Flexible plasma multi-jet source operated in radial discharge configuration

Following up on a recent study describing a flexible plasma source operated in planar geometry, the performance of a cold atmospheric plasma jet (CAPJ) matrix emanating radially from a soft cylindrical surface in the open air is presented. The plasma device, which has a set of small outlets produced in its side surface, has a length of 12 cm and an outer diameter of 5.4 cm. The dielectric barrier discharge (DBD) sustaining the plasma jets is generated in helium flowing between two coaxial electrodes, which are separated by both an insulating tape and a cylindrical wall made of polymer foam. Two operation modes are considered: four equidistant CAPJs at the same axial position (round brush mode) and three aligned CAPJs at constant azimuthal angle (comb mode). All discharges, excited by 15 kHz-AC voltages at 3.8 kV in amplitude, have resulted in uniform lengths and intensities of the jets. Consumed discharge powers of between 0.1 and 1.5 W have been estimated from current-voltage measurements. Optical emission spectroscopy has shown the preponderance of hydroxyl groups, nitrogen molecules, and helium atoms in the active DBD region and the jet afterglow zone. This new design of CAPJ anticipates promising applications for treating the inner surface of hollow and delicate components for activation or healing purposes.