JPH0567523A - Superconducting magnet - Google Patents

Abstract

PURPOSE:To suppress the occurrence of relative vibrations between the magnetic fields of radiation shield plates and reduce heat generation by eddy currents by forming the flat sections of a radiation shield facing both surfaces of a superconducting coil of the radiation shielding plates constituted of plate members which have high electric resistances and are respectively fitted with metallic thin films having low radiation efficiency on their surfaces, and so on. CONSTITUTION:This superconducting magnet is provided with a cryogenic inner tank container 8 housing a superconducting coil 7, outer tank container 10 housing the container 8 in a vacuum state, and radiation shield 19 which is provided in the container 10 so as to cover the container 8 and equipped with a cooling pipeline 11. In such superconducting magnet, the flat sections of the shield 19 facing both surfaces of the coil 7 are formed of radiation shield plates 15 constituted of plate members which have high electric resistances and respectively fitted with metallic thin films 16 having low radiation efficiency on their surfaces. In addition, the radiation shield 19 is constituted by sticking radiation shield plates 17 composed of metallic plates having high coefficient of thermal conductivity on the outer periphery of the plates 15 along the coil 7 and, at the same time, the cooling pipeline 11 is attached to the plates 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation shield for a superconducting magnet for a levitation railway.

[0002]

2. Description of the Related Art The structure of a levitation railway and a superconducting magnet will be described with reference to FIGS.

Superconducting magnet 2 mounted on a vehicle 1 of a levitation railway
Is attached to the left and right sides of the underframe 3 at the bottom of the vehicle 1 by the support cylinders 4, and the ground coils 6 are disposed on both side walls of the track 5 having a U-shaped cross section in which the vehicle travels so as to face the superconducting magnet 1. The vehicle is running with alternating current energized at a frequency commensurate with the speed.

The superconducting magnet 1 includes an inner vessel 8 for accommodating the superconducting coil 7 in a liquid helium refrigerant in order to keep it at an extremely low temperature where electric resistance is zero, and superconducting for suppressing heat intrusion and an AC magnetic field from the outside. A radiation shield 9 is arranged around the inner tank 8 that houses the coil 7, and an outer tank 10 that houses the inner tank 8 and the radiation shield 9 and holds them in a vacuum state.

A cooling pipe 11 of a radiation shield plate is joined to the radiation shield 9, and a liquid injection port 12 is attached to the underframe 3.
An on-vehicle pipe 13 provided with is arranged and connected to the refrigerant supply tank 14.

[0006] Conventionally, the radiation shield 9 is constructed and arranged by a radiation shield plate together with piping for cooling under a condition where it is exposed to a magnetic field and spatially restricted.

The main purpose of the radiation shield 9 is to prevent heat from entering due to radiation and an AC magnetic field from the outside with respect to the inner vessel 8 that houses the superconducting coil 7. Is required to be high and lightweight, and aluminum alloy, copper alloy, etc. are usually applied.

[0008]

However, the radiation shield plate 9 made of such a member has a high thermal conductivity but also a high electric resistance. Therefore, when the radiation shield plate 9 vibrates in a magnetic field, the superconducting coil Since the radiation shield plate is relatively displaced in the vicinity of the inner container for housing 7, an eddy current is generated in the radiation shield plate which is a good conductor, and an eddy current is also generated in the inner container 8 due to the action of the generated magnetic field, which causes Joule heat. Occurs.

When the superconducting magnet is subjected to electromagnetic fluctuations of harmonics in addition to levitating and propulsing while the vehicle is running and the superconducting magnet is vibrated in the resonance frequency band of the inner container, The relative vibration of the radiation shield plate 9 becomes severe. When the magnetic field fluctuation in the radiation shield plate 9 becomes severe, the inductive component to the inner tank container also becomes large, and the amount of heat penetration into the inner tank container 8 facing the radiation shield plate 9 in parallel increases rapidly, resulting in liquid helium. The evaporation amount of the refrigerant such as abruptly increases.

Further, the load increase phenomenon of the inner vessel of the superconducting coil becomes severe due to the eddy current loss generated in the radiation shield plate, and when the refrigerant refrigerating capacity is exceeded, the superconducting magnet may be quenched.

Therefore, in order to suppress the relative vibration of the radiation shield plate in the magnetic field and suppress the heat generation due to the eddy current,
It is conceivable to reinforce the radiation shield plate to increase the rigidity, but due to the structure of the superconducting magnet, there is basically a small space for its placement space and there is a constraint that it will be light in weight, so For this reason, this method is inappropriate.

In order to increase the resistance of the radiation shield plate in order to suppress the eddy current, there is a reinforced plastic material in which carbon fiber is impregnated with resin as a lightweight member having high electric resistance and high thermal conductivity. Since the ratio is remarkably larger than that of metal or the like, the member itself cannot be applied to the radiation shield plate.

On the other hand, since the reinforced plastic material obtained by impregnating carbon fiber with resin as the substrate material having high thermal conductivity has a mechanically very brittle surface, it has a complicated shape and a large thermal stress due to cooling. It is difficult to apply it to a radiation shield plate.

According to the present invention, the radiation shield plate is made into a practical structure by using a reinforced plastic material in which carbon fiber is impregnated with resin, the relative vibration of the radiation shield plate in the magnetic field is suppressed, and the heat generated by the eddy current is generated. The purpose is to reduce.

[0015]

To achieve the above object, the present invention provides a radiation shield plate having a high thermal conductivity and low emissivity thin film adhered to a plate surface formed of a high electrical resistance material on a superconducting coil surface. Formed as a flat part of the radiation shield facing each other, and a radiation shield plate made of a metal plate of a high thermal conductive member on this outer peripheral part,
It is constructed by joining along the outer circumference of the superconducting magnet. A low melting point metal inclusion is sandwiched between the joint surfaces, and the radiation shield plate cooling pipe is joined to the metal radiation shield plate side of the high thermal conductivity member.

[0016]

In the radiation shield having the above structure, the radiation shield plate of the high electric resistance member having the high thermal conductivity and the low emissivity thin film is arranged to face the superconducting coil surface as compared with the conventional one. Thereby, the eddy current loss due to the vibration in the resonance frequency band is significantly reduced, and the increase in the evaporation amount of the refrigerant such as liquid helium due to the increased heat load can be suppressed.

Further, since the outer peripheral portion of the radiation shield plate is composed of a metal plate having high strength and stable thermal conductivity, for example, an aluminum plate to which cooling pipes are attached, the radiation shield is easily assembled and cooled. It becomes a superconducting magnet with good properties and a strong structure.

[0018]

EXAMPLE A superconducting magnet of the present invention will be described with reference to the example shown in FIG.

The flat portions of the radiation shield 19 facing both sides of the superconducting coil 7 are formed on the surface of the substrate formed of a high electric resistance material 15 such as a reinforced plastic material in which carbon is impregnated with resin and not broken at low temperature. A low emissivity thin film 16 having a high thermal conductivity, such as copper, silver or gold, is attached by vapor deposition. Next, a highly heat-conducting radiation shield plate 17 made of a thin plate of an aluminum alloy, a copper alloy, or the like is arranged on the outer peripheral portion where the flat surface portion of the radiation shield 19 is along the superconducting coil 7, and the peripheral portion is bent, The radiation shield 19 is constructed by joining the flat surface portion of the radiation shield 19 with a rivet or the like. The substrate of the high electric resistance member 15 and the high thermal conductive member 1
A low-melting-point inclusion 18 such as an indium alloy is sandwiched between the joint surfaces of the metal plates 7 to prevent a decrease in heat conduction between both members.

The radiation shield 19 constructed as described above
Is disposed between the inner tank container 8 and the outer tank container 10 which house the superconducting coil 7 in the refrigerant, and surrounds the inner tank container 8.

The radiation shield plate cooling pipe 11 is usually fixed or joined to the metal plate side of the high thermal conductive member 17 from the viewpoint of ease of assembling the radiation shield 19.

With the above-mentioned structure, the effect of preventing heat intrusion from the outside of the radiation shield 19 from the functional viewpoint is secured as in the conventional case.

Next, for the eddy current generated in the radiation shield 19, the radiation shield plate 1 is provided by the high electric resistance member 15.
Since No. 5 is formed, it is possible to significantly reduce the number compared with the conventional one.

As described above, the structure of this radiation shield significantly suppresses an increase in the evaporation amount of liquid helium due to an increase in the heat load of the inner tank container, so that the superconducting magnet has a practical structure capable of stable cooling. ..

Another embodiment of the present invention will be described.

The metal plate of the high thermal conductive member 17 formed of a thin plate such as an aluminum alloy, a copper alloy, or a superconducting member forming the outer peripheral portion of the radiation shield 19 is divided along the outer peripheral portion of the super-electric coil 7 to form a partition. It is assumed that

As described above, the radiation shield plate 1 along the outer circumference of the superconducting coil 7 is formed by the divided structure of the high thermal conductive member 17.
The eddy current loss generated in No. 7 is reduced. Further, with this configuration, the difference in heat shrinkage between the substrate of the high electrical resistance member 15 having high thermal conductivity and the metal plate of the high thermal conductivity member 17 is alleviated.

Still another embodiment of the present invention will be described.

Radiation shield plate cooling pipe 1 joined to the metal plate of the high thermal conductive material 17 forming the outer peripheral portion of the radiation shield 19.
1 is arranged so that both the forward and return pipes are close to each other so that a loop along the outer circumference of the superconducting coil 7 is not formed.

When the forward and return pipes are arranged side by side and joined to the metal plate of the high thermal conductive member 17, heat exchange occurs between the pipes and the radiation shield plate 17 cannot be cooled.
Either one of the outward and return pipes is joined to the metal plate of the high thermal conductive member 17 to be thermally insulated from the other pipes.

With the above structure, an induction loop is not formed along the piping route of the radiation shield plate cooling pipe 11, and the eddy current loss generated in the pipe is suppressed.

Furthermore, as another embodiment of the present invention, a member 17 having a high thermal conductivity and a high electric resistance which constitutes the radiation shield plate 15 is provided.
It is also possible to use aluminum nitride instead of the carbon fiber reinforced plastic material applied to the substrate.

Furthermore, a metal plate having a high thermal conductivity, which is a thin plate of an aluminum alloy, a copper alloy, a superconducting member, or the like, may be applied to the secondary portion of this type of radiation shield material.

In the above embodiment, the case where the present invention is applied to the superconducting magnet for the levitation type railway has been described, but the present invention can be widely applied to devices related to the superconducting magnet.

[0035]

As described above, according to the present invention, the radiation shield constituted by the flat surface portion and the outer peripheral portion, to which different members are respectively applied, greatly reduces the eddy current loss and increases the heat load, such as liquid helium. A stable superconducting magnet can be obtained by suppressing an increase in the evaporation amount of the refrigerant, improving workability in assembling and manufacturing the radiation shield, and providing a solid structure with good cooling properties.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view of the structure of a floating railway.

FIG. 3 is a sectional perspective view of a conventional superconducting magnet.

[Explanation of symbols]

 7 Superconducting coil 8 Inner tank container 9, 19 Radiation shield (radiation shield plate) 10 Outer tank container 11 Radiation shield plate Cooling pipe 15 High electrical resistance member (radiation shield plate) 16 Low emissivity thin film 17 High thermal conductivity member (radiation shield plate) ) 18 Low melting point metal inclusions

Claims (7)

[Claims] 1. A cryogenic inner tank container containing a superconducting coil and an outer tank container containing the superconducting coil in a vacuum state. Further, the inner tank container is cooled between the outer tank container and the inner tank container. In a superconducting magnet provided with a radiation shield having piping, the flat portions of the radiation shield facing both sides of the superconducting coil are formed by a radiation shield plate made of a plate material having a high electrical resistance and a metal thin film having a low emissivity attached to the surface. Further, a radiation shield plate made of a metal plate having a high thermal conductivity is joined to the outer circumference of these radiation shield plates along the superconducting coil to form a radiation shield for covering the superconducting coil, and the metal radiation shield plate is also provided. A superconducting magnet characterized in that a cooling pipe is provided in the. 2. The superconducting magnet according to claim 1, wherein the plate material having a high electric resistance is a carbon fiber reinforced plastic material. 3. The superconducting magnet according to claim 1, wherein the plate material having a high electric resistance is an aluminum nitride material. 4. The superconducting magnet according to claim 1, wherein a metal of aluminum, copper, silver or gold is attached to the surface of a plate material having a high electric resistance by vapor deposition, plating or sputtering. 5. An inclusion of a low melting point metal of indium or indium-copper alloy is arranged at the joint between the radiation shield plate made of a plate material having high electric resistance and the radiation shield plate made of metal. 1 superconducting magnet. 6. The superconducting magnet according to claim 1, wherein the metal radiation shield plate along the outer circumference of the superconducting coil is divided into a plurality of divisions, and the divisions have a high electric resistance. 7. The superconducting magnet according to claim 1, wherein the cooling pipe joined to the radiation shield plate made of metal is non-inductively wound.