JP2003250777A - Magnetic field generator and nmr apparatus utilizing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic field generator and a NMR (nuclear magnetic resonance) apparatus, which can generate a uniform magnetic field space with grater magnetic field intensity at a place distant to some extent from the magnet surface. <P>SOLUTION: The magnetic field generator 10a includes a pair of magnets 12a, 12b which are formed with an interval open in between. An angle formed by respective magnetized directions of the magnets 12a, 12b is set so as to be neither 0° nor 180°. The magnets 12a, 12b are magnetically connected by a yoke 14. A supplementary magnet 18 can be disposed between the magnets 12a, 12b. The NMR apparatus can be obtained by additionally disposing a transmitting/receiving coil 20 between the magnets 12a, 12b. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field generator and an NMR (nuclear magnetic resonance) using the same.
More specifically, it relates to a non-opposed magnetic field generator and an NMR apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, an opposed type magnetic field generator can generate a static magnetic field stronger than other magnetic field generators, and is therefore preferably used in an NMR apparatus. In this apparatus, an object to be inspected is placed in the generated uniform magnetic field space for inspection, but the object to be inspected may not enter the magnetic field space of the opposed magnetic field generator. In this case, it is necessary to generate a magnetic field outside the magnetic field generator. Japanese Patent Laid-Open No. 51-127785 discloses an example of a conventional technique capable of generating a magnetic field outside a magnetic field generator. In addition, as another example, NM for surface analysis from BRUKER
An R device (brand name: mini-spec MOUSE) has been proposed.

[0003]

However, Japanese Patent Laid-Open No. 51-
In the technology disclosed in 127785, a uniform magnetic field space can be obtained at a certain distance from the magnet surface, but since the magnetic field strength in the uniform magnetic field space is small, N
The MR signal strength was weak and the inspection accuracy was not good. Also,
In the technique proposed by BRUKER, the magnetic field strength of the uniform magnetic field space is large, but since the uniform magnetic field space is formed only near the surface, it is possible to inspect only the shallow portion from the surface of the inspection object. Therefore, the main purpose of this invention is to
It is an object of the present invention to provide a magnetic field generator capable of obtaining a uniform magnetic field space having a larger magnetic field strength at a certain distance from the surface of a magnet and an NMR apparatus using the same.

[0004]

In order to achieve the above object, a magnetic field generator according to a first aspect of the present invention comprises a plurality of magnets provided at intervals and is formed by the magnetization directions of the plurality of magnets. It is characterized in that the angle is set to neither 0 ° nor 180 °. A magnetic field generator according to a second aspect is the magnetic field generator according to the first aspect, wherein an angle formed by the magnetization directions of the plurality of magnets is 10 ° or more and 110 ° or less.

A magnetic field generator according to a third aspect of the present invention comprises a plurality of magnets provided at intervals, and auxiliary magnets provided between the plurality of magnets, and a plurality of magnetic fluxes generated by the auxiliary magnets on the side of the uniform magnetic field space to be used. The auxiliary magnet is arranged so as to be in a direction opposite to the magnetic flux generated by the magnet. The magnetic field generating device according to claim 4 is the magnetic field generating device according to claim 3, wherein the surface of the auxiliary magnet on the side of the uniform magnetic field is set to be 0 mm or more and 20 mm or less from the surface of the plurality of magnets on the side of the uniform magnetic field. It is characterized by being done.

A magnetic field generator according to a fifth aspect is the magnetic field generator according to any one of the first to fourth aspects, further comprising a yoke for magnetically coupling a plurality of magnets. The magnetic field generator according to claim 6 is the magnetic field generator according to claim 3 or 4, further comprising a yoke that magnetically couples a plurality of magnets, and the auxiliary magnet is provided at a predetermined distance from the yoke. It is characterized by An NMR apparatus according to a seventh aspect comprises the magnetic field generating apparatus according to any one of the first to sixth aspects, and a transmission / reception coil provided between a plurality of magnets.

In the magnetic field generator according to the first aspect of the present invention, the magnetizing directions of the plurality of magnets are set so as not to be in the same direction or in the forward and reverse directions, so that a wide magnetic field having a larger magnetic field strength is provided at a position away from the surface of the magnet. A uniform magnetic field space can be obtained. Further, since the magnetic field distribution of the space changes depending on the magnetization directions of the plurality of magnets, a uniform magnetic field space can be obtained at a desired position by appropriately selecting the magnetization direction. In the magnetic field generator according to claim 2, the angle formed by the magnetization directions of the plurality of magnets is set to 10 ° or more and 110 ° or less so that the desired magnetic field strength is uniform at a desired position away from the surface of the magnet. A magnetic field space can be provided.

In the magnetic field generator of the third aspect, the strong magnetic field in the vicinity of the plurality of magnets is weakened by the magnetic field of the auxiliary magnet. As a result, a wider uniform magnetic field space can be obtained at a position farther from the magnet surface. In the magnetic field generator according to claim 4, by arranging the auxiliary magnet so that the surface on the magnetic field space side of the auxiliary magnet is submerged by 0 mm or more and 20 mm or less from the surface on the magnetic field space side of the plurality of magnets, a desired distance from the magnet surface is obtained. A uniform magnetic field space having a desired magnetic field strength can be provided at the position.

In the magnetic field generator according to the fifth aspect, the magnetic field generated can be further strengthened by magnetically coupling the plurality of magnets with the yoke, and the detection accuracy can be improved. In the magnetic field generator according to the sixth aspect, the auxiliary magnet is arranged at a predetermined distance from the yoke, so that the magnetic flux generated from the auxiliary magnet is not short-circuited by the yoke. In the NMR apparatus according to the seventh aspect, since the uniform magnetic field space required for the NMR apparatus can be formed by using the magnetic field generating apparatus described above, good detection accuracy can be obtained and the NMR apparatus can be applied to various applications. For example, in MRI, not only the shallow portion from the surface of the object to be imaged but also the inside thereof can be imaged with good imaging accuracy, and a useful NMR apparatus can be obtained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. With reference to FIGS. 1 and 2, a magnetic field generator 10a according to an embodiment of the present invention is a non-opposed transverse magnetic field type magnetic field generator that forms a uniform magnetic field space outside a space where magnets face each other, and is constant. It includes two rectangular parallelepiped magnets 12a and 12b provided at intervals. A yoke 14 made of, for example, iron and having a rectangular parallelepiped shape is connected to one ends of the magnets 12a and 12b.
And 12b are magnetically coupled.

As shown in FIG. 2, magnets 12a and 12
The respective magnetization angles of b are set to θ1 and θ2. The magnetization angle θ1 is an angle formed by the magnetization direction of the magnet 12a with respect to the main surface of the yoke 14 or the horizontal direction, and has a positive value in the clockwise direction. The magnetization angle θ2 is an angle formed by the magnetization direction of the magnet 12b with respect to the main surface of the yoke 14 or the horizontal direction, and has a positive value in the counterclockwise direction. Therefore,
The angle formed by the respective magnetization directions of the magnets 12a and 12b is calculated by (θ1 + θ2).

In such a magnetic field generator 10a, a uniform magnetic field space (for example, a region indicated by S) formed on the other ends of the magnets 12a and 12b is used for inspection.
When the magnets 12a and 12b are magnetized in the directions shown in FIG. 2, a magnetic flux as indicated by arrow A is generated.

According to the magnetic field generator 10a, the magnet 12a
The magnets 1 and 12b are set so that they are neither in the same direction nor in the forward and reverse directions, so that the magnet 1
A wide uniform magnetic field space with greater magnetic field strength can be obtained away from the surfaces of 2a and 12b. Further, since the magnetic field distribution in the space changes depending on the magnetization directions of the magnets 12a and 12b, the magnets 12a and 12b
A uniform magnetic field space can be obtained at a desired position by appropriately selecting the magnetization direction of b. Also, the magnet 12a
By magnetically coupling and 12b with the yoke 14, the generated magnetic field can be strengthened and the imaging accuracy can be improved.

An experimental example of the magnetic field generator 10a will be described. In the experiment, the magnets 12a and 12b have 60
0 mm (length L1) x 315 mm (width W1) x 350 m
An m (height H) R-Fe-B system permanent magnet (neodymium magnet: NEOMAX-35H) was used, and the magnets 12a and 12b were arranged with a gap of 190 mm. As the yoke 14, JISSS400 of 820 mm (length L2) × 600 mm (width W2) × 150 mm (height T) was used.

The magnetization angles θ1 and θ2 are variably set from 0 ° to 90 ° (θ1 is clockwise and θ2 is counterclockwise), and the central magnetic field of the uniform magnetic field space generated by the two magnets 12a and 12b is set. The strength, the position of the central magnetic field strength, and the uniform width are shown in FIG. Here, the position of the central magnetic field strength refers to the distance from the surfaces of the magnets 12a and 12b, and takes a positive value outward from the surfaces. The uniform width refers to the vertical width of the magnetic field region within ± 1% from the central magnetic field strength, that is, the vertical width of the uniform magnetic field space. The uniform width is important because a uniform magnetic field space of a certain size is required when performing NMR.

From FIG. 3, the magnetization angles θ1 and θ2 are set to 0.
When the magnetization directions of the two magnets 12a and 12b are parallel (the same direction), the central magnetic field strength is 0.020.
Although very small as 8T, the position of the central magnetic field strength is 33.2 mm from the magnet surface, and the uniform width is 4.8 mm. Also,
When the magnetization angles θ1 and θ2 are set to 5 °, the central magnetic field strength is as small as 0.0296T, but the position of the central magnetic field strength is 28.2 mm from the magnet surface, and the uniform width is 4.4 mm.
Therefore, when the magnetization angles θ1 and θ2 are 0 ° and 5 °, although the magnetic field strength is small, a relatively wide uniform magnetic field space is generated at a position considerably distant from the magnet surface. When the magnetization angles θ1 and θ2 are gradually increased, the central magnetic field strength increases, but the position approaches the magnet surface, and the uniform width decreases. The magnetization angles θ1 and θ2 may be different angles.

In this experimental example, assuming that the central magnetic field strength of the uniform magnetic field space is about 0.03 T or more and the position of the central magnetic field strength is about 5 mm or more, the magnetization angles θ1 and θ2.
Is 5 ° or more and 55 ° or less. Therefore, the angle formed by the respective magnetization directions of the two magnets 12a and 12b is preferably 10 ° or more and 110 ° or less. In this case, the magnet 1
Since a uniform magnetic field space having a desired magnetic field strength can be provided at a desired position apart from the surfaces of 2a and 12b, the use range of the magnetic field generation device 10a is further widened.

Next, another experimental example will be described with reference to FIGS. 4 and 5. Here, the U-shaped magnetic field generator shown in FIG. 4A and the U-shaped magnet shown in FIG. 4B, that is, no wedge-U type, wedge-U type having wedges 16a and 16b. , Wedge 16a
And 16b and the magnetization angles θ1 and θ2 of the magnets 12a and 12b are 45 °, U-shaped type,
U-shaped magnetic field generators having no wedges 16a and 16b and magnetizing angles θ1 and θ2 of the magnets 12a and 12b being 35 °, no wedges-U type, wedges having wedges 16a and 16b- The magnetic field strength distribution was measured for each U-shaped magnet.
The U-shaped magnetic field generator shown in FIG.
mm × 58 mm, magnets 12a and 12b are 40 mm ×
Wedges 16a and 1 of 10 mm x 48 mm and triangular prism shape
6b is 40 mm × 10 mm × 9 mm, magnets 12a and 12
The distance from b was set to 30 mm. Figure 4
The U-shaped magnet shown in (b) is 50 mm x 40 mm x 70 m
The wedges 16a and 16b having the same dimensions as those of FIG. Wedge 16a
And 16b are made of a yoke material such as iron. In FIG. 4A, the arrows shown on the magnets 12a and 12b indicate the magnetization directions.

When the magnetic field intensity distribution was measured for the magnetic field generator and the magnet of the above, the results shown in FIG. 5 were obtained. The horizontal axis in FIG. 5 represents the distance on the Z axis from the point P shown in FIGS. 4 (a) and 4 (b). Here, the point P is the magnet 1 in FIG.
The in-plane center including the surfaces (upper end surfaces) of 2a and 12b, the in-plane center including both upper end surfaces of the U-shaped magnet in FIG. 4 (b), and the positive value on the horizontal axis in FIG. (Below the point P), negative values indicate outside the magnet (above the point P).
The vertical axis in FIG. 5 represents the magnetic field strength on the Z axis.

From FIG. 5, the outside of the magnet is approximately 15 mm to 20 m.
In the vicinity of m, the magnetic field generators of the U-shaped type with a magnetization angle of 45 ° and the U-shaped type with a magnetization angle of 35 ° have better magnetic field homogeneity than the other types.
It can be seen that the U-shaped magnetic field with a magnetization angle of 35 ° is particularly uniform. Thus, if a magnet having a predetermined magnetization angle is used in the magnetic field generator, stable magnetic field uniformity can be obtained.

Next, a magnetic field generator 10b according to another embodiment of the present invention will be described with reference to FIG. The magnetic field generator 10b is a magnet 1 similar to the magnetic field generator 10a.
2a, 12b and a yoke 14, and further includes a magnet 12
It includes an auxiliary magnet 18 arranged in a space sandwiched by a and 12b. The auxiliary magnet 18 can be arranged between the magnets 12a and 12b by being placed on a non-magnetic member (not shown), for example. Further, the magnetic field direction of the auxiliary magnet 18 is leftward, and the magnetic flux generated by the auxiliary magnet 18 is
The direction is opposite to the magnetic flux generated by 2a and 12b (see FIG. 9).
The magnetizing angles of the magnets 12a and 12b are 9 respectively.
The magnets 12a and 12b are arranged such that the angle is 0 °, and therefore the different poles are on the same side. In addition, the auxiliary magnet 18
The magnetic field space is adjusted by changing the position of.

An experimental example of the magnetic field generator 10b will be described. In the experiment, the magnets 12a and 12b have 60
An R-Fe-B system permanent magnet (neodymium magnet: NEOMAX-35H) of 0 mm x 315 mm x 350 mm was used, and the magnets 12a and 12b were arranged with a gap of 190 mm. The yoke 14 has 820 mm x 600 mm
JISSS400 of × 150 mm was used. The auxiliary magnet 18 has a 90 mm x 600 mm x 425 mm R-
Fe-B system permanent magnet (neodymium magnet: NEOMAX-3
5H) was used.

The position D of the auxiliary magnet 18 is 0 mm to 30 mm when the direction of magnetization of the auxiliary magnet 18 is leftward (hereinafter, simply "leftward") and rightward (hereinafter simply "rightward"). Changed. Here, the position D of the auxiliary magnet 18 is represented by the distance between the upper surfaces of the magnets 12a and 12b (the surface on the side of the uniform magnetic field space) and the upper surface of the auxiliary magnet 18 (the surface on the side of the uniform magnetic field space).

As a result, as shown in FIG. 7, the central magnetic field strength of the uniform magnetic field space, the position of the central magnetic field strength, and the uniform width were obtained. 7A shows the case where the magnetization direction of the auxiliary magnet 18 is leftward, and FIG. 7B shows the case where the magnetization direction of the auxiliary magnet 18 is rightward. As shown in FIG. 7B, when the magnetization direction of the auxiliary magnet 18 is rightward, the central magnetic field strength of the uniform magnetic field space increases, but the position of the central magnetic field strength is at or near the surfaces of the magnets 12a and 12b. Become. Further, the width of the uniform magnetic field space is also reduced.

As shown in FIG. 8, this is the direction of the magnetic flux (indicated by arrow B) by the auxiliary magnet 18 and the magnets 12a, 12b.
The direction of the magnetic flux (indicated by the arrow A) due to and the two magnetic fluxes overlap each other, so that the uniform magnetic field space due to the magnets 12a and 12b is rather narrowed.
This is because a wide uniform magnetic field space cannot be formed at a position away from the surface of 12b.

On the other hand, as shown in FIG. 7A, when the magnetization direction of the auxiliary magnet 18 is leftward, for example, when the position D of the auxiliary magnet 18 is 0 mm, the surfaces of the magnets 12a and 12b and the auxiliary magnet 18 are set. It is possible to form a magnetic field space of approximately 0.3 T having a width in the height direction of 2.1 mm centered at a position of from 6.3 mm. The position D of the auxiliary magnet 18 is 10 mm
In the case of, the position of the central magnetic field strength is 1.5 mm, and a magnetic field space of approximately 0.4 T can be formed. In this way, the uniform magnetic field space having the desired central magnetic field strength is formed into the magnets 12a and 1a.
It can be formed at a position away from the surface of 2b.

Although a strong magnetic field is formed in the vicinity of the magnets 12a and 12b by the magnets 12a and 12b, as shown in FIG. 9, the direction of the magnetic flux (shown by the arrow B) by the auxiliary magnet 18 and the magnets 12a and 12b. By arranging the auxiliary magnet 18 so that the direction of the magnetic flux (indicated by the arrow A) due to
This is because the strong magnetic field near b is weakened by the magnetic field generated by the auxiliary magnet 18. In addition, as a result, the auxiliary magnet 18
The uniform magnetic field space can be increased as compared with the case where the magnetization direction is rightward. In FIGS. 8 and 9, white arrows indicate the magnetization direction of the magnet.

If the magnetic field direction of the auxiliary magnet 18 is leftward and the central magnetic field strength is approximately 0.3T or more and the position of the central magnetic field strength is approximately 0.5 mm or more, the position D of the auxiliary magnet 18 is It becomes 0 mm or more and 20 mm or less.
By arranging the auxiliary magnet 18 to be submerged within this range, a uniform magnetic field space having a desired magnetic field strength can be provided at a desired position away from the surfaces of the magnets 12a and 12b, and the use of the magnetic field generator 10b is possible. The range expands further. Furthermore, by providing the auxiliary magnet 18 at a predetermined distance (for example, 5 mm or more) from the yoke 14,
The magnetic flux generated from the auxiliary magnet 18 is not short-circuited by the yoke 14.

As long as the direction of the magnetic flux of the auxiliary magnet 18 and the direction of the magnetic flux of the magnets 12a and 12b are opposite to each other, the magnetization direction of the auxiliary magnet 18 is slightly tilted upward or downward from the state shown in FIG. Good. In the "reverse direction" here, not only the forward and reverse directions, but the magnetic flux of the auxiliary magnet 18 and the magnetic flux of the magnets 12a and 12b are the forward and reverse components (vector components that are the forward and reverse directions to each other).
Including the case of having.

In the magnetic field generator 10b, the magnetization angles θ1 and θ2 of the magnets 12a and 12b are 0 ° and 9 °, respectively.
It may be set to any angle other than 0 °. This makes it possible to form a magnetic field generator in which the magnetic field generators 10a and 10b are combined. Further, as shown in FIG. 10, the NMR apparatus 100 is obtained by disposing the transmitting / receiving coil 20 between the magnets 12a and 12b of the magnetic field generator 10b and on both sides of the auxiliary magnet 18.

According to the magnetic field generator 10b, the required uniform magnetic field space can be obtained on one side of the apparatus, and therefore the NMR apparatus 100b
According to this, good detection accuracy can be obtained, and there is no limitation on the inspection object, and it can be widely applied to various uses such as medical and industrial uses. For example, an MRI examination can be performed on a patient lying in bed as it is. Also,
It is possible to detect not only the shallow portion from the surface of the object to be imaged but also the inside thereof with good accuracy, and it can be used for inspection of a very large object and inspection of substances in walls and underground. In addition,
An NMR apparatus can be obtained by disposing the transmission / reception coil 20 between the magnets 12a and 12b of the magnetic field generator 10a, and in this case also, the same effect as described above can be obtained.

The magnetic field generator may be composed of three or more magnets, for example, FIGS. 11 (a) and 11 (b).
As shown in FIG. 4, four magnets may be used to form a vertical magnetic field type. In the case of the device shown in FIG. 11, a uniform magnetic field space is obtained centered on the area above the upper surface of the magnet 12 and surrounded by the four magnets 12 (for example, the area indicated by C). Further, the magnetic field generator may be formed in a hollow cylindrical shape. The present invention is also based on ESR (electron spin resona).
nce: electron spin resonance) device.

[0033]

According to the magnetic field generator of the present invention, it is possible to obtain a uniform magnetic field space having a larger magnetic field strength away from the surface of the magnet. Further, according to the NMR apparatus using the magnetic field generator of the present invention, good imaging accuracy can be obtained, and it can be applied to various uses.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

2 is an illustrative view showing the embodiment of FIG. 1. FIG.

FIG. 3 is a table showing the results of an experimental example of the embodiment of FIG.

FIG. 4 is a perspective view showing an apparatus used in another experimental example, (a) is a U-shaped magnetic field generator, and (b) is U.
A letter magnet is shown.

5 is a graph showing the results of an experimental example using the magnetic field generator shown in FIG.

FIG. 6 is an illustrative view showing another embodiment of the present invention.

7 is a table showing the results of an experimental example of the embodiment of FIG. 6, where (a) is the magnetization direction of the auxiliary magnet on the left side, (b).
Shows the case where the magnetization direction of the auxiliary magnet is on the right side.

8 is an illustrative view showing a magnetic flux distribution when an auxiliary magnet is arranged rightward in the magnetization direction in the embodiment of FIG. 6. FIG.

9 is an illustrative view showing a magnetic flux distribution when an auxiliary magnet is arranged to the left in the magnetization direction in the embodiment of FIG.

FIG. 10 is an illustrative view showing one example of an NMR apparatus.

11A is a perspective view showing another example of the magnetic field generator, and FIG. 11B is an illustrative view thereof.

[Explanation of symbols]

10a, 10b Magnetic field generator 12a, 12b magnet 14 York 18 auxiliary magnet 20 transmitter / receiver coil 100 nmr A, B magnetic flux D Auxiliary magnet position θ1, θ2 Magnetization angle

Claims (7)

[Claims] 1. A plurality of magnets provided at intervals, wherein an angle formed by the magnetization directions of the plurality of magnets is 0.
Set to an angle that is neither ° nor 180 °,
Magnetic field generator. 2. The magnetic field generator according to claim 1, wherein the angle is 10 ° or more and 110 ° or less. 3. A plurality of magnets provided at intervals, and an auxiliary magnet provided between the plurality of magnets, wherein the magnetic flux of the auxiliary magnet is opposite to the magnetic flux of the plurality of magnets on the side of the uniform magnetic field space to be used. A magnetic field generation device in which the auxiliary magnets are arranged so as to be oriented. 4. The surface of the auxiliary magnet on the side of the uniform magnetic field is 0 mm or more and 20 mm or more than the surface of the plurality of magnets on the side of the uniform magnetic field.
The magnetic field generation device according to claim 3, wherein the magnetic field generation device is set so as to be submerged by mm or less. 5. The magnetic field generator according to claim 1, further comprising a yoke that magnetically couples the plurality of magnets. 6. The magnetic field generator according to claim 3, further comprising a yoke that magnetically couples the plurality of magnets, wherein the auxiliary magnet is provided at a predetermined distance from the yoke. 7. An NMR apparatus comprising the magnetic field generator according to claim 1 and a transmission / reception coil provided between the plurality of magnets.