JPH0990009A - Magnetic field generating device for esr device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic field generating device which can generate a high magnetic field by means of a permanent-magnet magnetic circuit while maintaining high magnetic field uniformity, can change the intensity of the magnetic field over a wide range, and can easily change the direction of the generated magnetic field. SOLUTION: Cylindrical magnets 1 and 10 are respectively formed by assembling large numbers of triangular prism-like magnets 4 and 13 in sexadecimal prism-like states and a yoke-less cylindrical magnetic circuit is constituted in a nesting state by coaxially incorporating the small-diameter cylindrical magnet 10 in the large-diameter cylindrical magnet 1 so that magnetic fields can be generated in the same direction. When the two magnets 1 and 10 are overlapped upon another in the same direction, a magnetic field which is the double of the magnetic field generated by a single magnet can be obtained and, when the magnets 1 and 10 are rotated by the same angle in the overlapping state, the direction of the magnetic filed can be changed without changing the intensity. Therefore, magnetic fields of various intensities can be generated in various directions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet magnetic circuit applicable to a magnetic field generation source of an ESR device (electron spin resonance device) that requires changing the direction of magnetic field strength over a wide range, and a magnet having a triangular prism shape. By combining cylindrical magnets with different inner and outer diameters that are combined into a cylindrical shape and changing the relative rotation angle between them, the direction and strength of the generated magnetic field can be changed without changing the size of the magnetic field space. The present invention relates to a magnetic field generator for an ESR device that is capable of performing.

[0002]

2. Description of the Related Art ESR equipment has been studied for chemical analysis.
It is often used in the field of development. In addition, since the ESR device can detect unpaired electrons due to natural radiation damage of the object to be measured and can accurately date the relics, geological minerals, and fossils, recently, archeology and earth It is also used in the field of science.

The magnetic field generating device which constitutes the main part of the ESR device used for such an application needs to generate a uniform magnetic field with high precision in the void in which the object to be measured is placed. Conventionally, the magnetic field generator used in the ESR device usually uses an electromagnet. Generation of the magnetic field in the required air gap and continuous change of the magnetic field can be easily implemented by continuously changing the current applied to the electromagnet, but the entire device is large and expensive, and further running costs are required. It has the drawback of

[0004]

Further, there has been proposed a structure in which only a permanent magnet is used as a magnetic field generation source and the opposing distance (gap length) between them is changed to change the magnetic field strength. However, when the facing distance is changed, there is a disadvantage that the uniformity of the magnetic field is deteriorated due to factors such as the axes of the permanent magnets being moved.

On the other hand, the magnetic field normally required for an ESR device is required to have a highly accurate homogeneity of 0.01% or less. Conventionally, the ESR device using a permanent magnet as a magnetic field source has such homogeneity. There was nothing to satisfy. Therefore, the applicant has used an ESR device that uses a permanent magnet as a magnetic field generation source.
A configuration in which a permanent magnet of a magnetic field generation source and a magnetic resistance variable section including a movable yoke are arranged in parallel in a magnetic circuit as a configuration capable of continuously changing the magnetic field strength while maintaining highly accurate uniformity of 01% or less. Proposed the ESR device of
-104574).

However, with these methods, although a satisfactory value can be obtained for uniformity, there is a limit to the magnetic field strength generated in the void in which the object to be measured is placed, and a variable range of only several tens of mT can be obtained. Moreover, the fact that the direction of the generated magnetic field cannot be changed without moving the magnetic circuit has been a cause of limiting the applicable range.

An object of the present invention is to realize a magnetic field generator for an ESR device which needs to change the magnetic field strength direction over a wide range by a permanent magnet magnetic circuit, and to achieve a high magnetic field without increasing the size of the device. It is an object of the present invention to provide a magnetic field generator for an ESR device which can obtain strength, has a wide variable range of magnetic field strength, and can easily change the direction of a generated magnetic field.

[0008]

DISCLOSURE OF THE INVENTION The inventors have aimed at a magnetic circuit having a structure capable of generating a high magnetic field in a predetermined air gap, having a wide variable range of magnetic field strength, and easily changing the direction of the generated magnetic field. As a result of various investigations, a magnetic field is generated in the same direction in a yokeless cylindrical magnetic circuit, and the inner diameter is different.
When two tubular magnets are superposed in exactly the same direction by combining the two in a nested state, a magnetic field twice as large as the magnetic field generated by itself is obtained, and the two tubular magnets are superposed. Therefore, we found that when rotated at the same angle, the magnetic field direction can be changed without changing the strength, and by combining these operations, magnetic fields of various strengths can be generated at various angles. did.

Further, the inventors of the present invention can arrange a shim magnet at both ends of the cylindrical magnet to obtain a uniform magnetic field strength over a wide range in the cylinder, and further to make the cylindrical magnet non-magnetic. The present invention has been completed by discovering that a tubular structure material made of a material is also built-in or supported externally to facilitate assembly of the tubular magnet and the entire device, and to provide a magnetic field generator for an ESR device at low cost.

That is, according to the present invention, the cylindrical magnet is a combination of columnar magnets having a triangular cross section, the inner and outer peripheral surfaces are polygonal, and shim magnets are arranged at both ends to generate a magnetic field in the cylinder. In the configuration, a pair of the tubular magnets having different inner and outer diameters are coaxially arranged so that one of the tubular magnets is housed in the other with a predetermined gap, and the inner and outer tubular magnets are individually rotatably supported. It is a magnetic field generator for an ESR device.

Further, according to the present invention, in the above structure,
The outer cylindrical magnet is built in or externally supported by the large-diameter cylindrical structural material, and the inner cylindrical magnet is built in or externally supported by the small-diameter cylindrical structural material to rotate the large-diameter and small-diameter cylindrical structural materials. By doing so, a magnetic field generator for an ESR device in which the inner and outer cylindrical magnets are individually rotatably supported is also proposed.

[0012]

FIG. 1 shows an example of the structure of a magnetic field generator according to the present invention, and is a front explanatory view seen from the axial direction of a cylinder, and FIG. 2 is a vertical side view of FIG. As shown in FIG. 1 and FIG. 2, the magnetic field generator according to the present invention is a yokeless cylindrical magnetic circuit in which those having the same generated magnetic field but different inner diameters are combined in a nested state, that is, an outer cylindrical shape. The inner cylindrical magnet 10 is coaxially built in the magnet 1. The outer cylindrical magnet 1 is formed by combining a large number of triangular columnar magnets 4 into a hexagonal cylindrical shape.
The cylindrical magnet 1 has a non-magnetic hexagonal cylindrical structural material 2 on its outer peripheral surface.
It is bonded to the inner surface of the. Similarly, the inner cylindrical magnet 10 is also formed by combining a large number of triangular pole-shaped magnets 4 into a hexagonal cylindrical shape, and its outer peripheral surface is bonded to the inner peripheral surface of the non-magnetic hexagonal cylindrical structural material 11. There is.

Flanges 6 and 16 are formed on both ends of the cylindrical magnets 1 and 10, respectively, and the flanges 6 and 16 are provided with a stand 8 via bearings 18, respectively.
And the cylindrical magnets 1 and 10 are individually rotatable. Further, at both ends of the inner and outer cylindrical magnets 1 and 10, shim magnets 4a and 13a having a radial thickness larger than that of the triangular columnar magnet 4 arranged at the central portion thereof are arranged. FIG. 3 is a half perspective view showing a configuration example of a cylindrical magnet in the magnetic field generator according to the present invention, and 9a in the drawing is the shim magnet portion described above.

FIG. 4 shows an example of the construction of the magnetic field generator according to the present invention, and is an explanatory view seen from the axial direction of the cylinder. FIG. 5 shows the inner and outer cylindrical magnets in the opposite directions from the state of FIG. 1
FIG. 6 shows the case of rotating by 5 ° each, FIG. 6 shows the case of rotating by 60 ° similarly, and FIG. 7 shows the case of rotating by 90 ° similarly.

The magnetic field generator shown in FIG. 4 is basically the same as that shown in FIG.
Similar to the magnetic field generator shown in FIG. 1, and has a configuration in which an inner cylindrical magnet 30 in which a large number of triangular prism-shaped magnets 31 are combined is coaxially built in an outer cylindrical magnet 20 in which a large number of triangular-columnar magnets 21 are combined. Shim magnets 22 and 32 are arranged at both ends of the cylindrical magnets 20 and 30, respectively. Incidentally, FIG.
In FIG. 7, in order to clarify the magnetization directions of the triangular pole-shaped magnets 21 and 31, illustration of the tubular structural material is omitted.

Each of the triangular pole-shaped magnets 21 and 31 of the inner and outer cylindrical magnets 20 and 30 has a magnetization direction in the direction indicated by an arrow in the figure, and the cylindrical magnets 20 and 30 generate a magnetic field in the same direction. It is a composition. Two cylindrical magnets 2 as shown in FIG.
When 0 and 30 are superposed in exactly the same direction, as shown in FIG. 8, a generated magnetic field which is twice as large as the magnetic field generated individually is obtained.

As shown in FIGS. 5 to 7, the inner and outer cylindrical magnets 20 and 30 are moved in the opposite directions from the state of FIG. 4 by 15 ° to 9 °.
By rotating 0 °, that is, moving symmetrically, the sin components of the magnetic field cancel each other out and only the cos component remains, so that the magnetic field strength can be changed by the cos curve without changing the direction of the magnetic field as shown in FIG. it can. Further, when the inner and outer cylindrical magnets 20 and 30 are overlapped and rotated at the same angle, the magnetic field direction can be changed without changing the strength. Furthermore, by combining the above methods, it is possible to generate magnetic fields of various strengths at various angles.

In the present invention, the cylindrical magnet assembled by combining a large number of triangular pole-shaped magnets into a polygonal cylindrical shape can be formed of only the magnet and can be reinforced by using a non-magnetic structural material such as stainless steel. By using a structural material,
The strength of the tubular magnet can be reinforced, and the tubular magnet or the entire device can be easily assembled, and the device can be provided at low cost. The structural material can be appropriately selected depending on the size and shape of the magnet body, such as a cylindrical shape that covers the entire magnet body in the embodiment, a lattice shape or a partial use.

As for the non-magnetic structural material, for example, in the case of the embodiment, the outer cylindrical magnet is built in and supported by the large-diameter cylindrical structural material, and the inner cylindrical magnet is the small-diameter cylindrical structural material. Although it is fitted and supported on the outer peripheral surface, conversely, the cylindrical structural material can be arranged on the inner peripheral surface of the outer cylindrical magnet and the cylindrical structural material can be arranged on the outer side of the inner cylindrical magnet, A configuration in which magnets are arranged on either the inner or outer peripheral surface of the tubular structural material can also be adopted.

In the present invention, forming the cylindrical magnet with the triangular pole-shaped magnet makes it possible to obtain an equivalent magnetic field strength with a smaller magnet weight as compared with the case where a square pole-shaped magnet or a round pillar-shaped magnet is used. This is because the efficiency is excellent. As the permanent magnet, any known magnet such as a ferrite magnet, an alnico magnet, and a rare earth cobalt magnet can be used. Particularly, by using an Fe-BR permanent magnet showing an extremely high energy product of 30 MGOe or more, A high magnetic field of 0.5 T or more can be obtained at the center of the cylinder, and the size of the entire device can be significantly reduced.

Further, in the present invention, the cylindrical magnet includes
As shown in the perspective view of the half-divided state of FIG. 3, the required length x from the openings at both ends of the tubular magnet 9 formed of the triangular pole magnet.
By forming the shim magnets 9a, 9a in the shape of a cylinder using a triangular columnar magnet whose portion is thicker by y than other magnets,
The uniformity of the magnetic field generated inside the cylindrical magnet 9 can be improved. The length x of the shim magnet 9a and the thickness y thicker than the other magnets are appropriately selected according to the overall length of the tubular magnet 9, the magnet used, the required magnetic field uniformity, and the like. For the shim magnet, the same magnet material should be used to change the magnet size, and instead of changing the thickness dimension, the magnet material should be replaced with a stronger one to reinforce the magnetic force and to improve the magnetic field uniformity. You can

[0022]

EXAMPLE The inner and outer cylindrical magnets 1 and 10 shown in FIG. 1 are formed by combining triangular columnar magnets 4 and 13, respectively.
As shown in FIG. 2, the magnets 4 and 13 are supported by the cylindrical structural members 2 and 11 connected in the axial direction by the connecting pins 5 and 14, respectively. That is, in the large-diameter cylindrical structural member 2, the hexagonal columnar structural member 3 divided into seven in the axial direction is connected to the connecting pin 5.
Is connected and integrated in an axial direction with a flange 6 fixed to one end by a bolt 7, and a large number of axially divided triangular prism-shaped magnets 4 are formed on the inner peripheral surface of the tubular structural member 2. The tubular magnet 1 is assembled by assembling. In addition, shim magnets 4a, which are formed into a cylindrical shape by using triangular columnar magnets having a large radial thickness, are arranged at both ends of the cylindrical magnet 1 divided in the axial direction.

Similarly, for the small-diameter tubular structural member 11, six hexagonal columnar structural members 12 which are axially divided into six are connected by a connecting pin 14 in the axial direction to be integrated, and a tubular member is provided at one end. A flange 16 is fixed to a bolt 17 via a shaft member 15, and a large number of triangular columnar magnets 13 having a predetermined shape divided in the axial direction are attached to the outer peripheral surface of the tubular structural member 11. Furthermore, among the axially divided triangular columnar magnets 13, shim magnets 13a which are formed in a tubular shape by using triangular columnar magnets having a large radial thickness are arranged at both ends.

The inner diameter portion of the flange 6 of the large-diameter cylindrical structural member 2 is externally fitted to the cylindrical member 15 of the small-diameter cylindrical structural member 11, and the flange 6 and the flange 16 of the small-diameter cylindrical structural member 11 are joined together. The large-diameter and small-diameter cylindrical structural members 2 and 11 are rotatable via the bearing plate 18 on the stand 8 provided therebetween, that is,
The inner and outer cylindrical magnets 1 and 10 are individually rotatably supported. In addition, the flange 1 of the small-diameter tubular structural members 2 and 11
The pin 6 can be fixed to the stand 8 with a penetrating pin 19. A ferrite magnet having a maximum energy product (BH) max of 3.6 MGOe was used as the triangular columnar magnets 4 and 13.

In the magnetic field generator having the above-mentioned structure, when the inner and outer cylindrical magnets 1 and 10 are aligned with a predetermined reference position and the generated magnetic fields are superposed in exactly the same direction, 0.
A generated magnetic field of 2T (2000G) was obtained. Calculated and measured values of the magnetic field distribution at this time are shown in FIGS. 10 and 11. When the inner and outer cylindrical magnets 1 and 10 are superposed and rotated at the same angle, the magnetic field direction can be changed without changing the strength. The magnetic field difference at this time is shown in FIG.

[0026]

The magnetic field generator for an ESR device according to the present invention has a structure in which magnets in the shape of triangular prisms are combined and cylindrical magnets of different inner and outer diameters, which are shim magnets, are coaxially arranged at both ends. It is not necessary to obtain a high magnetic field while maintaining the uniformity of 0.01% or less, which is required for an ESR device, without moving the magnetic circuit body and without changing the size of the magnetic field space. By changing the relative rotation angle of the cylindrical magnet, it is possible to change the direction and strength of the generated magnetic field.

[Brief description of drawings]

FIG. 1 is a front explanatory view showing an example of the configuration of a magnetic field generator according to the present invention as viewed from the axial direction of a cylinder.

2 is a vertical side view of FIG.

FIG. 3 is a half-divided perspective view showing a configuration example of a tubular magnet.

FIG. 4 is a front explanatory view showing another configuration example of the magnetic field generator according to the present invention as viewed from the axial direction of the cylinder.

5 is a front explanatory view showing a case where the inner and outer cylindrical magnets are rotated by 15 ° in mutually opposite directions from the state of FIG. 4. FIG.

FIG. 6 is a front explanatory view showing a case where the inner and outer cylindrical magnets are rotated by 30 ° in mutually opposite directions from the state of FIG. 4;

FIG. 7 is a front explanatory view showing a case where the inner and outer cylindrical magnets are rotated by 90 ° in mutually opposite directions from the state of FIG. 4;

FIG. 8 is an explanatory diagram showing composition of generated magnetic fields when the generated magnetic fields of the inner and outer cylindrical magnets are superposed in the same direction in the magnetic field generator according to the present invention.

FIG. 9 is a graph showing a relationship between a rotation angle and a magnetic field.

FIG. 10 is a graph showing calculated values of the magnetic field distribution from the center position of the magnetic field generator according to the present invention.

FIG. 11 is a graph showing measured values of the magnetic field distribution from the center position of the magnetic field generator according to the present invention.

FIG. 12 is a graph showing the relationship between the rotation angle of the cylindrical magnet inside and outside the magnetic field generator according to the present invention and the difference between the generated magnetic fields.

[Explanation of symbols]

 1,9,10,20,30 Cylindrical magnet 2,11 Cylindrical structural material 3,12 16 Square columnar structural member 4,13,21,31 Triangular columnar magnet 4a, 9a, 13a, 22, 32 Shim magnet 5, 14 Connection Pin 6,16 Flange 7,17 Bolt 8 Stand 15 Cylindrical Shaft Material 18 Bearing Plate 19 Pin

Claims (2)

[Claims] 1. A cylindrical magnet has a structure in which columnar magnets having a triangular cross section are combined to form a polygonal inner and outer peripheral surface, and shim magnets are arranged at both ends to generate a magnetic field in the cylinder. A magnetic field for an ESR device in which a pair of cylindrical magnets having different diameters are coaxially arranged so that one of the cylindrical magnets is housed in the other through a required gap, and the cylindrical magnets inside and outside are individually rotatably supported. Generator. 2. The outer cylindrical magnet according to claim 1, which is built in or externally supported by the large-diameter cylindrical structural member, and the inner cylindrical magnet is built in or externally supported by the small-diameter cylindrical structural member. A magnetic field generator for an ESR device in which the inner and outer cylindrical magnets are individually rotatably supported by rotating a cylindrical structural member having a small diameter and a small diameter.