JP2003144415A - High frequency magnetic field generating detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resonator type high frequency magnetic field generating detector operated with high sensitivity and high frequency, simultaneously synchronizing with two kinds of frequencies. SOLUTION: This high frequency magnetic field generating detector composed of a resonator type coil comprises two guard rings made of conductors formed in approximately cylindrical outer shape and coaxially arranged with a vertical space; a cylindrical dielectric sheet wound around the guard rings; and a pair of conductor sheets arranged to cover the outside of the dielectric sheet. A pair of conductive sheets are provided with vertical band parts extending in the axial direction of a cylinder, wing parts laterally extending to both sides from the upper ends and lower ends of the vertical band parts to cover the outside of two guard rings, and complementary band parts in parallel with the opposed upper side wing parts to connect the vertical band parts to each other so that a high frequency current of low frequency selectively flows on the complementary band part side when the resonator type coil is operated by inductive reactance and that a high frequency current of high frequency selectively flows on the guard ring side when the resonator type coil is operated by capacitive reactance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency magnetic field generation detector of a probe used in a nuclear magnetic resonance apparatus (NMR), and particularly to a high-frequency magnetic field for exciting a sample and generating from the sample. The present invention relates to a high frequency magnetic field generation detector for detecting a high frequency signal.

[0002]

2. Description of the Related Art Conventionally, a solenoid coil or a saddle coil has been used to generate a high-frequency magnetic field for causing magnetic resonance in an observation nucleus and simultaneously detect a resonance frequency of the observation nucleus. When the frequency of high frequency is high, the dielectric loss of the sample is large when the frequency of the high frequency is high, and the length of the coil is close to 1/4 of the wavelength. . A coil called an Alderman-Grant type or a resonator type is known as a high-frequency magnetic field generation detector having a structure capable of reducing such defects and having high sensitivity even at a high frequency (DW Alderman a
nd DM Grant, Journal of Magnetic Resonance, 36 ,
447 (1979)). The perspective view is shown in FIG.

This coil has a substantially cylindrical outer shape, and two guard rings 1 and 2 made of a conductor, which are vertically spaced apart from each other so that the axes of the cylinders coincide with each other, and the guard rings 1 and 2. 2. Cylindrical dielectric sheet 3 wrapped around 2
And 1 arranged so as to cover the outside of the dielectric sheet 3.
It is composed of a pair of conductor sheets 4 and 5. The pair of conductor sheets 4 and 5 includes a vertical band portion 6 extending in the axial direction of the cylinder,
Wing portions 7 are provided so as to cover the outer sides of the two guard rings 1 and 2 and extend laterally from the upper and lower ends of the vertical band portion 6 to both sides. The tip of the wing portion 7 of the conductor sheet 4 and the tip of the wing portion 7 of the conductor sheet 5 face each other and are separated from each other.

The high frequency magnetic field generated by this coil is distributed in the region surrounded by the vertical band portions 6 and 6 and the guard rings 1 and 2, and the direction thereof is the direction perpendicular to the paper surface of FIG. As described above, this coil has a higher resonance frequency and higher sensitivity than the conventional solenoid coil and saddle coil.

FIG. 2 shows an equivalent circuit of this coil. The inductances L ₁ and L ₂ of this equivalent circuit correspond to the vertical band portions 6 and 6 of the conductor sheets 4 and 5, respectively, and the capacitors C ₁ and C ₂ are the upper wing portions of the conductor sheets 4 and 5, respectively. The capacitors C ₃ and C ₄ are formed between the guard rings 1 and 7, 7 and the guard rings 1, respectively, and are formed between the guard rings 2 and the lower wing portions 7 and 7 of the conductor sheets 4 and 5, respectively. In addition to the action of forming the capacitors C _{1 to} C ₄ described above, the guard rings 1 and 2 are themselves shielded against the fact that a high frequency electric field is generated between the conductor sheets 4 and 5 and dielectric loss occurs due to the measurement sample. It has a big effect of preventing by becoming.

The excitation pulse is the COLD-HOT in the figure.
Applied in between and the signal is taken from it. This coil cannot change the resonance frequency even if a variable capacitor is attached between COLD and HOT in the figure.

[0007]

Although the resonator type coil as described above operates with high sensitivity and high frequency, it cannot be used with two kinds of frequencies (double tuning) or more frequencies. So very difficult to use. In the measurement of NMR, a high frequency magnetic field having two kinds of frequencies is often used at the same time. Therefore, in such a case, the resonator type coil has a low practical value. If double tuning is possible, higher performance can be obtained than the conventional high-frequency magnetic field generation and detection coil due to the above characteristics.

The present invention has been made in view of such a situation, and an object thereof is to solve the problems of the conventional resonator type coil, to be able to tune to two kinds of frequencies simultaneously, and to have high sensitivity. The purpose of the present invention is to provide a high frequency magnetic field generation detector of a resonator type which operates at a high frequency.

[0009]

In order to achieve this object, a high-frequency magnetic field generation detector according to the present invention has a substantially cylindrical outer shape and is vertically spaced apart so that the axes of the cylinders coincide with each other. Two conductive guard rings and a cylindrical dielectric sheath wrapped around the guard rings.
And 1 arranged to cover the outside of the dielectric sheet
A high frequency magnetic field generation detector of a resonator type coil comprising a pair of conductor sheets, wherein the pair of conductor sheets covers a vertical band portion extending in the axial direction of the cylinder and two guard rings. In addition to the wing portions that extend laterally from the upper and lower ends of the vertical band portion to both sides, when the resonator type coil operates with inductive reactance, the high frequency current with a low frequency selects the supplemental band portion side. When the resonator coil operates with a capacitive reactance, the complementary band parts that connect the vertical band parts that allow high-frequency high-frequency current to selectively flow on the guard ring side are connected to the opposing upper wings. It is characterized in that it is provided in parallel with the section.

Further, the supplemental band portion operates as a distributed inductance corresponding to a half wavelength of the high frequency when a high frequency high frequency current flows through the guard ring.

The supplementary band portion is detachably attached to the conductor sheet.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a perspective view of an embodiment of the high-frequency magnetic field generation detector according to the present invention, and FIG. 4 is a component development view thereof. The common parts of both are:
The same numbers are assigned and shown.

In this embodiment, the outer shape is substantially cylindrical, and two guard rings 1 and 2 made of an electric conductor are arranged vertically apart from each other so that the axes of the cylinders coincide with each other, and the guard ring 1 2, a cylindrical dielectric sheet 3 wrapped around 2
And 1 arranged so as to cover the outside of the dielectric sheet 3.
It is composed of a pair of conductor sheets 4 and 5. The pair of conductor sheets 4 and 5 includes a vertical band portion 6 extending in the axial direction of the cylinder,
The vertical band portion 6 is provided in parallel with the wing portions 7 extending laterally from the upper and lower ends of the vertical band portion 6 so as to cover the outer sides of the two guard rings 1 and 2, and the opposing upper wing portions 7 and 7. , 6 supplemental band portions connecting 8 and 8
It has and. The tip of the wing portion 7 of the conductor sheet 4 and the tip of the wing portion 7 of the conductor sheet 5 face each other and are separated from each other.

The guard rings 1 and 2 and the conductor sheet 4,
5 is a metal foil having a diamagnetic property and a metal foil having a paramagnetic property, which are rolled and adhered to each other so that each has a predetermined thickness. It is made of a special metal foil whose magnetic susceptibility is corrected to match the magnetic susceptibility, and is manufactured by punching the metal foil into a predetermined pattern. In addition, the conductor sheets 4, 5
Of the complementary band portions 8 and 8 which are adjacent to each other when they are opposed to each other.
Is a magnetic susceptibility correction that mixes lead with diamagnetic properties and tin with paramagnetic properties at a predetermined ratio so that the total magnetic susceptibility matches the magnetic susceptibility of air. It is soldered and connected using the special solder that is used. In this way, by using a material whose magnetic susceptibility is strictly corrected, it is devised that the uniformity of the static magnetic field is not distorted when the guard ring or the conductor sheet is placed in the static magnetic field. ing.

In this embodiment, the vertical band portion is composed of a total of four vertical bands, each set of two parallel vertical bands. The operation is shown in FIG. There is basically no difference from the case of the vertical band portion composed of two vertical bands in which one vertical band is symmetrically arranged. If there is a difference, it is only that the smaller the width of the vertical band and the larger the number, the larger the value of the inductance in the vertical band portion.
In this way, the inductance value can be changed by variously selecting the shape such as the width and the length of the vertical band portion. Therefore, the shape of the vertical band portion is adjusted according to the frequency of the high frequency used.

The high frequency magnetic field generated by this coil is distributed in the area surrounded by the vertical band portions 6 and 6 and the guard rings 1 and 2 as in the case of FIG. 1, and the direction thereof is in the plane of the paper of FIG. The vertical direction. This coil is
As described above, it has a higher resonance frequency and higher sensitivity than conventional solenoid coils and saddle coils.

FIG. 5 shows an equivalent circuit of this coil. The inductances L ₁ and L ₂ of this equivalent circuit correspond to the vertical band portions 6 and 6 of the conductor sheets 4 and 5, respectively, and the capacitors C ₁ and C ₂ are the upper wing portions of the conductor sheets 4 and 5, respectively. The capacitors C ₃ and C ₄ are formed between the guard rings 1 and 7, 7 and the guard rings 1, respectively, and are formed between the guard rings 2 and the lower wing portions 7 and 7 of the conductor sheets 4 and 5, respectively. In addition to the action of forming the capacitors C _{1 to} C ₄ described above, the guard rings 1 and 2 are themselves shielded against the fact that a high frequency electric field is generated between the conductor sheets 4 and 5 and dielectric loss occurs due to the measurement sample. It has a big effect of preventing by becoming. In addition, the inductance L arranged in parallel with the capacitors C ₁ and C _2
3 corresponds to the supplemental band portions 8 and 8 in which the vertical band portions 6 and 6 of the conductor sheets 4 and 5 are tied together at their upper ends.

Inductor composed of the supplementary band portions 8 and 8.
Closet L_ThreeIs injected into this high frequency magnetic field generation detector
Two types of high frequency (that is, high frequency high frequency)
HF out of HF and LF that is a high frequency with a low frequency)
The distributed inductance is equivalent to half the wavelength of
The inductance L is₁, L _Two
And condenser C₁, C_TwoNode A, which is the connection point with
Respectively coupled to node B. This will
Coutance L₁, L_TwoAnd condenser C₁, C _TwoAnd
Indexer C_Three, C_FourThe LC resonator composed of
It can resonate at the F frequency. Also inductor
L_ThreeValue and condenser C₁, C _TwoAppropriate value of
By selecting, the inductive reactance, H
A circuit configuration that gives a capacitive reactance to F
can do.

As a result, when the resonator type coil operates with an inductive reactance, a high frequency current having a low frequency (for example, LF corresponding to the resonance frequency of phosphorus nuclei, carbon nuclei, nitrogen nuclei, etc., or deuterium nuclei). When a high frequency current having a high frequency (for example, a high frequency for locking, which corresponds to the resonance frequency of 1) flows selectively on the side of the supplemental band L ₃ and the resonator type coil operates with a capacitive reactance (for example, HF corresponding to the resonance frequency of hydrogen nuclei or fluorine nuclei) selectively flows on the side of the capacitors C ₁ and C ₂ formed by the guard ring 1 and the wings 7, 7. As a result, using one resonator coil,
It has become possible to resonate high frequencies of two types of frequencies at the same time.

The shapes of the conductor sheets 4 and 5 can be modified in various ways. FIG. 6 shows an example of a conductor sheet that can be used in the high frequency magnetic field generation detector of the present invention. The main difference in these examples is the difference in the shape of the supplemental band parts 8, 8 which tie the vertical band parts 6, 6 together at their upper ends. In the figure, (a) is an example in which the supplemental band portion is bent in a rectangular shape, (b) is an example in which the supplemental band portion is bent in a triangular wave shape, and (c) is a supplemental band portion in a spiral shape. , This is an example of connecting the centers of adjacent spirals with a jumper wire. As described above, the inductance forming the supplemental band portion may have any shape as long as it is a distributed inductance corresponding to the half-wave length of HF.

Further, as shown in FIG. 7, the supplemental band portion is a coil-shaped winding detachable from the conductor sheet, or an HF half-wave resonator detachable from the conductor sheet. You may make it the structure which attaches a corresponding line segment.

[0022]

As described above, according to the high-frequency magnetic field generation detector of the present invention, the supplemental band portion connecting the opposing vertical bands is provided in parallel with the guard ring at the upper end of the vertical band portion of the resonator type coil. If the resonator type coil operates with an inductive reactance,
When a high frequency current with a low frequency flows through the supplemental band part and the resonator type coil operates with a capacitive reactance, a high frequency current with a high frequency is configured to flow through the guard ring side. It has become possible to provide a high-frequency magnetic field generation detector that can be tuned to two kinds of frequencies at the same time by using a coil, and that operates with high sensitivity and high frequency.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a conventional high-frequency magnetic field generation detector.

FIG. 2 is a diagram showing an equivalent circuit of an example of a conventional high-frequency magnetic field generation detector.

FIG. 3 is a diagram showing an embodiment of a high frequency magnetic field generation detector according to the present invention.

FIG. 4 is a component development view of one embodiment of the high-frequency magnetic field generation detector according to the present invention.

FIG. 5 is a diagram showing an equivalent circuit of an embodiment of the high-frequency magnetic field generation detector according to the present invention.

FIG. 6 is a diagram showing another embodiment of the high-frequency magnetic field generation detector according to the present invention.

FIG. 7 is a diagram showing another embodiment of the high-frequency magnetic field generation detector according to the present invention.

[Explanation of symbols]

1 ... Guard ring, 2 ... Guard ring, 3 ... Dielectric sheet, 4 ... Conductor sheet, 5 ... Conductor sheet, 6 ...
・ Vertical band, 7 ... Wing, 8 ... Supplementary band,
L ₁ ... Inductance, L ₂ ... Inductance, L ₃
... _{inductance, C} 1 ... _{condenser, C} 2 ... _{Condenser, C} 3 ... _{condenser, C} 4 ... Condenser, A ... Node, B ... node.

Claims (3)

[Claims] 1. An outer shape of a substantially cylindrical shape, two guard rings made of a conductor, which are arranged vertically apart from each other in a manner to match the axes of the cylinders, and a cylinder wound around the guard rings. And a pair of conductor sheets arranged so as to cover the outer side of the dielectric sheet. The seat includes a vertical band portion that extends in the axial direction of the cylinder, and wing portions that extend laterally from the upper and lower ends of the vertical band portion so as to cover the outer sides of the two guard rings. When operating with an inductive reactance, a high frequency current with a low frequency selectively flows through the supplemental band side, and when the resonator coil operates with a capacitive reactance,
A high-frequency magnetic field generation detector, characterized in that a complementary band portion that connects vertical band portions such that a high-frequency high-frequency current selectively flows on the guard ring side is provided in parallel with the opposing upper wing portion. 2. The supplemental band portion operates as a distributed inductance corresponding to the length of a half wavelength of the high frequency when a high frequency high frequency current flows through the guard ring. High frequency magnetic field generator detector. 3. The high frequency magnetic field generation detector according to claim 1, wherein the supplemental band portion is detachably attached to the conductor sheet.