The effect of target position on Al plasma characteristics induced by a 355 nm nanosecond laser in the presence of an external non-uniform magnetic field

Abstract In this work, the effect of target position on Al plasma characteristics induced by a 355 nm nanosecond laser in the presence of an external non-uniform magnetic field was investigated by using the optical emission spectroscopy and fast imaging. The time-resolved spectra were recorded at various sample positions within the magnetic field at different time delays. It was observed that all spectral lines emitted from the Al ions or neutral atoms were enhanced in the presence of the magnetic field, and the emission intensity reached its maximum peak at delay time of 150 ns for Al II 281.6 nm and delay time of 600ns for Al I 394.6 nm. At the early stage of plasma plume expansion, the plasma plume front at M position is longer than that of at B position. As the delay time increasing, under the confinement of magnetic pressure, the plasma plume fronts for two position are near same. The observed differences in emission intensity at the various positions were attributed to the curvature and gradient of the magnetic field.