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Subject Re: IEEE Spectrum item: "Physics Projects Deflate for Lack of Helium-3"
Posted by Steven Sesselmann on 2010-09-02 07:33
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Chris,
Nothing to panic about....
Let me see, if all the guys in the forum (let's say 100) run their fusors 24 hours a day 365 days a year at 10e6 n/s then it would take how many years to make a litre of 3He?
(1 x 10^23) / [ (1 x 10^2) * (1 x 10^6 neutrons) * (3.2 x 10^7 seconds)] = ~ 31,250,000 years
Could come in handy if national security is still aproblem.
Steven |
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Subject Re: IEEE Spectrum item: "Physics Projects Deflate for Lack of Helium-3"
Posted by Steven Hosemans on 2010-09-02 18:42
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I'll give them the decay product if they let me look after some Tritium. 
Steve |
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Subject Re: IEEE Spectrum item: "Physics Projects Deflate for Lack of Helium-3"
Posted by bill fain on 2010-09-02 19:50
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| You would think that if they could find all those ten thousand plus tritium exit signs that Walmart "lost", they would have plenty. -bill |
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Subject Re: IEEE Spectrum item: "Physics Projects Deflate for Lack of Helium-3"
Posted by Richard Hull on 2010-09-03 09:54
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I'm glad I loaded up on spare 3He toobz early in this biz.
What is this sillycon-boron sensor? Is it as good as 3He in detection of smuggled nuke product? I would be stunned if it was. I thought BF3 was number two in neutron detection. It is certainly one of the oldest rather sensitive detectors.
Oh well, caught short again. No one saw this coming in the guv'ment?!
I'll bet there is no more D-3He burnin' in the U of W fusor! I seem to remember posting a quoted price from spectra gases some years ago when some here were eager to give it a whirl. I'll have to look for that post. It was high, naturally, but it seems 20 liters might have been under $3,000.00. In this new light I have ammended my old 2003 FAQ posting on fusion reactions.
http://www.fusor.net/board/view.php?bn=fusor_theory&bn=fusor_theory&key=1044561975
Also, Someone here told me at one of my HEAS conferences that he had stumbled onto a large cylinder of He3 and had it in his possesion!!!! My old ossified brain strains to remember.
Similarly, I hold about 1.5 kilos of elemental thallium in my lab. The stuff was last heard by me in 2008 going for $5100.00/ kilo!!! It seems no one wants to make much of the stuff anymore.
Richard Hull |
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Subject Re: IEEE Spectrum item: "Physics Projects Deflate for Lack of Helium-3"
Posted by Chris Bradley on 2010-09-03 11:15
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I luuv the comment at the end of that piece Bill references;
"Ontario Hydro also stated that it would cost $1 billion to lower tritium emissions to the level recommended by Ontario’s Advisory Committee on Environmental Standards, and in the end, no official action was taken."
..surely a take on Homer Simpson "If something's hard to do then it's not worth doing"? |
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Subject Re: IEEE Spectrum item: "Physics Projects Deflate for Lack of Helium-3"
Posted by Doug Coulter on 2010-09-03 12:09
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It's not worth it unless you're the DHS spending our money for "security theatre", which is the proximate cause of the shortage, along with the lowered production of nuclear weapons material. And then CERN needing lots for their helium dilution super cold cryo stuff.
For what it's worth, we here have tried all of
3He,
BF3
B10 lined tubes
Plastic scintillator and photo tube
And every single one is plenty sensitive for fusor work. Some not so good at detecting low rates of spontaneous fission as 3 He, but I'm not doing that, I'm doing fusors, and all of the above work just dandy. 3He to the point of near saturation (or real hard saturation in pulses) of the tubes, I have to "numb" mine down to make it useful!
So unless you're running He dilution cryo, have no tears -- you're going to be just fine.
Even those old B10 tubes counted really fast in a good moderator near my fusor -- too fast for good audio use. |
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Subject Re: IEEE Spectrum item: "Physics Projects Deflate for Lack of Helium-3"
Posted by Doug Coulter on 2010-09-06 21:37
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I just kludged up the simplest imaginable circuit for a B10 tube and got it working tonight, using my fusor as the source of neutrons. It worked fine with both of the tubes I have (anyone want to sell me more of these?).
Simple -- CCFL inverter a 12v in, 1kv out one, volt doubler using some fast diodes and the input cap it had on it, with a .01 output cap, 100k and another cap for final filtering. 100k resistor to the tube, and a .01 u cap to couple to the negative input of a tlo84 opamp (which shouldn't be fast enough, but is).
Used a 10 meg feedback resistor and another in the + input to ground, bypassed. It gives .5 to 5v output pulses, enough to drive a transistor base for counting the pulses, no fancy threshold etc needed. The circuit makes maybe 200-300mv noise pulses with a hot piece of ore sitting on the tube, and a foot from the fusor counts maybe a couple hundred counts/second.
The only big issue here is good noise shielding -- that power supply radiates quite a lot of 43 khz right next to a high impedance input. A little copper box works well for it.
So there's your answer to the lack of 3He.....and a cheap one.
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(Doug Coulter)