基于双光束腔增强光谱技术的多组分气体同位素丰度探测研究

High sensitivity detection for multi-component gases and isotope abundance has important scientific significance and application value in environmental monitoring, industrial process control, power systems and medical testing and other fields. Especially the measurement methods and the real time analysis of multiple and multi isotopic abundances are still very short on account of the low concentration of heavy isotopes. The project intends to use two continuous QCL lasers working at room temperature combined with the cavity enhanced spectroscopy to research the multi-compound and isotope abundance real-time detection with the miniaturized portable systems. The detection objects of the project are the greenhouse gases of CO2 and N2O with their isotopics measurements. The key points such as the following aspects: designing the high-quality optical cavity with three-mirrors to build stable and efficient optical system; studying the multi-component gases characteristic absorption spectrum and environmental adaptability to construct the removing interference model and compensation algorithm; developing the multi-function signal control system to achieve time-sharing scanning for QCLs, and the multi-frequency modulation function ensure the independence of the optimal modulation for multi-lines at the same time, moreover, the direct absorption combined with the wavelength modulation technology expand the dynamic measurement range to measure the multi-component gas simultaneously with high-sensitivity and high-precision. At last, the relationship between isotope detection precision and concentration will be analyzed, and the multi component dynamic monitoring of atmospheric CO2, N2O with C, O and N isotopes will be realized initially. So this project will provide a new method and new technology to carry out pollution sources identification of atmospheric environmental monitoring field.

多组分气体与多同位素丰度高灵敏探测在大气环境、工业过程控制、能源及医学检测等领域具有重要的科学意义和应用价值。由于重同位素分子浓度低，特别是多组分与多同位素丰度的实时分析，其测量手段依然很缺乏。项目拟通过研究双光束腔增强光谱技术，利用两个室温工作的连续QCL与腔增强光谱技术结合，开展小型化的多组分气体与同位素丰度原位实时探测新技术和方法研究。以CO2和N2O及其同位素分子为检测对象，通过设计高品质小容积光学腔，构建稳定高效的双光束光路系统；研究多组分气体特征吸收谱线和环境适应性，建立去除干扰模型和补偿算法；研究QCL分时扫描和多频调制技术，确保多谱线最优调制度的独立性，同时联合直接吸收和波长调制技术扩大动态测量范围，分析同位素探测精度与浓度的关系，初步实现大气CO2、N2O 及C、O、N同位素的多组分动态高效监，为我国开展污染源汇识别等大气环境监测领域提供新方法与新技术。

多组分气体与多同位素丰度高灵敏探测在大气环境、工业过程控制、能源及医学检测等领域具有重要的科学意义和应用价值。针对重同位素分子浓度低，特别是多组分与多同位素丰度的实时分析的需求，发展高灵敏测量技术迫在眉睫。项目重点研究了双光束腔增强光谱技术，通过两个室温工作的连续QCL与腔增强光谱技术结合，开展小型化的多组分气体与同位素丰度原位实时探测新技术和方法研究。. 腔增强吸收光谱技术（CEAS）由于使用密集的高阶模进行光谱探测, CEAS 输出信号强度较低, 使得探测灵敏度高度依赖于光源功率。针对该问题，项目首先开展了重入射光路结构研究，设计了三镜结构的重入射积分腔光路，使激光再次注入光腔, 以提高能量利用率和输出信号强度，通过使用三维光追踪模拟软件, 设计再入射结构, 研究了影响信号增益的多个因素，将信号增益提升一倍以上。同时以CO2和N2O及其同位素分子为检测对象，研究了双光路入射光路的特性，利用多光束传输原理，分别将中心波长4.3um和4.6um的两支QCL激光器从两个不同的位置以合适的角度入射至积分腔，谐振后形成两个同心的Herriott光环，构建稳定高效的双光束光路系统。为解决腔模噪声问题，将射频白噪声加载在QCL激光器上，通过展宽线宽有效抑制了腔模噪声，显著提高了信噪比。. 选择包含13C、18O、17O和15N同位素分子吸收谱线的波长，研究多组分气体特征吸收谱线和环境适应性，研制了高精度温度和压力控制装置，温控精度达到±0.001℃，压力精度达到±0.003mbar，解决了谱线干扰和波长漂移的问题。研究了QCL分时扫描和多频调制技术，确保多谱线最优调制度的独立性，同时联合直接吸收和波长调制技术扩大动态测量范围。分析了同位素探测精度与浓度的关系，初步实现大气CO2、N2O 及C、O、N同位素的多组分动态高效检测，为我国开展污染源汇识别等大气环境监测领域提供新方法与新技术。