CN219829147U - Large-cooling-capacity dilution refrigeration system for liquid helium closed-cycle precooling - Google Patents

Abstract

The utility model provides a large-cooling-capacity dilution refrigeration system for liquid helium closed-cycle precooling, which comprises a precooling module and a dilution refrigeration module, wherein the precooling module comprises a liquid helium inlet and a liquid helium outlet: the precooling module comprises a helium liquefier, a thermostat and a helium recovery mechanism, wherein a primary cold screen is arranged in the thermostat, a secondary cold screen is arranged in the primary cold screen, a tertiary cold screen is arranged in the secondary cold screen, and openings of the cold screens are respectively provided with a cold plate at each level; two (II)A liquid helium pool is arranged between the stage cooling plate and the third stage cooling plate, and an overflow liquid helium pool is arranged below the third stage cooling plate; the dilution refrigeration module comprises a distillation chamber, a double-pipe heat exchanger, a step heat exchanger, a mixing chamber, an air outlet pipe, a dilution refrigeration external circulation system, an air inlet pipe and a heat exchange heat sink; the four-stage cold screen is arranged in the three-stage cold screen, and a four-stage cold plate is arranged on an opening of the four-stage cold screen. The liquid helium closed circulation provides sufficient pre-cooling conditions for the large-cooling-capacity dilution refrigeration module, so that the pre-cooling conditions can be improved ³ He working medium flow rate to improve the refrigerating capacity of the dilution refrigerator.

Description

Large cooling capacity dilution refrigeration system with liquid helium closed cycle precooling

Technical field

The utility model relates to the technical field of ultra-low temperature refrigeration, and in particular to a large cooling capacity dilution refrigeration system with liquid helium closed cycle pre-cooling.

Background technique

With the rapid development of quantum computing, the number of qubits continues to increase, and dilution refrigerators with larger cooling capacity are needed to meet the cooling capacity requirements of quantum computing. Increasing the cooling capacity of the dilution refrigeration machine requires increasing the precooling capacity of the dilution refrigeration front-stage precooling system.

Currently, dilution refrigerators with small cooling capacity use dry refrigerators such as GM refrigerators to provide pre-cooling in temperature zones above 4K. As the cooling capacity of the dilution refrigerator increases, the precooling capacity also needs to increase. Using a parallel structure of multiple GM refrigerators will cause disadvantages such as large system volume, vibration interference, and high energy consumption. And the current dry dilution refrigerator uses a GM refrigerator as the front-stage pre-cooling system. This structure cannot significantly increase the cooling capacity and has poor scalability.

Therefore, there is an urgent need for a large cooling capacity dilution refrigeration system with liquid helium closed cycle precooling that can solve the above problems.

Utility model content

The utility model provides a large cooling capacity dilution refrigeration system with liquid helium closed cycle precooling. The liquid helium closed cycle provides sufficient precooling conditions for the large cooling capacity dilution refrigeration module, thereby increasing ^{the 3} He working fluid flow rate. To improve the refrigeration capacity of the dilution refrigerator, it has the advantages of compact structure and scalability.

The utility model provides a large cooling capacity dilution refrigeration system with liquid helium closed cycle precooling, which includes a precooling module and a dilution refrigeration module:

The pre-cooling module includes a helium liquefier, a thermostat and a helium recovery mechanism. The thermostat is equipped with a first-level cold screen. The first-level cold screen is equipped with a second-level cold screen. The second-level cold screen is equipped with a helium liquefier. A three-level cold screen is provided, a first-level cold plate is provided on the first-level cold screen, a second-level cold plate is provided on the second-level cold screen, and a third-level cold plate is provided on the third-level cold screen; A liquid helium pool is provided between the secondary cold plate and the third-level cold plate, and a superfluid liquid helium pool is provided below the third-level cold plate; the helium liquefier and the liquid helium pool are connected through pipelines. The liquid helium pool and the superfluid liquid helium pool are connected through pipelines, and the helium recovery mechanism is used to recover the helium evaporated from the liquid helium pool and the superfluid liquid helium pool to the helium liquefaction in the vessel;

The dilution refrigeration module includes a distillation chamber, a sleeve-type heat exchanger, a stepped heat exchanger, a mixing chamber, an air outlet pipe, a dilution refrigeration external circulation system and an air inlet pipe. The distillation chamber, the sleeve-type heat exchanger , the stepped heat exchanger and the mixing chamber are connected in sequence, the air outlet pipe, the dilution refrigeration external circulation system, and the air inlet pipe are connected in sequence, and one end of the air inlet pipe is exchanged with the sleeve type heat exchanger The outlet pipe is connected to the inlet of the device, one end of the gas outlet pipe is connected to the distillation chamber, and also includes the first-level cold plate, the second-level cold plate, the third-level cold plate and the fourth-level cold plate respectively. There are heat exchange heat sinks on the air intake pipe, and all of the heat exchange heat sinks can exchange heat with the air inlet pipe;

It also includes a fourth-level cold screen, the fourth-level cold screen is arranged in the three-level cold screen, the opening of the fourth-level cold screen is provided with a fourth-level cold plate, and the distillation chamber is arranged in the fourth-level cold screen. On the plate, the sleeve-type heat exchanger, the step-type heat exchanger and the mixing chamber are all arranged in the four-stage cold screen.

According to the large cooling capacity dilution refrigeration system for liquid helium closed cycle precooling provided by the utility model, the helium recovery mechanism includes a first recovery branch pipe and a second recovery branch pipe, and the first recovery branch pipe is located in the liquid helium pool. , the second recovery branch pipe is located in the superfluid liquid helium pool.

According to the large cooling capacity dilution refrigeration system for liquid helium closed cycle precooling provided by the utility model, a vacuum pump is provided on the second recovery branch pipe.

According to the large cooling capacity dilution refrigeration system for liquid helium closed cycle precooling provided by the utility model, the air inlet pipe is wound around each of the heat exchange heat sinks.

According to the large cooling capacity dilution refrigeration system for liquid helium closed cycle precooling provided by the utility model, a valve for regulating the flow rate of liquid helium is provided on the pipeline connecting the liquid helium pool and the superfluid liquid helium pool.

According to the liquid helium closed cycle precooling large cooling capacity dilution refrigeration system provided by the present utility model, it also includes an adjusting rod for adjusting the valve, and the end of the adjusting rod is arranged outside the thermostat.

According to the large cooling capacity dilution refrigeration system for liquid helium closed cycle precooling provided by the utility model, the liquid helium pool is arranged on the lower surface of the secondary cold plate, and the superfluid liquid helium pool is arranged on the third level of the cold plate. on the lower surface of the cold plate.

The large cooling capacity dilution refrigeration system for liquid helium closed cycle precooling provided by the present utility model also includes a vacuum evacuation device for evacuation in the thermostat.

The liquid helium closed cycle pre-cooled large cooling capacity dilution refrigeration system provided by the utility model includes a pre-cooling module and a dilution refrigeration module. The three-stage cooling in the pre-cooling module can provide sufficient pre-cooling conditions for the dilution refrigeration module. The first-level cold plate is pre-cooled by the cold energy of ⁴ He steam, the second-level cold plate is pre-cooled by the evaporation latent heat of ⁴ He in the liquid ammonia pool, and the third-level cold plate is pre-cooled by the evaporation latent heat of ⁴ He in the superfluid ammonia liquid pool; The dilution refrigeration module then reduces the temperature to the set value, and the helium recovery mechanism can recover the evaporated helium into the helium liquefier and repeatedly pass it into the liquid helium pool to form a liquid helium closed cycle structure, thus improving the liquid helium The circulation flow can increase the pre-cooling capacity and realize large-capacity dilution refrigeration systems with different refrigeration performance. In addition, placing the larger helium liquefier outside the thermostat also has the advantages of centralized refrigeration, low energy consumption, and small vibration interference.

Description of the drawings

In order to explain the technical solutions of the present invention or the prior art more clearly, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are: For some embodiments of the present invention, those of ordinary skill in the art can also obtain other drawings based on these drawings without exerting creative efforts.

Figure 1 is a schematic diagram of an embodiment of a liquid helium closed cycle pre-cooling large cooling capacity dilution refrigeration system provided by the present invention.

Reference signs:

1. Helium liquefier; 2. Thermostat; 3. First-level cold screen; 4. Second-level cold screen; 5. Third-level cold screen; 6. First-level cold plate; 7. Second-level cold plate; 8. Third-level Cold plate; 9. Liquid helium pool; 10. Superfluid liquid helium pool; 11. Distillation chamber; 12. Jacketed heat exchanger; 13. Stepped heat exchanger; 14. Mixing chamber; 15. Outlet pipe; 16 , Dilution refrigeration external circulation system; 17. Air inlet pipe; 18. Heat exchange heat sink; 19. Four-stage cold screen; 20. Four-stage cold plate; 21. First recovery branch pipe; 22. Second recovery branch pipe; 23. Vacuum pump ; 24. Valve; 25. Adjustment lever.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present utility model clearer, the technical solutions in the present utility model will be clearly and completely described below in conjunction with the drawings of the present utility model. Obviously, the described embodiments are the embodiments of the present utility model. Some, not all, of the new embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present utility model.

In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "horizontal", "upper", "lower", "front", "back", "left", "right" ", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of description The embodiments and simplified descriptions of the present invention do not indicate or imply that the devices or components mentioned must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as limitations to the embodiments of the present invention. Furthermore, the terms “first”, “second” and “third” are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly stated and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection. , or integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood in specific situations.

In the embodiments of the present invention, unless otherwise clearly stated and limited, the first feature "on" or "below" the second feature may be a direct contact between the first and second features, or the first and second features may be in direct contact with each other, or the first and second features may be in direct contact with Indirect contact through intermediaries. Furthermore, the terms "above", "above" and "above" the first feature is above the second feature may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is higher in level than the second feature. "Below", "below" and "beneath" the first feature to the second feature may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature has a smaller horizontal height than the second feature.

In the description of this specification, reference to the terms "one embodiment," "some embodiments," "an example," "specific examples," or "some examples" or the like means that specific features are described in connection with the embodiment or example. , structures, materials or features are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic expressions of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine different embodiments or examples and features of different embodiments or examples described in this specification unless they are inconsistent with each other.

The liquid helium closed cycle precooling large cooling capacity dilution refrigeration system of the present invention will be described below with reference to Figure 1 .

As shown in Figure 1, it is a schematic diagram of an embodiment of a liquid helium closed cycle pre-cooling large cooling capacity dilution refrigeration system provided by the present invention. The liquid helium closed cycle precooling large cooling capacity dilution refrigeration system of this embodiment includes a precooling module and a dilution refrigeration module:

The pre-cooling module includes a helium liquefier 1, a thermostat 2 and a helium recovery mechanism. The thermostat 2 is equipped with a first-level cooling screen 3, the first-level cooling screen 3 is equipped with a secondary cooling screen 4, and the second-level cooling screen 4 is equipped with There are three-level cold screens 5. The first-level cold screen 3 is provided with a first-level cold plate 6. The second-level cold screen 4 is provided with a second-level cold plate 7. The third-level cold screen 5 is provided with a third-level cold plate 8; A liquid helium pool 9 is provided between the cold plate 7 and the third-stage cold plate 8, and a superfluid liquid helium pool 10 is provided below the third-stage cold plate 8; the helium liquefier 1 and the liquid helium pool 9 are connected through pipelines, and the liquid helium pool 9 and the superfluid liquid helium pool 10 are connected through pipelines, and the helium recovery mechanism is used to recover the helium gas evaporated from the liquid helium pool 9 and the superfluid liquid helium pool 10 into the helium liquefier 1;

The dilution refrigeration module includes a distillation chamber 11, a sleeve-type heat exchanger 12, a stepped heat exchanger 13, a mixing chamber 14, an air outlet pipe 15, a dilution refrigeration external circulation system 16 and an air inlet pipe 17. The distillation chamber 11, a sleeve-type heat exchanger Heater 12, stepped heat exchanger 13 and mixing chamber 14 are connected in sequence, air outlet pipe 15, dilution refrigeration external circulation system 16, air inlet pipe 17 are connected in sequence, one end of air inlet pipe 17 is connected to the inlet of sleeve heat exchanger 12 , one end of the outlet pipe 15 is connected to the distillation chamber 11, and also includes heat exchange heat sinks 18 respectively provided on the first-level cold plate 6, the second-level cold plate 7, the third-level cold plate 8 and the fourth-level cold plate 20. All The heat exchange heat sink 18 can exchange heat with the intake pipe 17;

It also includes a fourth-level cold screen 19. The fourth-level cold screen 19 is arranged in the third-level cold screen 5. The opening of the fourth-level cold screen 19 is provided with a fourth-level cold plate 20. The distillation chamber 11 is arranged on the fourth-level cold plate 20. The sleeve-type heat exchanger 12, the stepped heat exchanger 13 and the mixing chamber 14 are all arranged in the four-stage cold screen 19.

Specifically, each heat exchange heat sink 18 located on the first-level cold plate 6, the second-level cold plate 7, the third-level cold plate 8 and the fourth-level cold plate 20 exchanges heat with the corresponding cold plate, and then the heat exchange heat sink 18 communicates with The gas outlet pipe 15 exchanges heat, and since the distillation chamber 11 is connected with the gas outlet pipe 15, the medium in the distillation chamber 11 can indirectly communicate with one of the first-level cold plate 6, the second-level cold plate 7, the third-level cold plate 8 and the fourth-level cold plate 20. heat exchange between. It should be noted that in the embodiment of the present utility model, the heat exchange heat sink 18 is made of copper pillars with excellent thermal conductivity. Each heat exchange heat sink 18 is installed on the first-level cold plate 6, the second-level cold plate 7, and the third-level cold plate. On the first-stage cold plate 8 and the fourth-stage cold plate 20, the installation method of the heat exchange heat sink 18 is not limited in this embodiment. In specific implementation, welding, threaded connection or riveting can be used. The sleeve-type heat exchanger 12 and the step-type heat exchanger 13 are used for heat exchange between dense phase ³ He and dilute phase ³ He- ⁴ He.

The liquid helium closed cycle precooling large cooling capacity dilution refrigeration system provided by the utility model can provide sufficient precooling conditions for the dilution refrigeration module through the three-stage cooling in the precooling module. The first-level cold plate 6 uses ⁴ He steam The second-stage cold plate 7 uses the latent heat of evaporation of ⁴ He in the liquid ammonia pool 9 for pre-cooling, and the third-stage cold plate 8 uses the latent heat of evaporation of ⁴ He in the superfluid ammonia pool 10 for pre-cooling; the dilution refrigeration module then The temperature is lowered to the set value, and the helium recovery mechanism can recover the evaporated helium into the helium liquefier 1 and repeatedly pass it into the liquid helium pool 9 to form a liquid helium closed circulation structure, thereby increasing the liquid helium circulation flow rate It can increase the pre-cooling capacity and realize large-capacity dilution refrigeration system with different refrigeration performance. Cold screens at all levels are set up in a step-by-step nesting manner. The system has a compact structure and strong scalability. In addition, placing the larger helium liquefier 1 outside the thermostat 2 also has the advantages of centralized refrigeration, low energy consumption, and small vibration interference.

In the embodiment of the present invention, the helium recovery mechanism includes a first recovery branch pipe 21 and a second recovery branch pipe 22. The first recovery branch pipe 21 is located in the liquid helium pool 9, and the second recovery branch pipe 22 is located in the superfluid liquid helium pool 10. . Specifically, the inlet ends of the first recovery branch pipe 21 and the second recovery branch pipe 22 are located at the upper parts of the liquid helium pool 9 and the superfluid liquid helium pool 10 respectively, so as to facilitate the recovery of helium in the upper parts of the liquid helium pool 9 and the superfluid liquid helium pool 10 respectively. Gas is recycled.

In the embodiment of the present invention, a vacuum pump 23 is provided on the second recovery branch pipe 22 . The vacuum pump 23 can evacuate the superfluid liquid helium pool 10 so that the superfluid liquid helium pool 10 is in a low-pressure state.

In the embodiment of the present invention, the air outlet pipe 15 is arranged around each heat exchange heat sink 18 . The contact area between the air outlet pipe 15 and the heat exchange heat sink 18 can be effectively increased, and the contact surface between the air outlet pipe 15 and the heat exchange heat sink 18 can be fixed by welding.

In the embodiment of the present invention, a valve 24 for adjusting the flow rate of liquid helium is provided on the pipeline connecting the liquid helium pool 9 and the superfluid liquid helium pool 10 . By setting the valve 24, the connection and closing of the pipeline between the liquid helium pool 9 and the superfluid liquid helium pool 10 can be controlled, and the flow rate of liquid helium can also be adjusted. By adjusting the valve 24, a stable liquid helium flow into the superfluid liquid helium can be maintained. Pool 10 can reach equilibrium with the evaporation rate of superfluid helium. In this embodiment, the valve 24 may be a needle valve.

In the embodiment of the present invention, an adjusting rod 25 for adjusting the valve 24 is also included, and the end of the adjusting rod 25 is arranged outside the thermostat 2 . It is convenient to directly control the valve 24 outside the thermostat 2 and is easy to operate.

In the embodiment of the present invention, the liquid helium pool 9 is arranged on the lower surface of the secondary cold plate 7 , and the superfluid liquid helium pool 10 is arranged on the lower surface of the third-level cold plate 8 . Specifically, in this embodiment, the liquid helium pool 9 and the superfluid liquid helium pool 10 are respectively fixed and installed on the lower surface of the secondary cold plate 7 and the lower surface of the tertiary cold plate 8 through bolts/nails. The liquid helium pool 9 and The open end of the superfluid liquid helium pool 10 is facing the lower surface of the secondary cold plate 7 and the lower surface of the tertiary cold plate 8, so that liquid helium can be used to cool the secondary cold plate 7 and the tertiary cold plate 8.

In the embodiment of the present invention, the large cooling capacity dilution refrigeration system with liquid helium closed cycle precooling also includes a vacuum device for vacuuming the inside of the thermostat 2 . During cooling, a high vacuum environment can be maintained in the thermostat 2 through a vacuum device. In this embodiment, the vacuum pump unit is used as an example for the vacuum pumping device.

The utility model's liquid helium closed cycle pre-cooled large-capacity dilution refrigeration system uses a vacuum device to maintain a high vacuum environment in the thermostat 2; ³ After He enters the thermostat 2, it passes through the first-level cold plate 6 and the second-level cold plate. The first-stage cold plate 7 and the third-stage cold plate 8 are cooled step by step and then enter the dilution refrigeration module for dilution refrigeration. A liquid helium pool 9 is arranged on the lower surface of the secondary cold plate 7, and a superfluid liquid helium pool 10 is arranged on the lower surface of the third-level cold plate 8. The working fluids in the liquid helium pool 9 and the superfluid liquid helium pool 10 are both ⁴ He, the liquid helium pool 9 is in a normal pressure state, and the liquid ⁴ He therein naturally evaporates. The superfluid helium liquid helium pool 9 maintains a low pressure state in the pool through the vacuum pump 23 provided on the second recovery branch pipe 22 . The first-level cold plate 6 maintains a low temperature state by recovering the cold energy of ⁴ He vapor. ^{The 4} He vapor evaporated from the liquid helium pool 9 and the superfluid liquid helium pool 10 passes through the first recovery branch pipe 21 and the second recovery branch pipe 22 in the thermostat 2 respectively. The outside is collected into the same pipeline and re-transported to helium liquefier 1. ⁴ He vapor is re-liquefied in the helium liquefier 1 and then transported back to the liquid helium pool 9 through the pipeline. The liquid helium pool 9 and the superfluid helium pool are connected through a pipeline, and a needle valve is provided on the pipeline for regulating the flow rate of liquid helium between the liquid helium pool 9 and the superfluid liquid helium pool 10 and controlling the passage of the pipeline. Break. ³ After the He gas is cooled to 1.5K by the pre-cooling module, it enters the dilution refrigeration module, where the dilution refrigeration process occurs to achieve millikelvin temperature zone refrigeration.

Among them, the refrigeration principle of the dilution refrigeration module is as follows: When the mixed solution of ³ He and ⁴ He is above 0.86K, in what proportion can liquid ³ He be dissolved in liquid ⁴ He? But when the temperature of the mixed solution drops below 0.86K , the mixed liquid is separated into two phases, the phase containing more ³ He is called the concentrated phase, and the phase containing less ³ He is called the dilute phase. At any temperature below 0.86K, there are dilute phases and concentrated phases corresponding to a certain ³ He content, and phase equilibrium is reached. When ³ He atoms are removed from the dilute phase, in order to maintain the balance of the two phases, ³ He from the concentrated phase enters the dilute phase through the phase interface to replenish the removed ³ He atoms. It can be calculated that the enthalpy and entropy of ³ He in the dilute phase are much greater than in the concentrated phase. So this dilution process needs to absorb heat.

Judging from the schematic diagram of the liquid helium closed cycle pre-cooling large cooling capacity dilution refrigeration system provided by the present utility model, the chamber containing the phase interface is called the mixing chamber 14. ³ He atoms pass from the concentrated phase through the phase interface and enter the dilute phase to be absorbed. Heat and cool, causing the temperature to drop. The chamber containing the free surface of the dilute phase is called distillation chamber 11 and the temperature is maintained at 0.6 to 0.8K. At this time, the saturated vapor pressure of ³ He is much higher than the saturated vapor pressure of ⁴ He, and it can be removed with an air extractor. At this time, ^{the 3} He atoms in the concentrated phase will continuously enter the dilute phase through the phase interface, and ^{the 3} He removed will After condensation, it is replenished into the concentrated phase to form a cycle, so that the dilution refrigeration module runs continuously.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it; although the present utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some of the technical features can be equivalently replaced; and these modifications or substitutions do not deviate from the essence of the corresponding technical solutions from the spirit of the technical solutions of the various embodiments of the present invention. and scope.

Claims (8)

1. A large cooling capacity dilution refrigeration system with liquid helium closed cycle precooling, which is characterized in that it includes a precooling module and a dilution refrigeration module: The pre-cooling module includes a helium liquefier, a thermostat and a helium recovery mechanism. The thermostat is equipped with a first-level cold screen. The first-level cold screen is equipped with a second-level cold screen. The second-level cold screen is equipped with a helium liquefier. A three-level cold screen is provided, a first-level cold plate is provided on the first-level cold screen, a second-level cold plate is provided on the second-level cold screen, and a third-level cold plate is provided on the third-level cold screen; A liquid helium pool is provided between the secondary cold plate and the third-level cold plate, and a superfluid liquid helium pool is provided below the third-level cold plate; the helium liquefier and the liquid helium pool are connected through pipelines. The liquid helium pool and the superfluid liquid helium pool are connected through pipelines, and the helium recovery mechanism is used to recover the helium evaporated from the liquid helium pool and the superfluid liquid helium pool to the helium liquefaction in the vessel; The dilution refrigeration module includes a distillation chamber, a sleeve-type heat exchanger, a stepped heat exchanger, a mixing chamber, an air outlet pipe, a dilution refrigeration external circulation system and an air inlet pipe. The distillation chamber, the sleeve-type heat exchanger , the stepped heat exchanger and the mixing chamber are connected in sequence, the air outlet pipe, the dilution refrigeration external circulation system, and the air inlet pipe are connected in sequence, and one end of the air inlet pipe is exchanged with the sleeve type heat exchanger The outlet pipe is connected to the inlet of the device, one end of the gas outlet pipe is connected to the distillation chamber, and also includes three or more cold plates respectively provided on the first-level cold plate, the second-level cold plate, the third-level cold plate and the fourth-level cold plate. Heat exchange heat sinks, all of the heat exchange heat sinks can exchange heat with the air inlet pipe; It also includes a fourth-level cold screen, the fourth-level cold screen is arranged in the three-level cold screen, the opening of the fourth-level cold screen is provided with a fourth-level cold plate, and the distillation chamber is arranged in the fourth-level cold screen. On the plate, the sleeve-type heat exchanger, the step-type heat exchanger and the mixing chamber are all arranged in the four-stage cold screen. 2. The large cooling capacity dilution refrigeration system with liquid helium closed cycle precooling according to claim 1, characterized in that the helium gas recovery mechanism includes a first recovery branch pipe and a second recovery branch pipe, and the first recovery branch pipe The branch pipe is located in the liquid helium pool, and the second recovery branch pipe is located in the superfluid liquid helium pool. 3. The large cooling capacity dilution refrigeration system with liquid helium closed cycle precooling according to claim 2, characterized in that a vacuum pump is provided on the second recovery branch pipe. 4. The large cooling capacity dilution refrigeration system with liquid helium closed cycle precooling according to claim 1, characterized in that the air inlet pipe is arranged around each of the heat exchange heat sinks. 5. The large cooling capacity dilution refrigeration system with liquid helium closed cycle precooling according to any one of claims 1 to 4, characterized in that, the pipeline connecting the liquid helium pool and the superfluid liquid helium pool There is a valve for regulating the flow of liquid helium. 6. The large-capacity dilution refrigeration system with liquid helium closed cycle precooling according to claim 5, characterized in that it also includes an adjusting rod for adjusting the valve, and the end of the adjusting rod is arranged at the Outside the thermostat. 7. The large cooling capacity dilution refrigeration system for liquid helium closed cycle precooling according to any one of claims 1 to 4, characterized in that the liquid helium pool is arranged on the lower surface of the secondary cold plate, The superfluid liquid helium pool is arranged on the lower surface of the three-stage cold plate. 8. The liquid helium closed cycle pre-cooling large cooling capacity dilution refrigeration system according to any one of claims 1 to 4, characterized in that it further includes a vacuum evacuation device for evacuation in the thermostat.