激光诱导击穿光谱(LIBS)技术是一种物质成分分析技术, 它利用脉冲激光聚焦在样品表面, 当激光烧蚀样品时产生等离子体, 光谱仪收集等离子体辐射的光谱, 计算机进行元素分析。 它具有操作简便快速, 检测元素全面等优点。 传统LIBS存在检测灵敏度低, 谱线背景噪声高等缺点, 将LIBS技术与腔体约束结合起来可以增强光谱强度, 同时信噪比和等离子体温度等一些参数也会有效提高。 使用PLA和铝两种材料的圆柱形约束腔固定在黄铜样品表面, 直径分别为5和6 mm, 高度分别为1, 2, 3, 4和5 mm。 利用光谱仪采集了Cu Ⅰ 510.55 nm, Cu Ⅰ 515.32 nm和Cu Ⅰ 521.82 nm三条Cu等离子体谱线, 并对其进行了分析研究。 实验结果表明相比于未加腔体约束, 光谱强度在每种腔体约束下都得到了增强。 针对Cu Ⅰ 515.32 nm谱线, 研究了它在各个约束腔下的增强因子和信噪比。 随着圆柱形约束腔高度的增加, 增强因子呈现先增大后减小的趋势, 在高度为4 mm时达到最大。 同一高度、 不同直径的约束腔, 直径为5 mm时比6 mm时要大。 而对于同一高度、 同一直径的腔体来说, 铝材料腔体约束下都比PLA材料的大。 在当前实验条件下, 高度4 mm、 直径5 mm的铝材料的约束腔增强效果最明显, 增强因子达到最大值28.29。 信噪比与增强因子变化趋势一致, 也在高度4 mm、 直径5 mm的铝材料的约束腔下达到最大值44.03, 是没有腔体约束时的13.89倍。 此外, 计算了等离子体温度, PLA材料的约束腔对等离子体温度影响较小, 而在铝约束腔下等离子体温度增加明显, 5 μs时在与没有约束腔时相差达到最大值467.35 K。 腔体约束装置简单, 与LIBS系统组合方便, 并且增强光谱效果明显, 具有广阔的应用前景。 本文研究了LIBS系统结合不同材料的腔体约束对激光诱导击穿Cu等离子体光谱的影响, 对腔体材料的选取有一定的参考价值。

Laser-induced Breakdown Spectroscopy (LIBS) is a material composition analysis technology. It uses a pulsed laser to focus on the surface of the sample. When the laser ablates the sample, the plasma is generated. The spectrometer collects the spectrum, and the computer performs the elemental analysis. It has the advantages of simple and rapid operation and comprehensive detection elements. Traditional LIBS has the disadvantages of low detection sensitivity and high spectral background noise. Combining LIBS technology with cavity confinement can enhance spectral intensity, while some parameters such as signal-to-noise ratio (SNR) and plasma temperature are also effectively improved. In this paper, the cylindrical cavity of PLA and aluminum were fixed on the surface of the brass sample, with diameters of 5 mm and 6 mm. And each diameter corresponded to five different heights:1, 2, 3, 4, and 5 mm, respectively. Three Cu plasma lines of Cu Ⅰ 510.55 nm, Cu Ⅰ 515.32 nm and Cu Ⅰ 521.82 nm were collected by the spectrometer and then were analyzed. The experimental results show that the spectral intensity is enhanced under each cavity confinement compared to without cavity. For the Cu 515.32 nm spectral line, the enhancement factor and signal-to-noise ratio under each cavity were studied. With the increase of the height of the cylindrical cavity, the enhancement factor firstly increases and then decreases, it reaches the maximum at the height of 4 mm. For a cavity of the same height and different diameter, it is larger at 5 mm than 6 mm in diameter. For a cavity of the same height and diameter, it is larger at the cavity of the aluminum material than PLA material. Under the current experimental conditions, when the height is 4 mm, and the diameter is 5 mm, the cavity of the aluminum material has the most obvious enhancement effect, the maximum enhancement factor is 28.29. The signal-to-noise ratio is consistent with the trend of the enhancement factor and reaches a maximum of 44.03 under the cavity of the aluminum material with a height of 4 mm and a diameter of 5 mm, which is 13.89 times compared to without cavity. In addition, the plasma temperature was calculated. The PLA cavity has little effect on the plasma temperature, while the plasma temperature increases obviously under the aluminum cavity, and excess value reaches a maximum of 467.35 K at 5 μs compared to without cavity. The cavity confinement device is simple and is convenient to combine with the LIBS system, and the enhanced spectral effect is obvious, so it has broad application prospects. This paper studied the influence of LIBS combined with cavity confinement of different materials on the spectrum of laser-induced breakdown Cu plasma, which has certain reference value for the selection of cavity materials.