JP2008028146A - Superconducting magnet heat shield, superconducting magnet apparatus, and magnetic resonance imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin and wide superconducting magnet thermal shield hardly causing the temperature difference. <P>SOLUTION: The superconducting magnet thermal shield 11 provided between a cryogenic container 9 for housing a superconducting coil 6 with a coolant 8 and a vacuum vessel 15 held vacuum inside for housing the cryogenic container 9 covers the container 9, and is cooled with a cooling source 16. It has opposed plates 12, 13 apart from each other and a coolant gas 14 inserted between the opposed plates 12, 13. The top of the coolant gas 14 is cooled with a cooling source 16 to cause such natural convection of the gas 14 as rising after lowering along the plates 12, 13. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a superconducting magnet device and a magnetic resonance imaging (hereinafter referred to as MRI) device using the same, and more particularly to a heat shield for a superconducting magnet used in the superconducting magnet device.

  The MRI system measures the electromagnetic waves emitted by hydrogen nuclear spins due to the nuclear magnetic resonance (hereinafter referred to as NMR) phenomenon, and uses the electromagnetic waves as signals to perform arithmetic processing to obtain a tomographic image of the subject based on the hydrogen nuclear density. It is to become. In the measurement of electromagnetic waves emitted by hydrogen nuclear spins, it is necessary to generate a high-intensity uniform magnetic field region as a measurement region.

  This is because the intensity of the electromagnetic field generated by the electromagnetic waves emitted by the hydrogen nuclear spins is proportional to the intensity of the static magnetic field in the uniform magnetic field region, so that it is necessary to increase the intensity of the static magnetic field in order to improve the resolution of the tomographic image. Therefore, a superconducting magnet device is used to generate a high-intensity static magnetic field.

  In the superconducting magnet device, since the temperature at which the superconducting coil is in the superconducting state is extremely low temperature, it is cooled using liquid helium (He) and insulated from room temperature in order to keep it at a very low temperature. For this reason, the superconducting coil is housed in a cryogenic container together with liquid helium, and the cryogenic container is installed in the vacuum container and insulated by vacuum while keeping the temperature of the superconducting coil and the cryogenic container at a very low temperature. In addition, since it is necessary to suppress the heat generated by heat transfer to the cryogenic container and the intrusion heat due to radiation as much as possible, the heat shield that keeps the surface of the cryogenic container at a medium to low temperature of several tens of K does not contact the cryogenic container. So that it covers.

  In order to keep the heat shield itself at a low temperature, the heat shield is vacuum insulated from the vacuum vessel, and is supported by a load support body that suppresses heat penetration due to heat transfer as much as possible. The heat shield is shielded by absorbing heat from room temperature as a thermal anchor of a load support that supports the cryogenic container on the vacuum container.

As the heat shield, a method of cooling the entire member of the heat shield by causing a cooling medium to flow in and out has been proposed (for example, see Patent Document 1). In addition, a method has been proposed in which a cooling medium is partially stored and the entire member is cooled by heat transfer (for example, see Patent Document 2). A method of cooling by a natural circulation method with reduced passage resistance and improved cooling efficiency has been proposed (see, for example, Patent Document 3). In Patent Document 3, it is proposed to prevent the generation of eddy current using a member having a large electric resistance. Furthermore, a method of thermally linking a heat shield and its cooling source with a heat conductor such as a copper braided wire has been proposed (for example, see Patent Document 4).
JP-A-6-61044 JP-A-6-69553 JP 200487776 A JP 2005-322756 A

  In the MRI apparatus, the diameter of the superconducting coil tends to be increased in order to increase the diameter so that a space for entering a subject can be taken as wide as possible inside the apparatus. On the other hand, in order to reduce the cost of the superconducting magnet device as much as possible, it is necessary to reduce the size of the device. As a result, the heat shield covering the cryogenic container is required to have a thin structure.

  In addition, when the heat shield is widened due to the enlargement of the superconducting coil, the heat load absorbed by the heat shield is absorbed by the refrigerator and exhausted, so the heat resistance at a location away from the refrigerator increases the thermal resistance, There was a problem that a temperature difference occurred in the heat shield itself, which increased the intrusion heat into the cryogenic container. In order to reduce the thermal resistance, it is not allowed from the above requirement to increase the thickness of the heat shield. In addition, it was thought that when a material with low thermal resistance was used to reduce thermal resistance, eddy currents were generated because materials with low thermal resistance generally had low electrical resistance, and vibrations due to eddy currents were generated. . As described above, a thin and wide heat shield corresponding to the increase in size of the superconducting coil has not been proposed.

  In addition, when the heat shield and the cooling source of the refrigerator are connected by a heat conductor such as a copper braided wire, it is considered that a temperature difference is likely to occur between the heat shield and the cooling source.

  An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a heat shield for a superconducting magnet that is thin and wide and hardly causes a temperature difference. Further, the superconducting magnet using the heat shield for a superconducting magnet It is to provide an apparatus and an MRI apparatus.

  In order to achieve the above object, a superconducting magnet heat shield, a superconducting electromagnet apparatus and an MRI apparatus according to the present invention comprise a plate facing away from each other and a refrigerant gas inserted between the plates facing each other in the superconducting magnet heat shield. And cooling the upper part of the refrigerant gas with a cooling source to cause natural convection in which the refrigerant gas rises after descending along the plate.

  According to such a heat shield for a superconducting magnet, a superconducting magnet device, and an MRI apparatus, it is possible to provide a heat shield for a superconducting magnet that is thin, wide, and hardly causes a temperature difference.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

(First embodiment)
As shown in FIG. 1, an MRI (magnetic resonance imaging) apparatus 1 according to the first embodiment includes a substantially cylindrical superconducting magnet apparatus 2 and a cylinder of the superconducting magnet apparatus 2 though a refrigerator 4 protrudes. And a control device 5 that analyzes a nuclear magnetic resonance signal from the subject using the superconducting magnet device 2 to form a tomographic image.

  As shown in FIG. 2, the superconducting magnet device 2 according to the first embodiment generates a magnetic field by passing a permanent current, and an annular superconducting coil 6 whose central axis is in the horizontal direction. 8 includes a cryogenic container 9 that is housed together, a heat shield 11 provided so as to surround the cryogenic container 9, and a vacuum container 15 that surrounds the heat shield 11 and holds the inside in a vacuum. ing. The refrigerant liquid 8 directly cools the superconducting coil 6, and specifically, liquid helium (He) is used. When the refrigerant liquid 8 is heated by the superconducting coil 6, it is cooled to a very low temperature by the second stage 17 of the refrigerator 4. The cryogenic container 9 is formed in an annular shape so as to be accommodated along the annular superconducting coil 6 and has a volume as small as possible. Similarly, the heat shield 11 is formed in an annular shape so as to cover along the annular cryogenic container 9 and has a surface area as small as possible.

  Even if the superconducting magnet device 2 is placed in a room temperature room, the vacuum vessel 15 is in a vacuum, so that the heat in the room is not transmitted to the cryogenic vessel 9 by conduction or natural convection. Moreover, since the heat shield 11 is cooled by the first stage 16 of the refrigerator 4, it absorbs radiant heat from the vacuum vessel 15 and releases it to the first stage 16 of the refrigerator 4. Will not be heated. The heat shield 11 may be set to a medium low temperature between the extremely low temperature of the refrigerant liquid 8 and the room temperature. The superconducting coil 6 and the cryogenic container 9 can be stably set to the cryogenic temperature of the refrigerant liquid 8.

  The superconducting coil 6 is supported by the cryogenic container 9 by the electromagnet support structure 7, and the heat shield 11 is also supported by the cryogenic container 9. The cryogenic container 9 having a large total load is supported by a vacuum container 15 serving as a base by a load support 22. The load support 22 is devised to reduce heat penetration. The refrigerator 4 is a refrigerator such as a two-stage GM refrigerator that has a second stage that cools to a very low temperature and a first stage that cools to a medium to low temperature. The refrigerator 4 is installed in the superconducting magnet device so as to be removable during maintenance. The heat shield 11 is cooled by the first stage 16, and the helium gas evaporated in the cryogenic container 9 is cooled and reliquefied in the second stage 17 to which the condenser is attached.

  An RF coil 19 and a gradient magnetic field coil 18 are provided on the inner peripheral surface of the vacuum vessel 15, respectively. The MRI apparatus 1 measures a nuclear magnetic resonance signal emitted from a hydrogen nuclear spin due to an NMR phenomenon, and performs an arithmetic process on the nuclear magnetic resonance signal to form a tomographic image of the inside of a subject based on the hydrogen nuclear density. At that time, a static magnetic field having a high intensity of 0.2 T or more and high static magnetic field uniformity is generated in the imaging space in which the subject enters. The pair of gradient magnetic field coils 18 in the upper and lower sides of the imaging space applies a gradient magnetic field in which the magnetic field is spatially changed to the imaging space for the purpose of obtaining positional information in the imaging space. Further, a pair of upper and lower RF coils 19 in the imaging space apply electromagnetic waves having a resonance frequency for causing an NMR phenomenon to the imaging space. Using these, the nuclear magnetic resonance signal emitted by the hydrogen nuclear spin is measured for each micro area in the imaging space, and the tomographic image of the inside of the subject is formed by the hydrogen nuclear density by processing the nuclear magnetic resonance signal. Can do.

  Between the superconducting coil 6 and the subject 21, the RF coil 19, the gradient magnetic field coil 18, the vacuum vessel 15, the heat shield 11, the cryogenic vessel 9, and the electromagnet support structure 7 are arranged in a narrow space. It can be seen that in order to widen the imaging space of the subject 21, it is necessary to make the heat shield 11 as thin as possible. The temperature of the heat shield 11 is increased by disposing the refrigerator 4 at the upper portion so that the temperature of the upper portion of the heat shield 11 is lowered and the refrigerant gas 14 at the upper portion is cooled to cool the inside of the double wall. The refrigerant gas 14 sinks downward. On the other hand, due to the radiant heat from the vacuum vessel 15 and the thermal load from the load support 22, the temperature of the lower part of the heat shield 11 is increased, and the lower refrigerant gas 14, whose density has been reduced, is moved upward by buoyancy. To rise. Thereby, the natural convection of the refrigerant gas 14 is generated in the entire double wall, and the heat of the plates 12 and 13 is efficiently exchanged by the refrigerant gas 14 by the natural convection.

  The heat shield 11 has a double wall structure composed of plates 12 and 13 that are opposed to each other at a distance, and a refrigerant gas 14 that is inserted between these plates 12 and 13, and the upper portion of the refrigerant gas 14 serves as a cooling source. Cooling at one stage 16 causes natural convection such that the refrigerant gas 14 rises after descending along the plates 12 and 13. By generating this natural convection, the temperature difference generated in the heat shield 11 is reduced. And the heat shield 11 is made into the double wall structure, and the total thickness of the heat shield 11 is made thin.

  As shown in FIG. 3, the double wall structure of the heat shield 11 can be abstracted in principle. In the heat shield 11, the upper refrigerant gas 14 is cooled and lowered by the first stage 16 of the cooling source, and the lower refrigerant gas 14 is warmed and raised by the load support 22. By these things, the natural convection 23 of the refrigerant gas 14 arises inside a double wall. This natural convection reduces the temperature of the heat shield 11 over a wide range and improves the temperature uniformity of the heat shield 11.

  The refrigerant gas 14 may be sealed in a double wall structure composed of the plates 12 and 13. Heat is input to the heat shield 11 by radiant heat from the vacuum vessel 15 and heat transfer from the load support 22. The first stage 16 of the refrigerator 4 is installed to take this heat. However, when the distance from the first stage 16 is increased, a temperature distribution is generated in the heat shield 11 due to heat generated from the radiation or the like. For this reason, a similar temperature distribution is generated in the refrigerant gas 14 sealed inside. This temperature distribution causes a difference in specific gravity of the refrigerant gas 14. Buoyancy occurs in the refrigerant gas 14 having a high temperature, and the refrigerant gas 14 having a low temperature tends to sink. By these movements, natural convection 23 of the refrigerant gas 14 is generated in the double wall structure, and the natural convection 23 removes heat from the plate surface on the high temperature side and transfers it to the plate surface on the low temperature side. The temperature difference between the wall plates 12 and 13 and the refrigerant gas 14 is difficult to occur. Since the main heat transfer is natural convection, the conduction of heat by the plates 12 and 13 may be auxiliary. For example, a stainless steel member that can form a strong structure even though it is thin, although its thermal conductivity is not high, It can be used for the heat shield 11.

  Since heat transfer in the heat shield 11 is performed by the refrigerant gas 14, the plates 12 and 13 of the heat shield 11 need only have a structure that can withstand the pressure of the refrigerant gas 14. Even if the thicknesses of 12 and 13 are added, the thickness can be made thinner than that in the case of a heat shield plate having a conventional single wall structure that can transport heat by the same material as the plates 12 and 13. Thus, since the amount of heat transported by the natural convection 23 is large, the temperature in the heat shield 11 can be made uniform over a wide range without increasing the thickness of the heat shield 11. By using this heat shield, it is possible to provide a superconducting magnet device that does not require the supply of the refrigerant liquid 8 for a long period of time.

The amount of heat transferred by the flat plates 12 and 13 standing vertically by the natural convection 23 is expressed by the following equation.
Q = h × A × ΔT
Here, Q is the amount of heat per hour (W), h is the heat transfer coefficient (W / m ² K) by natural convection, A is the area (m ² ) of the plates 12 and 13, and ΔT is the temperature difference ( K).

  Of these, the heat transfer coefficient h by natural convection is inversely proportional to the representative length L of the heat shield 11, the so-called ¼ power of the heat transfer distance. Since the heat transfer rate by heat conduction is inversely proportional to the heat transfer distance, in the heat shield 11 having a long representative length L, natural convection is more likely to transfer heat than heat conduction, and the temperature distribution is distributed to the heat shield 11 by natural convection. It turns out that it becomes difficult to occur. If the heat transfer coefficient is increased by heat conduction, it is necessary to increase the cross-sectional area, and the thickness of the heat shield with a long representative length L is increased. On the contrary, as the heat shield 11 by natural convection increases in size and area, the ability to transfer heat can be relatively increased as compared with the case of heat conduction without increasing the thickness.

  As shown in FIGS. 4A and 4B, opposing plates 12 and 13 as shown in FIG. Although the plates 12 and 13 are hollow and have a thick cylindrical shape, the plates 12 and 13 corresponding to the inner peripheral surfaces of the cylinders face each other, and the refrigerant gas 14 has a gap between the inner peripheral surfaces. Natural convection 23 that circulates through Further, the plate 12 and the plate 13 corresponding to the respective outer peripheral surfaces of the cylindrical shape are opposed to each other, and the natural convection 23 that circulates between the outer peripheral surfaces of the refrigerant gas 14 occurs. The plate 12 and the plate 13 corresponding to the respective end surfaces of the cylindrical shape face each other, and the natural convection 23 that circulates between the end surfaces occurs in the refrigerant gas 14.

  For the problem of preventing eddy currents, the main heat transfer is natural convection. Therefore, by reducing the cross-sectional area of the plates 12 and 13, the electrical resistance can be increased without impairing the heat transfer. Can be solved.

  Since heat transfer in the heat shield 11 is performed by the refrigerant gas 14, the plates 12 and 13 of the heat shield 11 need only have a structure that can withstand the pressure of the refrigerant gas 14, and are the same as the plates 12 and 13 in a single wall structure. The thickness of the conventional single-walled heat shield plate that can transport the same amount of heat can be made thinner and the electrical resistance can be increased, thereby preventing the generation of eddy currents.

(Second Embodiment)
As shown in FIG. 5, in the MRI apparatus according to the second embodiment, the space sandwiched between the plates 12 and 13 of the heat shield 11 is connected to the inside of the cryogenic container 9 by a connecting pipe 25. However, this is different from the MRI apparatus of the first embodiment. The connecting pipe 25 is provided at the upper part of the cryogenic container 9. In the upper part of the cryogenic container 9, helium gas of the refrigerant gas 24 which is vaporized when the liquid helium as the refrigerant liquid 8 cools the superconducting coil 6 is accumulated. Therefore, the refrigerant gas 24 is supplied to the heat shield 11 through the connecting pipe 25 as the refrigerant gas 14 of the heat shield 11. Thus, since the refrigerant gas 24 obtained by vaporizing the refrigerant liquid 8 in the cryogenic container 9 is used for the refrigerant gas 14 of the heat shield 11, it is necessary to supply the refrigerant gas 14 to the heat shield 11 separately. The structure can be simplified.

(Third embodiment)
As shown in FIG. 6, when the double wall structure of the heat shield 11 is abstracted in principle in correspondence with FIG. 3, the heat shield 11 of the third embodiment is divided into a plurality of plates 12 and 13. The point that the heat shield 11 is composed of a plurality of divided shields 27 is different from the heat shield 11 of the first embodiment. Each of the plates 12 and 13 includes a plurality of divided nonmagnetic conductive plates and a connection band 26 provided between the plurality of conductive plates and having an electrical resistivity higher than that of the conductive plates.

  Heat transfer is performed by the refrigerant gas 14, and the temperature of each of the divided plates 12 and 13 is kept uniform. A connecting band 26 is attached between the divided plates 12 in order to prevent heat input of radiant heat. The connection band 26 has an electrical resistivity higher than that of the plates 12 and 13 in order to make the heat shield 11 thinner, for example, an aluminum (Al) tape, or an aluminum having a high emissivity in order to reliably increase the electrical resistivity. It is possible to use a sheet of plastics or the like on which is deposited. By such division, the size of each eddy current eddy can be reduced and the total eddy current can be reduced.

  As shown in FIG. 7 and FIG. 8, in the MRI apparatus of the third embodiment, the heat shield 11 is arranged in a plurality of cylindrical shields 28 on the inner peripheral portion and the outer peripheral portion, and on the respective end portions. The MRI apparatus according to the first embodiment is different from the MRI apparatus according to the first embodiment in that it is divided into a donut-shaped shield 29 to be divided. The cylindrical shield 28 and the donut shield 29 function as the split shield 27 in FIG. 6, respectively, and the plates 12 and 13 that face each other apart from each other, and the refrigerant gas 14 that is inserted between the plates 12 and 13, have. The cylindrical shield 28 and the donut shield 29 are connected by a connecting band 26. The cryogenic vessel 9 is covered with a plurality of cylindrical shields 28, a pair of donut shields 29, and a plurality of connecting bands 26. Since these divisions can block eddy currents flowing in the axial direction of the cylinder, the size of eddy current eddies can be reduced and the total eddy current can be reduced.

(Fourth embodiment)
As shown in FIGS. 9 and 10, the MRI apparatus according to the fourth embodiment has a plurality of beams 32 extending in the horizontal direction between donut-shaped shields 29 instead of the cylindrical shield 28. This is different from the MRI apparatus of the third embodiment. In the cylindrical shield 28, the natural convection cannot collide with the plates 12 and 13 in the vertical direction. For this reason, the donut-shaped shield 29 flowing in the vertical direction can efficiently carry heat upward. Therefore, in the outer peripheral portion and the inner peripheral portion, heat is conducted to the donut-shaped shield 29 in the horizontal direction that is the shortest distance, and the heat collected in the donut-shaped shield 29 is collected upward, and is connected to the refrigerator via the gas pipe 31. Heat is discharged from the first stage 16 of the fourth. The plurality of beams 32 are laid out so that there is no gap, and the cryogenic container 9 is covered with the donut-shaped shield 29 and the beams 32. However, the adjacent beams 32 are insulated from each other so that no eddy current is generated across the beams 32. The beam 32 may be a plate made of aluminum or a hollow tube made of a drawn material.

  The refrigerant gas 14 cooled in the first stage 16 passes through the gas pipe 31 and enters the upper part of the donut-shaped shield 29 at the end. Natural convection occurs in the donut-shaped shield 29 by the refrigerant gas 14 cooled in the upper part. By natural convection, the temperature of the whole donut-shaped shield 29 can be lowered and made uniform. The plurality of beams 32 are cooled at both ends by the donut-shaped shield 29, so that the center is uniformly cooled to the same temperature as both ends by heat transfer. As described above, the entire heat shield 11 is cooled over a wide range and becomes a uniform temperature.

(Fifth embodiment)
As shown in FIG. 11, in the MRI apparatus according to the fifth embodiment, the first stage 16 of the refrigerator 4 does not cool the refrigerant gas 14 by cooling the plates 12 and 13, but the plate 12. , 13 is different from the MRI apparatus of the first embodiment in that the refrigerant gas 14 is cooled without going through. The warmed refrigerant gas 14 is reduced in density, rises from the top of the plates 12 and 13 through the flexible pipe 36, and is introduced into the refrigerant gas tank 35. The first stage 16 serving as a cooling source directly cools the heat shield cooling unit 33 and the heat exchange fins 34 connected to the heat shield cooling unit 33 are cooled. The refrigerant gas 14 is cooled by the cooled heat exchange fins 34. It is efficient because the refrigerant gas 14 is cooled more directly. Moreover, it is preferable to provide two or more large-diameter flexible pipes 36 so that a flow in one direction is generated for each flexible pipe 36 and a large natural convection is generated. Since the thermal expansion of the heat shield 11 with respect to the vacuum vessel 15 is absorbed by the flexible pipe 36, the refrigerant gas tank 35 and the heat shield cooling unit 33 are installed without being fixed on the heat shield 11 via the buffer material 38. The second stage 17 is disposed so as to pass through the through hole 37, and the through hole 37 is enlarged in consideration of thermal elongation. As described above, the refrigerant gas 14 cooled by the refrigerator 4 is efficiently supplied to the heat shield 11.

1 is a perspective view of a magnetic resonance imaging apparatus according to an embodiment of the present invention. It is sectional drawing of the AA direction of FIG. (A) is the perspective view which drew the principle of the heat shield for superconducting magnets which concerns on one Embodiment of this invention typically, (b) is sectional drawing of the BB direction of (a). (A) is a perspective view of the heat shield for superconducting magnets which concerns on one Embodiment of this invention, (b) is sectional drawing of CC direction of (a). 1 is a cross-sectional view of a magnetic resonance imaging apparatus according to an embodiment of the present invention. It is the perspective view which drew the principle of the heat shield for superconducting magnets concerning one embodiment of the present invention typically. 1 is a cross-sectional view of a magnetic resonance imaging apparatus according to an embodiment of the present invention. It is a perspective view of the heat shield for superconducting magnets concerning one embodiment of the present invention. 1 is a cross-sectional view of a magnetic resonance imaging apparatus according to an embodiment of the present invention. It is a perspective view of the heat shield for superconducting magnets concerning one embodiment of the present invention. It is sectional drawing of the periphery of the cooling source of the superconducting magnet apparatus which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic resonance imaging apparatus 2 Superconducting magnet apparatus 4 Refrigerator 6 Superconducting coil 8 Refrigerant liquid 9 Cryogenic container 11 Heat shield 12 Outer plate 13 Inner plate 14 Refrigerant gas 15 Vacuum vessel 16 First stage (cooling source)
DESCRIPTION OF SYMBOLS 22 Load support body 23 Natural convection of refrigerant gas 24 Refrigerant gas 25 Connection pipe 26 Connection zone 27 Split shield 28 Cylindrical shield 29 Donut type shield 31 Gas pipe 32 Split shield plate 33 Heat shield cooling part 34 Heat exchange fin 35 Refrigerant gas tank 36 Flexible piping 37 Through hole

Claims (8)

Provided between a cryogenic container that accommodates the superconducting coil together with the refrigerant liquid and a vacuum container that accommodates the cryogenic container and is maintained in a vacuum, covers the cryogenic container, and is cooled by a cooling source. In heat shield for superconducting magnets,
A plate facing away,
Refrigerant gas put between the opposing plates,
A heat shield for a superconducting magnet, wherein the refrigerant gas is cooled by the cooling source to cause natural convection in which the refrigerant gas rises after dropping along the plate.   The heat shield for a superconducting magnet according to claim 1, wherein a gas obtained by vaporizing the refrigerant liquid is used as the refrigerant gas. The plate is
A plurality of non-magnetic conductive plates;
The heat shield for a superconducting magnet according to claim 1 or 2, further comprising a connection band provided between the plurality of conductive plates and having an electrical resistivity higher than that of the conductive plates.   The heat shield for a superconducting magnet according to any one of claims 1 to 3, wherein the plate is a stainless steel member. A plurality of beams extending horizontally from the plate;
Arrange the plates upright,
The heat shield for a superconducting magnet according to any one of claims 1 to 3, wherein the cryogenic container is covered with the plate and the beam.   The heat shield for a superconducting magnet according to any one of claims 1 to 5, further comprising a pipe for guiding the refrigerant gas to the cooling source and connecting the refrigerant gas to an upper portion of the plate.   A superconducting magnet device using the heat shield for a superconducting magnet according to any one of claims 1 to 6.   A magnetic resonance imaging apparatus using the superconducting magnet apparatus according to claim 7.

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