JPH10116721A - Superconducting bulk body magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease a magnetic field applied by each magnetizing coil, by a method wherein both magnetic coils disposed on inner and outer peripheral sides apply a magnetic field to a bulk body. SOLUTION: A superconducting bulk magnet comprises mainly a cylindrical superconducting bulk body 1, an inner peripheral side magnetic coil 3 disposed along an inner periphery of the bulk body 1, and an outer peripheral side magnetic coil 5 disposed along an outer periphery of the bulk body 1. The superconducting bulk body 1 is manufactured with a Y-Ba-Cu-O superconducting material and a columnar bulk body by a melting method, and the columnar bulk body is made cylindrical by opening a hole. The inner peripheral side magnetic coil 3 sounding a copper wire is inserted into the inside of the superconducting bulk body 1, and future the outer peripheral side magnetic coil 5 winding a copper wire to the same direction as the inner peripheral side magnetic coil is disposed outside the superconducting bulk body 1 to constitute a superconducting bulk magnetic. Each coil and the superconducting bulk body are disposed so as to share a central axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnet using a bulk of a high-temperature superconductor.

[0002]

2. Description of the Related Art With the development of high-temperature superconductors, superconducting magnets utilizing these superconductors have been developed. For example, Japanese Unexamined Patent Publication No. Hei 3-289344 proposes a superconducting motor that uses a superconducting coil on the field side to generate a magnetic field when energized to apply a rotating force to an armature.

However, in the above-described apparatus, since a magnetic field is generated by energizing a coil of a superconducting wire, a quench may occur in a coil in a superconducting state. The quench means that a locally generated normal conducting state expands like an avalanche, and the entire superconductor rapidly transitions to the normal conducting state.
When quench occurs, not only does the coil of the superconducting wire not obtain the desired characteristics, but also there is a risk of damage to the device due to the large Joule heat generated in the normal conducting state, so it is necessary to eliminate quench as much as possible. is there. The quench is particularly likely to occur in a wire.

[0004] As a method for preventing the occurrence of quench and stabilizing the superconducting magnet, there are a cooling stabilization method in which the surface of the superconducting wire is sealed with high-purity copper or the like, and an adiabatic stabilization method using a superconducting wire having an ultra-fine multicore. There are various methods, but none of these methods is unavoidable in terms of cost and equipment size.

On the other hand, recently developed R (rare earth) -Ba
The -Cu-O-based superconductor is a second-class superconductor, and can be pinned even if it is a bulk body (solid piece) formed by a melting method, and can achieve a high critical current even at liquid nitrogen temperature. ing. The conventional superconducting bulk body has a drawback that superconductivity is broken by a small disturbance due to a small specific heat. However, the bulk body of the R (rare earth) -Ba-Cu-O-based superconductor has a large specific heat and a high resistance to disturbance. .

Therefore, Japanese Patent Application Laid-Open No. 7-8 / 1995 utilizing this characteristic has been proposed.
There has been proposed a superconducting magnet using a bulk (solid piece) of a superconductor as described in JP 7724 and JP-A-7-111213.

The superconducting motor disclosed in Japanese Patent Application Laid-Open No. 7-87724 uses a superconducting magnet having a structure in which a magnetizing coil is wound around a superconducting bulk body. This superconducting magnet uses a second type superconductor having a high pinning effect, supplies a pulse current to a magnetizing coil, and fixes the generated magnetic flux to a pinning point of the superconducting bulk body. Even if the generation of the magnetic field by the magnetizing coil ends, the superconductor tries to hold the magnetic flux fixed at the pinning point, so that a permanent current is generated inside the superconductor around the pinning point, and the magnetic flux is Will be saved. That is, the superconducting bulk body itself becomes a magnet.

On the other hand, in JP-A-7-111213, a composite magnet having a structure in which a superconducting bulk body is surrounded by a coil and a periphery of which is surrounded by a coil and a structure in which the periphery is surrounded by a ring-shaped superconducting bulk body around a coil is disclosed. magnet,
There has been proposed a composite magnet having a structure in which a superconducting bulk body is surrounded by a coil around a core and a ring-shaped superconducting bulk body is further arranged outside the coil.

In the above composite magnet, the magnetic field strength of the bulk superconducting magnet can be freely changed by the magnetic field applied by the coil. Further, the composite magnet of the present invention can improve the generated magnetic field by preventing the magnetic field from bending at the outer edge when the low-temperature superconducting coil is used. The composite magnet improves the magnetic field generated when a low-temperature superconducting coil is used, and can suppress abrupt changes because the bulk maintains a superconducting state even when the coil is quenched.

[0010]

However, in the superconducting magnets described in the above publications, since the magnetizing coil is disposed only on one of the inside and the outside of the superconducting bulk body, a bias occurs in the magnetic field applied to the bulk. . For example, when the magnetizing coil is arranged only outside the superconducting bulk body, the magnetic field applied outside the bulk is larger than the magnetic field applied inside the bulk. Also, when the magnetizing coil is arranged only inside the superconducting bulk body, the magnetic field applied inside the bulk becomes larger than the magnetic field applied outside the bulk.

Therefore, in the above-described superconducting magnet, if an attempt is made to magnetize the entire superconducting bulk, a magnetic field more than necessary is applied to the superconducting bulk near the magnetizing coil. Generally, the critical current density of a superconductor has a magnetic field dependence, and the critical current density decreases as the magnetic field increases. Therefore, it is not preferable to apply a magnetic field more than necessary to the superconducting bulk body.

When a coil made of a superconducting wire is used as the magnetizing coil of the superconducting magnet, a problem of the critical current density of the superconducting wire itself arises. In other words, the larger the magnetic field generated by the magnetized coil, the larger the magnetic field experienced by the superconducting wire itself and the lower the critical current density.Therefore, it is necessary to apply a large current to the superconducting magnetized coil to generate a large magnetic field. The size of the magnetic coil must be increased. Therefore, from the viewpoint of reducing the size and weight of the magnet, the smaller the magnetic field applied to capture the same magnetic flux in the superconducting bulk, the better.

The present invention relates to a superconducting bulk magnet comprising a superconducting bulk body and a magnetized coil, wherein a magnetic field generated by each magnetized coil is not applied to the superconducting bulk body without applying an excessive magnetic field. It is an object of the present invention to provide a superconducting bulk magnet having a small structure in which a magnetizing coil efficiently magnetizes the superconducting bulk.

[0014]

In order to achieve the above object, the present invention has the following constitution. (1) A superconducting bulk magnet in which the inner peripheral side magnetized coil is centered, the periphery thereof is surrounded by a cylindrical superconducting bulk body, and the outer side of the superconducting bulk body is surrounded by the outer peripheral side magnetized coil. (2) An inner peripheral magnetized coil and an outer peripheral magnetized coil for supplying currents in opposite directions to each other are arranged in a cylindrical superconducting bulk body, and a magnetic field in the same direction is applied to the superconducting bulk body. The superconducting bulk magnet according to the above (1). (3) 123 phase RBaCuO-based material in which 211 phases in which the material of the superconducting bulk body is fine are dispersed (R represents a rare earth element)
Alternatively, the superconducting bulk magnet according to the above (1) or (2), which is an Nd-based oxide superconductor. (4) The superconductor bulk according to the above (1), (2) or (3), wherein the inner peripheral side magnetized coil and the outer peripheral side magnetized coil apply a uniform magnetic field to the superconducting bulk body. magnet.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the shape of a superconducting bulk body is a hollow cylinder type, but more specifically, a hollow cylindrical shape, a rectangular parallelepiped, a hollow elliptical cylindrical shape, and the like are given. Can be The material of the superconducting bulk body is fine 2
A 123-phase RBaCuO-based (R represents a rare earth element) or Nd (neodymium) -based oxide superconductor in which 11 phases are dispersed is preferable. These superconductors are a type 2 superconductor, have a high pinning effect, and can obtain a high critical current density even in a high magnetic field. There is no particular limitation on the composition and manufacturing method of the constituent components of these superconductors, and any type of superconductor having a high pinning effect may be used.
As a production method, for example, an MPMG method in which a pulverizing step is added to the melt-solidification method described in Japanese Patent Publication No. 7-51463 is exemplified. Further, the superconducting bulk body may be directly manufactured into a hollow cylindrical shape, or a superconducting bulk body once manufactured in a solid shape without holes may be formed with a hole by machining or the like by machining. .

The inner peripheral side magnetized coil and the outer peripheral side magnetized coil of the present invention are made of a wire of a normal conductor such as a copper wire or an aluminum wire, or a wire of a superconductor such as a Bi-based silver sheath wire. Coil. The material of the inner peripheral side magnetized coil and the material of the outer peripheral side magnetized coil may be different.

According to the present invention, the inner peripheral side magnetized coil and the outer peripheral side magnetized coil are arranged on the inner and outer circumferences of the above-described superconducting bulk body so as to share the respective central axes.

When currents in opposite directions are applied to the inner and outer magnetized coils, the magnetic flux generated by the inner magnetized coil and the magnetic flux generated by the outer magnetized coil are reduced, as schematically shown in FIG. Are in the same direction in the space between both coils. That is, when currents in opposite directions are applied to the inner and outer magnetized coils, the magnetic field applied to the superconducting bulk body by the inner and outer magnetized coils is in the same direction, and the magnetic field generated by the inner and outer magnetized coils is applied to the superconducting bulk body. Are superimposed and applied.

Therefore, the magnetic field generated by each magnetizing coil may be smaller than that of a conventional superconducting magnet using a superconducting bulk body and a magnetizing coil. For this reason, when a coil made of a normal conducting wire is used as the magnetized coil, the current flowing through the magnetized coil can be reduced, so that heat generation can be reduced. Also,
When a coil made of a superconducting wire is used as the magnetized coil, the magnetic field experienced by each magnetized coil can be reduced, so that a decrease in the critical current density of the superconducting wire can be suppressed. Therefore, the size and weight of the superconducting magnetized coil can be reduced. FIG.
FIG. 2A shows the distribution of the magnetic field applied to the superconducting bulk when the magnetizing coil is arranged only on the outer peripheral side of the cylindrical superconducting bulk having a radius a and an inner diameter b. The magnetic field distribution when the magnetizing coils are arranged on both the inner peripheral side and the outer peripheral side of the cylindrical superconducting bulk body b is shown.

As shown in FIG. 2 (a), when the magnetizing coil is arranged only on one side, the applied magnetic field on the magnetizing coil side increases, and the critical current density decreases. And
If a magnetic field is to be applied to the entire bulk, the bias of the magnetic field applied to the bulk will be quite large.

On the other hand, if the magnetizing coils are arranged on both sides of the cylindrical superconducting bulk body as in the present invention, a magnetic field is applied from the magnetizing coils on both sides, and therefore, as shown in FIG. The maximum value of the magnetic field applied to the bulk can be reduced.

Further, if the magnetic field applied to the superconducting bulk body by the inner peripheral side magnetized coil and the outer peripheral side magnetized coil is made uniform, the density of the magnetic flux captured by the superconducting bulk body becomes uniform, As a result, it is possible to prevent a decrease in critical current density and increase the density of magnetic flux that can be captured.

In order to make the magnetic field applied to the superconducting bulk body uniform, the shapes and the number of turns of the inner and outer magnetized coils and the magnitude of the current to be supplied are adjusted. The degree of uniformity can be improved by optimally combining the shape, the number of turns, and the magnitude of the supplied current.

The superconducting bulk magnet of the present invention is obtained by cooling a cylindrical superconducting bulk in advance to a critical temperature or lower.
A magnetic field is applied to the superconductor by magnetizing coils arranged on the inner and outer peripheral sides. Alternatively, the superconducting bulk body is cooled to a critical temperature or lower while applying a magnetic field to the superconductor by the magnetizing coil.

As a method of cooling the superconducting bulk body, there are immersion cooling and conduction cooling. In the case of immersion cooling, liquid helium, liquid nitrogen, liquid neon, or the like is used as a refrigerant.
In the case of conduction cooling, surround the superconducting bulk body with a heat insulating member,
The heat conduction member is cooled by a refrigerator.

Here, if the intensity of the external magnetic field applied to the bulk is equal to or higher than the lower critical magnetic field and equal to or lower than the upper critical magnetic field,
The bulk becomes a mixed state, and an external magnetic field penetrates locally.
The penetrated magnetic flux is captured at the pinning point of the superconductor, and a vortex permanent current is generated around the pinned point. Even if the magnetic field applied to the bulk is eliminated, the magnetic flux captured at the pinning point is preserved. Accordingly, the superconducting bulk body itself is in a magnetized state.

When a magnetic field is applied by a magnetizing coil after the superconducting bulk body is cooled below the critical temperature, a pulse current may be applied to the magnetizing coil. The pulse current may be repeatedly applied to the magnetized coil.

When a superconducting coil is used as the magnetizing coil, heat generation from the magnetizing coil is suppressed, which is advantageous in maintaining the superconducting state of the superconducting bulk body. However, in this case, the magnetizing coil (superconducting coil) also needs to be cooled below the critical temperature. The cooling method is the same as the cooling method of the superconducting bulk body.

[0029]

Embodiments of the present invention will be described below. In FIG.
1 is a schematic sectional view of a superconducting bulk magnet according to one embodiment of the present invention. The superconducting bulk magnet is mainly composed of a cylindrical superconducting bulk body 1, an inner peripheral side magnetized coil 3 arranged along the inner periphery of the bulk body 1, and an outer peripheral side arranged along the outer periphery of the bulk body 1. It consists of a magnetizing coil 5.

The superconducting bulk body 1 is made of Y-Ba-Cu-O
A superconducting material was produced in a cylindrical bulk body having an outer diameter of 46 mm and a height of 20 mm by a melting method, and a hole having a diameter of 20 mm was formed in the cylindrical bulk body to obtain a cylindrical shape. Inside the superconducting bulk body 1, an inner peripheral side magnetized coil 3 wound with a copper wire having an outer diameter of 20 mm, an inner diameter of 16 mm, and a height of 20 mm is inserted, and an outer diameter of 50 mm and an inner diameter of 46 mm are further outside the superconducting bulk body 1. A superconducting bulk magnet was constructed by arranging an outer peripheral magnetizing coil 5 having a height of 20 mm and a copper wire wound in the same direction as the inner peripheral magnetizing coil. Each coil and the superconducting bulk body were arranged so as to share a central axis. Also, the upper surfaces of the superconducting bulk body and the magnetized coil were made to have the same height.

FIG. 4 shows the magnetic field in the superconducting bulk body when a current of 5000 A / cm ² is applied only to the magnetizing coil 5 on the outer peripheral side of the superconducting magnet. In this case, the minimum value of the magnetic field of the superconducting bulk body portion is 53
In contrast to mT, the maximum value reaches 84 mT on the outer peripheral side.

When a current is applied only to the inner peripheral side magnetized coil 3 to apply a magnetic field of 53 mT or more to the superconducting bulk body 1, 73810 A / c is applied to the inner peripheral side magnetized coil 3.
It is necessary to supply a current of m ² , and the maximum value of the magnetic field applied to the superconducting bulk body 1 reaches 175 mT.

On the other hand, when a current is applied to both the outer magnetizing coil 5 and the inner magnetizing coil 3, the minimum value of the magnetic field is 53
mT and the most uniform magnetic field applied to the bulk superconductor 1 is 679
5A / cm ² , 330 on the outer side magnetized coil 5
This was when a current of 0 A / cm ² was passed. The magnetic field of the superconducting bulk body at this time is shown by a dotted line in FIG. As shown in FIG. 4, while a magnetic field of 53 mT or more is applied to the superconducting bulk body 1, the maximum value of the magnetic field is suppressed to 60 mT.

Then, after applying the magnetic field to the superconducting bulk body 1 and cooling the superconducting bulk body 1 to a temperature below the critical temperature, the currents of the inner and outer magnetized coils 3 and 5 are simultaneously cut off. The superconducting bulk body 1 became a magnet while retaining the magnetic flux.

[0035]

According to the superconducting magnet of the present invention,
Since both magnetized coils arranged on the inner and outer peripheral sides apply a magnetic field to the superconducting bulk body, the magnetic field applied by each magnetized coil can be small. Therefore, when a normal-conducting magnetized coil is used, the amount of generated heat can be reduced, so that the temperature of the superconducting bulk body does not easily rise. When a superconducting magnetized coil is used, deterioration of the critical current density due to a magnetic field can be suppressed. Further, since the magnetic field applied to the superconducting bulk body can be made substantially uniform, it is also advantageous in capturing magnetic flux in the superconducting bulk body.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a magnetic field generated when currents in opposite directions are applied to both inner and outer magnetized coils.

FIG. 2A is a schematic diagram of a magnetic field distribution when a magnetizing coil is arranged only on the outer peripheral side. (B) Schematic diagram of the magnetic field distribution when magnetizing coils are arranged on the inner peripheral side and the outer peripheral side.

FIG. 3 is a schematic sectional view of one embodiment of the superconducting magnet of the present invention.

FIG. 4 is a schematic diagram of a magnetic field distribution in a bulk portion of a superconductor in one embodiment of the superconducting magnet of the present invention.

[Explanation of symbols]

 Reference Signs List 1 superconducting bulk body 3 inner peripheral side magnetized coil 5 outer peripheral side magnetized coil

Claims (4)

[Claims] 1. A superconducting bulk magnet in which an inner peripheral side magnetized coil is centered, a circumference thereof is surrounded by a cylindrical superconducting bulk body, and an outer side of the superconducting bulk body is surrounded by an outer peripheral side magnetized coil. 2. An inner peripheral magnetized coil and an outer peripheral magnetized coil for supplying currents in opposite directions to each other in a cylindrical superconducting bulk body, and a magnetic field in the same direction is applied to the superconducting bulk body. The superconducting bulk magnet according to claim 1, wherein: 3. The superconducting bulk material is a 123-phase RBaCuO-based (R is a rare-earth element) or Nd-based oxide superconductor in which 211 fine phases are dispersed. 2. The superconducting bulk magnet according to 2. 4. The superconducting bulk magnet according to claim 1, wherein the inner peripheral side magnetized coil and the outer peripheral side magnetized coil apply a uniform magnetic field to the superconducting bulk body.