光谱学与光谱分析, 2020, 40(8): 2345, 网络出版: 2020-08-01

光声池几何形状对光声光谱检测性能的影响

Influence of Photoacoustic Cell Geometrical Shape on the Performance of Photoacoustic Spectroscopy
作者单位

1安徽理工大学深部煤矿采动响应与灾害防控国家重点实验室, 安徽 淮南 232001

2中国科学院安徽光学精密机械研究所, 安徽 合肥 230031

摘要
随着现代化工业的高速发展, 痕量气体检测技术的重要性不言而喻, 目前痕量气体检测技术已广泛应用于环保、 化学工业、 生物生态以及医学检测等各个领域, 光声光谱技术由于它具有零背景检测、 探测器不受波长限制、 光学元件简单, 系统调节及维护方便等优点, 现已成为光谱学领域中非常重要的检测手段, 近些年来, 随着微弱信号检测与激光器技术的快速发展, 光声光谱技术也得到更多学者的关注与研究, 所取得的成果为光声光谱检测性能的提升提供了重要的设计参考, 然而, 当前文献报道较少地涉及到光声池的优化工作, 尤其是对光声池的形状构造等问题鲜有深入探索。 光声光谱检测系统中最核心的部件之一即为光声池, 它是承载待测气体的容腔以及产生光声耦合作用的场所, 其形状构型在很大程度影响着光-声之间的耦合状况, 以致于影响整机系统的信噪比与灵敏性, 因而探索设计光声池的形状具有重要的理论研究意义及工程应用价值。 为此, 基于传统圆柱形光声池的设计基础, 探索研究了纵向截面为圆形、 正三角形、 椭圆等8种典型形状的光声池结构模型, 并对其声场特性进行了仿真分析, 借助3D打印技术制作了各类光声池实物, 通过实验对比分析了8种光声池的性能指标, 在限定光声池纵向长度及纵向截面周长相等的条件下, 仿真结果表明, 8种形状各异的光声池工作纵向声学模态振型均相同, 实验结果表明, 8种光声池的工作声学共振频率值基本相同, 受其激光光源与腔内声学模态耦合的影响, 其品质因素从大到小依次为: 圆形、 短轴椭圆、 正五边形、 正方形、 大圆轴线形、 正三角形、 小圆轴线形、 长轴椭圆, 池常数从大到小依次为: 圆形、 长轴椭圆、 正五边形、 正方形、 大圆轴线形、 小圆轴线形、 正三角形、 短轴椭圆, 整体结果显示, 对于光声光谱光声池的设计, 在没有特殊要求的情况下, 光声池应优先为圆形形状, 研究过程与结果为光声光谱中光声池的设计与优化探索提供了借鉴与参考。
Abstract
With the rapid development of modern industry, the importance of trace gas detection technology is self-evident. At present, trace gas detection technology has been widely used in environmental protection, chemical industry, bio-ecological and medical detection and other fields. Photoacoustic spectroscopy (PAS) has become one of the most important analytical methods in spectroscopic detection due to its advantages of zero background detection, no wavelength limitation of detectors, simple optical elements, convenient system regulation and maintenance. In recent years, with the rapid development of weak signal detection and laser technology, photoacoustic spectroscopy has also attracted more attention of scholars. Relevant research results provide an important design reference for improving the detection performance of photoacoustic spectroscopy. However, the current literature report rarely involves the optimization of photoacoustic cells, such as the shape of photoacoustic cells. There is a lack of in-depth exploration on such problems as the shape structure. The photoacoustic cell is one of the most important core components in the photoacoustic spectroscopy detection system. It is the cavity for carrying the gas to be tested and the place where photoacoustic coupling occurs. Its shape greatly affects the relationship between light and sound. The coupling situation affects the signal-to-noise ratio and sensitivity of the whole system. Therefore, exploring the shape of the photoacoustic pool has important theoretical significance and engineering application value. Therefore, based on the design basis of the traditional cylindrical photoacoustic cell, this paper explores and studies the structural model of the photoacoustic cell with eight typical shapes such as circle, triangle, ellipse and so on, and simulates its sound field characteristics. 3D printing technology has produced all kinds of photoacoustic cells, and analyzed the performance indexes of 8 photoacoustic cells through experiments. The longitudinal length of the photoacoustic cell designed by the constraint is equal to the perimeter of the longitudinal section. The simulation results show that the longitudinal acoustic modes of the eight photoacoustic cells are the same. The experimental results show that the acoustic resonance frequencies of the eight photoacoustic cells are the same. The size is basically the same, and is affected by the coupling of the laser source and the acoustic mode in the cavity. Their quality factors are arranged from large to small: circular, short-axis ellipse, regular pentagon, square, large circular axis, and equilateral triangle. Small circle axis shape, long axis ellipse, their cell constants are arranged in order from large to small: circular, long axis ellipse, regular pentagon, square, large circular axis shape, small circular axis shape, regular triangle, short axis ellipse . The overall results show that for the design of the photoacoustic cell in photoacoustic spectroscopy, the shape of photoacoustic cell should be circular in priority without special requirements. The research process and results of this paper can provide a reference for the optimization design of the photoacoustic cell in photoacoustic spectroscopy.
00 11