JP7663166B2 - Magnetic field generating device, nuclear magnetic resonance device, and magnetic field generating method - Google Patents

Description

The present invention relates to a magnetic field generating device, a nuclear magnetic resonance device, and a magnetic field generating method.

Analysis techniques and imaging diagnostic techniques that utilize the nuclear magnetic resonance phenomenon have already been put to practical use, and their use has been increasing in recent years. Nuclear magnetic resonance devices that utilize these techniques include nuclear magnetic resonance analysis devices (hereinafter, simply referred to as "NMR analysis devices.""NMR" is an abbreviation for "Nuclear Magnetic Resonance") and magnetic resonance imaging devices (hereinafter, simply referred to as "MRI devices.""MRI" is an abbreviation for "Magnetic Resonance Imaging")). Nuclear magnetic resonance devices use a magnetic field generating device that utilizes a uniform static magnetic field space.
As a means for generating a static magnetic field for use in a nuclear magnetic resonance apparatus, a method is known that uses a superconducting strong magnetic field generator (such as a superconducting bulk magnet in which a superconductor is formed into a block), which can generate a stronger magnetic field than a magnetic field generator that uses a permanent magnet (see Patent Document 1).

For example, Patent Document 1 describes a magnetic field generating device that has a magnetic pole part equipped with a superconducting bulk magnet, and in a superconducting state, the magnetic field generated from the superconducting bulk magnet forms a magnetic field having a concave magnetic field distribution on the magnetic pole face of the magnetic pole part. Furthermore, Figures 1 and 2 of Patent Document 1 describe a magnetic field generating device that has opposing magnetic pole parts, in which an iron plate with no through holes is placed on the magnetic pole face of one of the magnetic pole parts, and no ferromagnetic material is placed on the magnetic pole face of the other magnetic pole part.

JP 2015-167576 A

Generally, superconducting strong magnetic field generators such as superconducting bulk magnets are characterized by forming a gradient magnetic field in which the magnetic field strength is greatest in the center. However, Patent Document 1 describes that even a magnetic field generating device that uses a superconducting bulk magnet as a single magnetic pole portion, or two parallel and coaxial magnetic pole portions, can form a uniform high magnetic field.
However, the magnetic field generating device described in Patent Document 1 could only form a uniform magnetic field surface at a specific distance from a single magnetic pole part equipped with a superconducting bulk magnet, or at approximately the midpoint between two magnetic pole parts equipped with parallel and coaxial superconducting bulk magnets. Therefore, depending on the shape and size of the object to be measured, it may still be difficult to place the measurement site on a uniform magnetic field surface (uniform magnetic field space). Therefore, there was a demand for further improving the design freedom of the magnetic field generating device by generating a uniform high magnetic field over a wide range.

The problem that this invention aims to solve is to provide a magnetic field generating device that can generate a uniform high magnetic field over a wide area.

As a result of intensive research by the inventors to solve the above problem, it was discovered that by arranging a ferromagnetic body having a shape that defines a through hole so that the through hole is located in the center of the magnetic pole part equipped with a superconducting strong magnetic field generator, and by positioning the through hole in the center of the direction parallel to the magnetic pole face of the magnetic field generated from the superconducting strong magnetic field generator, it is possible to generate a uniform high magnetic field over a wide range. The configuration of the present invention, which is a specific means for solving the above problem, and a preferred configuration of the present invention are described below.

[1] A magnetic pole part having a superconducting strong magnetic field generator;
A ferromagnetic body having a shape that defines a through hole,
A main surface of the ferromagnetic body is disposed in a direction substantially parallel to the magnetic pole surface of the magnetic pole portion,
A magnetic field generating device in which, in a superconducting state, a through hole is located at the center, in a direction parallel to a pole face, of a magnetic field generated from a superconducting strong magnetic field generator.
[2] The magnetic field generating device according to [1], wherein the ferromagnetic material is iron, nickel, cobalt, an alloy containing one or more of these, or ferrite.
[3] The magnetic field generating device according to [1] or [2], wherein the magnetic pole surface and the ferromagnetic body are arranged with a gap therebetween.
[4] A magnetic field generating device according to any one of [1] to [3], wherein an end of the ferromagnetic body extends to the same position as the end of the magnetic pole face or to the outside or inside of the end of the magnetic pole face in a direction approximately parallel to the magnetic pole face.
[5] The shape of the through hole is approximately circular in a direction approximately parallel to the magnetic pole surface, and
The magnetic field generating device according to any one of [1] to [4], wherein the main surface of the ferromagnetic body is a substantially circular plane whose central axis coincides with the through hole.
[6] The magnetic field generating device according to any one of [1] to [5], wherein the magnetic pole face is a substantially circular flat surface having a diameter of 10 to 1000 mm.
[7] The magnetic field generating device according to any one of [1] to [6], wherein the shape of the through hole is a substantially circular shape having a diameter of 4 to 6 mm in a direction substantially parallel to the magnetic pole face.
[8] The magnetic field generating device according to any one of [1] to [7], wherein the ferromagnetic body is a laminate including n ferromagnetic bodies, n being a natural number, counted from the side closest to the magnetic pole portion.
[9] The magnetic field generating device according to [8], wherein, in a direction approximately parallel to the magnetic pole face, m is an integer between 2 and n, and an end of the m-th ferromagnetic body from the side closest to the magnetic pole portion is located more inside than an end of the (m-1)-th ferromagnetic body.
[10] The magnetic field generating device according to [8] or [9], wherein the ends of the through holes defined by each of the n ferromagnetic bodies are positioned at approximately the same position.
[11] The magnetic field generating device according to any one of [1] to [10], wherein in a superconducting state, the magnetic field generated from the superconducting strong magnetic field generator forms a uniform magnetic field surface with a substantially uniform magnetic field distribution in a direction parallel to the magnetic pole face in a region having a thickness of 0.4 mm or more in the normal direction to the magnetic pole face.
[12] The magnetic field generating device according to [11], wherein the uniform magnetic field surface is formed at a position 0 mm or more away from a main surface of the ferromagnetic body opposite the magnetic pole surface in a normal direction to the magnetic pole surface.
[13] The magnetic field generating device according to any one of [1] to [12], wherein the magnetic pole faces are arranged in a substantially horizontal direction.
[14] The center of the magnetic field generated by the superconducting strong magnetic field generator in a direction parallel to the magnetic pole face is the center of the magnetic pole face,
The magnetic field generating device according to any one of [1] to [13], wherein the central portion of the magnetic pole face is a region on the long axis of the magnetic pole face that is 30% to 70% of the distance from one end of the magnetic pole face.
[15] The magnetic field generating device according to any one of [1] to [14], wherein the superconducting strong magnetic field generator is one selected from the group consisting of a superconducting bulk magnet; a bulk magnet obtained by stacking laminated tape wires; a laminate of a plurality of superconducting thin films, a plurality of superconducting thick films, or a laminate of a thin superconducting film and a thick superconducting film; or a pancake coil made of a superconducting wire or tape; or a combination thereof.
[16] A nuclear magnetic resonance apparatus comprising the magnetic field generating device according to any one of [1] to [15].
[17] A magnetic field generating method, comprising: using the magnetic field generating device according to any one of [1] to [15] to generate a uniform magnetic field surface having a substantially uniform magnetic field distribution in a direction parallel to the magnetic pole face; and generating a magnetic field in a region having a thickness of 0.4 mm or more in the normal direction to the magnetic pole face.
[18] The magnetic field generating method according to [17], in which the magnetic field generating device according to any one of [1] to [15] is used as a single magnetic pole part, and no other magnetic pole parts are used.

The present invention provides a magnetic field generating device that can generate a uniform high magnetic field over a wide range.

Fig. 1(A) is a schematic cross-sectional view of an example of a conventional magnetic field generating device, and Fig. 1(B) is a schematic cross-sectional view of an example of a magnetic field generating device of the present invention. Fig. 2(A) is a schematic diagram of the positional relationship between the main surface 11a of the ferromagnetic body 11, the through hole 12, and the measurement range 42 when the magnetic field generating device is viewed from above in the normal direction of the magnetic pole face (+z-axis direction). Fig. 2(B) is an enlarged view of the measurement range 42 in Fig. 2(A). 3(A), 3(B) and 3(C) are graphs showing the relationship between magnetic field strength and the coordinates y=-10 to 30 for five series z=2.2 to 3.0 when x=10 using the magnetic field generating devices of Examples 1 to 3, respectively. 4(A), 4(B) and 4(C) are graphs showing the relationship between magnetic field strength and the coordinates y=0 to 10 for five series z=2.2 to 3.0 when x=10 using the magnetic field generating devices of Examples 1 to 3, respectively. 5(A), 5(B) and 5(C) are graphs in which the distribution of magnetic field strength in the cases of FIG. 4(A), FIG. 4(B) and FIG. 4(C), respectively, is converted into the uniformity of the magnetic field strength.

The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment or a specific example, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range including the numerical values before and after "to" as the lower and upper limits.
In this specification, angles, lengths, shapes, etc. expressed using "approximately" may include an error that is acceptable in the technical field of magnetic field generating devices. For example, if two lines or planes are approximately parallel, the angle at which the two lines or planes intersect may be within ±10°, preferably within ±3°, and preferably within ±1°. If two lines or planes are approximately perpendicular, the angle at which the two lines or planes intersect may be within 90°±10°, preferably within 90°±3°, and preferably within 90°±1°.

[Magnetic field generator]
The magnetic field generating device of the present invention has a magnetic pole section equipped with a superconducting strong magnetic field generator, and a ferromagnetic body shaped to define a through hole, with the main surface of the ferromagnetic body arranged in a direction approximately parallel to the magnetic pole face of the magnetic pole section, and in a superconducting state, the through hole is located in the center, parallel to the magnetic pole face, of the magnetic field generated from the superconducting strong magnetic field generator.
With this configuration, the magnetic field generating device of the present invention can generate a uniform high magnetic field over a wide range.
Generally, when a ferromagnetic body is placed on a magnetic pole part, the magnetic field is shielded. Here, when a very strong magnetic field is applied to a ferromagnetic body by a magnetic pole part equipped with a superconducting bulk magnet, the magnetic field exceeds the saturation magnetic flux density, which is the limit of the magnetic flux density, and the magnetic field leaks to the back side of the ferromagnetic body. The shape of the magnetic field leaked to the back side of the ferromagnetic body is completely different from the original magnetic field shape (convex type), and a concave magnetic field can be formed. Although not bound by any theory, according to the present invention, by applying a very strong magnetic field to a ferromagnetic body having a shape that defines a through hole and magnetizing it, a magnetic field uniform surface that is neither convex nor concave and is uniform over a wide range in a direction approximately parallel to the magnetic pole surface can be formed, and the magnetic field uniform surface becomes uniform over a wide range in a direction approximately perpendicular to the magnetic pole surface. This phenomenon was not predicted at all in the past, and was a groundbreaking discovery that can easily achieve further improvement in the design freedom of a magnetic field generator by generating a uniform high magnetic field over a wide range. The shape of the magnetic field that is generated as a result of the mutual influence of the shape of the magnetic field leaking to the back side of a ferromagnetic material with a through hole and the shape of the magnetic field passing through a through hole placed in the center of the magnetic field generated by a superconducting strong magnetic field generator had not previously been predicted.
In addition, in [0076] of JP 2015-167576 A, it is merely stated that a magnetic plate as a magnetic field shielding member shields a part of the magnetic field generated by the superconducting bulk magnet, forming a concave magnetic field distribution. The present invention can generate a uniform high magnetic field over a wide range, which is remarkably different from what can be predicted from this description.
A preferred embodiment of the magnetic field generating device of the present invention will now be described.

<Overall configuration of magnetic field generating device>
A preferred embodiment of the overall configuration of the magnetic field generating device of the present invention will be described with reference to the drawings. Fig. 1(B) is a schematic cross-sectional view of an example of the magnetic field generating device of the present invention. In detail, the magnetic field generating device of the embodiment shown in Fig. 1(B) is a schematic cross-sectional view including the width direction x of the magnetic pole surface and the normal direction z of the magnetic pole surface.
The magnetic field generator of the embodiment shown in Fig. 1(B) has a magnetic pole part 1 equipped with a superconducting strong magnetic field generator 2, and two ferromagnetic bodies 11 shaped to define a through hole 12, with the main surface of the ferromagnetic body 11 disposed in a direction substantially parallel to the magnetic pole face 10 of the magnetic pole part 1, and in a superconducting state, the through hole 12 is located at the center, in a direction parallel to the magnetic pole face 10, of the magnetic field generated from the superconducting strong magnetic field generator 2. Fig. 1(B) shows an embodiment in which the superconducting strong magnetic field generator 2 is a superconducting bulk magnet, but the present invention is not limited to this embodiment.
1B shows an embodiment in which the center of the magnetic field generated from the superconducting strong magnetic field generator 2 in a direction parallel to the magnetic pole surface 10 is the center of the magnetic pole surface 10, but the present invention is not limited to this embodiment. For example, a magnetic pole part whose shape is not similar to the shape of the superconducting strong magnetic field generator may be used, so that the center of the magnetic pole surface does not coincide with the center of the superconducting strong magnetic field generator. Below, an embodiment in which the center of the magnetic field generated from the superconducting strong magnetic field generator 2 in a direction parallel to the magnetic pole surface 10 is the center of the magnetic pole surface 10 will be described.
The magnetic field generator shown in Fig. 1(B) is different from the conventional magnetic field generator shown in Fig. 1(A) in that a ferromagnetic body having a through hole in the center is provided on one surface above the magnetic pole face in the normal direction z. In Fig. 1(B), a circular iron plate having a circular through hole in the center is used as the ferromagnetic body having a through hole in the center.
In the magnetic field generating device of the embodiment shown in FIG. 1(B), the magnetic pole surface 10 and the ferromagnetic body 11 are arranged with a gap therebetween, and more specifically, a spacer 21 is arranged between the magnetic pole surface 10 and the ferromagnetic body 11.
In the magnetic field generating device of the embodiment shown in FIG. 1(B), when the magnetic field generated from the superconducting strong magnetic field generator in the superconducting state is measured at a measurement surface 41 at an arbitrary height in the normal direction z of the magnetic pole face, a uniform magnetic field surface is formed in which the magnetic field distribution is approximately uniform in the direction parallel to the magnetic pole face in a region of a specific thickness.
Preferred embodiments of each part constituting the magnetic field generating device of the present invention will now be described.

<Magnetic pole part>
In the present invention, the magnetic pole part comprises a superconducting strong magnetic field generator.
The internal configuration of the magnetic pole part is not particularly limited except that it has a superconducting strong magnetic field generator, and a known configuration can be adopted. For example, the configuration described in [0045] to [0054] of JP 2015-167576 A can be adopted, and the contents of this publication are incorporated herein by reference.

A specific preferred embodiment of the magnetic pole part will be described with reference to Fig. 1(B). In Fig. 1(B), the magnetic pole part 1 comprises a superconducting strong magnetic field generator 2, a vacuum vessel that contains the superconducting strong magnetic field generator 2 in a vacuum state, and a magnetic pole surface 10 that is formed by at least a part of the outer surface of the magnetic pole part. The entire magnetic pole part 1 is covered by a vacuum vessel, inside which the superconducting strong magnetic field generator 2, its holder 3, and a yoke 4 (yoke iron) are arranged in a substantially vacuum state. The main surface of the superconducting strong magnetic field generator 2 is arranged in a direction approximately parallel to the magnetic pole surface 10 of the magnetic pole part 1.
The superconducting strong magnetic field generator 2 and its holder 3 , as well as the yoke 4 (yoke iron) are placed on a heat transfer body 9 and fixed with set screws 7 via height supports 5 and lateral supports 6 .
A thermometer 8 is disposed at an arbitrary position on the heat transfer body 9 .
Furthermore, the magnetic pole part 1 preferably has a cooler (not shown) that can be connected to the heat transfer body 9 to cool the superconducting strong magnetic field generator 2, and a compressor (not shown) that drives this cooler.

(Superconducting strong magnetic field generator)
The superconducting strong magnetic field generator is preferably one selected from the group consisting of a superconducting bulk magnet, a bulk magnet obtained by stacking laminated tape wires (tape pieces), a laminate of a plurality of superconducting thin films, a plurality of superconducting thick films, or a laminate of a thin superconducting thin film and a thick superconducting film, or a pancake coil made of superconducting wire or tape, or a combination thereof. Among these, a superconducting bulk magnet is more preferable.
The superconducting bulk magnet is preferably a high-temperature superconducting bulk magnet. The superconducting bulk magnet is preferably a rare earth 123-based superconductor synthesized in a block by a melting method. In addition, the materials described in [0015] to [0016] of JP 2007-129158 A may be used, the contents of which are incorporated herein by reference.
The superconducting strong magnetic field generator is cooled by a refrigerator under vacuum insulation in a vacuum vessel to be in a superconducting state. In this superconducting state, a magnetic field is applied by a pulse magnetization method or the like to the superconducting strong magnetic field generator, and the magnetic field is captured by the superconducting strong magnetic field generator, thereby making it possible to stably generate a strong magnetic field.
The shape of the superconducting strong magnetic field generator is not particularly limited, but it is preferable that the superconducting strong magnetic field generator has a substantially cylindrical outer shape.
The central axis of the superconducting strong magnetic field generator preferably coincides (almost) with the central axis of the pole face, and also preferably coincides (almost) with the central axis of the through hole.

(magnetic pole face)
There is no particular restriction on the shape or size of the magnetic pole surface. From the viewpoint of generating a uniform high magnetic field over a wide range, the shape of the magnetic pole surface is preferably a regular polygon or a substantially circular plane, and more preferably a substantially circular plane. From the viewpoint of miniaturizing the magnetic field generating device of the present invention, particularly making it a tabletop device, the size of the magnetic pole surface is preferably 10 to 1000 mm in terms of the long axis (meaning the longest line segment formed by any two points on the periphery of a certain shape. However, if it is a circle, it means the diameter) of the magnetic pole surface, more preferably 20 to 500 mm, and particularly preferably 30 to 200 mm. In the present invention, it is preferable that the magnetic pole surface is a substantially circular plane with a diameter of 10 to 1000 mm. That is, it is preferable that the vacuum vessel of the magnetic pole portion has an overall substantially cylindrical outer shape.
In the present invention, it is preferable to arrange the magnetic pole face in a substantially horizontal direction. Since the magnetic field generating device of the present invention can form a uniform magnetic field surface with only a single magnetic pole part, by arranging the magnetic pole face in a substantially horizontal direction, the object to be measured can be arranged at any position in a substantially vertical direction. In particular, when the magnetic field generating device of the present invention is used on a tabletop or the like, arranging the magnetic pole face in a substantially horizontal direction can significantly increase the design freedom of the position of the object to be measured compared to arranging the magnetic pole face in a substantially vertical direction.
In the present invention, in the superconducting state, the through hole of the ferromagnetic material is located at the center of the magnetic field generated by the superconducting strong magnetic field generator in the direction parallel to the pole face. The center of the magnetic field generated by the superconducting strong magnetic field generator in the direction parallel to the pole face is preferably the center of the pole face. In other words, the through hole of the ferromagnetic material is preferably located at the center of the pole face. From the viewpoint of being able to generate a uniform high magnetic field over a wide range, the center of the pole face referred to here is preferably an area on the major axis of the pole face that is 30% to 70% of the distance from one end of the pole face, more preferably an area that is 40% to 60%, and particularly preferably an area that is 45% to 55% of the distance.

<Ferromagnetic material>
The magnetic field generating device of the present invention has a ferromagnetic body shaped to define a through hole, and the main surface of the ferromagnetic body is arranged in a direction approximately parallel to the magnetic pole face of the magnetic pole portion, and in a superconducting state, the through hole is located in the center, in a direction parallel to the magnetic pole face, of the magnetic field generated from the superconducting strong magnetic field generator.

There are no particular limitations on the material of the ferromagnetic body, and any known ferromagnetic body can be used. In the present invention, the ferromagnetic body is preferably iron, nickel, cobalt, or an alloy containing one or more of these, or ferrite, more preferably iron or an alloy containing at least iron, or ferrite, and even more preferably iron.

There is no particular restriction on the outer shape or size of the ferromagnetic body. From the viewpoint of generating a uniform high magnetic field over a wide range, the outer shape of the ferromagnetic body is preferably a regular polygon or a substantially circular plane, more preferably a substantially circular plane. From the viewpoint of miniaturizing the magnetic field generating device of the present invention, particularly making it a tabletop device, the size of the outer shape of the ferromagnetic body is preferably 10 to 1000 mm, more preferably 20 to 500 mm, and particularly preferably 30 to 200 mm, in terms of the length of the major axis of the outer shape of the ferromagnetic body. In the present invention, it is preferable that the outer shape of the ferromagnetic body is a substantially circular plane with a diameter of 10 to 1000 mm. That is, it is preferable that the outer shape of the ferromagnetic body is a substantially cylindrical outer shape, and has a shape that defines a through hole in the center.
The thickness of the ferromagnetic body is preferably 0.5 to 5.0 mm, and more preferably 1.0 to 2.0 mm from the viewpoint of generating a uniform high magnetic field over a wide range. When two or more ferromagnetic bodies are used, it is preferable that the thickness of each ferromagnetic body is in the above range.
In the present invention, it is preferable that the end (outer periphery) of the ferromagnetic body extends to the same position as the end of the pole face, or to the outside or inside of the pole face in a direction approximately parallel to the pole face. With this configuration, only when the saturation magnetic flux density is exceeded, the magnetic field from other than the through hole leaks to the back side of the ferromagnetic body, making it easier to generate a uniform high magnetic field over a wide range. From the viewpoint of ease of attachment and detachment of the ferromagnetic body from the pole part when there is no spacer between the pole face and the ferromagnetic body, it is preferable that the end (outer periphery) of the ferromagnetic body extends to the outside of the end of the pole face. Even in the case where the end (outer periphery) of the ferromagnetic body extends to the inside of the end of the pole face, that is, the length of the major axis of the outer periphery shape of the ferromagnetic body is smaller than the length of the major axis of the pole face, the effect of the present invention can be obtained, and it is preferable from the viewpoint of operability such as attachment and detachment of the configuration of the pole part.

The number of ferromagnetic bodies may be one or more. When two or more ferromagnetic bodies are used, it is preferable that the two or more ferromagnetic bodies are not arranged in the same plane, and that they are arranged by stacking them in the direction perpendicular to the magnetic pole face. That is, in the present invention, it is preferable that the ferromagnetic body is a laminate including n ferromagnetic bodies from the side closer to the magnetic pole part, where n is a natural number.
The number of ferromagnetic bodies is preferably 2 to 10, more preferably 2 to 4, and particularly preferably 2.
In the present invention, it is preferable that the end of the m-th ferromagnetic body from the side closest to the magnetic pole portion is located inside the end of the m-1-th ferromagnetic body, where m is an integer between 2 and n, in the direction approximately parallel to the magnetic pole surface. Without being bound by any theory, by making the end of the m-th ferromagnetic body from the side closest to the magnetic pole portion inside the end of the m-1-th ferromagnetic body (the ferromagnetic body farther from the magnetic pole portion), a phenomenon in which a repulsive force is generated between the ferromagnetic bodies and the positions of the through holes partitioned by each ferromagnetic body are less likely to occur compared to when they are located at the same position or on the outside.
On the other hand, it is preferable that the ends of the through holes defined by the n ferromagnetic bodies are located at approximately the same positions, from the viewpoint of generating a uniform high magnetic field over a wide range.
A spacer may be disposed between two or more ferromagnetic bodies.

(Through hole)
There is no particular restriction on the shape or size of the through hole. From the viewpoint of generating a uniform high magnetic field over a wide range, the shape of the through hole is preferably a regular polygon or a substantially circular plane, and more preferably a substantially circular plane. From the viewpoint of miniaturizing the magnetic field generating device of the present invention, particularly making it a tabletop device, the size of the through hole is preferably a major axis of the through hole of 1.0 to 100 mm, more preferably 2.0 to 10 mm, and particularly preferably 3.5 to 6.5 mm. Furthermore, from the viewpoint of generating a uniform high magnetic field over a wide range, it is more particularly preferable that the major axis of the through hole is 4.5 to 5.5 mm. In the present invention, it is preferable that the shape of the through hole is substantially circular in the direction substantially parallel to the magnetic pole surface. It is more preferable that the shape of the through hole is substantially circular with a diameter of 4 to 6 mm, and particularly preferably substantially circular with a diameter of 4.5 to 5.5 mm.
In the present invention, the through hole of the ferromagnetic body is preferably located in the center of the ferromagnetic body, which is preferably a region that is 30% to 70% of the distance from one end of the ferromagnetic body on the long axis of the ferromagnetic body, more preferably a region that is 40% to 60% of the distance, and particularly preferably a region that is 45% to 55% of the distance, from the viewpoint of generating a uniform high magnetic field over a wide range.
In the present invention, it is preferable that the main surface of the ferromagnetic body is a substantially circular flat surface whose central axis (almost) coincides with that of the through hole.

(Spacer)
In the present invention, it is preferable that the magnetic pole surface and the ferromagnetic body are arranged with a gap therebetween from the viewpoint of generating a uniform high magnetic field over a wide range, but for example, it is preferable that a spacer is arranged between the magnetic pole surface 10 and the ferromagnetic body 11. The gap between the magnetic pole surface and the ferromagnetic body, for example the thickness of the spacer, is preferably 0 to 2.0 mm, more preferably 0 to 0.4 mm. The effect of the present invention can be achieved even if the magnetic pole surface and the ferromagnetic body are arranged at a certain distance. The provision of the spacer is preferable because it can be effective in some cases in that the magnetic field strength can be adjusted by adjusting the distance between the magnetic pole surface and the ferromagnetic body to adjust the uniform magnetic field surface. In addition, it is preferable from the viewpoint of making it easy to attach and detach the ferromagnetic body from the magnetic pole part that the end (outer periphery) of the spacer is at the same position as the end of the magnetic pole surface or extends to the outside beyond the end. Therefore, since there is no problem in the configuration even if this spacer is not provided, the minimum value is set to 0. There is no particular restriction on the material of the spacer as long as it is not a ferromagnetic material (so-called non-magnetic material), and for example, cloth can be used.

<Magnetic Field>
In the present invention, in the superconducting state, the through hole of the ferromagnetic material is located in the center of the magnetic field generated from the superconducting strong magnetic field generator in the direction parallel to the magnetic pole face. From the viewpoint of generating a uniform high magnetic field over a wide range, the center of the magnetic field referred to here is preferably an area on the long axis of the superconducting strong magnetic field generator that is 30% to 70% of the distance from one end of the superconducting strong magnetic field generator, more preferably an area that is 40% to 60% of the distance, and particularly preferably an area that is 45% to 55% of the distance.
In the present invention, in the superconducting state, the magnetic field generated by the superconducting strong magnetic field generator preferably forms a uniform magnetic field surface having a substantially uniform magnetic field distribution in a direction parallel to the pole face in an area having a thickness of 0.4 mm or more in the normal direction to the pole face. The uniform magnetic field surface is more preferably formed in an area having a thickness of 0.6 mm or more in the normal direction to the pole face, particularly preferably formed in an area having a thickness of 0.8 mm or more, and even more particularly preferably formed in an area having a thickness of 1.0 mm or more.
The uniform magnetic field surface can be set to a uniform range of the distribution of the magnetic field strength according to the application of the magnetic field generating device. For example, when the change (difference) in the magnetic field strength of the measured values between two adjacent points in the z-axis direction is evaluated by dividing it by the larger magnetic field strength of the two, and expressed in parts per million (ppm), it is preferable to define the magnetic field surface as being 5000 ppm or less. When a more uniform distribution of the magnetic field strength is required, it is preferable to define the magnetic field surface as being 2000 ppm or less, and more preferably to define the magnetic field surface as being 1500 ppm or less.

The magnetic field generator of the present invention does not generate a uniform magnetic field surface in the internal space of the through-hole of the ferromagnetic material, but can form a uniform magnetic field surface in the open space outside the ferromagnetic material. In this respect, the magnetic field generator of the present invention is completely different from the embodiment described in the example of JP 2007-129158 A, which generates a uniform magnetic field surface in the hollow part of a hollow cylindrical superconducting strong magnetic field generator. In the present invention, it is preferable that the uniform magnetic field surface is formed at a position 0 mm or more away from the main surface of the ferromagnetic material on the side opposite the magnetic pole surface in the normal direction to the magnetic pole surface (0 mm means the same position as the main surface of the ferromagnetic material on the side opposite the magnetic pole surface), more preferably at a position 1.5 mm to 20 mm away, and particularly preferably at a position 2.0 mm to 15 mm away.

[Nuclear Magnetic Resonance Spectrometer]
The nuclear magnetic resonance apparatus of the present invention includes the magnetic field generating device of the present invention. There are no other particular limitations, and the magnetic field generating device of the present invention can be used as the magnetic pole of each known magnetic resonance apparatus.
In the nuclear magnetic resonance apparatus of the present invention, it is preferable to use the magnetic field generating device of the present invention as a single magnetic pole part and not use other magnetic pole parts.
The types of nuclear magnetic resonance apparatus include an NMR analyzer, an MRI apparatus, etc. As the nuclear magnetic resonance apparatus, the embodiment described in [0048] to [0049] of JP 2007-129158 A may be used, the contents of which are incorporated herein by reference.
There is no particular limitation on the method of extracting NMR signals using the magnetic field generating device of the present invention. For example, in order to perform spatial signal accumulation as NMR or MRI, after obtaining data on the magnetic field uniform surface, the object to be measured is scanned in the z-axis direction, or the magnetic pole surface is moved to scan the magnetic field uniform surface in the z-axis direction in the spatial direction, and the signal data at that time is accumulated and imaged, so that the spatial NMR signal can be extracted.

[Method of generating magnetic field]
The magnetic field generating method of the present invention is a magnetic field generating method that uses the magnetic field generating device of the present invention to generate a uniform magnetic field surface with a substantially uniform magnetic field distribution in a direction parallel to the magnetic pole face, and a magnetic field in a region having a thickness of 0.4 mm or more in the normal direction to the magnetic pole face.
In the magnetic field generating method of the present invention, it is preferable to use the magnetic field generating device of the present invention as a single magnetic pole part and not use other magnetic pole parts.
Other preferred aspects of the magnetic field generating method of the present invention are the same as the preferred aspects of the magnetic field generating apparatus of the present invention.

The present invention will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below.

[Examples 1 to 3]
A magnetic field generator as shown in Fig. 1(B) and in Table 1 below was prepared and used in Examples 1 to 3. Specifically, a magnetic field generator was used that had a magnetic pole part equipped with a superconducting bulk magnet and a ferromagnetic body shaped to define a through hole, with the main surface of the ferromagnetic body disposed in a direction approximately parallel to the magnetic pole face of the magnetic pole part, and with the through hole located in the center of the magnetic pole face.
The magnetic pole part used was a magnetic pole part equipped with a superconducting bulk magnet and other members inside a vacuum vessel having a diameter of 60 mm. That is, the diameter of the magnetic pole face of the magnetic pole part was 60 mm.
Between the magnetic pole surface of the magnetic pole portion and the first ferromagnetic material from the side closest to the magnetic pole surface, a spacer made of non-magnetic cloth having a thickness of 0.4 mm and an outer diameter of 60 mm was used.
In Example 1, the first ferromagnetic material used from the side closest to the pole face was a circular iron plate of JIS (Japanese Industrial Standard) SS400, with a thickness of 1.5 mm, an outer diameter of 60 mm, and a diameter (i.e., inner diameter) of a circular through hole of 6 mm. The second ferromagnetic material used from the side closest to the pole face in Example 1 was the same as the first ferromagnetic material in Example 1, except that the outer diameter was 50 mm.
In Example 2, the first ferromagnetic material used was a JIS SS400 iron plate with a thickness of 1.5 mm, an outer diameter of 60 mm, and a through hole diameter of 5 mm. The second ferromagnetic material used from the side closest to the pole face was the same as the first ferromagnetic material in Example 2, except that the outer diameter was 50 mm.
In Example 3, the first ferromagnetic material was a JIS SS400 iron plate with a thickness of 1.5 mm, an outer diameter of 60 mm, and a through hole diameter of 4 mm. The second ferromagnetic material from the side closest to the pole face was the same as the first ferromagnetic material in Example 3, except that the outer diameter was 50 mm.
In each example, the two ferromagnetic bodies were arranged so that their through holes were aligned with each other, and the central axis of the main surface of the ferromagnetic body was aligned with the central axis of the through hole. The end (outer periphery) of the first ferromagnetic body with an outer diameter of 60 mm was arranged at the same position as the end of the pole face with an outer diameter of 60 mm. No spacer was placed between the first and second ferromagnetic bodies.

<Distribution of magnetic field strength>
The distribution of the magnetic field strength was measured in the measurement range shown in Figure 2 (A) and Figure 2 (B). Specifically, a measurement range 42 of 40 mm x 40 mm was set on an arbitrary measurement surface 41 parallel to the magnetic pole surface above the main surface 11a of the second ferromagnetic body placed on the magnetic pole part, and the magnetic field strength in the z-axis direction was measured by scanning the Hall sensor. Note that the Hall sensor was installed in a hole (not shown) provided in a part of the holder 3 in Figure 1 (B) at a position corresponding to the through hole of the ferromagnetic body. Figure 2 (A) is a schematic diagram of the positional relationship between the main surface 11a of the ferromagnetic body 11, the through hole 12, and the measurement range 42 when the magnetic field generator is viewed from above (+z-axis direction) in the normal direction of the magnetic pole surface.
Fig. 2(B) is an enlarged view of the measurement range 42 in Fig. 2(A). As shown in Fig. 2(B), the x coordinate in the width direction of the pole face and the y coordinate in the vertical direction of the pole face were set to (x, y) = ((-10, -10) to (30, 30)) in the measurement range 42 (x and y are in mm). The coordinates of the through hole were located at a position where the central axis of the circular shape was approximately (x, y) = (10, 5).
The measurement pitch was 2 mm increments in the x-axis direction and 2 mm increments in the y-axis direction.
Furthermore, in the normal direction of the magnetic pole surface, i.e., in the z-axis direction, the main surface of the second ferromagnetic body opposite the magnetic pole surface was set to z=0, and measurements were made at a depth of 0.8 mm from the position of z=2.2 mm to the position of z=3.0 mm, with a measurement surface at 0.2 mm intervals, in a measurement range of 40 mm square. Among the results obtained, graphs of the relationship of magnetic field strength (magnetic field, unit: T) to coordinates of y=-10 to 30 for five series of z=2.2 to 3.0 when x=10 was used using the magnetic field generating devices of Examples 1 to 3 are shown in Figures 3(A), 3(B), and 3(C). Each graph is a regression curve obtained based on the measured values by the Hall sensor.
In addition, enlarged views of Figures 3(A), 3(B) and 3(C), specifically, graphs of the relationship between the magnetic field strength and the coordinates y = 0 to 10 for five series of z = 2.2 to 3.0 when x = 10 using the magnetic field generating devices of Examples 1 to 3, are shown in Figures 4(A), 4(B) and 4(C).

3(A), 3(B) and 3(C) show that the magnetic field strength changes in the z-axis direction differently for the magnetic field generating devices of Examples 1 to 3 using three types of iron plates with different diameters of through holes. Also, from these figures, it was found that the curves based on the plots of each series overlapped near y = 5 mm, meaning that the magnetic field distribution was uniform in the z-axis direction.
Furthermore, these were evaluated in more detail in Figures 4(A), 4(B) and 4(C) and the shapes of the graphs were compared. As a result, it was found that when the magnetic field generating device of Example 2 shown in Figure 4(B) (using two ferromagnetic bodies with a through hole diameter of 5 mm and a thickness of 1.5 mm) was used, the change in magnetic field strength in the z direction was the smallest and the overlapping magnetic field distribution was obtained at y = 4 mm.

<Uniformity of magnetic field strength>
The distribution of magnetic field strength in the cases of Figures 4(A), 4(B) and 4(C) was converted into the uniformity of magnetic field strength and shown in Figures 5(A), 5(B) and 5(C). Specifically, the uniformity of the distribution of magnetic field strength was evaluated by the following method: the change (difference) in magnetic field strength between two adjacent points in the z-axis direction was evaluated by dividing it by the larger magnetic field strength of the two, and expressed in parts per million (ppm).

The shapes of the graphs in Figures 5(A), 5(B) and 5(C) were compared. As a result, when the magnetic field generator of Example 2 shown in Figure 5(B) (through hole diameter 5 mm) was used, the uniformity of the magnetic field strength was the best in the range of y = 0 to 10 mm, with a maximum value of 3926 ppm (y = 0) or less. For example, the five data from z = 2.2 mm to 3 mm in Figure 5(B) almost overlap with one value in the vicinity of Y = 4 mm, and the best uniformity in the z-axis direction was obtained below the above value. In this case, when the magnetic field generator of Example 1 (through hole diameter 6 mm) was used, the maximum value was 12451 ppm, and when the magnetic field generator of Example 3 (through hole diameter 4 mm) was used, the maximum value was 5908 ppm. From the above, it was found that the best uniformity of the magnetic field strength in the z-axis direction was obtained when a ferromagnetic body with a through hole diameter of 5 mm was placed on the magnetic pole part. In other words, it was found that the magnetic field generator of Example 2 is the most capable of expanding the distribution of the uniformity of the magnetic field strength in the z-axis direction.

[Comparative Example 1]
A magnetic field generating device of Comparative Example 1 was produced in the same manner as in Example 1, except that a magnetic pole part having a circular magnetic pole face with a diameter of about 90 mm and a circular superconducting bulk magnet with a diameter of 65 mm was used, and only one circular ferromagnetic body with a thickness of 2.0 mm, an outer diameter of 20 mm, and no through holes was used. The magnetic field generating device of Comparative Example 1 has an aspect in which the end of the ferromagnetic body extends further inward than the end of the magnetic pole face in a direction approximately parallel to the magnetic pole face.

[Comparative Example 2]
A magnetic field generating device of Comparative Example 2 was produced in the same manner as Comparative Example 1, except that only one circular ferromagnetic body having a thickness of 2.0 mm, an outer diameter of 100 mm, and no through-holes was used.

<Uniformity of magnetic field strength distribution>
The distribution of magnetic field strength was obtained using the magnetic field generators of Comparative Examples 1 and 2 in the same manner as in Examples 1 to 3, except that the magnetic field strength in the z-axis direction was measured in a measurement range of 4 mm x 4 mm at each z value of z = 8.3 to 14.3. The distribution of magnetic field strength obtained was converted into the uniformity of magnetic field strength and is shown in Table 2 below.

From Table 2, it was found that in Comparative Example 1 and Comparative Example 2, which used a ferromagnetic material without through holes, the region in which a uniform high magnetic field can be generated is narrow. Specifically, in Comparative Examples 1 and 2, the uniformity of a 4 mm x 4 mm square in the xy plane was 1223 ppm and 2073 ppm at best when iron plates with outer diameters of 20 mm and 100 mm were used in the xy plane, respectively. In contrast, the uniformity in the z direction in Comparative Example 2, which used a 100 mm iron plate, was 7058.8 ppm at best even between adjacent 0.2 mm in the z direction of measurement, which was greater than the xy plane. In other words, when a ferromagnetic material without through holes was used, the uniformity in the z direction was inferior to that in the xy plane, and it was found that improvement in the uniformity in the z axis direction was necessary.
Furthermore, the results obtained in Comparative Examples 1 and 2 were compared with the results obtained in each Example using a ferromagnetic material with a through hole. In Comparative Example 2, the value was 7058.8 ppm per 0.2 mm at 1 mm between z=8.3 mm and 9.3 mm, and any 0.2 mm interval in the z direction was greater than this value. From this, the best z-direction uniformity obtained in Comparative Example 2 was only 7058.8 ppm or more. Therefore, it was found that the uniformity in the z direction without a through hole was inferior to the uniformity in each Example with a through hole, particularly the uniformity in Examples 2 and 3, and more particularly the best value of 3926 ppm in Example 2 with a through hole of 5 mm diameter. Therefore, it was found that the attachment of a ferromagnetic material with a through hole improved the uniformity in the z direction.

Table 3 below shows the calculation process for calculating the uniformity at 0.2 mm pitch in the z direction for Comparative Example 2 in Table 2. The difference in magnetic field strength between adjacent magnetic fields at 1 mm pitch was divided by the larger value to obtain the rate of change, and this was assumed to be linear over a 1 mm interval to determine the uniformity at 0.2 mm. For example, the difference dB = 0.03 T between the magnetic field strengths of 0.85 T and 0.82 T at z = 8.3 mm and z = 9.3 mm was divided by the larger value B = 0.85 T of the larger magnetic field to obtain the magnetic field variation (magnetic field uniformity) over a 1 mm span, which was then divided by 5 as a linear change and expressed as ppm/0.2 mm.

As shown in each embodiment, the magnetic field generating device of the present invention has high industrial applicability in that it can generate a uniform high magnetic field over a wide range.

Furthermore, the magnetic field generating method, magnetic field generating device, and nuclear magnetic resonance device of the present invention can generate a uniform high magnetic field over a wider range than conventional devices, and have a greater degree of spatial freedom, making it possible to reduce the size of these devices, particularly to make them tabletop devices, and therefore have high industrial applicability.
1 and 2 of JP 2015-167576 A discloses a magnetic field generating device having opposing magnetic pole parts, in which an iron plate without a through hole is arranged on the magnetic pole surface of one of the magnetic pole parts, and no ferromagnetic material is arranged on the magnetic pole surface of the other magnetic pole part. In this device, the object to be measured must be placed between a pair of magnetic pole parts, and the spatial freedom is limited by the distance between the magnetic pole parts. In other words, the freedom of the shape of the object to be measured and the measurement site may be limited.
In contrast, according to the present invention, the magnetic field generating device of the present invention is used with a single magnetic pole (monopole), and the measurement can be performed using a nuclear magnetic resonance device by bringing the object to be measured close to the magnetic pole surface, so that the spatial freedom of measurement is excellent. In other words, the freedom of the size, shape, and measurement site of the object to be measured can be dramatically improved. In this respect, the magnetic pole configuration using the magnetic field generating device of the present invention with a single pole is also advantageous.
In addition, according to the present invention, the magnetic field generator can be miniaturized by using a superconducting strong magnetic field generator, so that the leakage magnetic field from the magnetic field generator can be reduced, and the freedom of use is improved, such as being able to install it in the same room as other analytical devices. In particular, as the range of industrial applications expands, market demands are expected to be met, such as a small, lightweight, portable type, that can be installed anywhere, that can be used with simple installation and maintenance, that is compact, and that can be used in combination with other measuring devices, analytical devices, and diagnostic devices, even if the strong magnetic field space is small. The magnetic field generator of the present invention can be easily combined with other measuring devices, analytical devices, and diagnostic devices, so that new methods and fields of use that have not been seen before can be realized.

REFERENCE SIGNS LIST 1 Magnetic pole portion 2 Superconducting strong magnetic field generator 3 Holder 4 Yoke 5 Height support 6 Lateral support 7 Set screw 8 Thermometer 9 Heat transfer body 10 Magnetic pole surface 11 Ferromagnetic body 11a Main surface 12 Through hole 21 Spacer 31 Magnetic field distribution 41 Measurement surface 42 Measurement range x Width direction of magnetic pole surface y Longitudinal direction of magnetic pole surface z Normal direction of magnetic pole surface

Claims (15)

A nuclear magnetic resonance apparatus including a magnetic field generating device,
The magnetic field generating device has a magnetic pole part including a superconducting strong magnetic field generator and a ferromagnetic body having a shape that defines a through hole,
The superconducting strong magnetic field generator is a superconducting bulk magnet; a bulk magnet obtained by stacking laminated tape wires; or a laminate of a plurality of superconducting thin films, a plurality of superconducting thick films, or a laminate of a superconducting thin film and a superconducting thick film; or a combination thereof ;
a main surface of the ferromagnetic body is disposed in a direction substantially parallel to a magnetic pole surface of the magnetic pole portion,
In a superconducting state, the through hole is located at a central portion of a magnetic field generated from the superconducting strong magnetic field generator in a direction parallel to the magnetic pole face,
the ferromagnetic body is a laminate including n ferromagnetic bodies from the side closer to the magnetic pole portion, n being a natural number,
n is 2 to 10;
The nuclear magnetic resonance apparatus uses the magnetic field generating device as a single magnetic pole part and does not use any other magnetic pole parts. The nuclear magnetic resonance apparatus of claim 1, wherein the ferromagnetic material is iron, nickel, cobalt, an alloy containing one or more of these, or ferrite. The nuclear magnetic resonance apparatus according to claim 1 or 2, in which the magnetic pole face and the ferromagnetic body are arranged with a gap therebetween. The nuclear magnetic resonance apparatus according to any one of claims 1 to 3, wherein the end of the ferromagnetic body extends to the same position as the end of the magnetic pole face or to the outside or inside in a direction substantially parallel to the magnetic pole face. The through hole has a substantially circular shape in a direction substantially parallel to the magnetic pole surface, and
5. The nuclear magnetic resonance apparatus according to claim 1, wherein a main surface of the ferromagnetic body is a substantially circular flat surface whose central axis coincides with that of the through hole. The nuclear magnetic resonance apparatus according to any one of claims 1 to 5, wherein the magnetic pole face is a substantially circular flat surface having a diameter of 30 to 1000 mm. The nuclear magnetic resonance apparatus according to any one of claims 1 to 6, wherein the through-hole has a substantially circular shape with a diameter of 3.5 mm to 100 mm in a direction substantially parallel to the magnetic pole face. The nuclear magnetic resonance apparatus according to any one of claims 1 to 6, wherein the through-hole has a substantially circular shape with a diameter of 4 to 6 mm in a direction substantially parallel to the magnetic pole face. The nuclear magnetic resonance apparatus according to any one of claims 1 to 8, wherein, in a direction approximately parallel to the magnetic pole face, an end of the m-th ferromagnetic body from the side closer to the magnetic pole portion is located more inside than an end of the m-1-th ferromagnetic body, where m is an integer of 2 or more and n or less . 10. The nuclear magnetic resonance apparatus according to claim 1, wherein ends of the through holes defined by the n ferromagnetic bodies are at substantially the same position. The nuclear magnetic resonance apparatus according to any one of claims 1 to 10, wherein in a superconducting state, the magnetic field generated by the superconducting strong magnetic field generator forms a uniform magnetic field surface having a substantially uniform magnetic field distribution in a direction parallel to the magnetic pole face in a region having a thickness of 0.4 mm or more in a normal direction to the magnetic pole face. 12. The nuclear magnetic resonance apparatus according to claim 11 , wherein the uniform magnetic field surface is formed at a position 0 mm or more away from a main surface of the ferromagnetic body opposite to the magnetic pole surface in a normal direction to the magnetic pole surface. 13. The nuclear magnetic resonance apparatus according to claim 1 , wherein the magnetic pole faces are disposed in a substantially horizontal direction. The central part of the magnetic field generated by the superconducting strong magnetic field generator in a direction parallel to the magnetic pole face is the central part of the magnetic pole face,
The nuclear magnetic resonance apparatus according to any one of claims 1 to 13 , wherein the central portion of the magnetic pole face is a region on the major axis of the magnetic pole face that is 30% to 70% of the distance from one end of the magnetic pole face. A magnetic field generating method for generating a uniform magnetic field surface having a substantially uniform magnetic field distribution in a direction parallel to the magnetic pole surface, in a region having a thickness of 0.4 mm or more in a normal direction to the magnetic pole surface, using the nuclear magnetic resonance apparatus according to any one of claims 1 to 14.