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Making Large Vacuum Chambers

Posted: Thu Dec 12, 2019 5:21 am
by ian_krase
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?

Re: Making Large Vacuum Chambers

Posted: Thu Dec 12, 2019 10:12 am
by Richard Hull
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

Re: Making Large Vacuum Chambers

Posted: Fri Dec 13, 2019 7:31 am
by ian_krase
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.

Re: Making Large Vacuum Chambers

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

Re: Making Large Vacuum Chambers

Posted: Sat Dec 14, 2019 9:03 am
by ian_krase
Interesting. This makes me somewhat more optimistic -- one could substitute a heavy metal plate for the acrylic, and machine a conflat into it.

Re: Making Large Vacuum Chambers

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

Re: Making Large Vacuum Chambers

Posted: Sun Dec 15, 2019 2:36 am
by ian_krase
Who's S and S?

Re: Making Large Vacuum Chambers

Posted: Mon Dec 30, 2019 9:06 am
by Frank Sanns
There are entire industries using this kind of equipment. Lids are available with valves, viewports and the like. https://stainlesssteelexpress.com/produ ... gJRUPD_BwE

Re: Making Large Vacuum Chambers

Posted: Mon Dec 30, 2019 12:27 pm
by Jim Kovalchick
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.

Re: Making Large Vacuum Chambers

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