Fusor construction questions

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

Post by Joshua Turbyfill » Wed Jan 29, 2020 12:05 am

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 » Wed Jan 29, 2020 1:40 pm

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 » Wed Jan 29, 2020 9:42 pm

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

Joshua Turbyfill
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Re: Fusor construction questions

Post by Joshua Turbyfill » Fri Jan 31, 2020 3:36 pm

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 » Fri Jan 31, 2020 4:41 pm

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 » Fri Jan 31, 2020 5:23 pm

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

Joshua Turbyfill
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Re: Fusor construction questions

Post by Joshua Turbyfill » Fri Jan 31, 2020 6:32 pm

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 » Fri Jan 31, 2020 10:24 pm

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

Joshua Turbyfill
Posts: 46
Joined: Wed Jun 21, 2017 3:13 pm
Real name: Joshua Turbyfill

Re: Fusor construction questions

Post by Joshua Turbyfill » Sat Feb 01, 2020 2:00 am

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 663 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 » Sat Feb 01, 2020 4:25 am

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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