Cold storage material, cold storage material particle, granulated particle, cold storage device, and refrigerator

Abstract

The cold storage material of the embodiment contains a rare-earth oxysulfide containing at least one rare-earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, contains a Group 1 element in an amount of 0.001 atom% or more and 10 atom% or less, and has a maximum value of the volumetric heat capacity in a temperature range of 2 K or more and 10 K or less of 0.5 J / (cm 3 K) or more.

Description

Technical Field

[0001] The embodiments of the present invention relate to cold storage materials, cold storage material particles, granulated particles, cold storage devices, refrigerators, cryogenic pumps, superconducting magnets, nuclear magnetic resonance imaging devices, nuclear magnetic resonance devices, magnetic field applied single crystal pulling devices, and helium recondensation devices. Background Technology

[0002] In recent years, superconducting technology has made significant progress, and with its expanding application areas, the development of small and high-performance cryogenic refrigerators has become indispensable. These cryogenic refrigerators are required to be lightweight, compact, and thermally efficient, and are making progress in practical applications across various fields.

[0003] In cryogenic freezers, various cryogenic storage materials are housed within a cryogenic accumulator. For example, cold is generated by heat exchange between the cryogenic storage material and helium gas passing through the accumulator. Cryogenic pumps used in superconducting MRI devices, semiconductor manufacturing equipment, and other applications employ cryogenic cycles such as the Gifford-McMahon (GM) system, the Stirling system, or the pulse tube system.

[0004] Furthermore, in maglev trains, high-performance cryogenic systems are considered necessary to generate magnetic force using superconducting magnets. Moreover, recently, high-performance cryogenic systems have also been used in superconducting energy storage devices (SMES) and magnetic field-applied single-crystal pulling devices for manufacturing high-quality silicon wafers. The development and practical application of highly reliable pulse tube cryogenic systems are also actively underway.

[0005] Furthermore, in devices such as superconducting magnets and MRI machines, the replenishment of liquid helium becomes a problem due to its evaporation. In recent years, the helium depletion problem has intensified, becoming increasingly difficult to obtain and impacting industry.

[0006] To reduce the consumption of liquid helium and alleviate the burden of maintenance such as resupply, helium recondensation devices that re-condense evaporated helium have been put into practical use, leading to increased demand. In these helium recondensation devices, GM-type and pulse-tube refrigerators are also used to cool the temperature to 4K level in order to liquefy the helium.

[0007] In such a refrigerator, compressed helium (He) or other working medium flows in one direction within a accumulator containing cold storage material, supplying its heat energy to the material. Then, the expanding working medium within the accumulator flows in the opposite direction, absorbing heat energy from the cold storage material. As the reheating effect in this process improves, the thermal efficiency of the working medium circulation increases, enabling the achievement of even lower temperatures.

[0008] The higher the specific heat per unit volume of the cold storage material in the cold accumulator, the greater the amount of heat energy that the cold storage material can store, and thus the greater the freezing capacity of the refrigerator. Therefore, it is preferable to use a cold storage material with high specific heat at low temperatures on the low-temperature side of the cold accumulator and a cold storage material with high specific heat at high temperatures on the high-temperature side.

[0009] Magnetic cold storage materials exhibit high volumetric specific heat within a specific temperature range, depending on their composition. Therefore, by combining magnetic cold storage materials with different compositions that exhibit high volumetric specific heat in the target temperature range, the cold storage capacity is improved, thereby increasing the freezing capacity of the refrigerator.

[0010] Furthermore, the higher the thermal conductivity and heat transfer rate of the cold storage material installed in the cold accumulator, the higher the efficiency of heat transfer and the higher the efficiency of the refrigeration unit.

[0011] In the current refrigeration equipment, freezing at 4K can be achieved by combining lead (Pb), bismuth (Bi), tin (Sn) and other metal cold storage material particles on the high-temperature side with Er3Ni, ErNi, HoCu2 and other metal-based magnetic cold storage material particles on the low-temperature side below 20K.

[0012] In recent years, attempts have been made to improve the freezing capacity of refrigerators by replacing a portion of the metal-based magnetic cold storage material particles with ceramic magnetic cold storage material particles such as Gd2O2S, Tb2O2S, Dy2O2S, Ho2O2S, and GdAlO3, which have high specific heat in the temperature range of 2K to 10K.

[0013] As research progresses in applying the aforementioned refrigeration units to various cooling systems, the need for stable cooling of larger-scale objects necessitates further improvements in the freezing capacity of refrigeration units.

[0014] Existing technical documents

[0015] Patent documents

[0016] Patent Document 1: Japanese Patent Application Publication No. 2003-73661

[0017] Patent Document 2: Japanese Patent Application Publication No. 2003-213252

[0018] Patent Document 3: International Publication No. 2018 / 025581

[0019] Patent Document 4: Japanese Patent No. 5010071 Summary of the Invention

[0020] The problem that the invention aims to solve

[0021] The problem to be solved by this invention is to provide a cold storage material with high volumetric specific heat and high thermal conductivity.

[0022] Methods for solving problems

[0023] The cold storage material of the embodiment comprises a rare earth oxysulfide containing at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, containing 0.001 atomic% to 10 atomic% of a Group 1 element, and having a maximum volumetric specific heat of 0.5 J / (cm³) in a temperature range of 2 K to 10 K. 3 ·K) and above. Attached Figure Description

[0024] Figure 1 This is a schematic cross-sectional view showing the cold storage material particles of the second embodiment and the main components of the refrigerator of the fourth embodiment.

[0025] Figure 2 This is a cross-sectional view showing the schematic configuration of the cryogenic pump according to the fifth embodiment.

[0026] Figure 3 This is a perspective view showing the schematic configuration of the superconducting magnet according to the sixth embodiment.

[0027] Figure 4 This is a cross-sectional view showing the schematic configuration of the magnetic resonance imaging apparatus according to the seventh embodiment.

[0028] Figure 5 This is a cross-sectional view showing the schematic configuration of the nuclear magnetic resonance apparatus according to the eighth embodiment.

[0029] Figure 6 This is a perspective view showing the schematic configuration of the magnetic field applied single crystal pulling device according to the ninth embodiment.

[0030] Figure 7 This is a schematic diagram showing the general configuration of the helium recondensation apparatus according to the tenth embodiment. Detailed Implementation

[0031] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that in the following description, the same or similar components are marked with the same symbol, and the description of components that have been described before is sometimes appropriately omitted.

[0032] In this specification, "extremely low temperature" refers, for example, to the temperature range in which superconductivity can be usefully utilized industrially. Extremely low temperature is, for example, the temperature range below 20 K.

[0033] (First Implementation)

[0034] The cold storage material of the first embodiment comprises a rare earth oxysulfide containing at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), comprising 0.001 atomic% to 10 atomic% of a Group 1 element, and having a maximum volumetric specific heat of 0.5 J / (cm³) in a temperature range of 2 K to 10 K. 3 ·K) and above.

[0035] The cold storage material of the first embodiment has a volumetric specific heat of 0.5 J / (cm³) in a temperature range of 2.5 K or higher and 10 K or lower. 3 ·K) or above. Furthermore, the specific heat of the cold storage material in the first embodiment, for example, is 0.55 J / (cm³) in a temperature range of 2K or above and 8K or below. 3 • K) and above. Furthermore, the cold storage material of the first embodiment has a volumetric specific heat of 0.6 J / (cm³) in a temperature range of 4 K and above to 7 K and below. 3 ·K) and above.

[0036] The cold storage material of the first embodiment contains rare earth oxides, for example, those of the general formula R. 2±0.1 O2S 1±0.1 (In the formula, R represents at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.) In the rare earth oxides represented by the above general formula, the maximum volumetric specific heat differs from the temperature at which the maximum volumetric specific heat is observed, depending on the selected rare earth element. Therefore, the specific heat characteristics can be adjusted by appropriately adjusting the proportion of rare earth elements.

[0037] Rare earth elements may be, for example, at least one rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, and Er. The rare earth oxides contained in the cold storage material of the first embodiment may also contain two or more rare earth elements.

[0038] Rare earth oxides and sulfides are, for example, crystalline substances.

[0039] The cold storage material of the first embodiment uses rare earth oxides as its main component. Among the substances contained in the cold storage material of the first embodiment, rare earth oxides have the largest volume proportion. Among the substances contained in the cold storage material of the first embodiment, rare earth oxides have the largest molar ratio.

[0040] The cold storage material of the first embodiment comprises a total of 0.001 atomic% or more and 10 atomic% or less of a Group 1 element. The Group 1 element is at least one element selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). For example, the Group 1 element may be at least one element selected from the group consisting of Li, Na, and K. The cold storage material may also contain two or more Group 1 elements.

[0041] Group I elements contained in cold storage materials may exist, for example, in the crystals of rare earth oxygen sulfides. Group I elements contained in cold storage materials may exist, for example, in the grain boundaries of rare earth oxygen sulfides. Group I elements contained in cold storage materials may exist, for example, in the inner walls of pores present in the cold storage material. Group I elements contained in cold storage materials may exist, for example, in the crystalline grains of rare earth oxygen sulfides. Group I elements contained in cold storage materials may exist, for example, in crystalline grains other than rare earth oxygen sulfides contained in the cold storage material.

[0042] The cold storage material of the first embodiment, for example, contains, in addition to the aforementioned Group 1 elements, Group 2 elements totaling 0 atomic percent or more and 10 atomic percent or less. Furthermore, the cold storage material of the first embodiment, for example, contains, in addition to the aforementioned Group 1 elements, Group 2 elements totaling 0.001 atomic percent or more and 10 atomic percent or less.

[0043] Group II elements are at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). For example, a Group II element is at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

[0044] Cold storage materials may contain two or more Group 2 elements. Alternatively, cold storage materials may not contain any Group 2 elements.

[0045] Group II elements contained in cold storage materials may exist, for example, in the crystals of rare earth oxygen sulfides. Group II elements contained in cold storage materials may exist, for example, in the grain boundaries of rare earth oxygen sulfides. Group II elements contained in cold storage materials may exist, for example, in the inner walls of pores present in the cold storage material. Group II elements contained in cold storage materials may exist, for example, in the crystalline grains of rare earth oxygen sulfides. Group II elements contained in cold storage materials may exist, for example, in crystalline grains other than rare earth oxygen sulfides contained in the cold storage material.

[0046] The cold storage material of the first embodiment includes, for example, a substance derived from a sintering aid used in the manufacture of the cold storage material. Examples of sintering aids include alumina, magnesium oxide, yttrium oxide, zirconium oxide, or boron oxide.

[0047] The cold storage material of the first embodiment contains, for example, at least one element selected from the group consisting of aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), cobalt (Co), zirconium (Zr), and boron (B) at a rate of 0.01 atomic% to 20 atomic% or more. At least one element selected from the group consisting of Al, Fe, Cu, Ni, Co, Zr, and B is, for example, an element derived from a sintering aid.

[0048] It should be noted that the detection of elements contained in the cold storage material of the first embodiment and the determination of the atomic concentration of the elements can be performed, for example, by dissolving the cold storage material in a liquid and using inductively coupled plasma atomic emission spectrometry (ICP-AES). Alternatively, energy-dispersive X-ray spectrometry (EDX) or wavelength-dispersive X-ray analysis (WDX) can also be used.

[0049] The rare earth oxygen sulfide crystal structure contained in the cold storage material of the first embodiment is, for example, of the Ce2O2S type, with a space group of P-3m. The crystal structure can be confirmed by powder X-ray diffraction, observation of electron backscatter diffraction images using a scanning electron microscope, or observation using a transmission electron microscope.

[0050] The manufacturing method of the cold storage material in the first embodiment is not particularly limited. For example, it can be manufactured by mixing raw material powders using a ball mill or similar method to prepare a raw material mixture, and then shaping and sintering the obtained raw material mixture. Rare earth oxides or rare earth oxysulfides can be used as raw material powders. The types and proportions of rare earth oxides or rare earth oxysulfides are adjusted according to the target composition of the cold storage material.

[0051] By using carbonates, oxides, nitrides, or carbides containing Group 1 elements as raw material powders, it is possible to incorporate Group 1 elements into the cold storage material. Similarly, by using carbonates, oxides, nitrides, or carbides containing Group 2 elements as raw material powders, it is possible to incorporate Group 2 elements into the cold storage material.

[0052] Sintering aids may also be included in the raw material mixture. Examples of sintering aids include alumina, yttrium oxide, zirconium oxide, or boron oxide.

[0053] When rare earth oxides are used as raw material powder, the molded body is vulcanized. In this case, heat treatment is performed in a vulcanizing atmosphere. The vulcanizing atmosphere may contain gases containing sulfur atoms with negative oxidation states, such as hydrogen sulfide (H2S), carbon sulfide (CS2), or methanethiol (CH3SH). The heat treatment temperature is, for example, 400°C or higher and 700°C or lower. Furthermore, the heat treatment time is, for example, 1 hour or higher and 8 hours or lower.

[0054] The heat treatment of the obtained oxysulfide sintering is carried out, for example, in a pressurized atmosphere of an inert gas. The heat treatment temperature is, for example, above 1000°C and below 2000°C. The heat treatment temperature is, for example, above 1100°C and below 1700°C. The heat treatment time is, for example, above 1 hour and below 48 hours.

[0055] The cold storage material in the first embodiment may be, for example, a sintered body of cold storage material particles made from the first cold storage material.

[0056] Next, the function and effect of the cold storage material in the first embodiment will be explained.

[0057] In cryogenic refrigerators used for cooling superconducting devices, cryogenic materials are housed within a cryogenic accumulator. For example, cold is generated by heat exchange between the cryogenic material and helium gas passing through the accumulator. To improve the refrigerator's freezing capacity, the cryogenic material housed in the accumulator must possess excellent properties such as high specific heat and high thermal conductivity.

[0058] The upper limit of volumetric specific heat is limited by the composition of the material. Therefore, it is difficult to significantly increase volumetric specific heat. On the other hand, thermal conductivity can be increased by improving crystallinity and reducing the number of voids.

[0059] The maximum volumetric specific heat of the cold storage material in the first embodiment is 0.5 J / (cm³) in a temperature range of 2 K to 10 K. 3 ·K) or above. Therefore, the cold storage material of the first embodiment has a high volumetric specific heat.

[0060] Furthermore, the cold storage material in the first embodiment has a volumetric specific heat of 0.5 J / (cm³) in a temperature range of 2.5 K or higher and 10 K or lower. 3 ·K and above. Furthermore, for example, the volumetric specific heat in the temperature range of 2K and above but below 8K is 0.55 J / (cm³). 3 ·K and above. Furthermore, for example, the volumetric specific heat is 0.6 J / (cm³) in the temperature range above 4K and below 7K. 3 ·K) and above.

[0061] In this way, because the cold storage material of the first embodiment has a high volumetric specific heat, the cold storage device containing the cold storage material of the first embodiment has high cold storage performance. Moreover, the refrigerator equipped with the cold storage device containing the cold storage material of the first embodiment exhibits high freezing capacity.

[0062] Furthermore, the cold storage material of the first embodiment contains 0.001 atomic% or more and 10 atomic% or less of Group 1 elements in terms of atomic concentration. In the sintering process during the manufacture of the cold storage material, Group 1 elements promote the sintering of the formed body and reduce the number of voids in the resulting sintered body. Therefore, the cold storage material of the first embodiment has a high degree of sintering and high thermal conductivity.

[0063] To fully obtain the required properties of cold storage materials, such as thermal conductivity and specific heat, sufficient sintering temperature and time are necessary during the sintering process. The cold storage material of the first embodiment, through the sintering-promoting effect of Group 1 elements, can achieve a reduction in the required sintering temperature and time. Therefore, it can reduce the manufacturing cost of the cold storage material and provide an inexpensive cold storage material.

[0064] By increasing the atomic concentration of Group 1 elements in the cold storage material to over 0.001 atomic%, the degree of sintering increases, and the number of extremely small voids decreases. Therefore, the thermal conductivity of the cold storage material can be improved.

[0065] If the atomic concentration of Group I elements in the cold storage material exceeds 10 atomic%, sulfides containing rare earth elements and Group I elements are formed, resulting in a lower volumetric specific heat and a lower thermal conductivity. By ensuring that the atomic concentration of Group I elements in the cold storage material is 10 atomic% or less, the volumetric specific heat is high, the thermal conductivity is improved, and the freezing capacity of the refrigerator containing the cold storage material of the first embodiment is increased.

[0066] The first-group element contained in the cold storage material of the first embodiment is, for example, at least one element selected from the group consisting of Li, Na, K, Rb, Cs, and Fr. Furthermore, the first-group element is preferably at least one element selected from the group consisting of Li, Na, and K. Alternatively, it may contain, for example, two or more first-group elements.

[0067] By using carbonates, oxides, nitrides, or carbides containing Group I elements in raw material powders, it is possible to manufacture cold storage materials containing Group I elements. The concentration of Group I elements in the cold storage material can be adjusted by changing the amount of carbonates, oxides, nitrides, or carbides containing Group I elements.

[0068] The cold storage material of the first embodiment, for example, contains a total of 0 atomic percent or more and 10 atomic percent or less of Group II elements in terms of atomic concentration. Furthermore, for example, it contains a total of 0.001 atomic percent or more and 10 atomic percent or less of Group II elements in terms of atomic concentration. The Group II elements are at least one element selected from the group consisting of Be, Mg, Ca, Sr, Ba, and Ra. The atomic concentration of the Group II elements, for example, is a total of 0.001 atomic percent or more and 5 atomic percent or less. The cold storage material may also contain two or more Group II elements.

[0069] In the first embodiment, the cold storage material, in addition to Group 1 elements, contains at least 0.001 atomic% of Group 2 elements, thereby further improving sinterability and reducing the number of extremely small voids. This further improves thermal conductivity. Group 2 elements do not exhibit specific heat characteristics. Therefore, if the total content of Group 2 elements exceeds 10 atomic%, the volumetric specific heat of the cold storage material decreases, the cold storage performance of the cold accumulator decreases, and the freezing capacity of the refrigerator decreases.

[0070] By using carbonates, oxides, nitrides, or carbides containing Group II elements in the raw material powder, it is possible to manufacture cold storage materials containing Group II elements. The concentration of Group II elements in the cold storage material can be adjusted by changing the amount of carbonates, oxides, nitrides, or carbides containing Group II elements.

[0071] In manufacturing the cold storage material according to the first embodiment, in addition to the Group 1 elements, 0.01 atomic% or more of a sintering aid is added, based on the metal or half-metal element constituting the sintering aid, thereby further improving sinterability and reducing the number of extremely small voids. This further improves thermal conductivity. The metal or half-metal element constituting the sintering aid does not exhibit specific heat characteristics. Therefore, if the amount of the metal or half-metal element constituting the sintering aid added exceeds 20 atomic%, the volumetric specific heat of the cold storage material decreases, the cold storage performance of the cold accumulator decreases, and the freezing capacity of the refrigerator decreases.

[0072] The cold storage material of the first embodiment preferably contains at least one element selected from the group consisting of aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), cobalt (Co), zirconium (Zr), and boron (B) at a concentration of 0.01 atomic% or more and 20 atomic% or less. At least one element selected from the group consisting of Al, Fe, Cu, Ni, Co, Zr, and B is, for example, an element derived from a sintering aid. At least one element selected from the group consisting of Al, Fe, Cu, Ni, Co, Zr, and B is, for example, an example of a metallic or semi-metallic element constituting a sintering aid.

[0073] According to the first embodiment, a cold storage material with excellent properties such as high volumetric specific heat and high thermal conductivity can be achieved.

[0074] (Second Implementation)

[0075] The cold storage material particles of the second embodiment are formed from the cold storage material of the first embodiment, and have a particle size of 50 μm or more and 3 mm or less. The aspect ratio of the cold storage material particles is, for example, 1 or more and 5 or less. The aspect ratio of the cold storage material particles is the ratio of the major axis to the minor axis of the cold storage material particles. The shape of the cold storage material particles is, for example, spherical.

[0076] Hereinafter, some descriptions of content that are repeated in the first embodiment will be omitted.

[0077] The particle size of the cold storage material is the equivalent circle diameter. The equivalent circle diameter is the diameter of a circle whose area is equivalent to the area of ​​the shape observed in an image such as an optical microscope image or a scanning electron microscope image (SEM image). The particle size of the cold storage material can be determined, for example, by image analysis of an optical microscope image or an SEM image.

[0078] The manufacturing method of the cold storage material particles in the second embodiment is not particularly limited. For example, a raw material mixture can be prepared by mixing raw material powders using a ball mill or the like. The obtained raw material mixture is then shaped (granulated) into granules by rotary granulation, stirring granulation, extrusion, spraying (spraying method) or compression molding, and the obtained granulated granules are then sintered to manufacture the material.

[0079] The resulting granular material is called granulated particle.

[0080] In the above granulation method, the raw material powders are adhered to each other by adding a binder, thereby increasing the strength of the granulated particles. Examples of binders include polyvinyl alcohol, polyvinyl butyral, carboxymethyl cellulose, acrylic resin, or polyethylene glycol. The amount of binder added is, for example, 0.01% by weight or more and 20% by weight or less.

[0081] For raw material powders, rare earth oxides or rare earth oxysulfides can be used. The type and proportion of rare earth oxides or rare earth oxysulfides are adjusted according to the target composition of the cold storage material particles.

[0082] By using carbonates, oxides, nitrides, or carbides containing Group 1 elements in the raw material powder, it is possible to manufacture cold storage material particles containing Group 1 elements. Furthermore, by using carbonates, oxides, nitrides, or carbides containing Group 2 elements in the raw material powder, it is possible to manufacture cold storage material particles containing Group 2 elements.

[0083] By adding sintering aids to raw material powders, it is possible to manufacture cold storage material particles containing sintering aids. By reacting the sintering aids with rare earth oxides of the raw materials, oxide phases containing rare earth elements and metallic or semi-metallic elements constituting the sintering aids can sometimes be generated.

[0084] Alternatively, a slurry prepared by mixing raw material powder with an aqueous solution of alginate can be dropped into a gelling solution, and granulated by gelling the slurry. This method of granulation utilizes a cross-linking reaction generated by the polyvalent metal ions contained in the gelling solution to produce granules. Therefore, the strength of the granulated particles, i.e., the gelation strength, varies with the amount of alginate contained in the particles.

[0085] The amount of alginate contained in the particles can be varied by the concentration of alginate in the alginate aqueous solution or the ratio of the alginate aqueous solution to the raw material powder. The slurry is added dropwise to the gelling solution using, for example, a dropper, burette, pipette, syringe, dispenser, or inkjet printer. Hereinafter, the particle granulation method using this method will be referred to as the alginate gelation method.

[0086] In the alginate gelation method, the particle size and aspect ratio can be varied by adjusting the viscosity of the slurry, the diameter of the nozzle during dropwise addition, or the distance between the nozzle tip and the surface of the gelling solution. The nozzle diameter is, for example, 50 μm or more and 3000 μm or less. The slurry viscosity is, for example, 0.1 mPa·s or more and 1,000,000 mPa·s or less. Furthermore, the distance between the nozzle tip and the surface of the gelling solution is, for example, 0.1 mm or more and 1000 mm or less.

[0087] When using a distributor for spraying, any one of the following can be used as a device: an air pulse distributor, a plunger distributor, or a piezoelectric distributor.

[0088] Inkjet printing, as a method of ejection, is broadly divided into continuous and on-demand types, and either type can be used. Furthermore, on-demand printing is further divided into three types: piezoelectric, thermal, and valve-based, and any of these can be used.

[0089] A slurry, added dropwise to a gelling solution using a dropper, burette, pipette, syringe, dispenser, inkjet printer, etc., gels by being held in the gelling solution. By gelling the slurry, granulated particles containing raw material powder incorporating cold-storage material are formed.

[0090] The slurry is held in the gelation solution for, for example, more than 10 minutes and less than 48 hours. A short gelation time results in incomplete gelation, thus the strength of the granulated particles becomes lower than expected from the amount of alginate.

[0091] The alginate aqueous solution used in the alginate gelation method is, for example, an aqueous solution of sodium alginate, an aqueous solution of ammonium alginate, or an aqueous solution of potassium alginate. By using an aqueous solution of sodium alginate or potassium alginate containing Group 1 elements, it is possible to contain sodium or potassium in the cold storage material particles. By using a mixed aqueous solution of sodium alginate and potassium alginate in the slurry, it is possible to contain both sodium and potassium simultaneously.

[0092] The concentration of Group I elements in the particles is adjusted by varying the concentration of alginate containing Group I elements. The concentration of alginate, expressed as an aqueous solution, is, for example, 0.01% by weight or more and 5% by weight or less. If the concentration of the aqueous solution of alginate is less than 0.01% by weight, a gel of sufficient strength cannot be formed, and particles cannot be obtained.

[0093] Gelation solutions can be, for example, aqueous solutions containing group II elements, such as calcium lactate, calcium chloride, manganese(II) chloride, magnesium sulfate, beryllium sulfate, strontium nitrate, barium chloride, and barium hydroxide.

[0094] By using aqueous solutions of calcium lactate, calcium chloride, magnesium sulfate, beryllium sulfate, strontium nitrate, barium chloride, and barium hydroxide in the gelation solution, it is possible to make the cold storage material particles contain calcium, magnesium, beryllium, strontium, and barium.

[0095] By using aqueous solutions of aluminum chloride, aluminum nitrate, aluminum lactate, ferric chloride (II), ferric chloride (III), copper chloride (II), nickel chloride (II), and cobalt chloride (II) as gelling solutions, it is possible to incorporate aluminum, iron, copper, nickel, or cobalt into the cold storage material particles as sintering aids.

[0096] Since gelation is carried out through a cross-linking reaction caused by the polyvalent metal ions contained in the gelation solution, the amount of Group I and Group II elements contained in the particles can be adjusted by adjusting the immersion time of the particles in the gelation solution when the slurry is made of an aqueous solution containing Group I elements and the gelation solution is made of an aqueous solution containing Group II elements.

[0097] By mixing at least two aqueous solutions containing different metal elements selected from the group consisting of calcium lactate aqueous solution, calcium chloride aqueous solution, magnesium sulfate aqueous solution, beryllium sulfate aqueous solution, strontium nitrate aqueous solution, barium chloride aqueous solution and barium hydroxide aqueous solution, and using them as a gelling solution, it is possible to make the cold storage material particles contain two or more Group II elements.

[0098] The particle size of the granulated particles is, for example, 70 μm or more and 5 mm or less. The aspect ratio of the granulated particles is, for example, 1 or more and 5 or less.

[0099] Granulated particles undergo degreasing to remove a certain amount of organic components. If the raw material is an oxide, insufficient degreasing will result in incomplete vulcanization, failing to generate the necessary amount of oxysulfides. Furthermore, if degreasing is incomplete and excessive organic components remain, the density of the sintered particles will decrease. Consequently, the strength of the cold storage material particles will weaken, making them unsuitable for use in refrigeration units.

[0100] If degreasing is excessive, the organic components that guarantee strength will disappear, resulting in reduced strength of the degreased granules and the formation of cracks or gaps within the particles. Degreasing temperatures should be, for example, above 400°C and below 800°C, for a duration of 30 minutes to 12 hours.

[0101] When rare earth oxides are used as raw material powder, the granulated particles are sulfided. In this case, heat treatment is performed in a sulfiding atmosphere. The sulfiding atmosphere may contain gases containing sulfur atoms with negative oxidation states, such as hydrogen sulfide (H2S), carbon sulfide (CS2), or methanethiol (CH3SH). The heat treatment temperature is, for example, 400°C or higher and 700°C or lower. Furthermore, the heat treatment time is, for example, 1 hour or higher and 8 hours or lower.

[0102] The heat treatment of sintering oxygen sulfide particles is carried out, for example, in a pressurized atmosphere of an inert gas. 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.

[0103] Next, the function and effect of the cold storage material particles in the second embodiment will be explained.

[0104] The cold storage material particles of the second embodiment are made from the cold storage material of the first embodiment, and have a particle size of 50 μm or more and 3 mm or less. The aspect ratio of the cold storage material particles is, for example, 1 or more and 5 or less. The aspect ratio of the cold storage material particles is the ratio of the major axis to the minor axis of the cold storage material particles. The shape of the cold storage material particles is, for example, spherical.

[0105] The maximum volumetric specific heat of the cold storage material particles in the second embodiment is 0.5 J / (cm³). 3 (K) or above. Therefore, the cold storage material particles of the second embodiment have a high volumetric specific heat. Because the cold storage material particles of the second embodiment have a high volumetric specific heat, the cold storage accumulator equipped with the cold storage material particles of the second embodiment has high cold storage performance. In addition, the refrigerator equipped with the cold storage accumulator equipped with the cold storage material particles of the second embodiment exhibits high freezing capacity.

[0106] Furthermore, the cold storage material particles of the second embodiment contain 0.001 atomic% to 10 atomic% of Group 1 elements. During the sintering process of manufacturing the cold storage material particles, the Group 1 elements promote the sintering of the particles and reduce the number of voids contained within them. Therefore, the cold storage material particles have a high degree of sintering and high thermal conductivity.

[0107] In the first embodiment, the cold storage material, in addition to Group 1 elements, has sintering properties further improved and the number of extremely small voids reduced by adding 0.01 atomic% or more of a sintering aid, based on the metal or half-metal element constituting the sintering aid. This further improves thermal conductivity. The metal or half-metal element constituting the sintering aid does not exhibit specific heat characteristics. Therefore, if the amount of the metal or half-metal element constituting the sintering aid exceeds 20 atomic%, the volumetric specific heat of the cold storage material decreases, the cold storage performance of the cold accumulator decreases, and the freezing capacity of the refrigerator decreases.

[0108] To fully obtain the required properties of cold storage material particles, such as thermal conductivity and volumetric specific heat, sufficient sintering temperature and time are necessary in the sintering process. The cold storage material particles of the second embodiment, through the sintering-promoting effect of Group I elements, can achieve a reduction in the required sintering temperature and time. Therefore, the manufacturing cost of the cold storage material particles can be reduced, providing inexpensive cold storage material particles.

[0109] The particle size of the cold storage material in the second embodiment is 50 μm or more and 3 mm or less. More preferably, the particle size of the cold storage material is 1 mm or less, and even more preferably 500 μm or less.

[0110] By having the particle size of the cold storage material exceed the aforementioned lower limit, the packing density of the cold storage material particles in the cold storage unit decreases, reducing pressure loss of the working medium such as helium and improving the refrigeration performance of the refrigerator. On the other hand, by having the particle size of the cold storage material below the aforementioned upper limit, the distance from the surface of the cold storage material particle to its center decreases, making heat transfer between the working medium and the cold storage material particles easier to conduct to the center of the cold storage material, thus improving the refrigeration performance of the refrigerator.

[0111] The aspect ratio of the cold storage material particles is preferably 1 or more and 5 or less, more preferably 1 or more and 2 or less. By ensuring that the aspect ratio of the cold storage material particles is lower than the above upper limit, the voids when the cold storage material particles are filled into the cold accumulator become more uniform, thereby improving the freezing performance of the refrigeration unit.

[0112] In the second embodiment, if the granulated particles of the cold storage material do not meet a certain strength after degreasing, cracks or gaps may occur during operation. If cold storage material particles that deviate from a spherical shape are loaded into a refrigeration unit, the performance of the refrigeration unit will decrease, and therefore the granulated particles with cracks or gaps are discarded as defective products. Therefore, the granulated particles preferably have a certain strength that prevents cracking or gaps.

[0113] The strength of granulated particles mainly depends on the amount of binder or alginate, but excessive amounts of these organic components make vulcanization or sintering difficult. On the other hand, Group I elements promote the sintering of cold storage material particles. If the granulated particles contain 0.001 atomic% to 10 atomic% of Group I elements by atomic concentration, and further contain 0.01 wt% to 20 wt% of binder or carbon from alginate, then both sinterability and high strength can be achieved through the aforementioned two effects.

[0114] The carbon content is more preferably 10% by weight or less, and even more preferably 5% by weight or less. Even if it contains 0.001 atomic% or more and 10 atomic% or less of Group 1 elements in terms of atomic concentration, if the carbon content exceeds 20% by weight, it becomes difficult to remove the organic components or causes a significant decrease in the forming density after degreasing, and the sintering reaction will not occur even at high sintering temperatures. Therefore, the strength of the sintered particles is significantly low, and the recycling of the particles is difficult. If the carbon content is less than 0.01% by weight, the amount of binder or sodium alginate contained in the granulated particles is small, so the strength is weak, and cracking or gaps occur during the operation of the granulated particles.

[0115] If the degreased granulated particles contain 0.001 atomic% to 10 atomic% of Group 1 elements (based on atomic concentration), and further contain 0.001 wt% to 10 wt% of binder or carbon from alginate, then both sinterability and high strength can be achieved. The carbon content is more preferably 5 wt% or less, and more preferably 3 wt% or less. If the carbon content exceeds 10 wt%, the forming density is low, and therefore the density will not increase even after sintering, making it impossible to achieve the strength required for use in a freezer. If the density after sintering is increased by raising the sintering temperature, the particles adhere to each other, and the aspect ratio decreases significantly.

[0116] Considering the shrinkage caused by sintering, the particle size of the granulated particles is preferably 70 μm or more and 5 mm or less both before and after degreasing. The aspect ratio of the granulated particles is, for example, 1 or more and 5 or less both before and after degreasing.

[0117] According to the second embodiment, it is possible to obtain cold storage material particles with excellent properties such as high volumetric specific heat and high thermal conductivity.

[0118] (Third implementation method)

[0119] The cold storage device of the third embodiment is a cold storage device filled with a plurality of cold storage material particles of the second embodiment. Regarding the cold storage device of the third embodiment, for example, when the perimeter of the projected image of the plurality of cold storage material particles of the second embodiment is set to L, and the actual area of ​​the projected image is set to A, 4πA / L... 2 The proportion of cold storage material particles with a roundness R of less than 0.5 is less than 5%.

[0120] The roundness R can be determined by image processing of the shapes of multiple cold storage material particles using an optical microscope. Cold storage material particles with a roundness R of 0.5 or less indicate that they have irregularities or unevenness on their surface. If more than 5% of cold storage material particles containing such particles are filled into a cold accumulator, the porosity formed by the cold storage material particles becomes uneven, and the filling becomes unstable. Therefore, when the working medium flows in, the cold storage performance decreases. Alternatively, during the filling of the cold storage material particles or during the operation of the refrigeration unit, the stress applied to the cold storage material particles can cause them to move or break down, generating microparticles that clog the voids, thus reducing the refrigeration performance and long-term reliability of the refrigeration unit. The proportion of cold storage material particles with a roundness R of 0.5 or less is preferably 2% or less, and more preferably 0%.

[0121] (Fourth Implementation)

[0122] The refrigerator of the fourth embodiment is a refrigerator equipped with a cold storage device filled with a plurality of cold storage material particles of the first embodiment or the second embodiment. Hereinafter, some descriptions that are repeated in the first, second, and third embodiments will be omitted.

[0123] Figure 1 This is a schematic cross-sectional view showing the main components of a cryostat of a fourth embodiment, which includes a cryostat of a third embodiment filled with multiple cryogenic material particles of the second embodiment. The cryostat of the fourth embodiment is a two-stage cryogenic storage type cryostat 100 used for cooling superconducting devices and the like.

[0124] The cryogenic storage type cryogenic freezer 100 includes a first cylinder 111, a second cylinder 112, a vacuum container 113, a first accumulator 114, a second accumulator 115, a first sealing ring 116, a second sealing ring 117, a first cryogenic storage material 118, a second cryogenic storage material 119, a first expansion chamber 120, a second expansion chamber 121, a first cooling platform 122, a second cooling platform 123, and a compressor 124.

[0125] The cryogenic cryogenic freezer 100 has a vacuum container 113 equipped with a large-diameter first cylinder 111 and a small-diameter second cylinder 112 coaxially connected to the first cylinder 111. A first accumulator 114 is flexibly disposed in the first cylinder 111. A second accumulator 115, as an example of an accumulator in a third embodiment, is flexibly disposed in the second cylinder 112.

[0126] A first sealing ring 116 is disposed between the first cylinder 111 and the first accumulator 114. A second sealing ring 117 is disposed between the second cylinder 112 and the second accumulator 115.

[0127] The first cold storage device 114 contains a first cold storage material 118, such as a Cu mesh. The second cold storage device 115 contains a second cold storage material 119.

[0128] The first cold storage unit 114 and the second cold storage unit 115 each have a passage for a working medium disposed in the gaps between the first cold storage material 118 and the second cold storage material 119. The working medium is helium.

[0129] A first expansion chamber 120 is provided between the first cold accumulator 114 and the second cold accumulator 115. Furthermore, a second expansion chamber 121 is provided between the second cold accumulator 115 and the front end wall of the second cylinder 112. Moreover, a first cooling platform 122 is provided at the bottom of the first expansion chamber 120. Additionally, a second cooling platform 123, which is at a lower temperature than the first cooling platform 122, is formed at the bottom of the second expansion chamber 121.

[0130] For the aforementioned two-stage cryogenic storage refrigerator 100, a high-pressure working medium is supplied from the compressor 124. The supplied working medium passes through the first cryogenic storage material 118 housed in the first cryogenic storage unit 114 and then passes through the second cryogenic storage material 119 housed in the second cryogenic storage unit 115 and then passes through the second cryogenic storage material 119 housed in the second cryogenic storage unit 115 and then passes through the second expansion chamber 121.

[0131] At this time, the working medium supplies heat energy to the first cold storage material 118 and the second cold storage material 119, thereby cooling them. The working medium 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, generating cold. Then, the first cooling platform 122 and the second cooling platform 123 are cooled.

[0132] The expanded working medium flows in opposite directions between the first cold storage material 118 and the second cold storage material 119. After absorbing heat energy from the first cold storage material 118 and the second cold storage material 119, the working medium is discharged. The cold storage type cryogenic refrigerator 100 is configured such that the thermal efficiency of the working medium circulation increases as the reheating effect becomes better in this process, and a lower temperature is achieved.

[0133] The refrigeration unit of the fourth embodiment includes a cold storage unit that houses at least a portion of the cold storage material of the first embodiment as the second cold storage material 119 within the second cold storage unit 115. Furthermore, the second cold storage unit 115 may also be filled with a plurality of cold storage material particles of the second embodiment as at least a portion of the second cold storage material 119. When the perimeter of the projected image of each cold storage material particle is set to L, and the actual area of ​​the projected image is set to A, the plurality of cold storage material particles of the second embodiment are arranged in a ratio of 4πA / L. 2 The proportion of particles with a roundness R of 0.5 or less is preferably 5% or less.

[0134] In the fourth embodiment, the cold storage device of the third embodiment may also include multiple cold storage material filling layers of different types of cold storage materials. These different types of cold storage materials may also be separated by a mesh. This mesh may be, for example, a metal mesh. At least one of the multiple cold storage material filling layers is either the cold storage material of the first embodiment or cold storage material particles of the second embodiment. In the refrigerator of the fourth embodiment, the cold storage material of the first embodiment or multiple cold storage material particles of the second embodiment are, for example, filled on the low-temperature side of the cold storage device.

[0135] To improve the freezing capacity of the refrigerator, it is preferable to increase the specific heat per unit volume of the cold storage material and improve its thermal conductivity. The refrigerator of the fourth embodiment includes a cold storage material or cold storage material particles that maintain specific heat per unit volume and improve thermal conductivity.

[0136] For example, by utilizing the refrigeration unit of the fourth embodiment in a maglev train, the long-term reliability of the maglev train can be improved.

[0137] According to the fourth embodiment, by using a cold storage material or cold storage material particles with excellent properties, a refrigerator with excellent properties can be achieved.

[0138] (Fifth implementation method)

[0139] The cryogenic pump of the fifth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some descriptions that are repeated in the fourth embodiment will be omitted.

[0140] Figure 2This is a cross-sectional view showing the schematic configuration of the cryogenic pump according to the fifth embodiment. The cryogenic pump of the fifth embodiment is a cryogenic pump 500 equipped with the cold storage type ultra-low temperature freezer 100 of the fourth embodiment.

[0141] The cryogenic pump 500 includes a cryogenic panel 501 for condensing or adsorbing gas molecules, a cold storage type cryogenic freezer 100 for cooling the cryogenic panel 501 to a specified extremely low temperature, a shielding plate 503 disposed between the cryogenic panel 501 and the cold storage type cryogenic freezer 100, a baffle 504 disposed at the intake port, and a ring 505 for changing the exhaust speed of argon, nitrogen, hydrogen, etc.

[0142] According to the fifth embodiment, a cryogenic pump with excellent characteristics can be achieved by using a refrigerator with superior characteristics. Furthermore, by utilizing the cryogenic pump of the fifth embodiment in a semiconductor manufacturing apparatus, the long-term reliability of the semiconductor manufacturing apparatus can be improved.

[0143] (Sixth Implementation Method)

[0144] The superconducting magnet of the sixth embodiment includes the cryostat of the fourth embodiment. Hereinafter, some details that are repeated in the fourth embodiment will be omitted.

[0145] Figure 3 This is a perspective view showing the schematic configuration of the superconducting magnet according to the sixth embodiment. The superconducting magnet of the sixth embodiment is, for example, a superconducting magnet 600 for a maglev train equipped with the cryogenic storage type cryogenic refrigerator 100 of the fourth embodiment.

[0146] The superconducting magnet 600 for maglev trains includes a superconducting coil 601, a liquid helium tank 602 for cooling the superconducting coil 601, a liquid nitrogen tank 603 to prevent the liquid helium from evaporating, a laminated insulation material 605, a power lead wire 606, a permanent current switch 607, and a cryogenic storage type cryogenic freezer 100.

[0147] According to the sixth embodiment, a superconducting magnet with excellent properties can be achieved by using a cryostat with excellent properties.

[0148] (Seventh Implementation)

[0149] The magnetic resonance imaging apparatus of the seventh embodiment includes the cryostat of the fourth embodiment. Hereinafter, some descriptions that are repeated in the fourth embodiment will be omitted.

[0150] Figure 4 This is a cross-sectional view showing the schematic configuration of the magnetic resonance imaging (MRI) apparatus according to the seventh embodiment. The magnetic resonance imaging (MRI) apparatus of the seventh embodiment is an MRI apparatus 700 equipped with the cryogenic cryostat 100 of the fourth embodiment.

[0151] The magnetic resonance imaging device 700 includes a superconducting static magnetic field coil 701 that applies a spatially uniform and temporally stable static magnetic field to the human body, a correction coil (not shown) that corrects for non-uniformity of the generated magnetic field, a tilting magnetic field coil 702 that applies a magnetic field gradient to the measurement area, a radio wave transceiver probe 703, a cryostat 705, and a radiation-insulating shield 706. Furthermore, a cryogenic storage type cryogenic freezer 100 is used for cooling the superconducting static magnetic field coil 701.

[0152] According to the seventh embodiment, a magnetic resonance imaging device with excellent characteristics can be realized by using a cryostat with excellent characteristics.

[0153] (Eighth Implementation)

[0154] The nuclear magnetic resonance apparatus of the eighth embodiment includes the cryostat of the fourth embodiment. Hereinafter, some descriptions that are repeated in the fourth embodiment will be omitted.

[0155] Figure 5 This is a cross-sectional view showing the schematic configuration of the nuclear magnetic resonance (NMR) apparatus according to the eighth embodiment. The nuclear magnetic resonance (NMR) apparatus of the eighth embodiment is an NMR apparatus 800 equipped with the cryogenic cryogenic freezer 100 of the fourth embodiment.

[0156] 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 the induced current generated in a coil (not shown) around the sample tube 801. Furthermore, it includes a cryogenic storage cryostat 100 for cooling the superconducting static magnetic field coil 802.

[0157] According to the eighth embodiment, a nuclear magnetic resonance device with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0158] (Ninth Implementation)

[0159] The magnetic field-applied single crystal pulling apparatus of the ninth embodiment includes the cryostat of the fourth embodiment. Hereinafter, some descriptions that are repeated in the fourth embodiment will be omitted.

[0160] Figure 6 This is a perspective view showing the schematic configuration of the magnetic field-applied single crystal pulling device according to the ninth embodiment. The magnetic field-applied single crystal pulling device of the ninth embodiment is a magnetic field-applied single crystal pulling device 900 equipped with the cold storage type cryogenic refrigerator 100 of the fourth embodiment.

[0161] The magnetic field-applied single crystal pulling device 900 includes a single crystal pulling section 901 with a raw material melting crucible, a heater, and a single crystal pulling mechanism; a superconducting coil 902 that applies a static magnetic field to the molten raw material; a lifting mechanism 903 for the single crystal pulling section 901; current leads 905; a heat insulation plate 906; and a helium container 907. Furthermore, a cryogenic storage type cryogenic freezer 100 is used for cooling the superconducting coil 902.

[0162] According to the ninth embodiment, a magnetic field-applied single crystal pulling device with excellent characteristics can be realized by using a cryostat with excellent characteristics.

[0163] (Tenth Implementation)

[0164] The helium recondensation apparatus of the tenth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some descriptions that are repeated in the fourth embodiment will be omitted.

[0165] Figure 7 This is a schematic diagram showing the general configuration of the helium recondensation apparatus according to the tenth embodiment. The helium recondensation apparatus of the tenth embodiment is a helium recondensation apparatus 1000 equipped with the cryogenic storage type cryogenic refrigerator 100 of the fourth embodiment.

[0166] The helium recondensation unit 1000 includes a cold storage type ultra-low temperature refrigerator 100, an evaporation piping 1001, and a liquefaction piping 1002.

[0167] The helium recondensation apparatus 1000 can recondense helium gas evaporated from the liquid helium device of a device using liquid helium, such as a superconducting magnet, a nuclear magnetic resonance (NMR) device, a nuclear magnetic resonance imaging (MRI) device, a physical property measurement system (PPMS) or a magnetic property measurement system, to produce liquid helium.

[0168] Helium gas, not shown in the diagram, is introduced into the helium recondenser 1000 via evaporation piping 1001 from the liquid helium device. The helium gas is cooled to 4K below the liquefaction temperature of helium by a cryogenic cryostat 100. The condensed and liquefied liquid helium is returned to the liquid helium device via liquefaction piping 1002.

[0169] According to the tenth embodiment, a helium recondensation device with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0170] Example

[0171] Hereinafter, examples, comparative examples, and evaluation results of the cold storage material of the first embodiment and the cold storage material particles of the second embodiment will be described.

[0172] (Example 1)

[0173] Gd₂O₃ powder and Na₂CO₃ powder were mixed and pulverized in a ball mill for 24 hours to prepare a raw material mixture. The resulting raw material mixture was then dried and granulated using a rotary granulator to prepare granulated particles with a particle size of 0.3 mm to 0.5 mm. Polyvinyl alcohol was used as the binder and added at a ratio of 1.2% by weight relative to the raw material powder. The sodium concentration of the granulated particles was 0.52 atomic%, and the carbon concentration was 0.99% by weight. The resulting raw material mixture was then shaped to obtain a molded body.

[0174] To evaluate the strength of the granulated particles, the granulated particles were filled into... The container is filled with a cylindrical container with a diameter of 15 mm and a height of 5 mm. A sufficient amount of cold storage material is then added, ensuring the granulated particles are fixed and do not move freely within the container. A 1×10⁻⁶ pressure is applied to the container. 3 The amplitude of the second wave is 2 mm, and the maximum acceleration is 200 m / s². 2 The single vibration resulted in a failure rate of less than 0.1% by weight of the cold storage material.

[0175] The granulated particles and molded bodies were degreased at 600°C for 6 hours in an atmospheric atmosphere. The sodium concentration of the degreased granulated particles and molded bodies was 0.54 atomic%, and the carbon concentration was 0.51 wt%. The particles and molded bodies were then vulcanized by heat treatment at 500°C for 4 hours in an atmosphere containing hydrogen sulfide (H₂S). Finally, the particles and molded bodies were sintered by heat treatment at 1300°C for 12 hours in a pressurized atmosphere containing inert gases.

[0176] The main component of the cold storage material and its particles in Example 1 is gadolinium oxide. The sodium concentration in the cold storage material and its particles in Example 1 is 0.55 atomic%.

[0177] The maximum volumetric specific heat below 10 K and the thermal conductivity at 4.2 K of the cold storage material of Example 1 were determined. The measurements were performed using a physical property measurement system (PPMS).

[0178] 250g of the cold storage material particles from Example 1 were filled into Figure 1 The second stage of the two-stage GM refrigeration unit shown in the diagram is assembled by filling the low-temperature side with 250g of Pb-based cold storage material on the high-temperature side, and a freezing test is conducted to determine the freezing capacity at 4.2K. It should be noted that the first stage cold storage unit is subjected to a heat load at a temperature of 50K.

[0179] The results of the above freezing test show that the freezing capacity at 4.2K is 0.66W.

[0180] It should be noted that in the following examples and comparative examples, adjustments were made to ensure that the mixing time of the raw material powder, the conditions of the vulcanization heat treatment, and the conditions of the sintering heat treatment were suitable. Furthermore, the test conditions of the chiller were made identical.

[0181] (Example 2)

[0182] Except that Li2CO3 powder was used instead of Na2CO3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1.

[0183] (Example 3)

[0184] Except that K2CO3 powder was used instead of Na2CO3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1.

[0185] (Example 4)

[0186] In addition to Na2CO3 powder, CaCO3 powder was also used. Otherwise, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1.

[0187] (Example 5)

[0188] Except that Li2CO3 powder was used instead of Na2CO3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 4.

[0189] (Example 6)

[0190] Except that K2CO3 powder was used instead of Na2CO3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 4.

[0191] (Example 7)

[0192] Except that MgCO3 powder was used instead of CaCO3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 4.

[0193] (Example 8)

[0194] Except that SrCO3 powder was used instead of CaCO3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 4.

[0195] (Example 9)

[0196] Except that BaCO3 powder was used instead of CaCO3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 4.

[0197] (Example 10)

[0198] Except that Gd2O2S powder was used instead of Gd2O3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1.

[0199] (Example 11)

[0200] Except that Tb2O3 powder was used instead of Gd2O3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1.

[0201] (Example 12)

[0202] Except that Dy2O3 powder was used instead of Gd2O3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1.

[0203] (Example 13)

[0204] Except that Ho2O3 powder was used instead of Gd2O3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1.

[0205] (Example 14)

[0206] In addition to Na2CO3 powder, K2CO3 powder was also used. Otherwise, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1.

[0207] (Example 15)

[0208] In addition to Na2CO3 powder, Li2CO3 powder was also used. Otherwise, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1.

[0209] (Example 16)

[0210] In addition to Na2CO3 powder, K2CO3 powder and CaCO3 powder were also used. Otherwise, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1.

[0211] (Example 17)

[0212] In addition to Na2CO3 powder, CaCO3 powder and SrCO3 powder were also used. Otherwise, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1.

[0213] (Examples 18-20)

[0214] Except for reducing the weight of Na2CO3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1.

[0215] (Examples 21-23)

[0216] Except for increasing the weight of the Na2CO3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1.

[0217] (Examples 24 and 25)

[0218] Except for reducing the weight of CaCO3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 4.

[0219] (Examples 26-28)

[0220] Except for increasing the weight of the CaCO3 powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 4.

[0221] (Examples 29-31)

[0222] Except for replacing a portion of the Gd2O3 powder with Tb2O3, Dy2O3, or Ho2O3, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1.

[0223] (Example 32)

[0224] A slurry was prepared by adding Gd₂O₃ powder to an aqueous sodium alginate solution and mixing for 12 hours. The sodium alginate aqueous solution was added at a ratio of sodium alginate to the raw material powder of 2.3% by weight. The prepared slurry was then dropwise added to an aqueous calcium lactate solution, which served as the gelation solution. A syringe was used for the dropwise addition of the slurry. The syringe orifice was set to 510 μm, and the distance from the tip of the syringe to the surface of the calcium lactate aqueous solution was set to 100 mm. Furthermore, after filling the mold with the slurry, it was immersed in the gelation solution.

[0225] The slurry added by syringe and the slurry filled into the mold are kept in the gelation solution for 5 hours.

[0226] Next, the gelled granulated particles were washed with pure water. The slurry filled into the mold was removed and washed with pure water to obtain the molded body. After washing, the molded body and particles were dried. The sodium concentration of the granulated particles was 0.78 atomic%, and the carbon concentration was 0.82 wt%. After drying, the molded body and particles underwent degreasing, vulcanization, and sintering.

[0227] The granulated particles were degreased at 600°C for 6 hours in an atmospheric atmosphere, resulting in a sodium concentration of 1.0 atomic% and a carbon concentration of 0.54 wt%. After degreasing, the granulated particles were heat-treated at 500°C for 4 hours in an atmosphere containing hydrogen sulfide (H₂S) to vulcanize the molded body and particles. The molded body and particles were then sintered at 1300°C for 12 hours in a pressurized atmosphere containing an inert gas. The main component of the cold storage material and its particles in Example 32 is gadolinium oxide. The sodium concentration in the cold storage material and its particles in Example 32 is 0.83 atomic%.

[0228] (Example 33)

[0229] Except that potassium alginate aqueous solution was used instead of sodium alginate aqueous solution, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 32.

[0230] (Examples 34-38)

[0231] Except for increasing or decreasing the amount of potassium alginate aqueous solution, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 33.

[0232] (Example 39)

[0233] Except that an aqueous solution of magnesium chloride was used instead of an aqueous solution of calcium lactate, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 32.

[0234] (Example 40)

[0235] Except that a strontium chloride aqueous solution was used instead of a calcium lactate aqueous solution, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 32.

[0236] (Example 41)

[0237] Except that a barium chloride aqueous solution was used instead of a calcium lactate aqueous solution, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 32.

[0238] (Example 42)

[0239] K2CO3 powder was added as a raw material powder, and otherwise the cold storage material and cold storage material particles were manufactured in the same manner as in Example 32.

[0240] (Example 43)

[0241] Li2CO3 powder was added as a raw material powder, and otherwise the cold storage material and cold storage material particles were manufactured in the same manner as in Example 18.

[0242] (Example 44)

[0243] Instead of a syringe, an air pulse dispenser was used for filling the mold with slurry and for dripping the slurry. Otherwise, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 32. The nozzle diameter was set to 510 μm, and the distance from the tip of the nozzle to the surface of the calcium lactate aqueous solution was set to 100 mm.

[0244] (Example 45)

[0245] Instead of a syringe, a piezoelectric dispenser was used for filling the mold with slurry and for dripping the slurry. Otherwise, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 32. The nozzle diameter was set to 510 μm, and the distance from the tip of the nozzle to the surface of the calcium lactate aqueous solution was set to 100 mm.

[0246] (Examples 46-51)

[0247] The particle size or aspect ratio of the cold storage material particles in Examples 46-51 differs from that of the cold storage material particles in Example 44. In manufacturing the cold storage material particles in Examples 51-56, the distance from the syringe nozzle and the tip of the syringe to the surface of the gelled solution was changed compared to the manufacturing of the cold storage material particles in Example 1.

[0248] (Example 52)

[0249] Instead of a syringe, a continuous inkjet printer was used for filling the mold with slurry and for adding slurry dropwise. Otherwise, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 32. The nozzle diameter was set to 510 μm, and the distance from the tip of the nozzle to the surface of the calcium lactate aqueous solution was set to 100 mm.

[0250] (Examples 53-56)

[0251] Except for changing the weight of polyvinyl alcohol, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1. Furthermore, the strength of the granulated particles was measured in the same manner as in Example 1.

[0252] (Examples 57-60)

[0253] The amount of sodium alginate relative to the raw material powder was changed by altering the concentration of the sodium alginate aqueous solution or the ratio of the sodium alginate aqueous solution to the raw material powder. Otherwise, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 32. Furthermore, the strength of the granulated particles was measured in the same manner as in Example 1.

[0254] (Example 61)

[0255] Except that Al2O3 powder was also used in the raw material powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 1. The Al2O3 powder was added in such a way that the Al content in the cold storage material particles was 15 atomic%.

[0256] (Example 62)

[0257] Except that Al2O3 powder was also used in the raw material powder, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 4. The Al2O3 powder was added in such a way that the Al content in the cold storage material particles was 15 atomic%.

[0258] (Example 63)

[0259] The cold storage material and cold storage material particles were manufactured in the same manner as in Example 32, except that an aqueous solution of aluminum chloride was used instead of an aqueous solution of calcium lactate. The material was added in such a manner that the amount of Al contained in the cold storage material particles was 0.01 atomic%.

[0260] (Example 64)

[0261] In addition to the aqueous solution of calcium lactate, an aqueous solution of aluminum chloride was also used. Otherwise, the cold storage material and cold storage material particles were manufactured in the same manner as in Example 32. The material was added in such a way that the amount of Al contained in the cold storage material particles was 0.01 atomic%.

[0262] (Comparative Example 1)

[0263] The cold storage material and cold storage material particles of Comparative Example 1 differ from those of Example 1 in that the atomic concentration of sodium is as low as 0.0008 atomic%. In manufacturing the cold storage material and cold storage material particles of Comparative Example 1, the weight of Na2CO3 powder was reduced compared to the manufacturing of the cold storage material and cold storage material particles of Example 1.

[0264] (Comparative Example 2)

[0265] The cold storage material and particles of Comparative Example 2 differ from those of Example 1 in that the sodium atomic concentration is as high as 15 atomic%. In manufacturing the cold storage material and particles of Comparative Example 2, the weight of Na2CO3 powder was increased compared to the manufacturing of the cold storage material and particles of Example 1. In this case, in addition to Gd2O2S, NaGdS2 was also significantly generated.

[0266] (Comparative Example 3)

[0267] The cold storage material and cold storage material particles of Comparative Example 3 differ from those of Example 4 in that the calcium atomic concentration is as high as 15 atomic%. In manufacturing the cold storage material and cold storage material particles of Comparative Example 3, the weight of CaCO3 powder was increased compared to the manufacturing of the cold storage material and cold storage material particles of Example 4.

[0268] (Comparative Example 4)

[0269] The cold storage material and cold storage material particles of Comparative Example 4 differ from those of Example 1 in that they do not contain Group I elements. The cold storage material and cold storage material particles of Comparative Example 4 were not manufactured using powders containing Group I elements.

[0270] (Comparative Example 5)

[0271] The cold storage material granules of Comparative Example 5 differ from those of Example 1 in that they contain up to 25% carbon by weight. The carbon concentration of the granules in Comparative Example 5 after degreasing was 12% by weight, but cracks or gaps appeared in the sintered particles, making particle recovery impossible. Therefore, evaluations of specific heat, strength, and refrigeration tests could not be performed. In manufacturing the cold storage material and cold storage material particles of Comparative Example 5, the weight ratio of polyvinyl alcohol used in the binder relative to the raw material powder was increased to 34% by weight.

[0272] (Comparative Example 6)

[0273] The cold storage material granules of Comparative Example 6 differ from those of Example 1 in that the carbon content is as low as 0.005% by weight. In Comparative Example 6, the particles cannot be recovered after granulation. Therefore, it is impossible to perform evaluations of specific heat, strength, and refrigeration tests. In manufacturing the cold storage material and cold storage material granules of Comparative Example 6, the weight ratio of polyvinyl alcohol to the raw material powder was set to 0.2% by weight.

[0274] (Comparative Example 7)

[0275] The degreased granulated particles of Comparative Example 7 differ from those of Example 1 in that they contain up to 15% carbon by weight. The carbon concentration before degreasing was 19% by weight. The granulated particles of Comparative Example 7 were sintered to obtain the cold storage material and cold storage material particles. In manufacturing the cold storage material and cold storage material particles of Comparative Example 7, the polyvinyl alcohol content relative to the raw material powder was set to 24% by weight, and degreasing was performed at 400°C for 1 hour in an atmospheric atmosphere.

[0276] (Comparative Example 8)

[0277] The degreased cold storage material particles of Comparative Example 8 differ from those of Example 1 in that the carbon content is below the detection limit. The granulated particles of Comparative Example 8 developed cracks or gaps after degreasing. The carbon concentration before degreasing was 0.01% by weight. In manufacturing the cold storage material and cold storage material particles of Comparative Example 8, polyvinyl alcohol was set at 0.2% by weight relative to the raw material powder, and degreasing was performed at 800°C for 12 hours under atmospheric conditions.

[0278] (Comparative Example 9)

[0279] The cold storage material and cold storage material particles of Comparative Example 9 differ from those of Example 61 in that the cold storage material particles contain up to 25 atomic% Al. In manufacturing the cold storage material and cold storage material particles of Comparative Example 9, the weight of Al2O3 powder was increased compared to the manufacturing of the cold storage material and cold storage material particles of Example 61.

[0280] For the cold storage materials of each embodiment and comparative example, the maximum volumetric specific heat below 10 K and the thermal conductivity at 4.2 K were measured. The results are shown in Tables 1, 2 and 3.

[0281] The freezing capacity of the cold storage material particles of each embodiment and comparative example is shown in Tables 1, 2, and 3. 250g of the cold storage material particles of each embodiment and comparative example were filled into... Figure 1 The two-stage GM chiller shown in the diagram has its second stage cold accumulator filled with 250g of Pb-based cold storage material on the low-temperature side and its high-temperature side. A freezing test was conducted to determine the chilling capacity at 4.2K. It should be noted that the first stage cold accumulator was subjected to a heat load at a temperature of 50K.

[0282] The evaluation results of the strength of the granulated particles of the cold storage material before and after degreasing in each embodiment and comparative example are shown in Table 3. The granulated particles of each embodiment and comparative example were filled into... The container is filled with a cylindrical container with a diameter of 15 mm and a height of 5 mm. A sufficient amount of cold storage material is then added, ensuring the granulated particles are fixed within the container and do not move freely. A 1×10⁻⁶ pressure is applied to the container. 3 The amplitude of the second wave is 2 mm, and the maximum acceleration is 200 m / s². 2 The single vibration was evaluated. As a result, the proportion of granulated particles in the damaged cold storage material was assessed.

[0283]

[0284]

[0285]

[0286]

[0287] As with Comparative Examples 1 and 4, if the atomic concentration of Group I elements in the cold storage material is less than 0.001 atomic%, or if the cold storage material does not contain Group I elements, the thermal conductivity decreases to 0.005 W / cm·K and 0.004 W / (cm·K), respectively. This is believed to be due to the reduced proportion of Group I elements in the cold storage material, which decreases the sintering-promoting effect and increases the amount of fine voids.

[0288] It was found that, as in Comparative Example 2, if the atomic concentration of Group 1 elements in the cold storage material becomes greater than 10 atomic%, the volumetric specific heat decreases to 0.4 J / (cm²). 3 This is attributed to the increased proportion of Group 1 elements in the cold storage material, which generates sulfides containing both rare earth elements and Group 1 elements, thus reducing the relative amount of rare earth oxysulfides.

[0289] The results of Comparative Example 3 show that if the atomic concentration of Group II elements in the cold storage material becomes greater than 10 atomic%, the thermal conductivity increases, but the volumetric specific heat decreases to 0.4 J / (cm²). 3 (·K), the freezing capacity of the cold storage material particles is significantly reduced. This is believed to be due to the increased proportion of Group II elements and the relatively decreased proportion of rare earth elements in the cold storage material particles.

[0290] The results in Tables 1 and 4 show that adding sintering aids with the metal or half-metal elements derived from the sintering aids reaching 0.01 atomic% or more increases the strength. If the percentage exceeds 20 atomic%, the strength increases further, but the volumetric heat of heat decreases to 0.4 J / (cm³). 3 (·K), the freezing capacity of the cold storage material particles is significantly reduced. This is believed to be due to the increased proportion of sintering aids and the relatively decreased proportion of rare earth elements in the cold storage material particles.

[0291] As shown in Tables 1 and 2, if the particle size of the cold storage material is between 50 μm and 3000 μm, the freezing capacity at 4.2 K is significantly improved.

[0292] As shown in Tables 1 and 2, if the aspect ratio of the cold storage material particles is less than 5, the freezing capacity at 4.2K is significantly improved.

[0293] As shown in Tables 1 and 2, even if the methods of granulating cold storage materials are different, by appropriately adjusting the synthesis conditions, they exhibit the same particle size, aspect ratio, content of Group I and Group II elements, and thermal conductivity.

[0294] As shown in Tables 1 and 2, even if the cold storage material particles are granulated using different methods, if the particle size, aspect ratio, and thermal conductivity are the same, the performance and reliability of the refrigerator equipped with the cold storage material particles will also be the same.

[0295] Table 3 shows that if the granulated particles contain more than 0.001 atomic% and less than 10% of Group 1 elements, and contain more than 0.01 wt% and less than 20 wt% of carbon before defatting, the granulated particles have high strength. If the carbon concentration is less than 0.01 wt%, the granulated particles are very fragile and therefore cannot be recycled as particles.

[0296] Table 3 shows that if the particles contain 0.001 atomic% to 10% of Group 1 elements and have a carbon content of 0.001 wt% to 10 wt% after degreasing, both the strength and sinterability of the granulated particles can be balanced. Furthermore, the freezer carrying the obtained cold storage material particles exhibits high freezing performance. When the carbon concentration after degreasing exceeds 10 wt%, the particle strength is maintained even after degreasing, but the forming density is low, and the sinterability is poor. Therefore, the particle density, specific heat, and thermal conductivity decrease. Consequently, the freezing performance when carried in the freezer also decreases. If the carbon concentration is below 0.001 wt%, the degreased particles are very fragile and therefore cannot be recycled as particles.

[0297] Through the above embodiments, the effects of the cold storage material in the first embodiment and the cold storage material particles in the second embodiment have been confirmed.

[0298] As a distributor, the case of an air pulse distributor or a piezoelectric distributor is illustrated as an example, but a plunger distributor can also be used.

[0299] As an example of inkjet printing, continuous inkjet printing has been used, but on-demand inkjet printing can also be used.

[0300] Several embodiments of the present invention have been described, but these embodiments are provided by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. For example, the constituent elements of one embodiment can be substituted or modified with the constituent elements of other embodiments. These embodiments and their variations are included in the scope and spirit of the invention, and are also included in the invention as described in the claims and its equivalents.

[0301] Explanation of symbols

[0302] 100 Cold Storage Type Ultra-Low Temperature Refrigeration Unit

[0303] 114, 115 Cold accumulators

[0304] 118, 119 Cold storage materials

[0305] 500 Cryogenic Pump

[0306] 600 superconducting magnet

[0307] 700 Magnetic Resonance Imaging Device

[0308] 800 nuclear magnetic resonance device

[0309] 900 Magnetic Field Applied Single Crystal Pulling Device

[0310] 1000 helium recondenser

Claims

1. A cold storage material, wherein, Rare earth oxysulfides comprising at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, comprising 0.001 atomic% to 10 atomic% of a Group 1 element, and having a maximum volumetric specific heat of 0.5 J / (cm³) in a temperature range of 2 K to 10 K. 3 ·K) and above, wherein the first group element is at least one element selected from the group consisting of Li, Na and K.

2. The cold storage material according to claim 1, wherein, It contains more than 0 atomic percent and less than 10 atomic percent of Group 2 elements, wherein the Group 2 elements are at least one element selected from the group consisting of Mg, Ca, Sr and Ba.

3. The cold storage material according to claim 1, wherein, It contains more than 0.001 atomic% and less than 10 atomic% of Group 2 elements, wherein the Group 2 elements are at least one element selected from the group consisting of Mg, Ca, Sr and Ba.

4. The cold storage material according to claim 1 or claim 2, wherein, It contains at least one element selected from the group consisting of Al, Fe, Cu, Ni, Co, Zr and B, comprising 0.01 atomic% and less than 20 atomic% of the element.

5. A cold storage material particle, formed from any one of claims 1 to 4, having a particle size of 50 μm or more and 3 mm or less.

6. The cold storage material particles according to claim 5, wherein, The aspect ratio of the cold storage material particles is greater than 1 and less than 5.

7. A granulated particle, which is a raw material for the cold storage material particles of claim 5 or claim 6, comprising a rare earth oxide or a rare earth oxysulfide containing at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, comprising 0.001 atomic% or more and 10 atomic% or less of a Group 1 element, comprising 0.01 wt% or more and 20 wt% or less of carbon, having a particle size of 70 μm or more and 5 mm or less, and an aspect ratio of 1 or more and 5 or less.

8. A granulated particle, which is a degreased granulated particle that serves as the raw material for the cold storage material particles of claim 5 or claim 6, comprising a rare earth oxide or a rare earth oxysulfide containing at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, comprising 0.001 atomic% or more and 10 atomic% or less of a Group 1 element, comprising 0.001 wt% or more and 10 wt% or less of carbon, having a particle size of 70 μm or more and 5 mm or less, and an aspect ratio of 1 or more and 5 or less.

9. A cold storage device comprising the cold storage material according to any one of claims 1 to 4.

10. A cold storage device filled with a plurality of cold storage material particles as described in claim 5 or claim 6.

11. A refrigeration unit comprising the cold accumulator as described in claim 9 or claim 10.

12. A cryogenic pump comprising the refrigeration unit of claim 11.

13. A superconducting magnet comprising the cryostat of claim 11.

14. A magnetic resonance imaging device comprising the cryostat as described in claim 11.

15. A nuclear magnetic resonance apparatus comprising the cryostat as described in claim 11.

16. A magnetic field-applied single crystal pulling device comprising the cryostat as described in claim 11.

17. A helium recondensation apparatus comprising the refrigeration unit of claim 11.

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