Dans le cadre de l'Approche Elargie pour la Fusion conclue entre le Japon et l'Europe, le projet IFMIF (International Fusion Materials Irradiation Facility) a été lancé pour l'étude des futurs matériaux pour la fusion qui devront résister à d'intenses flux de neutrons. Un composant majeur en est son ensemble de deux accélérateurs à très haute puissance (2×5 MW) qui produit le flux de neutrons en bombardant une cible de Lithium avec un faisceau de Deutérium à une énergie de 40 MeV. Vues ces spécifications ambitieuses, une première phase appelée EVEDA (Engineering Validation and Engineering Design Activity) prévoit l'étude et la réalisation d'un accélérateur prototype à l'échelle un jusqu'à 9 MeV au Japon. Le travail de cette thèse concerne le domaine de la Physique des Accélérateurs. Il consiste en des études de dynamique faisceau pour l'accélérateur prototype LIPAc, caractérisé par une intensité et une puissance jamais encore réalisées, exigeant de ce fait des qualités de faisceau exceptionnelles. Les caractéristiques de cet accélérateur, font qu'il requiert de nombreuses études et simulations pour toutes les étapes de sa mise en service. En parallèle, des études de fond sur les interactions coeur-halo et les effets de la charge d'espace dans les accélérateurs intenses, seront aussi menées. En particulier une nouvelle définition du halo d'un faisceau de particules, adaptée à l'étude de ces accélérateurs sera proposée et appliquée. / As part of the Broader Approach to Fusion concluded between Japan and Europe, the IFMIF (International Fusion Materials Irradiation Facility) project was launched for the study of future fusion materials resisting intense neutron fluxes. A major component of it is the couple of twin high power accelerators (2 × 5 MW) which will produce the neutron flux by bombarding a Lithium target with a deuterium beam at an energy of 40 MeV. Considering these ambitious specifications, a first phase called EVEDA (Engineering Validation and Engineering Design Activity) is ongoing to provide the design and construction of an up to scale prototype accelerator to an energy of 9 MeV in Japan. The work of this thesis belongs to the field of Accelerators Physics. It consists of beam dynamics studies for the prototype accelerator LIPAc, characterized by unprecedented current and power, thereby requiring outstanding beam quality. The characteristics of this accelerator, makes many studies and simulations for all stages of its commissioning required. Concurrently, background studies on core-halo interactions and on the effects of space charge on high current beams will also be conducted. In particular a new definition of the halo of a particle beam, adapted to the study of these accelerators will be proposed and implemented.

Some experiments have indicated the possible existence of par ticles with a negative inertial mass. It is shown under which condit ions Weber’s electrodynamics gives rise to this effect. Some specific experiments related to this aspect of Weber’s law are described. Two particles equ ally electrified with charges of the same sign would then move toward one an other if they had negative effective inertial masses. A new concept for nuclear fusion is presented based on the possibility of creating a negative effective inertial mass for ions. It is then considered some properties of the inertial dipole, that is, a system composed by a pair of particles in which one particle has a positive effective inertial mass while the other particle has a negative effective inertial mass. The possible utilization of the inertialdipole as a propulsion system is briefly discussed.

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第24926号 / エネ博第468号 / 新制||エネ||88(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻 / (主査)准教授 南 貴司, 教授 稲垣 滋, 教授 田中 仁 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

The International Thermonuclear Experimental Reactor (ITER) will be a major step towards controlled energy fusion in tokamaks. Operation of the hot confined plasma inside the tokamak will have to be optimized and simulations will have to prove that each pulse conducted is feasible under the operational limits of the reactor. For such purpose a Pulse Design Simulator is developed at ITER. This workflow lacks a transport model to simulate the dynamics of the plasma caused by micro-instabilities driven by turbulences. The purpose of this thesis is the adaptation of such model into the Integrated Modelling and Analysis Suite (IMAS), namely mapping the inputs and outputs of an existing code for its integration to the workflow. This work presents a fast 1D core transport code capable of simulating the evolution of the poloidal flux, the temperature evolution of both ions and electrons and the particle density transport. The model is coupled to a neural network regression of the transport model QuaLiKiz for the computation of first-principle based turbulent heat and particle transport coefficients. / Internationella Termonukleära Experimentella Reaktorn (ITER) kommer att vara ett stort steg mot kontrollerad energifusion i tokamaker. Driften av det varma, instängda plasmaet inne i tokamaken måste optimeras, och simuleringar måste bevisa att varje pulsskötning är genomförbar inom reaktorns driftgränser. För detta ändamål utvecklas en pulsdessignsimulator vid ITER. Denna arbetsflöde saknar en transportmodell för att simulera plasmaets dynamik orsakad av mikroinstabiliteter drivna av turbulenser. Syftet med denna avhandling är anpassningen av en sådan modell till Integrated Modelling and Analysis Suite (IMAS), nämligen att kartlägga in- och utdata av en befintlig kod för dess integration i arbetsflödet. Denna arbete presenterar en snabb 1D-kärntransportkod som kan simulera utvecklingen av den poloidala flödet, temperaturutvecklingen för både joner och elektroner samt partikeltäthetstransporten. Modellen är kopplad till en neural nätverksregression av transportmodellen QuaLiKiz för beräkning av första principbaserade turbulenta värme- och partikeltransportkoefficienter.

O aumento no consumo energético mundial e a perspectiva de esgotamento das reservas de combustíveis fósseis têm estimulado o desenvolvimento de tecnologias e materiais para aplicações nos futuros reatores de fusão nuclear e reatores de fissão a nêutrons rápidos. O foco deste trabalho é avaliar a estabilidade microestrutural de um material tecnologicamente promissor por meio de diferentes técnicas de caracterização. O material estudado, o aço ODS-EUROFER, é um aço ferrítico-martensítico de atividade reduzida de composição 9%Cr-1%W (em massa) endurecido pela dispersão de 0,3% (em massa) de óxido de ítrio. Amostras foram laminadas até 80% de redução e submetidas a tratamentos isotérmicos em 800 °C por até 6 meses (4320 h) de duração para se investigar a ocorrência de fenômenos tais como recuperação, recristalização, crescimento de grão, precipitação e engrossamento de Ostwald. Outro conjunto de amostras foi recozido por 1 hora em temperaturas entre 900 e 1300 °C para se estudar a transformação martensítica neste material. Diversas técnicas de caracterização microestrutural complementares entre si (MEV, MET, DRX, EBSD, APT, ensaios de microdureza Vickers, dilatometria, DTA e magnetização) foram empregadas. Os resultados obtidos indicam que a dispersão de partículas nanométricas de Y2O3 confere uma grande resistência à recristalização primária, favorecendo a recuperação estática como principal mecanismo de amolecimento durante o recozimento prolongado deste aço. De modo similar, o crescimento de grão foi suprimido no campo austenítico em temperaturas tão altas quanto 1200 °C. / The rise in the world energy consumption and the possibility of depletion of the fossil fuel reserves have stimulated the development of new technologies and new materials for applications in the future nuclear fusion reactors and in the fast breeder fission reactors. The aim of this study is to evaluate the microstructural stability of a technologically promising material by using different characterization techniques. The investigated material, the ODS-EUROFER steel, is 9Cr-1W (%wt) reduced-activation ferritic-martensitic steel reinforced with a dispersion of 0.3%wt of yttrium oxide nanoparticles. Samples were cold rolled to 80% thickness reduction and subjected to isothermal annealing at 800 °C for up to 6 months (4,320 h) to investigate the occurrence of phenomena such as recovery, recrystallization, grain growth, precipitation, and Ostwald ripening. Another set of samples was annealed for 1 hour at temperatures between 900 and 1300 °C to study the martensitic transformation in this steel. Several complementary microstructural characterization techniques were employed (SEM, TEM, XRD, EBSD, APT, Vickers hardness, dilatometry, DTA and magnectic measurements). The results suggest that the dispersion of nanoscaled particles of Y2O3 provides a high resistance to discontinous recrystallization and favors static recovery as the main softening mechanism during long-term annealing in this steel. Similarly, grain growth was suppressed even in temperatures as high as 1200 °C in the austenitic field.

O aumento no consumo energético mundial e a perspectiva de esgotamento das reservas de combustíveis fósseis têm estimulado o desenvolvimento de tecnologias e materiais para aplicações nos futuros reatores de fusão nuclear e reatores de fissão a nêutrons rápidos. O foco deste trabalho é avaliar a estabilidade microestrutural de um material tecnologicamente promissor por meio de diferentes técnicas de caracterização. O material estudado, o aço ODS-EUROFER, é um aço ferrítico-martensítico de atividade reduzida de composição 9%Cr-1%W (em massa) endurecido pela dispersão de 0,3% (em massa) de óxido de ítrio. Amostras foram laminadas até 80% de redução e submetidas a tratamentos isotérmicos em 800 °C por até 6 meses (4320 h) de duração para se investigar a ocorrência de fenômenos tais como recuperação, recristalização, crescimento de grão, precipitação e engrossamento de Ostwald. Outro conjunto de amostras foi recozido por 1 hora em temperaturas entre 900 e 1300 °C para se estudar a transformação martensítica neste material. Diversas técnicas de caracterização microestrutural complementares entre si (MEV, MET, DRX, EBSD, APT, ensaios de microdureza Vickers, dilatometria, DTA e magnetização) foram empregadas. Os resultados obtidos indicam que a dispersão de partículas nanométricas de Y2O3 confere uma grande resistência à recristalização primária, favorecendo a recuperação estática como principal mecanismo de amolecimento durante o recozimento prolongado deste aço. De modo similar, o crescimento de grão foi suprimido no campo austenítico em temperaturas tão altas quanto 1200 °C. / The rise in the world energy consumption and the possibility of depletion of the fossil fuel reserves have stimulated the development of new technologies and new materials for applications in the future nuclear fusion reactors and in the fast breeder fission reactors. The aim of this study is to evaluate the microstructural stability of a technologically promising material by using different characterization techniques. The investigated material, the ODS-EUROFER steel, is 9Cr-1W (%wt) reduced-activation ferritic-martensitic steel reinforced with a dispersion of 0.3%wt of yttrium oxide nanoparticles. Samples were cold rolled to 80% thickness reduction and subjected to isothermal annealing at 800 °C for up to 6 months (4,320 h) to investigate the occurrence of phenomena such as recovery, recrystallization, grain growth, precipitation, and Ostwald ripening. Another set of samples was annealed for 1 hour at temperatures between 900 and 1300 °C to study the martensitic transformation in this steel. Several complementary microstructural characterization techniques were employed (SEM, TEM, XRD, EBSD, APT, Vickers hardness, dilatometry, DTA and magnectic measurements). The results suggest that the dispersion of nanoscaled particles of Y2O3 provides a high resistance to discontinous recrystallization and favors static recovery as the main softening mechanism during long-term annealing in this steel. Similarly, grain growth was suppressed even in temperatures as high as 1200 °C in the austenitic field.

The common observation that the onset of a core MARFE (edge localized, poloidally asymmetric, highly radiating region) is followed immediately by a High-to-Low confinement mode transition in DIII-D was investigated by comparing a theoretical prediction of the threshold non-radiative power across the separatrix needed to maintain H-mode with an experimental determination of the non-radiative power flowing across the separatrix. It was found that in three shots with continuous gas fueling that the increased neutral influx associated with the MARFE formation caused a sharp increase in the predicted threshold non-radiative power crossing the separatrix that was required for the plasma to remain in H-mode to a value comparable to the experimental power crossing the separatrix, indicating a theoretical prediction of a H-L transition in agreement with experimental observation.

The radioactivity induced by neutrons in the materials of future fusion devices represents a central topic of safety- and environmental-related investigations. For the design and operation of future fusion devices, like the International Experimental Thermonuclear Reactor ITER or power plants like DEMO, the activation performance of the materials during operation and after shut-down has to be simulated. The European Activation System (EASY), consisting of the inventory code FISPACT and the activation library EAF, is the world wide reference system for these calculations. The activation of the fusion reactor materials, as well as the EASY system have to be tested experimentally. In the present work several samples of materials from the European fusion technology program were irradiated in neutron fields of DT neutron generators at TU Dresden and at Sergiev Posad near Moscow. The radioactivity following irradiation was determined several times during decay by ?×-spectroscopy. The results are analysed with EASY and ratios of the calculated-to-experimental activation (C/E) are determined, to find limits for the experimental validation of EASY. For the future improvement of EASY integral cross sections are obtained from these C/E and discussed in connection with the EAF data, energy differential measurements from the EXFOR System of the International Atomic Energy Agency (IAEA), other energy integral measurements and evaluated data from libraries in the JANIS system of the Nuclear Energy Agency (NEA). The investigated materials of the present work are Tungsten, Yttrium, CuCrZr and Lead. Tungsten is the preferred material for the divertor plates of fusion devices an a constituent of reduced activation structural materials. Yttrium is used in the ODS steels, which are candidate materials for the first wall and blanket structure of. The characteristic feature of ODS steels is to introduce Y2O3 oxide particles into structural materials like EUROFER to improve the high-temperature strength and to maintain superior radiation resistance. CuCrZr alloys are used as a heat sink in the first wall of the blanket and in the divertor. The CuCrZr alloys contain impurities in consequence of the production technology, which can have an influence on the activation performance and thus have to be known accurately. In this work the neutron activation analysis has proved to be an appropriate instrument to measure the amount of some special impurities. Lead acts as a neutron multiplier and coolant in breeding blanket concepts such as the European Test Blanket Modules (TBM) with liquid Pb-17Li. Due to some large discrepancies between the measured activities and those calculated with EASY for tungsten, these cross sections are analysed with recent models of the nuclear reaction mechanisms. The sensitivity of the obtained cross sections with respect to different reaction models and parameters is investigated and limits for new evaluations are obtained with respect to the experimental results. / Die von Neutronen induzierten Aktivitäten in den Materialien zukünftiger Fusionsreaktoren stellen einen zentralen Punkt in der Forschung zur Sicherheit und Umweltverträglichkeit der gesteuerten Kernfusion dar. Für die Konstruktion und den Betrieb von Fusionsreaktoren, wie den Internationalen Thermonuklearen Experimental-Reaktor ITER oder Demonstrationskraftwerke wie DEMO, werden Simulationsrechnungen zum Aktivierungsverhalten der Materialien während des Betriebs und nach Abschalten des Reaktor durchgeführt. Das European Activation System EASY, bestehend aus dem Inventarcode FISPACT und der Datenbibliothek EAF, ist dabei weltweit das Referenzinstrument für derartige Rechnungen. Sowohl das Programmpaket als auch das Aktivierungsverhalten der im Fusionsreaktor verwendeten Materialien müssen experimentell getestet werden. Im Rahmen dieser Arbeit wurden zu diesem Zweck Proben von Materialien aus dem europäischen Fusionstechnologieprogramm in Neutronenfeldern der DT-Neutronengeneratoren der TU Dresden, bzw. an SNEG-13 im russischen Sergiev Posad bestrahlt. Die entstehende Radioaktivität wurde im Anschluss an die Bestrahlung zu verschiedenen Abklingzeiten mittels Gammaspektroskopie bestimmt. Die gemessenen Aktivitäten individueller Nuklide werden mit EASY analysiert und die Verhältnisse von gemessener Aktivität zu berechneter (C/E) werden für die einzelnen Aktivitäten bestimmt. Damit werden die Grenzen für die experimentelle Bestätigung der EASY-Berechungen ermittelt. Zur zukünftigen Verbesserung von EASY werden aus den C/E experimentelle Eingruppenwirkungsquerschnitte ermittelt, die im Kontext der EAF-Daten, energiedifferentieller Messungen aus dem EXFOR System der International Atomic Energy Agency (IAEA), vorangegangener energieintegraler Experimente und eingeschätzter Bibliotheksdaten aus dem JANIS System der Nuclear Energy Agency (NEA) diskutiert werden. Bei den untersuchten Materialien handelt es sich um Wolfram, Yttrium, CuCrZr und Blei. Wolfram ist ein bevorzugtes Material für den Divertor des Fusionsreaktors und zudem Bestandteil gering aktivierbarer Strukturmaterialien. Yttrium wird als Zusatz in den so genannten ODS Stählen verwendet, die in der ersten Wand und im Blanket eingesetzt werden. Diese entstehen aus Strukturmaterialien wie dem europäischen EUROFER, die bereits früher auf ihr Aktivierungsverhalten untersucht wurden, durch Hinzufügen von Y2O3-Partikeln, wodurch sie bei höheren Temperaturen und Neutronenflüssen einsetzbar werden. CuCrZr wird als Wärmeleiter in der ersten Wand des Blankets und im Divertor eingesetzt. Als Legierung ist CuCrZr mit technologisch bedingten Verunreinigungen versetzt, die sich auf das Aktivierungsverhalten auswirken können und deshalb genau bekannt sein müssen. Die Neutronenaktivierung hat sich dabei im Rahmen dieser Arbeit ebenfalls als geeignetes Mittel erwiesen. Blei agiert als Neutronenmultiplikator und Kühlmittel in Brutblanketkonzepten wie dem europäischen Test Blanket Module (TBM) das flüssiges Pb-17Li verwendet. Infolge der deutlichen Diskrepanzen zwischen der experimentellen und der mit EASY berechneten Aktivitäten bei Wolfram wird eine Analyse der Wirkungsquerschnitte mit Hilfe aktueller Modelle zum Mechanismus von Kernreaktionen vorgenommen. Dabei wird die Sensitivität der ermittelten Wirkungsquerschnitte auf verschiedene Reaktionsmodelle und Parameter getestet und ein Rahmen für Neueinschätzungen der Daten unter Berücksichtigung experimenteller Ergebnisse ermittelt.

Le transport anormal de l’energie observé en régime turbulent joue un rôle majeur dans les propriétés de stabilite des plasmas de fusion par confinement magnétique, dans des machines comme ITER. En effet, la turbulence plasma est intimement corrélée au temps de confinement de l’energie, un point clé des recherches en fusion thermonucléaire.<p>Du point de vue théorique, la turbulence plasma est décrite par les équations gyrocinétiques, un ensemble d équations aux dérivées partielles non linéaires couplées. Par suite des très différentes échelles spatiales mises en jeu dans des conditions expérimentales réelles, une simulation numérique directe et complète (DNS) de la turbulence gyrocinétique est totalement hors de portée des plus puissants calculateurs actuels, de sorte que démontrer la faisabilité d’une alternative permettant de réduire l’effort numérique est primordiale. En particulier, les simulations de grandes échelles (”Large-Eddy Simulations” - LES) constituent un candidat pertinent pour permettre une telle r éduction. Les techniques LES ont initialement été développées pour les simulations de fluides turbulents à haut nombre de Reynolds. Dans ces simulations, les plus grandes échelles sont explicitement simulées numériquement, alors que l’influence des plus petites est prise en compte via un modèle implémenté dans le code.<p>Cette thèse présente les premiers développements de techniques LES dans le cadre des équations gyrocinétiques (GyroLES). La modélisation des plus petites échelles est basée sur des bilans d’énergie libre. En effet, l’energie libre joue un rôle important dans la théorie gyrocinétique car elle en est un invariant non lin éaire bien connu. Il est démontré que sa dynamique partage de nombreuses propriétés avec le transfert d’energie dans la turbulence fluide. En particulier, il est montré l’existence d’une cascade d énergie libre, fortement locale et dirigée des grandes échelles vers les petites, dans le plan perpendiculaire â celui du champ magnétique ambiant.<p>La technique GyroLES est aujourd’hui implantée dans le code GENE et a été testée avec succès pour les instabilités de gradient de température ionique (ITG), connues pour jouer un rôle crucial dans la micro-turbulence gyrocinétique. A l’aide des GyroLES, le spectre du flux de chaleur obtenu dans des simulations à très hautes résolutions est correctement reproduit, et ce avec un gain d’un facteur 20 en termes de coût numérique. Pour ces raisons, les simulations gyrocinétiques GyroLES sont potentiellement un excellent candidat pour réduire l’effort numérique des codes gyrocinétiques actuels. <p>/ Anomalous transport due to plasma micro-turbulence is known to play an important role in confinement properties of magnetically confined fusion plasma devices such as ITER. Indeed, plasma turbulence is strongly connected to the energy confinement time, a key issue in thermonuclear fusion research. Plasma turbulence is described by the gyrokinetic equations, a set of nonlinear partial differential equations. Due to the various scales characterizing the turbulent fluctuations in realistic experimental conditions, Direct Numerical Simulations (DNS) of gyrokinetic turbulence remain close to the computational limit of current supercomputers, so that any alternative is welcome to decrease the numerical effort. In particular, Large-Eddy Simulations (LES) are a good candidate for such a decrease. LES techniques have been devised for simulating turbulent fluids at high Reynolds number. In these simulations, the large scales are computed explicitly while the influence of the smallest scales is modeled.<p>In this thesis, we present for the first time the development of the LES for gyrokinetics (GyroLES). The modeling of the smallest scales is based on free energy diagnostics. Indeed, free energy plays an important role in gyrokinetic theory, since it is known to be a nonlinear invariant. It is shown that its dynamics share many properties with the energy transfer in fluid turbulence. In particular, one finds a (strongly) local, forward (from large to small scales) cascade of free energy in the plane perpendicular to the background magnetic field.<p>The GyroLES technique is implemented in the gyrokinetic code Gene and successfully tested for the ion temperature gradient instability (ITG), since ITG is suspected to play a crucial role in gyrokinetic micro-turbulence. Employing GyroLES, the heat flux spectra obtained from highly resolved direct numerical simulations are recovered. It is shown that the gain of GyroLES runs is 20 in terms of computational time. For this reason, Gyrokinetic Large Eddy Simulations can be considered a serious candidate to reduce the numerical cost of gyrokinetic simulations. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Reduced activation oxide dispersion strengthened (ODS) steels are candidate alloys for use in fusion reactor systems and are fabricated by mechanically alloying yttrium oxide to a reduced activation ferritic steel powder. The product is consolidated at high temperature by hot isostatic pressing (HIP), producing a dispersion of nanometre sized oxide particles throughout the ferritic microstructure. These particles have been shown to both improve the high temperature mechanical properties of the alloy and provide trapping sites for helium gas. The use of these particles to sequester helium is of particular significance in the development of a structural ODS steel for fusion reactor systems. A fusion power reactor, based on the ITER design, is expected to produce over 2000 appm transmutant helium in any steel components exposed to the core neutron flux. At these gas concentrations, conventional steels undergo severe swelling and embrittlement, motivating the development of materials capable of managing helium accumulation. This thesis investigates the use of the oxide particle dispersion in sequestering helium introduced by ion implantation. An initial characterisation of a model Fe-14Cr-0.25Y₂O₃ (wt&percnt;) system was completed using high resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT). This demonstrated the efficacy of the production methods and the gas trapping capabilities of the oxide particles via argon gas, introduced during the mechanical alloying process. The subsequent consolidation of a full set of Fe-14Cr-3W-0.2Ti-0.25Y₂O₃ (wt&percnt;) ODS alloys at 1150&deg;C, 1050 &deg;C and 950 &deg;C produced a systematic variation in the density of the particle dispersion. The characterisation of these materials using APT provided an insight into the consistent Y₂Ti₃O₅ particle chemistry found in each consolidation, and identified a stoichiometric shift from Y₂Ti₃O₅ to YTiO2 following short term annealing periods at 1000&deg;C. Though further work is required, this shift is thought to be consistent with a thermodynamically mediated transition of the metastable clusters to stable oxide particles. Following implantation with 2000 appm helium and examination under TEM, the helium bubble and particle densities were found to be closely correlated thus providing evidence for an association between the particles and the gas bubbles. Controlling the helium bubble density via the particle dispersion demonstrates the potential use of processing temperature in controlling how helium accumulates in an implanted ODS microstructure. The effects of both bubble and particle densities on mechanical properties were investigated further using nanoindentation methods. Significant local variation in the hardness of the ODS steels was found to result from the bimodal grain size distribution of the material. By using only those measurements taken from large grained regions of the ODS, the grain refinement and particle hardening effects could be deconvolved and used to quantify particle hardening using a dispersed barrier model. The significant hardening effects with helium addition observed in the reference alloys were found to be almost entirely absent from the ODS systems, though anomalous softening in the 950&deg;C consolidation indicated a potentially unexpected interaction between the bubble and particle populations. A possible explanation for this anomaly and a proposal for further work to establish its origin is discussed.