Improving signal stability and analysis accuracy in laser-induced breakdown spectroscopy by multi-directional collection

Abstract

Poor spectral signal stability has always been a key problem limiting the development of laser-induced breakdown spectroscopy (LIBS). The spatiotemporal inhomogeneity of the plasma between pulses is one of the direct causes of the poor stability of the spectral signal. In this paper, a multi-directional plasma emission light collection method is proposed and its performance is tested. The main idea is to suppress the difference caused by the spatial fluctuation of the plasma by increasing the acquisition range and size. Plasma emission spectra of 11 kinds of mixed lithium ore standard samples are collected with 7 different collection schemes. The experimental results show that the intensity and stability of Ca, Al, and Mn spectral lines collected from multiple directions significantly improved compared to the single lateral and single coaxial collection methods. The mean characteristic spectral intensities are increased by a factor of 4.41 and 6.84, respectively. Meanwhile, the mean relative standard deviation of multiple-directional (1.95%) is much smaller than that of the single lateral (4.31%) or single coaxial (4.16%). The mean coefficient of determination of the univariate linear regression is also improved from RL2¯=0.8722 (single lateral) and RC2¯=0.8849 (single coaxial) to RC+4L2¯=0.9351 (multiple-directional). The innovative and developed system based on LIBS and the multi-directional plasma collection method can effectively improve the detection repeatability and accuracy and has application values in sample measurement.