D Tibbets wrote:
Concerning the potential well depth. By thinking of gas behavior I might have a better handle on the relationship. The ideal gas law (and plasma is an ionized gas) is PV= NkT or PV= nRT. The pressure is dependant on the density (n) and the temperature (T). The voltage (or eV)substitutes for the temperature. You can have a hot gas or a cold gas in a container. The number of particles can be constant but the temperature and resultant pressure can be different. In a Polywell you can have the same number of ions, but at 100 eV not much will happen. But the same number of ions at 80,000 eV is much more interesting....
i think in a polywell, PV=nRT is not exactly an accurate formula as the T refers to entropy of particles travelling random walks - a chaotic mess of billard balls, essentially. the P comes from the electromagnetic force per unit area that the billard balls, through their bouncing around, apply against a surface.
in a polywell, however, you don't have that kind of thermalization. you have two completely independent components: radial and axial. and while your radial "temperature" is very high if you measure it in terms of KE and forget about how "thermalized" it may or may not be. your axial "temperature" - as in the mean axial KE of particles - is very low. and so, thus, too, is the absolute variance of the axial component of the KE.
so now you have a very non-thermal system, and when talking about pressure you're a lot better off going down to first principles and realizing here you're just talking about the outward radial electromagnetic force of the ions against a spherical surface. now as far as magnetic flux goes, since their inertia is almost all tangential to the surface, there's virtually no magnetic flux from the ions. so now we're electrostatic and electrodynamic, i.e. voltage and current. and current is from voltage difference and em-field, and the ions reactions to em-fields is negligable compared to that of voltage, so we can disregard that component, leaving only voltage to determine current. .... long story short, as far as the ions are concerned, the pressure incident on a concentric surface is just the voltage flux through that surface.
as far as the electron temperature is concerned, well they're really cold in the center. so their electric pressure is pretty much the static electric field, which is pretty constant. the counterbalancing magnetic pressure is more complex to calculate directly. in any case if they're reaching electron densities higher than expected that is definitely good news. that means both that confinement is better than expected and that the well depth is higher than expected. and as ions are confined by the well, that also means ion density is higher than expected, and fusion yield is proportional to density squared.... so yeah, higher electron density = very good.
i'd fathom it's just both:
what i said in a prior post about harder to get electrons in a higher mag field.
they're running higher mag fields so now they need to scale up the electric current as well.
and in anycase means they're scaling up the mag field.