I don't know what Paul's qualifications are, or if he's relying on authority, what those authorities might be. But his arguments are at least coherent, and ones we should consider carefully.Let me summarize why Polywell is unlikely to work, at least with p-11B.
First, you CANNOT have a near-neutral plasma in the central interaction zone. If you
do, then either the electrons there are hot -- in which case, bremsstrahlung
exceeds fusion power -- or the electrons are cold, in which case the power of electron
drag on the ions far exceeds fusion power. For intermediate electron temperatures,
both effects will occur.
(Rostoker and Monkhorst recognized this and got around it by having the
boron ions and electrons both at low energy; these highly charged ions dominate
the interaction with the electrons.)
So, you need to have a non-neutral plasma there. But this severely limits
current density, due to the space charge limit. To get around this limit,
you need to focus the ions down to an extremely high density central peak
(the total power will scale as 1/r, where r is the diameter of the central
space-charge limited reaction zone).
But even slight lateral velocity will mean the ions miss this peak.
In particular, Ligon's notion that collisions out at the turn-around
point 'anneal' the distribution (never mind that getting one entropy-creating
process to cancel out another entropy-creating process doesn't make
sense thermodynamically) cannot then work, since collisions there will
add angular momentum to the ion orbits, causing them to miss the central
peak and take them out of the game.
In practice, non-uniformity of the Polywell configuration would prevent
any fine focusing of ions into the center to begin with.
Anybody have any thoughts on these objections?