FIELD

[0001] This disclosure relates to cooling devices, and in particular to cryogenic devices and methods of manufacture thereof.

BACKGROUND

[0002] Cryogenic devices provide cooling through the expansion of a working fluid. The working fluid is directed through a cold head, which typically includes a combination of internal channels, heat exchangers, reservoirs, and orifices, with a consequent reduction of the working fluid temperature at a portion of the cold head termed the cold tip. The cold tip is connected to an application to withdraw heat from the application.

[0003] Cryogenic devices may be custom-designed to suit cooling specifications of a particular application. A custom-designed cryogenic device is designed with specifically sized internal volumes, heat exchangers,

compressors, and other components.

SUMMARY

[0004] A cryogenic device may be provided with a cold head having a cross- sectional design to simplify the design and manufacture of cryogenic devices. Thus, according to an aspect of the specification, a cryogenic device includes a cold head, the cold head having a core layer having a fixed cross-sectional profile. The core layer includes a body having side walls outlining the fixed cross-sectional profile of the core layer. The side walls include inner walls to delimit cross-sectional volumes within the fixed cross-sectional profile of the core layer. The cross-sectional volumes accommodate working fluid of the cryogenic device.

[0005] According to another aspect of the specification, a cryogenic device includes a cold head, the cold head having a stack of core layers, each core layer having a fixed cross-sectional profile. Each core layer includes a body having side walls outlining the fixed cross-sectional profile of the core layer. The side walls include inner walls to delimit cross-sectional volumes within the fixed cross-sectional profile of the core layer. The cross-sectional volumes accommodate working fluid of the cryogenic device. Each core layer in the stack of core layers operates in parallel to direct working fluid through the cryogenic device.

[0006] According to another aspect of the specification, a method of manufacturing a cold head for a cryogenic device involves selecting a layout of functional volumes to direct working fluid through the cold head. The method further involves manufacturing a core layer of the cold head having a fixed cross-sectional profile. The fixed cross-sectional profile defines cross-sectional volumes through the core layer. The cross-sectional volumes correspond to the layout of functional volumes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 is a isometric view of an example core layer of a cold head of a cryogenic device, the core layer have a fixed cross-sectional profile.

[0008] FIG. 2 is a cross-sectional view of an example core layer of a cold head of a cryogenic device, the core layer having a cross-sectional profile according to a layout of a two-stage pulse tube cryogenic device.

[0009] FIG. 3 is an exploded view of layers of an example cold head of a cryogenic device, the cold head having a core layer with a fixed cross-sectional profile.

[0010] FIG. 4A is a isometric view of another example cold head of a cryogenic device. [0011] FIG. 4B is a isometric view of the cold head of FIG. 4A with portions broken away to reveal internal components of the cold head.

[0012] FIG. 4C is a isometric view of the cold head of FIG. 4A in longitudinal cross-section to reveal internal components of the cold head.

[0013] FIG. 5 is a isometric view of another example cold head of a cryogenic device, the cold head having recesses for insulative material.

[0014] FIG. 6 is a isometric view of an example cryogenic device.

[0015] FIG. 7 is a flowchart of an example method for manufacturing a core layer of a cold head of a cryogenic device.

[0016] FIG. 8 is a flow chart of an example method of assembling a cold head of a cryogenic device.

[0017] FIG. 9A is an isometric view of an example cold head and gas reservoir of a cryogenic device.

[0018] FIG. 9B is an isometric view of the cold head of FIG. 9A with insulative layer removed.

[0019] FIG. 9C is an isometric view of the cold head of FIG. 9A with insulative layer and sealing layer removed.

[0020] FIG. 10 is a close-up isometric view of the cold head of FIG. 9A showing detail of a flow diverter.

[0021] FIG. 11 A is an isometric view of an example cold head of a cryogenic device, the cold head including a stack of core layers.

[0022] FIG. 11 B is an isometric view of the cold head of FIG. 11 A in longitudinal cross-section to reveal cross-sectional volumes of the core layers.

[0023] FIG. 11C is an isometric view of the cold head of FIG. 11 A in lateral cross-section to reveal a vacuum pocket. [0024] FIG. 11 D is an isometric view of the cold head of FIG. 11 A with an insulative plate removed.

[0025] FIG. 12 is an isometric view of an example core layer of a core head of a cryogenic device, the core layer formed by material deformation.

[0026] FIG. 13A is an isometric view of an example wall of the core layer of FIG. 12.

[0027] FIG 13B is an isometric view of an example channel of formed by a wall of a core layer formed by material deformation.

[0028] FIG. 14A is an exploded isometric view of example interlocking sealing layers and core layer walls.

[0029] FIG. 14B is an isometric view of the interlocking sealing layers and core layer walls of FIG. 14A.

[0030] FIG. 15 is a cross-sectional view of an example core layer of a cold head of a cryogenic device, the core layer having a cross-sectional profile according to a layout of to a pulse tube cryocooler driven by a three-stage traveling-wave thermoacoustic heat engine.

DETAILED DESCRIPTION

[0031] The design and manufacturing processes of a customized cryogenic device generally involves selecting or manufacturing specifically sized internal volumes, heat exchangers, compressors, and other components. A customized design and manufacturing process is costly and fails to benefit from efficiencies which may be attained by designing and manufacturing cryogenic devices more systematically.

[0032] Cryogenic devices are generally assembled from a number of coaxially joined cylindrical components which terminate at a cold tip protruding from one end of the cryogenic device. The cold tip is generally not ideally positioned or oriented to interface directly with the cooling application, and thus extensive heat-transfer apparatus is installed to properly couple the cold tip to the application, further increasing costs.

[0033] A cryogenic device may be provided with a cold head having a cross- sectional design to simplify the design and manufacture process to thereby save manufacturing costs and increase the speed at which new cryogenic devices may be designed and manufactured. The cryogenic device may include a cold head having a core layer having a fixed cross-sectional profile. The core layer may include a body having side walls outlining the fixed cross-sectional profile of the core layer. The side walls may include inner walls which delimit cross- sectional volumes within the fixed cross-sectional profile of the core layer. The cross-sectional volumes may accommodate working fluid or functional components of the cryogenic device.

[0034] The cold head may be manufactured by selecting a layout of functional volumes to direct working fluid through the cold head, and

manufacturing a core layer having a fixed cross-sectional profile which defines cross-sectional volumes through the core layer corresponding to the layout of functional volumes.

[0035] Such a core layer may be manufactured by unidirectional cutting processes, such as laser cutting, water jetting, and the like. Thus, a principal component of the cold head may be manufactured by an efficient unidirectional cutting process. Further, different layouts of functional volumes can be cut into different core layers without the need for retooling. Thus, manufacturing may be simplified, costs may be reduced, and manufacturing speed may be increased. Further, a plurality of core layers may be stacked and operated in parallel to increase the capacity of the cryogenic device, further providing flexibility and repeatability to the manufacturing process.

[0036] FIG. 1 shows an example core layer 100 of a cold head of a cryogenic device. The core layer 100 includes a body 102 having side walls 110. The side walls 110 outline a fixed cross-sectional profile of the core layer 100. The side walls 110 include outer walls 114 to outlining the perimeter of the body 102, and inner walls 112 outlining cross-sectional volumes 120 of the core layer 100.

[0037] The inner walls 112 delimit cross-sectional volumes 120 within the fixed cross-sectional profile of the core layer 100. The cross-sectional volumes 120 are to accommodate working fluids or functional components of the cryogenic device. Thus, a cross-sectional volume 120 may be termed a functional volume. For example, a cross-sectional volume 120 may include a channel, chamber, orifice, or other volume through which working fluid is to travel. Cross-sectional volumes 120 may have functional components of the cryogenic device disposed therein. Thus, generally, the inner walls 112 direct working fluid within the core layer 100 or house functional components disposed in the core layer 100. The outer walls 114 bound the perimeter of the body 102.

[0038] The core layer 100 includes a first face 104 and a second face 106 opposite the first face 104. For example, the first face 104 may be referred to as the“top” face, and the second face 106 may be referred to as the“bottom” face, and vice versa. The first face 104 and second the second face 106 conform to the fixed cross-sectional profile of the core layer 100. In other words, the first face 104 includes through-gaps defined by the cross-sectional volumes 120, and facial surfaces comprising the facial portions of the body 102 between the cross-sectional volumes 120.

[0039] The side walls 110 are perpendicular to the first face 104 and the second face 106. The side walls 110 extend from the perimeter or perimeters of the first face 104 to the perimeter or perimeters of the second face 106.

[0040] In other words, the first face 104 and second face 106 are parallel, and the side walls 110 project at right angles from the perimeter or perimeters of the first face 104 to the perimeter or perimeters of the second face 106. The gaps in the body 102 between the inner walls 112 define the cross-sectional volumes 120. [0041] The first face 104 and second face 106 may be identical in shape and size.

[0042] Each cross-sectional volume 120 includes an opening to the first face 104 and an opening to the second face 106. Thus, each cross-sectional volume 120 extends through the body 102 from the first face 104 to the second face 106.

[0043] In some examples, the fixed cross-sectional profile of the core layer may be formed by subtracting material from the body 102 in a subtractive manufacturing process. For example, the inner walls 112 may be

unidirectionally cut into the body 102, such as via laser cutting, water jetting, or milling, to define side walls 110 which are perpendicular to the first face 104 throughout the fixed cross-sectional profile of the core layer 100. Thus, the fixed cross-sectional profile of the core layer may be unidirectionally cut from a substrate. Since the cross-sectional profile of the core layer 100 is cut using unidirectional cutting of the body 102, different layouts of cross-sectional volumes 120 can be cut into different core layers 100 without retooling manufacturing equipment.

[0044] In other examples, the body 102 and the fixed cross-sectional profile thereof may be formed by an additive manufacturing process whereby the cross-sectional volumes 120 are formed in the gaps between added materials. For example, material may be deposited onto a substrate to form the side walls 110 and facial surfaces of the body 102. The spaces remaining constitute the cross-sectional volumes 120.

[0045] In still other examples, the body 102 may be formed by material deformation. For example, the body 102 may be formed by bending one or more sheets of material according to conform to the contours of a layout of cross- sectional volumes 120.

[0046] In some examples, the body 102 of the core layer 100 may be of continuous thickness. In other words, all of the side walls 110 may be of equal height. All of the side walls 110 may be of equal height if the body 102 is formed from a planar block or slab of material. In other examples, the body 102 of the core layer 100 may be of variable thickness. In other words, some of the side walls 110 may be of different heights. Some of the side walls 110 may be of different heights if the body 102 is formed from a non-planar block of material or separate sheets of material.

[0047] The body 102 is made of a material capable of withstanding pressures and temperatures of pressurized working fluids moving through the cross-sectional volumes 120 in a cryogenic cooling process, such as, for example, stainless steel, inconel, or titanium.

[0048] As mentioned previously, the cross-sectional volumes 120 are to accommodate working fluids or functional components of the cryogenic device. For example, the cold head may include a regenerator, and a cross-sectional volume 120 may house the regenerator. As another example, the cold head may include a pulse tube, and a cross-sectional volume 120 may define the pulse tube. As another example, a cross-sectional volume 120 may define an insulative chamber. As another example, the cold head may include an insulative vacuum, and a cross-sectional volume 120 may contain the insulative vacuum. As another example, the cold head may include insulative material, and a cross-sectional volume 120 may contain the insulative material. As another example, the cold head may include a heat exchanger, and a cross- sectional volume 120 may house the heat exchanger.

[0049] Where the cold head includes insulative material, the insulative material may include any insulating material of low thermal conductivity, such as expanding foam. An insulating expanding foam may be sprayable. Insulating material may be contained within a cross-sectional volume 120 of the core layer 100, or the insulating material may be contained in another layer of the cold head.

[0050] Where the cold head includes an insulative vacuum, the insulative vacuum may be termed a vacuum pocket. As discussed herein, a vacuum pocket may be sealed by other layers of the cold head. Another layer of the cold head may include a fitting through which fluid may be evacuated from the vacuum pocket after assembly to form the insulative vacuum.

[0051] A combination of insulative techniques may be used to insulate the cold head 100. For example, a combination of insulative materials and vacuum pockets may be used. An example of multi-layer insulation includes a vacuum pocket to reduce conductive and convective heat transfer, wherein the vacuum pocked is lined with an insulative material, such as aluminum or gold foil, to reduce radiative heat transfer.

[0052] FIG. 2 is a shows an example core layer 200 of a cold head of a cryogenic device. The core layer 200 includes cross-sectional volumes 220 which accommodate working fluids and house functional components of the cryogenic device.

[0053] The core layer 200 includes a fixed cross-sectional profile according to a layout for a two-stage pulse tube cryogenic device. The core layer 200 includes a first chamber 222A and a second chamber 222B, the first chamber 222A to house a first regenerator 224A, the second chamber 222B to house the second regenerator 224B. The core layer 200 further includes a first channel 226A to act as a first pulse tube and a second channel 226B to act as a second pulse tube.

[0054] The core layer 200 further includes a fitting 230 to mate with a connection to an external compressor to supply compressed working fluid into the core layer 200. The core layer 200 includes additional connecting volumes 228 and orifices 229 through which working fluid flows during a cryocooling process.

[0055] The core layer 200 further includes insulative chambers 227, which may include insulative material, or may include a vacuum pocket.

[0056] The core layer 200 further includes locating features 218 to align the core layer 200 with other layers of the cryogenic device. A locating feature 218 may include a hole or slot to mate with peg or pin from an adjacent layer may be inserted to align the layers, or a locating feature 218 may include a peg or pin to mate with a hole or slot. Other combinations of mating features are also contemplated.

[0057] The core layer 200 further includes a cold tip 240 to provide cooling to an application.

[0058] FIG. 3 is an exploded view of an example cold head 300 of a cryogenic device. The cold head 300 includes a core layer 310, a first sealing layer 320, a first insulative layer 330, a second sealing layer 340, and a second insulative layer 350.

[0059] The core layer 310 has a fixed cross-sectional profile to

accommodate working fluids and functional components of the cryogenic device. Further description of the core layer 310 may be had with reference to the core layer 100 of FIG. 1 or the core layer 200 of FIG. 2, which may include like components.

[0060] The core layer 310 also includes a first face 304 and a second face 306 opposite the first face 304. Each cross-sectional volume includes an opening 308 to the first face 304 and an opening to the second face 306. Thus, each cross-sectional volume extends through the core layer 310 from the first face 304 to the second face 306. These openings 308 are sealed by sealing layers on each face 304, 306 of the core layer 310. For example, the first sealing layer 320 is to seal openings 308 to the first face 304, and the second sealing layer 340 is to seal openings 308 to the second face 306.

[0061] The first sealing layer 320 includes a first gasket 322 and a first seal plate 324. The first gasket 322 is compressed between the first face 304 of the core layer 310 and the first seal plate 324 to seal the openings 308 to the first face 304. The second sealing layer 340 includes a second gasket 342 and a second seal plate 344. The second gasket 342 is compressed between the second face 306 of the core layer 310 and the second seal plate 344 to seal the openings 308 to the second face 306. A seal plate 324, 344 may be made of the same material or a different material as the body of the core layer 310. A seal plate 324, 344 is of a material capable of resisting deformation due to pressurization of the working fluid in the core layer 310. A gasket 322, 342 is a compressible material which when compressed forms a seal between adjacent layers. In other examples, o-rings fitting into o-ring grooves, or other sealing techniques may be used. An o-ring may include indium wire. O-rings may be placed around individual cross-sectional volumes, such as vacuum pockets.

[0062] The first insulative layer 330 includes a first insulative layer gasket 332 and a first insulative plate 334. The first insulative layer gasket 332 is compressed between the first seal plate 324 and the first insulative plate 334. The second insulative layer 350 includes a second insulative layer gasket 352 and a second insulative plate 354. The second insulative layer gasket 352 is compressed between the second seal plate 344 and the second insulative plate 354. The insulative plates 334, 354 may include insulative material to insulate the cold head from ambient air.

[0063] The layers 310, 320, 330, 340, 350 may be joined by mechanical fasteners, welding, or other suitable techniques. Mechanical fastening may involve the alignment and engagement of locating features on adjacent layers. For example, holes 318 may be drilled and tapped into core layer 310 and the adjacent sealing layers 320, 340. The layers 310, 320, 340 may be aligned by the holes 318, and a mechanical fastener such as a bolt 319 may be inserted or threaded through the holes 318, and fastened, such as with a nut, thereby compressing the sealing layers 320, 340 against the core layer 310. Welding may involve welding seams between adjacent layers. Welding techniques may include tungsten inert gas welding, laser welding, electron beam welding, or other welding techniques. Combinations of joining techniques may be used. For example, core layers and sealing layers of a cold head may be welded together, and insulative layers may be mechanically fastened to the other layers with mechanical fasteners such as bolts. [0064] FIG. 4A shows an example cold head 400 of a cryogenic device. The cold head 400 is assembled with a core layer 410, first sealing layer 420, first insulative layer 430, second sealing layer 440, and second insulative layer 450. The cold head 400 further includes heat exchanger fins 462 to exchange heat with ambient air.

[0065] FIG. 4B shows the cold head 400 of FIG. 4A with portions of the first insulative layer 430 and first sealing layer 420 broken away to reveal internal components disposed in cross-sectional volumes 412 of the core layer 410. For example, a regenerator 414 is shown. The regenerator 414 includes internal webbing to regeneratively exchange heat with working fluid in the core layer 410. Further, a cold tip 416 is shown. The cold tip 416 does not protrude from any end of the cold head 400, but rather is contained within the cross-sectional profile of the cold head 400. In other words, the cold tip 416 has a contact point within the fixed cross-sectional profile of the core layer 410. Further, the cold tip 416 is located underneath insulation of the first insulative layer 430. The insulation in the first insulative layer 430 may include insulative foam or other malleable insulation through which connection to an application can be made to receive cooling from the cold tip 416.

[0066] FIG. 4C shows the cold head 400 of FIG. 4A with a cross-section revealing additional cross-sectional volumes 412 of the core layer 410. For example, a channel 418 to act as a pulse tube is shown.

[0067] FIG. 5 shows another example cold head 500 of a cryogenic device. The cold head 500 includes recesses 502 into which insulation may be filled. In particular, the cold head 500 may include recess 502A to enable contact with a cold tip. Insulation may be placed on the recesses 502, and an application may be connected with the cold tip through insulation to insulate the connection from ambient air. The insulation may include insulative foam or other malleable insulation through which connection to an application can be made to receive cooling from the cold tip. [0068] FIG. 6 shows an example cryogenic device 600. The components of the cryogenic device 600 are assembled on a skid 602. The cryogenic device 600 includes a cold head 610 through which working fluid undergoes expansion and cooling according to a cryocooling process. The cold head may include a core layer and other components as discussed herein.

[0069] The cryogenic device 600 further includes a gas reservoir 620 to supply the cold head 610 with working fluid. The cryogenic device 600 further includes a gas compressor 630 to pressurize gas from the gas reservoir 620, and an inertance tube 660 to cooperate with the gas reservoir 620 as a phase shift mechanism according to a cryogenic cooling process. The cryogenic device 600 further includes a water reservoir 640 and water pump 650 to supply cooling water to extract heat from the cold head 610 in a cryogenic cooling process. The cryogenic device 600 further includes a vacuum sensor 670 to monitor vacuum pressures in the cold head 610.

[0070] FIG. 7 is a flowchart showing an example method 700 of

manufacturing a core layer of a cold head of a cryogenic device.

[0071] At block 702, a layout of functional volumes of a cold head is selected. A layout may be selected from a pre-designed layouts, or may be custom designed. The functional volumes are to direct working fluid through the cold head. Some functional volumes may house functional components of the cold head. Where the layout is custom designed, the designing may involve sizing functional components to deliver a target cooling capacity and the required cross-sectional volume to house the components, selecting location of cold tip, selecting location of vacuum pockets or other insulation, and laying out additional volumes to direct working fluid through the cold head according to a cryocooling process.

[0072] At block 704, a core layer is manufactured having a fixed cross- sectional profile. The fixed cross-sectional profile defines cross-sectional volumes through the core layer. The cross-sectional volumes corresponding to the layout of functional volumes. [0073] In some examples, manufacturing the core layer involves a subtractive manufacturing method as discussed herein, such as unidirectionally cutting the layout of functional volumes into a substrate to remove the cross- sectional volumes from the core layer. The unidirectional cutting may involve laser cutting. The unidirectional cutting may involve water jetting. In other examples, manufacturing the core layer may involve additive manufacturing method as discussed herein, such as 3D printing.

[0074] FIG. 8 is a flowchart showing an example method 800 of assembling a cold head of a cryogenic device. The blocks of method 800 need not be performed in the exact sequence as shown.

[0075] At block 802, a core layer is obtained. A core layer may be obtained by a method of manufacture, such as the method 700 of FIG. 7. The core layer includes a fixed cross-sectional profile and cross-sectional volumes as discussed herein.

[0076] At block 804, functional components are installed in the core layer. For example, heat exchangers, regenerators, displacers, valves, fittings, sensors, or insulation, may be installed in cross-sectional volumes of the core layer. The functional components may be installed after a first sealing layer is joined to the core layer to close the openings to one face of the core layer, thereby allowing functional components to be installed on top of, or against, the first sealing layer.

[0077] At block 806, sealing layers are added to the cold head. Adding sealing layers involves adding a first sealing layer against one face of the core layer and a second sealing layer against the opposite face of the core layer to seal the openings from cross-sectional volumes in the core layer. The sealing layers may be selected or designed to conform to the cross-sectional profile of the core layer. For example, a gasket, o-ring, or other seal, may be designed to match the facial surfaces and/or o-ring grooves of the core layer. [0078] At block 808, insulation is added to the cold head. Adding insulation may involve adding insulative plates or insulative material around the sealing layers. Adding insulation may involve evacuating air from a cross-sectional volume of the core layer to form a vacuum pocket. The insulation layers may then be applied to the device. In some examples, adding insulation may involve the application of a low thermal conductivity material to recesses on the sealing layers or other specific areas of the outward facing surfaces of the sealing layers. Adding insulation may involve adding an insulative plate to the outward facing surfaces of the sealing layers.

[0079] In some examples, a plurality of core layers may be stacked to build a stack of core layers. The core layers in a stack may be separated by additional sealing layers.

[0080] FIG. 9A shows an example cold head 900 and a gas reservoir 910 of a cryogenic device. The cold head 900 includes a core layer 902, sealing layers 904, insulative layers 906, and fasteners 908.

[0081] FIG. 9B shows the cold head 900 of FIG. 9A with insulative layers 906 and fasteners 908 removed to reveal the core layer 902 and sealing layers 904. The core layer 902 includes vacuum pockets 912 to provide insulation, and a cold tip 914. The cold tip 914 may be connected to an application to provide cooling to the application. The cold tip 914 may be fitted with resistance thermometer to measure cold temperature output. Further, the cold tip 914 may be at least partly surrounded by a vacuum pocket or pockets.

[0082] FIG. 9C shows the cold head 900 of FIG. 9A with insulative layers 906, fasteners 908, and sealing layers 904 removed, to reveal the core layer 902 including pulse tube 917. The core layer 902 includes water supply heat exchangers 916 to withdraw heat from compressed working fluid according to a cryocooling process. The water supply heat exchangers 916 are located near the outlet 918 of compressed air and the inlet 919 of compressed working fluid. In a cryocooling process, compressed air is alternatively pushed through the inlet 919, through the pulse tube 917, and the through the outlet 918 to the gas reservoir 910, and drawn back in the reverse direction.

[0083] FIG. 10 shows a close up view of the cold head 900 of FIG. 9A with insulative layers 906, fasteners 908, and sealing layers 904 removed, showing a flow diverter 920 located between the inlet 919 of compressed working fluid and a water supply heat exchanger 916. The flow diverter 920 is to direct flow of working fluid to improve dispersant of working fluid. In the present example, the flow diverted 920 is placed between the inlet 919 and water supply heat exchanger 916 to improve dispersal of the inlet compressed working fluid to more fully accommodate the width of the water supply heat exchanger 916.

[0084] The flow diverter 920 may be subtractive formed during a subtractive manufacturing process of the core layer 902, or may be additively

manufactured the flow diverter 920 may be mounted in a slot, welded in a slot, joined by an adhesive, mechanical fastener, or otherwise fixed within the core layer 902.

[0085] FIG. 11A shows a cold head 1100 of a cryogenic device. The cold head 1100 includes a stack 1102 of core layers 1104 stacked between insulative layers 1103. Multiple core layers 1104 may be stacked to increase the capacity of the cold head 1100. Further, the core layers 1104 may be operated in parallel to deliver increased cooling capability while maintaining internal dimensions to achieve desired fluid flow characteristics of working fluid flowing though the core layers 1104. For example, the core layers 1104 in the stack 1102 may include cross-sectional profiles which, when stacked, achieve laminar flow of working fluid through pulse tubes and turbulent flow through heat exchangers.

[0086] Thus, the cryogenic device includes the cold head 1100, the cold head 1100 having a stack 1102 of core layers 1104, each core layer 1104 having a fixed cross-sectional profile. Each core layer 1104 includes a body having side walls outlining the fixed cross-sectional profile of the core layer 1104. The side walls include inner walls to delimit cross-sectional volumes within the fixed cross-sectional profile of the core layer 1104. The cross- sectional volumes are to accommodate working fluid of the cryogenic device. Each core layer 1104 in the stack 1102 of core layers 1104 operates in parallel to direct working fluid through the cryogenic device.

[0087] In the present example, the stack 1102 of core layers 1104 includes four core layers 1104. However, it is to be understood that another number of core layers 1104 may be stacked. Sealing layers may be placed between core layers 1104 to seal the cross-sectional volumes thereof to allow fluid to flow therethrough under pressure.

[0088] FIG. 11 B shows the cold head of 1100 of FIG. 11A in longitudinal cross-section to reveal that the core layers 1104 include cross-sectional volumes delimiting pulse tubes 1106 and a vacuum pocket 1108. The cross- sectional volumes corresponding to a pulse tube 1106 is sealed between core layers 1104. The cross-sectional volumes corresponding to the vacuum pocket are not sealed between core layers 1104 but rather in fluid communication, to form the vacuum pockets 1108 common to each of the core layers 1104 in the stack 1102 of core layers 1104. Further, the vacuum pocket 1108 surrounds the pulse tubes 1106.

[0089] FIG. 11 C shows the cold head 1100 of FIG. 11 A in lateral cross- section to reveal a vacuum pocket 1108. FIG. 11 D shows the cold head 1100 with an insulative plate of the insulative layer 1103 removed to reveal a cold tip heat exchanger 1109 running through the core layers 1104.

[0090] FIG. 12 shows an example core layer 1200 manufactured by material deformation. The core layer 1200 includes a body 1202 formed by bending one or more sheets of material according to conform to the contours of a layout of cross-sectional profile. The sheets of material may be of consistent width so that the core layer 1200 is of a continuous height throughout the fixed cross- sectional profile. The sheets of material may be welded or otherwise joined to adjacent sealing layers to seal cross-sectional volumes delimited by the sheets of material. [0091] The sheets of material may be bent using robotic manipulators which may have solid grips to grasp the work material and create bends via translation and/or rotation of the solid grips. The robotic manipulators may also have rollers that act in conjunction with grips to form more gradual curves in the strip. The strips of material may be joined as needed, by any means that allow the formed walls to perform their function, such as containing a working or maintaining a vacuum without leakage.

[0092] FIG. 13A shows an example wall 1210 of the core layer 1200 manufactured by bending a sheet of material. The wall 1210 includes bends 1212 at one or multiple increments along its length conforming to a specified cross-sectional profile of the core layer 1200. The wall 1210 is made from material sheets having good plastic deformation characteristics and should be of good strength and rigidity to resist stresses caused by pressurized volumes in the core layer 1200, such as sheet metal.

[0093] FIG. 13B shows two example walls 1220 of the core layer 1200 manufactured by bending a sheet of material. The two walls 1220 are joined along a seam 1222 and deformed to produce a narrowed channel 1224. The walls 1220 may be deformed by robotic manipulators.

[0094] FIG. 14A shows an exploded view of example interlocking sealing layers 1400 and core layer walls 1410 forming a channel. The sealing layers 1400 include deformation seal material 1402, seal plates 1404, and pressure plates 1406, which are used on both the top and bottom of the core layer walls 1410 to form the channel. The core layer walls 1410 are formed from a strip of material having notches 1411 which interlock with slots 1412 in seal plates 1404 to form the channel. The deformation seal materials 1402 are cut to fit within the channel and placed on or otherwise adhered to the pressure plates 1406. A pressure plate 1406 is also cut to fit within the channel 1450.

[0095] FIG. 14B shows two sealing layers 1400 joined together with core layer walls 1410 to form a channel 1450. When pressure is applied to the pressure plates 1406 by internal pressure of the system and/or by mechanical fasteners, the deformation seal material 1402 is compressed, and thus expands in the plane of the parallel layers, in accordance with Poisson’s ratio of the seal material. The expansion in the horizontal direction is contained by the core layer walls 1410, due to the interlocking notches 1411 between the core layer walls 1410 and seal plates 1404. The containment of such expansion results in a force applied to the core layer walls 1410, by the deformation seal material 1402, resulting in a seal of the channel 1450. The assembly of pressure plates 1406, deformation seal material 1402, and seal plates 1404 may also be compressed via mechanical fasteners through the assembly, or via one or multiple permanent magnets placed on an outward facing side of a seal plate 1404 and an inward facing side of a pressure plate 1406 with attractive forces compressing the assembly.

[0096] FIG. 15 shows a cold head 1500 of a cryogenic device. The cold head 1500 has a fixed cross-sectional profile defining cross-sectional volumes as discussed herein. The cold head 1500 is configured according to a pulse tube cryocooler driven by a three-stage traveling-wave thermoacoustic heat engine 1510. The cold head 1500 further includes regenerators 1520 which meet at a ringed cold tip 1522, pulse tubes 1530 with heat exchangers 1532, insulative cavities 1540, and additional volumes to direct working fluid through the cold head 1500. The cold head 1500 may be manufactured using a layered approach as discussed herein.

[0097] Thus, it may be seen that the design and manufacturing processes of a cryogenic device may be simplified using a cold head having a cross-sectional design. The cold head includes a core layer having a fixed cross-sectional profile to accommodate working fluid or functional components of the cryogenic device. The cold head may be manufactured by selecting a layout of functional volumes to direct working fluid through the cold head and manufacturing a core layer having a fixed cross-sectional profile corresponding to the layout of functional volumes. Such a core layer may be manufactured by an efficient unidirectional cutting processes, such as laser cutting, water jetting, and different layouts of functional volumes can be cut into different core layers without the need for retooling. Thus, manufacturing may be simplified, costs may be reduced, and manufacturing speed may be increased. Further, a plurality of core layers may be stacked and operated in parallel to increase the capacity of the cryogenic device.

[0098] It should be recognized that features and aspects of the various examples provided above can be combined into further examples that also fall within the scope of the present disclosure. In addition, the figures are not to scale and may have size and shape exaggerated for illustrative purposes.

[0099] The scope of the claims should not be limited by the above examples, but should be given the broadest interpretation consistent with the description as a whole.