  Following up 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 (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 W have been estimated from current-voltage measurements.
Optical emission spectroscopy (OES) 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.
