Any News about Polywell ?

[Axil]

Because neutrons make things radioactive, and alphas don't.

not to mention direct conversion means much less machinery, which means fewer people, and less noise--noise is important for navies who have to worry about subs.

Alphas impact has a cross section for neutron production with elements with Z less than or equal to Z=19: air, boron, nitrogen etc. Expect neutron activation.

[EricF]

Because neutrons make things radioactive, and alphas don't.

not to mention direct conversion means much less machinery, which means fewer people, and less noise--noise is important for navies who have to worry about subs.

Alphas impact has a cross section for neutron production with elements with Z less than or equal to Z=19: air, boron, nitrogen etc. Expect neutron activation.

I'm no scientist, but is the reaction not occuring in a vaccuum? And by the time the alpha particle impacts anything, even if it is the wall of the vaccuum chamber, its velocity will be so drastically reduced as it drives the current of the transformer (in essense giving up energy), that it won't have the energy required to fuse with anything, thus producing no neutrons?

[kunkmiester]

I do recall with your post, that there was expected to be some neutron radiation. It was supposed to be something like .1% or less of the total energy output though, due to the low probability of whatever it is that makes them.

I think it was mentioned on a thread on other reactions. There's a proton-nitrogen reaction, though I forget the isotope, but supposedly the energies involved kill any chance for neutrons or gammas. While boron might be used for almost everything, things like space launch might use it, since while it takes a bigger well to make it happen, there's no gamma or neutrons, meaning you're saving hundreds of tons on shielding.

[Axil]

Because neutrons make things radioactive, and alphas don't.

not to mention direct conversion means much less machinery, which means fewer people, and less noise--noise is important for navies who have to worry about subs.

Alphas impact has a cross section for neutron production with elements with Z less than or equal to Z=19: air, boron, nitrogen etc. Expect neutron activation.

I'm no scientist, but is the reaction not occuring in a vaccuum? And by the time the alpha particle impacts anything, even if it is the wall of the vaccuum chamber, its velocity will be so drastically reduced as it drives the current of the transformer (in essense giving up energy), that it won't have the energy required to fuse with anything, thus producing no neutrons?

Is a perfect vacuum possible? Do electrons and alphas combine to form helium in the reaction chamber? How about hydrogen and boron? Do they preclude a vacuum? How long does it take to clear these elements to a vacuum between shots?

[Axil]

“meaning you're saving hundreds of tons on shielding.”

Concrete and dirt are cheap.

[EricF]

Because neutrons make things radioactive, and alphas don't.

not to mention direct conversion means much less machinery, which means fewer people, and less noise--noise is important for navies who have to worry about subs.

Alphas impact has a cross section for neutron production with elements with Z less than or equal to Z=19: air, boron, nitrogen etc. Expect neutron activation.

I'm no scientist, but is the reaction not occuring in a vaccuum? And by the time the alpha particle impacts anything, even if it is the wall of the vaccuum chamber, its velocity will be so drastically reduced as it drives the current of the transformer (in essense giving up energy), that it won't have the energy required to fuse with anything, thus producing no neutrons?

Is a perfect vacuum possible? Do electrons and alphas combine to form helium in the reaction chamber? How about hydrogen and boron? Do they preclude a vacuum? How long does it take to clear these elements to a vacuum between shots?

Cheesy poofs.

[kunkmiester]

Concrete and dirt are cheap.

Reread my post. I was referring to weight sensitive operations for N+H

[krenshala]

Is a perfect vacuum possible? Do electrons and alphas combine to form helium in the reaction chamber? How about hydrogen and boron? Do they preclude a vacuum? How long does it take to clear these elements to a vacuum between shots?

Everything I've read here indicates they are going to be going for a steady-state system/machine, so it won't have "shots" ... it will be on, with a pump pulling out the He-ash while the ion/proton/e- guns feed and maintain the reaction. I seem to recall someone stating it shouldn't be too difficult to maintain the required level of vacuum even with a steady production of Helium due to steady-state fusion.

[ladajo]

Yes, the ultimate goal is a steady state machine.
However, lets first see that WB8 operates as predicted. And if we are lucky, WB8.1.
If I know anything about navy contracting, a=>b=>c etc. They will not parallel path this. Especially with Gates breathing down everyone's necks about costs.

Speaking of costs (good add for the Wiki TallDave):

http://www.governmentcontractswon.com/d ... .asp?yr=09

Govt Contracts (Defense) - Count/$ Dollar Amount
2009 6/$4,139,677
2008 1/$0
2007 1/$1,750,000
2006 0/$0
2005 1/$885,000
2004 1/$485,708
2003 2/$3,837,350
2002 1/$18,250,000
2001 1/$1,793,000
2000 1/$2,500,000


And, does anyone have this video?:

Bussard presented more of his thoughts on the potential world impact of fusion power at a Yahoo! Tech Talk on April 10, 2007.

The video is only available internally for Yahoo employees.

from: http://www.museumstuff.com/learn/topics ... orporation

[D Tibbets]

Several clarifications on the previous page of posts (based on my expertise ... er informed knowledge... er guesses )

The alpha particle energy in the PB11 reaction is divided between three separate particles, ~ 2.5 MeV each. Once slowed down an alpha particle is nothing but a fully ionized helium ion, like in a neon (er... helium) glow lamp.

I believe maintaining adequate vacuum levels in a production Polywell will be a challenging engeenering issue.

Someone's estimate for the neutron production in a PB11 Polywell was, I believe, ~ 1 part in ~ 50,000,000 or ~ 0.00005%. This assumed isotopically pure hydrogen, no 1 part per 6000 of naturally occurring deuterium. I believe that a greater radiation concern was the estimate of 1 gamma ray produced in one side reaction per ~ 10,000 main reactions. I've never seen what this reaction actually is.

Nitrogen15 reacts with a hydrogen to produce an alpha and a Carbon12, part of the CNO fusion cycle. Nitrogen15 makes up about 0.3% of natural nitrogen. This is one of the fastest reactions in the CNO reaction cycle. While I am uncertain, it may not be far behind the D-D reaction at high energies. I've seen one estimate of the CNO reaction being ~ 1% as fast as D-D fusion at several hundred thousand eV. Since the initial P-C12 reaction and several other steps in the CNO cycle are ~ 2 orders of magnitude slower than P-N15, this should place the P-N15 reaction close to the D-D reaction rate. In this case, the P-N15 reaction might be compared to the P-B11 reaction. The problems would be that the P-N15 reaction rate might be ~ 1/10th of the P-B11 reaction rate, Nitrogen has an even higher Z (more Bremsstrulung) and the isotopic purification would presumably be more difficult. Still, the idea of powering an advanced Polywell with air is intriging. I first learned to appreciate this possibility from a ChrisMB post.

Lets see, taking hydrogen from water, or humidity in the air; and purified Nitrogen15 from the air for fuel. ~ 350 liters of air would provide ~ 1 liter of nitrogen15 gas. At STP that would be ~ 1/22 moles or ~ 1.3 g of nitrogen15 gas (N2 gas). Assumeing a 10^6 power benifit over coal, would be equivalent of ~ 1300 kg of coal or oil. Of course the actual gain would depend on the magnitude of the positive Q that would be needed.
Even if you processed all of the Earth's atmospheric nitrogen to feed the power beast, you would have deprived the atmosphere of only ~ 0.3% of its nitrogen content. No major impact could be claimed on the environment. Besides for each nitrogen15 isotope consumed, a helium would be produced, there would be no direct change in the atmospheric density. Hydrogen is of course inexhaustible, in comparison to nitrogen15, Boron11, lithium, etc.

Dan Tibbets

[BenTC]

“meaning you're saving hundreds of tons on shielding.”

Concrete and dirt are cheap.

Not for a ship.

[MSimon]

And, does anyone have this video?:

I never saw that one.

[WizWom]

100 MW is 6x10^27 eV/sec; 7x10^19 p-B11 fusions per second. That's 1/100th a mole.
That is a really, really tiny amount of material.
Because the whiffle-ball effect is not perfect, what will be happening is hydrogen, boron and a teensy tiny amount of helium will all have to be collected, separated, and the hydrogen and boron recirculated. You can't really make a scavenger for only helium.

[D Tibbets]

That analysis ignores the relative confinement of the ions. The alpha might make ~ 1000 passes before it escapes (that is ~ 1000 passes at KE of ~ 2.5 MeV, or a speed ~ 5-10 times as fast as the fuel ions). So, a fuel ion might last 1,000,000 passes (or more) at ~1/10 the speed of the alphas, or last ~ 10,000,000 times as long as the fusion alphas. So, if you have ~ 10^20 alphas being produced per second, the fuel ions escaping would be ~ 10^13 ions per second. Actually, if the fuel ion density was ~ 10^22 fuel ions per m^3, ( the ion loss rate / alpha production (escape) rate would be ~ 1/10^5. Still alpha particle escape flows would exceed the fuel ion leakage rate by a factor of ~ 100,000. With this estimate the ion leakage rate is insignificant. Probably of more concern is the rate of recombination, neutral losses. At the voltages for PB11 reactions I suspect this number would be quite small, but compared to the fuel ion leak rate, it may be significant. Most if not almost all fuel ions would fuse before they managed to escape. In any case the loss of fuel would be irrelevent. What would be a concern would how this flow effected the pressure outside the magrid and subsequent arcing concerns. The slowed, and neutralized alphas would still be in the vast majority outside the magrid.They and the escaped electrons probably are the limiting factors that contribute to arcing if the vacuum pumping cannot keep up (this assumes outgassing and sputtering are not a problem).

The fusion products of D-D fusion are more problematical, as the high speed escaping He3 and Tritium might be worthwhile to recover and reuse as additional fuel. Also, the tritium is radioactive, and probably cannot be simply vented to the air.

Dan Tibbets

[KitemanSA]

They will not parallel path this. Especially with Gates breathing down everyone's necks about costs.

Govt Contracts (Defense) - Count/$ Dollar Amount
2009 6/$4,139,677

Your web site was wrong. There were two awards, the first of about $300k and the second totaling $7,855,504.00. The $4M above looks more like the option for WB8.1.

And Gates shouldn't have anything to do with this money per se. This is Recovery Act money, not DoD money.