Cette thèse est consacrée à l’optimisation des sources de lumière synchrotron. La dynamique de faisceau non linéaire de l'anneau de stockage du synchrotron SOLEIL est optimisée à l’aide d’algorithmes génétiques multiobjectifs (MOGA-ELEGANT). Le code ELEGANT est d’abord comparé avec le code étalon de SOLEIL, TRACY3. Le code MOGA est ensuite utilisé pour obtenir les meilleures configurations possible en termes d’ouvertures dynamiques et d’acceptances en énergie, qui sont fortement en rapport avec la durée de vie Touschek et l'efficacité d'injection respecti-vement. Après 1 mois de calcul sur le cluster de calcul de haute performance de SOLEIL en utilisant 200 CPU, un ensemble de solutions est trouvé. Elles sont testées expérimentalement dans la salle de contrôle du SOLEIL. L'amélioration de la durée de vie Touschek obtenue est confirmée par les mesures : la durée de vie du faisceau de l'anneau de stockage de SOLEIL est accrue de 50 à 60%. La deuxième partie de ce travail de thèse présente une étude expérimentale de la durée de vie du faisceau de l'anneau de stockage de SOLEIL. En particulier les contributions de la durée de vie Touschek et la durée de vie de gaz sont étudiées. La durée de vie du faisceau est mesurée en fonction de paramètres importants tels que le couplage, racleurs horizontaux et verticaux, et le courant. Les résultats expérimentaux sont comparés avec les durées de vie Touschek calculées par la formule Piwinski mise en œuvre dans le code TRACY3 et la durée de vie du gaz calculée analytiquement. Cette étude permet de montrer que la composition du gaz résiduel et la pression locale varient de manière importante le long de toute la machine: l’effet des ondulateurs sous-vide est dominant. Des nombres atomiques effectifs sont obtenus. La forme des courbes expérimentales est proche des courbes simulées et est compatible avec un nombre atomique effectif proche de 7. / This thesis is dedicated to the optimization of the nonlinear beam dynamics of synchrotron radiation light sources using Multi-objective Genetic Algorithms (MOGA-ELEGANT). In the first part the ELEGANT code is benchmarked against TRACY3; then MOGA is tuned and used to find the best settings of quadrupole and sextupole magnets in order to maximize the dynamic and momentum apertures, strongly related with the Touschek lifetime and the injection efficiency respectively. Solutions obtained after one month of computation in the high level computational cluster of SOLEIL using 200 CPUs are analyzed. The improvement of the Touschek lifetime obtained with MOGA is confirmed by the beam-based experiments. The beam lifetime of the SOLEIL storage ring is increased 50-60 % .The second part this PhD work is devoted to study experimentally the beam lifetime of the SOLEIL storage ring to improve the understanding of the beam lifetime and its contributions: the Touschek and gas lifetimes. The beam lifetime is measured in function of important parameters as coupling, horizontal and vertical scrapers, and bunch current. The experimental results are compared with the simulated ones. The Piwinski formula is implemented in the tracking code TRACY3 to replace Bruck approximation. The gas lifetimes were computed using analytical models. This study allows understanding that the composition of the residual gas and the local pressure along all the machine vary significantly between the arcs and the in-vacuum insertion devices: new effective atomic number are obtained. This type of measurement remains difficult to analyze without a large error margin; in-vacuum insertions have a dominant contribution. The shape of the experimental curves is closed to the expected ones and compatible with an effective atomic number of about 7.

In this thesis, the structural and mechanical changes, which took place in flake graphite cast iron after electron beam surface melting and chrome-nickel surface alloying, were studied. Furthermore, the effect of set parameters on properties and depth of the melted and alloyed region is also analyzed. In the experimental part, the analyzed microstructures, micro-hardness and the distribution of elements after melting and alloying, were presented. Structural differences of material regions caused by melting were described based on microstructures. In the end of diploma thesis, the conclusions of using EB technology for surface melting and alloying were discussed.

The aim of the diploma thesis is to evaluate the mechanical properties and fracture behavior of the weld join Ti6Al4V titanium alloy prepared by using an electron beam technology. The theoretical part deals with the welding of titanium alloys with the help of electron beam, the weldability evaluation of titanium alloys, the influence of electron beam welding on the microstructure and the methods of testing of weld joints. Using the experiments, the mechanical properties of the base material and the weld were evaluated and a structural analysis of the weld was performed.

Thermal barrier coatings (TBCs) are commonly used for thermal protection of components in modern gas turbine application and typically consisting of ceramic top coat and CoNiCrAlY bond coat (BC), both thermally sprayed. Nanostructured CoNiCrAlY bond coatings were deposited onto Ni-based alloy (Inconel 718) by both HVOF and CGDS spraying techniques. Subsequently the deposits were remelted by electron beam up to depth of about 100 m which resulted in removal of defects on the substrate to the bond coat interface. The primary objective of this thesis was to investigation of the influence of parameters used for EB remelting, including multiple remelting on the microstructural changes, phase modification and final state of the coatings. The amount of porosity in the coatings and surface roughness has been evaluated. Scanning electron microscopy and X-Ray diffraction were performed in order to characterize the phase modification before and after the applied treatment. The results indicated that multiple remelting process improved the coating properties in terms of porosity, smooth surface, strength and chemical homogeneity and at last but not least this study demonstrate that low-temperature processing of CoNiCrAlY bond coat represents an interesting and promising alternative for their manufacturing.

The master thesis is dealing with characterization of the structure and properties of the YSZ thermal barrier coating deposited by water hybrid plasma spray technology on the CoNiCrAlY bond coats modified by using electron beam and vacuum annealing. Deposition of the bond coats was performed via high velocity oxy-fuel technology and cold spray. In case of experimental evaluation, the microstructure and chemical composition of the ceramic top coat deposited with powder and suspension feedstock was analyzed. The same analysis procedure was used also for bond coats after electron beam remelting by using two sets of parameters. Furthermore, the changes in microstructure and chemical composition of the remelted and annealed bond coats was evaluated. Eventually, the micromechanical properties of the top coats and the bond coats were measured. The ceramic top coats deposited with powder feedstock exhibited the structure composed by splats, while the top coats deposited in form of suspension showed fine structure with columnar grains. The dendritic structure was observed on remelted bond coats. The annealing process had an influence on the structure in form of coarsened phases and the chemical composition was changed due to diffusion of the elements.

This thesis is focused on Radiation damage of samples in low-voltage transmission electron microscopy. In thesis is general description of transmission electron microscopy and their important parts. There is described how samples are damaged by primary electron beam and how samples for transmission electron microscopy are prepared and which degradation occurs from the point of view materials of sample and time dose of electrons from primary electron beam.

Magnetické vortexy jsou charakterizovány směrem stáčení magnetizace a polarizací vortexového jádra, přičemž každá z těchto veličin nabývá dvojice stavů. Ve výsledku jsou tak k dispozici čtyři možné stabilní konfigurace, čehož může být využito v multibitových paměťových zařízeních. Tato dizertační práce se zabývá selektivním zápisem stavů magnetického vortexu v magnetickém disku pulzem elektrického proudu stejně jako jejich následným elektrickým čtením. Před samotnou realizací elektrických měření byla provedena statická měření přepínání stavů vortexu pomocí různých proudových pulzů v kombinaci s technikami MFM a následně MTXM. Následně byl realizován dynamický odečet stavu vortexu kompletně založený na elektrických měřeních. Ovládání cirkulace vortexu je založeno na geometrické asymetrii vytvořené oříznutím magnetického disku a vytvořením fazety. Plochý okraj disku definuje preferenční smysl stáčení cirkulace během procesu nukleace vortexu. Řízení polarity se obvykle provádí ve dvou krocích. V prvním kroku, homogenně magnetizovaná vrstva s kolmou magnetickou anizotropií umístěná na dně disku definuje výchozí polaritu vortexu v době nukleace. V druhém kroku, je-li to nutné, je polarita vortexu přepnuta pomocí rychlého proudového pulzu. Proto je možné nastavit požadovaný stav cirkulace vysláním nanosekundového pulsu s nízkou amplitudou, následované nastavením polarity pikosekundovým pulsem s vysokou amplitudou. Stavy vortexů jsou pak detekovány elektrickou spektroskopií prostřednictvím anizotropní magnetorezistence. Vzorky pro všechna statická a dynamická měření byly připraveny pomocí elektronové litografie v kombinaci s lift-off procesem.

The presented Diploma thesis deals with the computer-generated diffractive structures or rather called computer generated holograms (CGH). We follow basic principles of classical holography and in the context of which we define a synthetic holography. We then show various types of digital holograms and methods of measurement of their quality. We deal with several iterative algorithms useful for computation of the Fourier transform as well as with methods of phase quantization. In the second part of the work, we describe briefly our computer code for iterative Fourier transform computation. With respect to the mentioned techniques, we further present the usability of the method for design of computer generated holograms in reflection regime. After a short introduction to the electron beam lithography and its exploitation for the origination of computer generated diffractive optical elements. We analyze reconstructions of produced holograms and evaluate its quality.

This thesis is focused on application samples with the inner insert used for Charpy impact test. This insert is welded to additional material by electron beam with pre-selected welded parameters. These parameters were chosen from data of performed experiments on homogenous welds. Resulting heterogenous weld was performed of evaluation of the microstructure, chemical composition and microhardness. Experimental materials were used austenitic steel 17 240 and ferritic steel 17 153 used on high-temperature applications.

In this thesis I present a study of nanowires, and, in particular, I apply EBIC microscopy for investigation of their electro-optical properties. First, I describe details of the EBIC analytical technique together with a brief historical overview of the electron microscopy, the physical principles of the EBIC, its space resolution, parameters defining the signal amplitude, and the information we can acquire concerning defects, electric fields, etc. Then I focus on the characterization of LEDs based on GaN nanowires, which were analyzed in a cross-section and in a top view configurations. The EBIC measurements were correlated with micro-electroluminescence mapping. Further, I address the fabrication and measurement of nanowire-based InGaN/GaN LEDs detached from their original substrate. I present the EBIC measurements of individual nanowires either cut from their substrate and contacted in a planar geometry or kept standing on supphire substrate and cleaved to reveal the horizontal cross-section.The next part of this thesis is dedicated to an EBIC study of irregular Si nanowire array-based solar cells, and then of the regular nanowire array devices. The current generation was analyzed on a submicrometer scale. Finally, I discuss the fabrication and EBIC measurements of GaN nanowires grown on Si substrate. In particular, I show that the p-n junction was induced in the Si substrate by Al atom diffusion during the nanowire growth. / Dans cette thèse je me propose d’étudier des nano-fils, et en particulier d’utiliser la technique EBIC pour explorer leurs propriétés électro-optiques. Je décris d’abord les détails de la technique d’analyse EBIC avec un bref retour historique sur la microscopie électronique, le principe physique de l’EBIC, sa résolution spatiale, les paramètres conditionnant l’amplitude du signal, et les informations que l’on peut en tirer sur le matériau en termes de défauts, champ électrique, etc. Je m’intéresse ensuite à la caractérisation de LEDs à nano-fils à base de GaN, qui ont été observés par EBIC, soit en coupe soit en vue plane (depuis le haut des fils). Les mesures EBIC sont comparées à celles de micro-électroluminescence. Plus loin j’adresse la fabrication et la mesure de nano-fils à base de GaN séparés de leur substrat d’origine. Je présente les mesures EBIC de nano-fils uniques entiers, puis de nano-fils en coupe horizontale.La partie suivante de la thèse traite d’étude EBIC des cellules solaires à base de nano-fils Si ayant d’abord une géométrie aléatoire, puis une géométrie régulière. La génération de courant dans ces cellules solaires est analysée à l’échelle submicronique. A la fin du manuscrit je discute la fabrication et les mesures EBIC de fils GaN épitaxiés sur Si. Je montre en particulier qu’une jonction p-n est enduite dans le substrat Si par la diffusion d’Al lors de la croissance de nanofils.