Resolution effects on spectral analysis of low alloy steel by laser-induced breakdown spectroscopy

The influence of resolution on spectral analysis is of great significance to improve the measurement accuracy of laser-induced breakdown spectroscopy (LIBS). In this study, low alloy steel samples were measured at different resolutions using a dual-channel spectrometer simultaneously to determine the plasma characteristics. The diffraction efficiency of the grating was different at different resolutions, which led to different spectral intensities measured at different resolutions. The resolution affected the LIBS spectral analysis. For plasma spectral analysis, the experimental results showed that the Boltzmann plot method was suitable for calculating the plasma temperature using the low-resolution spectra with 0.076 nm/pixel. Based on the high-resolution spectra with 0.01 nm/pixel, the Boltzmann double lines method was applied to calculate the plasma temperature, and the analysis line was I (FeI395.668)/I (FeI400.524). Due to the influence of instrument broadening, Stark broadening could only be used to characterize the electron density using the high-resolution spectra. For quantitative analysis in LIBS spectral analysis, support vector machine regression (SVR) with different inputs was used to quantitatively analyze the Mn content in the low alloy steel. The prediction accuracy of the low-resolution spectra was poor compared to the high-resolution spectra. When the input was the target spectral intensities and the plasma state, the fitting accuracy and prediction accuracy were improved. This showed that SVR combined with the plasma state was an effective method to improve the accuracy of the quantitative analysis of Mn content in low alloy steel by LIBS.