JPH08148326A - Superconducting magnet device - Google Patents

Abstract

PURPOSE: To suppress frictional heating at the time of cooling or acting the electromagnetic force by interposing a bearing between a superconducting coil and a gap piece or between the gap piece and a cooling vessel. CONSTITUTION: When a superconducting coil 2 is secured in a cooling vessel 3, it is secured secured on three sides except the inner side of the coil while being clamped by means of gap pieces 5A, 5B and a ceramic bearing 6. When liquid helium is injected into the cooling vessel 3 in order to cool the superconducting coil 2, the coil 2 contracts in the radial direction along the gap piece 5B on the side face to cause a relative displacement between the coil 2 and the cooling vessel 3. When a current is fed to the coil 2, the circular coil is subjected to a hoop force for spreading the coil outward thus causing a relative displacement between the coil 2 and the cooling vessel 3 along the gap piece 5A on the side face. Since the relative displacement takes place through the bearing 6, frictional heating is suppressed to retard quenching of the superconducting coil thus enhancing the stability and reliability thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting magnet device.

[0002]

2. Description of the Related Art A conventional superconducting magnet device will be described with reference to FIG. 4 and FIG. 1 for reference. Superconducting magnet device 1
Stores a circular superconducting coil 2 in a hollow cooling container 3 having the same shape as the coil, and cools it to a cryogenic temperature (about 4 to 0.01 K) with liquid helium to generate a superconducting state. The superconducting magnet device 1 is configured.

In the superconducting magnet having such a structure, the superconducting coil 2 is suspended in a cooling container 3 for cooling and fixed, but at this time, the self-weight of the superconducting coil and distortion of the coil due to electromagnetic force do not occur. Therefore, the spacing piece 4 that withstands these forces is interposed and fixed between the container and the coil.

Although there is a system in which a large force does not work between the superconducting coil and the cooling container, an electromagnetic force acting on the superconducting coil is used like a superconducting magnet used for driving a vehicle in a magnetic levitation railway. In the case of system,
Since the electromagnetic force is much larger than the dead weight of the superconducting coil, a spacing piece capable of withstanding a large load is required.

For this reason, the superconducting coil and the cooling container must be firmly fixed in a highly rigid state. Therefore, the superconducting coil and the cooling container are almost integrated with each other, and no large deformation occurs between the superconducting coil and the cooling container.

On the other hand, the superconducting coil is used in a state of being cooled to a cryogenic temperature together with the cooling container and the interval piece. Since the cooling container and the interval piece and the superconducting coil have different thermal contraction rates, the relative position is small. Is also displaced. This displacement occurs during cooling and causes quenching (a sudden and uncontrollable normal conduction transition caused by thermal, electromagnetic or mechanical disturbances in a superconducting conductor that is energized). A method of fixing with a force larger than the stress (described in JP-A-63-51524),
In order to reduce frictional heat generation due to displacement, a method of sandwiching a material having a small coefficient of friction between a spacer and a superconducting coil (as described in JP-A-58-73104 and JP-A-4-320304, FIG. It is a diagram showing a conventional example quoted from Japanese Patent Laid-Open No. 4-320304).

After the superconducting coil has been cooled, it is desired to fix it in a highly rigid state. However, like when mounted on a magnetic levitation vehicle, the electromagnetic force acting on the superconducting coil is large and it is difficult to fix it, and it moves by all means. In some cases (vibrates).

[0008]

The thermal stress generated during cooling of superconductivity is large, and if the relative displacement between the superconducting coil and the cooling container is prevented from occurring, the superconducting coil will not be able to withstand this thermal stress and will be damaged. There is also. Even if it does not break, internal stress remains in the superconducting coil, causing damage or quenching by a small external force. From this, it is desirable that the superconducting coil and the cooling container are in a free state without contact during cooling. The occurrence of relative displacement between the superconducting coil and the cooling container means that slippage occurs at the interface between the superconducting coil and the cooling container, that is, heat is generated. If there is no contact, no slippage occurs, but as long as there is contact, there is slippage and heat is generated.

The larger the force with which the cooling container presses (fixes) the superconducting coil, the greater the frictional resistance and the greater the relative displacement, the greater the amount of heat generation. When a contact surface having a small frictional resistance is used between the superconducting coil and the spacing piece, between the spacing piece and the cooling container, or both (for example, application of tetrafluoroethylene or molybdenum dichloride). -73104 and the one described in Japanese Patent Application Laid-Open No. 4-320304), the electromagnetic force cannot be effectively transmitted to the cooling container, and heat is generated due to friction due to the electromagnetic force. In order to effectively transmit the electromagnetic force acting on the superconducting coil to the cooling container, we want to fix it as rigid as possible.For example, both the superconducting coil and the spacing piece, and both the spacing piece and the cooling vessel are for cryogenic use. Method of adhering with the adhesive of JP
No. 3-51524), the coil cannot bear the thermal stress at the time of cooling and an excessive force remains in the coil.

Therefore, there is provided a method of fixing a superconducting coil which does not quench the thermal stress at the time of cooling, does not generate heat even with an electromagnetic force, and fixes the superconducting coil and the cooling container with sufficient rigidity. It is an object of the present invention.
That is, during cooling, the contact resistance at the interface between the superconducting coil and the spacing piece, the spacing piece and the cooling container, or both is small and slippery, and yet, while maintaining a high rigidity against electromagnetic force. It is to reduce frictional heat generation.

[0011]

When fixing the superconducting coil 2 to the cooling container 3 via the spacing piece 5, either between the superconducting coil and the spacing piece, or between the spacing piece and the cooling container, Alternatively, the bearing mechanism 6 is used for both.

A non-magnetic material is used as the material of the bearing. For example, fine ceramics is good. Further, a material having a low thermal conductivity, a hard material 7 having a high hardness, or both are interposed between the bearing and the superconducting coil. At this time, this is divided into the smallest possible pieces and bonded to the superconducting coil side. At this time, if possible, a material having a low thermal conductivity is bonded, and a material having a high hardness
Is even better.

[0013]

By interposing a bearing between the superconducting coil and the spacing piece or between the spacing piece and the cooling container, the sliding friction conventionally caused by the relative displacement between the two is changed to rolling friction. As a result, frictional heat generation is reduced in both cases of cooling and application of electromagnetic force. Moreover, the bearing can be fixed with high rigidity against a force in the direction perpendicular to the bearing. With respect to the same direction as the bearing, by pressing the bearing on the surface perpendicular to the surface of the bearing, the bearing can be rigidly fixed in either direction.

The use of a non-magnetic material for the bearing is to avoid the adverse effect of the strong magnetic field of the superconducting coil. Of the non-magnetic materials that can be used at low temperature, ceramic is the most preferable for the bearing, and since the coefficient of friction with metal is generally small, it is optimal for the purpose of the present invention. Sandwiching hard materials together is to compensate for when the superconducting coil or the spacing piece itself cannot withstand the pressure of the ball of the bearing, and sandwiching the material with low thermal conductivity is the heat generated in the bearing part. This is because it is difficult for it to be transmitted to the superconducting coil.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on the embodiments shown in FIGS. This is an example of a superconducting magnet in which a circular coil is housed in a hollow cooling container having an inner circle, that is, a donut shape.

Since the coil cross section is rectangular in order to fix the superconducting coil 2 in the cooling container 3, four rectangular pieces, that is, four side surfaces of the coil may be fixed, but one surface inside the coil is excluded. Fix the three sides.

The three surfaces except the inner surface of the superconducting coil 2 have an insulating layer of fiber reinforced plastic (FRP), and the superconducting coil 2 is fixed by sandwiching it with spacing pieces 5A, B and a ceramic bearing 6 (spherical). To

The cooling container 3 is made of stainless steel and is divided into two parts. The superconducting coil 2 is housed inside and then joined by welding to form a hollow donut shape.

At the time of this welding, the cooling container contracts, and the spacing piece 5
The superconducting coil is compressed and fixed inside the container via A and B. Refrigerant is injected into the space 8 between the cooling container and the superconducting coil 2.

When cooling the superconducting coil by injecting liquid helium as a cooling medium into the cooling container 3 having such a structure, the spacing pieces 5A and 5B serve to hold the superconducting coil in the cooling container in a space fishing condition. The coil 2 contracts in the radial direction along the side spacing piece 5B. At this time, a relative displacement occurs between the superconducting coil 2 and the cooling container 3, but since this moving surface serves as the ceramic bearing 6, there is no sliding friction and almost no heat is generated.

Next, when an electric current is passed through the superconducting coil 2, a force (hoop force) is applied to the circular coil to spread it out of the circle. At this time, in order to prevent the coil from spreading to the outside, the cooling container 3 holds the coil against the force via the spacing pieces 5A and 5B. At this time, the superconducting coil is again displaced relative to the cooling container 3 along the space piece A on the side surface, but since this moving surface becomes the bearing 6 again, there is no sliding friction and almost no heat is generated. However, the direction of displacement is opposite to that during cooling.

The coil of this embodiment is used for various purposes because it is used for testing a magnetic field. However, in the coil for a magnetic levitation train and the coil for MRI, since the external magnetic field changes due to alternating current, the coil Receives the force of alternating current in the axial direction. In other words, it reciprocates (displaces) in the direction perpendicular to the surfaces of the spacing pieces (spacers) 5A and 5B. Also at this time, the superconducting coil has no sliding friction and hardly generates heat. However, the superconducting coil 2 is firmly fixed in the radial direction by the spacing pieces A and B.

In this example, the coil does not need to be supported from the inside because no force acts on its inner circle side.

Further, since there is no layer of FRP and no space piece inside the superconducting coil, the liquid helium is in direct contact with it and the cooling performance is good.

As described above, when the same superconducting wire as the conventional one is used to form a magnet of the same size, the current can be made to flow to the same value as the conventional one, and the current is made to be in the superconducting state. When an electromagnetic coil that generates an alternating magnetic field is associated with the magnet, the superconducting coil is less likely to be quenched, and a superconducting magnet with high stability and reliability can be obtained.

[0026]

According to the present invention, frictional heat generated by external mechanical force is reduced, so that the superconducting coil is less likely to be quenched, and as a result, a superconducting magnet having high stability and reliability can be obtained. Become.

[Brief description of drawings]

FIG. 1 is a perspective view of a superconducting magnet device according to the present invention.

FIG. 2 is a partial detailed view of FIG.

FIG. 3 is a view taken along the line III-III of FIG.

FIG. 4 is a perspective view of a conventional superconducting magnet.

[Explanation of symbols]

 1 superconducting magnet device 2 superconducting coil 3 cooling container 4,5A, B spacing piece (spacer) 6 bearing

Claims (5)

[Claims] 1. A superconducting magnet device in which a superconducting coil is fixed in a cooling container to form a superconducting magnet via a spacing piece arranged around the outer periphery of a cross section of the superconducting coil. A superconducting magnet device having a bearing interposed. 2. The superconducting magnet device according to claim 1, wherein the bearing is composed of a plurality of balls made of a non-magnetic material. 3. The superconducting magnet device according to claim 1, wherein the bearing is made of a ceramic material. 4. A layer having a low thermal conductivity is interposed between the bearing and the superconducting coil.
The superconducting magnet device described in 1. 5. A layer having a low thermal conductivity is interposed between the surface of the superconducting coil and the bearing.
The superconducting magnet device described in 1.