An ultra-low-vibration cryogenic system

Abstract

The application discloses a kind of ultra-low vibration cryogenic systems, small cryogenic refrigerator vacuum is installed in closed type damping heat exchange cavity;Small cryogenic refrigerator top is provided with sealed cavity, two cavities are connected by air pipe, balance two cavity internal air pressure;Flow resistance and heat exchange element are equipped in cold box, the outer wall of cavity heat exchanger is provided with heat exchange pipe, and the both ends of heat exchange pipe are first inlet and first outlet respectively;Closed type damping heat exchange cavity upper portion is provided with second inlet communicated with its inner cavity, and first suction pipe is connected on dilution unit;First heat exchange coil pipe is arranged in first suction pipe;First inlet, first outlet, first heat exchange coil pipe, flow resistance, heat exchange element, first suction pipe form circulation loop;Closed type damping heat exchange cavity is injected with refrigerant.The application guarantees that the pressure inside damping heat exchange cavity is constant, avoids the instability of heat exchange and damping effect caused by pressure fluctuation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-temperature refrigeration, and particularly relates to a low-temperature system with ultra-low vibration. BACKGROUND

[0002] A low-temperature thermostat with liquid helium as a working medium can continuously provide a low-temperature environment from 4K to mK, and is widely used in the fields of quantum physics, aerospace, basic physics research and the like. Existing low-temperature systems mostly use Gifford-McMahon (GM) refrigerators and pulse-tube refrigerators as cold sources, and both types of refrigerators have corresponding mechanical components moving when running, thereby generating vibration, which will have an adverse effect on the temperature measurement of the system, so reducing the vibration of the system is an important part of the production of the low-temperature system.

[0003] To reduce the vibration generated by the cold source, Chinese patent 2022104849981 discloses a dilution refrigeration system, which places a low-temperature refrigerator in a damping heat exchange cavity. When the system is running, the gas working medium enters the damping heat exchange cavity, is pre-cooled by the low-temperature refrigerator, and also serves as a heat exchange medium between the low-temperature refrigerator and the damping heat exchange cavity. The cold energy of the low-temperature refrigerator is conducted to the wall surface of the damping heat exchange cavity and the pipeline surrounding the outside of the damping heat exchange cavity, so as to pre-cool the working medium of another loop circulating through the pipeline. However, the pre-cooling method has the following disadvantages: the pressure in the damping heat exchange cavity cannot be kept constant, because the gas working medium entering the inside of the damping heat exchange cavity is constantly circulating, and its circulation flow changes according to the change of the system working condition. When the system circulation flow changes, the pressure in the inside of the damping heat exchange cavity also changes. The pressure fluctuation in the damping heat exchange cavity has the following adverse effects: 1. Unstable heat exchange performance. When the cold energy of the low-temperature refrigerator is constant, the heat exchange between the low-temperature refrigerator and the wall surface of the damping heat exchange cavity in the inside of the damping heat exchange cavity depends on the mass of the gas medium participating in the heat exchange, that is, the pressure in the inside of the damping heat exchange cavity. When the pressure in the inside of the damping heat exchange cavity fluctuates, the heat exchange effect also fluctuates; 2. When the pressure in the inside of the damping heat exchange cavity is low, damping cannot be achieved. The low-temperature refrigerator is connected to the damping heat exchange cavity through an elastic bellows at the top of the damping heat exchange cavity. When the system is running, the bellows will contract or stretch due to the influence of the internal and external pressure difference. When the pressure in the inside of the damping heat exchange cavity is low, the bellows will contract greatly and lose elasticity. At this time, the connection between the low-temperature refrigerator and the damping heat exchange cavity is rigid, and the vibration of the low-temperature refrigerator will be directly transmitted to the damping heat exchange cavity, and then to the cold box, so that the system loses the damping effect.

[0004] To solve the influence of air pressure fluctuation, a suspended symmetrical damping low-temperature device is disclosed in Chinese Patent 2022213673527. Connecting the device with the vacuum cavity of the cryostat can effectively compensate for the influence of atmospheric pressure and the refrigerator on the damping assembly after vacuumizing. However, the device only places the refrigerator directly on the vacuum cavity flange, and the cold end of the refrigerator cannot achieve simultaneous damping and heat exchange with the components inside the cold box. SUMMARY

[0005] The purpose of the present application is to provide a small low-temperature refrigerator-based ultra-low vibration low-temperature system that ensures extremely low vibration levels while the heat exchange and damping performance are not affected by the circulation of the working medium.

[0006] Technical solution: The ultra-low vibration low-temperature system comprises a small low-temperature refrigerator, a closed damping heat exchange cavity, and a cold box. The small low-temperature refrigerator is installed in the closed damping heat exchange cavity through a room temperature flange and a damping bellows vacuum seal. The small low-temperature refrigerator has at least two cold ends, each connected to a cold end heat exchanger. The cavity wall of the closed damping heat exchange cavity is provided with at least two cavity heat exchangers, and there is a gap between the cavity heat exchanger and the cold end heat exchanger.

[0007] The cold box is provided with a flow resistance and a heat exchange element, and the outer wall of the cavity heat exchanger is provided with a heat exchange pipe. One end of the heat exchange pipe extending out of the cold box is a first inlet, and the other end is a first outlet. The upper part of the closed damping heat exchange cavity is provided with a second inlet communicating with the inner cavity, and the heat exchange element is connected with a first gas extraction pipe. The first gas extraction pipe is provided with a first heat exchange coil.

[0008] The first inlet, the first outlet, the first heat exchange coil, the flow resistance, the dilution unit, and the first gas extraction pipe form a circulation loop. The closed damping heat exchange cavity is filled with a refrigerant.

[0009] Preferably, the refrigerant in the closed damping heat exchange cavity of the circulation loop is helium-4 gas, and the circulation loop refrigerant is helium-3 or a mixture of helium-3 and helium-4. When the heat exchange element is a closed heat exchange cavity, the refrigerant is helium-3 gas, and when the heat exchange element is a dilution unit chamber, the refrigerant is a mixture of helium-3 and helium-4 gas.

[0010] Further, a top sealing cavity is provided on the top of the small low-temperature refrigerator. The sealing cavity comprises a top sealing plate and a bottom sealing plate. The top sealing plate is fixed to the room temperature flange by a support rod, and the bottom sealing plate is fixed to the top of the small low-temperature refrigerator by a support rod. The top sealing plate and the bottom sealing plate form a sealed cavity through a damping bellows, and the sealed cavity is connected to the inside of the closed damping heat exchange cavity through an air pipe.

[0011] Further, the flow resistance in the circulation loop can be located inside or outside the first gas extraction pipe.

[0012] Further, the closed shock-absorbing heat-exchanging cavity is connected with the cold box room temperature flange at the top of the cold box through the cavity room temperature flange at the top of the cavity.

[0013] Further, the heat-exchanging structure between the cavity heat exchanger and the cold end heat exchanger is staggered fin, interdigital or sleeve ring.

[0014] Preferably, the flow resistance is a capillary tube or a cryogenic valve.

[0015] Preferably, the small-sized cryogenic refrigerator is a Gifford-McMahon refrigerator or a pulse tube refrigerator.

[0016] Preferably, the cold box is provided with two-stage cold plates and two-stage cold screens.

[0017] Advantages: compared with the prior art, the present application has the following advantages: 1. The present application no longer sets up a separate helium-4 circuit, ensures the constant pressure inside the shock-absorbing heat-exchanging cavity, avoids the instability of heat exchange and shock absorption caused by pressure fluctuation, efficiently utilizes the refrigeration capacity of the small-sized cryogenic refrigerator, greatly increases the pre-cooling capacity of the system, and further improves the ground cooling capacity; 2. The present application separates the small-sized cryogenic refrigerator from the cold box based on the closed shock-absorbing heat-exchanging cavity structure, and can reduce the system vibration to far below 1 micron; 3. The present application balances the pressure inside the shock-absorbing heat-exchanging cavity by using the top closed cavity. When the pressure inside the shock-absorbing heat-exchanging cavity is low, the top closed cavity provides an upward force through the atmospheric pressure to offset the downward force of the atmospheric pressure on the shock-absorbing heat-exchanging cavity, thereby avoiding the contraction of the metal bellows on the shock-absorbing heat-exchanging cavity and losing elasticity. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Fig. 1 is a structural schematic diagram of the closed shock-absorbing heat-exchanging cavity.

[0019] Figure 2 Fig. 2 is a structural schematic diagram of the present application. DETAILED DESCRIPTION

[0020] The technical solutions of the present application will be further described below with reference to the accompanying drawings.

[0021] The low-temperature system with ultra-low vibration comprises a cold box 18, a first-stage cold plate 19, a second-stage cold plate 21, a first-stage cold shield 20 and a second-stage cold shield 22 arranged in the cold box 18. The cold box 18 is provided with a cold box room temperature flange 17 at the top. The cold box 18 is provided with a closed damping heat exchange cavity 15 at the top, which is assembled and welded by a cavity first-stage heat exchanger 4, a cavity second-stage heat exchanger 6 and a cavity wall plate 10. The closed damping heat exchange cavity 15 is inserted from the top of the cold box 18, connected with the cavity room temperature flange 16 and the cold box room temperature flange 17, and the cavity first-stage heat exchanger 4 is connected with the first-stage cold plate 19 and the cavity second-stage heat exchanger 6 is connected with the second-stage cold plate 21, so as to form a vacuum sealed cavity in the cold box 18.

[0022] The small-sized low-temperature refrigerator 1 is inserted into the closed damping heat exchange cavity 31 and connected with the closed damping heat exchange cavity 15 through the first damping bellows 2. The closed damping heat exchange cavity 31 is also formed with a vacuum sealed environment. The small-sized low-temperature refrigerator 1 has two-stage cold ends, including a first-stage cold end 11 and a second-stage cold end 12. The first-stage cold end 11 is connected with a cold end first-stage heat exchanger 5 and the second-stage cold end 12 is connected with a cold end second-stage heat exchanger 13. The cavity first-stage heat exchanger 4 is not in contact with the cold end first-stage heat exchanger 5 and the cavity second-stage heat exchanger 6 is not in contact with the cold end second-stage heat exchanger 13, so as to realize the vibration isolation between the small-sized low-temperature refrigerator 1 and the cold box 18. The cold box 18 is further provided with a flow resistance 9. The cavity wall plate 10, the cavity first-stage heat exchanger 4 and the cavity second-stage heat exchanger 6 are provided with heat exchange pipes. The heat exchange pipes are provided with a first inlet 3 and a first outlet 7. The closed damping heat exchange cavity 15 is provided with a second inlet 14 communicated with the inner cavity. The heat exchange elements in the cold box 18 are connected with a first gas suction pipe 23. The first gas suction pipe 23 is provided with a first heat exchange coil 8.

[0023] The first inlet 3, the first outlet 7, the first heat exchange coil 8, the flow resistance 9, the heat exchange elements 31 and the first gas suction pipe 23 form a circulation loop. The refrigerant is helium-3 or a mixture of helium-3 and helium-4. The refrigerant enters the cold box 18 from the first inlet 3, exchanges heat on the outer wall of the damping heat exchange cavity 10, the cavity first-stage heat exchanger 4 and the cavity second-stage heat exchanger 6 through the heat exchange pipes, is partially liquefied, passes through the first heat exchange coil 8 in the first gas suction pipe 23, is throttled by the flow resistance 9, flows into the heat exchange elements 31, is pumped back to the first inlet 3 by the first gas suction pipe 23 through a circulation pump.

[0024] In the closed shock-absorbing heat-exchange cavity, the helium-4 loop no longer circulates, but the helium-4 gas is filled into the closed shock-absorbing heat-exchange cavity through the second inlet 16, and is left in the shock-absorbing cavity after heat exchange through the first cold end 11, the second cold end 12, the cold end first heat exchanger 4 and the cold end second heat exchanger 5, and serves as the heat exchange medium between the first cold end 11, the second cold end 12, the cold end first heat exchanger 5, the cold end second heat exchanger 13 and the wall 10 and the cavity first heat exchanger 4 and the cavity second heat exchanger 6. In the embodiment, the temperature of the first cold plate 19 is between 30K and 70K, and the temperature of the second cold plate 217 is between 2K and 5K.

[0025] Further, a top sealing cavity 230 is arranged at the top of the small-sized low-temperature refrigerator 1, the sealing cavity 30 comprises a top sealing plate 26 and a bottom sealing plate 27, the top sealing plate 26 is fixed on the room-temperature flange 16 through the first supporting rod 24, the bottom sealing plate 27 is fixed at the top of the small-sized low-temperature refrigerator 1 through the second supporting rod 25, and the top sealing plate 26 and the bottom sealing plate 27 form a sealing cavity through the second shock-absorbing corrugated pipe 28, and the sealing cavity is connected with the inside of the closed shock-absorbing heat-exchange cavity 30 through the air pipe 29 to maintain constant pressure. The main function of the top sealing cavity 30 is that, without the structure, the pressure in the shock-absorbing heat-exchange cavity will gradually decrease when the temperature of the refrigerator decreases, at this time, the atmospheric pressure acts on the top of the refrigerator to press down the refrigerator, and the first shock-absorbing corrugated pipe 2 of the shock-absorbing heat-exchange cavity is compressed and loses the elasticity and the shock-absorbing function; and with the structure, although the pressure in the shock-absorbing heat-exchange cavity decreases when the temperature decreases, the atmospheric pressure presses down the refrigerator, but at the same time, the pressure of the top opposite cavity also decreases, the atmospheric pressure acts on the bottom sealing plate 27 to compress the second shock-absorbing corrugated pipe 28, and an upward force is formed, which offsets the force acting on the shock-absorbing heat-exchange cavity, so that the first shock-absorbing corrugated pipe 2 of the shock-absorbing heat-exchange cavity is not compressed and loses the shock-absorbing function.

[0026] Based on the special closed shock-absorbing heat-exchange cavity, the application can build a multi-stage efficient heat conduction to precool the refrigerant gas, and can realize the non-contact vibration isolation between the small-sized low-temperature refrigerator and the cold box to ensure the refrigeration effect.

Claims

1. An ultra-low vibration cryogenic system comprising a small cryogenic refrigerator (1), a closed shock-absorbing heat exchange cavity (15) and a cold box (18), the small cryogenic refrigerator (1) being mounted in the closed shock-absorbing heat exchange cavity (15) by means of a room temperature flange and a shock-absorbing bellows vacuum seal; characterized in that: The small-sized low-temperature refrigerator (1) has at least two cold ends, each of which is connected with a cold end heat exchanger, at least two cavity heat exchangers are arranged on the cavity wall plate (10) of the closed shock-absorbing heat exchange cavity (15), and there is a gap between the cavity heat exchanger and the cold end heat exchanger; The cold box (18) is provided with a flow resistance (9) and a heat exchange element (31), the outer wall of the cavity heat exchanger is provided with a heat exchange pipe, one end of the heat exchange pipe extending out of the cold box (18) is a first inlet (3), and the other end of the heat exchange pipe is a first outlet (7); the upper portion of the closed shock-absorbing heat exchange cavity (15) is provided with a second inlet (14) communicating with the inner cavity thereof, and the heat exchange element is connected with a first gas suction pipe (23); the first gas suction pipe (23) is provided with a first heat exchange coil (8); The first inlet (3), the first outlet (7), the first heat exchange coil (8), the flow resistance (9), the heat exchange element (10) and the first gas suction pipe (23) form a circulation loop, and the circulation loop and the closed shock-absorbing heat exchange cavity (15) are filled with refrigerant; A top sealing cavity (30) is arranged on the top of the small-sized low-temperature refrigerator (1), the sealing cavity comprises a top sealing plate (26) and a bottom sealing plate (27), the top sealing plate (26) is fixed on the room temperature flange through a first supporting rod (24), the bottom sealing plate (6) is fixed on the top of the small-sized low-temperature refrigerator (1) through a second supporting rod (25), a sealing cavity is formed between the top sealing plate (26) and the bottom sealing plate (27) through a second shock-absorbing corrugated pipe (28), and the sealing cavity is connected with the inside of the closed shock-absorbing heat exchange cavity (30) through a breather pipe (29).

2. The ultra-low vibration cryogenic system of claim 1, wherein: The heat exchange element (10) is a closed heat exchange cavity or a dilution unit.

3. The ultra-low vibration cryogenic system of claim 1, wherein: The refrigerant in the closed shock-absorbing heat exchange cavity is helium-4 gas; when the heat exchange element (10) is a closed heat exchange cavity, the refrigerant in the circulation loop is helium-3 gas; when the heat exchange element (10) is a dilution unit, the refrigerant in the circulation loop is a mixed gas of helium-3 and helium-4.

4. The ultra-low vibration cryogenic system of claim 1, wherein: The closed shock-absorbing heat exchange cavity (15) is connected with the cold box room temperature flange (17) on the top of the cold box (18) through the cavity room temperature flange (16) on the top thereof; the cold box (18) is provided with multiple-stage cold discs and multiple-stage cold screens, thereby forming multiple layers of low-temperature cavities; and the cavity heat exchanger is connected with the cold disc.

5. The ultra-low vibration cryogenic system of claim 1, wherein: The flow resistance (9) is arranged inside or outside the first gas suction pipe (23).

6. The ultra-low vibration cryogenic system of claim 1, wherein: The cavity heat exchanger and the cold end heat exchanger adopt staggered fins, interdigital or sleeve ring heat exchange structures.

7. The ultra-low vibration cryogenic system of claim 1, wherein: The flow resistance (9) adopts a capillary tube or a low-temperature valve.

8. The ultra-low vibration cryogenic system of claim 1, wherein: The small-sized low-temperature refrigerator (1) adopts a Gifford-McMahon refrigerator or a pulse tube refrigerator.

9. The ultra-low-vibration dilution refrigeration system of claim 4, wherein, The cold box (18) is provided with two-stage cold discs and two-stage cold screens.

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