Spatial distribution of plasma parameters of N2/O2 cascaded arc jet

The operation of cascaded arc jets in arc-heated wind tunnels for thermal protection material testing has largely been limited to inert gases, nitrogen gas or their mixtures. As a result, the plasma parameters of air or N 2 /O 2 mixture cascaded arc jet have not been extensively characterized. In this study, an N 2 /O 2 cascaded arc jet was generated using a decoupled injection scheme, in which nitrogen was introduced upstream near the cathode and oxygen was injected downstream through a symmetric six-hole nozzle. This configuration produced an air-equivalent arc jet while reducing cathode oxidation and ablation. Optical emission spectroscopy and Langmuir probes were used to obtain spatially resolved plasma parameters. At an arc current of 50 A and a total flow rate of 2 slm, the rotational temperature, vibrational temperature, and maximum electron density were 1950 K, 3750 K, and 3.41 × 10 17 m −3 , respectively. Radial profiles decreased monotonically from the jet center to the edge, while axial profiles decayed downstream from the nozzle exit. Electron and current densities increased with gas flow rate and arc current, consistent with enhanced collisional ionization. These results provide quantitative data for N 2 /O 2 cascaded arc jets and support improved thermal protection material testing and high purity flow simulation.