| Laser Induced Breakdown Spectroscopy(LIBS)technology is a new emerging material analysis method.Its unique characteristics such as no sample pretreatment,no contact,multi-component simultaneous detection,and real-time online measurement are widely used Kinds of fields.A high-energy pulsed laser focuses on the surface of the sample to generate a plasma.The plasma radiates a characteristic spectrum of the element when it encounters cold,and the qualitative and quantitative detection of the element is achieved by analyzing the spectrum.With the development of lasers,spectrometers,optical systems and other instruments and equipment,the LIBS system has become more and more widely used in the detection of long-distance substances.In the actual field measurement,due to factors such as the surrounding environment,sample size,sample status,etc.There is variation in the sample position,which changes the distance between the lens and the sample.distance.In order to explore the effect of sample position fluctuations on typical spectral characteristic parameters in long-distance detection,and the specific range that allows sample position fluctuations at a certain sample distance.This article is equipped with a remote LIBS optical system including the coaxial Schwarzschild telescope.When the position of the guide rail is fixed,the movement of the sample position is used to simulate the detection of the fluctuation of the surface position of the material on the site,and the typical spectral characteristic parameters,spectral repeatability,and spectral similarity Variation trends of parameters such as degree with increasing sample distance.The main contents are as follows:1.Equipped with a remote LIBS optical system including the coaxial Schwarzschild telescope.The movable range of the precision electronically controlled translation stage in the telescope is that the position of the guide rail varies from 0-16 mm.The position of the guide rail increases from the leftmost 0mm,and the step length It is 1mm.Collect the spectral intensity at each sample distance,the sample distance increases by 1 cm each time.The current system focus range is 1.9-4.1m.2.According to the collected original spectral data,after processing,the change trend of the spectral characteristic parameter with the increase of the sample distance at a certain rail position is obtained.Taking the detection results of the rails at 4mm and 12 mm respectively as an example for analysis,the relationship curves of the emission intensity of the LIBS spectral line,the characteristic spectral line intensity of the element and the plasma temperature and the sample distance are given.The characteristics are analyzed in conjunction with the physical mechanism The cause of the parameter change phenomenon.3.Calculate the relative standard deviation of the spectral data collected at a certain sample position,and then study the repeatability and stability of the experimental spectrum.In addition,the spectral similarity is obtained by means of the correlation coefficient method.Under a certain rail position,the spectral similarity corresponding to a certain sample distance is above 0.95.From the stability of the spectral similarity within a certain range,the specific value of the sample position fluctuation tolerance at a certain sample distance is obtained,and finally the correlation curve of the sample distance and the sample position fluctuation tolerance within the entire sample focusing range is fitted.In the case of spectral similarity of 0.99,the range of the sample position fluctuation tolerance is within the range of 70mm-220 mm.The study of the influence of sample position fluctuation on typical spectral characteristic parameters in LIBS long-distance detection is helpful for the design of remote LIBS optical system.At a certain sample distance,the determination of the fluctuation tolerance of the sample position improves the accuracy of spectral qualitative and quantitative analysis. |
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