JP5081002B2 - Antenna coil for NMR, low magnetic superconducting wire used therefor, method for manufacturing the same, method for adjusting magnetic susceptibility, 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 wire constituting the same. The wire of the present invention can be applied to an analyzer using a uniform magnetic field in the same manner as NMR.

  The NMR probe is composed of an antenna coil, a coil bobbin, an electric circuit, and the like for transmitting a high-frequency signal and receiving an FID signal. An antenna coil is combined with a tuning capacitor to form a tuning circuit, and an FID signal emitted from a resonator in the sample is received by irradiation 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 that represents the sharpness of the peak in the resonance circuit, and is obtained by Expression (1).

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

  An antenna coil having these characteristics is described in Patent Document 1 and the like.

JP 2003-11268 A

  Patent Document 1 describes that, for the purpose of reducing the magnetic susceptibility, a paramagnetic metal foil and a diamagnetic metal foil are alternately laminated to form an antenna coil made of a laminate.

  A laminated body having a low magnetic susceptibility can be obtained by adjusting and combining the thicknesses of the foils, films, and plates of the materials used so as to be low magnetic. 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 this case, in order to improve the Q value, it is necessary to enlarge the whole antenna coil or to have a multi-stage antenna structure, resulting in an increase in the size of the probe tip.

  In view of the above, an object of the present invention is to provide an antenna coil formed of a material having a low magnetic susceptibility and a higher Q value and the material thereof.

  The present invention relates to a low magnetic susceptibility wire formed by combining two or more kinds of metal bulks and powders having different magnetic susceptibilities into a round, flat, hexagonal or quadrangular cross-sectional shape, and the low magnetic susceptibility The NMR antenna coil is characterized in that it comprises an oxide superconducting layer covering the outer periphery of the wire, and the magnetic susceptibility of the metal bulk and the powder cancel each other to form a solenoidal coil.

  The present invention is a wire material applied to an antenna coil for detecting an NMR signal of an NMR probe, and a combination of two or more kinds of metal bulks and powders having different magnetic susceptibilities so that the magnetic susceptibility cancels each other. A low magnetic superconductivity for an NMR antenna coil, comprising: a low magnetic susceptibility wire formed into a hexagonal or quadrangular cross-sectional shape; and an oxide superconducting layer covering an outer periphery of the low magnetic susceptibility wire. It is in the wire.

  The present invention is a method for producing a low-magnetic superconducting wire for an NMR antenna coil having the above-described configuration, which is a combination of two or more kinds of metal bulks and powders having different magnetic susceptibility, and includes at least one of extrusion processing and drawing processing. A method for producing a low magnetic superconducting wire for an NMR antenna coil, characterized in that after forming into a low magnetic susceptibility wire by wire processing, the outer peripheral portion thereof is covered with an oxide superconducting layer.

  The present invention is a method for adjusting the magnetic susceptibility of a low-magnetic superconducting wire for an NMR antenna coil having the above-described configuration. After forming the low magnetic susceptibility wire, a film having a magnetization that cancels the magnetic susceptibility is formed on the outer periphery thereof. Or a step of dissolving and removing the outer peripheral portion until the magnetic susceptibility can be offset.

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

  According to the present invention, an antenna coil having both high Q value and low magnetism can be obtained. As a result, an NMR probe having high sensitivity and high resolution can be formed.

  In order to provide an antenna coil formed of a material having a low magnetic susceptibility and a higher Q value and its material, the paramagnetic material and the diamagnetic material are combined and the magnetization is canceled by canceling the mutual magnetic susceptibility. It is necessary to reduce the rate and satisfy the Q value improvement items described in the following (1) to (4).

  (1) The resistance is reduced by making the material having a low resistance value a round wire or a rectangular shape and increasing the cross-sectional area.

  (2) Lower the temperature of the antenna coil installation location and reduce the resistance.

  (3) Apply a superconducting material and reduce the resistance value to the limit.

  (4) A continuous solenoid shape with no connection portion is used.

  In the present invention, the magnetic susceptibility is reduced by combining two or more kinds of metal bulks and powders having different magnetic susceptibilities and canceling the mutual magnetic susceptibility. Moreover, the superconducting material was applied by covering the outer periphery of the low magnetic susceptibility wire composed of metal bulk and powder with an oxide superconducting layer. By applying a superconductor, the installation location of the antenna coil is inevitably lowered.

  The antenna coil and the wire constituting the antenna coil of the present invention are composed of a low magnetic susceptibility wire composed of a base material portion made of a metal bulk and powder, and an oxide superconducting layer covering the outer periphery of the base material portion. Here, the metal bulk constituting the base material portion is preferably made of Au, Ag, or an alloy thereof, and the powder is preferably made of copper oxide. By using a combination of a metal and an oxide, it is possible to prevent the constituent materials of the base material portion from reacting with each other during the generation heat treatment of the oxide superconductor covering the outer peripheral portion of the base material portion.

  It is possible to manufacture a wire with low magnetic susceptibility by loading copper oxide powder into a tube formed of a metal bulk made of Au, Ag, or an alloy thereof, and drawing or extruding the tube.

  In the present invention, the cross-sectional area is increased by making the base material portion a wire having a cross-sectional shape of round, flat, hexagonal or quadrangular. Among these cross-sectional shapes, a round shape or a rectangular shape is most preferable from the viewpoint of moldability.

  The thickness of the oxide superconducting layer is preferably 0.1 to 200 μm. If it is thinner than this range, there is no effect, and if it is thicker, it is difficult to adjust the magnetic susceptibility. As the material of the oxide superconductor, any of Y-based material or Bi-based material can be applied, but considering the adhesion with Au and Ag constituting the outer peripheral portion of the base material portion, Bi system is preferred. In particular, a combination of a Bi-based oxide superconductor and Ag is preferable.

  An antenna coil is a super-oxide superconductor after a low-susceptibility wire composed of a paramagnetic material and a diamagnetic material is wound around a wound bobbin composed of a low-magnetic material such as sapphire or alumina in a solenoid shape. The body material is preferably deposited. Further, at this time, it is preferable that the low magnetic susceptibility wire is a single wire having no connection portion to avoid the generation of resistance at the connection portion.

  In the following, examples of the present invention are shown in comparison with the conventional method.

First, as a comparative material, an antenna coil was manufactured by alternately laminating copper foil and aluminum foil by the method described in Patent Document 1, and the 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, materials were evaluated by comparing with the above data.

  FIG. 1 shows a cross-sectional structure of a composite rectangular wire made of Ag and copper oxide applied as a base material portion in the low magnetic superconducting wire produced in this example. FIG. 2 shows the shape of the antenna coil.

  In this example, copper oxide was used as the paramagnetic material, and Ag was used as the diamagnetic material. By making the shape of the antenna coil material flat, the resistance can be reduced and the Q value can be improved. Further, since the structure is wound around the bobbin, the strength of the entire antenna coil is improved, and a sturdy NMR probe can be configured. Further, by forming an antenna coil by winding one wire in a solenoid shape, a structure without a connection portion can be obtained, and generation of resistance at the connection portion can be avoided.

  The manufacturing process is shown below.

  First, as members necessary for wire production, an outer layer Ag tube of the diamagnetic material 2 and an inner layer copper oxide powder of the paramagnetic material 3 were prepared.

  After incorporating these, the wire was thinned by wire drawing and drawn to φ1.0 mm to produce a low magnetic susceptibility wire 1 made of Ag and copper oxide. The dimensions and thickness of the Ag tube at this time, and the filling amount of copper oxide were measured so that the susceptibility of the material used in advance was measured under the same conditions as the usage environment of the antenna coil, and the mixing ratio would be close to zero. Adjusted.

Next, the magnetization measurement of the produced low magnetic susceptibility wire 1 made of Ag and copper oxide was performed. As a result, it was found that the volume magnetic susceptibility was −8.0 × 10 ⁻⁸ , and the volume magnetic susceptibility was almost the same as the mixing ratio.

  Next, the produced low magnetic susceptibility wire 1 made of Ag and copper oxide was wound around a wound bobbin 5 in the form of a solenoid coil to obtain the coil shape shown in FIG. And the solution of Bi2212 was apply | coated to the outer peripheral part of the wire by the dip coating method, and it baked and formed the oxide superconductor layer which consists of Bi2212 superconductor. At this time, heat treatment was performed in an oxygen atmosphere with a partial melting time of 885 ° C. × 5 min and then a slow cooling time to 800 ° C. of 14 hours. Thus, the low magnetic superconducting wire 4 having the superconducting film 6 on the outer peripheral portion of the low magnetic susceptibility wire 1 was produced. A cross-sectional structure of the low magnetic superconducting wire 4 is shown in FIG.

Next, the Q value of the produced solenoid coil was measured in 4.2K. As a result, Q = 11000, which was significantly higher than the Q value of the conventional structure. Moreover, as a result of measuring the magnetic susceptibility of the wire having the superconducting film on the outer peripheral portion by 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.

  Moreover, it turned out that the same effect is acquired also by the following method.

  As a material applied to the metal bulk, Au, Ag, or an alloy thereof is effective. This is because they are materials that are difficult to oxidize because they are heat-treated in an oxygen atmosphere, have low temperature dependence of magnetization, are low resistance materials, and have relatively high toughness. Among these, it is most preferable to apply the prototype Ag.

  Metal bulk materials can also be applied to alloys, but the magnetic susceptibility and resistance may change due to variations in composition, etc., and if they exhibit Curie paramagnetism, magnetization in low and high magnetic fields Therefore, it is difficult to design a high magnetic field using experimental results of a low magnetic field. Therefore, it is desirable to apply pure metal as much as possible.

  Since the material of the base material part passes through the heat treatment for generating the oxide superconducting layer, it is desirable that the material has a melting point of 900 ° C. or higher.

  In the copper oxide, oxygen is dissociated by the heat treatment for generating the oxide superconducting layer, and a part thereof is changed to cuprous oxide. Although cuprous oxide and cupric oxide are the same paramagnetic material, they have different magnetic susceptibility. Therefore, either the method of making the mixing ratio considering them from the beginning at the time of wire preparation or the method of removing a part of Ag by dissolving the mixing ratio of Ag more than the ratio that can cancel out the magnetic field ratio later. It is desirable to apply.

  As the wire cross-sectional structure, as shown in FIG. 4, a similar effect can be obtained even in a multi-core structure of copper oxide.

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

  This time, 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 example, the volume magnetic susceptibility of the low magnetic susceptibility wire made of Ag and copper oxide was −8.0 × 10 ⁻⁸ , but when there was a shift in the blending ratio due to the effect of wire drawing, By forming a predetermined film on the outermost layer of the base material and finely adjusting it, it is possible to reduce the magnetism. When the processed wire is paramagnetic, it is preferable to form a diamagnetic material film of Ag or Au. When the processed wire is diamagnetic, it is difficult to oxidize such as Pt. It is preferable to form a film. At this time, a film thickness and material that do not affect the current-carrying characteristics after film formation are desirable. The method for forming the film is not limited to a manufacturing method such as dry or wet, but it is preferable to perform the film formation by a method that facilitates film thickness adjustment.

  As a fine adjustment method of the magnetic susceptibility, a part of the outer periphery of the base material can be dissolved and removed to obtain a predetermined magnetic susceptibility. For example, it is possible to dissolve and remove the base material by immersing it in the solution. This method is suitable for applying a material for forming an oxide superconducting layer by a dip coating method or the like because the unevenness of the surface becomes large.

The schematic sectional drawing of the preform | base_material part in the antenna coil of this invention. 1 is a schematic diagram of an antenna coil according to the present invention. The schematic sectional drawing of the low magnetic superconducting wire by one Example of this invention. The schematic sectional drawing of the low magnetic superconducting wire by the other Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Low magnetic susceptibility wire, 2 ... Diamagnetic material, 3 ... Paramagnetic material, 4 ... Low-magnetic superconducting wire, 5 ... Winding bobbin, 6 ... Superconducting film.

Claims (12)

Oite the antenna coil for detecting NMR signals NMR probe, in the metal bulk tube diamagnetic material, filled with a powder of the paramagnetic material, the diamagnetic material and the paramagnetic material, the magnetic susceptibility is canceled combined as each other, round shape by applying a pulling or extruded, flat shape, and a low magnetic susceptibility wire molded into one of the cross-sectional shape of a hexagonal shape or a square shape, the outer peripheral portion of the low magnetic susceptibility wire the comprises an oxide superconducting layer covering said a top surface of the low magnetic susceptibility wire, and the surface in contact with the oxide superconducting layer is made of a metallic bulk of Au or Ag diamagnetic material, said oxide superconducting An NMR antenna coil , wherein the layer is made of a Bi-based oxide superconductor, and the antenna coil is a solenoidal coil. NMR antenna coil according to claim 1, before Symbol powder, characterized in that the copper oxide is paramagnetic material.   The NMR antenna coil according to claim 1, wherein the metal bulk is made of pure silver, and the powder is made of copper oxide.   The NMR antenna coil according to claim 1, wherein a wound bobbin is used to form the solenoid coil.   2. The NMR antenna coil according to claim 1, wherein the coil wound in a solenoid shape is formed of a single wire and has no connection portion.   The NMR antenna coil according to claim 1, wherein the oxide superconducting layer has a thickness of 0.1 to 200 μm. It is a wire applied to an antenna coil for detecting NMR signals of an NMR probe, and a paramagnetic material powder is filled in a metal bulk tube of a diamagnetic material, and the diamagnetic material and the paramagnetic material are magnetized. A low magnetic susceptibility wire formed into a round shape, a rectangular shape, a hexagonal shape, or a quadrangular cross-sectional shape by drawing or extruding in combination so that the ratios cancel each other, and the low magnetic susceptibility wire Including an oxide superconducting layer covering the outer peripheral portion of the low magnetic susceptibility wire, and a surface in contact with the oxide superconducting layer is made of a metal bulk made of Au or Ag, which is a diamagnetic material, A low-magnetic superconducting wire for an NMR antenna coil, wherein the oxide superconducting layer is made of a Bi-based oxide superconductor . Low magnetic superconducting wire for NMR antenna coil according to claim 7 before Symbol powder, characterized in that the copper oxide is paramagnetic material. The low-magnetic superconducting wire for an NMR antenna coil according to claim 7 , wherein the oxide superconducting layer has a thickness of 0.1 to 200 µm. A method of manufacturing a wire applied to an antenna coil for detecting an NMR signal of an NMR probe, in which a paramagnetic material powder is filled in a metal bulk tube of a diamagnetic material, and the diamagnetic material and the paramagnetic material Combined so that the magnetic susceptibility of each other cancels out, the outermost surface is a metal bulk made of Au or Ag, and round, flat, hexagonal or square by wire drawing including at least one of extrusion and drawing For an NMR antenna coil, characterized in that it is formed into a low magnetic susceptibility wire having any cross-sectional shape, and the outer periphery of the low magnetic susceptibility wire is covered with an oxide superconducting layer made of a Bi-based oxide superconductor A method for producing a low magnetic superconducting wire. Some metal bulk tube diamagnetic material, filled with a powder of the paramagnetic material, combined as susceptibility cancel the diamagnetic material and the paramagnetic material, metal outermost surface made of Au or Ag bulk as consisting of, by drawing containing at least one of extruding and drawing, a round shape, rectangular shape, then molded into a low magnetic susceptibility wire having any cross-sectional shape of a hexagonal shape or a square shape, its low A method for adjusting the magnetic susceptibility of a low-magnetic superconducting wire for an NMR antenna coil in which an outer peripheral portion of a magnetic susceptibility wire is covered with an oxide superconducting layer made of a Bi-based oxide superconductor. A method of adjusting the magnetic susceptibility of a low magnetic superconducting wire for an NMR antenna coil, wherein the outer peripheral portion is dissolved and removed until the magnetic susceptibility can be canceled out.   An NMR system that detects an NMR signal using the NMR probe comprising the antenna coil according to claim 1.

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