JP2525016B2 - Superconducting wire - Google Patents

Description

The present invention relates to a structure of a superconducting wire having a large keystone angle which can be used for a dipole magnet or the like.

[Conventional technology and its problems]

A dipole magnet for deflecting the proton flux is used in the proton synchrotron, which is a particle accelerator for high energy physics research. This magnet is usually 50
A superconducting coil having an inner diameter of ˜200 mm, which is composed of a rectangular shaped stranded wire having a trapezoidal or keystone cross section.

Conventionally, two types of methods shown in FIG. 3 have been performed as the method of winding the above-mentioned formed stranded wire. That is, (1) The first method is to wind several layers of a superconducting wire 1b having a small keystone angle 2θ (shown in FIG. 4 (a)) representing the gradient of the formed stranded wire, as shown in the I quadrant of FIG. After the line, the central angle is adjusted by the spacer 2 to improve the magnetic field accuracy in the Y-axis direction. In this case, the structure of the superconducting wire 1b is shown in Fig. 4 (a).
As shown in, after compressing a plurality of superconducting wires 4 in which NbTi filaments are embedded in a Cu-stabilized metal,
It is covered with an insulator 3 such as a tape.

(2) In the second method, as shown in the second quadrant of FIG. 3, a spacer is built in advance so that the keystone angle 2θ (shown in FIG. 4 (b)) representing the gradient of the molded stranded wire becomes large. Superconducting wire
It is a winding of 1c. In this case, the structure of the superconducting wire 1c is as shown in FIG. 4 (b), and after compressing the superconducting element wires 4 into a plurality of stranded wires, taper spacers 2 are applied from both sides, and the outside thereof is covered with an insulator 3. Is coated with.

[Problems to be solved by the invention]

The above-mentioned proton synchroton has been increasing in size in recent years, and there is a recent demand for the development of a superconducting magnet with a high magnetic field of 5 to 10 T level. In contrast to this tendency, in the conventional winding method, as will be described in detail below, the normal conduction transition is apt to occur due to the frictional heat caused by the movement of the wire during energization, and therefore a large number of trainings and a high magnetic field can be obtained. I couldn't help but was having trouble.

That is, when the winding is performed by the above-mentioned first method, the keystone angle cannot be made large conventionally, so that the deviation from the arch structure is large when assembled in the structure shown in the quadrant I of FIG.
Moreover, it has a non-uniform structure in which spacers are inserted every few layers. Therefore, the balance of the forces in the X and Y directions is poor, and it is difficult to tighten it sufficiently from the outside. Therefore, mechanical stress due to thermal contraction or the like tends to cause misalignment between the wire rods, and in FIG. The electromagnetic force acts on the spacer 2, but the electromagnetic force does not act on the spacer 2, so that the wire rod is easily displaced from the spacer. Furthermore, since the keystone angle cannot be made large in the first method, it is not possible to make the coil inner diameter too small even if spacers are inserted every few layers, so the magnetic field distribution in the Y-axis and Z-axis directions is very good. There wasn't.

Further, when the winding is performed by the above-mentioned second method, the keystone angle is tentatively large and the arch structure has a good balance with respect to the mechanical stress. In FIG. 2B, the superconducting element wire 4 is likely to be displaced from the spacer 2 by the electromagnetic force. Further, since the flat structure has a complicated structure in which spacers are applied to both sides of the flat stranded wire, it is troublesome to manufacture and there is a problem in dimensional accuracy and the like.

[Means for solving problems]

The present invention has been made as a result of earnest research in order to solve such problems, and in a keystone-shaped molded stranded wire obtained by twisting and compressing a plurality of superconducting element wires, a keystone angle 2θ is obtained.
Is 2 tan ^-1 (α / N) or more, and a spacer consisting of a superconducting wire group with a triangular, trapezoidal or rectangular cross section is built in between the upper and lower strands of the cross section. is there. However, N is the number of strands, and α is a constant in the range of 0.3 to 1.0 depending on the type of superconducting wire.

In the present invention, N is the number of strands (however, N ≧ 3), and α is a constant determined by the type of superconducting wire and the manufacturing process (normal
When α> 0.4 for NbTi wire and α> 1 for Wind and React type Nb ₃ Sn wire, the keystone angle 2θ is 2tan ^-1 (α
/ N) The above limitation is that when it is less than 2tan ^-1 (α / N), the deviation from the complete and homogeneous arch structure is large when the flat twisted wire is wound, and the wire rod moves when energized. This is because a high magnetic field cannot be obtained even if the number of trainings is increased. Further, not only simply increasing the keystone angle 2θ, but also by incorporating a spacer between the superconducting wires as shown in FIG. 1, when the wires are subjected to centrifugal force due to electromagnetic force,
It is necessary to prevent the strands from moving relative to the spacers. If the spacers are not built in between the strands as shown in FIG. 4 (b), Will move and will be displaced with respect to the spacer. Furthermore, by incorporating a spacer, a cooling effect from the inside of the wire can be expected, and a reinforcing effect in the winding direction can also be expected.

As the spacer is made of a thin wire group of superconducting wires, an insulated thin copper wire or a thin copper wire coated with a high resistance material such as cupro-nickel is used, for example, by braiding. A higher critical current (I _C ) can be expected as compared with the case of

[Action]

In the present invention, the keystone angle 2θ is increased and a spacer made of a superconducting wire group is built in between the upper and lower strands of the cross section so that the movement of the wire due to mechanical stress and electromagnetic force does not occur. However, the normal conduction transition due to frictional heat during movement of the wire is eliminated, and it is possible to obtain a high magnetic field with a small number of trainings. Also, by increasing the keystone angle 2θ, the inner diameter of the coil can be made smaller, and the magnetic field distribution in the Y-axis and Z-axis directions became better.

Example 1 Next, the present invention will be described more specifically by way of examples. FIG. 1 is a cross-sectional view of a keystone shaped twisted wire according to the present invention, in which 1a is a superconducting wire (keystone shaped twisted wire), 2 is a spacer, 3 is an insulator, and 4 is a superconducting element wire. As the superconducting element wire 4, a superconducting wire (wire diameter: 0.648 mm, in which a plurality of Nb-46.5 wt% Ti alloy filaments are embedded in a copper-stabilized metal)
Filament diameter: about 5 μm, copper ratio: 1.69, twist pitch: 25 mm) was used. As the spacer 2, wire diameter 0.1 mm
Two pieces of braided 75 NbTi superconducting wires of No. 2 were stacked and formed by a turks head into (0.3 to 0.7) × 5.5 mm. Around the spacer 2, 30 superconducting wires 4 are stranded at a pitch of 72 mm, and (1.06
.About.1.50) .times.9.67 mm and processed by tape winding insulation as the insulator 3 to obtain the superconducting wire 1a. The keystone angle 2θ of the superconducting wire 1a is 2.60 °, and the critical current (I _C ) is 8700A and 3500A at 5T and 8T, respectively.
And the critical current (I _C ) of each spacer is 42
It was 0A and 170A. Further, when the superconducting coil is manufactured by winding the superconducting wire 1a, a dipole coil having an inner layer coil inner diameter of 40 mm and an outer layer coil outer diameter of 80.4 mm is obtained, and design characteristics (critical current (I _C ) : 5500A, central magnetic field: 6.5T).

[Example 2] As a superconducting element wire, a superconducting wire (wire diameter: 0.7) in which a plurality of Nb-46.5wt% Ti alloy filaments are embedded in a copper-stabilized metal.
48 mm, filament diameter: about 6 μm, copper ratio: 1.71, twist pitch: 25 mm), and the spacer 2 has a wire diameter
75 pieces of 0.1 mm NbTi superconducting wires were braided, and two pieces were piled up to have a size of 0.5 × 5.5 mm. Around the spacer, the 26 superconducting wires are twisted at a pitch of 72 mm, and after being processed into a size of (1.17 to 1.96) × 9.72 mm,
Tape winding insulation was performed and a superconducting wire was obtained. The keystone angle 2θ of the superconducting wire is 4.65 °, the critical currents (I _C ) are 10900A and 4200A at 5T and 8T, respectively, and the critical currents (I _C ) of the spacers are 860, respectively.
It was A, 350A. Further, when the superconducting coil was manufactured by winding the above-mentioned superconducting wire, a dipole coil having an inner layer coil diameter of 40 mm and an outer layer coil outer diameter of 80.4 mm was obtained, and the design characteristics were reached after two trainings.

[Conventional example]

The same superconducting element 4 as in Example 1 is used,
An insulated copper wedge is used as the spacer 2, and the superconducting wire 4 is 1.06 to 1.27 × as shown in FIG. 4 (a).
After processing the superconducting wire 1b obtained by coating the insulator 3 with a stranded wire to a dimension of 9.73 mm and winding several layers, the center angle was adjusted with the spacer 2 to produce a superconducting coil. A dipole coil having an outer diameter of 120 mm and an outer diameter of 160.4 mm was obtained. The dipole coil did not reach the design characteristics even after being energized (trained) 10 times, and the critical current (I _C ): 5
Only 200A, central magnetic field: 5.5T was obtained.

〔The invention's effect〕

When the coil is formed of the superconducting wire of the present invention, it is possible to obtain a high magnetic field with a small number of trainings as compared with the coil of the superconducting wire using the spacer formed of a conductor that is not a superconductor, and the coil inner diameter is It is small and has a good magnetic field distribution, and it can be expected to have a cooling effect, a reinforcing effect, and the like for the spacer portion composed of the superconducting thin wire group.

[Brief description of drawings]

FIG. 1 is a diagram showing the structure of the superconducting wire of the present invention, FIG. 2 is a diagram showing the range of the keystone angle 2θ of the superconducting wire of the present invention, and FIG.
FIG. 4 is a cross-sectional view of a dipole magnet winding portion, and FIG. 4 is a view showing a structure of a conventional superconducting wire. 1a, 1b, 1c ... Superconducting wire, 2 ... Spacer, 3 ... Insulator, 4 ... Superconducting element wire.

Claims (1)

(57) [Claims] 1. A keystone shaped twisted wire obtained by twisting and compressing a plurality of superconducting wires, wherein the keystone angle 2θ is 2 tan.
^-1 (α / N) or more and between the upper and lower strands of the cross section,
A superconducting wire having a built-in spacer composed of a superconducting thin wire group having a triangular, trapezoidal or rectangular cross section. However, N is the number of strands, and α is a constant in the range of 0.3 to 1.0 depending on the type of superconducting wire.