Raman detection system for in situ oxidation and ablation analysis in hypersonic wind tunnel

We have developed a system for remote Raman spectra detection in hypersonic wind tunnel, which can be used in extreme environments such as ultra-high temperature, high pressure, and complex airflow to measure in situ Raman spectra of ceramic matrix composites during oxidation, phase transformation or ablation. The designed system avoids stray light generated by windows and airflow through oblique incidence of excitation light. The time-resolved method combined with pulsed laser and intensified charge-coupled device (ICCD) was used to reduce the thermal emission background. An optical structure design based on fiber bundle is adopted to suppress the influence of aero-optical effects and mechanical vibration on Raman spectrum acquisition. We demonstrated the feasibility of in situ Raman spectra detection in a Mach 5 combustion wind tunnel system. The design of anti-interference prevents Raman spectra intensity from the influence of wind tunnel testing conditions.