Two-dimensional profile measurement of plasma parameters in radio frequency-driven argon atmospheric pressure plasma jet

Abstract

The two-dimensional profiles of the electron density, electron temperature, neutral translational temperature, and molecular rotational temperature are investigated in an argon atmospheric pressure plasma jet, which is driven by the radio frequency of 13.56 MHz by means of the laser scattering methods of Thomson, Rayleigh, and Raman. All measured parameters have maximum values at the center of the discharge and decrease toward the plasma edge. The results for the electron temperature profile are contrary to the results for the microwave-driven plasma. From our experimental results, the profiles of the plasma parameters arise from the radial contraction of plasmas and the time averaged profile of the electric field, which is obtained by a microwave simulation performed under identical conditions to the plasma jet. In the case of the neutral temperature, a higher translational temperature than the rotational temperature is measured, and its discrepancy is tentatively explained in terms of the low ion-neutral charge exchange rate and the additional degrees of freedom of the molecules. The description of our experimental results and the underlying physics are addressed in detail.