Nitrogen fixation cooling type high-temperature superconducting magnet

Abstract

The invention relates to the technical field of high-temperature superconducting magnets, and discloses a nitrogen fixation cooling type high-temperature superconducting magnet which comprises an outer Dewar, a nitrogen fixation cavity, a superconducting coil, an MgB2 superconducting switch and an excitation power source, and the nitrogen fixation cavity, the superconducting coil, the MgB2 superconducting switch and the excitation power source are arranged in the outer Dewar. The interior of the outer Dewar is a vacuum environment, the nitrogen fixation cavity is connected with the superconducting coil and the MgB2 superconducting switch, the nitrogen fixation cavity is cooled through a refrigerator so as to refrigerate the superconducting coil and the MgB2 superconducting switch, and the superconducting coil is connected with the MgB2 superconducting switch and the excitation power supply in parallel. Therefore, other parts do not need to be added, the winding difficulty of the superconducting constant-current switch can be reduced, and the change between the superconducting state and the natural state can be realized by utilizing the characteristics of the MgB2 superconducting material in the cooling process, so that the control reliability of the superconducting constant-current switch is improved.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature superconducting magnets, and in particular to a nitrogen-fixed cooling type high-temperature superconducting magnet. Background Art

[0002] Superconducting magnets have the advantages of zero resistance and large current. After excitation, superconducting magnets form a closed loop with nearly zero loss with constant current switches, which can maintain a highly stable strong magnetic field for a long time. Currently, they are widely used in fields such as nuclear magnetic resonance spectrometers and nuclear magnetic resonance imaging, but the mature application fields are basically in the field of low-temperature superconducting magnets.

[0003] There are three critical indicators for high-temperature superconducting tapes, namely critical current, critical temperature and critical magnetic field. When any of the three indicators does not meet the requirements of the superconducting state, the high-temperature superconducting tape will recover from the superconducting state to the resistive state. High-temperature superconducting switches use the zero resistance characteristics of superconducting wires, use a certain length of superconducting tape to wind into a non-inductive coil, and use the mutual conversion between the superconducting state and the normal state of the superconducting tape to realize the closing and opening of the switch in the closed loop formed with the superconducting magnet. At present, superconducting switches in the field of high-temperature superconducting magnets can be divided into thermal control superconducting switches, flow control superconducting switches and magnetic control superconducting switches according to the different ways of their conversion to recovery resistance. The key point is that all current high-temperature superconducting switches use YBCO high-temperature superconducting tapes and Bi-based high-temperature superconducting tapes, which can reach the superconducting state at a liquid nitrogen temperature of 77K. The conversion between the normal state and the superconducting state is achieved by thermal control, magnetic control and other methods.

[0004] A magnetically controlled superconducting switch requires a magnetically controlled coil. First, a power supply is used to pass current through the magnetically controlled coil. The magnetic field generated by the magnetically controlled coil is used to make the spatial magnetic field exceed the critical magnetic field of the superconducting tape, thereby allowing the superconducting switch to switch between the superconducting state and the normal resistance state.

[0005] A thermally controlled superconducting switch requires the addition of a heating wire, which is powered by an external small constant current source. When the heat generated by the heating wire makes the temperature of the superconducting tape higher than the critical temperature for maintaining the superconducting state, the superconducting switch realizes the conversion between the superconducting state and the normal resistance state.

[0006] The flow-controlled superconducting switch requires the addition of a trigger switch, and discharges to the superconducting switch through an external trigger source. When the current passing through the superconducting switch is greater than its critical current, the superconducting switch realizes the conversion between the superconducting state and the normal resistance state.

[0007] It can be seen that the current mainstream superconducting switches all use external devices to enable the superconducting switches to achieve conversion between the superconducting state and the normal resistance state. The three types of superconducting switches respectively utilize the three critical indicators of the superconducting tape (critical magnetic field, critical temperature and critical current). Among them, the magnetically controlled switch uses a magnetically controlled coil to make the magnetic field exceed the critical magnetic field of the superconducting switch, the thermally controlled switch uses a heating wire to make the magnetic field exceed the critical temperature of the superconducting switch, and the current-controlled switch triggers the power supply to make the current exceed the critical current of the superconducting switch.

[0008] However, all three types of switches use external devices to change the surrounding physical environment to achieve the conversion of the superconducting state. This method increases the complexity of the manufacturing of the superconducting switch itself, and there is also a certain degree of difficulty in controlling the change of physical quantities, and its precision and accuracy are even more difficult. Summary of the invention

[0009] The invention provides a nitrogen-cooled high-temperature superconducting magnet, which can solve the technical problems in the prior art.

[0010] The present invention provides a nitrogen-fixing cooling type high-temperature superconducting magnet, wherein the superconducting magnet comprises an outer dewar, a nitrogen-fixing chamber, a superconducting coil, a MgB2 superconducting switch and an excitation power supply, wherein the nitrogen-fixing chamber, the superconducting coil, the MgB2 superconducting switch and the excitation power supply are arranged in the outer dewar, the outer dewar is a vacuum environment, the nitrogen-fixing chamber is connected with the superconducting coil and the MgB2 superconducting switch, the nitrogen-fixing chamber is cooled by a refrigerator to cool the superconducting coil and the MgB2 superconducting switch, and the superconducting coil is connected in parallel with the MgB2 superconducting switch and the excitation power supply.

[0011] Preferably, the superconducting magnet further comprises a first cooling belt and a second cooling belt, the nitrogen fixing chamber is connected to the refrigerator via the first cooling belt, and the superconducting coil is connected to the nitrogen fixing chamber via the second cooling belt.

[0012] Preferably, the first cooling belt is made of a metal braided belt.

[0013] Preferably, the second cooling belt is made of a metal braided belt.

[0014] Preferably, the metal is copper.

[0015] Preferably, the superconducting coil is wound with a high-temperature superconducting tape.

[0016] Preferably, the superconducting magnet further comprises a cooling layer, and the cooling layer is arranged outside the superconducting coil.

[0017] Preferably, the cooling conduction layer is made of copper wire.

[0018] Through the above technical scheme, a superconducting constant current switch using MgB2 to wind a high-temperature superconducting coil does not need to add other components, which can reduce the difficulty of winding the superconducting constant current switch, and can use the characteristics of the MgB2 superconducting material itself during the cooling process to achieve the transition between the superconducting state and the natural state, thereby increasing the reliability of the superconducting constant current switch control. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 A schematic diagram showing the principle of a nitrogen-cooled high-temperature superconducting magnet is shown. DETAILED DESCRIPTION

[0021] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0023] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0024] Figure 1 A schematic diagram showing the principle of a nitrogen-cooled high-temperature superconducting magnet is shown.

[0025] like Figure 1 As shown, an embodiment of the present invention provides a nitrogen-fixing cooled high-temperature superconducting magnet, wherein the superconducting magnet comprises an outer dewar, a nitrogen-fixing chamber, a superconducting coil (high-temperature superconducting coil) 1, a MgB2 superconducting switch (high-temperature superconducting constant current switch PCS) 2 and an excitation power supply 3, wherein the nitrogen-fixing chamber, the superconducting coil 1, the MgB2 superconducting switch 2 and the excitation power supply 3 are arranged in the outer dewar, and the outer dewar is a vacuum environment, the nitrogen-fixing chamber is connected to the superconducting coil 1 and the MgB2 superconducting switch 2, the nitrogen-fixing chamber is cooled by a refrigerator to cool the superconducting coil 1 and the MgB2 superconducting switch 2, and the superconducting coil 1 is connected in parallel with the MgB2 superconducting switch 2 and the excitation power supply 3.

[0026] Among them, the non-inductive coil wound by MgB2 is used as the MgB2 superconducting switch, and no other components are added. The MgB2 superconducting switch plays the role of a switch in the closed loop of the high-temperature superconducting magnet. When its temperature rises, its resistance value increases, and it plays the role of a switch disconnection. When its temperature decreases, it plays the role of a switch closing.

[0027] Through the above technical scheme, a superconducting constant current switch using MgB2 to wind a high-temperature superconducting coil does not need to add other components, which can reduce the difficulty of winding the superconducting constant current switch, and can use the characteristics of the MgB2 superconducting material itself during the cooling process to achieve the transition between the superconducting state and the natural state, thereby increasing the reliability of the superconducting constant current switch control.

[0028] Among them, the cold head of the refrigerator is a component that outputs cold energy from the refrigerator. During actual refrigeration, the cooling of the nitrogen-fixing chamber is achieved by connecting it to the nitrogen-fixing chamber. A refrigerator is a device that converts electrical energy into cold energy. The nitrogen-fixing chamber is used to store liquid nitrogen. The temperature of liquid nitrogen is 77K. When the cold head of the refrigerator is used to cool it to below 77K, the liquid nitrogen will solidify to form solid nitrogen. Under the cooling of the refrigerator, the temperature of the solid nitrogen can be continuously reduced, for example, to 20K. After the solid nitrogen is formed, the cold energy can be stored similar to ice cubes, and then the solid nitrogen after cooling in the nitrogen-fixing chamber can be used as a cold source to continuously output cold energy to the superconducting coil. The vacuum environment of the external Dewar can greatly reduce the convective heat dissipation of the entire superconducting magnet system.

[0029] In the present invention, although the above description uses a refrigerator to cool the nitrogen fixing chamber, the present invention is not limited thereto, and other refrigeration systems such as a cold helium circulation system may also be used to cool the nitrogen fixing chamber.

[0030] According to one embodiment of the present invention, the superconducting magnet further includes a first cooling belt and a second cooling belt, the nitrogen fixing chamber is connected to the refrigerator via the first cooling belt, and the superconducting coil 1 is connected to the nitrogen fixing chamber via the second cooling belt.

[0031] That is, cold energy can be transferred between the nitrogen fixing chamber and the refrigerator, and between the nitrogen fixing chamber and the superconducting coil through the corresponding cooling belts.

[0032] Therefore, using a refrigerator to cool the nitrogen fixing chamber can further reduce the temperature of nitrogen fixing. After the refrigerator is separated from the superconducting magnet, the low temperature state of the superconducting coil can be maintained for a longer time and the superconducting magnet can be better used in a dynamic environment, reducing the weight increase and reliability reduction of the refrigerator in a moving environment.

[0033] According to an embodiment of the present invention, the first cooling belt is made of a metal braided belt.

[0034] That is, the refrigerator and the nitrogen fixing chamber are connected by the first cold conduction belt to achieve cold energy transfer between the refrigerator and the nitrogen fixing chamber.

[0035] According to an embodiment of the present invention, the second cooling belt is made of a metal braided belt.

[0036] That is, the nitrogen fixing chamber and the superconducting coil are connected by the second cold conducting belt to realize the cold transfer between the nitrogen fixing chamber and the superconducting coil.

[0037] According to an embodiment of the present invention, the metal is copper.

[0038] For example, the first cooling belt and the second cooling belt may be made of a soft copper braided belt.

[0039] Those skilled in the art should understand that the above description of the cooling belt material is merely exemplary and is not intended to limit the present invention.

[0040] According to an embodiment of the present invention, the superconducting coil 1 is wound with a high-temperature superconducting tape.

[0041] Among them, high-temperature superconducting tapes can reach a superconducting state at a liquid nitrogen temperature of 77K, so that large currents can pass through them losslessly to generate a very strong magnetic field.

[0042] According to an embodiment of the present invention, the superconducting magnet further includes a cooling layer, and the cooling layer is arranged outside the superconducting coil 1 .

[0043] By setting up the cooling layer, the cooling capacity of the refrigerator and the nitrogen fixing chamber can be fully utilized, and the cooling of the superconducting coil is more uniform, which can effectively prevent the superconducting coil from being quenched due to the increase of local temperature.

[0044] According to an embodiment of the present invention, the cooling layer is made of copper wire.

[0045] For example, floc-like thin copper wires can be used to wrap the outside of the superconducting coil to form a cooling layer. At the same time, the thin copper wires are connected to the cooling belt connected to the nitrogen solidifying chamber to achieve cold transfer between the nitrogen solidifying chamber and the superconducting coil. By wrapping the superconducting coil with very dense thin copper wires, uniform cooling of the superconducting coil can be achieved.

[0046] The nitrogen-cooled high-temperature superconducting magnet of the present invention is described below with reference to examples.

[0047] First, a refrigerator is used to cool the superconducting coil 1 and the MgB2 superconducting switch 2. Since the high-temperature superconducting magnet selected is a solid nitrogen refrigeration method, the superconducting coil 1 and the MgB2 superconducting switch 2 can both reach a temperature below 77K.

[0048] Assuming that the temperature reaches 45K, the excitation power supply 3 can be used to excite the superconducting coil 1. Since the MgB2 superconducting switch 2 can reach the superconducting state only when the temperature is lower than 39K, it has a certain resistance at 45K, and the superconducting coil 1 is already in the superconducting state at this time, so the current will not pass through the MgB2 superconducting switch 2 at this time. Under this condition, the current is directly increased to the working current I, the current passing through the superconducting coil 1 is I, and the current passing through the MgB2 superconducting switch 2 is 0.

[0049] When the output current of the excitation power supply 3 reaches the working current I, the refrigerator continues to cool the superconducting coil 1 and the MgB2 superconducting switch 2. When the temperature of the superconducting coil 1 and the MgB2 superconducting switch 2 drops below 39K, the MgB2 superconducting switch 2 also reaches the superconducting state, and the current passing through the MgB2 superconducting switch 2 is also I.

[0050] At this time, the superconducting coil 1 and the MgB2 superconducting switch 2 form a closed loop, which can reduce the output current of the excitation power supply 3 to 0. At this point, the high-temperature superconducting magnet has completed the excitation and can be separated from the excitation power supply to achieve closed-loop operation.

[0051] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0052] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0053] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A nitrogen-cooled high-temperature superconducting magnet, characterized in that: The superconducting magnet comprises an outer dewar, a nitrogen-fixing chamber, a superconducting coil (1), a MgB2 superconducting switch (2) and an excitation power supply (3); the nitrogen-fixing chamber, the superconducting coil (1), the MgB2 superconducting switch (2) and the excitation power supply (3) are arranged in the outer dewar; the outer dewar is a vacuum environment; the nitrogen-fixing chamber is connected to the superconducting coil (1) and the MgB2 superconducting switch (2); the nitrogen-fixing chamber is cooled by a refrigerator so as to cool the superconducting coil (1) and the MgB2 superconducting switch (2); the superconducting coil (1) is connected in parallel to the MgB2 superconducting switch (2) and the excitation power supply (3).

2. The superconducting magnet according to claim 1, characterized in that The superconducting magnet further comprises a first cooling belt and a second cooling belt, the nitrogen fixing chamber is connected to the refrigerator via the first cooling belt, and the superconducting coil (1) is connected to the nitrogen fixing chamber via the second cooling belt.

3. The superconducting magnet according to claim 2, characterized in that: The first cooling belt is made of a metal braided belt.

4. The superconducting magnet according to claim 3, characterized in that: The second cooling belt is made of a metal braided belt.

5. The superconducting magnet according to claim 4, characterized in that: The metal is copper.

6. The superconducting magnet according to claim 4, characterized in that: The superconducting coil (1) is wound with a high-temperature superconducting tape.

7. The superconducting magnet according to claim 6, characterized in that The superconducting magnet further comprises a cooling layer, wherein the cooling layer is arranged outside the superconducting coil (1).

8. The superconducting magnet according to claim 6, characterized in that: The cooling layer is made of copper wire.

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