Making Large Vacuum Chambers

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ian_krase
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Making Large Vacuum Chambers

Post by ian_krase » Thu Dec 12, 2019 5:21 am

Pipe tee fusors are all the rage nowadays, which is good because they are inexpensive to make without welding.

But sometimes, we want much larger chambers. Which typically are at least hundreds of dollars even used on Ebay.

Does anybody here have experience using pressure cookers, pressure pots, or similar non-vacuum chambers for high vacuum?

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Richard Hull
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Re: Making Large Vacuum Chambers

Post by Richard Hull » Thu Dec 12, 2019 10:12 am

We have had a couple of folks ask the same question, but they never demonstrated fusion in one or even went beyond the point your are merely positing now. Talk, but no action and no experimentation. We never heard from them again. Wanna be the first on your block? I would not hold out much hope of doing fusion this way.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

ian_krase
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Re: Making Large Vacuum Chambers

Post by ian_krase » Fri Dec 13, 2019 7:31 am

As is often the case, I'm not interested in specifically building a fusor. Though my requirements for hermeticity are arguably higher.

Meanwhile I have my own apprehension because the chamber types I am looking at still cost enough to not want to dive in blind (at the very least, would need to pay to attach KF40 flange to connect pump and another for gauge).

Herein lies the chicken or the egg problem.

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Rich Feldman
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Re: Making Large Vacuum Chambers

Post by Rich Feldman » Fri Dec 13, 2019 9:52 pm

Just realized that my 9-years-idle transformer tank is bigger than must spherical fusor chambers.
A cylinder about 10 inches long and 6 inches in diameter.
50 micron pressure in test, with a not too fancy hose and rotary pump.

viewtopic.php?f=10&t=4050&p=21458
All models are wrong; some models are useful. -- George Box

ian_krase
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Re: Making Large Vacuum Chambers

Post by ian_krase » Sat Dec 14, 2019 9:03 am

Interesting. This makes me somewhat more optimistic -- one could substitute a heavy metal plate for the acrylic, and machine a conflat into it.

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Rich Feldman
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Re: Making Large Vacuum Chambers

Post by Rich Feldman » Sat Dec 14, 2019 6:47 pm

Ian, you mentioned KF-40 plumbing.
Can adapt that to a flat baseplate without welding or precise machining; that's what bulkhead clamps are for.
Hole in plate needs to accomodate the flange detail of ordinary centering ring part. Hole saw time?
You can get disks of flat-machined aluminum plate from S and S, like Jerry said in another thread.
bulkhead.JPG
All models are wrong; some models are useful. -- George Box

ian_krase
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Re: Making Large Vacuum Chambers

Post by ian_krase » Sun Dec 15, 2019 2:36 am

Who's S and S?

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Frank Sanns
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Re: Making Large Vacuum Chambers

Post by Frank Sanns » Mon Dec 30, 2019 9:06 am

There are entire industries using this kind of equipment. Lids are available with valves, viewports and the like. https://stainlesssteelexpress.com/produ ... gJRUPD_BwE

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Jim Kovalchick
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Re: Making Large Vacuum Chambers

Post by Jim Kovalchick » Mon Dec 30, 2019 12:27 pm

My son's original fusor vacuum chamber was a stainless Kitchenaid mixer bowl. The bowl was cylindrical with a half-sphere base. It made a great bell jar type chamber. The base plate was made with a flat, 3/8" aluminum plate with KF and swagelok fittings for feedthrough, gas, and instrumentation penetrations. JB weld sealed all penetrations. A piece of viton was trimmed for the gasket ring and high vacuum grease was applied. Kitchenaid mixing bowls have a dimple in the base. This dimple was cut out leaving a rounded rim. Another viton gasket and a small half inch thick square of borosilicate glass on the rim made a nice view port. The mixer tab was a good place to fix a ground wire.To pull vacuum, he would hold the whole thing tight until the roughing pump pull enough vacuum to hold itself. The heat of plasma helped condition the chamber, and he often saw 10-7 torr on an ion gage. I still haven't matched his vacuum success with my own chambers.

He made lots of neutrons with it until he went off to college.
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Mark Rowley
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Re: Making Large Vacuum Chambers

Post by Mark Rowley » Mon Dec 30, 2019 6:48 pm

Back in the early 2000's I made one from the top portion of an air tank for scuba diving. I never hooked it up to a secondary pump but the roughing got it down to 15 or so mTorr.

Mark Rowley

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