JP6435927B2 - Superconducting bulk magnet and method of magnetizing superconducting bulk magnet - Google Patents

Description

  The present invention relates to a superconducting bulk magnet using an oxide superconducting bulk body and a method for magnetizing the superconducting bulk magnet.

In Patent Document 1, in an oxide superconductor composed of oxides of RE (rare earth elements including Y), Ba, and Cu, the structure RE ₁ Ba ₂ Cu ₃ O ₇₋ of the oxide superconductor of RE, Ba, and Cu is used. An oxide superconducting bulk material characterized by having a structure in which RE ₂ BaCuO ₅ having a diameter of 20 μm or less is dispersed in the _x phase has been proposed. In such single-crystal RE ₁ Ba ₂ Cu ₃ O _7-x (RE is one or more elements selected from Y or rare earth elements, x is an oxygen deficiency, 0.2 or less) Since the superconducting bulk material in which RE ₂ BaCuO ₅ is finely dispersed has a strong pinning force, it can be a very strong magnetic field generation source compared to a conventional permanent magnet. A magnetic field generation source using such a superconducting bulk body is called a superconducting bulk magnet.

According to the bean model that explains the principle of pinning force of superconductors, it is known that the magnetic field peak value and magnetic gradient in a superconducting bulk magnet are determined by the critical current density ( _Jc ) characteristic of the superconducting bulk body and the sample size. ing. That is, the magnetic gradient is proportional to the critical current density _Jc , and the magnetic field peak value is proportional to the product of the critical current density _Jc and the sample size. For this reason, in order to develop a superconducting bulk magnet having a strong magnetic field strength, research and development relating to the formation of a high critical current density _{Jc and an} increase in size of the superconducting bulk body are being carried out all over the world.

  Thus, superconducting bulk magnets have excellent features such as compact, strong magnetic field, and high magnetic gradient. Therefore, marine motors such as magnetic targeting and magnetic drug delivery systems in the medical field and magnetic separation in the environmental field are being used. In applications using magnets such as generators for wind turbines and wind power generators, these devices are expected to be significantly reduced in size and weight.

  As the shape of the superconducting bulk body used for the superconducting bulk magnet, as disclosed in Patent Document 2, a cylindrical shape is generally used. In the case of a cylindrical superconducting bulk body, the cylindrical flat surface (circular end surface) is magnetized so as to be a magnetic field generating surface. Furthermore, in patent document 2, in order to prevent destruction of the superconductor due to electromagnetic force, metal ring reinforcement is provided on the outer peripheral portion.

  In Patent Document 3, at least one of a convex portion having a height of 0.5 mm or more at the highest point and a concave portion having a depth of 0.5 mm or more at the deepest point is present on the working surface (magnetic field generating surface). It is disclosed that a magnetic field is trapped in a superconducting bulk body characterized by: It is said that the uniformity and directivity of the magnetic field generated from the magnetic field generating surface can be easily controlled by using such a superconducting bulk body. In Patent Document 3, regarding the directivity of the magnetic field, the magnetic field in a specific narrow range is increased, but the distribution of the magnetic gradient is not particularly described.

Japanese Patent Laid-Open No. 2-153803 JP 11-335120 A Japanese Patent Laid-Open No. 2014-138039

  In magnetic targeting and magnetic drug delivery systems in the medical field, which is one of the application fields of superconducting bulk materials, a magnetic field having a strong magnetic field and a high magnetic gradient is required in a relatively narrow region depending on the affected area. In such a case, the magnetic field distribution of the superconducting bulk magnet is desirably a magnetic field distribution in which the magnetic gradient continuously increases toward the central portion of the superconducting bulk magnet. That is, it is desirable that the magnetic gradient simultaneously increase near the central portion of the superconducting bulk body having the highest magnetic field strength.

However, in a conventional superconducting bulk magnet, the magnetic gradient is proportional to the material property (J _c ) and is therefore almost constant. For magnetic gradient obtained continuously larger such magnetic field distribution toward the superconducting bulk magnet central part, in such means as changing the material composition and microstructure such as the superconducting bulk material properties (J _c It is necessary to manufacture a superconducting bulk body so as to continuously improve the characteristics from the end toward the center. However, there is a problem that such a superconducting bulk body is not easy to manufacture.

  On the other hand, Patent Document 3 shows that the directivity of a magnetic field is strengthened and the magnetic field in a specific narrow range is increased. However, increasing the directivity of a magnetic field is not the same as increasing the magnetic gradient. . Increasing the magnetic field in a specific narrow range does not necessarily increase the magnetic gradient in that range. Therefore, simply using a superconducting bulk body with a convex portion on the magnetic field generating surface does not increase the magnetic gradient at the same time near the center of the superconducting bulk body where the magnetic field strength is the highest. The magnetic field distribution does not continuously increase toward the center.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a superconducting bulk magnet having a magnetic gradient that is also high near the center of the superconducting bulk body having the highest magnetic field strength. It is to provide.

  The superconducting bulk magnet using the superconducting bulk body of the present invention is as follows.

(1)
A superconducting bulk magnet using an oxide superconducting bulk in which RE ₂ BaCuO ₅ is dispersed in single-crystal RE ₁ Ba ₂ Cu ₃ O _7-x ,
The superconducting bulk magnet is characterized in that the shape of the oxide superconducting bulk body is a partial sphere composed of a flat surface portion and a partial spherical surface portion or a conical shape composed of a flat surface portion and a conical surface portion.
However, RE is one or more elements selected from rare earth elements, and the oxygen deficiency (x) is 0.2 or less.
(2)
A support plate for supporting the planar portion;
A reinforcing body that is disposed so as to surround the partial spherical surface portion or the conical surface portion and is connected to the support plate to reinforce the oxide superconducting bulk body;
The superconducting bulk magnet according to (1), further comprising:
(3)
The superconducting bulk magnet according to (2), wherein the reinforcing body is a metallic reinforcing body cut out in the same shape as a partial spherical surface portion or a conical surface portion of the oxide superconducting bulk body.
(4)
The reinforcing body is
A cylindrical reinforcing ring connected to the support plate;
A resin present in the space between the inner wall of the reinforcing ring and the partial spherical surface portion or the conical surface portion;
The superconducting bulk magnet according to (2), characterized by comprising:
(5)
(4) The columnar reinforcing ring has a flange that protrudes inward from the inner peripheral surface at an end opposite to the end connected to the support plate. Superconducting bulk magnet.
(6)
(1) It is a magnetizing method of the superconducting bulk magnet described in any one of (5),
A direction perpendicular to the plane portion of the oxide superconducting bulk body is cooled in a magnetic field in the direction of the magnetic field, and magnetized so that the partial spherical surface portion or the conical surface portion becomes a magnetic field generating surface. To magnetize a superconducting bulk magnet.
(7)
A superconducting bulk magnet using an oxide superconducting bulk in which RE ₂ BaCuO ₅ is dispersed in single-crystal RE ₁ Ba ₂ Cu ₃ O _7-x ,
The shape of the oxide superconducting bulk body is that the circular flat portion and the central portion of the flat portion are the thickest, the thickness continuously decreases toward the outer peripheral portion of the flat portion, and becomes zero at the outer peripheral portion. A superconducting bulk magnet characterized by having a shape comprising a three-dimensional part having a shape.
However, RE is one or more elements selected from rare earth elements, and the oxygen deficiency (x) is 0.2 or less.

  As described above, according to the present invention, it is possible to provide a superconducting bulk magnet in which the magnetic gradient is increased at the same time near the central portion of the superconducting bulk body having the highest magnetic field strength.

It is a conceptual diagram which shows an example of the superconducting bulk magnet which concerns on embodiment of this invention. It is a comparison figure of the magnetic field distribution of the superconducting bulk magnet which concerns on embodiment of this invention, and the conventional superconducting bulk magnet. It is a conceptual diagram which shows another aspect of the superconducting bulk magnet which concerns on embodiment of this invention. It is a conceptual diagram which shows another aspect of the superconducting bulk magnet which concerns on embodiment of this invention. It is a conceptual diagram which shows another aspect of the superconducting bulk magnet which concerns on embodiment of this invention. It is explanatory drawing which compares the structure of the superconducting bulk body in Example 1. FIG. It is explanatory drawing which compares the structure of the superconducting bulk magnet in Example 2. FIG. It is explanatory drawing which compares the structure of the superconducting bulk magnet in Example 3. FIG.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

The superconducting bulk used in the embodiment of the present invention is typified by a RE ₂ BaCuO ₅ phase (211 phase) having a diameter of 20 μm or less in a single crystal RE ₁ Ba ₂ Cu ₃ O _7-x phase (123 phase). In particular, a bulk material (so-called QMG (registered trademark) material) having a structure in which the non-superconducting phase is finely dispersed is desirable. Here, the term “single crystal” means that it is not a perfect single crystal, but also includes those having defects that may be practically used such as a low-angle grain boundary. RE in the 123 phase and the 211 phase is a rare earth element composed of Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof, and La, Nd, Sm, Eu, The 123 phase containing Gd deviates from the 1: 2: 3 stoichiometric composition, and Ba may be partially substituted at the RE site. In the 211 phase which is a non-superconducting phase, La and Nd are somewhat different from Y, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, and the ratio of metal elements is non-stoichiometric. It is known that it has a theoretical composition or a different crystal structure.

  Substitution of the Ba element described above tends to lower the critical temperature. Further, in an environment with a lower oxygen partial pressure, substitution of Ba element tends to be suppressed.

The 123 phase is a peritectic reaction between the 211 phase and a liquid phase composed of a composite oxide of Ba and Cu.
211 phase + liquid phase (complex oxide of Ba and Cu) → 123 phase. The temperature at which the 123 phase is formed by this peritectic reaction (Tf: 123 phase formation temperature) is substantially related to the ionic radius of the RE element, and Tf also decreases as the ionic radius decreases. Further, Tf tends to decrease with the addition of a low oxygen atmosphere and Ag.

A material in which the 211 phase is finely dispersed in the single-crystal 123 phase can be formed because 211 unreacted grains are left in the 123 phase when the 123 phase is crystal-grown. That is, the bulk material is
211 phase + liquid phase (complex oxide of Ba and Cu) → It can be performed by the reaction shown by 123 phase + 211 phase.

The fine dispersion of the 211 phase in the bulk material is extremely important from the viewpoint of improving the critical current density (J _c ). By adding a trace amount of at least one of Pt, Rh, or Ce, the grain growth of the 211 phase in the semi-molten state (a state composed of the 211 phase and the liquid phase) is suppressed, and as a result, the 211 phase in the material is reduced to about The size is reduced to about 1 μm. The addition amount is 0.2 to 2.0 mass% for Pt, 0.01 to 0.5 mass% for Rh, and 0.5 to 2.0 mass for Ce from the viewpoint of the amount of the effect of miniaturization and the material cost. The mass% is desirable. The added Pt, Rh, and Ce partially dissolve in the 123 phase. In addition, elements that could not be dissolved form a composite oxide with Ba and Cu and are scattered in the material.

In addition, the superconducting bulk body constituting the superconducting bulk magnet needs to have a high critical current density ( _Jc ) even in a magnetic field. In order to satisfy this condition, it is necessary that the phase is a single-crystal 123 phase that does not include large-angle grain boundaries that are superconductively weakly coupled. In order to have higher Jc characteristics, a pinning point for stopping the movement of magnetic flux is required. What functions as the pinning point is the finely dispersed 211 phase, and it is desirable that many finely dispersed. As described above, Pt, Rh, and Ce have a function of promoting the refinement of the 211 phase. Moreover, the possibility of BaCeO ₃ , BaSiO ₃ , BaGeO ₃ , BaSnO _3, etc. is known as a pinning point. Further, the non-superconducting phase such as the 211 phase has an important function of mechanically strengthening the superconducting bulk body by being finely dispersed in the 123 phase that is easy to cleave, and as a practical material.

211 phase ratio of 123 phase, from the viewpoint of _{J c} properties and mechanical strength, is desirably 5 to 35% by volume. Further, the material generally contains 5 to 20% by volume of voids (bubbles) of about 50 to 500 μm, and when Ag is added, 0 to about 1 to 500 μm of Ag or Ag compound is added depending on the addition amount. More than 25% by volume.

  In addition, the oxygen deficiency (x) of the superconducting bulk body after crystal growth is about 0.5, indicating a temperature change of the semiconductor resistivity. This is annealed in an oxygen atmosphere at 350 ° C. to 600 ° C. for about 100 hours by each RE system, so that oxygen is taken into the superconducting bulk body and the oxygen deficiency (x) is 0.2 or less, which is a good superconductivity. Show the characteristics. At this time, a twin structure is formed in the superconducting phase. However, including this point, it is referred to as a single crystal here.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing an example of a superconducting bulk body 110 constituting the superconducting bulk magnet in the present embodiment. In FIG. 1, the superconducting bulk body 110 has a partially spherical or conical shape. Here, the partial sphere means a shape obtained by cutting a part of the sphere with a plane. The partially spherical superconducting bulk body 110 includes a planar portion and a partially spherical portion that is a three-dimensional portion, and the conical superconducting bulk body 110 includes a planar portion and a conical surface portion that is a three-dimensional portion.

  The superconducting bulk body 110 in the superconducting bulk magnet is magnetized by a magnetic field cooling method or a pulse magnetizing method. In the magnetic field cooling method, an external magnetic field is applied in a state where the superconducting bulk body 110 is maintained at a critical temperature or higher, and the external magnetic field is demagnetized after being cooled to a predetermined temperature while the magnetic field is applied. This is a method of magnetizing the superconducting bulk body 110. The pulse magnetization method is a method of magnetizing the superconducting bulk body 110 by applying a pulsed external magnetic field in a state where the superconducting bulk body 110 is cooled to a predetermined temperature that is lower than the critical temperature. The pulse magnetizing method is simpler in the magnetizing equipment, but in order to make the best use of the magnetizing ability of the superconducting bulk body 110, the in-magnetic field cooling method is preferred.

  When the superconducting bulk body 110 having the shape as in the present embodiment is magnetized by a magnetic field cooling method or a pulse magnetizing method, the superconducting bulk body 110 is perpendicular to the bottom surface (planar portion) of the partial sphere or conical superconducting bulk body 110. By cooling in the magnetic field in the direction of the magnetic field, the superconducting bulk body 110 can be magnetized so that the partial spherical surface or the conical surface becomes the magnetic field generating surface 112. By forming the partial spherical surface or the conical surface of the superconducting bulk body 110 as the magnetic field generating surface 112, a superconducting bulk magnet having a high magnetic gradient is formed near the center of the superconducting bulk body 110 having the highest magnetic field strength. be able to. Regarding the thickness of the superconducting bulk body 110 in the magnetization direction, the central portion of the superconducting bulk body 110 is the thickest in both cases of a partial spherical shape or a conical shape. Further, the thickness of the superconducting bulk body 110 is continuously reduced toward the outer peripheral portion, and the thickness of the superconducting bulk body 110 is zero at the outer peripheral portion.

  Thus, the shape of the superconducting bulk body 110 includes a circular flat surface portion, a solid portion having a shape in which the central portion is the thickest, the thickness continuously decreases toward the outer peripheral portion, and becomes zero at the outer peripheral portion. As long as the shape is made of any shape, the same effect as in the present embodiment is obtained. When the objectivity of the magnetic field distribution is required or considering the ease of manufacture, the shape of the solid part is centered on a perpendicular extending from the center point of the circular flat part to the thickest point of the central part of the solid part It is preferable that the target is a three-dimensional axis. When emphasis is placed on the ease of manufacture, the shape of the superconducting bulk body 110 is preferably a partially spherical shape or a conical shape. As described above, the superconducting bulk body 110 is crystal-grown in a single crystal form, and is generally often grown using a cylindrical precursor. In such a case, the superconducting bulk body 110 having a predetermined shape such as a partially spherical shape or a conical shape can be formed by mechanical processing.

  FIG. 2 is a comparison of the magnetic field distribution between the superconducting bulk magnet in the present embodiment and the conventional superconducting bulk magnet. FIG. 2A is an example of the superconducting bulk body of the superconducting bulk magnet in this embodiment, and the superconducting bulk body 110 has a hemispherical shape. On the other hand, FIG. 2B is an example of a superconducting bulk body of a conventional superconducting bulk magnet, and the superconducting bulk body 11 has a cylindrical shape. The diameter of the hemispherical superconducting bulk body 110 in FIG. 2 (a) is the same as the diameter of the cylindrical superconducting bulk body 11 in FIG. 2 (b).

  Each superconducting bulk magnet is magnetized in the direction of the arrow in the figure. That is, the superconducting bulk body 110 in FIG. 2A has a partially spherical surface as a magnetic field generating surface, and the superconducting bulk body 11 in FIG. 2B has a flat cylindrical surface as a magnetic field generating surface. In the conventional superconducting bulk body 11 shown in FIG. 2B, the magnetic gradient is substantially constant. On the other hand, in the case of the superconducting bulk body 110 according to the present embodiment shown in FIG. 2A, the magnetic gradient continuously increases toward the central portion of the superconducting bulk body 110. That is, the magnetic gradient is also increased near the central portion of the superconducting bulk body 110 having the highest magnetic field strength. The superconducting bulk body 110 according to the present embodiment has such a magnetic field distribution that the shape of the superconducting bulk body 110 is the thickest at the center, continuously decreases toward the outer periphery, and becomes zero at the outer periphery. Because.

  By continuously reducing the thickness of the superconducting bulk body 110 toward the outer peripheral portion, the magnetic gradient distribution can be changed to some extent, and by setting the outer peripheral thickness to zero, the magnetic field strength of the outer peripheral portion can be changed. Can be reduced. As a result, the magnetic gradient in the vicinity of the central portion of the superconducting bulk body 110 having the strongest magnetic field strength can be significantly increased. Therefore, by adopting the structure of the superconducting bulk body 110 according to the present embodiment, it is possible to provide a superconducting bulk magnet having a high magnetic gradient at the same time in the vicinity of the central portion of the superconducting bulk body 110 having the highest magnetic field strength. In addition, although the thickness of the superconducting bulk body 110 according to the present embodiment is zero at the outer peripheral portion, the same effect can be obtained even if the thickness is about the chamfered shape during processing.

  Here, the superconducting bulk magnet can generate a very strong magnetic field of several T class that cannot be realized by a permanent magnet, but a strong electromagnetic force is generated in the superconducting bulk body 110 when the superconducting bulk body 110 is magnetized. In addition, the superconducting bulk body 110 may be destroyed. In order to prevent the superconducting bulk body 110 from being destroyed, it is preferable to provide a reinforcing body that reinforces the superconducting bulk body 110. In addition, by cooling the superconducting bulk magnet, a compressive stress acts on the superconducting bulk body 110 due to the difference in thermal shrinkage between the superconducting bulk body 110 and the reinforcing body, and electromagnetic force when the superconducting bulk body 110 is magnetized. Can be reduced. As the material of the reinforcing body, stainless steel, copper alloy, aluminum alloy, and titanium are preferable. By providing a thin resin layer between the superconducting bulk body 110 and the reinforcing body, the stress due to the reinforcing body is uniformly applied to the superconducting bulk body 110.

  However, the thickness of the superconducting bulk body 110 according to this embodiment is zero at the outer periphery. That is, since the outer peripheral portion does not have a straight side surface, the effect of fixing the superconducting bulk body 110 is small and sufficient only by using a conventional annular metal reinforcing ring having a straight inner side surface as a reinforcing body. Can not get a strong reinforcing effect. When a conventional annular metal reinforcement ring having a straight inner surface is used, the superconducting bulk body 110 easily moves up and down in the annular metal reinforcement ring.

  Therefore, in the superconducting bulk magnet 100A according to the present embodiment, when the superconducting bulk body 110 having one end connected to the support plate 130 is reinforced with the metal reinforcing ring 122, as shown in FIG. Resin 124 is filled in a large gap between 122 and superconducting bulk body 110. In the present embodiment, the metal reinforcing ring 122 and the filled resin 124 are collectively referred to as a reinforcing body 120A. By forming the reinforcing body 120A with the metal reinforcing ring 122 and the resin 124, the superconducting bulk body 110 can be effectively reinforced. Further, as shown in FIG. 3B, a gap 126 is provided on the end of the metal reinforcing ring 122 opposite to the end connected to the support plate 130 by projecting inward from the inner peripheral surface. It is possible to suppress the resin 124 and the superconducting bulk body 110 filled in the vertical displacement. As a result, since the superconducting bulk body 110 can be fixed more firmly, the effect of reinforcement by the reinforcing body 120B is further increased.

  Alternatively, like the superconducting bulk magnet 100C shown in FIG. 4, the reinforcing body 120C is formed by hollowing out a cylindrical aluminum alloy or the like into the same shape as the outer shape of the superconducting bulk body 110 (for example, a partial spherical surface portion or a conical surface portion). May be. Accordingly, it is possible to save the trouble of filling the resin into the large gap between the metal reinforcing ring and the superconducting bulk body, which is more preferable.

  When the superconducting bulk magnets 100A, 100B, and 100C are cooled by using the reinforcing bodies 120A, 120B, and 120C as shown in FIGS. 3A, 3B, and 4, the superconducting bulk body 110 and the reinforcing bodies 120A, 120B, and 120C Compressive stress acts in the superconducting bulk body 110 due to the difference in thermal contraction rate, and the electromagnetic force when the superconducting bulk body 110 is magnetized can be reduced. However, in the case of the superconducting bulk magnets 100A, 100B, and 100C according to the present embodiment, when compressive stress acts on the superconducting bulk body 110 from the reinforcing bodies 120A, 120B, and 120C, the superconducting bulk body 110 has a lower side, that is, a flat surface. There is a risk of jumping to the side and coming off.

  When the superconducting bulk body 110 is disengaged from the reinforcing bodies 120A, 120B, 120C during such cooling, it is mechanically attached to the flat surface side of the superconducting bulk body 110 with a bolt or the like, as shown in FIG. 3A, FIG. 3B, or FIG. This can be prevented by providing the support plate 130 fixed to the base plate. When superconducting bulk magnets 100A, 100B, and 100C are cooled by a refrigerator, the side opposite to the magnetic field generating surface is attached to the cold head of the refrigerator, but in that case, the support plate 130 is omitted. Also good.

  The superconducting bulk magnet according to the present embodiment has been described above. According to the present embodiment, the shape of the superconducting bulk body constituting the superconducting bulk magnet is the thickest at the center, continuously thins toward the outer periphery, and becomes zero at the outer periphery. The magnetic gradient distribution can be changed to some extent by continuously reducing the thickness of the superconducting bulk body toward the edge, and the magnetic field strength at the outer periphery can be reduced by reducing the thickness of the outer periphery to zero. be able to. As a result, it is possible to significantly increase the magnetic gradient near the center of the superconducting bulk body having the strongest magnetic field strength.

Example 1
A single crystal superconducting bulk body containing 0.5% by mass of Pt and 15% by mass of Ag and having Gd ₂ BaCuO ₅ finely dispersed in Gd ₁ Ba ₂ Cu ₃ O _y is mechanically processed. As shown in FIG. 5, superconducting bulk bodies 10A, 10B, and 10C were manufactured. The superconducting bulk body 10A having the structure of the present invention was formed in a hemispherical shape with a diameter of 30 mm as shown in FIG. 5A (Example A).

  As a comparative example, the superconducting bulk body 10B is a cylinder having a diameter of 30 mm and a height of 15 mm as shown in FIG. 5B (Comparative Example B), and the superconducting bulk body 10C is a cylindrical portion 12 as shown in FIG. The thickness of the cylindrical portion 12 was 5 mm (Comparative Example C).

  These superconducting bulk bodies 10A, 10B, and 10C were magnetized by a magnetic field cooling method in which they were cooled in liquid nitrogen in a 2T magnetic field. The magnetic field strengths of the central portions of the superconducting bulk bodies 10A, 10B, and 10C after magnetization were 0.69T, 0.83T, and 0.75T, respectively. The magnetic gradient of the superconducting bulk body 10B was substantially constant at 0.055 T / mm and 0.057 T / mm. In addition, although the magnetic gradient of the superconducting bulk body 10C was slightly changed at the end portion, the magnetic gradient in the vicinity of the central portion was substantially constant at 0.057 T / mm.

  In contrast to these comparative examples, in the superconducting bulk body 10A, the magnetic gradient was continuously increased toward the central portion of the superconducting bulk body, and the magnetic field gradient in the vicinity of the central portion was 0.065 T / mm. In the superconducting bulk body 10A, the magnetic gradient was simultaneously high near the central portion of the superconducting bulk body having the highest magnetic field strength. Comparing the magnetic gradients near the central portions of the superconducting bulk bodies 10A and 10B, the magnetic field gradient of the superconducting bulk body 10A was improved by about 18% compared to the superconducting bulk body 10B.

  From these results, it was found that the superconducting bulk magnet having a magnetic gradient also increased at the same time in the vicinity of the central portion of the superconducting bulk body having the highest magnetic field strength by using the configuration of the present invention.

(Example 2)
A single-crystal superconducting bulk material containing ₁ % by mass of CeO ₂ and 10% by mass of Ag and finely dispersed Y ₂ BaCuO _{5 in} Y ₁ Ba ₂ Cu ₃ O _y was subjected to mechanical processing shown in FIG. Thus, superconducting bulk bodies 20D, 20E, and 20F were manufactured. A superconducting bulk body 20D having the structure of the present invention has a conical shape with a diameter of 46 mm and a height of 15 mm as shown in FIG. 6A (Example D). As the reinforcing body 22D, a conical shape is cut out from a cylinder made of nonmagnetic stainless steel SUS316L, and the superconducting bulk body 20D is bonded and fixed to the reinforcing body 22D with an epoxy resin, and then a support plate 24D made of nonmagnetic stainless steel SUS316L is attached. It was provided on the back surface of the superconducting bulk body 20D and bolted.

  As a comparative example, the superconducting bulk body 20E is a cylinder having a diameter of 46 mm and a height of 15 mm as shown in FIG. 6B, and is bonded and fixed to a metal reinforcing ring 22E made of nonmagnetic stainless steel SUS316L with an epoxy resin. (Comparative Example E). As another comparative example, the superconducting bulk body 20F has a shape in which a cylindrical portion and a cone are combined as shown in FIG. 6C, and the thickness of the cylindrical portion is 5 mm. In the case of the superconducting bulk body 20F, a large gap is formed between the metal reinforcing ring 22Fa and the superconducting bulk body 20F, and the gap was filled with the resin 22Fb (Comparative Example F).

  These superconducting bulk bodies were magnetized by a magnetic field cooling method in which cooling was performed in liquid nitrogen in a magnetic field of 3.5T. The magnetic field strengths of the central portions of the superconducting bulk bodies 20D, 20E, and 20F after magnetization were 0.88T, 1.1T, and 0.95T, respectively. The magnetic gradient of the superconducting bulk body 20E was substantially constant at 0.048 T / mm. In addition, although the magnetic gradient of the superconducting bulk body 20F slightly changed at the end portion, the magnetic gradient in the vicinity of the center portion was almost constant at 0.05 T / mm.

  In contrast to these comparative examples, in the superconducting bulk body 20D, the magnetic gradient was continuously increased toward the central portion of the superconducting bulk body, and the magnetic field gradient in the vicinity of the central portion was 0.059 T / mm. In the superconducting bulk body 20D, the magnetic gradient was also increased at the same time near the central portion of the superconducting bulk body having the highest magnetic field strength. Comparing the magnetic gradient in the vicinity of the central portion of the superconducting bulk bodies 20D and 20E, the magnetic field gradient of the superconducting bulk body 20D was improved by about 23% compared to the superconducting bulk body 20E.

  From this result, it has been found that the present invention can provide a superconducting bulk magnet having a magnetic gradient that is also high near the central portion of the superconducting bulk body having the highest magnetic field strength.

Example 3
A single-crystal superconducting bulk material containing 2% by mass of CeO ₂ and 10% by mass of Ag and Eu ₂ BaCuO ₅ finely dispersed in Eu ₁ Ba ₂ Cu ₃ O _y was subjected to mechanical processing shown in FIG. Thus, superconducting bulk bodies 30G, 30H, 30I, and 30J were manufactured. The superconducting bulk body 30G having the reinforcing ring structure of the present invention was formed in a hemispherical shape having a diameter of 20 mm as shown in FIG. 7A (Example G). As the reinforcing body 32G, a hemispherical shape was cut out from an aluminum alloy column, and the superconducting bulk body 30G was bonded and fixed to the reinforcing body 32G with an epoxy resin, and then an aluminum alloy support plate 34G was bolted from the back.

  The superconducting bulk body 30H having another reinforcing body structure of the present invention is also in the shape of a hemisphere having a diameter of 20 mm, but is made of an aluminum alloy as shown in FIG. An annular shape with a flange 36H protruding inward from the surface is formed, and a large gap generated between the annular metal reinforcing ring 32H and the superconducting bulk body 30H is filled with an epoxy resin 32Hb (Example) H). Further, the superconducting bulk body 30I has a hemispherical shape with a diameter of 20 mm as in Examples G and H, and the reinforcing body 32I is made of a ring-shaped metal made of aluminum alloy without a flange as shown in FIG. The reinforcing ring 32Ia and an epoxy resin 32Ib filled with a large gap formed between the annular metal reinforcing ring 32Ia and the superconducting bulk body 30I were used.

  As a comparative example, the superconducting bulk body 30J has a hemispherical shape with a diameter of 20 mm as in Examples G, H, and I, and the reinforcing body 32J is similar to the reinforcing body 32G of the superconducting bulk body 30G. ), A superconducting bulk magnet without a support plate was verified (Comparative Example J).

  These superconducting bulk bodies were cooled to liquid nitrogen 10 times, and then magnetized by a magnetic field cooling method in which cooling was performed in liquid nitrogen in a 2T magnetic field. After the superconducting bulk body is magnetized and cooled, the reinforcing body is fixed with a jig, and then the firmly fixed iron block is slowly brought closer to the magnetic field generating surface of the superconducting bulk body and held at a distance of 1 cm. The experiment was conducted.

  The superconducting bulk body 30J, which is a comparative example, was not provided with a support plate, so that the superconducting bulk body 30J and the reinforcing body 32J were detached when the cooling was repeated five times without bringing the iron block closer. On the other hand, the superconducting bulk bodies 30G and 30H having the configuration of the present invention did not change significantly, although a strong suction force was generated between the superconducting bulk body and the iron block. Also for the superconducting bulk body 30I, the superconducting bulk body 30I was not detached from the support plate 34I only by repeated cooling.

  Here, the superconducting bulk material and the metal have different thermal shrinkage rates (the metal is larger), and therefore compressive stress acts during cooling. In a superconducting bulk magnet composed of a general disk-shaped superconducting bulk body and a metal reinforcing ring, the compressive stress acts evenly from the outer periphery, so it is unlikely that the superconducting bulk magnet will come off. In a superconducting bulk magnet in which the thickness of the superconducting bulk body changes and the thickness becomes zero at the end as in the structure, a part of the compressive stress acts to disengage the superconducting bulk body from the metal reinforcing ring. There is concern. When the iron block was brought close to the superconducting bulk body 30I of Example I, the superconducting bulk body 30I gradually started to deviate from the metal reinforcing ring 32Ia together with the filling resin 32Ib, and finally disengaged from the metal reinforcing ring 32Ia. Was attracted to.

  From this result, it has been clarified that a support plate is necessary for the superconducting bulk magnet having the structure of the present invention to effectively operate the reinforcing body. Further, as the reinforcing body, as in Example G, a reinforcing body formed by hollowing out the shape of the superconducting bulk body from a metal columnar shape such as an aluminum alloy, or inwardly protruding as in Example H It has been found that a reinforcing body made of a ring-shaped aluminum alloy member with a flange and a filling resin is more preferable.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

10A, 10B, 10C, 11, 20D, 20E, 20F, 30G, 30H, 30I, 30J, 110 Superconducting bulk body 22D, 32G, 32I, 32Ib, 32J, 120A, 120B, 120C Reinforcing body 22E, 22Fa, 32H, 32Ia , 122 Metal reinforcement ring 22Fb, 32Hb, 124 Resin 24D, 34G, 130 Support plate 36H, 126 Hook 100A, 100B, 100C Superconducting bulk magnet 112 Magnetic field generation surface

Claims (7)

A superconducting bulk magnet using an oxide superconducting bulk in which RE ₂ BaCuO ₅ is dispersed in single-crystal RE ₁ Ba ₂ Cu ₃ O _7-x ,
The superconducting bulk magnet is characterized in that the shape of the oxide superconducting bulk body is a partial sphere composed of a flat surface portion and a partial spherical surface portion or a conical shape composed of a flat surface portion and a conical surface portion.
However, RE is one or more elements selected from rare earth elements, and the oxygen deficiency (x) is 0.2 or less. A support plate for supporting the planar portion;
A reinforcing body that is disposed so as to surround the partial spherical surface portion or the conical surface portion and is connected to the support plate to reinforce the oxide superconducting bulk body;
The superconducting bulk magnet according to claim 1, further comprising:   3. The superconducting bulk magnet according to claim 2, wherein the reinforcing body is a metallic reinforcing body cut out in the same shape as the partial spherical surface portion or the conical surface portion of the oxide superconducting bulk body. The reinforcing body is
A cylindrical reinforcing ring connected to the support plate;
A resin present in the space between the inner wall of the reinforcing ring and the partial spherical surface portion or the conical surface portion;
The superconducting bulk magnet according to claim 2, comprising:   The columnar reinforcing ring has a flange portion protruding inward from an inner peripheral surface at an end portion opposite to an end portion connected to the support plate. Superconducting bulk magnet. A method for magnetizing a superconducting bulk magnet according to any one of claims 1 to 5,
A direction perpendicular to the plane portion of the oxide superconducting bulk body is cooled in a magnetic field in the direction of the magnetic field, and magnetized so that the partial spherical surface portion or the conical surface portion becomes a magnetic field generating surface. To magnetize a superconducting bulk magnet. A superconducting bulk magnet using an oxide superconducting bulk in which RE ₂ BaCuO ₅ is dispersed in single-crystal RE ₁ Ba ₂ Cu ₃ O _7-x ,
The shape of the oxide superconducting bulk body is that the circular flat portion and the central portion of the flat portion are the thickest, the thickness continuously decreases toward the outer peripheral portion of the flat portion, and becomes zero at the outer peripheral portion. A superconducting bulk magnet characterized by having a shape comprising a three-dimensional part having a shape.
However, RE is one or more elements selected from rare earth elements, and the oxygen deficiency (x) is 0.2 or less.

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