Infrared diode laser absorption spectroscopic characterization of the free-stream in the f4 wind tunnel

We report here on measurements performed with the infrared diode laser absorption spectroscopy (DLAS) in the hypersonic flows generated in the ONERA-F4 high enthalpy hot shot wind tunnel. Velocity and temperature characterization of the free stream of air or CO/sub 2/ flows has been carried out in a series of calibration tests aiming to better understand real-gas/chemistry and pollution effects typical to this kind of wind tunnel. We present a few results of measurements in air flows which have been seeded with carbon dust to enhance pollution effects in the aim to better quantify these effects. We also,describe measurements on both CO and CO/sub 2/ molecules for CO/sub 2/ flows, which have a more complex chemistry than air flows.