Research of continuous wave CO₂ laser-sustained Ar plasma

To investigate the fundamental characteristics of argon (Ar) plasma generated by a continuous wave CO₂ laser under various gas pressures and power levels, a continuous wave CO₂ laser was employed to sustain Ar plasma within a power range of 250 W to 500 W and in an argon environment with pressures ranging from 0.3 MPa to 0.6 MPa. Experimental data on the centroid position, stability, and morphological properties of the plasma were obtained. The results show that as the gas pressure increased from 0.3 MPa to 0.6 MPa and the laser power increased from 250 W to 500 W, the centroid of the Ar plasma move in the direction opposite to the incoming laser. The standard deviation of the plasma centroid position decreases from 0.04827 mm to 0.02135 mm, indicating improved stability. Regarding the morphological characteristics of the Ar plasma, it was observed that with increasing pressure, the volume of the plasma decreased while its brightness increased, and the sphericity ratio decreased, leading to a more spherical shape. An increase in laser power maintained the plasma's stable ellipticity while only increasing its size. Using the shadowgraph method, periodic rising air currents were observed around the plasma, confirming the critical impact of thermal gravitational convection on the stability of the plasma. The basic characteristics of Ar plasma excited by CO₂ laser under different conditions are obtained, which provides a theoretical basis for optimizing the plasma light source.