JP3239036B2 - Superconducting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting device in which various superconducting devices utilizing a superconducting magnet, a Josephson element, and the like are housed in a low-temperature container, and in particular, a current lead for supplying power from an external power supply to the various superconducting devices. The present invention relates to a superconducting device capable of improving withstand voltage in the periphery and blocking various electromagnetic noises.

[0002]

2. Description of the Related Art FIG. 16 shows an example of a conventional superconducting device in which a superconducting magnet is housed in a low-temperature container. In this figure, 3 is a superconducting coil, 1 is a current lead, and the current lead 1 is attached to the cryogenic vessel 2 by a mounting flange 5. The mounting flange 5 is usually made of a metal,
Attached to. 4 is a cooling substance for cooling the superconducting coil 3. Normally, liquid helium is the cooling substance 4
Helium gas is used as the current lead 1
Are cooled and discharged from the gas outlet 9 to the outside of the low-temperature container. FIG. 15 shows a structure 1 of the current lead 1.
This is an example. In this figure, the current lead 1 has a configuration in which a conductor 27 for energizing the superconducting coil 3 is inserted into a hollow tube 24 to which an insulator 25 is attached. FIG. 15A is a diagram showing a cross-sectional structure of a current lead, and FIG. 15B is a plan view at a CC ′ portion of FIG.

[0003]

In the conventional superconducting device as described above, as shown in FIG. 16, there is a space 6 in the mounting portion of the current lead 1, and this portion is filled with the evaporated helium gas. ing. When power is supplied to the superconducting coil 3 from an external power supply (not shown) via the current lead 1, a high electric field is generated in the vicinity of the mounting flange 5 particularly in the case of alternating current. Since the insulation performance of helium gas is very low as compared with air or the like, there is a possibility that discharge can easily occur between the current lead 1 and the mounting flange 5 around the space 6. In order to avoid this discharge, it is necessary to increase the insulation distance between the current lead 1 and the mounting flange 5. As a result, in order to operate the superconducting device stably, the current lead 1
The size of the superconducting device including the low-temperature container 2 was difficult because of the necessity of increasing the size of the low-temperature container 2 on which the device was mounted.

[0005] As shown in FIG. 15, in the current lead 1, an insulator 25 is provided on the outer periphery of a conductor 27.
It is conceivable to reduce the thickness of the insulator 25 to make the space 6 smaller. However, since the current lead 1 is attached and detached as necessary, the thickness of the insulator 25 is considered in consideration of the operability at the time of attachment and detachment. There is naturally a limit to this, and the space 6 cannot be made very small only by the thickness of the insulator of the current lead.
A proposal to reduce the size of the current lead mounting portion is disclosed in Japanese Patent Application Laid-Open No. 04-320305. In this proposal, a space for flowing a gas having good insulating properties, for example, dry air or nitrogen, is provided in a portion where the current lead is attached, thereby reducing the size of the portion where the current lead is attached and improving the dielectric strength. However, this method requires an apparatus for flowing a gas, and also needs to remove moisture in the gas.
For this reason, even if the current lead attachment portion of the low-temperature container 2 can be reduced in size, a device for flowing gas is indispensable, and reduction in size of the entire device cannot be achieved.

In the current lead, it is necessary not only to supply power from an external power source but also to prevent heat from entering from outside. Generally, a conductive metal is used for the conductor of the current lead. In addition, not only power but also external heat is transmitted to the superconducting device. For this reason, it has been proposed to use an oxide superconductor having a small thermal conductivity coefficient and zero electrical resistance as a current lead conductor. For example, in JP-A-03-283678, an oxide superconductor is attached to a metal core material having excellent mechanical strength, and in JP-A-04-369875, copper or the like is connected to the oxide superconductor. Conductor. Since the thermal conductivity coefficient of the oxide superconductor is small, the current leads disclosed therein are effective in preventing heat from entering from outside.

However, the oxide superconductor has a problem that the amount of current flowing in the superconductor is greatly reduced by an external magnetic field (see FIG. 17). In general, for applications such as superconducting magnets, a current density of about 10,000 A / cm ² or more is required. For this reason, although current penetration using an oxide superconductor as a conductor can prevent heat penetration, the amount of current supplied to superconducting equipment fluctuates due to an external magnetic field, and in some cases, the superconducting state may change. It can be torn. In particular, when the superconducting device is a superconducting magnet, the leakage magnetic field from the magnet is a serious problem.

In order for the superconducting device shown in FIG. 16 to operate normally, the reliability of the components of the device including the superconducting device is also important. It is also very important to take measures to prevent discharge and electromagnetic noise near the part. However, in the conventional superconducting device, as described above, a special device is required for preventing discharge, and noise countermeasures are not sufficient. Further, in the case of a superconducting magnet or the like, since the amount of current is large, an abnormality in the current lead portion is the same as that in which the superconducting device does not operate. Conventionally, the abnormality of the current lead, particularly the abnormality at the time of energization, is generally performed by detecting and judging the voltage generated at both ends of the conductor. There is no effect when a discharge occurs between them. Accordingly, an object of the present invention is to prevent the discharge near the current lead attachment portion without adding a special device in order to solve the above-mentioned problems of the prior art, and to further stabilize the current lead. Another object of the present invention is to provide a small-sized superconducting device which also takes noise countermeasures for operating the superconducting device.

[0008]

The above objects are achieved by the present invention described below. That is, the present invention relates to a superconducting device including a cryogenic container, a superconducting device housed in the cryogenic container, and a current lead attached to the cryogenic container and connected to the superconducting device. A structure for preventing discharge is arranged between the current lead mounting portion provided on the container and the structure, and the structure is insulated from the conductive layer.
A superconducting device comprising a laminate with an edge layer . Further, the present invention provides a cryogenic container,
Superconducting equipment housed inside
A superconductor consisting of a current lead connected to a superconducting device.
The current lead and the cryogenic container
Structure to prevent discharge between the current lead mounting part
The body is disposed, and the structure is an electromagnetic noise shield.
A superconducting device characterized by having a function as well.

[0009]

According to the present invention, there is provided a superconducting device, a low-temperature container for accommodating the superconducting device, and an electric power source mounted on the low-temperature container via a flange and connected to the superconducting device for introducing electric power from the external power supply to the superconducting device. In a superconducting device having a current lead, by providing a structure that also has a discharge prevention function between the current lead mounting portion of the low-temperature container and the current lead, and further has an electromagnetic noise shielding function, in the vicinity of the current lead of the superconducting device. Greatly reduces the probability of electric discharge. Also, by using a recovery type insulating material, even if a discharge occurs, the insulation characteristics are recovered after the discharge subsides and self-recovery is possible. It can be greatly reduced. Further, in the present invention, the current lead can be protected from various kinds of noises such as a leakage magnetic field, and further, by using a light transmitting material for the constituent members of the conductor, the abnormality of the conductor itself can be influenced by the electromagnetic noise. Since it is also possible to detect by an optical means that is not performed, it is possible to easily and quickly deal with abnormalities such as quench of the conductor.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to preferred embodiments of the present invention. The superconducting device of the present invention is a superconducting device comprising a cryogenic container, a superconducting device housed in the cryogenic container, and a current lead attached to the cryogenic container and connected to the superconducting device. A structure for preventing discharge is arranged between the low-temperature container and a current lead attachment portion. FIG. 1 shows a preferred embodiment of the superconducting device of the present invention. Since the configuration of the superconducting device of the present invention is basically the same as that shown in FIG. 16, FIG. Only the vicinity of the portion is shown. In FIG. 1, 1
Reference numeral 5 denotes a current lead, and reference numeral 5 denotes a flange for attaching the current lead 1 to the low-temperature container 2 via the insulating flange 10.
Reference numeral A denotes a structure for preventing discharge. In FIG. 1, the structure A includes an insulating layer 11 and a conductive layer 12, and in this figure, the insulating layer and the conductive layer are laminated two by two.
L in the figure is the shortest distance between the current lead 1 and the low-temperature container 2.

In the present invention, the structure A for preventing discharge which constitutes the superconducting device is not limited as long as it can effectively prevent discharge near the current lead mounting portion provided on the low temperature vessel 2. However, the structure A is preferably formed of a laminate including an insulating layer and a conductive layer. More preferably, as shown in FIG. 1, a laminate having at least two insulating layers and two or more conductive layers is used to further enhance the discharge prevention effect. With this configuration,
Discharge in the vicinity of the current lead attachment portion can be effectively prevented without using a special device.

In the present invention, a so-called recovery type insulating material is preferably used as the insulating material for forming the insulating layer. There are two types of insulators: a non-recoverable insulating material in which the insulating properties are lost or greatly deteriorated once the dielectric breakdown occurs, and a recoverable insulating material in which the insulating properties are restored again. The former non-recoverable insulation material generally has a high withstand voltage, but when a current flows inside the material,
After that, since the insulating properties are lost, the original performance cannot be exhibited unless the material is replaced. On the other hand, the latter recovery-type insulating material has a lower withstand voltage than the non-recovery-type insulating material, but has the characteristic that even if a dielectric breakdown occurs, the insulation characteristics are restored if the dielectric breakdown state does not last for a long time. is there. Therefore, in the present invention, a part or all of the insulator is made of a recoverable insulating material, so that even if a discharge occurs, the insulation characteristics are restored so that the fault is recovered and the insulator is replaced. Make it unnecessary.

The recovery type insulating material described above includes, for example, yttrium oxide (Y ₂ O ₃ ), and the non-recovery type insulating material includes alumina (Al ₂ O ₃ ) as a typical example. The insulating material used to form the insulating layer of the structure constituting the superconducting device of the present invention is not limited to these. Also, in the case of a device with low power consumption, such as a superconducting device using a Josephson element, only a recovery type insulating material may be used, but in the case of a large device using an AC superconducting magnet, etc. Therefore, it is desirable to use not only a recovery type insulating material but also a non-recovery type insulating material as an insulating material. When they are used in combination, they may be alternately laminated or used as a mixture.

The structure A constituting the superconducting device of the present invention
Is composed of a laminate consisting of an insulating layer and a conductive layer,
Even when the laminated structure has two or more layers, it is preferable that the insulating layer 11 is disposed on the side of the plurality of current leads 1 and the conductive layer 12 is disposed on the current lead attachment portion of the low-temperature container 2. In the present invention, the electric potential of the conductive layer alternately laminated with the insulating material is made equal to the electric potential of the low-temperature container 2 or grounded independently to prevent discharge between the insulator and the low-temperature container. I do. Further, in the present invention, it is preferable to use a magnetic material for at least a part of the material for forming the conductive layer 12. In this manner, the conductor of the current lead 1 can be shielded from noise such as a leakage magnetic field from the outside, and thus the superconducting device of the present invention can be operated stably. . The discharge between the current lead 1 and the cryogenic container 2
Although the probability of occurrence between the current lead 1 and the conductive portion existing at a short distance is the highest, in the present invention, the portion facing the current lead 1 is entirely formed of an insulating material as described above. I have. Therefore, even if a discharge occurs, all of the discharge will occur from the surface of the insulator,
The discharge starting voltage can be increased.

The conductive layer forming the structure A constituting the superconducting device of the present invention may be any conductive layer as long as it has conductivity, and is formed of at least one of a conductive material and a magnetic material. Preferably. Although there is no particular limitation on these materials, examples of the conductive material used in the present invention include stainless steel, copper, permalloy, and various superconductors. In addition, the conductive layer formed of a conductive material as described above and the insulating layer as described above have a structure A having a laminated structure made of the above, which has mechanical strength enough not to be damaged in normal handling. Although there is no particular limitation on the manufacturing method and size, it is preferable to adopt the following forms according to the characteristics of various materials and devices used.

For the conductor of the current lead 1, for example, an oxide superconducting material which is superconducting at a temperature higher than the boiling point of liquid nitrogen, which is called Bi-based, may be used. Since these oxide superconductors have a lower thermal conductivity than metals such as copper, thermal penetration into superconducting equipment can be significantly reduced. However, oxide superconducting materials are known to change the amount of current that can be conducted by an external magnetic field.
In the case of the Bi system, when the temperature exceeds about 30K, the amount of current is significantly reduced (FIG. 17). In such a case, in the present invention, a structure composed of a laminate of a conductive layer and an insulating layer is disposed so as to surround the conductor of the current lead as shown in FIG. It is preferable to function as a noise shielding material.

Further, according to the present invention, there is provided a conductor capable of detecting an abnormality at the time of energization occurring in a current lead or an abnormality due to the influence of electric discharge or the like when a large current is used as in a superconducting magnet device. I can do it. FIG. 13 shows a sectional view of the basic structure of such a conductor. A part of or all of the conductor has a structure in which a superconductor is attached to a light transmitting material as shown in FIG. As a result, when an external magnetic field, mechanical deformation, or the like acts on the superconductor through which current flows, the light transmitting material is deformed. Therefore, when light is incident on the light transmitting material as necessary, for example, an abnormality in the conductor can be detected because the amount of light transmission changes due to mechanical deformation of the light transmitting material. That is, in the device as described above, the abnormality can be detected by optical means.
It is possible to accurately detect a conductor abnormality without being affected by an electrical phenomenon such as electric discharge.

[0018]

Next, the present invention will be described in detail with reference to examples. In the following examples, a case where yttrium oxide is used as a recovery type insulating material and alumina is used as a non-recovery type insulating material will be mainly described, but it goes without saying that the present invention is not limited to this. . Embodiment 1 FIG. 1 is a structural principle diagram of the vicinity of a current lead attachment portion of a superconducting device of this embodiment. The basic configuration of the superconducting device is
As in the conventional apparatus shown in FIG. 16, the apparatus comprises a current lead 1 for supplying power from an external power supply, a superconducting device 3, a low-temperature container 2 for housing the same, and a cooling substance 4 for cooling the superconducting device 3. If necessary, for example, a measuring device such as a voltage lead may be attached to both ends of the current lead 1 or both ends of the magnet when the superconducting device 3 is a superconducting magnet. It may be stored.

In FIG. 1, reference numeral 1 denotes a current lead, and 5 denotes a flange for attaching the current lead 1 to the low-temperature container 2 via an insulating flange 10. In the present embodiment, the insulating material forming the insulating layer 11, a Y ₂ O ₃ were mixed at a ratio of 10g against Al ₂ O ₃ 100 g, cold isostatic (CI
It is obtained by pressure-molding by the P) method and then heat-treated at 500 ° C. for 5 hours in air. The conductive layer 12 is made of metal Cu attached to the outer periphery of the insulating layer 11 by the thermal spraying method as described above. When the conductive layer 12 is attached to the low-temperature container 2, the Cu layer 12 is in direct contact with the low-temperature container 2. In this embodiment, the insulating layer 1
1 and the conductive layer 12 are longer as the layer is closer to the current lead 1, and the insulating layer 11 is longer than the conductive layer 12. Further, the length of the insulating layer 11 is set such that the end of the insulating layer 11 facing the current lead 1 is lower than the end of the current lead 1 on the superconducting device side. In FIG. 1, components such as bolts for fixing current leads and a structure having a laminated structure to the low-temperature container are omitted. As described above, in the device of the present embodiment, the possibility of discharging from the current lead 1 is obtained by disposing the laminate A including the insulating layer 11 and the conductive layer 12 between the low-temperature container 2 and the current lead 1. Since the insulating layer 11 made of an insulating material faces all of the high-priced portions, it is possible to make it difficult to generate a discharge.

In this embodiment, the insulating layer 11 contains Y ₂ O ₃ which is a recovery type insulating material. However, the recovery type insulating material is a non-recovery type insulating material such as Al ₂ O ₃ . Since the withstand voltage is lower than that, even if a discharge occurs, the dielectric breakdown concentrates on the recoverable insulating material. Then, the current flowing by the discharge is released from the conductive layer 12 by a ground (not shown) attached to the low-temperature container 2. In general, since the discharge is extremely short, the recoverable insulating material that has been subjected to dielectric breakdown once recovers the insulating function again.

The effectiveness of the structure for preventing discharge having the above-mentioned laminated structure was examined using an apparatus as shown in FIG. In the figure, 1
Reference numerals 1 and 12 denote an insulating layer made of an insulating material and a conductive layer made of a conductive material, each of which is one layer. Insulating layer 1
The thickness of 1 was set to 1 mm in the apparatus of FIG. 1, but here, in order to examine the discharge characteristics, the one prepared by the same method as that of the apparatus of FIG. 1 was polished to 50 μm and used. The thickness of the Cu plate as the conductive layer 12 is 70 μm, which is the same as in FIG. The size of the structure is a rectangle having a width of 5 mm and a length of 20 mm. Although omitted in FIG. 5, the Cu layer 12 is grounded. Reference numeral 13 denotes a tungsten plate having a width of 15 mm, and its tip is thinned to facilitate discharge. A voltage of up to 10 kV was applied from the power supply 14 to the power supply 13, and the electric resistance of the insulating layer 11 before and after the discharge was examined. According to the measurement by the tester, no conduction was observed before the discharge.

With the distance between the insulating layer 11 and the tungsten plate 13 set to 0.5 mm, discharge was forcibly performed in helium gas. The discharge time was 0.1 second, and the discharge was repeated five times at intervals of 0.2 seconds. Then, a continuity test after the discharge was performed on the surface portion of the insulating layer 11 including the discharge region as shown in FIG. 6 by a tester. The continuity was examined in the discharge portion 15, but no continuity was observed as before the discharge. On the other hand, a structure for preventing discharge was formed using only alumina, which is a non-recovery type insulating material, and a similar discharge was performed. About 1k
The resistance was Ω, and the electric resistance was clearly reduced by the discharge.

Embodiment 2 FIG. 2 shows a structural principle diagram of the vicinity of a current lead attachment portion of a superconducting device of this embodiment. The conductive layer 12 has a thickness of 2 mm
Made of stainless steel, and sprayed with Y ₂ O ₃ and A
l ₂ O ₃ is 100 μm so that Al: Y = 100: 20.
The insulating layer 11 was formed with a thickness of m. Two such laminated structures are stacked and the insulating layer is similarly formed on the bottom surface of the structure as shown in FIG.
And The stainless plate 12 is in contact with the low temperature container 2. As described above, in the present embodiment, since the insulating layer 11 is also formed on the bottom portion of the structure A, the conductive material is not exposed to the portion facing the current lead 1 and the discharge starting voltage is high. Become.

The structure A used in this embodiment as described above
The discharge starting voltage of each sample was examined by the method shown in FIG. FIG. 7A is a diagram showing a measuring device for examining the discharge characteristics of a portion indicated by P of the structure A in the device of the present embodiment shown in FIG. 2, and FIG. 4 shows a measuring device for examining discharge characteristics for a structure in which the insulating layer 11 is not formed. In both cases (A) and (B), the tungsten plate 13 serving as a discharge electrode is a stainless steel plate 12.
Are arranged on the same straight line as the bottom surface of. As a result of the measurement, in the case of FIG. 7B, in a helium gas at room temperature,
The distance between the tungsten plate 13 and the surface of the insulating layer 11 is 0.
At the time of 5 mm, it was easily discharged at a voltage of 1 to 3 kV of the current lead. On the other hand, in FIG. 7A, no discharge was observed at a voltage of 5 kV or less. FIG. 7 (B)
, The same measurement was performed without the insulating layer on the tungsten plate 13 side. In this case, discharge occurred even at a voltage of about 100 V. Therefore, even in the case of the structure in which the insulating layer 11 is not formed on the bottom surface shown in FIG. 7B, the discharge starting voltage is improved, but it is confirmed in FIG. 7A that the improvement is further improved. Was done.

Embodiment 3 FIG. 3 shows a structural principle diagram near a current lead attachment portion of a superconducting device of this embodiment. In this embodiment, a mixture of Y ₂ O ₃ and Al ₂ O _{3 in} a ratio of 10 g to 100 g of Al ₂ O _{3 is} used as an insulating material for forming the insulating layer 11. The insulating material is filled between the layer 12 and the layer 12, and is formed under pressure by a cold isostatic pressure (CIP) method so as to have a sectional shape as shown in FIG.
For 5 hours to form a structure A. The resulting insulating layer 11 has a thickest portion of 7 mm and a thinnest portion of 1 mm, and the conductive layer 12 has a thickest portion of 3 mm.
mm, the thinnest part had a film thickness distribution of 1.5 mm.

In order to examine the effectiveness of the structure A for preventing discharge used in the present embodiment having the above structure, FIG.
The discharge characteristics were examined by the method described above. In this embodiment, since the thickness of the insulating layer 11 and the thickness of the conductive layer 12 are different as described above, the discharge for 0.05 to 0.1 second is performed at a plurality of locations at a voltage of up to 30 kV at intervals of 0.3 second. The change in resistance before and after the discharge was repeated five times. In the measurement with a tester, conduction was not observed before and after discharge.
In this embodiment, the reason why the cross-sectional thickness of the conductive layer 12 is changed is to prevent heat from entering from the outside. That is,
Since the conductive material is also a good conductor of heat, the heat from the low-temperature container is transmitted to the vicinity of the superconducting device. When a large-sized superconducting device is used, it is easily expected that the amount of the cooling substance used will greatly increase due to the heat penetration. Therefore, by providing a thin portion in the conductive layer 12 as in the present embodiment, heat penetration from the outside is prevented in the thin portion. In the case of this embodiment, the lower the conductive layer 1
Since the thickness of No. 2 is increased, it is easy to be cooled, and heat intrusion from the outside can be effectively reduced.

Embodiment 4 FIG. 4 is a structural view showing the vicinity of a current lead mounting portion of a superconducting device according to this embodiment. In this embodiment, the structure A including the insulating layer 11 and the conductive layer 12 is attached in contact with the current lead 1. This structure A may be integrated with the current lead 1, the low-temperature container 2, the mounting flange 10 of the current lead, and the like, but are shown as independent parts in this figure. In the present embodiment, the conductive layer 12 is made of a stainless steel plate, and Al ₂ O ₃ is formed thereon by a vacuum evaporation method.
Next, Y ₂ O ₃ is formed in the same manner as the insulating layer 11. At this time, four layers of Y ₂ O ₃ having a thickness of 1 μm and Al having a thickness of 1.5 μm were formed.
5 layers of ₂ O ₃ are alternately formed, and as shown in FIG.
2 and the insulating layer 11 were laminated, and the insulating layer 11 was further formed on the bottom surface so as to have the cross-sectional shape of FIG. Thereafter, the structure was heat-treated in oxygen.

As an insulating layer, only Al ₂ O ₃ was 11.5 μm.
The discharge characteristics of the structure A used in the superconducting device of the present embodiment and the case of forming the superconducting device having a thickness of m were examined with the device of FIG. In FIG. 7, the width 25 is set so as to have the same cross-sectional configuration as FIG.
A laminated structure having a thickness of 50 mm and a length of 50 mm was prepared, and the discharge characteristics were examined. As a result, when only Al ₂ O ₃ was used, a resistance of about 700Ω was observed by a tester measurement after the discharge, but in the structure A used in this example, continuity was observed even after the discharge. Did not. When only Y ₂ O ₃ was used as the insulating material, the discharge starting voltage was lower by 10 to 15% than in the above case. Furthermore, when the copper plate was arranged at the position of the structure without using the structure A of the present example, the discharge generation rate was 1 / 10,000 or less.

Fifth Embodiment FIG. 8 is a diagram showing the configuration near the current lead mounting portion of the superconducting device of this embodiment. 1 is a current lead, 5 is a low temperature container 2
Mounting flange, 10 is an insulating flange, 16 is a lead wire for connecting a current lead to a superconducting device (not shown), 17 is a port through which evaporated cooling gas flows to cool the current lead 1, and 18 is an external power supply. These terminals connect the lead wire 19 (not shown) to the current lead 1. 30 g of Y ₂ O ₃ and Al ₂
A mixture of O ₃ at a ratio of 70 g was used.
Consists of an oxide superconductor 12-1 and a silver plate 12-2. The above-mentioned oxide superconductor powder for the insulating materials 11 and 12-1 and the silver plate of 12-2 were put into a predetermined mold, and FIG.
Press molding to obtain a cross-sectional structure of
Heat treatment was performed at 50 ° C. for 1 hour to obtain a structure A. Also, 17
Was filled with a plurality of nets each formed by forming an oxide superconductor thin film on the surface of a silver wire. In this embodiment, Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _y is used as the oxide superconductor, but any material may be used as long as it becomes a superconductive state by the evaporated cooling substance.

The structure A for preventing discharge composed of 11, 12-1 and 12-2 is mounted on the mounting flange 5 via the insulating flange 10 and further from 12-2 independently of the low temperature vessel 2. Is grounded by the lead wire 20 of the first embodiment. In order to examine the effectiveness of the structure A of this example, the discharge characteristics of the plate-like structure manufactured by the same method were examined by the method shown in FIG. The discharge for 0.05 to 0.1 second at a voltage of up to 20 kV was repeated five times at 0.3 second intervals, and the change in resistance before and after the discharge was examined. The distance between the electrode 13 and the insulating material was 0.2 mm, and 12-
Discharge was performed while cooling No. 1 to a superconducting state. In the measurement with the tester, conduction was not observed before and after the discharge.

Further, in order to investigate the magnetic shielding effect of the structure A in the present embodiment, an experiment was conducted by using an apparatus shown in FIG. In FIG. 9, reference numeral 21 denotes Bi ₂ Sr ₂ C having a diameter of 2 mm.
a ₂ Cu ₃ O _y is processed into a round bar, and 22 is an electromagnet. 21 is placed in liquid nitrogen to be in a superconducting state. In this state, a current is supplied to 21 by the power supply 23. As a result, when the electromagnet 22 is not operated, 40,00
A current of 0 A / cm ² was able to flow. When the structure A used in the present example is arranged as shown in FIG. 9 and the structure A is cooled to about 10 K, even if a magnetic field of 1.0 Tesla is applied to 21 by the electromagnet 22, 34,000 A / cm ² could be passed. On the other hand, when the structure A is not used, when a magnetic field of 0.05 Tesla is applied to 21 by the electromagnet 22, the current that can flow through 21 is 1,500.
A / cm ² . The experimental results obtained by the above-described devices shown in FIGS.
Further, it is shown that the structure A used in the present embodiment also effectively acts on the magnetic shield from the external magnetic field.

Embodiment 6 FIG. 10 shows the structure near the current lead attachment portion of the superconducting device of this embodiment. Reference numeral 1 denotes a current lead, and its sectional structure is shown in FIG. As shown in FIG. 13, reference numeral 24 denotes a stainless steel hollow tube, and an insulator 25 made of Teflon is attached to the outer periphery thereof. 27 'is Bi ₂ Sr ₂ Ca
₂ Cu ₃ O _y in an oxide superconductor obtained by dispersing CaCuO, 7 silver, silver alloy, copper, copper alloy, stainless steel, a conductive material such as manganese alloy, if necessary, 27 'and 7 An intermediate layer such as MgO may be provided in the middle. This 27
The composite of 'and 7 forms the conductor of the current lead. As the conductor 27 of the current lead 1 used in the device of this embodiment, any one of FIGS. 13A and 13B may be used, or may be used in combination.

As shown in FIG. 10, the conductive layer 12 in this embodiment is made of a material in which Y ₂ BaCuO _z is dispersed in YBa ₂ Cu ₃ O _x , which is an oxide superconductor, and is formed into a cylindrical shape. It has been processed. Then, a Teflon resin in which Y ₂ O ₃ is dispersed by 5% by weight is coated on the surface to form the insulating layer 11. The conductive layer 12 is grounded independently of the low-temperature container 2 by a lead wire 20 whose surface is insulated.

In order to examine the effect of the structure A in this embodiment composed of the insulating layer 11 and the conductive layer 12, the current lead 1 was measured when the structure A was used and when it was removed.
A magnetic field was externally applied to the conductor. As a result, when no magnetic field is applied, about 50,000
A current of 0 A / cm ² was able to flow. When the structure A in this embodiment was attached, the amount of current did not change at all even when a magnetic field of 0.5 Tesla was applied. However, when the structure A was not used, 0.5 T When the magnetic field was applied, only a current of 1,100 A / cm ² could be passed.
The structure A was energized while being cooled to about 15K. These results indicate that in the absence of the structure A of the present embodiment, the leakage current from the superconducting device or the like causes the amount of current flowing through the current lead 1 to decrease, and as a result, the actual performance of the superconducting device decreases It can be limited by Further, when the leakage magnetic field applied to the current lead 1 fluctuates, the amount of current flowing to the current lead 1 also fluctuates, which also affects the reliability and stability of the superconducting device. In this embodiment, since the conductive layer 12 constituting the structure A is used in a superconducting state, an external magnetic field can be cut off by the Meissner effect. Insulator 1 because it is also a zero conductor
Unnecessary charges accumulated in 1 can be released through the lead wire 20.

Embodiment 7 FIG. 11 is a structural view showing the vicinity of the current lead attachment portion of the superconducting device of this embodiment. The materials used for the current leads 1 and the conductive layer 12 constituting the structure A are the same as those in the sixth embodiment. The insulating layer 11 is formed of an epoxy resin,
The cross-sectional shape is formed so as to cover the surface of the conductive layer 12 as shown in FIG. 11, and also serves as a mounting flange 5 of the current lead 1 and an insulating flange of the low-temperature container 2. In this embodiment, about 46,000 A /
Although a current of ² cm ² can be passed, by cooling the temperature of the structure A to 50 K or less, even when a magnetic field of 0.5 Tesla was applied from the outside, no change was observed in the amount of current. However, when the conductive layer 12 forming the structure A is removed, the amount of current is 1,2 due to an external magnetic field of about 0.4 Tesla.
It decreased to 00 A / cm ² .

Eighth Embodiment FIG. 12 shows a configuration diagram of the vicinity of a current lead mounting portion of the present embodiment. The structure and material of the current lead 1 are the same as those of the seventh embodiment. In this embodiment, as shown in FIG. 12, the powder of the oxide superconductor 12-1 is filled between the cylinders of the permalloy 12-2 having different diameters so that the permalloy and the oxide superconductor alternate. Insulation layer 1
1 was attached. The insulating layer 11 is made of 100 g of polyethylene.
Is a sheet in which yttrium oxide is kneaded at a rate of 5 g. A current of 50,000 A / cm ² was applied to the current lead 1 and a magnetic field of 1 Tesla was externally applied by an electromagnet (not shown). However, in the superconducting device of this embodiment, there was no change in the amount of current. Did not. However, the insulating layer 11
When the structure A according to the present embodiment including the conductive layer 12 and the conductive layer 12 was removed, a current of 100 A / cm ² or more could not flow through the current lead 1 due to a magnetic field of 1 Tesla.

Embodiment 9 In this embodiment, the structure is the same as that of Embodiment 8,
Then, a current lead 1 having a sectional structure as shown in FIG. 14 was used. In FIG. 14, reference numeral 8 denotes an aluminum hollow tube having a plurality of conductors 27 made of an oxide superconductor attached to the outer periphery thereof. The conductor 27 may be the oxide superconductor itself or a composite of the oxide superconductor 27 ′ and the conductive material 7 as shown in FIG. By using the conductor 27 having such a structure, it is possible to detect a mechanical deformation of the conductor 27 during energization. In other words, when a conductor using an oxide superconductor has a non-uniform portion in the conductor material due to some problem during fabrication,
During energization, heat is generated because the energization current density is reduced at that portion. In the current lead having the above configuration, the heat generated causes the aluminum tube to be deformed. Since the aluminum tube 8 is hollow and can transmit light inside, such deformation of the aluminum tube is the same as the deformation of the light transmitting material. This mechanical deformation also occurs when the current density of the conductor partially changes due to external noise.

Therefore, when light is incident on the aluminum tube 8 from the outside and the intensity change of the reflected light or transmitted light from the mechanically deformed portion generated for some reason is measured,
The mechanical deformation can be detected with high sensitivity. Generally, there is a high risk that mechanical deformation of the conductor will lead to cutting of the conductor. On the other hand, in the conductor according to the present embodiment, in order to detect mechanical deformation at an early stage, it is necessary to perform a quick measure such as temporarily reducing the amount of electricity or increasing the cooling capacity to cool the conductor to a lower temperature. Thereby, the safety of the entire superconducting device can be ensured.

The material 8 may be a rod or tube made of a shape memory alloy or quartz glass, or a polyimide resin, instead of the above-mentioned aluminum tube. A material having a light transmittance enough to detect light may be used. In addition, the light applied to the light 8 may not only be transmitted through the material but also propagated while reflecting the hollow portion, or may be formed by laminating materials having different refractive indexes. It may be passed. Generally, a material that satisfies this condition only needs to have a light transmittance of 1% or more per 1 m. In FIG. 14, eight superconductors 27 are attached to the aluminum tube 8, but the number is not limited. Further, a conductive material such as copper may be used simultaneously instead of the superconductor. The relative arrangement of 8 and 27 is not limited, and is not limited to the shape shown in FIG. 14 as long as 27 and 8 are in contact with each other.

The current lead 1 of the device of this embodiment is connected to 47,0
An electric current of 00 A / cm ² was applied and a magnetic field of 1 Tesla was applied from the outside by an electromagnet (not shown). However, in the superconducting device of this embodiment, no change was found in the amount of current. However, when the structure A of the present example including the insulating layer 11 and the conductive layer 12 was removed, only a current of 80 A / cm ² could flow through the current lead due to a magnetic field of 1 Tesla. Also, with the structure A removed,
Using a light source and a photodetector (not shown) at 8 in FIG. 14, light was incident on one end from 8 and the intensity of transmitted light exiting from multiple ends was measured. When the intensity when a magnetic field was applied was measured with the light intensity being 100, the intensity of the transmitted light decreased by 20 to 30% in about 0.1 second after the application of the magnetic field. When the amount of electricity was set to 80 A / cm ² and the temperature of the conductor 27 recovered before the application of the magnetic field, the transmittance became about 98%. The above is because the density of the current flowing through the conductor was reduced by the application of the magnetic field, and the
This indicates that the initial shape was almost restored when a mechanical deformation was generated and then the amount of current was reduced and the temperature was stabilized. Therefore, by using the structures A and 8 of this embodiment, it is possible to easily and quickly detect an abnormality such as a quench of the conductor.

[0041]

As described above, according to the present invention,
The probability of occurrence of discharge near the current lead of the superconducting device can be greatly reduced, and even if a discharge occurs, the insulation characteristics are restored after the discharge has subsided. The number of replacements can be greatly reduced. Further, according to the present invention, the current lead can be protected from various noises such as a leakage magnetic field. Further, by using a light-transmitting material for the constituent members of the conductor, it is possible to detect an abnormality of the conductor itself by optical means independent of electromagnetic noise.

[Brief description of the drawings]

FIG. 1 is a configuration principle diagram in the vicinity of a current lead attachment portion of a superconducting device according to a first embodiment.

FIG. 2 is a configuration principle diagram in the vicinity of a current lead attachment portion of a superconducting device according to a second embodiment.

FIG. 3 is a configuration principle diagram near a current lead attachment portion of a superconducting device according to a third embodiment.

FIG. 4 is a structural principle diagram of the vicinity of a current lead attachment portion of a superconducting device according to a fourth embodiment.

FIG. 5 is a principle diagram of an experiment for examining the effectiveness of the present invention.

FIG. 6 is a principle diagram of an experiment for examining the effectiveness of the present invention.

FIG. 7 is a principle diagram of an experiment for examining the effectiveness of the present invention.

FIG. 8 is a configuration principle diagram of a vicinity of a current lead attachment portion of a superconducting device according to a fifth embodiment.

FIG. 9 is a principle diagram of an experiment for examining the effectiveness of the present invention.

FIG. 10 is a structural principle diagram of the vicinity of a current lead attachment portion of a superconducting device according to a sixth embodiment.

FIG. 11 is a structural principle diagram of the vicinity of a current lead attachment portion of a superconducting device according to a seventh embodiment.

FIG. 12 is a structural principle diagram of the vicinity of a current lead attachment portion of a superconducting device according to an eighth embodiment.

FIG. 13 is a sectional configuration diagram of a current lead used in the superconducting device of the present invention.

FIG. 14 is a sectional view of a current lead used in the superconducting device of the present invention.

FIG. 15 is a cross-sectional configuration diagram of a conventional current lead.

FIG. 16 is a configuration diagram of a conventional superconducting device.

FIG. 17 is a diagram illustrating magnetic properties of an oxide superconductor.

[Explanation of symbols]

 1: Current lead 2: Cryogenic container 3: Superconducting device 4: Cooling substance 5: Mounting flange 6: Space 7: Conductive material 8: Light transmitting material 9: Gas outlet 10: Insulating flange 11: Insulating layer 12: Conductive layer 13 : Electrode 14: Power supply 15: Discharge area 16: Lead wire 17: Gas inlet 18: Terminal 19: Lead wire 20: Ground 21: Superconductor 22: Electromagnet 23: Power supply 24: Hollow tube 25: Insulator 26: Space 27 :conductor

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01F 6/00 H01L 39/00

Claims (12)

(57) [Claims] 1. A superconducting device comprising a cryogenic container, a superconducting device housed in the cryogenic container, and a current lead attached to the cryogenic container and connected to the superconducting device. A structure for preventing discharge is disposed between the current lead mounting portion and the current lead mounting portion , and the structure includes a laminate of a conductive layer and an insulating layer. Superconducting device. 2. The superconducting device according to claim 1 , wherein the superconducting device has at least two laminated structures of a conductive layer and an insulating layer. 3. A laminated body constituting a structure for preventing discharge has an insulating layer disposed on an electric lead side and a conductive layer disposed on a current lead mounting portion side of a low-temperature container. Item 2. A superconducting device according to item 1 . 4. The electric potential of a conductive layer of a laminate constituting a structure for preventing discharge is set to the same electric potential as that of a low-temperature container.
2. The superconducting device according to 1 . 5. The superconducting device according to claim 1 , wherein a conductive layer of a laminate constituting a structure for preventing discharge is grounded. 6. The superconducting device according to claim 1 , wherein the conductive layer of the laminate constituting the structure for preventing discharge has a film thickness distribution. 7. The superconducting device according to claim 1 , wherein a recovery type insulating material is contained in an insulating layer of a laminate constituting a structure for preventing discharge. 8. The superconducting device according to claim 1 , wherein the conductive layer of the laminated body constituting the structure for preventing discharge contains a magnetic material. 9. The superconducting device according to claim 1 , wherein a superconducting material is contained in the conductive layer of the laminate constituting the structure for preventing discharge. 10. A structure for preventing discharge is provided by electromagnetic noise.
2. The device according to claim 1, which also has a shielding function.
Superconducting device. 11. A cryogenic container, and housed in the cryogenic container.
Superconducting equipment and superconducting equipment attached to a cryogenic vessel
Superconducting device consisting of connected current leads
The current leads and the current leads provided on the cryogenic vessel.
Structure is arranged for discharge prevention between the de mounting portion
A superconducting device , wherein the structure also has an electromagnetic noise shielding function. 12. An electromagnetic noise shield function comprising:
The superconducting device according to claim 11, which includes a superconducting action.