JP2003142744A - Persistent current switch and superconductive magnet employing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-temperature superconductive persistent current switch, not giving damage to a superconductive film, high in stability and small in a thermal capacity. SOLUTION: The persistent current switch 1 is manufactured by a method wherein a high-temperature superconductive film 2 on an insulator substrate 3 is employed and a cooling plate 4 is arranged at the side of the insulator substrate 3 as the cooling means of the high-temperature superconductive film. Further, a heater 5 is integrated thermally. According to such a constitution, the high-temperature superconductive film 2 will not be deteriorated by a cooling stress whereby the persistent current switch, high in performance, can be provided. On the other hand, the persistent current switch 1 is often subjected to a thermal stress, vibration or the like in the using atmosphere of the same and the insulator substrate is often very brittle mechanically whereby the substrate necessitates reinforcement. However, the persistent current switch 1 is impregnated with an epoxy resin 9 or the like and the insulator substrate is received in a case 8 made of an FRP or the like whereby the strength of the whole of the same is increased. As a result, the persistent current switch 1, strong against the thermal stress or the vibration, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-temperature superconducting permanent current switch used in superconducting equipment and a superconducting magnet using the same.

[0002]

2. Description of the Related Art Since a superconducting wire has no electric resistance, it is possible to form a closed circuit and generate a magnetic field by a permanent current. A method using a permanent current switch is generally used to perform the persistent current operation. The persistent current switch is composed of a superconducting wire and means for switching the superconducting wire between the superconducting state and the normal conducting state. The persistent current switch is connected so that the superconducting coil is a closed circuit. When the permanent current switch is in the OFF state, that is, when the superconducting wire is in the normal conducting state, an electric resistance is generated and the superconducting coil is excited by the exciting power source connected in parallel with the permanent current switch. During excitation, a voltage is generated across the permanent current switch, but since the superconducting wire in the normal conducting state has a finite resistance, it is shunted and the permanent current switch heats up. The permanent current switch generates less heat as the electric resistance in the normal conduction state, that is, the off resistance, increases, and the excitation speed can be increased. Therefore, in order to increase the electric resistance of the persistent current switch, a superconducting film is formed on the insulator substrate, and in order to maintain the stability of the high temperature superconducting film, a cooling plate is placed on the superconducting film side via an insulator. Arranged structures have been devised.

FIG. 11 shows a conventional permanent current switch 1. A cooling plate 4 with an insulator 7 interposed on the high temperature superconducting film 2 side.
Is provided. With this structure, the high temperature superconducting film 2 can be efficiently cooled, but since the insulator 7 and the cooling plate 4 are directly bonded to the high temperature superconducting film 2, the high temperature superconducting film 2 may be damaged. .

Further, a superconducting coil is formed by conduction by a refrigerator.
When cooling the permanent current switch, the time of turning on / off the permanent current switch can be greatly improved by installing a thermal switch between the refrigerator and the permanent current switch. However, conventional thermal switches have complicated control. Also, installation is often difficult due to space and weight.

Further, in order to form a permanent current circuit, the permanent current switch and the superconducting coil are connected by a high temperature superconducting wire or the like. The resistance of this connection portion causes attenuation of the permanent current. A configuration that reduces

[0006]

In the prior art, in order to maintain the stability of the high temperature superconducting film, the cooling plate is arranged on the side of the superconducting film. It may have deteriorated.

Therefore, an object of the present invention is to provide a high temperature superconducting permanent current switch which does not damage the superconducting film, has high stability and a small heat capacity, and provides a high temperature superconducting magnet which can be easily operated in a persistent current. .

Another object of the present invention is to provide a heat switch which is simple, small, and lightweight in a conduction cooling superconducting magnet. Another object of the present invention is to provide a high-temperature superconducting magnet in which a non-uniform current does not easily occur in the permanent current switch.

[0009]

In order to solve the above-mentioned problems, the persistent current switch according to the invention of claim 1 uses a high temperature superconducting film formed on an insulating substrate, and as a cooling means for the high temperature superconducting film, A cooling plate is disposed on the side of the insulating material, and a heater is thermally integrated into a permanent current switch. With such a configuration, the high temperature superconducting film is not deteriorated by the cooling distortion, so that it is possible to provide a persistent current switch with high performance.

According to a second aspect of the present invention, the persistent current switch of the first aspect uses YBCO as the high temperature superconducting film. If YBCO is used, it is easy to form a film having a high critical current density on the insulating base material. By using the superconducting film having such a structure, it is possible to easily provide a permanent current switch having a large off resistance and a small heat capacity.

According to a third aspect of the present invention, the permanent current switch according to the first or second aspect uses sapphire or YSZ as the material of the insulating base material. Sapphire and YSZ have very high thermal conductivity and can efficiently cool the superconducting film.
With such a configuration, a highly stable persistent current switch can be easily provided.

According to a fourth aspect of the present invention, the permanent current switch according to the first to third aspects is impregnated with epoxy resin or the like. The environment in which the permanent current switch is used may be exposed to thermal strain, vibration, etc.
Insulator substrates are often mechanically brittle and need to be reinforced. By housing the insulating substrate in a case made of FRP or the like and impregnating it with epoxy, the overall strength is increased, and a permanent current switch that is resistant to thermal distortion and vibration can be provided.

According to a fifth aspect of the present invention, in the permanent current switch according to the fourth aspect, the surface of the high temperature superconducting film made of YBCO or the like is subjected to demolding treatment when impregnated with epoxy resin. . This releasing treatment does not deteriorate the high temperature superconducting film due to cooling distortion, so that a high performance persistent current switch can be provided.

According to a sixth aspect of the present invention, there is provided a superconducting magnet in which a permanent current switch, a high temperature superconducting coil according to any one of the first to fifth aspects, and a refrigerator thermally connected to them are housed in a vacuum container. With such a configuration, it is possible to provide a high temperature superconducting magnet that can be easily operated with a permanent current.

A superconducting magnet according to a seventh aspect of the present invention is the superconducting magnet according to the sixth aspect, in which the heat transfer plate is aluminum.
Copper or silver, or an alloy containing at least one of them. These materials are highly flexible and have a large change in thermal conductivity at 10K to 150K, and thus can have a function as a thermal switch. Therefore, it is possible to efficiently turn on / off the permanent current switch, and it is possible to provide a high-temperature superconducting magnet that can be easily operated with a persistent current.

A superconducting magnet according to an eighth aspect of the present invention is the high temperature superconducting magnet according to the seventh aspect, wherein the cross-sectional area / length ratio and the volume of the heat transfer plate are set to appropriate values.
It is possible to provide a high temperature superconducting magnet that can be easily turned on and off by taking out the function of a thermal switch.

In the superconducting magnet according to the invention of claim 9,
9. The superconducting magnet according to claim 6, wherein the number of permanent current switches, the number of high-temperature superconducting wires for electrically connecting the high-temperature superconducting coil and the persistent current switch, or both of them are It is the same as the parallel number, or an integer multiple or an integer fraction thereof. As a result, the connection between the permanent current switch and the superconducting coil becomes equal, and a high-temperature superconducting magnet with less drift of the permanent current switch can be provided.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. It should be noted that the present invention is not limited to the following embodiments, but can be implemented by being modified appropriately within the scope of the invention.

(First Embodiment) FIG. 1 is a sectional view of a permanent current switch 1 showing a first embodiment of the present invention. The high temperature superconducting film 2 is formed on the absolutely insulative substrate 3. An intermediate layer that promotes crystal growth of the high temperature superconducting film may be provided on the surface of the insulator substrate 3. The high temperature superconducting film 2 is cooled by a cooling plate 4 arranged on the side of the insulating substrate 3. Further, the heater 5 is provided, and the permanent current switch 1 is turned off by heating the heater 5. An electric current is applied to the high temperature superconducting film 2 via the terminal 6.

In the permanent current switch 1 of this embodiment, the positions of the heater 5 and the cooling plate 4 may be changed as shown in FIG. Further, the high temperature superconducting film 2 may be formed as a circuit-shaped current path on the surface of the insulating substrate 3 as shown in FIG.

FIG. 4 shows a persistent current switch 1 according to this embodiment.
It is a figure which shows the external appearance. A cooling plate 4 and a heater 5 are arranged on the back surface side of the absolutely insulative substrate 3 shown in FIG. 3, and a terminal 6 for connecting to the superconducting coil is provided.

In the persistent current switch 1 of the present embodiment, the materials for the high temperature superconducting film 2 are Bi2212, B.
i2223, MgO and YBCO are suitable. YBCO
Is particularly suitable because it has a high critical current density and can be designed with a high resistivity. Further, sapphire or YSZ having high thermal conductivity and high strength is suitable as a base material for forming the high temperature superconducting film 2.

According to the present embodiment, since the cooling plate 5 which disperses heat quickly without degrading the high temperature superconducting film 2 is provided, the off resistance is large, the heat capacity is small, and the stability is high. It is possible to provide a high-current persistent current switch.

(Second Embodiment) FIG. 5 is a sectional view of a persistent current switch 1 according to a second embodiment of the present invention.
For the purpose of forming the high-temperature superconducting film 2 having high performance, a single crystal is generally used for the insulator substrate 3, so that the strength is weak. Therefore, in the present embodiment, the first structure of the structure shown in FIG.
The permanent current switch of the above embodiment is housed in the impregnation case 8 and impregnated with the epoxy resin 9 to have a structure in which rigidity is enhanced. Here, the epoxy resin 9 is
It may be filled with filler such as glass or ceramics. The impregnation case 8 can also serve as a strength member.

If the high temperature superconducting film 2 is adhered to another member, it may be damaged by thermal strain during cooling, so that the surface of the high temperature superconducting film 2 is not adhered when the epoxy resin 9 is impregnated. It is even better to perform release processing. Figure 6
Is the configuration of the permanent current switch 1 when the release treatment is performed, and the reference numeral 10 is the release portion.

The impregnation case 8 can be removed after impregnation. FIG. 7 shows a cross section of the persistent current switch 1 having a structure in which the impregnation case 8 is removed after impregnation with the epoxy resin.

In order to increase the current capacity, a plurality of high temperature superconducting films 2 may be housed in the impregnation case 8 and impregnated. FIG. 8 shows the configuration of the persistent current switch 1 in that case.

According to the present embodiment, since the insulating substrate 3 which is weak in strength is impregnated with the epoxy resin 9, it is possible to provide the permanent current switch 1 which is reinforced in rigidity and resistant to vibration and the like.

(Third Embodiment) FIG. 9 shows the structure of a superconducting magnet according to a third embodiment of the present invention. The superconducting magnet according to the present embodiment is similar to that shown in FIG.
To the high-temperature superconducting coil 11 and the refrigerator 1 for cooling them.
2. Further, it is composed of a radiation shield 13 and a vacuum container 14 which surround them as a whole. FIG. 9 shows a configuration in which the permanent current switch 1 shown in FIG. 4 is mounted as an example of the permanent current switch 1.

The high temperature superconducting coil 11 is cooled by the refrigerator 12 via the heat transfer plate 15. The permanent current switch 1 is cooled by the refrigerator 12 via the heat switch heat transfer plate 16. Since the permanent current switch 1 and the high temperature superconducting coil 11 form a permanent current circuit, the high temperature superconducting wire 17 is connected to the terminal 6 of the permanent current switch 1. An exciting power source 18 is connected in parallel with the permanent current circuit, and performs a permanent current operation together with the permanent current switch 1.

When the persistent current switch 1 is kept in the ON state, that is, in the superconducting state, it is below the superconducting transition temperature, and
It is necessary to cool the coil to approximately the same temperature as the coil operating temperature, for example, about 20K. On the other hand, in order to keep the persistent current switch 1 in the off state, that is, in the normal conducting state, it is necessary to maintain the superconducting transition temperature or higher, for example, about 100K.

When the heat switch heat transfer plate 16 is made of a material having a high heat conductivity at 20K and a low heat conductivity at 100K, the heat switch heat transfer plate 16 can have a function of a heat switch. In addition, the operation as a thermal switch can be surely performed. As a material of the heat switch heat transfer plate 16, aluminum, copper, silver or an alloy containing at least one of them is suitable.

The time for switching the off state and the on state of the persistent current switch 1, that is, the time for switching the state of the persistent current switch 1 between about 100K and about 20K is
It is affected by the cross-sectional area and length of the heat switch heat transfer plate 16. If the value of cross-sectional area / length is large, the cooling characteristic from 100K to 20K is improved, and conversely, it takes time to heat from 20K to 100K. 1 if the value of cross-sectional area ÷ length is small
The cooling time from 00K to 20K becomes longer, but heating from 20K to 100K becomes easier. On the other hand, as the material of the heat switch heat transfer plate 16, the thermal conductivity is high at 20K and the heat conductivity is high.
When a material having a low thermal conductivity of 0K is used, the heat capacity of the heat switch heat transfer plate 16 greatly affects the time for switching the permanent current switch 1 from the OFF state to the ON state together with those conditions. This is because the thermal conductivity does not increase unless the temperature of the heat switch heat transfer plate 16 itself decreases.

In consideration of this, the heat switch heat transfer plate 16 was designed and verified by experiments. As a result, switching was performed under the conditions of the cross-sectional area / length value of 0.005 mm or more and the volume of 10 cm ³ or less. It took several seconds to several minutes, and it was found that the heat switch heat transfer plate 16 was suitable.

According to the present embodiment, since the heat transfer plate 16 having the functions of the permanent current switch 1 and the thermal switch having high stability is used, it is possible to provide the superconducting magnet which can be easily operated in the permanent current.

(Fourth Embodiment) FIG. 10 is a connection diagram of a permanent current circuit according to a fourth embodiment of the present invention. The high-temperature superconducting coil 11 may be wound by bundling a plurality of tape wires according to the current capacity. Similarly, the permanent current switch 1 may also need to be paralleled according to the current capacity. In the persistent current circuit, when the circuits are connected in parallel, the current drifts due to a slight resistance difference. The unbalanced current reduces the capacity of the persistent current switch 1 and facilitates quenching.

In the superconducting magnet of FIG. 10, the parallel number of the wire rods of the high temperature superconducting coil 11 and the parallel number of the permanent current switch 1 are made equal to each other, and they are connected by the high temperature superconducting wire 17. With this connection method, the number of connections and the connection conditions can be made the same in each of the parallel circuits, so that drift is less likely to occur.

The number of parallel wires of the high-temperature superconducting coil 11, the number of parallel permanent current switches 1 and the number of high-temperature superconducting wires 17 connecting them do not have to be exactly the same, but they are integer multiples or fractions. May be.

According to the present embodiment, the connection configuration can be made uniform in the parallel circuits, and the permanent current switch 1
It is possible to provide a superconducting magnet with less uneven flow and high stability.

[0040]

As described above, according to the persistent current switch of the present invention, it is possible to provide a switch having a large off resistance, a small heat capacity, a good responsiveness and a high stability.

Further, according to the superconducting magnet of the present invention, permanent current operation is easy.

[Brief description of drawings]

FIG. 1 is a sectional view of a persistent current switch according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a modification of the persistent current switch according to the first embodiment of the present invention.

FIG. 3 is an explanatory view showing the shape of a high temperature superconducting film according to the first embodiment of the present invention.

FIG. 4 is a perspective view of the permanent current switch according to the first embodiment of the present invention.

FIG. 5 is a sectional view of a persistent current switch according to a second embodiment of the present invention.

FIG. 6 is a cross-sectional view of a modification of the persistent current switch according to the second embodiment of the present invention.

FIG. 7 is a sectional view of another modification of the persistent current switch according to the second embodiment of the invention.

FIG. 8 is a cross-sectional view of still another modification example of the persistent current switch according to the second embodiment of the present invention.

FIG. 9 is a circuit diagram of a superconducting magnet according to a third embodiment of the present invention.

FIG. 10 is a circuit diagram of a superconducting magnet according to a fourth embodiment of the present invention.

FIG. 11 is a sectional view of a conventional persistent current switch.

[Explanation of symbols]

1 Permanent current switch 2 High temperature superconducting film 3 Insulator substrate 4 Cooling plate 5 heater 6 terminals 8 impregnation case 9 Epoxy resin 10 Release area 11 High temperature superconducting coil 12 refrigerator 14 Vacuum container 16 heat switch heat transfer plate 17 High temperature superconducting wire

Continued front page    (72) Inventor Katsuyuki Kuwano             1-4, Mei Station, Nakamura-ku, Nagoya City, Aichi Prefecture               Tokai Passenger Railway Co., Ltd. (72) Inventor Taizo Tosaka             2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa               Toshiba Keihin Office (72) Inventor Masahiko Takahashi             2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa               Toshiba Keihin Office (72) Inventor Toru Kuriyama             2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa               Toshiba Keihin Office F-term (reference) 4M114 AA01 AA11 AA15 AA24 AA30                       CC03 CC11 DA02 DA51 DB16                       DB30 DB32 DB33                 5G321 AA04 BA04 CB01

Claims (9)

[Claims] 1. A superconducting film formed on an insulating substrate,
A permanent current switch comprising a switch switching heating means, wherein a cooling plate for cooling the permanent current switch is disposed on the side of the insulator substrate. 2. The persistent current switch according to claim 1, wherein the superconducting film is YBCO. 3. The persistent current switch according to claim 1, wherein sapphire or YSZ is used as a base material of the insulator substrate. 4. A permanent current switch according to claim 1, wherein one or a plurality of permanent current switches are laminated and arranged in parallel, and an epoxy resin or a filler-containing epoxy resin is solidified and integrated. Permanent current switch to. 5. The persistent current switch according to claim 4, wherein the superconducting film side is separated. 6. A vacuum container contains the permanent current switch according to claim 1, a high-temperature superconducting coil electrically connected to the permanent current switch, and a refrigerator for cooling the high-temperature superconducting coil. In the superconducting magnet described above, a heat conducting plate for thermally connecting the cooling plate of the permanent current switch and the refrigerator is arranged. 7. The superconducting magnet according to claim 6, wherein the material of the heat transfer plate is aluminum, copper, silver or an alloy containing at least one of them. 8. The superconducting magnet according to claim 7, wherein the heat transfer plate has a cross-sectional area / length value of 0.005 mm.
A superconducting magnet having the above and a volume of 10 cm ³ or less. 9. The superconducting magnet according to claim 6, wherein the number of the permanent current switches connected in parallel, the number of superconducting wires electrically connecting the permanent current switch and the high temperature superconducting coil, or both of them are wound. 7. The superconducting magnet according to claim 6, wherein the number is the same as the number of the high-temperature superconducting tape wire rods arranged in parallel, and is an integral multiple or integer fraction thereof.