Design of Cold Plasma Flexible Brush and Evaluation of Its Oxidizing Plume

An easy to build design of a tabletop cold plasma flexible brush (CPFB) system is presented, wherein the ex situ helium (He) or argon (Ar) plume is available for utilization on local and remote samples in multiphase environs. The primary cold plasma is created in a floating, pyrex dielectric barrier discharge generator with bipolar HV supply at 20 kHz; downstream upon entering into a PTFE coated tygon tube, the plasma gets switched off, but thereafter reappears as ex situ plume of cross section ~7 mm
²
and visible length ≥15 mm at chosen sample location up to 2 m away. The major constituting in-plume luminous oxidizing species are O-atom, *OH radical, N*
₂
+, He*, or Ar*, while nonluminous oxidants include NO*
_x
, HNO
₃
, O
₃
, and H
₂
O
₂
. The most efficient conditions of plume generation are achieved at gas flow rates ranging from 6 to 17 mL · s
^-1
and applied high voltage from 6 to 8 kV p-p. Typically, with He flow of 10.5 mL . s
^-1
and applied 6.5 kV p-p, the total oxidants' number density near the CPFB exit is 1.9 × 10
¹¹
mm
^-3
(or 3.15 × 10
^-13
mol · mm
^-3
) and is 4.7 × 109 mm
^-3
at 11 mm from exit. With Ar flow of 10.5 mL.s
^-1
and applied 7.3 kV p-p, the corresponding values are 2.5 × 10
¹¹
mm
^-3
and 9.5 × 10
⁹
mm
^-3
, respectively. Near exit, for either gas, the oxidizing species' total maximum yield reached a value > 10 μmol · J
^-1
.