JPH07312309A - Superconducting device - Google Patents

Abstract

PURPOSE:To avoid electric discharge near current lead fixtures, without adding any special device, by disposing anti-discharging structures between current leads and current leads fixtures disposed at a low temp. vessel. CONSTITUTION:Antidischarging structures A are each composed of an insulation and conductive layers 11 and 12 and other two insulation layers and every two conductive layers laminated The potential of the conductive layers alternately laminated on insulation materials are equal to that of a low temp. vessel 2 or independently grounded to avoid discharge between the insulators and vessel. A magnetic material is preferably used for, at least, a part of the material for forming the layer 12. Thus, the conductor of current leads 1 can be shielded from noises such as external leaking magnetic fields and hence the superconducing device can be operated stably.

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 using a superconducting magnet, a Josephson element, etc. are housed in a low temperature container, and in particular, current leads for supplying electric power from various external 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 As an example of a conventional superconducting device, FIG. 16 shows a case where a superconducting magnet is housed in a cryogenic container. In this figure, 3 is a superconducting coil, 1 is a current lead, and the current lead 1 is attached to a cryogenic container 2 by an attachment flange 5. The mounting flange 5 is usually made of metal, and the cryocontainer 2 is connected via the insulator 10.
Attached to. Reference numeral 4 is a cooling substance for cooling the superconducting coil 3. Normally, liquid helium is the cooling substance 4.
The vaporized helium gas used as the current lead 1
The conductor is cooled and discharged from the gas outlet 9 to the outside of the cryogenic container. FIG. 15 shows the structure 1 of the current lead 1.
An example is shown. In this figure, the current lead 1 has a form 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. Note that FIG. 15A is a diagram showing a cross-sectional structure of the current lead, and FIG. 15B is a plan view of the 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 vaporized helium gas. ing. When electric power is supplied to the superconducting coil 3 from an external power source (not shown) through the current lead 1, a high electric field is generated in the vicinity of the mounting flange 5 especially when alternating current is applied. Since the insulating performance of helium gas is much lower than that of air or the like, there is a possibility that electric discharge may easily occur between the current lead 1 and the mounting flange 5 centering on 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
It was necessary to increase the size of the cryogenic container 2 for mounting the superconducting device, and it was difficult to downsize the superconducting device including the cryogenic container 2.

Further, as shown in FIG. 15, in the current lead 1, the insulator 25 is provided on the outer periphery of the conductor 27.
Although it is conceivable to reduce the thickness of the insulator 25 to reduce the space portion 6, the current lead 1 is attached and detached as necessary. Therefore, considering the operability when attaching and detaching, the thickness of the insulator 25 is small. However, the space 6 is naturally limited, and the space 6 cannot be made so small only by the thickness of the insulator of the current lead.
A proposal for reducing the size of the mounting portion of the current lead is disclosed in Japanese Patent Application Laid-Open No. 04-320305. In this proposal, the mounting portion of the current lead is provided with a space in which a gas having a good insulating property, for example, dry air or nitrogen is allowed to flow, so that the mounting portion of the current lead is downsized to improve the dielectric strength. However, this method requires a device for flowing the gas, and also needs to remove water in the gas.
For this reason, even if the current lead mounting portion of the cryogenic container 2 can be miniaturized, a device for flowing gas is indispensable, and the miniaturization of the entire device cannot be achieved.

Further, in the current lead, it is necessary not only to supply electric power from an external power source but also to prevent heat invasion from the outside, but generally, a conductive metal is used for the conductor of the current lead. , Not only electric power but also heat from the outside is transmitted to the superconducting device. For this reason, it has been proposed to use an oxide superconductor having a small coefficient of thermal conductivity and zero electric 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 an oxide superconductor. Is used as a conductor. Since the oxide superconductor has a low coefficient of thermal conductivity, the current leads disclosed therein are effective for preventing heat intrusion from the outside.

However, the oxide superconductor has a problem that the amount of current flowing in the superconductor is greatly reduced by the magnetic field from the outside (see FIG. 17). Generally, a current density of about 10,000 A / cm ² or more is required for applications such as superconducting magnets. For this reason, although the current lead using the oxide superconductor as a conductor can prevent heat intrusion, the amount of current supplied to the superconducting device fluctuates due to the magnetic field from the outside, and in some cases the superconducting state is There is also the possibility of breaking. 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, but the current lead attachment caused by operating the superconducting device is important. It is extremely important to take measures to prevent discharge and electromagnetic noise near the parts. However, in the conventional superconducting device, as described above, a special device is required to prevent discharge, and it cannot be said that noise countermeasures are 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 of the superconducting device not operating. Further, conventionally, the abnormality of the current lead, especially the abnormality at the time of energization, is generally judged by detecting the voltage generated at both ends of the conductor. There is no effect if a discharge occurs between them. Therefore, it is an object of the present invention to prevent the discharge near the current lead mounting portion without adding a special device in order to solve the above-mentioned problems of the prior art, and further to stabilize the current lead. An object of the present invention is to provide a small-sized superconducting device which is also provided with a noise countermeasure for operating.

[0008]

The above objects can be achieved by the present invention described below. That is, the present invention provides a superconducting device comprising a cryocontainer, a superconducting device housed in the cryocontainer, and a current lead attached to the cryocontainer and connected to the superconducting device. The superconducting device is characterized in that a structure for preventing discharge is arranged between a current lead mounting portion provided in the container.

[0009]

In the present invention, a superconducting device, a cryogenic container for accommodating the superconducting device, and a superconducting device attached to the cryocontainer via a flange and connected to the superconducting device for introducing electric power from an external power source to the superconducting device In a superconducting device having a current lead, by providing a structure having a discharge prevention function and an electromagnetic noise shield function between the current lead attachment part of the cryogenic container and the current lead, the vicinity of the current lead of the superconducting device is provided. The discharge occurrence probability of is greatly reduced. Also, by using a recovery-type insulation material, even if a discharge should occur, the insulation characteristics will be restored and self-recovery will be possible after the discharge has settled down, so it is possible to reduce the size of the device and replace parts. It 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. Furthermore, by using a light-transmissive material for the constituent members of the conductor, the abnormality of the conductor itself is affected by electromagnetic noise. Since it is also possible to detect it by an optical means that is not performed, it becomes possible to easily and promptly deal with abnormality such as quenching 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. It is characterized in that a structure for preventing discharge is arranged between the current lead mounting portion provided in the cryogenic container. A preferred embodiment of the superconducting device of the present invention is shown in FIG. 1. Since the structure of the superconducting device of the present invention is basically the same as that of FIG. 16, one of the pair of current leads is attached to FIG. Only the vicinity of the part is shown. 1 in FIG.
Is a current lead, and 5 is a flange for attaching the current lead 1 to the cryogenic container 2 via the insulating flange 10.
A is a structure for preventing discharge, which is composed of an insulating layer 11 and a conductive layer 12 in FIG. 1, and two insulating layers and two conductive layers are further laminated in this figure.
In addition, L in the drawing is the shortest distance between the current lead 1 and the cryogenic container 2.

In the present invention, the structure A for preventing discharge which constitutes the superconducting device may be any structure as long as it can effectively prevent discharge in the vicinity of the current lead mounting portion provided in the cryogenic container 2. However, preferably, the structure A is formed of a laminated body including an insulating layer and a conductive layer. More preferably, as shown in FIG. 1, a laminate having two or more insulating layers and two or more conductive layers is used to further enhance the discharge prevention effect. By configuring in this way,
It is possible to effectively prevent the discharge near the current lead attachment portion without using a special device.

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

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

Structure A constituting the superconducting device of the present invention
When is constituted by a laminated body composed 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 arranged on the side of the plurality of current leads 1 and the conductive layer 12 is arranged on the current lead attachment portion of the cryogenic container 2. Then, 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 cryogenic container 2 or is grounded independently to prevent discharge between the insulator and the cryogenic container. To do. Further, in the present invention, it is preferable to use a magnetic material as at least a part of the material forming the conductive layer 12. By doing so, the conductor of the current lead 1 can be shielded from noise such as a leakage magnetic field from the outside, so that the superconducting device of the present invention can be stably operated. . The discharge between the current lead 1 and the cryocontainer 2 is
Although the probability of occurring between the current lead 1 and a conductive portion existing at a short distance is the highest, in the present invention, the portion facing the current lead 1 is made of an insulating material as described above. There is. Therefore, even if a discharge should occur, all 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 one having conductivity, but is formed of at least one of a conductive material and a magnetic material. Preferably. Although these materials are not particularly limited, examples of the conductive material used in the present invention include stainless steel, copper, permalloy and various superconductors. Further, the conductive layer formed of a conductive material or the like as described above and the insulating layer as described above are so long as the structure A having a laminated structure composed of these has such a mechanical strength as not to be damaged during normal handling. Well, there is no limitation on the manufacturing method and the size, but it is preferable to adopt the form described below according to the characteristics of various materials and devices used.

The conductor of the current lead 1 may be made of, for example, an oxide superconducting material which is called Bi system and exhibits superconductivity at a temperature higher than the boiling point of liquid nitrogen. Since these oxide superconductors have a thermal conductivity smaller than that of a metal such as copper, it is possible to greatly reduce heat infiltration into the superconducting device. However, it is known that the amount of current that can be applied to an oxide superconducting material changes due to a magnetic field from the outside.
In the case of Bi system, the amount of energization drops drastically when the temperature exceeds about 30K (Fig. 17). In the present invention, in such a case, the structure composed of the laminated body of the conductive layer and the insulating layer is arranged so as to surround the conductor of the current lead as shown in FIG. It is preferable that it also functions as a noise shield material.

Further, the present invention provides a conductor capable of detecting an abnormality in the current lead at the time of energization or an abnormality due to discharge or the like when a large current is used like a superconducting magnet device. You can FIG. 13 shows a sectional view of the basic structure of such a conductor, but one or all of the conductors having a structure in which a superconductor is attached to a light transmissive material as shown in FIG. 13 are used. As a result, when a magnetic field or mechanical deformation from the outside acts on the superconductor in which the current flows, the light transmissive material is deformed. Therefore, when light is incident on the light transmissive material as needed, for example, the mechanical deformation of the light transmissive material causes a change in the amount of light transmitted, whereby an abnormality in the conductor can be detected. That is, in the above device, since it is possible to detect an abnormality by an optical means,
It is possible to accurately detect a conductor abnormality without being affected by an electrical phenomenon such as discharge.

[0018]

EXAMPLES Next, the present invention will be described in detail with reference to examples. In the following examples, the case where yttrium oxide is used as the recoverable insulating material and alumina is used as the non-recoverable insulating material will be mainly described, but it goes without saying that the present invention is not limited to this. . Example 1 FIG. 1 is a structural principle diagram in the vicinity of a current lead attachment portion of a superconducting device of this example. The basic configuration of the superconducting device is
Similar to the conventional device of FIG. 16, it comprises a current lead 1 for supplying electric power from an external power source, a superconducting device 3, a cryogenic container 2 containing 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. May be stored.

In FIG. 1, reference numeral 1 is a current lead, and 5 is a flange for attaching the current lead 1 to the cryogenic 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
After being pressure-molded by method P), it was heat-treated in air at 500 ° C. for 5 hours. 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, and when attached to the cryogenic container 2, the Cu layer 12 is in direct contact with the cryogenic container 2. In this embodiment, the insulating layer 1
1 and the conductive layer 12, the layers closer to the current lead 1 are longer, and the insulating layer 11 is longer than the conductive layer 12. Furthermore, the length of the insulating layer 11 is set so that the end of the insulating layer 11 facing the current lead 1 is located below the end of the current lead 1 on the superconducting device side. In FIG. 1, parts such as bolts for fixing the current leads and the laminated structure to the cryogenic container are omitted. As described above, in the device of the present embodiment, the possibility of discharge from the current lead 1 is obtained by disposing the laminated body A including the insulating layer 11 and the conductive layer 12 between the cryogenic container 2 and the current lead 1. Since the insulating layer 11 made of an insulating material faces all the high portions, it is possible to prevent discharge from occurring.

Further, in this embodiment, the insulating layer 11 is used by containing Y ₂ O ₃ which is a recovery type insulating material, but the recovery type insulating material is a non-recoverable 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 recovery type insulating material. Then, the electric current flowing by the discharge is emitted from the conductive layer 12 by the ground (not shown) attached to the low temperature container 2. Generally, since the discharge is extremely short, the recoverable insulating material that has once undergone dielectric breakdown restores its insulating function.

The effectiveness of the structure having the above-mentioned laminated structure for preventing discharge was examined by using a device as shown in FIG. 1 in the figure
Reference numerals 1 and 12 respectively 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 No. 1 was 1 mm in the apparatus of FIG. 1, but here, in order to investigate 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. Further, the thickness of the Cu plate which is 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 is a tungsten plate having a width of 15 mm, and its tip is thin so that it can be easily discharged. A voltage of up to 10 kV was applied to this 13 from a power source 14 to examine the electric resistance of the insulating layer 11 before and after discharge. According to the measurement by the tester, there was no continuity before the discharge.

The distance between the insulating layer 11 and the tungsten plate 13 was set to 0.5 mm, and the discharge was forcibly performed in helium gas. The discharge time was 0.1 seconds, and the discharge was repeated 5 times at intervals of 0.2 seconds. Then, with respect to the surface portion of the insulating layer 11 including the discharge region as shown in FIG. 6, a continuity test after discharge was conducted by a tester. Conduction was examined in the discharge part 15, but no conduction was observed as before the discharge. On the other hand, when a structure for discharge prevention was formed using only non-recoverable insulating material alumina and the same discharge was performed, it did not conduct before discharge, but after discharge About 1k
It became a resistance of Ω, and it was clearly observed that the electric resistance decreased due to discharge.

Embodiment 2 FIG. 2 shows a structural principle diagram in the vicinity of the current lead mounting portion of the superconducting device of this embodiment. The conductive layer 12 has a thickness of 2 mm
Consists of a stainless steel plate, in which the spraying method, Y ₂ O ₃ and A
l ₂ O ₃ is 100μ 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. 2, and the structure A used in this embodiment is used.
And The stainless plate 12 is in contact with the cryogenic container 2. As described above, in this embodiment, since the insulating layer 11 is also formed on the bottom surface of the structure A, the conductive material is not exposed at the portion facing the current lead 1, and the discharge start voltage is high. Become.

Structure A used in this embodiment as described above
The discharge starting voltage was examined by the method shown in FIG. FIG. 7 (A) is a diagram showing a measuring device for examining the discharge characteristic of the portion indicated by P of the structure A in the device of this embodiment shown in FIG. 2, and FIG. 7 (B) is a bottom view. 2 shows a measuring device for examining discharge characteristics for a structure having no insulating layer 11. In both cases (A) and (B), the tungsten plate 13 serving as the discharge electrode is the stainless steel plate 12.
It is arranged so as to be aligned with the bottom surface of the. As a result of the measurement, in the case of FIG. 7B, in helium gas at room temperature,
The distance between the tungsten plate 13 and the surface of the insulating layer 11 is 0.
When it was 5 mm, it was easily discharged by the voltage of the current lead of 1 to 3 kV. On the other hand, in FIG. 7 (A), no discharge was observed at a voltage of 5 kV or less. Also, FIG. 7 (B)
In the above, when 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 100V. Therefore, it is confirmed that the discharge start voltage is improved even in the case of the structure body in which the insulating layer 11 is not formed on the bottom surface shown in FIG. 7B, but is further improved in FIG. 7A. Was done.

Embodiment 3 FIG. 3 shows a structural principle diagram in the vicinity of the current lead mounting portion of the superconducting device of this embodiment. In this embodiment, as the insulating material forming the insulating layer 11, a mixture of Y ₂ O ₃ of 10 g with respect to 100 g of Al ₂ O ₃ is used, and a conductive material composed of a mold and pre-machined copper is used. The insulating material is filled between the layer 12 and the layer 12, and the mixture is pressure-molded by a cold isostatic pressure (CIP) method so as to have a cross-sectional shape as shown in FIG.
Then, the structure A was prepared by heat treatment for 5 hours. 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.
In 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, which is used in this embodiment having the above structure, FIG.
The discharge characteristics were examined by the method. In this embodiment, since the thicknesses of the insulating layer 11 and the conductive layer 12 are different as described above, 0.05 to 0.1 second discharge is performed at 0.3 second intervals at a voltage of up to 30 kV at a plurality of locations. The change in resistance before and after discharge was examined 5 times. When measured with a tester, conduction was not observed before or after discharge.
In the present embodiment, the cross-sectional thickness of the conductive layer 12 is changed in order to prevent heat intrusion from the outside. That is,
Since the conductive material is also a good conductor of heat, the heat from the cryogenic 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 this heat infiltration. Therefore, as in the present embodiment, by providing the conductive layer 12 with a thin portion, heat intrusion from the outside is prevented in the thin portion. In the case of the present embodiment, the conductive layer 1 is located downward.
Since the thickness of 2 is increased, cooling is facilitated, and heat intrusion from the outside can be effectively reduced.

Embodiment 4 FIG. 4 is a block diagram showing the vicinity of the current lead mounting portion of the superconducting device of 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 cryogenic container 2, the mounting flange 10 of the current lead, etc., but is shown as a separate part in this figure. In this embodiment, the conductive layer 12 is made of a stainless steel plate, on which Al ₂ O ₃ is formed by a vacuum evaporation method,
Next, Y ₂ O ₃ is similarly formed to form the insulating layer 11. At this time, 4 layers of 1 μm thick Y ₂ O ₃ and 1.5 μm thick Al
5 layers of ₂ O ₃ are formed alternately, and as shown in the figure, this conductive layer 1
Two laminated bodies composed of 2 and the insulating layer 11 were stacked, and the insulating layer 11 was further formed on the bottom surface so that the cross-sectional shape of FIG. 4 was obtained. Then, this structure was heat-treated in oxygen.

Al ₂ O ₃ alone is used as an insulating layer for 11.5 μm.
The discharge characteristics of the structure A used in the superconducting device of the present embodiment and the case of forming it to a thickness of m were examined with the device of FIG. In FIG. 7, the width 25
mm, and a length of 50 mm, a laminated structure was prepared and discharge characteristics were examined. As a result, when only Al ₂ O ₃ was used, a resistance of about 700Ω was observed in the tester measurement after discharge, but in the structure A used in this example, continuity was recognized even after discharge. There wasn't. Further, when only Y ₂ O ₃ was used as the insulating material, the discharge starting voltage was 10 to 15% lower than that in the above case. Further, when the copper plate was placed at the position of the structure without using the structure A of this example, the discharge occurrence rate was 1 / 10,000 or less.

Embodiment 5 FIG. 8 shows a configuration diagram of the vicinity of the current lead mounting portion of the superconducting device of this embodiment. 1 is a current lead, 5 is a cryogenic container 2
Mounting flange, 10 is an insulating flange, 16 is a lead wire for connecting a current lead and 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 It is a terminal for connecting the lead wire 19 (not shown) and the current lead 1. As the insulating material forming the insulating layer 11, 30 g of Y ₂ O ₃ and Al ₂
Using a mixture of O ₃ at a ratio of 70 g, the conductive layer 12
Is composed of an oxide superconductor 12-1 and a silver plate 12-2. The oxide superconductor powder for the insulating materials 11 and 12-1 and the silver plate 12-2 described above were put in a predetermined form,
Pressure-molded to obtain the cross-sectional structure of
Heat treatment was performed at 50 ° C. for 1 hour to obtain a structure A. Also, 17
The part of was filled with a plurality of nets each having an oxide superconductor thin film formed on the surface of the silver wire. As the oxide superconductor, Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _y was used in this embodiment, but any substance can be used as long as it becomes a superconducting state by the evaporated cooling substance.

The structure A for preventing discharge comprising 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 cryogenic container 2. It is grounded by the lead wire 20 of. In order to examine the effectiveness of the structure A of this example, the discharge characteristics of the plate-shaped structure manufactured by the same method were examined by the method of FIG. Discharge for 0.05 to 0.1 seconds at a voltage up to 20 kV was repeated 5 times at intervals of 0.3 seconds to examine the change in resistance before and after the discharge. The distance between the electrode 13 and the insulating material was 0.2 mm, and 12-
While cooling 1 to the superconducting state, discharge was performed. In the tester measurement, no continuity was observed before and after discharge.

Further, in order to examine the magnetic shield effect of the structure A in this embodiment, an experiment was conducted by the device shown in FIG. In FIG. 9, 21 is Bi ₂ Sr ₂ C having a diameter of 2 mm.
It is a product obtained by processing a ₂ Cu ₃ O _y into a round bar shape, and 22 is an electromagnet. 21 is put in liquid nitrogen to be in a superconducting state, and in this state, an electric current is passed through 21 by a power source 23. As a result, when the electromagnet 22 is not operated, 40,00
A current of 0 A / cm ² could be passed. When the structure A used in this 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 the structure 21 by the electromagnet 22, 34,000 A / A current of cm ² could be passed. On the other hand, when the structure A is not used, when a 0.05 Tesla magnetic field is applied to the 21 by the electromagnet 22, the current that can be passed through the 21 is 1,500.
It fell to A / cm ² . The above-mentioned experimental results obtained by the devices shown in FIGS. 5 and 9 show that the discharge can be prevented near the current lead 1.
Further, it is shown that the structure A used in this example also effectively acts on the magnetic shield from the external magnetic field.

Embodiment 6 FIG. 10 shows the structure in the vicinity of the current lead mounting portion of the superconducting device of this embodiment. Reference numeral 1 is a current lead, the cross-sectional structure of which is shown in FIG. As shown in FIG. 13, 24 is a stainless steel hollow tube, and an insulator 25 made of Teflon is attached to the outer circumference thereof. 27 'is Bi ₂ Sr ₂ Ca
_{2 is} an oxide superconductor in which CaCuO is dispersed in ₂ Cu ₃ O _y , 7 is a conductive material such as silver, silver alloy, copper, copper alloy, stainless steel, manganese alloy, etc. An intermediate layer such as MgO may be provided in the middle. This 27
The composite of'and 7 form the conductor of the current lead. As the conductor 27 of the current lead 1 used in the device of the present embodiment, either of (A) and (B) of FIG. 13 may be used, or they 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 made into a cylindrical shape. It has been processed. Then, a Teflon resin having Y ₂ O ₃ dispersed in a weight ratio of 5% is coated on the surface thereof to form the insulating layer 11. The conductive layer 12 is grounded independently of the cryogenic container 2 by a lead wire 20 whose surface is insulated.

In order to investigate the effect of the structure A including the insulating layer 11 and the conductive layer 12 in this embodiment, the current lead 1 is used when the structure A is used and when it is removed.
A magnetic field was externally applied to the conductor. As a result, when no magnetic field is applied, the current lead 1 has about 50000
A current of 0 A / cm ² could be passed. When the structure A of this example was attached, no change was observed in the energization amount even when a magnetic field of 0.5 Tesla was applied, but when the structure A was not used, 0.5 Tesla was used. When a magnetic field of 1 was applied, only a current of 1,100 A / cm ² could be passed.
In addition, the structure A was energized while being cooled to about 15K. These results indicate that in the absence of the structure A of this example, the leakage magnetic field from the superconducting device or the like reduces the energization amount of the current lead 1, and as a result, the actual performance of the superconducting device is reduced. It can be restricted by Furthermore, it is shown that when the leakage magnetic field applied to the current lead 1 fluctuates, the energization amount to the current lead 1 also fluctuates, which affects the reliability and stability of the superconducting device. In this example, since the conductive layer 12 constituting the structure A is used in a superconducting state, it is possible to block a magnetic field from the outside by the Meissner effect, and the superconducting state causes an electric resistance. Insulator 1 because it is also a zero conductor
It is also possible to discharge the unnecessary electric charge accumulated in 1 through the lead wire 20.

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

Embodiment 8 FIG. 12 is a block diagram showing the vicinity of the current lead mounting portion of this embodiment. The structure and material of the current lead 1 are the same as in the case of Example 7. In this embodiment, as shown in FIG. 12, powder of oxide superconductor 12-1 is filled between cylinders of permalloy 12-2 having different diameters so that the permalloy and the oxide superconductor alternate. Insulation layer 1 on pressure molded product
I installed 1. Insulating layer 11 is 100 g polyethylene
It is a sheet in which yttrium oxide is kneaded in a ratio of 5 g. A current of 50,000 A / cm ² was passed through the current lead 1 and a magnetic field of 1 Tesla was applied from the outside by an electromagnet (not shown). However, in the superconducting device of this example, no change was observed in the energization amount. There wasn't. However, the insulating layer 11
When the structure A of this example including the conductive layer 12 and the conductive layer 12 was removed, a current of 100 A / cm ² or more could not be applied to the current lead 1 due to the magnetic field of 1 Tesla.

Embodiment 9 In this embodiment, the current lead 1 is constructed similarly to the embodiment 8.
The current lead 1 having the sectional structure as shown in FIG. In FIG. 14, reference numeral 8 is 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 mechanical deformation of the conductor 27 during energization. That is, a conductor using an oxide superconductor has a non-uniform portion in the conductor material due to some problem during production.
When energized, heat is generated because the energized current density is reduced in that part. In the current lead having the above structure, this heat generation causes the aluminum tube to be deformed. Since the aluminum tube 8 is hollow and allows light to pass therethrough, such deformation of the aluminum tube is similar to deformation of the light transmitting material. It should be noted that this mechanical deformation also occurs when the current density of the conductor is partially changed by noise from the outside.

Therefore, when light is incident on the aluminum tube 8 from the outside and the intensity change of the reflected light or the transmitted light from the mechanically deformed portion generated for some reason is measured,
The mechanical deformation can be detected with high sensitivity. In general, mechanical deformation of the conductor also has a high risk of cutting the conductor. On the other hand, in the conductor of this embodiment, since mechanical deformation can be detected at an early stage, it is necessary to take a quick measure such as temporarily reducing the amount of electricity or increasing the cooling capacity to cool the conductor to a lower temperature. As a result, the safety of the entire superconducting device can be ensured.

The material of 8 may be a rod or tube of shape memory alloy or quartz glass, or a polyimide resin or the like instead of the above aluminum tube. Further, when light is incident from one end, it is transmitted from multiple ends. A material having a light transmittance that allows light to be detected may be used. Further, the light applied to 8 may not only be transmitted through the material, but may also be propagated while being reflected in the hollow portion, or the waveguide formed by laminating materials having different refractive indexes may be used. It may be passed. Generally, a material satisfying this condition may have a light transmittance of 1% or more per 1 m. Further, in FIG. 14, eight superconductors 27 are attached to the aluminum tube 8, but the number is not limited. Also, instead of the superconductor, a conductive material such as copper may be used at the same time. The relative arrangement of 8 and 27 is not limited, and if 27 and 8 are in contact with each other, the shape is not limited to the shape of FIG.

The current lead 1 of the device of this embodiment has 47,0 in the current lead 1.
A current of 00 A / cm ² was passed and a magnetic field of 1 Tesla was externally applied by an electromagnet (not shown), but the superconducting device of this example did not require any change in the energization amount. 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 be passed through the current lead due to the magnetic field of 1 Tesla. Also, with the structure A removed,
Using a light source and a photodetector (not shown) in FIG. 14, the intensity of the transmitted light emitted from the other end was measured by making the light incident on 8 from one end, and the transmission without a magnetic field from the outside was observed. When the intensity of the light was measured when the intensity of the light was set to 100, the intensity of the transmitted light was reduced by 20 to 30% in about 0.1 seconds after the application of the magnetic field. When the energization amount was set to 80 A / cm ² and the temperature of the conductor 27 was recovered before the magnetic field was applied, the transmittance became about 98%. The above is because the current density flowing through the conductor is reduced by the magnetic field application, and the conductor heats up.
It is shown that when the mechanical deformation was generated, the energization amount was reduced, and the temperature was stabilized, the shape returned to the initial shape. Therefore, by using the structures A and 8 of this embodiment, it is possible to easily and quickly detect an abnormality such as quenching of the conductor.

[0041]

As described above, according to the present invention,
The probability of occurrence of discharge near the current lead of a superconducting device can be significantly reduced, and even if a discharge should occur, the insulation characteristics will be restored after the discharge has settled down. 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. Furthermore, by using a light-transmissive material for the constituent members of the conductor, it becomes possible to detect abnormality of the conductor itself by an optical means that is not affected by electromagnetic noise.

[Brief description of drawings]

FIG. 1 is a structural principle diagram in the vicinity of a current lead mounting portion of a superconducting device of Example 1.

FIG. 2 is a structural principle diagram in the vicinity of a current lead mounting portion of a superconducting device of Example 2.

FIG. 3 is a structural principle diagram in the vicinity of a current lead mounting portion of the superconducting device of Example 3;

FIG. 4 is a structural principle diagram in the vicinity of a current lead mounting portion of a superconducting device of Example 4.

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 structural principle diagram in the vicinity of a current lead mounting portion of the superconducting device of Example 5;

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

FIG. 10 is a structural principle diagram in the vicinity of a current lead mounting portion of the superconducting device of Example 6;

FIG. 11 is a structural principle diagram in the vicinity of a current lead mounting portion of the superconducting device of Example 7.

FIG. 12 is a structural principle diagram in the vicinity of a current lead mounting portion of the superconducting device of Example 8.

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

FIG. 14 is a cross-sectional configuration diagram 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 showing magnetic characteristics of an oxide superconductor.

[Explanation of symbols]

 1: Current lead 2: Low temperature container 3: Superconducting device 4: Cooling material 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: Earth 21: Superconductor 22: Electromagnet 23: Power supply 24: Hollow tube 25: Insulator 26: Space 27 :conductor

Claims (11)

[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 superconducting device, wherein a structure for preventing discharge is arranged between the structure and a current lead mounting portion provided on the superconducting device. 2. The superconducting device according to claim 1, wherein the structure for preventing discharge is composed of a laminated body of a conductive layer and an insulating layer. 3. The superconducting device according to claim 2, which has at least two laminated structures of a conductive layer and an insulating layer. 4. A laminated body forming a structure for preventing discharge has an insulating layer arranged on the electric lead side and a conductive layer arranged on the current lead mounting portion side of the cryogenic container. Item 2. The superconducting device according to Item 2. 5. The superconducting device according to claim 2, wherein the electric potential of the conductive layer of the laminated body forming the structure for preventing discharge is the same as that of the cryogenic container. 6. The superconducting device according to claim 2, wherein the conductive layer of the laminated body constituting the structure for preventing discharge is grounded. 7. The superconducting device according to claim 2, wherein the conductive layer of the laminate forming the structure for preventing discharge has a film thickness distribution. 8. The superconducting device according to claim 2, wherein the insulating layer of the laminate constituting the structure for preventing discharge contains a recovery type insulating material. 9. The superconducting device according to claim 2, wherein a magnetic material is contained in the conductive layer of the laminated body constituting the structure for preventing discharge. 10. The superconducting device according to claim 2, wherein a superconducting material is contained in the conductive layer of the laminate constituting the structure for preventing discharge. 11. The superconducting device according to claim 1, wherein the structure for preventing discharge also has an electromagnetic noise shielding function.