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International audience; Potential and density structures in the vicinity of a RF electrode/antenna in a magnetized plasma are investigated using a RF compensated cylindrical Langmuir probe. These measurements were performed in the ALINE plasma device in which only electrons can be considered as well magnetized. Very precise 2-D maps of the plasma parameters are drawn thanks to a 3-D automatic manipulator on which the probe is mounted. The effect of the tilted magnetic angle between the RF biased surface and the magnetic lines is also studied thanks to a tilting electrode. Comparison of several simplistic models with the experiments proved the reliability of simple Langmuir probe measurements in such a RF and magnetized environment (space potential v.s. tilting angle of the antenna with respect to magnetic field lines, and recovering of the floating potential structure using measured currents). A fluid model based on total current density, and ion diffusion equations over the biased flux tube, provides the same density structures in front of the electrode than the measurements. Those density structures display a "bunny ears" shape, and can be explained using transverse RF and collisional current behaviour: in front of the antenna the transverse ion currents deplete the magnetized flux tube, while at the edge of the biased flux tube, the same currents rise the density.

International audience; In this paper we implement the stretched-coordinate Perfectly Matched Layer (PML) technique in [Texeira1998b] to emulate full power absorption outside the simulation domain for time-harmonic electromagnetic wave propagation in presence of gyrotropic dielectric tensor and curved geometry relevant for magnetized plasma devices. We recall the PML formulation as an artificial inhomogeneous lossy medium, following the stretching into the complex plane of a general system of three orthogonal curvilinear coordinates. We apply the general method in cylindrical and toroidal geometries. We then assess this technique in a simple case combining gyrotropy and coordinate curvature. Our test problem analytically quantifies the reflection of Transverse Electric (TE) cylindrical eigenmodes in a gyrotropic medium by a radial PML in cylindrical geometry. The obtained reflection coefficient involves wave, PML and geometric parameters at the PML location. The new coefficient generalizes the one obtained earlier with Cartesian coordinates, and becomes equivalent when the effects of the local cylindrical curvature at the PML (stretched) location can be neglected. These curvature effects are outlined and the limitations they impose on the properties of the PML are quantified as a function of the relevant parameters. Peculiarities related to the gyrotropy are also highlighted. Finite element calculations of the test problem in two-dimensional cylindrical geometry are exploited to verify these properties numerically. Indications are finally given on how to choose the PML parameters in order to obtain a minimal wave reflection at given numerical cost, taking into account errors associated with the numerical scheme.

International audience; Understanding and exploiting cylindrical Langmuir probe measurements in magnetized plasma is a real challenge, although this technique is the most common one used to access plasma parameters such as density, temperature, potential, etc. Since the magnetic field confines the electrons in the plasma, the measurement is actually done on the flux tube connected to the cylindrical probe. In some conditions, the I(V) characteristics displays a bump between the exponential growth and the saturation of the electronic current. We propose a new interpretation of such distorted characteristics as a function of the angle between the probe and the magnetic field lines, the RF-power and the magnetic field magnitude.; Comprendre et exploiter les mesures de la sonde cylindrique de Langmuir dans le plasma magnétisé est un véritable défi, bien que cette technique soit la plus courante utilisée pour accéder aux paramètres du plasma tels que la densité, la température, le potentiel, etc. Le champ magnétique confinant les électrons dans le plasma, le la mesure se fait en fait sur le tube de flux connecté à la sonde cylindrique. Dans certaines conditions, les caractéristiques I (V) affichent une bosse entre la croissance exponentielle et la saturation du courant électronique. Nous proposons une nouvelle interprétation de ces caractéristiques déformées en fonction de l'angle entre la sonde et les lignes de champ magnétique, la puissance RF et la magnitude du champ magnétique.

International audience; Understanding and exploiting cylindrical Langmuir probe measurements in magnetized plasma is a real challenge, although this technique is the most common one used to access plasma parameters such as density, temperature, potential, etc. Since the magnetic field confines the electrons in the plasma, the measurement is actually done on the flux tube connected to the cylindrical probe. In some conditions, the I(V) characteristics displays a bump between the exponential growth and the saturation of the electronic current. We propose a new interpretation of such distorted characteristics as a function of the angle between the probe and the magnetic field lines, the RF-power and the magnetic field magnitude.; Comprendre et exploiter les mesures de la sonde cylindrique de Langmuir dans le plasma magnétisé est un véritable défi, bien que cette technique soit la plus courante utilisée pour accéder aux paramètres du plasma tels que la densité, la température, le potentiel, etc. Le champ magnétique confinant les électrons dans le plasma, le la mesure se fait en fait sur le tube de flux connecté à la sonde cylindrique. Dans certaines conditions, les caractéristiques I (V) affichent une bosse entre la croissance exponentielle et la saturation du courant électronique. Nous proposons une nouvelle interprétation de ces caractéristiques déformées en fonction de l'angle entre la sonde et les lignes de champ magnétique, la puissance RF et la magnitude du champ magnétique.

International audience; Langmuir probe measurement is the most used technic to get access to plasma parameters : -Plasma temperature-Plasma density-Plasma potential

International audience; L’épopée, puis la tragédie offrent de Troie et de Thèbes l’image de forteresses inexpugnables, destinées cependant à tomber ou à vaciller sous les assauts de l’ennemi, agent de la Tyché. Cité en feu, cité déracinée, cité en butte à la tempête, telles sont les visions cataclysmiques qui hantent l’imaginaire ou la mémoire des assiégés, plus particulièrement des femmes, premières victimes de la guerre ; leurs cris et leurs plaintes se mêlent au fracas des armes, exprimant l’horreur de la captivité. Le tableau de la cité assiégée, dont Troie est l’archétype, revêt un caractère universel, en tant qu’il représente la vulnérabilité de toute construction humaine soumise aux fluctuations du destin.