Regenerative cryocooler, method for manufacturing regenerative cryocooler, and cryopump

Abstract

To provide a cold storage type cryogenic refrigerator containing cold storage material particles having high mechanical strength.SOLUTION: A heat regenerating cryogenic refrigerator of an embodiment includes a vacuum container, a first cylinder in the vacuum container, a second cylinder coaxially joined to the first cylinder and having a diameter smaller than a diameter of the first cylinder in the vacuum container, a first regenerator in which a first regenerator material is accommodated in the first cylinder, and a second regenerator in which regenerator material particles as a second regenerator material are accommodated in the second cylinder. The heat regenerating material particle includes a first element that is a rare earth element, a second element that is different from the first element and forms a polyvalent metal ion in an aqueous solution, a first phase containing the first element, and a second phase containing the second element and different from the first phase.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a regenerative cryogenic refrigerator, a method for manufacturing a regenerative cryogenic refrigerator, and a cryopump. [Background technology]

[0002] Cryogenic refrigerators, which are used to cool superconducting devices and create ultra-high vacuums, use regenerator particles containing a regenerator material with a high volumetric specific heat at low temperatures. Here, the specific heat per unit volume is defined as "volumetric specific heat." Examples of regenerator materials include metals such as lead (Pb) and bismuth (Bi), rare earth compounds such as HoCu2 and Er3Ni, oxides such as Ag2O and Cu2O, and oxysulfides such as Gd2O2S.

[0003] In a cryogenic refrigerator, multiple regenerator particles are packed into a regenerator. For example, cold is generated by heat exchange between the regenerator particles and helium gas passing through the regenerator. For example, refrigerators using refrigeration cycles such as the Gifford-McMahon (GM) system, Stirling system, or pulse tube system are used in superconducting nuclear magnetic resonance (MRI) devices and cryopumps.

[0004] High-performance refrigerators are also essential for magnetic levitation trains, which use superconducting magnets to generate magnetic force. Cryopumps are also used in semiconductor manufacturing equipment to create an ultra-high vacuum in the chambers where thin films are formed on wafers. Furthermore, high-performance refrigerators are now being used in superconducting energy storage systems (SMES) and magnetic field-applied single crystal pullers 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] In this type of refrigerator, a working medium such as compressed helium (He) gas flows in one direction through a regenerator filled with regenerator particles, supplying its thermal energy to the regenerator. The expanded working medium then flows in the opposite direction through the regenerator, receiving thermal energy from the regenerator particles. The improved heat recovery effect during this process improves the thermal efficiency of the working medium cycle, making it possible to achieve lower temperatures.

[0006] The regenerator particles are packed into the regenerator container of the refrigerator and exert their refrigeration capacity in the cryogenic range through heat exchange with the helium (He) gas that flows in as the working medium. During this process, the regenerator particles are subjected to pressure vibrations caused by the high-pressure helium gas acting on the refrigerator during operation, stress caused by the high-pressure helium gas, and impact forces caused by the high-pressure helium gas. In the case of a GM refrigerator, the regenerator particles are also subjected to stress caused by the reciprocating motion of the displacer (piston that compresses the working medium). Furthermore, when the refrigerator starts up, the temperature drops from near room temperature to a cryogenic temperature of around 4 K in a short period of time, which causes a large thermal shock to act on the regenerator particles.

[0007] In this way, the pressure vibrations and various stresses acting on the refrigerator during operation cause the cold storage material particles to break down and become fine particles. The fine particles can damage components such as the seals of the refrigerator, causing a significant decrease in the refrigerator's refrigeration capacity, which is a problem. In order to maintain the high refrigeration capacity of the refrigerator for a long period of time, that is, to improve the long-term reliability of the refrigerator, the cold storage material particles filled in the refrigerator's cold storage unit are required to have excellent properties, such as a high volumetric specific heat, high mechanical strength, high thermal conductivity, and high heat transfer coefficient. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-58079 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-64946 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-213252 [Patent Document 4] International Publication No. 2018 / 025581 Summary of the Invention [Problem to be solved by the invention]

[0009] The problem to be solved by the present invention is to provide a regenerative cryogenic refrigerator containing regenerative material particles having high mechanical strength. [Means for solving the problem]

[0010] The regenerative cryogenic refrigerator of one embodiment includes a vacuum vessel, a first cylinder provided in the vacuum vessel, a second cylinder provided in the vacuum vessel, coaxially joined 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, the regenerator particles including at least one first element selected from the group consisting of rare earth elements, and a second element different from the first element that forms polyvalent metal ions in an aqueous solution, the atomic concentration of the second element being 0.001 atomic % or more and 60 atomic % or less, and the maximum volumetric specific heat at a temperature of 20 K or less being 0.3 J / cm 3.K or higher, comprising a first phase containing the first element and a second phase containing the second element and different from the first phase, wherein the atomic concentration of the second element in the second phase is greater than the atomic concentration of the second element in the first phase, and a third phase containing the first element and the second element and different from the first phase and the second phase, wherein the first phase is an oxide of the first element or an oxysulfide of the first element, and the second element is selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), The particle is composed of at least one element selected from the group consisting of manganese (Mn), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), and cobalt (Co), and has a first region and a second region closer to the outer edge of the particle than the first region, wherein the concentration ratio (C2 / C1) of the atomic concentration (C2) of the second element in the second region to the atomic concentration (C1) of the second element in the first region is 1 or more, the proportion of the area occupied by the second phase in the cross section of the particle is 0.001% or more and 75% or less, and the area per second phase in the cross section of the particle is 0.001 μm 2 More than 6000μm 2 is as follows: and a second regenerator in which, in the cross section of the particle, 20% to 90% of the second phase is in contact with the third phase, the particle size is 50 μm to 3 mm, and the aspect ratio is 5 or less. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is an explanatory view of a cold storage material particle according to the first embodiment. [Figure 2] FIG. 6 is an explanatory diagram of a cold storage material particle according to a second embodiment. [Figure 3] FIG. 10 is an explanatory view of a cold storage material particle according to a third embodiment. [Figure 4] FIG. 10 is a schematic cross-sectional view showing the configuration of a main part of a GM refrigerator, which is an example of a refrigerator according to a fourth embodiment. [Figure 5] FIG. 10 is a cross-sectional view showing a schematic configuration of a cryopump according to a fifth embodiment. [Figure 6]FIG. 10 is a perspective view showing a schematic configuration of a superconducting magnet according to a sixth embodiment. [Figure 7] FIG. 13 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance imaging apparatus according to a seventh embodiment. [Figure 8] FIG. 13 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance spectrometer according to an eighth embodiment. [Figure 9] FIG. 13 is a perspective view showing a schematic configuration of a magnetic field application type single crystal pulling apparatus according to a ninth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] 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.

[0014] (First embodiment) The regenerator particles of the first embodiment contain at least one first element selected from the group consisting of rare earth elements, silver (Ag), and copper (Cu), and a second element that is different from the first element and forms polyvalent metal ions in an aqueous solution. The atomic concentration of the second element is 0.001 atomic % or more and 60 atomic % or less. The maximum volumetric specific heat at a temperature of 20 K or less is 0.3 J / cm. 3 ·K or higher.

[0015] Fig. 1 is an explanatory diagram of a cold storage material particle of the first embodiment. Fig. 1(a) is a schematic cross-sectional view of a cold storage material particle. Fig. 1(b) is a schematic cross-sectional view of an enlarged portion of a cold storage material particle. Fig. 1(b) is a schematic cross-sectional view of, for example, a region R in Fig. 1(a).

[0016] The regenerator particles 10 of the first embodiment are used in a refrigerator that realizes an extremely low temperature of, for example, 5K or less.

[0017] The shape of the cold storage material particle 10 is, for example, spherical. FIG. 1(a) shows a case where the cold storage material particle 10 is a perfect sphere. FIG. 1(a) is a cross section passing through the center of the cold storage material particle 10. The particle size of the cold storage material particle (D in FIG. 1(a)) is, for example, 50 μm or more and 3 mm or less. The aspect ratio of the cold storage material particle 10 is, for example, 5 or less. The aspect ratio of the cold storage material particle 10 is the ratio of the major axis to the minor axis of the cold storage material particle 10.

[0018] The particle diameter D of the cold storage material particle 10 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 diameter D of the cold storage material particle 10 can be determined, for example, by image analysis of the optical microscope image or the SEM image.

[0019] The maximum volumetric specific heat of the cold storage material particles 10 at a temperature of 20 K or less is 0.3 J / cm 3 ·K or more. The maximum value of the volumetric specific heat of the regenerator particles 10 at a temperature of 20K or less is 0.3 J / cm 3 Contains a cooling material with a temperature of K or higher.

[0020] The regenerator particles 10 contain a regenerator element. The regenerator element is at least one element selected from the group consisting of rare earth elements, silver (Ag), and copper (Cu). The rare earth element is at least one element selected from the group consisting of scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0021] The regenerative element is one of the elements that make up the regenerative material. The regenerative element is an example of the first element.

[0022] The regenerator particles 10 contain an additive metal element. The additive metal element is a metal element that forms polyvalent metal ions in an aqueous solution. The additive metal element is, for example, at least one element selected from the group consisting of calcium (Ca), magnesium (Mg), beryllium (Be), strontium (Sr), barium (Ba), radium (Ra), manganese (Mn), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), and cobalt (Co).

[0023] The additional metal element is an example of the second element. For example, the regenerator material particle 10 may contain two or more types of additional metal elements.

[0024] The atomic concentration of the added metal element in the cold storage material particle 10 is 0.001 atomic % or more and 60 atomic % or less. When the cold storage material particle 10 contains two or more types of added metal elements, the atomic concentration of the added metal element in the cold storage material particle 10 is the sum of the atomic concentrations of the respective added metal elements.

[0025] The atomic concentration of the additional metal element is, for example, smaller than the atomic concentration of the regenerative element, and the atomic concentration of the additional metal element is, for example, larger than the atomic concentration of the regenerative element.

[0026] The elements contained in the regenerator particles 10 can be detected and the atomic concentrations of the elements can be measured using, for example, energy dispersive X-ray spectroscopy (EDX) or wavelength dispersive X-ray analysis (WDX).

[0027] The atomic concentration of the added metal element in the heat regenerator particle 10 is, for example, the average value of the atomic concentrations measured at 13 measurement spots P1 to P13 as shown in FIG. 1(a). The atomic concentration of the added metal is the atomic concentration where the amount of all atoms measured by WDX or EDX is used as the denominator. The measurement spot has a diameter of, for example, 20 μm.

[0028] In addition, the detection of elements contained in the regenerator particles 10 and the measurement of the atomic concentration of the elements can also be performed, for example, by dissolving the regenerator particles 10 in a liquid and using inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0029] The cold storage material contained in the cold storage material particles 10 includes, for example, an oxysulfide. The cold storage material includes, for example, an oxysulfide as a main component. When the cold storage material includes an oxysulfide, the cold storage material particles 10 include oxygen (O) and sulfur (S).

[0030] The oxysulfide contained in the regenerator material includes, for example, gadolinium (Gd). The oxysulfide contained in the regenerator material is, for example, gadolinium oxysulfide. The oxysulfide contained in the regenerator material is, for example, Gd2O2S.

[0031] When the oxysulfide contained in the regenerator material is gadolinium oxysulfide, the regenerator element is gadolinium (Gd).

[0032] The cold storage substance contained in the cold storage material particles 10 can be identified by using, for example, powder X-ray diffraction (XRD).

[0033] The regenerator material contained in the regenerator particles 10 contains, for example, a rare earth compound as a main component. The rare earth compound contained in the regenerator material is, for example, HoCu2 or Er3Ni.

[0034] When the regenerative material contains HoCu2, the regenerative elements are holmium (Ho) and copper (Cu), and when the regenerative material contains Er3Ni, the regenerative element is erbium (Er).

[0035] The cold accumulating substance contained in the cold accumulating material particles 10 includes, for example, an oxide. The cold accumulating material includes, for example, an oxide as a main component. When the cold accumulating substance includes an oxide, the cold accumulating material particles 10 include oxygen (O).

[0036] The oxide contained in the cold storage material includes, for example, at least one of silver (Ag) and copper (Cu). The oxide contained in the cold storage material is, for example, silver oxide or copper oxide. The oxide contained in the cold storage material is, for example, Ag2O or Cu2O.

[0037] If the oxide contained in the regenerative substance is silver oxide, the regenerative element is silver (Ag). If the oxide contained in the regenerative substance is copper oxide, the regenerative element is copper (Cu).

[0038] The composition of the regenerative material can be analyzed using, for example, EDX or WDX, and the regenerative material can be identified using, for example, powder X-ray diffraction.

[0039] Fig. 1(b) is a schematic cross-sectional view of an enlarged portion of a regenerator particle, for example, a region R in Fig. 1(a).

[0040] As shown in FIG. 1(b), the cold storage material particle 10 of the first embodiment includes four phases: A phase, B phase, C phase, and D phase. The A phase, B phase, C phase, and D phase are different from each other. The A phase, B phase, C phase, and D phase are examples of a first phase, a second phase, a third phase, and a fourth phase, respectively. Note that two different phases means that at least the chemical compositions of the two phases are different.

[0041] Phases A, B, C, and D are, for example, crystalline phases. Phases A, B, C, and D may be, for example, amorphous phases.

[0042] Phase A is a regenerative material. Phase A contains a regenerative element. Phase A is, for example, gadolinium oxysulfide. Phase A is, for example, Gd2O2S.

[0043] When the A phase is gadolinium oxysulfide, the regenerative element is gadolinium (Gd). The A phase contains gadolinium (Gd), sulfur (S), and oxygen (O).

[0044] The cold storage material particle 10 includes, for example, two or more different additive metal elements. The cold storage material particle 10 includes a first additive metal element and a second additive metal element different from the first additive metal element. The first additive metal element is an example of element α. The second additive metal element is an example of element β.

[0045] Phase B includes a first additive metal element and a second additive metal element. Phase B includes two or more different elements including the first additive metal element and the second additive metal element. The atomic concentration of the additive metal element in phase B is greater than the atomic concentration of the additive metal element in phase A.

[0046] The B phase is, for example, an oxide containing calcium (Ca) and aluminum (Al). The B phase is, for example, a compound containing calcium (Ca), aluminum (Al), and oxygen (O). The B phase is, for example, CaO·6Al2O3.

[0047] When the B phase is an oxide containing calcium (Ca) and aluminum (Al), the first added metal element is calcium (Ca) and the second added metal element is aluminum (Al).

[0048] The B phase further includes, for example, a regenerative element. The B phase includes, for example, gadolinium (Gd). In this case, the B phase includes calcium (Ca), aluminum (Al), gadolinium (Gd), and oxygen (O).

[0049] The C phase contains a second additive metal element.

[0050] The C phase is, for example, aluminum oxide. The C phase is, for example, Al2O3.

[0051] When the C phase is aluminum oxide, the C phase contains aluminum (Al) and oxygen (O).

[0052] The D phase includes a regenerator element and a second additive metal element. The D phase is, for example, an oxide including gadolinium (Gd) and aluminum (Al). The D phase is, for example, a compound including gadolinium (Gd), aluminum (Al), and oxygen (O). The D phase is, for example, GdAlO.

[0053] In the cross section of the regenerator particle 10, for example, phase A surrounds phases B, C, and D. In the cross section of the regenerator particle 10, the proportion of the area occupied by phase A containing the regenerator elements is, for example, larger than the proportion of the area occupied by other phases.

[0054] In the cross section of the regenerator particle 10, the area ratio occupied by the B phase containing the added metal element is, for example, 0.001% or more and 75% or less.

[0055] In the cross section of the regenerator particle 10, the area ratio occupied by the A phase, the area ratio occupied by the B phase, the area ratio occupied by the C phase, and the area ratio occupied by the D phase can be determined, for example, by image analysis of an optical microscope image or a scanning electron microscope image (SEM image).

[0056] For example, by taking a backscattered electron image of the cross section of the regenerator particle 10 using a scanning electron microscope (SEM), the phases can be distinguished from the difference in the density of the image. Furthermore, by performing a composition analysis at a point within each phase using, for example, EDX or WDX, the type and concentration of elements contained in each phase can be determined. For example, by taking into account the results of XRD in addition to the results of EDX or WDX, the compounds contained in each phase can be determined.

[0057] In the image analysis of scanning electron microscope (SEM) images, for example, backscattered electron images are used. ImageJ, for example, is used as image analysis software. Regions corresponding to each phase can be extracted from the image based on the brightness of the backscattered electron image. When extracting the regions corresponding to each phase, for example, the brightness is binarized. For example, the extracted regions are compared with the original image with the naked eye, and if it is clear that the grain boundaries or interiors of the grains have not been properly extracted, the image is manually corrected before evaluating the area of ​​each phase. For example, Paint, a software that comes standard with Windows (registered trademark) 10, is used as software for correcting the image.

[0058] In the cross section of the regenerator particle 10, the area of ​​each B phase containing the additive metal element is, for example, 0.001 μm 2 More than 6000μm 2 The area of ​​each B phase containing an additive metal element is, for example, the median value of the areas of a plurality of B phases.

[0059] In the cross section of the regenerator particle 10, the particle size of each B phase containing the added metal element is, for example, 0.1 μm or more and 100 μm or less. Here, the particle size is, for example, the major axis of the B phase. The major axis of the B phase is the maximum length among the lengths between any two points on the periphery of the B phase. The particle size of each B phase containing the added metal element is, for example, the median value of the particle sizes of multiple B phases.

[0060] In the cross section of the regenerator particle 10, the area and particle size of the B phase containing the added metal element can be determined by, for example, image analysis of an optical microscope image or a scanning electron microscope image.

[0061] Next, an example of a method for producing the cold storage material particles 10 of the first embodiment will be described.

[0062] The method for manufacturing the cold storage material particles of the first embodiment includes mixing a powder containing at least one first element selected from the group consisting of rare earth elements, silver (Ag), and copper (Cu) with an alginic acid aqueous solution to form a slurry, ejecting the slurry in the form of droplets into a gelling solution containing a second element that forms polyvalent metal ions, retaining the slurry in the gelling solution to form gelled particles, and sintering the particles.

[0063] First, the raw material powder of the cold accumulator is added to an aqueous alginic acid solution and mixed to prepare a slurry. The cold accumulator contains a cold accumulator element. For example, a ball mill is used to mix the raw material powder of the cold accumulator and the aqueous alginic acid solution.

[0064] The mixing time is, for example, from one hour to one week. By changing the mixing time, it is possible to change, for example, the proportion of the second phase that is in contact with the third phase and the proportion of the second phase that is in contact with the fourth phase in the cross section of the produced regenerator particle.

[0065] Next, the slurry is ejected in droplets into a gelling solution containing a second element that forms polyvalent metal ions. The prepared slurry is dropped into the gelling solution to gel the slurry. A dropper, burette, pipette, syringe, dispenser, or inkjet is used as a device for dropping the slurry into the gelling solution.

[0066] The viscosity of the slurry suitable for dispensing varies depending on the device used for dispensing. For example, for syringe dispensing, it is 0.1 mPa·s to 1,000,000 mPa·s, for dispenser dispensing it is 50 mPa·s to 300,000 mPa·s, and for inkjet dispensing it is 1 mPa·s to 1,000 mPa·s. The viscosity of the slurry can be adjusted appropriately depending on the device used for dispensing.

[0067] The particle production speed varies depending on the ejection method. For example, when ejecting with a syringe, the particle production speed is about 1 particle per second, but when using a dispenser, it increases to about 1 to 400 particles per second, and when using an inkjet, it increases to about 500 to 2000 particles per second. The production speed can be further increased by adding more identical nozzles.

[0068] When a syringe is used, the diameter of the syringe outlet is, for example, 50 μm or more and 3000 μm or less. The distance from the tip of the syringe to the liquid surface of the gelling solution is, for example, 1 mm or more and 1000 mm or less. By changing the diameter of the syringe outlet and the distance from the tip of the syringe to the liquid surface of the gelling solution, for example, the particle size and aspect ratio of the particles can be changed.

[0069] When a dispenser is used for dispensing, any of an air pulse dispenser, a plunger dispenser, and a piezoelectric dispenser may be used. In an air pulse dispenser, the slurry is discharged drop by drop from the discharge port by a rod driven up and down by high-pressure air. In a piezoelectric dispenser, the slurry is discharged drop by drop by a pressure wave generated by the volume change of a rod or piezoelectric element driven up and down by a piezoelectric element. Here, the particle size can be changed by changing the diameter of the nozzle discharge port, i.e., the nozzle diameter. The nozzle diameter is, for example, 50 μm or more and 3000 μm or less.

[0070] As mentioned above, slurry is discharged by driving the rod up and down. Therefore, the particle production speed changes depending on the time the rod is driven up and down. The time the rod is driven is, for example, between 2.5 ms and 100 ms per cycle.

[0071] For example, the particle size and aspect ratio of the particles can be changed by changing the distance from the nozzle tip of the dispenser to the liquid surface of the gelling solution. The distance from the nozzle tip to the liquid surface of the gelling solution is, for example, 0.1 mm or more and 1000 mm or less.

[0072] Inkjet printers are broadly divided into continuous and on-demand types based on their ejection method, but either type can be used. Additionally, on-demand types are divided into three types: piezo, thermal, and valve, but any of these can be used.

[0073] In the continuous type, pressure waves are applied to the liquid column ejected by pressurizing the flow path, which encourages the liquid column to break down into particles. Pressure waves are applied using a pump, piezoelectric element, etc. On the other hand, in the on-demand type, liquid is ejected one droplet at a time, but the method of ejecting liquid droplets differs depending on the method.

[0074] In the piezo method, a voltage is applied to a piezo element, which causes a sudden change in volume of the element, generating a pressure wave that ejects droplets one by one.In the thermal method, a heater is used to generate bubbles in the ejected liquid, which ejects droplets one by one.In the valve method, a solenoid is used to open and close the nozzle opening cover, which ejects droplets one by one.

[0075] In the thermal method, the water content of the slurry evaporates when it is heated, which can cause the flow path to become clogged with raw material powder and inhibit ejection. For this reason, when using an on-demand inkjet printer, the piezo and valve methods are preferable to the thermal method.

[0076] The diameter of the nozzle outlet of the inkjet nozzle is, for example, 50 μm or more and 3000 μm or less. The distance from the nozzle tip to the liquid surface of the gelling solution is, for example, 0.1 mm or more and 1000 mm or less. By changing the diameter of the nozzle outlet and the distance from the syringe tip to the liquid surface of the gelling solution, it is possible to change, for example, the particle size and aspect ratio of the particles.

[0077] In inkjet printing, if the viscosity of the slurry changes, the amount of slurry coming out of the nozzle per unit time also changes, which in turn changes the particle size. For this reason, the nozzle diameter is adjusted according to the slurry viscosity to keep the particle size between 50 μm and 3 mm.

[0078] In continuous inkjet systems, the particle production rate can be changed by changing the waveform of the pressure wave applied to the ejected liquid column by pressurizing the flow channel. In on-demand piezoelectric inkjet systems, the particle production rate can be changed by changing the frequency of volume change in the piezoelectric element. In on-demand thermal inkjet systems, the particle production rate can be changed by changing the heater heating frequency. In on-demand valve inkjet systems, the particle production rate can be changed by changing the valve opening and closing frequency. The frequency for each inkjet system is, for example, 500 Hz or higher and 2000 Hz or lower. When the frequency is 500 Hz or higher and 2000 Hz or lower, the particle production rate is 500 particles / second or higher and 2000 particles / second or lower.

[0079] 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, spherical particles containing the raw material powder of the cold storage material are formed.

[0080] The gelling solution contains the added metal elements in the form of polyvalent metal ions. Gelation progresses through a cross-linking reaction caused by the polyvalent metal ions. As the slurry is held in the gelling solution for an extended period of time, the added metal elements permeate the particles from the outer edge toward the center. The distribution of the added metal elements within the particles can be controlled by changing the time the slurry is held in the gelling solution.

[0081] The retention time of the slurry in the gelling solution is, for example, 10 minutes to 48 hours. Hereinafter, the retention time of the slurry in the gelling solution will also be simply referred to as the gelling time. By setting the retention time of the slurry in the gelling solution to 10 minutes or more, it is possible to obtain particles in which the dropped slurry has gelled.

[0082] After the particles are formed by gelation, they are washed with pure water to remove the added metal elements adsorbed on the particle surface.

[0083] After washing the particles, the particles are dried. After drying the particles, the particles are sintered to increase the mechanical strength of the particles and the density of the cold accumulating material in the particles. When the cold accumulating material is an oxysulfide, for example, the particles are sulfurized before being sintered.

[0084] When sulfurizing the particles, 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.

[0085] The heat treatment for sintering the particles is carried out, for example, in an inert gas atmosphere. The heat treatment temperature is, for example, 1000°C or higher and 2000°C or lower. The heat treatment temperature is, for example, 1100°C or higher and 1700°C or lower. The heat treatment time is, for example, 1 hour or higher and 48 hours or lower.

[0086] When the particles are sintered, a first phase containing a regenerative element and a second phase containing an additive metal element are formed. In addition, by adding two or more kinds of additive metal elements, it is possible to form a third phase containing an additive metal element and a fourth phase containing a regenerative element and an additive metal element.

[0087] The second, third, or fourth phase can be formed, for example, by appropriately controlling the heat treatment temperature when sintering the particles and the temperature increase and decrease profiles of the heat treatment.

[0088] Furthermore, for example, by changing the heat treatment conditions for sulfurizing and sintering the particles, the area per second phase in the cross section of the particle and the particle size can be changed.

[0089] The regenerative material is, for example, silver oxide, copper oxide, or a rare earth oxysulfide, such as gadolinium oxysulfide.

[0090] The alginic acid aqueous solution is, for example, a sodium alginate aqueous solution, an ammonium alginate aqueous solution, or a potassium alginate aqueous solution.

[0091] Examples of gelling solutions include calcium lactate aqueous solution, calcium chloride aqueous solution, manganese(II) chloride aqueous solution, magnesium sulfate aqueous solution, beryllium sulfate aqueous solution, strontium nitrate aqueous solution, barium chloride aqueous solution, barium hydroxide aqueous solution, aluminum chloride aqueous solution, aluminum nitrate aqueous solution, aluminum lactate aqueous solution, iron(II) chloride aqueous solution, iron(III) chloride aqueous solution, copper(II) chloride aqueous solution, nickel(II) chloride aqueous solution, and cobalt(II) chloride aqueous solution.

[0092] The combination of cold storage material, alginic acid aqueous solution, and gelling solution is arbitrary. However, if the cold storage material is silver oxide, combining it with calcium chloride aqueous solution, manganese (II) chloride aqueous solution, barium chloride aqueous solution, aluminum chloride aqueous solution, iron (II) chloride aqueous solution, iron (III) chloride aqueous solution, copper (II) chloride aqueous solution, nickel (II) chloride aqueous solution, or cobalt (II) chloride aqueous solution as the gelling solution will produce silver chloride. Therefore, the above combinations are excluded.

[0093] The cold storage material particles 10 of the first embodiment can be manufactured by the above manufacturing method.

[0094] It is possible to control the atomic concentration distribution of the added metal element in the particle to any desired distribution by controlling the gelation time, for example, so that the added metal element penetrates to the center of the particle and is distributed almost uniformly in the particle.

[0095] In addition, by controlling the amount of raw material powder of the regenerative material, the atomic concentration of the added metal elements in the gelling solution, and the sintering conditions of the particles, it is possible to adjust the chemical composition of the first and second phases of the regenerative material particle 10, the area proportion of the first and second phases in the cross section of the regenerative material particle 10, and the area of ​​the first and second phases in the cross section of the regenerative material particle 10 to appropriate values.

[0096] Next, the function and effect of the regenerator particles 10 of the first embodiment will be described.

[0097] In cryogenic refrigerators used for cooling superconducting equipment, a plurality of regenerator particles are filled into a regenerator. For example, cold is generated by heat exchange between the regenerator particles and helium gas passing through the regenerator. The regenerator particles are required to have excellent properties, such as a high volumetric specific heat, high mechanical strength, high thermal conductivity, and high heat transfer coefficient.

[0098] The regenerator particles 10 of the first embodiment have a maximum volumetric specific heat of 0.3 J / cm at a temperature of 20 K or less. 3 ·K or more. Therefore, the regenerator particles 10 have a high volumetric specific heat at extremely low temperatures.

[0099] Furthermore, the cold storage material particles 10 of the first embodiment contain an additive metal element that forms polyvalent metal ions in an aqueous solution. The additive metal element has the effect of promoting sintering of the particles during sintering in the production of the cold storage material particles 10. Therefore, the cold storage material particles 10 have a high degree of sintering and high mechanical strength.

[0100] Furthermore, in order to fully obtain the properties required for the cold storage material particles 10, such as mechanical strength, thermal conductivity, heat transfer coefficient, and volumetric specific heat, a sufficient sintering temperature and sintering time are required in the sintering process. The sintering-promoting effect of the added metal elements makes it possible to lower the sintering temperature and sintering time required for sintering. This reduces the manufacturing cost of the cold storage material particles 10, making it possible to provide inexpensive cold storage material particles 10.

[0101] Furthermore, the cold storage material particles 10 of the first embodiment have a high degree of sintering inside the particles, and therefore have a high thermal conductivity. Furthermore, the cold storage material particles 10 of the first embodiment also have a high degree of sintering at the outer periphery of the particles, and therefore, for example, the heat transfer characteristics between the particles and helium gas in contact with the outer periphery are also improved. Therefore, the cold storage material particles 10 of the first embodiment have a high thermal conductivity.

[0102] The atomic concentration of the added metal element in the regenerator material particles 10 is 0.001 atomic % or more and 60 atomic % or less. The atomic concentration of the added metal element in the regenerator material particles 10 is more preferably 0.01 atomic % or more and 40 atomic % or less.

[0103] When the atomic concentration of the added metal element in the cold storage material particle 10 exceeds the lower limit, the degree of sintering increases, and the mechanical strength, thermal conductivity, and heat transfer coefficient of the cold storage material particle 10 increase. When the atomic concentration of the added metal element in the cold storage material particle 10 falls below the upper limit, the volumetric specific heat increases.

[0104] The additive metal element in the regenerator particle 10 is preferably at least one element selected from the group consisting of calcium (Ca), magnesium (Mg), beryllium (Be), strontium (Sr), barium (Ba), radium (Ra), manganese (Mn), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), and cobalt (Co). The additive metal element in the regenerator particle 10 is more preferably at least one element selected from the group consisting of calcium (Ca), magnesium (Mg), beryllium (Be), strontium (Sr), and barium (Ba).

[0105] The addition of the above metal elements further promotes sintering of the particles during the production of the regenerator particles 10. Therefore, the mechanical strength, thermal conductivity, and heat transfer coefficient of the regenerator particles 10 are increased.

[0106] The added metal element is preferably calcium (Ca) from the viewpoint of increasing the gelation rate of the slurry when producing the cold storage material particles 10. Furthermore, the added metal element is preferably aluminum (Al) from the viewpoint of increasing the mechanical strength, thermal conductivity, and heat transfer coefficient of the cold storage material particles 10. The added metal elements are preferably calcium (Ca) and aluminum (Al).

[0107] The regenerator particles 10 preferably contain an alkali metal element, which promotes sintering of the regenerator particles 10 in the sintering process. Therefore, the sintering of the regenerator particles 10 is promoted, and the mechanical strength, thermal conductivity, and heat transfer coefficient of the regenerator particles 10 are increased.

[0108] In order to fully obtain the properties required for the cold storage material particles 10, such as mechanical strength, thermal conductivity, heat transfer coefficient, and volumetric specific heat, a sufficient sintering temperature and sintering time are required in the sintering process. The sintering-promoting effect of the alkali metal element makes it possible to lower the sintering temperature and sintering time required for sintering. This reduces the manufacturing cost of the cold storage material particles 10, making it possible to provide inexpensive cold storage material particles 10.

[0109] The atomic concentration of the alkali metal element in the regenerator material particles 10 is preferably 0.0001 atomic % or more and 10 atomic % or less, and more preferably 0.001 atomic % or more and 5 atomic % or less.

[0110] In order to include an alkali metal element in the cold storage material particles 10, for example, a sodium alginate aqueous solution or a potassium alginate aqueous solution is used as the alginic acid aqueous solution when producing the cold storage material particles 10.

[0111] The regenerator particles 10 preferably include a first phase containing a regenerator element and a second phase containing an additive metal element and different from the first phase. For example, the presence of different phases increases the number density of grain boundaries compared to when the regenerator particles 10 are formed of a single phase.

[0112] Furthermore, the regenerator particles 10 preferably contain an additive metal element and a third phase different from the first and second phases. For example, compared to a case where the regenerator particles 10 are formed of two different phases, the presence of three different phases suppresses the grain growth of each phase, and the number density of grain boundaries further increases. Here, the number density of grain boundaries means the number of grain boundaries per unit volume.

[0113] Furthermore, the regenerator particles 10 preferably contain an additive metal element and a fourth phase different from the first, second, and third phases. For example, compared to the case where the regenerator particles 10 are formed of three different phases, the presence of four different phases further suppresses the grain growth of each phase, and the number density of the grain boundaries dramatically increases.

[0114] As the number density of the grain boundaries increases, the strength of the cold storage material particles 10 against plastic deformation increases. Therefore, by including a second phase different from the first phase, the mechanical strength of the cold storage material particles 10 increases. By including a third phase in addition to the second phase, the mechanical strength of the cold storage material particles 10 increases further. By including a third phase and a fourth phase in addition to the second phase, the mechanical strength of the cold storage material particles 10 increases even further.

[0115] The added metal element may be uniformly dispersed in the cold storage material particle 10, and the cold storage material particle 10 may be composed of a single phase. Here, uniform dispersion means that the added metal element is uniformly dispersed in the cold storage material particle 10 at the atomic level, and the atomic concentration of the added metal element is approximately constant throughout the cold storage material particle 10.

[0116] When the ice storage material particle 10 includes a first phase and a second phase, the area ratio of the second phase in the cross section of the ice storage material particle 10 is preferably 0.01% or more and 75% or less, and more preferably 0.01% or more and 50% or less.

[0117] When the area ratio of the second phase in the cross section of the cold storage material particle 10 exceeds the above lower limit, the number density of the grain boundaries increases, and the mechanical strength of the cold storage material particle 10 increases. Also, the degree of sintering of the cold storage material particle 10 increases, and the mechanical strength, thermal conductivity, and heat transfer coefficient increase. Also, when the area ratio of the second phase in the cold storage material particle 10 falls below the above upper limit, the proportion of the cold storage substance in the cold storage material particle 10 increases, and the volumetric specific heat increases.

[0118] In the cross section of the regenerator particle 10, the area of ​​each second phase is 0.001 μm 2 More than 6000μm 2 It is preferable that the area of ​​the second phase in the cross section of the cold storage material particle 10 is greater than the above lower limit, the number density of the grain boundaries is reduced, and the thermal conductivity of the cold storage material particle 10 is improved. Furthermore, when the area per second phase in the cold storage material particle 10 is less than the above upper limit, the number density of the grain boundaries in the cold storage material particle 10 is increased, and the mechanical strength of the cold storage material particle 10 is improved.

[0119] In the cross section of the cold storage material particle 10, the particle size of each second phase is preferably 0.1 μm or more and 100 μm or less. If the particle size of each second phase in the cross section of the cold storage material particle 10 exceeds the above lower limit, the number density of the grain boundaries decreases, improving the thermal conductivity of the cold storage material particle 10. If the particle size of each second phase in the cold storage material particle 10 is below the above upper limit, the number density of the grain boundaries in the cold storage material particle 10 increases, improving the mechanical strength of the cold storage material particle 10.

[0120] It is preferable that 20% to 90% of the second phase is in contact with the third phase, and it is preferable that 40% to 75% of the second phase is in contact with the third phase in the cross section of the regenerator particle 10. In other words, the proportion of the second phase in contact with the third phase is preferably 20% to 90%, and more preferably 40% to 75%.

[0121] The contact between the second and third phases suppresses the grain growth of the second and third phases during sintering, allowing the sintering temperature to be increased or the sintering time to be extended while maintaining the second and third phases fine.

[0122] Therefore, the proportion of voids present in the cold storage material particles can be reduced. That is, the void ratio present in the cold storage material particles can be reduced while maintaining a high number density of the grain boundary phase. Therefore, when the proportion of the second phase that is in contact with the third phase exceeds the above lower limit, the mechanical strength of the cold storage material particles is improved.

[0123] The second and third phases are thought to have different thermal expansion coefficients. Therefore, when the material is cooled from room temperature to a low temperature during refrigerator operation, stress is generated between the second and third phases due to the difference in thermal contraction. Similarly, the second and fourth phases are thought to have different thermal expansion coefficients. Therefore, when the material is cooled from room temperature to a low temperature during refrigerator operation, stress is generated between the second and fourth phases due to the difference in thermal contraction.

[0124] When the second phase is in contact with the third phase and the fourth phase simultaneously, the second phase is simultaneously subjected to stress due to the difference in thermal contraction between the third phase and the fourth phase, and the respective stresses are combined and increased. Therefore, by making the proportion of the second phase in contact with the third phase below the above upper limit, the proportion of the second phase in contact with the third phase and the fourth phase simultaneously can be reduced. As a result, the occurrence of cracks in the cold storage material particles 10 due to the difference in thermal contraction when cooled from room temperature to a low temperature during refrigerator operation can be suppressed.

[0125] In the cross section of the cold storage material particle 10, the proportion of the second phase in contact with the third phase is preferably higher than the proportion of the second phase in contact with the fourth phase. By increasing the proportion of the second phase in contact with the third phase, the mechanical strength of the cold storage material particle 10 is improved.

[0126] The particle size of the cold storage material particles 10 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 10 exceeds the above lower limit, the packing density of the cold storage material particles in the cold storage unit decreases, reducing the pressure loss of the working medium such as helium and improving the refrigeration performance of the refrigerator. On the other hand, when the particle size of the cold storage material particles 10 is below the above upper limit, the distance from the surface of the cold storage material particle to the center of the particle becomes shorter, making it easier for heat to be transferred between the working medium and the cold storage material particles to the center of the cold storage material, improving the refrigeration performance of the refrigerator.

[0127] The aspect ratio of the cold storage material particles 10 is preferably equal to or less than 5, and more preferably equal to or less than 2. When the aspect ratio of the cold storage material particles 10 is below the upper limit value, the voids when the cold storage material is filled into the cold storage unit become uniform, and the refrigeration performance of the refrigerator is improved.

[0128] The manufacturing method of the cold storage material particles of the first embodiment can reduce variations in the mechanical strength and thermal conductivity of the cold storage material particles by controlling the area, particle size, and contact ratio of each phase present in the particle.

[0129] As described above, according to the first embodiment, it is possible to realize regenerator particles having excellent properties such as a high volumetric specific heat, high mechanical strength, high thermal conductivity, and high heat transfer coefficient.

[0130] (Second embodiment) The cold storage material particles of the second embodiment differ from the cold storage material particles of the first embodiment in that they do not contain a fourth phase. Hereinafter, some of the description overlapping with the first embodiment will be omitted.

[0131] 2A and 2B are explanatory diagrams of a cold storage material particle according to a second embodiment. Fig. 2A is a schematic cross-sectional view of a cold storage material particle. Fig. 2B is a schematic cross-sectional view of an enlarged portion of a cold storage material particle. Fig. 2B is a schematic cross-sectional view of, for example, a region R in Fig. 2A.

[0132] As shown in Fig. 2(b), the regenerator particles 20 of the second embodiment include three phases: an X phase, a Y phase, and a Z phase. The X phase, the Y phase, and the Z phase are different phases. The X phase, the Y phase, and the Z phase are examples of a first phase, a second phase, and a third phase, respectively.

[0133] The X phase, Y phase, and Z phase are, for example, crystalline phases. The X phase, Y phase, and Z phase may be, for example, amorphous phases.

[0134] The X phase is a regenerative material. The X phase includes a regenerative element. The X phase is, for example, gadolinium oxysulfide. The X phase is, for example, Gd2O2S.

[0135] When the X phase is gadolinium oxysulfide, the regenerative element is gadolinium (Gd). The X phase contains gadolinium (Gd), sulfur (S), and oxygen (O).

[0136] The Y phase contains an additive metal element, and the atomic concentration of the additive metal element in the Y phase is greater than the atomic concentration of the additive metal element in the X phase.

[0137] The Y phase is, for example, an oxide containing aluminum (Al). The Y phase is, for example, aluminum oxide. The Y phase is, for example, Al2O3.

[0138] When the Y phase is an oxide containing aluminum oxide, the added metal element is aluminum (Al).

[0139] The Z phase contains a regenerator element and an additive metal element. The Z phase is, for example, an oxide containing gadolinium (Gd) and aluminum (Al). The Z phase is, for example, a compound containing gadolinium (Gd), aluminum (Al), and oxygen (O). The Z phase is, for example, GdAlO3.

[0140] The atomic concentration of the additive metal element in the second phase is preferably greater than the atomic concentration of the additive metal element in the first phase, for example, the atomic concentration of the additive metal element in the Y phase is preferably greater than the atomic concentration of the additive metal element in the X phase.

[0141] It is preferable that 20% to 90% of the second phase contacts the third phase, for example, 20% to 90% of the Y phase contacts the Z phase.

[0142] In the cross section of the regenerator particle, the area ratio of the second phase is preferably 0.001% to 75%. For example, in the cross section of the regenerator particle 20, the area ratio of the Y phase is preferably 0.001% to 75%.

[0143] In the cross section of the regenerator particle, the area of ​​each second phase is 0.001 μm 2 More than 6000μm 2 For example, in the cross section of the regenerator particle 20, the area per Y phase is preferably 0.001 μm 2 More than 6000μm 2 It is preferable that:

[0144] In the cross section of the regenerator particle, the particle size of each second phase is preferably 0.1 μm or more and 100 μm or less. For example, in the cross section of the regenerator particle 20, the particle size of each Y phase is preferably 0.1 μm or more and 100 μm or less.

[0145] The cold storage material particles 20 of the second embodiment can be manufactured by the same manufacturing method as the manufacturing method of the first embodiment.

[0146] As described above, according to the second embodiment, similar to the first embodiment, it is possible to realize regenerator particles having excellent properties such as high volumetric specific heat, high mechanical strength, high thermal conductivity, and high heat transfer coefficient.

[0147] (Third embodiment) The heat storage material particle of the third embodiment differs from the first embodiment in that it has a first region and a second region that is closer to the outer edge of the heat storage material particle than the first region and has a higher atomic concentration of the second element than the first region. Hereinafter, some of the description that overlaps with the first embodiment will be omitted.

[0148] 3A and 3B are explanatory diagrams of a cold storage material particle according to a third embodiment, in which Fig. 3A is a schematic cross-sectional view of a cold storage material particle, and Fig. 3B is a diagram showing the atomic concentration distribution of an added metal element in the cold storage material particle.

[0149] The regenerator particle 30 has a low concentration region 30a (first region) and a high concentration region 30b (second region). The atomic concentration of the added metal element in the high concentration region 30b is higher than the atomic concentration of the added metal element in the low concentration region 30a.

[0150] The high-concentration region 30b is closer to the outer edge of the cold storage material particle 30 than the low-concentration region 30a. The high-concentration region 30b surrounds the low-concentration region 30a. The low-concentration region 30a is, for example, a region including the center of the cold storage material particle 30, and the high-concentration region 30b is a region on the periphery of the low-concentration region 30a.

[0151] The low concentration region 30a and the high concentration region 30b contain a regenerative element. At least the high concentration region 30b contains a mixture of the regenerative element and an additive metal element. It is also possible to configure the low concentration region 30a so that the additive metal element is not contained.

[0152] The atomic concentration of the added metal element in the high concentration region 30b is, for example, not less than 0.1 atomic % and not more than 2.0 atomic %.

[0153] The atomic concentration of the added metal element in the high-concentration region 30b is, for example, 1.03 to 10 times the atomic concentration of the added metal element in the low-concentration region 30a. The distance (d in FIG. 3(b)) from the outer edge of the cold storage material particle 30 to the high-concentration region 30b, at which the atomic concentration of the added metal element in the high-concentration region 30b is 1.03 times or more the atomic concentration of the added metal element in the low-concentration region 30a, is, for example, 1 / 20 or more of the particle diameter D of the cold storage material particle 30.

[0154] The distance (d in FIG. 3(b)) from the outer edge of the regenerator particle 30 to the position where the atomic concentration of the added metal element is 1.03 times or more the atomic concentration of the added metal element in the low concentration region 30a is, for example, 10 μm or more.

[0155] The atomic concentration of the added metal element monotonically decreases, for example, from the outer edge of the regenerator material particle 30 toward the center.

[0156] The detection of the additive metal element contained in the heat storage material particle 30 and the measurement of the atomic concentration of the additive metal element can be performed, for example, by WDX. For example, WDX can be used to measure the concentration of the additive metal element at multiple locations from the outer edge toward the center of the heat storage material particle 30, determine whether a high-concentration region 30b near the outer edge of the heat storage material particle 30 exists, determine the atomic concentration of the additive metal element in the high-concentration region 30b, calculate the ratio of the atomic concentration of the additive metal element in the high-concentration region 30b to the atomic concentration of the additive metal element in the low-concentration region 30a, and calculate the distance from the outer edge of the heat storage material particle 30 (d in FIG. 3(b)) to the position where the atomic concentration of the additive metal element is 1.03 times or more the atomic concentration of the additive metal element in the low-concentration region 30a. Furthermore, for example, WDX can be used to map the atomic concentration of the additive metal element in the heat storage material particle 30, and identify whether the high-concentration region 30b surrounds the low-concentration region 30a.

[0157] The cold storage material particles 30 of the third embodiment can be manufactured by the same manufacturing method as the manufacturing method of the first embodiment.

[0158] When producing the regenerator particles 30 of the third embodiment, the atomic concentration distribution of the added metal element in the particle is controlled, for example, by controlling the gelation time. That is, by controlling the gelation time, a distribution is formed in which the atomic concentration of the added metal element is low in the central region of the particle and high in the outer peripheral region of the particle.

[0159] From the viewpoint of forming the above distribution, the gelation time is preferably as short as possible without causing the particle shape to be distorted in the subsequent step, and is preferably within 1 hour, more preferably within 30 minutes.

[0160] Next, the function and effect of the regenerator particles 30 of the third embodiment will be described.

[0161] The cold storage material particle 30 of the third embodiment has a high-concentration region 30b in which the atomic concentration of the added metal element is high in the outer peripheral region of the particle. The added metal element has the effect of promoting sintering of the particles during sintering when producing the cold storage material particle 30. Therefore, the high-concentration region 30b has a high degree of sintering and high mechanical strength. Therefore, the cold storage material particle 30 has high mechanical strength.

[0162] Furthermore, since the high concentration region 30b has a high degree of sintering, the high concentration region 30b has high thermal conductivity and high heat transfer coefficient, and therefore the regenerator particles 30 have high thermal conductivity and high heat transfer coefficient.

[0163] When the atomic concentration of the added metal element increases, the degree of sintering of the particles increases, but the volume fraction of the added metal element increases, which causes a problem of a decrease in the volume fraction of the regenerative material. In addition, the added metal element reacts with the regenerative material to form a compound with a low volumetric specific heat. Therefore, when the atomic concentration of the added metal element increases, the regenerative material may change into a compound with a low volumetric specific heat, which may cause a decrease in the volume fraction of the regenerative material.

[0164] The cold storage material particle 30 of the third embodiment has a low concentration region 30a in the center region of the particle, where the atomic concentration of the added metal element is low. Therefore, in the center region of the particle, a decrease in the volume ratio of the cold storage material due to the added metal element is suppressed. Therefore, the cold storage material particle 30 has a high volume specific heat.

[0165] The heat storage material particle 30 of the third embodiment has a high-concentration region 30b in the outer periphery of the particle, where the atomic concentration of the added metal element is high, thereby improving the mechanical strength, thermal conductivity, and heat transfer coefficient. On the other hand, the heat storage material particle 30 has a low-concentration region 30a in the central region of the particle, thereby improving the volumetric specific heat. The heat storage material particle 30 of the third embodiment has a high volumetric specific heat, high mechanical strength, high thermal conductivity, and high heat transfer coefficient by optimizing the concentration distribution of the added element in the particle.

[0166] The atomic concentration of the added metal element in the high concentration region 30b is preferably 0.1 atomic % or more, and more preferably 0.2 atomic % or more, which makes it possible to increase the mechanical strength, thermal conductivity, and heat transfer coefficient of the regenerator particle 30.

[0167] The atomic concentration of the added metal element in the high-concentration region 30b is preferably 1.03 times or more, more preferably 1.05 times or more, even more preferably 1.1 times or more, and most preferably 1.2 times or more, of the atomic concentration of the added metal element in the low-concentration region 30a, which makes it possible to achieve high mechanical strength, high thermal conductivity, high heat transfer coefficient, and high volumetric specific heat of the regenerator particles 30.

[0168] The distance (d in FIG. 3(b)) from the outer edge of the cold storage material particle 30 to the position where the atomic concentration of the added metal element becomes 1.03 times or more the added metal concentration in the low concentration region 30a is preferably 1 / 20 or more, more preferably 1 / 10 or more of the particle diameter D (D in FIG. 3(a)) of the cold storage material particle 30. This makes it possible to increase the mechanical strength, thermal conductivity, and heat transfer coefficient of the cold storage material particle 30.

[0169] The distance (d in FIG. 3(b)) from the outer edge of the cold storage material particle 30 to the position where the atomic concentration of the added metal element is 1.03 times or more the added metal concentration in the low concentration region 30a is preferably 10 μm or more, more preferably 20 μm or more, which makes it possible to increase the mechanical strength, thermal conductivity, and heat transfer coefficient of the cold storage material particle 30.

[0170] In order to achieve high mechanical strength, high thermal conductivity, high heat transfer coefficient, and high volumetric specific heat of the regenerator particles 30, it is preferable that the concentration of the added metal monotonically decreases from the outer edge to the center of the regenerator particles 30.

[0171] As described above, according to the third embodiment, it is possible to realize regenerator particles having excellent properties such as a high volumetric specific heat, high mechanical strength, high thermal conductivity, and high heat transfer coefficient.

[0172] (Fourth embodiment) The refrigerator of the fourth embodiment is a refrigerator including a regenerator filled with a plurality of regenerator particles of the first embodiment. Hereinafter, some of the description overlapping with the first embodiment will be omitted.

[0173] 4 is a schematic cross-sectional view showing the main configuration of a GM refrigerator, which is an example of a refrigerator according to the fourth embodiment. The refrigerator according to the fourth embodiment is a two-stage regenerative cryogenic refrigerator 100 used to cool superconducting equipment, etc. The regenerator filled with a plurality of regenerator particles according to the first embodiment may be a Stirling refrigerator, a pulse tube refrigerator, or the like, in addition to the GM refrigerator described above.

[0174] The regenerative cryogenic refrigerator 100 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.

[0175] The regenerative cryogenic refrigerator 100 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 fourth embodiment, is arranged in the second cylinder 112 so as to be able to reciprocate.

[0176] 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.

[0177] The first regenerator 114 contains a first regenerator material 118 such as a Cu mesh. The second regenerator 115 is filled with a plurality of regenerator particles 10 of the first embodiment as a second regenerator material 119.

[0178] The second regenerator 115 may be divided by a metal mesh material and may have a plurality of regenerator packed layers. When the second regenerator 115 is divided into a plurality of packed layers, at least one packed layer is filled with a regenerator particle group consisting of a plurality of the regenerator particles of the first embodiment, and is combined with at least one type of regenerator particle group selected from, for example, lead regenerator particle group, bismuth regenerator particle group, tin regenerator particle group, holmium copper regenerator particle group, erbium nickel regenerator particle group, erbium cobalt regenerator particle group, and gadolinium aluminum oxide regenerator particle group.

[0179] The combination of the regenerator particles is such that the particle group with the higher peak specific heat temperature is the first regenerator particle group, and the particle group with the lower peak specific heat temperature is the second regenerator particle group, and the combinations are made so that the peak specific heat temperatures decrease sequentially.

[0180] In the case of a two-layer type, a combination of using holmium copper cold accumulator particles as the first cold accumulator particle group and the cold accumulator particle group according to the first embodiment as the second cold accumulator particle group can be exemplified. Also, in the case of a three-layer type, a combination of using at least one cold accumulator particle group selected from lead cold accumulator particle group, bismuth cold accumulator particle group, and tin cold accumulator particle group as the first cold accumulator particle group, holmium copper cold accumulator particle group as the second cold accumulator particle group, and the cold accumulator particle group according to the first embodiment as the third cold accumulator particle group can be exemplified.

[0181] The holmium copper regenerator particles are preferably, for example, HoCu2 or HoCu, and the erbium nickel regenerator particles are preferably, for example, ErNi or Er3Ni.

[0182] 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.

[0183] 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.

[0184] The two-stage regenerative cryogenic refrigerator 100 described above is supplied with a high-pressure working medium from a compressor 124. The supplied working medium passes between first regenerator materials 118 housed in the first regenerator 114 and reaches the first expansion chamber 120. Then, it passes between second regenerator materials 119 housed in the second regenerator 115 and reaches the second expansion chamber 121.

[0185] 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.

[0186] 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 100 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.

[0187] By using the refrigerator of the fourth embodiment in a magnetic levitation train, a helium recondenser, or the like, it is possible to improve the long-term reliability of the magnetic levitation train, the helium recondenser, and the like.

[0188] As the second cold storage material 119, the cold storage material particles of the second embodiment or the third embodiment can also be applied.

[0189] As described above, according to the fourth embodiment, a refrigerator with excellent characteristics can be realized by using regenerator particles with excellent characteristics.

[0190] (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.

[0191] 5 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 100 according to the fourth embodiment.

[0192] The cryopump 500 includes a cryopanel 501 that condenses or adsorbs gas molecules, a regenerative cryogenic refrigerator 100 that cools the cryopanel 501 to a predetermined cryogenic temperature, a shield 503 installed between the cryopanel 501 and the regenerative cryogenic refrigerator 100, a baffle 504 installed at the intake port, and a ring 505 that changes the pumping speed of argon, nitrogen, hydrogen, etc.

[0193] 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 semiconductor manufacturing equipment, the long-term reliability of the semiconductor manufacturing equipment can be improved and the number of maintenance cycles for the semiconductor manufacturing equipment can be reduced. As a result, this contributes to improving the quality of the semiconductors manufactured and reducing manufacturing costs.

[0194] (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.

[0195] 6 is a perspective view showing a schematic configuration of a superconducting magnet according to a sixth embodiment. The superconducting magnet according to the sixth embodiment is a superconducting magnet 600 for a magnetic levitation train that includes the regenerative cryogenic refrigerator 100 according to the fourth embodiment.

[0196] 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 100.

[0197] According to the sixth embodiment, a superconducting magnet with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0198] (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.

[0199] 7 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance imaging apparatus according to the seventh embodiment. The nuclear magnetic resonance imaging (MRI) apparatus according to the seventh embodiment is a nuclear magnetic resonance imaging apparatus 700 equipped with the regenerative cryogenic refrigerator 100 according to the fourth embodiment.

[0200] 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 100 is used to cool the superconducting static magnetic field coil 701.

[0201] According to the seventh embodiment, a nuclear magnetic resonance imaging apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0202] (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.

[0203] 8 is a cross-sectional view 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 100 according to the fourth embodiment.

[0204] 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 100 that cools the superconducting static magnetic field coil 802.

[0205] According to the eighth embodiment, a nuclear magnetic resonance apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0206] (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.

[0207] 9 is a perspective view showing a 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 100 according to the ninth embodiment.

[0208] 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 100 is used to cool the superconducting coil 902.

[0209] 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.

[0210] The refrigerator of the fourth embodiment can improve long-term reliability by being used in magnetic levitation trains, helium recondensation devices, and the like. [Example]

[0211] Examples and comparative examples of the cold storage material particles according to the first to third embodiments, and their evaluation results will be described below.

[0212] The configurations and evaluation results of the regenerator particles of Examples 1 to 77 and Comparative Examples 1 to 7 are shown in Tables 1 to 7.

[0213] [Table 1]

[0214] [Table 2]

[0215] [Table 3]

[0216] [Table 4]

[0217] [Table 5]

[0218] [Table 6]

[0219] [Table 7]

[0220] Example 1 Gadolinium oxide powder was added to a sodium alginate solution as a raw material for the cold storage material, and the mixture was mixed to create a slurry. Aluminum oxide was also added to the slurry. The mixing time was 12 hours.

[0221] The slurry containing the cold storage material was dropped into the calcium lactate aqueous solution, which was the gelling solution. A syringe was used to drop the slurry. The diameter of the syringe outlet was 510 μm, and the distance from the tip of the syringe to the liquid surface of the calcium lactate aqueous solution was 100 mm.

[0222] The slurry was kept in the gelling solution for 5 hours.

[0223] The gelled particles were then washed with pure water. After washing, the particles were dried. After drying, the particles were sulfurized and sintered.

[0224] The particles were sulfurized by heat treatment at 500°C for 4 hours in an atmosphere containing hydrogen sulfide (H2S), and then sintered by heat treatment at 1300°C for 12 hours in a pressurized inert gas atmosphere.

[0225] The cold storage material particles of Example 1 were spherical.

[0226] The cold storage material of the cold storage material particles of Example 1 is gadolinium oxysulfide, the first element is gadolinium (Gd), and the second element is calcium (Ca) and aluminum (Al). The calcium concentration in the cold storage material particles of Example 1 is 0.12 atomic %. The aluminum concentration in the cold storage material particles is 23.3 atomic %.

[0227] In the regenerator particles, the concentration ratio (C2 / C1) of the atomic concentration (C2) of the second element in the second region to the atomic concentration (C1) of the second element in the first region was 1. That is, C2 / C1=1.

[0228] In the following examples and comparative examples, the mixing time of the raw material powder with the alginic acid aqueous solution, the retention time of the slurry in the gelling solution (gelling time), the conditions for the sulfurization heat treatment, the conditions for the sintering heat treatment, etc. are adjusted to be appropriate conditions.

[0229] Example 2 The regenerator particles were produced in the same manner as in Example 1, except that magnesium oxide was used in addition to aluminum oxide.

[0230] Example 3 Cool storage material particles were produced in the same manner as in Example 1, except that aluminum chloride was used as the gelling solution.

[0231] Example 4 Cool storage material particles were produced in the same manner as in Example 1, except that an aqueous magnesium sulfate solution was used as the gelling solution.

[0232] Example 5 The regenerator particles were produced in the same manner as in Example 1, except that an aqueous beryllium sulfate solution was used as the gelling solution.

[0233] Example 6 Cool storage material particles were produced in the same manner as in Example 1, except that an aqueous solution of strontium nitrate was used as the gelling solution.

[0234] Example 7 Cool storage material particles were produced in the same manner as in Example 1, except that an aqueous solution of barium chloride was used as the gelling solution.

[0235] Example 8 The cold storage material particles were produced in the same manner as in Example 1, except that an aqueous manganese chloride solution was used as the gelling solution.

[0236] Example 9 Cool storage material particles were produced in the same manner as in Example 1, except that an aqueous iron chloride solution was used as the gelling solution.

[0237] Example 10 Cool storage material particles were produced in the same manner as in Example 1, except that an aqueous copper chloride solution was used as the gelling solution.

[0238] Example 11 The cold storage material particles were produced in the same manner as in Example 1, except that an aqueous solution of nickel chloride was used as the gelling solution.

[0239] Example 12 The cold storage material particles were produced in the same manner as in Example 1, except that an aqueous solution of cobalt chloride was used as the gelling solution.

[0240] Example 13 The regenerator particles were produced in the same manner as in Example 1, except that part of the regenerator element gadolinium was replaced with yttrium (Y), the weight of the raw powder of the regenerator material in the slurry was increased, and aluminum oxide was not used.

[0241] Example 14 The regenerator particles were manufactured in the same manner as in Example 1, except that part of the regenerator element gadolinium was replaced with cerium (Ce), the weight of the raw powder of the regenerator material in the slurry was increased, aluminum oxide was not used, and magnesium chloride was used as the gelling solution.

[0242] Example 15 The regenerator particles were manufactured in the same manner as in Example 1, except that part of the regenerator element gadolinium was replaced with praseodymium (Pr), the weight of the raw powder of the regenerator material in the slurry was increased, aluminum oxide was not used, and a beryllium sulfate aqueous solution was used as the gelling solution.

[0243] Example 16 The regenerator particles were manufactured in the same manner as in Example 1, except that part of the regenerator element gadolinium was replaced with neodymium (Nd), the weight of the raw powder of the regenerator material in the slurry was increased, aluminum oxide was not used, and a strontium nitrate aqueous solution was used as the gelling solution.

[0244] Example 17 The regenerator particles were produced in the same manner as in Example 1, except that part of the regenerator element gadolinium was replaced with promethium (Pm), the weight of the raw powder of the regenerator material in the slurry was increased, aluminum oxide was not used, and a barium chloride aqueous solution was used as the gelling solution.

[0245] Example 18 The regenerator particles were produced in the same manner as in Example 1, except that part of the regenerator element gadolinium was replaced with samarium (Sm), aluminum oxide was not used, and a manganese chloride aqueous solution was used as the gelling solution.

[0246] Example 19 The regenerator particles were produced in the same manner as in Example 1, except that part of the regenerator element gadolinium was replaced with europium (Eu), aluminum oxide was not used, and an aqueous aluminum chloride solution was used as the gelling solution.

[0247] Example 20 The regenerator particles were produced in the same manner as in Example 1, except that a portion of the regenerator element gadolinium was replaced with terbium, aluminum oxide was not used, and an aqueous solution of iron chloride was used as the gelling solution.

[0248] (Examples 21 to 26) The regenerator particles were manufactured in the same manner as in Example 1, except that a portion of the regenerator element gadolinium (Gd) was replaced with dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), or lutetium (Lu), the weight of the raw powder of the regenerator material in the slurry was reduced, aluminum oxide was not used, and a copper chloride aqueous solution, nickel chloride aqueous solution, cobalt chloride aqueous solution, calcium chloride aqueous solution, or magnesium chloride aqueous solution was used as the gelling solution.

[0249] Example 27 The regenerator particles of Example 27 differ from those of Example 3 in that the added metal element is strontium (Sr).

[0250] Example 28 The regenerator particles of Example 28 are different from those of Example 3 in that the concentration of aluminum (Al) in the particles is high.

[0251] Example 29 The refrigerant particles of Example 29 differ from those of Example 1 in that the concentration ratio (C2 / C1) of the atomic concentration (C2) of the added metal element in the second region to the atomic concentration (C1) of the added metal element in the first region is 1.03.

[0252] The cold storage material particles of Example 29 were produced by the same method as in Example 1, but the gelling time was shorter than that of Example 1.

[0253] Example 30 The refrigerant particles of Example 30 differ from the refrigerant particles of Example 29 in that the concentration ratio (C2 / C1) of the atomic concentration (C2) of the added metal element in the second region to the atomic concentration (C1) of the added metal element in the first region is 1.05.

[0254] When producing the cold accumulator particles of Example 30, the gelling time was set to be shorter than when producing the cold accumulator particles of Example 29.

[0255] Example 31 The refrigerant particles of Example 31 differ from those of Example 29 in that the concentration ratio (C2 / C1) of the atomic concentration (C2) of the added metal element in the second region to the atomic concentration (C1) of the added metal element in the first region is 1.1.

[0256] When producing the cold accumulator particles of Example 31, the gelling time was set shorter than when producing the cold accumulator particles of Example 30.

[0257] Example 32 The regenerator particles of Example 32 differ from those of Example 1 in that they contain silver oxide as a regenerator material and silver (Ag) as a regenerator element. They also differ from those of Example 1 in that they contain magnesium (Mg) as an added metal element and do not contain aluminum (Al) as an added metal element. The regenerator particles of Example 32 contain an Ag-O phase and an Ag-Mg-O phase.

[0258] Example 33 The cold storage material particles of Example 32 differ from the cold storage material particles of Example 1 in that they contain silver oxide as a cold storage material and the cold storage element is silver (Ag). They also differ from the cold storage material particles of Example 1 in that they do not contain aluminum (Al) as an added metal element. The cold storage material particles of Example 33 contain an Ag-O phase and an Ag-Ca-O phase.

[0259] Example 34 The regenerator particles of Example 34 differ from those of Example 1 in that they contain copper oxide as a regenerator material and copper (Cu) as a regenerator element. They also differ from those of Example 1 in that they contain strontium (Sr) as an added metal element and do not contain aluminum (Al) as an added metal element. The regenerator particles of Example 34 contain a Cu-O phase and a Cu-Sr-O phase.

[0260] Example 35 The regenerator particles of Example 35 differ from those of Example 1 in that they contain copper oxide as a regenerator material and copper (Cu) as a regenerator element. They also differ from those of Example 1 in that they contain barium (Ba) as an added metal element and do not contain aluminum (Al) as an added metal element. The regenerator particles of Example 34 contain a Cu-O phase and a Cu-Ba-O phase.

[0261] Examples 36 to 41 The cold storage material particles of Examples 36 to 41 differ from the cold storage material particles of Example 1 in the area per second phase in the cross section of the cold storage material particle and the particle size. When producing the cold storage material particles of Examples 36 to 41, the sintering temperature and sintering time were changed compared to when producing the cold storage material particles of Example 1.

[0262] (Examples 42 to 50) The cold accumulator particles of Examples 42 to 50 differ from the cold accumulator particles of Example 1 in the proportion of the second phase that is in contact with the third phase and the proportion of the second phase that is in contact with the fourth phase in the cross section of the cold accumulator particle. When producing the cold accumulator particles of Examples 42 to 50, the mixing time of the raw material powder and the alginic acid aqueous solution was changed compared to when producing the cold accumulator particles of Example 1.

[0263] (Examples 51 to 56) The cold storage material particles of Examples 51 to 56 differ in particle size or aspect ratio from the cold storage material particles of Example 1. When producing the cold storage material particles of Examples 51 to 56, the diameter of the syringe outlet and the distance from the tip of the syringe to the surface of the gelling solution were changed compared to when producing the cold storage material particles of Example 1.

[0264] (Examples 57 to 59) Cool storage material particles were produced in the same manner as in Example 3, except that terbium oxide, holmium oxide, and dysprosium oxide were used instead of gadolinium oxide.

[0265] Example 60 Cool storage material particles were produced in the same manner as in Example 1, except that an air pulse dispenser was used instead of a syringe as a method for dropping the slurry. The rod was driven up and down for 10 ms per cycle, the nozzle outlet diameter was 510 μm, and the distance from the nozzle tip to the liquid surface of the calcium lactate aqueous solution was 100 mm. In this case, the particle production rate was 100 particles / second, which is an improvement over when dropping the slurry with a syringe.

[0266] In the following examples, the particle size was adjusted by adjusting the mixing time of the raw material powder with the alginic acid aqueous solution, the slurry viscosity, the retention time of the slurry in the gelling solution (gelling time), the conditions of the sulfurization heat treatment, the conditions of the sintering heat treatment, the time for driving the rod up and down, the liquid feed pressure, the diameter of the nozzle outlet, the distance from the tip of the nozzle to the liquid surface of the calcium lactate aqueous solution, etc.

[0267] Example 61 Cool storage material particles were produced in the same manner as in Example 60, except that magnesium oxide was used in addition to aluminum oxide.

[0268] Example 62 Cool storage material particles were produced in the same manner as in Example 60, except that aluminum chloride was used as the gelling solution.

[0269] (Examples 63 to 65) Cool storage material particles were produced in the same manner as in Example 60, except that terbium oxide, holmium oxide, and dysprosium oxide were used instead of gadolinium oxide.

[0270] Example 66 Cool storage material particles were produced in the same manner as in Example 1, except that a piezoelectric dispenser was used instead of a syringe to drip the slurry. The rod was driven up and down for 10 ms per cycle, the nozzle outlet diameter was 510 μm, and the distance from the nozzle tip to the liquid surface of the calcium lactate aqueous solution was 100 mm. In this case, the particle production rate was 100 particles / second, which is an improvement over when dripping with a syringe.

[0271] In the following examples, the particle size was adjusted by adjusting the mixing time of the raw material powder with the alginic acid aqueous solution, the slurry viscosity, the retention time of the slurry in the gelling solution (gelling time), the conditions of the sulfurization heat treatment, the conditions of the sintering heat treatment, the time the rod is driven up and down, the liquid feed pressure, the diameter of the nozzle outlet, the distance from the tip of the nozzle to the liquid surface of the calcium lactate aqueous solution, etc.

[0272] Example 67 Cool storage particles were produced in the same manner as in Example 66, except that magnesium oxide was used in addition to aluminum oxide.

[0273] Example 68 Cool storage material particles were produced in the same manner as in Example 66, except that aluminum chloride was used as the gelling solution.

[0274] (Examples 69 to 71) Cool storage material particles were produced in the same manner as in Example 66, except that terbium oxide, holmium oxide, and dysprosium oxide were used instead of gadolinium oxide.

[0275] Example 72 Cool storage material particles were produced in the same manner as in Example 1, except that a continuous inkjet was used instead of a syringe to drip the slurry. By appropriately controlling the waveform of the pressure wave applied to the liquid column, the particle production rate was set to 500 particles / second. This production rate is higher than the production rate when dripping is performed using a syringe. The nozzle outlet diameter was 510 μm, and the distance from the nozzle tip to the liquid surface of the calcium lactate aqueous solution was 100 mm.

[0276] In the following examples, the particle size was adjusted by adjusting the mixing time of the raw material powder with the alginic acid aqueous solution, the slurry viscosity, the retention time of the slurry in the gelling solution (gelling time), the conditions of the sulfurization heat treatment, the conditions of the sintering heat treatment, the particle production rate, the liquid feed pressure, the diameter of the nozzle outlet, the distance from the tip of the nozzle to the liquid surface of the calcium lactate aqueous solution, etc.

[0277] Example 73 Cool storage particles were produced in the same manner as in Example 72, except that magnesium oxide was used in addition to aluminum oxide.

[0278] Example 74 Cool storage material particles were produced in the same manner as in Example 72, except that aluminum chloride was used as the gelling solution.

[0279] (Examples 75 to 77) Cool storage material particles were produced in the same manner as in Example 72, except that terbium oxide, holmium oxide, and dysprosium oxide were used instead of gadolinium oxide.

[0280] (Comparative Example 1) The cold storage material particles of Comparative Example 1 differ from the cold storage material particles of Example 3 in that the atomic concentration of aluminum (Al) in the particles is as low as 0.0008 atomic %. When producing the cold storage material particles of Comparative Example 1, the weight of the raw material powder of the cold storage material in the slurry was increased compared to when producing the cold storage material particles of Example 3, and aluminum oxide was not used in the slurry.

[0281] (Comparative Example 2) The cold storage material particles of Comparative Example 2 differ from those of Example 3 in that they do not contain aluminum (Al) and have a high atomic concentration of calcium (Ca) in the particles of 47 atomic %. When producing the cold storage material particles of Comparative Example 2, the weight of the raw powder of the cold storage material in the slurry was reduced compared to when producing the cold storage material particles of Example 1, and aluminum oxide was not used in the slurry.

[0282] (Comparative Example 3) The cold storage material particles of Comparative Example 3 differ from those of Example 1 in that they do not contain aluminum (Al) and have a high atomic concentration of calcium (Ca) in the particles of 61 atomic %. When producing the cold storage material particles of Comparative Example 3, the weight of the raw powder of the cold storage material in the slurry was reduced compared to when producing the cold storage material particles of Example 1, aluminum oxide was not used in the slurry, and a copper chloride aqueous solution was used as the gelling solution.

[0283] Comparative Example 4 The cold storage material particles of Comparative Example 4 differ from those of Example 1 in that they do not contain aluminum (Al) and have a low atomic concentration of beryllium (Be) in the particles of 0.0005 atomic %. When producing the cold storage material particles of Comparative Example 4, the weight of the raw material powder of the cold storage material in the slurry was increased compared to when producing the cold storage material particles of Example 32, and a beryllium sulfate aqueous solution was used as the gelling solution.

[0284] (Comparative Example 5) The cold storage material particles of Comparative Example 5 differ from the cold storage material particles of Example 33 in that the atomic concentration of calcium (Ca) in the particles is high at 37 atomic %. When producing the cold storage material particles of Comparative Example 5, the weight of the raw material powder of the cold storage material in the slurry was reduced compared to when producing the cold storage material particles of Example 33.

[0285] (Comparative Example 6) The cold storage material particles of Comparative Example 6 differ from those of Example 1 in that they do not contain aluminum (Al) and have a low atomic concentration of iron (Fe) in the particles of 0.0005 atomic %. When producing the cold storage material particles of Comparative Example 6, the weight of the raw powder of the cold storage material in the slurry was increased compared to when producing the cold storage material particles of Example 34, and an aqueous iron chloride solution was used as the gelling solution.

[0286] (Comparative Example 7) The cold storage material particles of Comparative Example 7 differ from the cold storage material particles of Example 35 in that the atomic concentration of manganese (Mn) in the particles is as high as 40 atomic %. When producing the cold storage material particles of Comparative Example 7, the weight of the raw material powder of the cold storage material in the slurry was reduced compared to when producing the cold storage material particles of Example 35, and a manganese chloride aqueous solution was used as the gelling solution.

[0287] The maximum volumetric specific heat of each of the produced regenerator particles was measured at 20 K or less. The results are shown in Tables 1 to 7.

[0288] The mechanical strength required for the cold storage particles was evaluated when the cold storage particles were filled into the cold storage unit that constitutes the refrigerator and the refrigerator was operated. The manufactured cold storage particles were filled into cylindrical containers with a diameter of 15 mm and a height of 5 mm. A sufficient amount of cold storage particles was filled so that the cold storage particles were fixed inside the cylindrical container and did not move freely. The container was subjected to an amplitude of 2 mm and a maximum acceleration of 400 m / s. 2 Simple harmonic motion of 1×10 6 times and 1 x 10 7 As a result, the ratio of the destroyed cold storage material particles is shown in Tables 1 to 7.

[0289] The mechanical strength required of the cold storage particles was evaluated when they were filled into the cold storage unit that makes up the refrigerator and the refrigerator was operating. The resistance to temperature changes required of the cold storage particles, which occurs when the temperature of the cold storage material fluctuates between room temperature and cryogenic temperatures before and after the refrigerator is running, was also evaluated. The manufactured cold storage particles were filled into cylindrical containers with a diameter of 15 mm and a height of 5 mm. A sufficient amount of cold storage particles was filled so that the cold storage particles were fixed in the cylindrical container and did not move freely. After filling, the cylindrical container was cooled from room temperature to the temperature of liquid helium, and then returned to room temperature. The container was then subjected to a force of 2 mm amplitude and a maximum acceleration of 400 m / s. 2 Simple harmonic motion of 1×10 4 The ratio of the fractured particles of the regenerator material is shown in the table.

[0290] The thermal conductivity and refrigeration capacity of the regenerator particles at 4.2K are shown in the table. The refrigeration capacity was investigated using a two-stage GM refrigerator with a power consumption of 3.4kW. A Cu mesh was placed in the first regenerator, and the first layer on the high-temperature side of the second regenerator was filled with lead (Pb) as the regenerator material, the second layer was filled with HoCu2 as the regenerator material, and the third layer on the low-temperature side was filled with the regenerator particles to be evaluated.

[0291] It can be seen that when the atomic concentration of the added metal element in the cold storage material particle is greater than 60 atomic %, as in Comparative Example 3, the maximum value of the volumetric specific heat becomes smaller, less than 0.3. This is thought to be because the proportion of the cold storage substance in the cold storage material particle decreases as the proportion of the added metal element in the cold storage material particle increases.

[0292] When the atomic concentration of the added metal element in the regenerator particles is less than 0.001 atomic %, as in Comparative Examples 1, 4, and 6, the proportion of broken regenerator particles increases to 5 wt % or more. This is thought to be because the sintering of the regenerator particles does not proceed sufficiently due to the low atomic concentration of the added metal element.

[0293] Simple harmonic motion is 1 x 10 7The proportion of broken particles when the sintering was performed 10 times was compared between Examples 1 to 12. The proportion of broken particles was low in Examples 1 and 2, which contained calcium (Ca) as an added metal element. This is thought to be because calcium (Ca) has a particularly high ability to promote sintering of the regenerator particles.

[0294] Furthermore, as in Examples 29 to 31, when the concentration ratio (C2 / C1) of the atomic concentration (C2) of the added metal element in the second region to the atomic concentration (C1) of the added metal element in the first region becomes larger than 1, the maximum value of the volumetric specific heat becomes larger. This is thought to be because the proportion of the cold storage material in the center of the cold storage material particle becomes larger.

[0295] From Tables 1 to 7, it can be seen that when the area ratio of the second phase in the cross section of the regenerator particle exceeds 0.001%, the ratio of broken regenerator particles drops sharply, and when the area ratio of the second phase exceeds 0.001%, the mechanical strength improves.

[0296] On the other hand, when the area ratio of the second phase in the cross section of the regenerator particle is less than 75%, the maximum value of the volumetric specific heat below 20 K is shown to improve. By controlling the area ratio of the second phase in this way, it is possible to provide regenerator particles with high thermal conductivity and high strength.

[0297] From Tables 1 to 7, the area of ​​each second phase in the cross section of the regenerator particle is 0.001 μm 2 On the other hand, when the area of ​​each second phase in the cross section of the regenerator particle is 6000 μm, the thermal conductivity is significantly improved. 2 If the value is less than 1×10 7 The ratio of fractured particles after repeated application is significantly reduced. 2 It can be seen that the mechanical strength of the regenerator particles is improved when the area of ​​each phase is below 0.05. In this way, by controlling the area of ​​each phase, it is possible to provide regenerator particles with high thermal conductivity and high strength.

[0298] From Tables 1 to 7, it can be seen that when the particle size of each second phase in the cross section of the regenerator particle exceeds 0.1 μm, the thermal conductivity is significantly improved. On the other hand, when the particle size of each second phase in the cross section of the regenerator particle is less than 100 μm, the simple harmonic motion is 1×10 7 The ratio of fractured particles after repeated application is significantly reduced. It can be seen that the mechanical strength of the cold storage material particles is improved when the particle size of each second phase in the cross section of the cold storage material particle is less than 100 μm. In this way, by controlling the particle size of each phase, it is possible to provide cold storage material particles with high thermal conductivity and high strength.

[0299] From Tables 1 to 7, when the proportion of the second phase in contact with the third phase in the cross section of the regenerator particle exceeds 20%, the simple harmonic motion after changing the temperature from room temperature to the liquid helium temperature is 1 × 10 4 The ratio of broken particles decreases after the number of times of stress. It can be seen that when the ratio of the second phase in contact with the third phase exceeds 20%, the mechanical strength of the regenerator particles improves when a temperature change is applied.

[0300] On the other hand, if the proportion of the second phase in contact with the third phase in the cross section of the regenerator particle falls below 90%, the simple harmonic motion will be 1×10 4 The ratio of broken particles after repeated stressing decreases. When the ratio of the second phase in contact with the third phase in the cross section of the regenerator particle is below 90%, the mechanical strength of the regenerator particle when a temperature change is applied is shown to be improved. In this way, by controlling the ratio of the second phase and the third phase in contact, the mechanical strength of the regenerator particle when a temperature change is applied is improved.

[0301] From Tables 1 to 7, when the proportion of the second phase in contact with the third phase in the cross section of the regenerator particle exceeds the proportion of the second phase in contact with the fourth phase, the simple harmonic motion after changing the temperature from room temperature to the liquid helium temperature becomes 1 × 10 4It can be seen that when the proportion of the second phase in contact with the third phase in the cross section of the regenerator particle exceeds the proportion of the second phase in contact with the fourth phase, the mechanical strength of the regenerator particle when a temperature change is applied is improved.

[0302] It can be seen from Tables 1 to 7 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.

[0303] Tables 1 to 7 show that when the aspect ratio of the regenerator particles is 5 or less, the refrigeration capacity at 4.2K is significantly improved.

[0304] From Examples 60, 66 and 72, it can be seen that the production speed of the cold storage material particles is significantly improved when a dispenser or an ink jet is used compared to when a syringe is used.

[0305] Tables 1 to 7 show that regardless of whether the liquid is dispensed using a syringe, dispenser, or inkjet, as long as the conditions other than the method of dispensing the liquid are the same, the particles will exhibit equivalent particle size, aspect ratio, dispersion relationship of the phases within the particles, strength, and specific heat.

[0306] Tables 1 to 7 show that even if the method of dropping the liquid is different for particles, if the particle size, aspect ratio, dispersion relationship of the phases within the particle, strength, and specific heat are equivalent, the performance and reliability of the refrigerator equipped with the particles will be equivalent.

[0307] The above examples confirmed the effects of the regenerator particles of the first to third embodiments.

[0308] In the above, in the first to third embodiments, the rare earth element serving as the regenerative element is gadolinium (Gd), but the regenerative element may be a rare earth element other than gadolinium (Gd).

[0309] Furthermore, in the first to third embodiments, the case where the added metal element is calcium (Ca) or aluminum (Al) has been described as an example, but the added metal element may be magnesium (Mg), beryllium (Be), strontium (Sr), barium (Ba), radium (Ra), manganese (Mn), iron (Fe), copper (Cu), nickel (Ni), or cobalt (Co).

[0310] Furthermore, although the dispenser has been described as an air pulse dispenser or a piezo dispenser, a plunger dispenser may also be used.

[0311] Furthermore, although the description has been given using a continuous inkjet as an example of the inkjet, an on-demand inkjet may also be used.

[0312] 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. [Explanation of symbols]

[0313] 10. Cold storage material particles of the first embodiment 20 Second embodiment of the cold storage material particles 30 Cold storage material particles of the third embodiment 30a Low concentration area 30b High concentration area 100 Regenerative cryogenic refrigerator 500 Cryopump 600 Superconducting Magnet 700 Nuclear Magnetic Resonance Imaging Device 800 Nuclear Magnetic Resonance Spectrometer 900 Magnetic Field Application Type Single Crystal Pulling Apparatus

Claims

1. A vacuum vessel; a first cylinder provided in the vacuum vessel; a second cylinder provided in the vacuum vessel, coaxially joined 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 at least one first element selected from the group consisting of rare earth elements, a second element that is different from the first element and forms a polyvalent metal ion in an aqueous solution; the atomic concentration of the second element is 0.001 atomic % or more and 60 atomic % or less, The maximum volumetric specific heat at temperatures below 20K is 0.3 J / cm ３ ・K or higher, a first phase including the first element and a second phase including the second element and different from the first phase; the atomic concentration of the second element in the second phase is greater than the atomic concentration of the second element in the first phase; a third phase including the first element and the second element and different from the first phase and the second phase; the first phase is an oxide of the first element or an oxysulfide of the first element; the second element is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), manganese (Mn), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), and cobalt (Co); a first region and a second region closer to an outer edge of the particle than the first region, wherein a concentration ratio (C2 / C1) of the atomic concentration (C2) of the second element in the second region to the atomic concentration (C1) of the second element in the first region is 1 or more; In the cross section of the particle, the area ratio occupied by the second phase is 0.001% or more and 75% or less, In the cross section of the particle, the area of ​​each of the second phases is 0.001 μm ２ 6000 μm or more ２ is as follows: In the cross section of the particle, 20% to 90% of the second phase is in contact with the third phase, The particle size is 50 μm or more and 3 mm or less, a second regenerator having an aspect ratio of 5 or less; A regenerative cryogenic refrigerator equipped with:

2. The regenerative cryogenic refrigerator according to claim 1 , wherein the second element includes two or more different elements.

3. A vacuum vessel; a first cylinder provided in the vacuum vessel; a second cylinder provided in the vacuum vessel, coaxially joined 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 at least one first element selected from the group consisting of rare earth elements, a second element that is different from the first element and forms a polyvalent metal ion in an aqueous solution; the atomic concentration of the second element is 0.001 atomic % or more and 60 atomic % or less, The maximum volumetric specific heat at temperatures below 20K is 0.3 J / cm ３ ・K or higher, a first phase including the first element and a second phase including the second element and different from the first phase; the atomic concentration of the second element in the second phase is greater than the atomic concentration of the second element in the first phase; the second element includes two or more different elements including an element α and an element β, the second phase includes the element α and the element β, a third phase containing the element β and different from the first phase and the second phase; a fourth phase that includes the first element and the element β and is different from the first phase, the second phase, and the third phase; the first phase is an oxide of the first element or an oxysulfide of the first element; the second element is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), manganese (Mn), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), and cobalt (Co); a first region and a second region closer to an outer edge of the particle than the first region, wherein a concentration ratio (C2 / C1) of the atomic concentration (C2) of the second element in the second region to the atomic concentration (C1) of the second element in the first region is 1 or more; In the cross section of the particle, the area ratio occupied by the second phase is 0.001% or more and 75% or less, In the cross section of the particle, the area of ​​each of the second phases is 0.001 μm ２ 6000 μm or more ２ is as follows: In the cross section of the particle, 20% to 90% of the second phase is in contact with the third phase, The particle size is 50 μm or more and 3 mm or less, a second regenerator having an aspect ratio of 5 or less; A regenerative cryogenic refrigerator equipped with:

4. 4. The regenerative cryogenic refrigerator according to claim 3, wherein a proportion of the second phase in contact with the third phase is higher than a proportion of the second phase in contact with the fourth phase.

5. 5. The regenerative cryogenic refrigerator according to claim 1, wherein the particle size of each of the second phases in the cross section of the regenerative material particle is 0.1 μm or more and 100 μm or less.

6. 6. The regenerative cryogenic refrigerator according to claim 1, wherein the atomic concentration of the second element in the second region is higher than the atomic concentration of the second element in the first region.

7. the first element includes gadolinium (Gd), the second element includes at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra), and aluminum (Al); The regenerative cryogenic refrigerator according to claim 1 , further comprising sulfur (S).

8. The regenerative cryogenic refrigerator according to claim 7 , wherein the regenerative material particles include gadolinium oxysulfide.

9. the first element is at least one element selected from the group consisting of yttrium (Y), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu); 7. The regenerative cryogenic refrigerator according to claim 1, wherein the second element is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), manganese (Mn), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), and cobalt (Co).

10. 10. The regenerative cryogenic refrigerator according to claim 1, wherein the first regenerative material is a Cu mesh.

11. 11. The method for manufacturing a regenerative cryogenic refrigerator according to claim 1, wherein a plurality of the regenerative material particles are packed into the second regenerator.

12. A cryopump comprising the regenerative cryogenic refrigerator according to any one of claims 1 to 10.

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