US-12618593-B2 - Cryogenic cooling system

US12618593B2US 12618593 B2US12618593 B2US 12618593B2US-12618593-B2

Abstract

A cryogenic cooling system is provided comprising a cryogenic refrigerator assembly and two or more connected modules. The cryogenic refrigerator assembly comprises one or more cryogenic refrigerators. Each said connected module comprises: a housing defining an internal volume for the module, the housing having a plurality of side faces, and a plurality of stages arranged within the internal volume for the module, wherein one or more of the plurality of stages is thermally coupled to the cryogenic refrigerator assembly. The two or more said modules are mutually connected at respective side faces, and a first said stage of a first said module is thermally coupled to a first said stage of a second said module.

Inventors

Linshu Jiang
Robin Brzakalik
Chris Wilkinson
Anthony Matthews
Matthew Martin
Timothy Poole
Timothy Foster

Assignees

OXFORD NANOSCIENCE LIMITED

Dates

Publication Date: 20260505
Application Date: 20250430
Priority Date: 20220516

Claims (20)

1 . A cryogenic cooling system comprising: a cryogenic refrigerator assembly comprising one or more cryogenic refrigerators; and two or more connected modules, each of the two or more connected modules comprising: a housing defining an internal volume of the module, the housing having a plurality of side faces; and a plurality of stages arranged within the internal volume of the module, wherein one or more of the plurality of stages is thermally coupled to the cryogenic refrigerator assembly, wherein the stages are planar and spaced apart along a common axis perpendicular to the planes of the stages; wherein the two or more said modules are mutually connected at respective side faces; wherein the housings of the connected modules together define a common internal volume of the system which is hermetically sealed from the surrounding environment; and wherein two or more stages of the plurality of stages of a first said module are connected within the common internal volume to respective stages of the plurality of stages of a second said module, the cryogenic cooling system further comprising a plurality of extension plates, wherein each of the two or more stages of the first module is mechanically connected to a corresponding stage of the plurality of stages of the second module by a respective extension plate of the plurality of extension plates.
2 . The cryogenic cooling system of claim 1 , wherein one or more of the extension plates thermally couples a connected stage of the two or more stages of the first module to a corresponding connected stage of the two or more stages of the second module.
3 . The cryogenic cooling system of claim 1 , wherein the extension plates are planar.
4 . The cryogenic cooling system of claim 3 , wherein the extension plates are coplanar with the respective connected stages of the first module and the second module.
5 . The cryogenic cooling system of claim 1 , wherein the extension plates are configured to support a target assembly comprising electrical circuitry extending within the internal volume of the system and between the stages of two or more said connected modules.
6 . The cryogenic cooling system of claim 1 , wherein each said module comprises an aperture in a said side face of the housing, wherein the aperture extends around the plurality of stages, wherein said aperture is arranged at an interface between the two or more connected modules, wherein the extension plates extend across the interface between the first module and the second module.
7 . A cryogenic cooling system comprising: a cryogenic refrigerator assembly comprising one or more cryogenic refrigerators; and two or more connected modules, each of the two or more connected modules comprising: a housing defining an internal volume of the module, the housing having a plurality of side faces; and a plurality of stages arranged within the internal volume of the module, wherein one or more of the plurality of stages is thermally coupled to the cryogenic refrigerator assembly, wherein the stages are planar and spaced apart along a common axis perpendicular to the planes of the stages; wherein the two or more said modules are mutually connected at respective side faces; wherein the housings of the connected modules together define a common internal volume of the system which is hermetically sealed from the surrounding environment; and wherein two or more stages of the plurality of stages of a first said module are connected within the common internal volume to respective stages of the plurality of stages of a second said module, the cryogenic cooling system further comprising a plurality of expandable joints, each expandable joint of the plurality of expandable joints being configured to accommodate differential thermal contraction between connected stages of the plurality of stages of the first module and the plurality of stages of the second module.
8 . The cryogenic cooling system of claim 7 , further comprising a plurality of extension plates, wherein each stage of the two or more connected stages of the first module is connected to a corresponding stage of the two or more stages of the second module by a respective extension plate of the plurality of extension plates, wherein each expandable joint of the plurality of expandable joints forms part of a respective extension plate of the plurality of extension plates.
9 . The cryogenic cooling system of claim 7 , wherein one or more of the expandable joints thermally couples a respective connected stage of the two or more stages of the first module to a corresponding respective connected stage of the two or more stages of the second module.
10 . The cryogenic cooling system of claim 1 , wherein the two or more connected modules comprises three or more connected modules, wherein a first stage of the two or more connected stages of the first module is thermally coupled to a first stage of the two or more connected stages of the second module by a first stage of the two or more stages of a third said module.
11 . The cryogenic cooling system of claim 1 , wherein one or more of the two or more connected modules comprises a door provided on a side face of the plurality of side faces, wherein the door can be opened to provide access to the interior of the module.
12 . The cryogenic cooling system of claim 1 , wherein each said module is configured so that the housing has a prismatic form with a polygonal cross-section in a plane normal to the axis of alignment of the stages of the module.
13 . The cryogenic cooling system of claim 1 , wherein the housing of each module has a quadrilateral cross-section in a plane normal to the axis of alignment of the stages.
14 . A cryogenic cooling system comprising: a cryogenic refrigerator assembly comprising one or more cryogenic refrigerators; and two or more connected modules, each of the two or more connected modules comprising: a housing defining an internal volume of the module, the housing having a plurality of side faces; and a plurality of stages arranged within the internal volume of the module, wherein one or more of the plurality of stages is thermally coupled to the cryogenic refrigerator assembly, wherein the stages are planar and spaced apart along a common axis perpendicular to the planes of the stages; wherein the two or more said modules are mutually connected at respective side faces; wherein the housings of the connected modules together define a common internal volume of the system which is hermetically sealed from the surrounding environment; wherein two or more stages of the plurality of stages of a first said module are connected within the common internal volume to respective stages of the plurality of stages of a second said module; and wherein the first said module comprises a first dilution unit, the first dilution unit comprising a still mounted to a still stage of the plurality of stages of the first said module; and wherein the second said module comprises a second dilution unit, the second dilution unit comprising a still mounted to a still stage of the plurality of stages of the second said module, wherein the still stages of the first and second modules are connected by a connecting member arranged within the internal volume of the system.
15 . The cryogenic cooling system of claim 14 , wherein the still stages of the first and second modules are thermally coupled by the connecting member.
16 . The cryogenic cooling system according to claim 1 , wherein each of the connected modules comprises a nested assembly of heat radiation shields, each said heat radiation shield of the nested assembly being connected to a respective stage of the plurality of stages of the module.
17 . The cryogenic cooling system according to claim 16 , further comprising a plurality of shield extension sections, each shield extension section of the plurality of shield extension sections connecting respective surfaces of the nested assembly of heat radiation shields of adjacent modules of the two or more connected modules, wherein each shield extension section is configured to allow relative movement between the connected surfaces of the nested assembly of heat radiation shields of the adjacent modules.
18 . The cryogenic cooling system according to claim 17 , wherein each shield extension section comprises a flexible joint.
19 . The cryogenic cooling system of claim 16 , wherein the combination of each heat radiation shield and its respective connected stage defines a quadrilateral profile when viewed in a plane extending across an interface between two connected modules of the two or more connected modules.
20 . The cryogenic cooling system of claim 16 , wherein the nested assembly of heat radiation shields of each module comprises a plurality of shield surfaces, each shield surface being detachable from the nested assembly and comprising a handle.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a divisional application of and claims priority to U.S. patent application Ser. No. 18/673,039, filed on May 23, 2024, which is a continuation application based on and claims the benefit of International Application PCT/GB2023/051226, filed on May 10, 2023 (published on Aug. 24, 2023), which is itself based on and claims the benefit of Great Britain Application No. 2207170.8, filed on May 16, 2022, entitled “Cryogenic Cooling System”, all of which are hereby incorporated by reference in their entirety. FIELD OF THE INVENTION The present invention relates to the field of cryogenic cooling systems. A particularly desirable application of the technology is commercial-scale superconducting quantum computing. BACKGROUND TO THE INVENTION The scale-up of quantum computing, based on superconducting quantum information processing (QIP) devices, will require a continuously low temperature on the order of 10-20 mK or less for QIP device operation. For this, it is envisaged that dilution refrigerators (DRs) will be essential. Today's industrial QIP companies use commercially-available cryogen-free (“dry”) dilution refrigerators that follow a traditional form-factor: a series of vertically-spaced copper plates, with circular cross section, thermally isolated from each other, with a single dilution unit installed between the lower stage plates. Together with the pipework connected to the dilution unit inlet and outlet, and the pumping hardware, a closed cycle dilution refrigerator is created. Concentric, cylindrical radiation shields enclose each stage plate of the dilution refrigerator insert, to reduce the radiated heat load onto the dilution refrigerator stages (˜0.8 K at the still stage, down to below 10 mK at the mixing chamber stage). The whole assembly is enclosed in a cylindrical vacuum vessel. The assembly is often frame-mounted to enable radiation shield and outer vacuum chamber (OVC) removal. An example of a prior art dilution refrigerator, as discussed above, is shown by FIGS. 1 and 2. FIG. 1 shows a perspective view of a cylindrical outer vacuum chamber 1 supported by a cryostat support frame 10. External components of a helium gas handling system 2 and a cryogen-free refrigerator in the form of a pulse tube refrigerator (PTR) 3 are also visible. FIG. 2 is a perspective view of a cross-section taken through the outer vacuum chamber 1. The PTR and dilution unit are not shown in FIG. 2 for sake of clarity. There is a tiered arrangement of thermal stages 5-9, each in the form of a circular plate and being cooled to a respective temperature in use. A nested assembly of cylindrical radiation shields 4 is also visible, with each shield connected to a respective thermal stage. A first stage of the PTR 3 is mounted to a PT1 stage 5, and a second stage of the PTR 3 is mounted to a PT2 stage 6. A dilution unit forms part of the dilution refrigerator, the dilution unit comprising a still and a mixing chamber, connected by a set of heat exchangers. The still is mounted to a still stage 7 and the mixing chamber is mounted to a mixing chamber stage 9. An operational fluid formed of a helium-3/helium-4 mixture is circulated around the dilution unit during operation. The still and the mixing chamber cool the system as a result of a phase change or mixing of the operational fluid. Cooling is obtained at the mixing chamber from the enthalpy of mixing as helium-3 is diluted into helium-4. The mixing chamber is thereby operable so as to obtain the lowest temperature of any part of the dilution refrigerator. Helium-3 is boiled at the still, which removes energy due to the latent heat of vaporisation. A “cold plate” 8, forming a respective thermal stage, is arranged between the still stage 7 and the mixing chamber stage 9 and obtains an intermediate temperature in use. A cylindrical heat radiation shield is connected to each of the PT1 stage 5, PT2 stage 6 and the still stage 7 enclosing the lower temperature stages. In low temperature applications such as QIP, various dissipative elements are installed across different stages of the dilution refrigerator to ensure adequate thermalisation of experimental wiring. Dissipated heat from resistive elements and conductive wiring adds to the heat load on the dilution refrigerator, which means that more cooling power is required in order to maintain a given base temperature for the system. Although the above form-factor (described with reference to FIGS. 1 and 2) has worked very well in the academic environment, where most dry DR systems have been installed, as QIP scales up in an industrial setting, this form factor starts to become limiting. Large radiation shields are cumbersome to handle. Such a system is fixed in size, which limits the maximum experiment size and the available cooling power at each stage. Whilst it is possible to design a very large vacuum chamber and cryogenic refrigerators as a way of providing physical s