Plasma Characteristics Due to Helium and Oxygen Mixing in Argon-Based Atmospheric Plasmas

Summary form only given. Argon, helium, and oxygen gases are frequently used as a supply gas for generating stable plasmas and/or for aiding industrial applications of atmospheric plasmas. Since each gas demonstrates its own unique characteristics, choice of the gas may be important for a particular process due to the merits and drawbacks for the application. In this paper, results are presented first about the plasma characteristics based on the pure argon or helium plasmas produced in the ambient air, and then change of the characteristics brought about by mixing of He and O₂ gases as an additive gas to the Ar plasmas. Electrical and optical spectroscopic diagnostics show the variation of plasma characteristics such as breakdown voltage, I-V curve, rotation temperature, and spatial uniformity of the plasma. In the case of 10 slm flow rate of Ar and He, respectively, both breakdown voltage (V_b) and rotational temperature (T_rot) significantly decreased from 430 V to 300 V and from 470 K to 360 K. On the other hand, in the case of O₂ (10 sccm) mixing in Ar (10 slm), V_b and T_rot increased from 435 V to 450 V and from 490 K to 570 K. These changes can be explained by understanding their gas characteristics. In addition, increase of the additive gas amount resulted in deterioration of the spatial uniformity of the plasma in all cases. The experimental results illustrate that there exists a gas mixing ratio for optimum plasma condition, and it suggests that control of the atmospheric plasma characteristics can be possible to some extent by gas mixing for particular applications