JP2009115772A - Esr detector using transmission line - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the sensitivity by reducing the volume of an electromagnetic field section contributing to a sample of a detecting section of an ESR device, and to create a one-dimensional image, two-dimensional image, and three-dimensional image by increasing the resolution of the detecting section. <P>SOLUTION: A resonator is constituted by a transmission line so that electromagnetic wave does not spread spatially, and a place having the largest current is used as the detecting section to improve the sensitivity. The detecting section is constituted by a further narrow conductor, thereby further increasing the current density to improve the sensitivity. Additionally, since the narrow conductor is small, the resolution increases and the one-dimensional, two-dimensional, and three-dimensional images can be obtained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a detector for ESR.

ESR (Electro Spin Resonance, Electron Spin Resonance) is an observation technique used for analysis of molecular structure, analysis of magnetism generation mechanism, development of health food by measuring free radicals, etc. using electron spin resonance phenomenon. The principle is that an electromagnetic field is introduced into a static magnetic field, and the direction of the electromagnetic field is aligned so that the magnetic field in the electromagnetic field is orthogonal to the static magnetic field. A sample is placed in this perpendicular magnetic field to resonate the spins of the outer electrons of the atoms. In addition, the detectors used for ESR are roughly classified into a non-resonator type and a resonator type. Since the non-resonator type can change the frequency of the microwave and millimeter wave, it is convenient because the ESR signal can be detected under any conditions even if the static magnetic field strength is constant. However, the detection sensitivity is poor. On the other hand, in the resonator type, the input microwave and millimeter wave frequencies can be used only at the resonance frequency of the resonator. However, the detection sensitivity can be increased. For this reason, the mainstream of ESR is a resonator type.
Next, the resonator type will be described.
Resonators can be broadly classified by introducing an electromagnetic wave into a metal rectangular or cylindrical box to resonate, and using the magnetic field in this electromagnetic wave, and the magnetic field that passes through the coil by a resonator consisting of a coil and a capacitor. There is a method of using.
In both of these methods, the magnetic field is in a large volume, and it is difficult to increase the magnetic field density.

Problems to be solved by the invention

An object of the present invention is to improve sensitivity and resolution by reducing the volume of a magnetic field.

Means for solving the problem

TECHNICAL FIELD The present invention relates to a detector using a transmission line, and to a detector that can be highly sensitive when an electromagnetic field exists in a limited space. In addition to this, by increasing the current density by narrowing the conductor where the sample is placed, the magnetic field strength generated by this current can be increased. Since ESR is detected by the method, the position in a large sample can be specified. Since this position can be specified, ESR can be imaged.

The invention's effect

Use of the method of the present invention has the following effects.
・ Realization of higher sensitivity than twice the current sensitivity.
-Since the detection part is 2 mm or less, the ESR line image, 2D image, or 3D image can be drawn by moving the sample or the detector in one, two, or three dimensions.

FIG. 1 shows a block diagram for carrying out the present invention.
When 10 GHz is output from the oscillator 1, it enters the circulator 2 and goes to the detector 3. The detector 3 has a microstrip line structure, and has a transmission line structure in which a signal line is disposed on a ground 12 with a dielectric interposed therebetween. Reference numeral 5 denotes a resonator, which is coupled to the upper transmission line through a gap 13. The ground is coupled to the resonator 5 through a capacitor through the thickness of the dielectric and the gap 14. The resonator has an electrical length of ½ wavelength or 1 wavelength, and both ends have a maximum voltage and a minimum current. In the case of a half-wave resonator, the maximum current point is the center of the resonator. In the case of a one-wavelength resonator, the maximum current point is ¼ length from the top, or ¾ from the top, that is, the ¼ length from the bottom is the maximum current point. In the case of FIG. 1, since it is a one-wavelength resonator, the maximum current point is a quarter length from the bottom, and the magnetic field flows to the maximum by this current.
On the other hand, the signal conductor having a length of ¼ is cut and thinned with a cutter knife or the like. In this way, the current in this part is concentrated in a thin part, so the magnetic field generated around this part is large, and the sensitivity is greatly improved when the sample is attached to the part 8. Here, the resonator is parallel to the paper surface, but is actually orthogonal to the paper surface. In this way, the direction of the magnetic field where the sample is affixed is orthogonal to the static magnetic field generated by the coil 10 and follows the ESR principle. The reflected wave adjuster 6 adjusts the phase and amplitude so that the reflected wave returning to the circulator 2 is minimized when the sample 8 does not output an ESR signal.

FIG. 2 shows an example of a microstrip line resonator.
The resonator is connected by a coaxial cable 15. The electrical length of the resonator was set to one wavelength (1λ). When the effective relative permittivity is 2 at 10 GHz in the case of a microstrip line, λ is 21 mm. The gap 14 uses the dielectric thickness of the printed circuit board as it is. Then, when adjusting the resonance frequency, the end may be cut. On the other hand, the current I of the resonator is zero at both ends and the center. The current at 1 / 4λ from both ends is large. That is, the magnetic field generated by the current is large. When 1 mg of the radical agent DPPH was placed at points a and b, the ESR signal increased greatly. The signal was larger at the end than at the center of the line width of the signal line. On the other hand, the basics are the same whether the detector is a strip line or a coaxial cable. In order to put a sample, for example, a hole of 2 mmφ is made in the ground and dielectric of the strip line and the coaxial cable, and the sample is inserted therefrom. As with all transmission lines, when the static magnetic field is modulated, the conductor thickness of the ground is reduced so that the modulated magnetic field passes.

FIG. 3 shows a detector in which the transmission line in the portion where the current in the length direction of the transmission line forming the resonator flows is maximized. Although only the signal line is shown in the figure, the center at λ / 4 from the left is a thin conductor having a width of 0.2 mm and a length of 0.4 mm. The signal line has a width of 4 mm and a ground width of 10 mm. FIG. 4 shows a comparison of sensitivity using 1 mg of the radical agent DPPH. The frequency is 9.35 GHz, and the horizontal axis is a signal when the static magnetic field is increased from 324 mT to 340 mT.
The above signal is a rectangular resonator having a Q value of 8000 and is generally used conventionally.
The lower signal is when the microstrip line resonator of FIG. 3 is used. When a thin conductor was used, the signal level increased 9 times compared to the conventional rectangular resonator. This is because the magnetic field is concentrated around a thin conductor without spreading over a large resonator.

FIG. 5 shows an example of a detector in which the thinned portion of the transmission line is the end of the transmission line. The upper resonator 5 and the lower resonator 5 form one resonator. In this case, the total resonator length is ½λ. On the other hand, the thin part is the part where the most current flows, and this is connected with copper wire. Note that the resonance frequency differs if the thickness and length of the thin part are different, so the resonator length is particularly adjusted as appropriate. Note that the detector having the detection unit at the end is easy to contact the sample. It is also very convenient when creating one-dimensional, two-dimensional and three-dimensional images.

Configuration diagram of this ESR Microstrip line resonator Illustration of the part that makes the signal line thinner The sensitivity of this resonator compared to a conventional rectangular resonator The figure where the part which makes the signal line thin is arranged at the end of the detector

Explanation of symbols

1: Oscillator 2: Circulator 3: Detector 4: Connector 5: Resonator 6: Reflected wave regulator 7: Narrow part 8: Sample 9: Static magnetic field oscillator and amplifier 10: Static magnetic field generating coil 11: Signal amplifier 12: Ground 13: Gap 14: Gap 15: Coaxial cable

Claims (9)

An electron spin resonance (ESR) detector comprising a resonator using a transmission line. 2. The detector according to claim 1, wherein one end of the resonator is in a state in which the transmission line is cut. 2. The detector according to claim 1, wherein the transmission line in a portion where the current in the length direction of the transmission line constituting the resonator flows is maximized. 4. The detector according to claim 3, wherein the thinned portion of the transmission line is an end portion of the transmission line. 5. The reflection type detector according to claim 1, wherein the ESR signal returns to the transmission line for inputting microwaves and millimeter waves. 5. The detector according to claim 1, wherein the transmission line is a microstrip line. The detector according to claim 1, wherein the transmission line is a strip line. The detector according to claim 1, wherein the transmission line is a coaxial cable. 10. The imaging ESR apparatus according to claim 2, wherein a line image is moved by moving the sample or the detector at least one dimension, a two-dimensional image is moved by two-dimensional movement, and a three-dimensional image is drawn by moving three-dimensionally.

Images