Multifunctional integrated gas control system for dilution refrigerator

Abstract

The invention discloses a multifunctional integrated gas control system for a dilution refrigerator, and particularly relates to the field of refrigeration and low-temperature engineering, which comprises a liquid nitrogen cold trap, a gas buffer tank, an integrated valve box, a dilution refrigeration internal circulation pipeline, a diaphragm compressor, a roots pump, a turbo molecular pump and a vacuum suction pump set. According to the system, a highly-integrated valve box module is used and is responsible for implementing gas circuit control on different stages such as dilution refrigeration cycle starting, operation and shutdown rewarming; according to the invention, conductance optimization and heat loss reduction are carried out on gas paths with different temperature zones and different pressures, high air tightness of a full temperature zone from room temperature to extremely low temperature is ensured, the reliability and the automation degree of the dilution refrigerating machine are improved, and very positive significance is provided for practicability of a dilution refrigerating system.

Description

Technical Field

[0001] The present invention relates to the field of refrigeration and cryogenic engineering technology, and more particularly to a multifunctional integrated gas control system for a dilution refrigerator. Background Art

[0002] Dilution refrigerators are a current research hotspot in the milli-Kelvin (mK) temperature range for cryogenic refrigerators. They can achieve continuous cooling at temperatures down to 100 mK, while exhibiting remarkable electromagnetic interference-free and low-vibration characteristics. Consequently, they hold broad application prospects in fields such as superconducting quantum computing, extreme experimental setups, and deep space exploration. A mK dilution refrigerator utilizes the phase separation of a helium-3 and helium-4 mixture at extremely low temperatures, followed by the migration of helium-3 atoms across the phase interface, which increases entropy and absorbs heat, thereby lowering the system's minimum temperature to approximately 1 mK. The dilution refrigerator's power source requirements vary depending on the cooling process. The entire dilution refrigeration cycle includes pre-cooling, throttling, condensation heat exchange, dilution, reflux heat exchange, evaporation, and compression, primarily driven by a pump. During the cycle, the gas control system must provide the appropriate driving pressure, control the batched entry of gas from the gas buffer tank into the cycle, and guide the gas back into the gas buffer tank after the cycle completes. After system shutdown, the gas control system also requires inspection and leak detection of various components. Therefore, a good gas control system is the key to ensure the smooth operation of the dilution refrigerator.

[0003] Ideally, a gas control system for a dilution refrigerator should perform the following four functions:

[0004] 1) Prepare and initialize the dilution refrigerator. This is a fundamental step before the dilution refrigeration cycle begins, ensuring the system is in a safe and efficient state. The gas control system requires valve control to complete system vacuuming, pressure leak detection, and gas filling.

[0005] 2) The function of realizing the smooth operation of the dilution refrigeration cycle. This is the core working mode of the system, which is directly related to the cooling performance and steady-state maintenance of the dilution refrigerator. Through valve control combined with the pump group switch, the gas control system needs to realize the initial start-up and drive of the cycle, the flow and pressure regulation of the cycle process, and the path switching function of different cycle stages. Among them, the condensation and liquid accumulation process of the dilution refrigerator is accompanied by flow changes and pressure changes. The gas control system is required to control the timing of connecting multiple pumps to the system respectively. It also includes the control of the gas discharge in the gas buffer tank. Through the controlled opening and closing of the solenoid valve, the pressure after condensation is gradually reduced and the liquid level of the accumulated liquid is gradually increased until the dilution effect occurs.

[0006] 3) Realize the safety isolation function of the dilution refrigeration system. When maintaining or failure occurs, the entire dilution refrigeration system can be quickly divided into several independent vacuum sections or pressure sections by opening and closing the valve, facilitating problem troubleshooting and local repair without affecting the entire system.

[0007] 4) Realize the shutdown and rewarming function of the dilution refrigeration system. This function realizes the smooth and safe transition of the dilution refrigerator from operation to shutdown. The gas control system realizes the gas recovery function after shutdown, the function of maintaining system vacuum and sealing after recovering gas, and the controllable rewarming function by opening and closing the valve combined with the pump group switch.

[0008] The conventional dilution refrigerator gas circulation system currently has the disadvantages of loose system and dispersed functions, and in most cases manual operation is required, which has great reliability and stability risks. Especially when a single component of the system is damaged, the vacuum of the entire system is often broken to replace the component, which is prone to risk of working medium leakage. Moreover, the insufficient integration of the system leads to a large area occupied by the entire gas control system and complicated operation. SUMMARY

[0009] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present application provide a multifunctional integrated gas control system for a dilution refrigerator, which uses a highly integrated valve box module to implement gas path control in different stages such as dilution refrigeration cycle start, operation, shutdown and rewarming. By programmatic control of the specific opening and closing combination of the valves in the integrated valve box, the working mode of the system can be conveniently switched, the operation process is simplified and misoperation is avoided. Different materials and pipe diameters are used for the gas paths in different temperature zones and at different pressures to optimize the flow guide, reduce the heat capacity and reduce heat loss. A multi-stage sealing strategy is adopted to ensure high airtightness in the entire temperature range from room temperature to extremely low temperature. All the complex and dispersed gas path operations of the dilution refrigerator are highly centralized and automated, realizing multifunctional integrated control, which not only ensures efficient and stable operation of the refrigerator, but also brings greater improvement in safety, ease of use and maintainability.

[0010] To achieve the above-mentioned purposes, the present application provides the following technical solutions: a multifunctional integrated gas control system for a dilution refrigerator, comprising a liquid nitrogen cold trap, a gas buffer tank, an integrated valve box, a dilution refrigeration internal circulation pipeline, a diaphragm compressor, a Roots pump, a turbo molecular pump and a vacuum pumping pump group.

[0011] When the electromagnetic valves V1, V2, V9, V15, V17, V18 and V19 are opened, V3, V4 and V10 are controlled to open and close, and other valves are closed, the dilution refrigeration system starts initial cooling.

[0012] When the solenoid valves V3, V4, V5, V6, V9, V15, V17, V18, V19 are opened, V1, V2, V10 are controlled to open and close, and other valves are closed, the dilution refrigeration system starts to condense and liquefy;

[0013] Subsequently, V10 is closed, the rotational speed of the turbo molecular pump is controlled, and the dilution refrigeration system starts to realize the dilution effect;

[0014] When the solenoid valves V1, V2, V3, V4, V9, V11, V12, V14, V15, V17, V18, V19 are opened, and other valves are closed, the dilution refrigeration system starts to recover and recycle gas;

[0015] When the solenoid valve V13 is opened, and the opening and closing of the corresponding solenoid valves and bypass solenoid valves of different components are coordinated, the single component and the system can be repaired and leak tested; the liquid nitrogen cold trap uses a copper wire mesh heat exchanger with a large contact area to effectively ensure sufficient heat exchange and purification of the gas, and to preliminarily filter most of the gas impurities;

[0016] The gas buffer tank is the main gas storage container of the gas control system, and is externally connected to a long-life, high-vacuum diaphragm valve. The double-valve design of the inlet and outlet is conducive to the replacement of gas after the gas buffer tank is disassembled, and ensures that the impurity gas content in the tank remains at a very low level;

[0017] The integrated valve box is the core of the gas control system, and includes a valve cover, a valve body, and solenoid valves V1-V19. V1 and V2 are inlet and outlet valves of the diaphragm compressor, V3 and V4 are inlet and outlet valves of the Roots pump, V5 and V6 are inlet and outlet valves of the turbo molecular pump, V13 is a stop valve of the vacuum pumping pump group, V10 and V11 are inlet and outlet valves of the gas buffer tank, V12 and V14 are high and low pressure regulating valves of the dilution refrigeration internal circulation pipeline, V15 and V17 are inlet and outlet valves of the liquid nitrogen cold trap, V18 and V19 are inlet and outlet valves of the dilution refrigeration internal circulation pipeline. In order to facilitate system maintenance and replacement, and to meet the pressure requirements of the system under different working conditions, solenoid valves V7-V9 are used as bypasses of the pumps at different levels, and solenoid valve V16 is used as a bypass of the liquid nitrogen cold trap;

[0018] The dilution refrigeration internal circulation pipeline mainly includes a first-stage low-pressure gas pipeline, a 4K-above high-pressure gas pipeline, a second-stage low-pressure gas pipeline, a JT heat exchanger high-pressure gas pipeline, a JT heat exchanger low-pressure gas pipeline, an evaporation chamber high-pressure gas pipeline, a continuous heat exchanger gas pipeline, a separate heat exchanger gas pipeline, and a mixing chamber gas pipeline. The interface of the 4K-above high-pressure gas pipeline uses a VCR interface to ensure good airtightness. All sealed joints of the 4K-below gas pipelines, including the JT heat exchanger high-pressure gas pipeline, the continuous heat exchanger gas pipeline, the separate heat exchanger gas pipeline, and the mixing chamber gas pipeline, use gold wire sealing structures to ensure better airtightness. With the gas flow direction as the front, the front end of the solenoid valve V18 is connected to a high-pressure gauge and a negative feedback flow regulating valve;

[0019] Diaphragm compressor has the characteristics of large flow, adjustable pressure ratio, high cleanliness, which provides key front cycle power for the whole gas control system; Roots pump has the characteristics of adjustable flow, high cleanliness, low back pressure, which provides key front pressure for turbo molecular pump;

[0020] Turbo molecular pump has the characteristics of high pumping rate, high cleanliness, high pressure ratio, which provides extremely low pressure for the system at the key node of the dilution refrigeration system, facilitating the system to achieve further cooling and circulation;

[0021] Vacuum pumping group uses large flow mechanical pump and molecular pump coupling, which is used to build the overall vacuum environment of the system, system back temperature impurity, external helium mass spectrometer can realize the vacuum helium detection of the system and single component;

[0022] Nitrogen cold trap, gas buffer tank, integrated valve box, dilution refrigeration internal circulation pipeline, diaphragm compressor, roots pump, turbo molecular pump and vacuum pumping group are connected by high cleanliness pipeline of different sizes, thereby forming a multifunctional integrated gas control system for dilution refrigerator;

[0023] The manufacturing method of the multifunctional integrated gas control system for dilution refrigerator is as follows:

[0024] Liquid nitrogen cold trap uses stainless steel material to make liquid nitrogen cavity, uses oxygen-free copper material to make copper wire mesh of heat exchange condensing deposition cavity, uses the structure of foam copper and copper wire mesh superposition combination to ensure the smooth flow of gas flow; The gas buffer tank is made of stainless steel material or surface anodized aluminum material, the volume should be not less than 120L, the internal roughness requirement is RA≤0.4, the tank opening structure connected with double diaphragm valve should fully ensure the air tightness;

[0025] In the integrated valve box, the pipe diameter between low pressure gas path valves is 10-16mm, the pipe diameter between high pressure gas path valves is 4-6mm, the inlet and outlet diameter of electromagnetic valve is related to the pressure of valve position, the connecting pipe between integrated valve box and liquid nitrogen cold trap, gas buffer tank and diaphragm compressor is EP grade explosion-proof corrugated pipe, the pipe diameter is 4-6mm, the connecting pipe between integrated valve box and roots pump, turbo molecular pump and vacuum pumping group is flexible corrugated pipe, the pipe diameter is 10-16mm;

[0026] Stainless steel EP pipe is used in the high-pressure gas pipeline in the inner circulation pipeline of the dilution refrigerator, and the inner diameter varies with the temperature interval, wherein the pipe diameter is 4-6 mm at a temperature above 40 K, and the pipe diameter is 1-3 mm below 40 K; high-purity laser welding is used to connect the pipeline; copper-nickel alloy EP pipe is used in all high-pressure pipelines below 4 K, including the high-pressure gas pipeline of the JT heat exchanger, the high-pressure gas pipeline of the evaporation chamber, the gas pipeline of the continuous heat exchanger and the gas pipeline of the separated heat exchanger, and the connection pipe of the pipe itself and the components, and the pipe diameter is 1-3 mm; high-purity vacuum brazing technology is used to connect the pipeline; copper-nickel alloy EP pipe is used in the low-pressure pipeline of the continuous heat exchanger and the separated heat exchanger and the connection pipe of the components, and the pipe diameter is 4-6 mm; high-purity vacuum brazing technology is used to connect the pipeline; the pipe diameter of the first-stage low-pressure gas pipeline, the second-stage low-pressure gas pipeline and the low-pressure gas pipeline of the JT heat exchanger varies with the temperature interval, and all the pipes are EP-grade flexible bellows with gold wire sealing at both ends;

[0027] The high-pressure outer pipe between the inner circulation pipeline of the dilution refrigerator and the integrated valve box is an EP-grade explosion-proof bellows with a diameter of 4-6 mm, and the low-pressure outer pipe is an EP-grade high-flexibility bellows with a diameter of 100-160 mm; the integrated valve box comprises a valve cover, a valve body and electromagnetic valves V1-V19, wherein the valve cover and the valve body are made of stainless steel material, and reserved through holes are provided to ensure smooth connection of the gas pipelines; the electromagnetic valves V1-V19 are controlled to be opened and closed by a program, and simultaneously comprise a manual cut-off switch, which can be manually opened and closed in special cases; an opening and closing indicator lamp is embedded in the valve head of the electromagnetic valve;

[0028] In the integrated valve box, the pipe diameter of the low-pressure gas pipeline between valves is 10-16 mm, and the pipe diameter of the high-pressure gas pipeline between valves is 4-6 mm; the diameters of the inlet and outlet of the electromagnetic valve are related to the pressure at the valve position; the connecting pipe between the integrated valve box and the liquid nitrogen cold trap, the gas buffer tank and the diaphragm compressor is an EP-grade explosion-proof bellows with a diameter of 4-6 mm; the connecting pipe between the integrated valve box and the Roots pump, the turbo molecular pump and the vacuum pumping pump group is a flexible bellows connecting pipe with a diameter of 10-16 mm; and all the components are connected to form a multifunctional integrated gas control system for the dilution refrigerator.

[0029] Technical effects and advantages of the present application:

[0030] 1. According to the present application, all the valves of the gas control system of the dilution refrigerator are integrated to form an integrated valve group through highly integrated and modular design and multifunctional integrated control, so that the structure is compact, the space is saved, and the layout is clear; through the preset valve logic combination, a single valve box can realize the switching of multiple function modes such as vacuum pumping, pressure leak detection, mixed gas charging, dilution refrigeration cycle operation, shutdown hibernation and system rewarming, which greatly improves the operation convenience, repeatability and safety, and reduces the dependence on the experience of the operator.

[0031] 2、The application optimizes performance through differential flow channel design, adopts pipelines with different pipe diameters and materials according to the physical properties and functional requirements of the mixed working medium in different temperature zones; large-diameter pipelines are used in the room temperature high-vacuum region to increase the flow conductance and improve the pumping efficiency; thin-walled small-diameter stainless steel pipes or copper-nickel alloy EP pipes are used in the low-temperature region to reduce the heat capacity and radial heat leakage; the system's circulating dead volume is effectively reduced, the heat load of the refrigerator cold head is reduced, and thus the ultimate base temperature and refrigeration power are improved.

[0032] 3、The application adopts multi-stage temperature zone adaptive sealing technology, optimizes the sealing scheme at different positions according to the large temperature difference from room temperature to mK temperature zone inside the dilution refrigeration system; detachable VCR interface is used in the room temperature to 40K or above temperature zone to ensure ultra-high vacuum sealing; gold wire sealing structure is used in the low-temperature region to realize absolute airtightness at extremely low temperature; this combined sealing strategy comprehensively guarantees the sealing reliability of the entire system at all working temperatures, fundamentally preventing performance degradation caused by air leakage.

[0033] 4、The application highly centralizes and automates all complex and dispersed gas path operations of the dilution refrigerator, realizes multifunctional integrated control, not only guarantees efficient and stable operation of the refrigerator, but also brings greater improvement in safety, ease of use and maintainability. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is a schematic diagram of the overall structure of the application.

[0035] Figure 2 It is a schematic diagram of the dilution refrigeration inner circulation pipeline of the application.

[0036] Figure 3 It is a schematic diagram of the integrated valve box of the application.

[0037] Figure 4 It is a partial sectional view of the integrated valve box of the application.

[0038] Figure 5 It is a schematic diagram of the electromagnetic valve structure of the application.

[0039] The reference signs are: 1 liquid nitrogen cold trap, 2 gas buffer tank, 3 integrated valve box, 4 dilution refrigeration internal circulation pipeline, 5 pulse tube refrigerator, 6 evaporation chamber, 7 continuous heat exchanger gas path, 8 100mK cold plate, 9 split heat exchanger gas path, 10 mixing chamber gas path, 11 first-stage low-pressure gas path, 12 second-stage low-pressure gas path, 13 4K-above high-pressure gas path, 14 JT heat exchanger high-pressure gas path, 15 JT heat exchanger low-pressure gas path, 16 evaporation chamber high-pressure gas path, 17 valve cover of integrated valve box, 18 valve body of integrated valve box, 19 valve head of electromagnetic valve, P1 diaphragm compressor, P2 Roots pump, P3 turbo molecular pump, P4 vacuum pumping pump group, V1-V19 are electromagnetic valves. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0041] The present application provides a multifunctional integrated gas control system for a dilution refrigerator as shown in Figure 1 The present application provides a multifunctional integrated gas control system for a dilution refrigerator as shown in

[0042] Figure 2 The dilution refrigeration internal circulation pipeline in the present application is shown in the schematic diagram, which comprises a pulse tube refrigerator 5, an evaporation chamber 6, a continuous heat exchanger gas path 7, a 100mK cold plate 8, a split heat exchanger gas path 9, a mixing chamber gas path 10, a first-stage low-pressure gas path 11, a second-stage low-pressure gas path 12, a 4K-above high-pressure gas path 13, a JT heat exchanger high-pressure gas path 14, a JT heat exchanger low-pressure gas path 15, and an evaporation chamber high-pressure gas path 16.

[0043] Figure 3-5, the gas control system is composed of liquid nitrogen cold trap 1, gas buffer tank 2, integrated valve box 3, dilution refrigeration inner loop pipeline 4, diaphragm compressor P1, Roots pump P2, turbo molecular pump P3, vacuum pumping pump group P4; when electromagnetic valve V1, V2, V9, V15, V17, V18, V19 is opened, V3, V4 is opened with Roots pump P2 when the back pressure of Roots pump P2 is less than 1.5bar, V10 is intermittently opened and closed, and other valves are closed, the dilution refrigeration system starts initial cooling, and all gas paths are cooled from pulse tube refrigerator 5;

[0044] When electromagnetic valve V3, V4, V5, V6, V9, V15, V17, V18, V19 is opened, V1, V2 is closed with diaphragm compressor P1 when the back pressure of diaphragm compressor P1 is less than 1bar, V10 is intermittently opened and closed, and other valves are closed, the dilution refrigeration system starts condensation and liquefaction, and when the liquid level gradually accumulates to evaporation chamber 6, the liquefaction process is completed; subsequently, V10 is closed, the rotating speed of turbo molecular pump P3 is gradually reduced from 825Hz to 600Hz, and the dilution refrigeration system starts to realize dilution effect; it should be ensured that when the temperature of 100mK cold plate 8 is stable, the rotating speed of turbo molecular pump P3 approaches 600Hz;

[0045] When electromagnetic valve V1, V2, V3, V4, V9, V11, V12, V14, V15, V17, V18, V19 is opened, and other valves are closed, the dilution refrigeration system starts to recover temperature and carry out gas recovery. The liquid nitrogen cold trap 1 uses 400-mesh copper wire mesh to make a heat exchanger, which effectively ensures sufficient heat exchange and purification of the gas and preliminarily filters most of the gas impurities; the gas buffer tank 2 is used as the main gas storage container of the gas control system, is externally connected with long-life high-vacuum diaphragm valves, and the double-valve design is conducive to the replacement of the gas after the disassembly of the gas buffer tank 2, so as to ensure that the content of impurity gas in the tank is kept at a very low level;

[0046] The integrated valve box 3 is the control core of the gas control system, and contains valve cover 17, valve body 18 and electromagnetic valves V1-V19. Figure 1 All electromagnetic valves are arranged according to the gas path diagram shown in the figure, wherein V1 and V2 are inlet and outlet valves of diaphragm compressor P1, V3 and V4 are inlet and outlet valves of Roots pump P2, V5 and V6 are inlet and outlet valves of turbo molecular pump P3, V13 is a stop valve of vacuum pumping pump group P4, V10 and V11 are inlet and outlet valves of gas buffer tank 2, V12 and V14 are high and low pressure regulating valves of dilution refrigeration inner loop pipeline 4, V15 and V17 are inlet and outlet valves of liquid nitrogen cold trap 1, V18 and V19 are inlet and outlet valves of dilution refrigeration inner loop pipeline 4, at the same time, in order to facilitate system maintenance and replacement and meet the pressure requirements of the system under different working conditions, electromagnetic valves V7-V9 are used as bypasses of pumps at different levels, and electromagnetic valve V16 is used as a bypass of liquid nitrogen cold trap 1;

[0047] The dilution refrigeration inner loop pipeline 4 mainly includes a first low-pressure gas circuit 11, a 4K-above high-pressure gas circuit 13, a second low-pressure gas circuit 12, a JT heat exchanger high-pressure gas circuit 14, a JT heat exchanger low-pressure gas circuit 15, an evaporation chamber high-pressure gas circuit 16, a continuous heat exchanger gas circuit 7, a separation heat exchanger gas circuit 9 and a mixing chamber gas circuit 10. The interface of the 4K-above high-pressure gas circuit 13 uses a VCR interface to ensure good airtightness, and all the gas circuits below 4K, including the JT heat exchanger high-pressure gas circuit 14, the continuous heat exchanger gas circuit 7, the separation heat exchanger gas circuit 9 and the mixing chamber gas circuit 10, use a gold wire sealing structure to ensure better airtightness. In addition, the electromagnetic valve V18 is connected with a high-pressure gauge and a negative feedback flow regulating valve at the front end in the gas flow direction.

[0048] The liquid nitrogen cold trap 1 is made of stainless steel material for the liquid nitrogen cavity, oxygen-free copper material for the copper wire mesh of the heat exchange condensing deposition cavity, and the structure of the foam copper and the copper wire mesh superimposed combination to ensure the smooth flow of the gas flow. The gas buffer tank 2 is made of aluminum material with surface anodic oxidation, and has a volume of 150L, an internal roughness requirement of RA=0.2 and a tank opening structure connected with double diaphragm valves with good airtightness. The integrated valve box 3 includes a valve cover 17, a valve body 18 and electromagnetic valves V1-V19. The valve cover 17 and the valve body 18 are made of stainless steel material, and the reserved through holes ensure the smooth connection of the gas circuits. The electromagnetic valves V1-V19 are controlled by a program to open and close, and include a manual stop switch, which can be manually opened and closed in special cases. The valve head 19 of the electromagnetic valve is embedded with an opening and closing indicator lamp.

[0049] The 4K-above high-pressure gas path 7 in the dilution refrigeration inner circulation pipeline 4 uses stainless steel EP pipe, and the inner diameter is different with the temperature interval, the pipe diameter is 5mm above 40K, and the pipe diameter is 1.6mm below 40K, high-purity laser welding is used to connect the pipeline, all high-pressure pipelines below 4K, including the JT heat exchanger high-pressure gas path 14, the evaporation chamber high-pressure gas path 16, the continuous heat exchanger gas path 7 and the separation heat exchanger gas path 9, the high-pressure pipelines themselves and the connecting pipes of the components use copper-nickel alloy EP pipe, the pipe diameter is 1.5mm, high-purity vacuum brazing technology is used to connect the pipeline, the low-pressure pipelines of the continuous heat exchanger gas path 7 and the separation heat exchanger gas path 9 and the connecting pipes of the components use copper-nickel alloy EP pipe, the pipe diameter is 6mm, high-purity vacuum brazing technology is used to connect the pipeline, the pipe diameters of the first low-pressure gas path 11, the second low-pressure gas path 12 and the JT heat exchanger low-pressure gas path 15 are changed with the temperature interval, and all are EP level flexible bellows with gold wire sealing at both ends;

[0050] The high-pressure outer pipe between the dilution refrigeration inner circulation pipeline 4 and the integrated valve box 3 is an EP level explosion-proof bellows with a diameter of 6mm, and the low-pressure outer pipe is an EP level high-flexibility bellows with a diameter of 160mm; in the integrated valve box 3, the pipe diameter of the low-pressure gas path valve interconnection pipe is 16mm, the pipe diameter of the high-pressure gas path valve interconnection pipe is 5mm, the diameters of the electromagnetic valve inlet and outlet and the positions of the valves are related to the pressure, the connecting pipes between the integrated valve box 3 and the liquid nitrogen cold trap 1, the gas buffer tank 2 and the diaphragm compressor P1 are EP level explosion-proof bellows with a pipe diameter of 5mm, the connecting pipes between the integrated valve box 4 and the Roots pump P2, the turbo molecular pump P3 and the vacuum pumping pump group P4 are flexible bellows connecting pipes with a pipe diameter of 16mm; the connection between all components forms a multifunctional integrated gas control system for the dilution refrigerator.

[0051] Finally, the following points should be noted: first, in the description of the present application, it should be pointed out that unless otherwise specified and limited, the terms "mounting", "connection" and "connection" should be understood broadly, which can be mechanical connection or electrical connection, or the communication between two elements, or direct connection, "up", "down", "left", "right" and the like are only used to represent the relative positional relationship, when the absolute position of the described object changes, the relative positional relationship may change;

[0052] Secondly: the present application discloses only the structure related to the present application, other structures can refer to the general design, and the same embodiment and different embodiments of the present application can be combined with each other under the condition of no conflict;

[0053] Finally: the above only describes the preferred embodiments of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A multifunctional integrated gas control system for a dilution refrigerator, characterized by: The system comprises a liquid nitrogen cold trap (1), a gas buffer tank (2), an integrated valve box (3), a dilution refrigeration internal circulation pipeline (4), a diaphragm compressor (P1), a Roots pump (P2), a turbomolecular pump (P3) and a vacuum suction pump group (P4), wherein: The liquid nitrogen cold trap (1) uses a copper wire mesh heat exchanger with a large contact area to initially filter out most gas impurities; The gas buffer tank (2) is externally connected to a long-life, high-vacuum diaphragm valve, and the inlet and outlet double valve design is conducive to gas replacement after disassembly and assembly of the gas buffer tank (2), ensuring that the impurity gas content in the tank is kept at an extremely low level; The integrated valve box (3) is the core of the gas control system, including a valve cover (17), a valve body (18) and solenoid valves (V1-V19). The solenoid valves (V7-V9) are used as bypasses for each stage of the pump, and the solenoid valve (V16) is used as a bypass for the liquid nitrogen cold trap (1). The dilution refrigeration internal circulation pipeline (4) includes a primary low-pressure gas circuit (11), a secondary low-pressure gas circuit (12), a 4K or higher high-pressure gas circuit (13), a JT heat exchanger high-pressure gas circuit (14), a JT heat exchanger low-pressure gas circuit (15), an evaporation chamber high-pressure gas circuit (16), a continuous heat exchanger gas circuit (7), a separate heat exchanger gas circuit (9) and a mixing chamber gas circuit (10), and the front end of the solenoid valve (V18) is connected to a high-pressure meter and a negative feedback flow control valve; The diaphragm compressor (P1) provides critical fore-stage circulation power for the entire gas control system; The Roots pump (P2) provides critical foreline pressure for the turbomolecular pump (P3); The turbomolecular pump (P3) provides extremely low pressure for the system at the key node of the dilution refrigeration system; The vacuum suction pump group (P4) uses a large-flow mechanical pump coupled with a molecular pump to build a vacuum environment for the entire system, recover the system temperature and remove impurities, and connect an external helium mass spectrometer leak detector to realize vacuum helium detection of the system and individual components.

2. The multifunctional integrated gas control system for a dilution refrigerator according to claim 1, characterized in that: The V1 and V2 are the inlet and outlet valves of the diaphragm compressor (P1), V3 and V4 are the inlet and outlet valves of the Roots pump (P2), V5 and V6 are the inlet and outlet valves of the turbomolecular pump (P3), V13 is the stop valve of the vacuum suction pump group (P4), V10 and V11 are the inlet and outlet valves of the gas buffer tank (2), V12 and V14 are the high and low pressure regulating valves of the dilution refrigeration internal circulation pipeline (4), V15 and V17 are the inlet and outlet valves of the liquid nitrogen cold trap (1), and V18 and V19 are the inlet and outlet valves of the dilution refrigeration internal circulation pipeline (4).

3. The multifunctional integrated gas control system for a dilution refrigerator according to claim 1, characterized in that: The interface of the high-pressure gas circuit (13) above 4K uses a VCR interface to ensure good airtightness. All gas circuits below 4K include the JT heat exchanger high-pressure gas circuit (14), the continuous heat exchanger gas circuit (7), the separate heat exchanger gas circuit (9) and the mixing chamber gas circuit (10).

4. The multifunctional integrated gas control system for a dilution refrigerator according to claim 1, characterized in that: The liquid nitrogen cold trap (1), the gas buffer tank (2), the integrated valve box (3), the dilution refrigeration internal circulation pipeline (4), the diaphragm compressor (P1), the Roots pump (P2), the turbomolecular pump (P3) and the vacuum suction pump group (P4) are connected through high-clean pipelines of different sizes.

5. A method for manufacturing the multifunctional integrated gas control system for a dilution refrigerator according to any one of claims 1 to 4, characterized in that: The liquid nitrogen cold trap (1) uses stainless steel to make the liquid nitrogen chamber, uses oxygen-free copper to make the copper wire mesh and foam copper block of the heat exchange condensation deposition chamber, and uses a structure in which the foam copper and the copper wire mesh are superimposed to ensure smooth flow of airflow; The gas buffer tank (2) is made of stainless steel or anodized aluminum, with a volume of not less than 120 L and an internal roughness requirement of RA ≤ 0.

4. The tank opening structure connected to the double diaphragm valve should fully ensure airtightness; In the integrated valve box (3), the diameter of the connecting pipe between the low-pressure gas circuit valves is 10-16 mm, the diameter of the connecting pipe between the high-pressure gas circuit valves is 4-6 mm, and the inlet and outlet diameters of the solenoid valves are related to the pressure at the valve location; The integrated valve box (3) includes a valve cover (17), a valve body (18) and a solenoid valve (V1-V19), wherein the valve cover (17) and the valve body (18) are made of stainless steel, and through holes are reserved to ensure smooth connection of the gas paths of each part. The solenoid valves (V1-V19) are all opened and closed by program control and include a manual shut-off switch. The valve head (19) of the solenoid valve is embedded with an opening and closing indicator light.

6. The method for manufacturing a multifunctional integrated gas control system for a dilution refrigerator according to claim 5, characterized in that: The connecting pipes between the integrated valve box (3) and the liquid nitrogen cold trap (1), the gas buffer tank (2) and the diaphragm compressor (P1) are EP-grade explosion-proof bellows with a diameter of 4-6 mm, and the connecting pipes between the integrated valve box (3) and the Roots pump (P2), the turbomolecular pump (P3) and the vacuum suction pump group (P4) are flexible corrugated connecting pipes with a diameter of 10-16 mm.

7. The method for manufacturing a multifunctional integrated gas control system for a dilution refrigerator according to claim 5, characterized in that: The high-pressure gas circuit (13) above 4K in the dilution refrigeration internal circulation pipeline (4) uses a stainless steel EP tube, the inner diameter of which varies with the temperature range. The diameter of the tube in the temperature range above 40K is 4-6mm, and the diameter of the tube below 40K is 1-3mm. High-clean laser welding is used to connect the pipelines. All high-pressure gas circuits below 4K, including the high-pressure gas circuit of the JT heat exchanger (14), the high-pressure gas circuit of the evaporation chamber (16), the high-pressure gas circuit of the continuous heat exchanger (7), the high-pressure gas circuit of the separate heat exchanger (9), and the high-pressure gas circuit of the mixing chamber (10), themselves and the connecting pipes with the components use copper-nickel alloy EP tubes with a diameter of 1-3mm, and are brazed using high-clean vacuum welding. Technical connection pipelines, the low-pressure gas circuits and component connection pipes of the continuous heat exchanger gas circuit (7) and the separate heat exchanger gas circuit (8) use copper-nickel alloy EP tubes with a diameter of 4-6 mm. The high-clean vacuum brazing technology is used to connect the pipelines. The diameters of the first-level low-pressure gas circuit (11), the second-level low-pressure gas circuit (12) and the JT heat exchanger low-pressure gas circuit (15) vary with the temperature zone. They are all EP-grade flexible bellows with gold wire seals at both ends. The high-pressure outer pipe between the dilution refrigeration internal circulation pipe (4) and the integrated valve box (3) is an EP-grade explosion-proof bellows with a diameter of 4-6 mm, and the low-pressure outer pipe is an EP-grade high-flexible bellows with a diameter of 100-160 mm.

8. The method for manufacturing a multifunctional integrated gas control system for a dilution refrigerator according to claim 5, characterized in that: In the integrated valve box (3), the diameter of the connecting pipe between the low-pressure gas circuit valves is 10-16 mm, the diameter of the connecting pipe between the high-pressure gas circuit valves is 4-6 mm, the inlet and outlet diameters of the solenoid valves are related to the pressure at the valve location, the connecting pipes between the integrated valve box (3) and the liquid nitrogen cold trap (1), the gas buffer tank (2) and the diaphragm compressor (P1) are EP-grade explosion-proof bellows with a diameter of 4-6 mm, and the connecting pipes between the integrated valve box (3) and the Roots pump (P2), the turbomolecular pump (P3) and the vacuum suction pump group (P4) are flexible corrugated connecting pipes with a diameter of 10-16 mm.

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