Integrated and distributed cooling system

Abstract

A multi-stage cryogenic system and method of controlling cooldown for a multi-stage cryogenic system are provided. In one embodiment, a system includes a first stage, a second stage, and at least one pressurized cooling fluid source. A cryocooler includes a first fluid path thermally coupled to the first stage and the second stage and is configured to receive a cooling fluid via the first fluid path. The first stage is cooled with a relatively greater cooling power than the second stage. A distributed cooling network includes an inlet port and a second fluid path thermally coupled with the first and the second stage. The distributed cooling network is configured to extract heat from the second stage to the first stage. A feedback control system is configured to vary a cooling fluid flow through the second fluid path during a cooldown as a function of at least one system temperature.

Description

Integrated and Distributed Cooling SystemCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of United States provisional application no. 63 / 532,792 entitled “Technical Shunt for Pulse Tube Cooler” and filed August 15, 2023; United States provisional patent application no. 63 / 546,695 entitled “Thermally Shunted Cryostat” fiiled on October 31, 2023; and United States provisional patent application no. 63 / 655,017 entitled “Integrated and Distributed Cooling System” and filed on June 2, 2024, each application of which is hereby incorporated by reference as though fully set forth herein.BACKGROUNDField

[0002] The instant disclosure relates to an integrated and distributed cooling system operable with a cryocooler, such as a pulse tube cooler.Background

[0003] Cryocoolers usually generate more cooling power at their first stage than at their second stage. In the University of Colorado PCT application no. PCT / US2023 / 014047 entitled “DYNAMIC ACOUSTIC IMPEDANCE MATCHING FOR CRYOCOOLERS” published as WO 2023 / 211563 Al on November 01, 2023 [Dynamic Timing], for example, cooling power is increased by dynamically adjusting, among other things, the main orifices in a cryocooler during the cooldown period. PCT application no. PCT / US2023 / 014047 is incorporated by reference as if fully set forth herein.

[0004] Historically, to achieve desired system performance, several adjustments are made during the manufacturing process of a PTC. Further, other parameters within a PTC are not readily adjustable during manufacturing, but in principle can be varied with a resulting change in system performance. This is especially true for PTCs operating outside of the steady-state regime. In the Dynamic Tuning invention, parameters of a pulse tube cooler, those that are adjusted and those generally fixed during the initial manufacturing process of the PTC, are dynamically tuned in order to yield superior performance.

[0005] Prior work has also been performed where a two-stage Gifford-McMahon cryocooler (GMC) was implemented into a cryogenic system and a thermal shunt was employed. The thermal shunt comprised a heat exchanger attached to the first stage of the GMC, a heat exchanger attached to the second stage of the GMC, and a flow circuit through which a portion of the GMC compressor flow was diverted to connect the two heat exchangers, and a recuperative heat exchanger. In that work, the flow rate used was a very small fraction (2.5%) of the total compressor capacity, and that flow rate was intentionally maintained throughout the cooldown.BRIEF SUMMARY

[0006] To increase both the effectiveness and efficiency of cryocoolers, and to make the Dynamic Tuning more impactful, one embodiment provides establishing, during a cooldown period of a cryogenic system, a strong thermal connection between the first and second stages of the cryocooler as well as between the various parts of the cryogenic system, by employing an Integrated & Distributed Cooling System (IDCS). Further, because during cooldown of the system, the cryocooler first stage has superior cooling power than the cryocooler second stage, and because the cryocooler first stage is usually colder than the second cryocooler stage, establishing a strong thermal connection between the cryocooler first stage and cryocooler second stage allows heat from the cryocooler second stage (and in some embodiments further stages below the second stage) to be extracted (at a higher rate) by the cryocooler first stage, greatly improving the overall cooldown of the cryostat system.

[0007] The first stage of a two stage cryocooler typically has much greater cooling power than the second stage. In various embodiments, a distributed cooling network is provided comprising a cooling fluid path thermally coupled with the stages of the cryocooler.Further, many cryogenic cooling systems have more thermal mass that needs to be cooled attached to the second stage than the first. A distributed cooling network that extracts heat from components with high thermal mass and transports that heat to the first stage for removal can greatly improve cooldown efficiency. In a system with a single pressurized fluid source, the flow is be divided between the cryocooler and the distributed cooling network. At highertemperatures the flow is more useful flowing through the distributed cooling network when the cryocooler has greater cooling power. At lower temperatures, diminished flow has an increasingly greater detrimental effect on cryocooler performance. A controller can manage the flow split (e.g., continuously) during a cooldown to divert the flow most efficiently for the present state of the system, and can shut down the distributed cooling network when it is no longer beneficial. As the cryogenic system cools, the controller will shift flow from the distributed cooling network to the cryocooler until flow is shut off

[0008] Additionally, an IDCS system may access and / or use information from a dynamically tuned cryocooler to make adjustments to the Flow Control device of the IDCS in order to improve or optimize system performance and achieve cooling performance that would otherwise be unachievable by using only Dynamic Tuning, only IDCS, or neither.

[0009] The foregoing and other aspects, features, details, utilities, and advantages of the present invention will be apparent from reading the following description and claims, and from reviewing the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Fig. l is a schematic diagram showing an example embodiment of a cryogenic system.

[0011] Fig. 2 is a schematic diagram of an embodiment of a cryogenic system.

[0012] Fig. 3 is a schematic diagram of another embodiment of a cryogenic system.

[0013] Fig. 4 is a schematic diagram of another embodiment of a cryogenic system similar to the cryogenic system shown in Fig. 3 except that the second stage heat exchanger is attached to the cryocooler second stage.

[0014] Fig. 5 is a schematic diagram of another embodiment of a cryogenic system similar to the cryogenic system shown in Fig. 4 except that the second stage heat exchanger is fully integrated into the cryocooler second stage.

[0015] Fig. 6A is a schematic diagram of another embodiment of a cryogenic system in which the second stage heat exchanger is integrated in the cryostat second stage plate.

[0016] FIG. 6B is a plan view of the second stage heat exchanger shown in Fig. 6A.

[0017] Fig. 7 is a schematic diagram of another embodiment of a cryogenic system.

[0018] Fig. 8 is a schematic diagram of another embodiment of a cryogenic system.

[0019] Fig. 9 is a schematic diagram showing another example embodiment of a cryogenic system in which the cooled return gas flow is delivered to a cryocooler heat exchanger before being returned to a helium gas source.

[0020] Fig. 10 is a schematic diagram showing another example embodiment of a cryogenic system in which an additional gas flow is provided by a gas source to a cryocooler heat exchanger.

[0021] Fig. 11 is a schematic diagram showing another example embodiment of a cryogenic system in which independent gas sources are used to supply gas flows to a cryocooler and a distributed cooling network.

[0022] Fig. 12 is a schematic diagram showing another example embodiment of a cryogenic system similar to the cryogenic system shown in Fig. 10 in which the return path of the gas supply line is directed to a flow controller disposed in the cryocooler.

[0023] Fig. 13 is a schematic diagram showing another example embodiment of a cryogenic system similar to the cryogenic system shown in Fig. 12.

[0024] Fig. 14 is a schematic diagram of a flow control device for a distributed cooling network.

[0025] Fig. 15 is a schematic diagram showing another flow control device 105 that may be used within a cryogenic system described herein.

[0026] Fig. 16 is a schematic diagram of an example embodiment of cryogenic system including a dynamic tuning cooling system 2000 in combination with a distributed cooling network 103 of a cryocooler, such as described above with respect to Figs. 14 and 15.

[0027] Fig. 17 is a flowchart showing an example process for controlling a distributed cooling network flow.

[0028] FIG. 18 for example, shown is a block diagram depicting physical components that may be utilized to realize the controllers shown in FIGS. 1-17 according to an exemplary embodiment.DETAILED DESCRIPTION

[0029] The following description of the invention is provided as an enabling teaching of the invention in its best, currently known embodiment. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various aspects of the invention described herein, while still obtaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be obtained by selecting some of the features of the present invention without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not in limitation thereof.

[0030] As used throughout, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a” component can include two or more such components unless the context indicates otherwise. Also, the words “proximal” and “distal” are used to describe items or portions of items that are situated closer to and away from, respectively, a user or operator such as a surgeon. Thus, for example, the tip or free end of a device may be referred to as the distal end, whereas the generally opposing end or handle may be referred to as the proximal end.

[0031] All directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader’s understanding of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention. Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other.

[0032] Ranges can be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0033] As used herein, the terms “optional” or “optionally” mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0034] The term “substantially” as used herein may be applied to modify any quantitative representation which could permissibly vary without resulting in a change in the basic function to which it is related.

[0035] Fig. 1 is a schematic diagram showing an example embodiment of a cryogenic system 101. The cryogenic system 101 comprises a cooling system 102, a cooling fluid source 106, such as a helium gas source 106, and a controller 107. Although helium gas is used in various example embodiments, one of ordinary skill in the art would appreciate that any one of a number of cooling fluid sources may be used. In the embodiment shown in Fig. 1, the cooling system 102 comprises a cryocooler 104, such as a pulse tube cooler, coupled to the fluid source 106 (e.g., the helium gas source 106) to receive a cooling fluid supply for the cryocooler 104 as is typical. The cooling system also includes a flow control device 105 configured to control a supplemental cooling fluid (e g., helium gas) flow from the cooling fluid source 106 to a distributed cooling network 103 that serves to effectively transport the cooling generated by cryocooler 104 to other parts of the cooling system 102. As used herein, the supplemental cooling fluid and supplemental cooling fluid flow lines refer to cooling fluid and cooling fluid flow lines of the distributed cooling network 103.

[0036] In some embodiments described herein, the cryocooler 104 is described with reference to a pulse tube cooler implementation of a cryocooler for ease of description. A pulsetube cooler, however, is only one type of cryocooler 104 that may be used within a cryogenic system 101. For example, other implementations of a cryocooler may include Gifford-McMahon, Stirling, Joule-Thomson, and Brayton cryocoolers.

[0037] In this embodiment, the cryocooler 104 comprises a first stage 110 and a second stage 112, although additional stages of the cryocooler 104 may also be provided. The cryocooler 104 is coupled to the helium gas source 106 and utilizes a cooling fluid, such as helium gas, from the cooling fluid source 106 to cool the first stage 110 and the second stage 112. The first stage 110 and the second stage 112 of the cryocooler 104 are also coupled with the distributed cooling network 103 as shown in Fig. 1 .

[0038] A typical pulse tube cooler, for example, generates greater cooling power at the first stage 110 of the cryocooler 104 than at the second stage 112 of the cryocooler 104.

[0039] The distributed cooling network 103 is thermally coupled with the first stage 110 and the second stage 112 of the cryocooler 104. As used herein, a thermal coupling may be direct or indirect. The thermal connection between the distributed cooling network and the first stage 110 and the second stage 112 of the cryocooler 104 allow the distributed cooling network 103 to extract heat from the second stage 112 to the first stage 110, improving the overall cooldown performance of the cryogenic system 101. In typical cryogenic systems the lag in cooling of the second stage (and possible subsequent stages) of the cryogenic system can manifest as several hours and, in the case of large systems, even days of delayed cooldown.

[0040] Fig. 2 is a schematic diagram of an embodiment of a cryogenic system. In this embodiment, the cryogenic system comprises a cooling system 102 and a helium gas source 106 similar to the cryogenic system 101 shown in Fig. 1. The cooling system comprises a cryocooler 104, such as a pulse tube cooler, and a flow control device 105 configured to control a supplemental helium gas flow from the helium gas source 106 to a distributed cooling network 103 that serves to effectively transport the cooling generated by cryocooler 104 to other parts of the cooling system 102.

[0041] In this embodiment, the flow control device 105 comprises a pair of valves 120 and 122 that controllably couple the distributed cooling network 103 to the helium gas source 106. The pair of valves comprises a controllable inlet valve 120 coupled to the helium gas source 106 and configured to supply helium gas from the supply through the distributed cooling network103. The distributed cooling network 103 comprises a system of connected gas flow lines 206 that pass the cooling gas through the distributed cooling network to extract heat from one or more stages of the cryostat or other thermal masses in the system and return the gas to the helium gas source 106. In this embodiment, the gas flow lines 206 receive the helium gas from the helium gas source via a controllable inlet valve 120. The gas inlet line is passed through a recuperative heat exchanger 201 where the inlet gas supplied from the helium gas source 106 interacts with the return gas exiting the distributed cooling network 103 toward the helium gas source 106. The return gas has been cooled by exposure to one or more cryocooler 104 components as further described below. Heat in the inlet gas supply can be transferred from the inlet gas supply in the recuperative heat exchanger 201 to the return gas supply. This provides an increase in efficiency as energy used to cool the return gas supply in the distributed cooling network 103 is captured by pre-cooling the inlet gas supply to be introduced into the distributed cooling network 103. In one embodiment, for example, the gas supply and return lines may be implemented in a concentric arrangement in which an inner tube flows through an outer annular concentric supply line that can further provide heat transfer between the relatively warmer supply gas flow and the relatively cooler return gas flow that has already passed through the distributed cooling network 103.

[0042] The supply gas is then passed through a first stage heat exchanger 202 that is thermally coupled to the first stage 110 of the cryocooler 104 either directly or indirectly. The first stage heat exchanger 202 may be thermally coupled with the cryocooler first stage 110 in any manner, such as being mechanically fastened to, or fully integrated into the cryocooler first stage 110 and is configured to allow heat transfer from the supply gas flow to the cryocooler first stagel 10. As described above, the first stage of a cryocooler typically cools more rapidly than other stages of a cryocooler and the relatively cooler temperatures are used to cool the supplemental gas supply flow. The cooled supplemental gas supply flow is then used to extract heat transfer from one or more subsequent stages of the cryocooler 104, or other stages, or thermal masses of the cooling system 102, to assist in further cooling one or more subsequent stages, thereby reducing the overall cooling time of the cryogenic system 101 and increasing the overall cooling efficiency of the cryocooler 104 and that of the cooling system 102.

[0043] After passing through and being cooled via the first stage heat exchanger 202, the connecting flow lines 206 direct the gas to a second stage heat exchanger 203 that is thermally coupled to the second stage 112 of the cryocooler 104. In this embodiment, for example, the second stage heat exchanger 203 is thermally coupled with the second stage 112 of the cryocooler 104 via a thermal link 205. The thermal link 205 may be a flexible or inflexible link. Heat at the second stage 112 of the cryocooler 104 is transferred from the second stage 112 to the gas flow via the second stage heat exchanger 203 and removed by the gas flow through the gas flow line 206 exiting the second stage heat exchanger 203. Additionally, heat from the cryostat second stage plate 204 is transferred to the gas flow via the second stage heat exchanger 203.

[0044] After passing through the second stage heat exchanger 203, the gas then passes through a recuperative heat exchanger 201, returning to the helium gas source 106 via the return valve 122. As described above, the cooled return gas flowing through the recuperative heat exchanger is used to precool the incoming supply gas flow received from the gas source 106 via the inlet valve 120.

[0045] In this embodiment, the distributed cooling network 103 utilizes the recuperative heat exchanger and / or a more rapidly cooled cryocooler first stage to cool a supplemental gas supply. The cooled supplemental gas supply is then introduced to a second stage heat exchanger 203 to extract heat from the second stage 112 by coupling the cooled supplemental gas flow via the connecting flow lines 206 to the second stage heat exchanger 203. The second stage heat exchanger 203 is in turn thermally coupled with the cryocooler second stagel 12, in this embodiment, via a cryostat second stage plate 204 and a thermal link 205.

[0046] Fig. 3 is a schematic diagram of another embodiment of a cryogenic system. In this embodiment, the cryogenic system comprises a cooling system 102 and a helium gas source 106 similar to the cryogenic system 101 shown in Fig. 1 in which a first stage heat exchanger is integral with or directly connected to a cryocooler first stagel 10. In this embodiment, the cooling system 102 comprises a cryocooler 104, such as a pulse tube cooler, and a flow control device 105 configured to control a supplemental helium gas flow from the helium gas source 106 to a distributed cooling network 103 that yields enhanced cooling from the cryocooler 104.

[0047] In this embodiment, the flow control device 105 comprises a pair of valves 120 and122 that controllably couple the distributed cooling network 103 to the helium gas source 106.The pair of valves comprises a first controllable inlet valve 120 coupled to the helium gas source 106 and configured to receive a supplemental helium gas flow from the helium gas source 106 and supply the supplemental gas flow to the distributed cooling network 103. The distributed cooling network 103 comprises a system of connected gas flow lines 206 that pass the cooling gas through the distributed cooling network to extract heat from one or more stages of the cryocooler 104 (or from the cryostat second stage plate 204) and return the gas to the helium gas source 106. In this embodiment, the gas flow lines 206 receive the helium gas from the helium gas source via a controllable inlet valve 120.

[0048] The gas inlet supply line is passed through a recuperative heat exchanger 201 where the inlet gas supplied from the helium gas source 106 interacts with the return gas exiting the distributed cooling network 103 toward the helium gas source 106. The return gas has been cooled by exposure to one or more cryocooler 104 components as further described below. Heat in the inlet gas supply can be transferred from the inlet gas supply in the recuperative heat exchanger 201 to the relatively cooler return gas supply. This provides an increase in efficiency as energy used to cool the return gas supply in the distributed cooling network 103 is captured by pre-cooling the inlet gas supply to be introduced into the distributed cooling network 103. In one embodiment, for example, the gas supply and return lines may be implemented in a concentric arrangement (or other adjacent configuration) in one or more portions of the distributed cooling network 103 which an inner tube flows through an outer annular concentric supply line that can further provide heat transfer between the relatively warmer supply gas flow and the relatively cooler return gas flow that has already passed through the distributed cooling network 103.

[0049] The supply gas is then passed through a first stage heat exchanger 202 that is integral with or directly connected to and thermally coupled with the first stage 110 of the cryocooler 104, such as via a cryocooler first stage plate. In some embodiments, for example, the first stage heat exchanger 202 may be integrally formed with the cryocooler first stage 110 or securely attached (e.g., bolted onto) the cryocooler first stage 110.

[0050] As described above, the first stage of the cryocooler typically cools more rapidly than other stages of a cryocooler and the relatively cooler temperatures are used to cool the supplemental gas supply flow. The cooled supplemental gas supply flow is then used to extract heat transfer from one or more subsequent stages of the cryocooler 104, or other stages of thecooling system 102, or thermal masses of the cryogenic system 101, to assist in further cooling of the one or more subsequent stages, thereby reducing the overall cooling time and increasing the overall cooling efficiency of the cryocooler 104 and that of the cooling system 102.

[0051] After passing through and being cooled via the first stage heat exchanger 202, the connecting flow lines 206 direct the gas to a second stage heat exchanger 203 that is thermally coupled to the second stage 112 of the cryocooler 104. In this embodiment, for example, the second stage heat exchanger 203 is thermally coupled with the second stage 112 of the cryocooler 104 via a second stage cryostat plate 204 that is, in turn, coupled to the cryocooler second stage 112 via a thermal link 205. The thermal link 205 may be a flexible or inflexible link. Heat at the second stage 112 of the cryocooler 104 is transferred from the second stage 112 to the gas flow via the second stage heat exchanger 203 and removed by the gas flow through the gas flow line 206 exiting the second stage heat exchanger 203.

[0052] After passing through the second stage heat exchanger 203, the gas is then returned through a recuperative heat exchanger 201 to the helium gas source 106 via the return valve 122. As described above, the cooled return gas (relative to the inlet supply gas) flowing through the recuperative heat exchanger is used to precool the incoming supply gas flow received from the gas source 106 via the inlet valve 120.

[0053] In this embodiment, the distributed cooling network 103 utilizes the recuperative heat exchanger 201 and / or a more rapidly cooled cryocooler first stage 110, via the first stage heat exchanger 202 to cool a supplemental gas supply. Upon exiting the first stage heat exchanger 202, the cooled supplemental gas supply is then introduced to a second stage heat exchanger 203 to extract heat from the second stage 112 by coupling the cooled supplemental gas flow via the connecting flow lines 206 to the second stage heat exchanger 203. The second stage heat exchanger 203 is in turn thermally coupled with the cryocooler second stage 112, in this embodiment, via a cryostat second stage plate 204 and a thermal link 205.

[0054] Fig. 4 is a schematic diagram of another embodiment of a cryogenic system similar to the cryogenic system shown in Fig. 3 except that the second stage heat exchanger 203 is attached to the cryocooler second stage 112.

[0055] Fig. 5 is a schematic diagram of another embodiment of a cryogenic system similar to the cryogenic system shown in Fig. 4 except that the second stage heat exchanger 203 is fully integrated into the cryocooler second stage 112.

[0056] Fig. 6 is a schematic diagram of another embodiment of a cryogenic system in which the second stage heat exchanger 203 is integrated in the cryostat second stage plate 204. The second stage heat exchanger may comprise, for example, a flow tube embedded in the second stage plate, disposed below the second stage plate or otherwise constructed in conjunction with the cryostat second stage plate 204. Fig. 6B is a plan view of the second stage heat exchanger 203 disposed adjacent to a perimeter of the cryostat second stage plate 204.

[0057] After passing through the second stage heat exchanger 203, the gas is then returned through a recuperative heat exchanger 201 to the helium gas source 106 via the return valve 122. As described above, the cooled return gas flowing through the recuperative heat exchanger is used to precool the incoming supply gas flow received from the gas source 106 via the inlet valve 120.

[0058] In this embodiment, the distributed cooling network 103 utilizes the recuperative heat exchanger and / or a more rapidly cooled cryocooler first stage to cool a supplemental gas supply. The cooled supplemental gas supply is then introduced to a second stage heat exchanger 203 to extract heat from the second stage 112 by coupling the cooled supplemental gas flow via the connecting flow lines 206 to the second stage heat exchanger 203. The second stage heat exchanger 203 is in turn thermally coupled with the cryostat second stage plate 204.

[0059] Fig. 7 is a schematic diagram of another embodiment of a cryogenic system. In this embodiment, the cryogenic system comprises a cooling system 102 and a helium gas source 106 similar to the cryogenic system 101 shown in Fig. 1 but including one or more additional stages. The cooling system comprises a cryocooler 104, such as a pulse tube cooler, and a flow control device 105 configured to control a supplemental helium gas flow from the helium gas source 106 to a distributed cooling network 103 that yields enhanced cooling from the cryocooler 104.

[0060] In this embodiment, the flow control device 105 comprises a pair of valves 120 and 122 that controllably couple the distributed cooling network 103 to the helium gas source 106. The pair of valves comprises a controllable inlet valve 120 coupled to the helium gas source 106 and configured to supply helium gas from the supply through the distributed cooling network103. The distributed cooling network 103 comprises a system of connected gas flow lines 206 that pass the cooling gas through the distributed cooling network to extract heat from one or more stages of the cryocooler 104 (or from the cryostat second stage plate 204) and return the gas to the helium gas source 106. In this embodiment, the gas flow lines 206 receive the helium gas from the helium gas source via a controllable inlet valve 120. The gas inlet line is passed through a recuperative heat exchanger 201 where the inlet gas supplied from the helium gas source 106 interacts with the return gas exiting the distributed cooling network 103 toward the helium gas source 106. The return gas has been cooled by exposure to one or more cryocooler 104 components as further described below. Heat in the inlet gas supply can be transferred from the inlet gas supply in the recuperative heat exchanger 201 to the return gas supply. This provides an increase in efficiency as energy used to cool the return gas supply in the distributed cooling network 103 is captured by pre-cooling the inlet gas supply to be introduced into the distributed cooling network 103. In one embodiment, for example, the gas supply and return lines may be implemented in a concentric arrangement in which an inner tube flows through an outer annular concentric supply line that can further provide heat transfer between the relatively warmer supply gas flow and the relatively cooler return gas flow that has already passed through the distributed cooling network 103.

[0061] The supply gas is then passed through a first stage heat exchanger 202 that is thermally coupled to the first stage 110 of the cryocooler 104 via a cryocooler first stage plate 114. The first stage heat exchanger 202 may be thermally coupled with the cryocooler first stage plate 114 in any manner configured to allow heat transfer from the supply gas flow to the cryocooler first stage plate 114. The cooled supplemental gas supply flow is then used to extract heat transfer from one or more subsequent stages of the cryocooler 104 to assist in further cooling of the one or more subsequent stages, thereby reducing the overall cooling time and increasing the overall cooling efficiency of the cryocooler 104.

[0062] After passing through and being cooled via the first stage heat exchanger 202, the connecting flow lines 206 direct the gas to a second stage heat exchanger 203 that is thermally coupled to the second stage 1 12 of the cryocooler 104. In this embodiment, for example, the second stage heat exchanger 203 is thermally coupled with the second stage 112 of the cryocooler 104 via a second stage cryostat plate 204 that is, in turn, coupled to the cryocoolersecond stage 112 via a thermal link 205. The thermal link 205 may be a flexible or inflexible link. Heat at the second stage 112 of the cryocooler 104 is transferred from the second stage 112 to the gas flow via the second stage heat exchanger 203 and removed by the gas flow through the gas flow line 206 exiting the second stage heat exchanger 203.

[0063] After passing through the second stage heat exchanger 203, the gas flows to a third stage heat exchanger 702. The third stage heat exchanger 702 is thermally coupled to a cryostat third stage plate 701. The third stage heat exchanger may be coupled with the cryostat third stage plate 701 in any manner, such as being formed integrally with the cryostat third stage plate 701, bolted to the plate 701 , embedded into the plate, or the like. Heat at the cryostat third stage plate 701 is transferred from the cryostat third stage plate 701 to the gas flow via the third stage heat exchanger 702 and removed by the gas flow line exiting the third stage heat exchanger 702.Although a third cryostat stage is shown in Fig. 7, any number of additional stages may be added with one or more additional heat exchangers.

[0064] After passing through the third stage heat exchanger 702, the gas is then returned through a recuperative heat exchanger 201 to the helium gas source 106 via the return valve 122. As described above, the cooled return gas flowing through the recuperative heat exchanger is used to precool the incoming supply gas flow received from the gas source 106 via the inlet valve 120.

[0065] In this embodiment, the distributed cooling network 103 utilizes the recuperative heat exchanger and / or a more rapidly cooled cryocooler first stage to cool a supplemental gas supply. The cooled supplemental gas supply is then introduced to a second stage heat exchanger 203 to extract heat from the second stage 112 by coupling the cooled supplemental gas flow via the connecting flow lines 206 to the second stage heat exchanger 203 and then to a third stage heat exchanger 702 to extract heat from the cryostat third stage plate 701. The second stage heat exchanger 203 and third stage heat exchanger 702 are in turn thermally coupled with the cryocooler second stage plate 116 and the cryostat third stage plate 701.

[0066] Fig. 8 is a schematic diagram of another embodiment of a cryogenic system. In this embodiment, the cryogenic system comprises a cooling system 102 and a helium gas source 106 similar to the cryogenic system 101 shown in Fig. 7 in which cooling gas is routed differently between the second and third stages. The cooling system comprises a cryocooler 104, such as apulse tube cooler, and a flow control device 105 configured to control a supplemental helium gas flow from the helium gas source 106 to a distributed cooling network 103 that yields enhanced cooling from the cryocooler 104.

[0067] In this embodiment, the flow control device 105 comprises a pair of valves 120 and 122 that controllably couple the distributed cooling network 103 to the helium gas source 106. The pair of valves comprises a controllable inlet valve 120 coupled to the helium gas source 106 and configured to supply helium gas from the supply through the distributed cooling network 103. The distributed cooling network 103 comprises a system of connected gas flow lines 206 that pass the cooling gas through the distributed cooling network to extract heat from one or more stages of the cryocooler 104 (or from the cryostat second stage plate 204) and return the gas to the helium gas source 106. In this embodiment, the gas flow lines 206 receive the helium gas from the helium gas source via a controllable inlet valve 120. The gas inlet line is passed through a recuperative heat exchanger 201 where the inlet gas supplied from the helium gas source 106 interacts with the return gas exiting the distributed cooling network 103 toward the helium gas source 106. The return gas has been cooled by exposure to one or more cryocooler 104 components as further described below. Heat in the inlet gas supply can be transferred from the inlet gas supply in the recuperative heat exchanger 201 to the return gas supply. This provides an increase in efficiency as energy used to cool the return gas supply in the distributed cooling network 103 is captured by pre-cooling the inlet gas supply to be introduced into the distributed cooling network 103. In one embodiment, for example, the gas supply and return lines may be implemented in a concentric arrangement in which an inner tube flows through an outer annular concentric supply line that can further provide heat transfer between the relatively warmer supply gas flow and the relatively cooler return gas flow that has already passed through the distributed cooling network 103.

[0068] The supply gas is then passed through a first stage heat exchanger 202 that is thermally coupled to the first stage 110 of the cryocooler 104 via a cryocooler first stage plate 114. The first stage heat exchanger 202 may be thermally coupled with the cryocooler first stage 110 in any manner, such as being formed integrally with the cryostat third stage plate 701, bolted to the plate 701, embedded into the plate, or the like, and is configured to allow heat transfer from the supply gas flow to the cryocooler first stage plate 114. The cooled supplemental gassupply flow is then used to extract heat transfer from one or more subsequent stages of the cryocooler 104 to assist in further cooling of the one or more subsequent stages, thereby reducing the overall cooling time and increasing the overall cooling efficiency of the cryocooler 104.

[0069] After passing through and being cooled by the first stage heat exchanger 202, the gas flows to a third stage heat exchanger 702. The third stage heat exchanger 701 is thermally coupled to a cryostat third stage plate 701. The third stage heat exchanger may be coupled with the cryostat third stage plate 701 in any manner, such as being formed integrally with the cryostat third stage plate 701, bolted to the plate 701, embedded into the plate, or the like. Heat at the cryostat third stage plate 701 is transferred from the cryostat third stage plate 701 to the gas flow via the third stage heat exchanger 702 and removed by the gas flow line exiting the third stage heat exchanger 702. Although a third cryostat stage is shown in Figs. 7 and 8, any number of additional stages may be added with one or more additional heat exchangers.

[0070] After passing through the third stage heat exchanger 702 and extracting heat from the cryostat third stage plate 701, the connecting flow lines 206 direct the gas to a second stage heat exchanger 203 that is thermally coupled to the second stage 112 of the cryocooler 104. In this embodiment, for example, the second stage heat exchanger 203 is thermally coupled with the second stage 112 of the cryocooler 104 via a second stage cryostat plate 204 that is, in turn, coupled to a second stage cryocooler plate 116 of the cryocooler second stage 112 via a thermal link 205. The thermal link 205 may be a flexible or inflexible link. Heat at the second stage 112 of the cryocooler 104 is transferred from the second stage 112 to the gas flow via the second stage heat exchanger 203 and removed by the gas flow through the gas flow line 206 exiting the second stage heat exchanger 203.

[0071] As shown in Figs 7 and 8, the relatively cooler gas flow exiting the first stage heat exchanger may be directed to one or more additional stages in any order to enhance cooling at the respective stages. Depending on the relative thermal mass or other considerations, for example, the gas flow may be first directed to a stage that requires relatively greater heat extraction to cool the stage before being directed to additional stage(s).

[0072] After passing through the second stage heat exchanger 203, the gas is then returned through a recuperative heat exchanger 201 to the helium gas source 106 via the return valve 122. As described above, the cooled return gas flowing through the recuperative heat exchanger isused to precool the incoming supply gas flow received from the gas source 106 via the inlet valve 120.

[0073] In this embodiment, the distributed cooling network 103 utilizes the recuperative heat exchanger and / or a more rapidly cooled cryocooler first stage to cool a supplemental gas supply. The cooled supplemental gas supply is then introduced to a third stage heat exchanger 702 and then to a second stage heat exchanger 203 to extract heat from the cryostat third stage plate 701 and then the second stage 112 by coupling the cooled supplemental gas flow via the connecting flow lines 206 to the third stage heat exchanger 702 and the second stage heat exchanger 203. The third and second stage heat exchangers 702, 203 are in turn thermally coupled with the cryostat third stage plate 701 and the cryocooler second stage plate 116.

[0074] Fig. 9 is a schematic diagram showing another example embodiment of a cryogenic system in which the cooled return gas flow is delivered to a cryocooler heat exchanger 902 before being returned to a helium gas source 106. The cryogenic system, in this embodiment, comprises a cooling system 102, a gas source 106, such as a helium gas source, and a controller 107. The cooling system 102 comprises a cryocooler 104, such as a pulse tube cooler, coupled to a helium gas source 106 to receive a cooling gas supply for the cryocooler 104 as is typical. The cooling system also includes a flow control device 105 configured to control a supplemental helium gas flow from the helium gas source 106 to a distributed cooling network 103 that provides supplemental cooling for the cryocooler 104. The flow control device 105, in this embodiment, also directs the cooled return gas flow from the distributed cooling network 103 to a cryocooler heat exchanger 902 via a pair of controllable valves 124 and 126. The cryocooler heat exchanger 902 is thermally coupled with one or more components of the cryocooler 104. The cryocooler heat exchanger 902 may be thermally coupled, for example, with a warm end heat exchanger 901 of the cryocooler 104 or may be coupled with other thermal components such as a head of the cryocooler 104.

[0075] The cooled gas flow passed through the cryocooler heat exchanger 902 extracts heat from the cryocooler, such as the cryocooler warm end heat exchanger 901. The gas flow is then returned to the helium gas source 106 via the controllable valve 126.

[0076] Fig. 10 is a schematic diagram showing another example embodiment of a cryogenic system in which an additional gas flow is provided by a gas source to a cryocooler heatexchanger 902. The cryogenic system, in this embodiment, comprises a cooling system 102, a gas source 106, such as a helium gas source, and a controller 107. The cooling system 102 comprises a cryocooler 104, such as a pulse tube cooler, coupled to a helium gas source 106 to receive a cooling gas supply for the cryocooler 104 as is typical. The cooling system also includes a flow control device 105 configured to control a supplemental helium gas flow from the helium gas source 106 to a distributed cooling network 103 that provides supplemental cooling for the cryocooler 104. The flow control device 105, in this embodiment, also directs a separate gas supply to a cryocooler heat exchanger 902 via a pair of controllable valves 128 and 130. The cryocooler heat exchanger 902 is thermally coupled with one or more components of the cryocooler 104. The cryocooler heat exchanger 902 may be thermally coupled, for example, with a warm end heat exchanger 901 of the cryocooler 104 or may be coupled with other thermal components such as a head of the cryocooler 104.

[0077] The additional gas flow passed through the cryocooler heat exchanger 902 extracts heat from the cryocooler, such as the cryocooler warm end heat exchanger 901. The gas flow is then returned to the helium gas source 106 via the controllable valve 130.

[0078] Fig. 11 is a schematic diagram showing another example embodiment of a cryogenic system in which independent gas sources are used to supply gas flows to a cryocooler 104 and a distributed cooling network 103. In this embodiment, a helium gas source 106 supplies gas to the cryocooler 104, and a dedicated distributed cooling network compressor 1125 provides a gas supply to the distributed cooling network 103. The cryogenic system, in this embodiment, comprises a cooling system 102, a first gas source 106, such as a helium gas source, a second dedicated distributed cooling network compressor 1125, and a controller 107. The cooling system 102 comprises a cryocooler 104, such as a pulse tube cooler, coupled to the helium gas source 106 to receive a cooling gas supply for the cryocooler 104 as is typical. The cooling system also includes a flow control device 105 coupled to the dedicated distributed cooling network compressor 1125 to control a supplemental helium gas flow from the dedicated distributed cooling network compressor 1125 to the distributed cooling network 103 that provides supplemental cooling for the cryocooler 104. The flow control device 105, in this embodiment, also directs the cooled return gas flow from the distributed cooling network 103 toa cryocooler heat exchanger 902 via a pair of controllable valves 120 and 122. The cryocooler heat exchanger 902 is thermally coupled with one or more components of the cryocooler 104.

[0079] Fig. 12 is a schematic diagram showing another example embodiment of a cryogenic system similar to the cryogenic system shown in Fig. 10 in which the return path of the gas supply line is directed to a flow controller 105 disposed in the cryocooler 104. The flow controller is used to control the gas flow within the distributed cooling network 103. In this manner, a controller function may be handled by a controller 105 of the cryocooler 104.

[0080] Fig. 13 is a schematic diagram showing another example embodiment of a cryogenic system similar to the cryogenic system shown in Fig. 12. In this embodiment, a flow controller 105 disposed in the cryocooler 104 receives a gas flow supplied from a helium gas source. The flow controller 105 controls cooling of the cryocooler 104 using the gas supply, and also controls a gas flow supplied to the distributed cooling network 103. Thus, the flow controller 105 controls cooling functions both internally for the cryocooler and of the distributed cooling network 103.

[0081] Fig. 14 is a schematic diagram of a flow control device 105 for a distributed cooling network 103. In this embodiment, the flow control device 105 includes a plurality of valves 1403 for controlling a supply and return path of a gas flow delivered to the distributed cooling network 103 as described above. In one embodiment, the valves 1403 include a pair of variable flow valves operable under the control of a controller 107. The controller 107 receives input signals from a pair of pressure sensors 1402 configured to measure pressure conditions for the gas flow lines 206, a flow meter 1401, and temperature sensors 1404 disposed within the distributed cooling network (e.g., at one or more of the cryocooler stages, the cryostat, or in connection with one or more thermal masses disposed within the cryogenic system 101).

[0082] As described above, the first stage of a two stage cryocooler typically has much greater cooling power than the second stage. A distributed cooling network can be configured to extract heat from one stage to another stage and serve to effectively transport the cooling generated by cryocooler 104 to other parts of the cooling system 102. Further, many cryogenic cooling systems have more thermal mass that needs to be cooled attached to the second stage (or a subsequent stage) than at the first stage. A distributed cooling network that extracts heat from components with high thermal mass and transports that heat to the first stage for removal can greatly improve cooldown efficiency.

[0083] In a system with a single pressurized fluid source, the flow is divided between the cryocooler and the distributed cooling network. At higher temperatures the flow is more useful flowing through the distributed cooling network when the cryocooler has greater cooling power. At lower temperatures, diminished flow has an increasingly greater detrimental effect on cryocooler performance. A controller 107 manages the flow split continuously during a cooldown to divert the flow most efficiently for the present state of the system and shuts down the distributed cooling network when it is no longer beneficial. As the cryogenic system cools, the controller 107 will shift flow from the distributed cooling network to the cryocooler until flow is shut off.

[0084] In the embodiment shown in Fig. 14, for example, the controller 107 comprises input and output circuitry configured to receive one or more input signals (e.g., electrical signals) generated by the one or more sensors or other input devices in the flow control 105 and / or the distributed cooling network 103. In Fig. 14, for example, temperature sensor(s) 1404 are disposed within the distributed cooling network adjacent to one or more components of the cryocooler, such as a first stage and / or a second stage of the cryocooler. The temperature sensors are each configured to detect a temperature level and provide an output signal (e g., an output electrical signal) to the input circuitry of the controller 107. A flow meter 1401 and pressure sensors 1403 monitor a cooling fluid flow rate through and pressure in the flow line 206 and, similarly, provide output signals (e.g., electrical signals) to the input circuitry of the controller 107.

[0085] Those skilled in the art should be familiar with the use of controllers in process control applications, such as in controlling operations of components of instruments such as cryocoolers by receiving one or more input signals via an input circuit, processing the one or more input signals to determine a control operation to be performed, and generating one or more output signals (e.g., output electrical signals) to control the operation of one or more components of the instrument (e.g., one or more control valves 1403 in the flow control device 105). The output control signals are delivered to the one or more controllable components of the instrument and are used to control the operation of the controllable components of the instrument.

[0086] In Fig. 14, for example, sensor signals are received by the controller from one or more of the flow meter 1401, the pressure sensors 1402, and the temperature sensors 1404 atinput control circuitry. A processor of the controller (e.g., a programmable logic controller, a general purpose computer processor, a special purpose computer processor) is configured to execute one or more hardware and / or software operations to process the one or more input signals to determine one or more control operation for a component of the flow control device 105 of the distributed cooling network 103. Based on the determined one or more control operation, The controller is configured to generate one or more output control signals via the output control circuit and provide the output control signals to the one or more process control elements, such as the controllable valves 1403 of the flow control device 105 for the distributed cooling network 103. Controllers may be implemented in software, firmware, hardware or some suitable combination of at least two of the three.

[0087] Fig. 15 is a schematic diagram showing another flow control device 105 that may be used within a cryogenic system described herein. In this embodiment, the flow control device 105 includes a plurality of solenoid on-off valves 1501 for controlling a supply and return path of a gas flow delivered to the distributed cooling network 103 as described above. The solenoid controlled on-off valves are controlled by a controller 107. Similar to the embodiment shown in Fig. 14, the controller 107 receives input signals from a pair of pressure valves 1401 and 140 configured to measure pressure conditions for the gas flow lines 206, a flow meter 1401, and temperature sensors 1401 disposed within the distributed cooling network (e.g., at one or more of the cryocooler stages, the cryostat, or in connection with one or more thermal masses disposed within the cryogenic system 101).

[0088]

[0089] Fig. 16 is a schematic diagram of an example embodiment of cryogenic system including a dynamic tuning cooling system 2000 in combination with a distributed cooling network 103 of a cryocooler, such as described above with respect to Figs. 14 and 15. In this embodiment, a first controller 2106 of a dynamic tuning system captures system information, such as but not limited to the temperature of various components of a refrigerator 404 of the dynamic tuning cooling system 2000. By connecting a second controller 107 configured to control one or more operations of the distributed cooling network 103 to the first, Dynamic Tuning controller 2106, the cryogenic system can be configured to employ any information captured or otherwise determined (including the various temperatures) to make adjustments toone or more Control Valves 1403. For instance, when the cryogenic system starts a cooldown operation, and the system is near room temperature, the compressor typically has plenty of excess helium gas flow capacity. This excess flow can be utilized to produce a thermal short between the first and second stages of the system to effectively transfer cooling from the first stage of the cryocooler to the warmer areas of the Cryogenic System (by extracting heat from the relatively warmer areas to the relatively cooler areas) as described with reference to Figs. 14 and 15. Then, as the system cools, and the amount of the compressor’s excess capacity diminishes, the temperature information from the Dynamic Tuning cooling system 2000 can be utilized to determine one or more settings (e.g., one or more ideal / optimized / improved settings) of the control valves 1403 in the flow control device 105. In this manner, cooldown times can be drastically improved. Further, during the cooldown period, not only is it useful to direct the compressor’s excess flow capacity to couple the first and second stages of the PTC, there is an optimal / improved amount of additional flow that will result in optimal / improved cooldown performance.

[0090] In Fig. 16, the dynamic tuning cooling system 2000 comprises a multi-stage orifice pulse tube refrigerator coupled to a compressor. The dynamic tuning cooling system 2000 includes a compressor 2102, a refrigerator 404, and a dynamic tuning controller 2106. The compressor 2102 provides oscillating fluid flow to the refrigerator 404, and in particular to a multi-stage pulse-tube refrigerator 416, shown as a two-stage refrigerator. The multi-stage pulsetube refrigerator 416 can have an input 410 and a first-stage output 412 and a second-stage output 414. The first stage 408 can be coupled to an acoustic network comprising a resistance 2128 and a reservoir 2130 via a second fluid path 2156. The input 410 can be coupled to the compressor 2102 via a first fluid path 2152. The first stage 408 can be coupled to the second stage 418, and the second stage can be coupled to a second acoustic network via a third fluid path 454. The second acoustic network can include a resistance 440 and a reservoir 442. Oscillating flow in the refrigerator 404 can take two paths: a first oscillating flow between the input 410 and the first reservoir 2130 and a second oscillating flow between the input 410 and the second reservoir 442.

[0091] The compressor 2102 can provide high-pressure room temperature fluid to the input 410 of the multi-stage pulse-tube refrigerator 416 and receive low-pressure room temperaturefluid back from the multi-stage pulse-tube refrigerator 416 in a cyclic manner. The period or frequency of this oscillating fluid flow is governed by a drive frequency 2114 of the compressor 152. Where the drive frequency 2114 is adjustable, increasing the drive frequency 2114 decreases an acoustic impedance of the refrigerator 404, or more specifically, decreases an acoustic impedance of the reservoirs 2130 and 442. The high-pressure and low-pressure extremes of the cycle are normally proportional to the fluid power input to the multi-stage pulsetube refrigerator 416. The time phasing between the oscillating pressure and flow in a regenerator of the multistage pulse-tube refrigerator 416 serves to create an oscillating heat transfer between the working gas and regenerators of the first stage 408 and second stage 418 of the multi-stage pulse-tube refrigerator 416. The time phasing of this oscillating heat transfer creates a time- averaged transport of heat from a cold heat exchanger in the second stage 418 at temperature T2 back up to the input 410 at ambient temperature To. The heat is ultimately rejected to ambient temperature through a heat exchanger in the compressor 2102.

[0092] In some examples, the fluid (acoustic) power exits the first stage 408 at first-stage output 412 and into a terminating acoustic network comprising a flow resistance 2128 (e.g., an orifice valve) and a volume 2130 (also known as a reservoir or compliance), where it is dissipated and converted to heat. In some circumstances, the heat is rejected to ambient temperature by a warm heat exchanger at the first-stage output 412. The volume of the reservoir 2130 and / or the resistance 2128 along with the volume of the reservoir 442 and / or the resistance 440 control an acoustic impedance of the refrigerator 404 seen by the compressor 2012. In other words, control of one or more of the reservoir 2130, the resistance 2128, the reservoir 442, and the resistance 440 is responsible for setting a time phasing of oscillating pressure and flow and a magnitude of oscillating flow in the first stage 408 and the second stage 418. The first stage 408 can be coupled to the reservoir 180 via a second fluid path 2156 and fluid flow along the second fluid path 2156 is controlled via the resistance 2128. The second stage 418 can be coupled to the reservoir 442 via a third fluid path 454 and fluid flow along the third fluid path 454 is controlled via the resistance 440.

[0093] At a given temperature of the multi-stage pulse-tube refrigerator 416 (and in particular at a cold heat exchanger of the second stage 418), the controller 2106 seeks to optimize a fluid (acoustic) power flow from the compressor 2102 to the refrigerator 404 byadjusting an acoustic impedance of the refrigerator 404 seen by the compressor 2102. This may involve an increase or decrease in the acoustic impedance of the refrigerator 404 and thus may involve a decrease or increase in the volume of the volumes 2130 and / or 442 and / or a change in the value of the resistance 2128 and / or 440. For instance, where a volume of the volume 2130 is adjustable, the volume of the volume 2130 can be increased to reduce an impedance of the refrigerator 404. As another example, where the resistance 440 is implemented as a second-stage orifice valve, opening the second- stage orifice valve 440 decreases an acoustic impedance of the refrigerator 404. Thus, opening or closing the orifice valves (e.g., 2128 and 440) to an extent can tailor the refrigerator 404 acoustic impedance seen by the compressor 2102 and in this way maximize fluid (acoustic) power transfer from the compressor 2102 to the refrigerator 404 and maximize the cooling powers available at the cold ends of the first stage and second stage.

[0094] At the same time, or alternatively, the compressor 2102 can adjust the drive frequency 2114 to adjust an acoustic impedance seen by the compressor 2102. In other words, the controller 2106 can (1) adjust the drive frequency 164 and not adjust the volumes 2130 and 442 or resistances 2128and 440, (2) adjust the drive frequency 2114 and the volumes 2130and 442 and the resistances 2128 and 440, (3) adjust the drive frequency 2114 and the resistances 2128 and 440, but not the volumes 2130 and 442, (4) and other variations of the above. An increase in drive frequency 2114 typically results in a decrease in an acoustic impedance of the terminating networks (i.e., 2128 and 2130 and 440 and 442) and hence of the refrigerator 404 (i.e., the acoustic impedance seen by the compressor 2102).

[0095] Often, effective impedance matching involves adjusting the drive frequency 2114 by a factor of 1.5: 1 or 3: 1 or more. For instance, given a starting frequency of 1.5 Hz, the drive frequency can be adjusted up to 2.25 Hz or 4.5 Hz. In some cases, a linear compressor may not be able to achieve such large swings / adjustments in drive frequency, and thus other compressor types, such as a timed dual-valve compressor may be used.

[0096] An optimal acoustic impedance of the terminating networks (i.e., 2128 and 2130 for the first stage and 440 and 442 for the second stage do not remain constant during cooldown. The thermodynamic and fluid mechanical processes in the pulse tube refrigerator 416 transform the terminating networks’ impedances into the impedance seen by the compressor 2102, which determines the fluid (acoustic) power flowing into the pulse tube refrigerator 416 and the coolingpower available at the second-stage cold end. The lower the temperature of the cold end of the second stage below the nominally room -temperature fluid supplied by compressor 2102, the higher the acoustic impedance seen by the compressor 2102. Matching this increased impedance as temperature decreases involves decreasing resistance 2128, 440 and / or decreasing drive frequency 2114.

[0097] In a design where the drive frequency 2114, volumes 2130, 442, and resistances 2128, 440 are all fixed, these are chosen to match the impedance seen by the compressor to the maximum pressure and flow capabilities of a compressor when the multi-stage pulse tube refrigerator is at its nominal cold end operating temperature (e.g. 4-6 K). This matching seeks to create maximum fluid (acoustic) power flow from the compressor to the pulse tube refrigerator and maximum cooling power at its cold end.

[0098] During a cooldown to the nominal operating temperature, the impedance transformation at the higher cold end temperature of the multi-stage pulse tube refrigerator results in a higher impedance seen by the compressor, which lowers the fluid (acoustic) power flow from the compressor to the multi-stage pulse tube refrigerator and lowers the cooling power available at its second-stage cold end.

[0099] To improve the impedance matching between the compressor 2102 and multi-stage pulse tube refrigerator 416, increase cooling power, and decrease cooldown times, the controller 2106 not only adjusts one or more of drive frequency 2114, resistance 2128, volume 2130, resistance 440, and volume 442 to optimize acoustic impedance matching between compressor 2102 and refrigerator 404 at a given temperature, but further adjusts these ‘knobs’ over time during cooldown since every change in second-stage cold heat exchanger temperature is associated with a different optimum acoustic impedance. On average, the controller 2106 adjusts one or more of drive frequency 2114, resistance 2128, volume 180, resistance 440, and volume 442 to increase acoustic impedance as the second-stage cold heat exchanger temperature decreases. More specifically, the drive frequency 12114 can be lowered on average and / or a state of the resistances 2128 and 440 can be gradually closed on average (i.e., greater resistance), as the second-stage cold heat exchanger temperature decreases toward a steady state target (e g., 4-6 K).

[0100] The controller 2106 can be in communication with the compressor 2102 and the refrigerator 404 and can receive feedback from one or both used to adjust the acoustic impedance (i.e., to adjust one or more of 2114, 2128, 2130, 440, 442). More specifically, the controller 2106 can monitor a cooling characteristic, which is the basis for adjusting the drive frequency 2114, the resistance 2128, the volume 2130, the resistance 440, and / or the volume 442. In an embodiment, the cooling characteristic is a pressure in the compressor 2102 (many existing compressors have built-in pressure sensors) or a pressure in the multi-stage pule-tube refrigerator 408. For instance, the cooling characteristic can be the compressor output pressure or outputinput differential pressure. As another example, pressure can be monitored in a regenerator of the first stage 408, a regenerator of the second stage 418, or both regenerators. In another embodiment, the cooling characteristic is a rate of cooling in the multi-stage pulse-tube refrigerator 416, for instance a rate of cooling at the second- stage cold heat exchanger and / or the first-stage cold heat exchanger. In another embodiment, the cooling characteristic is a temperature in any one or more of the multiple stages, or a temperature difference between the stages. In yet another embodiment, the cooling characteristic is a combination of one or more of the above pressures and cooling rates. In another embodiment, the controller 2106 can be programmed with a calibration that maps settings for one or more of the drive frequency 2114, resistance 2128, volume 2130, resistance 440, and volume 442 to cooling characteristics, where this calibration can be performed before the refrigerator 404 is put into operation.

[0101] The dynamic tuning cooling system 2000 shown in Fig. 16 further includes two asymmetric bypass valves 2146 and 444. The first-stage asymmetric bypass valve 2146 is coupled between the first fluid path 2156 and the second fluid path 2158, while the second-stage asymmetric bypass vale 444 is coupled between the first fluid path [ ] 460 and the third fluid path 454. With the addition of the fluid paths 2158 and 460 some fluid in the first and second- stage oscillating flows is able to circulate through the asymmetric bypass valves 2146 and 444 rather than merely oscillate between the compressor 2102 and the reservoirs 2130 and 442. Fluid making these complete loops degrades the cooling power of the multi-stage pulse-tube refrigerator 408, and thus the asymmetric bypass valves 2146 and 444 have asymmetric resistance to fluid flow (i.e., more resistance in one direction than in the other). This asymmetry is adjusted in both 2146 and 444 until the time-averaged flows around the first-stage loop and thesecond- stage loop are suppressed or the steady- state thermodynamic performance of the overall multi-stage pulse- tube refrigerator 416 is maximized.Example

[0102] The flow from the pressurized cooling fluid source is split between the cryocooler and the distributed cooling network. The optimal division of flow depends on the distribution of thermal mass in the system and the temperature as the system cools because the cooling power of the cryocooler is a function of temperature and fluid flow. In one embodiment, a feedback controller will dynamically change the distributed cooling network flow rate to optimize the flow split for the prevailing state of the system. The data in Table 1 below is extracted from an experiment and demonstrates the changes in optimal flow rate and subsequent power transfer as a function of the first stage temperature of a cryocooler. The experimental setup is a typical cryogenic cooling system using a factory standard cryocooler and equipped with a prototype distributed cooling network.Table 1.

[0103] Fig. 17 is a flowchart showing an example process for controlling a distributed cooling network flow. In this embodiment, the process can characterize the cryogenic system behavior to establish an ideal / improved flow rate that would yield the most rapid / improvedcooldown rate for the system at any given temperature. The control system (implemented in controller 106) measures the current temperature of the first stage and determines an appropriate flow rate (e.g., use a lookup table or file to determine the appropriate flow) rate as established by the characterization. The flow rate would become the set point for a feedback control loop comprising the continuously variable valve and flow meter of the distributed cooling network. As the temperature of the first stage changes, the flow rate set point would be continuously updated until the system cools to the shut off temperature where flow would stop.

[0104] As shown in Fig. 17, the example process determines a first stage temperature, such as via a temperature sensor 1404 (shown in Figs. 14 and 15), in operation 1702. The process determines whether the temperature is above a shut off value in operation 1704. If the temperature is not above the shut off value, the distributed cooling network flow is shut off in operation 1706. If the temperature is above the shut off value in operation 1704, however, a flow rate set point is determined from the temperature reading in operation 1708. Based on the flow rate set point, one or more valve position is set in operation 1710, and a flow rate measurement is read in operation 1712. The measurement is used as a control for a feedback control loop to repeatedly or continuously adjust the valve position until system cools to the shut off temperature where flow would stop.

[0105] The methods described in connection with the embodiments disclosed herein may be embodied directly in hardware, in processor-executable code encoded in a non- transitory tangible processor readable storage medium, or in a combination of the two. Referring to FIG. 18 for example, shown is a block diagram depicting physical components that may be utilized to realize the controllers 107 and 2106 in FIGS. 1-17 according to an exemplary embodiment. As shown, in this embodiment a display portion 1112 and nonvolatile memory 1120 are coupled to a bus 1122 that is also coupled to random access memory ("RAM") 1124, a processing portion (which includes N processing components) 1126, an optional field programmable gate array (FPGA) 1127, and a transceiver component 1128 that includes N transceivers. Although the components depicted in FIG. 18 represent physical components, FIG. 18 is not intended to be a detailed hardware diagram; thus, many of the components depicted in FIG. 18 may be realized by common constructs or distributed among additional physical components. Moreover, it iscontemplated that other existing and yet-to-be developed physical components and architectures may be utilized to implement the functional components described with reference to FIG. 18.

[0106] The display portion 1112 generally operates to provide a user interface for a user, and in several implementations, the display is realized by a touchscreen display. In general, the nonvolatile memory 1120 is non-transitory memory that functions to store (e.g., persistently store) data and processor-executable code (including executable code that is associated with effectuating the methods described herein). In some embodiments for example, the nonvolatile memory 1120 includes bootloader code, operating system code, file system code, and non- transitory processor-executable code to facilitate the execution of a method described with reference to FIG. 17 described further herein.

[0107] In many implementations, the nonvolatile memory 1120 is realized by flash memory (e.g., NAND or ONENAND memory), but it is contemplated that other memory types may be utilized as well. Although it may be possible to execute the code from the nonvolatile memory 1120, the executable code in the nonvolatile memory is typically loaded into RAM 1124 and executed by one or more of the N processing components in the processing portion 1126.

[0108] The N processing components in connection with RAM 1124 generally operate to execute the instructions stored in nonvolatile memory 1120 to enable control of a distributed cooling system for cryocoolers. For example, non-transitory, processor executable code to effectuate the methods described with reference to FIGS. 1-17 may be persistently stored in nonvolatile memory 1120 and executed by the N processing components in connection with RAM 1124. As one of ordinarily skill in the art will appreciate, the processing portion 1126 may include a video processor, digital signal processor (DSP), micro-controller, graphics processing unit (GPU), or other hardware processing components or combinations of hardware and software processing components (e.g., an FPGA or an FPGA including digital logic processing portions).

[0109] In addition, or in the alternative, the processing portion 1126 may be configured to effectuate one or more aspects of the methodologies described herein. For example, non- transitory processor-readable instructions may be stored in the nonvolatile memory 1120 or inRAM 1124 and when executed on the processing portion 1126, cause the processing portion 1126 to perform control of the valve(s) 120, 122, 124, 126, 128, 130, 1403 and 1501 of the flow control device 105, in FIGS. 1-17. Alternatively, non-transitory FPGA-configuration-instructions may be persistently stored in nonvolatile memory 1120 and accessed by the processing portion 1126 (e.g., during boot up) to configure the hardware-configurable portions of the processing portion 1126 to effectuate the functions of the controller 106, 2106.

[0110] The input component 1130 operates to receive signals (e.g., corresponding to the temperature, flow monitor, pressure and / or other measurements via sensors such as 1401, 1402, 1404, or temperature or pressure measurements made in the compressor or in the regenerator(s)). The signals received at the input component may include, for example, the temperature measurements corresponding to one or more stages of the cryocooler via sensors 1404 of the distributed cooling network 103, and / or the pressure 1402 and flow rate 1401 readings in the flow control device 105 for the distributed cooling network at the compressor 102, to name nonlimiting examples. The output component generally operates to provide one or more analog or digital signals to effectuate an operational aspect of the controller 106, 2106. For example, the output portion 1132 may provide the control output signal(s) described with reference to FIGs. 1- 17. When the output component is realized by the controller 106, 2106, for example, the output signal may be a control output signal used for adjusting the valves 120, 122, 124, 126, 128, 130, 1403, 1501 or other control signals provided to the flow control device 105, distributed cooling network 103, and / or to the cryocooler 104.

[0111] The depicted transceiver component 1128 includes N transceiver chains, which may be used for communicating with external devices via wireless or wireline networks. Each of the N transceiver chains may represent a transceiver associated with a particular communication scheme (e.g., WiFi, Ethernet, Profibus, etc.).

[0112] Some portions are presented in terms of algorithms or symbolic representations of operations on data bits or binary digital signals stored within a computing system memory, such as a computer memory. These algorithmic descriptions or representations are examples of techniques used by those of ordinary skill in the data processing arts to convey the substance oftheir work to others skilled in the art. An algorithm is a self-consistent sequence of operations or similar processing leading to a desired result. In this context, operations or processing involves physical manipulation of physical quantities. Typically, although not necessarily, such quantities may take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared or otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to such signals as bits, data, values, elements, symbols, characters, terms, numbers, numerals or the like. It should be understood, however, that all of these and similar terms are to be associated with appropriate physical quantities and are merely convenient labels. Unless specifically stated otherwise, it is appreciated that throughout this specification discussions utilizing terms such as “processing,” “computing,” “calculating,” “determining,” and “identifying” or the like refer to actions or processes of a computing device, such as one or more computers or a similar electronic computing device or devices, that manipulate or transform data represented as physical electronic or magnetic quantities within memories, registers, or other information storage devices, transmission devices, or display devices of the computing platform.

[0113] As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit," "module" or "system." Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

[0114] As used herein, the recitation of "at least one of A, B and C" is intended to mean "either A, B, C or any combination of A, B and C." The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments withoutdeparting from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0115] Figs 1-16 depict a number of example embodiments of a distributed cooling network for use with a cryocooler. Each example depicts one or more variations that may be used in example embodiments. Although various features are shown in different example embodiments, this is for ease of understanding of those concepts. One of ordinary skill in the art would readily recognize that the various features are not limited to those individual examples. Rather, features described with reference to one embodiment may readily be incorporated into other example embodiments.

Claims

Claims1. A multi-stage cryogenic system comprising: a cryogenic cooling system comprising: a first stage; a second stage; at least one pressurized cooling fluid source; a primary cryocooler comprising a first fluid path thermally coupled to the first stage and the second stage, the primary cryocooler configured to receive a cooling fluid via the first fluid path, wherein the first stage is cooled with a greater cooling power than the second stage; a distributed cooling network comprising an inlet port and a second fluid path thermally coupled with the first and the second stage, the distributed cooling network configured to extract heat from the second stage to the first stage; and a feedback control system configured to vary a cooling fluid flow through the second fluid path of the distributed cooling network during a cooldown as a function of at least one system temperature.

2. The multi-stage cryogenic cooling system of claim 1, wherein the cryocooler comprises a pulse tube cooler.

3. The multi-stage cryogenic cooling system of claim 1, wherein the cryocooler comprises a dynamic acoustic impedance matching equipped pulse tube cooler.

4. The multi-stage cryogenic cooling system of claim 1, wherein the at least one pressurized fluid source comprises a variable output compressor.

5. The multi-stage cryogenic cooling system of claim 1, wherein the second fluid path of the distributed cooling network is configured to direct an input cooling fluid through a first stage heat exchanger thermally coupled with the first stage and through a second stage heat exchanger thermally coupled with the second stage.

6. The multi-stage cryogenic cooling system of claim 5, wherein the second stage heat exchanger of the distributed cooling network is located at or adjacent to a perimeter of a plate of the second stage.

7. The multi-stage cryogenic cooling system of claim 5, wherein the second fluid path of the distributed cooling network comprises a return path disposed after the second stage heat exchanger.

8. The multi-stage cryogenic cooling system of claim 5, wherein the distributed cooling network comprises a recuperative heat exchanger configured to provide heat transfer between a fluid supply flow and a return fluid flow of the second fluid path.

9. The multi-stage cryogenic cooling system of claim 7, wherein the distributed cooling network comprises a warm end heat exchanger of the cryocooler configured to provide heat transfer between the second fluid path and the warm end heat exchanger of the cryocooler.

10. The multi-stage cryogenic cooling system of claim 9, wherein the warm end heat exchanger of the cryocooler is configured to provide heat transfer between a return flow of the second fluid path and the warm end heat exchanger of the cryocooler.

11. The multi-stage cryogenic cooling system of claim 1, wherein the second fluid path of the distributed cooling network is thermally coupled with at least one additional stage of the primary cryocooler disposed beyond the second stage.

12. The multi-stage cryogenic cooling system of claim 11, wherein the second fluid path is thermally coupled with the at least one additional stage in series with the first stage and the second stage.

13. The multi-stage cryogenic cooling system of claim 11, wherein the distributed cooling network comprises a heat exchanger thermally coupled to the at least one additional stage of the cryocooler located at or adjacent to a perimeter of a plate of the third stage.

14. The multi-stage cryogenic cooling system of claim 1, wherein the second fluid path of the distributed cooling network is thermally coupled with a plurality of additional stages of the primary cryocooler in order of decreasing thermal mass.

15. The multi-stage cryogenic cooling system of claim 1 , wherein the feedback control system includes at least one valve configured to control cooling fluid flow through the second fluid path.

16. The multi-stage cryogenic cooling system of claim 15, wherein the at least one valve of the feedback control system comprises a continuously variable valve.

17. The multi-stage cryogenic cooling system of claim 15, wherein the at least one valve of the feedback control system valves comprises an on / off valve.

18. The multi-stage cryogenic cooling system of claim 1, wherein the at least one system temperature is associated with at least one of the first stage and the second stage.

19. The multi-stage cryogenic cooling system of claim 1, wherein the distributed cooling network comprises a heat exchanger disposed in a groove of a plate of the second stage of the primary cryocooler.

20. A method of controlling a cooldown of a cryogenic cooling system comprising: initiating a cooldown operation of a multi-stage cryocooler, wherein the cooldown operation provides relatively greater cooling power to a first stage of the cryocooler than to a second stage of the cryocooler; providing a cooling fluid to a fluid path of a distributed cooling network, wherein the fluid path is thermally coupled with the first stage and the second stage; extracting heat from the second stage to the first stage via the cooling fluid;measuring a temperature associated with the cryocooler; and controlling a flow rate of the cooling fluid through the fluid path based at least in part on the temperature.

21. The method of claim 20, wherein the temperature is associated with at least one of the first stage and the second stage.

22. The method of claim 20, wherein the cooling fluid is provided via a pressurized cooling fluid source providing cooling fluid to the cryocooler and the distributed cooling network.

23. The method of claim 20, wherein the fluid path is thermally coupled with the first stage via a first stage heat exchanger and is thermally coupled with the second stage via a second stage heat exchanger.

24. The method of claim 23, wherein the second stage heat exchanger of the distributed cooling network is located at or adjacent to a perimeter of a plate of the second stage.

25. The method of claim 23, wherein the fluid path of the distributed cooling network comprises a return path disposed after the second stage heat exchanger.

26. The method of claim 23, wherein the distributed cooling network comprises a recuperative heat exchanger configured to provide heat transfer between a fluid supply flow and a return fluid flow of the fluid path.

27. The method of claim 23, wherein the distributed cooling network comprises a warm end heat exchanger of the cryocooler configured to provide heat transfer between the fluid path and the warm end heat exchanger of the cryocooler.

28. The method of claim 27, wherein the warm end heat exchanger of the cryocooler is configured to provide heat transfer between a return flow of the fluid path and the warm end heat exchanger of the cryocooler.

29. The method of claim 20, wherein the fluid path of the distributed cooling network is thermally coupled with at least one additional stage of the cryocooler disposed beyond the second stage.

30. The method of claim 29, wherein the fluid path is thermally coupled with the at least one additional stage in series with the first stage and the second stage.

31. The method of claim 29, wherein the distributed cooling network comprises a heat exchanger thermally coupled to the at least one additional stage of the cryocooler located at or adjacent to a perimeter of a plate of the third stage.

32. The method of claim 20, wherein the fluid path of the distributed cooling network is thermally coupled with a plurality of additional stages of the primary cryocooler in order of decreasing thermal mass.

33. The method of claim 20, wherein the feedback control system includes at least one valve configured to control cooling fluid flow through the second fluid path.

34. The method of claim 33, wherein the at least one valve of the feedback control system comprises a continuously variable valve.

35. The method of claim 33, wherein the at least one valve of the feedback control system valves comprises an on / off valve.

36. The method of claim 20, wherein the distributed cooling network comprises a heat exchanger disposed in a groove of a plate of the second stage of the primary cryocooler.

Images