JP2013098449A - Superconducting magnet device and mri system with the same - Google Patents

Abstract

To provide a superconducting magnet device in which the strength of a radiation shield having a slit is improved.
A superconducting magnet device (2) includes a superconducting coil (3), a radiation shield (6) arranged so as to surround the superconducting coil (3) and having one or more slits (62), a superconducting coil (3), And a vacuum vessel 7 containing the radiation shield 6. The radiation shield 6 is characterized in that a spacer 63 formed of the same material as the radiation shield 6 is fitted into a slit 62 through an insulating layer 64 and fixed.
[Selection] Figure 2

Description

  The present invention relates to a superconducting magnet device having a radiation shield used for suppressing radiant heat to a superconducting coil, and an MRI (Magnetic Resonance Imaging) device including the same.

  A superconducting magnet device using a wire that is in a superconducting state in a cryogenic environment is necessary for an MRI apparatus (also referred to as “magnetic resonance imaging apparatus” and “magnetic resonance imaging apparatus”) and NMR (Nuclear Magnetic Resonance) apparatus. It is used as a magnet that generates a stable magnetic field at a high magnetic field, and development is underway to cope with further higher magnetic fields.

  In such a superconducting magnet device using a superconducting magnet, the superconducting magnet is used in a state of being immersed in liquid helium in order to make the temperature extremely low. Liquid helium is very expensive, and it is necessary to suppress the evaporation amount of liquid helium in order to increase the operating rate of the superconducting magnet device.

FIG. 14 is a cross-sectional view showing the structure of a general MRI apparatus using a conventional superconducting magnet apparatus.
Conventionally, the MRI apparatus 100 is used for diagnosis by superimposing the gradient magnetic field generated from the gradient coil 800 on the static magnetic field generated from the superconducting coil 300 and processing image information obtained through the diagnostic space. .

  A helium vessel 500 for storing liquid helium 400 is provided around the superconducting coil 300 so as to cover the inert liquid helium 400 around the coil. A radiation shield 600 is disposed outside the helium container 500, and a vacuum container 700 for vacuum insulation is disposed outside the helium container 500. On the coil axis side of the vacuum vessel 700, a gradient magnetic field coil 800 used for obtaining positional information when image information is taken out in the diagnostic space 900 is incorporated.

  The radiation shield 600 is disposed between the helium vessel 500 and the vacuum vessel 700. The radiation shield 600 serves to reduce the evaporation amount of the liquid helium 400 in the helium container 500 by radiation when cooled by a refrigerator (not shown).

  In order to give such a function to the radiation shield 600, the radiation shield 600 is generally made of a metal material such as an aluminum alloy or a copper alloy which has high heat transfer performance and is a nonmagnetic material. Such a metal material has a characteristic of high electrical conductivity. Therefore, when the superconducting coil 300 is quenched, a large eddy current and electromagnetic force are generated in the radiation shield 600. Therefore, if the strength of the radiation shield 600 is insufficient, damage may occur.

Even if the radiation shield 600 is not damaged, if the rigidity is insufficient, the radiation shield 600 is deformed, and when the radiation shield 600 comes into contact with the outer vacuum container 700 or the inner helium container 500, the amount of heat penetration is reduced. The amount of evaporation of the liquid helium 400 may increase.
In addition, when the rigidity of the radiation shield 600 is low, it may vibrate due to the influence of the surroundings, and the uniformity and stability of the magnetic field may be reduced.

  As a superconducting magnet device 200 used for such an MRI apparatus 100, for example, a superconducting magnet apparatus for an MRI apparatus (superconducting magnet for an MRI apparatus) disclosed in Patent Document 1 is known. In the superconducting magnet device for the MRI apparatus, even when the superconducting coil is quenched, the radiation shield is not damaged or deformed, and the radiation shield is not vibrated by electromagnetic force.

  A superconducting magnet device for an MRI apparatus intended to eliminate the influence on image information is disposed so as to surround a cylindrical superconducting coil and the superconducting coil, and has a plurality of slits in the axial direction. A radiation shield made of a cylindrical body provided at an appropriate interval, and a vacuum vessel having a superconducting coil and a radiation shield accommodated substantially coaxially and having a normal temperature bore in the center.

In the radiation shield, slits are formed in the axial direction on the coil shaft side, one of the outer peripheral surfaces, or both of the cylindrical body forming the radiation shield body.
The slit restrains the radiation shield from being damaged and deformed by restraining the movement of the radiation shield by electromagnetic force generated by overcurrent when quenched. The slit is fitted with an electrical insulator to prevent the radiation shield from vibrating when quenched. The electrical insulator includes an insulating bolt that closes a screw hole as a slit, an insulating plate that is fitted into the slit, an FRP layer that closes the slit, and the like.

JP 7-22231 A

  However, the superconducting magnet device for MRI apparatus described in Patent Document 1 does not mean that eddy currents disappear even if a slit is provided in the radiation shield, but rather eddy currents flow in a complicated form, There was a problem that the radiation shield vibrates due to electromagnetic force due to the eddy current.

  Moreover, there are cases where the restraint with respect to vibration is insufficient only with the connecting portions existing at both axial ends of each slit of the radiation shield. In such a case, when the superconducting coil is quenched, there is a problem that the radiation shield is damaged or deformed.

  Therefore, the superconducting magnet device for an MRI apparatus described in Patent Document 1 takes measures to increase rigidity by adding an FRP (Fiber Reinforced Plastics) layer. In general, the FRP layer has a lower rigidity than an aluminum alloy, and although a certain degree of improvement in rigidity can be expected, there is a problem that a structurally discontinuous portion is formed.

In addition, during quenching, in addition to thermal stress due to the difference in thermal shrinkage during cooling, the load due to the thermal expansion of the radiation shield is superimposed, so if there is not enough strength, the slit deforms and electrically insulates. There was a problem of damaging things.
In addition, since the FRP layer has no electromagnetic shielding effect, a leakage magnetic field from the gradient magnetic field coil enters from the slit toward the helium vessel, and eddy current is generated in the helium vessel, resulting in an increase in helium consumption. was there.

  Therefore, an object of the present invention is to provide a superconducting magnet device in which the strength of a radiation shield having a slit is improved, and an MRI apparatus including the superconducting magnet device.

In order to solve the above problems, a superconducting magnet device according to the present invention includes a superconducting coil, a radiation shield disposed so as to surround the superconducting coil and having one or more slits formed therein, and the superconducting magnet device. In a superconducting magnet device comprising a conductive coil and a vacuum vessel containing the radiation shield, the radiation shield is formed by inserting a spacer formed of the same material as the radiation shield into the slit via an insulating layer. It is fixed.
Here, the “equivalent material” refers to a material having a value close to the coefficient of thermal expansion (thermal contraction rate) and the longitudinal elastic modulus (Young's modulus). For example, an equivalent material has a difference in thermal expansion coefficient between these two members of 2 × 10 ⁻⁶ / ° C. or less (for example, in the case of an aluminum alloy, 22.5 × 10 ⁻⁶ / ° C. to 24.5 × 10 ⁻⁶ / ° C.), it is preferable to use a material having a difference in longitudinal elastic modulus of 10 GPa or less (for example, 68 to 78 GPa in the case of an aluminum alloy), and a difference in thermal expansion coefficient of 1 × 10 ⁻⁶ / ° C. or less. (For example, in the case of an aluminum alloy, 23 × 10 ⁻⁶ / ° C. to 24 × 10 ⁻⁶ / ° C.) A material having a difference in longitudinal elastic modulus of 5 GPa or less (for example, 70 to 75 GPa in the case of an aluminum alloy) is used. More preferably.

  According to this configuration, the superconducting magnet apparatus quenches the superconducting coil by fitting the spacer formed of the same material as the radiation shield into the slit of the radiation shield through the insulating layer. Even in this case, the radiation shield can be reduced from being damaged or deformed by an excessive eddy current, and can have high rigidity capable of suppressing vibrations generated by electromagnetic force. Thereby, the magnetic field generated by the superconducting coil can be stabilized.

Further, the superconducting magnet device is provided in an MRI apparatus.
Since the superconducting magnet device is provided in the MRI apparatus, the radiation shield can be prevented from vibrating or deforming during quenching.

  The present invention can provide a superconducting magnet device in which the strength of a radiation shield having a slit is improved, and an MRI apparatus including the superconducting magnet device.

It is a perspective view which shows an example of the superconducting magnet apparatus which concerns on embodiment of this invention. It is a schematic perspective view which shows the radiation shield of the superconducting magnet apparatus which concerns on embodiment of this invention. It is a principal part expansion schematic sectional drawing of the radiation shield which shows the installation state of the spacer of the superconducting magnet apparatus which concerns on embodiment of this invention. It is a schematic side view of the radiation shield showing the installation state of the spacer of the superconducting magnet device according to the embodiment of the present invention. It is a schematic longitudinal cross-sectional view of the superconducting magnet apparatus which concerns on embodiment of this invention. It is a schematic longitudinal cross-sectional view which shows the 1st modification of the superconducting magnet apparatus which concerns on embodiment of this invention. It is a figure which shows the 2nd modification of the superconducting magnet apparatus which concerns on embodiment of this invention, and is a schematic side view of a radiation shield. It is a figure which shows the 3rd modification of the superconducting magnet apparatus which concerns on embodiment of this invention, and is a schematic side view of a radiation shield. It is a figure which shows the 4th modification of the superconducting magnet apparatus which concerns on embodiment of this invention, and is a principal part schematic sectional drawing which shows the installation state of the spacer installed in the radiation shield. It is a figure which shows the 5th modification of the superconducting magnet apparatus which concerns on embodiment of this invention, and is a principal part schematic sectional drawing which shows the installation state of the spacer installed in the radiation shield. It is a figure which shows the 5th modification of the superconducting magnet apparatus which concerns on embodiment of this invention, and is a principal part schematic sectional drawing which shows the installation state of the spacer installed in the radiation shield. It is a figure which shows the 6th modification of the superconducting magnet apparatus which concerns on embodiment of this invention, and is a principal part schematic side view which shows the installation state of the spacer installed in the radiation shield. It is a figure which shows the 7th modification of the superconducting magnet apparatus which concerns on embodiment of this invention, and is a principal part schematic sectional drawing which shows the installation state of the spacer installed in the radiation shield. It is a schematic longitudinal cross-sectional view which shows the conventional superconducting magnet apparatus.

Hereinafter, a superconducting magnet apparatus according to an embodiment of the present invention and an MRI apparatus including the same will be described.
As shown in FIG. 1, the superconducting magnet apparatus 2 according to the present invention can be applied to an MRI apparatus 1 and an NMR apparatus (not shown) provided with a radiation shield 6. As an example, the MRI apparatus 1 will be described below. The case where it was used for will be described as an example.

≪Configuration of MRI system≫
As shown in FIG. 1, an MRI apparatus 1 is a so-called magnetic resonance imaging apparatus used when performing medical image diagnosis, and an imaging site of a patient (subject) placed under a predetermined static magnetic field. In addition, an RF pulse and a gradient magnetic field are applied in a predetermined pulse sequence, and echo signals generated thereby are collected and processed to obtain a magnetic resonance image.
The MRI apparatus 1 includes, for example, a substantially cylindrical superconducting magnet apparatus 2, a bed 11 on which a subject is placed, a refrigerator 12 detachably provided on the superconducting magnet apparatus 2, the superconducting magnet apparatus 2, and the freezing And a control device 13 for controlling the machine 12 to constitute a superconducting magnet system.

<Configuration of bed, refrigerator and control device>
The bed 11 is a movable bed that is inserted into the diagnostic space 9 in the substantially cylindrical superconducting magnet device 2.
The refrigerator 12 is a refrigerator for cooling the radiation shield 6. For example, a liquid refrigerant is used by adiabatically expanding helium gas by driving a piston containing a regenerator inside the refrigerator up and down. It consists of a mechanical refrigerator such as a GM refrigerator that can cool to extremely low temperatures.
The control device 13 is a device that analyzes a nuclear magnetic resonance signal from a subject by using the superconducting magnet device 2 and forms a tomographic image, and includes a display device and an input device.

≪Configuration of superconducting magnet device≫
As shown in FIG. 5, the superconducting magnet device 2 includes a plurality of cylindrical superconducting coils 3 whose central axis is a horizontal coil axis, and a refrigerant container 5 that houses the superconducting coils 3 together with a refrigerant 4. A radiation shield 6 provided so as to surround the refrigerant container 5, a vacuum container 7 surrounding the radiation shield 6 and holding the inside in a vacuum state, and a coil axis side of the vacuum container 7 And a gradient magnetic field coil 8 arranged in

  As shown in FIG. 2, the superconducting magnet device 2 has two slits 62 formed in a longitudinal direction in a radiation shield 6 formed of a cylindrical aluminum alloy, and the cylindrical body of the radiation shield 6 in the slit 62. A spacer 63 formed of an aluminum alloy equivalent to 61 is fitted and fixed.

≪Configuration of radiation shield≫
First, the radiation shield 6 of the superconducting magnet device 2 will be described. The radiation shield 6 includes a cylindrical body 61, a slit 62, a spacer 63, and an insulating layer 64 (insulating material), and is formed of, for example, a substantially cylindrical aluminum alloy. In the radiation shield 6, the refrigerant container 5 is housed inside the radiation shield 6, and the outside of the radiation shield 6 is covered with the vacuum container 7. When the radiation shield 6 is cooled by the refrigerator 12, the evaporation amount of the refrigerant 4 in the refrigerant container 5 due to radiation can be reduced.

<Configuration of cylindrical body>
The cylindrical body 61 is, for example, a cylindrical member that is incorporated into or integrally formed with the coil shaft side (inner diameter side) of the radiation shield 6, and is a non-magnetic material having high heat conductivity and electrical conductivity. Made of aluminum alloy or the like. The cylindrical body 61 is fixed by fitting a spacer 63 formed of the same material as the cylindrical body 61 into the slit 62 via an insulating layer 64.

<Slit configuration>
As shown in FIG. 2, the slits 62 are formed on the left and right side walls, for example, in order to reduce the damage or deformation of the radiation shield 6 due to electromagnetic force generated by overcurrent during quenching. The slit 62 is formed, for example, so as to penetrate from the outer peripheral portion of the cylindrical radiation shield 6 to the inside thereof, and is formed in a rectangular shape elongated in the front-rear direction along the coil axis. When the radiation shield 6 has a cylindrical shape, the slit 62 is disposed at the left and right positions that are axially symmetric with respect to the cylindrical body 61, and the symmetry of the overall structure and shape of the radiation shield 6 is maintained, so that the conditions are uniform. This is advantageous against the influence and deformation of eddy currents. Thus, the slit 62 is desirably formed at a symmetrical position of the cylindrical body 61.

  It should be noted that the slit 62 is desirably arranged at a position where the symmetry of the structure is not lost even when the radiation shield 6 is not cylindrical. Moreover, the number of the slits 62 should just be one or more, and the number is not specifically limited.

As shown in FIG. 5, the slit 62 may have the same length L1 as the length d1 of the imaging region 90 in order to suppress the influence on the imaging region 90 that is necessary for use in image diagnosis.
Moreover, if it can be formed longer than that, it is more effective. For example, when the imaging region 90 is a sphere having a diameter of 500 mm, if the length L1 of the slit 62 is the same 500 mm or more, the influence of the eddy current flowing through the radiation shield 6 can be sufficiently suppressed. .

<Spacer configuration>
As shown in FIG. 2, the spacer 63 is an elongated member fitted in the slit 62, and an insulating layer 64 (insulating material) is formed on each of the upper, lower, left, and right surfaces. By fitting the spacer 63 having a fitting surface formed of the electrically insulating insulating layer 64 into the slit 62 in this way, the spacer 63 suppresses the radiation shield 6 from vibrating during quenching. Contribute. The spacer 63 is made of the same material as the cylindrical body 61.

  The equivalent material refers to a material having a similar coefficient of thermal expansion (thermal contraction rate) and longitudinal elastic modulus. For example, in the case of an aluminum alloy, a pure aluminum-based aluminum alloy having a JIS symbol of A1050, and a JIS symbol of A5083. Al—Mg aluminum alloy (alloy for welding structure), Al—Cu aluminum alloy (super duralumin) with JIS symbol A2024, and the like.

  For example, both the radiation shield 6 and the spacer 63 may be an aluminum alloy having a JIS symbol of A1050. When the radiation shield 6 is made with a welded structure, the radiation shield 6 uses an aluminum alloy with a JIS symbol A5083 suitable for welding, and the spacer 63 uses an aluminum alloy with a JIS symbol A1050 suitable for alumite treatment. You may make the combination.

<Configuration of insulating layer>
The insulating layer 64 (insulating material) is an insulating member for insulating the slit 62 and the spacer 63, and is interposed between the inner wall surface of the slit 62 and the outer fitting surface of the spacer 63. 62 and the spacer 63 are fixed with no gap in a state of being insulated from each other.

For example, when the spacer 63 is made of an aluminum alloy, the spacer 63 is anodized and an alumina oxide film (anodized film) is used for the insulating layer 64. Since the alumite treatment can accurately control the film thickness by optimizing the conditions, the film thickness of the insulating layer 64 is set according to the required performance. When the thickness of the insulating layer 64 is increased, electrical insulation is improved and reliability is easily ensured.
Although the method of forming an alumina oxide film on the insulating layer 64 by alumite treatment has been described, the insulating layer 64 may be formed by using other methods of forming an aluminum oxide film.
The insulating layer 64 may be formed using a plating method or a method of forming a resin insulating film.

  If the insulating layer 64 is formed to have a film thickness of about several to 10 μm, it usually has a sufficient electric resistance and a strength that does not peel off. Note that the insulating layer 64 may be thinner than about several to 10 μm as long as sufficient electric resistance is obtained. In addition, the insulating layer 64 may have a film thickness of about several to 10 μm or more when eddy current is large and higher electrical resistance is required.

  When the spacer 63 with the insulating layer 64 made of such a film is inserted into the slit 62, it is necessary to prevent the insulating layer 64 from being damaged or peeled off. As the method, for example, there is a method of cooling the spacer 63 and fitting it by cold fitting. By adopting such an assembling method, the necessary coating state of the insulating layer 64 can be maintained.

As another assembling method, the spacer 63 is caulked to the slit 62 by pressing when forming the radiation shield 6 with a slight gap between the radiation shield 6 and the spacer 63 before assembling. Thus, a method of assembling the spacer 63 in a state in which the spacer 63 is in strong contact with the radiation shield 6 may be used.
In addition, any other assembly method may be used as long as the film of the insulating layer 64 does not damage or peel off and functions as the insulating layer 64.

  As the aluminum alloy used in these structures, for example, a pure aluminum plate having a JIS symbol of A1050 or an aluminum alloy plate having a JIS symbol of A5083 can be used. Since such an aluminum alloy is non-magnetic, it does not affect the magnetic field generated by the superconducting magnet, and since it has a high thermal conductivity, it can be efficiently cooled by the refrigerator 12, so that the radiation shield can be used. Suitable as material 6

≪Configuration of superconducting coil≫
The superconducting coil 3 is formed in a cylindrical shape around the coil axis, and is installed in the refrigerant container 5. The superconducting coil 3 is formed in a rectangular shape such as a square or a rectangle in the longitudinal sectional shape on the surface including the coil axis.

<< Configuration of refrigerant and refrigerant container >>
The refrigerant 4 is made of an inert material such as liquid helium, for example, and is filled in the outer peripheral portion of the superconducting coil 3 in the refrigerant container 5.
The refrigerant container 5 is a storage container that stores the superconducting coil 3 and the refrigerant 4 in a state where the periphery of the superconducting coil 3 is covered with an inert refrigerant 4 (liquid helium), and a hollow portion that forms the storage container It consists of the substantially cylindrical member which has. The refrigerant container 5 is covered with a radiation shield 6.

≪Configuration of vacuum vessel and gradient magnetic field coil≫
The vacuum container 7 is an airtight container that is disposed outside the radiation shield 6 and covers the radiation shield 6 in a vacuum insulated state.
The gradient magnetic field coil 8 is a coil used for obtaining positional information when taking out image information in the diagnostic space 9, and is incorporated on the coil axis side of the vacuum vessel 7.

≪Action≫
Next, the operation of the superconducting magnet device 2 according to the embodiment of the present invention will be described with reference mainly to FIGS.

  In the superconducting magnet device 2, the cylindrical body 61 of the radiation shield 6 is fitted with a spacer 63 having an insulating layer 64 attached to the outer periphery thereof in a slit 62 formed at a symmetrical position along the coil axis. It is fixed. For this reason, the slit 62 drilled in the radiation shield 6 is closed with the spacer 63 fitted therein while being insulated by the insulating layer 64. As a result, it is possible to suppress the radiation shield 6 from vibrating due to the electromagnetic force generated by the eddy current during quenching.

  The slit 62 and the insulating layer 64 are arranged on the radiation shield 6 symmetrically with respect to the coil axis line, and are arranged so as to match the position of the imaging region 90, so that the radiation shield 6 receives electromagnetic force. In this case, since it can be deformed in an axially symmetric and well-balanced state, a structure in which distortion or the like hardly occurs is obtained.

  Since the radiation shield 6 and the spacer 63 are integrally fixed, even if an eddy current flows through the radiation shield 6 due to the application of the gradient magnetic field coil 8 and electromagnetic force acts to obtain image information, the spacer 63. Are closely fixed in the slit 62 of the radiation shield 6 with the insulating layer 64 interposed therebetween. For this reason, the vibration of the cylindrical body 61 of the radiation shield 6 is suppressed, the vibration of the magnetic field due to the eddy current is also suppressed, and the noise to the image due to the vibration can be cut off.

[First Modification]
As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to the structure described in the said embodiment, Including suitably combining thru | or selecting the structure described in embodiment, The configuration can be changed as appropriate without departing from the spirit of the invention. In addition, the already demonstrated structure attaches | subjects the same code | symbol and abbreviate | omits the description.
FIG. 6 is a schematic longitudinal sectional view showing a first modification of the superconducting magnet device according to the embodiment of the present invention.

In the above-described embodiment, as shown in FIG. 5, the slit 62 is formed in the facing portion of the cylindrical body 61 of the radiation shield 6 facing the imaging region 90 in accordance with the imaging region 90, and the spacer 63 is provided in the slit 62. However, the present invention is not limited to this.
As shown in FIG. 6, in the radiation shield 6A, a slit 62A1 may be provided on the inner wall surface 6Aa on the coil axis side of the cylindrical body 61A, and slits 62A3 and 62A3 may be provided on the left and right end faces 6Ab and 6Ac.

  As shown in FIG. 6, in order to reduce the electromagnetic force at the time of quenching, the effect can be obtained by forming the slits 62A1, 62A2, 62A3 in the range covering the width L2 and the height H1 of the superconducting coil 3. be able to.

For example, when the superconducting coil 3 has a cylindrical shape with an inner diameter of 900 mm, an outer diameter of 1000 mm, and a width of 100 mm, a slit having a width of 100 mm or more on the inner diameter side in the vicinity of the radiation shield 6A adjacent to the superconducting coil 3. A sufficient effect can be obtained by forming 62A1 and forming slits 62A2 and 62A3 of 100 mm or more in the range covering the height H1 of the superconducting coil 3 on the end faces 6Ab and 6Ac on the side surfaces of the superconducting coil 3. .
In addition, although each slit 62A1, 62A2, 62A2 has an effect even if it is not connected, a higher effect is acquired when it is mutually connected.

  In this way, the insulating layers 64A1, 64A2, and 64A3 are interposed, and the radiation shield 6A and the spacers 63A1, 63A2, and 63A3 are made of the same material and are fitted, so that they are electrically discontinuous. A structurally uniform structure can be obtained.

  In addition, even if an eddy current flows through the radiation shield 6A at the time of quenching and the temperature rises, the insulating layers 64A1, 64A2, and 64A3 made of alumina have significantly higher thermal conductivity than FRP or the like, and surrounding members And the spacers 63A1, 63A2, 63A3 and other portions have no thermal strain difference, and therefore there is no possibility that excessive thermal stress is locally generated.

  Further, the slits 62A1, 62A2, and 62A3 are filled with the spacers 63A1, 63A2, and 63A3, which are metal members, and the insulating layers 64A1, 64A2, and 64A3. Since the heat generation due to the eddy current in the refrigerant container 5 can be suppressed, the consumption amount of the refrigerant 4 (liquid helium) can be reduced.

[Second Modification]
FIG. 7 is a diagram showing a second modification of the superconducting magnet device according to the embodiment of the present invention, and is a schematic side view of the radiation shield.

  In the said embodiment, the spacer 63 was demonstrated as 1 component (refer FIGS. 2-4). However, the spacer 63B is not limited to one component. For example, as shown in FIG. 7, the spacer 63B is divided into a plurality of parts and arranged in the cylindrical body 61B of the radiation shield 6B, and separated into the slit 62B. It is good also as a structure to arrange. By doing so, the effect of shielding the leakage magnetic field of the gradient magnetic field coil 8 (see FIG. 5) is reduced, but the manufacture and assembly of the parts are facilitated, and the cost can be reduced.

  Although FIG. 7 shows the case where there are two spacers 63B, the number of spacers 63B may be larger. The location where the spacer 63B is inserted into the slit 62B is not only the longitudinal front and rear end portions in the slit 62, but also the central position and other positions. The rigidity of the radiation shield 6B can be improved. Also in this case, the spacer 63B is fixed by welding means or an adhesive in the slit 62B with the insulating layer 64B interposed.

[Third Modification]
FIG. 8 is a view showing a third modification of the superconducting magnet device according to the embodiment of the present invention, and is a schematic side view of the radiation shield.

  Further, as shown in FIG. 8, the spacer 63C is attached to the outer peripheral surface of the spacers 63C1 and 63C2 divided in two so as to surround the outer peripheral portion with the partition-like insulating layer 64C2 interposed therebetween. The outer peripheral insulating layer 64C1 may be integrated, and the outer peripheral insulating layer 64C1 may be fixed in the slit 62C by welding, an adhesive, or the like.

  When the plurality of spacers 63C1 and 63C2 are integrated into one slit 62C and fixed to one slit 62C by such an assembling method, the spacer 63C and the insulating layer 64C are in a stage before the spacer 63C is fixed to the slit 62C. Insulating resistance of the insulating layer 64C can be confirmed without any damage to the partition-like insulating layer 62C2 when the spacer 63C is subsequently fixed in the slit 62C. Can be maintained.

  In FIG. 8, the example in which the spacer 63C is divided into two spacers 63C1 and 63C2 in the short direction has been described. However, the spacer 63C may be divided into two in the longitudinal direction, or may be divided into two or more. When it is difficult to manufacture by fitting due to the limitation of the dimension, it is also possible to manufacture with such a structure. In this case, it is preferable that the number of divisions is as small as possible and the division is performed equally.

[Fourth Modification]
FIG. 9 is a diagram showing a fourth modification of the superconducting magnet device according to the embodiment of the present invention, and is a schematic cross-sectional view of the main part showing the installation state of the spacers installed on the radiation shield.

Further, as shown in FIG. 9, the insulating layer 64D fixed to the inner surface of the slit 62D of the radiation shield 6D may be fixed to the inner surface 62Da of the slit 62D in advance, and then the spacer 63D may be fixed to the insulating layer 64D. Even if it does in this way, the effect similar to the said embodiment and the 1st-3rd modification is acquired.
If the insulating layer 64D is formed also on the spacer 63D side, higher insulating performance can be obtained.

[Fifth Modification]
FIG. 10 is a view showing a fifth modification of the superconducting magnet device according to the embodiment of the present invention, and is a schematic cross-sectional view of the main part showing the installation state of the spacers installed on the radiation shield.

In the above-described embodiment, it has been described that the radiation shield 6 and the spacer 63 illustrated in FIGS. 2 to 5 are formed of an aluminum alloy. However, the present invention is not limited to this.
For example, in the superconducting magnet device 2E, a slit 62E is formed in a radiation shield 6E formed of a cylindrical copper alloy, and a spacer 63E formed of a copper alloy of the same material as the cylindrical body 61E is fitted into the slit 62E and fixed. It may be of the structure. In this case, the slit 62E of the radiation shield 6 and the spacer 63E are fixed in an insulated state with the insulating layer 64E interposed therebetween.

Here, when the spacer 63E is made of a copper alloy, the insulating layer 64E may be an insulating film formed by plating an insulating material with respect to the spacer 63E.
When inserting the spacer 63E having a film formed by such plating into the slit 62E, an assembly method by cold fitting or caulking can be used as in the above embodiment. Also, other methods may be used as long as the film functions as the insulating layer 64E without being damaged or peeled off during assembly.

Further, the insulating layer 64E may be formed by depositing an insulating film formed in a film shape with an insulating resin on the surface of the spacer 63E. In this case, the resin may be an epoxy or an enamel used for a conductive film as long as it has insulating properties, necessary electrical resistance, adhesive strength, and low-temperature strength.
Further, the insulating layer 64E may be formed by other methods such as thermal spraying. Also in this case, it is necessary to assemble so that the insulating layer 64E is not damaged or peeled off during assembly.

  When the radiation shield 6E and the spacer 63E are made of a copper alloy, they are non-magnetic, so that they do not affect the magnetic field generated by the superconducting magnet and have high thermal conductivity. It can be cooled efficiently. Even when the radiation shield 6E and the spacer 63E are made of a copper alloy, a material (equivalent material) having a close thermal expansion coefficient and a longitudinal elastic modulus is used.

For example, when the radiation shield 6E and the spacer 63E are formed of copper alloys, a combination of commonly used copper alloys may be used, or both may be tough pitch copper, or the radiation shield 6E may be made of tough pitch copper. It is also possible to use a combination in which oxygen-free copper is used for the spacer 63E.
Even if it is such a structure, the effect similar to the said embodiment is acquired.

[Sixth Modification]
FIG. 11 is a diagram showing a sixth modification of the superconducting magnet device according to the embodiment of the present invention, and is a schematic cross-sectional view of the main part showing the installation state of the spacers installed on the radiation shield. FIG. 12 is a diagram showing a sixth modification of the superconducting magnet device according to the embodiment of the present invention, and is a schematic side view of the main part showing the installation state of the spacers installed on the radiation shield.

  The insulating layer 64F used in the above embodiment may be formed of an insulating resin as shown in FIG. In this case, the radiation shield 6F and the spacer 63F are made of an equivalent material, and a resin formed by appropriately managing the thickness between the two is used as the insulating layer 64F.

  As shown in FIGS. 11 and 12, the radiation shield 6F and the spacer 63F are an insulating first resin member 64F1 such as FRP for thickness management between the slit 62F and the spacer 63F, and the spacer 63F and the slit 62F. In a state where the gap with the inner surface of the glass is controlled, both are bonded with resin. In this case, the first resin members 64F1 are arranged at equal intervals on the front and rear sides and the upper and lower sides of the spacer 63F. At this time, the first resin member 64F1 may be provided one by one in the front and rear, upper and lower four directions, or more may be provided as appropriate.

  When the thickness of the resin forming the second insulating layer 64F2 is too thin, there is a possibility that a conductive portion is partially formed. Therefore, it is desirable that the thickness be about 0.01 to 0.1 mm. However, if the thickness of the resin can be accurately controlled and sufficient insulation performance can be ensured, the thickness may be made thinner than this.

  Since the resin insulating layer 64F has such a structure, the radiation shield 6F and the spacer 63F can be bonded together with the resin layer, and the function as the insulating layer 64F can be secured, so that an insulation process before assembly is unnecessary. And can be formed efficiently.

  The insulating layer 64F can be further insulated by previously forming the insulating layer 64F1 on the outer periphery of the spacer 63F and then adhering the insulating layer 64F2 spacer 63F made of a resin layer to the inner surface of the slit 62F. Since the property can be increased, it may be used in combination.

In the sixth modification, the material of the radiation shield 6F and the spacer 63F may be either a combination of aluminum alloys or a combination of copper alloys.
In addition, any material that is non-magnetic and has high thermal conductivity can be used.
Even if it is such a structure, the effect similar to above-mentioned embodiment is acquired.

[Seventh modification]
FIG. 13 is a view showing a seventh modification of the superconducting magnet device according to the embodiment of the present invention, and is a schematic cross-sectional view of the relevant part showing the installation state of the spacers installed on the radiation shield.
Further, as shown in FIG. 13, the spacer 63G provided in the slit 62G of the radiation shield 6G contacts the inner surface facing the slit 62G, and the insulating layer 64G is interposed with the insulating layer 64G formed therebetween. A structure may also be used.

  In this case, when an aluminum alloy is used for the radiation shield 6G, an oxide film of alumina is formed by anodizing the slit 62G, and then the entire surface of the radiation shield 6G is caulked so that the opposing surface of the slit 62G is formed. Contact to create a mechanically continuous structure.

In addition, other film forming methods may be used as long as an oxide film of alumina can be formed in the slit 62G.
Further, after plating or a resin film is formed on the slit 62G, the opposing inner surfaces of the slit 62G may be brought into contact with each other. When these methods are adopted, materials other than aluminum alloy may be used.

  Also, by pouring resin into the slit 62G and bonding the opposing inner surface of the slit 62G, the resin is used as the insulating layer 64G, and the opposing surface in the slit 62G is filled with the resin so as to be continuous. Is the same.

When the spacer 63G is eliminated and the insulating layer 64G is used as the spacer 63G in this manner, the manufacturability may be reduced, but the spacer 63G can be eliminated, so that the structure is simpler. Can do.
Even if it is such a structure, the effect similar to above-mentioned embodiment is acquired.

  In the above-described embodiment, an example of a device having a superconducting coil that performs medical image diagnosis is shown. However, in a device having a superconducting coil and a radiation shield similar to these devices, a similar radiation shield is provided. By using it, the same effect can be obtained.

DESCRIPTION OF SYMBOLS 1 MRI apparatus 2,2A-2G Superconducting magnet apparatus 3 Superconducting coil 6,6A-6G Radiation shield 7 Vacuum container 62,62A1,62A2,62A3,62B, 62C-62G Slit 63,63A1,63A2,63A3,63B- 63G spacer 64, 64A1, 64A2, 64A3, 64B, 64C1, 64C2, 64B to 64G Insulating layer

Claims (7)

A superconducting coil;
A radiation shield disposed so as to surround the superconducting coil and having one or more slits formed therein;
In a superconducting magnet device comprising the superconducting coil and a vacuum vessel containing the radiation shield,
The superconducting magnet device is characterized in that the radiation shield has a spacer formed of the same material as that of the radiation shield in the slit, and is fitted and fixed via an insulating layer. A superconducting coil;
A radiation shield disposed so as to surround the superconducting coil and having one or more slits formed therein;
In a superconducting magnet device comprising the superconducting coil and a vacuum vessel containing the radiation shield,
The superconducting magnet device according to claim 1, wherein the opposing surfaces of the slit of the radiation shield are in contact with each other through an insulating layer. The radiation shield and the spacer are made of an aluminum alloy,
The superconducting magnet device according to claim 1, wherein the insulating layer is made of an alumina film.   The superconducting magnet device according to claim 1, wherein the insulating layer is made of a resin.   The superconducting magnet device according to claim 1, wherein the insulating layer is formed by plating.   The superconducting magnet device according to any one of claims 1 to 5, wherein the insulating layer is divided into a plurality of pieces in the slit. The superconducting magnet device according to any one of claims 1 to 6,
The superconducting magnet device is provided in an MRI apparatus.

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