Langmuir probe diagnostics of an atmospheric pressure, vortex-stabilized nitrogen plasma jet

PREVOSTO, LEANDRO; KELLY, HÉCTOR; MANCINELLI ,BEATRIZ

JOURNAL OF APPLIED PHYSICS

AMER INST PHYSICS

Lugar: New York; Año: 2012 vol. 112 p. 3302 - 3308

0021-8979

Langmuir probe measurements in an atmospheric pressure direct current (dc) plasma jetare reported. Sweeping probes were used. The experiment was carried out using a dcnon?transferred arc torch with a rod?type cathode and an anode of 5 mm diameter. Thetorch was operated at a nominal power level of 15 kW with a nitrogen flow rate of 25 Nlmin-1. A flat ion saturation region was found in the current?voltage curve of the probe.The ion saturation current to a cylindrical probe in a high?pressure non local thermalequilibrium (LTE) plasma was modeled. Thermal effects and ionization/recombinationprocesses inside the probe perturbed region were taken into account. Averaged radialprofiles of the electron and heavy particle temperatures as well as the electron densitywere obtained. An electron temperature around 11000 K, a heavy particle temperaturearound 9500 K and an electron density of about 4 × 1022 m-3, were found at the jetcentre at 3.5 mm downstream from the torch exit. Large deviations from kineticequilibrium were found throughout the plasma jet. The electron and heavy particletemperature profiles showed good agreement with those reported in the literature byusing spectroscopic techniques. It was also found that the temperature radial profilebased on LTE was very close to that of the electrons. The calculations have shown thatthis method is particularly useful for studying spraying?type plasma jets characterizedby electron temperatures in the range 9000?14000 K.