A first simulation of soil-laser interaction investigation for soil characteristic analysis

Abstract

Laser Induced Breakdown Spectroscopy (LIBS) is an important technique utilized in several areas including that of agriculture and space exploration. However, whilst LIBS provides a new way of analyzing chemical composition of targeted soils or rocks, the quality and repeatability of the results are affected by the terrain and soil conditions as a result of physical matrix effects which occur due to varying properties like specific heat and thermal conductivity. These physical and chemical matrix effects cause difficulties with quantitative LIBS analysis. Together with this, the diverse areas in which LIBS is utilized means that it can require varying conditions of ablation techniques. Therefore, it is prudent to investigate theoretically the effect of different soil characteristics on the ablation process. The work presented here is the first simulation based research on soil quality analysis using LIBS. Aiming to gain insights into the soil breakdown process, laser coupling, sample temperature and its sensing performance through simulation of the laser ablation of soil using finite element modelling software. The proposed model within COMSOL Multiphysics was designed and developed to study the influence of multiple nanosecond (ns) laser pulses on the surface of samples of soil with varying properties. The simulation results reveal the simulated soil sensing behaviour for the first time. The computational results were compared to those obtained from LIBS experiments conducted for the Argibot project at the University of Strathclyde.