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, the low alloy steel samples were measured at different resolutions using dual-channel spectrometer simultaneously to discuss the plasma characteristics. The diffraction efficiency of the grating was different at different resolutions, which led to different spectral intensities measured at different resolutions. It 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, Boltzmann double lines method was applied to calculate the plasma temperature, and the analysis line was IFeI395.668/IFeI400.524. 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 analyse 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. It showed that SVR combined with the plasma state was an effective method to improve the accuracy of LIBS quantitative analysis of Mn content in low alloy steel.