A cooling system and superconducting magnet system

Abstract

The application belongs to the technical field of superconducting magnets, and specifically discloses a cooling system and a superconducting magnet system. The cooling system comprises a vacuum cover, a refrigerator and a first thermal switch. The refrigerator is provided with at least two, and each refrigerator has a cold head. The first thermal switch is arranged in one-to-one correspondence with the refrigerator. The cooled load, the cold head and the first thermal switch are located in the vacuum cover. The first thermal switch comprises a first low-temperature pulsating heat pipe. The evaporation section of the first low-temperature pulsating heat pipe is connected with the cooled load. The condensation section of the first low-temperature pulsating heat pipe is connected with the cold head. When the cold head is at the final refrigeration temperature, the first working medium in the first low-temperature pulsating heat pipe is in a two-phase flow state. The application can avoid the heat on the refrigerator from being transmitted to the cooled load when the refrigerator stops running or fails, thereby improving the operation safety and reliability of the cooled load.

Description

Technical Field

[0001] This invention relates to the field of superconducting magnet technology, and more particularly to a cooling system and a superconducting magnet system. Background Technology

[0002] The widespread application of superconductivity is inextricably linked to cryogenic temperatures. Superconductivity can only be achieved by cooling the magnet below its superconducting transition temperature. Exceeding this temperature can cause significant Joule heating, potentially damaging the magnet's structure and even leading to an explosion. Currently, the most widely used superconducting magnets are cryogenic superconducting magnets, with extremely low superconducting transition temperatures. For example, NbTi has a superconducting transition temperature of 9.6 K, and Nb3Sn has a superconducting transition temperature of 18.1 K. Even liquid nitrogen-temperature superconducting magnets, often referred to as high-temperature superconducting magnets, require a superconducting transition temperature of approximately 77 K. Therefore, ensuring the stable operation of superconducting magnets in cryogenic environments is crucial for the application of superconducting technology.

[0003] With the development of miniature cryogenic compressor technology, the application of direct cryogenic cooling of superconducting magnet systems is becoming increasingly widespread. Compared to the traditional cryogenic liquid immersion method, it offers advantages such as no liquid helium consumption, low cost, small size, compact structure, and ease of use and maintenance. A typical cryogenic compressor cooling system includes the load being cooled, a radiation shield, the cryogenic compressor, a vacuum container, and other accessories. The radiation shield is connected to the primary cold head of the cryogenic compressor, and the load being cooled is connected to the secondary cold head. During operation, the secondary cold head of the cryogenic compressor will reach the minimum temperature of the closed-loop cryogenic compressor.

[0004] In some applications of superconducting magnet systems, such as in space telescopes, due to the difficulty of system maintenance, redundant cryogenic systems are typically implemented. This extends the lifespan of each cryogenic unit by dividing its operating time among the redundant cryogenic units and reducing their duty cycles. Alternatively, it ensures that the load being cooled can continue operating normally if one cryogenic unit fails, allowing it to be cooled by the remaining cryogenic units. Therefore, a cryogenic thermal switch is located between the load being cooled and the cryogenic unit. When the cryogenic unit is operating, the thermal switch is on, with low thermal resistance, allowing for effective removal of the heat load at the design temperature. When the cryogenic unit stops operating or fails, the thermal switch is off, with high thermal resistance, thus blocking the heat transfer path between the cryogenic unit and the load being cooled, preventing heat from flowing from the cryogenic unit to the lower-temperature load, and ensuring the operation of the cryogenic system remains unaffected.

[0005] Cryogenic thermal switches typically include mechanical contact thermal switches, superconducting thermal switches, air-gap thermal switches, and magnetoresistive thermal switches. Mechanical contact thermal switches utilize the contact or disconnection of a movable surface to switch the thermal switch state. They have the advantages of an unrestricted operating temperature range and complete disconnection, but their thermal conductivity is limited by pressure and cannot be made very high. They also require an additional drive structure to move the thermal switch, making design more complex and requiring more space. Superconducting thermal switches utilize the difference in thermal conductivity between the normal and superconducting states of superconducting materials to switch the thermal switch. They have a high thermal conductivity when conducting, but are only suitable for temperatures below 0.5K. They also require an additional magnetic field acting on the superconducting thermal switch, increasing system complexity and cost. Furthermore, the magnetocaloric effect of applying a magnetic field to the thermal switch generates heat, and heat leakage occurs when the thermal switch is disconnected. Air-gap thermal switches operate at relatively low temperatures... The adsorbent is placed on the lower side. When the temperature on that side is low, the adsorbent adsorbs the gas, resulting in a low gas pressure in the blade gap, and the thermal switch is in the off state. As the temperature on that side rises, the adsorbent desorbs, the gas enters the gap, and the thermal switch is in the on state. It can be passively driven, but it requires a high preset operating temperature range and precision manufacturing, resulting in high cost. The principle of the magnetoresistive thermal switch is based on the magnetoresistive effect of certain metals. When a magnetic field is applied, the movement of the heat-carrying electrons is suppressed by the Lorentz force. The thermal conductivity of the material can be reduced to the level where heat is conducted only by phonons. Therefore, its switching capacity is relatively large. However, the magnetoresistive thermal switch is limited to extremely low temperature applications, requires a large magnetic field and corresponding electromagnets, resulting in high cost and large footprint. At the same time, the magnetoresistive material is too brittle and easily damaged, leading to increased processing and maintenance costs. Summary of the Invention

[0006] One object of the present invention is to provide a cooling system that can improve the operational safety and stability of the cooling system, improve the structural compactness of the cooling system, and reduce the installation cost of the cooling system.

[0007] Another objective of this invention is to provide a superconducting magnet system that improves the structural compactness of the superconducting magnet system and enhances its operating efficiency, safety, and reliability.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A cooling system for cooling a load to be cooled includes a vacuum chamber, a refrigerator and a first thermal switch. At least two refrigerators are provided, and each refrigerator has a cold head. The first thermal switch is provided in a one-to-one correspondence with the refrigerators. The load to be cooled, the cold head and the first thermal switch are all located inside the vacuum chamber.

[0010] The first thermal switch includes a first low-temperature pulsating heat pipe. The evaporation section of the first low-temperature pulsating heat pipe is connected to the cooled load, and the condensation section of the first low-temperature pulsating heat pipe is connected to the cold head. When the cold head is at the final cooling temperature, the first working fluid in the first low-temperature pulsating heat pipe is in a two-phase flow state.

[0011] As an optional technical solution for the refrigeration system, the cooling system also includes a primary radiation shield, which is suspended inside the vacuum chamber. The load to be cooled is located inside the primary radiation shield, and the cold head is thermally connected to the primary radiation shield.

[0012] As an optional technical solution for a refrigeration system, each of the refrigeration units includes two cold heads, namely a primary cold head and a secondary cold head. The condensation section of the first low-temperature pulsating heat pipe is connected to the secondary cold head, and the primary cold head is thermally connected to the primary radiation shield.

[0013] The cooling system further includes a second thermal switch, which includes a second low-temperature pulsating heat pipe. The condensing section of the second low-temperature pulsating heat pipe is thermally connected to the first-stage cold head, and the evaporating section of the second low-temperature pulsating heat pipe is thermally connected to the cooled load. The triple point in the second low-temperature pulsating heat pipe is critically higher than the final cooling temperature of the first-stage cold head.

[0014] As an optional technical solution for a refrigeration system, a secondary radiation shield is suspended inside the primary radiation shield, the load to be cooled is located inside the secondary radiation shield, and the secondary cold head is thermally connected to the secondary radiation shield.

[0015] As an optional technical solution for a refrigeration system, the secondary radiation shield is connected to the secondary cold head via a third thermal switch. The third thermal switch includes a third low-temperature pulsating heat pipe. The evaporation section of the third low-temperature pulsating heat pipe is thermally connected to the secondary radiation shield, and the condensation section of the third low-temperature pulsating heat pipe is thermally connected to the secondary cold head. When the secondary cold head is at the final refrigeration temperature, the third working fluid in the third low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state.

[0016] As an optional technical solution for a refrigeration system, the cold head is thermally connected to the primary radiation shield via a fourth thermal switch. The fourth thermal switch includes a fourth low-temperature pulsating heat pipe. The evaporation section of the fourth low-temperature pulsating heat pipe is thermally connected to the primary radiation shield, and the condensation section of the fourth low-temperature pulsating heat pipe is thermally connected to the cold head. When the cold head is at the final refrigeration temperature, the fourth working fluid in the fourth low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state.

[0017] As an optional technical solution for a refrigeration system, the cooling system includes a first charging system, which is used to charge a first working fluid into the first low-temperature pulsating heat pipe. The first charging system is configured in a one-to-one correspondence with the first thermal switch.

[0018] As an optional technical solution for a refrigeration system, the first working fluid is helium, hydrogen, neon, or nitrogen;

[0019] The second working fluid in the second low-temperature pulsating heat pipe is neon, argon, nitrogen, oxygen, or methane.

[0020] As an optional technical solution for a refrigeration system, the outer surface of the cold head and / or the first thermal switch is covered with an insulation layer;

[0021] And / or, the first thermal switch has a first connecting surface and a second connecting surface, the first connecting surface being thermally connected to the cold head, the second connecting surface being thermally connected to the cooled load, and the first connecting surface and / or the second connecting surface being provided with a thermally conductive coating and / or a thermally conductive sheet.

[0022] A superconducting magnet system includes a superconducting magnet and a cooling system as described above, wherein the superconducting magnet is the cooled load.

[0023] The beneficial effects of this invention are as follows:

[0024] The cooling system provided by this invention utilizes a first thermal switch including a first low-temperature pulsating heat pipe. When the refrigerator corresponding to the first thermal switch is operating normally, the temperature of the refrigerator's cold head can reach the final cooling temperature, allowing the first working fluid in the condensation section of the first low-temperature pulsating heat pipe to be condensed into a liquid state. Meanwhile, the first working fluid in the evaporation section of the first low-temperature pulsating heat pipe is evaporated into a gaseous state due to the influence of the temperature of the cooled load. Because of the small pipe diameter, the first working fluid in the first low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state due to capillary force, resulting in a high thermal conductivity and good heat transfer. The heat generated by the cooled load during operation can be quickly carried away through the first low-temperature pulsating heat pipe. When the refrigerator malfunctions or stops working, the temperature of the refrigerator's cold head rises, and the temperature of the condensation section connected to the refrigerator rises above the critical temperature of the first working fluid. The first working fluid in the condensation section converts into a gaseous state, increasing the thermal resistance of the first low-temperature pulsating heat pipe. The first thermal switch is then in an open state, preventing heat from being transferred to the cooled load through the first thermal switch.

[0025] The superconducting magnet system provided by this invention, by employing the aforementioned cooling system and by setting at least two refrigerators and connecting a first thermal switch including a first low-temperature pulsating heat pipe between the refrigerators and the cooled load, can prevent the high temperature of the refrigerators from being transferred to the cooled load in the event of a refrigerator failure. This ensures that the cooled load can operate safely and stably under the cooling effect of other refrigerators, thereby improving the operational safety and reliability of the superconducting magnet system. At the same time, since the thermal switch occupies a small space and can be flexibly arranged, it can effectively improve the structural compactness of the superconducting magnet system. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the superconducting magnet system provided in Embodiment 1 of the present invention;

[0027] Figure 2 This is a schematic diagram of the pulsating heat pipe provided in Embodiment 1 of the present invention;

[0028] Figure 3 This is a schematic diagram of the filling system provided in Embodiment 2 of the present invention;

[0029] Figure 4 This is a schematic diagram of the structure of the first thermal switch provided in Embodiment 3 of the present invention;

[0030] Figure 5 yes Figure 4 Top view of the structure;

[0031] Figure 6 yes Figure 4 Side view of the middle structure;

[0032] Figure 7 This is a schematic diagram of the structure of the first thermal switch provided in Embodiment 4 of the present invention;

[0033] Figure 8 This is a schematic diagram of the structure of the first thermal switch and the fourth thermal switch provided in Embodiment 5 of the present invention;

[0034] Figure 9 This is a schematic diagram of the structure of the superconducting magnet system provided in Embodiment Six of the present invention;

[0035] Figure 10 This is a schematic diagram of the structure of the superconducting magnet system provided in Embodiment 7 of the present invention;

[0036] Figure 11 This is a schematic diagram of the structure of the superconducting magnet system provided in Embodiment 8 of the present invention.

[0037] The markings in the image are as follows:

[0038] 1. Vacuum shroud; 11. Outer cylinder; 12. Flange; 2. Primary radiation shield; 3. Refrigeration unit; 31. Cold head; 31a. Primary cold head; 31b. Secondary cold head; 4. First thermal switch; 41. First low-temperature pulsating heat pipe; 411. Parallel tube section; 412. Bending section; 413. Connector tube section; 42. Condensing plate; 421. First positioning groove; 43. Evaporation plate; 431. Second positioning groove; 44. Liquid injection connector; 5. Second thermal switch; 6. Power supply assembly; 61. Superconducting wire; 62. High-temperature superconducting current lead; 64. External current wiring assembly; 65. Superconducting excitation power supply; 7. First support structure; 8. Second support structure; 9. Secondary radiation shield;

[0039] 10. Cooled load; 101. Room temperature orifice; 20. Filling system; 201. Buffer tank; 202. Gas cylinder; 203. Molecular pump unit; 204. First shut-off valve; 205. Second shut-off valve; 206. Third shut-off valve; 207. First pressure sensor; 208. Second pressure sensor; 209. Filling pipe; 30. Third thermal switch; 40. Fourth thermal switch;

[0040] 100a, Evaporation section; 100b, Condensation section; 100c, Insulation section; 100d, Gas plug; 100e, Liquid plug. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0042] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0043] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0044] In the description of this embodiment, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, 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 the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0045] Example 1

[0046] like Figure 1 As shown, this embodiment provides a cooling system that can cool the load 10 to a preset operating temperature, ensuring that the load 10 operates in a low-temperature environment and guaranteeing its operational safety and reliability. The load 10 can be a superconducting magnet or other device with a large specific heat capacity that needs to operate in a low-temperature environment.

[0047] Specifically, the cooling system includes a vacuum chamber 1, a refrigerator 3, and a first thermal switch 4. At least two refrigerators 3 are provided, each with a cold head 31. The first thermal switches 4 are configured in a one-to-one correspondence with each refrigerator 31. The cooled load 10, the cold head 31, and the first thermal switches 4 are all located inside the vacuum chamber 1. The first thermal switch 4 includes a first low-temperature pulsating heat pipe 41. The condensing section of the first low-temperature pulsating heat pipe 41 is thermally connected to the cold head 31, and the evaporating section of the first low-temperature pulsating heat pipe 41 is connected to the cooled load 10. When the cold head 31 is at its final cooling temperature, the first working fluid inside the first low-temperature pulsating heat pipe 41 is in a two-phase flow state.

[0048] The cooling system provided in this embodiment includes a first low-temperature pulsating heat pipe 41 in the first thermal switch 4. When the refrigerator 3 corresponding to the first thermal switch 4 is working normally, the temperature of the cold head of the refrigerator 3 can reach the final cooling temperature. This causes the condensation section of the first low-temperature pulsating heat pipe 41 to be below the saturation temperature, and the first working fluid inside the pipe can be condensed into a liquid state. Meanwhile, the evaporation section of the first low-temperature pulsating heat pipe 41 is above the saturation temperature, and the first working fluid inside the pipe is evaporated into a gaseous state due to the influence of the temperature of the cooled load 10. Because the capillary diameter is very small, under the action of capillary force, the first low-temperature pulsating heat pipe 41... The first working fluid in 1 is in a gas-liquid two-phase flow state, with a high thermal conductivity and good heat transfer. The heat generated by the cooled load 10 during operation can be quickly carried away through the first low-temperature pulsating heat pipe 41. When the refrigerator 3 malfunctions or stops working, the temperature of the cold head 31 of the refrigerator 3 rises, and the temperature of the condensing section connected to the refrigerator 3 rises to a level higher than the critical temperature of the first working fluid. The first working fluid in the condensing section is converted into a gaseous state, the thermal resistance of the first low-temperature pulsating heat pipe 41 increases, and the first thermal switch 4 is in the open state, preventing heat from being transferred to the cooled load 10 through the first thermal switch 4.

[0049] That is, the cooling system provided in this embodiment, by setting at least two refrigerators 3 and setting a first thermal switch 4 between the cold head 31 of the refrigerator 3 and the cooled load 10, can ensure the operational safety and reliability of the cooling system through the redundancy of the refrigerators 3; at the same time, when the first low-temperature pulsating heat pipe 41 is conducting, its thermal conductivity is several orders of magnitude higher than that of the heat-conducting metal, and its heat transfer efficiency is high, which can effectively improve the cooling efficiency of the cooled load 10. Furthermore, its switching ratio is relatively large (reaching over 2500), which can effectively ensure the insulation performance when the first thermal switch 4 is off, ensuring the reliability of the cooling system; moreover, because the first thermal switch... 4. It can automatically disconnect and connect according to the temperature change of the cold head 31 without mechanical and electromagnetic drive, reducing control difficulty, improving control accuracy, ensuring the reliability of the first thermal switch 4, and reducing the structural complexity and space occupation of the first thermal switch 4, thus reducing the cost of the cooling system. Furthermore, the first low-temperature pulsating heat pipe 41 is small in size, light in weight, and has a long heat transfer distance. It can also be arranged in a bent manner, which makes it easy to integrate the first low-temperature pulsating heat pipe 41 into a structure with strict mass and space constraints, improving the structural compactness of the cooling system. It is especially suitable for long-distance superconducting magnet applications that are sensitive to vibration, such as nuclear magnetic resonance imaging.

[0050] like Figure 2As shown, it is worth noting that the pulsating heat pipe is a passive heat transfer device. It is a serpentine tubular structure formed by repeatedly bending a metal capillary tube with a small inner diameter, typically 0.5–3 mm, between the hot and cold ends. The tube is filled with a two-phase fluid. Due to the sufficiently small tube diameter, capillary action dominates, and surface tension causes the working fluid to form randomly alternating gas plugs 100d and liquid plugs 100e within the capillary.

[0051] A pulsating heat pipe typically includes a condensing section 100b, an evaporating section 100a, and an adiabatic section 100c located between the condensing section 100b and the evaporating section 100a. During the operation of the pulsating heat pipe, a heat load is applied to the evaporating section 100a, causing the working fluid in the evaporating section 100a to absorb heat and evaporate inside the liquid or on the surface of the liquid film, generating new bubbles or increasing the volume of existing bubbles, resulting in an increase in the length of the gas plug 100d and an increase in the pressure within the evaporating section 100a. Simultaneously, a cooling load is applied to the condensing section 100b, causing the gaseous working fluid in the condensing section 100b to liquefy and release heat, becoming a liquid working fluid, which reduces or eliminates the bubbles within the condensing section 100b, thus reducing the pressure within the condensing section 100b. In a pulsating heat pipe, the temperature difference between the evaporation section 100a and the condensation section 100b creates a pressure difference that propels the working fluid from evaporation section 100a to condensation section 100b. The growth and collapse of bubbles cause a pressure difference between evaporation section 100a and condensation section 100b, as well as a pressure imbalance between adjacent sections. This drives the working fluid to pulsate or circulate within the pipe, transferring heat through the latent heat of the gas-liquid phase change and the sensible heat of the liquid plug 100e. In other words, the oscillating fluid flow and heat transfer within the pulsating heat pipe are entirely driven by the transient pressure difference caused by localized evaporation and condensation, requiring no mechanical power output and having no moving parts, thus exhibiting high reliability. Furthermore, compared to other types of heat pipes, the gas and liquid phases in a pulsating heat pipe typically flow in the same direction, eliminating the problem of gas hindering liquid recirculation. In addition to phase change heat transfer, the forced convection heat transfer between the working fluid and the pipe wall is also significant, resulting in stronger heat transfer capabilities.

[0052] The working fluid in the pulsating heat pipe is a working fluid with high thermal conductivity, and the low-temperature pulsating heat pipe is a pulsating heat pipe in which the critical temperature of the working fluid is relatively low. In this embodiment, based on the preset operating temperature of the load 10 to be cooled and the final cooling temperature that the first-stage cold head 31a can reach, the first working fluid can be selected as helium, neon, hydrogen, or nitrogen or other working fluids that can be used as the working fluid of the pulsating heat pipe. Among them, the gas-liquid saturation temperature of helium at normal pressure is about 4.2K, the gas-liquid saturation temperature of neon at normal pressure is about 25K, the gas-liquid saturation temperature of hydrogen at normal pressure is about 20K, and the gas-liquid saturation temperature of nitrogen at normal pressure is about 77K.

[0053] In this embodiment, the condensing section can be directly connected to the cold head 31, and / or the evaporating section can be directly connected to the cooled load 10. Alternatively, the condensing section and / or the evaporating section can be fixed on a high thermal conductivity metal plate, and then the metal plate can be connected to the corresponding cold head 31 or the cooled load 10.

[0054] It is understood that in this embodiment, the adiabatic section, evaporation section and / or condensation section of the first low-temperature pulsating heat pipe 41 can be arranged vertically or bent, depending on the suitability of the connection between the first low-temperature pulsating heat pipe 41 and the cold head 31 and the cooled load 10. The present invention does not impose specific limitations on this.

[0055] The first thermal switch 4 has a first connecting surface and a second connecting surface. The first connecting surface is thermally connected to the cold head 31, and the second connecting surface is connected to the load 10 being cooled. To improve heat transfer efficiency, the first connecting surface and / or the second connecting surface are provided with a thermally conductive structure, which includes a thermally conductive coating and / or a thermally conductive sheet to increase the thermal conductivity at the connection and reduce the contact thermal resistance. Preferably, the thermally conductive layer is an Apiezon N high thermal conductivity grease layer, and the thermally conductive sheet is an indium sheet.

[0056] like Figure 1 As shown, the chiller 3 is preferably a GM chiller or a pulse tube chiller. The cooling power of the chiller 3 and the final cooling temperature that the cold head 31 can achieve can be specifically selected and determined according to the preset operating temperature required by the cooled load 10. The chiller 3 is an existing mature product, and the specific structure of the chiller 3 will not be described in detail in this embodiment.

[0057] In this embodiment, the vacuum shroud 1 includes an outer cylinder 11 open at both ends and flanges 12 installed at the upper and lower ends of the outer cylinder 11. The flanges 12 are detachably connected to the outer cylinder 11 and seal the corresponding ports of the outer cylinder 11. This structural design of the vacuum shroud 1 facilitates the disassembly and assembly of the internal structure of the vacuum shroud 1, improving the ease of disassembly, assembly, and maintenance of the cooling system. In other embodiments, the outer cylinder 11 may only have an opening at the upper end, that is, one flange 12 is provided at the upper end of the outer cylinder 11.

[0058] The vacuum shroud 1 is preferably made of non-magnetic stainless steel to avoid corrosion and improve the stability of its internal structure. The outer cylinder 11 may be, but is not limited to, a cylinder, and the shape of the flange 12 is adapted to the shape of the outer cylinder 11.

[0059] The cooling system also includes a vacuum pumping device, which is used to evacuate the internal space of the vacuum chamber 1. An aviation socket and a vacuum evacuation port are provided on the flange 12 at the upper end of the vacuum chamber 1. The vacuum pumping device is located outside the vacuum chamber 1 and evacuates the inside of the vacuum chamber 1 through the vacuum evacuation port, thereby reducing gas heat conduction.

[0060] To further improve the cooling efficiency of the cooled load 10, the cooling system also includes a primary radiation shield 2, which is suspended inside the vacuum chamber 1, and the cooled load 10 is suspended inside the primary radiation shield 2. The primary radiation shield 2 is used to reduce heat radiation from the outside of the vacuum chamber 1 to the cooled load 10 and reduce the interference of the external environment on the cooled load 10.

[0061] The primary radiation shield 2 is preferably suspended inside the vacuum chamber 1 by a second support structure 8, with the cooled load 10 passing through the primary radiation shield 2 via the first support structure 7. The configuration of the first support structure 7 and the second support structure 8 can refer to existing technologies and can be made of high-strength, low-thermal-conductivity materials, such as G10 fiberglass; this invention does not limit this. The primary radiation shield 2 is preferably made of oxygen-free, high-purity copper.

[0062] The primary radiation shield 2 is preferably thermally connected to the cold head 31 so that the temperature of the primary radiation shield 2 is close to the temperature of the cold head 31, thereby reducing the radiative heat leakage from the external environment of the vacuum shield 1 to the cooling load 10.

[0063] Preferably, the cold head 31 is thermally connected to the primary radiation shield 2 via a fourth thermal switch 40. The fourth thermal switch 40 includes a fourth low-temperature pulsating heat pipe. The evaporation section of the fourth low-temperature pulsating heat pipe is thermally connected to the primary radiation shield 2, and the condensation section of the fourth low-temperature pulsating heat pipe is thermally connected to the cold head 31. When the cold head 31 is at the final cooling temperature, the fourth working fluid in the fourth low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state. This configuration ensures that when a refrigerator 3 stops or malfunctions, the fourth thermal switch 40 corresponding to that refrigerator 3 is disconnected, preventing heat from the refrigerator 3 from being transferred to the primary radiation shield 2.

[0064] In another embodiment, the cold head 31 can also be directly thermally connected to the primary radiation shield 2 to reduce costs. In yet another embodiment, the two chillers 3 can be a main chiller and a backup chiller, respectively. The cold head 31 of the main chiller is directly thermally connected to the primary radiation shield 2, while the cold head of the backup chiller can be thermally connected to the primary radiation shield 2 via a fourth thermal switch 40.

[0065] In this embodiment, the fourth working fluid in the fourth low-temperature pulsating heat pipe is the same as the first working fluid in the first low-temperature pulsating heat pipe.

[0066] To reduce radiative heat leakage, the outer surfaces of the primary radiation shield 2, the first thermal switch 4, the cooled load 10, the fourth thermal switch 40, and / or the cold head 31 are covered with an insulation layer, which is preferably made of high-vacuum multilayer insulation (MLI) material.

[0067] Furthermore, the cooling system also includes a charging system for filling the first low-temperature pulsating heat pipe 41 with a working fluid. The structure of the charging system and the method of filling the first low-temperature pulsating heat pipe 41 can refer to the prior art, and this embodiment does not limit them.

[0068] In this embodiment, preferably, each first thermal switch 4 is provided with a corresponding filling system to achieve individual liquid filling control of the first low-temperature pulsating heat pipe 41 in each first thermal switch 4. In other embodiments, all first thermal switches 4 can share the same filling system, that is, the same filling system synchronously fills the first low-temperature pulsating heat pipe 41 in all first thermal switches 4.

[0069] In one embodiment, each fourth thermal switch 4 is provided with a corresponding filling system to realize individual liquid filling control of the fourth low-temperature pulsating heat pipe in each fourth thermal switch 4.

[0070] This embodiment also provides a superconducting magnet system, which includes a superconducting magnet and the aforementioned cooling system, wherein the superconducting magnet is the cooled load 10. The superconducting magnet system provided in this embodiment, by setting at least two cryogenic units 3 and a first thermal switch 4, including a first low-temperature pulsating heat pipe 41, connecting the cryogenic units 3 and the cooled load 10, can prevent the high temperature of the cryogenic units 3 from being transferred to the cooled load 10 when the cryogenic units 3 fail, ensuring that the cooled load 10 can operate safely and stably under the cooling effect of the other cryogenic units 3, thus improving the operational safety and reliability of the superconducting magnet system. Simultaneously, because the first thermal switch 4 occupies a small space and is flexibly arranged, it can effectively improve the structural compactness of the superconducting magnet system, making it particularly suitable for long-distance superconducting magnet applications that are sensitive to vibration, such as nuclear magnetic resonance imaging.

[0071] It is understandable that the preset operating temperature of a superconducting magnet is lower than the superconducting transition temperature.

[0072] Furthermore, the superconducting magnet includes a superconducting magnet coil and a support frame for mounting the superconducting magnet coil. The superconducting magnet is fixed within the primary radiation shield 2 by a first support structure 7. The first support structure 7 may include a pull rod or a pull ring. The first support structure 7 is preferably made of a material with low thermal conductivity, high insulation, and high strength, such as G10 fiberglass. The support frame has a cylindrical structure with an inner hole forming a room temperature aperture 101 for placing the sample. When the superconducting magnet is running, a uniform magnetic field exists within the room temperature aperture 101.

[0073] To achieve high magnetic field strength, the superconducting magnet coil can consist of multiple coils. The coil materials can be conventional superconducting materials such as NbTi and Nb3Sn, or high-temperature superconducting materials such as magnesium diboride and yttrium barium copper oxide. The supporting frame can be made of materials such as 6063-T1 aluminum alloy.

[0074] The central axis of the room temperature aperture 101 can be set in a vertical or horizontal direction, or it can be arranged in other directions. That is, the central axis of the room temperature aperture 101 can be set according to the specific type of the superconducting magnet system and the application scenario.

[0075] In this embodiment, the evaporation section of the first thermal switch 4 is connected to the support frame to improve the connection convenience between the first thermal switch 4 and the superconducting magnet.

[0076] The superconducting magnet system also includes a diode assembly for quench protection of the superconducting magnet. The superconducting magnet system also includes a power supply assembly 6, which includes a superconducting excitation power supply 65 and a wire 61 connecting the superconducting excitation power supply 65 and the superconducting magnet coil. The superconducting excitation power supply 65 is located outside the vacuum chamber 1.

[0077] To better connect the superconducting magnet to the superconducting excitation power supply 65, the superconducting magnet system also includes an external current connection assembly 64 and a high-temperature superconducting current lead 62. The high-temperature superconducting current lead 62 is thermally connected to the cold head 31. Wires 61 are connected between the external current connection assembly 64 and the high-temperature superconducting current lead 62, as well as between the high-temperature superconducting current lead 62 and the cooled load 10. The external current connection assembly 64 is mounted on the vacuum chamber 1 to connect with the wires 61 located on both the inner and outer sides of the vacuum chamber 1. The external current connection assembly 64 is insulated from the vacuum chamber 1. The specific structure of the high-temperature superconducting current lead 62 and the external current connection assembly 64 can be found in existing technologies, and this invention will not elaborate on or limit them.

[0078] The superconducting magnet system provided in this embodiment can be applied to information technology, biomedicine, environmental technology, military industry, industrial processing, marine, transportation, large-scale scientific engineering and superconducting power, such as medical magnetic resonance imaging equipment MRI, nuclear magnetic resonance spectrometer MNR, superconducting magnetic separation system, superconducting energy storage system, superconducting motor, superconducting cable, superconducting transformer, superconducting current limiter, superconducting induction heating, superconducting particle accelerator, superconducting magnetic levitation train, etc. This invention does not limit the specific type and application scenario of the superconducting magnet system.

[0079] Example 2

[0080] This embodiment provides a cooling system and a superconducting magnet system. The cooling system and superconducting magnet system provided in this embodiment are further improvements based on the structure in Embodiment 1. This embodiment will not repeat the same structure as in Embodiment 1.

[0081] In this embodiment, the cooling system also includes a charging system 20, which is used to charge a first working fluid into the first low-temperature pulsating heat pipe 41 of the first thermal switch 4. The charging system 20 is mainly located outside the vacuum chamber 1.

[0082] Specifically, the filling system 20 includes a buffer tank 201, a gas storage cylinder 202, a molecular pump unit 203, and a filling pipe 209. The buffer tank 201 is connected to the gas inlet of the filling pipe 209 via a first pipe, the molecular pump unit 203 is connected to the gas inlet of the filling pipe 209 via a second pipe, the gas outlet of the filling pipe 209 is connected to a first thermal switch 4, and the gas storage cylinder 202 is connected to the gas inlet of the filling pipe 209 via a third pipe. A first shut-off valve 204 is installed on the filling pipe 209, a second shut-off valve 205 is installed on the second pipe, and a third shut-off valve 206 is installed on the third pipe.

[0083] The filling system 20 also includes a first pressure sensor 207, which is installed on the filling pipe 209 to detect pressure fluctuations in the condensation section of the first low-temperature pulsating heat pipe 41. A second pressure sensor 208 is installed at the buffer tank 201 to detect the pressure of the buffer tank 201 and calculate the filling rate.

[0084] The gas storage cylinder 202 stores a high-purity (99.999%) gaseous first working fluid. The specific operating steps for filling the first low-temperature pulsating heat pipe 41 are as follows:

[0085] (1) Collect and record temperature and pressure data.

[0086] (2) Use a high-purity first working fluid and a set of molecular pump units 203 to purge and purify the gas in the first low-temperature pulsating heat pipe 41, buffer tank 201 and filling system 20 to prevent residual air or other impurities in the pipes from affecting the experiment.

[0087] The specific process is as follows:

[0088] First, open the first shut-off valve 204 and the second shut-off valve 205, and close the third shut-off valve 206. Use the molecular pump unit 203 to evacuate the first low-temperature pulsating heat pipe 41 and the charging system 20 to a high vacuum (<1×10⁻⁶). -3 Pa);

[0089] Then close the second shut-off valve 205, open the first shut-off valve 204 and the third shut-off valve 206, and charge the 99.999% high-purity first working fluid from the gas storage cylinder 202 into the first low-temperature pulsating heat pipe 41 and the buffer tank 201.

[0090] Repeat the same process more than 5 times to thoroughly remove impurities from the pulsating heat pipe and the charging system 20, and then evacuate to a high vacuum.

[0091] (3) After the purification process is completed, open the third shut-off valve 206, close the first shut-off valve 204 and the second shut-off valve 205, open the gas storage bottle 202, fill the buffer tank 201 with high-purity first working fluid, then close the first shut-off valve 204, and record the initial pressure P0 of the buffer tank 201 at this time.

[0092] (4) Open the first shut-off valve 204, close the second shut-off valve 205 and the third shut-off valve 206, and the high-purity first working fluid will enter the first low-temperature pulsating heat pipe 41 from the buffer tank 201.

[0093] (5) Use another molecular pump unit 203 to evacuate the vacuum chamber 1 until the vacuum level inside the vacuum chamber 1 is less than 1×10⁻⁶. -3 After Pa, the refrigerator 3 is started to cool the first low-temperature pulsating heat pipe 41.

[0094] (6) As the temperature of the condensing section of the first low-temperature pulsating heat pipe 41 decreases, the pressure also decreases. When it drops to the gas-liquid two-phase flow temperature zone of the first working fluid, the liquid first working fluid begins to form, and the pressure drops rapidly. Under the action of gravity, the liquid first working fluid moves from the condensing section to the evaporating section and absorbs heat to evaporate, accelerating the cooling of the evaporating section to the working temperature. When the pressure of the buffer tank 201 drops to the pressure P1 corresponding to the target filling rate, the first shut-off valve 204 is closed, isolating the first low-temperature pulsating heat pipe 41 from the filling system 20. At this time, the first low-temperature pulsating heat pipe 41 is in an initial state of alternating gas plugs and liquid plugs, and the filling process ends.

[0095] The filling rate is used to represent the mass of the first liquid working fluid filled in the first low-temperature pulsating heat pipe 41. For comparison with existing research data, when the first working fluid is helium, the filling rate is defined as the ratio of the liquid helium volume to the pulsating heat pipe volume at 4.215K.

[0096] When calculating the filling rate, the first working fluid in the first low-temperature pulsating heat pipe 41 and the filling system 20 is considered as an ideal gas. According to the law of conservation of mass and the ideal gas law, the mass m of the first working fluid is... t It can be calculated using the following formula:

[0097]

[0098] Where: P0 and P1 are the initial and final pressures of buffer tank 201 at the start and end of the filling process, respectively, in Pa; V FT and V BT These are the volumes of the filling pipe (from the first shut-off valve 204 to the first low-temperature pulsating heat pipe 41) and the buffer tank 201, respectively, in cubic meters (m³). 3 ;T FT and T BT These are the average temperatures of the filling pipeline and buffer tank 201, respectively, in K; R g R is the gas constant of the first working substance, such as when the first working substance is helium. g =2077 J / (kg·K); m t The mass of the working fluid charged into the pulsating heat pipe is expressed in kg.

[0099] The mass of the liquid working fluid filled into the first cryogenic pulsating heat pipe 41 is the sum of the mass of the saturated gas and the saturated liquid of the first working fluid. Taking helium as the first working fluid as an example, the mass of liquid helium filled into the first cryogenic pulsating heat pipe 41 is the sum of the mass of saturated helium gas and the mass of saturated liquid helium. Since the densities of saturated helium gas and saturated liquid helium, as well as the mass of helium filled into the first cryogenic pulsating heat pipe 41, are known, the volume of saturated liquid helium can be obtained by the following formula:

[0100] m t =ρ l V l +ρ v (V PHP -V l (Equation 2);

[0101] Among them, V PHP and V l These represent the volume of the first low-temperature pulsating heat pipe 41 and the volume of liquid helium inside the pipe, respectively, in cubic meters (m³). 3 ;ρ v and ρ l These are the densities of saturated helium gas and saturated liquid helium at 4.215 K, respectively, in kg / m³. 3 .

[0102] Therefore, the filling rate is:

[0103]

[0104] By combining Equations 1 to 3, the filling rate of the first low-temperature pulsating heat pipe 41 can be determined based on the initial and final pressures of the buffer tank 201. The formula for calculating the filling rate takes into account the influence of the filling pipe volume, while the volume of the remaining pipes in the filling system 20 is considered as part of the volume of the buffer tank 201.

[0105] It should be noted that this filling method is also applicable to other cryogenic working fluids.

[0106] The recommended filling rate of the first low-temperature pulsating heat pipe 41 is between 20% and 80%. If the filling rate is too low, it is easy to burn dry. If the filling rate is too high, the flow resistance is large and it is difficult to start up and operate.

[0107] In addition to controlling the filling rate before the first low-temperature pulsating heat pipe 41 starts operating, the buffer tank 201 can also automatically adjust the filling rate and pressure during operation of the first low-temperature pulsating heat pipe 41 to prevent it from burning dry. Simply open the first shut-off valve 204 to connect the buffer tank 201 to the first low-temperature pulsating heat pipe 41 for operation.

[0108] It is worth noting that when the charging system corresponding to the fourth thermal switch 40 and the charging system corresponding to the first thermal switch 4 are set separately, the charging system of the fourth thermal switch 40 can be set with reference to the charging system of the first thermal switch 4.

[0109] Example 3

[0110] This embodiment provides a cooling system and a cryogenic superconducting magnetic system. The cooling system provided in this embodiment is a further improvement on the cooling system in Embodiment 1. This embodiment will not repeat the contents that are the same as in Embodiment 1.

[0111] like Figures 4-6 As shown, in this embodiment, the first thermal switch 4 further includes a condenser plate 42, an evaporator plate 43, and a liquid injection connector 44. The first low-temperature pulsating heat pipe 41 has a serpentine structure formed by bending capillary tubes, and includes a plurality of parallel tube sections 411 arranged parallel and spaced apart in a first direction and a bend 412 connecting two adjacent parallel tube sections 411. The parallel tube sections 411 have a condenser section, an insulation section, and an evaporator section connected in sequence.

[0112] The condenser plate 42 has multiple first positioning grooves 421, and the evaporator plate 43 has multiple second positioning grooves 431. Each of the first and second positioning grooves 421 corresponds to a parallel tube section 411. The condensing section of the parallel tube section 411 is located in the first positioning groove 421, and the evaporating section is located in the second positioning groove 431. Both the first and second positioning grooves 421 and 431 are filled with solder to fix the first low-temperature pulsating heat pipe 41 to the corresponding condenser plate 42 and evaporator plate 43, reduce thermal resistance, and ensure good thermal contact between the first low-temperature pulsating heat pipe 41 and the condenser plate 42 and evaporator plate 43. The bend 412 connected to the condensing section is located on the side of the condenser plate 42 away from the evaporator plate 43, and the bend 412 connected to the evaporator plate 43 is also located on the side of the evaporator plate 43 away from the condenser plate 42.

[0113] The width of the first positioning groove 421 and the second positioning groove 431 is preferably larger than the outer diameter of the first low-temperature pulsating heat pipe 41, so as to ensure that the first low-temperature pulsating heat pipe 41 is accommodated in the first positioning groove 421 and the second positioning groove 431, and to provide space for solder filling. Both the evaporator plate 43 and the condenser plate 42 are preferably made of pure copper, which has high heat conduction efficiency. The first low-temperature pulsating heat pipe 41 is preferably made of stainless steel or pure copper.

[0114] The first thermal switch 4 is preferably a multi-layer structure, that is, the parallel tube section 411 extends along the second direction, and the first thermal switch 4 preferably includes multiple layers of first low-temperature pulsating heat pipes 41 arranged side by side along the third direction. The evaporator plate 43 and the condenser plate 42 are each arranged in a one-to-one correspondence with the first low-temperature pulsating heat pipes 41, and the first direction, the second direction and the third direction are mutually perpendicular. The first thermal switch 4 with multiple layers of first low-temperature pulsating heat pipes 41 can increase the thermal conductivity while saving the space occupied by the first thermal switch 4 and improving the structural compactness of the first thermal switch 4.

[0115] In this embodiment, all evaporation plates 43 are stacked and securely connected in the third direction, and all condensation plates 42 are stacked and securely connected in the third direction.

[0116] The injection connector 44 is provided with an injection channel, through which the filling pipe of the filling system is connected to the first low-temperature pulsating heat pipe 41. In this embodiment, all the first low-temperature pulsating heat pipes 41 are arranged in parallel, and each of the first low-temperature pulsating heat pipes 41 has a connector tube portion 413 formed at both ends. The injection channel is arranged one-to-one with the first low-temperature pulsating heat pipe 41, and both connector tube portions 413 of each first low-temperature pulsating heat pipe 41 are inserted into the injection channel and sealed and connected to the injection channel. This arrangement simplifies the processing of the first thermal switch 4 and improves the ease of disassembly and assembly of the first thermal switch 4.

[0117] In other embodiments, all first low-temperature pulsating heat pipes 41 are connected in series, that is, the corresponding ends of two adjacent first low-temperature pulsating heat pipes 41 are connected. All first low-temperature pulsating heat pipes 41 have only two connector tubes 413. The liquid injection connector 44 is provided with a liquid injection channel. The two connector tubes 413 are inserted into the liquid injection channel and are sealed and connected to the liquid injection channel.

[0118] For example, the first low-temperature pulsating heat pipe 41 is provided with four layers, and each layer of the first low-temperature pulsating heat pipe 41 has 12 parallel tube sections 411. In other embodiments, the number of layers of the first low-temperature pulsating heat pipe 41 and the number of parallel tube sections 411 included in the first low-temperature pulsating heat pipe 41 can be set according to needs, such as three layers, five layers or more layers, and each layer includes 6 to 18 parallel tube sections 411.

[0119] Furthermore, during the processing of the first thermal switch 4, the evaporator plates 43 between two adjacent layers and the condenser plates 42 between two adjacent layers are first soldered to fill the gaps as much as possible with solder; then all evaporator plates 43 and all condenser plates 42 are secured with bolts or screws.

[0120] In another embodiment, the first thermal switch 4 may also include a plurality of first low-temperature pulsating heat pipes 41 arranged side by side in a first direction. Each first low-temperature pulsating heat pipe 41 is individually provided with a liquid injection connector 44 and a filling system, that is, each first low-temperature pulsating heat pipe 41 can be individually controlled to inject liquid. In yet another embodiment, the first thermal switch 4 may include a plurality of first low-temperature pulsating heat pipes 41 arranged side by side in a first direction. Both ends of each first low-temperature pulsating heat pipe 41 are connected to a connecting pipe, which is connected to the filling system.

[0121] The first thermal switch 4 has a first connecting surface and a second connecting surface. The first connecting surface is thermally connected to the cold head 31, and the second connecting surface is thermally connected to the load 10 being cooled. In this embodiment, the outermost evaporator plate 43 has a second connecting surface on the side away from the adjacent evaporator plate 43, and the outermost condenser plate 42 has a first connecting surface on the side away from the adjacent condenser plate 42.

[0122] To improve heat transfer efficiency, the first and / or second connecting surfaces are provided with a thermally conductive structure, which includes a thermally conductive coating and / or a thermally conductive sheet to increase the thermal conductivity at the connection and reduce contact thermal resistance. Preferably, the thermally conductive layer is an Apiezon N high thermal conductivity grease layer, and the thermally conductive sheet is an indium sheet.

[0123] It is worth noting that the structure of the fourth thermal switch 40 can be set with reference to the structure of the first thermal switch 4 described above, and will not be repeated here.

[0124] Example 4

[0125] like Figure 7 As shown, this embodiment provides a cooling system and a superconducting magnet system. The cooling system and superconducting magnet system provided in this embodiment are basically the same as those in Embodiment 3, with only some differences in configuration. This embodiment will not repeat the structures that are the same as those in Embodiment 3.

[0126] In this embodiment, the plurality of evaporation plates 43 are divided into at least two groups that are separately arranged. Each group of evaporation plates 43 includes one evaporation plate 43 or at least two evaporation plates 43 stacked together. The two adjacent groups of evaporation plates 43 are spaced apart in the first direction. Each group of evaporation plates 43 has a second connecting surface.

[0127] By setting at least two sets of evaporation plates 43, the contact points between the first thermal switch 4 and the cooled load 10 can be increased, thereby improving the cooling uniformity of the cooled load 10 and further improving the cooling efficiency.

[0128] In this embodiment, the first thermal switch 4 and the fourth thermal switch 40 are separately configured. The first thermal switch 4 has two sets of evaporation plates 43. The two second connecting surfaces of the two sets of evaporation plates 43 are respectively connected to the upper and lower ends of the load 10 being cooled, so as to improve the cooling uniformity of the load 10 being cooled while reducing costs.

[0129] Example 5

[0130] like Figure 8 As shown, this embodiment provides a cooling system and a superconducting magnet system. The cooling system and superconducting magnet system provided in this embodiment are basically the same as those in Embodiment 3, with only some differences in configuration. This embodiment will not repeat the structures that are the same as those in Embodiment 3.

[0131] In this embodiment, the first thermal switch 4 and the fourth thermal switch 40 are integrated, the evaporation plates 4 corresponding to the first thermal switch 4 and the fourth thermal switch 40 are staggered, the condensation plates corresponding to the first thermal switch 4 and the fourth thermal switch 40 are stacked, and the first thermal switch 4 and the fourth thermal switch 40 share a single liquid injection connector. This arrangement reduces the footprint of the first thermal switch 4 and the fourth thermal switch 40, improves structural compactness, and allows for simultaneous liquid injection into both the first thermal switch 4 and the fourth thermal switch 40.

[0132] It is understood that, in this embodiment, the first thermal switch 4 may also be provided with two or more sets of evaporating plates 42, each set of evaporating plates 42 being connected to the cooled load 10 to improve the cooling uniformity of the cooled load 10. The fourth thermal switch 40 may also be provided with two or more sets of evaporating plates, each set of evaporating plates being thermally connected to the primary radiation shield 2 to improve the cooling uniformity of the primary radiation shield 2.

[0133] Example 6

[0134] like Figure 9 As shown, this embodiment provides a cooling system and a superconducting magnet system. The basic structure of the cooling system and superconducting magnet system provided in this embodiment is the same as that in Embodiment 1, with only some differences in the settings. This embodiment will not repeat the contents that are the same as those in Embodiment 1.

[0135] In this embodiment, the refrigerator 3 has two cold heads 31, namely a primary cold head 31a and a secondary cold head 31b. When the refrigerator 3 is running normally, the final cooling temperature of the primary cold head 31a is higher than that of the secondary cold head 31b. The first thermal switch 4 is thermally connected to the secondary cold head 31b.

[0136] The refrigeration system also includes a second thermal switch 5, which includes a second low-temperature pulsating heat pipe. The evaporation section of the second low-temperature pulsating heat pipe is connected to the cooled load 10, and the condensation section of the second low-temperature pulsating heat pipe is connected to the first-stage cold head 31a. The triple point of the second working fluid in the second low-temperature pulsating heat pipe is critically higher than the final refrigeration temperature of the first-stage cold head 31a.

[0137] In the cooling system provided in this embodiment, since the critical temperature of the second low-temperature pulsating heat pipe is higher than the final cooling temperature of the first-stage cold head 31a, and the final cooling temperature of the first-stage cold head 31a is higher than the final coldest temperature of the second-stage cold head 31b, the working fluid in the first low-temperature pulsating heat pipe 41 is in a gaseous state when the refrigerator 3 is not working. At this time, the thermal resistance of the second thermal switch 5 is relatively large, and the second thermal switch 5 is in the open state. During the cooling process of the cooling system, the temperature of the first-stage cold head 31a first drops to the critical temperature of the second low-temperature pulsating heat pipe, and the second working fluid in the condensation section of the second low-temperature pulsating heat pipe is condensed into a liquid state. The second low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state, with a high thermal conductivity and high transfer effect, causing the second thermal switch to be in the conducting state, so that the first-stage cold head 31a is in the open state. The cooling capacity of the first-stage cold head 31a is transferred to the cooled load 10, accelerating the cooling of the cooled load 10 and shortening the time required for the cooled load 10 to cool to the preset operating temperature, thereby improving the operating efficiency of the cooling system. When the cooled load 10 is cooled to the triple point temperature of the second working fluid, the temperature of the condensation section of the second low-temperature pulsating heat pipe decreases below the triple point temperature of the second working fluid as the first-stage cold head 31a decreases. The second working fluid in the second low-temperature pulsating heat pipe turns into a solid, the flow stops, the thermal resistance increases, the second thermal switch 5 is in the open state, and the cooled load 10 mainly conducts heat through the first thermal switch 4. The temperature of the cooled load 10 decreases as the temperature of the second-stage cold head 31b decreases, and finally the cooled load 10 is cooled to the preset operating temperature.

[0138] Meanwhile, during the operation of the cooled load 10, if the temperature of the cooled load 10 rises to the triple point temperature of the second low-temperature pulsating heat pipe, the second working fluid in the evaporation section of the second low-temperature pulsating heat pipe melts into a liquid state. By controlling the temperature of the first-stage cold head 31a, the second working fluid in the second low-temperature pulsating heat pipe can be in a gas-liquid two-phase flow state, that is, the second thermal switch 5 is turned on. The heat of the cooled load 10 is quickly transferred to the first-stage cold head 31a through the thermal switch 5, realizing the heat conduction from the first thermal switch 5 to the first-stage cold head 31a, improving the heat transfer efficiency, avoiding a large temperature rise of the cooled load 10, effectively promoting the cooled load 10 to return to the normal working state from the temperature rise state, and shortening the time for the cooled load 10 to return to the normal working state.

[0139] That is, the cooling system provided in this embodiment can achieve the redundant design of the refrigerator 3, while also increasing the utilization of the cooling capacity of the refrigerator 3, improving the cooling efficiency of the cooled load 10, reducing the cooling time required, and effectively improving the operational reliability of the cooling system and the superconducting magnet system.

[0140] The second working medium filled in the second low-temperature pulsating heat pipe is preferably nitrogen, which has a lower cost. The working medium of the second low-temperature pulsating heat pipe can be argon, krypton, oxygen, ammonia, methane, etc., and the working medium of the first low-temperature pulsating heat pipe can be helium, hydrogen, neon, etc. The first working medium in the first low-temperature pulsating heat pipe and the second working medium in the second low-temperature pulsating heat pipe can be specifically selected according to the preset operating temperature required by the cooled load 10.

[0141] The structure of the second thermal switch 5 can be configured with reference to the structure of the first thermal switch 4 in Embodiment 1, Embodiment 3, or Embodiment 4, and will not be described again in this embodiment. Furthermore, the structure of the first thermal switch 4 in this embodiment can also adopt the structure of the thermal switches in Embodiments 3 and 4, and will not be described again here.

[0142] In this embodiment, the filling system and liquid filling method corresponding to the second low-temperature pulsating heat pipe can refer to the settings in Embodiment 2, and will not be repeated here.

[0143] Preferably, in this embodiment, the primary cold head 31a is thermally connected to the primary radiation shield 2 to absorb thermal radiation from the environment to the primary radiation shield 2.

[0144] The difference from Embodiment 1 is that in this embodiment, the primary cooling head 31a is connected to the primary radiation shield 2 via a fourth thermal switch 40. The fourth thermal switch 40 includes a fourth low-temperature pulsating heat pipe. The evaporation section of the fourth low-temperature pulsating heat pipe is thermally connected to the primary radiation shield 2, and the condensation section of the fourth low-temperature pulsating heat pipe is thermally connected to the primary cooling head 31a. When the primary cooling head 31a is at the final cooling temperature, the fourth working fluid in the fourth low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state. This configuration ensures that when a refrigerator 3 stops or malfunctions, the fourth thermal switch 40 corresponding to that refrigerator 3 is disconnected, preventing heat from the refrigerator 3 from being transferred to the primary radiation shield 2.

[0145] That is, in this embodiment, the fourth working medium is different from the first working medium. The triple point temperature of the fourth working medium is higher than that of the first working medium but lower than that of the second working medium. The type of the fourth working medium can be determined based on the final cooling temperature of the first-stage cold head 31a.

[0146] It should be noted that an insulation layer is wrapped around the outer side of the superconducting magnet, the outer side of the primary radiation shield 2, the outer surface of the first thermal switch 4, the outer surface of the second thermal switch 5, the outer surface of the fourth thermal switch 40, and the outer side of the primary cold head 31a and / or the secondary cold head 31b. The insulation layer is preferably made of MLI material to improve the insulation effect and reduce radiative heat leakage. The insulation layer preferably has at least 20 layers to further enhance the insulation effect.

[0147] Furthermore, each of the first thermal switch 4, each of the second thermal switch 5, and each of the fourth thermal switch 40 is provided with a corresponding filling system to achieve individual liquid filling control for each thermal switch.

[0148] Example 7

[0149] like Figure 10 As shown, this embodiment provides a cooling system and a superconducting magnet system. The cooling system provided in this embodiment is basically the same as the cooling system in embodiment five, with only some structural differences. This embodiment will not repeat the contents that are the same as those in embodiment six.

[0150] In this embodiment, the primary cooling head 31a is thermally connected to the primary radiation shield 2 via the fourth thermal switch 40, and the secondary cooling head 31b is thermally connected to the cooled load 10 via the first thermal switch 4.

[0151] That is, in this embodiment, the primary cold head 31a is not connected to the cooled load 10, or is connected to the cooled load 10 through other low-temperature thermal switches, while the fourth thermal switch 40 is connected to the primary radiation shield 2. This allows the primary cold head 31a to absorb heat from the primary radiation shield 2 during operation of the refrigerator 3, reducing the impact of thermal radiation on the cooled load 10. When the refrigerator 3 stops operating or malfunctions, the temperatures of both the primary cold head 31a and the secondary cold head 31b corresponding to the refrigerator 3 rise, and both the first thermal switch 4 and the fourth thermal switch are in the off state.

[0152] Example 8

[0153] like Figure 11 As shown, this embodiment provides a cooling system and a superconducting magnet system. The cooling system of the superconducting magnet system provided in this embodiment is a further improvement on the cooling system in any of the above embodiments. This embodiment will not repeat the same structure as the above embodiments.

[0154] In this embodiment, a secondary radiation shield 9 is suspended inside the primary radiation shield 2, and the load to be cooled 10 is located inside the secondary radiation shield 9. That is, by setting the secondary radiation shield 9 inside the primary radiation shield 2 and placing the load to be cooled 10 inside the secondary radiation shield 9, the heat radiation from the vacuum shield 1 to the load to be cooled can be better limited.

[0155] The primary cooling head 31a is thermally connected to the primary radiation shield 2 to absorb the radiative heat leakage of the primary radiation shield 2; the secondary cooling head 31b is thermally connected to the secondary radiation shield 9 to absorb the radiative heat leakage of the secondary radiation shield 9, and to keep the secondary radiation shield 9 at the same temperature as the cooled load 10, which is conducive to better maintaining the working environment temperature of the cooled load 10.

[0156] Preferably, in this embodiment, the secondary radiation shield 9 is connected to the secondary cold head 31b via a third thermal switch 30. The third thermal switch 30 includes a third low-temperature pulsating heat pipe. The evaporation section of the third low-temperature pulsating heat pipe is thermally connected to the secondary radiation shield 9, and the condensation section of the third low-temperature pulsating heat pipe is thermally connected to the secondary cold head 31b. When the secondary cold head 31b is at the final cooling temperature, the third working fluid in the third low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state.

[0157] The above settings ensure that when a refrigerator 4 stops or malfunctions, both the primary thermal switch 4 and the third thermal switch 30 corresponding to that refrigerator 4 are disconnected, preventing heat from the refrigerator 4 from being transferred to the secondary radiation shield 9 and affecting the temperature control of the secondary radiation shield 4, thereby improving the cooling effect.

[0158] In another embodiment, the secondary cold head 31b can also be directly thermally connected to the secondary radiation shield 9 to reduce costs. In yet another embodiment, the two chillers 3 can be a main chiller and a standby chiller, respectively. The secondary cold head 31b of the main chiller is directly thermally connected to the secondary radiation shield 9, while the secondary cold head 31b of the standby chiller can be thermally connected to the secondary radiation shield 9 through a third thermal switch 30.

[0159] In this embodiment, the third working fluid in the third low-temperature pulsating heat pipe is the same as the first working fluid in the first low-temperature pulsating heat pipe. The triple point temperature of the second working fluid in the second low-temperature pulsating heat pipe is higher than the triple point temperature in the fourth low-temperature pulsating heat pipe, and the triple point temperature in the fourth low-temperature pulsating heat pipe is higher than the triple point temperature of the first working fluid.

[0160] In this embodiment, the second thermal switch 5 and the third thermal switch 30 can be configured as described in any of the embodiments 2 to 5. That is, the second thermal switch 5 and the third thermal switch 30 can be configured separately or integrated. This embodiment will not elaborate further.

[0161] Preferably, both the primary radiation shield 2 and the secondary radiation shield 9 are covered with an insulation layer, which is preferably made of high-vacuum multilayer insulation material to further reduce radiation heat leakage.

[0162] Furthermore, the first-stage cold head 31a, the second-stage cold head 31b, the first thermal switch 4, the second thermal switch 5, the third thermal switch 30 and / or the fourth thermal switch 40 are all wrapped with an insulation layer, which is preferably made of high-vacuum multilayer insulation material.

[0163] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A cooling system for cooling a load (10) to be cooled, characterized in that, The cooling system includes a vacuum chamber (1), a refrigerator (3) and a first thermal switch (4). There are at least two refrigerators (3), and each refrigerator (3) has a cold head (31). The first thermal switch (4) is arranged in a one-to-one correspondence with the refrigerator (3). The cooled load (10), the cold head (31) and the first thermal switch (4) are all located inside the vacuum chamber (1). The first thermal switch (4) includes a first low-temperature pulsating heat pipe (41), the evaporation section of the first low-temperature pulsating heat pipe (41) is connected to the cooled load (10), and the condensation section of the first low-temperature pulsating heat pipe (41) is connected to the cold head (31). When the cold head (31) is at the final cooling temperature, the first working fluid in the first low-temperature pulsating heat pipe (41) is in a two-phase flow state. When the refrigerator (3) malfunctions or stops working, the temperature of the cold head (31) of the refrigerator (3) rises, and the temperature of the condensing section connected to the refrigerator (3) rises to a level higher than the critical temperature of the first working fluid. The first working fluid in the condensing section is converted into a gaseous state, the thermal resistance of the first low-temperature pulsating heat pipe (41) increases, and the first thermal switch (4) is in the open state, preventing heat from being transferred to the cooled load (10) through the first thermal switch (4). The cooling system also includes a primary radiation shield (2), which is suspended inside the vacuum chamber (1). The cooled load (10) is located inside the primary radiation shield (2), and the cold head (31) is thermally connected to the primary radiation shield (2). Each of the refrigeration units (3) includes two cold heads (31), which are a primary cold head (31a) and a secondary cold head (31b), respectively. The condensation section of the first low-temperature pulsating heat pipe (41) is connected to the secondary cold head (31b), and the primary cold head (31a) is thermally connected to the primary radiation shield (2). The cooling system also includes a second thermal switch (5), which includes a second low-temperature pulsating heat pipe. The condensing section of the second low-temperature pulsating heat pipe is thermally connected to the first-stage cold head (31a), and the evaporating section of the second low-temperature pulsating heat pipe is thermally connected to the cooled load (10). The triple point temperature of the second working fluid in the second low-temperature pulsating heat pipe is higher than the final cooling temperature of the first-stage cold head (31a).

2. The cooling system according to claim 1, characterized in that, The primary radiation shield (2) is equipped with a secondary radiation shield (9), the cooled load (10) is located inside the secondary radiation shield (9), and the secondary cold head (31b) is thermally connected to the secondary radiation shield (9).

3. The cooling system according to claim 2, characterized in that, The secondary radiation shield (9) is connected to the secondary cold head (31b) through a third thermal switch (30). The third thermal switch (30) includes a third low-temperature pulsating heat pipe. The evaporation section of the third low-temperature pulsating heat pipe is thermally connected to the secondary radiation shield (9), and the condensation section of the third low-temperature pulsating heat pipe is thermally connected to the secondary cold head (31b). When the secondary cold head (31b) is at the final cooling temperature, the third working fluid in the third low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state.

4. The cooling system according to any one of claims 1-3, characterized in that, The cold head (31) is thermally connected to the primary radiation shield (2) via a fourth thermal switch (40). The fourth thermal switch (40) includes a fourth low-temperature pulsating heat pipe. The evaporation section of the fourth low-temperature pulsating heat pipe is thermally connected to the primary radiation shield (2), and the condensation section of the fourth low-temperature pulsating heat pipe is thermally connected to the cold head (31). When the cold head (31) is at the final cooling temperature, the fourth working fluid in the fourth low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state.

5. The cooling system according to any one of claims 1-3, characterized in that, The cooling system also includes a first charging system (20), which is used to charge the first working fluid into the first low-temperature pulsating heat pipe (41). The first charging system (20) is configured in a one-to-one correspondence with the first thermal switch (4).

6. The cooling system according to any one of claims 1-3, characterized in that, The first working medium is helium, hydrogen, neon, or nitrogen; The second working fluid in the second low-temperature pulsating heat pipe is neon, argon, nitrogen, oxygen, or methane.

7. The cooling system according to any one of claims 1-3, characterized in that, The outer surface of the cold head (31) and / or the first thermal switch (4) is covered with an insulating layer; And / or, the first thermal switch (4) has a first connecting surface and a second connecting surface, the first connecting surface being thermally connected to the cold head (31), the second connecting surface being thermally connected to the cooled load (10), and the first connecting surface and / or the second connecting surface being provided with a thermally conductive coating and / or a thermally conductive sheet.

8. A superconducting magnet system, comprising a superconducting magnet, characterized in that, It also includes a cooling system as described in any one of claims 1-7, wherein the superconducting magnet is the cooled load (10).

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