飞灰含碳量是衡量火电厂锅炉燃烧效率的重要指标。目前利用激光诱导击穿光谱(LIBS)对飞灰碳元素进行定量分析的关键问题是测量精度不高且无法长期稳定测量，难以满足工业要求。本项目提出发展LIBS-LIF（激光诱导荧光）联用技术来增强C原子受激几率，提高测量精度，其中对LIBS诱导等离子体中C原子形成二次激发的247.9nm LIF激光基于非线性频率转换实现；基于McWhirter模型及双极扩散-复合理论，结合实验参数，建立等离子体局部热平衡态（LTE）判据，选择有效的荧光光谱；利用多元多阶非线性逆回归模型及多线法获得定标方程，消除元素间相互干扰，削弱基底效应；基于上述方法的实现，构建新的数据分析方法，进一步提高测量精度；采用激光功率负反馈控制技术锁定脉冲激光功率，提高长期测量稳定性。本项目方法和技术有助于提高LIBS的实用能力，并为下一步该技术原理真正用于指导火电厂的生产实践做好前期准备。

Unburned carbon content in fly ash is an important indicator to measure the combustion efficiency. The poor measurement precision and unguaranteed long-term measurement stability are currently the two key issues for quantitative analysis of carbon in fly ash using laser-induced breakdown spectroscopy (LIBS), which are unable to meet the industrial requirements. This project intends to ultilize the combined LIBS-LIF (laser-induced fluorenscence) to increase the stimulated emission transition probability of carbon atoms and improve the measurement accuracy, in which the 247.9nm LIF laser that is used for forming a secondary excitation of C atoms in LIBS-induced plasma can be generated through processes of nonlinear frequency conversion; based on the McWhirter model and bipolar diffusion-recombination theory, combined with the experimental parameters, try to build the plasma local thermal equilibrium (LTE) condition criterion to choose the effective fluorescence spectra; obtain calibration formula by using both the multi-order non-linear inverse regression model and the multi-line method, so as to remove interferences between elements and weaken the matrix effects; build new data analysis methods to further improve the measurement accuracy based on the above methods; lock the pulsed laser power using a negative feedback control method to guarantee the long-term measurement stability. The methods and technologies developed in the project will help to improve the practical ability of LIBS, and pave the way for application in thermal power plants in the future.