JPS60217610A - Superconductive device - Google Patents

Abstract

PURPOSE:To obtain a screening effect to a toroidal coil without reducing the effect of a poloidal coil at a superconductive device by a method wherein a low resistance metal is provided so as to surround an accommodating vessel. CONSTITUTION:A toroidal coil 1 is constructed of a wire 7 wound round in a solenoid type, and an accommodating vessel 8 to hold the wire thereof to the prescribed position. When the wire 7 is a superconductive wire, the accommodating vessel 8 surrounds the wire 7 to insure the stream of a liquid helium current. Moreover, when a low resistance metal 9 is provided on the periphery of the accommodating vessel 8 as to surround the vessel thereof, the low resistance metal 9 acts as a screening body to a fluctuating magnetic field formed by plasma, and besides the accommodating vessel 8 itself has sufficient strength to electromagnetic force. To a poloidal coil, because there exists division by the amount of the toroidal coil in the longitudinal direction, the current value of an eddy current is reduced.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a superconducting device. The present invention relates to a superconducting device equipped with a fixed storage container.

[Background of the invention]

In recent years, research on nuclear fusion devices has made significant progress, and many large-scale experimental devices have been constructed. Typical examples include ``Tokamas'', ``Stellarator'', and ``Mirror''.

The main part of each of these consists of a coil that generates a strong magnetic field.

Traditionally, these coils have been made using saws and aluminum conductors similar to those used in general electrical equipment, but recently large-scale magnetic fields have become required, resulting in increased coil temperature and excitation power. Due to technical and economical reasons such as increase in the number of coils, there are an increasing number of cases in which so-called cryogenic coils, which employ a cooling method using low-temperature liquefied gas such as liquid nitrogen, are being used instead of conventional water cooling. Also, as a conductor, Nb
-T i, Nb-T 1-Zr, Nb3Sn, V:l
There are many proposals to use superconducting wires made by bonding superconductors such as Ga with copper, aluminum, etc. into wires or tapes.

Generally, when a fluctuating magnetic field is applied to a superconducting wire, eddy currents are generated by the fluctuating magnetic field in the hooks and aluminum surrounding the wire.
It induces AC loss and generates heat.

This heat is cooled down by the evaporation of the liquid helium, but when the loss exceeds the allowable amount of heat radiation to the liquid helium, the temperature of the superconducting coil increases. When the temperature of the superconducting coil exceeds the critical temperature, the superconductivity is broken and a ``normal conduction transition'' occurs. If the normal conduction transition occurs over a wide range, the state will not return to the superconducting state, which is the so-called "quench state."

Since a nuclear fusion device ignites and maintains plasma, the plasma has a large current for a certain confinement time T, and generates an external changing magnetic field B as schematically shown in FIG. In recent years, as the performance of nuclear fusion devices has improved, the plasma confinement time T has become longer, and the plasma current has increased, shielding the fluctuating magnetic field B has become a major problem.

Now, if we consider the shielding body as an infinite cylinder as shown in Fig. 2 for the fluctuating magnetic field B shown in Fig. 1, we get
For that time constant, τ=μ. It is expressed as d a /2ρ...■. Here, d is the plate thickness, a is the radius, ρ is the low resistivity, and μ. is the vacuum permeability. It is known that in order to shield the fluctuating magnetic field as shown in Figure 1, it is sufficient to make a shield with low resistance and total bending such that r〉T...■.

Hereinafter, a conventional example will be explained using figures. Figure 3 shows an overview of torus-shaped nuclear fusion. Figure 3 shows a circular discharge tube 2 that confines plasma (not shown) inside, and a magnetic field applied in parallel to this discharge tube 2 to stabilize the plasma. At almost equal intervals along the longitudinal direction of the discharge tube 2,
A plurality of toroidal coils 1 are arranged in a solenoid shape so as to surround the circumference of the discharge tube 2. Furthermore, a current transformer coil 3 is arranged around the central axis of the torus for the purpose of heating the plasma by passing a large current through the plasma. The trondal coil 1 is connected to the frames 4 and 5 via sabots 1-6, and maintains structural strength against electromagnetic force and gravity. Further, a voloidal coil 15 is arranged parallel to the discharge tube 2 in order to compress the plasma and maintain equilibrium. Conventionally, in order to shield the fluctuating magnetic field associated with plasma confinement, a shield 16 has been installed on the inner periphery of the loidal coils 1 to 1 in parallel to the discharge tube 2.

However, as shown in FIG. 4, even when the current 17 is passed through the voloidal coil 15, an eddy current 18 that reduces the effect flows, so the shield 16 is It had a structure divided into eight parts in the longitudinal direction. In the future, as higher magnetic fields are required and the space between the toroidal coil l and the discharge tube 2 becomes smaller, the distance between the shield 16 and the voloidal coil 15 will become smaller, and even if the shield 16 is divided into eight parts, the effect of the eddy current 18 will be reduced. becomes impossible to miss.

However, if the shielding body 16 were to be divided into 20 parts by lO, the approximation of an infinite cylinder as shown in FIG. 2 could no longer be applied, and the original shielding effect would be lost.

[Purpose of the invention]

The present invention has been made in view of the above points, and its object is to provide a superconducting device that has sufficient strength for drawing and has a sufficient shielding effect.

[Summary of the invention]

That is, the present invention was developed based on the idea that instead of surrounding the source of the fluctuating magnetic field with a shield, the superconducting coil itself is surrounded with a shield, and a low-resistance metal is provided to surround the storage container. This makes it possible to obtain a shielding effect for the toroidal coil without reducing the effect of the voloidal coil.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described.
-Explanation will be given using drawings, taking a loidal coil as an example.

In FIGS. 5 and 6, the toroidal coil 1 is made up of a wire rod 7 wound in a solenoid shape and a storage container 8 for holding the coil in a predetermined position.
When superconducting wire is used, the storage container 8 not only holds the wire 7 in a predetermined position, but also surrounds the wire 7 to ensure the flow of liquid helium.

Therefore, if a low-resistance metal 9 is provided around the storage container 8 so as to surround it, the low-resistance gold R9 satisfies the conditions shown in FIG. It can itself have sufficient strength against electromagnetic force. At this time, for the voloidal coil, there is a division of 1-loidal coil in the longitudinal direction, so
The current value of the eddy current 18 as shown in FIG. 4 can be reduced. Here, as shown in FIG. 6, when the shield has a rectangular cross section, the radius a of the condition (2) may be a=L, L2/(L, +L2) -...-2. However, L, , L2 are two sides of the rectangle.

FIG. 7 shows another embodiment of the present invention. FIG. 7 shows a schematic diagram of another fusion device, a mirror type fusion device, in which plasma 12 is held in a mirror magnetic field 11. now,
When the coil 10 that moves the mirror magnetic field is a superconducting coil, the wire 7 is surrounded by a container 8 and held in a predetermined position. If the plasma 12 is confined and generates a fluctuating magnetic field, which may cause the wire 7 to "quench", it can be shielded by surrounding the storage container 8 with a low-resistance metal 9 that satisfies formulas (1), (2), and (3). The effect is the same. or,
The same applies even if the coil 10 is an "Ean coil" that generates a baseball magnetic field, as shown in FIG.

FIG. 9 shows still another embodiment of the present invention. ffi, Figure 9 is a schematic diagram of MHD power generation, and z by solenoid coil 7.
Due to the strong magnetic field in the axial direction, the plasma 11 running in the y direction generates a potential difference in the x axis direction and generates electricity.

Now, if solenoid coil 7 is a superconducting coil.

It is held by an inner wall 13 and an outer wall 14 to ensure a flow path for liquid helium. Now, a changing magnetic field is generated due to the fluctuation of the Braz 7 flow 12, and the superconducting coil 7 is "quenched".
When exposed to the danger, the same effect can be obtained by providing a low-resistance metal 9 that satisfies the conditions of formula (1) and (0) inside the inner wall 14.

〔Effect of the invention〕

As described in detail above, by equipping the storage container of the superconducting coil with a low-resistance metal so as to surround it, a sufficient shielding effect against the fluctuating magnetic field of a long pulse, such as plasma confinement, can be obtained. However, it is possible to create a storage container with sufficient structural strength by spinning the generation of eddy current that reduces the effect of the voloidal coil, and the effect is great.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of an external fluctuating magnetic field and a rectangular wave conversion time, Fig. 2 is a conceptual diagram showing the time constant of the shielding body against external fluctuations, and Fig. 3 is a diagram showing a conventional example. - A partially cutaway perspective view of the Las type fusion device, Figure 4 is the 3rd figure.
FIG. 5 is a cross-sectional view of a torus-type polar fusion device showing one embodiment of the present invention, and FIG. 6 is a partial perspective view of the superconducting toroidal coil adopted in FIG. 5. FIG. 7 is a perspective view showing a mirror-type nuclear fusion device; FIG. 8 is a perspective view showing a mirror-type nuclear fusion device using an ion coil; FIG. 9 is a perspective view showing MHD power generation. It is. h...Superconducting toroidal coil, 2...Plasma discharge point 3...Air core current transformer coil, 4...Bottom mount, 5...Top mount, 6...Support, 7...Superconducting wire ,
8... Superconducting wire storage container, 9... Low resistance metal, 1o
... Mirror magnetic field generating coil, 11... Lines of magnetic force (mirror's lift), 12... Plasma, 13... Inner wall of storage container, 14... Outer wall of storage container, 15... Voloidal coil, 16... Shielding body, 17... Voloidal coil current, 18... Polo also 2 figures and a half 3M, 5 figures, 6 figures of foil

Claims (1)

[Scope of Claims] (1) A superconducting device comprising a superconducting coil wound with a superconducting wire and a storage container for immersing the superconducting coil in a refrigerant and fixing it in a predetermined position. A superconducting device characterized by a low-resistance metal placed around a container. 2. The superconducting device according to claim 1, wherein the low resistance metal is made of aluminum. 3. The superconducting device according to claim 1, wherein the low resistance metal is made of copper.