JP4989414B2 - Antenna coil for NMR probe and manufacturing method thereof, low magnetic superconducting wire for NMR probe antenna coil, and NMR system - Google Patents

Description

  The present invention is an NMR applied in a nuclear magnetic resonance (NMR) apparatus for transmitting a high frequency signal at a predetermined resonance frequency and receiving a free induction decay (FID) signal with respect to a sample placed in a uniform magnetic field. The present invention relates to an antenna coil of a probe and a manufacturing method thereof. Moreover, it is related with the wire which comprises the antenna coil of a NMR probe, and a NMR system.

  The NMR probe includes an antenna coil for transmitting a high frequency signal and receiving an FID signal, a coil bobbin, an electric circuit, and the like. The antenna coil is combined with a tuning capacitor to form a tuning circuit, and receives an FID signal generated by a resonator in the sample when irradiated with a high frequency pulse.

  High sensitivity is required for an NMR probe that receives an FID signal generated in response to a high-frequency pulse. This is because when the amount of the measurement sample is small, such as protein, the strength of the FID signal is particularly weak, so that the measurement is time consuming due to the low sensitivity.

  In order to improve this sensitivity, it is effective to increase the Q value of the tuning circuit. The Q value is a value representing the sharpness of the peak in the resonance circuit, and is obtained by the following formula 1.

一方、ＮＭＲプローブは優れた分解能も必要であり、この分解能を向上させるためには、アンテナコイルを形成している物質固有の磁化率を低減し、静磁場の歪みを極限まで小さくすることが有効である。

On the other hand, the NMR probe also needs excellent resolution, and in order to improve this resolution, it is effective to reduce the magnetic susceptibility inherent in the material forming the antenna coil and to minimize the distortion of the static magnetic field. It is.

  In order to reduce the magnetic field distortion and improve the Q value, it is known that paramagnetic metal foils and diamagnetic metal foils are alternately bonded to cancel each other's magnetism (for example, Patent Document 1). reference).

JP2003-11268A (summary)

  Patent Document 1 discloses that a paramagnetic metal foil and a diamagnetic metal foil are alternately bonded to form a metal laminate by laminating at least four layers, and a low resistance metal foil having a predetermined thickness. Is arranged in the outermost layer of the metal laminate to finely adjust the magnetic susceptibility.

  As in this prior art, a paramagnetic metal foil and a diamagnetic metal foil are alternately laminated to cancel each other's magnetism, thereby obtaining a low magnetic susceptibility structure.

  However, since the material becomes thin in the thickness direction and the surface resistance (R) of the material cross section becomes small, an improvement in the Q value cannot be expected. In the metal laminate of the prior art, in order to improve the Q value, it is necessary to enlarge the entire antenna coil, to make a multistage antenna structure, and as a result, the probe tip is increased in size.

  An object of the present invention is to provide an NMR coil antenna coil formed of a material having a low magnetic susceptibility and a high Q value and the material thereof.

  The present invention comprises a base material portion in which a plurality of materials having different magnetic properties are combined so that magnetism cancels each other, and an oxide superconductor layer provided on an outer peripheral portion of the base material portion. The antenna coil for NMR probe is integrated, and has a coil cross-sectional shape of a round shape, a rectangular shape, a hexagonal shape, or a quadrangular shape, and is wound into a solenoid coil shape.

  In the present invention, a plurality of materials having different magnetism are combined so that magnetism cancels each other, and is clad by wire drawing to form a wire having a round, rectangular, hexagonal, or quadrangular cross section, and wound in a solenoid coil shape. In the method of manufacturing an antenna coil for NMR probe, the outer peripheral surface is covered with an oxide superconductor after the wire is drawn.

  The present invention comprises a base material portion in which a plurality of materials having different magnetic properties are combined so that magnetism cancels each other, and an oxide superconductor layer provided on an outer peripheral portion of the base material portion. The low magnetic superconducting wire for an NMR probe antenna coil is integrated and has a cross-sectional shape of a round shape, a rectangular shape, a hexagonal shape, or a quadrangular shape.

  The thickness of the oxide superconductor layer is preferably 10 μm or more, and particularly preferably in the range of 10 μm or more and 1 mm or less. In many cases, the oxide superconductor layer is formed by applying a solution of an oxide superconductor to the surface of the base material portion by a dip coating method and baking it. In order to prevent the oxide superconductor film from self-destructing by heat treatment after dipping, the upper limit value of the thickness is preferably 1 mm.

  The material forming the antenna is a single wire, and it is desirable not to have a connection point. The integration of the base material portion is preferably performed by cladding, and particularly by wire drawing such as extrusion or drawing.

  The base material portion is composed of a paramagnetic material and a diamagnetic material, and at least one selected from Pt, Ru, Rh, Pd or an alloy thereof is used as the paramagnetic material, and Au is used as the diamagnetic material. It is desirable to use at least one selected from Ag, alloys thereof.

  In addition, it is desirable to use a Bi-based oxide superconductor as the oxide superconductor.

  A film having a magnetization that cancels out the magnetic susceptibility of the base material portion can be provided between the base material portion and the oxide superconductor layer as necessary. For example, if there is a deviation in the mixing ratio of the base material part in the clad state after wire drawing, a film having a magnetization that cancels the magnetic susceptibility of the base material part is formed on the outer periphery of the base material part. Therefore, it is desirable to finely adjust the magnetic susceptibility.

  When the base material portion is paramagnetic in a state of being clad by wire drawing, it is desirable to form a diamagnetic material film such as Cu or Ag on the outer periphery of the base material portion. On the other hand, when the base material portion is diamagnetic while being clad by wire drawing, it is preferable to form a paramagnetic material film such as Pt or V on the outer periphery of the base material portion.

  The present invention resides in an NMR system for detecting an NMR signal using an NMR probe having an antenna coil having the above-described configuration.

  According to the present invention, an antenna coil wire having both high Q value and low magnetism was obtained, and an NMR probe having both high sensitivity and high resolution could be provided.

  In order to provide an antenna coil formed of a material having a low magnetic susceptibility and a higher Q value and its material, it is possible to combine a paramagnetic material and a diamagnetic material and cancel each other's magnetic susceptibility. It is necessary to reduce the rate and simultaneously satisfy the Q value improvement items described in the following (a) to (d).

  (A) The resistance is reduced by making the material having a low resistance value a round line shape and increasing the cross-sectional area.

  (B) The resistance is reduced by lowering the antenna coil installation location.

  (C) Applying a superconducting material and reducing the resistance value to the limit.

  (D) A continuous solenoid shape without a connecting portion is used.

  The present invention has been made based on such an idea.

Hereinafter, although the Example of this invention is shown, prior to this, the antenna coil was produced by the method of patent document 1 as a comparative material, and magnetic susceptibility and Q value (resonance at 300 MHz) were measured. As a result, the magnetic susceptibility was 1.5 × 10 ⁻⁷ (volume magnetic susceptibility), and the Q value was 300. In the following examples, the material was evaluated by comparing with the data of the antenna coil produced in this comparative example.

  FIG. 1 shows a cross-sectional structure of a composite round wire of Ag and Pt applied as a base material of a low magnetic superconducting wire. In this trial production, Pt as the paramagnetic material 3 and Ag as the diamagnetic material 2 were applied to the base material portion 1. By rounding the shape of the antenna coil material, the resistance can be reduced and the Q value can be improved. Further, since the antenna coil has a structure wound around the bobbin 10 as shown in FIG. 6, the strength of the whole antenna coil is improved, and a sturdy NMR probe can be configured. Furthermore, since the connection portion does not exist by forming the antenna coil with one wire, it is possible to avoid the generation of resistance at the connection portion.

  The manufacturing process of the antenna coil is shown below.

  As members necessary for wire preparation, an outermost layer Ag tube, an intermediate layer Pt sheet, and an innermost layer Ag rod were prepared.

  These were assembled in order, and then clad by wire drawing and further drawn to φ1.0 mm to produce a composite wire of Ag and Pt (hereinafter referred to as an Ag / Pt composite wire). At this time, the dimensions and thickness of the Ag tube and Ag rod, and the dimension and thickness of the Pt sheet were measured by measuring the magnetic susceptibility of the materials used in advance under the same conditions as the usage environment of the antenna coil. The mixing ratio was determined. In this case, a tube may be used instead of the Pt sheet.

Next, the magnetic susceptibility of the produced Ag · Pt composite wire was measured. As a result, it was found that the volume magnetic susceptibility was −9.0 × 10 ⁻⁸ , and the volume magnetic susceptibility was almost the same as the mixing ratio.

  Next, the produced Ag / Pt composite wire was wound around the bobbin 10 in a solenoid coil shape to form a coil shape. And the oxide superconductor layer 4 was formed in this outer peripheral part. The oxide superconductor layer 4 was formed by applying a Bi2212 solution by a dip coating method and baking it to form a Bi2212 superconducting film. At this time, the heating and holding time was 885 ° C. × 30 min, and heat treatment was performed in an oxygen atmosphere. FIG. 2 shows a cross-sectional structure of the low magnetic superconducting wire 5 manufactured in this way.

Next, the Q value of the produced solenoid coil was measured in 4.2K. As a result, Q = 12000, which is a result that greatly exceeds the Q value of the conventional structure. Further, the magnetic susceptibility of the Ag / Pt composite wire on which the superconducting layer was formed was measured. As a result of applying the field cool method, it was found that the volume magnetic susceptibility was −6.0 × 10 ⁻⁸ , which was a minute volume magnetic susceptibility.

  From the above results, it was possible to form a superconducting antenna coil having both a high Q value and low magnetism and its wire.

  The same effect can be obtained by the following method.

  Pt, Ru, Rh, Pd or an alloy thereof is effective as the paramagnetic material, and Au, Ag or an alloy thereof is effective as the diamagnetic material. This is because these are materials that are difficult to oxidize because they are heat-treated in an oxygen atmosphere, that the temperature dependence of magnetization is small, that they are low resistance materials, and that the toughness is relatively high. It is. Among these, the combination of Ag and Pt that has been prototyped is most preferable.

  The material of the base material can be an alloy, but the magnetic susceptibility and resistance may change due to variations in composition, etc., and if it shows Curie paramagnetism, it can be used in low and high magnetic fields. Since the rate of change of magnetization is different, it becomes difficult to design on the high magnetic field side using experimental results of a low magnetic field. Therefore, it is desirable to apply a pure metal rather than an alloy.

  In addition, the base material that can be combined is preferably a material having a melting point of 900 ° C. or higher because it undergoes heat treatment for generating the oxide superconducting layer.

  As the wire cross-sectional structure, as shown in FIGS. 3 to 5, a structure in which a high-strength Ag alloy exists in the center part, a five-layer structure, a Pt multi-core structure in which Pt is dispersed in the plane, and the like are applicable. There can be obtained the same effect as in the present embodiment. A similar effect can be obtained with a structure in which the arrangement of Ag and Pt is reversed. FIG. 3 shows a five-layer low magnetic superconducting wire 6 in which Ag and Pt are alternately arranged with the innermost layer being Ag and the outer side being Pt. FIG. 4 shows a low magnetic superconducting wire 7 in which Pt is dispersed in the plane of the Ag bar. FIG. 5 shows a low-magnetic superconducting wire 9 in which a high-strength Ag alloy 8 is present in the center, Ag is present outside thereof, and Pt and Ag are present alternately below.

  The same effect can be obtained by wire drawing, such as draw bench processing, extrusion processing, other wire drawing processing, isostatic pressing, and rolling.

  In this prototype, the final processing diameter is set to φ1.0 mm, but can be arbitrarily determined depending on the specifications of the inductance and dimensions of the antenna coil. In actual operation, φ0.1 mm to φ3.0 mm is desirable.

In this wire production, the volume magnetic susceptibility was −9.0 × 10 ⁻⁸ , but when there was a shift in the compounding ratio due to the effect of wire drawing, a predetermined film was formed on the outermost layer of the base material. By forming a film and finely adjusting it, it is possible to reduce the magnetism.

  When the processed wire is paramagnetic, a Cu or Ag diamagnetic material film is formed. When the processed wire is diamagnetic, a paramagnetic material film such as Pt or V is formed. In this case, a film thickness and a material that do not affect the energization characteristics after film formation are desirable. The film forming method may be any method such as a dry process or a wet process, but it is desirable that the film be formed by a method that facilitates film thickness adjustment.

  As a fine adjustment method of the magnetic susceptibility, it is also possible to etch the outer peripheral portion of the base material to obtain a predetermined magnetic susceptibility. This method is effective in the dip coating method or the like because the surface unevenness is increased.

  The wire shape is a round wire or a rectangular shape, but the same effect can be obtained by a hexagonal shape or a rectangular shape.

It is sectional drawing of the base material part of the low magnetic superconducting wire produced by this invention. It is sectional drawing of the low magnetic superconducting wire produced by this invention. It is sectional drawing which shows another example of the base material part in a low magnetic superconducting wire. It is sectional drawing which shows another example of the base material part in a low magnetic superconducting wire. It is sectional drawing which shows the other example of the base material part in a low magnetic superconducting wire. 1 is a perspective view of an antenna coil according to an embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Base material part, 2 ... Diamagnetic material, 3 ... Paramagnetic material, 4 ... Oxide superconductor layer, 5 ... Low magnetic superconducting wire, 6 ... Low magnetic superconducting wire, 7 ... Low magnetic superconducting wire, 8 ... Ag Alloy, 9 ... low magnetic superconducting wire, 10 ... bobbin.

Claims (14)

An NMR probe antenna coil wound in the form of a solenoid coil, wherein the NMR probe antenna coil is made of a paramagnetic material and a diamagnetic material having a tubular shape, a sheet shape, or a rod shape. A base metal part that is clad by performing wire drawing in combination so as to cancel each other, and formed into a circular, flat, hexagonal, or quadrangular coil cross-sectional shape , and an outer periphery of the base metal part The paramagnetic material is Pt, the diamagnetic material is Ag, and the oxide superconductor layer is a Bi-based oxide superconductor layer. A feature antenna coil for NMR probe.   The NMR probe antenna coil according to claim 1, wherein the oxide superconductor layer has a thickness of 10 µm or more.   The antenna coil for an NMR probe according to claim 1, wherein a material for forming the antenna is a single wire and does not have a connection portion. 2. The NMR according to claim 1, wherein when a plurality of materials having different magnetic properties are paramagnetic in a state of being clad by wire drawing, an Ag film is formed on the outer peripheral portion thereof to cancel the magnetism. Antenna coil for probe. 2. The NMR according to claim 1, wherein in the case of diamagnetism in a state in which the plurality of materials having different magnetism are clad by wire drawing, a Pt film is formed on the outer peripheral portion thereof to cancel the magnetism. Antenna coil for probe. Ag and Pt having a tubular shape, sheet shape, or rod shape are combined so that the magnetism cancels out, and is clad by wire drawing to have a round, flat, hexagonal, or quadrangular cross section . After winding any wire, into a solenoid coil shape, by applying a Bi-based oxide superconductor solution to the surface of the wire and firing,
A method for manufacturing an antenna coil for an NMR probe, wherein the outer peripheral surface of the wire is covered with a Bi-based oxide superconductor. The NMR according to claim 6 , wherein when a plurality of materials having different magnetic properties are paramagnetic in a state of being clad by wire drawing, an Ag film is formed on an outer peripheral portion thereof to cancel the magnetism. A method of manufacturing an antenna coil for a probe. 7. The NMR according to claim 6 , wherein when a plurality of materials having different magnetic properties are diamagnetic in a state of being clad by wire drawing, a Pt film is formed on the outer peripheral portion to cancel the magnetism. A method of manufacturing an antenna coil for a probe. The method of manufacturing an antenna coil for an NMR probe according to claim 6 , wherein an extrusion process or a drawing process is performed as the wire drawing process. A low-magnetic superconducting wire for an NMR probe antenna coil, which is formed by combining a paramagnetic material and a diamagnetic material having a tubular shape, a sheet shape, or a rod shape so that the magnetism cancels each other And a base material portion formed into a circular, flat, hexagonal, or quadrangular coil cross-sectional shape , and an oxide superconductor layer provided on the outer periphery of the base material portion. The paramagnetic material is Pt, the diamagnetic material is Ag, and the oxide superconductor layer is a Bi-based oxide superconductor layer. . The low magnetic superconducting wire for an NMR probe antenna coil according to claim 10 , wherein the oxide superconductor layer has a thickness of 10 μm or more. 11. The NMR according to claim 10, wherein in the case of paramagnetism in a state in which the plurality of materials having different magnetism are clad by wire drawing, an Ag film is formed on the outer peripheral portion to cancel the magnetism. Low magnetic superconducting wire for probe antenna coil . 11. The NMR according to claim 10, wherein in the case of diamagnetism in a state where the plurality of materials having different magnetism are clad by wire drawing, a Pt film is formed on the outer peripheral portion thereof to cancel the magnetism. Low magnetic superconducting wire for probe antenna coil. NMR system using a NMR probe, for detecting an NMR signal having an antenna coil according to any one of claims 1-5.

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