Reply To: Newbie pB11 Fuel Questions

[Ivy Matt]

I’d think neutrons would be preferable to gamma rays. You’re probably thinking of a couple of threads on Talk Polywell, here and here. The reaction under consideration was the p+N15 reaction. The advantage of the reaction is that it uses nitrogen, which is plentiful and gaseous at room temperature. The output is a C12 and a He4 ion, with a total of 5.0 MeV, as compared with 8.7 MeV from p+B11. As nitrogen is plentiful in the atmosphere it seems like a good candidate for a SSTO vehicle. The disadvantages of the p+N15 reaction are that it is more difficult to achieve than p+B11 (but see the next paragraph) and produces somewhat less energy. However, if net power from p+B11 fusion is possible, net power from p+N15 may not be far behind. Another disadvantage of p+N15 fusion is sort of the mirror opposite of a disadvantage of p+B11 fusion (using decaborane, at least). Whereas the input of the p+B11 reaction (decaborane) is solid at room temperature, an output of the p+N15 reaction (C12) is a solid at room temperature and would tend to coat the walls of the vacuum chamber in an ordinary fusion device. In a plasma focus device I imagine most, if not all, of the carbon would end up in the tube containing the coils and possibly on the coils themselves. But that would be an engineering problem….

Regarding D+D fusion, my understanding is that, according to Lerner’s theory, fusion is actually easier with heavier gases in this particular device, so there’s no reason to go with lighter elements that produce more neutronic reactions.

A p+B11 reactor will still need neutron shielding, but the neutrons are short-lived and will decay soon after the reactor is shut down, making maintenance of the reactor relatively safe and obviating the need for long-term storage of spent reactor materials.

I’m with James. I would expect all positive ions within the plasmoid to be expelled in the beam, but the high-energy alpha particles are the most interesting for generating electricity.

I believe I read somewhere on these forums about an experiment in which two plasma focus devices being pointed at each other, but I don’t recall if there were any interesting results. I don’t think LPP is currently looking into it.

Regarding the fuel for Focus Fusion, LPP is considering decaborane (B10H14), which is a solid at room temperature. I’m not sure where they get the B11 from…by enriching decaborane, maybe? There are other boranes that are gases at room temperature but, as boranes are toxic, they would prefer to work with one that is a solid at room temperature, as solids don’t tend to sneak up on you the way gases do.

As to what separates FF-1 from other plasma focus devices, I would say the main difference is that Eric Lerner has a theory for how fusion could work in a plasma focus device and, on a physical level, FF-1 is a small, high-voltage plasma focus device. Other plasma focus devices are either large and high-voltage or small and low-voltage. According to Lerner’s theory the combination of small size and high voltage should produce the best environment for nuclear fusion.