Integrated dilution refrigerator

Abstract

To provide systems and techniques for improved, user-friendly, and integrated dilution refrigerators.SOLUTION: The improved dilution refrigerator includes a plurality of thermalization plates configured to be cooled to a plurality of temperatures, where: a first thermalization plate of the plurality of thermalization plates comprises an integrated heat exchanger, the integrated heat exchanger comprises channels 542 formed in the first thermalization plate, and the channels 542 are configured to allow helium to flow through the first thermalization plate during operation of the dilution refrigerator.SELECTED DRAWING: Figure 5C

Description

[Technical Field]

[0001] This relates to an integrated dilution refrigerator. [Background technology]

[0002] Dilution refrigerators are used to provide cooling to temperatures of approximately 2 mK to 1 K. 3 He and 4 It is a cryogenic device that relies on the heat of a mixture of He isotopes. Conventional dilution refrigerators, or "wet" dilution refrigerators, 3 He / 4 Before further cooling the He mixture to below 4 K, a liquid nitrogen bath and 4 Using a He bath, 3 He / 4 The He mixture is pre-cooled. Modern dilution refrigerators, or "dry" dilution refrigerators, use devices such as cryocoolers rather than a cryogenic liquid bath to 3 He / 4 He pre-cool the mixture. Summary of the Invention [Problem to be solved by the invention]

[0003] An integrated dilution refrigerator is provided. [Means for solving the problem]

[0004] Some embodiments relate to a dilution refrigerator comprising a plurality of thermalization plates configured to be cooled to a plurality of temperatures, a first of the plurality of thermalization plates comprising an integrated heat exchanger, the integrated heat exchanger including a channel formed in the first thermalization plate, the channel configured to allow helium to flow through the first thermalization plate during operation of the dilution refrigerator.

[0005] In some embodiments, the integrated heat exchanger is formed by additive manufacturing. In some embodiments, the first thermalizer plate further comprises a removable portion, the removable portion including an integrated heat exchanger.

[0006] In some embodiments, the dilution refrigerator further comprises a replaceable dilution insert removably coupled to the removable portion of the first thermalizer plate. In some embodiments, the dilution insert is removably coupled to a condensate line of the dilution refrigerator and to three of the plurality of thermalization plates.

[0007] In some embodiments, the diluent insert comprises: 3 He and 4 From mixtures with He 3 A fractionator configured to perform cooling by fractionating He vapor is provided. In some embodiments, the dilution refrigerator includes a test volume thermally coupled to a coldest thermal plate among the plurality of thermal plates, and a still coupled to a second thermal plate having a higher temperature than the coldest thermal plate, 3 He and 4 From mixtures with He 3 The system further includes a fractionator configured to perform cooling by fractionating the He vapor, and a continuous heat exchanger disposed between the second thermalization plate and the coldest thermalization plate.

[0008] In some embodiments, the dilution refrigerator further comprises at least one heat exchanger thermally coupled to a thermalization plate of the plurality of thermalization plates, wherein the at least one heat exchanger comprises a nanomaterial.

[0009] In some embodiments, the nanomaterial comprises at least one of nanowires, nanofoams, nanopellets, and / or nanotubes. In some embodiments, the nanomaterial comprises nanowires, including one or more of copper nanowires, silver nanowires, gold nanowires, platinum nanowires, polymer nanowires, carbon nanowires, and / or carbon fiber nanowires.

[0010] In some embodiments, the at least one heat exchanger comprises one of a discrete heat exchanger and / or a heat exchanger disposed within a mixing chamber of a dilution refrigerator. In some embodiments, the dilution refrigerator further includes a condensation line configured to transport helium to the coldest thermalization plate of the plurality of thermalization plates; a still disposed along the condensation line before the coldest thermalization plate; a heat exchanger disposed along the condensation line between the still and the coldest thermalization plate; and a heat exchange line configured to transfer the returning helium mixture from the heat exchanger to the still and to reduce the temperature of the helium mixture in the condensation line at a location above the still.

[0011] In some embodiments, the dilution refrigerator further comprises a Joule-Thomson expander disposed along the condensation line before the still, and the heat exchange line is configured to reduce the temperature of the helium mixture in the condensation line at a location before the Joule-Thomson expander.

[0012] In some embodiments, the dilution refrigerator further comprises a condensation line configured to transport helium to a coldest thermalization plate of the plurality of thermalization plates, and a high surface area material disposed along the condensation line, the high surface area material configured to adsorb the transported helium onto the high surface area material during a cool-down cycle of the dilution refrigerator.

[0013] In some embodiments, a first end of the high surface area material is switchably thermally coupled to a higher temperature one of the plurality of thermalization plates by a first heat switch, and a second end of the high surface area material opposite the first end is switchably thermally coupled to a lower temperature one of the plurality of thermalization plates by a second heat switch.

[0014] In some embodiments, the dilution refrigerator further comprises at least one heater thermally coupled to the high surface area material, the heater configured to heat the high surface area material such that adsorbed helium is released from the high surface area material and cooled by moving between a higher temperature one of the plurality of thermalization plates and a lower temperature one of the plurality of thermalization plates.

[0015] In some embodiments, the dilution refrigerator further comprises a first valve disposed along the condensation line between the higher temperature thermalization plate and the high surface area material, and a second valve disposed along the condensation line between the high surface area material and the lower temperature thermalization plate, the first and second valves being configured to transport helium adsorbed on the high surface area material from the higher temperature thermalization plate to the lower temperature thermalization plate when the first valve is closed and the second valve is opened.

[0016] In some embodiments, the high surface area material comprises one of activated carbon or a metal powder. In some embodiments, the dilution refrigerator further includes a condensation line configured to transport helium from the helium inlet to the coldest thermalization plate of the plurality of thermalization plates, a first helium filter disposed along the condensation line, a second helium filter disposed along the condensation line in parallel with the first helium filter, and at least one valve configured to switch the flow of helium between the first helium filter and the second helium filter along the condensation line.

[0017] In some embodiments, the first helium filter and / or the second helium filter comprises a charcoal trap. In some embodiments, the dilution refrigerator further comprises a first counterflow heat exchanger disposed between the first helium filter and the helium inlet, and a second counterflow heat exchanger disposed between the second helium filter and the helium inlet.

[0018] In some embodiments, the dilution refrigerator further comprises a condensation line configured to transport helium to a coldest thermalization plate of the plurality of thermalization plates; a Joule-Thomson expander disposed along the condensation line; and a bypass disposed along the condensation line in parallel with the Joule-Thomson expander, the bypass configured to allow the transported helium to bypass the Joule-Thomson expander when the transported helium has a temperature above a threshold value and less than 300 K.

[0019] In some embodiments, the bypass comprises a material configured to allow the transported helium to diffuse through the material when the transported helium has a temperature above a threshold value and below 300 K. In some embodiments, the material comprises a polymer.

[0020] Some embodiments relate to a dilution refrigerator that includes a first thermal stage configured to be cooled to a first temperature, a second thermal stage configured to be cooled to a second temperature that is lower than the first temperature, a vacuum chamber that houses the first and second thermal stages, a first suspension system configured to suspend the first thermal stage from the vacuum chamber, and a second suspension system configured to suspend the second thermal stage from the vacuum chamber independently of the first thermal stage.

[0021] In some embodiments, the first suspension system comprises a rod configured to rigidly connect the first thermal stage to the vacuum chamber. In some embodiments, the rod comprises carbon fiber or stainless steel.

[0022] In some embodiments, the second suspension system comprises one or more springs configured to movably couple the second thermal stage to the vacuum chamber. In some embodiments, the one or more springs include a spring configured to provide a constant tension under different loads.

[0023] In some embodiments, the one or more springs include a first spring configured to provide vibration isolation for the second thermal stage along the first axis and a second spring configured to provide vibration isolation for the second thermal stage in a plane perpendicular to the first axis.

[0024] In some embodiments, the first spring comprises a leaf spring. In some embodiments, the leaf spring comprises stainless steel and / or spring steel. In some embodiments, the leaf spring comprises two leaves, and the tension of the leaf spring is determined based on the length of the two leaves.

[0025] In some embodiments, the leaf spring comprises two leaves, and the tension of the leaf spring is determined based on the pretensioning of the two leaves. In some embodiments, the second spring comprises a flexible rod.

[0026] In some embodiments, the first spring is connected to the second thermal stage by a flexible rod. In some embodiments, the flexible rod comprises a polymer. In some embodiments, the polymer comprises Delrin.

[0027] In some embodiments, the dilution refrigerator further comprises a third thermal stage configured to be cooled to a third temperature between the first temperature and the second temperature, and the first suspension system is further configured to suspend the third thermal stage from the first thermal stage.

[0028] In some embodiments, the dilution refrigerator further comprises a fourth thermal stage configured to be cooled to a fourth temperature lower than the second temperature, and a third suspension system configured to suspend the fourth thermal stage from the second thermal stage.

[0029] In some embodiments, the third suspension system includes a rod configured to rigidly connect the fourth thermal stage to the second thermal stage. In some embodiments, the second suspension system includes one or more springs configured to movably couple the second thermal stage to the vacuum chamber.

[0030] In some embodiments, the one or more springs include a first spring configured to provide vibration isolation for the second thermal stage along the first axis and a second spring configured to provide vibration isolation for the second thermal stage in a plane perpendicular to the first axis.

[0031] In some embodiments, the first suspension system includes a rod configured to rigidly connect the first thermal stage to the vacuum chamber. Some embodiments relate to a dilution refrigerator comprising an outer vacuum chamber including at least one substantially planar surface and at least one opening in the substantially planar surface configured to provide access to an interior of the outer vacuum chamber.

[0032] In some embodiments, the dilution refrigerator further comprises a sample stage housed within the outer vacuum chamber, the opening configured to provide access to the sample stage through the outer vacuum chamber.

[0033] In some embodiments, the dilution refrigerator further comprises one or more radiation shields housed within the outer vacuum chamber, wherein portions of the one or more radiation shields proximate the sample stage are slidable and / or removable to provide access to the sample stage.

[0034] In some embodiments, the at least one substantially planar surface includes a first surface disposed in a plane perpendicular to the plane of a floor supporting the dilution refrigerator. In some embodiments, the at least one substantially planar surface includes a first surface disposed in a plane perpendicular to the plane of a floor supporting the dilution refrigerator, and a second surface disposed in a plane parallel to the plane of the floor, the first surface and the second surface being arranged as a rectangular parallelepiped.

[0035] In some embodiments, the opening comprises a sealed opening. In some embodiments, the opening comprises a hinged door. In some embodiments, the dilution refrigerator further comprises one or more radiation shields housed within the outer vacuum chamber, wherein a portion of the one or more radiation shields adjacent the hinged door is slidable and / or removable to provide access to the interior of the outer vacuum chamber.

[0036] In some embodiments, the opening further comprises a load lock. In some embodiments, the outer vacuum chamber includes a first section and a second section suspended from the first section.

[0037] In some embodiments, the first section is connected to the second section by an integral clamp and / or cam. In some embodiments, the first and / or second sections of the outer vacuum chamber are configured to be at least partially removed from the dilution refrigerator to provide access to the interior of the outer vacuum chamber.

[0038] In some embodiments, the dilution refrigerator further comprises an external system configured to raise and / or lower the first section and / or the second section of the outer vacuum chamber.

[0039] In some embodiments, the external system includes pneumatic and / or hydraulic devices configured to raise and / or lower the first and / or second sections. In some embodiments, the external system includes a screw mechanism configured to raise and / or lower the first and / or second sections.

[0040] In some embodiments, the outer vacuum chamber is configured to fit within a server rack type container. In some embodiments, the server rack container is configured to integrate with commercially available server rack infrastructure.

[0041] In some embodiments, the server rack container is a 19 inch (48.26 centimeter) server rack. In some embodiments, the server rack-type container includes an exterior housing that includes an integral horizontal surface.

[0042] In some embodiments, the integral horizontal surface is configured to be stowed when not in use. Some embodiments relate to a distributed refrigeration system comprising a pre-cooling system thermally coupled to two or more cryogenic devices and configured to provide a first cooling stage for the two or more cryogenic devices.

[0043] In some embodiments, the distributed refrigeration system further comprises two or more cryogenic devices thermally coupled to the pre-cooling system. In some embodiments, the two or more cryogenic devices include at least one dilution refrigerator.

[0044] In some embodiments, the two or more cryogenic devices include a dilution refrigerator, a cryomicroscope system, 3 He refrigeration system and / or superconducting CMOS system. In some embodiments, the first cooling stage has a temperature of 5K or less.

[0045] In some embodiments, the pre-cooling system includes a cryogenic cooling system. In some embodiments, the cryogenic cooling system comprises a pulse tube. In some embodiments, the cryogenic cooling system includes a Brayton cryocooler.

[0046] In some embodiments, the cryogenic cooling system includes a helium liquefaction system. In some embodiments, the two or more cryogenic devices include a dilution refrigerator having a second cooling stage configured to reach a temperature of 1 K or less.

[0047] In some embodiments, the second cooling stage is configured to reach a temperature of 100 mK or less. In some embodiments, the distributed refrigeration system is configured to be integrated into one or more server racks.

[0048] In some embodiments, the pre-cooling system is installed in a first server rack and the two or more cryogenic devices are installed in a second server rack that is different from the first server rack.

[0049] In some embodiments, the pre-cooling system is installed in a first server rack, and the two or more cryogenic devices include dilution refrigerators, and the dilution refrigerators are installed in a second server rack different from the first server rack.

[0050] In some embodiments, the distributed refrigeration system further comprises a thermal coupling component configured to transfer heat from the two or more cryogenic devices to the pre-cooling system. In some embodiments, the thermal coupling component includes one or more fill lines.

[0051] In some embodiments, the thermal coupling component comprises one or more heat pipes. In some embodiments, the one or more heat pipes include one or more pulsed heat pipes.

[0052] In some embodiments, the thermal coupling component comprises a superfluid loop. In some embodiments, the thermal coupling component comprises one or more vacuum insulated pipes. Some embodiments relate to a dilution refrigerator comprising multiple thermal stages configured to be cooled to multiple temperatures, with a coldest thermal stage of the multiple thermal stages positioned above a warmer thermal stage of the multiple thermal stages such that the coldest thermal stage is positioned furthest from a floor supporting the dilution refrigerator.

[0053] In some embodiments, the dilution refrigerator includes a demixing chamber disposed above the coldest thermal stage and thermally coupled to the coldest thermal stage, a mixing chamber disposed farther from the floor than the demixing chamber, and a gas supply from the demixing chamber to the mixing chamber. 4and a fountain pump configured to transport He.

[0054] In some embodiments, the dilution refrigerator is 4 It further comprises a heat exchanger configured to cool the He. In some embodiments, the dilution refrigerator comprises: 3 He- 4 From He mixture 3 The present invention further includes a still configured to provide cooling by fractionating the He vapor, the still including a pumping port having a pipe that enters the still through a face of the still other than the face furthest from the floor of the still.

[0055] In some embodiments, the pipe enters the still at the face closest to the floor of the still. In some embodiments, the pipe is coupled to a trap, the trap being configured to couple a P-trap to a superfluid trap. 4 and a super leak configured to remove He.

[0056] In some embodiments, the pipe 4 A barrier is provided that is configured to prevent the He film from creeping up into the outlet of the pipe. In some embodiments, the barrier comprises one or more knife edges at the outlet of the pipe.

[0057] In some embodiments, the barrier comprises a ring barrier on the outer surface of the pipe. In some embodiments, the barrier comprises a ring barrier on the inner surface of the pipe. In some embodiments, the barrier comprises a heater.

[0058] In some embodiments, the dilution refrigerator comprises: 3 He / 4 a first impedance stage configured to cool the He mixture before passing through the first impedance stage; 3 He / 4a heat exchange stage configured to cool the He mixture received from the first impedance stage; 3 He / 4 From He mixture 3 and a still configured to fractionate the He.

[0059] In some embodiments, the heat exchange stage transfers cold water from the mixing chamber to the still. 3 By bringing back He 3 He / 4 The cooling system is configured to cool the He mixture. In some embodiments, the dilution refrigerator further comprises an outer vacuum chamber housing the multiple thermal stages, and an opening through a surface of the outer vacuum chamber configured to provide access to the coldest thermal stage of the dilution refrigerator.

[0060] In some embodiments, the opening is located proximate to a top surface of the outer vacuum chamber. In some embodiments, the opening comprises a sealed opening.

[0061] In some embodiments, the opening comprises a hinged door. In some embodiments, the outer vacuum chamber is configured to fit within a server rack type container.

[0062] In some embodiments, the server rack container is configured to integrate with commercially available server rack infrastructure. In some embodiments, the server rack container is a 19 inch (48.26 centimeter) server rack.

[0063] In some embodiments, the dilution refrigerator further comprises a pulse tube configured to cool one of the plurality of thermal stages to about 4K. The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in various figures is represented by a like numeral. For clarity, not every component is numbered in every figure. [Brief explanation of the drawings]

[0064] [Figure 1] FIG. 1 is a schematic diagram of a closed-cycle dilution refrigerator according to certain embodiments described herein. [Figure 2] FIG. 2 is a schematic diagram of a helium flushing device in the dilution refrigerator of FIG. 1 according to certain embodiments described herein. [Figure 3] FIG. 2 is a schematic diagram of a cool-down turbocharger arrangement in the dilution refrigerator of FIG. 1 according to certain embodiments described herein. [Figure 4] 1 is a schematic diagram of a still including an apparatus for separating 3He and 4He using the second sound effect, according to some embodiments described herein. [Figure 5A] 2 illustrates exemplary components of a removable dilution insert for the dilution refrigerator of FIG. 1 according to certain embodiments described herein. [Figure 5B] 5B is a diagram of an exemplary thermal plate insert of the removable dilution insert of FIG. 5A according to certain embodiments described herein. [Figure 5C] FIG. 2 is a cross-sectional view of an exemplary integrated heat exchanger showing channels for helium flow according to certain embodiments described herein. [Figure 5D] 1 is an image of a high surface area material used in an integrated heat exchanger according to some embodiments described herein. [Figure 5E] 2 is an exemplary implementation of a continuous heat exchanger and a split heat exchanger of the dilution refrigerator of FIG. 1 according to some embodiments described herein. [Figure 6A] FIG. 1 is a schematic diagram of an exemplary 4He film separation apparatus, according to some embodiments described herein. [Figure 6B]FIG. 1 is a schematic diagram of an exemplary 4He film separation apparatus, according to some embodiments described herein. [Figure 6C] FIG. 1 is a schematic diagram of an exemplary 4He film separation apparatus, according to some embodiments described herein. [Figure 6D] FIG. 1 is a schematic diagram of an exemplary 4He film separation apparatus, according to some embodiments described herein. [Figure 6E] FIG. 1 is a schematic diagram of an exemplary 4He film separation apparatus, according to some embodiments described herein. [Figure 6F] FIG. 1 is a schematic diagram of an exemplary 4He film separation apparatus, according to some embodiments described herein. [Figure 7A] 1 is an image of sintered metal particles used in heat exchangers. [Figure 7B] 1 is an image of nanowires used in a heat exchanger according to some embodiments described herein. [Figure 7C] 1 is an image of a nanocluster used in a heat exchanger according to some embodiments described herein. [Figure 7D] 1 includes images of different nanopellets used in heat exchangers according to some embodiments described herein. [Figure 8A] FIG. 2 is a schematic diagram of an exemplary vibration isolation system used in the dilution refrigerator of FIG. 1, according to certain embodiments described herein. [Figure 8B] 8B illustrates an exemplary spring for use in the vibration isolation system of FIG. 8A, according to certain embodiments described herein. [Figure 9] FIG. 1 illustrates a side view of an exemplary external support rack and integrated lift configured to raise and lower a portion of a vacuum chamber according to certain embodiments described herein. [Figure 10A] FIG. 2 is a side view of an exemplary implementation of the dilution refrigerator of FIG. 1 including elements configured to provide tool-less assembly of the vacuum chamber and access to the test volume, according to certain embodiments described herein. [Figure 10B]1A-1C illustrate an integrated latch in an open position and a closed position, respectively, configured to provide tool-less assembly of a vacuum chamber, according to some embodiments described herein. [Figure 10C] 1A-1C illustrate an integrated latch in an open position and a closed position, respectively, configured to provide tool-less assembly of a vacuum chamber, according to some embodiments described herein. [Figure 11] FIG. 1 illustrates an exterior view of a housing configured to support a dilution refrigerator according to some embodiments described herein. [Figure 12A] FIG. 1 is a schematic diagram of an inverting dilution refrigerator according to certain embodiments described herein. [Figure 12B] FIG. 2 is a schematic diagram of exemplary components of an inverting dilution refrigerator, according to certain embodiments described herein. [Figure 12C] FIG. 2 is a schematic diagram of exemplary components of an inverting dilution refrigerator, according to certain embodiments described herein. [Figure 13] FIG. 1 is a schematic diagram of a distributed cooling system according to certain embodiments described herein. [Figure 14] 1 illustrates schematically an exemplary computing device capable of implementing aspects of the technology described herein. DETAILED DESCRIPTION OF THE INVENTION

[0065] Dilution refrigerators are cryogenic devices that can provide cooling to temperatures of approximately 2 mK to 1 K and are used in a variety of applications requiring such extremely low temperatures. For example, dilution refrigerators can be used to support quantum computing (e.g., superconducting quantum computing techniques and qubits) and low-temperature condensed matter physics research, among other applications.

[0066] As mentioned above, a dilution refrigerator is used to provide cooling. 3 He and 4It relies on the heat of mixing of He isotopes. When cooled below about 870 mK, 3 He / 4 He mixtures undergo spontaneous phase separation, 3 He-rich phase ("rich" phase) and 3 A He-poor ("dilute") phase forms. These two phases are maintained in equilibrium in the mixing chamber, the coldest part of the dilution refrigerator, and are separated by a phase boundary. 3 He is diluted as it moves from the rich phase across the phase boundary into the dilute phase, and the heat required for this endothermic dilution process provides the cooling power of the dilution refrigerator.

[0067] However, conventional dilution refrigerators can have many drawbacks and disadvantages. For example, wet dilution refrigerators require significant amounts of liquid cryogen, which can be costly to maintain and supply. As another example, dry dilution refrigerators can be subject to undesirable mechanical vibrations introduced by the cryocooler system and / or can consume large amounts of energy to power the cryocooler.

[0068] Conventional dilution refrigerators also typically occupy a large footprint, which may preclude their use in applications requiring multiple dilution refrigerators. For example, a single conventional dry dilution refrigerator typically requires approximately 300 square feet (27.87 square meters) and a ceiling height of approximately 12 to 14 feet. This space is not only occupied by the dilution refrigerator itself, but is also required to support auxiliary systems such as pumps, compressors, water cooling systems, and / or cryocooler systems.

[0069] The inventors have recognized and understood that the quantum technology industry needs dilution refrigerators that are reliable, easy to use, easy to maintain, and compact in order for quantum computing and other quantum technologies to be easily scalable. Accordingly, the inventors have developed a dilution refrigerator and distributed cooling system that can be integrated with commercially available server rack infrastructure (e.g., 19-inch (48.26 centimeter) server racks). Furthermore, the inventors have developed many features described herein to facilitate dilution refrigerator maintenance, speed dilution refrigerator cooling without the use of mechanical pumps, and reduce the transmission of mechanical vibrations to the dilution refrigerator's test volume.

[0070] I. Improved closed-cycle dilution refrigerator 1 is a schematic diagram of a dry-type closed-cycle dilution refrigerator 100 according to some embodiments described herein. In some embodiments, the dilution refrigerator 100 includes an outer vacuum chamber 106 at room temperature (e.g., about 300 K) and multiple thermal stages 108 a- 108 f (e.g., thermal plates) maintained at decreasing temperature intervals (e.g., about 50 K, 9-10 K, 3 K, etc.). For example, the first thermal stage 108 a may be at about 50 K, the second thermal stage 108 b may be at about 9-10 K, the third thermal stage 108 c may be at about 3-4 K, the fourth thermal stage 108 d may be at about 800 mK, the fifth thermal stage 108 e may be at about 100 mK, and the sixth thermal stage 108 f may be at about 10 mK.

[0071] In some embodiments, the dilution refrigerator 100 includes: 3 He / 4 A pumping system 102 can be included to pressurize the He gas mixture (eg, to a pressure at or near 100 kPa (1 bar)). 3 He / 4 The He gas mixture may enter the outer vacuum chamber 106 through one or more inlets and then pass through the inner thermal stages 108a-108f through the condensation line 102a. 3He / 4 After the He gas mixture has performed its cooling function, it can return to the pumping system through return line 102b.

[0072] In some embodiments, 3 He / 4 The He mixture can be purified before passing through thermal stages 108a-108f along condenser line 102a. Contaminants in the helium flowing through the dilution refrigerator can clog some components (e.g., the Joule-Thomson expander or the capillaries of the heat exchangers), resulting in reduced performance or system failure. Traditionally, to mitigate the risk of contaminants entering the system, the helium is first passed through an external "scrub trap" filled with activated carbon before entering the dilution unit of the dilution refrigerator. These external traps must be surrounded by liquid nitrogen and refilled at frequent intervals, which requires maintenance and interaction by the user.

[0073] The present inventors have recognized and appreciated that a passive helium filter that does not require refilling with liquid nitrogen can improve the user experience of a dilution refrigeration system and reduce the frequency of maintenance. Accordingly, in some embodiments, dilution refrigerator 100 includes one or more helium cleaning devices 110. In some embodiments, when dilution refrigerator 100 includes two or more helium cleaning devices 110, it can further include a switching system 109 configured to direct the flow of helium to a single helium cleaning device 110.

[0074] 2 shows a schematic diagram of a helium cleaning apparatus 110 according to some embodiments described herein. The helium cleaning apparatus 110 can be coupled to the pumping system 102 by a switching system 109 located outside the outer vacuum chamber 106. The switching system 109 can include one or more helium-compatible valves. The switching system 109 can be configured to switch the flow of helium between each of the helium cleaning apparatuses 110. In this way, while the dilution refrigerator is in operation, one helium cleaning apparatus 110 can be used to actively filter helium, while the other helium cleaning apparatus can be cleaned (e.g., by heating and pumping out impurities), allowing for indefinite operation of the dilution refrigerator 100.

[0075] In some embodiments, helium scrubbing system 110 includes a counterflow heat exchanger 110a, a trap 110b, and a weak thermal contact 110c (e.g., a gas gap heat exchanger, a low thermal conductivity attachment, etc.). Counterflow heat exchanger 110a and weak thermal contact 110c can reduce the heat load of helium scrubbing system 110 on dilution refrigerator 100, eliminating the use of cryogenic valves in helium scrubbing system 110. Trap 110b can include, for example, a high surface area material (e.g., charcoal, activated carbon, and / or metal powder) configured to trap non-helium impurities within dilution refrigerator 100.

[0076] Returning to FIG. 1 , in some embodiments, the dilution refrigerator 100 can include a cooldown turbocharger device 111. Dry dilution refrigerators traditionally use an auxiliary compressor to allow the flow of warm helium, but helium initially has a high impedance and resists such movement. The extra pressure from the auxiliary compressor also pressurizes the helium, causing it to reach a pressure at a higher temperature where it begins isenthalpic expansion and cooling. These auxiliary mechanical compressor pumps are costly, prone to reliability issues, and can frequently leak and degrade over time. The inventors have recognized and appreciated that helium can alternatively be pulsed through the dilution refrigerator during cooldown without the use of an auxiliary mechanical pump, thereby enabling a faster and more efficient cooldown process.

[0077] 3 shows a schematic diagram of a cool-down turbocharger apparatus 111 according to some embodiments described herein. The cool-down turbocharger apparatus 111 can include a volume of high surface area material 111a, a heater 111b, a first valve 111c, and a second valve 111d. The first valve 111c and the second valve 111d can be, for example, cold valves located inside the vacuum chamber 106. As another example, the first valve 111c and the second valve 111d can be room temperature valves located outside the vacuum chamber 106. In some embodiments, the heater 111b and the first valve 111c and the second valve 111d can be communicatively coupled to a controller 330. The controller 330 can be, for example, a computer as described in connection with FIG. 14 herein.

[0078] In some embodiments, the cooldown turbocharger device 111 can be thermally coupled to a thermal stage (e.g., to a thermalization plate). In the example of Figure 3, the high surface area material 111a is thermally coupled to the second thermal stage 108b, but it should be appreciated that the high surface area material 111a can be thermally coupled to another thermal stage (e.g., the first thermal stage 108a) in some embodiments.

[0079] Alternatively, in some embodiments, the cool-down turbocharger apparatus 111 may be thermally coupled to multiple thermal stages (e.g., across two or more thermal stages 108a-108f). In such embodiments, the sequential heating and cooling of the high surface area material 111a may be regulated by a heat switch. For example, the cool-down turbocharger apparatus 111 may be switchably thermally coupled between a higher temperature thermal stage and a lower temperature thermal stage, such that the cool-down turbocharger apparatus 111 may be thermally coupled to either the higher temperature thermal stage or the lower temperature thermal stage. When the cool-down turbocharger apparatus 111 is thermally coupled to the higher temperature thermal stage, the high surface area material 111a may release any adsorbed helium. When the cool-down turbocharger apparatus 111 is thermally coupled to the lower temperature thermal stage, helium begins to adsorb onto the high surface area material 111a. In this manner, sequential flushing of helium through the condensate line 102a may be performed.

[0080] In some embodiments, the high surface area material 111 a can include a material with a porous and / or textured surface such that helium adsorbs onto the high surface area material 111 a during the cool-down process. For example, the high surface area material 111 a can include activated carbon, a metal powder (e.g., copper or silver powder), and / or a composite material formed of nanostructures (e.g., nanowires, nanoparticles, etc.).

[0081] In some embodiments, the cool-down turbocharger apparatus 111 can be operated using the sequential opening and closing of valves 111c, 111d in coordination with the operation of heater 111b. For example, to adsorb helium onto the high surface area material 111a, the first valve 111c can be closed to prevent helium from flowing to lower stages of the dilution refrigerator 100, and the second valve 111d can be opened to allow helium to reach the high surface area material 111a. In response to measured pressure or temperature, or in response to a timing signal generated by controller 330, the first valve 111c can be closed and the second valve 111d can be opened by controller 330.

[0082] In some embodiments, after sufficient helium has adsorbed onto the high surface area material 111 a, the second valve 111 d can be closed and the first valve 111 c can be opened. The first valve 111 c and the second valve 111 d can be opened or closed in response to measured temperature or pressure and / or in response to timing signals generated by the controller 330.

[0083] In some embodiments, when second valve 111d is closed and first valve 111c is opened, heater 111b can also be adapted to heat high surface area material 111a at the same or similar time in response to a signal generated by controller 330. For example, heater 111b can be a resistive heater adapted to heat high surface area material 111a by the flow of current through heater 111b. In response to the heat from heater 111b, helium adsorbed on high surface area material 111a can then be released from high surface area material 111a, acting as a reserve. This release of adsorbed helium can increase the pressure in the remainder of condensate line 102a, which can allow isenthalpic expansion to begin to speed up cooling of dilution refrigerator 100.

[0084] In some embodiments, once helium is released from high surface area material 111a, controller 330 can close first valve 111c, open second valve 111d, and turn off heater 111b, allowing new helium to adsorb onto high surface area material 111a. Controller 330 can be configured to open and close valves 111c, 111d periodically (e.g., at regular time intervals, at irregular time intervals, at time intervals determined by the temperature of the test volume, or at time intervals determined by the pressure of the test volume) and operate heater 111b to flush the helium intake path. In some embodiments, controller 330 can be configured to "pulse" helium from high surface area material 111a through condensate line 102a to cool the dilution refrigerator.

[0085] Returning to FIG. 1, during operation of the dilution refrigerator, condensate travels along condensate line 102a from first thermal stage 108a to mixing chamber 122. 3 He / 4 The He mixture can be gradually cooled. In a first thermal stage, the helium can be cooled initially to about 50K. 3 He / 4 After exiting the cooldown turbocharger device, the He mixture may then be cooled by a cryocooler 104. A portion of the cryocooler 104 may, in some embodiments, be partially located outside of the outer vacuum chamber 106. Vibrations may be prevented from being transmitted from the outer vacuum chamber 106 to the cryocooler 104 by a vibration isolation stage 105, which may include pads and / or any other suitable vibration isolation technique.

[0086] In some embodiments, the cryocooler 104 can be coupled to a cryocooler support 103. The cryocooler support 103 can be, for example, a compressor and / or a compression system in some embodiments. The cryocooler support 103 can include a cooling member 103a configured to provide air cooling to the dilution refrigerator 100. The cooling member 103a can be, by way of non-limiting example, cooling fins, a fan, and / or a heat pipe configured to remove waste heat generated by the cryocooler support 103 and / or the cryocooler 104.

[0087] Cooling element 103a contrasts with conventional closed-cycle dilution refrigerators, which typically rely on water cooling to remove waste heat generated by an integrated cryocooler. However, water cooling of the cryocooler requires the installation of a large and / or expensive water cooling system in conjunction with the dilution refrigerator. Furthermore, such water cooling systems are typically not integrated into commercial computing facilities, which typically rely on air cooling because they are less expensive and do not pose a risk to electronics (e.g., coolant leaks, flooding, etc.). Accordingly, the inventors have recognized that using air cooling to remove heat from a dilution refrigerator's cryocooler can reduce the cost of manufacturing dilution refrigerators and enable them to be used in commercial computing facilities.

[0088] In some embodiments, dilution refrigerator 100 can be located above a plenum (not shown) located below the floor supporting the dilution refrigerator. The plenum can supply airflow to cooling member 103a to provide air cooling. In some embodiments, cooling member 103a can include inlets and / or louvers configured to draw air from the plenum. Alternatively or additionally, in some embodiments, dilution refrigerator 100 can be located in a facility that includes piping and / or heat pipes (not shown) arranged to remove heat from cooling member 103a, cryocooler support 103, and / or cryocooler 104 and minimize vibrations experienced by dilution refrigerator 100.

[0089] In some embodiments, 3 He / 4 The He mixture can be cooled in two steps by the cryocooler 104. The condenser line 102a is 3 He / 4 It can be wrapped around the two parts of the cryocooler 104 to exchange heat between the He mixture and the cryocooler 104. In a first step, the cryocooler 104 3 He / 4 The He mixture can be cooled to about 10 K. In the second step, the cryocooler 104 3 He / 4 The He mixture can be cooled to about 3-4K.

[0090] In some embodiments, 3 He / 4After being cooled by the cryocooler 104, the He mixture can pass through the third thermal stage 108c, which in some embodiments can be thermally coupled to but mechanically decoupled from the cryocooler 104 to provide vibration isolation for subsequent thermal stages 108d-108f. As a non-limiting example, in some embodiments, the third thermal stage 108c can be mechanically decoupled from the cryocooler by a copper braid, heat strap, or other hanging component configured to maintain thermal coupling between the third thermal stage 108c and the cryocooler 104.

[0091] In some embodiments, 3 He / 4 After passing through the third thermal stage 108c, the He mixture may enter the primary impedance stage 112. The primary impedance stage 112 3 He / 4 The He mixture may be a Joule-Thomson expander configured to reduce the temperature and / or pressure of the He mixture. For example, in some embodiments, 3 He / 4 The He mixture may be at about 3-5K before entering the primary impedance stage 112 and at about 1K after leaving the primary impedance stage 112 .

[0092] In some embodiments, the primary impedance stage 112 can be a Joule-Thomson expander formed from fiber optic cable. Traditionally, Joule-Thomson expanders may be formed as metal tubes that are manufactured by drawing. However, such metal Joule-Thomson expanders may suffer from irregularities and / or have large diameters that reduce the cooling power of the device. A hollow-core fiber optic cable can reliably and reproducibly provide the narrow opening required for a Joule-Thomson expander.

[0093] In some embodiments, the dilution refrigerator 100 can include a bypass device 113a configured to increase the rate of cool-down of the dilution refrigerator 100. For example, during the initial cool-down of a dilution refrigerator, the helium flow rate may be low due to the high impedance of the Joule-Thomson expander within the dilution refrigerator and the warm, low-density, viscous circulating helium. This reduced helium flow rate slows the cooling rate of the lower portion of the refrigerator. To address this effect, conventionally, a needle valve may be installed at a location on the condensate line above the Joule-Thomson expander to initially reduce the impedance of the warm helium gas. However, needle valves include mechanical components that can fail over time. The inventors have understood and recognized that the helium flow rate can be improved without relying on mechanical components such as a needle valve.

[0094] In some embodiments, the bypass device 113a bypasses the primary impedance stage 112 along the condensation line 102a in parallel with the primary impedance stage 112 (e.g., 3 He / 4 A bypass device 113a may be disposed on a bypass line 113b (which allows the He mixture to flow around the primary impedance stage 112). The bypass device 113a may include a sheet of vacuum-compatible material configured to allow helium to diffuse through the material at temperatures above a threshold temperature value. For example, the bypass device 113a may be configured to allow helium to diffuse through the material at temperatures above a threshold temperature value within a range of approximately 40K to 300K, 50K to 300K, 80K to 300K, 100K to 300K, 150K, or any range within these ranges. 3 He / 4 The He mixture can be allowed to diffuse through the bypass device 113a. In some embodiments, the bypass device 113a can include a sheet of vacuum compatible polymeric material. For example, the bypass device 113a may be formed from a sheet of Kapton, PEEK, and / or mylar, as some non-limiting examples. Thus, the bypass device 113a can: 3He / 4 This allows the high impedance of the primary impedance stage 112 to be avoided when the He mixture is warm, thereby increasing the helium flow rate and the cooling rate of the dilution refrigerator 100. Once the dilution refrigerator 100 has cooled sufficiently (e.g., below a threshold temperature value), 3 He / 4 The He mixture will no longer diffuse through the bypass device 113 a and will instead flow through the primary impedance stage 112 .

[0095] In some embodiments, 3 He / 4 After exiting the primary impedance stage 112 or bypass device 113a, the He mixture passes through the fourth thermal stage 108d and enters the fractionator 114. The fractionator 114 receives 3 He / 4 The He mixture cools as it passes through condensate line 102a through still 114. 3 He / 4 In some embodiments, the condensate line can accommodate different mixtures of He. 3 He / 4 The He mixture can be cooled to about 400-900 mK by the still 114 .

[0096] In some embodiments, the still 114 may include a 3 The membrane can include one configured to use second sound waves to promote He evaporation. Second sound waves are a superfluid phenomenon present in superfluid helium and can be generated, for example, when a porous membrane is vibrated or a heated wire is circulated in a bath of superfluid helium. The two-fluid model dictates that superfluid helium in the mixture moves through the membrane, while non-superfluid components of the helium bath cannot pass through the porous membrane as easily. In superfluid helium, this induces enthalpy or temperature waves. Similarly, in helium mixtures, non-superfluid 3 He can be preferentially pushed by the vibrating membrane, but 4The He remains relatively stationary. We have implemented this second sound phenomenon in the still 114 to achieve a lower temperature 3 This increases the evaporation rate of He, and the vapor in the liquid helium mixture in the still 4 It was recognized and understood that the concentration of He could be reduced.

[0097] FIG. 4 illustrates a second acoustic wave effect according to some embodiments described herein. 3 He and 4 1 is a schematic diagram of a still 400 including an apparatus for separating He from the still 114 of the dilution refrigerator 100. In some embodiments, the still 400 can be implemented as the still 114 of the dilution refrigerator 100. The still 400 can include a fixed surface 402 and a porous movable membrane 404. The porous membrane 404 can be vibrated along the Z direction to separate He from the still 400. 3 This causes a standing concentration wave of He. 3 The low He concentration region 406 and 3 A region 408 with a high He concentration can be formed. 3 The He-rich region 408 can be arranged to be located adjacent to the outlet of the still, thereby 3 The purification of He can be improved.

[0098] Returning to FIG. 1, in some embodiments, 3 He / 4 After exiting the still 114, the He mixture can flow through a condensate line 102a to a secondary impedance stage 116. The secondary impedance stage 116 is a liquid 3 He / 4 The secondary impedance stage 116 can be configured to ensure that only He passes further downstream in the dilution refrigerator 100 and that gas cavitation within the still 114 does not occur (e.g., by maintaining a threshold pressure within the still 114). 3 He / 4 The downstream cooling load due to the latent heat of He can be reduced.

[0099] In some embodiments, 3 He / 4 After exiting the secondary impedance stage 116, the He mixture can flow into a first heat exchanger 118. The first heat exchanger 118 can be a series-type heat exchanger. For example, the first heat exchanger 118 can be a counterflow heat exchanger (e.g., a tube-tube heat exchanger), a cross counterflow heat exchanger, and / or a parallel flow heat exchanger. At the outlet of the first heat exchanger 118, the He mixture in the condensation line 102a 3 He / 4 The He mixture can be cooled to a temperature of about 20 mK.

[0100] In conventional closed-cycle dilution refrigerators, 3 He / 4 Before entering the still, the He mixture must typically pass through a first impedance stage, which typically acts as a separate refrigeration stage known as a Joule-Thomson refrigerator, where: 3 He / 4 The He mixture is cooled by isenthalpic expansion. 3 He / 4 In order to control the cooling power due to the expansion of the He mixture, 3 He / 4 The pressure of the He mixture is typically increased by an external compressor.

[0101] Before entering the first impedance stage, the inventors 3 He / 4 By reducing the temperature of the He mixture, a lower pressure differential can be used while achieving the same cooling effect (e.g., 3 He / 4 It has been recognized and understood that a He mixture can reach the same base temperature after passing through the first impedance stage. Such a configuration improves the efficiency of the dilution refrigerator and allows for the 3 He / 4The need to pressurize the He mixture can be reduced or eliminated. Furthermore, the inventors have found that prior to the first impedance stage 3 He / 4 The heat removed from the He mixture can be returned to the still, thereby reducing the amount of heat present in the still. 3 He / 4 It has been recognized that the need for an auxiliary heater in the still to increase the vapor pressure of the He mixture and enable its evaporation can be eliminated or reduced.

[0102] Thus, in some embodiments, the dilution refrigerator 100 can include a heat exchange line 117 configured to transfer heat from the incoming condensate line 102a to the returning helium mixture being transported from the first heat exchanger 118 to the still 114. The heat exchange line 117 can cool the condensate line 102a at a location above the primary impedance stage 112. The heat exchange line 117 can then cool the condensate line 102a at a location above the primary impedance stage 112. The heat exchange line 117 can then cool the condensate line 102a at a location above the primary impedance stage 112. 3 He / 4 The He mixture is cooled, and then the increased temperature mixture in the heat exchange line 117 is transported to the still 114.

[0103] coming in 3 He / 4 By cooling the He mixture before it enters the primary impedance stage 112, the primary impedance stage 112 will be in a liquid state rather than a vapor state. 3 High proportion of He 3 He / 4 The primary impedance stage 112 exhausts the circulating helium mixture. Thus, the inclusion of the additional heat exchange line 117 can make the primary impedance stage 112 more efficient. Furthermore, this increased efficiency can eliminate or reduce the need for auxiliary pressure (e.g., an external compressor) and lower the flow impedance of the circulating helium mixture. This is particularly useful for reducing the complexity and size of smaller dilution refrigerators, including smaller (i.e., lower power) pulse tubes or other cryocoolers.

[0104] In some embodiments, 3 He / 4 After exiting the first heat exchanger 118, the He mixture passes through the fifth thermal stage 108e and enters the continuous heat exchanger 119. The continuous heat exchanger 119 can be a countercurrent heat exchanger (e.g., a tube-in-tube heat exchanger), a cross-countercurrent heat exchanger, and / or a parallel-flow heat exchanger. The continuous heat exchanger 119 is disposed below the fifth thermal stage 108e. The fifth thermal stage 108e can be an intermediate cold plate (ICP) configured to be cooled to a temperature of approximately 100-200 mK. Continuous heat exchangers are typically more efficient than split-type heat exchangers, but their efficiency decreases below a temperature of approximately 80 mK. However, adding the continuous heat exchanger 119 below the fifth thermal stage 108e can allow the fifth thermal stage 108e to operate at a greater cooling power during the process of cooling the dilution refrigerator.

[0105] In some embodiments, 3 He / 4 After exiting the continuous heat exchanger 119, the He mixture enters the separated heat exchanger 120. The separated heat exchanger 120 may, in some embodiments, be formed of sintered nanoparticles. Alternatively or additionally, in some embodiments, the separated heat exchanger 120 may be formed of sintered nanowires, as described herein with respect to Figures 7A-7D. The separated heat exchanger 120 may: 3 He / 4 The He mixture can be further cooled to a temperature below about 10-20 mK.

[0106] The inventors further recognized and appreciated that the user experience could be improved by allowing a user to easily replace parts of the dilution refrigerator 100 (e.g., for maintenance, to change the characteristics of the dilution refrigerator 100, and / or to upgrade the dilution refrigerator 100 as technological innovations are developed). The inventors have accordingly developed a replaceable dilution insert that is easily removed and replaced. Figure 5A shows exemplary components of a removable dilution insert 540 for the dilution refrigerator 100 of Figure 1 according to certain embodiments described herein.

[0107] In some embodiments, the removable diluate insert 540 includes removable plates 540a, 540b, and 540c that are removably coupled to thermal stages 108d, 108e, and 108f, respectively. As shown in the example of FIG. 5A, the removable plates 540a, 540b, and 540c can be removably coupled using mechanical fasteners (e.g., bolts and / or screws). In some embodiments, the removable diluate insert 540 further includes a removable connection 540d to the condensate line 102a above the still (e.g., a flange) to further simplify replacement of the removable diluate insert 540.

[0108] 5B is a detailed view of the removable plate 540b of the removable dilution insert of FIG. 5A, according to some embodiments described herein. The removable plate 540b, in some embodiments, includes an inlet A and an outlet B that allow helium to flow through the removable plate 540b.

[0109] In some embodiments, the removable plates 540a, 540b, and / or 540c can include an integrated heat exchanger. In some embodiments, the integrated heat exchanger can be a channel 542 formed in the removable plates 540a and / or 540b, as shown by example in FIG. 5C , which shows a cross section through the removable plate 540b of FIG. 5B . The channel 542 can be configured to have a high surface area. By allowing helium to flow through the channels 542 in the removable plates 540a and / or 540b, the cooling rate of the helium can be increased. In some embodiments, the channel 542 can be formed by machining, welding, and / or by additive manufacturing techniques (e.g., three-dimensional printing techniques).

[0110] In some embodiments, the integrated heat exchanger may be a high surface area material structure formed on the removable plate 540c. For example, the integrated heat exchanger may be a lattice structure, as shown in the example of FIG. 5D. The lattice structure may be, by way of non-limiting example, a square lattice structure having a periodicity ranging from about 400 μm to about 1000 μm. For example, the lattice structure may have a periodicity of about 600 μm.

[0111] In some embodiments, the lattice structure can be fabricated using additive manufacturing techniques (e.g., three-dimensional printing techniques). The lattice structure can be fabricated with a rough surface texture to increase the surface area of ​​the material in contact with the helium mixture passing through the integrated heat exchanger, thereby improving heat exchange. In some embodiments, the lattice structure can be formed of a metal. As non-limiting examples, the lattice structure may be formed of copper, silver, and / or aluminum.

[0112] In some embodiments, the dilution insert 540 can include one or more heat exchangers, as described in connection with the dilution refrigerator 100 of Figure 1. Figure 5E shows an exemplary implementation of the series heat exchanger 119 and the separated heat exchanger 120, according to some embodiments described herein. As shown in Figure 5E, helium flows from a removable plate 540b coupled to the fifth thermal stage 108e into the series heat exchanger 119, and then into the separated heat exchanger 120 and removable plate 540c.

[0113] The refrigeration cycle of a cryocooler typically uses a method to control the flow of heat throughout the system. This control can be achieved using superconductors, gas gaps, or other mechanisms (i.e., heat switches) that thermally connect or disconnect components within the system. One common type of heat switch, the gas gap, typically contains two high-surface-area objects with a small gap between them that is filled with gas. When the system drops below a certain temperature, the conductive gas adsorbs to the surface area of ​​the heat switch, creating a vacuum and reducing heat transfer between the surfaces. Another common type of heat switch is the superconducting switch, in which a material passes through a superconducting transition, reducing its thermal conductivity.

[0114] In some embodiments, dilution refrigerator 100 can further include a composite gas gap and / or superconducting heat switch between thermal stages of dilution refrigerator 100. The example in Figure 5E shows such a composite gas gap and superconducting heat switch 550 thermally coupled between thermal stage 108e and thermal stage 108f. Composite gas gap and superconducting heat switch 550 includes both a superconducting material (e.g., aluminum, titanium) that becomes superconducting at a temperature higher than the target temperature of the thermally coupled thermal stage, and a gas gap heat switch that facilitates thermal insulation between the thermal stages.

[0115] Returning to Figure 1, 3 He / 4After exiting the split heat exchanger 120, the He mixture passes through the sixth thermal stage 108f and enters the mixing chamber 122. In the mixing chamber 122: 3 Pumping He atoms from the dense phase to the dilute phase (i.e., 4 He) can be mixed with this. 3 The He is cooled as it passes through a phase transition from a dense phase to a dilute phase, and this endothermic phase transition provides the final cooling power of the dilution refrigerator 100.

[0116] In some embodiments, a test volume 124 (e.g., a sample stage or plate) can be thermally coupled to the mixing chamber 122 and configured to support the sample and / or quantum device. Because the test volume 124 is thermally coupled to the mixing chamber 122, the sample and / or quantum device can be maintained at or near the temperature of the mixing chamber.

[0117] In some embodiments, when dilution refrigerator 100 is not in operation, a user can access test volume 124 through an opening in vacuum chamber 106 and door 125. Door 125, in some embodiments, may be a removable panel (e.g., secured with mechanical fasteners) or may be a hinged door that a user can open using a clamping handle (e.g., as shown in the example of FIG. 10A herein).

[0118] As shown in the example of FIG. 1, some components of the dilution refrigerator 100 may be thermally coupled to a thermal stage and may be located on one side (e.g., above or below) of the thermal stage. For example, the still 114 is shown as being located on the underside of the fourth thermal stage 108d. It should be understood that in some embodiments, such components may be located on either side of the associated thermal stage, as aspects of the technology described herein are not limited in this respect. For example, in some embodiments, the still 114 may be located on the top side of the fourth thermal stage 108d. As another example, in some embodiments, the helium scrubber 110 may be located on the underside of the first thermal stage 108a.

[0119] In some embodiments, 3 He / 4 After the He mixture enters the dilute phase, it can be pumped out of the mixing chamber 122, back through the dilution refrigerator 100, and out the outer vacuum chamber 106 through return line 102b. At low temperatures and pressures, 4 He forms a thick, mobile film that can move long distances across the surface, including against gravity. This helium crawling results in: 4 6A-6F show exemplary He dilution refrigeration systems that may be implemented, for example, at the outlet of mixing chamber 122 and / or still 114, according to some embodiments described herein. 4 FIG. 1 is a schematic diagram of a He separation device.

[0120] FIG. 6A illustrates a dilute phase helium mixture (e.g., 3 He / 4 6 shows a cooling stage 600 (e.g., still, mixing chamber, etc.) containing a bath 602 of helium (a mixture of helium and argon). Unless a barrier 606 prevents helium from creeping up, 4 He can creep up into the outlet pipes (e.g., still pump outlet pipe, mixing chamber outlet pipe) and exit cooling stage 600. In the example of Figure 6A, barrier 606 includes sharp edges on right-angled surfaces configured to prevent helium from exiting cooling stage 600 through the low-pressure pump outlet.

[0121] In the examples of Figures 6B, 6D and 6E, 4 Another embodiment of a barrier configured to prevent He creep-up is shown in Figure 6B. In the example of Figure 6B, a ring 608 with a knife edge 609 4 He 3 In some embodiments, the ring 608 is configured to prevent the He from exiting the outlet. 4A heating device (e.g., a resistive heater or any other suitable heater) may be included that is configured to cause the He to leave the superfluid phase, thereby mitigating creep-up.

[0122] In the examples of FIGS. 6C, 6D, and 6E, 4 He 3 A vertical knife edge is used to prevent He from exiting the outlet. In some embodiments, in the example of Figure 6C, knife edge 610 is on the outer periphery of the outlet pipe. Alternatively, knife edge 611 may be chamfered on the inner periphery of the outlet pipe, as shown in the example of Figure 6D. Furthermore, knife edge 612 may be chamfered on both the outer and inner periphery of the outlet pipe, as shown in the example of Figure 6E.

[0123] In some embodiments, as shown in the example of FIG. 6F: 3 The He outlet can include a P-trap 621, which can include: 4 It is configured to collect He 622 on the lower surface of the P trap 621. 3 The He outlet is either normal or superfluid. 4 A normal leak or super leak 624 configured to allow He to exit the P-trap 621 may be included, and a pump 626 (e.g., a fountain pump) may be included to 4 He can be transported away from the P-trap 621. In some embodiments, there may be an additional barrier 627 on the inner surface of the outlet pipe. For example, the barrier 627 may be configured as a ring. In some embodiments, the barrier 627 may be 4 A heating device may be included to further prevent He from escaping through the outlet.

[0124] The present inventors have recognized and appreciated that nanomaterials can offer advantages over conventional sintered metal powders (e.g., silver and / or copper powders) used in typical split-type heat exchangers. Accordingly, the present inventors have developed a nanomaterial heat exchanger that provides efficient heat exchange due to the large surface area, high mechanical contact strength, and good neck growth between nanowires of nanomaterials.

[0125] Typical split-type heat exchangers are generally made from sintered metal powders (e.g., silver and / or copper powders). Figure 7A shows an example of such sintered particulates. However, to achieve efficient heat exchange at sub-Kelvin temperatures, many factors must be correct regarding the heat exchanger material. The heat exchange material should have a large surface area, provide good mechanical and / or thermal contact between the liquid helium and the heat exchange material, allow for good neck growth, and provide space within the heat exchange material for the liquid helium to move through the heat exchanger.

[0126] FIG. 7B shows an image of nanomaterials including nanowires used in a heat exchanger. FIG. 7C shows an image of nanomaterials including nanoclusters used in a heat exchanger. FIG. 7D shows an image of nanomaterials including different example nanopellet shapes used in a heat exchanger according to some embodiments described herein. These nanomaterials can be implemented in the dilution refrigerator 100 within the separate heat exchanger 120 and / or within a block heat exchanger (e.g., present in the mixing chamber 122). While FIGS. 7B-7D show example nanomaterial shapes, it should be understood that the nanomaterial embodiments used in the separate heat exchanger are not so limited. For example, the nanomaterials may alternatively be nanofoams, nanotubes, and / or any other suitable nanoshapes.

[0127] In some embodiments, such nanomaterial-based heat exchangers can be formed by joining nanomaterials by sintering. For example, the nanomaterials can be formed as chemical precipitation and / or by electro-deposition or electroplating techniques. A substrate having a rough surface (e.g., containing nucleation sites) can be provided for growing or attaching the nanomaterials. In some embodiments, the heat exchanger can be fabricated under heat and / or compression. The nanomaterials can be held in a compressed state during the sintering process to form a nanowire heat exchanger. In some embodiments, the substrate can be patterned with macroscopic structures (e.g., a lattice or a series of posts). In some embodiments, the substrate can be a tube, and the nanomaterials can be attached to the interior or exterior surface of the tube. In some embodiments, the substrate can be formed of a material having a lower thermal conductivity than the nanomaterials attached to the substrate.

[0128] In some embodiments, the nanomaterial may be formed from one of a selection of vacuum-compatible materials, including, but not limited to, copper, silver, vacuum-compatible polymers, carbon, and / or carbon fiber. For example, the nanomaterial may be a nanowire, including at least one of copper nanowires, silver nanowires, gold nanowires, platinum nanowires, polymer nanowires, carbon nanowires, and / or carbon fiber nanowires.

[0129] II. Improved vibration isolation Many tests performed at sub-Kelvin temperatures are susceptible to vibration noise from both the ambient environment and the dilution refrigerator's cooling system pumps and components. Furthermore, at sub-Kelvin temperatures, mechanical vibrations can create thermal loads, reduce the cooling power of the dilution refrigerator, or generate triboelectric noise at the dilution refrigerator's electrical input and / or output. The inventors have recognized and appreciated that improving vibration isolation can improve the cooling power and other performance characteristics (e.g., magnetic flux disturbance) of the dilution refrigerator. Accordingly, the inventors have developed vibration isolation components configured to mechanically decouple the lower thermal stages 108d-108f from the upper thermal stages 108a-108c.

[0130] 8A shows another schematic diagram of a dilution refrigerator 100 including mechanical elements configured to provide vibration isolation, according to some embodiments described herein. The vibration isolation elements include a first suspension system 832, at least one second suspension system 840, and a third suspension system 834.

[0131] In some embodiments, the first suspension system 832 can be configured to suspend the first thermal stage 108a, the second thermal stage 108b, and / or the third thermal stage 108c from the top surface of the outer vacuum chamber 106. The first suspension system 832 can include one or more rods configured to rigidly couple the first, second, and / or third thermal stages 108a-108c to the top surface of the outer vacuum chamber 106. The rods can be formed of a material having a high spring constant. For example, the rods can be formed of carbon fiber and / or stainless steel.

[0132] In some embodiments, the second suspension system 840 can be configured to independently suspend the fourth thermal stage 108d, the fifth thermal stage 108e, and / or the sixth thermal stage 108f from the top surface of the outer vacuum chamber 106. This independent suspension of the lower thermal stages 108d-108f prevents vibrations from being transmitted from the upper thermal stages 108a-108c to the lower thermal stages 108d-108f, thereby improving vibration isolation of the lower thermal stages 108d-108f.

[0133] In some embodiments, the second suspension system 840 can include one or more springs 842, rods 843, and / or connectors 844. While the example of Figure 8A shows only one second suspension system 840, it should be appreciated that in some embodiments, multiple second suspension systems 840 can be used to suspend the lower thermal stages 108d-108f. For example, in some embodiments, there can be two, three, or four such second suspension systems 840.

[0134] In some embodiments, spring 842 can be configured to provide a constant spring tension under different loads (e.g., for different damping masses hanging from spring 842). An example of spring 842 is shown in FIG. 8B. Spring 842, in some embodiments, can be a suspension leaf spring and can include an upper flexure 842a separated from a lower flexure 842b by a rigid portion 842c. Spring 842 can flex due to the deflections of upper flexure 842a and lower flexure 842b to provide vibration isolation to lower thermal stages 108d-108f along the Z axis (e.g., perpendicular to the plane of the floor supporting dilution refrigerator 100). In some embodiments, the spring constant of spring 842 can be determined by pretensioning upper flexure 842a and / or lower flexure 842b. Alternatively or additionally, the spring constant of spring 842 may be determined by varying the length of upper flexure 842a and / or lower flexure 842b (e.g., longer lengths of flexures 842a, 842b have lower spring constants).

[0135] In some embodiments, spring 842 can be connected to third thermal stage 108d by rod 843. Rod 843 can be a flexible rod having a low spring constant. For example, in some embodiments, rod 843 can be formed from a polymer (e.g., Delrin). Due to its flexibility, rod 843 can provide vibration isolation for lower thermal stages 108d-108f in the XY plane (e.g., in a plane parallel to the plane of the floor supporting dilution refrigerator 100 and perpendicular to the Z axis).

[0136] In some embodiments, the connectors 844 can be arranged in a triangular configuration to provide stability to the suspension of the fourth thermal stage 108d. The connectors 844 can be made from a material configured to have a high spring constant. For example, the connectors 844 may be formed from stainless steel and / or carbon fiber.

[0137] In some embodiments, the third suspension system 834 can be configured to suspend the fourth thermal stage 108d through the fifth thermal stage 108e and the sixth thermal stage 108f. In this manner, all three lower thermal stages 108d-108f can be suspended from the top surface of the vacuum chamber 106 using the second suspension system 840. The third suspension system 834 can include one or more rods configured to rigidly couple the fifth thermal stage 108e and / or the sixth thermal stage 108f to the fourth thermal stage 108d. The rods can be formed of a material having a high spring constant. For example, the rods can be formed of carbon fiber and / or stainless steel in some embodiments.

[0138] 8A shows first suspension system 832 and third suspension system 834 as being formed from rods, it should be understood that in some embodiments, first suspension system 832 and / or third suspension system 834 may be formed from flexible springs, as aspects of the present disclosure are not limited in this respect. Additionally, while the example of FIG. 8A shows second suspension system 840 as being formed from springs, it should be understood that in some embodiments, second suspension system 840 may be formed from rods, as aspects of the present disclosure are not limited in this respect.

[0139] III. Integrated dilution refrigerator Conventional dilution refrigerator technologies often require large spaces and expensive supporting infrastructure, such as custom floating foundations, high ceilings, and / or access holes. These infrastructure requirements can reduce the scalability of quantum technologies that operate at low temperatures. As a non-limiting example, the adoption of some quantum computing technologies can be limited by the need for large dilution refrigerators. The inventors have recognized and appreciated that reducing the size and infrastructure requirements of dilution refrigerators can enable the scalability of quantum technologies. The inventors have further recognized that integrating dilution refrigerators with commercial computing infrastructure (e.g., commercial server infrastructure) can further enable the scalability of dilution refrigerators and associated quantum technologies that rely on them. Such integrated dilution refrigerators can be more easily integrated into telecommunications networks, can use existing telecommunications heat rejection architectures, and can be integrated with fiber optic networks and systems.

[0140] Figure 9 is a side view of an exemplary external support rack 950, according to some embodiments described herein. In some embodiments, the external support rack 950 can support the dilution refrigerator 100 by suspending the dilution refrigerator 100 from the floor below the dilution refrigerator 100. As shown in the example of Figure 9, the external support rack 950 can include arms 952 coupled to a portion of the top surface of the vacuum chamber 106 by vibration isolation components 954 to suspend the dilution refrigerator 100 from the floor. In some embodiments, the vibration isolation components 954 can be air pistons, electromagnetic dampers, and / or springs.

[0141] In some embodiments, the external support rack 950 can include casters (not shown) configured to aid in transporting the dilution refrigerator 100. The casters can be retractable so that the caster wheels do not contact the floor supporting the external support rack 950 when the dilution refrigerator 100 is not being transported and / or is in operation.

[0142] In some embodiments, the external support rack 950 further includes floor supports 958. The floor supports 958 can be configured to extend from the external support rack 950 when the dilution refrigerator 100 is not being transported. The floor supports 958 can extend from the external support rack 950 using, for example, screws. The floor supports 958 can be used to lift and / or level the external support rack 950 off the floor and / or to lift the casters of the external support rack 950 off the floor. In some embodiments, the floor supports 958 can be used to correct the positioning of the external support rack 950 in the case of an uneven floor surface.

[0143] In some embodiments, external support rack 950 can support additional components that are external to outer vacuum chamber 106 of dilution refrigerator 100. For example, external support rack 950 can house compressors, pumps, and / or cooling equipment configured to support operation of dilution refrigerator 100. Alternatively, these external components may be housed in a server rack-type container and / or support rack 950 adjacent to (e.g., distinct from) dilution refrigerator 100 in some embodiments.

[0144] In some embodiments, the external support rack 950 can include elements configured to provide tool-less assembly and / or disassembly of the vacuum chamber 106 and access to the test volume according to some embodiments described herein. As shown in the example of Figure 9, the vacuum chamber 106 includes three sections: a first section 106a, a second section 106b suspended from the first section 106a, and a third section 106c suspended from the second section 106b. It should be understood that the techniques described herein are not limited to three sections, and that the vacuum chamber may have one, two, four, five, or six sections in some embodiments.

[0145] In some embodiments, the vacuum chamber 106 can have one or more substantially planar surfaces. In some embodiments, at least one of the one or more substantially planar surfaces can be disposed in a plane perpendicular to the plane of the floor supporting the dilution refrigerator. As shown in the example of FIG. 9 , the sections 106a-106c can each have at least four substantially planar surfaces such that, when assembled, the vacuum chamber 106 forms a rectangular parallelepiped. In some embodiments, the vacuum chamber 106 can include two substantially planar surfaces disposed in a plane parallel to the plane of the floor and arranged to close the rectangular parallelepiped formed by the surfaces of the sections 106a-106c. In some embodiments, the vacuum chamber 106 can have an opening in at least one of the substantially planar surfaces accessible by a door 1070, as described below.

[0146] In some embodiments, the three sections 106a-106c of the vacuum chamber 106 may be partially or completely removable to provide access to the interior portions of the dilution refrigerator 100. For example, the three sections 106a-106c of the vacuum chamber 106 may, in some embodiments, include removable panels (e.g., side panels, panels attached to a frame, etc.). The three sections 106a-106c may be configured to allow a user of the dilution refrigerator 100 to remove the vacuum chamber 106 from the dilution refrigerator 100 without requiring large clearances above and below the dilution refrigerator 100 (e.g., without requiring a high ceiling or a hole below the dilution refrigerator 100).

[0147] In some embodiments, the external support rack 950 can include an integrated lift 956a configured to support the three sections 106a-106c of the vacuum chamber during assembly, disassembly, and / or maintenance of the dilution refrigerator 100. The integrated lift 956a can be configured to raise and / or lower the sections 106a-106c of the vacuum chamber. For example, the integrated lift 956a can be configured to raise and / or lower an arm 956b configured to support portions (e.g., flanges) of the three sections 106a-106c. In some embodiments, the integrated lift 956a can be manually operated (e.g., using screws and / or cables). In some embodiments, the integrated lift 956a can be operated using a powered machine (e.g., pneumatic or hydraulic).

[0148] In some embodiments, the external support rack 950 can include one or more carts 957. The cart 957 can be configured to receive one or more of the sections 106a-106c when lowered, either manually or by using an integrated lift 956a. For example, the integrated lift 956a can be used to lower the third section 106c onto the cart 957. The cart 957 can then be used to transport the third section 106c along direction C to provide a user of the dilution refrigerator 100 with space below the internal components of the dilution refrigerator 100.

[0149] In some embodiments, the integrated lift 956a can be removably coupled to the external support rack 950. For example, the integrated lift 956a can be slidably removable (e.g., slides horizontally outward along direction C) from the external support rack 950. Removal of the integrated lift 956a may be desired to provide extra space for a user (e.g., during maintenance of the dilution refrigerator 100).

[0150] In some embodiments, the three sections 106a-106c of the vacuum chamber 106 can be suspended from one another by integral clamps and / or cams. These integral clamps and / or cams can be configured to allow a user to loosen or tighten two of the three sections 106a-106c together without using any additional tools. Figures 10A-10C show an example of an integral cam 1060, with Figure 10B showing the integral cam 1060 in an open position and Figure 10C showing the integral cam 1060 in a closed position.

[0151] In some embodiments, the integrated cam 1060 includes a handle 1062 that allows a user to clamp two of the three sections 106a-c together or loosen them apart. The handle 1062 is connected to two latches 1064 that are configured to connect to a bar 1066. The handle 1062 and latches 1064 are hingedly connected to a section of the vacuum chamber 106 by a cam 1068, which provides the necessary range of motion to perform the clamping and loosening actions.

[0152] In some embodiments, compression layers can be included at the connection points between the three sections 106a-106c of the vacuum chamber 106 to ensure a proper vacuum-safe seal. For example, rubber O-rings, copper or indium gaskets, or other vacuum-safe compression layers can be placed between the sections 106a-106c.

[0153] Returning to FIG. 10A , in some embodiments, the vacuum chamber 106 can include an external opening that provides access to an internal volume within the dilution refrigerator 100. For example, the opening can provide access to a sample stage or test volume of the dilution refrigerator 100, or any other internal portion of the dilution refrigerator 100. In some embodiments, the opening can be sealed by a hermetic seal. In some embodiments, the opening can be sealed by a door 1070, as shown in the example of FIG. 10A . The door 1070 can be sealed using, for example, hinges and / or clamps that can be manually engaged and disengaged. In some embodiments, the door 1070 can be coupled to the opening by a load lock.

[0154] In some embodiments, door 1070 may provide access through all of an inner radiation shield (not shown) (which may be thermally coupled to one or more of thermal stages 108a-108f) of dilution refrigerator 100, allowing a user to access the test volume. For example, a portion of the inner radiation shield (not shown) may be coupled to door 1070 such that when a user opens door 1070, the inner radiation shield slides or otherwise moves to provide the user access to the interior portion of the dilution refrigerator. In some embodiments, a portion of the inner radiation shield may be removable and / or slidable through door 1070.

[0155] In some embodiments, the external support rack 950 can be configured to integrate with a server rack-type container. For example, the external support rack 950 may be configured to integrate the dilution refrigerator 100 with a commercially available server rack infrastructure (e.g., a server rack). In some embodiments, the external support rack 950 may be configured to integrate the dilution refrigerator 100 with a 19-inch (48.26 centimeter) server rack.

[0156] In some embodiments, the external support rack 950 and the dilution refrigerator 100 can be housed within an outer housing. FIG. 11 shows an example of an outer housing 1100. In some embodiments, the outer housing 1100 can include an integrated horizontal surface 1110. For example, the integrated horizontal surface 1110 can be used as a desk or support surface when a user interacts with the dilution refrigerator. The integrated horizontal surface 1110 can be configured to be stored by folding or sliding when not in use (as shown in the example of FIG. 11). In some embodiments, the outer housing 1100 can further include one or more storage locations (e.g., drawers, shelves) for storing related parts and / or tools for maintenance of the dilution refrigerator 100.

[0157] In some embodiments, outer housing 1100 can further include a door 1125 that provides access to the test volume of dilution refrigerator 100 through opening 1120. For example, door 1125 can open to provide access to the test volume through vacuum chamber 106 and a radiation shield inside vacuum chamber 106. In some embodiments, the vacuum chamber exterior and / or the radiation shield can be coupled to door 1125 such that a user can open vacuum chamber exterior 106 and / or the radiation shield when door 1125 is opened. In some embodiments, the radiation shield can alternatively be slidably and / or hingedly movable so that a user can move the radiation shield so that it no longer obstructs access to the test volume, as needed.

[0158] In some embodiments, the housing 1100 can be further configured to provide sound attenuation. For example, the housing 1100 can include sound-deadening material to provide passive sound attenuation. Alternatively, or in addition, the housing 1100 can include audio equipment (e.g., speakers) configured to provide active sound attenuation through the emission of destructive interference of sounds generated by functional components of the system.

[0159] IV. Reverse Dilution Refrigerator Traditionally, dilution refrigerators are designed with the hotter thermal stage positioned towards the top of the system. 3 He / 4 The thermal stages are oriented to become progressively cooler as the He mixture advances to the bottom of the dilution refrigerator. The inventors recognized and appreciated that an inverted configuration, in which the coldest stage is located at the top of the system (e.g., furthest from the floor), can simplify operation and use of the dilution refrigerator by making the test volume more accessible to the user and can provide improved thermodynamic quality compared to conventional dilution refrigerators. Accordingly, the inventors developed an inverted dry dilution refrigerator.

[0160] 12A is a schematic diagram of an inverting dilution refrigerator 1200 according to some embodiments described herein. 3 He / 4 The inverted dilution refrigerator 1200 can include a pump system 1202 configured to circulate the He mixture. The inverted dilution refrigerator 1200 can also include a cryocooler 1204. The cryocooler can be coupled to a cryocooler support (not shown), as described herein with reference to the cryocooler support 103.

[0161] In some embodiments, the inverted dilution refrigerator 1200 can include an outer vacuum chamber 1206 and a series of thermal stages 1208a-1208f disposed within the outer vacuum chamber 1206. The series of thermal stages 1208a-1208f can be maintained at the same or similar temperatures as the thermal stages 108a-108f described herein in connection with FIG.

[0162] In some embodiments, inverted dilution refrigerator 1200 may include an opening in outer vacuum chamber 1206 and / or through the inner radiation shield to facilitate access to the coldest stage of inverted dilution refrigerator 1200. In some embodiments, the opening may include a hermetic seal and / or an opening mechanism 1225 that can withstand the vacuum in the outer vacuum chamber when inverted dilution refrigerator 1200 is in operation. For example, opening mechanism 1225 may include a hinged door and / or a removable panel.

[0163] In some embodiments, the inverted dilution refrigerator 1200 can include multiple components arranged along the length of the dilution refrigerator (e.g., from within the vacuum chamber 1206 to within the sixth thermal stage 1208f). The components can be arranged such that the coldest thermal stage, the mixing chamber 1222, is located above the warmer thermal stages (e.g., still 1214, impedance stages 1212 and 1216, heat exchangers 1218, 1219, 1220, etc.).

[0164] In some embodiments, the reversing dilution refrigerator 1200 includes a demixing chamber 1224 coupled to the mixing chamber 1222. In some embodiments, the demixing chamber 1224 may be thermally coupled to the mixing chamber 1222 by a heat exchanger 1223 (e.g., a parallel flow heat exchanger). The demixing chamber 1224 3 The demixing chamber 1224 may be fluidly connected to the mixing chamber 1222 to transport He from the demixing chamber 1224 to the mixing chamber 1222, providing additional cooling to the mixing chamber 1222. The demixing chamber 1224 may further include a flow channel for absorbing He from the still 1214 and the mixing chamber 1222 to reduce the concentration gradient formed between the still 1214 and the mixing chamber 1222. 4 He is injected into the demixing chamber 1224. 3 He and 4 A parallel flow of He can be provided.

[0165] 12B and 12C are schematic diagrams of exemplary internal components of an inverting dilution refrigerator, according to some embodiments described herein. It should be understood that the exemplary components of Figures 12B and 12C can be implemented within the inverting dilution refrigerator 1200 of Figure 12A (e.g., within the third thermal stage 1208c).

[0166] As shown in the example of FIG. 12B, in some embodiments, the inverting dilution refrigerator: 4 configured to transport He from the still 1214 to the demixing chamber 1224. 4 In some embodiments, a He line 1226 may be included. 4 He line 1226 4 A pump 1228 configured to assist in transporting the He to the demixing chamber 1224 may be included. The pump 1228 may, in some embodiments, be a fountain pump, for example. Alternatively or additionally, 4 The He line 1226 is connected to the demixing chamber 1224. 4 An additional heat exchanger may be included to cool the He.

[0167] As shown in the example of FIG. 12C, in some embodiments, the inverting dilution refrigerator includes an inlet impedance stage 1212 before the primary impedance stage 1212. 3 He / 4 1, a heat exchange stage 1230 configured to cool the He mixture may be included. As should be understood from the description of FIG. 1, such a configuration may improve the efficiency of the first impedance stage and / or reduce the amount of incoming He. 3 He / 4 The need for pressurization of the He mixture can be eliminated or reduced.

[0168] V. Distributed cooling Dilution refrigerators generally have the following features: 3 He / 4The dilution refrigerator includes an integrated cryocooler (e.g., a pulse tube or Gifford-McMahon cryocooler) for pre-cooling the He gas mixture to below 5 K. Traditionally, one dilution refrigerator is paired with at least one of these cryocoolers, and the dilution refrigerators do not share a cooling system. These small-scale dilution refrigerator systems typically rely on low-power cryocoolers that are relatively inefficient (e.g., requiring more electrical power per watt of cooling power at 4 K) compared to larger, more powerful cryocoolers. The inventors have recognized and appreciated that a single high-efficiency cooling system can be thermally coupled to multiple cryocooler systems, such as dilution refrigerators, to distribute this first-stage cooling across multiple cryocooler systems. Thus, this distributed cooling can improve cooling efficiency across multiple cryocooler systems.

[0169] 13 is a schematic diagram of a distributed cooling system 1300 according to some embodiments described herein. The distributed cooling system 1300 can include multiple housings 1305. In some embodiments, the housings 1305 can be server rack-type containers (e.g., commercially available server rack infrastructure, 19-inch (48.26 centimeter) server racks).

[0170] 13, each housing 1305 can include a cooling system 1310 or a cryogenic device 1320. It should be understood that in some embodiments, the cryogenic devices 1320 and / or the cooling systems 1310 can be grouped within the housing 1305. While FIG. 13 shows three cryogenic devices 1320 coupled to the cooling system 1310, it should be further understood that in some embodiments, there can be two, four, ten, or even dozens of cryogenic devices 1320 coupled to the cooling system 1310, as aspects of the present disclosure are not so limited.

[0171] In some embodiments, the cooling system 1310 can be a cryogenic cooling system configured to cool the first stage of the cryogenic device 1320 to a temperature of at least 5 K and / or to a temperature of about 4-5 K. In some embodiments, the cooling system 1310 can be a pulse tube. For example, the cooling system 1310 can be a pulse tube, a helium liquefaction system, and / or a Brayton cryocooler.

[0172] In some embodiments, cooling system 1310 can be thermally coupled to multiple cryogenic devices 1320. Cooling can be distributed from cooling system 1310 to cryogenic devices 1320 by cooling lines 1312. Additionally, heat can be returned from cryogenic devices 1320 to the cooling system by return lines 1314. Cooling lines 1312 and / or return lines 1314 can be lines configured to transport liquid and / or gaseous helium. For example, cooling lines 1312 and / or return lines 1314 can be vacuum-insulated pipes to maintain the temperature of the transported helium. In some embodiments, cooling lines 1312 and / or return lines 1314 can be fill lines, heat pipes (e.g., conventional heat pipes and / or oscillating heat pipes), and / or superfluid loops.

[0173] In some embodiments, cryogenic device 1320 may comprise any suitable refrigeration system configured to reach temperatures of 5 K or less. In some embodiments, cryogenic device 1320 may comprise one or more dilution refrigerators (e.g., dilution refrigerator 100 described herein configured to reach temperatures below 1 K). Alternatively or additionally, cryogenic device 1320 may comprise a cryogenic system other than a dilution refrigerator (e.g., a microscope system, such as a scanning tunneling microscope or an atomic force microscope system, 3 It should be understood that the present invention may also include other systems (e.g., He refrigeration systems, superconducting CMOS systems, etc.).

[0174] 14 , computer 1400 includes a processing unit 1401 having one or more processors and a non-transitory computer-readable storage medium 1402, which may include, for example, volatile and / or non-volatile memory. Memory 1402 may store one or more instructions that program processing unit 1401 to perform any of the functions described herein. In addition to system memory 1402, computer 1400 may also include other types of non-transitory computer-readable media, such as storage device 1405 (e.g., one or more disk drives). Storage device 1405 may also store one or more application programs and / or resources used by application programs (e.g., software libraries), which may be loaded into memory 1402.

[0175] Computer 1400 may have one or more input and / or output devices, such as devices 1406 and 1407 shown in FIG. 14. These devices may be used, among other things, to present a user interface. Examples of output devices that may be used to provide a user interface include a printer or display screen for visually presenting output and a speaker or other sound-generating device for audibly presenting output. Examples of input devices that may be used for a user interface include a keyboard and pointing devices such as a mouse, touchpad, and digitizing tablet. As another example, input device 1407 may include a microphone for capturing audio signals, and output device 1406 may include a display screen for visually rendering recognized text and / or a speaker for audibly rendering recognized text.

[0176] 14, computer 1400 may also include one or more network interfaces (e.g., network interface 1410) to enable communication over various networks (e.g., network 1420). Examples of networks include local area networks or wide area networks, such as an enterprise network or the Internet. Such networks may be based on any suitable technology and may operate according to any appropriate protocol, including wireless networks, wired networks, or fiber optic networks. Such networks may include analog and / or digital networks.

[0177] Various aspects of the above-described embodiments may be used alone, in combination, or in various arrangements not specifically contemplated in the embodiments described above, and are therefore not limited in application to the details and arrangements of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.

[0178] All definitions defined and used herein should be understood to supersede dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0179] The indefinite articles "a" and "an" as used in this specification and claims, unless expressly indicated to the contrary, should be understood to mean "at least one."

[0180] The phrase "and / or," as used in the specification and claims, should be understood to mean "either or both" of the elements so conjoined, i.e., elements present conjunctively in some cases and disjunctively in other cases. Multiple elements listed with "and / or" should be construed similarly, i.e., to mean "one or more" of the elements so conjoined. Other elements other than the elements specifically identified by the "and / or" clause may optionally be present, whether related to the elements specifically identified or not. Thus, as a non-limiting example, a reference to "A and / or B," when used in conjunction with open-ended language such as "comprising," can refer in one embodiment to A only (optionally including elements other than B), in another embodiment to B only (optionally including elements other than A), in yet another embodiment to both A and B (optionally including other elements), etc.

[0181] As used herein and in the claims, the phrase "at least one" in reference to a list of one or more elements should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed in the list of elements, and not excluding any combination of elements in the list of elements. This definition also contemplates that elements other than those specifically identified in the list of elements to which the phrase "at least one" refers may optionally be present, whether related to the specifically identified elements or not. Thus, as a non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B" or, equivalently, "at least one of A and / or B") can refer in one embodiment to at least one A, optionally including more than one, with no B (optionally including elements other than B); in another embodiment to at least one B, optionally including more than one, with no A (optionally including elements other than A); in yet another embodiment to at least one A, optionally including more than one, and at least one B (optionally including other elements), optionally including more than one; etc.

[0182] In the claims, the use of ordinal terms such as "first," "second," "third," etc. to modify claim elements does not, in itself, imply any priority, precedence, or order of one claim element relative to another, or the temporal order in which method actions are performed; these terms are merely used as markers to distinguish one claim element having a certain name from another claim element having the same name (although using ordinal terms).

[0183] In the claims, as well as in the specification above, all transitional phrases such as "comprise," "include," "carry," "have," "contain," "include," "hold," "consisting of," and the like, shall be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively.

[0184] The terms "nearly," "about," and "substantially" can be used in some embodiments to mean within ±20% of a target value, in some embodiments within ±10% of a target value, in some embodiments within ±5% of a target value, and in some embodiments within ±2% of a target value. The terms "nearly," "about," and "substantially" may include the target value.

[0185] Having thus described several aspects of at least one embodiment, it should be understood that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the principles described herein. Accordingly, the foregoing description and drawings are by way of example only.

Claims

1. A dilution refrigerator, comprising: A plurality of thermal plates configured to be cooled to a plurality of temperatures Equipped with a first thermalization plate of the plurality of thermalization plates having an integrated heat exchanger; the integrated heat exchanger includes channels formed in the first thermalizer plate; The dilution refrigerator, wherein the channel is configured to allow helium to flow through the first thermalizer plate during operation of the dilution refrigerator.

2. The dilution refrigerator of claim 1 , wherein the integrated heat exchanger is formed by additive manufacturing.

3. The dilution refrigerator according to claim 1 or 2, wherein the first thermalizer plate further comprises a detachable portion, the detachable portion including the integrated heat exchanger.

4. The dilution refrigerator according to any one of claims 1 to 3, further comprising a replaceable dilution insert detachably coupled to the detachable portion of the first thermalization plate.

5. The dilution insert is a condensation line of the dilution refrigerator; Three thermalization plates among the plurality of thermalization plates; The dilution refrigerator according to any one of claims 1 to 4, wherein the dilution refrigerator is detachably connected to a

6. The dilution insert is ３ He and ４ From a mixture with He ３ 6. The dilution refrigerator according to claim 1, comprising a still configured to perform cooling by fractionating He vapor.

7. a test volume thermally coupled to the coldest thermal plate of the plurality of thermal plates; A still connected to a second thermal plate having a temperature higher than that of the coldest thermal plate, ３ He and ４ From a mixture with He ３ a still configured to provide cooling by fractionating He vapor; a continuous heat exchanger disposed between the second thermalization plate and the coldest thermalization plate; The dilution refrigerator according to any one of claims 1 to 6, further comprising:

8. 8. The dilution refrigerator according to claim 1, further comprising at least one heat exchanger thermally coupled to a thermalization plate of the plurality of thermalization plates, wherein the at least one heat exchanger comprises a nanomaterial.

9. The dilution refrigerator of claim 8 , wherein the nanomaterial comprises at least one of nanowires, nanofoams, nanopellets, and / or nanotubes.

10. 10. The dilution refrigerator of claim 8 or 9, wherein the nanomaterial comprises nanowires comprising one or more of copper nanowires, silver nanowires, gold nanowires, platinum nanowires, polymer nanowires, carbon nanowires and / or carbon fiber nanowires.

11. The dilution refrigerator according to any one of claims 8 to 10, wherein the at least one heat exchanger comprises one of a heat exchanger disposed in a mixing chamber of the dilution refrigerator and / or a separated type heat exchanger.

12. a condensation line configured to transport helium to a coldest one of the plurality of thermalization plates; a still positioned along the condensation line before the coldest thermal plate; a heat exchanger disposed along the condensation line between the still and the coldest thermal plate; a heat exchange line configured to transfer the return helium mixture from the heat exchanger to the still and to reduce the temperature of the helium mixture in the condensate line at a location above the still; The dilution refrigerator according to any one of claims 1 to 11, further comprising:

13. a Joule-Thomson expander disposed along the condensate line before the still; 13. The dilution refrigerator according to claim 1, wherein the heat exchange line is configured to reduce the temperature of the helium mixture in the condensation line at a position before the Joule-Thomson expander.

14. a condensation line configured to transport helium to a coldest one of the plurality of thermalization plates; a high surface area material disposed along the condensation line, the high surface area material configured to adsorb the transported helium onto the high surface area material during a cool-down cycle of the dilution refrigerator; The dilution refrigerator according to any one of claims 1 to 13, further comprising:

15. a first end of the high surface area material is switchably thermally coupled to a higher temperature thermal plate among the plurality of thermal plates by a first heat switch; 15. The dilution refrigerator according to claim 14, wherein a second end of the high surface area material opposite the first end is switchably thermally coupled to a thermalization plate having a lower temperature among the plurality of thermalization plates by a second heat switch.

16. 16. The dilution refrigerator according to claim 14 or 15, further comprising at least one heater thermally coupled to the high surface area material, wherein the heater is configured to heat the high surface area material such that the adsorbed helium is released from the high surface area material and cooled by moving between a higher temperature one of the plurality of thermalization plates and a lower temperature one of the plurality of thermalization plates.

17. a first valve positioned along the condensation line between the hotter thermal plate and the high surface area material; a second valve positioned along the condensation line between the high surface area material and the cooler thermal plate; Furthermore, 17. The dilution refrigerator according to claim 14, wherein the first valve and the second valve are configured such that, when the first valve is closed and the second valve is opened, helium adsorbed on the high surface area material is transported from the thermalization plate having a higher temperature to the thermalization plate having a lower temperature.

18. 18. The dilution refrigerator according to claim 14, wherein the high surface area material comprises one of activated carbon or metal powder.

19. a condensation line configured to transport helium from a helium inlet to a coldest plate of the plurality of thermalization plates; a first helium filter disposed along the condensation line; a second helium filter disposed in parallel with the first helium filter along the condensate line; at least one valve configured to switch the flow of helium along the condensate line between the first helium filter and the second helium filter; The dilution refrigerator according to any one of claims 1 to 18, further comprising:

20. 20. The dilution refrigerator according to claim 1, wherein the first helium filter and / or the second helium filter includes a charcoal trap.

21. a first countercurrent heat exchanger disposed between the first helium filter and the helium inlet; a second countercurrent heat exchanger disposed between the second helium filter and the helium inlet; The dilution refrigerator according to any one of claims 1 to 20, further comprising:

22. a condensation line configured to transport helium to a coldest one of the plurality of thermalization plates; a Joule-Thomson expander disposed along the condensation line; and a bypass disposed along the condensation line in parallel with the Joule-Thomson expander, the bypass configured to allow the transported helium to bypass the Joule-Thomson expander when the transported helium has a temperature above a threshold value and below 300 K; The dilution refrigerator according to any one of claims 1 to 21, further comprising:

23. 23. The dilution refrigerator of any one of claims 1 to 22, wherein the bypass comprises a material configured to allow the transported helium to diffuse through the material when the transported helium has a temperature above a threshold value and below 300 K.

24. 24. The dilution refrigerator of claim 23, wherein the material comprises a polymer.

25. a first thermal stage configured to be cooled to a first temperature; a second thermal stage configured to be cooled to a second temperature lower than the first temperature; a vacuum chamber containing the first and second thermal stages; a first suspension system configured to suspend the first thermal stage from the vacuum chamber; a second suspension system configured to suspend the second thermal stage from the vacuum chamber independently of the first thermal stage; A dilution refrigerator comprising:

26. 26. The dilution refrigerator of claim 25, wherein the first suspension system comprises a rod configured to rigidly connect the first thermal stage to the vacuum chamber.

27. 27. The dilution refrigerator of claim 26, wherein the rod comprises carbon fiber or stainless steel.

28. 28. The dilution refrigerator of claim 25, wherein the second suspension system comprises one or more springs configured to movably couple the second thermal stage to the vacuum chamber.

29. 30. The dilution refrigerator of claim 28, wherein the one or more springs include a spring configured to provide a constant tension under different loads.

30. the one or more springs: a first spring configured to provide vibration isolation for the second thermal stage along a first axis; a second spring configured to provide vibration isolation for the second thermal stage in a plane perpendicular to the first axis; 30. The dilution refrigerator according to claim 28 or 29, comprising:

31. 31. The dilution refrigerator of claim 30, wherein the first spring comprises a leaf spring.

32. 32. The dilution refrigerator of claim 31 , wherein the leaf spring comprises stainless steel and / or spring steel.

33. 33. The dilution refrigerator according to claim 31 or 32, wherein the leaf spring includes two spring leaves, and the tension of the leaf spring is determined based on the lengths of the two spring leaves.

34. The dilution refrigerator according to any one of claims 31 to 33, wherein the leaf spring includes two spring plates, and the tension of the leaf spring is determined based on pretensioning of the two spring plates.

35. The dilution refrigerator according to any one of claims 30 to 34, wherein the second spring comprises a flexible rod.

36. 36. The dilution refrigerator of claim 35, wherein the first spring is connected to the second thermal stage by the flexible rod.

37. 37. The dilution refrigerator of claim 35 or 36, wherein the flexible rod comprises a polymer.

38. 38. The dilution refrigerator of claim 37, wherein the polymer comprises Delrin.

39. a third thermal stage configured to be cooled to a third temperature between the first temperature and the second temperature; 39. The dilution refrigerator of any one of claims 25 to 38, wherein the first suspension system is further configured to suspend the third thermal stage from the first thermal stage.

40. a fourth thermal stage configured to be cooled to a fourth temperature lower than the second temperature; a third suspension system configured to suspend the fourth thermal stage from the second thermal stage; The dilution refrigerator according to any one of claims 25 to 39, further comprising:

41. 41. The dilution refrigerator of claim 40, wherein the third suspension system includes a rod configured to rigidly connect the fourth thermal stage to the second thermal stage.

42. 42. The dilution refrigerator of claim 40 or 41, wherein the second suspension system includes one or more springs configured to movably couple the second thermal stage to the vacuum chamber.

43. the one or more springs: a first spring configured to provide vibration isolation for the second thermal stage along a first axis; a second spring configured to provide vibration isolation for the second thermal stage in a plane perpendicular to the first axis; 43. The dilution refrigerator of claim 42, comprising:

44. 44. The dilution refrigerator of any one of claims 40 to 43, wherein the first suspension system includes a rod configured to rigidly connect the first thermal stage to the vacuum chamber.

45. an outer vacuum chamber including at least one substantially planar surface; an opening in the at least one substantially planar surface configured to provide access to an interior of the outer vacuum chamber; A dilution refrigerator comprising:

46. 46. ​​The dilution refrigerator of claim 45, further comprising a sample stage housed within the outer vacuum chamber, the opening configured to provide access to the sample stage through the outer vacuum chamber.

47. 47. The dilution refrigerator of claim 45 or 46, further comprising one or more radiation shields housed within the outer vacuum chamber, portions of the one or more radiation shields proximate the sample stage being slidable and / or removable to provide access to the sample stage.

48. 48. The dilution refrigerator of any one of claims 45 to 47, wherein the at least one substantially planar surface includes a first surface disposed in a plane perpendicular to the plane of a floor supporting the dilution refrigerator.

49. the at least one substantially planar surface being: a first surface disposed in a plane perpendicular to the plane of a floor supporting the dilution refrigerator; a second surface disposed in a plane parallel to the plane of the floor, the first surface and the second surface being disposed as a rectangular parallelepiped; The dilution refrigerator according to any one of claims 45 to 48, comprising:

50. The dilution refrigerator according to any one of claims 45 to 49, wherein the opening includes a sealed opening.

51. The dilution refrigerator of any one of claims 45 to 50, wherein the opening comprises a hinged door.

52. 52. The dilution refrigerator of claim 51, further comprising one or more radiation shields housed within the outer vacuum chamber, a portion of the one or more radiation shields adjacent the hinged door being slidable and / or removable to provide access to the interior of the outer vacuum chamber.

53. The dilution refrigerator according to any one of claims 45 to 52, wherein the opening further comprises a load lock.

54. the outer vacuum chamber The first section, a second section suspended from the first section; and The dilution refrigerator according to any one of claims 45 to 53, comprising:

55. 55. The dilution refrigerator of claim 54, wherein the first section is connected to the second section by an integral clamp and / or cam.

56. 56. The dilution refrigerator of claim 54 or 55, wherein the first and / or second sections of the outer vacuum chamber are configured to be at least partially removed from the dilution refrigerator to provide access to an interior of the outer vacuum chamber.

57. 57. The dilution refrigerator of any one of claims 54 to 56, further comprising an external system configured to raise and / or lower the first section and / or the second section of the outer vacuum chamber.

58. 58. The dilution refrigerator of claim 57, wherein the external system includes pneumatic and / or hydraulic devices configured to raise and / or lower the first and / or second sections.

59. 59. The dilution refrigerator of claim 57 or 58, wherein the external system includes a screw mechanism configured to raise and / or lower the first and / or second sections.

60. 60. The dilution refrigerator of any one of claims 45 to 59, wherein the outer vacuum chamber is configured to fit within a server rack type container.

61. 61. The dilution refrigerator of claim 60, wherein the server rack container is configured to integrate with commercially available server rack infrastructure.

62. 62. The dilution refrigerator according to claim 60 or 61, wherein the server rack type container is a 19-inch (48.26 centimeter) server rack.

63. 63. The dilution refrigerator of any one of claims 60 to 62, wherein the server rack type container includes an outer housing including an integral horizontal surface.

64. 64. The dilution refrigerator of claim 63, wherein the integral horizontal surface is configured to be stowed when not in use.

65. A distributed refrigeration system comprising: a pre-cooling system thermally coupled to two or more cryogenic devices and configured to provide a first cooling stage for the two or more cryogenic devices.

66. 66. The distributed refrigeration system of claim 65, further comprising the two or more cryogenic devices thermally coupled to the pre-cooling system.

67. 67. The distributed refrigeration system of claim 65 or 66, wherein the two or more cryogenic devices comprise at least one dilution refrigerator.

68. The two or more cryogenic devices include a dilution refrigerator, a cryomicroscope system, ３ 68. A distributed refrigeration system according to any one of claims 65 to 67, comprising two or more of a He refrigeration system and / or a superconducting CMOS system.

69. 69. A distributed refrigeration system according to any one of claims 65 to 68, wherein the first cooling stage has a temperature of 5K or less.

70. 70. A distributed refrigeration system according to any one of claims 65 to 69, wherein the pre-cooling system comprises a cryogenic cooling system.

71. 71. The distributed refrigeration system of claim 70, wherein the cryogenic cooling system comprises a pulse tube.

72. 71. The distributed refrigeration system of claim 70, wherein the very low temperature cooling system comprises a Brayton cryocooler.

73. 71. The distributed refrigeration system of claim 70, wherein the cryogenic cooling system comprises a helium liquefaction system.

74. 74. A distributed refrigeration system according to any one of claims 65 to 73, wherein the two or more cryogenic devices comprise dilution refrigerators having a second cooling stage configured to reach a temperature of 1 K or less.

75. 75. A distributed refrigeration system according to any one of claims 65 to 74, wherein the second cooling stage is configured to reach a temperature of 100 mK or less.

76. 76. A distributed refrigeration system according to any one of claims 65 to 75, configured to be integrated into one or more server racks.

77. the pre-cooling system is installed in a first server rack; 77. The distributed refrigeration system of claim 76, wherein the two or more cryogenic units are installed in a second server rack different from the first server rack.

78. the pre-cooling system is installed in a first server rack; 77. The distributed refrigeration system of claim 76, wherein the two or more cryogenic devices include a dilution refrigerator, the dilution refrigerator being installed in a second server rack different from the first server rack.

79. 79. The distributed refrigeration system of any one of claims 65 to 78, further comprising a thermal coupling component configured to transfer heat from the two or more cryogenic devices to the pre-cooling system.

80. 80. The distributed refrigeration system of claim 79, wherein the thermal coupling components include one or more fill lines.

81. 80. The distributed refrigeration system of claim 79, wherein the thermal coupling component comprises one or more heat pipes.

82. 82. The distributed refrigeration system of claim 81, wherein the one or more heat pipes comprise one or more oscillating heat pipes.

83. 80. The distributed refrigeration system of claim 79, wherein the thermal coupling component comprises a superfluid loop.

84. 84. A distributed refrigeration system according to any one of claims 79 to 83, wherein the thermal coupling components comprise one or more vacuum insulated pipes.

85. 1. A dilution refrigerator comprising multiple thermal stages configured to be cooled to multiple temperatures, a dilution refrigerator, wherein a coldest thermal stage of the plurality of thermal stages is disposed above a warmer thermal stage of the plurality of thermal stages such that the coldest thermal stage is positioned furthest from a floor supporting the dilution refrigerator.

86. a demixing chamber disposed above and thermally coupled to the coldest thermal stage; a mixing chamber located farther from the floor than the demixing chamber; From the demixing chamber to the mixing chamber ４ a fountain pump configured to transport He; 86. The dilution refrigerator of claim 85, further comprising:

87. When transported from the demixing chamber to the mixing chamber ４ 87. The dilution refrigerator of claim 86, further comprising a heat exchanger configured to cool the He.

88. ３ He- ４ From He mixture ３ 88. The dilution refrigerator of any one of claims 85 to 87, further comprising a still configured to provide cooling by fractionating He vapor, the still comprising a pumping port comprising a pipe that enters the still through a face of the still other than a face of the still farthest from the floor.

89. 89. The dilution refrigerator of claim 88, wherein the pipe enters the still at a face of the still closest to the floor.

90. The pipe is connected to a trap, the trap comprising: P-trap and Superfluid from the P trap ４ a superleak configured to remove He; 90. The dilution refrigerator of claim 88 or 89, comprising:

91. The pipe is ４ 91. The dilution refrigerator of any one of claims 88 to 90, comprising a barrier configured to prevent a He film from creeping up into the outlet of the pipe.

92. 92. The dilution refrigerator of claim 91 , wherein the barrier comprises one or more knife edges at the outlet of the pipe.

93. 93. The dilution refrigerator of claim 91 or 92, wherein the barrier comprises a ring barrier on an outer surface of the pipe.

94. 94. The dilution refrigerator of any one of claims 91 to 93, wherein the barrier comprises a ring barrier on the inner surface of the pipe.

95. The dilution refrigerator according to any one of claims 91 to 94, wherein the barrier includes a heater.

96. ３ He / ４ a first impedance stage configured to cool the He mixture; before passing through the first impedance stage ３ He / ４ a heat exchange stage configured to cool the He mixture; The impedance received from the first impedance stage ３ He / ４ From He mixture ３ a still configured to fractionate the He; The dilution refrigerator according to any one of claims 85 to 95, further comprising:

97. The heat exchange stage transfers cold water from the mixing chamber to the still. ３ By returning He, ３ He / ４ 97. The dilution refrigerator of claim 96 configured to cool a He mixture.

98. an outer vacuum chamber containing the plurality of thermal stages; an opening through a surface of the outer vacuum chamber configured to provide access to the coldest thermal stage of the dilution refrigerator; The dilution refrigerator according to any one of claims 85 to 97, further comprising:

99. 99. The dilution refrigerator of claim 98, wherein the opening is located proximate to a top surface of the outer vacuum chamber.

100. 100. The dilution refrigerator of claim 98 or 99, wherein the opening comprises a sealed opening.

101. The dilution refrigerator of any one of claims 98 to 100, wherein the opening comprises a hinged door.

102. 102. The dilution refrigerator of any one of claims 98 to 101, wherein the outer vacuum chamber is configured to fit within a server rack type container.

103. 103. The dilution refrigerator of claim 102, wherein the server rack container is configured to integrate with commercially available server rack infrastructure.

104. 104. The dilution refrigerator according to claim 102 or 103, wherein the server rack type container is a 19-inch (48.26 centimeter) server rack.

105. The dilution refrigerator of any one of claims 85 to 104, further comprising a pulse tube configured to cool one of the plurality of thermal stages to about 4K.

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