Plasma properties measurements of parallel-plane electrodes in argon by coupling OES and PLIF

Plasma properties are diagnosed in parallel-plane electrodes under 1-15 kPa within input power of 0-25 W by coupling Optical Emission Spectroscopy (OES) and Planar Laser-induced fluorescence (PLIF). Electron excitation temperature (T_e), electron density (N_e) are obtained based on the intensities and broadenings of atomic and ionic spectral lines of argon. The spatial resolution of T_e and N_e are measured by a high-precision setup based on fiber. At the gas pressure of 1 kPa, T_e reaches maximum of 8.745×10³ K while the peak of N_e appears in 15 kPa, is 3.237×10¹⁶ cm^-3 . Besides, spatial distribution of 1s₅ metastable atoms (Ar^M) with transition scheme 4s( ²P⁰ _3/2)₂ -4p ( P (²P⁰ _1/2)₁-4s(²P⁰ _3/2)₁ are revealed by PLIF, as a complementary of plasma properties. The number density of Ar^M also shows a larger number density in 15 kPa. Combined with OES, T_e, N_e and number of Ar^M are higher around the surface of anode within discharge area. The current experimental results are demonstration of optimal plasma state under different external parameters and validation of relevant discharge models