A plasma image-spectrum fusion correction strategy for improving spectral stability based on radiation model in laser induced breakdown spectroscopy

Abstract

Spectral fluctuation is one of the main obstacles affecting the further development of LIBS, and it is also the current research hotspot and difficulty. To meet the requirements of industrial monitoring, a novel method named plasma image-spectrum fusion laser induced breakdown spectroscopy (PISF-LIBS) was proposed to correct the spectral fluctuation and improve the quantitative accuracy. In this method, by systematically analyzing the spectral radiation model, six main factors affecting the spectral stability were obtained. Further, the standard spectrum in the ideal plasma state which is not affected by these six factors was calculated, and the deviation from the actual spectrum was obtained. According to the above analysis, the calculated deviation was mainly affected by these six factors and can be estimated through them. Therefore, this study creatively proposed to use the effective information in the plasma images and spectra to indirectly characterize the deviation, so as to realize the correction of spectral fluctuation. To verify the wide applicability of PISF-LIBS in experimental conditions, the LIBS spectra of aluminum alloy obtained under four different experimental conditions were used. After PISF-LIBS correction, the R² increased to more than 0.974, and the RMSE, MAPE and RSD of the prediction set decreased by 44.789%, 47.854% and 51.687% on average. To further verify the wide applicability of PISF-LIBS in experimental samples, alloy steel samples and pressed samples were also used. For alloy steel samples, after PISF-LIBS correction, the R² increased to more than 0.996, and the RMSE, MAPE and RSD of the prediction set decreased by 48.337%, 52.856% and 25.819% evenly. For pressed samples, the R² increased over 0.992, and the RMSE, MAPE and RSD of the prediction set decreased by 61.493%, 61.080% and 39.945% averagely. The experimental results prove the effectiveness and wide applicability of PISF-LIBS in spectral fluctuation correction.

Keywords: Laser-induced breakdown spectroscopy; Plasma image-spectrum fusion; Plasma images; Spectral instability; Spectral radiation model.