Multi-component pollution gas high-resolution and multi-temperature gradient standard absorption cross section detection method and device

Abstract

The invention discloses a method and a device for detecting a high-resolution and multi-temperature gradient standard absorption cross section of multi-component pollution gas. The method comprises the following steps: a light source unit realizes broadband emergent light by switching sub light sources; the light path unit divides emergent light into two parts, and the two parts of emergent light respectively enter a first resonant cavity and a second resonant cavity which are formed by two plano-concave reflectors and are reflected for multiple times in the two resonant cavities; the long-optical-path absorption cell unit is used for sealing the first resonant cavity and the second resonant cavity and respectively accommodating background gas, background gas and gas to be detected, so that light reflected for multiple times in the two resonant cavities is subjected to long-optical-path absorption; the gas control unit is used for adjusting the total gas amount, the proportioning temperature and the pressure intensity; and the detection and calculation unit adopts two detectors to respectively receive output light reflected by the two resonant cavities for multiple times and calculates an absorption cross section. According to the invention, wider wavelength, temperature and pressure ranges can be covered, the signal-to-noise ratio of measured data is improved, high-sensitivity detection of low-concentration gas is realized, and multi-component gas absorption cross section detection is more accurate.

Description

Technical Field

[0001] The invention belongs to the technical field of optical measurement, and in particular relates to a method and device for detecting a multi-component polluted gas with high resolution and multiple temperature gradient standard absorption cross sections. Background Art

[0002] Polluted gas monitoring based on absorption spectroscopy technology, as an important means in the field of environmental monitoring, focuses on the accurate identification and analysis of the absorption spectrum of the target gas. The effectiveness of this technology not only depends on the accurate identification of the absorption spectrum characteristics, but also on the ability to accurately measure the absorption line structure and intensity of polluted gas molecules and the rate at which they change with environmental conditions, that is, the accurate measurement of the absorption cross section. The absorption cross section is a comprehensive reflection of the inherent properties of gas molecules. It directly determines the absorption capacity of the gas at a specific wavelength and is the basis for building an accurate monitoring model.

[0003] However, in practical applications, the existing standard molecular absorption structure database faces many challenges. First, the species coverage of the database is insufficient, and many newly emerging or relatively rare pollutant gases are not included, which limits the scope of application of the monitoring technology. Secondly, the quality of the data is uneven, and some data have large errors and uncertainties due to limitations in measurement technology or experimental conditions, which affects the accuracy of the monitoring results. In addition, auxiliary conditions such as temperature and pressure in the database often deviate from the actual detection environment, which further exacerbates the error between the monitoring results and the actual situation.

[0004] For new species, there are problems such as unclear absorption characteristics, instability, and easy cross-absorption with other components in the atmosphere, which seriously restricts the expansion of pollutant gas monitoring components. In addition, due to factors such as the power limitation of ultraviolet light sources, light source stability, and the higher difficulty in processing optical components, the signal-to-noise ratio of data measured in existing studies in this band is relatively low, which not only increases the complexity of data processing, but also may lead to systematic deviations in data between different laboratories, affecting the reliability and comparability of monitoring results. Therefore, developing a multi-component absorption cross-section detection device that covers a wider range of wavelengths, temperatures, and pressures, and improving the signal-to-noise ratio of measurement data and reducing systematic errors is one of the current problems that need to be solved.

[0005] Cavity-enhanced absorption spectroscopy uses a resonant cavity composed of two high-reflectivity plano-concave mirrors to reflect light multiple times, thereby increasing the effective absorption optical path. Its sensitivity is significantly higher than that of traditional direct absorption spectroscopy. However, the increase in detection sensitivity amplifies the error in gas sample concentration and the error caused by the uncertainty of the material state. Therefore, when using cavity-enhanced absorption spectroscopy for polluted gas monitoring, it is also necessary to add a system that can accurately control the material state and dynamically balance the temperature and pressure of low-concentration gas samples to the device to ensure the accuracy and stability of the measurement results.

[0006] Based on the above problems, a high-quality absorption cross-section detection device that can regulate the state of low-concentration gas samples and achieve a wide range of temperature and pressure conditions and high precision is developed. This is of great value for enriching the existing standard molecular absorption structure database, improving the accuracy and applicability of pollutant gas monitoring technology, and applying it to optical remote sensing monitoring of greenhouse gases, VOCs, odors and other pollutant gases. Summary of the invention

[0007] In view of the above, the purpose of the present invention is to provide a high-resolution, multi-temperature gradient standard absorption cross-section detection method and device for multi-component polluted gas, and cover a wider range of wavelengths, temperatures and pressures. A wider band range is obtained through a broadband light source with spectral splicing, covering the bands where the absorption characteristics of more components of gas are located, and realizing continuous detection of changes in molecular absorption structures; using cavity-enhanced optical path enhancement technology to achieve high-sensitivity detection of low-concentration gas samples, solving problems such as instability of some gases and cross-absorption; by optimizing the optical path structure to obtain a reference spectrum in real time to improve the signal-to-noise ratio, overcome the problem of weak gas absorption, and thus obtain high-quality spectral data; using a scattering filtering algorithm to reduce the interference of Rayleigh scattering and Mie scattering of the background gas on the absorption cross-section detection; through more accurate temperature and pressure control and dynamic environment simulation, ensure the reliability and universality of the measurement data in actual application scenarios.

[0008] In order to achieve the above-mentioned invention object, the technical solution provided by the present invention is as follows:

[0009] The embodiment of the present invention provides a high-resolution, multi-temperature gradient standard absorption cross-section detection device for multi-component polluted gas, comprising: a light source unit, an optical path unit, a long optical path absorption cell unit, a gas control unit, and a detection and calculation unit;

[0010] The light source unit is used to generate output light with stable power, and realize broadband output light by switching sub-light sources with different wavelength ranges;

[0011] The optical path unit is used to perform secondary processing on the outgoing light of the light source unit, so that the outgoing light is split into two and enters a first resonant cavity composed of two plano-concave reflectors and a second resonant cavity composed of two plano-concave reflectors respectively, and multiple reflections occur in the two resonant cavities, and only a small amount of light is allowed to pass through the plano-concave reflectors at the ends of the first resonant cavity and the second resonant cavity for output each time;

[0012] The long optical path absorption cell unit is used to seal the first resonant cavity and contain the background gas, and seal the second resonant cavity and contain the background gas and the gas to be measured, so that the light reflected multiple times in the two resonant cavities undergoes long optical path absorption inside;

[0013] The gas control unit is used to adjust the total amount and ratio of the gas in the long optical path absorption cell unit, and control the temperature and pressure of the gas at set values;

[0014] The detection and calculation unit is used to receive the output light of the first resonant cavity and the second resonant cavity after multiple reflections through the first detector and the second detector respectively, generate spectral data after time integration of the output light and then generate spectral data through photoelectric conversion, and calculate the absorption cross section based on the spectral data using a scattering interference filtering algorithm.

[0015] Preferably, the light source unit comprises: a power supply, a control module, a plurality of sub-light sources of different wavelength ranges mounted on a substrate, a motor for rotating and switching the sub-light sources, and a liquid-electric integrated conductive slip ring for continuous power supply and continuous temperature control when rotating and switching the sub-light sources. When working, the power supply provides electric energy to the motor, the motor is connected to the sub-light source on the substrate through the liquid-electric integrated conductive slip ring, and the control module controls the rotation angle of the substrate and the sub-light source switch to switch different sub-light sources.

[0016] Preferably, the light source unit also includes: a temperature control platform consisting of a coolant circulation unit, a liquid-electric integrated conductive slip ring, a cooling plate, and a temperature sensor fixed on a substrate, wherein the coolant circulation unit includes a coolant circulation pump, a coolant pipeline, and a coolant. When working, the power supply provides electric energy to the coolant circulation pump and the temperature sensor, the coolant circulation pump is connected to the cooling plate through the liquid-electric integrated conductive slip ring, the working temperature of the sub-light source is detected by the temperature sensor, and the control module adjusts the coolant flow rate according to the temperature data obtained by the detection, the heat emitted by the sub-light source is transferred from the substrate to the cooling plate and then conducted to the coolant for absorption, and the coolant is driven by the coolant circulation pump and circulates in the coolant pipeline to keep the temperature of the sub-light source stable.

[0017] Preferably, the optical path unit comprises: a collimating sleeve, a collimating mirror, a beam splitter, a converging mirror and a plano-concave reflector respectively arranged at the front ends of the first resonant cavity and the second resonant cavity, a plano-concave reflector respectively arranged at the ends of the first resonant cavity and the second resonant cavity, a filter, a focusing mirror, and optical fibers respectively connected to the first detector and the second detector. All optical components of the optical path unit are installed in the collimating sleeve. When working, the output light of the light source unit is collimated into parallel light by the collimating mirror, and then the parallel light is divided into mutually perpendicular reflected light and transmitted light by the beam splitter. The reflected light and the transmitted light are respectively coupled by the converging mirrors in front of the first resonant cavity and the second resonant cavity, and then enter the first resonant cavity and the second resonant cavity composed of two plano-concave reflectors, and multiple light reflections occur therein respectively. The light emitted by the plano-concave reflectors at the ends of the first resonant cavity and the second resonant cavity passes through their respective filters to retain the light in the wavelength band to be measured, and is respectively transmitted to the optical fiber after being coupled by their respective focusing mirrors.

[0018] Preferably, the collimating mirror is a plano-convex lens and is installed with a plane facing the light source, the beam splitter is a semi-transparent and semi-reflective mirror and makes the light intensity of the reflected light and the transmitted light equal, the focal length of the converging mirror and the distance to the plano-convex lens at the front end of each resonant cavity should ensure that the parallel light emitted by the collimating mirror is converged and imaged in the middle position of the resonant cavity, the curvature radius of the two plano-concave reflectors at the front and end of each resonant cavity and the distance between the two lenses satisfy the symmetrical confocal cavity mode, and the setting of all optical elements satisfies the equal optical path of the reflected light path and the transmitted light path.

[0019] Preferably, the long optical path absorption pool unit is a first cylindrical closed container and a second cylindrical closed container which are double-nested by an outer shell and an inner shell. The collimating sleeves of the two optical paths in the optical path unit are respectively arranged at the two ends of the two cylindrical closed containers. The first resonant cavity and the second resonant cavity are respectively enclosed in the first cylindrical closed container and the second cylindrical closed container. There is an interlayer space between the outer shell and the inner shell of each cylindrical closed container for passing the heat flow medium.

[0020] Preferably, each cylindrical closed container is provided with an air inlet for purging the plano-concave reflector, a port for installing a vacuum pump, a pressure gauge, a vacuum gauge, and a vacuum thermocouple, an air inlet for introducing background gas or gas to be measured, an inlet and outlet for the entry and exit of heat flow, an electric heating coil is wound around the outer wall of the inner shell, and a plurality of semiconductor refrigeration plates and their heat sinks are arranged on the inner wall of the outer shell.

[0021] Preferably, the gas control unit includes a gas pumping and extraction subsystem, a gas state monitoring subsystem, and a gas state adjustment subsystem. Gas is injected into or extracted from the long optical path absorption cell unit through the gas pumping and extraction subsystem, and the gas state parameters inside the long optical path absorption cell unit are obtained through the gas state monitoring subsystem and fed back to the gas state adjustment subsystem. The gas state adjustment subsystem regulates the temperature and pressure in the absorption cell until the set values ​​are reached.

[0022] Preferably, the temperature control of the gas state adjustment subsystem includes primary temperature control and secondary temperature control, which are used to adjust different temperature gradients; wherein, the primary temperature control adopts inter-wall heat exchange, and realizes temperature control of the gas in the resonance cavity by adjusting the circulation flow time and flow rate of the heat medium fluid introduced at the set temperature, and stops the flow of the heat medium fluid when the temperature reaches the set value ±1°C and switches to the secondary temperature control; the secondary temperature control includes heating and cooling, which is used to regulate the temperature with an accuracy of ±0.1°C and maintain it constant. The heating process controls the heat gain by adjusting the power-on time of the heat coil wrapped around the outer wall of the inner shell, and the cooling process contacts the heat medium fluid through the cold end of multiple semiconductor refrigeration plates arranged on the inner wall of the outer shell, and the hot end is connected to the radiator to dissipate the heat to the outside, and the heat increased or decreased by the secondary temperature control is transferred to the gas in the long optical path absorption cell unit through the heat medium fluid.

[0023] To achieve the above-mentioned purpose of the invention, the embodiment of the present invention further provides a method for detecting a multi-component polluted gas with high resolution and multiple temperature gradient standard absorption cross sections, which is implemented by using the above-mentioned multi-component polluted gas with high resolution and multiple temperature gradient standard absorption cross sections detection device, and includes the following steps:

[0024] The light source unit is used to generate output light with stable power, and broadband output light is achieved by switching sub-light sources with different wavelength ranges;

[0025] The light emitted from the light source unit is processed twice by using the optical path unit, so that the emitted light is split into two and enters a first resonant cavity composed of two plano-concave reflectors and a second resonant cavity composed of two plano-concave reflectors respectively, and multiple reflections occur in the two resonant cavities, and only a small amount of light is allowed to be output through the plano-concave reflectors at the ends of the first resonant cavity and the second resonant cavity each time;

[0026] The first resonant cavity is sealed and the background gas is contained by using a long optical path absorption cell unit, and the second resonant cavity is sealed and the background gas and the gas to be measured are contained, so that the light reflected multiple times in the two resonant cavities undergoes long optical path absorption inside;

[0027] The gas control unit is used to adjust the total amount and ratio of the gas in the long optical path absorption cell unit, and the temperature and pressure of the gas are controlled at the set values;

[0028] The detection and calculation unit receives the output light of the first resonant cavity and the second resonant cavity after multiple reflections through the first detector and the second detector respectively, integrates the output light time and then generates spectral data through photoelectric conversion, and calculates the absorption cross section based on the spectral data using a scattering interference filtering algorithm.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention obtains a wider band range by using the spectrum splicing broadband light source of the light source unit, covering the bands where the absorption characteristics of more component gases are located; the background gas and the gas to be measured are measured simultaneously by optimizing the structure of the optical path unit to obtain a reference spectrum in real time, thereby improving the signal-to-noise ratio and identifying weaker absorption characteristics; the optical path enhancement technology based on cavity enhancement is adopted to achieve high-sensitivity detection of low-concentration gas samples; the long-optical path absorption cell unit and the gas control unit control adopt multi-stage temperature control and dynamic temperature and pressure balance methods to achieve more accurate temperature and pressure control and dynamic environment simulation of gas samples, ensuring the reliability and universality of the measurement data in actual application scenarios; the scattering filtering algorithm is adopted in the detection and calculation unit to reduce the interference of Rayleigh scattering and Mie scattering of the background gas on the absorption cross-section detection.

[0031] Compared with the technology using laser as the light source, the measurement band bandwidth of the present invention is increased, and more polluted gas components can be measured; compared with the same type of absorption cross-section detection device, the signal-to-noise ratio of the spectral data of the present invention is improved, and the recognition of weaker absorption characteristics can be achieved; the present invention can achieve high-sensitivity detection of low-concentration gas samples, overcoming the problems of instability of some gases and cross-absorption; the present invention can achieve precise control of multiple temperature and pressure gradients of gas components, the measured spectral data has higher resolution, and the calculated absorption cross-section is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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 some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 It is a structural schematic diagram of a high-resolution, multi-temperature gradient standard absorption cross-section detection device for multi-component polluted gas provided by an embodiment of the present invention;

[0034] Figure 2 is a structural schematic diagram of a light source unit provided by an embodiment of the present invention;

[0035] Figure 3 is a schematic diagram of a light source switching effect provided by an embodiment of the present invention;

[0036] Figure 4 is a structural schematic diagram of an optical path unit provided by an embodiment of the present invention;

[0037] Figure 5 is a schematic structural diagram of a long optical path absorption cell unit provided in an embodiment of the present invention;

[0038] Figure 6is a schematic diagram of the operation process of the gas control unit provided by an embodiment of the present invention;

[0039] Figure 7 is a schematic diagram of the absorption cross-section detection process provided by an embodiment of the present invention;

[0040] Figure 8 is a schematic diagram of an absorption cross-section calculation algorithm provided in an embodiment of the present invention;

[0041] Fig. 9 It is a flow chart of a method for detecting a multi-component polluted gas with high resolution and multiple temperature gradient standard absorption cross sections provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0042] To make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the scope of protection of the present invention.

[0043] The inventive concept of the present invention is: in view of the problems of low signal-to-noise ratio, limited temperature and pressure adjustment range and insufficient precision in the detection of wide-band low-concentration gas absorption cross-section in the prior art, the embodiment of the present invention provides a high-resolution, multi-temperature gradient standard absorption cross-section detection method and device for multi-component polluted gas, which realizes broadband light output by adjusting different sub-light sources to fully cover the ultraviolet-visible band; by optimizing the structure of the optical path unit, the light source is divided into two and respectively introduced into a long optical path absorption cell unit for background gas and a long optical path absorption cell unit for gas to be tested, and the reference spectrum under the background gas is obtained in real time to improve the signal-to-noise ratio; in the long optical path absorption cell unit, the optical path enhancement technology based on cavity enhancement is used to realize high-sensitivity detection of low-concentration gas, and the long optical path absorption cell unit and the gas control unit are combined to realize multi-stage temperature control and dynamic environment simulation; finally, a scattering filtering algorithm is used to reduce the interference of Rayleigh scattering and Mie scattering of the background gas on the absorption cross-section detection, thereby improving the accuracy of the absorption cross-section detection.

[0044] Figure 1 Schematic diagram of a high-resolution, multi-temperature gradient standard absorption cross-section detection device for multi-component polluted gas provided by an embodiment of the present invention. Figure 1As shown, the embodiment provides a high-resolution, multi-temperature gradient standard absorption cross-section detection device for multi-component polluted gas, including: a light source unit, an optical path unit, a long optical path absorption cell unit, a gas control unit, and a detection and calculation unit. Among them, the light source unit is used to generate output light with stable power, and realize broadband output light by rotating and switching sub-light sources of different wavelength ranges; the optical path unit is used to perform secondary processing on the output light of the light source unit, so that the output light is divided into two and then enters a first resonant cavity composed of two plano-concave reflectors and a second resonant cavity composed of two plano-concave reflectors respectively, and multiple reflections occur in the two resonant cavities, and only a trace amount of light is allowed to be output through the plano-concave reflectors at the ends of the first resonant cavity and the second resonant cavity each time; the long optical path absorption cell unit is used as a cavity to seal the first resonant cavity and contain the background gas, while sealing The second resonant cavity is closed and contains background gas and gas to be measured, so that the light reflected multiple times in the two resonant cavities undergoes long optical path absorption inside; the gas control unit adjusts the total amount and ratio of the gas in the long optical path absorption cell unit by pumping or extraction, and controls the temperature and pressure of the gas at the set value; the detection and calculation unit is used to receive the output light after multiple reflections in the first resonant cavity and the second resonant cavity through the first detector and the second detector respectively, and use the computer to perform time integration on the output light and then generate spectrum data through photoelectric conversion, and calculate the absorption cross section based on the spectrum data using the scattering interference filtering algorithm. The following is a detailed description of each unit.

[0045] like Figure 2 As shown, the light source unit includes: a power supply, a control module, a plurality of sub-light sources of different wavelength ranges mounted on a substrate, a motor for rotating and switching the sub-light sources, a liquid-electric integrated conductive slip ring for continuous power supply and temperature control when rotating and switching the sub-light sources, and a liquid-cooled light source temperature control platform. The purpose of the light source unit is to obtain a stable wide-band light output, and the output light power meets the IBBCEAS technical requirements for the measurement of the absorption cross section of low-concentration substances.

[0046] In the light source unit, the sub-light source uses high-power LED lamp beads with an emission angle of 30°. The length and width of the chip are both 3.5mm. The LED lamp beads are installed on the copper substrate by welding, and are connected to the constant current power supply through the substrate. Based on the power provided by the constant current power supply, a beam with high intensity and wide spectrum is emitted. During welding, it is necessary to ensure that the normal direction of the LED lamp bead is perpendicular to the plane of the substrate to ensure that the 0° direction of the light emitted by the light source is on the main optical axis, so as to ensure the collimation of the subsequent optical path components to maximize the use of the light energy of the light source. The copper substrate is then evenly and tightly pasted on the cooling plate through thermal conductive silicone to reduce the impact of the LED lamp beads on the light power due to the large amount of heat emitted during use. The central wavelength of each sub-light source is different, and the band range is different. The bands are combined to cover the working band of the optical elements used in the system. The motor and the slip ring rotor are connected by a rotating shaft, and the slip ring rotor is connected to the cooling plate through a connecting shaft, so that the substrate rotates when the motor is running, thereby switching the sub-light sources of different wavelength ranges. The power required for the light output of the light source is transmitted through the hydraulic-electric integrated conductive slip ring to ensure continuous power supply during rotation. like Figure 3 As shown, the control module controls the rotation angle and the sub-light source switch to ensure that the sub-light source rotated to the corresponding collimator position emits light, while other sub-light sources do not emit light.

[0047] In the light source unit, the liquid-cooled temperature control platform includes a coolant circulation unit, a liquid-electric integrated conductive slip ring, a cooling plate, and a temperature sensor fixed on the substrate. The coolant circulation unit includes a coolant circulation pump, a coolant pipeline, and a coolant. The heat emitted by the sub-light source is transferred from the substrate to the cooling plate, and then conducted to the coolant for absorption. The coolant is driven by the coolant circulation pump to circulate in the coolant pipeline. The liquid-electric integrated conductive slip ring ensures the continuous circulation of the coolant during the rotation process. The heat emitted by the sub-light source is received by the substrate and then monitored by a temperature sensor attached to the substrate. The current change of the temperature monitored by the temperature sensor is transmitted to the temperature control module in the control module, and the PID algorithm is used to adjust the coolant flow rate of the coolant circulation pump so that the temperature fluctuation range is controlled within ±0.1°C to ensure the stable output of the sub-light source.

[0048] like Figure 4 As shown, the optical path unit includes: a collimating sleeve, a collimating mirror, a beam splitter, a converging mirror and a plano-concave reflector respectively arranged at the front end of the first resonant cavity and the second resonant cavity, a plano-concave reflector respectively arranged at the end of the first resonant cavity and the second resonant cavity, a filter, a focusing mirror, and optical fibers respectively connected to the first detector and the second detector. The purpose of the optical path unit is to secondary process the output light of the light source unit, so that the output light of the light source is split into two and then reflected multiple times in the corresponding resonant cavities, and the light energy of the light source unit is maximized.

[0049] In the optical path unit, all optical components are installed in the collimation sleeve and are tightened together without leakage through vacuum seals and long optical path absorption cell units. There are threads inside the collimation sleeve for the clamping ring to install each optical component in the specified position. The light source unit and the optical fiber probe are connected to the collimation sleeve through threads respectively.

[0050] In the optical path unit, the outgoing light is collimated into parallel light by a collimator, which is a plano-convex lens and is installed with a plane facing the light source to minimize spherical aberration; it is then divided into mutually perpendicular reflected light and transmitted light by a beam splitter, which is a semi-transparent and semi-reflective mirror, so that the intensity of the reflected light and the transmitted light is equal and is half of the intensity of the outgoing light from the light source unit. The optical element parameters of the transmitted light path and the reflected light path are the same, and the optical path is equal, so as to ensure that the light intensity at the detection end of the two light paths is consistent.

[0051] In the optical path unit, the reflected light and the transmitted light are coupled through the converging mirror into the first resonant cavity and the second resonant cavity formed by the two plano-concave reflectors, and intersect and form an image between the plano-concave reflectors. The focal length of the converging mirror and the distance to the plano-convex lens at the front end of each resonant cavity should ensure that the parallel light emitted by the collimator is imaged at the middle position of the resonant cavity after being converged, so as to maximize the use of the light emitted from the edge of the light source. The curvature radius of the two plano-concave reflectors at the front and end of each resonant cavity and the distance between the two lenses meet the symmetrical confocal cavity mode. After imaging, the converged light continues to transmit and reaches the reflection surface at the end of each resonant cavity to achieve parallel reflection and then converge at the middle position by the front reflection surface. This is repeated, and each reflection has a weak light output through the resonant cavity subsystem and forms an image at its middle position. The base material of the plano-concave reflector is ultraviolet fused quartz to resist thermal expansion, and the dimensions of 50.8mm in diameter and 9.5mm in thickness ensure that it can withstand high vacuum and high pressure. The concave surface of the plano-concave reflector is coated with a multilayer dielectric reflective film, and the reflectivity should be greater than 99.9% in the working band. The other surfaces of the lens are coated with an anti-reflection film to reduce light loss. The curvature radius of the plano-concave reflector is 1000mm, which ensures that the physical length of the resonant cavity is sufficient in the symmetrical confocal cavity mode.

[0052] In the optical path unit, the light emitted from the plano-concave reflector at the end of each resonant cavity is the superposition of the light intensity of each order. After passing through the respective filters to retain the light of the wavelength band to be measured, it is coupled into the optical fiber through the respective focusing mirrors. The numerical aperture value of the focusing mirror is smaller than the numerical aperture value of the optical fiber used. The distance between the focusing mirror and the plano-concave reflector at the end of the resonant cavity and the distance from the end face of the optical fiber to the focusing mirror are determined by the size of the focused light spot at the end face of the optical fiber. The set distance needs to ensure the smallest light spot. The optical fiber is a 7-core 200μm multimode optical fiber, which is arranged in the form of concentric rings at the receiving end and arranged vertically at the slit end of the incident spectrometer to maximize the light flux incident on the spectrometer. The end of the optical fiber close to the optical path is a 6-core multimode optical fiber arranged around a 1-core optical fiber, and the end close to the spectrometer (detector) is a 7-core optical fiber arranged side by side, which converts the circular light spot output by the focusing mirror into a light that fits the slit shape and inputs it into the internal optical path of the spectrometer.

[0053] like Figure 5 As shown, the long optical path absorption cell unit is made of stainless steel, and consists of a first cylindrical closed container and a second cylindrical closed container with double nested outer shells and inner shells, with an overall length of 0.9m and a diameter of 0.5m. The collimating sleeves of the two optical paths in the optical path unit are respectively arranged at the two ends of the two cylindrical closed containers, and the first resonant cavity and the second resonant cavity are respectively enclosed in the first cylindrical closed container and the second cylindrical closed container. There is an interlayer space for passing the heat flow medium between the outer shell and the inner shell of each cylindrical closed container. The function of this unit is to place the gas to be measured with a good concentration, and to make the light repeatedly pass through the gas to be measured to undergo long optical path absorption.

[0054] In the long optical path absorption cell unit, the inner shell wall thickness of the main double-layer structure is relatively thick (10mm) to ensure that the long optical path absorption cell unit -7 It can support most mechanical constraints when operating in the pressure range of atm to 2atm, and support the overall structure in high vacuum and high pressure environments. The outer wall thickness is relatively thin (2mm), which is only used to form a sandwich space (10mm) between the two walls to facilitate the circulation of heat medium fluid to control the temperature in the long optical path absorption cell unit. The inner wall of the inner shell of the long optical path absorption cell unit is plated with a passivation layer material to prevent the active component gas from reacting with stainless steel or adsorbing on the surface of stainless steel.

[0055] In the long optical path absorption cell unit, both ends are sealed by stainless steel covers. Two ports with a diameter of 50 mm are opened in the center of the stainless steel cover, and a vacuum sealing flange is provided for the installation of the collimation sleeve of the optical path unit. The two ports are extended outward for a certain distance so that the spacing between the two plano-concave reflectors of the resonant cavity subsystem is 1m, corresponding to the curvature radius value of the two plano-concave reflectors, forming a symmetrical confocal cavity mode. A lens purge gas port is provided at the port extension, which is used to purge the surface of the plano-concave reflector with inert gas to remove the residual gas attached to its surface. There are also multiple vacuum flange ports and fluid ports on the stainless steel covers at both ends, which are used for the installation of vacuum pumps, barometers, vacuum gauges, and vacuum thermocouples, and air inlets for introducing background gas or gas to be measured, inlets and outlets for the entry and exit of hot fluid, electric heating coils are wound on the outer wall of the inner shell, and multiple semiconductor cooling plates and radiators are arranged on the inner wall of the outer shell. The ports for fluid injection and extraction are made of polytetrafluoroethylene or stainless steel. Four adjustable anti-vibration mounts are mounted on the outside of the absorption tank to limit the impact of vibrations from the ground and pumping system, and are connected to the ground to prevent charge accumulation.

[0056] The gas control unit includes a gas pumping and extraction subsystem, a gas state monitoring subsystem, and a gas state adjustment subsystem. Gas is injected into or extracted from the long optical path absorption cell unit through the gas pumping and extraction subsystem, and the gas state parameters inside the long optical path absorption cell unit are obtained through the gas state monitoring subsystem and fed back to the gas state adjustment subsystem. The gas state adjustment subsystem regulates the temperature and pressure in the absorption cell until the set values ​​are reached.

[0057] In the gas control unit, the gas pumping and extraction subsystem includes a gas pumping module, a vacuum pump, background gas, gas to be tested, and a gas cylinder. Among them, the vacuum pump is divided into a front-stage mechanical pump and a molecular pump: the mechanical pump is used to extract most of the original gas in the absorption cell to a primary vacuum state, and the molecular pump is used to extract trace residual gas to a high vacuum state. The gas cylinder is used to store background gas and gas to be tested. The vacuum pump extracts the original gas in the absorption cell, and then injects the background gas to reach the set pressure. After the air pressure stabilizes, the gas to be tested is injected into the absorption cell. In order to prevent the formation of polymers and reduce the partial pressure of the gas to be tested, the amount of gas to be tested needs to ensure that it does not affect the gas pressure in the absorption cell. The gas pumping module is used to control the pumping and extraction speed of the gas.

[0058] In the gas control unit, the gas state monitoring subsystem is composed of a vacuum thermocouple, a barometer and a vacuum gauge. The vacuum thermocouple monitors the gas temperature in the absorption cell, the barometer monitors the air pressure value, and the vacuum gauge monitors the vacuum degree in the long optical path absorption cell unit when the vacuum pump is running to determine whether the original gas in the long optical path absorption cell unit is clear and clean.

[0059] In the gas control unit, the gas state adjustment subsystem consists of a temperature and pressure control module, a temperature module, and a pressure module, which are used to control the temperature and pressure of the gas in the absorption cell. The temperature and pressure module obtains relevant parameters from the gas state monitoring subsystem, and then adjusts the power of the temperature module and the pressure module through the PID algorithm to make the gas state in the long optical path absorption cell unit reach the set value. The temperature adjustment adopts the heat conduction method. The heat medium fluid introduced into the interlayer between the inner and outer walls of the long optical path absorption cell unit transfers heat to the stainless steel material of the inner wall, and then transfers it to the gas to be measured in the long optical path absorption cell unit. The heat medium fluid used is a fluorinated liquid to ensure rapid absorption of heat without damaging electronic components. The pressure module extracts mixed gas from the long optical path absorption cell unit or adjusts the pressure by increasing the background gas injection amount.

[0060] The temperature control of the gas state adjustment subsystem is divided into two levels, including primary temperature control and secondary temperature control, which are used to adjust different temperature gradients. The primary temperature control adopts inter-wall heat exchange, and realizes the temperature control of the gas in the resonant cavity by adjusting the circulation flow time and flow rate of the heat medium fluid with the set temperature. When the temperature reaches the set value ±1°C, the flow of the heat medium fluid is stopped and switched to the secondary temperature control. The secondary temperature control includes heating and cooling, which is used to regulate the temperature with an accuracy of ±0.1°C and maintain it constant. The heating process controls the heat increment by adjusting the power-on time of the heat coil wrapped around the outer wall of the inner shell. The cooling process is through the cold end of multiple semiconductor refrigeration plates arranged on the inner wall of the outer shell in contact with the heat medium fluid, and the hot end is connected to the radiator to dissipate the heat to the outside. The heat increased or decreased by the secondary temperature control is finally transferred to the gas in the long optical path absorption cell unit through the heat medium fluid.

[0061] like Figure 6 As shown, the gas state control in the absorption cell includes the following steps:

[0062] (1) using a vacuum pump to extract the gas in the cavity of the long optical path absorption cell unit to a high vacuum degree, calculating the amount of background gas and the amount of gas to be measured according to the concentration value to be measured and the set pressure value, and pumping the specified amount of background gas into the long optical path absorption cell unit;

[0063] (2) The vacuum thermocouple and barometer measure the temperature and pressure in the long optical path absorption cell unit respectively and transmit them to the STM32 microcontroller through A / D conversion;

[0064] (3) The STM32 microcontroller receives the temperature value and compares it with the set value, and adjusts the flow rate of the heat medium fluid valve and the gas pumping amount according to the deviation;

[0065] (4) When the temperature reaches the set value within ±1°C, the heat medium fluid valve is closed to stop the heat medium circulation, and the electric heating coil heating or semiconductor cooling is selected according to the temperature difference for further temperature control, so that the temperature is controlled within the range of ±0.1°C;

[0066] (5) Introduce a small amount of the gas to be tested into the long optical path absorption cell unit and continuously monitor until the gas pressure and temperature are stable.

[0067] like Figure 1 As shown, the detection and calculation unit includes a spectrometer for detecting the intensity of the optical fiber output light signal and a computer with calculation function. The purpose of the detection and calculation unit is to convert the output light of the detection optical path unit into spectral data and calculate the absorption cross section by integrating multiple sets of measurement data.

[0068] In the detection and calculation unit, the spectrometer models used at the detection ends of the transmitted light path and the reflected light path are consistent to reduce data errors caused by different detectors. The reflected light path and the transmitted light path respectively collect the background gas spectrum and the spectrum of the sample to be tested (the gas to be tested diluted to a certain concentration by the background gas, including the background gas and the gas to be tested) spectrum, and perform them simultaneously to eliminate the error of light intensity change. The computer with processing function uses the spectrum splicing method to process the multiple different band spectra obtained by measuring the light emitted by different sub-light sources to obtain a more complete spectrum. The band of each sub-light source only takes the spectrum extending from the central wavelength to the half-height width, and the overlapping area between the sub-light source bands selects the spectrum band data with a higher signal-to-noise ratio.

[0069] like Figure 7 As shown, the absorption cross section detection process of the overall operation of the system includes the following steps:

[0070] (1) Connect all units of the absorption cross section detection device and power on to check whether the instrument can be used normally;

[0071] (2) After the instrument is normal, turn on the vacuum pump to extract the gas in the long optical path absorption cell unit (the reflected light path is absorption cell 1, and the transmitted light path is absorption cell 2) to make it reach a high vacuum degree, and turn on the light source to make it run stably;

[0072] (3) Measure the absorption cell 1 on the reflected light path: Rotate and switch the light source, measure the vacuum spectra of all sub-light sources and perform spectral splicing to obtain the vacuum spectrum of the complete measurement band (without any gas, the concentration data is recorded as n zero , the spectral data is recorded as I zero (λ));

[0073] (4) introducing the calculated background gas into absorption cell 1, and introducing the calculated background gas and the gas to be measured into absorption cell 2, so that the pressure reaches the set value;

[0074] (5) Adjusting the gas temperature in absorption tank 1 and absorption tank 2 to within the range of ±0.1°C of the set temperature through multi-stage temperature control;

[0075] (6) Measuring the absorption cell 1 on the reflected light path: Rotate and switch the light source, measure the background gas spectra of all sub-light sources and perform spectral splicing to obtain the measured background gas spectrum of the complete measurement band (the concentration of the gas to be measured is n0=0, and the spectral data is recorded as I0(λ));

[0076] (7) Simultaneously measure the absorption cell 2 on the optical path of the transmitted light: rotate and switch the light source, measure the spectra of the gas to be measured of all sub-light sources and perform spectral splicing to obtain the spectrum of the gas to be measured in the complete measurement band (the concentration of the gas to be measured is n1(λ), ​​and the spectral data is recorded as I1(λ));

[0077] (8) Continue to inject the gas to be tested that does not affect the pressure change into the absorption cell 2, and adjust the concentration of the gas to be tested (the concentration of each group is n1, n2, ..., n N ), measure the corresponding spectrum (spectral data are recorded as I1(λ), ​​I2(λ), ..., I N (λ));

[0078] (9) The absorption cross section σ(λ) is calculated based on the absorption cross section algorithm based on the principle of broadband cavity enhanced absorption spectroscopy.

[0079] like Figure 8 The figure shows the calculation algorithm of the absorption cross section. After calculating the absorption coefficient of each group, the algorithm uses the absorption coefficient of each two groups of gases to be tested to filter out the scattering term, and then divides it by the concentration difference to get the absorption cross section, and then averages the multiple results. According to the measured spectral data, the absorption cross section calculation algorithm mainly includes the following steps:

[0080] (1) Obtain the reflectivity R(λ) of the concave reflector used in the resonant cavity, the physical cavity length L, and the effective cavity length d when the inert gas mirror purge protection is turned on eff ;

[0081] (2) Calculate the Rayleigh scattering coefficient α of the background gas based on the zero gas spectrum and the background gas spectrum Ray (λ):

[0082]

[0083] Where λ represents the wavelength;

[0084] (3) Based on the background gas spectrum I0(λ) and multiple groups of gas spectrum data of different concentrations I1(λ), ​​I2(λ), ..., I N (λ) Calculate the absorption coefficient α of each group of gases to be tested i (λ), as shown in the formula:

[0085]

[0086] Among them, α Mie(λ) represents the Mie scattering coefficient;

[0087] (4) Absorption coefficient α of each two groups of gases to be tested i (λ), α j (λ) is used to filter out the scattering term, and then combined with the concentration of the gas to be measured n i 、n j The absorption cross section is calculated and the average of multiple measurement results is taken to obtain the final measurement value σ(λ), as shown in the formula:

[0088] α i (λ)-α j (λ) = n i ×σ i (λ)-n j ×σ j (λ)

[0089]

[0090] Since there is no particulate matter, the Mie scattering coefficient is 0, and since the background gas is consistent, the Rayleigh scattering coefficient of each group is consistent. Therefore, the calculation method provided by the embodiment of the present invention is used without actually calculating α Mie (λ) and α Ray (λ), by directly subtracting the two sets of gas absorption coefficients, only the product of concentration and absorption cross section is left, and the absorption cross section σ(λ) is finally calculated.

[0091] Based on the same inventive concept, Fig. 9 As shown, the embodiment of the present invention also provides a high-resolution, multi-temperature gradient standard absorption cross-section detection method for multi-component polluted gas, comprising the following steps:

[0092] S1, using a light source unit to generate output light with stable power, and realizing broadband output light by switching sub-light sources with different wavelength ranges;

[0093] S2, using the optical path unit to perform secondary processing on the outgoing light of the light source unit, so that the outgoing light is split into two and enters a first resonant cavity composed of two plano-concave reflectors and a second resonant cavity composed of two plano-concave reflectors respectively, and multiple reflections occur in the two resonant cavities and only a small amount of light is allowed to pass through the plano-concave reflectors at the ends of the first resonant cavity and the second resonant cavity for output each time;

[0094] S3, using a long optical path absorption cell unit to seal the first resonant cavity and contain the background gas, and at the same time seal the second resonant cavity and contain the background gas and the gas to be measured, so that the light reflected multiple times in the two resonant cavities undergoes long optical path absorption inside;

[0095] S4, using a gas control unit to adjust the total amount and ratio of the gas in the long optical path absorption cell unit, and control the temperature and pressure of the gas at set values;

[0096] S5, using the detection and calculation unit to receive the output light of the first resonant cavity and the second resonant cavity after multiple reflections through the first detector and the second detector respectively, integrating the output light over time and then converting it into spectral data through photoelectric conversion, and calculating the absorption cross section based on the spectral data using a scattering interference filtering algorithm.

[0097] It should be noted that the high-resolution, multi-temperature gradient standard absorption cross-section detection method for a multi-component pollutant gas provided in the above-mentioned embodiment belongs to the same inventive concept as a high-resolution, multi-temperature gradient standard absorption cross-section detection device for a multi-component pollutant gas. The specific implementation process is detailed in the embodiment of a high-resolution, multi-temperature gradient standard absorption cross-section detection device for a multi-component pollutant gas, which will not be repeated here.

[0098] The specific implementation methods described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-resolution, multi-temperature gradient standard absorption cross-section detection device for multi-component polluted gas, characterized in that: include: A light source unit, an optical path unit, a long optical path absorption cell unit, a gas control unit, and a detection and calculation unit; The light source unit is used to generate output light with stable power, and realize broadband output light by switching sub-light sources with different wavelength ranges; The optical path unit is used to perform secondary processing on the outgoing light of the light source unit, so that the outgoing light is split into two and enters a first resonant cavity composed of two plano-concave reflectors and a second resonant cavity composed of two plano-concave reflectors respectively, and multiple reflections occur in the two resonant cavities, and only a small amount of light is allowed to pass through the plano-concave reflectors at the ends of the first resonant cavity and the second resonant cavity for output each time; The long optical path absorption cell unit is used to seal the first resonant cavity and contain the background gas, and seal the second resonant cavity and contain the background gas and the gas to be measured, so that the light reflected multiple times in the two resonant cavities undergoes long optical path absorption inside; The gas control unit is used to adjust the total amount and ratio of the gas in the long optical path absorption cell unit, and control the temperature and pressure of the gas at set values; The detection and calculation unit is used to receive the output light of the first resonant cavity and the second resonant cavity after multiple reflections through the first detector and the second detector respectively, generate spectral data after time integration of the output light and then generate spectral data through photoelectric conversion, and calculate the absorption cross section based on the spectral data using a scattering interference filtering algorithm.

2. The high-resolution, multi-temperature gradient standard absorption cross-section detection device for multi-component polluted gas according to claim 1, characterized in that: The light source unit includes: a power supply, a control module, a plurality of sub-light sources with different wavelength ranges mounted on a substrate, a motor for rotating and switching the sub-light sources, and a liquid-electric integrated conductive slip ring for continuous power supply and continuous temperature control when rotating and switching the sub-light sources. When working, the power supply provides electric energy to the motor, the motor is connected to the sub-light source on the substrate through the liquid-electric integrated conductive slip ring, and the control module controls the rotation angle of the substrate and the sub-light source switch to switch different sub-light sources.

3. The high-resolution, multi-temperature gradient standard absorption cross-section detection device for multi-component polluted gas according to claim 2, characterized in that: The light source unit also includes: a temperature control platform consisting of a coolant circulation unit, a liquid-electric integrated conductive slip ring, a cooling plate, and a temperature sensor fixed on a substrate. The coolant circulation unit includes a coolant circulation pump, a coolant pipeline, and a coolant. When working, the power supply provides electric energy to the coolant circulation pump and the temperature sensor. The coolant circulation pump is connected to the cooling plate through the liquid-electric integrated conductive slip ring. The working temperature of the sub-light source is detected by the temperature sensor, and the control module adjusts the coolant flow rate according to the temperature data obtained by the detection. The heat emitted by the sub-light source is transferred from the substrate to the cooling plate and then conducted to the coolant for absorption. The coolant is driven by the coolant circulation pump and circulates in the coolant pipeline to keep the temperature of the sub-light source stable.

4. The high-resolution, multi-temperature gradient standard absorption cross-section detection device for multi-component polluted gas according to claim 1, characterized in that: The optical path unit comprises: a collimating sleeve, a collimating mirror, a beam splitter, a converging mirror and a plano-concave reflecting mirror respectively arranged at the front ends of the first resonant cavity and the second resonant cavity, a plano-concave reflecting mirror respectively arranged at the ends of the first resonant cavity and the second resonant cavity, a filter, a focusing mirror, and optical fibers respectively connected to the first detector and the second detector. All optical components of the optical path unit are installed in the collimating sleeve. When working, the output light of the light source unit is collimated into parallel light by the collimating mirror, and then the parallel light is divided into mutually perpendicular reflected light and transmitted light by the beam splitter. The reflected light and the transmitted light are respectively coupled by the converging mirrors in front of the first resonant cavity and the second resonant cavity, and enter the first resonant cavity and the second resonant cavity composed of two plano-concave reflecting mirrors, and multiple light reflections occur therein respectively. The light outputted by the plano-concave reflecting mirrors at the ends of the first resonant cavity and the second resonant cavity passes through respective filters to retain the light of the wavelength band to be measured, and is respectively transmitted to the optical fiber after being coupled by respective focusing mirrors.

5. The high-resolution, multi-temperature gradient standard absorption cross-section detection device for multi-component polluted gas according to claim 4, characterized in that: The collimator is a plano-convex lens and is installed with a flat surface facing the light source. The beam splitter is a semi-transparent and semi-reflective mirror and makes the intensity of reflected light and transmitted light equal. The focal length of the converging mirror and the distance to the plano-convex lens at the front end of each resonant cavity should ensure that the parallel light emitted by the collimator is converged and imaged in the middle position of the resonant cavity. The curvature radius of the two plano-concave reflectors at the front and end of each resonant cavity and the distance between the two lenses satisfy the symmetrical confocal cavity mode. The settings of all optical components satisfy the equality of the optical path of the reflected light and the optical path of the transmitted light.

6. The high-resolution, multi-temperature gradient standard absorption cross-section detection device for multi-component polluted gas according to claim 4, characterized in that: The long optical path absorption cell unit is a first cylindrical closed container and a second cylindrical closed container which are double-nested by an outer shell and an inner shell. The collimating sleeves of the two optical paths in the optical path unit are respectively arranged at the two ends of the two cylindrical closed containers. The first resonant cavity and the second resonant cavity are respectively enclosed in the first cylindrical closed container and the second cylindrical closed container. An interlayer space for passing a heat flow medium is provided between the outer shell and the inner shell of each cylindrical closed container.

7. The high-resolution, multi-temperature gradient standard absorption cross-section detection device for multi-component polluted gas according to claim 6, characterized in that: Each cylindrical closed container is provided with an air inlet for purging the plano-concave reflector, a port for installing a vacuum pump, a pressure gauge, a vacuum gauge, and a vacuum thermocouple, an air inlet for introducing background gas or gas to be measured, an inlet and outlet for the inlet and outlet of heat flow medium, an electric heating coil is wound around the outer wall of the inner shell, and a plurality of semiconductor cooling plates and their radiators are arranged on the inner wall of the outer shell.

8. The high-resolution, multi-temperature gradient standard absorption cross-section detection device for multi-component polluted gas according to claim 7, characterized in that: The gas control unit includes a gas pumping and extraction subsystem, a gas state monitoring subsystem, and a gas state adjustment subsystem. Gas is injected into or extracted from the long optical path absorption cell unit through the gas pumping and extraction subsystem, and the gas state parameters inside the long optical path absorption cell unit are obtained through the gas state monitoring subsystem and fed back to the gas state adjustment subsystem. The gas state adjustment subsystem regulates the temperature and pressure in the absorption cell until the set values ​​are reached.

9. The high-resolution, multi-temperature gradient standard absorption cross-section detection device for multi-component polluted gas according to claim 8, characterized in that: The temperature control of the gas state adjustment subsystem includes primary temperature control and secondary temperature control, which are used to adjust different temperature gradients; wherein, the primary temperature control adopts inter-wall heat exchange, and realizes temperature control of the gas in the resonant cavity by adjusting the circulation flow time and flow rate of the heat medium fluid introduced at the set temperature, and stops the flow of the heat medium fluid when the temperature reaches the set value ±1°C and switches to the secondary temperature control; the secondary temperature control includes heating and cooling, which is used to regulate the temperature with an accuracy of ±0.1°C and maintain it constant. The heating process controls the heat increment by adjusting the power-on time of the heat coil wrapped around the outer wall of the inner shell, and the cooling process contacts the heat medium fluid through the cold end of multiple semiconductor refrigeration plates arranged on the inner wall of the outer shell, and the hot end is connected to the radiator to dissipate the heat to the outside, and the heat increased or decreased by the secondary temperature control is transferred to the gas in the long optical path absorption cell unit through the heat medium fluid.

10. A method for detecting a multi-component polluted gas with high resolution and multiple temperature gradient standard absorption cross sections, which is implemented by using the multi-component polluted gas with high resolution and multiple temperature gradient standard absorption cross sections detection device according to any one of claims 1 to 9, characterized in that: The steps include: The light source unit is used to generate output light with stable power, and broadband output light is achieved by switching sub-light sources with different wavelength ranges; The light emitted from the light source unit is processed twice by using the optical path unit, so that the emitted light is split into two and enters a first resonant cavity composed of two plano-concave reflectors and a second resonant cavity composed of two plano-concave reflectors respectively, and multiple reflections occur in the two resonant cavities, and only a small amount of light is allowed to pass through the plano-concave reflectors at the ends of the first resonant cavity and the second resonant cavity for output each time; The first resonant cavity is sealed and the background gas is contained by using a long optical path absorption cell unit, and the second resonant cavity is sealed and the background gas and the gas to be measured are contained, so that the light reflected multiple times in the two resonant cavities undergoes long optical path absorption inside; The gas control unit is used to adjust the total amount and ratio of the gas in the long optical path absorption cell unit, and the temperature and pressure of the gas are controlled at the set values; The detection and calculation unit receives the output light of the first resonant cavity and the second resonant cavity after multiple reflections through the first detector and the second detector respectively, integrates the output light time and then generates spectral data through photoelectric conversion, and calculates the absorption cross section based on the spectral data using a scattering interference filtering algorithm.

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