JP7122007B2 - Superconducting device and magnet device - Google Patents

Description

The present invention relates to a superconducting device provided in a magnet device and a magnet device.

2. Description of the Related Art A magnet device having a magnet unit that generates a strong magnetic field is used as a magnet device included in, for example, a magnetic resonance imaging (MRI) device. U.S. Pat. No. 7,944,208 discloses a magnetic resonance imaging system in which opposite magnetic poles of a main magnet are arranged along a horizontal axis and detect the magnetic field generated by the main magnet. Techniques are disclosed for defining an open magnetic resonance imaging region configured to.

In a magnet device that generates such a strong magnetic field, in order to prevent or suppress leakage of the strong magnetic field to the outside of the magnet part and to reduce the strength of the magnetic field around the magnet part, along the annular path A magnetic material with high magnetic permeability such as iron may be provided as a magnetic circuit member so that a magnetic circuit is formed from one magnetic pole of the magnet portion to the other magnetic pole of the magnet portion via the magnetic material. .

Japanese Patent Laying-Open No. 7-178071 (Patent Document 2) discloses a magnet assembly for an MRI apparatus, which includes a lower base yoke having a lower permanent magnet attached to its upper surface and a column yoke erected from the edge of the lower base yoke. and an upper base yoke supported by the column yoke and having an upper permanent magnet attached to the lower surface facing the lower permanent magnet.

On the other hand, in magnet devices other than MRI devices, for example, a superconducting bulk body is used as a magnet portion that generates a strong magnetic field. Non-Patent Document 1 and Non-Patent Document 2 disclose a technique in which a superconducting bulk body made of magnesium diboride (MgB ₂ ) is used as a permanent magnet.

U.S. Pat. No. 7,944,208 JP-A-7-178071

A. Yamamoto et al., “Permanent magnet with MgB2 bulk superconductor”, Applied Physics Letters 105 (2014) 032601 S. Sugino et al., “Enhanced trapped field in MgB2 bulk magnets by tuning grain boundary pinning through milling”, Superconductor Science and Technology 28 (2015) 055016

When a magnetic material with high magnetic permeability such as iron is provided as a magnetic circuit member, the strength of the magnetic field outside the magnetic material can be reduced by confining the magnetic field in the magnetic material with high magnetic permeability.

However, since the magnetic permeability of a magnetic material such as iron decreases as the strength of the applied magnetic field increases, when the strength of the magnetic field inside the magnetic material saturates as the strength of the applied magnetic field increases, If the strength of the magnetic field increases further, the strength of the magnetic field leaking out of the magnetic body increases because the magnetic field cannot be confined within the magnetic body.

In order to confine the applied magnetic field inside the magnetic body even when the intensity of the magnetic field is high, it is necessary to increase the cross-sectional area of the magnetic circuit, that is, the cross-sectional area perpendicular to the circular path of the magnetic body. Therefore, when a magnetic material such as iron is used as a magnetic circuit member, it is necessary to increase the volume of the magnetic circuit member, making it difficult to reduce the size or weight of the magnetic circuit.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art as described above. An object of the present invention is to provide a magnet device in which a magnetic circuit can be easily reduced in size or weight.

A brief outline of typical inventions disclosed in the present application is as follows.

A superconducting device as one aspect of the present invention is provided in a magnet device having a magnet unit that generates a magnetic field. The superconducting device has a first superconducting bulk body provided outside the magnet unit, the first superconducting bulk body capturing a magnetic field in a superconducting state, and a first superconducting bulk body capturing the magnetic field. A magnetic circuit is formed by the conductive bulk body and the magnet portion.

Further, as another aspect, the magnet part has a first magnetic pole having a first polarity and a second magnetic pole having a second polarity opposite to the first polarity, and the first magnetic pole and the first superconducting The bulk body and the second magnetic pole are arranged along an annular path about the first axis in the order of the first magnetic pole, the first superconducting bulk body, the second magnetic pole, and along the annular path from the first magnetic pole to the second magnetic pole. A magnetic circuit may be formed through one superconducting bulk body and back to the second pole.

In another aspect, the magnet section has a first magnet and a second magnet spaced apart from each other along an annular path, and the first magnet has a first magnetic pole and a second polarity. a third magnetic pole having a first polarity; and the second magnet may have a fourth magnetic pole having a first polarity and a second magnetic pole. The first magnetic pole, the first superconducting bulk body, the second magnetic pole, the fourth magnetic pole and the third magnetic pole are arranged along an annular path along the first magnetic pole, the first superconducting bulk body, the second magnetic pole, the fourth magnetic pole, the third magnetic pole. The three magnetic poles may be arranged in order.

Further, as another aspect, the superconducting device has a first superconducting bulk body group including a plurality of first superconducting bulk bodies arranged along a circular path, a first magnetic pole, a first superconducting bulk body The conducting bulk body group and the second magnetic pole are arranged in the order of the first magnetic pole, the first superconducting bulk body group and the second magnetic pole along the annular path, and along the annular path from the first magnetic pole to the first superconducting A magnetic circuit may be formed through the bulk bodies and back to the second pole. Each of the plurality of first superconducting bulk bodies contained in the first superconducting bulk body group captures a magnetic field in a superconducting state, so that the magnetic flux emitted from the first magnetic pole is , arranged along an annular path to sequentially pass through the plurality of first superconducting bulk bodies and back to the second pole.

Moreover, as another aspect, the plurality of first superconducting bulk bodies may be arranged with a space therebetween.

Also, as another aspect, the first superconducting bulk body group may be adjacent to the first magnetic pole and not adjacent to the second magnetic pole along the annular path. Among the plurality of first superconducting bulk bodies, the first superconducting bulk body arranged on the side closest to the first magnetic pole along the circular path has an outer circumference length of a cross section perpendicular to the circular path, It may be longer than the outer circumference length of the cross section perpendicular to the annular path of the first superconducting bulk body arranged on the opposite side of the side closest to the first magnetic pole along the annular path among the one superconducting bulk bodies. .

Further, as another aspect, the outer circumference length of the cross section of each of the plurality of first superconducting bulk bodies perpendicular to the annular path is the closest to the first magnetic pole along the annular path from the side closest to the first magnetic pole. The order of arrangement of the plurality of first superconducting bulk bodies may decrease from the near side to the opposite side.

Further, as another aspect, the superconducting device has a second superconducting bulk body group including a plurality of second superconducting bulk bodies arranged along a circular path, and a plurality of second superconducting bulk bodies Each of the bodies captures a magnetic field in a superconducting state, the first magnetic pole, the first superconducting bulk group, the second superconducting bulk group and the second magnetic pole along an annular path, the first magnetic pole, the second A first superconducting bulk body group, a second superconducting bulk body group, and a second magnetic pole are arranged in this order, and the first superconducting bulk body group and the second superconducting bulk body group are sequentially arranged from the first magnetic pole along an annular path. A magnetic circuit may be formed to return to the second pole. The plurality of first superconducting bulk bodies contained in the first superconducting bulk body group and the plurality of second superconducting bulk bodies contained in the second superconducting bulk body group are the plurality of first superconducting bulk bodies and Each of the plurality of second superconducting bulk bodies captures a magnetic field in a superconducting state, so that the magnetic flux emitted from the first magnetic pole sequentially travels through the plurality of first superconducting bulk bodies and the plurality of second superconducting bulk bodies. It may be arranged along a circular path through and back to the second pole. The second superconducting bulk body group is adjacent to the second magnetic pole along the annular path, and among the plurality of second superconducting bulk bodies, the second superconducting bulk body group is arranged on the side closest to the second magnetic pole along the annular path. The outer circumference length of the cross section of the two superconducting bulk bodies perpendicular to the annular path is the second superconducting bulk body arranged on the side opposite to the side closest to the second magnetic pole along the annular path among the plurality of second superconducting bulk bodies. 2 It may be longer than the perimeter length of the cross-section perpendicular to the annular path of the superconducting bulk body.

Further, as another aspect, the outer circumference length of the cross section of each of the plurality of second superconducting bulk bodies perpendicular to the annular path is the closest to the second magnetic pole along the annular path from the side closest to the second magnetic pole. The plurality of second superconducting bulk bodies may decrease in order of arrangement from the near side to the opposite side.

Further, as another aspect, each of the plurality of first superconducting bulk bodies includes a cylindrical first cylindrical portion centered on an axis along the annular path, and the plurality of first superconducting bulk bodies are: When each of the plurality of first superconducting bulk bodies captures the magnetic field along the axis in the superconducting state, the magnetic flux emitted from the first magnetic pole is included in each of the plurality of first superconducting bulk bodies. They may be arranged along an annular path to sequentially pass through the first barrel and back to the second pole.

Further, as another aspect, each of the plurality of first superconducting bulk bodies includes an extension extending along the annular path, and the plurality of first superconducting bulk bodies includes a plurality of first superconducting bulk bodies. By capturing the magnetic field along the annular path in each of the bulk bodies in the superconducting state, the magnetic flux emitted from the first magnetic pole sequentially travels through the plurality of extensions included in each of the plurality of first superconducting bulk bodies. It may be arranged along a circular path through and back to the second pole.

Further, as another aspect, the superconducting device has a third superconducting bulk body including a cylindrical second cylindrical part surrounding the magnet part, and the third superconducting bulk body is in a superconducting state and magnetic field A magnetic circuit may be formed by a plurality of first superconducting bulk bodies each capturing a magnetic field, a third superconducting bulk body capturing a magnetic field, and the magnet section.

Moreover, as another aspect, the first superconducting bulk body may be made of iron pnictide or magnesium diboride.

Further, as another aspect, the superconducting device has a cooling part that cools the first superconducting bulk body, and the first superconducting bulk body is cooled by the cooling part, whereby the first superconducting bulk body The body may become superconducting. The first superconducting bulk body is made of a second-class superconductor, and the first superconducting bulk body, in a superconducting state, is capable of pinning magnetic flux in a magnetic field exceeding the lower critical magnetic field and equal to or lower than the upper critical magnetic field. A magnetic circuit, which is a closed circuit through which magnetic flux passes, is formed by the first superconducting bulk body and the magnet portion that captures the magnetic field, and the magnetic flux emitted from one magnetic pole of the magnet portion is the first superconducting It may return through the bulk body to the other pole of the magnet portion.

A superconducting device as one aspect of the present invention is provided in a magnet device having a magnet unit that generates a magnetic field. The superconducting device has a first superconducting bulk body including a tubular first cylinder surrounding a magnet part, the first superconducting bulk body capturing a magnetic field in a superconducting state and capturing the magnetic field. A magnetic circuit is formed by the first superconducting bulk body and the magnet part.

Further, as another aspect, the superconducting device has a second superconducting bulk body provided outside the magnet unit, and the second superconducting bulk body captures a magnetic field in a superconducting state, A magnetic circuit may be formed by the second superconducting bulk body capturing the magnetic field, the first superconducting bulk body capturing the magnetic field, and the magnet part.

Also, as another aspect, the magnet section may have a first magnetic pole having a first polarity and a second magnetic pole having a second polarity opposite to the first polarity. The first magnetic pole, the second superconducting bulk body and the second magnetic pole are arranged along an annular path about the first axis in the order of the first magnetic pole, the second superconducting bulk body and the second magnetic pole, along the annular path. A magnetic circuit may be formed along the first magnetic pole through the second superconducting bulk body and back to the second magnetic pole.

Further, as another aspect, the superconducting device has a first superconducting bulk body group including a plurality of second superconducting bulk bodies arranged along a circular path, a first magnetic pole, a first superconducting bulk body The conducting bulk body group and the second magnetic pole are arranged in the order of the first magnetic pole, the first superconducting bulk body group and the second magnetic pole along the annular path, and along the annular path from the first magnetic pole to the first superconducting A magnetic circuit may be formed through the bulk bodies and back to the second pole. The plurality of second superconducting bulk bodies included in the first superconducting bulk body group captures a magnetic field in each of the plurality of second superconducting bulk bodies in a superconducting state, so that the magnetic flux emitted from the first magnetic pole is , arranged along an annular path through the plurality of second superconducting bulk bodies in sequence and back to the second pole.

Moreover, as another aspect, the first superconducting bulk body may be made of iron pnictide or magnesium diboride.

Further, as another aspect, the superconducting device has a cooling part that cools the first superconducting bulk body, and the first superconducting bulk body is cooled by the cooling part, whereby the first superconducting bulk body The body may become superconducting. The first superconducting bulk body is made of a second-class superconductor, and the first superconducting bulk body, in a superconducting state, is capable of pinning magnetic flux in a magnetic field exceeding the lower critical magnetic field and equal to or lower than the upper critical magnetic field. A magnetic circuit, which is a closed circuit through which magnetic flux passes, is formed by the first superconducting bulk body and the magnet portion that captures the magnetic field, and the magnetic flux emitted from one magnetic pole of the magnet portion flows into the first cylinder It may return through the interior to the other pole of the magnet portion.

A magnet device as one aspect of the present invention includes a magnet unit that generates a magnetic field, and a superconducting device provided outside the magnet unit. The superconducting device has a superconducting bulk body provided outside the magnet section, the superconducting bulk body capturing a magnetic field in a superconducting state, and the superconducting bulk body capturing the magnetic field and the magnet section. A magnetic circuit is formed by

A magnet device as one aspect of the present invention includes a magnet unit that generates a magnetic field and a superconducting device that surrounds the magnet unit. A superconducting device has a superconducting bulk body including a cylindrical tubular portion surrounding a magnet portion, the superconducting bulk body capturing a magnetic field in a superconducting state, and a superconducting bulk body capturing the magnetic field. A magnetic circuit is formed by the magnet part,

By applying one aspect of the present invention, it is possible to reduce the volume of a magnetic circuit member in a magnet device including a magnet portion that generates a strong magnetic field, and easily reduce the size or weight of the magnetic circuit. can be done.

1 is a plan view schematically showing a magnet device provided with a superconducting device according to an embodiment; FIG. 1 is a perspective view schematically showing a magnet device provided with a superconducting device according to an embodiment; FIG. 1 is a perspective view schematically showing part of a superconducting device according to an embodiment; FIG. 1 is a cross-sectional view schematically showing part of a superconducting device according to an embodiment; FIG. 3 is a perspective view schematically showing another portion of the superconducting device of the embodiment; FIG. 3 is a cross-sectional view schematically showing another portion of the superconducting device of the embodiment; FIG. It is a sectional view showing typically the 1st modification of the superconducting device of an embodiment. It is a sectional view showing typically the 2nd modification of the superconducting device of an embodiment. It is a top view which shows typically the 1st modification of the magnet apparatus of embodiment. It is a top view which shows typically the 2nd modification of the magnet apparatus of embodiment. It is a top view which shows typically the 3rd modification of the magnet apparatus of embodiment. It is a top view which shows typically the 4th modification of the magnet apparatus of embodiment. It is a top view which shows typically the 5th modification of the magnet apparatus of embodiment. 1 is a block diagram showing an MRI apparatus having a magnet device equipped with a superconducting device according to an embodiment; FIG. 3 is a flowchart showing some steps of a method for manufacturing a superconducting bulk body of the superconducting device of Example 1. FIG. 4 is a graph showing external magnetic field dependence of local magnetic flux density measured by five Hall elements arranged in the superconducting device of Example 1. FIG. 5 is a graph showing time dependence of local magnetic flux density measured by five Hall elements arranged in the superconducting device of Example 1. FIG.

Each embodiment of the present invention will be described below with reference to the drawings.

It should be noted that the disclosure is merely an example, and those skilled in the art will naturally include within the scope of the present invention any appropriate modifications that can be easily conceived while maintaining the gist of the invention. In addition, in order to make the description clearer, the drawings may schematically show the width, thickness, shape, etc. of each part compared to the embodiment, but this is only an example, and the interpretation of the present invention is not limited. It is not limited.

In addition, in this specification and each figure, the same reference numerals may be given to the same elements as those described above with respect to the previous figures, and detailed description thereof may be omitted as appropriate.

Furthermore, in the drawings used in the embodiments, hatching for distinguishing structures may be omitted depending on the drawing.

In the following embodiments, when a range is indicated as A to B, it indicates A or more and B or less, unless otherwise specified.

(Embodiment)
<Magnet device and superconducting device>
First, a magnet device and a superconducting device having a superconducting device according to an embodiment of the present invention will be described.

FIG. 1 is a plan view schematically showing a magnet device provided with a superconducting device according to an embodiment. FIG. 2 is a perspective view schematically showing a magnet device provided with the superconducting device of the embodiment. In FIG. 2, for the sake of easy understanding, the illustration of the magnet device including the superconducting device other than the superconducting bulk portion is omitted. Further, the arrangement shown in FIG. 1 is not necessarily limited to the arrangement when viewed from above, and may be the arrangement when viewed from the front (the same applies to FIGS. 9 to 13 described later).

As shown in FIGS. 1 and 2, a magnet device 2 including a superconducting device 1 of this embodiment includes a magnet unit 3 that generates a magnetic field. That is, the superconducting device 1 of this embodiment is provided in the magnet device 2 having the magnet portion 3 and is provided outside the magnet portion 3 .

The superconducting device 1 of this embodiment has a superconducting bulk body, that is, a superconducting bulk portion 4, which is provided outside the magnet portion 3 and made of a second-class superconductor. In the superconducting state, the superconducting bulk portion 4 captures a magnetic field that exceeds the lower critical magnetic field and is equal to or lower than the upper critical magnetic field by pinning the magnetic flux, and the superconducting bulk portion 4 and the magnet portion capture the magnetic field. 3 form a magnetic circuit 5 which is a closed circuit through which magnetic flux passes, and the magnetic flux emitted from one magnetic pole of the magnet portion 3 returns to the other magnetic pole of the magnet portion 3 through the superconducting bulk portion 4 .

In the specification of the present application, a magnetic circuit means a passage through which magnetic flux, ie, lines of magnetic force pass. Alternatively, as used herein, a magnetic circuit means a medium that carries a high density magnetic flux, or a medium that captures and transmits or transmits high density magnetic flux so that it does not leak in directions in which it is not desired to leak. It means a passage through which it propagates. Alternatively, in this specification, a magnetic circuit means a closed circuit through which a magnetic flux passes, confining the magnetic field or magnetic flux at a desired location. At this time, although it depends on the magnetic permeability inside the magnetic circuit, in and around the magnetic circuit, most of the magnetic flux is confined inside the magnetic circuit and circulates along the longitudinal direction of the magnetic circuit. It is partly or entirely, and only partly or none of the total magnetic flux crosses the longitudinal direction of the magnetic circuit.

Specifically, the magnet portion 3 has an N pole PL1 as a first magnetic pole having a first polarity and an S pole PL2 as a second magnetic pole having a second polarity opposite to the first polarity. The N-pole PL1, the superconducting bulk portion 4 and the S-pole PL2 are arranged along an annular path 7 around an axis 6 in the order N-pole PL1, superconducting bulk portion 4 and S-pole PL2.

1 and 2, the magnet unit 3 has two magnets MG1 and MG2 spaced apart from each other along the annular path 7, the magnet MG1 being connected to the north pole PL1. , and an S pole PL3 as a third magnetic pole having a second polarity, and the magnet MG2 has an N pole PL4 as a fourth magnetic pole having a first polarity and an S pole PL2. N-pole PL1, superconducting bulk 4, S-pole PL2, N-pole PL4 and S-pole PL3 are connected along annular path 7 to N-pole PL1, superconducting bulk 4, S-pole PL2, N-pole PL4, S-pole They are arranged in the order of PL3.

A so-called Helmholtz coil can be used as the magnet unit 3 having the magnets MG1 and MG2. Between the magnets MG1 and MG2, the south pole PL3 of the magnet MG1 faces the north pole PL4 of the magnet MG2. As a result, an object to be processed (an object such as a human body in the case of an MRI apparatus) to be processed by applying a magnetic field can be easily taken in and out of the space 8 between the magnets MG1 and MG2. A ferromagnetic permanent magnet such as a neodymium magnet made of a neodymium-iron-boron (boron) alloy can also be used as the magnet portion 3 .

The polarities of all of the N pole PL1, S pole PL2, S pole PL3, and N pole PL4 may be collectively replaced with opposite polarities.

2. Description of the Related Art As described later with reference to FIG. 14, a magnet device having a magnet unit that generates a strong magnetic field is used as a magnet device included in, for example, a magnetic resonance imaging (MRI) device. In such a magnet device, in order to prevent or suppress leakage of a strong magnetic field to the outside of the magnet portion and to reduce the strength of the magnetic field around the magnet portion, one side of the magnet portion is provided along the annular path. A magnetic material having a high magnetic permeability such as iron may be provided as a magnetic circuit member so that a magnetic circuit is formed from one magnetic pole to the other magnetic pole of the magnet portion through the magnetic material. In this case, the strength of the magnetic field outside the magnetic body can be reduced by confining the magnetic field in the magnetic body with high magnetic permeability. At this time, a magnetic circuit is formed on the outside of the magnet part along a circular path, which goes out from one magnetic pole (for example, the N pole) of the magnet part, passes through the magnetic body, and returns to the other magnetic pole (for example, the S pole). be done.

However, since the magnetic permeability of a magnetic material such as iron decreases as the strength of the applied magnetic field increases, the strength of the magnetic field inside the magnetic material gradually decreases as the strength of the applied magnetic field increases. Saturate. When the strength of the magnetic field inside the magnetic body saturates and the strength of the magnetic field increases further, the magnetic field cannot be confined only inside the magnetic body. strength increases.

In order to confine the applied magnetic field inside the magnetic body even when the intensity of the magnetic field is high, it is necessary to increase the cross-sectional area of the magnetic circuit, that is, the cross-sectional area perpendicular to the circular path of the magnetic body. Therefore, when a magnetic material such as iron is used as a magnetic circuit member, it is necessary to increase the volume of the magnetic circuit member, making it difficult to reduce the size or weight of the magnetic circuit.

On the other hand, in the present embodiment, the magnetic circuit 5 is formed by the superconducting bulk body capturing the magnetic field in the superconducting state, that is, the superconducting bulk portion 4 and the magnet portion 3 . In the case of a superconducting bulk body, if the critical current density in the superconducting state is large enough, a magnetic field stronger than the saturation magnetic field, which is the magnetic field at which the magnetic body saturates, can be captured. In other words, a magnetic field stronger than the saturation magnetic field of the magnetic material can be confined inside the superconducting bulk material. Therefore, when confining a strong magnetic field inside a superconducting bulk body, the cross-sectional area of the magnetic circuit, that is, the cross-sectional area perpendicular to the circular path of the superconducting bulk body, must be made smaller than when confining it inside a magnetic body. can be done. Therefore, when a superconducting bulk body is used as a magnetic circuit member, the volume of the magnetic circuit member can be reduced, and the magnetic circuit can be easily reduced in size or weight.

Also, consider the case where the magnet device 2 including the magnet portion 3 that generates a strong magnetic field is used as the magnet device of the MRI apparatus, and the magnet portion 3 includes the magnet MG1 and the magnet MG2. In such a case, since the space 8 between the magnets MG1 and MG2 is open, there is space between the magnets MG1 and MG2, such as a human being, as a subject to be examined by picking up a tomographic image. Even if the patient enters for the examination, the examination can be performed without feeling a sense of blockage.

As a method of capturing a strong magnetic field in the superconducting bulk portion 4 to form a magnetic circuit, the superconducting bulk portion 4 is cooled from a normal conducting state to a superconducting state while applying a strong magnetic field to the superconducting bulk portion 4. A method of trapping the magnetic field in the superconducting bulk portion 4 by medium cooling is conceivable. Specifically, a magnet portion different from the magnet portion 3 is provided for applying a magnetic field in the vicinity of the superconducting bulk portion 4, and the superconducting bulk portion 4 is cooled in the magnetic field using the magnet portion provided for applying the magnetic field. Thus, a magnetic circuit can be formed by trapping a strong magnetic field in the superconducting bulk portion 4 . Alternatively, the superconducting bulk portion 4 cooled in the magnetic field outside the magnet device 2 to trap the strong magnetic field can be moved into the magnet device 2 while trapping the strong magnetic field to form a magnetic circuit. . Alternatively, the superconducting bulk portion 4 is allowed to capture the strong magnetic field by cooling the superconducting bulk portion 4 in a state in which the magnet portion 3 generates a magnetic field stronger than the magnetic field generated when the magnet portion 3 is normally used. A magnetic circuit can be formed.

The superconducting bulk portion 4 is made of a so-called second-class superconductor having a lower critical magnetic field _Hc1 and an upper critical magnetic field _Hc2 . When the external magnetic field is lower than the lower critical magnetic field H _c1 , the second-class superconductor exhibits the Meissner effect, becomes a state in which magnetic flux is excluded from the second-class superconductor, and exhibits so-called perfect diamagnetism. In addition, when the external magnetic field exceeds the lower critical magnetic field _Hc1 and is equal to or lower than the upper critical magnetic field _Hc2 , the magnetic flux penetrates into the second-class superconductor. A superconducting current can flow in a state of zero electrical resistance by pinning the magnetic flux by the conductive phase, etc. By pinning the magnetic flux in this way, a superconducting bulk part made of a second-class superconductor 4 can capture strong magnetic fields. For example, at a temperature of about 10 K, the lower critical magnetic field H _c1 of iron pnictide is about 0.01-0.03 T (Tesla), and the upper critical magnetic field H _c2 of iron pnictide is greater than 50 T. Further, for example, at a temperature of about 10 K, the lower critical magnetic field H _c1 of magnesium diboride (MgB ₂ ) is about 0.01 to 0.03 T, and the upper critical magnetic field H _c2 of MgB ₂ is about 30 T. .

In Example 1 described later, the superconducting bulk body made of MgB ₂ captures a magnetic field of 2T, and in Example 2 described later, the superconducting bulk body made of iron pnictide also captures the magnetic field. Therefore, the superconducting bulk portion 4 of the present embodiment made of, for example, MgB ₂ and iron pnictide is a second-class superconductor, and the lower critical magnetic field H _c1 is generated by pinning the magnetic flux instead of the Meissner effect. It can be seen that it captures a strong magnetic field that exceeds the upper critical magnetic field _Hc2 and is less than or equal to the upper critical magnetic field Hc2.

Preferably, at least a portion of the superconducting bulk portion 4 may be divided into a plurality of members (a plurality of superconducting bulk bodies) arranged along the annular path 7 . Even in such a case, substantially the same effect as in the case where the superconducting bulk portion 4 is integrally formed can be obtained, so the magnetic circuit 5 is formed by the magnet portion 3 and the superconducting bulk portion 4. , the superconducting bulk portion 4 can be easily formed or manufactured. In the following, the case where the superconducting bulk portion 4 is entirely divided into a plurality of members arranged along the annular path 7 will be described as an example.

As shown in FIGS. 1 and 2, the superconducting bulk portion 4 preferably has a plurality of member groups as superconducting bulk body groups. That is, the superconducting bulk portion 4 has member groups SG1, SG2 and SG3. The member group SG1 includes a plurality of members SB1 as superconducting bulk bodies arranged along the annular path 7 . The member group SG2 includes a plurality of members SB2 as superconducting bulk bodies arranged along the annular path 7 . The member group SG3 includes a plurality of members SB3 as superconducting bulk bodies arranged along the annular path 7 . Each of the plurality of members SB1, the plurality of members SB2 and the plurality of members SB3 captures the magnetic field in a superconducting state.

The N pole PL1, the member group SG2, the member group SG1, the member group SG3, the S pole PL2, the N pole PL4, and the S pole PL3 are arranged along the annular path 7 to form the N pole PL1, the member group SG2, the member group SG1, and the member group SG3, S pole PL2, N pole PL4, and S pole PL3 are arranged in this order. A magnetic circuit 5 is formed along the circular path 7 from the N pole PL1 to the S pole PL2 through the member group SG2, the member group SG1, and the member group SG3 in order.

In such a case, the plurality of members SB2 included in the member group SG2, the plurality of members SB1 included in the member group SG1, and the plurality of members SB3 included in the member group SG3 are the plurality of members SB2 and the plurality of members SB1. And each of the plurality of members SB3 captures the magnetic field in a superconducting state, so that the magnetic flux 9 emitted from the N pole PL1 sequentially passes through the plurality of members SB2, the plurality of members SB1 and the plurality of members SB3, and reaches the S pole PL2. are arranged along the circular path 7 so as to return to the .

Note that the superconducting bulk portion 4 may not have a plurality of member groups, and may have only one of the member groups SG1, SG2, and SG3.

FIG. 3 is a perspective view schematically showing part of the superconducting device of the embodiment. FIG. 4 is a cross-sectional view schematically showing part of the superconducting device of the embodiment. 3 and 4 illustrate and explain the member group SG1 as the superconducting device of the embodiment. 3 and 4 illustrate an example in which the spacer SP1 is arranged between two members SB1 adjacent to each other along the axis 11. As shown in FIG.

As shown in FIGS. 3 and 4, each of the plurality of members SB1 includes a tubular portion CP1 centered on an axis 11 along the annular path 7. As shown in FIGS. Each of the plurality of members SB1 captures a magnetic field along the axis 11, so that the magnetic flux 9 emitted from the N pole PL1 (see FIG. 1) is included in each of the plurality of members SB1. are arranged along the annular path 7 so as to return to the S pole PL2 (see FIG. 1) through the cylindrical portion CP1 of the . The cylindrical part CP1 that has captured the magnetic field functions as a magnetized tube, that is, a magnetic tube.

When the cylindrical portion CP1 has a cylindrical shape, as shown in FIG. 4, the outer diameter centered on the axis 11 of the cylindrical portion CP1 is defined as the outer diameter DM1, the inner diameter of the cylindrical portion CP1 is defined as the inner diameter DM2, and the axial line of the cylindrical portion CP1. Let the length along 11 be length HT1. Note that FIG. 3 shows an example in which the tubular portion CP1 is cylindrical, but the tubular portion CP1 may have any shape as long as it has a tubular shape, such as an elliptical tubular shape, or a square tubular shape such as a square tubular shape.

As shown in FIG. 3, the outer perimeter lengths LN1 of the sections perpendicular to the annular path 7 of each of the plurality of members SB1 may be equal to each other. In such a case, the outer diameter of each of the plurality of members SB1 can be reduced, the volume of the magnetic circuit member can be reduced, and the magnetic circuit can be easily reduced in size or weight.

Also, the plurality of members SB1 may be arranged at intervals. In the superconducting device of Example 1, which will be described later, a strong magnetic field along the axis 11 can be captured even when a plurality of members SB1 are arranged at intervals as described with reference to FIG. . Also by this, the volume of the magnetic circuit member can be reduced, and the magnetic circuit can be further reduced in size or weight. As shown in FIG. 4, a gap GP1 is defined as a gap GP1 between two cylindrical portions CP1 of two members SB1 adjacent to each other along the axis 11. As shown in FIG.

As shown in FIG. 4, between two members SB1 adjacent to each other along the axis 11, a spacer SP1 may be arranged. As a result, when each of the plurality of members SB1 captures the magnetic field, it is possible to prevent two members SB1 adjacent to each other along the axis 11 from being attracted by the magnetic attraction force. Incidentally, as shown in FIG. 4, the length of the spacer SP1 along the axis 11 is equal to the gap GP1.

FIG. 5 is a perspective view schematically showing another portion of the superconducting device of the embodiment. FIG. 6 is a cross-sectional view schematically showing another portion of the superconducting device of the embodiment. 5 and 6 illustrate the member groups SG2 and SG3 as other parts of the superconducting device of the embodiment. First, the case of illustrating the member group SG2 will be described. 5 and 6 show an example in which two members SB2 adjacent to each other along the axis 11 are arranged with a space therebetween, but no spacer is arranged between the two members SB2 adjacent to each other. Illustrated.

As shown in FIGS. 5 and 6, each of the plurality of members SB2 also includes a tubular portion CP2 centered on the axis 11 along the annular path 7, similarly to each of the plurality of members SB1. Each of the plurality of members SB2 captures a magnetic field along the axis 11 so that the magnetic flux 9 emitted from the N pole PL1 (see FIG. 1) is contained in each of the plurality of members SB2. They are arranged along the annular path 7 so as to sequentially pass through the plurality of cylindrical portions CP2 and return to the S pole PL2 (see FIG. 1).

As shown in FIGS. 1, 2, 5 and 6, the member group SG2 is adjacent to the N pole PL1 and not adjacent to the S pole PL2 along the annular path 7. FIG. In addition, among the plurality of members SB2, the member SB2 arranged on the side closest to the N pole PL1 along the annular path 7 has an outer peripheral length LN2 (see FIG. 5) of a cross section perpendicular to the annular path 7. is longer than the outer peripheral length LN2 of the cross section perpendicular to the annular path 7 of the member SB2 arranged on the side opposite to the side closest to the N pole PL1 along the annular path 7 among the members SB2.

As a result, on the side of the member group SG2 closest to the N pole PL1, the cross section perpendicular to the circular path 7 of the member SB2 is matched to the outer circumference length of the cross section perpendicular to the circular path 7 of the N pole PL1 of the magnet portion 3. It is possible to lengthen the outer peripheral length LN2 of the member SB2, that is, to thicken the member SB2. Therefore, the magnetic field formed by the magnetic flux 9 emitted from the N pole PL1 of the magnet portion 3 can be confined in the superconducting bulk portion 4 efficiently. On the other hand, on the opposite side of the member group SG2 from the side closest to the N pole PL1, the outer circumference length LN2 of the cross section perpendicular to the annular path 7 of the member SB2 can be shortened, that is, the member SB2 can be thinned. Therefore, the volume of the magnetic circuit member can be reduced, and the magnetic circuit can be reduced in size or weight.

When the outer circumference length LN2 (see FIG. 5) of the member SB2 in the cross section perpendicular to the annular path 7 varies uniformly along the annular path 7, the central portion of the member SB2 along the annular path 7 The outer circumference length of the section perpendicular to the annular path 7 of the portion located at is defined as the outer circumference length LN2.

Preferably, the outer circumference length LN2 of each of the plurality of members SB2 in the cross section perpendicular to the annular path 7 extends along the annular path 7 from the side closest to the N pole PL1 to the side closest to the N pole PL1 and the side opposite to the side closest to the N pole PL1. decreases in the order in which the plurality of members SB2 are arranged.

Thereby, the outer peripheral length LN2 of each of the plurality of members SB2 can be uniformly decreased from the side closest to the N-pole PL1 toward the side opposite to the side closest to the N-pole PL1. Therefore, the magnetic flux 9 captured by each of the plurality of members SB2 can be uniformly converged from the side closest to the N-pole PL1 toward the side opposite to the side closest to the N-pole PL1. Therefore, it is possible to prevent or suppress the local concentration of the magnetic field at, for example, the corners of the plurality of members SB2, the strong magnetic field can be efficiently captured by the plurality of members SB2, and the strong magnetic field can be efficiently captured. It can be confined within the member group SG2. A portion of the member group SG2 on the N pole PL1 side may have a trumpet shape, a horn shape, or a morning glory shape.

Next, a case where FIG. 5 illustrates the member group SG3 will be described. In this case, in FIGS. 5 and 6, two members SB3 adjacent to each other along the axis 11 are arranged with a space therebetween, but no spacer is arranged between the two members SB3 adjacent to each other. is illustrated.

As shown in FIGS. 5 and 6, each of the plurality of members SB3 also includes a tubular portion CP3 centered on the axis 11 along the annular path 7, similarly to each of the plurality of members SB1. Each of the plurality of members SB3 captures a magnetic field along the axis 11 so that the magnetic flux 9 emitted from the N pole PL1 (see FIG. 1) is contained in each of the plurality of members SB3. They are arranged along the annular path 7 so as to sequentially pass through the plurality of cylindrical portions CP3 and return to the S pole PL2 (see FIG. 1). The direction of the magnetic flux 9 shown in FIG. 6 indicates the direction of the magnetic flux 9 when FIG. 5 illustrates the member group SG2, and is opposite to the direction of the magnetic flux 9 when FIG. 5 illustrates the member group SG3. Oriented.

As shown in FIGS. 1, 2, 5 and 6, member group SG3 is adjacent to S pole PL2 along annular path 7 and not adjacent to N pole PL1. Further, among the plurality of members SB3, the member SB3 arranged on the side closest to the S pole PL2 along the annular path 7 has an outer peripheral length LN3 (see FIG. 5) of a cross section perpendicular to the annular path 7. is longer than the outer peripheral length LN3 of the cross section perpendicular to the annular path 7 of the member SB3 arranged on the side opposite to the side closest to the S pole PL2 along the annular path 7 among the members SB3.

As a result, on the side of the member group SG3 closest to the S pole PL2, the cross section perpendicular to the circular path 7 of the member SB3 is adjusted to match the outer circumference length of the cross section perpendicular to the circular path 7 of the S pole PL2 of the magnet portion 3. It is possible to lengthen the outer peripheral length LN3 of the member SB3, that is, to thicken the member SB3. Therefore, the magnetic field formed by the magnetic flux 9 returning to the S pole PL2 of the magnet portion 3 can be confined in the superconducting bulk portion 4 efficiently. On the other hand, on the opposite side of the member group SG3 that is closest to the S pole PL2, the outer circumference length LN3 of the cross section perpendicular to the annular path 7 of the member SB3 can be shortened, that is, the member SB3 can be thinned. Therefore, the volume of the magnetic circuit member can be reduced, and the magnetic circuit can be reduced in size or weight.

Preferably, the outer circumference length LN3 of the cross section perpendicular to the annular path 7 of each of the plurality of members SB3 is from the side closest to the S pole PL2 along the annular path 7 to the side closest to the S pole PL2 and the side opposite to the side closest to the S pole PL2. decreases in the order in which the plurality of members SB3 are arranged.

As a result, the outer peripheral length LN3 of each of the plurality of members SB3 can be uniformly increased from the side opposite to the side closest to the S pole PL2 toward the side closest to the S pole PL2. Therefore, the magnetic flux 9 captured by each of the plurality of members SB3 can be spread uniformly from the side opposite to the side closest to the S pole PL2 toward the side closest to the S pole PL2. Therefore, it is possible to prevent or suppress the local concentration of the magnetic field on, for example, the corners of the plurality of members SB3, so that the strong magnetic field can be efficiently captured by the plurality of members SB3. It can be confined within the member group SG3. A portion of the member group SG3 on the S pole PL2 side may have a trumpet shape, a trumpet shape, a horn shape, or a morning glory shape.

Moreover, as shown in FIG. 1, the superconducting device 1 may have a refrigerator 21 such as a GM refrigerator as a cooling unit for cooling the superconducting bulk portion 4 . The refrigerator 21 is provided outside the magnet portion 3 and includes a main body portion 22 and a cold head 23 . Moreover, the superconducting device 1 may have a cryocontainer (not shown) that stores the superconducting bulk portion 4 in a state in which the superconducting bulk portion 4 is insulated from the outside. The superconducting bulk part 4 and the cold head 23 are arranged in a cryocontainer, and the superconducting bulk part 4 is in thermal contact with the cold head 23 . By cooling the superconducting bulk portion 4 to below the critical temperature of the superconducting bulk portion 4 by the refrigerator 21, the superconducting bulk portion 4 can be brought into a superconducting state.

<First modification of superconducting device>
FIG. 7 is a cross-sectional view schematically showing a first modification of the superconducting device of the embodiment. FIG. 7 shows a member group corresponding to the member group SG1 in the superconducting device of the embodiment as a member group SG1. Two adjacent members SB1 are illustrated and explained. Also, FIG. 7 illustrates an example in which no spacer is arranged between two members SB1 adjacent to each other along the annular path 7 .

As shown in FIG. 7 , the member group SG1 may include a plurality of members SB1, and each of the plurality of members SB1 may include an extension EX1 extending along the annular path 7. As shown in FIG. Each of the plurality of members SB1 captures a magnetic field along the annular path 7 while each of the plurality of members SB1 is in a superconducting state. are arranged along the annular path 7 so as to sequentially return to the S pole PL2 through the extension EX1 of the .

Even when the member SB1 includes the extension EX1, each of the plurality of members SB1 captures the magnetic field along the annular path 7 in a superconducting state, as in the case when the member SB1 includes the tubular portion CP1 (see FIG. 4). By doing so, the cross-sectional area of the magnetic circuit, that is, the cross-sectional area perpendicular to the circular path of the superconducting bulk body can be reduced. Therefore, when a superconducting bulk body is used as a magnetic circuit member, the volume of the magnetic circuit member can be reduced compared with the case where a magnetic body is used as the magnetic circuit member, and the magnetic circuit can be easily reduced in size or size. It can be made lighter. However, when the member SB1 includes the extension portion EX1, the weight increases compared to when the member SB1 includes the tubular portion CP1, so the above-described effect of weight reduction is reduced to some extent.

Alternatively, each of the plurality of members SB1 may include a plate portion PP1 having a front surface and a back surface that are perpendicular to the circular path 7 . Each of the plurality of members SB1 captures a magnetic field along the annular path 7 while each of the plurality of members SB1 is in a superconducting state. are arranged along the annular path 7 so as to return to the S pole PL2 through the plate portions PP1 of the .

Even when the member SB1 includes the plate portion PP1, each of the plurality of members SB1 captures the magnetic field along the annular path 7 in a superconducting state, as in the case when the member SB1 includes the tubular portion CP1 (see FIG. 4). Thereby, the cross-sectional area of the magnetic circuit, that is, the cross-sectional area perpendicular to the circular path of the superconducting bulk body can be reduced. Therefore, when a superconducting bulk body is used as a magnetic circuit member, the volume of the magnetic circuit member can be reduced compared with the case where a magnetic body is used as the magnetic circuit member, and the magnetic circuit can be easily reduced in size or size. It can be made lighter.

As shown in FIG. 7, the outer perimeter lengths LN1 (see FIG. 3) of the sections perpendicular to the annular path 7 of each of the plurality of members SB1 may be equal to each other. That is, the outer diameters DM1 about the axis 11 of each of the plurality of members SB1 may be equal to each other. In such a case, the outer diameter DM1 of each of the plurality of members SB1 can be reduced, the volume of the magnetic circuit member can be reduced, and the magnetic circuit can be reduced in size or weight.

Also, the plurality of members SB1 may be arranged at intervals. This also allows the volume of the magnetic circuit member to be reduced, and the magnetic circuit to be reduced in size or weight.

The member SB1 including the extension EX1 means, for example, that the ratio of the length HT1 along the axis 11 of the member SB1 to the outer diameter DM1 of the member SB1 exceeds one. Further, that the member SB1 includes the plate portion PP1 means, for example, that the ratio of the length HT1 along the axis 11 of the member SB1 to the outer diameter DM1 of the member SB1 is 1 or less.

<Second modification of superconducting device>
FIG. 8 is a cross-sectional view schematically showing a second modification of the superconducting device of the embodiment. In addition, FIG. 8 illustrates and demonstrates the member group corresponding to the member group SG2 in the superconducting device of embodiment as member group SG2. In addition, FIG. 8 illustrates an example in which no spacer is arranged between two members SB2 adjacent to each other along the annular path 7. As shown in FIG.

As shown in FIG. 8, the member group SG2 includes a plurality of members SB2, and each of the plurality of members SB2 has an outer peripheral length LN2 (see FIG. 5) of a section perpendicular to the annular path 7 along the annular path 7. It may also include a platform TL2 that varies uniformly with the Each of the plurality of members SB2 captures a magnetic field along the annular path 7 while each of the plurality of members SB2 is in a superconducting state. They are arranged along the annular path 7 so as to sequentially return to the S pole PL2 through the platform TL2.

Even when the member SB2 includes the pedestal TL2, each of the plurality of members SB2 captures the magnetic field along the annular path 7 in a superconducting state, similar to when the member SB2 includes the tubular portion CP2 (see FIG. 6). Thereby, the cross-sectional area of the magnetic circuit, that is, the cross-sectional area perpendicular to the circular path of the superconducting bulk body can be reduced. Therefore, when a superconducting bulk body is used as a magnetic circuit member, the volume of the magnetic circuit member can be reduced compared with the case where a magnetic body is used as the magnetic circuit member, and the magnetic circuit can be easily reduced in size or size. It can be made lighter. However, when the member SB2 includes the base portion TL2, the weight increases compared to when the member SB2 includes the cylindrical portion CP2, so the above-described effect of weight reduction is reduced to some extent.

Preferably, the outer circumference length LN2 (see FIG. 5) of the cross section perpendicular to the circular path 7 of each of the plurality of members SB2 is the distance from the side closest to the N pole PL1 to the N pole PL1 along the circular path 7. It decreases in order of arrangement of the plurality of members SB2 toward the near side and the opposite side.

Thereby, the outer peripheral length LN2 of each of the plurality of members SB2 can be uniformly decreased from the side closest to the N-pole PL1 toward the side opposite to the side closest to the N-pole PL1. Therefore, the magnetic flux 9 captured by each of the plurality of members SB2 can be uniformly converged from the side closest to the N-pole PL1 toward the side opposite to the side closest to the N-pole PL1. Therefore, it is possible to prevent or suppress local concentration of the magnetic field on, for example, the corners of the plurality of members SB2. In addition, although the effect is slightly smaller than when the member SB2 includes the cylindrical portion CP2, the strong magnetic field can be efficiently captured by the plurality of members SB2, and the strong magnetic field can be efficiently confined within the member group SG2. can be done.

It should be noted that the member SB3 included in the member group SG3 may include the base portion TL3 in the same way that the member SB2 included in the member group SG2 includes the base portion TL2. At this time, the outer circumference length LN3 (see FIG. 5) of the cross section perpendicular to the circular path 7 of each of the plurality of members SB3 is the closest to the S pole PL2 along the circular path 7 from the side closest to the S pole PL2. It may decrease in order of arrangement of the plurality of members SB3 toward the opposite side. As a result, compared to the case where the member SB3 includes the tubular portion CP3 (see FIG. 6), although the effect is slightly reduced, the volume of the magnetic circuit member can be reduced to some extent, and the magnetic circuit can be miniaturized to some extent. Or it can be made lighter.

<Material of superconducting bulk body>
A sintered body bulk of magnesium diboride (MgB ₂ ) or a sintered body bulk of iron pnictide can be used as the superconducting bulk body. That is, the superconducting bulk portion 4 is preferably made of magnesium diboride or iron pnictide.

_The critical temperature _Tc of MgB2 is about 39K, which is higher than both the critical temperature of NbTi alloy (9K) and the critical temperature of Nb3Sn ₍ 18K). Therefore, MgB ₂ can maintain a superconducting state at a temperature of about 10 to 30 K, which is extremely high compared to the temperature of liquid helium (4.2 K). A cooling method using a refrigerator can be used instead of liquid helium. As a result, even when the superconducting device of the present embodiment is used as a magnetic circuit member of a magnet device, the magnetic circuit can be reduced in size or weight.

_The superconducting bulk body made of MgB2 is made of a sintered body of MgB2, and although there _are various methods for synthesizing it, for example, powders of magnesium (Mg) and boron (B) are mixed. It can be easily formed by sintering a molded body obtained by molding the mixture. Thereby, a large superconducting bulk body can be easily formed as a superconducting bulk body made of MgB ₂ . Therefore, the superconducting device of the present embodiment can be easily enlarged by using a large-sized superconducting bulk material. It can be easily used as a magnetic circuit member of a magnet device that generates a strong magnetic field. From this point of view as well, when the superconducting device of the present embodiment is used as a magnetic circuit member of a magnet device instead of a magnetic material such as iron, the magnetic circuit can be easily reduced in size or weight. can.

Also, the directional dependence of the critical current density in the crystal of _MgB2 is small. That is, the critical current density characteristics of MgB ₂ are less anisotropic and substantially isotropic. Therefore, in a superconducting bulk body made of a sintered body of MgB2, even if the angle formed by the orientation directions of _two adjacent crystal grains is away from 0°, the gap between the two crystal grains The critical current density flowing across the interface is not significantly reduced. Therefore, when forming a superconducting bulk body made of a sintered body of MgB2, it is not necessary to control the orientation direction of crystal grains, so a large _- sized superconducting bulk body can be easily formed. can do.

The average particle diameter of MgB ₂ in the superconducting bulk body made of MgB ₂ should be as small as possible from the viewpoint of capturing the magnetic field. In the range of the lower limit value or more, the average particle size is more preferably 200 to 400 nm. When the average particle size of MgB2 is ₂₀₀ nm or more, the average particle size can be easily adjusted to a desired value compared to when the average particle size of MgB2 is less than ₂₀₀ nm. On the other hand, when the _average grain size of MgB2 is 400 nm or less, compared with the case where the _average grain size of MgB2 exceeds 400 nm, the uniformity of the internal structure of the superconducting bulk body can be easily improved, and the critical current density can be increased. can be easily improved.

Iron pnictides refer to compounds of iron (Fe) and group 15 elements such as arsenic (As). _The critical temperature _Tc of iron pnictides varies depending on the composition, but is about the same as the critical temperature _Tc of MgB2 or higher _than the critical temperature _Tc of MgB2. Therefore, even when a superconducting bulk body made of iron pnictide is used instead of a superconducting bulk body made of MgB ₂ as a magnetic circuit member of a magnet device, it is less effective than using a magnetic material such as iron as a magnetic circuit member. As for the effect of easily miniaturizing or lightening the magnetic circuit by using the superconducting bulk body made of MgB ₂ , the effect is comparable to that of using the superconducting bulk body made of MgB ₂ , or more than the effect of using the superconducting bulk body made of MgB 2 . A big effect is obtained.

Materials used as iron pnictides include REFeAsO _1-x F _x (0<x<1, RE is a rare earth element), (AE, A) (Fe, TM) ₂ (As, Pn) ₂ (AE is an alkaline earth element). element, A is an alkali element, TM is a transition metal element, Pn is a nictogen element), A _1-x (Fe, TM) (As, Pn) (0<x<1, A is an alkali element, TM is a transition metal element , Pn is a nictogen element), SmFeAsO _1-x H _x (0<x<1), NdFeAsO _1-x H _x (0<x<1), CeFeAsO _1-x H _x (0<x<1), LaFeAsO _{1- xHx} (0< _x <1), SmFeAs1 _- yPyO1-xHx (0< _x <1, 0< _y <1), _{LaFe1 -} yZnyAsO1 _- xH _x (0<x<1, 0<y<1), LaFeAsO _0.85 H _x (0≦x≦0.85), LaFeAsO _1-x (0<x<1), CaFe _1-x Co _x AsH (0<x<1), Ca1-xLaxFeAsH (0< _x <1), Ca1 _{-xSmxFeAsH (0<x<1), CaFeAsF1-x ( 0 <} x<1), Sr _1-x La _x Fe ₂ As ₂ (0<x<1), (Ba, La) Fe ₂ As ₂ , (Ba, Ce) Fe ₂ As ₂ , (Ba, Pr) Fe ₂ As ₂ , (Ba , Nd) _Fe2As2 , (Sr,La) _Fe2As2 , ₍ Ca,La)Fe2 ₍ As,P) ₂ , Ba ₍ Fe,Pt) _2As2 , ₍ Ca,La) _FeAs2 , (Ca, La) Fe(As, Sb) ₂ , (Ca, RE) Fe(As, Sb) ₂ (RE=La, Ce, Pr, Nd), Ca ₁₀ (Ir ₄ As ₈ ) (Fe ₂ As ₂ ) ₅ , Na _0.65 Fe _1.93 Se ₂ , (Na, NH ₃ ) Fe ₂ Se ₂ and LaFeAs(O, C ₂ ). That is, the iron pnictide is preferably composed of one or more selected from the group consisting of the compounds represented by the above compositional formulas.

<First Modification of Magnet Device>
FIG. 9 is a plan view schematically showing a first modification of the magnet device of the embodiment.

As shown in FIG. 9, the magnet unit 3 has only one magnet MG3 provided along the annular path 7, and the magnet unit 3 has an N pole PL1 as a first magnetic pole having a first polarity. , and the south pole PL2 as a second magnetic pole having a second polarity opposite to the first polarity. The N pole PL1, the superconducting bulk portion 4, and the S pole PL2 may be arranged along the circular path 7 in the order of the N pole PL1, the superconducting bulk portion 4, and the S pole PL2.

In such a case, compared to the case where the magnet portion 3 is composed of a so-called Helmholtz coil, it is difficult to put a subject such as a human body into and out of the space 8 inside the magnet portion 3, but a magnetic material is used as a magnetic circuit member. Compared to the case of using such a material, the effect of reducing the volume of the magnetic circuit member can be obtained, and the effect of easily reducing the size or weight of the magnetic circuit can be obtained.

<Second Modification of Magnet Device>
FIG. 10 is a plan view schematically showing a second modification of the magnet device of the embodiment.

As shown in FIG. 10, the superconducting bulk portion 4 may have only the member group SG1 without the member groups SG2 and SG3 (see FIG. 1). In the portion of the annular path 7 that exits the N pole PL1 and returns to the S pole PL2, the outer peripheral lengths LN1 (see FIG. 3) of the sections perpendicular to the annular path 7 of each of the plurality of members SB1 are equal to each other. good too. In such a case, although the degree of effect is smaller than that of the magnet device of the embodiment described with reference to FIGS. The volume of the member can be reduced to some extent, and the magnetic circuit can be made smaller or lighter to some extent.

<Third Modification of Magnet Device>
FIG. 11 is a plan view schematically showing a third modification of the magnet device of the embodiment.

As shown in FIG. 11, the superconducting bulk body, ie, the superconducting bulk portion 4, may not be divided along the annular path 7, but may be integrally formed. In such a case, the superconducting bulk portion 4 can be formed more easily than the magnet apparatus of the embodiment described above with reference to FIGS. However, the volume of the magnetic circuit member can be reduced to some extent, and the size and weight of the magnetic circuit can be reduced to some extent.

<Fourth Modification of Magnet Device>
In the magnet device of the embodiment, the superconducting bulk body, that is, the superconducting bulk portion 4 is provided outside the magnet portion 3 . However, the end portion of the superconducting bulk portion 4 may surround the magnet portion 3 and a part of the magnet portion 3 may enter the inside of the end portion of the superconducting bulk portion 4 . Such a magnet device will be described as a fourth modified example of the magnet device.

FIG. 12 is a plan view schematically showing a fourth modification of the magnet device of the embodiment. Note that FIG. 12 shows a cross section of the members SB4 and SB5 for easy understanding.

As shown in FIG. 12, the superconducting device provided in the magnet device of the fourth modification has a superconducting bulk portion 4 as a superconducting bulk body. In addition, the superconducting bulk portion 4 includes a member SB4 as a superconducting bulk body including a tubular portion CP5 surrounding a portion of the magnet MG1, ie, the magnet portion 3, and the magnet MG2, ie, another portion of the magnet portion 3. and a member SB5 as a superconducting bulk body including a cylindrical tubular portion CP6. Each of member SB4 and member SB5 is made of a type II superconductor and, in the superconducting state, traps a magnetic field above the lower critical field and below the upper critical field by pinning the magnetic flux.

In the example shown in FIG. 12, the member group SG2 including a plurality of members SB2, the member group SG1 including a plurality of members SB1, and the member group SG3 including a plurality of members SB3 have been described with reference to FIG. It can be the same as the magnet device of the embodiment.

Further, in the example shown in FIG. 12, the member SB4, the plurality of members SB2, the plurality of members SB1, the plurality of members SB3, and the member SB5 are arranged along an annular path 7 around an axis 6 to form the member SB4, the plurality of members SB2, the plurality of members SB1, the plurality of members SB3, and the member SB5 are arranged in this order. That is, the N pole PL1, the member group SG2, the member group SG1, the member group SG3, and the S pole PL2 are arranged along the annular path 7 to form the N pole PL1, the member group SG2, the member group SG1, the member group SG3, and the S pole PL2. are arranged in order. A member SB4 capturing a magnetic field, a plurality of members SB2 each capturing a magnetic field, a plurality of members SB1 each capturing a magnetic field, and a plurality of members SB3 each capturing a magnetic field. , the member SB5 that captures the magnetic field, and the magnet portion 3 form a magnetic circuit 5 . That is, a magnetic circuit 5 is formed along the circular path 7 from the N pole PL1 to the S pole PL2 via the plurality of members SB2, the plurality of members SB1, and the plurality of members SB3 in order. Both of the tubular portions CP5 and CP6 are tubular portions having an axis 11 (see FIG. 3) along the annular path 7 as a center. Further, the magnetic flux emitted from the N pole PL1 returns to the S pole PL2 through the interior of the cylindrical portion CP5 and the interior of the cylindrical portion CP6 in sequence.

In the example shown in FIG. 12, the plurality of members SB2 included in the member group SG2, the plurality of members SB1 included in the member group SG1, and the plurality of members SB3 included in the member group SG3 are the plurality of members SB2 and the plurality of members SB3. Since each of the member SB1 and the plurality of members SB3 captures the magnetic field in a superconducting state, the magnetic flux emitted from the N pole PL1 passes through the plurality of members SB2, the plurality of members SB1 and the plurality of members SB3 in sequence to reach the S pole. Arranged along a circular path 7 leading back to PL2.

In FIG. 12, the case where the superconducting device has two members SB4 and two members SB5 will be described as an example. The number of may be 1 or more. Also, in the fourth modification, as in the embodiment, the superconducting bulk portion 4 including the members SB4 and SB5 is preferably made of magnesium diboride or iron pnictide. Also in the fourth modification, as in the embodiment, the superconducting device has a refrigerator 21 such as a GM refrigerator as a cooling unit for cooling the superconducting bulk portion 4 including the members SB4 and SB5. You may

In the fourth modified example, similarly to the embodiment, the volume of the magnetic circuit member can be reduced, and the magnetic circuit can be reduced in size or weight. On the other hand, in the fourth modified example, the ends of the superconducting bulk portion 4 surround the magnet portion 3 , and part of the magnet portion 3 enters inside the ends of the superconducting bulk portion 4 . Therefore, in the fourth modified example, a strong magnetic field can be efficiently confined in the superconducting bulk portion 4 around the magnet portion 3 compared to the embodiment.

The superconducting bulk portion 4 may have none of the plurality of members SB2, the plurality of members SB1, and the plurality of members SB3, and may have only the member SB4 or the member SB5. At this time, the magnetic circuit 5 is formed by the member SB4 or the member SB5 that captures the magnetic field and the magnet portion 3 . Even in such a case, the volume of the magnetic circuit member can be reduced, and the magnetic circuit can be made smaller or lighter than when the superconducting bulk portion 4 is not provided in the magnet device.

10, the portion of the superconducting bulk portion 4 other than the members SB4 and SB5 may have only the member group SG1 without the member groups SG2 and SG3. In the portion of 7 that exits from the N pole PL1 and returns to the S pole PL2, the outer circumference length LN1 (see FIG. 3) of the cross section perpendicular to the circular path 7 of each of the plurality of members SB1 may be equal to each other. Alternatively, portions of the superconducting bulk portion 4 other than the members SB4 and SB5 may be integrally formed without being divided along the annular path 7 as shown in FIG. In addition, the member groups SG1, SG2, and SG3 can be the same as the member group SG1 shown in FIG. 7, or the member group SG2 or member group SG3 shown in FIG.

<Fifth Modification of Magnet Device>
In the magnet device of the embodiment, the superconducting bulk body, that is, the superconducting bulk portion 4 is provided outside the magnet portion 3 . However, the middle portion of the superconducting bulk portion 4 may surround the magnet portion, and the magnet portion may be provided inside the middle portion of the superconducting bulk portion 4 . Such a magnet device will be described as a fifth modification of the magnet device.

FIG. 13 is a plan view schematically showing a fifth modification of the magnet device of the embodiment. Note that FIG. 13 shows an enlarged cross-sectional view of a region RG1 surrounded by a two-dot chain line.

As shown in FIG. 13, in the magnet device of the fifth modification, instead of the magnet portion 3 (see FIG. 1), a magnet portion 3a is provided inside the superconducting bulk body, that is, the superconducting bulk portion 4. It has The magnet part 3a has a magnet MG4, and the magnet MG4 has an N pole PL1 as a first magnetic pole having a first polarity and an S pole PL2 as a second magnetic pole having a second polarity opposite to the first polarity. , have

Moreover, the superconducting device provided in the magnet device of the fifth modified example has a superconducting bulk portion 4 as a superconducting bulk body. Also, the superconducting bulk portion 4 has a member SB6 as a superconducting bulk body including a tubular portion CP7 surrounding the magnet MG4, that is, the magnet portion 3a. The tubular portion CP7 is a tubular portion having an axis 11 (see FIG. 3) along the annular path 7 as a center. The member SB6 is made of a type II superconductor and, in the superconducting state, traps a magnetic field above the lower critical field and below the upper critical field by pinning the magnetic flux. The N-pole PL1, the superconducting bulk portion 4 and the S-pole PL2 are arranged along an annular path 7 around an axis 6 in the order N-pole PL1, superconducting bulk portion 4 and S-pole PL2.

In the example shown in FIG. 13, the member group SG2 including a plurality of members SB2, the member group SG1 including a plurality of members SB1, and the member group SG3 including a plurality of members SB3 have been described with reference to FIG. It can be the same as the magnet device of the embodiment. On the other hand, in the example shown in FIG. 13, a member SB6 is arranged between a plurality of members SB2 and a plurality of members SB1, and a plurality of members SB7 are arranged between the plurality of members SB2 and SB6. A member group SG4 is arranged as a superconducting bulk body group. Each of the plurality of members SB7 includes a cylindrical tubular portion CP8 centered on an axis 11 (see FIG. 3) along the annular path 7. As shown in FIG. The member group SG4 including a plurality of members SB7 can be configured in the same manner as the member group SG1 including a plurality of members SB1. The plurality of members SB2, the plurality of members SB7, the plurality of members SB1, and the plurality of members SB3 are provided outside the magnet portion 3a. Also, each of the plurality of members SB7 captures the magnetic field in a superconducting state.

Further, in the example shown in FIG. 13, the plurality of members SB2, the plurality of members SB7, the plurality of members SB6, the plurality of members SB1 and the plurality of members SB3 are arranged along an annular path 7 around a given axis 6 to form the plurality of members SB2 , a plurality of members SB7, a plurality of members SB6, a plurality of members SB1, and a plurality of members SB3. That is, the N pole PL1, the member group SG1, the member group SG3, the member group SG2, the member group SG4, and the S pole PL2 are arranged along the annular path 7 to form the N pole PL1, the member group SG1, the member group SG3, the member group SG2, The member group SG4 and the S pole PL2 are arranged in this order. A plurality of members SB2 each capturing a magnetic field, a plurality of members SB7 each capturing a magnetic field, a member SB6 each capturing a magnetic field, and a plurality of members SB1 each capturing a magnetic field. , a magnetic circuit 5 is formed by a plurality of members SB3 each capturing a magnetic field, and the magnet portion 3a. That is, a magnetic circuit 5 is formed along the circular path 7 from the N pole PL1 to the S pole PL2 via the plurality of members SB1, the plurality of members SB3, the plurality of members SB2, and the plurality of members SB7 in order. Also, the magnetic flux emitted from the N pole PL1 returns to the S pole PL2 through the inside of the cylindrical portion CP7.

In the example shown in FIG. 13, the plurality of members SB1 included in the member group SG1, the plurality of members SB3 included in the member group SG3, the plurality of members SB2 included in the member group SG2, and the plurality of members included in the member group SG4 In the member SB7, each of the plurality of members SB1, the plurality of members SB3, the plurality of members SB2, and the plurality of members SB7 captures a magnetic field in a superconducting state. , a plurality of members SB3, a plurality of members SB2 and a plurality of members SB7, and back to the S pole PL2.

Also in the fifth modification, the superconducting bulk portion 4 including the member SB6 is preferably made of magnesium diboride or iron pnictide, as in the embodiment. Also in the fifth modification, as in the embodiment, the superconducting device has a refrigerator 21 such as a GM refrigerator as a cooling unit for cooling the superconducting bulk portion 4 including the member SB6. good too.

In the fifth modification, the middle portion of the superconducting bulk portion 4 surrounds the magnet portion 3a, and the magnet portion 3a is provided inside the middle portion of the superconducting bulk portion 4. FIG. Even in such a case, as in the embodiment, the volume of the magnetic circuit member can be reduced, and the magnetic circuit can be reduced in size or weight. Therefore, compared to the embodiment, the positions at which the magnet units are arranged can be changed, so that the degree of freedom in designing the magnet device can be improved.

The superconducting bulk portion 4 may have only the member SB6 without having any of the plurality of members SB2, the plurality of members SB7, the plurality of members SB1, and the plurality of members SB3. At this time, the magnetic circuit 5 is formed by the member SB6 that captures the magnetic field and the magnet portion 3a. Even in such a case, the volume of the magnetic circuit member can be reduced, and the magnetic circuit can be made smaller or lighter than when the superconducting bulk portion 4 is not provided in the magnet device.

10, the portion of the superconducting bulk portion 4 other than the member SB6 may have only the member groups SG1 and SG4 without the member groups SG2 and SG3. In the portion of 7 that exits the N pole PL1 and returns to the S pole PL2, the outer perimeter lengths of cross sections perpendicular to the annular path 7 of each of the plurality of members SB1 and SB7 may be equal to each other.

<MRI device>
Next, an MRI apparatus having a magnet device equipped with the superconducting device of this embodiment will be described.

FIG. 14 is a block diagram showing an MRI apparatus having a magnet device equipped with a superconducting device according to an embodiment.

The MRI apparatus 31 obtains a tomographic image of the biological tissue of the subject 32 using the nuclear magnetic resonance (NMR) phenomenon. As shown in FIG. 14, the MRI apparatus 31 includes a static magnetic field generating magnet 33, a gradient magnetic field coil 34 and a gradient magnetic field power supply 35, an RF (Radio Frequency) transmission coil 36 and an RF transmission section 37, an RF reception coil 38 and A signal processing unit 39 and a measurement control unit 41 are provided. Although not shown in FIG. 14, the MRI apparatus 31 includes an overall control unit that controls the entire MRI apparatus 31, a display/operation unit that performs measurement operations and displays measurement results and the like, and a subject 32. a conveying device for taking the magnetic field generating magnet 33 into and out of the static magnetic field generating magnet 33 .

As the static magnetic field generating magnet 33, the magnet device 2 including the superconducting device 1, which is the superconducting device of the present embodiment, and the magnet unit 3 (see FIG. 1) can be used. As described above with reference to FIGS. 1 and 2, the magnet unit 3 (see FIG. 1) provided in the magnet device 2 may generate a DC magnetic field along the annular path 7 (see FIG. 1). Just do it. A permanent magnet, or an electromagnet such as a normal-conducting coil wound with a copper wire or the like or a superconducting coil wound with a superconducting wire can be used as the magnet unit 3 (see FIG. 1). In the example shown in FIG. 14, as described above with reference to FIG. 1, an electromagnet composed of a Helmholtz coil is used as the static magnetic field generating magnet 33, that is, the magnet unit 3 (see FIG. 1) provided in the magnet device 2. is provided.

The gradient magnetic field coil 34 is wound around each of the three axial directions of the X-axis, the Y-axis and the Z-axis which intersect each other, preferably orthogonal to each other in the real space coordinate system (stationary coordinate system) of the MRI apparatus 31. Contains 3 coils. The gradient magnetic field coils 34 are connected to a gradient magnetic field power supply 35 . A gradient magnetic field power supply 35 supplies current to the gradient magnetic field coil 34 . Specifically, the gradient magnetic field power supply 35 supplies current to the gradient magnetic field coil 34 according to control by the measurement control section 41 . As a result, gradient magnetic fields are generated in three axial directions of the X-axis, Y-axis and Z-axis. Therefore, the gradient magnetic field coil 34 and the gradient magnetic field power supply 35 form a gradient magnetic field generator for generating a gradient magnetic field.

The RF transmission coil 36 is a coil that irradiates the subject 32 with an RF pulse signal. The RF transmission coil 36 is connected to the RF transmission section 37 . The RF transmission section 37 supplies a high frequency pulse current to the RF transmission coil 36 . As a result, an NMR phenomenon is induced in the spins of atoms forming the biological tissue of the subject 32 . Specifically, under the control of the measurement control unit 41, the RF transmission unit 37 amplitude-modulates the high-frequency pulse current, amplifies it, and supplies it to the RF transmission coil 36, so that the subject 32 is irradiated with the RF pulse signal. be. Therefore, the RF transmission coil 36 and the RF transmission section 37 form an RF pulse generation section for generating an RF pulse signal.

The RF receiving coil 38 is a coil that receives echo signals emitted by the NMR phenomenon of the living tissue of the subject 32 . The RF receiving coil 38 is connected to the signal processing section 39 . The echo signal received by the RF receiving coil 38 is sent to the signal processing section 39 .

The signal processing unit 39 performs detection processing of echo signals received by the RF receiving coil 38 . Specifically, the signal processing unit 39 amplifies the received echo signal under the control of the measurement control unit 41, divides it into two orthogonal signals by quadrature phase detection, samples each by a certain number, The sampled signal is A/D converted to obtain echo data as digital data. The signal processing unit 39 then performs various types of processing on the echo data and sends the processed echo data to the measurement control unit 41 .

The measurement control unit 41 transmits control signals to the gradient magnetic field power supply 35, the RF transmission unit 37, and the signal processing unit 39 in order to collect echo data necessary for forming a tomographic image of the subject 32, and controls them. Department.

Specifically, the measurement control unit 41 controls the gradient magnetic field power supply 35, the RF transmission unit 37, and the signal processing unit 39 based on control data of a certain imaging sequence, and transmits an RF pulse signal to the subject 32. and application of gradient magnetic field pulses, and detection of echo signals from the subject 32 are repeatedly executed to collect echo data necessary for forming a tomographic image of the imaging region of the subject 32 .

The strength of the magnetic field generated by the static magnetic field generating magnet 33 as the magnet device of the MRI apparatus 31 is stronger than the strength of the magnetic field generated by the magnet devices of devices other than the MRI apparatus. Therefore, in the static magnetic field generating magnet 33 of the MRI apparatus 31, it is necessary to increase the cross-sectional area of the magnetic circuit in order to confine the magnetic field inside the magnetic circuit. Therefore, the need to increase the volume of the magnetic material increases. Therefore, the problem that the magnetic circuit cannot be reduced in size or weight in the magnet device of the MRI apparatus is the problem that the magnetic circuit cannot be reduced in size or weight in the magnet apparatus of the apparatus other than the MRI apparatus. , is a remarkable one.

Therefore, when the magnet device provided with the superconducting device of the present embodiment is used as the magnet device of the MRI apparatus, the effect of reducing the size or weight of the magnetic circuit is the same as the magnet device provided with the superconducting device of the present embodiment. This is remarkable compared to the case where the magnet device is used as a magnet device possessed by a device other than the MRI device.

As described above with reference to FIGS. 1 and 2, consider the case where the magnet unit 3 provided in the magnet device 2 has the magnet MG1 and the magnet MG2 and is composed of a Helmholtz coil. In such a case, since the space 8 between the magnets MG1 and MG2 is open, even if a human being as a subject enters between the magnets MG1 and MG2 for examination, the feeling of blockage will not be felt. You can take the test without feeling too much.

On the other hand, as described above with reference to FIG. 9, consider the case where the magnet unit 3 provided in the magnet device 2 has only the magnet MG3. In such a case, compared to the case where the magnet portion 3 has the magnets MG1 and MG2, it is difficult to put a subject such as a human body into and out of the inside of the magnet portion 3. Compared to the case of using , the effect of reducing the volume of the magnetic circuit member can be obtained, and the effect of easily reducing the size or weight of the magnetic circuit can be obtained.

Hereinafter, this embodiment will be described in further detail based on examples. In addition, the present invention is not limited to the following examples.

(Example 1)
_In the following, the member SB1 including the cylindrical portion CP1 described in the embodiment with reference to FIGS. An evaluation test was conducted to evaluate whether the superconducting device of Example 1 can confine a magnetic field. As a superconducting device of Example 1, a superconducting device 1 having four members SB1 as superconducting bulk bodies each including a tubular portion CP1 centered on the axis 11 was formed. The four members SB1 were spaced apart from each other along the axis 11 .

[Formation of superconducting bulk body]
_First , as a superconducting bulk body, a member SB1 as a superconducting bulk body including a tubular portion CP1 and made of MgB2 was formed.

FIG. 15 is a flowchart showing some steps of a method for manufacturing a superconducting bulk body of the superconducting device of Example 1. FIG.

First, magnesium (Mg) powder with a particle size of 325 mesh and a purity of 99.9% and boron (B) powder with a particle size of 300 mesh and a purity of 99% are mixed together. The powders were mixed so that the mixing ratio was 1:2 in terms of molar ratio, that is, the atomic number ratio, and the mixed powder was pulverized (step S11 in FIG. 15).

Next, the mixed and pulverized powder was uniaxially pressed to form a disk-shaped pellet (step S12 in FIG. 15). In this molded pellet, the outer diameter around the pellet axis was 30 mm and the length along the pellet axis was 10 mm. Moreover, the pressure at the time of pressurization was 100 MPa.

Next, the molded disk-shaped pellet was heat-treated at 850° C. for 3 hours using a tubular furnace whose internal atmosphere was controlled to be an argon (Ar) atmosphere (step S13 in FIG. 15). The reason why the heat treatment is performed in the Ar atmosphere is that Mg is reacted with _B without being oxidized to form MgB2. As a result, a disk-shaped superconducting bulk body made of a sintered body of MgB ₂ was formed. _The critical temperature _Tc of the formed superconducting bulk body of MgB2 was about 39K. _{The average} grain size of MgB2 in the formed superconducting bulk body made of MgB2 was 300 nm.

Next, a through hole was formed through the disk-shaped superconducting bulk body along the axis (step S14 in FIG. 15). As a result, as shown in FIGS. 3 and 4, a superconducting bulk body, that is, a member SB1 including a tubular portion CP1 and made of MgB ₂ was formed. As described above, in this superconducting bulk body, that is, the member SB1, the outer diameter DM1 (see FIG. 4) of the axis 11 of the tubular portion CP1 is 30 mm, and the inner diameter DM2 (see FIG. 4) of the tubular portion CP1 is 10 mm, and the length HT1 (see FIG. 4) along the axis 11 of the cylindrical portion CP1 was 10 mm.

In Example 1, the mixed and pulverized powder was molded into disc-shaped pellets, heat-treated to form a disc-shaped sintered body, and then through holes were formed to form a cylindrical cylindrical portion. A superconducting bulk body containing However, the mixed and pulverized powder may be shaped into a tube and heat-treated to form a superconducting bulk body including a tubular portion.

[Formation of superconducting device]
Next, as a superconducting device of Example 1, a superconducting device 1 having four members SB1 as superconducting bulk bodies each including a tubular portion CP1 centered on the axis 11 was formed. The four cylindrical portions CP1 of each of the four members SB1 are arranged along the axis 11 at intervals. As described above, the outer diameter DM1 (see FIG. 4) of the cylindrical portion CP1 is 30 mm, the inner diameter DM2 (see FIG. 4) of the cylindrical portion CP1 is 10 mm, and the length along the axis 11 of the cylindrical portion CP1 The height HT1 (see FIG. 4) was 10 mm. Also, the distance between the two cylindrical portions CP1 of each of the two members SB1 adjacent to each other along the axis 11, that is, the gap GP1 (see FIG. 4) was 3 mm.

As shown in FIGS. 3 and 4, in Example 1, the spacer SP1 is arranged between the two cylindrical portions CP1 of each of the two members SB1 adjacent to each other. The spacer SP1 prevents the two cylindrical portions CP1 of each of the two members SB1 adjacent to each other from being attracted to each other by magnetic attraction when the superconducting device 1 captures a magnetic field. In Example 1, a stainless ring made of stainless steel was used as the spacer SP1. The spacer SP1 has a tubular portion CP4 centered on the axis 11 . The outer diameter (outer diameter DM1) centered on the axis 11 of the cylindrical portion CP4 is 30 mm, and the inner diameter (inner diameter DM2) centered on the axis 11 of the cylindrical portion CP4 is 10 mm. The length (gap GP1) along the was 3 mm.

[Evaluation test to evaluate whether a superconducting device can confine a magnetic field]
Next, an evaluation test was conducted to evaluate whether the superconducting device of Example 1 can confine a magnetic field.

First, a magnetic field (external magnetic field) parallel to the axis 11 of each cylindrical portion CP1 of each of the four members SB1 of the superconducting device 1 is applied to the superconducting device 1, and with the external magnetic field applied, , by a GM (Gifford-McMahon) refrigerator to a temperature of 10 K, which is lower _than the transition temperature of MgB2 ₍ approximately 39 K), to bring MgB2 into a superconducting state. In this state, the intensity of the external magnetic field was reduced to 0 to remove the external magnetic field. As a result, the magnetic field was captured by the four members SB1 in the superconducting state.

As shown in FIG. 4, five Hall elements (trade name: Model HGT-2101 Magnetic Field Sensor, manufactured by Lake Shore) 51 to 55 arranged on the axis 11 are used to produce the superconducting device of Example 1. The strength of the captured magnetic field was measured.

As shown in FIG. 4, the Hall element 51 is located on the axis 11 and between the tubular portion CP1 of the first member SB1 and the tubular portion CP1 of the second member SB1 from the top in FIG. 4 is arranged in the cylindrical portion CP4 of the first spacer SP1 from the top. The Hall element 52 was arranged in the cylindrical portion CP1 of the second member SB1 from the top in FIG. The Hall element 53 is located on the axis 11 and between the cylindrical portion CP1 of the second member SB1 from the top and the cylindrical portion CP1 of the third member SB1 in FIG. It was arranged in the cylindrical portion CP4 of the spacer SP1. The Hall element 54 is arranged in the cylindrical portion CP1 of the third member SB1 from the top in FIG. The Hall element 55 is located on the axis 11 and between the cylindrical portion CP1 of the third member SB1 from the top and the cylindrical portion CP1 of the fourth member SB1 in FIG. It was arranged in the cylindrical portion CP4 of the spacer SP1.

16 is a graph showing external magnetic field dependence of local magnetic flux density measured by five Hall elements arranged in the superconducting device of Example 1. FIG. As described above, FIG. 16 shows a state in which an external magnetic field of 20,000 Oe (2 T) is applied at a temperature of 10 K, and the intensity of the external magnetic field is reduced to 0 to remove the external magnetic field. shows local magnetic flux densities measured using the Hall elements 51 to 55 when trapping . In FIG. 16, Ch1, Ch2, Ch3, Ch4, and Ch5 indicate local magnetic flux densities measured by Hall elements 51, 52, 53, 54, and 55, respectively.

As a result, the measured value of the Hall element 51 (Ch1 in FIG. 16), the measured value of the Hall element 52 (Ch2 in FIG. 16), the measured value of the Hall element 53 (Ch3 in FIG. 16), the measured value of the Hall element 54 (Fig. 16 Ch4) and the measured value of the Hall element 55 (Ch5 in FIG. 16), the local magnetic flux density was approximately 2T (20000 G). That is, in any of the measured values of the Hall elements 51 to 55, the amount of decrease in the measured value of the local magnetic flux density in the process of removing the external magnetic field is 1 when the external magnetic field of 20000 Oe is applied as a reference. % and was not substantially attenuated.

Further, as shown in FIG. 16, when the external magnetic field is zero, that is, when the magnetic field is captured in the superconducting device 1, the difference between the measured values of the Hall element 52 and the measured value of the Hall element 54, that is, the gap When an external magnetic field of 20000 Oe is applied as a reference, , was within 1%. In addition, the difference between the measured value of the Hall element 52 and the measured value of the Hall element 51 or 53 is also within 1% when an external magnetic field of 20000 Oe is applied as a reference, and the measured value of the Hall element 54 and the measured value of the Hall element 53 or 55 was also within 1% when based on the state in which an external magnetic field of 20000 Oe was applied.

Therefore, in the superconducting device of Example 1, the four members SB1 as superconducting bulk bodies arranged at intervals can capture the magnetic field. It became clear that transmission with loss is possible. Therefore, it has been clarified that the superconducting device of Example 1 can reduce the size and weight of the magnetic circuit.

Next, we measured the time dependence of the magnetic field trapped in the superconducting device.

17 is a graph showing time dependence of local magnetic flux density measured by five Hall elements arranged in the superconducting device of Example 1. FIG. As described above, FIG. 17 shows the local magnetic flux measured using the Hall elements 51 to 55 when a magnetic field of 2 T (20000 G) is captured at a temperature of 10 K and then held at a temperature of 20 K for about 17 hours. Indicates density. In FIG. 17, Ch1, Ch2, Ch3, Ch4, and Ch5 normalize the local magnetic flux densities measured by the Hall elements 51, 52, 53, 54, and 55, respectively, with the local magnetic flux densities at the start of measurement. showing.

As a result, the measured value of the Hall element 51 (Ch1 in FIG. 17), the measured value of the Hall element 52 (Ch2 in FIG. 17), the measured value of the Hall element 53 (Ch3 in FIG. 17), the measured value of the Hall element 54 (Fig. 17 Ch4) and the measured value of the Hall element 55 (Ch5 in FIG. 17), the amount of decrease in the measured value of the local magnetic flux density with the passage of the holding time is within 1%, and there is no substantial attenuation. rice field.

Therefore, in the superconducting device of Example 1, the four members SB1 as superconducting bulk bodies can stably capture the magnetic field even after the passage of time. It was found that the magnetic field can be stably transmitted without loss even after the passage of time.

(Example 2)
Next, an embodiment is performed in the same manner as the superconducting device of Example 1, except that a superconducting bulk body made of iron pnictide is used instead of the superconducting bulk body made of magnesium diboride (MgB ₂ ). The member SB1 including the cylindrical portion CP1 described with reference to FIGS. 3 and 4, that is, the magnetic tube is formed as the superconducting device of Example 2, and whether the superconducting device of Example 2 can confine the magnetic field is evaluated. We conducted an evaluation test to As a superconducting device of Example 2, a superconducting device 1 having four members SB1 as superconducting bulk bodies each including a tubular portion CP1 centered on the axis 11 was formed. The four cylindrical portions CP1 of each of the four members SB1 are arranged along the axis 11 at intervals.

In Example 2, a superconducting bulk body made of (Ba, K)Fe ₂ As ₂ or the like was synthesized as a superconducting bulk body made of iron pnictide. First, raw material powders weighed so that the molar ratio of barium (Ba), potassium (K), iron (Fe), and arsenic (As) is the molar ratio represented by the above compositional formula were pulverized and mixed. . Next, after molding the mixed raw material powder into a predetermined shape, it is heat-treated at, for example, 500 to 1100° C. for 24 to 240 hours. _The critical temperature _Tc of the formed superconducting bulk body of iron pnictides was about 30 K, which was comparable to the critical temperature _Tc of the superconducting bulk body of MgB2.

Next, the superconducting device of Example 2 was formed by a method similar to that described in Example 1, a magnetic field was trapped in the superconducting device in a superconducting state, and the trapped magnetic field was measured. As a result, although it can be expected from the fact that the critical temperature of the superconducting bulk body made of iron pnictide is as high as the critical temperature of the superconducting bulk body made of MgB ₂ , the results are similar to those described with reference to FIGS. 16 and 17. Similar results were obtained. Substantially the same results were obtained when the various iron pnictides described above were used as the iron pnictides. As a result, it has been clarified that even when iron pnictide is used instead of MgB ₂ , the magnetic circuit can be made smaller or lighter as in the superconducting device of the first embodiment.

Although the invention made by the present inventor has been specifically described based on the embodiment, the invention is not limited to the above embodiment, and can be variously modified without departing from the gist of the invention. Needless to say.

Within the scope of the idea of the present invention, those skilled in the art can conceive of various modifications and modifications, and it is understood that these modifications and modifications also fall within the scope of the present invention.

For example, a person skilled in the art may appropriately add, delete, or change the design of components, or add, omit, or change the conditions of the above-described embodiments. As long as it has the gist, it is included in the scope of the present invention.

INDUSTRIAL APPLICABILITY The present invention is effective when applied to a superconducting device provided in a magnet device and a magnet device.

REFERENCE SIGNS LIST 1 superconducting device 2 magnet device 3, 3a magnet section 4 superconducting bulk section 5 magnetic circuit 6 axis 7 annular path 8 space 9 magnetic flux 11 axis line 21 refrigerator 22 body section 23 cold head 31 MRI apparatus 32 subject 33 static magnetic field generation Magnet 34 Gradient magnetic field coil 35 Gradient magnetic field power supply 36 RF transmission coil 37 RF transmission section 38 RF reception coil 39 Signal processing section 41 Measurement control section 51 to 55 Hall elements CP1 to CP8 Cylindrical section DM1 Outer diameter DM2 Inner diameter EX1 Extension section GP1 Gap HT1 Length LN1 to LN3 Peripheral length MG1 to MG4 Magnet PL1, PL4 N pole PL2, PL3 S pole PP1 Plate RG1 Region SB1 to SB7 Member SG1 to SG4 Member group SP1 Spacer TL2, TL3 Base

Claims (17)

In a superconducting device provided in a magnet device having a magnet unit that generates a magnetic field,
a first superconducting bulk body group including a plurality of first superconducting bulk bodies provided outside the magnet unit;
The magnet part is
a first magnetic pole having a first polarity;
a second magnetic pole having a second polarity opposite the first polarity;
has
Said first magnetic pole, said first superconducting bulk group and said second magnetic pole are arranged along an annular path about a first axis, said first magnetic pole, said first superconducting bulk group and said second magnetic pole. are arranged in the order of
each of the plurality of first superconducting bulk bodies traps a magnetic field in a superconducting state;
The plurality of first superconducting bulk bodies each capturing a magnetic field and the magnet portion form a closed circuit through which magnetic flux passes, and along the annular path from the first magnetic pole to the first superconducting a magnetic circuit is formed through the bulk bodies and back to the second magnetic pole;
Each of the plurality of first superconducting bulk bodies contained in the first superconducting bulk body group captures a magnetic field in a superconducting state, thereby arranged along the annular path such that emitted magnetic flux sequentially passes through the plurality of first superconducting bulk bodies and returns to the second magnetic pole;
the first superconducting bulk body group is adjacent to the first magnetic pole and not adjacent to the second magnetic pole along the annular path;
Out of the plurality of first superconducting bulk bodies, the first superconducting bulk body arranged on the side closest to the first magnetic pole along the circular path has an outer circumference length of a cross section perpendicular to the circular path: , of the first superconducting bulk body arranged on the side opposite to the side closest to the first magnetic pole along the annular path, among the plurality of first superconducting bulk bodies, of the cross section perpendicular to the annular path A superconducting device that is longer than its perimeter. A superconducting device according to claim 1,
the magnet unit has a first magnet and a second magnet spaced apart from each other along the annular path;
The first magnet is
the first magnetic pole;
a third magnetic pole having the second polarity;
has
The second magnet is
a fourth magnetic pole having the first polarity;
the second magnetic pole;
has
The first magnetic pole, the first superconducting bulk group, the second magnetic pole, the fourth magnetic pole and the third magnetic pole are arranged along the annular path to form the first magnetic pole and the first superconducting bulk group. , the second magnetic pole, the fourth magnetic pole, and the third magnetic pole are arranged in this order,
A superconducting device, wherein a space between the first magnet and the second magnet is open. In the superconducting device according to claim 1 or 3,
The length of the outer circumference of each of the plurality of first superconducting bulk bodies in the cross section perpendicular to the annular path is from the side closest to the first magnetic pole to the side closest to the first magnetic pole along the annular path. A superconducting device decreasing in order of arrangement of said plurality of first superconducting bulk bodies toward opposite sides. A superconducting device according to claim 1, 3 or 7,
a second superconducting bulk body group including a plurality of second superconducting bulk bodies arranged along the annular path;
each of the plurality of second superconducting bulk bodies traps a magnetic field in a superconducting state;
The first magnetic pole, the first superconducting bulk body group, the second superconducting bulk body group and the second magnetic pole are arranged along the annular path to form the first magnetic pole, the first superconducting bulk body group, Arranged in the order of the second superconducting bulk body group and the second magnetic pole,
the magnetic circuit is formed along the annular path from the first magnetic pole through the first superconducting bulk body group and the second superconducting bulk body group in order and back to the second magnetic pole;
The plurality of first superconducting bulk bodies contained in the first superconducting bulk body group and the plurality of second superconducting bulk bodies contained in the second superconducting bulk body group are formed from the plurality of first superconducting bulk bodies Each of the superconducting bulk body and the plurality of second superconducting bulk bodies captures a magnetic field in a superconducting state, so that the magnetic flux emitted from the first magnetic pole is transferred to the plurality of first superconducting bulk bodies and the plurality of superconducting bulk bodies. arranged along the annular path sequentially through the second superconducting bulk of the and back to the second pole;
the second superconducting bulk body group is adjacent to the second magnetic pole along the annular path;
Of the plurality of second superconducting bulk bodies, the second superconducting bulk body arranged on the side closest to the second magnetic pole along the circular path has an outer circumference length of a cross section perpendicular to the circular path: , of the second superconducting bulk body arranged on the side opposite to the side closest to the second magnetic pole along the annular path, among the plurality of second superconducting bulk bodies, of the cross section perpendicular to the annular path A superconducting device that is longer than its perimeter. A superconducting device according to claim 8,
Each of the plurality of second superconducting bulk bodies has an outer circumference length of a cross section perpendicular to the annular path along the annular path from the side closest to the second magnetic pole to the side closest to the second magnetic pole. A superconducting device, decreasing in order of arrangement of said plurality of second superconducting bulk bodies toward opposite sides. A superconducting device according to any one of claims 1, 3 or 7 to 9,
each of the plurality of first superconducting bulk bodies includes a tubular first tubular portion centered on an axis along the annular path;
Each of the plurality of first superconducting bulk bodies captures a magnetic field along the axis while each of the plurality of first superconducting bulk bodies is in a superconducting state. a superconducting device arranged along said annular path to return to said second magnetic pole sequentially through a plurality of first cylinders respectively contained in each of said first superconducting bulk bodies of . A superconducting device according to any one of claims 1, 3 or 7 to 9,
each of the plurality of first superconducting bulk bodies includes an extension extending along the annular path;
Each of the plurality of first superconducting bulk bodies captures a magnetic field along the annular path while each of the plurality of first superconducting bulk bodies is in a superconducting state. A superconducting device arranged along said annular path to sequentially return to said second magnetic pole through a plurality of extensions respectively included in each of a plurality of first superconducting bulk bodies. A superconducting device according to any one of claims 1, 3 or 7 to 11,
a third superconducting bulk body including a cylindrical second cylindrical portion surrounding the magnet portion;
the third superconducting bulk body captures a magnetic field in a superconducting state;
A superconducting device in which the magnetic circuit is formed by the plurality of first superconducting bulk bodies each capturing a magnetic field, the third superconducting bulk body capturing a magnetic field, and the magnet section. . A superconducting device according to any one of claims 1, 3 or 7 to 12,
A superconducting device, wherein the first superconducting bulk body is made of iron pnictide or magnesium diboride. 14. A superconducting device according to any one of claims 1, 3 or 7 to 13,
Having a cooling part for cooling the first superconducting bulk body,
By cooling the first superconducting bulk body in the cooling unit, the first superconducting bulk body enters a superconducting state,
The first superconducting bulk body is made of a second-class superconductor,
A superconducting device, wherein the first superconducting bulk body captures a magnetic field above a lower critical magnetic field and below an upper critical magnetic field in a superconducting state by pinning the magnetic flux. a superconducting device according to any one of claims 1, 3 or 7 to 14;
the magnet unit;
A magnet device. In a superconducting device provided in a magnet device having a magnet unit that generates a magnetic field,
a first superconducting bulk body group including a plurality of first superconducting bulk bodies provided outside the magnet unit;
The magnet part is
a first magnetic pole having a first polarity;
a second magnetic pole having a second polarity opposite the first polarity;
has
Said first magnetic pole, said first superconducting bulk group and said second magnetic pole are arranged along an annular path about a first axis, said first magnetic pole, said first superconducting bulk group and said second magnetic pole. are arranged in the order of
each of the plurality of first superconducting bulk bodies traps a magnetic field in a superconducting state;
The plurality of first superconducting bulk bodies each capturing a magnetic field and the magnet portion form a closed circuit through which magnetic flux passes, and along the annular path from the first magnetic pole to the first superconducting a magnetic circuit is formed through the bulk bodies and back to the second magnetic pole;
each of the plurality of first superconducting bulk bodies includes an extension extending along the annular path;
Each of the plurality of first superconducting bulk bodies captures a magnetic field along the annular path while each of the plurality of first superconducting bulk bodies is in a superconducting state. A superconducting device arranged along said annular path to sequentially return to said second magnetic pole through a plurality of extensions respectively included in each of a plurality of first superconducting bulk bodies. 24. A superconducting device according to claim 23, wherein
the magnet unit has a first magnet and a second magnet spaced apart from each other along the annular path;
The first magnet is
the first magnetic pole;
a third magnetic pole having the second polarity;
has
The second magnet is
a fourth magnetic pole having the first polarity;
the second magnetic pole;
has
The first magnetic pole, the first superconducting bulk group, the second magnetic pole, the fourth magnetic pole and the third magnetic pole are arranged along the annular path to form the first magnetic pole and the first superconducting bulk group. , the second magnetic pole, the fourth magnetic pole, and the third magnetic pole are arranged in this order,
A superconducting device, wherein a space between the first magnet and the second magnet is open. A superconducting device according to claim 23 or 24,
Having a second superconducting bulk body including a tubular portion surrounding the magnet portion,
the second superconducting bulk body captures a magnetic field in a superconducting state;
A superconducting device in which the magnetic circuit is formed by the plurality of first superconducting bulk bodies each capturing a magnetic field, the second superconducting bulk body capturing a magnetic field, and the magnet section. . A superconducting device according to any one of claims 23 to 25,
A superconducting device, wherein the first superconducting bulk body is made of iron pnictide or magnesium diboride. A superconducting device according to any one of claims 23 to 26,
Having a cooling part for cooling the first superconducting bulk body,
By cooling the first superconducting bulk body in the cooling unit, the first superconducting bulk body enters a superconducting state,
The first superconducting bulk body is made of a second-class superconductor,
A superconducting device, wherein the first superconducting bulk body captures a magnetic field above a lower critical magnetic field and below an upper critical magnetic field in a superconducting state by pinning the magnetic flux. A superconducting device according to any one of claims 23 to 27;
the magnet unit;
A magnet device.

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