JP2007003445A - Fabry-perot resonator for esr, and esr device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Fabry-Perot resonator that is compatible with a temperature adjustable device, is also compatible with a magnet device for generating a static magnetic field in the Y-axial direction, and can improve the degree of freedom of a measured sample, and to provide an ESR (electron spin resonance) device using such a Fabry-Perot resonator. <P>SOLUTION: A pair of reflectors that are bent in a concave shape and have a shape obtained by cutting a concave section in a cylindrical inner wall with planes parallel with a cylindrical axis are arranged so as to face the concave surfaces to each other while matching the axial directions. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a Fabry-Perot resonator that resonates a high frequency, and a high magnetic field / high frequency ESR device using the resonator.

  An ESR apparatus is a type of magnetic resonance apparatus that irradiates a sample to be measured placed in a static magnetic field with microwaves and records the state in which the irradiated microwave is absorbed by the sample to be measured as a spectrum. . When free radicals are present in the sample to be measured, microwave absorption occurs as the static magnetic field is swept, and an absorption spectrum reflecting the free radical molecular structure is recorded in the recorder. By analyzing this absorption spectrum, information on the molecular structure of the free radical can be obtained.

  In recent years, in order to dramatically improve the sensitivity and resolution of an ESR apparatus, attempts have been made to increase the strength of the static magnetic field applied to the sample to be measured and to increase the electromagnetic wave used for resonance from the microwave band to the millimeter wave band. ing.

  FIG. 1 shows a basic configuration of a high magnetic field ESR apparatus. In the figure, reference numeral 5 denotes a magnet device that generates a strong static magnetic field, such as a superconducting magnet. Inside the vertical hole along the central axis (Y axis) of the cylindrical dome-shaped magnet device 5, a detector 1 containing a substance to be measured is disposed.

  In general, an electromagnetic wave having a constant frequency is continuously supplied from the high-frequency circuit unit 2 to the detector 1 while sweeping the magnetic field of the magnet device 5. During the sweep, when the resonance condition of the measurement substance is satisfied with a certain magnetic field strength, the amount of electromagnetic waves reflected from the detector 1 changes. The change of the reflected wave at this time is detected by the high frequency circuit unit 2, converted into a spectrum through the signal processing unit 3, and displayed on the spectrum display device 4.

When performing ESR measurement using a high magnetic field and a high frequency, the detector 1 disposed in the magnet device 5 is mainly a cavity resonator or a Fabry-Perot resonator. The performance of the resonator is generally evaluated by the Q value and the intensity B ₁ of the generated high frequency magnetic field.

The cavity resonator is widely used as a detector for ESR measurement because it has a high Q value and a strong B ₁ intensity. However, in the case of a cavity resonator, when the measurement frequency is in a high frequency region, the Q value is reduced in proportion to the square root of the frequency. Furthermore, the volume of the resonator is reduced, and the volume of the measurement sample that can be used is severely limited.

For example, in the case of a TE ₀₁₁ type cylindrical mode resonator that resonates at 95 GHz, both the diameter and height are 4 mm. Since the measurement sample is filled in a glass tube having a diameter of 1 mm or less and inserted into the resonator, the dimensions are small and extremely difficult to handle. As the resonance frequency is further increased, the use of a cavity resonator is practically disadvantageous because the resonator dimensions and sample volume must be made smaller and smaller in inverse proportion to the increase in frequency.

  On the other hand, a Fabry-Perot resonator is composed of two reflectors, and has a higher Q value and a larger measurement volume than a cavity resonator in a high-frequency region above millimeter waves. Widely used for the ESR measurement used (Patent Document 1).

  2 and 3 show two typical Fabry-Perot resonators. First, the Fabry-Perot resonator of the type shown in FIG. 2 is used when the static magnetic field generated by the magnet device 5 of FIG. 1 is oriented in the Y-axis direction. The basic configuration is composed of a concave mirror 7 processed with a spherical surface and a reflecting mirror 10 made of a flat plate, and a high-frequency magnetic field 8 (and an electric field with a phase difference of 90 degrees) supplied from the waveguide 6 is multiplexed as shown in the figure. reflect. At this time, the measurement sample 9 is placed at the center of the reflecting mirror 10 (Non-Patent Document 1). Since the high frequency magnetic field 8 has a component on the ZX plane perpendicular to the static magnetic field direction Y, magnetic resonance can occur.

  On the other hand, a Fabry-Perot resonator of the type shown in FIG. 3 is composed of a pair of spherically processed concave mirrors 12, and a high-frequency magnetic field 13 (and an electric field with a phase difference of 90 degrees) supplied from the waveguide 11 is obtained. As shown in the figure, multiple reflections are made between concave mirrors. At this time, the measurement sample 14 is placed at an exactly middle position between the pair of concave mirrors 12. Since the high-frequency magnetic field 13 has a component on the XY plane, in order to cause magnetic resonance, the static magnetic field generated by the magnet device 5 in FIG. 1 is desirably in the Z-axis direction.

Japanese Patent Laid-Open No. 10-123072 Japan Society for Invention and Innovation Technical Report 2005-501662

By the way, in the case of a Fabry-Perot resonator of the type shown in FIG. 2, when this resonator is installed in a sealed space such as a temperature variable device, the measurement unit of the temperature variable device usually has a shape elongated in the Y-axis direction. Therefore, there is a problem that it is difficult to replace the measurement sample. Further, since the Fabry-Perot resonator of the type shown in FIG. 2 has poor symmetry of the resonator and the high-frequency standing wave is easily distorted, the strength of the high-frequency magnetic field B ₁ applied to the measurement sample becomes weak, and the sensitivity Becomes worse. In addition, since the measurement sample is placed directly on the reflecting mirror, an experiment in which the sample angle is rotated cannot be performed.

  On the other hand, since the Fabry-Perot resonator of the type shown in FIG. 3 employs a spherical mirror, the high-frequency magnetic field can have components in both the X and Y directions. Therefore, when the magnet device 5 that generates a static magnetic field in the Y-axis direction is used, there is a disadvantage that an ESR signal cannot be obtained unless a high-frequency magnetic field is generated in the X-axis direction. Therefore, in an experiment using the magnet device 5 that generates a static magnetic field in the Y-axis direction, a special device is required to reliably generate a high-frequency magnetic field in the X-axis direction. When a high-frequency magnetic field in either X or Y direction is used for resonance detection, a magnet device in the Z-axis direction is required. However, as the magnetic field becomes higher, a static magnetic field is generated in the Z-axis direction. This method is disadvantageous because it is difficult to obtain a magnet device.

  In view of the above points, the object of the present invention is a Fabry-Perot that is compatible with a temperature variable device, is compatible with a magnet device that generates a static magnetic field in the Y-axis direction, and can improve the degree of freedom of a measurement sample. It is an object of the present invention to provide a resonator and an ESR device using such a Fabry-Perot resonator.

In order to achieve this object, a Fabry-Perot resonator according to the present invention includes:
A Fabry-Perot resonator for ESR in which a pair of reflecting plates curved in a concave shape having a shape obtained by cutting a concave portion of a cylindrical inner wall along a plane parallel to a cylindrical axis are arranged to face each other with the concave surfaces facing each other while matching the axial direction. And
A high frequency is introduced from one side of the reflecting plate, and a measurement sample is set near the center of the gap between the pair of reflecting plates.

  The pair of reflectors is characterized in that the radii of curvature of the cylinders are equal to each other.

  The pair of reflectors is characterized in that the concave side is a mirror surface.

  Further, the ESR device according to the present invention has a pair of reflecting plates curved in a concave shape having a shape obtained by cutting a concave portion of a cylindrical inner wall along a plane parallel to a cylindrical axis, and opposingly arranges the concave surfaces with each other while matching the axial direction. The detection unit is provided with a Fabry-Perot resonator.

  In addition, the ESR device is configured such that the resonator axis of the Fabry-Perot resonator coincides with the static magnetic field axis.

According to the Fabry-Perot resonator of the present invention, a pair of reflecting plates curved in a concave shape having a shape obtained by cutting a concave portion of a cylindrical inner wall along a plane parallel to the cylindrical axis are opposed to each other while matching the axial direction. An ESR Fabry-Perot resonator disposed,
Since a high frequency is introduced from one side of the reflector and a measurement sample is set near the center of the gap between the pair of reflectors,
It has become possible to provide a Fabry-Perot resonator that is compatible with a temperature variable device, is compatible with a magnet device that generates a static magnetic field in the Y-axis direction, and can improve the degree of freedom of a measurement sample.

Further, according to the ESR apparatus of the present invention, a pair of reflecting plates curved in a concave shape having a shape obtained by cutting out the concave portion of the cylindrical inner wall along a plane parallel to the cylindrical axis are arranged opposite to each other while matching the axial direction. A Fabry-Perot resonator for ESR,
Since a high frequency is introduced from one side of the reflecting plate, and a Fabry-Perot resonator that is used by setting a measurement sample in the vicinity of the center of the gap between the pair of reflecting plates,
It has become possible to provide an ESR device that has good compatibility with a temperature variable device, good compatibility with a magnet device that generates a static magnetic field in the Y-axis direction, and can improve the degree of freedom of a measurement sample.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a diagram illustrating a Fabry-Perot resonator according to the present invention. In the figure, reference numeral 21 denotes a pair of reflecting plates curved in a concave shape having a shape obtained by cutting out the concave portion of the cylindrical inner wall along a plane parallel to the cylindrical axis. This reflector has a semi-cylindrical shape in which bamboo cylinders are divided vertically and arranged face to face. By arranging the concave surfaces to face each other while matching the cylindrical axis direction, a high-frequency magnetic field 23 (and an electric field with a phase difference of 90 degrees) supplied from one side of the reflecting plate 21 through the waveguide 22 is also paired. Resonance between the reflecting plates 21 can be achieved. The resonance frequency can be changed by changing the distance between the reflecting plates 21.

  For the waveguide 22, a waveguide or a dielectric waveguide is used. Although it is not impossible to use a coaxial cable, the loss is too large in the 95 GHz band, which is not preferable. When the waveguide 22 is a waveguide, the waveguide 22 and the reflection plate 21 are coupled by dropping both the waveguide wall and the reflection plate 21 to the ground and opening a coupling hole in the reflection plate 21. The degree of coupling is finely adjusted by a coupling degree adjusting pin called a stub and a moving wall called a short plunger. On the other hand, when the waveguide 22 is a dielectric waveguide, the waveguide wall and the reflection plate 21 are both dropped to the ground, a coupling hole is opened in the reflection plate 21, and the dielectric core is a Fabry-Perot resonator. The degree of coupling is finely adjusted by adjusting the way of protruding the core. The positions of these coupling holes are preferably near the center of the reflector 21, but coupling is not impossible even if they are deviated from the center.

  The feature of this Fabry-Perot resonator is that it is compatible with the case where the static magnetic field generated by the magnet device 5 of FIG. 1 is oriented in the Y-axis direction. The high-frequency magnetic field 23 is sent from the waveguide 22 between the pair of reflecting plates 21 and is generated so as to have a component in the X-axis direction orthogonal to the static magnetic field direction Y. Thus, if the ESR device is configured by aligning the resonator axis (cylindrical axis) of the Fabry-Perot resonator according to the present invention with the static magnetic field axis (Y axis), the ESR phenomenon of the measurement sample 24 can be captured with high sensitivity. Can do. Further, since the sample space is elongated in the Y-axis direction, compatibility with the temperature variable device is good, and angular rotation and sample insertion and removal are easy. The measurement sample is set near the center of the gap between the pair of reflecting plates 21.

  In order to clarify the characteristics of the Fabry-Perot resonator according to the present invention, a comparison between the Fabry-Perot resonator composed of a conventional spherical mirror and the present plan by electromagnetic field calculation was performed. The resonance condition of the Fabry-Perot resonator is defined by the following approximate expression as shown in FIG.

ここで、Ｌはミラー間距離、λは共振波長、ｑは高周波電界のノードの数、Ｒはミラーの曲率半径である。計算に当たっては、図６に示すように、Ｌ＝Ｒ＝６．３ｍｍ、λ＝３．１５６ｍｍ（９５ＧＨｚにおける自由空間波長）、ｑ＝４というパラメータ設定を行なった。その他に、球面鏡の直径Ｈ＝７．２６ｍｍ、半円筒鏡の高さＨ＝１０．０ｍｍとした。

Here, L is the distance between the mirrors, λ is the resonance wavelength, q is the number of nodes of the high-frequency electric field, and R is the radius of curvature of the mirror. In the calculation, as shown in FIG. 6, parameters were set such that L = R = 6.3 mm, λ = 3.156 mm (free space wavelength at 95 GHz), and q = 4. In addition, the diameter H of the spherical mirror was 7.26 mm, and the height H of the semi-cylindrical mirror was 10.0 mm.

FIG. 7 illustrates the intensity distribution of the high-frequency magnetic field B ₁ obtained by the electromagnetic field calculation. In the figure, the horizontal axis represents the position in the X-axis direction (unit: mm), and the vertical axis represents the position in the Y-axis direction (unit: mm). The high-frequency magnetic field B ₁ is generated in the X-axis direction, that is, in the lateral direction of the paper. Comparing the intensity distribution between the spherical mirror and the semi-cylindrical mirror, the strong area of the high-frequency magnetic field B ₁ is narrowly distributed in the circular mirror, whereas the semi-cylindrical mirror has a high intensity of the high-frequency magnetic field B _1. It can be seen that the region is widely distributed in a vertically long rectangular shape.

When this is displayed as a graph of B ₁ intensity, it is as shown in FIG. The vertical axis represents intensity values of the high frequency magnetic field B ₁ of Figure (unit: gauss / √W), the horizontal axis represents the position in the Y-axis direction (unit: mm) is. As is apparent from the figure, the intensity value of the high-frequency magnetic field B ₁ shows a distribution that is strongest at the center position of the inter-mirror space in both the spherical mirror and the semi-cylindrical mirror, and gradually decreases as the distance from the center increases in the Y direction.

However, there is a difference in the state of the distribution. In the spherical mirror, the intensity value of the high-frequency magnetic field B ₁ is very high at the center position of the inter-mirror space. Te, instead the intensity value of the high-frequency magnetic field B ₁ at the vicinity of the center of the mirror between the space in the semi-cylindrical mirror is not so high, even away from the center of the mirror in the Y direction, the intensity value of the high-frequency magnetic field B ₁ represents, very rapidly It will not drop. As a result, in the semi-cylindrical mirror, a region where the intensity value of the high-frequency magnetic field B ₁ is strong is distributed over a relatively wide range.

FIG. 9 compares the effective volume of a sample that can be used for measurement in a spherical mirror type Fabry-Perot resonator and a semi-cylindrical mirror type Fabry-Perot resonator. As is apparent from the figure, the effective sample volume of the spherical mirror type Fabry-Perot resonator is 3.63 × 3.63 × 1.0 mm ³ , whereas the semi-cylindrical mirror type Fabry-Perot resonator is used. The effective sample volume is 7.26 × 10.0 × 1.0 mm ³ , which is about 7.3 times. Thereby, in the Fabry-Perot resonator of the present proposal, the measurement sensitivity can be improved by increasing the sample amount.

  It can be widely used as a detector for high magnetic field / high frequency ESR devices.

It is a figure which shows the basic composition of the conventional high magnetic field ESR apparatus. It is a figure which shows the conventional Fabry-Perot resonator. It is a figure which shows the conventional Fabry-Perot resonator. It is a figure which shows one Example of the Fabry-Perot resonator concerning this invention. It is a figure which shows the resonance conditions of a Fabry-Perot resonator. It is a figure which shows the model calculation parameter of a Fabry-Perot resonator. It is a figure which shows the model comparison result of a Fabry-Perot resonator. It is a figure which shows the model comparison result of a Fabry-Perot resonator. It is a figure which shows the model comparison result of a Fabry-Perot resonator.

Explanation of symbols

1: detector, 2: high frequency circuit unit, 3: signal processing unit, 4: spectrum display device, 5: magnet device, 6: waveguide, 7: concave mirror, 8: high frequency magnetic field, 9: measurement sample, 10: reflection Mirror, 11: Waveguide, 12: Concave mirror, 13: High frequency magnetic field, 14: Measurement sample, 21: Reflector, 22: Waveguide, 23: High frequency magnetic field, 24: Measurement sample

Claims (5)

A Fabry-Perot resonator for ESR in which a pair of reflecting plates curved in a concave shape having a shape obtained by cutting a concave portion of a cylindrical inner wall along a plane parallel to a cylindrical axis are arranged to face each other with the concave surfaces facing each other while matching the axial direction. And
A Fabry-Perot resonator for ESR, wherein a high frequency is introduced from one side of the reflector and a measurement sample is set near the center of the gap between the pair of reflectors. 2. The Fabry-Perot resonator for ESR according to claim 1, wherein the pair of reflectors have the same radius of curvature of a cylinder. 2. The Fabry-Perot resonator for ESR according to claim 1, wherein the pair of reflectors has a mirror surface on the concave side. An ESR apparatus comprising the Fabry-Perot resonator according to claim 1 in a detection unit. 5. The ESR apparatus according to claim 4, wherein the ESR apparatus is configured such that a resonator axis of the Fabry-Perot resonator coincides with a static magnetic field axis.

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