A liquid helium-free superconducting magnet for animal imaging

Abstract

The present invention provides a liquid helium-free superconducting magnet for animal imaging, comprising a superconducting magnet, a liquid helium-free cryogenic system, and a pull rod. The superconducting magnet comprises a main magnet, a shielding magnet, and a 4K container. The main coil is wound within the external wire slots of the main frame to form the main magnet, the shielding coil is wound within the external wire slots of the shielding frame to form the shielding magnet, and the 4K container contains the superconducting magnet. The liquid helium-free cryogenic system comprises a refrigerator, a first-stage cold head of the refrigerator, a cold shield, a second-stage cold head of the refrigerator, a cooling ring, a cooling belt, and a dewar container. The first-stage cold head of the refrigerator is directly connected to the cold shield to achieve first-stage cooling, the second-stage cold head of the refrigerator is directly connected to the cooling ring, and the cooling ring is connected to the shielding coil and the main coil via a cooling belt to achieve second-stage cooling of the superconducting magnet. The dewar container is used to create a vacuum environment for the cryogenic system. The superconducting magnet and the cold shield are suspended and fixed inside the dewar container by a pull rod to reduce contact heat leakage in the system. The diameter of the inner hole of the superconducting magnet is suitable for small animal imaging.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting magnets and relates to a liquid helium-free animal imaging superconducting magnet. Background Art

[0002] Superconducting magnets are widely used in the development of medical diagnostics and scientific instruments. Superconducting MRI equipment has become one of the most popular clinical diagnostic devices in the world. However, the stable operation of superconducting MRI equipment requires maintaining a low-temperature environment. The traditional refrigeration method is liquid helium refrigeration, which consumes a large amount of liquid helium materials for long-term use and is relatively expensive.

[0003] With the continuous development of new materials and cryogenic technology in recent years, refrigerators with low cooling power can achieve low energy consumption at a temperature of 4.2K, resulting in low daily operation and maintenance costs. Using refrigerators to cool superconducting magnets can avoid the use of liquid helium. In typical superconducting magnets, the refrigerator's secondary cold head directly cools both ends of the magnet through a cold plate. However, for larger magnets, this can easily lead to uneven magnet temperatures, affecting the uniformity of the magnetic field. Optimizing the temperature distribution of the secondary refrigeration system is necessary.

[0004] CN113035486A discloses a refrigeration system for a low-temperature superconducting magnet. The refrigeration system includes a cold shield, a lead cooling channel, a cold shield cooling channel, a first liquid helium inlet, a first helium outlet, a helium tank, a liquid helium inlet pipe, and a helium outlet pipe. The cold shield is disposed outside the low-temperature superconducting coil. The helium tank is disposed between the cold shield and the low-temperature superconducting coil and does not contact either. The liquid helium inlet pipe and the helium outlet pipe are both connected to the helium tank. Liquid helium is injected into the helium tank from the first liquid helium inlet via the liquid helium inlet pipe. Helium volatilized from the helium tank is discharged from the first helium outlet via the helium outlet pipe. The lead cooling channel is connected between the helium outlet pipe and the superconducting current lead to conduct cold water to cool the superconducting current lead. The cold shield cooling channel is connected between the helium outlet pipe and the cold shield to conduct cold water to cool the cold shield. This effectively reduces the volatilization of liquid helium and reduces the risk of quenching in the low-temperature superconducting magnet.

[0005] CN202384127U discloses a cryogenic container system for a superconducting magnet with zero liquid helium consumption, providing a cryogenic container system for a superconducting magnet with zero liquid helium consumption that has good thermal insulation and can effectively improve the cooling effect of a cold head. The cryogenic container system includes an inner container base disposed on the top of the inner container, a heat exchanger mounted on the inner container base, a magnetic shield sleeved on the inner container base, an intermediate radiation-proof cold shield wrapped around the outer side of the inner container, a copper flange disposed on the top of the intermediate radiation-proof cold shield, and a cold head. The heat exchanger is located in the magnetic shield, the copper flange is located above the magnetic shield, one end of the cold head passes through the copper flange and is connected to the heat exchanger within the magnetic shield. The system also includes a lower bellows located within the magnetic shield, the lower bellows sleeved on the cold head, one end of the lower bellows is connected to the top of the copper flange, and the other end is inserted into the inner container base.

[0006] CN102436898A discloses a system for realizing a cooling method of a low-temperature superconducting magnet, comprising a liquid nitrogen filling valve, a liquid helium filling valve, a liquid nitrogen level gauge, a liquid nitrogen valve, a central hole, a helium exhaust valve, a vacuum valve, a vacuum chamber, a liquid nitrogen pipe, a liquid helium filling pipe, a helium exhaust pipe, a liquid nitrogen storage chamber, and a liquid helium storage chamber; a liquid helium storage chamber is provided at the center of a closed space, a liquid nitrogen storage chamber is provided outside the liquid helium storage chamber, and a vacuum chamber is provided at the outermost portion; an end cap is provided at the upper end of the closed space, and a A central hole is provided, through which a high-temperature superconducting wire connected to a liquid nitrogen tube and a lower end of a liquid nitrogen level gauge is inserted into a liquid helium storage chamber; a liquid nitrogen valve is provided on the liquid nitrogen tube; an end cover located in the liquid helium storage chamber is provided with a liquid helium filling valve and a liquid helium filling tube inserted into the liquid helium storage chamber, as well as a helium exhaust valve and a helium exhaust tube inserted into the liquid helium storage chamber; an end cover located in the liquid nitrogen storage chamber is provided with a liquid nitrogen filling valve, and an end cover located in the vacuum chamber is provided with a vacuum valve; and a central portion of the liquid helium storage chamber is provided with an annular groove extending toward the liquid nitrogen storage chamber.

[0007] Therefore, how to provide a magnet suitable for animal imaging that does not require the consumption of liquid nitrogen, uses a refrigerator to provide the low-temperature environment required by superconducting magnets, and ensures uniform temperature distribution in the magnetic field and low heat leakage has become an urgent problem that needs to be solved. Summary of the Invention

[0008] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a liquid helium-free superconducting magnet for animal imaging, which adopts a refrigerator for cooling and an internal cooling structure to provide the low-temperature environment required by the superconducting magnet. By arranging cooling rings and cooling belts, the temperature field inside the superconducting magnet is ensured to be uniform, thereby ensuring good magnetic field uniformity.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a liquid helium-free superconducting magnet for animal imaging, comprising a superconducting magnet, a liquid helium-free cryogenic system and a pull rod, wherein the superconducting magnet, the liquid helium-free cryogenic system and the pull rod are all in a vacuum environment.

[0011] The liquid helium-free cryogenic system includes a refrigerator, a first-level cold head of the refrigerator, a cold shield, a second-level cold head of the refrigerator, a cooling structure and a Dewar container. The cold shield is mounted in the Dewar container, and the superconducting magnet is arranged in the cold shield. The cooling structure includes a cooling ring and a cooling belt. The cooling ring is arranged around the superconducting magnet and is fixedly connected to the superconducting magnet through a support rod. The first-level cold head of the refrigerator is directly connected to the cold shield to realize first-level cooling, and the second-level cold head of the refrigerator is directly connected to the cooling ring. The cooling ring is connected to the coil of the superconducting magnet through the cooling belt to realize second-level cooling.

[0012] The superconducting magnet and the cold shield are suspended inside the Dewar container through the tie rods.

[0013] The present invention realizes primary refrigeration by directly connecting the first-stage cold head of the refrigerator to the cold shield. Furthermore, by providing a conductive cooling ring, a plurality of conductive cooling belts provided along the circumferential direction of the conductive cooling ring are utilized to connect the coils of the superconducting magnet for heat transfer, thereby realizing secondary refrigeration and realizing synchronous conductive cooling of the superconducting magnet in the circumferential direction. While increasing the cooling rate, the uniformity of the temperature field inside the superconducting magnet is improved, thereby ensuring good magnetic field uniformity. In addition, by providing a pull rod, the superconducting magnet and the cold shield are suspended in the Dewar container to avoid direct contact with the Dewar container and reduce heat leakage of the magnet. The present invention uses a refrigerator for cooling without consuming liquid helium, and has the characteristics of simple structure, low cost, uniform temperature field and uniform magnetic field.

[0014] It should be noted that the present invention is suitable for in vivo imaging of small animals. The diameter of the central through-hole of the magnet is smaller than that of the human body imaging system. Those skilled in the art can reasonably select the inner hole diameter according to the size of the animal to be measured. The inner hole diameter of the currently available animal imaging magnet is 200 to 400 mm. The inner hole diameter of the magnet corresponding to the present invention covers the existing range but is not limited to this range.

[0015] It should be noted that a Dewar vessel is a double-walled container. A high vacuum is drawn between the walls to reduce heat transfer from the gas. The opposing surfaces of the double walls are silver-plated or polished to reduce emissivity, thereby minimizing radiative heat transfer. In the present invention, a Dewar vessel is used to create a vacuum refrigeration environment for the superconducting magnet, wherein a refrigerator is located at the top of the Dewar vessel's outer wall.

[0016] It should be noted that, in the present invention, the material of the cooling ring and the material of the cooling belt should preferably be selected from materials with high thermal conductivity. Those skilled in the art can reasonably select the material of the cooling ring and the material of the cooling belt according to the cooling requirements. For example, the material of the cooling ring and the material of the cooling belt are both copper, and the cooling ring can optionally be a large circular ring structure, and is coaxially arranged with the superconducting magnet and the cold screen.

[0017] As a preferred technical solution of the present invention, the superconducting magnet includes a main magnet, two shielding magnets and a 4K container.

[0018] It is well known to those skilled in the art that a 4K container is a container that maintains a temperature environment of 4K.

[0019] Preferably, the main magnet is formed by a main coil wound in the external wire groove of the main frame, and the shielding magnet is formed by a shielding coil wound in the external wire groove of the shielding frame. The two shielding magnets are symmetrically distributed at both ends of the main magnet and are coaxial with the main magnet. The 4K container encloses the main magnet and the two shielding magnets.

[0020] It should be noted that, in the present invention, the 4K container can be optionally arranged coaxially with the main magnet and the two shielding magnets.

[0021] Preferably, the support rod is fixedly connected to the main skeleton of the superconducting magnet.

[0022] As a preferred technical solution of the present invention, the main skeleton is a symmetrical hollow cylindrical structure.

[0023] Preferably, the outer ring of the main frame is provided with at least two first wire grooves, and the first wire grooves are used to wind the main coil to form the main magnet together with the main frame.

[0024] As a preferred technical solution of the present invention, the shielding magnet includes a shielding frame, the outer ring of the shielding frame is provided with a second wire groove, the second wire groove is used for winding the shielding coil, and forms a shielding magnet with the shielding frame.

[0025] Preferably, the shielding skeleton is a double-layer hollow cylindrical structure.

[0026] It should be noted that those skilled in the art should be able to understand that the shielding magnet is arranged in such a way that the shielding frame is sleeved on both ends of the main magnet.

[0027] As a preferred technical solution of the present invention, the main coil and the shielding coil are coils wound by superconducting wires.

[0028] Preferably, the 4K container is in a 4K ultra-low temperature environment.

[0029] As a preferred technical solution of the present invention, the cold screen is a closed thin-walled double-cylinder structure.

[0030] Preferably, the superconducting magnet and the cooling ring are both located inside the closed cylinder of the cold shield.

[0031] As a preferred technical solution of the present invention, the cooling ring is centrally arranged between the two shielding magnets.

[0032] As a preferred technical solution of the present invention, the cooling belt has connecting fins at both ends, the fin at one end of the cooling belt is connected to the cooling ring, and the other end is divided into two parts, one part is connected to the shielding coil in the superconducting magnet, and the other part is connected to the main coil in the main magnet.

[0033] As a preferred technical solution of the present invention, the axes of the main skeleton and the shielding skeleton coincide with each other.

[0034] Preferably, the main frame and the shielding frame are connected by welding.

[0035] Preferably, the 4K container is fixed to the main magnet and the two shielding magnets by welding.

[0036] As a preferred technical solution of the present invention, one end of the pull rod is connected to the inner wall of the Dewar container, and the other end is connected to the 4K container in the superconducting magnet.

[0037] Preferably, a connecting block is provided on the pull rod, and the connecting block is used to connect the pull rod with the cold screen.

[0038] Preferably, the pull rods are distributed around the end surfaces on both sides of the superconducting magnet.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention realizes primary refrigeration by directly connecting the first-stage cold head of the refrigerator to the cold screen. Furthermore, by providing a conductive cooling ring, a plurality of conductive cooling belts provided along the circumferential direction of the conductive cooling ring are utilized to connect the coils of the superconducting magnet for heat transfer, thereby realizing secondary refrigeration and realizing synchronous conductive cooling of the superconducting magnet in the circumferential direction. While increasing the cooling rate, the uniformity of the temperature field inside the superconducting magnet is improved, thereby ensuring good magnetic field uniformity. In addition, by providing a pull rod, the superconducting magnet and the cold screen are suspended in the Dewar container to avoid direct contact with the Dewar container and reduce heat leakage of the magnet. The present invention uses a refrigerator for cooling without consuming liquid helium. It has the characteristics of simple structure, low cost, uniform temperature field and uniform magnetic field, and is suitable for animal imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic overall cross-sectional view of a liquid helium-free animal imaging superconducting magnet provided in one embodiment of the present invention;

[0042] Figure 2 This is a diagram of the internal structure of a liquid helium-free animal imaging superconducting magnet provided in a specific embodiment of the present invention.

[0043] Among them, 1-refrigerator; 2-first-stage cold head of refrigerator; 3-second-stage cold head of refrigerator; 4-cooling structure; 41-support rod; 42-cooling ring; 43-cooling belt; 5-Dewar container; 6-cold shield; 7-superconducting magnet; 71-main frame; 72-main coil; 73-shielding frame; 74-shielding coil; 75-4K container; 8-pull rod. DETAILED DESCRIPTION

[0044] It should be understood that, in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0045] It should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0046] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0047] In one embodiment, the present invention provides a liquid helium-free superconducting magnet for animal imaging, such as Figure 1 and Figure 2 As shown, the liquid helium-free animal imaging superconducting magnet includes a superconducting magnet 7, a liquid helium-free cryogenic system and a pull rod 8, and the superconducting magnet 7, the liquid helium-free cryogenic system and the pull rod 8 are all in a vacuum environment.

[0048] The liquid helium-free cryogenic system includes a refrigerator 1, a first-level cold head 2 of the refrigerator, a cold shield 6, a second-level cold head 3 of the refrigerator, a cooling structure 4 and a Dewar container 5. The cold shield 6 is sleeved in the Dewar container 5, and the superconducting magnet 7 is arranged in the cold shield 6. The cooling structure 4 includes a cooling ring 42 and a cooling belt 43. The cooling ring 42 is arranged around the superconducting magnet 7 and is fixedly connected to the superconducting magnet 7 through a support rod 41; the first-level cold head 2 of the refrigerator is directly connected to the cold shield 6 to achieve first-level refrigeration, the second-level cold head 3 of the refrigerator is directly connected to the cooling ring 42, and the cooling ring 42 is connected to the coil of the superconducting magnet 7 through the cooling belt 43 to achieve second-level refrigeration.

[0049] The superconducting magnet 7 and the cold shield 6 are suspended inside the Dewar container 5 through the tie rods 8 .

[0050] Optionally, the present invention is suitable for in vivo imaging of small animals. The inner hole diameter of the currently available animal imaging magnet is 200 to 400 mm. The inner hole diameter of the magnet corresponding to the present invention covers the existing range, and the aperture can be reasonably selected for design according to the size of the animal to be measured.

[0051] Specifically, the refrigerator 1 is arranged at the top of the outer wall of the Dewar container 5; the material of the cooling ring 42 and the cooling belt 43 are both copper, the cooling ring 42 is a large ring structure, and is coaxially arranged with the superconducting magnet 7 and the cold shield 6.

[0052] Specifically, the superconducting magnet 7 includes a main magnet, two shielding magnets, and a 4K container 75. Furthermore, the main magnet is formed by winding a main coil 72 in the external wire slot of a main skeleton 71, and the shielding magnet is formed by winding a shielding coil 74 in the external wire slot of a shielding skeleton 73. The two shielding magnets are symmetrically distributed at both ends of the main magnet and are coaxial with the main magnet. The 4K container 75 encloses the main magnet and the two shielding magnets. Optionally, the 4K container 75 is coaxial with the main magnet and the two shielding magnets.

[0053] Specifically, the support rod 41 is fixedly connected to the main skeleton 71 of the superconducting magnet 7 .

[0054] Specifically, the main frame 71 is a symmetrical hollow cylindrical structure. Furthermore, the outer ring of the main frame 71 is provided with at least two first wire grooves, which are used to wind the main coil 72 and form a main magnet together with the main frame 71.

[0055] Specifically, the shielding magnet includes a shielding frame 73, the outer ring of which is provided with a second wire groove for winding a shielding coil 74, forming a shielding magnet together with the shielding frame 73. Furthermore, the shielding frame 73 is a double-layer hollow cylindrical structure.

[0056] Specifically, the main coil 72 and the shielding coil 74 are coils wound by superconducting wires. The interior of the 4K container 75 is a 4K ultra-low temperature environment.

[0057] Specifically, the cold shield 6 is a closed thin-wall double-cylinder structure. The superconducting magnet 7 and the cooling ring 42 are both located inside the closed cylinder of the cold shield 6.

[0058] Specifically, the cooling ring 42 is centrally disposed between the two shielding magnets.

[0059] Specifically, the two ends of the cooling belt 43 have connecting fins. The fin at one end of the cooling belt 43 is connected to the cooling ring 42, and the other end is divided into two parts, one part is connected to the shielding coil 74 in the superconducting magnet 7, and the other part is connected to the main coil 72 in the main magnet.

[0060] Specifically, the axes of the main skeleton 71 and the shielding skeleton 73 coincide with each other.

[0061] Specifically, the main frame 71 and the shield frame 73 are connected by welding. The 4K container 75 is fixed to the main magnet and the two shield magnets by welding.

[0062] Specifically, one end of the pull rod 8 is connected to the inner wall of the Dewar container 5 , and the other end is connected to the 4K container 75 in the superconducting magnet 7 .

[0063] Specifically, the tie rods 8 are provided with connecting blocks, and the connecting blocks are used to connect the tie rods 8 to the cold shield 6. Furthermore, the tie rods 8 are distributed around the end surfaces of both sides of the superconducting magnet 7.

[0064] Through a specific embodiment, the present invention realizes primary refrigeration by providing a first-stage cold head 2 of the refrigerator directly connected to the cold shield 6. Furthermore, by providing a conductive cooling ring 42, a plurality of conductive cooling belts 43 provided along the circumferential direction of the conductive cooling ring 42 are utilized to connect the coils of the superconducting magnet 7 for heat transfer, thereby realizing secondary refrigeration and realizing synchronous conductive cooling of the superconducting magnet 7 in the circumferential direction. While increasing the cooling rate, the uniformity of the temperature field inside the superconducting magnet 7 is improved, thereby ensuring good magnetic field uniformity. In addition, by providing a pull rod 8, the superconducting magnet 7 and the cold shield 6 are suspended in the Dewar container 5 to avoid direct contact with the Dewar container 5 and reduce heat leakage of the magnet. The present invention performs cooling through the refrigerator 1 without consuming liquid helium, and has the characteristics of simple structure, low cost, uniform temperature field and uniform magnetic field.

[0065] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A liquid helium-free superconducting magnet for animal imaging, characterized in that: The liquid helium-free animal imaging superconducting magnet comprises a superconducting magnet, a liquid helium-free cryogenic system and a pull rod, and the superconducting magnet, the liquid helium-free cryogenic system and the pull rod are all in a vacuum environment; The superconducting magnet includes a main magnet, two shielding magnets and a 4K container; The main magnet is formed by winding a main coil in an external wire slot of the main frame, and the shielding magnet is formed by winding a shielding coil in an external wire slot of the shielding frame. The two shielding magnets are symmetrically distributed at both ends of the main magnet and are coaxial with the main magnet. The 4K container encloses the main magnet and the two shielding magnets. The liquid helium-free cryogenic system includes a refrigerator, a first-stage cold head of the refrigerator, a cold shield, a second-stage cold head of the refrigerator, a cooling structure and a Dewar container. The cold shield is sleeved in the Dewar container, and the superconducting magnet is arranged in the cold shield. The cooling structure includes a cooling ring and a cooling belt. The cooling ring is arranged around the superconducting magnet and is fixedly connected to the superconducting magnet through a support rod. The first-stage cold head of the refrigerator is directly connected to the cold shield to realize first-stage refrigeration, and the second-stage cold head of the refrigerator is directly connected to the cooling ring. The cooling ring is connected to the coil of the superconducting magnet through the cooling belt to realize second-stage refrigeration. The two ends of the cooling belt are provided with connecting fins, one end of the cooling belt is connected to the cooling ring, and the other end is divided into two parts, one part is connected to the shielding coil in the superconducting magnet, and the other part is connected to the main coil in the main magnet; The superconducting magnet and the cold shield are suspended inside the Dewar container through the tie rods.

2. The cryogen-free animal imaging superconducting magnet according to claim 1, characterized in that: The support rods are fixedly connected to the main frame of the superconducting magnet.

3. The liquid helium-free animal imaging superconducting magnet according to claim 2, characterized in that: The main skeleton is a symmetrical hollow cylindrical structure.

4. The liquid helium-free animal imaging superconducting magnet according to claim 2, characterized in that: The outer ring of the main frame is provided with at least two first wire grooves, and the first wire grooves are used for winding the main coil to form a main magnet with the main frame.

5. The cryogen-free animal imaging superconducting magnet according to claim 1, characterized in that: The shielding magnet comprises a shielding frame, wherein the outer ring of the shielding frame is provided with a second wire groove, and the second wire groove is used for winding the shielding coil to form the shielding magnet together with the shielding frame.

6. The liquid helium-free animal imaging superconducting magnet according to claim 5, characterized in that: The shielding frame is a double-layer hollow cylindrical structure.

7. The cryogen-free superconducting magnet for animal imaging according to claim 1, characterized in that: The main coil and the shielding coil are coils wound by superconducting wires.

8. The cryogen-free superconducting magnet for animal imaging according to claim 1, characterized in that: The 4K container is in a 4K ultra-low temperature environment.

9. The cryogen-free superconducting magnet for animal imaging according to claim 1, characterized in that: The cold screen is a closed thin-walled double-cylinder structure.

10. The cryogen-free superconducting magnet for animal imaging according to claim 9, characterized in that: The superconducting magnet and the cooling ring are both located inside the closed cylinder of the cold shield.

11. The cryogen-free superconducting magnet for animal imaging according to claim 1, characterized in that: The cooling ring is centrally arranged between the two shielding magnets.

12. The cryogen-free superconducting magnet for animal imaging according to claim 1, characterized in that: The axes of the main frame and the shielding frame coincide with each other.

13. The cryogen-free superconducting magnet for animal imaging according to claim 1, characterized in that: The main frame and the shielding frame are connected by welding.

14. The cryogen-free superconducting magnet for animal imaging according to claim 1, characterized in that: The 4K container is fixed to the main magnet and two shielding magnets by welding.

15. The cryogen-free superconducting magnet for animal imaging according to claim 1, characterized in that: One end of the pull rod is connected to the inner wall of the Dewar container, and the other end is connected to the 4K container in the superconducting magnet.

16. The cryogen-free superconducting magnet for animal imaging according to claim 1, characterized in that: The pull rod is provided with a connecting block, and the connecting block is used to connect the pull rod with the cold screen.

17. The cryogen-free superconducting magnet for animal imaging according to claim 1, characterized in that: The pull rods are distributed around the end surfaces on both sides of the superconducting magnet.

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