A jointless closed loop high temperature superconducting coil and superconducting magnet

Abstract

This invention discloses a seamless closed-loop high-temperature superconducting coil and a superconducting magnet, comprising a coil frame and a four-panel coil. The coil frame includes two double-panel ring frames, each comprising an inner coil winding ring and an outer coil winding ring. The four-panel coil is wound using a seamless winding method: the superconducting tape is separated along a central dividing line, forming two unseparated ends (left and right) and two separated superconducting tapes; the right portions of the two separated superconducting tapes are wound onto the two outer coil winding rings in a first winding direction, and the left portions of the two separated superconducting tapes are wound onto the two inner coil winding rings in a second winding direction, the first winding direction being opposite to the second winding direction; one of the double-panel ring frames is rotated 180°, exchanging the positions of the inner and outer coils wound on it, resulting in the four-panel coil. This invention eliminates the need for coil joints, enabling zero-resistance closed-loop operation of the high-temperature superconducting magnet.

Description

Technical Field

[0001] This invention relates to the field of high-temperature superconducting magnet technology, and in particular to a seamless closed-loop high-temperature superconducting coil and a superconducting magnet. Background Technology

[0002] Second-generation high-temperature superconducting materials mainly include REBCO, composed of rare earth (RE), barium (Ba), copper (Cu), and oxygen (O) elements. These materials have high critical transition temperatures and high irreversible fields, and are widely used in the field of superconducting magnet technology. Superconducting magnets are powered by a power source, and their magnetic field stability is affected by the stability of the power supply. In magnetic resonance imaging (MRI) and nuclear magnetic resonance spectrometry (NMR) applications, the magnetic field stability must reach 0.1 ppm / h or higher, requiring the superconducting magnet to operate stably in a closed loop. Existing MRI equipment is mainly made of low-temperature superconducting wire (NbTi). NbTi superconducting wires can only operate in the liquid helium temperature range (4.2 K). Liquid helium is a rare resource, and my country's reserves are insufficient. Furthermore, NbTi superconducting wires have a low critical magnetic field; the critical field strength of an NbTi superconductor at 4.2 K is only 10.5 T. Therefore, it is difficult to manufacture high-field MRI equipment and further improve imaging quality. REBCO, as a second-generation high-temperature superconducting material, can operate in the inexpensive liquid nitrogen temperature range (77K) and has a high critical magnetic field, making it of great value in high-temperature and high-field applications.

[0003] Currently, REBCO tapes are not widely used in MRI and NMR equipment, primarily because they are layered ceramic materials, making the connection of superconducting layers extremely difficult, and the technology for fabricating joints is not yet mature. Whether it's brazed joints, silver diffusion bonded joints, or superconducting joints, all have a certain joint resistance, and the lower the resistance, the more complex the manufacturing process, making it impossible to achieve zero-resistance closed-loop operation of high-temperature superconducting magnets. Therefore, in superconducting magnet applications, especially during the winding of second-generation high-temperature superconducting magnets, it is crucial to minimize the number of superconducting joints, or even avoid them altogether. Summary of the Invention

[0004] The purpose of this invention is to provide a seamless closed-loop high-temperature superconducting coil and a superconducting magnet to solve the problems existing in the prior art, eliminate the coil joint, and achieve zero-resistance closed-loop operation of the high-temperature superconducting magnet.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] This invention provides a seamless closed-loop high-temperature superconducting coil, comprising a coil frame and a four-panel coil;

[0007] The coil frame includes two coaxially arranged double-circle frames, each comprising an inner coil winding ring and an outer coil winding ring, with the two inner coil winding rings arranged adjacent to each other and located between the two outer coil winding rings.

[0008] The four-coil coils are wound using a jointless winding method, which is as follows:

[0009] The superconducting tape is separated along a central dividing line, the length of which is less than the length of the superconducting tape, forming two unseparated ends on the left and right and two separated superconducting tapes;

[0010] The right portions of the two separated superconducting tapes are wound in a first winding direction onto the two outer coil winding rings to form two outer coils. The left portions of the two separated superconducting tapes are wound in a second winding direction onto the two inner coil winding rings to form two inner coils. The first winding direction is opposite to the second winding direction. During winding, the left portions of the two separated superconducting tapes pass through the gap between the right portions of the two separated superconducting tapes.

[0011] One of the double-circle coil skeletons is flipped 180°, and the inner and outer coils wound on it are swapped to obtain the four-circle coil.

[0012] Preferably, in the seamless winding method, when winding the two separated superconducting tapes, the left half of the two separated superconducting tapes is first wound onto the transition coil skeleton to form a transition coil. Then, the transition coil skeleton and the transition coil are rotated together with the coil skeleton to wind the right half of the two separated superconducting tapes to form two outer coils. During the winding of the outer coils, the transition coil skeleton and the transition coil pass through the gap between the right half of the two separated superconducting tapes.

[0013] Preferably, after the outer coil is wound, the transition coil is released from the transition coil skeleton, and then the released transition coil is rewound onto the two inner coil winding rings in the second winding direction to form two inner coils.

[0014] Preferably, each of the two separated superconducting tapes has a current lead solder joint at one end, and the two current lead solder joints are located at the same end of the two separated superconducting tapes. One end of one of the separated superconducting tapes is also provided with a superconducting thermal switch. The superconducting thermal switch and the current lead solder joint are located at the same end of the separated superconducting tape, and the superconducting thermal switch is disposed between the current lead solder joint and the non-separated end at the same end.

[0015] Preferably, the transition coil frame is a circular ring frame.

[0016] The present invention also provides a seamless closed-loop high-temperature superconducting magnet, comprising a magnet skeleton, a superconducting coil unit, and a cryogenic Dewar. The superconducting coil unit is sleeved on the magnet skeleton and comprises multiple seamless closed-loop high-temperature superconducting coils stacked coaxially. The seamless closed-loop high-temperature superconducting coils are connected in parallel. The cryogenic Dewar is used to encapsulate the magnet skeleton and the superconducting coil unit in a liquid nitrogen environment.

[0017] Preferably, the cryogenic Dewar includes a liquid nitrogen tank and a vacuum insulation chamber, the liquid nitrogen tank is disposed in the vacuum insulation chamber, a vacuum insulation layer is formed between the liquid nitrogen tank and the vacuum insulation chamber, and the magnet frame and the superconducting coil unit are encapsulated in the liquid nitrogen tank.

[0018] Preferably, two current lead terminals are provided outside the vacuum insulation layer. One end of each current lead terminal passes through the vacuum insulation layer and extends into the liquid nitrogen tank. The two current lead terminals are respectively connected to the two poles of the superconducting coil unit.

[0019] Preferably, the vacuum insulation chamber is provided with a liquid nitrogen valve connected to the liquid nitrogen tank, and the vacuum insulation chamber is also provided with a vacuum insulation evacuation valve.

[0020] Preferably, the vacuum insulation chamber is provided with a magnet room temperature hole that connects to the internal space of the superconducting coil unit.

[0021] The present invention achieves the following technical effects compared to the prior art:

[0022] The present invention provides a jointless closed-loop high-temperature superconducting coil and a superconducting magnet. The closed-loop superconducting tape is wound on the coil frame to obtain a four-coil coil by a jointless winding method. The coil joint is eliminated, and the loop resistance caused by the immature joint process is prevented. The high-temperature superconducting magnet can achieve zero-resistance closed-loop operation. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of the jointless closed-loop high-temperature superconducting coil provided by the present invention;

[0025] Figure 2This is a schematic diagram of the superconducting tape segmentation in this invention;

[0026] Figure 3 This is a schematic diagram of the outer coil wound around the transition coil frame and the coil frame in this invention;

[0027] Figure 4 This is a schematic diagram of the inner and outer coils being wound in this invention;

[0028] Figure 5 This is a schematic diagram of the structure of the superconducting coil unit in this invention;

[0029] Figure 6 This is a schematic diagram of the jointless closed-loop high-temperature superconducting magnet in this invention;

[0030] In the diagram: 1-coil frame, 2-four-panel coil, 3-double-panel ring frame, 301-inner coil winding ring, 302-outer coil winding ring, 4-superconducting tape, 5-center dividing line, 6-unseparated end, 7-separated superconducting tape, 8-outer coil, 9-inner coil, 10-gap, 11-transition coil frame, 12-transition coil, 13-current lead solder joint, 14-superconducting thermal switch, 15-superconducting coil unit, 16-liquid nitrogen tank, 17-vacuum insulation chamber, 18-current lead terminal, 19-liquid nitrogen valve, 20-vacuum insulation evacuation valve, 21-magnet room temperature hole, 22-twisted tape. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The purpose of this invention is to provide a seamless closed-loop high-temperature superconducting coil and a superconducting magnet to solve the problems existing in the prior art, eliminate the coil joint, and enable zero-resistance closed-loop operation of the high-temperature superconducting magnet.

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Example 1

[0035] like Figures 1-4 As shown, this embodiment provides a seamless closed-loop high-temperature superconducting coil, including a coil frame 1 and a four-panel coil 2;

[0036] The coil frame 1 includes two coaxially arranged double-circle frame 3. The double-circle frame 3 includes an inner coil winding ring portion 301 and an outer coil winding ring portion 302. The two inner coil winding ring portions 301 are arranged adjacent to each other and located between the two outer coil winding ring portions 302.

[0037] The four-panel coil 2 is wound using a jointless winding method, which is as follows:

[0038] The superconducting tape 4 is separated along the central dividing line 5. The length of the central dividing line 5 is less than the length of the superconducting tape 4, forming two unseparated ends 6 on the left and right and two separated superconducting tapes 7.

[0039] The right portions of the two separate superconducting tapes 7 are wound in the first winding direction onto the two outer coil winding rings 302 to form two outer coils 8. The left portions of the two separate superconducting tapes 7 are wound in the second winding direction onto the two inner coil winding rings 301 to form two inner coils 9. The first winding direction is opposite to the second winding direction. During winding, the left portions of the two separate superconducting tapes 7 pass through the gap 10 between the right portions of the two separate superconducting tapes 7.

[0040] Flip one of the double-circle ring skeletons 3 by 180°, so that the inner coil 9 and the outer coil 8 wrapped on it are swapped, resulting in a four-circle coil 2.

[0041] Two inner coils 9 and two outer coils 8 are wound onto two double-ring skeletons 3 of the coil skeleton 1 using a jointless winding method. Then, one of the double-ring skeletons 3 is rotated 180°, and the inner coils 9 and outer coils 8 are swapped to obtain a four-ring coil 2. This eliminates the need for coil joints and prevents loop resistance caused by immature joint technology. This enables zero-resistance closed-loop operation of the high-temperature superconducting magnet. Furthermore, because the inner coils 9 and outer coils 8 on one double-ring skeleton 3 are swapped, when the same end of the two separated superconducting strips 7 is energized, the magnetic fields generated by the coils on the two double-ring skeletons 3 can be prevented from canceling each other out. Instead, the magnetic fields generated by the coils on the two double-ring skeletons 3 are superimposed, ensuring the normal operation of the magnet. This is of great significance for the closed-loop operation of second-generation high-temperature superconducting magnets. After the double-ring skeleton 3 is rotated 180°, the inner coil 9 and outer coil 8 wound on the double-ring skeleton 3 will twist with the unseparated end 6 to form a twisted strip 22.

[0042] In this embodiment, when winding two separate superconducting tapes 7 in the jointless winding method, the left half of the two separate superconducting tapes 7 is first wound onto the transition coil skeleton 11 to form a transition coil 12. Then, the transition coil skeleton 11 and the transition coil 12 are rotated together with the coil skeleton 1 to wind the right half of the two separate superconducting tapes 7 to form two outer coils 8. During the winding of the outer coils 8, the transition coil skeleton 11 and the transition coil 12 pass through the gap 10 between the right half of the two separate superconducting tapes 7.

[0043] In this embodiment, after the outer coil 8 is wound, the transition coil 12 is released from the transition coil skeleton 11, and then the released transition coil 12 is rewound in the second winding direction onto the two inner coil winding ring portions 301 to form two inner coils 9.

[0044] In this embodiment, each of the two separated superconducting strips 7 has a current lead solder joint 13 at one end, and the two current lead solder joints 13 are located at the same end of the two separated superconducting strips 7. One end of one of the separated superconducting strips 7 is also provided with a superconducting thermal switch 14. The superconducting thermal switch 14 and the current lead solder joint 13 are located at the same end of the separated superconducting strip 7, and the superconducting thermal switch 14 is located between the current lead solder joint 13 and the unseparated end 6 at the same end. The two current lead solder joints 13 are connected to an external DC power supply system through two current leads, respectively. The excitation of the seamless closed-loop high-temperature superconducting coil is achieved by opening and closing the superconducting thermal switch 14. The critical transition temperature of the second-generation high-temperature superconducting material is 93K, and it is in a superconducting state at liquid nitrogen temperature (77K). The superconducting magnet requires the superconducting material to operate in the superconducting state, that is, the operating temperature is below the critical transition temperature. The superconducting thermal switch 14 heats a portion of the strip (approximately 5 cm in length) to above the critical transition temperature using a thin-film heater, causing it to lose its superconductivity. Compared to the superconducting state, the resistance of the lost-superconducting portion is equivalent to infinite, at which point the superconducting switch is in an open-circuit state. When the thin-film heater stops heating, the superconducting thermal switch 14 returns to the conducting state. By controlling the opening and closing of the superconducting thermal switch 14, the superconducting magnet can be energized.

[0045] In this embodiment, the transition coil frame 11 is a circular ring frame.

[0046] Example 2

[0047] like Figures 5-6As shown, this embodiment provides a seamless closed-loop high-temperature superconducting magnet, including a magnet frame, a superconducting coil unit 15, and a cryogenic Dewar. The superconducting coil unit 15 is sleeved on the magnet frame and includes multiple seamless closed-loop high-temperature superconducting coils as described in Embodiment 1, stacked coaxially. These seamless closed-loop high-temperature superconducting coils are connected in parallel. The cryogenic Dewar is used to encapsulate the magnet frame and the superconducting coil unit 15 in a liquid nitrogen environment. In each seamless closed-loop high-temperature superconducting coil, the solder joints 13 of the current leads on the same side are connected to the first current lead, and the solder joints 13 of the current leads on the other side are connected to the second current lead. The first and second current leads are connected to an external power source, thus achieving parallel connection of the seamless closed-loop high-temperature superconducting coils. The external power source excites each seamless closed-loop high-temperature superconducting coil.

[0048] In this embodiment, the cryogenic Dewar includes a liquid nitrogen tank 16 and a vacuum insulation chamber 17. The liquid nitrogen tank 16 is disposed inside the vacuum insulation chamber 17, and a vacuum insulation layer is formed between the liquid nitrogen tank 16 and the vacuum insulation chamber 17. The magnet frame and the superconducting coil unit 15 are encapsulated inside the liquid nitrogen tank 16. Liquid nitrogen is placed in the liquid nitrogen tank 16, and the cryogenic environment required by the superconductor is maintained by liquid nitrogen. The vacuum insulation layer reduces heat leakage.

[0049] In this embodiment, two current lead terminals 18 are provided outside the vacuum insulation chamber 17. One end of the current lead terminal 18 passes through the vacuum insulation layer and extends into the liquid nitrogen tank 16. The two current lead terminals 18 are respectively connected to the two poles of the superconducting coil unit 15. The first current lead and the second current lead serve as the two poles of the superconducting coil unit 15, and the two current lead terminals 18 are respectively connected to the first current lead and the second current lead.

[0050] In this embodiment, the vacuum insulation chamber 17 is equipped with a liquid nitrogen valve 19 connected to the liquid nitrogen tank 16, and a vacuum insulation evacuation valve 20 is also provided on the vacuum insulation chamber 17. The liquid nitrogen valve 19 is used as a safety valve, and the vacuum insulation evacuation valve 20 is used for creating a vacuum environment.

[0051] In this embodiment, the vacuum insulation chamber 17 is provided with a magnet room temperature hole 21 that connects to the internal space of the superconducting coil unit 15, and related magnet tests can be carried out through the magnet room temperature hole 21.

[0052] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A jointless closed loop high temperature superconducting coil, characterized by: The coil framework comprises two double-biscuit toroidal frameworks arranged coaxially and side by side, and the double-biscuit toroidal framework comprises inner coil winding toroidal sections and outer coil winding toroidal sections, and the two inner coil winding toroidal sections are arranged adjacently and located between the two outer coil winding toroidal sections. The four-biscuit coil is wound by a jointless winding method, and the jointless winding method is as follows: The superconducting tapes are separated along a center separation line, the length of the center separation line is less than the length of the superconducting tapes, and left and right non-separated end portions and two separated superconducting tapes are formed. The right portions of the two separated superconducting tapes are wound on the two outer coil winding toroidal sections in a first winding direction respectively, and two outer coils are formed, and the left portions of the two separated superconducting tapes are wound on the two inner coil winding toroidal sections in a second winding direction respectively, and two inner coils are formed, the first winding direction is opposite to the second winding direction, and the left portions of the two separated superconducting tapes pass through the gap between the right portions of the two separated superconducting tapes during winding. One of the double-biscuit toroidal frameworks is turned over by 180°, and the inner coil and the outer coil wound thereon are exchanged in position, and the four-biscuit coil is obtained. In the jointless winding method, the left half of the two separated superconducting tapes is wound on a transition coil framework as a whole to form a transition coil, and then the transition coil framework and the transition coil are rotated with the coil framework to wind the right half of the two separated superconducting tapes to form the two outer coils, and the transition coil framework and the transition coil pass through the gap between the right half of the two separated superconducting tapes during winding of the outer coils.

2. The jointless closed loop high temperature superconducting coil of claim 1, wherein: After the winding of the outer coils is completed, the transition coil is released from the transition coil framework, and then the released transition coil is wound on the two inner coil winding toroidal sections in the second winding direction to form the two inner coils.

3. The jointless closed loop high temperature superconducting coil of claim 2, wherein: One end of each of the two separated superconducting tapes is provided with a current lead solder joint, and the two current lead solder joints are located at the same end of the two separated superconducting tapes, and one end of one of the two separated superconducting tapes is further provided with a superconducting thermal switch, the superconducting thermal switch and the current lead solder joint are located at the same end of the separated superconducting tape, and the superconducting thermal switch is arranged between the current lead solder joint and the non-separated end portion at the same end.

4. The jointless closed loop high temperature superconducting coil of claim 1, wherein: The transition coil framework is a toroidal framework.

5. The jointless closed loop high temperature superconducting coil of claim 2, wherein: The magnet framework, the superconducting coil unit and the low-temperature dewar are provided, the superconducting coil unit is sleeved on the magnet framework, the superconducting coil unit comprises a plurality of jointless closed loop high temperature superconducting coils according to any one of claims 1-5 arranged coaxially and sequentially, each jointless closed loop high temperature superconducting coil is connected in parallel, and the low-temperature dewar is used to package the magnet framework and the superconducting coil unit in a liquid nitrogen environment.

6. A jointless closed loop high temperature superconducting magnet characterized by: ​ 7. The jointless closed loop high temperature superconducting magnet of claim 6, wherein: The low-temperature dewar comprises a liquid nitrogen tank and a vacuum insulation chamber, the liquid nitrogen tank is arranged in the vacuum insulation chamber, a vacuum insulation layer is formed between the liquid nitrogen tank and the vacuum insulation chamber, and the magnet skeleton and the superconducting coil unit are packaged in the liquid nitrogen tank.

8. The jointless closed loop high temperature superconducting magnet of claim 7, wherein: Two current lead terminals are arranged outside the vacuum insulation chamber, one end of each of the current lead terminals penetrates the vacuum insulation layer and extends into the liquid nitrogen tank, and the two current lead terminals are connected to two poles of the superconducting coil unit respectively.

9. The jointless closed loop high temperature superconducting magnet of claim 7, wherein: A liquid nitrogen valve connected to the liquid nitrogen tank is arranged on the vacuum insulation chamber, and a vacuum insulation air extraction valve is also arranged on the vacuum insulation chamber.

10. The jointless closed loop high temperature superconducting magnet of claim 7, wherein: A magnet room temperature hole communicating with the internal space of the superconducting coil unit is arranged on the vacuum insulation chamber.

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