A novel cold plasma jet generated by atmospheric dielectric barrier capillary discharge

In the paper, an easy-operated scheme is presented to generate a novel kind of atmospheric cold plasma millimeter jet. The jet is achieved in several kinds of gases at atmosphere pressure, such as Ar, He and N2, in a capillary quartz dielectric barrier discharge (DBD) system powered by a pulsed power source with a frequency of 15 kHz. Via an CCD camera, the initial discharge filaments in the DBD gap are found to be transited into diffusion discharges or glow-like discharges by the flowing gas through the DBD gap and a plasma jet is formed in the outlet of the capillary simultaneously. The critical gas flow velocity for the plasma jet formation is determined to be 3–8 m/s for different gases by a well-designed Pitot tube probe. The jet range for a special gas can be changed by varying the gas flow velocity, while the jet range for different gases varies a lot and the Helium jet takes the longest range of about 44 mm when the helium flows at a velocity of about 20 m/s. Beyond the velocity limit of 20 m/s for laminar helium flow, the jet of helium plasma becomes torrent and unstable and its range turns shorter.