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.
To error is human... and I'm very human.