Time-integrated optical emission studies on laser-produced copper plasma in the presence of magnetic field in air ambient at atmospheric pressure

Abstract

We report on the effect of laser fluence variation on ablation rate and the time-integrated optical emission of copper plasma in the presence of static transverse magnetic field in air. In the presence of magnetic field, the ablation rate at 14 Jcm−2 laser fluence is around two times higher than that in the absence of magnetic field. It is attributed to an increase in melt ejection caused by recoil pressure of ablated mass in the presence of magnetic field. We also simulated the laser ablation rate using finite element method to justify that the ablation rate is higher in the presence of magnetic field. The intensity of atomic/ionic transition is enhanced in the presence of magnetic field. The enhancement in the intensity of spectral line depends on laser fluence and it is pronounced at fluence 14 Jcm−2. The intensity enhancement is due to an increase in electron-impact excitation and recombination process as a result of magnetic confinement of plasma. The ionic line also showed intensity enhancement in the presence of the magnetic field. It is due to the increase in ionization of atom in the presence of magnetic field. The ionization potential is lowered in the presence of magnetic field which results in more ionization. The electron density and temperature initially increased with fluence and then decreased slightly at higher fluence. In the presence of magnetic field, the electron density and temperature followed the same trend; however, higher compared with that in the absence of magnetic field. It is attributed to magnetic confinement of plasma. The spatially resolved optical emission measurements showed that the intensity with magnetic field decreased with lateral distance. However, it is higher than that without magnetic field up to 2 mm and beyond that the intensity with and without magnetic field remained almost the same.