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Production d'équivalents d'aérosols de l'atmosphère de Titan par plasma radio-fréquence

Grégoire Alcouffe 1
1 IMPEC - LATMOS
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
Abstract : The experiment PAMPRE is designed to produce analogues of Ttan's aerosols, thanks to a radio frequency plasma in N2-CH4 mixtures. The first goal of this work is to study the plasma to characterize the energy source inducing this chemistry. Electron density measurements show this latter is weaker in N2-CH4 mixtures than in pure N2. A plasma study by optical emission spectroscopy show that this decrease in electron density can be compensated by an increase in their energy to maintain the discharge. The second goal is to study the growth of aerosols by ex situ and in situ measurements. Observations of the particles by SEM allow to point out the influence of experimental parameters on the aerosols size: for large amounts of CH4 or low gas flow rates, the produced particles are larger, and their diameter can reach 1 µm. With a plasma in pulsed mode, and with a duration of 10 s, the particles have a diameter of about 90 nm, close to the diameter of Titan's aerosols. A study of the plasma in pulsed mode also allowed to measure the formation time of particles, of few tenth of seconds. This formation time is reduced when the CH4 amount is low or chen the pressure is high. At last, an experimental set up was designed during this PhD to measure in situ and in real time the growth of aerosols. The measured variations of the polarization degree are fitted by Mie scattering simulations, and allow to deduce a variation of particles radius with time. The obtained growth rate are of about 4 nm per second.
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https://tel.archives-ouvertes.fr/tel-00597792
Contributor : Grégoire Alcouffe <>
Submitted on : Thursday, June 2, 2011 - 12:54:00 AM
Last modification on : Friday, January 10, 2020 - 3:42:29 PM
Long-term archiving on: : Saturday, September 3, 2011 - 2:20:48 AM

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  • HAL Id : tel-00597792, version 1

Citation

Grégoire Alcouffe. Production d'équivalents d'aérosols de l'atmosphère de Titan par plasma radio-fréquence. Astrophysique [astro-ph]. Université Versailles Saint Quentin en Yvelines, 2010. Français. ⟨tel-00597792⟩

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