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为了使激光诱导击穿光谱(LIBS)实验装置中的多个关键参数达到最优化设置,以便更好地服务于煤质分析,实验中对这些参数与煤粉等离子体中待测元素发射谱线信噪比间的关系进行了详细研究,并根据信噪比大小来进行最优化参数的选择。实验结果表明,对于本LIBS实验装置,其最优化参数设置是将激光脉冲能量设为120 mJ.Pulse-1,光谱仪的曝光延迟时间设为200 ns,激光聚焦点位于样品表面以下3～5mm,样品池转速设为2.7 r.min-1,并在激光出射光路中放置中心频率为1 064 nm的窄带滤波片和中心孔径为1.5 mm的光阑。优化后的LIBS实验装置对煤粉中C元素测量的标准偏差(SD)由6.7%降至1.6%,对其他微量元素测量的相对标准偏差(RSD)由28%降至10%,测量精度得到了较大提高。
In order to optimize the setting of several key parameters in the LIBS experimental apparatus in order to better serve the coal quality analysis, these parameters are closely related to the emission spectra of the elements to be measured in pulverized coal plasma The relationship between the signal to noise ratio carried out a detailed study, and according to the size of the signal to noise ratio to optimize the choice of parameters. The experimental results show that for the LIBS experimental apparatus, the optimal parameters are set as follows: laser pulse energy is set to 120 mJ. Pulse-1, the exposure delay time of the spectrometer is set to 200 ns, the laser focus point is 3 to 5 mm below the sample surface, The sample cell speed was set at 2.7 r.min-1 and a narrow-band filter with a center frequency of 1,064 nm and a stop with a center aperture of 1.5 mm were placed in the laser exit beam path. The optimized LIBS experimental device reduced the standard deviation (SD) of C element in pulverized coal from 6.7% to 1.6%, reduced the relative standard deviation (RSD) of other trace elements from 28% to 10%, and obtained the measurement accuracy A big increase.