Characteristics and analysis of atmospheric pressure plasma jet under magnetic field constraint

Atmospheric pressure plasma jet possesses strong practicality in various fields such as surface cleaning, surface treatment, disinfection and sterilization, film preparation, exhaust gas and wastewater treatment. While the beneficial effects of external magnetic field on plasma jet have been reported, the influence of different magnetic fields on plasma jet discharge are yet to be fully described. This study employed three types of magnetic field to investigate the effects of atmospheric pressure plasma jet discharge. These three types of magnetic fields are parallel magnetic field, non-orthogonal magnetic field, and perpendicular magnetic field. The jet discharges were carried by two types of structure with needle ring and double ring electrodes. Experimental analysis was conducted on the electrical and optical characteristics of plasma jets generated under magnetic field constraints. To evaluate the effect of plasma jet under magnetic field constraint, the jet was applied to surface modification. The results reveal that the magnetic field confinement plays a significant positive effect on enhancing the plasma jet discharge efficiency. The discharge current, discharge power, length, luminous intensity, and spectral intensity of the plasma jet all increase with the magnetic field increasing. The results of surface modification show that the contact angle of the film surface decreases with the magnetic field increasing. Under the same conditions, the discharge effect of needle ring electrode type is better than that of double ring electrode type. Compared with non-orthogonal magnetic field and perpendicular magnetic field, applying a parallel magnetic field can result in higher discharge intensity and stronger chemical activity of the plasma jet, and higher efficiency in surface treatment.