A superconducting magnet quench protection method and device

Abstract

This application belongs to the field of superconducting magnets and specifically discloses a method and device for quench protection of superconducting magnets. The method includes: when a superconducting magnet quenches, applying an alternating magnetic field of a preset amplitude and frequency to the superconducting magnet, causing the superconducting magnet to increase energy loss, decrease critical current, and / or increase temperature, thereby accelerating the overall quench propagation of the superconducting magnet and achieving quench protection for the superconducting magnet; the component of the alternating magnetic field acting in the radial direction of the superconducting magnet is relatively large. Through this application, in quench protection of superconducting magnets, propagation of the normal conductive region after the quench can be achieved with high efficiency, and the reliability of quench protection is high.

Description

Technical Field

[0001] The present application relates to the field of superconducting magnets, and more specifically, to a superconducting magnet quench protection method and device. Background Art

[0002] Due to their exceptional current-carrying capacity, superconducting materials have become the preferred current-carrying material for many high-current, high-magnetic-field applications. They are widely used in superconducting motors, superconducting cables, steady-state high-field magnets, superconducting magnetic levitation technology, particle accelerators, and superconducting magnetic energy storage systems. The process by which a superconducting material transitions from its superconducting state to its normal state due to various factors (such as external magnetic field interference, temperature fluctuations, or mechanical disturbances) is called a quench. This process is accompanied by the sudden appearance of resistance and the release of energy. Superconducting magnets face a serious quenching problem during operation. Once a quench occurs, a large amount of energy is released in the quench region of the superconducting magnet, causing a significant temperature rise. In severe cases, it can cause the superconducting magnet and related equipment to burn out, seriously threatening the safe operation of the superconducting magnet and related equipment. Therefore, superconducting materials and devices made from them require reliable quench protection methods and means during operation.

[0003] Existing quench protection methods can be divided into passive quench protection and active quench protection according to the way the protection action is triggered. The principle of passive quench protection is to use a specific circuit, based on unidirectional self-breaking devices such as diodes, to automatically connect energy-releasing resistor devices or arrays to the superconducting magnet circuit to release the energy in the magnet through the change in voltage in the magnet circuit after the quench, thereby achieving the purpose of quench protection. The main disadvantage of passive quench protection is its slow response. Its application scope is mainly small superconducting magnets with low cost, small scale and weak safety margin requirements. It has fundamental limitations for its application in large superconducting magnets and related equipment.

[0004] Active quench protection relies on a pre-installed quench detection system, triggering the protection device upon detection of a quench. A common active quench protection method is the heater method. This method activates a heater upon detection of a quench by the quench detection device, heating the superconducting magnet to a temperature above the critical superconducting temperature. This accelerates the quench propagation and transitions from the superconducting state to the normal state, dissipating the energy within the magnet uniformly as heat throughout the magnet, thus avoiding localized overheating caused by energy accumulation in hot spots after the quench. A disadvantage of the heater method is that the rate of heat conduction depends on the thermal conductivity of the medium and the distance over which it is conducted. On the one hand, magnets wound with some types of superconducting wire have poor radial thermal conductivity, especially for magnets with inter-turn insulation made of poorly conductive materials. On the other hand, for large magnets with large overall volumes and long winding lengths, the longer heat transfer distance reduces the speed of heat conduction, limiting the reliability of the heater method's quench protection. Summary of the Invention

[0005] In view of the defects of the prior art, the purpose of this 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 objectives, in a first aspect, the present application provides a superconducting magnet quench protection method, comprising:

[0007] When a superconducting magnet quenches, an alternating magnetic field of a preset amplitude and frequency is applied to the superconducting magnet, causing the superconducting magnet to increase energy loss, decrease critical current, and / or increase temperature, thereby accelerating the overall quench propagation of the superconducting magnet and achieving quench protection for the superconducting magnet; the component of the alternating magnetic field acting in the radial direction of the superconducting magnet is relatively large.

[0008] It should be noted that the dynamic resistance loss generated by a superconducting magnet under the action of an alternating magnetic field increases its energy loss, and the above-mentioned alternating magnetic field can reduce the critical current of the superconducting magnet. In addition, the AC loss and dynamic resistance loss generated by the superconducting magnet under the AC magnetic field generate heat, thereby causing the temperature of the superconducting magnet to rise. The above-mentioned relatively large radial direction component means that the component or component mean acting in the radial direction is greater than the component or component mean acting in the perpendicular radial direction. The above-mentioned preset amplitude and preset frequency are based on the ability to achieve the expected quench protection effect. Those skilled in the art can design them as needed, and this application does not impose any restrictions on this.

[0009] It can be understood that by applying an alternating magnetic field with a large radial component to the superconducting magnet, the overall quench propagation of the superconducting magnet can be effectively accelerated, thereby improving the reliability of quench protection.

[0010] 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.

[0011] In some embodiments, the alternating magnetic field is generated by a powered coil, and the directions of the currents in adjacent turns of the powered coil are opposite along the axial direction of the superconducting magnet; and / or the powered coil is coaxially arranged and / or co-wound with the superconducting magnet.

[0012] In some embodiments, the alternating magnetic field is a magnetic field or a superposition of multiple magnetic fields selected from the group consisting of a triangular wave, a square wave, a trapezoidal wave, a sine wave, and a sinusoidal oscillation decay wave magnetic field with symmetrical or asymmetrical positive and negative half waves.

[0013] In a second aspect, the present application provides a superconducting magnet quench protection device, comprising: an alternating magnetic field generating coil;

[0014] The alternating magnetic field generating coil comprises: a multi-turn coil, the multi-turn coil being coaxially arranged with the superconducting magnet and / or being coaxially wound with the superconducting magnet, wherein when 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;

[0015] When quench protection is required for the superconducting magnet, an alternating current is passed through the alternating magnetic field generating coil to generate an alternating magnetic field acting on the superconducting magnet. The alternating magnetic field and the heat generated by the alternating magnetic field generating coil after being energized act together on the superconducting magnet, accelerating the overall quench propagation of the superconducting magnet and achieving quench protection for the superconducting magnet.

[0016] It should be noted that the aforementioned need for quench protection of the superconducting magnet refers to the detection of a quench in the superconducting magnet. At this point, the alternating magnetic field generating coil is triggered to generate an alternating magnetic field, applying an alternating magnetic field of a certain amplitude and rate of change to the superconducting magnet. This allows the alternating magnetic field and the heat generated by the alternating magnetic field generating coil upon energization to act together on the superconducting magnet, promoting the quenching of the non-quenched portion of the superconducting magnet. This allows the normal conductive region after the quench to spread rapidly, dissipating the energy within the superconducting magnet evenly throughout the magnet, and preventing damage to the magnet caused by energy release in a localized area.

[0017] The present application utilizes the structural design of the alternating magnetic field generating coil and the corresponding current flow method and strategy design to ensure that, when quench protection is required, the alternating magnetic field generating coil can generate an alternating magnetic field with a large radial component acting on the superconducting magnet, thereby achieving propagation into the normally conductive region after the quench with higher efficiency and having higher reliability of quench protection. Furthermore, the device has a simple structure, a small size, a very short heat transfer distance, and a simple control method, thereby increasing the reliability of the overall device.

[0018] In some embodiments, the multi-turn coil is coaxially arranged with the superconducting magnet, comprising:

[0019] The multi-turn coil is obtained by winding a wire along the axial direction of the superconducting magnet, and adjacent turns of the coil in the axial direction of the superconducting magnet are wound in opposite directions, so that when current is passed through the multi-turn coil, the current directions of adjacent turns of the coil in the axial direction of the superconducting magnet are opposite.

[0020] It should be noted that the above-mentioned wire can be a single wire or multiple wires. If it is a single wire, it can be directly axially wound according to the above-mentioned method. If it is multiple wires, each wire can be wound and then stacked and wound along the radial direction of the superconducting magnet.

[0021] In some embodiments, the multi-turn coil is coaxially arranged with the superconducting magnet, comprising:

[0022] The multi-turn coil is obtained by winding 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 current is passed through the multi-turn coil, current is passed through each first-type wire and / or second-type wire, and the directions of current passing through any adjacent first-type wires along the axial direction of the superconducting magnet are opposite, and / or the directions of current passing through all second-type wires are the same.

[0023] The first type of wires are preferably an even number, so as to ensure that when currents in opposite directions are passed through any adjacent wires, the currents in any adjacent turns of the coil in the axial direction of the superconducting magnet are in opposite directions.

[0024] Specifically, it is understood that when the alternating magnetic field generating coil is coaxially disposed with the superconducting magnet, it can be wound around the periphery of the superconducting magnet or within the axial gap region within the superconducting magnet. Furthermore, it can be in close contact with the superconducting magnet, or the gap between it and the superconducting magnet can be relatively narrow, such as the gap distance 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 sufficiently small and the energy utilization efficiency of the alternating magnetic field is guaranteed.

[0025] 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 obtained by winding a superconducting tape in a layer-by-layer manner;

[0026] The multi-turn coil is coaxially wound with the superconducting magnet, and includes:

[0027] The multi-turn coil is obtained by winding at least two strips; the winding is closely wound with the superconducting strip in each single-plate superconducting coil;

[0028] 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;

[0029] When the superconducting magnet includes multiple superconducting coils, the superconducting tape corresponding to each single superconducting coil is closely attached to at least one tape, and the at least one tape is arranged in the axial direction of the superconducting magnet;

[0030] When current is passed through the multi-turn coil, current is passed through each strip, and the directions of current passing through any two adjacent strips along the axial direction of the superconducting magnet are opposite.

[0031] In some embodiments, the currents flowing through two adjacent turns of the coil or two adjacent strips in the axial direction of the superconducting magnet may have the same or different waveforms and the same or different amplitudes. These waveforms and amplitudes may be the same or different, as long as the currents are in opposite directions, to achieve the desired quench protection effect. Those skilled in the art may design the waveforms and amplitudes of these oppositely directed currents based on actual needs.

[0032] In some embodiments, the material of the multi-turn coil or the at least two strips is a normal conductive material or a superconducting material.

[0033] In some embodiments, the alternating current is one current or a superposition of multiple currents selected from the group consisting of a triangular wave, a square wave, a trapezoidal wave, a sine wave, and a sinusoidal oscillation decay wave current with symmetrical or asymmetrical positive and negative half waves.

[0034] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the existing technologies:

[0035] The present application provides a method and apparatus for quench protection of a superconducting magnet. 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 method can effectively accelerate the propagation of the entire quench in the superconducting magnet, thereby improving the reliability of quench protection. Furthermore, if the alternating magnetic field is generated by an energized coil, it is only necessary to control the current directions of adjacent turns of the energized coil along the axial direction of the superconducting magnet in opposite directions to generate the alternating magnetic field with a large radial component, thereby achieving quench protection for the superconducting magnet. This method has a simple structure and simple control. When the energized coil is coaxially arranged on the periphery of the superconducting magnet and / or is coaxially wound with the superconducting magnet, the heat transfer distance is short, and the reliability of the above-mentioned solution is high, which has great application prospects.

[0036] The present application provides a superconducting magnet quench protection method and device. When a superconducting magnet quench is detected, an alternating magnetic field generating coil is triggered to generate an alternating magnetic field to apply an 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 together on the superconducting magnet, promoting the non-quenched part of the superconducting magnet to also quench, so that the normal conductive area after the quench propagates rapidly, so that the internal energy of the superconducting magnet is evenly consumed in the entire magnet, avoiding damage to the magnet caused by energy release in a local area. The present application, through the structural design of the alternating magnetic field generating coil and the corresponding input current design, makes it possible for the alternating magnetic field generating coil to generate an alternating magnetic field with a large radial component acting on the superconducting magnet when quench protection is required, and the heat transfer distance is short, so that the propagation of the normal conductive area after the quench is achieved with higher efficiency, and has higher reliability of quench protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A flow chart of a superconducting magnet quench protection method provided in an embodiment of the present application;

[0038] Figure 2 A schematic diagram of a quench protection device based on an external alternating magnetic field provided in an embodiment of the present application;

[0039] Figure 3 A schematic diagram of the structure of an alternating magnetic field generating coil in a quench protection device based on an external alternating magnetic field provided in an embodiment of the present application;

[0040] FIG4( a ) is another schematic structural diagram of an alternating magnetic field generating coil provided in an embodiment of the present application;

[0041] FIG4( b ) is another structural schematic diagram of an alternating magnetic field generating coil provided in an embodiment of the present application;

[0042] Figure 5 Schematic diagram of the principle of the quench protection device for an external alternating magnetic field based on the co-winding of a normal conductive metal tape and a superconducting tape provided in an embodiment of the present application;

[0043] Figure 6 A schematic diagram of the magnet winding method and cross-sectional development of the quench protection device for an applied alternating magnetic field based on the co-winding of a normal conductive metal tape and a superconducting tape provided in an embodiment of the present application;

[0044] Figure 7 A schematic diagram of using an alternating magnetic field generating coil to generate a symmetrical sinusoidal magnetic field for quench protection according to an embodiment of the present application;

[0045] Figure 8 A schematic diagram of an embodiment of the present application providing a method for quench protection using an alternating magnetic field generating coil to generate a sinusoidal oscillating decaying waveform magnetic field;

[0046] Figure 9 A schematic diagram of a co-winding structure of a normal conductive metal tape and a superconducting tape provided in an embodiment of the present application, wherein the co-winding metal tape is used to generate an asymmetric triangular wave magnetic field to provide quench protection for the co-winding magnet;

[0047] Figure 10 A schematic diagram of a co-winding structure of a normal conductive metal tape and a superconducting tape provided in an embodiment of the present application, wherein a symmetrical rectangular wave magnetic field is generated by the co-winding metal tape to provide quench protection for the co-winding magnet;

[0048] In all the drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 denotes a superconducting magnet, 2 denotes an alternating magnetic field generating coil, and 3 denotes a quench detection and AC magnetic field coil triggering controller. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0050] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0051] The embodiment of the present application proposes a new solution for quench protection of superconducting magnets, the main advantage of which is that it can achieve the propagation of the normal conductive area after the 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 provided. The quench protection device proposed in the present application triggers an alternating magnetic field generating coil after the quench detection system detects the quench, and applies an alternating magnetic field with a certain amplitude and a certain change rate to the superconducting magnet, thereby promoting the quenching of the non-quenched part of the superconducting magnet, causing the normal conductive area after the quench to propagate rapidly, so that the internal energy of the superconducting magnet is evenly consumed throughout the magnet, avoiding magnet damage caused by energy release in a local area. The detailed principle explanation is described in the following embodiments.

[0052] Figure 1 Flowchart of the superconducting magnet quench protection method provided in the embodiment of the present application; Figure 1 As shown, the following steps are included:

[0053] Step S101: When a superconducting magnet quenches, an alternating magnetic field of a preset amplitude and 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 increases, thereby 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.

[0054] Optionally, 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.

[0055] For example, the alternating magnetic field is generated by a powered coil, and the current directions of adjacent turns of the powered coil are opposite along the axial direction of the superconducting magnet; and / or the powered coil is coaxially arranged and / or co-wound with the superconducting magnet.

[0056] For example, the above-mentioned alternating magnetic field is a magnetic field or a superposition of multiple magnetic fields among the triangular wave, square wave, trapezoidal wave, sine wave and sinusoidal oscillation decay wave magnetic fields with symmetrical or asymmetrical positive and negative half waves; it can be understood that if the above-mentioned 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.

[0057] It is understandable that the core of the quench protection method for superconducting magnet quench protection is to promote the rapid diffusion of the quench region throughout the magnet to achieve the purpose of uniform energy release. The principle of the solution proposed in this application to quickly promote the diffusion of the quench region is mainly based on the following three points:

[0058] (1) Superconducting materials will produce dynamic resistance loss under an alternating magnetic field, which will consume 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, causing the energy loss inside the superconducting magnet to be faster.

[0059] (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. The greater the degree of critical current reduction, the faster the corresponding quench propagation.

[0060] (3) The AC loss and dynamic resistance loss generated by the superconducting magnet under the AC magnetic field will generate heat, which will then 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 of 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.

[0061] 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 the 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.

[0062] Figure 2A schematic diagram of the quench protection device is given. 1 represents the superconducting magnet used 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 ) acts on the superconducting magnet, and according to the principles described in (1), (2), and (3) in the above principle introduction, the superconducting magnet is protected from quenching. B app ( t ) can be a triangular wave, square wave, trapezoidal wave and sine wave with symmetrical or asymmetrical positive and negative half-waves, can be the superposition of the above waveforms, or can be a sinusoidal oscillation attenuation waveform generated by discharging a capacitor to an alternating magnetic field generating coil; it can be understood that when the corresponding current is passed through the above alternating magnetic field generating coil, an alternating magnetic field will be generated, and the waveform of the alternating magnetic field is determined by the waveform of the alternating current passed through, and is consistent with the waveform of the alternating current. The embodiment of the present application does not limit the wire material of the alternating magnetic field generating coil 2. For the superconducting magnet 1, in terms of 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.

[0063] In one possible implementation, the present application provides a superconducting magnet quench protection device, which includes an alternating magnetic field generating coil, wherein the alternating magnetic field generating coil includes: a multi-turn coil, wherein the multi-turn coil is coaxially arranged with the superconducting magnet and / or co-wound with the superconducting magnet, and 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 a quench protection is required for the superconducting magnet, an alternating current is passed through the alternating magnetic field generating coil 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 together on the superconducting magnet, thereby accelerating the overall quench propagation of the superconducting magnet and achieving quench protection for the superconducting magnet.

[0064] It should be noted that the multi-turn coils can be coaxially arranged only on the periphery or inside of the superconducting magnet, coaxially wound only with the superconducting magnet, or arranged on the periphery, inside, and coaxially wound with the superconducting magnet in a variety of configurations at the same time, so as to achieve the expected quench protection effect.

[0065] In some embodiments, the multi-turn coil is coaxially arranged with the superconducting magnet, comprising:

[0066] The multi-turn coil is obtained by winding a wire along the axial direction of the superconducting magnet, and adjacent turns of the coil in the axial direction of the superconducting magnet are wound in opposite directions, so that when current is passed through the multi-turn coil, the current directions of adjacent turns of the coil in the axial direction of the superconducting magnet are opposite.

[0067] In some embodiments, the multi-turn coil is coaxially arranged with the superconducting magnet, comprising:

[0068] The multi-turn coil is obtained by winding 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 current is passed through the multi-turn coil, current is passed through each first-type wire and / or second-type wire, and the directions of current passing through any adjacent first-type wires along the axial direction of the superconducting magnet are opposite, and / or the directions of current passing through all second-type wires are the same.

[0069] Optionally, when the alternating magnetic field generating coil is coaxially arranged with the superconducting magnet, it can be wound around the periphery of the superconducting magnet, or wound around the axial gap region inside the superconducting magnet ( Figure 2 (This is explained using the example of being wound closely around a superconducting magnet.) Furthermore, the coil can be closely attached to the superconducting magnet, or the gap between the coil and the superconducting magnet can be relatively narrow, such as the gap distance can be smaller than a preset value, so that the heat conduction distance between the alternating magnetic field generating coil and the superconducting magnet is sufficiently small, and the energy utilization efficiency of the alternating magnetic field is ensured.

[0070] In some scenarios, 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 obtained by winding a superconducting tape in layers.

[0071] In one embodiment, the multi-turn coil is coaxially wound with the superconducting magnet, comprising:

[0072] The multi-turn coil is obtained by winding at least two strips; the winding is closely wound with the superconducting strip in each single-plate superconducting coil;

[0073] 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;

[0074] When the superconducting magnet includes multiple superconducting coils, the superconducting tape corresponding to each single superconducting coil is closely attached to at least one tape, and the at least one tape is arranged in the axial direction of the superconducting magnet;

[0075] When current is passed through the multi-turn coil, current is passed through each strip, and the directions of current passing through any two adjacent strips along the axial direction of the superconducting magnet are opposite.

[0076] It should be noted that the currents flowing in opposite directions through adjacent turns of coils or strips in the axial direction of the superconducting magnet are intended to ensure that the alternating magnetic field generated between the coils of adjacent turns or strips has a sufficiently large radial component acting on the superconducting magnet. Referring to Ampere's Law for a straight wire carrying current: Hold the wire in your right hand with your thumb pointing in the direction of the current. The direction of the magnetic field surrounding the wire is indicated by the direction of the four fingers. This indicates that when the currents flowing through adjacent turns of coils or strips are in opposite directions, the magnetic fields at the gap between them (the adjacent turns of coils or strips) cannot cancel each other out, effectively superimposing each other. Furthermore, according to Ampere's Law, the magnetic field at the gap between the coils or strips has a larger radial component (greater than the component perpendicular to the radial direction or the average of the components). Therefore, the above-described device and design ensure that the alternating magnetic field at the gap has a relatively large radial component.

[0077] Those skilled in the art will understand that, for a superconducting magnet, the greater the radial component of the applied magnetic field, the greater the drop in critical current, and the faster the corresponding quench propagation. Furthermore, it is also readily understood that the greater the amplitude and / or frequency of the alternating magnetic field, the faster the quench propagation. Because the embodiments of the present application utilize the unique design of the alternating magnetic field generating coil and the corresponding current, the alternating magnetic field can efficiently propagate into the normally conductive region after the quench, resulting in highly reliable quench protection.

[0078] Furthermore, in some embodiments, the currents flowing through two adjacent turns of coils or two adjacent strips in the axial direction of the superconducting magnet can be controlled to have the same or different waveforms, the same or different amplitudes, and opposite directions. Those skilled in the art will appreciate that the directions of the two adjacent axial currents must be opposite, and the waveforms and amplitudes can be the same, different, or different, as long as they produce the desired effect of accelerating the propagation of a quench in the superconducting magnet. This design can be flexibly tailored to meet specific needs, and the present embodiments do not impose any limitations thereto.

[0079] In some embodiments, the material of the multi-turn coil or the at least two strips is a normal conductive material or a superconducting material.

[0080] In some embodiments, the alternating current is one current or a superposition of multiple currents selected from the group consisting of a triangular wave, a square wave, a trapezoidal wave, a sine wave, and a sinusoidal oscillation decay wave current with symmetrical or asymmetrical positive and negative half waves.

[0081] It is understandable that Figure 2The quench detection and AC magnetic field coil trigger controller 3 parts are not the focus of the technology of this application, and their specific internal structure is not of concern, so a black box is used to represent their integrated system. The above-mentioned trigger controller is based on the ability to detect the superconducting magnet quench and trigger the alternating magnetic field generating coil, and can be implemented with reference to relevant existing technologies.

[0082] In a specific embodiment, the alternating magnetic field generating coil 2 can be made into a shape that fits the periphery of the superconducting magnet so that the alternating magnetic field generated by it can be applied relatively evenly to the superconducting magnet. It should be noted that the material of the alternating magnetic field generating coil here can be a normal conductive material or a superconducting material. The embodiment of the present application does not make further restrictions on this. Those skilled in the art can make a selection according to actual needs to achieve the expected quench protection effect; at the same time, the alternating magnetic field generating coil can be placed close to the periphery of the superconducting magnet, and the heat transfer distance is short, such as Figure 3 As shown in (a), it creates thermal contact with the periphery of the superconducting magnet. In this way, on the basis of promoting the overall quench of the superconducting magnet by applying an alternating magnetic field, the heating of the coil generated by the alternating magnetic field can further accelerate the overall quench propagation of the superconducting magnet.

[0083] Figure 3 Given Figure 2 Schematic diagram of the structure of the alternating magnetic field generating coil. Figure 3 (a) is a schematic diagram of the alternating magnetic field generating coil after winding. Figure 3 (b) shows a side view of the alternating magnetic field generating coil, where the arrow indicates the direction of the current. After the alternating magnetic field generating coil is triggered, currents flow in opposite directions through the upper and lower adjacent turns of the coil. This generates an AC magnetic field with a large perpendicular component (perpendicular to the circumference of the superconducting magnet and parallel to the radial direction of the superconducting magnet, also called the parallel radial component) between the upper and lower turns. This magnetic field acts uniformly throughout the superconducting magnet, accelerating the propagation of the superconducting magnet's quench.

[0084] FIG4( a ) shows another schematic diagram of the structure of the alternating magnetic field generating coil. Referring to FIG4( a ), taking the alternating magnetic field generating coil obtained by winding two wires as an example, the two wires are wound closely around the periphery of the superconducting magnet (i.e., the superconducting magnet is arranged closely inside the solenoid coil wound by the two wires in FIG4( a ), which is omitted in FIG4( a ) and can be seen in FIG4( a ). Figure 2 As shown in the figure, one wire is drawn in blue and the other in red. If currents in different directions are passed through the blue and red wires, a magnetic field perpendicular to the surface of the superconducting magnet can be generated in the area between each red and blue wire. The principle is the same as Figure 3 Same, I won’t go into details here.

[0085] Similarly, Figure 4(b) shows a folded wire wrapped around a superconducting magnet. When current flows through the wire, the current in the red and blue parts of the folded wire flows in opposite directions.

[0086] It is understandable that Figure 3 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.

[0087] Furthermore, for a superconducting magnet based on superconducting tape, a superconducting tape is usually wound in layers along the radial direction to form a single superconducting coil. A superconducting magnet based on superconducting tape may include a single superconducting coil or multiple superconducting coils.

[0088] 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-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 similar to the current flow direction. 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 and a superconducting magnet are co-wound. Figure 5 (b) is the alternating magnetic field generated at the cross section B app ( t ) acting on a superconducting magnet.

[0089] 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 5In the description, the superconducting tape corresponding to each single-disc superconducting coil is closely attached to a metal tape. In the following embodiments of the present application, the co-wound tapes are also only taken as metal tapes. It can be understood by those skilled in the art that the superconducting tape corresponding to each single-disc superconducting coil can also be closely attached to multiple metal tapes, as long as the current directions of the two adjacent tapes in the axial direction of the alternating magnetic field generating coil are opposite.

[0090] Furthermore, when quench protection is activated, currents in opposite directions are passed through the upper and lower metal strips. This, on the one hand, can uniformly generate an alternating magnetic field in the superconducting magnet. This alternating magnetic field has a large vertical component acting across the width of the superconducting magnet strip, which can more effectively reduce the critical current density of the superconducting strip and promote a uniform quench of the superconducting magnet as a whole after a local quench. On the other hand, because the metal strips and the superconducting strips are tightly wound together and the heat transfer distance is short, the Joule heat generated by the current flowing through the normal-conducting metal strips can also accelerate the uniform quench of the superconducting magnet as a whole.

[0091] Figure 6 Given Figure 5 Expanded cross-section of the structure shown. The dashed box represents a co-wound unit, the shaded area represents the superconducting tape, the black solid dots and black crosses represent the co-wound alternating magnetic field generating coil, and the black solid dots and black crosses represent the current flow in the alternating magnetic field generating coil after quench protection is triggered.

[0092] Figure 7 An embodiment of the present application is given. 1 represents a superconducting magnet, 2 represents an alternating magnetic field generating coil, and 3 represents a quench detection and AC magnetic field coil triggering controller. When the quench detection and AC magnetic field coil triggering controller 3 detects a quench signal, it controls the alternating magnetic field generating coil 2 to trigger the alternating magnetic field. B app ( t ) acts on the superconducting magnet and heats 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, and the conductive material used in the superconducting magnet can be a 10 mm wide YBCO high temperature superconducting tape. The applied alternating magnetic field B app ( t )The waveform is a symmetrical sine wave.

[0093] Figure 8 Another embodiment of the present application is given. 1 represents a superconducting magnet, 2 represents an alternating magnetic field generating coil, and 3 represents a quench detection and AC magnetic field coil triggering controller. When the quench detection and AC magnetic field coil triggering controller 3 detects a quench signal, it controls the alternating magnetic field generating coil 2 to trigger the alternating magnetic field. B app (t ) acts on the superconducting magnet, and at the same time heats the superconducting magnet and provides quench protection for 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 peripheral 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 ) waveform is a sinusoidal oscillation attenuation wave generated by discharging a capacitor to an alternating magnetic field generating coil. L w represents the circuit inductance, R w Represents the line resistance, C represents the discharge capacitance, L r represents the series resonant inductor, C r represents the series resonant capacitor, C p Represents the parallel resonant capacitor.

[0094] Figure 9 Another embodiment of the present application is given, where a superconducting magnet is a multi-pancake superconducting coil as an example, where 1 represents a superconducting magnet, 2 represents an alternating magnetic field generating coil, and 3 represents a quench detection and AC magnetic field coil triggering controller. Figure 9 (a) is a schematic diagram of the quench protection device. Figure 9 (b) is the alternating magnetic field generated at the cross section B app ( t ) acting on a superconducting magnet. The superconducting magnet employs a winding structure in which a conventional metal tape and a superconducting tape are co-wound (where the conventional metal tape is wound to form an alternating magnetic field generating coil 2). Furthermore, the conventional metal tape can be replaced with a superconducting tape to form an alternating magnetic field generating coil 2. Figure 10 When the quench detection and AC magnetic field coil trigger controller 3 detects the quench signal, it will control the alternating magnetic field generating coil 2 to pass a certain amount of current in opposite directions to the upper and lower adjacent metal strips, triggering the alternating magnetic field. B app ( t ) acts on the superconducting magnet to protect it from quenching. Figure 9 In this example, the superconducting tape corresponding to each single superconducting coil is closely attached to a metal tape. In this embodiment, the alternating magnetic field generating coil is a metal tape wound together with the superconducting magnet. The superconducting magnet can be wound with a 10 mm wide high-temperature superconducting tape. The applied alternating magnetic field Bapp ( t ) The waveform is an asymmetrical triangle wave.

[0095] Figure 10 Another embodiment of the present application is given, where a superconducting magnet is a multi-pancake superconducting coil as an example, where 1 represents a superconducting magnet, 2 represents an alternating magnetic field generating coil, and 3 represents a quench detection and AC magnetic field coil triggering controller. Figure 10 (a) is a schematic diagram of the quench protection device. Figure 10 (b) is the alternating magnetic field generated at the cross section B app ( t ) acting on a superconducting magnet. Figure 10 In the example, the superconducting tape corresponding to each single superconducting coil is closely attached to two metal tapes. The superconducting magnet adopts a winding structure of a normal conductive metal tape and a superconducting tape, wherein one superconducting tape is co-wound with two adjacent metal tapes arranged in parallel above and below. 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 pass a certain amount of current in opposite directions through the upper and lower adjacent metal tapes, triggering the alternating magnetic field. B app ( t ) acts on the superconducting magnet to protect the superconducting magnet from quenching. In this embodiment, the alternating magnetic field generating coil is a metal strip wound together with the superconducting magnet. The superconducting magnet can be wound with a 10 mm wide high-temperature superconducting strip. The applied alternating magnetic field B app ( t )The waveform is a symmetrical rectangular wave.

[0096] It should be understood that expressions such as "include" and "may include" used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "include" and / or "have" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0097] In addition, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0098] 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 to each other and the relative position relationship after the connection remains unchanged. "Rotational connection" means that the two are connected to each other and can rotate relative to each other after the connection. "Sliding connection" means that the two are connected to each other and can slide relative to each other after the connection. The directional terms mentioned in the embodiments of the present application, such as "top", "bottom", "inside", "outside", "left", "right", etc., are only reference to the directions of the accompanying drawings. Therefore, the directional 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 therefore cannot be understood as a limitation on the embodiments of the present application.

[0099] In addition, in the embodiments of the present application, the mathematical concepts mentioned include symmetry, equality, parallelism, and perpendicularity. These limitations are all for the current state of the art, rather than being absolutely strict definitions in a mathematical sense. A small amount of deviation is allowed, and it is possible to be approximately symmetric, approximately equal, approximately parallel, or approximately perpendicular. For example, A and B are parallel, which means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. A and B are perpendicular, which means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0100] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A superconducting magnet quench protection method, characterized in that: include: When the superconducting magnet quenches, an alternating magnetic field of a preset amplitude and 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 increases, thereby 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; The alternating magnetic field is generated by a powered coil, and the current directions of adjacent turns of the powered coil are opposite along the axial direction of the superconducting magnet; the powered coil is coaxially arranged and / or co-wound with the superconducting magnet.

2. The method according to claim 1, characterized in that 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.

3. The method according to any one of claims 1 to 2, characterized in that The alternating magnetic field is one magnetic field or a superposition of multiple magnetic fields among triangular wave, square wave, trapezoidal wave, sine wave and sinusoidal oscillation decay wave magnetic fields with symmetrical or asymmetrical positive and negative half waves.

4. A superconducting magnet quench protection device, characterized in that: include: Alternating magnetic field generating coil; The alternating magnetic field generating coil comprises: a multi-turn coil, the multi-turn coil being coaxially arranged with the superconducting magnet and / or being coaxially wound with the superconducting magnet, wherein when 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 quench protection is required for the superconducting magnet, an alternating current is passed through the alternating magnetic field generating coil to generate an alternating magnetic field acting on the superconducting magnet. The alternating magnetic field and the heat generated by the alternating magnetic field generating coil after being energized act together on the superconducting magnet, accelerating the overall quench propagation of the superconducting magnet and achieving quench protection for the superconducting magnet.

5. The device according to claim 4, characterized in that The multi-turn coil is coaxially arranged with the superconducting magnet, comprising: The multi-turn coil is obtained by winding a wire along the axial direction of the superconducting magnet, and adjacent turns of the coil in the axial direction of the superconducting magnet are wound in opposite directions, so that when current is passed through the multi-turn coil, the current directions of adjacent turns of the coil in the axial direction of the superconducting magnet are opposite.

6. The device according to claim 4, characterized in that The multi-turn coil is coaxially arranged with the superconducting magnet, comprising: The multi-turn coil is obtained by winding 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 current is passed through the multi-turn coil, current is passed through each first-type wire and / or second-type wire, and the directions of current passing through any adjacent first-type wires along the axial direction of the superconducting magnet are opposite, and / or the directions of current passing through all second-type wires are the same.

7. The device according to claim 4, characterized in that 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 obtained by winding a superconducting tape in a layer-by-layer manner; The multi-turn coil is coaxially wound with the superconducting magnet, and includes: The multi-turn coil is obtained by winding at least two strips; the winding is closely wound with the superconducting strip in each single-plate 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 multiple superconducting coils, the superconducting tape corresponding to each single superconducting coil 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 strip, and the directions of current passing through any two adjacent strips along the axial direction of the superconducting magnet are opposite.

8. The device according to any one of claims 5 to 7, characterized in that The material of the multi-turn coil or the at least two strips is a normal conductive material or a superconducting material.

9. The device according to any one of claims 4 to 7, characterized in that The alternating current is one current or a superposition of multiple currents selected from triangular wave, square wave, trapezoidal wave, sine wave and sinusoidal oscillation decay wave currents with symmetrical or asymmetrical positive and negative half waves.

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