Archived - Fusor II

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John Futter
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Re: Fusor II

Post by John Futter » Thu Apr 22, 2010 2:54 am

The Turbovac50's can run in any position
they are not maglevs, they run Barden SiN balled greased bearings.
I know, I have had lots of them apart fixing / cleaning them (all ex Ebay).

Anyway nice setup Roman

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Mike Beauford
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Re: Fusor II

Post by Mike Beauford » Thu Apr 22, 2010 11:47 am

Hi Roman,

I will add my appreciation to all the others regarding your setup. Are you going to add a MCA into the mix on your setup?

Mike Beauford
Mike Beauford

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Doug Coulter
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Re: Fusor II

Post by Doug Coulter » Thu Apr 22, 2010 12:17 pm

Nooooooo!

Don't flood fast, the rotor tips will burn up! That's at least one source of the evil noise -- sonic booms off the rotor tips.

I have some experience with this one. I have two pfeiffer pumps obtained new. If just let spin down in a good vacuum (which takes a long time) then they may have hit a minor acoustic resonance for a bit while doing that. After just one too-quick flooding, they are noisier due to imbalances created by uneven rotor tip wear -- an inrush accident is about the worst thing you can do to one -- and the resulting moan/howl is something you never want to hear even the first time -- and after once, never again.

If it's easy to hear how fast its slowing down -- you're doing it too fast. Takes most of my systems a few minutes to go from programmed speed to 25% of that (standby mode) at the fastest rate I dare do it. Takes maybe half an hour or more if the vacuum is good. These have some amazing bearings, and a heck of a lot of stored mechanical energy.

There is an astonishing amount of foot pounds of energy stored in a turbo rotor, even a little one, about like a car crash in a big one. Enough to be mechanically dangerous, tear out the mounting bolts etc on an inrush accident in some designs-- Pfeiffer literature is full of warnings about this. You can even wring off a bellows you use to keep vibrations away from the main tank -- easy. (I use one on the big turbo here and it makes things a lot happier re noise and vibration).

So in slowdown or shutdown -- do let in a bit of gas to save time, but you're already over the top if the pump is noisy at more than one resonant speed -- you're burning off rotor tips with frictional heat. Say stay below e-1 millibar for that process more or less. Even the normal running pressure of a fusor (esp if you turn off the backing pump) is plenty to get one stopped in reasonable time.

If I'm just going to go to bed anyway, I just let it happen in high vacuum, it gets done.

The very best place to vent is behind the turbo, assuming you have a turbo-drag pump. This lets the more robust drag part have nearly all the friction and heat, and it can take it much better. Even a pure turbo -- better to wear the rotor tips that matter least.
Why guess when you can know? Measure!

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Richard Hull
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Re: Fusor II

Post by Richard Hull » Thu Apr 22, 2010 2:07 pm

Very, very nice Roman. It's fusing and that is the bottom line.

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.

Linda Haile
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Re: Fusor II

Post by Linda Haile » Thu Apr 22, 2010 6:46 pm

I think you may have mis-understood me John.

I said these turbovacs will run in any orientation, but I wouldn't use a mag-lev in any position other than vertical.

I wouldn't buy a mag-lev from Ebay because there is no way of knowing if it has 'crash landed'.

BTW, Do you know if it is possible to rebuild a maglev that has crashed?

myID
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low Voltage Performance of fusor and "paintcan"

Post by myID » Tue Jun 01, 2010 1:22 pm

Dear all,

I finished my shadow cone shield (20cm Paraffin Block with channels for samples, 5cm highly borated Paraffin, 10mm Lead) and felt better about doing some tests.

The 2 He 3 tubes were both in a distance of 30cm to the center of the grid. The smaller one uses the paintcan setup, the bigger one was connected to my homebrew preamp and my NimBin and inserted in the Paraffin Block.
D2 was regulated with a needle valve, Turbo and forepump were running at full speed, Power came from the 1kW Bertan supply.
Chamber size is about 13cm x 13cm x 13cm, Grid dia 2.5cm.

The values for U and I are about +-1; vacuum values- perhaps in the ballpark..?
Runs were pretty stable for few minutes, I just had to regulate the gas flow a little some times.

I attached the table with the values. The NimBin failed due to missing shielding (I guess), the "Paintcan" performed admirably well!

Intersting observations:
Even at low accelerating voltage significant count rates!
No star mode evident- could be expected due to non symetric field in cubical chamber (?)
The (what I think) hot plasma zone looks more like a glowing disc- the videos I recorded are empty... Shoot...

I would advise everybody to use the "paintcan" approach- can not be more simple than this, Noise immunity is good, Background is low, reliable due to few parts:
Paraffin filled paintcan, He3 (B10, BF3) tube in the center, a MHV plug (SHV) in the lid, a cable to the meter... Every meter with adjustable (high enough) sensitivity and adjustanble(high enough) Bias should do.

Kind regards
Roman
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Steven Sesselmann
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Re: low Voltage Performance of fusor and "paintcan"

Post by Steven Sesselmann » Wed Jun 02, 2010 8:38 am

Roman,

Nice tidy experimental data, well done..

Do you have any idea what the TIER was during the runs?

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

Andreas Welzmüller
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Re: low Voltage Performance of fusor and "paintcan"

Post by Andreas Welzmüller » Fri Apr 15, 2011 11:54 am

Hello Roman,
Iam also a new guy who works on a fusor-project in Germany.
Is it possible to cantact you?
best regards
Andreas

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