Fusor construction questions

For posts specifically relating to fusor design, construction, and operation.
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Joshua Turbyfill
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Fusor construction questions

Post by Joshua Turbyfill » Sun Nov 24, 2019 5:31 pm

I've finished the fusor but my deuterium setup isn't really working. I'm using the PEM cell design with the over and under pressure chambers.

I open the needle valve to evacuate the air from the deuterium chamber and then I turn on the PEM cell to displace the oil with deuterium. However, instead of displacing oil, the two oil chambers just equalize. Even if the two larger orange chambers are disconnected from everything else and their rubber stoppers are removed, they will always equalize if the tube connecting them already has oil in it. Does anyone have any ideas on how to fix this?
20191124_120240-min.jpg
PEM cell with two oil chambers which connect to drierite chamber which goes to needle valve
20191124_121351-min.jpg
Two oil chambers just equalize no matter what
20191124_120312-min.jpg
Tube is hot glued to needle valve
Last edited by Joshua Turbyfill on Tue Nov 26, 2019 2:40 am, edited 1 time in total.

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Bob Reite
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Re: Deuterium electrolysis question

Post by Bob Reite » Sun Nov 24, 2019 10:20 pm

That operation is correct. The chamber with the three tubes will not displace oil unless the output from the PEM cell is greater than what is being dawn off through the needle valve.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.

Joshua Turbyfill
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Re: Fusor construction questions

Post by Joshua Turbyfill » Wed Nov 27, 2019 10:10 pm

Okay thank you Mr. Reite. Yeah after leaving the PEM cell on for 15 min or so it displaced all the oil.

Peter Schmelcher
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Re: Fusor construction questions

Post by Peter Schmelcher » Thu Nov 28, 2019 9:12 am

You might consider getting a gas dryer that could also double as a reservoir to isolate the cell. Make the gas in a batch and then later run and adjust the fusor and don't think about the gas generation. ebay item number 150382481448 (Supelco # 20619 Molecular Sieve Water Vapor Trap 200 cc).
-Peter

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Dennis P Brown
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Re: Fusor construction questions

Post by Dennis P Brown » Thu Nov 28, 2019 10:35 am

From posts by others that generate their deuterium from heavy water, they (and others here in the know) indicate that it is essential to use drying agents for the gas; otherwise, fusion will mostly fail.

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Mark Rowley
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Re: Fusor construction questions

Post by Mark Rowley » Thu Nov 28, 2019 4:10 pm

PEM cells appear to provide a comparatively dry product in relation to classic electrolysis so employing a drying segment in the system has not been necessary, at lest in my experience. Once learling how to drive my fusor, generating a bunch of neutrons has never been an issue. Additionally, I use the same method for both the Fusor and Pinch Tube. The pinch tube being much more susceptible to gas impurities would assuredly not work if the gas was wet. In the August 1958 issue of the Journal of Applied Physics, the article "Neutron Generation from Straight Pinches" stated this:

Effect of Impurities
The neutron yield was sensitive to the presence of impurities in the discharge. The addition of less than 0.2% of xenon, nitrogen, or air caused the yield to drop below a detectable level. The addition of approximately 5% helium or 10% hydrogen reduced the average yield of 3X 10 7 neutrons/discharge by about one-half.


The Fusor does not appear to be affected as much buy this. As a side note,I vaguely recall someone here on the group injecting heavy water into a fusor and generating neutrons. Definitely not the most efficient method and it's not something I'd recommend.

I've had excellent results by directly capturing PEM cell generated deuterium into a large 100ml syringe. It takes about 30 minutes to fill and can provide an hour plus of operation in a 2.75" system. It's very simple and effective. Additionally, it really does not add any extra time to the startup procedure. While initiating pump-down and heating the diff pump, I'll have the PEM generating a 100ml D2 charge. By the time I hit 1mTorr in the chamber, my D2 is ready to go.

Mark Rowley

Joshua Turbyfill
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Re: Fusor construction questions

Post by Joshua Turbyfill » Wed Dec 04, 2019 9:11 pm

Peter, thanks for the sieve idea. Right now I've got that third smaller chamber in the picture which is filled with drierite. Its good to hear the drier isnt necessary but I'll keep it just in case.

Joshua Turbyfill
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Re: Fusor construction questions

Post by Joshua Turbyfill » Fri Dec 06, 2019 10:47 pm

If e-4 torr acceptable for fusion? That's the lowest that I can get my chamber to. I originally was using used conflat gaskets so I swapped to new properly torqued down gaskets. Also I originally had 40" of kf16 tubing inbetween the pumps so I cut it down to 20". Neither of these made any difference in base vacuum.

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Richard Hull
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Re: Fusor construction questions

Post by Richard Hull » Fri Dec 06, 2019 11:32 pm

If it is a genuine 10e-4 torr, yes you can do fusion as a back fill to 10e-2 torr of deuterium is the norm.

Richard Hull
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Fusion is the energy of the future....and it always will be
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Joshua Turbyfill
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Re: Fusor construction questions

Post by Joshua Turbyfill » Sat Dec 07, 2019 1:28 am

Oh great. Thank you Mr. Hull.

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