YBCO coil series joint and preparation method thereof

Abstract

The invention provides a YBCO coil series joint and a preparation method thereof. The method comprises a first superconductive stacked cable (10), a second superconductive stacked cable (20) and a superconductive tape (30), the first superconductive stacked cable (10) and the second superconductive stacked cable (20) are in lap joint in the length direction and are bonded through a conductive solder (40). The side face of the lap joint area of the first superconductive stacked cable (10) and the second superconductive stacked cable (20) is attached to the superconductive strip (30) and bonded through the conductive solder (40). The resistivity of the binding face, facing the lap joint area, of the superconducting strip (30) is smaller than the resistivity of Hastelloy layers in the first superconducting stacked cable (10) and the second superconducting stacked cable (20), the resistance of a series connector of the YBCO coil can be reduced, local heating of the connector is avoided, the thermal stability of the connector is improved, and safe operation of the connector is guaranteed.

Description

Technical Field

[0001] This application relates to the field of high-temperature superconducting applications, and particularly to a YBCO coil series connection joint and a preparation method thereof. Background Art

[0002] In high-field applications, superconducting magnets need to achieve a specific magnetic field distribution through the series or parallel connection of multiple YBCO (Yttrium Barium Copper Oxide) coils. Superconducting joints are required to connect between YBCO coils to maintain current consistency.

[0003] Currently, in the prior art, the series connection joints of YBCO coils generally adopt direct welding or riveting processes.

[0004] However, the existing series connection joints have poor thermal stability and are prone to forming local hot spots, which affect the safe operation of the joints. Summary of the Invention

[0005] This application provides a YBCO coil series connection joint and a preparation method thereof to solve the technical problem that the existing series connection joints have poor thermal stability, are prone to forming local hot spots, and affect the safe operation of the joints.

[0006] In a first aspect, this application provides a YBCO coil series connection joint, including: a first superconducting stacked cable (10), a second superconducting stacked cable (20), and a superconducting tape (30);

[0007] The first superconducting stacked cable (10) is led out from a first yttrium barium copper oxide YBCO coil, and the second superconducting stacked cable (20) is led out from a second YBCO coil;

[0008] The first superconducting stacked cable (10) and the second superconducting stacked cable (20) are overlapped along the length direction and bonded by a conductive solder (40);

[0009] The side surface of the overlapping area of the first superconducting stacked cable (10) and the second superconducting stacked cable (20) is attached to the superconducting tape (30) and bonded by the conductive solder (40);

[0010] The resistivity of the bonding surface of the superconducting tape (30) facing the overlapping area is less than the resistivity of the Hastelloy layer in the first superconducting stacked cable (10) and the second superconducting stacked cable (20).

[0011] In a possible implementation manner, the superconducting tape (30) is a Bi-based tape or a YBCO superconducting tape.

[0012] In a possible implementation manner, the conductive solder (40) is a solder sheet or solder paste.

[0013] In a possible implementation, the overlapping area of the first superconducting stacked cable (10) and the second superconducting stacked cable (20) has four sides; the four sides of the overlapping area are attached to the superconducting tape (30) and bonded by the conductive solder (40).

[0014] In a possible implementation, the widths of the first superconducting stacked cable (10), the second superconducting stacked cable (20), and the superconducting tape (30) are the same.

[0015] In a possible implementation, the overlapping area of the first superconducting stacked cable (10) and the second superconducting stacked cable (20) has four sides; the upper surface of the overlapping area is bonded to the filling block (50); the lower surface of the overlapping area is bonded to the filling block (50); wherein, the filling block (50) is the conductive solder (40) and the YBCO superconducting tape placed alternately; the height of the overlapping area after being bonded to the filling block (50) is the same as the width of the superconducting tape (30); the four sides of the overlapping area after being bonded to the filling block (50) are attached to the superconducting tape (30) and bonded by the conductive solder (40).

[0016] In a possible implementation, under the condition of liquid nitrogen temperature of 77K, the resistance of the YBCO coil series joint is less than 50 nΩ.

[0017] In a second aspect, the present application provides a preparation method for the YBCO coil series joint as described in the first aspect, including:

[0018] S1. Perform critical current tests on the pre-prepared first superconducting stacked cable, second superconducting stacked cable, and superconducting tape, wherein the first superconducting stacked cable is led out from the first YBCO coil, and the second superconducting stacked cable is led out from the second YBCO coil;

[0019] S2. After the critical current test is passed, align and overlap the first superconducting stacked cable and the second superconducting stacked cable along the length direction by a preset length, and bond them with a conductive solder;

[0020] S3. After grinding and cleaning the sides of the overlapping area of the first superconducting stacked cable and the second superconducting stacked cable, attach the superconducting tape to the sides of the overlapping area, and place the conductive solder on the contact surface between the overlapping area and the superconducting tape;

[0021] S4. Use a welding tooling to press the overlapping area processed in step S3 and heat it until the conductive solder melts;

[0022] S5. After the heated overlapping area is naturally cooled, remove the tooling to obtain the YBCO coil series joint.

[0023] In a possible implementation, the overlapping area of the first superconducting stacked cable and the second superconducting stacked cable has four sides; correspondingly, after step S2, the method further includes: S6. Conduct a critical current test on the pre-prepared YBCO superconducting tape and ensure that the critical current test passes; S7. If the side height of the overlapping area is less than the width of the superconducting tape, alternately place conductive solder and YBCO superconducting tape above and below the overlapping area to form a filling block, so that the side height of the overlapping area is equal to the width of the superconducting tape.

[0024] In a possible implementation, before alternately placing conductive solder and YBCO superconducting tape above and below the overlapping area, the method further includes: cleaning the surface of the YBCO superconducting tape with ethanol.

[0025] The YBCO coil series joint and its preparation method provided by the present application overlap the first superconducting stacked cable 10 and the second superconducting stacked cable 20, and a superconducting tape 30 is attached to the side of the overlapping area. The resistivity of the bonding surface of the superconducting tape 30 facing the overlapping area is less than the resistivity of the Hastelloy layer in the first superconducting stacked cable 10 and the second superconducting stacked cable 20. In the superconducting state, the resistance of the overlapping area between the first superconducting stacked cable 10 and the second superconducting stacked cable 20 is zero, and the current is evenly distributed throughout the overlapping area of the first superconducting stacked cable 10 and the second superconducting stacked cable 20, and there will be no skin effect in which the current accumulates on the surface of the joint due to resistance; when the current reaches the current-carrying upper limit, that is, at the moment of quench, the first superconducting stacked cable 10 and the second superconducting stacked cable 20 have resistance and a skin effect occurs. The current transfers from the side of the overlapping area of the first superconducting stacked cable 10 and the second superconducting stacked cable 20 to the superconducting tape 30 with low resistance, which can reduce the resistance of the YBCO coil series joint, avoid local heating of the joint, improve the thermal stability of the joint, and ensure the safe operation of the joint. Description of the Drawings

[0026] The drawings here are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0027] Figure 1 Structural schematic of the YBCO coil series joint provided by the embodiment of the present application Figure 1 ;

[0028] Figure 2 Structural schematic of the YBCO coil series joint provided by the embodiment of the present application Figure 2 ;

[0029] Figure 3 Flow schematic of the preparation method of the YBCO coil series joint provided by an embodiment of the present application.

[0030] Through the above-mentioned drawings, specific embodiments of the present application have been shown, and will be described in more detail hereinafter. These drawings and the written description are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by reference to specific embodiments.

[0031] Among them, the above-mentioned drawings include the following reference numerals:

[0032] 10 - First superconducting stacked cable; 20 - Second superconducting stacked cable; 30 - Superconducting tape; 40 - Conductive solder; 50 - Filling block. Detailed implementation manners

[0033] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0034] Currently, the series joints of YBCO coils generally adopt direct welding or riveting processes. The welding resistance and structural defects of the joints will inevitably cause local heating and generate heat loss, thereby affecting the safe operation of the joints.

[0035] The series joint of the YBCO coil provided by the present application is formed by overlapping the first superconducting stacked cable 10 and the second superconducting stacked cable 20, and the superconducting tape 30 is attached to the side surface of the overlapping area. The resistivity of the attachment surface of the superconducting tape 30 facing the overlapping area is less than the resistivity of the Hastelloy layer in the first superconducting stacked cable 10 and the second superconducting stacked cable 20, which can reduce the resistance of the series joint of the YBCO coil, improve the thermal stability of the series joint, and provide guarantee for the safe operation of the joint.

[0036] The following uses specific embodiments to detail the technical solutions of the present application and how the technical solutions of the present application solve the above technical problems. These several specific embodiments below can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below with reference to the drawings.

[0037] See Figure 1, an embodiment of the present application provides a YBCO coil series joint, including: a first superconducting stacked cable 10, a second superconducting stacked cable 20, and a superconducting tape 30; the first superconducting stacked cable 10 is led out from a first yttrium barium copper oxide (YBCO) coil, and the second superconducting stacked cable 20 is led out from a second YBCO coil; the first superconducting stacked cable 10 and the second superconducting stacked cable 20 are overlapped along the length direction and bonded by a conductive solder 40; the side surface of the overlapping area of the first superconducting stacked cable 10 and the second superconducting stacked cable 20 is attached to the superconducting tape 30 and bonded by the conductive solder 40; the resistivity of the bonding surface of the superconducting tape 30 facing the overlapping area is less than the resistivity of the Hastelloy layer in the first superconducting stacked cable 10 and the second superconducting stacked cable 20.

[0038] Among them, the superconducting tape 30 can be a composite superconducting tape or a non-composite superconducting tape; if the superconducting tape 30 is a composite superconducting tape, the bonding surface of the superconducting tape 30 facing the overlapping area is the superconducting surface of the superconducting tape 30.

[0039] Among them, both the first YBCO coil and the second YBCO coil can be YBCO double-pancake coils.

[0040] Among them, the first YBCO coil, the second YBCO coil, the first superconducting stacked cable 10, and the second superconducting stacked cable 20 are all composed of YBCO superconducting tape and the conductive solder 40.

[0041] Among them, the conductive solder 40 can be a solder sheet or solder paste.

[0042] Among them, the overlapping area of the first superconducting stacked cable 10 and the second superconducting stacked cable 20 is a multi-layer composite structure: superconducting layer - tin layer - superconducting layer - Hastelloy layer - tin layer - superconducting layer.

[0043] Among them, the widths of the first superconducting stacked cable 10, the second superconducting stacked cable 20, and the superconducting tape 30 are the same. Among them, under the condition of liquid nitrogen temperature of 77K, the resistance of the YBCO coil series joint is less than 50 nΩ.

[0044] In this embodiment, the side surface of the overlapping area between the first superconducting stacked cable 10 and the second superconducting stacked cable 20 is attached to the superconducting tape 30, and the resistivity of the bonding surface of the superconducting tape 30 facing the overlapping area is less than the resistivity of the Hastelloy layer in the first superconducting stacked cable 10 and the second superconducting stacked cable 20; in the superconducting state, the resistance of the overlapping area between the first superconducting stacked cable 10 and the second superconducting stacked cable 20 is zero, and the current is evenly distributed throughout the overlapping area between the first superconducting stacked cable 10 and the second superconducting stacked cable 20, and the skin effect of the current gathering towards the joint surface due to resistance will not occur; when the current reaches the current-carrying upper limit, that is, at the moment of quench, the first superconducting stacked cable 10 and the second superconducting stacked cable 20 have resistance, and the skin effect appears. The current transfers from the side surface of the overlapping area between the first superconducting stacked cable 10 and the second superconducting stacked cable 20 to the superconducting tape 30 with low resistance, which can reduce the resistance of the YBCO coil series joint, avoid local heating of the joint, improve the thermal stability of the joint, and ensure the safe operation of the joint.

[0045] In one embodiment of the present application, the superconducting tape 30 can be a Bi-based tape or a YBCO superconducting tape.

[0046] In this embodiment, the superconducting tape 30 is selected as a Bi tape. The Bi-based tape has rigidity and flexibility, which can improve the toughness and mechanical strength of the YBCO coil series joint; the Bi-based tape has good stability in a magnetic field, which can improve the stability of the joint in a strong magnetic field; the cost of the Bi-based tape is low, which can reduce the cost of the joint.

[0047] See Figure 1 , in one embodiment of the present application, the overlapping area between the first superconducting stacked cable 10 and the second superconducting stacked cable 20 has four side surfaces; the four side surfaces of the overlapping area are attached to the superconducting tape 30 and bonded by a conductive solder 40.

[0048] In this embodiment, when the current reaches the current-carrying upper limit, that is, at the moment of quench, the first superconducting stacked cable 10 and the second superconducting stacked cable 20 have resistance, and the skin effect appears. The current transfers from the side surface of the overlapping area between the first superconducting stacked cable 10 and the second superconducting stacked cable 20 to the superconducting tape 30 with low resistance, which can reduce the resistance of the YBCO coil series joint, avoid local heating of the joint, improve the thermal stability of the joint, and ensure the safe operation of the joint.

[0049] See Figure 2, in an embodiment of the present application, the overlapping area between the first superconducting stacked cable 10 and the second superconducting stacked cable 20 has four sides; the upper surface of the overlapping area is bonded to the filling block 50; the lower surface of the overlapping area is bonded to the filling block 50; wherein, the filling block 50 is composed of alternately arranged conductive solder 40 and YBCO superconducting tapes; the height of the overlapping area after being bonded to the filling block 50 is the same as the width of the superconducting tape 30; the four sides of the overlapping area after being bonded to the filling block 50 are in contact with the superconducting tape 30 and are bonded through the conductive solder 40.

[0050] In this embodiment, the upper surface of the overlapping area is bonded to the filling block 50; the lower surface of the overlapping area is bonded to the filling block 50; the filling block 50 is composed of alternately arranged conductive solder 40 and YBCO superconducting tapes; it can enhance the current-carrying performance of the YBCO coil series joint; the height of the overlapping area after being bonded to the filling block 50 is the same as the width of the superconducting tape 30, reducing the processing complexity and errors.

[0051] In an embodiment of the present application, the widths of the first superconducting stacked cable 10, the second superconducting stacked cable 20, and the superconducting tape 30 are the same; the overlapping area between the first superconducting stacked cable 10 and the second superconducting stacked cable 20 has four sides; the upper surface of the overlapping area is bonded to the filling block 50; the lower surface of the overlapping area is bonded to the filling block 50; wherein, the filling block 50 is composed of alternately arranged conductive solder 40 and YBCO superconducting tapes; the height of the overlapping area after being bonded to the filling block 50 is the same as the width of the superconducting tape 30; the four sides of the overlapping area after being bonded to the filling block 50 are in contact with the superconducting tape 30 and are bonded through the conductive solder 40.

[0052] In this embodiment, the widths of the first superconducting stacked cable 10, the second superconducting stacked cable 20, and the superconducting tape 30 are the same, and the height of the overlapping area after being bonded to the filling block 50 is the same as the width of the superconducting tape 30. The regular joint shape can reduce material waste and improve material utilization efficiency; the cross-section of the YBCO coil series joint is a square, which can make the stress distribution more uniform, enhance the stability of the joint, improve the ability of the joint to withstand pressure or bending, and increase the rigidity of the joint.

[0053] Figure 3 It is a schematic flow chart of the preparation method of the YBCO coil series joint provided in an embodiment of the present application. As Figure 3 shown, the preparation method includes:

[0054] S1. Conduct critical current tests on the pre-prepared first superconducting stacked cable, second superconducting stacked cable, and superconducting tape, wherein the first superconducting stacked cable is led out from the first YBCO coil, and the second superconducting stacked cable is led out from the second YBCO coil.

[0055] Specifically, critical current tests are performed on the pre-prepared first superconducting stacked cable, second superconducting stacked cable, and superconducting tape at liquid nitrogen temperature.

[0056] S2. After the critical current test is passed, the first superconducting stacked cable and the second superconducting stacked cable are aligned and overlapped along the length direction by a preset length, and bonded with a conductive solder.

[0057] Among them, the preset length can be 20 cm, which can be changed according to the actual situation, and this application does not make any limitations in this regard.

[0058] Among them, the conductive solder can be a solder sheet or solder paste.

[0059] S3. After the sides of the overlapping area of the first superconducting stacked cable and the second superconducting stacked cable are polished and cleaned, a superconducting tape is attached to the side of the overlapping area, and a conductive solder is placed on the contact surface between the overlapping area and the superconducting tape.

[0060] Specifically, the sides of the overlapping area of the first superconducting stacked cable and the second superconducting stacked cable are polished with a lint-free cloth, and the sides of the overlapping area are cleaned with anhydrous ethanol. Then, a superconducting tape is attached to the side of the overlapping area, and a conductive solder is placed on the contact surface between the overlapping area and the superconducting tape.

[0061] Among them, the superconducting tape can be a composite superconducting tape or a non-composite superconducting tape.

[0062] Specifically, if the superconducting tape is a composite superconducting tape, the superconducting surface of the superconducting tape is attached to the side of the overlapping area.

[0063] Among them, the superconducting tape can be a Bi-based tape or a YBCO superconducting tape.

[0064] S4. The overlapping area processed in step S3 is pressed tightly by a welding tooling and heated until the conductive solder melts.

[0065] Specifically, the overlapping area processed in step S3 is pressed tightly by a welding tooling to ensure that the sides are aligned. Then, the processing tooling is heated up, and the heating temperature is set according to the melting temperature of the conductive solder. After the temperature rises to the heating temperature, keep it warm for 1 min.

[0066] S5. After the heated overlapping area is naturally cooled, the tooling is removed to obtain a YBCO coil series joint.

[0067] Specifically, the heated overlapping area is naturally cooled to 60 °C, the tooling is removed, and the surface is cleaned to obtain a YBCO coil series joint.

[0068] It should be noted that during the cooling process, air cooling and spraying alcohol are not allowed to accelerate the cooling process. The melted conductive solder is prone to voids and cracks during the rapid cooling process, increasing the joint resistance.

[0069] The method for preparing the YBCO coil series joint provided by the embodiment of the present application can reduce the resistance of the YBCO coil series joint and improve the thermal stability of the series joint by overlapping the first superconducting stacked cable and the second superconducting stacked cable and attaching superconducting tapes to the sides of the overlapping area, providing guarantee for the safe operation of the joint.

[0070] In an embodiment of the present application, there are four sides in the overlapping area of the first superconducting stacked cable and the second superconducting stacked cable. On the basis of the above embodiment, after step S2, the process of placing filling blocks on the upper and lower surfaces of the overlapping area is further included, which is described in detail as follows:

[0071] S6. Conduct a critical current test on the pre-prepared YBCO superconducting tape and ensure that the critical current test passes.

[0072] S7. If the side height of the overlapping area is less than the width of the superconducting tape, alternately place conductive solder and YBCO superconducting tapes on the upper and lower surfaces of the overlapping area to form a filling block, so that the side height of the overlapping area is equal to the width of the superconducting tape.

[0073] It should be noted that the superconducting stacked cable led out from the YBCO coil itself comes with conductive solder. Therefore, when placing filling blocks on the upper and lower surfaces of the overlapping area, it can be decided according to the actual situation whether to place conductive solder on the surfaces of the filling blocks and the overlapping area for welding (the resistance of the YBCO coil series joint decreases with the reduction of conductive solder).

[0074] The method for preparing the YBCO coil series joint provided by the embodiment of the present application can enhance the current-carrying performance of the YBCO coil series joint by alternately placing conductive solder and YBCO superconducting tapes on the upper and lower surfaces of the overlapping area to form a filling block, so that the side height of the overlapping area is equal to the width of the superconducting tape; reduce material waste and improve material utilization efficiency; make the stress distribution more uniform, improve the stability of the joint, enhance the ability of the joint to withstand pressure or bending, and increase the rigidity of the joint.

[0075] In an embodiment of the present application, on the basis of the above embodiment, before alternately placing conductive solder and YBCO superconducting tapes on the upper and lower surfaces of the overlapping area in step S7, cleaning the surface of the YBCO superconducting tape with ethanol is also included.

[0076] The method for preparing the YBCO coil series joint provided by the embodiment of the present application can further reduce the resistance of the YBCO coil series joint.

[0077] In one embodiment of the present application, another method for preparing a YBCO coil series joint is further provided, which is described in detail as follows:

[0078] Sa: Perform critical current tests on the pre-prepared first superconducting stacked cable, second superconducting stacked cable, and superconducting tape.

[0079] Sb: After passing the critical current test, align and overlap the first superconducting stacked cable and the second superconducting stacked cable along the length direction by 20 cm, and bond them using solder sheets.

[0080] Sc: Prepare 4 Bi-tape materials with a length of 20 cm.

[0081] Sd: According to the width of the Bi-tape material, place solder sheets and YBCO superconducting tapes at intervals and evenly above and below the overlapping area of the first superconducting stacked cable and the second superconducting stacked cable, and perform welding heating on them using a heating plate until the height of the overlapping area is the same as the width of the Bi-tape material.

[0082] Se: Polish the overlapping area with a lint-free cloth, and clean the surface dust and flux with anhydrous ethanol.

[0083] Sf: Attach 4 Bi-tape materials to the four sides of the overlapping area, and place the contact surface between the Bi-tape material and the overlapping area into a solder sheet.

[0084] It should be noted that solder sheets must be added when attaching the Bi-tape materials to the four sides of the overlapping area. Therefore, there are two layers of tin layers at the joint between the Bi-tape material and the YBCO superconducting tape in the overlapping area.

[0085] Sg: Use a welding fixture to press the overlapping area processed in step Sf, heat it to the melting temperature of the solder sheet, keep it warm for 1 min, and then cool it naturally.

[0086] Sh: After the temperature drops to 60 °C, remove the fixture and perform surface cleaning to obtain a YBCO coil series joint.

[0087] The method for preparing a YBCO coil series joint provided by the embodiment of the present application can reduce the resistance of the YBCO coil series joint and improve the thermal stability of the series joint by overlapping the first superconducting stacked cable and the second superconducting stacked cable and attaching Bi-tape materials to the sides of the overlapping area, providing guarantee for the safe operation of the joint.

[0088] It should be noted that the phrases such as "an embodiment", "embodiments", "exemplary embodiments", "some embodiments", etc. mentioned in the specification indicate that the described embodiments may include specific features, structures or characteristics, but not necessarily every embodiment includes such specific features, structures or characteristics. In addition, such phrases do not necessarily refer to the same embodiment. Moreover, when combining specific features, structures or characteristics with an embodiment, it is within the knowledge scope of those skilled in the art to implement such features, structures or characteristics in combination with other embodiments, whether explicitly or implicitly described.

[0089] Generally speaking, terms should be understood at least in part based on their use in context. For example, at least in part according to the context, the term "one or more" used in the text can be used to describe any feature, structure or characteristic in the sense of singularity, or can be used to describe a combination of features, structures or characteristics in the sense of plurality. Similarly, at least in part according to the context, terms such as "a" or "the" can also be understood to convey singular usage or plural usage.

[0090] It should be easily understood that the terms "on", "above" and "over" in this application should be interpreted in the broadest manner, so that "on" not only means "directly on something", but also includes the meaning of "on something" with intermediate features or layers therebetween, and "above" or "over" not only includes the meaning of "above" or "over something", but also can include the meaning of "above" or "over something" with no intermediate features or layers therebetween (i.e., directly on something).

[0091] In addition, for the convenience of description, spatial relative terms such as "below", "beneath", "under", "above", "over" etc. may be used in the text to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatial relative terms are intended to include different orientations of the device in use or operation in addition to the orientation shown in the drawings. The device may have other orientations (rotated 90° or in other orientations), and the spatial relative descriptive terms used in the text can be correspondingly interpreted as well.

[0092] Finally, it should be noted that: after considering the specification and practicing the invention disclosed herein, those skilled in the art will easily think of other implementation schemes of this application. This application aims to cover any variations, uses or adaptive changes of this application, which follow the general principles of this application and include the common general knowledge or conventional technical means in this technical field not disclosed in this application. It is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is only limited by the appended claims.

Claims

1. A YBCO coil series joint, characterized in that: include: A first superconducting stacking cable (10), a second superconducting stacking cable (20) and a superconducting tape (30); The first superconducting stacking cable (10) is led out from a first yttrium barium copper oxide (YBCO) coil, and the second superconducting stacking cable (20) is led out from a second YBCO coil; The first superconducting stacking cable (10) and the second superconducting stacking cable (20) are overlapped along the length direction and bonded by a conductive solder (40); The side surfaces of the overlapping regions of the first superconducting stacking cable (10) and the second superconducting stacking cable (20) are in contact with the superconducting tape (30) and bonded by the conductive solder (40); The resistivity of the bonding surface of the superconducting tape (30) facing the overlapping area is smaller than the resistivity of the Hastelloy alloy layer in the first superconducting stacking cable (10) and the second superconducting stacking cable (20).

2. The YBCO coil series connector according to claim 1, characterized in that: The superconducting tape (30) is a Bi-based tape or a YBCO superconducting tape.

3. The YBCO coil series joint according to claim 1, characterized in that: The conductive solder (40) is a solder sheet or tin paste.

4. The YBCO coil series joint according to claim 1, characterized in that: The overlapping region of the first superconducting stacking cable (10) and the second superconducting stacking cable (20) has four side surfaces; the four side surfaces of the overlapping region are in contact with the superconducting tape (30) and bonded by the conductive solder (40).

5. The YBCO coil series joint according to claim 1, characterized in that: The first superconducting stack cable (10), the second superconducting stack cable (20) and the superconducting tape (30) have the same width.

6. The YBCO coil series joint according to claim 1 or 5, characterized in that: The overlapping area between the first superconducting stacking cable (10) and the second superconducting stacking cable (20) has four side surfaces; The upper surface of the overlapping area is bonded to the filling block (50); and the lower surface of the overlapping area is bonded to the filling block (50); Wherein, the filling block (50) is the conductive solder (40) and the YBCO superconducting tape placed alternately; The height of the overlapping area after bonding with the filling block (50) is the same as the width of the superconducting tape (30); The four side surfaces of the overlapping area after bonding with the filling block (50) are in contact with the superconducting tape (30) and bonded by the conductive solder (40).

7. The YBCO coil series joint according to any one of claims 1 to 5, characterized in that: Under the condition of liquid nitrogen temperature of 77K, the resistance of the YBCO coil series joint is less than 50nΩ.

8. A method for preparing a YBCO coil series joint as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: S1, performing a critical current test on a first superconducting stacking cable, a second superconducting stacking cable and a superconducting tape prepared in advance, wherein the first superconducting stacking cable is led out from a first YBCO coil, and the second superconducting stacking cable is led out from a second YBCO coil; S2. After the critical current test is passed, aligning the first superconducting stacking cable and the second superconducting stacking cable along the length direction to overlap by a preset length, and bonding them with a conductive solder; S3, after polishing and cleaning the side of the overlapping area of ​​the first superconducting stacking cable and the second superconducting stacking cable, attaching the superconducting tape to the side of the overlapping area, and placing the conductive solder on the contact surface between the overlapping area and the superconducting tape; S4, using a welding tool to press the overlapped area processed in step S3, and heat it until the conductive solder melts; S5. After the heated overlapped area is naturally cooled, the tooling is removed to obtain a YBCO coil series joint.

9. The preparation method according to claim 8, characterized in that: The overlapping area of ​​the first superconducting stacking cable and the second superconducting stacking cable has four sides; Accordingly, after step S2, the method further includes: S6. Perform a critical current test on the pre-prepared YBCO superconducting tape and ensure that the critical current test passes; S7. If the side height of the overlapping area is less than the width of the superconducting tape, conductive solder and YBCO superconducting tape are alternately placed above and below the overlapping area to form filling blocks so that the side height of the overlapping area is equal to the width of the superconducting tape.

10. The preparation method according to claim 9, characterized in that: Before alternately placing conductive solder and YBCO superconducting tape on and below the overlapping area, the method further comprises: The surface of the YBCO superconducting tape was cleaned with ethanol.

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