Laser induced breakdown spectroscopy analysis of lunar simulants under high vacuum conditions

Abstract

Application of laser induced breakdown spectroscopy (LIBS) is considered for compositional analysis of materials on planetary surfaces. In many such applications, LIBS measurements are conducted in high vacuum and the propagation of the plume produced during laser ablation plays a significant role. Therefore a proper understanding of the plasma parameters under high vacuum is significant for any improvement in the LIBS system. In this study, hydrodynamic equations are used to model plasma dynamics. A model is used to understand laser assisted ablation and plume dynamics under high vacuum condition. Further, experimental studies are performed to analyze the lunar simulant soil. Experimentally observed lunar simulant plasma temperature was comparable with the theoretically estimated Si plasma temperature. This shows that plasma characteristic of lunar soil is mainly influenced by silicon which is the major constituent element present. The emission life time of silicon and lunar simulant are measured under different ambient pressure conditions. The measured life time is very short in vacuum as compared to that of at an atmospheric pressure. This is due to the high velocity and fast expansion of the plume under high vacuum (5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> bar) condition.