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Spectroscopie DRASC en régime hybride fs/ps à haute cadence (kHz) appliquée à la thermométrie des gaz.

Abstract : Coherent spectroscopy such as Coherent Anti-Stokes Raman Scattering (CARS) is commonly used for the study of reactive media.Following the recent progress encountered in laser sources and detectors, this thesis work proposes an adaptation of the technique for temperature measurements that exploits the ultra-short pulse regime (femtosecond, picosecond) to operate at high repetition-rate.The developed hybrid fs/ps-CARS setup delivers a 30-ps probe pulse using a femtosecond laser source and a Volume Bragg Grating. The obtained spectral resolution is 0,7 cm-1, which represents, within this pulse generation framework, the state of the art. This setup is applied to ro-vibrational spectroscopy of several molecular species.The interaction in the hybrid regime is described through a CARS simulation model that has been implemented. The modelling takes into account both the amplitude and the phase profiles of the probe pulse, and its delay to the femtosecond excitation. Influence of molecular collisions in the hybrid regime is also discussed.This modelling has been validated by fitting calculated spectra on experimental spectra recorded in ambient air, and in a premixed CH4/air flame. Temperature has been then measured at atmospheric pressure in these media. The precision is similar to the hybrid fs/ps-CARS thermometry state of the art.This work validates our N2 thermometry approach based on both the developed CARS setup and simulation model. Short term perspectives of this work are measurements on real combustion chambers at ONERA, by extrapolating our simulation model at high pressure.
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Submitted on : Monday, March 26, 2018 - 5:02:58 PM
Last modification on : Tuesday, October 27, 2020 - 2:34:38 PM
Long-term archiving on: : Thursday, September 13, 2018 - 9:46:15 AM


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  • HAL Id : tel-01743825, version 1


Malik Nafa. Spectroscopie DRASC en régime hybride fs/ps à haute cadence (kHz) appliquée à la thermométrie des gaz.. Optique [physics.optics]. Université Bourgogne Franche-Comté, 2017. Français. ⟨NNT : 2017UBFCD001⟩. ⟨tel-01743825⟩