Rebuilding my fusor.
- Rich Gorski
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- Location: Illinois
Re: Rebuilding my fusor.
Here is some direct advice that might improve your vacuum system. Before I get into it let me say that it would be a much better option to search on Ebay for a good inexpensive vacuum chamber and rebuild from there with proper feedthroughs and fittings.
1. Using silicone to seal is not a good idea. For one thing it's hard to remove when you need to open up the chamber or remove things.
2. For the large top seal you might try an L shaped rubber o-ring such as used on greased bell jar systems. Make sure the metal edge of the chamber is nice and smooth. The problem will be finding one that fits your chamber diameter. Another option might be to use L shaped rubber cord stock that you cut yourself to the proper length. You will have to seal the ends together to form an o-ring. I think you can use super glue for this but you have to build a fixture so the ends are properly aligned. You can find L -shaped cord stock at McmasterCarr. Link below.
https://www.mcmaster.com/products/rubbe ... ~90-angle/
3. For the various feedthroughs and fittings use greased rubber o-ring instead of silicone. You might be able to find o-rings of proper size to fit under the shoulder of your fittings. If they are brass fittings you could also solder a brass washer on to make a flat shoulder for the o-ring. Solder seals are good for vacuum if they are done well and cleaned up of flux after. To seal on a cylindrical vessel the o-ring will have to have enough thickness so it can deform to the curved shape.
Your vacuum level of 2200 microns is poor. You need 50X better than this to reach the interesting pressure region where fusion might take place. At 2200 microns (~2 Torr) the MFP is so small (<< 1 mm) that the electric field has very little space to accelerate ions to fusion velocities before they collide with another molecule and loose kinetic energy.
Hope that helps.
Rich G.
1. Using silicone to seal is not a good idea. For one thing it's hard to remove when you need to open up the chamber or remove things.
2. For the large top seal you might try an L shaped rubber o-ring such as used on greased bell jar systems. Make sure the metal edge of the chamber is nice and smooth. The problem will be finding one that fits your chamber diameter. Another option might be to use L shaped rubber cord stock that you cut yourself to the proper length. You will have to seal the ends together to form an o-ring. I think you can use super glue for this but you have to build a fixture so the ends are properly aligned. You can find L -shaped cord stock at McmasterCarr. Link below.
https://www.mcmaster.com/products/rubbe ... ~90-angle/
3. For the various feedthroughs and fittings use greased rubber o-ring instead of silicone. You might be able to find o-rings of proper size to fit under the shoulder of your fittings. If they are brass fittings you could also solder a brass washer on to make a flat shoulder for the o-ring. Solder seals are good for vacuum if they are done well and cleaned up of flux after. To seal on a cylindrical vessel the o-ring will have to have enough thickness so it can deform to the curved shape.
Your vacuum level of 2200 microns is poor. You need 50X better than this to reach the interesting pressure region where fusion might take place. At 2200 microns (~2 Torr) the MFP is so small (<< 1 mm) that the electric field has very little space to accelerate ions to fusion velocities before they collide with another molecule and loose kinetic energy.
Hope that helps.
Rich G.
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Re: Rebuilding my fusor.
I know there are drawbacks to using silicone, but there are also some advantages to using it.
If the gasket gets warn or damaged, it can be repaired by simply applieing another layer.
I then sanded the rim of the chamber with 220 grit sandpaper to round the edges a bit and remove any scratches or nicks and polished it with 660.
Last edited by William_Estlick on Wed Jan 15, 2025 10:19 pm, edited 1 time in total.
"If you always do what you've always done, you'll always get what you've always gotten."
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-Henry Ford
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Re: Rebuilding my fusor.
12kv and air.
Even at 3181 microns and a 4" gap, you can see the glow discharge of a DC arc. The bottom electrode is the anode and the orange is the positive column.
The top electrode is the cathode and the purple plasma surounding the cathode is the negative glow. The negative glow consists of several layers, the aston dark space, cathode glow, cathode dark space and the negative glow.
This is what I am interested in and I will be focusing that negative glow on the point of 2 tungsten cathodes.
"By the way, don't tell Richard that I still have a leak, it seems to upset him."
But now I know where it is and I will fix it over the weekend.
Last edited by William_Estlick on Wed Jan 15, 2025 10:46 pm, edited 2 times in total.
"If you always do what you've always done, you'll always get what you've always gotten."
-Henry Ford
-Henry Ford
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Re: Rebuilding my fusor.
How are you attaching this scrap copper to the chamber? I wouldn't consider any method that doesn't form a solid, reliable connection. All it takes is for that scrap to slip off your chamber and suddenly the whole assembly will become a potential death trap.
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Re: Rebuilding my fusor.
I placed the chamber on top of the cooper with the points facing up. The chamber weighs about 8 lbs. and pushes down on the copper creating a solid but temporary bond.
When I place the chamber in the lead shielding, I will drill a hole and bolt the ground wire to it.
When I place the chamber in the lead shielding, I will drill a hole and bolt the ground wire to it.
"If you always do what you've always done, you'll always get what you've always gotten."
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Re: Rebuilding my fusor.
I'd reccomend that you ground your chamber in more than one place. This way the ground would be fail-safe and might save your life one day.
Cinar Kagan
Cinar Kagan
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Re: Rebuilding my fusor.
I do apreciate everyone's concern for safty.
"If you always do what you've always done, you'll always get what you've always gotten."
-Henry Ford
-Henry Ford
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Re: Rebuilding my fusor.
Cintering new cathodes.
"If you always do what you've always done, you'll always get what you've always gotten."
-Henry Ford
-Henry Ford
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Re: Rebuilding my fusor.
12kv and air.
"If you always do what you've always done, you'll always get what you've always gotten."
-Henry Ford
-Henry Ford
- Rich Feldman
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Re: Rebuilding my fusor.
Nice pictures. Where caption says 12 kV, is that measured voltage or NST nameplate voltage? Are you planning to measure current?
All models are wrong; some models are useful. -- George Box
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Re: Rebuilding my fusor.
Thanks, Rich.
It's the nameplate voltage.
I'm using 2 identical 12kv transformers with full bridge rectifiers in paralell.
It's the nameplate voltage.
I'm using 2 identical 12kv transformers with full bridge rectifiers in paralell.
"If you always do what you've always done, you'll always get what you've always gotten."
-Henry Ford
-Henry Ford
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Re: Rebuilding my fusor.
I now have a solid vacuum.
These are some of the images I took while pumping down the chamber.
I do have some stray voltage leaks, but nothing I can't fix with more splice tape.
11428 Microns
11250 Microns
8571 Microns
6915 Microns
6833 Microns
5796 Microns
5942 Microns
5423 Microns
3913 Microns
-----------------------------------
I should just make a video!
These are some of the images I took while pumping down the chamber.
I do have some stray voltage leaks, but nothing I can't fix with more splice tape.
11428 Microns
11250 Microns
8571 Microns
6915 Microns
6833 Microns
5796 Microns
5942 Microns
5423 Microns
3913 Microns
-----------------------------------
I should just make a video!
"If you always do what you've always done, you'll always get what you've always gotten."
-Henry Ford
-Henry Ford
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Re: Rebuilding my fusor.
I 'm setting up to video each run.
While I am videoing each run, I am going to measure the vacuum and any x-rays.
I will also measure the amperage used by the nst's in future runs.
"If you always do what you've always done, you'll always get what you've always gotten."
-Henry Ford
-Henry Ford
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Re: Rebuilding my fusor.
Can anyone tell me what the reading on my dosimeter means?
4141 Microns (+/-) of air.
Both 12kv NES transformers and4141 Microns (+/-) of air.
"If you always do what you've always done, you'll always get what you've always gotten."
-Henry Ford
-Henry Ford
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Re: Rebuilding my fusor.
This topic has 264 posts and is may be the most trivial meander to nowhere of any thread on this site.
It keeps appearing at the top of the active topics and is tiresome for those here for the advanced technical portion of the site.
Not trying to dis your work but you need to learn and think this through on your own. 264 questions and answers!!!! That is absurd to make everybody else do the thinking for you.
You are welcome to post a significant update if that occurs but these hand holding threads are over.
This thread is now locked.
It keeps appearing at the top of the active topics and is tiresome for those here for the advanced technical portion of the site.
Not trying to dis your work but you need to learn and think this through on your own. 264 questions and answers!!!! That is absurd to make everybody else do the thinking for you.
You are welcome to post a significant update if that occurs but these hand holding threads are over.
This thread is now locked.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS