Fig. 1. Schematic diagram of the experimental device

Fig. 2. Intensities of Ni and Ba with delay time under two LIBS conditions

Fig. 3. The SNR of two elements under different conditions
(a): Ni Ⅱ 221.648 nm; (b): Ba Ⅱ 475.709 nm

Fig. 4. The enhancement factors of Ni and Ba elements with delay time

Fig. 5. Cumulative contribution rate of principal components after PCA dimensionality reduction

Fig. 6. The prediction results of Ni element using different models
(a): Lasso; (b): AdaBoost; (c): RF

Fig. 7. The prediction results of Ba element using different models
(a): Lasso; (b): AdaBoost; (c): RF