Superconducting magnet cooling device

Abstract

The utility model discloses a superconducting magnet cooling device which comprises a GM refrigerator, a Stirling refrigerator and a vacuum cavity. A low-temperature heat exchanger of the GM refrigerator is arranged in a low-temperature cold screen of the vacuum cavity; an outlet of the Stirling cryocooler is divided into two paths after being connected with a first inlet pipeline, and an inlet of the Stirling cryocooler is divided into two paths after being connected with a first outlet pipeline; a first branch of the first inlet pipeline is connected with a first branch of the first outlet pipeline through a pneumatic valve, a second branch of the first inlet pipeline is connected with an inlet of the low-temperature heat exchanger, and a second branch of the first outlet pipeline is sequentially connected with the low-temperature fan, the second inlet pipeline and the air return low-temperature pipeline and then connected with an outlet of the superconducting magnet cavity. An outlet of the low-temperature heat exchanger is divided into three paths, namely a second outlet pipeline, a pressure relief pipeline and an air supply recovery pipeline; the second outlet pipeline is connected with an inlet of the superconducting magnet cavity through an air inlet low-temperature pipeline. According to the utility model, the usage amount of helium can be greatly reduced, and the problem of non-uniform temperature of the magnet is avoided.

Description

Technical Field

[0001] The utility model belongs to the field of refrigeration equipment, in particular to a superconducting magnet cooling device. Background Art

[0002] Magnetic resonance imaging technology is widely used in clinical testing, well exploration, archaeology, non-destructive testing, non-metallic material structure analysis and other fields. The high-intensity magnetic fields equipped in MRI equipment are all low-temperature superconducting magnets, which are currently mostly cooled by liquid helium immersion or conduction cooling.

[0003] Liquid helium immersion cooling consumes a large amount of liquid helium, is costly and has poor economic efficiency.

[0004] Conduction cooling uses a GM refrigerator cold head to cool the magnet by solid heat conduction. For example, the Chinese patent document with publication number CN215183350U discloses a magnetic resonance superconducting magnet cooling device, including a single-stage GM refrigerator, a double-stage GM refrigerator, a low-temperature heat exchanger, a temperature acquisition system, and a 50K magnet cold screen. However, this method has a slow cooling speed and poor magnet temperature uniformity. If multiple GM refrigerator cold heads are required for rapid cooling, the equipment space is large and the economy is poor.

[0005] At the same time, in order to cool the magnet to superconducting temperature faster, it is necessary to pre-cool the magnet with liquid nitrogen. This pre-cooling method has a large cold shock, the cooling process is uncontrollable, and after the pre-cooling is completed, it is still necessary to wait for the residual nitrogen to be processed. Utility Model Content

[0006] The utility model provides a superconducting magnet cooling device, which can greatly reduce the usage of helium and avoid the problem of uneven magnet temperature.

[0007] A superconducting magnet cooling device comprises a GM refrigerator, a Stirling refrigerator and a vacuum chamber, wherein a low-temperature cold shield is arranged in the vacuum chamber;

[0008] A low-temperature heat exchanger is installed at the cold head of the GM refrigerator, and the low-temperature heat exchanger is arranged in a low-temperature cold screen;

[0009] The outlet of the Stirling refrigerator is connected to the No. 1 inlet pipeline and then divided into two branches, and the inlet of the Stirling refrigerator is connected to the No. 1 outlet pipeline and then divided into two branches; the first branch of the No. 1 inlet pipeline is connected to the first branch of the No. 1 outlet pipeline through a pneumatic valve, the second branch of the No. 1 inlet pipeline is connected to the inlet of the low-temperature heat exchanger, and the second branch of the No. 1 outlet pipeline is connected to the outlet of the superconducting magnet cavity after being connected to the low-temperature fan, the No. 2 inlet pipeline, and the return air low-temperature pipeline in sequence; the part of the No. 2 inlet pipeline located inside the vacuum cavity is wound around the surface of the low-temperature cold screen;

[0010] The outlet of the low-temperature heat exchanger is divided into three branches, namely, outlet pipeline No. 2, pressure relief pipeline and air supply recovery pipeline; outlet pipeline No. 2 is connected to the inlet of the superconducting magnet cavity through the air intake low-temperature pipeline; the outlet of the air supply recovery pipeline is divided into two branches, the first branch is connected to the venting pipeline, the exhaust valve, and the helium recovery tank in sequence, and the second branch is connected to the air supply pipeline, the air supply valve, the helium pressure reducing valve, and the high-pressure helium cylinder in sequence.

[0011] Furthermore, a pressure sensor is provided inside the superconducting magnet cavity, and temperature sensors are provided on the No. 2 inlet pipeline, the No. 2 outlet pipeline and the outer wall of the low-temperature heat exchanger.

[0012] Furthermore, a safety valve is provided at the outlet end of the pressure relief pipeline.

[0013] Furthermore, the air intake low-temperature pipeline and the air return low-temperature pipeline both adopt a double-layer metal hose structure, and the sandwich area between the two layers of metal hoses is vacuum.

[0014] Furthermore, the low-temperature fan and the pneumatic valve are arranged in the vacuum chamber.

[0015] Furthermore, the vacuum chamber is connected to the vacuum pumping equipment through a pipeline with a vacuum gate valve.

[0016] Compared with the prior art, the utility model has the following beneficial effects:

[0017] The utility model uses a Stirling refrigerator and a GM refrigerator for combined refrigeration to cool low-temperature helium, drives the low-temperature helium to circulate through a low-temperature fan to cool the magnet, thereby realizing a system without liquid helium, greatly reducing the amount of helium used, and avoiding the problem of uneven magnet temperature caused by a conductive cooling method. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The utility model is a schematic diagram of the overall structure of a superconducting magnet cooling device. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0020] like Figure 1As shown, a superconducting magnet cooling device includes a GM refrigerator 1, a low-temperature fan 2, a low-temperature heat exchanger 3, a low-temperature cold shield 4, a vacuum cavity 5, a pneumatic valve 6, a No. 1 inlet pipeline 7, a No. 1 outlet pipeline 8, a Stirling refrigerator 9, a high-pressure helium cylinder 10, a helium recovery tank 11, an exhaust valve 12, a gas supply valve 13, a No. 2 outlet pipeline 14, a No. 2 inlet pipeline 15, an intake low-temperature pipeline 16, a return low-temperature pipeline 17, a pressure sensor 18, a safety valve 19, a pressure relief pipeline 20, a gas supply recovery pipeline 21, a gas supply pipeline 22, a gas release pipeline 23, a superconducting magnet cavity 24, a helium pressure reducing valve 25, a No. 1 temperature sensor 26, a No. 2 temperature sensor 27, a No. 3 temperature sensor 28, a No. 4 temperature sensor 29, and an evacuation gate valve 30.

[0021] The outlet of the Stirling refrigerator 9 is connected to the No. 1 inlet pipeline 7, and the inlet of the Stirling refrigerator 9 is connected to the No. 1 outlet pipeline 8. The outlet of the No. 1 inlet pipeline 7 is divided into two branches, the first branch is connected to the outlet of the pneumatic valve 6, and the second branch is connected to the inlet of the low-temperature heat exchanger 3. The outlet of the No. 1 outlet pipeline 8 is divided into two branches, the first branch is connected to the inlet of the pneumatic valve 6, and the first branch is connected to the low-temperature fan 2, the No. 2 inlet pipeline 15, the return air low-temperature pipeline 17, and then to the outlet of the superconducting magnet cavity 24.

[0022] The low-temperature heat exchanger 3 is divided into three branches, namely, the No. 2 outlet pipeline 14, the pressure relief pipeline 20, and the air replenishment recovery pipeline 21. The No. 2 outlet pipeline 14 is connected to the inlet of the superconducting magnet cavity 24 through the air intake low-temperature pipeline 16. The outlet of the pressure relief pipeline 20 is connected to the inlet of the safety valve 19 to realize the overpressure protection function.

[0023] The outlet of the gas replenishment recovery pipeline 21 is divided into two branches. The first branch is connected to the exhaust pipeline 23, the exhaust valve 12, and the helium recovery tank 11 in sequence to realize the helium recovery function; the second branch is connected to the gas replenishment pipeline 22, the gas replenishment valve 13, the helium pressure reducing valve 25, and the high-pressure helium cylinder 10 in sequence to realize the helium gas replenishment function.

[0024] The pressure sensor 18 is installed inside the superconducting magnet cavity 24 and connected to the detection system through a signal line for detecting the internal pressure.

[0025] The first temperature sensor 26 is installed on the outer wall of the second inlet pipeline 15 and is connected to the detection system through a signal line to detect the temperature at that location.

[0026] The second temperature sensor 27 is installed on the outer wall of the second outlet pipeline 14 and is connected to the detection system through a signal line to detect the temperature at that location.

[0027] The third temperature sensor 28 and the fourth temperature sensor 29 are installed on the outer wall of the low-temperature heat exchanger 3 and are connected to the detection system through signal lines to detect the temperature at the location.

[0028] The evacuation gate valve 30 is connected to the inside of the vacuum chamber 5. When the evacuation gate valve 30 is closed, the vacuum chamber 5 is completely closed. The vacuum chamber 5 can be evacuated by connecting the vacuum pump group through the evacuation gate valve 30.

[0029] Both the air inlet cryogenic pipeline 16 and the air return cryogenic pipeline 17 are double-layer metal hose structures, and the sandwich area between the two metal hoses is vacuum, so that a good heat insulation effect is achieved during the low-temperature gas transportation process.

[0030] The pneumatic valve 6 is a low-temperature pneumatic stop valve, which is in a normally closed state and is installed inside the vacuum chamber 5 . When opened, it isolates the low-temperature helium flow from flowing through the Stirling refrigerator 9 .

[0031] The part of the second inlet pipeline 15 located inside the vacuum chamber 5 is wound around the surface of the low-temperature cold shield 4 and fixed by brazing to cool the low-temperature cold shield 4. The low-temperature cold shield 4 is fixed inside the vacuum chamber 5 by a low thermal conductivity material to play a role in heat shielding and reducing heat load.

[0032] The low-temperature heat exchanger 3 is installed at the cold head position of the GM refrigerator 1 to cool the low-temperature helium.

[0033] The cryogenic blower 2 is placed inside the vacuum chamber 5 to provide power for the helium circulation.

[0034] The method for cooling using the superconducting magnet cooling device of the utility model comprises the following steps:

[0035] S100, flow wash replacement:

[0036] S101, the outlet of the evacuation gate valve 30 is connected to a vacuum pumping device, and the evacuation gate valve 30 is opened to evacuate the vacuum chamber 5. After completion, the evacuation gate valve 30 is closed and the vacuum pumping device is removed.

[0037] S102, disconnect the helium recovery tank 11 from the exhaust valve 12, connect the outlet of the exhaust valve 12 to the vacuum equipment, open the exhaust valve 12, the air supply valve 13, and the pneumatic valve 6, close the other valves, open the vacuum equipment to evacuate the system pipeline, and when the vacuum degree reaches the specified value and the predetermined time is reached, the evacuation is completed.

[0038] S103. After the evacuation is completed, close the exhaust valve 12, slowly open the helium pressure reducing valve 25 to inject helium into the system, and when the value of the pressure sensor 18 is observed to be 1.01-1.05 bar, close the helium pressure reducing valve 25, slowly open the exhaust valve 12, and turn on the vacuum equipment to evacuate the system pipeline. When the vacuum degree reaches the specified value and the predetermined time is reached, the evacuation is completed.

[0039] S104, repeat steps S101 to S103 three times, and the flow washing and replacement is completed.

[0040] S200, replenishing air and cooling down:

[0041] S201. After the flow washing and replacement is completed, close the pneumatic valve 6 and the exhaust valve 12. Slowly open the helium pressure reducing valve 25 to inject helium into the system, and adjust the outlet pressure of the helium pressure reducing valve 25 to 1.1-1.3 bar.

[0042] S202, turn on the low-temperature fan 2, the Stirling refrigerator 9, and the GM refrigerator 1 in sequence, and observe the temperatures of the No. 1 temperature sensor 26, the No. 2 temperature sensor 27, the No. 3 temperature sensor 28, and the No. 4 temperature sensor 29.

[0043] S203, when the temperature of the second temperature sensor 27 reaches the specified temperature 77K, the pneumatic valve 6 is opened, the Stirling refrigerator 9 is closed, and when the temperature of the magnet drops to the specified temperature, the helium pressure reducing valve 25 is closed.

[0044] S300, stop:

[0045] S301, connect the helium recovery tank 11 and the exhaust valve 12, evacuate the connecting pipeline through the helium recovery tank 11, close the GM refrigerator 1, open the exhaust valve 12, start the recovery pump group on the helium recovery tank 11, and perform exhaust recovery.

[0046] The utility model uses a Stirling refrigerator and a GM refrigerator for combined refrigeration to cool low-temperature helium, drives the low-temperature helium to circulate through a low-temperature fan to cool the magnet, thereby realizing a system without liquid helium, greatly reducing the amount of helium used, and avoiding the problem of uneven magnet temperature caused by a conductive cooling method.

[0047] During the 300K-77K pre-cooling process, the Stirling refrigerator and the GM refrigerator work simultaneously. Relying on the large cooling capacity of the Stirling refrigerator, rapid cooling from 300K to 77K is achieved, and the cooling process is uniform and controllable.

[0048] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A superconducting magnet cooling device, characterized in that: It comprises a GM refrigerator (1), a Stirling refrigerator (9) and a vacuum chamber (5), wherein a low-temperature cold shield (4) is arranged in the vacuum chamber (5); A low-temperature heat exchanger (3) is installed at the cold head of the GM refrigerator (1), and the low-temperature heat exchanger (3) is arranged in a low-temperature cold shield (4); The outlet of the Stirling refrigerator (9) is connected to the No. 1 inlet pipeline (7) and then divided into two branches, and the inlet of the Stirling refrigerator (9) is connected to the No. 1 outlet pipeline (8) and then divided into two branches; the first branch of the No. 1 inlet pipeline (7) is connected to the first branch of the No. 1 outlet pipeline (8) through a pneumatic valve (6), the second branch of the No. 1 inlet pipeline (7) is connected to the inlet of the low-temperature heat exchanger (3), and the second branch of the No. 1 outlet pipeline (8) is connected to the low-temperature fan (2), the No. 2 inlet pipeline (15), and the return air low-temperature pipeline (17) in sequence, and then connected to the outlet of the superconducting magnet cavity (24); the part of the No. 2 inlet pipeline (15) located inside the vacuum cavity (5) is wound around the surface of the low-temperature cold shield (4); The outlet of the low-temperature heat exchanger (3) is divided into three branches, namely, a No. 2 outlet pipeline (14), a pressure relief pipeline (20) and a gas replenishment recovery pipeline (21); the No. 2 outlet pipeline (14) is connected to the inlet of the superconducting magnet cavity (24) through an air intake low-temperature pipeline (16); the outlet of the gas replenishment recovery pipeline (21) is divided into two branches, the first branch is connected to the exhaust pipeline (23), the exhaust valve (12), and the helium recovery tank (11) in sequence, and the second branch is connected to the gas replenishment pipeline (22), the gas replenishment valve (13), the helium pressure reducing valve (25), and the high-pressure helium cylinder (10) in sequence.

2. The superconducting magnet cooling device according to claim 1, characterized in that: A pressure sensor (18) is provided inside the superconducting magnet cavity (24), and temperature sensors are provided on the second inlet pipeline (15), the second outlet pipeline (14) and the outer wall of the low-temperature heat exchanger (3).

3. The superconducting magnet cooling device according to claim 1, characterized in that: A safety valve (19) is provided at the outlet end of the pressure relief pipeline (20).

4. The superconducting magnet cooling device according to claim 1, characterized in that: The air intake low-temperature pipeline (16) and the air return low-temperature pipeline (17) both adopt a double-layer metal hose structure, and the sandwich area between the two layers of metal hoses is vacuum.

5. The superconducting magnet cooling device according to claim 1, characterized in that: The low-temperature fan (2) and the pneumatic valve (6) are arranged in the vacuum chamber (5).

6. The superconducting magnet cooling device according to claim 1, characterized in that: The vacuum chamber (5) is connected to the vacuum pumping equipment via a pipeline with a vacuum gate valve (30).

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