微区激光诱导击穿光谱分析金属铀的光谱稳定性及改进方法研究

Poor spectral stability is an main obstacle for the application of micro laser-induced breakdown spectroscopy (micro-LIBS) in nuclear materials analysis. The instable laser source and matrix effect of uranium are the main course of spectral instability. As the fluctuation of laser is complex and uncontrollable, the mechanism of laser fluctuation contribute to the instability of micro-LIBS is difficult to study. This project proposes that the fluctuation of laser pulse widths is an important factor affecting the stability of micro-LIBS, and studies the mechanisms of laser fluctuations infuence the stability of micro-LIBS by building a database including pulse energies, pulse widths, and uranium spectral intensity. With the help of those mechanisms, a high stable micro-LIBS method is proposed by compensating the spectral intensity using laser parameters as references. Using the proposed high stable micro-LIBS, the influence of uranium crystal phases on micro-LIBS spectrum is studied. Results of this study will promote the appplication of micro-LIBS in surface element analysis of nuclear materials.

光谱稳定性差是阻碍微区激光诱导击穿光谱（micro laser-induced breakdown spectroscopy，简称微区LIBS）用于核材料表面成分定量分析的重要因素，而激光源不稳定与铀基体效应是导致光谱稳定性差的主要原因。激光波动复杂且难以控制，研究其对微区LIBS光谱稳定性的影响机制十分困难。本项目提出激光脉冲宽度波动可能对微区LIBS光谱稳定性具有重要影响，通过积累“脉冲能量—脉冲宽度—铀光谱强度”大数据，从大数据中寻找规律并研究激光波动对铀微区LIBS光谱稳定性的影响机制。在认识问题、掌握机制的基础上，依靠波动的核心源头激光参数，去校正波动的结果微区LIBS光谱强度，从而建立金属铀的高稳定微区LIBS分析方法，并研究金属铀晶相对微区LIBS光谱强度的影响规律。本项目的研究结果能够促进微区LIBS在核材料表面成分分析领域的应用。

光谱稳定性差是阻碍微区激光诱导击穿光谱（micro laser-induced breakdown spectroscopy，简称微区LIBS）用于核材料表面成分定量分析的重要因素，而激光源不稳定与铀基体效应是导致光谱稳定性差的主要原因。本项目对激光参数波动、样品定位精度、晶相对微区LIBS光谱强度的影响规律开展了高精度研究。结果表明，激光脉冲能量增大2%，将使微区LIBS光强增大约4%；物镜景深幅度定位误差引起的微区LIBS光谱强度变化约±2.5%；样品晶相对微区LIBS光谱强度存在约3%-8%的微小影响；纳秒激光脉冲内部诸多纵模间的光强分布剧烈变化，可能是导致单脉冲LIBS光谱波动的重要原因。上述结论，有助于理解微区LIBS光谱强度波动的物理本质，可能成为进一步改进LIBS光谱稳定性、制定LIBS分析方法标准的重要参考。在前述研究基础上，项目继续开展金属铀光谱性质、重点元素分析方法研究，并成功应用于铀表面氢同位素的空间/深度分辨分析。