Diagnosis of electron temperature and density of helium atmospheric-pressure plasma jet by using line intensity ratio

Atmospheric-pressure plasma jet (APPJ) has attracted much attention because it has been expected to be applied in medical and dental fields. However, it was hard to determine the electron temperature and density in non-equilibrium plasma such as APPJ, so they have not been treated correctly. In this study, helium excited-level number density is obtained by integration of two methods, which are optical emission spectroscopy (OES) measurement, and helium collisional-radiative model (CR model); In OES, helium line intensity can be measured, which leads to extract excited-level number densities, while in the CR model, theoretical excited-level number densities are obtained by assuming electron temperature and density as input parameters. Then, some ratios of excited-level number densities in different levels are calculated. Finally, the discrepancy of the ratios is minimized to diagnose the electron temperature and density in the He APPJ.