Evaluation of discharge uniformity and area in surface dielectric barrier discharge at atmospheric pressure

•We estimate discharge uniformity and discharge area by image processing method.•Diffuse discharge with a larger area behaves a good uniformity and stability.•Surface discharge uniformity and area is not sensitive to the applied frequency.•Admixture of noble gases makes the large-scale diffuse discharge more likely to form.•Proper gas flow velocity produces an accumulation of metastable and active species.

The discharge uniformity and area of surface dielectric barrier discharge (DBD) has recently attracted lots of attention. In this study, morphological images of surface DBD are acquired by an intensified charge-couples device (ICCD) camera from the top view of the exposed electrode. Spatial and transient characteristics of plasma have been visualized with the gate width of 5 μs and 120 μs The discharge uniformity and discharge area are respectively estimated by calculating the number of pixels and the full width at half maximum (FWHM) of gray frequency by MATLAB software with microsecond time scale. The results offer a new estimated method for the characteristics of homogenous discharge. The formation of diffuse plasma mainly depends on an increase of the ionization coefficient and a creation of sufficient seed electrons by the Penning Effect at low electric fields. Accordingly, experimental measurements show that the diffuse discharge with a larger area behaves a good uniformity and stability comparing with the filamentary discharge. Applied frequency is not capable of exerting significant influence on the discharge uniformity and area. By adding noble gases into N2, the diffuse discharge is more likely to form. And the diffuse discharge also can be stabilized by the helium flow with gas velocity of 0.6–0.8 cm/s.