Esta tese apresentada uma proposta de desenvolvimento de uma ferramenta computacional para metrologia com microtomografia computadorizada que possa ser implantada em sistemas de microtomógrafos convencionais. O estudo concentra-se nas diferentes técnicas de detecção de borda utilizadas em processamento de imagens digitais.Para compreender a viabilidade do desenvolvimento da ferramenta optou-se por utilizar o Matlab 2010a. A ferramenta computacional proposta é capaz de medir objetos circulares e retangulares. As medidas podem ser horizontais ou circulares, podendo ser realizada várias medidas de uma mesma imagem, uma medida de várias imagens ou várias medidas de várias imagens. As técnicas processamento de imagens digitais implementadas são a limiarização global com escolha do threshold manualmente baseado no histograma da imagem ou automaticamente pelo método de Otsu, os filtros de passa-alta no domínio do espaço Sobel, Prewitt, Roberts, LoG e Canny e medida entre os picos mais externos da 1 e 2 derivada da imagem. Os resultados foram validados através de comparação com os resultados de teste realizados pelo Laboratório de Ensaios Mecânicos e Metrologia (LEMec) do Intstituto Politécnico do Rio de Janeiro (IPRJ), Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburdo- RJ e pelo Serviço Nacional da Indústria Nova Friburgo (SENAI/NF). Os resultados obtidos pela ferramenta computacional foram equivalentes aos obtidos com os instrumentos de medição utilizados, demonstrando à viabilidade de utilização da ferramenta computacional a metrologia. / This thesis presents a proposal to develop a computational tool for metrology using computed microtomography (microCT) systems that can be implemented in conventional microCT systems.This study focuses on the different techniques used for edge detection in image processing.To test the feasibility of developing the tool we chose to use the Matlab 2010a. The proposed computational tool is capable of measuring circular and rectangular objects.The measures can be horizontal or circular and can be performed several measurements of the same image, a measure of multiple images or more measures of multiple images.The techniques implemented of processing digital images are global thresholding with choice of threshold manually based on the image histogram or automatically by the Otsu method, the high-pass filter in the space domain Sobel, Prewitt, Roberts, LoG and Canny and the distance between the outermost "peaks" of the 1st and 2nd derivative image.The results were validated by comparison with test results performed by the Mechanical Testing Laboratory and Metrology (LEMec) Polytechnic Intstituto of Rio de Janeiro (IPRJ), State University of Rio de Janeiro (UERJ), Nova Friburdo- RJ and the National Industry Service - Nova Friburgo (SENAI / NF).The results obtained by computational tool were equivalent to those obtained with the measuring instruments used, demonstrating the feasibility of using of computational tool for metrology.

La simulation à l'échelle mésoscopique de la déformation des renforts composites fournit des informations importantes. En particulier, elle donne la direction et la densité de fibres qui conditionne la perméabilité du renfort textile et les propriétés mécaniques du composite final. Ces analyses mésoscopiques par éléments finis dépendent fortement de la qualité de la géométrie initiale du modèle. Certains logiciels ont été développés pour décrire ces géométries de renforts composites. Mais, les géométries obtenues impliquent une simplification (notamment dans la section transversale de mèche) qui peut perturber le calcul de déformation du renfort. Le présent travail présente une méthode directe utilisant la microtomographie à rayon X pour générer des modèles éléments finis, basée sur la géométrie réelle de l'armure textile. Le modèle EF peut être obtenu pour tout type de renfort, plus ou moins complexe. Les problèmes d’interpénétrations de mèches sont évités. Ces modèles sont utilisés avec deux lois de comportement : une loi hypoélastique et une loi hyperélastique. Les propriétés de chacune d'entre elles, ainsi que les grandeurs caractéristiques nécessaires à leur implémentation dans le logiciel ABAQUS sont développées. Enfin, une identification des paramètres matériau à l'aide d'une méthode inverse est proposée. Les résultats obtenus pour les simulations de mise en forme sont comparés avec les résultats expérimentaux et montrent une bonne correspondance entre les deux. / The simulation at meso-scale of textile composite reinforcement deformation provides important information. In particular, it gives the direction and density of the fibres that condition the permeability of the textile reinforcement and the mechanical properties of the final composite. These meso FE analyses are highly dependent on the quality of the initial geometry of the model. Some software have been developed to describe composite reinforcement geometries. The obtained geometries imply simplification that can disrupt the reinforcement deformation computation. The present work presents a direct method using computed microtomography to determine finite element models based on the real geometry of the textile reinforcement. The FE model is obtained for any specificity or variability of the textile reinforcement, more or less complex. The yarns interpenetration problems are avoided. These models are used with two constitutive laws : a hypoelastic law and a hyperelastic one. An analysis of their properties is presented and their implementation in the software ABAQUS is detailed. Finally, an identification method is presented and the results of forming simulations are compared to experimental tests, which shows a good fit between the both.

La Tomographie Volumique à Faisceau Conique (TVFC) est une technologie d’imagerie tridimensionnelle très pertinente à utiliser en odontologie. Notre travail a pour objectifs de montrer ses intérêts et les applications spécifiques en endodontie. Après avoir redéfini les conséquences délétères possibles per et post opératoires des traitements endodontiques et expliqué les principes de la TVFC, nous explorons dans un premier temps les effets de la préparation canalaire in vitro à l’aide de la microtomographie à haute résolution puis, dans un second temps, la problématique et les intérêts de la création de reconstructions tridimensionnelles fiables et précises. Cette dernière partie aborde les notions de traitement des images issues de TVFC avant d’expliquer la démarche adoptée pour élaborer une classification tridimensionnelle des lésions inflammatoires périapicales d’origine endodontique sous formes numérique et physique. / Cone Beam Computerized Tomography (CBCT) is a highly relevant three-dimensional imaging technology for use in dentistry. Our work aims to show its interests and specific applications in endodontics. After having redefined the possible deleterious per and post-operative consequences of endodontic treatments and explained the principles of CBCT, we first explore the effects of in vitro canal preparation, using high resolution microtomography and then, in a second time, the problematic and the interests of the creation of reliable and precise three-dimensional reconstructions. This last part deals with the notions of CBCT image processing before explaining the approach adopted to develop a three-dimensional classification of endodontic periapical lesions in digital and physical form.

L’étude des dépôts de tsunamis est une science relativement jeune, et si de nombreux progrès ont été faits, en particulier au cours des trois dernières décennies, les techniques disponibles à l’heure actuelle ne permettent pas l’étude exhaustive des dépôts, que ce soit à cause de problèmes de conservation, fréquemment rencontrés, ou de limites liées aux techniques analytiques elles-mêmes. En effet, leur résolution spatiale s’avère insuffisante pour les dépôts fins (fractions sableuses et inférieures), soit par leur principe même (absence de visualisation en trois dimensions sur des lames minces, par exemple), soit à cause des techniques d’échantillonnage dont elles dépendent. Ce travail a permis d’explorer les applications d’une technique analytique jusqu’à présent inutilisée dans ce domaine, la microtomographie par rayons X, appliquée à trois dépôts de tsunamis : les dépôts du tsunami de Lisbonne en 1755 sur les côtes Andalouses, ceux d’un tsunami causé en 1996 dans le Lac Karymskoye au Kamchatka, et un potentiel dépôt de tsunami datant de l’Holocène à Ninety Mile Beach, sur le littoral ouest de l’Australie. Les problématiques liées aux techniques d’échantillonnage et au traitement des données brutes et à leur exploitation sont passées en revue et les solutions retenues sont exposées. Les résultats obtenus sont comparés à ceux obtenus par l’utilisation de techniques analytiques dont la pertinence et l’utilité ont été démontrées lors de précédentes études. Cette technique se révèle extrêmement utile pour les analyses structurales (organisation interne des dépôts), texturales (distributions de tailles de grains, fabrique sédimentaire et dynamiques d’écoulements), ainsi que les analyses de composition (abondances en bioclastes et en minéraux lourds par exemple). Le croisement des études structurales et texturales du dépôt du tsunami de 1755 mettent en avant des dynamiques de mise en place allant parfois à l’encontre des scenarii généralement admis et offre un nouveau point de vue sur les dépôts de tsunami. / The study of tsunami deposits is a relatively young science, and even if substantial progress has been made (especially during the last three decades) the techniques available at present day do not allow exhaustive studies of the deposits, weither poor conservation of the deposits, which is a common problem, is to blame, or because of limitations of the techniques themselves. Their spatial resolution often appears to be insufficient for fine deposits (sand size fractions and finer) because of their working principle (lack of three dimensional visualisation of structures on thin sections for instance) or because of the sampling techniques they depend on. This work allowed exploring the applications of an analytic technique, X-ray computed microtomography, which had to this day never used before for the study of tsunami deposits. Three distinct case studies have been made: deposits from the 1755 Lisbon tsunami on the western coast of Spain (Andalusia), deposits from the 1996 tsunami triggered in Karymskoye Lake, and a potential mid-Holocene tsunami deposit at Ninety Mile Beach, western Australia. Problematic linked to sampling techniques and raw data processing and exploitation are addressed. Chosen solutions are exposed. The results are compared to those obtained using techniques whose relevance and usefulness have been proven in previous studies. This technique proves to be extremely useful for structural (deposits inner organisation), textural (grain size distribution, sedimentary fabrics and flow dynamics), and composition (bioclasts and heavy minerals abundances) analyses. Crossing structural and textural analysis of the 1755 Lisbon tsunami deposit unravels deposition modes which go against the usually admitted scenario and offers a new point of view on tsunami deposits.

Orientador: Carlos Manuel Giles Antunez de Mayolo / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-28T08:31:04Z (GMT). No. of bitstreams: 1 Lussani_FernandoCesar1985-_D.pdf: 17433522 bytes, checksum: 73b3d625a81aa4bef21c60e28b981e0e (MD5) Previous issue date: 2015 / Resumo: O escopo desta tese foi o estudo, implementação, caracterização e aplicação das técnicas de imagens de raios X por contraste de fase e contraste de espalhamento. Este trabalho inicialmente descreve a formação das imagens por contraste de fase pelo método da propagação. Apresenta simulações de primeiros princípios para esta técnica comparando estes com a literatura. Em seguida reporta o desenvolvimento da instrumentação para uma estação experimental de microtomografias de raios X bem como os métodos de processamento de dados para reconstruções tomográficas. Microtomografias com alta resolução foram obtidas e são apresentadas com o intuito de caracterizar a instrumentação e suas aplicações. Essa técnica de instrumentação foi aplicada, em particular, no estudo da histomorfometria óssea em ratos Sprague-Dawley com o objetivo de quantificar os efeitos da dieta alimentar na estrutura óssea trabecular e compacta. Argumenta-se que ocorre uma ligeira tendência a diferenciação nesses tecidos em função da dieta alimentar. Além disso, neste trabalho foi implementado, caracterizado e aplicado a técnica de imagens harmônicas por espalhamento em amostras biológicas, detecção de fraturas e espalhamento anisotrópico. Também são descritos os esforços na melhoria da qualidade sinal-ruído dessa técnica / Abstract: The main scope of this work was the study, implementation, characterization and application of x-ray phase contrast and scattering constrast imaging techniques. First we describe the production of phase constrast images and early attempts to simulate phase contrast phenomena following the known literature. We also report efforts toward development of an experimental x-ray microtomography station as well as imaging processing techniques for tomography reconstruction. We present results on high resolution x-ray microtomography. This technique was applied in the study of Sprague-Dawley bone morphometric properties aiming quantification of high-fat diet effects on compact and trabecular bone structuture. It is argued about a tendency to differentiation on these tissues according to the diet. We also implemented, characterized and applied harmonic scattering imaging in biological samples, fracture detection and anisotropic scattering describing efforts to enhance signal to noise ratio in this technique / Doutorado / Física / Doutor em Ciências / 142800/2010-4 / CNPQ

<div>In contrast to traditional steel and aluminum, short fiber reinforced polymer composites (SFRCs) provide promising alternatives in material selection for automotive and aerospace applications due to their potential to decrease weight while maintaining excellent mechanical properties. However, uncertainties about the influence of complex microstructures and defects on mechanical response have prevented widespread adoption of material models for</div><div>SFRCs. In order to build confidence in models’ predictions requires deepened insight into the heterogenous damage mechanisms. Therefore, this research takes a micro-mechanics standpoint of assessing the damage behavior of SFRCs, particularly micro-void nucleation at the fiber tips, by passing information of microstructural attributes within neighborhoods of incipient damage and non-damage sites, into a framework that establishes correlations between the microstructural information and damage. To achieve this, in-situ x-ray tomography of the gauge sections of two cylindrical injection molded dog-bone specimens, composed of E-glass fibers in a polypropylene matrix, was conducted while the specimens were monotonically loaded until failure. This was followed by (i) the development of microstructural characterization frameworks for segmenting fiber and porosity features in 3D images, (ii) the development of a digital volume correlation informed damage detection framework that confines search spaces of potential damage sites, and (iii) the use of a Gaussian process classification framework to explore the dependency of micro-void nucleation on neighboring microstructural defects by ranking each of their contributions. Specifically, the analysis considered microstructural metrics related to the closest fiber, the closest pore, and the local stiffness, and the results demonstrated that less stiff resin rich areas were more relevant for micro-void nucleation than clustered fiber tips, T-intersections of fibers, or varying porosity volumes. This analysis provides a ranking of microstructural metrics that induce microvoid nucleation, which can be helpful for modelers to validate their predictions on proclivity of damage initiation in the presence of wide distributions of microstructural features and</div><div>manufacturing defects. </div>

[pt] A indústria mineral vem presenciando, ao longo das últimas décadas, uma redução da qualidade de minério de ferro extraído e o surgimento de novas demandas ambientais. Esta conjuntura fortalece a busca por produtos provenientes do minério de ferro que atendam aos requisitos da indústria siderúrgica, como é o caso de novos aglomerados de minério de ferro. A Microtomografia de Raios-X (microCT) permite a caracterização da estrutura tridimensional de uma amostra, com resolução micrométrica, de forma não-destrutiva. Entretanto, tal técnica apresenta diversas limitações. Quanto melhor a resolução, maior o tempo de análise e menor o volume de amostra adquirido. Modelos de Super Resolução (SR), baseados em Deep Learning, são uma poderosa ferramenta para aprimorar digitalmente a resolução de imagens tomográficas adquiridas em pior resolução. Este trabalho propõe o desenvolvimento de uma metodologia para treinar três modelos de SR, baseados na arquitetura EDSR, a partir de imagens tomográficas de briquetes de redução direta: Um modelo para aumento de resolução de 16 um para 6 um, outro para aumento de 6 um para 2 um, e o terceiro para aumento de 4 um para 2 um. Esta proposta tem como objetivo mitigar as limitações do microCT, auxiliando o desenvolvimento de novas metodologias de Processamento Digital de Imagens para os aglomerados. A metodologia inclui diferentes propostas para avaliação do desempenho da SR, como comparação de PSNR e segmentação de poros. Os resultados apontam que a SR foi capaz de aprimorar a resolução das imagens tomográficas e mitigar ruídos habituais da tomografia. / [en] The mining industry has been witnessing a reduction of extracted iron ore s quality and the advent of new environmental demands. This situation reinforces a search for iron ore products that meet the requirements of the steel industry, such as new iron ore agglomerates. X-ray microtomography (microCT) allows the characterization of a sample s three-dimensional structure, with micrometer resolution, in a non-destructive analysis. However, this technique presents several limitations. Better resolutions greatly increase analysis time and decrease the acquired sample’s volume. Super-Resolution (SR) models, based on Deep Learning, are a powerful tool to digitally enhance the resolution of tomographic images acquired at lower resolutions. This work proposes the development of a methodology to train three SR models, based on EDSR architecture, using tomographic images of direct reduction briquettes: A model for enhancing the resolution from 16 um to 6 um, another for enhancing from 6 um to 2 um, and the third for enhancing 4 um to 2 um. This proposal aims to mitigate the limitations of microCT, assisting the development and implementation of new Digital Image Processing methodologies for agglomerates. The methodology includes different proposals for SR s performance evaluation, such as PSNR comparison and pore segmentation. The results indicate that SR can improve the resolution of tomographic images and reduce common tomography noise.

[pt] Uma das características mais relevantes nos aglomerados de minério de ferro é a sua porosidade, que impacta fortemente no desempenho desses materiais nos processos siderúrgicos. O desempenho é diretamente dependente da existência de uma rede porosa que permite o fluxo de gases pelo interior desses aglomerados sem comprometer sua integridade física. Neste trabalho, amostras de diferentes tipos de aglomerados de minério de ferro foram caracterizadas com o auxílio de técnicas de microtomografia computadorizada de raios X (microCT), processamento digital de imagens e modelagem de rede de poros (PNM). Com isso, a influência da microestrutura desses aglomerados na variação da sua porosidade e permeabilidade foi avaliada. O uso de microCT permitiu uma visualização 3D da estrutura dos aglomerados, permitindo realizar uma análise da estrutura interna das amostras para a discriminação do espaço poroso. O pixel size ideal foi estipulado por meio de diversas capturas com resoluções diferentes. A PNM foi utilizada para realizar a simulação da permeabilidade absoluta das amostras, correlacionando com a porosidade, conectividade dos poros e diâmetro de poros e conexões. Foi realizada uma variação de mais ou menos 5 tons de cinza nos limiares de segmentação para estipular a sensibilidade do impacto desse parâmetro nos resultados da modelagem. Os dois aglomerados apresentaram porosidade parecida, em torno de 20 por cento. Os resultados para piores resoluções apresentaram uma inconsistência, em muitos casos não possuindo sequer permeabilidade. As imagens adquiridas com um tamanho de voxel de 2 micrômetros resultaram em cálculos consistentes de permeabilidade, em torno de 0,4 a 2,4 mD para os briquetes e 0,03 a 1,6 mD para as pelotas, sugerindo que os briquetes são levemente mais permeáveis. A variação do limiar de segmentação dos poros teve forte impacto nos resultados das modelagens, influenciando diretamente no valor do cálculo da permeabilidade absoluta. / [en] One of the most relevant features of iron ore agglomerates is their porosity, which strongly impacts the performance of these materials in steelmaking processes. Performance is directly dependent on the existence of a porous network that allows gas flow through the interior of these agglomerates without compromising their physical integrity. This study characterized samples of different iron ore agglomerates using X-ray microcomputed tomography (microCT), digital image processing, and pore network modeling (PNM). The influence of the microstructure of these agglomerates on the variation of their porosity and permeability was evaluated. MicroCT enabled a 3D visualization of the agglomerate structure, allowing for an analysis of the internal structure of the samples to discriminate the porous space. The ideal pixel size was determined through various captures at different resolutions. PNM was used to simulate the absolute permeability of the samples, correlating it with porosity, pore connectivity, and pore and connection diameter. A variation of more or less 5 gray tones in the segmentation thresholds was performed to determine the sensitivity of this parameter s impact on the modeling results. The two agglomerates had similar porosity of around 20 percent. The results for lower resolutions showed inconsistency, with many cases lacking permeability altogether. Images acquired with a pixel size of 2 micrometers resulted in consistent permeability calculations, ranging from 0.4 to 2.4 mD for briquettes and 0.03 to 1.6 mD for pellets, indicating that briquettes are slightly more permeable. The variation of pore segmentation threshold had a strong impact on the modeling results, directly influencing the value of the absolute permeability calculation.

[pt] O processo de formação de pelotas de minério de ferro consiste na preparação das matérias-primas, formação da pelota crua e endurecimento por meio da queima. O produto final deve ser um material poroso que permita a difusão de gases no forno de redução e que, simultaneamente, resista a compressão, característica relevante durante o transporte e no carregamento do forno. No entanto, durante o tratamento térmico e o transporte podem surgir trincas que comprometem a integridade das pelotas. A discriminação de poros e trincas é, portanto, um importante fator para a análise microestrutural e controle de qualidade do material. A microtomografia de raios-x é uma técnica não destrutiva que gera imagens tridimensionais, o que permite uma visualização completa da pelota. No entanto, a metodologia usual de processamento digital de imagens, baseada em extração de atributos de tamanho e forma, apresenta limitações para discriminar poros de trincas. Redes Neurais Deep Learning são uma alternativa poderosa para classificar tipos de objetos em imagens, utilizando como entrada as intensidades dos pixels e atributos automaticamente determinados pela rede. Após treinar um modelo com os padrões correspondente a cada classe, é possível atribuir cada pixel da imagem a uma das classes presentes, permitindo uma segmentação semântica. Nesta dissertação, otimizou-se uma rede Deep Learning com arquitetura U-Net, usando como conjunto de treinamento poucas camadas 2D da imagem 3D original. Aplicando o modelo à pelota utilizada no treinamento foi possível discriminar poros de trincas de forma adequada. A aplicação do modelo a outras pelotas exigiu a incorporação de camadas destas pelotas ao treinamento e otimização de parâmetros do modelo. Os resultados apresentaram classificação adequada, apesar de apresentar dificuldades de criar um modelo geral para discriminação entre poros e trincas em pelotas de minério de ferro. / [en] The iron ore pellet forming process consists of preparing the raw materials, forming the raw pellet and hardening by firing. The end product must be a porous material which allows gas to diffuse in the blast furnace and at the same time resists compression, which is a relevant feature during transport and loading of the furnace. However, during heat treatment and transport cracks may appear that compromise the integrity of the pellets. The discrimination of pores and cracks is therefore an important factor for microstructural analysis and material quality control. X-ray microtomography is a non-destructive technique that generates three-dimensional images, allowing a full view of the pellet. However, the usual methodology of digital image processing, based on extraction of size and shape attributes, has limitations to discriminate crack from pores. Deep Learning Neural Networks are a powerful alternative to classifying object types in images, using as input the pixel intensities and attributes automatically determined by the network. After training a model with the patterns corresponding to each class, it is possible to assign each pixel of the image to one of the classes present, allowing a semantic segmentation. In this dissertation, a Deep Learning network with U-Net architecture was optimized, using as a training set a few 2D layers of the original 3D image. Applying the model to the pellet used in training it was possible to discriminate cracks pores properly. Application of the model to other pellets required the incorporation of layers of these pellets into the training and optimization of model parameters. The results were adequately classified, despite the difficulty of creating a general model for discrimination between pores and cracks in iron ore pellets.

Afin de préciser l'origine des volatils terrestres et les flux actuels et passés vers l’atmosphère, de nombreuses études s’intéressent à la composition du manteau. Ce réservoir est échantillonné naturellement lors des éruptions volcaniques, mais une grande partie des gaz est alors émise dans l'atmosphère, de sorte que la composition des volatils du manteau reste peu contrainte. Nous cherchons à préciser les mécanismes de dégazage sous les dorsales océaniques afin de corriger ces fractionnements. L'analyse (He-Ne-Ar-CO2) de verres basaltiques issus de la dorsale des Galápagos, dans la zone d'influence du point chaud des Galápagos, montre que la composition en volatils des laves s'explique par distillation de Rayleigh d'une source unique. Cette source est distincte de celle du point chaud (isotopes du néon), impliquant un dégazage en profondeur du panache ou une hétérogénéité spatiale de sa composition.Plusieurs verres volcaniques issus de la dorsale Atlantique et Est Pacifique ont été imagés par micro-tomographie aux rayons X. L'étude met en évidence des mécanismes de nucléation et de croissance des bulles différents sous les deux dorsales. De la convection en périphérie de la chambre magmatique avant l’éruption a été mise en évidence par l’étude pétrologique des verres. Les vésicules imagées ont ensuite été ouvertes individuellement sous vide par ablation laser et analysées (CO2, 4He, isotopes de l'argon). La composition des bulles est hétérogène dans certains échantillons et compatible avec une distillation de Rayleigh. Les tendances de dégazage obtenues permettent d'obtenir localement la composition de la source mantellique, qui est hétérogène.L'étude permet également d'appréhender l'hétérogénéité des rapports 40Ar/36Ar dans les chambres magmatiques par la technique d’ablation laser qui diminue la contamination atmosphérique par rapport à la technique classique de broyage / The composition of mantle volatiles is related to the origin of Earth's volatiles and to the past and present volatile fluxes to the atmosphere. Although this reservoir is naturally sampled during volcanic eruptions, most of the volatiles are lost to the atmosphere during this event, thus the composition of mantle volatiles is still uncertain. We try here to precise the processes of degassing below mid-oceanic ridges to correct the lava compositions for degassing.The He-Ne-Ar-CO2 analyses of basaltic glasses sampled along the Galapagos Spreading Center, in the area of influence of the Galapagos hotspot, show that the volatile composition of lavas is fully explained by a Rayleigh distillation of a unique source distinct from the plume source. These results imply that the plume degasses at depth or is heterogeneous.Several volcanic glasses from Mid-Atlantic ridge and East Pacific Rise have been imaged by X-rays microtomography. The mechanisms of vesicle nucleation and growth appear to be different below the two ridges. A step of convection at the magma body margin has been evidenced by the petrologic study of the glasses. Imaged vesicles have been subsequently opened under vacuum by laser ablation and analysed (CO2, 4He, argon isotopes). We observe, depending on the samples, either a single composition for all bubbles, or variations in composition between bubbles consistent with a trend of equilibrium degassing in an open system. The trends of degassing allow extrapolating locally to the volatile composition of the mantle source, which is heterogeneous. We also studied the heterogeneity of 40Ar/36Ar ratios in magmatic chambers using the laser opening method, which lowers the contribution of atmospheric gases compared to the classical crushing method