Using laser-generated air spark to suppress the self-reversal effect of laser-induced breakdown spectroscopy (LIBS) for quantitative in-situ analysis of high-concentration Al in Ti-Al alloys

Ti-Al alloy is one of the most critical alloys that the world requires today. As a result, a rapid quantitative detection method to determine the Al concentration in this alloy, which typically ranges between 5 and 50%, is required. However, due to the self-reversal effect, ordinary laser-induced breakdown spectroscopy (LIBS), one of the most advanced, accurate, fast, and inexpensive quantitative detection methods, is challenging to detect high Al concentrations in those alloys. In this study, we developed a simple method to suppress the self-reversal effect in the plasma to improve the performance of LIBS for quantitative in-situ analysis of high-concentration Al in Ti-Al alloy. We created an air spark and target plasma simultaneously using single laser irradiation to enhance the homogeneity of the target plasma. By positioning the tail of the air spark between the sample surface and the outer part of the target plasma, completely free self-reversal Al I 394.40 nm and Al I 396.15 nm emission lines are obtained both for time-resolved and time-integrated measurements. Additionally, using the results of time-integrated measurement, we achieve a linear calibration curve for Al at weight concentrations ranging from 5 to 50%, which is essentially needed for quantitative in-situ analysis.