Two-stage cold storage type cryogenic refrigeration machine, cryopump and semiconductor manufacturing device

Abstract

To provide a two-stage cold storage type cryogenic refrigeration machine that comprises cold storage material particles having high volumetric specific heat and high heat conductivity.SOLUTION: A two-stage cold storage type cryogenic refrigeration machine according to an embodiment comprises: a vacuum container; a first cylinder provided in the vacuum container; a second cylinder provided in the vacuum container, connected coaxially with the first cylinder, and having a diameter smaller than that of the first cylinder; a first cold accumulator provided in the first cylinder and storing a first cold material; and a second cold accumulator provided in the second cylinder and storing a second cold material, wherein the second cold material is composed of cold material particles, the cold material particles include rare-earth oxysulfide including at least one rare earth element selected from the group of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and also include 0.001 atom% or more and 10 atom% or less of a group 1 element, and a maximum value of a volumetric specific ratio in a temperature range of 2 K or more and 10 K or less is 0.5 J / (cm3 K) or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, superconducting technology has made remarkable progress, and as its application fields expand, the development of small, high-performance cryogenic refrigerators has become essential. Such cryogenic refrigerators are required to be lightweight, small, and highly thermally efficient, and their practical application is progressing in various application fields.

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

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

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

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

[0007] In this type of refrigerator, a working medium such as compressed helium (He) gas flows in one direction through a regenerator housing a regenerator material, supplying its thermal energy to the regenerator material. The expanded working medium then flows in the opposite direction through the regenerator, receiving thermal energy from the regenerator material. As the heat recovery effect in this process improves, the thermal efficiency of the working medium cycle improves, making it possible to achieve lower temperatures.

[0008] The higher the specific heat per unit volume of the regenerator material, the more heat energy the regenerator material can store, improving the refrigeration capacity of the refrigerator. Therefore, it is desirable to install a regenerator material with a high specific heat at low temperatures on the low-temperature side of the regenerator, and a regenerator material with a high specific heat at high temperatures on the high-temperature side.

[0009] Magnetic regenerator materials exhibit high volumetric heat capacity in a specific temperature range depending on their composition. Therefore, by combining magnetic regenerator materials with different compositions that exhibit high volumetric heat capacity in the target temperature range, the regenerator capacity can be increased, and the refrigeration capacity of the refrigerator can be improved.

[0010] Furthermore, the higher the thermal conductivity and heat transfer coefficient of the regenerator material used in the regenerator, the more efficient the transfer of thermal energy becomes, and the more efficient the refrigerator becomes.

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

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

[0013] As applications of the above-described refrigerators to various cooling systems are being considered, there is a need to stably cool larger objects to be cooled, and therefore there is a demand for refrigerators with even greater cooling capacity. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-73661 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-213252 [Patent Document 3] International Publication No. 2018 / 025581 [Patent Document 4] Patent No. 5010071 Summary of the Invention [Problem to be solved by the invention]

[0015] The problem to be solved by the present invention is to provide a two-stage regenerative cryogenic refrigerator equipped with regenerative material particles having a high volumetric specific heat and high thermal conductivity. [Means for solving the problem]

[0016] The two-stage regenerative cryogenic refrigerator of the embodiment includes a vacuum vessel, a first cylinder provided in the vacuum vessel, a second cylinder provided in the vacuum vessel, coaxially connected to the first cylinder, and having a diameter smaller than that of the first cylinder, a first regenerator provided in the first cylinder and accommodating a first regenerator material, and a second regenerator provided in the second cylinder and accommodating a second regenerator material, the second regenerator material being regenerator particles, the regenerator particles comprising 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, and containing 0.001 atomic % to 10 atomic % of a Group 1 element, and having a maximum volumetric specific heat of 0.5 J / (cm) in a temperature range of 2 K to 10 K. 3 and a second regenerator having a temperature of at least 1000 K. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 4 is a schematic cross-sectional view showing the main configuration of a cold storage material particle according to a second embodiment and a refrigerator according to a fourth embodiment. [Figure 2] FIG. 10 is a cross-sectional view showing a schematic configuration of a cryopump according to a fifth embodiment. [Figure 3] FIG. 10 is a perspective view showing a schematic configuration of a superconducting magnet according to a sixth embodiment. [Figure 4] FIG. 13 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance imaging apparatus according to a seventh embodiment. [Figure 5] FIG. 13 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance spectrometer according to an eighth embodiment. [Figure 6] 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. [Figure 7] FIG. 22 is a schematic diagram showing the general configuration of a helium recondensation device according to a tenth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] 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.

[0019] In this specification, the term "extremely low temperature" refers to a temperature range in which the superconducting phenomenon can be utilized industrially in a useful manner, for example, a temperature range of 20 K or lower.

[0020] (First embodiment) The regenerator material of the first embodiment includes a rare earth oxysulfide containing at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and contains 0.001 atomic % to 10 atomic % of a Group 1 element, and has a maximum volumetric specific heat of 0.5 J / (cm) in a temperature range of 2 K to 10 K. 3 ·K) or more.

[0021] The regenerator material of the first embodiment has a volumetric specific heat of 0.5 J / (cm 3 ·K) or more. The regenerator material of the first embodiment has a volumetric specific heat of 0.55 J / (cm ) in the temperature range of 2 K or more and 8 K or less. 3 ·K) or more. The regenerator material of the first embodiment has a volumetric specific heat of 0.6 J / (cm ) in the temperature range of 4 K or more and 7 K or less. 3 ·K) or more.

[0022] The rare earth oxysulfide contained in the regenerator material of the first embodiment is, for example, a compound represented by the general formula R 2±0.1 O2S 1±0.1(wherein R represents at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu). In the rare earth oxysulfide represented by the above general formula, the maximum value of the volumetric specific heat and the temperature at which the maximum value of the volumetric specific heat is exhibited vary depending on the rare earth element selected. Therefore, the specific heat characteristics can be adjusted by appropriately adjusting the ratio of the rare earth element.

[0023] The rare earth element is, for example, at least one rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, and Er. The rare earth oxysulfide contained in the regenerator material of the first embodiment may contain, for example, two or more kinds of rare earth elements.

[0024] The rare earth oxysulfide is, for example, crystalline.

[0025] The cold accumulator of the first embodiment is mainly composed of rare earth oxysulfide. Among the substances contained in the cold accumulator of the first embodiment, for example, the volume ratio of the rare earth oxysulfide is the largest. Among the substances contained in the cold accumulator of the first embodiment, for example, the molar ratio of the rare earth oxysulfide is the largest.

[0026] The cold accumulator material of the first embodiment contains a total of 0.001 atomic % to 10 atomic % of Group 1 elements. The Group 1 elements are at least one element selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). The Group 1 elements are, for example, at least one element selected from the group consisting of Li, Na, and K. The cold accumulator material may contain, for example, two or more types of Group 1 elements.

[0027] The Group 1 element contained in the cold accumulator material exists, for example, in the crystals of the rare earth oxysulfide. The Group 1 element contained in the cold accumulator material exists, for example, in the crystal grain boundaries of the rare earth oxysulfide. The Group 1 element contained in the cold accumulator material exists, for example, on the inner wall surfaces of voids present in the cold accumulator material. The Group 1 element contained in the cold accumulator material exists, for example, in the crystal grains of the rare earth oxysulfide. The Group 1 element contained in the cold accumulator material exists, for example, in crystal grains other than the rare earth oxysulfide contained in the cold accumulator material.

[0028] The cold accumulating material of the first embodiment contains, for example, the above-mentioned Group 1 elements and, in addition, a total of 0 atomic % to 10 atomic % of Group 2 elements.Furthermore, the cold accumulating material of the first embodiment contains, for example, the above-mentioned Group 1 elements and, in addition, a total of 0.001 atomic % to 10 atomic % of Group 2 elements.

[0029] The Group 2 element is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). The Group 2 element is, for example, at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

[0030] The regenerator material may contain, for example, two or more types of Group II elements. The regenerator material does not necessarily have to contain any Group II elements.

[0031] The Group 2 element contained in the cold accumulator material exists, for example, in the crystals of the rare earth oxysulfide. The Group 2 element contained in the cold accumulator material exists, for example, in the crystal grain boundaries of the rare earth oxysulfide. The Group 2 element contained in the cold accumulator material exists, for example, on the inner wall surfaces of voids present in the cold accumulator material. The Group 2 element contained in the cold accumulator material exists, for example, in the crystal grains of the rare earth oxysulfide. The Group 2 element contained in the cold accumulator material exists, for example, in crystal grains other than the rare earth oxysulfide contained in the cold accumulator material.

[0032] The regenerator material of the first embodiment contains a substance derived from a sintering aid used in manufacturing the regenerator material, such as aluminum oxide (alumina), magnesium oxide, yttrium oxide, zirconium oxide, or boron oxide.

[0033] The regenerator material of the first embodiment 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) in an amount of 0.01 atomic % to 20 atomic %. The 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.

[0034] The detection of elements contained in the regenerator material of the first embodiment and the measurement of the atomic concentration of the elements can be performed by dissolving the regenerator material in a liquid and using inductively coupled plasma atomic emission spectroscopy (ICP-AES), or by using energy dispersive X-ray spectroscopy (EDX) or wavelength dispersive X-ray spectroscopy (WDX).

[0035] The crystal structure of the rare earth oxysulfide contained in the regenerator material of the first embodiment is, for example, Ce2O2S type, and its space group is P-3m. The crystal structure can be confirmed by powder X-ray diffraction measurement, observation of an electron backscatter diffraction image using a scanning electron microscope, or observation using a transmission electron microscope.

[0036] The method for producing the cold accumulator of the first embodiment is not particularly limited, but can be, for example, by mixing raw material powders using a ball mill or the like to prepare a raw material mixture, and then molding and sintering the obtained raw material mixture. Rare earth oxides or rare earth oxysulfides can be used as the raw material powder. The type and proportion of the rare earth oxides or rare earth oxysulfides are adjusted according to the target composition of the cold accumulator.

[0037] By using a carbonate containing a Group 1 element, an oxide containing a Group 1 element, a nitride containing a Group 1 element, or a carbide containing a Group 1 element as the raw material powder, it becomes possible to incorporate the Group 1 element into the regenerator material. By using a carbonate containing a Group 2 element, an oxide containing a Group 2 element, a nitride containing a Group 2 element, or a carbide containing a Group 2 element as the raw material powder, it becomes possible to incorporate the Group 2 element into the regenerator material.

[0038] The raw material mixture may contain a sintering aid, such as aluminum oxide (alumina), yttrium oxide, zirconium oxide, or boron oxide.

[0039] When rare earth oxides are used as the raw material powder, the molded body is sulfurized. In this case, heat treatment is performed in a sulfurization atmosphere. The sulfurization atmosphere contains a gas containing sulfur atoms with a negative oxidation number, such as hydrogen sulfide (HS), carbon sulfide (CS), or methanethiol (CHSH). The heat treatment temperature is, for example, 400°C or higher and 700°C or lower. The heat treatment time is, for example, 1 hour or higher and 8 hours or lower.

[0040] The heat treatment for sintering the obtained oxysulfide is carried out, for example, in a pressurized inert gas atmosphere. The heat treatment temperature is, for example, 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.

[0041] The cold storage material of the first embodiment may be, for example, a sintered body of cold storage material particles made of the first cold storage material.

[0042] Next, the function and effect of the regenerator material of the first embodiment will be described.

[0043] In cryocoolers used for cooling superconducting equipment, a regenerator material is housed in a regenerator. For example, cold is generated by heat exchange between the regenerator material and helium gas passing through the regenerator. To improve the refrigeration capacity of the refrigerator, the regenerator material must have excellent properties, such as a high volumetric specific heat and high thermal conductivity.

[0044] The upper limit of volumetric heat capacity is limited by the composition of the material. For this reason, it is difficult to significantly improve volumetric heat capacity. On the other hand, thermal conductivity can be improved by improving crystallinity and reducing the number of voids.

[0045] The regenerator material of the first embodiment has a maximum volumetric specific heat of 0.5 J / (cm 3 Therefore, the regenerator material of the first embodiment has a high volumetric specific heat.

[0046] The regenerator material of the first embodiment has a volumetric specific heat of 0.5 J / (cm) in the temperature range of 2.5 K or more and 10 K or less. 3 ·K) or more. For example, the volumetric specific heat in the temperature range of 2K to 8K is 0.55J / (cm 3 ·K) or more. For example, the volumetric specific heat in the temperature range of 4K to 7K is 0.6J / (cm 3 ·K) or more.

[0047] As described above, since the cold storage material of the first embodiment has a high volumetric specific heat, the cold storage unit containing the cold storage material of the first embodiment has high cold storage performance, and the refrigerator including the cold storage unit containing the cold storage material of the first embodiment exhibits high refrigeration capacity.

[0048] The cold storage material of the first embodiment contains a Group 1 element in an atomic concentration of 0.001 atomic % or more and 10 atomic % or less. The Group 1 element has the effect of accelerating the sintering of the compact during the sintering process for producing the cold storage material and reducing 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.

[0049] In order to fully obtain the properties required for a cold storage material, such as thermal conductivity and volumetric specific heat, a sufficient sintering temperature and sintering time are required in the sintering process. The cold storage material of the first embodiment allows the sintering temperature and sintering time required for sintering to be reduced due to the sintering-promoting effect of the Group 1 elements. This reduces the manufacturing cost of the cold storage material, making it possible to provide an inexpensive cold storage material.

[0050] By ensuring that the atomic concentration of Group 1 elements in the regenerator material is 0.001 atomic % or more, the degree of sintering is increased and the number of minute voids is reduced, thereby enabling the regenerator material to have a high thermal conductivity.

[0051] If the atomic concentration of the Group 1 element in the regenerator material exceeds 10 atomic %, sulfides containing rare earth elements and Group 1 elements are generated, resulting in a low volumetric specific heat and low thermal conductivity. If the atomic concentration of the Group 1 element in the regenerator material is 10 atomic % or less, it becomes possible to increase the volumetric specific heat and thermal conductivity, thereby improving the refrigeration capacity of a refrigerator containing the regenerator material of the first embodiment.

[0052] The Group 1 element contained in the regenerator 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. The Group 1 element is preferably at least one element selected from the group consisting of Li, Na, and K. Furthermore, for example, two or more types of Group 1 elements may be contained among the Group 1 elements.

[0053] A cold accumulator containing a Group 1 element can be manufactured by using a carbonate, oxide, nitride, or carbide containing a Group 1 element as the raw material powder. The concentration of the Group 1 element contained in the cold accumulator can be adjusted by adjusting the amount of the carbonate, oxide, nitride, or carbide containing the Group 1 element.

[0054] The cold storage material of the first embodiment contains, for example, a total of 0 atomic % to 10 atomic % of Group 2 elements in atomic concentration. Also, for example, the cold storage material contains, for example, a total of 0.001 atomic % to 10 atomic % of Group 2 elements in atomic concentration. The Group 2 element is at least one element selected from the group consisting of Be, Mg, Ca, Sr, Ba, and Ra. The atomic concentration of the Group 2 element is, for example, 0.001 atomic % to 5 atomic % in total. The cold storage material may contain, for example, two or more types of Group 2 elements.

[0055] The cold storage material of the first embodiment further improves sinterability and reduces the number of minute voids by containing 0.001 atomic % or more of a group 2 element in addition to a group 1 element. This further improves thermal conductivity. Group 2 elements do not exhibit specific heat properties. 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 storage unit decreases, and the refrigeration capacity of the refrigerator decreases.

[0056] A cold accumulator containing a Group 2 element can be manufactured by using a carbonate, oxide, nitride, or carbide containing a Group 2 element as the raw material powder. The concentration of the Group 2 element contained in the cold accumulator can be adjusted by adjusting the amount of the carbonate, oxide, nitride, or carbide containing the Group 2 element.

[0057] When manufacturing the cold storage material of the first embodiment, adding a sintering aid as a metal or metalloid element constituting the sintering aid in an amount of 0.01 atomic % or more in addition to the first group element further improves sinterability and reduces the number of minute voids. This further improves thermal conductivity. The metal or metalloid element constituting the sintering aid does not exhibit specific heat characteristics. Therefore, if the amount of metal or metalloid 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 storage unit decreases, and the refrigeration capacity of the refrigerator decreases.

[0058] The regenerator 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) in an amount of 0.01 atomic % to 20 atomic %. The 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. The 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 metal or semimetal element constituting a sintering aid.

[0059] As described above, according to the first embodiment, a regenerator material having excellent properties such as a high volumetric specific heat and a high thermal conductivity can be realized.

[0060] (Second embodiment) The cold storage material particles of the second embodiment are formed from the cold storage material of the first embodiment, and have a particle size of 50 μm or more and 3 mm or less. 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 long axis to the short axis of the cold storage material particles. The shape of the cold storage material particles is, for example, spherical.

[0061] Hereinafter, some of the content that overlaps with the first embodiment may be omitted.

[0062] The particle size of the regenerator particles is the equivalent circle diameter. The equivalent circle diameter is the diameter of a perfect circle corresponding to the area of ​​a figure observed in an image such as an optical microscope image or a scanning electron microscope image (SEM image). The particle size of the regenerator particles can be determined, for example, by image analysis of the optical microscope image or the SEM image.

[0063] The method for producing the ice accumulator particles of the second embodiment is not particularly limited, but for example, raw material powders are mixed using a ball mill or the like to prepare a raw material mixture, and the obtained raw material mixture is molded (granulated) into granules by a rolling granulation method, an agitation granulation method, an extrusion method, an atomization method (spray method), a press molding method, or the like, and then the obtained granular molded body is sintered.

[0064] The resulting granular compacts are referred to as granulated particles.

[0065] In the granulation method, a binder is added to adhere the raw material powders together, thereby improving the strength of the granulated particles. Examples of binders include polyvinyl alcohol, polyvinyl butyral, carboxymethyl cellulose, acrylic resin, and polyethylene glycol. The amount of binder added is, for example, 0.01% by weight or more and 20% by weight or less.

[0066] The raw material powder can be made of rare earth oxides or rare earth oxysulfides, and the type and ratio of the rare earth oxides or rare earth oxysulfides are adjusted according to the target composition of the regenerator particles.

[0067] By using a carbonate containing a Group 1 element, an oxide containing a Group 1 element, a nitride containing a Group 1 element, or a carbide containing a Group 1 element as the raw material powder, it is possible to produce cold accumulator particles containing a Group 1 element. Also, by using a carbonate containing a Group 2 element, an oxide containing a Group 2 element, a nitride containing a Group 2 element, or a carbide containing a Group 2 element as the raw material powder, it is possible to produce cold accumulator particles containing a Group 2 element.

[0068] By adding a sintering aid to the raw material powder, it is possible to manufacture regenerator particles containing the sintering aid. The reaction between the sintering aid and the raw material rare earth oxide may produce an oxide phase containing the rare earth element and the metal or semi-metal element that constitutes the sintering aid.

[0069] Alternatively, the raw material powder may be added to an aqueous alginic acid solution, mixed to form a slurry, and then dropped into a gelling solution to gel the slurry. This method produces granules by promoting gelation through a crosslinking reaction caused by the polyvalent metal ions contained in the gelling solution. Therefore, the strength of the granulated particles, i.e., the gelling strength, varies depending on the amount of alginate contained in the particles.

[0070] The amount of alginate contained in the particles can be changed by changing the concentration of alginate contained in the alginic acid aqueous solution or the ratio of the alginic acid aqueous solution to the raw material powder. The slurry can be dropped into the gelling solution using, for example, a dropper, burette, pipette, syringe, dispenser, or inkjet. Hereinafter, this method for granulating particles is referred to as the alginic acid gel method.

[0071] In the alginate gel method, the particle size and aspect ratio can be changed by adjusting the viscosity of the slurry, the diameter of the nozzle when dropping, or the distance between the tip of the nozzle and the liquid surface of the gelling solution. The diameter of the nozzle is, for example, 50 μm or more and 3000 μm or less. The viscosity of the slurry is, for example, 0.1 mPa·s or more and 1,000,000 mPa·s or less. The distance between the tip of the nozzle and the liquid surface of the gelling solution is, for example, 0.1 mm or more and 1,000 mm or less.

[0072] When a dispenser is used for discharging, any of an air pulse dispenser, a plunger dispenser, and a piezo dispenser may be used as the device.

[0073] Inkjet printers are broadly divided into continuous and on-demand types based on their ejection method, but either type may be used. Furthermore, on-demand types are further divided into three types: piezo, thermal, and valve, but any of these may be used.

[0074] The slurry dropped into the gelling solution using a dropper, burette, pipette, syringe, dispenser, inkjet, etc. is gelled by being held in the gelling solution. By gelling the slurry, granulated particles containing the raw material powder of the heat accumulator are formed.

[0075] The retention time of the slurry in the gelling solution is, for example, 10 minutes to 48 hours. If the gelling time is too short, gelling does not proceed sufficiently, and the strength of the granulated particles will be lower than that expected from the amount of alginate.

[0076] The alginic acid aqueous solution used in the alginic acid gel method is, for example, a sodium alginate aqueous solution, an ammonium alginate aqueous solution, or a potassium alginate aqueous solution. By using a sodium alginate aqueous solution or a potassium alginate aqueous solution containing a Group 1 element, sodium or potassium can be contained in the cold storage material particles. By using a mixed aqueous solution of a sodium alginate aqueous solution and a potassium alginate aqueous solution as a slurry, sodium and potassium can be contained simultaneously.

[0077] The concentration of the Group 1 element contained in the particles is adjusted by adjusting the concentration of the alginate containing the Group 1 element. The concentration of the alginate as an alginate aqueous solution is, for example, 0.01% by weight or more and 5% by weight or less. If the concentration of the alginate aqueous solution is lower than 0.01% by weight, a gel with sufficient strength cannot be formed, and particles cannot be obtained.

[0078] The gelling solution may be an aqueous solution containing a Group 2 element, such as an aqueous solution of calcium lactate, an aqueous solution of calcium chloride, an aqueous solution of manganese (II) chloride, an aqueous solution of magnesium sulfate, an aqueous solution of beryllium sulfate, an aqueous solution of strontium nitrate, an aqueous solution of barium chloride, or an aqueous solution of barium hydroxide.

[0079] By using a calcium lactate aqueous solution, a calcium chloride aqueous solution, a magnesium sulfate aqueous solution, a beryllium sulfate aqueous solution, a strontium nitrate aqueous solution, a barium chloride aqueous solution, or a barium hydroxide aqueous solution as the gelling solution, calcium, magnesium, beryllium, strontium, and barium can be contained in the ice accumulator particles.

[0080] By using an aqueous aluminum chloride solution, an aqueous aluminum nitrate solution, an aqueous aluminum lactate solution, an aqueous iron (II) chloride solution, an aqueous iron (III) chloride solution, an aqueous copper (II) chloride solution, an aqueous nickel (II) chloride solution, or an aqueous cobalt (II) chloride solution as a gelling solution, aluminum, iron, copper, nickel, or cobalt can be contained in the regenerator particles as a sintering aid.

[0081] Gelation proceeds through a crosslinking reaction caused by the polyvalent metal ions contained in the gelling solution. Therefore, when an aqueous solution containing a Group 1 element is used as the slurry and an aqueous solution containing a Group 2 element is used as the gelling solution, the amount of Group 1 element and Group 2 element contained in the particles can be adjusted by adjusting the immersion time in the gelling solution of the particles granulated by dropping the particles into the gelling solution.

[0082] At least two types of aqueous solutions containing different metal elements selected from the group consisting of calcium lactate aqueous solution, calcium chloride aqueous solution, magnesium sulfate aqueous solution, beryllium sulfate aqueous solution, strontium nitrate aqueous solution, barium chloride aqueous solution, and barium hydroxide aqueous solution are mixed together and used as a gelling solution, thereby making it possible to incorporate two or more types of Group 2 elements into the ice storage material particles.

[0083] The particle size of the granulated particles is, for example, 70 μm or more and 5 mm or less, and the aspect ratio of the granulated particles is, for example, 1 or more and 5 or less.

[0084] A certain amount of organic components can be removed from granulated particles by degreasing them. If the raw material is an oxide, insufficient degreasing will prevent sulfurization from progressing sufficiently, and the required amount of oxysulfide cannot be produced. Furthermore, if degreasing is insufficient and too much organic components remain, the density of the sintered particles will decrease. This weakens the strength of the regenerator particles, making them unable to withstand use in refrigerators.

[0085] If debinding is carried out too far, the organic components that ensure strength will disappear, reducing the strength of the granulated particles after debinding and causing cracks or chips in the particles. The debinding temperature is, for example, 400°C or higher and 800°C or lower, and the time is 30 minutes or higher and 12 hours or lower.

[0086] When rare earth oxides are used as the raw material powder, the granulated particles are sulfurized. In this case, heat treatment is performed in a sulfurization atmosphere. The sulfurization atmosphere contains a gas containing sulfur atoms with a negative oxidation 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.

[0087] The heat treatment for sintering the oxysulfide particles is carried out, for example, in a pressurized 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.

[0088] Next, the function and effect of the cold storage material particles of the second embodiment will be described.

[0089] The cold storage material particles of the second embodiment are made of 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 long axis to the short axis of the cold storage material particles. The shape of the cold storage material particles is, for example, spherical.

[0090] The cold storage material particles of the second embodiment have a maximum volumetric specific heat of 0.5 J / (cm 3 ·K) or more. Therefore, the cold storage material particles of the second embodiment have a high volumetric specific heat. Since the cold storage material particles of the second embodiment have a high volumetric specific heat, a cold storage unit equipped with the cold storage material particles of the second embodiment has high cold storage performance. Furthermore, a refrigerator equipped with a cold storage unit equipped with the cold storage material particles of the second embodiment exhibits high refrigeration capacity.

[0091] The cold storage material particles of the second embodiment contain a Group 1 element at an atomic concentration of 0.001 atomic % to 10 atomic %. The Group 1 element has the effect of accelerating the sintering of the cold storage material particles during sintering to produce the cold storage material particles and reducing the number of voids contained in the cold storage material particles. Therefore, the cold storage material particles have a high degree of sintering and high thermal conductivity.

[0092] In the cold storage material of the first embodiment, by adding a sintering aid of 0.01 atomic % or more as a metal or metalloid element constituting the sintering aid in addition to the Group 1 element, the sinterability is further improved and the number of minute voids is reduced. This further improves the thermal conductivity. The metal or metalloid element constituting the sintering aid does not exhibit specific heat characteristics. Therefore, if the amount of metal or metalloid 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 storage unit decreases, and the refrigeration capacity of the refrigerator decreases.

[0093] In order to fully obtain the properties required for the cold storage material particles, such as thermal conductivity and volumetric specific heat, a sufficient sintering temperature and sintering time are required in the sintering process. The cold storage material particles of the second embodiment enable a reduction in the sintering temperature and sintering time required for sintering due to the sintering-promoting effect of the Group 1 elements. This reduces the manufacturing cost of the cold storage material particles, making it possible to provide inexpensive cold storage material particles.

[0094] The particle size of the cold storage material particles in the second embodiment is 50 μm to 3 mm, more preferably 1 mm or less, and further preferably 500 μm or less.

[0095] When the particle size of the cold storage material particles is above the lower limit, the packing density of the cold storage material particles in the cold storage unit is lowered, the pressure loss of the working medium such as helium is reduced, and the refrigeration performance of the refrigerator is improved. On the other hand, when the particle size of the cold storage material particles is below the upper limit, the distance from the surface of the cold storage material particle to the center of the particle is shortened, and heat transfer between the working medium and the cold storage material particles is facilitated to the center of the cold storage material, and the refrigeration performance of the refrigerator is improved.

[0096] The aspect ratio of the cold storage material particles is preferably 1 or more and 5 or less, and more preferably 1 or more and 2 or less. When the aspect ratio of the cold storage material particles is below the upper limit value, the voids become uniform when the cold storage material particles are filled into the cold storage unit, and the refrigeration performance of the refrigerator is improved.

[0097] In the second embodiment, if the granulated particles after degreasing do not have a certain level of strength, they will crack or chip during handling. If non-spherical granulated particles are installed in a refrigerator, the refrigerator performance will decrease, and cracked or chipped granulated particles will be discarded as defective products. For this reason, it is desirable that the granulated particles have a certain level of strength that will not crack or chip.

[0098] The strength of the granulated particles depends mainly on the amount of binder or alginate, but if the amount of these organic components is too high, sulfurization or sintering becomes difficult. On the other hand, Group 1 elements promote the sintering of the regenerator particles. If the granulated particles contain a Group 1 element in an atomic concentration of 0.001 atomic % to 10 atomic % and also contain a binder or alginate-derived carbon component in an amount of 0.01 wt % to 20 wt %, the above two effects can achieve both sinterability and high strength.

[0099] The carbon content is more preferably 10% by weight or less, and even more preferably 5% by weight or less. Even if the atomic concentration of Group 1 elements is between 0.001 and 10 atomic percent, if the carbon content exceeds 20% by weight, it becomes difficult to properly remove organic components, or the molding density after degreasing decreases significantly, and the sintering reaction does not proceed even at high sintering temperatures. As a result, the strength of the sintered particles is significantly low, making them difficult to recover as particles. 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, resulting in weak strength and causing cracks or chips when the granulated particles are handled.

[0100] Defatted granulated particles containing 0.001 atomic % to 10 atomic % of Group 1 elements in atomic concentration and 0.001 wt % to 10 wt % of a binder or alginate-derived carbon component can achieve both sinterability and high strength. The carbon component is preferably 5 wt % or less, and even more preferably 3 wt % or less. If the carbon component exceeds 10 wt %, the molded density is low, and the density does not increase even after sintering, resulting in a lack of strength sufficient for use in a freezer. Attempting to increase the density after sintering by increasing the sintering temperature results in adhesion between particles, significantly reducing the aspect ratio.

[0101] Considering shrinkage due to sintering, the particle size of the granulated particles is preferably 70 μm or more and 5 mm or less both before and after debinding. The aspect ratio of the granulated particles is, for example, 1 or more and 5 or less both before and after debinding.

[0102] As described above, according to the second embodiment, it is possible to realize regenerator particles having excellent properties such as a high volumetric specific heat and a high thermal conductivity.

[0103] (Third embodiment) The regenerator of the third embodiment is a regenerator filled with a plurality of regenerator particles of the second embodiment. For example, when the perimeter of the projected image of the regenerator particles of the second embodiment is L and the actual area of ​​the projected image is A, the regenerator of the third embodiment has a surface area of ​​4πA / L. 2 The ratio of the cold storage material particles having a circularity R of 0.5 or less is 5% or less.

[0104] The circularity R can be determined by image processing of the shapes of multiple cold storage material particles using an optical microscope. Cold storage material particles with a circularity R of 0.5 or less exhibit a shape with irregularities on the surface. When multiple cold storage material particles containing more than 5% of such particles are packed into a cold storage unit, the voids formed by the cold storage material particles become non-uniform within the cold storage unit, resulting in unstable packing. This can lead to a decrease in cold storage performance when the working medium flows in. Furthermore, stresses applied to the cold storage material particles during packing or operation of the refrigerator can cause the cold storage material particles to move or break, generating fine particles that clog the voids, reducing the refrigerator's refrigeration performance and long-term reliability. Preferably, the number of cold storage material particles with a circularity R of 0.5 or less is 2% or less, and even more preferably 0%.

[0105] (Fourth embodiment) The refrigerator of the fourth embodiment is a refrigerator including a regenerator filled with a plurality of the regenerator material of the first embodiment or the regenerator particles of the second embodiment. Hereinafter, some of the descriptions overlapping with the first, second, and third embodiments will be omitted.

[0106] 1 is a schematic cross-sectional view showing the main configuration of a refrigerator according to a fourth embodiment, which includes the regenerator of the third embodiment filled with a plurality of regenerator particles of the second embodiment. The refrigerator according to the fourth embodiment is a two-stage regenerator-type cryogenic refrigerator 100 used for cooling superconducting equipment and the like.

[0107] 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.

[0108] 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 third embodiment, is arranged in the second cylinder 112 so as to be able to reciprocate.

[0109] 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.

[0110] The first regenerator 114 contains a first regenerator material 118 such as a Cu mesh. The second regenerator 115 contains a second regenerator material 119.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] The cold storage unit provided in the refrigerator of the fourth embodiment accommodates the cold storage material of the first embodiment in the second cold storage unit 115 as at least a part of the second cold storage material 119. Furthermore, the second cold storage unit 115 may be filled with a plurality of cold storage material particles of the second embodiment as at least a part of the second cold storage material 119. The plurality of cold storage material particles of the second embodiment have a perimeter of 4πA / L, where L is the perimeter of the projected image of each cold storage material particle and A is the actual area of ​​the projected image. 2 It is preferable that the circularity R of 0.5 or less is 5% or less.

[0117] In the fourth embodiment, the regenerator of the third embodiment may include, for example, a plurality of regenerator material packed layers of different types of regenerator material. The different types of regenerator material may be separated by a mesh. The mesh is, for example, a metal mesh. At least one of the plurality of regenerator material packed layers is the regenerator material of the first embodiment or the regenerator material particles of the second embodiment. In the refrigerator of the fourth embodiment, the regenerator material of the first embodiment or a plurality of regenerator material particles of the second embodiment is packed, for example, on the low-temperature side of the regenerator.

[0118] To improve the refrigeration capacity of a refrigerator, it is desirable to improve the specific heat per unit volume of the regenerator material and the thermal conductivity. The refrigerator of the fourth embodiment is equipped with a regenerator material or regenerator particles that maintain the volumetric specific heat and have improved thermal conductivity.

[0119] For example, by using the refrigerator of the fourth embodiment in a magnetic levitation train, the long-term reliability of the magnetic levitation train can be improved.

[0120] As described above, according to the fourth embodiment, by using a cold storage material or cold storage material particles with excellent characteristics, a refrigerator with excellent characteristics can be realized.

[0121] (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.

[0122] 2 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.

[0123] 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.

[0124] According to the fifth embodiment, a cryopump with excellent characteristics can be realized by using a refrigerator with excellent characteristics. Furthermore, by using the cryopump of the fifth embodiment in a semiconductor manufacturing apparatus, the long-term reliability of the semiconductor manufacturing apparatus can be improved.

[0125] (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.

[0126] 3 is a perspective view showing a schematic configuration of a superconducting magnet according to the sixth embodiment. The superconducting magnet according to the sixth embodiment is, for example, a superconducting magnet 600 for a magnetic levitation train, which includes the regenerative cryogenic refrigerator 100 according to the fourth embodiment.

[0127] 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.

[0128] According to the sixth embodiment, a superconducting magnet with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0129] (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.

[0130] 4 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.

[0131] 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.

[0132] According to the seventh embodiment, a nuclear magnetic resonance imaging apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0133] (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.

[0134] 5 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance (NMR) apparatus according to the eighth embodiment. The 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.

[0135] 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.

[0136] According to the eighth embodiment, a nuclear magnetic resonance apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0137] (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.

[0138] 6 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 fourth embodiment.

[0139] 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.

[0140] 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.

[0141] (Tenth embodiment) The helium recondensing device of the tenth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some of the description overlapping with the fourth embodiment will be omitted.

[0142] 7 is a schematic diagram showing the general configuration of a helium recondensation apparatus according to a tenth embodiment. The helium recondensation apparatus according to the tenth embodiment is a helium recondensation apparatus 1000 equipped with the regenerative cryogenic refrigerator 100 according to the fourth embodiment.

[0143] The helium recondensation device 1000 includes a regenerative cryogenic refrigerator 100 , an evaporation pipe 1001 , and a liquefaction pipe 1002 .

[0144] The helium recondensation device 1000 can recondense helium gas that evaporates from a liquid helium device provided in a device that uses liquid helium, such as a superconducting magnet, a nuclear magnetic resonance (NMR) device, a nuclear magnetic resonance imaging (MRI) device, a physical property measurement system (PPMS), or a magnetic property measurement system, to produce liquid helium.

[0145] Helium gas is introduced into the helium recondenser 1000 from a liquid helium device (not shown) through evaporation piping 1001. The helium gas is cooled to 4 K, which is below the liquefaction temperature of helium, by the regenerative cryogenic refrigerator 100. The condensed and liquefied liquid helium returns to the liquid helium device through liquefaction piping 1002.

[0146] According to the tenth embodiment, a refrigerator with excellent characteristics is used, thereby realizing a helium recondensing device with excellent characteristics. [Example]

[0147] Examples and comparative examples of the cold storage material of the first embodiment and the cold storage material particles of the second embodiment, as well as the evaluation results thereof, will be described below.

[0148] Example 1 Gd2O3 powder and Na2CO3 powder were mixed and ground 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 rolling 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 to the raw material powder at a concentration of 1.2 wt%. The sodium concentration of the granulated particles was 0.52 atomic %, and the carbon concentration was 0.99 wt%. The resulting raw material mixture was molded to obtain a compact.

[0149] To evaluate the strength of the granulated particles, the granulated particles were filled into a cylindrical container with a diameter of 15 mm and a height of 5 mm. At this time, a sufficient amount of cold storage material was filled so that the granulated particles were fixed in the cylindrical container and did not move freely. The container was subjected to an amplitude of 2 mm and a maximum acceleration of 200 m / s. 2 Simple harmonic motion of 1×10 3 As a result, the proportion of destroyed regenerator material was less than 0.1% by weight.

[0150] The granulated particles and the compact were debound at 600°C for 6 hours in an air atmosphere. After debinding, the granulated particles and the compact had a sodium concentration of 0.54 atomic % and a carbon concentration of 0.51 wt %. The particles and the compact were sulfurized by heat treatment at 500°C for 4 hours in an atmosphere containing hydrogen sulfide (HS). The particles and the compact were sintered by heat treatment at 1300°C for 12 hours in a pressurized inert gas atmosphere.

[0151] The main constituent of the regenerator material and the regenerator particles of Example 1 is gadolinium oxysulfide. The sodium concentration in the regenerator material and the regenerator particles of Example 1 is 0.55 atomic %.

[0152] The maximum value of the volumetric specific heat at 10 K or less and the thermal conductivity at 4.2 K of the regenerator material according to Example 1 were measured. The measurements were carried out using a physical property measurement system (PPMS).

[0153] 250 g of the regenerator particles according to Example 1 was packed into the low-temperature side of the second-stage regenerator of the two-stage GM refrigerator shown in Fig. 1, while 250 g of Pb regenerator material was packed into the high-temperature side to assemble the refrigerator according to Example 1, and a refrigeration test was carried out to measure the refrigeration capacity at 4.2 K. A heat load was applied to the first-stage regenerator so that the temperature reached 50 K.

[0154] As a result of the above refrigeration test, a refrigeration capacity of 0.66 W at 4.2 K was obtained.

[0155] In the following examples and comparative examples, the mixing time of the raw material powder, the conditions of the sulfurization heat treatment, the conditions of the sintering heat treatment, etc. were adjusted to be appropriate conditions. In addition, the test conditions of the refrigerator were made equal.

[0156] Example 2 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that Li2CO3 powder was used instead of Na2CO3 powder.

[0157] Example 3 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that K2CO3 powder was used instead of Na2CO3 powder.

[0158] Example 4 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that CaCO3 powder was used in addition to Na2CO3 powder.

[0159] Example 5 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 4, except that Li2CO3 powder was used instead of Na2CO3 powder.

[0160] Example 6 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 4, except that K2CO3 powder was used instead of Na2CO3 powder.

[0161] Example 7 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 4, except that MgCO3 powder was used instead of CaCO3 powder.

[0162] Example 8 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 4, except that SrCO3 powder was used instead of CaCO3 powder.

[0163] Example 9 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 4, except that BaCO3 powder was used instead of CaCO3 powder.

[0164] Example 10 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that Gd2O2S powder was used instead of Gd2O3 powder.

[0165] Example 11 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that Tb2O3 powder was used instead of Gd2O3 powder.

[0166] Example 12 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that Dy2O3 powder was used instead of Gd2O3 powder.

[0167] Example 13 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that Ho2O3 powder was used instead of Gd2O3 powder.

[0168] Example 14 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that K2CO3 powder was used in addition to Na2CO3 powder.

[0169] Example 15 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that Li2CO3 powder was used in addition to Na2CO3 powder.

[0170] Example 16 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that K2CO3 powder and CaCO3 powder were used in addition to Na2CO3 powder.

[0171] Example 17 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that CaCO3 powder and SrCO3 powder were used in addition to Na2CO3 powder.

[0172] (Examples 18 to 20) A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that the weight of the Na2CO3 powder was reduced.

[0173] Examples 21 to 23 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that the weight of the Na2CO3 powder was increased.

[0174] (Examples 24 and 25) A cold accumulator and cold accumulator particles were produced in the same manner as in Example 4, except that the weight of the CaCO3 powder was reduced.

[0175] (Examples 26 to 28) A cold accumulator and cold accumulator particles were produced in the same manner as in Example 4, except that the weight of the CaCO3 powder was increased.

[0176] (Examples 29 to 31) A cold accumulator and cold accumulator particles were produced in the same manner as in Example 1, except that a part of the Gd2O3 powder was changed to Tb2O3, Dy2O3, and Ho2O3.

[0177] Example 32 Gd2O3 powder was added to a sodium alginate solution and mixed for 12 hours to create a slurry. The sodium alginate solution was added so that the sodium alginate content was 2.3% by weight relative to the raw material powder. The created slurry was then dropped into a calcium lactate solution, which served as a gelling solution. A syringe was used to drop the slurry. The syringe had a diameter of 510 μm, and the distance from the tip of the syringe to the liquid surface of the calcium lactate solution was 100 mm. The slurry was then filled into a mold, which was then immersed in the gelling solution.

[0178] The slurry dropped by syringe and the slurry filled into the mold were kept in the gelling solution for 5 hours.

[0179] The gelled granulated particles were then washed with pure water. The slurry filled in the mold was removed from the mold and washed with pure water to obtain a green body. After washing the green body and particles, they were dried. The sodium concentration of the granulated particles was 0.78 atomic % and the carbon concentration was 0.82 wt %. After drying the green body and particles, they were degreased, sulfurized and sintered.

[0180] The material was degreased at 600°C for 6 hours in an air atmosphere. After degreasing, the sodium concentration of the granulated particles was 1.0 atomic % and the carbon concentration was 0.54 wt %. After degreasing, the compact and particles were sulfurized by heat treatment at 500°C for 4 hours in an atmosphere containing hydrogen sulfide (HS). The compact and particles were sintered by heat treatment at 1300°C for 12 hours in a pressurized inert gas atmosphere. The main component of the regenerator material and regenerator particles of Example 32 was gadolinium oxysulfide. The sodium concentration in the regenerator material and regenerator particles of Example 32 was 0.83 atomic %.

[0181] Example 33 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 32, except that a potassium alginate aqueous solution was used instead of the sodium alginate aqueous solution.

[0182] (Examples 34 to 38) A cold storage material and cold storage material particles were produced in the same manner as in Example 33, except that the amount of the potassium alginate aqueous solution was increased or decreased.

[0183] Example 39 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 32, except that a magnesium chloride aqueous solution was used instead of the calcium lactate aqueous solution.

[0184] Example 40 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 32, except that an aqueous strontium chloride solution was used instead of an aqueous calcium lactate solution.

[0185] Example 41 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 32, except that a barium chloride aqueous solution was used instead of the calcium lactate aqueous solution.

[0186] Example 42 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 32, except that K2CO3 powder was added as the raw material powder.

[0187] Example 43 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 18, except that Li2CO3 powder was added as the raw material powder.

[0188] Example 44 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 32, except that an air pulse dispenser was used instead of a syringe to fill the slurry into the mold and to drip the slurry. The nozzle diameter was 510 μm, and the distance from the tip of the nozzle to the liquid surface of the calcium lactate aqueous solution was 100 mm.

[0189] Example 45 Except for using a piezoelectric dispenser instead of a syringe to fill the slurry into the mold and to drip the slurry, the cold accumulator and cold accumulator particles were produced in the same manner as in Example 32. The nozzle diameter was 510 μm, and the distance from the tip of the nozzle to the liquid surface of the calcium lactate aqueous solution was 100 mm.

[0190] (Examples 46 to 51) The cold storage material particles of Examples 46 to 51 differ in particle size or aspect ratio from the cold storage material particles of Example 44. When producing the cold storage material particles of Examples 51 to 56, the diameter of the syringe 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.

[0191] Example 52 A cold storage material and cold storage material particles were produced in the same manner as in Example 32, except that a continuous inkjet was used instead of a syringe to fill the slurry into the mold and to drip the slurry. The nozzle diameter was 510 μm, and the distance from the tip of the nozzle to the liquid surface of the calcium lactate aqueous solution was 100 mm.

[0192] (Examples 53 to 56) Except for changing the weight of polyvinyl alcohol, a cold accumulator and cold accumulator particles were produced in the same manner as in Example 1. Further, in the same manner as in Example 1, the strength of the granulated particles was measured.

[0193] (Examples 57 to 60) A cold accumulator and cold accumulator particles were produced in the same manner as in Example 32, except that the amount of sodium alginate relative to the raw material powder was changed by changing the concentration of the sodium alginate aqueous solution or the ratio of the sodium alginate aqueous solution to the raw material powder. Also, the strength of the granulated particles was measured in the same manner as in Example 1.

[0194] Example 61 Except for using Al2O3 powder as the raw material powder, the cold accumulator and cold accumulator particles were manufactured in the same manner as in Example 1. The Al2O3 powder was added so that the Al content in the cold accumulator particles was 15 atomic %.

[0195] Example 62 Except for using Al2O3 powder as the raw material powder, the cold accumulator and cold accumulator particles were manufactured in the same manner as in Example 4. The Al2O3 powder was added so that the Al content in the cold accumulator particles was 15 atomic %.

[0196] Example 63 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 32, except that an aluminum chloride aqueous solution was used instead of the calcium lactate aqueous solution. Al was added so that the amount of Al contained in the cold accumulator particles was 0.01 atomic %.

[0197] Example 64 A cold accumulator and cold accumulator particles were produced in the same manner as in Example 32, except that an aluminum chloride aqueous solution was used in addition to the calcium lactate aqueous solution. The amount of Al contained in the cold accumulator particles was added so that it was 0.01 atomic %.

[0198] (Comparative Example 1) The cold accumulator and cold accumulator particles of Comparative Example 1 differ from those of Example 1 in that the atomic concentration of sodium is low at 0.0008 atomic %. When producing the cold accumulator and cold accumulator particles of Comparative Example 1, the weight of Na2CO3 powder was reduced compared to when producing the cold accumulator and cold accumulator particles of Example 1.

[0199] (Comparative Example 2) The cold accumulator and cold accumulator particles of Comparative Example 2 differ from those of Example 1 in that the atomic concentration of sodium is as high as 15 atomic %. When producing the cold accumulator and cold accumulator particles of Comparative Example 2, the weight of Na2CO3 powder was increased compared to when producing the cold accumulator and cold accumulator particles of Example 1. At this time, in addition to Gd2O2S, NaGdS2 was significantly produced.

[0200] (Comparative Example 3) The cold accumulator and cold accumulator particles of Comparative Example 3 differ from those of Example 4 in that the atomic concentration of calcium is as high as 15 atomic %. When producing the cold accumulator and cold accumulator particles of Comparative Example 3, the weight of CaCO3 powder was increased compared to when producing the cold accumulator and cold accumulator particles of Example 4.

[0201] Comparative Example 4 The cold accumulator and cold accumulator particles of Comparative Example 4 differ from those of Example 1 in that they do not contain a Group 1 element. The cold accumulator and cold accumulator particles of Comparative Example 4 were produced without using powder containing a Group 1 element.

[0202] (Comparative Example 5) The granulated particles of the cold storage material of Comparative Example 5 differ from those of Example 1 in that the carbon content is high at 25% by weight. The granulated particles of Comparative Example 5 had a carbon concentration of 12% by weight after degreasing, but cracks or chips occurred in the particles after sintering, making it impossible to recover the particles. For this reason, evaluation of specific heat and strength and refrigerator tests could not be performed. When producing the cold storage material and cold storage material particles of Comparative Example 5, the weight ratio of polyvinyl alcohol used as a binder was increased to 34% by weight relative to the raw material powder.

[0203] (Comparative Example 6) The cold storage material granules of Comparative Example 6 differ from Example 1 in that the carbon content is as low as 0.005% by weight. In Comparative Example 6, the particles could not be recovered after granulation. Therefore, evaluation of specific heat and strength and a refrigerator test could not be performed. When producing the cold storage material and cold storage material particles of Comparative Example 6, the weight ratio of polyvinyl alcohol to the raw material powder was set to 0.2% by weight.

[0204] (Comparative Example 7) The cold accumulator granulated particles after degreasing treatment in Comparative Example 7 differ from Example 1 in that the carbon content is as high as 15 wt %. The carbon concentration before degreasing was 19 wt %. The granulated particles in Comparative Example 7 were sintered to obtain a cold accumulator and cold accumulator particles. When producing the cold accumulator and cold accumulator particles in Comparative Example 7, the polyvinyl alcohol content relative to the raw material powder was 24 wt %, and degreasing was performed at 400°C in an air atmosphere for 1 hour.

[0205] (Comparative Example 8) The degreased cold accumulator particles of Comparative Example 8 differ from Example 1 in that the carbon content was as low as below the detection limit. The granulated particles of Comparative Example 8 were cracked or chipped after degreasing. The carbon concentration before degreasing was 0.01 wt %. When producing the cold accumulator and cold accumulator particles of Comparative Example 8, polyvinyl alcohol was added in an amount of 0.2 wt % relative to the raw material powder, and degreasing was performed at 800°C for 12 hours in an air atmosphere.

[0206] (Comparative Example 9) The cold storage material and cold storage material particles of Comparative Example 9 differ from those of Example 61 in that the Al content in the cold storage material particles is as high as 25 atomic %. When producing the cold storage material and cold storage material particles of Comparative Example 9, the weight of Al2O3 powder was increased compared to when producing the cold storage material and cold storage material particles of Example 61.

[0207] The regenerator materials according to the examples and comparative examples were measured for the maximum volumetric specific heat at 10 K or less and the thermal conductivity at 4.2 K. The results are shown in Tables 1, 2, and 3.

[0208] The refrigeration capacities of the regenerator particles according to each Example and Comparative Example are shown in Tables 1, 2, and 3. 250 g of the regenerator particles according to each Example and Comparative Example was packed into the low-temperature side of the second-stage regenerator of the two-stage GM refrigerator shown in Fig. 1, while 250 g of Pb regenerator was packed into the high-temperature side, and the refrigerator was assembled. A refrigeration test was carried out and the refrigeration capacity at 4.2 K was measured. A thermal load was applied to the first-stage regenerator so that the temperature reached 50 K.

[0209] The evaluation results of the strength of the granulated particles of cold storage material before and after degreasing for each Example and Comparative Example are shown in Table 3. The granulated particles for each Example and Comparative Example were filled into a cylindrical container with a diameter of 15 mm and a height of 5 mm. At this time, a sufficient amount of cold storage material was filled so that the granulated particles were fixed in the cylindrical container and did not move freely. The container was subjected to an amplitude of 2 mm and a maximum acceleration of 200 m / s. 2 Simple harmonic motion of 1×10 3 As a result, the percentage of broken granulated particles of the regenerator material was evaluated.

[0210] [Table 1]

[0211] [Table 2]

[0212] [Table 3]

[0213] [Table 4]

[0214] It can be seen that when the atomic concentration of the Group 1 element in the regenerator material is less than 0.001 atomic % or the regenerator material does not contain any Group 1 element, as in Comparative Examples 1 and 4, the thermal conductivity is reduced to 0.005 W / cm K and 0.004 W / (cm K). This is thought to be because the sintering promotion effect is reduced as the proportion of the Group 1 element in the regenerator material decreases, and the number of fine voids increases.

[0215] As in Comparative Example 2, when the atomic concentration of the first group element in the regenerator material is greater than 10 atomic %, the volumetric specific heat is 0.4 J / (cm 3 ·K). This is thought to be because sulfides containing rare earths and group 1 elements are generated as the ratio of group 1 elements in the regenerator material increases, and the relative amount of rare earth oxysulfides decreases.

[0216] From the results of Comparative Example 3, when the atomic concentration of the Group 2 element in the regenerator material becomes larger than 10 atomic %, the thermal conductivity becomes high, but the volume specific heat becomes 0.4 J / (cm 3 The refrigeration capacity using these regenerator particles decreased significantly. This is thought to be due to the relative decrease in the proportion of rare earth elements as the proportion of group 2 elements in the regenerator particles increases.

[0217] From the results of Tables 1 and 4, it can be seen that strength increases when sintering aids are added so that the metal or semi-metal element derived from the sintering aid is 0.01 atomic % or more. If it is more than 20 atomic %, strength increases further, but the volumetric specific heat is 0.4 J / (cm 3 The refrigeration capacity using these regenerator particles decreased significantly. This is thought to be due to the relatively decreased proportion of rare earth elements caused by the increased proportion of sintering aids in the regenerator particles.

[0218] It can be seen from Tables 1 and 2 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.

[0219] Tables 1 and 2 show that when the aspect ratio of the regenerator particles is 5 or less, the refrigeration capacity at 4.2K is significantly improved.

[0220] Tables 1 and 2 show that even if the methods for granulating the regenerator particles are different, by appropriately adjusting the synthesis conditions, the particles will have similar particle size, aspect ratio, content of Group 1 and Group 2 elements, and thermal conductivity.

[0221] Tables 1 and 2 show that even if the granulation methods for the cold storage particles are different, as long as the particle size, aspect ratio, and thermal conductivity are the same, the performance and reliability of the refrigerator equipped with the cold storage particles will be the same.

[0222] Table 3 shows that the strength of the granulated particles is high when the content of Group 1 elements is 0.001 atomic % to 10 atomic % and the content of carbon before degreasing is 0.01 weight % to 20 weight %. If the carbon concentration is lower than 0.01 weight %, the granulated particles are too brittle to be recovered as particles.

[0223] Table 3 shows that when the material contains 0.001 atomic % to 10% of Group 1 elements and 0.001 wt % to 10 wt % of carbon after debinding, both the strength and sinterability of the granulated particles can be achieved. Furthermore, refrigerators equipped with the resulting regenerator particles exhibit high refrigeration performance. When the carbon concentration after debinding exceeds 10 wt %, the particle strength is maintained even after debinding, but the compact density is low and the sinterability is poor, resulting in low particle density, specific heat, and thermal conductivity. This also results in poor refrigeration performance when installed in a refrigerator. When the carbon concentration is less than 0.001 wt %, the particles are very fragile after debinding and cannot be recovered as particles.

[0224] The above examples confirmed the effects of the cold storage material of the first embodiment and the cold storage material particles of the second embodiment.

[0225] Although the dispenser has been described as an air pulse dispenser or a piezo dispenser, a plunger dispenser may also be used.

[0226] Although the description has been given taking a continuous type inkjet as an example of the inkjet, an on-demand type inkjet may also be used.

[0227] 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]

[0228] 100 Regenerative cryogenic refrigerator 114, 115 Regenerator 118, 119 Cold storage material 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 1000 Helium Recondenser

Claims

1. A vacuum vessel; a first cylinder provided in the vacuum vessel; a second cylinder provided in the vacuum vessel, coaxially connected to the first cylinder, and having a diameter smaller than that of the first cylinder; a first regenerator provided in the first cylinder and accommodating a first regenerator material; The second cylinder is provided with a second cold accumulator accommodated therein, the second cold accumulator being cold accumulator particles, the cold accumulator particles including a rare earth oxysulfide containing at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and containing 0.001 atomic % to 10 atomic % of a Group 1 element, and having a maximum volumetric specific heat of 0.5 J / (cm) in a temperature range of 2 K to 10 K. ３ - K) or more, and A two-stage regenerative cryogenic refrigerator equipped with:

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

3. 2. The two-stage regenerative cryogenic refrigerator according to claim 1, wherein the Group 1 element is at least one element selected from the group consisting of Li, Na, and K.

4. 4. The two-stage regenerator type cryogenic refrigerator according to claim 1, wherein the regenerator particles contain 0 atomic % to 10 atomic % of a Group II element.

5. 4. The two-stage regenerator type cryogenic refrigerator according to claim 1, wherein the regenerator particles contain 0.001 atomic % to 10 atomic % of a Group II element.

6. 6. The two-stage regenerative cryogenic refrigerator according to claim 4, wherein the Group II element is at least one element selected from the group consisting of Mg, Ca, Sr, and Ba.

7. 7. The two-stage regenerative cryogenic refrigerator according to claim 1, wherein the regenerative material particles contain at least one element selected from the group consisting of Al, Fe, Cu, Ni, Co, Zr, and B in an amount of 0.01 atomic % to 20 atomic %.

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

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

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

11. A semiconductor manufacturing device comprising the cryopump according to claim 10.

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