Extremely-low-temperature heat-insulation demagnetizing refrigeration device and working method thereof

Abstract

The invention provides an extremely-low-temperature heat-insulation demagnetizing refrigeration device and a working method thereof. The working method comprises the specific steps that a thermal switch is switched off, a heat transfer loop between a magnetocaloric module and a heat sink is switched off, the magnetic field of a magnet is increased, and magnetocaloric materials are magnetized; after a certain magnetic field is obtained through adiabatic magnetization, a heat switch is conducted, so that a heat transfer loop between the magnetocaloric module and the heat sink is conducted, the magnetic field of the magnet continues to be increased, and isothermal magnetization is conducted on the magnetocaloric material till the required maximum magnetic field is achieved; when the thermal switch is switched off, a heat transfer loop between the magnetocaloric module and the heat sink is switched off, the magnetic field of the magnet is reduced, and the magnetocaloric material is adiabatic and demagnetized; and after the required refrigeration temperature is reached, the off state of the thermal switch is kept, the change rate of the magnetic field intensity of the magnet is controlled to keep the temperature constant at the target refrigeration temperature, and refrigerating capacity is provided for the load. According to the application, the magnetocaloric module can be adapted to various magnetocaloric materials of different types and different specifications, so that the optimal magnetocaloric material can be quickly and conveniently replaced according to the target refrigeration temperature.

Description

Technical Field

[0001] The present invention relates to the field of refrigeration technology, and in particular to an extremely low temperature adiabatic demagnetization refrigeration device and a working method thereof. Background Art

[0002] As the development of space resources continues, the refrigeration temperature required for space exploration is getting lower and lower. At the same time, with the continuous progress of the ground quantum field, the demand for high-performance, ultra-low temperature refrigerators is increasing. Ultra-low temperature refrigeration plays a vital role in space exploration, quantum computing, condensed matter physics and other fields.

[0003] Adiabatic demagnetization refrigeration uses the magnetocaloric effect of magnetocaloric materials to work. It is a solid refrigeration method that uses solid materials as refrigerants, so there is no risk of fluid leakage. The magnetocaloric effect is the adiabatic temperature change or isothermal entropy change phenomenon caused by the change in the magnetic moment of the magnetocaloric material when the external magnetic field changes. Adiabatic temperature change, that is, in the adiabatic case: when a magnetic field is applied to the magnetocaloric material, the order of the internal magnetic moment of the material increases, the magnetic entropy of the material decreases, the temperature entropy increases, and the temperature rises; when the magnetic field applied to the magnetocaloric material is reduced, the order of the internal magnetic moment of the material decreases, the magnetic entropy of the material increases, the temperature entropy decreases, and the temperature decreases. Isothermal entropy change, that is, in the isothermal case: when a magnetic field is applied to the magnetocaloric material, the temperature entropy remains unchanged, the magnetic entropy decreases, and the material releases heat to the outside; when the magnetic field applied to the magnetocaloric material is reduced, the temperature entropy remains unchanged, the magnetic entropy increases, and the material absorbs heat from the outside. Adiabatic demagnetization refrigeration has the advantages of high efficiency, no noise, no vibration, etc., and is an extremely low temperature refrigeration technology that does not rely on gravity and is very suitable for space applications. Summary of the invention

[0004] In view of this, it is necessary to provide a magnetocaloric module that can easily replace magnetocaloric materials to address the defects of the prior art, so as to maximize the refrigeration performance of the magnetocaloric materials and provide an ultra-low temperature adiabatic demagnetization refrigeration device and its working method that can improve the refrigeration efficiency.

[0005] To solve the above problems, this application adopts the following technical solutions:

[0006] One of the purposes of the present application is to provide a very low temperature adiabatic demagnetization refrigeration device, comprising: a magnetocaloric module (100), a magnet assembly (200), a heat sink (7) and a thermal switch (13), wherein:

[0007] The magnetic thermal module (100) comprises an upper metal rod (1), a magnetic thermal material (2), a connecting rod (3), and a lower metal rod (4); two ends of the connecting rod (3) are respectively inserted into one end connecting the upper metal rod (1) and the lower metal rod (4); and the magnetic thermal material (2) is sleeved on the connecting rod (3);

[0008] The magnet assembly (200) comprises a magnetic shielding shell (8), a magnetic shielding cover plate (9) and a magnet (10); the magnetic shielding shell (8) and the magnetic shielding cover plate (9) contain the magnet (10); and the magnet (10) is arranged around the magnetic thermal material (2) in the magnetic thermal module (100);

[0009] The heat sink (7) is connected to one end of the magnetic shielding shell (8), and the other end of the magnetic shielding shell (8) is provided with the magnetic shielding cover plate (9);

[0010] One end of the thermal switch (13) is connected to the heat sink (7), and the other end is connected to the magnetic thermal module (100).

[0011] In some of the embodiments, the ultra-low temperature adiabatic demagnetization refrigeration device further comprises a suspension assembly (300), wherein the suspension assembly (300) comprises an upper suspension (11), wherein the upper suspension (11) is installed on the upper part of the magnet assembly (200) or on the heat sink (7), and one end of the magnetic thermal module (100) is suspended inside the magnet assembly (200) via the upper suspension (11).

[0012] In some of the embodiments, the suspension assembly (300) further includes a lower suspension (12), which is installed at the lower part of the magnet assembly (200), and the lower suspension (12) is connected to the other end of the magnetic thermal module (100), and the position of the magnetic thermal module (100) in the magnet assembly (200) is positioned and controlled by the upper suspension (11) and the lower suspension (12).

[0013] In some of the embodiments, the upper suspension (11) and the lower suspension (12) include n suspension units, where n is an integer greater than or equal to 1, and any one of the suspension units is connected to the magnetic thermal module (100).

[0014] In some of the embodiments, the position or suspension length of the upper suspension (11) and / or the lower suspension (12) is adjustable, and the position of the magnetic thermal module (100) inside the magnet assembly (200) is changed by adjusting the position or the suspension length.

[0015] In some of the embodiments, the magnetocaloric module (100) does not have direct contact with the magnet assembly (200) and the heat sink (7).

[0016] In some of the embodiments, the heat sink (7) can provide pre-cooling of the magnetocaloric module (100), the magnet assembly (200), the suspension assembly (300) and the thermal switch (13) to a temperature of 20K or below; and can absorb the heat released by the magnetocaloric module (100).

[0017] In some of the embodiments, the upper metal rod (1) and the lower metal rod (4) are each provided with a flange plane, and the two end surfaces of the magnetocaloric material (2) are in contact with the flange planes of the upper metal rod (1) and the lower metal rod (4) respectively.

[0018] In some of the embodiments, the first heat transfer medium (5) and the second heat transfer medium (6) are respectively arranged between the two end surfaces of the magnetocaloric material (2) and the flange planes of the upper metal rod (1) and the lower metal rod (4).

[0019] In some embodiments, the first heat transfer medium (5) and the second heat transfer medium (6) include indium or silver or N-type low-temperature vacuum grease.

[0020] In some of the embodiments, the magnetocaloric material (2) is one or more of gadolinium gallium garnet, lithium gadolinium tetrafluoride, dysprosium gallium garnet, and ytterbium gallium garnet.

[0021] In some of the embodiments, the magnet (10) includes n magnet units, where n is an integer greater than or equal to 1, and the n magnets are enclosed in the magnetic shielding shell (8) and the magnetic shielding cover plate (9).

[0022] The second object of the present application is to provide a working method of the ultra-low temperature adiabatic demagnetization refrigeration device, comprising the following steps:

[0023] The thermal switch (13) is disconnected, the heat transfer loop between the magnetocaloric module (100) and the heat sink (7) is disconnected, the magnetic field of the magnet (10) is increased, and the magnetocaloric material (2) is magnetized; after adiabatic magnetization to a certain magnetic field, the thermal switch (13) is turned on to connect the heat transfer loop between the magnetocaloric module (100) and the heat sink (7), the magnetic field of the magnet (10) is further increased, and the magnetocaloric material (2) is isothermally magnetized until the required maximum magnetic field is reached; the thermal switch (13) is disconnected, the heat transfer loop between the magnetocaloric module (100) and the heat sink (7) is disconnected, the magnetic field of the magnet (10) is reduced, and the magnetocaloric material (2) is adiabatically demagnetized; after reaching the required cooling temperature, the thermal switch (13) is kept disconnected, the rate of change of the magnetic field strength of the magnet (10) is controlled to keep the temperature constant at the target cooling temperature, and provide cooling capacity for the load.

[0024] This application adopts the above technical solution, and its beneficial effects are as follows:

[0025] The present application provides an extremely low temperature adiabatic demagnetization refrigeration device and a working method thereof, and the specific process is as follows: disconnecting the thermal switch (13), disconnecting the heat transfer circuit between the magnetocaloric module (100) and the heat sink (7), increasing the magnetic field of the magnet (10), and magnetizing the magnetocaloric material (2); after adiabatically magnetizing to a certain magnetic field, turning on the thermal switch (13), connecting the heat transfer circuit between the magnetocaloric module (100) and the heat sink (7), continuing to increase the magnetic field of the magnet (10), and isothermally magnetizing the magnetocaloric material (2) until the required maximum magnetic field is reached; disconnecting the thermal switch (13), disconnecting the heat transfer circuit between the magnetocaloric module (100) and the heat sink (7), reducing the magnetic field of the magnet (10), and adiabatically demagnetizing the magnetocaloric material (2); after reaching the required refrigeration temperature, keeping the thermal switch (13) disconnected, controlling the rate of change of the magnetic field strength of the magnet (10) to keep the temperature constant at the target refrigeration temperature, and providing refrigeration capacity for the load. The present application can realize the adaptation of the magnetocaloric module (100) to a variety of magnetocaloric materials (2) of different types and specifications, and facilitates the rapid and convenient replacement of the optimal magnetocaloric material (2) according to the target refrigeration temperature, so that the magnetocaloric material (2) can work in the large entropy change region, give full play to the refrigeration performance of the magnetocaloric material (2), reduce the requirements for the maximum magnetic field strength, expand the refrigeration range of the refrigerator, and improve the overall performance of the refrigerator. It can be applied to space exploration, quantum computing, condensed matter physics and other research to provide extremely low temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 A schematic cross-sectional view of a magnetic thermal module provided in an embodiment of the present application.

[0028] Figure 2 A schematic cross-sectional view of an extremely low temperature adiabatic demagnetization refrigeration device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0030] In the description of the present application, it should be understood that the terms "upper", "lower", "horizontal", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0031] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0032] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0033] See also Figure 1 to Figure 2 , a schematic structural diagram of a very low temperature adiabatic demagnetization refrigeration device provided in an embodiment of the present application, comprising: a magnetocaloric module (100), a magnet assembly (200), a heat sink (7) and a thermal switch (13). The specific structure of each component and its implementation method are described in detail below.

[0034] The magnetic thermal module (100) comprises an upper metal rod (1), a magnetic thermal material (2), a connecting rod (3), and a lower metal rod (4).

[0035] Specifically, the two ends of the connecting rod (3) are respectively inserted into one end connecting the upper metal rod (1) and the lower metal rod (4), and the magnetic thermal material (2) is sleeved on the connecting rod (3).

[0036] In this embodiment, the upper metal rod (1) and the lower metal rod (4) each have a flange plane, and the two end surfaces of the magnetic thermal material (2) are in contact with the flange planes of the upper metal rod (1) and the lower metal rod (4) to form a whole. The material of the upper metal rod (1) and the lower metal rod (4) includes: one or more of gold, silver, copper, and aluminum.

[0037] It can be understood that, since the magnetocaloric material (2) passes through the connecting rod (3), the magnetocaloric material (2) is in close contact with the flange surfaces of the upper metal rod (1) and the lower metal rod (4), and in a low-temperature environment, due to the shrinkage of the connecting rod (3), the magnetocaloric material (2) and the flange are in closer contact, thereby enhancing the heat transfer effect between the contact surfaces.

[0038] In this embodiment, the first heat transfer medium (5) and the second heat transfer medium (6) are respectively arranged between the two end surfaces of the magnetocaloric material (2) and the flange planes of the upper metal rod (1) and the lower metal rod (4).

[0039] It can be understood that since a heat transfer medium is arranged between the two end surfaces of the magnetocaloric material (2) and the flange planes of the upper metal rod (1) and the lower metal rod (4), the heat transfer effect between the contact surfaces can be enhanced, and the heat transfer medium includes but is not limited to indium, silver, and N-type low-temperature vacuum grease.

[0040] In this embodiment, the heat transfer medium preferably uses a softer material such as indium. Since indium has good thermal conductivity at low temperatures, indium as a heat transfer medium can not only ensure a good heat transfer effect, but also adjust the pressure between the magnetocaloric material and the upper metal rod and the lower metal rod flange contact surface by changing the thickness of the heat transfer medium, thereby avoiding the stress caused by the cold shrinkage of the connecting rod from damaging the magnetocaloric material.

[0041] Furthermore, threaded holes are provided on the upper part of the upper metal rod (1) and the lower part of the lower metal rod (4) for installing a thermometer to facilitate obtaining the real-time temperature of the magnetocaloric module, or for connecting to a required thermal connection.

[0042] The magnet assembly (200) comprises a magnetic shielding shell (8), a magnetic shielding cover plate (9) and a magnet (10); the magnetic shielding shell (8) and the magnetic shielding cover plate (9) contain the magnet (10); and the magnet (10) is arranged around the magnetic thermal material (2) in the magnetic thermal module (100).

[0043] It can be understood that the magnetic thermal module (100) is arranged inside the magnet assembly (200), and the magnetic thermal module (100) does not have direct contact with the magnet assembly (200) and the heat sink (7).

[0044] The heat sink (7) is connected to one end of the magnetic shielding shell (8), and the other end of the magnetic shielding shell (8) is provided with the magnetic shielding cover plate (9).

[0045] It can be understood that since the magnet (10) is wrapped inside the magnetic shielding shell (8), one end of the magnetic shielding shell (8) is connected to the heat sink (7), and the heat sink (7) pre-cools the magnet assembly (200).

[0046] One end of the thermal switch (13) is connected to the heat sink (7), and the other end is connected to the magnetic thermal module (100).

[0047] It can be understood that, since the thermal switch (13) is disposed between the magnetocaloric module (100) and the heat sink (7), the on-off state of the heat transfer circuit between the magnetocaloric module (100) and the heat sink (7) is controlled by controlling the on-off state of the thermal switch (13). The thermal switch (13) includes an active thermal switch and a passive thermal switch.

[0048] In this embodiment, the ultra-low temperature adiabatic demagnetization refrigeration device also includes a suspension assembly (300), and the suspension assembly (300) includes an upper suspension (11). The upper suspension (11) is installed on the upper part of the magnet assembly (200) or on the heat sink (7), and one end of the magnetic thermal module (100) is suspended inside the magnet assembly (200) through the upper suspension (11).

[0049] Furthermore, the suspension assembly (300) further comprises a lower suspension (12), wherein the lower suspension (12) is installed at the lower part of the magnet assembly (200), and the lower suspension (12) is connected to the other end of the magnetic thermal module (100), and the position of the magnetic thermal module (100) in the magnet assembly (200) is positioned and controlled by the upper suspension (11) and the lower suspension (12).

[0050] Furthermore, the upper suspension (11) and the lower suspension (12) include n suspension units, where n is an integer greater than or equal to 1, and any one of the suspension units is connected to the magnetic thermal module (100).

[0051] It should be noted that the position or suspension length of the upper suspension (11) and / or the lower suspension (12) is adjustable, and the position of the magnetic thermal module (100) inside the magnet assembly (200) is changed by adjusting the position or the suspension length.

[0052] It can be understood that, under the action of the suspension assembly (300), it can be ensured that the magnetic thermal module (100) does not have direct contact with the magnet assembly (200) and the heat sink (7).

[0053] In this embodiment, the magnetocaloric material (2) is one or more of gadolinium gallium garnet, lithium gadolinium tetrafluoride, dysprosium gallium garnet, and ytterbium gallium garnet.

[0054] In this embodiment, the magnet (10) includes n magnet units, where n is an integer greater than or equal to 1; the n magnets are enclosed in the magnetic shielding shell (8) and the magnetic shielding cover plate (9).

[0055] The installation process of the extremely low temperature adiabatic demagnetization refrigeration device provided in this embodiment is as follows:

[0056] According to the above structure, the magnet (10) is installed inside the magnetic shielding shell (8), and the magnetic shielding cover plate (9) is connected to the magnetic shielding shell (8). The magnet (10), the magnetic shielding shell (8), and the magnetic shielding cover plate (9) constitute a magnet assembly (200). The magnet assembly (200) is installed at the bottom of the heat sink (7).

[0057] For the assembly of the magnetic thermal material (2), the connecting rod (3) and the lower metal rod (4) are connected to form a whole by means of threads, a heat transfer medium (6) is applied or placed on the flange surface of the lower metal rod (4), the magnetic thermal material (2) is sleeved on the connecting rod (3), and the end face of the magnetic thermal material (2) is fitted with the flange surface of the lower metal rod (4) through the heat transfer medium (6), the heat transfer medium (5) is applied or placed on the other end face of the magnetic thermal material (2), the upper metal rod (1) is connected to the connecting rod (3) by means of threads to form a whole, and the end face of the magnetic thermal material (2) is fitted with the flange surface of the upper metal rod (1) through the heat transfer medium (5), and the preload force is adjusted by adjusting the distance between the upper and lower metal rods or by adjusting the thickness of the heat transfer medium.

[0058] The upper metal rod (1), the magnetocaloric material (2), the connecting rod (3), the lower metal rod (4), the heat transfer medium (5), and the heat transfer medium (6) are assembled to form a magnetocaloric module (100). The upper suspension (11) is installed on the upper part of the magnet assembly (200). The assembled magnetocaloric module (100) is suspended inside the magnet assembly (200) through the upper suspension (11), and the lower suspension (12) is installed on the lower part of the magnet assembly (200) and connected to the magnetocaloric module (100). The position of the magnetocaloric module (100) in the magnet (10) is positioned and controlled by the upper suspension (11) and the lower suspension (12). One side of the heat switch (13) is connected to the magnetocaloric module (100), and the other side is connected to the heat sink (7). In this way, the assembly of the extremely low temperature adiabatic demagnetization refrigeration device is realized.

[0059] The working method of the extremely low temperature adiabatic demagnetization refrigeration device provided in this embodiment includes the following steps:

[0060] a. Precooling: The heat sink (7) is precooled to an initial temperature, and the magnet assembly (200), the thermal switch (13), the magnetothermal module (100), and the suspension assembly (300) are cooled to the temperature of the heat sink (7) through the heat sink (7);

[0061] b. Adiabatic magnetization: disconnect the thermal switch (13), disconnect the heat transfer circuit between the magnetocaloric module (100) and the heat sink (7), increase the magnetic field of the magnet (10), and magnetize the magnetocaloric material (2);

[0062] c. Isothermal magnetization: After adiabatic magnetization to a certain magnetic field, the thermal switch (13) is turned on to connect the heat transfer circuit between the magnetocaloric module (100) and the heat sink (7), thereby increasing the magnetic field of the magnet (10) and continuing to magnetize the magnetocaloric material (2) until the required maximum magnetic field is reached;

[0063] d. Adiabatic demagnetization: disconnect the thermal switch (13), disconnect the heat transfer circuit between the magnetocaloric module (100) and the heat sink (7), reduce the magnetic field of the magnet (10), and demagnetize the magnetocaloric material (2);

[0064] e. Isothermal demagnetization: After reaching the desired cooling temperature, for example 0.8K, keep the thermal switch (13) in the off state, control the rate of change of the magnetic field strength of the magnet (10) to keep the temperature constant at the target cooling temperature, and provide cooling capacity for the load;

[0065] f. When the magnetic field decreases to 0, a refrigeration cycle is completed, and steps b, c, d, and e are repeated for the next refrigeration cycle;

[0066] g. When the magnetic thermal material (2) needs to be replaced, replace the magnetic thermal material (2) according to the installation steps, and then perform the refrigeration process according to a, b, c, d, e, and f.

[0067] The ultra-low temperature adiabatic demagnetization refrigeration device and its working method provided in the above-mentioned embodiment of the present application can realize the adaptation of the magnetocaloric module (100) to a variety of magnetocaloric materials (2) of different types and specifications, and facilitate the rapid and convenient replacement of the optimal magnetocaloric material (2) according to the target refrigeration temperature, so that the magnetocaloric material (2) can work in the large entropy change region, give full play to the refrigeration performance of the magnetocaloric material (2), reduce the requirements for the maximum magnetic field strength, expand the refrigeration range of the refrigerator, and improve the overall performance of the refrigerator. It can be applied to space exploration, quantum computing, condensed matter physics and other research to provide ultra-low temperature.

[0068] It can be understood that the technical features of the above-described embodiments can be arbitrarily combined. In order to make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The above are only preferred embodiments of the present application, and only specifically describe the technical principles of the present application. These descriptions are only for explaining the principles of the present application and cannot be interpreted as limiting the scope of protection of the present application in any way. Based on the explanation here, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application, and other specific implementation methods of the present application that can be associated with the technicians in this field without creative work, should be included in the scope of protection of the present application.

Claims

1. A very low temperature adiabatic demagnetization refrigeration device, characterized in that: include: A magnetothermal module (100), a magnet assembly (200), a heat sink (7) and a thermal switch (13), wherein: The magnetic thermal module (100) comprises an upper metal rod (1), a magnetic thermal material (2), a connecting rod (3), and a lower metal rod (4); two ends of the connecting rod (3) are respectively inserted into one end connecting the upper metal rod (1) and the lower metal rod (4); and the magnetic thermal material (2) is sleeved on the connecting rod (3); The magnet assembly (200) comprises a magnetic shielding shell (8), a magnetic shielding cover plate (9) and a magnet (10); the magnetic shielding shell (8) and the magnetic shielding cover plate (9) contain the magnet (10); and the magnet (10) is arranged around the magnetic thermal material (2) in the magnetic thermal module (100); The heat sink (7) is connected to one end of the magnetic shielding shell (8), and the other end of the magnetic shielding shell (8) is provided with the magnetic shielding cover plate (9); One end of the thermal switch (13) is connected to the heat sink (7), and the other end is connected to the magnetic thermal module (100).

2. The extremely low temperature adiabatic demagnetization refrigeration device according to claim 1, characterized in that: The extremely low temperature adiabatic demagnetization refrigeration device further comprises a suspension assembly (300), wherein the suspension assembly (300) comprises an upper suspension (11), wherein the upper suspension (11) is installed on the upper part of the magnet assembly (200) or on the heat sink (7), and one end of the magnetic thermal module (100) is suspended inside the magnet assembly (200) via the upper suspension (11).

3. The extremely low temperature adiabatic demagnetization refrigeration device according to claim 2, characterized in that: The suspension assembly (300) further comprises a lower suspension (12), wherein the lower suspension (12) is installed at the lower part of the magnet assembly (200), and the lower suspension (12) is connected to the other end of the magnetic thermal module (100), and the position of the magnetic thermal module (100) in the magnet assembly (200) is positioned and controlled by the upper suspension (11) and the lower suspension (12).

4. The extremely low temperature adiabatic demagnetization refrigeration device according to claim 3, characterized in that: The upper suspension (11) and the lower suspension (12) include n suspension units, where n is an integer greater than or equal to 1, and any one of the suspension units is connected to the magnetic thermal module (100).

5. The extremely low temperature adiabatic demagnetization refrigeration device according to claim 4, characterized in that: The position or suspension length of the upper suspension (11) and / or the lower suspension (12) is adjustable, and the position of the magnetic thermal module (100) inside the magnet assembly (200) is changed by adjusting the position or the suspension length.

6. The extremely low temperature adiabatic demagnetization refrigeration device according to claim 5, characterized in that: The magnetocaloric module (100) is not in direct contact with the magnet assembly (200) or the heat sink (7).

7. The extremely low temperature adiabatic demagnetization refrigeration device according to claim 5, characterized in that: The heat sink (7) can provide pre-cooling of a temperature of 20K or below for the magnetocaloric module (100), the magnet assembly (200), the suspension assembly (300) and the thermal switch (13); and can absorb heat released by the magnetocaloric module (100).

8. The extremely low temperature adiabatic demagnetization refrigeration device according to claim 1, characterized in that: The upper metal rod (1) and the lower metal rod (4) are each provided with a flange plane, and the two end surfaces of the magnetocaloric material (2) are in contact with the flange planes of the upper metal rod (1) and the lower metal rod (4) respectively.

9. The extremely low temperature adiabatic demagnetization refrigeration device according to claim 8, characterized in that: The first heat transfer medium (5) and the second heat transfer medium (6) are respectively arranged between the two end surfaces of the magnetocaloric material (2) and the flange planes of the upper metal rod (1) and the lower metal rod (4).

10. The extremely low temperature adiabatic demagnetization refrigeration device according to claim 8, characterized in that: The first heat transfer medium (5) and the second heat transfer medium (6) include but are not limited to indium or silver or N-type low-temperature vacuum grease.

11. The extremely low temperature adiabatic demagnetization refrigeration device according to claim 1, characterized in that: The magnetocaloric material (2) is one or more of gadolinium gallium garnet, lithium gadolinium tetrafluoride, dysprosium gallium garnet, and ytterbium gallium garnet.

12. The extremely low temperature adiabatic demagnetization refrigeration device according to claim 1, characterized in that: The magnet (10) comprises n magnet units, where n is an integer greater than or equal to 1; the n magnets are enclosed in the magnetic shielding shell (8) and the magnetic shielding cover plate (9).

13. A method for operating the extremely low temperature adiabatic demagnetization refrigeration device according to claim 1, characterized in that: The steps include: The thermal switch (13) is disconnected, the heat transfer loop between the magnetocaloric module (100) and the heat sink (7) is disconnected, the magnetic field of the magnet (10) is increased, and the magnetocaloric material (2) is magnetized; after adiabatically magnetizing to a certain magnetic field, the thermal switch (13) is turned on to connect the heat transfer loop between the magnetocaloric module (100) and the heat sink (7), the magnetic field of the magnet (10) is continued to be increased, and the magnetocaloric material (2) is isothermally magnetized until the required maximum magnetic field is reached; the thermal switch (13) is disconnected, the heat transfer loop between the magnetocaloric module (100) and the heat sink (7) is disconnected, the magnetic field of the magnet (10) is reduced, and the magnetocaloric material (2) is adiabatically demagnetized; after reaching the required cooling temperature, the thermal switch (13) is kept disconnected, the rate of change of the magnetic field strength of the magnet (10) is controlled to keep the temperature constant at the target cooling temperature, and provide cooling capacity for the load.

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