CN117929327A - Handheld LIBS system with space constraint and magnetic field constraint and element analysis method - Google Patents

Abstract

The invention discloses a handheld LIBS system with space constraint and magnetic field constraint and an element analysis method, wherein the handheld LIBS system is arranged in a shell, and comprises a laser generator, a spectrometer, an optical fiber, a microcomputer, a power supply system and a power meter, a plasma enhanced probe outside the shell, a touch display screen, a heat dissipation channel, a trigger, an external power supply interface and a telescopic base. The probe is provided with a hemispherical binding cavity, and two sides of the binding cavity are provided with magnetic field generating devices; the power supply system provides working power for the whole device; the LIBS system, the power meter, the touch display screen and the trigger are all connected with the microcomputer. The portable LIBS device has the characteristics of light weight, portability and simple operation, and does not need sample pretreatment; the probe can strengthen the plasma, and can be detached and replaced by probes of different materials, sizes and shapes to spatially restrict the plasma, and the microcomputer can calibrate the data according to the laser energy measured by the power meter, so that the analysis capability of the device is improved.

Description

Handheld LIBS system with space constraint and magnetic field constraint and element analysis method

Technical Field

The invention belongs to the technical field of optical instrument and spectrum detection, and particularly relates to a handheld LIBS system with space constraint and magnetic field constraint and an element analysis method.

Background

Laser-induced breakdown spectroscopy (Laser-Induced Breakdown Spectroscopy, LIBS for short) is an advanced analysis technique for forming plasma on the surface of a sample by focusing pulse Laser, and further analyzing the emission spectrum of the plasma to determine the elemental composition and content of the sample. Compared with the traditional analysis method, the LIBS adopts pulse laser as an excitation source, has a plurality of advantages, and is widely applied to a plurality of fields such as environmental pollution detection, space exploration, material analysis, cultural relic identification and the like. In addition, LIBS technology is particularly suitable for in-situ and online detection of various physical samples in the industrial field production process.

At present, although the performance of a desk type instrument based on the LIBS technology is excellent, the in-situ online analysis capability of the LIBS technology is difficult to fully develop due to the defects of large volume, difficult transportation, external power supply and the like. The existing hand-held LIBS analyzer can only adopt low-energy laser as an excitation light source (tens to hundreds of micro-foci) and a simple light path due to the limitation of an internal space, and the resolution of the spectrometer is insufficient, and the ICCD cannot be used for carrying out time resolution on plasma, so that the analysis performance is insufficient. On the other hand, due to the complexity of the interaction of the laser-target material and the laser-plasma, the time transient and the spatial gradient of the plasma are uneven during spectrum acquisition, and the plasma is easily influenced by the physical and chemical properties of the surface of the sample and the environment where the plasma is positioned, so that the repeatability of LIBS signals is poor, thereby reducing the accuracy of qualitative and quantitative analysis and severely restricting the commercialization and industrial application of the LIBS technology.

Accordingly, there is a need to provide a handheld LIBS with spatial and magnetic constraints to address the above-described issues.

Disclosure of Invention

The invention aims to solve the technical problems in the background art, and aims to provide a handheld LIBS with space constraint and magnetic field constraint,

In order to solve the technical problems, the technical scheme of the invention is as follows:

A handheld LIBS system with space constraint and magnetic field constraint comprises a shell, a laser generator, a spectrometer, a microcomputer, a power supply system and a power meter, wherein the laser generator, the spectrometer, the microcomputer, the power supply system and the power meter are arranged inside the shell;

The front end of the shell is fixedly provided with a detachable plasma enhanced probe, a hemispherical binding cavity is formed in the plasma enhanced probe, and magnetic field generating devices are arranged on two sides of the hemispherical binding cavity; the hemispherical binding cavity is provided with a collecting surface; the collecting surface is positioned at the muzzle of the front end of the shell;

The rear end of the shell is fixedly provided with a touch control display screen, the front end of the touch control display screen is provided with a heat dissipation channel, and an external power supply interface is arranged below the touch control display screen;

the lower part of the shell is provided with a holding handle, the lower part of the holding handle is provided with a telescopic base, and the upper front part of the holding handle is provided with a trigger;

The back inside the shell is a microcomputer, a power supply system is arranged below the microcomputer, a laser generator is arranged at the upper front side, a spectrometer is arranged at the middle front side, the laser generator is connected with the hemispherical binding cavity through an optical path, a power meter is arranged between the laser generator and the hemispherical binding cavity, and the spectrometer is coupled with the optical path through an optical fiber.

The plasma enhanced probe is fixed in the shell through threads; the hemispherical binding cavity is provided with a hole, and the hole is coupled with the optical passage;

the hemispherical binding cavity takes the collecting surface as a diameter surface, the hemispherical formed by the collecting surface and the diameter surface is in a non-closed shape, and the diameter of the hemispherical binding cavity has various sizes;

The magnetic field generating device is tangential to the hemispherical binding cavity and perpendicular to the collecting surface, and the size of the magnetic field generating device is determined by the diameter of the hemispherical binding cavity.

The optical path includes: the device comprises a beam splitter, a dichroic mirror, a first converging lens and a second converging lens; a beam splitter, a dichroic mirror and a second converging lens are sequentially arranged on a linear light path from the laser generator to the hemispherical binding cavity; the power meter is positioned on a branch optical path of the beam splitter; the second converging lens is positioned on the reflecting light path of the dichroic mirror and is connected with the spectrometer through an optical fiber.

The beam splitter has various beam splitting ratios, the dichroic mirror is placed at 45 degrees, and the focal length of the second converging lens is determined according to the distance between the second converging lens and the acquisition surface.

The power supply system is connected with an external power supply interface, a switch, a laser generator, a spectrometer, a microcomputer, a power meter and a touch display screen through an electric energy transmission channel; the power supply system comprises a rechargeable battery, a voltage transformation module and is connected with the switch.

The laser generator is a single pulse laser generator or a multi-pulse laser generator.

The spectrometer is arranged in a single channel or in a multi-channel side-by-side manner, and the number of corresponding optical fibers is single or multiple.

The microcomputer is connected with the trigger, the laser generator, the touch display screen, the power meter and the spectrometer through signal wires;

The microcomputer is preset with a spectrum processing program and an optimized neural network model, and the collected spectrum data are converted into sample element contents and displayed through the touch display screen.

The method of the spectrum processing program comprises the following steps: carrying out normalization processing on the current acquired data, removing abnormal values, and compensating the spectrum according to the laser power; then, characteristic peaks are extracted from the spectrum, and the number of input variables is reduced.

The microcomputer is preset with an optimized neural network model, and the method for constructing the optimized neural network model comprises the following steps:

dividing the historical data set into a training set and a verification set;

firstly, initializing a BP neural network, determining input and output structures of the network, and initializing a connection weight and a threshold value; then, converting the initial weights and the thresholds into position vectors of the improved WOA, and initializing other basic parameters of an algorithm, including a population scale N, a maximum iteration number Tmax, an initial minimum weight w1, an initial maximum weight w2 and a convergence factor a;

Meanwhile, defining an adaptation function F (x) of the improved WOA as a mean square error between a model prediction output value and an actual measurement value; the position of the optimal fitness value is found through calculating the fitness value of the individual, and the position vector is recorded and used as the current optimal individual position xbest (t);

then, adopting different position updating strategies according to the value of A, updating the position of the next generation according to a specific formula when the value of A is more than or equal to 1, and adopting another formula to update when the value of A is less than 1;

And finally, after the maximum iteration times are met or the error precision requirement is met, terminating the optimizing algorithm, and assigning the current optimal parameters to the BP neural network, so that the optimization of the initial weight and the threshold value of the neural network is realized.

The invention also provides an element analysis method of the handheld LIBS system with space constraint and magnetic field constraint, which comprises the following steps:

S1, opening equipment by pressing a switch, attaching an acquisition surface to the surface of a sample, and acquiring a spectrum signal through a trigger;

The collecting surface is attached to the surface of the sample to ensure that laser is focused on the surface of the sample, and a good optical signal is obtained; the acquisition instructions are sent to the microcomputer through the trigger), the microcomputer controls the parts to work, firstly, the laser generator emits laser, laser energy information is acquired by the power meter and is transmitted to the microcomputer, light of plasma generated by the laser is captured by the spectrometer, then the spectral information is transmitted to the microcomputer, the microcomputer processes data to acquire sample component information, and finally, the information is transmitted to the touch display screen to be displayed;

s2, acquiring an optical signal, wherein the optical signal is obtained by a spectrometer in a distinguishing way through excitation of a sample, and meanwhile, the laser energy of the secondary optical signal is acquired and the laser energy is acquired by a power meter;

And S3, performing data processing on the optical signals to obtain element component information, and displaying the element component information on a touch display screen.

Further, step S3 comprises the sub-steps of:

Step S31, normalizing the acquired spectrum information to obtain a normalized spectrum signal;

S32, removing abnormal values of the normalized spectrum signals, and deleting outliers through a k-means algorithm;

S33, performing spectrum compensation on the spectrum signal with the outlier removed according to the current laser energy;

Step S34, extracting spectral characteristic peaks according to a preset threshold value, reserving the characteristic peaks at preset wavelengths, and rearranging the characteristic peaks into a characteristic peak matrix;

step S35, performing dimension reduction on the characteristic peak matrix according to a preset principal component analysis coefficient matrix, reducing redundant information and obtaining a dimension reduction matrix;

Step S36, inputting the dimension reduction matrix into the optimized neural network to analyze the element components of the sample;

Step S37, classifying the data subjected to history pretreatment under each environmental parameter into a training set and a verification set;

Step S38, the training set is sent to a BP neural network for training, a whale optimization algorithm is adopted to optimize the BP neural network model, wherein the steps include initializing the BP neural network, determining the input and output structures of the network, and initializing the connection weight and the threshold; then, converting the initial weights and the thresholds into position vectors of the improved WOA, and initializing other basic parameters of an algorithm, including a population scale N, a maximum iteration number Tmax, an initial minimum weight w1, an initial maximum weight w2 and a convergence factor a; meanwhile, defining an adaptation function F (x) of the improved WOA as a mean square error between a model prediction output value and an actual measurement value; the position of the optimal fitness value is found through calculating the fitness value of the individual, and the position vector is recorded and used as the current optimal individual position xbest (t);

Step S39, adopting different position updating strategies according to the value of A, updating the position of the next generation according to a specific formula when the value of A is more than or equal to 1, and adopting another formula to update when the value of A is less than 1; and finally, after the maximum iteration times are met or the error precision requirement is met, terminating the optimizing algorithm, and assigning the current optimal parameters to the BP neural network, so that the optimization of the initial weight and the threshold value of the neural network is realized.

Compared with the prior art, the invention has the advantages that:

According to the invention, the plasma life is regulated, the plasma collision probability is increased, the plasma temperature is increased, so that the abundance of excited state particles is increased, the signal intensity is improved, the sensitivity is improved, the stability of a spectrum is increased, and the space constraint is beneficial to avoiding the interaction with impurities or interference of an adjacent area, so that the signal-to-noise ratio is improved, the diffusion of free electrons is limited by the magnetic field constraint, the contribution of background radiation is reduced, and the signal is more easily distinguished from the background. The shape and the size of the plasma can be regulated and controlled by changing the shape of the constraint cavity and the shape of the magnetic field, and the plasma generating device does not need additional energy consumption, and has the advantages of simple structure, strong expansibility, simple and convenient operation and high stability.

Drawings

FIG. 1, a schematic diagram of the structure of the present invention;

FIG. 2 is a schematic cross-sectional view of the present invention;

FIG. 3 is a schematic diagram of the optical path structure relationship of the present invention;

FIG. 4 is a flow chart of the elemental composition measurement of the present invention;

fig. 5 is a schematic diagram of a neural network optimization flow according to the present invention.

Reference numerals:

1. A switch; 2. a plasma enhanced probe; 3. a touch display screen; 4. an external power supply interface; 5. a trigger; 6. a heat dissipation channel; 7. a microcomputer; 8. a laser generator; 9. a power meter; 10. a magnetic field generating device; 11. a hemispherical binding cavity; 12. a spectrometer; 13. a power supply system; 14. a housing (14); 15. a retractable base; 16. a grip handle; 17. an optical channel; 18. an optical fiber; 19. a hole; 20. a thread; 21. a beam splitter; 22. a dichroic mirror; 23 a first converging lens, 24, a second converging lens; 25. and (5) collecting a surface.

Detailed Description

The following describes specific embodiments of the present invention with reference to examples:

It should be noted that the structures, proportions, sizes and the like illustrated in the present specification are used for being understood and read by those skilled in the art in combination with the disclosure of the present invention, and are not intended to limit the applicable limitations of the present invention, and any structural modifications, proportional changes or size adjustments should still fall within the scope of the disclosure of the present invention without affecting the efficacy and achievement of the present invention.

Also, the terms such as "upper", "lower", "left", "right", "front", "rear", "middle" and "a" and the like are used in this specification for convenience of description, and are not intended to limit the scope of the present invention, but rather to change or adjust the relative relationship thereof without substantially changing the technical content, and are considered to be within the scope of the present invention.

Example 1:

Referring to fig. 1, 2 and 3, the present embodiment provides a handheld LIBS system with space constraint and magnetic field constraint, which includes a housing 14, a laser generator 8, a spectrometer 12, a microcomputer 7, a power supply system 13 and a power meter 9, which are disposed inside the housing 14, a plasma enhanced probe 2, a touch display 3, a heat dissipation channel 6, a trigger 5, an external power supply interface 4 and a retractable base 15, which are disposed outside the housing 14;

The front end of the shell 14 is fixedly provided with a detachable plasma enhanced probe 2, a hemispherical binding cavity 11 is formed in the plasma enhanced probe 2, and magnetic field generating devices 10 are arranged at two sides of the hemispherical binding cavity 11; the hemispherical binding cavity 11 is provided with a collecting surface 25; the collecting surface 25 is positioned at the muzzle of the front end of the housing 14;

the rear end of the shell 14 is fixedly provided with a touch display screen 3, the front end of the touch display screen 3 is provided with a heat dissipation channel 6, and an external power supply interface 4 is arranged below the touch display screen 3;

a holding handle 16 is arranged below the shell 14, a telescopic base 15 is arranged below the holding handle 16, and a trigger 5 is arranged in front of the upper part of the holding handle 16;

The back inside the shell 14 is a microcomputer 7, a power supply system 13 is arranged below the microcomputer 7, a laser generator 8 is arranged at the upper front, a spectrometer 12 is arranged at the middle front, the laser generator 8 is connected with the hemispherical binding cavity 11 through an optical path 17, a power meter 9 is arranged between the laser generator 8 and the hemispherical binding cavity, and the spectrometer 12 and the optical path 17 are coupled through an optical fiber 18.

The plasma enhanced probe 2 not only adjusts the service life of plasma, increases the collision probability of the plasma and increases the temperature of the plasma, thereby increasing the abundance of excited state particles, improving the signal intensity and the sensitivity and realizing the stability of spectrum enhancement, but also the space constraint is helpful to avoid the interaction with impurities or interference of adjacent areas, thereby improving the signal-to-noise ratio, the magnetic field constraint limits the diffusion of free electrons and reduces the contribution of background radiation, so that the signal is easier to distinguish from the background. The shape and the size of the plasma can be regulated and controlled by changing the shape of the constraint cavity and the shape of the magnetic field, and the plasma generating device does not need additional energy consumption, and has the advantages of simple structure, strong expansibility, simple and convenient operation and high stability.

The plasma enhanced probe 2 is fixed in the shell 14 through threads 20; the hemispherical binding cavity 11 is provided with a hole 19, and the hole 19 is coupled with the optical path 17;

The plasma enhanced probe 2 with different parameters can be replaced through the screw thread 20, the magnetic field generating device 10 is positioned at the two sides 11 of the hemispherical binding cavity, the influence of the magnetic field generating device on the shape 11 of the hemispherical binding cavity can be avoided, the magnetic field generating device 10 can be replaced by any parameter, and the hole 19 and the optical path 17 are coupled to ensure that the optical path can normally pass through the hole 19 to reach the acquisition surface 25.

The hemispherical binding cavity 11 takes the collecting surface 25 as a diameter surface, the hemispherical shape formed by the collecting surface 25 and the diameter of the hemispherical binding cavity 11 is in a non-closed shape, and the diameter of the hemispherical binding cavity is various in size; the collecting surface 25 is a diameter surface of the hemispherical binding cavity 11, so that the shock wave generated by exciting the plasma by the laser can be bounced by the binding cavity at the same time, the optimal plasma enhancement effect is achieved, and the hemispherical binding cavity 11 has various sizes, so that the most suitable binding cavity can be found under different working conditions.

The magnetic field generating device 10 is tangential to the hemispherical confinement chamber 11 and perpendicular to the collection surface 25, and its size is determined by the diameter of the hemispherical confinement chamber 11.

The optical path 17 includes: a beam splitter 21, a dichroic mirror 22, a first converging lens 23, a second converging lens 24; a beam splitter 21, a dichroic mirror 22 and a second converging lens 24 are sequentially arranged on a linear light path from the laser generator 8 to the hemispherical binding cavity 11; the power meter 9 is positioned on a branch optical path of the beam splitter 21; a second converging lens 24 is positioned in the light path reflected by the dichroic mirror 22 and is connected to the spectrometer 12 by an optical fiber 18.

The beam splitter 21 of the light path 17 splits the laser light to the power meter 9 to obtain laser energy information, the dichroic mirror 22 allows the laser light to pass smoothly and reflects the light emitted from the plasma, the light path 17 is miniaturized,

The beam splitter 21 has various beam splitting ratios, the dichroic mirror 22 is disposed at 45 degrees, and the focal length of the second focusing lens 24 is determined according to the distance from the collecting surface 25.

The beam splitter 21 limits the energy transmitted to the power meter 9 by various beam splitting ratios, so that the power meter is prevented from being damaged beyond a threshold value, the dichroic mirror 22 can accurately reflect light at 45 degrees, the focal length of the converging lens 23 is selected according to focusing laser light on the collecting surface 25, and the focal length of the converging lens 24 is selected according to focusing light emitted by plasma on the optical fiber 18.

The power supply system 13 is connected with the external power supply interface 4, the switch 1, the laser generator 8, the spectrometer 12, the microcomputer 7, the power meter 9 and the touch display screen 3 through an electric energy transmission channel; the power supply system 13 comprises a rechargeable battery, a transformation module and is connected to the switch 1. The power supply system 13 needs to supply power to the laser generator 8, the spectrometer 12, the microcomputer 7, the power meter 9 and the touch display screen 3 at the same time, and can be charged and supplied by the external power supply interface 4, and the power supply of the power supply system 13 is controlled by the switch 1. The power supply system uses the rechargeable battery to separate from external power supply to supply power for the device, so that the outdoor working requirement of a user is met, the voltage transformation module ensures that different devices work and rated voltage and power are guaranteed, and the switch 1 controls the power supply system, so that the working state of the whole device is controlled.

The laser generator 8 is a single pulse laser generator or a multi-pulse laser generator. The laser generator 8 excites plasma on the surface of the sample by laser light, thereby analyzing the sample.

The spectrometer 12 is arranged for single channel or multiple channels side by side, and the number of corresponding optical fibers 8 is single or multiple. The resolution of the spectrometer 12 affects the spectral quality, and by placing the multi-channel spectrometers side by side, the volume can be reduced and the resolution increased.

The microcomputer 7 is connected with the trigger 5, the laser generator 8, the touch display screen 3, the power meter 9 and the spectrometer 12 through signal lines;

The microcomputer 7 is triggered by the trigger 5 to start working, firstly the laser generator 8 emits laser, the laser energy information is acquired by the power meter 9 and transmitted to the microcomputer 7, the light of plasma generated by the laser is captured by the spectrometer 12, then the spectral information is transmitted to the microcomputer 7, the microcomputer 7 processes the data to acquire the sample component information, and finally the information is transmitted to the touch display screen 3 for display.

The microcomputer 7 is preset with a spectrum processing program and an optimized neural network model, converts the collected spectrum data into sample element contents, and displays the sample element contents through the touch display screen 3.

The spectrum processing program can process the original spectrum, so that the spectrum signal is easier to process by the neural network, the training failure caused by insufficient performance of the microcomputer can be avoided by the preset neural network, and the spectrum processing program can work with optimal parameters. The method of the spectrum processing program comprises the following steps: carrying out normalization processing on the current acquired data, removing abnormal values, and compensating the spectrum according to the laser power; then, characteristic peaks are extracted from the spectrum, and the number of input variables is reduced.

Example 2:

Fig. 4 and 5 show that the present embodiment provides a method for analyzing elements of a handheld LIBS system with space constraint and magnetic field constraint, and the method includes step S1, step S2 and step S3.

S1, opening the equipment by pressing a switch, attaching the acquisition surface to the surface of a sample, and acquiring a spectrum signal through a trigger.

The collecting surface 25 is attached to the surface of the sample to ensure that laser is focused on the surface of the sample, and a good optical signal is obtained; the trigger 5 sends an acquisition instruction to the microcomputer 7, the microcomputer 7 controls a plurality of parts to work, firstly the laser generator 8 emits laser, laser energy information is acquired by the power meter 9 and transmitted to the microcomputer 7, light of plasma generated by the laser is captured by the spectrometer 12, then the spectral information is transmitted to the microcomputer 7, the microcomputer 7 processes data to acquire sample component information, and finally the information is transmitted to the touch display screen 3 for display;

S2, acquiring an optical signal, wherein the optical signal is obtained by the resolution of a spectrometer 12 after the excitation of a sample, and simultaneously acquiring the laser energy of the secondary optical signal, wherein the laser energy is acquired by a power meter 9;

And S3, performing data processing on the optical signals to obtain element component information, and displaying the element component information on the touch display screen 3.

It can be understood that the invention can analyze the element information contained in the optical signal by preprocessing the optical signal, thereby increasing the accuracy of analysis.

In this step, step S3 includes:

Step S31, normalizing the acquired spectrum information to obtain a normalized spectrum signal;

S32, removing abnormal values of the normalized spectrum signals, and deleting outliers through a k-means algorithm;

And step S33, performing spectrum compensation on the spectrum signal with the outlier removed according to the current laser energy.

And S34, extracting spectral characteristic peaks according to a preset threshold value, reserving the characteristic peaks at preset wavelengths, and rearranging the characteristic peaks into a characteristic peak matrix.

And S35, performing dimension reduction on the characteristic peak matrix according to a preset principal component analysis coefficient matrix, reducing redundant information and obtaining a dimension reduction matrix.

And S36, inputting the dimension reduction matrix into the optimized neural network to analyze the element components of the sample.

It can be understood that the step is to normalize the spectrum, remove the abnormal value, improve the quality of the obtained spectrum, then compensate the spectrum signal to obtain the compensated spectrum signal, extract the principal component analysis to reduce the dimension and the calculated amount, and finally input the principal component analysis to the neural network for analysis to obtain the element components of the sample.

In this step, step S3 further includes step S37, step S38, and step S39.

Step S37, classifying the data subjected to history pretreatment under each environmental parameter into a training set and a verification set;

Step S38, the training set is sent to a BP neural network for training, a whale optimization algorithm is adopted to optimize the BP neural network model, wherein the training set comprises initialization of the BP neural network, input and output structures of the BP neural network are determined, and connection weights and thresholds are initialized. These initial weights and thresholds are then converted into position vectors for the improved WOA and other basic parameters of the algorithm are initialized, including population size N, maximum number of iterations Tmax, initial minimum weight w1, initial maximum weight w2, and convergence factor a. Meanwhile, the fitness function F (x) of the improved WOA is defined as the mean square error between the model predicted output value and the measured value. And (3) calculating the fitness value of the individual, finding the position of the optimal fitness value, recording the position vector, and taking the position vector as the current optimal individual position xbest (t).

Step S39, adopting different position updating strategies according to the value of A, updating the position of the next generation according to a specific formula when the value of A is more than or equal to 1, and adopting another formula to update when the value of A is more than or equal to 1. And finally, after the maximum iteration times are met or the error precision requirement is met, terminating the optimizing algorithm, and assigning the current optimal parameters to the BP neural network, so that the optimization of the initial weight and the threshold value of the neural network is realized.

It can be appreciated that the neural network is optimized by the whale optimization algorithm in this step, so that the analysis of the components of the sample is realized.

While the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes may be made without departing from the spirit of the present invention within the knowledge of those skilled in the art.

Many other changes and modifications may be made without departing from the spirit and scope of the invention. It is to be understood that the invention is not to be limited to the specific embodiments, but only by the scope of the appended claims.

Claims (10)

1. The handheld LIBS system with space constraint and magnetic field constraint is characterized by comprising a shell (14), a laser generator (8), a spectrometer (12), a microcomputer (7), a power supply system (13) and a power meter (9) which are arranged in the shell (14), a plasma enhanced probe (2), a touch display screen (3), a heat dissipation channel (6), a trigger (5), an external power supply interface (4) and a telescopic base (15) which are arranged outside the shell (14);

The front end of the shell (14) is fixedly provided with a detachable plasma enhanced probe (2), a hemispherical binding cavity (11) is formed in the plasma enhanced probe (2), and magnetic field generating devices (10) are arranged on two sides of the hemispherical binding cavity (11); the hemispherical binding cavity (11) is provided with a collecting surface (25); the collecting surface (25) is positioned at the muzzle of the front end of the shell (14);

A touch display screen (3) is fixed at the rear end of the shell (14), a heat dissipation channel (6) is arranged at the front end of the touch display screen (3), and an external power supply interface (4) is arranged below the touch display screen (3);

A holding handle (16) is arranged below the shell (14), a telescopic base (15) is arranged below the holding handle (16), and a trigger (5) is arranged in front of the upper part of the holding handle (16);

The rear part inside the shell (14) is a microcomputer (7), a power supply system (13) is arranged below the microcomputer (7), a laser generator (8) is arranged in front of the upper part, a spectrometer (12) is arranged in front of the middle part, the laser generator (8) is connected with the hemispherical binding cavity (11) through an optical path (17), a power meter (9) is arranged between the laser generator and the hemispherical binding cavity, and the spectrometer (12) and the optical path (17) are coupled through an optical fiber (18).

2. The hand-held LIBS system with spatial confinement and magnetic field confinement according to claim 1 wherein the plasma enhanced probe (2) is secured within the housing (14) by threads (20); the hemispherical constraint cavity (11) is provided with a hole (19), and the hole (19) is coupled with the light passage (17);

The hemispherical binding cavity (11) takes a collecting surface (25) as a diameter surface, the hemispherical shape formed by the collecting surface and the diameter of the hemispherical binding cavity (11) is in a non-closed shape, and the diameter of the hemispherical binding cavity is of various sizes;

The magnetic field generating device (10) is tangential to the hemispherical binding cavity (11) and is perpendicular to the collecting surface (25), and the size of the magnetic field generating device is determined by the diameter of the hemispherical binding cavity (11).

3. A hand-held LIBS system with spatial and magnetic constraints according to claim 1 characterised in that the optical pathway (17) comprises: a beam splitter (21), a dichroic mirror (22), a first converging lens (23), and a second converging lens (24); a beam splitter (21), a dichroic mirror (22) and a second converging lens (24) are sequentially arranged on a linear light path from the laser generator (8) to the hemispherical binding cavity (11); the power meter (9) is positioned on a branch optical path of the beam splitter (21); the second converging lens (24) is positioned on the light path reflected by the dichroic mirror (22) and is connected with the spectrometer (12) through an optical fiber (18).

4. A hand-held LIBS system with spatial and magnetic constraints according to claim 3 characterised in that the beam splitter (21) has a plurality of beam splitting ratios, the dichroic mirror (22) is placed at 45 ° and the focal length of the second converging lens (24) is dependent on the distance from the acquisition plane (25).

5. The hand-held LIBS system with spatial and magnetic constraints according to claim 1 characterized in that the power supply system (13) is connected with the external power supply interface (4), the switch (1), the laser generator (8), the spectrometer (12), the microcomputer (7), the power meter (9) and the touch display screen (3) through the power transmission channel; the power supply system (13) comprises a rechargeable battery, a voltage transformation module and is connected with the switch (1).

6. Hand-held LIBS system with spatial and magnetic confinement according to claim 1 characterized in that the laser generator (8) is a single-pulse laser generator or a multi-pulse laser generator.

7. The hand-held LIBS system with spatial and magnetic constraints according to claim 1 characterized in that the spectrometer (12) is arranged for single channel or multiple channels side by side, the number of corresponding optical fibers (8) being single or multiple.

8. The hand-held LIBS system with spatial and magnetic constraints according to claim 1 characterized in that the microcomputer (7) is connected to the trigger (5), the laser generator (8), the touch display screen (3), the power meter (9) and the spectrometer (12) by signal lines;

the microcomputer (7) is preset with a spectrum processing program and an optimized neural network model, and converts the collected spectrum data into sample element content to be displayed through the touch display screen (3).

9. A method of elemental analysis of a hand-held LIBS system having spatial constraints and magnetic field constraints according to any one of claims 1 to 8 characterised by the steps of:

S1, opening equipment by pressing a switch, attaching an acquisition surface to the surface of a sample, and acquiring a spectrum signal through a trigger;

the collecting surface (25) is attached to the surface of the sample to ensure that laser is focused on the surface of the sample, and good optical signals are obtained; the acquisition instruction is sent to the microcomputer (7) through the trigger) (5), the microcomputer (7) controls the parts to work, firstly, the laser generator (8) emits laser, laser energy information is acquired by the power meter (9) and is transmitted to the microcomputer (7), light of plasma generated by the laser is captured by the spectrometer (12), then the spectral information is transmitted to the microcomputer (7), the microcomputer (7) processes the data to acquire sample component information, and finally the information is transmitted to the touch display screen (3) to be displayed;

S2, acquiring an optical signal, wherein the optical signal is obtained by a spectrometer (12) in a distinguishing way when the sample is excited, and meanwhile, the laser energy of the secondary optical signal is acquired and the laser energy is acquired by a power meter (9);

S3, performing data processing on the optical signals to obtain element component information, and displaying the element component information on a touch display screen (3).

10. The method of elemental analysis of a handheld LIBS system with spatial constraints and magnetic field constraints according to claim 9 wherein step S3 comprises the sub-steps of:

Step S31, normalizing the acquired spectrum information to obtain a normalized spectrum signal;

S32, removing abnormal values of the normalized spectrum signals, and deleting outliers through a k-means algorithm;

S33, performing spectrum compensation on the spectrum signal with the outlier removed according to the current laser energy;

Step S34, extracting spectral characteristic peaks according to a preset threshold value, reserving the characteristic peaks at preset wavelengths, and rearranging the characteristic peaks into a characteristic peak matrix;

step S35, performing dimension reduction on the characteristic peak matrix according to a preset principal component analysis coefficient matrix, reducing redundant information and obtaining a dimension reduction matrix;

Step S36, inputting the dimension reduction matrix into the optimized neural network to analyze the element components of the sample;

Step S37, classifying the data subjected to history pretreatment under each environmental parameter into a training set and a verification set;

Step S38, the training set is sent to a BP neural network for training, a whale optimization algorithm is adopted to optimize the BP neural network model, wherein the steps include initializing the BP neural network, determining the input and output structures of the network, and initializing the connection weight and the threshold; then, converting the initial weights and the thresholds into position vectors of the improved WOA, and initializing other basic parameters of an algorithm, including a population scale N, a maximum iteration number Tmax, an initial minimum weight w1, an initial maximum weight w2 and a convergence factor a; meanwhile, defining an adaptation function F (x) of the improved WOA as a mean square error between a model prediction output value and an actual measurement value; the position of the optimal fitness value is found through calculating the fitness value of the individual, and the position vector is recorded and used as the current optimal individual position xbest (t);

Step S39, adopting different position updating strategies according to the value of A, updating the position of the next generation according to a specific formula when the value of A is more than or equal to 1, and adopting another formula to update when the value of A is less than 1; and finally, after the maximum iteration times are met or the error precision requirement is met, terminating the optimizing algorithm, and assigning the current optimal parameters to the BP neural network, so that the optimization of the initial weight and the threshold value of the neural network is realized.