Cold storage material particle, cold storage material particle group, cold storage device, refrigerator, cryopump, superconducting magnet, nuclear magnetic resonance imaging apparatus, nuclear magnetic resonance apparatus, magnetic field application-type single crystal pulling apparatus, and helium re-condensation apparatus

Abstract

A cold storage material particle according to an embodiment of the present invention comprises: a first region that includes at least one first element selected from the group consisting of Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb, and at least one second element selected from the group consisting of Ni, Co, Cu, Ag, Ga, Bi, Si, Al, and Ru; and a second region in which the chemical composition is different from that of the first region, a surface area ratio in a cross section is smaller than that of the first region, the minimum distance to the outer edge of the particle in the cross section is 5 μm or greater, and at least one third element selected from the group consisting of C, O, and N is included.

Description

Cold storage particles, cold storage particle clusters, cold storage units, refrigerators, cryopumps, superconducting magnets, nuclear magnetic resonance imaging devices, nuclear magnetic resonance devices, magnetic field application type single crystal pulling devices, and helium recondensation devices

[0001] Embodiments of the present invention relate to regenerator particles, regenerator particle groups, regenerators, refrigerators, cryopumps, superconducting magnets, nuclear magnetic resonance imaging devices, nuclear magnetic resonance devices, magnetic field application type single crystal pulling devices, and helium recondensation devices.

[0002] In recent years, superconducting technology has made remarkable progress, and as the fields of application of superconducting technology expand, the development of small, high-performance cryogenic refrigerators has become essential. Cryogenic refrigerators are required to be lightweight, small, and highly thermally efficient. Cryogenic refrigerators are being put to practical use in a variety of application fields.

[0003] A cryogenic refrigerator includes a regenerator filled with a plurality of regenerator particles. For example, cold is generated by heat exchange between the regenerator particles and helium gas passing through the regenerator. To prevent the regenerator particles from breaking during operation of the cryogenic refrigerator, the regenerator particles must have high mechanical strength.

[0004] Japanese Patent Application Laid-Open No. 2018-173268

[0005] The problem to be solved by the present invention is to provide regenerator particles having high mechanical strength.

[0006] The regenerator particles of the embodiment are composed of at least one first element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb), and nickel (Ni), cobalt (Co), copper (Cu), silver (Ag), and the like. and a second region having a chemical composition different from that of the first region, a smaller area ratio in a cross section than that of the first region, a minimum distance to the outer edge of the particle in the cross section of 5 μm or more, and containing at least one third element selected from the group consisting of carbon (C), oxygen (O), and nitrogen (N).

[0007] 1. A schematic cross-sectional view of a cold storage material particle of a first embodiment. 2. An enlarged schematic cross-sectional view of a cold storage material particle of the first embodiment. 3. A diagram showing the specific heat and mechanical strength of a cold storage material particle. 4. A schematic cross-sectional view of a cold storage material particle of a second embodiment. 5. An enlarged schematic cross-sectional view of a cold storage material particle of the second embodiment. 6. A schematic cross-sectional view showing the configuration of a main part of a refrigerator of a fourth embodiment. 7. A cross-sectional view showing the schematic configuration of a cryopump of a fifth embodiment. 8. A perspective view showing the schematic configuration of a superconducting magnet of a sixth embodiment. 9. A cross-sectional view showing the schematic configuration of a nuclear magnetic resonance imaging apparatus of a seventh embodiment. 10. A cross-sectional view showing the schematic configuration of a nuclear magnetic resonance apparatus of an eighth embodiment. 11. A perspective view showing the schematic configuration of a magnetic field application type single crystal pulling apparatus of a ninth embodiment. 12. A schematic view showing the schematic configuration of a helium recondensation apparatus of a tenth embodiment.

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same or similar components will be designated by the same reference numerals, and the description of components that have already been described may be omitted as appropriate.

[0009] In this specification, the term "extremely low temperature" refers to a temperature range in which the superconducting phenomenon can be industrially utilized, for example, a temperature range of 25 K or lower.

[0010] (First embodiment) The regenerator particles of the first embodiment contain at least one first element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb), and at least one first element selected from the group consisting of nickel (Ni), cobalt (Co), copper (Cu), and the like. and a second region having a chemical composition different from that of the first region, a smaller area ratio in a cross section than that of the first region, a minimum distance to the outer edge of the particle in a cross section of 5 μm or more, and containing at least one third element selected from the group consisting of carbon (C), oxygen (O), and nitrogen (N).

[0011] Fig. 1 is a schematic cross-sectional view of a cold storage material particle of the first embodiment. Fig. 2 is an enlarged schematic cross-sectional view of a cold storage material particle of the first embodiment. Fig. 2 is an enlarged schematic cross-sectional view of a part of the cross section shown in Fig. 1. The cold storage material particle 100 of the first embodiment is a magnetic cold storage material particle containing a rare earth element and a metal.

[0012] The particle size of the cold storage material particles 100 is, for example, 50 μm or more and 3 mm or less. The shape of the cold storage material particles 100 is, for example, spherical. The shape of the cold storage material particles 100 may be, for example, spindle-shaped or an irregular shape with an uneven surface.

[0013] In this specification, the particle size of the regenerator particles refers to the circle-equivalent diameter. The circle-equivalent diameter is the diameter of a perfect circle corresponding to the area of ​​a figure observed in an image such as an optical microscope image or a scanning electron microscope image. The particle size of the regenerator particles can be determined, for example, by image analysis of the optical microscope image or the scanning electron microscope image.

[0014] When the perimeter of the projected image of the regenerator particle 100 is L and the actual area of ​​the projected image is A, 4πA / L ２The circularity R expressed by the following formula is, for example, greater than 0.5. The circularity R of the regenerator particle 100 can be determined by, for example, image analysis of an optical microscope image or a scanning electron microscope image.

[0015] The aspect ratio of the cold storage material particle 100 is, for example, not less than 1 and not more than 5. The aspect ratio of the cold storage material particle 100 is the ratio of the major axis to the minor axis of the cold storage material particle 100. The aspect ratio of the cold storage material particle 100 can be determined, for example, by image analysis of an optical microscope image or a scanning electron microscope image.

[0016] The maximum value of the volumetric specific heat of the regenerator particles 100 in the temperature range of 25 K or less is, for example, 0.38 J / (cm ３ ・K) or above.

[0017] The cold storage material particle 100 of the first embodiment includes a first region 10a and a second region 10b. The cold storage material particle 100 of the first embodiment includes, for example, a plurality of second regions 10b.

[0018] The first region 10a includes at least one first element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb), and at least one second element selected from the group consisting of nickel (Ni), cobalt (Co), copper (Cu), silver (Ag), gallium (Ga), bismuth (Bi), silicon (Si), aluminum (Al), and ruthenium (Ru).

[0019] The first element is a rare earth element. The second element is a metal element. The first region 10a includes, for example, a compound of a rare earth element and a metal element. The first region 10a is, for example, composed of a compound of a rare earth element and a metal element.

[0020] The chemical composition of the compound contained in the first region 10 a can be expressed, for example, as RMx (R is at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb); M is at least one metal element selected from the group consisting of nickel (Ni), cobalt (Co), copper (Cu), silver (Ag), gallium (Ga), bismuth (Bi), silicon (Si), aluminum (Al), and ruthenium (Ru); and x is 1 or more and 13 or less).

[0021] The first region 10a includes, for example, holmium (Ho) and nickel (Ni). The first region 10a includes, for example, a compound of holmium (Ho) and nickel (Ni). The first region 10a includes, for example, HoNi ２ Or HoNi.

[0022] The first region 10a includes, for example, holmium (Ho) and copper (Cu). The first region 10a includes, for example, a compound of holmium (Ho) and copper (Cu). The first region 10a includes, for example, HoCu ２ Or HoCu.

[0023] The first region 10a includes, for example, erbium (Er) and nickel (Ni). The first region 10a includes, for example, a compound of erbium (Er) and nickel (Ni). The first region 10a includes, for example, Er ３ Contains Ni or ErNi.

[0024] The first region 10a includes, for example, erbium (Er) and cobalt (Co). The first region 10a includes, for example, a compound of erbium (Er) and cobalt (Co). The first region 10a includes, for example, Er ３ Contains Co.

[0025] The second region 10b has a chemical composition different from that of the first region 10a and includes at least one third element selected from the group consisting of carbon (C), oxygen (O), and nitrogen (N).

[0026] The third element contained in the second region 10b is, for example, carbon (C) and oxygen (O).

[0027] The first region 10a may or may not contain a third element. When the first region 10a contains a third element, the atomic concentration of the third element contained in the second region 10b is higher than the atomic concentration of the third element contained in the first region 10a. The atomic concentration of the third element contained in the second region 10b is higher than the atomic concentration of the third element contained in the first region 10a, for example, by 10 atomic % or more. The difference between the atomic concentration of the third element contained in the second region 10b and the atomic concentration of the third element contained in the first region 10a is, for example, 10 atomic % or more and 50 atomic % or less.

[0028] The second region 10b may contain, for example, the same first element and the same second element as those contained in the first region 10a. For example, if the first region 10a contains holmium (Ho) and nickel (Ni), the second region 10b may also contain holmium (Ho) and nickel (Ni). For example, if the first region 10a contains holmium (Ho) and copper (Cu), the second region 10b may also contain holmium (Ho) and copper (Cu). For example, if the first region 10a contains erbium (Er) and nickel (Ni), the second region 10b may also contain erbium (Er) and nickel (Ni). For example, if the first region 10a contains erbium (Er) and cobalt (Co), the second region 10b may also contain erbium (Er) and cobalt (Co).

[0029] The elements contained in the first region 10a or the second region 10b and the atomic concentrations of the elements can be determined by, for example, energy dispersive X-ray spectroscopy (EDX).

[0030] The compounds contained in the regenerator particles 100 can be identified by powder X-ray diffraction (PXRD).

[0031] The first region 10a is, for example, a main phase that has a dominant effect on the specific heat characteristics of the regenerator particle 100. The second region 10b is, for example, a subphase of the regenerator particle 100.

[0032] The first region 10a is, for example, a matrix of the regenerator material particle 100. The second region 10b is, for example, a precipitate formed when the regenerator material particle 100 is manufactured.

[0033] 1, the plurality of second regions 10b are dispersed within the regenerator particle 100. Each of the second regions 10b is surrounded by the first region 10a, for example.

[0034] 2, for example, the first region 10a is polycrystalline. The first region 10a includes a plurality of crystal grains. The second region 10b exists, for example, at the grain boundary of the first region 10a. Also, the second region 10b exists, for example, within the crystal grains of the first region 10a.

[0035] In the cross section of the heat storage material particle 100, the minimum distance (d in FIG. 1) of the second region 10b to the outer edge of the heat storage material particle 100 is, for example, 5 μm or more. The minimum distance (d in FIG. 1) to the outer edge of at least one second region 10b among the plurality of second regions 10b is, for example, 5 μm or more.

[0036] The second region 10b is also present, for example, in the center of the cold storage material particle 100. The minimum distance (d in FIG. 1 ) to the outer edge of at least one of the plurality of second regions 10b is, for example, one-fourth or more of the particle diameter of the cold storage material particle 100.

[0037] The area ratio of the second region 10b in the cross section of the cold storage material particle 100 is smaller than the area ratio of the first region 10a in the cross section of the cold storage material particle 100. The area ratio of the second region in the cross section of the cold storage material particle 100 is, for example, 0.01% or more and 15% or less.

[0038] The area ratio of the first region 10a and the area ratio of the second region 10b can be determined, for example, by observing a backscattered electron image of a cross section of the regenerator particle 100 with a scanning electron microscope (SEM). For example, the area occupied by a region identified as the first region 10a or the second region 10b in the backscattered electron image is measured using image processing software. Whether a region is the first region 10a or the second region 10b can be determined, for example, by energy dispersive X-ray spectroscopy.

[0039] When the first region 10a is polycrystalline, the average length of the crystal grains in the first region 10a is, for example, greater than or equal to 5 times and less than or equal to 100 times the average length of the crystal grains in the second region 10b.

[0040] The major axis of the crystal grains in the first region 10a and the major axis of the crystal grains in the second region 10b can be measured by observing the cross section of the regenerator particle 100 with a transmission electron microscope (TEM), for example.

[0041] Next, an example of a method for manufacturing the cold storage material particles 100 of the first embodiment will be described. Hereinafter, an example will be described in which the first element is holmium (Ho), the second element is nickel (Ni), and the third element is carbon (C). The cold storage material particles 100 of the first embodiment are manufactured by a rotating disk process (RDP process).

[0042] First, HoNi ２ Alloys and nickel carbides, Ni ３ Prepare C. Next, Ni ３ C-added HoNi ２ The alloy is melted and dropped onto a rotating disk in an argon atmosphere, where it is rapidly cooled and solidified. The molten alloy is then rapidly cooled and solidified to produce regenerator particles.

[0043] HoNi ２ Ni in alloy ３ By adding C, HoNi ２The regenerator particles 100 are produced, each having a first region 10a containing ZnO (C) and a second region 10b containing carbon (C).

[0044] For example, when producing the cold storage material particle 100 having the second region 10b containing oxygen (O), HoNi ２ NiO, an oxide of nickel, can be added to the alloy. ２ Ni in alloy ３ By adding C and NiO, it is possible to make the second region 10b contain carbon (C) and oxygen (O).

[0045] In addition, for example, when producing the cold storage material particle 100 having the second region 10b containing nitrogen (N), HoNi ２ The alloy contains nickel nitride, Ni ３ N should be added.

[0046] In addition, when forming the first region 10a containing HoNi, HoNi ２ Instead of the alloy, a HoNi alloy may be used.

[0047] By the above-described manufacturing method, the cold storage material particles 100 of the first embodiment can be manufactured.

[0048] A cryogenic refrigerator includes a regenerator filled with a plurality of regenerator particles. For example, cold is generated by heat exchange between the regenerator particles and helium gas passing through the regenerator. To prevent the regenerator particles from breaking during operation of the cryogenic refrigerator, the regenerator particles must have high mechanical strength.

[0049] The cold storage material particle 100 of the first embodiment includes the second region 10b, and thus can achieve higher mechanical strength than, for example, cold storage material particles that do not include the second region 10b.

[0050] 3 is a diagram showing the specific heat and mechanical strength of the cold storage material particle. The horizontal axis represents the area ratio of the second region 10b in the cross section of the cold storage material particle, the left vertical axis represents the maximum volumetric specific heat of the cold storage material particle, and the right vertical axis represents the mechanical strength of the cold storage material particle. The mechanical strength of the cold storage material particle is shown as a ratio based on the mechanical strength of the cold storage material particle excluding the second region 10b. In FIG. 3, black triangles represent specific heat, and white circles represent mechanical strength.

[0051] The volumetric specific heat of the regenerator particles can be measured using, for example, a Physical Property Measurement System (PPMS), and the mechanical strength of the regenerator particles can be measured using, for example, a micro-compression tester.

[0052] The first region 10a of the regenerator particle in FIG. ２ The second region 10b contains carbon (O) and oxygen (O). The regenerator particles in Fig. 3 exhibit a maximum volumetric specific heat in a temperature range of, for example, 10 K or higher and 15 K or lower. For reference, the specific heat of lead (Pb) is shown in Fig. 3 by a dashed line.

[0053] 3, as the area ratio of the second region 10b of the cold storage material particle increases, the mechanical strength of the cold storage material particle increases, while the specific heat of the cold storage material particle decreases as the area ratio of the second region 10b of the cold storage material particle increases.

[0054] The area ratio of the second region 10b in the cross section of the cold storage material particle 100 is preferably 0.01% or more and 15% or less, and more preferably 0.1% or more and 1% or less. By satisfying the above lower limit, the mechanical strength of the cold storage material particle 100 is further improved. Furthermore, by satisfying the above upper limit, a decrease in the specific heat of the cold storage material particle 100 can be suppressed.

[0055] For example, by setting the area ratio of the second region 10b to 15% or less, the specific heat of the second region 10b can be greater than that of lead, which is a regenerator material, and can be used as a replacement for lead, which is a regenerator material that is of concern for its environmental impact.

[0056] From the viewpoint of increasing the mechanical strength of the regenerator particle 100, the atomic concentration of the third element contained in the second region 10b is preferably 10 atomic % or more of the atomic concentration of the third element contained in the first region 10a, and more preferably 20 atomic % or more.

[0057] In the cross section of the cold storage material particle 100, the minimum distance (d in FIG. 1) of the second region 10b to the outer edge of the cold storage material particle 100 is 5 μm or more, more preferably 3 μm or more, and even more preferably 2 μm or more. The presence of the second region 10b up to near the outer edge means that the second region 10b is present throughout the cold storage material particle 100. This further improves the mechanical strength of the cold storage material particle 100. The minimum distance (d in FIG. 1) to the outer edge of at least one second region 10b among the multiple second regions 10b is, for example, 5 μm or more, more preferably 3 μm or more, and even more preferably 2 μm or more. The presence of the second region 10b inside the cold storage material particle 100 improves the mechanical strength of the cold storage material particle 100. From the viewpoint of improving the mechanical strength of the cold storage material particle 100, it is preferable that there is a second region 10b in the cross section of the cold storage material particle 100 whose distance to the outer edge of the cold storage material particle 100 is greater than 5 μm, it is more preferable that there is a second region 10b whose distance to the outer edge of the cold storage material particle 100 is 10 μm or more, and it is even more preferable that there is a second region 10b whose distance to the outer edge of the cold storage material particle 100 is 20 μm or more.

[0058] The maximum value of the volumetric specific heat of the regenerator particles 100 in the temperature range of 25 K or less is 0.3 J / (cm ３ ·K) or more, and 0.38 J / (cm ３ ·K) or more, and more preferably 0.4 J / (cm ３ It is more preferable that the value is equal to or greater than K.

[0059] From the viewpoint of suppressing breakage of the cold storage material particles, the cold storage material particles are preferably spherical. In other words, it is preferable that the circularity R of the cold storage material particles 100 is large, and the circularity R is preferably close to 1. The circularity R of the cold storage material particles 100 is preferably larger than 0.5, more preferably 0.7 or more, and even more preferably 0.9 or more.

[0060] A plurality of the cold storage material particles 100 of the first embodiment can be collected to form a cold storage material particle group. For example, a cold storage material particle group containing 90% or more of the cold storage material particles 100 of the first embodiment in terms of number can be formed.

[0061] As described above, according to the first embodiment, it is possible to provide regenerator particles having high mechanical strength.

[0062] (Second embodiment) The cold storage material of the second embodiment differs from the cold storage material particle of the first embodiment in that it further includes a third region having a different chemical composition from the first region and the second region, a smaller area ratio in the cross section than the first region, and containing the same first element and second element as the first region. Hereinafter, some description of the content that overlaps with the first embodiment may be omitted.

[0063] Fig. 4 is a schematic cross-sectional view of a cold storage material particle of the second embodiment. Fig. 5 is an enlarged schematic cross-sectional view of a cold storage material particle of the second embodiment. Fig. 5 is an enlarged schematic cross-sectional view of a part of the cross section shown in Fig. 4. The cold storage material particle 200 of the second embodiment is a magnetic cold storage material particle containing a rare earth element and a metal.

[0064] The cold storage material particle 200 of the second embodiment includes a first region 10 a, a second region 10 b, and a third region 10 c. The cold storage material particle 200 of the second embodiment includes, for example, a plurality of second regions 10 b and a plurality of third regions 10 c.

[0065] The third region 10c has a different chemical composition from the first region 10a and the second region 10b, and contains the same first element as the first region 10a and the same second element as the first region 10a.

[0066] For example, if the first region 10a includes a first compound containing a first element and a second element, the third region 10c includes a second compound containing the same first element and the same second element but having a different chemical composition from the first compound. For example, if the first region 10a is composed of a first compound of a first element and a second element, the third region 10c is composed of a second compound containing the same first element and the same second element but having a different chemical composition from the first compound.

[0067] For example, if the first region 10a contains holmium (Ho) and nickel (Ni), the third region 10c also contains holmium (Ho) and nickel (Ni). For example, if the first region 10a contains a compound of holmium (Ho) and nickel (Ni), the third region 10c also contains a compound of holmium (Ho) and nickel (Ni).

[0068] For example, if the first region 10a is HoNi ２ For example, when the first region 10a contains HoNi, the third region 10c contains HoNi. ２ When the third region 10c is made of HoNi, the third region 10c is made of HoNi.

[0069] For example, if the first region 10a contains HoNi, the third region 10c contains HoNi. ２ For example, if the first region 10a is made of HoNi, the third region 10c is made of HoNi. ２ It consists of:

[0070] For example, if the first region 10a contains holmium (Ho) and copper (Cu), the third region 10c also contains holmium (Ho) and copper (Cu). For example, if the first region 10a contains a compound of holmium (Ho) and copper (Cu), the third region 10c also contains a compound of holmium (Ho) and copper (Cu).

[0071] For example, if the first region 10a is HoCu ２ For example, when the first region 10a contains HoCu, the third region 10c contains HoCu. ２ When the third region 10c is made of HoCu, the third region 10c is made of HoCu.

[0072] For example, if the first region 10a contains HoCu, the third region 10c contains HoCu. ２ For example, if the first region 10a is made of HoCu, the third region 10c is made of HoCu. ２ It consists of:

[0073] For example, if the first region 10a contains erbium (Er) and nickel (Ni), the third region 10c also contains erbium (Er) and nickel (Ni). For example, if the first region 10a contains a compound of erbium (Er) and nickel (Ni), the third region 10c also contains a compound of erbium (Er) and nickel (Ni).

[0074] For example, if the first region 10a is Er ３ For example, when the first region 10a contains Er, the third region 10c contains ErNi. ３ When made of Ni, the third region 10c is made of ErNi.

[0075] For example, if the first region 10a contains ErNi, the third region 10c contains ErNi. ３ For example, if the first region 10a is made of ErNi, the third region 10c may contain Er. ３ It is composed of Ni.

[0076] The third region 10c may or may not contain a third element. The atomic concentration of the third element contained in the second region 10b is higher than the atomic concentration of the third element contained in the third region 10c. The atomic concentration of the third element contained in the second region 10b is higher than the atomic concentration of the third element contained in the third region 10c by, for example, 10 atomic % or more. The difference between the atomic concentration of the third element contained in the second region 10b and the atomic concentration of the third element contained in the third region 10c is, for example, 10 atomic % or more and 50 atomic % or less.

[0077] The first region 10a is, for example, a main phase that has a dominant effect on the specific heat characteristics of the regenerator particle 100. The second region 10b and the third region 10c are, for example, subphases that do not have a dominant effect on the specific heat characteristics of the regenerator particle 100.

[0078] The first region 10a is, for example, a matrix of the cold storage material particle 100. The second region 10b is, for example, a precipitate formed during the manufacturing of the cold storage material particle 100. The third region 10c is, for example, a crystalline phase formed during the manufacturing of the cold storage material particle 100.

[0079] 4, the plurality of second regions 10b and the plurality of third regions 10c are dispersed, for example, inside the cold storage material particle 100. Each of the plurality of second regions 10b and each of the plurality of third regions 10c are, for example, surrounded by the first region 10a.

[0080] As shown in FIG. 5 , for example, the first region 10a is polycrystalline. The first region 10a includes a plurality of crystal grains. The second region 10b exists, for example, at the grain boundary of the first region 10a. The second region 10b also exists, for example, within the crystal grains of the first region 10a. The third region 10c also exists, for example, at the grain boundary of the first region 10a. The third region 10c also exists, for example, within the crystal grains of the first region 10a.

[0081] The area ratio of the third region 10c in the cross section of the cold storage material particle 100 is smaller than the area ratio of the first region 10a in the cross section of the cold storage material particle 100. The area ratio of the third region in the cross section of the cold storage material particle 100 is, for example, 0.01% or more and 30% or less.

[0082] When the first region 10a is polycrystalline, the average length of the crystal grains in the first region 10a is greater than the average length of the crystal grains in the third region 10c, for example.

[0083] As described above, according to the second embodiment, it is possible to provide regenerator particles having high mechanical strength.

[0084] (Third embodiment) The regenerator of the third embodiment is a regenerator filled with a plurality of regenerator particles of the first or second embodiment. For example, when the perimeter of the projected image of the regenerator particles of the first or second embodiment is L and the actual area of ​​the projected image is A, the regenerator of the third embodiment has a surface area of ​​4πA / L. ２The ratio of the cold storage material particles having a circularity R of 0.5 or less is 5% or less.

[0085] The circularity R can be determined by image processing of the shapes of a plurality of cold storage material particles in an image obtained using an optical microscope. Cold storage material particles having a circularity R of 0.5 or less have, for example, irregularities on the surface.

[0086] For example, if the regenerator is filled with a plurality of regenerator particles containing more than 5% of the regenerator particles with uneven surfaces, the porosity in the regenerator may become uneven or the regenerator may become unstable, which may result in a decrease in the regenerator's regenerative capacity when the working medium flows in.

[0087] Furthermore, for example, if a plurality of cold storage material particles containing more than 5% of the cold storage material particles have uneven surfaces are filled into a cold storage unit, the cold storage material particles will be destroyed by the stress applied to the cold storage material particles during operation of the refrigerator. When the cold storage material particles are destroyed, fine particles are generated. The generated fine particles may clog, for example, voids inside the cold storage unit. When the voids inside the cold storage unit are clogged, the refrigeration performance and long-term reliability of the refrigerator will be reduced.

[0088] Therefore, the amount of cold storage material particles with a circularity R of 0.5 or less packed in the cold storage unit is preferably 2% or less, and more preferably 0%.

[0089] As described above, according to the third embodiment, by using regenerator particles with excellent properties, a regenerator with excellent properties can be realized.

[0090] (Fourth embodiment) A refrigerator of the fourth embodiment is a refrigerator including the regenerator of the third embodiment filled with a plurality of regenerator particles of the first or second embodiment. Hereinafter, some of the description overlapping with the first, second, or third embodiment will be omitted.

[0091] Fig. 6 is a schematic cross-sectional view showing the configuration of a main part of a refrigerator according to a fourth embodiment. Fig. 6 is a schematic cross-sectional view showing the configuration of a main part of a GM refrigerator, which is an example of a refrigerator according to the fourth embodiment. The GM refrigerator, which is an example of a refrigerator according to the fourth embodiment, includes the regenerator according to the third embodiment, which is filled with a plurality of regenerator particles according to the first or second embodiment.

[0092] The refrigerator of the fourth embodiment is a two-stage regenerative cryogenic refrigerator 300 used to cool superconducting equipment, etc. The refrigerator may be, for example, a Stirling type refrigerator or a pulse tube type refrigerator.

[0093] The regenerative type cryogenic refrigerator 300 (refrigerator) includes a first cylinder 111, a second cylinder 112, a vacuum container 113, a first regenerator 114, a second regenerator 115 (regenerators), a first seal ring 116, a second seal ring 117, a first regenerator material 118, a second regenerator material 119 (regenerator particles), a first expansion chamber 120, a second expansion chamber 121, a first cooling stage 122, a second cooling stage 123, and a compressor 124.

[0094] The regenerative cryogenic refrigerator 300 includes a vacuum vessel 113 provided with a large-diameter first cylinder 111 and a small-diameter second cylinder 112 coaxially connected to the first cylinder 111. A first regenerator 114 is arranged in the first cylinder 111 so as to be able to move back and forth. A second regenerator 115, which is an example of a regenerator, is arranged in the second cylinder 112 so as to be able to move back and forth.

[0095] A first seal ring 116 is disposed between the first cylinder 111 and the first regenerator 114. A second seal ring 117 is disposed between the second cylinder 112 and the second regenerator 115.

[0096] The first regenerator 114 is filled with a first regenerator material 118 such as a Cu mesh. The second regenerator 115 is filled with a plurality of regenerator particles according to the first or second embodiment as a second regenerator material 119.

[0097] The second regenerator 115 may be divided by a metal mesh material and may have a plurality of regenerator material filled layers. When the second regenerator 115 is divided into a plurality of filled layers, at least one filled layer is filled with a regenerator material particle group consisting of a plurality of the regenerator material particles of the first or second embodiment. The regenerator material particle group is then combined with at least one type of regenerator material particle group selected from, for example, rare earth oxide regenerator material particle group, rare earth oxysulfide regenerator material particle group, lead regenerator material particle group, bismuth regenerator material particle group, tin regenerator material particle group, holmium nickel regenerator material particle group, holmium copper regenerator material particle group, erbium nickel regenerator material particle group, erbium cobalt regenerator material particle group, and gadolinium aluminum oxide regenerator material particle group.

[0098] The combination of the regenerator particles is such that the particle group with the higher peak specific heat temperature is the first regenerator particle group, and the particle group with the lower peak specific heat temperature is the second regenerator particle group, and the combinations are made so that the peak specific heat temperatures decrease sequentially.

[0099] The first regenerator 114 and the second regenerator 115 each have a passage for the working medium provided in the gap of the first regenerator material 118 or the second regenerator material 119. The working medium is helium gas.

[0100] A first expansion chamber 120 is provided between the first regenerator 114 and the second regenerator 115. A second expansion chamber 121 is provided between the second regenerator 115 and the tip wall of the second cylinder 112. A first cooling stage 122 is provided at the bottom of the first expansion chamber 120. A second cooling stage 123, which has a lower temperature than the first cooling stage 122, is formed at the bottom of the second expansion chamber 121.

[0101] The two-stage regenerative cryogenic refrigerator 300 described above is supplied with a high-pressure working medium from the compressor 124. The supplied working medium passes through the first regenerator material 118 filled in the first regenerator 114 and reaches the first expansion chamber 120. Then, it passes through the second regenerator material 119 filled in the second regenerator 115 and reaches the second expansion chamber 121.

[0102] At this time, the working medium is cooled by supplying thermal energy to the first and second cold storage materials 118 and 119. The working medium passing between the first and second cold storage materials 118 and 119 expands in the first and second expansion chambers 120 and 121 to generate cold. As a result, the first and second cooling stages 122 and 123 are cooled.

[0103] The expanded working medium flows in the opposite direction between the first and second regenerator materials 118 and 119. The working medium is discharged after receiving thermal energy from the first and second regenerator materials 118 and 119. The regenerative cryogenic refrigerator 300 is configured to improve the thermal efficiency of the working medium cycle as the heat recovery effect improves during this process, thereby achieving even lower temperatures.

[0104] The regenerator included in the regenerative cryogenic refrigerator 300 of the fourth embodiment has a second regenerator 115 filled with a plurality of regenerator particles of the first or second embodiment as a second regenerator material 119. At least a part of the second regenerator material 119 is the regenerator particle of the first or second embodiment.

[0105] In the first or second embodiment, when the perimeter of each projected image of the plurality of cold storage particles is L and the actual area of ​​the projected image is A, the ratio of the perimeter to the actual area of ​​the projected image is 4πA / L. ２ It is preferable that the amount of the cold storage material particles having a circularity R of 0.5 or less, expressed by the following formula, is 5% or less.

[0106] For example, by using the regenerative cryogenic refrigerator 300 of the fourth embodiment in a magnetic levitation train, the long-term reliability of the magnetic levitation train can be improved.

[0107] As described above, according to the fourth embodiment, by using regenerator particles with excellent characteristics, a refrigerator with excellent characteristics can be realized.

[0108] Fifth Embodiment A cryopump according to a fifth embodiment includes the refrigerator according to the fourth embodiment. Hereinafter, some of the description overlapping with the fourth embodiment will be omitted.

[0109] 7 is a cross-sectional view showing a schematic configuration of a cryopump according to the fifth embodiment. The cryopump according to the fifth embodiment is a cryopump 500 including the regenerative cryogenic refrigerator 300 according to the fourth embodiment.

[0110] The cryopump 500 includes a cryopanel 501 that condenses or adsorbs gas molecules, a regenerative cryogenic refrigerator 300 that cools the cryopanel 501 to a predetermined cryogenic temperature, a shield 503 installed between the cryopanel 501 and the regenerative cryogenic refrigerator 300, a baffle 504 installed at the intake port, and a ring 505 that changes the pumping speed of argon, nitrogen, hydrogen, etc.

[0111] According to the fifth embodiment, a cryopump with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0112] Sixth Embodiment A superconducting magnet according to a sixth embodiment includes the refrigerator according to the fourth embodiment. Hereinafter, some of the description overlapping with the fourth embodiment will be omitted.

[0113] 8 is a perspective view showing a schematic configuration of a superconducting magnet according to the sixth embodiment. The superconducting magnet according to the sixth embodiment is a superconducting magnet 600 for a magnetically levitated train, which is equipped with the regenerative cryogenic refrigerator 300 according to the fourth embodiment.

[0114] The superconducting magnet 600 for a magnetic levitation train includes a superconducting coil 601, a liquid helium tank 602 for cooling the superconducting coil 601, a liquid nitrogen tank 603 for preventing the evaporation of the liquid helium, a laminated heat insulating material 605, a power lead 606, a persistent current switch 607, and a regenerative cryogenic refrigerator 300.

[0115] According to the sixth embodiment, a superconducting magnet with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0116] Seventh Embodiment A nuclear magnetic resonance imaging apparatus according to a seventh embodiment includes the refrigerator according to the fourth embodiment. Hereinafter, some of the description overlapping with the fourth embodiment will be omitted.

[0117] 9 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance imaging apparatus according to the seventh embodiment. The nuclear magnetic resonance imaging (MRI) apparatus according to the seventh embodiment is a nuclear magnetic resonance imaging apparatus 700 equipped with the regenerative cryogenic refrigerator 300 according to the fourth embodiment.

[0118] The nuclear magnetic resonance imaging apparatus 700 includes a superconducting static magnetic field coil 701 that applies a spatially uniform and temporally stable static magnetic field to the human body, a correction coil (not shown) that corrects non-uniformity of the generated magnetic field, a gradient magnetic field coil 702 that applies a magnetic field gradient to the measurement region, a radio frequency wave transmitting / receiving probe 703, a cryostat 705, and a radiation heat insulating shield 706. A regenerative cryogenic refrigerator 300 is used to cool the superconducting static magnetic field coil 701.

[0119] According to the seventh embodiment, a nuclear magnetic resonance imaging apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0120] Eighth Embodiment A nuclear magnetic resonance apparatus according to an eighth embodiment includes the refrigerator according to the fourth embodiment. Hereinafter, some of the description overlapping with the fourth embodiment will be omitted.

[0121] 10 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance (NMR) apparatus according to an eighth embodiment. The nuclear magnetic resonance (NMR) apparatus according to the eighth embodiment is a nuclear magnetic resonance apparatus 800 equipped with the regenerative cryogenic refrigerator 300 according to the fourth embodiment.

[0122] The nuclear magnetic resonance apparatus 800 includes a superconducting static magnetic field coil 802 that applies a magnetic field to a sample such as an organic substance placed in a sample tube 801, a high-frequency oscillator 803 that applies radio waves to the sample tube 801 in the magnetic field, and an amplifier 804 that amplifies an induced current generated in a coil (not shown) around the sample tube 801. The apparatus also includes a regenerative cryogenic refrigerator 300 that cools the superconducting static magnetic field coil 802.

[0123] According to the eighth embodiment, a nuclear magnetic resonance apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0124] Ninth Embodiment A magnetic field application type single crystal pulling apparatus according to a ninth embodiment includes the refrigerator according to the fourth embodiment. Hereinafter, some of the description overlapping with the fourth embodiment will be omitted.

[0125] 11 is a perspective view showing a schematic configuration of a magnetic field application type single crystal pulling apparatus according to the ninth embodiment, which is a magnetic field application type single crystal pulling apparatus 900 equipped with the regenerative cryogenic refrigerator 300 according to the fourth embodiment.

[0126] The magnetic field application type single crystal pulling apparatus 900 includes a single crystal pulling section 901 having a crucible for melting raw material, a heater, a single crystal pulling mechanism, etc., a superconducting coil 902 that applies a static magnetic field to the raw material melt, a lifting mechanism 903 for the single crystal pulling section 901, a current lead 905, a heat shield plate 906, and a helium container 907. A regenerative cryogenic refrigerator 300 is used to cool the superconducting coil 902.

[0127] According to the ninth embodiment, a magnetic field application type single crystal pulling apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0128] Tenth Embodiment A helium recondensing device according to a tenth embodiment includes the refrigerator according to the fourth embodiment. Hereinafter, some of the description overlapping with the fourth embodiment will be omitted.

[0129] 12 is a schematic diagram showing the general configuration of a helium recondensation apparatus according to a tenth embodiment. The helium recondensation apparatus according to the tenth embodiment is a helium recondensation apparatus 1000 including the regenerative cryogenic refrigerator 300 according to the fourth embodiment.

[0130] The helium recondensation device 1000 includes a regenerative cryogenic refrigerator 300 , an evaporation pipe 1001 , and a liquefaction pipe 1002 .

[0131] The helium recondensing device 1000 can recondense helium gas evaporated from a liquid helium device into liquid helium, such as a superconducting magnet, a nuclear magnetic resonance (NMR) device, a nuclear magnetic resonance imaging (MRI) device, a physical property measurement system (PPMS), or a magnetic property measurement system.

[0132] Helium gas is introduced into the helium recondenser 1000 from a liquid helium device (not shown) through evaporation piping 1001. The helium gas is cooled to 4 K, which is below the liquefaction temperature of helium, by the regenerative cryogenic refrigerator 300. The condensed and liquefied liquid helium returns to the liquid helium device through liquefaction piping 1002.

[0133] According to the tenth embodiment, a refrigerator with excellent characteristics is used, thereby realizing a helium recondensing device with excellent characteristics.

[0134] Examples of the embodiment, comparative examples, and their evaluation results will be described below.

[0135] (Example 1) HoNi ２ Alloys and nickel carbides, Ni ３ Next, Ni ３ C-added HoNi ２ The alloy was melted at about 1500° C. The molten alloy was then dropped onto a rotating disk in an argon atmosphere at a pressure of about 101 kPa, where it was rapidly cooled and solidified, thereby producing the regenerator particles of Example 1.

[0136] In the regenerator particles of Example 1, the first element is holmium (Ho), the second element is nickel (Ni), and the third element is carbon (C).

[0137] The cross section of the produced cold accumulator particle was observed using a scanning electron microscope for backscattered electron images. First and second regions with different chemical compositions were observed. The second regions were dispersed inside the cold accumulator particle. The minimum distance from the second region to the outer edge of the cold accumulator particle was 5 μm or more.

[0138] The elements and element concentrations contained in the first and second regions were measured by energy dispersive X-ray spectroscopy.

[0139] The area ratios of the first and second regions were measured from backscattered electron images taken with a scanning electron microscope using image processing software ImageJ.

[0140] The produced regenerator particles were measured by powder X-ray diffraction to identify the crystalline phase of the first region.

[0141] The mechanical strength of the produced regenerator particles was measured using a micro-compression tester.

[0142] The maximum volumetric specific heat of the produced regenerator particles was measured at 25 K or less using a physical property measurement system (PPMS).

[0143] The results of the above measurements are shown in Table 1. In Table 1, the column for chemical composition of the first region shows the chemical composition of the crystalline phase whose presence was confirmed. In Table 1, the column for chemical composition of the second region shows the elements whose presence was confirmed.

[0144] Table 1 also shows the difference in atomic concentration of the third element between the first region and the second region, which is the value obtained by subtracting the atomic concentration of the third element in the first region from the atomic concentration of the third element in the second region.

[0145] In Table 1, the ratio of mechanical strength is based on the mechanical strength of regenerator particles having the same chemical composition as the first region and not including the third region.

[0146] (Examples 2 to 6) HoNi ２ Ni added to the alloy ３ The cold storage material particles were produced in the same manner as in Example 1 except that the amount of C was changed. The same measurements as in Example 1 were carried out. The results are shown in Table 1.

[0147] (Example 7) HoNi ２ The alloy contains Ni ３ The regenerator particles were produced in the same manner as in Example 1, except that NiO, an oxide of nickel, was added instead of C. The same measurements as in Example 1 were carried out. The results are shown in Table 1.

[0148] (Example 8) HoNi ２ The alloy contains Ni ３ Except for adding C and NiO, the cold storage material particles were produced in the same manner as in Example 1. The same measurements as in Example 1 were carried out. The results are shown in Table 1.

[0149] (Example 9) HoNi２ The alloy contains Ni ３ Instead of C, nickel nitride Ni ３ Except for adding N, the cold storage material particles were produced in the same manner as in Example 1. The same measurements as in Example 1 were carried out. The results are shown in Table 1.

[0150] (Example 10) HoNi ２ Except for using a HoNi alloy instead of the alloy, regenerator particles were produced in the same manner as in Example 1. The same measurements as in Example 1 were carried out. The results are shown in Table 1.

[0151] (Example 11) HoNi ２ Except for adding a HoNi alloy to the alloy, regenerator particles were produced in the same manner as in Example 1. The same measurements as in Example 1 were carried out. The results are shown in Table 1.

[0152] (Example 12) HoNi ２ Instead of alloy, HoCu ２ Except for using the alloy, the regenerator particles were produced in the same manner as in Example 1. The same measurements as in Example 1 were carried out. The results are shown in Table 1.

[0153] (Example 13) HoNi ２ Instead of alloy, Er ３ Except for using a Ni alloy, regenerator particles were produced in the same manner as in Example 1. Measurements were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0154] (Comparative Example 1) HoNi ２ Ni in alloy ３ Except for not adding C, the cold storage material particles were produced in the same manner as in Example 1. The same measurements as in Example 1 were carried out. The results are shown in Table 1.

[0155] (Comparative Example 2) Ho ２ Ni alloy with Ni ３ Except for not adding C, the cold storage material particles were produced in the same manner as in Example 10. The same measurements as in Example 1 were carried out. The results are shown in Table 1.

[0156] (Comparative Example 3) HoCu ２ Ni in alloy ３Except for not adding C, the cold storage material particles were produced in the same manner as in Example 12. The same measurements as in Example 1 were carried out. The results are shown in Table 1.

[0157] (Comparative Example 3) Er ３ Ni alloy with Ni ３ Except for not adding C, the cold storage material particles were produced in the same manner as in Example 13. The same measurements as in Example 1 were carried out. The results are shown in Table 1.

[0158]

[0159] As is clear from Table 1, HoNi ２ By providing the second region, the cold storage material particles have improved mechanical strength compared to particles without the second region. Example 3 and Comparative Example 1 show that the strength improves when the area ratio of the second region is 0.01% or more. Example 3 and Comparative Example 4 show that the strength improves further when the area ratio of the second region is 0.1% or more. This is thought to be because the second region contains 10 atomic % or more of atoms of the third element compared to the first region, which improves the strength of the particle itself.

[0160] Furthermore, from Examples 1, 5, and 6, it can be seen that the specific heat decreases when the area ratio of the second region exceeds 1%, and further decreases when it exceeds 15%. From the above, it can be seen that the area ratio of the second region is preferably 0.01% to 15%, and more preferably 0.1% to 1%. The presence of the second region improves strength, but since the second region does not contribute to the specific heat, it is thought that the specific heat decreases as the amount of the second region increases.

[0161] Furthermore, from Examples 1 to 6 and Comparative Example 1, it is possible to shorten the minimum distance between the second region and the outer edge of the regenerator particle by increasing the area ratio of the second region. The shorter the distance, the higher the strength, but if it is shorter than 2 μm, the area ratio of the second region increases too much, and the specific heat becomes smaller than that of lead.

[0162] Examples 10, 12, and 13 and Comparative Examples 2, 3, and 4 show that HoNi ２ Besides, HoNi, HoCu ２ , Er ３The strength of the regenerator material such as Ni is also improved by including a second region in which the minimum distance to the outer edge of the regenerator material particle is 5 μm or more.

[0163] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. For example, components of one embodiment may be replaced or changed with components of another embodiment. These embodiments and modifications thereof are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0164] The technical solutions of the present invention are described below, and the following technical solutions are included in the scope of the present invention.

[0165] (Technical proposal 1) A first region including at least one first element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb), and at least one second element selected from the group consisting of nickel (Ni), cobalt (Co), copper (Cu), silver (Ag), gallium (Ga), bismuth (Bi), silicon (Si), aluminum (Al), and ruthenium (Ru); a second region having a chemical composition different from that of the first region, an area ratio in a cross section smaller than that of the first region, a minimum distance to the outer edge of the particle in the cross section of 5 μm or more, and containing at least one third element selected from the group consisting of carbon (C), oxygen (O), and nitrogen (N).

[0166] (Technical Solution 2) The regenerator particle according to Technical Solution 1, wherein the second region includes the at least one first element and the at least one second element.

[0167] (Technical proposal 3) The first region may or may not contain the at least one third element, and the atomic concentration of the at least one third element contained in the second region is higher than the atomic concentration of the at least one third element contained in the first region, the regenerator particles described in Technical proposal 1 or Technical proposal 2.

[0168] (Technical proposal 4) The regenerator particles according to Technical proposal 3, wherein the atomic concentration of the at least one third element contained in the second region is 10 atomic % or more higher than the atomic concentration of the at least one third element contained in the first region.

[0169] (Technical Scheme 5) The cold storage material particle according to any one of Technical Schemes 1 to 4, wherein the area ratio of the second region in the cross section is 0.01% or more and 15% or less.

[0170] (Technical Solution 6) The regenerator particles according to any one of Technical Solutions 1 to 5, wherein the at least one third element is carbon (O) and oxygen (O).

[0171] (Technical proposal 7) A regenerator particle described in any one of Technical proposals 1 to 6, further comprising a third region having a different chemical composition from the first region and the second region, an area proportion in the cross section smaller than that of the first region, and containing the at least one first element and the at least one second element.

[0172] (Technical proposal 8) The first region is polycrystalline, and the average value of the long diameter of the crystal grains in the first region is larger than the average value of the long diameter of the crystal grains in the second region.

[0173] (Technical Scheme 9) The cold storage material particles according to any one of Technical Schemes 1 to 8, having a particle size of 50 μm or more and 3 mm or less.

[0174] (Technical proposal 10) The maximum volumetric specific heat in the temperature range below 25K is 0.3 J / (cm ３ The cold storage material particles according to any one of Technical Schemes 1 to 9, wherein the cold storage material particles are at least K).

[0175] (Technical Solution 11) The regenerator particles according to any one of Technical Solutions 1 to 10, wherein the at least one first element is holmium (Ho), and the at least one second element is nickel (Ni).

[0176] (Technical Scheme 12) A group of cold storage particles containing 90% or more of the cold storage particles according to any one of Technical Schemes 1 to 11.

[0177] (Technical Scheme 13) A regenerator filled with a plurality of regenerator particles according to any one of Technical Schemes 1 to 11.

[0178] (Technical proposal 14) A refrigerator equipped with the regenerator according to Technical proposal 13.

[0179] (Technical proposal 15) A cryopump equipped with the refrigerator described in Technical proposal 14.

[0180] (Technical proposal 16) A superconducting magnet equipped with the refrigerator described in Technical proposal 14.

[0181] (Technical proposal 17) A nuclear magnetic resonance imaging device equipped with the refrigerator described in Technical proposal 14.

[0182] (Technical proposal 18) A nuclear magnetic resonance apparatus equipped with the refrigerator described in Technical proposal 14.

[0183] (Technical proposal 19) A magnetic field application type single crystal pulling apparatus equipped with the refrigerator described in Technical proposal 14.

[0184] (Technical proposal 20) A helium recondenser equipped with the refrigerator described in Technical proposal 14.

[0185] 10a First region 10b Second region 10c Third region 100 Regenerator particles 115 Second regenerator (regenerator) 200 Regenerator particles 300 Regenerator cryogenic refrigerator (refrigerator) 500 Cryopump 600 Superconducting magnet 700 Nuclear magnetic resonance imaging device 800 Nuclear magnetic resonance device 900 Magnetic field application type single crystal pulling device 1000 Helium recondensation device

Claims

1. A first region including at least one first element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb), and at least one second element selected from the group consisting of nickel (Ni), cobalt (Co), copper (Cu), silver (Ag), gallium (Ga), bismuth (Bi), silicon (Si), aluminum (Al), and ruthenium (Ru); a second region having a chemical composition different from that of the first region, an area ratio in a cross section smaller than that of the first region, a minimum distance to the outer edge of the particle in the cross section of 5 μm or more, and containing at least one third element selected from the group consisting of carbon (C), oxygen (O), and nitrogen (N).

2. The regenerator particle according to claim 1, wherein said second region includes said at least one first element and said at least one second element.

3. The regenerator particles according to claim 1, wherein the first region contains or does not contain the at least one third element, and the atomic concentration of the at least one third element contained in the second region is higher than the atomic concentration of the at least one third element contained in the first region.

4. The regenerator particles according to claim 3, wherein the atomic concentration of the at least one third element contained in the second region is 10 atomic % or more higher than the atomic concentration of the at least one third element contained in the first region.

5. The regenerator particle according to claim 1, wherein the area ratio of the second region in the cross section is 0.01% or more and 15% or less.

6. The regenerator particles according to claim 1, wherein the at least one third element is carbon (O) and oxygen (O).

7. The regenerator particle according to claim 1, further comprising a third region having a chemical composition different from that of the first region and the second region, an area proportion of the third region in the cross section smaller than that of the first region, and containing the at least one first element and the at least one second element.

8. The regenerator particle according to claim 1, wherein the first region is polycrystalline, and the average major axis of the crystal grains in the first region is larger than the average major axis of the crystal grains in the second region.

9. The regenerator particles according to claim 1, having a particle size of 50 μm or more and 3 mm or less.

10. The maximum volumetric specific heat in the temperature range below 25K is 0.3 J / (cm ３ The regenerator particles according to claim 1, wherein the regenerator particles have a molecular weight of 1.0 or more.

11. The regenerator particles of claim 1, wherein said at least one first element is holmium (Ho) and said at least one second element is nickel (Ni).

12. A group of cold storage particles containing 90% or more of the cold storage particles according to claim 1.

13. A regenerator filled with a plurality of regenerator particles according to claim 1.

14. A refrigerator equipped with the regenerator according to claim 13.

15. A cryopump equipped with the refrigerator according to claim 14.

16. A superconducting magnet equipped with the refrigerator according to claim 14.

17. A nuclear magnetic resonance imaging apparatus equipped with the refrigerator according to claim 14.

18. A nuclear magnetic resonance apparatus equipped with the refrigerator according to claim 14.

19. A magnetic field application type single crystal pulling apparatus equipped with the refrigerator according to claim 14.

20. A helium recondensing device comprising the refrigerator according to claim 14.

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