What is the sealing mechanism of UHV view ports & electrical interconnects?

  1. Knife edges on the edges of flanges with a maleable material gasket like copper is often used for creating UHV chamber environments.

    For UHV view ports, typically say quartz or some other material, how is the UHV seal accomplished?

    Is it the same mechanism? E.g. knife edges machined on quartz windows and then encapsulated by two UHV chamber 'rings/flange cover' with a gasket inbetween the two mating surfaces?

    What about electrical interconnects/feedthroughs? How do you seal them to create UHV (and still create electrical insulation because UHV chambers are often metal and you cant generally use polymers because of outgasing)? Do they use ceramics between the metal connects and the chamber or high purity polymers/epoxy like polyimide?

    How is the UHV seal maintained for electrical feedthroughs also?
     
  2. jcsd


  3. http://en.m.wikipedia.org/wiki/Glass-to-metal_seal

    browsing through these vacuum system
    Threads, I found this unanswered question, and thought I would contribute information I found on Wikipedia
     
  4. UltrafastPED

    UltrafastPED 1,919
    Science Advisor
    Gold Member

    Electrical feedthroughs use ceramics bonded to a metal surface which is then welded into the chamber using vacuum compatible techniques.

    The ceramic-metal bonding is similar to glass-metal bonding.

    Obtaining materials with similar coefficients of thermal expansion is mandatory, or else the seal will fail when the chamber is heated for de-gassing.

    You can find more details here: http://www.mdcvacuum.com/DisplayContentPage.aspx?d=MDC&cc=33c1ded3-4381-4d1b-8eed-bd5622ccaa5f
    and here: http://mpfpi.com/
     
    Modulo2pi likes this.
  5. ...

    Obtaining materials with similar coefficients of thermal expansion is mandatory, or else the seal will fail when the chamber is heated...




    yes and I understand similar coefficient of thermal expansion is required simply for the manufacturing process.

    Dissimilar cte will cause the bond to fail as the newly fabricated part cools


    (!
     
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