Spatial Distribution of Absorbance in Laser-Induced Lithium Plasma Measured by Laser Absorption Spectroscopy

Li is currently being investigated as a material for breeding blankets in the field of nuclear fusion. To enhance the efficiency of these breeding blankets, the separation and analysis of Li isotopes is required. Generally, High-Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS) has been used to analysis isotopes traditionally. However, this method requires expensive equipment and intricate preprocessing procedures. Laser-Induced Breakdown self-Reversal Isotopic Spectrometry (LIBRIS) is one of the alternative method to analyze Li isotopes. LIBRIS is a technique that employs the self-absorption phenomenon observed in laser-induced plasma emissions. Due to its narrower linewidth compared to emission light, self-absorption plays a crucial role in the precision of LIBRIS. In this study, understanding of the self-absorption phenomenon was focused. Li plasma was produced using an 1064 nm Nd:YAG laser with the pulse duration of 10 ns. Laser absorption spectroscopy was employed to measure the absorbance profile of Li atoms and a tunable laser with the center wavelength of 670 nm was used as the Li absorption light source. An iCCD array was used for the assessment of the intensity distribution, allowing for the precise identification of the point of maximum self-absorption.