Experimental research on species compositions of nonequilibrium air plasma based on two-color Mach-Zehnder interferometry

An experimental method for the air plasma composition based on two-color Mach-Zehnder interferometry was established. By applying two laser beams with different wavelengths, the distributions of the temperature and nonequilibrium parameter were obtained. In the arc center, the energy exchange between the electrons and heavy particles is sufficient enough to make the plasma reach the equilibrium state. In this case, by comparing the electron density and neutral particle density derived from the interferograms, the calculated species compositions of air plasma under local thermal equilibrium were validated. Additionally, the distribution of the nonequilibrium parameter indicates that departure from the equilibrium occurs at the edge of the plasma and that the nonequilibrium area gradually expands during the arc decay phase. This trend is in good agreement with the two-temperature arc simulation, indicating the validity of the two-temperature arc model in many previous works.