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Accueil > Séminaires et conférences > Séminaires, soutenances de thèses et HDR précédents > 2011 > Séminaires 2011 > Mercredi 13 juillet à 10h30

Mercredi 13 juillet à 10h30

Prof. Gerrit Kroesen (université Tue d’Eindhoven) : "Unraveling electrical fields, ion densities and dust particle charge in an RF plasma sheath by single particle experiments under hypergravity and microgravity."

Prof. Gerrit Kroesen (université Tue d’Eindhoven) : "Unraveling electrical fields, ion densities and dust particle charge in an RF plasma sheath by single particle experiments under hypergravity and microgravity."

Mercredi 13 juillet à 10h30 - Palaiseau, salle de réunion du CPHT

The sheath of RF plasmas is studied intensively by many groups in the world. However, independent diagnostics that determine the electrical field and the ion density are scarce. When dust particles are inserted in the plasma, they will be suspended in the sheath by an equilibrium of the electrical force and gravity. The charge of these particles is unknown and very difficult to measure. I our experiments, we have exposed the plasma to hypergravity by implementing it in a centrifuge. Furthermore, we have applied microgravity by implementing the experiment in an airplane and conduct parabolic flights. In this way, the equilibrium position of the particle is determined as a function of apparent gravity, in the range 0-10 g. Also, the RF power was modulated, and the resonance frequency was recorded. By combining these experimental findings with the equation of motion of the particles, the Poisson equation, and the assumption that the sheath is collisional, the electrical field, the particle charge and the ion density can be calculated in a self-consistent way. It appears that the sheath is slightly non-linear.

Gerrit Kroesen


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Tutelles : CNRS Ecole Polytechnique Sorbonne Université Université Paris Sud Observatoire de Paris Convention : CEA
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