减小飞灰等离子体谱线干扰的参数优化研究

针对激光诱导击穿光谱技术测量飞灰含碳量时存在的C和Fe谱线干扰问题展开分析,并进行了基于参数优化的减小谱线干扰的实验研究.根据C和Fe元素谱线的激发特性和时间演化特性,对比分析了不同脉冲能量和等离子体信号探测延时下的谱线干扰情况,以获得减小谱线干扰的参数优化条件.在此基础上,进一步对比分析了分别采用峰值强度和积分强度建立飞灰含碳量的多元回归模型.研究结果显示,通过合理优化脉冲能量和延时,可有效减小248 nm附近C和Fe元素谱线的干扰.在优化后的测量条件下,不仅Fe 247.98 nm谱线强度得以弱化,而且可获取具有较高信噪比的C 247.86 nm谱线.由峰值强度建立的飞灰含碳量多元回归模型的拟合度r2达到了0.999,截距为0.005,具有良好的可靠性.

This paper deals with the interference of C and Fe plasma lines existing in the measurement of unburned carbon in fly ash by means of laser-induced breakdown spectroscopy (LIBS), and explores the interference suppression based on the parameter optimization by experiments. In the investigation, first, according to the excitation and time evolution properties of C and Fe lines, the spectral line interference at various pulse energy and time delay are analyzed in a comparison way, and the optimized parameters are obtained. Then, two multiple regression models describing the unburned carbon are constructed respectively by using the peak intensity and the integrated intensity of elemental lines. Analytical results show that the interference between C and Fe lines at about 248 nm can effectively be reduced by optimizing the pulse energy and the time delay; and that, in the optimized conditions, the intensity of Fe 247.98 nm line decreases, while C 247.86 nm line with high signal-to-noise ratio is obtained. Moreover, it is found that the multiple regression model constructed by peak intensity is reliable, with a regression coefficient r² of 0.999 and an intercept of 0.005.