CN112730383B - A Fiber Array LIBS Detection System for Online Detection - Google Patents

Abstract

The invention discloses a fiber array LIBS detection system for on-line detection, comprising a laser fiber coupling module, a laser control module and a spectrum acquisition module; wherein, the laser fiber coupling module includes a nanosecond laser, a dichroic mirror, a plano-convex lens and a and transmission fiber; laser control module includes beam splitter 1, beam splitter 2, photodiode, laser energy meter and programmable pulse delay generator; spectrum acquisition module includes plano-convex lens 2, collection fiber, spectrometer and ICCD; emitted from nanosecond laser The laser beam finally enters the fiber array LIBS probe through the transmission fiber. The optical fiber array module is installed directly above the equipment to be tested, and the 16 fiber optic sleeves on it can realize the synchronous detection of the two-dimensional array on the entire surface of the equipment. The invention can realize on-site real-time online detection of the running state of special equipment.

Description

A Fiber Array LIBS Detection System for Online Detection

technical field

The invention belongs to the technical field of laser diagnosis, and relates to an optical fiber array LIBS detection system for online detection.

Background technique

Condition monitoring, maintenance and evaluation technology of key equipment in the nuclear power, chemical and metallurgical industries is an important support for evaluating safety and economy. The key components of nuclear power equipment are subject to in-service and pre-service non-destructive testing. Since the above-mentioned key special equipment often has harsh operating environments such as high radioactivity, high temperature, and high pressure, conventional detection methods, such as X-ray photography technology, ultrasonic technology, and eddy current technology, are difficult to achieve long-distance online measurement. The newly developed remote online detection technologies such as acoustic emission technology and electrochemical technology also have their own limitations: for example, acoustic emission technology can only detect the pressure wave signal emitted by the material that is being damaged, but cannot evaluate and predict its life. ; Electrochemical technology needs to add small-amplitude electrical signal disturbances to the nuclear power system, which may adversely affect the system.

Laser Induced Breakdown Spectroscopy (LIBS) is a measurement technology that quantitatively measures the elemental composition and mechanical parameters of a sample by using the emission spectrum of the plasma generated on the surface of the material to be measured by laser induction. Compared with other detection methods, LIBS technology has obvious advantages: remote on-line in-situ detection, samples are slightly damaged or even non-destructive, no sample preprocessing is required, and simultaneous analysis of multiple elements can be achieved.

Optical fiber transmission laser-induced breakdown spectroscopy (hereinafter referred to as fiber LIBS technology) is an improvement and innovation of the previous traditional induced breakdown spectroscopy technology, and is more suitable for detection tasks in extreme occasions: using optical fiber transmission laser to focus the sample surface to form plasma, At the same time, the plasma emission spectrum is collected and analyzed by spectral post-processing algorithm to determine the material composition and content of the sample to be tested. This technology has huge potential application value in nuclear power plants, nuclear power plant maintenance and maintenance enterprises, nuclear fuel manufacturing plants, spent fuel processing plants and other places. It can detect equipment pipes or steam superheated elbows in high temperature, high pressure and high radiation production lines through optical fiber LIBS technology. In places that are difficult to reach by humans.

However, the currently developed optical fiber LIBS devices also have the following disadvantages. On the one hand, traditional portable fiber-optic LIBS detection systems cannot adapt to special working environments such as the main pipeline of nuclear power plants, nor can they go deep into designated areas inside special equipment for remote control detection (for example, Huazhong University of Science and Technology, Zeng Xiaoyan, etc., Portable laser detectors based on fiber lasers). Needle Composition Analyzer, [P], China, 2013107403189.20151104); on the other hand, because the energy density of the optical fiber LIBS technology to transmit laser bombardment target materials is generally lower than that of traditional LIBS, resulting in poor element sensitivity and element detection limit, resulting in some The detection capability of key elements is insufficient or even invalid. In order to solve this problem, it is necessary to create a corresponding special gas medium environment according to the detection requirements of specific elements, improve the signal-to-background ratio of spectral signals, and improve the detection sensitivity of key elements. In addition, in terms of testing equipment, the LIBS system that can realize remote control and reliable operation for harsh working environments such as complex radiation fields, high temperature and high humidity still needs to be further developed.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problems in the prior art and provide an optical fiber array LIBS detection system for on-line detection. The present invention uses an imaging method to focus the laser-induced breakdown spectrum, and is mainly used for the on-line characterization and analysis of surface elements of special equipment. Quantitative analysis to realize the status detection of equipment.

To achieve the above object, the present invention adopts the following technical solutions to realize:

An optical fiber array LIBS detection system for online detection, comprising:

a laser fiber coupling module, the laser fiber coupling module is used for outputting laser light, which is incident on the device to be tested through the fiber array LIBS probe; the laser control module is provided;

a laser control module, which is arranged on the output optical path of the laser fiber coupling module, and is used to monitor the actual energy of the output laser and adjust the delay between the output optical signal and the gate width signal;

The spectrum acquisition module includes a spectrometer and an ICCD, and the spectrometer is used to collect the plasma spectrum generated on the surface of the device to be tested, and transmit the spectrum information to a computer for analysis and comparison.

The further improvement of the present invention is:

The laser fiber coupling module includes a nanosecond laser, and the output laser light of the nanosecond laser enters the first plano-convex lens after being reflected by the dichroic mirror, and is focused by the first plano-convex lens and then transmitted from the transmission fiber to the fiber array LIBS probe.

The fiber input end face of the transmission fiber is located 3mm behind the focal point of the first plano-convex lens; the nanosecond laser 1 is an Nd:YAG nanosecond laser, the output laser wavelength is 1064nm, the frequency is 1-10Hz, the pulse width FWHM is 10ns, and the maximum pulse The energy is 150mJ and the laser beam diameter is 6mm.

The optical fiber array LIBS probe includes an optical fiber beam splitter and an optical fiber array module, and several optical fiber sleeves are installed on the optical fiber array module; each optical fiber sleeve is equipped with a focusing lens, and the focusing lens is installed on the optical fiber sleeve by two snap rings. The transmission fiber is split into several fibers by the fiber splitter, and each fiber enters a fiber sleeve.

The optical fiber array module is arranged above the equipment to be tested, and has a diameter of 5m; the optical fiber array module is connected to the lifting platform, and the lifting and lowering of the optical fiber array module is controlled by the lifting platform.

There are 16 optical fiber sleeves; the transmission optical fibers are split into 16 optical fibers by the optical fiber beam splitter; the diameter of the focusing lens 18 is 25.4 mm, and the focal length is 35 mm.

The laser control module includes a first beam splitter and a second beam splitter arranged on the optical path between the nanosecond laser and the dichroic mirror; a part of the output laser projects the first beam splitter to the second beam splitter, and the other part is captured by the first beam splitter. The beam splitter reflects on the photodiode, part of the output laser projected to the second beam splitter is projected to the dichroic mirror, and the other part is reflected by the second beam splitter to the laser energy meter.

The nanosecond laser, the first beam splitter, the second beam splitter, and the dichroic mirror are all located on the same optical path, and the center of the laser optical axis of the nanosecond laser, the center of the first beam splitter, the center of the second beam splitter, and the dichroic mirror The centers are all located on the same straight line; the first beam splitter, the second beam splitter, and the dichroic mirror all form an angle with the output laser optical axis of the nanosecond laser.

The spectrum acquisition module also includes a second plano-convex lens, and the plasma generated on the surface of the device to be tested is reversely transmitted along the original optical path, and becomes parallel light after passing through the fiber array LIBS probe, the transmission fiber and the first plano-convex lens, and the parallel light passes through. The dichroic mirror and the second plano-convex lens are focused into the collection fiber, and the other end of the collection fiber is connected to the spectrometer.

The transmission fiber is a multimode fiber with silica cladding, the length is 3m, the fiber core diameter is 800μm, the numerical aperture is 0.37, and the maximum power density is 1GW/cm ² ; both ends of the fiber are connected by SMA905 stainless steel fiber optic connectors The dichroic mirror is a short-wave pass dichroic mirror with a diameter of 50.8mm and a cut-off wavelength of 805nm; the length of the collecting fiber is 1m, the fiber core diameter is 400μm, and the numerical aperture is 0.22.

Compared with the prior art, the present invention has the following beneficial effects:

The invention realizes the detection of the optical fiber array LIBS on the surface of the line to be tested, and the advantages compared with the traditional detection method are: no need to destroy the line to be tested, the detection speed is fast, and the detection accuracy is high; the LIBS of the two-dimensional array on the entire line surface can be obtained at the same time. Spectral information, quantitatively determine the content of chromium element on the online surface, so as to predict the corrosion law of the pipeline, and then evaluate the service life.

Description of drawings

In order to describe the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings that need to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore do not It should be regarded as a limitation of the scope, and for those of ordinary skill in the art, other related drawings can also be obtained according to these drawings without any creative effort.

Fig. 1 is the overall structure diagram of the optical fiber array LIBS detection system used for online detection;

FIG. 2 is a schematic diagram of a fiber array LIBS probe for testing the device.

In the picture: 1-nanosecond laser, 2-first beam splitter, 3-second beam splitter, 4-second plano-convex lens, 5-dichroic mirror, 6-laser energy meter, 7-first plano-convex lens, 8-Transmission fiber, 9-fiber array LIBS probe, 10-device under test, 11-collection fiber, 12-photodiode, 13-programmable pulse delay generator, 14-spectrometer, 15-ICCD, 16-fiber splitter 17-fiber array module, 18-focusing lens, 19-retaining ring, 20-fiber connector, 21-fiber sleeve, 22-lifting platform.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all embodiments. The components of the embodiments of the invention generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations.

Thus, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

It should be noted that like numerals and letters refer to like items in the following figures, so once an item is defined in one figure, it does not require further definition and explanation in subsequent figures.

In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inside", etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings , or the orientation or positional relationship that the product of the invention is usually placed in use, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed in a specific orientation and operation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are only used to differentiate the description and should not be construed to indicate or imply relative importance.

Furthermore, the presence of the term "horizontal" does not imply that the component is required to be absolutely horizontal, but rather may be tilted slightly. For example, "horizontal" only means that its direction is more horizontal than "vertical", it does not mean that the structure must be completely horizontal, but can be slightly inclined.

In the description of the embodiments of the present invention, it should also be noted that, unless otherwise expressly specified and limited, the terms "set", "installed", "connected" and "connected" should be understood in a broad sense. It can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, and it can be internal communication between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

Below in conjunction with accompanying drawing, the present invention is described in further detail:

Referring to FIG. 1 , an embodiment of the present invention discloses a fiber array LIBS detection system for online detection, including a laser fiber coupling module, a laser control module, and a spectrum acquisition module. The laser fiber coupling module includes a nanosecond laser 1, a dichroic mirror 5, a first plano-convex lens 7 and a transmission fiber 8; the laser control module includes a first beam splitter 2, a second beam splitter 3, a photodiode 12, and a laser energy meter 6 and a programmable pulse delay generator 13; the spectrum acquisition module includes a second plano-convex lens 4, a collection fiber 11, a spectrometer 14 and an ICCD 15; the laser beam emitted from the nanosecond laser 1 finally enters the fiber array LIBS probe 9 through the transmission fiber 8 .

The nanosecond laser 1, the first beam splitter 2, the second beam splitter 3, and the dichroic mirror 5 are all located on the same optical path, and the center of the laser optical axis of the nanosecond laser 1, the center of the first beam splitter 2, and the center of the second beam splitter 3 The centers of the dichroic mirrors 5 and 5 are all located on the same straight line; the first beam splitter 2 , the second beam splitter 3 , and the dichroic mirror 5 all form an included angle of 45° with the output laser axis of the nanosecond laser 1 .

The output laser of the nanosecond laser 1 passes through the first beam splitter 2, and is split into the photodetector 12. The photodetector 12 is externally connected to the oscilloscope for monitoring the output signal of the main pulse laser; The laser light of the beam splitter 2 continues to pass through the second beam splitter 3 all the way, and is split all the way to the laser energy meter 6. The laser energy meter 6 is externally connected to the computer, and the laser energy entering the laser energy meter 6 is measured in advance through experiments. The proportion of the laser energy output by the nanosecond laser 1, and the corresponding spectral coefficient is set in the computer, so that the actual energy of the laser output by the nanosecond laser 1 can be monitored.

The dichroic mirror 5 is a short-wave pass dichroic mirror with a diameter of 50.8 mm and a cut-off wavelength of 805 nm. For light with a wavelength of 830-1300 nm, the reflectivity of the dichroic mirror 5 can reach more than 96%; for light with a wavelength of 400-792 nm, the light transmittance can also reach more than 90%.

The parallel laser beam reflected by the dichroic mirror 5 is focused by the first plano-convex lens 7 into the transmission fiber 8 for transmission. The fiber input end face of the transmission fiber 8 is placed about 3 mm behind the focal point of the first plano-convex lens 7 to avoid The strong focused energy during fiber coupling damages the boundary of the core cladding of the multimode fiber.

FIG. 2 is a schematic diagram of the online detection of the fiber array LIBS probe. The fiber array LIBS probe 9 consists of a fiber beam splitter 16 and a fiber array module 17; the fiber array module 17 is installed and fixed with 16 fiber sleeves 21; each fiber sleeve 21 is equipped with a focusing lens 18, and the focusing lens 18 consists of 2 Each snap ring 19 is installed in a fixed position on the optical fiber sleeve 21; the transmission optical fiber 8 is split into 16 optical fibers by the optical fiber splitter 16, and each optical fiber enters an optical fiber sleeve 21; the lifting platform 22 and the optical fiber array The modules 17 are connected and can be controlled to rise and fall.

The fiber array module 17 is installed directly above the device under test 10, and its diameter is 5m, which is equivalent to the diameter of the line; the distance between the focusing lens 18 and the surface of the device under test 10 is adjusted by the lifting platform 22 to obtain the best laser focusing effect; The 16 optical fiber sleeves 21 on the array module 17 can realize the synchronous detection of the two-dimensional array on the entire surface of the device under test 10 .

Preferably, the transmission fiber 8 used in the present invention is a silica-clad multimode fiber. The length of the transmission fiber 8 is 3m, the fiber core diameter is 800μm, the numerical aperture is 0.37, and the maximum power density is 1GW/cm ² ; the two ends of the fiber are connected by SMA905 stainless steel fiber connectors, and the large numerical aperture is conducive to the transmission of light at the input end of the fiber. Coupling in, but at the output end, due to the divergence and off-axis of multimode fiber, the output laser is difficult to focus and target; low numerical aperture provides lower beam divergence and uniform spot size, which can help the beam Focus the beam after propagation. Multimode fibers of different types, lengths, diameters and numerical apertures can be replaced according to actual needs.

After the laser energy output from the transmission fiber 8 passes through the fiber beam splitter 16, the laser energy is equally divided into 16 parts and enters into the 16 fibers respectively; the 16 parts of the laser energy output from the 16 fibers pass through the 16 fiber sleeves 21 at the same time In the middle; the 16 focusing lenses 18 fixed in the 16 fiber sleeves 21 simultaneously focus the 16 pieces of laser energy to penetrate the surface of the device under test 10 to form plasma.

The fiber output end faces of the 16 fibers are placed outside the focal length of the focusing lens 18 in the fiber sleeve 21. According to the imaging law of the convex lens, the laser light passing through the lens will form an inverted real image on the other side of the focusing lens 18. During this process, the laser is focused on the other side of the focusing lens 18 ; the lifting height of the lifting platform 22 is controlled by the computer, so that the focusing point of the focusing lens 18 is located at the surface of the device under test 10 .

The laser is focused and broken down on the surface of the device under test 10 through the focusing lens 18 to generate plasma. Since the optical path is reversible, the generated plasma luminous beam travels backward along the original optical path. The photons emitted by the plasma plume are focused into the 16 fibers through the focusing lens 18 in the fiber sleeve 21, and the plasma self-luminous beams output by the 16 fibers pass through the fiber beam splitter 16, and then converge into the transmission fiber 8 at the same time, Then the plasma self-luminous beam starts to propagate in the opposite direction along the transmission fiber 8 . At this time, the laser output end of the transmission fiber 8 becomes the photon input end, and the laser input end of the transmission fiber 8 becomes the photon output end.

The dichroic mirror 5, the first plano-convex lens 7, and the second plano-convex lens 4 of the present invention are all located on the same optical path. The center of the input end face of the transmission fiber 8, the center of the first plano-convex lens 7, the center of the dichroic mirror 5, and the second plano-convex lens 4 The center and the center of the input end face of the collecting fiber 11 are all located on the same straight line; the dichroic mirror 5 forms an included angle of 45° with the laser light path and the plasma self-luminous light path.

The plasma self-luminous beam propagating backward from the transmission fiber 8 becomes parallel light through the first plano-convex lens 7 , and the parallel light is focused into the collection fiber 11 through the dichroic mirror 5 and the second plano-convex lens 4 , and then input to the spectrometer 14 middle.

Preferably, the length of the collecting fiber 11 is 1 m, the fiber core diameter is 400 μm, and the numerical aperture is 0.22.

Preferably, the diameter of the focusing lens 18 is 25.4mm, and the focal length is 35mm.

The nanosecond laser 1 used in the present invention is a Nd:YAG nanosecond laser, the output laser wavelength is 1064 nm, the frequency is 1-10 Hz, the pulse width FWHM is 10 ns, the maximum pulse energy is 150 mJ, and the laser beam diameter is 6 mm.

The preparatory work of the present invention before the two-dimensional fiber array LIBS synchronous detection is performed on the surface of the device to be tested 10 is as follows: setting the parameters of the programmable pulse delay generator 13, changing the delay between the light output signal of the nanosecond laser 1 and the gate width signal of the ICCD 15, At the same time, the lifting and lowering of the lifting platform 22 is further fine-tuned by the computer, so that the signal-to-background ratio of the spectral intensity of the characteristic spectral lines of the relevant elements and the ordinate of the spectral graph are observed on the software of the computer to be the largest.

The spectrometer 14 will sample the ambient background spectrum before each measurement of the surface of the device to be tested 10 is performed. During each measurement, the nanosecond laser will emit 20 pulses of laser light at a frequency interval of 1 Hz, and the plasma spectrum generated by the laser breakdown on the surface of the device under test 10 is transmitted to the spectrometer 14 through the optical path; the spectrometer 14 will collect the The spectral accumulation generated by the 20 pulses is transmitted to the computer and provided to the user. The software can automatically analyze and compare the obtained spectral data with the LIBS element spectral information in the database, and provide the element species contained in the surface of the device under test 10. and the corresponding spectral line intensity, and the content of chromium element contained in the device to be tested 10 can be further determined through the calibration curve.

Principle of the present invention:

The transmission optical fiber of the present invention is a high-power transmission optical fiber, specifically a multimode optical fiber with silica cladding. The length of the transmission fiber is 3m, the core diameter of the fiber is 800μm, the numerical aperture is 0.37, and the maximum power density is 1GW/cm ² . At the output end, due to the divergence and off-axis of multimode fiber, the output laser is difficult to focus and target; low numerical aperture provides lower beam divergence and uniform spot size, which can help beam propagation rear focus beam. Multimode fibers of different types, lengths, diameters and numerical apertures can be replaced according to actual needs.

The optical fiber array module of the present invention is installed directly above the line, and its diameter is 5m, which is equivalent to the diameter of the line; the distance between the focusing lens and the surface of the line is adjusted by the lifting platform to obtain the best laser focusing effect; 16 fiber sleeves on the fiber array module The cartridge can realize the simultaneous detection of the two-dimensional array of the entire in-line surface.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (4)

1. A fiber array LIBS detection system for on-line detection, comprising:

the laser fiber coupling module is used for outputting laser, and the laser is incident on equipment to be tested (10) through a fiber array LIBS probe (9); setting a laser control module; the laser fiber coupling module comprises a nanosecond laser (1), wherein laser output by the nanosecond laser (1) enters a first plano-convex lens (7) through reflection of a dichroic mirror (5), is focused by the first plano-convex lens (7), and is transmitted to an optical fiber array LIBS probe (9) through a transmission fiber (8); the fiber input end face of the transmission fiber (8) is positioned 3mm behind the focus of the first plano-convex lens (7); the nanosecond laser 1 is Nd: YAG nanosecond laser, output laser wavelength is 1064nm, frequency is 1-10Hz, pulse width FWHM is 10ns, maximum pulse energy is 150mJ, and laser beam diameter is 6mm; the optical fiber array LIBS probe (9) comprises an optical fiber beam splitter (16) and an optical fiber array module (17), wherein a plurality of optical fiber sleeves (21) are installed on the optical fiber array module (17); each optical fiber sleeve (21) is internally provided with a focusing lens (18), and the focusing lens (18) is arranged on the optical fiber sleeve (21) through 2 snap rings (19); the transmission optical fiber (8) is split into a plurality of optical fibers by an optical fiber splitter (16), and each optical fiber enters an optical fiber sleeve (21);

the laser control module is arranged on an output light path of the laser fiber coupling module and used for monitoring the actual energy of the output laser and adjusting the time delay of an outgoing light signal and a gate width signal; the laser control module comprises a first spectroscope (2) and a second spectroscope (3) which are arranged on a light path between a nanosecond laser (1) and a dichroic mirror (5); one part of the output laser is projected to the first spectroscope (2) to the second spectroscope (3), the other part of the output laser is reflected to the photodiode (12) by the first spectroscope (2), one part of the output laser projected to the second spectroscope (2) is projected to the dichroic mirror (5), and the other part of the output laser is reflected to the laser energy meter (6) by the second spectroscope (3);

the spectrum acquisition module comprises a spectrometer (14) and an ICCD (15), wherein the spectrometer (14) is used for collecting a plasma spectrum generated on the surface of the equipment to be tested (10) and transmitting spectrum information to the computer for analysis and comparison; the spectrum acquisition module further comprises a second plano-convex lens (4), plasma generated on the surface of the device to be measured (10) reversely passes back along an original light path, and is changed into parallel light after passing through an optical fiber array LIBS probe (9), a transmission optical fiber (8) and a first plano-convex lens (7), the parallel light is focused into a collection optical fiber (11) through a dichroic mirror (5) and the second plano-convex lens (4), and the other end of the collection optical fiber (11) is connected with a spectrometer (14);

the transmission optical fiber (8) is a silica-clad multimode optical fiber with the length of 3m, the core diameter of 800 μm, the numerical aperture of 0.37 and the maximum power density of 1GW/cm ² (ii) a Two ends of the optical fiber are connected by an SMA905 stainless steel optical fiber connector; the dichroic mirror (5) is a short-wave-pass dichroic mirror, the diameter of the dichroic mirror is 50.8mm, and the cutoff wavelength is 805nm; the length of the collection fiber (11) was 1m, the fiber core diameter was 400 μm, and the numerical aperture was 0.22.

2. The fiber array LIBS detection system for on-line detection according to claim 1, wherein the fiber array module (17) is disposed above the device under test (10) and has a diameter of 5m; the optical fiber array module (17) is connected with the lifting platform (22) and is controlled to lift through the lifting platform (22).

3. The fiber optic array LIBS detection system for on-line detection as claimed in claim 1, wherein the fiber optic sleeve (21) is provided with 16; the transmission optical fiber (8) is split into 16 optical fibers by an optical fiber splitter (16); the focusing lens 18 has a diameter of 25.4mm and a focal length of 35mm.

4. The fiber array LIBS detection system for on-line detection according to claim 1, wherein the nanosecond laser (1), the first beam splitter (2), the second beam splitter (3) and the dichroic mirror (5) are all located on the same optical path, and the laser optical axis center of the nanosecond laser (1), the center of the first beam splitter (2), the center of the second beam splitter (3) and the center of the dichroic mirror (5) are all located on the same straight line; the first spectroscope (2), the second spectroscope (3) and the dichroic mirror (5) form (45) degrees included angles with an output laser optical axis of the nanosecond laser (1).

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