Real-time online monitoring system for stable isotope abundance

Abstract

The invention discloses a stable isotope abundance real-time online monitoring system, and relates to the technical field of stable isotope detection, the stable isotope abundance real-time online monitoring system comprises a control module, a sample collection module, a laser module, a sample detection chamber, a temperature and pressure detection module, and a photoelectric detection module; the sample collection module preprocesses collected air and then sends the air into the sample detection chamber, the control module controls the laser module to output detection laser with set frequency and light intensity according to a stable isotope absorption peak, the detection laser is continuously reflected and absorbed in the sample detection chamber according to a set light path, and the photoelectric detection module detects emergent light intensity. The control module obtains the temperature and pressure of the sample gas in real time through the temperature and pressure detection module, and calculates the abundance value of the stable isotope to be detected by combining the incident light intensity, the emergent light intensity and the optical path. The gas stable isotope detection device has the characteristics of good timeliness of gas stable isotope detection, suitability for real-time monitoring of isotope abundance of various different gases, capability of adjusting the detection sensitivity according to the detected gas, and high detection sensitivity.

Description

Technical Field

[0001] The invention relates to the technical field of stable isotope detection, and more particularly to a real-time online monitoring system for stable isotope abundance. Background Art

[0002] With the development of science and technology, isotope analysis has been widely studied and applied in the fields of ecological environment protection, food safety testing, drug metabolism research, geological exploration, etc. For example, stable isotope tracing is used to analyze the sources of air pollution and study water resources and mining resources. The accurate and rapid measurement of stable isotope abundance has important basic significance in these analytical studies.

[0003] However, the current measurement of stable isotope abundance is mainly based on mass spectrometry. Although the technology is mature and the analysis accuracy is high, mass spectrometry analysis requires special tools such as mass spectrometers and liquid nitrogen refrigeration equipment. The structure is complex and the volume is large. The equipment is expensive. In addition, the detection process also involves complex sample collection and processing. The detection process is complicated and the real-time performance is poor. Therefore, it is only suitable for certain specific occasions. For example, for the monitoring and analysis of a large range of atmospheric environmental pollution sources, it is necessary to conduct rapid real-time monitoring of the stable isotope abundance of different gases in the air at different monitoring points, which puts higher requirements on the speed of stable isotope abundance detection and the cost of detection equipment.

[0004] Therefore, how to quickly and accurately detect stable isotopes is an urgent problem that needs to be solved by those skilled in the art. Summary of the invention

[0005] In view of this, the present invention provides a real-time online monitoring system for stable isotope abundance, which is based on the absorption peaks of different stable isotope gases, detects the light intensity before and after laser absorption and measures the pressure and temperature of the gas, thereby quickly and accurately detecting stable isotopes.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention discloses a real-time online monitoring system for stable isotope abundance, comprising: a control module, and a sample collection module, a laser module, a sample detection chamber, a temperature and pressure detection module, and a photoelectric detection module respectively connected to the control module by signal;

[0008] The sample collection module is connected to the pipeline of the sample detection chamber, and the sample gas is obtained by pre-processing the collected air and sent to the sample detection chamber;

[0009] The laser module outputs a detection laser of set frequency and light intensity to the sample detection chamber, and sends incident light intensity data of the output laser to the control module;

[0010] The sample detection chamber contains the sample gas and adjusts the optical path of the detection laser in the sample gas;

[0011] The temperature and pressure detection module detects the temperature and pressure of the sample gas in the sample detection chamber in real time, and sends the temperature and pressure data to the control module in real time;

[0012] The photoelectric detection module detects the detection laser emitted from the sample detection chamber, and sends the detected emission light intensity data and frequency data to the control module;

[0013] The control module controls the sample collection module to output the sample air; sends power and frequency control instructions to the laser module and sends optical path instructions to the sample detection chamber according to the absorption peak wavelength of the stable isotope to be detected; and calculates the abundance value of the stable isotope to be detected according to the incident light intensity data, the temperature and pressure data, the output light intensity data, and the optical path of the detection laser in the sample gas.

[0014] Furthermore, the sample collection module includes: an air intake port, an air pump, an air drying unit, an air filter unit, and a first air outlet valve. The air at the monitoring point enters the sample collection module through the air intake port, is pressurized by the air pump, and then enters the air drying unit for drying. The dried air is filtered through the air filter unit to obtain the sample gas, and is controlled to enter the sample detection chamber through the first air outlet valve.

[0015] Furthermore, the laser module includes: a power adjustment unit, a random laser, a laser tuner, a collimating lens, a Glan prism, a light intensity meter, and an output optical path;

[0016] The power adjustment unit adjusts the power of the random laser according to the instructions of the control module; the laser tuner tunes the laser emitted by the random laser according to the instructions of the control module to obtain laser light of a set wavelength, which is collimated by the collimating lens and then emitted into the Glan prism; the Glan prism totally reflects the o light in the laser to the light intensity meter, and outputs the e light in the laser through the output optical path.

[0017] Furthermore, the sample detection chamber includes: a light-transmitting body, a light-transmitting piston, an optical path adjustment module, an air inlet, a second air outlet valve, and a temperature and pressure detection port;

[0018] The light-transmitting body is hollow to form a cavity for accommodating the sample air; a laser incident surface and a laser exit surface are respectively arranged at the lower part of the light-transmitting body; a cylinder is formed at the upper part of the light-transmitting body, and cooperates with the light-transmitting piston to form an adjustable liquid cylinder; the optical path adjustment module can adjust the volume of the light-transmitting liquid in the liquid cylinder according to the optical path instruction, change the optical path of the detection laser in the sample detection chamber, and thus adjust the optical path of the detection laser in the sample gas.

[0019] Furthermore, the four laser exit / incident surfaces of the cavity form a square, the optical path of the detection laser is perpendicular to the laser exit / incident surfaces, the laser incident surface is parallel to two laser exit / incident surfaces, and the laser exit surface is parallel to the other two laser exit / incident surfaces;

[0020] The light-transmitting body and the light-transmitting piston form four total reflection surfaces with the outside air, and the planes where the total reflection surfaces are located form a rectangle, the width of the rectangle is fixed, and the length is adjusted by adjusting the moving distance of the light-transmitting piston. When the volume of the liquid cylinder is the smallest, the length and width of the rectangle are equal;

[0021] The angle between the total reflection surface and the laser exit / incident surface is 45 degrees, so that the detection laser is continuously reflected by the total reflection surface, and the optical path is changed by adjusting the difference between the length and width of the rectangle.

[0022] Furthermore, the optical path is calculated by the following formula:

[0023]

[0024] Where L is the total optical path of the detection laser in the sample gas, l s is the side length of the square, l a is the side length of the rectangle, l b is the width of the rectangle l r is the laser input offset value l c Laser emission offset value.

[0025] Furthermore, the calculation of the abundance value of the stable isotope to be detected specifically includes:

[0026] Step 1: The control module determines the first laser frequency and the first laser light intensity, the second laser frequency and the second laser light intensity according to the absorption peak wavelengths of different stable isotopes, and determines the optical path length of absorption;

[0027] Step 2: The control module sends an optical path instruction to the sample detection chamber, so that the detection laser optical path is the same as the optical path determined in step 1;

[0028] Step 3: The control module sends power and frequency control instructions, and adjusts the power control instructions according to the incident light intensity data returned by the laser module until the returned incident light intensity data is equal to the first laser light intensity; and adjusts the frequency control instructions according to the frequency data returned by the photoelectric detection module until the frequency data is equal to the first laser frequency;

[0029] Step 4: the control module reads the temperature and pressure data sent by the temperature and pressure detection module, and the output light intensity data of the photoelectric detection module, and calculates the concentration of the first stable isotope gas;

[0030] Step 5: The control module sends power and frequency control instructions, and adjusts the power control instructions according to the incident light intensity data returned by the laser module until the returned incident light intensity data is equal to the second laser light intensity; and adjusts the frequency control instructions according to the frequency data returned by the photoelectric detection module until the frequency data is equal to the second laser frequency;

[0031] Step 6: The control module reads the temperature and pressure data sent by the temperature and pressure detection module, and the output light intensity data of the photoelectric detection module, and calculates the concentration of the second stable isotope gas;

[0032] Step 7: Calculate the abundance value of the stable isotope to be detected based on the first stable isotope gas concentration and the second stable isotope gas concentration.

[0033] Furthermore, in step 4 and step 6, the gas concentration calculation formula is as follows:

[0034]

[0035] Where X is the molar molecular concentration of the detection gas, P is the sample gas pressure, L is the total optical path of the detection laser in the sample gas, and I o is the incident light intensity, I is the outgoing light intensity, S(T) is the absorption line intensity of the gas molecule at temperature T, and g(v) is the absorption line function of the detected gas;

[0036] The calculation formula for the gas molecule absorption line intensity is as follows:

[0037]

[0038] Where S(T0) is the absorption line intensity at the reference temperature T0, Q is the distribution function, h is Planck's constant, c is the speed of light, v0 is the center frequency of the transition line, k is the Boltzmann constant, and E is the low-energy state transition energy.

[0039] Furthermore, in step 7, the calculation formula of abundance value δ is: Where X1 is the concentration of the stable isotope to be detected, and X2 is the concentration of the comparative stable isotope.

[0040] Furthermore, it also includes a communication module, which provides communication services for the control module and the monitoring center, sends the monitoring command of the monitoring center to the control module, and uploads the abundance value of the stable isotope to be detected to the monitoring center.

[0041] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a real-time online monitoring system for stable isotope abundance. Based on the different absorption peaks of different stable isotopes, detection lasers of different frequencies are obtained by tuning, so that the abundance of multiple different stable isotope gases can be monitored; moreover, the detection laser optical path can be adjusted according to the characteristics of different stable isotope absorption peaks, so as to improve the detection sensitivity and ensure the accuracy of the detection result; moreover, the detection equipment does not require complex and expensive equipment such as mass spectrometers, the detection process is fast and simple, can be completed remotely and automatically, the detection is timely, and the equipment deployment cost and monitoring cost of stable isotope abundance monitoring are low. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0043] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0044] Figure 2 It is a schematic front view of a sample detection chamber according to an embodiment of the present invention.

[0045] Figure 3 It is a schematic side view of a sample detection chamber according to an embodiment of the present invention.

[0046] In the figure, 1. light-transmitting body; 2. light-transmitting piston; 3. laser incident surface; 4. laser exit surface; 5. cavity; 6. liquid cylinder; 7. total reflection surface; 8. laser exit / incident surface; 9. air inlet; 10. second air outlet valve; 11. temperature and pressure detection port; 12. optical path adjustment module. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] The embodiment of the present invention discloses a real-time online monitoring system for stable isotope abundance, such as Figure 1 As shown, it includes: a control module, and a sample collection module, a laser module, a sample detection chamber, a temperature and pressure detection module, and a photoelectric detection module respectively connected to the control module signal;

[0049] The sample collection module is connected to the sample detection chamber pipeline, and the sample gas is obtained after pre-processing the collected air and sent to the sample detection chamber;

[0050] The laser module outputs a detection laser of set frequency and light intensity to the sample detection chamber, and sends the incident light intensity data of the output laser to the control module;

[0051] A sample detection chamber, containing sample gas and adjusting the optical path of the detection laser in the sample gas;

[0052] The temperature and pressure detection module detects the temperature and pressure of the sample gas in the sample detection chamber in real time, and sends the temperature and pressure data to the control module in real time;

[0053] The photoelectric detection module detects the detection laser emitted from the sample detection chamber and sends the detected emission light intensity data and frequency data to the control module;

[0054] The control module controls the sample collection module to output sample air; sends power and frequency control instructions to the laser module and sends optical path instructions to the sample detection chamber according to the absorption peak wavelength of the stable isotope to be detected; and calculates the abundance value of the stable isotope to be detected according to the incident light intensity data, temperature and pressure data, the output light intensity data, and the optical path of the detection laser in the sample gas.

[0055] In a specific embodiment, the sample collection module includes: an air inlet, an air pump, an air drying unit, an air filter unit, and a first air outlet valve. The air at the monitoring point enters the sample collection module from the air inlet, is pressurized by the air pump, and then enters the air drying unit for drying. The dried air is filtered by the air filter unit to obtain sample gas, which is controlled to enter the sample detection chamber through the first air outlet valve. The interference of water vapor or fog in the air is removed by drying, and the interference of solids such as suspended particles in the air is removed by filtering; the control module controls the sample gas to enter the sample detection chamber by controlling the switches of the air pump, the first air outlet valve, and the second air outlet valve.

[0056] In a specific embodiment, the laser module includes: a power adjustment unit, a random laser, a laser tuner, a collimating lens, a Glan prism, a light intensity meter, and an output optical path;

[0057] The power adjustment unit adjusts the power of the random laser according to the instructions of the control module; the laser tuner tunes the laser emitted by the random laser according to the instructions of the control module to obtain the laser of the set wavelength, which is collimated by the collimating lens and then shot into the Glan prism; the Glan prism totally reflects the o light in the laser to the light intensity meter and outputs the e light in the laser through the output optical path. The laser emitted by the random laser is non-polarized light, which is shot into the Glan prism after tuning and collimation. The Glan prism can separate the o light and e light of different polarization directions in the laser. The separation ratio can be measured experimentally. According to the measured separation ratio, the intensity of the o light can be measured by the light intensity meter to obtain the intensity of the e light.

[0058] In a specific embodiment, Figure 2-3 As shown, the sample detection chamber includes: a light-transmitting body 1, a light-transmitting piston 2, an optical path adjustment module 12, an air inlet 9, a second air outlet valve 10, and a temperature and pressure detection port 11;

[0059] The light-transmitting body 1 is hollow to form a cavity 5 for accommodating sample air; the lower part of the light-transmitting body 1 is respectively provided with a laser incident surface 3 and a laser emitting surface 4; the upper part of the light-transmitting body 1 forms a cylinder, and cooperates with the light-transmitting piston 2 to form an adjustable liquid cylinder 6; the optical path adjustment module 12 can adjust the volume of the light-transmitting liquid in the liquid cylinder 6 according to the optical path instruction, change the optical path of the detection laser in the sample detection chamber, and thus adjust the optical path of the detection laser in the sample gas. Specifically, the side of the liquid cylinder 6 is connected to the optical path adjustment module 12 through a microhole, and the optical path adjustment module 12 is provided with a liquid storage tank, and the liquid volume in the liquid cylinder 6 is accurately adjusted by a high-precision gear pump.

[0060] In a specific embodiment, the four laser exit / incident surfaces 8 of the cavity 5 form a square, the optical path of the detection laser is perpendicular to the laser exit / incident surfaces 8, the laser incident surface 3 is parallel to two laser exit / incident surfaces 8, and the laser exit surface 4 is parallel to the other two laser exit / incident surfaces 8;

[0061] The light-transmitting body 1 and the light-transmitting piston 2 form four total reflection surfaces 7 with the outside air. The planes where the total reflection surfaces 7 are located form a rectangle. The width of the rectangle is fixed, and the length is adjusted by adjusting the moving distance of the light-transmitting piston 2. When the volume of the liquid cylinder 6 is the smallest, the length and width of the rectangle are equal.

[0062] The angle between the total reflection surface 7 and the laser exit / incident surface 8 is 45 degrees, so that the detection laser is continuously reflected by the total reflection surface 7, and the optical path is changed by adjusting the difference between the length and width of the rectangle. Specifically, the light-transmitting body 1 and the light-transmitting piston 2 are both composed of light-transmitting materials with the same refractive index, so that the critical angle of total reflection of the total reflection surface 7 is less than 45 degrees (for example, the critical angle of total reflection of the interface between glass and air is 42 degrees), but the critical angle of total reflection of the interface formed by the light-transmitting material and the liquid in the liquid cylinder 6 is greater than 45 degrees; in order to simplify the optical path, the light-transmitting material and the liquid have the same refractive index, so that the laser does not refract at the interface formed by the light-transmitting material and the liquid. When the length and width of the rectangle are equal, since the four total reflection surfaces 7 are square, the incident laser will continuously reflect in a cycle along the same rectangular optical path; when the light-transmitting piston 2 moves upward by an offset value, the reflection point of the laser on the total reflection surface 7 formed by the light-transmitting piston 2 will generate an offset in each cycle reflection until the detection laser is emitted. By adjusting the size of the offset value, the number of cycle reflections can be adjusted, thereby adjusting the optical path.

[0063] In a specific embodiment, the optical path length is calculated by the following formula:

[0064]

[0065] Where L is the total optical path of the detection laser in the sample gas, l s is the side length of the square, l a is the side length of the rectangle, l b The width of the rectangle is l r is the laser input offset value l c Laser emission offset value.

[0066] In a specific embodiment, calculating the abundance value of the stable isotope to be detected specifically includes:

[0067] Step 1: The control module determines the first laser frequency and the first laser light intensity, the second laser frequency and the second laser light intensity according to the absorption peak wavelengths of different stable isotopes, and determines the absorption optical path;

[0068] Step 2: The control module sends an optical path instruction to the sample detection chamber so that the detection laser optical path is the same as the optical path determined in step 1;

[0069] Step 3: The control module sends power and frequency control instructions, and adjusts the power control instructions according to the incident light intensity data returned by the laser module until the returned incident light intensity data is equal to the first laser light intensity; and adjusts the frequency control instructions according to the frequency data returned by the photoelectric detection module until the frequency data is equal to the first laser frequency;

[0070] Step 4: The control module reads the temperature and pressure data sent by the temperature and pressure detection module, and the output light intensity data of the photoelectric detection module, and calculates the concentration of the first stable isotope gas;

[0071] Step 5: The control module sends power and frequency control instructions, and adjusts the power control instructions according to the incident light intensity data returned by the laser module until the returned incident light intensity data is equal to the second laser light intensity; and adjusts the frequency control instructions according to the frequency data returned by the photoelectric detection module until the frequency data is equal to the second laser frequency;

[0072] Step 6: The control module reads the temperature and pressure data sent by the temperature and pressure detection module, and the output light intensity data of the photoelectric detection module, and calculates the concentration of the second stable isotope gas;

[0073] Step 7: Calculate the abundance value of the stable isotope to be detected based on the first stable isotope gas concentration and the second stable isotope gas concentration.

[0074] In a specific embodiment, in step 4 and step 6, the gas concentration calculation formula is as follows:

[0075]

[0076] Where X is the molar molecular concentration of the detection gas, P is the sample gas pressure, L is the total optical path of the detection laser in the sample gas, and I o is the incident light intensity, I is the outgoing light intensity, S(T) is the absorption line intensity of the gas molecule at temperature T, and g(v) is the absorption line function of the detected gas;

[0077] The calculation formula for the intensity of gas molecule absorption spectrum is as follows:

[0078]

[0079] In the formula, S(T0) is the intensity of the absorption line at the reference temperature T0, Q is the distribution function, h is Planck's constant, c is the speed of light, v0 is the center frequency of the transition line, k is the Boltzmann constant, and E is the low-energy state transition energy. Due to the different compositions of different stable isotope gas molecules, the energy required for the transition of molecules is different. When the energy of the radiated photon is equal to the difference E between the two transition energies, the molecule undergoes transition and absorbs photons. A molecule only absorbs photons of a specific frequency.

[0080] In a specific embodiment, in step 7, the abundance value δ is calculated as: Where X1 is the concentration of the stable isotope to be detected, and X2 is the concentration of the comparative stable isotope.

[0081] In a specific embodiment, a communication module is also included, which provides communication services for the control module and the monitoring center, sends the monitoring command of the monitoring center to the control module, and uploads the abundance value of the stable isotope to be detected to the monitoring center.

[0082] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0083] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A real-time online monitoring system for stable isotope abundance, It is characterized in that include: A control module, and a sample collection module, a laser module, a sample detection chamber, a temperature and pressure detection module, and a photoelectric detection module respectively connected to the control module by signal; The sample collection module is connected to the pipeline of the sample detection chamber, and the sample gas is obtained by pre-processing the collected air and sent to the sample detection chamber; The laser module outputs a detection laser of set frequency and light intensity to the sample detection chamber, and sends incident light intensity data of the output laser to the control module; The sample detection chamber contains the sample gas and adjusts the optical path of the detection laser in the sample gas; The temperature and pressure detection module detects the temperature and pressure of the sample gas in the sample detection chamber in real time, and sends the temperature and pressure data to the control module in real time; The photoelectric detection module detects the detection laser emitted from the sample detection chamber, and sends the detected emission light intensity data and frequency data to the control module; The control module controls the sample collection module to output the sample air; sends power and frequency control instructions to the laser module and sends optical path instructions to the sample detection chamber according to the absorption peak wavelength of the stable isotope to be detected; and calculates the abundance value of the stable isotope to be detected according to the incident light intensity data, the temperature and pressure data, the output light intensity data, and the optical path of the detection laser in the sample gas.

2. A stable isotope abundance real-time online monitoring system according to claim 1, It is characterized in that The sample collection module includes: an air intake port, an air pump, an air drying unit, an air filtering unit, and a first air outlet valve. The air at the monitoring point enters the sample collection module through the air intake port, is pressurized by the air pump, and enters the air drying unit for drying. The dried air is filtered through the air filtering unit to obtain the sample gas, and is controlled to enter the sample detection chamber through the first air outlet valve.

3. A stable isotope abundance real-time online monitoring system according to claim 1, It is characterized in that The laser module includes: a power adjustment unit, a random laser, a laser tuner, a collimating lens, a Glan prism, a light intensity meter, and an output optical path; The power adjustment unit adjusts the power of the random laser according to the instructions of the control module; the laser tuner tunes the laser emitted by the random laser according to the instructions of the control module to obtain laser light of a set wavelength, which is collimated by the collimating lens and then emitted into the Glan prism; the Glan prism totally reflects the o light in the laser to the light intensity meter, and outputs the e light in the laser through the output optical path.

4. A stable isotope abundance real-time online monitoring system according to claim 1, It is characterized in that The sample detection chamber comprises: a light-transmitting body, a light-transmitting piston, an optical path adjustment module, an air inlet, a second air outlet valve, and a temperature and pressure detection port; The light-transmitting body is hollow to form a cavity for accommodating the sample air; a laser incident surface and a laser exit surface are respectively arranged at the lower part of the light-transmitting body; a cylinder is formed at the upper part of the light-transmitting body, and cooperates with the light-transmitting piston to form an adjustable liquid cylinder; the optical path adjustment module can adjust the volume of the light-transmitting liquid in the liquid cylinder according to the optical path instruction, change the optical path of the detection laser in the sample detection chamber, and thus adjust the optical path of the detection laser in the sample gas.

5. A stable isotope abundance real-time online monitoring system according to claim 4, It is characterized in that The four laser exit / incident surfaces of the cavity form a square, the optical path of the detection laser is perpendicular to the laser exit / incident surfaces, the laser incident surface is parallel to two laser exit / incident surfaces, and the laser exit surface is parallel to the other two laser exit / incident surfaces; The light-transmitting body and the light-transmitting piston form four total reflection surfaces with the outside air, and the planes where the total reflection surfaces are located form a rectangle, the width of the rectangle is fixed, and the length is adjusted by adjusting the moving distance of the light-transmitting piston. When the volume of the liquid cylinder is the smallest, the length and width of the rectangle are equal; The angle between the total reflection surface and the laser exit / incident surface is 45 degrees, so that the detection laser is continuously reflected by the total reflection surface, and the optical path is changed by adjusting the difference between the length and width of the rectangle.

6. A stable isotope abundance real-time online monitoring system according to claim 5, It is characterized in that The optical path length is calculated by the following formula: Where L is the total optical path of the detection laser in the sample gas, l s is the side length of the square, l a is the side length of the rectangle, l b is the width of the rectangle l r is the laser input offset value l c Laser emission offset value.

7. A stable isotope abundance real-time online monitoring system according to claim 1, It is characterized in that The calculating the abundance value of the stable isotope to be detected specifically includes: Step 1: The control module determines the first laser frequency and the first laser light intensity, the second laser frequency and the second laser light intensity according to the absorption peak wavelengths of different stable isotopes, and determines the optical path length of absorption; Step 2: The control module sends an optical path instruction to the sample detection chamber, so that the detection laser optical path is the same as the optical path determined in step 1; Step 3: The control module sends power and frequency control instructions, and adjusts the power control instructions according to the incident light intensity data returned by the laser module until the returned incident light intensity data is equal to the first laser light intensity; and adjusts the frequency control instructions according to the frequency data returned by the photoelectric detection module until the frequency data is equal to the first laser frequency; Step 4: the control module reads the temperature and pressure data sent by the temperature and pressure detection module, and the output light intensity data of the photoelectric detection module, and calculates the concentration of the first stable isotope gas; Step 5: The control module sends power and frequency control instructions, and adjusts the power control instructions according to the incident light intensity data returned by the laser module until the returned incident light intensity data is equal to the second laser light intensity; and adjusts the frequency control instructions according to the frequency data returned by the photoelectric detection module until the frequency data is equal to the second laser frequency; Step 6: The control module reads the temperature and pressure data sent by the temperature and pressure detection module, and the output light intensity data of the photoelectric detection module, and calculates the concentration of the second stable isotope gas; Step 7: Calculate the abundance value of the stable isotope to be detected based on the first stable isotope gas concentration and the second stable isotope gas concentration.

8. A stable isotope abundance real-time online monitoring system according to claim 7, It is characterized in that In step 4 and step 6, the gas concentration calculation formula is as follows: Where X is the molar molecular concentration of the detection gas, P is the sample gas pressure, L is the total optical path of the detection laser in the sample gas, and I o is the incident light intensity, I is the outgoing light intensity, S(T) is the absorption line intensity of the gas molecule at temperature T, and g(v) is the absorption line function of the detected gas; The calculation formula for the gas molecule absorption line intensity is as follows: In the formula, S(T 0 ) is the reference temperature T 0 The absorption line intensity at the time, Q is the distribution function, h is Planck's constant, c is the speed of light, v 0 is the center frequency of the transition spectral line, k is the Boltzmann constant, and E is the low-energy state transition energy.

9. A stable isotope abundance real-time online monitoring system according to claim 7, It is characterized in that In step 7, the calculation formula of abundance value δ is: Where X 1 is the concentration of the stable isotope to be detected, X 2 To compare stable isotope concentrations.

10. A stable isotope abundance real-time online monitoring system according to claim 1, It is characterized in that It also includes a communication module, which provides communication services for the control module and the monitoring center, sends the monitoring command of the monitoring center to the control module, and uploads the abundance value of the stable isotope to be detected to the monitoring center.

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