L'objectif principal du présent travail était d'étudier, comment la cinétique du plasma change dans les conditions de dépôt d'énergie spécifique élevé dans des champs électriques réduits élevé. La décharge capillaire nanoseconde a été utilisée comme outil expérimental. Les mesures sont effectuées dans l'azote pur et dans les mélanges azote/oxygène. Les paramètres électriques de la décharge sont mesurés: la tension appliquée, le dépôt d'énergie, le champ électrique et le courant électrique. Les spectres de l'émission optique de la décharge sont obtenus. La densité électronique dans les impulsions de décharge est mesurée. La décroissance du plasma est étudiée par les mesures de la densité électronique dans la post‐luminescence de la décharge. Les processus contrôlant la décroissance du plasma sont déterminés. La dépopulation de molécules excitées sur l'exemple de l'azote moléculaire N2(C) est étudié dans des mélanges azote/oxygène. Les processus responsables de la dépopulation des espèces excitées lors de la post‐luminescence de la décharge de nanoseconde à les conditions de dépôt d'énergie spécifique élevé dans des champs électriques réduits élevé sont examinés. La distribution radiale des espèces excitées à différentes compositions de gaz sont étudiée et comparées. L'étude expérimentale et numérique des processus responsables du chauffage rapide du gaz dans l'azote pur et dans les mélanges azote/oxygène dans la post‐luminescence de la décharge capillaire à la nanoseconde sont effectuées. Les particularités du chauffage rapide du gaz aux conditions de la décharge de nanoseconde à de dépôt d'énergie spécifique élevé dans des champs électriques réduits élevé sont étudués. La modification du schéma cinétique actuellement utilisé est proposée. / The main aim of the present work was to investigate, how the plasma kinetics changes at the conditions of high specific energy deposition at high reduced electric fields. The nanosecond capillary discharge was used as an experimental tool. The measurements are performed for pure nitrogen and nitrogen/oxygen mixtures. Electric parameters of the discharge are measured: the applied voltage, the energy deposition, the electric field, and the electric current. The spectra of the optical emission of the discharge are obtained. The electron density in the discharge pulses is measured. The plasma decay is studied by the measurements of the electron density in the afterglow of the discharge as well. The processes controlling the plasma decay are determined. Depopulation of excited molecules on the example of N2(C) state of molecular nitrogen is studied in nitrogen/oxygen mixtures. The processes responsible for depopulation of excited species in the afterglow of the nanosecond discharge at high specific deposited energy at high reduced electric field are discussed. The radial distributions of the excited species at different gas compositions are investigated and compared. The experimental and numerical studies of the processes responsible for fast gas heating in pure nitrogen and in nitrogen/oxygen mixtures in the afterglow of nanosecond capillary discharge are performed. The peculiarities of the fast gas heating at conditions of the nanosecond discharge at high specific deposited energy at high reduced electric field are discussed. The modification of the kinetic scheme currently in use is proposed.

Electronic devices define our everyday lives. They are often large, rigid, and brittle. Modern medical science has come so far as to start using miniature electronic devices to monitor many types of diseases. Especially, neurological disorders pose obstacles hard to overcome when treating them but it also motivates finding methods that allow for continuous monitoring. Implementing a small electronic device inside the human body adds requirements on the device to be stretchable, biocompatible, and more. Not only is the device limited by these factors, but also, current fabrication methods are not efficient for creating nanoscale versions for these types of devices. patterninglaser ablation is a growing field for cutting out and pattern nano-materialistic devices with high precision and good repeatability. This project is focused on using a laser engraving tool from metaquip on different substrates. This project is focused on the development of methods for laser fabrication of soft neural electrodes. The requiered steps are the alignment of samples to assure good precision when engraving it with the laser engraving tool, that also will be called “laserpatterner”, finding good parameters for cutting out devices and pattern conductors for said devices. On top of that, a linear force stretching will be used to characterize samples that were cut, in the form of strips, using the laserpatterner. The stretching behavior of strips consisting of the elastomer polydimethylsiloxane, which in turn will be the insulator for silver nanowires, is examined in the stretching setup. Parameter optimization is relevant in all experiments done in this project and lay the foundations for cutting and patterning silver nanowires devices. All factors included will eventually lead to a good method for fabricating soft neural electrode devices and this project is stepping stone towards that goal. / <p>Examensarbetet är utfört vid Institutionen för teknik och naturvetenskap (ITN) vid Tekniska fakulteten, Linköpings universitet</p>

Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2016-08-26T12:45:07Z No. of bitstreams: 0 / Made available in DSpace on 2016-08-26T12:45:07Z (GMT). No. of bitstreams: 0 / Medidas de espectroscopia gama de alta resolução têm diversas aplicações. Aplicações envolvendo medidas de radioisótopos de meia-vida curta podem apresentar problemas de baixa precisão nas contagens quando a fonte radioativa está distante do detector e de perda de acurácia por efeitos de tempo morto e empilhamento de pulsos em situação de altas taxas de contagens. Um modo de minimizar esses problemas é alterando a posição da fonte radioativa durante o processo de medição, aproximando-a do detector conforme sua atividade diminui e assim maximizando o número de contagens medidas. Neste trabalho, foi desenvolvido o Movimentador de Amostras Radioativas Automatizado (MARA), um aparato de baixo custo, feito com materiais de baixo número atômico e leve, projetado e construído para auxiliar nas medidas de espectroscopia gama, capaz de controlar a distância entre a fonte e o detector, permitindo inclusive que ocorra alteração dessa distância durante o processo de medição. Por ser automatizado ele otimiza o tempo do operador, que tem total liberdade para criar suas rotinas de medidas no dispositivo, além de evitar que o mesmo tome uma parcela da dose radioativa. Foi também feita uma interface que permite controle do MARA e a programação do sistema de aquisição de dados. Foram realizados testes para otimização da operação do sistema MARA e foi verificada a segurança de operação do MARA, não apresentando nenhuma falha durante seus testes. Foi aplicado o teste de repetitividade, por meio de medições com uma fonte calibrada de 60Co, e verificou-se que o sistema de movimentação de prateleiras automatizado reproduziu os resultados do sistema estático com confiabilidade de 95%. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

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