Emission of charged particles from the surface of a moving target acted on by cw CO2 laser radiation

An experimental investigation was made of the emission of charged particles due to the irradiation of moving steel and graphite targets with cw CO₂ laser radiation. The characteristics of the emission current signals were determined for different laser irradiation regimes. The maximum emission current density from the surface of a melt pool (~1.1 X 10 ^– 2 A/cm²) and the average temperature of the liquid metal (~ 2040 K) were measured for an incident radiation power density of 550 W and for horizontal and vertical target velocities of respectively ~ 1.5 mm/s and ~ 0.17 mm/s. The authors propose to utilize this phenomenon for monitoring the laser processing of materials.