JPS5928923B2 - Compound superconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a compound superconducting coil, and more particularly to a compound superconducting conductor formed by integrally attaching a stabilizing material to a compound superconducting wire formed by embedding a plurality of compound superconducting core wires in a matrix. This invention relates to improvements in the constructed compound superconducting coil.

A conventional superconducting coil using a compound superconducting conductor formed by integrally adhering a stabilizing material to a compound superconducting wire is composed of a conductor having a hollow cross-sectional shape as shown in FIG.

That is, FIG. 1 shows a compound superconducting wire 3 in which a plurality of compound superconducting core wires 2 are embedded in a rectangular matrix 1 in a symmetrical distribution about the center lines x and X' of the matrix 1. A stabilizing material 4 made of copper, aluminum, etc. is attached integrally with the metal. The stabilizing material 4 includes, for example, a stabilizing material piece 6 having a U-shaped cross section and having five grooves into which the compound superconducting wire 3 is fitted, and the compound superconducting wire fitted into the groove 5 of the stabilizing material piece 6. 3, the stabilizing material piece 7 is metallically bonded to the upper surface of the matrix 1, and the center line x of the matrix 1 is
, X' are set in a symmetrical dimensional relationship. Conventional compound superconducting coils using such conductors have had the disadvantage that the critical current deteriorates due to stress caused by bending or electromagnetic force that occurs when the conductor is assembled into superconducting equipment.

The present invention has been made in view of the above circumstances, and its purpose is to provide a compound superconducting coil that has less deterioration of critical current due to bending stress and can further improve the stability of superconducting equipment. It is in.

The present invention provides a compound superconducting coil constructed by winding a compound superconducting conductor formed by embedding a plurality of compound superconducting core wires in a matrix and integrally attaching a stabilizing material to the compound superconducting wire, in which the conductor crosses the The distance between the position of one neutral axis drawn on the surface and the position of the center line parallel to the neutral axis in the range where the compound superconducting core wire is distributed in the cross section is calculated as follows: It is set to approximately 1/6 of the diameter in the direction orthogonal to the center line of the distributed range, and the neutral axis is set on the side where the tensile stress of the compound superconducting conductor is applied with respect to the center line. By setting and winding the compound superconducting conductor, the compound superconducting coil has an excellent effect that the critical current does not deteriorate even when stress is applied to the conductor.

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 2 shows a cross section of a conductor according to an embodiment of the present invention, and this conductor is roughly divided into a compound superconducting wire 11 and a stabilizing material 12 integrally attached to this compound superconducting wire 11. It is made up of.

The compound superconducting wire 11 is constructed by embedding, for example, twelve compound superconducting core wires 14 in a symmetrical relationship about the center lines X and X' of the matrix 13 in a matrix 13 having a rectangular cross section, for example. ing. Note that Nb wire is used as the material for the compound superconducting core wire 14, and a Cu-Sn alloy is used as the matrix 13. After attaching the stabilizing material 12, heat treatment is performed to form compound superconducting wire on the surface of the Nb wire. The substance Nb3Sn
It is made up of layers. Therefore, the stabilizing material 12 is made of copper, aluminum, etc.
A stabilizing material piece 16 having a U-shaped cross section and having a groove 15 into which the compound superconducting wire 11 described above is inserted, and this stabilizing material piece 16
These stabilizing material pieces 16 and 17 are attached to the compound superconducting wire 11 so as to completely cover the outer periphery of the compound superconducting wire 11 as shown in the figure. The material is integrally attached to the outer surface of the material by low melting point metal joining, pressure welding, welding, etc.

The so-called side walls 16a, 1 of the stabilizing material piece 16 are
6b are set to equal values, and the stabilizing material pieces 16
(The thickness of the so-called bottom wall 16c is set as follows with respect to the thickness of the stabilizing material piece 17. In other words, the bottom surface in the figure along the longitudinal direction of this conductor is now on the inside of the bend. When the neutral axis drawn when applying a bending stress such as Specifically, the neutral axis Z is above the center line X in the figure, and the distance between the neutral axis Z and the center line X is the center line X in the range where the compound superconducting core wire 14 is distributed. The thickness of the bottom wall 16c is set to be approximately 1/6 of the diameter Y in the direction perpendicular to the diameter Y. The thickness of the bottom wall 16c of the stabilizing material piece 16 is set so that the neutral axis z is approximately located on the line divided into A:B-1:2 from top to bottom in the figure. By winding the constructed compound superconductor into a coil so that the bottom surface in the figure is always located on the inside of the curve, the critical current can be maintained even when the coil is manufactured or when bending stress is applied due to electromagnetic force. The reason for this will be explained in comparison with the conventional compound superconducting coil shown in FIG. The compound superconducting core wires 2 are distributed and buried in a symmetrical relationship with X' as the center, and the dimensions of the stabilizing material 4 are also set in a symmetrical relationship.For a conductor configured in this way, for example, If a bending force is applied that causes the lower surface in the figure along the longitudinal direction of the conductor to be located on the inside of the bend, the neutral axis position of the conductor at this time will be at the position of the center line They match.L. Therefore, a compressive force acts on the lower side of the figure from the center line X, and a tensile force acts on the upper side.The relationship between the compressive force and the tensile force is the tensile stress (strain). When compressive stress (strain) occurs, the critical current deteriorates by 1/2 the amount of strain compared to when compressive stress (strain) occurs.
do.

Note that the compound superconducting wire is Nb3 by heat treatment.
Since a compound superconductor such as Sn is generated, on the contrary, after cooling, the compound superconductor such as Nb3Sn is in a state where normal K compressive stress is applied, and the apparent stress-free state of the compound superconducting wire is the N line in Figure 3. It will be at that place. Further, the negative side of tensile strain indicates compressive stress, and the positive side indicates tensile stress. Now, for example, if the same stress of 0.5% is applied as compressive stress and tensile stress, the ratio of critical current 1e under stress to critical current c under no stress ((7) becomes 9
0% and 42%, which indicates that the critical current deteriorates approximately twice as much under tensile stress as compared to under compressive stress. Therefore, in the conductor having the structure shown in Fig. 1, the distance A from the center line X, that is, the neutral axis, to the outermost layer of the compound superconducting core wire is
, B are equal on both the tension side and the compression side, and the same stress is applied, so the deterioration on the tension side is large and it is a so-called weak conductor with respect to this bending stress.
On the other hand, in the configuration of the invention of the present application as described above, since the center line X and the neutral axis Z are shifted by 1/6 Y, the six compound superconducting Core wire 1
The tensile stress (strain) applied to 4 is approximately 1/2 of the compressive stress (strain) applied to the six compound superconducting core wires 14 located below.
This is a very small value.

This stress ratio is approximately equal to the stress ratio at which critical current deterioration is observed simultaneously in the compound superconducting core wire subjected to compressive stress and the compound superconducting core wire subjected to tensile stress. This means that with the above configuration, the bending radius at which critical current deterioration occurs can be made smaller than that of the conventional one, and as a result, when bending stress is applied, the bending direction is always constant; In the case of FIG. 2, by winding the coil so that the lower surface in the figure is always positioned on the inside of the bend, critical current deterioration due to bending stress can be significantly reduced compared to the conventional method. The inventors used a compound superconducting wire with a rectangular cross section of 5 x 1011101, and changed the thickness of each part of the stabilizing material integrally attached around the superconducting wire, so that the ratio of A and B described above was 1: 1 cross section 10×20n10
1 sample (conventional) and 1:2 cross section 10X20? When the relationship between bending diameter (bending stress, strain) and critical current Ic was investigated for these two types of samples, the results shown in FIG. 4 were obtained.

In the figure, the horizontal axis shows the bending diameter, and the vertical axis shows the ratio of Ic under bending stress to Ic under no stress (!
fl), the P curve shows the conductor used in the compound superconducting coil according to the present invention, and the Matomo Q curve shows the characteristics of the conductor shown in FIG. As is clear from this figure, the conductor used in the compound superconducting coil according to the present invention can be used up to a smaller bending diameter than conventional conductors. In other words, it is understood that it is a so-called strong conductor against bending stress GD. In addition, in the above-mentioned embodiment, the ratio of A and B is approximately 1:
2, and the larger one is located on the inside of the bend, but even if the above ratio varies somewhat, the corresponding effect described above can be obtained.

In addition, in the above-mentioned embodiment, the position of the neutral axis Z was shifted by adjusting the wall thickness of each part of the stabilizing material, but it is also possible to embed a reinforcing material in the stabilizing material or The position of the neutral axis Z may be shifted by attaching a reinforcing material to the material. In addition, in the above-mentioned friend embodiment, the lower surface in FIG. Alternatively, the thickness of the stabilizing material piece 17 may be made thinner, or a reinforcing material may be integrally attached to the lower surface so as to obtain the above relationship. Further, in the above embodiments, a monolith type compound superconducting core wire is used, but it goes without saying that a strand type or braided cable type can also be used. As detailed above, if the present invention is implemented, the deterioration of the critical current can be prevented even when large bending stress is applied during installation into superconducting equipment or when large bending stress is applied due to electromagnetic force. less,
A compound superconducting coil that is easy to use can be provided.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a conventional conductor, Fig. 2 is a cross-sectional view of a conductor used in a compound superconducting coil according to an embodiment of the present invention, and Fig. 3 is a tensile strain-critical current characteristic of a compound superconducting conductor. 4 are diagrams showing the results of an experiment in which the bending diameter-critical current characteristics of the conductor used in the compound superconducting coil of the present invention and a conventional conductor were investigated. 11... Compound superconducting wire, 12... Stabilizing material, 13... Matrix, 14...
...Compound superconducting core wire, Z...neutral axis.

Claims (1)

[Claims] 1. In a compound superconducting coil constructed by winding a compound superconducting conductor formed by integrally attaching a stabilizing material to a compound superconducting wire formed by embedding a plurality of compound superconducting core wires in a matrix, The distance between the position of one neutral axis drawn and the position of a center line parallel to the neutral axis in the range where the compound superconducting core wires are distributed in the cross section is defined as the distribution of the compound superconducting core wires. and the neutral axis is set on the side where the tensile stress of the compound superconducting conductor is applied with respect to the center line. A compound superconducting coil characterized by being made by winding a conductor.