METHOD AND APPARATUS FOR THE HERMETIC SEALING OF MARTENSITIC METALS FOR PRECOMPRESSION FOR CRYOGENIC APPLICATIONS

Abstract

Disclosed is a hermetically sealed assembly for precompression of a martinsetic metal for use in negative pressure energy transfer systems, and method of making same. The assembly comprising a martinsetic metal disposed between and in contact with flanged sapphire windows, the flanges defining an open area therebetween to accommodate expansion and contraction of the martinsetic metal. Hermetic sealing means include a bellows element, which can comprise a convoluted cross section, at the periphery of the assembly to enable operation over temperature ranges from ambient to cryogenic without loss of integrity or leakage.

Claims

1. A hermetically sealed assembly for precompression of a martinsetic metal comprising: a first sapphire window and a second sapphire window, the first and second sapphire windows having a space therebetween; a martinsetic metal disposed in the space and in contact with the first and second sapphire windows; the first sapphire window comprising an outwardly extending peripheral first flange, and the second sapphire window comprising an outwardly extending peripheral second flange, the first flange and the second flange configured to define an open area between the first and second flanges and around the perimeter of the martinsetic material, the open area extending outwardly from the space and sized to permit expansion and contraction of the martinsetic metal within the open area; and means for coupling the first and second sapphire windows and hermetically sealing the space and the open area.

2. The assembly of claim 1 wherein the first and second flanges are rectangular in cross section and are parallel to each other.

3. The assembly of claim 1 wherein the first and second flanges comprise the same dimensions.

4. The assembly of claim 2 wherein the first flange is coplanar with the outside surface of the first sapphire window.

5. The assembly of claim 2 wherein the second flange is coplanar with the outside surface of the second sapphire window.

6. The assembly of claim 2 wherein the first flange is coplanar with the outside surface of the first sapphire window; the second flange is coplanar with the outside surface of the second sapphire window.

7. The assembly of claim 1 further comprising containment means extending around and secured to the perimeter of the martinsetic metal.

8. The assembly of claim 7 wherein the containment means is configured to form a seal between the open area and the first and second sapphire windows at cryogenic temperatures.

9. The assembly of claim 8 wherein the containment means is a washer.

10. The assembly of claim 9 wherein the washer is comprised of stainless steel, nickel, iron-nickel-cobalt alloys, nickel-iron alloys, or combinations thereof.

11. The assembly of claim 1 wherein the means for coupling the first and second sapphire windows and hermetically sealing the space and the open area comprises a metallic sealing member interposed between and extending around the periphery of first and second flanges.

12. The assembly of claim 11 wherein the metallic sealing member comprises a first metallic seal, the first metallic seal being secured to the first flange; a second metallic seal, the second metallic seal being secured to the second flange; and a bellows element interposed between, and attached to, the first metallic seal and the second metallic seal.

13. The assembly of claim 12 wherein the first metallic seal is secured to the first flange by brazing or soldering to a metalized area on the first sapphire window, and the second metallic seal is secured to the second flange by brazing or soldering to a metalized area on the second sapphire window.

14. The assembly of claim 12 wherein the bellows element has a convoluted cross section, and is attached to the first and second sealing elements by brazing or welding, or combinations thereof.

15. The assembly of claim 12 wherein the first metallic seal, the second metallic seal, and the bellows element have substantially the same thermal coefficient of expansion.

16. The assembly of claim 15 wherein the first metallic seal, the second metallic seal, and the bellows element are each independently comprised of stainless steel, nickel, iron-nickel-cobalt alloys, nickel-iron alloys, or combinations thereof.

17. The assembly of claim 1 further comprising a micro lens located on an outside surface of the first sapphire window, the second sapphire window, or both.

18. The assembly of claim 1 wherein the martinsetic metal comprises lithium.

19. The assembly of claim 18 wherein the lithium comprises a dopant.

20. The assembly of claim 19 wherein the dopant comprises boron carbide.

21. A sapphire window for a hermetically sealed assembly for precompression of a martinsetic metal, the sapphire window being circular and comprising a planar outside surface and a planar inside surface, the outside surface and the inside surface parallel to each other, and a peripheral flange extending outwardly from and around the sapphire window and coplanar with the outside surface, the flange having an inside face and forming a step to the inside surface of the sapphire window.

22. The sapphire window of claim 21 wherein the inside face of the flange comprises a metalized area that extends around the periphery of the inside face of the flange.

23. The sapphire window of claim 22 wherein the metalized area comprises stainless steel, nickel, an iron-nickel-cobalt alloy, a nickel-iron ally, or combinations thereof.

24. The sapphire window of claim 21 further comprising a metallic seal secured to the metalized area of the inside face of the flange, the metallic seal spaced away from the step and extending along the periphery of the inside face of the flange.

25. The sapphire window of claim 24 wherein the metallic seal comprises stainless steel, nickel, an iron-nickel-cobalt alloy, a nickel-iron ally, or combinations thereof.

26. The sapphire window of claim 24 wherein the metallic seal has a substantially squared U-shaped cross section.

27. The sapphire window of claim 24 wherein the metallic seal is secured to the metalized area by brazing, welding, or combinations thereof.

28. The sapphire window of claim 24 wherein the metallic seal comprises a guard flange configured to protect the outside edge of the flange.

29. The sapphire window of claim 24 further comprising a bellows element secured to at least a portion of the metallic seal.

30. The sapphire window of claim 29 wherein the bellows element has a convoluted cross section.

31. The sapphire window of claim 30 wherein the bellows element comprises two or more convolutions.

32. The sapphire window of claim 31 wherein the bellows element comprises three to twelve convolutions.

33. The sapphire window of claim 21 further comprising a micro lens located on a portion of the planar outside surface.

34. A method of sealing an assembly for precompression of a martinsetic metal comprising: (i) providing an assembly for precompression of a martinsetic metal comprising a first sapphire window and a second sapphire window, the first and second sapphire windows having a space therebetween; and a martinsetic metal disposed in the space and in contact with the first and second sapphire windows, the first sapphire window comprising an outwardly extending peripheral first flange; and the second sapphire window comprising an outwardly extending peripheral second flange, the first flange and the second flange configured to define an open area between the first and second flanges and around the perimeter of the martinsetic material, the open area extending outwardly from the space and sized to permit expansion and contraction of the martinsetic metal within the open area; and (ii) sealing the first and second sapphire windows to each other by means of a bellows element having a first side secured to a first metallic seal attached to the first flange, and a second side secured to a second metallic seal attached to the second flange.

35. The method of claim 34 wherein the first and second sides of the bellows element are secured by brazing or welding or combinations thereof.

36. The method of claim 34 wherein the bellows element has a convoluted cross section

37. The method of claim 34 wherein (i) further comprises providing to the assembly means to relieve pressure from the martinsetic metal in order to prevent rupture of the martinsetic metal.

38. The method of claim 37 wherein the means to relieve pressure comprises one or more spring chock pins.

39. A method of precompressing a martinsetic metal comprising: (i) providing an assembly for precompression of a martinsetic metal comprising a first sapphire window and a second sapphire window, the first and second sapphire windows having a space therebetween; and a martinsetic metal disposed in the space and in contact with the first and second sapphire windows, the first sapphire window comprising an outwardly extending peripheral first flange; and the second sapphire window comprising an outwardly extending peripheral second flange, the first flange and the second flange configured to define an open area between the first and second flanges and around the perimeter of the martinsetic material, the open area extending outwardly from the space and sized to permit expansion and contraction of the martinsetic metal within the open area, and containment means extending around and secured to the perimeter of the martinsetic metal configured to form a seal between with the open area and the first and second sapphire windows at cryogenic temperatures; (ii) sealing the first and second sapphire windows to each other with a bellows element having a first side secured to a first metallic seal hermetically attached to the first flange and a second side secured to a second metallic seal hermetically attached to the second flange; and (iii) pressurizing the martinsetic metal to within the range of the plastic point of the martinsetic metal without rupturing the martinsetic metal.

40. The method of claim 39 wherein the pressuring of step (iii) further comprises sealing the space within which the martinsetic metal is disposed with the containment means.

41. The method of claim 40 wherein the pressurizing of step (iii) occurs: (a) during cooling of the assembly to cryogenic temperature, or (b) when the assembly is already at cryogenic temperature.

42. The method of claim 39 wherein (i) further comprises providing to the assembly means for relieving pressure from the martinsetic metal to prevent rupture of the martinsetic metal.

43. The method of claim 42 wherein the pressurizing of step (iii) further comprises activating the means to relieve pressure from the martinsetic metal in order to prevent rupturing of the martinsetic metal.

44. The method of claim 39 wherein in (ii) the first and second sides of the bellows element are secured by brazing or welding or combinations thereof.

45. The method of claim 42 wherein the means to relieve pressure comprises one or more spring chock pins.

46. The method of claim 41 further comprising, after step (iii): (iv) depressuring the martinsetic metal within the range of the plastic point of the martinsetic metal without rupturing the martinsetic metal.

47. The method of claim 46 wherein the depressurizing of (iv) occurs at cryogenic temperature.

48. The method of claim 39 wherein the bellows element has a convoluted cross section.

49. A sapphire window for a hermetically sealed assembly for precompression of a martinsetic metal comprising: a sapphire window of circular shape having an inside face and an inner periphery; and a metalized area located on the inner periphery.

50. The sapphire window of claim 49 wherein the metalized area comprises stainless steel, nickel, iron-nickel-cobalt alloys, nickel-iron alloys, or combinations thereof.

51. The sapphire window of claim 49 further comprising a metallic seal secured to the metalized area located on the inner periphery.

52. The sapphire window of claim 51 wherein the metallic seal comprises opposed side walls separated by a spacer, and wherein one of the sidewalls is secured to the metalized area.

53. The sapphire window of claim 52 wherein the metallic seal comprises stainless steel, nickel, iron-nickel-cobalt alloys, nickel-iron alloys, or combinations thereof.

54. The sapphire window of claim 52 further comprising a bellows element attached to the side of the metallic seal that is not secured to the metalized area.

55. The sapphire window of claim 54 wherein the bellows element comprises one or more U-shaped cross sections.

56. The sapphire window of claim 54 wherein the bellows element comprises stainless steel, nickel, iron-nickel-cobalt alloys, nickel-iron alloys, or combinations thereof.

57. The sapphire window of claim 49 further comprising a micro lens assembly located on the outside surface of the window.

58. A martinsetic metal assembly for a hermetically sealed assembly for the precompression of the martinsetic metal comprising: a martinsetic metal having a circular shape and a perimeter, and a washer extending around and secured to the perimeter of the martinsetic metal.

59. The martinsetic metal assembly of claim 58 wherein the martinsetic metal comprises lithium.

60. The martinsetic metal assembly of claim 59 wherein the lithium comprises a dopant.

61. The martinsetic metal assembly of claim 60 wherein the dopant is boron carbide.

62. A metallic sealing member for a hermetically sealed assembly for the precompression of the martinsetic metal comprising: a metallic seal comprising opposed side walls separated by a spacer; and a bellows element attached to one of the sidewalls of the metallic seal.

63. The metallic sealing member of claim 62 wherein the metallic seal comprises stainless steel, nickel, iron-nickel-cobalt alloys, nickel-iron alloys, or combinations thereof.

64. The metallic sealing member of claim 63 wherein the bellows element comprises one or more U-shaped cross sections.

65. The metallic sealing member of claim 64 wherein the bellows element comprises stainless steel, nickel, iron-nickel-cobalt alloys, nickel-iron alloys, or combinations thereof.

66. The assembly of claim 12 wherein the bellows element comprises a single unitary structure with either or both of the first metallic seal and the second metallic seal.

67. The assembly of claim 66 wherein the bellows element has a convoluted cross section.

68. The sapphire window of claim 24 wherein the metallic seal further comprises a bellows element, and the metallic seal and the bellows element comprise a single unitary structure.

69. The sapphire window of claim 68 wherein the bellows element has a convoluted cross section.

70. The method of claim 34 wherein the bellows element comprises a single unitary structure with either or both of the first metallic seal and the second metallic seal.

71. The method of claim 70 wherein the bellows element has a convoluted cross section.

72. The method of claim 39 wherein the bellows element comprises a single unitary structure with either or both of the first metallic seal and the second metallic seal.

73. The method of claim 72 wherein the bellows element has a convoluted cross section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 depicts, in cross section, an embodiment of the assembly of the disclosure employing a gasket, at ambient temperature.

[0012] FIG. 2 depicts, in cross section, the embodiment of FIG. 1 at cryogenic temperature.

[0013] FIG. 3 depicts, in cross section, an embodiment of sapphire windows for an assembly of the disclosure.

[0014] FIG. 3A depicts a plan view of the inner face of a sapphire window of the disclosure having a metalized area.

[0015] FIG. 4 depicts, in cross section, the sapphire windows of FIG. 3 having metallic seals secured.

[0016] FIG. 4A depicts, in cross section, an embodiment of a bellows element of the disclosure.

[0017] FIG. 4B is a perspective view of the bellows element of FIG. 4A.

[0018] FIG. 5 depicts, in cross section, another embodiment of the disclosure employing a metallic sealing element, at ambient temperature.

[0019] FIG. 6 depicts, in cross section, the embodiment of FIG. 5 at cryogenic temperature.

[0020] FIG. 7 depicts, in cross section, another embodiment of first and second sapphire windows for another embodiment of an assembly of the disclosure wherein the windows each comprise an outwardly extending peripheral flange.

[0021] FIG. 8 depicts a plan view of the inside surface and the inside face of the flange of the first sapphire window of FIG. 7 having a metalized area.

[0022] FIG. 9 depicts, in cross section, the sapphire windows of FIG. 7, having metallic seals.

[0023] FIG. 10 depicts, in cross section, an embodiment of the disclosure employing another embodiment of a metallic sealing element, at ambient temperature.

[0024] FIG. 11 depicts, in cross section, the embodiment of FIG. 10 at cryogenic temperature.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0025] Referring to FIG. 1 in detail, there is illustrated a cross sectional view of one embodiment of the hermetically sealed assembly for precompression of a martinsetic metal that employs a gasket according to the disclosure. The assembly of FIG. 1 is shown at ambient temperature. The assembly comprises first sapphire window 2 and second sapphire window 4 which are spatially situated relative to each other to form a space therebetween within which space is disposed martinsetic metal 9. The sapphire windows 2 and 4 can be of any geometrical shape, e.g., circular, rectangular, square and the like. In one practice the sapphire windows 2 and 4 are circular and are of substantially the same size having substantially the same dimensions, preferably identical in shape and having identical dimensions for the features discussed herein.

[0026] In the context of negative pressure energy transfer systems as described, for example, in U.S. Pat. Nos. 5,113,661 and 7,581,403, and in Deeks, D. H., “Entropy Driven Absolute Negative Pressure Systems for the Future of Electric Power,” IEEE XPlore 2015, the thinner the thickness of the sapphire windows 2 and 4, the greater the thermal transfer; however, the thinner the sapphire window is, the weaker it becomes, causing the need for a lattice or grill work to be attached to the exterior faces of one or both sapphire windows to strengthen them. The thickness of the sapphire window can also affect the focal point of the cryogenically cooled fused silica micro-lens assembly through which a laser beam passes. This beam is produced by either a standard laser or fused silica fiber coupled laser. The laser beam is used to drive the process by acting on the optical doping material in the martinsetic metal. This optical doping may take the form of a Boron Carbide (dopant) and/or other hard high melting point material, and can comprise one or more targets embedded in the metallic lithium. One or more micro lens assemblies are used to concentrate the laser beam so as to heat the optical dopants to a temperature greater than the boiling point of the pre-compressed martensitic metal but not concentrate the laser beam to a strength sufficient to damage the optical doping (dopant). The laser beam must be adequately focused as it passes through the sapphire window so as not to produce too small a spot size on the doping material, nor can it be of an intensity substantially greater than needed to drive the application, otherwise the cryogenically-cooled fused silica lens assembly could degrade.

[0027] With these parameters in mind, as shown in more detail in FIG. 3, the first sapphire window 2 has a groove 15a offset by distance “d” from the outer edge 2a and extending around the periphery of the inside face of the sapphire window, whereas second sapphire window 4 has a groove 15b offset by distance “d” from the outer edge 4a and extending around the periphery of the inside face of the sapphire window. The sapphire windows 2 and 4 are spatially situated to create a space between inner faces 16a and 16b within which the martinsetic metal 9 is disposed. Any martinsetic metal is serviceable for 9, with metal lithium being preferred, including isotopes of martinsetic metals, such as lithium that are alloyed and/or optically doped and/or electronically or magnetically doped.

[0028] As shown in FIG. 1, martinsetic metal 9 is in contact with inner faces 16a and 16b of the first and second sapphire windows. Grooves 15a and 15b are configured so that when they are superposed or aligned they define internal channel (or void) 10, which extends outwardly and also preferably orthogonally from the space within which martinsetic metal 9 is disposed to accommodate expansion and contraction of the martinsetic metal as it cycles between ambient temperature (e.g. about 25° C.) and cryogenic temperatures (e.g. about −250°) C. As depicted, internal channel 10 is substantially rectangular in cross section, although other cross sectional shapes may be employed.

[0029] Martinsetic metal 9 has a perimeter. Secured to the perimeter and extending around it is containment means 8. The containment means is configured to form a seal between the internal channel 10 and the first and second sapphire windows 2 and 4 when the assembly is at cryogenic temperatures. In one embodiment, the containment means comprises a washer. Materials of construction for the containment means includes, without limitation, stainless steel (e.g. 316 stainless steel), nickel, iron-nickel-cobalt alloys (such as commercially available KOVAR), nickel-iron alloys (such as commercially available INVAR), or combinations thereof. The assembly has means for coupling the first and second sapphire windows and hermetically sealing the internal channel 10 and space within which martinsetic metal 9 is located. Internal channel 10 may be filled with an inert gas such as argon.

[0030] In one embodiment, the means coupling the first and second sapphire windows and hermetically sealing the internal channel and martinsetic metal space are located at the periphery of the first and second sapphire windows and comprise a gasket 3 interposed between the first and second sapphire windows, the gasket 3 extending around the periphery of the first and second sapphire windows 2 and 4. The gasket 3 may optionally comprise a contiguous bellows or comprise discrete bellows segments, e.g. the gasket 3 may be contiguously U-shaped in cross section or have can have discrete segments that are U-shaped in cross section. A plurality of fasteners preferably having positive pressure components is used to secure the gasket 3 and the sapphire windows 2 and 4. Positive pressure components include, without limitation, washers, springs, disc springs, wave springs, belleville disc springs, spring washers, and combinations thereof.

[0031] The means for coupling depicted in FIG. 1 include bolts 1 (screws and the like may also be employed) extending through holes 1a bored through the first and second sapphire windows 2 and 4 and gasket 3 secured with washers 5, and nuts 7. The positive pressure components depicted in FIG. 1 are wave springs 6. Preferably, gasket 3 has substantially the same coefficient of thermal expansion as the sapphire windows. Serviceable materials of construction for gasket 3 include, without limitation, glass-filled polytetrafluoroethylene (PTFE) (e.g. 25% glass filled PTFE), PTFE, stainless steel, gortex, nickel, iron-nickel-cobalt alloys (such as commercially available KOVAR), nickel-iron alloys (such as commercially available INVAR), or combinations thereof. FIG. 1 further depicts a silica micro lens 11 and a dopant 12.

[0032] The assembly of FIG. 1 is shown at ambient temperature. As illustrated, martinsetic material 9 extends into internal channel 10. FIG. 2 depicts the assembly of FIG. 1 at cryogenic temperature. As seen in FIG. 2, martinsetic metal 9 has contracted and a seal has been formed between containment washer 8 and sapphire windows 2 and 4. FIG. 2 also depicts the contraction (narrowing) of the space between sapphire windows 2 and 4 as compared to FIG. 1. Martinsetic metal 9 is maintained in positive pressure contact with the sapphire windows during contraction by wave springs 6 shown in FIG. 2 in a compressed state. Means for compressing and decompressing the first and second sapphire windows while maintaining contact with the martinsetic metal include, without limitation, lock washer 13, which can precisely control the amount of pressure exerted, and also causes the martinsetic metal to maintain positive pressure contact with the sapphire windows.

[0033] FIG. 5 depicts the assembly having another embodiment of the means for coupling the first and second sapphire windows and hermetically sealing the internal channel 10 and space within which martinsetic metal 9 is located. In FIG. 5, the means comprises a metallic sealing member interposed between the first and second sapphire windows, and extending around the periphery of the first and second sapphire windows. Referring to FIGS. 3, 3A, 4 and 4A and 5 for this embodiment: in one practice, FIGS. 3 and 3A (FIG. 3A depicts one of the two identical sapphire windows, in particular the upper sapphire window 2 of FIG. 3 along line 3A) illustrate first and second sapphire windows 2 and 4 having grooves 15a and 15b offset from outer edges 2a and 4a respectively. Each of inner peripheral faces, extending from outer edges 2a to 2b, and from 4a to 4b respectively, has, at least for purposes of the embodiment of FIG. 5, metalized areas, 14a and 14b. The metalized areas can be vacuum deposited with one or more metals or metal alloys, such as, without limitation, stainless steel, nickel, iron-nickel-cobalt alloys (such as commercially available KOVAR), nickel-iron alloys (such as commercially available INVAR), or combinations thereof.

[0034] As shown in FIG. 4, the metallic sealing member comprises a first metallic seal having opposed sidewalls 18a and 19a separated by spacer 17a. Sidewall 18a is secured to the first sapphire window 2 through metalized area 14a, by brazing or soldering, e.g., silver solder brazing. Similarly, a second metallic seal having sidewalls 18b and 19b separated by spacer 17b is secured to the second sapphire window 4 through metalized area 14b by brazing or soldering. The first and second metallic seals have flanges 20a and 20b, respectively, that surround and protect the outer edges 2a and 2b of the first and second sapphire windows. The metallic seals can either integrally comprise the component sidewalls, space, flange; or these components can be separately provided and connected together by means known in the art, e.g. welding and the like.

[0035] FIG. 4A shows bellows element, 21, in cross section, as a ring embodiment, although other configurations for the bellows element consistent with the shape of the sapphire windows can be used. FIG. 4B shows a perspective view of the bellows ring 21 of FIG. 4A. The bellows ring 21 is interposed between and attached to the first and second metallic sealing elements. As depicted in FIG. 5, bellows ring 21 has a substantially U-shaped cross section to permit compression and decompression when the assembly is cycled between ambient temperatures and cryogenic temperatures, and extends around the periphery of the first and second sapphire windows 2 and 4.

[0036] In one embodiment, bellows ring 21 has the outer surface of one of the U-shaped sides 21a attached, by brazing or welding or combinations thereof, to sidewall 18a of the first metallic seal. The containment washer 8 containing the metallic lithium 9 or other martensitic metal is then placed into the center of the bellows ring. Next the second metallic seal is aligned with the outer perimeter of the outer circumference of the bellows ring, and then the other outer surface of the U-shaped side 21b is attached, by brazing or welding or combinations thereof, to the sidewall 18b of the second metallic seal. At ambient temperature, the containment washer 8, may, but is not required to form a seal with the sapphire windows 2 and 4 so to confine the martensitic metal at ambient temperatures. An inert gas, such as argon gas, can be used to fill internal channel 10. Silica micro-lens assembly 11 can be fused to the optical fiber of the fiber coupled laser while being cryogenically cooled. In operation, the mitigation or elimination of pressure is achieved by at least one of either lock washer 13, and/or the positive pressure components, e.g. wave springs 6. One or more spring chock pins 22 is used to use to avoid rupture of the lithium while the containment washer 8 is unsealed from the sapphire windows 2 and 4. At ambient temperature, spring chock pin 22 is extended.

[0037] Preferably, the bellows ring 21 and the components of the first metallic seal (18a, 17a, 19a 20a) and second metallic seal (18b, 17b, 19b, 20b) all have substantially the same thermal coefficient of expansion. Serviceable materials of construction for the bellows ring and the components of the first and second metallic seals include without limitation, stainless steel, nickel, iron-nickel-cobalt alloys (such as commercially available KOVAR), nickel-iron alloys (such as commercially available INVAR), or combinations thereof.

[0038] The assembly of FIG. 5 is shown at ambient temperature. As illustrated, martinsetic material 9 extends into internal channel 10. FIG. 6 depicts the assembly of FIG. 5 at cryogenic temperature. As seen in FIG. 6, martinsetic metal 9 has contracted and a seal has been formed between containment washer 8 and sapphire windows 2 and 4. U-shaped bellows ring 21 compresses and decompresses sufficiently to maintain positive pressure contact of the martinsetic metal 9 and the sapphire windows 2 and 4 during contraction. Wave spring 13 or other suitable means for compressing and decompressing the first and second sapphire windows can precisely control the pressure exerted.

[0039] Referring to FIG. 6, at cryogenic temperature, the metal containment washer 8 forms a seal with the sapphire windows 2 and 4 and confines the martensitic metal 9 within the space. Application of pressure from at least one of lock washer (13), or spring, disc spring, belleville disc spring, wave disc spring, spring washer, wave spring, or combinations thereof, result in a confined martensitic metal 9 subjected to a pressure within plastic point range of the martinsetic metal. Spring chock pin 22 is retracted at cryogenic temperature.

[0040] The present assembly provides precise tuning of the positive pressure necessary for the precompression of the martensitic metal without rupture or leakage of the martinsetic metal. The application of this precompression may occur in different stages. The initial precompression used to seal the martensitic metal using the bellows element, for example, is much less than the plastic point of the martensitic metal. However, the application of the necessary precompression for cryogenic applications must be in the range of the plastic point of the martensitic metal. The prior art, e.g., Hori et al., Journal of Japan Institute of Light Metal, Vol. 50, No. 12 (2000), pp. 660-665 “Plastic Workability of Pure Lithium,” the contents of which are incorporated herein by reference, discusses the workability of the martinsetic metal lithium, and in particular, the application of plastic point pressure versus the time to rupture (movement of the metal due to the application of this pressure). This rupture must be avoided as the lithium metal would leak out of the containment washer, prior to cooling the application to cryogenic temperatures, and prior to the containment washer contracting against the sapphire widow to seal the lithium. The application of the correct pressure for the precompression to the specific pressure in the plastic point pressure range is thus time critical to the final assembly of the cryogenic application prior to operation. Such plastic point ranges are known in the art, for example, FIG. 8. of Hori et al. specifically shows the applied pressure versus time to rupture for lithium. The precompression of the martensitic metal to the plastic point has to occur during the final stages of assembly and/or cooling and/or just prior to operation of the cryogenic devices. The remaining time to assemble a cryogenic application device after pre-pressurization to the plastic point should be taken based on the time given for a specific pressure based on this graph.

[0041] Likewise this pressurization of the martensitic metal to the plastic point range must be removed (depressurized or decompressed) when the cryogenic application is allowed to warm to ambient temperature, or to above a temperature at which the containment washer no longer seals the martinsetic metal against the sapphire windows. This is also time critical, and governed by the same applied pressure versus time to rupture relationship as exemplified, e.g. in Hori; however this critical time may be somewhat extended due to the heat of reversion of the martensitic crystalline phase change.

[0042] In another embodiment the disclosure relates to a method of sealing an assembly for precompression of a martinsetic metal. The method comprises (i) providing an assembly, as e.g. herein described, for precompression of a martinsetic metal the assembly comprising first and second sapphire windows having a space therebetween, and having the martinsetic metal disposed in the space and in contact with the first and second sapphire windows, the first and second sapphire windows configured to define an internal channel around the perimeter of the martinsetic metal, the internal channel extending outwardly from the space and sized to accommodate expansion and contraction of the martinsetic metal within the internal channel; (ii) sealing the first and second windows to each other by means of a gasket interposed between the first and second sapphire windows and extending around the periphery of the first and second sapphire windows; and (iii) securing the first and second sapphire windows to each other by a plurality of fasteners having positive pressure components, the fasteners extending through the first and second sapphire windows and the gasket, wherein the fasteners can comprise, e.g. bolts, screws and combinations thereof, and the positive pressure components comprise washers, springs, disc springs, wave springs, belleville disc springs, spring washers, and combinations thereof. In another embodiment, the assembly of (i) further comprises providing means to relieve pressure from the martinsetic metal to prevent rupture of the martinsetic metal when the martinsetic metal is pressurized; means to relieve pressure in this regard include without limitation one or more rupture pins, for example one or more spring chock pins.

[0043] In another embodiment the disclosure relates to a method of sealing an assembly for precompression of a martinsetic metal, the method comprises (i) providing an assembly as herein described for precompression of a martinsetic metal comprising first and second sapphire windows having a space therebetween, and having the martinsetic metal disposed in the space and in contact with the first and second sapphire windows, the first and second sapphire windows configured to define an internal channel around the perimeter of the martinsetic metal, the internal channel extending outwardly from the space and sized to accommodate expansion and contraction of the martinsetic metal within the internal channel; and (ii) sealing the first and second windows to each other by means of a bellows element having a first side secured to a first metallic seal attached to the first sapphire window and a second side secured to a second metallic seal attached to the second sapphire window, wherein, e.g. the first and second sides of the bellows element are secured by brazing or welding or combinations thereof. In another embodiment, the assembly of (i) further comprises providing means to relieve pressure from the martinsetic metal to prevent rupture of the martinsetic metal means to relieve pressure in this regard include without limitation one or more rupture pins, for example one or more spring chock pins.

[0044] In another embodiment the disclosure relates to a method of precompressing a martinsetic metal comprising (i) providing an assembly as herein described for precompression of a martinsetic metal comprising first and second sapphire windows having a space therebetween, and having the martinsetic metal disposed in the space and in contact with the first and second sapphire windows, the first and second sapphire windows configured to define an internal channel around the perimeter of the martinsetic metal, the internal channel extending outwardly from the space and sized to accommodate expansion and contraction of the martinsetic metal within the internal channel, and containment means extending around and secured to the perimeter of the martinsetic metal configured to form a seal between with the internal channel and the first and second sapphire windows at cryogenic temperatures; (ii) sealing the first and second sapphire windows to each other with either of (a) a gasket interposed between the first and second sapphire windows and extending around the periphery of the first and second sapphire windows, and a plurality of fasteners having positive pressure components, the fasteners can comprise e.g. bolts, screws and combinations thereof, and the positive pressure components comprise washers, springs, disc springs, wave springs, belleville disc springs, spring washers, and combinations thereof, the fasteners extending through the first and second sapphire windows and the gasket, or (b) a bellows element having a first side secured to a first metallic seal hermetically attached to the first sapphire window and a second side secured to a second metallic seal hermetically attached to the second sapphire window, e.g. the first and second sides of the bellows element can be secured by brazing or welding or combinations thereof; and (iii) pressurizing the martinsetic metal to within the range of the plastic point of the martinsetic metal without rupturing the martinsetic metal. Such plastic points are known in the art, see e.g. Hori, FIG. 8, cited above, the contents of which are incorporated herein, for lithium. In another embodiment, the pressuring of step (iii) further comprises hermetically sealing the space within which the martinsetic metal is disposed, as well as optionally hermetically sealing the internal channel, with the containment means, e.g. washer 8. For example, the pressurizing of step (iii) can occur: (a) during cooling of the assembly to cryogenic temperature, or (b) when the assembly is at cryogenic temperature, whereupon in either case, the martinsetic metal would contract or commence contracting and the containment means would move to form a hermetic seal against the sapphire windows. The pressurizing may be performed by means of a wave spring 13 in conjunction with the positive pressure components, such as wave spring 6, or the bellows element, for example, having a U-shaped cross section which permits sufficient flex to complement the pressurizing of step (iii). In one embodiment, when the assembly is being cooled to cryogenic temperatures, or when it is already at cryogenic temperatures, the martinsetic metal is sealed within the space by the containment means in an amount of time that is less than the time required to rupture the martinsetic metal as it is pressurized to within the range of the plastic point. In another embodiment, the assembly of (i) further comprises providing means to the assembly relieve pressure from the martinsetic metal in order to prevent rupture of the martinsetic metal as it is pressurized and the hermetically sealed in the space; and the pressurizing of step (iii) further comprises activating this means to relieve pressure, such means including without limitation one or more rupture pins, such as one or more spring chock pins, from the martinsetic metal to prevent rupturing of the martinsetic metal. In one embodiment, the means to relieve pressure are situated external to the assembly and are not part of it; that is, they are separate from the assembly and are configured to impinge on the assembly; in one embodiment, the one or more spring chock pins impinge upon the assembly to provide a scissor lift action to the pressurization mechanism, which action can relieve the pressure. The means for relieving pressure, e.g. the one or more spring chock pins can be manually operated or automatically operated being triggered by temperature and/or pressure values that are preset. The spring chock pin(s) 183 can be extended and/or retracted by electrically and/or manually; in one practice a mechanism as conventionally known can be used to extend and/or retract the spring shock pin(s), which mechanism can be internal to and/or external from the cryogenic dewar that contains the assembly.

[0045] In another embodiment, when the assembly is allowed to warm to temperatures above cryogenic, the hermetic sealing of the martinsetic metal into the space, i.e. the seal that was formed between the containment means and the sapphire windows, begins to break, and de-pressurization of the martinsetic metal before this breaking of the seal occurs is time critical, and takes place within the range of the plastic point of the martinsetic metal.

[0046] Another embodiment of the disclosure is now described with reference to FIGS. 7 to 11. In one practice of this other embodiment, the sapphire windows each individually comprise an outwardly extending peripheral flange which gives the sapphire window a T configuration in profile, and the bellows element comprises a convoluted cross section. The terminology, definitions, and description for the practices shown in FIGS. 1 to 6 remain the same subject to the following detailed description.

[0047] Referring to FIGS. 7, 8, and 9, thereat is depicted another embodiment of the disclosure showing first sapphire window 102 and second sapphire window 104. First sapphire window 102 comprises an outwardly extending peripheral first flange 154a. In the practice shown, first sapphire window 102 is circular and has a planar outside surface 150a and a planar inside surface 116a which in one embodiment is parallel to planar outside surface 150a. Peripheral first flange 154a extends continuously around the entire circumference of first sapphire window 102 and is coplanar with outside surface 150a. First flange 154a comprises an inside face 156a which forms a step 152a, which step 152a can be, without limitation, at a right angle to inside face 156a and inside surface 116a. The second sapphire window 104 is identical to window 102, as depicted, but need not be. As shown, second sapphire window 104 comprises an outwardly extending peripheral second flange 154b. In the practice shown, second sapphire window 104 is circular and has a planar outside surface 150b and a planar inside surface 116b which in one embodiment is parallel to planar outside surface 150b. Peripheral second flange 154b extends continuously around the entire circumference of second sapphire window 104 and is coplanar with outside surface 150b. Second flange 154b comprises an inside face 156b which forms a step 152b, which step 152b can be, without limitation, at a right angle to inside face 156b and inside surface 116b. In one practice, inside face 156a is coplanar with outside surface 150a, and inside face 156b is coplanar with outside surface 150b.

[0048] FIG. 8 depicts a plan view of the underside of first sapphire window 102 in the direction shown by the arrows in FIG. 7. It will be understood that the following description and practices for FIG. 8 and the first sapphire window 102 are applicable to the second sapphire window 104 as well and are not reiterated here for sake of brevity. As shown in FIG. 8, the inside face 156a of first flange 154a comprises a metalized area 160a (160a in FIG. 8 denoting the series of Xs shown therein) which extends around the entire perimeter of first flange 154a. This metalized area 160a can be located anywhere on inside face 156a, including the entirety of the inside face 156a, or only a portion thereof, e.g. only along the periphery proximate the outside edge 158a of first flange 154a. Without limitation, the metalized area 160a can comprise stainless steel, nickel, iron-nickel-cobalt ally, nickel-iron alloy, or combinations thereof.

[0049] In the assembly depicted at FIGS. 10 and 11, and with reference to FIGS. 7, 8, and 9, the first and second sapphire windows 102 and 104 have a space therebetween, and disposed within which space is a martinsetic metal 174 which is in contact with the first and second sapphire windows. In one embodiment, the martinsetic metal 174 comprises lithium, and can comprise a dopant 176, such as without limitation, boron carbide (B.sub.4C). Further, the first and second sapphire windows 102 and 104 are configured to have a spatial relationship relative to one another so that first flange 154a and second flange 154b juxtapose to define an open area 182, generally extant between first flange inside face 156a and second flange inside face 156b, the open area extending around the perimeter of the martinsetic metal 174 and extending outwardly from the space and sized to permit expansion and contraction of the martinsetic metal 174 within the open area. In one instance, as shown in FIG. 7, the open area is not formed by a groove that is offset from the edge of the sapphire window, as in the embodiments of FIGS. 1-6, but is instead delimited by first and second flanges 154a and 154b and steps 152a and 152b. In the assembly depicted, the first flange 154a and second flange 154b are each independently rectangular in cross section and are parallel to each other; in one practice, the first and second flanges 154a and 154b have the same dimensions; in another practice, the first flange 154a is coplanar with the outside surface 150a of the first sapphire window 102; in another practice, the second flange 154b is coplanar with the outside surface 150b of the second sapphire window 104. The assembly further comprises containment means, as hereinbefore described, and which can comprise, among other things, a washer 172, extending around and secured to the perimeter of the martinsetic metal 174; the containment means, e.g. washer 172, is configured to form a seal between the open area 182 and the first and second sapphire windows 102, 104 at cryogenic temperatures, as shown in FIG. 11 wherein washer 172 is up against steps 152a and 152b thereby forming the seal. Without limitation, the washer 172 can comprise a suitable metal such as, without limitation, stainless steel, nickel, iron-nickel-cobalt alloys (e.g. commercially available KOVAR), nickel-iron alloys (e.g. commercially available INVAR), or combinations thereof.

[0050] The assembly comprises means for coupling the first and second sapphire windows 102 and 104 and hermetically sealing the space and the open area, which means can comprise a metallic sealing member interposed between and extending around the periphery of first and second flanges 154a and 154b wherein the metallic sealing member comprises a first metallic seal 162a and a second metallic seal 162b. The first metallic seal 162a is secured to the first flange 154a by, e.g. brazing or soldering to the metalized area 160a on the first sapphire window 102; and the second metallic seal 162b is secured the second flange 154b by e.g. by brazing or soldering to a metalized area (not shown) on the second sapphire window 104. In one practice, the metallic seals 164a and 164b are each optionally spaced away from the respective steps 152a and 152 and extend along the periphery of the inside face of the respective flange. Metallic seals 164a and 164b can each independently comprise a suitable metal or metal alloy such as, without limitation, stainless steel, nickel, iron-nickel-cobalt alloys (e.g. KOVAR), nickel-iron alloys (e.g. INVAR), or combinations thereof; and can be manufactured by means such as, without limitation, etching, machining, vacuum and/or chemical deposition. As depicted, metallic seals 162a and 162b can each individually comprise a substantially squared U-shaped cross section, and each can individually comprise a guard flange 16a1 and 164b that is configured to respectively protect the outside edges 158a and 158b of the first and second flanges.

[0051] A bellows element 170 is interposed between, and attached to, the first metallic seal 162a and the second metallic seal 162b. The bellows element can be of any shape to accommodate the compression and decompression of the assembly as described herein. For example, in one non-limiting embodiment, the bellows element comprises a convoluted cross section. In one non-limiting practice, a convoluted cross section comprises one or more U-shaped cross sections wherein each U-shaped cross section is a convolution. In a preferred practice, the bellows element comprises more than one U-shaped cross sections, e.g. two or more convolutions (FIGS. 10 and 11 show two convolutions 171 and 172, each having a U-shaped cross section atop one another); in one practice, three to twelve convolutions are employed (including all integers and ranges therewithin), e.g. three to six convolutions (including all integers and ranges therewithin); in general, the greater numbers convolutions provide improved compression and decompression of the bellows element when the assembly is cycled between ambient and cryogenic temperatures.

[0052] The bellows element 170 can comprise a unitary structure or can be comprised of segments joined together by soldering or brazing or other suitable method of joinder, e.g. when the bellows element is convoluted and comprises more than one U-shaped cross sectional segments, each segment can be joined to the others or can be a single unitary structure having multiple U-shaped cross sections. In one practice, the first metallic seal 164a, the second metallic seal 164b, and the bellows element 170 have substantially the same thermal coefficient of expansion, and each independently comprised partly or entirely of a suitable metal or metal alloy such as, without limitation, stainless steel, nickel, iron-nickel-cobalt alloys (e.g. KOVAR), nickel-iron alloys (e.g. INVAR), or combinations thereof; the bellows element can be manufactured by means such as, without limitation, etching, machining, vacuum and/or chemical deposition. In one practice, the bellows element and the first and second metallic seals comprise the same metal or metal alloy which provides the bellows element and the metallic seals with same or at least a compatible coefficient of thermal expansion. In one non-limiting practice that applies to all embodiments herein, the bellows element, e.g. 170, and either or both of the first and second metallic seals, e.g. 162a, 162b, can be formed as a single unitary structure; that is, no separate attachment of the bellows element to either or both of the metallic seals is required inasmuch as they are all an integrated unitary piece. Micro lens assembly 180 can be located on a portion of the planar outside surface 150a of first sapphire window 102 as described herein. Mitigation or elimination of pressure can be achieved by at least one lock washer 178 and/or other positive pressure components as herein described. One or more spring chock pins 183 can be used to avoid rupture of the martinsetic metal while containment washer 172 is unsealed from the sapphire windows; at ambient temperature, spring chock pin 183 is extended as herein described.

[0053] In another practice, the disclosure relates to a method of sealing an assembly for precompression of a martinsetic metal. The method comprises (i) providing an assembly for precompression of a martinsetic metal comprising a first sapphire window and a second sapphire window, the first and second sapphire windows having a space therebetween; and a martinsetic metal disposed in the space and in contact with the first and second sapphire windows, the first sapphire window comprising an outwardly extending peripheral first flange; and the second sapphire window comprising an outwardly extending peripheral second flange, the first flange and the second flange configured to define an open area between the first and second flanges and around the perimeter of the martinsetic material, the open area extending outwardly from the space and sized to permit expansion and contraction of the martinsetic metal within the open area; and (ii) sealing the first and second sapphire windows to each other by means of a bellows element, which can comprise a convoluted cross section, having a first side secured to a first metallic seal attached to the first flange, and a second side secured to a second metallic seal attached to the second flange. The first and second sides of the bellows element can be secured by brazing or welding or combinations thereof. The method can further comprise providing to the assembly means to relieve pressure from the martinsetic metal in order to prevent rupture of the martinsetic metal; means to relieve pressure can comprise, e.g., one or more spring chock pins.

[0054] In another practice, the disclosure is directed to a method of precompressing a martinsetic metal where the method comprises (i) providing an assembly for precompression of a martinsetic metal comprising a first sapphire window and a second sapphire window, the first and second sapphire windows having a space therebetween; and a martinsetic metal disposed in the space and in contact with the first and second sapphire windows, the first sapphire window comprising an outwardly extending peripheral first flange; and the second sapphire window comprising an outwardly extending peripheral second flange, the first flange and the second flange configured to define an open area between the first and second flanges and around the perimeter of the martinsetic material, the open area extending outwardly from the space and sized to permit expansion and contraction of the martinsetic metal within the open area, and containment means extending around and secured to the perimeter of the martinsetic metal configured to form a seal between with the open area and the first and second sapphire windows at cryogenic temperatures; (ii) sealing the first and second sapphire windows to each other with a bellows element, which bellows element can comprise a convoluted cross section, having a first side secured to a first metallic seal hermetically attached to the first flange and a second side secured to a second metallic seal hermetically attached to the second flange; and (iii) pressurizing the martinsetic metal to within the range of the plastic point of the martinsetic metal without rupturing the martinsetic metal. The pressuring of step (iii) can further comprises sealing the space within which the martinsetic metal is disposed with the containment means. The method can further comprise, in step (i), providing to the assembly means for relieving pressure from the martinsetic metal to prevent rupture of the martinsetic metal. In various instances, the pressurizing of step (iii) occurs: (a) during cooling of the assembly to cryogenic temperature, or (b) when the assembly is already at cryogenic temperature. The pressurizing of step (iii) can also further comprise activating the means to relieve pressure from the martinsetic metal in order to prevent rupturing of the martinsetic metal. After step (iii), the method can further comprise (iv) depressuring the martinsetic metal within the range of the plastic point of the martinsetic metal without rupturing the martinsetic metal. The depressurizing of step (iv) can occur at cryogenic temperature.

EXAMPLE

[0055] In one non-limiting practice for preparation of the assembly, the assembly is sealed by respectively brazing each of the first and second flanges to a first and second metallic seal which metallic seals are comprised of a metal and/or metallic alloy containing one or more of the following: KOVAR, INVAR, stainless steel, nickel or other suitable metal. The bellows element is comprised partly or entirely of a metal and/or metallic alloy containing one or more of the following: KOVAR, INVAR, stainless steel, nickel or other suitable metal; preferably, the first and second metallic seals and the bellows element are comprised of the same metal and/or alloy so as to provide a compatible coefficient of thermal expansion between them. The construction of the assembly occurs in a high purity inert gas, e.g. argon or other noble gas or mixture of noble gases and/or under pure mineral oil. The construction can be performed by the following steps:

1. A metalized area on the inside faces of the first and second flanges, from the outer edge of the flanges to the steps, is formed by vacuum deposition with a metal and/or metallic alloy containing one or more of the following: KOVAR, INVAR, Stainless Steel, Nickel or other suitable metal (see FIGS. 7 and 8).
2. The metallic seals are silver soldered or brazed the metallic areas on the first and second flanges windows at the area where the vacuum deposition occurred (see FIG. 9).
3. One end of the bellows element is brazed and or welded to one of the metallic seals. The containment washer containing the martensitic metal, such as lithium with a boron carbide dopant, is then placed into the center of the bellows element. The lithium may be pressed into the containment washer and the boron carbide dopant strategically placed while under pure mineral oil and/or in an inert gas (e.g. argon) atmosphere. Next the other metallic seal is aligned with the outer circumference of the bellows element and then these parts welded or brazed together. Note that at ambient temperature (see FIG. 10) the containment washer may, but is not required to form a seal with the first and second sapphire windows, or it may not confine the martensitic metal at ambient temperatures. A noble gas, e.g. argon gas, fills the open area defined by the first and second flanges. Cryogenically cooling fuses a silica micro-lens assembly to a portion of the top surface of the first sapphire window. Pressure can be mitigated or eliminated by using one of lock washer (as shown in FIG. 10), spring, disc spring and/or belleville disc spring and/or wave disc spring, spring washer, wave spring at ambient temperature, and/or by use of one or more spring chock pins to avoid rupture of the lithium while the containment washer is not sealed to the sapphire windows. The spring chock pin is extended at ambient temperature (see position in FIG. 10).
4. At cryogenic temperature (see FIG. 11) the containment washer forms a seal with the first and second sapphire windows and confines the martensitic metal. Application of pressure from at least one of the lock washer (as shown in FIG. 11), spring, disc spring and/or belleville disc spring and/or wave disc spring, spring washer, wave spring at the final assembly of the cryogenic application causes the constrained and/or confined martensitic metal to be subjected to a pressure in plastic point range as described elsewhere herein. Cryogenic cooling fuses a silica micro-lens assembly to a portion of the top surface of the first sapphire window. Spring chock pin is retracted at cryogenic temperature (see position in FIG. 11).

[0056] The foregoing description and the embodiments disclosed are by way of example only and are not limiting to the scope of the invention.