TALIF measurements of atomic oxygen density in L2K plasma wind tunnel

Abstract

Absolute atomic oxygen concentration measurements using two-photon absorption laser induced fluorescence experimental technique have been carried out in high-enthalpy plasma flow. The measurements have been conducted in L2K hypersonic wind tunnel at DLR. The test campaign is performed at 600 A of arc current in air with a mass flow rate of 36 g/s and a stagnation pressure of 105 Pa. The averaged total enthalpy is ~8.4 MJ/kg and the temperature is assumed to be equal to 4218 K. The investigation has been conducted in the freestream and into the shock layer, i.e., 5 mm upstream from the model surface. The estimation of the atomic oxygen concentration is performed by using relative fluorescence signals considering xenon 6p’[3/2]2 transition as reference gas. The effect of the quenching for the atomic oxygen determines a reduction of the lifetimes τ, i.e., 28.8 ns in the freestream and 11.4 ns into the shock layer. The estimation of the atomic oxygen concentration is performed by using relative fluorescence signals considering xenon as reference gas. The number density is equal to ~3.33 × 1023 m-3 in the freestream and ~15.6 × 1023 m-3 into the shock layer.