JPH0250564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a superconducting wire used in a superconducting coil of a superconducting magnet such as a nuclear fusion reactor, and particularly to a type of superconducting wire that is forcedly circulated and cooled by a cooling medium.

Recently, a so-called hollow superconducting wire with a cooling medium passage formed in the center of its cross section has been used, and a cooling medium such as supercritical pressure helium is forced to circulate in the cooling medium passage to forcibly cool the superconducting wire from the inside. Various coils have been proposed. A hollow superconducting wire used in such a superconducting coil is, for example, as shown in FIG. A model in which the strands 3A are embedded, or a model in which the ultrafine multicore superconducting strands 3B are wound or twisted around the outer surface of a stabilizing base material 2 made of copper or the like, which also has a rectangular cross section, as shown in Fig. 2. Furthermore, as shown in FIG. 3, grooves 4 are formed on the outer surface of the stabilizing base material 2 having a rectangular cross section, and shaped superconducting wires 3C are fitted and fixed in each groove 4. There are things etc.

In superconducting magnets using such forced cooling type superconducting wires, the cooling medium is forced to circulate inside the conductor, so each part is evenly cooled, and the coil is compact and has high mechanical strength. However, on the other hand, since the superconducting wires are cooled indirectly through a stabilizing base material such as copper, the cooling efficiency is low, which may cause some problems. There is a problem in that when a heat spot occurs in a part of the superconducting wire and the superconducting properties are lost, the recovery is delayed.

On the other hand, as shown in FIG. 4, a large number of superconducting strands 3B are housed inside a rectangular cylindrical body 6, and a cooling medium such as liquid helium is allowed to flow through the gaps 7 between the superconducting strands. A bundle type superconducting wire has also been proposed, and in this case, superconducting wire 3B
Direct cooling is performed by bringing the cooling medium into direct contact with the surface. However, in this type of superconducting wire, it is extremely difficult to allow the coolant to flow smoothly, and the flow of the coolant can locally become stagnant, causing the temperature to rise, creating heat spots, or causing heat spots to recover quickly. There is a drawback that it is not carried out.

Therefore, the present inventors took advantage of the above-mentioned hollow superconducting wire and the direct cooling type superconducting wire shown in FIG. 4 to achieve a high overall cooling efficiency and good local stability. A superconducting wire with a structure that can withstand electromagnetic force was proposed in Japanese Patent Application No. 1-31244. An example of this proposed superconducting wire is shown in FIG.

In FIG. 5, inside the stabilizing base material 10, which is hollow and has a rectangular cross section and is made of a highly conductive material such as copper, copper alloy, high-purity aluminum, or aluminum alloy, Nb-Ti alloy, Nb-Ti-Ta A plurality of superconducting strands 11 made of an alloy-based superconducting material such as an alloy or a compound-based superconducting material such as Nb ₃ , Sn, V ₃ Ga, Nb ₃ Ge, etc. are accommodated. and stabilizing base material 10
The outside of the stabilizer is surrounded by an outer sheath 13 having a rectangular cross section made of copper, stainless steel, titanium, titanium alloy, etc., with an appropriate number of separators 12 made of the same material as the stabilizing base material 10 or stainless steel, etc. The separator 12 creates a coolant flow path 14 between the outer surface of the stabilizing base material 10 and the inner surface of the jacket 13.
is ensured. Further, the stabilizing base material 10 is formed with a plurality of communicating passages 15 in the form of round holes, elongated holes, or slits, which communicate the cooling medium flow path 14 on the outside with the space on the inside. Therefore, a cooling medium such as supercritical pressure helium flowing through the cooling medium flow path 14 flows through the communication path 15 and passes through the gaps 16 between the superconducting wires 11 inside the stabilizing base material 10.
The cooling medium flows into the superconducting wire 11 and comes into direct contact with the superconducting strands 11. A flow of the cooling medium also occurs in the inter-wire gaps 16 of the superconducting wires 11 inside the stabilizing base material 10.

In the above-proposed superconducting wire, overall cooling is achieved by a steady flow of the cooling medium flowing through the cooling medium channel 14 outside the stabilizing base material 10, so that it is similar to the case of the conventional hollow superconducting wire. Uniform cooling is performed, and since the linear cooling medium comes into contact with the superconducting wire 11 itself inside the stabilizing base material 10 and is directly cooled, the cooling efficiency is high, and the cooling efficiency is high. A communication path 15 is connected to the inner cooling medium.
Because the superconducting wire is exchanged by flowing in and out through There is very little delay in cooling, and therefore the total cooling efficiency is excellent, and at the same time, steady stability and transient stability are also extremely excellent. In addition, in the superconducting wire proposed above, when a disturbance occurs and the superconducting state is broken and a magnetic flux flow state occurs, the current is shunted to the stabilizing base material, so heat is generated even in the stabilizing base material. However, since the heat generated by this stabilizing base material is also cooled by the cooling medium on the outside,
Compared to the conventional bundle type direct cooling method shown in Figure 4, the superconducting state can be recovered quickly, and as mentioned above, the cooling medium inside and outside the stabilizing base material can flow in and out through the communication path. In order to
Even if the aggregate structure of the superconducting strands in the stabilizing base material is such that the cooling medium does not flow smoothly in the longitudinal direction, such as a braided structure or a formed strand structure, there is no particular problem; Since there are no restrictions on the aggregate structure of the superconducting wire, there is a high degree of freedom in its design.Also, since the superconducting wire is placed in the center of the superconducting wire, the superconducting wire will not be affected by bending strain when wound around a coil such as a magnet. Compared to conventional superconductors, there is little deterioration in the characteristics of the wire, and since the superconducting wire is protected by the outer stabilizing base material, damage and deterioration of the superconducting wire due to electromagnetic force from the outside is effectively prevented. It has much superior characteristics compared to wire.

In addition, in the superconducting wire shown in FIG.
7B are stacked in two layers and accommodated in the stabilizing base material 10, and the two-layer superconducting wire aggregates 17A, 17B
A thin tape 18 made of a high-low conductive material such as Cypronickel is inserted between the two layers, so that the superconducting wire assemblies 17A and 17B in each layer do not come into direct contact with each other. With this configuration, it is possible to prevent deterioration of superconducting properties when a coupling current flows between each layer and the excitation speed is extremely high, such as in pulse drive. Furthermore, in the superconducting wire shown in FIG.
A thin tape 19 made of the same high-resistance conductive material as described above is also inserted between the stabilizing base material 10 and the stabilizing base material 10.
It plays a role in preventing coupling current from flowing between both layers via. However, although FIG. 5 shows a state where the tape 19 is provided on the entire outer surface of each layer 17A and 17B for the sake of simplicity, in reality, it is shown that the tape 19 is provided on the entire outer surface of each layer 17A, 17B, but in reality, the tape 19 is provided so as not to obstruct the inflow of the cooling medium from the communication path 15. It is usual to form a space as appropriate.

As described above, the proposed superconducting wire has better cooling efficiency and stability than conventional superconducting wires, and also has excellent mechanical strength against bending and external forces. It is ideal for various applications such as machinery, energy storage, magnetic resonance absorption, magnetic separation, etc., especially for superconducting wires for large, high-field magnets, and is especially suitable for tapes made of high-resistance conductive materials that contain superconducting wires in multiple layers. When 18 or 19 is inserted, the coupling current between each layer is prevented by the high-resistance conductive tape, making it ideal for pulse applications using large currents. However, when the present inventors conducted further research for practical application, it became clear that the above-mentioned proposed superconducting wire had the following problems.

As described above, the separator 12 is disposed between the outer surface of the stabilizing base material 10 and the inner surface of the jacket 13, and the separator 12 allows the cooling medium flow path 14 to be
is ensured. As a means for providing this separator 12, a rectangular separator 12 may be wound in an open spiral around the outside of the stabilizing base material 10, as shown in FIG. The reason why the separator 12 is rectangular is as follows. That is, as shown in FIG. 7a, a double pancake coil 20 is formed from a superconducting wire with a round separator 12,
When the electromagnetic force G acts on the double buncake coil 20, the separator 12 may be crushed by the electromagnetic force G and become elliptical. and,
When the separator 12 is crushed into an elliptical shape in this way, gaps 21, 21 are created between the superconducting wires of the double pancake coil in the radial direction of the coil, and these gaps 21, 21 are This can lead to fatally defective wire movements. Therefore, in order to prevent such a situation, it is necessary to make the separator 12 into a rectangular shape in advance, as described above.

However, even if the rectangular separator 12 is provided in advance for the above reasons, there are further difficult problems as described below. That is, firstly, if a method is adopted in which the flat wire is cabled to the stabilizing base material from the beginning, it is very difficult to tightly wrap the flat wire around the stabilizing base material. Second, if a round wire is first cabled to the stabilizing base material and then rolled down to make a rectangular wire, the superconducting wires housed in the stabilizing base material will be damaged during rolling down. There is this inconvenience.

In view of the above circumstances, the present invention provides a separator that can be formed by tightly wrapping a rectangular wire that has high strength against electromagnetic force around a stabilizing base material when producing a forced cooling type superconducting wire. The purpose is to provide a method for forming.

That is, in the present invention, a plurality of superconducting strands are housed inside a hollow stabilizing base material having a rectangular cross section, and a separator is disposed between the stabilizing base material and an outer sheath surrounding the stabilizing base material. The separator forms a cooling medium flow path that is continuous in the longitudinal direction of the stabilizing base material, and the stabilizing base material has a communication path that communicates between the inside and outside of the stabilization base material, and the cooling medium flow path is formed in the stabilization base material. The separator of the forced cooling type superconducting wire is configured such that the cooling medium flowing through the passageway flows into the gap between the superconducting wires in the stabilizing base material to directly cool the superconducting wires. In this process, a round wire to be the material of the separator is attached in an open spiral to a core having the same dimensions as the stabilizing base material, and the round wire wound around the core is rolled together with the core. The rolled rectangular wire is made into a rectangular wire and brought into close contact with the outer surface of the core, and then the rolled rectangular wire is compressed in the longitudinal direction of the core so that the pitch becomes narrower, thereby lifting it from the core and removing it from the core. After fitting the removed rectangular wire into the stabilizing base material, the rectangular wire is stretched to the same pitch as when rolled on the core body, so that the rectangular wire is brought into close contact with the stabilizing base material to form the separator. The present invention is characterized in that a separator can be formed by tightly wrapping a rectangular wire around a stabilizing base material without damaging the stabilizing base material.

The method for forming the superconducting wire separator of the present invention will be explained in more detail below.

FIG. 8 is a diagram showing each step of the method for forming a separator of the present invention.

First, as shown in FIG. 8a, a round wire 23 is wound in an open spiral at a predetermined pitch around a core 22 having the same dimensions as the stabilizing base material of the superconducting wire. As the core body 22, a hard material is used so that it will not be crushed by the pressure even if the rolled round wire 23 is subjected to rolling processing, which will be described later. Next, as shown in FIG. 8b, the round wire 23 wound around the core 22 is rolled together with the core to form a rectangular wire 24 of a predetermined size, and is tightly attached to the core 22. let This rolling may be performed while winding the round wire 23 around the core body 22. Next, as shown in FIG. 8c, the rectangular wire 24 rolled on the core 22 is compressed in the longitudinal direction of the core 22 so that the pitch becomes narrower. By doing so, the rectangular wire 24 that has been tightly wound around the core body 22 is lifted from the core body 22, and can be inserted into and removed from the core body 22. Finally, the rectangular wire 24 removed from the core body 22 is fitted into a stabilizing base material having superconducting wires inside.
The fitted rectangular wire 24 is rolled on the core body 22 and stretched to the pitch when it is made into a rectangular wire, as described above. As a result, since the stabilizing base material and the core body 22 have the same dimensions as described above, the rectangular wire 24 comes into close contact with the outer surface of the stabilizing base material and is tightly wound around the stabilizing base material. The state will be as follows. After that, predetermined operations such as attaching the outer sheath are performed, and the production of the superconducting wire according to the above proposal is completed.

As is clear from the above description, according to the method for forming a separator of the present invention, a round wire is wound around a core made of a hard material and has the same dimensions as the stabilizing base material.
The round wire wound around the core is rolled into a rectangular wire of a predetermined size, and is brought into close contact with the core, and the rectangular wire is compressed in the longitudinal direction of the core so that it is compressed and lifted off the core. A separator is formed between the outer surface of the stabilizing base material and the inner surface of the jacket of the superconducting wire by inserting the rectangular wire into the stabilizing base material and stretching it to the pitch of the rectangular wire on the core body. By doing so, the rectangular wire, which is strong against the action of electromagnetic force, can be arranged as a separator in a state where it is tightly wound around the stabilizing base material. Then, when making the wire into a rectangular wire, as in the case where a round wire is wound as it is around a stabilizing base material and rolled down to make it into a rectangular wire,
There is no damage to the superconducting wires inside the stabilizing base material. In addition, by making the separator into a rectangular wire, a double pancake coil is formed, which prevents deformation of the separator due to electromagnetic force when used as a magnet, and prevents wire movement caused by gaps between the superconducting wires. This can prevent the superconducting wire from quenching.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views showing an example of a conventional hollow superconducting wire, FIG. 4 is a cross-sectional view showing an example of a conventional directly cooled superconducting wire, and FIG. 5 is a cross-sectional view showing an example of a conventional directly cooled superconducting wire. FIG. 6 is a perspective view showing an example of the proposed superconducting wire, FIG. 6 is a perspective view showing the stabilizing base material and separator in the superconducting wire of FIG. 5, and FIG. 7 is a partial cross-sectional view of a double pancake coil. FIG. 7a shows the separator before deformation, and FIG. 7b shows the state where wire movement has occurred due to deformation of the separator. FIG. 8 is an explanatory diagram of each process of this invention, FIG. 8a is a diagram showing a state in which a round wire is wound around a core, and FIG. 8b is a diagram showing a state in which a round wire is wound around a core. FIG. 8c is a diagram showing a state in which the rectangular wire is compressed on the core body in the longitudinal direction of the core body. 10... Stabilizing base material, 11... Superconducting wire, 1
2...Separator, 13...Outer jacket, 14...Cooling medium passage, 15...Communication path, 20...Double pancake coil, 22...Core, 23...Round wire, 2
4...Flat line.

Claims (1)

[Scope of Claims] 1. A plurality of superconducting strands are housed inside a hollow stabilizing base material with a rectangular cross section, and a separator is provided between the stabilizing base material and an outer sheath surrounding it. is arranged, and the separator forms a cooling medium flow path continuous in the longitudinal direction of the stabilizing base material, and the stabilizing base material has a communication path that communicates between the inside and outside of the stabilizing base material. The separator of the forced cooling type superconducting wire is configured such that the cooling medium flowing through the medium flow path flows into the gap between the superconducting wires in the stabilizing base material through the communication path to directly cool the superconducting wires. When forming, the round wire that is the material of the separator is wound in an open spiral around a core having the same dimensions as the stabilizing base material, and the round wire wound around the core is rolled together with the core. Then, the rolled rectangular wire is compressed in the longitudinal direction of the core so that the pitch becomes narrower, so that it is lifted from the core and removed from the core. After fitting the removed rectangular wire into the stabilizing base material, the rectangular wire is brought into close contact with the stabilizing base material by stretching it to the pitch when rolled on the core body, and the separator is formed. 1. A method for forming a separator in a forced cooling superconducting wire.