Thermally compensated multi-channel spectroscopy gas cell

Abstract

The present disclosure provides a thermally compensated multi-pass spectroscopy gas cell including a cylindrical cell housing composed of a first material having a first coefficient of thermal expansion (CTE) and defining an interior. The cell includes a first mirror assembly and a second mirror assembly, each mirror assembly including a mirror holder and a mirror secured within the holder. The mirror assemblies are positioned at opposite ends of the cylindrical cell housing to create a multi-pass optical configuration. The mirror holders are composed of a second material having a second CTE greater than the first CTE to provide thermal compensation for stable mirror separation over an entire operating temperature range.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 744,284, filed January 12, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments disclosed herein relate generally to gas spectroscopy, and more specifically, to thermally compensated multichannel spectroscopy gas cells and systems. Background Technology

[0004] The applicant has identified numerous technical challenges associated with thermal stability in gas cells, including multichannel spectroscopic gas cells. Through effort, ingenuity, and innovation, many of these identified problems have been addressed by the developed solutions, including those described in the embodiments of this disclosure, and numerous examples of these solutions are detailed herein. Summary of the Invention

[0005] The various embodiments of this disclosure relate generally to gas spectroscopy, and more specifically, to thermally compensated multichannel spectral gas cells.

[0006] According to one aspect of this disclosure, a thermally compensated multichannel spectroscopic gas cell is provided. The thermally compensated multichannel spectroscopic gas cell comprises gas cells having a first coefficient of thermal expansion (CTE). cell_cyl The first material constitutes and defines the internal cylindrical cell housing. The thermally compensated multichannel spectroscopic gas cell includes a first mirror assembly comprising a first mirror holder and a first mirror fixed within the first mirror holder. The thermally compensated multichannel spectroscopic gas cell includes a second mirror assembly comprising a second mirror holder and a second mirror fixed within the second mirror holder. The first and second mirror assemblies are positioned at opposite ends of the cylindrical cell housing to create a multichannel optical configuration. The first and second mirror holders are composed of a second CTE (CTE value) greater than the first CTE. mirror_hldr The second material composition provides thermal compensation for stable mirror separation throughout the entire operating temperature range.

[0007] According to other aspects of this disclosure, a thermally compensated multichannel spectroscopic gas cell may include one or more of the following features: A cylindrical cell housing may define a first length L. cell_cyl Furthermore, each of the first mirror holder and the second mirror can define a second length L. mirror_hldr Wherein, the first length and the second length can be based on the thermal compensation relationship L cell_cyl ×CTE cell_cyl =2×Lmirror_hldr ×CTE mirror_hldr To choose. The first material can include carbon steel. The first CTE can be 11.2 × 10 -6 / Celsius to 12.0×10 -6 The temperature range is [temperature range missing]. The second material may include polyvinylidene fluoride (PVDF). The second CTE may be approximately 102 × 10 [degrees missing]. -6 / Celsius to 158×10 -6 Within a temperature range of / degrees Celsius. The thermally compensated multichannel spectroscopic gas cell may further include an inner tube positioned inside the cylindrical cell housing, wherein the inner tube may be made of a second material. The first and second mirrors may be made of fused silica. The thermally compensated multichannel spectroscopic gas cell may further include a first window assembly and a second window assembly positioned at opposite ends of the cylindrical cell housing, wherein the first window assembly may include a first window holder and a light inlet window fixed within the first window holder, and wherein the second window assembly may include a second window holder and a light outlet window fixed within the second window holder. The first and second window holders may be made of a second material. The light inlet window and the light outlet window may be made of fused silica and may have a wedge geometry. The first mirror may define a light inlet aperture, and the second mirror may define a light outlet aperture, wherein the light inlet aperture and the light inlet window may be aligned, and wherein the light outlet aperture and the light outlet window may be aligned. The thermally compensated multichannel spectroscopic gas cell may further include a chamber defined at least partially by the cylindrical cell housing, the first mirror, and the second mirror. The thermally compensated multichannel spectroscopic gas cell may also include a gas inlet port for introducing a gas sample into the chamber and a gas outlet port for removing a gas sample from the chamber. The thermally compensated multichannel spectroscopic gas cell may also include a pressure-temperature sensor for monitoring operating conditions. The operating temperature range may be -20°C to +60°C.

[0008] According to another aspect of this disclosure, a gas detection system is provided. The gas detection system includes a thermally compensated multichannel spectroscopic gas cell comprising a cylindrical cell housing defined by and having an interior of a first material having a first CTE. The thermally compensated multichannel spectroscopic gas cell includes a first mirror assembly comprising a first mirror holder and a first mirror fixed within the first mirror holder. The thermally compensated multichannel spectroscopic gas cell includes a second mirror assembly comprising a second mirror holder and a second mirror fixed within the second mirror holder. The first mirror assembly and the second mirror assembly are positioned at opposite ends of the cylindrical cell housing to create a multichannel optical configuration. The first mirror holder and the second mirror holder are constructed of a second material having a second CTE greater than the first CTE to provide thermal compensation for stable mirror separation over the entire operating temperature range. The gas detection system includes a light emitter configured to emit a light beam toward the thermally compensated multichannel spectroscopic gas cell. The gas detection system includes a light receiver configured to receive light exiting the compensated multichannel spectroscopic gas cell.

[0009] According to other aspects of this disclosure, the gas detection system may include one or more of the following features: The first material may include carbon steel, and the second material may include PVDF. The gas detection system may also include an inner tube positioned within the interior of a cylindrical tank housing, wherein the inner tube may be made of the second material. The first and second reflectors may be made of fused silica.

[0010] The above description of the invention is provided merely to outline some exemplary embodiments in order to provide a basic understanding of some aspects of this disclosure. Therefore, it should be understood that the above embodiments are merely illustrative and should not be construed as limiting the scope or substance of this disclosure in any way. It should be understood that, in addition to those outlined herein, the scope of this disclosure covers many possible embodiments, some of which will be further described below. Attached Figure Description

[0011] The description of the exemplary embodiments can be read in conjunction with the accompanying drawings. It should be understood that, for simplicity and clarity of illustration, the elements illustrated in the figures are not necessarily drawn to scale unless otherwise described. For example, unless otherwise described, the dimensions of some elements may be exaggerated relative to others. Embodiments incorporating the teachings of this disclosure are shown and described with reference to the accompanying drawings, in which:

[0012] Figure 1 An example perspective view of a thermally compensated multichannel spectroscopic gas cell according to at least some example embodiments of the present disclosure is shown.

[0013] Figure 2 A portion of an example thermally compensated multichannel spectroscopic gas cell is illustrated according to at least some example embodiments of this disclosure.

[0014] Figure 3 An exploded view of an example thermally compensated multichannel spectroscopic gas cell according to at least some example embodiments of the present disclosure is shown.

[0015] Figure 4A A side view of an example thermally compensated multichannel spectroscopic gas cell according to at least some example embodiments of the present disclosure is shown.

[0016] Figures 4B to 4C Each example mirror of an example thermally compensated multichannel spectroscopic gas cell according to at least some example embodiments of the present disclosure is illustrated.

[0017] Figure 5 A portion of an example thermally compensated multichannel spectroscopic gas cell according to at least some example embodiments of the present disclosure is illustrated, which illustrates mirror separation thermal compensation.

[0018] Figure 6A Example material CTE versus temperature graphs are illustrated according to at least some example embodiments of this disclosure.

[0019] Figure 6B Example compensation CTE versus temperature graphs are illustrated according to at least some example embodiments of this disclosure.

[0020] Figure 6C Example mirror separation thermal offset plots are illustrated according to at least some example embodiments of the present disclosure.

[0021] Figure 7A Example beam propagation and alignment in an example thermally compensated multichannel spectroscopic gas cell are illustrated according to at least some embodiments of the present disclosure.

[0022] Figure 7B Example beam coverage areas according to at least some embodiments of this disclosure are illustrated.

[0023] Figure 8 Thermal analysis of mirror separation according to at least some embodiments of the present disclosure is illustrated.

[0024] Figure 9 This is a block diagram of an example system for gas spectroscopy according to an example embodiment of the present disclosure. Detailed Implementation

[0025] Some embodiments of this disclosure will be described more fully below with reference to the accompanying drawings, which illustrate some, but not all, embodiments of this disclosure. In fact, this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will meet applicable legal requirements. Similar reference numerals always refer to similar elements.

[0026] Unless otherwise indicated, the term “or” as used herein has both alternative and combined meanings. The terms “illustrative” and “example” are used for examples without an indication of quality level. Terms such as “calculate,” “determine,” “generate,” and / or similar words are used interchangeably herein to refer to the creation, modification, or identification of data. Furthermore, the terms “based on,” “partially based on,” “at least based on,” “on…”, and / or similar words are used interchangeably in an open-ended manner herein, such that they do not indicate that the data is based solely on or only on one or more of the referenced elements, unless so indicated.

[0027] As used herein, terms such as “front,” “rear,” “top,” “bottom,” “left,” “right,” etc., in the examples provided below, are used for illustrative purposes to describe the relative positions of certain parts or portions of parts. Furthermore, as will be apparent to those skilled in the art based on this disclosure, the terms “substantially” and “approximately” indicate that the referenced element or associated description is accurate within applicable engineering tolerances.

[0028] As used herein, the term “comprising” means including but not limited to, and should be interpreted in the manner in which it is typically used in the patent context. The use of broader terms such as “comprising,” “including,” and “having” should be understood to provide support for narrower terms such as “consisting of,” “substantially composed of,” and “substantially constituted by.”

[0029] The phrases “in one embodiment,” “according to one embodiment,” “in some embodiments,” etc., generally mean that the specific feature, structure, or characteristic following the phrase may be included in at least one embodiment of this disclosure, and may be included in more than one embodiment of this disclosure (importantly, such phrases do not necessarily refer to the same embodiment).

[0030] The phrases “in one example,” “according to one example,” “in some examples,” etc. generally mean that the particular feature, structure, or characteristic following the phrase may be included in at least one example of this disclosure, and may be included in more than one example of this disclosure (importantly, such phrases do not necessarily refer to the same example).

[0031] If the specification states that a component or feature "may," "can," "should," "will," "preferably," "possibly," "usually," "optionally," "for example," "as an example," "in some examples," "often," or "may" (or other such language) be included or have that characteristic, then the specific component or feature is not required to be included or have that characteristic. Such a component or feature may be optionally included in some examples or excluded.

[0032] The terms “example” or “exemplary” as used herein mean “used as an example, instance, or illustration.” Any specific implementation described herein as an “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other specific implementations.

[0033] In this disclosure, the terms “electrically connected,” “electrically coupled,” “electrically coupled,” “communicating with,” “electronically communicating with,” or “connection” refer to two or more elements or components connected by wired and / or wireless means such that signals, voltages / currents, data, and / or information can be transmitted to and / or received from these elements or components.

[0034] The term "component" can refer to an article of writing, device, or apparatus that may include one or more surfaces, portions, layers, and / or elements. For example, an example component may include one or more substrates that may provide one or more underlying layers for the component, and may include one or more elements that may form a portion on top of the substrate and / or one or more elements that may be disposed on top of the substrate. The term "element" can refer to an article of writing, device, or apparatus that can provide one or more functions.

[0035] Overview

[0036] Multichannel spectroscopic gas cells utilize multiple reflections between mirrors to achieve extended optical path lengths for sensing absorption spectroscopic gases. A high number of reflections may require high cell thermal stability to maintain reflection accuracy under varying temperature conditions. Traditional methods for achieving thermal stability in multichannel spectroscopic gas cells face significant limitations restricting their practical application.

[0037] Conventional aluminum-based multichannel gas cells can operate within a narrow temperature range of just a few degrees Celsius to maintain the reflective accuracy required by multichannel optical systems. This limited temperature range may restrict aluminum-based cells to laboratory applications only, thus preventing their use in outdoor or real-world environments where temperature variations are common.

[0038] Alternative approaches using extremely low thermal expansion materials, such as nickel-iron alloys (Invar alloys), lithium aluminum silicon oxide glass-ceramics (microcrystalline glass), or similar ultra-low expansion materials, can achieve thermal stability but suffer from high material costs and machining expenses. The extreme costs of these materials and their associated manufacturing methods may significantly limit the commercial viability of multichannel spectroscopic gas sensing products and applications.

[0039] Various embodiments of this disclosure provide a thermally compensated multichannel spectroscopic gas cell that overcomes, at least in part, the aforementioned technical challenges and difficulties associated with spectroscopic gas cells by utilizing a combination of materials (e.g., a combination of their CTEs) to provide improved pool thermal stability and thus enhanced reflection accuracy in the gas cell.

[0040] Furthermore, various implementations are associated with low material and manufacturing costs (e.g., leveraging low material and manufacturing costs), which expands the applications that can utilize multichannel spectroscopic gas sensing technology. Some gas cells, such as, for example, aluminum-based multichannel gas cells (e.g., low-cost aluminum-structured multichannel gas cells), can only be used or otherwise operated within a narrow operating temperature range to achieve and maintain reflectance accuracy (e.g., multi-reflectance accuracy). This narrow operating temperature range may limit such gas cells to laboratory use. The exemplary embodiments of this disclosure provide a thermally compensated multichannel spectroscopic gas cell with a wider operating temperature range (e.g., extending the operating range of the multichannel spectroscopic gas cell), which allows for real-world utilization of the multichannel spectroscopic gas cell (e.g., outdoor real-world use beyond the laboratory).

[0041] This system can employ a combination of materials with different coefficients of thermal expansion (CTE) in the gas pool cylinder and mirror retainer components to generate a compensated thermal response. In some examples, thermal compensation of the gas pool can be achieved using a carbon steel chamber cylinder combined with a polyvinylidene fluoride (PVDF) mirror retainer. The CTE difference between these materials (where PVDF has approximately ten times the thermal expansion of carbon steel) can be thermally compensated through geometric design, in which a short, recessed, high-CTE PVDF mirror retainer operates against a long, low-CTE carbon steel pool cylinder.

[0042] The nonlinear temperature-dependent CTE characteristics of PVDF can provide additional advantages for extending the operating temperature range. Compensation between the carbon steel pool cylinder and the PVDF mirror holder can exhibit non-monotonic residual thermal effects, resulting in a non-zero combined effective CTE at different temperatures. This bidirectional combined effective CTE behavior can further extend the operating temperature range to cover real-world applications.

[0043] In this regard, various embodiments of the present disclosure provide a thermally compensated multichannel spectroscopic gas cell that overcomes the aforementioned limitations of existing systems by utilizing a material combination approach that achieves thermal stability over a wide operating temperature range while maintaining low material and manufacturing costs.

[0044] Example systems and apparatus of this disclosure

[0045] As noted above, various implementation schemes address the technical issues associated with thermal stability in gas cells. Thermal stability can refer to the ability of a gas cell to maintain consistent optical and mechanical properties under varying temperature conditions, which enables accurate and reliable spectroscopic measurements.

[0046] Spectroscopic analysis of a sample (e.g., a fluid sample) can be used to determine one or more components within the fluid sample by illuminating it with light of a specific wavelength and monitoring the absorption of the light along the optical path length. Each component (atom or molecule) of the sample may have a unique absorption characteristic that can be used to identify the presence and / or concentration of the component within the sample, or, in some examples, the absence of a target gas (e.g., a leaked toxic gas) in the sample. For example, the concentration of methane, carbon dioxide, and / or other gases can be measured by illuminating the sample with light of different wavelengths and analyzing the absorption characteristics at various wavelengths. The accuracy of such measurements can depend on maintaining a precise optical path length and mirror position, which can be significantly affected by the thermal expansion and contraction of the gas pool components.

[0047] Multichannel spectroscopic gas cells can utilize multiple reflections between their mirrors to achieve extended optical path lengths for sensing absorption spectroscopic gases. In this multichannel configuration, light can bounce multiple times between opposing mirrors before leaving the cell, effectively increasing the interaction path length with the gas sample without requiring a physically longer cell. To achieve and maintain reflection accuracy, cell thermal stability (e.g., high thermal stability relative to the gas cell) may be required. Even small changes in mirror separation due to thermal expansion can cause the beam to deviate from its intended path, potentially leading to beam clipping, reduced signal strength, or complete loss of optical alignment.

[0048] Various embodiments of this disclosure provide a thermally compensated spectroscopic gas cell that achieves and maintains desired thermal stability by utilizing a combination of the material's coefficients of thermal expansion (CTE), thereby providing thermal compensation between the components of the gas cell. In various embodiments, the coefficient of thermal expansion (CTE) is a material property that quantifies the degree to which the material expands or contracts per unit length per degree of temperature change, and can be expressed in units of 1 / ℃ or ppm / ℃.

[0049] Thermally compensated multichannel spectroscopic gas cell

[0050] See now Figures 1 to 4A This provides a thermally compensated multichannel spectroscopic gas cell 100 according to at least some example embodiments of this disclosure. Specifically, Figure 1 A perspective view of an example thermally compensated multichannel spectroscopic gas cell 100 according to at least some example embodiments of the present disclosure is shown. Figure 2 A portion of an example thermally compensated multichannel spectroscopic gas cell 100 is illustrated. Figure 3 An exploded view of an example thermally compensated multichannel spectroscopic gas cell 100 is shown. Figure 4A A central cross-sectional side view of an example thermally compensated multichannel spectroscopic gas cell 100 is illustrated. The thermally compensated multichannel spectroscopic gas cell 100 may include various components that work together to provide stable optical performance over a wide temperature range. The thermally compensated multichannel spectroscopic gas cell 100 may include a gas cell cylinder, a mirror with an associated mirror holder, an optical window element with a window holder, an airflow component, and a sensing element.

[0051] In various embodiments, the example thermally compensated multichannel spectroscopic gas cell 100 includes a cell housing 102 defining the interior. In various embodiments, the cell housing 102 may have a cylindrical shape. For example, the cell housing 102 may include a cylindrical body. In this regard, in some embodiments, the multichannel spectroscopic gas cell 100 may include a gas cell cylinder (e.g., a cylindrical cell housing 102). Figure 3 As shown, in various embodiments, the thermally compensated multichannel spectroscopic gas cell 100 may include an inner tube 103 positioned within the cell housing 102. The inner tube 103 may serve as a liner providing chemical resistance and / or helping to define the gas flow path within the cell housing 102.

[0052] In various embodiments, the thermally compensated multichannel spectroscopic gas cell 100 includes a first mirror 110 (also referred to herein as an inlet mirror) and a second mirror 120 (also referred herein as an outlet mirror), which are attached or otherwise coupled to opposite ends of the cell housing 102, thereby defining, as Figure 3The chamber 104 shown is an example of a cavity or similar term. Chamber 104 can be configured to receive the gas to be analyzed. The thermally compensated multichannel spectroscopic gas cell 100 may include a first mirror holder 111 for receiving a first mirror 110 and a second mirror holder 121 for receiving a second mirror 120. The mirror holders (e.g., first mirror holder 111 and second mirror holder 121) can serve as mounting structures for positioning and securing the mirrors (e.g., mirrors 110 and 120). For example, the thermally compensated multichannel spectroscopic gas cell 100 may include a pair of mirrors (e.g., first mirror 110 and second mirror 120) positioned within the mirror holders (e.g., first mirror holder 111 and second mirror holder 121) to produce a multichannel optical configuration. The first mirror 110 may be positioned within the first mirror holder 111, and the second mirror 120 may be positioned within the second mirror holder 121. In this regard, in various embodiments, the thermally compensated multichannel spectroscopic gas cell 100 includes a first mirror assembly and a second mirror assembly positioned at opposite ends of the cell housing 102 to produce a multichannel optical configuration. The first mirror assembly includes a first mirror holder 111 and a first mirror 110 fixed within the first mirror holder 111, and the second mirror assembly includes a second mirror holder 121 and a second mirror 120 fixed within the second mirror holder. The first and second mirror assemblies are positioned at opposite ends of the cylindrical cell housing to produce a multichannel optical configuration.

[0053] In various embodiments, the thermally compensated multichannel spectroscopic gas cell 100 also includes a pressure-temperature sensor 105 (e.g., a combined pressure and temperature sensor), an inlet 106 through which the gas to be analyzed is added to the chamber 104, and an outlet 108 through which the gas to be analyzed is removed from the chamber 104. In this regard, the inlet 106 and outlet 108 can be configured to allow gas to flow through the gas cell for detection. In various embodiments, the pressure-temperature sensor 105 is configured to measure, detect, collect, etc., gas flow pressure and temperature readings for gas sensing data analysis.

[0054] The housing 102 may form the main structural framework of the thermally compensated multichannel spectroscopic gas cell 100 and may define a length (e.g., overall length dimension) corresponding to the separation distance between the first reflector 110 and the second reflector 120. The housing 102 may be machined to precise dimensional tolerances to ensure proper optical alignment and may include mounting features for securing other components of the thermally compensated multichannel spectroscopic gas cell 100.

[0055] In various embodiments, the pool shell 102 is constructed of carbon steel or other materials with low thermal expansion. The carbon steel configuration of the pool shell 102 can provide several advantages over other configurations, including aluminum. Compared to aluminum or some other low-expansion materials, carbon steel can provide a low coefficient of thermal expansion while maintaining cost-effectiveness. For example, the pool shell 102 can be constructed of materials with a thermal expansion coefficient of approximately 11.2 × 10⁻⁶. -6 / Celsius to 12.0×10 -6 Carbon steel with a CTE in the range of / degrees Celsius exhibits a relatively low CTE compared to many other structural materials, including aluminum, and is cost-effective compared to some other low-expansion materials, such as Invar alloys or microcrystalline glass.

[0056] The relatively low CTE exhibited by carbon steel allows the pool housing 102 to function as a stable structure against which higher expansion components can be positioned for thermal compensation. The carbon steel pool housing 102 can define an interior (e.g., an internal cavity) with precise dimensional tolerances, housing other components of the thermally compensated multichannel spectroscopic gas pool 100 while maintaining structural stability under temperature variations. The material properties of carbon steel provide sufficient strength and stiffness to support the mirror and window assemblies while resisting deformation under thermal stress. Furthermore, carbon steel offers favorable machinability, enabling the pool cylinder to be manufactured cost-effectively with the required dimensional accuracy. In this respect, the carbon steel construction of the pool housing 102 provides structural stability and durability while maintaining manufacturability through machining processes.

[0057] The inner tube 103 can be positioned within the carbon steel pool cylinder to form or otherwise create a stable gas pool structure. In various embodiments, the inner tube is made of polyvinylidene fluoride (PVDF) or other materials with high thermal expansion. For example, PVDF can exhibit a thermal expansion of approximately 10² × 10⁻⁶. -6 / Celsius to 158×10 -6 The CTE is within the range of / degrees Celsius, which is higher (e.g., significantly higher) than the CTE of the carbon steel that may constitute the cell housing 102. The PVDF inner tube 103 provides a gas-containing surface and chemical resistance to a wide range of gases. In other words, the PVDF inner tube 103 provides a chemically inert surface that contacts the gas sample being analyzed. PVDF provides excellent chemical resistance to a wide range of gases, which prevents contamination or degradation of the thermally compensated multichannel spectroscopic gas cell 100 over extended operating cycles.

[0058] The PVDF inner tube 103 can be sized to fit (e.g., slide fit) within the inner diameter of the carbon steel tank housing 102, while providing a defined gas volume for spectroscopic analysis. For example, the PVDF inner tube 103 can be sized to fit (e.g., slide fit) within the internal cavity of the carbon steel tank housing 102, while allowing for different thermal expansion between the two materials. The inner tube 103 can be secured within the cylinder via a slide fit. The inner tube 103 provides a smooth inner surface, which minimizes airflow turbulence and facilitates cleaning or maintenance procedures.

[0059] The combination of a carbon steel outer shell 102 and a PVDF inner tube 103 creates a dual-material structure that balances thermal, chemical, and mechanical performance requirements. The carbon steel construction of the outer shell 102 provides structural integrity and dimensional stability, and its low coefficient of thermal expansion contributes to thermal compensation, while the PVDF construction of the inner tubes 1-3 provides chemical compatibility. In this respect, the combination of the carbon steel outer shell 102 and the PVDF inner tube 103 creates a double-wall structure that combines the structural benefits and low thermal expansion characteristics of carbon steel with chemical compatibility. Furthermore, this material combination (e.g., the carbon steel material of the outer shell 102 and the PVDF material of the inner tube 103) enables cost-effective manufacturing while achieving performance characteristics suitable for demanding gas sensing applications.

[0060] The choice of carbon steel for the outer shell 102 and PVDF for the inner tube 103 offers a cost advantage compared to alternative approaches using external low-expansion materials. The cost-effectiveness of these materials (e.g., carbon steel and PVDF) enables large-scale production of thermally compensated gas pools for a wide range of commercial applications, where cost constraints could otherwise limit the adoption of multichannel spectroscopy techniques. Both carbon steel and PVDF are readily available commercial materials that can be processed using standard manufacturing techniques.

[0061] Mirrors 110 and 112 can provide optical performance characteristics for effective multichannel spectroscopy. For example, mirrors 110 and 120 can be fused silica mirrors, where fused silica provides high optical quality, low absorption, and / or excellent surface properties, enabling efficient light reflection during multiple passes through the thermally compensated multichannel spectroscopy gas cell 100. The material properties of fused silica can also contribute to long-term stability and resistance to optical degradation under various operating conditions.

[0062] Mirror holders 111, 121 can be configured to securely hold mirrors 110, 120 while facilitating or otherwise providing thermal compensation as described herein. Mirror holders 111, 121 may include mounting features such as recesses, grooves, or mechanical retaining elements that position and secure the mirrors with precise optical alignment.

[0063] In various embodiments, the first mirror holder 111 and the second mirror holder 121 are made of PVDF material, which provides a high coefficient of thermal expansion, thus achieving thermal compensation within the gas pool 100. As described above, the PVDF material can exhibit a coefficient of thermal expansion of approximately 10² × 10⁻⁶. -6 / Celsius to 158×10 -6 The coefficient of thermal expansion in the range of / degrees Celsius can be about ten times that of the carbon steel material of the pool shell 102. This significant difference in thermal expansion characteristics enables the mirror holders 111, 121 to provide compensating dimensional changes to offset the thermal expansion of the pool shell 102.

[0064] The geometry of the PVDF mirror holders 111 and 121 can be specifically designed to utilize the high thermal expansion properties of PVDF for compensation purposes. For example, the PVDF mirror holders 111 and 121 can be configured with specific geometries to achieve thermal compensation for the carbon steel tank housing 102. In some examples, the mirror holders 111 and 121 can be configured as short, recessed components extending from each end of the tank housing 102 into the tank housing 102, positioning a pair of mirrors 110 and 120 at precise locations within the tank housing 102. In this regard, the high coefficient of thermal expansion of PVDF allows for the use of relatively short mirror holder lengths to achieve the desired thermal compensation effect. This geometric advantage simplifies the mechanical design of the mirror assembly while maintaining structural integrity to support precise mirror alignment. PVDF material also offers additional benefits, including low material cost, favorable machinability, and excellent chemical resistance, making it suitable for gas tank applications.

[0065] The geometry allows for the positioning of the mirror holders 111 and 121 such that their thermal expansion acts in opposition to the thermal expansion of the longer carbon steel tank housing 102, thereby maintaining a stable mirror separation distance during temperature changes. For example, as the temperature rises, the high thermal expansion of the PVDF mirror holders 111 and 121 may cause them to expand and move the mirrors 110 and 120 in a direction that counteracts the thermal expansion of the carbon steel tank housing 102.

[0066] Thermal compensation can be operated through differential expansion between the carbon steel tank housing 102 and the PVDF mirror holders 111, 121. For example, as the temperature rises, the carbon steel tank housing 102 can expand, increasing the total internal length of the tank housing 102 or the gas tank 100. Simultaneously, the PVDF mirror holders 111, 121 can expand at a higher rate due to their significantly higher coefficient of thermal expansion. The expansion of the PVDF mirror holders 111, 121 can cause the mirrors to move inward relative to the ends of the tank housing 102, thereby reducing the effective mirror separation distance. In this respect, thermal compensation can operate based on the principle that as the temperature rises, the tank housing 102 expands longitudinally, which generally increases the mirror separation distance. However, the mirror holders 111, 121, with their higher CTE, expand more rapidly, effectively pushing the mirrors 110, 120 inward to counteract the expansion of the tank housing 102. In this regard, in various embodiments, the low-heat carbon steel material of the pool housing 102 and the high thermal expansion PVDF of the mirror holders 111, 121 are selected to compensate for thermal variations in the pool length, thereby eliminating thermal variations between the pool housing 102 and the mirror holders 111, 121 and minimizing thermal positional offsets of the mirrors 110, 120.

[0067] The positional and dimensional design of the PVDF mirror retainers 111 and 121 can be configured to achieve substantial elimination of thermal effects across the entire operating temperature range. The relationship between the pool shell length, the mirror retainer length, and their respective coefficients of thermal expansion determines the degree of thermal compensation achieved. In some examples, the thermal compensation can be designed such that the thermal expansion of the pool shell length multiplied by the pool cylinder CTE is approximately equal to the thermal expansion of the mirror retainer length multiplied by twice the mirror retainer CTE.

[0068] In some examples, the mirror separation within the thermally compensated multichannel spectroscopic gas cell 100 can have a nominal length of 385.2 mm between the opposing mirrors 110 and 120. This separation distance can be determined by subtracting the combined length of the two mirror holders 111 and 121 extending from each end into the cylinder from the length of the cell housing 102. A nominal separation of 385.2 mm provides sufficient optical path length for multichannel spectroscopic measurements while maintaining manageable overall component dimensions.

[0069] In some examples, the thermal compensation design can accommodate acceptable separation variations of approximately ±0.1 mm while maintaining adequate optical performance. Within this tolerance range, the thermally compensated multichannel spectroscopic gas cell 100 can maintain reflection accuracy and optical path stability over the expected operating temperature range. The ±0.1 mm variation tolerance can be achieved by carefully selecting the length ratio between the carbon steel cell housing 102 and the PVDF mirror holders 111, 121 based on their respective coefficients of thermal expansion.

[0070] The PVDF material of mirror retainers 111 and 121 provides sufficient structural stability to maintain mirror positioning while accommodating thermal expansion and contraction cycles without degrading optical performance. The combination of a fused silica mirror and PVDF mirror retainers 111 and 121 produces a mirror assembly that maintains stable optical performance while utilizing cost-effective materials. Thermal compensation provided by the PVDF mirror retainers allows the gas cell 102 to operate over an extended temperature range without the optical losses or alignment degradation that might occur in uncompensated or other configurations. This approach eliminates the need for expensive, ultra-low expansion materials while achieving comparable thermal stability. Mirror retainers 111 and 121 also provide mounting interfaces for additional optical components. For example, the properties of the PVDF material allow window retainers or other optical mounting features to be integrated into mirror retainers 111 and 121.

[0071] The thermally compensated multichannel spectroscopic gas cell 100 may include optical components that provide optical access for light introduction and collection while maintaining gas containment within the gas cell structure. In various embodiments, the thermally compensated multichannel spectroscopic gas cell 100 includes an inlet optical window element 113 (e.g., also referred to herein as a light inlet window 113) and an outlet optical window element 123 (e.g., also referred herein as a light outlet window 123). In various embodiments, a first reflector 110 may define and / or include a light inlet via 112, and a second reflector 120 may define and / or include a light outlet via 122. The light inlet via may be configured to allow light to enter and exit the chamber 104 (e.g., a multichannel cavity) while maintaining reflective surfaces for multichannel optical configuration.

[0072] In various embodiments, optical window elements are positioned within a thermally compensated multichannel spectroscopic gas cell 100 such that an inlet optical window element 113 is aligned with a light inlet aperture 112, and an outlet optical window element 123 is aligned with a light outlet aperture 122. In various embodiments, the inlet optical window element 113 is secured to the cell housing 102 via a first window holder 116, and the outlet optical window element 123 is secured to the cell housing 102 via a second window holder 126. In various embodiments, a light beam enters the chamber 104 via the light inlet aperture 112 and / or the inlet optical window element 113, and exits the chamber 104 via the light outlet aperture 122 and / or the outlet optical window element 123. In some examples, the light inlet aperture 112 and the light outlet aperture 122 may be conical or other suitable shapes to, for example, minimize unwanted reflections and / or optimize beam coupling.

[0073] As described above, mirrors 110 and 120 may be made of fused silica or other similar near-infrared optical materials with a highly reflective coating that provides high reflectivity and low absorption in the spectral wavelength range of interest. In various embodiments, optical window elements 113 and 123 are made of fused silica or other similar near-infrared optical materials with anti-reflective properties and may be configured with a wedge geometry to provide, for example, optical coupling to the thermally compensated multichannel spectroscopic gas cell 100. For example, the thermally compensated multichannel spectroscopic gas cell 100 may include a pair of fused silica wedge-shaped optical window elements 113 and 123 (e.g., two fused silica wedge-shaped optical window elements 113 and 123), wherein the wedge angle may be configured to, for example, reduce back reflections that may interfere with measurements.

[0074] The wedge geometry of optical window elements 113 and 123 can be used to minimize unwanted reflections that may interfere with the multichannel optical configuration. When light encounters an optical window with parallel sides, a portion of the light can be reflected from both the incident and exit surfaces of the window. These reflections can produce ghosting images or stray optical signals, which can degrade the performance of spectral measurements. The wedge configuration solves this problem by making one surface of the window angled relative to the other. The wedge window design allows reflections from the incident and exit surfaces to propagate in different directions, rather than back along the incident optical path. This angular separation of the reflected beams prevents reflected light from interfering with the master optical signal traveling through the thermally compensated multichannel spectral gas cell 100. The wedge angle can be selected to provide sufficient separation of unwanted reflections while maintaining acceptable light transmission through the window.

[0075] In various embodiments, the first window retainer 116 and the second window retainer 126 are made of PVDF. The PVDF window retainers 116 and 126 can fix and position the optical window elements 113 and 123 within the thermally compensated multichannel spectroscopic gas cell 100, while also contributing to overall thermal compensation. Similar to the PVDF mirror retainers 111 and 121, the PVDF window retainers 116 and 126 can exhibit the high coefficient of thermal expansion characteristics of PVDF material, which can be approximately 10² × 10⁻⁶. -6 / Celsius to 158×10 -6 Within a range of / degrees Celsius. This high coefficient of thermal expansion allows the window retainer to expand and contract in coordination with the PVDF mirror retainers 111 and 121 as the temperature changes.

[0076] The integration of PVDF window retainers 116, 126 with PVDF mirror retainers 111, 121 creates a coordinated thermal compensation system in which the optical elements move together in response to temperature changes. This coordinated movement maintains consistent optical alignment between mirrors 110, 120 and optical window elements 113, 123 throughout the operating temperature range. The retention and dimensions of window retainers 116, 126 are designed to ensure that wedge-shaped optical window elements 113, 123 remain correctly aligned with the optical path when the mirror position is adjusted due to the thermal compensation effect.

[0077] PVDF window retainers 116 and 126 offer additional benefits beyond thermal compensation, including chemical resistance that protects the window mounting interface from corrosive gases or vapors present in the thermally compensated multichannel spectroscopic gas pool 100. The material properties of PVDF enable window retainers 116 and 126 to maintain structural integrity and sealing performance across the entire operating temperature range, while accommodating varying thermal expansion between different pool components.

[0078] Window retainers 116, 126 can be configured to adapt to the wedge geometry of fused silica optical window elements 113, 123 while providing proper sealing and mechanical retention. Window retainers 116, 126 may include mounting features such as recesses or grooves that conform to the shape of the wedge-shaped window element and can provide secure positioning without inducing mechanical stresses that could affect optical performance. The PVDF material can provide sufficient flexibility to accommodate the difference in thermal expansion between the retainer material and the fused silica window. In various embodiments, a first window retainer 116 (e.g., an inlet window retainer) and a second window retainer 126 (e.g., an outlet window retainer) can be housed within a first mirror retainer 111 and a second mirror retainer 121, respectively. The combination of the wedge-shaped fused silica window and the PVDF window retainer achieves effective optical performance while contributing to the overall cost-effectiveness and thermal stability of the gas pool system. Sealing elements can be incorporated between the window retainers 116, 126 and the pool structure to prevent gas leakage while allowing thermal movement.

[0079] The thermally compensated multichannel spectroscopic gas cell 100 may include sealing rings, such as sealing ring 128, to provide hermetically tight integrity across various component interfaces while accommodating the thermal expansion of various materials. The sealing rings may be positioned at critical locations where gas containment could be compromised, such as between the mirror retainer and the cell housing 102, between the window retainer and the cell structure, and / or at other component interfaces where gas leakage may occur. These sealing elements may be constructed of materials that maintain sealing effectiveness across the entire operating temperature range of the gas cell. In some embodiments, the sealing rings may be made of an elastomeric material that provides sufficient compression and recovery properties to maintain sealed contact as various cell components expand and contract with temperature variations. In some examples, the sealing rings may include O-rings or other sealing elements that provide predictable sealing performance and cost-effective replacement when maintenance is required. The material selection for the sealing rings may take into account chemical compatibility with the gas sample being analyzed to prevent degradation or contamination of the sealing surfaces.

[0080] The thermally compensated multichannel spectroscopic gas cell 100 may include fasteners, such as fasteners 130, to hold the various components of the gas cell 102 together while allowing the thermal movement required for the compensation mechanism to function effectively. Fasteners may include bolts, screws, or other mechanical fastening elements that provide sufficient clamping force to maintain structural integrity and seal compression. The fastener material and configuration can be selected to withstand the mechanical stresses associated with thermal cycling within the operating temperature range. The combination of the sealing ring and fasteners creates a complete sealing system that maintains gaseous integrity throughout the thermal compensation process. As the PVDF components expand and contract relative to the carbon steel cell cylinder, the sealing components can accommodate these movements while preventing gas leakage that could affect measurement accuracy or cause safety issues.

[0081] In various embodiments, the thermally compensated multichannel spectroscopic gas cell 100 includes a gas inlet port 106 and a gas outlet port 108. For example, a pair of gas inlet and outlet ports can be integrated into the gas cell structure to enable the introduction and removal of gas samples during spectroscopic analysis operations. The gas inlet port 106 and gas outlet port 108 can provide flow paths for introducing gas samples into the chamber 104 (e.g., the cell cavity) and removing the samples after analysis. The gas inlet and outlet configuration can enable continuous flow operation, in which fresh gas samples are continuously introduced while samples being analyzed are removed, or batch operation, in which discrete gas samples are introduced, analyzed, and then removed.

[0082] Gas inlet port 106 can be positioned to introduce the gas sample into chamber 104 in a manner that promotes efficient mixing and uniform distribution throughout the optical path region. Gas inlet port 106 can be configured to minimize turbulence or flow disturbances that could affect optical measurements by inducing density changes or pressure fluctuations within the gas sample. Gas inlet port 106 may include suitable fittings or connectors capable of integration with external gas supply systems, sample handling equipment, or gas delivery manifolds. Gas outlet port 108 can be positioned to enable efficient removal of the gas sample from chamber 104 after spectral analysis. The location of gas outlet port 108 can be selected to promote complete gas exchange and prevent stagnation areas where old gas samples might remain and interfere with subsequent measurements. Gas outlet port 108 may also include suitable fittings or connectors for integration with external gas handling systems, vacuum pumps, or gas disposal systems, depending on specific application requirements. The positioning of gas inlet port 106 and gas outlet port 108 within the gas pool structure can be configured to minimize interference with the multi-channel optical path while ensuring adequate airflow characteristics. The gas inlet port 106 and the gas outlet port 108 can be positioned away from the main beam path to prevent obstruction of light reflection between the mirrors.

[0083] The thermally compensated multichannel spectroscopic gas cell 100 can realize a gas flow system designed to adapt to various gas sample types and flow rates according to specific spectroscopic application requirements. The size and configuration of the gas inlet port 106 and gas outlet port 108 can be selected to provide sufficient flow capacity for the expected gas sample while maintaining an appropriate residence time within the thermally compensated multichannel spectroscopic gas cell 100 for efficient optical absorption measurements. The gas inlet port 106 and gas outlet port 108 can be configured to handle different gas pressures, from sub-atmospheric conditions for vacuum applications to elevated pressures for high-pressure gas analysis.

[0084] The gas flow configuration implemented by the gas inlet port 106 and the gas outlet port 108 can support various operating modes, including continuous monitoring applications and batch sampling procedures. In continuous monitoring mode, gas can flow continuously through the cell, enabling real-time analysis of changing gas composition. In batch sampling mode, discrete gas samples can be introduced into the cell for analysis, with the outlet port allowing sample removal after measurement. The flow configuration can be adapted to different flow rates and pressure conditions to meet specific application requirements.

[0085] Gas inlet port 106 and gas outlet port 108 can be combined with sealing elements to maintain hermetically tight integrity at the port connection while allowing for thermal expansion of the cell structure. The sealing elements prevent gas leakage, which could affect measurement accuracy or create safety issues, especially when analyzing hazardous or toxic gas samples. The sealing method at the gas ports can be coordinated with the entire sealing system of the gas cell to ensure consistent performance across the entire operating temperature range. The gas flow path of the thermally compensated multichannel spectroscopic gas cell 100 can be designed to provide a uniform gas distribution along the optical path length while minimizing the dead volume where gas samples may stagnate. The internal flow configuration can promote laminar flow conditions that reduce optical interference while ensuring complete gas exchange during sample switching operations. The flow path design can also take into account the chemical compatibility requirements of the analyzed gas samples to prevent contamination or degradation of the gas flow surface.

[0086] In various implementations, the thermally compensated multichannel spectroscopic gas cell 100 includes a combined pressure-temperature sensor 105. The pressure-temperature sensor 105 can be configured to monitor operating conditions within the gas sample during spectroscopic analysis operations. The pressure-temperature sensor 105 can provide simultaneous measurements of both gas pressure and temperature parameters, which can be used for integrated gas sensing data analysis and system monitoring. The combined sensor approach offers advantages over individual pressure and temperature sensors by reducing the number of times the sensor penetrates into the gas cell while providing coordinated measurements from a single sensing location.

[0087] The pressure-temperature sensor 105's pressure sensing capability allows for the measurement of gas pressure within a cell cavity across an operating pressure range suitable for various spectroscopic applications. Pressure measurements can be used to characterize gas sample conditions and to compensate for pressure-dependent effects in spectroscopic analysis. Gas absorption characteristics can vary with pressure due to pressure broadening effects, impact-induced absorption changes, and density variations affecting the effectiveness of optical path lengths. The pressure-temperature sensor 105's temperature sensing capability monitors the gas temperature within the cell cavity to provide data for temperature-dependent spectral analysis corrections. Gas absorption spectra can exhibit temperature-dependent characteristics, including line intensity variations, spectral line broadening effects, and wavelength shifts that can affect measurement accuracy. Temperature measurements enable real-time compensation for these temperature-dependent effects, improving the accuracy and reliability of gas concentration determination.

[0088] The combined pressure-temperature sensor 105 provides measurement data characterizing the thermodynamic state of a gas sample within the chamber. This state information can be used in a gas sensing algorithm that considers the relationship between gas density, pressure, and temperature based on gas laws. The sensor data can be converted between different concentration units, such as parts per million by volume, mass concentration, or molar concentration, depending on specific application requirements. Sensor measurements can be integrated with spectral data analysis to provide enhanced measurement accuracy and reliability. Pressure and temperature data can be used to normalize spectral absorption measurements for variations in gas density and molecular absorption characteristics. This normalization process ensures consistent gas concentration measurements under varying environmental conditions and improves the long-term stability and repeatability of the spectral analysis system.

[0089] A pressure-temperature sensor 105 can be positioned within the gas cell structure to provide a representative measurement of gas conditions in the optical path region where spectral analysis occurs. The location of the pressure-temperature sensor 105 can be selected to minimize interference with the multi-channel optical configuration while ensuring that the measured pressure and temperature values ​​accurately reflect the conditions experienced by the gas sample during optical analysis. The sensor positioning can also take into account the gas flow pattern within the cell to ensure that the measurement represents the bulk gas conditions rather than local variations.

[0090] The pressure-temperature sensor 105 can be configured to operate over the entire temperature range of the thermally compensated gas reservoir system (e.g., from approximately -20°C to +60°C) while maintaining measurement accuracy and reliability. The pressure-temperature sensor 105 can be constructed from materials and components that provide stable performance characteristics over this extended temperature range. Sensor calibration and compensation algorithms can take into account temperature-dependent sensor characteristics to ensure accurate measurements throughout the entire operating temperature range.

[0091] The output signal of the pressure-temperature sensor 105 can be processed and transmitted to an external data acquisition system or gas analysis equipment for integration with spectral measurement data. The pressure-temperature sensor 105 can provide analog or digital output signals depending on specific sensor design and system integration requirements. Sensor data can be synchronized with optical measurements to achieve real-time correlation between gas conditions and spectral absorption characteristics.

[0092] The combined pressure-temperature sensor 105 contributes to the overall cost-effectiveness and simplicity of the gas pool system by eliminating the need for separate pressure and temperature sensing devices. This integrated approach reduces the complexity of gas pool design while providing comprehensive monitoring of gas sample conditions. The pressure-temperature sensor 105 can also provide diagnostic information about gas pool operation, including detecting gas leaks, flow blockages, or other operational issues that may affect measurement performance.

[0093] Thermal compensation mechanism

[0094] The thermal compensation mechanism operates by utilizing the differential thermal expansion between the carbon steel pool cylinder and the PVDF mirror holder to maintain stable mirror separation across temperature variations. The compensation principle is based on the significant difference in the coefficients of thermal expansion between these materials, with PVDF exhibiting approximately 10 times the coefficient of thermal expansion of carbon steel. This difference allows for the design of a compensation system where the thermal expansion effects essentially cancel each other out.

[0095] like Figure 5 As shown, the complete compensation condition can be expressed as L cell_cyl ×CTE cell_cyl =2×L mirror_hldr ×CTE mirror_hldr L cell_cyl Indicates the length of the pool cylinder, CTE cell_cyl L represents the coefficient of thermal expansion of the cylindrical material of the pool. mirror_hldr Indicates the length of the mirror retainer, and CTE mirror_hldr This represents the coefficient of thermal expansion of the mirror holder material. This relationship defines the geometric proportions required to achieve thermal compensation between the expansion tank cylinder and the expansion mirror holder.

[0096] In this regard, in some implementations, one or more components of the thermally compensated multichannel spectroscopic gas cell 100 may be selected based on full compensation conditions (e.g., thermal compensation relationships). For example, the length of the cell housing 102 and / or the length of the mirror holders 111, 121 may be selected based on thermal compensation conditions.

[0097] The compensated mirror separation change can be expressed as the following equation or calculated using this equation: ΔL mirror_sep =L cell_cyl ×CTE cell_cyl ×ΔT-2×L mirror_hdr ×CTE mirror_hldr ×ΔT=0, where ΔL mirror_sep The equation represents the change in mirror separation, ΔT represents the temperature change, and the factor 2 accounts for the presence of mirror retainers at both ends of the pool cylinder. When this equation equals zero, the thermal expansion of the pool cylinder can be balanced by the thermal expansion of the mirror retainers, thus preventing a net change in mirror separation.

[0098] Carbon steel tank cylinders can exhibit a size of 11.2 × 10⁻⁶. -6 / Celsius to 12.0×10 -6 The coefficient of thermal expansion is within a certain range of / degrees Celsius, thus providing a relatively low rate of thermal expansion, which serves as the baseline for the compensation mechanism. PVDF mirror retainers can exhibit a coefficient of thermal expansion of 102 × 10⁻⁶ degrees Celsius. -6 / Celsius to 158×10-6 The coefficient of thermal expansion at 60°C is approximately 8 to 14 times that of carbon steel. This difference in the coefficient of thermal expansion allows for the use of geometrically shorter recessed PVDF mirror holders to offset the thermal expansion of longer carbon steel pool cylinders.

[0099] The geometric advantages provided by different coefficients of thermal expansion allow the mirror retainer to be designed as a relatively short component, while still providing sufficient compensation for the thermal expansion of the much longer pool cylinder. The high coefficient of thermal expansion of PVDF material allows small changes in the length of the mirror retainer to produce an equivalent compensation effect to changes in the length of the much larger pool cylinder. This geometric relationship simplifies mechanical design while maintaining the structural integrity required for precise mirror positioning.

[0100] Now for reference Figures 6A to 6C By carefully selecting material coefficients and geometric proportions, the thermal compensation mechanism can achieve a mirror separation variation tolerance of ±0.1 mm over the operating temperature range. This tolerance level is sufficient to maintain the optical alignment accuracy required for effective multichannel spectroscopy operation, while accommodating thermal expansion effects occurring over an extended temperature range from approximately -20°C to +60°C.

[0101] like Figure 6A As shown, PVDF materials can exhibit nonlinear temperature-dependent thermal expansion coefficient characteristics. This nonlinear behavior may lead to non-monotonic compensation characteristics, where the combined effective thermal expansion coefficient varies over the temperature range.

[0102] like Figure 6B As shown, the nonlinear thermal expansion behavior of PVDF can produce a compensated system with a negative combined effective thermal expansion coefficient at low temperatures and a positive combined effective thermal expansion coefficient at high temperatures. At low temperatures, thermal compensation causes a net contraction of the mirror separation with increasing temperature, while at high temperatures, compensation causes a net expansion of the mirror separation with increasing temperature. This bidirectional compensation behavior can extend the effective operating temperature range by providing compensation in both directions from the center temperature point.

[0103] like Figure 6C As shown, the non-monotonic compensation behavior allows the gas pool system to maintain mirror separation within the required tolerances over a wider temperature range than is possible for linearly thermally expanding materials. The varying compensation characteristics provide enhanced thermal stability at temperature limits where conventional linear compensation methods may exceed acceptable tolerance limits. This extended temperature range capability enables the gas pool to operate effectively in real-world applications with highly variable and unpredictable temperatures.

[0104] The thermal compensation mechanism operates automatically without requiring an active control or regulation system. When temperature changes occur, the different thermal expansions between the carbon steel tank cylinder and the PVDF mirror retainer respond immediately to maintain stable mirror positioning. This passive compensation method provides reliable thermal stability without the complexity, cost, and potential failure modes associated with active temperature control systems.

[0105] System Operation

[0106] During operation, the thermally compensated multichannel spectroscopic gas cell 100 can serve as an integrated system in which optical, thermal, and gas flow components work together to achieve accurate spectral measurements over a wide temperature range. For example, the thermally compensated multichannel spectroscopic gas cell 100 can realize a multichannel spectroscopic gas detection system or be configured to perform one or more operations of a multichannel spectroscopic gas detection system.

[0107] System operation may involve the coordinated interaction between optical path configuration, gas sample processing, thermal compensation mechanisms, and sensor data collection to achieve reliable gas detection and analysis. The optical path of the thermally compensated multichannel spectroscopic gas cell 100 can begin with light entering through one of the fused silica wedge windows (e.g., light inlet window 113) positioned at the end of the gas cell assembly. The wedge geometry of the light inlet window 113 guides the incident beam into the gas cell volume while minimizing unwanted reflections that could interfere with spectroscopic measurements. The beam can travel through a gas-filled volume defined by a PVDF inner tube 103 within a carbon steel cylinder (e.g., carbon steel cell housing 102), where the beam can interact with gas molecules present in the sample.

[0108] For example, such as Figure 7A As shown, a beam 700 from an emitter (such as one or more optical frequency combs) can pass through the light inlet aperture 112 of the first reflector 110 and through the light inlet window 113 into the chamber 104. The inner surfaces of the reflectors 110 and 120 can be shaped and positioned such that the beam 700 reflects back and forth between the reflectors 110 and 120 according to a pattern that avoids collisions between any reflections. This multi-channel configuration allows the effective optical path length to be many times the physical length of the pool. The multi-channel optical configuration can be achieved through multiple reflections between a pair of reflectors positioned at opposite ends of the gas pool assembly. The reflectors can be mounted in a PVDF reflector holder and separated by a nominal distance (e.g., 385.2 mm in some examples), thereby creating an optical cavity (e.g., chamber 104) that allows the beam to traverse the gas sample multiple times before leaving the system. Each reflection between the reflectors can increase the effective optical path length through the gas sample, thereby enhancing the absorbed signal intensity to improve detection sensitivity.

[0109] The light beam can undergo multiple reflections between the mirrors, with each reflection contributing to the accumulation of the absorbed signal. A multi-channel configuration multiplies the effective path length by the number of reflections, making it possible to detect trace gas concentrations that might otherwise be impossible to measure with a single-channel optical system. Figure 7B As shown, the optical path can be designed to ensure that the beam coverage area remains within the aperture of the mirror and window throughout the entire reflection sequence.

[0110] In various embodiments, after back-and-forth reflections (which may involve dozens or hundreds of reflections) according to a pattern defined by the surface of the mirrors, for example, beam 700 can exit chamber 104 through light exit window 123 and be received by a light receiver through light exit aperture 122 defined in a second mirror 120. For example, after completing a multichannel sequence, the beam can exit the gas cell through light exit window 123 and through light exit aperture 122 at the opposite ends of the gas cell relative to light inlet window 113 and light inlet aperture 112. The wedge geometry of the exit window prevents reflected light from re-entering the optical system while providing efficient transmission of the analytical beam to external detection equipment. The transmitted light can carry spectral information about the composition of the gas sample based on wavelength-specific absorption that occurs during multichannel propagation.

[0111] Gas flow through the cell can occur simultaneously with optical measurements, enabling continuous monitoring or batch analysis depending on application requirements. Gas inlet port 106 introduces fresh gas samples into the PVDF inner tube volume, while gas outlet port 108 removes the analyzed gas from the gas cell. The gas flow path can be designed to ensure uniform gas distribution throughout the optical path region while maintaining stable flow conditions that do not introduce optical interference.

[0112] Airflow configuration enables the system to analyze flowing gas streams in real-time applications or process discrete gas samples in batch analysis modes. During continuous monitoring, the gas composition within the optical path may change as new gas enters through the inlet port and the gas being analyzed exits through the outlet port. Flow rate and residence time can be controlled to ensure sufficient measurement time while maintaining representative sampling of the monitored airflow.

[0113] When the operating temperature varies within the range of -20℃ to +60℃, the thermal compensation mechanism can maintain stable mirror alignment and separation. As the ambient temperature changes, the carbon steel cylinder can adjust its position according to its 11.2×10⁻⁶ mm diameter. -6 / Celsius to 12.0×10 -6 The PVDF mirror retainer expands or contracts within a range of 102 × 10⁻⁶ degrees Celsius, based on its coefficient of thermal expansion. -6 / Celsius to 158×10 -6The coefficient of thermal expansion in the range of / degrees Celsius expands or contracts at a much higher rate.

[0114] Thermal compensation works through a geometric relationship where the thermal expansion of the carbon steel cylinder length can be balanced by twice the thermal expansion of the mirror retainer length. As temperature increases, the carbon steel cylinder may expand and tend to increase the mirror separation distance. Simultaneously, the PVDF mirror retainer can expand at approximately ten times the rate of the carbon steel, extending further into the cylinder, and tends to reduce the mirror separation distance by an amount that essentially offsets the cylinder expansion effect.

[0115] The nonlinear temperature-dependent characteristics of PVDF can provide additional thermal compensation benefits, extending the operating temperature range beyond what can be achieved using only linear thermal expansion. At low and high temperatures, the combined slightly positive coefficient of thermal expansion exhibits positive values, resulting in a slight increase in mirror separation. At moderate temperatures, the combined effective coefficient may exhibit slightly negative values, resulting in a slight decrease in mirror separation with temperature. This bidirectional behavior allows the system to maintain mirror separation within a tolerance of ±0.1 mm across the entire temperature range of -20°C to +60°C.

[0116] like Figure 8 As shown, even when the mirror separation variation reaches ±0.4 mm, thermal compensation maintains optical performance, providing an operating margin exceeding the nominal ±0.1 mm specification. The optical system design can accommodate these large separation variations without experiencing light loss or unwanted reflections that would degrade measurement quality. This tolerance margin ensures robust operation under extreme conditions or manufacturing variations exceeding the nominal design parameters.

[0117] The combined pressure-temperature sensor can collect real-time data on gas conditions within the cell during spectroscopic measurements. Pressure measurements indicate the gas density within the optical path, which can affect the intensity of the absorption signal and the relationship between absorption measurements and gas concentration. Temperature measurements provide information on the effect of gas temperature on molecular absorption characteristics and enable temperature-corrected analysis of the spectral data.

[0118] Pressure and temperature data can be combined with optical absorption measurements to improve the accuracy of gas concentration determination. Pressure correction can account for the effect of gas density variations on absorption line intensity, while temperature correction can account for temperature-dependent changes in the absorption cross-section and line broadening effects. Combined sensor data allows for real-time compensation for pressure and temperature effects that could otherwise introduce errors into gas concentration calculations.

[0119] Sensor data also provides system monitoring capabilities, enabling the detection of operational problems or changes in airflow conditions. Pressure readings can indicate appropriate airflow through inlet and outlet ports and can detect blockages, leaks, or other flow-related issues. Temperature readings can provide feedback on thermal compensation performance and allow verification that the system operates within the design temperature range where thermal compensation is effective.

[0120] The integration of optical measurements with pressure and temperature data enables advanced analytical techniques that improve measurement reliability and accuracy. Coordinated data collection supports algorithms that consider the complex interactions between gas properties, light absorption characteristics, and environmental conditions. Compared to systems that rely solely on optical measurements without environmental compensation, this integrated approach provides more robust gas detection and analysis capabilities.

[0121] The sealing system, including sealing rings and fasteners, maintains gas containment across the entire operating temperature range while allowing the thermal compensation mechanism to function correctly. The seals accommodate differential thermal expansion between carbon steel and PVDF components without compromising sealing effectiveness or limiting the thermal movement required for compensation. The sealing assembly prevents gas leaks that could affect measurement accuracy while enabling coordinated operation of optical, thermal, and gas flow components.

[0122] In this regard, by using PVDF material in various components of the thermally compensated multichannel spectroscopic gas cell 100, as described above, the exemplary embodiments of this disclosure provide a gas cell 100 with properties desired in multichannel gas cell applications. These properties include, but are not limited to, high structural stability, improved chemical resistance (particularly important for corrosive gases), and low cost (e.g., low material and manufacturing costs compared to conventional low-expansion materials such as Invar alloys or microcrystalline glass). In various embodiments, a low-CTE carbon steel gas cell housing 102 with high-CTE PVDF tube 103 components (including tube 103 and mirror holders 111, 121) forms a stable gas cell 100. In various embodiments, the high-CTE PVDF mirror holders 111, 121 provide compensation for the carbon steel cell housing 102, which also houses an inlet optical window element 113 and an outlet optical window element 123 (e.g., by housing PVDF window holders 116, 126 including windows 113, 123).

[0123] Example thermally compensated multichannel spectroscopic gas detection system

[0124] See now Figure 9A block diagram of an example thermally compensated multichannel spectroscopic gas detection system 900 according to an example embodiment of the present disclosure is provided. The example system 900 may include a thermally compensated multichannel spectroscopic gas cell (such as an example thermally compensated multichannel spectroscopic gas cell), a control device 901, a light emitter 910, and / or a light receiver 912. The light emitter 910 may be configured to emit light toward and / or emit light into the gas cell, as described above. The light receiver 912 may be configured to receive light exiting the gas cell 100, as described above.

[0125] Figure 9 The illustrated example control device 901 includes a processor or processing circuitry 902, a memory circuitry 904, an input / output circuitry 906, and a communication circuitry 908. In some embodiments, one or more portions of the control device 901 (e.g., one or more components thereof) are configured to perform and conduct the operations described herein. In some embodiments, the control device 901 may be configured to control the operation of the light emitter 910, the light receiver 912, and / or the gas pool 100. For example, in some such embodiments, the control device 901 may function as a controller within the system 900. In some embodiments, the control device 901 may be configured to analyze output from the gas pool 100 or received by the light receiver 912 to determine the presence of one or more target gases.

[0126] While these components are described with respect to functional limitations, it should be understood that at least some specific implementations in a particular embodiment necessarily include the use of specific computing hardware. It should also be understood that in some implementations, certain components of the components described herein include similar or common hardware. For example, in some implementations, two circuit groups utilize the same processor, memory, circuitry, etc., to perform their associated functions, so that each circuit group does not require duplicate hardware.

[0127] The processing circuitry 902 can be embodied in a variety of different ways. In various embodiments, the use of the terms "processor" or "processing circuitry" should be understood to include a single-core processor, a multi-core processor, multiple processors within the example device 901, and / or one or more remote or "cloud" processors external to the example device 901. In some example embodiments, the processing circuitry 902 may include one or more processing devices configured to execute independently. Alternatively or additionally, the processing circuitry 902 may include one or more processors configured in series via a bus to enable independent execution of operations, instructions, pipelines, and / or multithreading.

[0128] In example embodiments, processing circuitry 902 may be configured to execute instructions stored in memory circuitry 904 or otherwise accessible by a processor. Alternatively or additionally, processing circuitry 902 may be configured to perform hard-coded functions. Thus, whether configured by hardware or software methods, or by a combination thereof, processing circuitry 902 may represent an entity (e.g., physically embodied in circuit form) capable of performing operations according to embodiments of this disclosure. Alternatively or additionally, processing circuitry 902 may be embodied as an executor of software instructions that specifically configure processing circuitry 902 to execute various algorithms embodied in one or more operations described herein when such instructions are executed. In some embodiments, processing circuitry 902 includes hardware, software, firmware, and / or combinations thereof for performing one or more operations described herein.

[0129] In some implementations, processing circuitry 902 (and / or a coprocessor or any other processing circuitry that assists the processor or is otherwise associated with the processor) communicates with memory circuitry 904 via a bus for transferring information between components of example device 901.

[0130] The memory or memory circuitry 904 may be non-transitory and may include, for example, one or more volatile and / or non-volatile memories. In some embodiments, the memory circuitry 904 includes or embodies an electronic storage device (e.g., a computer-readable storage medium). In some embodiments, the memory circuitry 904 is configured to store information, data, content, applications, instructions, etc., for enabling the example device 901 to perform various operations and / or functions according to the example embodiments of this disclosure.

[0131] Input / output circuitry 906 may be included in example device 901. In some embodiments, input / output circuitry 906 may provide output to a user and / or receive input from a user. Input / output circuitry 906 may communicate with processing circuitry 902 to provide such functionality. Input / output circuitry 906 may include one or more user interfaces. In some embodiments, the user interface may include a display that includes an interface presented as a web user interface, application user interface, user device, back-end system, etc. In some embodiments, input / output circuitry 906 may also include a keyboard, mouse, joystick, touchscreen, touch area, softkeys, microphone, speaker, or other input / output mechanism. Processing circuitry 902 and / or input / output circuitry 906 may be configured to control one or more operations and / or functions of one or more user interface elements via computer program instructions (e.g., software and / or firmware) stored in processor-accessible memory (e.g., memory circuitry 904, etc.). In some embodiments, input / output circuitry 906 includes or utilizes user-oriented applications to provide input / output functionality to a computing device and / or other display associated with a user. In some implementations, the input / output circuit 906 includes one or more indicator lights, etc., for providing user notifications (e.g., alarms or warnings).

[0132] Communication circuitry 908 may be included in example device 901. Communication circuitry 908 may include any means, such as devices or circuits embodied in hardware or a combination of hardware and software, configured to receive and / or transmit data from / to a network and / or any other device, circuitry, or module communicating with example device 901. In some embodiments, communication circuitry 908 includes, for example, a network interface for enabling communication with wired or wireless communication networks. Additionally or alternatively, communication circuitry 908 may include one or more network interface cards, antennas, buses, switches, routers, modems, and supporting hardware, firmware, and / or software, or any other device suitable for enabling communication via one or more communication networks. In some embodiments, communication circuitry 908 may include circuitry for interacting with antennas and / or other hardware or software to induce reception of signals transmitted via the antenna and / or processing signals received via the antenna. In some embodiments, communication circuitry 908 enables the transmission and / or reception of data to and / or from user equipment, one or more sensors, and / or other external computing devices communicating with example device 901.

[0133] In some embodiments, two or more circuits in the group 902-908 are composable. Alternatively or additionally, one or more circuits in the group 902-908 perform some or all of the operations and / or functionalities described herein as associated with another circuit. In some embodiments, two or more circuits in the group 902-908 are combined into a single module embodied in hardware, software, firmware, and / or combinations thereof.

[0134] While the foregoing description provides examples of an example system 900 and an example control device 901, it should be noted that the scope of this disclosure is not limited to the above description. In some examples, the example system 900 and / or control device according to this disclosure may be in other forms. In some examples, the example system 900 and / or control device 901 may include one or more additional and / or alternative elements, and / or may be compatible with... Figure 9 The structures shown are different.

[0135] The operations and procedures described herein support combinations of components for performing specified functions and combinations of operations for performing specified functions. It should be understood that one or more operations, and combinations of operations, can be implemented by a computer system based on dedicated hardware or a combination of dedicated hardware and computer instructions to perform the specified functions.

[0136] In some example implementations, some of the operations described herein may be modified or further expanded as described below. Additionally, in some implementations, additional optional operations may be included. It should be understood that each of the modifications, optional additions, or expansions described herein may be included in the operations herein, either individually or in combination with any other feature described herein.

[0137] The foregoing description of methods and processes is provided as illustrative examples only and is not intended to require or imply that the steps of the various embodiments must be performed in the presented order. As those skilled in the art will understand, the order of steps in the above embodiments can be performed in any order. Words such as “after,” “then,” “next,” and similar terms are not intended to limit the order of steps; these words are merely used to guide the reader through the description of the method. Furthermore, any reference to singular claim elements, for example, using the articles “a,” “an,” or “the,” should not be construed as limiting the element to the singular and, in some cases, may be interpreted in the plural form.

[0138] Although various embodiments based on the principles disclosed herein have been shown and described above, modifications can be made by those skilled in the art without departing from the teachings of this disclosure. The embodiments described herein are representative only and not intended to be limiting. Many variations, combinations, and modifications are possible and are within the scope of this disclosure. Alternative embodiments resulting from the merging, integration, and / or omission of features of the embodiments are also within the scope of this disclosure. Therefore, the scope of protection is not limited by the description set forth above, but is defined by the following claims, which include all equivalents of the subject matter of the claims. Each claim is incorporated into the specification as further disclosure, and the claims are embodiments of this disclosure. Furthermore, any of the foregoing advantages and features may relate to specific embodiments, but the application of such published claims should not be limited to methods and structures that achieve any or all of the above advantages or have any or all of the above features.

[0139] Furthermore, the chapter titles used in this article are intended to correspond with 37 CFR. The recommendations in 1.77 are consistent with or provide organizational clues. These headings should not limit or characterize the disclosure set forth in any of the claims published in this disclosure. For example, the description of the technology in “Background Art” should not be interpreted as an admission that a certain technology is prior art to any disclosure in this disclosure. Nor should “Summary of the Invention” be considered a limiting characterization of the disclosure set forth in the published claims. Furthermore, any reference in this disclosure to the singular forms “Disclosure” or “Simplification” should not be used to prove that there is only one novel point in this disclosure. Multiple embodiments of this disclosure may be set forth according to the limitations of the multiple claims published in this disclosure, and such claims accordingly define the disclosure protected by them and its equivalents. In all cases, the scope of these claims should be considered in accordance with the advantages of the claims themselves, and should not be limited by the headings set forth herein.

[0140] Furthermore, without departing from the scope of this disclosure, the systems, subsystems, apparatuses, techniques, and methods described and illustrated in various embodiments in a discrete or separate manner can be combined or integrated with other systems, modules, techniques, or methods. Other devices or components shown or discussed as being interconnected or communicating with each other can be indirectly interconnected through some intermediate devices or components, whether such interconnection is made electrically, mechanically, or otherwise. Other examples of variations, substitutions, and modifications that can be identified by those skilled in the art without departing from the scope of this disclosure are also provided.

[0141] Those skilled in the art to which these embodiments pertain will recognize numerous modifications and other embodiments of the disclosure set forth herein, which benefit from the teachings presented in the foregoing description and associated drawings. Although the drawings show only certain components of the apparatuses and systems described herein, various other components may be used in conjunction with the components and structures disclosed herein. Therefore, it should be understood that this disclosure is not limited to the specific embodiments disclosed, and modifications and other embodiments are intended to be included within the scope of the appended claims. For example, various elements or components may be combined, rearranged, or integrated into another system, or certain features may be omitted or not implemented. Furthermore, the steps in any of the methods described above may not necessarily occur in the order depicted in the drawings, and in some examples, one or more of the depicted steps may occur substantially simultaneously, or additional steps may be involved. Although specific terms are used herein, they are used only in a general and descriptive sense and not for limiting purposes.

Claims

1. A thermally compensated multichannel spectroscopic gas cell, the thermally compensated multichannel spectroscopic gas cell comprising: A cylindrical pool shell, the cylindrical pool shell being made of materials having a first coefficient of thermal expansion (CTE) CTE cell_cyl The first material constitutes and defines the interior; A first reflector assembly, the first reflector assembly including a first reflector holder and a first reflector fixed within the first reflector holder; and The second reflector assembly includes a second reflector holder and a second reflector fixed within the second reflector holder; The first and second mirror assemblies are positioned at opposite ends of the cylindrical pool housing to create a multi-channel optical configuration, and Wherein, the first mirror holder and the second mirror holder are composed of a second CTE having a CTE greater than that of the first CTE. mirror_hldr The second material composition provides thermal compensation for stable mirror separation across the entire operating temperature range.

2. The thermally compensated multichannel spectroscopic gas cell according to claim 1, wherein the cylindrical cell shell defines a first length L. cell _ cyl And each of the first mirror holder and the second mirror defines a second length L. mirror_hldr The first length and the second length are based on the thermal compensation relationship L. cell _ cyl ×CTE cell_cyl =2×L mirror_hldr ×CTE mirror_hldr To choose.

3. The thermally compensated multichannel spectroscopic gas cell according to claim 1, wherein the first material comprises carbon steel.

4. The thermally compensated multichannel spectroscopic gas cell according to claim 1, wherein the first CTE is at 11.2 × 10⁻⁶. -6 / Celsius to 12.0×10 -6 Within the range of / degrees Celsius.

5. The thermally compensated multichannel spectroscopic gas cell according to claim 1, wherein the second material comprises polyvinylidene fluoride (PVDF).

6. The thermally compensated multichannel spectroscopic gas cell according to claim 1, wherein the second CTE is at 102 × 10⁻⁶. -6 / Celsius to 158×10 -6 Within the range of / degrees Celsius.

7. The thermally compensated multichannel spectroscopic gas cell according to claim 1, wherein the thermally compensated multichannel spectroscopic gas cell further includes an inner tube positioned inside the cylindrical cell shell, wherein the inner tube is made of the second material.

8. The thermally compensated multichannel spectroscopic gas cell according to claim 1, wherein the first mirror and the second mirror are made of fused silica.

9. The thermally compensated multichannel spectroscopic gas cell according to claim 1, wherein the thermally compensated multichannel spectroscopic gas cell further comprises: A first window assembly and a second window assembly are positioned at the opposite ends of the cylindrical pool housing, wherein the first window assembly includes a first window retainer and a light inlet window fixed within the first window retainer, and wherein the second window assembly includes a second window retainer and a light outlet window fixed within the second window retainer.

10. A gas detection system, the gas detection system comprising: A thermally compensated multichannel spectroscopic gas cell, the thermally compensated multichannel spectroscopic gas cell comprising: A cylindrical pool shell, the cylindrical pool shell being constructed of a first material having a first CTE and defining the interior; A first reflector assembly, the first reflector assembly including a first reflector holder and a first reflector fixed within the first reflector holder; and The second mirror assembly includes a second mirror holder and a second mirror fixed within the second mirror holder; wherein the first mirror assembly and the second mirror assembly are positioned at opposite ends of the cylindrical pool housing to create a multi-channel optical configuration, and wherein the first mirror holder and the second mirror holder are made of a second material having a second CTE greater than the first CTE to provide thermal compensation for stable mirror separation over the entire operating temperature range; A light emitter configured to emit a light beam toward the thermally compensated multichannel spectroscopic gas cell; and A light receiver configured to receive light exiting the compensated multichannel spectral gas cell.

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