A sub-Kelvin temperature range refrigeration mechanism

Abstract

The present invention discloses a sub-Kelvin temperature range refrigeration mechanism, comprising a pulse tube refrigeration unit, a first pre-cooling heat exchanger, a throttling refrigeration unit, a second pre-cooling heat exchanger, an adsorption refrigeration unit, a third pre-cooling heat exchanger, and a dilution refrigeration unit. The pulse tube refrigeration unit includes a pulse tube refrigeration unit, which is connected to the throttling refrigeration unit via the first pre-cooling heat exchanger to pre-cool the throttling refrigeration unit. The throttling refrigeration unit includes a throttling refrigeration unit, which is connected to the adsorption refrigeration unit via the second pre-cooling heat exchanger to pre-cool the adsorption refrigeration unit. The adsorption refrigeration unit includes an adsorption refrigeration unit, which is connected to the dilution refrigeration unit via the third pre-cooling heat exchanger to pre-cool the dilution refrigeration unit. The dilution refrigeration unit includes a dilution refrigeration unit, which serves as the refrigeration terminal of the sub-Kelvin temperature range refrigeration mechanism. Compared to the prior art, the refrigeration mechanism of the present invention can achieve lower cooling temperatures and greater cooling capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of refrigeration equipment, and in particular to a sub-Kelvin temperature zone refrigeration mechanism. Background Art

[0002] To reduce background noise and improve the signal-to-noise ratio, sensitivity, and resolution of optical detectors such as superconducting quantum interference devices (SQUIDs), superconducting photon detectors (SNSPDs), superconducting terahertz detectors, and millimeter-submillimeter wave detectors, these detectors and their associated optical and electronic equipment often need to operate in sub-Kelvin cryogenic environments. Currently, these cryogenic environments are typically achieved using adiabatic demagnetization refrigerators, adiabatic demagnetization refrigerators, and dilution refrigerators. Summary of the Invention

[0003] The purpose of the present invention is to provide a sub-Kelvin temperature range refrigeration mechanism, which combines a throttling refrigeration unit, a pulse tube refrigeration unit, an adsorption refrigeration unit and a dilution refrigeration unit to improve the refrigeration effect through a multi-stage pre-cooling method.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention discloses a sub-Kelvin temperature zone refrigeration mechanism, comprising a pulse tube refrigeration unit, a first pre-cooling heat exchanger, a throttling refrigeration unit, a second pre-cooling heat exchanger, an adsorption refrigeration unit, a third pre-cooling heat exchanger and a dilution refrigeration unit; the pulse tube refrigeration unit comprises a pulse tube refrigeration part, which is connected to the throttling refrigeration unit through the first pre-cooling heat exchanger to pre-cool the throttling refrigeration unit; the throttling refrigeration unit comprises a throttling refrigeration part, which is connected to the adsorption refrigeration unit through the second pre-cooling heat exchanger to pre-cool the adsorption refrigeration unit; the adsorption refrigeration unit comprises an adsorption refrigeration part, which is connected to the dilution refrigeration unit through the third pre-cooling heat exchanger to pre-cool the dilution refrigeration unit; the dilution refrigeration unit comprises a dilution refrigeration part, which is the refrigeration terminal of the sub-Kelvin temperature zone refrigeration mechanism.

[0006] Preferably, the throttling refrigeration unit includes a throttling compressor, a throttling valve and the throttling refrigeration part, the output end of the throttling compressor is connected to the input end of the throttling valve, the output end of the throttling valve is connected to the input end of the throttling refrigeration part, and the output end of the throttling refrigeration part is connected to the input end of the throttling compressor; the first pre-cooling heat exchanger is located between the throttling compressor and the throttling valve, and is used to cool the gas output by the throttling compressor.

[0007] Preferably, the throttling refrigeration unit further includes a counter-flow heat exchanger, which is located between the throttling compressor and the throttling valve and is used to cool the gas output by the throttling compressor.

[0008] Preferably, the pulse tube refrigeration unit is a two-stage pulse tube refrigeration unit, comprising a first-stage pulse tube phase adjustment component, a pulse tube main drive compressor, a second-stage pulse tube phase adjustment component, a first-stage pulse tube hot end, a second-stage pulse tube hot end, a first-stage pulse tube regenerator, a second-stage pulse tube high-temperature section regenerator, a pulse tube intermediate heat exchanger, a second-stage pulse tube low-temperature section regenerator and the pulse tube refrigeration unit; the output end of the pulse tube main drive compressor is simultaneously connected to the first-stage pulse tube hot end and the second-stage pulse tube hot end; the first-stage pulse phase adjustment component, the first-stage pulse hot end, the second-stage pulse tube hot end, the first-stage pulse tube regenerator, the second-stage pulse tube low-temperature section regenerator and the pulse tube refrigeration unit. The first-level pulse tube regenerator and the pulse tube intermediate heat exchanger are connected in sequence; the second-level pulse tube phase adjustment component, the second-level pulse tube hot end, the second-level pulse tube high-temperature section regenerator, the pulse tube intermediate heat exchanger, the second-level pulse tube low-temperature section regenerator, and the pulse tube refrigeration part are connected in sequence; the first pre-cooling heat exchanger includes a first-level pre-cooling heat exchanger and a second-level first pre-cooling heat exchanger, the first-level pre-cooling heat exchanger is connected to the pulse tube intermediate heat exchanger, and the second-level first pre-cooling heat exchanger is connected to the pulse tube refrigeration part.

[0009] Preferably, the adsorption refrigeration unit is a two-stage adsorption refrigeration unit, including a first-stage adsorption pump, a second-stage adsorption pump, a first-stage evaporator, a second-stage evaporator and the adsorption refrigeration part; the second pre-cooling heat exchanger includes a first-stage second pre-cooling heat exchanger and a second-stage second pre-cooling heat exchanger; the first-stage adsorption pump is connected to the first-stage evaporator through a first-stage pipeline; the second-stage adsorption pump is connected to the second-stage evaporator through a second-stage pipeline; the first-stage second pre-cooling heat exchanger is in contact with the first-stage pipeline, the second-stage pipeline and the throttling refrigeration part for heat exchange at the same time, the second-stage second pre-cooling heat exchanger is in contact with the first-stage evaporator and the second-stage pipeline for heat exchange at the same time, and the adsorption refrigeration part is in contact with the second-stage evaporator.

[0010] Preferably, the dilution refrigeration unit comprises a suction pump, a mixing chamber, a distiller and the dilution refrigeration unit; the input end of the suction pump is connected to the dilution refrigeration unit by a suction pump. 3 The He circulation pipeline is connected to the first output end of the distiller, and the output end of the suction pump is connected to the first output end of the distiller. 3 The He circulation pipeline is connected to the first input end of the mixing chamber, and the output end of the mixing chamber is connected to the first input end of the mixing chamber. 3 He- 4 The He mixed fluid circulation capillary is connected to the input end of the distiller; the second output end of the distiller is connected to the input end of the distiller; 4 The He circulation pipeline is connected to the second input end of the mixing chamber; the dilution refrigeration unit is connected to the mixing chamber; the third pre-cooling heat exchanger is connected to the 3 He- 4He mixed fluid circulation capillary 4.6, 4 He circulation pipeline 4.4, 3 The adsorption refrigeration unit is in contact with the He circulation pipeline 4.2, and the adsorption refrigeration unit is in contact with the third pre-cooling heat exchanger.

[0011] Preferably, the dilution refrigeration unit further comprises a first intermediate heat exchanger, a second intermediate heat exchanger and a third intermediate heat exchanger. 3 The He circulation pipeline passes through the first intermediate heat exchanger, the second intermediate heat exchanger and the third intermediate heat exchanger; the first pre-cooling heat exchanger includes a first-stage first pre-cooling heat exchanger and a second-stage first pre-cooling heat exchanger; the first intermediate heat exchanger is in contact with the first-stage first pre-cooling heat exchanger; the second intermediate heat exchanger is in contact with the second-stage first pre-cooling heat exchanger; the third intermediate heat exchanger is in contact with the throttling refrigeration part.

[0012] Preferably, it also includes a first cold screen, a second cold screen, a third cold screen and an outer shell; the first pre-cooling heat exchanger includes a first-level first pre-cooling heat exchanger and a second-level first pre-cooling heat exchanger; the first cold screen and the throttling refrigeration part form a first closed space, the second cold screen and the second-level first pre-cooling heat exchanger form a second closed space, the third cold screen and the first-level first pre-cooling heat exchanger form a third closed space, and the outer shell forms a fourth closed space; the first closed space, the second closed space, the third closed space and the fourth closed space are nested in sequence from the inside to the outside; the dilution refrigeration part and the adsorption refrigeration part are located in the first closed space; the pulse tube refrigeration part is located in the third closed space and outside the second closed space.

[0013] Preferably, the throttling refrigeration unit is connected to one of the first pre-cooling heat exchangers via a first thermal switch.

[0014] Compared with the prior art, the present invention has achieved the following technical effects:

[0015] The sub-Kelvin temperature range refrigeration mechanism of the present invention utilizes a multi-stage pre-cooling approach, achieving lower refrigeration temperatures and greater cooling capacity compared to direct refrigeration using a single refrigeration unit. Furthermore, because the dilution refrigeration unit terminates the sub-Kelvin temperature range refrigeration mechanism, which operates continuously, it can maintain the dilution refrigeration unit's temperature below 300 mK, or even below 50 mK, for extended periods of time. This provides the sub-Kelvin-level cryogenic environment required for the operation of various equipment, such as aviation detectors and their associated optical and electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 Schematic diagram of the sub-Kelvin temperature range refrigeration mechanism of this embodiment;

[0018] Explanation of reference numerals: 1.1 - throttling compressor; 1.2 - low-pressure pipeline; 1.3 - high-pressure pipeline; 1.4 - primary countercurrent heat exchanger; 1.5 - primary first pre-cooling heat exchanger; 1.6 - secondary countercurrent heat exchanger; 1.7 - secondary first pre-cooling heat exchanger; 1.8 - supporting structure; 1.9 - first thermal switch; 1.10 - throttle valve; 1.11 - tertiary countercurrent heat exchanger; 1.12 - throttling refrigeration unit; 1.13 - first cold screen; 1.14 - second cold screen; 1.15 - third cold screen; 1.16 - housing; 2.1 - primary pulse tube phase adjustment component; 2.2 - pulse tube main drive compressor; 2.3 - secondary pulse tube phase adjustment Phase components; 2.4-First-stage pulse tube hot end; 2.5-Second-stage pulse tube hot end; 2.6-Sealing flange; 2.7-First-stage pulse tube regenerator; 2.8-Second-stage pulse tube high-temperature section regenerator; 2.9-Pulse tube intermediate heat exchanger; 2.10-Second-stage pulse tube low-temperature section regenerator; 2.11-Pulse tube cooling unit; 3.1-First-stage adsorption pump; 3.2-Second-stage adsorption pump; 3.3-Second-stage thermal switch; 3.4-Third-stage thermal switch; 3.5-First-stage second pre-cooling heat exchanger; 3.6-First-stage evaporator; 3.7-Second-stage second pre-cooling heat exchanger; 3.8-Second-stage evaporator; 3.9-Adsorption cooling unit; 4.1-Suction pump; 4.2- 3 He circulation pipeline; 4.3.1-first intermediate heat exchanger; 4.3.2-second intermediate heat exchanger; 4.3.3-third intermediate heat exchanger; 4.4- 4 He circulation pipeline; 4.5-distiller; 4.6- 3 He- 4 He mixed fluid circulation capillary; 4.7-third pre-cooling heat exchanger; 4.8-mixed fluid stop valve; 4.9-fourth thermal switch; 4.10-mixing chamber; 4.11-dilution refrigeration unit. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] The purpose of the present invention is to provide a sub-Kelvin temperature range refrigeration mechanism, which combines a throttling refrigeration unit, a pulse tube refrigeration unit, an adsorption refrigeration unit and a dilution refrigeration unit to improve the refrigeration effect through a multi-stage pre-cooling method.

[0021] To make the above-mentioned objects, features and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. The sub-Kelvin temperature range referred to in this embodiment refers to a temperature range of 5mK to 300mK.

[0022] Reference Figure 1 This embodiment provides a sub-Kelvin temperature range refrigeration mechanism, comprising a pulse tube refrigeration unit, a first pre-cooling heat exchanger, a throttling refrigeration unit, a second pre-cooling heat exchanger, an adsorption refrigeration unit, a third pre-cooling heat exchanger 4.7, and a dilution refrigeration unit. The pulse tube refrigeration unit comprises a pulse tube refrigeration unit 2.11, which is connected to the throttling refrigeration unit via the first pre-cooling heat exchanger to pre-cool the throttling refrigeration unit. The throttling refrigeration unit comprises a throttling refrigeration unit 1.12, which is connected to the adsorption refrigeration unit via the second pre-cooling heat exchanger to pre-cool the adsorption refrigeration unit. The adsorption refrigeration unit comprises an adsorption refrigeration unit 3.9, which is connected to the dilution refrigeration unit via the third pre-cooling heat exchanger 4.7 to pre-cool the dilution refrigeration unit. The dilution refrigeration unit comprises a dilution refrigeration unit 4.11, which serves as the refrigeration terminal of the sub-Kelvin temperature range refrigeration mechanism.

[0023] The sub-Kelvin refrigeration mechanism operates as follows: the pulse tube refrigeration unit (PTU) first operates, bringing PTU refrigeration section 2.11 to a specified temperature range (e.g., 15K to 90K) to pre-cool the throttling refrigeration unit. Next, the throttling refrigeration unit operates, bringing throttling refrigeration section 1.12 to a specified temperature range (e.g., 1.5K to 6K) to pre-cool the adsorption refrigeration unit. Next, the adsorption refrigeration unit operates, bringing adsorption refrigeration section 3.9 to a specified temperature range (e.g., 300mK to 1K) to pre-cool the dilution refrigeration unit. Finally, the dilution refrigeration unit operates, with dilution refrigeration section 4.11 serving as the cooling terminal. The temperature of dilution refrigeration section 4.11 represents the minimum cooling temperature of the sub-Kelvin refrigeration mechanism. Because the sub-Kelvin refrigeration mechanism utilizes a multi-stage pre-cooling approach, it can achieve lower cooling temperatures and greater cooling capacity compared to direct cooling using a single refrigeration unit. In addition, since the end of the sub-Kelvin temperature zone refrigeration mechanism is a dilution refrigeration unit, the refrigeration method of the dilution refrigeration unit is continuous refrigeration, so the temperature of the dilution refrigeration part 4.11 can be maintained below 300mK or even below 50mK for a longer period of time, providing various equipment (such as aviation detectors and their associated optical and electronic equipment) with the sub-Kelvin deep low temperature environment required for their operation.

[0024] Reference Figure 1 As a possible example, a throttling refrigeration unit includes a throttling compressor 1.1, a throttling valve 1.10, and a throttling refrigeration unit 1.12. The output of throttling compressor 1.1 is connected to the input of throttling valve 1.10, the output of throttling valve 1.10 is connected to the input of throttling refrigeration unit 1.12, and the output of throttling refrigeration unit 1.12 is connected to the input of throttling compressor 1.1. A first precooling heat exchanger is located between throttling compressor 1.1 and throttling valve 1.10 and is used to cool the gas output by throttling compressor 1.1.

[0025] After throttling compressor 1.1 compresses helium, it enters throttle valve 1.10 for throttling cooling, achieving the desired cooling temperature and capacity in throttling refrigeration unit 1.12. Before entering throttle valve 1.10, the compressed helium is pre-cooled in a pulse tube cooler 2.11, using the first pre-cooling heat exchanger as an intermediate structure.

[0026] Before the compressed helium enters the throttle valve 1.10, in order to further cool the compressed helium, in this embodiment, the throttling refrigeration unit further includes a countercurrent heat exchanger. The countercurrent heat exchanger is located between the throttling compressor 1.1 and the throttle valve 1.10 and is used to cool the gas output from the throttling compressor 1.1. The number and connection order of the first pre-cooling heat exchanger and the countercurrent heat exchanger can be selected by those skilled in the art as needed. For example, referring to Figure 1, three countercurrent heat exchangers and two first precooling heat exchangers are connected in series. The three countercurrent heat exchangers are the first-stage countercurrent heat exchanger 1.4, the second-stage countercurrent heat exchanger 1.6, and the third-stage countercurrent heat exchanger 1.11. The two first precooling heat exchangers are the first-stage first precooling heat exchanger 1.5 and the second-stage first precooling heat exchanger 1.7. The first-stage first precooling heat exchanger 1.5 is set between the first-stage countercurrent heat exchanger 1.4 and the second-stage countercurrent heat exchanger 1.6, and the second-stage first precooling heat exchanger 1.7 is set between the second-stage countercurrent heat exchanger 1.6 and the third-stage countercurrent heat exchanger 1.11. It can be understood that the pipeline connected to the output end of the throttling compressor 1.1 should be the high-pressure pipeline 1.3, and the pipeline connected to the input end of the throttling compressor 1.1 should be the low-pressure pipeline 1.2. The helium pressure in the high-pressure pipeline 1.3 is greater than the helium pressure in the low-pressure pipeline 1.2.

[0027] Reference Figure 1 As a possible example, the pulse tube cooling unit is a two-stage pulse tube cooling unit, using the same cooling principle as a coaxial pulse tube refrigerator. The pulse tube cooling unit includes a primary pulse tube phase adjustment component 2.1, a pulse tube main drive compressor 2.2, a secondary pulse tube phase adjustment component 2.3, a primary pulse tube hot end 2.4, a secondary pulse tube hot end 2.5, a primary pulse tube regenerator 2.7, a secondary pulse tube high-temperature regenerator 2.8, a pulse tube intermediate heat exchanger 2.9, a secondary pulse tube low-temperature regenerator 2.10, and a pulse tube cooling unit 2.11. The primary and secondary pulse tube phase adjustment components 2.1 and 2.3 can be phase adjustment compressors, used to achieve active phase adjustment in the pulse tube cooling unit. The output of the pulse tube main drive compressor 2.2 is connected to both the primary pulse tube hot end 2.4 and the secondary pulse tube hot end 2.5, driving refrigerant flow through the pulse tube main drive compressor 2.2. The primary pulse tube phase adjustment component 2.1, the primary pulse tube hot end 2.4, the primary pulse tube regenerator 2.7, and the pulse tube intermediate heat exchanger 2.9 are connected in sequence. The secondary pulse tube phase adjustment component 2.3, the secondary pulse tube hot end 2.5, the secondary pulse tube high-temperature segment regenerator 2.8, the pulse tube intermediate heat exchanger 2.9, the secondary pulse tube low-temperature segment regenerator 2.10, and the pulse tube cooling unit 2.11 are connected in sequence. The first precooling heat exchanger includes the primary first precooling heat exchanger 1.5 and the secondary first precooling heat exchanger 1.7. The primary first precooling heat exchanger 1.5 is connected to the pulse tube intermediate heat exchanger 2.9, and the secondary first precooling heat exchanger 1.7 is connected to the pulse tube cooling unit 2.11.

[0028] The minimum temperature of the pulse tube intermediate heat exchanger 2.9 is approximately 60K to 1000K, and is used to precool the primary first precooling heat exchanger 1.5 and the secondary pulse tube low-temperature regenerator 2.10. After the secondary pulse tube low-temperature regenerator 2.10 is precooled, the minimum temperature of the pulse tube cooling section 2.11 is approximately 15K to 20K.

[0029] Reference Figure 1As a possible example, the adsorption refrigeration unit is a two-stage adsorption refrigeration unit, comprising a primary adsorption pump 3.1, a secondary adsorption pump 3.2, a primary evaporator 3.6, a secondary evaporator 3.8, and an adsorption refrigeration unit 3.9. The second pre-cooling heat exchanger comprises a primary second pre-cooling heat exchanger 3.5 and a secondary second pre-cooling heat exchanger 3.7. The primary adsorption pump 3.1 is connected to the primary evaporator 3.6 via a primary pipeline, with refrigerant circulating between the primary adsorption pump 3.1 and the primary evaporator 3.6. The secondary adsorption pump 3.2 is connected to the secondary evaporator 3.8 via a secondary pipeline, with refrigerant circulating between the secondary adsorption pump 3.2 and the secondary evaporator 3.8. The primary second pre-cooling heat exchanger 3.5 simultaneously exchanges heat with the primary pipeline, the secondary pipeline, and the throttling refrigeration unit 1.12. The secondary second pre-cooling heat exchanger 3.7 simultaneously exchanges heat with the primary evaporator 3.6 and the secondary pipeline. The adsorption refrigeration unit 3.9 is in contact with the secondary evaporator 3.8.

[0030] When in use, the throttling refrigeration unit 1.12 precools the first-stage second precooling heat exchanger 3.5, which precools the refrigerant in the first-stage pipeline. The first-stage evaporator 3.6 precools the refrigerant in the second-stage pipeline through the second-stage precooling heat exchanger 3.7.

[0031] Reference Figure 1 As a possible example, the dilution refrigeration unit includes a suction pump 4.1, a mixing chamber 4.10, a distiller 4.5 and a dilution refrigeration unit 4.11. The input end of the suction pump 4.1 is connected to the dilution refrigeration unit 4.11. 3 The He circulation pipeline 4.2 is connected to the first output end of the distiller 4.5, and the output end of the suction pump 4.1 is connected to the first output end of the distiller 4.5. 3 The He circulation pipe 4.2 is connected to the first input end of the mixing chamber 4.10, and the output end of the mixing chamber 4.10 is connected to the first input end of the mixing chamber 4.10. 3 He- 4 The He mixed fluid circulation capillary 4.6 is connected to the input end of the distiller 4.5. 3 He- 4 A mixed fluid stop valve 4.8 is installed on the He mixed fluid circulation capillary 4.6. The second output end of the distiller 4.5 is connected to the distiller 4.5. 4 The He circulation pipe 4.4 is connected to the second input end of the mixing chamber 4.10. The dilution refrigeration unit 4.11 is connected to the mixing chamber 4.10. The third pre-cooling heat exchanger 4.7 is also connected to the 3He-4He mixed fluid circulation capillary 4.6, 4 He circulation pipeline 4.4, 3 The He circulation pipeline 4.2 is in contact with the adsorption refrigeration unit 3.9 and the third pre-cooling heat exchanger 4.7.

[0032] 3 He, 4 When the He mixture is above 860mK, the liquid3 He can be dissolved in liquid at any ratio. 4 However, when the temperature of the mixed solution drops below 860mK, the mixed solution separates into two phases, one of which contains 3 The phase with more He is called concentrated phase, and the phase with 3 The phase with less He is called dilute phase. 3 He is concentrated phase. Adsorption refrigeration unit 3.9 uses 3 He- 4 The He mixed fluid circulates to cool the fluid in the capillary 4.6, thereby keeping the temperature of the distiller 4.5 below 860 mK. 3 The saturated vapor pressure of He is much higher than 4 The saturated vapor pressure of He, in distiller 4.5 3 He is pumped away by the suction pump 4.1. 3 He vaporizes and absorbs heat. In order to maintain the two-phase equilibrium, the 3 He atoms pass through 3 He- 4 He mixed fluid circulates through capillary 4.6 and enters distiller 4.5, while the 3 He is condensed and then replenished into the concentrated phase in the mixing chamber 4.10 to form a cycle. 3 He releases heat during the condensation process, which can be transferred to the adsorption refrigeration unit 3.9 to maintain 3 At the same time, the temperature in the distiller 4.5 4 He passed 4 He is pumped into the mixing chamber 4.10 by a suction pump, and then the 4 He atoms pass through 3 He- 4 The He mixed fluid circulates through the capillary 4.6 and enters the distiller 4.5, completing the system. 4 He's cycle.

[0033] Reference Figure 1 In this embodiment, the dilution refrigeration unit further includes a first intermediate heat exchanger 4.3.1, a second intermediate heat exchanger 4.3.2 and a third intermediate heat exchanger 4.3.3. 3He circulation pipeline 4.2 passes through the first intermediate heat exchanger 4.3.1, the second intermediate heat exchanger 4.3.2, and the third intermediate heat exchanger 4.3.3. The first pre-cooling heat exchanger includes the first-stage first pre-cooling heat exchanger 1.5 and the second-stage first pre-cooling heat exchanger 1.7. The first intermediate heat exchanger 4.3.1 is in contact with the first-stage first pre-cooling heat exchanger 1.5. The second intermediate heat exchanger 4.3.2 is in contact with the second-stage first pre-cooling heat exchanger 1.7. The third intermediate heat exchanger 4.3.3 is in contact with the throttling refrigeration unit 1.12. The first intermediate heat exchanger 4.3.1, the second intermediate heat exchanger 4.3.2, and the third intermediate heat exchanger 4.3.3 obtain low temperatures through the first-stage first pre-cooling heat exchanger 1.5, the second-stage first pre-cooling heat exchanger 1.7, and the throttling refrigeration unit 1.12, respectively, and make 3 He circulation line 4.2 3 He cools down.

[0034] Reference Figure 1 As a possible example, the sub-Kelvin temperature range refrigeration mechanism further includes a first cold shield 1.13, a second cold shield 1.14, a third cold shield 1.15, and an outer shell 1.16. The first pre-cooling heat exchanger includes a first-stage first pre-cooling heat exchanger 1.5 and a second-stage first pre-cooling heat exchanger 1.7. The first cold shield 1.13 and the throttling refrigeration unit 1.12 form a first enclosed space, the second cold shield 1.14 and the second-stage first pre-cooling heat exchanger 1.7 form a second enclosed space, the third cold shield 1.15 and the first-stage first pre-cooling heat exchanger 1.5 form a third enclosed space, and the outer shell 1.16 forms a fourth enclosed space. The first, second, third, and fourth enclosed spaces are nested in sequence from the inside out. The dilution refrigeration unit 4.11 and the adsorption refrigeration unit 3.9 are located within the first enclosed space. The pulse tube refrigeration unit 2.11 is located within the third enclosed space and outside the second enclosed space. A supporting structure is provided between the secondary first pre-cooling heat exchanger and the throttling refrigeration part, and two ends of the supporting structure are fixedly connected to the secondary first pre-cooling heat exchanger and the throttling refrigeration part respectively.

[0035] The first, second and third cold screens are made of materials with good thermal conductivity, preferably oxygen-free copper in this embodiment. For example, when the temperature of the first enclosed space drops, the temperature of the first cold screen 1.13 outside it can drop quickly, thereby reducing the cooling consumption in the first enclosed space. The outer shell 1.16 and the third cold screen 1.15 are used to form a vacuum environment through vacuuming (the vacuum degree is maintained at 10 -4 Pa or higher) to limit gas flow and heat transfer, thereby reducing the impact of gas convection on the cooling effect. In this embodiment, housing 1.16 is preferably made of stainless steel, which has weaker thermal conductivity than oxygen-free copper. This can reduce the loss of cold energy within the fourth enclosed space to the outside through housing 1.16.

[0036] In this embodiment, the pulse tube cooling unit further includes a sealing flange 2.6, which is fixedly connected to the primary pulse tube regenerator 2.7, the secondary pulse tube high-temperature segment regenerator 2.8, and the housing 1.16. The primary pulse tube hot end 2.4 and the secondary pulse tube hot end 2.5 are both located outside the fourth enclosed space. The primary pulse tube regenerator 2.7 and the secondary pulse tube high-temperature segment regenerator 2.8 are located within the fourth enclosed space and outside the third enclosed space.

[0037] Reference Figure 1 As a possible example, the throttling refrigeration unit 1.12 is connected to the secondary first pre-cooling heat exchanger 1.7 via a first thermal switch 1.9. The primary adsorption pump 3.1 is connected to the throttling refrigeration unit 1.12 via a second thermal switch 3.3. The secondary adsorption pump 3.2 is connected to the throttling refrigeration unit 1.12 via a third thermal switch 3.4. The adsorption refrigeration unit 3.9 is connected to the mixing chamber 4.10 via a fourth thermal switch 4.9. In this embodiment, the first thermal switch 1.9, the second thermal switch 3.3, the third thermal switch 3.4, and the fourth thermal switch 4.9 are all air-gap thermal switches.

[0038] The thermal switch has a low thermal resistance when on and a high thermal resistance when off. When the temperature of the throttling refrigeration unit 1.12 rises to a certain level, the first thermal switch 1.9 turns on, allowing the secondary first pre-cooling heat exchanger 1.7 to cool the throttling refrigeration unit 1.12. When the temperature of the throttling refrigeration unit 1.12 drops to a certain level, the first thermal switch 1.9 turns off. Similarly, when the temperature of the primary adsorption pump 3.1 rises to a certain level, the second thermal switch 3.3 turns on, allowing the throttling refrigeration unit 1.12 to cool the primary adsorption pump 3.1. When the temperature of the primary adsorption pump 3.1 drops to a certain level, the second thermal switch 3.3 turns off. When the temperature of the secondary adsorption pump 3.2 rises to a certain level, the third thermal switch 3.4 turns on, allowing the throttling refrigeration unit 1.12 to cool the secondary adsorption pump 3.2. When the temperature of the secondary adsorption pump 3.2 drops to a certain level, the third thermal switch 3.4 turns off. When the temperature of the mixing chamber 4.10 rises to a certain level, the fourth thermal switch 4.9 is turned on, causing the adsorption refrigeration unit 3.9 to cool the mixing chamber 4.10; when the temperature of the mixing chamber 4.10 drops to a certain level, the third thermal switch 3.4 is turned off.

[0039] The adsorption capacity of the adsorbent material (e.g., activated carbon) in the primary adsorption pump 3.1 and the secondary adsorption pump 3.2 for refrigerant (e.g., helium) increases as the temperature decreases. When the second thermal switch 3.3 is on, the temperature of the primary adsorption pump 3.1 drops, and the adsorption capacity of the adsorbent material within it increases. The condensed refrigerant in the primary evaporator 3.6 evaporates and absorbs heat, cooling the secondary second pre-cooling heat exchanger 3.7. This, in turn, cools the refrigerant in the secondary pipeline connected to the secondary second pre-cooling heat exchanger 3.7, further lowering the temperature of the secondary evaporator 3.8. When the third thermal switch 3.4 is on, the temperature of the secondary adsorption pump 3.2 drops, and the adsorption capacity of the adsorbent material within it increases. The condensed refrigerant in the secondary evaporator 3.8 evaporates and absorbs heat, cooling the secondary evaporator 3.8.

[0040] This specification uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A sub-Kelvin temperature range refrigeration mechanism, characterized in that: The invention comprises a pulse tube refrigeration unit, a first pre-cooling heat exchanger, a throttling refrigeration unit, a second pre-cooling heat exchanger, an adsorption refrigeration unit, a third pre-cooling heat exchanger and a dilution refrigeration unit; the pulse tube refrigeration unit comprises a pulse tube refrigeration part, which is connected to the throttling refrigeration unit through the first pre-cooling heat exchanger to pre-cool the throttling refrigeration unit; the throttling refrigeration unit comprises a throttling refrigeration part, which is connected to the adsorption refrigeration unit through the second pre-cooling heat exchanger to pre-cool the adsorption refrigeration unit; the adsorption refrigeration unit comprises an adsorption refrigeration part, which is connected to the dilution refrigeration unit through the third pre-cooling heat exchanger to pre-cool the dilution refrigeration unit; the dilution refrigeration unit comprises a dilution refrigeration part, which is the refrigeration terminal of the sub-Kelvin temperature zone refrigeration mechanism; The adsorption refrigeration unit is a two-stage adsorption refrigeration unit, comprising a primary adsorption pump, a secondary adsorption pump, a primary evaporator, a secondary evaporator, and the adsorption refrigeration part; the second pre-cooling heat exchanger comprises a primary second pre-cooling heat exchanger and a secondary second pre-cooling heat exchanger; the primary adsorption pump is connected to the primary evaporator via a primary pipeline; the secondary adsorption pump is connected to the secondary evaporator via a secondary pipeline; the primary second pre-cooling heat exchanger is in contact with the primary pipeline, the secondary pipeline, and the throttling refrigeration part at the same time for heat exchange, the secondary second pre-cooling heat exchanger is in contact with the primary evaporator and the secondary pipeline at the same time for heat exchange, and the adsorption refrigeration part is in contact with the secondary evaporator; The dilution refrigeration unit includes a suction pump, a mixing chamber, a distiller and the dilution refrigeration unit; the input end of the suction pump is connected to the dilution refrigeration unit. 3 The He circulation pipeline is connected to the first output end of the distiller, and the output end of the suction pump is connected to the first output end of the distiller. 3 The He circulation pipeline is connected to the first input end of the mixing chamber, and the output end of the mixing chamber is connected to the first input end of the mixing chamber. 3 He- 4 The He mixed fluid circulation capillary is connected to the input end of the distiller; the second output end of the distiller is connected to the input end of the distiller; 4 The He circulation pipeline is connected to the second input end of the mixing chamber; the dilution refrigeration unit is connected to the mixing chamber; the third pre-cooling heat exchanger is connected to the 3 He- 4 He mixed fluid circulation capillary 4.6, 4 He circulation pipeline 4.4, 3 The He circulation pipeline 4.2 is in contact with the adsorption refrigeration unit and the third pre-cooling heat exchanger; The dilution refrigeration unit further comprises a first intermediate heat exchanger, a second intermediate heat exchanger and a third intermediate heat exchanger. 3 The He circulation pipeline passes through the first intermediate heat exchanger, the second intermediate heat exchanger, and the third intermediate heat exchanger; the first pre-cooling heat exchanger includes a first-stage first pre-cooling heat exchanger and a second-stage first pre-cooling heat exchanger; the first intermediate heat exchanger is in contact with the first-stage first pre-cooling heat exchanger; the second intermediate heat exchanger is in contact with the second-stage first pre-cooling heat exchanger; and the third intermediate heat exchanger is in contact with the throttling refrigeration unit; The sub-Kelvin temperature zone refrigeration mechanism further includes a first cold screen, a second cold screen, a third cold screen and an outer shell; the first pre-cooling heat exchanger includes a first-stage first pre-cooling heat exchanger and a second-stage first pre-cooling heat exchanger; the first cold screen and the throttling refrigeration unit form a first closed space, the second cold screen and the second-stage first pre-cooling heat exchanger form a second closed space, the third cold screen and the first-stage first pre-cooling heat exchanger form a third closed space, and the outer shell forms a fourth closed space; the first closed space, the second closed space, the third closed space and the fourth closed space are nested in sequence from the inside to the outside; the dilution refrigeration unit and the adsorption refrigeration unit are located in the first closed space; the pulse tube refrigeration unit is located in the third closed space and outside the second closed space; The throttling refrigeration part is connected to the secondary first pre-cooling heat exchanger through a first thermal switch; the primary adsorption pump is connected to the throttling refrigeration part through a second thermal switch; the secondary adsorption pump is connected to the throttling refrigeration part through a third thermal switch; the adsorption refrigeration part is connected to the mixing chamber through a fourth thermal switch.

2. The sub-Kelvin temperature range refrigeration mechanism according to claim 1, characterized in that: The throttling refrigeration unit includes a throttling compressor, a throttling valve and the throttling refrigeration part, the output end of the throttling compressor is connected to the input end of the throttling valve, the output end of the throttling valve is connected to the input end of the throttling refrigeration part, and the output end of the throttling refrigeration part is connected to the input end of the throttling compressor; the first pre-cooling heat exchanger is located between the throttling compressor and the throttling valve, and is used to cool the gas output by the throttling compressor.

3. The sub-Kelvin temperature range refrigeration mechanism according to claim 2, characterized in that: The throttling refrigeration unit further includes a counter-flow heat exchanger, which is located between the throttling compressor and the throttling valve and is used to cool the gas output by the throttling compressor.

4. The sub-Kelvin temperature range refrigeration mechanism according to claim 1, characterized in that: The pulse tube refrigeration unit is a two-stage pulse tube refrigeration unit, including a first-stage pulse tube phase adjustment component, a pulse tube main drive compressor, a second-stage pulse tube phase adjustment component, a first-stage pulse tube hot end, a second-stage pulse tube hot end, a first-stage pulse tube regenerator, a second-stage pulse tube high-temperature section regenerator, a pulse tube intermediate heat exchanger, a second-stage pulse tube low-temperature section regenerator and the pulse tube refrigeration unit; the output end of the pulse tube main drive compressor is connected to the first-stage pulse tube hot end and the second-stage pulse tube hot end at the same time; the first-stage pulse phase adjustment component, the first-stage pulse hot end, the first-stage pulse tube The first-stage pulse tube regenerator and the pulse tube intermediate heat exchanger are connected in sequence; the second-stage pulse tube phase adjustment component, the second-stage pulse tube hot end, the second-stage pulse tube high-temperature section regenerator, the pulse tube intermediate heat exchanger, the second-stage pulse tube low-temperature section regenerator, and the pulse tube refrigeration part are connected in sequence; the first pre-cooling heat exchanger includes a first-stage pre-cooling heat exchanger and a second-stage first pre-cooling heat exchanger, the first-stage first pre-cooling heat exchanger is connected to the pulse tube intermediate heat exchanger, and the second-stage first pre-cooling heat exchanger is connected to the pulse tube refrigeration part.

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