Cold storage material, cold storage particle, regenerator, refrigerator, cryopump, superconducting magnet, nuclear magnetic resonance imaging apparatus, nuclear magnetic resonance apparatus, magnetic field application-type single crystal pulling-out apparatus, and helium recondensing apparatus

Abstract

A cold storage material of an embodiment includes: a SmNiGe3-type crystal phase; and holmium (Ho), erbium (Er), nickel (Ni), and silicon (Si) and / or germanium (Ge).

Description

COLD STORAGE MATERIAL, COLD STORAGE PARTICLE, REGENERATOR, REFRIGERATOR, CRYOPUMP, SUPERCONDUCTING MAGNET, NUCLEAR MAGNETIC RESONANCE IMAGING APPARATUS, NUCLEAR MAGNETIC RESONANCE APPARATUS, MAGNETIC FIELD APPLICATION-TYPE SINGLE CRYSTAL PULLING-OUT APPARATUS, AND HELIUM RECONDENSING APPARATUS

[0001] Embodiments of the present invention relate to a cold storage material, a cold storage particle, a regenerator, a refrigerator, a cryopump, a superconducting magnet, a nuclear magnetic resonance imaging apparatus, a nuclear magnetic resonance apparatus, a magnetic field application-type single crystal pulling-out apparatus, and a helium recondensing apparatus.

[0002] In recent years, superconducting technologies have remarkably developed, and expansion of application fields of the superconducting technologies has led to an indispensable demand for development of small and high-performance cryogenic refrigerators. Cryogenic refrigerators need to be lightweight, compact, and highly thermally efficient. Cryogenic refrigerators have been put into practical use in various application fields.

[0003] A cryogenic refrigerator includes a regenerator filled with a plurality of cold storage materials. For example, cooling is performed by heat exchange between the cold storage materials and helium gas passing through the regenerator.

[0004] Examples of the cold storage material include a magnetic cold storage material containing a rare-earth element and a metal. Examples of the magnetic cold storage material containing a rare-earth element and a metal include HoCu2. In order to improve the performance of the cryogenic refrigerator, realization of a cold storage material having good specific heat characteristics is anticipated.

[0005] WO 2022 / 224783

[0006] Fabiana R. Arantes et al., ”Structure, magnetism, and transport of single-crystalline RNiSi3(R=Y,Gd-Tm,Lu)”, Physical Review Materials 2,044402(2018)

[0007] An object of the present invention is to provide a cold storage material having good specific heat characteristics.

[0008] A cold storage material of an embodiment includes: a SmNiGe3-type crystal phase; and holmium (Ho), erbium (Er), nickel (Ni), and silicon (Si) and / or germanium (Ge).

[0009] FIG. 1 is a schematic cross-sectional view of a cold storage material of a first embodiment.FIG. 2 is a graph illustrating an example of specific heat characteristics of the cold storage material of the first embodiment.FIG. 3 is a schematic cross-sectional view illustrating a configuration of a main part of a refrigerator of a fourth embodiment.FIG. 4 is a cross-sectional view illustrating a schematic configuration of a cryopump of a fifth embodiment.FIG. 5 is a perspective view illustrating a schematic configuration of a superconducting magnet of a sixth embodiment.FIG. 6 is a cross-sectional view illustrating a schematic configuration of a nuclear magnetic resonance imaging apparatus of a seventh embodiment.FIG. 7 is a cross-sectional view illustrating a schematic configuration of a nuclear magnetic resonance apparatus of an eighth embodiment.FIG. 8 is a perspective view illustrating a schematic configuration of a magnetic field application-type single crystal pulling-out apparatus of a ninth embodiment.FIG. 9 is a schematic view illustrating a schematic configuration of a helium recondensing apparatus of a tenth embodiment.

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same or similar members and the like are denoted by the same reference numerals, and the description of the members and the like which have been described once may be appropriately omitted.

[0011] In the present specification, a cryogenic temperature is, for example, a temperature range in which a superconducting phenomenon can be industrially used. The cryogenic temperature is, for example, in a temperature range of 20 K or lower.

[0012] (First Embodiment) A cold storage material of a first embodiment includes a SmNiGe3-type crystal phase and holmium (Ho), erbium (Er), nickel (Ni), and silicon (Si) and / or germanium (Ge). The cold storage material of the first embodiment includes the SmNiGe3-type crystal phase, holmium (Ho), erbium (Er), nickel (Ni), and at least one element selected from the group consisting of silicon (Si) and germanium (Ge). The cold storage material of the first embodiment may contain only one of silicon and germanium or may contain both.

[0013] FIG. 1 is a schematic cross-sectional view of the cold storage material of the first embodiment. A cold storage material 100 of the first embodiment is a magnetic cold storage material containing a rare-earth element and a metal.

[0014] As illustrated in FIG. 1, the cold storage material 100 contains a plurality of crystal grains 10. The cold storage material 100 is polycrystalline.

[0015] The cold storage material 100 includes the SmNiGe3-type crystal phase. For example, of crystal phases included in the cold storage material 100, the SmNiGe3-type crystal phase is a main crystal phase. The fact that the SmNiGe3-type crystal phase is the main crystal phase means that a percentage of the SmNiGe3-type crystal phase in the cold storage material 100 is higher than percentages of the other crystal phases. For example, the crystal grains 10 are the SmNiGe3-type crystal phase.

[0016] Whether or not the cold storage material 100 includes the SmNiGe3-type crystal phase can be identified by powder X-ray diffraction (XRD). In addition, whether or not the SmNiGe3-type crystal phase is the main crystal phase of the crystal phases included in the cold storage material 100 can be determined, for example, by comparing peak intensities of crystal phases obtained by powder X-ray diffraction. In addition, a weight proportion of a crystal phase present in a sample is analyzed by Rietveld analysis of a diffraction pattern obtained by XRD, and whether or not the SmNiGe3-type crystal phase is the main crystal phase can be determined by comparing values obtained through the analysis.

[0017] In addition, whether or not the SmNiGe3-type crystal phase is the main crystal phase of the crystal phases included in the cold storage material 100 can be determined, for example, by observing a backscattered electron image of a cross section of the cold storage material 100 with a scanning electron microscope (SEM). For example, the determination can be made by comparing an occupied area of the crystal grains 10 identified as the SmNiGe3-type crystal phase on the backscattered electron image with an occupied area of other crystal grains 10 by using the image processing software. Whether or not the crystal grains 10 is the SmNiGe3-type crystal phase can be determined by, for example, the energy dispersive X-ray spectroscopy (EDX).

[0018] The cold storage material 100 contains holmium (Ho), erbium (Er), nickel (Ni), and silicon (Si) and / or germanium (Ge). The cold storage material 100 contains holmium (Ho), erbium (Er), nickel (Ni), and at least one of silicon (Si) and germanium (Ge). For example, the crystal grains 10 contain holmium (Ho), erbium (Er), nickel (Ni), and silicon (Si) and / or germanium (Ge). For example, the crystal grains 10 contain holmium (Ho), erbium (Er), nickel (Ni), and at least one of silicon (Si) and germanium (Ge).

[0019] A chemical composition of the SmNiGe3-type crystal phase included in the cold storage material 100 can be represented by, for example, (Ho1-xErx)1±zNi1±z(SiyGe1-y)3±z. In the composition formula, x is larger than 0 and smaller than 1 (0 ＜ X ＜ 1). In the composition formula, y is equal to or larger than 0 and equal to or smaller than 1 (0 ≦ y ≦ 1). In the composition formula, z is equal to or larger than 0 and equal to or smaller than 0.1 (0 ≦ z ≦ 0.1).

[0020] The cold storage material 100 includes, for example, a solid solution in which Ho or Er is present at a Sm atom position of a SmNiGe3-type crystal.

[0021] A sum of an atomic concentration of holmium (Ho) and an atomic concentration of erbium (Er) contained in the cold storage material 100 is, for example, equal to or higher than 15 at% and equal to or lower than 25 at%. An atomic concentration of nickel (Ni) contained in the cold storage material 100 is, for example, equal to or higher than 15 at% and equal to or lower than 25 at%. In addition, a sum of an atomic concentration of silicon (Si) and an atomic concentration of germanium (Ge) contained in the cold storage material 100 is, for example, equal to or higher than 50 at% and equal to or lower than 70 at%.

[0022] The atomic concentration of holmium (Ho) contained in the cold storage material 100 is preferably higher than the atomic concentration of erbium (Er) contained in the cold storage material 100, for example.

[0023] A sum of an atomic concentration of holmium (Ho) and an atomic concentration of erbium (Er) contained in the crystal grain 10 is, for example, equal to or larger than 15 at% and equal to or smaller than 25 at%, An atomic concentration of nickel (Ni) contained in the crystal grain 10 is, for example, equal to or larger than 15 at% and equal to or smaller than 25 at%. In addition, a sum of an atomic concentration of silicon (Si) and an atomic concentration of germanium (Ge) contained in the crystal grain 10 is, for example, equal to or larger than 50 at% and equal to or smaller than 70 at%.

[0024] The atomic concentration of holmium (Ho) contained in the crystal grain 10 is preferably higher than the atomic concentration of erbium (Er) contained in the crystal grain 10, for example.

[0025] Detection of an element contained in the cold storage material 100 and measurement of an atomic concentration of the element can be performed by using, for example, inductively coupled plasma atomic emission spectroscopy (ICP-AES). For example, the cold storage material 100 is dissolved in a liquid, and the dissolved cold storage material 100 is measured by inductively coupled plasma atomic emission spectroscopy.

[0026] Detection of an element contained in the cold storage material 100 or the crystal grain 10, and measurement of an atomic concentration of the element can be performed by using, for example, energy dispersive X-ray spectroscopy (EDX) or wave dispersive spectroscopy (WDX).

[0027] It is assumed that a peak temperature of volumetric specific heat of HoNiSi3in a temperature range of 20 K or lower is defined as T1 (K), and a peak temperature of volumetric specific heat of ErNiSi3is defined as T2 (K). Then, an atomic proportion of erbium (Er) to a sum of an atomic proportion of holmium (Ho) and the atomic proportion of erbium (Er) in the cold storage material 100 is defined as X (0 ＜ X ＜ 1). In this case, a peak temperature TX (K) of volumetric specific heat of the cold storage material 100 is lower than, for example, T1 - (T1 - T2)X.

[0028] Similarly, it is assumed that a peak temperature of volumetric specific heat of HoNiGe3in the temperature range of 20 K or lower is defined as T3 (K), and a peak temperature of volumetric specific heat of ErNiGe3is defined as T4 (K). Then, an atomic proportion of erbium (Er) to a sum of an atomic proportion of holmium (Ho) and the atomic proportion of erbium (Er) in the cold storage material 100 is defined as X (0 ＜ X ＜ 1). In this case, the peak temperature TX (K) of volumetric specific heat of the cold storage material 100 is lower than, for example, T3 - (T3 - T4)X.

[0029] In a case where the peak temperature of the volumetric specific heat of the cold storage material 100 in the temperature range of 20 K or lower is defined as TX (K), and the atomic proportion of erbium (Er) to the sum of the atomic proportion of holmium (Ho) and the atomic proportion of erbium (Er) is defined as X (0 ＜ X ＜ 1), for example, the following inequality is established in a (Ho, Er)NiSi3system. TX ＜ -6.7X + 10.4

[0030] Similarly, in the (Ho, Er) NiGe3system, the following inequality holds. TX ＜ -4.5X + 10.2

[0031] Next, an example of a method for manufacturing the cold storage material of the first embodiment will be described.

[0032] The method for manufacturing magnetic cold storage particles of the first embodiment is not particularly limited, and various manufacturing methods can be applied. For example, manufacturing can be performed by melting a raw material by a high-frequency melting method to form a melted alloy or the like and pouring the melted alloy into a mold. In addition, for example, manufacturing can be performed by mixing raw material powders to prepare a raw material mixture, molding the obtained raw material mixture, and sintering the mixture in a vacuum furnace. In addition, manufacturing can be performed by melting a raw material by an arc melting method to form a melted alloy and cooling the melted alloy on a Cu hearth.

[0033] The cold storage material 100 of the first embodiment can be manufactured by the above-described manufacturing method.

[0034] A cold storage material 100 of the first embodiment includes a SmNiGe3-type crystal phase and holmium (Ho), erbium (Er), nickel (Ni), and silicon (Si) and / or germanium (Ge). A chemical composition of the SmNiGe3-type crystal phase included in the cold storage material 100 can be represented by, for example, (Ho1-xErx)1±zNi1±z(SiyGe1-y)3±z. In the composition formula, x is larger than 0 and smaller than 1 (0 ＜ X ＜ 1). In the composition formula, y is equal to or larger than 0 and equal to or smaller than 1 (0 ≦ y ≦ 1). In the composition formula, z is equal to or larger than 0 and equal to or smaller than 0.1 (0 ≦ z ≦ 0.1).

[0035] The cold storage material 100 of the first embodiment can realize, for example, higher volumetric specific heat than HoCu2can.

[0036] In addition, in the cold storage material 100 of the first embodiment, for example, an atomic proportion of the contained rare-earth elements is smaller than that in HoCu2. Since the atomic proportion of the expensive rare-earth elements is small, manufacturing costs of the cold storage material 100 can be reduced.

[0037] FIG. 2 is a graph illustrating an example of specific heat characteristics of the cold storage material of the first embodiment. In FIG. 2, the horizontal axis represents an amount ratio of holmium (Ho) and erbium (Er) contained in the cold storage material 100, and the vertical axis represents a peak temperature of volumetric specific heat.

[0038] The peak temperature of the volumetric specific heat is a temperature at which a peak appears in a distribution of the volumetric specific heat of the cold storage material. The peak temperature of the volumetric specific heat corresponds to a magnetic transition temperature of the cold storage material.

[0039] As illustrated in FIG. 2, regarding the cold storage material 100 of the first embodiment, it is possible to change the peak temperature of the volumetric specific heat to a desired value by changing the amount ratio of contained holmium (Ho) and erbium (Er). Hence, for example, the degree of freedom in designing the refrigerator can be improved by using the cold storage material 100.

[0040] FIG. 2 illustrates a case where a peak temperature T1 of volumetric specific heat of HoNiSi3is 10.4 K and a peak temperature T2 of volumetric specific heat of ErNiSi3is 3.7 K. Regarding the cold storage material 100 of the first embodiment, it is possible to change the peak temperature of the volumetric specific heat to a desired value between 10.4 K and 3.7 K by changing the amount ratio of contained holmium (Ho) and erbium (Er).

[0041] It is assumed that a peak temperature of volumetric specific heat of HoNiSi3in a temperature range of 20 K or lower is defined as T1 (K), and a peak temperature of volumetric specific heat of ErNiSi3is defined as T2 (K). Then, an atomic proportion of erbium (Er) to a sum of an atomic proportion of holmium (Ho) and the atomic proportion of erbium (Er) in the cold storage material 100 is defined as X (0 ＜ X ＜ 1). In this case, the peak temperature TX (K) of the volumetric specific heat of the cold storage material 100 is lower than, for example, T1 - (T1 - T2)X.

[0042] As illustrated in FIG. 2, in a case where the peak temperature of the volumetric specific heat of the cold storage material 100 in the temperature range of 20 K or lower is defined as TX (K), and the atomic proportion of erbium (Er) to the sum of the atomic proportion of holmium (Ho) and the atomic proportion of erbium (Er) is defined as X (0 ＜ X ＜ 1), for example, the following inequality is established. TX ＜ -6.7X + 10.4

[0043] Since the inequality is established, by substituting holmium (Ho) with a small amount of erbium (Er), the peak temperature of the volumetric specific heat of the cold storage material 100 can be significantly lowered from the peak temperature of the volumetric specific heat of HoNiSi3.

[0044] In a case where the chemical composition is ErNiSi3, the volumetric specific heat is lowered as compared with the case where the chemical composition is HoNiSi3. The lowering of the volumetric specific heat is considered to be proportional to the substitution amount of erbium (Er).

[0045] In the cold storage material 100, the peak temperature of the volumetric specific heat can be lowered by substituting holmium (Ho) with a small amount of erbium (Er). Hence, according to the cold storage material 100, it is conceivable that the peak temperature of the volumetric specific heat can be lowered while the lowering of the volumetric specific heat is suppressed.

[0046] In a range in which the atomic concentration of holmium (Ho) is higher than the atomic concentration of erbium (Er), that is, in a case where an atomic proportion X of erbium (Er) to the sum of the atomic proportion of holmium (Ho) and the atomic proportion of erbium (Er) is lower than 0.5, the amount of change in the peak temperature TX of the volumetric specific heat of the cold storage material 100 with respect to the change in the atomic proportion X is large. Hence, it is easy to adjust the peak temperature of the volumetric specific heat of the cold storage material 100. In addition, it is conceivable that the peak temperature of the volumetric specific heat can be lowered while the lowering of the volumetric specific heat of the cold storage material 100 is suppressed.

[0047] Since the cold storage material 100 is polycrystalline, for example, the mechanical strength is improved as compared with the case of single crystalline.

[0048] As described above, according to the first embodiment, it is possible to provide the cold storage material having good specific heat characteristics.

[0049] (Second Embodiment) Cold storage particles of a second embodiment are formed from the cold storage material 100 of the first embodiment. Hereinafter, the repeated descriptions of the details described in the first embodiment may be partially omitted.

[0050] The cold storage particles of the second embodiment have a particle size of, for example, equal to or larger than 50 μm and equal to or smaller than 3 mm. An aspect ratio of the cold storage particles is, for example, equal to or higher than 1 and equal to or lower than 5. The aspect ratio of the cold storage particles is a ratio of the major axis to the minor axis of the cold storage particles. A shape of the cold storage particles is, for example, spherical.

[0051] The method for manufacturing magnetic cold storage particles of the second embodiment is not particularly limited, and various manufacturing methods can be applied. For example, a method can be applied in which a melted alloy of a master alloy having a predetermined composition is rapidly cooled and solidified by a centrifugal spray method, a plasma rotating electrode method, a gas atomization method, a rotating electrode, or the like and is granulated. The master alloy can be manufactured by the same method as the method for manufacturing the magnetic cold storage material of the first embodiment.

[0052] As described above, according to the second embodiment, it is possible to provide the cold storage particles having good specific heat characteristics.

[0053] (Third Embodiment) A regenerator of a third embodiment is a regenerator filled with a plurality of cold storage particles of the second embodiment. In the regenerator of the third embodiment, for example, when the perimeter of the projection image of the plurality of filled cold storage particles of the second embodiment is denoted by L and the actual area of the projection image is denoted by A, a percentage of the cold storage particles having the circularity R equal to or lower than 0.5 which is represented by 4πA / L2is equal to or lower than 5%.

[0054] The circularity R can be obtained by performing image processing on the shapes of the plurality of cold storage particles in an image obtained using an optical microscope. The cold storage particle having the circularity R equal to or lower than 0.5 has, for example, unevenness on a surface thereof.

[0055] For example, when the regenerator is filled with a plurality of cold storage particles of which the cold storage particles having the unevenness on the surfaces thereof are more than 5%, a void fraction in the regenerator becomes non-uniform, or fillability becomes unstable. Therefore, for example, when a working medium flows into the regenerator, the cold storage performance of the regenerator is deteriorated.

[0056] In addition, for example, due to stress applied to the cold storage particles at the time of filling of the cold storage particles or at the time of operating the refrigerator, the cold storage particles are moved, or the cold storage particles are broken to form fine particles that may clog voids in the regenerator. The clogging of the voids degenerates refrigeration performance or long-term reliability of the refrigerator.

[0057] Hence, the cold storage particles having the circularity R equal to or lower than 0.5 with which the regenerator is filled is preferably equal to or lower than 2%, and more preferably 0%.

[0058] As described above, according to the third embodiment, it is possible to realize the regenerator having good characteristics by using the cold storage particles having good characteristics.

[0059] (Fourth Embodiment) A refrigerator of a fourth embodiment is a refrigerator including the regenerator of the third embodiment filled with the plurality of the cold storage particles of the second embodiment. Hereinafter, the repeated descriptions of the details described in the second and third embodiments are partially omitted.

[0060] FIG. 3 is a schematic cross-sectional view illustrating a configuration of a main part of the refrigerator of the fourth embodiment. FIG. 3 is a schematic cross-sectional view illustrating a configuration of a main part of a GM refrigerator which is an example of the refrigerator of the fourth embodiment. The GM refrigerator which is an example of the refrigerator of the fourth embodiment includes the regenerator of the third embodiment filled with the plurality of cold storage particles of the second embodiment.

[0061] The refrigerator of the fourth embodiment is a two-stage regenerative cryogenic refrigerator 300 used for cooling a superconducting machine or the like. The refrigerator may be, for example, a Stirling refrigerator or a pulse tube refrigerator.

[0062] The regenerative 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 (regenerator), a first seal ring 116, a second seal ring 117, a first cold storage material 118, a second cold storage material 119 (cold storage 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.

[0063] The regenerative cryogenic refrigerator 300 includes the vacuum container 113 in which a first cylinder 111 having a large diameter and a second cylinder 112 having a small diameter which is coaxially connected to the first cylinder 111 are provided. The first regenerator 114 is disposed in the first cylinder 111 to freely perform reciprocating motion. In the second cylinder 112, the second regenerator 115 which is an example of the regenerator of the fourth embodiment is disposed to freely perform reciprocating motion.

[0064] The first seal ring 116 is disposed between the first cylinder 111 and the first regenerator 114. The second seal ring 117 is disposed between the second cylinder 112 and the second regenerator 115.

[0065] The first regenerator 114 is filled with a first cold storage material 118 such as Cu mesh. The second regenerator 115 is filled with a plurality of the cold storage particles of the second embodiment as the second cold storage material 119.

[0066] The second regenerator 115 may be divided by a metal mesh material and may include a plurality of cold storage material filling layers. In a case where the second regenerator 115 is divided into a plurality of filling layers, at least one filling layer is filled with a cold storage particle group including a plurality of cold storage particles of the second embodiment. Then, for example, a combination with at least one cold storage particle group selected from a rare-earth oxide cold storage particle group, a rare-earth oxysulfide cold storage particle group, a lead cold storage particle group, a bismuth cold storage particle group, a tin cold storage particle group, a holmium copper cold storage particle group, an erbium nickel cold storage particle group, an erbium cobalt cold storage particle group, and a gadolinium aluminum oxide cold storage particle group is used.

[0067] In the combination of the cold storage materials, the one having a higher peak temperature of specific heat is defined as a first cold storage particle group, the one having a lower peak temperature of specific heat is defined as a second cold storage particle group, and the combination is performed so that the peak temperature of specific heat is sequentially lowered.

[0068] The first regenerator 114 and the second regenerator 115 each have a passage of a working medium which is provided in a gap or the like between the first cold storage material 118 and the second cold storage material 119. The working medium is helium gas.

[0069] The first expansion chamber 120 is provided between the first regenerator 114 and the second regenerator 115. In addition, the second expansion chamber 121 is provided between the second regenerator 115 and a distal end wall of the second cylinder 112. The first cooling stage 122 is provided at the bottom of the first expansion chamber 120. In addition, the second cooling stage 123 having a temperature lower than that of the first cooling stage 122 is formed at the bottom of the second expansion chamber 121.

[0070] A high-pressure working medium is supplied from the compressor 124 to the above-described two-stage regenerative cryogenic refrigerator 300. The supplied working medium passes through the first cold storage material 118, with which the first regenerator 114 is filled, and reaches the first expansion chamber 120. Then, the working medium passes through the second cold storage material 119, with which the second regenerator 115 is filled, and reaches the second expansion chamber 121.

[0071] At this time, the working medium is cooled by supplying thermal energy to the first cold storage material 118 and the second cold storage material 119. The working medium passing through the first cold storage material 118 and the second cold storage material 119 expands in the first expansion chamber 120 and the second expansion chamber 121, and cooling is performed. Then, the first cooling stage 122 and the second cooling stage 123 are cooled.

[0072] The expanded working medium flows in an opposite direction through the first cold storage material 118 and the second cold storage material 119. The working medium receives thermal energy from the first cold storage material 118 and the second cold storage material 119 and then is discharged. The regenerative cryogenic refrigerator 300 is configured such that thermal efficiency of the working medium cycle is enhanced as a recuperative effect is improved in such a process, and a lower temperature is realized.

[0073] In the regenerator included in the regenerative cryogenic refrigerator 300 of the fourth embodiment, the second regenerator 115 is filled with the plurality of cold storage particles of the second embodiment as the second cold storage material 119. At least a part of the second cold storage material 119 is the cold storage particles of the second embodiment.

[0074] Regarding the plurality of cold storage particles of the second embodiment, when the perimeter of each projection image of the cold storage particles is denoted by L and the actual area of the projection image is denoted by A, the cold storage particles having the circularity R equal to or lower than 0.5 which is represented by 4πA / L2are preferably equal to or lower than 5%.

[0075] In order to improve the refrigerating capacity of the refrigerator, it is desirable to improve specific heat per unit volume of the cold storage material and improve thermal conductivity and a heat transfer coefficient. The regenerative cryogenic refrigerator 300 of the fourth embodiment includes a cold storage material or cold storage particles which maintain volumetric specific heat and are improved in the thermal conductivity and the thermal conductivity. The regenerative cryogenic refrigerator 300 of the fourth embodiment includes a cold storage material or cold storage particles enabling the manufacturing costs to be reduced.

[0076] The regenerative cryogenic refrigerator 300 of the fourth embodiment includes the cold storage particles of the second embodiment which enable the peak temperature of the volumetric specific heat to be changed to a desired value. Hence, the degree of freedom in designing the refrigerator is improved.

[0077] 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.

[0078] As described above, according to the fourth embodiment, it is possible to realize the refrigerator having good characteristics by using the cold storage particles having good characteristics.

[0079] (Fifth Embodiment) A cryopump of a fifth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, the repeated descriptions of the details described in the fourth embodiment are partially omitted.

[0080] FIG. 4 is a cross-sectional view illustrating a schematic configuration of the cryopump of the fifth embodiment. The cryopump of the fifth embodiment is a cryopump 500 including the regenerative cryogenic refrigerator 300 of the fourth embodiment.

[0081] The cryopump 500 includes a cryopanel 501 that condenses or adsorbs gas molecules, the regenerative cryogenic refrigerator 300 that cools the cryopanel 501 to a predetermined cryogenic temperature, a shield 503 provided between the cryopanel 501 and the regenerative cryogenic refrigerator 300, a baffle 504 provided at an inlet, and a ring 505 that changes an exhaust velocity of argon, nitrogen, hydrogen, or the like.

[0082] According to the fifth embodiment, it is possible to realize the cryopump having good characteristics by using the refrigerator having good characteristics.

[0083] (Sixth Embodiment) A superconducting magnet of a sixth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, the repeated descriptions of the details described in the fourth embodiment are partially omitted.

[0084] FIG. 5 is a perspective view illustrating a schematic configuration of the superconducting magnet of the sixth embodiment. The superconducting magnet of the sixth embodiment is a superconducting magnet 600 for a magnetic levitation train, the superconducting magnet including the regenerative cryogenic refrigerator 300 of the fourth embodiment.

[0085] 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 liquid helium from volatilizing, a multi-layer insulation material 605, a power lead 606, a permanent current switch 607, and the regenerative cryogenic refrigerator 300.

[0086] According to the sixth embodiment, it is possible to realize the superconducting magnet having good characteristics by using the refrigerator having good characteristics.

[0087] (Seventh Embodiment) A nuclear magnetic resonance imaging apparatus of a seventh embodiment includes the refrigerator of the fourth embodiment. Hereinafter, the repeated descriptions of the details described in the fourth embodiment are partially omitted.

[0088] FIG. 6 is a cross-sectional view illustrating a schematic configuration of the nuclear magnetic resonance imaging apparatus of the seventh embodiment. The nuclear magnetic resonance imaging (MRI) apparatus of the seventh embodiment is a nuclear magnetic resonance imaging apparatus 700 including the regenerative cryogenic refrigerator 300 of the fourth embodiment.

[0089] 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 a human body, a correction coil (not illustrated) that corrects nonuniformity of a generated magnetic field, a gradient magnetic field coil 702 that gives a magnetic field gradient to a measurement region, a radio wave transmission / reception probe 703, a cryostat 705, and a radiation adiabatic shield 706. The regenerative cryogenic refrigerator 300 is used for cooling the superconducting static magnetic field coil 701.

[0090] According to the seventh embodiment, it is possible to realize the nuclear magnetic resonance imaging apparatus having good characteristics by using the refrigerator having good characteristics.

[0091] (Eighth Embodiment) A nuclear magnetic resonance apparatus of an eighth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, the repeated descriptions of the details described in the fourth embodiment are partially omitted.

[0092] FIG. 7 is a cross-sectional view illustrating a schematic configuration of the nuclear magnetic resonance apparatus of the eighth embodiment. The nuclear magnetic resonance (NMR) apparatus of the eighth embodiment is a nuclear magnetic resonance apparatus 800 including the regenerative cryogenic refrigerator 300 of the fourth embodiment.

[0093] 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 a radio wave to the sample tube 801 in a magnetic field, and an amplifier 804 that amplifies an induced current generated in a coil (not illustrated) around the sample tube 801. In addition, the nuclear magnetic resonance apparatus 800 includes the regenerative cryogenic refrigerator 300 that cools the superconducting static magnetic field coil 802.

[0094] According to the eighth embodiment, it is possible to realize the nuclear magnetic resonance apparatus having good characteristics by using the refrigerator having good characteristics.

[0095] (Ninth Embodiment) A magnetic field application-type single crystal pulling-out apparatus of a ninth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, the repeated descriptions of the details described in the fourth embodiment are partially omitted.

[0096] FIG. 8 is a perspective view illustrating a schematic configuration of the magnetic field application-type single crystal pulling-out apparatus of the ninth embodiment. The magnetic field application-type single crystal pulling-out apparatus of the ninth embodiment is a magnetic field application-type single crystal pulling-out apparatus 900 including the regenerative cryogenic refrigerator 300 of the fourth embodiment.

[0097] The magnetic field application-type single crystal pulling-out apparatus 900 includes a single crystal pulling-out unit 901 having a raw material melting crucible, a heater, a single crystal pulling-out mechanism, and the like, a superconducting coil 902 that applies a static magnetic field to raw material melt, a lifting-lowering mechanism 903 of the single crystal pulling-out unit 901, a current lead 905, a heat shield plate 906, and a helium container 907. The regenerative cryogenic refrigerator 300 is used for cooling the superconducting coil 902.

[0098] According to the ninth embodiment, it is possible to realize the magnetic field application-type single crystal pulling-out apparatus having good characteristics by using the refrigerator having good characteristics.

[0099] (Tenth Embodiment) A helium recondensing apparatus of a tenth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, the repeated descriptions of the details described in the fourth embodiment are partially omitted.

[0100] FIG. 9 is a schematic view illustrating a schematic configuration of the helium recondensing apparatus of the tenth embodiment. The helium recondensing apparatus of the tenth embodiment is a helium recondensing apparatus 1000 including the regenerative cryogenic refrigerator 300 of the fourth embodiment.

[0101] The helium recondensing apparatus 1000 includes the regenerative cryogenic refrigerator 300, an evaporation pipe 1001, and a liquefaction pipe 1002.

[0102] The helium recondensing apparatus 1000 can recondense helium gas evaporating from a liquid helium apparatus into liquid helium. The liquid helium apparatus is, for example, the superconducting magnet, the nuclear magnetic resonance (NMR) apparatus, the nuclear magnetic resonance imaging (MRI) apparatus, a physical property measurement system (PPMS), or a magnetic property measurement system.

[0103] Helium gas is introduced from the liquid helium apparatus (not illustrated) into the helium recondensing apparatus 1000 through the evaporation pipe 1001. The helium gas is cooled to 4 K equal to or lower than the liquefaction temperature of helium by the regenerative cryogenic refrigerator 300. The condensed and liquefied liquid helium returns to the liquid helium apparatus through the liquefaction pipe 1002.

[0104] According to the tenth embodiment, it is possible to realize the helium recondensing apparatus having good characteristics by using the refrigerator having good characteristics.

[0105] Although some embodiments of the present invention have been described, these embodiments have been presented as examples, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. For example, a component of one embodiment may be replaced with or changed into a component of another embodiment. These embodiments and modifications thereof are included in the scope or gist of the invention and are included in the invention described in WHAT IS CLAIMED IS: and the scope of equivalents thereof.

[0106] Hereinafter, technical proposals of the present invention will be described. The following technical proposals are included in the scope of the present invention.

[0107] (Technical Proposal 1) A cold storage material including: a SmNiGe3-type crystal phase; and holmium (Ho), erbium (Er), nickel (Ni), and silicon (Si) and / or germanium (Ge).

[0108] (Technical Proposal 2) The cold storage material according to Technical Proposal 1, in which a sum of an atomic concentration of holmium (Ho) and an atomic concentration of erbium (Er) is equal to or higher than 15 at% and equal to or lower than 25 at%, an atomic concentration of nickel (Ni) is equal to or higher than 15 at% and equal to or lower than 25 at%, and a sum of an atomic concentration of silicon (Si) and an atomic concentration of germanium (Ge) is equal to or higher than 50 at% and equal to or lower than 70 at%.

[0109] (Technical Proposal 3) The cold storage material according to Technical Proposal 1 or 2, in which the cold storage material is polycrystalline.

[0110] (Technical Proposal 4) The cold storage material according to any one of Technical Proposals 1 to 3, in which a percentage of the SmNiGe3-type crystal phase is higher than a percentage of other crystal phases.

[0111] (Technical Proposal 5) The cold storage material according to any one of Technical Proposals 1 to 4, in which, in a case where a peak temperature of volumetric specific heat of HoNiSi3is defined as T1 (K), a peak temperature of volumetric specific heat of ErNiSi3is defined as T2 (K), and an atomic proportion of erbium (Er) to a sum of an atomic proportion of holmium (Ho) and the atomic proportion of erbium (Er) is defined as X (0 ＜ X ＜ 1), a peak temperature TX (K) of volumetric specific heat is lower than T1 - (T1 - T2)X.

[0112] (Technical Proposal 6) The cold storage material according to any one of Technical Proposals 1 to 4, in which, in a case where a peak temperature of volumetric specific heat of HoNiGe3is defined as T1 (K), a peak temperature of volumetric specific heat of ErNiSi3is defined as T2 (K), and an atomic proportion of erbium (Er) to a sum of an atomic proportion of holmium (Ho) and the atomic proportion of erbium (Er) is defined as X (0 ＜ X ＜ 1), a peak temperature TX (K) of volumetric specific heat is lower than T1 - (T1 - T2)X.

[0113] (Technical Proposal 7) The cold storage material according to any one of Technical Proposals 1 to 6, in which an atomic concentration of holmium (Ho) is higher than an atomic concentration of erbium (Er).

[0114] (Technical Proposal 8) Cold storage particles formed of the cold storage material according to any one of Technical Proposals 1 to 7 and having a particle size equal to or larger than 50 μm and equal to or smaller than 3 mm.

[0115] (Technical Proposal 9) A regenerator filled with a plurality of the cold storage particles described in Technical Proposal 8.

[0116] (Technical Proposal 10) A refrigerator including the regenerator according to Technical Proposal 9.

[0117] (Technical Proposal 11) A cryopump including the refrigerator according to Technical Proposal 10.

[0118] (Technical Proposal 12) A superconducting magnet including the refrigerator according to Technical Proposal 10.

[0119] (Technical Proposal 13) A nuclear magnetic resonance imaging apparatus including the refrigerator according to Technical Proposal 10.

[0120] (Technical Proposal 14) A nuclear magnetic resonance apparatus including the refrigerator according to Technical Proposal 10.

[0121] (Technical Proposal 15) A magnetic field application-type single crystal pulling-out apparatus including the refrigerator according to Technical Proposal 10.

[0122] (Technical Proposal 16) A helium recondensing apparatus including the refrigerator according to Technical Proposal 10.

[0123] 100 Cold storage material 115 Second regenerator (regenerator) 119 Second cold storage material (cold storage particle) 200 Granulated particle for cold storage particles 300 Regenerative cryogenic refrigerator (refrigerator) 500 Cryopump 600 Superconducting magnet 700 Nuclear magnetic resonance imaging apparatus 800 Nuclear magnetic resonance apparatus 900 Magnetic field application-type single crystal pulling-out apparatus 1000 Helium recondensing apparatus

Claims

1. A cold storage material comprising: a SmNiGe3-type crystal phase; and holmium (Ho), erbium (Er), nickel (Ni), and silicon (Si) and / or germanium (Ge).

2. The cold storage material according to claim 1, wherein a sum of an atomic concentration of holmium (Ho) and an atomic concentration of erbium (Er) is equal to or higher than 15 at% and equal to or lower than 25 at%, an atomic concentration of nickel (Ni) is equal to or higher than 15 at% and equal to or lower than 25 at%, and a sum of an atomic concentration of silicon (Si) and an atomic concentration of germanium (Ge) is equal to or higher than 50 at% and equal to or lower than 70 at%.

3. The cold storage material according to claim 1, wherein the cold storage material is polycrystalline.

4. The cold storage material according to claim 1, wherein a percentage of the SmNiGe3-type crystal phase is higher than a percentage of other crystal phases.

5. The cold storage material according to claim 1, wherein, in a case where a peak temperature of volumetric specific heat of HoNiSi3is defined as T1 (K), a peak temperature of volumetric specific heat of ErNiSi3is defined as T2 (K), and an atomic proportion of erbium (Er) to a sum of an atomic proportion of holmium (Ho) and the atomic proportion of erbium (Er) is defined as X (0 ＜ X ＜ 1), a peak temperature TX (K) of volumetric specific heat is lower than T1 - (T1 - T2)X.

6. The cold storage material according to claim 1, wherein, in a case where a peak temperature of volumetric specific heat of HoNiGe3is defined as T3 (K), a peak temperature of volumetric specific heat of ErNiGe3is defined as T4 (K), and an atomic proportion of erbium (Er) to a sum of an atomic proportion of holmium (Ho) and the atomic proportion of erbium (Er) is defined as X (0 ＜ X ＜ 1), a peak temperature TX (K) of volumetric specific heat is lower than T3 - (T3 - T4)X.

7. The cold storage material according to claim 1, wherein an atomic concentration of holmium (Ho) is higher than an atomic concentration of erbium (Er).

8. Cold storage particles formed of the cold storage material according to claim 1 and having a particle size equal to or larger than 50 μm and equal to or smaller than 3 mm.

9. A regenerator filled with a plurality of the cold storage particles according to claim 8.

10. A refrigerator comprising the regenerator according to claim 9.

11. A cryopump comprising the refrigerator according to claim 10.

12. A superconducting magnet comprising the refrigerator according to claim 10.

13. A nuclear magnetic resonance imaging apparatus comprising the refrigerator according to claim 10.

14. A nuclear magnetic resonance apparatus comprising the refrigerator according to claim 10.

15. A magnetic field application-type single crystal pulling-out apparatus comprising the refrigerator according to claim 10.

16. A helium recondensing apparatus comprising the refrigerator according to claim 10.

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