JPWO2017169422A1 - Superconducting magnetic field generating element and manufacturing method thereof - Google Patents

Abstract

The superconducting magnetic field generating element 1 includes a columnar or cylindrical superconducting bulk 2, an inner cylindrical member 4 attached to the superconducting bulk 2 so that the inner peripheral surface thereof is in contact with the outer peripheral surface of the superconducting bulk 2, and the inner side An outer cylindrical member 5 attached to the inner cylindrical member 4 so that the inner peripheral surface thereof contacts the outer peripheral surface of the cylindrical member 4. The inner cylindrical member 4 and the outer cylindrical member 5 are each formed of a material having a thermal contraction rate larger than that of the superconducting bulk 2. The outer cylindrical member 5 is attached to the inner cylindrical member 4 so that compressive stress acts on the superconducting bulk 2 at room temperature.

Description

  The present invention relates to a superconducting magnetic field generating element and a method for manufacturing the same.

  A superconducting magnetic field generating element configured using a superconducting bulk generates a magnetic field much larger than the magnetic field generated by a permanent magnet. For example, a superconducting magnetic field generating element configured using a superconducting bulk made of a high-temperature superconducting material of Re-Ba-Cu-O type (Re is one or more of rare earth elements) has a magnetic field of 10 T or more. Can be generated.

  When a superconducting magnetic field generating element using a superconducting bulk generates a magnetic field, the superconducting bulk is captured in a state where the superconducting magnetic field generating element is cooled to a temperature equal to or lower than the superconducting transition temperature. When the superconducting bulk captures a magnetic field, a circular current flows in the superconducting bulk. An electromagnetic force based on the circular current and the trapped magnetic field of the superconducting bulk acts on the superconducting bulk. This electromagnetic force acts in the direction from the center of the superconducting bulk toward the outside. Therefore, when the superconducting bulk is formed in a cylindrical shape or a columnar shape, the electromagnetic force acts in a direction from the central axis of the superconducting bulk toward the radially outward direction. For this reason, the superconducting bulk expands to increase its diameter, and tensile stress acts on the superconducting bulk so as to be torn in the circumferential direction by such expansion force. When the tensile stress exceeds the mechanical strength of the superconducting bulk, the superconducting bulk breaks.

  In order to prevent damage to the superconducting bulk based on the tensile stress described above, a superconducting magnetic field generating element configured to reinforce the superconducting bulk by applying compressive stress against the tensile stress (expansion force) to the superconducting bulk has been developed. Has been. For example, Patent Document 1 discloses a superconducting magnetic field generating element configured by embedding a cylindrical superconducting bulk at a room temperature through a resin layer inside a cylindrical member composed of a metal having a larger thermal contraction rate. Is disclosed. According to this configuration, the outer peripheral surface of the columnar superconducting bulk is covered with the cylindrical member via the resin layer. When such a superconducting magnetic field generating element is cooled to a temperature equal to or lower than the superconducting transition temperature, which is its use temperature, the cylindrical member clamps the superconducting bulk due to the difference in thermal shrinkage rate. For this reason, pressure is applied to the outer periphery of the superconducting bulk, and as a result, compressive stress acts inside the superconducting bulk. By offsetting this compressive stress and the tensile stress (expansion force) generated in the superconducting bulk, the net stress acting on the superconducting bulk is reduced. For this reason, cracking of the superconducting bulk can be effectively prevented, and therefore a higher magnetic field can be magnetized in the superconducting bulk.

  Patent Document 2 discloses a superconducting magnetic field generating element in which a reinforcing member is provided on at least one of an upper end surface and a lower end surface in addition to an outer peripheral surface of a columnar or cylindrical superconducting bulk. According to this configuration, since the reinforcing member is provided not only on the outer peripheral surface of the superconducting bulk, but also on at least one of the upper end surface and the lower end surface, the compressive stress applied to the superconducting bulk increases, and therefore the reinforcing effect. Is increased.

  Patent Document 3 discloses a superconducting magnetic field generating element configured by attaching a heated cylindrical member to the outer peripheral surface of a columnar or cylindrical superconducting bulk. According to this configuration, after the heated cylindrical member is attached to the outer peripheral surface of the superconducting bulk, the cylindrical member is cooled to room temperature, whereby the cylindrical member is shrink-fitted into the superconducting bulk. Patent Document 3 also discloses a superconducting magnetic field generating element configured by attaching a cylindrical member at room temperature to a superconducting bulk cooled to 77K. According to this configuration, after attaching the cylindrical member at room temperature to the cooled superconducting bulk, the cylindrical member is cooled and fitted into the superconducting bulk by raising the temperature of the superconducting bulk to room temperature. By compressing or fitting the cylindrical member into the superconducting bulk, compressive stress can be applied to the superconducting bulk from the cylindrical member at the stage of manufacturing the superconducting magnetic field generating element.

Japanese Patent No. 3389094 JP 2014-146760 A Japanese Patent No. 4012311

(Problems to be solved by the invention)
According to the superconducting magnetic field generating element described in Patent Document 1, when a larger compressive stress is applied to the superconducting bulk to increase the reinforcing effect, the thickness (wall thickness) of the cylindrical member is increased. . When the thickness of the cylindrical member is increased, the outer diameter of the superconducting magnetic field generating element is increased accordingly. However, since the superconducting magnetic field generating element is magnetized while being inserted into the bore of the magnetizing magnet, the outer diameter of the superconducting magnetic field generating element must be smaller than the inner diameter of the bore of the magnetizing magnet. Goodbye. For this reason, the increase in the thickness of the cylindrical member is limited by the diameter of the bore of the magnetizing magnet. Thus, there may be a case where the thickness of the cylindrical member cannot be increased so that sufficient compressive stress is applied to the superconducting bulk. Further, even if the thickness of the cylindrical member is increased, the reinforcing effect (compressive stress) does not increase in proportion to the thickness, but the reinforcing effect gradually decreases and eventually becomes saturated. On the other hand, the tensile stress generated in the superconducting bulk increases in proportion to the square of the magnetic field strength trapped in the superconducting bulk. For this reason, when trying to capture a high magnetic field of, for example, 10 T or more in a cylindrical superconducting bulk having a large diameter, simply increasing the thickness of the cylindrical member counteracts the tensile stress generated in the superconducting bulk. A sufficiently large compressive stress that can be applied cannot be applied to the superconducting bulk, and as a result, the superconducting bulk may break.

  Further, according to the superconducting magnetic field generating element described in Patent Document 2, since the reinforcing member is attached to the upper end surface or the lower end surface in addition to the outer peripheral surface of the columnar or cylindrical superconducting bulk, the upper end surface or the lower Compared with the case where the reinforcing member is not attached to the end face, the compressive stress acting on the superconducting bulk is increased. However, since the reinforcing member attached to the upper end surface or the lower end surface of the superconducting bulk is not directly subjected to the tensile stress generated in the superconducting bulk, the degree of improvement in the reinforcing effect (degree of increase in compressive stress) is small. Therefore, when trying to capture a large magnetic field in the superconducting bulk, it is not possible to apply a sufficiently large compressive stress to the superconducting bulk that can counter the tensile stress generated in the superconducting bulk.

  According to Patent Document 3, since the cylindrical member having a temperature difference from the superconducting bulk is directly attached to the superconducting bulk, the thermal shock due to the temperature difference acts on the superconducting bulk. For this reason, the superconducting bulk may be damaged. Note that, even if an attempt is made to attach the cylindrical member to the superconducting bulk via the resin layer based on the technique described in Patent Document 3, for example, a problem such as melting of the resin layer due to the heat of the heated cylindrical member occurs. . For this reason, as long as the technique of patent document 3 is used, a cylindrical member cannot be attached to the outer peripheral surface of a superconducting bulk through a resin layer.

  As described above, in the conventional technology, when a large magnetic field of, for example, 10 T or more is attempted to be captured in the superconducting bulk, a sufficiently large compressive stress that can counter the tensile stress generated in the superconducting bulk is applied. It was not possible to act on the superconducting bulk. An object of the present invention is to provide a superconducting magnetic field generating element configured to allow a sufficiently large compressive stress to act on the superconducting bulk, and a method for manufacturing such a superconducting magnetic field generating element.

(Means for solving the problem)
The present invention includes a cylindrical or cylindrical superconducting bulk (2), an inner cylindrical member (4) attached to the superconducting bulk so that the inner peripheral surface thereof is in contact with the outer peripheral surface of the superconducting bulk, and the inner cylinder. And an outer cylindrical member (5) attached to the inner cylindrical member so that the inner peripheral surface is in contact with the outer peripheral surface of the cylindrical member, and the inner cylindrical member and the outer cylindrical member are respectively superconducting The outer cylindrical member is formed of a material having a thermal contraction rate larger than that of the bulk, and the outer cylindrical member is formed on the inner cylindrical member so that compressive stress acts on the superconducting bulk through the inner cylindrical member at room temperature. A superconducting magnetic field generating element (1, 1A, 1B) is provided. In the present invention, the “normal temperature” is a temperature of about “5 ° C. to 35 ° C.”.

  The superconducting magnetic field generating element according to the present invention is configured such that the superconducting bulk is reinforced by a plurality of cylindrical members (an inner cylindrical member and an outer cylindrical member) stacked in the radial direction. The outer cylindrical member is attached to the inner cylindrical member so that compressive stress acts on the superconducting bulk via the inner cylindrical member at room temperature. Therefore, when the superconducting magnetic field generating element is cooled to a temperature below the superconducting transition temperature in order to capture the magnetic field in the superconducting bulk, in addition to the compressive stress caused by the thermal contraction of the inner cylindrical member and the outer cylindrical member, The resulting compressive stress is added. For this reason, the compressive stress that can resist the tensile stress generated in the superconducting bulk when the magnetic field is trapped in the superconducting bulk is increased by the amount of the compressive stress already generated at room temperature.

  Thus, according to the present invention, a plurality of cylindrical members are used to reinforce the superconducting bulk, and one of the cylindrical members already exerts compressive stress on the superconducting bulk at room temperature. A superconducting magnetic field generating element is configured. Therefore, a larger compressive stress can be applied to the superconducting bulk as compared with the case where the superconducting bulk is reinforced using one cylindrical member having the same thickness. That is, according to the present invention, it is possible to provide a superconducting magnetic field generating element configured to allow a sufficiently large compressive stress to act on the superconducting bulk.

  The inner cylindrical member is preferably attached to the superconducting bulk so that the inner peripheral surface thereof is bonded to the outer peripheral surface of the superconducting bulk via the adhesive layer (3). According to this, since the adhesive layer is interposed between the inner cylindrical member and the superconducting bulk, the inner peripheral surface of the inner cylindrical member is uniformly contacted with the entire outer peripheral surface of the superconducting bulk through the adhesive layer. Can be made. Therefore, when the superconducting bulk and the inner cylindrical member are brought into direct contact, the contact area is not limited (that is, both are in partial contact) due to the unevenness of the contact surfaces or distortion of the shape. For this reason, the superconducting bulk is damaged due to partial pressure increase due to limited contact area (partial contact), that is, due to unevenness of the contact surfaces or distortion of the shape of both surfaces. This can be effectively prevented.

  In this case, it is preferable that the adhesive layer interposed between the outer peripheral surface of the superconducting bulk and the inner cylindrical member is made of resin. According to this, the resin as the adhesive layer can uniformly transmit the compressive stress to the superconducting bulk by filling the gap between the outer peripheral surface of the superconducting bulk and the inner peripheral surface of the inner cylindrical member.

  In addition, the inner peripheral surface of the inner cylindrical member is a second region in which a gap (G) is formed between the first region (A) in direct contact with the outer peripheral surface of the superconducting bulk and the outer peripheral surface of the superconducting bulk. B) and the filler (6) is filled in the gap so that the second region is in indirect contact with the outer peripheral surface of the superconducting bulk via the filler. According to this, due to unevenness or voids formed on the contact surface between the inner cylindrical member and the superconducting bulk, or due to distortion of the shape, the inner peripheral surface of the inner cylindrical member directly contacts the outer peripheral surface of the superconducting bulk. The first region is not in direct contact with the outer peripheral surface of the superconducting bulk, and a second region in which a gap is formed between both surfaces is formed. And the filler is filled in the gap formed on the second region. By comprising in this way, the inner peripheral surface of an inner cylindrical member and the outer peripheral surface of a superconducting bulk can be made to contact the whole surface directly and indirectly.

  In this case, the filler may be formed of a material having fluidity. According to this, the filler interposed between the inner peripheral surface of the inner cylindrical member and the outer peripheral surface of the superconducting bulk flows by receiving a compressive stress from the outer cylindrical member. The flowing filler is reliably filled in the gap formed on the second region of the inner peripheral surface of the inner cylindrical member by the compressive stress from the outer cylindrical member.

  Furthermore, in this case, the filler may be formed of a material whose fluidity decreases with time. According to this, when it has fluidity | liquidity, the fluidity | liquidity of the filler with which it filled in the clearance gap formed on the 2nd area | region of the internal peripheral surface of an inner side cylindrical member declines with progress of time after that. For this reason, the filler that has entered the gap can be retained in the gap. An example of a material whose fluidity decreases with time is an epoxy adhesive.

  Moreover, the filler may be comprised with the material which is a solidified state below predetermined temperature. According to this, by lowering the temperature of the filler filled in the gap formed on the second region of the inner peripheral surface of the inner cylindrical member to a temperature equal to or lower than the predetermined temperature, the filler is solidified. The filler that has entered the gap can be retained in the gap. As the predetermined temperature, for example, a temperature when using a superconducting magnetic field generating element (for example, about −200 ° C.) can be exemplified. Examples of the filler that is solidified below a predetermined temperature include silicon grease.

  In the present invention, the outer cylindrical member may be shrink-fitted to the inner cylindrical member. According to this, the outer cylindrical member heated to a temperature higher than normal temperature is attached to the outer peripheral surface of the inner cylindrical member at normal temperature, and then the outer cylindrical member is cooled to normal temperature to heat the outer cylindrical member. By shrinking, the outer cylindrical member is shrink-fitted to the inner cylindrical member at room temperature. At this time, compressive stress acts on the inner cylindrical member from the outer cylindrical member, and further, compressive stress acts on the superconducting bulk attached to the inner peripheral side of the inner cylindrical member via the inner cylindrical member. . In this case, since the inner cylindrical member is interposed between the outer cylindrical member and the superconducting bulk, the heat of the outer cylindrical member at the time of shrink fitting is prevented from being directly transferred to the superconducting bulk. . Therefore, it is possible to prevent damage to the superconducting bulk due to thermal shock, and therefore it is possible to apply a larger compressive stress to the superconducting bulk. In addition, when an adhesive layer or filler is interposed between the outer peripheral surface of the superconducting bulk and the inner peripheral surface of the inner cylindrical member, heat from the outer cylindrical member is prevented from being directly transferred to the adhesive layer or filler. Is done. For this reason, it is possible to prevent a decrease in the adhesive ability of the adhesive layer (for example, when the adhesive layer is made of resin, the resin melts due to heat to lower the adhesive ability) or deterioration of the filler.

  Further, the outer cylindrical member may be cold-fitted to the inner cylindrical member. According to this, the outer cylindrical member of normal temperature is attached to the outer peripheral surface of the inner cylindrical member cooled to a temperature lower than normal temperature, and then the inner cylindrical member is heated to normal temperature and the inner cylindrical member is By thermally expanding, the outer cylindrical member is cooled and fitted to the inner cylindrical member at room temperature. At this time, compressive stress acts on the inner cylindrical member from the outer cylindrical member, and further, compressive stress acts on the superconducting bulk attached to the inner peripheral side of the inner cylindrical member via the inner cylindrical member. . In this case, the inner cylindrical member is slowly cooled together with the superconducting bulk, and after the outer cylindrical member is attached, the inner cylindrical member is slowly heated together with the superconducting bulk, so that the superconducting bulk due to thermal shock is increased. Can be prevented from being damaged.

  The outer cylindrical member may be made of a material having a thermal contraction rate equal to the thermal contraction rate of the inner cylindrical member or a thermal contraction rate larger than that of the inner cylindrical member. According to this, when the superconducting magnetic field generating element is cooled to a temperature equal to or lower than the superconducting transition temperature, the outer cylindrical member is thermally contracted to be equal to or higher than the inner cylindrical member, so that no gap is generated between them. Therefore, the compressive stress generated by the thermal contraction of both the outer cylindrical member and the inner cylindrical member can be applied to the superconducting bulk.

  Further, the outer cylindrical member may be constituted by a plurality of cylindrical members (5A, 5B) stacked in the radial direction. In this case, it is better to be configured so that stress in the compression direction acts on the contact surfaces of the adjacent cylindrical members at room temperature. According to this, the sum total of the compressive stress which each cylindrical member which comprises an outer cylindrical member generate | occur | produces at normal temperature can be made to act on a superconducting bulk.

  In this case, each cylindrical member constituting the outer cylindrical member is made of a material having a thermal contraction rate equal to or greater than the thermal contraction rate of the cylindrical member disposed adjacent to the inner diameter. Good. Alternatively, each cylindrical member constituting the outer cylindrical member may be made of a material having a Young's modulus equal to or greater than the Young's modulus of the cylindrical member adjacently disposed radially inward. Good. According to this, when the superconducting magnetic field generating element is cooled to a temperature equal to or lower than the superconducting transition temperature, the sum of the compressive stresses accompanying the thermal contraction of each cylindrical member constituting the outer cylindrical member is applied to the superconducting bulk. Can do.

  Further, the outer cylindrical member and the inner cylindrical member may be made of the same material. For example, both the outer cylindrical member and the inner cylindrical member may be made of an aluminum alloy. According to this, by forming the outer cylindrical member and the inner cylindrical member with the same material, it is possible to reduce the manufacturing cost as compared with the case of using different materials.

  Further, the total thickness (T) which is the sum of the inner thickness (t_in) which is the thickness in the radial direction of the inner cylindrical member and the outer thickness (t_out) which is the thickness in the radial direction of the outer cylindrical member. The ratio (t_in / T) of the inner wall thickness (t_in) with respect to is preferably 3/4 or less. In other words, the ratio (t_out / T) of the outer wall thickness (t_out) to the total wall thickness (T) is preferably 25% or more. According to this, it can be prevented that the compressive stress of the outer cylindrical member does not sufficiently act on the superconducting bulk due to the thickness of the inner cylindrical member being too large.

  Moreover, the ratio (t_in / T) of the inner wall thickness (t_in) to the total wall thickness (T) is preferably 1/10 or more. When the outer cylindrical member is shrink-fitted to the inner cylindrical member, the heat of the outer cylindrical member is transmitted to the inner cylindrical member. It is desirable that the heat transferred to the inner cylindrical member is radiated to the outside so as not to be transferred to the superconducting bulk located on the inner peripheral side, or to the adhesive layer or filler. In this case, the ratio (t_in / T) of the inner wall thickness (t_in) to the total wall thickness (T) is 1/10 or more, that is, the ratio of the inner wall thickness to the total wall thickness is 10% or more. Thus, the heat dissipation effect can be improved.

  The present invention also provides a cylindrical or cylindrical superconducting bulk (2), an inner cylindrical member (4) attached to the outer peripheral surface of the superconducting bulk, and an outer cylindrical member attached to the outer peripheral surface of the inner cylindrical member. A superconducting magnetic field generating element (1, 1A, 1B) comprising: a first step of attaching the inner cylindrical member to the outer peripheral surface of the superconducting bulk; and a temperature higher than the temperature of the inner cylindrical member The outer cylindrical member is disposed with respect to the inner cylindrical member so that the inner peripheral surface of the outer cylindrical member of the temperature faces the outer peripheral surface of the inner cylindrical member, and then the temperature of the inner cylindrical member and the outer A method of manufacturing a superconducting magnetic field generating element is provided that includes a second step of attaching an outer cylindrical member to an outer peripheral surface of an inner cylindrical member by reducing a difference from the temperature of the cylindrical member.

  According to the present invention, in the second step, the outer cylindrical member is arranged such that the inner peripheral surface of the outer cylindrical member having a temperature higher than the temperature of the inner cylindrical member faces the outer peripheral surface of the inner cylindrical member. Arranged against the inner cylindrical member, after which the difference between the temperature of the inner cylindrical member and the temperature of the outer cylindrical member is reduced. At this time, the outer cylindrical member is attached to the outer periphery of the inner cylindrical member by thermal contraction of the outer cylindrical member or by thermal expansion of the inner cylindrical member, and the outer cylindrical member tightens the inner cylindrical member. Thus, compressive stress from the outer cylindrical member acts on the superconducting bulk via the inner cylindrical member. For this reason, compressive stress is already acting on the superconducting bulk from the outer cylindrical member at the stage of manufacturing the superconducting magnetic field generating element. Therefore, when the superconducting magnetic field generating element is subsequently cooled to the superconducting transition temperature, in addition to the compressive stress generated by the thermal contraction of the inner cylindrical member and the outer cylindrical member, the compressive stress already generated in the manufacturing stage is added. . For this reason, the compressive stress that can counter the tensile stress generated in the superconducting bulk when the magnetic field is trapped in the superconducting bulk is increased by the compressive stress that has already occurred in the manufacturing stage. As described above, according to the present invention, it is possible to provide a method for manufacturing a superconducting magnetic field generating element configured to allow a sufficiently large compressive stress to act on the superconducting bulk.

  The first step includes a step of applying an adhesive on the outer peripheral surface of the superconducting bulk or the inner peripheral surface of the inner cylindrical member or both surfaces thereof, and the inner periphery of the inner cylindrical member on the outer peripheral surface of the superconducting bulk via the adhesive. Attaching the inner cylindrical member to the superconducting bulk so that the surfaces are in contact. According to this, since the adhesive layer is interposed between the inner cylindrical member and the superconducting bulk, the inner cylindrical member can be uniformly brought into contact with the entire outer peripheral surface of the superconducting bulk through the adhesive layer. Therefore, when the superconducting bulk and the inner cylindrical member are brought into direct contact with each other, it is effective that the superconducting bulk is damaged due to partial pressure increase due to unevenness or distortion of the shape of the contact surfaces of both. Can be prevented.

  The first step is a step of applying a fluid filler to the outer peripheral surface of the superconducting bulk or the inner peripheral surface of the inner cylindrical member or both surfaces thereof, and the inner side of the outer surface of the superconducting bulk through the filler. And attaching the inner cylindrical member to the superconducting bulk so that the inner peripheral surface of the cylindrical member contacts. In this case, the filler is made of a material that can change from a fluid state to a non-fluid state (that is, a solidified state), and the second step is superconductivity in the first step. It may be executed when the filler interposed between the outer peripheral surface of the bulk and the inner peripheral surface of the inner cylindrical member has a fluidity.

  According to the above invention, the filler is interposed between the outer peripheral surface of the superconducting bulk and the inner cylindrical member in the first step. And in a 2nd process, when a filler is a fluid state, an outer side cylindrical member is attached to the outer peripheral surface of an inner side cylindrical member. At this time, the filler flows due to the compressive stress acting on the superconducting bulk from the outer cylindrical member through the inner cylindrical member. Further, due to the compressive stress, the filler may be formed on the contact surface between the inner cylindrical member and the superconducting bulk. The gap is filled so as to almost completely close the gap formed between the two. On the other hand, in the portion where the gap is not formed, the inner peripheral surface of the inner cylindrical member is in direct contact with the outer peripheral surface of the superconducting bulk without using a filler. In this way, the inner peripheral surface of the inner cylindrical member and the outer peripheral surface of the superconducting bulk can be brought into direct contact with each other, so that the superconducting bulk and the inner cylindrical member are in partial contact with each other to concentrate stress. It is possible to effectively prevent the superconducting bulk from being damaged.

  In the second step, the outer cylindrical member is placed on the inner side so that the inner peripheral surface of the outer cylindrical member heated to a temperature higher than the temperature of the inner cylindrical member faces the outer peripheral surface of the inner cylindrical member. It is good to be a process of attaching an outer cylindrical member to an outer peripheral surface of an inner cylindrical member by arranging the cylindrical member and then cooling the outer cylindrical member. That is, the outer cylindrical member may be attached to the inner cylindrical member by shrink fitting. Alternatively, in the second step, the outer cylindrical member is placed on the inner side so that the inner peripheral surface of the outer cylindrical member faces the outer peripheral surface of the inner cylindrical member cooled to a temperature lower than the temperature of the outer cylindrical member. The step may be a step of attaching the outer cylindrical member to the outer peripheral surface of the inner cylindrical member by arranging the cylindrical member and then raising the temperature of the inner cylindrical member. That is, the outer cylindrical member may be attached to the inner cylindrical member by cold fitting.

  Further, the outer cylindrical member is constituted by a plurality of cylindrical members (5A, 5B) stacked in the radial direction, and the second step includes a step of attaching the plurality of cylindrical members in order from the inner diameter side, And at least the temperature at the time of attachment of the cylindrical member attached to the i-th is good to be made higher than the temperature of the cylindrical member attached to the i-1st. According to this, at least one of the plurality of cylindrical members constituting the outer cylindrical member is shrink-fitted or cold-fitted, thereby applying a compressive stress from the outer cylindrical member to the superconducting bulk at room temperature. Can do.

FIG. 1 is a perspective view showing a schematic configuration of a superconducting magnetic field generating element according to the first embodiment and the second embodiment. FIG. 2A is a diagram showing a first step of the manufacturing method according to the first embodiment. FIG. 2B is a perspective view showing a schematic configuration of an intermediate assembly produced by performing the first step of the manufacturing method according to the first embodiment. FIG. 3 is a diagram illustrating a second step of the manufacturing method according to the first embodiment. FIG. 4 is a perspective view showing a schematic configuration of the superconducting magnetic field generating element according to the third embodiment. FIG. 5A is a diagram showing a first step of the manufacturing method according to the third embodiment. FIG. 5B is a perspective view illustrating a schematic configuration of a first intermediate assembly that is manufactured by performing the first step of the manufacturing method according to the third embodiment. FIG. 6A is a diagram showing an inner shrinkage fitting step of the second step of the manufacturing method according to the third embodiment. FIG. 6B is a perspective view illustrating a schematic configuration of a second intermediate assembly that is manufactured by performing an inner shrinkage fitting step of the second step of the manufacturing method according to the third embodiment. FIG. 7 is a view showing an outer shrink-fitting process of the second process of the manufacturing method according to the third embodiment. FIG. 8 is a diagram illustrating a schematic configuration of the superconducting magnetic field generating element used for calculation of the compressive stress according to the first embodiment. FIG. 9 is a diagram illustrating a method for shrink fitting the outer cylindrical member shown in the case 1 of the first embodiment. FIG. 10 is a diagram illustrating a schematic configuration of a superconducting magnetic field generating element used for calculation of compressive stress according to the second embodiment. FIG. 11 is a perspective view showing a schematic configuration of the superconducting magnetic field generating element according to the fourth embodiment. FIG. 12A is a diagram showing a part of a cross section obtained by cutting the superconducting magnetic field generating element according to the fourth embodiment along a plane including its axis. FIG. 12B is a detailed view of a portion C which is a region portion including a contact interface between the inner cylindrical member and the superconducting bulk in FIG. 12A. FIG. 12C is a diagram showing a part of a cross section obtained by cutting the superconducting magnetic field generating element according to the first embodiment along a plane including its axis. FIG. 13A is a diagram showing a first step of the manufacturing method according to the fourth embodiment. FIG. 13B is a perspective view showing a state in which the inner cylindrical member is attached to the superconducting bulk by performing the first step of the manufacturing method according to the fourth embodiment. FIG. 14 is a diagram illustrating a second step of the manufacturing method according to the fourth embodiment.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described. FIG. 1 is a perspective view showing a schematic configuration of a superconducting magnetic field generating element 1 according to the first embodiment. As shown in FIG. 1, the superconducting magnetic field generating element 1 according to the first embodiment includes a superconducting bulk 2, an adhesive layer 3, an inner cylindrical member 4, and an outer cylindrical member 5.

  The superconducting bulk 2 is a massive high-temperature superconducting molded body produced mainly by a melting method. Examples of the high-temperature superconducting material constituting the superconducting bulk 2 include yttrium (Y—Ba—Cu—O), samarium (Sm—Ba—Cu—O), and neodymium (Nd—Ba—Cu—O). System), europium-based (Eu-Ba-Cu-O-based) and other high-temperature superconducting materials.

  In this embodiment, the shape of the superconducting bulk 2 is a cylindrical shape in which a hole 2a having a circular cross section is formed at the center. An inner cylindrical member 4 is disposed on the outer peripheral surface of the cylindrical superconducting bulk 2. An adhesive layer 3 made of a resin (for example, epoxy resin) is provided between the outer peripheral surface of the superconducting bulk 2 and the inner peripheral surface of the inner cylindrical member 4. That is, the inner cylindrical member 4 is attached to the superconducting bulk 2 such that the inner peripheral surface thereof is in contact with the outer peripheral surface of the superconducting bulk 2 via the adhesive layer 3.

  The outer cylindrical member 5 is attached to the inner cylindrical member 4 such that the inner peripheral surface thereof is in contact with the outer peripheral surface of the inner cylindrical member 4. Therefore, as shown in FIG. 1, the superconducting bulk 2, the inner cylindrical member 4, and the outer cylindrical member 5 are coaxially disposed, and the inner cylindrical member 4 surrounds the outer peripheral surface of the superconducting bulk 2, The outer cylindrical member 5 surrounds the outer peripheral surface of the inner cylindrical member 4.

  In the present embodiment, both the inner cylindrical member 4 and the outer cylindrical member 5 are made of a metal material. The inner cylindrical member 4 and the outer cylindrical member 5 are both made of a metal material having a thermal contraction rate larger than that of the superconducting bulk 2. Further, the outer cylindrical member 5 is made of a metal material having a contraction rate equal to the thermal contraction rate of the inner cylindrical member 4 or a thermal contraction rate larger than that of the inner cylindrical member 4. In other words, when the thermal contraction rate of the superconducting bulk 2 is α1, the thermal contraction rate of the inner cylindrical member 4 is α2, and the thermal contraction rate of the outer cylindrical member 5 is α3, α1 <α2 ≦ α3. . Examples of the material forming the inner cylindrical member 4 having such a thermal shrinkage relationship include aluminum, aluminum alloy, or titanium, and examples of the material forming the outer cylindrical member 5 include aluminum or aluminum alloy. When the thermal contraction rate α2 of the inner cylindrical member 4 and the thermal contraction rate α3 of the outer cylindrical member 5 are the same, the inner cylindrical member 4 and the outer cylindrical member 5 are made of the same material (for example, aluminum or aluminum alloy). ).

  Further, both the inner cylindrical member 4 and the outer cylindrical member 5 may be made of a material having a Young's modulus larger than that of the superconducting bulk 2. Further, the outer cylindrical member 5 may be made of a material having a Young's modulus equal to the Young's modulus of the inner cylindrical member 4 or a Young's modulus larger than the Young's modulus of the inner cylindrical member 4. That is, when the Young's modulus of the superconducting bulk 2 is β1, the Young's modulus of the inner cylindrical member 4 is β2, and the Young's modulus of the outer cylindrical member 5 is β3, the relationship is β1 <β2 ≦ β3.

  The adhesive layer 3 is made of, for example, an epoxy resin. The adhesive layer 3 is provided between the outer peripheral surface of the superconducting bulk 2 and the inner peripheral surface of the inner cylindrical member 4. The adhesive layer 3 has a function of uniformly bonding the outer peripheral surface of the superconducting bulk 2 and the inner peripheral surface of the inner cylindrical member 4.

  In the superconducting magnetic field generating element 1 according to the first embodiment, the outer cylindrical member 5 fastens the inner cylindrical member 4 at room temperature. Accordingly, the tightening force of the outer cylindrical member 5 is transmitted to the superconducting bulk 2 via the inner cylindrical member 4. For this reason, stress in the direction from the outer peripheral side toward the center side, that is, compressive stress, acts on the superconducting bulk 2. That is, the outer cylindrical member 5 is attached to the inner cylindrical member 4 so that compressive stress acts on the superconducting bulk 2 at room temperature.

  When generating a magnetic field in the superconducting magnetic field generating element 1 having such a configuration, for example, the superconducting magnetic field generating element 1 is put into a bore provided in the magnetizing apparatus. Next, an external magnetic field for magnetization is applied to the superconducting magnetic field generating element 1. The magnitude of this external magnetic field is, for example, 10T. Thereafter, the superconducting magnetic field generating element 1 is cooled to a temperature not higher than the superconducting transition temperature of the superconducting bulk 2, for example, about 50K, using a refrigerant or a cooler. After cooling is completed, the applied external magnetic field is removed. At this time, a magnetic field is trapped in the superconducting bulk 2. Thereby, a magnetic field is generated from the superconducting magnetic field generating element 1.

  The magnetizing method described above is a magnetizing method called FC (cooling in a magnetic field), but the magnetizing method may be ZFC (cooling in a zero magnetic field) or PFM (pulse magnetizing method). .

  When the superconducting magnetic field generating element 1 generates a magnetic field, the superconducting bulk 2 is cooled to a temperature equal to or lower than the superconducting transition temperature by any magnetization method. By this cooling, the superconducting bulk 2, the inner cylindrical member 4, and the outer cylindrical member 5 are thermally contracted. Here, the thermal contraction rate of the inner cylindrical member 4 and the outer cylindrical member 5 is larger than the thermal contraction rate of the superconducting bulk 2, respectively. Further, the thermal contraction rate of the outer cylindrical member 5 is equal to or higher than the thermal contraction rate of the inner cylindrical member 4. Therefore, when the superconducting bulk 2 captures a magnetic field (hereinafter sometimes referred to as using the superconducting magnetic field generating element 1), the inner cylindrical member 4 is caused to contract by the thermal contraction of the inner cylindrical member 4. 2, and the outer cylindrical member 5 tightens the inner cylindrical member 4 and the superconducting bulk 2 by heat shrinkage of the outer cylindrical member 5. Thus, when the superconducting magnetic field generating element 1 is used, the superconducting bulk 2 is subjected to compressive stress from the inner cylindrical member 4 and compressive stress from the outer cylindrical member 5 due to thermal contraction during cooling.

  Further, when the superconducting bulk 2 captures a magnetic field, tensile stress acts on the superconducting bulk 2 as described above. The compressive stress acts on the superconducting bulk 2 to counter this tensile stress. Here, in this embodiment, in addition to the compressive stress generated due to the thermal contraction of the inner cylindrical member 4 and the outer cylindrical member 5 during cooling, the outer cylindrical member 5 already has a superconducting bulk at room temperature. It is attached to the inner cylindrical member 4 so as to apply a compressive stress to 2. Therefore, the compressive stress obtained when the superconducting magnetic field generating element 1 is used is a conventional superconducting magnetic field generating element configured to reinforce the superconducting bulk by one cylindrical member having the same outer dimensions as the outer cylindrical member 5 ( Compared with the compressive stress obtained at the time of use of the conventional element), it is increased by the amount of the compressive stress already generated at room temperature. Therefore, compared with the conventional element using the cylindrical member of the same dimension, the compressive stress which can oppose a tensile stress is high. As a result, the magnetic field that can be magnetized in the superconducting bulk 2 without the superconducting bulk 2 being cracked by tensile stress can be increased.

  In addition, since the adhesive layer 3 for bonding both surfaces of the superconducting bulk 2 and the inner cylindrical member 4 is interposed between the superconducting bulk 2 and the inner cylindrical member 4, the inner cylindrical member 4 is attached to the outer peripheral surface of the superconducting bulk 2 via the adhesive layer 3. Contact the entire surface evenly. Therefore, when the superconducting bulk 2 and the inner cylindrical member 4 are brought into direct contact with each other, they are partially in contact with each other due to unevenness and distortion of the shape of the contact surfaces, and compressive stress is concentrated on the contact portion. It is possible to effectively prevent the superconducting bulk 2 from being damaged by (increasing pressure).

  Next, a method for manufacturing the superconducting magnetic field generating element 1 according to the first embodiment will be described. The manufacturing method of the superconducting magnetic field generating element 1 according to the first embodiment includes a first step and a second step. FIG. 2A is a diagram showing the first step, and FIG. 2B is a perspective view showing a schematic configuration of the intermediate assembly 11 produced by performing the first step. Moreover, FIG. 3 is a figure which shows a 2nd process.

  In the first step, an adhesive made of epoxy resin is applied to the outer peripheral surface of the superconducting bulk 2 or the inner peripheral surface of the inner cylindrical member 4, and then the outer peripheral surface of the cylindrical superconducting bulk 2 is the inner cylindrical member 4. The superconducting bulk 2 is concentrically arranged on the inner peripheral side of the inner cylindrical member 4 so as to face the outer peripheral surface of the inner cylindrical member 4. If the temperature of the superconducting bulk 2 and the inner cylindrical member 4 at the time of performing the first step is the temperature T1, the outer diameter OD_B of the superconducting bulk 2 is higher than the inner diameter ID1 of the inner cylindrical member 4 at the temperature T1. small. Accordingly, the adhesive is filled between the outer peripheral surface of the superconducting bulk 2 arranged concentrically and the inner cylindrical member 4. Then, it is allowed to stand until the filled adhesive is solidified. 2B, in which the inner cylindrical member 4 is attached to the superconducting bulk 2 such that the inner peripheral surface of the inner cylindrical member 4 contacts the outer peripheral surface of the superconducting bulk 2 via the adhesive layer 3. The assembly 11 is produced. The temperature T1 is preferably normal temperature (5 ° C. to 35 ° C.), for example.

  In the second step, the outer cylindrical member 5 is attached to the outer peripheral surface of the inner cylindrical member 4 attached to the outer peripheral surface of the superconducting bulk 2 via the adhesive layer 3, that is, the outer peripheral surface of the intermediate assembly 11. In this case, first, an outer cylindrical member 5 having a temperature T1 is prepared. The inner diameter ID2 of the outer cylindrical member 5 is slightly smaller than the outer diameter OD1 of the inner cylindrical member 4 at the temperature T1 attached to the outer periphery of the superconducting bulk 2 at the temperature T1. That is, ID2 <OD1 at the temperature T1.

  Next, the prepared outer cylindrical member 5 having a temperature T1 is heated to a temperature T2 higher than the temperature T1. For example, when the temperature T1 is normal temperature, the outer cylindrical member 5 is heated to about 300 ° C. in the second step. By this heating, the outer cylindrical member 5 is thermally expanded. For this reason, the inner diameter ID2 of the outer cylindrical member 5 widens, and the inner diameter ID2 of the outer cylindrical member 5 becomes larger than the outer diameter OD1 of the inner cylindrical member 4 provided in the intermediate assembly 11.

  Next, as shown in FIG. 3, the outer peripheral surface of the outer cylindrical member 5 heated to the temperature T <b> 2 faces the outer peripheral surface of the inner cylindrical member 4 (the outer peripheral surface of the intermediate assembly 11). The cylindrical member 5 is disposed concentrically with the inner cylindrical member 4. Thereafter, the outer cylindrical member 5 is cooled to a temperature T1. The cooling method is not particularly limited, but the outer cylindrical member 5 is cooled by, for example, natural cooling or by supplying cold air to the outer cylindrical member 5. Due to the heat shrinkage due to the cooling, the inner diameter ID2 of the outer cylindrical member 5 becomes smaller. When the temperature of the outer cylindrical member 5 is cooled to the temperature T1, the inner diameter ID2 of the outer cylindrical member 5 in the natural state becomes smaller than the outer diameter OD1 of the inner cylindrical member 4. Therefore, the outer cylindrical member 5 is attached to the outer peripheral surface of the inner cylindrical member 4 (the outer peripheral surface of the intermediate assembly 11), and the inner cylindrical member 4 is tightened. Such a tightening force acts on the superconducting bulk 2.

  The superconducting magnetic field generating element 1 according to the first embodiment as shown in FIG. 1 is manufactured through the first process and the second process described above. According to this manufacturing method, in the second step, the inner peripheral surface of the outer cylindrical member 5 having a temperature (T2) higher than the temperature (T1) of the inner cylindrical member 4 becomes the outer peripheral surface of the inner cylindrical member 4. The outer cylindrical member 5 is disposed with respect to the inner cylindrical member 4 so as to face each other. Thereafter, the outer cylindrical member 5 is cooled, so that the difference between the temperature of the inner cylindrical member 4 and the temperature of the outer cylindrical member 5 is reduced. At this time, the outer cylindrical member 5 is attached to the outer periphery of the inner cylindrical member 4 by the thermal contraction of the outer cylindrical member 5, and the outer cylindrical member 5 fastens the inner cylindrical member 4. That is, the outer cylindrical member 5 is shrink-fitted to the inner cylindrical member 4. For this reason, the compressive stress from the outer cylindrical member 5 acts on the superconducting bulk 2 via the inner cylindrical member 4. Thus, compressive stress has already been applied from the outer cylindrical member 5 to the superconducting bulk 2 at the stage of manufacturing the superconducting magnetic field generating element 1. Therefore, when the superconducting magnetic field generating element 1 is subsequently cooled to a temperature equal to or lower than the superconducting transition temperature, in addition to the compressive stress generated by the thermal contraction of the inner cylindrical member 4 and the outer cylindrical member 5, it has already occurred in the manufacturing stage. Compressive stress is applied. For this reason, the compressive stress that can resist the tensile stress generated in the superconducting bulk 2 when the superconducting bulk 2 captures the magnetic field is increased by the compressive stress that has already occurred in the manufacturing stage. Further, since the adhesive layer 3 is interposed between the inner cylindrical member 4 and the superconducting bulk 2, the inner cylindrical member 4 is uniformly brought into contact with the entire outer peripheral surface of the superconducting bulk 2 through the adhesive layer 3. be able to. Therefore, when the superconducting bulk 2 and the inner cylindrical member 4 are brought into direct contact with each other, the superconducting bulk 2 may be damaged due to partial pressure increase due to unevenness or distortion of the shape of the contact surfaces of both. Can be effectively prevented. As described above, according to the present embodiment, the superconducting magnetic field generating element configured so that a sufficiently large compressive stress can be applied uniformly to the superconducting bulk 2 without destroying the superconducting bulk 2 at the time of use. A manufacturing method can be provided.

  Moreover, since the inner cylindrical member 4 is interposed between the outer cylindrical member 5 and the superconducting bulk 2, the heat of the outer cylindrical member 5 when the outer cylindrical member 5 is shrink-fitted in the second step is reduced. Further, direct transmission to the superconducting bulk 2 and the adhesive layer 3 is prevented. Therefore, damage to the superconducting bulk 2 due to thermal shock can be prevented, and the adhesive ability of the adhesive layer 3 is reduced by heat (for example, when the adhesive layer 3 is made of resin, the resin is melted by heat. The adhesive ability is reduced).

(Second embodiment)
The configuration of the superconducting magnetic field generating element according to the second embodiment is the same as the configuration of the superconducting magnetic field generating element 1 according to the first embodiment shown in FIG. Therefore, the superconducting magnetic field generating element 1 shown in FIG. 1 is also a superconducting magnetic field generating element according to the second embodiment.

  The manufacturing method of the superconducting magnetic field generating element according to the second embodiment includes a first step and a second step, as in the manufacturing method of the superconducting magnetic field generating element according to the first embodiment. The first step is the same as the first step of the method for manufacturing a superconducting magnetic field generating element according to the first embodiment. That is, in the first step, an adhesive made of epoxy resin is applied to the outer peripheral surface of the superconducting bulk 2 or the inner peripheral surface of the inner cylindrical member 4, and then the outer peripheral surface of the cylindrical superconducting bulk 2 is the inner cylindrical member. The superconducting bulk 2 is concentrically arranged on the inner peripheral side of the inner cylindrical member 4 so as to face the outer peripheral surface of the inner cylindrical member 4. If the temperature of the superconducting bulk 2 and the inner cylindrical member 4 at the time of performing the first step is the temperature T1, the outer diameter OD_B of the superconducting bulk 2 is higher than the inner diameter ID1 of the inner cylindrical member 4 at the temperature T1. small. Accordingly, the adhesive is filled between the outer peripheral surface of the superconducting bulk 2 arranged concentrically and the inner cylindrical member 4. Then, it is allowed to stand until the filled adhesive is solidified. 2B, in which the inner cylindrical member 4 is attached to the superconducting bulk 2 such that the inner peripheral surface of the inner cylindrical member 4 contacts the outer peripheral surface of the superconducting bulk 2 via the adhesive layer 3. The assembly 11 is produced.

  In the second step, the outer cylindrical member 5 is attached to the outer peripheral surface of the inner cylindrical member 4 attached to the outer peripheral surface of the superconducting bulk 2 via the adhesive layer 3, that is, the outer peripheral surface of the intermediate assembly 11. In this case, first, an outer cylindrical member 5 having a temperature T1 is prepared. The inner diameter ID2 of the outer cylindrical member 5 is slightly smaller than the outer diameter OD1 of the inner cylindrical member 4 at the temperature T1 attached to the outer periphery of the superconducting bulk 2 at the temperature T1. That is, ID2 <OD1 at the temperature T1.

  Next, the superconducting bulk 2 and the inner cylindrical member 4 attached to the superconducting bulk 2 via the adhesive layer 3 are cooled to a temperature T0 lower than the temperature T1. For example, when the temperature T1 is normal temperature, the superconducting bulk 2 and the inner cylindrical member 4 are cooled to −196 ° C. with liquid nitrogen in this second step. In this cooling process, the superconducting bulk 2 and the inner cylindrical member 4 are filled with liquid nitrogen over time in a container in which they are placed so that stress due to thermal shock does not occur. Thereby, the superconducting bulk 2 and the inner cylindrical member 4 are slowly cooled. By this cooling, the inner cylindrical member 4 is thermally contracted. For this reason, the outer diameter OD1 of the inner cylindrical member 4 shrinks, and the inner diameter ID2 of the outer cylindrical member 5 becomes larger than the outer diameter OD1 of the inner cylindrical member 4.

  Next, the outer cylindrical member 5 is placed on the inner cylindrical member 4 so that the inner peripheral surface of the outer cylindrical member 5 faces the outer peripheral surface of the cooled inner cylindrical member 4 (the outer peripheral surface of the intermediate assembly 11). Are concentrically arranged. Thereafter, the superconducting bulk 2 and the inner cylindrical member 4 are heated to a temperature T1. The temperature raising method is not particularly limited, but it is preferable to raise the temperature slowly so that stress due to thermal shock is not generated. For example, the superconducting bulk 2 and the inner cylindrical member 4 are slowly heated by stopping the cooling of the inner cylindrical member 4 and leaving it to stand at room temperature for a predetermined time. Due to the thermal expansion due to the temperature increase, the inner diameter ID1 of the inner cylindrical member 4 increases. When the temperature of the inner cylindrical member 4 is raised to the temperature T1, the outer diameter OD1 of the inner cylindrical member 4 in the natural state becomes larger than the inner diameter ID2 of the outer cylindrical member 5. Therefore, the outer cylindrical member 5 is attached to the inner cylindrical member 4 and the inner cylindrical member 4 is tightened. Such a tightening force acts on the superconducting bulk 2.

  The superconducting magnetic field generating element 1 according to the second embodiment is manufactured through the first process and the second process described above. According to this manufacturing method, the inner peripheral surface of the outer cylindrical member 5 having a temperature (T1) higher than the temperature (T0) of the inner cylindrical member 4 cooled in the second step is the inner cylindrical member 4. The outer cylindrical member 5 is disposed on the inner cylindrical member 4 so as to face the outer peripheral surface of the inner cylindrical member 4. Thereafter, the inner cylindrical member 4 is heated (heated), whereby the difference between the temperature of the inner cylindrical member 4 and the temperature of the outer cylindrical member 5 is reduced. At this time, due to thermal expansion of the inner cylindrical member 4, the outer cylindrical member 5 is attached to the outer periphery of the inner cylindrical member 4, and the outer cylindrical member 5 fastens the inner cylindrical member 4. That is, the outer cylindrical member 5 is cold-fitted to the inner cylindrical member 4. For this reason, the compressive stress from the outer cylindrical member 5 acts on the superconducting bulk 2 via the inner cylindrical member 4. Thus, compressive stress has already been applied from the outer cylindrical member 5 to the superconducting bulk 2 at the stage of manufacturing the superconducting magnetic field generating element 1. Therefore, when the superconducting magnetic field generating element 1 is subsequently cooled to a temperature equal to or lower than the superconducting transition temperature, in addition to the compressive stress generated by the thermal contraction of the inner cylindrical member 4 and the outer cylindrical member 5, it has already occurred in the manufacturing stage. Compressive stress is applied. For this reason, the compressive stress that can resist the tensile stress generated in the superconducting bulk 2 when the superconducting bulk 2 captures the magnetic field is increased by the compressive stress that has already occurred in the manufacturing stage. Further, since the adhesive layer 3 is interposed between the inner cylindrical member 4 and the superconducting bulk 2, the inner cylindrical member 4 is uniformly brought into contact with the entire outer peripheral surface of the superconducting bulk 2 through the adhesive layer 3. be able to. Therefore, when the superconducting bulk 2 and the inner cylindrical member 4 are brought into direct contact with each other, the superconducting bulk 2 may be damaged due to partial pressure increase due to unevenness or distortion of the shape of the contact surfaces of both. Can be effectively prevented. As described above, according to the present embodiment, there is provided a method for manufacturing a superconducting magnetic field generating element configured to allow a sufficiently large compressive stress to uniformly act on the superconducting bulk 2 without destroying the superconducting bulk 2. Can be provided.

(Third embodiment)
Next, the superconducting magnetic field generating element according to the third embodiment will be described. FIG. 4 is a perspective view showing a schematic configuration of the superconducting magnetic field generating element according to the third embodiment. As shown in FIG. 4, the superconducting magnetic field generating element 1A according to the third embodiment is similar to the superconducting magnetic field generating element 1 according to the first embodiment, in that a superconducting bulk 2, an adhesive layer 3, and an inner cylindrical member 4 are used. And an outer cylindrical member 5.

  The configurations of the superconducting bulk 2, the adhesive layer 3, and the inner cylindrical member 4 are the same as the configurations of the superconducting bulk 2, the adhesive layer 3, and the inner cylindrical member 4 provided in the superconducting magnetic field generating element according to the first embodiment. Since they are the same, a specific description thereof is omitted.

  In the present embodiment, the outer cylindrical member 5 includes a first outer cylindrical member 5A and a second outer cylindrical member 5B. The first outer cylindrical member 5A is disposed inside the second outer cylindrical member 5B. In the assembled state, the outer peripheral surface of the first outer cylindrical member 5A faces the inner peripheral surface of the second outer cylindrical member 5B. Contact. That is, in the present embodiment, the outer cylindrical member 5 includes a plurality of (two in the present embodiment) cylindrical members (first outer cylindrical member 5A and second outer cylindrical member 5B) stacked in the radial direction. ).

  In the present embodiment, the second outer cylindrical member 5B is made of a metal material having a thermal contraction rate equal to or greater than that of the first outer cylindrical member 5A. Further, the thermal contraction rate of the first outer cylindrical member 5A is equal to or greater than the thermal contraction rate of the inner cylindrical member 4, and the thermal contraction rate of the inner cylindrical member 4 is the thermal contraction of the superconducting bulk 2. Greater than rate. That is, the heat shrinkage rate of the superconducting bulk 2 is α1, the heat shrinkage rate of the inner cylindrical member 4 is α2, the heat shrinkage rate of the first outer cylindrical member 5A is α3_1, and the heat of the second outer cylindrical member 5B. When the contraction rate is α3_2, there is a relationship of α1 <α2 ≦ α3_1 ≦ α3_2. That is, each cylindrical member (5A, 5B) constituting the outer cylindrical member 5 has a thermal contraction rate equal to or larger than the thermal contraction rate of the cylindrical member disposed adjacent to the inner side in the diameter. It is comprised by the material which has. Further, when the thermal contraction rate α2 of the inner cylindrical member 4, the thermal contraction rate α3_1 of the first outer cylindrical member 5A, and the thermal contraction rate α3_2 of the second outer cylindrical member 5B are the same, the inner cylindrical member 4, The first outer cylindrical member 5A and the second outer cylindrical member 5B may be made of the same material (for example, aluminum or aluminum alloy).

  The second outer cylindrical member 5B may be made of a material having a Young's modulus equal to or greater than the Young's modulus of the first outer cylindrical member 5A. In this case, the Young's modulus of the superconducting bulk 2 is β1, the Young's modulus of the inner cylindrical member 4 is β2, the Young's modulus of the first outer cylindrical member 5A is β3_1, and the Young's modulus of the second outer cylindrical member 5B is When β3_2, a relationship of β1 <β2 ≦ β3_1 ≦ β3_2 may be satisfied. That is, each cylindrical member (5A, 5B) constituting the outer cylindrical member 5 is made of a material having a Young's modulus equal to or larger than the Young's modulus of the cylindrical member adjacently arranged radially inward. You may comprise by.

  Other configurations are the same as the respective configurations provided in the superconducting magnetic field generating element 1 described in the first embodiment, and thus the detailed description thereof is omitted.

  In the superconducting magnetic field generating element 1A according to the third embodiment, one or both of the first outer cylindrical member 5A and the second outer cylindrical member 5B constituting the outer cylindrical member 5 is an inner cylinder at room temperature. The member 4 is tightened. Accordingly, the tightening force of the outer cylindrical member 5 is transmitted to the superconducting bulk 2 via the inner cylindrical member 4. For this reason, stress in the direction from the outer peripheral side toward the center side, that is, compressive stress, acts on the superconducting bulk 2. That is, the outer cylindrical member 5 is attached to the inner cylindrical member 4 so that compressive stress acts on the superconducting bulk 2 at room temperature.

  Therefore, the compressive stress obtained when using the superconducting magnetic field generating element 1A according to the third embodiment is configured to reinforce the superconducting bulk by one cylindrical member having the same outer dimensions as the second outer cylindrical member 5B. Compared with the compressive stress obtained when the conventional superconducting magnetic field generating element (conventional element) is used, it is increased by the amount of compressive stress already generated at room temperature. Therefore, compared with the conventional element using the cylindrical member of the same dimension, the compressive stress which can oppose a tensile stress is high. As a result, the magnetic field that can be magnetized in the superconducting bulk 2 without the superconducting bulk 2 being cracked by tensile stress can be increased.

  In addition, since the adhesive layer 3 for bonding both surfaces of the superconducting bulk 2 and the inner cylindrical member 4 is interposed between the superconducting bulk 2 and the inner cylindrical member 4, the inner cylindrical member 4 is attached to the outer peripheral surface of the superconducting bulk 2 via the adhesive layer 3. Contact the entire surface evenly. Therefore, when the superconducting bulk 2 and the inner cylindrical member 4 are brought into direct contact with each other, the superconducting bulk 2 is damaged due to partial pressure increase due to unevenness and distortion of the shape of the contact surfaces of both. It can be effectively prevented.

  Next, a method for manufacturing the superconducting magnetic field generating element 1 according to the third embodiment will be described. The manufacturing method of the superconducting magnetic field generating element 1A according to the third embodiment also includes the first step and the second step, similarly to the manufacturing method of the superconducting magnetic field generating element 1 according to the first embodiment. FIG. 5A is a diagram showing the first step, and FIG. 5B is a perspective view showing a schematic configuration of the first intermediate assembly 12 produced by performing the first step.

  In the first step, an adhesive made of epoxy resin is applied to the outer peripheral surface of the superconducting bulk 2 or the inner peripheral surface of the inner cylindrical member 4, and then the outer peripheral surface of the cylindrical superconducting bulk 2 is the inner cylindrical member 4. The superconducting bulk 2 is concentrically arranged on the inner peripheral side of the inner cylindrical member 4 so as to face the outer peripheral surface of the inner cylindrical member 4. When the temperature at the time of performing the first step is T1, the outer diameter OD_B of the superconducting bulk 2 is smaller than the inner diameter ID1 of the inner cylindrical member 4 at the temperature T1. Accordingly, the adhesive is filled between the outer peripheral surface of the superconducting bulk 2 arranged concentrically and the inner cylindrical member 4. Then, it is allowed to stand until the filled adhesive is solidified. As a result, the inner cylindrical member 4 is attached to the superconducting bulk 2 so that the inner peripheral surface of the inner cylindrical member 4 is in contact with the outer peripheral surface of the superconducting bulk 2 via the adhesive layer 3. One intermediate assembly 11 is produced. The temperature T1 is preferably normal temperature (5 ° C. to 35 ° C.), for example.

  In the second step, the outer cylindrical member 5 is attached to the outer peripheral surface of the inner cylindrical member 4 attached to the outer peripheral surface of the superconducting bulk 2 via the adhesive layer 3, that is, the outer peripheral surface of the first intermediate assembly 12. It is done. In the third embodiment, the second process includes an inner shrink fitting process and an outer shrink fitting process. In the inner shrink fitting process, the first outer cylindrical member 5 </ b> A is shrink fitted to the outer peripheral surface of the inner cylindrical member 4. In the outer shrink fitting process, the second outer cylindrical member 5B is shrink fitted to the outer peripheral surface of the first outer cylindrical member 5A. FIG. 6A is a diagram showing the inner shrink fitting process, and FIG. 6B is a perspective view showing a schematic configuration of the second intermediate assembly 13 produced by performing the inner shrink fitting process.

  In the inner shrink fitting process, first, a first outer cylindrical member 5A having a temperature T1 is prepared. The inner diameter ID2 of the first outer cylindrical member 5A is slightly smaller than the outer diameter OD1 of the inner cylindrical member 4 at the temperature T1 provided in the first intermediate assembly 12 at the temperature T1. That is, ID2 <OD1 at the temperature T1.

  Next, the prepared first outer cylindrical member 5A having the temperature T1 is heated to a temperature T2 higher than the temperature T1. For example, when the temperature T1 is normal temperature, the first outer cylindrical member 5A is heated to about 300 ° C. By this heating, the first outer cylindrical member 5A is thermally expanded. For this reason, the inner diameter ID2 of the first outer cylindrical member 5A expands, and the inner diameter ID2 of the first outer cylindrical member 5A becomes larger than the outer diameter OD1 of the inner cylindrical member 4 provided in the first intermediate assembly 12. .

  Next, the first outer cylindrical member 5A is heated so that the inner peripheral surface of the first outer cylindrical member 5A heated to the temperature T2 faces the outer peripheral surface of the inner cylindrical member 4 (first intermediate assembly 12). Are arranged concentrically with respect to the inner cylindrical member 4. Thereafter, the first outer cylindrical member 5A is cooled to a temperature T1. Although the cooling method is not particularly limited, for example, the first outer cylindrical member 5A is cooled by natural cooling or by supplying cold air to the first outer cylindrical member 5A. Due to the heat shrinkage due to the cooling, the inner diameter ID2 of the first outer cylindrical member 5A becomes smaller. When the temperature of the first outer cylindrical member 5A is cooled to the temperature T1, the inner diameter ID2 of the first outer cylindrical member 5A in the natural state is smaller than the outer diameter OD1 of the inner cylindrical member 4. Therefore, the first outer cylindrical member 5A is attached to the outer peripheral surface of the inner cylindrical member 4 (the outer peripheral surface of the first intermediate assembly 12), and the second intermediate assembly 13 as shown in FIG. 6B is produced. . When the second intermediate assembly 13 is thus produced, the first outer cylindrical member 5 </ b> A of the second intermediate assembly 13 fastens the inner cylindrical member 4. Such a tightening force acts on the superconducting bulk 2.

  FIG. 7 is a diagram showing an outer shrink fitting process of the second process. In the following description, the outer shrink fitting process is performed after the inner shrink fitting process. In the outer shrink fitting process, a second outer cylindrical member 5B having a temperature T1 is prepared. The inner diameter ID3 of the second outer cylindrical member 5B is the outer diameter OD2 of the first outer cylindrical member 5A at the temperature T1 attached to the outer periphery of the inner cylindrical member 4 of the second intermediate assembly 13 at the temperature T1. Slightly smaller than. That is, ID3 <OD2 at the temperature T1.

  Next, the prepared second outer cylindrical member 5B having the temperature T1 is heated to a temperature T3 higher than the temperature T1. For example, when the temperature T1 is normal temperature, the second outer cylindrical member 5B is heated to about 400 ° C. By this heating, the second outer cylindrical member 5B is thermally expanded. For this reason, the inner diameter ID3 of the second outer cylindrical member 5B is widened, and the inner diameter ID3 of the second outer cylindrical member 5B is the outer diameter of the first outer cylindrical member 5A at the temperature T1 provided in the second intermediate assembly 13. It becomes larger than OD2.

  Next, the second outer cylindrical member 5B heated to the temperature T3 is second so that the inner peripheral surface of the second outer cylindrical member 5B faces the outer peripheral surface of the first outer cylindrical member 5A (the outer peripheral surface of the second intermediate assembly 13). The outer cylindrical member 5B is disposed concentrically with the first outer cylindrical member 5A. Thereafter, the second outer cylindrical member 5B is cooled to the temperature T1. Although the cooling method is not particularly limited, for example, the second outer cylindrical member 5B is cooled by natural cooling or by supplying cold air to the second outer cylindrical member 5B. Due to the heat shrinkage due to the cooling, the inner diameter ID3 of the second outer cylindrical member 5B becomes smaller. When the temperature of the second outer cylindrical member 5B is reduced to the temperature T1, the inner diameter ID3 of the second outer cylindrical member 5B in the natural state is the outer diameter OD2 of the first outer cylindrical member 5A of the second intermediate assembly 13. Smaller than. Therefore, the second outer cylindrical member 5B is attached to the outer peripheral surface of the first outer cylindrical member 5A, and the first outer cylindrical member 5A is tightened. Such tightening force acts on the superconducting bulk 2 via the inner cylindrical member 4.

  The superconducting magnetic field generating element 1A according to the present embodiment is manufactured through the first process and the second process described above. According to this manufacturing method, the inner peripheral surface of the first outer cylindrical member 5A having a temperature (T2) higher than the temperature (T1) of the inner cylindrical member 4 is the inner cylinder in the inner shrink fitting process of the second process. The first outer cylindrical member 5 </ b> A is disposed with respect to the inner cylindrical member 4 so as to face the outer peripheral surface of the cylindrical member 4. Then, after that, the first outer cylindrical member 5A is cooled, so that the difference between the temperature of the inner cylindrical member 4 and the temperature of the first outer cylindrical member 5A is reduced. At this time, the first outer cylindrical member 5A is attached to the outer periphery of the inner cylindrical member 4 by the thermal contraction of the first outer cylindrical member 5A, and the first outer cylindrical member 5A fastens the inner cylindrical member 4. That is, the first outer cylindrical member 5 </ b> A is shrink-fitted to the inner cylindrical member 4. For this reason, the compressive stress from the first outer cylindrical member 5 </ b> A acts on the superconducting bulk 2 via the inner cylindrical member 4. Further, in the outer shrink fitting step of the second step, the inner peripheral surface of the second outer cylindrical member 5B having a temperature (T3) higher than the temperature (T1) of the first outer cylindrical member 5A is the first outer cylindrical shape. The second outer cylindrical member 5B is disposed with respect to the first outer cylindrical member 5A so as to face the outer peripheral surface of the member 5A. Then, after that, the second outer cylindrical member 5B is cooled, so that the difference between the temperature of the first outer cylindrical member 5A and the inner cylindrical member 4 and the temperature of the second outer cylindrical member 5B is reduced. . At this time, the second outer cylindrical member 5B is attached to the outer periphery of the first outer cylindrical member 5A by the thermal contraction of the second outer cylindrical member 5B, and the second outer cylindrical member 5B is attached to the first outer cylindrical member. Tighten 5A. That is, the second outer cylindrical member 5B is shrink-fitted to the first outer cylindrical member 5A. For this reason, the compressive stress from the second outer cylindrical member 5 </ b> B acts on the superconducting bulk 2 via the first outer cylindrical member 5 </ b> A and the inner cylindrical member 4.

  Thus, at the stage of manufacturing the superconducting magnetic field generating element 1A, the compressive stress has already been applied to the superconducting bulk 2 from the outer cylindrical member 5 (the first outer cylindrical member 5A and the second outer cylindrical member 5B). Yes. Therefore, when the superconducting magnetic field generating element 1 is subsequently cooled to the superconducting transition temperature, in addition to the compressive stress generated by the thermal contraction of the inner cylindrical member 4 and the outer cylindrical member 5, the compressive stress already generated in the manufacturing stage is Added. For this reason, the compressive stress that can resist the tensile stress generated in the superconducting bulk 2 when the superconducting bulk 2 captures the magnetic field is increased by the compressive stress that has already occurred in the manufacturing stage. Further, since the adhesive layer 3 is interposed between the inner cylindrical member 4 and the superconducting bulk 2, the inner cylindrical member 4 is uniformly brought into contact with the entire outer peripheral surface of the superconducting bulk 2 through the adhesive layer 3. be able to. Therefore, when the superconducting bulk 2 and the inner cylindrical member 4 are brought into direct contact with each other, the superconducting bulk 2 may be damaged due to partial pressure increase due to unevenness or distortion of the shape of the contact surfaces of both. Can be effectively prevented. As described above, according to the present embodiment, there is provided a method for manufacturing a superconducting magnetic field generating element configured to allow a sufficiently large compressive stress to uniformly act on the superconducting bulk 2 without destroying the superconducting bulk 2. Can be provided.

  In addition, since the inner cylindrical member 4 is interposed between the first outer cylindrical member 5A and the superconducting bulk 2, the outer cylindrical member 5 when the outer cylindrical member 5 is shrink-fitted in the second step. Heat is prevented from being directly transferred to the superconducting bulk 2 and the adhesive layer 3. Therefore, damage to the superconducting bulk 2 due to thermal shock can be prevented, and the adhesive ability of the adhesive layer 3 is reduced by heat (for example, when the adhesive layer 3 is made of resin, the resin is melted by heat. The adhesive ability is reduced).

  The second step of the manufacturing method according to the third embodiment is a step of attaching a plurality of cylindrical members (first outer cylindrical member 5A and second outer cylindrical member 5B) in order from the inner diameter side (inner shrink fitting step). And the temperature (T3) at the time of attachment of the second outer cylindrical member 5B attached to the second (i-th) is attached to the first (i-1) -th. The temperature is set higher than the temperature (T2) of the outer cylindrical member 5A. For this reason, at least one of the plurality of cylindrical members constituting the outer cylindrical member 5 is securely shrink-fitted. Thereby, a compressive stress can be made to act reliably from the outer cylindrical member 5 to the superconducting bulk 2 at normal temperature.

  In the above example, the outer shrinkage fitting process is performed after the inner shrinkage fitting process. However, the heating is performed at a temperature T3 rather than the outer diameter of the first outer cylindrical member 5A heated to the temperature T2. If the inner diameter of the second outer cylindrical member 5B is large, the inner shrink fitting process and the outer shrink fitting process can be performed simultaneously. According to this, process time can be shortened.

(Example 1: Confirmation of reinforcement effect by double ring (inner cylindrical member and outer cylindrical member))
The compressive stress generated on the inner peripheral surface of the superconducting bulk when the superconducting magnetic field generating element 21 as shown in FIG. Here, the superconducting magnetic field generating element 21 includes a cylindrical superconducting bulk 22, an inner cylindrical member 24, and an outer cylindrical member 25. The superconducting bulk 22, the inner cylindrical member 24, and the outer cylindrical member 25 are arranged concentrically. The superconducting bulk 22 has an outer diameter (OD_B) of 64 mm and an inner diameter (ID_B) of 28 mm. The inner cylindrical member 24 is made of aluminum or aluminum alloy. The inner cylindrical member 24 is disposed outside the superconducting bulk 22. The inner peripheral surface of the inner cylindrical member 24 is bonded to the outer peripheral surface of the superconducting bulk 22 via a resin adhesive layer 23 having a thickness of 0.1 mm. The material of the outer cylindrical member 25 is the same as that of the inner cylindrical member 24 (made of aluminum or aluminum alloy), and its outer diameter (OD2) is 74 mm. The outer cylindrical member 25 is disposed outside the inner cylindrical member 24 so that the inner peripheral surface thereof faces the outer peripheral surface of the inner cylindrical member 24, and is attached to the inner cylindrical member 24 by shrink fitting. .

The outer diameter (OD1) of the inner cylindrical member 24 of the superconducting magnetic field generating element 21 having the above-described configuration at the normal temperature in the natural state and the inner diameter (ID2) of the outer cylindrical member 25 at the normal temperature in the natural state are changed to various values. For the four cases (Case 1 to Case 4), the circumferential compressive stress generated on the inner peripheral surface of the superconducting bulk 22 when it was cooled to the operating temperature (50 K) was calculated. For comparison, the compression stress was also calculated for the case where the outer diameter (OD1) of the inner cylindrical member 24 was 74 mm and the outer cylindrical member 25 was not used. In calculating the compressive stress, the axial length of the superconducting bulk 22 was infinite. The calculation results of the compressive stress according to each case and the comparative example are the outer diameter (OD1) of the inner cylindrical member 24 at normal temperature, the inner diameter (ID2) of the outer cylindrical member 25 at normal temperature, and the normal temperature of the outer cylindrical member 25. Table 1 together with the outer diameter (OD2 = 74 mm).

  When the ring-shaped (cylindrical) superconducting bulk is magnetized at the operating temperature (50K), an annular superconducting current flows in the superconducting bulk. Based on this superconducting current, a force acting in the direction of spreading the superconducting bulk outward is generated in the superconducting bulk. It is known that the tensile stress that tears the superconducting bulk in the circumferential direction on the inner peripheral surface of the superconducting bulk is the highest among the stresses acting in the superconducting bulk due to the force. Since the compressive stress calculated in Table 1 works in the opposite direction to the tensile stress, increasing the compressive stress increases the effect of preventing the destruction of the superconducting bulk due to the tensile stress when a higher magnetic field is magnetized. It is thought that. Even in the conventional method of bonding a single cylindrical member as a reinforcing ring to the superconducting bulk as shown in the comparative example, when the cooling ring is cooled to 50 K (use temperature), the thermal shrinkage of the reinforcing ring becomes the thermal shrinkage of the superconducting bulk. The compressive stress is generated. On the other hand, like the case 1-4, the structure of the reinforcing ring is a double ring structure including the inner cylindrical member 24 and the outer cylindrical member 25, and the outer cylindrical member 25 is the inner cylindrical member 24. It can be seen that compressive stress of 1.4 to 2 times that of the comparative example can be obtained even if the total thickness of the reinforcing ring is the same (that is, the outer diameter of the reinforcing ring is the same). .

Further, in Table 1, the numerical values shown in the column of “Gap at 300 ° C.” are obtained when the outer cylindrical member 25 is heated to 300 ° C. when the outer cylindrical member 25 is shrink-fitted in Case 1-4. The difference (diameter difference) between the outer diameter of the inner cylindrical member 24 at room temperature and the inner diameter of the outer cylindrical member 25 at 300 ° C. is represented. As can be seen from the numerical values shown in this column, the fitting allowance (the difference between the outer diameter (OD1) of the inner cylindrical member 24 and the inner diameter (ID2) of the outer cylindrical member 25 at room temperature) is 0.1 mm to 0.2 mm. When the outer cylindrical member 25 is heated to 300 ° C., it can be seen that a sufficient gap (a gap of 0.2 mm or more) necessary for shrink fitting can be secured.

  Further, in this example, the inner cylindrical member 24 has an outer diameter OD1 of 66 mm (case 1, case 2) or 68 mm (case 3, case 4), and the inner cylindrical member 24 has an inner diameter ID1 of the superconducting bulk 22. It is 64 mm which is almost equal to the outer diameter. Accordingly, the radial thickness (inner wall thickness t_in) of the inner cylindrical member 24 is 1 mm (case 1, case 2) or 2 mm (case 3, case 4). In this example, the outer cylindrical member 25 has an outer diameter OD2 of 74 mm, and the outer cylindrical member 25 has an inner diameter ID2 of about 66 mm (case 1, case 2) or about 68 mm (case 3, case 4). . Therefore, the radial thickness (outer wall thickness t_out) of the outer cylindrical member 25 is 4 mm (case 1, case 2) or 3 mm (case 3, case 4).

  In all cases, the total thickness T, which is the sum of the thickness of the inner cylindrical member 24 (inner thickness t_in) and the thickness of the outer cylindrical member 25 (outer thickness t_out), is 5 mm. The ratio (t_in / T) of the thickness (inner wall thickness t_in) of the inner cylindrical member 24 to the total wall thickness T (5 mm) is 20% in cases 1 and 2, and 40% in cases 3 and 4. It is. That is, in any case, the ratio (t_in / T) is 75% or less. If the ratio (t_in / T) is 75% or less, preventing the compressive stress of the outer cylindrical member 25 from sufficiently acting on the superconducting bulk 22 due to the thickness of the inner cylindrical member 24 being too large. Can do.

  In addition, in any case, the ratio (t_in / T) is 10% or more. When the ratio (t_in / T) is 10% or more, the heat dissipation effect when the outer cylindrical member 25 is shrink-fitted can be improved.

  FIG. 9 shows an example of a method for shrink fitting the outer cylindrical member 25 shown in the case 1. First, a copper plate 31 having a diameter larger than that of the outer cylindrical member 25 was prepared. A first intermediate assembly 12 in which the superconducting bulk 22 is embedded in an inner cylindrical member 24 having an outer diameter (OD1) of 66.0 mm is placed on the copper plate 31 via a resin adhesive layer 23 having a thickness of 0.1 mm. It was. On the first intermediate assembly 12 placed on the copper plate 31, a tapered copper plate 32 having a truncated cone shape having an outer diameter equal to the outer diameter of the inner cylindrical member 24 is concentrically stacked.

  In addition, the outer cylindrical member 25 having a size shown in Case 1 having an outer diameter of 74.0 mm and an inner diameter of 65.9 mm at room temperature is heated for 10 minutes or more using an electric furnace, so that the temperature of the outer cylindrical member 25 is 300 The temperature was raised to ° C. Thereafter, the door of the electric furnace was opened, and the outer cylindrical member 25 was quickly taken out from the electric furnace using a heat-resistant glove. The taken-out outer cylindrical member 25 was immediately placed on the tapered copper plate 32 superimposed on the first intermediate assembly 12, and the outer cylindrical member 25 was dropped along the outer periphery of the tapered copper plate 32. The outer cylindrical member 25 that has dropped along the outer periphery of the tapered copper plate 32 is placed on the upper surface of the copper plate 31. At this time, the outer cylindrical member 25 is disposed concentrically on the outer side of the first intermediate assembly 12 positioned below the tapered copper plate 32.

  Immediately thereafter, the copper ring 33 was placed on the outer cylindrical member 25. The inner diameter of the copper ring 33 is slightly larger than the inner diameter of the outer cylindrical member 25 and smaller than the outer diameter of the outer cylindrical member 25. Further, the outer diameter of the copper ring 33 is slightly larger than the outer diameter of the outer cylindrical member 25. Therefore, the upper end surface of the outer cylindrical member 25 is in surface contact with the lower end surface of the copper ring 33, and the lower end surface of the outer cylindrical member 25 is in surface contact with the upper surface of the copper plate 31. The heat of the outer cylindrical member 25 is removed by the copper ring 33 and the copper plate 31 at the surface contact portion, whereby the outer cylindrical member 25 is cooled. As a result, the outer cylindrical member 25 is shrink-fitted to the inner cylindrical member 24. In such a procedure, the outer cylindrical member 25 was cooled to the temperature touched with bare hands in about 5 seconds, and the outer cylindrical member 25 was shrink-fitted. In this way, by cooling the outer cylindrical member 25 in a short time, the outer cylindrical member 25 can be shrink-fitted so as not to affect the superconducting bulk 22 and the adhesive layer 23.

(Example 2: Confirmation of reinforcing effect by triple ring (inner cylindrical member, first outer cylindrical member, second outer cylindrical member))
The compressive stress generated on the inner peripheral surface of the superconducting bulk when the superconducting magnetic field generating element 41 as shown in FIG. Here, the superconducting magnetic field generating element 41 includes a cylindrical superconducting bulk 42, an inner cylindrical member 44, and an outer cylindrical member 45. The outer cylindrical member 45 includes a first outer cylindrical member 45A and a second outer cylindrical member 45B. Superconducting bulk 42, inner cylindrical member 44, first outer cylindrical member 45A, and second outer cylindrical member 45B are arranged concentrically.

  The superconducting bulk 42 has an outer diameter (OD_B) of 64 mm and an inner diameter (ID_B) of 28 mm. The inner cylindrical member 44 is made of aluminum or aluminum alloy. The outer diameter (OD1) of the inner cylindrical member 44 is 66 mm. The inner cylindrical member 44 is disposed outside the superconducting bulk 42. The inner peripheral surface of the inner cylindrical member 44 is bonded to the outer peripheral surface of the superconducting bulk 42 via a resin adhesive layer 43 having a thickness of 0.1 mm. The material of the first outer cylindrical member 45A and the second outer cylindrical member 45B is the same as that of the inner cylindrical member 44 (aluminum or aluminum alloy). The outer diameter (OD2) of the first outer cylindrical member 45A is 68 mm. The first outer cylindrical member 45A is disposed on the outer side of the inner cylindrical member 44 so that the inner peripheral surface thereof faces the outer peripheral surface of the inner cylindrical member 44. It is attached. The outer diameter (OD3) of the second outer cylindrical member 45B is 74 mm. The second outer cylindrical member 45B is disposed on the outer side of the first outer cylindrical member 45A so that its inner peripheral surface faces the outer peripheral surface of the first outer cylindrical member 45A. It is attached to the outer cylindrical member 45A.

Two cases (Case 5 and Case 6) in which the inner diameter (ID3) of the second outer cylindrical member 45B at the normal temperature in the natural state of the superconducting magnetic field generating element 41 having the above configuration was changed to the use temperature (50K). In this case, the compressive stress generated on the inner peripheral surface of the superconducting bulk 42 was calculated. In calculating the compressive stress, the axial length of the superconducting bulk 42 was infinite. The calculation results of the compressive stress relating to each case are the outer diameter (OD1) of the inner cylindrical member 44 at room temperature, the outer diameter (OD2) and inner diameter (ID2) of the first outer cylindrical member 45A at room temperature, the second Table 2 shows the outer diameter (OD3) and inner diameter (ID3) of the outer cylindrical member 45B at room temperature.

  In Table 2, the fitting allowance A represents the difference between OD2 and ID3, and the fitting allowance B represents the difference between OD1 and ID2. Further, when the first outer cylindrical member 45A is heated to 300 ° C. when the first outer cylindrical member 45A is shrink-fitted, the gap C is equal to the outer diameter (OD1) and 300 of the inner cylindrical member 44 at room temperature. The difference (diameter difference) from the inner diameter of the first outer cylindrical member 45A at ° C is represented. Further, the gap D is the outer diameter (OD2) of the first outer cylindrical member 45A at room temperature when the second outer cylindrical member 45B is heated to 400 ° C. when the second outer cylindrical member 45B is shrink-fitted. And the difference (diameter difference) between the inner diameter of the second outer cylindrical member 45B at 400 ° C.

  As can be seen from Table 2, the outer diameter OD3 of the outermost second outer cylindrical member 45B is 74 mm, which is the same as in the case of Example 1, but in comparison with Case 1-4 of Example 1, the Example The compressive stress of the cases 5 and 6 of 2 is larger. This is because, in the cases 5 and 6 of the second embodiment, the cylindrical member has a triple structure, and the compressive stress due to shrink fitting of the first outer cylindrical member 45A and the compressive stress due to shrink fitting of the second outer cylindrical member 45B. This is because both act on the superconducting bulk 42.

(Fourth embodiment)
Next, a superconducting magnetic field generating element according to the fourth embodiment will be described. The superconducting magnetic field generating element according to the fourth embodiment is basically the structure of the superconducting magnetic field generating element according to the first embodiment except for the contact state between the inner peripheral surface of the inner cylindrical member and the outer peripheral surface of the superconducting bulk. Is the same.

  FIG. 11 is a perspective view showing a schematic configuration of a superconducting magnetic field generating element 1B according to the fourth embodiment. As shown in FIG. 11, the superconducting magnetic field generating element 1B according to the fourth embodiment is similar to the superconducting magnetic field generating element 1 according to the first embodiment, in the superconducting bulk 2, the inner cylindrical member 4, and the outer cylindrical shape. And a member 5.

  The shapes of the superconducting bulk 2, the inner cylindrical member 4, and the outer cylindrical member 5 are the same as the shapes of the superconducting bulk 2, the inner cylindrical member 4, and the outer cylindrical member 5 included in the superconducting magnetic field generating element 1 according to the first embodiment. Since they are the same, a specific description thereof is omitted.

  Also in the superconducting magnetic field generating element 1B according to the fourth embodiment, the outer cylindrical member 5 clamps the inner cylindrical member 4 at room temperature, as in the superconducting magnetic field generating element 1 according to the first embodiment. . Accordingly, the tightening force of the outer cylindrical member 5 is transmitted to the superconducting bulk 2 via the inner cylindrical member 4. For this reason, stress in the direction from the outer peripheral side toward the center side, that is, compressive stress, acts on the superconducting bulk 2. That is, the outer cylindrical member 5 is attached to the inner cylindrical member 4 so that compressive stress acts on the superconducting bulk 2 at room temperature.

  FIG. 12A is a diagram showing a part of a cross section obtained by cutting the superconducting magnetic field generating element 1B according to the fourth embodiment along a plane including its axis. FIG. 12B is a detailed view of a portion C which is a region portion including a contact interface between the inner cylindrical member 4 and the superconducting bulk 2 in FIG. 12A. As shown in FIGS. 12A and 12B, fine irregularities are formed on the inner peripheral surface of the inner cylindrical member 4 and the outer peripheral surface of the superconducting bulk 2 that are in contact with each other. In particular, when the superconducting bulk 2 is formed into a cylindrical shape by a melting method, many irregularities are formed on the outer peripheral surface thereof. Here, the irregularities include holes. Therefore, even when the outer peripheral surface of the superconducting bulk 2 is brought into contact with the inner peripheral surface of the inner cylindrical member 4, a portion that does not directly contact with both surfaces is formed due to unevenness or shape distortion on both surfaces.

  Therefore, the inner peripheral surface of the inner cylindrical member 4 has a gap G (see FIG. 12B) between the first region that is in direct contact with the outer peripheral surface of the superconducting bulk 2 and the outer peripheral surface of the superconducting bulk without direct contact. It has a second region formed. In FIG. 12B, the first area is represented by area A and the second area is represented by area B. In the present embodiment, the gap 6 formed on the second region B is filled with the filler 6. Therefore, in the second region B, the inner cylindrical member 4 is in indirect contact with the superconducting bulk 2 via the filler 6.

  FIG. 12C is a diagram showing a part of a cross section obtained by cutting the superconducting magnetic field generating element 1 according to the first embodiment along a plane including its axis. As shown in FIG. 12C, in the superconducting magnetic field generating element 1 according to the first embodiment, the adhesive layer 3 is interposed almost entirely between the inner peripheral surface of the inner cylindrical member 4 and the outer peripheral surface of the superconducting bulk 2. doing. Therefore, the inner peripheral surface of the inner cylindrical member 4 and the outer peripheral surface of the superconducting bulk 2 are not in direct contact with each other, and both surfaces are in indirect contact with each other through the adhesive layer 3. On the other hand, in the superconducting magnetic field generating element 1B according to the fourth embodiment, the first region A on the inner peripheral surface of the inner cylindrical member 4 is in direct contact with the outer peripheral surface of the superconducting bulk 2, and the inner cylindrical member 4 The second region B on the inner peripheral surface is in indirect contact with the outer peripheral surface of the superconducting bulk 2 via the filler 6.

  Even when the superconducting magnetic field generating element 1B is configured as shown in the fourth embodiment, the inner cylindrical member 4 and the superconducting bulk 2 can be directly and indirectly brought into contact with each other. In addition, since there is a portion where the inner cylindrical member 4 and the superconducting bulk 2 are in direct contact with each other, the filler 6 is deteriorated and it is difficult to transmit compressive stress from the second region B to the superconducting bulk 2 through the filler 6. Even in this case, compressive stress can be transmitted from the first region A in direct contact to the superconducting bulk 2. Therefore, durability and reliability of the superconducting magnetic field generating element 1B can be improved.

  Next, a method for manufacturing the superconducting magnetic field generating element 1B according to the fourth embodiment will be described. The manufacturing method of the superconducting magnetic field generation element 1B according to the fourth embodiment also includes the first step and the second step, similarly to the manufacturing method of the superconducting magnetic field generation element 1 according to the first embodiment. FIG. 13A is a diagram illustrating the first step, and FIG. 13B is a perspective view illustrating a state in which the inner cylindrical member 4 is attached to the superconducting bulk 2 by performing the first step. Moreover, FIG. 14 is a figure which shows a 2nd process.

  In the first step, the filler 6 having fluidity is applied to the outer peripheral surface of the superconducting bulk 2 or the inner peripheral surface of the inner cylindrical member 4, and then the outer peripheral surface of the cylindrical superconducting bulk 2 is the inner cylindrical member. The superconducting bulk 2 is concentrically arranged on the inner peripheral side of the inner cylindrical member 4 so as to face the outer peripheral surface of the inner cylindrical member 4. When the temperature of the superconducting bulk 2 and the inner cylindrical member 4 at the time of performing the first step is the temperature T1, the outer diameter OD_B of the superconducting bulk 2 is higher than the inner diameter ID1 of the inner cylindrical member 4 at the temperature T1. Slightly small. Therefore, the filler 6 is filled between the outer peripheral surface of the superconducting bulk 2 arranged concentrically and the inner cylindrical member 4. Examples of the filler 6 include an adhesive made of an epoxy resin or grease. The temperature T1 is preferably normal temperature (5 ° C. to 35 ° C.), for example. By this first step, an inner cylindrical shape is formed on the outer peripheral surface of the superconducting bulk 2 with a fluid filler 6 interposed between the outer peripheral surface of the superconducting bulk 2 and the inner peripheral surface of the inner cylindrical member 4. The inner cylindrical member 4 is attached to the superconducting bulk 2 so that the inner peripheral surface of the member 4 contacts.

  In the second step, the outer cylindrical member 5 is formed on the outer peripheral surface of the inner cylindrical member 4 to which the superconducting bulk 2 is attached on the inner peripheral side with the filler 6 having fluidity interposed in the first step. It is attached. In this case, first, an outer cylindrical member 5 having a temperature T1 is prepared. The inner diameter ID2 of the outer cylindrical member 5 is slightly smaller than the outer diameter OD1 of the inner cylindrical member 4 at the temperature T1 attached to the outer periphery of the superconducting bulk 2 at the temperature T1. That is, ID2 <OD1 at the temperature T1.

  Next, the prepared outer cylindrical member 5 having a temperature T1 is heated to a temperature T2 higher than the temperature T1. For example, when the temperature T1 is normal temperature, the outer cylindrical member 5 is heated to about 300 ° C. in the second step. By this heating, the outer cylindrical member 5 is thermally expanded. For this reason, the inner diameter ID2 of the outer cylindrical member 5 increases, and the inner diameter ID2 of the outer cylindrical member 5 becomes larger than the outer diameter OD1 of the inner cylindrical member 4 at room temperature.

  Next, as shown in FIG. 14, the outer cylindrical member 5 is moved to the inner cylindrical member so that the inner peripheral surface of the outer cylindrical member 5 heated to the temperature T <b> 2 faces the outer peripheral surface of the inner cylindrical member 4. 4 are arranged concentrically. Thereafter, the outer cylindrical member 5 is cooled to a temperature T1. The cooling method is not particularly limited, but the outer cylindrical member 5 is cooled by, for example, natural cooling or by supplying cold air to the outer cylindrical member 5. Due to the heat shrinkage due to the cooling, the inner diameter ID2 of the outer cylindrical member 5 becomes smaller. When the temperature of the outer cylindrical member 5 is cooled to the temperature T1, the inner diameter ID2 of the outer cylindrical member 5 in the natural state becomes smaller than the outer diameter OD1 of the inner cylindrical member 4. Therefore, the outer cylindrical member 5 is attached to the outer peripheral surface of the inner cylindrical member 4 and the inner cylindrical member 4 is tightened. That is, the outer cylindrical member 5 is shrink-fitted to the inner cylindrical member 4. A tightening force by shrink fitting acts on the superconducting bulk 2 via the inner cylindrical member 4.

  Here, in the second step according to the fourth embodiment, the filler 6 interposed between the outer peripheral surface of the superconducting bulk 2 and the inner peripheral surface of the inner cylindrical member 4 in the first step has fluidity. It is executed when Therefore, due to the compressive stress acting on the superconducting bulk 2 from the outer cylindrical member 5 through the inner cylindrical member 4 by performing the second step, the filler 6 is removed from the outer peripheral surface of the superconducting bulk 2 and the inner cylindrical member 4. It flows between the contact interfaces with the peripheral surface. The flowing filler 6 is formed by the inner peripheral surface of the inner cylindrical member 4 and the outer peripheral surface of the superconducting bulk 2 due to unevenness, holes, or shape distortion formed on the contact surface between the inner cylindrical member 4 and the superconducting bulk 2. A gap G (see FIG. 12B) formed between the two is filled. Here, the fine holes formed on the outer peripheral surface of the superconducting bulk 2 may not be filled simply by applying the filler 6 to the outer peripheral surface of the superconducting bulk 2. On the other hand, according to the present embodiment, the compressive stress from the outer cylindrical member 5 acts on the filler 6 between the superconducting bulk 2 and the inner cylindrical member 4 in the second step. Due to the stress, the filler 6 can also enter the fine holes. On the other hand, in the portion where the gap G is not formed, the inner peripheral surface of the inner cylindrical member 4 is in direct contact with the outer peripheral surface of the superconducting bulk 2 without the filler 6 interposed. In this way, the entire inner peripheral surface of the inner cylindrical member 4 and the outer peripheral surface of the superconducting bulk 2 can be brought into direct contact with each other.

  The superconducting magnetic field generating element 1B according to the fourth embodiment as shown in FIG. 11 is manufactured through the first process and the second process described above. According to this manufacturing method, compressive stress due to shrink fitting has already been applied from the outer cylindrical member 5 to the superconducting bulk 2 at the stage of manufacturing the superconducting magnetic field generating element 1B. Therefore, when the superconducting magnetic field generating element 1B is subsequently cooled to the superconducting transition temperature, in addition to the compressive stress generated by the thermal contraction of the inner cylindrical member 4 and the outer cylindrical member 5, the compressive stress already generated in the manufacturing stage is Added. For this reason, the compressive stress that can resist the tensile stress generated in the superconducting bulk 2 when the superconducting bulk 2 captures the magnetic field is increased by the compressive stress that has already occurred in the manufacturing stage. Moreover, according to this manufacturing method, the inner peripheral surface of the inner cylindrical member 4 and the outer peripheral surface of the superconducting bulk 2 can be brought into direct and indirect contact with each other. Therefore, since a compressive stress can be applied uniformly to the outer peripheral surface of the superconducting bulk 2, a sufficiently large compressive stress can be uniformly applied to the superconducting bulk 2 without destroying the superconducting bulk 2.

  Moreover, since the inner cylindrical member 4 is interposed between the outer cylindrical member 5 and the superconducting bulk 2, the heat of the outer cylindrical member 5 when the outer cylindrical member 5 is shrink-fitted in the second step is reduced. Direct transmission to the superconducting bulk 2 and the filler 6 is prevented. Therefore, breakage of the superconducting bulk 2 due to thermal shock can be prevented, and thermal deterioration of the filler 6 can be prevented.

  Further, according to the manufacturing method according to the fourth embodiment, the filler 6 interposed between the superconducting bulk 2 and the inner cylindrical member 4 in the first step has fluidity during the second step. It is necessary to be in the state. On the other hand, after the second step is performed, the fluidity of the filler 6 may be lowered when a predetermined condition is satisfied. For example, when a predetermined time has elapsed, or when the temperature of the filler 6 is lowered to a predetermined temperature or less, the fluidity of the filler 6 is reduced, or the filler 6 is solidified. Good. That is, the filler 6 is made of a material that can change from a fluid state to a non-fluid state, and the second step is the outer peripheral surface of the superconducting bulk 2 in the first step. And when the filler 6 interposed between the inner cylindrical member 4 and the inner peripheral surface of the inner cylindrical member 4 is in a fluid state, and when the predetermined condition is satisfied after the second step is performed, the filler 6 It should be solidified.

  For example, when an epoxy adhesive is used as the filler 6, the filler 6 initially has fluidity but solidifies over time. Therefore, when an epoxy adhesive is used as the filler 6 in this embodiment, the second step is performed before the filler 6 is solidified. Thereafter, after a predetermined time has elapsed, the filler 6 is solidified in the gap G formed at the contact interface between the inner cylindrical member 4 and the superconducting bulk 2. For this reason, since the filler 6 is solidified when using the manufactured superconducting magnetic field generating element 1B, the filler 6 can be kept in the gap G during use. Further, when grease is used as the filler 6, the filler 6 has fluidity at a predetermined temperature or higher, and is solidified at a temperature lower than the predetermined temperature (for example, the use temperature of the superconducting magnetic field generating element 1B). Therefore, in this case, when the superconducting magnetic field generating element 1B is cooled to a temperature of about 50K when the manufactured superconducting magnetic field generating element 1B is used, the filler 6 is solidified in the gap G. Thereby, the filler 6 can be kept in the gap G during use.

(Example 3: When an epoxy adhesive is used as a filler)
An EuBaCuO-based superconducting bulk having an outer shape of 63.95 mm, an inner diameter of 28.0 mm, and a height of 20 mm was prepared. A two-component mixed epoxy adhesive was applied to the outer peripheral surface of the prepared superconducting bulk. This epoxy adhesive has fluidity, but the fluidity decreases with the passage of time, and eventually solidifies. Next, the outer peripheral surface of a superconducting bulk in which an outer peripheral surface is coated with an epoxy adhesive on the inner peripheral surface of an inner cylindrical member made of an aluminum alloy having an outer diameter of 68.0 mm, an inner diameter of 64.0 mm, and a height of 20 mm at room temperature Were placed on the inner peripheral side of the inner cylindrical member so that they face each other. As a result, the inner cylindrical member was attached to the outer peripheral surface of the superconducting bulk with the flowable epoxy adhesive interposed between the outer peripheral surface of the superconducting bulk and the inner peripheral surface of the inner cylindrical member. (First step).

  Next, an outer cylindrical member made of an aluminum alloy having an outer diameter of 74.0 mm, an inner diameter of 67.75 mm, and a height of 20 mm was heated in an electric furnace at 200 ° C. for 10 minutes. By this heating, the inner diameter of the outer cylindrical member was expanded to 68 mm or more. Thereafter, the outer cylindrical member was taken out from the electric furnace. And the outer cylindrical member was arrange | positioned on the outer side of the inner cylindrical member so that the inner peripheral surface of an outer cylindrical member may face the outer peripheral surface of an inner cylindrical member. In this case, the inner diameter of the outer cylindrical member is 68 mm or more, and the epoxy adhesive interposed between the outer peripheral surface of the superconducting bulk and the inner peripheral surface of the inner cylindrical member has fluidity. The outer cylindrical member was placed outside the inner cylindrical member within a certain time. Thereafter, the outer cylindrical member was cooled to room temperature. Due to this heat shrinkage due to cooling, the inner diameter of the outer cylindrical member becomes smaller. When the temperature of the outer cylindrical member decreases to room temperature, the inner diameter of the outer cylindrical member in the natural state is smaller than the outer diameter of the inner cylindrical member. Therefore, the outer cylindrical member is attached to the outer peripheral surface of the inner cylindrical member, and the inner cylindrical member is tightened. That is, the outer cylindrical member is shrink-fitted to the inner cylindrical member (second step).

  By performing the second step, the compressive stress from the outer cylindrical member acts on the superconducting bulk through the inner cylindrical member. The compressive stress also acts on the epoxy adhesive between the superconducting bulk and the inner cylindrical member. For this reason, the epoxy adhesive flows between the contact interfaces between the superconducting bulk and the inner cylindrical member. By this flow, the epoxy-based adhesive is filled in a minute gap formed between both surfaces due to unevenness or distortion of the outer peripheral surface of the superconducting bulk and the outer peripheral surface of the inner cylindrical member. Moreover, in the location where the clearance gap is not formed, the outer peripheral surface of a superconducting bulk and the outer peripheral surface of an inner cylindrical member contact directly with the said compressive stress. The adhesive that has not been filled in the gap overflows to both end faces of the superconducting magnetic field generating element. The overflowing adhesive is wiped off. When a predetermined time elapses after shrink fitting, the epoxy adhesive in the gap is solidified. In this way, a superconducting magnetic field generating element was manufactured.

The circumferential compressive stress generated on the inner peripheral surface of the superconducting bulk was calculated when the superconducting magnetic field generating element produced as described above was cooled to the working temperature (50K). In this case, the compression stress was calculated on the assumption that half of the epoxy adhesive interposed between the superconducting bulk and the inner cylindrical member in the first step overflowed by the second step. . The calculation result is shown in Case 7 of Table 3. For comparison, a superconducting magnetic field generating element manufactured by performing the first process using an inner cylindrical member having an outer diameter of 74.0 mm and an inner diameter of 64.0 mm, that is, 1 without performing the second implementation process. For the superconducting magnetic field generating element composed of a cylindrical member with a heavy ring (only the inner cylindrical member only), the circumferential compressive stress generated on the inner peripheral surface of the superconducting bulk when it is cooled to the operating temperature (50K) is calculated. did. The calculation result is shown in Case 8 in Table 3. In addition, the superconducting magnetic field generating element manufactured by performing the second step after the adhesive applied in the first step is solidified also occurs on the inner peripheral surface of the superconducting bulk when cooled to the use temperature (50K). The circumferential compressive stress was calculated. The calculation result is shown in Case 9 in Table 3. Further, the superconducting magnetic field generating element manufactured by performing the first step and the second step without using an adhesive also compresses in the circumferential direction generated on the inner peripheral surface of the superconducting bulk when cooled to the use temperature (50K). Stress was calculated. The calculation result is shown in Case 10 of Table 3. In calculating the compressive stress, the axial length of the superconducting bulk was set to an infinite length.

  In Table 3, “double structure” described in the column of “cylindrical member” means that the superconducting magnetic field generating element includes an inner cylindrical member and an outer cylindrical member, and these constitute a cylindrical member. Represents that. The “single structure” in Table 3 represents that the superconducting magnetic field generating element is configured to include only the inner cylindrical member as the cylindrical member.

  As can be seen from Table 3, the compressive stress is high when the cylindrical member has a double structure, that is, when the superconducting magnetic field generating element is configured as in cases 7, 9, and 10. On the other hand, when the cylindrical member has a single structure, that is, when the superconducting magnetic field generating element is configured as in the case 8, the compressive stress is low. Further, whether the cylindrical member has a single structure or a double structure, the total thickness of the cylindrical members is the same. From this, it can be seen that the compressive stress is sufficiently increased by configuring the cylindrical member in a double structure.

  Case 9 corresponds to the case where no filler (epoxy adhesive) overflowed from the contact interface between the inner cylindrical member and the superconducting bulk during the second step. This corresponds to the case where all the filler overflows from the contact interface between the inner cylindrical member and the superconducting bulk during the two steps. Therefore, in the superconducting magnetic field generating elements according to cases 7, 9, and 10, when the amount of filler remaining at the contact interface between the inner cylindrical member and the superconducting bulk is compared, the case where the remaining amount of filler is the largest Is the case 9, the case where the remaining amount of the filler is the next largest is the case 7, and the case where the remaining amount of the filler is the smallest is the case 10.

  When the filler overflows in the second step, the compressive stress acting on the outer peripheral surface of the superconducting bulk decreases due to the thermal contraction of the outer cylindrical member. However, as shown in Table 3, the case 10 corresponding to the case where all of the filler overflows can be much higher than the compressive stress in the case 8 having the same cylindrical member thickness and a single structure. Recognize.

(Example 4: When vacuum grease is used as a filler)
An EuBaCuO-based superconducting bulk having an outer shape of 63.95 mm, an inner diameter of 28.0 mm, and a height of 20 mm was prepared. Vacuum grease was applied to the outer peripheral surface of the prepared superconducting bulk. This vacuum grease has fluidity when performing shrink fitting in the second step to be described later. However, when the temperature is lowered, the viscosity increases and the fluidity is lost. In effect, it becomes an individual state.

  Next, the outer peripheral surface of the superconducting bulk, in which vacuum grease is applied to the outer peripheral surface, faces the inner cylindrical member made of an aluminum alloy having an outer diameter of 68.0 mm, an inner diameter of 64.0 mm, and a height of 20 mm at room temperature. The superconducting bulk was arranged on the inner peripheral side of the inner cylindrical member. As a result, the inner cylindrical member was attached to the outer peripheral surface of the superconducting bulk in a state where the fluid grease was interposed between the outer peripheral surface of the superconducting bulk and the inner peripheral surface of the inner cylindrical member. One step).

  Next, an outer cylindrical member made of an aluminum alloy having an outer diameter of 74.0 mm, an inner diameter of 67.75 mm, and a height of 20 mm was heated in an electric furnace at 250 ° C. for 20 minutes. By this heating, the inner diameter of the outer cylindrical member was expanded to 68 mm or more. Thereafter, the outer cylindrical member was taken out from the electric furnace. When the inner diameter of the outer cylindrical member is 68 mm or more, the outer cylindrical member is placed outside the inner cylindrical member so that the inner peripheral surface of the outer cylindrical member faces the outer peripheral surface of the inner cylindrical member. Arranged. Thereafter, the outer cylindrical member was cooled to room temperature. Due to this heat shrinkage due to cooling, the inner diameter of the outer cylindrical member becomes smaller. When the temperature of the outer cylindrical member decreases to room temperature, the inner diameter of the outer cylindrical member in the natural state is smaller than the outer diameter of the inner cylindrical member. Therefore, the outer cylindrical member is attached to the outer peripheral surface of the inner cylindrical member, and the inner cylindrical member is tightened. That is, the outer cylindrical member is shrink-fitted to the inner cylindrical member (second step).

  By performing the second step, the compressive stress from the outer cylindrical member acts on the superconducting bulk through the inner cylindrical member. The compressive stress also acts on the vacuum grease between the superconducting bulk and the inner cylindrical member. For this reason, the vacuum grease flows between the contact interfaces between the superconducting bulk and the inner cylindrical member. By this flow, the vacuum grease is filled in a minute gap formed between both surfaces due to unevenness or distortion of the outer peripheral surface of the superconducting bulk and the outer peripheral surface of the inner cylindrical member. Moreover, in the location where the clearance gap is not formed, the outer peripheral surface of a superconducting bulk and the outer peripheral surface of an inner cylindrical member contact directly with the said compressive stress. The vacuum grease that has not been filled in the gap overflows to both end faces of the superconducting magnetic field generating element. The spilled vacuum grease is wiped off. Through the above steps, a superconducting magnetic field generating element was manufactured.

  Similarly to the superconducting magnetic field generating element according to Example 3 (Case 7), the inner cylindrical member and the superconducting bulk are directly and indirectly via vacuum grease in the superconducting magnetic field generating element according to Example 4. Full contact is made. Further, the compressive stress generated on the inner peripheral surface of the superconducting bulk when the superconducting magnetic field generating element was cooled to 50K was also equal to the compressive stress for the superconducting magnetic field generating element according to Example 3 (Case 7).

  In the superconducting magnetic field generating element according to Example 4, the filler (vacuum grease) present in the gap at the contact interface between the inner cylindrical member and the superconducting bulk has fluidity at room temperature. However, since it is cooled to 50K during use, the filler (vacuum grease) present in the gap at the contact interface between the inner cylindrical member and the superconducting bulk is solidified. For this reason, it can prevent that a filler flows down from the clearance gap formed in the contact interface of an inner side cylindrical member and a superconducting bulk at the time of use, and a compressive stress falls.

Claims (22)

A cylindrical or cylindrical superconducting bulk;
An inner cylindrical member attached to the superconducting bulk such that its inner peripheral surface contacts the outer peripheral surface of the superconducting bulk;
An outer cylindrical member attached to the inner cylindrical member so that the inner peripheral surface thereof contacts the outer peripheral surface of the inner cylindrical member;
The inner cylindrical member and the outer cylindrical member are each formed of a material having a thermal contraction rate larger than the thermal contraction rate of the superconducting bulk,
The superconducting magnetic field generating element, wherein the outer cylindrical member is attached to the inner cylindrical member so that compressive stress acts on the superconducting bulk via the inner cylindrical member at room temperature. The superconducting magnetic field generating element according to claim 1,
The superconducting magnetic field generating element, wherein the inner cylindrical member is attached to the superconducting bulk so that an inner peripheral surface thereof is bonded to an outer peripheral surface of the superconducting bulk via an adhesive layer. The superconducting magnetic field generating element according to claim 2,
A superconducting magnetic field generating element, wherein the material of the adhesive layer is a resin. The superconducting magnetic field generating element according to claim 1,
The inner peripheral surface of the inner cylindrical member has a first region in direct contact with the outer peripheral surface of the superconducting bulk and a second region in which a gap is formed between the outer peripheral surface of the superconducting bulk,
A superconducting magnetic field generating element in which the second region is in indirect contact with the outer peripheral surface of the superconducting bulk through the filler by filling the gap with a filler. The superconducting magnetic field generating element according to claim 4,
The filler is a superconducting magnetic field generating element composed of a fluid material. The superconducting magnetic field generating element according to claim 5,
The superconducting magnetic field generating element, wherein the filler is made of a material that is solidified at a predetermined temperature or lower. The superconducting magnetic field generating element according to any one of claims 1 to 6,
A superconducting magnetic field generating element, wherein the outer cylindrical member is shrink-fitted to the inner cylindrical member. The superconducting magnetic field generating element according to any one of claims 1 to 7,
A superconducting magnetic field generating element, wherein the outer cylindrical member is cold-fitted to the inner cylindrical member. The superconducting magnetic field generating element according to any one of claims 1 to 8,
The superconducting magnetic field generating element, wherein the outer cylindrical member is made of a material having a thermal contraction rate equal to a thermal contraction rate of the inner cylindrical member or a thermal contraction rate larger than that of the inner cylindrical member. The superconducting magnetic field generating element according to any one of claims 1 to 9,
The outer cylindrical member is composed of a plurality of cylindrical members stacked in the radial direction, and is configured such that stress in the compression direction is generated on the contact surface of the adjacent cylindrical member at normal temperature. A superconducting magnetic field generating element. The superconducting magnetic field generating element according to claim 10,
Each cylindrical member constituting the outer cylindrical member is made of a material having a thermal contraction rate equal to or greater than the thermal contraction rate of the cylindrical member disposed adjacent to the inner side of the diameter. Superconducting magnetic field generator. The superconducting magnetic field generating element according to claim 10 or 11,
Each of the cylindrical members constituting the outer cylindrical member is made of a material having a Young's modulus equal to or greater than the Young's modulus of the cylindrical member disposed adjacent to the inner diameter in the superconducting magnetic field. Generating element. The superconducting magnetic field generating element according to any one of claims 1 to 12,
A superconducting magnetic field generating element in which the outer cylindrical member and the inner cylindrical member are made of the same material. The superconducting magnetic field generating element according to any one of claims 1 to 13,
The total thickness (T) which is the sum of the inner thickness (t_in) which is the thickness in the radial direction of the inner cylindrical member and the outer thickness (t_out) which is the thickness in the radial direction of the outer cylindrical member. A superconducting magnetic field generating element having a ratio (t_in / T) of the inner wall thickness (t_in) to 3/4 or less. The superconducting magnetic field generating element according to any one of claims 1 to 14,
The total thickness (T) which is the sum of the inner thickness (t_in) which is the thickness in the radial direction of the inner cylindrical member and the outer thickness (t_out) which is the thickness in the radial direction of the outer cylindrical member. The superconducting magnetic field generating element, wherein a ratio (t_in / T) of the inner wall thickness (t_in) to 1/10 is 1/10 or more. A method of manufacturing a superconducting magnetic field generating element comprising a columnar or cylindrical superconducting bulk, an inner cylindrical member attached to the outer peripheral surface of the superconducting bulk, and an outer cylindrical member attached to the outer peripheral surface of the inner cylindrical member Because
A first step of attaching the inner cylindrical member to the outer peripheral surface of the superconducting bulk;
The outer cylindrical member is positioned with respect to the inner cylindrical member such that the inner peripheral surface of the outer cylindrical member having a temperature higher than the temperature of the inner cylindrical member faces the outer peripheral surface of the inner cylindrical member. A second step of attaching the outer cylindrical member to the outer peripheral surface of the inner cylindrical member by disposing and then reducing the difference between the temperature of the inner cylindrical member and the temperature of the outer cylindrical member; ,
A method for manufacturing a superconducting magnetic field generating element. In the manufacturing method of the superconducting magnetic field generating element according to claim 16,
The first step includes a step of applying an adhesive to the outer peripheral surface of the superconducting bulk or the inner peripheral surface of the inner cylindrical member, and the outer cylindrical surface of the superconducting bulk via the adhesive. Attaching the inner cylindrical member to the superconducting bulk so that the inner peripheral surface is in contact with the superconducting bulk. In the manufacturing method of the superconducting magnetic field generating element according to claim 16,
The first step includes a step of applying a fluid filler to the outer peripheral surface of the superconducting bulk or the inner peripheral surface of the inner cylindrical member, and the outer surface of the superconducting bulk via the filler. Attaching the inner cylindrical member to the superconducting bulk so that the inner circumferential surface of the inner cylindrical member is in contact with the inner cylindrical member. The method of manufacturing a superconducting magnetic field generating element according to claim 18,
The filler is made of a material that can change from a fluid state to a non-fluid state,
The second step is performed when the filler interposed between the outer peripheral surface of the superconducting bulk and the inner peripheral surface of the inner cylindrical member in the first step has a fluidity. A method of manufacturing a superconducting magnetic field generating element. In the manufacturing method of the superconducting magnetic field generating element according to any one of claims 16 to 19,
In the second step, the outer cylindrical shape is formed such that the inner peripheral surface of the outer cylindrical member heated to a temperature higher than the temperature of the inner cylindrical member faces the outer peripheral surface of the inner cylindrical member. Superconducting magnetic field generation, which is a step of attaching the outer cylindrical member to the outer peripheral surface of the inner cylindrical member by arranging a member with respect to the inner cylindrical member and then cooling the outer cylindrical member. Device manufacturing method. In the manufacturing method of the superconducting magnetic field generating element according to any one of claims 16 to 19,
In the second step, the outer cylindrical member is arranged so that the inner peripheral surface of the outer cylindrical member faces the outer peripheral surface of the inner cylindrical member cooled to a temperature lower than the temperature of the outer cylindrical member. A superconducting magnetic field, which is a step of attaching the outer cylindrical member to the outer peripheral surface of the inner cylindrical member by arranging a member with respect to the inner cylindrical member and then heating the inner cylindrical member. A method for producing a generating element. In the manufacturing method of the superconducting magnetic field generating element according to any one of claims 16 to 21,
The outer cylindrical member is composed of a plurality of cylindrical members stacked in the radial direction,
The second step includes a step of attaching the plurality of cylindrical members in order from the inner diameter side, and at least the temperature at the time of attaching the i-th attached cylindrical member is the i-1th attached cylinder. A method of manufacturing a superconducting magnetic field generating element that is higher than the temperature of the member.

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