Arc Wind-Tunnel Flow Diagnostics by Cavity-Enhanced Absorption Spectroscopy

Cavity-enhanced absorption spectroscopy was applied to an arc wind-tunnel flow to measure the number density and the temperature distributions. With installed Brewster windows on a vacuum chamber, a cavity was constructed between a pair of high-reflectance mirrors placed outside of the chamber. Consequently, sensitivity was improved by more than 2 orders of magnitude compared with conventional single-pass laser absorption spectroscopy. The temperature distribution of 0.2% diluted oxygen estimated by cavity-enhanced absorption spectroscopy shows a good agreement with that of argon estimated by single-pass laser absorption spectroscopy.