skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Optical emission spectroscopy of a RF plasma for laboratory simulation of Titan's aerosols

Abstract

A RF capacitively coupled plasma in nitrogen methane mixture is used to simulate the production of aerosols observed in the atmosphere of Titan, satellite of Saturn. Plasma characteristics are studied by Optical Emission Spectroscopy. The gas temperature is deduced from the rotational spectra of the nitrogen second positive system. An evolution of the electron mean energy is also pointed out from the intensity evolution of this second positive system. A tentative of correlation between plasma spectroscopy and solid particles composition is done.

Authors:
;  [1];  [2];  [3]
  1. Service d'Aeronomie, CNRS-UVSQ-UPMC BP No 391371 Verrieres le Buisson (France)
  2. GREMI, University of Orleans, BP 6744 - 45067 Orleans France (France)
  3. LISA, University of Creteil, 94010 Creteil (France)
Publication Date:
OSTI Identifier:
20726763
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 799; Journal Issue: 1; Conference: 4. international conference on the physics of dusty plasmas, Orleans (France), 13-17 Jun 2005; Other Information: DOI: 10.1063/1.2134615; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AEROSOLS; CORRELATIONS; ELECTRONS; EMISSION SPECTROSCOPY; EVOLUTION; METHANE; MIXTURES; NITROGEN; PARTICLES; PLANETARY ATMOSPHERES; PLASMA; PLASMA DIAGNOSTICS; SIMULATION; SOLIDS

Citation Formats

Cernogora, G., Szopa, C., Boufendi, L., and Jolly, A. Optical emission spectroscopy of a RF plasma for laboratory simulation of Titan's aerosols. United States: N. p., 2005. Web. doi:10.1063/1.2134615.
Cernogora, G., Szopa, C., Boufendi, L., & Jolly, A. Optical emission spectroscopy of a RF plasma for laboratory simulation of Titan's aerosols. United States. doi:10.1063/1.2134615.
Cernogora, G., Szopa, C., Boufendi, L., and Jolly, A. Mon . "Optical emission spectroscopy of a RF plasma for laboratory simulation of Titan's aerosols". United States. doi:10.1063/1.2134615.
@article{osti_20726763,
title = {Optical emission spectroscopy of a RF plasma for laboratory simulation of Titan's aerosols},
author = {Cernogora, G. and Szopa, C. and Boufendi, L. and Jolly, A.},
abstractNote = {A RF capacitively coupled plasma in nitrogen methane mixture is used to simulate the production of aerosols observed in the atmosphere of Titan, satellite of Saturn. Plasma characteristics are studied by Optical Emission Spectroscopy. The gas temperature is deduced from the rotational spectra of the nitrogen second positive system. An evolution of the electron mean energy is also pointed out from the intensity evolution of this second positive system. A tentative of correlation between plasma spectroscopy and solid particles composition is done.},
doi = {10.1063/1.2134615},
journal = {AIP Conference Proceedings},
number = 1,
volume = 799,
place = {United States},
year = {Mon Oct 31 00:00:00 EST 2005},
month = {Mon Oct 31 00:00:00 EST 2005}
}
  • The atmosphere of Titan, the biggest satellite of Saturn, contains aerosols produced by the organic chemistry induced by the photochemistry of N2 and CH4, the major gaseous atmospheric compounds. In spite of their importance for the properties of the Titan's atmosphere, and for organic chemistry, only few direct information are available about them because of the limitations of the observational techniques, and their processes of formation and growth are not understood. In order to bring answers to these questions, we developed a new type of laboratory simulation to produce analogues of Titan's aerosols (known as tholins) with a low pressuremore » Radio Frequency plasma discharge. The main originality of this experiment (named PAMPRE) comes from its ability to produce particles in volume, as they are maintained in levitation by electrostatic forces compensating gravity, whereas the other experiments produce tholins on the reactors walls or a substrate. We initiated our investigations by a study of the properties of the produced particles as a function of the plasma operating conditions (i.e. amount of CH4 in N2, injected RF power, pressure, and gas flow). We here present the results of this study.« less
  • The CCP-RF discharge PAMPRE experiment produces analogues of Titan's aerosols. Here are presented the plasma characteristics as a function of gas mixtures and dust formation. Electronic density, optical emission spectroscopy, and self-bias voltage measurements are presented.
  • Titan, the biggest satellite of Saturn, have a dense atmosphere mainly composed of N2 and a few amount of CH4. High energy solar photons and electrons from the magnetosphere of Saturn generate a wide range of organic species from simple volatiles to organic solid particles. All around Titan, a dense and opaque brown aerosol layers prevents the observation of the soil. To get more information on Titan's atmosphere, the Cassini-Huygens space probes launched in 1997 and the Huygens module descend in the atmosphere of Titan on the 14th January 2005.Before the Cassini-Huygens program, laboratory simulation approach was already initiated formore » the production of analogues of Titan's aerosols, named 'tholins'. Different types of plasmas have been used. Elementary analysis of 'tholins' have also been done. From plasma modelling, the Electron Energy Distribution Function is calculated and compared to the solar energy spectrum. Some results on composition of tholins produced in RF plasmas are presented: morphology from MEB observation, elemental composition. A tentative of correlation between plasma properties and tholins composition is done.« less
  • This paper reports the modelling of CCP-RF discharges (13.56 MHz) in pure nitrogen, produced within a cylindrical parallel-plate reactor, similar to a GEC reference cell surrounded by a lateral grounded grid, at 0.1-2 mbar pressures and 10-50 W coupled powers. This study is a first step in simulating Titan's chemistry at laboratory scale, using the PAMPRE experiment. Modelling results are compared with experimental measurements of the average electron density, and the self-bias potential at the polarized electrode.
  • A radio-frequency discharge in a N{sub 2}-CH{sub 4} gaseous mixture is used to reproduce Titan's aerosols. To understand the dust growth mechanisms, the effect of different parameters on their size is studied. It is shown that the tholins are bigger for a large amount of methane and for a lower gas flow in the plasma. The evolution of tholins' size with plasma duration is also presented.