CN209927723U - Aerosol detection device based on laser-induced breakdown spectroscopy - Google Patents

Abstract

The utility model relates to the field of laser-induced breakdown spectroscopy, in particular to an aerosol detection device based on laser-induced breakdown spectroscopy, comprising an aerosol storage mechanism, a laser-induced breakdown module and a detection processing module. During the experiment, the air pump was turned on, and the aerosol gas generated by the aerosol generating mechanism was used to turn on the scattering laser after a certain delay by the delay pulse generator of the laser-induced breakdown module. After a period of time delay, turn on the pulse generator. It is focused on the aerosol particles to generate plasma, and the aerosol is detected by the scattered laser, and the pulsed laser is accurately focused on the aerosol after a fixed time delay. The utility model greatly increases the hit rate of the pulsed laser.

Description

An aerosol detection device based on laser-induced breakdown spectroscopy

technical field

The invention relates to the field of laser-induced breakdown spectroscopy, in particular to an aerosol detection device based on laser-induced breakdown spectroscopy.

Background technique

Aerosol is a mixed gaseous substance composed of solid and liquid particles floating in the atmosphere. Its chemical composition is complex and has a huge impact on the ecological environment and biosphere on the earth. The chemical substances in the aerosols in the atmosphere, especially the aerosols produced by industrial pollution, will cause global pollution under the action of the atmospheric wind system and have a huge impact on the living environment of human beings.

LIBS (Laser Induced Breakdown Spectroscopy), namely Laser Induced Breakdown Spectroscopy, is a laser ablation spectroscopic analysis technology and a new type of composition analysis technology. The basic process of measurement is that the pulsed laser is projected on the target sample, plasma is formed by ablation, the spectral data of the plasma is obtained from the optical device, and the qualitative or quantitative analysis of the target sample is realized by processing the spectral data. The technology has the advantages of simultaneous analysis of multiple elements, no complex sample pretreatment, fast detection rate, small sample loss and high sensitivity.

However, when using LIBS technology to detect aerosols. Often because the focal point of the pulsed laser cannot be accurately focused on the aerosol particles, the intensity of the detected spectral data is low, making it difficult to perform subsequent element identification and other processing.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide an aerosol detection device based on laser-induced breakdown spectroscopy, which can solve the problem that the focus point of the pulsed laser cannot be accurately focused on the aerosol particles, so that the detected spectral data intensity is low, It is difficult to perform subsequent processing such as element identification.

The present invention is realized in this way,

An aerosol detection device based on laser-induced breakdown spectroscopy, the device comprising:

The aerosol storage mechanism stores the aerosol, and a pulse switch is arranged at the opening, and a pressure pump is arranged at the other end;

The laser-induced breakdown module includes an aerosol tube with openings at the upper and lower ends, one end of the aerosol tube is open to the pulse switch, and the other end is open to the air hole of an air pump. A scattering laser and a photomultiplier tube are arranged on the corresponding two sides, and a pulse laser is arranged on one side of the other height of the aerosol tube. The scattering laser continuously emits laser light to the photomultiplier tube. The laser is blocked, so that the photomultiplier tube cannot receive the laser light and generates a light pulse, and triggers the delay pulse generator connected to the photomultiplier tube. After a preset delay time, the pulse laser emits a pulse laser and hits the aerosol. generate plasma;

The detection and processing module is arranged on the same plane as the pulsed laser, and receives the spectral data of the plasma generated after the laser generated by the pulsed laser passes through the aerosol.

Further, the pulse switch is in the shape of a funnel, and the head is in the shape of a thin tube, which is controlled by a controller to close and open, and the switching period of the pulse switch is Ts. The released aerosol gas flows in the aerosol tube under the suction of the air pump to detect the aerosol. During the experiment, the pressure pump is pressed down to press the aerosol in the aerosol storage mechanism.

Further, the length of the aerosol tube is 200 to 300 mm, the diameter is 50 to 60 mm, and the plane at the lower 50 to 60 mm of the entrance of the aerosol tube is provided with a scattering laser and a photomultiplier tube, and the scattering laser emission laser can directly hit the photoelectricity. On the multiplier tube and can pass through the tube axis of the aerosol tube, a pulsed laser and a corresponding detection processing module are installed on the plane 100-150mm below the plane of the scattering laser and the photomultiplier tube. The pulsed laser emits laser light that can be focused to On the axis of the aerosol tube, use the detection and processing module to collect plasma spectral data.

Further, the delay time is the time required for the aerosol to move from the scattering laser plane to the pulsed laser plane, so that the pulsed laser emitted by the pulsed laser can accurately hit the aerosol airflow flowing to the pulsed laser plane.

Further, the detection and processing module is composed of a spectrometer, a CCD and a computer, wherein the spectrometer and the computer are respectively connected with the CCD, the CCD is used to collect spectral information, and the spectrometer converts the collected spectral information into spectral data, and transmits the spectral data to the CCD. computer.

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

The invention uses the laser-induced breakdown spectroscopy technology to detect the aerosol, and has the advantages of simultaneous identification of multiple elements and no need for sample pretreatment. And the precise timing control is adopted to make the pulsed laser focus precisely on the aerosol, which greatly increases the hit rate and hit efficiency of the pulsed laser.

Description of drawings

Fig. 1 is the structural block diagram of the present invention;

Fig. 2 is the schematic diagram of the laser-induced breakdown module in Fig. 1;

FIG. 3 is a schematic diagram of the detection processing module in FIG. 1 .

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

Referring to FIG. 1 in conjunction with FIG. 2 , an aerosol detection device based on laser-induced breakdown spectroscopy technology includes an aerosol storage mechanism 1 , a laser-induced breakdown module 2 and a detection processing module 3 .

The aerosol storage mechanism stores the aerosol, and a pulse switch is arranged at the opening, and a pressure pump is arranged at the other end;

The laser-induced breakdown module includes an aerosol tube with openings at the upper and lower ends, one end of the aerosol tube is open to the pulse switch, and the other end is open to the air hole of an air pump. A scattering laser and a photomultiplier tube are arranged on the corresponding two sides, and a pulse laser is arranged on one side of the other height of the aerosol tube. The scattering laser continuously emits laser light to the photomultiplier tube. The laser is blocked, so that the photomultiplier tube cannot receive the laser light and generates a light pulse, and triggers the delay pulse generator connected to the photomultiplier tube. After a preset delay time, the pulse laser emits a pulse laser and hits the aerosol. generate plasma;

The detection and processing module is arranged on the same plane as the pulsed laser, and receives the spectral data of the plasma generated after the laser generated by the pulsed laser passes through the aerosol.

Among them, the lower part of the aerosol storage mechanism 1 is a pulse switch, and the upper part is a pressure pump. The pulse switch is funnel-shaped, and the head is a thin tube. The funnel-shaped design can gradually gather the messy aerosol gas in the aerosol storage mechanism, and then restrain the aerosol into a thinner gas flow by the thin tube-shaped head. The pulse switch It is controlled by the controller to close and open. The switching period of the pulse switch is 1s. In each period, it is opened for 1ms and then closed for 999ms. The aerosol gas released in the 1 ms is made to flow in the aerosol tube under the suction of the air pump, and the detection of the aerosol is carried out. During the experiment, the pressure pump was pressed down to press out the aerosol in the aerosol storage mechanism, and the pressure was 8 MPa, so that the moving speed of the aerosol in the aerosol tube was 50 m/s.

The laser-induced breakdown module 2 is composed of a scattering laser 5, a photomultiplier tube 6, a time delay pulse generator 7, a pulse laser 8, an aerosol container 9 and an air pump 10, wherein the aerosol tube 9 is located in the center of the module, and the upper part corresponds to the pulse switch 4. The air pump 10 is below it, the scattering laser 5 is on one side of the upper middle plane, the photomultiplier tube 6 is on the other side on the same plane as the scattering laser 6, and the other plane at a certain distance below the photomultiplier tube 6 is Pulsed laser 8.

The scattering laser corresponds to the photomultiplier tube in the same plane, and the scattering laser continuously emits laser light to the photomultiplier tube. When passing through the aerosol, the aerosol particles block the laser light, so that the photomultiplier tube cannot receive the laser light and generate light pulses. Since the peak-to-peak voltage of the electrical pulse needs to reach 5V to successfully trigger the delay pulse generator, the peak-to-peak value of the optical pulse needs to be large enough, that is, the area where the laser is blocked is large enough, that is, the aerosol concentration is large enough. Only then can the delay pulse generator be successfully triggered. The photomultiplier tube converts the light pulses into electrical pulses and outputs them to the delay pulse generator. After the delay time preset by the device, that is, the time required for the aerosol to move from the scattering laser plane to the pulse laser plane, the pulse laser emits a pulse laser to hit the pulse laser. onto the aerosol, creating a plasma.

In a preferred embodiment, the length of the aerosol tube 9 is 200mm, the diameter is 50mm, and the plane at the lower 50mm of the entrance above the aerosol tube is provided with a scattering laser and a photomultiplier tube, and the scattering laser emission laser can directly hit the photomultiplier. On the tube and can pass the tube axis of the aerosol tube. A pulsed laser and a corresponding spectrometer CCD are installed on the plane 100 mm below the plane of the scattering laser and photomultiplier tube. The laser emits laser light that can be focused on the axis of the aerosol tube, and the plasma spectral data is collected by a spectrometer CCD.

The distance from the plane of the scattering laser and the photomultiplier tube to the plane of the pulsed laser is 100mm. The flow rate of the aerosol gas is controlled by the pressure of the air pump. The preferred pressure is 8MPa, and the flow rate of the aerosol is 50m/s. The initial velocity of the aerosol coming out of the aerosol storage mechanism is the same, and the uniform linear motion is maintained in the aerosol tube. Dividing the distance by the flow rate gives a time of 2 ms for the aerosol to flow from the plane of the scattering laser to the plane of the pulsed laser.

The conversion time of the selected photomultiplier tube is 36 μs, which is negligible compared to the flow time of the aerosol from the scattering laser plane to the pulsed laser. Therefore, when the delay pulse generator receives the electrical pulse signal of the photomultiplier tube, a delay of 2ms is required. . In this way, the pulsed laser emitted by the pulsed laser can accurately hit the aerosol airflow flowing to the plane of the pulsed laser. Because the delay time of the delay pulse generator is set to 2ms, a microsecond-level delay device is used, which can maintain the accuracy of the entire sequence control device.

As shown in FIG. 3 , the detection processing module 3 is composed of a spectrometer, a CCD and a computer 11 , wherein the spectrometer and the computer 11 are respectively connected to the CCD. The CCD is used to collect spectral information, and the spectrometer converts the collected spectral information into spectral data, and transmits the spectral data to the computer.

The workflow of the present invention is:

The air pump 10 sucks the aerosol generated by the aerosol generating device into the aerosol tube 9, and at the same time, the scattering laser 5 emits laser light after a certain delay time is set by the delay pulse generator 7. When the photomultiplier tube 6 detects the aerosol, the delay pulse generator 7 is used to set a certain delay time, and a pulsed laser is emitted to focus on the aerosol particles to generate plasma. The spectral data of the plasma is received by the spectrometer and the CCD, and transmitted to the computer with the corresponding relationship between the spectral intensity and the wavelength.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (5)

1. An aerosol detection device based on laser-induced breakdown spectroscopy, the device comprising:

the aerosol storage mechanism is used for storing aerosol, a pulse switch is arranged at the opening, and a pressure pump is arranged at the other end of the aerosol storage mechanism;

the laser induced breakdown module comprises an aerosol tube with openings at the upper end and the lower end, wherein one end opening of the aerosol tube is aligned with the pulse switch, the other end opening of the aerosol tube is aligned with an air hole of the air pump, a scattering laser and a photomultiplier are arranged at two corresponding sides of a height plane of the aerosol tube, a pulse laser is arranged at one side of the other height of the aerosol tube, the scattering laser continuously emits laser to the photomultiplier, when the aerosol passes through, the aerosol particles shield the laser, so that the photomultiplier cannot receive the laser and generate light pulses, a delay pulse generator connected with the photomultiplier is triggered, and after the preset delay time, the pulse laser is emitted by the pulse laser to strike the aerosol to generate plasma;

and the detection processing module is arranged on the same plane with the pulse laser and is used for receiving plasma generated after laser generated by the pulse laser passes through the aerosol.

2. The device of claim 1, wherein the pulse switch is funnel-shaped, the head is thin tube-shaped, the closing and opening of the pulse switch are controlled by a controller, the switching period of the pulse switch is Ts, and in each period, after T1ms is opened, T2ms is closed, so that aerosol gas released from T1ms flows in the aerosol tube under the suction force of the air pump to perform aerosol detection, and in the experiment, the pressure pump is pressed down to press the aerosol in the aerosol storage mechanism.

3. The apparatus of claim 1, wherein the aerosol tube has a length of 200 ~ 300mm and a diameter of 50 ~ 60mm, the lower 50 ~ 60mm plane of the inlet of the aerosol tube is provided with a scattering laser and a photomultiplier tube, the scattering laser emits laser light capable of impinging directly on the photomultiplier tube and passing through the tube axis of the aerosol tube, a pulsed laser and a corresponding detection processing module are mounted at a plane 100 ~ 150mm below the plane of the scattering laser and photomultiplier tube, the pulsed laser light is capable of focusing on the axis of the aerosol tube, and the plasma spectrum is collected by the detection processing module.

4. The apparatus of claim 1, wherein the flow rate of the aerosol gas is controlled by the pressure of a pressure pump.

5. The apparatus of claim 1, wherein the detection processing module comprises a spectrometer, a CCD and a computer, wherein the spectrometer and the computer are respectively connected with the CCD, the CCD is used for collecting spectral information, the spectrometer converts the collected spectral information into spectral data, and the spectral data is transmitted to the computer.

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