Characterizing laser induced plasma and ablation of Mg-alloy in the presence and absence of magnetic field

Abstract

The influence of magnetic field on the plasma parameters and surface modification of Mg-alloy has been explored. Nd: YAG laser was employed at different laser irradiances changing from 0.3 GW/cm2 to 2.6 GW/cm2 to irradiate Mg-alloy under 5 torr pressure of Argon, Neon, and Helium. It is revealed that emission intensity of Mg lines are significantly reduced in the existence of field as compared to field free case. The plasma parameters such as excitation temperature (Texc) & electron number density (ne) of Mg-alloy plasma evaluated by Laser induced breakdown spectroscopy (LIBS) technique are significantly enhanced in the existence of magnetic field as compared to field free case. It is true for all irradiances as well as under all environmental conditions. It was also found that trends of both Texc and ne are increasing with increasing irradiance changing from 0.3 GW/cm2 to 2 GW/cm2. For the highest used irradiances of 2.3 GW/cm2 & 2.6 GW/cm2, the decrease in both parameters is observed. We have analytically calculated values of thermal beta, directional beta and magnetic confinement radius for laser-irradiated Mg-alloy plasma which confirm the validity of magnetic confinement. Scanning Electron Microscope analysis is utilized to explore the surface modifications of laser irradiated Mg samples and reveals the formation of hillocks, islands, craters, cones and pores. Pronounced and well-defined structuring is observed in the presence of field as compared to field free case. It is also revealed that calculated plasma parameters play a significant role for the growth of surface structures on Mg-alloy.