Two-stage regenerative cryogenic refrigerator, cryopump and dilution refrigerator

Abstract

To provide a two-stage regenerative cryogenic refrigerator including regenerative material particles with high volumetric specific heat and high strength.SOLUTION: A two-stage regenerative cryogenic refrigerator includes a vacuum vessel, a first cylinder provided in the vacuum vessel, a second cylinder provided in the vacuum vessel, coaxially connected to the first cylinder, and having a diameter smaller than that of the first cylinder, a first regenerator that is provided in the first cylinder and in which a first regenerative material is stored, and a second regenerator that is provided in the second cylinder and in which a second regenerative material is stored. The second regenerative material contains a rare earth oxysulfide containing a rare earth element, a garnet-type rare earth oxide containing a rare earth element and Al, and an aluminum oxide, and a ratio of an X-ray diffraction peak intensity of the garnet-type rare earth oxide to an X-ray diffraction peak intensity of the rare earth oxysulfide is 0.1% or more and 40% or less.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] Embodiments of the present invention relate to a two-stage regenerative cryogenic refrigerator, a cryopump, and a dilution refrigerator. [Background technology]

[0002] In recent years, superconducting technology has made remarkable progress, and as its application fields expand, the development of high-performance and highly reliable cryogenic refrigerators has become essential. Such cryogenic refrigerators are required to maintain high thermal efficiency for a long period of time.

[0003] In a cryogenic refrigerator, multiple regenerators are placed inside a regenerator. For example, cold is generated by heat exchange between the regenerators and helium gas passing through the regenerator. For example, superconducting MRI devices and cryopumps use refrigerators with refrigeration cycles such as the Gifford-McMahon (GM) system, Stirling system, or pulse tube system.

[0004] High-performance refrigerators are also essential for magnetic levitation trains, which use superconducting magnets to generate magnetic force. Furthermore, high-performance refrigerators are now being used in superconducting energy storage systems (SMES) and magnetic field-applied single crystal growing systems for producing high-quality silicon wafers. Active efforts are also being made to develop and commercialize pulse tube refrigerators, which are expected to offer even higher reliability.

[0005] Furthermore, in the superconducting magnets and MRI devices mentioned above, the liquid helium used evaporates, making replenishing it a problem. In recent years, the helium depletion problem has become more serious, making it difficult to obtain, and affecting the industrial sector.

[0006] To reduce the consumption of liquid helium and ease the burden of maintenance such as replenishment, helium recondensing devices that recondense evaporated helium have been put into practical use and are in high demand. These helium recondensing devices also use GM refrigerators or pulse tube refrigerators to cool the helium to a temperature of 4K in order to liquefy it.

[0007] In addition, GM refrigerators and pulse tube refrigerators can be used to liquefy gases other than helium or to prevent evaporation when storing liquefied gases. An example of a gas other than helium is hydrogen. Since the boiling point of liquefied hydrogen is approximately 20 K, evaporation of liquefied hydrogen can be reduced by keeping the temperature below 20 K.

[0008] In refrigerators equipped with a regenerator, a working medium such as compressed helium (He) gas flows in one direction through a regenerator housing the regenerator material, supplying its thermal energy to the regenerator material. The expanded working medium then flows in the opposite direction through the regenerator, receiving thermal energy from the regenerator material. As the heat recovery effect in this process improves, the thermal efficiency of the working medium cycle improves, making it possible to achieve lower temperatures.

[0009] The higher the specific heat per unit volume of the regenerator material, the more heat energy the regenerator material can store, improving the refrigeration capacity of the refrigerator. Therefore, it is desirable to install a regenerator material with a high specific heat at low temperatures on the low-temperature side of the regenerator, and a regenerator material with a high specific heat at high temperatures on the high-temperature side.

[0010] Depending on the composition of the regenerator material, it exhibits a high volumetric specific heat in a specific temperature range. Therefore, by combining regenerator materials with different compositions that exhibit a high volumetric specific heat in the target temperature range, the regenerator capacity can be increased, and the refrigeration capacity of the refrigerator can be improved.

[0011] In previous refrigerators, freezing at 4K was achieved by combining metallic refrigerant materials such as lead (Pb), bismuth (Bi) and tin (Sn) on the high-temperature side with metallic magnetic refrigerant materials such as Er3Ni, ErNi and HoCu2 on the low-temperature side below 20K.

[0012] In recent years, attempts have been made to improve the refrigeration capacity of refrigerators by replacing some of the metallic magnetic regenerator particles with ceramic magnetic regenerator particles such as Gd2O2S, Tb2O2S, Dy2O2S, Ho2O2S, and GdAlO3, which have high specific heat in the temperature range from 2K to 10K.

[0013] Furthermore, when refrigerators are used to prevent the evaporation of superconducting equipment or liquefied gases, they are required to maintain high thermal efficiency for a long period of time. During the cycle of heat exchange between the regenerator material and the working substance, mechanical vibrations are applied to the regenerator material. For this reason, while the refrigerator is operating, the regenerator material is constantly vibrating at the refrigerator's operating temperature. If the amount of regenerator material damaged by this vibration exceeds a certain level, the flow of the working medium, such as helium (He) gas, becomes poor, and thermal efficiency decreases. If the regenerator material is severely damaged, the flow of the working medium, such as He gas, will stop, and the refrigerator will stop.

[0014] Therefore, to improve the long-term reliability of refrigerators, the regenerator material must be able to withstand long-term vibrations at the refrigerator operating temperature without breaking down to a certain extent. In particular, ceramic magnetic regenerator particles are brittle, so they must have high strength. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-73661 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-213252 [Patent Document 3] International Publication No. 2018 / 025581 Summary of the Invention [Problem to be solved by the invention]

[0016] The problem to be solved by the present invention is to provide a two-stage regenerative cryogenic refrigerator equipped with regenerative material particles having high volumetric specific heat and high strength.

[0017] Patent Documents 2 and 3 report that adding a compound such as Al2O3 (alumina) to a rare earth oxysulfide regenerator material improves its strength. Patent Document 2 also reports that reducing the size of crystal grains improves its strength. However, to further improve the reliability of refrigerators, it is necessary to further improve its strength while maintaining a high volumetric specific heat. [Means for solving the problem]

[0018] The two-stage regenerative cryogenic refrigerator of the embodiment includes a vacuum vessel, a first cylinder provided in the vacuum vessel, a second cylinder provided in the vacuum vessel, coaxially connected to the first cylinder, and having a diameter smaller than that of the first cylinder, a first regenerator provided in the first cylinder and accommodating a first regenerator material, and a second regenerator provided in the second cylinder and accommodating a second regenerator material, the second regenerator material being regenerator particles, and the regenerator particles may be selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er. a second regenerator including a rare earth oxysulfide 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, a garnet-type rare earth oxide containing Al and 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 aluminum oxide, wherein the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide to the X-ray diffraction peak intensity of the rare earth oxysulfide is 0.1% or more and 40% or less. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 2 is a schematic cross-sectional view of the regenerator material of the first embodiment. [Figure 2] FIG. 4 is a schematic cross-sectional view of a regenerator material according to a modified example of the first embodiment. [Figure 3] FIG. 6 is a schematic cross-sectional view of a cold storage material particle according to a second embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view of a granulated particle according to a second embodiment. [Figure 5] FIG. 10 is a schematic cross-sectional view showing the configuration of a main part of a refrigerator according to a fourth embodiment. [Figure 6] FIG. 10 is a schematic cross-sectional view showing the general configuration of a cryopump according to a fifth embodiment. [Figure 7] FIG. 10 is a schematic perspective view showing the general configuration of a superconducting magnet according to a sixth embodiment. [Figure 8] FIG. 13 is a schematic cross-sectional view showing the schematic configuration of a nuclear magnetic resonance imaging apparatus according to a seventh embodiment. [Figure 9] FIG. 13 is a schematic diagram showing the schematic configuration of a nuclear magnetic resonance spectrometer according to an eighth embodiment. [Figure 10] FIG. 13 is a schematic perspective view showing the general configuration of a magnetic field application type single crystal pulling apparatus according to a ninth embodiment. [Figure 11] FIG. 22 is a schematic diagram showing the general configuration of a helium recondensation device according to a tenth embodiment. [Figure 12] FIG. 22 is a schematic diagram showing the general configuration of a dilution refrigerator according to an eleventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same or similar components will be designated by the same reference numerals, and the description of components that have already been described may be omitted as appropriate.

[0021] In this specification, the term "extremely low temperature" refers to a temperature range in which the superconducting phenomenon can be industrially utilized, for example, a temperature range of 20 K or less.

[0022] (First embodiment) The regenerator material of the first embodiment is a rare earth oxysulfide 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 a rare earth oxysulfide 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), The material includes a garnet-type rare earth oxide containing aluminum (Al) and at least one rare earth element selected from the group consisting of dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and aluminum oxide, wherein the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide to the X-ray diffraction peak intensity of the rare earth oxysulfide is 0.1% or more and 40% or less.

[0023] 1 is a schematic cross-sectional view of a regenerator material 100 according to the first embodiment. The regenerator material 100 according to the first embodiment is a ceramic magnetic regenerator material.

[0024] The regenerator material 100 of the first embodiment includes a rare earth oxysulfide 10, a garnet-type rare earth oxide 11, and aluminum oxide 12. Hereinafter, aluminum oxide may be referred to as alumina.

[0025] The regenerator material 100 of the first embodiment has a maximum volumetric specific heat of 0.5 J / (cm 3 ·K) or more. The cold storage material 100 of the first embodiment has a volumetric specific heat of 0.5 J / (cm ) in the temperature range of 2.5 K or more and 10 K or less. 3 ·K) or more. The cold storage material 100 of the first embodiment has a volumetric specific heat of 0.55 J / (cm 3·K) or more. The cold storage material 100 of the first embodiment has a volumetric specific heat of 0.6 J / (cm 3 ·K) or more.

[0026] The rare earth oxysulfide 10 contained in the regenerator material 100 of the first embodiment 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), oxygen (O), and sulfur (S). The chemical composition of the rare earth oxysulfide 10 is, for example, represented by the general formula R 2±0.1 O2S 1±0.1 (wherein R represents 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).

[0027] In the rare earth oxysulfide 10 having the chemical composition represented by the general formula above, the maximum value of the volumetric specific heat and the temperature at which the maximum value of the volumetric specific heat is exhibited vary depending on the selected rare earth element. Therefore, the specific heat characteristics can be adjusted by appropriately adjusting the type and ratio of the rare earth element. The rare earth element contained in the rare earth oxysulfide 10 is, for example, at least one element selected from the group consisting of Gd, Tb, Dy, Ho, and Er. The rare earth oxysulfide 10 contained in the regenerator material 100 of the first embodiment may contain, for example, two or more types of rare earth elements.

[0028] The rare earth oxysulfide 10 is, for example, crystalline. The crystal structure of the rare earth oxysulfide 10 contained in the regenerator material 100 of the first embodiment is, for example, Ce2O2S type, and its space group is P-3m.

[0029] The cold storage material 100 of the first embodiment is mainly composed of, for example, rare earth oxysulfide 10. Of the substances contained in the cold storage material 100 of the first embodiment, for example, the volume ratio of the rare earth oxysulfide 10 is the largest. Of the substances contained in the cold storage material 100 of the first embodiment, for example, the molar ratio of the rare earth oxysulfide 10 is the largest.

[0030] The garnet-type rare earth oxide 11 contained in the regenerator material 100 of the first embodiment 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), aluminum (Al), and oxygen (O).

[0031] The garnet-type rare earth oxide 11 is, for example, crystalline. The garnet-type rare earth oxide 11 contained in the regenerator material 100 of the first embodiment has a garnet-type crystal structure, and its space group is Ia-3d.

[0032] The at least one rare earth element contained in the garnet-type rare earth oxide 11 and the at least one rare earth element contained in the rare earth oxysulfide 10 are, for example, the same rare earth element. Also, the at least one rare earth element contained in the garnet-type rare earth oxide 11 and the at least one rare earth element contained in the rare earth oxysulfide 10 are, for example, the same rare earth element.

[0033] The aluminum oxide 12 contained in the regenerator material 100 of the first embodiment is, for example, crystalline.

[0034] The cold storage material 100 of the first embodiment contains, for example, 0.001 atomic % to 10 atomic % of Group 2 elements in total. The cold storage material 100 may also contain, for example, two or more types of Group 2 elements.

[0035] The Group 2 element is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). The Group 2 element is, for example, at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

[0036] The cold accumulating material may contain, for example, two or more types of Group 2 elements. The cold accumulating material does not necessarily contain any Group 2 elements. The Group 2 elements contained in the cold accumulating material 100 of the first embodiment are contained in the garnet-type rare earth oxide 11, for example.

[0037] The detection of elements contained in the regenerator material 100 of the first embodiment and the measurement of the atomic concentration of the elements can be performed, for example, by dissolving the regenerator material 100 in a liquid and using inductively coupled plasma atomic emission spectroscopy (ICP-AES). Alternatively, the detection can be performed using energy dispersive X-ray spectroscopy (EDX) or wavelength dispersive X-ray spectroscopy (WDX).

[0038] The compounds contained in the regenerator material 100 of the first embodiment can be identified, for example, by powder X-ray diffraction measurement (XRD) or observation of an electron backscatter diffraction image using a scanning electron microscope (SEM), or observation using a transmission electron microscope.

[0039] The crystal structure of the compound contained in the regenerator material 100 of the first embodiment can be identified by powder X-ray diffraction measurement (XRD), observation of an electron backscatter diffraction image using a scanning electron microscope (SEM), or observation using a transmission electron microscope.

[0040] In the regenerator material 100 of the first embodiment, the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 is 0.1% or more and 40% or less. The X-ray diffraction peak intensities of the rare earth oxysulfide 10 and the garnet-type rare earth oxide 11 are measured by powder X-ray diffraction measurement.

[0041] For the powder X-ray diffraction measurement, for example, a D8 ADVANCE manufactured by Bruker is used. For example, Cu is used as the radiation source for the measurement. For the identification of phases in the powder X-ray diffraction measurement, for example, DIFFRAC.SUITE, an analysis software manufactured by Bruker, is used.

[0042] In powder X-ray diffraction measurements, the maximum peak of Ce2O2S-type rare earth oxysulfide (space group P-3m) is, for example, at 28 degrees or more and 32 degrees or less. The maximum peak of garnet-type rare earth oxide (space group Ia-3d) is, for example, at 32 degrees or more and 34 degrees or less. The maximum peak of aluminum oxide is, for example, at 34 degrees or more and 36 degrees or less.

[0043] The ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 can be determined, for example, from the ratio of the intensity of the maximum peak present at an angle of 28 degrees to 32 degrees and the intensity of the maximum peak present at an angle of 32 degrees to 34 degrees. Note that the angle at which the maximum peak intensity exists varies depending on the composition of the compound. Therefore, the phases of the rare earth oxysulfide 10 and the garnet-type rare earth oxide 11 are identified using analysis software, and the ratio of the maximum peak intensities of each phase is determined.

[0044] The presence of rare earth elements and Al in the garnet-type rare earth oxide 11 can be confirmed by comprehensively assessing the results of powder X-ray diffraction measurements and the results of observations using a scanning electron microscope-energy dispersive X-ray analyzer (SEM-EDX). Specifically, based on the fact that regions with high contrast in the backscattered electron image of the SEM contain a large amount of light elements, the crystalline phases detected in the XRD measurements are assigned to regions with different contrasts in the SEM image. As a result, by performing SEM-EDX measurements on the contrast regions assigned to the garnet-type rare earth oxide 11, the elements contained in the garnet-type rare earth oxide 11 can be confirmed.

[0045] The grain size (particle size) of the compound contained in the cold storage material 100 of the first embodiment is, for example, 1 μm or more and 10 μm or less. For example, the grain size of the rare earth oxysulfide 10, the garnet-type rare earth oxide 11, and the aluminum oxide 12 contained in the cold storage material 100 is 1 μm or more and 10 μm or less.

[0046] The grain size of the compound contained in the regenerator material 100 of the first embodiment can be determined by observing a backscattered electron image of a scanning electron microscope (SEM) of a cross section of the regenerator material 100. The grain size is calculated, for example, by the following formula. d=1.56C / (MN) (d: grain size, C: length of a line drawn arbitrarily on a high-resolution image such as an SEM, N: number of crystal grains on the line drawn arbitrarily, M: magnification of the image)

[0047] The method for manufacturing the cold storage material 100 of the first embodiment is not particularly limited. For example, the cold storage material can be manufactured by mixing raw material powders using a ball mill or the like to prepare a raw material mixture, and then molding and sintering the obtained raw material mixture. Rare earth oxides or rare earth oxysulfides can be used as the raw material powder. The type and proportion of the rare earth oxides or rare earth oxysulfides are adjusted according to the target composition of the cold storage material.

[0048] The raw material powder has a specific surface area of ​​1m 2 / g or more 5m 2By adding alumina in an amount of 0.1 atomic % or less to the total amount of the raw material powder, a cold storage material containing garnet-type rare earth oxide 11 containing a rare earth element and Al can be manufactured. The amount of alumina used in the raw material powder is preferably 0.1 atomic % or more and 30 atomic % or less with respect to the total amount of the raw material powder.

[0049] For example, by using a substance containing a Group 2 element as the raw material powder, it is possible to manufacture a regenerator material containing a garnet-type rare earth oxide 11 containing a Group 2 element. The substance containing a Group 2 element can be a carbonate containing a Group 2 element, an oxide containing a Group 2 element, a nitride containing a Group 2 element, or a carbide containing a Group 2 element.

[0050] The concentration of the Group 2 element contained in the regenerator material is adjusted by adjusting the amount of the carbonate containing the Group 2 element, the oxide containing the Group 2 element, the nitride containing the Group 2 element, or the carbide containing the Group 2 element.

[0051] When rare earth oxides are used as the raw material powder, the molded body is sulfurized. In this case, heat treatment is performed in a sulfurization atmosphere. The sulfurization atmosphere contains a gas containing sulfur atoms with a negative oxidation state, such as hydrogen sulfide (HS), carbon sulfide (CS), or methanethiol (CHSH). The heat treatment temperature is, for example, 400°C or higher and 700°C or lower. The heat treatment time is, for example, 1 hour or higher and 8 hours or lower.

[0052] The heat treatment for sintering the obtained oxysulfide is carried out, for example, in a pressurized inert gas atmosphere. The heat treatment temperature is, for example, 1300°C or higher and 2000°C or lower. The heat treatment temperature is, for example, 1350°C or higher and 1700°C or lower. The heat treatment time is, for example, 1 hour or higher and 48 hours or lower.

[0053] The regenerator material 100 of the first embodiment may be a sintered body of regenerator particles containing, for example, a rare earth oxysulfide 10, a garnet-type rare earth oxide 11, and aluminum oxide 12.

[0054] Next, the function and effect of the regenerator material of the first embodiment will be described.

[0055] In cryocoolers used for cooling superconducting equipment, a regenerator material is housed in a regenerator. For example, cold is generated by heat exchange between the regenerator material and helium gas passing through the regenerator. To improve the refrigeration capacity of the refrigerator, the regenerator material must have a high volumetric specific heat.

[0056] Furthermore, the regenerator material installed in a cryogenic refrigerator is constantly vibrated while the refrigerator is in operation. Therefore, if the regenerator material is weak, it may crack or chip. If cracks or chips occur, the performance of the refrigerator will decrease. Therefore, improving the strength of the regenerator material is required to improve the reliability of the refrigerator.

[0057] The upper limit of the volumetric specific heat of the regenerator material is limited by the composition of the material, while the strength of the regenerator material can be improved by reducing the grain size or by adding alumina, as previously reported in publicly known literature.

[0058] Regarding reducing the grain size, there is a practical limit to the minimum grain size. Therefore, it is difficult to further improve strength by controlling the grain size. Also, improving strength by adding alumina has the drawback that the volumetric specific heat decreases as the amount of alumina added increases.

[0059] The regenerator material 100 of the first embodiment has a maximum volumetric specific heat of 0.5 J / (cm 3 Therefore, the regenerator material 100 of the first embodiment has a high volumetric specific heat.

[0060] The regenerator material 100 of the first embodiment achieves a high volumetric specific heat by including the rare earth oxysulfide 10 having a high volumetric specific heat. The regenerator material 100 is a ceramic magnetic regenerator material having a high volumetric specific heat.

[0061] Furthermore, the cold storage material 100 of the first embodiment has increased strength due to the inclusion of the garnet-type rare earth oxide 11. This makes it possible to suppress a decrease in the proportion of the rare earth oxysulfide 10, which would otherwise be caused by increasing the amount of alumina added. This makes it possible to suppress a decrease in the volumetric specific heat of the cold storage material 100, thereby achieving a high volumetric specific heat.

[0062] The regenerator material of the first embodiment has a volumetric specific heat of 0.5 J / (cm) in the temperature range of 2.5 K or more and 10 K or less. 3 ·K) or more. For example, the volumetric specific heat in the temperature range of 2K to 8K is 0.55J / (cm 3 ·K) or more. For example, the volumetric specific heat in the temperature range of 4K to 7K is 0.6J / (cm 3 ·K) or more.

[0063] As described above, the cold storage material 100 of the first embodiment has a high volumetric specific heat. Therefore, for example, a cold storage unit containing the cold storage material 100 of the first embodiment has high cold storage performance. Furthermore, a refrigerator including a cold storage unit containing the cold storage material 100 of the first embodiment exhibits high refrigeration capacity.

[0064] The regenerator material 100 of the first embodiment includes a rare earth oxysulfide 10, a garnet-type rare earth oxide 11 containing a rare earth element and Al, and aluminum oxide 12. The ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 is 0.1% or more and 40% or less.

[0065] When the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 is 0.1% or more, the strength of the cold storage material 100 is improved. When the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 exceeds 40%, the abundance ratio of the rare earth oxysulfide 10 decreases, resulting in a significant decrease in volumetric specific heat. In other words, when the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 is 40% or less, the cold storage material 100 can achieve a high volumetric specific heat.

[0066] Furthermore, the cold storage material 100 of the first embodiment has a high strength even when the grain size of the included compounds is large, compared to a cold storage material that does not include the garnet-type rare earth oxide 11. This is thought to be because the garnet-type rare earth oxide 11 is a cubic crystal and therefore has high symmetry, and can isotropically dissipate force even when an external force is applied.

[0067] The strength-enhancing effect of including the garnet-type rare earth oxide 11 is not affected by the amount of other subphases. For example, when alumina or a perovskite-type rare earth oxide is included as a subphase, the strength-enhancing effect is achieved as long as the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 is 0.1% or more and 40% or less, regardless of the ratio of the X-ray diffraction peak intensity of the alumina or the perovskite-type rare earth oxide to the X-ray diffraction peak intensity of the rare earth oxysulfide 10. This is thought to be because the strength-enhancing effect is derived solely from the presence of the garnet-type rare earth oxide 11 and is not affected by other subphases.

[0068] From the viewpoint of improving the strength of the regenerator material 100, the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 is preferably 1% or more, and more preferably 3% or more. Furthermore, from the viewpoint of realizing a high volumetric specific heat of the regenerator material 100, the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less.

[0069] The Group 2 element has the effect of promoting the formation of the garnet-type rare earth oxide 11. This is thought to be because the Group 2 element occupies the rare earth site of the garnet-type rare earth oxide 11, thereby stabilizing the garnet structure. Therefore, by including the Group 2 element in the regenerator material 100, the strength of the regenerator material 100 is further improved.

[0070] The atomic concentration of the Group 2 element in the cold storage material 100 is preferably 0.001 atomic % or more, more preferably 0.01% or more, and even more preferably 0.05% or more. When the atomic concentration of the Group 2 element exceeds the lower limit, the generation of the garnet-type rare earth oxide 11 is promoted, and the strength of the cold storage material 100 is improved.

[0071] The atomic concentration of the Group 2 element contained in the cold storage material 100 is preferably 10 atomic % or less, and more preferably 5 atomic % or less. The Group 2 element does not contribute to improving the volumetric specific heat of the cold storage material 100. Therefore, when the atomic concentration of the Group 2 element is below the upper limit, the cold storage material 100 can achieve a high volumetric specific heat.

[0072] The Group 2 element contained in the cold storage material 100 is preferably at least one element selected from the group consisting of Mg, Ca, Sr, and Ba. When the Group 2 element is one of the above elements, the strength of the cold storage material 100 can be improved and the cold storage material 100 can have a high volumetric specific heat.

[0073] Furthermore, the Group 2 elements have the effect of promoting sintering, and therefore can lower the sulfurization and sintering temperatures.

[0074] (Variation)

[0075] A modification of the regenerator material of the first embodiment includes a perovskite rare earth oxide.

[0076] FIG. 2 is a schematic cross-sectional view of a regenerator material according to a modified example of the first embodiment.

[0077] The regenerator material 101 of the modified example of the first embodiment includes a rare earth oxysulfide 10, a garnet-type rare earth oxide 11, aluminum oxide 12, and a perovskite-type rare earth oxide 13.

[0078] The perovskite rare earth oxide 13 contained in the regenerator material 101 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), aluminum (Al), and oxygen (O).

[0079] The at least one rare earth element contained in the perovskite-type rare earth oxide 13, the at least one rare earth element contained in the rare earth oxysulfide 10, and the at least one rare earth element contained in the garnet-type rare earth oxide 11, for example, are the same rare earth element. Also, the at least one rare earth element contained in the perovskite-type rare earth oxide 13, the at least one rare earth element contained in the rare earth oxysulfide 10, and the at least one rare earth element contained in the garnet-type rare earth oxide 11, for example, are the same rare earth element.

[0080] The perovskite rare earth oxide 13 is, for example, crystalline. The crystal structure of the perovskite rare earth oxide 13 contained in the regenerator material 101 is perovskite, and its space group is Pnma.

[0081] In powder X-ray diffraction measurement, the maximum peak of the perovskite rare earth oxide 13 is, for example, at 33.5 degrees or more and 35 degrees or less. The maximum peak intensity of the perovskite rare earth oxide 13 is lower than the maximum peak intensity of the rare earth oxysulfide 10. The maximum peak intensity of the perovskite rare earth oxide 13 is lower than the maximum peak intensity of the garnet rare earth oxide 11, for example.

[0082] As described above, according to the first embodiment and the modified examples, a regenerator material having excellent properties such as a high volumetric specific heat and high strength can be realized.

[0083] (Second embodiment) The cold storage material particles of the second embodiment are formed from the cold storage material of the first embodiment, and have a particle size of 50 μm or more and 3 mm or less. Hereinafter, some descriptions that overlap with the first embodiment may be omitted.

[0084] 3 is a schematic cross-sectional view of a cold storage material particle of the second embodiment. The cold storage material particle 200 of the second embodiment is formed from the cold storage material 100 of the first embodiment.

[0085] The shape of the cold storage material particle 200 of the second embodiment is, for example, spherical. The particle size of the cold storage material particle 200 is 50 μm or more and 3 mm or less.

[0086] The particle size of the cold storage material particle 200 is a circle-equivalent diameter. The circle-equivalent diameter is the diameter of a perfect circle that corresponds to the area of ​​a figure observed in an image such as an optical microscope image or a scanning electron microscope image (SEM image). The particle size of the cold storage material particle 200 can be determined, for example, by image analysis of the optical microscope image or the SEM image.

[0087] The aspect ratio of the cold storage material particle 200 is, for example, not less than 1 and not more than 5. The aspect ratio of the cold storage material particle is the ratio of the long diameter of the cold storage material particle 200 to the short diameter of the cold storage material particle 200.

[0088] The regenerator particles 200 of the second embodiment contain a rare earth oxysulfide 10 , a garnet-type rare earth oxide 11 , and aluminum oxide 12 .

[0089] The method for manufacturing the cold accumulator particles 200 of the second embodiment is not particularly limited. When manufacturing the cold accumulator particles 200, for example, raw material powder is used to form granulated particles that serve as raw materials for the cold accumulator particles 200. Thereafter, the granulated particles are sintered to manufacture the cold accumulator particles 200.

[0090] In the first method for forming granulated particles, for example, raw material powders are mixed using a ball mill or the like to prepare a raw material mixture, and the obtained raw material mixture is then molded (granulated) into granules by a rolling granulation method, an agitation granulation method, an extrusion method, an atomization method (spray method), a press molding method, or the like to form granulated particles.

[0091] In the first method, a binder is added to adhere the raw material powders together, thereby improving the strength of the granulated particles. Examples of the binder include polyvinyl alcohol, polyvinyl butyral, carboxymethyl cellulose, acrylic resin, and polyethylene glycol. The amount of binder added is, for example, 0.01% by weight or more and 20% by weight or less.

[0092] The raw material powder can be made of rare earth oxides or rare earth oxysulfides, and the type and ratio of the rare earth oxides or rare earth oxysulfides are adjusted according to the target composition of the regenerator particles.

[0093] For example, if the raw material powder has a specific surface area of ​​1m 2 / g or more 5m 2By using alumina having a content of 0.1 atomic % or less and a substance containing a Group 2 element, it is possible to produce cold storage material particles containing a garnet-type rare earth oxide. The amount of alumina used in the raw material powder is, for example, 0.1 atomic % or more and 30 atomic % or less relative to the total amount of the raw material powder. Furthermore, as the substance containing a Group 2 element, a carbonate containing a Group 2 element, an oxide containing a Group 2 element, a nitride containing a Group 2 element, or a carbide containing a Group 2 element can be used.

[0094] In the second method for forming granulated particles, a slurry is prepared by adding raw material powder to an aqueous alginic acid solution and mixing the mixture. The slurry is then dropped into a gelling solution, and the resulting granulated particles are formed by gelling. The second method granulates particles by promoting gelation through a crosslinking reaction caused by polyvalent metal ions contained in the gelling solution. The slurry can be dropped into the gelling solution using, for example, a dropper, burette, pipette, syringe, dispenser, or inkjet. Hereinafter, the second method for granulating particles is referred to as the alginic acid gel method.

[0095] In the alginate gel method, the particle size and aspect ratio can be changed by adjusting the viscosity of the slurry, the diameter of the nozzle when dropping, or the distance between the tip of the nozzle and the liquid surface of the gelling solution. The diameter of the nozzle is, for example, 50 μm or more and 3000 μm or less. The viscosity of the slurry is, for example, 0.1 mPa·s or more and 1,000,000 mPa·s or less. The distance between the tip of the nozzle and the liquid surface of the gelling solution is, for example, 0.1 mm or more and 1,000 mm or less.

[0096] When a dispenser is used for discharging, any of an air pulse dispenser, a plunger dispenser, and a piezo dispenser may be used as the device.

[0097] Inkjet printers are broadly divided into continuous and on-demand types based on their ejection method, but either type may be used. Furthermore, on-demand types are further divided into three types: piezo, thermal, and valve, but any of these may be used.

[0098] The slurry dropped into the gelling solution using a dropper, burette, pipette, syringe, dispenser, inkjet, etc. is gelled by being held in the gelling solution. By gelling the slurry, granulated particles containing the raw material powder of the cold storage material are formed. The holding time of the slurry in the gelling solution is, for example, 10 minutes to 48 hours.

[0099] The alginic acid aqueous solution used in the alginic acid gel method is, for example, a sodium alginate aqueous solution, an ammonium alginate aqueous solution, or a potassium alginate aqueous solution.

[0100] The gelling solution may be an aqueous solution containing a Group 2 element, such as an aqueous solution of calcium lactate, an aqueous solution of calcium chloride, an aqueous solution of manganese (II) chloride, an aqueous solution of magnesium sulfate, an aqueous solution of beryllium sulfate, an aqueous solution of strontium nitrate, an aqueous solution of barium chloride, or an aqueous solution of barium hydroxide.

[0101] In addition, aqueous solutions of aluminum chloride, aluminum nitrate, aluminum lactate, iron(II) chloride, iron(III) chloride, copper(II) chloride, nickel(II) chloride, and cobalt(II) chloride can be used as the gelling solution.

[0102] By using a calcium lactate aqueous solution, a calcium chloride aqueous solution, a magnesium sulfate aqueous solution, a beryllium sulfate aqueous solution, a strontium nitrate aqueous solution, a barium chloride aqueous solution, or a barium hydroxide aqueous solution as the gelling solution, Group II elements such as calcium, magnesium, beryllium, strontium, and barium can be contained in the ice accumulator particles.

[0103] At least two types of aqueous solutions containing different metal elements selected from the group consisting of calcium lactate aqueous solution, calcium chloride aqueous solution, magnesium sulfate aqueous solution, beryllium sulfate aqueous solution, strontium nitrate aqueous solution, barium chloride aqueous solution, and barium hydroxide aqueous solution are mixed together and used as a gelling solution, thereby making it possible to incorporate two or more types of Group 2 elements into the ice storage material particles.

[0104] 4 is a schematic cross-sectional view of a granulated particle of the second embodiment. The granulated particle 201 of the second embodiment is a granulated particle for producing the cold storage material particle 200 of the second embodiment. The granulated particle 201 of the second embodiment is a raw material for the cold storage material particle 200 of the second embodiment.

[0105] 4, the granulated particles 201 of the second embodiment include, for example, raw material powder 201a, a binder 201b, and voids 201c. The granulated particles 201 may contain, for example, a dispersion medium instead of the binder 201b. The granulated particles 201 may contain, for example, a gelling agent instead of the binder 101b. The raw material powder 201a may contain, for example, a sintering aid for promoting sintering when producing the regenerator particles 200.

[0106] The granulated particles 201 are formed by granulating raw material powder 201a by, for example, the first method or the second method described above. The granulated particles 201 are formed by, for example, binding a plurality of raw material powders 201a with a binder 201b.

[0107] The granulated particles 201 are, for example, a gel. The granulated particles 201 are formed, for example, by gelling a plurality of raw material powders 201a using a gelling agent (gelling solution). The raw material powders 201a have, for example, lost their independent mobility and are in a solidified aggregate state.

[0108] The particle size of the granulated particle 201 is, for example, 70 μm or more and 5 mm or less. The aspect ratio of the granulated particle 201 is, for example, 1 or more and 5 or less.

[0109] By degreasing the granulated particles 201, a certain amount of organic components can be removed. If the raw material is an oxide, if the degreasing is insufficient, sulfurization will not proceed sufficiently, and the required amount of oxysulfide will not be produced. Furthermore, if the degreasing is insufficient and too much organic components remain, the density of the sintered particles will be low. This will weaken the strength of the regenerator particles 200, making them unable to withstand use in a refrigerator.

[0110] If debinding is excessive, the organic components that ensure strength are lost, resulting in a decrease in the strength of the granulated particles 201 after debinding, and cracks or chips occurring in the particles. The debinding temperature is, for example, 400°C or higher and 800°C or lower, and the debinding time is 30 minutes or higher and 12 hours or lower.

[0111] When a rare earth oxide is used as the raw material powder, the granulated particles 201 are sulfurized. In this case, heat treatment is performed in a sulfurization atmosphere. The sulfurization atmosphere contains a gas containing sulfur atoms with a negative oxidation number, such as hydrogen sulfide (HS), carbon sulfide (CS), or methanethiol (CHSH). The heat treatment temperature is, for example, 400°C or higher and 700°C or lower. The heat treatment time is, for example, 1 hour or higher and 8 hours or lower.

[0112] The heat treatment for sintering the granulated particles 201 is carried out, for example, in a pressurized inert gas atmosphere. The heat treatment temperature is, for example, 1300° C. or higher and 1700° C. or lower. The heat treatment time is, for example, 1 hour or higher and 48 hours or lower.

[0113] Next, the function and effect of the cold storage material particles of the second embodiment will be described.

[0114] The cold storage material particles 200 of the second embodiment are formed from the cold storage material of the first embodiment. Therefore, the cold storage material particles 200 of the second embodiment have a maximum volumetric specific heat of 0.5 J / (cm) in the temperature range of 2 K or more and 10 K or less. 3 Therefore, the regenerator particles 200 of the second embodiment have a high volumetric specific heat.

[0115] The cold storage material particles 200 of the second embodiment have a volumetric specific heat of 0.5 J / (cm) in the temperature range of 2.5 K or more and 10 K or less. 3 ·K) or more. For example, the volumetric specific heat in the temperature range of 2K to 8K is 0.55J / (cm 3 ·K) or more. For example, the volumetric specific heat in the temperature range of 4K to 7K is 0.6J / (cm 3 ·K) or more.

[0116] Since the cold storage material particles 200 of the second embodiment have a high volumetric specific heat, a cold storage unit containing the cold storage material particles 200 of the second embodiment has high cold storage performance. Also, a refrigerator equipped with a cold storage unit containing the cold storage material particles 200 of the second embodiment exhibits high refrigeration capacity.

[0117] The regenerator particles 200 of the second embodiment include a rare earth oxysulfide 10, a garnet-type rare earth oxide 11 containing a rare earth element and Al, and aluminum oxide 12. The ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 is 0.1% or more and 40% or less.

[0118] When the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 is 0.1% or more, the strength of the cold storage material particles 200 is improved. When the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 exceeds 40%, the abundance ratio of the rare earth oxysulfide 10 decreases, and the volumetric specific heat decreases significantly. In other words, when the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 is 40% or less, the cold storage material particles 200 can achieve a high volumetric specific heat.

[0119] Furthermore, the cold storage material particles 200 of the second embodiment have a higher strength even if the grain size of the included compound is larger than that of cold storage material particles that do not contain the garnet-type rare earth oxide 11. This is thought to be because the garnet-type rare earth oxide 11 is a cubic crystal and therefore has high symmetry, and can isotropically dissipate force even when an external force is applied.

[0120] The strength-enhancing effect of including the garnet-type rare earth oxide 11 is not affected by the amount of other subphases. For example, when alumina or a perovskite-type rare earth oxide is included as a subphase, the strength-enhancing effect is achieved as long as the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 is 0.1% or more and 40% or less, regardless of the ratio of the X-ray diffraction peak intensity of the alumina or the perovskite-type rare earth oxide to the X-ray diffraction peak intensity of the rare earth oxysulfide 10. This is thought to be because the strength-enhancing effect is derived solely from the presence of the garnet-type rare earth oxide 11 and is not affected by other subphases.

[0121] From the viewpoint of improving the strength of the regenerator particles 200, the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 is preferably 1% or more, and more preferably 3% or more. Furthermore, from the viewpoint of realizing a high volumetric specific heat of the regenerator particles 200, the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide 11 to the X-ray diffraction peak intensity of the rare earth oxysulfide 10 is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less.

[0122] The Group 2 element has the effect of promoting the formation of the garnet-type rare earth oxide 11. This is thought to be because the Group 2 element occupies the rare earth site of the garnet-type rare earth oxide 11, thereby stabilizing the garnet structure. Therefore, by including the Group 2 element in the regenerator particle 200, the strength of the regenerator particle 200 is improved.

[0123] The improved strength of the cold storage material particles 200 makes it difficult for the cold storage material particles 200 to break, thereby improving the reliability of a refrigerator equipped with a cold storage unit filled with the cold storage material particles 200.

[0124] The atomic concentration of the Group 2 element in the regenerator material particles 200 is preferably 0.001 atomic % or more, more preferably 0.01% or more, and more preferably 0.05% or more. When the atomic concentration of the Group 2 element exceeds the lower limit, the generation of the garnet-type rare earth oxide 11 is promoted, and the strength of the regenerator material particles 200 is improved.

[0125] The atomic concentration of the Group 2 element contained in the cold storage material particles 200 is preferably 10 atomic % or less, and more preferably 5 atomic % or less. The Group 2 element does not contribute to improving the volumetric specific heat of the cold storage material particles 200. Therefore, when the atomic concentration of the Group 2 element is below the upper limit, the cold storage material particles 200 can achieve a high volumetric specific heat.

[0126] By using a carbonate containing a Group 2 element, an oxide containing a Group 2 element, a nitride containing a Group 2 element, or a carbide containing a Group 2 element as the raw material powder, it is possible to manufacture the cold storage material particles 200 containing a Group 2 element. The concentration of the Group 2 element contained in the cold storage material particles 200 can be adjusted by adjusting the amount of the carbonate containing a Group 2 element, the oxide containing a Group 2 element, the nitride containing a Group 2 element, or the carbide containing a Group 2 element.

[0127] Furthermore, the Group 2 elements have the effect of promoting sintering, and therefore can lower the sulfurization and sintering temperatures.

[0128] In the second embodiment, the particle size of the cold storage material particles 200 is preferably 50 μm or more and 3 mm or less, more preferably 1 mm or less, and even more preferably 500 μm or less. When the particle size of the cold storage material particles 200 exceeds the above lower limit, the packing density of the cold storage material particles 200 in the cold storage unit decreases, the pressure loss of the working medium such as helium decreases, and the refrigeration performance of the refrigerator improves. On the other hand, when the particle size of the cold storage material particles 200 is below the above upper limit, the distance from the surface of the cold storage material particle 200 to the particle center becomes shorter, and heat transfer between the working medium and the cold storage material particles is more easily transmitted to the center of the cold storage material, improving the refrigeration performance of the refrigerator.

[0129] The aspect ratio of the cold storage material particles 200 is preferably 1 or more and 5 or less, and more preferably 1 or more and 2 or less. When the aspect ratio of the cold storage material particles 200 is below the upper limit value, the voids become uniform when the cold storage material particles 200 are filled into a cold storage unit, and the refrigeration performance of the refrigerator is improved.

[0130] As described above, according to the second embodiment, it is possible to realize regenerator particles having excellent properties such as a high volumetric specific heat and high strength.

[0131] (Third embodiment) The regenerator of the third embodiment is a regenerator filled with a plurality of the regenerator material of the first embodiment or the regenerator material particles of the second embodiment.

[0132] In the regenerator of the third embodiment, when the peripheral length of the projected image of the plurality of regenerator particles of the second embodiment is L and the actual area of ​​the projected image is A, the ratio is 4πA / L 2 It is preferable that the ratio of cold storage material particles having a circularity R of 0.5 or less is 5% or less.

[0133] The circularity R can be determined by image processing of the shapes of multiple cold storage material particles using an optical microscope. Cold storage material particles with a circularity R of 0.5 or less exhibit a shape with irregularities on the surface. When multiple cold storage material particles containing more than 5% of such cold storage material particles are packed into a cold storage unit, the voids formed by the cold storage material particles become non-uniform within the cold storage unit, and the packing becomes unstable. This can result in a decrease in cold storage performance when the working medium flows in. Furthermore, stresses applied to the cold storage material particles during packing or operation of the refrigerator can cause the cold storage material particles to move or break, generating fine particles and clogging the voids. This can reduce the refrigeration performance and long-term reliability of the refrigerator. It is more preferable that the circularity R of cold storage material particles be 0.5 or less, and even more preferable that it be 2% or less, and even more preferably 0%.

[0134] As described above, according to the third embodiment, a regenerator including a regenerator material or regenerator particles having excellent properties such as a high volumetric specific heat and high strength can be realized.

[0135] (Fourth embodiment) The refrigerator of the fourth embodiment is a refrigerator equipped with a cold storage unit filled with the cold storage material of the first embodiment or a plurality of cold storage material particles of the second embodiment. The refrigerator of the fourth embodiment is a refrigerator equipped with the cold storage unit of the third embodiment. Hereinafter, some of the description overlapping with the first, second, and third embodiments will be omitted.

[0136] 5 is a schematic cross-sectional view showing the main configuration of a refrigerator according to a fourth embodiment. The refrigerator according to the fourth embodiment includes the regenerator according to the third embodiment, which is filled with a plurality of the regenerator material according to the first embodiment or the regenerator particles according to the second embodiment. The refrigerator according to the fourth embodiment is a two-stage regenerator-type cryogenic refrigerator 400 used for cooling superconducting equipment and the like. The refrigerator according to the fourth embodiment is a two-stage GM refrigerator.

[0137] The regenerative cryogenic refrigerator 400 includes a first cylinder 111, a second cylinder 112, a vacuum vessel 113, a first regenerator 114, a second regenerator 115, a first seal ring 116, a second seal ring 117, a first regenerator material 118, a second regenerator material 119, a first expansion chamber 120, a second expansion chamber 121, a first cooling stage 122, a second cooling stage 123, and a compressor 124.

[0138] The regenerative 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 the regenerator of the third embodiment, is arranged in the second cylinder 112 so as to be able to reciprocate.

[0139] A first seal ring 116 is disposed between the first cylinder 111 and the first regenerator 114. A second seal ring 117 is disposed between the second cylinder 112 and the second regenerator 115.

[0140] The first regenerator 114 contains a first regenerator material 118 such as a Cu mesh. The second regenerator 115 contains a second regenerator material 119.

[0141] The first regenerator 114 and the second regenerator 115 each have a passage for the working medium provided in the gap between the first regenerator material 118 and the second regenerator material 119. The working medium is helium gas.

[0142] 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 front end wall of the second cylinder 112. A first cooling stage 122 is provided at the bottom of the first expansion chamber 120. A second cooling stage 123, which has a lower temperature than the first cooling stage 122, is formed at the bottom of the second expansion chamber 121.

[0143] The two-stage regenerative cryogenic refrigerator 400 described above is supplied with a high-pressure working medium from the compressor 124. The supplied working medium passes between the first regenerator materials 118 housed in the first regenerator 114 and reaches the first expansion chamber 120. Then, it passes between the second regenerator materials 119 housed in the second regenerator 115 and reaches the second expansion chamber 121.

[0144] 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 that has passed between 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 to generate cold. Then, the first cooling stage 122 and the second cooling stage 123 are cooled.

[0145] The expanded working medium flows in the opposite direction between the first and second cold storage materials 118 and 119. The working medium is discharged after receiving thermal energy from the first and second cold storage materials 118 and 119. The regenerative cryogenic refrigerator 400 is configured to improve the thermal efficiency of the working medium cycle as the heat recovery effect improves during this process, thereby achieving even lower temperatures.

[0146] The cold storage unit provided in the refrigerator of the fourth embodiment accommodates, for example, the cold storage material 100 of the first embodiment in the second cold storage unit 115 as at least a part of the second cold storage material 119. Also, for example, the second cold storage unit 115 may be filled with a plurality of cold storage material particles 200 of the second embodiment as at least a part of the second cold storage material 119. The plurality of cold storage material particles 200 of the second embodiment have an area ratio of 4πA / L, where L is the perimeter of the projected image of each cold storage material particle and A is the actual area of ​​the projected image. 2 It is preferable that the circularity R of 0.5 or less is 5% or less.

[0147] In the fourth embodiment, the regenerator of the third embodiment may include, for example, a plurality of regenerator material packed layers of different types of regenerator material. The different types of regenerator material may be separated by a mesh. The mesh is, for example, a metal mesh. At least one of the plurality of regenerator material packed layers includes the regenerator material 100 of the first embodiment or the regenerator material particles 200 of the second embodiment. In the refrigerator of the fourth embodiment, the regenerator material 100 of the first embodiment or a plurality of regenerator material particles 200 of the second embodiment is packed, for example, on the low-temperature side of the regenerator.

[0148] To improve the refrigeration capacity and long-term reliability of a refrigerator, it is desirable to improve the specific heat per unit volume of the regenerator material and the strength of the regenerator material. The refrigerator of the fourth embodiment is equipped with a regenerator material or regenerator particles having a high volumetric specific heat and high strength. This improves the refrigeration capacity and long-term reliability of the refrigerator.

[0149] For example, by using the refrigerator of the fourth embodiment in a magnetic levitation train, a helium recondenser, or the like, the long-term reliability of the magnetic levitation train and the helium recondenser can be improved.

[0150] As described above, according to the fourth embodiment, a refrigerator with excellent characteristics can be realized by using a regenerator material or regenerator particles with excellent characteristics.

[0151] (Fifth embodiment) The cryopump of the fifth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some of the description that overlaps with the fourth embodiment will be omitted.

[0152] 6 is a cross-sectional view showing a schematic configuration of a cryopump according to the fifth embodiment. The cryopump according to the fifth embodiment is a cryopump 500 including the regenerative cryogenic refrigerator 400 according to the fourth embodiment.

[0153] The cryopump 500 includes a cryopanel 501 that condenses or adsorbs gas molecules, a regenerative cryogenic refrigerator 400 that cools the cryopanel 501 to a predetermined cryogenic temperature, a shield 503 installed between the cryopanel 501 and the regenerative cryogenic refrigerator 400, a baffle 504 installed at the intake port, and a ring 505 that changes the pumping speed of argon, nitrogen, hydrogen, etc.

[0154] According to the fifth embodiment, a cryopump with excellent characteristics can be realized by using a refrigerator with excellent characteristics. Furthermore, by using the cryopump of the fifth embodiment in a semiconductor manufacturing apparatus, the long-term reliability of the semiconductor manufacturing apparatus can be improved.

[0155] (Sixth embodiment) The superconducting magnet of the sixth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some of the description overlapping with the fourth embodiment will be omitted.

[0156] 7 is a schematic perspective view showing the general configuration of a superconducting magnet according to the sixth embodiment. The superconducting magnet according to the sixth embodiment is, for example, a superconducting magnet 600 for a magnetic levitation train, which includes the regenerative cryogenic refrigerator 400 according to the fourth embodiment.

[0157] The superconducting magnet 600 for a magnetic levitation train includes a superconducting coil 601, a liquid helium tank 602 for cooling the superconducting coil 601, a liquid nitrogen tank 603 for preventing the evaporation of the liquid helium, a laminated insulation material 605, a power lead 606, a persistent current switch 607, and a regenerative cryogenic refrigerator 400.

[0158] According to the sixth embodiment, a superconducting magnet with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0159] (Seventh embodiment) The nuclear magnetic resonance imaging apparatus of the seventh embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some of the description overlapping with the fourth embodiment will be omitted.

[0160] 8 is a schematic cross-sectional view showing the general configuration of a nuclear magnetic resonance imaging apparatus according to the seventh embodiment. The nuclear magnetic resonance imaging (MRI) apparatus according to the seventh embodiment is a nuclear magnetic resonance imaging apparatus 700 equipped with the regenerative cryogenic refrigerator 400 according to the fourth embodiment.

[0161] The nuclear magnetic resonance imaging apparatus 700 includes a superconducting static magnetic field coil 701 that applies a spatially uniform and temporally stable static magnetic field to the human body, a correction coil (not shown) that corrects non-uniformity of the generated magnetic field, a gradient magnetic field coil 702 that applies a magnetic field gradient to the measurement region, a radio frequency wave transmitting / receiving probe 703, a cryostat 705, and a radiation heat insulating shield 706. A regenerative cryogenic refrigerator 400 is used to cool the superconducting static magnetic field coil 701.

[0162] According to the seventh embodiment, a nuclear magnetic resonance imaging apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0163] (Eighth embodiment) The nuclear magnetic resonance apparatus of the eighth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some of the description overlapping with the fourth embodiment will be omitted.

[0164] 9 is a schematic diagram showing a schematic configuration of a nuclear magnetic resonance (NMR) apparatus according to the eighth embodiment. The nuclear magnetic resonance (NMR) apparatus according to the eighth embodiment is a nuclear magnetic resonance apparatus 800 equipped with the regenerative cryogenic refrigerator 400 according to the fourth embodiment.

[0165] The nuclear magnetic resonance apparatus 800 includes a superconducting static magnetic field coil 802 that applies a magnetic field to a sample such as an organic substance placed in a sample tube 801, a high-frequency oscillator 803 that applies radio waves to the sample tube 801 in the magnetic field, and an amplifier 804 that amplifies an induced current generated in a coil (not shown) around the sample tube 801. The apparatus also includes a regenerative cryogenic refrigerator 400 that cools the superconducting static magnetic field coil 802.

[0166] According to the eighth embodiment, a nuclear magnetic resonance apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0167] (Ninth embodiment) The magnetic field application type single crystal pulling apparatus of the ninth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some of the description overlapping with the fourth embodiment will be omitted.

[0168] 10 is a schematic perspective view showing the schematic configuration of a magnetic field application type single crystal pulling apparatus according to the ninth embodiment. The magnetic field application type single crystal pulling apparatus according to the ninth embodiment is a magnetic field application type single crystal pulling apparatus 900 equipped with the regenerative cryogenic refrigerator 400 according to the fourth embodiment.

[0169] The magnetic field application type single crystal pulling apparatus 900 includes a single crystal pulling section 901 having a crucible for melting raw material, a heater, a single crystal pulling mechanism, etc., a superconducting coil 902 for applying a static magnetic field to the raw material melt, a lifting mechanism 903 for the single crystal pulling section 901, a current lead 905, a heat shield plate 906, and a helium container 907. A regenerative cryogenic refrigerator 400 is used to cool the superconducting coil 902.

[0170] According to the ninth embodiment, a magnetic field application type single crystal pulling apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0171] (Tenth embodiment) The helium recondensing device of the tenth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some of the description overlapping with the fourth embodiment will be omitted.

[0172] 11 is a schematic diagram showing the general configuration of a helium recondensation apparatus according to a tenth embodiment. The helium recondensation apparatus according to the tenth embodiment is a helium recondensation apparatus 1000 equipped with the regenerative cryogenic refrigerator 400 according to the fourth embodiment.

[0173] The helium recondensation device 1000 includes a regenerative cryogenic refrigerator 400 , an evaporation pipe 1001 , and a liquefaction pipe 1002 .

[0174] The helium recondensation device 1000 can recondense helium gas that evaporates from a liquid helium device provided in a device that uses liquid helium, such as a superconducting magnet, a nuclear magnetic resonance (NMR) device, a nuclear magnetic resonance imaging (MRI) device, a physical property measurement system (PPMS), or a magnetic property measurement system, to produce liquid helium.

[0175] Helium gas is introduced into the helium recondenser 1000 from a liquid helium device (not shown) through evaporation piping 1001. The helium gas is cooled to 4 K, which is below the liquefaction temperature of helium, by a regenerative cryogenic refrigerator 400. The condensed and liquefied liquid helium returns to the liquid helium device through liquefaction piping 1002.

[0176] According to the tenth embodiment, a refrigerator with excellent characteristics is used, thereby realizing a helium recondensing device with excellent characteristics.

[0177] (Eleventh embodiment) The dilution refrigerator of the eleventh embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some of the description overlapping with the fourth embodiment will be omitted.

[0178] 12 is a schematic diagram showing the general configuration of a dilution refrigerator according to the 11th embodiment. The dilution refrigerator according to the 11th embodiment is a dilution refrigerator 1100 equipped with the regenerative cryogenic refrigerator 400 according to the fourth embodiment.

[0179] The dilution refrigerator 1100 includes a mixing chamber 1101, a distillation chamber 1102, a circulation pump 1103, a Joule-Thomson valve 1104, and a regenerative cryogenic refrigerator 400.

[0180] Helium exists in two isotopes: normal helium 4 (4He), which has an atomic weight of 4, and lighter helium 3 (3He), which has 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 generated when helium 4 and helium 3 are mixed.

[0181] A mixture of liquid helium 4 and liquid helium 3 exists in the mixing chamber 1101. An interface between the phase-separated liquid helium 4 and liquid helium 3 exists in the mixing chamber 1101. The mixing chamber 1101 has the lowest temperature. The temperature of the mixing chamber is, for example, less than 0.1K.

[0182] The fractionation chamber 1102 is connected to the mixing chamber 1101. The fractionation chamber 1102 is maintained at, for example, 0.5 K. In the fractionation chamber 1102, only helium 3 is selectively evaporated to become a gas.

[0183] The circulation pump 1103 has a function of circulating the gaseous helium 3.

[0184] The regenerative cryogenic refrigerator 400 has a function of cooling gaseous helium 3 to, for example, 4K.

[0185] The Joule-Thomson valve 1104 has a function of liquefying helium 3 cooled to, for example, 4K.

[0186] The dilution refrigerator 1100 can achieve an extremely low temperature of, for example, less than 0.1 K by forcibly dissolving liquid helium 3 in liquid helium 4 in the mixing chamber 1101.

[0187] According to the eleventh embodiment, a dilution refrigerator with excellent characteristics can be realized by using a refrigerator with excellent characteristics. [Example]

[0188] Examples and comparative examples of the cold storage material of the first embodiment and the cold storage material particles of the second embodiment, as well as the evaluation results thereof, will be described below.

[0189] Example 1 Gd2O3 powder, Al2O3 powder, and CaCO3 powder were mixed and ground in a ball mill for 24 hours to prepare a raw material mixture. The Al2O3 powder has a specific surface area of ​​approximately 4 m 2 / g was used. Next, the obtained raw material mixture was dried and then granulated using a tumbling granulator to prepare granulated particles with a particle size of 0.3 to 0.5 mm. The obtained raw material mixture was molded to obtain a compact.

[0190] The compact and particles were sulfurized by heat treatment at 500°C for 4 hours in an atmosphere containing hydrogen sulfide (HS), and then sintered by heat treatment at 1350°C for 12 hours in a pressurized inert gas atmosphere.

[0191] The main component of the regenerator material and regenerator particles of Example 1 is gadolinium oxysulfide. Subphases include garnet-type rare earth oxide and alumina. The ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide to the X-ray diffraction peak intensity of the rare earth oxysulfide was 4%. The calcium concentration in the regenerator material and regenerator particles of Example 1 was 0.055 atomic %.

[0192] In order to evaluate the reliability when the cold storage material particles according to Example 1 are filled into a cold storage unit and a refrigerator is operated, the cold storage material particles according to Example 1 are filled into a cylindrical container having a diameter of 15 mm and a height of 5 mm at room temperature, and the container is cooled to a cryogenic temperature, and the temperature is measured with an amplitude of 2 mm and a maximum acceleration of 400 m / s. 2 Simple harmonic motion of 2×10 9 The weight percentage of the regenerator particles that were destroyed after the vibration test was 0.014%.

[0193] In the following examples and comparative examples, the mixing time of the raw material powder, the conditions of the sulfurization heat treatment, the conditions of the sintering heat treatment, etc. were adjusted to be appropriate conditions. In addition, the test conditions of the refrigerator were made equal.

[0194] Example 2 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that MgCO3 powder was used instead of CaCO3 powder.

[0195] Example 3 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that SrCO3 powder was used instead of CaCO3 powder.

[0196] Example 4 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that BaCO3 powder was used instead of CaCO3 powder.

[0197] Example 5 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that Tb2O3 powder was used instead of Gd2O3 powder.

[0198] Example 6 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that Dy2O3 powder was used instead of Gd2O3 powder.

[0199] Example 7 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 2, except that Ho2O3 powder was used instead of Gd2O3 powder.

[0200] Example 8 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that MgCO3 powder was used in addition to CaCO3 powder.

[0201] Example 9 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that SrCO3 powder was used in addition to CaCO3 powder.

[0202] (Examples 10 to 14) The cold accumulator and the cold accumulator particles were produced in the same manner as in Example 1, except that the weight of the CaCO3 powder was changed.

[0203] (Examples 15 to 17) A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that a part of the Gd2O3 powder was changed to Tb2O3, Dy2O3, and Ho2O3.

[0204] (Examples 18 to 21) The regenerator material and the regenerator particles were produced in the same manner as in Example 1, except that the specific surface area and amount of Al2O3 powder were changed.

[0205] Example 22 Gd2O3 powder and Al2O3 powder were added to a sodium alginate solution and mixed for 12 hours to create a slurry. The created slurry was then added dropwise to a calcium lactate solution, which served as a gelling solution. A syringe was used to add the slurry. The syringe had a diameter of 510 μm, and the distance from the tip of the syringe to the surface of the calcium lactate solution was 100 mm. The slurry was then filled into a mold, which was then immersed in the gelling solution.

[0206] The slurry dropped by syringe and the slurry filled into the mold were kept in the gelling solution for 5 hours.

[0207] The gelled granulated particles were then washed with pure water. The slurry filled in the mold was removed from the mold and washed with pure water to obtain a compact. After washing the compact and particles, they were dried. After drying the compact and particles, they were degreased, sulfurized and sintered.

[0208] The compact and particles were degreased at 600°C for 6 hours in an air atmosphere. After degreasing, the compact and particles were sulfurized by heat treatment at 500°C for 4 hours in an atmosphere containing hydrogen sulfide (HS). The compact and particles were sintered by heat treatment at 1350°C for 12 hours in a pressurized inert gas atmosphere.

[0209] Example 23 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 22, except that a magnesium chloride aqueous solution was used instead of the calcium lactate aqueous solution.

[0210] Example 24 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 22, except that an aqueous strontium chloride solution was used instead of an aqueous calcium lactate solution.

[0211] Example 25 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 22, except that a barium chloride aqueous solution was used instead of the calcium lactate aqueous solution.

[0212] Example 26 Except for using an air pulse dispenser instead of a syringe to drop the slurry, the cold storage particles were produced in the same manner as in Example 22. The nozzle diameter was 510 μm, and the distance from the nozzle tip to the liquid surface of the calcium lactate aqueous solution was 100 mm.

[0213] Example 27 Except for using a piezoelectric dispenser instead of a syringe to drop the slurry, the cold storage particles were produced in the same manner as in Example 22. The nozzle diameter was 510 μm, and the distance from the tip of the nozzle to the liquid surface of the calcium lactate aqueous solution was 100 mm.

[0214] Example 28 Except for using a continuous inkjet instead of a syringe to drop the slurry, the cold storage particles were produced in the same manner as in Example 22. The nozzle diameter was 510 μm, and the distance from the nozzle tip to the liquid surface of the calcium lactate aqueous solution was 100 mm.

[0215] (Examples 29 to 34) The cold accumulator particles of Examples 29 to 34 differ in particle size or aspect ratio from the cold accumulator particles of Example 26. When producing the cold accumulator particles of Examples 29 to 34, the nozzle diameter and the distance from the nozzle tip to the surface of the gelling solution were changed compared to when producing the cold accumulator particles of Example 26.

[0216] Example 35 The regenerator particles of Example 35 differ from those of Example 26 in that they contain perovskite-type GdAlO in addition to gadolinium oxysulfide, garnet-type rare earth oxide, and alumina. When producing the regenerator particles of Example 35, the firing temperature was changed to 1300°C compared to when producing the regenerator particles of Example 26.

[0217] (Comparative Example 1) The cold accumulator and cold accumulator particles of Comparative Example 1 differ from those of Example 1 in that the X-ray diffraction peak intensity ratio of the garnet-type rare earth oxide to the rare earth oxysulfide is as low as 0.08%. When producing the cold accumulator and cold accumulator particles of Comparative Example 1, the weight of alumina powder was reduced compared to when producing the cold accumulator and cold accumulator particles of Example 1.

[0218] (Comparative Example 2) The cold accumulator and cold accumulator particles of Comparative Example 2 differ from those of Example 1 in that the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide to the X-ray diffraction peak intensity of the rare earth oxysulfide is as high as 41%. When producing the cold accumulator and cold accumulator particles of Comparative Example 2, the weight of the alumina powder was increased compared to when producing the cold accumulator and cold accumulator particles of Example 1.

[0219] (Comparative Example 3) The cold accumulator and cold accumulator particles of Comparative Example 3 differ from those of Example 1 in that the atomic concentration of calcium is as low as 0.0008 atomic %. When producing the cold accumulator and cold accumulator particles of Comparative Example 3, the weight of CaCO3 powder was reduced compared to when producing the cold accumulator particles of Example 1.

[0220] Comparative Example 4 The cold accumulator and cold accumulator particles of Comparative Example 4 differ from those of Example 4 in that the atomic concentration of calcium is as high as 15 atomic %. When producing the cold accumulator and cold accumulator particles of Comparative Example 4, the weight of CaCO3 powder was increased compared to when producing the cold accumulator and cold accumulator particles of Example 1.

[0221] (Comparative Example 5) The cold accumulator and cold accumulator particles of Comparative Example 5 differ from those of Example 1 in that they do not contain garnet-type rare earth oxide. When producing the cold accumulator and cold accumulator particles of Comparative Example 5, the alumina powder had a specific surface area of ​​150 m compared to when producing the cold accumulator and cold accumulator particles of Example 1. 2 The calcination temperature was 1250°C. The constituent phases were gadolinium oxysulfide, alumina, and perovskite-type GdAlO3.

[0222] The ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide to the X-ray diffraction peak intensity of the rare earth oxysulfide of the regenerator material and regenerator material particles according to each Example and Comparative Example, particle size, aspect ratio, maximum volumetric specific heat, vibration test results, and percentage change in refrigerator performance before and after the vibration test are shown in Table 1. The molded body was used to measure the maximum volumetric specific heat, and regenerator particles were used to measure the other items.

[0223] To evaluate the refrigeration performance, 250g of regenerator particles were packed into the low-temperature side of the second-stage regenerator of the two-stage GM refrigerator shown in Figure 5, while 250g of Pb regenerator was packed into the high-temperature side, and the refrigerator was assembled and a refrigeration test was carried out to measure the refrigeration capacity at 4.2K. A thermal load was applied to the first-stage regenerator so that the temperature reached 50K.

[0224] The reliability of a refrigerator can be evaluated by looking at the ratio of refrigeration performance before and after the vibration test. The smaller the rate of decrease in refrigeration performance before and after the vibration test, the higher the reliability of the refrigerator.

[0225] [Table 1]

[0226] The results of Comparative Example 1 and Examples 18 to 21 show that when the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide to the X-ray diffraction peak intensity of the rare earth oxysulfide in the regenerator material is less than 1%, the intensity is significantly reduced and the reliability of the refrigerator is also reduced. This is thought to be due to the low abundance ratio of the garnet-type rare earth oxide in the regenerator material.

[0227] The results of Comparative Example 2 and Examples 18 to 21 show that when the ratio of the X-ray diffraction peak intensity of the garnet-type rare earth oxide to the X-ray diffraction peak intensity of the rare earth oxysulfide in the regenerator material is greater than 40%, the specific heat decreases to 0.4 J / K cc. This is thought to be because the relative amount of rare earth oxysulfide in the regenerator material decreases.

[0228] The results of Comparative Example 3 and Examples 10 to 14 show that when the atomic concentration of the Group 2 element in the regenerator material is 0.001 atomic % or more, the production rate of garnet-type rare earth oxide increases, improving the strength and thereby increasing the reliability of the refrigerator.

[0229] From the results of Comparative Example 4 and Examples 10 to 14, it was found that when the atomic concentration of the Group II element in the regenerator material was greater than 10 atomic %, the volumetric specific heat was 0.4 J / (cm 3 ·K), and the refrigeration capacity of a refrigerator using these regenerator particles drops significantly. This is thought to be because the proportion of group 2 elements in the regenerator particles increases, causing a relative decrease in the proportion of rare earth elements.

[0230] From the results of Comparative Example 5 and Example 1, it was found that the specific surface area of ​​the alumina powder was 120 m 2 It can be seen that when the concentration exceeds 1 / g, garnet-type rare earth oxides are not produced even if calcium is contained.

[0231] The results of Example 35 show that perovskite rare earth oxides may be present in the regenerator material and regenerator particles. Furthermore, perovskite rare earth oxides have a specific heat peak at a slightly lower temperature than rare earth oxysulfides, improving the specific heat characteristics at low temperatures.

[0232] From Table 1, it can be seen that when the particle size of the regenerator particles is in the range of 50 μm or more and 3000 μm or less, the refrigeration capacity at 4.2 K is significantly improved.

[0233] Table 1 shows that when the aspect ratio of the regenerator particles is 5 or less, the refrigeration capacity at 4.2K is significantly improved.

[0234] Table 1 shows that even if the granulation method for the regenerator particles is different, by appropriately adjusting the synthesis conditions, the particles will have similar particle size, aspect ratio, garnet phase content, and Group 2 element content.

[0235] Table 1 shows that even if the granulation method is different for the cold storage particles, if the particle size, aspect ratio, and specific heat are the same, the performance and reliability of the refrigerator equipped with the cold storage particles will be the same.

[0236] The above examples confirmed the effects of the regenerator particles of the first embodiment.

[0237] Although the dispenser has been described as an air pulse dispenser or a piezo dispenser, a plunger dispenser may also be used.

[0238] Although the description has been given taking a continuous type inkjet as an example of the inkjet, an on-demand type inkjet may also be used.

[0239] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. For example, components of one embodiment may be replaced or changed with components of another embodiment. These embodiments and modifications thereof are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

Claims

1. A vacuum vessel; a first cylinder provided in the vacuum vessel; a second cylinder provided in the vacuum vessel, coaxially connected to the first cylinder, and having a diameter smaller than that of the first cylinder; a first regenerator provided in the first cylinder and accommodating a first regenerator material; a second heat exchanger material is disposed in the second cylinder, the second heat exchanger material being heat exchanger particles; The regenerator particles include a rare earth oxysulfide 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; a garnet-type rare earth oxide containing Al and 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; aluminum oxide, a second regenerator in which a ratio of an X-ray diffraction peak intensity of the garnet-type rare earth oxide to an X-ray diffraction peak intensity of the rare earth oxysulfide is 0.1% or more and 40% or less; A two-stage regenerative cryogenic refrigerator equipped with:

2. 2. The two-stage regenerative cryogenic refrigerator according to claim 1, wherein the regenerative material particles further contain 0.001 atomic % to 10 atomic % of a Group II element.

3. 3. The two-stage regenerative cryogenic refrigerator according to claim 2, wherein the Group II element is at least one element selected from the group consisting of Mg, Ca, Sr, and Ba.

4. 4. The two-stage regenerative cryogenic refrigerator according to claim 1, wherein the regenerative material particles further contain a perovskite rare earth oxide.

5. 5. The two-stage regenerative cryogenic refrigerator according to claim 1, wherein the regenerative material particles have a particle size of 50 [mu]m or more and 3 mm or less.

6. 6. The two-stage regenerator type cryogenic refrigerator according to claim 1, wherein the regenerator particles have an aspect ratio of 1 or more and 5 or less.

7. When the peripheral length of the projected image of the plurality of regenerator particles filled in the second regenerator is L and the actual area of ​​the projected image is A, 4πA / L ２ 7. The two-stage regenerator type cryogenic refrigerator according to claim 1, wherein the ratio of the regenerator particles having a circularity R of 0.5 or less is 5% or less.

8. 8. The two-stage regenerative cryogenic refrigerator according to claim 1, wherein the first regenerative material is a Cu mesh.

9. 9. The two-stage regenerative type cryogenic refrigerator according to claim 1, wherein the second regenerator includes a plurality of regenerative material packed layers of different types of regenerative material, and the regenerative material particles are packed on the low-temperature side of the second regenerator.

10. A cryopump comprising the two-stage regenerative cryogenic refrigerator according to any one of claims 1 to 9.

11. A dilution refrigerator comprising the two-stage regenerative cryogenic refrigerator according to any one of claims 1 to 9.

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