Preparation method of low-loss high-thermal-conductivity NbTi superconducting cable

Abstract

This invention relates to the field of superconducting composite wire and cable processing technology, and discloses a method for preparing a low-loss, high-thermal-conductivity NbTi superconducting cable, including the preparation of a single-core ingot. The single-core ingot is welded, extruded, and drawn to obtain a single-core rod. Subsequently, the single-core rod is assembled, welded, extruded, and drawn to obtain a composite rod. A copper tube containing a high specific heat material is placed in the core of an oxygen-free copper tube, and oxygen-free copper inserts are used to fill the internal gaps of the oxygen-free copper tube. Then, combined with drawing and multiple aging heat treatments, a composite wire is obtained. One oxygen-free copper tube is used as the central component, and six composite wires are placed around it; the wires are then stranded to obtain a superconducting cable. This invention introduces a Cu tube between the NbTi rod and CuNi in the single-core ingot, effectively conducting the heat generated by the NbTi core wire. A copper tube containing high specific heat powder is introduced into the core of the composite wire. During stranding, a thin copper tube is used instead of copper wire in the central region, achieving the dual effect of "core wire thermal conductivity + core wire isolation to reduce coupling loss".

Description

Technical Field

[0001] This invention relates to the field of superconducting composite wire processing technology, and in particular to a method for preparing a low-loss, high-thermal-conductivity NbTi superconducting cable. Background Technology

[0002] Conventional NbTi superconducting cables are made of NbTi / Cu superconducting wires and are widely used in high-voltage fields such as power transmission, nuclear fusion, and accelerators. However, with continuous technological innovation, the current during service is gradually increasing, posing a significant challenge to the thermal conductivity of NbTi / Cu composite wires and cables. Previously, researchers had developed CuNi-based low-loss NbTi superconducting wires. By replacing the Cu matrix with a CuNi matrix, this wire effectively reduces losses by hindering NbTi core wire coupling; however, the increased resistivity also reduces its thermal conductivity, severely limiting its application. To address the thermal conductivity challenges posed by the higher current service conditions of superconducting cables, it is urgent to simultaneously improve the thermal conductivity of low-loss wires from both the wire and cable perspectives, thus resolving the thermal conductivity issues of both the wire and cable materials. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing low-loss, high-thermal-conductivity NbTi superconducting cables, which solves the problem of insufficient thermal conductivity in low-loss NbTi / CuNi superconducting wires and cables processed by existing methods.

[0004] The technical solution adopted in this invention is a method for preparing a low-loss, high-thermal-conductivity NbTi superconducting cable, which is implemented according to the following steps:

[0005] Step 1: Prepare NbTi / Nb / Cu / CuNi single-core ingots with oxygen-free copper tube interlayers;

[0006] All raw materials are cleaned. An Nb cylinder is wrapped around the outside of the NbTi rod as a barrier layer. An oxygen-free copper tube is wrapped around the outside of the Nb cylinder as a heat conduction channel. A CuNi tube is placed on the outermost layer to avoid core wire coupling. From the inside out, the NbTi rod, Nb cylinder, oxygen-free copper tube, and CuNi tube are assembled together to form an NbTi / Nb / Cu / CuNi single-core ingot. The diameter of the NbTi rod is 90-310 mm, the thickness of the Nb cylinder is 0.2-4 mm, the thickness of the oxygen-free copper tube is 5-20 mm, and the thickness of the CuNi tube is 15-60 mm. It should be noted that the oxygen-free copper tube is located outside the NbTi rod and Nb cylinder, between the Nb cylinder and the CuNi tube, in order to promote the heat conduction of the NbTi rod.

[0007] Step 2: Prepare NbTi / Nb / Cu / CuNi single core rods;

[0008] The assembled NbTi / Nb / Cu / CuNi single-core ingot is subjected to vacuum electron beam welding, extrusion, drawing, and length cutting to obtain NbTi / Nb / Cu / CuNi single-core rods.

[0009] Step 3: Prepare NbTi-Nb-Cu-CuNi / Cu composite rods;

[0010] The NbTi / Nb / Cu / CuNi single-core rods, oxygen-free copper tubes, and oxygen-free copper inserts are cleaned and assembled. The NbTi / Nb / Cu / CuNi single-core rods are arranged in a circular stacking manner inside the oxygen-free copper tubes, and the internal gaps of the oxygen-free copper tubes are filled with oxygen-free copper inserts. Subsequently, the composite ingot undergoes processes such as welding, extrusion, drawing, and cutting to length to obtain NbTi-Nb-Cu-CuNi / Cu composite rods.

[0011] Step 4: Prepare a copper tube filled with a high specific heat material;

[0012] A high specific heat material is placed in a thin copper tube, and the two sides are plugged with plugs. Through multiple drawing operations with a small processing rate, that is, the cross-sectional area is reduced by 5%-15% in a single processing, the high specific heat material is uniformly distributed inside the copper tube. The high specific heat material has a specific heat greater than 0.39×103J / (kg·℃) and a heat resistance temperature greater than 450℃. The material can be an alloy of metals such as aluminum and lithium or their oxides, and the material form can be any combination of bulk or powder.

[0013] Step 5: Prepare NbTi-Nb-Cu-CuNi / Cu composite wire;

[0014] The NbTi-Nb-Cu-CuNi / Cu composite rods, oxygen-free copper tubes, oxygen-free copper inserts, and copper tubes filled with high specific heat materials are cleaned and assembled. During assembly, the NbTi-Nb-Cu-CuNi / Cu composite rods are arranged in a circular stacking manner. The copper tubes filled with high specific heat materials are placed in the core of the oxygen-free copper tubes to improve the heat conduction of the core. Oxygen-free copper inserts are used to fill the internal gaps of the oxygen-free copper tubes. Subsequently, NbTi-Nb-Cu-CuNi / Cu composite wires are obtained by combining drawing and multiple aging heat treatments.

[0015] Step 6: Fabrication of NbTi-Nb-Cu-CuNi / Cu superconducting cable.

[0016] One oxygen-free copper tube is used as the central component, and six NbTi-Nb-Cu-CuNi / Cu composite wires are placed around it. The NbTi-Nb-Cu-CuNi / Cu superconducting cable is obtained by stranding the wires. The outer diameter of the oxygen-free copper tube used for stranding the wires is 0.5-1.5 mm, and the thickness of the copper tube is 0.1-0.5 mm.

[0017] Compared with the prior art, the present invention has the following technical advantages and beneficial effects:

[0018] (1) In the existing NbTi / CuNi single core rod, an oxygen-free copper tube is added between the NbTi rod and CuNi. The first step is to effectively realize the heat conduction of the NbTi rod deformation heat generation through oxygen-free copper. The second step is to effectively hinder the coupling between NbTi core wires through CuNi, thereby achieving the dual effect of "core wire heat conduction + core wire isolation to reduce coupling loss", which further improves the heat generation near the core wire and reduces wire loss.

[0019] (2) Introducing a copper tube containing high specific heat powder into the core of the composite wire can effectively absorb the heat generated by the deformation of the core without causing a temperature rise, effectively alleviating the heat generation state of the core of the composite wire, which is conducive to the uniform deformation of the core wire in the core area, thereby further improving the critical current density.

[0020] (3) When twisting the cable, a thin copper tube is used instead of a copper wire in the central area. During service, liquid helium or helium gas is passed through the end of the copper tube to achieve better heat conduction than copper wire and improve the overall thermal stability of the superconducting cable. Attached Figure Description

[0021] Figure 1 A schematic diagram of a NbTi / Nb / Cu / CuNi single-core ingot provided as an example of this application;

[0022] Figure 2 A schematic diagram of an NbTi-Nb-Cu-CuNi / Cu composite line provided as an example of this application, wherein the composite rod refers to the NbTi-Nb-Cu-CuNi / Cu composite rod;

[0023] Figure 3 A schematic diagram of an NbTi-Nb-Cu-CuNi / Cu superconducting cable provided as an example of this application, wherein the composite line refers to... Figure 2 NbTi-Nb-Cu-CuNi / Cu composite wire. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged in various different configurations and in a circular stacking manner.

[0025] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0026] Reference Figures 1 to 3 This invention relates to a method for fabricating a low-loss, high-thermal-conductivity NbTi superconducting cable, which is implemented according to the following steps:

[0027] Step 1: Prepare an NbTi / Nb / Cu / CuNi single-core ingot with an oxygen-free copper tube sandwich. Clean all raw materials. Wrap the Nb cylinder around the NbTi rod as a barrier layer, wrap the oxygen-free copper tube around the outside of the Nb cylinder as a heat conduction channel, and place the CuNi tube on the outermost layer to avoid core wire coupling. From the inside out, the components are NbTi rod, Nb cylinder, oxygen-free copper tube, and CuNi tube, assembled together to form an NbTi / Nb / Cu / CuNi single-core ingot. The NbTi rod diameter is 90–310 mm, the Nb cylinder thickness is 0.2–4 mm, the oxygen-free copper tube thickness is 5–20 mm, and the CuNi tube thickness is 15–60 mm. It should be noted that the oxygen-free copper tube is positioned outside the NbTi rod and Nb cylinder, between the Nb cylinder and the CuNi tube, to promote heat conduction of the NbTi rod.

[0028] Step 2: Prepare NbTi / Nb / Cu / CuNi single core rods; perform vacuum electron beam welding, extrusion, drawing, and length cutting on the assembled NbTi / Nb / Cu / CuNi single core rods.

[0029] Step 3: Prepare NbTi-Nb-Cu-CuNi / Cu composite rods. NbTi / Nb / Cu / CuNi single-core rods, oxygen-free copper tubes, and oxygen-free copper inserts are cleaned and assembled. The NbTi / Nb / Cu / CuNi single-core rods are arranged in a circular stacking pattern inside the oxygen-free copper tube, and the internal gaps of the oxygen-free copper tube are filled with oxygen-free copper inserts. Subsequently, the composite ingot undergoes welding, extrusion, drawing, and length-cutting processes to obtain the NbTi-Nb-Cu-CuNi / Cu composite rods.

[0030] Step 4: Prepare a copper tube containing a high specific heat material. The high specific heat material is placed inside a thin copper tube, and both sides are plugged. Through multiple drawing operations with a small processing rate (i.e., a reduction in cross-sectional area of ​​5%-15% in a single processing step), the high specific heat material is uniformly distributed inside the copper tube. The high specific heat material has a specific heat greater than 0.39 × 10³ J / (kg·℃) and a heat resistance temperature greater than 450℃. The material can be an alloy of metals such as aluminum or lithium, or their oxides, and can be in any form, such as a block or powder, or a combination thereof.

[0031] Step 5: Prepare NbTi-Nb-Cu-CuNi / Cu composite wire. Clean and assemble the NbTi-Nb-Cu-CuNi / Cu composite rods, oxygen-free copper tubes, oxygen-free copper inserts, and copper tubes filled with high specific heat material. During assembly, the NbTi-Nb-Cu-CuNi / Cu composite rods are arranged in a circular stacking pattern. The copper tubes filled with high specific heat material are placed in the core of the oxygen-free copper tube to improve core thermal conductivity. Oxygen-free copper inserts are used to fill the internal gaps of the oxygen-free copper tube. Subsequently, NbTi-Nb-Cu-CuNi / Cu composite wire is obtained through drawing and multiple aging heat treatments.

[0032] Step 6: Fabrication of NbTi-Nb-Cu-CuNi / Cu superconducting cable. One oxygen-free copper tube is used as the central component, surrounded by six NbTi-Nb-Cu-CuNi / Cu composite wires. The NbTi-Nb-Cu-CuNi / Cu superconducting cable is obtained by stranding the tube. The outer diameter of the oxygen-free copper tube used for stranding is 0.5–1.5 mm, and the thickness is 0.1–0.5 mm.

[0033] Example 1

[0034] Step 1: Prepare an NbTi / Nb / Cu / CuNi single-core ingot with an oxygen-free copper tube sandwich. Clean all raw materials. Wrap the Nb cylinder around the NbTi rod as a barrier layer, wrap the oxygen-free copper tube around the outside of the Nb cylinder as a heat conduction channel, and place the CuNi tube on the outermost layer to avoid core wire coupling. From the inside out, the order is NbTi rod, Nb cylinder, oxygen-free copper tube, and CuNi tube, assembled together to form an NbTi / Nb / Cu / CuNi single-core ingot. The NbTi rod has a diameter of 90 mm, the Nb cylinder thickness is 0.2 mm, the oxygen-free copper tube thickness is 5 mm, and the CuNi tube thickness is 15 mm. It should be noted that the oxygen-free copper tube is positioned outside the NbTi rod and Nb cylinder, between the Nb cylinder and the CuNi tube, to promote heat conduction of the NbTi rod.

[0035] Step 2: Prepare NbTi / Nb / Cu / CuNi single core rods; perform vacuum electron beam welding, extrusion, drawing, and length cutting on the assembled NbTi / Nb / Cu / CuNi single core rods.

[0036] Step 3: Prepare NbTi-Nb-Cu-CuNi / Cu composite rods. NbTi / Nb / Cu / CuNi single-core rods, oxygen-free copper tubes, and oxygen-free copper inserts are cleaned and assembled. The NbTi / Nb / Cu / CuNi single-core rods are arranged in a circular stacking pattern inside the oxygen-free copper tube, and the internal gaps of the oxygen-free copper tube are filled with oxygen-free copper inserts. Subsequently, the composite ingot undergoes welding, extrusion, drawing, and length-cutting processes to obtain the NbTi-Nb-Cu-CuNi / Cu composite rods.

[0037] Step 4: Prepare a copper tube containing a high specific heat material. The high specific heat material is placed inside a thin copper tube, and both sides are plugged. Through multiple drawing operations with a small processing rate (i.e., a reduction in cross-sectional area of ​​5%-15% in a single processing step), the high specific heat material is uniformly distributed inside the copper tube. The high specific heat material has a specific heat greater than 0.39 × 10³ J / (kg·℃) and a heat resistance temperature greater than 450℃. The material can be an alloy of metals such as aluminum or lithium, or their oxides, and can be in any form, such as a block or powder, or a combination thereof.

[0038] Step 5: Prepare NbTi-Nb-Cu-CuNi / Cu composite wire. Clean and assemble the NbTi-Nb-Cu-CuNi / Cu composite rods, oxygen-free copper tubes, oxygen-free copper inserts, and copper tubes filled with high specific heat material. During assembly, the NbTi-Nb-Cu-CuNi / Cu composite rods are arranged in a circular stacking pattern. The copper tubes filled with high specific heat material are placed in the core of the oxygen-free copper tube to improve core thermal conductivity. Oxygen-free copper inserts are used to fill the internal gaps of the oxygen-free copper tube. Subsequently, NbTi-Nb-Cu-CuNi / Cu composite wire is obtained through drawing and multiple aging heat treatments.

[0039] Step 6: Fabrication of NbTi-Nb-Cu-CuNi / Cu superconducting cable. One oxygen-free copper tube is used as the central component, surrounded by six NbTi-Nb-Cu-CuNi / Cu composite wires. The NbTi-Nb-Cu-CuNi / Cu superconducting cable is obtained by stranding the tube. The oxygen-free copper tube used for stranding has an outer diameter of 0.5 mm and a thickness of 0.1 mm.

[0040] Example 2

[0041] Step 1: Prepare an NbTi / Nb / Cu / CuNi single-core ingot with an oxygen-free copper tube sandwich. Clean all raw materials. Wrap the Nb cylinder around the NbTi rod as a barrier layer, wrap the oxygen-free copper tube around the outside of the Nb cylinder as a heat conduction channel, and place the CuNi tube on the outermost layer to avoid core wire coupling. From the inside out, the ingot consists of an NbTi rod, an Nb cylinder, an oxygen-free copper tube, and a CuNi tube, assembled together to form an NbTi / Nb / Cu / CuNi single-core ingot. The NbTi rod has a diameter of 310 mm, the Nb cylinder is 4 mm thick, the oxygen-free copper tube is 20 mm thick, and the CuNi tube is 60 mm thick. It should be noted that the oxygen-free copper tube is positioned outside the NbTi rod and Nb cylinder, between the Nb cylinder and the CuNi tube, to promote heat conduction of the NbTi rod.

[0042] Step 2: Prepare NbTi / Nb / Cu / CuNi single core rods; perform vacuum electron beam welding, extrusion, drawing, and length cutting on the assembled NbTi / Nb / Cu / CuNi single core rods.

[0043] Step 3: Prepare NbTi-Nb-Cu-CuNi / Cu composite rods. NbTi / Nb / Cu / CuNi single-core rods, oxygen-free copper tubes, and oxygen-free copper inserts are cleaned and assembled. The NbTi / Nb / Cu / CuNi single-core rods are arranged in a circular stacking pattern inside the oxygen-free copper tube, and the internal gaps of the oxygen-free copper tube are filled with oxygen-free copper inserts. Subsequently, the composite ingot undergoes welding, extrusion, drawing, and length-cutting processes to obtain the NbTi-Nb-Cu-CuNi / Cu composite rods.

[0044] Step 4: Prepare a copper tube containing a high specific heat material. The high specific heat material is placed inside a thin copper tube, and both sides are plugged. Through multiple drawing operations with a small processing rate (i.e., a reduction in cross-sectional area of ​​5%-15% in a single processing step), the high specific heat material is uniformly distributed inside the copper tube. The high specific heat material has a specific heat greater than 0.39 × 10³ J / (kg·℃) and a heat resistance temperature greater than 450℃. The material can be an alloy of metals such as aluminum or lithium, or their oxides, and can be in any form, such as a block or powder, or a combination thereof.

[0045] Step 5: Prepare NbTi-Nb-Cu-CuNi / Cu composite wire. Clean and assemble the NbTi-Nb-Cu-CuNi / Cu composite rods, oxygen-free copper tubes, oxygen-free copper inserts, and copper tubes filled with high specific heat material. During assembly, the NbTi-Nb-Cu-CuNi / Cu composite rods are arranged in a circular stacking pattern. The copper tubes filled with high specific heat material are placed in the core of the oxygen-free copper tube to improve core thermal conductivity. Oxygen-free copper inserts are used to fill the internal gaps of the oxygen-free copper tube. Subsequently, NbTi-Nb-Cu-CuNi / Cu composite wire is obtained through drawing and multiple aging heat treatments.

[0046] Step 6: Fabrication of NbTi-Nb-Cu-CuNi / Cu superconducting cable. One oxygen-free copper tube is used as the central component, surrounded by six NbTi-Nb-Cu-CuNi / Cu composite wires. The NbTi-Nb-Cu-CuNi / Cu superconducting cable is obtained by stranding the wires. The oxygen-free copper tube used for stranding has an outer diameter of 1.5 mm and a thickness of 0.5 mm.

[0047] Example 3

[0048] Step 1: Prepare an NbTi / Nb / Cu / CuNi single-core ingot with an oxygen-free copper tube sandwich. Clean all raw materials. Wrap the Nb cylinder around the NbTi rod as a barrier layer, wrap the oxygen-free copper tube around the outside of the Nb cylinder as a heat conduction channel, and place the CuNi tube on the outermost layer to avoid core wire coupling. From the inside out, the ingot consists of an NbTi rod, an Nb cylinder, an oxygen-free copper tube, and a CuNi tube, assembled together to form an NbTi / Nb / Cu / CuNi single-core ingot. The NbTi rod has a diameter of 230 mm, the Nb cylinder is 3 mm thick, the oxygen-free copper tube is 14 mm thick, and the CuNi tube is 40 mm thick. It should be noted that the oxygen-free copper tube is positioned outside the NbTi rod and Nb cylinder, between the Nb cylinder and the CuNi tube, to promote heat conduction of the NbTi rod.

[0049] Step 2: Prepare NbTi / Nb / Cu / CuNi single core rods; perform vacuum electron beam welding, extrusion, drawing, and length cutting on the assembled NbTi / Nb / Cu / CuNi single core rods.

[0050] Step 3: Prepare NbTi-Nb-Cu-CuNi / Cu composite rods. NbTi / Nb / Cu / CuNi single-core rods, oxygen-free copper tubes, and oxygen-free copper inserts are cleaned and assembled. The NbTi / Nb / Cu / CuNi single-core rods are arranged in a circular stacking pattern inside the oxygen-free copper tube, and the internal gaps of the oxygen-free copper tube are filled with oxygen-free copper inserts. Subsequently, the composite ingot undergoes welding, extrusion, drawing, and length-cutting processes to obtain the NbTi-Nb-Cu-CuNi / Cu composite rods.

[0051] Step 4: Prepare a copper tube containing a high specific heat material. The high specific heat material is placed inside a thin copper tube, and both sides are plugged. Through multiple drawing operations with a small processing rate (i.e., a reduction in cross-sectional area of ​​5%-15% in a single processing step), the high specific heat material is uniformly distributed inside the copper tube. The high specific heat material has a specific heat greater than 0.39 × 10³ J / (kg·℃) and a heat resistance temperature greater than 450℃. The material can be an alloy of metals such as aluminum or lithium, or their oxides, and can be in any form, such as a block or powder, or a combination thereof.

[0052] Step 5: Prepare NbTi-Nb-Cu-CuNi / Cu composite wire. Clean and assemble the NbTi-Nb-Cu-CuNi / Cu composite rods, oxygen-free copper tubes, oxygen-free copper inserts, and copper tubes filled with high specific heat material. During assembly, the NbTi-Nb-Cu-CuNi / Cu composite rods are arranged in a circular stacking pattern. The copper tubes filled with high specific heat material are placed in the core of the oxygen-free copper tube to improve core thermal conductivity. Oxygen-free copper inserts are used to fill the internal gaps of the oxygen-free copper tube. Subsequently, NbTi-Nb-Cu-CuNi / Cu composite wire is obtained through drawing and multiple aging heat treatments.

[0053] Step 6: Fabrication of NbTi-Nb-Cu-CuNi / Cu superconducting cable. One oxygen-free copper tube is used as the central component, surrounded by six NbTi-Nb-Cu-CuNi / Cu composite wires. The NbTi-Nb-Cu-CuNi / Cu superconducting cable is obtained by stranding the wires. The oxygen-free copper tube used for stranding has an outer diameter of 1.2 mm and a thickness of 0.35 mm.

[0054] Implementation Principle: In existing NbTi / CuNi single-core rods, an oxygen-free copper tube is added between the NbTi rod and the CuNi core. Firstly, the oxygen-free copper effectively conducts heat generated by the deformation of the NbTi rod. Secondly, the CuNi effectively hinders coupling between the NbTi core wires, achieving a dual effect of "core wire heat conduction + core wire isolation reducing coupling loss," further improving heat generation near the core wires and reducing wire loss. Introducing a copper tube filled with high specific heat powder into the core of the composite wire effectively absorbs the heat generated by core deformation with almost no temperature rise, effectively alleviating the core heating state of the composite wire and promoting uniform deformation of the core wires in the core area, thereby further increasing the critical current density. During cable stranding, a thin copper tube replaces the copper wire in the central area. During service, liquid helium or helium gas is passed through the ends of the copper tube, achieving better heat conduction than copper wire and improving the overall thermal stability of the superconducting cable.

[0055] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0056] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

[0057] It should be noted that the connection relationships of components not specifically mentioned in this application are all assumed to be based on existing technology. Since they do not involve the inventive point and are commonly used in existing technology, the structural connection relationships are not described in detail.

Claims

1. A method for fabricating a low-loss, high-thermal-conductivity NbTi superconducting cable, characterized in that, include: Step 1: Clean all raw materials and assemble them into NbTi / Nb / Cu / CuNi single-core ingots; Step 2: Vacuum electron beam welding, extrusion, drawing, and length cutting are performed on the assembled NbTi / Nb / Cu / CuNi single core ingot to obtain NbTi / Nb / Cu / CuNi single core rods. Step 3: Clean and assemble the NbTi / Nb / Cu / CuNi single core rod, oxygen-free copper tube, and oxygen-free copper insert to form an NbTi-Nb-Cu-CuNi / Cu composite ingot. Further process the NbTi-Nb-Cu-CuNi / Cu composite ingot to obtain an NbTi-Nb-Cu-CuNi / Cu composite rod. Step 4: Prepare a copper tube filled with a high specific heat material; Step 5: Clean and assemble the NbTi-Nb-Cu-CuNi / Cu composite rod, oxygen-free copper tube, oxygen-free copper insert, and copper tube containing high specific heat material to obtain NbTi-Nb-Cu-CuNi / Cu composite wire. The high specific heat material introduced into the NbTi-Nb-Cu-CuNi / Cu composite wire has a specific heat greater than 0.39×103J / (kg·℃) and a heat resistance temperature greater than 450℃. The high specific heat material introduced into the NbTi-Nb-Cu-CuNi / Cu composite wire includes alloys of aluminum and lithium metals and their oxides, and the material form can be any combination of bulk or powder. Step 6: Use one oxygen-free copper tube as the central component, place six NbTi-Nb-Cu-CuNi / Cu composite wires around it, and obtain an NbTi-Nb-Cu-CuNi / Cu superconducting cable by stranding the wires.

2. The method for fabricating a low-loss, high-thermal-conductivity NbTi superconducting cable according to claim 1, characterized in that, In step 1, an Nb cylinder is wrapped around an NbTi rod as a barrier layer, an oxygen-free copper tube is wrapped around the outside of the Nb cylinder as a heat conduction channel, and a CuNi tube is placed on the outermost layer to avoid core wire coupling. From the inside out, the NbTi rod, Nb cylinder, oxygen-free copper tube, and CuNi tube are assembled together to form an NbTi / Nb / Cu / CuNi single-core ingot.

3. The method for fabricating a low-loss, high-thermal-conductivity NbTi superconducting cable according to claim 1, characterized in that, In step 3, NbTi / Nb / Cu / CuNi single core rods are arranged in a circular stacking manner inside the oxygen-free copper tube, and the internal gaps of the oxygen-free copper tube are filled with oxygen-free copper inserts to form NbTi-Nb-Cu-CuNi / Cu composite ingots. Subsequently, the NbTi-Nb-Cu-CuNi / Cu composite ingots are subjected to welding, extrusion, drawing, and length-cutting processes to obtain NbTi-Nb-Cu-CuNi / Cu composite rods.

4. The method for fabricating a low-loss, high-thermal-conductivity NbTi superconducting cable according to claim 1, characterized in that, In step 4, the high specific heat material is loaded into a thin copper tube, and the two sides are plugged with plugs. By using a small processing rate, that is, the cross-sectional area is reduced by 5%-15% in a single processing, multiple drawing operations are performed to achieve a uniform distribution of the high specific heat material inside the copper tube, thus preparing a copper tube filled with high specific heat material.

5. The method for fabricating a low-loss, high-thermal-conductivity NbTi superconducting cable according to claim 1, characterized in that, In step 5, during assembly, the NbTi-Nb-Cu-CuNi / Cu composite rods are arranged in a circular stacking manner. A copper tube containing a high specific heat material is placed in the core of the oxygen-free copper tube to improve the heat conduction of the core. Oxygen-free copper inserts are used to fill the internal gaps of the oxygen-free copper tube. Then, NbTi-Nb-Cu-CuNi / Cu composite wire is obtained by combining drawing and multiple aging heat treatments.

6. The method for fabricating a low-loss, high-thermal-conductivity NbTi superconducting cable according to claim 1, characterized in that NbTi... The dimensions of each component in the Ti / Nb / Cu / CuNi single-core ingot assembly are as follows: the NbTi rod diameter is 90~310mm, the Nb cylinder thickness is 0.2~4mm, the oxygen-free copper tube thickness is 5~20mm, and the CuNi tube thickness is 15~60mm. The oxygen-free copper tube is located outside the NbTi rod and the Nb cylinder, between the Nb cylinder and the CuNi tube, in order to promote the heat conduction of the NbTi rod.

7. The method for fabricating a low-loss, high-thermal-conductivity NbTi superconducting cable according to claim 1, characterized in that, In step S6, the outer diameter of the oxygen-free copper tube used for stranding is 0.5~1.5mm, and the thickness of the copper tube is 0.1~0.5mm.

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