The doctoral thesis is focused on measurements of neutron cross-sections mainly cross-sections of (n,xn) threshold reactions. With the dawn of advanced nuclear systems such as fast reactors of GenIV, accelerator driven system or even fusion reactors, monitoring of fast neutron fields will gain on importance. The activation detectors are one of the viable options how to monitor these neutron fields and (n,xn) reactions would be one of the best options how to do such monitoring. There is one condition though. We need to have good cross- section data in high neutron energy region. Unfortunately, the current situation is rather bad. There is only a small amount of reliable data for neutron energies above 20 MeV and with increasing energy, the situation gets only worse. For this reason, we measure the cross-sections of (n,xn) reactions on perspective materials such as yttrium, gold and tantalum with neutron energies from 17.4 up to 94 MeV. In this thesis, the measurements together with motivation and methodology are described. Obtained results are in agreement with existing data. Severe discrepancies were observed between the predictions and experimental data for high order (n,xn) reactions. This problem is discussed and solved. The results in this region are in form of cross-section values and also...

Cette thèse en création littéraire est centrée sur le mot « bohème » et sur l’imaginaire que ce terme conjure. Le premier volet de la thèse, soit son aspect théorique, trace l’évolution de l’imaginaire qui auréole le mot « boesme » depuis ses origines gitanes jusqu’à son éclosion en symbole de l’écrivain. Malgré les déclarations répétées que « la bohème ne veut plus rien dire du tout », l’argument fondamental de cette thèse est que la « bohème » constitue une configuration mythique, à tendance initiatique, qui demeure pertinente aujourd’hui. Le deuxième volet, soit l’apport créatif de cette thèse, consiste en un court roman épisodique intitulé Chimères. Cette création actualise le mythe de la bohème en l'illustrant au sein d’histoires propres à notre époque, tout en calquant sa structure sur celle des Scènes de la vie de bohème d’Henry Murger (1851), roman central au mythe de la bohème littéraire. Le troisième et dernier volet constitue une réflexion sur l’évolution de cette thèse, sur le rôle caché des mythes dans nos vies ainsi que sur la transformation qu’ils opèrent sur nous. Combinant recherche universitaire et créativité subjective, cette thèse illustre et incarne un processus d’initiation. Passer d’une naïveté chimérique à une sagesse plus réaliste, céder le personnage au profit de la personne, c’est à la fois le processus et la fin de la bohème, soit l’atteinte de la transformation qu’elle recèle. Néanmoins, il résulte de ce travail la conclusion que, telle la jeunesse même, la bohème sera toujours apte à être régénérée et toujours sera-t-elle condamnée à passer.

Das Institut für Kern- und Teilchenphysik (IKTP) der Technischen Universität Dresden (TUD) hat im Forschungszentrum Dresden-Rossendorf (FZD) ein Labor zur Untersuchung von neutroneninduzierten kernphysikalischen Prozessen in Materialien, die für die Fusionsforschung relevant sind, aufgebaut. Das Labor ist ausgestattet mit drei intensiven Neutronenquellen: einer 14 MeV-Neutronenquelle, einer weißen kontinuierlichen Photoneutronen-Quelle, die näher in dieser Arbeit beschrieben wird, und einer gepulsten Photoneutronen-Quelle, die vom FZD inKooperation mit der TUD aufgebaut wurde. Die kontinuierliche Photoneutronen-Quelle basiert auf einem Radiator aus Wolfram (engl. Tungsten Photoneutron Source (TPNS)). TPNS nutzt die im ELBE-Beschleuniger (Elektronen Linearbeschleuniger für Strahlen hoher Brillianz und niedriger Emittanz (ELBE)) beschleunigten Elektronen zur Neutronenerzeugung. Der Prozess läuft über Zwischenschritte ab, indem bei der Abbremsung der Elektronen im Radiator Bremsstrahlungsphotonen entstehen, die anschließend Neutronen durch (γ,xn)-Reaktionen erzeugen. Das Neutronenspektrum der TPNS kann mittels Moderatoren so modifiziert werden, dass es dem in der ersten Wand im Fusionsreaktor entspricht. Dies ermöglicht Untersuchungen mit einem für einen Fusionsreaktor typischen Neutronenspektrum. Die technische Verwirklichung des Projektes, die Inbetriebnahme der Anlage sowie die Durchführung der ersten Experimente zur Neutronenerzeugung ist Inhalt dieser Arbeit. Die Neutronenquelle ist insbesondere für qualitative Untersuchungen in der Fusionsneutronik bestimmt. Der Fusionsreaktor produziert, im Vergleich zu einem Spaltungsreaktor, keine langlebigen Isotope als Abfall. Die wesentliche Aktivität des Reaktors ist in Konstruktionsmaterialien akkumuliert. Durch sorgfältige Auswahl der Materialien kann man die Aktivierung minimieren und damit künftig wesentlich weniger radioaktives Inventar produzieren als in Spaltreaktoren. Ziel der kernphysikalischen Untersuchungen ist, solche Materialien für den Aufbau eines Fusionsreaktors zu erforschen, die niedrigaktivierbar sind, das heißt wenig Aktivität akkumulieren können, und eine Halbwertzeit von einigen Jahren haben. Es ist das Ziel, alle Konstruktionsmaterialien nach 100 Jahren wiederverwenden zu können. Die Neutronenflussdichte einer Photoneutronenquelle ist einige Größenordnungen höher als die, die mittels eines DT-Neutronengenerators mit anschließender Moderation erreicht werden kann. Die gesamte Arbeit ist in drei Teile geteilt. Der erste Teil leitet in die Problematik der Energieversorgung ein und zeigt die Kernfusion als eine vielversprechende Energiequelle der naher Zukunft auf. Das Neutronenlabor der TUD, in dem die TPNS aufgebaut ist, wird ebenfalls kurz vorgestellt. Der zweite Teil befasst sich mit der TPNS selbst, mit ihrem physikalischen Entwurf, der Konstruktion und dem Aufbau bis zu der Inbetriebnahme sowie dem ersten Experiment an der TPNS. Der letzte, dritte Teil ist die Zusammenfassung der vorhandenen Ergebnisse und gibt einen Ausblick auf die zukünftige Vorhaben. / The Institute for Nuclear and Particle Physics at the Technische Universität Dresden (TUD) has build a neutron physics laboratory at Forschungszentrum Dresden-Rossendorf (FZD) to investigate nuclear processes in materials. The experiments are focused on materials relevant to nuclear fusion. The laboratory is equipped with three intensive neutron sources. The first is a 14 MeV monochromatic neutron source based on the DT reaction (owned by TUD); the other two are continuous and pulsed white photoneutron sources based on (γ,xn) reactions. One pulsed photoneutron source is realized by FZD in cooperation with the TUD. The continuous photoneutron source utilises a tungsten radiator (Tungsten Photoneutron Source) to produce neutrons with a wide energy spectra. The TPNS uses the ELBE-accelerator as a source of electrons for neutron production. This process involves an intermediate step, where slowed down electrons produce bremsstrahlung (γ -rays) absorbed by tungsten nuclei. Consecutively, the excited nuclei emit neutrons. The neutron flux of the photoneutron source is five orders of magnitude higher than the flux of the DT neutron sources with appropriate moderation. The neutron spectrum of TPNS can be modified by moderators, in such a way that the spectrum is comparable to that in the first wall of a Tokamak-Reactor. That allows investigations with the typical neutron spectrum of the fusion reactor. The technical solution, initial operation and the first experiment are described in this work. The neutron source is, in particular, dedicated to quantitative investigations in fusion neutronics. A fusion reactor produces radioactive isotopes as a nuclear waste. The main activity is accumulated in the structural materials. Carefully selected structural materials can significantly minimize the activity and thereby the amount of nuclear waste. The purpose of this project is to find constructional materials with half-lives shorter than several years, which can be recycled after about 100 years. The work is divided into three parts. The first part is dedicated to the energy supply problem and nuclear fusion is addressed as a promising solution of the near future. The neutron laboratory housing the TPNS is also briefly described. The second part deals with the tungsten photoneutron source, the design, construction, operation and the first experiments for neutron production. The third part summarises results and presents an outlook for future experiments with the TPNS.

Das Institut für Kern- und Teilchenphysik (IKTP) der Technischen Universität Dresden (TUD) hat im Forschungszentrum Dresden-Rossendorf (FZD) ein Labor zur Untersuchung von neutroneninduzierten kernphysikalischen Prozessen in Materialien, die für die Fusionsforschung relevant sind, aufgebaut. Das Labor ist ausgestattet mit drei intensiven Neutronenquellen: einer 14 MeV-Neutronenquelle, einer weißen kontinuierlichen Photoneutronen-Quelle, die näher in dieser Arbeit beschrieben wird, und einer gepulsten Photoneutronen-Quelle, die vom FZD inKooperation mit der TUD aufgebaut wurde. Die kontinuierliche Photoneutronen-Quelle basiert auf einem Radiator aus Wolfram (engl. Tungsten Photoneutron Source (TPNS)). TPNS nutzt die im ELBE-Beschleuniger (Elektronen Linearbeschleuniger für Strahlen hoher Brillianz und niedriger Emittanz (ELBE)) beschleunigten Elektronen zur Neutronenerzeugung. Der Prozess läuft über Zwischenschritte ab, indem bei der Abbremsung der Elektronen im Radiator Bremsstrahlungsphotonen entstehen, die anschließend Neutronen durch (γ,xn)-Reaktionen erzeugen. Das Neutronenspektrum der TPNS kann mittels Moderatoren so modifiziert werden, dass es dem in der ersten Wand im Fusionsreaktor entspricht. Dies ermöglicht Untersuchungen mit einem für einen Fusionsreaktor typischen Neutronenspektrum. Die technische Verwirklichung des Projektes, die Inbetriebnahme der Anlage sowie die Durchführung der ersten Experimente zur Neutronenerzeugung ist Inhalt dieser Arbeit. Die Neutronenquelle ist insbesondere für qualitative Untersuchungen in der Fusionsneutronik bestimmt. Der Fusionsreaktor produziert, im Vergleich zu einem Spaltungsreaktor, keine langlebigen Isotope als Abfall. Die wesentliche Aktivität des Reaktors ist in Konstruktionsmaterialien akkumuliert. Durch sorgfältige Auswahl der Materialien kann man die Aktivierung minimieren und damit künftig wesentlich weniger radioaktives Inventar produzieren als in Spaltreaktoren. Ziel der kernphysikalischen Untersuchungen ist, solche Materialien für den Aufbau eines Fusionsreaktors zu erforschen, die niedrigaktivierbar sind, das heißt wenig Aktivität akkumulieren können, und eine Halbwertzeit von einigen Jahren haben. Es ist das Ziel, alle Konstruktionsmaterialien nach 100 Jahren wiederverwenden zu können. Die Neutronenflussdichte einer Photoneutronenquelle ist einige Größenordnungen höher als die, die mittels eines DT-Neutronengenerators mit anschließender Moderation erreicht werden kann. Die gesamte Arbeit ist in drei Teile geteilt. Der erste Teil leitet in die Problematik der Energieversorgung ein und zeigt die Kernfusion als eine vielversprechende Energiequelle der naher Zukunft auf. Das Neutronenlabor der TUD, in dem die TPNS aufgebaut ist, wird ebenfalls kurz vorgestellt. Der zweite Teil befasst sich mit der TPNS selbst, mit ihrem physikalischen Entwurf, der Konstruktion und dem Aufbau bis zu der Inbetriebnahme sowie dem ersten Experiment an der TPNS. Der letzte, dritte Teil ist die Zusammenfassung der vorhandenen Ergebnisse und gibt einen Ausblick auf die zukünftige Vorhaben. / The Institute for Nuclear and Particle Physics at the Technische Universität Dresden (TUD) has build a neutron physics laboratory at Forschungszentrum Dresden-Rossendorf (FZD) to investigate nuclear processes in materials. The experiments are focused on materials relevant to nuclear fusion. The laboratory is equipped with three intensive neutron sources. The first is a 14 MeV monochromatic neutron source based on the DT reaction (owned by TUD); the other two are continuous and pulsed white photoneutron sources based on (γ,xn) reactions. One pulsed photoneutron source is realized by FZD in cooperation with the TUD. The continuous photoneutron source utilises a tungsten radiator (Tungsten Photoneutron Source) to produce neutrons with a wide energy spectra. The TPNS uses the ELBE-accelerator as a source of electrons for neutron production. This process involves an intermediate step, where slowed down electrons produce bremsstrahlung (γ -rays) absorbed by tungsten nuclei. Consecutively, the excited nuclei emit neutrons. The neutron flux of the photoneutron source is five orders of magnitude higher than the flux of the DT neutron sources with appropriate moderation. The neutron spectrum of TPNS can be modified by moderators, in such a way that the spectrum is comparable to that in the first wall of a Tokamak-Reactor. That allows investigations with the typical neutron spectrum of the fusion reactor. The technical solution, initial operation and the first experiment are described in this work. The neutron source is, in particular, dedicated to quantitative investigations in fusion neutronics. A fusion reactor produces radioactive isotopes as a nuclear waste. The main activity is accumulated in the structural materials. Carefully selected structural materials can significantly minimize the activity and thereby the amount of nuclear waste. The purpose of this project is to find constructional materials with half-lives shorter than several years, which can be recycled after about 100 years. The work is divided into three parts. The first part is dedicated to the energy supply problem and nuclear fusion is addressed as a promising solution of the near future. The neutron laboratory housing the TPNS is also briefly described. The second part deals with the tungsten photoneutron source, the design, construction, operation and the first experiments for neutron production. The third part summarises results and presents an outlook for future experiments with the TPNS.

Made available in DSpace on 2016-04-28T14:16:40Z (GMT). No. of bitstreams: 1 Marcelo Akira Hueda.pdf: 931223 bytes, checksum: ed10fcfcb79a8f804f3accfcea991962 (MD5) Previous issue date: 2009-05-18 / Secretaria da Educação do Estado de São Paulo / Published anonymously in 1844, the book Vestiges of the natural history of creation triggered one of the greatest public debates which took place in the 19th century. Its author Robert Chambers proposed the transformation of living beings and the origin of new species by natural causes. The first aim of this dissertation is to describe some evolutionary concepts presented in the book. The second one is to compare them to the final version of Lamarck s theory on the progression of animals. This dissertation contains an introduction and four chapters. Chapter 1 discusses the evolutionary precedents and the general context in which Chambers presented his views concerning the transmutation of species. It also describes his career and professional interests. Chapter 2 deals with Chambers main evolutionary ideas. Chapter 3 provides a comparison between Chambers' and Lamarck's views, showing their similarities and differences. Chapter 4 offers some final remarks on the subject. This study led to the conclusion that although several similarities between Chambers' and Lamarck's evolutionary ideas may be found in some respects, such as gradualism, progression, uniformitarism, natural laws and no interference of God in natural processes, there were also some relevant differences such as the way in which they attempted to provide a foundation for their theories. Whereas Chambers presented many arguments using the fossil records as well as some other ones related to rudimentary organs and embryology, Lamarck made scarce use of the fossil record for the foundation of his theory. Instead of this, he provided a huge mass of facts showing the existence of a progression of the great taxonomical groups of animals. The arrangement of those groups in a progressive scale, however, did not provide an empirical foundation for what had happened in time. On the other hand, Chambers presented laws different from Lamarck's. However, although he did not propose a law dealing with the increase of the complexity of the great groups or individuals as Lamarck did, this idea permeated all of Chambers' ideas on the transmutation of species / Publicado anonimamente em 1844, o livro Vestiges of the natural history of creation desencadeou uma das maiores discussões públicas que ocorreram durante o século XIX. Seu autor, Robert Chambers, defendeu a transmutação dos seres vivos e a origem de novas espécies através de causas naturais. O primeiro objetivo desta dissertação é descrever algumas concepções evolutivas apresentadas neste livro e o segundo é compará-las à versão final da teoria da progressão dos animais de Lamarck. Esta dissertação contém uma introdução e quatro capítulos. O capítulo 1 discute os precedentes evolutivos e o contexto geral no qual Chambers apresentou suas idéias sobre a transmutação das espécies, tratando também de sua carreira e interesses profissionais. O capítulo 2 lida com alguns aspectos das concepções evolutivas de Chambers. O capítulo 3 oferece uma comparação entre as concepções de Chambers e Lamarck mostrando suas similaridades e diferenças. O capítulo 4 apresenta algumas considerações sobre o que foi discutido nos capítulos anteriores. Este estudo levou à conclusão de que embora possam ser detectadas diversas semelhanças entre alguns aspectos das concepções evolutivas de Chambers e as concepções evolutivas de Lamarck, tais como o gradualismo, a progressão, o uniformitarismo, as leis naturais e a não intervenção divina nos processos naturais, há também diferenças tais como o modo pelo qual eles procuraram fundamentar suas teorias. Enquanto Chambers apresentou exemplos obtidos principalmente a partir do registro fóssil e alguns relacionados à presença de órgãos rudimentares e à embriologia, Lamarck fez pouco uso do registro fóssil para fundamentar sua teoria. Em vez disso, forneceu uma grande massa de fatos mostrando a existência de uma progressão entre os grandes grupos de animais. O arranjo desses grupos em uma escala progressiva, entretanto, não proporcionou uma fundamentação empírica para o que ocorreu em termos cronológicos. Por outro lado, Chambers apresentou leis diferentes das apresentadas por Lamarck. Entretanto, apesar de não propor uma lei tratando da tendência para o aumento de complexidade existente na natureza em relação aos grandes grupos ou indivíduos como Lamarck, esta idéia permeou as concepções de Chambers sobre a transmutação das espécies

Thèse préparée en cotutelle en anthropologie (Université de Montréal) et en ethnomusicologie (École des Hautes Études en Sciences Sociales). / Cette recherche propose une recension socio-historique des contacts interculturels et du processus d’évangélisation chez les Noons de Thiès (Sénégal) afin d’y retracer la transmutation de symboliques culturelles depuis l’animisme au catholicisme, jusqu’à un état de vicariance entre les cultures en présence. Des travaux ont été effectués dans les archives des Spiritains, au Sénégal et à Paris; au Service historique de la Défense, à Vincennes; dans les Archives du Sénégal, à Dakar; et dans les archives de l’Abbaye de Keur Moussa. Des entrevues ont aussi été menées sur le terrain entre mars 2019 et mars 2020, enrichies d’une démarche renouvelée de bimusicalité selon Mantle Hood (1960), afin de mettre en lumière la perpétuation de symboles identitaires pendant la période coloniale jusqu’à aujourd’hui dans le mbilim, pratique musicale noon au coeur de la recherche. Cette recherche s’inscrit dans un contexte d’acculturation et de syncrétisme au sein d’une population faisant l’objet d’une exclusion systématique de la littérature historique écrite et s’inscrit dans la foulée d’une ethnomusicologie appliquée abordant le musical comme sujet holistique, observable et explicable selon diverses représentations de la communauté, une construction dynamique relevant de la rencontre entre plusieurs cultures dans le temps et se modulant selon l’utilisateur et le contexte d’utilisation (Berlioz et al., 1989). Je propose ainsi de reconsidérer le travail d’archives sur l’histoire et l’expérience coloniale et missionnaire afin de repenser les modèles classiques de syncrétisme et d’acculturation pour comprendre la construction d’une identité culturelle et musicale (ré)actualisée qui puisse permettre à la communauté visée de se projeter dans l’espace politique et socioculturel du Sénégal. / This research proposes a socio-historical review of cross-cultural contacts and of the evangelisation process among the Noons of Thiès (Senegal) in order to trace the transmutation of cultural symbolics from animism to Catholicism up to a state of vicariousness between the cultures in encounter. Work has been carried out in the archives of the Spiritans, in Senegal and Paris; at the Defense Historical Service, in Vincennes; in the National Archives of Senegal, in Dakar; and in the archives of Keur Moussa Abbey. Interviews were also conducted on the field between March 2019 and March 2020, enriched with a renewed approach of bi-musicality according to Mantle Hood (1960), in order to highlight the perpetuation of identity symbols during the colonial period until today in the mbilim, a musical practice of the Noons at the core of this research which is part of a context of acculturation and syncretism within a population subject to systematic exclusion from written historical literature. This research takes also part of an applied ethnomusicology approaching the musical as holistic subject, observable and explicable according to various representations of the community, a dynamic construction arising from the encounter between several cultures over time and modulating according to the user and the context of use (Berlioz et al., 1989). I thus propose to reconsider the work on the history and the colonial and missionary experience in the archives in order to rethink the classical models of syncretism and acculturation to understand the construction of a (re)actualised cultural and musical identity which can allow the community in question to project itself into the political and socio-cultural space of Senegal.

This master’s thesis deals with usage of burn-up (spent) nuclear fuel in nuclear power plants of next generation – accelerator driven transmutation plants which is produced in current nuclear power plants. This system could significantly reduce the volume of dangerous long-lived radioisotopes and moreover they would be able to take advantage of its great energy potential due to fast neutron spectrum. In the introduction are listed basic knowledge and aspects of spent nuclear fuel along with its reprocessing and the possibility of further use while minimizing environmental impact. As another point detailed description of accelerator driven systems is described together with its basic components. In addition this search is followed by individual chronological enumeration of projects of global significance concerning their current development. Emphasis is placed on SAD and MYRRHA projects, which are used like base for calculations. This last, computational part, deals with the creation of the geometry of subcritical transmutation reactor driven by accelerator and subsequent evaluation which assembly is the most effective for transmutation and energy purposes along with changing of target, nuclear fuel and coolant/moderator.

<p>Accelerator-driven systems for transmutation of nuclear waste have been suggested as a means for dealing with spent fuel components that pose potential radiological hazard for long periods of time. While not entirely removing the need for underground waste repositories, this nuclear waste incineration technology provides a viable method for reducing both waste volumes and storage times. Potentially, the time spans could be diminished from hundreds of thousand years to merely 1.000 years or even less. A central aspect for accelerator-driven systems design is the prediction of safety parameters and fuel economy. The simulations performed rely heavily on nuclear data and especially on the precision of the neutron cross section representations of essential nuclides over a wide energy range, from the thermal to the fast energy regime. In combination with a more demanding neutron flux distribution as compared with ordinary light-water reactors, the expanded nuclear data energy regime makes exploration of the cross section sensitivity for simulations of accelerator-driven systems a necessity. This fact was observed throughout the work and a significant portion of the study is devoted to investigations of nuclear data related effects. The computer code package EA-MC, based on 3-D Monte Carlo techniques, is the main computational tool employed for the analyses presented. Directly related to the development of the code is the extensive IAEA ADS Benchmark 3.2, and an account of the results of the benchmark exercises as implemented with EA-MC is given. CERN's Energy Amplifier prototype is studied from the perspectives of neutron source types, nuclear data sensitivity and transmutation. The commissioning of the n_TOF experiment, which is a neutron cross section measurement project at CERN, is also described.</p>

Accelerator-driven systems for transmutation of nuclear waste have been suggested as a means for dealing with spent fuel components that pose potential radiological hazard for long periods of time. While not entirely removing the need for underground waste repositories, this nuclear waste incineration technology provides a viable method for reducing both waste volumes and storage times. Potentially, the time spans could be diminished from hundreds of thousand years to merely 1.000 years or even less. A central aspect for accelerator-driven systems design is the prediction of safety parameters and fuel economy. The simulations performed rely heavily on nuclear data and especially on the precision of the neutron cross section representations of essential nuclides over a wide energy range, from the thermal to the fast energy regime. In combination with a more demanding neutron flux distribution as compared with ordinary light-water reactors, the expanded nuclear data energy regime makes exploration of the cross section sensitivity for simulations of accelerator-driven systems a necessity. This fact was observed throughout the work and a significant portion of the study is devoted to investigations of nuclear data related effects. The computer code package EA-MC, based on 3-D Monte Carlo techniques, is the main computational tool employed for the analyses presented. Directly related to the development of the code is the extensive IAEA ADS Benchmark 3.2, and an account of the results of the benchmark exercises as implemented with EA-MC is given. CERN's Energy Amplifier prototype is studied from the perspectives of neutron source types, nuclear data sensitivity and transmutation. The commissioning of the n_TOF experiment, which is a neutron cross section measurement project at CERN, is also described.