Superconducting magnet quenching protection method and device

Abstract

The invention belongs to the field of superconducting magnets, and particularly discloses a superconducting magnet quenching protection method and device, and the method comprises the steps: applying an alternating magnetic field with a preset amplitude and a preset frequency to a superconducting magnet when the superconducting magnet is quenched, enabling the energy loss of the superconducting magnet to be increased, enabling the critical current to be reduced, and / or enabling the temperature to be increased, the overall quench propagation of the superconducting magnet is accelerated, and quench protection of the superconducting magnet is achieved; and the component of the alternating magnetic field acting in the radial direction of the superconducting magnet is relatively large. According to the invention, the method can achieve the propagation of a normal conduction region after quenching with high efficiency in the quenching protection of the superconducting magnet, and is higher in reliability of quenching protection.

Description

Technical Field

[0001] This application belongs to the field of superconducting magnets. More specifically, it relates to a superconducting magnet quench protection method and device. Background Art

[0002] Due to its excellent current-carrying capacity, superconducting materials have become the preferred current-carrying materials in many high-current and high-magnetic-field application scenarios, and are widely used in fields such as superconducting motors, superconducting cables, steady-state high-field magnets, superconducting maglev technology, particle accelerators, and superconducting magnetic energy storage systems. The process in which superconducting materials change from the superconducting state to the normal state due to certain reasons (such as external magnetic field interference, temperature change, mechanical perturbation, etc.) is called quenching, and this process is accompanied by the sudden appearance of resistance and the sudden release of energy. Superconducting magnets face severe quenching problems during operation. Once quenched, a large amount of energy will be released in the quenched area of the superconducting magnet, causing a significant temperature rise. Seriously, it will lead to the burning of the superconducting magnet and related equipment, seriously threatening the safe operation of the superconducting magnet and equipment. Therefore, when superconducting materials and devices made thereof are in operation, reliable quench protection methods and means are required.

[0003] Existing quench protection methods can be divided into passive quench protection and active quench protection according to the way of triggering the protection action. The principle of passive quench protection is to automatically connect an energy-releasing resistor device or array to the superconducting magnet circuit based on the change in voltage in the magnet circuit after quenching through a specific circuit using unidirectional self-opening devices such as diodes to release the energy in the magnet and achieve the purpose of quench protection. The main disadvantage of passive quench protection is its slow reaction. Its application range is mainly small superconducting magnets with low cost, small scale, and weak safety margin requirements, and it has fundamental limitations for the application on large superconducting magnets and related devices.

[0004] Active quench protection relies on a pre-set quench detection system to trigger the protection device after detecting a quench. A common active quench protection method is the heater method. Its principle is to trigger the heater to work after the quench detection device detects a quench, and heat the superconducting magnet as a whole so that its temperature is higher than the superconducting critical temperature, accelerating the quench propagation to achieve the transformation from the superconducting state to the normal conducting state, and making the energy in the magnet dissipate uniformly in the whole magnet in the form of heat, avoiding local overheating caused by the aggregation of hot spot energy after quenching. The disadvantage of the heater method is that since the rate of heat conduction depends on the thermal conductivity of the medium and the heat conduction distance, on the one hand, the radial thermal conductivity of magnets wound with some types of superconducting wires is poor, especially for magnets with inter-turn insulation using poor heat-conducting materials; on the other hand, for large magnets with a large overall volume and a long winding length, the long heat transfer distance reduces the speed of heat conduction, limiting the reliability of the quench protection by the heating method. Summary of the Invention

[0005] Aiming at the defects of the prior art, the purpose of the present application is to provide a superconducting magnet quench protection method and device, aiming to solve the problem of limited reliability of the existing superconducting magnet quench protection device.

[0006] To achieve the above object, in a first aspect, the present application provides a superconducting magnet quench protection method, including: When the superconducting magnet quenches, an alternating magnetic field with a preset amplitude and a preset frequency is applied to the superconducting magnet, so that the energy loss of the superconducting magnet increases, the critical current decreases and / or the temperature rises, accelerating the overall quench propagation of the superconducting magnet and realizing the quench protection of the superconducting magnet; the component of the alternating magnetic field acting in the radial direction of the superconducting magnet is relatively large.

[0007] It should be noted that the superconducting magnet generates dynamic resistance loss under the action of the alternating magnetic field, which will increase its energy loss. Moreover, the above alternating magnetic field can reduce the critical current of the superconducting magnet, and the alternating loss and dynamic resistance loss generated by the superconducting magnet under the alternating magnetic field will generate heat, thereby causing the temperature of the superconducting magnet to rise; the relatively large component in the radial direction means that the component or the average value of the component acting in the radial direction is greater than the component or the average value of the component acting in the direction perpendicular to the radial direction. The above preset amplitude and preset frequency are based on being able to achieve the expected quench protection effect, and those skilled in the art can design according to needs, and the present application does not make any limitations on this.

[0008] It can be understood that by applying an alternating magnetic field with a relatively large component in the radial direction to the superconducting magnet, the overall quench propagation of the superconducting magnet can be effectively accelerated, and the reliability of the quench protection is improved.

[0009] In some embodiments, the amplitude and / or frequency of the alternating magnetic field are adjustable; and / or the greater the amplitude and frequency, the faster the overall quench propagation of the superconducting magnet.

[0010] In some embodiments, the alternating magnetic field is generated by an energized coil, and the energized current directions of adjacent turns of the coil in the energized coil are opposite along the axial direction of the superconducting magnet; and / or the energized coil is coaxially arranged with the superconducting magnet and / or coaxially wound together with the superconducting magnet.

[0011] In some embodiments, the alternating magnetic field is one magnetic field or a superposition of multiple magnetic fields among a triangular wave, a square wave, a trapezoidal wave, a sine wave, and a sine oscillation decay wave magnetic field with symmetric or asymmetric positive and negative half-waves.

[0012] In a second aspect, the present application provides a superconducting magnet quench protection device, including: an alternating magnetic field generating coil; The alternating magnetic field generating coil includes: a multi-turn coil, which is coaxially arranged with the superconducting magnet and / or coaxially wound together with the superconducting magnet. When a current is passed through the multi-turn coil, the current directions of any two adjacent turns of the coil in the axial direction of the superconducting magnet are opposite; When the superconducting magnet needs to be protected against quench, the alternating magnetic field generating coil is passed through an alternating current to generate an alternating magnetic field acting on the superconducting magnet. The alternating magnetic field and the heat generated after the alternating magnetic field generating coil is energized act together on the superconducting magnet to accelerate the overall quench propagation of the superconducting magnet and achieve quench protection for the superconducting magnet.

[0013] It should be noted that the above-mentioned need to protect the superconducting magnet against quench means that the quench of the superconducting magnet is detected. At this time, the alternating magnetic field generating coil is triggered to generate an alternating magnetic field to apply an alternating magnetic field with a certain amplitude and a certain rate of change to the superconducting magnet, so that the alternating magnetic field and the heat generated after the alternating magnetic field generating coil is energized act together on the superconducting magnet, promoting the quench of the non-quenched part of the superconducting magnet, making the normal conducting area spread rapidly after quench, and enabling the internal energy of the superconducting magnet to be evenly consumed in the whole magnet, avoiding the damage of the magnet caused by the release of energy in a local area.

[0014] Through the structural design of the alternating magnetic field generating coil and the corresponding current-carrying method and strategy design in this application, when quench protection is required, the above-mentioned alternating magnetic field generating coil can generate an alternating magnetic field with a larger component in the radial direction of the superconducting magnet, realize the propagation of the normal conducting area after quench with higher efficiency, and have higher reliability of quench protection; and the above-mentioned device has a simple structure, a small volume, a short heat transfer distance, and a simple control method, increasing the reliability of the overall device.

[0015] In some embodiments, the multi-turn coil is coaxially arranged with the superconducting magnet, including: The multi-turn coil is wound by a wire along the axial direction of the superconducting magnet, and the winding directions of adjacent turns of the coil in the axial direction of the superconducting magnet are opposite, so that when a current is passed through the multi-turn coil, the current directions of adjacent turns of the coil along the axial direction of the superconducting magnet are opposite.

[0016] It should be noted that the above-mentioned wire can be a single wire or multiple wires. When it is a single wire, it is directly wound axially in the above manner. When it is multiple wires, each wire can be wound and then layer-wound around its periphery along the radial direction of the superconducting magnet.

[0017] In some embodiments, the multi-turn coil is coaxially arranged with the superconducting magnet, including: The multi-turn coil is wound by a composite wire wound in the axial direction of the superconducting magnet; the composite wire includes a plurality of first-type wires arranged side by side in the axial direction of the superconducting magnet and / or at least one second-type wire that is folded in half and arranged side by side in the axial direction of the superconducting magnet; when a current is passed through the multi-turn coil, a current is passed through each first-type wire and / or second-type wire, and the directions of the currents passed through any two adjacent first-type wires in the axial direction of the superconducting magnet are opposite, and / or the directions of the currents passed through all the second-type wires are the same.

[0018] Among them, the above-mentioned first-type wires are preferably even in number to ensure that when the directions of the currents passed through any two adjacent wires are opposite, the directions of the currents in any two adjacent turns of the coil in the axial direction of the superconducting magnet are opposite.

[0019] Specifically, it can be understood that when the above-mentioned alternating magnetic field generating coil is coaxially arranged with the superconducting magnet, it can be wound around the outside of the superconducting magnet or around the inner axial gap region of the superconducting magnet. And it can be in close contact with the superconducting magnet, or the gap with the superconducting magnet is relatively narrow, such as the distance of the gap can be less than a preset value, so that the heat conduction distance between the alternating magnetic field generating coil and the superconducting magnet is small enough, and the energy utilization efficiency of the alternating magnetic field is ensured.

[0020] In some embodiments, the superconducting magnet includes a single-pancake superconducting coil or a multi-pancake superconducting coil; the multi-pancake superconducting coil includes a plurality of single-pancake superconducting coils stacked in the axial direction of the superconducting magnet, and the single-pancake superconducting coil is wound by a superconducting tape through a layer winding method; The multi-turn coil is coaxially wound with the superconducting magnet, including: The multi-turn coil is wound by at least two tapes; the winding is in close contact and co-wound with the superconducting tape inside each single-pancake superconducting coil; When the superconducting magnet includes a single-pancake superconducting coil, the superconducting tape corresponding to the single-pancake superconducting coil is in close contact with at least two tapes, and the at least two tapes are arranged in the axial direction of the superconducting magnet; When the superconducting magnet includes a multi-pancake superconducting coil, the superconducting tape corresponding to each single-pancake superconducting coil inside it is in close contact with at least one tape, and the at least one tape is arranged in the axial direction of the superconducting magnet; When a current is passed through the multi-turn coil, a current is passed through each tape, and the directions of the currents passed through any two adjacent tapes in the axial direction of the superconducting magnet are opposite.

[0021] In some embodiments, the waveforms of the currents passed through two adjacent turns of the coil and two adjacent strips in the axial direction of the superconducting magnet are the same or different, and the amplitudes are the same or different. Among them, the above waveforms and amplitudes can be the same or different, as long as the current directions are opposite, so as to achieve the expected quench protection effect. Those skilled in the art can design the waveforms and amplitudes of the currents in opposite directions according to actual needs.

[0022] In some embodiments, the material of the multi-turn coil or at least two strips is a normal conducting material or a superconducting material.

[0023] In some embodiments, the alternating current is one current or a superposition of multiple currents among triangular waves, square waves, trapezoidal waves, sine waves, and sinusoidal oscillatory decay waves with symmetric or asymmetric positive and negative half-waves.

[0024] Generally speaking, compared with the prior art, the above technical solutions conceived by this application have the following beneficial effects: This application provides a method and device for superconducting magnet quench protection. By applying an alternating magnetic field with a large magnetic field component in the radial direction of the superconducting magnet to the superconducting magnet, the overall quench propagation of the superconducting magnet can be effectively accelerated, and the reliability of quench protection is improved. And if the above alternating magnetic field is generated by an energized coil, only by controlling the directions of the energizing currents of adjacent turns of the coil along the axial direction of the superconducting magnet to be opposite, the above alternating magnetic field with a large radial component can be generated to achieve quench protection for the superconducting magnet. It can be seen that the structure is simple and the control is simple; when the energized coil is coaxially arranged outside the superconducting magnet and / or co-wound coaxially with the superconducting magnet, the heat transfer distance is relatively short, and the reliability of the above solution is relatively high, with great application prospects.

[0025] This application provides a method and device for superconducting magnet quench protection. When a quench of the superconducting magnet is detected, an alternating magnetic field generating coil is triggered to generate an alternating magnetic field to apply the alternating magnetic field to the superconducting magnet, so that the alternating magnetic field and the heat generated after the alternating magnetic field generating coil is energized act on the superconducting magnet together, promoting the quench of the unquenched part of the superconducting magnet, making the normal conducting area spread rapidly after quench, and evenly consuming the internal energy of the superconducting magnet throughout the magnet, avoiding the damage of the magnet caused by the release of energy in a local area. Through the structural design of the alternating magnetic field generating coil and the corresponding design of the applied current in this application, when quench protection is required, the above alternating magnetic field generating coil can generate an alternating magnetic field with a large component in the radial direction of the superconducting magnet, and the heat transfer distance is relatively short, so as to realize the spread of the normal conducting area after quench with higher efficiency and have a high reliability of quench protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flowchart of the superconducting magnet quench protection method provided by the embodiment of this application; Figure 2 Schematic diagram of the quench protection device based on an externally applied alternating magnetic field provided by an embodiment of the present application; Figure 3 Structural unfolded diagram of the alternating magnetic field generating coil in the quench protection device based on an externally applied alternating magnetic field provided by an embodiment of the present application; Figure 4(a) is another structural schematic diagram of the alternating magnetic field generating coil provided by an embodiment of the present application; Figure 4(b) is yet another structural schematic diagram of the alternating magnetic field generating coil provided by an embodiment of the present application; Figure 5 Principle schematic diagram of the externally applied alternating magnetic field quench protection device based on the co-winding of a normal conducting metal strip and a superconducting strip provided by an embodiment of the present application; Figure 6 Magnet winding method and cross-section unfolded diagram of the externally applied alternating magnetic field quench protection device based on the co-winding of a normal conducting metal strip and a superconducting strip provided by an embodiment of the present application; Figure 7 Schematic diagram of using the alternating magnetic field generating coil to generate a symmetric sine wave magnetic field for quench protection provided by an embodiment of the present application; Figure 8 Schematic diagram of using the alternating magnetic field generating coil to generate a sine oscillation decaying waveform magnetic field for quench protection provided by an embodiment of the present application; Figure 9 Schematic diagram of using the co-wound metal strip to generate an asymmetric triangular wave magnetic field to quench protect the co-wound magnet based on the co-winding structure of a normal conducting metal strip and a superconducting strip provided by an embodiment of the present application; Figure 10 Schematic diagram of using the co-wound metal strip to generate a symmetric rectangular wave magnetic field to quench protect the co-wound magnet based on the co-winding structure of a normal conducting metal strip and a superconducting strip provided by an embodiment of the present application; In all the drawings, the same reference numerals are used to represent the same elements or structures, where: 1 represents a superconducting magnet, 2 represents an alternating magnetic field generating coil, and 3 represents a quench detection and alternating magnetic field coil trigger controller. Detailed implementation manners

[0027] In order to make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0028] The embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application.

[0029] An embodiment of the present application proposes a new scheme for quench protection of a superconducting magnet. Its main advantage is that it can achieve the propagation of the normal-conducting region after a quench with high efficiency and has high reliability of quench protection. Based on the quench protection method provided by the present application, a corresponding possible quench protection device can be given. The quench protection device proposed in the present application triggers an alternating magnetic field generating coil after the quench detection system detects a quench, and applies an alternating magnetic field with a certain amplitude and a certain rate of change to the superconducting magnet, promoting the quench of the non-quenched part of the superconducting magnet, making the normal-conducting region after the quench spread rapidly, and enabling the internal energy of the superconducting magnet to be evenly consumed throughout the magnet, avoiding damage to the magnet caused by energy release in a local area. The detailed principle explanation is shown in the description of the following embodiments.

[0030] Figure 1 It is a flowchart of the quench protection method for a superconducting magnet provided by an embodiment of the present application; as Figure 1 shown, it includes the following steps: Step S101, when the superconducting magnet quenches, apply an alternating magnetic field with a preset amplitude and a preset frequency to the superconducting magnet, so that the energy loss of the superconducting magnet increases, the critical current decreases, and / or the temperature rises, accelerating the overall quench propagation of the superconducting magnet; the component of the alternating magnetic field acting in the radial direction of the superconducting magnet is relatively large.

[0031] Optionally, the amplitude and / or frequency of the above alternating magnetic field can be adjusted; and / or the larger the amplitude and frequency, the faster the overall quench propagation of the superconducting magnet.

[0032] Exemplarily, the above alternating magnetic field is generated by an energized coil, and the energized current directions of adjacent turns of the coil in the axial direction of the superconducting magnet are opposite; and / or the energized coil is coaxially arranged with the superconducting magnet and / or co-wound coaxially with the superconducting magnet.

[0033] Exemplarily, the above alternating magnetic field is one magnetic field or a superposition of multiple magnetic fields among triangular waves, square waves, trapezoidal waves, sine waves, and sine oscillating decay waves that are symmetric or asymmetric in positive and negative half-waves; it can be understood that if the above alternating magnetic field is generated by an energized coil, the waveform of the alternating magnetic field is consistent with the waveform of the energized current.

[0034] It can be understood that the core of the quench protection method for realizing quench protection of a superconducting magnet is to promote the rapid diffusion of the quenched region within the entire magnet range to achieve the purpose of uniform energy release. The main principles for the proposed scheme in the present application to quickly promote the diffusion of the quenched region are as follows: (1) Superconducting materials will produce dynamic resistance loss under an alternating magnetic field, which will consume the energy inside the superconducting magnet. The greater the amplitude and frequency of the alternating magnetic field, the greater the AC loss and dynamic resistance loss, and the faster the energy consumption of the superconducting magnet. The AC loss can be increased by increasing the frequency of the applied alternating magnetic field, making the energy loss inside the superconducting magnet faster.

[0035] (2) The current carrying capacity of superconducting materials is related to the magnitude of the external magnetic field. The greater the amplitude and frequency of the external magnetic field, the lower the critical current density of the superconducting material. When the operating current of the superconducting magnet is less than the critical current, the closer the operating current is to the critical current, the greater the loss of the superconducting magnet. When the operating current of the superconducting magnet is greater than the critical current, the superconducting magnet enters a non-superconducting state. By increasing the amplitude of the external alternating magnetic field, the critical current density of the superconducting material can be reduced, the critical current can be reduced, the loss of the superconducting magnet can be increased, and the superconducting magnet can be uniformly quenched as a whole. The greater the degree of critical current reduction, the faster the corresponding quench propagation.

[0036] (3) The AC loss and dynamic resistance loss generated by the superconducting magnet under the AC magnetic field will generate heat, which will cause the temperature of the superconducting magnet to rise. At the same time, the alternating magnetic field can induction heat the normal conductive metal part in the superconducting magnet (where the normal conductive metal here refers to the normal conductive metal in the substrate layer of the superconducting magnet), which will also cause the temperature of the superconducting magnet to rise. In addition, the heat generated after the alternating magnetic field generating coil is passed through the current will also cause the temperature of the superconducting magnet to rise. The higher the temperature of the superconducting magnet, the lower the critical current of the superconducting material. When the operating current of the superconducting magnet is less than the critical current, the closer the operating current is to the critical current, the greater the loss of the superconducting magnet. When the operating current of the superconducting magnet is greater than the critical current, the superconducting magnet enters a non-superconducting state. When the temperature is higher than the critical temperature, the superconducting magnet enters a non-superconducting state.

[0037] It should be noted that the heat generated by the above-mentioned alternating magnetic field generating coil can be divided into two situations: if the alternating magnetic field generating coil is made of a normal conductive material, the heat comes from the Joule heat generated after current passes through the coil; if the alternating magnetic field generating coil is made of a superconducting material, the heat comes from the heat generated by the AC loss and dynamic resistance loss of the alternating magnetic field generating coil.

[0038] Figure 2 A schematic diagram of the quench protection device is given. Among them, 1 represents the superconducting magnet of the device for quench protection, 2 represents the alternating magnetic field generating coil, and 3 represents the quench detection and AC magnetic field coil trigger controller. When the quench detection and AC magnetic field coil trigger controller 3 detects a quench signal, it controls the alternating magnetic field generating coil 2 to trigger the alternating magnetic field. B app ( t)Act on the superconducting magnet, and perform quench protection on the superconducting magnet according to the principles described in (1), (2), and (3) in the above principle introduction. Among them, the applied alternating magnetic field B app ( t ) can be a triangular wave, square wave, trapezoidal wave, and sine wave with symmetric or asymmetric positive and negative half-waves, can be a superposition of the above waveforms, or can be a sinusoidal oscillation decay waveform generated by discharging a capacitor to the alternating magnetic field generating coil; it can be understood that when the alternating magnetic field generating coil is energized with a corresponding current, an alternating magnetic field will be generated, and the waveform of this alternating magnetic field is determined by the waveform of the applied alternating current and is consistent with the alternating current waveform. The embodiments of the present application do not limit the wire material of the alternating magnetic field generating coil 2. For the superconducting magnet 1, in terms of the working mode, it can be a closed-loop operating magnet or an open-loop operating magnet; in terms of the type of magnet wire material, it can be a high-temperature superconducting magnet, a low-temperature superconducting magnet, or a hybrid magnet.

[0039] In a possible implementation manner, the present application provides a superconducting magnet quench protection device, which includes an alternating magnetic field generating coil. The above-mentioned alternating magnetic field generating coil includes: a multi-turn coil, the multi-turn coil is coaxially arranged with the superconducting magnet and / or coaxially wound with the superconducting magnet. When the multi-turn coil is energized, the current directions of any two adjacent turns of the coil in the axial direction of the superconducting magnet are opposite; when quench protection needs to be performed on the superconducting magnet, the alternating magnetic field generating coil is energized with an alternating current to generate an alternating magnetic field acting on the superconducting magnet, and the alternating magnetic field and the heat generated after the alternating magnetic field generating coil is energized act on the superconducting magnet together to accelerate the overall quench propagation of the superconducting magnet and achieve quench protection for the superconducting magnet.

[0040] It should be noted that the above multi-turn coil can be only coaxially arranged outside or inside the superconducting magnet, only coaxially wound with the superconducting magnet, or configured in multiple situations such as outside, inside the superconducting magnet, and coaxially wound with the superconducting magnet at the same time, subject to achieving the expected quench protection effect.

[0041] In some embodiments, the multi-turn coil is coaxially arranged with the superconducting magnet, including: The multi-turn coil is wound by a wire along the axial direction of the superconducting magnet, and the winding directions of adjacent turns of the coil in the axial direction of the superconducting magnet are opposite, so that when the multi-turn coil is energized, the current directions of adjacent turns of the coil along the axial direction of the superconducting magnet are opposite.

[0042] In some embodiments, the multi-turn coil is coaxially arranged with the superconducting magnet, including: The multi-turn coil is obtained by winding a composite wire wound in the axial direction of the superconducting magnet; the composite wire includes a plurality of first-type wires arranged side by side in the axial direction of the superconducting magnet and / or at least one second-type wire folded in half and arranged side by side in the axial direction of the superconducting magnet; when a current is passed through the multi-turn coil, a current is passed through each first-type wire and / or second-type wire, and the directions of the currents passed through any two adjacent first-type wires in the axial direction of the superconducting magnet are opposite, and / or the directions of the currents passed through all the second-type wires are the same.

[0043] Optionally, when the above-mentioned alternating magnetic field generating coil is coaxially arranged with the superconducting magnet, it can be wound around the outside of the superconducting magnet or in the inner axial gap area of the superconducting magnet ( Figure 2 Taking the example of being tightly wound around the outside of the superconducting magnet for illustration). And it can be in close contact with the superconducting magnet, or the gap with the superconducting magnet is relatively narrow, such as the distance of the gap can be less than a preset value, so that the heat conduction distance between the alternating magnetic field generating coil and the superconducting magnet is small enough, and the energy utilization efficiency of the alternating magnetic field is ensured.

[0044] In some scenarios, the above-mentioned superconducting magnet includes a single-pancake superconducting coil or a multi-pancake superconducting coil; the multi-pancake superconducting coil includes a plurality of single-pancake superconducting coils stacked in the axial direction of the superconducting magnet, and the single-pancake superconducting coil is obtained by winding a superconducting strip in a layer winding manner.

[0045] In one embodiment, the multi-turn coil and the superconducting magnet are coaxially wound together, including: The multi-turn coil is obtained by winding at least two strips; the winding is in close contact and co-wound with the superconducting strip in each single-pancake superconducting coil; When the superconducting magnet includes a single-pancake superconducting coil, the superconducting strip corresponding to the single-pancake superconducting coil is in close contact with at least two strips, and the at least two strips are arranged in the axial direction of the superconducting magnet; When the superconducting magnet includes a multi-pancake superconducting coil, the superconducting strip corresponding to each single-pancake superconducting coil therein is in close contact with at least one strip, and the at least one strip is arranged in the axial direction of the superconducting magnet; When a current is passed through the multi-turn coil, currents are passed through each strip, and the directions of the currents passed through any two adjacent strips in the axial direction of the superconducting magnet are opposite.

[0046] It should be noted that the directions of the currents passed through two adjacent turns of the coil and two adjacent strips in the axial direction of the superconducting magnet are opposite, in order to make the component of the alternating magnetic field generated between the adjacent turns of the coil and between the coils corresponding to the two adjacent strips in the radial direction of the superconducting magnet large enough. Referring to Ampere's first rule for a straight current-carrying wire: Hold the straight current-carrying wire with the right hand and let the thumb point to the direction of the current in the straight wire, then the direction indicated by the four fingers is the direction of the magnetic field around the current-carrying wire. It can be seen that when the current directions of two adjacent turns of the coil or two adjacent strips are opposite, the magnetic fields at the gaps therebetween (between the two adjacent turns of the coil or the two adjacent strips) cannot cancel each other out and are effectively superimposed; and according to Ampere's first rule, it can be known that the component of the magnetic field of the coil or strip at the above-mentioned gap in the radial direction of the superconducting magnet is relatively large (greater than the component or the average value of the component perpendicular to the radial direction). Therefore, the above device and design make the component of the alternating magnetic field at the gap in the radial direction of the superconducting magnet relatively large.

[0047] Those skilled in the art can understand that for a superconducting magnet, the greater the component of the externally applied magnetic field in its radial direction, the greater the degree of decrease in the critical current and the faster the corresponding quench propagation; among them, it is not difficult to understand that the greater the amplitude and / or the frequency of the alternating magnetic field, the faster the above-mentioned quench propagation. Because in the embodiment of the present application, through the above unique design of the alternating magnetic field generating coil and the corresponding current passed through, the above-mentioned alternating magnetic field can achieve the propagation of the normal conducting region after quench with high efficiency and has high reliability of quench protection.

[0048] Furthermore, in some embodiments, it is possible to control the waveforms of the currents passed through two adjacent turns of the coil or two adjacent strips in the axial direction of the superconducting magnet to be the same or different, the amplitudes to be the same or different, and the directions to be opposite. For those skilled in the art, the directions of the two currents passed through adjacent in the axial direction must be opposite, and the waveforms and amplitudes can be the same, or not completely the same or different, as long as the corresponding effect of accelerating the quench propagation of the superconducting magnet can be produced, and flexible design can be carried out according to needs. The embodiments of the present application do not make any limitations thereto.

[0049] In some embodiments, the material of the multi-turn coil or at least two strips is a normal conducting material or a superconducting material.

[0050] In some embodiments, the alternating current is one current or a superposition of multiple currents among triangular waves, square waves, trapezoidal waves, sine waves, and sine oscillation decay waves with symmetric or asymmetric positive and negative half-waves.

[0051] It can be understood that Figure 2The quench detection and AC magnetic field coil trigger controller 3 are not the focus of the technology of this application, and the specific internal structure is not concerned, so a black box is used to represent its integrated system. The above trigger controller can detect the quench of the superconducting magnet and trigger the alternating magnetic field generating coil, and can be implemented with reference to relevant existing technologies.

[0052] In a specific embodiment, for the alternating magnetic field generating coil 2, it can be made into a shape that fits the periphery of the superconducting magnet, so that the generated alternating magnetic field can be applied to the superconducting magnet relatively uniformly. It should be noted that the material of the alternating magnetic field generating coil here can be normal conducting material or superconducting material, and this application embodiment does not make further limitations, and those skilled in the art can choose according to actual needs to achieve the expected quench protection effect; at the same time, the placement position of the alternating magnetic field generating coil can be made to be close to the periphery of the superconducting magnet, with a short heat transfer distance, as Figure 3 shown in (a) below. It makes thermal contact on the periphery of the superconducting magnet. In this way, on the basis of applying an alternating magnetic field to promote the overall quench of the superconducting magnet, the heat generation of the alternating magnetic field generating coil can further accelerate the overall quench propagation of the superconducting magnet.

[0053] Figure 3 shows Figure 2 the structural schematic diagram of the alternating magnetic field generating coil in the figure below. Figure 3 (a) in the figure is the schematic diagram after the alternating magnetic field generating coil is wound, Figure 3 (b) in the figure is the side expansion view of the alternating magnetic field generating coil, where the arrow indicates the current direction. After the alternating magnetic field generating coil is triggered, the upper and lower adjacent turns of the coil pass through currents in opposite directions, and an alternating magnetic field with a large vertical component (perpendicular to the circumferential surface of the superconducting magnet, parallel to the radial direction of the superconducting magnet, also called the component parallel to the radial direction) can be generated between the upper and lower turns of the coil, which uniformly acts on the entire superconducting magnet and accelerates the overall quench propagation of the superconducting magnet.

[0054] Figure 4(a) shows another structural schematic diagram of the alternating magnetic field generating coil. Referring to Figure 4(a), taking the example of winding the above alternating magnetic field generating coil with two wires, the above two wires are closely wound around the periphery of the superconducting magnet (that is, the superconducting magnet is closely arranged inside the solenoid coil wound by the two wires in Figure 4(a), which is omitted in Figure 4(a) and can be referred to Figure 2 shown in the figure below). One wire is drawn in blue and the other wire is drawn in red; if different directions of current are passed through the blue wire and the red wire, at this time a magnetic field perpendicular to the surface of the superconducting magnet can be generated in the region between each red and blue wire, and its principle is the same as Figure 3 that, which will not be elaborated here.

[0055] Similarly, Figure 4(b) takes a folded wire as an example, which is wound around the periphery of the superconducting magnet after being folded. When current is passed through the wire, the current directions of the red part of the folded wire and the blue part of the wire are opposite.

[0056] Understandably, Figure 3 The schemes given in Figures 4(a) and 4(b) can be applied to superconducting magnets such as superconducting cable magnets, superconducting wire magnets, superconducting bulk magnets, and superconducting tape magnets.

[0057] Furthermore, for a superconducting magnet based on a superconducting tape, a superconducting tape is usually wound in layers along a radial direction to form a single-pancake superconducting coil, and a superconducting magnet based on a superconducting tape may include a single-pancake superconducting coil or a multi-pancake superconducting coil.

[0058] In a specific embodiment, for multi-pancake superconducting coils, the present application proposes another quench protection structure and a corresponding magnet winding method, that is, using a normal conductive metal tape or a superconducting tape to be wound together with a superconducting tape, and the wound magnet structure is a staggered distribution of adjacent turns of normal conductive metal tape or superconducting tape and superconducting tape. After the winding is completed, the part of the winding wound by the above-mentioned superconducting tape serves as a superconducting magnet, and the working current of the magnet is passed through it under normal working conditions; the part of the winding wound by the above-mentioned normal conductive metal tape or superconducting tape is an alternating magnetic field generating coil, and no current is passed through it under normal working conditions. When the quench protection is activated, the alternating magnetic field generating coils adjacent to the upper and lower pancakes are passed with current in opposite directions, and their magnetic field distribution is related to the current flow direction as shown in the figure. Figure 5 As shown, Figure 5 (a) is a schematic diagram of an external alternating magnetic field quench device in which an alternating magnetic field generating coil is wound together with a superconducting magnet. Figure 5 (b) is the alternating magnetic field generated at the cross section B app ( t ) acting on a superconducting magnet.

[0059] It should be noted that in the co-winding scheme protected by the above-mentioned other quench protection structure, the strip co-wound with the superconducting magnet can be a metal strip or a superconducting strip, whichever can achieve the expected quench protection effect. The following is an example of a metal strip as an example. The above-mentioned strip is a superconducting strip. Similarly, it is only necessary to replace the corresponding metal strip with a superconducting strip. Those skilled in the art can select it according to their needs to achieve the expected quench protection effect. Figure 5Taking the example that the superconducting tape corresponding to each single-pancake superconducting coil is closely attached to a metal strip, and in the following embodiments of the present application, only the co-wound strip is taken as an example of the metal strip; those skilled in the art can understand that the superconducting tape corresponding to each single-pancake superconducting coil can also be closely attached to multiple metal strips, as long as the current directions of two adjacent strips in the axial direction of the alternating magnetic field generating coil are opposite.

[0060] Furthermore, when the quench protection action occurs, opposite-direction currents are passed through the upper and lower pancake metal strips. On the one hand, an alternating magnetic field can be uniformly generated in the superconducting magnet, and this alternating magnetic field has a large vertical component acting on the width of the superconducting tape of the superconducting magnet, which can more effectively reduce the critical current density of the superconducting tape and promote the overall uniform quench of the superconducting magnet after local quench; on the other hand, due to the close co-winding of the metal strip and the superconducting strip, the heat transfer distance is short, and the Joule heat generated by the energization of the normal-conducting metal strip can also accelerate the overall uniform quench of the superconducting magnet.

[0061] Figure 6 gives Figure 5 The cross-sectional expansion view of the shown structure is given. Among them, the part within the dashed box represents a co-winding unit, the part marked with shading represents the superconducting tape, the parts marked with black solid dots and black cross dots represent the co-wound alternating magnetic field generating coil, and the black solid dots and black cross dots respectively represent the current flow directions in the alternating magnetic field generating coil after the quench protection is triggered.

[0062] Figure 7 An embodiment of the present application is given. Among them, 1 represents the superconducting magnet, 2 represents the alternating magnetic field generating coil, and 3 represents the quench detection and alternating magnetic field coil trigger controller. When the quench detection and alternating magnetic field coil trigger controller 3 detects a quench signal, it will control the alternating magnetic field generating coil 2 to trigger an alternating magnetic field B app ( t ) acting on the superconducting magnet, and at the same time heating the superconducting magnet to achieve quench protection for the superconducting magnet. In this embodiment, the alternating magnetic field generating coil is wound with square copper wire, the conductive material used for the superconducting magnet can be a 10 mm wide YBCO high-temperature superconducting tape, and the applied alternating magnetic field B app ( t ) waveform is a symmetric sine wave.

[0063] Figure 8 Another embodiment of the present application is given. Among them, 1 represents the superconducting magnet, 2 represents the alternating magnetic field generating coil, and 3 represents the quench detection and alternating magnetic field coil trigger controller. When the quench detection and alternating magnetic field coil trigger controller 3 detects a quench signal, it will control the alternating magnetic field generating coil 2 to trigger an alternating magnetic field B app (t ) acts on the superconducting magnet, while heating the superconducting magnet to perform quench protection on the superconducting magnet. In this embodiment, the alternating magnetic field generating coil is wound with square copper wire. The superconducting magnet is a hybrid magnet. The outer low-temperature superconducting magnet is wound with NbTi wire, and the inserted high-temperature superconducting magnet can be wound with 10 mm wide YBCO high-temperature superconducting tape. The applied alternating magnetic field B app ( t ) The waveform is a sinusoidal oscillation decay wave generated by discharging a capacitor to the alternating magnetic field generating coil. In the quench detection and AC magnetic field coil trigger controller 3 L w represents the circuit inductance, R w represents the line resistance, C represents the discharge capacitor, L r represents the series resonance inductance, C r represents the series resonance capacitor, C p represents the parallel resonance capacitor.

[0064] Figure 9 Another embodiment of the present application is given. Taking the multi-pancake superconducting coil as the superconducting magnet as an example, where 1 represents the superconducting magnet, 2 represents the alternating magnetic field generating coil, and 3 represents the quench detection and AC magnetic field coil trigger controller. Figure 9 In (a) is a schematic diagram of the quench protection device, Figure 9 In (b) is the alternating magnetic field generated at the cross-section B app ( t ) A schematic diagram of the action on the superconducting magnet. The superconducting magnet adopts a winding structure of co-winding a normal conducting metal strip - superconducting tape (where the normal conducting metal strip is wound to obtain the alternating magnetic field generating coil 2); further, the above-mentioned normal conducting metal strip can also be replaced with a superconducting tape to obtain the alternating magnetic field generating coil 2 after winding, Figure 10 Similarly in. When the quench detection and AC magnetic field coil trigger controller 3 detects a quench signal, it will control the alternating magnetic field generating coil 2 to trigger the alternating magnetic field by passing currents of a certain magnitude and opposite directions through the metal strips adjacent up and down, B app ( t ) to act on the superconducting magnet to perform quench protection on the superconducting magnet. Similarly, Figure 9 In, taking the superconducting tape corresponding to each single-pancake superconducting coil being closely attached to a metal strip as an example for illustration. In this embodiment, the alternating magnetic field generating coil is a metal strip co-wound with the superconducting magnet. The superconducting magnet can be wound with 10 mm wide high-temperature superconducting tape, and the applied alternating magnetic field Bapp ( t ) The waveform is an asymmetric triangular wave.

[0065] Figure 10 Another embodiment of the present application is given. Taking a multi-pancake superconducting coil as a superconducting magnet as an example, where 1 represents the superconducting magnet, 2 represents the alternating magnetic field generating coil, and 3 represents the quench detection and alternating magnetic field coil trigger controller. Figure 10 In (a) is a schematic diagram of the quench protection device. Figure 10 In (b) is the alternating magnetic field generated at the cross-section. B app ( t ) A schematic diagram of the action on the superconducting magnet. Figure 10 In this example, it is illustrated by taking the superconducting tape corresponding to each single-pancake superconducting coil being closely attached to two metal tapes. The superconducting magnet adopts a winding structure of co-winding a normal-conducting metal tape and a superconducting tape. Among them, one superconducting tape is co-wound with two adjacent metal tapes arranged side by side vertically. When the quench detection and alternating magnetic field coil trigger controller 3 detects a quench signal, it will control the alternating magnetic field generating coil 2 to trigger the alternating magnetic field by passing currents of a certain magnitude and opposite directions through the adjacent upper and lower metal tapes. B app ( t ) The action on the superconducting magnet to provide quench protection for the superconducting magnet. In this embodiment, the alternating magnetic field generating coil is a metal tape co-wound with the superconducting magnet. The superconducting magnet can be wound with a 10-mm-wide high-temperature superconducting tape, and the applied alternating magnetic field B app ( t ) The waveform is a symmetric rectangular wave.

[0066] It should be understood that expressions such as "including" and "may include" that can be used in the present application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In the present application, terms such as "including" and / or "having" can be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but cannot be interpreted as excluding the existence or possibility of addition of one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0067] In addition, in the present application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" can include A, can include B, or can include both A and B.

[0068] In the description of the embodiments of the present application, it should be noted that unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Among them, "fixed connection" means that the two are connected and the relative position relationship after connection remains unchanged. "Rotational connection" means that the two are connected and can rotate relative to each other after connection. "Sliding connection" means that the two are connected and can slide relative to each other after connection. The orientation terms mentioned in the embodiments of the present application, such as "top", "bottom", "inner", "outer", "left", "right", etc., are only references to the direction of the attached drawings. Therefore, the orientation terms used are for better and clearer explanation and understanding of the embodiments of the present application, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the embodiments of the present application.

[0069] In addition, in the embodiments of the present application, mathematical concepts such as symmetry, equality, parallelism, and perpendicularity are mentioned. These limitations are all in view of the current technological level, rather than absolute strict definitions in the mathematical sense, allowing for a small amount of deviation. Approximations to symmetry, equality, parallelism, perpendicularity, etc. are all acceptable. For example, when it is said that A is parallel to B, it means that A is parallel to B or approximately parallel to B, and the included angle between A and B can be between 0 degrees and 10 degrees. When it is said that A is perpendicular to B, it means that A is perpendicular to B or approximately perpendicular to B, and the included angle between A and B can be between 80 degrees and 100 degrees.

[0070] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of changes or substitutions, which should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for quench protection of a superconducting magnet, characterized in that, Comprising: When the superconducting magnet quenches, an alternating magnetic field with a preset amplitude and a preset frequency is applied to the superconducting magnet, so that the energy loss of the superconducting magnet increases, the critical current decreases, and / or the temperature rises, accelerating the overall quench propagation of the superconducting magnet; the component of the alternating magnetic field acting in the radial direction of the superconducting magnet is relatively large.

2. The method according to claim 1, characterized in that The amplitude and / or frequency of the alternating magnetic field can be adjusted; and / or the larger the amplitude and frequency are, the faster the overall quench propagation of the superconducting magnet is.

3. The method according to claim 1, wherein The alternating magnetic field is generated by an energized coil, and the energized current directions of adjacent turns of the coil in the axial direction of the superconducting magnet are opposite; and / or the energized coil is coaxially arranged with the superconducting magnet and / or coaxially wound together with the superconducting magnet.

4. The method according to any one of claims 1 to 3, characterized in that, The alternating magnetic field is one magnetic field or a superposition of multiple magnetic fields among triangular waves, square waves, trapezoidal waves, sine waves, and sine oscillation decay waves with symmetric or asymmetric positive and negative half-waves.

5. A superconducting magnet quench protection device, characterized in that, Comprising: An alternating magnetic field generating coil; The alternating magnetic field generating coil includes: a multi-turn coil, the multi-turn coil is coaxially arranged with the superconducting magnet and / or coaxially wound together with the superconducting magnet, and when the multi-turn coil is energized, the energized current directions of any two adjacent turns of the coil in the axial direction of the superconducting magnet are opposite; When quench protection needs to be performed on the superconducting magnet, the alternating magnetic field generating coil is energized with an alternating current to generate an alternating magnetic field acting on the superconducting magnet, and the alternating magnetic field and the heat generated after the alternating magnetic field generating coil is energized act on the superconducting magnet together, accelerating the overall quench propagation of the superconducting magnet and realizing quench protection for the superconducting magnet.

6. The device according to claim 5, characterized in that, The multi-turn coil is coaxially arranged with the superconducting magnet, including: The multi-turn coil is wound by a wire along the axial direction of the superconducting magnet, and the winding directions of adjacent turns of the coil in the axial direction of the superconducting magnet are opposite, so that when the multi-turn coil is energized, the energized current directions of adjacent turns of the coil along the axial direction of the superconducting magnet are opposite.

7. The device according to claim 5, characterized in that, The multi-turn coil is coaxially arranged with the superconducting magnet, including: The multi-turn coil is wound by a composite wire wound in the axial direction of the superconducting magnet; the composite wire includes multiple first-type wires arranged side by side in the axial direction of the superconducting magnet, and / or at least one second-type wire folded in half and arranged side by side in the axial direction of the superconducting magnet; when the multi-turn coil is energized, each first-type wire and / or second-type wire is energized, and the energized current directions of any two adjacent first-type wires along the axial direction of the superconducting magnet are opposite, and / or the energized current directions of all second-type wires are the same.

8. The device according to claim 5, characterized in that The superconducting magnet includes a single-pancake superconducting coil or a multi-pancake superconducting coil; the multi-pancake superconducting coil includes multiple single-pancake superconducting coils stacked in the axial direction of the superconducting magnet, and the single-pancake superconducting coil is wound by a superconducting tape through a layer winding method; The multi-turn coil is coaxially wound together with the superconducting magnet, including: The multi-turn coil is wound by at least two tapes; the winding is in close co-winding with the superconducting tape inside each single-pancake superconducting coil; When the superconducting magnet includes a single-pancake superconducting coil, the superconducting tape corresponding to the single-pancake superconducting coil is closely attached to at least two tapes, and the at least two tapes are arranged in the axial direction of the superconducting magnet; When the superconducting magnet includes multi-pancake superconducting coils, the superconducting tape corresponding to each single-pancake superconducting coil therein is closely attached to at least one tape, and the at least one tape is arranged in the axial direction of the superconducting magnet; When current is passed through the multi-turn coil, current is passed through each tape, and the directions of current passed through any two adjacent tapes along the axial direction of the superconducting magnet are opposite.

9. The device according to any one of claims 6 to 8, characterized in that The material of the multi-turn coil or at least two tapes is normal conducting material or superconducting material.

10. The device according to any one of claims 5 to 8, characterized in that The alternating current is one current or a superposition of multiple currents among triangular wave, square wave, trapezoidal wave, sine wave, and sine oscillation decay wave currents with symmetric or asymmetric positive and negative half-waves.

Images