Enhancement mechanisms analysis using microwave plasma torch-assisted laser-induced breakdown spectroscopy

Abstract

Laser-induced breakdown spectroscopy (LIBS) has been extensively applied across various fields for elemental analysis, due to its rapid, in-situ, and multi-element detection capabilities. However, its application is often constrained by matrix effects and the weak signal intensity of emission spectra, particularly in the detection of irregular targets and (ultra-)trace elements. To address these challenges, this study introduces an approach to enhance LIBS spectral signal intensity through the assistance of a microwave plasma torch (MPT). Using a pure silicon target, the research systematically examines the primary mechanisms by which MPT influences laser-induced plasma under different laser energy conditions and identifies the sources of signal enhancement, resulting in significant improvements in LIBS spectral intensity. The MPT-assisted enhancement was further validated using an aluminum alloy target, confirming that the effect is non-selective and can significantly improve the LIBS signals for both metallic and non-metallic targets. Overall, by creating an environment that combines the benefits of flame, microwave, and argon gas (Ar), MPT effectively reduces the demands on target surface quality and minimizes target damage during LIBS analysis. This approach offers superior signal enhancement compared to single enhancement methods, positioning MPT as a promising re-excitation strategy in LIBS applications. This capability makes it possible to integrate MPT with compact laser systems, thereby advancing the use of LIBS technology for in-situ and online detection in field or harsh environments.