JP2007114111A - Nmr probe and nmr device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an NMR probe and an NMR device for inexpensively and efficiently dissipating heat of a magnetic gradient coil in the NMR probe to the outside without being followed by eddy current. <P>SOLUTION: This NMR probe is equipped with a heat sink for dissipating heat of the magnetic gradient coil provided on a bobbin insufficient in heat exhaust to the outside. The heat sink is made by arranging a plurality of metal wires in a plate shape to get them lined up in the axial direction of the NMR probe, with the metal wires insulated from each other by insulative coatings. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an NMR probe and an NMR apparatus, and more particularly to an NMR probe and an NMR apparatus with improved heat dissipation of a magnetic field gradient coil.

  An NMR device applies a strong static magnetic field to a sample, causes precession about the static magnetic field direction to occur in the magnetic moment of the nucleus with nuclear spin in the sample, and is orthogonal to the static magnetic field direction. A high frequency magnetic field is applied to excite the precession of the magnetic moment of the nucleus, and then the NMR signal emitted when the precession of the nuclear magnetic moment returns from the excited state to the ground state, It is an analyzer that observes as a high-frequency magnetic field having a frequency unique to.

  The positional relationship between a conventional NMR probe and a superconducting magnet that generates a static magnetic field is shown in FIG. In the figure, 1 is a superconducting magnet. Inside the superconducting magnet 1, a main coil (not shown) is wound with a superconducting wire. The main coil is usually placed in a heat insulating container (not shown) that can store liquid helium or the like, and is cooled to a cryogenic temperature.

  The NMR probe 2 is composed of a bowl-shaped base portion arranged outside the superconducting magnet 1 and a cylindrical portion inserted inside the superconducting magnet 1. The superconducting magnet 1 is inserted in the upward direction from the lower opening toward the inside of the cylindrical room temperature bore 3 penetrating along the central axis.

  A shim bobbin (shim mold) 4 is provided on the outer periphery of the measurement portion of the NMR probe 2. The shim bobbin 4 is formed by winding a shim coil for correcting a strong static magnetic field generated by the superconducting magnet 1 and forming a static magnetic field with high uniformity. ing. The shim bobbin 4 is disposed at the tip of a room temperature shim 5 inserted into the room temperature bore 3 of the superconducting magnet 1. The room temperature shim 5 is inserted coaxially with the NMR probe 2 from the lower opening of the room temperature bore 3 provided in the superconducting magnet 1 so as to surround the outer periphery of the NMR probe 2. Yes.

  FIG. 2 is an enlarged view of the NMR probe. In the figure, 6 is an NMR sample in a sample tube. A detection coil 8 and a magnetic field gradient (FG) coil 9 are installed in the detection coil section 7 at the tip of the NMR probe so as to surround the sample 6. Below the detection coil unit 7 is a tuning circuit unit 10 incorporating a tuning coil for the NMR frequency, and the outside of the detection coil unit 7 and the tuning circuit unit 10 is firmly protected by a metal probe cover 11. Yes.

  When measuring the NMR signal, a pulsed high-frequency magnetic field is applied from the detection coil 8 to the sample 6, and at the same time, a pulsed gradient magnetic field is applied from the FG coil 9 to the sample 6. After applying the high frequency magnetic field and the gradient magnetic field, the NMR signal emitted from the sample 6 is detected by the detection coil 8 at a predetermined timing. The detected NMR signal is sent to the tuning circuit unit 10, amplified by a preamplifier provided in the tuning circuit unit 10, and taken out of the NMR probe.

  The FG coil 9 is usually wound around a non-metallic inner bobbin 12 and a non-metallic outer bobbin 13 and is constituted by a double coil as shown in FIG. These double coils mainly generate a gradient magnetic field required for measurement by an inner coil, and cancel an unnecessary magnetic field due to an eddy current flowing in a peripheral metal such as the probe cover 11 by an outer coil. FIG. 3 is an example of a Z gradient coil. The X and Y gradient coils may be formed of a flexible printed circuit board.

U.S. Pat. No. 5,508,613.

U.S. Pat. No. 5,289,151.

JP 2003-61930 A.

Japanese Patent Laid-Open No. 9-51888.

JP-A-6-90924.

  By the way, at the time of NMR measurement, when the gradient magnetic field is generated by the FG coil 9, a pulse current of 10 to 100A is passed through the FG coil. At this time, a large amount of heat is generated in the FG coil 9. This heat not only causes the problem of heating the sample and disturbing the stability control of the sample temperature, but also may cause the coil to burn out in some cases.

  In order to prevent this, forced cooling such as water cooling and air cooling is performed according to the amount of heat generated by the FG coil 9, but the structure of the NMR probe is complicated by water cooling, which is a heavy burden on design and production. In many cases, the desired cooling effect cannot be obtained by air cooling. Alternatively, the internal space of the NMR probe is too narrow, and even air cooling pipes are sometimes difficult to install, and forced cooling is often given up and left to natural cooling.

  Considering the heat dissipation path, heat is transmitted well in the circumferential direction because the wire is metal, but in the cylindrical axis direction, heat is transmitted through the wire coating or non-metallic bobbin, so it is compared with the circumferential direction. Then the transmission of heat is bad.

  In many cases, the FG coil 9 is wound in a jumping manner. In practice, the heat conduction through the bobbin becomes dominant, and the heat radiation efficiency is extremely deteriorated. If the bobbin is made of a metal having high thermal conductivity such as aluminum, naturally, the cooling efficiency can be improved, but on the other hand, it is induced by the pulse gradient magnetic field to generate an eddy current, and the FG that generates the pulse gradient magnetic field. The function of the coil 9 cannot be performed. That is, the rise and fall of the pulse gradient magnetic field are extremely poor. Although it is possible to make the bobbin with ceramics such as aluminum nitride having excellent heat resistance and thermal conductivity, it is too expensive.

  Furthermore, in the cryogenic probe that has come to be used in recent years, the inside of the probe of FIG. 2 is evacuated, and the detection coil 8, the FG coil 9, and the tuning circuit unit 10 are cooled to a cryogenic temperature of 10 to 20K. In this case, neither water cooling nor air cooling is possible, and there is no other way than limiting the output magnetic field so that the temperature rise falls within an allowable range.

  In view of the above points, an object of the present invention is to provide an NMR probe and an NMR apparatus capable of efficiently and efficiently releasing the heat of the FG coil in the NMR probe to the outside without accompanying eddy current.

  In order to achieve this object, an NMR probe according to the present invention is an NMR probe comprising a heat dissipation plate for releasing heat of an FG coil provided on a bobbin with insufficient exhaust heat to the outside. Is characterized in that a plurality of metal wires insulated from each other by an insulating film are aligned in the axial direction of the NMR probe and arranged in a plate shape.

  Further, the heat radiating plate is in contact with the magnetic field gradient coil.

  Moreover, the said heat sink is embed | buried under the said bobbin, It is characterized by the above-mentioned.

  In addition, the NMR apparatus according to the present invention includes an NMR probe provided with a heat radiating plate in which a plurality of metal wires insulated from each other by an insulating coating are aligned in the axial direction of the NMR probe and arranged in a plate shape. It is characterized by that.

  According to the NMR probe and the NMR apparatus of the present invention, the heat sink is provided with a heat radiating plate for releasing the heat of the FG coil provided on the bobbin with insufficient exhaust heat to the outside. Since a plurality of insulated metal wires are aligned in the axial direction of the NMR probe and arranged in a plate shape, the heat of the FG coil in the NMR probe can be efficiently and inexpensively released to the outside without eddy currents. Can

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, by using a commercially available self-bonding wire 14 with an insulating film (wires that can be bonded to each other by heating or the like), a cooling plate 15 in which fine wires as shown in FIG. This can be easily produced by winding a self-bonding wire with an insulating film around a suitable bobbin, fusing it, and cutting it along the axis of the bobbin.

  If this is adhered to the surface of the FG coil and further connected to the heat sink 16 (heat dissipating fin), the heat dissipating efficiency is greatly increased. In the example of FIG. 3, as described above, the heat conduction in the axial direction is substantially governed by the thermal conductivity of the bobbin, but the cooling plate made of the self-bonding wire 14 with an insulating film as shown in FIG. If 15 is brought into contact with the FG coil 9 and the wire 14 is wound around the bobbin surface in accordance with the axial direction of the bobbin, comparatively high thermal conductivity can be ensured in the axial direction even for a thin wire. It is.

  For example, if the bobbin is an epoxy resin (thermal conductivity 0.3 W / m · K), the inner diameter is 30 mm, and the thickness is 1 mm, the heat transfer amount that gives a temperature difference of 1 K per 1 mm is 0.028 W / K. On the other hand, when a bundle of copper wires (thermal conductivity 400 W / m · K) having a shape as shown in FIG. 4 and having a diameter of 1 mm and a width of 10 mm (1/10 of the bobbin circumference) is used, similarly, 1 mm The amount of heat transfer that gives a temperature difference of 1K is improved by about 11 times to 0.31 W / K. Actually, since a thicker wire and a wider cooling plate can be used, the cooling effect is several tens of times.

  The position of the heat sink 16 may not be the lower side of the bobbin as shown in FIG. 5, but may be another place such as the upper side of the bobbin, or the heat radiating plate 15 may be brought into contact with the probe cover 11 to serve as a heat radiating fin. Even if the heat radiating plate 15 is not connected to the heat sink 16, the cooling capacity is improved as compared with the case without the heat radiating plate 15 due to an increase in the heat radiating area to the surrounding air.

  In the present plan, since the direction of the self-bonding wire 14 with the insulating film is wound around the bobbin surface in accordance with the axial direction of the bobbin, it goes without saying that the current in the circumferential direction of the bobbin is limited and no eddy current is generated. Yes. Also, self-bonding wires can be purchased at a very low cost.

  The effect of the present invention is particularly remarkable in a cryogenic probe. When a wire placed in a vacuum generates heat, heat dissipation is very difficult and the temperature rises easily. If the temperature rises, heat radiation can be performed by heat radiation, but this state is inconvenient because it leads to heating of surrounding structures such as the detection coil to be cooled. At extremely low temperatures, the electrical resistance of metals generally decreases, so heat generation can be reduced to 1/10 or less. However, a temperature increase due to heat radiation of a magnetic field gradient coil reduces this effect. However, according to the present invention, an increase in electrical resistance accompanying a temperature increase can be greatly reduced, and as a result, a large gradient magnetic field due to a larger current can be obtained.

  In the example of FIG. 5, the heat sink 15 is placed outside the FG coil 9, but this is because the heat sink 15 is placed between the wire of the FG coil 9 and the bobbin as shown in FIG. 6. Also good.

  As another example, the heat sink 15 may be disposed inside the bobbin material. Although this seems to be difficult at first glance, resin materials such as bakelite and glass epoxy can be produced by laminating prepregs, and it is easy to sandwich a cooling plate in the middle of this lamination. .

  The coated wire may be any metal such as a copper wire or an aluminum wire as long as it has a good thermal conductivity. Further, when the wires are aligned and bonded, a wire that is not a self-bonding wire may be bonded with an adhesive. The wire may be a round wire or a flat wire. Further, although the FG coil is exemplified only for the Z-axis direction coil, the same can be said for the X- and Y-direction coils.

  It can be widely used for NMR probes and NMR apparatuses.

It is a figure which shows the detection part of the conventional NMR apparatus. It is a figure which shows the conventional NMR probe. It is a figure which shows the relationship between the conventional bobbin and a magnetic field gradient coil. It is a figure which shows one Example of the heat sink concerning this invention. It is a figure which shows one example of mounting to the bobbin of the heat sink concerning this invention. It is a figure which shows another example of mounting to the bobbin of the heat sink concerning this invention. It is a figure which shows another example of mounting to the bobbin of the heat sink concerning this invention.

Explanation of symbols

1: Superconducting magnet, 2: Probe, 3: Room temperature bore, 4: Sim bobbin, 5: Room temperature shim, 6: Sample, 7: Detection coil section, 8: Detection coil, 9: Magnetic field gradient coil, 10: Tuning circuit section , 11: probe cover, 12: inner bobbin, 13: outer bobbin, 14: self-bonding wire, 15: heat sink (cooling plate), 16: heat sink

Claims (4)

An NMR probe comprising a heat dissipation plate for releasing heat from a magnetic field gradient coil provided on a bobbin with insufficient exhaust heat to the outside,
The heat radiation plate is formed by arranging a plurality of metal wires insulated from each other with an insulating film in a plate shape in the axial direction of the NMR probe. The NMR probe according to claim 1, wherein the heat radiating plate is in contact with the magnetic field gradient coil. The NMR probe according to claim 1, wherein the heat dissipation plate is embedded in the bobbin. An NMR apparatus comprising the NMR probe according to claim 1.

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