Atmospheric pressure plasma jet
systems have been developed such as the RF or microwave torch
[6–8], arc discharges [9] and AC discharges [10–12] generated in
narrow tubes or capillaries with an axial geometry of the electrodes.
They have been attracting tremendous attention from researchers
worldwide. From a practical point of view, the interesting and
attractive features of these plasma systems are a long afterglow
propagating in open air and a relatively low input power. The afterglow can propagate into the surrounding air at distances from some
mm up to 10 cm when the discharge is ignited in noble gases [6–8].
It should however be noticed that even if pure noble gases are used,
the plasma jet will contain a small amount of oxygen and nitrogen species, since the APPJ generates a plasma plume which expands
into the surrounding air