JPH0326485B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in compound superconducting conductors, and particularly to reinforcement structures thereof. In addition, the present invention improves the mechanical strength of compound superconducting conductors, as well as improves flexibility and
The purpose is to improve cooling efficiency and critical current characteristics.

Conventionally, a superconducting conductor of this type as shown in FIG. 1 has been proposed. In FIG. 1a, superconducting wires 2 are twisted around a reinforcing body 1. In FIG. In FIG. 1b, superconducting strands 2 are twisted in advance and secondary strands 3 are stranded around the reinforcing body 1. In FIG. In FIG. 1c, reinforcing strands 1' and superconducting strands 2 are twisted and then wound around a tape-shaped reinforcing body 1. In FIG. 1d, superconducting strands 2 are twisted and solidified with solder 50 inside a reinforcing body 1 having grooves 4 therein. Fig. 1e shows superconducting secondary strands 3 similar to those shown in Fig. 1b being twisted around a reinforcing body 1'' and then being placed inside a U-shaped reinforcing body 1 with one side open. Figure 1f shows a superconducting secondary wire 3 similar to that shown in Figure 1b, which has been twisted in advance and stored in a tube of a reinforcing body 1 having cooling holes 5 on the side. It is something.

When these structures are applied to compound superconducting conductors, there are the following drawbacks.

1 The superconducting conductor shown in Figures 1a and b has the superconducting strands 2 or secondary strands 3 located in the outermost layer, so there is no protection function against external stress and strain received during the insulation treatment process, winding process, etc. 2. The superconducting conductor shown in Figure 1c has unevenness in the longitudinal direction because the reinforcing bodies 1 are disposed discontinuously outside the wire, and as a result of these unevenness coming into contact between adjacent turns of the coil in a disordered manner during the winding process. , an irregular gap occurs in that part, stress concentration occurs, and the current characteristics deteriorate.

3 The superconducting conductors shown in Figure 1 d, e, and f have a protective function against strain caused by external stress, but because the reinforcing bodies are manufactured by machining such as cutting and extrusion, they are thick. However, the weight cannot be reduced, resulting in an excessive space factor, and the current density of the conductor as a whole decreases accordingly. Also,
Since the reinforcing body is thick, flexibility during the winding process is poor. Furthermore, there is a limit to densely distributing a large number of cooling holes added by machining, and since the coil after winding has a low probability that the cooling holes of adjacent conductors will meet each other, the refrigerant liquid He or He gas The passages do not communicate with adjacent conductors, resulting in poor cooling efficiency.

Compound superconducting conductors inherently have excellent superconducting properties such as critical temperature, critical magnetic field, and critical current density, and are promising as winding wires for high magnetic fields. However, unlike alloy superconducting conductors, compound superconducting conductors are strain-sensitive, meaning that their superconducting properties significantly deteriorate when subjected to strain, and they are usually unusable in the strain range of 0.2 to 0.6% or more. On the other hand, the requirements of the users of compound superconducting conductors are that they must be able to be bent to a small radius of curvature, have a large current capacity, be a long continuous large conductor, and have a uniform reinforcement effect in the coil. It is that you are.

Wire assembly type compound superconducting conductors are attracting attention as a material that meets these demands. Typical forms of wire assembly type compound superconducting conductors are stranded wires, braided wires,
Dislocation lines and compression molding of these.

However, the essential drawbacks of the wire assembly type compound superconducting conductor are that it easily expands in the longitudinal direction and contracts in the radial direction under small tension, so the conductor size changes during winding, etc., and there are many gaps between the wires. Therefore, if the filling rate of the strands is low and if the strands are locally restrained, such as by tightening the conductor at specified intervals with a reinforcing body, etc., when the strands are made into a coil, the strong electromagnetic force generated in the coil will cause damage. Stress and strain concentrate on the strands in the non-tightened portion, resulting in a significant deterioration of superconducting properties. Reinforcement of aggregated compound superconducting conductors must therefore be of a structure that overcomes the above-mentioned essential drawbacks and minimizes the concomitant reductions in flexibility, cooling efficiency, and current density.

In view of the above, and as a result of various studies, the present invention has been developed by adding a reinforcing body to a conductor in such a way that the butt part meanders in a zigzag manner in the longitudinal direction of the conductor, and a gap is created between the butt part. We have discovered a compound superconducting conductor with excellent properties, strength, cooling efficiency, and current density.

That is, the present invention provides a compound superconducting conductor having a reinforcing body on at least one of the outer periphery and the inside of a compound superconducting aggregate formed by assembling a plurality of compound superconducting strands. This is a compound superconducting conductor characterized in that it is provided along the longitudinal direction of the compound superconducting conductor.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 2 is an example of the compound superconducting conductor according to the present invention, and is a perspective view showing a partially expanded state of the reinforcing body. As is clear from the figure, this conductor is
A band-shaped reinforcing body 1 having corrugated portions 7 on both edges is placed around a strand-aggregated compound superconducting conductor 6 made of strands of so-called multicore superconducting strands 2, which incorporates a large number of compound superconducting filaments 20. 7 is formed so that a gap 9 remains at the abutting portion 8.

In this way, in the present invention, the strip-shaped reinforcing body 1 can be provided around the aggregated compound superconducting conductor 6 by forming, so that the thickness of the strip-shaped reinforcing body 1 can be kept to the necessary minimum. Therefore, compared to conventional reinforcement bodies made by machine processing,
Since the conductor can be made thinner and lighter, the current density of the entire conductor can be improved.

Furthermore, in the present invention, even if the conductor is bent when forming a coil or the like, bending wrinkles or the like will not occur in the reinforcing body. That is, since there is a meandering gap 9 in the abutting part 8 of the reinforcing body 1, if this abutting part 8 is bent so as to be on the inside of the bend on a certain surface, the reinforcing body 1 will be longitudinally A contraction force acts in the direction, but since the gap 9 is meandering, this gap 9
Shrinkage strain is absorbed by the reinforcing body 1, and this surface of the reinforcement 1 can be smoothly curved without wrinkles.

The shape of the corrugated portion 7 is appropriately determined depending on the size of the conductor, the radius of curvature when curving, the placement location of the reinforcing body, the required cooling rate, and the like. For example, when the radius of curvature is small, the wave height of the waveform portion 7 is made high and the wavelength (pitch) is made short. In addition, if a compound superconducting conductor is bent with a radius of curvature smaller than the allowable bending radius, the superconducting properties will be severely degraded and it will become unusable.
Avoid bending smaller than the allowable bending radius.
The interval of the gap 9 between the abutting portions 8 can also be set. That is, when bent to an allowable bending radius, the adjacent corrugated portions 7 of the abutting portions 8 come into contact with each other, which acts as a stopper and prevents further bending.

In addition, in the present invention, the gap 9 functions as a refrigerant inlet and outlet for liquid helium and helium gas to flow into and out of the conductor 6, so the spacing and meandering of the gap 9 can be adjusted according to the required cooling rate. You can decide the ups and downs.

Although FIG. 2 shows an example in which the abutting portion 8 is provided only on one side of the reinforcing body, the abutting portion 8 is not limited to this, and the abutting portion 8 is provided on only one side of the reinforcing body.
As shown in Figures a, b, c and d, a butt portion spanning two or three sides of the reinforcing body may be provided to facilitate bending of the conductor in multiple directions. In each of FIGS. 3A and 3B, only the reinforcing body provided around the conductor is shown, and the illustration of the conductor is omitted. Fig. 3a shows a reinforcing body 1 having a meandering gap 9 extending from one side surface X to the upper base surface Y, and the side surface X or the upper base surface Y cannot be bent so as to be on the inside of the bend. Can be done. Fig. 3b shows a reinforcing body 1 having a gap 9 meandering from one side X to the upper bottom surface Y and the lower bottom surface Z. It can be bent so that it is on the inside of the bend. Fig. 3c shows a reinforcing body 1 having a meandering gap 9 spanning three sides X, top Y, and W, and any of these three sides X, Y, and W can be bent. It can also be bent so that it is on the inside. FIG. 3d has a meandering gap 9 spanning the side surface X and the top surface Y of the reinforcing body 1, as in FIG. 3a, but the difference is that the corrugated portion 7 is inclined in one direction. It is different from Fig. 3a.

In the present invention, the reinforcing body provided in the wire assembly type compound superconducting conductor is not only provided around the conductor 6 as shown in FIG. In some cases, the conductor is provided in both directions, that is, in both the inside and the outer periphery of the conductor.

Further, in the present invention, as shown in FIG.
Inorganic material film 10 such as Al ₂ O ₃ and MgO on the outer peripheral surface of
It is preferable to provide electrical insulation between adjacent turns when a coil is formed. The above object can be achieved by providing the film 10 not only on the outer circumferential surface of the reinforcing body 1 but also on the inner circumferential surface thereof to electrically insulate the conductor 6 and the reinforcing body 1. Of course, it may be provided on both the inner and outer circumferential surfaces of the reinforcing body. Further, this film 10 also functions as a separator to prevent sintering between adjacent turns when a coil is manufactured by the wind and react method.

The material constituting the reinforcing body is non-magnetic, such as stainless steel, copper alloy, aluminum alloy, etc., and a single substance or a composite thereof can be used.

Further, the wire assembly type compound superconducting conductor used in the present invention is not specified in any way, but has been used conventionally. Twisted wires, braided wires, dislocation wires, or compression-molded wires made of a plurality of multicore compound superconducting strands, and wire or strip-shaped reinforcements for the cores of such stranded wires, braided wires, dislocation wires, and compression-molded wires. In addition, these wires may be used as primary wires, such as twisted wires, braided wires, dislocation wires, compression molded wires, etc. in the same manner as described above.

Although FIGS. 2 and 3 show a so-called keystone type cross-sectional shape in which the conductor and reinforcing body have different widths between the upper and lower surfaces, the present invention is not limited to this, and various cross-sectional shapes can be used. It may be something like that.

Next, examples of the present invention will be shown.

Example (internal reinforcement) Wavelength 3 on both edges of 0.2 mm thick stainless steel tape
Forming the one with a waveform part of mm and forming the fourth
As shown in the figure, thickness 0.4 mm, width 14 mm, adjacent corrugated part 7
A reinforcing body with a gap 9 of about 12 μm was obtained, and an alumina coating 10 was formed on the surface of the reinforcing body to obtain an internal reinforcing body 1.

(Tape for outer reinforcement) Thickness 0.2mm, maximum width (length between the crests of the waves on both edges)
A stainless steel tape measuring 46 mm in length and having corrugated portions with a wavelength of 5 mm on both edges was prepared for the outer reinforcing body.

(Secondary strand) 505 Nb cores are embedded in a Cu-Sn bronze matrix rod, and a Ta tube is coated on the outside as a diffusion barrier layer, and a high-purity copper tube is further coated on the outside as a stabilizing copper. The coated wire was subjected to surface reduction processing to obtain a strand with an outer diameter of 0.37 mm and a stabilized copper space factor of 50%. Next, we twisted these 7 strands and made 2 wires with outer diameter of 1.1mm
The next strand was obtained.

(Production of compound superconducting conductor and helium) Next, the secondary strands are placed around the internal reinforcing body.
Thirty wires were twisted together and compression molded using a roll to obtain a keystone-shaped stranded wire with external dimensions (upper base 2.0 mm, lower base 2.5 mm in cross section, height between both bases 16.5 mm). Next, form the above-mentioned outer reinforcing body tape on the outside of this formed stranded wire, and
A reinforced composite wire with a lower base of 2.9 mm, a height between both bases of 16.9 mm) and a meandering gap formed at the butt part with a spacing of approximately 12.5 μm was obtained, and alumina corrugated wire was applied to the outer surface of the wire.

Next, this composite wire was wound around a saddle form with a minimum bending radius of 25 mm, and after fixing, diffusion heat treatment was performed at 650℃ for 10 days.
A Nb ₃ Sn ₄ compound layer was formed at the interface between the bronze matrix and the niobium core in each strand. After that,
The coil was fixed with a metal collar from the outside of the saddle-shaped coil.

Next, we conducted an experiment to energize this coil in liquid helium (4.2〓), and found that the magnetic field was 10 Tesla.
A current value of 15500A was measured. This value is calculated from the critical current value of 73A (at 10 Tesla) of the Nb ₃ Sn compound superconducting wire obtained by performing the same diffusion heat treatment on the wire with an outer diameter of 0.37 mm (15330A). ) was confirmed to be in good agreement.

As a result of the above measurements, it was found that the compound superconducting conductor according to the present invention has a structure that can sufficiently withstand local tightening by a metal collar or the like and stress and strain caused by electromagnetic force.

Further, the following tests were conducted to determine the cooling characteristics of the superconducting magnet coil made of the conductor of the present invention.

The above coil was impregnated with epoxy resin, filling and sealing all the gaps between all the wires and between the wires and the reinforcing body under exactly the same conditions as above (liquid helium 4.2〓, magnetic field 10 Tesla ), a current value of 7200A was measured. This indicates that the compound superconducting conductor of the present invention has extremely excellent cooling properties.

Next, after the above test, the resin-impregnated coil was cut and observed, and it was found that the conductor was in good contact with both the inner and outer reinforcing bodies, even near the minimum bending radius, and there were local wrinkles on both reinforcing bodies due to curvature. No bumps or bumps were observed. Therefore, it was found that the reinforcing body could be bent well even if it was curved during coil winding, and it was found that the wire properties were excellent. In the above embodiment, the superconducting coil is wind and
Although it was produced by the react method, the present invention is not limited to this, and can also be produced by the react and wind method.

As explained above, the compound superconducting conductor according to the present invention not only facilitates mechanical reinforcement of the compound superconducting conductor with a simple reinforcing body, but also significantly improves flexibility, windability, and cooling properties, and Since it is a reinforcing material, it is possible to use a reinforcing material with the minimum necessary thickness, which improves the current density of the conductor accordingly.In addition, it has the same characteristics as the so-called short current characteristics obtained by measuring short conductors. Since it is reliably held even when it is made into a coil, it has extremely excellent advantages such as being able to significantly improve the current density of the coil as a whole.

[Brief explanation of drawings]

Figures 1a, b, d, e, and f are all cross-sectional views of conventional wire assembly type compound superconducting conductors, Figure 1c is a perspective view of a conventional wire assembly type compound superconducting conductor, and Figure 2 is a cross-sectional view of a conventional wire assembly type compound superconducting conductor. A perspective view showing a partially expanded state of the reinforcing body, which is an example of the compound superconducting conductor according to the present invention,
FIGS. 3a, b, c, and d are perspective views showing various examples of reinforcing bodies used in the present invention, and FIG. 4 is a perspective view showing an internal reinforcing body used in the embodiments of the present invention. 1: Reinforcement body, 2: Superconducting strand, 3: Secondary strand,
4: Groove, 5: Cooling hole, 6: Compound superconductor,
7: Corrugated portion, 8: Butt portion, 9: Gap, 10: Inorganic material film, 20: Compound superconducting filament,
X: side surface, Y: upper base surface, Z: lower base surface.

Claims (1)

[Scope of Claims] 1. In a compound superconducting conductor having a reinforcing body on at least one of the outer periphery and inside of a compound superconducting assembly formed by collecting a plurality of compound superconducting strands, a meandering gap is provided in the reinforcing body. A compound superconducting conductor, characterized in that it is provided along the longitudinal direction of the conductor. 2. The compound superconducting conductor according to claim 1, wherein the gap is provided so as to be located inside the bend of the winding of the compound superconducting conductor. 3. Claim 1, characterized in that the reinforcing body has an inorganic material coating on at least one side.
The compound superconducting conductor described in Section 1. 4. The compound superconducting conductor according to claim 1, wherein the reinforcing body is made of a non-magnetic material.