CN102507512A - An In-Situ Detection Method of Infrared-Ultraviolet Double Pulse Laser-Induced Breakdown Spectroscopy - Google Patents

Abstract

The invention discloses an online in-situ detection method for infrared and ultraviolet double-pulse laser-induced breakdown spectroscopy, which at least comprises the following steps: A. the pulse delay time is set to control the time interval between the two lasers according to the excitation characteristics of the sample. B. The infrared band laser outputs laser firstly, the laser is focused on a position to be detected through remote convergence adjustment, a sample is ablated to generate plasma C. D. The spectrum signal is received by the spectrum remote collection device, coupled into the optical fiber, transmitted to the spectrometer, and the spectrum data information can be obtained through the matched software. E. Collecting the obtained spectral data, and obtaining a detection component analysis conclusion by using a free calibration-free analysis method.

Description

An In-Situ Detection Method of Infrared-Ultraviolet Double Pulse Laser-Induced Breakdown Spectroscopy

technical field

The invention can meet the strict requirements of on-line in-situ detection, is widely applicable to multiple technical fields such as analysis, detection, measurement and diagnosis, and specifically relates to an on-line in-situ detection method of infrared-ultraviolet double-pulse laser-induced breakdown spectroscopy.

Background technique

On-line in-situ detection technology is a new and important part of modern detection technology. It can quickly, conveniently and effectively detect the performance of materials in in-service equipment, and discover the damage of in-service structures and vulnerable parts. It is the key to preventing accidents and ensuring equipment Effective means of operational security. The technical difficulties of in-situ testing are mainly manifested in the following aspects: on the one hand, the testing site conditions are harsh and cannot be compared with ideal conditions such as laboratories; on the other hand, the structures or materials to be tested are in an assembled state, and the time and space allowed for testing are limited. Compared with off-site detection, online in-situ detection has higher requirements and is more difficult.

In-situ detection generally includes defect detection, fault diagnosis, condition monitoring, and performance parameter measurement, among which defect detection and performance parameter measurement are the most widely used, both of which are based on the acquisition of sample composition information, and the results directly affect their detection capabilities Therefore, it is very important to accurately determine the composition information of the sample to be tested.

Traditional component detection techniques mainly include X-ray fluorescence analysis, atomic absorption spectroscopy (AAS), inductively coupled plasma emission spectroscopy (ICP-AES) and inductively coupled plasma emission mass spectrometry (ICP-MS). Among them, the X-ray fluorescence analysis method can realize rapid detection, but its sensitivity is low; while the AAS method and ICP-AES method have high detection accuracy and good stability, but both require sample pretreatment, and it is difficult to ensure that the samples to be tested are not Contaminated or lost; ICP-MS method can make up for the above shortcomings, but due to the expensive and bulky detection equipment, the detection process takes a long time, it is difficult to meet the space and time requirements of in-situ detection, and it cannot be used in a large number of applications.

Laser Induced Breakdown Spectroscopy (LIBS for short), as a new real-time, in-situ, continuous and non-contact detection technology, makes up for the shortcomings of the above detection methods and can meet the technical requirements of on-line in-situ detection. This technology does not require cumbersome sample pretreatment process, and the size requirements of solid (conductor or non-conductor), liquid or gas samples in various forms are not strict, and the sample consumption is extremely low. It can perform rapid and simultaneous determination of multiple elements. Wide, easy to operate remotely.

Compared with traditional detection techniques, LIBS technology has incomparable technical advantages for on-line in-situ detection, but the analysis sensitivity of single-pulse LIBS technology is not high, which restricts its application in the field of trace element detection. LIBS is based on the interaction between high-power laser and matter to generate transient plasma, and study the emission spectrum of plasma (continuous background spectrum and characteristic spectrum of analyte elements), so as to realize qualitative and quantitative analysis of sample components . The temperature and density of the plasma excited by single-pulse LIBS are low, and the intensity of the emission spectrum formed is limited, so the analytical sensitivity is relatively low and the detection limit is relatively high.

Contents of the invention

In view of the insufficiency of traditional detection technology, the present invention based on DP-LIBS technology invented an infrared ultraviolet double-pulse laser-induced breakdown spectroscopy online in-situ detection method, the sample consumption of this detection method is as low as about 0.1ug-0.1mg, in-situ The spatial resolution of the micro-area can reach 1-100um, and its analytical sensitivity is 1-2 orders of magnitude higher than that of single-pulse LIBS technology.

An infrared-ultraviolet double-pulse laser-induced breakdown spectroscopy online in-situ detection method provided by the present invention comprises the following steps:

Step A. According to the excitation characteristics of the sample to be detected, set the delay time of the pulse delay controller to control the time interval between the two lasers; in the initial stage of plasma formation, it takes atoms from the sample to be detected to enter the plasma until it is completely evaporated. Due to the different evaporation energy and ablation amount of elements of different species, the time required for the spectral lines of the elements to reach the maximum emission intensity is also different.

Step B. The infrared band laser is triggered by the pulse delay controller to first output the nanosecond pulse laser in the infrared band, through the beam remote convergence adjustment device, focus on the position to be detected on the surface of the sample, and ablate the position to be detected on the sample to generate plasma.

Step C. Under the trigger of the pulse delay controller, the ultraviolet band laser outputs the nanosecond pulse laser in the ultraviolet band after a delay time, and focuses on the same position on the sample surface through the beam remote convergence adjustment device to excite the plasma to enhance the spectral signal; The selection of the wavelength, frequency and intensity of the two nanosecond pulsed lasers in step B and step C is mainly determined by the excitation characteristics of the sample to be detected. For different species of elements, the laser wavelength, frequency and intensity can be adjusted online during the detection process to achieve the best detection conditions.

Step D. In step C, the enhanced spectral signal is received by the remote spectral collection device, coupled into the optical fiber, and transmitted to the spectrometer. Through the supporting computer program, the full-band spectral data information can be obtained.

Step E. According to the collected full-band spectral data information, the conclusion of the detection component analysis can be obtained by using the physical parameters of the plasma and the free calibration and correction analysis method.

The concrete steps of described step E are:

E1. According to the collected full-band spectral data information, obtain the linear integral intensity measured by the transition of a certain atomic species s between two different energy levels Ek and Ei ,Expressed as:

          （1）

(1)

 为对特定谱线的跃概率；为k能级简并度；

为波尔兹曼常数；为等离子体温度；F 为常数，与光收集装置的效率有关，不同效率的光收集装置所对应的常数F不同（有什么关系？），与波长无关，在检测过程中保持不变；

是发射物种s的分配函数，表示为： in, is the transition wavelength; is the concentration of the emitting atomic species;

is the jump probability for a specific spectral line; is the k-level degeneracy;

is the Boltzmann constant; is the plasma temperature; F is a constant, which is related to the efficiency of the light collection device. The constant F corresponding to the light collection device with different efficiency is different (what is the relationship?), has nothing to do with the wavelength, and remains unchanged during the detection process;

is the distribution function of the emitting species s, expressed as:

 （2）；

(2);

Step E2. Take the logarithm of equation (1), and make the following assumptions:

 ，

     （3） ,,

,

(3)

； get the linear equation with respect to the parameters y and x

;

 及光谱数据库中的已知光谱参数 

、 和 

，可绘出y关于x的直线，得到斜率m和截距

，通过斜率可得， 

 ； Step E3. According to the measured

and known spectral parameters in the spectral database

, and

, you can draw a straight line of y with respect to x, and get the slope m and intercept

, can be obtained by the slope,

;

Step E4. Normalizing the concentration of all species components can get F, that is

 ；

;

 计算得出，即可得到待检测样品成分分析结果。 The concentration of species components can be obtained by the formula

After calculation, the component analysis result of the sample to be detected can be obtained.

The present invention provides an infrared-ultraviolet double-pulse laser-induced breakdown spectroscopy online in-situ detection method, which can realize fixed-point sampling and detection of samples to be inspected, and complete in-situ analysis, real-time analysis, and precise detection of trace elements.

The invention adopts double-pulse LIBS technology, uses the first laser pulse to irradiate the surface of the sample to generate plasma, and later the second laser pulse to irradiate the plasma to enhance the emission of spectral lines, realizing the two functions of material ablation and plasma excitation. The distribution optimization of the stage, if two lasers are used to output two laser beams respectively, the flexible optimization of laser parameters (such as energy, time, etc.) can be realized.

In summary, the present invention provides an infrared-ultraviolet double-pulse laser-induced breakdown spectrum online in-situ detection method, which can effectively enhance the spectral radiation intensity of laser plasma, prolong the radiation relaxation time, improve the sensitivity of spectral detection, and realize The fixed-point sampling and testing of the samples to be tested can realize in-situ analysis, real-time analysis, and accurate detection of trace elements, and is widely used in many technical fields such as analysis, detection, measurement, and diagnosis.

Description of drawings

Figure 1 is a schematic structural view of a detection device used in the detection method of the present invention.

Figure 2 is a partial enlarged view of the beam remote convergence adjustment device in Figure 1.

Fig. 3 is a partial enlarged view of the optical radiation collecting device in Fig. 1.

Fig. 4 is a flowchart of the detection method of the present invention.

Reference signs and description: 1. Infrared band laser (take 1064nm Nd:YAG nanosecond pulse laser as an example); 2. Ultraviolet band laser (take 193nm ArF excimer nanosecond pulse laser as an example); 3. Pulse delay control 4. The first beam remote convergence adjustment device; 5. The second beam remote convergence adjustment device; 6. Spectrum remote receiving device; 7. Seven-channel high-resolution micro-optical fiber; 8. Full-band laser-induced attenuation spectrometer; 9. Computer; 10. Focusing lens; 11. Special mirror; 12. First lens; 13. Second lens; 14. Third lens. the

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

The structure of the detection device used in the method of the present invention is: an infrared-ultraviolet double-pulse laser-induced breakdown spectrum online in-situ detection device, and the core components include an infrared band laser (taking a 1064nm Nd:YAG nanosecond pulse laser as an example), an ultraviolet band laser ( Take the 193nm ArF excimer nanosecond pulse laser as an example), pulse delay controller, remote beam convergence adjustment device, remote spectrum receiving device, seven-channel high-resolution micro-optical fiber, full-band laser-induced attenuation spectrometer and computer, etc.

The beam remote convergence adjustment device is composed of a focusing lens and a special mirror, which can not only realize long-distance laser focusing and prolong the detection distance, but also realize the free selection of detection angle and detection surface, thereby overcoming the constraints of special-shaped devices and narrow detection space , to achieve fixed-point sampling detection.

The telescope system is formed by a group of lenses inside the spectrum remote receiving device. During the process of receiving spectrum signals, try to ensure that the focus of the telescope system coincides with the position where the laser focuses on the sample, so as to receive more emission spectra and improve the signal-to-noise ratio.

Since the working principle of the detection device adopted in the present invention is based on DP-LIBS technology, it requires that the elemental composition represented by the spectral line intensity in the obtained full-band spectral data must be consistent with the elemental composition on the actual sample surface. Theoretically, the requirements can be met by calibrating the spectrometer and comparing it with the spectral intensity signal of a standard light source. However, the full-band spectral data in the actual detection process not only depends on the laser parameters and the geometric distribution of the plasma, but also is affected by the matrix effect (the composition, surface conditions, and thermodynamic properties of the sample are collectively referred to as the matrix effect).

Calibration-free analysis is based on the following three reasonable assumptions:

A. The composition of each element in the plasma is exactly the same as that of the sample before ablation;

B. In the actual time-space observation gate, the plasma is in thermal dynamic equilibrium;

C. The emitting light source is small enough.

It can make up for the above shortcomings, overcome the influence of the matrix effect, and meet the strict requirements of the detection technology.

          (1)式中 ， According to the above assumptions, the linear integral intensity measured by the transition of a certain atomic species s between two different energy levels Ek and Ei can be expressed as

(1) where ,

 ---跃迁波长；

 ---发射原子物种的浓度；

 ---对特定谱线的跃迁概率；  

---k能级简并度；---波尔兹曼常数； 

---等离子体温度；F  --常数，与光收集装置的效率有关，与波长无关，在检测过程中保持不变；

--- Transition wavelength;

--- the concentration of the emitting atomic species;

--- Transition probability for a specific spectral line;

---k level degeneracy; ---Boltzmann constant;

---Plasma temperature; F ---Constant, related to the efficiency of the light collection device, independent of the wavelength, and remains constant during the detection process;

--发射物种s的分配函数。可表示为 （2）         对方程（1）取对数，并作如下假设：

-- The distribution function of the emitting species s. It can be expressed as (2) Take the logarithm of equation (1), and make the following assumptions:

，

 ，     （3） ,

,

, (3)

 根据测得的 

 及光谱数据库中的已知光谱参数 

、 

和 ，可绘出y关于x的直线（波尔兹曼曲线），得到斜率m和截距，通过斜率可得( 

 )。对所有物种成分的浓度归一化可得出F,即   

 而物种成分的浓度

可通过公式 A linear equation with respect to the parameters y and x can be obtained

According to the measured

and known spectral parameters in the spectral database

,

and , you can draw a straight line (Boltzmann curve) of y with respect to x, and get the slope m and intercept, which can be obtained through the slope (

). Normalizing the concentrations of all species components yields F, that is

while the concentration of species constituents

available through the formula

After the calculation, the analysis result of the component of the sample to be tested can be obtained.

Embodiment: Figure 1 to Figure 3 show the structure of the detection device used in the detection method of the present invention. The core components include infrared band laser 1 (take 1064nm Nd:YAG nanosecond pulse laser as an example); ultraviolet band laser 2 (take 193nm ArF excimer nanosecond pulse laser as an example); pulse delay controller 3; the first beam remote Convergence adjustment device 4; second beam remote convergence adjustment device 5; spectrum remote receiving device 6; seven-channel high-resolution micro-optical fiber 7; full-band laser-induced attenuation spectrometer 8; and computer 9, etc.

As shown in Figure 4, it is a flow chart of an infrared-ultraviolet double-pulse laser-induced breakdown spectroscopy online in-situ detection method according to the present invention, which includes the following steps:

The first step, according to the excitation characteristics of the sample to be detected, set the delay time of the pulse delay controller 3 to control the time interval between the two lasers.

In the second step, the infrared band laser 1 (taking the 1064nm Nd:YAG nanosecond pulse laser as an example), under the trigger of the pulse delay controller 3, first outputs a high power density nanosecond pulse laser, and passes through the first beam remote convergence adjustment device 4. Focus on the position to be detected on the surface of the sample, and ablate the position to be detected on the sample to generate plasma.

The third step, the ultraviolet band laser 2 (taking the 193nm ArF excimer nanosecond pulse laser as an example), under the trigger of the pulse delay controller 3, outputs a high power density nanosecond pulse laser after a delay time, through the second The beam remote converging adjustment device 5 focuses on the same position on the sample surface, and excites the plasma to enhance the spectral signal. the

The fourth step, the spectral signal is received by the spectral remote collection device 6, coupled into the optical fiber 7, and transmitted to the spectrometer 8, and the spectral data information can be obtained through the supporting software.

The fifth step, according to the collected full-band spectral data information, establish a quantitative analysis model for the mathematical relationship between the spectral line intensity and the physical parameters of the plasma, such as the energy of the atomic transition, and the plasma temperature, and use the free calibration correction analysis method (calibration-free) can draw the analysis conclusion of the detected components.

The above-mentioned specific detection methods and the determination of the laser wavelength are all preferred embodiments, and cannot limit the claims of the present invention. Any other changes or other equivalent replacement methods that do not deviate from the technical solution of the invention are included in the protection scope of the present invention.

Claims (2)

1. An infrared-ultraviolet double-pulse laser-induced breakdown spectroscopy online in-situ detection method, comprising the following steps: Step A. According to the excitation characteristics of the sample to be detected, set the delay time of the pulse delay controller to control the time interval between the two lasers; Step B. The infrared band laser is triggered by the pulse delay controller to first output the nanosecond pulse laser in the infrared band, and through the beam remote convergence adjustment device, focus on the position to be detected on the surface of the sample, and ablate the position to be detected on the sample to generate plasma; Step C. Under the trigger of the pulse delay controller, the ultraviolet band laser outputs the nanosecond pulse laser in the ultraviolet band after a delay time, and focuses on the same position on the sample surface through the beam remote convergence adjustment device to excite the plasma to enhance the spectral signal; Step D. In step C, the enhanced spectral signal is received by the spectral remote collection device, coupled into the optical fiber, and transmitted to the spectrometer. Through the supporting computer program, the full-band spectral data information can be obtained; Step E. According to the collected full-band spectral data information, the conclusion of the detection component analysis can be obtained by using the physical parameters of the plasma and the free calibration and correction analysis method. 2. The infrared-ultraviolet double-pulse laser-induced breakdown spectroscopy online in-situ detection method according to claim 1, wherein the specific steps of the step E are: E1. According to the collected full-band spectral data information, obtain the linear integral intensity measured by the transition of a certain atomic species s between two different energy levels Ek and Ei

,Expressed as:

(1) in,

is the transition wavelength;

is the concentration of the emitting atomic species;

is the jump probability for a specific spectral line;

is the k-level degeneracy;

is the Boltzmann constant; is the plasma temperature; F is a constant, which is related to the efficiency of the light collection device, independent of the wavelength, and remains constant during the detection process;

is the distribution function of the emitting species s, expressed as:

(2); Step E2. Take the logarithm of equation (1), and make the following assumptions:

,

,

, (3) get the linear equation with respect to the parameters y and x

; Step E3. According to the measured and known spectral parameters in the spectral database

,

and

, you can draw a straight line of y with respect to x, and get the slope m and intercept

, can be obtained by the slope, ; Step E4. Normalizing the concentration of all species components can get F, that is

; concentration of species constituents

It can be calculated by the formula, and the analysis result of the component of the sample to be detected can be obtained.

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