Adsorption type cryostat

Abstract

An adsorption type cryostat comprises an adsorber assembly which comprises an inflation tube and an adsorption cavity, the adsorption cavity is used for containing an adsorbent, and the inflation tube is connected to the upper end of the adsorption cavity and used for being connected with helium; the evaporator assembly comprises an evaporation pipe and an evaporation cavity, and the evaporation pipe is communicated with the adsorption cavity and the evaporation cavity; the heat shield assembly covers the adsorber assembly and the evaporator assembly; the vacuum assembly is arranged outside the heat shield assembly in a covering mode so as to form a shell of the cryostat, a vacuumizing opening used for external connection is formed in the vacuum assembly so as to maintain vacuum of an inner cavity of the vacuum assembly, and the vacuum assembly is provided with a refrigeration part connected with the heat shield assembly and the evaporation pipe; and the thermal switch assembly is connected with the refrigerating part and the adsorber assembly and controls the on-off of heat between the refrigerating part and the adsorber assembly. Pressure reduction and cooling of liquid helium are realized through strong adsorbability of the adsorbent at low temperature, the low-temperature limit of a conventional neutron scattering low-temperature sample environment is expanded, and a low-temperature environment is provided for the sample.

Description

Technical Field

[0001] The invention relates to the technical field of low-temperature refrigeration, and in particular to an adsorption type low-temperature thermostat. Background Art

[0002] Neutrons are uncharged, have magnetic moments, are highly penetrating, and can distinguish light elements, isotopes, and neighboring elements, all of which are powerful means for humans to explore the microscopic structure of matter. Neutron scattering spectrometers are the main equipment for neutron testing, among which sample environment equipment is an important auxiliary equipment of neutron scattering spectrometers. Since neutrons have strong penetrating power, they can easily penetrate the cryostat window that maintains the sample temperature, allowing the sample to be measured at different temperatures. Among them, cryostat is the most used sample environment equipment.

[0003] Sample environment equipment can be divided into 4K cryostat, 1.5K cryostat, adsorption cryostat, helium 3 plug-in, dilution refrigerator, etc. according to different refrigeration principles. Among them, 4K cryostat uses GM refrigerator or liquid helium to achieve a low temperature of 4K; 1.5K cryostat reduces the liquid helium to a low temperature of 1.5K through a needle valve and a circulating pump to achieve a decompression and cooling process; adsorption cryostat uses the high pumping speed of the adsorbent at low temperature to further reduce the liquid helium to below 1K, and can achieve a minimum low temperature of 0.7K; helium 3 plug-in also works on the principle of adsorbent decompression and cooling, but the working medium is different from the aforementioned cryostat, using helium isotope helium 3 working fluid, which can achieve a minimum low temperature of 0.3K; the working principle of the dilution refrigerator is based on the mixed liquid characteristics of helium 3 and helium 4, and achieves an ultra-low temperature environment through phase separation and evaporative cooling, which can be reduced to about 10mK.

[0004] With the continuous development of science and technology, the demand for detecting or testing the physical properties of materials in extreme environments is becoming more and more urgent, especially in the extremely low temperature environment of 1K. Among the existing equipment, compared with the expensive helium-3 plug-in and the complex and expensive dilution refrigerator, the adsorption type cryostat can greatly expand the low temperature limit of the conventional neutron scattering low temperature sample environment due to its simple structure and easy operation, and provide a low temperature environment for the sample. Summary of the invention

[0005] The present invention provides an adsorption type cryostat, which utilizes the strong adsorption of an adsorbent at low temperature to reduce the pressure and cool down liquid helium, thereby achieving a low temperature environment below 1K.

[0006] In one embodiment of the present application, an adsorption type cryostat is provided, comprising:

[0007] The adsorber assembly comprises an air filling tube and an adsorption chamber, wherein the adsorption chamber is used to contain the adsorbent, and the air filling tube is connected to the upper end of the adsorption chamber and is used to receive helium;

[0008] An evaporator assembly, comprising an evaporation tube and an evaporation chamber, wherein the upper end of the evaporation tube is connected to the adsorption chamber, and the lower end of the evaporation tube is connected to the evaporation chamber to collect liquid helium condensed from the evaporation tube;

[0009] A heat shield assembly is arranged outside the adsorber assembly and the evaporator assembly to reduce heat radiation into the heat shield assembly;

[0010] A vacuum assembly, wherein the vacuum assembly is covered outside the heat shield assembly to form an outer shell of a cryostat, and the vacuum assembly is provided with an external vacuum port to maintain the vacuum in the inner cavity of the vacuum assembly, and the vacuum assembly is provided with a refrigeration component, and the refrigeration component is connected to the heat shield assembly and the evaporation tube; and

[0011] A heat switch assembly is connected to the refrigeration component and the adsorber assembly to control the heat on and off between the refrigeration component and the adsorber assembly.

[0012] In another embodiment, the adsorption chamber includes an adsorber end cover, an adsorber cylinder and an adsorber base, wherein the adsorber end cover and the adsorber base are respectively arranged at the upper end and the lower end of the adsorber cylinder to seal the adsorber cylinder, and a plurality of layers of adsorption annular fins are arranged on the adsorber base, and adsorbent is filled between adjacent adsorption annular fins.

[0013] In another embodiment, an evaporation installation hole connected to the evaporation tube is provided on the adsorber base, and a molecular sieve is provided at the evaporation installation hole to limit the leakage of the adsorbent.

[0014] In another embodiment, the evaporation chamber includes an evaporator cylinder and an evaporator base, the evaporator base is sealed at the lower end of the evaporator cylinder, and a plurality of layers of evaporation annular fins are arranged on the evaporator base, and the evaporation annular fins are used to transfer the temperature of liquid helium.

[0015] In another embodiment, a choke ring is installed in the evaporation tube, the choke ring is provided with a guide hole, and the choke ring has a guide portion for guiding the liquid helium to the guide hole to reduce the film climbing effect of the superfluid helium along the tube wall.

[0016] In another embodiment, the refrigeration component includes a refrigerator, a refrigeration flange and a heat conduction plate. The refrigerator is installed on the vacuum component through the refrigeration flange. The heat conduction plate connects the secondary cold head of the refrigerator and the evaporator tube to achieve heat transfer between the refrigerator and the evaporator tube.

[0017] In another embodiment, the thermal switch assembly includes a temperature control seat, a heat-conducting cylinder, an upper heat-conducting part, a lower heat-conducting part and a switching piece, wherein the upper heat-conducting part and the lower heat-conducting part are respectively arranged at two ends of the heat-conducting cylinder, the lower heat-conducting part is connected to the heat-conducting plate, the upper heat-conducting part is connected to the temperature control seat, and the temperature control seat is connected to the adsorption cavity, and the switching piece is used to realize thermal conduction between the upper heat-conducting part and the lower heat-conducting part.

[0018] In another embodiment, a heater is provided on the temperature control seat to heat the adsorbent in the adsorption chamber.

[0019] In another embodiment, the switch includes a heating part, a connecting part and a release cavity filled with an adsorbent, the connecting part is used to connect the release cavity and the heat-conducting cylinder, the heating part is used to heat the release cavity, and the adsorbent adsorbs helium.

[0020] In another embodiment, the heat shield assembly includes a heat shield top flange and a heat shield cylinder. The heat shield top flange is installed at the upper end of the heat shield cylinder and is used to connect the first-stage cold head of the refrigerator. The heat shield top flange has openings for leading out the inflation pipe and routing the signal line. The heat shield cylinder is sealed to reduce heat radiation inside the heat shield cylinder.

[0021] According to the adsorption type cryostat of the above embodiment, high-pressure helium is filled into the evaporation chamber, evaporation tube and evaporation chamber through the gas filling tube, and the 4K low temperature is transferred to the evaporation tube through the refrigeration element, so that the high-pressure helium passing through is condensed and gathered in the evaporation chamber under the action of gravity. In this process, the adsorbent in the adsorption chamber is kept at 40K by the thermal switch component to ensure that the helium is not adsorbed and is completely condensed; when the adsorbent is cooled, the thermal switch is turned on so that the temperature of the refrigeration element is transferred to the adsorption chamber, and the adsorbent is cooled to achieve adsorption of helium. The present application utilizes the strong adsorption of the adsorbent at low temperature to achieve decompression and cooling of liquid helium, thereby achieving a low-temperature environment below 1K, which is convenient for observation and measurement of samples at low temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the overall appearance structure diagram of the adsorption type cryostat;

[0023] Figure 2 is a structural diagram of a heat shield assembly in one embodiment;

[0024] Figure 3 is an overall structural diagram of an adsorption unit in an embodiment;

[0025] Figure 4 It is the overall front view of the adsorption type cryostat;

[0026] Figure 5An exploded view of a main flange of a thermostat in one embodiment;

[0027] Figure 6 A schematic diagram of the structure of an adsorption unit in an embodiment;

[0028] Figure 7 A schematic diagram of the cross-sectional structure of an adsorption component in an embodiment;

[0029] Figure 8 is a schematic diagram of the cross-sectional structure of an evaporation component in one embodiment;

[0030] Fig. 9 A schematic diagram of the structure of a choke ring in an embodiment;

[0031] Fig.10 Schematic diagram of the internal structure of a heat-conducting cylinder in an embodiment.

[0032] Reference numerals:

[0033] 1. Vacuum assembly; 11. Thermostat main flange; 12. Upper vacuum cover cylinder; 13. Lower vacuum cover cylinder; 131. Upper connecting section; 132. Middle section; 133. Bottom section; 14. Refrigeration parts; 141. Refrigeration machine; 142. Refrigeration flange; 143. Heat conduction plate; 144. Vacuum port; 15. Flange interface; 151. Inner ring flange; 152. Outer ring flange;

[0034] 2. Heat shield assembly; 21. Heat shield top flange; 22. Heat shield upper cylinder; 23. Heat shield lower cylinder; 231. Connecting flange; 232. Inlet and outlet cylinder; 24. Opening;

[0035] 3. Adsorber assembly; 31. Inflating pipe; 32. Adsorber end cover; 33. Adsorber cylinder; 34. Adsorber base; 35. Inflating valve; 36. Evaporation mounting hole; 37. Adsorption annular fin; 38. Molecular sieve;

[0036] 4. Evaporator assembly; 41. Evaporator tube; 42. Evaporator barrel; 43. Evaporator base; 44. Evaporator annular fin; 45. Heat transfer flange; 46. Choke ring; 461. Guide part; 462. Diversion hole;

[0037] 5. Thermal switch assembly; 51. Temperature control seat; 52. Heat-conducting cylinder; 53. Upper heat-conducting part; 531. Flange; 532. Oxygen-free copper fin; 54. Lower heat-conducting part; 55. Belt; 56. Heat-conducting seat; 57. Switch; 571. Connecting part; 572. Release cavity. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments adopt associated similar element numbers. In the following embodiments, many detailed descriptions are for making the present application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different situations, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present application are not shown or described in the specification, this is to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0039] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementations. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a required sequence, unless otherwise specified that a certain sequence must be followed.

[0040] The serial numbers of the components in this document, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings).

[0041] Cryostat is the most commonly used sample environment equipment. Sample environment equipment can be divided into 4K cryostat, 1.5K cryostat, adsorption cryostat, helium 3 plug-in, dilution refrigerator 141, etc. according to different refrigeration principles. Among them, 4K cryostat uses GM refrigerator 141 or liquid helium to achieve a low temperature of 4K; 1.5K cryostat reduces the liquid helium to a low temperature of 1.5K through a needle valve and a circulating pump to achieve a decompression and cooling process; adsorption cryostat uses the high pumping speed of the adsorbent at low temperature to further reduce the liquid helium to below 1K, and can achieve a minimum low temperature of 0.7K; helium 3 plug-in also works on the principle of adsorbent decompression and cooling, but the working medium is different from the aforementioned cryostat, using helium isotope helium 3 working medium, which can achieve a minimum low temperature of 0.3K; the working principle of dilution refrigerator 141 is based on the mixed liquid characteristics of helium 3 and helium 4, and achieves an ultra-low temperature environment through phase separation and evaporative cooling, which can be reduced to about 10mK. Among the existing equipment, compared with the helium-3 plug-in that requires expensive helium-3, and the dilution refrigerator 141 that is complex and expensive, the adsorption-type cryostat can greatly expand the low temperature limit of the conventional neutron scattering low-temperature sample environment due to its simple structure and easy operation, and provide a low-temperature environment below 1K for the sample.

[0042] In an embodiment of the present invention, an adsorption type cryostat is provided, which utilizes the strong adsorption of an adsorbent at low temperatures to achieve decompression and cooling of liquid helium to achieve a low temperature environment below 1K.

[0043] Embodiment 1:

[0044] Please refer to Figure 1 , Figure 2 and Figure 3 In one embodiment of the present application, an adsorption type cryostat is provided, comprising a vacuum component 1, a heat shield component 2, an adsorber component 3, an evaporator component 4 and a heat switch component 5; the vacuum component 1 is covered outside the heat shield component 2 to form an outer shell of the cryostat as a whole, and a vacuum port 144 for external connection is opened on the vacuum component 1 to evacuate and maintain the vacuum in the inner cavity of the vacuum component 1, and the vacuum component 1 is provided with a refrigeration component 14, which extends into the inner cavity of the vacuum component 1 to cool the evaporator component 4; the heat shield component 2 is covered between the adsorber component 3 and the evaporator component 4, and the heat switch component 5 is provided with a refrigeration component 1 ... The adsorber assembly 4 is outside the heat shield assembly 2 to reduce the heat radiation to the heat shield assembly 2; the adsorber assembly 3 includes an inflation tube 31 and an adsorption cavity, the adsorption cavity is used to hold the adsorbent, and the inflation tube 31 is connected to the upper end of the adsorption cavity and is used to access the helium; the evaporator assembly 4 includes an evaporation tube 41 and an evaporation cavity, the upper end of the evaporation tube 41 is connected to the adsorption cavity, and the lower end of the evaporation tube 41 is connected to the evaporation cavity to collect the liquid helium condensed from the evaporation tube 41; the thermal switch assembly 5 is connected to the refrigeration component 14 and the adsorber assembly 3 to control the heat on and off between the refrigeration component 14 and the adsorber assembly 3.

[0045] According to the adsorption type cryostat of the above embodiment, high-pressure helium is filled into the evaporation chamber, the evaporation tube 41 and the evaporation chamber through the gas filling tube 31, and the 4K low temperature is transferred to the evaporation tube 41 through the refrigeration element 14, so that the high-pressure helium passing through is condensed and gathered in the evaporation chamber under the action of gravity. In this process, the adsorbent in the adsorption chamber is kept at 40K by the thermal switch component 5 to ensure that the helium is not adsorbed and is completely condensed; when the adsorbent is cooled, the thermal switch is turned on so that the temperature of the refrigeration element 14 is transferred to the adsorption chamber, and the adsorbent is cooled to achieve adsorption of helium. The present application utilizes the strong adsorption of the adsorbent at low temperature to achieve decompression and cooling of liquid helium, thereby achieving a low-temperature environment below 1K, which is convenient for observation and measurement of samples at low temperatures.

[0046] For further information, please refer to Figure 4 and Figure 5 The function of the vacuum component 1 is to maintain the vacuum of the entire low-temperature thermostat cavity; the vacuum component 1 includes a low-temperature thermostat main flange 11, an upper vacuum cover cylinder 12 and a lower vacuum cover cylinder 13, and the refrigeration component 14 includes a refrigerator 141, a refrigeration flange 142 and a heat conduction plate 143; a flange interface 15 is provided at the upper end of the upper vacuum cover cylinder 12, and the flange interface 15 includes an inner ring flange 151 and an outer ring flange 152. The upper end opening of the upper vacuum cover is closed by the refrigeration flange 142 and connected to the refrigeration flange 142 through the inner ring flange 151. The refrigeration flange 142 is used to install the refrigerator 141, and the heat conduction plate 143 is used to connect the secondary cold head of the refrigerator 141 and the evaporation tube 41 to realize heat transfer between the refrigerator 141 and the evaporation tube 41.

[0047] Please refer to Figure 5 The upper vacuum cover is connected to the cryostat main flange 11 through the outer ring flange 152. The cryostat main flange 11 is used to support the cryostat on the spectrometer scattering chamber flange. The refrigeration flange 142, the upper vacuum cover cylinder 12 and the cryostat flange are all made of stainless steel. The refrigeration flange 142 is also provided with an electrical connector socket and a vacuum port 144. The vacuum port 144 is connected to an external pump body such as a molecular pump to vacuum the inner cavity of the upper vacuum cover cylinder 12 and the lower vacuum cover cylinder 13 to prevent air condensation during the cooling process and affect the cryostat system.

[0048] Please refer to Figure 4 and Figure 5The lower end opening of the upper vacuum cover is provided for connecting to the lower vacuum cover. The lower vacuum cover includes an upper connecting section 131, a middle section 132 and a bottom supporting section 133. The upper connecting section 131 is used to connect to the lower end opening of the upper vacuum cover. The upper connecting section 131 and the bottom supporting section 133 are made of oxygen-free copper, and the middle section 132 is made of vanadium foil with a thickness of 0.5 mm. Vacuum electron beam welding is used to achieve vacuum welding and sealing of each section. The material in the neutron inlet and outlet direction of the low-temperature thermostat is set to vanadium foil, which can reduce the background caused by the beam window itself. In the embodiment of the present application, all connections between the upper vacuum cover cylinder 12 and the lower vacuum cover cylinder 13 are O-ring vacuum seals.

[0049] For further information, please refer to Figure 2 The heat shield assembly 2 is used to reduce the heat radiation of the vacuum assembly 1 to the low-temperature system in the heat shield assembly 2; the heat shield assembly 2 includes a heat shield top flange 21 and a heat shield cylinder, the heat shield cylinder is adapted to the outer shell setting of the vacuum assembly 1, and includes a heat shield upper cylinder 22 and a heat shield lower cylinder 23; the heat shield top flange 21 is made of oxygen-free copper, the heat shield top flange 21 is installed at the upper end of the heat shield cylinder, and is used to connect the first-stage cold head of the refrigerator 141, the heat shield top flange 21 has an opening 24 for leading out the inflation pipe 31 and routing the signal line; the heat shield upper cylinder 22 is made of oxygen-free copper, and is used to connect the heat shield top flange 21 and the heat shield lower cylinder 23.

[0050] Please refer to Figure 2 The lower cylinder 23 of the heat shield includes a connecting flange 231 and an inlet and outlet tube 232. The connecting flange 231 is made of oxygen-free copper, and its upper end is used to connect to the upper cylinder 22 of the heat shield, and its lower end is fixed to the inlet and outlet tube 232 by aluminum tape. The inlet and outlet tube 232 is the neutron inlet and outlet direction, and its material is 0.05mm thick vanadium foil; in order to enhance thermal conductivity, each connecting surface of the heat shield assembly 2 is also coated with thermal grease or filled with indium sheets.

[0051] In this embodiment, please refer to Figure 6 The evaporator assembly 4, the adsorber assembly 3, the thermal switch assembly 5 and related accessories together constitute the core working adsorption unit of the adsorption type cryostat. The main working principle of the adsorption type cryostat is to utilize the extremely strong adsorption force of the adsorbent (activated carbon is used in this application) on helium at 4K to achieve the reduction of the saturated vapor pressure of liquid helium. The temperature of liquid helium is positively correlated with the saturated vapor pressure, and the reduction in pressure will cause the temperature of liquid helium to decrease. When the liquid helium is completely evaporated, the activated carbon is heated to above 40K, and the activated carbon hardly adsorbs helium, so that the helium is desorbed from the activated carbon and can be condensed into liquid helium again. The activated carbon is cooled to 4K again, and the above cooling process is repeated.

[0052] Specifically, the adsorber assembly 3 utilizes the strong adsorption of activated carbon to liquid helium vapor at 4K, thereby reducing the pressure and temperature of the liquid helium. Figure 1The adsorption chamber includes an adsorber end cover 32, an adsorber cylinder 33 and an adsorber base 34. The upper and lower ends of the adsorber cylinder 33 are both opened, and the upper and lower ends of the adsorber cylinder 33 are both provided with indium wire grooves and screw holes for connecting with the adsorber end cover 32 and the adsorber base 34, thereby sealing the adsorber cylinder 33; the lower end of the inflation tube 31 is welded to the adsorber end cover 32 and to the adsorber cylinder 33, and the upper end of the inflation tube 31 is connected to the inflation valve 35, which is connected to an external helium gas source through the inflation valve 35, so as to fill the entire system with high-pressure helium.

[0053] In this embodiment, the adsorber end cover 32 and the adsorber cylinder 33 are made of stainless steel, and the adsorber base 34 is made of oxygen-free copper.

[0054] Please refer to Figure 6 and Figure 7 The adsorber base 34 is provided with an evaporation mounting hole 36 connected to the evaporation tube 41 for helium circulation, and the adsorber base 34 is provided with multiple layers of adsorption annular fins 37 around the evaporation mounting hole 36, and the space between adjacent adsorption annular fins 37 is used to fill adsorbent, namely activated carbon.

[0055] Please refer to Figure 7 In order to prevent the activated carbon from leaking into the evaporation tube 41 and the evaporator, a molecular sieve 38 is provided at the evaporation installation hole 36 .

[0056] For further information, please refer to Figure 6 and Figure 8 The evaporation chamber is used to collect the liquid helium condensed from the evaporation tube 41, including an evaporator barrel 42 and an evaporator base 43. The lower end of the adsorber base 34 is provided with a threaded hole, and the upper and lower ends of the evaporator barrel 42 are provided with indium wire grooves and threaded holes, so that the lower end of the evaporation tube 41 is sealed and connected with the upper end of the evaporator barrel 42, the upper end of the evaporation tube 41 is sealed and connected with the adsorber base 34, and the lower end of the evaporator barrel 42 is sealed and connected with the evaporator base 43. The bottom wall of the oxygen-free copper base is the cold end with the lowest temperature, which is used to install and cool the sample to be tested. The evaporator base 43 is provided with multi-layer evaporation annular fins 44, which are used to fully transfer the temperature of the liquid helium to the lower end.

[0057] Please refer to Figure 6 and Figure 8 The evaporator barrel 42 is made of stainless steel, the evaporator base 43 is made of oxygen-free copper, the evaporator tube 41 is made of thin-walled stainless steel tube, and a heat-conducting flange 45 made of oxygen-free copper is brazed in the middle to transfer the low temperature of the 4K heat-conducting plate 143 to the internal helium of the evaporator tube 41 to achieve helium condensation.

[0058] Please refer to Figure 8 and Fig. 9A choke ring 46 is installed in the evaporation tube 41. The choke ring 46 is provided with a guide hole 462, and the choke ring 46 has a guide portion 461 for guiding the liquid helium to the guide hole 462. Specifically, the choke ring 46 is configured as a stainless steel part similar to a conical funnel, the guide portion 461 is the conical curved surface of the conical funnel, and the guide hole 462 is the middle hole of the conical funnel. The circumference of the choke ring 46 is tightly installed with the evaporation tube 41, so that the liquid ammonia falls from the guide hole 462 along the guide portion 461, thereby reducing the film climbing effect of the superfluid helium along the tube wall, reducing the liquid helium consumption and ensuring the lowest temperature.

[0059] For further information, please refer to Figure 3 and Figure 6 The thermal switch assembly 5 is a device for realizing heat switching between the adsorber assembly 3 and the heat conducting plate 143, and includes a temperature control seat 51, a heat conducting cylinder 52, an upper heat conducting part 53, a lower heat conducting part 54, a heat conducting belt 55 and a switching piece 57. The temperature control seat 51 is connected to the lower end of the adsorber base 34, the upper heat conducting part 53 and the lower heat conducting part 54 are respectively arranged at the two ends of the heat conducting cylinder 52, the lower heat conducting part 54 is connected to the heat conducting plate 143, the two ends of the heat conducting belt 55 are arranged as heat conducting seats 56, the upper heat conducting part 53 is connected to any heat conducting seat 56, and the other heat conducting seat 56 is connected to the temperature control seat 51, and the switching piece 57 is used to realize thermal conduction between the upper heat conducting part 53 and the lower heat conducting part 54.

[0060] In this embodiment, please refer to Fig.10 The upper heat conducting part 53 and the lower heat conducting part 54 have the same structure, including a flange 531 and an oxygen-free copper fin 532 arranged on one side of the flange 531. The two flanges 531 are respectively fixed at both ends of the heat conducting cylinder 52. The two groups of oxygen-free copper fins 532 extend into the heat conducting cylinder 52 and are staggered. After installation, there are gaps between the oxygen-free copper fins 532 and between the oxygen-free copper fins 532 and the opposite oxygen-free copper flanges. The flange 531 of the upper heat conducting part 53 is connected to the temperature control seat 51 through the heat conducting belt 55. The lower end of the adsorber base 34 is provided with a threaded hole and a sealing groove for installing the temperature control seat 51. The flange 531 of the lower heat conducting part 54 is connected to the heat conducting plate 143.

[0061] Please refer to Figure 6 The switch 57 includes a heating part, a connecting part 571 and a release cavity 572 filled with an adsorbent. The connecting part 571 is used to connect the release cavity 572 and the heat-conducting cylinder 52. The heating part is used to heat the release cavity 572, and the adsorbent adsorbs helium. The adsorbent in the release cavity 572 is activated carbon, the heating part is a heating wire and is wound outside the release cavity 572, and the activated carbon in the release cavity 572 adsorbs a small amount of helium.

[0062] Specifically, the heat-conducting cylinder 52 and the release cavity 572 are both made of stainless steel cylinders. When the heating wire is powered on, the activated carbon releases helium. When the helium enters the heat-conducting cylinder 52 along the connecting portion 571 and fills between the oxygen-free copper fins 532, the upper and lower flanges 531 are thermally conductive. The heat of the two flanges 531 can be transferred through the oxygen-free copper fins 532, the helium between the oxygen-free copper fins 532, the heat radiation between the components, and the stainless steel heat-conducting cylinder 52, that is, the thermal switch assembly 5 is in the open state at this time. When the heating wire is powered off, the activated carbon is cooled and adsorbs helium. At this time, the heat between the two flanges 531 can only be transferred by the heat radiation between the heat-conducting cylinder 52 and its components. The heat transfer efficiency of heat radiation and stainless steel is very low, that is, the thermal switch assembly 5 is in the closed state.

[0063] Please refer to Figure 6 In order to ensure that the activated carbon in the adsorption chamber can be restored to 40K, a heater and a thermometer are arranged on the temperature control seat 51; the activated carbon in the adsorption chamber is reduced to 4K through heat transfer through the thermal switch component 5 and the heat conducting belt 55.

[0064] The specific working process of this embodiment is: high-pressure helium is filled into the adsorption chamber, evaporation tube 41 and evaporation chamber through the gas filling pipe 31 and the gas filling valve 35 at the upper end of the adsorber assembly 3. The 4KGM refrigerator 141 transfers the 4K low temperature to the evaporation tube 41 through the heat conduction plate 143, so that the high-pressure helium in the above chamber is condensed and gathered in the evaporation chamber under the action of gravity; at this time, the thermal switch assembly 5 is in the closed state, and the activated carbon in the adsorption chamber is kept at 40K through the heater and thermometer on the temperature control seat 51, so as to ensure that all the helium is desorbed and condensed. The thermal switch is located between the heat conducting plate 143 and the adsorption chamber. When the temperature of the adsorption chamber is maintained at 40K, the thermal switch is adjusted to the closed state to prevent the temperature of the adsorber from being transferred to the heat conducting plate 143. Otherwise, the temperature of the heat conducting plate 143 is higher than 4K and condensation cannot be achieved. When the adsorber needs to be cooled to 4K, the thermal switch assembly 5 is adjusted to the open state to transfer the temperature of the 4K heat conducting plate 143 to the adsorber, thereby realizing the adsorber's adsorption of helium.

[0065] The adsorption type low temperature thermostat in this embodiment is also equipped with other heat transfer components, thermometers, heaters, electrical connectors and valves when in use, which are specifically arranged according to assembly requirements.

[0066] The adsorption type cryostat in this embodiment is first installed and connected, please refer to Figure 1-Figure 10 , the installation process is as follows:

[0067] Place the cryostat main flange 11 on the spectrometer scattering chamber flange, and install the upper vacuum cover cylinder 12 on the main flange; install the GM refrigerator 141, the valves at the vacuum port 144, the electrical connector accessories, etc. at the corresponding positions of the refrigerator 141 flange; connect the heat shield top flange 21 to the primary cold head of the refrigerator 141;

[0068] Paste the molecular sieve 38 to the evaporation installation hole 36 of the adsorber base 34, connect the adsorber base 34 to the evaporation tube 41, fill the activated carbon into the adsorption annular fin 37 and compact it, and then install the adsorber end cover;

[0069] The evaporator base 43, the evaporator cylinder 42 and the evaporation tube 41 are connected, and the choke ring 46 is fixed in the evaporation tube 41;

[0070] The adsorber assembly 3, the heat conducting plate 143, and the evaporator assembly 4 are connected and fixed, and the heat conducting plate 143 is connected to the secondary cold head of the GM refrigerator 141; the temperature control seat 51 is installed at the lower end of the adsorber base 34; thermometers are arranged on the heat conducting plate 143, the evaporator base 43, and the temperature control seat 51 to measure the temperature at the corresponding positions respectively; a heater is arranged on the adsorption temperature control seat 51 to cooperate with the thermometer there to realize the control of the activated carbon temperature;

[0071] Fill the thermal switch assembly 5 with a small amount of helium, seal and assemble it, and then fix it on the heat conducting plate 143, and connect the heat conducting seats 56 at both ends of the heat conducting belt 55 to the upper end of the upper heat conducting part 53 and the lower end of the adsorber base 34 respectively;

[0072] Connect the inflation valve 35 on the adsorber end cover 32 to the KF25 vacuum port for a long time to evacuate the activated carbon in the adsorption chamber. During the desorption process, the adsorber cylinder 33 is heated by the temperature control seat 51 to accelerate the desorption of the gas inside the activated carbon. After the desorption is completed, the adsorption unit is inflated with high-purity helium at a pressure of 30 Bar.

[0073] Connect the heat shield top flange 21, the heat shield upper cylinder 22 and the heat shield lower cylinder 23 in sequence;

[0074] The refrigeration flange 142 is fixed to the upper vacuum cover cylinder 12, and the lower vacuum cover cylinder 13 is connected to the upper vacuum cover cylinder 12 to complete the installation of the adsorption type cryostat.

[0075] After the adsorption type cryostat disclosed in this embodiment is assembled, a cooling test can be performed. The specific test method is as follows:

[0076] S1: Evacuate the inner cavity of the cylinder of the vacuum component 1 from the vacuum port 144 on the refrigeration flange 142 to a level of 10^-4Pa and keep the molecular pump group open.

[0077] S2: Connect the adsorption type low temperature thermostat with auxiliary equipment such as a compressor, a temperature controller, and a chiller, and turn on the chiller, the compressor, and the temperature controller in sequence, and wait for the equipment to cool down; during the cooling process, set the temperature of the temperature control seat 51 to 40K.

[0078] S3: After the temperature of the heat conducting plate 143 drops to 4K, the helium in the evaporation tube 41 begins to condense. After a certain period of time, the helium is completely condensed.

[0079] The condensation time of helium can be obtained based on relevant test experience, or the filling pipe 31 on the adsorber end cover 32 can be led out to the outside of the refrigeration flange 142 and a pressure gauge can be installed to obtain the condensation end time based on the pressure reading; after the filling pipe 31 is led out to the refrigeration flange 142, the filling pipe 31 and the refrigeration flange 142 need to be sealed.

[0080] After the helium is completely condensed, the temperature of the evaporator base 43 is about 4K.

[0081] S4: Turn off the heating output of the temperature control seat 51 and heat the activated carbon cavity of the thermal switch assembly 5. At this time, the thermal switch assembly 5 is opened, and the 4K temperature of the heat conduction plate 143 is finally transferred to the activated carbon in the adsorption cavity. The activated carbon begins to decompress and cool the liquid helium, and finally reduces the temperature of the evaporator base 43 to below 1K, and maintains an idle time of more than 10 hours.

[0082] Specifically, since the temperature of liquid helium is related to its vapor pressure, and the vapor pressure is related to the adsorption capacity of the adsorber assembly 3, and the adsorption capacity of the adsorber assembly 3 is determined by the temperature of the activated carbon, the lower the temperature, the stronger the adsorption of the activated carbon. When the temperature exceeds 40K, the activated carbon hardly adsorbs helium. By setting the temperature of the temperature control seat 51 at the lower end of the adsorber base 34, the temperature change of the activated carbon can be achieved, and then the temperature control of any point of the evaporator base 43 from the lowest temperature to 4K can be achieved. For temperature control above 4K, a heater can be installed on the evaporator base 43 to achieve temperature control from 4K to 300K.

[0083] S5: After the evaporation of liquid helium is completed, liquid helium regeneration operation is required. By turning off the heating of the thermal switch assembly 5 and setting the temperature of the temperature control seat 51 to 40K, the helium starts to desorb and is condensed again.

[0084] S6: Repeat the above process to achieve the lowest temperature again.

[0085] Embodiment 2:

[0086] The difference between the embodiment of the present application and the embodiment one is that: the working mode of the adsorption type cryostat disclosed in the embodiment one is called single-shot mode, that is, the liquid helium needs to be desorbed and condensed again after evaporation; in this embodiment, the adsorber assembly 3, the evaporator assembly 4 and the heat switch assembly 5 are arranged as a set of adsorption units in two groups, and the two groups of heat switch assemblies 5 are simultaneously connected to the same heat conducting plate 143, which will be used as the final sample holder for installing and fixing the sample.

[0087] Specifically, during operation, the on and off states of the two sets of thermal switch components 5 are opposite, one set of adsorption units is in the adsorption process, and the thermal switch component 5 between the adsorption unit and the heat conducting plate 143 is in the open state, and the other set of adsorption units is in the regeneration process, and the thermal switch component 5 between the adsorption unit and the heat conducting plate 143 is in the closed state. After the first set of adsorption units finishes adsorption, the second set of adsorption units is turned on for adsorption, so that it can be ensured that there is always a set of adsorption units in adsorption, so as to maintain the temperature on the heat conducting plate 143 at the lowest temperature.

[0088] In actual operation, the second set of adsorption can be started before the first set of adsorption units completely finishes adsorption, so as to ensure the continuity of the lowest temperature.

[0089] Embodiment three:

[0090] The difference between the embodiment of the present application and the first embodiment is that: in the present embodiment, the adsorber assembly 3, the evaporator assembly 4 and the thermal switch assembly 5 are provided as a set of adsorption units in two groups, the first set of adsorption units is filled with high-pressure helium 4 gas, and the second set of adsorption units can be filled with 10L of normal-pressure helium 3 gas.

[0091] Since the lowest temperature of the adsorption-type cryostat made of helium-4 gas is about 0.7K, helium-3 gas has a greater vapor pressure than helium-4 gas at the same temperature. At 0.5K, the vapor pressure of helium-3 is 10,000 times that of helium-4. Therefore, activated carbon can easily adsorb liquid helium-3 to a low temperature of about 0.3K.

[0092] In this embodiment, the first adsorption unit is filled with high-pressure helium 4 gas to provide a low temperature of 1K, and the heat-conducting flange 45 on the evaporation tube 41 of the second adsorption unit is cooled by the heat-conducting structure to achieve the condensation of helium 3 gas. After the helium 3 is completely condensed, the evaporator base of the second adsorption unit can be cooled to below 0.3K with reference to the operation process of the first embodiment.

[0093] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the concept of the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. An adsorption type cryostat, characterized in that: include: An adsorber assembly (3) comprises an air filling tube (31) and an adsorption chamber, wherein the adsorption chamber is used to contain an adsorbent, and the air filling tube (31) is connected to the upper end of the adsorption chamber and is used to receive helium; An evaporator assembly (4) comprises an evaporation tube (41) and an evaporation chamber, wherein the upper end of the evaporation tube (41) is connected to the adsorption chamber, and the lower end of the evaporation tube (41) is connected to the evaporation chamber to collect liquid helium condensed from the evaporation tube (41); A heat shield assembly (2) is arranged outside the adsorber assembly (3) and the evaporator assembly (4) to reduce heat radiation into the heat shield assembly (2); A vacuum component (1), the vacuum component (1) being arranged outside the heat shield component (2) to form a low temperature thermostat housing, and the vacuum component (1) being provided with a vacuum extraction port (144) for external connection to maintain the vacuum in the inner cavity of the vacuum component (1), the vacuum component (1) being provided with a refrigeration element (14), the refrigeration element (14) being connected to the heat shield component (2) and the evaporation tube (41); and A heat switch assembly (5) connects the refrigeration element (14) and the adsorber assembly (3) to control the heat on and off between the refrigeration element (14) and the adsorber assembly (3).

2. The adsorption type cryostat according to claim 1, characterized in that The adsorption chamber comprises an adsorber end cover (32), an adsorber cylinder (33) and an adsorber base (34); the adsorber end cover (32) and the adsorber base (34) are respectively arranged at the upper end and the lower end of the adsorber cylinder (33) to seal the adsorber cylinder (33); a plurality of adsorption annular fins (37) are arranged on the adsorber base (34), and spaces between adjacent adsorption annular fins (37) are used to fill adsorbent.

3. The adsorption type cryostat according to claim 2, characterized in that An evaporation installation hole (36) communicating with the evaporation tube (41) is provided on the adsorber base, and a molecular sieve (38) is provided at the evaporation installation hole (36) to limit leakage of the adsorbent.

4. The adsorption type cryostat according to claim 1, wherein: The evaporation chamber comprises an evaporator barrel (42) and an evaporator base (43); the evaporator base (43) is sealed and arranged at the lower end of the evaporator barrel (42); and a plurality of layers of evaporation annular fins (44) are arranged on the evaporator base (43); the evaporation annular fins (44) are used to transfer the temperature of liquid helium.

5. The adsorption type cryostat according to claim 4, characterized in that A choke ring (46) is installed in the evaporation tube (41), the choke ring (46) is provided with a guide hole (462), and the choke ring (46) has a guide portion (461) for guiding liquid helium to the guide hole (462) to reduce the film creeping effect of superfluid helium along the tube wall.

6. The adsorption type cryostat according to claim 1, wherein: The refrigeration component (14) comprises a refrigerator (141), a refrigeration flange (142) and a heat conduction plate (143); the refrigerator (141) is connected to the vacuum component (1) via the refrigeration flange (142); the heat conduction plate (143) connects the secondary cold head of the refrigerator (141) and the evaporation tube (41) to achieve heat transfer between the refrigerator (141) and the evaporation tube (41).

7. The adsorption type cryostat according to claim 6, characterized in that The thermal switch assembly (5) comprises a temperature control seat (51), a heat-conducting cylinder (52), an upper heat-conducting part (53), a lower heat-conducting part (54) and a switching piece (57); the upper heat-conducting part (53) and the lower heat-conducting part (54) are respectively arranged at two ends of the heat-conducting cylinder (52); the lower heat-conducting part (54) is connected to the heat-conducting plate (143); the upper heat-conducting part (53) is connected to the temperature control seat (51); and the temperature control seat (51) is connected to the adsorption chamber; the switching piece (57) is used to realize thermal conduction between the upper heat-conducting part (53) and the lower heat-conducting part (54).

8. The adsorption type cryostat according to claim 7, characterized in that The temperature control seat (51) is provided with a heater to heat the adsorbent in the adsorption chamber.

9. The adsorption type cryostat according to claim 7, wherein: The switch (57) comprises a heating portion, a connecting portion (571) and a release cavity (572) filled with an adsorbent, wherein the connecting portion (571) is used to connect the release cavity (572) and the heat-conducting cylinder (52), the heating portion is used to heat the release cavity (572), and the adsorbent adsorbs helium.

10. The adsorption type cryostat according to claim 6, wherein: The heat shield assembly (2) comprises a heat shield top flange (21) and a heat shield cylinder. The heat shield top flange (21) is installed at the upper end of the heat shield cylinder and is used to connect the first-stage cold head of the refrigerator (141). The heat shield top flange (21) has an opening (24) for leading out the inflation pipe (31) and routing the signal line. The heat shield cylinder is sealed to reduce heat radiation inside the heat shield cylinder.

Images