JPS6338848B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a toroidal coil using a superconducting wire, and in particular, a toroidal coil that is an important component of a torus-shaped nuclear fusion device is constructed using a superconducting wire. Regarding.

[Background of the invention]

In recent years, research on torus-shaped fusion devices has made significant progress, and many large-scale experimental devices have been constructed.
Typical examples are "tokamak" and "stellarator"
etc. The main part of each of these consists of a toroidal coil that generates an annular magnetic field. Traditionally, toroidal coils have been made of copper or aluminum conductors similar to those used in general electrical equipment, but recently, large-scale toroidal magnetic fields have become required, which has caused problems such as increases in coil temperature and excitation power. Due to technical and economical reasons such as increase in the number of cooling devices, there is an increasing number of cases in which so-called cryogenic coils, which employ cooling methods using low-temperature liquefied gas such as liquid nitrogen, rather than conventional water cooling, are being used. In addition, Nb-Ti, Nb-Ti-Zr, Nb ₃ Sn,
There are many proposals to use superconducting wires made by combining superconductors such as V ₃ Ga with copper, aluminum, etc. in the form of wires or tapes.

FIGS. 1 and 2 show a toroidal coil, and the toroidal coil 1 is wound around a space in which the annular magnetic field is generated so as to generate an annular magnetic field. Looking at the magnetic flux density in the toroidal coil 1, the magnetic flux density in the toroidal coil 1 is high on the inner layer side of the coil and low on the outer layer side. In addition, in FIGS. 1 and 2, the torus center radius (also referred to as the main radius) of the toroidal coil 1 is R, the coil radius (also referred to as the minor radius) is a,
If the total number of turns of the coil is N and the excitation current is I, the magnetic flux density B at a point P inside the coil is approximately calculated by the following equation.

B≒μNI/2πr ...(1) (However, r is the distance from the torus center (Z-Z axis) 0 to point P, and μ is the magnetic permeability.) As is clear from equation (1), the toroidal coil The magnetic flux density B within 1 is half proportional to the distance r from the torus center 0. Therefore, the highest magnetic flux density in the toroidal coil 1 occurs at the inner layer point Pm on the 0 side of the torus center, and its magnitude is Bm≈μNI/2π(R−a) (2). From this, in the toroidal coil 1, the part near the torus center 0 becomes a high magnetic field,
The far side has a low magnetic field.

Generally, the allowable current of a superconducting wire (the current that can be safely passed without transitioning to normal conductivity) is limited by the magnetic flux density (experienced magnetic field) at the position where the superconducting wire is placed, and even for the same superconducting wire, the allowable current in a high magnetic field is lower than that in a low magnetic field. smaller than that in . Therefore, when constructing the toroidal coil 1 with superconducting wire, the part near the torus central axis (Z-Z), that is, in Fig. 1,
It is necessary to wind the superconducting wire with a superconducting wire that does not transition to normal conductivity at a specified current even in a magnetic field near the Pm point. However, this results in the use of superconducting wires of excessive quality with extremely large margins for portions far from the central axis of the torus. Furthermore, if the toroidal coil 1 is constructed using only superconducting wires for low magnetic fields, the current that can be passed through the superconducting wires will be reduced. The number of turns of the wire must be increased, resulting in a significant increase in the weight of the toroidal coil 1.

As described above, conventional toroidal coils using superconducting wires have the drawback that if one aspect is satisfied, favorable results cannot be obtained for the other, and an effective coil configuration cannot be achieved.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide an economical and effective arrangement that balances both high and low magnetic field parts even if a high magnetic field part and a low magnetic field part occur in the coil. The purpose of the present invention is to provide a toroidal coil using a superconducting wire.

[Summary of the invention]

In order to generate an annular magnetic field, the present invention divides a toroidal coil formed by winding a superconducting wire surrounding the annular magnetic field generation space into an inner layer coil and an outer layer coil, and the inner layer coil is divided into an inner layer coil and an outer layer coil. The side of the innermost layer of the coil near the center of the torus is formed by winding a superconducting wire with a high critical current density in a high magnetic field, and the side of the inner layer coil far from the center of the torus is formed of a winding of a superconducting wire for low magnetic fields. Further, the outer layer coil is configured by winding a superconducting wire for low magnetic fields, and the inner layer coil and outer layer coil using the superconducting wire for low magnetic fields and high magnetic fields are connected in series so that the same current flows. By configuring it as follows, it is possible to achieve the intended purpose.

[Embodiments of the invention]

The present invention will be described below based on embodiments shown in the drawings.

FIG. 3 shows an embodiment of the present invention, and FIG. 4 shows the distribution of the toroidal magnetic field B generated in the toroidal coil 1 illustrated in FIG. 3 in the direction of the toroidal radius r in comparison with FIG. That is, C ₁ , C ₂ ,
The magnetic fields at each point of C ₃ , C ₄ , and C ₅ are B ₁ , B ₂ , and
They are _B3 , _B4 , and _B5 .

The example shown in Fig. 3 shows a coarsely wound coil in which the coil is not wound tightly in the toroidal direction but is divided into multiple coil units and arranged with gaps between the coil units. For a coil like this, it will look like the dotted line in Figure 4,
The magnetic field at point C ₄ becomes B ₄ ′. In the example of Fig. 3, for example, if R = 6 m, a = 3 m, t ₁ = 0.5 m, t ₂ = 0.5 m, and magnetomotive force NI = 1.35 × 10 ⁸ (AT), then the magnetic field at each point in Fig. 3 is B ₁ ≒0, B ₂ ≒4.5wb/m ² , B ₀
≒4.5wb/m ² and B ₄ ≒3wb/m ² . Therefore, in this embodiment, the toroidal coil 1 is divided into an inner layer coil 2 and an outer layer coil 3, and the winding on the side closer to the torus center (Z-Z axis) of the inner layer coil 2,
In other words, the area surrounded by the line connecting D ₃ −D ₂ −C ₂ −D ₅ −D ₄ −C ₃ −D ₃ is wound with a superconducting wire having a high critical current density in a high magnetic field, and the side far from the center of the torus is The area surrounded by the wire connecting D ₃ −D ₂ −D ₅ −D ₄ −C ₄ −D ₃ is constructed by winding the superconducting wire for low magnetic field, and the outer layer coil 3 is It uses superconducting wire for low magnetic fields. The toroidal coil 1 consisting of the inner layer and outer layer coils 2 and 3 is connected in series so that the same current flows therethrough. In addition, each turn of the inner layer coil 2 has parts D ₂ to _{D 3} ,
And in parts _D4 to _D5 , the superconducting wire for high magnetic field and the superconducting wire for low magnetic field are connected by soldering, pressure welding, explosion welding, or the like. Compound wires such as Nb ₃ Sn and V ₃ Ga can be used as superconducting wires for high magnetic fields, but the composition of alloy superconducting wires such as Nb-Ti-Zr, Nb-Ti, and Nb-Zr The cross-sectional configuration, heat treatment, etc. may be designed to be suitable for high magnetic fields. For example, in the case of a composite superconducting wire in which a superconducting wire made of Nb-Ti alloy is embedded in a base metal such as copper or aluminum, the cross-sectional area of the superconducting wire is increased for high magnetic fields than for low magnetic fields. One way is to use .

With this configuration, the magnetic flux density can be
All parts larger than B ₂ use superconducting wires that have a large critical current even in high magnetic fields, so
A specified current can be passed through the toroidal coil, and a specified magnetic field can be generated using a small toroidal coil. In addition, since a superconducting wire for low magnetic fields is used for other purposes, it is possible to obtain an effective and economical product.

〔Effect of the invention〕

According to the toroidal coil using the superconducting wire of the present invention described above, the toroidal coil is constructed by winding the superconducting wire surrounding the annular magnetic field generation space so that the annular magnetic field is generated. It is divided into a coil and an outer layer coil, and the inner layer coil is constructed by winding a superconducting wire with a high critical current density in a high magnetic field on the innermost side of the coil, which is closer to the torus center, and the inner layer coil is formed on the side far from the torus center. is constructed by winding superconducting wire for low magnetic fields,
Further, the outer layer coil is configured by winding a superconducting wire for low magnetic fields, and the inner layer coil and outer layer coil using the superconducting wire for low magnetic fields and high magnetic fields are connected in series so that the same current flows. Therefore, even if a high magnetic field part and a low magnetic field part occur in the coil, the superconducting wire can be arranged in an effective arrangement that matches both, making this type of coil economical. can be obtained.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing a conventional toroidal coil, Figure 2 is a sectional view taken along line A-A in Figure 1, and Figure 3 is an embodiment of a toroidal coil using the superconducting wire of the present invention. The cross-sectional view, FIG. 4, is an explanatory diagram showing the magnetic flux density of each part of the device shown in FIG. 3. 1...Toroidal coil, 2...Inner layer coil,
3...Outer layer coil.

Claims (1)

[Claims] 1. In a toroidal coil constructed by winding a superconducting wire surrounding a space in which the annular magnetic field is generated so that a magnetic field is generated in an annular shape, the toroidal coil is divided into an inner layer coil and an outer layer coil, and the inner layer coil is divided into an inner layer coil and an outer layer coil. The innermost layer of the coil, on the side near the torus center, is composed of windings of superconducting wire that has a high critical current density in high magnetic fields, and the side of the innermost layer of the coil, far from the torus center, is composed of windings of superconducting wire for low magnetic fields. and the outer layer coil is formed by winding a superconducting wire for low magnetic field, and the inner layer coil and outer layer coil using the superconducting wire for low magnetic field and high magnetic field are connected in series and are identical. A toroidal coil using superconducting wire that is characterized by being configured to allow current to flow.