Superconducting magnet for plasma confinement and testing device

Abstract

This application discloses a superconducting magnet and testing device for plasma confinement. The superconducting magnet includes a superconducting coil, a cooling medium tank, and a cold screen. The two ends of the superconducting coil are connected to a superconducting power supply. The cold screen also has an abnormal energy discharge circuit and a quench failure energy discharge circuit. When the superconducting magnet malfunctions, the abnormal energy discharge circuit is activated; when the superconducting magnet loses quench, the quench failure energy discharge circuit is activated. This application connects the abnormal energy discharge circuit and the quench failure energy discharge circuit in parallel across the two ends of the superconducting coil. Both circuits contain resistors. When the superconducting magnet malfunctions or loses quench, a portion of the energy in the superconducting coil is rapidly released to the ambient temperature environment through the resistors, significantly reducing the cooling pressure of the cooling medium tank. This not only improves the safety of the superconducting coil but also shortens the cooling time of the cooling medium tank.

Description

Technical Field

[0001] This application relates to the field of superconducting technology, and in particular to a superconducting magnet and testing device for plasma confinement. Background Technology

[0002] Nuclear fusion research is a major international collaborative project undertaken by the global scientific community to address humanity's future energy challenges. Unlike non-renewable energy and conventional clean energy, fusion energy boasts advantages such as unlimited resources, no environmental pollution, and no production of high-level radioactive nuclear waste. It is one of the dominant forms of energy for humanity's future and a crucial pathway recognized to ultimately solve human society's energy and environmental problems, promoting sustainable development. The International Thermonuclear Experimental Reactor (ITER) project is one of the world's largest and most far-reaching international scientific research collaborations. The ITER device is a superconducting tokamak capable of generating large-scale nuclear fusion reactions, commonly known as an "artificial sun." The ITER project is an essential step towards the commercialization of fusion energy, aiming to verify the scientific and technological feasibility of peacefully utilizing fusion energy.

[0003] The divertor is a core component of the translation chamber in magnetic confinement fusion reactors, forming part of toroidal fusion devices (such as tokamak). This device diverts charged particles from the outer discharge layer into a separate chamber where they bombard baffles, becoming neutral particles and being extracted. This method prevents charged particles in the outer layer from bombarding the main discharge chamber wall, thus preventing the release of secondary particles that could cool the discharge. Therefore, studying its performance under plasma conditions is crucial for the successful design and manufacture of commercially viable divertors. Researching the material performance of divertors in a plasma environment requires the construction of large-scale experimental platforms to simulate plasma parameters under real nuclear fusion conditions. However, when the core component of the experimental platform—the large superconducting magnet device—experiences an anomaly or loses quench, the energy of the superconducting coil is converted into heat and slowly discharged to the room temperature environment. This requires the superconducting magnet device to be shut down and cooled for a long time, which not only poses a risk of burning out the superconducting coil, but also incurs significant time and, especially, economic costs, which is not conducive to the use and promotion of the superconducting magnet device. Summary of the Invention

[0004] This application provides a superconducting magnet and testing device for plasma confinement, which solves the problem in the prior art where the heat generated by the superconducting coil after an abnormality or loss of quench in the superconducting magnet device causes the superconducting magnet to require a long period of power-off shutdown and recooling.

[0005] On one hand, embodiments of this application provide a superconducting magnet for plasma confinement, comprising:

[0006] Superconducting coils;

[0007] A cooling medium tank is filled with a cooling medium, and a superconducting coil is placed inside the cooling medium tank.

[0008] The cooling medium tank is located inside the cold screen.

[0009] The two ends of the superconducting coil are electrically connected to the superconducting power supply through current leads, and the superconducting power supply is located outside the cold shield. The outside of the cold shield also has an abnormal energy discharge circuit and a quench energy discharge circuit, which are connected in parallel with the superconducting power supply. The abnormal energy discharge circuit includes an abnormal energy discharge resistor, an abnormal energy discharge diode and an abnormal energy discharge circuit breaker connected in series. The quench energy discharge circuit includes a quench energy discharge resistor, a quench energy discharge diode and a quench energy discharge circuit breaker connected in series. When the superconducting magnet malfunctions, the abnormal energy discharge circuit breaker closes. When the superconducting magnet loses quench, the quench energy discharge circuit breaker closes.

[0010] On the other hand, embodiments of this application provide a plasma confinement testing device, including an ion source, a test sample, and a superconducting magnet for plasma confinement as described above. The ion source is positioned directly opposite the test sample, and the ion source and the test sample are arranged inside the superconducting magnet along its axial direction.

[0011] The superconducting magnet and testing device for plasma confinement described in this application have the following advantages:

[0012] 1. A magnet protection scheme is proposed that can realize abnormal energy leakage, active and passive dual quench protection, and energy leakage protection. This scheme ensures the feasibility and reliability of system operation, avoids the damage to the magnet caused by high voltage generated inside the superconducting coil when only active protection is used after the magnet quenches, or when the quench detection is not timely or even fails. It also avoids practical engineering problems such as excessive temperature rise in the cold part after the quench due to excessive energy stored in the magnet, resulting in high cooling time and economic costs for the superconducting coil.

[0013] 2. It can provide a superconducting magnet equipment solution with large space and high magnetic field strength for materials or devices involved in nuclear fusion research, such as divertors, that need to be tested and studied under the action of plasma environment. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1This is a schematic diagram of the internal structure of a superconducting magnet for plasma confinement provided in an embodiment of this application;

[0016] Figure 2 This is a schematic diagram of the structure of a cold screen provided in an embodiment of this application;

[0017] Figure 3 This is a schematic diagram of the overall circuit of the superconducting magnet provided in an embodiment of this application;

[0018] Figure 4 A schematic diagram of the power supply status of a superconducting magnet during normal operation, provided in an embodiment of this application;

[0019] Figure 5 This is a schematic diagram of the power supply process for a superconducting magnet provided in an embodiment of this application;

[0020] Figure 6 This is a circuit diagram of a superconducting magnet in the prior art;

[0021] Figure 7 This is a schematic diagram of the quench protection process for superconducting magnets in the prior art;

[0022] Figure 8 A circuit diagram for abnormal energy discharge provided in an embodiment of this application;

[0023] Figure 9 A schematic diagram of the abnormal energy leakage process provided in the embodiments of this application;

[0024] Figure 10 A circuit diagram for quench protection provided in an embodiment of this application;

[0025] Figure 11 This is a schematic diagram of the overrun protection process provided in an embodiment of this application;

[0026] Figure 12 A schematic diagram comparing the highest temperature of the cold body after quenching in magnet energy leakage-free and energy leakage schemes provided in the embodiments of this application;

[0027] Figure 13 This is a schematic diagram of the structure of a plasma confinement testing device provided in an embodiment of this application;

[0028] Figure 14 This is a schematic diagram of the motion trajectory of the superconducting coil inside the superconducting magnet and the plasma under magnetic field confinement, provided in an embodiment of this application.

[0029] Figure labeling: 1-Superconducting magnet, 2-Ion source, 3-Test sample. 101-Refrigerator, 102-Superconducting coil, 103-Frame, 104-Cooling medium tank, 105-Cold shield, 105-A-Protruding structure, 106-Vacuum Dewar inner cylinder, 107-Current lead, 108-Axial lifting rod, 109-Radial lifting rod, 110-Support base, 111-Superconducting power supply, 112-Power circuit breaker, 113-Quake detector, 114-Protection diode, 115-Abnormal energy leakage diode, 116-Abnormal energy leakage circuit breaker, 117-Abnormal energy leakage resistor, 118-Quake energy leakage circuit breaker, 119-Quake energy leakage resistor, 120-Quake energy leakage diode. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] In existing technologies, when a superconducting magnet used for plasma confinement experiences an anomaly or quench failure, the energy of the superconducting coil is converted into heat and slowly dissipated to room temperature. This necessitates prolonged power-off shutdowns and recooling of the superconducting magnet device. For example, in Chinese invention patent application CN114974797A, a protection diode is used to release the energy generated when the superconducting coil quenches. However, after the energy is converted into heat by the superconducting coil, all the heat accumulates in the cooling medium tank. This rapid accumulation of a large amount of heat poses a significant threat to the safety of the superconducting coil, and the dissipation of the heat also takes a long time, greatly reducing the efficiency of research and testing.

[0032] To address the problems in the prior art, this application proposes a superconducting magnet and testing device for plasma confinement. An abnormal energy discharge circuit and a quench failure energy discharge circuit are connected in parallel across the two ends of the superconducting coil. Both circuits contain resistors. When the superconducting magnet malfunctions or loses quench, a portion of the energy in the superconducting coil will be rapidly released to the ambient temperature environment through the resistors, greatly reducing the cooling pressure of the cooling medium bath. This not only improves the safety of the superconducting coil but also shortens the cooling time of the cooling medium bath.

[0033] Figure 1-3 This is a schematic diagram illustrating the composition of a superconducting magnet for plasma confinement, provided in an embodiment of this application. This application provides a superconducting magnet for plasma confinement, comprising:

[0034] Superconducting coil 102;

[0035] Cooling medium tank 104 is filled with cooling medium, and superconducting coil 102 is disposed inside cooling medium tank 104;

[0036] The cooling screen 105 has a cooling medium tank 104 disposed inside it.

[0037] The two ends of the superconducting coil 102 are electrically connected to the superconducting power supply 111 through current leads 107. The superconducting power supply 111 is located outside the cold screen 105. The cold screen 105 also has an abnormal energy discharge circuit and a quench failure energy discharge circuit. The abnormal energy discharge circuit and the quench failure energy discharge circuit are connected in parallel with the superconducting power supply 111. The abnormal energy discharge circuit includes an abnormal energy discharge resistor 117, an abnormal energy discharge diode 115 and an abnormal energy discharge circuit breaker 116 connected in series. The quench failure energy discharge circuit includes a quench failure energy discharge resistor 119, a quench failure energy discharge diode 120 and a quench failure energy discharge circuit breaker 118 connected in series. When the superconducting magnet is abnormal, the abnormal energy discharge circuit breaker 116 closes. When the superconducting magnet loses quench, the quench failure energy discharge circuit breaker 118 closes.

[0038] For example, a frame 103 is provided inside the cooling medium tank 104, and a superconducting coil 102 is disposed on the frame 103. Specifically, the frame 103 is a hollow cylindrical structure, and the superconducting coil 102 is wound on the outer surface of the frame 103. The superconducting coil 102 needs to be configured as at least three segments connected in series, and each segment may contain at least two smaller coils connected in series. Two segments of the superconducting coil are wound at both ends of the frame 103, while the other segment is wound in the middle of the frame 103. The cooling medium inside the cooling medium tank 104 can be liquid helium. After the cooling medium tank 104 is surrounded by a cold shield 105, the thermal radiation load of the external high temperature on the cooling medium tank 104 can be effectively reduced. The combination of the superconducting coil 102, frame 103, cooling medium tank 104, and cold shield 105 is referred to as the cryogenic section.

[0039] In the embodiments of this application, a vacuum Dewar inner cylinder 106 is disposed outside the cold screen 105, and the space between the cold screen 105 and the vacuum Dewar inner cylinder 106 is in a vacuum state. The superconducting magnet also includes: a radial lifting rod 109 disposed outside the frame 103, the radial lifting rod 109 passing through the cooling medium tank 104, the cold screen 105 and the vacuum Dewar inner cylinder 106, and extending outside the vacuum Dewar inner cylinder 106; and an axial lifting rod 108 parallel to the axis of the frame 103, the axial lifting rod 108 passing through the cooling medium tank 104, the cold screen 105 and the vacuum Dewar inner cylinder 106, and extending outside the vacuum Dewar inner cylinder 106.

[0040] With the radial lifting rod 109 and axial lifting rod 108, the entire cryogenic section is suspended inside the vacuum Dewar inner cylinder 106 by the axial lifting rod 108 and radial lifting rod 109. The cooling medium tank 104, the cold shield 105 and the vacuum Dewar inner cylinder 106 have no contact except for the connection of the lifting rods, which further reduces heat leakage.

[0041] In the embodiments of this application, a refrigerator 101 is disposed on the outer surface of the vacuum Dewar inner cylinder 106, and the cold head of the refrigerator 101 contacts the superconducting coil 102 and the cold screen 105. Further, the cold head includes a primary cold head and a secondary cold head. The secondary cold head contacts the superconducting coil 102 through a condenser, and the primary cold head contacts the cold screen 105. Specifically, the side of the cold screen 105 has a protruding structure 105-A, and the primary cold head contacts this protruding structure 105-A.

[0042] A support base 110 is provided on the bottom side of the vacuum Dewar inner cylinder 106 to provide stable support for the entire superconducting magnet.

[0043] The power supply, abnormal energy dissipation, and quench energy dissipation circuit states of the superconducting magnet are as follows: Figure 4-5 As shown in Figures 8-11, the quench failure and energy dissipation circuit states of superconducting magnets in the prior art are as follows: Figure 6-7 As shown. In this application, the two ends of the superconducting coil 102 are connected to the current lead 107, and finally connected to the superconducting power supply 111. A power supply circuit breaker 112 is provided on the connected circuit to realize power-on and power-off in different states. In the embodiment of this application, a protection diode 114 is also connected in parallel to the two ends of the superconducting coil 102. The multiple superconducting coils 102 are COIL 1-6, and the six superconducting coils 102 are divided into three groups and connected in sequence. The two ends of the two superconducting coils 102 in each group are connected in parallel with a protection diode 114. The protection diode 114 needs to be composed of two reverse diodes connected in parallel to discharge the excessive voltage generated when the superconducting coil 102 loses its overvoltage.

[0044] When an abnormal situation occurs during the power-on process or operation of the magnet system, if there is an abnormality in the power supply or other system components, rather than a true quench failure of the magnet, it is necessary to quickly remove the electromagnetic energy stored in the magnet to a normal temperature environment. Since the magnet has not quenched, the internal protection diode 114 is not conducting. At this time, by closing the abnormal energy discharge circuit breaker 116 and opening the power supply circuit breaker 112, the current will form a energy discharge circuit through the superconducting coil 102, the abnormal energy discharge diode 115, the abnormal energy discharge circuit breaker 116, and the abnormal energy discharge resistor 117. The current flowing through the abnormal energy discharge resistor 117 will generate Joule heat Q = I^2*R, consuming the energy stored in the magnet, thus achieving energy discharge of the magnet system. It should be noted that the resistance value of the abnormal energy discharge resistor 117 should not be too large to avoid excessively rapid energy consumption causing excessive current decay, resulting in dynamic AC attenuation in the superconducting coil 102, which could lead to a true quench failure of the superconducting coil 102.

[0045] Furthermore, a quench detector 113 is connected in parallel across the two ends of the superconducting coil 102. The quench detector 113 is used to detect the voltage across the superconducting coil 102 and determine whether the superconducting coil 102 has lost quench based on the voltage change. Specifically, the quench detector 113 has three detection terminals, which are connected to the two ends and the midpoint of the superconducting coil 102, respectively. The voltages between two adjacent detection terminals are V1 and V2, respectively. The quench detector 113 constantly monitors the change in the difference between V1 and V2. When the voltage difference exceeds 1V for more than 1 second, it is considered that the superconducting magnet 1 has lost quench.

[0046] When the superconducting magnet 1 is powered on or in operation, and the quench detector 113 detects that the magnet has actually quenched, the quench energy discharge circuit breaker 118 is closed first, and the power supply circuit breaker 112 and the abnormal energy discharge circuit breaker 116 are disconnected. As the quenched portion of the superconducting magnet 1 expands, a resistance voltage and an inductance voltage are formed inside. When the sum of these two voltages is greater than the conduction voltage of the protection diode 114, a portion of the current will be diverted to the protection diode 114. This will result in the quench energy discharge circuit and the protection diode 114 simultaneously generating Joule heat. At this time, both active and passive protection will be activated simultaneously. Active protection will discharge energy through the protection diode 114, while passive protection will discharge energy through the quench energy discharge resistor 119 and the quench energy discharge diode 120. This energy dissipation circuit is mainly used to quickly remove a portion of the electromagnetic energy stored in the superconducting coil 102 to the room temperature environment when the superconducting magnet 1 truly loses its quench. This prevents all the stored energy from being released into the cryogenic part as heat, which would cause excessive temperature rise and ultimately lead to excessive cooling time and economic costs. Furthermore, this application employs a combination of active and passive protection methods. This avoids the risk of excessive temperature rise due to passive protection alone, and the risk of inaccurate or untimely detection by the quench detector 113 due to active protection alone, which could lead to high voltage buildup inside the superconducting coil 102 and cause coil breakdown.

[0047] like Figure 12 As shown, the active protection scheme can greatly reduce the maximum temperature of the superconducting coil 102. Therefore, while protecting the superconducting coil 102, it also reduces the time and economic cost of recooling, which has good engineering significance.

[0048] Embodiments of this application also provide a testing apparatus for plasma confinement, such as... Figure 13-14 As shown, it includes an ion source 2, a test sample 3, and a superconducting magnet 1 for plasma confinement as described above. The ion source 2 is positioned directly opposite the test sample 3, and the ion source 2 and the test sample 3 are arranged inside the superconducting magnet 1 along the axial direction of the superconducting magnet 1.

[0049] For example, after the superconducting magnet 1, ion source 2, and test sample 3 are installed, a vacuum unit is first used to evacuate the space between the cold screen 105 and the vacuum dewar inner cylinder 106. When the vacuum level reaches 10... -2 When the temperature is in the Pa range, the refrigerator 101 is turned on to cool the superconducting magnet 1, and a temperature sensor is used to monitor the temperature at important temperature detection points. When the temperature of the superconducting coil 102 inside the superconducting magnet 1 is lower than the critical temperature Tc of the superconducting wire, the superconducting coil 102 enters the superconducting state and has the ability to be energized.

[0050] Meanwhile, the cavity inside the superconducting magnet 1 containing the ion source 2 and the test sample 3 is evacuated. After other conditions are ready, if gas is introduced into the ion source in the absence of a magnetic field, the plasma will quickly disperse due to the lack of confinement and will not be able to effectively reach the test sample 3. Therefore, the required plasma flux density cannot be achieved.

[0051] During normal use, firstly, based on the theoretically calculated magnetic field strength requirements for plasma confinement, the power supply circuit breaker 112 is closed, simultaneously energizing the superconducting power supply 111 to the superconducting coils COIL 1-6. Once the current in the superconducting coil 102 reaches the set value, plasma is generated using an ion source. Relevant parameters at the sample location are measured using specialized sensors. If magnetic field strength adjustment is needed, the entire superconducting power supply 111 can be adjusted to meet the plasma confinement requirements until the desired confinement conditions for different working fluids are achieved. Finally, the performance of the relevant materials under plasma confinement is tested.

[0052] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0053] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A superconducting magnet for plasma confinement, characterized in that, include: A superconducting coil (102); a cooling medium tank (104) filled with a cooling medium, wherein the superconducting coil (102) is disposed inside the cooling medium tank (104); A cold screen (105) is provided inside the cooling medium tank (104); A quench detector (113) is connected in parallel across the two ends of the superconducting coil (102) to detect whether the superconducting coil (102) has lost quench and to generate a quench trigger signal; The two ends of the superconducting coil (102) are electrically connected to the superconducting power supply (111) through current leads (107), and the superconducting power supply (111) is located outside the cold screen (105). The cold screen (105) also has an abnormal energy discharge circuit and a quench energy discharge circuit outside, which are connected in parallel with the superconducting power supply (111). The abnormal energy discharge circuit includes an abnormal energy discharge resistor (117), an abnormal energy discharge diode (115), and an abnormal energy discharge circuit breaker (116) connected in series. The quench energy discharge circuit includes an abnormal energy discharge resistor (117), an abnormal energy discharge diode (115), and an abnormal energy discharge circuit breaker (116) connected in series. The superconducting magnet (1) includes a quench energy dissipation resistor (119), a quench energy dissipation diode (120), and a quench energy dissipation circuit breaker (118). The quench energy dissipation circuit breaker (118) is configured to close in response to the quench trigger signal. The abnormal energy dissipation circuit breaker (116) is configured to close in response to an abnormal signal from an external system. When the superconducting magnet (1) is energized or in operation, and the quench depth detector (113) detects that the magnet has actually quenched, the quench energy dissipation circuit breaker (118) is closed first, and the power supply circuit breaker (112) and the abnormal energy dissipation circuit breaker (116) are disconnected.

2. A superconducting magnet for plasma confinement according to claim 1, characterized in that, A quench detector (113) is connected in parallel across the two ends of the superconducting coil (102). The quench detector (113) is used to detect the voltage across the two ends of the superconducting coil (102) and determine whether the superconducting coil (102) has lost quench based on the voltage change.

3. A superconducting magnet for plasma confinement according to claim 1, characterized in that, A protection diode (114) is also connected in parallel at both ends of the superconducting coil (102).

4. A superconducting magnet for plasma confinement according to claim 1, characterized in that, The cooling medium tank (104) is provided with a frame (103) inside, and the superconducting coil (102) is disposed on the frame (103).

5. A superconducting magnet for plasma confinement according to claim 4, characterized in that, The cold screen (105) is provided with a vacuum Dewar inner cylinder (106) outside, and the space between the cold screen (105) and the vacuum Dewar inner cylinder (106) is in a vacuum state.

6. A superconducting magnet for plasma confinement according to claim 5, characterized in that, Also includes: A radial lifting rod (109) is provided on the outside of the frame (103). The radial lifting rod (109) passes through the cooling medium tank (104), the cold screen (105) and the vacuum Dewar inner cylinder (106), and extends out of the vacuum Dewar inner cylinder (106). An axial lifting rod (108) is parallel to the axis of the frame (103). The axial lifting rod (108) passes through the cooling medium tank (104), the cold screen (105) and the vacuum Dewar inner cylinder (106), and extends outside the vacuum Dewar inner cylinder (106).

7. A superconducting magnet for plasma confinement according to claim 5, characterized in that, A refrigerator (101) is provided on the outer surface of the vacuum Dewar inner cylinder (106), and the cold head of the refrigerator (101) is in contact with the superconducting coil (102) and the cold screen (105).

8. A superconducting magnet for plasma confinement according to claim 7, characterized in that, The cold head of the refrigerator (101) includes a primary cold head and a secondary cold head. The secondary cold head is in contact with the superconducting coil (102) through a condenser, and the primary cold head is in contact with the cold screen (105).

9. A superconducting magnet for plasma confinement according to claim 5, characterized in that, A support base (110) is provided on the bottom side of the vacuum Dewar inner cylinder (106).

10. A testing apparatus for plasma confinement, characterized in that, The device includes an ion source (2), a test sample (3), and a superconducting magnet (1) for plasma confinement as described in any one of claims 1-9. The ion source (2) is positioned opposite the test sample (3), and the ion source (2) and the test sample (3) are positioned inside the superconducting magnet (1) along the axial direction of the superconducting magnet (1).

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