Superconducting switch and superconducting current lead combined test device

Abstract

The invention relates to the technical field of superconducting magnet system testing, and discloses a superconducting switch and superconducting current lead combined testing device which comprises a low-temperature system, a superconducting switch, a superconducting current lead and a testing system. The low-temperature system comprises a low-temperature cavity formed by an outer barrel and a radiation screen, a refrigerator and a heat exchange module, the radiation screen is coaxially arranged in the outer barrel, the heat exchange module is installed below a first-stage cold head of the refrigerator, an airflow channel is formed in the heat exchange module, the interior of the superconducting switch is hollow, and the two ends of the superconducting switch are communicated with the airflow channel through circulation pipelines to form a closed gas circulation pipeline; a secondary cold head of the refrigerator is connected with the superconducting switch through a hot connecting column; the high-temperature end of the superconducting current lead is installed on the heat exchange module, the low-temperature end is connected with a secondary cold head of the refrigerator, and outgoing lines of the low-temperature end are connected with two outgoing lines of the superconducting switch. The superconducting switch is provided with two stages of heat conduction loops, so that the cooling efficiency is improved; the test of the superconducting current lead and the superconducting switch can be realized, and the test efficiency and economy are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of superconducting magnet system testing, and particularly to a combined testing device for superconducting switches and superconducting current leads. Background Art

[0002] At present, there are mainly two cooling methods for superconducting switches in the cryogenic system of superconducting magnets. One is cryocooler conduction cooling, and the other is liquid helium immersion cooling. Generally speaking, cryocooler conduction cooling cools down through the heat conduction between the second-stage cold head of the cryocooler and the superconducting switch. This scheme mainly relies on the cooling capacity of the second-stage cold head to cool the superconducting switch. For example, in Chinese Patent Application CN103377788A (Invention Name: Superconducting Magnet System, Publication Date: October 30, 2013), it is disclosed that the superconducting coil is directly connected to the second-stage cold head of the cryocooler through an inverted cold bridge. Since the cooling capacity of the second-stage cold head is small during the initial cooling, the cooling time of the superconducting switch is long, and the testing efficiency is reduced; moreover, the thermal uniformity of heat conduction is poor. Therefore, a large amount of materials with high thermal conductivity are required to cool the superconducting switch during the heat conduction design, and the testing cost is high. Liquid helium immersion cooling usually cools the superconducting switch by immersing it in liquid helium. This scheme has a high cooling efficiency, but since helium is a scarce resource and the price of liquid helium is particularly expensive, for superconducting switches with batch long-term testing, the testing cost is too high and it is not very applicable.

[0003] At present, the testing environment for superconducting current leads in the cryogenic system of superconducting magnets is usually a 77K liquid nitrogen environment. For testing in temperature ranges below 77K, a separate cryogenic testing device needs to be built. A complete testing circuit needs to be built for the superconducting current leads in the testing device. In addition to the superconducting current leads, the testing circuit usually also includes room-temperature copper leads and superconducting magnets (or superconducting wires). Building a set of testing devices separately for testing superconducting current leads has poor economic benefits.

[0004] Therefore, inventing an efficient and economical combined testing device for superconducting switches and superconducting current leads has important commercial value and significance. Summary of the Invention

[0005] To solve the above deficiencies in the prior art, the present invention provides a combined testing device for superconducting switches and superconducting current leads, which improves the cooling efficiency of the cryogenic system, realizes the combined testing of superconducting current leads and superconducting switches, and improves the testing efficiency and economy.

[0006] To achieve the above technical objectives, the technical solution adopted by the present invention is: A combined testing device for superconducting switches and superconducting current leads, comprising a cryogenic system, a superconducting switch, a superconducting current lead, and a testing system; The cryogenic system includes a cryogenic cavity constructed by an outer cylinder and a radiation shield, a refrigerator, and a heat exchange module. The radiation shield is coaxially arranged inside the outer cylinder. The refrigerator is installed on the outer cylinder. The first-stage cold head and the second-stage cold head of the refrigerator are inserted into the interior of the outer cylinder. The heat exchange module is installed below the first-stage cold head and extends into the radiation shield. The top of the heat exchange module is connected to the top plate of the radiation shield. The superconducting switch and the superconducting current lead are arranged inside the radiation shield. An air flow channel is provided inside the heat exchange module. The interior of the superconducting switch is hollow. Both ends of the superconducting switch are connected to the air flow channel of the heat exchange module through a circulation pipeline to form a closed gas circulation pipeline. A circulating gas is filled in the gas circulation pipeline to form a first-stage heat conduction loop. The second-stage cold head of the refrigerator is connected to a heat connection column, and the other end of the heat connection column is connected to the superconducting switch to form a second-stage heat conduction loop. There are two superconducting current leads in total. The high-temperature ends of the superconducting current leads are installed on the heat exchange module. The high-temperature ends are connected to the low-temperature ends of the copper leads. The normal-temperature ends of the copper leads extend out of the outer cylinder. The low-temperature ends of the superconducting current leads are connected to the second-stage cold head of the refrigerator, and the outgoing wires at the low-temperature ends are connected to the two outgoing wires of the superconducting switch. The test system includes an excitation power supply, a monitoring module, and a comprehensive test module. The excitation power supply, the monitoring module, and the comprehensive test module are electrically connected. The excitation power supply is connected to the normal-temperature end of the copper lead and is used to supply current to the superconducting current lead and the superconducting switch. The monitoring module is used to monitor the temperature, voltage signal, and pressure condition in the cryogenic system. The comprehensive test module is used to record and display the monitored data and the change trend.

[0007] Further, the heat exchange module includes a heat exchange plate and a heat exchange block. The heat exchange plate is L-shaped and includes a heat exchange top plate and a side vertical plate. A circular hole is reserved in the center of the heat exchange top plate. Two sets of circumferential holes are arranged on the outer periphery of the circular hole. The inner circumferential hole is used to connect with the flange of the first-stage cold head of the refrigerator, and the outer circumferential hole is used to connect with the top plate of the radiation shield. The heat exchange block is strip-shaped and is connected to the bottom of the heat exchange top plate of the heat exchange plate and is arranged parallel to the side away from the side vertical plate of the heat exchange plate. A plurality of air flow channels are reserved between the heat exchange block and the heat exchange plate. Both ends of the air flow channel are connected to stainless steel pipes, and the stainless steel pipes are connected to the circulation pipeline. A plurality of mounting holes are reserved on the side vertical plate of the heat exchange plate for connecting the high-temperature ends of the superconducting current leads and the low-temperature ends of the copper leads.

[0008] Further, a check valve is provided in the circulation pipeline. The circulation pipeline is communicated with a gas filling pipeline. The gas filling pipeline passes through the radiation shield and the outer cylinder in sequence and is fixed on the outer cylinder. A gas filling port and a pressure monitoring device are provided at the inlet end of the gas filling pipeline.

[0009] Further, the one-way valve is a passive one-way valve. The one-way valve includes a valve body, a flow channel is defined in the valve body, the caliber of the flow channel gradually decreases from the inlet end to the outlet end, a gas baffle is provided at the outlet end of the flow channel, one end of the gas baffle is connected to the outlet end, and the other end is inclined away from the flow channel. The projection of the gas baffle at the outlet end of the flow channel is larger than the caliber of the flow channel and smaller than the outer dimension of the valve body.

[0010] Further, the superconducting switch is composed of a framework, superconducting wires, a baffle and a heater. The framework is of a hollow circular tube type. Baffles for fixing the superconducting wires are installed at both ends of the framework. The superconducting wires are evenly wound around the framework in a non-inductive winding manner; the heater is a thin film resistance heating sheet fixed on the surface of the switch; externally extended circular tubes are welded at both ends of the framework for connecting the circulation pipeline.

[0011] Further, the thermal connection column is made of two materials with different thermal conductivities connected in series. The section close to the second-stage cold head of the refrigerator is the low-thermal-conductivity section, and the section close to the superconducting switch is the high-thermal-conductivity section.

[0012] Preferably, the low-thermal-conductivity section is made of brass, and the high-thermal-conductivity section is made of oxygen-free copper.

[0013] Further, the superconducting current lead is a high-temperature superconducting current lead, mainly composed of superconducting tape, a support device, an upper copper end and a lower copper end. Both ends of the superconducting tape are respectively connected to the upper copper end and the lower copper end. The superconducting tape is installed inside the support device; an interface for welding with a low-temperature superconducting wire is reserved at the lower copper end, and the low-temperature superconducting wire is inserted and welded into the interface of the lower copper end to form the outgoing line at the low-temperature end of the superconducting current lead; an interface for connecting with the low-temperature end of the copper lead is reserved at the upper copper end.

[0014] Further, the low-temperature end of the superconducting current lead is thermally connected to the second-stage cold head of the refrigerator through a copper bus bar / copper braid. The high-temperature end of the superconducting current lead and the low-temperature end of the copper lead are both fixedly connected to the side vertical plate of the heat exchange plate; two test signal lines are respectively connected to the upper copper end and the lower copper end of the superconducting current lead for monitoring the voltage condition of the superconducting current lead.

[0015] Further, the monitoring module includes a pressure monitoring sub-module, a temperature monitoring sub-module, a voltage monitoring sub-module, and a heating sub-module. The pressure monitoring sub-module is used to monitor the pressure in the gas circulation pipeline. The temperature monitoring sub-module is used to monitor the temperatures of key components in the low-temperature system. The voltage monitoring sub-module is used to monitor the voltage signals of the superconducting current lead and the superconducting switch. The heating sub-module is used to heat the superconducting switch.

[0016] The beneficial effects of the present invention are as follows: The combined test device for superconducting switches and superconducting current leads of the present invention. The superconducting switch and the first-stage cold head of the refrigerator form a first-stage heat conduction loop through a gas circulation pipeline. The first-stage cold head of the refrigerator has a large cooling capacity and can quickly cool the circulating gas, enabling the temperature of the superconducting switch to quickly drop to the temperature of the first-stage cold head. A second-stage heat conduction loop is formed between the superconducting switch and the second-stage cold head of the refrigerator through a heat connection column, enabling the superconducting switch to reach a lower temperature. Under the combined cooling of the first-stage and second-stage cold heads of the refrigerator and the efficient circulation of the gas, the cooling efficiency is improved, the usage amount of heat conduction materials is reduced, and the temperature uniformity of the superconducting switch is enhanced. In the test device, the superconducting switch is used as a superconducting coil (or superconducting wire), and both ends are connected to the superconducting current leads to form a complete test circuit. In this way, a combined test device is formed, which can not only realize the test of the superconducting current leads but also the test of the superconducting switch, improving the test efficiency and economy.

[0017] The combined test device for superconducting switches and superconducting current leads of the present invention. The heat exchange module is connected to the first-stage cold head of the refrigerator, which can not only provide the cooling capacity of the first-stage cold head for the first-stage heat conduction loop but also provide cooling for the high-temperature end of the superconducting current lead and the low-temperature end of the copper lead. The heat exchange plate is L-shaped, and the heat exchange blocks are arranged at intervals with the side vertical plate, which can not only make full use of the heat exchange space and improve the heat exchange efficiency of the first-stage cold head but also provide an intermediate throttling temperature for the first-stage heat conduction loop and the high-temperature end of the superconducting current lead, reducing the heat leakage into the superconducting switch and maintaining the temperature stability of the system.

[0018] The combined test device for superconducting switches and superconducting current leads of the present invention. The one-way valve provided in the circulation pipeline enables the circulating gas injected through the gas filling port to circulate in a specific direction in the circulation pipeline, thereby achieving the purpose of quickly reducing the temperature of the superconducting switch. When the circulating gas is cooled to a low-pressure / low-temperature state, due to the action of the one-way valve, the flow rate of the gas or condensate liquid slows down, thereby inhibiting the heat conduction between the first-stage cold head of the refrigerator and the superconducting switch. The lowest temperature at which the superconducting switch cools down is mainly controlled by the second-stage cold head of the refrigerator. Under the cooling action of the second-stage cold head, the superconducting switch and the low-temperature end of the superconducting current lead can be cooled to a temperature range of about 2.5K.

[0019] The combined test device for superconducting switches and superconducting current leads of the present invention. The heat connection column connecting the superconducting switch and the second-stage cold head of the refrigerator is made of two materials with different thermal conductivities connected in series. When the superconducting switch generates heat, its heat is quickly transferred to the low-thermal-conductivity section through the high-thermal-conductivity section. Since the rate of heat transfer in the low-thermal-conductivity section decreases, the heat transfer to the second-stage cold head of the refrigerator can be effectively slowed down or blocked, so that the superconducting switch will not transfer most of its heat to the second-stage cold head when generating heat, thus ensuring the overall thermal stability of the system. Description of the Drawings

[0020] To more clearly illustrate the technical solutions of the embodiments of the present application, the accompanying drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following accompanying drawings only show some embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related accompanying drawings can also be obtained based on these drawings without creative efforts.

[0021] Figure 1 is a schematic diagram of the principle of the joint test device of the present invention; Figure 2 is a schematic diagram of the structure of the cryogenic system; Figure 3 is a front view of the heat exchange module; Figure 4 is Figure 3 a sectional view taken along line A-A in Figure 5 is a schematic diagram of the structure of the check valve.

[0022] Reference numerals: 1 - superconducting switch, 2 - superconducting current lead, 3 - outer cylinder, 4 - radiation shield, 5 - refrigerator, 501 - first-stage cold head, 502 - second-stage cold head, 6 - heat exchange module, 601 - heat exchange plate, 602 - heat exchange block, 603 - stainless steel pipe, 604 - air flow channel, 605 - side vertical plate, 7 - circulation pipeline, 8 - gas filling pipeline, 9 - check valve, 901 - valve body, 902 - flow channel, 903 - gas baffle, 10 - thermal connection column, 101 - low thermal conductivity section, 102 - high thermal conductivity section, 11 - copper lead, 12 - gas filling port, 13 - pressure monitoring device, 14 - test signal line, 15 - cryogenic superconducting wire, 16 - interface, 17 - excitation power supply, 18 - monitoring module, 19 - comprehensive test module. Detailed implementation manners

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Usually, the components of the embodiments of the present application described and shown in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0024] A joint test device for a superconducting switch and a superconducting current lead includes a cryogenic system, a superconducting switch 1, a superconducting current lead 2, and a test system.

[0025] The cryogenic system includes a cryogenic cavity constructed by an outer cylinder 3 and a radiation shield 4, a refrigerator 5, and a heat exchange module 6. The radiation shield 4 is coaxially arranged inside the outer cylinder 3. The refrigerator 5 is installed on the outer cylinder 3. The first-stage cold head 501 and the second-stage cold head 502 of the refrigerator 5 are inserted into the interior of the outer cylinder 3. The heat exchange module 6 is installed below the first-stage cold head 501 and extends into the radiation shield 4. The top of the heat exchange module 6 is connected to the top plate of the radiation shield 4. The superconducting switch 1 and the superconducting current lead 2 are arranged inside the radiation shield 4. An air flow channel 604 is provided inside the heat exchange module 6. The interior of the superconducting switch 1 is hollow, and both ends are connected to the air flow channel 604 of the heat exchange module 6 through a circulation pipeline 7 to form a closed gas circulation pipeline. A circulation gas is filled in the gas circulation pipeline to form a first-stage heat conduction loop to provide the refrigeration capacity from the first-stage cold head 501 of the refrigerator 5 to the superconducting switch 1. The second-stage cold head 502 of the refrigerator is connected to a heat connection column 10, and the other end of the heat connection column 10 is connected to the superconducting switch 1 to form a second-stage heat conduction loop to provide the refrigeration capacity from the second-stage cold head 502 of the refrigerator to the superconducting switch 1 and provide a lower temperature for the superconducting switch 1. There are two superconducting current leads 2 in total. The high-temperature ends of the superconducting current leads 2 are installed on the heat exchange module 6, the high-temperature ends are connected to the low-temperature ends of copper leads 11, the normal-temperature ends of the copper leads 11 extend out of the outer cylinder 3, the low-temperature ends of the superconducting current leads 2 are connected to the second-stage cold head 502 of the refrigerator, and the outgoing wires at the low-temperature ends are connected to the two outgoing wires of the superconducting switch 1.

[0026] The test system includes an excitation power supply 17, a monitoring module 18, and a comprehensive test module 19. The excitation power supply 17, the monitoring module 18, and the comprehensive test module 19 are electrically connected. The excitation power supply 17 is connected to the high-temperature end of the copper lead 11. The excitation power supply 17 is used to conduct current through the superconducting current lead 2 and the superconducting switch 1. The monitoring module 18 is used to monitor the temperature, voltage signal, pressure condition, etc. in the cryogenic system.

[0027] Specifically, the outer cylinder 3 is a circular cavity, mainly including a top flange, a circumferential cylinder, and a circular bottom plate. The outer cylinder 3 can be made of stainless steel. Its function is to isolate the interior of the outer cylinder 3 from the room temperature environment and provide a high-vacuum environment inside it. The top flange of the outer cylinder 3 has a reserved interface 16 for installing relevant test devices such as the refrigerator 5, the copper lead 11, the gas filling pipeline 8, and the test signal line 14.

[0028] The radiation shield 4 is a circular cylinder, coaxially arranged with the outer cylinder 3, and mainly consists of a top plate, a circumferential cylinder, and a bottom plate. The radiation shield 4 is made of materials with relatively high thermal conductivity such as aluminum alloy or copper. It is mainly used to shield the thermal radiation from room temperature and reduce the radiative heat leakage of the system. The top plate of the radiation shield 4 is reserved with relevant channels to facilitate the cold head of the refrigerator or relevant test devices to enter the low-temperature environment from room temperature. The top plate of the radiation shield 4 is reserved with relevant threaded holes for connecting with the top of the heat exchange module 6. The inner cylinder space of the radiation shield 4 is the test environment for the superconducting switch 1 and the superconducting current lead 2.

[0029] The refrigerator 5 adopts a GM refrigerator. The room-temperature flange of the refrigerator 5 is connected to the top flange of the outer cylinder 3. The first-stage cold head 501 and the second-stage cold head 502 of the refrigerator are inserted into the inner part of the outer cylinder 3. The heat exchange module 6 is installed below the first-stage cold head 501. The heat exchange module 6 is used to install the radiation shield 4, the superconducting current lead 2, and the circulation pipeline 7, and provide the cold quantity from the first-stage cold head 501 for them.

[0030] The heat exchange module 6 includes a heat exchange plate 601 and a heat exchange block 602. The heat exchange plate 601 is an L-shaped copper plate, including a heat exchange top plate and a side vertical plate 605. A circular channel is reserved in the center of the heat exchange top plate to facilitate the second-stage cold head 502 of the refrigerator to pass through. Two sets of circumferential holes are arranged on the outer periphery of the circular channel. The inner circumferential holes are used to connect with the flange of the first-stage cold head 501 of the refrigerator for positioning the heat exchange module 6. The outer circumferential holes are used to connect with the threaded holes on the top plate of the radiation shield 4, for positioning the radiation shield 4 and at the same time transferring the cold quantity from the first-stage cold head 501 of the refrigerator. The heat exchange block 602 is strip-shaped and is connected to the bottom of the heat exchange top plate of the heat exchange plate 601, and is arranged in parallel on one side away from the side vertical plate 605 of the heat exchange plate 601. A number of air flow channels 604 are reserved between the heat exchange block 602 and the heat exchange plate 601. The two ends of the air flow channel 604 are connected to stainless steel pipes 603, and the stainless steel pipes 603 are connected to the circulation pipeline 7. Both ends of the superconducting switch 1 are communicated with the air flow channel 604 through the circulation pipeline 7 to form a closed gas circulation pipeline, that is, the first-stage heat conduction loop. The gas injected through the gas filling pipeline 8 circulates in the circulation pipeline 7 in a specific direction. The gas fully exchanges heat with the heat exchange plate 601 in the air flow channel 604 to provide the refrigerating capacity from the first-stage cold head 501 of the refrigerator for the superconducting switch 1, achieving the purpose of quickly reducing the temperature of the superconducting switch 1. The heat exchange block 602 and the heat exchange plate 601 can be connected together by welding to ensure the heat conductivity between them. A plurality of mounting holes are reserved on the side vertical plate 605 of the heat exchange plate 601 for connecting the high-temperature end of the superconducting current lead 2 and the low-temperature end of the copper lead 11, so as to cool the superconducting current lead 2 and provide an intermediate cut-off temperature for it to reduce the heat leakage into the superconducting switch 1.

[0031] The described circulation pipeline 7 is made by bending a stainless steel pipe. It is located inside the radiation shield 4 and can be connected to the stainless steel pipe 603 of the heat exchange module 6 and both sides of the superconducting switch 1 to form a closed gas circulation pipeline. The circulation pipeline 7 is connected to a gas filling pipeline 8. The gas filling pipeline 8 passes through the radiation shield 4 and the outer cylinder 3 in sequence and is fixed on the top flange of the outer cylinder 3. A gas filling port 12 and a pressure monitoring device 13 are arranged at the inlet end of the gas filling pipeline 8 outside the outer cylinder 3. The circulating gas injected into the circulation pipeline 7 through the gas filling port 12 can circulate in the circulation pipeline 7, so as to achieve the purpose of quickly reducing the temperature of the superconducting switch 1. Among them, the injected circulating gas is generally a high-pressure gas, and the injected circulating gas exists in the form of a solid or a liquid at a temperature below 30K. For example: nitrogen, argon, helium, etc. The pressure monitoring device 13 is mainly used to monitor the pressure during the whole experiment to ensure the safety and reliability of the experiment.

[0032] A check valve 9 is installed in the circulation pipeline 7. The check valve 9 is a passive check valve. The check valve 9 includes a valve body 901. A flow channel 902 is opened in the valve body 901. The caliber of the flow channel 902 gradually decreases from the inlet end to the outlet end. A gas baffle 903 is arranged at the outlet end of the flow channel 902. One end of the gas baffle 903 is connected to the outlet end, and the other end is inclined away from the flow channel 902. The projection of the gas baffle 903 at the outlet end of the flow channel 902 is larger than the caliber of the flow channel 902 and smaller than the outer dimension of the valve body 901. The check valve 9 increases the flow resistance of the gas while enabling the circulating gas to flow in a specific direction. When the gas is in a high temperature / high pressure state, the circulation speed of the gas in the circulation pipeline 7 is relatively fast, and the superconducting switch 1 can be quickly cooled; when the gas is cooled to a low pressure / low temperature state, due to the action of the check valve 9, the flow rate of the gas or the condensed liquid slows down, thereby inhibiting the heat conductivity between the first-stage cold head 501 of the refrigerator and the superconducting switch 1, so that the lowest temperature of the superconducting switch 1 is mainly controlled by the second-stage cold head 502 of the refrigerator.

[0033] The superconducting switch 1 is mainly composed of a skeleton, superconducting wires, baffles and heaters. Among them, the skeleton is a hollow circular tube type and is made of oxygen-free copper by processing. Baffles for fixing superconducting wires are installed at both ends of the skeleton. The superconducting wires are evenly wound around the skeleton by a non-inductive winding method; the heater is a thin-film resistance heating sheet fixed on the surface of the switch and is used to heat the switch. Outer extension circular tubes are welded at both ends of the skeleton. The outer extension circular tubes can be made of stainless steel pipes and are used to connect the circulation pipeline 7 to form a closed gas circulation loop. One side of the skeleton is provided with a plane connected to the heat connection column 10. By connecting the heat connection column 10 through this plane, the superconducting switch 1 can form a secondary heat conduction loop with the second-stage cold head 502 of the refrigerator to achieve a lower cooling temperature.

[0034] Preferably, the thermal connection post 10 connecting the superconducting switch 1 to the second-stage cold head 502 of the refrigerator is made of two materials with different thermal conductivities connected in series. The low-thermal-conductivity section 101 is closer to the second-stage cold head 502 of the refrigerator, and the high-thermal-conductivity section 102 is closer to the superconducting switch 1. Preferably, the low-thermal-conductivity section 101 is made of brass, and the high-thermal-conductivity section 102 is made of oxygen-free copper. When the superconducting switch 1 generates heat, its heat is quickly transferred to the low-thermal-conductivity section 101 through the high-thermal-conductivity section 102. Since the rate of heat transfer in the low-thermal-conductivity section 101 decreases, the heat transfer to the second-stage cold head 502 of the refrigerator can be effectively slowed down or blocked, so that most of the heat is not transferred to the second-stage cold head 502 of the refrigerator when the superconducting switch 1 generates heat, thus ensuring the overall thermal stability of the system.

[0035] The superconducting current lead 2 is a high-temperature superconducting current lead, mainly composed of superconducting tapes, a support device, an upper copper end and a lower copper end. The two ends of the superconducting tape are respectively connected to the upper copper end and the lower copper end, and the superconducting tape is installed inside the support device. The high-temperature end of the superconducting current lead 2 is on the side close to the first-stage cold head 501 of the refrigerator, and the low-temperature end is on the side close to the second-stage cold head 502 of the refrigerator. The low-temperature end of the superconducting current lead 2 and the second-stage cold head 502 of the refrigerator are thermally connected through a copper bus / copper braid (not shown in the figure); the high-temperature end of the superconducting current lead 2 and the low-temperature end of the copper lead 11 are jointly fixed on the side vertical plate 605 of the heat exchange plate 601. During normal operation, the high-temperature end of the superconducting current lead 2 is in the temperature range of 30 - 50K, and the low-temperature end is at a temperature of about 2.5K - 4.2K, providing a good low-temperature environment for its superconducting state. In particular, the thermal connection points between the low-temperature end and the high-temperature end of the superconducting current lead 2 and the first-stage cold head 501 and the second-stage cold head 502 of the refrigerator need to be well insulated. Usually, insulating materials such as Mylar insulating film or aluminum nitride insulating sheet can be added at the thermal connection points. In order to realize the test of the superconducting current lead 2, two test signal lines 14 are respectively connected to the upper copper end and the lower copper end of the superconducting current lead 2 to monitor the voltage condition of the superconducting current lead 2.

[0036] Specifically, an interface for welding with the low-temperature superconducting wire 15 is reserved at the copper end of the superconducting current lead 2. The low-temperature superconducting wire 15 is inserted into and welded to the interface of the lower copper end to form an outgoing line at the low-temperature end of the superconducting current lead 2, which is convenient for connecting to the outgoing line end of the superconducting switch 1. Particularly, the outgoing line of the superconducting switch 1 and the outgoing line of the low-temperature end of the superconducting current lead 2 are connected in a lapping manner. During lapping, first wind with tinned copper wire and then weld. The lapping length should be greater than 60 mm as much as possible to minimize the resistance of the welded joint. An interface for connecting to the low-temperature end of the copper lead 11 is reserved at the high-temperature end of the superconducting current lead 2. The two are jointly fixed on the side vertical plate 605 of the heat exchange plate 601, receiving the cold quantity from the first-stage cold head 501 of the refrigerator while completing the electrical connection, providing an intermediate current-cutting temperature for the low-temperature end of the copper lead 11 and reducing its heat leakage. The room-temperature end of the copper lead 11 is fixed on the flange of the outer cylinder 3. In terms of circuit testing, the two outgoing lines of the superconducting switch 1 are respectively connected to the outgoing lines of the two low-temperature ends of the superconducting current lead 2. The high-temperature end of the superconducting current lead 2 is connected to the low-temperature end of the copper lead 11, and the copper lead 11 is further connected to the external excitation power supply 17, forming a complete circuit test loop in a progressive manner, which can be used for the current-carrying test of the superconducting switch 1 and the superconducting current lead 2.

[0037] Further, the cryogenic system and the test system are connected through the signal line interface 16 and the copper lead 11, as shown in the appendix Figure 2 shown. The monitoring module 18 includes a pressure monitoring sub-module, a temperature monitoring sub-module, a voltage monitoring sub-module, and a heating sub-module. The pressure monitoring sub-module is communicatively connected to the pressure monitoring device 13 for monitoring the pressure in the gas circulation pipeline. The temperature monitoring sub-module is used to monitor the temperatures of key components in the cryogenic system. The voltage monitoring sub-module is connected to the test signal line 14 for monitoring the voltage signals of the superconducting current lead 2 and the superconducting switch 1. The heating sub-module is connected to the heater for heating the superconducting switch 1 to test its recovery status between the superconducting state and the normal state. The data monitored by the monitoring module 18 are integrated into the comprehensive test module 19 through the communication interface, and relevant data and change trends can be viewed in real time.

[0038] After completing the above device connection and cooling, the cooling and current-carrying performance tests of the superconducting switch 1 and the superconducting current lead 2 can be carried out. The entire experimental process is as follows: First, fill the internal circulation pipeline 7 with high-pressure gas (such as nitrogen, argon, or helium) through the gas filling port 12. After the pressure reaches the target value, close the gas filling port 12 and start the refrigerator 5 to start cooling the superconducting switch 1 and the superconducting current lead 2.

[0039] The superconducting switch 1 is cooled jointly by the first-stage cold head 501 and the second-stage cold head 502 of the refrigerator. The high-temperature end of the superconducting current lead 2 is cooled by the first-stage cold head 501 of the refrigerator, and the low-temperature end is cooled by the second-stage cold head 502 of the refrigerator. In the initial stage of this cooling process, the first-stage cold head 501 of the refrigerator has a large amount of cooling capacity and can quickly cool the circulating gas. Through the gas circulation, the superconducting switch 1 can be quickly cooled to the temperature of the first-stage cold head 501. When the temperature of the superconducting switch 1 is lower than the temperature of the first-stage cold head 501, at this time, due to the action of gravity and the one-way valve 9, the condensed liquid or solid deposits at the bottom of the gas circulation pipeline 7 (at the skeleton of the superconducting switch 1), greatly weakening the thermal connection between the superconducting switch 1 and the first-stage cold head 501. Under the cooling action of the second-stage cold head 502, the low-temperature ends of the superconducting switch 1 and the superconducting current lead 2 can be cooled to a temperature range of about 2.5K.

[0040] After reaching the target temperature, the superconducting switch 1 and the superconducting current lead 2 are subjected to a current-carrying test through the external excitation power supply 17. During the experiment, the temperature and voltage signals are monitored in real time, and whether the performance of the superconducting switch 1 and the superconducting current lead 2 meets the requirements is judged through the quench temperature and the quench voltage, so as to achieve the test purpose.

[0041] Through the innovative design of the structures of the superconducting switch 1 and the superconducting current lead 2, and at the same time, the innovative introduction of the heat exchange module 6, the circulation pipeline 7 and the one-way valve 9, the present invention can efficiently and quickly realize the combined cooling and current-carrying test of the superconducting switch 1 and the superconducting current lead 2, and can achieve a number of beneficial effects in terms of system testing; on the one hand, the present invention greatly reduces the heat leakage of the system. Compared with the liquid helium immersion cooling, its test temperature range is lower, and the lowest can reach about 2.5K, improving the reliability of the test. On the other hand, the present invention performs excellently in improving the system cooling performance. It can not only improve the cooling efficiency, but also improve the temperature uniformity. From the comparison of the relevant test results, compared with the conduction cooling method of the refrigerator, the present invention can keep the overall temperature uniformity of the superconducting switch 1 within 0.2K, and the system cooling efficiency is increased by at least 30%.

[0042] Certainly, the present invention can also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations should all fall within the protection scope of the appended claims of the present invention.

Claims

1. A combined test device for a superconducting switch and a superconducting current lead, characterized in that: It includes a cryogenic system, a superconducting switch, superconducting current leads, and a test system; The cryogenic system includes a cryogenic cavity constructed by an outer cylinder and a radiation shield, a refrigerator, and a heat exchange module. The radiation shield is coaxially arranged inside the outer cylinder. The refrigerator is installed on the outer cylinder. The first-stage cold head and the second-stage cold head of the refrigerator are inserted into the interior of the outer cylinder. The heat exchange module is installed below the first-stage cold head and extends into the radiation shield. The top of the heat exchange module is connected to the top plate of the radiation shield; The superconducting switch and superconducting current leads are arranged inside the radiation shield; an air flow channel is provided inside the heat exchange module. The superconducting switch is hollow inside. Both ends of the superconducting switch are connected to the air flow channel of the heat exchange module through a circulation pipeline to form a closed gas circulation pipeline. A circulating gas is filled in the gas circulation pipeline to form a first-stage heat conduction loop; the second-stage cold head of the refrigerator is connected to a heat connection column, and the other end of the heat connection column is connected to the superconducting switch to form a second-stage heat conduction loop; There are two superconducting current leads in total. The high-temperature ends of the superconducting current leads are installed on the heat exchange module. The high-temperature ends are connected to the low-temperature ends of the copper leads. The normal-temperature ends of the copper leads extend out of the outer cylinder; the low-temperature ends of the superconducting current leads are connected to the second-stage cold head of the refrigerator, and the outgoing lines at the low-temperature ends are connected to the two outgoing lines of the superconducting switch; The test system includes an excitation power supply, a monitoring module, and a comprehensive test module. The excitation power supply, the monitoring module, and the comprehensive test module are electrically connected. The excitation power supply is connected to the normal-temperature end of the copper lead. The excitation power supply is used to supply current to the superconducting current leads and the superconducting switch; the monitoring module is used to monitor the temperature, voltage signal, and pressure conditions in the cryogenic system. The comprehensive test module is used to record and display the monitoring data and the change trend.

2. The superconducting switch and superconducting current lead combined test device according to claim 1, characterized in that: The heat exchange module includes a heat exchange plate and a heat exchange block; the heat exchange plate is L-shaped and includes a heat exchange top plate and a side vertical plate. A circular hole is reserved in the center of the heat exchange top plate. Two sets of circumferential holes are arranged on the outer periphery of the circular hole. The inner circumferential holes are used to connect to the flange of the first-stage cold head of the refrigerator, and the outer circumferential holes are used to connect to the top plate of the radiation shield; the heat exchange block is strip-shaped and is connected to the bottom of the heat exchange top plate of the heat exchange plate and is arranged parallel to one side far from the side vertical plate of the heat exchange plate. Several air flow channels are reserved between the heat exchange block and the heat exchange plate. Both ends of the air flow channel are connected to stainless steel pipes, and the stainless steel pipes are connected to the circulation pipeline; a plurality of installation holes are reserved on the side vertical plate of the heat exchange plate for connecting the high-temperature ends of the superconducting current leads and the low-temperature ends of the copper leads.

3. The superconducting switch and superconducting current lead combined test device according to claim 1, characterized in that: A check valve is provided in the circulation pipeline. The circulation pipeline is connected to a gas filling pipeline. The gas filling pipeline passes through the radiation shield and the outer cylinder in sequence and is fixed on the outer cylinder. A gas filling port and a pressure monitoring device are provided at the inlet end of the gas filling pipeline.

4. The superconducting switch and superconducting current lead combined test device according to claim 3, wherein: The check valve is a passive check valve. The check valve includes a valve body. A flow channel is opened inside the valve body. The caliber of the flow channel gradually decreases from the inlet end to the outlet end. A gas baffle is provided at the outlet end of the flow channel. One end of the gas baffle is connected to the outlet end, and the other end is inclined away from the flow channel. The projection of the gas baffle at the outlet end of the flow channel is larger than the caliber of the flow channel and smaller than the outer dimension of the valve body.

5. The superconducting switch and superconducting current lead combined test device according to claim 1, characterized in that: The superconducting switch is composed of a skeleton, superconducting wires, baffles and heaters. The skeleton is a hollow circular tube. Baffles for fixing the superconducting wires are installed at both ends of the skeleton. The superconducting wires are evenly wound around the skeleton in a non-inductive winding manner. The heater is a thin film resistance heating sheet fixed on the surface of the switch. Outer extended circular tubes are welded at both ends of the skeleton for connecting the circulation pipeline.

6. The superconducting switch and superconducting current lead combined test device according to claim 1, characterized in that: The thermal connection column is made by connecting two materials with different thermal conductivities in series. The section near the second-stage cold head of the refrigerator is the low-thermal-conductivity section, and the section near the superconducting switch is the high-thermal-conductivity section.

7. The superconducting switch and superconducting current lead combined test device according to claim 6, characterized in that: The low-thermal-conductivity section is made of brass, and the high-thermal-conductivity section is made of oxygen-free copper.

8. The superconducting switch and superconducting current lead combined test device according to claim 2, characterized in that: The superconducting current lead uses a high-temperature superconducting current lead, which mainly consists of superconducting tape, a support device, an upper copper end and a lower copper end. The two ends of the superconducting tape are respectively connected to the upper copper end and the lower copper end. The superconducting tape is installed inside the support device. An interface for welding with a low-temperature superconducting wire is reserved at the lower copper end, and the low-temperature superconducting wire is inserted and welded into the interface of the lower copper end to form the outgoing line of the low-temperature end of the superconducting current lead. An interface for connecting with the low-temperature end of the copper lead is reserved at the upper copper end.

9. The superconducting switch and superconducting current lead combined test device according to claim 8, characterized in that: The low-temperature end of the superconducting current lead is thermally connected to the second-stage cold head of the refrigerator through a copper bar / copper braid. The high-temperature end of the superconducting current lead and the low-temperature end of the copper lead are both fixedly connected to the side vertical plate of the heat exchange plate. Two test signal lines are respectively connected to the upper copper end and the lower copper end of the superconducting current lead to monitor the voltage condition of the superconducting current lead.

10. The superconducting switch and superconducting current lead combined test device according to claim 1, characterized in that: The monitoring module includes a pressure monitoring sub-module, a temperature monitoring sub-module, a voltage monitoring sub-module and a heating sub-module. The pressure monitoring sub-module is used to monitor the pressure in the gas circulation pipeline. The temperature monitoring sub-module is used to monitor the temperatures of key components in the low-temperature system. The voltage monitoring sub-module is used to monitor the voltage signals of the superconducting current lead and the superconducting switch. The heating sub-module is used to heat the superconducting switch.

Images