A detection method and device for high-resolution and multi-temperature-gradient standard absorption cross-sections of multi-component polluted gases

Abstract

The present invention discloses a method and device for detecting the high-resolution, multi-temperature gradient standard absorption cross section of multi-component pollutant gases, comprising: a light source unit that achieves broadband output light by switching sub-light sources; an optical path unit that splits the output light into two, which then enter a first and a second resonant cavity composed of two plano-concave reflectors, where multiple reflections occur in the two resonant cavities; a long optical path absorption cell unit that seals the first and second resonant cavities and respectively accommodates background gas, background gas, and gas to be measured, so that the light reflected multiple times in the two resonant cavities undergoes long optical path absorption; a gas control unit that adjusts the total amount of gas, the ratio of temperature, and the pressure; and a detection and calculation unit that uses two detectors to receive the output light after multiple reflections in the two resonant cavities and calculate the absorption cross section. The present invention can cover a wider range of wavelengths, temperatures, and pressures, improve the signal-to-noise ratio of measurement data, achieve high-sensitivity detection of low-concentration gases, and make multi-component gas absorption cross section detection more accurate.

Description

Technical Field

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

[0002] Polluted gas monitoring based on absorption spectroscopy technology, as an important means in the field of environmental monitoring, its core lies in 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 more crucially, on whether the absorption spectral line structure, intensity of the polluted gas molecules and their variation rate with environmental conditions can be accurately measured, that is, the accurate measurement of the absorption cross-section. The absorption cross-section is a comprehensive manifestation of the inherent properties of gas molecules, which directly determines the absorption ability of the gas at a specific wavelength and is the basis for constructing 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 emerged or relatively rare polluted gases are not included, which limits the application scope of the monitoring technology. Second, the data quality is uneven. Due to the limitations of measurement technology or experimental conditions, some data have large errors and uncertainties, affecting the accuracy of the monitoring results. In addition, the accessory 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 often problems such as unclear, unstable absorption characteristics and easy cross-absorption with other components in the atmosphere, which severely restricts the expansion of the monitoring components of polluted gases. Moreover, due to factors such as the power limitation of ultraviolet light sources, the stability of light sources, and the relatively high processing difficulty of optical components, the signal-to-noise ratio of the data measured in the existing research in this wavelength band is relatively low. This not only increases the complexity of data processing, but also may lead to systematic deviations in the data between different laboratories, affecting the reliability and comparability of the monitoring results. Therefore, developing a multi-component absorption cross-section detection device that covers a wider wavelength, temperature and pressure range, improving the signal-to-noise ratio of measurement data, and reducing systematic errors is one of the urgent problems to be solved at present.

[0005] The cavity-enhanced absorption spectroscopy technique utilizes a resonant cavity composed of two highly reflective plano-concave mirrors, enabling light to be reflected multiple times, thereby increasing the effective absorption optical path. Its sensitivity is significantly higher than that of traditional direct absorption spectroscopy techniques. However, the improvement in detection sensitivity amplifies the errors caused by the uncertainty in the concentration of gas samples and the physical state of substances. Therefore, when using the cavity-enhanced absorption spectroscopy technique for monitoring polluting gases, it is necessary to add a system to accurately control the physical state and achieve dynamic temperature and pressure balance for low-concentration gas samples to ensure the accuracy and stability of measurement results.

[0006] Based on the above problems, it is of great value to develop 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 with high precision. This is important for enriching the existing standard molecular absorption structure database, improving the accuracy and applicability of polluting gas monitoring technologies, and being applied to the optical remote sensing monitoring of greenhouse gases, VOCs, and odorous polluting gases. Summary of the Invention

[0007] In view of the above, the object of the present invention is to provide a method and device for detecting the standard absorption cross-section of multi-component polluting gases with high resolution and multi-temperature gradients, covering a wider range of wavelengths, temperatures, and pressures. A wider wavelength band range is obtained through a broadband light source with spectral splicing, covering the absorption characteristic bands of more component gases, and achieving continuous detection of changes in the molecular absorption structure; the optical path enhancement technology based on cavity enhancement is adopted to achieve high-sensitivity detection of low-concentration gas samples, solving problems such as instability of some gases and cross-absorption; the reference spectrum is obtained in real time by optimizing the optical path structure to improve the signal-to-noise ratio, overcoming the problem of weak gas absorption, thereby obtaining high-quality spectral data; the scattering filtering algorithm is used to reduce the interference of Rayleigh scattering and Mie scattering of the background gas on the detection of the absorption cross-section; through more precise temperature and pressure control and dynamic environment simulation, the reliability and universality of measurement data in actual application scenarios are ensured.

[0008] To achieve the above object of the invention, the technical solutions provided by the present invention are as follows:

[0009] A device for detecting the standard absorption cross-section of multi-component polluting gases with high resolution and multi-temperature gradients provided by an embodiment of the present invention includes: 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 achieve 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, splitting the outgoing light into two parts and respectively entering the first resonant cavity composed of two plano-concave mirrors and the second resonant cavity composed of two plano-concave mirrors. Multiple reflections occur in the two resonant cavities, and only a small amount of light is allowed to pass through the plano-concave mirrors 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 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;

[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 the set values;

[0014] 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, perform time integration on the output light and then generate spectral data through photoelectric conversion, and calculate the absorption cross section using the scattering interference filtering algorithm based on the spectral data.

[0015] Preferably, the light source unit includes: a power supply, a control module, multiple 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. During operation, the power supply supplies electrical energy to the motor, the motor is connected to the sub-light sources on the substrate through the liquid-electric integrated conductive slip ring, and the control module controls the rotation angle of the substrate and the switch of the sub-light sources to switch different sub-light sources.

[0016] Preferably, the light source unit further includes: a temperature control platform composed of 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 coolant. During operation, the power supply supplies electrical energy to the cooling 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 sources is detected by the temperature sensor, and the control module adjusts the coolant flow rate according to the detected temperature data. The heat emitted by the sub-light sources 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 sources stable.

[0017] Preferably, 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 ends of the first resonant cavity and the second resonant cavity, plano-concave reflectors 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 a first detector and a second detector. All the optical elements of the optical path unit are installed in the collimating sleeve. During operation, the light emitted by the light source unit is collimated into parallel light by the collimating mirror, and then the parallel light is split by the beam splitter into a reflected light and a transmitted light that are perpendicular to each other. 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 respectively undergo multiple light reflections therein. The light emitted from the plano-concave reflectors at the ends of the first resonant cavity and the second resonant cavity respectively passes through their respective filters to retain the light in the wavelength band to be measured and is coupled by their respective focusing mirrors and then respectively transmitted to the optical fibers.

[0018] Preferably, the collimating mirror is a plano-convex lens and its plane is installed facing the light source, the beam splitter is a semi-transparent and semi-reflective mirror and makes the light intensities 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 at the middle position of the resonant cavity. The radius of curvature of the two plano-concave reflectors at the front end and the end of each resonant cavity and the distance between the two lenses satisfy the symmetric confocal cavity mode. The settings of all the optical elements satisfy that the optical paths of the reflected light and the transmitted light are equal.

[0019] Preferably, the long optical path absorption cell unit is a first cylindrical closed container and a second cylindrical closed container with a double-layer nested outer shell and 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 sealed in the first cylindrical closed container and the second cylindrical closed container. There is a sandwich space for passing a heat transfer medium between the outer shell and the inner shell of each cylindrical closed container.

[0020] Preferably, an air port for purging the plano-concave reflector, ports for installing a vacuum pump, a pressure gauge, a vacuum gauge, and a vacuum thermocouple, an air inlet for introducing a background gas or a gas to be measured, and inlets and outlets for the heat transfer medium are provided on each cylindrical closed container. An electric heating coil is wound around the outer wall of the inner shell, and a plurality of semiconductor refrigerators and their radiators 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 then the gas state parameter inside the long optical path absorption cell unit is 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 for adjusting different temperature gradients. Among them, the primary temperature control adopts wall heat exchange, and realizes the temperature control of the gas in the resonance cavity by adjusting the circulating flow time and flow rate of the heat medium fluid introduced at a 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 control the temperature with an accuracy of ±0.1°C and maintain a constant temperature. During the heating process, the heat increment is controlled by adjusting the energization time of the heating coil wound around the outer wall of the inner shell. During the cooling process, the cold ends of multiple semiconductor refrigerators arranged on the inner wall of the outer shell are in contact with the heat medium fluid, and the hot ends are connected to the radiator to dissipate heat to the outside. 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 invention purpose, the embodiment of the present invention also provides a method for detecting the standard absorption cross-section of multi-component polluted gas with high resolution and multi-temperature gradients, which is realized by using the above-mentioned device for detecting the standard absorption cross-section of multi-component polluted gas with high resolution and multi-temperature gradients, and includes the following steps:

[0024] Utilize the light source unit to generate output light with stable power, and realize broadband output light by switching sub-light sources in different wavelength ranges;

[0025] Utilize the optical path unit to perform secondary processing on the output light of the light source unit, divide the output light into two parts and respectively enter the first resonance cavity composed of two plano-concave mirrors and the second resonance cavity composed of two plano-concave mirrors, and multiple reflections occur in the two resonance cavities and only a small amount of light is allowed to pass through the plano-concave mirrors at the ends of the first resonance cavity and the second resonance cavity each time for output;

[0026] Utilize the long optical path absorption cell unit to seal the first resonance cavity and accommodate the background gas, and at the same time seal the second resonance cavity and accommodate the background gas and the gas to be measured, so that the light reflected multiple times in the two resonance cavities undergoes long optical path absorption inside;

[0027] Utilize the 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 the set values;

[0028] Utilize the detection and calculation unit to receive the output light after multiple reflections in the first resonance cavity and the second resonance cavity through the first detector and the second detector respectively, perform time integration on the output light and then generate spectral data through photoelectric conversion, and calculate the absorption cross-section according to the spectral data using the scattering interference filtering algorithm.

[0029] Compared with the prior art, the beneficial effects of the present invention at least include:

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

[0031] Compared with the technology using laser as the light source, the measurement wavelength band width of the present invention increases, and more polluting 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 identification of weaker absorption characteristics can be realized; the present invention can achieve high-sensitivity detection of low-concentration gas samples, overcoming problems such as instability of some gases and cross absorption; the present invention can achieve precise control of the multi-temperature and pressure gradients of the gas components, the resolution of the measured spectral data is higher, and the calculated absorption cross section is more accurate. Brief Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to these drawings without creative efforts.

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

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

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

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

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

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

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

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

[0041] Figure 9 It is a schematic flow chart of a method for detecting the standard absorption cross-section of multi-component polluted gas with high resolution and multi-temperature gradient provided by an embodiment of the present invention. Specific Embodiments

[0042] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the protection scope of the present invention.

[0043] The inventive concept of the present invention is as follows: Aiming at the problems of low signal-to-noise ratio, limited temperature and pressure adjustment range, and insufficient accuracy in detecting the absorption cross-section of wide-band low-concentration gas in the prior art, an embodiment of the present invention provides a method and device for detecting the standard absorption cross-section of multi-component polluted gas with high resolution and multi-temperature gradient. By adjusting different sub-light sources, broadband light output is realized to fully cover the ultraviolet-visible band; by optimizing the structure of the optical path unit, the light source is divided into two parts and respectively introduced into the long optical path absorption cell units for background gas and the gas to be measured, 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, high-sensitivity detection of low-concentration gas is realized based on the cavity-enhanced optical path improvement technology, and multi-stage temperature control and dynamic environment simulation are realized by combining the long optical path absorption cell unit and the gas control unit; finally, the 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 and improve the accuracy of the absorption cross-section detection.

[0044] Figure 1 It is a schematic structural diagram of a device for detecting the standard absorption cross-section of multi-component polluted gas with high resolution and multi-temperature gradient provided by an embodiment of the present invention. As Figure 1As shown in the figure, the embodiment provides a multi-component polluted gas high-resolution and multi-temperature gradient standard absorption cross-section detection device, 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 realizes broadband output light by rotating and switching sub-light sources with 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 split into two parts and enters the first resonant cavity composed of two plano-concave mirrors and the second resonant cavity composed of two plano-concave mirrors 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 mirrors at the ends of the first resonant cavity and the second resonant cavity each time for output; the long optical path absorption cell unit serves as a cavity, which is used to seal the first resonant cavity and accommodate the background gas, and at the same time seal the second resonant cavity and accommodate 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 adjusts the total amount and ratio of the gas in the long optical path absorption cell unit by pumping or extracting, and controls the temperature and pressure of the gas at the set values; 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, perform time integration on the output light by using a computer and then generate spectral data through photoelectric conversion, and calculate the absorption cross-section according to the spectral data by using a scattering interference filtering algorithm. The following will explain each unit in detail.

[0045] As Figure 2 shown, the light source unit includes: a power supply, a control module, multiple sub-light sources with different wavelength ranges installed 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 continuous temperature control when rotating and switching the sub-light sources, and a liquid-cooled light source temperature control platform. The purpose of this light source unit is to obtain stable broadband light output, and the output light power meets the technical requirements of IBBCEAS, so as to be used for the measurement of the absorption cross-section of low-concentration substances.

[0046] In the light source unit, the sub-light sources adopt high-power LED lamp beads with an emission angle of 30°. The length and width of the chip are both 3.5 mm. 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 electrical energy provided by the constant current power supply, a beam with relatively high intensity and a relatively wide spectrum is emitted. During welding, it is necessary to ensure that the light-emitting normal direction of the LED lamp bead is perpendicular to the substrate plane to ensure that the light in the 0° direction of the light source output is on the main optical axis, so as to ensure the collimation of the subsequent optical path components and maximize the utilization of the light energy of the light source. The copper substrate is then evenly and tightly pasted on the cooling plate through thermal conductive silica gel to reduce the influence of the large amount of heat generated by the LED lamp beads during use on the optical power. The central wavelengths of each sub-light source are different, and the wavelength bands are different. The wavelength bands are combined to cover the working wavelength band of the optical components used in the system. The motor is connected to the slip ring rotor through 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 operates, thereby switching the sub-light sources with different wavelength ranges. The electrical energy required for the light source to output light is transmitted through a liquid-electric integrated conductive slip ring to ensure continuous power supply during the rotation process. As Figure 3 shown, the control module controls the rotation angle and the sub-light source switch to ensure that the sub-light source whose light is emitted rotates to the position of the corresponding collimating mirror, while the other sub-light sources do not emit light.

[0047] In the light source unit, the liquid cooling 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, coolant pipes, and coolant. The heat generated 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 pipes, and the liquid-electric integrated conductive slip ring ensures the continuous circulation of the coolant during the rotation process. The heat generated by the sub-light source is received by the substrate and then monitored by a temperature sensor adhered to the substrate. The current change of the monitored temperature of the temperature sensor is transmitted to the temperature control module in the control module, and the coolant flow rate of the coolant circulation pump is adjusted using the PID algorithm to control the temperature fluctuation range within ±0.1 °C to ensure the stable output of the sub-light source.

[0048] As Figure 4 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 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. The purpose of this optical path unit is to secondarily process the light emitted by the light source unit, split the light emitted by the light source into two parts, and cause multiple reflections in their respective corresponding resonant cavities, and maximize the utilization of the light energy of the light source unit.

[0049] In the optical path unit, all optical components are installed inside the collimating sleeve and fastened together without leakage through a vacuum seal and a long optical path absorption cell unit. The inside of the collimating sleeve has threads for the snap ring to install each optical component at the designated position. The light source unit and the fiber optic probe are respectively connected to the collimating sleeve through threads.

[0050] In the optical path unit, the outgoing light is collimated into parallel light by a collimating mirror. The collimating mirror is a plano-convex lens with the plane facing the light source to minimize spherical aberration. Then, it is split into mutually perpendicular reflected light and transmitted light by a beam splitter. The beam splitter is a semi-transparent and semi-reflective mirror, making the light intensities of the reflected light and the transmitted light equal and half of the light intensity of the outgoing light from the light source unit. The optical component parameters of the transmitted light optical path and the reflected light optical path are the same, and the optical paths are equal, thus ensuring that the light intensities at the detection ends of the two optical paths are consistent.

[0051] In the optical path unit, the reflected light and the transmitted light respectively enter the first resonant cavity and the second resonant cavity formed by two plano-concave mirrors through a converging mirror and intersect and form an image between the plano-concave mirrors. 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 at the middle position of the resonant cavity to maximize the utilization of the light emitted from the edge of the light source. The radius of curvature of the two plano-concave mirrors at the front end and the end of each resonant cavity and the distance between the two lenses satisfy the symmetric confocal cavity mode. After imaging, the converging light continues to transmit and reaches the reflecting surface at the end of each resonant cavity to achieve parallel reflection and then converges at the middle position by the front reflecting surface. This process repeats, and a weak light passes through the resonant cavity subsystem and is imaged at the middle position every time it is reflected. The base material of the plano-concave mirror is ultraviolet fused silica to resist thermal expansion, and the size of 50.8 mm in diameter and 9.5 mm in thickness ensures that it can withstand high vacuum and high pressure. The concave surface of the plano-concave mirror is coated with a multi-layer dielectric reflection 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 radius of curvature of the plano-concave mirror is 1000 mm, ensuring that the physical length of the resonant cavity is sufficient in the symmetric confocal cavity mode.

[0052] In the optical path unit, the light emerging from the plano-concave mirrors at the ends of each resonator is the superposition of the light intensities of each order. After passing through their respective filters to retain the light in the wavelength band to be measured, it is coupled into the optical fiber through their respective focusing lenses. The numerical aperture value of the focusing lens is smaller than that of the optical fiber used. The distance between the focusing lens and the plano-concave mirror at the end of the resonator, and the distance from the end face of the optical fiber to the focusing lens are determined by the size of the focused light spot on the end face of the optical fiber. The set distance needs to ensure the smallest light spot. The optical fiber is a 7-core 200-μm multimode optical fiber, arranged in a concentric ring form at the receiving end and vertically arranged at the slit end of the incident spectrometer to maximize the light flux of the incident spectrometer. One end of the optical fiber close to the optical path is arranged with 6-core multimode optical fibers surrounding 1-core optical fiber, and the end close to the spectrometer (detector) is arranged with 7-core optical fibers side by side, converting the circular light spot output by the focusing lens into light that fits the shape of the slit and inputting it into the internal optical path of the spectrometer.

[0053] As Figure 5 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 a double-layer nested outer shell and inner shell. The overall length is 0.9 m and the diameter is 0.5 m. The collimating sleeves of the two optical paths in the optical path unit are respectively arranged at both ends of the two cylindrical closed containers. The first resonator and the second resonator are respectively sealed in the first cylindrical closed container and the second cylindrical closed container. There is a sandwich space for passing the heat transfer 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 configured concentration and make the light undergo long optical path absorption when passing through the gas to be measured repeatedly.

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

[0055] In the long optical path absorption cell unit, both ends are sealed by stainless steel covers. The centers of the stainless steel covers are provided with two opposite ports with a diameter of 50 mm, and vacuum sealing flanges are provided for the installation of the collimating sleeves of the optical path unit. The two ports extend outward for a certain distance so that the distance between the two plano-concave mirrors of the resonant cavity subsystem is 1 m, corresponding to the radius of curvature values of the two plano-concave mirrors, forming a symmetric confocal cavity mode. At the port extension, there is a lens purge air port for purging the surfaces of the plano-concave mirrors with inert gas to remove the residual gas attached to their surfaces. 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, pressure gauges, vacuum gauges, and vacuum thermocouples respectively, and an air inlet for introducing background gas or the gas to be measured is set, as well as an inlet and outlet for the thermal fluid to flow in and out. Electric heating coils are wound around the outer wall of the inner shell, and multiple semiconductor refrigerators and their 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 brackets are installed outside the absorption cell to limit the vibration influence from the ground and the 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. The gas pumping and extraction subsystem is used to inject gas into or extract gas from the long optical path absorption cell unit, and then the gas state monitoring subsystem obtains the gas state parameters inside the long optical path absorption cell unit and feeds them back to the gas state adjustment subsystem. The gas state adjustment subsystem regulates the temperature and pressure inside 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, the gas to be measured, and gas cylinders. Among them, the vacuum pump is divided into a fore-stage mechanical pump and a molecular pump: the mechanical pump is used to pump out most of the original gas in the absorption cell to the primary vacuum state, and the molecular pump is used to pump out the trace residual gas to the high vacuum state. The gas cylinders are used to store background gas and the gas to be measured. The vacuum pump pumps out the original gas in the absorption cell, and then injects background gas to reach the set pressure. After the air pressure is stable, the gas to be measured is injected into the absorption cell. In order to prevent the formation of polymers and reduce the partial pressure of the gas to be measured, the amount of the gas to be measured needs to be ensured so as not to 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 consists of a vacuum thermocouple, a pressure gauge, and a vacuum gauge. The vacuum thermocouple monitors the gas temperature in the absorption cell, the pressure gauge monitors the pressure value, and the vacuum gauge monitors the vacuum degree in the long optical path absorption cell unit during the operation of the vacuum pump to judge whether the original gas in the long optical path absorption cell unit has been completely removed.

[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 method of heat conduction. 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 inner wall stainless steel material, and then to the gas to be measured in the long optical path absorption cell unit. The heat medium fluid used is a fluorinated liquid, which ensures rapid heat absorption and does not damage electronic components. The pressure module adjusts the pressure by pumping out the mixed gas from the long optical path absorption cell unit or by increasing the injection amount of the background gas.

[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 the method of wall heat exchange, and realizes the temperature control of the gas in the resonator by adjusting the circulation time and flow rate of the heat medium fluid introduced at the set temperature. When the temperature reaches the set value ±1°C, the flow of the heat medium fluid stops, and the system switches to the secondary temperature control. The secondary temperature control includes heating and cooling, which are used to control the temperature with an accuracy of ±0.1°C and maintain a constant temperature. During the heating process, the heat increment is controlled by adjusting the energization time of the heating coil wound around the outer wall of the inner shell. During the cooling process, the cold ends of multiple semiconductor refrigerators arranged on the inner wall of the outer shell are in contact with the heat medium fluid, and the hot ends are connected to the radiator to dissipate 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] As Figure 6 shown, the gas state control in the absorption cell includes the following steps:

[0062] (1) Use a vacuum pump to extract the gas in the long optical path absorption cell unit to a high vacuum degree, calculate 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 pump the specified amount of background gas into the long optical path absorption cell unit;

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

[0064] (3) The STM32 single-chip microcomputer 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 control reaches within the range of ±1°C of the set value, the heat medium fluid valve is closed, the heat medium circulation stops, and further temperature control is performed by selecting the heating method of the electric heating coil or the semiconductor refrigeration according to the temperature difference, so that the temperature is controlled within the range of ±0.1°C;

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

[0067] As Figure 1 shown, the detection and calculation unit includes a spectrometer for detecting the optical signal intensity of the detection optical fiber and a computer with calculation function. The purpose of this 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 synthesizing multiple groups of measurement data.

[0068] In the detection and calculation unit, the spectrometer models used at the detection ends of the transmission light optical path and the reflection light optical path are the same to reduce the data error caused by different detectors. The background gas spectrum and the spectrum of the sample to be measured (the gas to be measured diluted to a certain concentration by the background gas, containing the background gas and the gas to be measured) are respectively collected for the reflection light optical path and the transmission light optical path, and are carried out simultaneously to eliminate the error of light intensity change. The computer with processing function processes the multiple different band spectra measured for the light emitted by different sub-light sources by means of spectrum splicing to obtain a more complete spectrum. For each sub-light source, only the spectrum extending from the central wavelength to the full width at half maximum range is taken, and the spectrum segment data with a higher signal-to-noise ratio is selected for the overlapping region between the sub-light source bands.

[0069] As Figure 7 shown, the absorption cross-section detection process for 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, and 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 (absorption cell 1 for the reflection light optical path and absorption cell 2 for the transmission light optical path) to reach a high vacuum degree, and turn on the light source to make it operate stably;

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

[0073] (4) Introduce the calculated background gas into absorption cell 1 and introduce the calculated background gas and the gas to be measured into absorption cell 2 to make the pressure reach the set value;

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

[0075] (6) Measure 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 splice the spectra 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 denoted as I0(λ));

[0076] (7) Measure the absorption cell 2 on the transmitted light path simultaneously: Rotate and switch the light source, measure the spectra of the gas to be measured of all sub-light sources and splice the spectra to obtain the spectra of the gas to be measured of the complete measurement band (the concentration of the gas to be measured is n1(λ), and the spectral data is denoted as I1(λ));

[0077] (8) Continuously inject the gas to be measured that does not affect the pressure change amount into the absorption cell 2, adjust the concentration of the gas to be measured (each group of concentrations is n1, n2,..., n N ), and measure the corresponding spectra (the spectral data is denoted as I1(λ), I2(λ),..., I N (λ));

[0078] (9) Calculate the absorption cross-section σ(λ) according to the absorption cross-section algorithm based on the principle of broadband cavity enhanced absorption spectroscopy.

[0079] As Figure 8 shown in the calculation algorithm of the absorption cross-section, after calculating the absorption coefficient of each group, this algorithm uses the difference between the absorption coefficients of every two groups of the gas to be measured to filter out the scattering term, then divides by the concentration difference to obtain the absorption cross-section, and then takes the average of 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 mirror used in the resonant cavity, the physical cavity length L, and the effective cavity length d when the inert gas lens purge protection is turned on eff ;

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

[0082]

[0083] where λ represents the wavelength;

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

[0085]

[0086] where α Mie(λ) represents the Mie scattering coefficient;

[0087] (4) The absorption coefficient α of every two groups of gases to be measured i (λ), α j (λ) Subtract the scattering term by taking the difference, and then combine with the concentration n of the gas to be measured i 、n j Calculate the absorption cross-section, and take the average of the results of multiple measurements to obtain the final measured 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 are no particulate matters, the Mie scattering coefficient is 0, and since the background gases are the same and the Rayleigh scattering coefficients of each group are the same, therefore, by using the calculation method provided in the embodiment of the present invention, it is not necessary to actually calculate α Mie (λ) and α Ray (λ), directly subtracting the absorption coefficients of two groups of gases to be measured leaves only the product of the concentration and the absorption cross-section, and finally the absorption cross-section σ(λ) is calculated.

[0091] Based on the same inventive concept, as Figure 9 shown, the embodiment of the present invention also provides a method for detecting the standard absorption cross-section of multi-component polluted gases with high resolution and multi-temperature gradients, including the following steps:

[0092] S1, Use the light source unit to generate an output light with stable power, and realize broadband output light by switching sub-light sources with different wavelength ranges;

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

[0094] S3, Use the long optical path absorption cell unit to seal the first resonant cavity and accommodate the background gas, and at the same time seal the second resonant cavity and accommodate 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, Use the gas control unit to adjust the total amount and ratio of the gases in the long optical path absorption cell unit, and control the temperature and pressure of the gases at the set values;

[0096] S5. The detection and calculation unit receives the output light after multiple reflections of the first resonant cavity and the second resonant cavity through the first detector and the second detector respectively, performs time integration on the output light, and then generates spectral data through photoelectric conversion. The absorption cross section is calculated using the scattering interference filtering algorithm based on the spectral data.

[0097] It should be noted that the above-described method for detecting the standard absorption cross section of multi-component polluted gas with high resolution and multi-temperature gradient and the device for detecting the standard absorption cross section of multi-component polluted gas with high resolution and multi-temperature gradient belong to the same inventive concept. For the specific implementation process, please refer to the embodiments of the device for detecting the standard absorption cross section of multi-component polluted gas with high resolution and multi-temperature gradient, which will not be elaborated here.

[0098] The above specific embodiments have elaborated in detail 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 used to limit the present invention. Any modifications, supplements, equivalent replacements, etc. made within the principle scope of the present invention shall 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 gases, characterized in that, 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; The light source unit is used to switch sub-light sources with different wavelength ranges in a rotating and switching manner to achieve spliced continuous broadband output light to fully cover the ultraviolet-visible band, and output light with stable power through temperature control; The optical path unit is used to perform secondary processing on the output light of the light source unit, divide the output light into two beams with equal light intensity, and then enter a first resonant cavity composed of two plano-concave mirrors and a second resonant cavity composed of two plano-concave mirrors perpendicularly to each other 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 mirrors 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 background gas, and at the same time seal the second resonant cavity and contain 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. Among them, the temperature of the gas is controlled at the set value by a multi-stage temperature control combined with a PID algorithm. The primary temperature control realizes the regulation with an accuracy of ±1°C through wall-type heat exchange, and the secondary temperature control realizes the regulation with an accuracy of ±0.1°C through a heating coil + a semiconductor refrigeration sheet; 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, integrate the output light time, generate spectrum data through photoelectric conversion, and perform spectrum splicing to obtain complete spectrum data, and calculate the absorption cross section based on the complete spectrum data using a scattering interference filtering algorithm. The scattering interference filtering algorithm calculates the absorption cross section by dividing the absorption coefficient of each two groups of gases to be measured by α i (λ) 、 α j (λ) Perform differential filtering to remove the scattered items, and then combine them with the concentration of the gas to be measured n i 、 n j Calculate the absorption cross section and average the multiple measurement results to obtain the final absorption cross section measurement value σ (λ) .

2. The high-resolution and 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, multiple sub-light sources with different wavelength ranges installed 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. During operation, the power supply provides electrical energy to the motor, the motor is connected to the sub-light sources on the substrate through the liquid-electric integrated conductive slip ring, and the control module controls the rotation angle of the substrate and the switching of the sub-light sources to switch different sub-light sources.

3. The high-resolution and multi-temperature-gradient standard absorption cross-section detection device for multi-component polluted gas according to claim 2, wherein, The light source unit further includes: a temperature control platform composed of 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 coolant. During operation, the power supply provides electrical energy to the cooling 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 sources is detected by the temperature sensor, and the control module adjusts the coolant flow rate according to the detected temperature data. The heat generated by the sub-light sources 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 sources stable.

4. The high-resolution and 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 includes: 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, plano-concave reflectors 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 a first detector and a second detector. All the optical elements of the optical path unit are installed in the collimating sleeve. During operation, the outgoing light from the light source unit is collimated into parallel light by the collimating mirror, and then the parallel light is split by the beam splitter into a reflected light and a transmitted light that are perpendicular to each other. 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 emerging from the plano-concave reflectors at the ends of the first resonant cavity and the second resonant cavity respectively passes through their respective filters to retain the light in the wavelength band to be measured, and is coupled by their respective focusing mirrors and then transmitted to the optical fibers respectively.

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 collimating mirror is a plano-convex lens with the plane facing the light source. The beam splitter is a semi-transparent and semi-reflective mirror that makes the light intensities 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 imaged at the middle position of the resonant cavity after being converged. The radius of curvature of the two plano-concave reflectors at the front end and the end of each resonant cavity and the distance between the two lenses satisfy the symmetric confocal cavity mode. The settings of all the optical elements ensure that the optical paths of the reflected light and the transmitted light are equal.

6. The high-resolution and 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 with a double-layer nested outer shell and 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 sealed in the first cylindrical closed container and the second cylindrical closed container. There is a sandwich space for passing a heat transfer medium between the outer shell and the inner shell of each cylindrical closed container.

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

8. The multi-component polluted gas high-resolution and multi-temperature gradient standard absorption cross-section detection device 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 then the gas state parameter inside the long optical path absorption cell unit is 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 multi-component polluted gas high-resolution and multi-temperature gradient standard absorption cross-section detection device 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. Among them, the primary temperature control adopts partition heat exchange, and realizes the temperature control of the gas in the resonant cavity by adjusting the circulating flow time and flow rate of the heat medium fluid introduced at a set temperature. When the temperature reaches the set value ±1°C, the flow of the heat medium fluid stops and switches to the secondary temperature control. The secondary temperature control includes heating and cooling, which are used to control the temperature with an accuracy of ±0.1°C and maintain a constant temperature. The heating process controls the heat increment by adjusting the energization time of the heating coil wound around the outer wall of the inner shell. The cooling process makes the cold ends of multiple semiconductor refrigerators arranged on the inner wall of the outer shell contact the heat medium fluid, and the hot ends are connected to the radiator to dissipate heat to the outside. 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 the standard absorption cross-section of multi-component polluted gas with high resolution and multi-temperature gradient is realized by using the multi-component polluted gas high-resolution and multi-temperature gradient standard absorption cross-section detection device described in any one of claims 1-9, characterized in that, It includes the following steps; The light source unit uses the method of rotational switching to switch sub-light sources with different wavelength ranges to achieve spliceable continuous broadband output light to comprehensively cover the ultraviolet-visible band, and outputs light with stable power through temperature control. The optical path unit performs secondary processing on the output light of the light source unit, divides the output light into two beams with equal light intensity, and then enters the first resonant cavity composed of two plano-concave mirrors and the second resonant cavity composed of two plano-concave mirrors perpendicular to each other 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 mirrors at the ends of the first resonant cavity and the second resonant cavity each time for output. The long optical path absorption cell unit is used 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. The gas control unit adjusts the total amount and ratio of the gas in the long optical path absorption cell unit, and controls the temperature and pressure of the gas at the set values. Among them, the temperature of the gas is controlled at the set value by the method of combining multi-stage temperature control with the PID algorithm. The primary temperature control realizes the regulation with an accuracy of ±1°C through partition heat exchange, and the secondary temperature control realizes the regulation with an accuracy of ±0.1°C through the heating coil + semiconductor refrigerators. The detection and calculation unit uses the first detector and the second detector to receive the output light after multiple reflections of the first resonant cavity and the second resonant cavity respectively, integrates the output light time, generates spectrum data through photoelectric conversion, and performs spectrum splicing to obtain complete spectrum data. The absorption cross section is calculated based on the complete spectrum data using the scattering interference filtering algorithm. The scattering interference filtering algorithm calculates the absorption cross section by dividing the absorption coefficient of each two groups of gases to be measured by α i (λ) 、 α j (λ) Perform differential filtering to remove the scattered items, and then combine them with the concentration of the gas to be measured n i 、 n j Calculate the absorption cross section and average the multiple measurement results to obtain the final absorption cross section measurement value σ(λ) .

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