Granulated particles for cold storage material particles, granulated particle group for cold storage material particles, cold storage material particles, cold storage material particle group, cold storage device, refrigerator, cryopump, superconducting magnet, nuclear magnetic resonance imaging device, nuclear magnetic resonance device, magnetic field application-type single crystal pulling device, helium recondensation device, and dilution refrigerator

Abstract

Granulated particles for cold storage material particles according to an embodiment contain a rare earth oxide containing at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and have a first region containing at least one rare earth element and O and a second region containing Ca, C, and O on the surface.

Description

Granulated particles for thermal storage materials, groups of granulated particles for thermal storage materials, thermal storage materials, groups of thermal storage materials, thermal storage units, refrigerators, cryopumps, superconducting magnets, nuclear magnetic resonance imaging devices, nuclear magnetic resonance devices, magnetic field applied single crystal pulling devices, helium recondensing devices, and dilution refrigerators.

[0001] Embodiments of the present invention relate to granulated particles for thermal storage material particles, groups of granulated particles for thermal storage material particles, thermal storage material particles, groups of thermal storage material particles, thermal storage devices, refrigerators, cryopumps, superconducting magnets, nuclear magnetic resonance imaging devices, nuclear magnetic resonance devices, magnetic field applied single crystal pulling devices, helium recondensing devices, and dilution refrigerators.

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

[0003] Cryogenic refrigerators are equipped with a regenerator filled with multiple cold storage materials. For example, cold is generated by heat exchange between the cold storage materials and helium gas passing through the regenerator. For example, cryopumps used in superconducting MRI devices and semiconductor manufacturing equipment use refrigerators with refrigeration cycles such as the Gifford-McMahon (GM) method, the Stirling method, or the pulse tube method.

[0004] Furthermore, high-performance refrigerators are essential for generating magnetic force using superconducting magnets in magnetic levitation trains. More recently, high-performance refrigerators are also being used in superconducting energy storage systems (SMES) and magnetic field-applied single-crystal pulling systems for manufacturing high-quality silicon wafers. In addition, the development and practical application of pulse tube refrigerators, which are expected to offer high reliability, are being actively pursued.

[0005] In superconducting magnets and MRI machines, as mentioned above, the liquid helium used evaporates, making the replenishment of liquid helium a problem. In recent years, the helium depletion problem has become serious, making it difficult to obtain and impacting industry.

[0006] To reduce the consumption of liquid helium and lessen the burden of maintenance such as replenishment, helium recondensation equipment that recondenses evaporated helium has been put into practical use and is in high demand. These helium recondensation equipment also use GM refrigerators or pulse tube refrigerators that cool the temperature to the 4K level in order to liquefy the helium.

[0007] In a refrigerator, a working medium, such as compressed helium (He) gas, flows in one direction through a regenerator filled with a thermal storage material, supplying its thermal energy to the material. Then, the expanding working medium flows in the opposite direction through the regenerator, receiving thermal energy from the thermal storage material. As the regeneration effect in this process improves, the thermal efficiency of the working medium cycle increases, making it possible to achieve lower temperatures. For smooth thermal energy exchange between He gas and the thermal storage material, a high thermal conductivity of the thermal storage material is desirable.

[0008] Here, the higher the specific heat per unit volume of the thermal storage material installed in the chiller, the greater the amount of thermal energy that the thermal storage material can store, thus improving the chilling capacity of the refrigerator. For this reason, it is desirable to fill the low-temperature side of the chiller with a thermal storage material that has a high specific heat per unit volume at low temperatures, and the high-temperature side with a thermal storage material that has a high specific heat per unit volume at high temperatures.

[0009] Magnetic thermal storage materials exhibit high volumetric specific heat in a specific temperature range, depending on their composition. Therefore, combining magnetic thermal storage materials with different compositions that exhibit different volumetric specific heats increases the thermal storage capacity, thereby improving the cooling capacity of the refrigerator.

[0010] Furthermore, the higher the thermal conductivity and heat transfer coefficient of the thermal storage material used to fill the chiller, the more efficient the transfer of thermal energy becomes, and thus the more efficient the chiller becomes.

[0011] In conventional refrigeration systems, metal thermal storage particles such as lead (Pb), bismuth (Bi), or tin (Sn) are filled into the high-temperature side of the regenerator, and Er is used on the low-temperature side of the regenerator below 20K. ３ Ni, ErNi, HoCu ２ By filling them with metallic magnetic thermal storage particles, 4K freezing has been achieved.

[0012] In recent years, attempts have been made to improve the refrigeration capacity of a refrigerator by replacing some of the metal-based magnetic regenerator particles with ceramic magnetic regenerator particles such as Gd ２ O ２ S, Tb ２ O ２ S, Dy ２ O ２ S, Ho ２ O ２ S, GdAlO ３ and the like.

[0013] It is preferable that the plurality of regenerator particles filled in the regenerator have little variation in shape. If the shapes of the plurality of regenerator particles filled in the regenerator vary, for example, the regenerator particles are likely to be damaged in the regenerator, and there is a risk of clogging in the regenerator. When clogging occurs in the regenerator, for example, the flow of the working medium is hindered and the efficiency of the refrigerator decreases. Therefore, it is desired to manufacture regenerator particles with a stable shape.

[0014] Japanese Patent Application Laid-Open No. 2003-73661, Japanese Patent Application Laid-Open No. 2003-213252, International Publication No. 2018 / 025581, Patent No. 5656842

[0015] The problem to be solved by the present invention is to provide granulated particles for regenerator particles for manufacturing regenerator particles with a stable shape and improving the refrigeration performance of a refrigerator.

[0016] The granulated particles for regenerator particles of the embodiment contain a rare earth oxide containing at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and on the surface, a first region containing the at least one rare earth element and oxygen (O), and a second region containing calcium (Ca), carbon (C), and oxygen (O).

[0017] Schematic diagram of granulated particles for thermal storage material particles of the first embodiment. Schematic diagram of granulated particles for thermal storage material particles of a comparative example. Schematic cross-sectional view showing the main components of the refrigerator of the fifth embodiment. Cross-sectional view showing the schematic configuration of the cryopump of the sixth embodiment. Perspective view showing the schematic configuration of the superconducting magnet of the seventh embodiment. Cross-sectional view showing the schematic configuration of the nuclear magnetic resonance imaging apparatus of the eighth embodiment. Cross-sectional view showing the schematic configuration of the nuclear magnetic resonance apparatus of the ninth embodiment. Perspective view showing the schematic configuration of the magnetic field applied single crystal pulling apparatus of the tenth embodiment. Schematic diagram showing the schematic configuration of the helium recondenser of the eleventh embodiment. Schematic diagram showing the schematic configuration of the dilution refrigerator of the twelfth embodiment.

[0018] Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same or similar components will be denoted by the same reference numerals, and components that have already been described may be omitted from the description as appropriate.

[0019] In this specification, cryogenic temperatures refer to, for example, the temperature range in which superconductivity can be utilized industrially. Cryogenic temperatures refer to, for example, temperatures below 20 K.

[0020] (First Embodiment) The granulated particles for the cold storage material of the first embodiment contain a rare earth oxide containing at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and have a first region on its surface containing at least one rare earth element and oxygen (O), and a second region containing calcium (Ca), carbon (C), and oxygen (O).

[0021] The granulated particles for the thermal storage material particles in the first embodiment are granulated particles 100 for manufacturing thermal storage material particles.

[0022] Figure 1 is a schematic diagram of granulated particles for a thermal storage material according to the first embodiment. Figure 1 is a schematic diagram of a scanning electron microscope image (SEM image) obtained when the surface of the granulated particles 100 is observed using a scanning electron microscope (SEM).

[0023] The shape of the granulated particles 100 is, for example, spherical or spindle-shaped.

[0024] The particle size of the granulated particles 100 is, for example, 50 μm or more and 7 mm or less. Also, the aspect ratio of the granulated particles 100 is, for example, 1 or more and 5 or less. The aspect ratio of the granulated particles 100 is the ratio (long diameter / short diameter) of the long diameter to the short diameter of the granulated particles 100.

[0025] In this specification, the particle size of the granulated particles 100 is the equivalent circle diameter. The equivalent circle diameter is the diameter of a true 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 granulated particles 100 can be determined, for example, by image analysis of an optical microscope image or an SEM image. Also, the long diameter and short diameter of the granulated particles 100 can be determined, for example, by an optical microscope image or an SEM image.

[0026] The granulated particles 100 of the first embodiment contain a rare earth oxide. The rare earth oxide contains at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0027] The determination of whether the granulated particles 100 contain a rare earth oxide and the identification of the type of rare earth element contained in the rare earth oxide can be achieved, for example, by using X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX).

[0028] As shown in FIG. 1, the granulated particles 100 of the first embodiment include a first region 10 and a second region 20 on the surface. The second region 20 covers the first region 10.

[0029] The first region 10 includes rare earth elements contained in rare earth oxides and oxygen (O). The first region 10 includes, for example, at least one additive element selected from the group consisting of aluminum (Al), zirconium (Zr), gallium (Ga), silicon (Si), germanium (Ge), and copper (Cu).

[0030] The first region 10 may or may not contain calcium (Ca). The first region 10 may or may not contain carbon (C).

[0031] The above-mentioned rare earth elements and oxygen (O) are, for example, the main constituent elements of the first region 10. The statement that the above-mentioned rare earth elements and oxygen (O) are the main constituent elements of the first region 10 means that among the elements contained in the first region 10, there are no elements with a higher atomic concentration than the above-mentioned rare earth elements or oxygen (O).

[0032] The first region 10 includes, for example, rare earth oxides. The atomic concentration of rare earth elements in the first region 10 is, for example, between 10 atomic percent and 50 atomic percent. The atomic concentration of oxygen (O) in the first region 10 is, for example, between 40 atomic percent and 70 atomic percent.

[0033] The second region 20 contains calcium (Ca), carbon (C), and oxygen (O). Calcium (Ca), carbon (C), and oxygen (O) are, for example, the main constituent elements of the second region 20. The fact that calcium (Ca), carbon (C), and oxygen (O) are the main constituent elements of the second region 20 means that among the elements contained in the second region 20, there are no elements with a higher atomic concentration than calcium (Ca), carbon (C), or oxygen (O).

[0034] The atomic concentration of calcium (Ca) in the second region 20 is, for example, greater than the atomic concentration of calcium (Ca) in the first region 10. The atomic concentration of calcium (Ca) in the second region 20 is, for example, 10 times or more the atomic concentration of calcium (Ca) in the first region 10. The atomic concentration of calcium (Ca) in the second region 20 is, for example, between 1% atoms and 30 atomic percent. The atomic concentration of calcium (Ca) in the first region 10 is, for example, less than 1 atomic percent.

[0035] The atomic concentration of carbon (C) in the second region 20 is, for example, greater than the atomic concentration of carbon (C) in the first region 10. The atomic concentration of carbon (C) in the second region 20 is, for example, 10 times or more the atomic concentration of carbon (C) in the first region 10. The atomic concentration of carbon (C) in the second region 20 is, for example, between 1 atomic percent and 60 atomic percent. The atomic concentration of carbon (C) in the first region 10 is, for example, less than 1%. The atomic concentration of oxygen (O) in the second region 20 is, for example, between 20 atomic percent and 70 atomic percent.

[0036] The second region 20 may or may not contain the above-mentioned rare earth elements. The second region 20 may or may not contain the above-mentioned additive elements. The atomic concentration of the rare earth elements in the second region 20 is, for example, 0.1 atomic percent or more and 5 atomic percent or less.

[0037] The types of elements and their atomic concentrations contained in the first region 10 and the second region 20 can be determined, for example, using the EDX method.

[0038] The second region 20 contains crystals. The crystals in the second region 20 are, for example, plate-like, columnar, or needle-like. The crystals in the second region 20 contain, for example, calcium (Ca), carbon (C), and oxygen (O). The crystals in the second region 20 are, for example, crystals of calcium carbonate.

[0039] Whether or not the second region 20 contains crystals can be determined, for example, from the appearance of the surface of the second region 20. That is, whether or not the second region 20 contains crystals can be determined, for example, by whether or not crystal habits appear on the surface of the second region 20. That is, whether or not the second region 20 contains crystals can be determined, for example, by whether or not plate-like, columnar, or needle-like crystal habits appear on the surface of the second region 20.

[0040] The ratio of the area of ​​the second region 20 to the sum of the areas of the first region 10 and the second region 20 is, for example, 30% or more and 90% or less.

[0041] In the SEM image of granulated particles 100 shown in Figure 1, the brightness of the first region 10 is higher than that of the second region 20. For example, by defining the high-brightness region as the first region 10 and the low-brightness region as the second region 20 in the SEM image and performing image analysis, the areas of the first region 10 and the second region 20 can be determined. Using this method, the ratio of the area of ​​the second region 20 to the sum of the areas of the first region 10 and the second region 20 can be calculated.

[0042] Furthermore, in the SEM image of granulated particles 100 as shown in Figure 1, it is possible to create a distribution map of calcium atomic concentration using the EDX method. In the distribution map of calcium (Ca) atomic concentration, the region where the calcium atomic concentration is less than 1 atomic percent is defined as the first region 10, and the region where the calcium atomic concentration is 1 atomic percent or more is defined as the second region 20. By performing image analysis, the areas of the first region 10 and the second region 20 can be determined. Using this method, the ratio of the area of ​​the second region 20 to the sum of the areas of the first region 10 and the second region 20 can be calculated.

[0043] In the SEM image of the granulated particles 100 shown in Figure 1, the thickness of the second region 20 (t in Figure 1) is, for example, 10 μm or more and 100 μm or less. The thickness t of the second region 20 can be defined, for example, as shown in Figure 1, by the distance between the tangent line to the outer edge of the first region 10 at the point where the first region 10 and the second region 20 intersect, and the line segment parallel to the tangent line and tangent to the outer edge of the second region 20.

[0044] Next, an example of a method for producing granulated particles for thermal storage material particles according to the first embodiment will be described.

[0045] A slurry is prepared by adding a raw material powder containing rare earth oxides and a sintering aid to an alginic acid aqueous solution and mixing them. The alginic acid aqueous solution can be, for example, a sodium alginate aqueous solution, an ammonium alginate aqueous solution, or a potassium alginate aqueous solution. The prepared slurry is dropped dropwise into a calcium lactate aqueous solution, which is a gelling solution in a container, using a syringe. The slurry dropped into the calcium lactate aqueous solution gels, forming gel-like granulated particles.

[0046] The granulated particles are dried while immersed in an aqueous calcium lactate solution in a container. By evaporating the aqueous calcium lactate solution in the container, the granulated particles 100 of the first embodiment shown in Figure 1 are produced.

[0047] The rare earth elements and oxygen (O) contained in the first region 10 of the granulated particles 100 originate from the rare earth oxides in the raw material powder. Furthermore, the additive elements contained in the first region 10 of the granulated particles 100 originate, for example, from the sintering aid.

[0048] The calcium (Ca), carbon (C), and oxygen (O) contained in the second region 20 of the granulated particles 100 are thought to originate from the calcium lactate aqueous solution.

[0049] The crystals contained in the second region 20 of the granulated particles 100 are thought to have precipitated from the calcium lactate aqueous solution when the granulated particles were dried. In addition to the calcium lactate aqueous solution, a calcium chloride aqueous solution can also be used as the gelling solution.

[0050] Next, the operation and effects of the granulated particles for the thermal storage material according to the first embodiment will be described.

[0051] The granulated particles for the cold storage material are subjected to a heat treatment for sintering to produce the cold storage material particles. The produced cold storage material particles are then filled, for example, into the cold storage unit of a refrigerator.

[0052] It is preferable that the multiple refrigerant particles packed into the chiller have minimal variation in shape. If the shapes of the multiple refrigerant particles packed into the chiller vary, for example, the particles may become more prone to damage within the chiller, potentially causing clogging. If clogging occurs within the chiller, for example, the flow of the working medium may be obstructed, reducing the efficiency of the chiller. Therefore, the production of refrigerant particles with a stable shape is desirable.

[0053] Figure 2 is a schematic diagram of granulated particles for a comparative example of a thermal storage material particle. The granulated particles for a thermal storage material particle in the comparative example are granulated particles 200 for manufacturing thermal storage material particles. Figure 2 corresponds to Figure 1 of the first embodiment.

[0054] The granulated particles 200 of the comparative example differ from the granulated particles 100 of the first embodiment in that they do not have a second region 20 on their surface.

[0055] By subjecting the granulated particles 200 of the comparative example to a heat treatment for sintering, cold storage material particles are produced.

[0056] Granulated particles 200 before heat treatment do not necessarily possess high mechanical strength. Therefore, for example, the granulated particles 200 may deform during handling for heat treatment. If the granulated particles 200 deform, this may result in greater variation in the shape of the multiple refrigerant particles that fill the refrigerator.

[0057] The granulated particles 100 of the first embodiment have a second region 20 on their surface. Having the second region 20 on its surface, the granulated particles 100 possess higher mechanical strength compared to the granulated particles 200 of the comparative example. Therefore, deformation of the granulated particles 100 is suppressed, for example, during handling for heat treatment. Consequently, the shape of the refrigerant particles produced from the granulated particles 100 is stabilized. Thus, the variation in the shape of the multiple refrigerant particles filled into the cooler is reduced.

[0058] Therefore, damage to the refrigerant particles within the coolant storage unit is suppressed. Consequently, the efficiency of the refrigeration unit is improved.

[0059] Furthermore, the second region 20 of the granulated particle 100 disappears due to the heat treatment for sintering.

[0060] From the viewpoint of increasing the mechanical strength of the granulated particles 100, the atomic concentration of calcium (Ca) in the second region 20 is preferably 10 times or more, more preferably 50 times or more, and even more preferably 100 times or more, than the atomic concentration of calcium (Ca) in the first region 10.

[0061] From the viewpoint of increasing the mechanical strength of the granulated particles 100, the atomic concentration of calcium (Ca) in the second region 20 is preferably 1 atomic percent or more, more preferably 5 atomic percent or more, and even more preferably 10 atomic percent or more.

[0062] From the viewpoint of increasing the mechanical strength of the granulated particles 100, the atomic concentration of carbon (C) in the second region 20 is preferably 10 times or more than the atomic concentration of carbon (C) in the first region 10, more preferably 50 times or more, and even more preferably 100 times or more.

[0063] From the viewpoint of increasing the mechanical strength of the granulated particles 100, the atomic concentration of carbon (C) in the second region 20 is preferably 1 atomic percent or more, more preferably 10 atomic percent or more, and even more preferably 20 atomic percent or more.

[0064] From the viewpoint of increasing the mechanical strength of the granulated particles 100, it is preferable that the second region 20 contains crystals.

[0065] From the viewpoint of increasing the mechanical strength of the granulated particles 100, the ratio of the area of ​​the second region 20 to the sum of the area of ​​the first region 10 and the area of ​​the second region 20 is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more.

[0066] When the granulated particles 100 are heat-treated, from the viewpoint of eliminating the second region 20, the ratio of the area of ​​the second region 20 to the sum of the area of ​​the first region 10 and the area of ​​the second region 20 is preferably 95% or less, more preferably 90% or less, and even more preferably 80% or less.

[0067] From the viewpoint of increasing the mechanical strength of the granulated particles 100, the thickness of the second region 20 is preferably 10 μm or more, and more preferably 20 μm or more.

[0068] From the viewpoint of increasing the mechanical strength of the granulated particles 100, it is preferable that the first region 10 contains at least one additive element selected from the group consisting of aluminum (Al), zirconium (Zr), gallium (Ga), silicon (Si), germanium (Ge), and copper (Cu). The additive element can be included, for example, by adding it as a sintering aid in the form of an oxide at an amount of 5% by weight or less.

[0069] As described above, according to the first embodiment, it is possible to provide granulated particles for producing cold storage material particles that have high mechanical strength, stable shape, and improve the refrigeration performance of a refrigerator.

[0070] (Second Embodiment) The granulated particle group for thermal storage material particles of the second embodiment contains multiple granulated particles for thermal storage material particles of the first embodiment, and the proportion of granulated particles for thermal storage material particles of the first embodiment is 50% or more. Hereafter, some descriptions may be omitted if they overlap with those of the first embodiment.

[0071] The granulated particle group for the thermal storage material particles of the second embodiment includes a plurality of granulated particles 100 of the first embodiment, each having a first region 10 and a second region 20 on its surface. The proportion of granulated particles 100 included in the granulated particle group for the thermal storage material particles is 50% or more.

[0072] When the group of granulated particles for the cold storage material obtained by sintering the group of granulated particles for the cold storage material according to the second embodiment is filled into a refrigerator, the variation in the shape of the cold storage material particles is reduced. Therefore, damage to the cold storage material particles in the refrigerator is suppressed. As a result, the efficiency of the refrigerator is improved.

[0073] The particle size and aspect ratio of the granulated particles in the granulated particle group for the thermal storage material in the second embodiment can be determined by selecting, for example, 50 or more granulated particles from optical microscope images or SEM images and performing image analysis, and then calculating the average value of the selected granulated particles. The standard deviation can also be calculated, for example, from the individual values ​​of 50 or more selected granulated particles.

[0074] When the group of granulated particles for the cold storage material obtained by sintering the group of granulated particles for the cold storage material according to the second embodiment is filled into a refrigerator, from the viewpoint of further improving the refrigeration performance of the refrigerator, it is preferable that the number ratio of granulated particles 100 contained in the group of granulated particles for the cold storage material be 60% or more, and more preferably 70% or more.

[0075] As described above, according to the second embodiment, a group of granulated particles for cold storage material is provided for manufacturing a group of cold storage material particles that improves the refrigeration performance of a refrigerator.

[0076] (Third Embodiment) The cold storage material particles of the third embodiment are cold storage material particles obtained by sintering the granulated particles for cold storage material particles of the first embodiment.

[0077] A method for producing the cold storage material particles according to a third embodiment will be described.

[0078] The cold storage material particles of the third embodiment are manufactured by subjecting the granulated particles 100 of the first embodiment to, for example, heat treatment for degreasing and heat treatment for sintering. For example, the granulated particles 100 may be subjected to a heat treatment for sulfidation after the heat treatment for degreasing and before the heat treatment for sintering.

[0079] The degreasing heat treatment is carried out, for example, in an atmospheric environment. The temperature of the degreasing heat treatment is, for example, between 400°C and 700°C. The duration of the degreasing heat treatment is, for example, between 30 minutes and 6 hours.

[0080] When using oxides as the raw material powder for granulated particles 100 to produce cold storage material particles containing oxysulfides, the granulated particles 100 are subjected to sulfidation. In this case, heat treatment is performed in a sulfidation atmosphere. The sulfidation atmosphere is, for example, hydrogen sulfide (H ２ S), carbon sulfide (CS) ２ ), or methanethiol (CH ３ The gas contains sulfur atoms with a negative oxidation state, such as SH. The temperature for the sulfidation heat treatment is, for example, between 400°C and 600°C. The duration of the sulfidation heat treatment is, for example, between 1 hour and 5 hours.

[0081] The heat treatment for sintering the degreased granulated particles or the obtained oxysulfide is carried out, for example, in an inert gas atmosphere. The heat treatment temperature is, for example, 1100°C to 2000°C. The heat treatment temperature is, for example, 1200°C to 1800°C. The heat treatment time is, for example, 1 hour to 48 hours.

[0082] Furthermore, by heat treatment of the granulated particles 100, the second region 20 on the surface of the granulated particles 100 disappears.

[0083] In the third embodiment, the refrigerant particles are manufactured using granulated particles 100, which stabilizes the shape of the refrigerant particles and reduces variations in their shape. Consequently, damage to the refrigerant particles within the refrigerator is suppressed, thereby improving the efficiency of the refrigerator.

[0084] The thermal storage material particles of the third embodiment have a maximum volumetric specific heat of 0.5 J / cm² in the temperature range of 2 K to 10 K. ３ ・K) or higher.

[0085] As described above, according to the third embodiment, it is possible to provide a thermal storage material particle that has a stable shape and improves the refrigeration performance of a refrigerator.

[0086] (Fourth Embodiment) The fourth embodiment of the cooler is a cooler filled with a plurality of the cooler material particles of the third embodiment. For example, the cooler of the fourth embodiment is filled with a group of cooler material particles obtained by sintering the group of granulated particles for cooler material of the second embodiment.

[0087] As described above, according to the fourth embodiment, a cold storage device that improves the cooling performance of a refrigerator can be provided by filling it with the cold storage material particles of the third embodiment.

[0088] (Fifth Embodiment) The fifth embodiment of the refrigerator is a refrigerator equipped with a regenerator of the fourth embodiment, which is filled with a plurality of the regenerative material particles of the third embodiment. Hereafter, some descriptions that overlap with the third and fourth embodiments will be omitted.

[0089] Figure 3 is a schematic cross-sectional view showing the main components of the fifth embodiment of the refrigerator. The fifth embodiment of the refrigerator is a two-stage regenerative cryogenic refrigerator 400 used for cooling superconducting equipment and the like.

[0090] The cryogenic refrigerator 400 (refrigeration unit) comprises a first cylinder 111, a second cylinder 112, a vacuum vessel 113, a first regenerator 114, a second regenerator 115 (regenerator), a first seal ring 116, a second seal ring 117, a first regenerator material 118, a second regenerator material 119 (regenerator material 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.

[0091] The cryogenic refrigerator 400 has a vacuum vessel 113 in which a large-diameter first cylinder 111 and a small-diameter second cylinder 112 coaxially connected to the first cylinder 111 are installed. A first regenerator 114 is arranged in the first cylinder 111 so as to be able to reciprocate. A second regenerator 115, which is an example of a regenerator according to the fourth embodiment, is arranged in the second cylinder 112 so as to be able to reciprocate.

[0092] A first seal ring 116 is positioned between the first cylinder 111 and the first regenerator 114. A second seal ring 117 is positioned between the second cylinder 112 and the second regenerator 115.

[0093] The first cooler 114 is filled with a first coolant 118, such as a Cu mesh. The second cooler 115 is filled with a plurality of coolant particles of the third embodiment as a second coolant 119.

[0094] The second cooler 115 may be divided by a metal mesh material and comprise multiple packing layers of coolant. When the second cooler 115 is divided into multiple packing layers, at least one packing layer is filled with a group of coolant particles consisting of multiple coolant particles of the third embodiment, and is combined with at least one group of coolant particles selected from, for example, a group of lead coolant particles, a group of bismuth coolant particles, a group of tin coolant particles, a group of holmium copper coolant particles, a group of erbium nickel coolant particles, a group of erbium cobalt coolant particles, and a group of gadolinium aluminum oxide coolant particles.

[0095] The combination of thermal storage materials shall be such that the group with the highest specific heat peak temperature is designated as the first group of thermal storage material particles, the group with the lowest specific heat peak temperature is designated as the second group of thermal storage material particles, and the combinations shall be made so that the peak specific heat temperatures progressively decrease.

[0096] In the case of a two-layer type, examples include using a holmium copper cold storage particle group as the first cold storage particle group and a particle group containing the cold storage particle according to the third embodiment as the second cold storage particle group. In the case of a three-layer type, examples include using at least one cold storage particle group selected from a lead cold storage particle group, a bismuth cold storage particle group, and a tin cold storage particle group as the first cold storage particle group, using a holmium copper cold storage particle group as the second cold storage particle group, and a particle group containing the cold storage particle according to the third embodiment as the third cold storage particle group.

[0097] Holmium copper refrigerant particles are, for example, HoCu ２ Alternatively, HoCu is preferable. The erbium nickel refrigerant particles are, for example, ErNi or Er ３ It is preferable that it be Ni.

[0098] The first cooler 114 and the second cooler 115 each have passages for a working medium provided in the gaps between the first coolant 118 and the second coolant 119, respectively. The working medium is helium gas.

[0099] 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 is colder than the first cooling stage 122, is formed at the bottom of the second expansion chamber 121.

[0100] The two-stage cryogenic refrigerator 400 described above is supplied with a high-pressure working medium from a compressor 124. The supplied working medium passes through the first thermal storage material 118 filled in the first regenerator 114 and reaches the first expansion chamber 120. Then it passes through the second thermal storage material 119 filled in the second regenerator 115 and reaches the second expansion chamber 121.

[0101] During this process, the working medium is cooled by supplying thermal energy to the first and second cold storage materials 118 and 119. The working medium that has passed between the first and second cold storage materials 118 and 119 expands in the first and second expansion chambers 120 and 121, generating cold. Then, the first cooling stage 122 and the second cooling stage 123 are cooled.

[0102] The expanded working medium flows in opposite directions between the first and second thermal storage materials 118 and 119. The working medium is discharged after receiving thermal energy from the first and second thermal storage materials 118 and 119. The regenerative cryogenic refrigerator 400 is configured such that as the reheating effect improves during this process, the thermal efficiency of the working medium cycle improves, and even lower temperatures can be achieved.

[0103] The chiller of the fifth embodiment has a second chiller 115 into which a plurality of the cold storage material particles of the third embodiment are filled as the second cold storage material 119. At least a portion of the second cold storage material 119 is the cold storage material particles of the third embodiment.

[0104] In the third embodiment, the plurality of thermal storage material particles have a ratio of 4πA / L, where L is the perimeter of the projection image of each thermal storage material particle and A is the actual area of ​​the projection image. ２ Preferably, the percentage of materials with a circularity R of 0.5 or less is 5% or less.

[0105] Although the GM chiller has been described above as an example of a chiller, the chiller may be any other chiller equipped with the regenerator of the fourth embodiment, such as a Stirling chiller or a pulse tube chiller.

[0106] As described above, according to the fifth embodiment, a refrigerator with excellent properties can be realized by using thermal storage material particles with excellent properties.

[0107] (Sixth Embodiment) The cryopump of the sixth embodiment is equipped with the refrigerator of the fifth embodiment. Hereafter, some descriptions that overlap with the fifth embodiment will be omitted.

[0108] Figure 4 is a cross-sectional view showing the schematic configuration of a cryopump according to the sixth embodiment. The cryopump according to the sixth embodiment is a cryopump 500 equipped with the regenerative cryogenic refrigerator 400 of the fifth embodiment.

[0109] The cryopump 500 includes a cryopanel 501 for condensing or adsorbing gas molecules, a regenerative cryogenic refrigerator 400 for cooling the cryopanel 501 to a predetermined cryogenic temperature, a shield 503 provided between the cryopanel 501 and the regenerative cryogenic refrigerator 400, a baffle 504 provided at the intake port, and a ring 505 for changing the exhaust velocity of argon, nitrogen, hydrogen, etc.

[0110] According to the sixth embodiment, a cryopump with superior characteristics can be realized by using a refrigerator with superior characteristics. Furthermore, by using the cryopump of the sixth embodiment in semiconductor manufacturing equipment, the long-term reliability of the semiconductor manufacturing equipment can be improved, and the number of maintenance cycles for the semiconductor manufacturing equipment can be reduced. As a result, this contributes to improving the quality of the semiconductors manufactured and reducing manufacturing costs.

[0111] (Seventh Embodiment) The superconducting magnet of the seventh embodiment is equipped with the refrigerator of the fifth embodiment. Hereafter, some descriptions that overlap with the fifth embodiment will be omitted.

[0112] Figure 5 is a perspective view showing the schematic configuration of a superconducting magnet according to the seventh embodiment. The superconducting magnet of the seventh embodiment is a superconducting magnet 600 for a magnetic levitation train, for example, which is equipped with the regenerative cryogenic refrigerator 400 of the fifth embodiment.

[0113] The superconducting magnet 600 for the magnetic levitation train comprises a superconducting coil 601, a liquid helium tank 602 for cooling the superconducting coil 601, a liquid nitrogen tank 603 to prevent the evaporation of liquid helium, a laminated insulation material 605, a power lead 606, a permanent current switch 607, and a regenerative cryogenic refrigerator 400.

[0114] According to the seventh embodiment, a superconducting magnet with excellent properties can be realized by using a refrigerator with excellent properties.

[0115] (Eighth Embodiment) The nuclear magnetic resonance imaging apparatus of the eighth embodiment is equipped with the refrigerator of the fifth embodiment. Hereinafter, some descriptions that overlap with the fifth embodiment will be omitted.

[0116] Figure 6 is a cross-sectional view showing the schematic configuration of a nuclear magnetic resonance imaging apparatus according to the eighth embodiment. The nuclear magnetic resonance imaging (MRI) apparatus of the eighth embodiment is a nuclear magnetic resonance imaging apparatus 700 equipped with a regenerative cryogenic refrigerator 400 according to the fifth embodiment.

[0117] 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 for non-uniformity of the generated magnetic field, a gradient magnetic field coil 702 that provides a magnetic field gradient to the measurement area, a radio wave transmitting and receiving probe 703, a cryostat 705, and a radiative adiabatic shield 706. A regenerative cryogenic refrigerator 400 is used to cool the superconducting static magnetic field coil 701.

[0118] According to the eighth embodiment, a nuclear magnetic resonance imaging apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0119] (Ninth Embodiment) The nuclear magnetic resonance apparatus of the ninth embodiment is equipped with the refrigerator of the fifth embodiment. Hereafter, some descriptions that overlap with the fifth embodiment will be omitted.

[0120] Figure 7 is a cross-sectional view showing the schematic configuration of a nuclear magnetic resonance apparatus according to the ninth embodiment. The nuclear magnetic resonance (NMR) apparatus of the ninth embodiment is a nuclear magnetic resonance apparatus 800 equipped with a regenerative cryogenic refrigerator 400 according to the fifth embodiment.

[0121] The nuclear magnetic resonance spectrometer 800 includes a superconducting static magnetic field coil 802 for applying a magnetic field to a sample such as organic matter placed in a sample tube 801, a high-frequency oscillator 803 for applying radio waves to the sample tube 801 in the magnetic field, and an amplifier 804 for amplifying the induced current generated in a coil (not shown) around the sample tube 801. It also includes a regenerative cryogenic refrigerator 400 for cooling the superconducting static magnetic field coil 802.

[0122] According to the ninth embodiment, a nuclear magnetic resonance apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0123] (Tenth Embodiment) The magnetic field applied single crystal pulling apparatus of the tenth embodiment is equipped with the refrigerator of the fifth embodiment. Hereinafter, some descriptions that overlap with the fifth embodiment will be omitted.

[0124] Figure 8 is a perspective view showing the schematic configuration of a magnetic field applied single crystal pulling apparatus according to the tenth embodiment. The magnetic field applied single crystal pulling apparatus of the tenth embodiment is a magnetic field applied single crystal pulling apparatus 900 equipped with a regenerative cryogenic refrigerator 400 according to the fifth embodiment.

[0125] The magnetic field applied single crystal pulling apparatus 900 comprises a single crystal pulling section 901 having a crucible for melting raw materials, a heater, a single crystal pulling mechanism, etc., a superconducting coil 902 for applying a static magnetic field to the molten raw materials, a lifting mechanism 903 for the single crystal pulling section 901, current leads 905, a heat shield plate 906, and a helium container 907. A regenerative cryogenic refrigerator 400 is used for cooling the superconducting coil 902.

[0126] According to the tenth embodiment, a magnetic field applied single crystal pulling apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0127] (Eleventh Embodiment) The helium recondenser of the eleventh embodiment is equipped with the refrigerator of the fifth embodiment. Hereinafter, some descriptions that overlap with the fifth embodiment will be omitted.

[0128] Figure 9 is a schematic diagram showing the general configuration of the helium recondenser according to the 11th embodiment. The helium recondenser according to the 11th embodiment is a helium recondenser 1000 equipped with the regenerative cryogenic refrigerator 400 of the 5th embodiment.

[0129] The helium recondenser 1000 comprises a regenerative cryogenic refrigerator 400, an evaporation pipe 1001, and a liquefaction pipe 1002.

[0130] The helium recondenser 1000 can recondense helium gas evaporated from a liquid helium apparatus equipped with a superconducting magnet, such as a superconducting magnet, a nuclear magnetic resonance (NMR) apparatus, a nuclear magnetic resonance imaging (MRI) apparatus, a physical property measurement system (PPMS), or a magnetic property measurement system, to produce liquid helium.

[0131] Helium gas is introduced from a liquid helium apparatus (not shown) through evaporation pipe 1001 to the helium recondenser 1000. The helium gas is cooled to 4K, below the liquefaction temperature of helium, by a regenerative cryogenic refrigerator 400. The condensed liquid helium returns to the liquid helium apparatus through liquefaction pipe 1002.

[0132] According to the eleventh embodiment, a helium recondenser with excellent properties can be realized by using a refrigerator with excellent properties.

[0133] (Twelfth Embodiment) The dilution refrigerator of the twelfth embodiment is equipped with the refrigerator of the fifth embodiment. Hereafter, some descriptions that overlap with the fourth embodiment will be omitted.

[0134] Figure 10 is a schematic diagram showing the general configuration of the dilution refrigerator of the twelfth embodiment. The dilution refrigerator of the twelfth embodiment is a dilution refrigerator 1100 equipped with the regenerative cryogenic refrigerator 400 of the fifth embodiment.

[0135] The dilution refrigerator 1100 comprises a mixing chamber 1101, a distillation chamber 1102, a circulation pump 1103, a Joule-Thomson valve 1104, and a regenerative cryogenic refrigerator 400.

[0136] Helium has two isotopes: normal helium-4 (4He) with an atomic weight of 4, and lighter helium-3 (3He) with an atomic weight of 3. The dilution refrigerator 1100 can achieve extremely low temperatures, for example, below 0.1 K, by utilizing the heat of dilution when mixing helium-4 and helium-3.

[0137] A mixture of liquid helium 4 and liquid helium 3 exists in the mixing chamber 1101. An interface exists between the phase-separated liquid helium 4 and liquid helium 3 in the mixing chamber 1101. The mixing chamber 1101 has the lowest temperature. The temperature of the mixing chamber is, for example, less than 0.1 K.

[0138] The fractional distillation chamber 1102 is connected to the mixing chamber 1101. The fractional distillation chamber 1102 is maintained at, for example, 0.5 K. In the fractional distillation chamber 1102, only helium-3 selectively evaporates and becomes a gas.

[0139] The circulation pump 1103 has the function of circulating the helium 3, which has turned into a gas.

[0140] The cryogenic refrigerator 400 has the function of cooling gaseous helium-3 to, for example, 4K.

[0141] The Joule-Thomson valve 1104 has the function of liquefying helium 3 cooled to, for example, 4K.

[0142] The dilution refrigerator 1100 can achieve extremely low temperatures, for example, below 0.1 K, by forcibly dissolving liquid helium 3 in liquid helium 4 in the mixing chamber 1101.

[0143] According to the eleventh embodiment, a dilution refrigerator with excellent properties can be realized by using a refrigerator with excellent properties.

[0144] The following describes examples, comparative examples, and evaluation results relating to the granulated particles for thermal storage material particles of the first embodiment.

[0145] (Example 1) Gd ２ O ３ Powder and Al ２ O ３ A slurry was prepared by adding the sintering aid to an aqueous sodium alginate solution and mixing for 12 hours. ２ O ３The powder is a raw material powder for granulated particles used in thermal storage materials. Sodium alginate aqueous solution was added to the raw material powder so that the sodium alginate content was 2.3% by weight. The prepared slurry was added dropwise to calcium lactate aqueous solution. The calcium lactate aqueous solution is a gelling solution. A syringe was used to drop the slurry. The syringe bore was 510 μm, and the distance from the tip of the syringe to the surface of the calcium lactate aqueous solution was 100 mm.

[0146] The slurry, dropped using a syringe, was held in the gelling solution for 5 hours. The slurry gelled, forming granulated particles. The granulated particles were then immersed in the gelling solution and dried in the container until the gelling solution evaporated completely.

[0147] After drying, the surface of the obtained granulated particles was observed using SEM imaging. The particle size of the granulated particles was 400 μm. The aspect ratio of the granulated particles was 1.2. In addition, the standard deviation (SD) of the aspect ratio was calculated for 50 granulated particles to check for variations in shape.

[0148] A first region and a second region were observed on the surface of the granulated particles. The atomic concentrations of elements on the surface of the granulated particles were measured. The first region contained 36 atomic percent gadolinium (Gd), 49 atomic percent oxygen (O), and 14 atomic percent aluminum (Al). Calcium (Ca) and carbon (C) in the first region were below the detection limit.

[0149] The second region contained 11 atomic percent calcium (Ca), 46 atomic percent carbon (C), 40 atomic percent oxygen (O), and 3 atomic percent gadolinium (Gd). The amount of aluminum (Al) in the second region was below the detection limit.

[0150] The second region contained needle-shaped crystals. The shape of the crystals contained in the second region was needle-shaped. The thickness of the second region was 30 μm. The ratio of the area of ​​the second region to the sum of the areas of the first and second regions (area ratio of the second region) was 55%.

[0151] The granulated particles were degreased at 600°C for 6 hours in an atmospheric environment. After degreasing, the granulated particles were sintered by heat treatment at 1300°C for 12 hours in a pressurized atmosphere of inert gas to obtain refrigerant particles. No region corresponding to the second region was observed on the surface of the refrigerant particles.

[0152] The mechanical strength required for the thermal storage particles was evaluated when the thermal storage particles were filled into the regenerators of a refrigerator and the refrigerator was operated. Each manufactured thermal storage particle was filled into a cylindrical container with a diameter of 15 mm and a height of 5 mm. A sufficient amount of thermal storage particles was filled to fix the particles in place within the cylindrical container and prevent them from moving freely. An amplitude of 2 mm and a maximum acceleration of 400 m / s² were applied relative to the container. ２ The simple harmonic motion of 1 × 10 ８ The treatment was administered multiple times. As a result, the percentage (by weight) of destroyed thermal storage material particles was confirmed.

[0153] (Example 2) Raw material powder is Gd ２ O ３ From powder, Y ２ O ３ Granulated particles were produced using the same manufacturing method as in Example 1, except that the material was changed to powder, and their respective properties were measured.

[0154] (Example 3) Raw material powder is Gd ２ O ３ From powder, EU ２ O ３ The powder was changed, and the sintering aid was changed to SiO ２ Except for the above, granulated particles were produced using the same manufacturing method as in Example 1, and their respective properties were measured.

[0155] (Example 4) Raw material powder is Gd ２ O ３ From powder, Tb ２ O ３ The powder was changed, and the sintering aid was changed to ZrO ２ Except for the above, granulated particles were produced using the same manufacturing method as in Example 1, and their respective properties were measured.

[0156] (Comparative Example) Granulated particles and cold storage material particles were manufactured in the same manner as in the Example, except that after forming the granulated particles, the granulated particles were removed from the gelling solution before drying and the particles were dried.

[0157] No second region was observed on the surface of the granulated particles. The average aspect ratio was 1.2. However, several deformed granulated particles with an aspect ratio of up to 1.8 were observed, confirming a large variation in shape. Furthermore, a mechanical strength test similar to that in Example 1 was performed on the sintered refrigerant particles to confirm the proportion of fractured refrigerant particles.

[0158] Table 1 summarizes the evaluation results of granulated particles and thermal storage particles from the examples and comparative examples. The granulated particles for thermal storage particles according to the embodiment have high strength, which prevents deformation during the manufacturing process and results in small variations in shape. Therefore, the variation in shape of the thermal storage particles after sintering is small, and the packing efficiency when the thermal storage particle group is filled into the regenerator is improved. As a result, the rate of thermal storage particle breakage due to vibrations during operation of the refrigerator can be significantly reduced. Consequently, the long-term reliability of the refrigerator can be improved.

[0159]

[0160] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. For example, components of one embodiment may be replaced or modified with components of another embodiment. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0161] 10 First Region 20 Second Region 100 Granulated Particles (Granulated Particles for Cold Storage Material) 115 Second Cold Storage Unit (Cold Storage Unit) 119 Second Cold Storage Material (Cold Storage Material Particles) 200 Cold Storage Material Particles 400 Cold Storage Type Cryogenic Refrigerator (Refrigerator) 500 Cryopump 600 Superconducting Magnet 700 Nuclear Magnetic Resonance Imaging System 800 Nuclear Magnetic Resonance System 900 Magnetic Field-Applied Single Crystal Pulling System 1000 Helium Recondenser 1100 Dilution Refrigerator

Claims

1. Granulated particles for cold storage material particles, comprising a rare earth oxide containing at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and having a first region on its surface containing the at least one rare earth element and oxygen (O), and a second region containing calcium (Ca), carbon (C), and oxygen (O).

2. The granulated particle for thermal storage material according to claim 1, wherein the first region contains or does not contain calcium (Ca), and the atomic concentration of calcium (Ca) in the second region is greater than the atomic concentration of calcium (Ca) in the first region.

3. The granulated particles for thermal storage material according to claim 2, wherein the atomic concentration of calcium (Ca) in the second region is 10 times or more the atomic concentration of calcium (Ca) in the first region.

4. Granulated particles for thermal storage material particles according to claim 2, wherein the atomic concentration of calcium (Ca) in the second region is 1% or more, and the atomic concentration of calcium (Ca) in the first region is less than 1%.

5. Granulated particles for thermal storage material particles according to claim 1, wherein the first region contains or does not contain carbon (C), and the atomic concentration of carbon (C) in the second region is greater than the atomic concentration of carbon (C) in the first region.

6. Granulated particles for thermal storage material particles according to claim 5, wherein the atomic concentration of carbon (C) in the second region is 10 times or more the atomic concentration of carbon (C) in the first region.

7. Granulated particles for thermal storage material particles according to claim 5, wherein the atomic concentration of carbon (C) in the second region is 1% or more, and the atomic concentration of carbon (C) in the first region is less than 1%.

8. Granulated particles for thermal storage material particles according to claim 1, wherein the second region includes crystals.

9. Granulated particles for cold storage material particles according to claim 8, wherein the crystals are plate-shaped, columnar, or needle-shaped.

10. The granulated particles for thermal storage material according to claim 1, wherein the ratio of the area of ​​the second region to the sum of the areas of the first region and the second region is 30% or more.

11. The granulated particle for cold storage material particles according to claim 1, wherein the thickness of the second region is 10 μm or more.

12. The granulated particle for thermal storage material according to claim 1, wherein the first region further comprises at least one element selected from the group consisting of aluminum (Al), zirconium (Zr), gallium (Ga), silicon (Si), germanium (Ge), and copper (Cu).

13. Granulated particles for cold storage material particles according to claim 1, wherein the particle size is 50 μm or more and 7 mm or less.

14. Granulated particles for thermal storage material particles according to claim 1, wherein the aspect ratio is 1 or more and 5 or less.

15. A group of granulated particles for cold storage materials, comprising multiple granulated particles for cold storage materials, wherein the proportion of the granulated particles for cold storage materials described in claim 1 is 50% or more.

16. A refrigerant particle obtained by sintering a granulated particle for refrigerant particle according to any one of claims 1 to 14.

17. The maximum volumetric specific heat in the temperature range of 2K to 10K is 0.5 J / cm². ３ - The thermal storage material particles according to claim 16, wherein the particle size is K or greater.

18. A group of granulated particles for refrigerant particles obtained by sintering the group of refrigerant particles for refrigerant particles described in claim 15.

19. A cooler filled with a plurality of the coolant particles described in claim 16.

20. A refrigerator equipped with the coolant storage device described in claim 19.

21. A cryopump comprising the refrigerator described in claim 20.

22. A superconducting magnet equipped with the refrigerator described in claim 20.

23. A nuclear magnetic resonance imaging apparatus comprising the refrigerator described in claim 20.

24. A nuclear magnetic resonance apparatus comprising the refrigerator described in claim 20.

25. A magnetic field applied single crystal pulling apparatus equipped with the refrigerator described in claim 20.

26. A helium recondenser comprising the refrigerator described in claim 20.

27. A dilution refrigerator equipped with the refrigerator described in claim 20.

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