Diagnosis of Electronic Excitation Temperature in Surface Dielectric Barrier Discharge Plasmas at Atmospheric Pressure

The electronic excitation temperature of a surface dielectric barrier discharge (DBD) at atmospheric pressure has been experimentally investigated by optical emission spectroscopic measurements combined with numerical simulation. Experiments have been carried out to deter- mine the spatial distribution of electric field by using FEM software and the electronic excitation temperature in discharge by calculating ratio of two relative intensities of atomic spectral lines. In this work, we choose seven Ar atomic emission lines at 415.86 nm
[(3s ² 3p ⁵ )5p → (3s ² 3p ⁵ )4s] and 706.7 nm, 714.7 nm, 738.4 nm, 751.5 nm, 794.8 nm and 800.6 nm
[(3s ² 3p ⁵ )4p → (3s ² 3p ⁵ )4s] to estimate the excitation temperature under a Boltzmann approximation. The average electron energy is evaluated in each discharge by using line ratio of 337.1 nm (N ₂ (C ³ Π _u →B ³ Π _g )) to 391.4 nm (N ⁺₂ (B ² Σ⁺ _u →X ² Σ⁺ _g )). Furthermore, variations of the electronic excitation tempera- ture are presented versus dielectric thickness and dielectric materials. The discharge is stable and uniform along the axial direction, and the electronic excitation temperature at the edge of the copper electrode is the largest. The corresponding average electron energy is in the range of 1.6- 5.1 eV and the electric field is in 1.7-3.2 MV/m, when the distance from copper electrode varies from 0 cm to 6 cm. Moreover, the electronic excitation temperature with a higher permittivity leads to a higher dissipated electrical power.