JP7114881B2 - Superconducting magnetic field generator and nuclear magnetic resonance device - Google Patents

Description

The present invention relates to a superconducting magnetic field generator and a nuclear magnetic resonance apparatus.

Nuclear magnetic resonance (NMR) is a resonance phenomenon of nuclear spin (magnetic moment) energy generated when an electromagnetic wave is applied to a sample placed in a strong magnetic field. A nuclear magnetic resonance apparatus (NMR apparatus) is a device that analyzes the structure of a sample using such resonance phenomena. Since the sensitivity and resolution of the NMR signal increase as the magnetic field strength increases, the NMR apparatus is equipped with a magnetic field generator for generating a strong magnetic field.

A superconducting magnetic field generator that generates a magnetic field by magnetizing a superconductor has been developed as a magnetic field generator that generates a strong magnetic field. A high-temperature superconductor, which has a high superconducting transition temperature and is relatively easy to cool, is preferably used as the superconductor provided in the superconducting magnetic field generator.

A superconductor provided in a superconducting magnetic field generator used in an NMR apparatus is formed, for example, in a cylindrical shape. In this case, the superconductor is magnetized by the following procedure.
(1) Magnetic field application step In the magnetic field application step, magnetic flux is generated in the inner peripheral space (hereinafter also referred to as bore) of the superconductor at a temperature higher than the superconducting transition temperature (critical temperature) Tc of the cylindrical superconductor. A magnetic field (applied magnetic field) is applied to the superconductor by an external magnetic field generator so as to generate a magnetic field passing in the axial direction.
(2) Magnetic Field Cooling Step In the magnetic field cooling step, the superconductor to which the magnetic field has been applied by the external magnetic field generator as described above is cooled to a temperature T0 below the superconducting transition temperature Tc.
(3) Demagnetization Step In the demagnetization step, the applied magnetic field generated by the external magnetic field generator is removed (the applied magnetic field strength is made zero) while the temperature of the superconductor is maintained at temperature T0.

When the applied magnetic field is removed in the demagnetization process, the superconductor picks up the magnetic field so as to maintain the applied magnetic field. This magnetizes the superconductor and induces a superconducting current in the superconductor. This flow of superconducting current in the superconductor creates a magnetic field in the bore of the superconductor through which the magnetic flux passes in the axial direction. That is, in the demagnetization process, a magnetic field (captured magnetic field) is generated by capturing the magnetic field applied to the superconductor. A space (room-temperature bore space) in which the sample is placed is formed in the bore of the superconductor in which the trapping magnetic field is generated. By applying an electromagnetic wave to a sample placed in a room temperature bore space, a weak electromagnetic wave is emitted from the sample. An NMR spectrum is obtained by detecting this electromagnetic wave.

When analyzing the molecular structure of a sample with an NMR apparatus, if the uniformity of the magnetic field strength in the bore of the superconductor is low, the NMR spectrum obtained will be broad and the molecular structure of the sample cannot be properly identified. Therefore, the superconducting magnetic field generator used in the NMR apparatus is preferably configured so as to generate a strong magnetic field and improve the uniformity of the magnetic field strength in the room-temperature bore space in which the sample is placed. . Therefore, conventionally, development of a superconducting magnetic field generator capable of improving the uniformity of the magnetic field strength in the bore of a cylindrical superconductor has been advanced.

Patent Document 1 discloses a superconducting magnetic field generator having a cylindrical superconductor formed by coaxially arranging cylindrical superconducting bulks with low magnetic susceptibility on both end surfaces of a cylindrical superconducting bulk with high magnetic susceptibility. disclose. According to the superconducting magnetic field generator disclosed in Patent Document 1, the uniformity of the magnetic field strength in the axial direction of the superconductor is enhanced by designing the magnetic susceptibility and shape of the superconducting bulk so as to satisfy certain conditions. A magnetic field space can be formed within the bore of the superconductor.

Patent Document 2 discloses a superconducting magnetic field generator having correction coils arranged around a superconductor composed of a cylindrical superconducting bulk. According to the superconducting magnetic field generator disclosed in Patent Document 2, when a magnetic field is applied to the superconductor, the correction coil corrects the applied magnetic field, thereby improving the uniformity of the magnetic field strength in the axial direction of the superconductor. A magnetic field space can be formed within the bore of the superconductor.

Patent Document 3 discloses a superconducting magnetic field generator having a superconductor formed in a cylindrical shape such that the inner diameter of the center portion in the axial direction is larger than the inner diameter of the end portions. According to the superconducting magnetic field generator disclosed in Patent Document 3, the inner diameter of the central portion in the axial direction of the cylindrical superconductor is made larger than the inner diameter of the end portions, so that a non-uniform magnetic field generated by the magnetization of the superconductor. A canceling magnetic field flows in the bore of the superconductor. By removing the non-uniform magnetic field in this way, a magnetic field space with enhanced uniformity of the magnetic field intensity in the axial direction of the superconductor can be formed in the bore of the superconductor.

Patent Document 4 discloses a magnetic field generator in which a cylindrical inner superconductor is disposed inside a cylindrical outer superconductor. A magnetic field space with enhanced uniformity of magnetic field strength is formed in the bore of the superconductor by correcting the non-uniform trapping magnetic field using the anisotropy of the critical current densities of the outer superconductor and the inner superconductor. can do.

JP 2008-034692 A JP 2009-156719 A JP 2014-053479 A JP 2016-006825 A

(Problems to be solved by the invention)
As described above, when depositing a superconductor, a magnetic field application step, a magnetic field cooling step, and a demagnetization step are performed. Here, when the superconductor is cooled to the superconducting transition temperature Tc or lower in the magnetic field cooling step, the superconductor enters a superconducting state, and part of the magnetic field passing through the superconductor is expelled to the outside of the superconductor by the Meissner effect. . The amount of magnetic field that is expelled outside the superconductor is greater at lower temperatures. Therefore, if the superconductor is not uniformly cooled in the magnetic field cooling process, that is, if the temperature uniformity within the superconductor is low, the amount of the magnetic field excluded into the bore differs depending on the location. The homogeneity of the magnetic field of Then, when the demagnetization process is performed in that state (when the superconductor is magnetized), the magnetic field whose uniformity is lost is supplemented. As a result, the uniformity of the magnetic field strength within the bore is reduced.

In addition, the critical current density Jc (the density of the current flowing through the superconductor with zero electrical resistance), which is a measure of the captured magnetic field performance, has temperature dependence. Critical current density Jc is large. Therefore, if the superconductor is not uniformly cooled when the demagnetization step is performed (ie, the temperature uniformity within the superconductor is low), the amount of magnetic field that can be captured varies from place to place. These locational differences in the amount of trapped magnetic field reduce the uniformity of the magnetic field strength within the bore.

Thus, when the uniformity of the temperature (cooling temperature) of the superconductor is low when the superconductor is magnetized, the uniformity of the magnetic field intensity within the bore is also reduced. Therefore, improving the uniformity of the temperature of the superconductor is one of the necessary requirements for improving the uniformity of the magnetic field intensity in the bore.

According to the technology described in the above patent documents, improvements have been made to the shape and structure of the superconductor in order to increase the uniformity of the magnetic field intensity within the bore. not applied. For example, FIG. 7 of Patent Document 3 shows a configuration in which one end surface of a cylindrical superconductor is in contact with the cold head of a cooling device. In such a configuration, when the cooling device operates, the portion on the one end side of the superconductor is sufficiently cooled, but the portion on the other end side is not sufficiently cooled. That is, the superconductor is not uniformly cooled in the axial direction. As a result, the magnetic field space in the bore cannot be sufficiently homogenized, or the area where the magnetic field is uniform decreases.

If the magnetic field intensity in the bore of the superconductor used in the NMR apparatus is non-uniform, accurate measurement cannot be performed. is made uniform. Here, when the degree of non-uniformity of the magnetic field strength is large, the number of correction coils is increased to make the magnetic field strength in the bore uniform. In this case, many correction coils are arranged in the narrow room temperature bore space, resulting in the problem that a sufficiently large sample space cannot be secured in the room temperature bore space. On the other hand, if the cooling temperature of the superconductor is highly uniform, the number of correction coils can be reduced, and as a result, a sufficiently large sample space can be secured in the room temperature bore space. For this reason, it is preferable that the superconductor is uniformly cooled during magnetization.

Accordingly, the present invention provides a superconducting magnetic field generator configured to increase the uniformity of the temperature of a superconductor during magnetization of the superconductor, and a nuclear magnetic resonance apparatus comprising such a superconducting magnetic field generator. It is an object to provide a device.

(means for solving the problem)
The present invention relates to a superconductor (1) which is formed in a cylindrical shape and generates a magnetic field by capturing a magnetic field applied in a state cooled to a temperature below the superconducting transition temperature, and a superconductor (1) which is cooled to a temperature below the superconducting transition temperature a cooling device (2) comprising a cold head (3) for generating cold heat for cooling to a temperature of the superconductor so as to cool the superconductor from one end face (1a) of the superconductor A stage portion (32) thermally connected to one end face of the superconductor, and a stage portion (32) thermally connected to the stage portion and to the other end face of the superconductor so as to cool the superconductor from the other end face (1b) of the superconductor a thermally connected extension (33), the extension being thermally spaced from the outer peripheral surface of the superconductor (101, 102, 103, 104) ) , the superconductor has an inner peripheral surface (4d) which is formed in a cylindrical shape and is thermally connected to the outer peripheral surface (1c) of the superconductor, and holds the superconductor from the outer peripheral side of the superconductor. An outer cylindrical heat transfer holder (4) disposed on the outer peripheral side and having one end surface (4a) thermally connected to the stage portion and the other end surface (4b) thermally connected to the extension portion A superconducting magnetic field generator is provided.

According to the superconducting magnetic field generator of the present invention, the cold head that generates cold heat is configured such that the cylindrical superconductor is cooled from both ends in the axial direction by cold heat from the cold head. By cooling the superconductor from both axial ends, the temperature difference in the axial direction of the superconductor can be reduced. As a result, the temperature uniformity of the superconductor when the superconductor is magnetized, particularly the temperature uniformity in the axial direction of the superconductor (hereinafter sometimes referred to as axial temperature uniformity) can be enhanced.

In addition , the cold head includes a stage portion (32) thermally connected to one end face of the superconductor so as to cool the superconductor from one end face (1a) of the superconductor, and from the other end face (1b) of the superconductor. and an extension (33) thermally connected to the other end face of the superconductor so as to cool the superconductor . According to this, the superconductor is cooled from one end face by the stage portion of the cold head, and cooled from the other end face by the extended portion of the cold head. Therefore, the superconductor is cooled from both ends in the axial direction. Therefore, it is possible to improve the axial temperature uniformity of the superconductor when the superconductor is magnetized.

The extension has one end face (331a) and the other end face (331b) on the opposite side, the first extension part (331) having one end face thermally connected to the stage part, and the first extension part (331). a second extension (332) thermally connected to the other end face of the superconductor and thermally connected to the other end face of the superconductor. It is preferable that the first extension portion is thermally separated from the outer peripheral surface of the superconductor. According to this, the superconductor is cooled from one end face by the stage portion of the cold head, and cooled from the other end face by the second extended portion of the cold head. Therefore, the superconductor is cooled from both ends in the axial direction. Therefore, it is possible to improve the axial temperature uniformity of the superconductor when the superconductor is magnetized.

Further, the superconducting magnetic field generator according to the present invention is formed in a cylindrical shape and has an inner peripheral surface (4d) that is thermally connected to the outer peripheral surface (1c) of the superconductor. It is arranged on the outer peripheral side of the superconductor so as to hold the body, one end face (4a) is thermally connected to the stage part, and the other end face (4b) is thermally connected to the extension part. It has an outer cylindrical heat transfer holder (4) . According to this, since both ends of the outer cylindrical heat transfer holder which holds the superconductor from its outer peripheral side and is thermally connected to the outer peripheral surface of the superconductor are thermally connected to the cold head, the cooling device When the is activated, this outer cylindrical heat transfer holder is also uniformly cooled from both ends thereof. The outer cylindrical heat transfer holder cooled in this manner also cools the superconductor from its outer peripheral surface. In other words, the superconductor is cooled from its one end surface, the other end surface, and the outer peripheral surface. By further increasing the surface on which the superconductor is cooled in this manner, the temperature uniformity of the superconductor during magnetization can be further enhanced.

In this case, the thermal contraction rate of the outer cylindrical heat transfer holder is preferably equal to or higher than the thermal contraction rate of the superconductor. According to this, when the superconductor and the outer cylindrical heat transfer holder are cooled by the operation of the cooling device, the heat shrinkage amount of the outer cylindrical heat transfer holder is larger than the heat shrinkage amount of the superconductor. A heat transfer holder clamps the superconductor from its outer peripheral side. This tightening force acts as a compressive stress on the superconductor. Also, an electromagnetic stress (hoop force) acts on the superconductor during magnetization. Due to this electromagnetic stress, the superconductor receives a force that expands radially outward. That is, the electromagnetic stress acts on the superconductor as tensile stress. This tensile stress is counteracted by a compressive stress from the outer cylindrical heat transfer holder acting on the superconductor. Therefore, damage to the superconductor due to electromagnetic stress can be effectively prevented.

In addition, it is preferable that the cross-sectional area perpendicular to the central axis at both ends of the outer cylindrical heat transfer holder in the axial direction is larger than the cross-sectional area perpendicular to the central axis at the central portion in the axial direction. The heat transferred from the superconductor to the central portion of the outer cylindrical heat transfer holder in the axial direction in the magnetic field cooling process is transferred to both ends of the outer cylindrical heat transfer holder. transmitted to the head. Also, heat is directly transferred from the superconductor to both ends of the outer cylindrical heat transfer holder. Therefore, at both ends of the outer cylindrical heat transfer holder, the heat transferred from the axial central portion of the outer cylindrical heat transfer holder and the heat transferred from the superconductor join together. Therefore, a large amount of heat flows to both ends of the outer cylindrical heat transfer holder. Here, as in the present invention, by making the cross-sectional area of both ends of the outer cylindrical heat transfer holder larger than the cross-sectional area of the center, the heat is efficiently transferred from both ends of the outer cylindrical heat transfer holder where much heat flows. can be communicated to the coldhead. That is, the heat dissipation efficiency of the outer cylindrical heat transfer holder is improved. Therefore, the superconductor can be quickly cooled, and it is possible to effectively prevent the temperature uniformity of the superconductor from deteriorating due to heat stagnation in the outer cylindrical heat transfer holder. Regarding the electromagnetic stress (hoop force) generated when the superconductor is magnetized, it is known that the electromagnetic stress acting on both ends of the superconductor is greater than the electromagnetic stress acting on the central portion in the axial direction of the superconductor. It is In this regard, it is possible to increase the reinforcing effect against electromagnetic stress by increasing the cross-sectional area of both ends of the outer cylindrical heat transfer holder and increasing the strength of both ends of the outer cylindrical heat transfer holder as in the present invention. can be done.

Further, the superconducting magnetic field generator according to the present invention is formed in a cylindrical shape, the inner peripheral surface (8d) of which is in contact with the outer peripheral surface of the superconductor, and the outer peripheral surface (8c) of which is the inner surface of the outer cylindrical heat transfer holder. It is arranged between the superconductor and the outer cylindrical heat transfer holder so as to be in contact with the peripheral surface, one end face (8a) is thermally connected to the stage part, and the other end face (8b) is A reinforcing member (8) may be provided which is thermally connected to the extension. According to this, since the reinforcing member is attached to the outer peripheral surface of the superconductor, the effect of reinforcing the electromagnetic stress (hoop force) generated when the superconductor is magnetized can be enhanced.

In this case, the thermal contraction rate of the outer cylindrical heat transfer holder is preferably equal to or higher than that of the reinforcing member, and the thermal contraction rate of the reinforcing member is preferably equal to or higher than that of the superconductor. According to this, when the superconductor is cooled, a compressive stress acts on the superconductor due to thermal contraction of the outer cylindrical heat transfer holder and the reinforcing ring. In other words, the superconductor is double reinforced by the compressive stress from the outer cylindrical heat transfer holder and the compressive stress from the reinforcing ring. Therefore, the effect of reinforcing the electromagnetic stress (hoop force) generated when the superconductor is magnetized can be further enhanced.

Further, the superconducting magnetic field generator according to the present invention is formed in a cylindrical shape and has an outer peripheral surface (5c) that is thermally connected to the inner peripheral surface (1d) of the superconductor. It is arranged on the inner peripheral side of the superconductor so as to hold the superconductor, one end face (5a) is thermally connected to the stage part, and the other end face (5b) is thermally connected to the extension part. It may also comprise an inner cylindrical heat transfer holder (5) which is lined. According to this, both ends of the inner cylindrical heat transfer holder which holds the superconductor from its inner peripheral side and is thermally connected to the inner peripheral surface of the superconductor are thermally connected to the cold head. When the cooling device is activated, this inner cylindrical heat transfer holder is also uniformly cooled from both ends thereof. The inner cylindrical heat transfer holder thus cooled also cools the superconductor from its inner peripheral surface. In other words, the superconductor is cooled from its one end surface, the other end surface, and the inner peripheral surface. By further increasing the surface on which the superconductor is cooled in this manner, the temperature uniformity of the superconductor during magnetization can be further enhanced. In addition, since the inner cylindrical heat transfer holder is interposed between the superconductor and the room temperature bore space formed on the inner peripheral side of the superconductor, the temperature of the superconductor due to heat radiation from the room temperature bore space side A rise can be prevented.

Moreover, the superconducting magnetic field generator according to the present invention may comprise a first cup-shaped heat transfer holder (61) and a second cup-shaped heat transfer holder (62) thermally connected to the cold head. The first cup-shaped heat transfer holder is formed in a cup shape and has a disk-shaped first bottom wall portion (611) thermally connected to one end surface of the superconductor, and a first bottom wall portion (611). A cylindrical first side wall portion (612 ) and is disposed against the superconductor so as to hold one side portion. The second cup-shaped heat transfer holder is formed in a cup shape and has a disk-shaped second bottom wall portion (621) thermally connected to the other end surface of the superconductor, and a second bottom wall portion (621). A cylindrical second side wall portion (622 ) and is disposed against the superconductor so as to hold the other side portion.

According to this, since the first cup-shaped heat transfer holder and the second cup-shaped heat transfer holder are thermally connected to the cold head, these cup-shaped heat transfer holders are also cooled by the cold head. In addition, by the first cup-shaped heat transfer holder, the portion (one side portion) from the central position in the axial direction of the superconductor to one end face is cooled from the end face (one end face) and the outer peripheral surface thereof, and the second cup-shaped heat transfer holder cools the second cup-shaped heat transfer holder. By the heat holder, the portion (other side portion) from the central position in the axial direction of the superconductor to the other end face is cooled from the end face (other end face) and the outer peripheral surface. Since the superconductor is cooled from both end faces and the outer peripheral face in this manner, the temperature uniformity in the axial direction of the superconductor can be enhanced when the superconductor is magnetized.

In addition, the first cup-shaped heat transfer holder has a first connection portion (613) extending radially outward from the other end of the first side wall portion, and the second cup-shaped heat transfer holder has a second side wall portion. It is preferable to have a second connecting portion (623) extending radially outward from the other end of the portion. Then, the first cup-shaped heat transfer holder and the second cup-shaped heat transfer holder are connected with the first connection portion and the second connection portion facing each other, and the first connection portion and the second connection portion are connected to the cold head. They are preferably thermally connected.

According to this, by thermally connecting the first connection portion of the first cup-shaped heat transfer holder and the second connection portion of the second cup-shaped heat transfer holder, which are arranged facing each other, to the cold head, one of the superconductors The distance from the heat of the side portion to the cold head via the first cup-shaped heat transfer member and the distance from the heat of the other side portion of the superconductor to the cold head via the second cup-shaped heat transfer member can be made approximately equal. Therefore, the cooling rate can be substantially constant over the entire superconductor. Thereby, the superconductor can be cooled more uniformly.

Also, the thermal contraction rates of the first cup-shaped heat transfer holder and the second cup-shaped heat transfer holder are preferably equal to or higher than the thermal contraction rate of the superconductor. According to this, when the superconductor is cooled in the cooling step in the magnetic field, the thermal contraction of the first side wall portion of the first cup-shaped heat transfer holder causes compressive stress to act on the one side portion of the superconductor. Compressive stress acts on the other side portion of the superconductor due to thermal contraction of the second side wall portion of the two-cup-shaped heat transfer holder. Therefore, the effect of reinforcing the electromagnetic stress (hoop force) generated when the superconductor is magnetized can be enhanced.

Further, the superconducting magnetic field generator according to the present invention is formed in a cylindrical shape, the inner peripheral surface (8d) of which is in contact with the outer peripheral surface of the superconductor, and the outer peripheral surface (8c) of which is the inner peripheral surface of the first side wall portion. (612d) and the inner peripheral surface (622d) of the second side wall are disposed between the superconductor and the first side wall and the second side wall, and one end face (8a) thereof is It is preferable to provide a reinforcing member (8) thermally connected to the first bottom wall and having the other end face (8b) thermally connected to the second bottom wall. According to this, by attaching the cylindrical reinforcing member to the outer periphery of the superconductor, it is possible to enhance the reinforcing effect against the electromagnetic stress (hoop force) generated when the superconductor is magnetized.

In this case, the thermal contraction rate of the first cup-shaped heat transfer holder and the second cup-shaped heat transfer holder is equal to or greater than the thermal contraction rate of the reinforcing member, and the thermal contraction rate of the reinforcing member is equal to or greater than the thermal contraction rate of the superconductor. Good to have. According to this, when the superconductor is cooled, compressive stress is applied to the superconductor due to thermal contraction of the first side wall portion of the first cup-shaped heat transfer holder, the second side wall portion of the second cup-shaped heat transfer holder, and the reinforcing member. works. That is, the superconductor is double reinforced by the compressive stress from each cup-shaped heat transfer holder and the compressive stress from the reinforcing member. Therefore, the effect of reinforcing the electromagnetic stress (hoop force) generated when the superconductor is magnetized can be further enhanced.

Further, the superconducting magnetic field generator according to the present invention has an outer peripheral surface (5c) formed in a cylindrical shape and thermally connected to the inner peripheral surface of the superconductor, and the superconductor is supplied from the inner peripheral side of the superconductor. It is arranged on the inner peripheral side of the superconductor so as to hold it, one end face (5a) is thermally connected to the first bottom wall part, and the other end face (5b) is thermally connected to the second bottom wall part It may be provided with an inner cylindrical heat transfer holder (5) which is rigidly connected. According to this, both ends of the inner cylindrical heat transfer holder thermally connected to the inner peripheral surface of the superconductor are thermally connected to the bottom wall portion of the cup-shaped heat transfer member, respectively, so that the cooling device is In operation, this inner cylindrical heat transfer holder is also uniformly cooled from both ends thereof. The inner cylindrical heat transfer holder thus cooled also cools the superconductor from its inner peripheral surface. That is, the superconductor is cooled from its one end surface, the other end surface, the outer peripheral surface and the inner peripheral surface. By further increasing the surface on which the superconductor is cooled, the superconductor can be cooled more uniformly. In addition, since the inner cylindrical heat transfer holder is interposed between the superconductor and the room temperature bore space formed on the inner peripheral side of the superconductor, the temperature of the superconductor due to heat radiation from the room temperature bore space side A rise can be prevented.

The present invention also provides a nuclear magnetic resonance apparatus (110) equipped with the superconducting magnetic field generator described above. According to this, the superconductor is magnetized in a state in which the uniformity of the cooling temperature of the superconductor is enhanced by the superconducting magnetic field generator, so that a uniform magnetization space is formed in the room-temperature bore space. Therefore, it is possible to improve the measurement accuracy of the nuclear magnetic resonance apparatus.

FIG. 1 is a schematic diagram showing a cross section of the superconducting magnetic field generator according to the first embodiment taken along a plane including the center line along the vertical direction. FIG. 2 is a diagram showing a schematic configuration of a nuclear magnetic resonance apparatus. FIG. 3 shows the magnetic field intensity distribution in the bore in the axial direction of the superconductor obtained when the trapped magnetic field is formed in the bore of the superconductor using the superconducting magnetic field generator according to the first embodiment. It is a graph written together with the temperature distribution in a direction. FIG. 4 is a schematic diagram showing a cross section of the superconducting magnetic field generator according to the second embodiment taken along a plane including the center line along the vertical direction. FIG. 5 is a schematic diagram showing a cross section of the superconducting magnetic field generator according to the third embodiment taken along a plane including the center line along the vertical direction. FIG. 6 is a schematic diagram showing a cross section of the superconducting magnetic field generator according to the fourth embodiment taken along a plane including the center line along the vertical direction. FIG. 7 is a schematic diagram showing a cross section of the superconducting magnetic field generator according to the fifth embodiment taken along a plane including the center line along the vertical direction. FIG. 8 is a schematic diagram showing a cross section of the superconducting magnetic field generator according to the sixth embodiment taken along a plane including the center line along the vertical direction. FIG. 9 is a schematic diagram showing a cross section of the superconducting magnetic field generator according to the seventh embodiment taken along a plane including the center line along the vertical direction. FIG. 10 is a schematic diagram showing a cross section of a conventional superconducting magnetic field generator cut along a plane including the center line along the vertical direction. FIG. 11 shows the magnetic field strength distribution in the bore in the axial direction of the superconductor obtained when a trapped magnetic field is formed in the bore of the superconductor using a conventional superconducting magnetic field generator. It is a graph written together with temperature distribution.

(First embodiment)
A first embodiment of the present invention will be described below. FIG. 1 is a schematic diagram showing a cross section of a superconducting magnetic field generator 101 according to the first embodiment taken along a plane including a center line along the vertical direction. As shown in FIG. 1 , the superconducting magnetic field generator 101 includes a superconductor 1 , a cooling device 2 , a cold head 3 , an outer cylindrical heat transfer holder 4 and a vacuum insulation container 7 .

As shown in FIG. 1, the superconductor 1 is formed in a cylindrical shape by coaxially stacking a plurality of cylindrical superconducting bulks having a predetermined radial length along the axial direction. In FIG. 1, there are six cylindrical superconducting bulks (first superconducting bulk 11, second superconducting bulk 12, third superconducting bulk 13, fourth superconducting bulk 14, fifth superconducting bulk 15, sixth superconducting bulk 16). are coaxially stacked in this order from the bottom to the top along the axial direction to form the superconductor 1 . The number of superconducting bulks is not particularly limited. It should be noted that the cylindrical superconductor 1 may be composed of one superconducting bulk. Such a cylindrical superconductor 1 has one end surface 1a (lower end surface), the other end surface 1b (upper end surface), an outer peripheral surface 1c, and an inner peripheral surface 1d in the axial direction. The shape of one end surface 1a and the other end surface 1b is ring-shaped. A space surrounded by the inner peripheral surface 1 d of the superconductor 1 is the bore (inner peripheral space) of the superconductor 1 .

The superconductor 1 is made of a high temperature superconducting material. In this embodiment, the superconductor 1 is an RE-Ba-Cu-O (RE is a rare earth element containing Y) system superconductor, and is formed by a known melting method. The superconductor 1 has a layered crystal structure in which the c-axis direction is the stacking direction (perpendicular to the layers). Formed by growing.

The cooling device 2 may be of any type as long as it can generate cold heat below the superconducting transition temperature (critical temperature) Tc (for example, 90K) of the superconductor 1, for example, cold heat of about 50K. Examples of the cooling device 2 include a pulse tube refrigerator, a GM refrigerator, and a Stirling refrigerator. The cooling device 2 is preferably one that generates cold heat by performing a refrigeration cycle operation, but is a substance such as liquid nitrogen that can provide a temperature below the superconducting transition temperature Tc of a high-temperature superconductor. good too.

A cold head 3 is provided in the cooling device 2 . The cold head 3 is a member for transmitting cold heat generated by the cooling device 2 to the outside. Therefore, the cold head 3 generates cold heat due to the operation of the cooling device. In this embodiment and the following embodiments, the cold head 3 generates cold heat for cooling the superconductor 1 to a temperature T0 below the superconducting transition temperature Tc. The cold head 3 is made of a non-magnetic material with high thermal conductivity. In this embodiment and the following embodiments, the cold head 3 is made of copper.

The cold head 3 has a columnar shaft portion 31 , a disk-shaped stage portion 32 , and an extension portion 33 . One end of the shaft portion 31 is brought into contact with a cold heat generating portion (not shown) of the cooling device 2 . For example, if the cooling device 2 is a pulse tube refrigerator, the shaft 31 is in contact with the cold end of the regenerator, and if the cooling device 2 is a GM refrigerator, the shaft 31 is a cylinder defining an expansion space. part is touched. In FIG. 1 , the shaft portion 31 is provided on the upper side of the cooling device 2 . A disk-shaped stage portion 32 is formed continuously and coaxially at the upper end (the other end) of the shaft portion 31 .

The disk-shaped stage portion 32 has one end surface 32a (lower end surface) and the other end surface 32b (upper end surface) in the axial direction, and an outer peripheral surface 32c. One end face 32 a of stage portion 32 is connected to the upper end of shaft portion 31 . Then, the superconductor 1 is placed on the stage portion 32 so that the one end face 1a of the cylindrical superconductor 1 contacts the other end face 32b of the stage portion 32 facing upward in FIG. Contact between one end face 1a of superconductor 1 and the other end face 32b of stage portion 32 thermally connects superconductor 1 and cold head 3 (stage portion 32). As described above, cold head 3 generates cold heat for cooling superconductor 1 . Therefore, cold head 3 (stage portion 32) is thermally connected to one end surface 1a of superconductor 1 so as to cool superconductor 1 from one end surface 1a of superconductor 1. FIG.

The superconductor 1 extends upward from the other end surface 32b of the stage portion 32 in FIG. Also, the stage portion 32 and the superconductor 1 are arranged coaxially. Furthermore, the outer diameter of the stage portion 32 is larger than the outer diameter of the superconductor 1 . Therefore, the other end face 32b of the stage portion 32 has a ring-shaped superconductor contact area with which the one end face 1a of the superconductor 1 is in contact, a circular area on the inner peripheral side of the superconductor contact area, and a ring-shaped area on the outer peripheral side of the superconductor contact area. exists. A bore of the superconductor 1 is formed on the inner circular area. As will be described later, the extension 33 and the outer cylindrical heat transfer holder 4 are mounted on the ring-shaped region on the outer peripheral side.

The extension 33 has a first extension 331 and a second extension 332 . The first extension part 331 is formed in a cylindrical shape. The cylindrical first extension portion 331 has one end surface 331a (lower end surface) and the other end surface 331b (upper end surface) on the opposite side in the axial direction, an outer peripheral surface 331c, and an inner peripheral surface 331d. Also, the outer diameter of the first extension portion 331 is substantially equal to the outer diameter of the stage portion 32 , and the inner diameter of the first extension portion 331 is larger than the outer diameter of the superconductor 1 . Also, the axial length of the first extension portion 331 is equal to the axial length of the superconductor 1 . The first extension portion 331 is placed coaxially on the stage portion 32 so that one end surface 331a of the first extension portion 331 contacts a portion of the other end surface 32b of the stage portion 32 near the outer periphery. As a result, one end surface 331 a of the first extension portion 331 is thermally connected to the stage portion 32 .

The first extension portion 331 extends upward in FIG. 1 from the other end face 32b of the stage portion 32, similarly to the superconductor 1. The superconductor 1 is arranged on the inner peripheral side of the first extension portion 331, and the outer peripheral surface 1c of the superconductor 1 and the inner peripheral surface 331d of the first extension portion 331 face each other with a predetermined distance therebetween. That is, the first extension portion 331 is arranged on the outer peripheral side of the superconductor 1 so as to be spaced apart from the outer peripheral surface 1 c of the superconductor 1 .

The second extension portion 332 is formed in a disc shape and has one end face 332a (lower end face) and the other end face 332b (upper end face) in the axial direction. A circular hole 333 is formed in the center of the disk-shaped second extension portion 332 so as to penetrate in the axial direction from one end face 332a to the other end face 332b. Therefore, the second extension portion 332 has an outer peripheral surface 332 c and an inner peripheral surface 332 d surrounding the circular hole 333 .

The inner diameter of the second extension 332 (the diameter of the circular hole 333 ) is substantially equal to the inner diameter of the superconductor 1 , and the outer diameter of the second extension 332 is substantially equal to the outer diameter of the first extension 331 . The second extension portion 332 is arranged coaxially on the first extension portion 331 so that a circumferential region of the one end surface 332 a near the outer peripheral surface 332 c contacts the other end surface 331 b of the first extension portion 331 . is set. This thermally connects the second extension portion 332 to the first extension portion 331 . At this time, as shown in FIG. 1, a circumferential region of one end surface 332a of the second extension portion 332, which is close to the inner peripheral surface 332d, contacts the other end surface 1b of the superconductor 1. As shown in FIG. As a result, the second extension portion 332 is thermally connected to the other end face 1b of the superconductor 1 . Therefore, the second extension portion 332 is thermally connected to the other end surface 331b of the first extension portion 331 at a circumferential region near the outer periphery of the one end face 332a, and near the inner periphery of the one end face 332a. It is configured such that the circumferential region is thermally connected to the other end surface 1 b of the superconductor 1 .

As described above, the extended portion 33 of the cold head 3 is thermally connected to the stage portion 32 at its first extended portion 331, and is connected to the other end surface 1b of the superconductor 1 at its second extended portion 332. are also thermally connected. Therefore, the cold head 3 (extension portion 33) is thermally connected to the other end face 1b of the superconductor 1 so as to cool the superconductor 1 from the other end face 1b of the superconductor 1. That is, the cold head 3 is configured to cool the superconductor 1 from the one end face 1a side at the stage portion 32 and cool the superconductor 1 from the other end face 1b side at the extension portion 33 thereof. In other words, the cold head 3 is configured such that the superconductor 1 is cooled from both ends in the axial direction by cold heat from the cold head 3 .

As shown in FIG. 1, an outer cylindrical heat transfer holder 4 is arranged between the superconductor 1 and the first extension 331 . The outer cylindrical heat transfer holder 4 is arranged on the outer peripheral side of the superconductor 1 so as to hold the superconductor 1 from the outer peripheral side of the superconductor 1 . The outer cylindrical heat transfer holder 4 is made of a non-magnetic material with high thermal conductivity. In this embodiment, the outer cylindrical heat transfer holder 4 is made of aluminum or an aluminum alloy.

The outer cylindrical heat transfer holder 4 is formed in a cylindrical shape and has one end surface 4a and the other end surface 4b in the axial direction, an outer peripheral surface 4c, and an inner peripheral surface 4d. The inner diameter of the outer cylindrical heat transfer holder 4 is substantially equal to the outer diameter of the superconductor 1 , and the outer diameter of the outer cylindrical heat transfer holder 4 is smaller than the inner diameter of the first extension 331 of the extension 33 . Further, the axial length of the outer cylindrical heat transfer holder 4 is equal to the axial length of the superconductor 1 . The outer cylindrical heat transfer holder 4 is arranged with respect to the superconductor 1 so that the inner peripheral surface 4d of the outer cylindrical heat transfer holder 4 is in contact with the outer peripheral surface 1c of the superconductor 1 . The contact between the inner peripheral surface 4d of the outer cylindrical heat transfer holder 4 and the outer peripheral surface 1c of the superconductor 1 thermally connects the inner peripheral surface 4d of the outer cylindrical heat transfer holder 4 to the outer peripheral surface 1c of the superconductor 1. be done. At this time, the outer cylindrical heat transfer holder 4 is arranged on the inner peripheral side of the first extension portion 331 of the extension portion 33 so as to be spaced apart from the first extension portion 331 .

Further, the outer cylindrical heat transfer holder 4 is arranged so that one end face 4a thereof contacts the other end face 32b of the stage portion 32 and the other end face 4b contacts one end face 332a of the second extension portion 332 of the extension portion 33. , is placed on the stage section 32 . By these contacts, one end surface 4a of the outer cylindrical heat transfer holder 4 is thermally connected to the stage portion 32, and the other end surface 4b of the outer cylindrical heat transfer holder 4 is connected to the extension portion 33 (second extension portion 332). Connected. That is, both ends of the outer cylindrical heat transfer holder 4 are thermally connected to the cold head 3 .

At both end portions of the outer cylindrical heat transfer holder 4, brim portions 41a and 41b are formed which are enlarged radially outward. The cross-sectional areas of the flanges 41a and 41b cut along a plane perpendicular to the central axis of the outer cylindrical heat transfer holder 4 are larger than the cross-sectional areas of the other portions. That is, the outer cylindrical heat transfer holder 4 is configured such that the cross-sectional area perpendicular to the central axis at both ends in the axial direction is larger than the cross-sectional area perpendicular to the central axis at the central portion in the axial direction. By fixing the collar portions 41a and 41b to the stage portion 32 and the second extension portion 332 by screwing or the like, both ends of the outer cylindrical heat transfer holder 4 are attached to the cold head 3 (the stage portion 32 and the extension portion 33). Combined.

Further, the outer cylindrical heat transfer holder 4 is made of a material having a heat shrinkage rate equal to or higher than that of the superconductor 1 . In this embodiment, the outer cylindrical heat transfer holder 4 is made of aluminum or an aluminum alloy. As is well known, the thermal contraction rate of aluminum or an aluminum alloy is about 1.7×10 ⁻⁵ /K, and this thermal contraction rate is comparable to the thermal contraction rate of a Re—Ba—Cu—O system superconductor (5 .7×10 ⁻⁶ /K). Therefore, in this embodiment, the thermal contraction rate of the outer cylindrical heat transfer holder 4 is greater than that of the superconductor 1 .

The vacuum insulation container 7 comprises an outer container 71 and an inner container 72 . The outer container 71 includes a cylindrical body portion 711 having an inner diameter larger than the outer diameter of the stage portion 32 of the cold head 3, and a body portion 711 extending radially outward from the lower end of the body portion 711 in FIG. It has a fixed portion 712 formed in a ring shape, and a cover portion 713 formed in a ring shape by radially extending radially inward from the upper end of the body portion 711 in FIG. A fixing portion 712 of the outer container 71 is airtightly fixed to the upper surface of the cooling device 2 . The body portion 711 extends upward in FIG. 1 from the fixed portion 712, and accommodates the cold head 3, the outer cylindrical heat transfer holder 4, and the superconductor 1 in the inner peripheral space thereof. It is arranged coaxially with the component. At this time, the cover portion 713 of the outer container 71 is arranged above the second extension portion 332 of the extension portion 33 of the cold head 3 with a predetermined gap therebetween.

As shown in FIG. 1, a circular hole 713a is formed in the center of the ring-shaped cover portion 713 so as to extend therethrough in the axial direction. The diameter of circular hole 713 a is slightly smaller than the inner diameter of superconductor 1 . Also, the central axis of the circular hole 713 a coincides with the central axis of the inner circumferential space of the superconductor 1 . The inner container 72 is inserted into the inner peripheral space of the body portion 711 through the circular hole 713a.

The inner container 72 has a bottomed cylindrical container portion 721 and a ring-shaped lid portion 722 extending radially outward from the open end of the container portion 721 . The outer diameter of the lid portion 722 is larger than the diameter of the circular hole 713 a provided in the cover portion 713 of the outer container 71 . Also, the outer diameter of the container portion 721 is equal to or slightly smaller than the diameter of the circular hole 713a. Then, the container portion 721 is inserted into the inner peripheral space of the main body portion 711 through the circular hole 713 a , and the lid portion 722 is placed on the upper surface of the cover portion 713 of the outer container 71 . Here, as described above, the central axis of the circular hole 713a coincides with the central axis of the inner circumferential space (bore) of the superconductor 1. FIG. Accordingly, the container portion 721 inserted into the inner peripheral space of the main body portion 711 enters the bore (inner peripheral space) of the superconductor 1 . That is, the container part 721 is arranged inside the bore of the superconductor 1 . A sample to be analyzed by, for example, an NMR device is placed in the space inside the container part 721 . A space in the container part 721 is provided substantially in the center of the bore of the superconductor 1 . This space is called the room temperature bore space.

1 of the container portion 721 of the inner container 72 and the inner peripheral wall surface of the cover portion 713 of the outer container 71 forming the circular hole 713a is sealed by sealing means (not shown). is sealed to As a result, the circular hole 713a formed in the cover portion 713 is closed. In addition, the fixing portion 712 of the outer container 71 of the vacuum insulation container 7 is airtightly fixed to the cooling device 2 as described above. Therefore, a sealed space is formed above the cooling device 2 in FIG. 1 by the vacuum insulation container 7 and the cooling device 2 . A superconductor 1, a cold head 3, and an outer cylindrical heat transfer holder 4 are arranged in this sealed space. The vacuum insulation container 7 is made of a non-magnetic material such as an aluminum alloy.

Next, a method of magnetizing the superconductor 1 and generating a magnetic field in the bore of the superconductor 1 using the superconducting magnetic field generator 101 having the above configuration will be described. This magnetic field generation method includes a decompression step, a magnetic field application step, a magnetic field cooling step, and a demagnetization step.

In the decompression step, the inside of the sealed space is evacuated using an exhaust device (not shown in FIG. 1). As a result, the air pressure in the sealed space is brought to a vacuum state of 0.1 Pa or less, for example.

In the magnetic field application step, an external magnetic field generator (not shown in FIG. 1) is operated to apply a magnetic field to the superconductor 1 at a temperature higher than the superconducting transition temperature Tc of the superconductor 1 (for example, room temperature). As a result, a magnetic field is formed in the space inside the bore of the superconductor 1 such that the magnetic flux passes along the axial direction of the superconductor 1 . Further, a magnetic field is applied to the space within the bore of the superconductor 1 such that the magnetic field intensity distribution is axially symmetrical and the magnetic field intensity within the room temperature bore space is uniformly distributed in the radial direction and the axial direction. .

In the magnetic field cooling step, the cooling device 2 is operated while the magnetic field is applied to the superconductor 1 by the operation of the external magnetic field generator. Thereby, the cooling device 2 generates cold heat, and the generated cold heat is transmitted to the cold head 3 . This causes the cold head 3 to generate cold heat. Also, the cold heat of the cold head 3 is transmitted from the stage portion 32 and the extension portion 33 of the cold head 3 to the superconductor 1 thermally connected to the cold head 3 . Thereby, the superconductor 1 is cooled to a temperature T0 below the superconducting transition temperature Tc, for example, 50K. When the temperature of the superconductor 1 is lowered to a temperature equal to or lower than the superconducting transition temperature Tc by cooling by the cooling device 2, the superconductor 1 is brought into a superconducting state.

Note that the magnetic field adjustment process may be performed during the magnetic field cooling process. In this magnetic field adjustment step, when the superconductor 1 is cooled to a temperature slightly higher than the superconducting transition temperature Tc of the superconductor 1 during the cooling step in the magnetic field, the external magnetic field generator is controlled to The applied magnetic field is adjusted so that a uniform magnetic field having a uniform magnetic field strength distribution in the axial and radial directions of the superconductor 1 is formed in the space. This magnetic field adjustment process cancels out the influence of the magnetization change that has occurred in the superconductor 1 on the applied magnetic field.

In the demagnetization step, the operation of the external magnetic field generator is stopped while the temperature of the superconductor 1 is maintained at a temperature T0 below the superconducting transition temperature Tc. This removes the magnetic field applied to the superconductor 1 that has been cooled to a temperature below the superconducting transition temperature Tc (that is, brought into a superconducting state). Then, a superconducting current is induced in the superconductor 1 so as to restore the state of the magnetic field in response to the change in magnetic field strength caused by the removal of the applied magnetic field. The superconducting current is a circular current that flows in a plane perpendicular to the central axis of the superconductor 1 with the central axis of the superconductor 1 as the center. A magnetic field is generated when the superconducting current thus induced flows through the superconductor 1 . That is, the superconductor 1 is magnetized. The magnetic field generated by magnetizing the superconductor 1 is basically the same magnetic field as the applied magnetic field generated by the operation of the external magnetic field generator. That is, the superconducting current flows through the superconductor 1, so that the superconductor 1 captures the applied magnetic field generated by the operation of the external magnetic field generator. A magnetic field is generated in the bore of the superconductor 1 by the superconductor 1 capturing an applied magnetic field. A magnetic field generated by magnetic field trapping is sometimes referred to as a trapped magnetic field.

As described above, the superconducting magnetic field generator 101 is configured to generate a magnetic field in the bore of the superconductor 1 through the magnetic field application process, the magnetic field cooling process, and the demagnetization process.

Next, a nuclear magnetic resonance apparatus using a trapped magnetic field generated by the superconducting magnetic field generator 101 will be briefly described. FIG. 2 is a diagram showing a schematic configuration of the nuclear magnetic resonance apparatus 110. As shown in FIG. A nuclear magnetic resonance apparatus 110 includes a superconducting magnetic field generator 101 , a detection coil 120 and analysis means 130 . The detection coil 120 is arranged inside the container portion 721 (inside the room temperature bore space) of the inner container 72 arranged inside the bore of the superconductor 1 . A sample P to be measured is arranged on the inner peripheral side of the detection coil 120 . Furthermore, a shim coil 91 is arranged on the outer peripheral side of the detection coil 120 in the room temperature bore space. The analysis means 130 also includes a radio frequency generator 131, a pulse programmer (transmitter) 132, a radio frequency amplifier 133, a preamplifier (signal amplifier) 134, a phase detector 135, an analog-to-digital (A/D) converter 136, and a computer. 137.

When the superconducting magnetic field generator 101 is activated, a trapping magnetic field is formed within the bore of the superconductor 1 as described above. Next, by adjusting the trapping magnetic field with the shim coils 91, the uniformity of the magnetic field strength of the trapping magnetic field is enhanced. At this time, the trapping magnetic field is adjusted by the shim coil 91 so that the uniformity of the magnetic field strength in the room temperature bore space is 1 ppm or less. Then, the sample P is placed in the room-temperature bore space in which the uniformity of the magnetic field intensity is enhanced. In this state, the high frequency generator 131 is activated. Then, a high-frequency pulse generated by the high-frequency generator 131 is passed through the pulse programmer 132 and the high-frequency amplifier 133 to energize the detection coil 120, and the sample P is irradiated with pulsed electromagnetic waves (radio waves). A weak electric current flows through the detection coil 120 provided around the sample P due to nuclear magnetic resonance that occurs when the sample P placed in a magnetic field is irradiated with radio waves. A signal (NMR signal) representing this minute current is transferred to the computer 137 via the preamplifier 134 , the phase detector 135 and the A/D converter 136 . Computer 137 calculates an NMR spectrum based on the passed NMR signal. The molecular structure of sample P is analyzed from the obtained NMR spectrum.

When analyzing the molecular structure of a sample using an NMR apparatus equipped with a superconducting magnetic field generator, if there is a large variation in the strength of the trapped magnetic field within the bore of the superconductor, the resulting NMR spectrum will be broad, allowing the molecular structure of the sample to be properly identified. I can't. Therefore, the superconducting magnetic field generator used in the NMR apparatus is preferably configured so as to be able to form a magnetic field (uniform magnetic field) with a uniform trapped magnetic field strength in the room-temperature bore space in which the sample is placed.

For high-resolution NMR measurement, high uniformity of magnetic field intensity variation of 1 ppm or less is required. A highly uniform magnetic field space with a magnetic field strength variation of 1 ppm or less can be achieved by adjusting the magnetic field with a shim coil (magnetic field correction coil), as described above. In other words, the variation in magnetic field intensity of the trapped magnetic field generated in the room-temperature bore space by the superconducting magnetic field generator must be at least on the order of ppm, which can be corrected by the shim coils.

In order to homogenize the trapped magnetic field in the room-temperature bore space, the magnetic field (applied magnetic field) applied to the room-temperature bore space in the magnetic field application step must be uniform, and the superconducting transition temperature Tc or less must be cooled. A high temperature uniformity of the superconductor 1 is also required. Therefore, it is preferable that the superconducting magnetic field generator be configured so that the superconductor 1 can be uniformly cooled.

However, in the conventional superconducting magnetic field generator, it is difficult to improve the uniformity of the temperature of the superconductor 1 during the magnetization of the superconductor. This will be explained first. FIG. 10 is a schematic diagram showing a cross section of a conventional superconducting magnetic field generator cut along a plane including the center line along the vertical direction. A superconducting magnetic field generator 100</b>C according to this example (conventional example) includes a superconductor 1 , a cooling device 2 , a cold head 3 , and a vacuum insulation container 7 . The configurations of the superconductor 1 and the vacuum insulation container 7 are the same as those of the superconducting magnetic field generator 101 according to the first embodiment. Also, the cold head 3 provided in the superconducting magnetic field generator 100</b>C has a shaft portion 31 and a stage portion 32 . These configurations are the same as those of the shaft portion 31 and the stage portion 32 of the cold head 3 of the superconducting magnetic field generator 101 according to the first embodiment. The superconducting magnetic field generator 100C also includes a holder H as a configuration corresponding to the outer cylindrical heat transfer holder 4 included in the superconducting magnetic field generator 101 according to the first embodiment.

As shown in FIG. 10, the superconductor 1 is formed in a cylindrical shape and placed on the stage portion 32 so that one end face 1a thereof contacts the other end face 32b (upper end) of the stage portion 32 of the cold head 3. be. Thus, cold head 3 is thermally connected to one end face 1a of superconductor 1. As shown in FIG. The holder H is made of an aluminum alloy and has a ring-shaped fixed portion H1, a cylindrical portion H2, and a disc-shaped lid portion H3 having a circular hole formed in the center. The holder H is placed on the stage portion 32 with the fixing portion H1 in contact with the other end face 32b of the stage portion 32 of the cold head 3. As shown in FIG. The cylindrical portion H2 is erected from the inner peripheral edge of the fixed portion H1 and covers the outer peripheral surface 1c of the superconductor 1. As shown in FIG. The lid portion H3 is formed radially inward from the upper end of the cylindrical portion H2 and covers the other end face 1b of the superconductor 1. As shown in FIG.

In obtaining a trapped magnetic field using the conventional superconducting magnetic field generator 100C, when the cooling device 2 is operated in the magnetic field cooling step, the superconductor 1 mainly comes into contact with the stage portion 32 of the cold head 3. It is cooled from the one end face 1a side. Further, since the aluminum alloy holder H is thermally connected to the stage portion 32 of the cold head 3, the holder H is also cooled in the magnetic field cooling process. Therefore, the holder H also cools the other end surface 1b of the superconductor 1, but since the holder H is cooled by the cold heat of the cold head 3, its cooling capacity is lower than that of the cold head 3. Therefore, the portion of superconductor 1 on the side of one end face 1a is sufficiently cooled, but the portion on the side of the other end face 1b is not sufficiently cooled. As a result, the temperature on the one end surface 1a side of the superconductor 1 is low, and the temperature on the other end surface 1b side is high. That is, the superconductor 1 is not uniformly cooled in the magnetic field cooling process. In particular, the superconductor 1 is not uniformly cooled along its axial direction, and there is a temperature distribution in the axial direction. In other words, the temperature uniformity in the axial direction of the superconductor 1 is low.

When the superconductor 1 is magnetized by performing the demagnetization step in a state in which the temperature uniformity in the axial direction of the superconductor 1 is low, and a trapped magnetic field is formed in the bore of the superconductor 1, the formed trapped magnetic field Uniformity is low. FIG. 11 shows the magnetic field intensity distribution in the bore in the axial direction of the superconductor 1 obtained when a trapped magnetic field is formed in the bore of the superconductor 1 using the conventional superconducting magnetic field generator 100C. 2 is a graph together with temperature distribution in the axial direction of . FIG. 11(a) is a graph showing the temperature distribution in the axial direction of the superconductor 1 cooled in the magnetic field cooling process, where the vertical axis is the axial position Z of the superconductor 1 and the horizontal axis is the temperature T. . FIG. 11(b) is a diagram showing the distribution in the axial direction of the superconductor 1 of the strength of the trapped magnetic field formed in the bore by performing the demagnetization process. The axis is the magnetic field strength B in the bore. FIG. 11(c) is a schematic diagram of the superconductor 1 corresponding to the vertical axis (axial position) of each graph described above. In FIG. 11, the axial position of one end face 1a of superconductor 1 corresponds to the position Z=0, and the position of the other end face 1b of superconductor 1 corresponds to the position Z=h.

As shown in FIG. 11(a), the temperature T increases as the axial position Z of the superconductor 1 increases, that is, as the superconductor 1 moves from one end surface 1a toward the other end surface 1b. That is, the temperature uniformity in the axial direction of the superconductor 1 is low. Further, as shown in FIG. 11(b), along the axial direction of the superconductor 1, there is almost no region where the trapping magnetic field strength B is constant. It can be seen that the trapping magnetic field strength B decreases as the directional position Z increases. That is, the trapped magnetic field strength along the axial direction of the superconductor 1 is not uniform. Therefore, the trapped magnetic field strength in the room temperature bore space is also not uniform. Alternatively, the region where the magnetic field strength is uniform within the room temperature bore space is extremely narrow. Therefore, when a sample is analyzed by an NMR apparatus using the conventional superconducting magnetic field generator 100C, the NMR spectrum becomes broad due to the nonuniformity of the trapped magnetic field strength in the room temperature bore space, and sufficiently accurate analysis is performed. can't do Alternatively, many shim coils must be incorporated into the room temperature bore space to homogenize the magnetic field strength within the room temperature bore space, resulting in insufficient sample space within the room temperature bore space.

Regarding this point, according to the superconducting magnetic field generator 101 according to the first embodiment, the superconductor 1 can be cooled substantially uniformly in the magnetic field cooling step. In the superconducting magnetic field generator 101 according to the first embodiment, the cold head 3 has the stage portion 32 and the extension portion 33 as described above. Stage portion 32 is thermally connected to one end surface 1 a of superconductor 1 , and extension portion 33 (second extension portion 332 ) is thermally connected to the other end surface 1 b of superconductor 1 . That is, cold head 3 is thermally connected to both ends of superconductor 1 . Therefore, in the magnetic field cooling process, superconductor 1 is cooled from one end face 1a by stage portion 32 of cold head 3, and is cooled from the other end face 1b by extension portion 33 of cold head 3. FIG. That is, the superconductor 1 is cooled from both ends. In other words, the cold head 3 is configured such that the superconductor 1 is cooled from both ends in the axial direction by cold heat from the cold head 3 . By cooling the superconductor 1 from both ends, the superconductor 1 is evenly cooled along its axial direction. Therefore, the axial temperature uniformity of the superconductor 1 is enhanced.

Furthermore, the superconducting magnetic field generator 101 according to this embodiment includes an outer cylindrical heat transfer holder 4 . One end surface 4a of the outer cylindrical heat transfer holder 4 is in contact with the stage portion 32 of the cold head 3, and the other end surface 4b is in contact with the extended portion 33 (second extended portion 332) of the cold head 3. That is, both end surfaces of the outer cylindrical heat transfer holder 4 are thermally connected to the cold head 3 . Therefore, the outer cylindrical heat transfer holder 4 is cooled from both ends thereof by the cold head 3 in the cooling process in the magnetic field. Therefore, the outer cylindrical heat transfer holder 4 is uniformly cooled along the axial direction. The outer peripheral surface 1c of the superconductor 1 is thermally connected to the inner peripheral surface 4d of the outer cylindrical heat transfer holder 4 which is uniformly cooled along the axial direction. Therefore, the superconductor 1 is uniformly cooled along the axial direction also from the outer peripheral surface 1c.

In FIG. 1, arrows indicate the flow of heat from the superconductor 1 when the superconductor 1 according to this embodiment is cooled in the magnetic field cooling process. As can be seen from FIG. 1, the heat of the superconductor 1 flows out from one end surface 1a, the other end surface 1b, and the outer peripheral surface 1c. Since the superconductor 1 is cooled from many surfaces in this way, the superconductor 1 is uniformly cooled.

FIG. 3 shows the magnetic field strength distribution in the bore in the axial direction of the superconductor 1 obtained when the trapped magnetic field is formed in the bore of the superconductor 1 using the superconducting magnetic field generator 101 according to the first embodiment. 3 is a graph together with temperature distribution in the axial direction of the body 1. FIG. FIG. 3(a) is a graph showing the temperature distribution in the axial direction of the superconductor 1 cooled in the magnetic field cooling process, where the vertical axis is the axial position Z of the superconductor 1 and the horizontal axis is the temperature T. . FIG. 3(b) is a diagram showing the distribution in the axial direction of the superconductor 1 of the trapped magnetic field trapped in the demagnetization process, where the vertical axis is the axial position Z of the superconductor 1 and the horizontal axis is the strength of the supplemental magnetic field. It is B. FIG. 3(c) is a schematic diagram of the superconductor 1 corresponding to the vertical axis of each graph described above. As shown in FIG. 3, the axial position of one end face 1a of superconductor 1 corresponds to the position Z=0, and the position of the other end face 1b of superconductor 1 corresponds to the position Z=h. FIG. 3(c) shows the direction of the superconducting current flowing through the superconductor 1 and the direction of the magnetic field formed in the bore of the superconductor 1 by performing the demagnetization process. According to FIG. 3( c ), the superconducting current flows in a direction perpendicular to the axial direction of the superconductor 1 . Also, the direction of the magnetic field in the bore is upward.

As shown in FIG. 3(a), the temperature T of the superconductor 1 is substantially constant along the axial direction. That is, the temperature uniformity in the axial direction of the superconductor 1 is high. Further, as shown in FIG. 3(b), the magnetic field intensity B is substantially constant in the regions along the axial direction of the superconductor 1, excluding both end portions. That is, the trapping magnetic field intensity along the axial direction of the superconductor 1 is uniform. Therefore, the trapped magnetic field strength in the room temperature bore space is also uniform. Therefore, by using the superconducting magnetic field generator 101 according to the first embodiment in the NMR apparatus, the trapped magnetic field space in the room-temperature bore space becomes a uniform magnetic field. Therefore, sufficiently accurate analysis can be performed. Alternatively, the number of shim coils used to improve the homogeneity of the supplemental magnetic field space in the room temperature bore space can be reduced, thereby ensuring a sufficiently large sample space within the room temperature bore space.

As described above, the cold head 3 included in the superconducting magnetic field generator 101 according to the first embodiment is configured such that the superconductor 1 is cooled from both ends in the axial direction by cold heat from the cold head 3 . Specifically, the cold head 3 includes a stage portion 32 thermally connected to one end face 1a of the superconductor 1, and a stage portion 32 thermally connected to the stage portion 32 and thermally connected to the other end face 1b of the superconductor 1. and an extension 33 connected to the . Therefore, since the superconductor 1 is cooled from both ends in the magnetic field cooling step, the temperature uniformity in the axial direction of the superconductor 1 can be improved when the superconductor 1 is magnetized.

The superconducting magnetic field generator 101 according to the first embodiment also includes an outer cylindrical heat transfer holder 4 . The outer cylindrical heat transfer holder 4 also cools the superconductor 1 from its outer peripheral surface 1c during the magnetic field cooling step. Therefore, the temperature uniformity of the superconductor can be further improved.

Also, the thermal contraction rate of the outer cylindrical heat transfer holder 4 is greater than the thermal contraction rate of the superconductor 1 . Therefore, when the superconductor 1 and the outer cylindrical heat transfer holder 4 are cooled in the cooling process in the magnetic field, the thermal contraction amount of the outer cylindrical heat transfer holder 4 is larger than that of the superconductor 1. , the superconductor 1 is clamped to the outer cylindrical heat transfer holder 4 from its outer peripheral surface 1c side. This tightening force acts on the superconductor 1 as compressive stress. Therefore, the superconductor 1 undergoes the demagnetization process while receiving compressive stress from the outer cylindrical heat transfer holder 4 .

Here, when the applied magnetic field is removed in the demagnetization step and the superconductor 1 is magnetized, an electromagnetic stress (hoop force) acts on the superconductor 1 . This electromagnetic stress acts in a direction that pulls the superconductor 1 radially outward. In response to this electromagnetic stress, the compressive stress from the outer cylindrical heat transfer holder 4 described above acts on the superconductor 1 in the direction opposite to the electromagnetic stress. Therefore, the electromagnetic stress is canceled by the compressive stress. By canceling out the electromagnetic stress in this way, the superconductor 1 is effectively prevented from being damaged by the electromagnetic stress.

Moreover, the magnitude of the above-described electromagnetic stress is greater at both end portions than at the central portion in the axial direction of the superconductor 1 . Here, flanges 41a and 41b are provided at both end portions of the outer cylindrical heat transfer holder 4 according to this embodiment. Therefore, the cross-sectional area perpendicular to the axial direction at both ends of the outer cylindrical heat transfer holder 4 in the axial direction is larger than the cross-sectional area perpendicular to the axial direction at the central portion in the axial direction. Therefore, the strength of both end portions of the outer cylindrical heat transfer holder 4 is higher than the strength of the central portion in the axial direction. Therefore, the superconductor 1 is sufficiently reinforced by the outer cylindrical heat transfer holder 4 having a large cross-sectional area at both ends and a high strength against the electromagnetic stress acting on both ends of the superconductor 1 in the axial direction. As a result, the effect of reinforcing the entire superconductor 1 can be enhanced.

Also, the heat transferred from the superconductor 1 to the outer cylindrical heat transfer holder 4 in the cooling process in the magnetic field is transferred from both ends of the outer cylindrical heat transfer holder 4 to the cold head 3 . In this case, since the flanges 41a and 41b are formed at both ends of the outer cylindrical heat transfer holder 4, respectively, and the cross-sectional areas of the both ends are large, the large cross-sectional areas are utilized to efficiently dissipate heat. It can be handed over to the coldhead 3 . In other words, heat sweep is good. Thereby, the superconductor 1 can be cooled more uniformly.

(Second embodiment)
Next, a second embodiment of the present invention will be described. It has the same configuration as the superconducting magnetic field generator 101 . The following description focuses on the configuration that is different from the superconducting magnetic field generator 101 according to the first embodiment.

FIG. 4 is a schematic diagram showing a cross section of the superconducting magnetic field generator 102 according to the second embodiment taken along a plane including the center line along the vertical direction. As shown in FIG. 4, the superconducting magnetic field generator 102 according to the second embodiment includes a superconductor 1, a cooling device 2, a cold head 3, an outer cylindrical A heat transfer holder 4 and a vacuum insulation container 7 are provided.

The superconducting magnetic field generator 102 also includes an inner cylindrical heat transfer holder 5 . The inner cylindrical heat transfer holder 5 is arranged on the inner peripheral side of the superconductor 1 so as to hold the superconductor 1 from the inner peripheral side of the superconductor 1 . The inner cylindrical heat transfer holder 5 is made of a non-magnetic material with high thermal conductivity. In this embodiment, the inner cylindrical heat transfer holder 5 is made of aluminum or an aluminum alloy.

The inner cylindrical heat transfer holder 5 is formed in a cylindrical shape and has one end surface 5a and the other end surface 5b in the axial direction, an outer peripheral surface 5c, and an inner peripheral surface 5d. The outer diameter of the inner cylindrical heat transfer holder 5 is substantially equal to the inner diameter of the superconductor 1, and the inner diameter of the inner cylindrical heat transfer holder 5 is equal to the inner diameter of the second extension 332 of the cold head 3 (that is, the second extension 332 is equal to the diameter of the circular hole 333 provided in the center of the . The axial length of the inner cylindrical heat transfer holder 5 is equal to the axial length of the superconductor 1 . The inner cylindrical heat transfer holder 5 is arranged with respect to the superconductor 1 so that the outer peripheral surface 5c of the inner cylindrical heat transfer holder 5 is in contact with the inner peripheral surface 1d of the superconductor 1 . The contact between the outer peripheral surface 5c of the inner cylindrical heat transfer holder 5 and the inner peripheral surface 1d of the superconductor 1 thermally connects the outer peripheral surface 5c of the inner cylindrical heat transfer holder 5 to the inner peripheral surface 1d of the superconductor 1. be done.

Also, in the superconducting magnetic field generator 102 , the inner diameter of the second extension portion 332 is smaller than the inner diameter of the superconductor 1 . Therefore, when the other end face 1b of the superconductor 1 and the one end face 332a of the second extension portion 332 are arranged coaxially so that they are in contact with each other, the difference in inner diameter between the second extension portion 332 and the superconductor 1 causes the second extension portion A portion of 332 close to the inner peripheral side protrudes slightly radially inward from the inner peripheral surface 1d of the superconductor 1 in a ring shape. Then, the other end surface 5b of the inner cylindrical heat transfer holder 5 comes into contact with the one end surface 332a of the portion of the second extension portion 332 protruding radially inward from the inner circumference of the superconductor 1 in a ring shape as described above. do. One end face 5 a of the inner cylindrical heat transfer holder 5 contacts the other end face 32 b of the stage portion 32 of the cold head 3 . In this manner, the inner cylindrical heat transfer holder 5 is arranged on the inner peripheral side of the superconductor 1 so that the outer peripheral surface 5c thereof is thermally connected to the inner peripheral surface 1d of the superconductor 1, and One end surface 5a is thermally connected to the stage portion 32, and the other end surface is thermally connected to the extension portion 33 (second extension portion 332).

Of the configuration of the superconducting magnetic field generator 102 according to the second embodiment, the configuration other than the configuration described above is the same as the configuration of the superconducting magnetic field generator 101 according to the first embodiment. Therefore, detailed description of those configurations will be omitted.

According to the superconducting magnetic field generating apparatus 102 according to the second embodiment, as in the superconducting magnetic field generating apparatus 101 according to the first embodiment, the cold head 3 is configured such that the superconductor 1 is moved to both ends in the axial direction by cold heat from the cold head 3. configured to be cooled from Specifically, the cold head 3 includes a stage portion 32 thermally connected to one end face 1a of the superconductor 1, and a stage portion 32 thermally connected to the stage portion 32 and thermally connected to the other end face 1b of the superconductor 1. and an extension 33 connected to the . Therefore, since the superconductor 1 is cooled from both ends in the cooling step in the magnetic field, the temperature uniformity in the axial direction of the superconductor 1 can be enhanced when the superconductor 1 is magnetized.

Also, the superconducting magnetic field generator 102 according to the second embodiment includes the inner cylindrical heat transfer holder 5 . One end surface 5 a of the inner cylindrical heat transfer holder 5 is thermally connected to the stage portion 32 , and the other end surface 5 b is thermally connected to the extension portion 33 . Therefore, the inner cylindrical heat transfer holder 5 is cooled from both ends thereof by the cold head 3 in the cooling process in the magnetic field. Therefore, the inner cylindrical heat transfer holder 5 is uniformly cooled along the axial direction. The inner peripheral surface 1d of the superconductor 1 is thermally connected to the outer peripheral surface 5c of the inner cylindrical heat transfer holder 5 which is uniformly cooled along the axial direction. Therefore, the superconductor 1 is uniformly cooled along the axial direction also from the inner peripheral surface 1d. Therefore, the uniformity of the temperature of the superconductor 1 can be further improved.

Further, according to the superconducting magnetic field generator 102 according to the second embodiment, the outer peripheral surface 1c of the superconductor 1 is located on the inner peripheral surface 4d of the outer cylindrical heat transfer holder 4, and the inner peripheral surface 1d of the superconductor 1 is located on the inner cylindrical surface. Both end surfaces of the superconductor 1 are thermally connected to the cold head 3 on the outer peripheral surface 5 c of the heat transfer holder 5 . That is, the entire surface of superconductor 1 is thermally connected to the cold head or heat transfer holder. Therefore, the superconductor 1 can be cooled from its entire surface. Therefore, when the superconductor 1 is cooled in the magnetic field cooling process, the heat of the superconductor 1 flows out from all the surfaces as indicated by the arrows in FIG. Therefore, the superconductor 1 can be cooled more uniformly, and the cooling efficiency is improved.

Further, according to the superconducting magnetic field generator 102 according to the second embodiment, by providing the inner cylindrical heat transfer holder 5 on the inner peripheral side of the superconductor 1 , the inner cylindrical heat transfer holder 5 is provided between the room temperature bore space and the superconductor 1 . A heat transfer holder 5 is interposed. This prevents radiant heat from the room-temperature bore space from being directly transferred to the superconductor 1 . As a result, it is possible to suppress the temperature rise of the superconductor 1 due to heat radiation from the room-temperature bore space.

(Third embodiment)
Next, a third embodiment of the present invention will be described. The superconducting magnetic field generator according to this embodiment is basically the same as that of the first embodiment, except that the shape of the outer cylindrical heat transfer holder is different. It has the same configuration as the superconducting magnetic field generator 101 . The following description focuses on the configuration that is different from the superconducting magnetic field generator 101 according to the first embodiment.

FIG. 5 is a schematic diagram showing a cross section of the superconducting magnetic field generator 103 according to the third embodiment taken along a plane including the center line along the vertical direction. As shown in FIG. 5, the superconducting magnetic field generator 103 according to the third embodiment includes an outer cylindrical heat transfer holder 4A. As with the outer cylindrical heat transfer holder 4 according to the first embodiment, the outer cylindrical heat transfer holder 4A is formed in a cylindrical shape and has one end surface 4a and the other end surface 4b in the axial direction, an outer peripheral surface 4c, an inner It has a peripheral surface 4d. Further, the axial length of the outer cylindrical heat transfer holder 4A is equal to the axial length of the superconductor 1 . One end surface 4a of the outer cylindrical heat transfer holder 4A is thermally connected to the stage portion 32 of the cold head 3, and the other end surface 4b of the outer cylindrical heat transfer holder 4A is connected to the extended portion 33 (second It is thermally connected to the extension 332).

Further, in this embodiment, the outer cylindrical heat transfer holder 4A has a first portion 41A, a second portion 42A, and a third portion 43A, and these portions extend axially from one end face 4a toward the other end face 4b. They are formed in this order along the direction.

The second portion 42A forms a central region in the axial direction of the outer cylindrical heat transfer holder 4A, and the outer diameter of the second portion 42A is constant along the axial direction. The first portion 41A is a portion that forms an end region closer to the one end surface 4a of the outer cylindrical heat transfer holder 4A than the second portion 42A. It is a portion forming an end region on the side of the other end surface 4b of the heat transfer holder 4A.

The outer diameter of the portion of the first portion 41A connected to the second portion 42A is equal to the outer diameter of the second portion 42A. Similarly, the outer diameter of the portion of the third portion 43A connected to the second portion 42A is equal to the outer diameter of the second portion 42A. The first portion 41A is tapered so that the outer diameter increases as it approaches the one end surface 4a from the portion connected to the second portion 42A, and the third portion 43A is connected to the second portion 42A. It is formed in a tapered shape so that the outer diameter increases as it approaches the other end face 4b from the tapered portion. In other words, the outer cylindrical heat transfer holder 4A is formed so that the outer diameter at the ends thereof is larger than the outer diameter at the central portion in the axial direction.

Moreover, the inner diameters of the first portion 41A, the second portion 42A, and the third portion 43A are constant along the axial direction, and these inner diameters are substantially equal to the outer diameter of the superconductor 1 . Therefore, the outer cylindrical heat transfer holder 4A is formed such that the cross-sectional area perpendicular to the axial direction is the smallest at the axial center portion, and the cross-sectional area increases from the center portion toward the end portions.

The outer cylindrical heat transfer holder 4A is arranged with respect to the superconductor 1 so that the inner peripheral surface 4d thereof contacts the outer peripheral surface 1c of the superconductor 1. As shown in FIG. Due to the contact between the inner peripheral surface 4d of the outer cylindrical heat transfer holder 4A and the outer peripheral surface 1c of the superconductor 1, the inner peripheral surface 4d of the outer cylindrical heat transfer holder 4A is thermally connected to the outer peripheral surface 1c of the superconductor 1. be done. At this time, the outer cylindrical heat transfer holder 4 is arranged on the inner peripheral side of the first extension portion 331 of the extension portion 33 so as to be spaced apart from the first extension portion 331 . In the superconducting magnetic field generator 103 according to the third embodiment, the configuration other than the outer cylindrical heat transfer holder 4A is the same as each configuration of the superconducting magnetic field generator 101 according to the first embodiment. Description is omitted.

According to the superconducting magnetic field generating device 103 according to the third embodiment, as in the superconducting magnetic field generating device 101 according to the first embodiment, the cold head 3 is configured so that the superconductor 1 is moved to both ends in the axial direction by cold heat from the cold head 3. configured to be cooled from Specifically, the cold head 3 includes a stage portion 32 thermally connected to one end face 1a of the superconductor 1, and a stage portion 32 thermally connected to the stage portion 32 and thermally connected to the other end face 1b of the superconductor 1. and an extension 33 connected to the . Therefore, since the superconductor 1 is cooled from both ends in the cooling step in the magnetic field, the temperature uniformity in the axial direction of the superconductor 1 can be enhanced when the superconductor 1 is magnetized.

Further, the outer cylindrical heat transfer holder 4A is thermally connected to the outer peripheral surface 1c of the superconductor 1 at its inner peripheral surface 4d. Therefore, in the magnetic field cooling process, the heat of the superconductor 1 is transferred from the outer peripheral surface 1c to the first portion 41A, the second portion 42A, and the third portion 43A of the outer cylindrical heat transfer holder 4A. . In this case, the heat transferred to the second portion 42A of the outer cylindrical heat transfer holder 4A flows to the portions on both end sides of the outer cylindrical heat transfer holder 4A, that is, the first portion 41A or the third portion 43A. portion to the cold head 3 (stage portion 32 or extension portion 33). Therefore, in the first portion 41A and the third portion 43A, the heat directly transferred from the outer peripheral surface 1c of the superconductor 1 to these portions and the heat transferred from the first portion 41A join. Therefore, if the cross-sectional areas of the first portion 41A and the third portion 43A are small, the amount of heat passing through these portions may exceed the transport capacity of these portions. In such a case, the transfer of heat from the second portion 42A to the first portion 41A or the third portion 43A is hindered, and as a result, the central portion of the superconductor 1 in the axial direction may not be sufficiently cooled.

Regarding this point, in the present embodiment, the cross-sectional area perpendicular to the axial direction of the first portion 41A and the third portion 43A constituting both end portions of the outer cylindrical heat transfer holder 4A is equal to that of the central portion of the outer cylindrical heat transfer holder 4A. is larger than the cross-sectional area perpendicular to the axial direction of the second portion 42A constituting the . Therefore, the heat transport capacity at both end portions of the outer cylindrical heat transfer holder 4A is improved. That is, according to this embodiment, the heat dissipation of the outer cylindrical heat transfer holder 4A is improved. Therefore, it is possible to prevent the above-described stagnation of heat transport, thereby sufficiently cooling even the central portion in the axial direction of the superconductor 1 . As a result, the axial temperature uniformity of the superconductor 1 can be further enhanced when the superconductor 1 is magnetized.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. The superconducting magnetic field generating apparatus according to this embodiment is basically the same as the superconducting magnetic field generating apparatus 101 according to the first embodiment, except that a reinforcing ring is provided. They have the same configuration. The following description focuses on the configuration that is different from the superconducting magnetic field generator 101 according to the first embodiment.

FIG. 6 is a schematic diagram showing a cross section of the superconducting magnetic field generator 104 according to the fourth embodiment taken along a plane including the center line along the vertical direction. As shown in FIG. 6, the superconducting magnetic field generator 104 according to the fourth embodiment includes a reinforcing ring 8 as a reinforcing member for reinforcing the superconductor 1. As shown in FIG.

In this embodiment, the reinforcing ring 8 is composed of six cylindrical ring members (first ring member 81, second ring member 82, third ring member 83, fourth ring member 84, fifth ring member 85, third ring member 85). The six ring members 86) are coaxially stacked in this order along the axial direction to form a cylindrical shape. The outer peripheral surfaces of the six ring members form the outer peripheral surface 8c of the reinforcing ring 8, and the inner peripheral surfaces of the six ring members form the inner peripheral surface 8d of the reinforcing ring 8. As shown in FIG. One end surface 8a of the reinforcing ring 8 is formed by the end surface of the first ring member 81 facing downward in FIG. 6, and the other end surface 8b of the reinforcing ring 8 is formed by the end surface of the sixth ring member 86 facing upward in FIG. be done.

In addition, the superconducting magnetic field generator 104 includes the superconductor 1 and the outer cylindrical heat transfer holder 4 in the same manner as the superconducting magnetic field generator 101 according to the first embodiment. larger than the outer diameter of body 1; Therefore, when the outer cylindrical heat transfer holder 4 is arranged coaxially with the outer circumference of the superconductor 1, a cylindrical space is formed between the inner peripheral surface 4d of the outer cylindrical heat transfer holder 4 and the outer peripheral surface 1c of the superconductor 1. is formed. A reinforcing ring 8 is arranged in this cylindrical space.

Also in the fourth embodiment, as in the first embodiment, the superconductor 1 includes six cylindrical superconducting bulks (first superconducting bulk 11, second superconducting bulk 12, third superconducting bulk 13, fourth superconducting bulk It is formed by stacking a superconducting bulk 14, a fifth superconducting bulk 15, and a sixth superconducting bulk 16) in this order along the axial direction. And six ring members (81, 82, 83, 84, 85, 86) constituting the reinforcing ring 8 are attached to each of the six superconducting bulks (11, 12, 13, 14, 15, 16), They can be installed accordingly. Specifically, the first ring member 81 is attached to the first superconducting bulk 11, the second ring member 82 is attached to the second superconducting bulk 12, the third ring member 83 is attached to the third superconducting bulk 13, A fourth ring member 84 is attached to the fourth superconducting bulk 14 , a fifth ring member 85 is attached to the fifth superconducting bulk 15 , and a sixth ring member 86 is attached to the sixth superconducting bulk 16 .

At this time, the inner peripheral surface of the first ring member 81 contacts the outer peripheral surface of the first superconducting bulk 11, the inner peripheral surface of the second ring member 82 contacts the outer peripheral surface of the second superconducting bulk 12, and the third ring The inner peripheral surface of the member 83 contacts the outer peripheral surface of the third superconducting bulk 13, the inner peripheral surface of the fourth ring member 84 contacts the outer peripheral surface of the fourth superconducting bulk 14, and the inner peripheral surface of the fifth ring member 85. is in contact with the outer peripheral surface of the fifth superconducting bulk 15, and the inner peripheral surface of the sixth ring member 86 is in contact with the outer peripheral surface of the sixth superconducting bulk 16. be. Further, the outer peripheral surface of each ring member contacts the inner peripheral surface 4 d of the outer cylindrical heat transfer holder 4 . Therefore, the reinforcement ring 8 made up of six ring members has an inner peripheral surface 8d that contacts the outer peripheral surface 1c of the superconductor 1 that is made up of six superconducting bulks, and an outer peripheral surface 8c that contacts the outer peripheral surface 1c. It is arranged between the superconductor 1 and the outer cylindrical heat transfer holder 4 so as to contact the inner peripheral surface 4 d of the cylindrical heat transfer holder 4 .

The lower end surface of the first ring member 81 forming the one end surface 8a of the reinforcing ring 8 is in contact with the other end surface 32b of the stage portion 32 of the cold head 3, and the sixth ring forming the other end surface 8b of the reinforcing ring 8. The upper end surface of the member 86 is in contact with one end surface 332 a of the second extension portion 332 of the extension portion 33 of the cold head 3 . Therefore, one end face 8a of the reinforcing ring 8 is thermally connected to the stage portion 32 (cold head 3), and the other end face 8b is thermally connected to the extension portion 33 (cold head 3). Configured.

The reinforcing ring 8 is made of a material having a thermal shrinkage rate greater than that of the superconductor 1 . That is, the thermal contraction rate of the reinforcing ring 8 is greater than or equal to that of the superconductor 1 . In this embodiment, the reinforcing ring 8 is made of aluminum or an aluminum alloy. The thermal contraction rate of aluminum or an aluminum alloy is greater than that of a Re--Ba--Cu--O system superconductor. That is, in the present embodiment, the thermal contraction rate of the reinforcing ring 8 is greater than that of the superconductor 1 . Moreover, the reinforcing ring 8 is preferably made of a material having a thermal contraction rate equal to or lower than that of the outer cylindrical heat transfer holder 4 . That is, the thermal contraction rate of the outer cylindrical heat transfer holder 4 is preferably greater than that of the reinforcing ring 8 . In this embodiment, the outer cylindrical heat transfer holder 4 is made of the same material as the reinforcing ring 8 (aluminum or aluminum alloy). Therefore, the thermal contraction rate of the outer cylindrical heat transfer holder 4 and the thermal contraction rate of the reinforcing ring 8 are equal.

Of the configurations of the superconducting magnetic field generator 104 according to the fourth embodiment, configurations other than those described above are the same as the configurations of the superconducting magnetic field generator 101 according to the first embodiment. Therefore, detailed description thereof will be omitted.

According to the superconducting magnetic field generating device 104 according to the fourth embodiment, as in the superconducting magnetic field generating device 101 according to the first embodiment, the cold head 3 is configured such that the superconductor 1 is cooled to both ends in the axial direction by cold heat from the cold head 3 . configured to be cooled from Specifically, the cold head 3 includes a stage portion 32 thermally connected to one end face 1a of the superconductor 1, and a stage portion 32 thermally connected to the stage portion 32 and thermally connected to the other end face 1b of the superconductor 1. and an extension 33 connected to the . Therefore, since the superconductor 1 is cooled from both ends in the cooling step in the magnetic field, the temperature uniformity in the axial direction of the superconductor 1 can be enhanced when the superconductor 1 is magnetized.

A reinforcing ring 8 is provided in contact with the outer peripheral surface 1c of the superconductor 1. One end surface 8a of the reinforcing ring 8 is thermally connected to the stage portion 32 of the cold head 3, and the other end surface 8b is the cold head. It is thermally connected to the extension 33 of the head 3 . Therefore, the reinforcing ring 8 is uniformly cooled along the axial direction in the cooling process in the magnetic field. Therefore, the superconductor 1 is cooled by the reinforcing ring 8 not only from the one end surface 1a and the other end surface 1b but also from the outer peripheral surface 1c. Thereby, the uniformity of the temperature of the superconductor 1 can be further improved.

Further, since the reinforcing ring 8 is arranged on the outer peripheral side of the superconductor 1 in contact with the outer peripheral surface 1c of the superconductor 1, the electromagnetic stress generated when the superconductor 1 is magnetized by performing the demagnetization process The reinforcing ring 8 reinforces the superconductor 1 against (hoop force). Therefore, damage to the superconductor 1 caused by electromagnetic stress can be effectively prevented.

Further, since the thermal contraction rate of the reinforcing ring 8 is larger than that of the superconductor 1, when the reinforcing ring 8 is cooled together with the superconductor 1 in the cooling process in the magnetic field, the reinforcing ring 8 is The superconductor 1 is tightened by the reinforcing ring by shrinking more than the above. Therefore, the superconductor 1 receives a greater compressive stress from the reinforcing ring 8, and the compressive stress thus received cancels out the electromagnetic stress, thereby more effectively preventing damage to the superconductor 1 caused by the electromagnetic stress. can do. In addition, according to this embodiment, the outer cylindrical heat transfer holder 4 is provided on the outer peripheral side of the reinforcing ring 8 . The thermal contraction rate of the outer cylindrical heat transfer holder 4 is the same as that of the reinforcing ring 8 and larger than that of the superconductor 1 . Therefore, in the magnetic field cooling process, the superconductor 1 is double reinforced by the compressive stress from the outer cylindrical heat transfer holder 4 and the compressive stress from the reinforcing ring 8 . Therefore, the effect of reinforcing the electromagnetic stress (hoop force) generated when the superconductor 1 is magnetized can be further enhanced.

(Fifth embodiment)
Next, a fifth embodiment of the invention will be described. The superconducting magnetic field generator according to the fifth embodiment differs from the superconducting magnetic field generator 101 according to the first embodiment in the structure of the heat transfer holder that holds the superconductor 1 . The following description will focus on the differences.

FIG. 7 is a schematic diagram showing a cross section of the superconducting magnetic field generator 105 according to the fifth embodiment taken along a plane including the center line along the vertical direction. As shown in FIG. 7, the superconducting magnetic field generator 105 includes a superconductor 1, a cooling device 2, a cold head 3, and a vacuum insulation container 7, like the superconducting magnetic field generator 101 according to the first embodiment. Prepare. The structures of the superconductor 1, the cooling device 2, and the vacuum insulation container 7 are the same as those of the superconductor 1, the cooling device 2, and the vacuum insulation container 7 provided in the superconducting magnetic field generator according to the first embodiment. Therefore, detailed description of these structures is omitted.

Also, the cold head 3 according to this embodiment has a stage portion 32 and an extension portion 34 . The structure of the stage section 32 is the same as that of the stage section 32 included in the superconducting magnetic field generator 101 according to the first embodiment. The extension part 34 is formed in a cylindrical shape like the first extension part 331 of the extension part 33 provided in the superconducting magnetic field generator 101 according to the first embodiment, and has one end surface 34a (lower end surface) in the axial direction and the opposite end surface 34a. side other end surface 34b (upper end surface), an outer peripheral surface 34c, and an inner peripheral surface 34d. The outer diameter of the extension portion 34 is substantially equal to the outer diameter of the stage portion 32 , and the inner diameter of the extension portion 34 is larger than the outer diameter of the superconductor 1 . Further, the axial length of the extension portion 34 is slightly longer than half the axial length of the superconductor 1 . The extension portion 34 is coaxially mounted on the stage portion 32 so that one end surface 34a of the extension portion 34 contacts a portion of the other end surface 32b of the stage portion 32 near the outer periphery. As a result, the one end surface 34 a of the extension portion 34 is thermally connected to the stage portion 32 .

Further, the superconducting magnetic field generator 105 according to the present embodiment does not include the outer cylindrical heat transfer holder 4 included in the superconducting magnetic field generator 101 according to the first embodiment, and instead includes a pair of cup-shaped heat transfer holders 6 Prepare. The pair of cup-shaped heat transfer holders 6 is composed of a first cup-shaped heat transfer holder 61 and a second cup-shaped heat transfer holder 62 . The pair of cup-shaped heat transfer holders 6 are made of a non-magnetic material with high thermal conductivity. In this embodiment, the pair of cup-shaped heat transfer holders 6 are made of aluminum or an aluminum alloy.

The first cup-shaped heat transfer holder 61 has a cup shape, and includes a first bottom wall portion 611 forming a bottom portion, a first side wall portion 612 forming a side wall portion, and a first heat transfer holder formed near the opening surface. It has one connection 613 . The first bottom wall portion 611 is formed in a disc shape having an inner side surface 611a and an outer side surface 611b on the opposite side. A circular hole is formed in the center of the first bottom wall portion 611 so as to penetrate in the axial direction from the inner side surface 611a to the outer side surface 611b. The diameter of this circular hole is approximately the same as the inner diameter of the superconductor 1 . The first side wall portion 612 is formed in a cylindrical shape having an outer peripheral surface 612c and an inner peripheral surface 612d. One end of the first side wall portion 612 is connected to the peripheral edge of the first bottom wall portion 611 . Thereby, the first side wall portion 612 is erected upward from the peripheral edge of the first bottom wall portion 611 in FIG. The axial length of the inner peripheral surface 612 d of the cylindrical first side wall portion 612 is half the axial length of the superconductor 1 . The first connection portion 613 extends radially outward from the other axial end of the cylindrical first side wall portion 612 (the end opposite to the end to which the first bottom wall portion 611 is connected) in a ring shape. deferred. The first connecting portion 613 has a ring-shaped contact surface 613a flush with the opening surface of the first cup-shaped heat transfer holder 61 (the surface surrounded by the other end of the first side wall portion 612).

Also, the inner diameter of the first side wall portion 612 is substantially equal to the outer diameter of the superconductor 1 . The first cup-shaped heat-conducting holder 61 includes three superconducting bulks (first superconducting bulk 11, second superconducting bulk 12, third superconducting bulk The inner peripheral surface 612d of the first side wall portion 612 is in contact with the outer peripheral surface of the one side portion 1A composed of the bulk 13) (that is, the first side wall portion 612 is thermally connected to the outer peripheral surface of the one side portion 1A), and superconducting The superconductor 1 is provided so that the inner side surface 611a of the first bottom wall portion 611 is in contact with the one end surface 1a of the body 1 (that is, the first bottom wall portion 611 is thermally connected to the one end surface 1a of the superconductor). are coaxially arranged with respect to each other. By arranging the first cup-shaped heat transfer holder 61 with respect to the superconductor 1 in this manner, the first cup-shaped heat transfer holder 61 holds the one side portion 1A of the superconductor 1 .

The second cup-shaped heat transfer holder 62 has the same cup shape as the first cup-shaped heat transfer holder 61, and has a second bottom wall portion 621 forming a bottom portion and a second side wall portion forming a side wall portion. 622 and a second connecting portion 623 formed near the opening surface. The second bottom wall portion 621 is formed in a disc shape having an inner side surface 621a and an outer side surface 621b on the opposite side. A circular hole is formed in the center of the second bottom wall portion 621 so as to penetrate in the axial direction from the inner side surface 621a to the outer side surface 621b. The diameter of this circular hole is approximately the same as the inner diameter of the superconductor 1 . The second side wall portion 622 is formed in a cylindrical shape having an outer peripheral surface 622c and an inner peripheral surface 622d. One end of the second side wall portion 622 is connected to the peripheral edge of the second bottom wall portion 621 . Thereby, the second side wall portion 622 is erected downward from the peripheral edge of the second bottom wall portion 621 in FIG. The axial length of the inner peripheral surface 622 d of the cylindrical second side wall portion 622 is half the axial length of the superconductor 1 . The second connection portion 623 extends radially outward from the other axial end of the cylindrical second side wall portion 622 (the end opposite to the end to which the second bottom wall portion 621 is connected) in a ring shape. deferred. The opening surface of the second cup-shaped heat transfer holder 62 (the surface surrounded by the other end of the second side wall portion 612) has a flush ring-shaped contact surface 623a.

Also, the inner diameter of the second side wall portion 622 is substantially equal to the outer diameter of the superconductor 1 . The second cup-shaped heat-conducting holder 62 includes three superconducting bulks (fourth superconducting bulk 14, fifth superconducting bulk 15, sixth superconducting bulk The inner peripheral surface 622d of the second side wall portion 622 is in contact with the outer peripheral surface of the other side portion 1B made of the bulk 16) (that is, the second side wall portion 622 is thermally connected to the outer peripheral surface of the other side portion 1B), and superconducting The superconductor 1 is provided so that the inner surface 621a of the second bottom wall portion 621 is in contact with the other end surface 1b of the body 1 (that is, the second bottom wall portion 621 is thermally connected to the other end surface 1b of the superconductor). are coaxially arranged with respect to each other. By arranging the second cup-shaped heat transfer holder 62 with respect to the superconductor 1 in this way, the second cup-shaped heat transfer holder 62 holds the other side portion 1B of the superconductor 1 .

When the first cup-shaped heat transfer holder 61 and the second cup-shaped heat transfer holder 62 are arranged with respect to the superconductor 1 as described above, the first cup-shaped heat transfer holder 61 faces upward. The second cup-shaped heat transfer holder 62 forms the upper half of the superconductor 1 with its opening facing downward. cover the other side portion 1B. For this reason, the opening surface of the first cup-shaped heat transfer holder 61 and the opening surface of the second cup-shaped heat transfer holder 62 are butted against each other, and the first connection portion 613 of the first cup-shaped heat transfer holder 61 and the second cup The second connecting portions 623 of the heat transfer holders 62 are placed facing each other with their contact surfaces (613a, 623s) facing each other. The first connection portion 613 and the second connection portion 623 that are arranged to face each other are connected via fastening means such as screws, for example. Thereby, the first cup-shaped heat transfer holder 61 and the second cup-shaped heat transfer holder 62 are connected.

In addition, the outer diameters of the first connecting portion 613 and the second connecting portion 623 which are respectively formed in a ring shape are substantially equal to the inner diameter of the extension portion 34 . Then, while the outer peripheral surfaces of the first connecting portion 613 and the second connecting portion 623 that are connected to each other face the portion of the inner peripheral surface 34d of the extension portion 34 near the other end surface 34b, both the connecting portions (613 , 623) are connected to the extension 34 via fastening means, for example screws. At this time, the first bottom wall portion 611 of the first cup-shaped heat transfer holder 61 is not in contact with the stage portion 32 of the cold head 3, and the second bottom wall portion 621 of the second cup-shaped heat transfer holder 62 is outside. The connection position between the connecting portions (613, 623) and the extension portion 34 is adjusted so that the cover portion 713 of the container 71 is not contacted.

As can be seen from the above description and FIG. 7, the first cup-shaped heat transfer holder 61 and the second cup-shaped heat transfer holder 62 have the same shape, and when the connecting portions (613, 623) are butted against each other, are arranged symmetrically with respect to a plane perpendicular to The lower half portion (one side portion 1A) of the superconductor 1 is covered with the first cup-shaped heat transfer holder 61, and the upper half portion (the other side portion 1B) of the superconductor 1 is covered with the second cup-shaped heat transfer holder 62. covered with At this time, the outer peripheral surface and the one end surface 1a of the lower half portion (one side portion 1A) of the superconductor 1 are thermally connected to the first cup-shaped heat transfer holder 61, and the upper half portion (the other side portion) of the superconductor 1 is connected. 1B) and the other end face 1b are thermally connected to the second cup-shaped heat transfer holder 62 . Also, the first cup-shaped heat transfer holder 61 and the second cup-shaped heat transfer holder 62 are thermally connected to the cold head 3 (extension portion 34) at respective connection portions (613, 623). Therefore, in this embodiment, the superconductor 1 is thermally connected to the cold head 3 via the cup-shaped heat transfer holder 6 at all of its one end face 1a, the other end face 1b, and the outer peripheral face 1c. It will be.

The configuration of the superconducting magnetic field generator 105 according to the fifth embodiment, except for the configuration described above, is the same as the configuration of the superconducting magnetic field generator 101 according to the first embodiment. Therefore, description of these configurations is omitted.

According to the superconducting magnetic field generator 105 according to the fifth embodiment, the one end face 1a of the superconductor 1 is thermally connected to the first cup-shaped heat transfer holder 61, and the other end face 1b of the superconductor 1 is the second cup-shaped. It is thermally connected to the heat transfer holder 62 . Also, the first cup-shaped heat transfer holder 61 and the second cup-shaped heat transfer holder 62 are both thermally connected to the cold head 3 (extension portion 34). Therefore, in the magnetic field cooling process, the superconductor 1 is cooled from both ends via the cup-shaped heat transfer holder 6 by cold heat generated by the cold head 3 . Therefore, the axial temperature uniformity of the superconductor 1 can be improved when the superconductor 1 is magnetized.

7, of the outer peripheral surface 1c of the superconductor 1, the outer peripheral surface of the lower half portion (one side portion 1A) is thermally connected to the first side wall portion 612 of the first cup-shaped heat transfer holder 61, and the upper half portion The outer peripheral surface of the portion (the other side portion 1B) is thermally connected to the second side wall portion 622 of the second cup-shaped heat transfer holder 62 . That is, the outer peripheral surface 1 c of the superconductor 1 is thermally connected to the cup-shaped heat transfer holder 6 . Therefore, in the magnetic field cooling process, the superconductor 1 is cooled from both end surfaces (1a, 1b) and the outer peripheral surface 1c. In FIG. 7, arrows indicate the flow of heat from the superconductor 1 when the superconductor 1 according to this embodiment is cooled in the magnetic field cooling process. As can be seen from FIG. 7, the heat of the superconductor 1 flows from the one end surface 1a, the other end surface 1b, and the outer peripheral surface 1c to the cup-shaped heat transfer holder 6, and further flows from the cup-shaped heat transfer holder 6 to the cold head 3. Since the superconductor 1 is cooled from many surfaces in this manner, the temperature uniformity of the superconductor 1, particularly the temperature uniformity in the axial direction, can be further enhanced.

Further, the first cup-shaped heat transfer holder 61 and the second cup-shaped heat transfer holder 62 have the same shape, and are connected to the extension part 34 in a state where the connection parts (613, 623) face each other. . Therefore, when the superconductor 1 is cooled in the magnetic field cooling process, the heat from the one side portion 1A of the superconductor 1 passes through the first cup-shaped heat transfer holder 61 to the cold head 3 (extension 34). ) and the length of the path for the heat from the other side portion 1B of the superconductor 1 to reach the cold head 3 (extension portion 34) via the second cup-shaped heat transfer holder 62 are equal. Therefore, the heat transfer speed from the superconductor 1 to the cold head 3 can be reduced depending on the location, so that the cooling speed can be substantially constant over the entire superconductor 1 . As a result, the temperature uniformity of the superconductor 1 can be further improved.

The cup-shaped heat transfer holder 6 is made of aluminum or an aluminum alloy, and its thermal contraction rate is greater than that of the superconductor 1 . Therefore, when the superconductor 1 and the cup-shaped heat transfer holder 6 are cooled in the cooling process in the magnetic field, thermal contraction of the side wall portions (the first side wall portion 612 and the second side wall portion 622) of the cup-shaped heat transfer holder 6 Since the amount is larger than the thermal contraction amount of the superconductor 1, the superconductor 1 is clamped to the cup-shaped heat transfer holder 6 from the outer peripheral surface 1c side. This tightening force acts on the superconductor 1 as compressive stress. Therefore, the superconductor 1 undergoes the demagnetization process while receiving compressive stress from the outer cylindrical heat transfer holder 4 . The compressive stress received in this way cancels out the electromagnetic stress acting on the superconductor 1 in the demagnetization process, so that damage to the superconductor 1 caused by the electromagnetic stress can be more effectively prevented.

(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described. It has the same configuration as the superconducting magnetic field generator 105 concerned. The following description focuses on the configuration that is different from the superconducting magnetic field generator 105 according to the fifth embodiment.

FIG. 8 is a schematic diagram showing a cross section of the superconducting magnetic field generator 106 according to the sixth embodiment taken along a plane including the center line along the vertical direction. As shown in FIG. 8, the superconducting magnetic field generator 106 according to the sixth embodiment includes a superconductor 1, a cooling device 2, a cold head 3, a cup-shaped conductor, as in the superconducting magnetic field generator 105 according to the fifth embodiment. A heat holder 6 and a vacuum insulation container 7 are provided.

The superconducting magnetic field generator 106 also includes an inner cylindrical heat transfer holder 5 . The inner cylindrical heat transfer holder 5 is arranged on the inner peripheral side of the superconductor 1 so as to hold the superconductor 1 from the inner peripheral side of the superconductor 1 . The inner cylindrical heat transfer holder 5 is made of a non-magnetic material with high thermal conductivity. In this embodiment, the inner cylindrical heat transfer holder 5 is made of aluminum or an aluminum alloy.

The inner cylindrical heat transfer holder 5 is formed in a cylindrical shape and has one end surface 5a and the other end surface 5b in the axial direction, an outer peripheral surface 5c, and an inner peripheral surface 5d. The outer diameter of the inner cylindrical heat transfer holder 5 is substantially equal to the inner diameter of the superconductor 1, and the inner diameter of the inner cylindrical heat transfer holder 5 is about the same as the bottom walls (first bottoms) of the pair of cup-shaped heat transfer holders 6. equal to the inner diameter of the wall portion 611 and the second bottom wall portion 621). The axial length of the inner cylindrical heat transfer holder 5 is equal to the axial length of the superconductor 1 . The inner cylindrical heat transfer holder 5 is arranged with respect to the superconductor 1 so that the outer peripheral surface 5c of the inner cylindrical heat transfer holder 5 is in contact with the inner peripheral surface 1d of the superconductor 1 . The contact between the outer peripheral surface 5c of the inner cylindrical heat transfer holder 5 and the inner peripheral surface 1d of the superconductor 1 thermally connects the outer peripheral surface 5c of the inner cylindrical heat transfer holder 5 to the inner peripheral surface 1d of the superconductor 1. be done.

Also, in the superconducting magnetic field generator 106 , the inner diameter of the bottom wall ( 611 , 612 ) of each cup-shaped heat transfer holder 6 ( 61 , 62 ) is smaller than the inner diameter of the superconductor 1 . Therefore, the first cup-shaped heat transfer holder 61 is attached to the superconductor 1 so that the one end surface 1a of the superconductor 1 contacts the inner surface 611a of the first bottom wall portion 611 of the first cup-shaped heat transfer holder 61. In the case of coaxial arrangement, due to the difference in inner diameter between the first bottom wall portion 611 and the superconductor 1 , the portion near the inner peripheral side of the first bottom wall portion 611 is slightly ringed radially inward from the inner periphery of the superconductor 1 . protrude into a shape. One end surface 5a of the inner cylindrical heat transfer holder 5 is located on the inner surface 611a of the portion of the first bottom wall portion 611 protruding radially inward from the inner circumference of the superconductor 1 in a ring shape as described above. Contact. Further, the second cup-shaped heat transfer holder 62 is attached to the superconductor 1 so that the other end surface 1b of the superconductor 1 contacts the inner surface 621a of the second bottom wall portion 621 of the second cup-shaped heat transfer holder 62. In the case of coaxial arrangement, due to the difference in inner diameter between the second bottom wall portion 621 and the superconductor 1 , the portion near the inner peripheral side of the second bottom wall portion 621 is slightly ringed radially inward from the inner periphery of the superconductor 1 . protrude into a shape. The other end surface 5b of the inner cylindrical heat transfer holder 5 is formed on the inner surface 621a of the portion of the second bottom wall portion 621 protruding radially inward from the inner circumference of the superconductor 1 in a ring shape as described above. Contact. In this manner, the inner cylindrical heat transfer holder 5 is disposed on the inner peripheral side of the superconductor 1 so that the outer peripheral surface 5c thereof is thermally connected to the inner peripheral surface 1d of the superconductor 1, and One end surface 5a is thermally connected to the first bottom wall portion 611 of the first cup-shaped heat transfer holder 61, and the other end surface 5b is thermally connected to the second bottom wall portion 621 of the second cup-shaped heat transfer holder 62. configured to be connected.

Of the configuration of the superconducting magnetic field generator 106 according to the sixth embodiment, the configuration other than the configuration described above is the same as the configuration of the superconducting magnetic field generator 105 according to the fifth embodiment. Therefore, detailed description of those configurations will be omitted.

According to the superconducting magnetic field generator 106 according to the sixth embodiment, the one end face 1a of the superconductor 1 is thermally connected to the first cup-shaped heat transfer holder 61 in the same manner as the superconducting magnetic field generator 105 according to the fifth embodiment. , and the other end surface 1 b of the superconductor 1 is thermally connected to the second cup-shaped heat transfer holder 62 . Also, the first cup-shaped heat transfer holder 61 and the second cup-shaped heat transfer holder 62 are both thermally connected to the cold head 3 (extension portion 34). Therefore, in the magnetic field cooling process, the superconductor 1 is cooled from both ends via the cup-shaped heat transfer holder 6 by cold heat generated by the cold head 3 . Therefore, the axial temperature uniformity of the superconductor 1 can be improved when the superconductor 1 is magnetized.

Also, the superconducting magnetic field generator 106 according to the sixth embodiment includes the inner cylindrical heat transfer holder 5 . One end face 5a of the inner cylindrical heat transfer holder 5 is thermally connected to the first bottom wall portion 611 of the first cup-shaped heat transfer holder 61, and the other end face 5b of the second cup-shaped heat transfer holder 62 It is thermally connected to the two bottom walls 621 . Therefore, the inner cylindrical heat transfer holder 5 is cooled from both ends thereof by the pair of cup-shaped heat transfer holders 6 in the cooling process in the magnetic field. Therefore, the inner cylindrical heat transfer holder 5 is uniformly cooled along the axial direction. The inner peripheral surface 1d of the superconductor 1 is thermally connected to the outer peripheral surface 5c of the inner cylindrical heat transfer holder 5 which is uniformly cooled along the axial direction. Therefore, the superconductor 1 is uniformly cooled along the axial direction also from the inner peripheral surface 1d. Therefore, the temperature uniformity of the superconductor can be further improved.

Further, according to the superconducting magnetic field generator 106 according to the sixth embodiment, the one end surface 1a, the other end surface 1b, and the outer peripheral surface 1c of the superconductor 1 are thermally connected to the cup-shaped heat transfer holder 6, and the superconducting The inner peripheral surface 1 d of the body 1 is thermally connected to the inner cylindrical heat transfer holder 5 . That is, all portions of the surface of superconductor 1 are thermally connected to the heat transfer member. Therefore, when the superconductor 1 is cooled in the magnetic field cooling process, the heat of the superconductor 1 flows out from all the surfaces as indicated by the arrows in FIG. Therefore, the superconductor 1 can be cooled more uniformly, and the cooling efficiency is improved.

Further, according to the superconducting magnetic field generator 106 according to the sixth embodiment, by providing the inner cylindrical heat transfer holder 5 on the inner peripheral side of the superconductor 1 , the inner cylindrical heat transfer holder 5 is provided between the room temperature bore space and the superconductor 1 . A heat transfer holder 5 is interposed. This prevents radiant heat from the room-temperature bore space from being directly transferred to the superconductor 1 . As a result, it is possible to suppress the temperature rise of the superconductor 1 due to heat radiation from the room-temperature bore space.

(Seventh embodiment)
Next, a seventh embodiment of the present invention will be described. The superconducting magnetic field generator according to this embodiment is basically the same as the superconducting magnetic field generator 105 according to the fifth embodiment, except that a reinforcing ring is provided. They have the same configuration. The following description focuses on the configuration that is different from the superconducting magnetic field generator 105 according to the fifth embodiment.

FIG. 9 is a schematic diagram showing a cross section of the superconducting magnetic field generator 107 according to the seventh embodiment taken along a plane including the center line along the vertical direction. As shown in FIG. 9, the superconducting magnetic field generator 107 according to the seventh embodiment includes a reinforcing ring 8 as a reinforcing member for reinforcing the superconductor 1. As shown in FIG.

The reinforcing ring 8 according to this embodiment includes six cylindrical ring members (first ring member 81, second ring member 82, third ring member 83, fourth ring member 84, fifth ring member 85, and sixth ring member 86) are coaxially stacked in this order along the axial direction to form a cylindrical shape. The outer peripheral surfaces of the six ring members form the outer peripheral surface 8c of the reinforcing ring 8, and the inner peripheral surfaces of the six ring members form the inner peripheral surface 8d of the reinforcing ring 8. As shown in FIG. One end surface 8a of the reinforcing ring 8 is formed by the end surface of the first ring member 81 facing downward in FIG. 9, and the other end surface 8b of the reinforcing ring 8 is formed by the end surface of the sixth ring member 86 facing upward in FIG. be done.

Moreover, the superconducting magnetic field generator 107 includes the superconductor 1 and a pair of cup-shaped heat transfer holders 6 in the same manner as the superconducting magnetic field generator 105 according to the fifth embodiment. The inner diameter of the side walls (612, 622) is larger than the outer diameter of the superconductor 1. Therefore, when the pair of cup-shaped holders 6 are arranged coaxially with respect to the superconductor 1, the inner peripheral surfaces (612d, 622d) of the side walls (612, 622) of the pair of cup-shaped heat transfer holders 6 and the superconductor A cylindrical space is formed between it and the outer peripheral surface 1c of 1 . A reinforcing ring 8 is arranged in this cylindrical space.

In the seventh embodiment, as in the first and fifth embodiments, the superconductor 1 includes six cylindrical superconducting bulks (first superconducting bulk 11, second superconducting bulk 12, third superconducting bulk It is formed by stacking a bulk 13, a fourth superconducting bulk 14, a fifth superconducting bulk 15, and a sixth superconducting bulk 16) in this order along the axial direction. Six ring members (81, 82, 83, 84, 85, 86) are attached to each of the six superconducting bulks (11, 12, 13, 14, 15, 16) correspondingly. . The correspondence relationship between the six superconducting bulks and the six ring members and the attachment structure of the reinforcing ring to the superconducting bulk are the same as the correspondence relationship and attachment structure described in the fourth embodiment. The explanation is omitted.

The inner peripheral surface 8d of the reinforcing ring 8 made up of six ring members contacts the outer peripheral surface 1c of the superconductor 1 made up of six superconducting bulks. Thereby, the inner peripheral surface 8 d of the reinforcing ring 8 is thermally connected to the outer peripheral surface 1 c of the superconductor 1 . In addition, the outer peripheral surface 8c of the reinforcing ring 8 contacts the inner peripheral surfaces (612d, 622d) of the side wall portions (612, 622) of either of the pair of cup-shaped heat transfer holders 6. As shown in FIG. Specifically, the outer peripheral surfaces of the first ring member 81, the second ring member 82, and the third ring member 83 are in contact with the inner peripheral surface 612d of the first side wall portion 612 of the first cup-shaped heat transfer holder 61, The outer peripheral surfaces of the fourth ring member 84 , the fifth ring member 85 , and the sixth ring member 86 contact the inner peripheral surface 622 d of the second side wall portion 622 of the second cup-shaped heat transfer holder 62 . Thereby, the outer peripheral surface of the reinforcing ring 8 is thermally connected to the pair of cup-shaped heat transfer holders 6 .

Also, the lower end surface of the first ring member 81 forming the one end surface 8 a of the reinforcing ring 8 contacts the inner surface 611 a of the first bottom wall portion 611 of the first cup-shaped heat transfer holder 61 . As a result, the one end surface 8 a of the reinforcing ring 8 is thermally connected to the first bottom wall portion 611 . Also, the upper end surface of the sixth ring member 86 forming the other end surface 8 b of the reinforcing ring 8 contacts the inner surface 621 a of the second bottom wall portion 621 of the second cup-shaped heat transfer holder 62 . Thereby, the other end surface 8 b of the reinforcing ring 8 is thermally connected to the second bottom wall portion 621 .

The reinforcing ring 8 is made of a material having a thermal shrinkage rate greater than that of the superconductor 1 . That is, the thermal contraction rate of the reinforcing ring 8 is greater than or equal to that of the superconductor 1 . In this embodiment, the reinforcing ring 8 is made of aluminum or an aluminum alloy. The thermal contraction rate of aluminum or an aluminum alloy is greater than that of a Re--Ba--Cu--O system superconductor. That is, in the present embodiment, the thermal contraction rate of the reinforcing ring 8 is greater than that of the superconductor 1 . Moreover, the reinforcing ring 8 is preferably made of a material having a thermal contraction rate equal to or lower than that of the cup-shaped heat transfer holder 6 . That is, the thermal contraction rate of the cup-shaped heat transfer holder 6 is preferably greater than that of the reinforcing ring 8 . In this embodiment, the cup-shaped heat transfer holder 6 is made of the same material as the reinforcing ring 8 (aluminum or aluminum alloy). Therefore, the thermal contraction rate of the cup-shaped heat transfer holder 6 and the thermal contraction rate of the reinforcing ring 8 are the same.

Of the configurations of the superconducting magnetic field generator 107 according to the seventh embodiment, configurations other than those described above are the same as the configurations of the superconducting magnetic field generator 105 according to the fifth embodiment. Therefore, detailed description thereof will be omitted.

According to the superconducting magnetic field generator 107 according to the seventh embodiment, the one end surface 1a of the superconductor 1 is thermally connected to the first cup-shaped heat transfer holder 61, similarly to the superconducting magnetic field generator 105 according to the fifth embodiment. , and the other end surface 1 b of the superconductor 1 is thermally connected to the second cup-shaped heat transfer holder 62 . Also, the first cup-shaped heat transfer holder 61 and the second cup-shaped heat transfer holder 62 are both thermally connected to the cold head 3 (extension portion 34). Therefore, in the magnetic field cooling process, the superconductor 1 is cooled from both ends via the cup-shaped heat transfer holder 6 by cold heat generated by the cold head 3 . Therefore, the axial temperature uniformity of the superconductor 1 can be improved when the superconductor 1 is magnetized.

A reinforcing ring 8 is provided in contact with the outer peripheral surface 1 c of the superconductor 1 , and one end surface 8 a of the reinforcing ring 8 thermally contacts the first bottom wall portion 611 of the first cup-shaped heat transfer holder 61 . The other end surface 8 b is thermally connected to the second bottom wall portion 621 of the second cup-shaped heat transfer holder 62 . Therefore, the reinforcing ring 8 is uniformly cooled along the axial direction in the cooling process in the magnetic field. Therefore, the superconductor 1 is cooled by the reinforcing ring 8 not only from the one end surface 1a and the other end surface 1b but also from the outer peripheral surface 1c. Thereby, the superconductor 1 is uniformly cooled.

Further, since the reinforcing ring 8 is arranged on the outer peripheral side of the superconductor 1 in contact with the outer peripheral surface 1c of the superconductor 1, the electromagnetic stress generated when the superconductor 1 is magnetized by performing the demagnetization process The reinforcing ring 8 reinforces the superconductor 1 against (hoop force). Therefore, damage to the superconductor 1 caused by electromagnetic stress can be effectively prevented.

Further, since the thermal contraction rate of the reinforcing ring 8 is larger than that of the superconductor 1, when the reinforcing ring 8 is cooled together with the superconductor 1 in the cooling process in the magnetic field, the reinforcing ring 8 is The superconductor 1 is tightened by the reinforcing ring by shrinking more than the above. Therefore, the superconductor 1 receives a greater compressive stress from the reinforcing ring 8, and the compressive stress thus received cancels out the electromagnetic stress, thereby more effectively preventing damage to the superconductor 1 caused by the electromagnetic stress. can do. In addition, according to this embodiment, the side walls (612, 622) of the pair of cup-shaped heat transfer holders 6 are provided on the outer peripheral side of the reinforcing ring 8. As shown in FIG. The heat shrinkage of these cup-shaped heat transfer holders is the same as that of the reinforcing ring 8 and greater than that of the superconductor 1 . Therefore, in the magnetic field cooling process, the superconductor 1 is double reinforced by the compressive stress from the cup-shaped heat transfer holder 6 and the compressive stress from the reinforcing ring 8 . Therefore, the effect of reinforcing the electromagnetic stress (hoop force) generated when the superconductor 1 is magnetized can be further enhanced.

Although various embodiments of the present invention have been described above, the present invention should not be limited to the above embodiments. For example, the first extension portion 331 of the cold head 3 according to the first to fourth embodiments is formed in a cylindrical shape, but one end is thermally connected to the stage portion 32 and the other end is the first extension portion 331 . The first extension portion 331 may be configured by a plurality of rod-shaped members that are thermally connected to the second extension portion 332 and arranged at predetermined intervals along the circumferential direction of the stage portion 32 . Further, the extended portion 34 of the cold head 3 according to the fifth to seventh embodiments is also formed in a cylindrical shape. The extension portion 34 may be configured by a plurality of rod-shaped members that are thermally connected to the connection portions (613, 623) of the heat transfer holder 6 and arranged at predetermined intervals along the circumferential direction of the stage portion 32. good. In this case, the connecting portions may be provided only at positions facing the plurality of rod-shaped extensions.

In each of the above-described embodiments, the heat transfer holders (4, 5, 6) are made of aluminum or an aluminum alloy. A holder (4, 5, 6) may be formed.

Further, the extended portion 33 of the cold head 3 according to the first to fourth embodiments is composed of a cylindrical first extended portion 331 and a disk-shaped second extended portion 332. 32 and the other end surface 1b of the superconductor 1, any configuration may be employed.

Moreover, in each of the above embodiments, the superconductor 1 is configured by stacking a plurality of cylindrical superconducting bulks, but it may be configured integrally. In addition, when the superconductor 1 is composed of a plurality of cylindrical superconducting bulks, a heat conductive sheet such as an indium sheet is interposed between the contact interfaces of each superconducting bulk to fill the unevenness of the contact interface. It is also possible to reduce thermal resistance (improve thermal contact).

Further, the contact interface between the cold head 3 and the superconductor 1, the contact interface between the reinforcing ring 8 and the superconductor 1, the contact interface between each heat transfer holder (4, 5, 6) and the superconductor 1, the outer cylindrical conductor In the same manner as described above, the contact interface between the heat holder 4 and the cold head 3 and the contact interface between the inner cylindrical heat transfer holder 5 and the cold head 3 are interposed with an indium sheet to improve the thermal contact or to reduce the contact object. An adhesive or the like may be interposed to the extent that the thermal connection between them is not lost. In this manner, the present invention can be modified without departing from its gist.

Reference Signs List 1 Superconductor 1A One side portion 1B Other side portion 1a One end surface 1b Other end surface 1c Outer peripheral surface 1d Inner peripheral surface 2 Cooling device 3 Cold head 32 Stage portion 32a...one end face 32b...other end face 32c...peripheral face 33...extension part 331...first extension part 331a...one end face 331b...other end face 331c...peripheral face 331d...inner peripheral face , 332 second extension 332a one end face 332b other end face 332c outer peripheral face 332d inner peripheral face 333 circular hole 34 extension 34a one end face 34b other end face 34c Outer peripheral surface 34d Inner peripheral surface 4, 4A Outer cylindrical heat transfer holder 4a One end face 4b Other end face 4c Outer peripheral surface 4d Inner peripheral surface 41a, 41b Flange 41A First portion 42A Second portion 43A Third portion 5 Inner cylindrical heat transfer holder 5a One end surface 5b Other end surface 5c Outer peripheral surface 5d Inner peripheral surface 6 Cup shape Heat transfer holder 61 First cup-shaped heat transfer holder 611 First bottom wall 611a Inner surface 611b Outer surface 612 First side wall 612c Outer peripheral surface 612d Inner peripheral surface 613... First connection part 62... Second cup-shaped heat transfer holder 621... Second bottom wall part 621a... Inner surface 621b... Outer surface 622... Second side wall part 622c... Peripheral surface 622d... Inside Peripheral surface 623 Second connection part 7 Vacuum insulation container 71 Outer container 72 Inner container 8 Reinforcing ring (reinforcing member) 8a One end surface 8b Other end surface 8c Outer peripheral surface 8d... Inner peripheral surface 101, 102, 103, 104, 105, 106, 107... Superconducting magnetic field generator 110... Nuclear magnetic resonance apparatus

Claims (9)

a superconductor that is formed in a cylindrical shape and generates a magnetic field by capturing an applied magnetic field in a state cooled to a temperature below the superconducting transition temperature;
a cooling device comprising a cold head that generates cold heat for cooling the superconductor to a temperature below the superconducting transition temperature;
with
The cold head is
a stage portion thermally connected to one end face of the superconductor so as to cool the superconductor from the one end face of the superconductor;
an extension portion thermally connected to the stage portion and thermally connected to the other end face of the superconductor so as to cool the superconductor from the other end face of the superconductor;
has
The extension is thermally spaced from the outer peripheral surface of the superconductor,
In the superconducting magnetic field generator,
It is formed in a cylindrical shape, has an inner peripheral surface that is thermally connected to the outer peripheral surface of the superconductor, and is arranged on the outer peripheral side of the superconductor so as to hold the superconductor from the outer peripheral side of the superconductor. a superconducting magnetic field generator, comprising an outer cylindrical heat transfer holder having one end face thermally connected to the stage portion and the other end face thermally connected to the extension portion. In the superconducting magnetic field generator according to claim 1,
The extension is
a first extension portion having one end face and the other end face on the opposite side thereof, the one end face being thermally connected to the stage portion;
a second extension portion thermally connected to the other end surface of the first extension portion and thermally connected to the other end surface of the superconductor;
A superconducting magnetic field generator, wherein the first extension is thermally spaced from an outer peripheral surface of the superconductor. In the superconducting magnetic field generator according to claim 1 or 2 ,
The superconductor and the outer cylindrical heat transfer holder are formed in a cylindrical shape such that the inner peripheral surface thereof contacts the outer peripheral surface of the superconductor and the outer peripheral surface contacts the inner peripheral surface of the outer cylindrical heat transfer holder. A superconducting magnetic field generator, comprising a reinforcing member disposed between a heat transfer holder and having one end surface thermally connected to the stage portion and the other end surface thermally connected to the extension portion. . In the superconducting magnetic field generator according to any one of claims 1 to 3 ,
It is formed in a cylindrical shape, has an outer peripheral surface thermally connected to the inner peripheral surface of the superconductor, and extends from the inner peripheral side of the superconductor to the inner peripheral side of the superconductor so as to hold the superconductor. A superconducting magnetic field generator comprising an inner cylindrical heat transfer holder disposed and having one end surface thermally connected to the stage portion and the other end surface thermally connected to the extension portion. a superconductor that is formed in a cylindrical shape and generates a magnetic field by capturing an applied magnetic field in a state cooled to a temperature below the superconducting transition temperature;
a cooling device comprising a cold head that generates cold heat for cooling the superconductor to a temperature below the superconducting transition temperature;
A disc-shaped first bottom wall part formed in a cup shape and thermally connected to one end face of the superconductor; and a cylindrical first side wall portion thermally connected to the outer peripheral surface of the one side portion extending from the central position in the axial direction to the one end face, and holding the one side portion. a first cup-shaped heat transfer holder disposed against;
A disc-shaped second bottom wall part formed in a cup shape and thermally connected to the other end surface of the superconductor; and a cylindrical second sidewall portion thermally connected to the outer peripheral surface of the other side portion, which is a portion from the central position in the axial direction to the other end surface, and the superconductor so as to hold the other side portion. a second cup-shaped heat transfer holder disposed against
A superconducting magnetic field generator, wherein the first cup-shaped heat transfer holder and the second cup-shaped heat transfer holder are thermally connected to the cold head. In the superconducting magnetic field generator according to claim 5 ,
The first cup-shaped heat transfer holder has a first connection portion extending radially outward from the other end of the first side wall portion,
The second cup-shaped heat transfer holder has a second connecting portion extending radially outward from the other end of the second side wall portion,
The first cup-shaped heat transfer holder and the second cup-shaped heat transfer holder are connected with the first connection portion and the second connection portion facing each other,
A superconducting magnetic field generator, wherein the first connecting portion and the second connecting portion are thermally connected to the cold head. In the superconducting magnetic field generator according to claim 5 or 6 ,
It is formed in a cylindrical shape, the inner peripheral surface thereof is in contact with the outer peripheral surface of the superconductor, and the outer peripheral surface thereof is in contact with the inner peripheral surface of the first side wall portion and the inner peripheral surface of the second side wall portion, is disposed between the superconductor and the first side wall and the second side wall, one end of which is thermally connected to the first bottom wall, and the other end of which is the second bottom A superconducting magnetic field generator comprising a reinforcing member thermally connected to a wall. In the superconducting magnetic field generator according to any one of claims 5 to 7 ,
It is formed in a cylindrical shape, has an outer peripheral surface thermally connected to the inner peripheral surface of the superconductor, and extends from the inner peripheral side of the superconductor to the inner peripheral side of the superconductor so as to hold the superconductor. A superconducting superconducting device provided with an inner cylindrical heat transfer holder having one end surface thermally connected to the first bottom wall portion and the other end surface thermally connected to the second bottom wall portion. Magnetic field generator. A nuclear magnetic resonance apparatus comprising the superconducting magnetic field generator according to any one of claims 1 to 8 .

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