Please let us know your experience with glass to metal seal

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
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Bob Reite
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Re: Please let us know your experience with glass to metal s

Post by Bob Reite » Sun Nov 09, 2014 12:43 am

Most hard vacuum "thermionic valves" aka "vacuum tubes". have a "getter" that continues to get rid of excess gasses after the tube has been sealed off. You may want to consider that for your project.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.

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Re: Please let us know your experience with glass to metal s

Post by steve_rb » Sun Nov 09, 2014 2:29 am

Yes I have noticed this. It looks getter material should be heated after tube sealed? Any experience with getter materials?

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Re: Please let us know your experience with glass to metal s

Post by John Futter » Sun Nov 09, 2014 3:12 am

You can get samples from Seas getters in Italy.
They are usually heated by inductive heating of the getter part that is on its own somewhere within the vacuum
Look at any Vacuum tube (ValvE) you will see a circular thing usually near the top of the valve and the mirror metalisation that came from the getter ring after it was heated to cherry red hot.
They are made from Zirconium and various reactive rare earths that are selected to getter various gases ie nitrogen hydrogen oxygen

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Re: Please let us know your experience with glass to metal s

Post by Jerry Biehler » Sun Nov 09, 2014 7:49 pm

steve_rb wrote:I need the second sort. The one that holds the vacuum for years.
Then all bets are off. You will need a commercial metal-glass transition and probably a getter like other have mentioned, There are getters that are fired electrically, the materials are deposited on a filament and you apply power to evaporate and activate the strip. Of course they need hermetic electrical feedthroughs.

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Re: Please let us know your experience with glass to metal s

Post by Richard Hull » Sun Nov 09, 2014 8:52 pm

I agree with Jerry. Go commercial. They have years in the biz and have made reputations on good, long lasting seals. Gettering is really important if you hope to hold better than a 10e-5 torr seal forever. Common old receiving tubes are a prime example of how it is done right!

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Re: Please let us know your experience with glass to metal s

Post by steve_rb » Mon Nov 10, 2014 3:09 am

I am OK with getters but no knowledge regarding this "metal-glass transition" thing. If I have got it right you mean all seals above not suitable for sealed tubes and I only have to use metal-glass transition (the one was at the above houskeeper video) right?
In that video copper gets hot and oxidized. Then glass melts and sticks to the copper oxide. Do you mean this sort of seal with "metal-glass transition"?

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Chris Bradley
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Re: Please let us know your experience with glass to metal s

Post by Chris Bradley » Mon Nov 10, 2014 6:57 am

Might be easier to describe what your objective is, than the means you think you need to use to achieve it.

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Re: Please let us know your experience with glass to metal s

Post by steve_rb » Mon Nov 10, 2014 8:59 am

I am trying to build a custom made vacuum tubes like X-ray tube for a home made simple X-ray diffractometer. Also try to repair a few broken X-ray tube we have (1 target melted, 2 filament burned). Be windows are all OK. I might also give a scintillation detectors a try too.

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Re: Please let us know your experience with glass to metal s

Post by Jerry Biehler » Tue Nov 11, 2014 9:02 am

Good quality metal to glass transitions use something like kovar which has a similar CoE to glass and will bond and not shatter when it cools down. http://www.lesker.com/newweb/flanges/fl ... cfm?pgid=0

You can get x-ray tubes pretty cheap on ebay. And be darned careful with that beryllium, that stuff is pretty toxic.

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Re: Please let us know your experience with glass to metal s

Post by steve_rb » Tue Nov 11, 2014 9:56 am

Tubes in eBay are not suitable for X-ray diffractometers.
Thank you for your notice. Yes I am aware of Be toxicity.
Anyone has practical experience with Kovar seals?

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