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building a (small) vacuum chamber-type device

Don't make it, buy it. What you want is a Kovar feedthrough. These have a piece of Kovar rod that passes through a piece of ceramic insulator, which also serves as the vacuum seal. The material of the port needs to be as

This is exactly why Kovar was developed. It matches the thermal expansion of glass and ceramic materials, and also wets the glass, providing a strong mechanical bond. it is what is used to make the connections through vacuum tubes. If this is a hobby project, you can salvage the base of an all-glass vacuum tube or CRT.

Jon

Reply to
Jon Elson
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For 0.1 atmosphere, RTV around a wire is more than sufficient. The vacuum side is only 14.7PSI and that really isn't much pressure trying to get in. The reason for the glass seals and so forth is that when you are down at nano torr values, the inflow is sufficient to drop that vacuum level real fast. At 0.1 of air pressure, the inflow is so small that it will take years to do significant damage to the vacuum. Remember that a steel (not even a polished steel but just run of the mill steel surface) to rubber interface holds air in a tire for many years in an automobile tire.

-- Why do penguins walk so far to get to their nesting grounds?

Reply to
Bob May

You also didn't indicate the size ,but this

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ebay item 7569065039 might fit your bill. Already has feed thrus

wrote:

jk

Reply to
jk

There are tons of vacuum pumps on ebay. I bought a nice welch pump for 130 dollars. This pump will pull .02 Torr on a tight system and will pump .5 torr with very crude plumbing (like automotive PS rubber hose). Way more than you say you need (.1 atm which is 76 torr).

It can pump down a small 1 gal bell jar in 10 seconds. BTW, I bought a bell jar from fisher scientific. It works but the glass is very poor. The price was right though at ~50 bucks.

However it sounds like you might learn a lot by looking at Sam's laser page. Google for it. There is a ton of info there that might be right up your alley.

chuck

Reply to
Chuck Sherwood

Hey, funny you say that, I have precisely been re-reading sam's laser and specifically the vacuum page !

bruno

Reply to
bschwand

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