Pressure burst free high capacity cryopump

• US 20080168778A1
• Filed: 01/15/2008
• Published: 07/17/2008
• Est. Priority Date: 01/17/2007
• Status: Active Grant

• Current Assignee: Edwards Vacuum, LLC (Atlas Copco AB)
• Original Assignee: Brooks Automation Incorporated (Azenta, Inc.)
• Inventors: Johnson, William L., Sullivan, Robert P., Bartlett, Allen J., Syssoev, Sergei, Eacobacci, Michael J., Stira, Mark A., Driscoll, Michael A., Casello, John J.
• Granted Patent: US 10,760,562 B2
• Time in Patent Office: Days
• US Class Current: 62/55.5
• CPC Class Codes: B01D 8/00 Cold traps; Cold baffles pumps for evacuating by condensing or freezing F04B37/08
• CPC Class Codes: F04B 37/08 by condensing or freezing, e.g. cryogenic pumps
• CPC Class Codes: F04B 37/085 Regeneration of cryo-pumps

Abstract

A cryopump includes a refrigerator with at least first and second stages. A radiation shield surrounds the second stage and is in thermal contact with the first stage. The radiation shield includes a drain hole to permit cryogenic fluid to traverse through the drain hole during regeneration. The cryopump also includes a primary pumping surface supporting adsorbent in thermal contact with the second stage. The second stage array assembly includes a primary condensing surface, protected surfaces having adsorbent, and non-primary condensing surfaces. A baffle is disposed over the drain hole. The baffle redirects gas from an annular space disposed between the radiation shield and the vacuum vessel that attempts to traverse through the drain hole to prevent the gas from condensing on a non-primary condensing surface. The baffle directs gas to condense on the primary condensing surface.

Claims

1. A method of directing flow from between a vacuum vessel and a radiation shield to control the location of condensate film growth, the method comprising:

blocking the flow from an annular spaced defined between the vacuum vessel and the radiation shield; and

redirecting the flow to a primary pumping surface; and

condensing the gases at the primary pumping surface to form frost.

2. The method of claim 1, further comprising blocking the flow from beneath a radiation shield.

3. The method of claim 1, further comprising blocking the flow from a side of a radiation shield.

4. A cryopump comprising:

a refrigerator having at least first and second stages;

a radiation shield which surrounds the second stage and is in thermal contact with the first stage, the radiation shield including a drain hole to permit fluid to traverse through the drain hole during regeneration;

a primary pumping surface supporting adsorbent in thermal contact with the second stage and having a second stage array including a primary condensing surface, protected surfaces having adsorbent, and non-primary condensing surfaces; and

a baffle disposed over the drain hole, the baffle redirecting gas from traversing through the drain hole to prevent the gas from condensing on a non-primary condensing surface, the baffle directing gas to condense on the primary condensing surface.

5. The cryopump of claim 4, wherein the baffle is substantially “

U”

shaped.

6. The cryopump of claim 4, wherein the baffle includes a first arm connected to a bottom surface of the radiation shield, and a second arm connected to the bottom surface, and an intermediate section being connected to the first and the second arm.

7. The cryopump of claim 4, wherein the baffle is curved to permit cryogenic liquid to traverse through the drain hole during regeneration of the cryopump.

8. The cryopump of claim 4, further comprising a hole in a lateral side wall of the radiation shield, the hole being configured to permit an electrical connection through the hole, the hole being occluded.

9. The cryopump of claim 4, wherein the drain hole is generally circular and has a size optimized to prevent gas to pass therethrough to condense on the non-primary condensing surfaces.

10. The cryopump of claim 4, wherein the radiation shield includes an inner surface facing the primary pumping surface and an outer surface, wherein the baffle is connected to the inner surface or the outer surface.

11. The cryopump of claim 4, wherein the baffle is connected by a bonding.

12. The cryopump of claim 4, wherein the radiation shield includes a cylindrical surface facing the primary pumping surface and wherein the cylindrical surface is impermeable to gas flow.

13. The cryopump of claim 4, wherein the radiation shield comprises an opening, and a solid side wall free of an aperture to prevent gas from entering the radiation shield in a direction other than that the opening for pumping.

14. A radiation shield configured for use with a cryopump comprising:

a housing including a bottom, and a lateral side wall connected to the bottom, the housing having a volume sufficient to hold a primary pumping surface of the cryopump;

a drain hole located on the bottom to permit cryogenic liquid and gas to traverse therethrough during a regeneration operation; and

a baffle covering the drain hole and configured to divert gases from entering the radiation shield through the drain hole, and being pumped on a non-primary surface by redirecting gases to a primary pumping surface of the cryopump.

15. A cryopump comprising:

a refrigerator having at least first and second stages, said second stage including a cylinder;

a radiation shield which surrounds the second stage and is in thermal contact with the first stage;

a second stage cylinder shield in thermal contact with the coldest section of the second stage and surrounding the cylinder;

a passageway with a substantially uniform temperature differential formed between the cylinder shield and an extension in thermal contact with the first stage by the radiation shield such that molecular collisions with and condensation on the cold surface of the cylinder shield are assured to tightly bond the gas molecules to the cylinder shield and prevent condensation on the second stage refrigerator cylinder; and

the cylinder shield including an end, the end located adjacent the extension, the end including a flare, the flare providing a clearance between the extension and the cylinder shield, the clearance being suitable to prevent frost at the end from contacting the extension.

16. The cryopump of claim 15, wherein the clearance is about 0.25 inches.

17. The cryopump of claim 15, wherein the cylinder shield surrounds the extension.

18. The cryopump of claim 15, wherein the extension includes at least two surfaces and the two surfaces generally perpendicular to one another.

19. The cryopump of claim 15, further comprising a primary pumping surface in thermal contact with the second stage, the primary pumping surface including an array of baffles with a top baffle being a unitary member, the unitary member configured to allow a uniform distribution of frost.

20. The cryopump of claim 19, wherein the top baffle includes a notch configured to provide a clearance for frost to aggregate without contacting surrounding surfaces.

21. The cryopump of claim 20, wherein the notch is generally orthogonal and located adjacent the extension.

22. The cryopump of claim 20, wherein the notch provides for a clearance distance of about 0.25 inches between the extension and the top baffle.

23. The cryopump of claim 15, wherein the ratio of the length of the passageway relative to its width is greater than or about equal to 5.

24. The cryopump of claim 15, wherein extension includes a bracket, the bracket connecting the extension to the radiation shield and being in thermal contact with the first stage.

25. The cryopump of claim 19, further comprising an adsorbent supported on at least one of the baffles.

37. The cryopump of claim 24, wherein the surface forms a deposited film having a non-uniform thickness, wherein the non-uniform film thickness prevents cracking of the film.

26. A cryopump comprising:

a refrigerator having at least first and second stages;

a radiation shield which surrounds the second stage and is in thermal contact with the first stage;

a primary pumping surface supporting adsorbent in thermal contact with the second stage, the primary pumping surface including a primary condensing surface, protected surfaces having adsorbent, and non-primary condensing surfaces; and

the non-primary condensing surfaces include a surface being configured to reduce crack-forming stress in the condensed deposits as gas is deposited on the non-primary condensing surfaces.

27. The cryopump of claim 26, wherein the surface results in a low stress deposited film.

28. The cryopump of claim 26, wherein the surface inhibits the formation of a continuous deposited film.

29. The cryopump of claim 26, wherein the surface includes a pattern on the non-primary condensing surface.

30. The cryopump of claim 26, wherein the surface includes a plurality of protrusions having a feature, the feature being selected from the group consisting of a hole or a bend.

31. The cryopump of claim 26, wherein the non-primary condensing surface of the cryopump includes a planar surface with a protrusion.

32. The cryopump of claim 26, wherein the radiation shield includes a sealed electrical feed through hole.

33. The cryopump of claim 26, wherein the radiation shield includes an occlusion where a purge hole is located on the radiation shield.

34. The cryopump of claim 26, wherein the radiation shield includes a baffle located over the drain hole to redirect gas from the non-primary condensing surface to the primary condensing surface.

35. The cryopump of claim 26, wherein the surface forms a non-contiguous film as the gas is deposited on the non-primary condensing surface.

36. The cryopump of claim 26, wherein the primary condensing surface includes a notch to prevent condensation from thermally contacting surfaces in contact with the radiation shield, wherein the surfaces are about 100 degrees Kelvin.

38. A cryopump comprising:

a refrigerator having at least first and second stages;

a radiation shield which surrounds the second stage and is in thermal contact with the first stage;

a second stage array supporting adsorbent in thermal contact with the second stage; and

the primary pumping surface including a top plate being sectioned into at least a first section and a second section, the first section and the second section being joined by a rigid connection that prevents relative movement of deposited condensation formed on the first section and the second section.

39. The cryopump of claim 38, wherein the first section and the second section are joined by at least one of a bracket, an interlocking interface, or joined by a soldering.

40. The cryopump of claim 38, wherein the top plate is configured to allow a uniform distribution of frost on a top planar surface of the top plate.

41. The cryopump of claim 38, wherein the top plate includes a notch in a radial side of the top plate, the notch configured to prevent condensation from contacting an extension in thermal contact with the radiation shield.

42. The cryopump of claim 41, wherein the notch is generally orthogonally shaped.

43. The cryopump of claim 38, wherein the top plate includes that the first section overlaps the second section.

44. The cryopump of claim 38, wherein the second section overlaps the first section.

45. The cryopump of claim 38, wherein the top plate is made from at least three or more sections with at least the three or more sections being mechanically coupled to one another to inhibit relative motion.

46. The cryopump of claim 38, wherein the top plate comprises more than two pieces connected to prevent movement of deposited condensation formed thereon.

47. A method of managing growth of condensation on a primary pumping surface being formed from a first section and a second section, the method comprising:

blocking the flow from an annular spaced defined between the vacuum vessel and the radiation shield;

redirecting the flow to the primary pumping surface being formed from the first section and the second section;

condensing the gases at the primary pumping surface to form thick frost; and

mechanically coupling the first section and the second section to one another in a rigid manner to prevent condensation deposited on the first section from moving and contacting the condensation deposited on the second section during operation.

48. A cryopump comprising:

a refrigerator having at least first and second stages;

a radiation shield which surrounds the second stage and is in thermal contact with the first stage;

a second stage array supporting adsorbent in thermal contact with the second stage, the second stage array including a primary condensing surface, protected surfaces having adsorbent, and non-primary condensing surfaces; and

at least a first structure to minimize condensation on the non-primary condensing surfaces, or a second structure to minimize crack-forming stress in condensation deposits as gas is deposited on the non-primary condensing surfaces.

49. The cryopump of claim 48, wherein the second structure is a surface having a feature, the feature being selected from the group consisting of a protrusion, a hollow protrusion, a bent protrusion, or a combination thereof.

50. The cryopump of claim 48, wherein the first structure includes at least one occlusion associated with a hole formed through a radiation shield, the occlusion redirecting gas during operation and permitting fluid to traverse through the occlusion during regeneration.

51. The cryopump of claim 48, wherein the primary pumping surface includes a top plate that is a unitary member.

52. The cryopump of claim 48, wherein the primary pumping surface includes a top plate with a first section and a second section that are connected in a rigid manner to prevent condensation deposited on the first section from moving and contacting the condensation deposited on the second section.

53. The cryopump of claim 48, wherein contact between the condensation deposits and surfaces in contact with a first stage surface is minimized.

54. A cryopump comprising:

a refrigerator having at least first and second stages;

a radiation shield which surrounds the second stage, and is in thermal contact with the first stage;

a second stage array comprising primary condensing surfaces, protected surfaces having adsorbent, and non-primary condensing surfaces, the primary condensing surface comprising a planar surface configured for a general uniform distribution of condensed material.

55. The cryogenic pump of claim 54, wherein the surface is a flat top plate being generally level.

56. The cryogenic pump of claim 55, wherein the top plate includes a notch in a radial side of the top plate.

57. The cryogenic pump of claim 54, wherein the top plate permits frost to distribute in a generally cylindrical manner thereon.

58. A method of preventing pressure excursions in a chamber comprising:

pumping gases from the chamber to form condensed gases; and

preventing the condensed gases from forming with an internal stress configuration that creates flakes and a spontaneous warming of the ejected flakes causing the pressure excursion.