An underwater microimage long-pulse LIBS system: Development and preliminary testing

In recent years, underwater systems based on Laser-Induced Breakdown Spectroscopy (LIBS) technology have successfully performed elemental analysis of seawater and seabed minerals. Long-pulse LIBS has demonstrated its advantages for deep-sea mineral in-situ detection. However, current reports on deep-sea long-pulse LIBS systems face challenges such as large system size, the requirement for commercial long-pulse laser, and the lack of synchronized imaging capabilities. These issues have somewhat hindered the further application of long-pulse LIBS in deep-sea exploration. This paper presents, for the first time, a miniaturized deep-sea long-pulse LIBS in-situ detection system with integrated microscopic imaging capabilities (iLIBSea). The system uses a custom-designed, commercially available compact long-pulse laser, and incorporates a synchronized microscopic imaging module with a 1.46*1.46 mm field of view and a lateral resolution of 7.8 μm. The system has a maximum operational depth of 5000 m and a total weight of 60 kg. Through special design, the ultraviolet spectral signal is preserved to the maximum extent. High-quality spectral detection was achieved with a low energy of 4 mJ, and the detection limits for Cu and Mn were determined to be 97.1 ppm and 21.7 ppm, respectively. And the long-pulse LIBS was able to acquire high-quality spectra even under simulated 50 MPa pressure conditions. With the further system miniaturization, the long-pulse LIBS system would be widely used in deep-sea mineral exploration.