Thermal coupling device for use in cryogenic systems

Abstract

The present disclosure relates to a thermal coupling device (200), comprising a body (210) configured to provide a thermal interface between a cryogenic material (20) and a thermal bus, the body (210) having an interface surface (IFS) configured to establish thermal contact between the body (210) and the cryogenic material (20).

Description

THERMAL COUPLING DEVICE FOR USE IN CRYOGENIC SYSTEMSFIELD

[0001] The present disclosure relates to a thermal coupling device configured for use in a cryogenic system, as well as to a cryogenic system including one or more such thermal coupling devices. More particularly, the present disclosure relates to thermal coupling between a cryogenic material, capable of providing ultra-low temperatures in the subKelvin or milli-Kelvin range, and a thermal bus.BACKGROUND

[0002] A cryostat is generally used to maintain low temperatures of samples mounted within the cryostat. Low temperatures may be achieved by using, for example, a cryogenic fluid bath such as liquid helium. However, the cooling medium, such as liquid helium, continuously evaporates due to external and / or internal heat input in the cryostat and therefore needs to be refilled regularly. This requires considerable time and resources, whereby the operating costs of such cryostats are high.

[0003] To overcome the above drawbacks, cryogen-free cryostats have been developed. Cryogen-free cryostats may employ a cryogen-free closed cycle system, such a pulse tube cryocooler. Modern pulse tube cryocoolers can achieve temperatures down to 1.2K. To achieve sub-Kelvin temperatures, a magnetic cooling stage can be used in addition to the cryogen-free closed cycle system. The magnetic cooling stage may be an adiabatic demagnetization refrigerator (ADR), which can achieve temperatures down to a few milli-Kelvin. ADR is based on the magneto-caloric effect. When a medium is magnetized, its magnetic moments get aligned and the heat of magnetization is released. Vice versa, if the medium is demagnetized its temperature drops.

[0004] In many cooling systems, the cryogenic material responsible for providing cooling must be thermally coupled to a thermal bus through a thermal coupling device such as a heat exchanger. However, the thermal conductivity is primarily constrained by the interface resistance between the cryogenic material and the thermal coupling device,posing a significant challenge in achieving effective thermal coupling between the cryogenic material and the thermal bus.

[0005] In view of the above, new thermal coupling devices configured for use in a cryogenic system and cryogenic systems including one or more such thermal coupling devices that overcome at least some of the problems in the art are beneficial.SUMMARY

[0006] It is an object of the present disclosure to provide a thermal coupling device and a cryogenic system including one or more such thermal coupling devices, which can improve a thermal coupling between a cryogenic material and a thermal bus.

[0007] According to an independent aspect of the present disclosure, a thermal coupling device is provided. The thermal coupling device includes a body configured to provide a thermal interface between a cryogenic material and a thermal bus, the body having an interface surface configured to establish thermal contact between the body and the cryogenic material.

[0008] A “thermal bus” refers to a component or system designed to transfer thermal energy from one part of the cryogenic system to another. It acts as a conduit for heat, enabling efficient thermal management. The thermal bus can be made from materials with high thermal conductivity, such as copper or aluminum, and can be designed in various forms, including solid bars, plates, or more complex geometries to suit specific applications.

[0009] According to some embodiments, which can be combined with other embodiments described herein, the body is embedded or immersed in the cryogenic material such that the interface surface of the body is essentially entirely covered by the cryogenic material.

[0010] According to some embodiments, which can be combined with other embodiments described herein, a surface to volume ratio of the body with respect to the cryogenic material is at least 10 / cm, preferably at least 12 / cm, preferably at least 14 / cm,preferably at least 16 / cm, preferably at least 18 / cm, or preferably at least 20 / cm or at most 5000 / cm. For example, the surface to volume ratio of the body with respect to the cryogenic material can be at least 14 / cm. It is to be understood that equivalent surface to volume ratios can be expressed in other units such as 1 / m or 1 / mm.

[0011] According to some embodiments, which can be combined with other embodiments described herein, the surface to volume ratio of the body with respect to the cryogenic material is in a range between 10 / cm and 40 / cm, preferably in a range between 10 / cm and 30 / cm, or preferably in a range between 10 / cm and 20 / cm. It is to be understood that equivalent surface to volume ratios can be expressed in other units such as 1 / m or 1 / mm.

[0012] The surface to volume ratio is the ratio of the interface surface of the body relative to a total volume of the cryogenic material in which it is embedded. The interface surface can be expressed in units of cm2, and the total volume of the cryogenic material can be expressed in units of cm3, but the present disclosure is not limited thereto.

[0013] According to some embodiments, which can be combined with other embodiments described herein, a ratio of the interface surface of the body relative to a volume of the body is at least 50 / cm, preferably at least 60 / cm, preferably at least 70 / cm, preferably at least 80 / cm, preferably at least 90 / cm, or preferably at least 100 / cm or at most 10000 / cm. For example, the ratio of the interface surface of the body relative to the volume of the body can be at least 78 / cm. It is to be understood that equivalent surface to volume ratios can be expressed in other units such as 1 / m or 1 / mm.

[0014] According to some embodiments, which can be combined with other embodiments described herein, the ratio of the interface surface of the body relative to the volume of the body is in a range between 50 / cm and 100 / cm, preferably in a range between 60 / cm and 90 / cm, or preferably in a range between 70 / cm and 80 / cm. It is to be understood that equivalent ratios can be expressed in other units such as 1 / m or 1 / mm.

[0015] The interface surface of the body can be expressed in units of cm2, and the volume of the body can be expressed in units of cm3, but the present disclosure is notlimited thereto. The volume of the body refers to the amount of three-dimensional space that a material the body is made of occupies. This can be calculated based on the shape and dimensions of the body.

[0016] According to some embodiments, which can be combined with other embodiments described herein, the interface surface of the body has a roughness of at least 3pm, preferably at least 5pm, preferably at least 8pm, preferably at least 10pm, preferably at least 15 pm, or preferably at least 20pm or at most 100pm. For example, the interface surface of the body has a roughness of at least 18pm. In some embodiments, the roughness can be up to 20% of the feature size of the body. In this context feature size refers to the dimension of smallest geometrical structures that make up, in combination with multiple equivalent or non-equi valent structures, the entirety of the body.

[0017] According to some embodiments, which can be combined with other embodiments described herein, the interface surface of the body has a roughness in a range between 5pm and 30pm, preferably in a range between 5pm and 20 / cm, or preferably in a range between 5pm and 10pm.

[0018] The roughness of the interface surface of the body refers to Ra - arithmetical means roughness value and / or other values pursuant to EN ISO 4287 (definitions) and / or EN ISO 4288 (evaluation).

[0019] According to some embodiments, which can be combined with other embodiments described herein, the interface surface of the body includes a granular structure. The term “granular structure” refers to the microscopic arrangement and characteristics of the individual grains or crystals that make up the body. Each grain is a single crystal with a distinct orientation, and the boundaries between these grains are known as grain boundaries.

[0020] According to some embodiments, which can be combined with other embodiments described herein, the thermal coupling device further includes a containing structure configured to accommodate the body and the cryogenic material. In some embodiments, the containing structure surrounds the body and the cryogenic material,particularly such that the body and the cryogenic material are fully enclosed by the containing structure.

[0021] Preferably, the containing structure has a cylindrical shape. For example, the containing structure can be a hollow cylinder a closed (or an open) and a closed (or an open) bottom.

[0022] According to some embodiments, which can be combined with other embodiments described herein, an outer diameter of the body and an inner diameter of the containing structure are essentially the same.

[0023] According to some embodiments, which can be combined with other embodiments described herein, the body is made of copper or a copper-containing material.

[0024] According to some embodiments, which can be combined with other embodiments described herein, the body is made of heat-treated copper.

[0025] According to some embodiments, which can be combined with other embodiments described herein, the body is made of a material (e.g., heat-treated copper) having a thermal conductivity of at least 400 W / m / K at 4K, preferably at least 500 W / m / K at 4K, preferably at least 600 W / m / K at 4K, preferably at least 700 W / m / K at 4K, or preferably at least 800 W / m / K at 4K or at most 25000 W / m / K at 4K. For example, the body can be made of a material (e.g., heat-treated copper) having a thermal conductivity of at least 600 W / m / K at 4K.

[0026] According to some embodiments, which can be combined with other embodiments described herein, the body is made of a material (e.g., heat-treated copper) having a thermal conductivity of in a range between 400 W / m / K and 800 W / m / K at 4K (or at most 25000 W / m / K at 4K), or preferably in a range between 500 W / m / K and 700 W / m / K at 4K (or at most 25000 W / m / K at 4K).

[0027] According to some embodiments, which can be combined with other embodiments described herein, the body is a single piece. A body which is a single piecerefers to an object that is composed entirely of a material (e.g., copper) and is not made up of multiple parts or pieces joined together. This single-piece body can be essentially homogeneous in composition and structure, meaning it is essentially uniform throughout without any joints, seams, or composite materials.

[0028] According to some embodiments, which can be combined with other embodiments described herein, the body is fabricated using an additive manufacturing technique. Additive manufacturing techniques can be used to 3D-print the body layer-by- layer from a material such as copper.

[0029] According to some embodiments, which can be combined with other embodiments described herein, the thermal coupling device includes a base, wherein the body is deposited (or arranged) on the base. For example, the body can be deposited on the base using an additive manufacturing technique.

[0030] In some embodiments, the base is a thermal bus. This allows the body to be added to existing structures, enhancing thermal coupling characteristics of the (existing) thermal bus.

[0031] According to some embodiments, which can be combined with other embodiments described herein, the body has a longitudinal axis, and its cross-sectional shape in a plane perpendicular to the longitudinal axis is star-shaped and / or fan shaped.

[0032] According to some embodiments, which can be combined with other embodiments described herein, the body has a center portion extending along the longitudinal axis and a plurality of protrusions radially protruding from the center portion.

[0033] In some embodiments, plurality of protrusions can plates and / or blades and / or fans and / or fins. Fur example, the plurality of protrusions can be radial fins.

[0034] According to some embodiments, which can be combined with other embodiments described herein, the body includes a stabilizing structure. The stabilizing structure can be configured to improve post-processing reliability of the thermal couplingdevice, such as machining of thermal contact surfaces, sealing surfaces, or mechanical connection interfaces (e.g., for screws).

[0035] According to some embodiments, which can be combined with other embodiments described herein, the stabilizing structure is provided by at least one protrusion of the plurality of protrusions.

[0036] In some embodiments, the plurality of protrusions include at least one first protrusion (e.g., a plurality of first protrusions) and at least one second protrusion (e.g., two or more second protrusions). The at least one second protrusion can be configured to provide the stabilizing structure.

[0037] In some embodiments, the at least one first protrusion has a first thickness and the at least one second protrusion has a second thickness, wherein the second thickness is greater than the first thickness.

[0038] In some embodiments, the second thickness is at least 2 times, at least 3 times, at least 4 times or at least 5 times greater than the first thickness.

[0039] According to some embodiments, which can be combined with other embodiments described herein, the stabilizing structure includes, or is, a linking structure connecting two or more protrusions of the plurality of protrusions.

[0040] In some embodiments, the linking structure is a tangentially extending linking structure.

[0041] In some embodiments, the linking structure interconnects multiple neighboring protrusions.

[0042] In some embodiments, the linking structure may include a first linking plane and a second linking plane (and optionally one or more further linking planes) which are radially spaced apart from each other. Each of the first linking plane and the second linking plane can interconnect multiple neighboring protrusions so that each protrusion is connected to both the first linking plane and the second linking plane.

[0043] In some embodiments, the linking structure includes one or more interruptions. The one or more interruptions can be configured to avoid forming a closed conductive loop, in order to suppress eddy currents when the thermal coupling device is operated in a magnetic field environment.

[0044] According to some embodiments, which can be combined with other embodiments described herein, the at least one second protrusion extends radially beyond the at least one first protrusion prior to post-processing and is radially shortened during or after post-processing. This extension enables improved clamping and secure fixation of the body during mechanical processing, such as CNC machining. In a subsequent processing step, the at least one second protrusion may be reduced to align with the final outer shape or diameter of the thermal coupling device.

[0045] According to some embodiments, which can be combined with other embodiments described herein, the body is configured as a heat exchanger, a thermal bus or a thermalization platform.

[0046] According to some embodiments, which can be combined with other embodiments described herein, the cryogenic material is an adiabatic demagnetization material. An adiabatic demagnetization material is a paramagnetic substance that, when subjected to a changing magnetic field under adiabatic conditions, can achieve significant cooling. Examples of adiabatic demagnetization materials include paramagnetic salts, such as Ce2Mg3(NO3)12 24H2O (CMN), CrK(SO4)2 12H2O (CPA), Fe(SO4)2(NH4) 12H2O (FAA), Mn(SO4)2(NH4)2 6H2O (MAS) and frustrated quantum magnets KBaYb(BO3)2, KYbP2O7 and NaYbP2O7.

[0047] According to some embodiments, which can be combined with other embodiments described herein, the cryogenic material is a liquid. The liquid can be, but is not limited to, hydrogen or a He3 / He4 mixture, liquid Hes, or liquid He4.

[0048] According to some embodiments, which can be combined with other embodiments described herein, the cryogenic material is a gas. The gas can be, but is not limited to, hydrogen or a thermoacoustic gas used in a closed cycle refrigerator.

[0049] According to some embodiments, which can be combined with other embodiments described herein, the thermal coupling device is configured to cool gas for liquefaction.

[0050] Preferably, the thermal coupling device is configured for use in hydrogen liquefaction.

[0051] According to an independent aspect of the present disclosure, a thermal coupling device is provided. The thermal coupling device includes a body configured to provide a thermal interface between a cryogenic material and a thermal bus, the body having an interface surface configured to establish thermal contact between the body and the cryogenic material, wherein a surface to volume ratio of the body with respect to the cryogenic material is at least 10 / cm, preferably at least 12 / cm, preferably at least 14 / cm, preferably at least 16 / cm, preferably at least 18 / cm, or preferably at least 20 / cm or at most 5000 / cm.

[0052] According to an independent aspect of the present disclosure, a thermal coupling device is provided. The thermal coupling device includes a body configured to provide a thermal interface between a cryogenic material and a thermal bus, the body having an interface surface configured to establish thermal contact between the body and the cryogenic material, wherein a ratio of the interface surface of the body relative to a volume of the body is at least 50 / cm, preferably at least 60 / cm, preferably at least 70 / cm, preferably at least 80 / cm, preferably at least 90 / cm, or preferably at least 100 / cm or at most 10000 / cm.

[0053] According to an independent aspect of the present disclosure, a thermal coupling device is provided. The thermal coupling device includes a body configured to provide a thermal interface between a cryogenic material and a thermal bus, the body having an interface surface configured to establish thermal contact between the body and the cryogenic material, wherein the interface surface of the body has a roughness of at least 5pm, preferably at least 5pm, preferably at least 8pm, preferably at least 10pm, preferably at least 15pm, or preferably at least 20pm or at most 100pm.

[0054] According to another independent aspect of the present disclosure, a cryogenic system is provided. The cryogenic system includes a vacuum chamber and a cooling system inside the vacuum chamber, wherein the cooling system includes one or more thermal coupling devices according to the embodiments described in this document.

[0055] A vacuum is generally understood as a space essentially devoid of matter. The term “vacuum” as used throughout the present application is in particular understood as a technical vacuum, i.e., a region with a gaseous pressure much less than atmospheric pressure. The vacuum inside the vacuum chamber can be high vacuum, ultra-high vacuum or extremely high vacuum (XHV). One or more vacuum generation sources, such as turbo pumps and / or cryo pumps and / or ion-getter pumps, can be connected to the vacuum chamber to generate the vacuum.

[0056] According to some embodiments, which can be combined with other embodiments described herein, the cooling system includes, or is, a cryogen-free system, such as a cryogen-free closed cycle system.

[0057] According to some embodiments, which can be combined with other embodiments described herein, the cooling system includes, or is, a pulse tube cryocooler and / or an adiabatic demagnetization refrigerator and / or a Gifford-McMahon cryocooler and / or a Peltier cooler.

[0058] According to some embodiments, which can be combined with other embodiments described herein, the cryogenic system includes an object stage in the vacuum chamber. The cooling system can be configured to cool the object stage and / or at least one object (e.g., one or more electronic devices) attached to the object stage.

[0059] According to some embodiments, which can be combined with other embodiments described herein, the cooling system can be configured to cool the object stage and / or the at least one object to a temperature in range between ImK and 300K, particularly in a range between ImK and 4K.

[0060] According to some embodiments, which can be combined with other embodiments described herein, the cooling system can be configured to control atemperature of the object stage and / or the at least one object (e.g., one or more electronic devices) attached to the object stage within a predetermined temperature range. The predetermined temperature range may be 5mK to 0.5K, particularly 5mK to IK, particularly 5mK to 4K, particularly 5mK to 10K, particularly 5mK to 100K, and more particularly 5mK (or 50mK or lOOmK or 300mK) to 300K (e.g., room temperature).

[0061] According to some embodiments, which can be combined with other embodiments described herein, the at least one electronic device is selected from the group including, or consisting of, an integrated circuit, a quantum chip, a wafer, a semiconductor device, a component of an integrated circuit, and a component of quantum chip. However, the present disclosure is not limited thereto, and the at least one electronic device can be any electronic device suitable for testing and / or operating at low temperatures, such as any conductive, semi conductive, superconductive, quantum dot based, electromechanical and / or electrooptical circuit. In particular, the at least one electronic device can be any sub-component of an integrated circuit, such as a transistor, transformer, and the like.

[0062] According to some embodiments, which can be combined with other embodiments described herein, the cryogenic system includes a thermal path between a cooling source location of the cooling system and a cooling target location. The thermal path can be provided by the thermal bus to which the body of the thermal coupling device is connected.

[0063] Preferably, the cooling source location corresponds to a location of the cryogenic material which acts as a cooling source. For example, the cooling source can be a pumped Hes / He-t mixture in a dilution refrigerator, pumped liquid Hes, pumped liquid He4, an adiabatic refrigeration material in changing magnetic field, or a thermoacoustic gas expanded in a closed cycle refrigerator (e.g. pulse tube).

[0064] Preferably, the cooling target location corresponds to a location of the cooling target which is to be cooled by the cooling system. The cooling target can include, but is not limited to, at least one radiation shield, at least one intermediate thermal stage forreduction of parasitic heat, the object stage and / or the at least one object attached to the object stage.

[0065] According to some embodiments, which can be combined with other embodiments described herein, the thermal path includes (or is provided by) substantially only one thermal element for thermal transfer between the cooling source location and the cooling target location.

[0066] The term “substantially only one thermal element” refers to a configuration in which, for the majority of the length of the thermal path, only a single thermal element, such as a single-piece element, is provided. This can be at least 50% of the length of the thermal path, preferably at least 70%, and more preferably at least 90% or at most 99% or at most 100%. In some embodiments, the entire length of the thermal path is provided by a single thermal element, such as a single-piece element.

[0067] According to another independent aspect of the present disclosure, a thermal coupling device is provided. The thermal coupling device includes a body (for providing a thermal interface between a cryogenic material and a thermal bus), wherein the body comprises a surface (for establishing thermal contact between the body and the cryogenic material), wherein a surface to volume ratio of the body with respect to the cryogenic material is at least 20 / cm.

[0068] Further aspects, benefits, and features of the present disclosure are apparent from the claims, the description, and the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0069] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following:FIG. 1 shows a schematic view of a cryogenic system according to the embodiments of the present disclosure;FIG. 2 shows a cross-sectional view of a thermal coupling device according to the embodiments of the present disclosure;FIG. 3 shows another cross-sectional view of a thermal coupling device according to the embodiments of the present disclosure;FIG. 4 shows a perspective view of a body of a thermal coupling device according to the embodiments of the present disclosure;FIG. 5 shows a cross-sectional view of a body of a thermal coupling device according to the embodiments of the present disclosure;FIG. 6 shows a perspective view of a body of a thermal coupling device prior to pre-processing according to further embodiments of the present disclosure; andFIG. 7 shows a perspective view of a body of a thermal coupling device after pre-processing according to the further embodiments of the present disclosure.DETAILED DESCRIPTION OF EMBODIMENTS

[0070] Reference will now be made in detail to the various embodiments of the disclosure, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the disclosure and is not meant as a limitation of the disclosure. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet afurther embodiment. It is intended that the description includes such modifications and variations.

[0071] This document includes references to “one embodiment” or “an embodiment”. The appearances of the phrases “in one embodiment” or “in an embodiment” do not necessarily refer to the same embodiment. Particular features, structures, or characteristics may be combined in any suitable manner consistent with this disclosure.

[0072] The terms “comprising” and “including” are open-ended. As used in the appended claims, these terms do not foreclose additional structure or steps.

[0073] Various units, circuits, or other components may be described or claimed as “configured to” perform a task or tasks. In such contexts, “configured to” is used to connote structure by indicating that the units / circuits / components include structure (e.g., circuitry) that performs those task or tasks during operation. As such, the unit / circuit / component can be said to be configured to perform the task even when the specified unit / circuit / component is not currently operational (e.g., is not on). The units / circuits / components used with the “configured to” language include hardware, for example, circuits, memory storing program instructions executable to implement the operation, etc. Additionally, “configured to” can include generic structure (e.g., generic circuitry) that is manipulated by software and / or firmware (e.g., an FPGA or a general- purpose processor executing software) to operate in a manner that is capable of performing the task(s) at issue.

[0074] As used herein, the terms “first”, “second”, etc. are used as labels for nouns that they precede, and do not imply any type of ordering (e.g., spatial, temporal, logical, etc.).

[0075] As used herein, the term “based on” is used to describe one or more factors that affect a determination. This term does not foreclose additional factors that may affect a determination. That is, a determination may be solely based on those factors or based, at least in part, on those factors. Consider the phrase “determine A based on B.” While in this case, B is a factor that affects the determination of A, such a phrase does not foreclosethe determination of A from also being based on C. In other instances, A may be determined based solely on B.

[0076] FIG. l shows a schematic view of a cryogenic system 100 according to exemplary embodiments of the present disclosure. The cryogenic system 100 can be used to test and / or operate electronic devices under defined thermal conditions, e.g., at ultralow temperatures in the sub-Kelvin or milli-Kelvin range.

[0077] The cryogenic system 100 includes a vacuum chamber 110, an object stage 120 in the vacuum chamber 110, and a cooling system 130 configured to cool the object stage 120.

[0078] The vacuum chamber 110 has an interior space 111 which is configured to contain a vacuum. The vacuum chamber 110 seals the interior space 111 from the outside essentially gas-tight, vacuum-tight, heat-impermeable, and / or radiation-impermeable. Optionally, the vacuum chamber 110 may electrically insulate the interior space 111 from the outside.

[0079] At least one object 10 (or an object holder having the at least one object 10 attached thereto) can be connectable, particularly releasably connectable, to the object stage 120 for testing and / or operating the at least one object 10 (e.g., electronic device(s)) under defined thermal conditions, e.g., at ultra-low temperatures in the sub-Kelvin or milli-Kelvin range. In particular, a loading mechanism 150 can be used to load the at least one object 10 or object holder into and / or unload the at least one object 10 or object holder from the cryogenic system 100. The object holder can be a puck or similar device which can be attached to an object stage 120 inside the cryogenic system 100.

[0080] The cryogenic system 100 may include an access port 140 having an inner space and a vacuum lock. The vacuum lock may seal the interior space 111 from the inner space of the access port 140 essentially vacuum -tight in a closed state and may allow an access to the interior space 111 in an open state.

[0081] For example, the vacuum lock can be closed and the object holder having the at least one object 10 attached thereto can be placed in the inner space of the access port140, e.g., under atmospheric pressure. The inner space of the access port 140 can be sealed from the outside and a technical vacuum can be generated in the inner space. Then, the vacuum lock can be opened to connect the interior space 111 of the vacuum chamber 110 and the inner space of the access port 140. The object holder having the at least one object 10 attached thereto can be inserted into the vacuum chamber 110 using the transfer mechanism 150. The object holder attached thereto can be mechanically attached to a base (e.g., including or being the object stage 120), the object holder can be released from the transfer mechanism 150, and the transfer mechanism 150 can be removed from the inner space 111. The vacuum lock can be closed and the cryogenic system 100 can be operated for testing and / or operating the at least one object 10, such as an electronic device.

[0082] The access port 140 and / or the loading mechanism 150 are optional and other means to transfer the at least one object 10 inside the cryogenic system 100 can be used.

[0083] According to some embodiments, the cryogenic system 100 can be configured to cool the object stage and thus the at least one object 10 attached thereto using the cooling system 130. In particular, the cooling system 130 can be thermally connected to the object stage which in turn can be thermally connected to the at least one object 10.

[0084] The cryogenic system 100 can be configured to cool the object stage and thus the at least one object 10 attached thereto to temperatures in a range between ImK and 300K, 5mK to 0.5K, particularly 5mK to IK, particularly 5mK to 4K, particularly 5mK to 10K, particularly 5mK to 100K, and more particularly 5mK (or 50mK or lOOmK or 300mK) to 300K (e.g., room temperature). In some implementations, even if the system is a cryostat, temperatures up to room temperature can be provided.

[0085] According to some embodiments, which can be combined with other embodiments described herein, the cryogenic system 100 includes, or is, an adiabatic demagnetization refrigerator (ADR), and in particular a multi-stage adiabatic demagnetization refrigerator. The multi-stage adiabatic demagnetization refrigerator may be configured to operate at IK or below, particularly at 500mK or below, particularly at lOOmK or below, and particularly at 50mK or below. However, as mentioned above, thepresent disclosure is not limited thereto and the cryogenic system 100 can be operated at higher temperatures, i.e., temperatures of IK or higher, e.g., up to room temperature.

[0086] Cooling may be provided by a cryogenic material. In case of ADR, the cryogenic material may be an adiabatic demagnetization material. An adiabatic demagnetization material is a paramagnetic substance that, when subjected to a changing magnetic field under adiabatic conditions, can achieve significant cooling. Examples of adiabatic demagnetization materials include paramagnetic salts, but the present disclosure is no limited thereto.

[0087] A cooling source location (e.g., the cryogenic material) and a cooling target location (e.g., the object stage) are thermally connected via a thermal path, which may be provided by a thermal bus.

[0088] In some embodiments, the thermal path includes (or is provided by) substantially only one thermal element for thermal transfer between the cooling source location and the cooling target location.

[0089] The term “substantially only one thermal element” refers to a configuration in which, for the majority of the length of the thermal path, only a single thermal element, such as a single-piece element, is provided. This can be at least 50% of the length of the thermal path, preferably at least 70%, and more preferably at least 90%. In some embodiments, the entire length of the thermal path is provided by a single thermal element, such as a single-piece element.

[0090] To thermally connect the cooling source location (e.g., the cryogenic material) to the cooling target location (e.g., the object stage) via the thermal path, the cooling system 130 includes a thermal coupling device.

[0091] In the following, an exemplary and non-limiting embodiment of the thermal coupling device are described in detail.

[0092] FIG. 2 shows a cross-sectional view of a thermal coupling device 200 according to the embodiments of the present disclosure. FIG. 3 shows another cross-sectional viewof the thermal coupling device 200. FIG. 4 shows a perspective view of a body 210 of the thermal coupling device 200 according to the embodiments of the present disclosure. FIG. 5 shows a cross-sectional view of the body 210.

[0093] The thermal coupling device 200 includes a body 210 configured to provide a thermal interface between a cryogenic material 20 and a thermal bus (not shown), the body 210 having an interface surface IFS configured to establish thermal contact between the body 210 and the cryogenic material 20. The interface surface ISF is large, enhancing the thermal coupling between the cryogenic material 20 and the body 210.

[0094] The body 210 is embedded or immersed in the cryogenic material 20 such that the interface surface IFS of the body 210 is essentially entirely covered by the cryogenic material 20. This further enhances the thermal coupling between the cryogenic material 20 and the body 210.

[0095] The body 210 can be made of copper or a copper-containing material, but the present disclosure is not limited thereto. In some embodiments, the body 210 can made of heat-treated copper. Heat-treating the body 210 significantly enhances the thermal conductivity characteristics of the body 210.

[0096] In some embodiments, the body 210 can be made of a material (e.g., heat-treated copper) having a thermal conductivity of at least 400 W / m / K at 4K, preferably at least 500 W / m / K at 4K, preferably at least 600 W / m / K at 4K, preferably at least 700 W / m / K at 4K, or preferably at least 800 W / m / K at 4K. For example, the body can be made of a material (e.g., heat-treated copper) having a thermal conductivity of at least 600 W / m / K at 4K.

[0097] In some embodiments, the body 210 is a single piece. A body 210 which is a single piece refers to an object that is composed entirely of a material (e.g., copper) and is not made up of multiple parts or pieces joined together. This single-piece body can be essentially homogeneous in composition and structure, meaning it is essentially uniform throughout without any joints, seams, or composite materials.

[0098] In some embodiments, the body 210 has a longitudinal axis LA, and its cross- sectional shape in a plane perpendicular to the longitudinal axis LA is star-shaped and / or fan shaped. For example, the body 210 can have a center portion 212 extending along the longitudinal axis LA and a plurality of protrusions 214 radially protruding from the center portion 21. The plurality of protrusions 214 can be plates and / or blades and / or fans, but the present disclosure is not limited thereto.

[0099] In some embodiments, the body 210 include one or more connection portions 216 configured to be connected to the thermal bus providing the thermal path to the colling target location, such as the object stage shown in FIG. 1.

[0100] A surface to volume ratio of the body 210 with respect to the cryogenic material 20 can be at least 10 / cm, preferably at least 12 / cm, preferably at least 14 / cm, preferably at least 16 / cm, preferably at least 18 / cm, or preferably at least 20 / cm. For example, the surface to volume ratio of the body 210 with respect to the cryogenic material 20 can be at least 14 / cm. Such a surface to volume ratio of the body 210 with respect to the cryogenic material 20 significantly enhances the thermal coupling between the cryogenic material 20 and the body 210.

[0101] Additionally, or alternatively, a ratio of the interface surface IFS of the body 210 relative to a volume of the body 210 is at least 50 / cm, preferably at least 60 / cm, preferably at least 70 / cm, preferably at least 80 / cm, preferably at least 90 / cm, or preferably at least 100 / cm. For example, the ratio of the interface surface of the body relative to the volume of the body can be at least 78 / cm. Such a ratio of the interface surface IFS of the body 210 relative to a volume of the body 210 provides a substantial interface surface IFS, thereby enhancing the thermal coupling between the cryogenic material 20 and the body 210.

[0102] Additionally, or alternatively, the interface surface IFS of the body 210 has a roughness of at least 5 pm, preferably at least 5 pm, preferably at least 8pm, preferably at least 10pm, preferably at least 15pm, or preferably at least 20pm. For example, the interface surface IFS of the body 210 has a roughness of at least 18pm. Such a ratio of the interface surface IFS of the body 210 relative to a volume of the body 210 provides asubstantial interface surface IFS, thereby enhancing the thermal coupling between the cryogenic material 20 and the body 210.

[0103] Additionally, or alternatively, the interface surface IFS of the body 210 includes a granular structure. The term “granular structure” refers to the microscopic arrangement and characteristics of the individual grains or crystals that make up the body 210. Each grain is a single crystal with a distinct orientation, and the boundaries between these grains are known as grain boundaries. By employing a granular structure, the surface “roughness” can be adjusted to match the feature size of the body. This alignment enhances the effective surface area, which in turn improves thermal coupling.

[0104] In some embodiments, the thermal coupling device 200 further includes a containing structure 220 configured to accommodate the body 210 and the cryogenic material 20. In some embodiments, the containing structure 220 surrounds the body 210 and the cryogenic material 20, particularly such that the body 210 and the cryogenic material 20 are fully enclosed by the containing structure 220.

[0105] Preferably, the containing structure 220 has a cylindrical shape with a cylinder axis coinciding with the longitudinal axis LA of the body 210. For example, the containing structure 220 can be a hollow cylinder a closed (or an open) and a closed (or an open) bottom.

[0106] According to some embodiments, which can be combined with other embodiments described herein, an outer diameter of the body 210 and an inner diameter of the containing structure 220 are essentially the same, or an outer diameter of the body 210 is smaller than the inner diameter of the containing structure 220.

[0107] FIG. 6 shows a perspective view of a body 310 of a thermal coupling device prior to pre-processing according to further embodiments of the present disclosure. FIG. 7 shows a perspective view of the body 310 after pre-processing.

[0108] The body 310 includes a stabilizing structure 320. The stabilizing structure 320 can be configured to improve post-processing reliability of the thermal coupling device, such as machining of thermal contact surfaces, sealing surfaces, or mechanical connectioninterfaces (e.g., for screws). Thereby, mechanical failure or deformation during preprocessing can be reduced.

[0109] In some embodiments, the plurality of protrusions include at least one first protrusion 214 (e.g., a plurality of first protrusions) and at least one second protrusion 218 (e.g., two or more second protrusions). The at least one first protrusion 214 and the at least one second protrusion 218 can be radial fins, but the present disclosure is not limited thereto.

[0110] The at least one second protrusion 218 can be configured to provide at least a part of the stabilizing structure 320. For example, the at least one first protrusion 214 has a first thickness and the at least one second protrusion 218 has a second thickness, wherein the second thickness is greater than the first thickness. In other words, the at least one second protrusion 218 can have an increased wall thickness. In some embodiments, the second thickness is at least 2 times, at least 3 times, at least 4 times or at least 5 times greater than the first thickness.

[0111] In some embodiments, the stabilizing structure 320 can include a tangentially extending linking structure 322 interconnecting two or more protrusions of the plurality of protrusions. For example, multiple first protrusions 214 can be interconnected by the tangentially extending linking structure 322.

[0112] The linking structure 322 may include one or more interruptions 324. The one or more interruptions 324 can be arranged tangentially along the linking structure 322 and can be configured to avoid forming a closed conductive loop, in order to suppress eddy currents when the thermal coupling device is operated in a magnetic field environment

[0113] Additionally, or alternatively, the linking structure 322 may include a first linking plane Pl and a second linking plane P2 (and optionally one or more further linking planes) which are radially spaced apart from each other. In other words, the first linking plane Pl and the second linking plane P2 can be tangential planes. Each of the first linking plane Pl and the second linking plane P2 can interconnect multiple neighboringprotrusions (such as multiple first protrusions 214) so that each protrusion is connected to both the first linking plane Pl and the second linking plane P2.

[0114] In some embodiments, the at least one second protrusion 218 extends radially beyond the at least one first protrusion 214 prior to post-processing (see FIG. 6) and is radially shortened during or after post-processing (see FIG. 7). This extension enables improved clamping and secure fixation of the body 310 during mechanical processing, such as CNC machining. In a subsequent processing step, the at least one second protrusion 218 may be reduced to align with the final outer shape or diameter of the thermal coupling device.

[0115] While the foregoing is directed to embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

CLAIMS1. Thermal coupling device (200), comprising: a body (210) configured to provide a thermal interface between a cryogenic material (20) and a thermal bus, the body (210) having an interface surface (IFS) configured to establish thermal contact between the body (210) and the cryogenic material (20), wherein a surface to volume ratio of the body (210) with respect to the cryogenic material (20) is at least 20 / cm, preferably at least 50 / cm.

2. Thermal coupling device (200), comprising: a body (210) configured to provide a thermal interface between a cryogenic material (20) and a thermal bus, the body (210) having an interface surface (IFS) configured to establish thermal contact between the body (210) and the cryogenic material (20), wherein a ratio of the interface surface (IFS) of the body (210) relative to a volume of the body (210) is at least 100 / cm, preferably at least 125 / cm.

3. Thermal coupling device (200), comprising: a body (210) configured to provide a thermal interface between a cryogenic material (20) and a thermal bus, the body (210) having an interface surface (IFS) configured to establish thermal contact between the body (210) and the cryogenic material (20), wherein the interface surface (IFS) of the body (210) has a roughness of at least 50pm, preferably at least 100pm.

4. Thermal coupling device (200) of claim 3, wherein the interface surface (IFS) of the body (210) includes a granular structure.

5. Thermal coupling device (200) of any one of claims 1 to 4, further including a containing structure (220) configured to accommodate the body (210) and the cryogenic material (20), particularly wherein the containing structure (220) has a cylindrical shape.

6. Thermal coupling device (200) of any one of claims 1 to 5, wherein the body (210) is made of copper, in particular wherein the body (210) is made of heat-treated copper having a thermal conductivity of at least 400 W / m / K at 4K, preferably at least 600 W / m / K at 4K.

7. Thermal coupling device (200) of any one of claims 1 to 6, wherein the body (210) is a single piece and / or the thermal coupling device (200) includes a base on which the body (210) is deposited.

8. Thermal coupling device (200) of any one of claims 1 to 7, wherein the body (210) has a longitudinal axis (LA), and its cross-sectional shape in a plane perpendicular to the longitudinal axis (LA) is star shaped or fan shaped.

9. Thermal coupling device (200) of any one of claims 1 to 8, wherein the body (310) includes: at least one first protrusion (214); at least one second protrusion (218); and a stabilizing structure (320) provided by the at least one second protrusion (218), in particular wherein the at least one first protrusion (214) has a first thickness and the at least one second protrusion (321) has a second thickness greater than the first thickness.

10. Thermal coupling device (200) of claim 9, wherein the stabilizing structure (320) includes a tangentially extending linking structure (322) which interconnects multiple neighboring first protrusions (214), in particular wherein the linking structure (322) includes one or more interruptions (324).

11. Thermal coupling device (200) of any one of claims 1 to 10, wherein the body (210) is configured as a heat exchanger, a thermal bus or a thermalization platform.

12. Thermal coupling device (200) of any one of claims 1 to 11, wherein the cryogenic material (20) is an adiabatic demagnetization material.

13. Thermal coupling device (200) of any one of claims 1 to 12, wherein the thermal coupling device (200) is configured to cool gas for liquefaction, particularly wherein the thermal coupling device (200) is configured for use in hydrogen liquefaction.

14. Cryogenic system (100), comprising: a vacuum chamber (110); and a cooling system (130) inside the vacuum chamber (110), wherein the cooling system (130) includes one or more thermal coupling devices (200) of any one of claims 1 to 13.

15. Cryogenic system (100) of claim 14, further comprising a thermal path between a cooling source location of the cooling system (130) and a cooling target location, wherein the thermal path includes substantially only one thermal element for thermal transfer between the cooling source location and the cooling target location.

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