WO2017169422A1

WO2017169422A1 - Superconducting magnetic field generating element and production method therefor

Info

Publication number: WO2017169422A1
Application number: PCT/JP2017/007393
Authority: WO
Inventors: 柳　陽介; 伊藤　佳孝; 吉川　雅章
Original assignee: 株式会社イムラ材料開発研究所
Priority date: 2016-03-31
Filing date: 2017-02-27
Publication date: 2017-10-05
Also published as: JP6883565B2; JPWO2017169422A1

Abstract

This superconducting magnetic field generating element 1 is provided with: a circular columnar or circular cylindrical superconductor bulk 2; an inner circular cylindrical member 4 fitted to the superconductor bulk 2 such that the inner circumferential surface thereof comes into contact with the outer circumferential surface of the superconductor bulk 2; and an outer circular cylindrical member 5 fitted to the inner circular cylindrical member 4 such that the inner circumferential surface thereof comes into contact with the outer circumferential surface of the inner circular cylindrical member 4. The inner circular cylindrical member 4 and the outer circular cylindrical member 5 are respectively formed with a material having a greater heat shrinkage rate than that of the superconductor bulk 2. The outer circular cylindrical member 5 is fitted to the inner circular cylindrical member 4 such that compressive stress is exerted on the superconductor bulk 2 at ambient temperature.

Description

Superconducting magnetic field generating element and method of manufacturing the same

The present invention relates to a superconducting magnetic field generating element and a method of 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 system (Re is one or more of rare earth elements) can generate a magnetic field of 10 T or more. Can occur.

When a magnetic field is generated in the superconducting magnetic field generating element using the superconducting bulk, the magnetic field is captured by the superconducting bulk in a state where the superconducting magnetic field generating element is cooled to a temperature lower than the superconducting transition temperature. When the superconducting bulk captures a magnetic field, 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. The electromagnetic force acts outward from the center of the superconducting bulk. Therefore, when the superconducting bulk is formed in a cylindrical shape or a cylindrical shape, the electromagnetic force acts in a direction radially outward from the central axis of the superconducting bulk. For this reason, the superconducting bulk expands in an attempt to increase its diameter, and such an expansion force causes tensile stress to act on the superconducting bulk so as to tear in the circumferential direction. And, when the tensile stress exceeds the mechanical strength of the superconducting bulk, the superconducting bulk is broken.

In order to prevent the breakage of the superconducting bulk based on the above-mentioned tensile stress, development of a superconducting magnetic field generating element constructed such that the superconducting bulk is reinforced by applying a compressive stress against the tensile stress (expansion force) to the superconducting bulk It is done. For example, Patent Document 1 discloses a superconducting magnetic field generating element formed by embedding a cylindrical superconducting bulk into a cylindrical member made of a metal having a larger thermal contraction rate than that via a resin layer at room temperature. Disclose. 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 contraction rate. Therefore, pressure is applied to the outer periphery of the superconducting bulk, and as a result, compressive stress acts on the inside of the superconducting bulk. By offsetting the compressive stress and the tensile stress (expansion force) generated in the superconducting bulk, the net stress acting on the superconducting bulk is reduced. Thus, cracking of the superconducting bulk can be effectively prevented, and hence 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 the upper end surface or the lower end surface in addition to the outer peripheral surface of a cylindrical 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 or the lower end surface, the compressive stress to be applied to the superconducting bulk is increased. Is enhanced.

Patent Document 3 discloses a superconducting magnetic field generating element configured by attaching a heated cylindrical member to the outer peripheral surface of a cylindrical 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 sintered to the superconducting bulk by cooling the cylindrical member to room temperature. 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 the cylindrical member at room temperature is attached to the cooled superconducting bulk, the cylindrical member is cooled and fitted to the superconducting bulk by raising the temperature of the superconducting bulk to room temperature. By shrink-fitting or cold-fitting the cylindrical member to 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.

Patent No. 3389094 Specification JP, 2014-146760, A Patent No. 4012311 specification

(Problems to be solved by the invention)
According to the superconducting magnetic field generating element described in Patent Document 1, when attempting to increase the reinforcing effect by causing a larger compressive stress to act on the superconducting bulk, the thickness (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. Follow For this reason, the increase in thickness of the cylindrical member is limited by the diameter of the bore of the magnetizing magnet. Therefore, it may also occur when the thickness of the cylindrical member can not be increased so as to apply sufficient compressive stress to the superconducting bulk. In addition, 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 saturates. 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 attempting to capture a high magnetic field of, for example, 10 T or more in a cylindrical superconducting bulk having a large diameter, merely increasing the thickness of the cylindrical member opposes the tensile stress generated in the superconducting bulk. It is impossible to apply a compressive stress of a sufficient magnitude to the superconducting bulk, and as a result, the superconducting bulk may be broken.

Further, according to the superconducting magnetic field generating element described in Patent Document 2, in addition to the outer peripheral surface of the cylindrical or cylindrical superconducting bulk, the reinforcing member is attached also to the upper end surface or the lower end surface. The compressive stress applied to the superconducting bulk is increased as compared with the case where the reinforcing member is not attached to the end face. However, since the reinforcing members attached to the upper end surface or the lower end surface of the superconducting bulk are not directly subjected to the tensile stress generated in the superconducting bulk, the degree of improvement of the reinforcing effect (the 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 exert a compressive stress on the superconducting bulk that is large enough to resist the tensile stress generated in the superconducting bulk.

Further, according to Patent Document 3, since a cylindrical member having a temperature difference with the superconducting bulk is directly attached to the superconducting bulk, a thermal shock due to the temperature difference acts on the superconducting bulk. For this reason, there is a possibility that the superconducting bulk may be damaged. In addition, even if it is going to attach a cylindrical member to a superconducting bulk via a resin layer based on the technique of patent document 3, for example, the problem that a resin layer melts with the heat of the heated cylindrical member is produced. . Therefore, as long as the technique of Patent Document 3 is used, the cylindrical member can not be attached to the outer peripheral surface of the superconducting bulk via the resin layer.

As described above, in the prior art, when attempting to capture a large magnetic field of, for example, 10 T or more in the superconducting bulk, a compressive stress of a sufficient magnitude that can resist the tensile stress generated in the superconducting bulk is used. It was not possible to act on the superconducting bulk. An object of the present invention is to provide a superconducting magnetic field generating device configured to be able to apply a sufficiently large compressive stress to a superconducting bulk, and a method of manufacturing such a superconducting magnetic field generating device.

(Means to solve the problem)
The present invention comprises a cylindrical or cylindrical superconducting bulk (2), an inner cylindrical member (4) attached to the superconducting bulk such that the inner peripheral surface is in contact with the outer peripheral surface of the superconducting bulk, and an inner cylinder An outer cylindrical member (5) attached to the inner cylindrical member such that the inner peripheral surface is in contact with the outer peripheral surface of the outer member, the inner cylindrical member and the outer cylindrical member each being superconducting The outer cylindrical member is formed of a material having a thermal contraction rate larger than the thermal contraction rate of the bulk, and the outer cylindrical member is applied to the inner cylindrical member so that compressive stress acts on the superconducting bulk through the inner cylindrical member at normal temperature. Provided is a superconducting magnetic field generating element (1, 1A, 1B) attached. In the present invention, “normal temperature” is a temperature of about “5 ° C. to 35 ° C.”.

According to the superconducting magnetic field generating element according to the present invention, the superconducting bulk is reinforced by the plurality of cylindrical members (inner cylindrical member and 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 through the inner cylindrical member at normal 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 generated by the thermal contraction of the inner cylindrical member and the outer cylindrical member, The resulting compressive stress is applied. For this reason, the compressive stress that can resist the tensile stress generated in the superconducting bulk when the magnetic field is captured in the superconducting bulk is increased by the amount of the compressive stress already generated at normal temperature.

As described above, according to the present invention, a plurality of cylindrical members are used to reinforce the superconducting bulk, and one of the cylindrical members has a compressive stress already applied to the superconducting bulk at room temperature. And a superconducting magnetic field generating element is configured. Therefore, larger compressive stress can be exerted on the superconducting bulk as compared with the case of reinforcing the superconducting bulk using one cylindrical member of the same thickness. That is, according to the present invention, it is possible to provide a superconducting magnetic field generating element configured to be able to apply a sufficiently large compressive stress to a superconducting bulk.

The inner cylindrical member may be attached to the superconducting bulk such that the inner circumferential surface thereof is bonded to the outer circumferential 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 to the entire outer peripheral surface of the superconducting bulk through the adhesive layer. It can be done. Therefore, when the superconducting bulk and the inner cylindrical member are brought into direct contact, the contact area is not limited (i.e., both are in partial contact) due to the unevenness of the contact surfaces of the two and the distortion of the shape. For this reason, the superconducting bulk is broken due to the partial pressure increase due to the limited contact area (partial contact), that is, due to the unevenness or shape distortion of the contact surfaces of the two. It is possible to effectively prevent such things.

In this case, the adhesive layer interposed between the outer peripheral surface of the superconducting bulk and the inner cylindrical member may be made of resin. According to this, the compressive stress can be reliably transmitted to the superconducting bulk by uniformly filling the gap between the outer peripheral surface of the superconducting bulk and the inner peripheral surface of the inner cylindrical member uniformly with the resin as the adhesive layer.

In addition, the inner circumferential surface of the inner cylindrical member is a second region (G) in which a gap (G) is formed between the first region (A) in direct contact with the outer circumferential surface of the superconducting bulk and the outer circumferential surface of the superconducting bulk. B) and by filling the gap with the filler (6), the second region can be configured to be in indirect contact with the outer peripheral surface of the superconducting bulk via the filler. According to this, the inner peripheral surface of the inner cylindrical member is in direct contact with the outer peripheral surface of the superconducting bulk due to the unevenness, the holes, or the shape distortion formed on the contact surface between the inner cylindrical member and the superconducting bulk. A first region and a second region which is not in direct contact with the outer peripheral surface of the superconducting bulk and in which a gap is formed between both surfaces is formed. Then, a filler is filled in the gap formed on the second region. With this configuration, the inner circumferential surface of the inner cylindrical member and the outer circumferential surface of the superconducting bulk can be entirely and directly in contact with each other.

In this case, the filler may be made of a fluid material. 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 flowed 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 the passage of time. According to this, when it has fluidity, the fluidity of the filler filled in the gap formed on the second region of the inner circumferential surface of the inner cylindrical member decreases with the passage of time thereafter. For this reason, the filler which got into the clearance can be kept in the clearance. An epoxy adhesive etc. can be illustrated as a material to which fluidity | liquidity falls with progress of time.

The filler may be made of a material which is in a solidified state at a predetermined temperature or less. According to this, by lowering the temperature of the filler filled in the gap formed on the second region of the inner circumferential surface of the inner cylindrical member to a temperature not higher than the predetermined temperature, the filler is solidified. The filler which has entered the gap can be retained in the gap. As the predetermined temperature, for example, a temperature (for example, about -200.degree. C.) when using the superconducting magnetic field generating element can be exemplified. A silicone grease etc. can be illustrated as a filler which is a solidification state below predetermined temperature.

In the present invention, the outer cylindrical member may be shrink-fit 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-fit to the inner cylindrical member at normal temperature. At this time, compressive stress acts on the inner cylindrical member from the outer cylindrical member, and compressive stress also 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. . Thus, damage to the superconducting bulk due to thermal shock can be prevented, and hence, a larger compressive stress can be imparted 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, the heat of the outer cylindrical member is prevented from being directly transmitted to the adhesive layer or filler. Be done. For this reason, it is possible to prevent deterioration of the adhesive ability of the adhesive layer (for example, when the adhesive layer is made of a resin, the resin is melted by heat and the adhesive ability is lowered) or the filler is deteriorated.

Also, the outer cylindrical member may be cold-fit 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 temperature of the inner cylindrical member is raised to normal temperature and the inner cylindrical member is By thermal expansion, the outer cylindrical member is cooled and fitted to the inner cylindrical member at normal temperature. At this time, compressive stress acts on the inner cylindrical member from the outer cylindrical member, and compressive stress also 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, whereby the superconducting bulk due to thermal shock is obtained. Can be prevented.

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 the thermal contraction rate 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 shrunk equal to or more than the inner cylindrical member, and thus no gap is generated between them. Therefore, compressive stress generated by 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 preferable that the contact surface of the adjacent cylindrical member at normal temperature be structured so that stress in the compression direction acts on it. According to this, the sum of the compressive stress generated by the respective cylindrical members constituting the outer cylindrical member can be applied to the superconducting bulk at normal temperature.

In this case, each of the cylindrical members constituting the outer cylindrical member is made of a material having a thermal contraction rate equal to or higher than the thermal contraction rate of the cylindrical members disposed radially inwardly adjacent thereto. It is good. Alternatively, each cylindrical member constituting the outer cylindrical member is made of a material having a Young's modulus equal to or larger than the Young's modulus of the cylindrical member disposed radially inwardly adjacent thereto. Good. According to this, when cooling the superconducting magnetic field generating element to a temperature equal to or lower than the superconducting transition temperature, the sum of compressive stress accompanying thermal contraction of the respective cylindrical members constituting the outer cylindrical member is applied to the superconducting bulk Can.

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 making the outer cylindrical member and the inner cylindrical member of the same material, the manufacturing cost can be reduced as compared with the case of being made of different materials.

Moreover, total thickness (T) which is the sum of inner thickness (t_in) which is the thickness in the radial direction of the inner cylindrical member and 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) to may be 3/4 or less. In other words, the ratio (t_out / T) of the outer thickness (t_out) to the total thickness (T) is preferably 25% or more. According to this, it is possible to prevent that the compressive stress of the outer cylindrical member does not sufficiently act on the superconducting bulk when the thickness of the inner cylindrical member is too large.

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

The present invention also relates to 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 (5) A method of manufacturing a superconducting magnetic field generating element (1, 1A, 1B) comprising: (1) a first step of attaching an inner cylindrical member to the outer peripheral surface of a superconducting bulk; and a temperature higher than the temperature of the inner cylindrical member. The outer cylindrical member is disposed relative to the inner cylindrical member such that the inner peripheral surface of the outer cylindrical member at the temperature faces the outer peripheral surface of the inner cylindrical member, and then the temperature and outer diameter 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 reducing the difference with the temperature of the cylindrical member, and providing a method of manufacturing a superconducting magnetic field generating element.

According to the present invention, in the second step, the outer cylindrical member is such that the inner peripheral surface of the outer cylindrical member at a temperature higher than the temperature of the inner cylindrical member faces the outer peripheral surface of the inner cylindrical member. Disposed relative to the inner cylindrical member, the difference between the temperature of the inner cylindrical member and the temperature of the outer cylindrical member is then reduced. At this time, the outer cylindrical member is attached to the outer periphery of the inner cylindrical member by heat contraction of the outer cylindrical member or thermal expansion of the inner cylindrical member, and the outer cylindrical member clamps the inner cylindrical member. The compressive stress from the outer cylindrical member acts on the superconducting bulk through the inner cylindrical member. For this reason, at the stage of manufacturing the superconducting magnetic field generating element, compressive stress has already acted on the superconducting bulk from the outer cylindrical member. 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 capturing the magnetic field in the superconducting bulk is increased by the amount of the compressive stress already generated in the manufacturing stage. As described above, according to the present invention, it is possible to provide a method of manufacturing a superconducting magnetic field generating element configured to be able to cause a sufficiently large compressive stress to act on the superconducting bulk.

The first step includes applying an adhesive 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 peripheral surface of the inner cylindrical member on the outer peripheral surface of the superconducting bulk through the adhesive. Attaching the inner cylindrical member to the superconducting bulk such 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 contacted to 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, it is effective that the partial pressure of the superconducting bulk is broken due to the increase in pressure due to the unevenness or shape of the contact surface of the two. Can be prevented.

In the first step, a flowable filler is applied 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 peripheral surface of the superconducting bulk through the filler is provided. Attaching the inner cylindrical member to the superconducting bulk such that the inner circumferential surfaces of the cylindrical members are in contact with each other. 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 in the second step, the first step is superconducting. It may be carried out when the filler interposed between the outer circumferential surface of the bulk and the inner circumferential surface of the inner cylindrical member is in a fluid state.

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. Then, in the second step, the outer cylindrical member is attached to the outer peripheral surface of the inner cylindrical member when the filler is in a fluidized state. At this time, the filler flows by the compressive stress acting on the superconducting bulk from the outer cylindrical member through the inner cylindrical member. Furthermore, due to the above-mentioned compressive stress, the filler is formed on the contact surface between the inner cylindrical member and the superconducting bulk, and the inner peripheral surface of the inner cylindrical member and the outer peripheral surface of the superconducting bulk due to distortion of the cavity or shape. The gap is filled so as to almost completely close the gap formed therebetween. On the other hand, in the portion where the above-mentioned 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 interposing the filler. In this manner, the inner peripheral surface of the inner cylindrical member and the outer peripheral surface of the superconducting bulk can be directly and indirectly brought into full contact, so that the superconducting bulk and the inner cylindrical member partially contact and stress concentration is caused. It is possible to effectively prevent the breakage of the superconducting bulk caused by the

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. 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 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 inside, 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. It is preferable that the outer cylindrical member be attached to the outer circumferential 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 of 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 i-th attached cylindrical member may be higher than the temperature of the i−1-th attached cylindrical member. According to this, at least one of the plurality of cylindrical members constituting the outer cylindrical member is caused to exert a compressive stress on the superconducting bulk from the outer cylindrical member at normal temperature by shrink fitting or cold fitting. Can.

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 manufactured by performing the first step of the manufacturing method according to the first embodiment. FIG. 3 is a view showing a second step of the manufacturing method according to the first embodiment. FIG. 4 is a perspective view showing a schematic configuration of a 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 showing a schematic configuration of a first intermediate assembly produced by performing the first step of the manufacturing method according to the third embodiment. FIG. 6A is a view showing an inner shrink fitting step of the second step of the manufacturing method according to the third embodiment. FIG. 6B is a perspective view showing a schematic configuration of a second intermediate assembly produced by performing the inner shrink fitting step of the second step of the manufacturing method according to the third embodiment. FIG. 7 is a view showing the outer shrink fitting step of the second step of the manufacturing method according to the third embodiment. FIG. 8 is a view showing a schematic configuration of a superconducting magnetic field generating element used for calculation of compressive stress according to the first embodiment. FIG. 9 is a view showing a method of shrink fitting the outer cylindrical member shown in the case 1 of the first embodiment. FIG. 10 is a view showing 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 a superconducting magnetic field generating element according to the fourth embodiment. FIG. 12A is a view 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. 12B is a detailed view of a portion C which is a region portion including the contact interface between the inner cylindrical member and the superconducting bulk in FIG. 12A. FIG. 12C is a view 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 the axis thereof. 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 the implementation of the first step of the manufacturing method according to the fourth embodiment. FIG. 14 is a diagram showing 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 mainly manufactured by the melting method. As high temperature superconducting materials constituting the superconducting bulk 2, for example, yttrium-based (Y-Ba-Cu-O-based), samarium-based (Sm-Ba-Cu-O-based), neodymium-based (Nd-Ba-Cu-O-based) Examples are high temperature superconducting materials such as europium series (Eu-Ba-Cu-O series) and the like.

In the present 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. Between the outer peripheral surface of the superconducting bulk 2 and the inner peripheral surface of the inner cylindrical member 4, an adhesive layer 3 made of a resin (for example, an epoxy resin) is provided. That is, the inner cylindrical member 4 is attached to the superconducting bulk 2 such that the inner peripheral surface 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 so that the inner peripheral surface 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, An outer cylindrical member 5 surrounds the outer peripheral surface of the inner cylindrical member 4.

In the present embodiment, the inner cylindrical member 4 and the outer cylindrical member 5 are both made of a metal material. Further, both the inner cylindrical member 4 and the outer cylindrical member 5 are made of a metal material having a thermal contraction rate larger than the thermal contraction rate of the superconducting bulk 2. Furthermore, 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 the thermal contraction rate of the inner cylindrical member 4. That is, 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, there is a relationship of α1 <α2 ≦ α3. . As a material for forming the inner cylindrical member 4 having such a thermal contraction ratio, aluminum, an aluminum alloy or titanium can be exemplified, and as a material for forming the outer cylindrical member 5, aluminum or an aluminum alloy can be exemplified. 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 It is good to comprise by).

In addition, 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. Furthermore, 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, there is a relationship of 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 clamps the inner cylindrical member 4 at normal temperature. Accordingly, the clamping force of the outer cylindrical member 5 is transmitted to the superconducting bulk 2 via the inner cylindrical member 4. Therefore, stress in the direction from the outer peripheral side to the center side, that is, compressive stress is applied to the superconducting bulk 2. That is, the outer cylindrical member 5 is attached to the inner cylindrical member 4 so that a compressive stress acts on the superconducting bulk 2 at normal temperature.

When a magnetic field is generated in the superconducting magnetic field generating element 1 having such a configuration, for example, the superconducting magnetic field generating element 1 is inserted into a bore provided in a magnetizing device. 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 equal to or lower than the superconducting transition temperature of the superconducting bulk 2, for example, about 50 K, using a refrigerant or a cooler. After cooling is complete, the applied external magnetic field is removed. At this time, a magnetic field is captured by the superconducting bulk 2. Thereby, a magnetic field is generated from the superconducting magnetic field generating element 1.

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

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 shrunk. Here, the thermal contraction rates of the inner cylindrical member 4 and the outer cylindrical member 5 are respectively larger than the thermal contraction rate of the superconducting bulk 2. 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 the time of use of the superconducting magnetic field generating element 1), the inner cylindrical member 4 becomes a superconducting bulk due to the thermal contraction of the inner cylindrical member 4 The outer cylindrical member 5 clamps the inner cylindrical member 4 and the superconducting bulk 2 by the thermal contraction of the outer cylindrical member 5 while the second cylindrical member 5 is clamped. Thus, when the superconducting magnetic field generating element 1 is used, the superconducting bulk 2 is subjected to the compressive stress from the inner cylindrical member 4 and the compressive stress from the outer cylindrical member 5 due to the thermal contraction at the time of cooling.

Also, 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 bulk superconductor 2 so as to oppose the tensile stress. Here, in the present 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 at the time of cooling, the outer cylindrical member 5 is already a superconducting bulk at normal temperature. It is attached to the inner cylindrical member 4 so as to apply a compressive stress to it. Therefore, the compressive stress obtained when using the superconducting magnetic field generating element 1 is a conventional superconducting magnetic field generating element configured to reinforce the superconducting bulk with one cylindrical member having the same external 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 normal temperature. Therefore, compared with the conventional element which used the cylindrical member of the same dimension, the compressive stress which can oppose tensile stress is high. As a result, it is possible to enlarge the magnetic field which can magnetize the superconducting bulk 2 without the superconducting bulk 2 being broken by the tensile stress.

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

Next, a method of manufacturing the superconducting magnetic field generating element 1 according to the first embodiment will be described. The method of manufacturing the superconducting magnetic field generating element 1 according to the first embodiment includes a first step and a second step. FIG. 2A is a view showing a first step, and FIG. 2B is a perspective view showing a schematic configuration of an 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 an 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 disposed 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. Assuming that the temperature of the superconducting bulk 2 and the inner cylindrical member 4 at the time of performing the first step is a temperature T1, the outer diameter OD_B of the superconducting bulk 2 is greater than the inner diameter ID1 of the inner cylindrical member 4 at the temperature T1. small. Therefore, the adhesive is filled between the outer peripheral surface of the concentrically disposed superconducting bulk 2 and the inner cylindrical member 4. Thereafter, the filled adhesive is left to solidify. Thus, the intermediate cylindrical member 4 is attached to the superconducting bulk 2 such that the inner cylindrical member 4 is attached to the superconducting bulk 2 such 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 The assembly 11 is produced. The temperature T1 may be, for example, normal temperature (5 ° C. to 35 ° C.).

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, the outer cylindrical member 5 at the 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, at temperature T1, ID2 <OD1.

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

Then, as shown in FIG. 3, the outer peripheral surface of the outer cylindrical member 5 heated to the temperature T2 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 the temperature T1. The cooling method is not particularly limited. For example, natural cylindrical cooling or cold air is supplied to the outer cylindrical member 5 to cool the outer cylindrical member 5. By the heat contraction 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 (the outer peripheral surface of the intermediate assembly 11) of the inner cylindrical member 4, and the inner cylindrical member 4 is tightened. Such a clamping 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 above-described first and second steps. According to this manufacturing method, the inner peripheral surface of the outer cylindrical member 5 at a temperature (T2) higher than the temperature (T1) of the inner cylindrical member 4 is formed on the outer peripheral surface of the inner cylindrical member 4 in the second step. An outer cylindrical member 5 is disposed relative to the inner cylindrical member 4 so as to face each other. Then, by cooling the outer cylindrical member 5 thereafter, 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 clamps the inner cylindrical member 4. That is, the outer cylindrical member 5 is shrink-fit to the inner cylindrical member 4. Therefore, the compressive stress from the outer cylindrical member 5 acts on the superconducting bulk 2 via the inner cylindrical member 4. Thus, at the stage of manufacturing the superconducting magnetic field generating element 1, compressive stress has already been applied to the superconducting bulk 2 from the outer cylindrical member 5. 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 already occurs at the manufacturing stage. Compressive stress is applied. For this reason, the compressive stress which can counter the tensile stress generated in the superconducting bulk 2 when the superconducting bulk 2 captures a magnetic field is increased by the amount of the compressive stress already generated 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 contacted to the entire outer peripheral surface of the superconducting bulk 2 via the adhesive layer 3. be able to. Therefore, when the superconducting bulk 2 and the inner cylindrical member 4 are brought into direct contact, the superconducting bulk 2 is broken due to partial pressure increase due to the unevenness of the contact surfaces of the two and the shape of the contact surface. Can be effectively prevented. As described above, according to the present embodiment, a superconducting magnetic field generating element configured such that a sufficiently large compressive stress can be uniformly applied to the superconducting bulk 2 without destroying the superconducting bulk 2 at the time of use. A manufacturing method can be provided.

Further, 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-fit in the second step is Direct transfer 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 a resin, the resin is melted by heat) Of the adhesive ability) can be prevented.

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

The method of manufacturing the superconducting magnetic field generating device according to the second embodiment includes the first step and the second step as in the method of manufacturing the superconducting magnetic field generating device according to the first embodiment. The first step is the same as the first step of the method of manufacturing the superconducting magnetic field generating element according to the first embodiment. That is, in the first step, an adhesive made of an 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 thereafter, the outer peripheral surface of the cylindrical superconducting bulk 2 is the inner cylindrical member The superconducting bulk 2 is concentrically disposed 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. Assuming that the temperature of the superconducting bulk 2 and the inner cylindrical member 4 at the time of performing the first step is a temperature T1, the outer diameter OD_B of the superconducting bulk 2 is greater than the inner diameter ID1 of the inner cylindrical member 4 at the temperature T1. small. Therefore, the adhesive is filled between the outer peripheral surface of the concentrically disposed superconducting bulk 2 and the inner cylindrical member 4. Thereafter, the filled adhesive is left to solidify. Thus, the intermediate cylindrical member 4 is attached to the superconducting bulk 2 such that the inner cylindrical member 4 is attached to the superconducting bulk 2 such 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 The assembly 11 is produced.

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 a 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 the superconducting bulk 2 and the inner cylindrical member 4 are disposed so that stress due to thermal shock is not generated. Thereby, the superconducting bulk 2 and the inner cylindrical member 4 are cooled slowly. This cooling causes the inner cylindrical member 4 to thermally shrink. Therefore, the outer diameter OD1 of the inner cylindrical member 4 is contracted, and the inner diameter ID2 of the outer cylindrical member 5 becomes larger than the outer diameter OD1 of the inner cylindrical member 4.

Then, 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). Distribute concentrically with Thereafter, the superconducting bulk 2 and the inner cylindrical member 4 are heated to a temperature T1. The method of raising the temperature is not particularly limited, but it is preferable to raise the temperature slowly so as not to generate stress due to thermal shock. For example, by stopping the cooling of the inner cylindrical member 4 and leaving it for a predetermined time at normal temperature, the temperature of the superconducting bulk 2 and the inner cylindrical member 4 are slowly raised. The inner diameter ID1 of the inner cylindrical member 4 is increased by the thermal expansion due to the temperature rise. 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 clamping force acts on the superconducting bulk 2.

The superconducting magnetic field generating element 1 according to the second embodiment is manufactured through the above-described first and second steps. According to this manufacturing method, the inner peripheral surface of the outer cylindrical member 5 at a temperature (T1) higher than the temperature (T0) of the inner cylindrical member 4 being cooled in the second step is the inner cylindrical member 4 An outer cylindrical member 5 is disposed relative to the inner cylindrical member 4 so as to face the outer peripheral surface of the inner cylinder 4. Then, by raising (heating) the inner cylindrical member 4 after 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 expansion of the inner cylindrical member 4, and the outer cylindrical member 5 clamps the inner cylindrical member 4. That is, the outer cylindrical member 5 is cold-fit to the inner cylindrical member 4. Therefore, the compressive stress from the outer cylindrical member 5 acts on the superconducting bulk 2 via the inner cylindrical member 4. Thus, at the stage of manufacturing the superconducting magnetic field generating element 1, compressive stress has already been applied to the superconducting bulk 2 from the outer cylindrical member 5. 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 already occurs at the manufacturing stage. Compressive stress is applied. For this reason, the compressive stress which can counter the tensile stress generated in the superconducting bulk 2 when the superconducting bulk 2 captures a magnetic field is increased by the amount of the compressive stress already generated 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 contacted to the entire outer peripheral surface of the superconducting bulk 2 via the adhesive layer 3. be able to. Therefore, when the superconducting bulk 2 and the inner cylindrical member 4 are brought into direct contact, the superconducting bulk 2 is broken due to partial pressure increase due to the unevenness of the contact surfaces of the two and the shape of the contact surface. Can be effectively prevented. Thus, according to the present embodiment, there is provided a method of manufacturing a superconducting magnetic field generating element configured to be able to apply a sufficiently large compressive stress uniformly to the superconducting bulk 2 without destroying the superconducting bulk 2. Can be provided.

Third Embodiment
Next, a superconducting magnetic field generating element according to the third embodiment will be described. FIG. 4 is a perspective view showing a schematic configuration of a 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 the same as the superconducting magnetic field generating element 1 according to the first embodiment, including the superconducting bulk 2, the adhesive layer 3, and the inner cylindrical member 4 And the 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 it is the same, the specific description is omitted.

Further, in the present embodiment, the outer cylindrical member 5 includes the first outer cylindrical member 5A and the second outer cylindrical member 5B. The first outer cylindrical member 5A is disposed inside the second outer cylindrical member 5B, and 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 is 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. It consists of.

In the present embodiment, the second outer cylindrical member 5B is made of a metal material having a thermal contraction rate equal to or larger 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 larger 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 the rate. That is, the thermal contraction rate of the superconducting bulk 2 is α1, the thermal contraction rate of the inner cylindrical member 4 is α2, the thermal contraction 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 relation α1 <α2 ≦ α3_1 ≦ α3_2. That is, each of the cylindrical members (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 members disposed radially adjacent thereto than that. It is comprised by the material which it has. 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 an aluminum alloy).

The second outer cylindrical member 5B may be made of a material having a Young's modulus equal to or larger than that 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. In the case of β3_2, it may have a relationship of β1 <β2 ≦ β3_1 ≦ β3_2. That is, each of the cylindrical members (5A, 5B) constituting the outer cylindrical member 5 is a material having a Young's modulus equal to or larger than the Young's modulus of the cylindrical member disposed radially adjacent thereto than that. It may be configured by

The other configuration is the same as each configuration provided in the superconducting magnetic field generating element 1 described in the first embodiment, so the specific description thereof will be omitted.

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

Therefore, the compressive stress obtained at the time of use of 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 external dimensions as the second outer cylindrical member 5B. Compared with the compressive stress obtained when using the conventional superconducting magnetic field generating element (conventional element), the compressive stress already generated at normal temperature is increased. Therefore, compared with the conventional element which used the cylindrical member of the same dimension, the compressive stress which can oppose tensile stress is high. As a result, it is possible to enlarge the magnetic field which can magnetize the superconducting bulk 2 without the superconducting bulk 2 being broken by the tensile stress.

Further, since the adhesive layer 3 for bonding the entire surface between the superconducting bulk 2 and the inner cylindrical member 4 is interposed, the inner cylindrical member 4 is formed on the outer peripheral surface of the superconducting bulk 2 via the adhesive layer 3. Contact the entire surface uniformly. 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 broken due to partial pressure increase due to the unevenness of the contact surfaces and the shape of the contact surfaces. It can be effectively prevented.

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

In the first step, an adhesive made of an 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 disposed 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 in the first step is a temperature T1, the outer diameter OD_B of the bulk superconductor 2 is smaller than the inner diameter ID1 of the inner cylindrical member 4 at the temperature T1. Therefore, the adhesive is filled between the outer peripheral surface of the concentrically disposed superconducting bulk 2 and the inner cylindrical member 4. Thereafter, the filled adhesive is left to solidify. Thereby, 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 through the adhesive layer 3, as shown in FIG. One intermediate assembly 11 is produced. The temperature T1 may be, for example, normal temperature (5 ° C. to 35 ° C.).

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. Be In the third embodiment, the second step includes an inner shrink fitting step and an outer shrink fitting step. In the inner shrink fitting step, the first outer cylindrical member 5 </ b> A is shrink fit to the outer peripheral surface of the inner cylindrical member 4. In the outer shrink fitting step, the second outer cylindrical member 5B is shrink fit to the outer peripheral surface of the first outer cylindrical member 5A. FIG. 6A is a view showing an inner shrink fitting step, and FIG. 6B is a perspective view showing a schematic configuration of a second intermediate assembly 13 produced by performing the inner shrink fitting step.

In the inner shrink fitting step, first, a first outer cylindrical member 5A at 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 at the first intermediate assembly 12 at the temperature T1. That is, at temperature T1, ID2 <OD1.

Next, the first outer cylindrical member 5A at the prepared temperature T1 is heated to a temperature T2 higher than the temperature T1. For example, when the temperature T1 is a normal temperature, the first outer cylindrical member 5A is heated to about 300.degree. By this heating, the first outer cylindrical member 5A thermally expands. Therefore, the inner diameter ID2 of the first outer cylindrical member 5A is expanded, and the inner diameter ID2 of the first outer cylindrical member 5A is 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 made such 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 the inner cylindrical member 4. Thereafter, the first outer cylindrical member 5A is cooled to the temperature T1. The cooling method is not particularly limited. For example, natural first cooling or cold air is supplied to the first outer cylindrical member 5A, whereby the first outer cylindrical member 5A is cooled. By the heat contraction 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 becomes 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 (the outer peripheral surface of the first intermediate assembly 12) of the inner cylindrical member 4, and the second intermediate assembly 13 as shown in FIG. 6B is produced. . Thus, when the second intermediate assembly 13 is produced, the first outer cylindrical member 5A of the second intermediate assembly 13 clamps the inner cylindrical member 4. Such a clamping force acts on the superconducting bulk 2.

FIG. 7 is a view showing the outer shrink fitting step of the second step. The outer shrink fitting step is performed after the inner shrink fitting step is performed in the following description. In the outer shrink fitting step, the second outer cylindrical member 5B at 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 of 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, at temperature T1, ID3 <OD2.

Next, the second outer cylindrical member 5B at the prepared temperature T1 is heated to a temperature T3 higher than the temperature T1. For example, when the temperature T1 is a 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 spreads, 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 circumferential surface of the second outer cylindrical member 5B heated to the temperature T3 faces the outer circumferential surface of the first outer cylindrical member 5A (the outer circumferential 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. The cooling method is not particularly limited. For example, natural second cooling or cold air is supplied to the second outer cylindrical member 5B to cool the second outer cylindrical member 5B. The inside diameter ID3 of the second outer cylindrical member 5B decreases as a result of the heat contraction due to the cooling. When the temperature of the second outer cylindrical member 5B is lowered 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. It becomes 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 a clamping 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 via the first and second steps described above. According to this manufacturing method, the inner circumferential surface of the first outer cylindrical member 5A at a temperature (T2) higher than the temperature (T1) of the inner cylindrical member 4 in the inner shrink fitting step of the second step is the inner cylinder. The first outer cylindrical member 5A is disposed relative to the inner cylindrical member 4 so as to face the outer peripheral surface of the second member 4. Thereafter, the first outer cylindrical member 5A is cooled, whereby 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 clamps the inner cylindrical member 4. That is, the first outer cylindrical member 5A is shrink-fit to the inner cylindrical member 4. Therefore, the compressive stress from the first outer cylindrical member 5A acts on the superconducting bulk 2 via the inner cylindrical member 4. Furthermore, in the outer shrink fitting step of the second step, the inner peripheral surface of the second outer cylindrical member 5B at 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 relative to the first outer cylindrical member 5A so as to face the outer peripheral surface of the member 5A. Then, by cooling the second outer cylindrical member 5B thereafter, the difference between the temperature of the first outer cylindrical member 5A and the temperature of 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 a first outer cylindrical member Tighten 5A. That is, the second outer cylindrical member 5B is shrink-fit to the first outer cylindrical member 5A. Therefore, compressive stress from the second outer cylindrical member 5B acts on the superconducting bulk 2 via the first outer cylindrical member 5A and the inner cylindrical member 4.

Thus, at the stage of manufacturing the superconducting magnetic field generating element 1A, compressive stress already acts on the superconducting bulk 2 from the outer cylindrical member 5 (the first outer cylindrical member 5A and the second outer cylindrical member 5B). There is. 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 occurring in the manufacturing stage It is added. For this reason, the compressive stress which can counter the tensile stress generated in the superconducting bulk 2 when the superconducting bulk 2 captures a magnetic field is increased by the amount of the compressive stress already generated 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 contacted to the entire outer peripheral surface of the superconducting bulk 2 via the adhesive layer 3. be able to. Therefore, when the superconducting bulk 2 and the inner cylindrical member 4 are brought into direct contact, the superconducting bulk 2 is broken due to partial pressure increase due to the unevenness of the contact surfaces of the two and the shape of the contact surface. Can be effectively prevented. Thus, according to the present embodiment, there is provided a method of manufacturing a superconducting magnetic field generating element configured to be able to apply a sufficiently large compressive stress uniformly to 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-fit 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 a resin, the resin is melted by heat) Of the adhesive ability) can be prevented.

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 to be attached second (i-th) including the first and second (i-th) The temperature (T2) of the outer cylindrical member 5A is set higher. Therefore, at least one of the plurality of cylindrical members constituting the outer cylindrical member 5 is securely shrink-fit. Thereby, compressive stress can be reliably applied to the superconducting bulk 2 from the outer cylindrical member 5 at normal temperature.

In the above example, the outer shrink fitting step is performed after the inner shrink fit step, but the temperature is heated to a temperature T3 more 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 step and the outer shrink fitting step can be performed simultaneously. According to this, the process time can be shortened.

(Example 1: Confirmation of reinforcement effect by double ring (inner cylindrical member and outer cylindrical member))
When the superconducting magnetic field generating element 21 as shown in FIG. 8 was cooled to the operating temperature (50 K), the compressive stress generated on the inner peripheral surface of the superconducting bulk was determined by calculation. 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 outer diameter (OD_B) of the superconducting bulk 22 is 64 mm, and the inner diameter (ID_B) is 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 an adhesive layer 23 of resin having a thickness of 0.1 mm. The material of the outer cylindrical member 25 is the same as the material of the inner cylindrical member 24 (made of aluminum or aluminum alloy), and the outer diameter (OD2) thereof is 74 mm. The outer cylindrical member 25 is disposed on the outer side of 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. .

Change the outer diameter (OD1) at normal temperature of the inner cylindrical member 24 of the superconducting magnetic field generating element 21 of the above configuration in the natural state and the inner diameter (ID2) at normal temperature in the natural state of the outer cylindrical member 25 to various values. For the four cases (case 1-case 4), the circumferential compressive stress generated on the inner peripheral surface of the superconducting bulk 22 when cooled to the operating temperature (50 K) was calculated. Further, for comparison, the compressive stress was also calculated in 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 the calculation of the compressive stress, the axial length of the superconducting bulk 22 is made infinite. The calculation results of the compressive stress according to each case and the comparative example, 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, the normal temperature of the outer cylindrical member 25 It shows in Table 1 with the outer diameter (OD2 = 74 mm) in.

When the ring-shaped (cylindrical) superconducting bulk is magnetized at an operating temperature (50 K), an annular superconducting current flows in the superconducting bulk. Based on this superconducting current, a force is generated in the superconducting bulk that acts in the direction of spreading the superconducting bulk outward. It is known that the tensile stress which tears the superconducting bulk in the circumferential direction on the inner circumferential 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 enhances the effect of preventing the fracture of the superconducting bulk due to the tensile stress when magnetizing a higher magnetic field. It is thought that Even when a conventional single-layered cylindrical member shown as a comparative example is bonded to a superconducting bulk as a reinforcing ring, the amount of thermal contraction of the reinforcing ring equals the amount of thermal contraction of the superconducting bulk when cooled to 50 K (use temperature) Because it is larger, compressive stress occurs. On the other hand, as in 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 understood that, even if the total thickness of the reinforcing ring is the same (that is, the outer diameter of the reinforcing ring is the same), compression stress of 1.4 to 2 times that of the comparative example can be obtained .

Further, in Table 1, the numerical values shown in the column of “gap at 300 ° C.” are 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 normal temperature and the inner diameter of the outer cylindrical member 25 at 300 ° C. is shown. As understood from the numerical values shown in this column, the fitting margin (difference between the outer diameter (OD1) of the inner cylindrical member 24 and the inner diameter (ID2) of the outer cylindrical member 25 at normal temperature) is 0.1 mm to 0.2 mm. It is understood that when the outer cylindrical member 25 is heated to 300 ° C., a gap (a gap of 0.2 mm or more) necessary for shrink fitting can be sufficiently secured.

In this example, the outer diameter OD1 of the inner cylindrical member 24 is 66 mm (case 1, case 2) or 68 mm (case 3, case 4), and the inner diameter ID1 of the inner cylindrical member 24 is the superconducting bulk 22. It is 64 mm approximately equal to the outer diameter. Therefore, the thickness (inner thickness t_in) in the radial direction of the inner cylindrical member 24 is 1 mm (case 1, case 2) or 2 mm (case 3, case 4). In the present example, the outer diameter OD2 of the outer cylindrical member 25 is 74 mm, and the inner diameter ID2 of the outer cylindrical member 25 is about 66 mm (case 1, case 2) or about 68 mm (case 3, case 4). . Therefore, the thickness (outside thickness t_out) in the radial direction 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 (outside thickness t_out) is 5 mm. The ratio (t_in / T) of the thickness (inner thickness t_in) of the inner cylindrical member 24 to the total 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 that the compressive stress of the outer cylindrical member 25 does not sufficiently act on the superconducting bulk 22 due to the thickness of the inner cylindrical member 24 being too large Can.

In addition, in any case, the ratio (t_in / T) is 10% or more. If the ratio (t_in / T) is 10% or more, the heat radiation effect at the time of shrink fitting of the outer cylindrical member 25 can be improved.

FIG. 9 shows an example of a method of 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. On this copper plate 31, the first intermediate assembly 12 in which the superconducting bulk 22 is embedded is placed on the inner cylindrical member 24 having an outer diameter (OD1) of 66.0 mm via the adhesive layer 23 of resin having a thickness of 0.1 mm. The On the first intermediate assembly 12 placed on the copper plate 31, a truncated copper plate 32 having a truncated cone shape whose outer diameter at the bottom is equal to the outer diameter of the inner cylindrical member 24 is concentrically stacked.

In addition, the temperature of the outer cylindrical member 25 is set to 300 by heating the outer cylindrical member 25 of the size shown in Case 1 having an outer diameter of 74.0 mm and an inner diameter of 65.9 mm at normal temperature using an electric furnace for 10 minutes or more. It heated up to ° C. Thereafter, the door of the electric furnace was opened, and the outer cylindrical member 25 was quickly taken out of 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 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 concentrically disposed outside the first intermediate assembly 12 located below the tapered copper plate 32.

Thereafter, the copper ring 33 was immediately 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 one size larger than the outer diameter of the outer cylindrical member 25. Accordingly, 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 dissipated to the copper ring 33 and the copper plate 31 at the surface contact portion, whereby the outer cylindrical member 25 is cooled. Thereby, the outer cylindrical member 25 is shrink-fit 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-fit. By cooling the outer cylindrical member 25 in a short time in this way, the outer cylindrical member 25 can be shrink-fit 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))
When the superconducting magnetic field generating element 41 as shown in FIG. 10 was cooled to the operating temperature (50 K), the compressive stress generated on the inner peripheral surface of the superconducting bulk was determined by calculation. 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. Further, the outer cylindrical member 45 includes a first outer cylindrical member 45A and a second outer cylindrical member 45B. The superconducting bulk 42, the inner cylindrical member 44, the first outer cylindrical member 45A, and the second outer cylindrical member 45B are arranged concentrically.

The outer diameter (OD_B) of the superconducting bulk 42 is 64 mm, and the inner diameter (ID_B) is 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 through the adhesive layer 43 of resin having a thickness of 0.1 mm. The materials of the first outer cylindrical member 45A and the second outer cylindrical member 45B are both the same as the material of the inner cylindrical member 44 (made of 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, and the first outer cylindrical member 45A is attached to the inner cylindrical member 44 by shrink fitting. 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 the inner circumferential surface thereof faces the outer circumferential surface of the first outer cylindrical member 45A, and the first outer cylindrical member 45B is 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 normal temperature in the natural state of the superconducting magnetic field generating element 41 of the above configuration is changed to the operating temperature (50 K) In this case, the compressive stress generated on the inner peripheral surface of the superconducting bulk 42 was calculated. In the calculation of the compressive stress, the axial length of the superconducting bulk 42 is made infinite. The calculation results of the compressive stress related to each case are as follows: the outer diameter (OD1) of the inner cylindrical member 44 at ordinary temperature, the outer diameter (OD2) and the inner diameter (ID2) of the first outer cylindrical member 45A at ordinary temperature, the second The results are shown in Table 2 together with the outer diameter (OD3) and the inner diameter (ID3) of the outer cylindrical member 45B at normal 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. In addition, when the first outer cylindrical member 45A is heated to 300 ° C. when the first outer cylindrical member 45A is shrink-fit, the gap C has an outer diameter (OD1) of the inner cylindrical member 44 at normal temperature and 300 The difference (diameter difference) of the inside diameter of the first outer cylindrical member 45A in ° C. is represented. In addition, when the second outer cylindrical member 45B is heated to 400 ° C. when the second outer cylindrical member 45B is shrink-fit, the gap D is the outer diameter (OD2) of the first outer cylindrical member 45A at normal temperature. And the inner diameter of the second outer cylindrical member 45B at 400.degree. C. (diameter difference).

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, Example 4 The compressive stress of

Case

5, 6 of 2 is larger. The reason for this is that in the

cases

5 and 6 of the second embodiment, the cylindrical members have a triple structure, and the compressive stress by the shrink fitting of the first outer cylindrical member 45A and the compressive stress by the shrink fitting of the second outer cylindrical member 45B. Both act on the superconducting bulk 42.

Fourth Embodiment
Next, a superconducting magnetic field generating device according to a fourth embodiment will be described. The superconducting magnetic field generating element according to the fourth embodiment basically has 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 as

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 device 1B according to the fourth embodiment has the superconducting bulk 2, the inner cylindrical member 4, and the outer cylindrical shape, similarly to the superconducting magnetic field generating device 1 according to the first embodiment. And a member 5.

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

Further, 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 normal temperature as in the superconducting magnetic field generating element 1 according to the first embodiment. . Accordingly, the clamping force of the outer cylindrical member 5 is transmitted to the superconducting bulk 2 via the inner cylindrical member 4. Therefore, stress in the direction from the outer peripheral side to the center side, that is, compressive stress is applied to the superconducting bulk 2. That is, the outer cylindrical member 5 is attached to the inner cylindrical member 4 so that a compressive stress acts on the superconducting bulk 2 at normal temperature.

FIG. 12A is a view showing a part of a cross section obtained by cutting the superconducting magnetic field generating element 1B according to the fourth embodiment including a plane including the axis thereof. 12B is a detailed view of a portion C which is a region portion including the 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 circumferential surface of the inner cylindrical member 4 and the outer circumferential surface of the superconducting bulk 2 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 unevenness includes 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, due to the unevenness or shape distortion of both surfaces, a portion which is not in direct contact with the portion directly contacting both surfaces is formed.

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

FIG. 12C is a view 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 substantially in the entire area 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 do not come in direct contact with each other, but both surfaces are in indirect contact via 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 of the inner peripheral surface of the inner cylindrical member 4 is in direct contact with the outer peripheral surface of the superconducting bulk 2. The second region B of the inner circumferential surface is in indirect contact with the outer circumferential 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 entirely and directly in contact with each other. Further, since there is a portion where the inner cylindrical member 4 and the superconducting bulk 2 are in direct contact, the filler 6 is deteriorated and it is difficult to transmit compressive stress from the second region B to the superconducting bulk 2 via the filler 6 Even in the case, compressive stress can be transmitted from the first region A in direct contact to the superconducting bulk 2. Therefore, the durability and the reliability of the superconducting magnetic field generating element 1B can be improved.

Next, a method of manufacturing the superconducting magnetic field generating element 1B according to the fourth embodiment will be described. The method of manufacturing the superconducting magnetic field generating element 1B according to the fourth embodiment also includes the first step and the second step, similarly to the method of manufacturing the superconducting magnetic field generating element 1 according to the first embodiment. 13A is a view showing a first step, and FIG. 13B is a perspective view showing a state in which the inner cylindrical member 4 is attached to the superconducting bulk 2 by the execution of 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 thereafter, the outer peripheral surface of the cylindrical superconducting bulk 2 is the inner cylindrical member The superconducting bulk 2 is concentrically disposed 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. Assuming that the temperature of the superconducting bulk 2 and the inner cylindrical member 4 at the time of performing the first step is a temperature T1, the outer diameter OD_B of the superconducting bulk 2 is greater than the inner diameter ID1 of the inner cylindrical member 4 at the temperature T1. Slightly smaller. Therefore, the filler 6 is filled between the outer peripheral surface of the concentrically disposed superconducting bulk 2 and the inner cylindrical member 4. As the filler 6, an adhesive made of an epoxy resin, or a grease can be exemplified. The temperature T1 may be, for example, normal temperature (5 ° C. to 35 ° C.). In the first step, the outer peripheral surface of the superconducting bulk 2 is cylindrically shaped in the state where the filler 6 having fluidity is 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 in the first step. It is attached. In this case, first, the outer cylindrical member 5 at the 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, at temperature T1, ID2 <OD1.

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

Then, as shown in FIG. 14, the outer cylindrical member 5 is placed on the inner cylindrical member so that the inner peripheral surface of the outer cylindrical member 5 heated to the temperature T2 faces the outer peripheral surface of the inner cylindrical member 4. Arrange concentrically to 4). Thereafter, the outer cylindrical member 5 is cooled to the temperature T1. The cooling method is not particularly limited. For example, natural cylindrical cooling or cold air is supplied to the outer cylindrical member 5 to cool the outer cylindrical member 5. By the heat contraction 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-fit to the inner cylindrical member 4. Then, 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. 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 the execution of the second step, the filler 6 is formed on the outer peripheral surface of the superconducting bulk 2 and the inside of the inner cylindrical member 4 It flows between the contact interfaces with the circumferential surface. The flowed filler 6 is formed on the contact surface between the inner cylindrical member 4 and the superconducting bulk 2 due to irregularities, holes or distortion of the shape, and the inner peripheral surface of the inner cylindrical member 4 and the outer peripheral surface of the superconducting bulk 2 And a gap G (see FIG. 12B) formed therebetween. Here, it is conceivable that the fine pores formed on the outer peripheral surface of the superconducting bulk 2 may not be filled by merely applying the filler 6 to the outer peripheral surface of the superconducting bulk 2. On the other hand, according to the present embodiment, in the second step, 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. By the stress, the filler 6 can be intruded into the fine pores. 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 intervening filler 6. In this manner, the inner peripheral surface of the inner cylindrical member 4 and the outer peripheral surface of the superconducting bulk 2 can be entirely and directly in 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 step and the second step described above. According to this manufacturing method, at the stage of manufacturing the superconducting magnetic field generating element 1B, compressive stress due to shrink fitting is already applied to the superconducting bulk 2 from the outer cylindrical member 5. 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 It is added. For this reason, the compressive stress which can counter the tensile stress generated in the superconducting bulk 2 when the superconducting bulk 2 captures a magnetic field is increased by the amount of the compressive stress already generated in the manufacturing stage. Further, 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 entirely and directly in contact with each other. Therefore, since compressive stress can be applied uniformly to the outer peripheral surface of the superconducting bulk 2, sufficiently large compressive stress can be uniformly applied to the superconducting bulk 2 without breaking the superconducting bulk 2.

Further, 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-fit in the second step is Direct transfer to the superconducting bulk 2 and the filler 6 is prevented. Thus, damage to the superconducting bulk 2 due to thermal shock can be prevented, and thermal deterioration of the filler 6 can be prevented.

Moreover, according to the manufacturing method of the fourth embodiment, the filler 6 interposed between the superconducting bulk 2 and the inner cylindrical member 4 in the first step has fluidity at the time of the second step. Need to be in a state of On the other hand, after the execution of the second step, when the predetermined conditions are satisfied, the flowability of the filler 6 may be reduced. For example, when the predetermined time has passed, or when the temperature of the filler 6 falls below the predetermined temperature, the fluidity of the filler 6 decreases, 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 in the second step, the outer peripheral surface of the superconducting bulk 2 is obtained in the first step. Is performed when the filler 6 interposed between the inner cylindrical member 4 and the inner circumferential surface of the inner cylindrical member 4 is in a fluid state, and the filler 6 satisfies a predetermined condition after the second step is performed. It is good to be solidified.

For example, when an epoxy-based adhesive is used as the filler 6, the filler 6 initially has fluidity, but solidifies over time. Therefore, in the case of using an epoxy-based adhesive as the filler 6 in the present embodiment, the second step is performed before solidification of the filler 6. Thereafter, after a predetermined time has elapsed, the filler 6 solidifies 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 generation element 1B, the filler 6 can be kept in the gap G at the time of use. When grease is used as the filler 6, the filler 6 has fluidity at a predetermined temperature or higher, and is in a solidified state at a temperature lower than the predetermined temperature (for example, the operating 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 50 K when using the manufactured superconducting magnetic field generating element 1B, the filler 6 solidifies in the gap G. Thereby, the filler 6 can be kept in the gap G at the time of use.

(Example 3: In the case of using an epoxy adhesive as a filler)
An EuBaCuO-based superconducting bulk having an outer diameter 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. The epoxy-based adhesive has fluidity, but the fluidity decreases with the passage of time, and eventually solidifies. Next, the outer peripheral surface of the superconducting bulk in which the epoxy adhesive is applied to the outer peripheral surface of the inner peripheral surface of an aluminum alloy inner cylindrical member having an outer diameter of 68.0 mm, an inner diameter of 64.0 mm, and a height of 20 mm at normal temperature. The superconducting bulk was disposed on the inner circumferential side of the inner cylindrical member so that Thus, the inner cylindrical member is attached to the outer peripheral surface of the superconducting bulk in a state in which an epoxy adhesive having fluidity is 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 increased to 68 mm or more. Thereafter, the outer cylindrical member was taken out of the electric furnace. Then, the outer cylindrical member is disposed 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. 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 on the outer side of the inner cylindrical member within a period of time. Thereafter, the outer cylindrical member was cooled to room temperature. Due to the heat contraction due to the 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 becomes 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-fit to the inner cylindrical member (second step).

By performing the second step, 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. This causes the epoxy adhesive to flow 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 distortion of the unevenness or shape of the outer peripheral surface of the superconducting bulk and the outer peripheral surface of the inner cylindrical member. Further, at the portion where the gap is not formed, the outer peripheral surface of the superconducting bulk and the outer peripheral surface of the inner cylindrical member are in direct contact with each other due to the above-mentioned compressive stress. The adhesive that has not been filled in the gap overflows on both end faces of the superconducting magnetic field generating element. The adhesive that has spilled out is wiped off. After the shrink fitting, when a predetermined time passes, the epoxy adhesive in the gap solidifies. Thus, a superconducting magnetic field generating element was manufactured.

The circumferential compressive stress generated on the inner peripheral surface of the superconducting bulk when the superconducting magnetic field generating device manufactured as described above was cooled to the operating temperature (50 K) was calculated. In this case, assuming that half of the epoxy adhesive interposed between the superconducting bulk and the inner cylindrical member in the first step overflowed by the execution of the second step, the compressive stress was calculated. . The calculation results are shown in Case 7 of Table 3. In addition, for comparison, a superconducting magnetic field generating element manufactured by performing the first step using an inner cylindrical member having an outer diameter of 74.0 mm and an inner diameter of 64.0 mm, ie, without performing the second implementation step 1 Also for the superconducting magnetic field generating element in which the cylindrical member is constituted by the heavy ring (only the inner cylindrical member), the circumferential compressive stress generated on the inner peripheral surface of the superconducting bulk when cooled to the operating temperature (50 K) is calculated did. The calculation results are shown in Case 8 of Table 3. In addition, the superconducting magnetic field generating device manufactured by performing the second step after the adhesive applied in the first step is solidified is also generated on the inner peripheral surface of the superconducting bulk when cooled to the operating temperature (50 K) The circumferential compressive stress was calculated. The calculation results are shown in Case 9 of Table 3. Furthermore, with regard to the superconducting magnetic field generating device manufactured by performing the first step and the second step without using an adhesive, circumferential compression that occurs on the inner circumferential surface of the superconducting bulk when cooled to the operating temperature (50 K) The stress was calculated. The calculation results are shown in Case 10 of Table 3. In addition, in calculation of compressive stress, the axial direction length of the superconducting bulk was set to infinite length.

In Table 3, in the “double structure” described in the column “Cylindrical member”, the superconducting magnetic field generating element comprises an inner cylindrical member and an outer cylindrical member, and these constitute a cylindrical member. Represents that. The “single-layer structure” in Table 3 indicates that the superconducting magnetic field generating element is configured as a cylindrical member provided with only the inner 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 the cases 7, 9 and 10. On the other hand, when the cylindrical member has a single-layer structure, that is, when the superconducting magnetic field generating element is configured as in case 8, the compressive stress is low. Moreover, the thickness of the total cylindrical member is the same whether the cylindrical member has a single-layer structure or a double-layer structure. From this, it is understood that the compressive stress can be sufficiently increased by forming the cylindrical member in a double structure.

Case 9 corresponds to the case where no filler (epoxy adhesive) overflows from the contact interface between the inner cylindrical member and the superconducting bulk at the time of execution of the second step, and case 10 is the second case. This corresponds to the case where all the filler overflows from the contact interface between the inner cylindrical member and the superconducting bulk when performing the two steps. Therefore, when comparing the amount of filler remaining at the contact interface between the inner cylindrical member and the superconducting bulk for the superconducting magnetic field generating element according to cases 7, 9 and 10, the case where the amount of filler remaining is the largest Is the case 9, and the case where the residual amount of the filler is large is the case 7 and the case where the residual 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 is reduced by the thermal contraction of the outer cylindrical member by the overflowing amount. However, as shown in Table 3, even in Case 10, which corresponds to the case where all the filler overflows, the thickness of the cylindrical member is much higher than the compressive stress in Case 8, which has the same single-layer structure. Recognize.

Example 4 When Vacuum Grease is Used as a Filler
An EuBaCuO-based superconducting bulk having an outer diameter 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 shrink fitting is performed in the second step described later, but the viscosity increases as the temperature decreases and the fluidity is lost, and it is cooled to a temperature (use temperature) to operate as a superconducting magnetic field generating element , Become substantially individualized.

Next, the outer peripheral surface of the superconducting bulk coated with vacuum grease on the outer peripheral surface faces the inner cylindrical member made of aluminum alloy and having an outer diameter of 68.0 mm, an inner diameter of 64.0 mm, and a height of 20 mm at normal temperature. The superconducting bulk was disposed on the inner circumferential side of the inner cylindrical member. As a result, the inner cylindrical member is attached to the outer peripheral surface of the superconducting bulk in a state in which the flowable vacuum grease is 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 increased to 68 mm or more. Thereafter, the outer cylindrical member was taken out of the electric furnace. And, when the inner diameter of the outer cylindrical member is 68 mm or more, the outer cylindrical member is placed on the outer side of 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. Placed. Thereafter, the outer cylindrical member was cooled to room temperature. Due to the heat contraction due to the 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 becomes 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-fit to the inner cylindrical member (second step).

By performing the second step, 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. This causes vacuum grease to flow 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 the both surfaces by distortion of the unevenness or shape of the outer peripheral surface of the superconducting bulk and the outer peripheral surface of the inner cylindrical member. Further, at the portion where the gap is not formed, the outer peripheral surface of the superconducting bulk and the outer peripheral surface of the inner cylindrical member are in direct contact with each other due to the above-mentioned compressive stress. The vacuum grease which has not been filled in the gap overflows on both end faces of the superconducting magnetic field generating element. The spilled vacuum grease is wiped off. A superconducting magnetic field generating element was manufactured through the above steps.

Also in the superconducting magnetic field generating element according to the fourth embodiment, as in the superconducting magnetic field generating element according to the third embodiment (case 7), the inner cylindrical member and the superconducting bulk directly and indirectly via the vacuum grease. The whole surface is touched. The compressive stress generated on the inner peripheral surface of the superconducting bulk when the superconducting magnetic field generating element was cooled to a temperature of 50 K was also equivalent to the compressive stress of the superconducting magnetic field generating element according to Example 3 (Case 7).

Further, in the superconducting magnetic field generating element according to Example 4, the filler (vacuum grease) present in the gap between the contact interface between the inner cylindrical member and the superconducting bulk at normal temperature has fluidity. However, since it is cooled to 50 K in use, the filler (vacuum grease) present in the gap between the contact interface between the inner cylindrical member and the superconducting bulk solidifies. Therefore, the filler can be prevented from flowing out from the gap formed at the contact interface between the inner cylindrical member and the superconducting bulk at the time of use, and the compressive stress can be prevented from being reduced.

Claims

Cylindrical or cylindrical superconducting bulk;
An inner cylindrical member attached to the superconducting bulk such that the inner circumferential surface is in contact with the outer circumferential surface of the superconducting bulk;
An outer cylindrical member attached to the inner cylindrical member such that the inner peripheral surface is in contact with 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 is attached to the inner cylindrical member so that compressive stress acts on the superconducting bulk via the inner cylindrical member at normal temperature.
In the superconducting magnetic field generating element according to claim 1,
The superconducting magnetic field generating element is attached to the superconducting bulk such that the inner cylindrical member is bonded to the outer circumferential surface of the superconducting bulk through an adhesive layer.
In 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.
In the superconducting magnetic field generating element according to claim 1,
The inner circumferential surface of the inner cylindrical member has a second region in which a gap is formed between the first region in direct contact with the outer circumferential surface of the superconducting bulk and the outer circumferential surface of the superconducting bulk,
A superconducting magnetic field generating element, wherein the second region is in indirect contact with the outer peripheral surface of the superconducting bulk via the filler by filling the gap with the filler.
In the superconducting magnetic field generating element according to claim 4,
The superconductive magnetic field generating element, wherein the filler is made of a material having fluidity.
In the superconducting magnetic field generating element according to claim 5,
The superconductive magnetic field generating element, wherein the filler is made of a material which is solidified at a predetermined temperature or less.
The superconducting magnetic field generating device according to any one of claims 1 to 6,
A superconducting magnetic field generating element, wherein the outer cylindrical member is shrink-fit to the inner cylindrical member.
The superconducting magnetic field generating device according to any one of claims 1 to 7.
A superconducting magnetic field generating element, wherein the outer cylindrical member is cold-fit to the inner cylindrical member.
The superconducting magnetic field generating device 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 that of the inner cylindrical member or a thermal contraction rate larger than that of the inner cylindrical member.
The superconducting magnetic field generating device 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 so that a stress in the compression direction is generated on the contact surface of the adjacent cylindrical members at normal temperature. The superconducting magnetic field generating element.
In the superconducting magnetic field generating element according to claim 10,
Each of the cylindrical members 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 members disposed radially inwardly adjacent thereto. Superconducting magnetic field generating element.
In 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 larger than the Young's modulus of a cylindrical member disposed adjacent to the diameter inward than that, a superconducting magnetic field Generating element.
The superconducting magnetic field generating device according to any one of claims 1 to 12.
A superconducting magnetic field generating element, wherein the outer cylindrical member and the inner cylindrical member are made of the same material.
In the superconducting magnetic field generating device according to any one of claims 1 to 13,
Total thickness (T) which is the sum of inner thickness (t_in) which is the thickness in the radial direction of the inner cylindrical member and outer thickness (t_out) which is the thickness in the radial direction of the outer cylindrical member The superconducting magnetic field generating element, wherein the ratio (t_in / T) of the inner wall thickness (t_in) to is 3⁄4 or less.
The superconducting magnetic field generating device according to any one of claims 1 to 14,
Total thickness (T) which is the sum of inner thickness (t_in) which is the thickness in the radial direction of the inner cylindrical member and outer thickness (t_out) which is the thickness in the radial direction of the outer cylindrical member The superconducting magnetic field generating element, wherein the ratio (t_in / T) of the inner wall thickness (t_in) to is 1/10 or more.
A method of manufacturing a superconducting magnetic field generating element comprising: a cylindrical 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 And
A first step of attaching the inner cylindrical member to an outer peripheral surface of the superconducting bulk;
The outer cylindrical member is placed against the inner cylindrical member such that the inner peripheral surface of the outer cylindrical member at a temperature higher than the temperature of the inner cylindrical member faces the outer peripheral surface of the inner cylindrical member. And a second step of attaching the outer cylindrical member to the outer peripheral surface of the inner cylindrical member by disposing and thereafter reducing the difference between the temperature of the inner cylindrical member and the temperature of the outer cylindrical member. ,
And a method of manufacturing a superconducting magnetic field generating element.
In the method of manufacturing a superconducting magnetic field generation device according to claim 16,
In the first step, an adhesive is applied 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 is provided with the adhesive via the adhesive. Attaching the inner cylindrical member to the superconducting bulk so that the inner circumferential surfaces are in contact with each other.
In the method of manufacturing a superconducting magnetic field generation device according to claim 16,
The first step is a step of applying a filler having fluidity to the outer peripheral surface of the superconducting bulk or the inner peripheral surface of the inner cylindrical member, and the outer peripheral surface of the superconducting bulk via the filler. Attaching the inner cylindrical member to the superconducting bulk such that the inner circumferential surface of the inner cylindrical member is in contact with the inner cylindrical member.
In the method of manufacturing a superconducting magnetic field generation device according to claim 18,
The filler is made of a material that can change from a fluid state to a non-flowable 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. Method of manufacturing a superconducting magnetic field generating element.
In the method of manufacturing a superconducting magnetic field generating device according to any one of claims 16 to 19,
In the second step, the outer cylindrical surface 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. Superconductive magnetic field generation, which is a step of disposing a member on the inner cylindrical member and thereafter cooling the outer cylindrical member to attach the outer cylindrical member to the outer peripheral surface of the inner cylindrical member Method of manufacturing a device
In the method of manufacturing a superconducting magnetic field generating device according to any one of claims 16 to 19,
In the second step, the outer cylindrical surface is formed such 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 superconductive magnetic field, which is a step of disposing a member on the inner cylindrical member and thereafter attaching the outer cylindrical member to the outer peripheral surface of the inner cylindrical member by raising the temperature of the inner cylindrical member. Method of manufacturing a generating element.
A method of manufacturing a superconducting magnetic field generation device 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 the 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 i-th attached cylindrical member is the i-1st attached cylinder The manufacturing method of the superconducting magnetic field generation element made higher than the temperature of the rod-shaped member.