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Visualisation du plasma et des particules générés pendant l'ablation laser pulsée de peinture


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Titre du congrès :EMSLIBS 2007 (Euro-Mediterranean Symposium on Laser-Induced Breakdown Spectroscopy 2007) Ville du congrès :Paris Date du congrès :10/09/2007

Résumé

  Coupled with atomic emission spectroscopy in LIBS or with mass spectroscopy in LA-ICP-MS, laser ablation is powerful for direct chemical analysis with minimal sample preparation. Nevertheless "fractionation" may occur during matter removal which is a complex phenomenon since atoms, ions, molecular species, small and large particles or droplets can be ejected.
This study aims at understanding the phenomena involved in the generation of particles produced by laser ablation of paints. For this purpose, in situ characterization techniques are used in order to obtain real time information on both the particles plume and the plasma generated during one laser shot on the paint. The ablation is performed with an infrared pulsed Nd :YAG laser operating at a 1064 nanometers wavelength, with 100 nanoseconds pulse duration.
On one hand, the light intensity emitted by the plasma is measured through an ICCD camera at different times after the shot, which also provides information on the dynamics of the plasma. On the other hand, the particles plume is analysed through transmission and scattering measurements, in order to determine the space-time evolutions of the expanding material density as well as of the particles size. For these experiments, the plume is illuminated with a visible pulsed Nd :YAG laser operating at a 532 nanometers wavelength with a 5 nanoseconds pulse duration. A CCD and an ICCD camera measure respectively the transmitted and the scattered light intensity. All the instruments are accurately synchronized with the ablation laser so as to achieve a 10 nanoseconds time resolution.
First results have provided some frames of the plume, from the birth of the shockwave to the ejection and the expansion of the matter. The light intensity of the plasma and the light scattered by the particles appear to have independent dynamics, and their space distributions are very different.