Development of Cavity Enhanced Absorption Spectroscopy for O2 Measurements in Reentry Flows
Résumé
Spectroscopic measurements involving chemical compounds in the low-concentration/pressure range and having weak absorption (02) require a very long interaction path length. Cavity Ring Down Spectroscopy (CRDS) and Multi Pass Cavity (MPC) are gas sensing tools which answer to this requirement. In both cases, light is trapped between two mirrors and travels back and forth enabling long absorption lengths. We present both approaches, involving a simple and versatile instrument, performed by detecting a forbidden transition of molecular oxygen near 766 nm during a few-ms (<=3ms) single sweep of the laser frequency.