Signal stability improvement of underwater LIBS for a submerged Al target assisted with circulating sink

Abstract

With the advantages of fast, real-time, multi-element detection and little or no sample pretreatment, laser-induced breakdown spectroscopy (LIBS) technology has a broad range of applications in seafloor hydrothermal chimneys and mineral resource exploration. However, most of the analyses are still mainly dependent on laboratory tests after sampling. Underwater LIBS suffers from low detection sensitivity and poor stability due to the attenuation of laser energy by the water and confinement and quenching effects of the plasma. For long-time underwater solids LIBS analysis, particles, debris, etc. generated by pulsed laser ablation of solid samples further degrade the underwater LIBS signal intensity and stability. Aiming at this issue, we proposed a new method for underwater solids LIBS analysis assisted by circulating sink.The effect of the circulating sink on the LIBS emission intensity and signal stability for underwater solid targets was investigated by using spectroscopy and imaging techniques with an Al target immersed in deionized water. It is shown that the emission intensity of the Al I lines is increased by 21.5% and the signal stability, i.e., relative standard deviation (RSD), is decreased by 38.8% after utilizing the circulating sink compared to the ordinary sink. The plasma image results show that the plasma obtained by utilizing the circulating sink is more compact in size, more intense in emission, and more stable. The results demonstrate that the use of the circulating sink can effectively improve the quality and stability of LIBS signals for underwater solid targets, which provides a new means of long-time laboratory LIBS analysis of underwater solid targets, and will also play an important role in the accurate quantitative analysis of underwater LIBS.