JPH05249215A - Loop gap resonator - Google Patents

Abstract

PURPOSE:To obtain a loop gap resonator which can make uniform a modulation magnetic field within a loop gap resonator with a simple configuration. CONSTITUTION:A loop gap resonator 1 is constituted by applying conductor thin plates 4a-4d so that gaps 3a-3d over an entire length in axial direction are formed at intervals of 90 degrees on an outer-periphery surface of a cylindrical body 2 with a low dielectric constant. Slits 5a-5c for preventing eddy current which are extended in the circumferential direction and a cut part 6 which communicates the slits 5a-5c and the gaps 4a and 4c are provided on the conductor thin plates 4a-4d and a magnetic flux is allowed to enter the resonator through the cut part 9 and the slits 5a-5c in addition to upper and lower sample insertion opening and the gaps 4a-4c, thus enabling a modulation magnetic field within the resonator to be uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loop gap resonator used in an electron spin resonance method for imaging a sample structure such as a biological material.

[0002]

2. Description of the Related Art Recently, an electron spin resonance method has been used for nondestructively knowing the structure of a material, and a loop gap resonator has been applied to this. As shown in FIG. 13, the loop gap resonator 1 has a structure in which a gap 13 extending over the entire axial length is formed at 90 ° intervals on the outer peripheral surface of a low dielectric constant cylindrical support 12 having a cavity x. It has a configuration in which one resonator body 14a to 14d is fixed. Each of the resonator bodies 14a to 14d is formed of, for example, a copper plate, and a predetermined number of, for example, three rectangular slits 15a extending in the circumferential direction to prevent the generation of an eddy current on its cylindrical surface.
.About.15c are arranged side by side at a predetermined interval in the axial direction and perforated.

Loop gap resonator 1 having the above structure
For example, in order to nondestructively know the structure of a biological substance, after inserting a biological sample into the cavity x of the cylindrical support 12 of the loop gap resonator 1, the loop gap resonator 1 is externally exposed. Is irradiated with microwaves of a constant frequency from the inside of the resonator to cause resonance of the microwaves in the resonator in which the biological sample is inserted, and by the modulation coil and the DC magnetic field generator arranged in the vicinity of the resonator, A modulation magnetic field is applied to the inside of the resonator to obtain an electron spin resonance signal from the spectrum obtained by sweeping the DC magnetic field inside the resonator, and this signal is processed to image the structure of the biological sample, that is, perform imaging measurement. It was

In such a loop gap resonator, when performing an imaging measurement, if there is a variation in the intensity of the modulating magnetic field inside the resonator, that is, if the modulating magnetic field is non-uniform, the electron If the electron spin resonance signal obtained by the spin resonance method is not corrected, accurate and clear imaging measurement cannot be performed. Therefore, it is necessary to know the magnetic field strength of the modulating magnetic field inside the resonator, and it is desired to make the magnetic field distribution of the modulating magnetic field inside the resonator uniform.

[0005]

However, in the above-mentioned conventional loop gap resonator, it was not possible to achieve uniform magnetic field distribution of the modulation magnetic field inside the resonator with a simple structure. That is, in the above-mentioned conventional loop gap resonator, the higher the frequency of the modulating magnetic field generated by the modulating coil is, the more difficult it is to penetrate through the conductive wall of the resonator main body, so that it acts on the biological sample inside the resonator. The modulating magnetic field is formed only by the magnetic flux that does not pass through the conductive wall and enters from the cavity gap and the upper and lower openings. As a result, the magnetic field strength is made uniform inside the resonator. There is an unsolved problem that you cannot do it.
Further, even in the case of the loop gap resonator having the slit as described above, there is no entry of the modulation magnetic field from the slit, and the biological sample inside the resonator has the same structure as described above and the gap of the resonator and the upper and lower parts. Since only the magnetic flux entering from the opening or the like is used as the modulation magnetic field, there is an unsolved problem that the magnetic field strength cannot be made uniform inside the resonator.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example, and an object thereof is to make the modulation magnetic field inside the loop gap resonator uniform with a simple structure. It is to provide a loop gap resonator that can be performed.

[0007]

In order to achieve the above object, a loop gap resonator according to the present invention irradiates a microwave into a resonator in which a sample is inserted to resonate the microwave in the resonator. And a modulation magnetic field was applied to the resonator to sweep the DC magnetic field in the resonator to obtain an electron spin resonance signal, and the signal processing was performed to image the sample structure. A loop gap resonator having an axial gap and a slit applied to the electron spin resonance method is characterized in that a notch is provided so as to communicate between the slit and the gap.

[0008]

According to the present invention, a simple structure is provided in which the slit and the gap of the loop gap resonator are provided so as to communicate these slits with each other. Also, the magnetic flux can enter, and since the magnetic flux is formed by combining these magnetic flux and the magnetic flux that enters from the gap of the resonator and the upper and lower openings, the homogenization of the modulating magnetic field inside the loop gap resonator is achieved. can do.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on its embodiments with reference to the accompanying drawings. FIG. 1 is a schematic explanatory view showing a first embodiment of the loop gap resonator according to the present invention. Referring to FIG. 1, there is shown a schematic diagram of a loop gap resonator 1 according to the present invention, which has a thickness of, for example, 0.3, similar to the conventional example.
A cylindrical support 2 made of, for example, PTFE (polytetrafluoroethylene) having a low dielectric constant of about 0.5 mm and having a cavity x inside, and 90 on the outer peripheral surface of the cylindrical support 2.
It has a configuration in which four resonator bodies 4a to 4d are fixed by adhesion or the like so as to form four gaps 3a to 3d over the entire length in the axial direction at intervals.

Here, each of the resonator bodies 4a to 4d is formed of, for example, a copper plate having a thickness of about 1 mm, and a predetermined number extending in the circumferential direction, for example, to prevent the generation of eddy currents on the cylindrical surface of the copper plate. The three rectangular slits 5a to 5c are provided so as to be arranged side by side at a predetermined interval in the axial direction, and the slits 5a to 5c and the gap 3a of the resonator bodies 4a and 4b are formed.
A notch 6 is provided between the slits 5a to 5c of the resonator bodies 4c and 4d and the gap 3c.

A copper plate 7 for shielding an electric field is arranged on the inner peripheral surface of the cylindrical support 2 at a position facing the gaps 3a to 3d over the entire length in the axial direction. The operation of the above-described embodiment having such a configuration will be described below. Now, the loop gap resonator 1 having the above-mentioned configuration
Is in an operating state, that is, from outside the resonator 1
A microwave having a frequency of 1.2 GHz, for example, is radiated from the upper end of the sample insertion side to cause resonance of the microwave in the resonator, and by a modulation coil (not shown) arranged in the vicinity of the resonator. , A modulation magnetic field is applied to the resonator, and the distribution of this modulation magnetic field in the resonator is detected. In this embodiment, an enameled wire having a diameter of 0.15 mm is applied to the iron core at about 4 mm.
Using 0 windings), measurement was performed at each measurement point (unit: mm) of the XYZ coordinate system as shown in FIG. 2, and the measurement result as shown in FIG. 3 was obtained.

The measurement points are 9 points on the XY plane as shown in FIG. 2 and 5 points with respect to the depth in the Z-axis direction. These measurements were made at 45 points in total, and the arrangement for measurement was set so that the gaps 3a and 3c of the resonator were overlapped on the X axis and the gaps 3b and 3d were overlapped on the Y axis, and the modulation magnetic field was It is hung parallel to the X axis.

As is clear from the measurement results, at the point near the sample insertion port where the sample is inserted into the loop gap resonator 1 (Z = 0, 28 mm in the coordinate system shown in FIG. 2),
The center is weakest in the X-axis direction, and is strong at both ends. At a point at the approximate center of the resonator 1 (Z = 7, 14, 21 mm in the coordinate system shown in FIG. 2), there is a substantially uniform magnetic field distribution in the XY biaxial directions. Further, as a comparative example, the magnetic field inside the resonator is stronger as a whole as compared with a resonator having only slits which will be described later. Thereby, the slits 5a to 5c are notched, and the slits 5a to 5c are cut.
It is understood that by connecting the 5c and the gaps 3a, 3c to each other, the magnetic flux can enter the resonator through the slits 5a to 5c and the notch 6, and the magnetic field distribution inside the resonator can be made uniform. To be done.

Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment has substantially the same structure as the resonator of the embodiment shown in FIG. 1, but as shown in FIG.
1 is different from the resonator of the first embodiment shown in FIG.
From the resonator of the first embodiment shown in FIG.
The point is that the. The other structure is the same as that of the first embodiment shown in FIG. 1. Corresponding parts are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 5 shows the measurement result of measuring the distribution of the modulation magnetic field inside the resonator using the resonator of the second embodiment. The measurement conditions are the same as in the case of the first embodiment shown in FIG. As is apparent from FIG. 5, the resonator of the second embodiment has a stronger magnetic field than that of the resonator of the first embodiment shown in FIG. Also,
Sample insertion point (Z = 0, 28 m in the coordinate system shown in FIG. 2)
In m), the center is weakest, and the arcuate magnetic field distribution is strong at both ends. A point near the center of the resonator (Fig. 2
(Z = 7, 14, 21 mm in the coordinate system shown in Fig. 3), the magnetic field distribution is substantially uniform in the X-axis direction, but in the Y-axis direction, both ends are weak and the magnetic field at the center is considerably stronger than in Fig. 3. It is understood that the arc-shaped distribution is as follows. From this, it is understood that the passage of the magnetic flux is obstructed by the copper plate 7 for the electric field shield, and the magnetic field is weakened thereby.

Next, a third embodiment of the present invention will be described with reference to FIG. This third embodiment, as shown in FIG.
The resonator of the first embodiment shown in FIG. 6 has exactly the same configuration as that of the first embodiment except that the resonator of the first embodiment is rotated 45 degrees clockwise about the Z axis. The detailed description thereof will be omitted.

FIG. 7 shows the measurement result of measuring the distribution of the modulation magnetic field inside the resonator using the resonator of the third embodiment. The measurement conditions are the same as in the case of the first embodiment shown in FIG. Also in the resonator of the third embodiment, the strength of the magnetic field is stronger than that of the resonator shown in FIG. In the X-axis direction, the center has a weak arcuate magnetic field distribution, and in the Y-axis direction, the center has the strongest arcuate magnetic field distribution. In this way, since the magnetic field is strong in the outer peripheral portion in the X-axis direction, the slit 5a
It is understood that the magnetic flux is entering from ~ 5c, and Y
In the axial direction, since the magnetic field is weaker on the outer peripheral side, it is understood that the modulating magnetic field parallel to the X axis is blocked by the copper plate 7 for electric field shield and weakens the passing magnetic flux.

Next, a fourth embodiment of the present invention will be described with reference to FIG. The fourth embodiment has substantially the same structure as the resonator of the first embodiment shown in FIG. 1, but the first embodiment shown in FIG.
The difference from the resonator of the embodiment is that the resonator of the first embodiment shown in FIG. 1 has four resonator bodies 4 so as to form four gaps 3a to 3d in the circumferential direction of the cylindrical portion.
The fourth embodiment is different in that it has two resonator bodies 4a and 4b so as to form only two gaps 3a and 3b. .. The other structure is the same as that of the resonator of the first embodiment shown in FIG. 1, and the portions corresponding to those of the resonator of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and the detailed description thereof will be omitted. To do.
The resonator of the fourth embodiment is arranged so that the gaps 3a and 3b overlap on the X axis of the coordinate system of FIG.

FIG. 9 shows the measurement result obtained by measuring the distribution of the modulation magnetic field inside the resonator using the resonator of the fourth embodiment. The measurement conditions are the same as in the first embodiment shown in FIG. In the resonator of the fourth embodiment, as is clear from the measurement results shown in FIG. 9, a point near the insertion port where the sample is inserted into the loop gap resonator (Z = 0 in the coordinate system shown in FIG. 2, 28 mm) has an arcuate magnetic field distribution with the weakest center in the X-axis direction. At a point near the center of the resonator (Z = 7, 14, 21 mm in the coordinate system shown in FIG. 2),
The magnetic field distribution is substantially uniform in the X-axis direction. It will be understood that the magnetic field distribution is substantially uniform in the Y-axis direction.

Next, a fifth embodiment of the present invention will be described with reference to FIG. In the fifth embodiment, the loop gap resonator of the fourth embodiment shown in FIG. 8 is rotated 90 degrees about the Z axis, and the gaps 3a and 3b are superposed on the Y axis of the coordinate system of FIG. It is a thing. FIG. 11 shows the measurement result of measuring the distribution of the modulation magnetic field inside the resonator using the resonator of the fifth embodiment. The measurement conditions are the same as in the case of the first embodiment shown in FIG.

As can be seen from the measurement results shown in FIG. 11, the loop gap resonator of the fifth embodiment has a stronger magnetic field as a whole than the resonator of the fourth embodiment shown in FIG. There is. In the X-axis direction, the center has the weakest arcuate magnetic field distribution, and in the Y-axis direction, the center has the strongest arcuate magnetic field distribution. Therefore, in the resonator of the fourth embodiment shown in FIG. 8, it can be seen that the copper plate 7 for electric field shields the magnetic flux and weakens the magnetic field, and from the fifth embodiment, the slits 5a to 5c allow the inside of the resonator. It will be understood that the magnetic flux enters.

Incidentally, as a comparative example, a conventional loop gap resonator having only the slit shown in FIG. 13 and not having the cut portion 6 was used under the same measurement conditions as in the first embodiment described above. FIG. 14 shows the result of measuring the distribution of the modulation magnetic field of the. As is clear from FIG. 14, in the case of the comparative example, the strength of the magnetic field is generally weaker than in the case of the resonators shown in the respective examples of the present invention. Point (Z = in the coordinate system shown in FIG. 2)
(0, 28 mm), the center is weakest in the X-axis direction and is strong at both ends. A point near the center of the resonator (Z = 7, 14, 21 mm in the coordinate system shown in FIG. 2)
In, the magnetic field distribution is substantially uniform in the X-axis direction. In the Y-axis direction, the center is strongest, and the arc-shaped magnetic field distribution is weak at both ends. Therefore,
It will be understood that magnetic flux does not enter from the slit. Therefore, the magnetic flux distribution inside the resonator could not be made uniform.

In the above embodiments, the loop gap resonator having four or two gaps has been described, but the present invention is not limited to this, and the number of gaps can be set arbitrarily. Further, in each of the above-described embodiments, one end of the slits 5a to 5c in the circumferential direction and the gap 3a,
The case where the notch 6 is provided between the slit 3a and the groove 3c has been described. However, the present invention is not limited to this, and the notch 5 may be provided between the circumferential ends of the slits 5a to 5c and the gaps 3a to 3d. Well, further, as shown in FIG. 12, the slits 5a to 5c are divided into two at the central portion in the circumferential direction, and the gaps 3a to 3d side and the gaps 3a to 3 of both the divided slits.
The notches 6 may be provided between them and d.

Further, in the loop gap resonator of the present invention, the copper plate 7 for electric field blocking interferes with the magnetic flux and weakens the strength of the magnetic field, so that this can be adjusted or the modulation coil can be adjusted to make the modulation magnetic field uniform. It is possible to make the magnetic field distribution inside the resonator even more uniform.

[0025]

As described above, according to the loop gap resonator of the present invention, since the slit of the loop gap resonator having the slit is provided to communicate between the slit and the gap, this cut is provided. It is possible to enter the modulation magnetic field into the inside of the loop gap resonator through the slits and slits, and these are used as the modulation magnetic field together with the magnetic flux entering through the gap of the resonator and the upper and lower openings. It is possible to achieve the homogenization of the modulating magnetic field and to strengthen the magnetic field inside the resonator.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing a first embodiment of a loop gap resonator according to the present invention.

FIG. 2 is a diagram showing a coordinate system showing points for measuring a magnetic field distribution in the first embodiment of FIG.

FIG. 3 is a diagram showing a measurement result of a magnetic field distribution of the first embodiment of FIG.

FIG. 4 is a schematic explanatory view showing a second embodiment of the loop gap resonator according to the present invention.

FIG. 5 is a diagram showing the measurement result of the magnetic field distribution of the second embodiment of FIG.

FIG. 6 is a schematic explanatory view showing a third embodiment of the loop gap resonator according to the present invention.

FIG. 7 is a diagram showing the measurement result of the magnetic field distribution of the third embodiment of FIG.

FIG. 8 is a schematic explanatory view showing a fourth embodiment of the loop gap resonator according to the present invention.

FIG. 9 is a diagram showing the measurement result of the magnetic field distribution of the fourth example of FIG.

FIG. 10 is a schematic explanatory view showing a fifth embodiment of the loop gap resonator according to the present invention.

11 is a diagram showing the measurement result of the magnetic field distribution of the fifth embodiment of FIG.

FIG. 12 is a schematic explanatory diagram showing a modified example of the present invention.

FIG. 13 is a schematic explanatory diagram of a conventional loop gap resonator.

FIG. 14 is a diagram showing the measurement result of the magnetic field distribution of the conventional example of FIG.

[Explanation of symbols]

 1 Loop gap resonator 2 Cylindrical support 3a-3d Gap 4a-4d Resonator body 5a-5c Slit 6 Cut part 7 Copper plate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location 9118-2J G01N 24/10 R

Claims (1)

[Claims] 1. A direct current magnetic field in a resonator, wherein a microwave having a sample inserted therein is irradiated with microwaves to cause microwave resonance in the resonator and a modulation magnetic field is applied to the resonator. In a loop gap resonator having an axial gap and a slit, which is applied to an electron spin resonance method in which an electron spin resonance signal is swept to obtain an image of a sample structure by processing the signal. A loop gap resonator, wherein a cut portion is provided so as to communicate between the slit and the gap.