Thermal insensitive multi-reflection cavity for enhancing gas Raman spectrum

Abstract

The invention belongs to the field of gas Raman scattering, and particularly discloses a heat-insensitive multi-reflection cavity for enhancing gas Raman spectrums.The heat-insensitive multi-reflection cavity comprises an inner-layer cavity and an outer-layer cavity, the inner-layer cavity is arranged in the outer-layer cavity, and the space between the inner-layer cavity and the outer-layer cavity is vacuumized; the inner layer cavity comprises a neck part, a main body and a tail part; the neck part comprises a cavity opening with the constant outer diameter and a shoulder part which is continuous with the tail side of the cavity opening and the outer diameter of which is gradually increased; an opening is formed in the head side of the cavity opening, and an incidence window for sealing the opening is formed in the opening; the incidence window is used for providing an incidence channel for obtaining laser required by the Raman spectrum of the gas to be detected; the main body is in a cylinder shape with two open ends, the outer diameter is unchanged, and the opening in the head side of the main body is continuous with the tail side of the shoulder part. The opening side of the tail curved surface is the head side of the tail, and the head side of the tail is continuous with the opening of the tail side of the main body; and the curvature radius of the shoulder part is smaller than that of the tail part. According to the application, a heat insensitive environment can be provided for the to-be-detected gas, so that the Raman spectrum signal of the to-be-detected gas is more stable.

Description

Technical Field

[0001] The present application belongs to the field of gas Raman scattering, and more specifically, relates to a heat-insensitive multi-reflection cavity for enhancing gas Raman spectroscopy. Background Art

[0002] Raman spectroscopy is a spectral analysis technology based on the Raman scattering effect of matter. It detects the Raman scattered light generated by the excitation light irradiating the matter to form different scattered light wavelength spectra. The type of the substance is determined by the different scattered wavelength positions, and the content of the substance is determined by the different scattered light intensities. As a highly sensitive molecular detection method, Raman spectroscopy has been widely used in the field of gas analysis. Cavity-enhanced Raman technology is a technology that has received much attention in recent years. It uses lasers to generate constructive interference of multiple beams in the cavity, increase the laser intensity and the effective optical path of the laser, and achieve the enhancement of Raman scattering signals. In order to further improve the detection sensitivity and application level of this technology, researchers have designed chambers of different configurations to meet the application needs of different scenarios.

[0003] However, according to the research in the literature [Journal of Raman Spectroscopy 51.3 (2020): 555-568], it is found that in the application of cavity-enhanced gas Raman, temperature not only affects the Raman scattering cross section of gas molecules, but also may change the optical properties and gas distribution in the cavity, making the Raman signal intensity unstable. Temperature changes will cause the redistribution of the vibration and rotation energy levels of gas molecules, causing significant fluctuations in the Raman signal intensity, further increasing the uncertainty of the signal. Summary of the invention In view of the defects of the prior art, the purpose of the present application is to provide a heat-insensitive multi-reflection cavity for enhancing gas Raman spectroscopy, aiming to solve the problem that in the application of existing cavity-enhanced gas Raman, temperature will affect the intensity of Raman signal in the cavity, causing uncertainty in the intensity of Raman signal.

[0004] To achieve the above-mentioned object, the present application provides a heat-insensitive multi-reflection cavity for enhancing gas Raman spectroscopy, which is used to carry the gas to be measured so as to obtain the Raman spectrum of the gas to be measured, and the heat-insensitive multi-reflection cavity comprises: an inner cavity and an outer cavity, the inner cavity is arranged in the outer cavity, and the space between the inner cavity and the outer cavity is evacuated; The inner cavity includes: a neck, a main body and a tail; The neck portion comprises: a cavity opening with a constant outer diameter, and a shoulder portion which is continuous with the rear side of the cavity opening and has a gradually increasing outer diameter; an opening is provided at the front side of the cavity opening, and an incident window is provided on the opening to seal the opening; the incident window is used to provide an incident channel for the laser required to obtain the Raman spectrum of the gas to be measured; The main body is in the shape of a cylinder with openings at both ends and a constant outer diameter, and the opening at the front side of the main body is continuous with the rear side of the shoulder; The tail portion is a centrally symmetrical curved surface, the opening side of the curved surface is the head side of the tail portion, and the head side of the tail portion is continuous with the opening of the tail side of the main body, and is used to seal the tail side of the main body; The radius of curvature of the shoulder is smaller than the radius of curvature of the tail.

[0005] It should be noted that the above-mentioned reflection cavity provided in the present application has a small curvature radius at both ends of the neck and the tail, which can significantly enhance the multi-angle high reflection performance, so that the excitation light can be reflected multiple times in the chamber. At the same time, the main part is a non-spherical cylinder, which can increase the effective action distance of a single reflection of the excitation light and the gas within a certain space. The high-reflectivity silver-plated lining can reduce the optical loss of the laser in each reflection, improve the laser utilization rate, and further enhance the multi-reflection signal of the gas Raman spectrum.

[0006] Furthermore, since the reflective cavity has a multi-curvature configuration, the tail is an incomplete sphere with a relatively small curvature radius, which can reflect the thermal radiation in the cavity to the curved side, and the main body forms a thermal radiation propagation channel, so that the thermal radiation converges to the side close to the neck; the neck has a cavity mouth and a shoulder with a smaller curvature radius, and the shoulder with a small curvature radius and the tail with a large curvature radius have strong focusing and weak focusing characteristics respectively. By utilizing the balance between strong and weak focusing, the cross-sectional size of the beam can be controlled to enhance the concentration of the beam, while increasing the Rayleigh length to slow down the divergence of the beam and make the beam more stable. In this process, multiple reflections are performed to excite the gas molecules to be measured multiple times, and the effective action distance between the laser beam and the gas molecules to be measured is increased. Further, the thermal radiation field formed can make the thermal radiation of the neck converge to the cavity mouth, and then conduct heat to the outside from the incident window of the cavity mouth, thereby realizing the processing of the temperature radiation generated by multiple reflections of the laser beam in the cavity, providing a heat-insensitive environment for the inside of the cavity, and obtaining a relatively stable Raman scattering signal.

[0007] In a possible implementation, the outer side of the inner cavity and the inner side of the outer cavity are both coated with a high-reflective material.

[0008] In a possible implementation manner, a gas conduit is provided on the incident window.

[0009] In a possible implementation, the cavity opening, shoulder, main body and tail are smoothly transitioned and continuous to form a smooth curved surface.

[0010] In a possible implementation, the height of the cavity opening is smaller than the height of the main body, and the height of the shoulder is larger than the height of the tail.

[0011] In one possible implementation, the curvature radius of the cavity opening ranges from 15 mm to 30 mm, the curvature radius of the shoulder ranges from 5 mm to 25 mm, and the curvature radius of the transition portion between the shoulder and the cavity opening ranges from 2 mm to 15 mm; the height of the cavity opening ranges from 10 mm to 30 mm, and the height of the shoulder ranges from 15 mm to 45 mm.

[0012] In a possible implementation, the curvature radius of the main body ranges from 30 mm to 60 mm, and the height of the main body ranges from 50 mm to 200 mm.

[0013] In a possible implementation, the curvature radius of the tail portion ranges from 20 mm to 40 mm, and the height of the tail portion ranges from 20 mm to 60 mm.

[0014] In a possible implementation, the inner cavity and the outer cavity are integrally formed; and / or the gap between the inner cavity and the outer cavity ranges from 1 mm to 5 mm.

[0015] In a possible implementation, the incident window is a quartz window plate; The inner cavity and the outer cavity are both made of glass.

[0016] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art: The present application provides a heat-insensitive multi-reflection cavity for enhancing gas Raman spectroscopy. In the present application, the heat-insensitive multi-reflection cavity has three major parts: a neck, a main body and a tail. Its configuration has been optimized and designed to have different curvatures. The neck includes a cavity mouth and a shoulder. The curvature radius at both ends of the shoulder and the tail is small, which can significantly enhance the multi-angle high reflection performance, so that the excitation light can be reflected multiple times in the cavity. At the same time, the main body is a non-spherical cylinder, which can increase the effective action distance of a single reflection of the excitation light and the gas within a certain space. The high-reflectivity lining can reduce the optical loss of the laser in each reflection and improve the laser utilization rate, thereby further enhancing the multi-reflection signal of the gas Raman spectrum.

[0017] The present application provides a heat-insensitive multi-reflection cavity for enhancing gas Raman spectroscopy. Since the complete cavity of the heat-insensitive multi-reflection cavity has a multi-curvature configuration, the tail is an incomplete sphere with a relatively small curvature radius, which can reflect the thermal radiation in the cavity to the curved side, and the main body forms a thermal radiation propagation channel, so that the thermal radiation converges to the side close to the neck; and the neck has a cavity opening and a shoulder with a small curvature radius, and the thermal radiation field formed by it can make the thermal radiation of the neck converge to the cavity opening, and then conduct heat to the outside from the incident window of the cavity opening, so as to achieve the processing of the temperature radiation generated by multiple reflections of the laser beam in the cavity; therefore, the reflection cavity provided by the present application can form a special temperature field inside the cavity, and can provide an internal heat-insensitive environment for the gas molecules to be excited, which is very important in the multi-reflection Raman enhancement system; because the change in temperature will affect the energy level distribution and Raman scattering cross section of the gas molecules and the stability of the optical path in the cavity, resulting in significant fluctuations in the intensity of the Raman signal, and the excitation light will inevitably produce temperature release in the process of multiple reflections and the interaction with the gas molecules, making the signal unstable.

[0018] The present application provides a heat-insensitive multi-reflection cavity for enhancing gas Raman spectroscopy. Since the heat-insensitive multi-reflection cavity has a double-layer vacuum structure design, the gas in the cavity can be isolated from the external environment, blocking the heat transfer and heat convection paths. The high-reflectivity lining coated on the cavity can also suppress the infrared thermal radiation interference of the external environment. Through the above-mentioned heat shielding mechanism, a heat-insensitive environment that is not affected by the external temperature and can derive the internal temperature can be provided for the gas molecules in the cavity, making the multi-reflection enhanced gas Raman spectroscopy signal more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of the structure of a heat-insensitive multi-reflection cavity provided in an embodiment of the present application; Figure 2 This is a structural diagram of a quartz high-transmittance window provided in an embodiment of the present application: Figure 3 is a structural block diagram of a gas detection device provided in an embodiment of the present application; Figure 4 This is a comparison diagram of the gas Raman intensity of the heat-insensitive multi-reflection cavity provided by the embodiment of the present application and the traditional quartz glass gas chamber; Figure 5 is a schematic diagram of the change of gas Raman intensity at different external temperatures in a heat-insensitive multi-reflection cavity provided in an embodiment of the present application; In all the drawings, the same reference numerals are used to represent the same elements or structures, wherein 1 is a heat-insensitive multi-reflection cavity; 11 is a neck; 111 is a shoulder, 112 is a cavity opening; 12 is a main body; 13 is a tail; 14 is a quartz high-transmittance window; 141 is an air inlet; 142 is an air outlet; 143 is a gas duct; 15 is an inner cavity layer; 16 is an outer cavity layer; 17 is a laser beam; 2 is a laser driver; 3 is a fiber collimating lens; 4 is a filter; 5 is a fiber collecting lens; 6 is a grating spectrometer; 7 is a CCD detector; and 8 is a computer device. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0021] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0022] The present application relates to the field of gas Raman scattering, and discloses a heat-insensitive multi-reflection cavity for enhancing gas Raman spectrum; in the present application, the heat-insensitive multi-reflection cavity has a multi-curvature configuration in its complete cavity, and a special temperature field can be formed inside the cavity, so that the temperature release generated in the process of the multi-reflected excitation light beam in the cavity interacting with the gas molecules can be processed, and an internal heat-insensitive environment can be provided for the gas molecules to be excited; in addition, the heat-insensitive multi-reflection cavity has a vacuum isolation layer and a high-reflectivity silver-plated lining, which can block the heat transfer and heat convection paths with the external environment, and suppress the interference of thermal radiation, and can provide the gas molecules to be excited with an external heat-insensitive environment, so as to obtain a heat-insensitive relatively stable gas Raman signal; the multi-heat-insensitive multi-reflection cavity has a high-reflectivity silver-plated lining, and the curvature configuration makes the laser reflection angle small, so that the laser can form a multi-pass round-trip light beam in the cavity, so as to enhance the Raman scattering signal, and in addition, the radiation field formed by the cavity makes the Raman scattered light be converged to the port, so as to further enhance the gas Raman signal.

[0023] In order to improve the gas Raman scattering intensity while reducing the interference of temperature changes on the gas Raman signal. The present application provides a heat-insensitive multi-reflection cavity for enhancing the gas Raman spectrum, the heat-insensitive multi-reflection cavity has a high-reflectivity silver-plated lining, and the curvature configuration makes the laser reflection angle small, which can make the laser form a multi-pass round-trip light beam in the cavity to enhance the Raman scattering signal; the heat-insensitive multi-reflection cavity includes a double-layer vacuum optical chamber, the structure of the heat-insensitive multi-reflection cavity is divided into an inner cavity and an outer cavity, the inner layer is a multi-reflection chamber, which is used to contain gas and complete Raman signal detection, and the outer layer is a structural chamber, which is used to maintain the stability of the chamber, and a vacuum isolation layer is formed between the inner layer and the outer layer, and the vacuum isolation layer can significantly reduce the influence of heat conduction and heat convection. The outer surface of the inner cavity and the inner surface of the outer cavity of the heat-insensitive multi-reflection cavity are coated with a high-reflectivity silver-plated lining, which can suppress the thermal radiation interference of the external environment, so that the temperature in the inner multi-reflection cavity is not affected by the external environment; The heat-insensitive multi-reflection cavity is a multi-curvature cavity, which is defined as a heat-insensitive temperature field that can be formed inside the heat-insensitive multi-reflection cavity; the high-reflectivity silver-plated lining is chemical silver-plated, which utilizes a chemical reducing agent to reduce silver ions into metallic silver, which is uniformly deposited on the surface of the heat-insensitive multi-reflection cavity.

[0024] Preferably, the silver-plated lining has a laser reflectivity greater than 95%.

[0025] Preferably, the heat-insensitive multi-reflection cavity includes three different configurations: a neck, a body and a tail.

[0026] Preferably, the neck of the heat-insensitive multi-reflection cavity is a narrow-mouth cylinder or cone, consisting of a shoulder and a cavity mouth, the curvature radius of the cavity mouth ranges from 15mm to 30mm, the curvature radius of the shoulder ranges from 5mm to 25mm, the curvature radius of the transition part between the shoulder and the cavity mouth ranges from 2mm to 15mm, the height of the cavity mouth ranges from 10mm to 30mm, and the height of the shoulder ranges from 15mm to 45mm.

[0027] Preferably, the heat-insensitive multi-reflection cavity body is a regular cylinder or a truncated cone, the radius of curvature ranges from 30 mm to 60 mm, and the body height ranges from 50 mm to 200 mm.

[0028] Preferably, the tail of the heat-insensitive multi-reflection cavity is arc-shaped or hemispherical, with a radius of curvature ranging from 20 mm to 40 mm, and a height of the tail ranging from 20 mm to 60 mm.

[0029] Preferably, the neck port of the heat-insensitive multi-reflection cavity is joined to an optical quartz high-transmittance window plate, the thickness of the quartz high-transmittance window plate is 0.5 mm, the quartz window plate has two penetration holes, the diameter of the penetration holes is 6.5 mm, and the center of the penetration holes is 7.5 mm away from the edge of the window plate.

[0030] Preferably, the heat-insensitive multi-reflection cavity comprises an inner cavity and an outer cavity, and the inner cavity and the outer cavity are coaxial glass bodies.

[0031] Preferably, the inner cavity and the outer cavity are fused together by heating and melting, fixed at the sealing point at the front end, and a vacuum isolation layer is formed between the two layers.

[0032] Preferably, the thickness of the inner cavity glass ranges from 1 mm to 1.5 mm.

[0033] Preferably, the thickness of the outer cavity glass ranges from 2 mm to 3 mm.

[0034] Preferably, the vacuum layer gap between the inner and outer glass layers ranges from 1 mm to 5 mm.

[0035] Preferably, the heat-insensitive multi-reflection cavity is made of borosilicate material.

[0036] The present application also provides a gas detection device, including a Raman scattering light detector, which is arranged near the neck window of the cavity and includes a laser and a detector. The laser is used to generate a laser light beam to be incident on the heat-insensitive multi-reflection cavity to excite the gas molecules to be detected to generate Raman scattering light; the detector is arranged near the neck window of the cavity to collect the Raman scattering light generated by the gas molecules.

[0037] Preferably, the laser comprises a laser driver, a multimode optical fiber and a fiber collimating lens. The laser and the fiber collimating lens are connected by a multimode optical fiber. The multimode optical fiber transmits the laser beam generated by the laser to the fiber collimating lens. The fiber collimating lens focuses the beam transmitted by the multimode optical fiber into the heat-insensitive multi-reflection cavity to excite the gas molecules to be measured to generate Raman scattering signals.

[0038] Preferably, the detector includes a fiber optic collecting lens, a multimode optical fiber, a grating spectrometer and a CCD detector. The fiber optic collecting lens is arranged at the neck window to collect the gas Raman scattered light generated in the heat-insensitive multi-reflection cavity into the multimode optical fiber. The multimode optical fiber transmits the Raman scattered light collected by the fiber optic collecting lens to the grating spectrometer.

[0039] Preferably, the grating spectrometer transmits the filtered Raman scattered light to the grating through the slit, the grating separates the Raman scattered light of different wavelengths, and the grating spectrometer focuses the separated Raman scattered light into the CCD detector; the CCD detector converts the optical signal into an electrical signal, and the pixels at different positions record the light intensity of different wavelengths.

[0040] Preferably, a computer device is also included, and the computer device is connected to the output end of the CCD detector to control the CCD detector and perform Raman spectrum analysis.

[0041] Preferably, the Raman frequency shift range detected by the grating spectrometer and the CCD detector includes the Raman frequency shift range of the gas to be measured.

[0042] Preferably, the laser excitation wavelength reduces the fluorescence effect as much as possible while maintaining a certain power.

[0043] like Figure 1 As shown, a preferred embodiment of the present application provides a heat-insensitive multi-reflection cavity 1 for enhancing gas Raman spectroscopy, which comprises: an inner cavity 15 and an outer cavity 16, wherein the inner cavity 15 is arranged in the outer cavity 16, and a vacuum is drawn between the inner cavity and the outer cavity; the inner cavity 15 comprises: a neck 11, a main body 12, and a tail 13; the neck 11 comprises: a cavity opening 112 with a constant outer diameter, and a shoulder 111 which is continuous with the tail side of the cavity opening and has an outer diameter gradually increasing; an opening is arranged at the front side of the cavity opening 112, and an incident window 14 (also called a quartz window plate) is arranged on the opening to seal it; the incident window 14 is used to provide an incident channel for the laser required to obtain the Raman spectrum of the gas to be measured; The main body 12 is cylindrical with openings at both ends and a constant outer diameter, and the opening at the front side of the main body 12 is continuous with the rear side of the shoulder 111; The tail portion 13 is a centrally symmetrical curved surface, the opening side of the curved surface is the head side of the tail portion 13, and the head side of the tail portion 13 is continuous with the opening of the tail side of the main body 12, and is used to seal the tail side of the main body 12; The curvature radius of the shoulder portion 111 is smaller than the curvature radius of the tail portion 13 .

[0044] It should be noted that the radius of curvature refers to the direction from any point on the curved surface to the tangent line at that point, pointing to the center of curvature. The center of curvature of the shoulder 111 and the tail 13 refers to the center of curvature of their section curves; the center of curvature of the cavity opening 112 and the main body 12 refers to the center of curvature of their cross-sectional curves, and their radius of curvature is the radius of the cylinder presented. It can be understood that the above-mentioned section refers to the plane presented after cutting along the symmetry axis of the heat-insensitive multi-reflection cavity 1; the above-mentioned cross section refers to the plane presented after cutting perpendicular to the symmetry axis of the heat-insensitive reflective cavity 1.

[0045] Further preferably, the heat-insensitive multi-reflection cavity 1 is a double-layer vacuum coaxial glass body, including an inner cavity 15 and an outer cavity 16. The inner cavity 15 and the outer cavity 16 are fused and fixed at the front sealing point by a heating and melting method; the side close to the inner cavity 15 is defined as the inner side, the side close to the outer cavity 16 is defined as the outer side, and the middle layer between the inner side and the outer side is defined as a vacuum isolation layer. The inner cavity 15 and the outer cavity 16 can be parallel or non-parallel to each other, and the inner cavity 15 can be contained by the outer cavity 16. Figure 1 An example is given for explanation that the inner cavity 15 and the outer cavity 16 are parallel to each other.

[0046] Specifically, the principle of using the heat-insensitive multi-reflection cavity 1 to enhance the gas Raman spectrum is as follows: the heat-insensitive multi-reflection cavity 1 is set on the same platform as the laser beam 17, so that the laser beam 17 can be incident from the quartz window 14 into the cavity without obstruction. When testing, the laser beam 17 is incident from one end of the quartz window 14 at a certain angle, passes through the neck 11, passes through the main body 12, and irradiates the tail 13. After the laser beam 17 is reflected by the tail 13, it is irradiated on the neck 11, and then after being reflected by the neck 11, it is irradiated on the tail 13 again. Finally, the excitation beam 17 that travels back and forth multiple times is formed inside the heat-insensitive multi-reflection cavity 1. In this process, the laser beam 17 excites the gas molecules to be measured to produce a Raman scattering effect, and then forms a corresponding gas Raman spectrum. The Raman frequency shift of the Raman spectrum generated by the gas to be measured is related to the type of gas molecules, and the Raman spectrum intensity is related to the concentration of the gas to be measured. Therefore, the type and concentration information of the gas to be measured can be obtained by analyzing the gas Raman spectrum.

[0047] In the existing technology, the temperature of the internal environment of the cavity is not processed. After the laser beam 17 is reflected multiple times in the cavity, temperature release will be generated inside the cavity, resulting in changes in the energy level distribution and Raman scattering cross section of the gas molecules, causing fluctuations in the Raman scattering intensity, and thus reducing the accuracy of gas detection. On the other hand, the temperature of the external environment of the cavity must also be thermally shielded to make the multi-reflection cavity in a thermally insensitive environment and obtain a relatively stable Raman scattering signal. In the existing technology, the enhanced gas Raman cavity is in a closed state to avoid not processing the thermal radiation generated by the internal multi-reflection laser. In addition, the existing internal laser temperature processing is sensor control or a thermal compensation mechanism is constructed through an algorithm. The source of thermal radiation is not directly processed. The thermal radiation in the cavity cannot be directly and immediately derived, resulting in unstable gas Raman scattering intensity. On the other hand, the additional component settings will also increase the complexity and instability of the gas detection system, reducing the actual application space.

[0048] In the present embodiment, firstly, the complete cavity of the heat-insensitive multi-reflection cavity 1 has a multi-curvature configuration, the tail 13 is an incomplete sphere with a relatively small curvature radius, which can reflect the thermal radiation in the cavity to the curved side, and the main body 12 forms a thermal radiation propagation channel. The radiation field formed by the tail 13 and the main body 12 can make the thermal radiation converge to the cavity opening side close to the neck 11, and the neck 11 has a neck-shaped transition configuration and a small curvature radius. The thermal radiation field formed by it can make the thermal radiation of the neck 11 converge to the cavity opening, and the neck-shaped configuration of the neck 11 can keep the thermal radiation converged by the thermal radiation conduction field formed by the tail 13 and the main body 12 at the cavity opening, and then conduct heat to the outside from the quartz high-transmittance window plate 14 at the cavity opening, so as to realize the processing of the temperature radiation generated by multiple reflections of the laser beam 17 in the cavity, provide a heat-insensitive environment for the inside of the cavity, and obtain a relatively stable Raman scattering signal.

[0049] Secondly, the heat-insensitive multi-reflection cavity 1 can also achieve heat shielding for the external environment. The inner cavity 15 and the outer cavity 16 are fused into shape at the port of the neck 11 by a heating and melting method. The only connection between the inner cavity 15 and the outer cavity 16 is the port formed by melting at the neck 11, thereby avoiding the excess contact area between the inner cavity 15 and the outer cavity 16 and reducing the heat transfer path; while the inner cavity 15 and the outer cavity 16 are fused into one, a vacuum isolation layer is formed between the inside and the outside, the external environment contacts the outer cavity 16 on the outside, and the gas molecules to be excited contact the inner cavity 15 on the inside, and the vacuum isolation layer formed in the middle physically separates the outer cavity 16 and the inner cavity 15 Isolated, when the external environment temperature changes, because there is a vacuum isolation layer between the outer cavity 16 and the inner cavity 15, there is no heat transfer between gas molecules and solid molecules, the heat conduction path between the outside and the inside is blocked, and there will be no heat convection; in addition, the outer cavity 16 and the inner cavity 15 are coated with a high reflectivity material on the side close to the vacuum isolation layer, which can rebound the thermal radiation of the external environment to the external environment, thereby suppressing the infrared thermal radiation interference of the external environment, thereby achieving temperature shielding between the inner gas molecules to be excited and the outer external environment, providing a heat-insensitive environment inside the cavity, and obtaining a relatively stable Raman scattering signal. The specific principle is as follows: The temperature heat transfer orientation of the chamber is closely related to the thermal radiation field formed by the chamber configuration. Taking the tail of the cavity axial direction as the coordinate origin and the direction along the cavity mouth as the positive direction, the heat conduction equation is used to describe the diffusion of heat in the cavity along the one-dimensional direction (the axial direction of the cavity):

[0050] in, Indicates the position in the cavity The temperature at x is the distance relative to the origin of the coordinate system), is the thermal diffusivity, Indicates the heat source per unit volume. When thermal shielding is achieved against the external environment and there is no external heat source, , we can get:

[0051] For a cavity with multiple curvatures, its cross-sectional area Will vary with location Changes in cross-sectional area will affect the flow of heat, and the rate of heat flow is inversely proportional to the cross-sectional area. According to the continuity equation, the heat flux density It can be expressed as:

[0052] in, represents thermal conductivity, Indicates location The cross-sectional area at is the temperature gradient along the cavity. , For the location The radius of curvature at the neck of the cavity is smaller, and the cross-sectional area at the cavity mouth is Smaller, the heat flux increases, resulting in a temperature gradient in the area Enhanced, causing the temperature to converge at the neck of the cavity.

[0053] The cavity body is a regular column, which is connected to the cavity tail and cavity neck respectively. The heat diffusion is relatively uniform. According to the steady-state heat diffusion equation , the points can be obtained: , and we can get ,in, and are constants, representing the temperature gradient and the offset of the temperature distribution. and neck cavity Boundary conditions We can get: , , substituting into , so the temperature distribution in the middle part of the cavity body is:

[0054] It can be seen that the temperature is linearly distributed from the tail to the neck cavity opening along the central axis of the cavity body. In the heat-insensitive multi-reflection cavity of this embodiment, since the curvature radius of the cavity tail is small and has a hemispherical cavity shape, the thermal radiation will have a strong large-area reflection in this area, the cavity body is a steady-state distribution with a small change amplitude, and it will gradually change in the neck. The curvature radius of the transition part of the cavity at the shoulder and the cavity opening is reduced, which will shorten the path of the reflected thermal radiation beam, so that different thermal radiation waves are superimposed in space, which has a convergence effect on the thermal radiation wave, and its cross-sectional area gradually decreases, and the heat flux density increases accordingly. The heat generated by the light beams and gas molecules going back and forth at the shoulder and the tail is more smoothly converged to the cavity opening through the transition part of the cavity shoulder with a smaller curvature radius. The columnar configuration and small curvature radius of the cavity opening can lock the heat gathered from the chamber at the cavity opening, maintain a high-density heat flow, thereby guiding the temperature to the cavity opening and releasing it to the outside, thereby realizing the processing of the temperature release generated by the gas molecules to be excited during multiple reflection excitation, and providing a multi-reflection enhanced chamber environment with internal thermal insensitivity.

[0055] The thermal radiation shielding of the external environment is mainly achieved by reducing the effects of heat conduction, heat convection and heat radiation. There is a vacuum between the inner cavity layer and the outer cavity layer, and the heat conduction It can be expressed as:

[0056] in, represents thermal conductivity, represents the contact area of ​​the cavity layer, represents the temperature difference between the inner and outer layers, Represents the distance between cavity layers, due to the vacuum , heat conduction is blocked.

[0057] Convective heat transfer It can be expressed as:

[0058] in, is the convective heat transfer coefficient, due to the vacuum , convective heat transfer can be neglected.

[0059] According to the Stefan-Boltzmann law, thermal radiation It can be expressed as:

[0060] Among them, the Stefan-Boltzmann constant , represents the radiating surface area, represents the emissivity of the material, , Indicates the temperature of the inner and outer cavities.

[0061] Combining the above formulas, we can see that the main heat loss is determined by thermal radiation. is the equivalent radiation rate, which can be expressed as , if the two surface emissivities are the same ( ),but , by coating with high reflectivity materials, the problem of thermal radiation can be greatly solved. In the heat-insensitive multi-reflection cavity 1 of this embodiment, the vacuum isolation layer prevents gas molecules and solid molecules from transferring heat, the heat conduction path between the outside and the inside is blocked, and there is no heat convection. The only connection between the inner cavity 15 and the outer cavity 16 is the port formed by melting at the neck 11, thereby avoiding the redundant contact area between the inner cavity 15 and the outer cavity 16, reducing the heat transfer path, and achieving heat shielding from the external environment. Together with the aforementioned processing of the temperature release of the multiple reflection excitation beam 17 inside the cavity, a complete heat-insensitive multi-reflection cavity is formed, so that the obtained enhanced gas Raman signal is relatively stable.

[0062] In some embodiments, the glass thickness of the inner cavity 15 ranges from 1 mm to 1.5 mm, the glass thickness of the outer cavity 16 ranges from 2 mm to 3 mm, and the vacuum insulation layer gap between the inner cavity 15 and the outer cavity 16 glass ranges from 1 mm to 5 mm.

[0063] In a specific embodiment, the glass thickness of the inner cavity 15 is 1.2 mm, the glass thickness of the outer cavity 16 is 2.5 mm, and the gap between the vacuum isolation layer formed by the inner cavity 15 and the outer cavity 16 is 2 mm.

[0064] In this embodiment, the port formed by melting the neck 11 is also covered with a high-transmittance quartz window 14. The laser beam will pass through the quartz window 14 and the gas to be measured in the chamber 1 to generate Raman scattered light and pass through the quartz window 14 again to the detector.

[0065] Specifically, the high transmittance range of the quartz window 14 includes the wavelength of the laser beam 17 and the wavelength of the Raman scattered light excited by the gas to be measured. The quartz window 14 is Up to 2500 The wavelengths of light have good transmittance, for 280 Up to 1500 The light transmittance of the wavelength is more than 90%. After the laser beam passes through the quartz window 14, it will reach the inside of the cavity 1 and produce Raman scattering with the gas molecules to be excited. The generated Raman scattered light will pass through the quartz window 14 and be received by the optical fiber collection lens 5.

[0066] In a specific embodiment, the laser beam 17 is an excitation light with a wavelength of 785 nm as the center; Figure 2As shown, the quartz window plate 14 is provided with two penetration holes and a gas duct 143, and the two penetration holes are defined as an air inlet 141 and an air outlet 142; the diameter of the penetration hole is 6.5 mm, and the center of the penetration hole is 7.5 mm away from the edge of the quartz window plate 14; the outer diameter of the gas duct 143 is 6 mm, and one end of the gas duct 143 is wrapped with a raw tape, and rotated in the same direction from the penetration hole to achieve close contact with the penetration hole, and then the penetration holes on both sides of the quartz window plate 14 are sealed with glass glue with good airtightness.

[0067] The present application can also provide multi-reflection gas Raman signal enhancement. The heat-insensitive multi-reflection cavity 1 includes a neck 11, a main body 12, a tail 13, and a high-reflection silver-plated lining uniformly deposited on the cavity surface of the inner cavity 15 and the outer cavity 16 close to the vacuum isolation layer. The surfaces of different parts of the cavity have different curvatures, which can reflect the laser beam 17 multiple times, thereby increasing the effective action length of the laser beam 17 and the gas molecules to be excited, thereby enhancing the Raman intensity.

[0068] Specifically, the principle of using the heat-insensitive multi-reflection cavity 1 to enhance the gas Raman spectrum is as follows: the heat-insensitive multi-reflection cavity 1 is set on the same platform as the laser beam 17, so that the laser beam 17 can be incident from the quartz window 14 into the cavity without obstruction. When testing, the laser beam 17 is incident from one end of the quartz window 14 at a certain angle, passes through the neck 11, passes through the main body 12, and irradiates the tail 13, exciting the gas molecules to be measured for the first time, and then the laser beam 17 is reflected by the tail 13 and irradiated on the neck 11, exciting the gas molecules to be measured for the second time, and then after being reflected by the neck 11, it is irradiated on the tail 13 again, exciting the gas molecules to be measured for the third time, and this cycle is repeated. Finally, the heat-insensitive multi-reflection cavity 1 forms an excitation beam 17 that travels back and forth for multiple times. Because the gas molecules are evenly distributed in the inner space of the cavity, the more times the laser beam 17 travels back and forth, the longer the effective length of the laser beam 17 acting on the gas molecules to be measured will be, thereby achieving gas Raman spectrum enhancement.

[0069] In the present embodiment, firstly, the surfaces of the cavity neck 11, the cavity body 12 and the cavity tail 13 have a multi-curvature configuration, especially the smaller curvature radius of the cavity neck 11 and the cavity tail 13, which can reduce the laser reflection angle and make it easier for the laser to travel back and forth in the cavity; in addition, the cavity body 12 is a regular cylinder, which can provide a longer excitation path for the laser beam 17 reflected back and forth between the cavity neck 11 and the cavity tail 13.

[0070] Furthermore, according to the aforementioned processing of the internal temperature release of the heat-insensitive multi-reflection cavity 1, it can be known that the radiation field in the heat-insensitive multi-reflection cavity 1 can be concentrated to the port area of ​​the cavity neck 11, so that the Raman scattered light can be collected intensively.

[0071] In some embodiments, the cavity mouth 112 has a curvature radius ranging from 15mm to 25mm, and a height ranging from 15mm to 20mm; the shoulder 111 has a curvature radius ranging from 10mm to 25mm, and a height ranging from 20mm to 40mm. Furthermore, the transition portion has a curvature radius ranging from 5mm to 10mm; the cavity tail 13 is arc-shaped or hemispherical, with a curvature radius ranging from 20mm to 35mm, and a height ranging from 30mm to 50mm; the cavity body 12 is a regular cylinder or a truncated cone, with a curvature radius ranging from 40mm to 50mm, and a height ranging from 70mm to 120mm.

[0072] In a more specific embodiment, the radius of curvature of the cavity mouth 112 is 23 mm and the height is 18 mm, the radius of curvature of the transition part ranges from 5 mm to 9 mm, the radius of curvature of the shoulder 111 is 20 mm and the height is 30 mm, the radius of curvature of the cavity tail 13 is 30 mm and the height is 50 mm, the radius of curvature of the cavity body 12 is 50 mm and the height is 100 mm; in addition, the laser beam 17 and the optical fiber collection lens 5 are on the same horizontal plane.

[0073] In some embodiments, different incident angles of the laser beam 17 will cause the laser beam to irradiate different positions of the cavity. Due to the different curvatures of various parts of the heat-insensitive multi-reflection cavity 1, different reflection directions will be generated, forming different multi-pass reflection light paths.

[0074] like Figure 3 As shown, the structure of the detection device used in the embodiment of the present application is shown, including a Raman scattering signal excitation device 9, a Raman scattering signal receiving device 10 and the heat-insensitive multi-reflection cavity 1 mentioned above; the excitation light beam 17 is output by the Raman scattering signal excitation device, and the excitation light beam 17 enters the heat-insensitive multi-reflection cavity 1 and excites the gas molecules to be detected to generate Raman scattered light, and the Raman scattered light is received and analyzed by the Raman scattering signal receiving device 10.

[0075] Furthermore, the heat-insensitive multi-reflection cavity 1 serves as a gas pool for accommodating the gas to be measured, so as to maintain the temperature stability of the gas environment to be measured and to enhance the gas Raman spectrum signal; the Raman scattering signal excitation device 9 includes a laser driver 2, a fiber collimating lens 3 and a filter 4; the Raman scattering signal receiving device 10 includes a fiber collecting lens 5, a grating spectrometer 6, a CCD detector 7 and a computer device 8.

[0076] Specifically, the laser driver 2 can provide a high-energy, highly coherent laser beam 17 to excite the gas molecules to be measured; the fiber collimating lens 3 can focus the laser beam 17 into the heat-insensitive multi-reflection cavity 1; the filter 4 can make the output laser beam purer; the fiber collecting lens 5 can collect the generated Raman scattered light into the optical fiber; the grating spectrometer 6 can be used to split the Raman scattered light; the CCD detector 7 can form a spectrum for the split light beam; the computer device 8 is used to analyze the spectrum and control the CCD detector 7.

[0077] In a specific embodiment, the laser driver 2 provides a laser beam 17 centered at a wavelength of 785 nm and having a maximum power of 210 mW; the focal length of the optical fiber collimating lens 3 is 15 mm, the focal length of the focusing lens is 100 mm, and the collimated light spot diameter is 4 mm; the filter 4 can transmit light beams in the wavelength range of 820 nm to 2000 nm and cut off in the wavelength range of 200 nm to 780 nm; the focal length of the optical fiber collecting lens 5 is 100 mm; the grating spectrometer 6 and the CCD detector 7 can detect light in the wavelength range of 775.42 nm to 928.13 nm, and the Raman frequency shift range that can be detected is -153 Until 1969 .

[0078] In a more specific embodiment, the laser driver 2 provides a 785nm wavelength laser, which is focused into the heat-insensitive multi-reflection cavity 1 through the fiber collimating lens 3. The fiber collimating lens 3 is adjusted to be 40mm away from the neck 11 port, so that the focus of the incident laser is in the heat-insensitive multi-reflection cavity 1, and the beam waist is on the same plane as the focal plane of the fiber collecting lens 5, so that the high-power laser can excite the gas molecules; after the light beam is reflected multiple times in the heat-insensitive multi-reflection cavity 1, the effective action distance between the laser and the molecules to be measured is increased, and an enhanced gas Raman signal is obtained, and is transmitted to the neck 11 port through the light reflection field, and the filter 4 can filter out excess pump light to reduce interference from other light beams, and the Raman scattered light is then collected by the fiber collecting lens 5 into the grating spectrometer 6, and a spectrum is generated by the CCD detector 7, wherein the fiber collecting lens 5 is adjusted to be 30mm away from the neck 11 port, so that the signal receiving distance and the signal receiving angle achieve a higher efficiency; finally, the CCD detector 7 is controlled and the gas concentration is calculated through the program on the computer device 8.

[0079] In a specific embodiment, the laser beam 17 is an excitation light centered at a wavelength of 785 nm. The laser beam 17 is on the same horizontal line as the optical fiber collection lens 5 and is incident into the chamber at a horizontal angle of 25 degrees. Most of the gas molecules to be measured are located on the focal line of the optical fiber collection lens 5 for the first time, so as to obtain a higher intensity Raman scattered light. The laser beam 17 irradiates the tail 13 with a curvature radius of 30 mm, and then reflects again to the cavity shoulder 111 with a curvature radius of 20 mm. The shoulder 111 with a small curvature radius and the tail 13 with a large curvature radius are incident on the cavity. The laser beam 17 has the characteristics of strong focusing and weak focusing respectively. By balancing the strong and weak focusing, the beam cross-sectional size can be controlled to enhance the concentration of the beam. At the same time, the Rayleigh length is increased to slow down the divergence of the beam, making the beam more stable. In this process, multiple reflections are performed to excite the gas molecules to be measured multiple times, thereby increasing the effective action distance between the laser beam 17 and the gas molecules to be measured. The Raman scattered light generated in all directions is also in the reflected light field, collected at the port 11 of the cavity neck, passes through the quartz window 14, and then received by the optical fiber collection lens 5, thereby obtaining a gas Raman spectrum enhanced several times, such as Figure 4 shown.

[0080] Further, such as Figure 5 As shown, the change of external temperature is controlled by a heating device to detect the thermal shielding effect of the heat-insensitive multi-reflection cavity 1. By setting the gradient ambient temperature of room temperature to 25°C, 40°C, 60°C, and 80°C, the gas Raman molecules in the chamber are excited, and a gas Raman spectrum with strong thermal stability can be obtained, demonstrating that the chamber has an excellent thermal shielding effect.

[0081] In some embodiments, the cavity is made of borosilicate glass.

[0082] Specifically, the effects provided by the device are as follows: Figure 3 and Figure 4 As shown, the experimental gas type is carbon dioxide, and the Raman shift of the Fermi branch is 1286cm -1 and 1388cm -1 Location, Figure 3 The Raman spectrum intensity comparison between the heat-insensitive multi-reflection cavity 1 and the traditional quartz glass gas chamber is shown. Figure 4 The stability of the Raman intensity of the heat-insensitive multi-reflection cavity 1 under different temperature conditions is demonstrated; Figure 3 The gas Raman spectrum intensity (solid line) of the medium heat-insensitive multi-reflection cavity is significantly higher than that of the traditional quartz glass gas chamber (dashed line), and the gas Raman enhancement can be several times higher in the Raman shift of the Fermi branch of carbon dioxide. Figure 4In the figure, the Raman intensity at room temperature 25°C is represented by a solid line, the Raman intensity at 40°C is represented by a dotted line, the Raman intensity at 60°C is represented by a diamond dotted line, and the Raman intensity at 80°C is represented by a triangular dotted line. When the external temperature changes drastically, the gas Raman intensity in the thermally insensitive multi-reflection cavity 1 maintains a relatively consistent level and is hardly significantly affected by the external temperature change, with excellent thermal insensitivity. In summary, the embodiment of the present application provides a heat-insensitive multi-reflection cavity 1 for enhancing gas Raman spectroscopy. The complete cavity of the heat-insensitive multi-reflection cavity 1 has a multi-curvature configuration, and a special temperature conduction field can be formed inside the cavity. As the radius of curvature changes, the heat flux density of different parts inside the cavity changes accordingly. The tail 13 with a larger curvature radius can reflect the thermal radiation over a large area, and the shoulder with a smaller curvature radius can converge the thermal radiation wave. The transition part of the cavity then guides the converged thermal radiation generated inside the cavity to the cavity mouth, and locks the thermal radiation at the cavity mouth and releases it to the outside, so that the temperature release generated in the process of the multi-reflected excitation light beam 17 interacting with the gas molecules can be processed, and an internal heat-insensitive environment can be provided for the gas molecules to be excited. In the heat-insensitive multi-reflection cavity 1, its inner cavity layer 15 and the outer cavity layer 16 form The vacuum isolation layer can isolate the gas in the cavity from the external environment to block the heat transfer and heat convection pathways. The high-reflectivity silver lining coated on the outer surface of the inner cavity layer 15 and the inner surface of the outer cavity layer 16 can suppress the thermal radiation interference of the external environment. Through the above-mentioned heat shielding mechanism, an external heat-insensitive environment can be provided for the gas molecules to be excited; the shoulder 111 has a smaller curvature radius and the chamber tail 13 has a relatively larger curvature radius, which balances the strong and weak focusing, and can control the cross-sectional size of the beam to enhance the concentration of the beam. At the same time, the Rayleigh length is increased to slow down the divergence of the beam and make the beam more stable. The cavity body 12 is a regular cylinder, which can provide a longer effective action length for the laser beam 17 after reflection, thereby enhancing the gas Raman signal to achieve high-quality round trip in the cavity more easily. In addition, the radiation field formed by the cavity causes the Raman scattered light to be converged to the port, further enhancing the gas Raman signal.

[0083] It should be understood that expressions such as "including" and "may include" that may be used in the present application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In the present application, terms such as "including" and / or "having" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0084] In addition, in the present application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0085] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Among them, "fixed connection" means that the relative position relationship after connection remains unchanged. "Rotational connection" means that the two are connected to each other and can rotate relative to each other after connection. "Sliding connection" means that the two are connected to each other and can slide relative to each other after connection. The directional terms mentioned in the embodiments of the present application, such as "top", "bottom", "inside", "outside", "left", "right", etc., are only reference directions of the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present application, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0086] In addition, in the embodiments of the present application, the mathematical concepts mentioned are symmetry, equality, parallelism, verticality, etc. These limitations are all for the current state of the art, rather than being absolutely strict definitions in a mathematical sense, and allow a small amount of deviation, approximation to symmetry, approximation to equality, approximation to parallelism, approximation to verticality, etc. are all possible. For example, A and B are parallel, which means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. A and B are perpendicular, which means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees. The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A heat-insensitive multi-reflection cavity for enhancing gas Raman spectroscopy, used for carrying a gas to be measured so as to obtain a Raman spectrum of the gas to be measured, characterized in that: The heat-insensitive multi-reflection cavity comprises: an inner cavity and an outer cavity, wherein the inner cavity is arranged in the outer cavity, and a vacuum is drawn between the inner cavity and the outer cavity; The inner cavity includes: a neck, a main body and a tail; The neck portion comprises: a cavity opening with a constant outer diameter, and a shoulder portion which is continuous with the rear side of the cavity opening and has a gradually increasing outer diameter; an opening is provided at the front side of the cavity opening, and an incident window is provided on the opening to seal the opening; the incident window is used to provide an incident channel for the laser required to obtain the Raman spectrum of the gas to be measured; The main body is in the shape of a cylinder with openings at both ends and a constant outer diameter, and the opening at the front side of the main body is continuous with the rear side of the shoulder; The tail portion is a centrally symmetrical curved surface, the opening side of the curved surface is the head side of the tail portion, and the head side of the tail portion is continuous with the opening of the tail side of the main body, and is used to seal the tail side of the main body; The radius of curvature of the shoulder is smaller than the radius of curvature of the tail.

2. The heat-insensitive multi-reflection cavity according to claim 1, characterized in that: The outer side of the inner cavity and the inner side of the outer cavity are both coated with high reflective materials.

3. The heat-insensitive multi-reflection cavity according to claim 1, characterized in that: A gas conduit is arranged on the incident window.

4. The heat-insensitive multi-reflection cavity according to claim 1, characterized in that: The cavity opening, shoulder, main body and tail are smoothly transitioned and continuous to form a smooth curved surface.

5. The heat-insensitive multi-reflection cavity according to claim 1, characterized in that: The height of the cavity is smaller than the height of the main body, and the height of the shoulder is larger than the height of the tail.

6. The heat-insensitive multi-reflection cavity according to any one of claims 1 to 5, characterized in that: The curvature radius of the cavity opening ranges from 15mm to 30mm, the curvature radius of the shoulder ranges from 5mm to 25mm, and the curvature radius of the transition portion between the shoulder and the cavity opening ranges from 2mm to 15mm; the height of the cavity opening ranges from 10mm to 30mm, and the height of the shoulder ranges from 15mm to 45mm.

7. The heat-insensitive multi-reflection cavity according to any one of claims 1 to 5, characterized in that: The curvature radius of the main body ranges from 30 mm to 60 mm, and the height of the main body ranges from 50 mm to 200 mm.

8. The heat-insensitive multi-reflection cavity according to any one of claims 1 to 5, characterized in that: The curvature radius of the tail portion ranges from 20 mm to 40 mm, and the height of the tail portion ranges from 20 mm to 60 mm.

9. The heat-insensitive multi-reflection cavity according to claim 1, characterized in that: The inner cavity and the outer cavity are integrally formed; and / or the gap between the inner cavity and the outer cavity ranges from 1 mm to 5 mm.

10. The heat-insensitive multi-reflection cavity according to claim 1, characterized in that: The incident window is a quartz window; The inner cavity and the outer cavity are both made of glass.

Images