JPH01102812A - Superconductive wire - Google Patents

Abstract

PURPOSE:To provide high magnetic field with a small number of trainings by enlarging the keystone angle, and incorporating a spacer between upper and lower element wires at the cross section. CONSTITUTION:Keystone angle 2theta is enlarged, and a spacer 2 is incorporated between upper and lower element wires at the cross section, and thereby wire movement due to mechanical stress and electromagnetic force is hindered. This eliminates normal conductive transfer due to friction heat at the time of wire movement, and it is now practicable to obtain high magnetic field with a smaller number of trainings. Enlargement of the keystone angle 2theta enables making the coil inner dia. smaller, and the magnetic field distribution in the Y and Z directions will be better.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a superconducting wire with a large keystone angle that can be used in dipole magnets and the like.

[Conventional technology and its problems]

The proton synchroton, a particle accelerator for high-energy physics research, uses a dipole magnet to deflect the proton flux. This magnet usually has 50
The superconducting coil has an inner diameter of ~200 mm and is constructed from rectangular shaped strands with a trapezoidal or keystone cross section.

The method of winding the above-mentioned formed stranded wire is as shown in Figure 3.
Several types of methods have been used in the past. That is, (1) the first method involves winding the superconducting wire 1b in several layers with a small keystone angle 2θ (shown in FIG. 4(a)) representing the slope of the formed stranded wire, as shown in the first quadrant of FIG. After the line, the center angle is adjusted using a spacer 2 to improve the precision of the magnetic field in the Y-axis direction.

In this case, the structure of the superconducting wire 1b is as shown in FIG. It is covered with an insulator 3.

(2) The second method is to incorporate a spacer in advance so that the keystone angle 2θ (shown in Fig. 4 (b)) representing the slope of the formed stranded wire becomes large, as shown in the first quadrant of Fig. 3. The superconducting wire 1c is wound. In this case, the structure of the superconducting wire 1c is as shown in FIG. It is coated with

[Problems to be solved by the invention] -The proton synchroton mentioned above has been becoming increasingly larger in recent years, and recently
There is a demand for the development of superconducting magnets with high magnetic fields of IOT class. In response to this tendency, with conventional wire winding methods, as detailed below, normal conduction transition is likely to occur due to frictional heat due to wire movement during energization, which requires a large number of training sessions and makes it difficult to obtain a high magnetic field. (It was causing trouble.)

That is, when winding wires using the first method described above, conventionally it was not possible to obtain a large keystone angle, so when assembled into the structure shown in the first quadrant of Figure 3, there was a large deviation from the arch structure, and the number of It has a non-uniform structure with spacers inserted in every other layer. Therefore, the balance of forces in the X and Y directions is poor,
Since it is difficult to tighten the wires sufficiently from the outside, mechanical stress caused by heat shrinkage etc. easily causes the wires to become misaligned, and as shown in Figure 4 (
In a), an electromagnetic force acts on the superconducting wire 1b, but no electromagnetic force acts on the spacer 2, which tends to cause the wire to shift relative to the spacer. Furthermore, in the first method, since the keystone angle cannot be made large, the inner diameter of the coil cannot be made very small even if spacers are inserted every few layers, and therefore the magnetic field distribution in the Y-axis and Z-axis directions is not very good. There wasn't.

In addition, when the wire is wound using the second method described above, the keystone angle becomes larger and the arch structure has a good balance against mechanical stress. In Figure (b)-a, the superconducting wire 4 was likely to be displaced from the spacer 2 due to electromagnetic force. Furthermore, since it has a complicated structure in which spacers are placed on both sides of each individual rectangular stranded wire, manufacturing is time-consuming and there are problems in terms of dimensional accuracy, etc.

[Means for solving problems]

The present invention was made as a result of intensive research to solve these problems, and the keystone angle 2θ is 2tan-1 (α/ N) A superconducting wire which is the above and is characterized in that a spacer consisting of a group of thin wires having a triangular, trapezoidal or rectangular cross section is built in between the upper and lower wires in the cross section. However, N is the number of strands, and α is a constant ranging from 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 N
For bTi line, a > 0.4, W in dand
For React type Nb and Sn lines, when α>1), the keystone angle 2θ is 2tan-1 (ff, /N)
The above limitation is due to the fact that if it is less than 2 t a n-1 (α/N), there will be a large deviation from a perfect and homogeneous arch structure when winding rectangular stranded wire, and the wire will move when energized. This is because it is not possible to obtain a high magnetic field even if the number of training sessions is increased. In addition to simply increasing the keystone angle 2θ, a spacer is built between the superconducting strands as shown in Figure 1, so that when the strands are subjected to centrifugal force due to electromagnetic force, the strands touch the spacer. It is necessary to prevent the wires from moving relative to each other, and if the spacer is not built in between the wires as shown in Figure 4(b), the wires may move and the spacer Further, by incorporating a spacer, a cooling effect from inside the cotton can be expected, and a reinforcing effect in the winding direction can also be expected.

As a spacer, a thin insulated copper wire or a thin copper wire coated with a high-resistance material such as cupronickel, for example braided, can be used.
In order to obtain the value of (IC), it is preferable to use a spacer made of a group of thin superconducting wires.

[Effect]

The present invention prevents movement of the wire due to mechanical stress and electromagnetic force by increasing the keystone angle 2θ and incorporating a spacer between the upper and lower wires in the cross section. The normal conduction transition due to frictional heat during movement is eliminated, making it possible to obtain a high magnetic field with fewer training sessions. Also, by increasing the keystone angle 2θ, it is possible to reduce the inner diameter of the coil, and Y
The magnetic field distribution in the axial and Z-axis directions became better.

(Example 1) Next, the present invention will be explained in more detail with reference to Examples. 1st
The figure is a cross-sectional view of a keystone shaped stranded wire according to the present invention, where 1a is a superconducting vA (keystone shaped stranded wire), 2
is a spacer, 3 is an insulator, and 4 is a superconducting wire. The superconducting wire 4 is a superconducting wire in which a plurality of Nb46,5W L%Ti-containing Ti filaments are embedded in a copper stabilized metal.
Wire diameter: 0.648mm, filament diameter: approximately 5μm1
Copper ratio: 1.69, twist pitch: 25 mm) was used. The spacer 2 has a wire diameter of 0. l m m Nb
Two layers of 75 braided Ti superconducting wires were stacked together and then (0.3 to 0.7) x 5.
A piece molded to 5 mm was used. Thirty superconducting strands 4 are twisted around the spacer 2 at a pitch of 72 mm, and processed to have dimensions of (1,6 to 1.5 (1) x 9.67 mm), and then used as an insulator 3. A superconducting wire 1a was obtained by tape wrapping and insulation.

The keystone angle 2θ of the superconducting wire 1a is 2.60", and the critical 'r!i current (1,) is 8700A and 3500A at 5T and 8T, respectively, and the critical current (IC) of the spacer is 420A, respectively. , 170A. When a superconducting coil was manufactured by winding the superconducting wire 1a, a dipole coil with an inner coil inner diameter of 40 mm and an outer coil outer diameter of 80.4 mm was obtained, and the design characteristics were achieved after two training sessions. (Critical current (Ic): 55
00A, central magnetic field: 6.57).

[Example 2] As a superconducting wire, a plurality of Nb 46.5 wt% Ti alloy filaments were embedded in a copper stabilized metal.
Wire (wire diameter: 0.748mm, 74 lament diameter: approx. 5p
The spacer 2 is made of 75 braided NbTi superconducting wires with a wire diameter of 0.1 mm, which are stacked together to form a 0.5
A sample having dimensions of 5.5 mm x 5.5 mm was used. Around the spacer, 26 superconducting wires are arranged at a pitch of 7.
Twist the wires at 2mm, (1,17~1.96) X9.7
After processing the wire to a size of 2 mm, it was wrapped with tape for insulation, and a superconducting wire was obtained. Keystone angle 2 of the superconducting wire
θ is 4.65°, and the critical current (+c) is 10900A and 4200A at 5T and 8T, respectively, of which the spacer critical current (I, ) is 860A, respectively.
A, it was 350A. In addition, when a superconducting coil was manufactured by winding the superconducting wire, the inner diameter of the inner layer coil was 40 mm.
A dipole coil with an outer layer outer diameter of 80.4 mm was obtained, and the design characteristics were reached after two training sessions.

[Conventional example] The same superconducting wire 4 as in Example 1 was used, and the spacer 2 was made of insulated copper.
As shown in a), the superconducting wire 4 has a thickness of 1.06 to 1.
After stranding the wire to a size of 27 x 9.73 mm, insulator 3
After winding the superconducting wire 1b obtained by coating several layers, the center angle was adjusted using a spacer 2 to manufacture a superconducting coil.The inner layer coil inner diameter was 120 mm, and the outer layer coil outer diameter was 16 mm.
A dipole coil of 0.4 mm was obtained. The dipole coil did not reach its design characteristics even after energization (training) 10 times, and the critical current (IC) was 5200A.

Central magnetic field: Only a value of 5.57 was obtained.

〔Effect of the invention〕

The present invention has made it possible to obtain a high magnetic field with a small number of training sessions. In addition, the coil of the present invention has a small coil inner diameter and a good °ζ magnetic field distribution, and can be expected to have a cooling effect, a reinforcing effect, etc. in the spacer portion, and has remarkable industrial effects.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of the superconducting wire of the present invention, FIG. FIG. 2 is a diagram showing the structure of a conventional superconducting wire. 1 a, 1 b, 1 c--1 superconducting wire, 2.
-Spacer, 3...-Insulator, 4...-Superconducting wire. Patent applicant Furukawa Electric Co., Ltd. 1 Number of strands N Figure 2

Claims (2)

[Claims] (1) In a keystone-shaped stranded wire made by compressing multiple superconducting strands, the keystone angle 2θ is 2tan^-^
1 (α/N) or more, and a superconducting wire characterized by incorporating a spacer consisting of a group of thin wires with a triangular, trapezoidal, or rectangular cross section between the upper and lower wires in the cross section, where N is an element. is the number of wires, and α is a constant ranging from 0.3 to 1.0 depending on the type of superconducting wire. (2) The superconducting wire according to claim 1, wherein the spacer is made of a group of thin superconducting wires.