Enhancement of Laser-induced Annular Plasma by Parallel-Plate confinement

Abstract

This study proposes the use of two parallel plates to confine the plasma generated by an annular beam, thereby simultaneously enhancing spectral intensity and improving plasma spatial uniformity. The results demonstrate that parallel plate confinement enhances the spectral emission from the laser induced annular plasma, with a more pronounced enhancement observed for ionic lines than for atomic lines. As the distance between the parallel plates increases, the maximum enhancement factor of spectral intensity decreases, and the corresponding optimal acquisition delay shifts toward longer times.At a plate distance of 4 mm and an acquisition delay of 3 μs, the spectral intensity reached its maximum enhancement. The two-dimensional spatial evolution of spectral intensity confirms that the main reason for the enhancement of annular plasma is that the shock wave reflected by the parallel plates compresses the plasma, inhibits the lateral expansion distance of the annular plasma. The results of elemental quantitative analysis show that the annular plasma with parallel plate confinement further improves the detection accuracy and analytical performance for trace elements.