A liquid helium dewar with high structural strength and low heat leakage

Abstract

The application discloses a high-strength and low-heat-leakage liquid helium Dewar structure, which comprises a vacuum cover, three reinforcing rings are arranged in the vacuum cover, a cold shield is connected with the cold shield through three vertical hangers and three horizontal pull rods, a liquid nitrogen Dewar is arranged above the cold shield, a liquid helium Dewar is arranged in the cold shield and is supported through the three vertical hangers and the three horizontal pull rods, a liquid conveying pipe of the liquid helium Dewar passes through the middle of the cold shield and is welded on the vacuum cover and is in contact with the liquid nitrogen Dewar through a heat sink. The liquid helium Dewar structure can meet the requirements of high structural strength and low heat leakage of the liquid helium Dewar.

Description

TECHNICAL FIELD

[0001] The application relates to the field of liquid helium Dewar, and particularly relates to a liquid helium Dewar with high structural strength and low heat leakage. BACKGROUND

[0002] Some scientific experiments need to be carried out below the liquid helium temperature, and a common method for obtaining the liquid helium temperature is to immerse a scientific sample in a liquid helium container. Liquid helium is generally stored by using a liquid helium Dewar, but the liquid helium temperature is extremely low, the latent heat is small, and the liquid helium is easy to evaporate, so the liquid helium storage time is short, and in some scientific experiments, liquid helium cannot be replenished, and long-time storage of liquid helium is a main factor considered in designing the liquid helium Dewar.

[0003] The liquid helium Dewar is generally composed of a vacuum cover, a cold shield and a liquid helium cavity, and is a structure for long-time storage of low-temperature liquid helium or long-time maintenance of the liquid helium temperature. For example, the liquid helium Dewar disclosed in a patent with the application number CN2020115998552 and the name of a liquid helium Dewar is composed of a vacuum cover, a liquid nitrogen cavity, a liquid nitrogen cold shield, a liquid helium cavity, a vacuum layer, a hanger and a radiation shield. The liquid nitrogen cavity is connected with the liquid nitrogen cold shield, liquid nitrogen is used to provide cold energy for the cold shield, the radiation heat leakage received by the liquid helium cavity is reduced, and the liquid helium storage time can be well increased. However, when the liquid helium Dewar is used in an impact and vibration environment, the hanger structure needs to be improved and strengthened, at this time, the heat conduction of the hanger is greatly increased, and the requirement of long-time storage of liquid helium cannot be met.

[0004] In order to reduce the structural heat leakage, the existing liquid helium Dewar makes the connecting structure between the liquid helium cavity and the cold shield as few as possible, and the connecting structure is in the form of a slender rod. When the liquid helium Dewar is used in an impact and vibration environment, the structures are difficult to meet the use requirement. SUMMARY

[0005] The application provides a liquid helium Dewar which can simultaneously meet the requirements of high structural strength and low heat leakage.

[0006] Technical solution: The high-strength and low-heat leakage liquid helium Dewar structure provided by the application can meet the use requirements of airborne vibration and impact environment, comprising a vacuum cover, a shock absorber, a cold shield, a liquid nitrogen cavity, a liquid helium cavity, a heat sink, a liquid nitrogen cavity liquid conveying pipe and a liquid helium cavity liquid conveying pipe; the cold shield, the liquid nitrogen cavity and the heat sink are located inside the vacuum cover; the liquid helium cavity is located inside the cold shield; the cold shield is located below the liquid nitrogen cavity, and is fixed in the vacuum cover through a plurality of cold shield hangers and a plurality of cold shield pull rods; the bottom surface of the liquid nitrogen cavity is connected with the top of the cold shield, the upper segment of the liquid helium cavity is connected with the inner side of the top of the cold shield through a plurality of liquid helium cavity hangers, and the lower segment of the liquid helium cavity is fixed on the inner side wall of the cold shield through a plurality of liquid helium cavity pull rods; the liquid nitrogen cavity is connected with the liquid nitrogen cavity liquid conveying pipe, the liquid helium cavity is connected with the liquid helium cavity liquid conveying pipe, the liquid nitrogen cavity is axially provided with a middle passage penetrating through the liquid nitrogen cavity from bottom to top, the liquid helium cavity liquid conveying pipe penetrates through the middle passage of the liquid nitrogen cavity and is coaxial with the liquid nitrogen cavity but does not contact the liquid nitrogen cavity, and the liquid helium liquid conveying pipe is connected with the liquid nitrogen cavity above through the heat sink; the bottom of the vacuum cover is provided with a plurality of shock absorbers.

[0007] Preferably, the upper flange of the vacuum cover is provided with a vacuum suction port.

[0008] Preferably, the liquid nitrogen liquid conveying pipe and the liquid nitrogen cavity are connected through a metal bellows.

[0009] Preferably, the liquid helium cavity hanger, the cold shield hanger, the liquid helium cavity pull rod and the cold shield pull rod are made of G10.

[0010] Preferably, the heat sink is an oxygen-free copper solid body.

[0011] Preferably, the liquid helium cavity pull rod and the cold shield pull rod are in a hollow cylindrical structure.

[0012] Preferably, the liquid helium cavity hanger and the cold shield hanger are in a plate structure.

[0013] Preferably, the reinforcing rings in the vacuum cover are distributed at equal intervals.

[0014] Preferably, the liquid helium liquid conveying pipe port is installed at the center of the upper flange of the vacuum cover.

[0015] Preferably, the inner layer of the vacuum cover is provided with a plurality of reinforcing rings.

[0016] Beneficial effects: The application has high structural strength and low heat leakage. The cold shield and the liquid helium cavity are supported by the pull rods and the hangers at the same time, which can meet the structural strength requirements under the airborne impact and vibration. The main material of the pull rods and the hangers is G10, which has very small thermal conductivity at low temperature. The heat sink structure is adopted between the liquid helium liquid conveying pipe and the liquid nitrogen cavity, which greatly reduces the heat leakage of the support structure. The liquid nitrogen cavity body provides cold energy for the cold shield, reduces the radiation heat leakage of the liquid helium cavity body, and the overall heat leakage is small. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 This is a schematic diagram of the structure of the present invention;

[0018] Figure 2 for Figure 1 Enlarged view of area A in the middle;

[0019] Figure 3 This is a schematic diagram of the boom;

[0020] Figure 4 This is a schematic diagram of the pull rod. Detailed Implementation

[0021] like Figures 1-4 As shown, a high-strength, low-heat-leakage liquid helium Dewar includes a vacuum chamber 4. The inner layer of the vacuum chamber 4 is provided with three reinforcing rings 14. The flange on the vacuum chamber 4 is provided with a vacuum extraction port 13, a liquid nitrogen inlet pipe 12, and a liquid helium inlet pipe 9. The liquid nitrogen inlet pipe 12 is connected to the liquid nitrogen chamber 3. The liquid helium inlet pipe 9 passes through the liquid nitrogen chamber 3 and is connected to the liquid helium chamber 1. The liquid helium inlet pipe 9 and the liquid nitrogen chamber 3 are in contact through a heat sink 11. The liquid helium chamber 1 is fixed to the cold screen 2 by three hangers and three tie rods. The cold screen 2 is installed below the liquid nitrogen chamber 3 and is supported on the vacuum chamber 4 by three hangers and three tie rods. The Dewar is mounted on four shock absorbers 5.

[0022] To reduce direct heat conduction when the liquid helium infusion tube 9 is connected to the liquid helium chamber 1, the liquid helium infusion tube 9 is connected to the liquid nitrogen chamber via a heat sink 11 at the furthest point from the liquid helium chamber 1, thereby reducing the heat leakage of the liquid helium infusion tube 9 from 4.2K to 300K to 4.2K to 77K.

[0023] The upper section of the liquid helium chamber 3 is connected to the cold screen 2 by a liquid helium chamber hanger 7, while the lower section of the liquid helium chamber 3 is fixed to the cold screen 2 by a liquid helium chamber tie rod 6, ensuring the stability and safety of the liquid helium chamber in high-impact and high-vibration environments. To reduce heat leakage from the two types of fixed supports, the liquid helium chamber tie rod 6 is made of G10 material, and the middle of the support column is hollowed out while ensuring structural strength to reduce the heat transfer path; the liquid helium chamber hanger 7 is a plate-like structure made of G10 material, and it has also been optimized and cut to reduce the heat leakage path.

[0024] The cold screen 2 and the vacuum chamber 4 are also supported by both tie rods and suspension rods, which ensures the safety and stability of the cold screen in airborne impact and high vibration environments. Furthermore, the cold screen 2 is in contact with the liquid nitrogen chamber 3, and the heat leakage from the radiative heat of the cold screen 2 and the heat leakage from the support structure of the vacuum chamber 4 is compensated by the evaporation of liquid nitrogen.

[0025] The vacuum cover 4 adopts a thin-wall structure plus a reinforcing ring 14, which meets the use environment of airborne impact and vibration, ensures the vacuum sealing requirement, and has little effect on the overall weight. The Dewar is mounted on four shock absorbers 5, and most of the impact and vibration effects are absorbed by the shock absorbers, which greatly reduces the impact of the airborne environment on the liquid helium Dewar body.

[0026] In use, the internal vacuum degree is first extracted to below 10-2 Pa through the vacuum extraction port 13, and the vacuum extraction is continuously maintained for 2 hours. Then the vacuum extraction port 13 is closed, liquid nitrogen is slowly and continuously filled into the liquid nitrogen cavity 3 through the liquid nitrogen filling pipe 12, and after the liquid nitrogen cavity 3 is filled, the filling is stopped, the liquid nitrogen filling pipe 12 is kept open, the liquid nitrogen is naturally evaporated, the liquid helium filling pipe 12 is inserted into the liquid helium filling pipe 9 and reaches the bottom of the liquid helium cavity 1, then slow liquid helium filling is performed, after the liquid helium cavity 1 is filled, the liquid helium filling pipe 9 is pulled out, and the liquid helium filling pipe is kept open, at this time the liquid helium can be stored in the liquid helium Dewar for a long time, and the bottom of the liquid helium Dewar is kept at 4.2K liquid helium temperature.

[0027] When it is needed to lower the temperature inside the liquid helium Dewar to below 4.2K, the vacuum pump is connected to the liquid helium filling pipe 9, a needle valve is installed between the vacuum pump and the liquid helium filling pipe, the vacuum pump is started, the vacuum pump extraction speed is adjusted by adjusting the opening of the needle valve, so that the liquid helium cavity is kept in a negative pressure state, at this time the temperature of the liquid helium cavity can be lower than 4.2K, and can be stably maintained at this temperature.

Claims

1. A high-strength low-heat-leak liquid helium dewar structure, characterized by, The device comprises a vacuum cover (4), a shock absorber (5), a cold shield (2), a liquid nitrogen cavity (3), a liquid helium cavity (1), a heat sink (11), a liquid nitrogen cavity liquid delivery pipe (12), and a liquid helium cavity liquid delivery pipe (9); the cold shield (2), the liquid nitrogen cavity (3), and the heat sink (11) are located inside the vacuum cover (4); the liquid helium cavity (1) is located inside the cold shield (2); the cold shield (2) is fixed in the vacuum cover (4) by a plurality of cold shield hangers (8) and a plurality of cold shield pull rods (10); the bottom surface of the liquid nitrogen cavity (3) is connected to the top of the cold shield (2); the upper section of the liquid helium cavity (1) is connected to the inner side of the top of the cold shield (2) by a plurality of liquid helium cavity hangers (7); the lower section of the liquid helium cavity (1) is fixed to the inner wall of the cold shield (2) by a plurality of liquid helium cavity pull rods (6); the liquid nitrogen cavity (3) is connected to the liquid nitrogen cavity liquid delivery pipe (12); the liquid helium cavity (1) is connected to the liquid helium cavity liquid delivery pipe (9); the liquid nitrogen cavity (3) is provided with a middle passage penetrating the liquid nitrogen cavity (3) from bottom to top; the liquid helium cavity liquid delivery pipe (9) penetrates the middle passage of the liquid nitrogen cavity (3) and is coaxial with the liquid nitrogen cavity (3) but does not contact the liquid nitrogen cavity (3); the liquid helium cavity liquid delivery pipe (9) is connected to the liquid nitrogen cavity (3) above by the heat sink (11); the bottom of the vacuum cover (4) is provided with a plurality of shock absorbers (5).

2. The high-strength, low-heat-leak liquid-helium dewar structure according to claim 1, characterized by, A vacuum suction port (13) is arranged on the upper flange of the vacuum cover (4).

3. The high strength low heat leak liquid helium dewar structure of claim 1, wherein, The liquid nitrogen cavity liquid delivery pipe (12) and the liquid nitrogen cavity (3) are connected by a metal bellows.

4. The high strength low heat leak liquid helium dewar structure of claim 1, wherein, The liquid helium cavity hanger (7), the cold shield hanger (8), the liquid helium cavity pull rod (6), and the cold shield pull rod (10) are made of G10.

5. The high strength low heat leak liquid helium dewar structure of claim 1, wherein, The heat sink (11) is an oxygen-free copper solid body.

6. The high strength, low heat leak liquid helium dewar structure of claim 1, wherein, The liquid helium cavity pull rod (6) and the cold shield pull rod (10) are hollow cylindrical structures.

7. The high strength, low heat leak liquid helium dewar structure of claim 1, wherein, The liquid helium cavity hanger (7) and the cold shield hanger (8) are plate structures.

8. The high strength, low heat leak liquid helium dewar structure of claim 1, wherein, The reinforcing rings (14) in the vacuum cover (4) are distributed at equal intervals.

9. The high strength, low heat leak liquid helium dewar structure of claim 1, wherein, The liquid helium cavity liquid delivery pipe (9) is installed at the center of the upper flange of the vacuum cover (4).

10. The high-strength, low-heat-leak liquid-helium dewar structure of claim 1, wherein, The vacuum cover (4) is provided with a plurality of reinforcing rings (14) on the inner layer.

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