Terahertz spectrum measurement cavity suitable for pipeline gas sensing and application of terahertz spectrum measurement cavity

Abstract

The invention provides a terahertz spectrum measurement cavity suitable for pipeline gas sensing and application of the terahertz spectrum measurement cavity, and belongs to the field of gas sensing detection. According to the terahertz spectrum measurement cavity suitable for pipeline gas sensing, the optical path is greatly increased in a limited space through multiple reflections, the detection sensitivity is improved, the optical path is accurately calculated based on the geometrical optics principle to meet the time delay condition of THz-TDS, and high-sensitivity pipeline gas spectrum detection is achieved by adapting to a pipeline installation scene. The structure of the terahertz spectrum measurement cavity suitable for pipeline gas sensing can simultaneously meet the requirement of accurate calculation of an optical path (meet the requirement of terahertz waves on a delay condition), the volume of the gas chamber is small, and the interior of the gas chamber has a long optical path (the operating distance between the terahertz waves and gas to be measured is increased as much as possible in a limited space) through multiple reflections; the device is suitable for high-sensitivity terahertz gas detection inside / outside a pipeline.

Description

Technical Field

[0001] The present invention belongs to the field of gas sensing detection, and particularly relates to a terahertz spectroscopic measurement cavity applicable to pipeline gas sensing and its application. Background Technique

[0002] Common gases have significant fingerprint spectral characteristics in the terahertz frequency band. Therefore, terahertz spectroscopic measurement technology can be used to detect and identify gases. Compared with traditional non-dispersive infrared spectroscopic gas detection technology, differential absorption spectroscopic gas detection technology, laser absorption spectroscopic gas detection and other technologies, the outstanding advantages of terahertz spectroscopic technology applied to gas detection are: (1) The ultra-wideband characteristic of the terahertz spectral range enables a single device to simultaneously detect multiple gas components; (2) The terahertz wave has a longer wavelength and has stronger penetration ability for smoke and dust in the gas compared with lasers. Therefore, the gas detection technology based on terahertz spectroscopy is more suitable for detecting the mixed gas components in harsh scenarios such as thick smoke and fog.

[0003] Figure 11 It is a connection relationship block diagram of a terahertz spectroscopic gas detection device under the prior art. The connection relationship of the terahertz spectroscopic gas detection device under the prior art is as Figure 11As shown in the figure, the terahertz spectroscopy gas detection device 200 includes a terahertz wave emission probe 201, a gas chamber 202, a terahertz wave reception probe 203, and a THZ-TDS host 204. Both sides of the sealed gas chamber 202 are provided with transmission windows, and the inside of the gas chamber 202 is used to introduce the gas to be detected. The terahertz wave emitted by the terahertz wave emission probe 201 passes through the transmission windows on both sides of the gas chamber 202 and then passes through the gas to be detected inside, and is received by the terahertz wave reception probe 203. The THZ-TDS host 204 is connected to the terahertz wave emission probe 201 and the terahertz wave reception probe 203, so as to control the terahertz wave emission probe 201 to emit terahertz waves and record the terahertz waves received by the terahertz wave reception probe 203, and then perform signal modulation, so as to collect and analyze the spectrum of the gas in the gas chamber 202. In the existing reported gas sensing detection technical solutions based on THz-TDS, usually on the basis of the THz-TDS system, in the terahertz optical path between its terahertz emission probe and reception probe, a sealed gas chamber structure filled with the gas to be detected is inserted, and the terahertz beam passes through this gas chamber structure once (hereinafter referred to as the "direct-through type gas cavity structure"). The working distance between the terahertz transceiver probes is usually less than 1 meter, and the diameter of the terahertz beam is about 1-2 inches. Since the absorption coefficient of the gas in the terahertz frequency band is usually small, the sensitivity of terahertz gas sensing is low. In order to improve the sensitivity of terahertz gas sensing, it can be solved by increasing the interaction distance between the gas and the terahertz wave. For the direct-through type gas cavity structure, in order to meet certain sensitivity requirements, the length of the gas chamber cavity needs to reach several meters, which to a certain extent limits the installation and deployment of this solution in scenarios with narrow installation spaces. The Herriot type gas chamber mentioned in the paper "Sensitive multi-species photoacoustic gas detection based on mid-infrared supercontinuum source and miniature multipass cell" (DOI: 10.1039 / d2cp01731h) is a "multiple reflection type gas cavity structure" that can achieve an equivalent long transmission distance in a small space; however, it is very difficult to accurately calculate the propagation optical path of the detection light in the gas chamber. Since the THz-TDS technology is sensitive to the optical delay condition, this "multiple reflection type gas cavity structure" that cannot determine the accurate propagation optical path (which has a corresponding relationship with "delay") is not applicable to the gas sensing system based on THz-TDS.

[0004] For a terahertz gas detection system using a direct-through gas cavity structure, there is a problem with detection sensitivity. Although the detection sensitivity can be improved by increasing the length of the gas chamber cavity, this requires an installation space of several meters, which limits the installation and deployment in practice. The above-reported multi-reflection gas cavity structures working in the visible or infrared bands are not applicable to gas detection technologies based on terahertz time-domain spectroscopy because the optical path inside cannot be accurately calculated. Summary of the Invention

[0005] The present invention is made to solve the above problems, and the purpose is to provide a terahertz spectroscopy measurement cavity applicable to pipeline gas sensing and its application.

[0006] The present invention provides a terahertz spectroscopy measurement cavity applicable to pipeline gas sensing, having the following characteristics: including a reflection gas chamber, which is a hollow cylindrical structure in the shape of a regular K-prism, where K is an integer not less than 3. At different positions in the length direction of the side wall of the reflection gas chamber, an incident window reserved opening and an exit window reserved opening are respectively provided. The geometric centers of the incident window reserved opening and the exit window reserved opening are both located on the symmetry axis in the length direction of the side wall where they are located. The inner wall of the reflection gas chamber is a reflecting surface, and the inside of the reflection gas chamber is used to introduce the mixed gas to be detected; an incident window and an exit window are respectively arranged at the incident window reserved opening and the exit window reserved opening and completely cover the incident window reserved opening and the exit window reserved opening; a transmitting probe and a receiving probe are arranged outside the reflection gas chamber and are respectively located at the incident window and the exit window. Among them, the terahertz parallel light emitted by the transmitting probe passes through the geometric center of the incident window reserved opening and is reflected several times along a spiral winding path on the inner wall of the hollow cylindrical structure of the regular K-prism of the reflection gas chamber, then exits from the center of the exit window reserved opening and is received by the receiving probe; and a TDS host is connected to the transmitting probe and the receiving probe, used to control the transmitting probe to emit terahertz parallel light, record the terahertz parallel light signal received by the receiving probe, and then perform signal modulation, so as to collect and analyze the spectrum of the mixed gas.

[0007] In the terahertz spectroscopy measurement cavity applicable to pipeline gas sensing provided by the present invention, it may also have the following characteristics: where the angle formed by the projection of the terahertz parallel light emitted by the transmitting probe on the regular K-sided bottom surface of the regular K-prism of the reflection gas chamber and the side of the regular K-sided polygon is denoted as θ xy , The length direction of the reflection gas chamber is denoted as the z-axis, and the angle between the terahertz parallel light emitted by the transmitting probe and the z-axis is θ z , and the total optical path of the terahertz parallel light in the reflection gas chamber is Let \(n\) be the relative refractive index of the terahertz parallel light in the reflection gas chamber, \(L\) be the distance between the geometric centers of the incident window reserved opening and the exit window reserved opening in the \(z\)-axis direction, and denote the side length of the regular \(K\)-sided polygon at the bottom of the regular \(K\)-prismatic reflection gas chamber as \(a\). When the terahertz parallel light reflects in a spiral coiled path in the reflection gas chamber, the height difference in the \(z\)-axis direction for each spiral period is The angle between the emission probe and the \(z\)-axis is \(\theta\). z The angle between the receiving probe and the \(z\)-axis is \(\theta'\). z \(= 180^{\circ}-\theta\). z .

[0008] In the terahertz spectroscopic measurement cavity applicable to pipeline gas sensing provided by the present invention, it may also have the following feature: wherein, the height difference \(d\) is greater than the maximum spot diameter of the terahertz parallel light in the \(z\)-axis direction.

[0009] In the terahertz spectroscopic measurement cavity applicable to pipeline gas sensing provided by the present invention, it may also have the following feature: wherein, adjustment components are provided on both the emission probe and the receiving probe, and the adjustment components are used to adjust the angles between the emission probe and the receiving probe and the \(z\)-axis.

[0010] In the terahertz spectroscopic measurement cavity applicable to pipeline gas sensing provided by the present invention, it may also have the following feature: wherein, the inner wall material of the reflection gas chamber includes gold, silver or aluminum, and the material of the incident window and / or the exit window includes high-resistance silicon or HDPE.

[0011] In the terahertz spectroscopic measurement cavity applicable to pipeline gas sensing provided by the present invention, it may also have the following feature: wherein, an anti-reflection film is plated on the inner wall of the reflection gas chamber.

[0012] In the terahertz spectroscopic measurement cavity applicable to pipeline gas sensing provided by the present invention, it may also have the following feature: wherein, the incident window reserved opening and the exit window reserved opening are respectively opened at both ends in the length direction of the side wall of the reflection gas chamber, and the incident window reserved opening and the exit window reserved opening are located on the same side wall or different side walls of the hollow cylindrical structure of the regular \(K\)-prismatic reflection gas chamber.

[0013] The present invention also provides an application of a terahertz spectroscopic measurement cavity applicable to pipeline gas sensing in detecting the gas components in a pipeline, having the following feature: the terahertz spectroscopic measurement cavity applicable to pipeline gas sensing described in any one of the foregoing is used to detect the components of the mixed gas in the pipeline, wherein both ends in the length direction of the reflection gas chamber are respectively connected to the pipeline, so that the mixed gas in the pipeline can be introduced into the reflection gas chamber.

[0014] The present invention also provides an application of a terahertz spectroscopy measurement cavity suitable for pipeline gas sensing in detecting gas leakage on the outer wall of a pipeline, which has the following characteristics: the terahertz spectroscopy measurement cavity suitable for pipeline gas sensing described in any one of the foregoing is used to detect gas leakage on the outer wall of the pipeline, wherein the pipeline passes through its internal cavity along the length direction of the reflection gas chamber, and both ends of the reflection gas chamber in the length direction are closed.

[0015] In the application of the terahertz spectroscopy measurement cavity suitable for pipeline gas sensing provided by the present invention in detecting gas leakage on the outer wall of a pipeline, it may also have the following characteristics: wherein, the axis of the pipeline coincides with the axis of the reflection gas chamber, and the pipeline is fixed therein by support columns at both ends of the reflection gas chamber in its length direction, and the outer wall radius range of the pipeline a is the side length of the regular K-sided polygon at the bottom of the regular K-prism-shaped reflection gas chamber.

[0016] Functions and effects of the invention

[0017] According to a terahertz spectroscopy measurement cavity suitable for pipeline gas sensing and its application involved in the present invention, since the terahertz spectroscopy measurement cavity suitable for pipeline gas sensing includes: a reflection gas chamber, which is a hollow cylindrical structure in the shape of a regular K-prism, where K is an integer not less than 3, and incident window reserved openings and exit window reserved openings are respectively provided at different positions in the length direction of the side wall of the reflection gas chamber. The geometric centers of the incident window reserved opening and the exit window reserved opening are respectively located on the axis of symmetry in the length direction of the side wall where they are located. The inner wall of the reflection gas chamber is a reflecting surface, and the inside of the reflection gas chamber is used to introduce the mixed gas to be detected; an incident window and an exit window are respectively arranged at the incident window reserved opening and the exit window reserved opening and completely cover the incident window reserved opening and the exit window reserved opening; a transmitting probe and a receiving probe are arranged outside the reflection gas chamber and are respectively located at the incident window and the exit window. Among them, the terahertz parallel light emitted by the transmitting probe passes through the geometric center of the incident window reserved opening and is reflected several times along a spiral winding path on the inner wall of the hollow cylindrical structure of the regular K-prism of the reflection gas chamber, and then exits from the center of the exit window reserved opening and is received by the receiving probe; and a TDS host is connected to the transmitting probe and the receiving probe, and is used to control the transmitting probe to emit terahertz parallel light and record the terahertz parallel light signal received by the receiving probe, and then perform signal modulation, so as to collect and analyze the spectrum of the mixed gas.

[0018] Therefore, the structure of the terahertz spectroscopy measurement cavity suitable for pipeline gas sensing of the present invention can simultaneously meet the requirements of accurate calculation of the optical path (meet the requirements of the delay condition for terahertz waves), has a small gas chamber volume, and has a long optical path through multiple reflections inside (increase the interaction distance between terahertz waves and the gas to be measured as much as possible in a limited space), and is suitable for high-sensitivity terahertz gas detection inside / outside the pipeline. Description of the drawings

[0019] Figure 1 are the perspective views of the reflection gas chamber of Embodiment 1 of the present invention when K is 3, 6, 10, and 12 respectively;

[0020] Figure 2 are the radial projections of the reflection gas chamber of Embodiment 1 of the present invention when K is 3, 6, and 10 respectively;

[0021] Figure 3 are the front view and bottom view of the terahertz spectroscopy measurement cavity for pipeline gas sensing of Embodiment 2 of the present invention;

[0022] Figure 4 are the perspective views of the terahertz spectroscopy measurement cavity for pipeline gas sensing of Embodiment 2 of the present invention from two perspectives;

[0023] Figure 5 is the schematic diagram of the three-dimensional space optical path in the reflection gas chamber of Embodiment 2 of the present invention;

[0024] Figure 6 is Figure 5 the schematic diagram of the radial projection of the optical path at the emission probe and the receiving probe in the corresponding reflection gas chamber;

[0025] Figure 7 is the schematic diagram of the equivalent optical path after the reflection gas chamber of Embodiment 2 of the present invention is unfolded along the axial direction;

[0026] Figure 8 are the perspective views of the terahertz spectroscopy measurement cavity for pipeline gas sensing of Embodiment 3 of the present invention when applied to detect the composition of the mixed gas in the pipeline;

[0027] Figure 9 is Figure 8 the corresponding plan view;

[0028] Figure 10 is the structural schematic diagram of the terahertz spectroscopy measurement cavity for pipeline gas sensing of Embodiment 4 of the present invention when applied to detect the gas leakage on the outer wall of the pipeline;

[0029] Figure 11 is the connection relationship block diagram of the terahertz spectroscopy gas detection device under the prior art. Detailed implementation manners

[0030] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the following embodiments will specifically describe a terahertz spectroscopy measurement cavity for pipeline gas sensing and its application in the present invention in conjunction with the accompanying drawings.

[0031] <Embodiment 1>

[0032] As shown in Figure 1 and Figure 2 shown, this embodiment provides a reflection gas chamber 10.

[0033] The reflection gas chamber 10 is a hollow cylindrical structure in the shape of a regular K - prism, where K is an integer not less than 3. Among them, Figure 1 stereograms of the reflection gas chamber 10 when K is 3, 6, 10, and 12 respectively are provided, Figure 2 and radial projections of the reflection gas chamber 10 when K is 3, 6, and 10 respectively are provided.

[0034] As shown in Figure 1 shown, incident window reserved openings 10a and exit window reserved openings 10b are respectively provided at different positions in the length direction of the rectangular side wall of the reflection gas chamber 10. Among them, both the incident window reserved opening 10a and the exit window reserved opening 10b are circular holes, and the centers of the incident window reserved opening 10a and the exit window reserved opening 10b are respectively located on the symmetry axis in the length direction of the rectangular side wall where they are located.

[0035] Specifically in this embodiment, the incident window reserved opening 10a and the exit window reserved opening 10b are respectively provided at both ends in the length direction of the same rectangular side wall of the reflection gas chamber 10.

[0036] The inner wall of the reflection gas chamber 10 is a reflective surface, on which an anti - reflection - enhancing film is plated. The material of the inner wall of the reflection gas chamber 10 includes gold, silver, or aluminum.

[0037] The inside of the reflection gas chamber 10 is used to introduce the mixed gas to be detected.

[0038] <Example 2>

[0039] Figure 3 are the front view and bottom view of the terahertz spectroscopy measurement cavity applicable to pipeline gas sensing in Example 2 of the present invention; Figure 4 are the stereograms of the terahertz spectroscopy measurement cavity applicable to pipeline gas sensing in Example 2 of the present invention from two perspectives.

[0040] As shown in Figure 3 and Figure 4 shown, this embodiment provides a terahertz spectroscopy measurement cavity 100 applicable to pipeline gas sensing, including a reflection gas chamber 10, an incident window (not shown in the figure), an exit window (not shown in the figure), a transmitting probe 20, a receiving probe 30, and a TDS host (not shown in the figure).

[0041] The reflection gas chamber 10 in this embodiment is the same as that in Example 1 and will not be repeated. Specifically in this embodiment, the value of K of the reflection gas chamber 10 is selected as 12, that is, the reflection gas chamber 10 in this embodiment is a hollow cylindrical structure in the shape of a regular dodecagonal prism.

[0042] The incident window and the exit window are respectively arranged at the incident window reserved opening 10a and the exit window reserved opening 10b and completely cover the incident window reserved opening 10a and the exit window reserved opening 10b. The materials of the incident window and the exit window include high-resistance silicon or HDPE. Since they are transparent, they are not shown or marked in Figure 3 and Figure 4 it.

[0043] The transmitting probe 20 is arranged outside the reflection gas chamber 10 and at the incident window; the receiving probe 30 is arranged outside the reflection gas chamber 10 and at the exit window.

[0044] Among them, the terahertz parallel light emitted by the transmitting probe 20 passes through the center of the incident window reserved opening 10a and is reflected several times on the inner wall of the regular dodecagonal hollow cylindrical structure of the reflection gas chamber 10 in a spiral winding path, and then exits from the center of the exit window reserved opening 10b and is received by the receiving probe 30.

[0045] Figure 5 is the schematic diagram of the three-dimensional space optical path in the reflection gas chamber of Embodiment 2 of the present invention; Figure 6 is Figure 5 the schematic diagram of the projection in the radial direction of the optical path at the transmitting probe and the receiving probe in the corresponding reflection gas chamber.

[0046] As Figure 5 and Figure 6 shown, take the endpoints of the regular dodecagon of the reflection gas chamber 10 as the coordinate origin O, record the length direction of the reflection gas chamber 10 as the z-axis, and record the incident direction of the terahertz parallel light (before reflection) emitted by the transmitting probe 20 as the x-axis. Then the z-axis and the x-axis are perpendicular to each other, and another y-axis perpendicular to the xOz plane is established.

[0047] Figure 7 is the schematic diagram of the equivalent optical path after the reflection gas chamber of Embodiment 2 of the present invention is unfolded along the axis direction.

[0048] As Figures 5 to 7 shown, the terahertz parallel light is successively reflected on the symmetry axes in the z-axis direction of the 12 rectangular side faces of the inner wall of the regular dodecagon. The three-dimensional optical path is approximately a regular dodecagon composed of spiral broken lines. The included angle θ xy between the projection of the incident terahertz parallel light on the xOy plane and the edge where the polygon of the inner wall of the dodecagon intersects is equal to half of the central angle of the corresponding regular polygon of the edge, that is, the angle θ xy formed between the projection of the terahertz parallel light emitted by the transmitting probe 20 on the regular dodecagon bottom surface of the regular dodecagonal shape of the reflection gas chamber 10 (on the xOy plane) and the side of the regular dodecagon is:

[0049]

[0050] Specifically in this embodiment, since K = 12, then θ xy = 15°.

[0051] Among them, in Figure 2 the radial projections (on the xOy plane) of the reflection gas chamber 10 and the reflection optical path therein when K is 3, 6, and 10 respectively are also shown. As Figure 2 shown, when the reflection gas chamber 10 is a regular triangular prism, a regular hexagonal prism, and a regular decagonal prism respectively, the corresponding θ xy are 60°, 30°, and 18° respectively.

[0052] As Figures 5 to 7 shown, in the z-axis direction: due to the geometric properties of the regular dodecagonal prism of the reflection gas chamber 10, the optical path trajectory of multiple reflections is also in the shape of a regular dodecagonal prism in space, and the projection of the optical path trajectory on the xOy plane is also a regular dodecagon (connecting the midpoints of each side of the bottom regular dodecagon). The optical path trajectory can be unfolded, which is equivalent to the hypotenuse length of a right triangle. The angle between this hypotenuse and the z-axis is θ z , that is, the angle between the terahertz parallel light emitted by the emission probe 20 and the z-axis is θ z , and the total optical path of the terahertz parallel light in the reflection gas chamber 10 is:

[0053]

[0054] Among them, n is the relative refractive index of the terahertz parallel light in the reflection gas chamber 10, and L is the distance between the centers of the incident window reserved opening 10a and the exit window reserved opening 10b in the z-axis direction.

[0055] Specifically in this embodiment, adjustment components 40 are provided on both the emission probe 20 and the receiving probe 30. The adjustment component 40 is used to adjust the angle θ z between the emission probe 20 and the receiving probe 30 and the z-axis, and further adjust the total optical path S.

[0056] Denote the side length of the regular dodecagon at the bottom of the regular dodecagonal prism of the reflection gas chamber 10 as a. When the terahertz parallel light is reflected in a spiral coiled path in the reflection gas chamber 10, the height difference in the z-axis direction for each spiral period is:

[0057]

[0058] Among them, the height difference d is greater than the maximum spot diameter of the terahertz parallel light in the z-axis direction, so that the optical paths in the reflection gas chamber 10 do not overlap, which can ensure that the light will not generate interference phenomena due to overlap in the reflection gas chamber 10. And the maximum spot diameter of the terahertz parallel light in the z-axis direction is not greater than the inner diameters of the incident window reserved opening 10a and the exit window reserved opening 10b.

[0059] The included angle between the transmitting probe 20 and the z-axis is θ z , and the included angle between the receiving probe 20 and the z-axis is:

[0060] θ′ z = 180° - θ z

[0061] As Figure 5 shown, the directions of the x-axis and y-axis are reset according to the position of the exit window reserved opening 10b and the direction of the outgoing light of the terahertz parallel light (denoted as the x'-axis and y'-axis), in the same way as the transmitting end (the incident window reserved opening 10a and the incident light of the terahertz parallel light). In the x'-y' direction: the outgoing direction of the terahertz parallel light is parallel to the x'-axis, and the center of the optical axis of the terahertz parallel light will theoretically pass through the center of the circle of the exit window reserved opening 10b.

[0062] In this embodiment, after the x-y direction probes (the transmitting probe 20 and the receiving probe 30) are deployed, they are not adjusted anymore; in the z-axis direction: the included angles between the transmitting probe 20 and the receiving probe 30 and the z-axis are θ z and θ′ z , and this angle can be adjusted for the transmitting probe 20 and the receiving probe 30 through the adjusting component 40, and always satisfies the calculation formula of the optical path S in the gas chamber.

[0063] The TDS host is connected to the transmitting probe 20 and the receiving probe 30, and is used to control the transmitting probe 20 to emit terahertz parallel light (the photoconductive antenna generates a divergent terahertz beam, which is converted into a parallel terahertz beam through an off-axis parabolic mirror) and record the terahertz parallel light signal received by the receiving probe 30, and then perform signal modulation, so as to collect and analyze the spectrum of the mixed gas introduced into the reflection gas chamber 10.

[0064] Among them, the system formed by connecting the transmitting probe 20, the receiving probe 30 and the TDS host specifically selects the THz-TDS system of the model BT-FTS5500 or BT-FTS3500-H produced by Botahertz (Shanghai) Optoelectronic Technology Co., Ltd.

[0065] The usage process of a terahertz spectrum measurement cavity 100 applicable to pipeline gas sensing in this embodiment:

[0066] S10, arrange the transmitting probe 20:

[0067] (1) In the x-y direction: the incident direction of the terahertz parallel light is parallel to the x-axis, and the center of the incident optical axis needs to pass through the center of the circle of the incident window reserved opening 10a.

[0068] (2) In the z-axis direction: Due to the geometric properties of the regular dodecagonal prism, the optical path trajectory of multiple reflections also forms a regular dodecagonal prism shape in space, and its projection on the x-y plane is also a regular dodecagon. The radial distance L in the z-axis direction between the geometric centers A and M’ of the incident window reserved opening 10a and the exit window reserved opening 10b is used to determine the total optical path S of the terahertz parallel light in the reflection chamber 10 (adjust the angle θ between the emission probe 20 and the z-axis through the adjustment component 40 on the emission probe 20 z to a preset value, and the optical path S corresponding to this angle θ z needs to meet the delay condition of the THz-TDS system).

[0069] S20, arrange the receiving probe 30:

[0070] (1) Reset the coordinate system according to the position of the exit window reserved opening 10b in the same way as the transmitting end.

[0071] (2) In the x’-y’ direction: The terahertz parallel light exits in a direction parallel to the x’-axis, and the center of the exit optical axis theoretically passes through the center of the circle of the exit window reserved opening 10b.

[0072] (3) In the z-axis direction: Adjust the angle θ between the receiving probe 30 and the z-axis through the adjustment component 40 on the receiving probe 30 z .

[0073] S30, after connecting the TDS host to the emission probe 20 and the receiving probe 30, start the entire system for signal modulation, and then the gas spectrum in the reflection chamber 10 can be collected and analyzed.

[0074] Among them, after the emission probe 20 and the receiving probe 30 are started, the terahertz parallel light enters the reflection chamber 10 from the center of the circle of the incident window reserved opening 10a, and then is reflected successively at the symmetry axis positions in the z-axis direction of the 12 rectangular sides on the inner wall of the regular dodecagonal prism (the reflection points in each cycle are successively at points A, B, C, D, E, F, G, H, I, J, K, L, M, and the reflection points are all on the symmetry axes in the z-axis direction of the 12 rectangular sides on the inner wall of the regular dodecagonal prism). Due to the geometric properties of the regular prism, the light can reach the midpoint of the next side after each reflection. The length of the three-dimensional broken line ABCDEFGHIJKLM is the geometric path of one reflection cycle. After every 12 reflections, the terahertz parallel light changes 360° in the direction perpendicular to the z-axis of the regular prism gas chamber, that is, it is in the same direction as the incident direction, and advances a small distance in the z-axis direction. Repeating this process, the distance advanced by each cyclic optical path in the z-axis direction is denoted as d until it exits from the reserved exit window reserved opening 10b.

[0075] <Example 3>

[0076] Figure 8A perspective view of the terahertz spectroscopy measurement cavity for pipeline gas sensing in Embodiment 3 of the present invention when it is applied to detect the composition of the mixed gas in the pipeline; Figure 9 is Figure 8 the corresponding plan view.

[0077] As Figure 8 and Figure 9 shown, this embodiment provides an application of the terahertz spectroscopy measurement cavity for pipeline gas sensing in the detection of the gas composition in the pipeline. It uses the terahertz spectroscopy measurement cavity 100 for pipeline gas sensing in Embodiment 2 to detect the composition of the mixed gas in the pipeline 50.

[0078] Among them, the reflection gas chamber 10 is arranged along the length direction of the pipeline 50, and both ends of the length direction of the reflection gas chamber 10 are respectively communicated with the pipeline 50, so that the mixed gas in the pipeline 50 can be introduced into the reflection gas chamber 10.

[0079] Specifically in this embodiment, the system formed by connecting the emission probe 20, the receiving probe 30 and the TDS host specifically selects the THz-TDS system with the model number of BT-FTS5500 or BT-FTS3500-H produced by Botaihertz (Shanghai) Optoelectronic Technology Co., Ltd. Among them, BT-FTS5500 is applicable to the measurement of the composition of the mixed gas with a low gas flow rate in the pipeline 50, and BT-FTS3500-H is applicable to the measurement of the composition of the mixed gas with a high gas flow rate in the pipeline 50.

[0080] <Embodiment 4>

[0081] Figure 10 A structural schematic diagram of the terahertz spectroscopy measurement cavity for pipeline gas sensing in Embodiment 4 of the present invention when it is applied to detect the gas leakage on the outer wall of the pipeline.

[0082] As Figure 10 shown, this embodiment provides an application of the terahertz spectroscopy measurement cavity for pipeline gas sensing in the detection of the gas leakage on the outer wall of the pipeline. It uses the terahertz spectroscopy measurement cavity 100 for pipeline gas sensing in Embodiment 2 to detect the gas leakage on the outer wall of the pipeline 51.

[0083] The pipeline 51 penetrates through its internal cavity along the length direction of the reflection gas chamber 10, and the axis of the pipeline 51 coincides with that of the reflection gas chamber 10. The reflection gas chamber 10 fixes the pipeline 51 therein through the support columns 10c at both ends of its length direction.

[0084] Both ends of the annular space formed by the reflection gas chamber 10 and the pipeline 51 are closed. ( Figure 10In order to more intuitively show the connection relationship between the reflection chamber 10 and the pipeline 51 through the support column 10c, the closed states at both ends in the length direction of the annular space are not shown.)

[0085] In this embodiment, the range of the outer wall radius of the pipeline 51 that can be detected is:

[0086]

[0087] Wherein, a is the side length of the regular K-sided polygon at the bottom of the regular K-prismatic shape of the reflection chamber.

[0088] In this embodiment, the TDS host is used to detect whether there is a mixed gas in the annular space formed by the reflection chamber 10 and the pipeline 51, so as to realize the leakage detection of the gas on the outer wall of the pipeline 51.

[0089] Specifically in this embodiment, the system formed by connecting the transmitting probe 20, the receiving probe 30 and the TDS host specifically selects the THz-TDS system with the model number BT-FTS5500 produced by Botahertz (Shanghai) Optoelectronic Technology Co., Ltd. (BT-FTS5500 is applicable to the measurement of the components of mixed gases with low gas flow rates. In this embodiment, when detecting the gas leakage on the outer wall of the pipeline 51, it is default that the leaked gas has a low flow rate in the annular space formed by the reflection chamber 10 and the pipeline 51).

[0090] Functions and effects of the embodiment

[0091] According to Embodiments 1 to 4, a reflection chamber, a terahertz spectrum measurement cavity applicable to pipeline gas sensing and its application are provided. Since the terahertz spectrum measurement cavity applicable to pipeline gas sensing includes: a reflection chamber, which is a hollow cylindrical structure in the shape of a regular K-prism, where K is an integer not less than 3. Incident window reserved openings and outgoing window reserved openings are respectively provided at different positions in the length direction of the side wall of the reflection chamber. The geometric centers of the incident window reserved opening and the outgoing window reserved opening are respectively located on the symmetry axes in the length direction of their respective side walls. The inner wall of the reflection chamber is a reflective surface, and the inside of the reflection chamber is used to introduce the mixed gas to be detected; an incident window and an outgoing window are respectively arranged at the incident window reserved opening and the outgoing window reserved opening and completely cover the incident window reserved opening and the outgoing window reserved opening; a transmitting probe and a receiving probe are arranged outside the reflection chamber and are respectively located at the incident window and the outgoing window. Among them, the terahertz parallel light emitted by the transmitting probe passes through the geometric center of the incident window reserved opening and is reflected several times along a spiral winding path on the inner wall of the hollow cylindrical structure of the regular K-prismatic shape of the reflection chamber, and then exits from the center of the outgoing window reserved opening and is received by the receiving probe; and a TDS host is connected to the transmitting probe and the receiving probe, and is used to control the transmitting probe to emit terahertz parallel light and record the terahertz parallel light signal received by the receiving probe, and then perform signal modulation, so as to collect and analyze the spectrum of the mixed gas.

[0092] Therefore, the reflective gas chambers, the terahertz spectroscopy measurement cavities applicable to pipeline gas sensing, and their applications in Embodiments 1 to 4 have the following beneficial effects:

[0093] (1) The terahertz spectroscopy measurement cavity applicable to pipeline gas sensing has a small space occupation and a long internal optical path: the gas chamber cavity belongs to a multi-reflection gas chamber, and terahertz waves can be reflected multiple times within a limited space, maximizing the optical path within a small space range, thereby improving the detection sensitivity.

[0094] (2) The internal optical path of the cavity can be calculated: the main body of the gas chamber structure is a regular K-prism cylinder structure with a reflective mirror on the inner wall (K is an integer not less than 3). The optical path can be accurately calculated based on the law of reflection and the geometric properties of the regular prism.

[0095] (3) Anti-interference design: that is, it is required that the optical paths in the gas chamber do not overlap. It only needs to satisfy that the height difference corresponding to adjacent spiral periods of the optical axis is slightly larger than the maximum spot diameter in the z-axis direction, so as to ensure that light rays will not interfere due to overlap in the gas chamber.

[0096] (4) Adjustable: The optical path can be adjusted by adjusting the spatial position and inclination of the probe deployment.

[0097] Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A terahertz spectroscopy measurement cavity applicable to pipeline gas sensing, characterized in that Comprising: A reflection gas chamber, which is a hollow cylindrical structure in the shape of a regular K - prism, where K is an integer not less than 3. At different positions in the length direction of the side wall of the reflection gas chamber, an incident window reserved opening and an exit window reserved opening are respectively provided. The geometric centers of the incident window reserved opening and the exit window reserved opening are both located on the axis of symmetry in the length direction of their respective side walls. The inner wall of the reflection gas chamber is a reflecting surface, and the inside of the reflection gas chamber is used to introduce the mixed gas to be detected; An incident window and an exit window, which are respectively arranged at the incident window reserved opening and the exit window reserved opening and completely cover the incident window reserved opening and the exit window reserved opening; A transmitting probe and a receiving probe, which are arranged outside the reflection gas chamber and are respectively located at the incident window and the exit window. Among them, the terahertz parallel light emitted by the transmitting probe passes through the geometric center of the incident window reserved opening and is reflected several times along a helical winding path on the inner wall of the hollow cylindrical structure of the regular K - prism of the reflection gas chamber, and then exits from the center of the exit window reserved opening and is received by the receiving probe; and A TDS host, which is connected to the transmitting probe and the receiving probe, is used to control the transmitting probe to emit terahertz parallel light, record the terahertz parallel light signal received by the receiving probe, and then perform signal modulation, so as to collect and analyze the spectrum of the mixed gas.

2. The terahertz spectroscopy measurement cavity for pipeline gas sensing according to claim 1, wherein: Among them, Denote the angle formed by the projection of the terahertz parallel light emitted by the transmitting probe on the regular K-sided polygon bottom surface of the positive K-prism of the reflection gas chamber and the side of the regular K-sided polygon as θ xy , The length direction of the reflection gas chamber is denoted as the z-axis, and the angle between the terahertz parallel light emitted by the emission probe and the z-axis is θ z , and the total optical path of the terahertz parallel light in the reflection gas chamber is n is the relative refractive index of the terahertz parallel light in the reflection gas chamber, and L is the distance between the geometric centers of the incident window reserved opening and the exit window reserved opening in the z-axis direction Let the side length of the regular \(K\)-sided polygon base of the regular \(K\)-prismatic reflection chamber be denoted as \(a\). When the terahertz parallel light is reflected along a spiral path in the reflection chamber, the height difference in the \(z\)-axis direction for each spiral period is The included angle between the transmitting probe and the z-axis is θ z , and the included angle between the receiving probe and the z-axis is θ' z = 180° - θ z .

3. The terahertz spectroscopy measurement cavity for pipeline gas sensing according to claim 2, wherein: Among them, The height difference d is greater than the maximum spot diameter of the terahertz parallel light in the z - axis direction.

4. The terahertz spectroscopy measurement cavity for pipeline gas sensing according to claim 2, wherein: Among them, Adjusting components are provided on both the transmitting probe and the receiving probe, and the adjusting components are used to adjust the angles between the transmitting probe and the receiving probe and the z - axis.

5. The terahertz spectroscopy measurement cavity for pipeline gas sensing according to claim 1, wherein: Among them, The inner wall material of the reflection gas chamber includes gold, silver or aluminum, and the material of the incident window and / or the exit window includes high - resistivity silicon or HDPE.

6. The terahertz spectroscopy measurement cavity for pipeline gas sensing according to claim 1, wherein: Among them, An anti - reflection film is plated on the inner wall of the reflection gas chamber.

7. The terahertz spectroscopy measurement cavity for pipeline gas sensing according to claim 1, wherein: Among them, The incident window reserved opening and the exit window reserved opening are respectively provided at both ends in the length direction of the side wall of the reflection gas chamber, and the incident window reserved opening and the exit window reserved opening are located on the same side wall or different side walls of the hollow cylindrical structure of the regular K - prism of the reflection gas chamber.

8. Application of a terahertz spectroscopy measurement cavity suitable for pipeline gas sensing in the detection of gas components in a pipeline, characterized in that, The terahertz spectroscopy measurement cavity for pipeline gas sensing according to any one of claims 1 to 7 is used to detect the composition of the mixed gas in the pipeline, wherein both ends in the length direction of the reflection gas chamber are respectively connected to the pipeline, so as to allow the mixed gas in the pipeline to enter the reflection gas chamber.

9. Application of a terahertz spectroscopy measurement cavity suitable for pipeline gas sensing in detecting gas leakage on the outer wall of a pipeline, characterized in that, The terahertz spectroscopy measurement cavity applicable to pipeline gas sensing described in any one of claims 1 to 7 is used to detect gas leakage on the outer wall of the pipeline. Wherein, the pipeline penetrates through the inner cavity thereof along the length direction of the reflection chamber. Both ends of the reflection chamber in the length direction are closed.

10. The application of the terahertz spectroscopy measurement cavity applicable to pipeline gas sensing in the detection of gas leakage on the outer wall of the pipeline according to claim 9, characterized in that: Among them, The axis of the pipeline coincides with that of the reflection chamber. The pipeline is fixed therein by support columns at both ends of the reflection chamber in the length direction. The outer wall radius range of the pipeline a is the side length of the regular K-sided polygon at the bottom of the regular K-prism-shaped reflection gas chamber.

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