JP2736472B2 - ESR device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron spin resonance apparatus using a permanent magnet magnetic circuit as a magnetic field generator, and by continuously changing the distance between opposing surfaces of a yoke. Ultra-compact size by combining a permanent magnet magnetic circuit with a movable yoke for continuously adjusting the magnetic field strength inside the unit and a microwave receiver / transmitter
Regarding ESR equipment.

2. Description of the Related Art Electron spin resonance devices (hereinafter, referred to as ESR devices) are widely used in research and development for chemical analysis.

In addition, the ESR device can detect unpaired electrons due to natural radiation damage to the measured object, and relics, geological minerals,
Since it can accurately measure the age of fossils, it has recently been used in the fields of archeology and earth science.

An ESR device used for such an application includes a magnetic field generator and a microwave transmitting / receiving device connected to the magnetic field generator. It is necessary to generate a uniform magnetic field with an intensity determined according to a physical property value, a microwave frequency, and the like with high accuracy.

In addition, the ESR device measures the magnetic field strength that causes magnetic resonance by continuously changing the generated high-precision and uniform magnetic field during measurement. An electromagnet magnetic circuit has been used which can easily perform the continuous change of the magnetic field strength by continuously changing the applied current to the electromagnet.

However, an ESR device using an electromagnet magnetic circuit has a disadvantage that the entire device is large and expensive, weighing 1 to 2 tons,
The configuration of the microwave receiving / transmitting device is also complicated, which has been a factor of increasing the size and the price.

On the other hand, by using only permanent magnets as a magnetic field source and changing the facing distance (gap length) of a pair of permanent magnets,
A configuration for changing the magnetic field strength has been proposed.

However, the magnetic field required for the ESR device is required to have a high degree of uniformity of 0.01% or less, and when changing the facing distance, due to factors such as the axes of the permanent magnets moving with respect to each other, It has the disadvantage that the uniformity of the magnetic field becomes worse,
ESR devices using permanent magnet magnetic circuits have not been put into practical use.

Problems to be Solved by the Invention Therefore, the applicant examined a configuration in which the magnetic field strength in the required air gap was continuously changed without changing the facing distance of the permanent magnet, and first used a permanent magnet magnetic circuit. An ESR device was proposed.

That is, a permanent magnet is disposed on each of the opposing surfaces of the pair of yoke opposing each other via the gap, and the distance between the opposing surfaces of the yoke is continuously changed on at least one of the pair of yoke. A configuration was proposed in which a movable yoke was arranged, the magnetic reluctance formed by the permanent magnet, the yoke, and the movable yoke was continuously varied by operating the movable yoke, and the magnetic field intensity in the air gap could be continuously adjusted (actual Kaihei 1-10457
Four).

Further, as a configuration capable of changing the magnetic field strength in the required gap with high accuracy, a movable yoke is disposed on each of the pair of yokes, and these movable yokes approach and separate symmetrically with respect to the center cross section of the gap. A magnetic circuit for generation has been proposed (Japanese Patent Application No. 1-154875).

For the same purpose, a plurality of movable yokes each arranged on a yoke are constituted, and for example, these are arranged coaxially, and a magnetic field for generating a magnetic field which achieves a finer magnetic field intensity adjustment by moving each is provided. A circuit was proposed (Japanese Patent Application No. 1-218233).

These proposals have made it possible to adopt four magnetic circuits using permanent magnets as the magnetic field generation source of the ESR device.

However, in order to improve the practicality of the ESR device, along with the improvement of the magnetic circuit, these magnetic circuits are effectively arranged,
In addition, it is necessary to reduce the size and weight of the entire ESR device, including peripheral devices for accurately reading the value of the magnetic field causing magnetic resonance.

The present invention is capable of continuously and highly accurately changing the magnetic field strength while maintaining good uniformity of the magnetic field strength in the air gap and maintaining high uniformity. The purpose is to provide the device at low cost.

It is another object of the present invention to provide an ESR device that can accurately read the value of a magnetic field that causes magnetic resonance during measurement, and that can directly observe and record an ESR absorption curve.

In addition, it is easy to manufacture and maintain and has a traditional ESR
The purpose is to provide an ESR device that is extremely cheap compared to the device.

Means for Solving the Problems The ESR device according to the present invention, as a magnetic field generating device, arranges a permanent magnet on each of opposing surfaces of a pair of yokes opposing each other via an air gap, and attaches a pole piece to the permanent magnet. A movable yoke for continuously changing a distance between opposing surfaces of the yoke is disposed on at least one of the pair of yoke, and a magnetic path formed by a permanent magnet, a yoke, and a movable yoke. Is characterized by using a magnetic circuit that forms a continuously changing magnetic field in a gap facing a permanent magnet.

Also, around the pole piece or permanent magnet of the magnetic circuit,
Or a coil for applying a modulating magnetic field for applying an alternating current to apply a modulating magnetic field to the gap around the movable yoke and / or a coil for applying a direct current to sweep a magnetic field in the gap. Further, a cavity resonator into which a sample to be measured can be inserted is arranged in the gap, and a microwave circuit including a Doppler radar gun diode is directly connected to the cavity resonator. An ESR device characterized by the following.

Further, in the ESR apparatus of the present invention, various means 2 to 17 described later can be combined with the above-described means 1.

The modulating magnetic field applying coil is provided around a magnetic pole piece or a permanent magnet (means 2), the modulating magnetic field applying coil is provided around a movable yoke (means 3), and the sweep magnetic field applying coil is provided as a magnetic pole. That the coil for applying the sweep magnetic field is provided around the movable yoke (means 5); and the coil for applying the modulated magnetic field is provided around the pole piece or permanent magnet. In addition, the sweep magnetic field applying coil is provided around the movable yoke (means 6). In the means 2 and 3, AC power supply means capable of supplying an alternating current to the modulating magnetic field applying coil is provided. Display means for outputting the microwave detection signal to the oscilloscope (means 7). In means 4 and 5, a DC power supply means capable of supplying a DC current to the sweep magnetic field applying coil; Display means for outputting a microwave detection signal upon application of a sweep magnetic field to an XY recorder (means 8); AC power supply means capable of supplying an AC current to a coil for applying a modulation magnetic field is provided; DC power supply means capable of supplying a DC current to the coil for applying a DC magnetic current to the sweep magnetic field applying coil, applying a sweep magnetic field, and applying an AC current to the modulation magnetic field applying coil to apply the modulation magnetic field. An electric circuit for increasing the detection signal voltage when these magnetic fields are superimposed and improving the sensitivity and a display means for outputting the detection signal are provided (means 9). In the means 9, the detection signal voltage is increased. The electric circuit that improves sensitivity by using a rocking amplifier (means 10), a microwave circuit that integrates a microwave oscillator and a microwave detector into a single module (Means 11), the cavity resonator is a TE ₁₀₂ mode rectangular cavity resonator (means 12), and the permanent magnet is an Fe-BR-based permanent magnet (means 1).
3) The movable yoke is a bolt member that penetrates the yoke and moves forward and backward (means 14). In the means 14, the bolt member has a configuration in which a plurality of bolt members are coaxially arranged (means 15). 15, the bolt member is composed of a large-diameter coarse moving screw and a small-diameter fine moving screw (means 16); a movable yoke is provided on one of a pair of yokes and a fixed yoke is provided on the other (means 17); A movable yoke is provided on both of the pair of yoke (means 1
8).

In the present invention, the yoke for disposing the permanent magnet can be arbitrarily selected according to the shape and magnetic properties of the permanent magnet, such as a rectangular plate.

As the permanent magnet serving as a magnetic field generating source, it is desirable to select a known material and a shape thereof according to the required magnetic field strength, the size of the device, and the like, such as a rare earth magnet and a ferrite magnet. In particular, R is a resource-rich light rare earth element such as Nd or Pr, and has an extremely high energy product of 30 MGOe or more containing B and Fe as main components. By using the Fe-BR-based permanent magnet, the size can be significantly reduced.

Further, the pole piece attached to the permanent magnet is effective for improving the uniformity of the magnetic field in the air gap.

In particular, when a plurality of block-shaped permanent magnets are used integrally, variations in the magnetic characteristics of each block-shaped permanent magnet can be reduced, and magnetic flux can be effectively concentrated in the air gap.

Various known configurations can be adopted as the pole piece.
In particular, a configuration in which an annular protrusion having a trapezoidal cross section or a rectangular shape is provided on the peripheral portion of the disk-shaped pole piece is desirable.

In addition, as shown in FIG. 2, for example, a movable yoke for continuously changing the magnetic resistance of the magnetic path includes a large-diameter coarse movement screw and a small-diameter fine movement screw coaxially arranged. After finely adjusting the magnetic field strength by moving forward and backward, fine adjustment is performed by moving the fine movement screw forward and backward, so that the change in the required gap Bg can be moderated.

As shown in FIG. 7, even with a single screw member, the magnetic field can be adjusted with high precision by selecting the outer diameter of the screw member, the screw pitch, and the like, and the object of the present invention can be achieved.

The shape and the like of the movable yoke can be arbitrarily selected, and known moving means such as a configuration of a rack and pinion, a hydraulic stone, and a slide mechanism can be adopted. The arrangement of the movable yokes on the yoke is not limited to the configuration in which the ones having different diameters are arranged in parallel as shown in the embodiment, the plural ones having the same diameter are arranged in parallel, or the plural small diameter movable yokes are arranged around one large diameter movable yoke. Can be arranged as appropriate.

Further, as shown in FIG. 8, a pair of movable yokes may be used so that the pair of movable yokes face each other and symmetrically approach and separate from the center cross section of the gap.

A microwave circuit that oscillates and detects microwaves is directly bonded to a cavity resonator using a Doppler radar gun diode in which a microwave oscillator and a microwave detector are integrated into a module as shown in the embodiment.

In the present invention, a modulation magnetic field applying coil for applying an alternating current to apply a modulation magnetic field into the air gap and / or a magnetic field in the air gap is swept around the pole piece or the permanent magnet, or around the movable yoke. For this purpose, a sweep magnetic field applying coil for supplying a direct current is arranged.

Regarding the arrangement and operation of these coils,
As will be described later with reference to FIGS. 6 to 6, particularly when these coils are arranged near the permanent magnet, adverse effects on the permanent magnet due to heat generation of the coil, for example, a magnetic field in a gap due to a temperature change of the permanent magnet. In consideration of a decrease in strength, a decrease in uniformity, and the like, it is desirable that the current to be supplied be as small as possible.

By providing a known AC power supply means capable of applying an AC current to the modulation magnetic field applying coil, and providing a known display means for outputting a detection signal when the modulation magnetic field is applied to an oscilloscope, the ESR absorption curve can be measured with an oscilloscope. It is easy to see directly.

Also, a known DC power supply means capable of supplying a DC current to the sweep magnetic field applying coil is provided, and after adjusting the movable yoke to set the magnetic field intensity near the magnetic resonance point, the DC current is supplied to the sweep magnetic field applying coil. Also, by sweeping the magnetic field in the air gap, the ESR absorption curve can be directly viewed with the XY recorder in the same manner as described above.

Further, by using both the sweep magnetic field applying coil and the modulation magnetic field applying coil, it is possible to perform more accurate measurement.

That is, after setting the magnetic field strength near the magnetic field resonance point,
By applying a direct current to the sweep magnetic field applying coil to sweep the magnetic field in the air gap, and applying an alternating current to the modulating magnetic field applying coil, the modulating magnetic field is superimposed on the sweep magnetic field, and the microwave in that state is superimposed. A signal (detection signal voltage) is boosted by a known electric circuit such as a rockin amplifier to improve the sensitivity and connected to a device that outputs the signal to a known recorder. It can be recorded on a recorder or the like as an absorption curve.

In this configuration, by performing processing such as differentiation, second derivative, and integration on the ESR absorption curve, as compared to the ESR absorption curve obtained by the configuration in which only the modulation magnetic field application coil or the sweep magnetic field application coil is arranged. The value of the magnetic field intensity that causes magnetic resonance can be obtained with high accuracy, and the linearity of the ESR absorption line can be measured with higher resolution.

DISCLOSURE OF THE INVENTION Based on the Drawings The present invention will be described in more detail below with reference to the drawings.

Configuration In the ESR device and its magnetic circuit shown in FIGS. 1 and 2, a pair of plate-shaped yokes (1a) and (1b) are provided with yoke supporting members (5a) and (5b) made of a non-magnetic material. The disk-shaped permanent magnets (3a) and (3b) attached to the opposing surfaces of the plate yokes (1a) and (1b), respectively, are arranged with the different magnetic poles facing each other. The pole pieces (4a) and (4b) are fixed to the facing surface, and a required gap (2) is formed between the pole pieces (4a) and (4b).

A coil (20) for applying a modulating magnetic field is provided around the pole pieces (4a) and (4b).

In FIG. 2, a large-diameter coarse yoke (6) is disposed on the lower yoke (1a). That is, the coarse yoke (6) is formed of a bolt member threaded on the outer peripheral surface at a required thread pitch, and is screwed into the hole of the yoke (1a).

Further, a fine yoke (7) composed of a small-diameter bolt member threaded at a fine thread pitch is coaxially screwed with the coarse yoke (6).

When the handle (6a) provided on the top of the coarse yoke (6) is rotated, the coarse yoke (6) can be continuously moved in the vertical direction in the drawing, and similarly, the handle of the fine yoke (7) By rotating (7a), the fine movement yoke (7) can be moved continuously.

On the other hand, a fixed yoke (8) is fixed to the inner surface of the upper yoke (1b) in the figure, and is arranged opposite to the coarse yoke (6) and the fine yoke (7) to form a gap (9). ing.

A cavity (11) is arranged in a required gap (2) between the pole pieces (4a) and (4b), and is supported by the yoke (1a) (1b) by its flange member (13). On the outer surface of the member (13), a microwave circuit (14) composed of a Doppler radar gun diode in which a microwave oscillator and a microwave detector are integrally modularized is provided. In the drawing, reference numeral 10 denotes a cover, 12 denotes a sample tube, and 15 denotes an oscillation frequency volume.

A DC power supply (16), an AC power supply (17), and an oscilloscope (18) are connected to the microwave circuit (14).

Operation and Effect With the configuration shown in FIG. 2 described in detail, a magnetic path indicated by a broken line in the figure is formed in the magnetic circuit. Here, the coarse moving yoke (6) is screwed forward and backward to form the coarse moving yoke (6). The distance opposed to the fixed yoke (8), that is, the air gap (9) can be continuously changed, and the magnetic field strength in the air gap (2) formed by the pole pieces (4a) (4b) is continuously changed. It is possible to do.

That is, when the opposing distance between the coarse yoke (6) and the fixed yoke (8) is increased, the magnetic field intensity in the gap (2) is weakened. Conversely, when the opposing distance is reduced, the gap (2) is reduced.
The magnetic field strength in the inside increases.

After the required distance between the coarse yoke (6) and the fixed yoke (8) is set, the fine yoke (7) having a fine thread pitch is further screwed forward and backward, so that the fine yoke (7) can be connected to the fixed yoke (8). By appropriately selecting the facing distance, the magnetic field intensity in the gap (2) can be increased or decreased by a small amount.

When the two types of movable yokes are rotated, the required ESR absorption can be obtained by increasing or decreasing the magnetic field intensity by a small amount, and the change in the magnetic field can be quantitatively grasped by the number of rotations, and the magnetic pole pieces (4a) (4
b) A modulating magnetic field application coil (20) is arranged around and a modulating magnetic field is applied by applying an alternating current.
The ESR signal can be observed directly on the oscilloscope (18).

Other Configurations In the above description, the coil (20) disposed around the pole pieces (4a) (4b) was described as a modulation magnetic field application coil for applying a modulation magnetic field by applying an alternating current. DC power supply means is attached to the coil (20), and the magnetic field in the air gap (2) is swept by applying a DC current, and the ESR signal is directly observed on an XY recorder (not shown) as described above. It is also possible.

In the magnetic circuit shown in FIG. 3, the sweep magnetic field applying coil (21) is arranged around the coarse yoke (6) without disposing the modulating magnetic field applying coil around the pole pieces (4a) (4b). This is the configuration.

DC power supply means is attached to the sweep magnetic field applying coil (21), and the gap (2) is formed by applying a DC current.
The internal magnetic field can be swept. This coil (2
It is also possible to provide an AC power supply means in 1) and apply a modulation magnetic field in the gap (2) by supplying an AC current.

The magnetic circuit shown in FIG. 4 has a configuration in which the modulation magnetic field applying coil (20) and the sweep magnetic field applying coil (21) described in FIG. 2 and FIG. A DC current is applied to the coil (21) to sweep the magnetic field, and an alternating current is applied to the modulation magnetic field applying coil (20), and these magnetic fields are superimposed to detect the detected signal voltage during this measurement. Do not boost with a rockin amplifier,
By inputting it to a recorder, the detected signal can be drawn and recorded as an ESR absorption curve.

The magnetic circuit shown in FIGS. 5 and 6 shows a configuration in which a modulation magnetic field applying coil (20) and a sweep magnetic field applying coil (21) are arranged close to each other. In FIG. The coils (20) and (21) are arranged around the pole pieces (4a) and (4b) and the permanent magnets (3a) and (3b), and in FIG. Since it is arranged around the moving yoke, the same effect as the magnetic circuit of FIG. 4 can be obtained.

The magnetic circuit shown in FIGS. 7 and 8 is based on the magnetic circuit shown in FIG. 2, and the movable yoke is formed by a single screw member (6 ').
(Fig. 7) and a pair of yokes (1a)
FIG. 8 shows a configuration (FIG. 8) in which movable yokes (6 ') and (6') are arranged in each of (1b). All of them can achieve the object of the present invention. An ESR absorption curve similar to that used was observed.

Example 1 Example 1 Using a magnetic circuit shown in FIG. 2, BH (max) was applied to a permanent magnet.
Using 35MGOe Fe-B-Nd based magnet, 20mmΦ for plate yoke
The coarse movement screw and 7 mmΦ fine movement screw are coaxially arranged as a movable yoke, and a gun diode for a Doppler radar combining a microwave oscillator and a detector is directly connected to a TE ₁₀₂ mode rectangular cavity resonator. When the ESR device shown was assembled, the dimensions were 70 (height) x 160 (width) x 120 (depth)
Conventional ESR using an electromagnet with a total weight of 1.5 kg (mm)
It was possible to achieve an ultra-compact size that was incomparable with the device.

In addition, it is possible to continuously change the magnetic field in the air gap with high accuracy of ± 1 G or less by one rotation of the fine movement screw,
The change of the magnetic field was obtained with an accuracy of 0.1G unit for the absorption line width of about 1G signal in ESR measurement.

For example, by setting Bg = 375.6 mT and superimposing a 60 m-cycle modulated magnetic field of 2 mT, the ninth oscilloscope displays
An ESR absorption curve as shown in the figure could be drawn.

Example 2 Using the ESR apparatus of the present invention shown in Example 1, the weight of DPPH powder (1.1-Dipheny-1-picryl-hydrazil) was changed, and an ESR absorption curve was observed for each weight.

As a result, as shown in FIG. 10, it was confirmed that the relative signal intensity obtained from the ESR absorption curve was proportional to the number of radicals of the DPPH powder.

In this measurement, after setting the magnetic field in the air gap to Bg = 375 mT in advance, an ESR absorption curve was drawn on an oscilloscope by superimposing a 60 m cycle modulated magnetic field of 3 mT.

Example 3 Using the ESR apparatus of the present invention shown in Example 1, bituminous coal powders from various places were sampled, and the superposition thereof was changed.
The R absorption curve was observed. As a result, as shown in FIG.
It can be confirmed that the relationship between the relative signal strength and the weight obtained from the SR absorption curve differs from place to place.

That is, it was clarified that the spin concentration changes depending on the production location and sampling depth of these bituminous coal powders. In FIG. 11, a circle indicates a bituminous coal powder from the Kushiro Pacific Coal Mine, Hokkaido (7 central west layers), a cross indicates a Kyushu-Matsushima Coal Mine (lower layer in southern No. 4), and a cross indicates a bituminous coal powder from the Akahira Coal Mine, Hokkaido (8 layers).

In this measurement, after setting the magnetic field in the air gap to Bg = 373 to 375 mT according to each sample, an ESR absorption curve was drawn on an oscilloscope by superimposing a 60 m cycle modulation magnetic field of 3 mT.

Advantages of the Invention As is clear from the embodiment, the conventional ES which is not portable
Compared to the R device, the ESR device according to the present invention has an advantage that the total weight is 2 kg or less and the volume can be extremely small, so that the ESR device can be carried to the measurement magnetic field with one hand.

In addition, by using a permanent magnet magnetic circuit, a large power supply that generates a static magnetic field in the air gap of the magnetic circuit, a water cooling device is unnecessary, and the microwave circuit also has a Doppler radar gun diode directly connected to the cavity resonator, The number of parts is greatly reduced due to simplification compared to the conventional method,
It is easy to manufacture and maintain, and can be provided at a much lower cost than conventional ESR devices are expensive. It can also be used as an ESR applied measuring instrument such as a radiation dosimeter.

Furthermore, despite the simple configuration, the magnetic field inside the cavity resonator is maintained at a high accuracy of ± 1G or less and continuously changed with 0.1G accuracy, despite the simple configuration using a movable yoke in the permanent magnet magnetic circuit. be able to.

[Brief description of the drawings]

FIG. 1 is an explanatory perspective view showing one embodiment of an ESR device according to the present invention. FIG. 2 is a longitudinal sectional view showing one embodiment of a magnetic circuit used in the ESR device of FIG. 3 to 8 are longitudinal sectional views showing another embodiment of the magnetic circuit used in the ESR device of FIG. FIG. 9 is a diagram showing an image of an oscilloscope of the ESR device according to the present invention. FIG. 10 is a graph showing measurement results of DPPH (diphenyl-picryl-hydrazyl) powder using the ESR apparatus according to the present invention. FIG. 11 is a graph showing measurement results of bituminous coal powder using the ESR device according to the present invention. 1a, 1b ... yoke, 2 ... gap, 3a, 3b ... permanent magnet, 4a, 4b ... pole piece, 5a, 5b ... yoke support material, 6, 6 '... coarse movement yoke, 7 …… Fine yoke, 10… Cover, 11… Cavity resonator, 12 …… Sample tube, 13 …… Flange member, 14 …… Microwave circuit, 15 …… Oscillation frequency volume, 16 …… DC power supply, 17 …… AC power supply, 18 …… Oscilloscope, 20 …… Modulation magnetic field application coil, 21 …… Sweep magnetic field application coil.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A Sho 53-60882 (JP, U) JP 3-56006 (JP, Y2) JP 7-43668 (JP, Y2)

Claims (1)

(57) [Claims] 1. A permanent magnet is arranged on each of opposing surfaces of a pair of yoke opposing each other with a gap therebetween, and a pole piece is attached to the permanent magnet. A movable yoke for continuously changing the distance between the opposed surfaces of the permanent magnet, the magnetic resistance of the magnetic path formed by the permanent magnet, the yoke, and the movable yoke is made continuously variable, and the space between the permanent magnets is opposed. A magnetic circuit that forms a magnetic field that continuously changes in the gap; a coil for applying a modulation magnetic field in the gap; and / or a coil for applying a sweep magnetic field in the gap; In an ESR device consisting of a cavity resonator in which a sample to be measured can be inserted and a microwave circuit that oscillates and detects microwaves, the microwave circuit consists of a Doppler radar gun diode, One that is directly connected to the cavity resonator ESR apparatus according to claim.