Fusor construction questions

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

Post by Joshua Turbyfill »

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?
PEM cell with two oil chambers which connect to drierite chamber which goes to needle valve
PEM cell with two oil chambers which connect to drierite chamber which goes to needle valve
Two oil chambers just equalize no matter what
Two oil chambers just equalize no matter what
Tube is hot glued to needle valve
Tube is hot glued to needle valve
Last edited by Joshua Turbyfill on Mon Nov 25, 2019 9:40 pm, edited 1 time in total.
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Bob Reite
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Re: Deuterium electrolysis question

Post by Bob Reite »

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 »

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 »

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 »

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 »

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 »

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 »

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 »

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
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Fusor construction questions

Post by Joshua Turbyfill »

Oh great. Thank you Mr. Hull.
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Re: Fusor construction questions

Post by Joshua Turbyfill »

Should I turn off my backing pump when its still connected to the pumped down chamber and then open it up to atmosphere once its off or do I open it up to atmosphere and then turn it off? I've been doing the latter but after a couple times the pump now hums for a couple of seconds after I turn it on before it starts pumping down so I don't know if I may have damaged it. Funny enough its now pumping far lower than before.
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Dennis P Brown
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Re: Fusor construction questions

Post by Dennis P Brown »

For oil vane pumps, open to atmosphere isn't a big deal for short periods. Some (minor) amount of oil will be lost via misting. However, this isn't unlike a bleed air vent to remove trapped water vapor from a pump. Since your vacuum quality improved, that is/was a likely issue. So, you might want to preform that (the bleed valve for that purpose) from time to time.
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Richard Hull
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Re: Fusor construction questions

Post by Richard Hull »

Good vacuum practice is all about valves....Good valves. A valve should isolate the mechanical pump from the for line. bleed valve might be between the pump foreline valve to obviate the suck back issue.
Close the big foreline valve first. turn off the mechanical pump and immediately open the bleed valve to let the pump up to air. then immediately close the bleed valve. It is important to never let the working mechanical pump draw in outside air, unless you have to let your entire system up to air. (as in repairs, changes or additions to the vacuum system). Once you have a good system down to vacuum keep it there, via valving. when shutting down only let the mechanical pump up to air.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Joshua Turbyfill
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Re: Fusor construction questions

Post by Joshua Turbyfill »

Im somewhat confused.

My shutdown procedure is:
shutdown_diagram.png
1. Turn off turbo pump and wait for it to stop spinning
2. Close ball valve and then open turbo's bleed valve to put chamber back to atmosphere
3. Open KF16 connection to let air into the backing pump and immediately after turnoff backing pump

I read somewhere that you dont want to turn off the backing pump when the inlet is at vacuum because it will suck oil into the chamber.

Is this setup & procedure good or is it flawed?

Thanks
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Dennis P Brown
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Re: Fusor construction questions

Post by Dennis P Brown »

That method is fine.

One point: Unless you need to access the fusor, keeping it under vacuum (ball valve closed; turbo off) is a good idea. Far less water vapor introduced into the fusor chamber.
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Richard Hull
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Re: Fusor construction questions

Post by Richard Hull »

If you are planning to do fusion. You will need a superlative bellows high vacuum valve between the turbo and your chamber. your procedure is great. once the ball valve is closed you must then turn off the mechanical pump and within seconds open the KF fitting to air to avoid suck back. then refit the KF fitting. your HV line is still under vacuum and your mechanical pump is up to air. This is how I do it. suck back is not instantaneous.

Question........did you ever look at the FAQ in the vacuum forum that was so very important that I labeled it number one? You will note two valves are demanded at minimum for a successful fusor system. You cannot control a system without a valve between the turbo or diff pump and the fusor.

viewtopic.php?f=25&t=9291

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Joshua Turbyfill
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Re: Fusor construction questions

Post by Joshua Turbyfill »

I didn't want to have to a buy an 8" conflat gate valve as those run over $1000. Is fusion totally impossible without one? I do have the turbo throttled down to 20% power if that helps any.
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Richard Hull
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Re: Fusor construction questions

Post by Richard Hull »

You will have extreme issues it you turbo has an 8" throat. I assume you have an 8" conflat flange on your fusor chamber as well. I find it difficult to imagine a worse situation for gobbling up Deuterium at a prodigious rate.
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Joshua Turbyfill
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Re: Fusor construction questions

Post by Joshua Turbyfill »

Yeah it blows through the deuterium that it took the PEM cell an hour to make in about 30 seconds.

I do have a 2.75" bellows valve and a 2.75" conflat 5 way cross. So I could essentially build a 2.75" fusor and connect it to the main chamber via said bellows valve.
fusor2_diagram.png
fusor2_diagram.png (16.67 KiB) Viewed 5327 times
Will this work or could I just lay a plate of aluminum on top of the turbo's inlet shield to block gas?
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Richard Hull
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Re: Fusor construction questions

Post by Richard Hull »

A good bit better. An 8" throat on a turbo pump means it is a very serious pump and very aggressive devourer of air or deuterium.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Joshua Turbyfill
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Re: Fusor construction questions

Post by Joshua Turbyfill »

Okay I'll build that then. I read in one of the faq's that arcing can be an issue. I have a thick copper wire wrapped around the main 8" cross which goes straight to ground on a wall outlet. Is there any risk of arcing destroying any of the equipment (Turbo, turbo controller, vacuum gauge, etc)? Also is there anything else I need to know before operating a 2.75" fusor?

Currently I've got a table about 12' from the fusor which has the variac for voltage control, a laptop for neutron monitoring, and a big screen showing 4 different cameras mounted on the reactor. I was intending to remotely operate it. Since the needle valve which admits deuterium and the bellows valve are manually operated, will I need to run the fusor standing next to it?
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Richard Hull
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Re: Fusor construction questions

Post by Richard Hull »

Wrap no bare wire around the cross for a Ground!! A proper ground is a copper tab or solder lug with a hole the size of one of the bolt threads placed under the bolt head and torqued down as part of a flange within the cross end plates. A wire is then secured to the copper lug mechanically and then soldered to it. This and this alone, is now a proper ground connection to the chamber. It may then be taken to a star point ground and the star point then connected to the mains ground.

The star point ground is explain in the power wsupply forum FAQ's.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Joshua Turbyfill
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Re: Fusor construction questions

Post by Joshua Turbyfill »

I'll change that then. Heres the new fusor. What do yall think?
20200202_154636-min.jpg
20200202_154610-min.jpg
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Richard Hull
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Re: Fusor construction questions

Post by Richard Hull »

Beautiful and very impressive. We look forward to reports on operation.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
ian_krase
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Re: Fusor construction questions

Post by ian_krase »

Looks pretty impressive.

Have never seen a fusor wearing a crucifix before, even if I did pray the rosary during pumpdown.
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