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Re: [VacuumX] High Voltge supply

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  • Brian
    James, I m no expert but with regards to the argon...save that for sputtering. If you are coating mirrors with alu then you need the final coat to be oxide,
    Message 1 of 9 , Nov 13, 2004
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      James,
          I'm no expert but with regards to the argon...save that for sputtering. If you are coating mirrors with alu' then you need the final coat to be oxide, when you let the "dirty" air in the aluminium coat willl oxidize with o2 only at the surface. Argon is inert so will only delay oxidation until you let air to the work. Aluminium oxide is very transparent and stable.. hence the protected finish.If my chemistry/physics is correct you could purge the chamber with o2 to form the stable oxide before you vent to air. o2 can be a bit dodgy in vac chambers so best to keep to filtered air. I worked on vac chamber electronics a couple of years ago with a good group of experts and picked up a few tips. With regard to the glow discharge I think the bar should be positive... Any ionized gas molecules want their electron back so are pulled to  the negative chamber or work (much the same as sputtering) thereby cleaning the surfaces.I do this on my own chamber and it really makes a difference to the base pressure and pump down times. Some people use argon as opposed to air for the glow discharge as it should be cleaner?
         
          Thought these comments may help.....Brian
    • t_janstrom
      Just a quick follow up, does the current for the discharge arc have to be DC or can it be AC? Clear skies, Thomas Janstrom http://www.tjanstrom.com
      Message 2 of 9 , Dec 1, 2004
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        Just a quick follow up, does the current for the discharge arc have to
        be DC or can it be AC?

        Clear skies,
        Thomas Janstrom
        http://www.tjanstrom.com
        http://www.norsewines.com.au
        "Your nobody untill you've been ignored by your seventh cranio-facial
        nerve."


        -
      • James Lerch
        Mine s AC, but I d love to try DC, glow bar Negative, Chamber Positive. I ve also got a bottle of Argon I m going to use to back fill the chamber with next
        Message 3 of 9 , Dec 1, 2004
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          Mine's AC, but I'd love to try DC, glow bar Negative, Chamber Positive.

          I've also got a bottle of Argon I'm going to use to back fill the chamber with
          next time I do a coating. Will be interesting to see if it makes any
          difference...

          Take Care,
          James Lerch
          http://lerch.no-ip.com/atm (My telescope construction,testing, and coating site)

          "Anything that can happen, will happen" -Stephen Pollock from:
          "Particle Physics for Non-Physicists: A Tour of the Microcosmos"

          " Press on: nothing in the world can take the place of perseverance.
          Talent will not; nothing is more common than unsuccessful men with talent.
          Genius will not; unrewarded genius is almost a proverb.
          Education will not; the world is full of educated derelicts.
          Persistence and determination alone are omnipotent. "
          Calvin Coolidge
          ----- Original Message -----
          From: "t_janstrom" <t_janstrom@...>
          To: <VacuumX@yahoogroups.com>
          Sent: Wednesday, December 01, 2004 19:17
          Subject: RE: [VacuumX] High Voltge supply


          >
          > Just a quick follow up, does the current for the discharge arc have to
          > be DC or can it be AC?
          >
          > Clear skies,
          > Thomas Janstrom
          > http://www.tjanstrom.com
          > http://www.norsewines.com.au
          > "Your nobody untill you've been ignored by your seventh cranio-facial
          > nerve."
          >
          >
          > -
          >
          >
          >
          >
          >
          >
          > Yahoo! Groups Links
          >
          >
          >
          >
          >
          >
          >
        • James Lerch
          Hi Brian, I was planning on using the argon during the glow discharge cleaning cycle. I ve played with backfilling with O2 from the cutting torch after
          Message 4 of 9 , Dec 1, 2004
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            Hi Brian,
             
            I was planning on using the argon during the glow discharge cleaning cycle.  I've played with backfilling with O2 from the cutting torch after evaporating the AL, but it didn't seem to make any difference over plain old Air. 
             
            Your comments on glow bar DC negative make sense.  I was thinking of electron flow originally, but what we really want during GDC is positively charged ions impacting the surface.. 
             
            Take Care,
            James Lerch
            http://lerch.no-ip.com/atm (My telescope construction,testing, and coating site)
             
            "Anything that can happen, will happen" -Stephen Pollock from:
            "Particle Physics for Non-Physicists: A Tour of the Microcosmos"
             
            " Press on: nothing in the world can take the place of perseverance.
            Talent will not; nothing is more common than unsuccessful men with talent.
            Genius will not; unrewarded genius is almost a proverb.
            Education will not; the world is full of educated derelicts.
            Persistence and determination alone are omnipotent. "
                                                                       Calvin Coolidge
            ----- Original Message -----
            From: Brian
            Sent: Saturday, November 13, 2004 19:49
            Subject: Re: [VacuumX] High Voltge supply

            James,
                I'm no expert but with regards to the argon...save that for sputtering. If you are coating mirrors with alu' then you need the final coat to be oxide, when you let the "dirty" air in the aluminium coat willl oxidize with o2 only at the surface. Argon is inert so will only delay oxidation until you let air to the work. Aluminium oxide is very transparent and stable.. hence the protected finish.If my chemistry/physics is correct you could purge the chamber with o2 to form the stable oxide before you vent to air. o2 can be a bit dodgy in vac chambers so best to keep to filtered air. I worked on vac chamber electronics a couple of years ago with a good group of experts and picked up a few tips. With regard to the glow discharge I think the bar should be positive... Any ionized gas molecules want their electron back so are pulled to  the negative chamber or work (much the same as sputtering) thereby cleaning the surfaces.I do this on my own chamber and it really makes a difference to the base pressure and pump down times. Some people use argon as opposed to air for the glow discharge as it should be cleaner?
               
                Thought these comments may help.....Brian

          • Guy Brandenburg
            At one of the major observatories in California, they do ion discharge cleaning with oxygen; then with nitrogen; then with oxygen. Or maybe it s the other way
            Message 5 of 9 , Dec 2, 2004
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              At one of the major observatories in California, they
              do ion discharge cleaning with oxygen; then with
              nitrogen; then with oxygen. Or maybe it's the other
              way around.
              We just use whatever air is left in the chamber.
              Guy

              --- James Lerch <jlerch1@...> wrote:

              > Hi Brian,
              >
              > I was planning on using the argon during the glow
              > discharge cleaning cycle. I've played with
              > backfilling with O2 from the cutting torch after
              > evaporating the AL, but it didn't seem to make any
              > difference over plain old Air.
              >
              > Your comments on glow bar DC negative make sense. I
              > was thinking of electron flow originally, but what
              > we really want during GDC is positively charged ions
              > impacting the surface..
              >
              > Take Care,
              > James Lerch
              >

              =====
              Guy Brandenburg
              Washington, DC
              My home page:
              http://home.earthlink.net/~gfbranden/GFB_Home_Page.html
            • SVC
              ... Attached is a pdf document on glow discharge cleaning that some may find of interest. An ideal power supply for glow discharge is the old CVC LC-031 high
              Message 6 of 9 , Dec 2, 2004
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                >Dear all,


                Attached is a pdf document on glow discharge cleaning that some may
                find of interest. An ideal power supply for glow discharge is the
                old CVC LC-031 high voltage DC power supply. It used mercury vapor
                rectifiers and if you have a short it just grunts and the tubes light
                up - it doesn't blow expensive solid state rectifiers.

                Regards,

                Don Mattox


                --
                ____________________________________
                Donald M. Mattox
                Technical Director
                Society of Vacuum Coaters
                71 Pinon Hill Place NE
                Albuquerque, NM 87122-1914

                Telephone 505/856-7188
                FAX 505/856-6716
                E-mail donmattox@...
                WebSite http://www.svc.org
              • Ken Hunter
                ... light ... Hi Don... Thanks for trying the post. Unfortunately, Yahoo does not allow attachments to messages any more. You will need to save it to the files
                Message 7 of 9 , Dec 2, 2004
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                  --- In VacuumX@yahoogroups.com, SVC <donmattox@s...> wrote:
                  > >Dear all,
                  >
                  >
                  > Attached is a pdf document on glow discharge cleaning that some may
                  > find of interest. An ideal power supply for glow discharge is the
                  > old CVC LC-031 high voltage DC power supply. It used mercury vapor
                  > rectifiers and if you have a short it just grunts and the tubes
                  light
                  > up - it doesn't blow expensive solid state rectifiers.
                  >
                  > Regards,
                  >
                  > Don Mattox
                  >

                  Hi Don...

                  Thanks for trying the post. Unfortunately, Yahoo does not allow
                  attachments to messages any more. You will need to save it to the
                  files section for it to show up here. You probably wouldn't believe
                  all the hoops I had to jump through to dispose of some Mercury Vapor
                  tubes last year. Totally insane.

                  Ken Hunter
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