Applying CARS to HEG at Mach 6 Conditions

Kurzfassung

The HEG (High Enthalpy Shock Tunnel Göttingen) was recently modified to produce a Mach 6 flowfield for missile research. The previously installed measurement equipment at HEG provides stagnation pressure, Pitot pressure, static pressure, heat transfer, and forces and moments. Up to now the gas temperature in the flow field could not be measured and had to be calculated by CFD. To obtain validation data for rotational and vibrational temperatures an approach based on the use of a CARS laser diagnostic (Coherent Anti-Stokes Raman Scattering) promises good results for probing nitrogen molecules in such flowfields, as demonstrated from simulations performed at Trot= 210K and Tvib= 1400K. This feasibility study describes a spectroscopic set-up for the HEG when operated at Mach 6 conditions including two calibration tools (static cell, red chamber at Mach 4.4) which are required for the laser system tests at Göttingen. Broadband CARS (602 nm to 608 nm for the Stokes laser and 532 nm for the pump laser) is proposed for single-shot measurements of temperature.