researchers. Instead a view summarised as “knowledge in pieces” has been proposed in which it is suggested that much smaller units of ideas are brought together dynamically depending on the situation at hand and that context plays an important role in how students respond to questions. Thus, the thesis explores to what extent context plays a role in their responses by preceding the question with four different scenarios which are suggested as the contexts in which the question is being asked. In summary, the guiding questions for the present work are: (1) What do students understand by the term radiation and (2) To what extent do student response patterns depend on “textual priming”. The thesis is divided into two parts (1) a pilot study in which the methodology is established and (2) a follow up study (main study) in which the effect of textual priming on the responses is explored.
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Allman, D. M. "Radiation damage assessment in AlxGa1-xAs." Thesis, Lancaster University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306409.
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Ilic, Ognjen. "Nanophotonics for tailoring the flow of thermal electromagnetic radiation." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/103227.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 117-129).
In this thesis, we explore the interaction of thermal radiation with nano-scale structures. First, we introduce the concept of radiative energy transfer between two objects of different temperatures in the near field, and theoretically argue that the radiation tunneling of evanescent surface modes can enable energy transfer that is orders of magnitude stronger than the energy transfer in the far field. Specifically, we develop a new computational approach-based on a finite-difference time-domain (FDTD) method that incorporates the Langevin approach to Brownian motion-which enables calculations of heat transfer for arbitrary geometries and materials. Second, we study the near-field heat transfer between two sheets of graphene and show that thermally excited plasmon-polariton modes can strongly mediate, enhance, and tune the energy exchange in this system. We predict maximum transfer at low doping and for plasmons in two graphene sheets in resonance, with orders-of-magnitude enhancement over the Stefan-Boltzmann law. Third, we develop the concept of a near-field thermophotovoltaic (NFTPV) system, and analyze several different implementations that use plasmonic materials as thermal emitters. In particular, we quantify the properties of an optimal near-field photovoltaic cell, argue that large plasmonic losses can-contrary to intuition-be helpful in enhancing the overall heat transfer, and propose and develop the concept of graphene as a tunable thermal emitter for a NFTPV system. Fourth, we tailor the far-field thermal emission from objects at high temperatures and experimentally demonstrate a method where the emission spectrum is controlled on the cold-side by implementing a nano-layer structure that surrounds the hot emitter and recycles unwanted emission. We find that this approach can enable lighting sources with luminous efficiencies close to the fundamental limit for lighting applications. Finally, we study opto-thermal effects in asymmetric nanoparticles. Specifically, we show that a type of metal-dielectric (Janus) particle in uniform light field exhibits a new class of stable rotational dynamics. We demonstrate (in a simulation) opto-thermal guiding of a composite asymmetric particle by switching the light beam frequency, without regard to the direction or the shape of the light beam.
by Ognjen Ilic.
Ph. D.
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Pelc, Jason 1984. "Radiation pressure effects in a suspended Fabry-Perot cavity." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36124.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.Includes bibliographical references (p. 65-67).
We report on experimental observation of radiation-pressure induced effects in a high-power optical cavity. These effects play an important role in next generation gravitational wave detectors, as well as quantum non-demolition devices. We describe two experiments in which a low-transmission input mirror and near-perfectly-reflective end mirror are suspended as pendulums. A unified model of optomechanical coupling is presented, whereby a strong coherent laser field interacts with a classical harmonic oscillator. We show that such a system is well described using standard techniques from control theory. We measure the properties of an optical spring, whereby the optical field increases the rigidity of the pendulum mode of the mirrors; during our first (Phase 1) experiment, we measure an optical rigidity of K = (3.08 t 0.09) x 104 N/m, corresponding to an optical rigidity that is 6000 times stiffer than the mechanical stiffness. In our second (Phase 2) experiment with higher finesse and lower mirror mass, we find an unprecedented optical rigidity Ko = (9.60 ± 0.12) x 105 N/m. We also measure and characterize the parametric instability, caused by the coupling of the cavity field to the acoustic modes of the mirror, and find an instability strength R - 3.
(cont.) We discuss the noise suppression features of an optically rigid system, and demonstrate a strong-coupling radiation pressure cooling of the mirror motion. A discussion of the path towards a measurement of the quantum mechanical state of the bulk mirror motion in future experiments is included.
by Jason Scott Pelc.
S.B.
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Quintero, Eric Antonio. "The cosmic ray muon energy spectum via Čerenkov radiation." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61261.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. [55]).
In this thesis, I designed and constructed a basic Cerenkov detector to measure the energy spectrum of cosmic ray muons for use in the graduate experimental physics courses, 8.811/2. The apparatus consists of a light-tight central volume with a phototube to detect the Cerenkov radiation of muons whose speed is higher than the speed of light in the medium with which the volume is filled. The measurement is triggerd by coincidence in scintillating detectors above and below the volume. I constructed a signal chain for measurement, collected data for muon energies with the goal of constructing the muon energy spectrum from different Cerenkov spectra. In the range 20-100 GeV, the spectrum is found to obey a power law with exponent -a = -2.90 t .04, which compares well to the value of -2.844 found in the literature. In addition, calculations and considerations were made to aid in the use of this apparatus in a pedagogical manner.
by Eric Antonio Quintero.
S.B.
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Livas, Jeffrey C. (Jeffrey Clark). "Upper limits for gravitational radiation from some astrophysical sources." Thesis, Massachusetts Institute of Technology, 1987. https://hdl.handle.net/1721.1/123082.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1987.Title as it appeared in Massachusetts Institute of Technology Graduate List: Upper limits on gravitational radiation from some astrophysical sources.
Bibliography: leaves 155-159.
by Jeffrey Clark Livas.
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1987.
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Mostoslavsky, Michael. "Hawking radiation photosphere around microscopic black holes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0004/MQ44227.pdf.
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Várnai, Tamás. "Reflection of solar radiation by inhomogeneous clouds." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40459.
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The goal of this study is to improve knowledge about how cloud inhomogeneities affect the reflection of solar radiation. In particular, it addresses two main questions: what the processes through which inhomogeneities influence solar reflection are, and how this influence can be taken into account in albedo retrievals based on future satellite measurements.The first question is important, since present methods give numerical results only about the overall radiative effect of cloud inhomogeneities, but cannot determine the degree to which various mechanisms are responsible for this overall effect. This study establishes a theoretical framework which defines and evaluates the various processes through which cloud inhomogeneities influence solar radiation. This framework is then used to examine quantitatively the inhomogeneity effects that occur in irregular cloud fields. Among other insights, it is shown and explained that identical variations in cloud optical thickness can cause much stronger inhomogeneity effects if they are due to variations in geometrical cloud thickness, and not in volume extinction coefficient (as assumed in previous studies of irregular cloud fields). The differences in albedo can exceed 0.05, and the relative differences in reflectance toward the zenith can be greater than 25% for overhead sun, and 50% for oblique sun. Also, a possible explanation is given for a phenomenon observed in previous studies: that cloud reflectivity toward the zenith increases with decreasing solar elevation.
This study also develops an albedo retrieval algorithm that considers radiative inhomogeneity effects. The algorithm takes advantage of the unique multi-view capability of the Multi-angle Imaging SpectroRadiometer (MISR) placed on the Earth Observing System-AM satellite (to be launched in 1998). This instrument will offer new possibilities for albedo retrievals since, unlike present instruments, it will measure the radiation reflected in not only one, but nine directions. The potential accuracy of the algorithm is analyzed for a dataset obtained by using a Monte Carlo model to simulate radiative transfer through a large number of irregular cloud fields. The results indicate that using multi-view measurements can improve the accuracy of satellite-based albedo retrievals by a factor of three or more.
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Stambaugh, Cassandra. "The Evaluation and Study of Modern Radiation Dosimetry Methods as Applied to Advanced Radiation Therapy Treatments Using Intensity Modulated Megavoltage Photon Beams." Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5587.
Full textAbstract:
The purpose of this work is to evaluate quasi-3D arrays for use with intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) and to determine their clinical relevance. This is achieved using a Delta4 from Scandidos and ArcCheck from Sun Nuclear and the associated software. While certain aspects of these devices and software have been previously evaluated, the main goal of this work is to evaluate the new aspects, such as reconstructing dose on a patient CT set, and extending the capabilities. This includes the capability to reconstruct the dose based on a helical delivery as well as studying the dose to a moving target using measurement-guided motion simulations.
It was found that Sun Nuclear's ArcCheck/3DVH system exhibited excellent agreement for dose reconstruction for IMRT/VMAT using a traditional C-arm linear accelerator and stringent 2%/2mm comparison constraints. It also is a powerful tool for measurement-guided dose estimates for moving targets, allowing for many simulations to be performed based on one measurement and the target motion data. For dose reconstruction for a helical delivery, the agreement was not as good for the stringent comparison but was reasonable for the clinically acceptable 3%/3mm comparison. Scandidos' Delta4 shows good agreement with stringent 2%/2mm constraints for its dose reconstruction on the phantom. However, the dose reconstruction on the patient CT set was poor and needs more work.
Overall, it was found that quasi-3D arrays are powerful tools for dose reconstruction and treatment plan comparisons. The ability to reconstruct the dose allows for a dose resolution comparable to the treatment plan, which negates the previous issues with inadequate sampling and resolution issues found when just comparing the diodes. The ability to quickly and accurately compare many plans and target motions with minimum setup makes the quasi-3D array an attractive tool for both commissioning and patient specific quality assurance.
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Sheikh, Zahoor Ahmad. "Measurement of the coherence length of atomic two-photon radiation." Thesis, University of Stirling, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359253.
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