Characterization of Ar/H$_{2}$/Air Supersonic Flowing Microwave Discharges

We performed a detailed characterization of a microwave cavity discharge in the supersonic flow of Ar/H$_{2}$/Air mixtures. The supersonic flow was generated using a convergent-divergent nozzle upstream of the discharge region. Gases were premixed in the stagnation chamber at room temperature by adding up to 10{\%} hydrogen and up to 45{\%} air to pure argon. A cylindrical cavity was used to sustain a discharge in the mixtures in the pressure range of 100-600 Pa. Optical emission spectroscopy was used to observe the effects of hydrogen and air admixtures to plasma parameters and populations of excited species.