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Modélisation des phénomènes physiques intervenant au cours de l’émission électronique sous haute tension sous vide

Abstract : Electron emission in vacuum from a cathode at high voltage is an important physical phenomenon for the study of vacuum breakdown or electron sources. In the vacuum breakdown, the first step of this mechanism is electron emission at the top of the microprotrusions on the surface. Microprotrusions or emitters in electron sources have the shape of a tip. A numerical model describing the thermo-field emission has been developed for a 2D axisymmetric tip. The problem is multi-physical and it is necessary to solve problems of different natures: quantum mechanics, electrostatic, electric current and thermal heating. With this model, it is possibleto study electron emission and vacuumbreakdown when nanosecond high voltage pulses are applied. Furthermore, the study of electron emission when a picosecond pulsed laser illuminates a high voltage cathode has been performed. A new model has been developped to describe the photo-electric effect and a two-temperature model has been implemented to describe the heating of the cathode in a non-equilibrium regime. Finally, the modeling of the interaction between microparticles and electron emission from microprotusions has been realised, in order to study the breakdown voltage. Different trajectories of microparticles have been identified based on the results, depending on the electron emission current.
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Benjamin Seznec. Modélisation des phénomènes physiques intervenant au cours de l’émission électronique sous haute tension sous vide. Physique Numérique [physics.comp-ph]. Université Paris Saclay (COmUE), 2017. Français. ⟨NNT : 2017SACLS525⟩. ⟨tel-01709866⟩

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