Effects of Temperature and Aerosol Content on Laser-Induced Breakdown Spectroscopy Detection Limits

Abstract

Research to analyze effects of ambient temperature and aerosol dispersity on Laser-Induced Breakdown Spectroscopy (LIBS) detection limits is presented in this study. The theoretical results are applicable to future gas turbine exhaust monitoring with LIBS. Modification of a traditional LIBS system provides a method for in situ sampling in a gas turbine exhaust stream. Data collection in a controlled laboratory environment was performed with a LIBS system modified with an intrusive sampling probe to study the effects of temperature and aerosol dispersity on the limits of detection for chromium (Cr), magnesium (Mg), manganese (Mn), and titanium (Ti) particulate. Results show that increasing the temperature of the aerosol flow decreases the elemental mass required for LIBS detection, thereby increasing system sensitivity. Similar gains in system sensitivity occur when samples are taken from monodisperse aerosol relative to polydisperse aerosol. The lowest detection limits of 117 fg Cr, 95 fg Mg, 106 fg Mn, and 841 fg Ti occur when sampling from monodisperse aerosol flow at room temperature conditions.