Distributed cryogenic pipeline evacuation system and method of use thereof

Abstract

The present application relates to the field of particle accelerator ultra-high vacuum technology, and particularly relates to a distributed cryogenic pipeline pumping system and a use method thereof. The pumping system comprises: a vacuum pipeline comprising a plurality of vacuum tubes arranged sequentially along a beam direction; a cryogenic cold screen assembly arranged on the inner side of the vacuum pipeline, used for condensing and adsorbing residual gas in the vacuum pipeline to improve the vacuum degree; and a refrigerator arranged on the outer side of the vacuum pipeline; wherein the cryogenic cold screen assemblies and the refrigerators are distributed along the length direction of the vacuum pipeline in a one-to-one correspondence, and the cold head of the refrigerator penetrates the side wall of the vacuum tube and is in thermal connection with the cryogenic cold screen assembly. In the present application, the cryogenic cold screen assembly and the refrigerator are used to form a modular pumping unit, and a plurality of the pumping units are arranged along the vacuum pipeline, which can overcome the flow conductance limitation, realize uniform distribution of the vacuum degree, and make the pumping system easy to install and maintain.

Description

Technical Field

[0001] This invention relates to the field of ultra-high vacuum technology for particle accelerators, and in particular to a distributed cryogenic pipeline pumping system and its usage method. Background Technology

[0002] In particle accelerators (such as storage rings and colliders), the beam operates in an ultra-high vacuum (UHV) environment for extended periods. Residual gas molecules scatter with the beam particles, directly leading to a shortened beam lifetime and increased background noise. To maintain beam lifetime, the vacuum level must be raised to ultra-high vacuum.

[0003] Currently, the vacuum environment in the vacuum pipes of particle accelerators is mainly achieved using the following methods: Discrete vacuum pumps are used: high-speed vacuum pumps (such as sputtering ion pumps, NEG pumps, and cryogenic pumps) are installed at intervals along the vacuum pipeline. However, due to the large length and limited flow conductance of the vacuum pipeline, a vacuum gradient often exists between two adjacent vacuum pumps, making it difficult to ensure uniform vacuum throughout the entire beam channel.

[0004] Distributed NEG coating: A NEG thin film is deposited on the inner wall of the vacuum pipe. However, the NEG film requires high temperature (≥180℃) activation to function as a pumping agent, and the activation process is complex and places high demands on the pipe heating system. Furthermore, the NEG film cannot function as a pumping agent for inert gases and methane.

[0005] Setting up a liquid helium cryogenic system: Traditional cryogenic pumps usually use centralized liquid helium refrigeration, which requires complex helium liquefaction devices and transmission pipelines. The system is large, expensive, and has a wide impact if it leaks or fails.

[0006] In view of this, there is an urgent need for a vacuum system that is low in cost, easy to install and maintain, has high redundancy after failure, can overcome flow conduction limitations, and can achieve uniform vacuum distribution. Summary of the Invention

[0007] This invention aims to solve the technical problems existing in related technologies. To this end, this invention proposes a distributed cryogenic pipeline pumping system and its usage method to solve the problem that existing accelerator vacuum pipelines have vacuum gradients and require complex and large systems to maintain ultra-high vacuum levels.

[0008] In a first aspect, the present invention provides a distributed cryogenic pipeline evacuation system, comprising: A vacuum tube, comprising multiple vacuum tubes arranged sequentially along the beam direction; A low-temperature cooling shield assembly is disposed inside the vacuum pipe to condense and adsorb residual gas in the vacuum pipe to improve the vacuum level. A refrigeration unit is located outside the vacuum pipe; Among them, several low-temperature cold shield assemblies and several refrigerators are distributed along the length of the vacuum pipe in a one-to-one correspondence, and the cold head of the refrigerator penetrates the side wall of the vacuum pipe and is thermally connected to the low-temperature cold shield assembly.

[0009] According to the present invention, a distributed cryogenic pipeline extraction system includes a cryogenic cold shield assembly comprising: The cold screen is configured as a hollow cylindrical surface with a radius of curvature smaller than that of the vacuum tube; A connecting flange is located in the middle of the cold shield and is connected to the cold head of the refrigeration unit; A support member for connecting the cold screen and the vacuum tube.

[0010] According to the distributed cryogenic pipeline gas extraction system provided by the present invention, the inner wall of the cold shield is provided with a layer of activated carbon, and the outer wall of the cold shield is provided with a corrugated structure to enhance the gas adsorption capacity.

[0011] According to a distributed cryogenic pipeline extraction system provided by the present invention, the operating temperature of the cryogenic cold shield assembly is controlled between 4K and 20K by the refrigeration unit.

[0012] According to the present invention, a distributed cryogenic pipeline pumping system is provided, wherein the inner wall of the vacuum tube is provided with an Al / SiO2 double-layer film for reflecting and shielding thermal radiation.

[0013] According to the present invention, a distributed cryogenic pipeline extraction system is provided, wherein the cold shield is made of oxygen-free copper.

[0014] According to a distributed cryogenic pipeline evacuation system provided by the present invention, the vacuum pipeline further includes: A vacuum chamber is disposed between two adjacent vacuum tubes; A molecular pump, mounted on the vacuum chamber, is used to establish an initial vacuum; A manual slide gate valve is installed between the vacuum chamber and the molecular pump; A vacuum gauge, installed on the vacuum chamber, is used to monitor changes in vacuum level.

[0015] Secondly, the present invention also provides a method of using a distributed cryogenic pipeline extraction system, applied to the distributed cryogenic pipeline extraction system, the method comprising: The molecular pump is started to perform rough evacuation of the system to obtain a vacuum level of less than 1×10⁻⁶. -3 The initial vacuum of Pa; The molecular pump is turned off, and the refrigerator is started to cool the temperature of the low-temperature cold shield assembly to between 4K and 20K. The low-temperature cold shield assembly is used to condense and adsorb residual gas in the vacuum pipeline.

[0016] The method of using a distributed cryogenic pipeline air extraction system provided by the present invention further includes: After a preset time, the refrigeration unit stops working and uses heating to raise the temperature of the low-temperature cold shield component, so that the low-temperature cold shield component releases the adsorbed residual gas. At the same time, the molecular pump is started to extract the residual gas released by the low-temperature cold shield component.

[0017] According to a method of using a distributed cryogenic pipeline extraction system provided by the present invention, the step of raising the temperature of the cryogenic cooling shield assembly by heating includes: A heating element is installed on the outer wall of the vacuum chamber to raise the temperature of the low-temperature cold screen component to 300K.

[0018] The above-described one or more technical solutions of this invention have at least one of the following technical effects: In this invention, the distributed cryogenic pipeline pumping system uses cryogenic cold shield components and a refrigeration unit to form a modular pumping unit. Several of these pumping units are distributed along the vacuum pipeline, which can overcome flow conduction limitations, achieve uniform vacuum distribution, and provide high fault redundancy for the pumping system. This makes the pumping system easy to install and maintain, thereby reducing the operating cost of the pumping system.

[0019] In addition to the technical problems solved by the present invention, the technical features of the technical solutions constituted by the present invention, and the advantages brought about by the technical features of these technical solutions as described above, other technical features of the present invention and the advantages brought about by these technical features will be further explained in conjunction with the accompanying drawings, or will be learned through the practice of the present invention. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a distributed cryogenic pipeline air extraction system provided in an embodiment of the present invention.

[0022] Figure 2 This is a cross-sectional view of a distributed cryogenic pipeline extraction system provided in an embodiment of the present invention.

[0023] Figure 3This is a schematic diagram of the assembly of the refrigeration unit and the low-temperature cold shield assembly provided in an embodiment of the present invention.

[0024] Figure 4 for Figure 2 A magnified view of a portion of point A in the middle.

[0025] Figure label: 10. Vacuum piping; 11. Vacuum tube; 12. Vacuum chamber; 13. Molecular pump; 14. Manual slide gate valve; 15. Vacuum gauge; 20. Cryogenic cold shield assembly; 21. Cold shield; 22. Connecting flange; 30. Refrigeration unit. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] In an embodiment of the present invention, a distributed cryogenic pipeline pumping system is described. This pumping system is mainly used in the annular vacuum pipelines of large particle accelerators such as heavy ion accelerators and proton storage rings. It is used to establish and maintain an ultra-high vacuum environment within the beam operation channel, solving problems such as large vacuum gradients, uneven pumping, system complexity, and difficult maintenance in long-distance annular pipelines.

[0028] like Figure 1 and Figure 2 As shown, the distributed cryogenic pipeline evacuation system mainly includes a vacuum pipeline 10, a cryogenic cold shield assembly 20, and a refrigerator 30.

[0029] The vacuum conduit 10 includes a plurality of vacuum tubes 11 arranged sequentially along the beam direction.

[0030] The low-temperature cooling shield assembly 20 is disposed inside the vacuum pipe 10 and distributed along the extension direction of the vacuum pipe 10. It is used to condense and adsorb residual gases in the vacuum pipe 10, thereby maintaining and improving the vacuum level of the vacuum pipe 10. The residual gases include water vapor, carbon monoxide, carbon dioxide, nitrogen, oxygen, hydrogen, etc.

[0031] The refrigerator 30 is located outside the vacuum tube 10. The refrigerator 30 extends into the vacuum tube 11 through an opening in the side wall and is thermally connected to the low-temperature cold shield assembly 20 to control the temperature of the low-temperature cold shield assembly 20 within the target low-temperature range.

[0032] Several low-temperature cold shield components 20 correspond one-to-one with several refrigerators 30, and are evenly distributed along the length of the vacuum pipe 10 to form modular and independent low-temperature pumping units. Each pumping unit covers a certain length of pipe area and independently completes the functions of refrigeration, low-temperature condensation, and adsorption pumping. Adjacent pumping units maintain a reasonable distance to avoid mutual thermal interference and ensure that the pumping coverage is free of dead zones and vacuum gradients.

[0033] In this embodiment, the distributed cryogenic pipeline pumping system uses a cryogenic cold shield assembly 20 and a refrigerator 30 to form a modular pumping unit. Several of these pumping units are distributed along the vacuum pipeline 10. This not only disperses the pumping points throughout the entire vacuum pipeline 10, completely overcoming the vacuum gradient defects caused by the excessive length and flow conduction limitations of the vacuum pipeline 10, and achieving a uniform distribution of vacuum, but also forms a modular structure, which allows for the adaptive increase or decrease of the number of pumping units according to the length of the vacuum pipeline 10. This makes the pumping system easy to install and maintain, and reduces the cost of the pumping system.

[0034] Based on the above embodiments, in another embodiment of the present invention, the structure of the low-temperature cold screen assembly 20 is further defined.

[0035] like Figure 3 and Figure 4 As shown, the low-temperature cold shield assembly 20 includes a cold shield 21, a connecting flange 22, and a support component.

[0036] The cold shield 21 is a hollow cylindrical curved surface with a radius of curvature smaller than that of the vacuum tube 11. A connecting flange 22 is located in the middle of the cold shield 21 and connects to the cold head of the refrigerator 30. A support component is used to connect the cold shield 21 and the vacuum tube 11.

[0037] The cold screen 21 is a hollow cylindrical curved surface. The radius of curvature of the cold screen 21 is smaller than the radius of curvature of the inner wall of the vacuum tube 11, so that a gap is maintained between the cold screen 21 and the inner wall of the vacuum tube 11. This avoids interfering with the beam operation space and maximizes the effective area for cryogenic pumping, thereby increasing the probability of gas molecule collision and condensation. For example, the cold screen 21 can be set as a cylindrical curved surface with a circular cross-section or a cylindrical curved surface with an elliptical cross-section.

[0038] Preferably, the cold screen 21 is a cylindrical surface with a thickness of 3mm and a length of 800mm, and a uniform annular gap is maintained between it and the inner wall of the vacuum tube 11. This reduces the heat capacity while ensuring structural rigidity, thereby achieving rapid cooling and uniform temperature distribution.

[0039] Furthermore, the cold shield 21 is made of oxygen-free copper with high thermal conductivity. The surface of the cold shield 21 is precision polished and nickel-plated, with a surface roughness Ra < 0.4μm, in order to reduce thermal radiation absorption, improve radiation shielding capability, and suppress vacuum material outgassing.

[0040] One end of the support is fixedly connected to the cold shield 21, and the other end is fixedly connected to the inner wall of the vacuum tube 11, for stably supporting the cold shield 21 at a set position in the vacuum tube 10. Preferably, the support can adopt a multi-point support structure to ensure that the cold shield 21 is installed firmly, while minimizing the heat conduction from the cold shield 21 to the vacuum tube 10, thereby reducing energy consumption and improving cooling efficiency.

[0041] A flexible oxygen-free copper sheet or copper foil is provided between the cold head of the refrigeration unit 30 and the connecting flange 22 to absorb the errors caused by thermal expansion and contraction between the refrigeration unit 30 and the cold screen 21, as well as installation errors.

[0042] Furthermore, the vacuum pipeline 10 also includes a vacuum chamber 12, a molecular pump 13, a manual slide gate valve 14, and a vacuum gauge 15. The vacuum chamber 12 is located between two adjacent vacuum pipe sections 11, serving as a transitional connection and functional integration cavity, and provides installation interfaces for the molecular pump 13, the manual slide gate valve 14, and the vacuum gauge 15. It has a compact structure and a reasonable layout.

[0043] The molecular pump 13 is a turbomolecular pump with a pumping speed of 300-600 L / s. It is installed on the side wall of the vacuum chamber 12 through a flange seal and is used for rapid rough pumping during the system startup phase to pump the pipeline from atmospheric pressure to a low vacuum state, providing initial conditions for subsequent cryogenic pumping.

[0044] A manual slide gate valve 14 is installed between the vacuum chamber 12 and the molecular pump 13. Specifically, the manual slide gate valve 14 is installed at the corresponding evacuation port of the vacuum chamber 12 to control the connection and disconnection between the molecular pump 13 and the vacuum pipeline 10, facilitating unit maintenance, regeneration, and fault isolation. It is easy to operate and has reliable sealing.

[0045] Vacuum gauge 15 is a composite vacuum gauge to accommodate both low and high vacuum measurements. The measuring range of vacuum gauge 15 is 1 × 10⁻⁶. 5 Pa to 1×10 -8 Pa is used to monitor the vacuum level changes in the vacuum pipeline 10 in real time, providing data feedback for the entire process of system startup, operation, and regeneration, facilitating automated control and status judgment.

[0046] By configuring a vacuum chamber 12, a molecular pump 13, a manual slide valve 14, and a vacuum gauge 15 in the vacuum pipeline 10, the distributed cryogenic pipeline pumping system can quickly establish an initial vacuum, shortening the system startup time; it can also monitor the vacuum status in real time, ensuring safe and controllable operation.

[0047] In this embodiment, the cold screen 21 and the vacuum pipe 10 are matched by the radius of curvature, which can ensure that the cold screen 21 is installed close to the side wall of the vacuum pipe 10 to avoid the core area of ​​the vacuum pipe 10 used to transport the beam, thereby reducing the impact on the beam transmission and improving the condensation and adsorption pumping efficiency of the cold screen 21 for residual gas.

[0048] Furthermore, a layer of activated carbon is bonded to the inner wall of the cooling screen 21 (the side facing the beam). The activated carbon is high specific surface area coconut shell carbon, with a specific surface area of ​​not less than 1500 m². 2 / g. Activated carbon is bonded and cured using high-temperature resistant vacuum adhesive, resulting in high bonding strength, low vacuum outgassing rate, and no detachment or volatile pollution at low temperatures. Activated carbon exhibits extremely strong physical adsorption capacity for gases that are difficult to condense, such as hydrogen, at deep cryogenic temperatures, significantly improving the system's hydrogen pumping speed and capacity, thus solving the problem of insufficient hydrogen removal capacity in traditional cryogenic pumps.

[0049] The outer wall of the cold shield 21 (the side facing the tube wall) is provided with a corrugated, finned or sintered porous layer structure to increase the surface area.

[0050] Preferably, the corrugated structure on the outer wall of the cooling screen 21 has a height of 5 mm, a spacing of 10 mm, and extends along the length of the cooling screen 21. The corrugated structure can significantly increase the adsorption surface area without significantly increasing the weight and heat capacity of the cooling screen 21, thereby further enhancing its ability to condense and capture condensable gases.

[0051] Based on the above embodiments, in another embodiment of the present invention, the operating temperature range and control method of the low-temperature cold screen component 20 are further defined.

[0052] The refrigeration unit 30 is a small pulse tube refrigeration unit or a GM refrigeration unit. The working temperature of the low temperature cold shield component 20 is precisely controlled through two-stage cooling capacity output, and the working temperature is controlled between 4K and 20K.

[0053] In particular, the operating temperature of the low-temperature cold shield component 20 can be set to a more precise range according to the type of gas to be evacuated and the vacuum requirement.

[0054] When the low-temperature cooling shield component 20 operates in the 4K-20K temperature range, the cooling shield 21, together with the activated carbon adsorption layer, mainly achieves efficient condensation of gases such as water vapor, hydrogen, carbon monoxide, carbon dioxide, nitrogen, and oxygen, significantly enhancing the physical adsorption capacity and meeting the strict requirements of the accelerator's ultra-high vacuum for the partial pressure of various gases.

[0055] Furthermore, the refrigeration unit 30 is also equipped with a closed-loop temperature control function. By attaching a precision temperature sensor to the cold screen 21, the temperature signal is collected in real time. Then, the input power and cooling output of the refrigeration unit 30 are adjusted using the feedback temperature signal, so that the temperature of the cold screen 21 can be stably controlled so that the temperature fluctuation does not exceed ±0.5K, ensuring stable and reliable air extraction performance.

[0056] By controlling the cryogenic cooling shield component 20 to operate in different temperature ranges, the system can perform targeted processing on different gases, balancing pumping efficiency and energy economy. Furthermore, by precisely controlling the operating temperature, the cooling shield 21 can be guaranteed to operate stably for a long time, avoiding gas desorption caused by temperature fluctuations and ensuring a stable vacuum environment.

[0057] Furthermore, the inner wall of the vacuum tube 11 is provided with an Al / SiO2 double-layer film for reflecting and shielding thermal radiation.

[0058] The inner wall of vacuum tube 11 is coated with an Al / SiO2 double film by magnetron sputtering. The high infrared reflectivity of the aluminum layer and the environmental isolation and optical optimization function of the SiO2 protective layer are combined to increase the reflection and shielding of thermal radiation.

[0059] The bottom layer of the Al / SiO2 bilayer film is a metallic aluminum layer with a thickness of 10-20nm, which is in the mid-to-far infrared skin depth range. It has a high reflectivity of 90%-95% for infrared thermal radiation, which can reflect most of the thermal radiation transmitted from the outer wall of the vacuum tube 11 and the room temperature component back, significantly reducing radiative heat leakage.

[0060] The aluminum layer is covered with a dense SiO2 protective layer, 50-200nm thick, which serves multiple functions: First, it physically blocks oxygen, water vapor, and corrosive gases, preventing oxidation and sulfidation of the aluminum layer that would reduce reflectivity and maintain high reflectivity over the long term. Second, SiO2 is transparent in the infrared band and has a refractive index between that of air and aluminum. Through interference, it slightly improves the coupling efficiency of incident infrared light entering the aluminum layer, compensating for the additional reflection loss caused by the introduction of the protective layer. Third, it enhances the adhesion of the film. The SiO2 layer can enhance the adhesion between the aluminum layer and subsequent coatings or the external environment, and prevent the aluminum layer from falling off under mechanical cleaning or airflow erosion.

[0061] In addition, a method for using a distributed cryogenic pipeline evacuation system is introduced, which can be applied to the distributed cryogenic pipeline evacuation system in any of the above embodiments. The method includes the following steps: Step S1: Start the molecular pump 13 to perform rough evacuation of the system to obtain a vacuum degree of less than 1×10⁻⁶. -3 Pa of initial vacuum.

[0062] Step S2: Turn off the molecular pump 13 and start the refrigerator 30 to cool the temperature of the cryogenic cold screen assembly 20 to between 4K and 20K. The cryogenic cold screen assembly 20 is used to condense and adsorb the residual gas in the vacuum pipeline 10, so as to exert the dual pumping effect of the cryogenic cold screen assembly 20 and improve the vacuum degree.

[0063] Further, the method further includes the following steps: Step S3: After a preset time, the refrigerator 30 stops working, and the temperature of the cryogenic cold screen assembly 20 is increased by heating, so that the cryogenic cold screen assembly 20 releases the adsorbed residual gas. At the same time, the molecular pump 13 is started to extract the residual gas released by the cryogenic cold screen assembly 20.

[0064] Specifically, after the system runs for a period of time, the gas adsorbed by the cold screen 21 tends to be saturated. At this time, a baking component for heating the system is arranged on the outer wall of the vacuum chamber 12, and the temperature of the cryogenic cold screen assembly 20 is raised to 300K, so that the cryogenic cold screen assembly 20 releases the adsorbed gas, and the pumping function of the cryogenic cold screen assembly 20 can be restored.

[0065] Specifically, when establishing a vacuum environment using a distributed cryogenic pipeline pumping system: Confirm that all manual gate valves 14 are in the open state. After checking that the system is well sealed, start the molecular pump 13 supporting the vacuum chamber 12 to conduct rough pumping on the entire vacuum pipeline 10 and the vacuum chamber 12, and quickly discharge the gas in the system. When the system vacuum degree reaches and is stably better than 1×10 -3 Pa, the initial vacuum is established; Then, start all refrigerators 30. The cold heads of the refrigerators 30 gradually cool the cryogenic cold screen assembly 20 to the target temperature range of 4K - 20K. The cold screen 21 simultaneously plays the dual roles of condensation pumping and physical adsorption pumping in the target temperature range, realizes high-uniformity pumping, and quickly raises the vacuum degree to below 5×10 -6 Pa, reaching the ultra-high vacuum level to meet the requirements for stable operation of the beam.

[0066] Particularly, when the distributed cryogenic pipeline pumping system operates for a long time, the condensation and adsorption of gas on the surface of the cold screen 21 gradually become saturated, and the pumping performance decreases. The cold screen 21 needs to be heated to restore the pumping ability. The specific steps are as follows: Stop the operation of the refrigerator 30, cut off the cooling capacity input of the cold screen 21, and let the temperature of the cold screen 21 rise naturally; Set a baking component for heating the system on the outer wall of the vacuum chamber 12. The baking component adopts a flexible heating film and insulation layer structure and evenly wraps the vacuum chamber 12 and the corresponding pipeline section. Start the baking component and steadily raise the temperature of the cryogenic cold screen assembly 20 to about 300K. The high temperature vaporizes the condensed gas on the surface of the cold screen 21 and desorbs the adsorbed gas by the activated carbon, releasing the trapped residual gas.

[0067] Maintain the baking temperature while starting molecular pump 13 to continuously extract the gas released by desorption.

[0068] Turn off the baking components, stop heating, restart the refrigeration unit 30, cool the cold screen 21 to the working temperature, restore the system's efficient low-temperature air extraction capability, and continue to operate.

[0069] In this embodiment, the regeneration process of the distributed cryogenic pipeline pumping system can be completed in situ inside the vacuum system without disassembling the pipeline, cold shield 21 and refrigerator 30, or damaging the vacuum system seal. It is simple to operate, time-saving, and efficient, and can achieve periodic regeneration to ensure long-term stable operation of the system.

[0070] In the description of the embodiments of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0071] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0072] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0073] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms are not limited to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A distributed cryogenic pipeline air extraction system, characterized in that, include: A vacuum tube, comprising multiple vacuum tubes arranged sequentially along the beam direction; A low-temperature cooling shield assembly is disposed inside the vacuum pipe to condense and adsorb residual gas in the vacuum pipe to improve the vacuum level. A refrigeration unit is located outside the vacuum pipe; Among them, several low-temperature cold shield assemblies and several refrigerators are distributed along the length of the vacuum pipe in a one-to-one correspondence, and the cold head of the refrigerator penetrates the side wall of the vacuum pipe and is thermally connected to the low-temperature cold shield assembly.

2. The distributed cryogenic pipeline air extraction system according to claim 1, characterized in that, The low-temperature cooling screen assembly includes: The cold screen is configured as a hollow cylindrical surface with a radius of curvature smaller than that of the vacuum tube; A connecting flange is located in the middle of the cold shield and is connected to the cold head of the refrigeration unit; A support member for connecting the cold screen and the vacuum tube.

3. The distributed cryogenic pipeline air extraction system according to claim 2, characterized in that, The inner wall of the cold shield is provided with a layer of activated carbon, and the outer wall of the cold shield is provided with a corrugated structure to enhance the gas adsorption capacity.

4. The distributed cryogenic pipeline extraction system according to any one of claims 1 to 3, characterized in that, The operating temperature of the low-temperature cold shield assembly is controlled between 4K and 20K by the refrigeration unit.

5. The distributed cryogenic pipeline extraction system according to any one of claims 1 to 3, characterized in that, The inner wall of the vacuum tube is provided with an Al / SiO2 double-layer film for reflecting and shielding thermal radiation.

6. The distributed cryogenic pipeline air extraction system according to claim 2, characterized in that, The cold screen is made of oxygen-free copper.

7. The distributed cryogenic pipeline air extraction system according to claim 4, characterized in that, The vacuum pipeline also includes: A vacuum chamber is disposed between two adjacent vacuum tubes; A molecular pump, mounted on the vacuum chamber, is used to establish an initial vacuum; A manual slide gate valve is installed between the vacuum chamber and the molecular pump; A vacuum gauge, installed on the vacuum chamber, is used to monitor changes in vacuum level.

8. A method of using a distributed cryogenic pipeline air extraction system, characterized in that, Applied to the distributed cryogenic pipeline evacuation system as described in claim 7, the method includes: The molecular pump is started to perform rough evacuation of the system to obtain a vacuum level of less than 1×10⁻⁶. -3 The initial vacuum of Pa; The molecular pump is turned off, and the refrigerator is started to cool the temperature of the low-temperature cold shield assembly to between 4K and 20K. The low-temperature cold shield assembly is used to condense and adsorb residual gas in the vacuum pipeline.

9. The method of using the distributed cryogenic pipeline air extraction system according to claim 8, characterized in that, Also includes: After a preset time, the refrigeration unit stops working and the temperature of the low-temperature cold shield component is raised by heating so that the low-temperature cold shield component releases the adsorbed residual gas. At the same time, the molecular pump is started to extract the residual gas released by the low-temperature cold shield component.

10. The method of using the distributed cryogenic pipeline extraction system according to claim 9, characterized in that, The method of raising the temperature of the low-temperature cold screen component by heating includes: A heating element is installed on the outer wall of the vacuum chamber to raise the temperature of the low-temperature cold screen component to 300K.

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