Enhancement of optical signal and characterization of palladium plasma by magnetic field-assisted laser-induced breakdown spectroscopy

Optical emission signal enhancement from palladium (Pd) plasma by magnetic field-assisted laser-induced breakdown spectroscopy (MF-LIBS) is reported. Plasma from Pd target was produced by second harmonic generation (532 nm, 5 ns) of Nd:YAG laser using fluence values in the range of 12.6–38.1 J/cm2. In the designed experiment, the magnetic field was parallel to the axis of plasma expansion direction with a maximum strength of 0.12 T at the target surface. Optical signals of the emission from the plasma were recorded in the spectral range of 200−700 nm with a LIBS2000+ spectrometer. A significant enhancement was noticed particularly at low fluence values for both atomic and singly ionized Pd lines. For the minimum fluence 12.6 J/cm2, an intensity enhancement of 3–4 fold was observed for Pd-I and Pd-II lines and dropped exponentially for the increased fluence values. At low fluence values, the trace elements viz., Ca and Mg were detected only in the presence of magnetic field. The optical signal enhancement effect of magnetic field was different for Pd, Ca, Mg, and H; suggesting that the field enhanced effect is strictly element dependent for plasma at the same conditions. The field influenced the plasma parameters; the electron number density (ne), and temperature (T) which were increased considerably compared to without field. Expectedly, these attributes come from the plasma confinement by the external magnetic field and have been explained in the framework of magneto hydrodynamic (MHD) model.