Made available in DSpace on 2014-10-09T12:26:20Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:32Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Made available in DSpace on 2014-10-09T12:26:20Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:32Z (GMT). No. of bitstreams: 0 / O Laboratório de Calibração de Instrumentos do Instituto de Pesquisas Energéticas e Nucleares oferece serviços de calibração de detectores de radiação utilizados em radioproteção, radiodiagnóstico e radioterapia, para o IPEN e também para instalações externas, públicas e particulares. Uma parte de suas instalações estão localizadas no prédio principal, junto com outros laboratórios e salas de estudo, e uma outra parte num prédio isolado, semienterrado (Bunker). Para a otimização, a modernização e principalmente a segurança, os laboratórios situados no prédio principal precisam ser transferidos para um local isolado. Neste trabalho foi desenvolvido um projeto de um laboratório integrado, que será uma expansão do atual Laboratório de Calibração de Instrumentos do IPEN. Para isto, foram feitos levantamentos radiométricos no local escolhido e levantadas todas as necesidades da equipe quanto a espaço e disposição das salas. No projeto, os laboratórios com equipamentos de radiação X, e fontes radioativas alfa e beta ficaram isolados numa parte do prédio, e as blindagens das paredes foram determinadas, dependendo do uso de cada laboratório. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:51:02Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:05Z (GMT). No. of bitstreams: 1 11132.pdf: 10371292 bytes, checksum: 1b7d4e1304d84398e9d2d5f40d72ea2b (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Nous étudions la génération de rayonnement TeraHertz (THz) dans des microplasmas produits par des lasers femtosecondes. Cette technique est prometteuse pour créer efficacement des sources THz compactes et étendue spectralement (0.3-30 THz), qui intéressent de nombreuses applications, comme l’identification spectroscopique de substances dangereuses ou encore l’imagerie en biologie et médecine. Contrairement aux sources conventionnelles, comme les interrupteurs photo-conducteur, les sources THz basées sur des plasmas ne sont pas limitées par la tenue au flux et couvrent l’ensemble du spectre THz. Afin de modéliser des microplasmas générés par des faisceaux laser fortement focalisés, nous présentons un nouvel algorithme qui permet d’injecter tout type de laser dans des codes électromagnétiques. Nous dérivons aussi un modèle compatible avec les équations de Maxwell qui inclut les deux mécanismes générateurs de THz: le courant d’ionisation (IC) et le mécanisme “Transition-Cherenkov” (TC). Ce dernier mécanisme domine la production de THz pour des lasers à plusieurs cycles optiques, où l’émission est produite par les courants d’électron longitudinaux. Dans le cas des microplasmas où un champ électrostatique externe est ajouté, le taux de conversion énergétique laser/THz peut être augmenté de deux ordres de grandeur via le mécanisme IC lorsque le champs statique ou la pression du gaz sont accrus. De plus, les simulations 3D montrent que pour un faisceau laser à deux couleurs et dans des conditions optimales de focalisation, une énergie laser de 10 micro-Joule est suffisante pour atteindre des taux de conversion bien au-dessus de 10−4. Dans ce cas, la nature transverse du courant IC est cruciale pour accroitre l’efficacité avec la longueur du plasma. En considérant un faisceau laser à deux couleurs de forme elliptique, nous proposons de contrôler les spectres d’émission en exploitant les effets plasmoniques résonants. / We investigate terahertz (THz) generation in fs-laser-induced microplasmas, which are promising candidates for compact and efficient broadband THz sources (0.3-30 THz). Such sources have various applications as spectroscopic identification of hazardous substances or THz imaging in biology and medicine. Unlike conventional THz sources as photoconductive switches, gas-plasma-based THz sources do not suffer from irreversible material damage and can cover the whole THz range at once. To simulate tightly-focused-laser-induced microplasmas, we propose an efficient numerical algorithm that can introduce any arbitrarily shaped laser pulses into electromagnetic codes. We derive a Maxwell-consistent model that includes two major THz generation mechanisms, the ionization current (IC) and transition-Cherenkov mechanisms (TC). The latter mechanism is shown to dominate for single-color multi-cycle lasers pulses where the emission is driven by longitudinal electron currents. For microplasmas a constant electric field can boost the laser-to-THz converison efficiency by two orders of magnitude via the IC mechanism when increasing the gas-pressure and bias-voltage. Moreover for two-color-driving laser pulses, Maxwell-consistent 3D simulations show, that only 10 μJ laser pulse energy are sufficient to reach conversion efficiencies well above 10−4 when optimizing the focusing conditions. Here, the transverse nature of the IC currents is crucial for the up-scaling of the efficiency with the plasma length. By using elliptically-shaped two-color-driving laser beams, we propose to control the emission spectra by exploiting resonant plasmonic effects.

Doctorat en philosophie et lettres / info:eu-repo/semantics/nonPublished

Les deux codes de lois de l'époque babylonienne ancienne consacrent plusieurs rubriques à la nipûtum, elles ont été transcrites, traduites et commentées à de multiples reprises. D’autre part, des dizaines de textes éparpillés, auxquels il n'est fait que de vagues allusions dans les commentaires, abordent le même sujet; chaque fois qu'ils sont cités, ils ne le sont que parce qu'ils peuvent éclairer un peu le sens des codes .<p>Nous avons décidé d'agir en sens contraire de la recherche traditionnelle et de proposer une définition de la nipûtum grâce aux textes de la pratique .Les codes semblent en effet traiter de l'anormal plutôt que du normal .La nipûtum n'y est définie qu'en termes d'abus :saisie non justifiée ou mauvais traitements pouvant entraîner la mort de la personne saisie .De plus, ils ne parlent de la nipûtum qu'en cas de dettes et seulement pour des opérations entre particuliers, mettant face à face un banquier tout puissant et un citoyen pauvre en difficulté .<p>L'institution des nipûtum se met tout d'abord en valeur par sa grande extension chronologique, elle est présente dès le début des dynasties amorrites jusqu’au dernier roi de Babylone, soit pendant trois siècles .En ce qui concerne la répartition géographique, elle est en usage dans l'ensemble de la Mésopotamie, du nord au sud, de Sippar à Ur, et d'est en ouest, même dans des zones tout à fait éloignées, comme Mari .<p>\ / Doctorat en Langues et lettres / info:eu-repo/semantics/nonPublished

>Magister Scientiae - MSc / The ultimate aim of any multiply-charged ion source, like the Electron Cyclotron Resonance Ion Source, ECRIS, is the production of multiply-charged ions, in sufficiently large quantities. These multiplycharged ions, in the case of the ECRIS, are created by a step-by-step ionisation process, whereby neutral atoms are ionised by energetic electrons. The goal of this thesis was to gain an understanding of the relative importance of various ECRIS parameters on the production of these energetic electrons. This was done by measuring the bremsstrahlung continuum emitted by the mirror confined plasma of an ECR ion source. The focus of our study was to investigate the influence of neutral pressure, incident microwave power and magnetic field configuration on spectral temperature and electron density of the warm electron population of the ECRIS plasma. The thesis begins by familiarising the reader with various aspects of plasma physics as it relates to the measurements. The measurements were done with a high-purity germanium detector and processed with the DGF Pixie-4 module. Analyses of the measured spectra were done with subroutines written in Root. From the measured result, it was concluded that by increasing the incident microwave power from 50 W to 300 W, the spectral temperature increases by 14.01% for helium plasma and 7.88% for argon plasma. Evidence of saturation of spectral temperature and electron density with increasing microwave power was also noticed, as reported by other groups investigating plasma bremsstrahlung. The increase of spectral temperature with neutral pressure was found to be considerable, increasing by 20.23% as the neutral pressure in the plasma chamber of the ECRIS was decreased. This increase in spectral temperature was accompanied by a 40.33% decrease in electron density, which led us to conclude that the increase in spectral temperature was most likely due to an increase in the mean free path of the electrons. The influence of the magnetic field configuration on both spectral temperature and electron density was also investigated. During this investigation, one of the solenoid coil currents was increased, whilst keeping the other constant. This amounts to moving the plasma volume around axially in the plasma chamber of the ECRIS. This was found to significantly enhance the spectral temperature and this effect was attributed to more efficient heating of the electrons near the resonance zone. The electron density on the other hand was found to remain relatively constant, if one excludes the electron density as a result of one particularly setting of the solenoid coils. The decrease of electron density as a result of this particular setting of the solenoid coils enhanced the electron losses through the magnetic bottle. This is evidenced by the increase in photon counts as measured by our detector. The influence of neutral pressure, incident microwave power and magnetic field configuration on the extracted ion beam intensities was also investigated. This investigation led us to conclude that the mean charge state extracted increases with spectral temperature. This result was in agreement with those measured by other groups.

As part of the fight against global warming, the European Union has opted for increase in support for renewable energy at the cost of conventional sources. This policy was subsequently implemented into national legislation. At the same time, the Czech Republic has framed an Updated State Energy Policy, which sets out the direction for Czech energy to evolve. This thesis tries to analyze whether the Czech Republic is ready for future energy development or not. This analysis shows that the Czech Republic is not entirely ready to provide energy stability in the context of a transforming market.

Le risque environnemental lié à la présence de plastiques dans les milieux aquatiques a été suggéré, pour le milieu marin, dès les années 1970. Même s’il reste incomplètement cerné (d’un point de vue écotoxicologique essentiellement), il ressort de la littérature qu’il est significatif. Même si certains travaux suggèrent qu’une grande partie de ces plastiques provient des eaux continentales, il n’existe aujourd’hui peu d’étude sur les niveaux d’imprégnation des milieux aquatiques en milieu continental et aucune à l’échelle des bassins versants urbains pour préciser l’importance des différentes sources urbaines.Dans cette étude, les macroplastiques (> 5 mm) ainsi que les microplastiques (<5 mm) sont considérés. Les flux de macroplastiques dans la Seine ont été estimés à l’aide d’une étude de terrain mais aussi à l’aide d’une approche théorique. En ce qui concerne les microplastics, les fibres (synthétiques et artificielles) ainsi que les fragments ont été étudiés dans différent compartiments du système urbain. L’air intérieur, les retombées atmosphériques, les eaux de ruissellement, les effluents et affluents de stations d’épuration ainsi que les rejets urbains en temps de pluie ont été étudiés.Les concentrations en microplastiques dans le milieu récepteur ont aussi été estimées. Le suivi de la contamination des eaux de surface a été abordé selon deux méthodes d’échantillonnage distinctes : échantillonnage par un filet avec une maille de 80 μm et par un filet de 330 µm. L’homogénéité des fibres le long de la section a aussi été estimée, tout comme la variabilité temporelle à court terme. Pour finir, un suivi mensuel sur 19 mois a été effectué en amont et en aval de Paris.Cette étude a permis de montrer que les flux de microplastiques dans la Seine représentent une masse négligeable par rapport aux flux de macroplastiques. Elle confirme aussi l’ubiquité des fibres dans tous les compartiments. Les fragments sont quant à eux particulièrement concentrés dans les rejets urbains en temps de pluie. Pour la première fois, il a été montré que le compartiment atmosphérique jouait un rôle potentiellement important, autant que source de microplastiques / Plastic pollution has been widely studied in marine environment since 1972 and mostly since 2004. Investigations on plastic pollution in freshwater and especially in urban catchments just started at the beginning of the decade, and urban plastic pollution sources and its related fluxes in rivers remains mainly unknown. Thus a specific attention should be paid to the plastic contamination in catchments exposed to severe anthropogenic pressure, especially within the urban areas. This PhD thesis focuses on the case of the Paris agglomeration and its impact on the Seine River. A double approach was carried out as both macro- (>5mm) and micro- (<5mm) plastics were considered.The amount of macroplastics conveyed by the Seine River was estimated with a field study and with a theoretical approach.Regarding microplastics, fibers (made with synthetic but also man-made polymers) and fragments were both investigated in different compartments of the urban system. The study focused on the air compartment (indoor and outdoor air as well as atmospheric fallout), the sewer system (from the washing machine disposals to the WWTP influents and effluents), and the inputs during wet weathers periods, i.e, runoff and combined sewer overflows. Fibers and fragments were also examined on the Seine River.This work aimed at providing relevant methodological keys to address sampling of microplastic in rivers. Two mesh size nets were tested (80 µm vs. 300 µm). The homogeneity of fibers distribution in rivers was also verified as the short term temporal and spatial variabilities were evaluated. In order to highlight the potential impact of the Paris agglomeration, a monthly monitoring on 5 sites upstream and downstream Paris was carried out as well.This thesis mainly highlighted the ubiquity of fibers in all compartments. Fibers were predominant in comparison to fragments in all compartments. Combined sewer overflows exhibited particularly high amounts of fragments. On the other hand, the flux of microplastics in the Seine River was proved be negligible in terms of mass in comparison to macroplastics. This study is also the first one showing that the atmospheric compartment needs to be considered as a potential significant source of microplastics