Literatura académica sobre el tema "Cathode émissive"
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Artículos de revistas sobre el tema "Cathode émissive"
-VANOVERSCHELDE, André. "Tubes à cathodes froides à émission de champ". Revue de l'Electricité et de l'Electronique -, n.º 04 (2001): 35. http://dx.doi.org/10.3845/ree.2001.042.
Texto completoBrenac, A., R. Baptist, G. Chauvet y R. Meyer. "Caractéristiques énergétiques de cathodes à micropointes à émission de champ". Revue de Physique Appliquée 22, n.º 12 (1987): 1819–34. http://dx.doi.org/10.1051/rphysap:0198700220120181900.
Texto completoTesis sobre el tema "Cathode émissive"
Sary, Gaétan. "Modélisation d'une cathode creuse pour propulseur à plasma". Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30182/document.
Texto completoA hollow cathode is a critical component of plasma thrusters. In a plasma thruster, a propellant gas is ionized in a discharge chamber and accelerated out of it so as to generate thrust. In Hall thrusters in particular, the ionization of the gas is caused by an intense electron current (from a few to hundred amps) which flows through the discharge chamber. The hollow cathode is the device which is responsible for providing the discharge current. This key element is often idealized in thruster numerical models and its physical behavior is rarely studied for its own sake. Yet, developing high power Hall thrusters, designed to propel in the long run every type of space mission, requires new hollow cathodes able to supply an intense electron current (over 100 A) over a duration on the order of ten thousand hours. So far, designing new cathodes proved difficult because of the lack of model capable of predicting the performance of a cathode based on its design. In this work, we build up a predictive model of a hollow cathode capable of simulating the physics relevant to the operation of the cathode. In the end, we aim at using this model to associate design characteristics of the cathode to key aspects of the cathode performance during operation. Our goal with this model is to guide the development of future high power hollow cathodes. We will first briefly describe the range of application of hollow cathodes related to space propulsion. Then we will give a brief account of the working principles of the cathode and we will set the numerical models available in the literature prior to this one out. The numerical model developed in this work will then be described. It includes a fluid treatment of the plasma as well as an account of the heat fluxes to the walls which largely control the performance of the cathode. Simulation results will be thoroughly compared to experimental measurements available in the literature and specific aspects of the model will be refined to match up simulation results with the physical reality. For instance, a model that specifically represents the transition region between the internal plasma of the cathode and the plume of the cathode will be described. This model will enable us to highlight plasma instability phenomena which were so far observed experimentally, yet never properly included in hollow cathode models. Using the model just developed, we will analyze the physics of a particular hollow cathode which has been developed by NASA at the Jet Propulsion Laboratory, the NSTAR hollow cathode. Then, thanks to the numerical model, we will be able to carry out a parametric study revolving around the design of the NSTAR cathode. This will allow us to bring out the influence of the design on the cathode performance and we will eventually express recommendations regarding the design of future high power cathodes. To conclude, the versatility of the numerical model built up here will also be displayed through simulations of the behavior of a hollow cathode based on an alternate geometry
Désangles, Victor. "Forçage à grande échelle d'une colonne de plasma faiblement magnétisée : influence d'une cathode émissive de grande taille". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEN064/document.
Texto completoThe goal of this PhD is to develop a setup controlling the rotation profile of a plasma column. This study is realized within the aim of developing a new type of experiments using the strongly ionized plasmas to study magnetic induction phenomena. A great number of plasma diagnostics have been set up during the PhD, including electrostatic and optical diagnostics. These measurement technics have allowed us to characterize the evolution of the plasma parameters depending on the experimental conditions and to build a better description of the plasma. A special focus has been made on the measurement of the ion temperature by two different setups: a Fabry-Pérot with a high finesse and a Laser Induced Fluorescence (LIF) setup. The mean azimuthal velocity profile of the plasma has been measured using Mach probes and explained based on the plasma parameters radial profiles. The effect of localized current injection inside the plasma by a large size emissive electrode has been studied. We have shown that the shape and the amplitude of the velocity profile can be controlled thanks to this setup. Finally, the appearance of drift waves with high magnetic fields has been observed, along with the interaction between the current injection and the dynamic of these waves
Pagaud, Francis. "Control and stability of magnetised plasma columns : plasma-cathode interactions and helicon plasma operation". Electronic Thesis or Diss., Lyon, École normale supérieure, 2024. http://www.theses.fr/2024ENSL0016.
Texto completoRadial transport, azimuthal waves and instabilities are common features in magnetised plasmas, causing major challenges for plasma propulsion, plasma wakefield particle acceleration or fusion devices. Plasma properties control is desirable yet complex. This PhD thesis follows two goals, one being the use of an emissive cathode as a new parameter control and the other being the fundamental understanding of the helicon plasma operational stability. Firstly, the role of the injection of electrons inside a magnetised plasma column has been studied experimentally and numerically. The experimental set-up is a 80 cm long and 20 cm diameter vacuum vessel connected to a 11 cm wide glass tube. The argon gas at a base pressure of 0.13 Pa is ionised by a 3-turns inductive radio-frequency antenna supplied at 1 kW. Magnetic field ranging from 170 G to 340 G, ensures a weak magnetisation of the plasma. A large tungsten hot cathode was placed at the end of the plasma column to inject an important thermionic current. Electrical and optical measurements of the cathode temperature revealed a highly inhomogeneous cathode temperature profile due to plasma–cathode interactions. A detailed thermal modelling solved numerically accurately reproduces the heterogeneous rise in temperature witnessed experimentally. The operating regime was predicted in excellent agreement with experimental results.The fine understanding of the emissive cathode behaviour in presence of a surrounding magnetised plasma permitted to explore its influence on the plasma properties, and especially the plasma potential. An analytical approach based on a two-fluids plasma model and anisotropic electrical conductivities, predicting plasma potential control and plasma rotation regulation as a function of thermionic emission, has been applied and compared to a wide experimental dataset of plasma properties. The works presented confront the role of cross-field ion transport to experimental radial plasma potential scans with a semi-quantitative agreement, highlighting a new major application of emissive cathodes.Finally, a state-of-the-art helicon plasma source has been implemented to produce higher ionization rates. This new system required a complete characterisation of plasma properties through electrostatic probes and high-speed camera imaging. It reproduced well-known helicon plasma features such as E-H-W mode transitions, bistability and hysteresis, chirality emerging from the external magnetic field direction and the propagation of m = +1 whistler waves. Besides, it displayed complex behaviours such as H-W and W-W oscillations, or coexisting low-frequency Kelvin-Helmholtz and Rayleigh-Taylor instabilities. A strong multiscale core instability at 1080 G was also briefly investigated. Wave-mode identification based on theoretical growth rates, 2DFT modal decomposition and POD has been conducted, unravelling the physical mechanisms at stake
Boutoudj, Rachid. "Conception technologique et modélisations de réseaux de micropointes à émission par effet de champ sur matériau GaAs". Lille 1, 2002. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2002/50376-2002-195-196.pdf.
Texto completoSabaut, Lucie. "Cathode commutable à nanotubes de carbone pour tube à rayons X". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX078/document.
Texto completoThis work chooses to improve the electron source by replacing thermionic emission with field emission. More especially, carbon nanotubes based cold cathodes stand out by their ability to supply high currents (>1A/cm^2) while responding fast.Through the development of an innovative structure of in-plane gated carbon nanotube based cathode, this study aims at making switchable and regulated sources for miniature, portable or polyvalent X-rays sources.The electrostatic modelling of the new structure led to the fabrication of optimized gated cathodes, where a vertically aligned array of carbon nanotubes is grown. Default analysis allows to get reliable insulated devices.Field emission characterization shows unprecedented current modulation of 10^6 at +/-40V bias voltage. Current regulation is also achieved with a stability of 0.02% over 100 h.Another structure with a burried gate electrode was designed to successfully cope with leak current and parasitic growth. A new way of growing short and thin nanotubes was tackled.Finally, gated cathodes were integrated in a compact X-ray tube and showed a current modulation of 2000 at a high voltage of 60 kV
Kropfeld, Pascal. "Conception et caractérisation de réseaux de microémetteurs à effet de champ sur matériau GaAs". Lille 1, 1999. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1999/50376-1999-379.pdf.
Texto completoYaradou, Olivier. "Simulation, conception et caractérisation de microcathodes à émission de champ sur arséniure de gallium : intégration d'une grille de commande". Lille 1, 2000. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2000/50376-2000-49.pdf.
Texto completoFall, Papa Alioune. "Contribution à la modélisation du circuit d'entrée d'un tube à cathode froide". Lille 1, 2003. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2003/50376-2003-23.pdf.
Texto completoPlankl, Elke. "Contribution à la construction et à la mise au point d'un système de détection pour le plan focal du spectromètre magnétique BBS : application à l'étude de la décroissance par émission de neutrons d'états résonnants peuplés par la réaction (4He, 3He) à 42 MeV/u dans les noyaux 208Pb et 209Pb". Paris 7, 1999. http://www.theses.fr/1999PA077202.
Texto completoCadoret, Katell. "Etude de matériaux à base d'oxydes ou de tungstates de terres rares pour la réalisation de cathodes thermo-émissives : relations entre les propriétés physico-chimiques, l'émission thermo-électronique et le vieillissement en service". Orléans, 2001. http://www.theses.fr/2001ORLE2014.
Texto completo