Fault-tolerant cryogenic refrigeration

Abstract

A gas handling system for a cryogenic refrigerator includes a first gas handling chain made up of plural components connected in series. A reconfigurable gas interconnection network interconnects the components of the gas handling chain with corresponding substitute components. The gas interconnection network is configurable to substitute a corresponding standby component for a component of the gas handling chain by changing states of valves of the gas interconnection network. The substitute components may form a second gas handling chain. A control system may control gas interconnection network based on sensor signals to detect problems with the components and to substitute corresponding standby components for components for which problems were detected, without interrupting operation of the gas handling system.

Description

FAULT-TOLERANT CRYOGENIC REFRIGERATIONCross-Reference to Related Application

[0001] This application claims priority from US application No. 63 / 752498 filed 31 January 2025 and entitled FAULT-TOLERANT CRYOGENIC REFRIGERATION which is hereby incorporated herein by reference for all purposes. For purposes of the United States of America, this application claims the benefit under 35 U.S.C. §119 of US application No. 63 / 752498 filed 31 January 2025 and entitled FAULT-TOLERANT CRYOGENIC REFRIGERATION which is hereby incorporated herein by reference for all purposes.Field

[0002] The present technology relates to cryogenic refrigeration technology. Aspects of the invention provide cryogenic refrigerators, gas handling systems for cryogenic refrigerators and methods associated with providing fault tolerant cooling to cryogenic temperatures.Background

[0003] Cryogenic refrigerators can be used to cool payloads (a payload could be anything that it is desired to cool to cryogenic temperatures) to very low temperatures (e.g. lower than the boiling point of liquid nitrogen, which is about 77 K at atmospheric pressure). Some cryogenic refrigerators can cool payloads to extremely low temperatures (e.g. temperatures at or below the boiling point of liquid helium - which is about 4.2 Kelvin at atmospheric pressure).

[0004] Still lower temperatures may be achieved by providing a bath of liquid helium in a cryostat and reducing the pressure in the cryostat to below atmospheric pressure. The reduction in pressure causes depression of the boiling point of the helium, which results in the liquid helium bath becoming colder.

[0005] Some cryogenic refrigerators include a liquid helium bath in a cryostat, a vacuum system which draws down the pressure in a volume above the liquid helium bath, a gas compressing system that compresses helium gas collected by the vacuum system and a source of liquid helium for replenishing the helium bath.

[0006] Cryogenic refrigeration has a wide range of applications. For example, cryogenic refrigerators can be used to cool scientific apparatus to temperatures very close to absolute zero. At these temperatures, physical phenomena such as Bose-Einstein condensates, superconductivity, superfluidity, and others can be studied.

[0007] Another example application of cryogenic refrigerators is to cool quantum computing apparatus. In quantum computing, information is stored in the quantum states of quantum systems. For example, information may be stored in the quantum states of quantum systems such as electron spins, nuclear spins, superconducting Josephson junctions, trapped ions, trapped neutral atoms, or the like, keeping the quantum systems at temperatures close to absolute zero.

[0008] The quantum states of quantum systems are fragile. Over time, changes in the quantum state of the quantum system by a process called “decoherence” which involves interactions of the quantum system with its environment. The rate at which the fidelity of quantum information decreases as a result of decoherence can be reduced by keeping the quantum systems in which information is stored at temperatures that are close to absolute zero (typically temperatures that are lower than the boiling point of liquid helium - about 4.2 Kelvin at atmospheric pressure).

[0009] In addition to keeping the temperature of the quantum systems that are used to store quantum information in a cryogenic operating temperature range, it is highly desirable to minimize temperature fluctuations. It is also desirable to reduce the number of times that the quantum computing apparatus is cycled from cryogenic temperatures to room temperature and back. Such cycles can take significant time, during which quantum computing cannot be performed. Also, temperature cycling can apply stresses to components and thereby increase the likelihood of failure.

[0010] Cryogenic refrigeration systems typically incorporate multiple mechanical components such as pumps, orifices, heat exchangers or the like. Failure or degradation of any of these components can cause the cryogenic refrigerator to stop working entirely or to work at reduced capacity. Each of these components could fail.

[0011] There is a need for cryogenic refrigeration systems that are reliable. There is a particular need for cryogenic refrigeration systems that can provide consistent operating temperature for cooled components over extended periods of time.Summary

[0012] The present technology has several aspects that may be used together or separately. These aspects include, without limitation: cryogenic refrigeration systems, gas handling systems for use in cryogenic refrigeration applications; control systems configured to perform functions for managing gas handling systems of cryogenicrefrigeration systems and methods for operating cryogenic refrigeration systems.

[0013] One aspect of the present technology provides a gas handling system for a cryogenic refrigerator. The gas handling system comprises: an inlet; an outlet; a first plurality of gas handling components; and a second plurality of gas handling components. Each gas handling component of the second plurality of gas handling components corresponds to and is functionally equivalent to a corresponding gas handling component of the first plurality of gas handling components. The gas handling system includes a gas interconnection network comprising a plurality of valves. The gas interconnection network is configurable to connect the first plurality of gas handling components in series to provide a first gas handling chain connected between the inlet and the outlet. The gas handling interconnection network is reconfigurable to substitute a selected one of the second plurality of gas handling components for the corresponding gas handling component of the first plurality of gas handling components so that the selected one of the second gas handling components is connected to carry gas flowing from the inlet to the outlet and the corresponding one of the first gas handling components is no longer connected to carry gas flowing from the inlet to the outlet.

[0014] In some embodiments, the gas interconnection network is configurable to connect the second plurality of gas handling components in series to provide a second gas handling chain connected between the inlet and the outlet. In some such embodiments, either the first gas handling chain or the second gas handling chain may be used to provide the desired functionality of the gas handling system.

[0015] In some embodiments, the gas interconnection network is operable to substitute for any group of two or more of the first plurality of gas handling components that are sequential in the first gas handling chain, a corresponding group of the second plurality of gas handling components that are sequential in the second gas handling chain.

[0016] In some embodiments, the gas interconnection network comprises: a plurality of cross conduits each of the cross conduits providing fluid connectivity between the first gas handling chain and the second gas handling chain, the cross conduits spaced apart along the first and second gas handling chains, each of the cross conduits connected to the first gas handling chain at a corresponding first location along the first gas handling chain; and connected to the second gas handling chain ata corresponding second location along the second gas handling chain.

[0017] In some embodiments, for each of a plurality of the cross conduits, the valves of the gas interconnection network include one or more valves operable to selectively: connect the cross conduit to a portion of the first gas handling chain upstream from the corresponding first location while blocking flow between the cross conduit and a portion of the first gas handling chain that is downstream from the corresponding first location; or connect the cross conduit to the portion of the first gas handling chain that is downstream from the corresponding first location while blocking flow between the cross conduit and the portion of the first gas handling chain that is downstream from the corresponding first location; or connect the portion of the first gas handling chain upstream from the corresponding first location and the portion of the first gas handling chain downstream from the corresponding first location while blocking flow between the first gas handling chain and the second gas handling chain through the cross conduit.

[0018] In some embodiments, for each of the plurality of the cross conduits, the plurality of valves of the gas interconnection network include one or more valves operable to selectively: connect the cross conduit to a portion of the second gas handling chain that is downstream from the corresponding second location while blocking flow between the cross conduit and a portion of the second gas handling chain that is upstream from the corresponding second location; or connect the cross conduit to the portion of the second gas handling chain that is upstream from the corresponding second location while blocking flow between the cross conduit and the portion of the second gas handling chain that is downstream from the corresponding second location; or connect the portion of the second gas handling chain that is upstream from the corresponding second location and the portion of the second gas handling chain that is downstream from the corresponding second location while blocking flow between the first gas handling chain and the second gas handling chain through the cross conduit.

[0019] In some embodiments, each gas handling component of the first plurality of gas handling components corresponds to at least one of the gas handling components of the second plurality of gas handling components and the gas interconnection network is reconfigurable to substitute for any one of the first plurality of gas handling components, the corresponding gas handling component of thesecond plurality of gas handling components.

[0020] In some embodiments, the gas handling system is reconfigurable while the gas handling system is in operation to switch between a first configuration in which the first gas handling chain is in an operational mode, the second gas handling chain is in a standby mode, and the plurality of valves are set to direct gas flow from the inlet to pass through the first gas handling chain and a second configuration in which the second gas handling chain is in the operational mode, the first gas handling chain is in the standby mode, and the plurality of valves are set to direct gas flow from the inlet to pass through the second gas handling chain.

[0021] In some embodiments, for each components of the first gas handling chain, the components of the second gas handling chain includes a corresponding component that is functionally equivalent to the component of the first gas handling chain.

[0022] In some embodiments, the gas interconnection network includes a plurality of ports, the plurality of valves of the gas interconnection network include valves configurable to isolate each of the plurality of ports, and the plurality of ports are arranged to allow connection of a third gas handling chain without interrupting operation of the first gas handling chain or the second gas handling chain.

[0023] In some embodiments, the gas interconnection network is selectively configurable to, while the gas handing system is in operation, the first gas handling chain is operating and the second gas handling chain is in a standby mode, switch to operating the second gas handling chain and place the first gas handling chain in the standby mode.

[0024] In some embodiments, the second plurality of gas handling components includes gas handling components of at least two distinct types, each of the distinct typers providing different functionality.

[0025] In some embodiments, the first plurality of gas handling components and the second plurality of gas handling components each include at least one vacuum pump.

[0026] In some embodiments, the first plurality of gas handling components and the second plurality of gas handling components each include at least one orifice.

[0027] In some embodiments, the first plurality of gas handling components and the second plurality of gas handling components each include at least one gas compressor.

[0028] In some embodiments, the first plurality of gas handling components and the second plurality of gas handling components each include at least one heat exchanger.

[0029] In some embodiments, the first gas handling chain includes a vacuum pump and a gas compressor located downstream from the vacuum pump in a direction of flow from the inlet of the gas handling system to the outlet of the gas handling system.

[0030] In some embodiments, the gas interconnect network is configurable, while the gas handing system is in operation, to change a path by which gas can flow from the input of the gas handling system to the output of the gas handling system.

[0031] In some embodiments, the gas interconnection network is configurable to, while the selected one of the second plurality of gas handling components is substituted for the corresponding gas handling component of the first plurality of gas handling components, isolate the corresponding gas handling component of the first plurality of gas handling components.

[0032] In some embodiments, the gas handling system comprises an auxiliary vacuum pump connectable to, while the corresponding gas handling component of the first plurality of gas handling components is isolated and the selected one of the second plurality of components is substituted for the corresponding gas handling component of the first plurality of gas handling components, evacuate the corresponding gas handling component of the first plurality of gas handling components.

[0033] In some embodiments, the gas handling system comprises a vacuum leak detector, wherein the gas interconnection network is configurable to isolate a region of the gas handling system comprising one or more of the first plurality of gas handling components or one or more of the second plurality of gas handling components from the inlet and the outlet of the gas handling system and to connect the vacuum leak detector to detect leaks in the portion of the gas handling system.

[0034] In some embodiments, the second plurality of gas handling components includes at least three gas handling components.

[0035] In some embodiments, the gas handling system comprises a control system, wherein the control system is connected to receive one or more sensor signals, the sensor signals indicative of conditions within the gas handling system and to identify a failing component by processing the sensor signals.

[0036] In some embodiments, the control system is configured to, if the failing component is one of the first plurality of components that has failed or is at risk of failing, control the gas interconnection network to identify and select as the selected one of the second plurality of gas handling components, one of the second plurality of gas handling components that corresponds to the failing component.

[0037] In some embodiments, the control system is connected to control the plurality of valves of the gas interconnection network.

[0038] In some embodiments, the control system is configured to automatically reconfigure the gas interconnection network to substitute the selected one of the second plurality of gas handling components for the failing gas handling component.

[0039] In some embodiments, the control system is configured to, in response to a command to substitute the selected one of the plurality of second gas handling components for the corresponding one of the first plurality of gas handling components, automatically control the gas interconnection network to perform the commanded substitution.

[0040] In some embodiments, the command is generated by the control system.

[0041] In some embodiments, the control system comprises a user interface operable to generate the command in response to user input.

[0042] In some embodiments, the control system is configured to substitute the selected one of the second plurality of gas handling components for the corresponding one of the first plurality of gas handling components, by controlling the plurality of valves to gradually equalize pressure of the selected one of the plurality of second gas handling components with the corresponding one of the first plurality of gas handling components, prior to causing gas flowing from the inlet to the outlet to pass though the selected one of the second plurality of gas handling components.

[0043] In some embodiments, the first plurality of gas handling components comprises a first heat exchanger, the second plurality of gas handling components comprises a second heat exchanger, the first heat exchanger and the second heat exchanger correspond to one another and the control system is configured to identify the first heat exchanger as a failing component in response to determining from the sensor signals that a measure of a pressure drop across the first heat exchanger exceeds a pressure drop threshold and / or is increasing relative to a prior value of the pressure drop at a rate that exceeds a pressure drop increase rate threshold.

[0044] In some embodiments, the control system is configured to, in changing states of the valves of the gas interconnection network to substitute a standby component for an active component of the gas handling system, slowly equalize pressure at the standby component with pressure of gas at the active component.

[0045] In some embodiments, the control system is configured to, in changing states of the valves of the gas interconnection network to substitute a standby component for an active component of the gas handling system, setting the valves to allow gas to start flowing through the standby component before setting the valves to isolate the active component.

[0046] In some embodiments, the control system is configured to set the valves to allow gas flow in both the active component and the standby component for a time period.

[0047] In some embodiments, the control system is configured to, during the time period while gas is flowing in both the active component and the corresponding standby component, change settings of the valves gradually, thereby allowing gas flow in the standby component to increase while gas flow in the active component decreases, until all of the gas flow is through the standby component.

[0048] In some embodiments, the control system is configured to access scheduling information relating to a payload and the control system is scheduled to make changes in the configuration of the gas interconnection network at times when the scheduling information indicates that such changes are acceptable.

[0049] In some embodiments, the control system has access to a calendar of scheduled maintenance for one or more of the components of the gas handing system and the control system is configured to, if a component is active and requires scheduled maintenance, control the valves of the gas interconnection network to substitute a corresponding standby component for the component that requires scheduled maintenance.

[0050] In some embodiments, the plurality of valves of the gas interconnection network are pneumatically controlled.

[0051] Another aspect of the present technology provides a method for operating a gas handling system for a cryogenic refrigerator. In some embodiments, the gas handling system comprises: an inlet, an outlet, a plurality of gas handling components, and a gas interconnection network. The gas interconnection networkcomprises a plurality of valves configurable to connect selected ones of the plurality of components in series in a sequence between the inlet and the outlet to provide a first gas handling chain. The first gas handling chain is operable to support operation of a cryogenic refrigerator. The method comprising: operating the first gas handling chain; selecting one of the components of the first gas handling chain to be taken out of service; while the first gas handling chain is operating, reconfiguring the gas interconnection network to substitute for the selected component another one of the components that corresponds to the selected component and isolating the selected component from the first gas handling chain.

[0052] In some embodiments, the method comprises gradually equalizing pressure between the selected component and the component that corresponds to the selected component prior to isolating the selected component.

[0053] In some embodiments, the method comprises, fora period of time prior to isolating the selected component, configuring the gas interconnection network to flow gas through both of the selected component and the component that corresponds to the selected component.

[0054] In some embodiments, the method comprises, during the time period, decreasing the flow of the gas through the selected component while increasing the flow of the gas through the component that corresponds to the selected component.

[0055] In some embodiments, the method comprises replacing the selected component with a replacement component while the selected component is isolated from the gas handling chain.

[0056] In some embodiments, the method comprises evacuating the replacement component and subsequently reconfiguring the gas interconnection network to substitute the replacement component for the component that corresponds to the selected component.

[0057] In some embodiments, the method comprises leak testing the replacement component prior to substituting the replacement component for the component that corresponds to the selected component.

[0058] In some embodiments, the gas interconnection network comprises first conduits extending between sequentially adjacent components of the first gas handling chain, second conduits extending between sequentially adjacent components of a second gas handling chain and cross conduits that each connectone of the first conduits to a corresponding one of the second conduits. In such embodiments, reconfiguring the gas interconnection network to substitute for the selected component another one of the components that corresponds to the selected component may comprise opening one of the cross conduits to allow gas to flow to the corresponding component in the second gas handling chain while blocking gas flow to the selected component in the first gas handling chain.

[0059] In some embodiments, the method is performed by an automatic control system connected to control the gas interconnection network.

[0060] Another aspect of the present technology provides a control system comprising a data processor configured by machine readable instructions to perform a method for operating a gas handling system for a cryogenic refrigerator as described herein.

[0061] Another aspect of the present technology provides a non-transitory medium containing machine readable instructions which, when executed by a data processor of a control system cause the data processor to execute a method for operating a gas handling system for a cryogenic refrigerator.

[0062] Another aspect of the present technology provides a gas handling system for a cryogenic refrigerator. The gas handling system comprises a first gas handling chain comprising a plurality of gas handling components connected in series between an inlet to the gas handling system and an outlet from the gas handling system and a second gas handling chain comprising a plurality of gas handling components. A plurality of the components of the second gas handling chain are each functionally equivalent to a corresponding one of the components of the first gas handling chain. The gas handling system comprises a gas interconnection network that comprises valves operable to substitute for a selected one of the components of the first gas handling chain the corresponding component from the second gas handling chain by diverting gas from flowing through the selected one of the components of the first gas handling chain to instead flow though the one of the components of the second gas handling chain that corresponds to the selected component of the first gas handling chain.

[0063] In some embodiments, the gas interconnection network comprises a plurality of first conduits that connect the components of the first gas handling chain in series, a plurality of second conduits that connect the components of the second gashandling chain in series, and a plurality of third conduits connected between corresponding ones of the first and second conduits. The third conduits cross between locations along the first and second gas handling chains and may therefore be called “cross-conduits”.

[0064] In some embodiments, for each of a plurality of the third conduits, the valves of the gas interconnection network include one or more valves operable to selectively: connect the third conduit to an upstream segment of the corresponding first conduit that is upstream from a junction of the corresponding first conduit and the third conduit; or connect a downstream segment of the corresponding first conduit that is downstream from the junction of the corresponding first conduit to the third conduit; or connect the upstream segment of the corresponding first conduit to the downstream segment of the corresponding first conduit while blocking flow between the third conduit and the corresponding first conduit.

[0065] In some embodiments, for each of the plurality of the third conduits, the valves of the gas interconnection network include one or more valves operable to selectively: connect the third conduit to an upstream segment of the corresponding second conduit that is upstream from a junction of the corresponding second conduit and the third conduit; or connect a downstream segment of the corresponding second conduit that is downstream from the junction of the corresponding second conduit and the third conduit to the third conduit; or connect the upstream segment of the corresponding second conduit to the downstream segment of the corresponding second conduit while blocking flow between the third conduit and the corresponding second conduit.

[0066] In some embodiments, the gas interconnection network is selectively configurable to, while the gas handing system is in operation, the first gas handling chain is operating and the second gas handling chain is in a standby mode, switch to operating the second gas handling chain and place the first gas handling chain in the standby mode.

[0067] In some embodiments, for each of the components of the first gas handling chain, the components of the second gas handling chain includes a component that corresponds to the component of the first gas handling chain.

[0068] In some embodiments, the components of the first gas handling chain include a vacuum pump and a gas compressor located downstream from the vacuum pumpin a direction of flow from the inlet of the gas handling system to the outlet of the gas handling system.

[0069] In some embodiments, the second gas handling chain includes at least three components that respectively correspond to corresponding components of the first gas handling chain and the gas interconnection network includes valves operable to substitute any one of the components of the second gas handling chain fora corresponding one of the components of the first gas handling chain.

[0070] In some embodiments, the second gas handling chain includes at least three components that respectively correspond to corresponding components of the first gas handling chain and the gas interconnection network includes valves operable to substitute any group of two or more sequential ones of the components of the second gas handling chain fora corresponding group of two or more sequential ones of the components of the first gas handling chain.

[0071] In some embodiments, the valves of the gas interconnection network comprise valves operable to isolate the selected one of the components of the first gas handling chain while the corresponding component from the second gas handling chain is operating.

[0072] In some embodiments, the gas handling system comprises an auxiliary pump connectable to evacuate the selected one of the components of the first gas handling chain while the corresponding component from the second gas handling chain is operating.

[0073] In some embodiments, the gas interconnection network includes a plurality of ports, and the valves of the gas interconnection network include valves configurable to isolate each of the ports, and the ports are arranged to allow connection of a third gas handling chain without interrupting operation of the first gas handling chain or the second gas handling chain.

[0074] In some embodiments, the gas handling system comprises a control system connected to control the valves of the gas interconnection network, wherein the control system is configured to, in response to a command to substitute for the selected one of the components of the first gas handling chain the corresponding component from the second gas handling chain, automatically control the valves to perform the commanded substitution.

[0075] In some embodiments, the selected component of the first gas handling chainis a heat exchanger and the controller is configured to configured to identify the selected component of the first gas handling chain by processing the sensor signals to obtain a measure of a pressure drop across the heat exchanger and determining that the pressure drop exceeds a threshold and / or is increasing relative to a prior value of the pressure drop.

[0076] In some embodiments, the control system is configured to, in changing states of the valves of the gas interconnection network to substitute a standby component for an active component of the gas handling system, slowly equalize pressure at the standby component with pressure of gas at the active component;

[0077] In some embodiments, the control system is configured to, in changing states of the valves of the gas interconnection network to substitute a standby component for an active component of the gas handling system, setting the valves to allow gas to start flowing through the standby component before setting the valves to isolate the active component.

[0078] In some embodiments, the controller is configured to set the valves to allow gas flow in both the active component and the standby component for a time period.

[0079] In some embodiments, the control system is configured to, during the time period while gas is flowing in both the active component and the corresponding standby component, change settings of the valves gradually, thereby allowing gas flow in the standby component to increase while gas flow in the active component decreases, to the point where all of the gas flow is through the standby component.

[0080] In some embodiments, the control system has access to scheduling information relating to a payload and the control system is scheduled to make changes in the configuration of the gas interconnection network at times when the payload scheduling information indicates that such changes are acceptable.

[0081] In some embodiments, the control system has access to a calendar of scheduled maintenance for one or more components of the gas handing system and the control system is configured to, if a component is active and requires scheduled maintenance, control the valves of the gas interconnection network to substitute a corresponding standby component for the component that requires scheduled maintenance.

[0082] In some embodiments, the control system is configured to identify the selected component of the first gas handling chain based on sensor signals from sensorsassociated with the gas handling system and to generate the command in response to processing of the sensor signals indicating that the selected component of the first gas handling chain is failing or has failed.

[0083] Another aspect of the invention provides a cryogenic refrigerator system that incorporates a gas handling system according to any of the embodiments described herein. In some embodiments, the inlet of the gas handling system is in fluid communication with a volume of an evaporator in a cryostat, and the outlet of the gas handling system is in fluid communication with a helium liquification system that is connected to deliver liquid helium to a helium bath in the evaporator.

[0084] In some embodiments, the cryogenic refrigerator system is operable to cool a payload to a temperature of less than 4.2 Kelvin.

[0085] Other aspects of the present technology are described in the following disclosure, including the accompanying claims, and / or illustrated in the accompanying drawings.

[0086] It is emphasized that the invention relates to all combinations of the features, described in this disclosure even if these are recited in different claims.

[0087] Use of the present technology may provide benefits such as one or more of: extending the time that a cryogenic refrigeration system can be operated continuously; reducing undesired temperature excursions at a payload, reducing degradation of a payload and / or components of a cryogenic refrigeration system due to unnecessary thermal cycling; reducing or avoiding time consuming recalibration of a payload as a result of temperature excursions; providing an environment at which a temperature at a payload is maintained within an operating temperature range with reduced temperature fluctuations which may enhance the accuracy, speed and / or success of sensitive operations involving states of quantum systems such as quantum informatics processing and science experiments.Brief Description of the Drawings

[0088] The accompanying drawings illustrate non-limiting example embodiments of the present technology.

[0089] Fig. 1 is a functional block diagram showing a cryogenic refrigeration system according to an example embodiment;

[0090] Fig. 2A is a schematic illustration showing an example gas handling systemhaving redundant components and gas interconnection network configurable to substitute one or more components for corresponding components of the gas handling system.

[0091] Fig. 2B is a schematic illustration showing the example gas interconnection network of Fig. 2A configured so that one redundant component is substituted for a corresponding component of the gas handling system.

[0092] Fig. 2C is a schematic illustration showing the example gas interconnection network of Fig. 2A configured so that several redundant components are respectively substituted for corresponding components of the gas handling system.

[0093] Fig. 3 is a schematic illustration showing an example control system for a gas handling system.

[0094] Figs. 4A through 4D are schematic illustrations that depict example modules that may be used to construct gas interconnection network for a gas handling system.

[0095] Fig. 5 is a schematic diagram showing an example control system and a portion of a gas handling system 18 controlled by control system.Detailed Description

[0096] Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive sense.Overview of cryogenic refrigeration system

[0097] Fig. 1 is a schematic block diagram of a cryogenic refrigeration system 10 according to an example embodiment of the present technology. System 10 includes a cryostat 12 that contains an evaporator 13 which, when system 10 is being operated, contains a liquid helium bath 14.

[0098] System 10 includes a gas handling system 18. Gas handling system 18 operates to evacuate gas from a volume 16 which contains helium gas which has escaped from liquid helium bath 14. Evacuation of the helium gas lowers the temperature of liquid helium bath 14 by reducing pressure in volume 16.

[0099] Helium gas collected by gas handling system 18 is compressed. Thecompressed helium gas is input from gas handling system 18 to a helium liquefaction system 19. Helium liquefaction system 19 liquifies at least some of the helium. Liquid helium from helium liquefaction system 19 may be delivered to replenish helium bath 14.

[0100] Helium liquefaction system 19 may have any of a wide range of constructions. In some embodiments, helium liquefaction system 19 comprises one or more cryocoolers. The cryocooler(s) may operate on any suitable cycles. For example, the cryocoolers may operate on cycles such as Joule-Thomson, Brayton, Claude, Stirling, Solvay, Pulse tube, Gifford-McMahon or variants of these. In some embodiments, the working fluid of the cryocoolers is segregated from the helium gas of gas handling system 18. In some embodiments helium gas from gas handling system 18 is used as a working fluid in helium liquefaction system 19. The architecture described herein may be applied, for example, in liquid helium, and dilution refrigerator systems.

[0101] In some embodiments, gas from gas handling system 18 is cooled and liquefied by contact with cold head(s) of one or more cryocoolers (see e.g. Fig. 3). In some embodiments, gas from gas handling system 18 is cooled by heat exchange with gas being drawn into gas handling system 18 from volume 16 prior to liquefaction.

[0102] System 10 is intended to maintain a payload at a cryogenic temperature. For example, the payload may comprise an apparatus A1 that is in direct or indirect thermal contact with helium bath 14.

[0103] In some embodiments, apparatus A1 comprises quantum informatics apparatus. For example, apparatus A1 may incorporate quantum systems (not shown in Fig. 1) that have quantum states that can be controlled to store and / or manipulate information by interfaces of apparatus A1.

[0104] In some embodiments the cryogenic temperature is lower than 4.2 Kelvin. In some embodiments the cryogenic temperature is lower than 2 Kelvin.

[0105] Gas handling system 18 includes one or more gas handling chains (Fig. 1 shows two gas handling chains 18-1 and 18-2). Each of the gas handling chains comprises a vacuum system connected in series with a gas compression system. The vacuum system may, for example, comprise one or more vacuum pumps. Helium gas output from the vacuum system is supplied to a gas compression system. The gas compression system may, for example, comprise one or more gas compressors andone or more heat exchangers arranged to remove heat from compressed helium gas output by the one or more gas compressors.

[0106] In the example system 10 which is illustrated in Fig. 1, gas handling chain 18-1 comprises a vacuum system 15-1 connected in series with a gas compression system 17-1. Gas handling chain 18-2 comprises a vacuum system 15-2 connected in series with a gas compression system 17-2. Most or all of the components of gas handling chains 18-1 and 18-2 can be located outside of cryostat 12 and do not need to operate at cryogenic temperatures.

[0107] System 10 is made to be resilient to failures of components of gas handling system 18. Non limiting examples of components are: a vacuum pump, compressor, heat exchanger, orifice, gas storage vessel or the like. A “component” is not limited to a single discrete item or device. A component may be a group of two or more items or devices that provide some functionality in system 10.

[0108] In particular, gas handling system 18 includes one or more “standby components”. Each of the standby components corresponds to an active component of gas handling system 18. An “active” component is a component that is in operation. A “standby component” is a redundant component that can be substituted for another component that the standby component corresponds to. The standby component may be the same as or functionally equivalent to the component (e.g., active component) that it corresponds to.

[0109] In system 10 of Fig. 1, each of gas handling chains 18-1 and 18-2, if operating properly, is capable of independently performing the required functions of gas handling system 18. If gas handling chain 18-1 is active and gas handling chain 18-2 is not being used, then gas handling chain 18-2 may be considered to be on standby.

[0110] As discussed in more detail elsewhere herein, in some embodiments, individual components and / or groups of components of gas handling chain 18-2 may be substituted for corresponding individual components or groups of components of gas handling chain 18-1. In such embodiments, the individual components or groups of components of gas handling chain 18-2 may be considered to be standby components or groups of components for corresponding components or groups of components of active gas handling chain 18-1.

[0111] If gas handling chain 18-2 is active and gas handling chain 18-1 is not being used, then the components and / or groups of components of gas handling chain 18-1may be considered to be standby components or standby groups of components for the corresponding components or groups of components of active gas handling chain 18-2.

[0112] System 10, as illustrated in Fig. 1, includes valves V1 and M2. Valves V1 and M2 may be set to direct gas being handled by gas handling system 18 through either gas handling chain 18-1 or gas handling chain 18-2. Valves V1 and M2 may be called “selector valves”. As discussed below, gas handling system 18 may incorporate a reconfigurable gas interconnection network which facilitates substitution of individual components or groups of components of gas handling chain 18-1 by corresponding components or corresponding groups of components of gas handling chain 18-2 and vice versa. As discussed below, gas handling system 18 may additionally include a gas interconnection network (not shown in Fig. 1) that is configurable to substitute individual components or groups of components from gas handling chain 18-1 for components or groups of components of gas handling chain 18-2 or vice versa.

[0113] When gas handling chain 18-1 is active and a component of gas handling chain 18-1 fails then the failure may be remediated by substituting the entire gas handling chain 18-2 for gas handling chain 18-1 or by substituting for the failed component of gas handling chain 18-1 the component of gas handling chain 18-2 that corresponds to the failed component.

[0114] In some embodiments, system 10 includes a standby component that corresponds to each component of a gas handling chain (e.g. 18-1 or 18-2). As described elsewhere herein, standby components can be substituted for active components of system 10 while system 10 is running and without bringing the payload (e.g. A1) of system 10 to room temperature. In some embodiments, the substitution of a standby component for an active component can be performed with substantially no effect on the temperature of evaporator 13 or payload A1 and / or while maintaining payload ,A1 at a temperature not exceeding 4.2 Kelvin.

[0115] Gas handling systems according to some embodiments of the present technology include a plurality of standby components that are functionally equivalent to corresponding active components of gas handling system 18 and a reconfigurable gas interconnection network that enables one of the standby components to be substituted for the corresponding active component with no significant interruption in the operation of system 10. A gas interconnection network may, for example, madeup of vacuum system components such as flanges, vacuum lines, vacuum hoses, flanges, elbows, tees, valves and the like.Example gas interconnection network for redundant gas handling components

[0116] In some embodiments, system 10 includes gas interconnection network 21 (see Figs. 2A to 2C) which is configurable by setting valves to substitute a component of gas handling chain 18-1 fora corresponding component of gas handling chain 18-2 or vice versa. In some embodiments, gas handling chain 18-1 and gas handling chain 18-2 are functionally equivalent (i.e. either one of gas handling chains 18-1 and 18-2 can provide all required functions of gas handling system 18 on its own, when functioning properly). In some embodiments, corresponding components of gas handling chains 18-1 and 18-2 are the same (e.g. the same part number). In some embodiments, it does not matter which of gas handling chains 18-1 and 18-2 is chosen to be “standby” and which of the gas handling chains 18-1, 18-2 is chosen to be “active”. In such embodiments, either one of gas handling chains 18-1 and 18-2 can satisfy the gas handling requirements of system 10.

[0117] In some embodiments, gas handling chain 18-2 comprises components corresponding to all components of gas handling chain 18-1. In some embodiments, gas handling chain 18-2 lacks some components of gas handling chain 18-1. For example, gas handling chain 18-2 may incorporate selected components that correspond to components of gas handling chain 18-1 that have a higher likelihood of failure and may lack components that correspond to one or more components of gas handling chain 18-1 that have a lower likelihood of failure.

[0118] Figs. 2A through 2C schematically illustrate gas interconnection network 21 which can be configured to maintain operation of a gas handling system 18 of apparatus 10 despite failures of one or more components of gas handling chain 18-1 or 18-2. In this example, gas handling chain 18-1 incorporates components 18A-1 through 18E-1 and gas handling chain 18-2 includes components 18A-2 through 18E-2 which respectively correspond to components 18A-1 to 18E-1. For example, components 18A-1 to 18E-1 may include components such as vacuum pumps, booster pumps, gas compressors, heat exchangers, gas storage vessels, and the like.

[0119] Gas interconnection network 21 includes conduits 22-1 that connect the components of gas handling chain 18-1 in series and conduits 22-2 that connect thecomponents of gas handling chain 18-2 in series. Cross-conduits 23 extend between conduits 22-1 and conduits 22-2.

[0120] Gas interconnection network 21 has a ladder-like structure in which conduits 23 correspond to rungs and conduits 22-1 and 22-2 correspond to rails. Conduits 23 provide paths which can be opened to carry gas from gas handling chain 18-1 to gas handling chain 18-2 or vice versa.

[0121] Valves 24 are settable to allow individual ones of components 18A-1 to 18E-1 and 18A-2 to 18E-2 to be isolated as well as to divert flow of helium that would otherwise pass through a particular component of gas handling chain 18-1 to cross to gas handling chain 18-12 and pass instead through a corresponding component of gas handling chain 18-2 or vice versa.

[0122] Various functionally equivalent arrangements of valves 24 may be used to achieve the above configurability.

[0123] Figs. 2A, 2B and 2C illustrate various configurations of valves 24 in a conceptually simple example in which each of valves 24 can be either open or closed. In Figs. 2A, 2B and 2C, a valve 24 that has circle filled with black is closed and a valve 24 that has a circle filled with white is open. Open valves 24 are marked with arrows that indicate a direction of gas flow through the valve.

[0124] Fig. 2A shows a first configuration of valves 24 in which gas handling chain 18-1 is in use and gas handling chain 18-2 is on standby.

[0125] Fig. 2B shows another example configuration in which component 18C-1 of gas handling system 18 has been isolated by closing valves 24 that are immediately upstream and downstream from component 18C-1. Gas interconnection network 21 is additionally configured to direct gas flow to component 18C-2 in place of component 18C-1. After passing through component 18C-2, the gas is returned to gas handling chain 18-1 where the gas continues through component 18D-1.

[0126] With gas interconnection network 21 configured as shown in Fig. 2B, component 18C-1 may be removed from gas handling system 18 or serviced while gas handling system continues to run.

[0127] In embodiments in which the gas interconnection network comprises crossconduits that extend between corresponding locations along the first and second gas handling chains, the gas interconnection network may be configured (e.g. by setting the states of valves) to cause a flow of gas to be carried between the first gashandling chain to the second gas handling chain by one of the cross-conduits. In some embodiments, the gas interconnection network is configurable to provide a gas flow path from the inlet of the gas handling system, through one or more gas handling components of the first gas handling chain, cross to the second gas handling chain, and pass through one or more gas handling components of the second gas handling chain. In such embodiments the gas interconnection network may be further configured so that the gas flow path returns to the first gas handling chain after passing through the one or more gas handling components of the second gas handling chain.

[0128] Reconfiguring the gas interconnection network may, for example have the result of substituting a selected one or more of the gas handling components of the second gas handling chain for a corresponding one or more gas handling component of the first of gas handling chain. After such reconfiguration of the gas interconnection network, the selected one or more of the second gas handling components is connected to carry gas flowing from the inlet to the outlet and the corresponding one or more of the gas handling components of the first gas handling chain is no longer connected to carry gas flowing from the inlet to the outlet. The corresponding one or more of the gas handling components of the first gas handling chain may be serviced or replaced while the gas handling system continues to operate.

[0129] Fig. 2C shows another example configuration of valves 24 in which components 18C-1, 18D-1 and 18E-1 of gas handling chain 18-1 have been isolated and gas that has passed through components 18A-1 and 18B-1 is re-routed to pass through components 18C-2, 18D-2 and 18-E-2.

[0130] With gas handling system 18 in the configuration shown in Fig. 2C, any or all of isolated components 18C-1, 18D-1 and 18E-1 may be removed from gas handling system 18 or serviced while gas handling system 18 continues to run.

[0131] Corresponding components of gas handling chains 18-1 and 18-2 are the same or functionally equivalent. When a component of gas handling chain 18-1 or 18-2 needs to be taken offline for any reason, gas interconnection network 21 may be reconfigured to substitute the corresponding component of the other gas handling system (18-2 or 18-1) for the component that is to be taken offline. A component may be taken offline for various reasons including, for example, the component has failed, the component is showing signs that it is failing or behaving abnormally, thecomponent should be taken offline for preventative maintenance, the component is to be replaced with a new, refurbished or improved component, etc.

[0132] In some embodiments, the components of gas handling chains 18-1 and 18-2 are respectively mounted to separate chassis. This facilitates removing or adding one of gas handling chains 18-2 and 18-1 as a unit. Gas interconnection network 21 may be configured to allow removal of gas handling chain 18-1 or 18-2 without interrupting the operation of system 10, which can continue operation using the other one of gas handling chains 18-2, 18-1. For example, in the embodiment shown in Figs. 2A to 2C, conduits 23 each include two valves 24. With both of these valves 24 closed in each of conduits 23, conduits 23 may be disconnected between the closed valves (e.g. by uncoupling a coupler in conduit 23). In some embodiments, gas handling chains 18-1 and 18-2 are substantially identical.Example gas interconnection network variations

[0133] Gas interconnection network 21 may be varied to accommodate gas handling chains that have any practical number of series-connected components. In some embodiments, gas interconnection network 21 supports three or more gas handling chains.

[0134] The functionality as described herein may be achieved with valves of other types than the simple valves illustrated in Figs. 2A to 2C. For example, some embodiments incorporate three-way valves that can provide the functionality of two or more of the valves 24 shown in Figs. 2A to 2C.Another gas interconnection network example

[0135] Fig. 3 is a diagram showing another example of gas interconnection network 21 that includes details not shown in Figs. 2A to 2C. Fig. 3 uses the same references as used in Figs. 2A to 2C to reference elements that are described above.

[0136] System 10 as shown in Fig. 3 includes a cryocooler 31 that cools and liquefies helium gas provided by gas handling system 18. Cryocooler 31 is driven by a supply of compressed helium gas circulated around a circuit 33 by a compressor 32.

[0137] Fig. 3 also shows that gas interconnection network 21 can include ports 34. Valves 24 may be configured to place a selected port 34 in fluid communication with a particular component of gas handling system 18 and / or a section of gas interconnection network 21. A port 34 may be connected to an auxiliary vacuumpump to evacuate a component and / or section of gas interconnection network 21 with which the port 34 is in fluid communication.

[0138] A port 34 may also be used to prefill a component of gas handling system 18 and / or a portion of gas interconnection network 21 with which the component is in fluid communication with helium gas.

[0139] Ports 34 may also be used to leak check portions of gas interconnection network 21 and / or standby components or groups of standby components of gas handling system 18 while system 10, including gas handling system 18, continues to operate.

[0140] A set of ports 34 may also be used to connect an additional redundant gas handling chain or individual gas handling components or groups of gas handling components. The added gas handling chain or components may be placed into active use or be used as standbys for a corresponding gas handling chain, gas handling component or group of gas handling components as applicable.

[0141] Fig. 3 also shows example sensors 36 which may be provided to monitor gas conditions (e.g. pressure, temperature and / or flow rate) at various points along gas handling chains 18-1, 18-2. Signals output by sensors 36 may be input to a control system as described elsewhere herein.

[0142] The gas interconnection network of gas handling systems as described herein may have a modular construction. Figs. 4A, 4B, and 4C collectively show a set of modular elements 41 (individually identified as elements 41 A, 41 B, 41 C and 41 D that can be used to construct gas interconnection network 21 for a gas handling system 18. A module 41 A is provided at the input of the gas handling system, a module 41 D is provided at the output of the gas handling system. A minimal gas handling system additionally includes one module 41 B which supports two components of a gas handling chain 18-1 and one module 41 C which supports two components of a gas handling chain 18-2.

[0143] For each additional component of the gas handling chains of the gas handling system being designed an additional pair of modules 41 B, 41 C may be added. The modular design illustrated in Figs. 4A to 4D can support gas handling chains of any practical length.

[0144] Modules similar to modules 41 A to 41 D may be assembled to provide gas interconnection network for any practical number of gas handling chains. Ideally eachgas handling chain includes a port 34 in each section of the corresponding conduit 22 that is connected to a conduit 23. Where there are three or more gas handling chains, conduits 23 may be arranged to provide different topologies. For example, three gas handling chains may be connected by conduits 23 so that a middle gas handling chain is directly connectable to each of the other gas handling chains by conduits 23 while the other two gas handling chains are not directly connected by a conduit 23. In another topology, conduits 23 are arranged so that each of the gas handling chains is directly connectable to each of the other gas handling chains by corresponding conduits 23.Example control system

[0145] In some embodiments, valves 24, and optionally other components of system 10 such as components of gas handling chains 18-1 and 18-2 are controlled automatically by a control system. The control system may, for example, comprise a data processor configured by software (e.g. firmware) instructions to provide control system functionality as described herein. The control system monitors the performance of a system 10. If the monitoring indicates that the performance of system 10 is falling or that system 10 has failed as a result of a problem with gas handling system 18 of apparatus 10 then control system may take action to correct the problem. For example, control system may be configured to substitute a standby gas handling component (e.g. a component of gas handling chain 18-2) for a failed, failing, or degraded gas handling system component (e.g. a corresponding component of gas handling chain 18-1).

[0146] The control system may reconfigure gas interconnection network of a gas handling system 18 to correct a detected problem by selectively opening and / or closing selected ones of valves and, if necessary, preparing the standby gas handling component for operation (e.g. by powering the standby gas handling system component).

[0147] Fig. 5 is a schematic diagram showing an example control system 50 and a portion of a gas handling system 18 controlled by control system 50. Control system 50 is connected to control valves 24 of gas handling system 18. Valves 24 may, for example, be electrically controlled or pneumatically controlled.

[0148] A system 10 that includes controller 50 and gas handling system 18 is instrumented with sensors 36 which measure parameters relevant to the performanceof gas handling system 18. Control system 50 is connected to receive signals 36A from sensors 36.

[0149] In some embodiments, control system 50 presents the sensor readings for review by a human operator. The human operator may decide that the sensor readings indicate a problem that should be remediated by switching an active component of gas handling system 18 for a corresponding standby component of gas handling system 18. Control system 18 may receive a control input from the human operator commanding that the switching be performed. Control system 50 may then implement the switching of the active and standby components as described herein.

[0150] In some embodiments, control system 50 processes the received signals 36A to determine whether there are developing or fully manifested problems with the performance of system 10 and, if so, whether there are actions that control system 50 can take to remediate these problems.

[0151] Sensors 36 may, for example, include sensors selected from the group consisting of: temperature sensors (temperature sensors may, for example, measure temperature of liquid helium bath 14, apparatus A1 , one or more heat exchangers of gas handling system 18, gas temperature at selected locations in gas handling system 18, operating temperatures of components of gas handling system 18 etc.), pressure sensors (some pressure sensors may be located to directly or indirectly measure differential pressures across components such as vacuum pumps, heat exchangers, gas compressors etc. and / or absolute gas pressures at locations in system 10), vibration sensors (e.g. arranged to measure vibration in pumps, compressors, etc.), power consumption monitors for powered components (e.g. pumps, compressors), gas flow sensors, etc.

[0152] In some embodiments, apparatus A1 includes instrumented quantum systems and information regarding the quantum states of the instrumented quantum systems may be provided to control system 50. Such information can provide sensitive measures of the performance of system 10 in maintaining steady temperatures that are sufficiently close to absolute zero. For example, Control system 50 may be connected to receive information regarding measurements of decoherence times for one or more quantum systems of apparatus A1. The quantum systems used as sensor(s) may optionally also be exploited for other purposes (e.g. quantum informatics processing).

[0153] Control system 50 may determine that one or more gas handling components is causing a degradation in the performance of system 10 from patterns in sensor readings 36A. For example:• an increase in differential pressure across a component such as a heat exchanger may indicate that flowthrough the component is being impeded, for example by trapped debris.• a problem with a vacuum pump or compressor may be detected by one or more of: lower than expected output pressure, higher or lower than expected power consumption, higher than expected temperature of parts of the component, change in temperature of gas output from the component and / or a specific pattern or magnitude of vibration and / or change in vibration of the component.• a problem with a vacuum pump may be detected by higher than expected pressure at an input of the vacuum pump.• a problem with system 10 generally may be detected by directly or indirectly determining that a temperature of the payload or helium bath 14 is changing and / or is outside of a desired operating range.

[0154] Control system 50 may also include a function for managing preventative maintenance of gas handling system components. For example, control system 50 may track an operating time of each gas handling component in system 10 since the component was last serviced. When the operating time of the component reaches a service interval, control system 50 may generate a request that the component be serviced and, if the component to be serviced is currently active, may automatically or in response to a user input, place the component to be serviced in a standby mode (as long as there is a good corresponding component that can be made active to keep the gas handling system operational).

[0155] Control system 50 may include a user interface that graphically or in some other way indicates the current configuration of a gas handling system 18 (e.g. which components are standby components, which components are active components. In some embodiments the user interface may indicate components which are scheduled to receive preventative maintenance. The user interface may incorporate controls which allow a user to command control system 50 to switch a particular active component for a particular available standby component.

[0156] Control system 50 may be configured to monitor currently active components and current standby components and to determine whether there are component failures that could not be remediated by switching from an active component to a standby component. Control system 25 may base this determination on either or both of the availability of corresponding standby components and the configurability of gas interconnection network 21 to switch over from each active component to an available standby component. Control system 50 may generate warning messages or indications if it determines that there are potential failures that cannot currently be remediated.

[0157] In some embodiments, control system 50 includes self-diagnostics to detect problems with control system 50 and / or is configured to monitor for problems with valves 24 or the ability of control system 50 to control valves 24. Control system 50 may be configured to, in response to detecting such problems, take an action such as: inhibiting control of gas handling system 18 if control system 50 is faulty or inhibit operations for controlling gas handling system 18 where the operation involves changing the state of any valve for which control system 50 has detected problems with controlling the valve. Control system 50 may detect problems with controlling a valve by monitoring output signals from sensors that should change in response to the state of the valve being changed or by receiving data that indicates the state of the valve if the valve is equipped with a position monitor.

[0158] In some embodiments, control system 50 is implemented using specifically designed hardware, configurable hardware, programmable data processors configured by the provision of software (which may optionally comprise “firmware”) capable of executing on the data processors, special purpose computers or data processors that are specifically programmed, configured, or constructed to perform one or more steps in a method as explained in detail herein and / or combinations of two or more of these. Examples of specifically designed hardware are: logic circuits, application-specific integrated circuits (“ASICs”), large scale integrated circuits (“LSIs”), very large scale integrated circuits (“VLSIs”), and the like. Examples of configurable hardware are: one or more programmable logic devices such as programmable array logic (“PALs”), programmable logic arrays (“PLAs”), and field programmable gate arrays (“FPGAs”). Examples of programmable data processors are: microprocessors, digital signal processors (“DSPs”), embedded processors,graphics processors, math co-processors, general purpose computers, server computers, cloud computers, mainframe computers, computer workstations, and the like. For example, one or more data processors in a control circuit for a device may implement methods as described herein by executing software instructions in a program memory accessible to the processors.

[0159] Processing may be centralized or distributed. Where processing is distributed, information including software and / or data may be kept centrally or distributed. Such information may be exchanged between different functional units by way of a communications network, such as a Local Area Network (LAN), Wide Area Network (WAN), or the Internet, wired or wireless data links, electromagnetic signals, or other data communication channel.

[0160] Aspects of the present technology may also be provided in the form of a program product. The program product may comprise any non-transitory medium which carries a set of computer-readable instructions which, when executed by a data processor, cause the data processor to execute a method as described herein (e.g. one or more functions of control system 50). Program products according to the present technolo gy may be in any of a wide variety of forms. The program product may comprise, for example, non-transitory media such as magnetic data storage media including floppy diskettes, hard disk drives, optical data storage media including CD ROMs, DVDs, electronic data storage media including ROMs, flash RAM, EPROMs, hardwired or preprogrammed chips (e.g., EEPROM semiconductor chips), nanotechnology memory, or the like. The computer-readable signals on the program product may optionally be compressed or encrypted.Switch over considerations

[0161] It can be desirable to keep system 10 operating for an extended period of time while avoiding fluctuations in conditions that could affect the performance of a payload (e.g. apparatus A1) that is being maintained at a cryogenic temperature by system 10. These conditions may include temperatures, temperature gradients and other conditions such as gas pressure in cryostat 12. It is desirable to maintain the payload at the desired temperature with very small or no significant temperature fluctuations. Where there are fluctuations of temperature or other conditions at the payload it is typically desirable that these fluctuations have a slow rate of change as well as a small magnitude.

[0162] System 10 may include features which help to: reduce the magnitude of fluctuations of temperature and / or other conditions in cryostat 12; and / or reduce the rate of change of temperature and / or other conditions in cryostat 12 within cryostat 12 during and after a switch from using one or more active gas handling components to using one or more corresponding standby gas handling components. Such fluctuations may be caused, for example by:• one or more transient flow conditions in gas handling system 18 that occur when the states of valves 24 are changed;• differences between the performance of corresponding standby components and the gas handling components that the standby components are substituted for;• differences in temperature of the standby components and the corresponding components that the standby components substitute for;• changes in temperature and operating characteristics of the standby components as the standby components warm up;• changes in the distribution of helium in system 10 resulting from a failure of a gas handling component; such as fluctuations in the amount of liquid helium in helium bath 14;• etc.

[0163] Gas handling components that are on “standby” while system 10 is running may be maintained in a state in which they are ready to be put into use. For example, volumes within standby components that hold gas when the components are in operation may be maintained under vacuum, may be pre-filled with helium gas while the components are on standby or may be evacuated or evacuated and filled with helium gas, as part of a switch over procedure managed by control system 50.

[0164] In some embodiments, control system 50 is configured to avoid or reduce fluctuations in temperature and / or other conditions in cryostat 12 by coordinating changes in the states of valves 24 and / or changing states of valves 24 slowly. For example, in substituting a standby component for an active component, fluctuations in gas flow through gas handling system 18 may be avoided or reduced by one or more of:setting valves 24 to slowly equalize pressure at the standby component with pressure of gas at the active component (e.g. at the output of the activecomponent) before setting valves 24 to allow gas to start flowing through the standby component;• setting valves 24 to allow gas to start flowing through the standby component before setting valves 24 to isolate the active component. In some embodiments valves 24 are set to allow gas flow in both the active component and the standby component for a time period. In some embodiments, control system 50 is configured to, during the time period while gas is flowing in both the active component and the corresponding standby component, change the settings of valves 24 gradually, thereby allowing gas flow in the standby component to increase while gas flow in the active component decreases, to the point where all of the gas flow is through the standby component (which then has the role of active component).

[0165] In some embodiments, timing of switching between active components and corresponding standby components may be based in part on operations of a payload (e.g. apparatus A1). The payload may have periods where it is relatively insensitive to fluctuations of conditions in cryostat 25 and other periods where it is more important to minimize such fluctuations. For example, if the payload comprises apparatus for quantum informatics processing it may be desirable to minimize fluctuations of conditions at the payload when sensitive computations are being performed (especially computations which require accurate performance of a long series of quantum operations). Quantum informatics processing typically involves executing steps at a very high rate so a delay on the order of seconds or less may reduce the likelihood that fluctuations in conditions in cryostat 12 could affect the outcome of the quantum informatics process.

[0166] As another example, where the payload comprises apparatus for a science experiment, it may be necessary to minimize fluctuations of conditions at the payload while the experiment is being run.

[0167] Control system 50 may have access to scheduling information relating to a payload and may schedule changes in the configuration of gas handling system 18 at times when any fluctuations resulting from such changes are least likely to adversely affect a payload.

[0168] In some embodiments, control system 50 is operative to directly or indirectly control timing of operations on a payload. For example, if control system 50 detects achange in state of gas handling system 18 that will require remedial action then control system may directly or indirectly (e.g. emitting a signal to a system that controls operations on the payload) inhibit operations on the payload at times when fluctuations in conditions at the payload may be present as a result of a failure or impending failure of gas handling system 18 and / or as a result of a remedial action taken by control system 50 as a result of such failure or impending failure.

[0169] In some embodiments, control system 50 is configured to estimate fluctuations in conditions at a payload as a result of a change in configuration of gas handling system 12 based on fluctuations caused by previous changes of configuration of gas handling system 18.Replacing gas handling components without system shut down

[0170] In some embodiments, a gas handling component may be removed from gas handling system 18 (e.g. because the component requires service or replacement) and replaced without interrupting operation of gas handling system 18. If the component is not already a standby component, the component is made to be a standby component by swapping the component with a corresponding standby component as described elsewhere herein. The component to be removed is then not involved in the functioning of gas handling system 18, which can continue operating without interruption. With the component to be removed isolated from other parts of the gas handling system the component can be removed.

[0171] A replacement component may then be connected in place of the removed component. The replacement component may then be prepared for service by, for example, evacuating the replacement component with an auxiliary vacuum pump to remove any air or other impurities. Leak checking may then be performed to verify that the section of gas handling system 18 that includes the replaced component is leak free. The replacement component may then be prepared for service. In some embodiments, the preparation involves pre filling the replacement component with helium gas. The replacement component may then be made active or kept as a standby component.Fail-safe valve operation

[0172] Valves 24 of gas interconnection network 21 may be configured to adopt a safe configuration if control is lost (e.g. control system 50 is not able to control valves24 because there is a failure of an electrical or pneumatic valve control system - such as a loss of pneumatic pressure, or a failure of control system 50 itself). Selected valves 24 may be “normally open” (open unless there is a valid control input causing the valve to close) or “normally closed” (closed unless there is a valid control input causing the valve to open) or “double-acting” (retain current position in the absence of a control input).

[0173] Valves having different operating characteristics when control is lost may be arranged to achieve different outcomes if control is lost. In some embodiments, for example, valves 24 may default to a state In which flowthrough gas handling system 18 is most direct. This may be achieved for example, by making valves 24 that are connected in line with conduits 22 “normally open” and by making valves 24 that are in line with conduits 23 normally closed”.

[0174] Another option is to make valves 24 that are inline with conduits 22 and valves 24 that are inline with conduits 23 between conduits 22 double acting. In this example, if gas handling system was configured to work properly immediately before loss of control of valves 24, gas handling system 18 should continue operating properly after loss of control (since the valves will not change state just because control was lost.

[0175] In some embodiments, normally closed valves are provided in selected locations to prevent short circuits in the helium flow if valve control is lost.Interpretation of Terms

[0176] Where any element of a system or method as described herein (e.g. a valve, set of valves, sensor, pump, compressor, cryocooler, control system, software, processor, assembly, device, circuit, etc.) is referred to herein, unless otherwise indicated, reference to that element (including a reference to a “means”) should be interpreted as including as equivalents of that element any element which performs the function of the described component (i.e., that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which performs the function in the illustrated exemplary embodiments of the present technology.

[0177] All headings in this disclosure are for convenience only and are not intended to be used to aid in interpretation of any part of this disclosure.

[0178] Unless the context clearly requires otherwise, throughout the description andthe claims:• “comprise”, “comprising”, and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”;• “connected”, “coupled”, or any variant thereof, means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, ora combination thereof;• “herein”, “above”, “below”, and words of similar import, when used to describe this specification, shall refer to this specification as a whole, and not to any particular portions of this specification;• “or”, in reference to a list of two or more items, covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list;• the singular forms “a”, “an”, and “the” also include the meaning of any appropriate plural forms. These terms (“a”, “an”, and “the”) mean one or more unless stated otherwise;• “and / or” is used to indicate one or both stated cases may occur, for example A and / or B includes both (A and B) and (A or B);• “approximately” when applied to a numerical value means the numerical value ± 10%;• where a feature is described as being “optional” or “optionally” present or described as being present “in some embodiments” it is intended that the present disclosure encompasses embodiments where that feature is present and other embodiments where that feature is not necessarily present and other embodiments where that feature is excluded. Further, where any combination of features is described in this application this statement is intended to serve as antecedent basis for the use of exclusive terminology such as "solely," "only" and the like in relation to the combination of features as well as the use of "negative" limitation(s)” to exclude the presence of other features; and• “first” and “second” are used for descriptive purposes and cannot be understood as indicating or implying relative importance or indicating thenumber of indicated technical features.

[0179] Words that indicate directions such as “vertical”, “transverse”, “horizontal”, “upward”, “downward”, “forward”, “backward”, “inward”, “outward”, “left”, “right”, “front”, “back”, “top”, “bottom”, “below”, “above”, “under”, and the like, used in this description and any accompanying claims (where present), depend on the specific orientation of the apparatus described and illustrated. The subject matter described herein may assume various alternative orientations. Accordingly, these directional terms are not strictly defined and should not be interpreted narrowly.

[0180] Where a range fora value is stated, the stated range includes all sub-ranges of the range. It is intended that the statement of a range supports the value being at an endpoint of the range as well as at any intervening value to the tenth of the unit of the lower limit of the range, as well as any subrange or sets of sub ranges of the range unless the context clearly dictates otherwise or any portion(s) of the stated range is specifically excluded. Where the stated range includes one or both endpoints of the range, ranges excluding either or both of those included endpoints are also included in the invention.

[0181] Certain numerical values described herein are preceded by "about". In this context, "about" provides literal support for the exact numerical value that it precedes, the exact numerical value ±5%, as well as all other numerical values that are near to or approximately equal to that numerical value. Unless otherwise indicated a particular numerical value is included in “about” a specifically recited numerical value where the particular numerical value provides the substantial equivalent of the specifically recited numerical value in the context in which the specifically recited numerical value is presented. For example, a statement that something has the numerical value of “about 10” is to be interpreted as: the set of statements:• in some embodiments the numerical value is 10;• in some embodiments the numerical value is in the range of 9.5 to 10.5;and if from the context the person of ordinary skill in the art would understand that values within a certain range are substantially equivalent to 10 because the values with the range would be understood to provide substantially the same result as the value 10 then “about 10” also includes:• in some embodiments the numerical value is in the range of C to D where Cand D are respectively lower and upper endpoints of the range that encompasses all of those values that provide a substantial equivalent to the value 10.

[0182] Specific examples of systems, methods and apparatus have been described herein for purposes of illustration. These are only examples. The technology provided herein can be applied to systems other than the example systems described above. Many alterations, modifications, additions, omissions, and permutations are possible within the practice of this invention. This invention includes variations on described embodiments that would be apparent to the skilled addressee, including variations obtained by: replacing features, elements and / or acts with equivalent features, elements and / or acts; mixing and matching of features, elements and / or acts from different embodiments; combining features, elements and / or acts from embodiments as described herein with features, elements and / or acts of other technology; and / or omitting combining features, elements and / or acts from described embodiments.

[0183] As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any other described embodiment(s) without departing from the scope of the present invention.

[0184] Any aspects described above in reference to apparatus may also apply to methods and vice versa.

[0185] Any recited method can be carried out in the order of events recited or in any other order which is logically possible. For example, while processes or blocks are presented in a given order, alternative examples may perform routines having steps, or employ systems having blocks, in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and / or modified to provide alternative or subcombinations. Each of these processes or blocks may be implemented in a variety of different ways. Also, while processes or blocks are at times shown as being performed in series, these processes or blocks may instead be performed in parallel, simultaneously or at different times.

[0186] Various features are described herein as being present in “some embodiments”. Such features are not mandatory and may not be present in all embodiments. Embodiments of the invention may include zero, any one or anycombination of two or more of such features. All possible combinations of such features are contemplated by this disclosure even where such features are shown in different drawings and / or described in different sections or paragraphs. This is limited only to the extent that certain ones of such features are incompatible with other ones of such features in the sense that it would be impossible for a person of ordinary skill in the art to construct a practical embodiment that combines such incompatible features. Consequently, the description that “some embodiments” possess feature A and “some embodiments” possess feature B should be interpreted as an express indication that the inventors also contemplate embodiments which combine features A and B (unless the description states otherwise or features A and B are fundamentally incompatible). This is the case even if features A and B are illustrated in different drawings and / or mentioned in different paragraphs, sections or sentences.

[0187] It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions, omissions, and sub-combinations as may reasonably be inferred. The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

Claims

WHAT IS CLAIMED IS:

1. A gas handling system for a cryogenic refrigerator, the gas handling system comprising:an inlet;an outlet;a first plurality of gas handling components;a second plurality of gas handling components wherein each gas handling component of the second plurality of gas handling components corresponds to and is functionally equivalent to a corresponding gas handling component of the first plurality of gas handling components;a gas interconnection network comprising a plurality of valves, the gas interconnection network configurable to connect the first plurality of gas handling components in series to provide a first gas handling chain connected between the inlet and the outlet, the gas handling interconnection network being reconfigurable to substitute a selected one of the second plurality of gas handling components for the corresponding gas handling component of the first plurality of gas handling components so that the selected one of the second gas handling components is connected to carry gas flowing from the inlet to the outlet and the corresponding one of the first gas handling components is no longer connected to carry gas flowing from the inlet to the outlet.

2. The gas handling system according to claim 1 wherein the gas interconnection network is configurable to connect the second plurality of gas handling components in series to provide a second gas handling chain connected between the inlet and the outlet.

3. The gas handling system according to claim 2 wherein the gas interconnection network is operable to substitute for any group of two or more of the first plurality of gas handling components that are sequential in the first gas handling chain, a corresponding group of the second plurality of gas handling components that are sequential in the second gas handling chain.

4. The gas handling system according to claim 2 or 3, wherein the gasinterconnection network comprises:a plurality of cross conduits each of the cross conduits providing fluid connectivity between the first gas handling chain and the second gas handling chain, the cross conduits spaced apart along the first and second gas handling chains, each of the cross conduits connected to the first gas handling chain at a corresponding first location along the first gas handling chain; and connected to the second gas handling chain at a corresponding second location along the second gas handling chain.

5. The gas handling system according to claim 4 wherein, for each of a plurality of the cross conduits, the valves of the gas interconnection network include one or more valves operable to selectively:connect the cross conduit to a portion of the first gas handling chain upstream from the corresponding first location while blocking flow between the cross conduit and a portion of the first gas handling chain that is downstream from the corresponding first location; orconnect the cross conduit to the portion of the first gas handling chain that is downstream from the corresponding first location while blocking flow between the cross conduit and the portion of the first gas handling chain that is downstream from the corresponding first location; orconnect the portion of the first gas handling chain upstream from the corresponding first location and the portion of the first gas handling chain downstream from the corresponding first location while blocking flow between the first gas handling chain and the second gas handling chain through the cross conduit.

6. The gas handling system according to claim 5 wherein, for each of the plurality of the cross conduits, the plurality of valves of the gas interconnection network include one or more valves operable to selectively:connect the cross conduit to a portion of the second gas handling chain that is downstream from the corresponding second location while blocking flow between the cross conduit and a portion of the second gas handling chain that is upstream from the corresponding second location; orconnect the cross conduit to the portion of the second gas handling chain that is upstream from the corresponding second location while blocking flow between thecross conduit and the portion of the second gas handling chain that is downstream from the corresponding second location; orconnect the portion of the second gas handling chain that is upstream from the corresponding second location and the portion of the second gas handling chain that is downstream from the corresponding second location while blocking flow between the first gas handling chain and the second gas handling chain through the cross conduit.

7. The gas handling system according to any of claims 1 to 3 wherein each gas handling component of the first plurality of gas handling components corresponds to at least one of the gas handling components of the second plurality of gas handling components and the gas interconnection network is reconfigurable to substitute for any one of the first plurality of gas handling components, the corresponding gas handling component of the second plurality of gas handling components.

8. The gas handling system according to any of claims 2 to 7 wherein the gas handling system is reconfigurable while the gas handling system is in operation to switch between a first configuration in which the first gas handling chain is in an operational mode, the second gas handling chain is in a standby mode, and the plurality of valves are set to direct gas flow from the inlet to pass through the first gas handling chain and a second configuration in which the second gas handling chain is in the operational mode, the first gas handling chain is in the standby mode, and the plurality of valves are set to direct gas flow from the inlet to pass through the second gas handling chain.

9. The gas handling system according to any of claims 2 to 8 wherein, for each components of the first gas handling chain, the components of the second gas handling chain includes a corresponding component that is functionally equivalent to the component of the first gas handling chain.

10. The gas handling system according to any of claims 2 to 9, wherein the gas interconnection network includes a plurality of ports, the plurality of valves of the gas interconnection network include valves configurable to isolate each of the plurality ofports, and the plurality of ports are arranged to allow connection of a third gas handling chain without interrupting operation of the first gas handling chain or the second gas handling chain.

11. The gas handling system according to any of claims 2 to 10 wherein the gas interconnection network is selectively configurable to, while the gas handing system is in operation, the first gas handling chain is operating and the second gas handling chain is in a standby mode, switch to operating the second gas handling chain and place the first gas handling chain in the standby mode.

12. The gas handling system according to any of the preceding claims wherein the second plurality of gas handling components includes gas handling components of at least two distinct types, each of the distinct typers providing different functionality.

13. The gas handling system according to any of the preceding claims wherein the first plurality of gas handling components and the second plurality of gas handling components each include at least one vacuum pump.

14. The gas handling system according to any of the preceding claims wherein the first plurality of gas handling components and the second plurality of gas handling components each include at least one orifice.

15. The gas handling system according to any of the preceding claims wherein the first plurality of gas handling components and the second plurality of gas handling components each include at least one gas compressor.

16. The gas handling system according to any of the preceding claims wherein the first plurality of gas handling components and the second plurality of gas handling components each include at least one heat exchanger.

17. The gas handling system according to any of the preceding claims wherein the first gas handling chain includes a vacuum pump and a gas compressor located downstream from the vacuum pump in a direction of flow from the inlet of the gashandling system to the outlet of the gas handling system.

18. The gas handling system according to any of the preceding claims, wherein the gas interconnect network is configurable, while the gas handing system is in operation, to change a path by which gas can flow from the input of the gas handling system to the output of the gas handling system.

19. The gas handling system according to any of the preceding claims wherein the gas interconnection network is configurable to, while the selected one of the second plurality of gas handling components is substituted for the corresponding gas handling component of the first plurality of gas handling components, isolate the corresponding gas handling component of the first plurality of gas handling components.

20. The gas handling system according to claim 19, comprising an auxiliary vacuum pump connectable to, while the corresponding gas handling component of the first plurality of gas handling components is isolated and the selected one of the second plurality of components is substituted for the corresponding gas handling component of the first plurality of gas handling components, evacuate the corresponding gas handling component of the first plurality of gas handling components.

21. The gas handling system according to any of the preceding claims comprising a vacuum leak detector, wherein the gas interconnection network is configurable to isolate a region of the gas handling system comprising one or more of the first plurality of gas handling components or one or more of the second plurality of gas handling components from the inlet and the outlet of the gas handling system and to connect the vacuum leak detector to detect leaks in the portion of the gas handling system.

22. The gas handling system according to any of the preceding claims wherein the second plurality of gas handling components includes at least three gas handling components.

23. The gas handling system according to any of the preceding claims comprising a control system, wherein the control system is connected to receive one or more sensor signals, the sensor signals indicative of conditions within the gas handling system and to identify a failing component by processing the sensor signals.

24. The gas handling system according to claim 23 wherein the control system is configured to, if the failing component is one of the first plurality of components that has failed or is at risk of failing, control the gas interconnection network to identify and select as the selected one of the second plurality of gas handling components, one of the second plurality of gas handling components that corresponds to the failing component.

25. The gas handling system according to claim 24, wherein the control system is connected to control the plurality of valves of the gas interconnection network.

26. The gas handling system according to claim 25 wherein the control system is configured to automatically reconfigure the gas interconnection network to substitute the selected one of the second plurality of gas handling components for the failing gas handling component.

27. The gas handling system according to claim 25 wherein the control system is configured to, in response to a command to substitute the selected one of the plurality of second gas handling components for the corresponding one of the first plurality of gas handling components, automatically control the gas interconnection network to perform the commanded substitution.

28. The gas handling system according to claim 27, wherein the command is generated by the control system.

29. The gas handling system according to claim 27, wherein the control system comprises a user interface operable to generate the command in response to user input.

30. The gas handling system according to any of claims 23 to 29 wherein the control system is configured to substitute the selected one of the second plurality of gas handling components for the corresponding one of the first plurality of gas handling components, by controlling the plurality of valves to gradually equalize pressure of the selected one of the plurality of second gas handling components with the corresponding one of the first plurality of gas handling components, prior to causing gas flowing from the inlet to the outlet to pass though the selected one of the second plurality of gas handling components.

31. The gas handling system according to any of claims 23 to 30 wherein the first plurality of gas handling components comprises a first heat exchanger, the second plurality of gas handling components comprises a second heat exchanger, the first heat exchanger and the second heat exchanger correspond to one another and the control system is configured to identify the first heat exchanger as a failing component in response to determining from the sensor signals that a measure of a pressure drop across the first heat exchanger exceeds a pressure drop threshold and / or is increasing relative to a prior value of the pressure drop at a rate that exceeds a pressure drop increase rate threshold.

32. The gas handling system according to any of claims 23 to 31 wherein the control system is configured to, in changing states of the valves of the gas interconnection network to substitute a standby component for an active component of the gas handling system, slowly equalize pressure at the standby component with pressure of gas at the active component.

33. The gas handling system according to any of claims 23 to 32 wherein the control system is configured to, in changing states of the valves of the gas interconnection network to substitute a standby component for an active component of the gas handling system, setting the valves to allow gas to start flowing through the standby component before setting the valves to isolate the active component.

34. The gas handling system according to claim 33 wherein the control system isconfigured to set the valves to allow gas flow in both the active component and the standby component for a time period.

35. The gas handling system according to claim 34 wherein the control system is configured to, during the time period while gas is flowing in both the active component and the corresponding standby component, change settings of the valves gradually, thereby allowing gas flow in the standby component to increase while gas flow in the active component decreases, until all of the gas flow is through the standby component.

36. The gas handling system according to any of claims 23 to 35 wherein the control system is configured to access scheduling information relating to a payload and the control system is scheduled to make changes in the configuration of the gas interconnection network at times when the scheduling information indicates that such changes are acceptable.

37. The gas handling system according to any of claims 23 to 36 wherein the control system has access to a calendar of scheduled maintenance for one or more of the components of the gas handing system and the control system is configured to, if a component is active and requires scheduled maintenance, control the valves of the gas interconnection network to substitute a corresponding standby component for the component that requires scheduled maintenance.

38. The gas handling system according to any of the preceding claims wherein the plurality of valves of the gas interconnection network are pneumatically controlled.

39. A cryogenic refrigerator system incorporating the gas handling system according to any of the preceding claims, wherein the inlet of the gas handling system is in fluid communication with a volume of an evaporator in a cryostat, and the outlet of the gas handling system is in fluid communication with a helium liquification system that is connected to deliver liquid helium to a helium bath in the evaporator.

40. The cryogenic refrigerator system according to claim 39 wherein the cryogenicrefrigerator system is operable to cool a payload to a temperature of less than 4.2 Kelvin.

41. A method for operating a gas handling system for a cryogenic refrigerator, the gas handling system comprising:an inlet,an outlet,a plurality of gas handling components, anda gas interconnection network comprising a plurality of valves configurable to connect selected ones of the plurality of components in series in a sequence between the inlet and the outlet to provide a first gas handling chain which is operable to support operation of a cryogenic refrigerator, the method comprising:operating the first gas handling chain;selecting one of the components of the first gas handling chain to be taken out of service;while the first gas handling chain is operating, reconfiguring the gas interconnection network to substitute for the selected component another one of the components that corresponds to the selected component and isolating the selected component from the first gas handling chain.

42. The method according to claim 41 comprising gradually equalizing pressure between the selected component and the component that corresponds to the selected component prior to isolating the selected component.

43. The method according to claim 41 or 42 comprising, for a period of time prior to isolating the selected component, configuring the gas interconnection network to flow gas through both of the selected component and the component that corresponds to the selected component.

44. The method according to claim 32 comprising, during the time period, decreasing the flow of the gas through the selected component while increasing the flow of the gas through the component that corresponds to the selected component.

45. The method according to any of claims 41 to 44 further comprising replacing the selected component with a replacement component while the selected component is isolated from the gas handling chain.

46. The method according to claim 44 comprising evacuating the replacement component and subsequently reconfiguring the gas interconnection network to substitute the replacement component for the component that corresponds to the selected component.

47. The method according to claim 45 comprising leak testing the replacement component prior to substituting the replacement component for the component that corresponds to the selected component.

48. The method according to any of claims 41 to 47 wherein the gas interconnection network comprises first conduits extending between sequentially adjacent components of the first gas handling chain, second conduits extending between sequentially adjacent components of a second gas handling chain and cross conduits that each connect one of the first conduits to a corresponding one of the second conduits and reconfiguring the gas interconnection network to substitute for the selected component another one of the components that corresponds to the selected component comprises opening one of the cross conduits to allow gas to flow to the corresponding component in the second gas handling chain while blocking gas flow to the selected component in the first gas handling chain.

49. The method according to any one of claims 41 to 48 wherein the method is performed by an automatic control system connected to control the gas interconnection network.

50. A control system comprising a data processor configured by machine readable instructions to perform a method according to any of claims 41 to 48.

51. A non-transitory medium containing machine readable instructions which, when executed by a data processor of a control system cause the data processor to execute a method according to any of claims 41 to 48.

52. A gas handling system for a cryogenic refrigerator, the gas handling system comprising:a first gas handling chain comprising a plurality of gas handling components connected in series between an inlet to the gas handling system and an outlet from the gas handling system;a second gas handling chain comprising a plurality of gas handling components, wherein a plurality of the components of the second gas handling chain are each functionally equivalent to a corresponding one of the components of the first gas handling chain;a gas interconnection network comprising valves operable to substitute for a selected one of the components of the first gas handling chain the corresponding component from the second gas handling chain by diverting gas from flowing through the selected one of the components of the first gas handling chain to instead flow though the one of the components of the second gas handling chain that corresponds to the selected component of the first gas handling chain.

53. The gas handling system according to claim 52 wherein the gas interconnection network comprises a plurality of first conduits that connect the components of the first gas handling chain in series, a plurality of second conduits that connect the components of the second gas handling chain in series, and a plurality of third conduits connected between corresponding ones of the first and second conduits.

54. The gas handling system according to claim 53 wherein, for each of a plurality of the third conduits, the valves of the gas interconnection network include one or more valves operable to selectively:connect the third conduit to an upstream segment of the corresponding first conduit that is upstream from a junction of the corresponding first conduit and the third conduit; orconnect a downstream segment of the corresponding first conduit that is downstream from the junction of the corresponding first conduit to the third conduit; or connect the upstream segment of the corresponding first conduit to the downstream segment of the corresponding first conduit while blocking flow between the third conduit and the corresponding first conduit.

55. The gas handling system according to claim 54 wherein, for each of the plurality of the third conduits, the valves of the gas interconnection network include one or more valves operable to selectively:connect the third conduit to an upstream segment of the corresponding second conduit that is upstream from a junction of the corresponding second conduit and the third conduit; orconnect a downstream segment of the corresponding second conduit that is downstream from the junction of the corresponding second conduit and the third conduit to the third conduit; orconnect the upstream segment of the corresponding second conduit to the downstream segment of the corresponding second conduit while blocking flow between the third conduit and the corresponding second conduit.

56. The gas handling system according to any of claims 52 to 55 wherein the gas interconnection network is selectively configurable to, while the gas handing system is in operation, the first gas handling chain is operating and the second gas handling chain is in a standby mode, switch to operating the second gas handling chain and place the first gas handling chain in the standby mode.

57. The gas handling system according to any of claims 52 to 56 wherein, for each of the components of the first gas handling chain, the components of the second gas handling chain includes a component that corresponds to the component of the first gas handling chain.

58. The gas handling system according to any of claims 52 to 57 wherein the components of the first gas handling chain include a vacuum pump and a gas compressor located downstream from the vacuum pump in a direction of flow fromthe inlet of the gas handling system to the outlet of the gas handling system.

59. The gas handling system according to any of claims 52 to 58 wherein the second gas handling chain includes at least three components that respectively correspond to corresponding components of the first gas handling chain and the gas interconnection network includes valves operable to substitute any one of the components of the second gas handling chain for a corresponding one of the components of the first gas handling chain.

60. The gas handling system according to any of claims 52 to 59 wherein the second gas handling chain includes at least three components that respectively correspond to corresponding components of the first gas handling chain and the gas interconnection network includes valves operable to substitute any group of two or more sequential ones of the components of the second gas handling chain for a corresponding group of two or more sequential ones of the components of the first gas handling chain.

61. The gas handling system according to any of claims 52 to 60 wherein the valves of the gas interconnection network comprise valves operable to isolate the selected one of the components of the first gas handling chain while the corresponding component from the second gas handling chain is operating.

62. The gas handling system according to any of claims 52 to 61 comprising an auxiliary pump connectable to evacuate the selected one of the components of the first gas handling chain while the corresponding component from the second gas handling chain is operating.

63. The gas handling system according to any of claims 52 to 62 wherein the gas interconnection network includes a plurality of ports, and the valves of the gas interconnection network include valves configurable to isolate each of the ports, and the ports are arranged to allow connection of a third gas handling chain without interrupting operation of the first gas handling chain or the second gas handling chain.

64. The gas handling system according to any of claims 52 to 63 comprising a control system connected to control the valves of the gas interconnection network, wherein the control system is configured to, in response to a command to substitute for the selected one of the components of the first gas handling chain the corresponding component from the second gas handling chain, automatically control the valves to perform the commanded substitution.

65. The gas handling system according to claim 64 wherein the selected component of the first gas handling chain is a heat exchanger and the controller is configured to configured to identify the selected component of the first gas handling chain by processing the sensor signals to obtain a measure of a pressure drop across the heat exchanger and determining that the pressure drop exceeds a threshold and / or is increasing relative to a prior value of the pressure drop.

66. The gas handling system according to claim 64 or 65 wherein the control system is configured to, in changing states of the valves of the gas interconnection network to substitute a standby component for an active component of the gas handling system, slowly equalize pressure at the standby component with pressure of gas at the active component;67. The gas handling system according to any of claims 64 to 66 wherein the control system is configured to, in changing states of the valves of the gas interconnection network to substitute a standby component for an active component of the gas handling system, setting the valves to allow gas to start flowing through the standby component before setting the valves to isolate the active component.

68. The gas handling system according to claim 67 wherein the controller is configured to set the valves to allow gas flow in both the active component and the standby component for a time period.

69. The gas handling system according to claim 67 wherein the control system is configured to, during the time period while gas is flowing in both the active component and the corresponding standby component, change settings of the valves gradually,thereby allowing gas flow in the standby component to increase while gas flow in the active component decreases, to the point where all of the gas flow is through the standby component.

70. The gas handling system according to any of claims 64 to 69 wherein the control system has access to scheduling information relating to a payload and the control system is scheduled to make changes in the configuration of the gas interconnection network at times when the payload scheduling information indicates that such changes are acceptable.

71. The gas handling system according to any of claims 64 to 70 wherein the control system has access to a calendar of scheduled maintenance for one or more components of the gas handing system and the control system is configured to, if a component is active and requires scheduled maintenance, control the valves of the gas interconnection network to substitute a corresponding standby component for the component that requires scheduled maintenance.

72. The gas handling system according to any of claims 64 to 71 wherein the control system is configured to identify the selected component of the first gas handling chain based on sensor signals from sensors associated with the gas handling system and to generate the command in response to processing of the sensor signals indicating that the selected component of the first gas handling chain is failing or has failed.

73. A cryogenic refrigerator system incorporating the gas handling system according to any of claims 52 to 72 wherein the inlet of the gas handling system is in fluid communication with a volume of an evaporator in a cryostat, the outlet of the gas handling system is in fluid communication with a helium liquification system that is connected to deliver liquid helium to a helium bath in the evaporator and the cryogenic refrigerator is operable to cool a payload to a temperature of less than 4.2 Kelvin.

4. Apparatus comprising any new and inventive feature, combination of features,or sub-combination of features as described herein.

75. Methods comprising any new and inventive steps, acts, combination of steps and / or acts or sub-combination of steps and / or acts as described herein.

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