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Accueil > Séminaires et conférences > Séminaires, soutenances de thèses et HDR précédents > 2009 > Soutenances de thèses et HDR 2009 > Thèse de Laurent Liard le 8 décembre à 14h

Thèse de Laurent Liard le 8 décembre à 14h

Soutenance de thèse le mardi 8 décembre à 14h00, amphi Pierre Curie à
l’Ecole Polytechnique

Transport non linéaire dans un réacteur hélicon appliqué à la propulsion spatiale.

Co-directeurs de thèse : Pascal Chabert et Jean-Luc Raimbault

Low-temperature plasmas are commonly used in the industry. In
microelectronics, the ionization rate stays usually near 10-4 . In
low-temperature plasma used for microelectronics, the ionization
fraction remains sufficiently small (around 10-4 ) so that plasma
diffusion is only driven by ion and electron fluids.

Research has tended to develop new plasmas sources with high electronic
densities, such as ICP’s or helicons, which enable significant
ionization rate, close to 1 %. These conditions become therefore close
to plasma thrusters, where the ionization rate reaches 10 %.

The present thesis is divided into two main parts : on one hand, we
investigated this high ionization regime with a fluid modeling to
understand the new transport equilibrium of the plasma, which included
the neutral fluid. The influence of the magnetic field, necessary to
create helicon waves, is addressed. Results show the apparition of a
minimum of the neutral density at the center of the discharge, called
neutral depletion in the literature. The neutrals energy equation is
also included to avoid uniform temperature assumption, dubious at high
ionization rate.

On the other hand, we present measurements of different variables
(neutral density, neutral temperature, electronic density and electronic
temperature) of the plasma in a helicon reactor. On steady state,
results confirm qualitatively the model. A study of the transient state
allows separating two causes of the neutral depletion by their time scale.


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Tutelles : CNRS Ecole Polytechnique Sorbonne Université Université Paris Sud Observatoire de Paris Convention : CEA
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©2009-2019 Laboratoire de Physique des Plasmas (LPP)

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Exploitant du site : Laboratoire de Physique des Plasmas, Ecole Polytechnique route de Saclay F-91128 PALAISEAU CEDEX
Hébergeur : Laboratoire de Physique des Plasmas, Ecole Polytechnique route de Saclay F-91128 PALAISEAU CEDEX
Directeur de la publication : Pascal Chabert (Directeur)