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  1. Vacuum Science and Technology in Accelerators Ron Reid Consultant ASTeC Vacuum Science Group (r.j.reid@dl.ac.uk) Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  2. Session 7 Components and Construction Techniques Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  3. Aims • To examine constructional techniques of particular relevance to vacuum performance. • To understand why some standard vacuum components are designed in the way that they are. Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  4. Vacuum Seals • Every accelerator incorporates many demountable vacuum joints. Clearly these have to be reliable. • The seal is the most unreliable part of such joints. • Seals are made of elastomers or metals. • The requirements are that the seal is deformable, elastic and stable. • In accelerators, radiation resistance of seal materials can be of importance. Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  5. Elastomers • Suitable elastomers include • Buna N • Neoprene • Fluoroelastomer (VitonTM) • Silicone • PTFE • Polyimide (VespelTM, KalrezTM) Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  6. Elastomer seals • Limited temperature range • Buna N, Neoprene ~ 85oC • Viton ~ 150oC • Polyimide, PTFE ~ 275oC • Limited radiation reistance • PTFE – poor • Viton – moderate • Polyimide - reasonable Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  7. Elastomers Permeation Compression set Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  8. Elastomer seal configurations Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  9. Metal Seals • Copper • Gold • Aluminium • Tin • Indium Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  10. Metal Seals • Metal O-rings (usually called wire seals) can be used in the same configurations as elastomer seals (except “L” seals) when higher temperatures are required. • In addition, there are three important types of seal • “Diamond” • Knife-edge • HelicoflexTM Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  11. Metal Seals • Diamond seal Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  12. Metal Seals HelicoflexTM Knife edge - ConflatTM Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  13. Knife edge seals Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  14. Metal Gasket Material • “Copper” • OFHC • OFS (0.1% Silver) • Silver plated • Helicoflex • Many different metal sealing jackets available Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  15. Flanges • Material as for vessel construction • Harder than seal • For wire and diamond seals, roughness should be ~ 1μ • Lap finish should be parallel to the seal run • Knife edge (“ConflatTM”) flanges • N hardened aluminium • 304 or 316 Stainless steel • For highest reliability, 316LN should be used Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  16. Metal Stock Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  17. Construction Techniques Brazing Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  18. Construction Techniques Welds Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  19. Construction Techniques Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  20. Construction Techniques Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  21. Construction Techniques Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  22. Construction Techniques Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  23. Construction Techniques Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  24. Components Windows (Viewports) Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  25. Components Feedthroughs Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  26. Components Motions (Rotary) Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  27. Components Motion (Linear) Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  28. Components Bellows Edge welded Formed Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  29. Components Shielded Bellows Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  30. Components Right Angle Valve Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  31. Components Gate valve Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  32. Components RF Shielded Gate Valve Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  33. Lubrication • Lubricants may be required for bearing surfaces, especially in UHV where cold welding can occur. • Moving surfaces in contact should be designed so that the possibility of galling or scraping is minimised. • Lubricants should be chosen so that the vapour pressure is sufficiently low e.g. ptfe greases, FomblinTM oil or, better solid lubricants should be used Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  34. Lubrication • Solid lubricants • PTFE • Graphite • MoS2 • Implanted Lead • WSe2 or WS2 Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007

  35. In an accelerator there can be many moving components – valves, shutters, beam stops, scrapers, septa, beam monitors. • These are the components most susceptible to leaks and so must be designed and operated with care. • Care has to be taken regarding the generation of particulates. This can only be done by good design. Vacuum Science and Technology in Accelerators Cockcroft Institute Lectures - 2007