A method for manufacturing a conductively cooled variable pitch NbTi superconducting coil

Abstract

This invention discloses a method for fabricating NbTi superconducting coils with variable wire diameters for conductive cooling. The coils are wound on the same magnet frame using an odd-even winding method with enameled wire insulated NbTi superconducting wires of varying diameters, decreasing in diameter from the inside to the outside. Insulating plates and low-temperature resistant insulating cloths are used to insulate the inner wall of the frame flange and the frame cylinder. To ensure the winding accuracy of each layer, the outer diameter error is measured after each layer is completed, and the coil dimensions are adjusted using fiberglass cloth of different thicknesses. After winding, the coil is protected with fiberglass cloth, and then a prestressed coil is wound. Stainless steel wire / flat copper strip / aluminum alloy strip is added to the outside of the copper foil to maintain fit. Finally, flexible connecting components are attached or welded to both ends of the copper foil for heat conduction. This method achieves precise winding, prevents wire collapse, ensures effective heat conduction, and meets the requirements for high-precision distribution characteristics. It is of great significance for developing superconducting magnets with special magnetic field configuration requirements.

Description

Technical Field

[0001] This invention belongs to the field of superconducting coil fabrication, specifically relating to a method for fabricating a conductive cooling variable diameter NbTi superconducting coil. Background Technology

[0002] Strictly toleranced coil frames and precise magnet winding techniques are core technologies for developing magnet coils with special magnetic field configuration requirements. Examples include the main coil and compensation coil mentioned in the authorized invention patent "Conductive Cooling Superconducting Magnet System for Gyrotrons," and the superconducting magnet mentioned in the authorized invention patent "Superconducting Magnet System for High-Power Microwave Source Focusing and Gyrotron Electronic Devices." For magnets with special magnetic field configuration requirements, a method of using a main coil plus compensation coils is typically employed to control the magnetic field configuration. Each coil uses the same type of superconducting wire, and a single magnet contains multiple magnet frames. This requires high assembly precision, results in relatively large magnet dimensions, and leads to a complex structure. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a method for fabricating a conductive cooling variable-diameter NbTi superconducting coil. The coil is wound on the same magnet frame using an odd-even winding method with various diameters of enameled wire insulated NbTi superconducting wire spirally wound. The diameter of the superconducting wire used in the coil decreases sequentially from the inside to the outside. Insulating plates and low-temperature resistant insulating cloth are used to insulate the inner wall of the frame flange and the frame cylinder, respectively. To ensure the winding accuracy of each layer, the outer diameter of the coil is measured after each layer and compared with the theoretical calculation value, controlling the single-layer winding accuracy within ±0.1%. Based on the outer diameter error of each layer, glass of different thicknesses is added. The coil size is adjusted using silk cloth, which also increases the adsorption effect of epoxy resin on the inner layer of the coil during vacuum epoxy impregnation. As the wire diameter gradually decreases, coils of different wire diameters may experience wire collapse. To further prevent this, thin film material is used to support coils of different wire diameters and adjust the coil winding accuracy. After the coil is wound, it is protected with fiberglass cloth, and then a prestressed coil is wound. A copper sheet is added to the outside of the prestressed coil for low-temperature cooling. To ensure the adhesion between the copper sheet and the coil surface, a high-prestress stainless steel wire / flat copper strip or aluminum strip is wound on the outside of the copper sheet. Flexible connecting parts for cooling are connected or welded to both ends of the copper sheet. This method enables precise winding of superconducting coils with varying wire diameters, avoids wire collapse caused by overlapping wires of different diameters, enhances the success rate of vacuum epoxy impregnation of the coil, and ensures the cooling effect of the conductive cooling magnet. Compared with the traditional winding process of superconducting coils, it can meet the requirements of high-precision magnetic field distribution characteristics. It is of great significance for the development of superconducting magnets with special magnetic field configuration requirements, such as gyrotron superconducting magnets and microwave magnets.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for fabricating a conductive cooling variable diameter NbTi superconducting coil, characterized by comprising the following steps:

[0006] Step 1: The magnet frame is made of stainless steel. A layer of low-temperature resistant insulating tape is laid on the surface of the magnet frame cylinder. Insulating plates are installed on the inner end faces of the upper and lower flanges of the magnet frame. The superconducting coil includes first to fourth enameled wire insulated NbTi superconducting wires.

[0007] Step 2: Before winding the superconducting coil, lay a layer of glass fiber cloth on the surface of the low-temperature resistant insulating tape.

[0008] Step 3: The first to fourth enameled wire insulated NbTi superconducting wires are wound using an odd-even close winding method. First, the first enameled wire insulated NbTi superconducting wire with the largest diameter is wound. The diameter of the superconducting coils wound from the inside out decreases sequentially. A supporting film is laid between superconducting coils of different diameters. Multiple circular holes are evenly distributed on the surface of the supporting film. After each layer of superconducting coil is wound, the outer diameter of the superconducting coil is measured and compared with the theoretical calculation value. Glass fiber cloth pads of different thicknesses are used to adjust the outer diameter of the superconducting coil to ensure that the actual value of the outer diameter of each layer of superconducting coil has an error of less than ±0.1% compared with the theoretical value.

[0009] Step 4: After the outermost fourth enameled wire insulated NbTi superconducting wire is wound, two layers of glass fiber cloth are evenly laid on the outside of the fourth enameled wire insulated NbTi superconducting wire, leaving a certain gap between the starting end and the ending end, and then stainless steel round wire is evenly wound.

[0010] Step 5: Vacuum epoxy impregnation is performed on the superconducting coil after the stainless steel round wire is wound. During the impregnation process, ensure that the tooling is in close contact with the surface of the superconducting coil.

[0011] Step 6: After the superconducting coil is impregnated with resin, a soft oxygen-free copper plate with a thickness of 1-2 mm is wound around it. The oxygen-free copper plate is fastened to the magnet frame on both sides by fastening bolts. Stainless steel wire / flat copper strip / aluminum alloy strip is evenly wound around the outside of the oxygen-free copper plate.

[0012] Step 7: The oxygen-free copper plate is welded with copper braided strips to form a flexible oxygen-free copper connection component, which is then tightly connected to the upper and lower cooling flanges of the magnet frame to form a cooling path.

[0013] Furthermore, the metal strip is stainless steel wire, flat copper strip, or aluminum alloy strip.

[0014] Furthermore, the magnet frame 1 is made of weakly magnetic stainless steel, and the roughness of the outer surface of the cylinder and the inner end faces of the upper and lower flanges of the magnet frame 1 is Ra3.2.

[0015] Beneficial effects:

[0016] This invention designs the number of layers and turns per layer of NbTi coils with different wire diameters according to specific magnetic field configuration requirements during the magnet design stage. During the coil winding stage, the outer diameter of each layer of the magnet coil is detected and strictly controlled using the methods described in this invention. This ensures that the coil generates a magnetic field configuration that meets the design requirements during excitation. This provides a key technology for winding superconducting magnet coils with high-precision magnetic field distribution requirements for special applications, such as electron gyroscope superconducting magnets and microwave magnets. This type of magnet system can be further applied to plasma heating, material processing, enhanced nuclear magnetic resonance, electromagnetic countermeasures, and other fields. The magnet coil conductive cooling component winding method described in this invention is simple to operate, has good fit with the magnet coil, and its functions are easy to implement. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the conductive cooling variable diameter NbTi superconducting coil involved in this invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0019] like Figure 1 As shown, the conductive cooling variable diameter NbTi superconducting coil disclosed in this embodiment includes a magnet frame 1, low-temperature resistant insulating cloth 2, glass fiber cloth 3, insulating plate 4, superconducting coil, supporting film 6, stainless steel round wire 10, oxygen-free copper plate 11, metal wire strip 12, fixing bolts 13, and upper and lower cooling flanges 14. The superconducting coil includes a first enameled insulated NbTi superconducting wire 5, a second enameled insulated NbTi superconducting wire 7, a third enameled insulated NbTi superconducting wire 8, and a fourth enameled insulated NbTi superconducting wire 9, with the wire diameter decreasing from the inside to the outside.

[0020] The method for preparing the conductive cooling variable diameter NbTi superconducting coil of the present invention is as follows: Two layers of low-temperature resistant insulating cloth 2 are laid flat on a magnet frame 1 with a surface roughness of Ra3.2. The inner end faces of the upper and lower flanges of the magnet frame 1 are insulated with insulating plates 4. The inner side of the insulating plate 4 is tightly attached to the outer surface of the low-temperature resistant insulating cloth 2. Before winding the coil, a layer of glass fiber cloth 3 is wound on the surface of the insulated magnet frame 1. The first enameled insulated NbTi superconducting wire 5 with the largest wire diameter is wound on the insulated magnet frame 1 using a tight winding method. Each layer of winding is used to test the insulation between the outer diameter of the coil and the frame. By padding with glass fiber cloth 3 of different thicknesses, the error between the measured value and the design value of the superconducting coil outer diameter is kept within ±0.1%. The first enameled insulated NbTi superconducting wires of different diameters are used. 5. To prevent wire collapse between the second enameled insulated NbTi superconducting wire 7, the third enameled insulated NbTi superconducting wire 8, and the fourth enameled insulated NbTi superconducting wire 9, a supporting film 6 is used. After the coil is wound, two layers of glass fiber cloth 3 are laid on the outer layer of the coil, and multiple layers of stainless steel round wire 10 are wound. After vacuum impregnation, an oxygen-free copper plate 11 is wound on the surface of the stainless steel round wire 10, and a metal wire strip 12 is evenly wound on the outside of the oxygen-free copper plate 11 to make the oxygen-free copper plate 11 and the stainless steel round wire 10 fit tightly together. At the same time, the two sides of the oxygen-free copper plate 11 are fastened to the upper and lower flange sides of the magnet frame 1 by fastening bolts 13. Oxygen-free copper flexible connection components are welded on both sides of the oxygen-free copper plate 11 and are tightly connected to the upper and lower cooling flanges 14 by bolts.

[0021] The metal strip 12 is made of stainless steel, flat copper, or aluminum alloy.

[0022] The magnet frame 1 is made of weakly magnetic stainless steel, and the roughness of the outer surface of the cylinder and the inner end face of the upper and lower flanges of the magnet frame 1 is Ra3.2.

[0023] The surface of the magnet frame 1 is covered with two layers of smooth, low-temperature resistant insulating tape; the inner arc surface of the insulating plate is tightly bonded to the low-temperature resistant insulating tape on the surface of the cylinder, and the outer arc surface of the insulating plate is fixed to the upper and lower flanges of the magnet frame with tape.

[0024] One end of the NbTi round wire is wound around the outside of the winding fixture, and then passed through the wire inlet of the magnet skeleton 1 to tightly wind the solenoid coil. During winding, the wire turn spacing detection system is used to detect the gap between turns in real time and adjust the gap between turns in real time. After each layer is wound, the insulation between the coil and the magnet skeleton 1 is detected, and the outer diameter of the coil is detected. The detected value is compared with the theoretical design value. The outer diameter of the magnet coil is adjusted by adding or removing glass fiber cloth 3 of different thicknesses to control the error between it and the theoretical value within ±0.1%.

[0025] The calculation method for the outer diameter of each layer of the coil is as follows:

[0026] D n =D0+2t0+4t1+g+(n+1)d w +(n-1)d1, n=1,3,5,7…;

[0027] D n =D0+2t0+4t1+g+n(d w +d1), n=2,4,6,8…;

[0028] Among them, D n D0 is the outer diameter of the innermost coil; t0 is the aperture of the magnet skeleton; t1 is the wall thickness of the magnet skeleton; g is the interlayer gap; n is the number of layers; d w d1 is the insulation diameter of the superconducting wire; d1 is the equivalent thickness increment of an even-numbered layer.

[0029] Specifically, the surface of the supporting film 6 has evenly distributed holes, which serve as impregnation channels. The supporting film 6 can effectively prevent the collapse of small-diameter superconducting wires at the coil ends, further ensuring the flatness and uniformity of the coil winding. This method is used to wind smaller-diameter superconducting coils sequentially until the superconducting coil winding is completed.

[0030] Specifically, a layer of glass fiber cloth 3 is laid flat on the outside of the superconducting coil to provide insulation protection and enhance the impregnation effect;

[0031] Specifically, multiple layers of stainless steel round wire 10 are uniformly wound around the outside of the glass fiber cloth 3. The main function is to tighten and protect the superconducting coil and prevent damage to the coil surface insulation during the impregnation operation.

[0032] Specifically, the annealed oxygen-free copper plate 11 is slowly wound onto the surface of the superconducting coil after it has been impregnated and cured. The oxygen-free copper plate 11 is fixed to the upper and lower flanges of the magnet frame 1 by bolts on both sides.

[0033] Specifically, a metal wire strip 12 is wound evenly with sufficient tension on the outside of the oxygen-free copper plate 11, and the position of the oxygen-free copper plate 11 is adjusted so that the oxygen-free copper plate 11 is in close contact with the surface of the superconducting coil. The two sides of the oxygen-free copper plate 11 are fastened to the upper and lower flanges of the magnet frame 1 by fastening bolts 13.

[0034] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating a conductive cooling variable diameter NbTi superconducting coil, characterized in that, Includes the following steps: Step 1: The magnet frame is made of stainless steel. A layer of low-temperature resistant insulating tape is laid on the surface of the magnet frame cylinder. Insulating plates are installed on the inner end faces of the upper and lower flanges of the magnet frame. The superconducting coil includes first to fourth enameled wire insulated NbTi superconducting wires. Step 2: Before winding the superconducting coil, lay a layer of glass fiber cloth on the surface of the low-temperature resistant insulating tape. Step 3: Using an odd-even close-wound method, wind the first, second, third, and fourth enameled wire insulated NbTi superconducting wires. First, wind the first enameled wire insulated NbTi superconducting wire with the largest diameter. The diameter of the superconducting coils decreases sequentially from the inside out. A supporting film is laid between superconducting coils of different diameters, and multiple circular holes are evenly distributed on the surface of the supporting film. After each layer of superconducting coils is wound, the outer diameter of the superconducting coil is measured and compared with the theoretical calculation value. Glass fiber cloth pads of different thicknesses are used to adjust the outer diameter of the superconducting coils to ensure that the actual value of the outer diameter of each layer of superconducting coils has an error of within ±0.1% compared with the theoretical value. Step 4: After the outermost fourth enameled wire insulated NbTi superconducting wire is wound, two layers of glass fiber cloth are evenly laid on the outside of the fourth enameled wire insulated NbTi superconducting wire, leaving a certain gap between the starting end and the ending end, and then stainless steel round wire is evenly wound. Step 5: Vacuum epoxy impregnation is performed on the superconducting coil after the stainless steel round wire is wound. During the impregnation process, ensure that the tooling is in close contact with the surface of the superconducting coil. Step 6: After the superconducting coil is impregnated with resin, a soft oxygen-free copper plate with a thickness of 1-2 mm is wound around it. The oxygen-free copper plate is fastened to the magnet frame on both sides by fastening bolts. Metal wire strips are evenly wound around the outside of the oxygen-free copper plate. Step 7: The oxygen-free copper plate is welded with copper braided strips to form a flexible oxygen-free copper connection component, which is then tightly connected to the upper and lower cooling flanges of the magnet frame to form a cooling path.

2. The method for fabricating a conductive cooling variable diameter NbTi superconducting coil according to claim 1, characterized in that, The metal strip is stainless steel wire, flat copper strip, or aluminum alloy strip.

3. The method for fabricating a conductive cooling variable diameter NbTi superconducting coil according to claim 1, characterized in that, The magnet skeleton is made of weakly magnetic stainless steel, and the roughness of the outer surface of the cylinder and the inner end faces of the upper and lower flanges is Ra3.2.

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