Influence of Ar Gas Flow Rate on the Properties and Coupling Behavior of Iron Plasma

Abstract

Optical Emission Spectroscopy (OES) was used to study the features of Fe plasma according to the Ar gas flow rate. With increasing gas flow rate from 1.0 to 2.0 L/min, the electron temperature increased from 0.369 to 0.480 eV, and the electron density increased from 12.162 ± 0.58 ×1017 to 13.851±0.67 ×1017 cm⁻³. There was also an increase in plasma frequency (9.90×10¹² to 10.57×10¹² Hz) and a slight increase in Debye length (4.091±0.32 ×10⁻⁶ to 4.373±0.37 ×10⁻⁶ cm). These trends suggest that increased flow rates promote a higher degree of excitation and steadiness, producing stronger supporting gas (N₂ and Ar) and Fe I emission lines. In addition, an analysis of the behavior of the coupling parameter (Γ) indicates that plasma remains near ideal with Γ = 0.671±0.19, 0.561±0.08, and 0.539±0.08 with the average inter-particle distance of 5.8116±0.41, 5.6111±0.37, and 5.5651±0.39 nm, respectively. As the Ar flow rate increases, Γ decreases, indicating that under higher gas flow conditions, the plasma is closer to an ideal state and less strongly coupled.