JP2010197055A - Nmr probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of keeping the temperature of a magnetic field gradient coil at room temperature by a simple method. <P>SOLUTION: An NMR probe includes: (1) an NMR detection coil 7 which is cooled to a low temperature to enhance sensitivity; (2) a magnetic field gradient coil 10 which is arranged outside the NMR detection coil concentrically with the coil, and generates a pulsed magnetic field gradient inside while being kept at near room temperature; and (3) a vacuum container 1 which is arranged outside the magnetic field gradient coil, shuts off the NMR detection coil and the magnetic field gradient coil from the air while kept at room temperature, and keeps them under a vacuum condition. In the NMR probe, a thermal shield 41 set at an intermediate temperature between the low temperature and the room temperature is provided between the NMR detection coil and the magnetic field gradient coil. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an NMR probe that cools and uses a detection unit, and more particularly, to a mounting method of a self-shielding magnetic field gradient coil provided in the vicinity of the detection unit.

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

  Since the NMR signal is usually very weak, in order to increase its detection sensitivity, a low temperature gas pipe is provided on the NMR probe in which the detection unit is incorporated, and the detection unit is cooled to a very low temperature, so that the heat of the NMR apparatus is increased. It has been attempted to reduce the noise and increase the sensitivity of the NMR apparatus.

  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, A is a superconducting magnet. Inside the superconducting magnet A, a main coil B is wound by a superconducting wire. The main coil B is usually placed in a heat insulating container (not shown) that can store liquid helium and the like, and is cooled to a cryogenic temperature. The NMR probe C is composed of a bowl-shaped base portion 60 disposed on the outside of such a magnet, and a cylindrical portion 61 inserted into a hole (bore) of the magnet. The superconducting magnet A is inserted upward from the lower opening toward the inside of the cylindrical bore D that penetrates along the central axis of the superconducting magnet A.

  Next, the structure of a conventional NMR probe is shown in FIG. 2A shows the overall configuration of the NMR probe, and FIG. 2B shows a self-shielding magnetic field gradient coil. In the figure, reference numeral 101 denotes a refrigerator vacuum container. A GM refrigerator 102 is provided in the refrigerator heat insulating container vacuum container 101. Reference numerals 109 and 110 denote high-pressure and low-pressure helium gas pipes necessary for operating the GM refrigerator 102, respectively. Reference numerals 103 and 104 denote heat exchangers provided in the first stage and the second stage of the refrigerator 102 for cooling the helium gas sent to the probe. Reference numeral 105 denotes a heat exchanger for returning and returning helium gas. Helium gas for cooling the probe is supplied from the helium gas pipe 106 and collected by the helium gas pipe 107.

  The helium gas pipes 106, 107, 109, and 110 are connected to a helium gas compressor (not shown). The refrigerator 102 and the helium gas pipe of the probe are connected by a flexible transfer line 20. The heat exchanger 104 is connected to a helium gas pipe 21 that supplies low temperature helium gas to the probe. A helium gas pipe 22 for collecting helium gas from the probe is connected to a helium gas pipe 107 via a heat exchanger 105.

  The probe is housed in an adiabatic vacuum vessel 1 to cool the internal components. The helium gas pipes 21 and 22 are connected to the heat exchanger 5. The heat exchanger 5 is in thermal contact with the frame 4.

  In the figure, the detection coil 7 is illustrated as a single coil, but in actuality, it is composed of a plurality of coils such as an irradiation coil and an observation coil. The RF (high frequency) shield 8 is a cylindrical conductive member, and shields the high frequency magnetic field generated by the detection coil 7 from leaking to the outside. The electric circuit 6 is a tuning matching circuit or a double tuning circuit for the detection coil 7, and is composed of a variable capacitor, a capacitor, a coil, and the like. Actually, a shaft for adjusting the variable condenser is necessary, but it is not shown.

  The detection coil 7, the RF shield 8, and the electric circuit 6 are attached to the frame 4 to cool them. The electric circuit 6 is connected to an NMR spectrometer (not shown) via a connector 17 by a coaxial cable 16.

  The frame 4 is attached to the cylindrical heat insulating member 3 for fixing. The frame 4 is stabbed into a pin 15 at the top of a support column 14 attached to the inside of the heat insulating vacuum vessel 1 and temporarily fixed so as to be movable up and down, and then fixed to the lid 2 via a cylindrical heat insulating member 3 (patent) Reference 1).

  The pipe 13 penetrating the vacuum heat insulating container 1 up and down is made of a non-conductive material such as quartz glass so that a high-frequency magnetic field can be transmitted near or the entire detection coil 7. The NMR sample tube 11 is inserted into the pipe 13 by being supported by the holder 12 from above the probe. A temperature variable gas such as air enters from the lower part of the pipe 13 to adjust the temperature. Although not shown, the gas flows between the NMR sample tube 11 and the pipe 13 and then is exhausted to the outside.

  A self-shielding magnetic field gradient coil 10 for applying a short pulse magnetic field gradient to the sample is attached to the lid 2 so as to be positioned outside the RF shield 8. FIG. 2B shows a schematic diagram of the self-shielding magnetic field gradient coil. Coated electric wires 31 and 33 are wound around two cylindrical coil bobbins 30 and 32 to constitute an inner coil and an outer coil, respectively.

  A magnetic field gradient is generated in the vicinity of the center of the coil by connecting these two coils in series and passing a current. However, no magnetic field is generated outside the coil. Therefore, since no eddy current is generated in the outer conductive member (for example, the adiabatic vacuum container 1), a pulse magnetic field gradient that rises and falls quickly is obtained.

  The cylindrical portion of a standard probe that enters the bore of the superconducting magnet has an outer diameter of about 40 mm. As an example, the dimensions of the self-shielding magnetic field gradient coil mounted thereon are 28 mm in inner diameter, and the bobbin thickness of the inner and outer coils is about 1 mm.

  The magnetic field gradient coil 10 is attached in close proximity to the RF shield 8, the detection coil 7, and the frame 4 that are at a low temperature. When the temperature of the magnetic field gradient coil 10 is lowered, the insulating coatings of the electric wires 31 and 33 may be damaged, causing a short circuit. Further, when the bobbins 30 and 32 are cooled and cause a large thermal contraction, the bobbins 30 and 32 themselves may be deformed or the wire coating may be damaged.

  Therefore, it is necessary to prevent the temperature from lowering by making thermal contact with the lid 2 maintained at room temperature, and high thermal conductivity is therefore necessary. Moreover, it is necessary to be a non-conductive material in which eddy current does not flow so as not to inhibit generation of the pulse magnetic field gradient. Therefore, the bobbins 30 and 32 are made of a ceramic material such as alumina.

  In this example, when the probe is cooled, the detection coil 7, the RF shield 8, and the magnetic field gradient coil 10 adjacent to the frame 4 are deprived of heat, but the bobbins 30 and 32 are made of ceramic and maintained at room temperature. Since the lid 2 is in thermal contact with the lid 2, the magnetic field gradient coil 10 is kept near room temperature. As a result, since the insulated wires 31 and 33 of the magnetic field gradient coil 10 do not cause insulation failure, a magnetic field gradient pulse that rises and falls quickly is obtained.

  Next, an example of another conventional NMR probe is shown in FIG. The configuration is almost the same as in FIG. This is a case where the magnetic field gradient coil 10 is made of a resin material such as glass epoxy (epoxy resin containing glass fiber) or bakelite, and the magnetic field gradient coil 10 is covered with a heat conducting member 35 attached to the lid 2 as shown in the figure. And keep at room temperature. Since it is necessary to reduce the thermal resistance between the heat conducting member 35 and the magnetic field gradient coil 10, they are bonded together with a molding material or the like without a gap.

  In this example, when the probe is cooled, the magnetic field gradient coil 19 is kept at substantially room temperature by the heat conducting member 35. Therefore, the bobbins 30 and 32 are not deformed due to thermal contraction due to low temperature, and the covered wires 31 and 33 are Since no insulation failure occurs, a magnetic field gradient pulse with a fast rise and fall can be obtained.

  Next, another example of a conventional NMR probe is shown in FIG. For example, even if the magnetic field gradient coil operates normally as shown in FIGS. 2 and 3, the eddy current generated in the RF shield 8 of FIGS. That is, since the RF shield 8 is formed by winding a copper foil having a thickness of about 10 μm around an insulating material such as quartz glass, the electrical resistance decreases when cooled to a low temperature, for example, about 25K. For this reason, the decay time of the eddy current generated when the pulse magnetic field gradient is applied becomes long, and the rise and fall of the pulse magnetic field gradient become long. In this example, therefore, the RF shield 8 is omitted.

  As a result, since there is no RF shield 8 in this example, a magnetic field gradient pulse with a fast rise and fall can be obtained.

Japanese Patent No. 4133777

[Problem 1 of the prior art]
When a ceramic bobbin is used, there is a problem that the bobbin becomes expensive, difficult to handle, and easily damaged. For example, it is difficult in terms of processing technology to manufacture a bobbin with a ceramic material such as alumina. Further, if the position accuracy of the electric wire is poor, the leakage magnetic field becomes large, and the rise and fall times of the pulse magnetic field become long. Also, the processing cost is high and it is difficult to handle because it is easy to break.

[Problem 2 of the prior art]
When a glass epoxy bobbin is used, the coil is covered with a heat conducting member and kept in room temperature by being in thermal contact with the room temperature member. However, since it is actually mounted in a vacuum heat insulating container, it is necessary to fill with a molding material or the like so that there is no gap between the coil and its heat conducting member.

  If a coil composed of a thin bobbin as described above and a heat conducting member are attached over a wide range with this molding material or the like, the coil is distorted due to curing of the molding material. Since a distorted self-shielding magnetic field gradient coil cannot generate a magnetic field as designed, the leakage magnetic field becomes large. Therefore, an eddy current is generated in the conductive member outside the coil, and the rise time and fall time of the pulse magnetic field become long.

  In addition, since the RF shield that is at a low temperature and the magnetic field gradient coil are close to each other, it is necessary to reduce the thermal resistance between the lid and the coil at room temperature in order to keep the coil close to room temperature. However, a thick copper foil or the like that slows the decay of eddy currents cannot be used as the heat conducting member for that purpose because the pulse magnetic field gradient is not hindered. Alternatively, it is conceivable to arrange the insulation-coated copper wires along the axial direction of the coil, but it is difficult in terms of dimensions to obtain the necessary heat conduction. This method also requires a mold for thermal contact, and coil distortion due to this is inevitable.

[Problem 3 of the prior art]
When the RF coil is omitted, the electrical loss of the detection coil 7 increases due to the inductive coupling between the detection coil 7 and the magnetic field gradient coil 10, so that the Q value of the detection coil 7 decreases. As a result, the NMR detection sensitivity decreases. Further, NMR background signals are output from the bobbins 30 and 32 and the covered electric wires 31 and 33 which are components of the magnetic field gradient coil 10.

  In view of the above points, the present invention is to provide a method capable of maintaining the temperature of a magnetic field gradient coil at room temperature by a simple method without degrading the performance of the NMR probe.

In order to achieve this object, the NMR probe according to the present invention comprises:
(1) NMR detection coil cooled to low temperature to increase sensitivity,
(2) A magnetic field gradient coil arranged concentrically with the coil outside the NMR detection coil and generating a pulse magnetic field gradient inside while being maintained near room temperature;
(3) A vacuum vessel that is placed outside the magnetic field gradient coil and that keeps the NMR detection coil and the magnetic field gradient coil out of the atmosphere while being kept at room temperature, and places them under vacuum,
In an NMR probe comprising
A heat shield set at a temperature between low temperature and room temperature is concentrically provided between the NMR detection coil and the magnetic field gradient coil.

  In addition, an RF shield that is concentrically disposed between the NMR detection coil and the heat shield and shields a high-frequency magnetic field generated by the NMR detection coil from outside while being cooled to a low temperature is provided. Yes.

  The low temperature is 25K or less.

  The temperature between the low temperature and room temperature is about 200K.

  In addition, the heat shield has a thickness of conductor foil, conductor foil tape, or conductor wire that does not hinder the transmission of the magnetic field gradient pulse generated by the magnetic field gradient coil, and transfers heat of the outside world by arranging the surface on the surface. It is characterized by being maintained at a temperature between the low temperature and room temperature.

  The bobbin of the heat shield is made of a resin material or a ceramic material.

  The RF shield is characterized in that a conductor film or a conductor foil is arranged on the surface of a cylindrical body made of ceramic material, quartz glass, resin material or the like.

  Also, the conductor film or conductor foil disposed on the surface of the RF shield is thicker than the skin thickness of the high-frequency current used for NMR measurement, and more than the thickness that inhibits the transmission of the magnetic field gradient pulse generated by the magnetic field gradient coil. It is thin.

  Further, the RF shield is made by plating a surface of a brass foil or phosphor bronze foil with a highly conductive material.

  The highly conductive material is gold, silver, or aluminum.

According to the NMR probe of the present invention,
(1) NMR detection coil cooled to low temperature to increase sensitivity,
(2) A magnetic field gradient coil arranged concentrically with the coil outside the NMR detection coil and generating a pulse magnetic field gradient inside while being maintained near room temperature;
(3) A vacuum vessel that is placed outside the magnetic field gradient coil and that keeps the NMR detection coil and the magnetic field gradient coil out of the atmosphere while being kept at room temperature, and places them under vacuum,
In an NMR probe comprising
Since a heat shield set at an intermediate temperature between low temperature and room temperature is provided between the NMR detection coil and the magnetic field gradient coil in a concentric manner,
It has become possible to provide a method capable of maintaining the temperature of the magnetic field gradient coil at room temperature by a simple method without degrading the performance of the NMR probe.

It is a figure which shows the conventional NMR apparatus. It is a figure which shows an example of the conventional cooling type NMR probe. It is a figure which shows another example of the conventional cooling type NMR probe. It is a figure which shows another example of the conventional cooling type NMR probe. It is a figure which shows one Example of the cooling type NMR probe concerning this invention. It is a figure which shows one Example of the heat shield used for the cooling type NMR probe concerning this invention. It is a figure which shows another Example of the heat shield used for the cooling type NMR probe concerning this invention. It is a figure which shows another Example of the cooling type | mold NMR probe concerning this invention. It is a figure which shows another Example of the cooling type | mold NMR probe concerning this invention. It is a figure which shows another Example of the cooling type | mold NMR probe concerning this invention. It is a figure which shows one Example of RF shield used for the cooling type NMR probe concerning this invention. It is a figure which shows another Example of the RF shield used for the cooling type NMR probe concerning this invention. It is a figure which shows another Example of the RF shield used for the cooling type NMR probe concerning this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 5 shows a schematic view of the vicinity of the detection coil of this embodiment. Portions not shown are the same as those in FIGS. 2 and 3 of the prior art.

  The probe is housed in an adiabatic vacuum vessel 1 to cool the internal components. The helium gas pipes 21 and 22 are connected to the heat exchanger 5. The heat exchanger 5 is in thermal contact with the frame 4.

  In the figure, 7 is a detection coil. The detection coil 7 is illustrated as a single coil, but actually includes a plurality of coils such as an irradiation coil and an observation coil. The RF shield 8 is a cylindrical conductive member. The high frequency magnetic field generated by the detection coil 7 is shielded so as not to leak outward. The electric circuit 6 includes a tuning matching circuit for the detection coil 7 and a double tuning circuit.

  The detection coil 7, the RF shield 8, and the electric circuit 6 are attached to the frame 4 to cool them. The electric circuit 6 is connected to an NMR spectrometer (not shown) via a connector 17 by a coaxial cable 16.

  The frame 4 is attached to the cylindrical heat insulating member 3 for fixing. The frame 4 is stabbed into a pin 15 at the top of a support column 14 attached to the inside of the heat insulating vacuum vessel 1 and temporarily fixed so as to be movable up and down, and then fixed to the lid 2 via the cylindrical heat insulating member 3.

  The heat shield 41 has a shape with a ring-shaped ridge on the lower side of the cylinder, and includes a heat shield bobbin 43 and a copper foil 42. The heat shield bobbin 43 is made of an insulating material that does not generate eddy current so as not to disturb short magnetic field gradient pulses. Examples include resin materials such as glass epoxy and bakelite.

  In order to increase thermal conductivity, a copper foil 42 is affixed inside the heat shield bobbin 43. The copper foil 42 is also made thin so that the decay time of the eddy current is sufficiently short so as not to inhibit the short magnetic field gradient pulse, thereby increasing the electric resistance value. As an example, in the case of NMR measurement, since this copper foil does not become low temperature in this example, a thickness of about 10 μm is sufficient. The copper foil 42 may be outside the heat shield bobbin 43. Moreover, nonmagnetic materials other than copper, such as aluminum foil, may be used.

  The heat shield 41 is fixed to the lid 2 whose upper end is at room temperature, and at the same time, the copper foil 42 is brought into thermal contact with the lid 2. The cylindrical portion of the heat shield 41 is attached between the RF shield 8 and the magnetic field gradient coil 10 so as not to contact each other. If it is difficult to avoid contact, insert a point contact spacer to ensure sufficient thermal resistance.

  The ring-shaped flanges below the heat shield 41 are arranged so as not to contact each other between the magnetic field gradient coil 10 and the frame 4 as described above. If it is difficult to avoid contact, insert a point contact spacer to ensure sufficient thermal resistance.

  Here, the operation will be described in the case where the bobbins 30 and 32 (see FIG. 2) of the magnetic field gradient coil 10 are made of a general resin material such as glass epoxy or bakelite.

  First, the probe is cooled, and the detection coil 7, the RF shield 8, and the electric circuit 6 that are in thermal contact with the frame 4 are cooled. As an example, the frame 4 is kept around 25K or less.

  The heat shield 41 provided between the magnetic field gradient coil 10 and the low-temperature frame 4, the detection coil 7, and the RF shield 8 is caused by the heat conduction action of the copper foil 42 that is in thermal contact with the lid 2 at room temperature. , The temperature does not drop too much. As an example, even if the frame 4 is 25K, the heat shield 41 can be lowered only to about 200K. Therefore, since the temperature difference between the heat shield 41 and room temperature is about 100 K, the magnetic field gradient coil 10 is kept approximately at room temperature by the heat conduction action from the lid 2.

  Since the temperature of the magnetic field gradient coil 10 does not drop and is kept near room temperature, a pulse magnetic field gradient that rises and falls quickly can be obtained.

  FIG. 6 shows the heat shield 41 of this embodiment. Others are the same as FIG. 5 of Example 1. FIG. In the present embodiment, as shown in the figure, the copper foil tape 45 is attached to the heat shield bobbin 43 from the upper part to the inside of the cylindrical portion and the collar part so as not to contact each other. The copper foil tape 45 may be outside the heat shield bobbin 43. Moreover, nonmagnetic materials other than copper, such as an aluminum foil tape, may be used.

  The operation is the same as in the first embodiment. That is, since the copper foil tapes 45 are pasted so as not to contact each other, the eddy current decays faster. As a result, a magnetic field gradient pulse having a rapid fall and rise is obtained.

  FIG. 7 shows the heat shield 41 of this embodiment. As shown in the figure, the copper wires 46 are pasted on the heat shield bobbin 43 from the upper part to the inside of the cylindrical portion and the collar so as not to contact each other. Instead of the copper wire 46, a coated copper wire may be used, and the cylindrical portion may be attached with no gap. The copper wire 46 may be outside the heat shield bobbin 43. Further, nonmagnetic materials other than copper, such as aluminum wires, may be used.

  The operation is the same as in the second embodiment. That is, since the copper wire 46 is used, the generation of eddy current is suppressed, and the magnetic field gradient coil is easily kept at room temperature due to the high heat conduction effect.

  FIG. 8 shows this embodiment. The heat shield 41 composed of the heat shield bobbin 43 and the copper foil 42 covers the entire magnetic field gradient coil 10 so as not to contact the magnetic field gradient coil 10.

  The operation is the same as in the first embodiment. Since the entire magnetic field gradient coil 10 is covered with the heat shield 41, the temperature of the magnetic field gradient coil 10 is more uniformly maintained near room temperature.

  FIG. 9 shows this embodiment. A heat shield 41 composed of a heat shield bobbin 43 having only a cylindrical portion without a wrinkle with a copper foil 42 attached is provided between the RF shield 8 and the magnetic field gradient coil 10. A sufficient gap is provided between the lower end of the magnetic field gradient coil 10 not covered by the heat shield 41 and the frame 4.

  The operation is the same as in the first embodiment. Although the lower end of the magnetic field gradient coil 10 close to the frame 4 is not covered with the heat shield 41, there is a sufficient gap, so that the temperature of the magnetic field gradient coil 10 is kept near room temperature.

  FIG. 10 shows this embodiment. The magnetic field gradient coil 10 is brought into thermal contact with the lid 2 maintained at room temperature for the purpose of keeping the magnetic field gradient coil 10 at room temperature and facilitating heat dissipation during heating. At that time, a copper foil 50 or the like is attached in order to increase the heat conduction efficiency. Instead of the copper foil 50, a copper foil tape or a copper wire may be attached. In that case, since a large heat conduction efficiency is not required, a thin copper foil or a thin electric wire is sufficient, and there is no fear that the magnetic field gradient coil 10 is deformed even if these are bonded. Copper foil, copper foil tape, copper wire, etc. may be attached to either the inside or the outside of the magnetic field gradient coil 10. Moreover, nonmagnetic materials other than copper, such as aluminum foil and aluminum wire, may be used.

  The operation is the same as in the first embodiment. When the magnetic field gradient coil 10 is energized, the heat generated by the magnetic field gradient coil 10 itself is radiated through the copper foil 50 and the like.

  FIG. 11 shows this embodiment. The heat shield 41 is made of alumina, which is a high heat conductive material and is also an insulating material, and is attached between the magnetic field gradient coil 10 and the RF shield 8.

  The operation is the same as in the first embodiment. Due to the heat conduction effect of the heat shield 41 itself, the temperature of the magnetic field gradient coil 10 is kept near room temperature.

  FIGS. 12A and 12B show the configuration of this example and the outline of the RF shield. Also in the present embodiment, the heat shield 41 similar to that in the first to seventh embodiments is provided. However, the feature of this embodiment is not the heat shield but the RF shield.

  As shown in FIG. 12B, the RF shield 8 of this embodiment is a component obtained by plating an RF shield bobbin 53 made of an insulating material having a high thermal conductivity, for example, alumina. The RF shield bobbin 53 is brought into thermal contact with the frame 4.

  The thickness of the plating 51 is reduced so that the decay time of the eddy current generated when the pulse magnetic field gradient is applied is sufficiently short even at a low temperature. For example, in the case of copper plating, the thickness is preferably about 1 μm.

  The operation of the heat shield 41 is the same as in the first to seventh embodiments. On the other hand, since the RF shield bobbin 43 is made of alumina having high thermal conductivity, it is cooled by the helium gas heat exchanger 5 via the frame 4. As a result, since the plating 51 is cooled, its electrical resistance is lowered, and the electrical loss resulting from shielding the RF magnetic field from the detection coil is reduced.

  When a pulse magnetic field gradient is applied at a low temperature, an eddy current is also generated in the RF shield 8. However, since the plating 51 of the RF shield 8 is sufficiently thin, the decay of the eddy current is fast. A gradient is obtained.

  In addition, if it supplements, the electric current sent through a magnetic field gradient coil is a frequency component of about ~ 100 kHz. On the other hand, the high frequency magnetic field generated by the detection coil is several tens of MHz or more. Therefore, if this frequency difference is utilized, by adjusting the plating material and its thickness, there is little electrical loss for high-frequency magnetic fields, and sufficiently shortens the eddy current decay time for magnetic field gradient pulses. be able to.

  In the case of high frequency, current flows only near the surface due to the skin effect, so that the electrical loss is small if the plating is thicker than the depth of the skin effect. In comparison, the thickness of the current having a frequency of about 100 kHz is too thin, so that the electrical resistance increases, the loss increases, and the eddy current decays faster.

  FIG. 13 shows the RF shield of this example. Other configurations are the same as those in the eighth embodiment. In this embodiment, the RF shield bobbin 53 is manufactured from quartz glass, a resin material or the like having a low thermal conductivity. Then, plating 51 is applied to the surface, and a tape-like copper foil 52 is attached to the outside of the plating 51. The lower end of the tape-shaped copper foil 52 is brought into thermal contact with the frame 4.

  In the present embodiment, the plating 51 is cooled by the tape-shaped copper foil 52, the electrical resistance thereof is lowered, and the electrical loss resulting from shielding the RF magnetic field from the detection coil is reduced. When a pulse magnetic field gradient is applied, the tape-shaped copper foil 50 only covers a part of the cylindrical surface, so that the decay time of the eddy current is sufficiently short and a pulse magnetic field gradient with a fast rise and fall can be obtained. .

  As a modification of the eighth and ninth embodiments, the plating material may be gold, silver, aluminum, or the like instead of copper. The plating may be performed by any method such as electroless plating or vapor deposition. The plating may be performed on the inside of the bobbin.

  Instead of plating directly on the RF shield, a metal foil such as a brass foil may be wound. In that case, if the brass foil is plated with a highly conductive material such as gold, silver, or aluminum, the electrical loss resulting from shielding the RF magnetic field can be reduced.

  It should be noted that, even if brass is placed at a low temperature, the electrical resistance does not become small like copper, so the decay time of eddy current does not increase. In addition to brass, a material that does not decrease electrical resistance at low temperatures, such as phosphor bronze, can be used for the foil material.

  Further, instead of directly plating the RF shield, a resin material foil such as polyimide or polyester plated with highly conductive aluminum or copper may be wound.

  Can be widely used in NMR apparatus.

1: heat insulation vacuum vessel, 2: lid, 3: cylindrical heat insulating member, 4: frame, 5: heat exchanger, 6: electric circuit, 7: detection coil, 8: RF shield, 10: magnetic field gradient coil, 11: NMR sample tube, 12: holder, 13: pipe, 14: support, 15: pin, 16: coaxial cable, 17: connector, 20: flexible transfer line, 21: helium gas piping, 22: helium gas piping, 30: coil bobbin 31: Coated wire, 32: Coil bobbin, 33: Coated wire, 41: Heat shield, 42: Copper foil, 43: Heat shield bobbin, 45: Copper foil tape, 46: Copper wire, 50: Copper foil, 51: Plating 52: Copper foil, 53: RF shield bobbin, 60: Base part, 61: Cylindrical part, A: Superconducting magnet, B: Main coil, C: NMR probe, D: Bore

Claims (10)

(1) NMR detection coil cooled to low temperature to increase sensitivity,
(2) A magnetic field gradient coil arranged concentrically with the coil outside the NMR detection coil and generating a pulse magnetic field gradient inside while being maintained near room temperature;
(3) A vacuum vessel that is placed outside the magnetic field gradient coil and that keeps the NMR detection coil and the magnetic field gradient coil out of the atmosphere while being kept at room temperature, and places them under vacuum,
In an NMR probe comprising
An NMR probe characterized in that a heat shield set at a temperature between low temperature and room temperature is concentrically provided between the NMR detection coil and the magnetic field gradient coil. An RF shield is disposed concentrically between the NMR detection coil and the heat shield, and shields a high-frequency magnetic field generated by the NMR detection coil from outside while being cooled to a low temperature. Item 1. The NMR probe according to Item 1. The NMR probe according to claim 1 or 2, wherein the low temperature is 25K or less. The NMR probe according to claim 1, wherein the intermediate temperature between the low temperature and room temperature is about 200K. The heat shield has a conductor foil, conductor foil tape, or conductor wire having a thickness that does not hinder the transmission of the magnetic field gradient pulse generated by the magnetic field gradient coil, and transfers heat from the outside to transfer the low temperature. The NMR probe according to claim 1, wherein the NMR probe is maintained at a temperature intermediate between the temperature and room temperature. 6. The NMR probe according to claim 5, wherein the bobbin of the heat shield is made of a resin material or a ceramic material. 3. The NMR probe according to claim 2, wherein the RF shield is made by arranging a conductor film or a conductor foil on the surface of a cylindrical body made of a ceramic material, quartz glass, or a resin material. . The conductor film or conductor foil disposed on the surface of the RF shield is thicker than the skin thickness of the high-frequency current used for NMR measurement and thinner than the thickness that inhibits the transmission of the magnetic field gradient pulse generated by the magnetic field gradient coil. The NMR probe according to claim 7. The NMR probe according to claim 2, wherein the RF shield is made by plating a highly conductive material on the surface of a brass foil or phosphor bronze foil. The NMR probe according to claim 9, wherein the highly conductive material is gold, silver, or aluminum.

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