JP2005093464A - Magnet and nmr spectroscope, mri system or icr mass spectrograph - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact and lightweight magnet capable of suppressing a leakage magnetic field and the disturbance of field uniformity, and an NMR spectrometer, an MRI system or an ICR mass spectrograph employing that magnet. <P>SOLUTION: The magnet 1 comprises a hollow tube 2, a main coil 3 generating a magnetic field, two shield coils 4 for suppressing the leakage of a magnetic field to the outside of the main coil 3, a first cryogenic container 5 arranged internally with the main coil 3, a second cryogenic container 6 arranged internally with the first cryogenic container 5, an outer container 7 arranged internally with the second cryogenic container 6, a pipe 8 communicating between the inside and the outside of the first cryogenic container 5 through the outer container 7 and the second cryogenic container 6, a base 9 for supporting the outer container 7 fixedly, and a pipe 14 making the inside and the outside of the double outer tubes 6a of the second cryogenic container 6 communicate with each other through the outer container 7 wherein at least one of the double outer tubes 6a of the second cryogenic container 6 and cover parts 6b at the opposite ends are made of magnetic bodies. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnet for suppressing magnetic field leakage and an NMR analyzer, MRI apparatus or ICR mass spectrometer using the magnet.

Conventionally, for example, a magnet for suppressing magnetic field leakage and an MRI apparatus using this magnet have been known.
For example, there are those disclosed in Patent Document 1 and Patent Document 2 below. The thing of patent document 1 is the superconducting magnet coil for MRI tomography. This superconducting magnet coil includes five main coils made of an oxide superconducting wire that generates a uniform magnetic field in a coil bore, and a shield coil made of an oxide superconducting wire that cancels the external magnetic field of the main coil.
The thing of patent document 2 is installing the MRI apparatus using magnets, such as a horizontal magnetic field system, in a magnetic shield room.
Japanese Patent Laid-Open No. 5-90022 JP 2002-172102 A

  In the case of Patent Document 1, if it is allowed to dispose the shield coil as far as possible from the main coil, it is not difficult to suppress it to, for example, about 20 gauss or less, which is a safety standard for cardiac pacemakers. However, in this case, it is necessary to make the diameter of the shield coil about twice as large as the outer diameter of the main coil, and a useless space is created in the cryogenic container, resulting in a very inefficient design. Further, in order to obtain a device having a reasonably large shield coil diameter, it has been extremely difficult to reduce the magnetic field strength near the outer surface of the cryogenic vessel to about 100 gauss or less.

  In the case of Patent Document 2, it is necessary to construct an iron plate having a thickness of at least several millimeters over the entire room, resulting in high costs. Further, if the iron plate has room temperature fluctuation, the position of the iron plate is displaced due to expansion / contraction, and the magnetic susceptibility is changed, so that the magnetic field uniformity is disturbed in the sample space at the center of the magnet.

  Accordingly, an object of the present invention is to provide a compact and lightweight magnet that suppresses a leakage magnetic field and magnetic field uniformity disturbance, and an NMR analyzer, an MRI apparatus, or an ICR mass spectrometer using the magnet.

Means and effects for solving the problems

The magnet of the present invention includes a hollow cylinder that serves as a sample space, a main coil that is provided along the outer periphery of the hollow cylinder, generates a magnetic field in the sample space, and is provided outside the main coil. At least one shield coil that suppresses magnetic field leakage to the outside, a double cylinder, and the cylinders of the double cylinder are fixed to each other at both ends of the cylinder, and the hollow cylinder communicates with the outside. A first cryogenic container having a lid portion provided with a hole to be made, a double outer cylinder, an inner cylinder disposed inside the double outer cylinder, the double outer cylinder, and the inner A second cryogenic container having a lid portion provided with a hole for fixing the double outer cylinder and the inner cylinder and communicating the hollow cylinder with the outside at both ends of the cylinder; , Disposed inside the double cylinder of the first cryogenic container, A cryogenic container is disposed between the double outer cylinder and the inner cylinder of the second cryogenic container, and at least one of the double outer cylinders of the second cryogenic container and the both ends The lid is made of a magnetic material.
With the above configuration, it is possible to provide a compact and lightweight magnet that sufficiently suppresses the leakage magnetic field from the magnet to the outside and the magnetic field uniformity disturbance in the sample space.

In the magnet of the present invention, it is preferable that the central axes of the main coil, the shield coil, and the second cryogenic container are on the central axis of the hollow cylinder.
With the above configuration, the magnet is mechanically stabilized because the imbalance of the attractive force due to the magnetic field generated from the main coil and the shield coil is eliminated. In addition, since the non-uniform component of the magnetic field in the radial direction is suppressed, it is possible to further suppress the magnetic field uniformity disturbance in the sample space.

In the magnet of the present invention, it is preferable that the main coil and the shield coil are made of a superconductor.
With the above configuration, a strong magnetic field can be generated, and a magnet having the above-described effects while being a strong magnetic field can be provided.

In the magnet of the present invention, it is preferable that the main coil and the shield coil are connected in series to the same power source.
With the above configuration, since the same amount of current flows through the main coil and the shield coil, the magnetic field can be easily adjusted. Therefore, high magnetic field uniformity can be achieved regardless of the magnetic field strength of the main coil.

The NMR analyzer, MRI apparatus, and ICR mass spectrometer of the present invention preferably include any of the magnets described above.
With the above configuration, it is possible to provide a high-resolution NMR analyzer, MRI apparatus, and ICR mass spectrometer having the above effects.

  Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing a magnet according to a first embodiment of the present invention. The magnet 1 is provided along a hollow cylinder 2 serving as a sample space, an outer peripheral portion of the hollow cylinder 2, a main coil 3 that generates a magnetic field in the sample space, and provided outside the main coil 3. Two shield coils 4 that suppress external magnetic field leakage, a first cryogenic container 5 in which the main coil 3 is disposed, a second cryogenic container 6 in which the first cryogenic container 5 is disposed, 2 The outer container 7 in which the cryogenic container 6 is disposed, the pipe 8 that communicates the inside and the outside of the first cryogenic container 5 via the outer container 7 and the second cryogenic container 6, and the outer container 7 are fixedly supported. The base 9 is provided with a pipe 14 that communicates the inside and outside of the double outer cylinder 6 a of the second cryogenic container 6 via the outer container 7. The magnet 1 further includes a radiation shield (not shown) between the first low-temperature container 5 and the second low-temperature container 6.

  The hollow cylinder 2 is arranged horizontally so as to communicate with the outside. When the magnet 1 is used in an NMR analyzer, an MRI apparatus, or an ICR mass spectrometer, the vicinity of the center of the hollow cylinder 2 becomes a sample space or a test space. When the magnet 1 is used in the MRI apparatus, the diameter of the hollow cylinder 2 is such that the subject can pass through the hollow cylinder 2 in a supine state.

  Since the main coil 3 can generate a strong magnetic field, the main coil 3 is preferably made of a superconductor. If a strong magnetic field can be generated, when the magnet 1 is used in an NMR analyzer, an MRI apparatus, or an ICR mass spectrometer, the effects of increasing the signal intensity and increasing the resolution can be obtained.

  The shield coil 4 cancels the external magnetic field of the main coil by flowing a current in the opposite direction to the main coil. Further, when the main coil 3 is made of a superconductor, the shield coil 4 is preferably made of a superconductor in order to cancel the strong magnetic field outside the main coil 3. The two shield coils 4 and the main coil 3 are connected in series to the same power source.

  The first cryogenic vessel 5 includes a double cylinder composed of an outer cylinder 5a and an inner cylinder 5c arranged so that the central axes are at least parallel, and an outer cylinder 5a at both ends of the outer cylinder 5a and the inner cylinder 5c. And a lid 5b provided with a hole for communicating the hollow cylinder 2 with the outside. Specifically, the first cryogenic vessel 5 is surrounded by an inner peripheral portion of the outer cylinder 5a, an outer peripheral portion of the inner cylinder 5c, and an inner wall of the lid portion 5b, and is used as a liquid helium tank. Note that liquid helium is supplied into the first cryogenic vessel 5 through a pipe 8.

Second cryocontainer 6, a double outer tube 6a made of outer tubular 6a ₁ and the inner cylinder 6a _2, and inner cylinder 6c disposed inside the double of the outer cylinder 6a, the outer tube of the double 6a and the inner cylinder 6c are provided with a lid 6b provided with holes for connecting the double outer cylinder 6a and the inner cylinder 6c to form a sealed space, and further communicating the hollow cylinder 2 with the outside. doing. The second cryocontainer 6, in particular, is used space surrounded by _first inner circumferential portion outer cylinder 6a and the inner cylinder 6a ₂ outer peripheral portion and the lid portion 6b inner wall as liquid nitrogen tank, inside the inner tubular 6a ₂ peripheral The first cryogenic container 5 is disposed in a space surrounded by the portion, the inner cylinder 6c, and the inner wall of the lid portion 6b. Further, the tubes 14, a space surrounded by the _first inner peripheral portion the outer tubular 6a and the inner cylinder 6a ₂ outer peripheral portion and the lid portion 6b inner wall, in communication with the outside, the outer tubular 6a _first inner circumferential from the tube 14 in a space surrounded by the parts and the inner cylinder 6a ₂ outer peripheral portion and the lid portion 6b inner wall has a liquid nitrogen can be supplied.
The second cryocontainer 6, and the outer tubular 6a ₁ and both ends of the lid portion 6b of the double tube 6a of the second cryocontainer is composed of iron. In addition, this iron member is not limited to this, A magnetic body or a ferromagnetic body may be sufficient. Although not shown, the inner cylinder 6a ₂ may be a magnetic body such as iron instead of the outer cylinder 6a ₁ of the double cylinder 6a, and both the outer cylinder 6a ₁ and the inner cylinder 6a ₂ are magnetic bodies such as iron. It may be.

  The outer container 7 has a cylinder 7a and lids 7b that communicate the hollow cylinder 2 with the outside at both ends of the cylinder 7a. In order to insulate heat outside the outer container 7, the inside is evacuated.

Next, the operation of the magnet 1 will be described. When a current is passed through the main coil 3 and the two shield coils 4 connected in series to the same power source, the main coil 3 and the shield coil 4 are configured so that the current flows in the opposite direction. 3 cancels and suppresses the magnetic field generated by the shield coil 4. Further, even by an outer tube 6a ₁ and both ends of the lid portion 6b of the second cryocontainer double tube 6a made of a magnetic material such as iron, it can be suppressed the external magnetic field.

  According to the magnet 1 of the first embodiment, a compact and lightweight magnet 1 that can generate a strong magnetic field and sufficiently suppresses the leakage magnetic field from the magnet 1 to the outside and the magnetic field uniformity disturbance in the sample space is provided. it can. Further, since the same amount of current flows through the main coil and the shield coil, the magnetic field can be easily adjusted, so that high magnetic field uniformity can be achieved regardless of the magnetic field strength of the main coil.

  Next, a magnet according to a second embodiment of the present invention will be described. FIG. 2 is a view showing a magnet according to a second embodiment of the present invention. The magnet 10 has substantially the same configuration as the magnet 1 of the first embodiment, but the central axes of the main coil 3, the shield coil 4, and the second cryogenic vessel 6 are arranged on the central axis of the hollow cylinder 2. Different in that it is.

  Next, the operation of the magnet 10 will be described. The magnet 10 has the same function as the magnet 1 of the first embodiment. Further, since the central axes of the main coil 3, the shield coil 4 and the second cryogenic vessel 6 are arranged on the same axis, there is no attraction of attraction due to the magnetic field generated from the main coil and the shield coil, and the magnetic field The non-uniform component in the radial direction is suppressed.

  According to the magnet 10 of the second embodiment, the magnet has the same effect as the magnet 1 of the first embodiment, and there is no imbalance in attractive force due to the magnetic field generated from the main coil and the shield coil. There is also an advantage that it is stable. In addition, since the non-uniform component of the magnetic field in the radial direction is suppressed, it is possible to further suppress the magnetic field uniformity disturbance in the sample space.

  Further, although not shown, according to the magnet of each of the above embodiments, the signal intensity is high, so that it is possible to provide an NMR analyzer, an MRI apparatus, and an ICR mass spectrometer including the magnet of each of the above embodiments with high resolution.

Next, examples of the magnet 1 according to the first embodiment of the present invention will be described. First, the dimensions of the main components of the magnet 1 in FIG. 1 will be described. The hollow cylinder 2 has an inner diameter of 100 mm, a length of 990 mm, the main coil 3 has an inner diameter of 140 mm, an outer diameter of 230 mm, a length of 500 mm, and the shield coil 4 has an inner diameter of 410 mm and an outer diameter of 440 mm. The two shield coils 4 are spaced 140 mm apart on the same central axis, and are arranged so that the distance between the outer ends is 480 mm. Moreover, it arrange | positions so that the center of the distance of outer ends may be on the same straight line as the center of a main coil.
The inner diameter of the outer cylinder 5a of the first cryogenic container 5 is 600 mm, the length is 780 mm, the inner diameter of the outer cylinder 6a ₁ (iron member) of the second cryogenic container 6 is 790 mm, the length is 856 mm, the wall thickness is 5 mm, The inner cylinder 6a _{2 has} an inner diameter of 700 mm, the outer cylinder 7 has an inner diameter of 865 mm, and a length of 990 mm. The lid 6b has a diameter of 795 mm and a wall thickness of 5 mm. The weight of the outer cylinder 6a ₁ and the lid portion 6b of the second cryocontainer 6 is 110 kg.

FIG. 3 is a diagram showing a leakage magnetic field distribution when current is passed through the main coil 3 and the two shield coils 4 of the magnet 1 of the first embodiment. When a current of 83 amperes is passed through the main coil 3 and the two shield coils 4 of the magnet 1 per second, the magnetic field in the vicinity of the outer surface of the outer container 7 is all except for the vicinity of the hollow cylinder 2 as shown in FIG. It was confirmed that it became 10 gauss or less at the point. Specifically, the distribution line of 20 gauss was from the end of the hollow cylinder 2 to 12 cm at the maximum, and the distribution line of 5 gauss was from the end of the hollow cylinder 2 to 28 cm at the maximum. Here, the leakage magnetic field was measured with a Gauss meter. The same applies to the following comparative examples.
Further, when the magnetic field uniformity was measured in a cylindrical space having a radius of 25 mm and a length of 80 mm as the sample space, the difference between the maximum value and the minimum value was within 5 ppm.
The magnetic field in the sample space was 7 Tesla.

Comparative Example 1

Next, Comparative Example 1 will be described. FIG. 4 is a diagram showing a leakage magnetic field distribution when a current is passed through the main coil 3 and the two shield coils 4 in the magnet 11 of the first comparative example. Magnet 11 of Comparative Example 1, the outer tube 6a ₁ of the second cryocontainer 6 in the magnet 1, in which aluminum was used in place of iron. As shown in FIG. 4, a leakage field of 100 gauss was confirmed even at a position 40 cm away from the outer wall surface of the magnet 11.

Comparative Example 2

Next, Comparative Example 2 will be described. FIG. 5 is a diagram showing a leakage magnetic field distribution when a current is passed through the main coil 3 in the magnet 12 of the comparative example 2. As shown in FIG. Magnet 12 of Comparative Example 2, which does not comprise a shield coil 4 in the magnet 1, the outer tube 6a ₁ of the second cryocontainer 6, in which aluminum was used in place of iron. A magnetic shield 13, which is an iron plate having a thickness of 20 cm, is disposed so as to cover the entire surface at a distance of 30 cm from the outer peripheral portion of the outer container 7 of the magnet 12. As shown in FIG. 5, the leakage magnetic field could be suppressed to about 50 Gauss in the vicinity of the hollow cylinder 2. The weight of the iron plate was 4.2 t.

  Therefore, in the above comparative example 1, the leakage magnetic field is not sufficiently suppressed, and in the above comparative example 2, the leakage magnetic field can be suppressed, but the floor load by the iron plate having a weight of 4.2 t or the like. Problems arise in the installation environment. On the other hand, it can be seen that the magnet 1 of Example 1 is a compact magnet that is light in weight and maintains high magnetic field uniformity while sufficiently suppressing the leakage magnetic field.

  The present invention can be changed in design without departing from the scope of the claims, and is not limited to the above-described embodiments and examples.

The figure which shows the magnet which concerns on 1st Embodiment of this invention. The figure which shows the magnet which concerns on 2nd Embodiment of this invention. The figure which shows the leakage magnetic field distribution of the magnet of Example 1. FIG. The figure which shows the leakage magnetic field distribution of the magnet of the comparative example 1. FIG. The figure which shows the leakage magnetic field distribution of the magnet of the comparative example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 10, 11, 12 Magnet 2 Hollow cylinder 3 Main coil 4 Shield coil 5 1st low temperature container 5a Outer cylinder 5b, 6b, 7b Cover part 5c, 6c Inner cylinder 6 2nd low temperature container 6a Double outer cylinder 6a ₁ Outer tube 6a ₂ Inner tube 7 Outer container 7a Tube 8, 14 Tube 13 Magnetic shield

Claims (5)

A hollow cylinder serving as a sample space;
A main coil provided along the outer periphery of the hollow cylinder and generating a magnetic field in the sample space;
At least one shield coil which is provided outside the main coil and suppresses magnetic field leakage to the outside of the main coil;
A lid provided with a double cylinder and a hole at both ends of each cylinder of the double cylinder to fix the cylinders of the double cylinder to form a sealed space and to communicate the hollow cylinder with the outside A first cryogenic container having a portion;
The double outer cylinder and the inner cylinder are fixed at both ends of the double outer cylinder, the inner cylinder disposed inside the double outer cylinder, the double outer cylinder and the inner cylinder. And a second cryogenic container having a lid portion provided with a hole for forming a sealed space and further communicating the hollow cylinder with the outside,
The main coil is disposed inside the double cylinder of the first cryogenic container, and the first cryocontainer is disposed between the double outer cylinder and the inner cylinder of the second cryogenic container. And
A magnet in which at least one of the double outer cylinders of the second cryogenic container and the lids at both ends are made of a magnetic material.   The magnet according to claim 1, wherein each central axis of the main coil, the shield coil, and the second cryogenic container is on a central axis of the hollow cylinder.   The magnet according to claim 1, wherein the main coil and the shield coil are made of a superconductor.   The magnet according to claim 1, wherein the main coil and the shield coil are connected in series to the same power source.   An NMR analyzer, an MRI apparatus, or an ICR mass spectrometer comprising the magnet according to claim 1.

Images