Dry type superconducting magnet temperature changing system

Abstract

The invention belongs to the technical field of refrigeration temperature changing, and particularly discloses a dry type superconducting magnet temperature changing system which comprises a vacuum cover used for providing a vacuum environment; the sample testing tube is hollow and is sequentially provided with a sample placing cavity and a low-temperature circulating cavity from inside to outside, the sample testing tube is fixedly connected to the vacuum cover, and the air inlet end of the low-temperature circulating cavity is located in the vacuum cover; the refrigerating machine body is installed on the vacuum cover and provided with a cold head unit located in the vacuum cover; the helium grading heat exchange mechanism is arranged in the vacuum cover and is in hot connection with the cold head unit of the refrigerator body through a flexible heat conductor; two ends of the helium refrigerant circulating pipeline are respectively communicated with the gas inlet end and the gas outlet end of the low-temperature circulating cavity so as to form a closed helium circulating loop; the superconducting magnet is used for providing a magnetic field environment for the interior of the sample placing cavity. Through the structural design, the measurement precision of the physical property parameters of the sample can be effectively improved, and the refrigerating machine is convenient to disassemble, replace and maintain.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of refrigeration temperature change, and more particularly relates to a dry superconducting magnet temperature change system. BACKGROUND

[0002] As extreme physical conditions, strong magnetic field and ultra-low temperature have important application value in the fields of material physical property research, performance control and new effect exploration. At present, a comprehensive test device integrating superconducting magnet and low temperature environment has been developed, which can realize arbitrary sequence scanning of temperature and magnetic field through programmed control, so as to accurately measure the material properties under various physical field combinations. Such device is usually composed of two parts of superconducting magnet and low temperature thermostat, wherein the low temperature thermostat includes multiple cold screens, a refrigeration unit (usually a pulse tube refrigerator), a helium refrigerant circuit, a sample test chamber and a matching temperature control system.

[0003] In the helium refrigeration cycle, helium needs to flow through the primary and secondary cold heads of the refrigerator in turn for stepwise cooling, realizing the process from precooling to liquefaction. The current heat exchange modes mainly include cold head coil type and natural convection type. The cold head coil type adopts rigid connection of helium pipeline and refrigerator cold head, but the vibration generated during the operation of the refrigerator will be transmitted to the helium pipeline and the sample area through the rigid structure, thereby affecting the measurement of the physical parameters of the sample. Therefore, the existing system mostly uses pulse tube refrigerator with low vibration level, but this model has problems such as high purchase cost and difficulty in obtaining technology. At the same time, the welded connection also makes it difficult to disassemble the refrigerator, which is not conducive to equipment maintenance and component replacement. The other natural convection heat exchange scheme places the refrigerator in the Dewar cavity, and after the helium enters the Dewar cavity, it exchanges heat with the primary and secondary cold heads through the high-efficiency helium refrigerant heat exchanger, thereby realizing the purpose of liquefaction. This method also cannot avoid the influence of cold head vibration due to the close cooperation of the Dewar cavity structure with the shape of the refrigerator, and also limits the selection and replacement flexibility of the refrigerator model, which also brings inconvenience to system upgrading and maintenance. SUMMARY

[0004] In view of the defects of the prior art, the present application provides a dry superconducting magnet temperature change system, which aims to solve the problems of inaccurate measurement of sample physical property parameters and poor interchangeability of the refrigerator due to vibration in the existing device.

[0005] The dry superconducting magnet temperature change system provided by the present application specifically comprises: A vacuum cover for providing a vacuum environment; A sample test tube, which is hollow and sequentially provided with a sample placement cavity and a low temperature circulation cavity from inside to outside, is fixedly connected to the vacuum cover, and the gas inlet end of the low temperature circulation cavity is located inside the vacuum cover; A refrigerator body is mounted on the vacuum cover and is provided with a cold head unit inside the vacuum cover; A helium gas staged heat exchange mechanism is arranged inside the vacuum cover and is in thermal connection with the cold head unit of the refrigerator body through a flexible heat conductor; A helium refrigerant circulation pipeline passes through the helium gas staged heat exchange mechanism and is in communication with the gas inlet end and the gas outlet end of the low-temperature circulation cavity respectively to form a closed helium gas circulation loop. A superconducting magnet is used to provide a magnetic field environment for the inside of the sample placement cavity.

[0006] Compared with the prior art, the above technical scheme conceived by the present application can effectively prevent the transmission of refrigerator vibration to the sample test area, thereby improving the sample parameter measurement accuracy, and at the same time realizes the modular decoupling of the refrigerator and the temperature changing system, facilitates disassembly, replacement and maintenance, and significantly improves the beneficial effects of equipment maintenance convenience, component replacement and system upgrade flexibility.

[0007] As a further preferred, the helium gas staged heat exchange mechanism includes a helium refrigerant heat exchanger and a helium refrigerant condenser, both of which are in thermal connection with the cold head unit, the helium refrigerant heat exchanger and the helium refrigerant condenser are arranged in sequence along the gas flow direction, and the helium refrigerant circulation pipeline penetrates the inside of the helium refrigerant heat exchanger and the helium refrigerant condenser.

[0008] As a further preferred, the cold head unit includes a primary cold head and a secondary cold head, the primary cold head is in thermal connection with the helium refrigerant heat exchanger through a flexible heat conductor, and the secondary cold head is in thermal connection with the helium refrigerant condenser through a flexible heat conductor.

[0009] As a further preferred, the flexible heat conductor is an oxygen-free copper braid or a red copper foil.

[0010] As a further preferred, the temperature changing system further includes a temperature adjusting unit, which is connected to the helium refrigerant circulation pipeline and located between the helium refrigerant condenser and the low-temperature circulation cavity, and is used to control the flow of helium refrigerant in the low-temperature circulation cavity to adjust the test temperature in the sample placement cavity.

[0011] As a further preferred, the variable temperature system further comprises a heat shield, which is wrapped with a plurality of layers of thermal insulation, and which is located inside the vacuum chamber and fixedly connected with the primary cold head, and the helium gas staged heat exchange mechanism and the gas inlet end of the low-temperature circulation cavity are both located inside the heat shield.

[0012] As a further preferred, the superconducting magnet is coaxially installed with the sample test tube and corresponds to the position of the sample to be measured.

[0013] As a further preferred, the superconducting magnet is fixedly connected with a superconducting magnet heat exchanger, which is connected with the secondary cold head.

[0014] As a further preferred, on the helium refrigerant circulation pipeline connected with the gas outlet end of the low-temperature circulation cavity, a baffle valve for controlling the on-off of gas flow, a circulating dry pump for providing circulation power, a gas buffer tank for stabilizing the system pressure, and an inlet needle valve for precisely adjusting the helium gas inlet speed are sequentially arranged in the direction of gas flow.

[0015] As a further preferred, the variable temperature system further comprises: a first pressure gauge, which is fixedly installed on the sample test tube and communicates with the sample placement cavity, for monitoring the pressure in the sample placement cavity; a second pressure gauge, which is fixedly installed on the gas buffer tank and communicates with the inside thereof, for monitoring the pressure in the gas buffer tank.

[0016] Overall, compared with the prior art, the above technical solutions conceived by the present application mainly have the following technical advantages: 1. The present application thermally connects the refrigeration machine cold head unit and the helium gas staged heat exchange mechanism inside the vacuum chamber through a flexible heat conductor, which can isolate the transmission of refrigeration machine operation vibration to the sample test area, thereby providing a stable environment for sample physical property parameter measurement and effectively improving the measurement accuracy.

[0017] 2. The present application realizes step-by-step cooling of helium by setting a closed helium circulation loop with a helium gas staged heat exchange mechanism and a sample test tube, and independently fixing the refrigeration machine body, sample test tube and other components on the vacuum chamber by using modular design. The system has a compact overall structure, and the decoupling of the refrigeration machine and the variable temperature core not only improves the refrigeration efficiency of the system, but also improves the flexibility of equipment maintenance, component replacement and system upgrading.

[0018] 3. This application, by setting up a baffle valve, a circulating dry pump, a gas buffer tank, and an inlet needle valve in a closed helium circulation loop, and by setting up a pressure gauge for monitoring the pressure of the sample placement chamber and the gas buffer tank, can accurately and stably control the system flow resistance, pressure, and circulating airflow, thereby precisely adjusting the sample testing temperature, and making the start-up, shutdown, maintenance, and fault diagnosis of the entire gas loop safer and more convenient, ensuring the reliability, repeatability, and operability of the system operation. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the variable temperature system provided in the embodiments of this application.

[0020] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1. Vacuum hood; 2. Sample test tube; 201. Sample placement chamber; 202. Low-temperature circulation chamber; 3. Refrigeration unit; 301. Cold head unit; 3011. First-stage cold head; 3012. Second-stage cold head; 4. Helium staged heat exchange mechanism; 401. Helium refrigerant heat exchanger; 402. Helium refrigerant condenser; 5. Flexible heat conductor; 6. Helium refrigerant circulation pipeline; 7. Temperature control unit; 8. Thermal shield; 9. Superconducting magnet; 901. Superconducting magnet heat exchanger; 10. Baffle valve; 11. Circulating dry pump; 12. Gas buffer tank; 13. Inlet needle valve; 14. First pressure gauge; 15. Second pressure gauge. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0022] Reference Figure 1 This embodiment provides a dry superconducting magnet temperature-controlled system, which, through its modular structure and vibration isolation technology, provides a stable and controllable low-temperature magnetic field environment for measuring the physical parameters of samples. The temperature-controlled system mainly includes a vacuum chamber 1, a sample test tube 2, a refrigerator body 3, a helium staged heat exchange mechanism 4, a helium refrigerant circulation pipeline 6, and a superconducting magnet 9.

[0023] The vacuum chamber 1 serves as the main load-bearing structure of the entire system, providing installation references and physical protection for all core components, ensuring the stability and reliability of the overall structure. The vacuum chamber 1 is made of high-strength materials such as 304 stainless steel with low outgassing rates. The interior of the vacuum chamber 1 is evacuated to a high vacuum state, effectively isolating heat transfer pathways such as gas molecule heat convection and gas heat conduction, providing the necessary vacuum insulation environment for the variable temperature system in this embodiment. In this embodiment, the core cryogenic components of the variable temperature system are all located inside the vacuum chamber.

[0024] Specifically, the sample test tube 2 is fixedly mounted on the vacuum chamber 1 via a sealing flange. Its structure is hollow, forming a sample placement chamber 201 and a cryogenic circulation chamber 202 sequentially from the inside out. The sample placement chamber 201 accommodates the sample rod containing the sample to be tested, while the cryogenic circulation chamber 202 is the key flow channel for helium refrigerant circulation. The inlet of the cryogenic circulation chamber 202 extends into the vacuum chamber 1. The helium refrigerant circulation pipeline 6 passes through the helium staged heat exchange mechanism 4 and is connected to the inlet and outlet of the cryogenic circulation chamber 202 to form a closed helium circulation loop. During sample testing, cryogenic helium or liquid helium flows in the cryogenic circulation chamber 202. By introducing static helium into the sample placement chamber 201 as a heat transfer medium, the thermal contact between the sample and the sample placement chamber 201 is improved, accelerating the transfer of cold energy to the sample at the bottom of the sample rod. The cold energy is then efficiently transferred to the internal sample placement chamber 201 through the tube wall of the sample test tube 2, thereby achieving sample cooling and temperature control. The sample testing tube includes an outer sample chamber tube, an inner sample chamber tube, and a sample rod. Both the outer and inner sample chamber tubes are constructed of thin-walled stainless steel. The annular gap between the outer and inner sample chamber tubes forms a low-temperature circulation chamber 202, and the interior of the inner sample chamber tube is configured as a sample placement chamber 201. To achieve wide-range, high-precision temperature control, a temperature sensor and a heater are integrated on the sample rod. The sample temperature can be adjusted by controlling the heater power and the helium pressure in the inner sample chamber tube, thereby enabling temperature scanning measurement. When it is necessary to raise the sample temperature or maintain a constant temperature at a target point, the control system applies controllable heat to the sample by adjusting the heater power to suppress the cooling effect of the helium refrigerant, thus achieving precise temperature balance.

[0025] More specifically, the refrigerator body 3 is sealed and mounted on the vacuum chamber 1 via flanges and shock-absorbing bellows, ensuring an airtight connection between the refrigerator body 3 and the vacuum chamber 1, capable of withstanding atmospheric pressure, and providing stable mechanical fixation for the entire assembly. The shock-absorbing bellows effectively attenuate the mechanical vibrations generated during refrigerator operation from being transmitted into the vacuum chamber, thereby reducing the impact of refrigerator vibrations on the measurement system. High-frequency mechanical vibrations generated by moving parts inside the refrigerator (such as the discharger and piston) are effectively attenuated and filtered by the flexible walls of the bellows. The refrigerator body 3 is selected from GM refrigerators, pulse tube refrigerators, or other cryogenic refrigerators capable of reaching liquid helium temperatures (e.g., around 4K). Its cold head unit 301 is located inside the vacuum chamber 1 and is responsible for generating cooling capacity; the portion outside the vacuum chamber 1 is used to connect to the compressor.

[0026] The GM refrigerator is a cryogenic refrigeration device based on the principle of adiabatic gas release refrigeration. It consists of a primary and a secondary cold head. In this embodiment, the cold head unit 301 includes a primary cold head 3011 (temperature range of approximately 30K-80K) and a secondary cold head 3012 (temperature as low as 3K-4K). The primary cold head 3011 precools the helium gas, and the secondary cold head 3012 liquefies the helium gas. To achieve efficient heat exchange and completely isolate vibration, the cold head unit 301 and the helium gas staged heat exchange mechanism 4 are thermally connected by a flexible heat conductor 5 (such as oxygen-free copper braided tape or copper foil). The connection method using the flexible heat conductor 5 is a soft connection. This soft connection is the key to achieving high stability measurement in this system. Compared with the existing device that achieves thermal connection between the helium gas channel and the refrigerator cold head by welding, it has the advantages of reducing the impact of cold head vibration on system measurement and facilitating refrigerator replacement.

[0027] Furthermore, the helium staged heat exchange mechanism 4 is located inside the vacuum chamber 1 and is thermally connected to the cold head unit 301 of the refrigerator via a flexible heat conductor 5. It includes a helium refrigerant heat exchanger 401 and a helium refrigerant condenser 402, both made of oxygen-free copper. The helium refrigerant heat exchanger 401 and the helium refrigerant condenser 402 are arranged sequentially along the gas flow direction, and a helium refrigerant circulation pipeline runs through the interiors of both. Specifically, the helium refrigerant heat exchanger 401 is connected to the first-stage cold head 3011 via the flexible heat conductor 5, using the cooling capacity of the first-stage cold head 3011 to pre-cool the circulating helium. The helium refrigerant condenser 402 is connected to the second-stage cold head 3012 via the flexible heat conductor 5, using the cryogenic temperature of the second-stage cold head 3012 to liquefy the pre-cooled helium.

[0028] The helium refrigerant circulation pipeline 6 forms a closed loop, constructed from seamless stainless steel tubing. It sequentially passes through the interiors of the helium refrigerant heat exchanger 401 and the helium refrigerant condenser 402. To improve heat exchange and cooling efficiency, the pipeline is coiled into a spiral shape within both heat exchangers and condensers to extend the transport path, before connecting to the inlet and outlet of the cryogenic circulation chamber 202 of the sample test tube 2. Helium circulates within this loop, achieving a continuous and efficient stepped cooling process: pre-cooling in heat exchanger 401 → liquefaction in condenser 402 → cooling through the sample area → re-pre-cooling.

[0029] Inside the vacuum chamber, with gas convection and conduction effectively eliminated, thermal radiation becomes the primary heat transfer pathway. To reduce radiative heat leakage, the variable temperature system also includes a heat shield 8. The heat shield 8 suppresses thermal radiation through active cooling. Specifically, the heat shield 8 is fixedly installed inside the vacuum chamber 1. Made of 6063 aluminum alloy, the heat shield 8 is connected to the flange of the primary cold head 3011 via oxygen-free copper braided straps to maintain its low temperature. The sample test tube 2 forms a thermal connection with the thermal radiation shielding layer through a heat sink. The helium staged heat exchange mechanism 4 and the bottom inlet of the sample placement chamber 201 are both enclosed inside the heat shield 8. Multiple layers of super-insulating material can be added externally to further enhance the insulation effect.

[0030] To achieve precise temperature control for sample property parameter measurement, a temperature regulation unit 7 is installed on the helium refrigerant circulation line 6. Specifically, the temperature regulation unit 7 is fixedly installed between the helium refrigerant condenser 402 and the sample test tube 2. The temperature regulation unit 7 adjusts the test temperature within the sample placement chamber 201 by controlling the helium refrigerant flow rate in the low-temperature circulation chamber 202. In this embodiment, the temperature regulation unit 7 can be a throttling needle valve or a replaceable capillary flow resistance section. When a throttling needle valve is used, the helium refrigerant circulation line 6 at the tail end of the throttling needle valve is connected to the outer tube of the sample chamber via a VCR interface for easy disassembly. The sample rod is located in the inner tube of the sample chamber, and its valve body is connected to the heat shield 8 via a heat sink to stabilize its temperature. Simultaneously, the control knob of the throttling needle valve is located at the atmospheric end of the vacuum chamber 1. The valve rod is sealed at room temperature, and the diameter of the liquid helium channel can be controlled by adjusting the height of the valve rod, thereby achieving throttling and cooling. By adjusting the valve rod opening, the cross-sectional area of ​​the liquid helium flow is changed, achieving a throttling effect, thus precisely controlling the refrigerant flow rate and temperature entering the sample area. By coordinating the control of this temperature regulation unit 7 and the heater on the sample rod, a wide-range, precise temperature control of the sample from below 1.5K to room temperature can be achieved. When a capillary flow resistance system is used, it is connected to the helium refrigerant circulation line 6 via a VCR connector for easy replacement and adjustment of the flow resistance.

[0031] Furthermore, in this embodiment, the superconducting magnet 9 provides a stable, strong magnetic field environment for sample testing. This superconducting magnet is a conductive-cooled dry superconducting magnet, coaxially mounted on the outside of the sample testing tube 2 and positioned corresponding to the sample placement cavity 201. To achieve magnet cooling, a superconducting magnet heat exchanger 901 is fixed to the superconducting magnet 9. This heat exchanger 901 is thermally connected to the secondary cold head 3012 of the refrigerator via a flexible heat conductor 5 (such as oxygen-free copper braided tape), achieving modular, vibration-free cooling. The superconducting magnet 9 and the refrigerator 3 are modularly decoupled, facilitating the replacement of superconducting magnets 9 of different specifications and sizes.

[0032] On the helium refrigerant circulation pipeline 6 connected to the gas outlet of the sample placement chamber 201, in sequence according to the gas flow direction, there are a baffle valve 10 for controlling the gas flow interruption, a circulation dry pump 11 for providing helium circulation power, a gas buffer tank 12 for stabilizing system pressure, the gas buffer tank 12 is used to transfer and store helium for circulation in the system, during the system startup phase, helium can be replenished into the system through the gas buffer tank 12 using a steel cylinder, and an inlet needle valve 13 for precisely adjusting the helium inlet speed.

[0033] To improve the stability and safety of the system, the variable temperature system also includes a first pressure gauge 14 and a second pressure gauge 15. The first pressure gauge 14 is fixedly installed on the sample test tube 2 and communicates with the sample placement chamber 201. It is configured to monitor the helium pressure in the sample placement chamber 201. The range of the first pressure gauge 14 is -1 bar to 1 bar. The second pressure gauge 15 is fixedly installed on the gas buffer tank 12 and communicates with its interior. It is configured to monitor the pressure in the gas buffer tank 12.

[0034] It should be understood that expressions such as "comprising" and "may include" as used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "comprising" and / or "having" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or combination thereof, but should not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0035] It should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0037] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0038] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A dry superconducting magnet temperature-changing system, characterized in that, include: Vacuum shroud (1), the vacuum shroud (1) being used to provide a vacuum environment; The sample test tube (2) is hollow and has a sample placement cavity (201) and a low temperature circulation cavity (202) arranged sequentially from the inside to the outside. The sample test tube (2) is fixedly connected to the vacuum hood (1) and the air inlet of the low temperature circulation cavity (202) is located inside the vacuum hood (1). The refrigerator body (3) is mounted on the vacuum shroud (1) and is provided with a cold head unit (301) located inside the vacuum shroud (1). Helium staged heat exchange mechanism (4) is disposed inside the vacuum shroud (1) and is thermally connected to the cold head unit (301) of the refrigerator body (3) through a flexible heat conductor (5). Helium refrigerant circulation pipeline (6) passes through the helium staged heat exchange mechanism (4) and the two ends of the helium refrigerant circulation pipeline (6) are respectively connected to the inlet and outlet of the low temperature circulation chamber (202) to form a closed helium circulation loop. A superconducting magnet (9) is used to provide a magnetic field environment for the interior of the sample placement cavity (201).

2. The dry superconducting magnet temperature-changing system as described in claim 1, characterized in that, The helium staged heat exchange mechanism (4) includes a helium refrigerant heat exchanger (401) and a helium refrigerant condenser (402). Both the helium refrigerant heat exchanger (401) and the helium refrigerant condenser (402) are thermally connected to the cold head unit (301). The helium refrigerant heat exchanger (401) and the helium refrigerant condenser (402) are arranged sequentially along the gas flow direction. The helium refrigerant circulation pipeline (6) passes through the interior of the helium refrigerant heat exchanger (401) and the helium refrigerant condenser (402).

3. The dry superconducting magnet temperature-changing system as described in claim 2, characterized in that, The cold head unit (301) includes a primary cold head (3011) and a secondary cold head (3012). The primary cold head (3011) is thermally connected to the helium refrigerant heat exchanger (401) through a flexible heat conductor (5), and the secondary cold head (3012) is thermally connected to the helium refrigerant condenser (402) through a flexible heat conductor (5).

4. The dry superconducting magnet temperature-changing system as described in claim 3, characterized in that, The flexible heat conductor (5) is an oxygen-free copper braided strip or a copper foil.

5. The dry superconducting magnet temperature-changing system as described in claim 3, characterized in that, The variable temperature system also includes a temperature regulating unit (7), which is connected to the helium refrigerant circulation pipeline (6) and located between the helium refrigerant condenser (402) and the low temperature circulation chamber (202). The temperature regulating unit (7) is used to control the flow rate of helium refrigerant in the low temperature circulation chamber (202) to regulate the test temperature in the sample placement chamber (201).

6. The dry superconducting magnet temperature-changing system as described in claim 3, characterized in that, The temperature-changing system also includes a heat shield (8), which is wrapped with multiple layers of heat insulation. The heat shield (8) is located inside the vacuum shield (1) and is fixedly connected to the first-stage cold head (3011). The inlet of the helium staged heat exchange mechanism (4) and the low-temperature circulation chamber (202) are both located inside the heat shield (8).

7. The dry superconducting magnet temperature-changing system as described in claim 3, characterized in that, The superconducting magnet (9) is coaxially mounted with the sample test tube (2) and corresponds to the position of the sample to be tested.

8. The dry superconducting magnet temperature-changing system as described in claim 7, characterized in that, A superconducting magnet heat exchanger (901) is fixedly connected to the superconducting magnet (9), and the superconducting magnet heat exchanger (901) is connected to the secondary cold head (3012).

9. The dry superconducting magnet temperature-changing system as described in claim 1, characterized in that, On the helium refrigerant circulation pipeline (6) connected to the outlet of the cryogenic circulation chamber (202), a baffle valve (10) for controlling the gas flow interruption, a circulation dry pump (11) for providing circulation power, a gas buffer tank (12) for stabilizing system pressure, and an inlet needle valve (13) for precisely adjusting the helium inlet speed are arranged in sequence according to the gas flow direction.

10. A dry superconducting magnet temperature-changing system as described in claim 9, characterized in that, The variable temperature system also includes: The first pressure gauge (14) is fixedly installed on the sample test tube (2) and communicates with the sample placement cavity (201) to monitor the pressure inside the sample placement cavity (201); The second pressure gauge (15) is fixedly installed on the gas buffer tank (12) and communicates with its interior, and is used to monitor the pressure inside the gas buffer tank (12).

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