New insights on the propagation of Pulsed Atmospheric Plasma Streams: from single jet to multi jet arrays
Résumé
Atmospheric pressure plasma propagation inside long dielectric tubes is analyzed for the first
time through nonintrusive and nonperturbative time resolved bi-directional electric field (EF)
measurements. This study unveils that plasma propagation occurs in a region where longitudinal
EF exists ahead the ionization front position usually revealed from plasma emission with ICCD
measurement. The ionization front propagation induces the sudden rise of a radial EF component.
Both of these EF components have an amplitude of several kV/cm for helium or neon plasmas and
are preserved almost constant along a few tens of cm inside a capillary. All these experimental
measurements are in excellent agreement with previous model calculations. The key roles of the
voltage pulse polarity and of the target nature on the helium flow patterns when plasma jet is
emerging in ambient air are documented from Schlieren visualization. The second part of this work
is then dedicated to the development of multi jet systems, using two different setups, based on a
single plasma source. Plasma splitting in dielectric tubes drilled with sub millimetric orifices, but
also plasma transfer across metallic tubes equipped with such orifices are reported and analyzed
from ICCD imaging and time resolved EF measurements. This allows for the design and the
feasibility validation of plasma jet arrays but also emphasizes the necessity to account for voltage
pulse polarity, target potential status, consecutive helium flow modulation, and electrostatic
influence between the produced secondary jets.