Experimental Investigation on Atmospheric Pressure Plasma Jet under Locally Divergent Magnet Field

Regulating the parameters of the atmospheric pressure plasma jet (APPJ) is meaningful for industrial applications. Since plasma is a typical functional fluid in the magnetic field, it is possible to control the discharge characteristics via the Lorentz force. In this study, the effects of a locally divergent magnetic field on the generation and propagation of APPJ were examined experimentally. The experiments used a coplanar dielectric barrier discharge (CDBD) device driven by a 30 kHz AC high-voltage source to generate a helium APPJ. A locally divergent magnetic field of 250 mT (maximum) was applied coupled with the electric field, and noticeable enhancement was observed. The results showed that the magnetic field changed the motion state of electrons and promoted collision ionization, leading to a 40% improvement in the APPJ length (0.6 cm) and a 23% increase in the intensity of line O (777.2 nm). In addition, the spatiotemporal evolution and flow field of APPJ were diagnosed by ICCD and schlieren technique. The combination of electric and magnetic fields may effectively optimize the APPJ in practical applications.