JPS5855649B2 - Superconducting coil manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing large-sized superconducting coils used in nuclear fusion devices, energy storage devices, and the like.

The use of superconducting coils as a component of energy storage devices and magnetic field generators for fusion reactors is being considered, but the size of superconducting coils is gigajoule (GJ = 109J).
) or more.

FIG. 1 is a partially cutaway perspective view of a pancake-shaped superconducting coil, which is a type of large-sized superconducting coil. It has a structure in which a plurality of superconducting wires 2 are stacked and fixed in a winding frame 5 via interlayer spacers 4.
Both the turns and layers are electrically insulated by interturn spacers 3 and interlayer spacers 4, and interlayer spacers 4 form gaps 6 through which a cooling medium such as liquid helium flows.

This gap 6 has the role of allowing air bubbles of the cooling medium generated on the surface of the superconducting wire 2 to escape, and the role of supplying the cooling medium.

FIG. 2 is a cross-sectional view of a disk-shaped superconducting coil, which is a type of large superconducting coil. In this superconducting coil 1, a plurality of coil grooves 8 are formed on both sides of a plate-shaped holding member 7 made of metal or an insulator. A plurality of superconducting disks 200 formed by storing superconducting wires 2 in the coil grooves are stacked,
It is assembled by tightening bolts 9 and nuts 10.

The disk-shaped superconducting coil 1 includes a circular coil 1 shown in FIG. 3a, similar to the pancake-shaped superconducting coil shown in FIG.
This is the racetrack coil 1 shown in the figure or the D-type coil 1 shown in FIG. 3C.

A solder type superconducting wire is considered to be optimal as the large current capacity superconducting wire 2 used in these large superconducting coils.

FIGS. 4a and 4b are perspective views of a solder-type superconducting wire, in which an aggregate 14 of a plurality of superconducting strands 13 is placed in a groove 12 cut in a normal-conducting metal base material 11 with solder (a metallic adhesive such as pbSn). ) 15 and has been usurped.

The normally conductive metal base material 11 is made of copper or aluminum, which has low electrical resistivity at extremely low temperatures (for example, liquid helium temperature of 4.2 K), and copper is currently often used.

The normal conductive wire 13 may be a superconductor itself such as NbTi+Nb3Sn, but it may also be a superconductor coated with copper or aluminum, or an ultra-fine multilayer wire in which multiple superconducting filaments are embedded in a normal conductive metal such as copper. It may be a core superconducting wire or an ultrafine multicore twisted superconducting wire in which the superconducting filament is twisted and embedded in a normal conducting metal.

The superconducting strand assembly 14 is produced by rolling a hollow stranded wire in which the superconducting strands 13 are arranged on the same circumference in cross section, as shown in the perspective view in FIG. 5a, for example. A flat aggregate 14 as shown can be easily obtained.

Although the above-mentioned aggregate 14 is a band-shaped twisted wire, a band-shaped braided wire may be used instead of the band-shaped twisted wire.

Although the superconducting wire 2 in FIG. 4 is provided with grooves 12, it is a superconducting wire in which a superconducting strand assembly 14 is fixed with solder to the side surface of a rectangular normal-conducting metal substrate 11 without grooves. can also be used.

Next, a conventional method for manufacturing superconducting coils will be described.

A superconducting wire 2 manufactured by fixing a superconducting wire 13 to a groove 12 of a normal conducting metal base material 11 with a solder 15,
The superconducting coil 1 is formed by winding it into the shape shown in FIG.

The bending of the superconducting wire during coil winding is flat-wise in the pancake-shaped superconducting coil shown in FIG. 1, and edge-wise in the disk-shaped superconducting coil shown in FIG.

The superconducting coil 1 used in energy storage devices and nuclear fusion reactors is gigantic and has an energy of gigajoules or more, and the superconducting wire 2 wound around it is capable of carrying a large current, for example, 30,000 amperes. It has large dimensions such as outer dimensions of 10 mm x 6,011 mm and 11 mm.

When winding such a large superconducting wire 2 in the shape shown in Figure 3, the minimum bending radius of the coil should be set to, for example, 1 m.
Then, a strain of 0.5% flat-wise and 3% edge-wise occurs in the superconducting wire 2.

Especially in the case of edgewise bending, the distortion is large.

This distortion of the superconducting wire during coil winding greatly reduces the supercurrent capacity of the superconducting wire 13, which is a basic component of the superconducting wire 2, and as a result, the magnetic field created by the superconducting coil 1 is lower than the design value. It can be significantly reduced.

In particular, when the superconductor is a compound such as Nb3Sn, the deterioration of superconducting properties is significant.

FIG. 6 shows an example of a prior art method for manufacturing a superconducting coil, which was made to eliminate the drawbacks of the conventional method for manufacturing a superconducting coil, as shown in FIG. 6a. 11 into a coil shape and fixing it, for example, in the coil groove 8 provided in the plate-shaped holding member 7 shown in FIG. 2, the superconducting strand assembly 14 is bent as shown in FIG. A disk-shaped superconducting coil 1 is formed by fixing it in the groove 12 of the normal-conducting metal base material 11 with solder.

In this way, according to this prior art, it is impossible to generate distortion caused by winding the superconducting wire 13 after it is fixed to the normal conductive metal base material 11, so that a superconducting coil without deterioration of superconducting properties is provided. can do.

In the above superconducting coil, the normal conducting metal base material 11 is formed into a coil shape and then the superconducting strand assembly 14 is fixed, but the superconducting strand assembly 14 is fixed by bending the normal conducting base material 11 into a substantially coil shape. The superconducting wire 2 created by fixing the superconducting wires 14 can then be completely shaped into a coil to form a superconducting coil.

In this case, almost no distortion occurs due to bending of the superconducting wire 2. Also, according to this method, the superconducting wire assembly 14 can be fixed to both sides of the normal conducting base material 11 as shown in FIG. However, the pancake-shaped superconducting coil shown in FIG. 1 can also be manufactured.

By the method of manufacturing a superconducting coil of the prior art as described above, it is possible to prevent a decrease in superconducting current capacity in a superconducting coil manufactured by the prior art.

However, in the prior art superconducting coil manufacturing method, the superconducting wire 2 is created by bending the normal conducting metal base material 11 into a coil shape or a substantially coil shape and fixing the superconducting strand assembly 14. The conductive metal base material 11 is subjected to bending and work hardened, and as a result, the normal conductive metal base material 11
The resistivity of increases.

When the resistivity ρ (Ω-CrrL) of the normal conductive metal base material 11 increases, the stabilized current of the superconducting wire 2 decreases.

Here, A (cit) is the cross-sectional area of the normally conducting metal base material,
5 (CII'L) is the cooling perimeter of the part where the superconducting wire is in contact with the cooling medium, η is the cooling rate of the superconducting wire, q (W/i)
is the critical heat flux at the surface of the superconducting wire.

Large superconducting coils for energy storage devices and fusion reactors.
The normal and orthodox design method is to make the design current Id of the superconducting coil slightly lower than the stabilizing current Ir.

Therefore, an increase in the resistivity ρ of the normally conducting metal base material that causes a decrease in the stabilizing current Ir is not preferable.

For example, the resistivity ρ of copper as a normal conductive metal base material when the working degree is 3% and 10% is approximately 120% and approximately 160%,
The stabilizing current drops to about 90% and about 70%, respectively.

Furthermore, when the bending radius of the normally conducting metal base material is made smaller and the degree of working is increased, the resistivity ρ of copper further increases and the stabilized current further decreases.

Although the above applies to copper, the same holds true for aluminum and other normal conducting metal substrates. In this way, the prior art method for manufacturing superconducting coils requires that the resistivity ρ of the normal conducting metal substrate This has the disadvantage that the stabilizing current of the superconducting wire is decreased as a result.

This invention was made in order to eliminate the drawbacks of the prior art as described above, and by heat-treating the normal conductive metal base material 11 bent into a coil shape or approximately coil shape,
It is possible to provide a large superconducting coil for use in energy storage devices and nuclear fusion reactors that does not cause a drop in stabilizing current.

One embodiment of the method for manufacturing a superconducting coil of this invention is the sixth embodiment of the method for manufacturing a superconducting coil.
By bending the normal conductive metal base material 11 into a coil shape as shown in Figure a, fixing it in the coil groove 8 provided in the plate-shaped holding member 1 shown in Figure 2, for example, and then subjecting it to heat treatment. The resistivity ρ of the normal conductive metal base material 11 is lowered to the resistivity before bending, and the superconducting wire assembly 1 is made as shown in FIG.
The disk-shaped superconducting coil 1 is formed by fixing the coil 4 to the groove 12 of the normal-conducting metal base material 11 with solder.

When the normal conductive metal base material 11 is made of copper, for example, the heat treatment of the normal conductive metal base material 11 is carried out in a vacuum furnace at a heat treatment temperature of 400 to 500.
The heat treatment is usually performed at 00° C. for 0.5 to 2 hours, but is not limited to the above conditions.

As described above, according to the present invention, the superconducting strand 13 is fixed to the normal conducting metal base material 11 by winding.
Not only is it impossible to generate the distortion caused by the bending of the normal conducting metal base material 11, but also the distortion caused by bending the normal conducting metal base material 11 can be removed. A superconducting coil without a decrease in capacity and stabilizing current can be provided.

In addition, in the above superconducting coil, the normal conducting metal base material 11 is formed into a coil shape, and then the holding member 7 to which the normal conducting metal base material 11 is fixed is heat-treated to fix the superconducting strand assembly 14. It is also possible to form a superconducting coil by bending the normal conducting metal base material 11 into a substantially coil shape and heat-treating it, and then winding the normal conducting metal base material 11 into a coil shape and fixing the superconducting strand assembly 14. .

In this case, since it is only necessary to heat treat the normal conductive metal base material 11, there is an advantage that the heat treatment apparatus can be simplified.

Furthermore, in another embodiment of the method for manufacturing a superconducting coil according to the present invention, the normal conducting metal base material 11 is bent into a substantially coil shape and heat treated, and the superconducting strand aggregates 14 are formed on the surface of the normal conducting metal base material 11. A superconducting wire 2 created by fixing a superconducting wire or winding and fixing a superconducting strand can then be completely formed into a coil shape to form a superconducting coil.

In this case, almost no distortion occurs due to bending of the superconducting wire 2.

Furthermore, according to this method, the superconducting wire assembly 14 can be fixed to both sides of the normal conducting metal base material 11 as shown in Fig. 4, and the pancake-shaped superconducting coil shown in Fig. 1 can also be manufactured. You can also.

As described above, according to the present invention, the superconducting wire is fixed after the normal conducting metal base material is wound into a coil shape or a substantially coil shape and heat treated, so that the bending radius of the superconducting wire is not a constraint. Therefore, it is possible to manufacture a large superconducting coil without deterioration in superconducting current capacity and stabilizing current.

[Brief explanation of the drawing]

Figure 1 is a partially cutaway view of a pancake-shaped superconducting coil, Figure 2
Figure 3 is a cross-sectional view of a disk-shaped superconducting coil, Figure 3 is a perspective view showing the shape of the superconducting coil, Figure 4 is a perspective view showing the completed state as a conventional solder type superconducting wire, and Figure 5 is a stranded wire and strip-shaped twisted wire. A perspective view showing lines, FIG. 6, is one embodiment of a prior art method of manufacturing superconducting coils. In the figure, 1 is a superconducting coil, 2 is a superconducting wire, 11 is a normal conducting metal base material, 12 is a groove, 13 is a superconducting wire, 14 is a superconducting wire assembly, and 15 is a solder. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A step of winding a normal conducting metal base material into a coil shape, a step of heat treating the normal conducting metal base material wound into a coil shape, and a surface of the heat treated normal conducting metal base material. A method for manufacturing a normal conductive coil, which comprises the step of fixing superconducting wires with solder. 2. A step of bending the normal conducting metal base material into a substantially coil shape, a step of heat treating the normal conducting metal base material bent into the substantially coil shape, a step of winding the heat treated normal conducting metal base material into a coil shape, A method for manufacturing a superconducting coil comprising the step of fixing a superconducting wire with solder to the surface of a normal-conducting metal base material wound into a coil shape. 3. A step of bending a normal conducting metal base material into a substantially coil shape, a step of heat treating the normal conducting metal base material bent into a substantially coil shape, and a step of applying a superconducting wire to the surface of the heat treated normal conducting metal base material with solder. A method for manufacturing a superconducting coil comprising the steps of fixing to form a substantially coil-shaped superconducting wire, and winding the substantially coil-shaped superconducting wire into a coil shape.