Posted: Thu Apr 30, 2009 2:22 am
Yeah. What he said.
a discussion forum for Polywell fusion
https://www.talk-polywell.org/bb/
The issue is that there are electrons and ions, and they are mobile in the waffleball. So, as they transit that ball, so their density will increase as they all converge in the centre. Nothing to do with where the acceleration and/or charge regions are, this is just plain congestion of the particles on the surface of a sphere all passing down to a central focus.93143 wrote:It sounds like you've misunderstood the proposed geometry of the wiffleball. The idea of ions being accelerated towards a small central magnetically-confined electron-rich region, which they are initially outside, is wrong. That's what it sounds like you are describing.chrismb wrote:I'm certainly in no position to say yes or no, but the collisions are meant to happen mostly in the centre of the reaction voulme, and the free electrons constrained further to the interior (I thought). Why would ionisation happen more where the ion density is less, and further away from the region of slightly-over-net electrons?
Yes. That is quite true. But it is also true that for a globally-circulating system like this, assuming steady-state operation, the areas with the highest fractional residence time per pass will tend to have the highest particle density. Combine this with the inverse-square effect and you find that the density of the ions has two maxima - the edge region and the core.chrismb wrote: The issue is that there are electrons and ions, and they are mobile in the waffleball. So, as they transit that ball, so their density will increase as they all converge in the centre. Nothing to do with where the acceleration and/or charge regions are, this is just plain congestion of the particles on the surface of a sphere all passing down to a central focus.
No, I specifically noted that since the electrons are high-energy and radially-directed at the edge, they do NOT form a sheath; rather they penetrate deeply into the wiffleball. There may actually be two electron density maxima, now that I think about it; one at the edge of the virtual anode where the electrons are at their slowest (or rather slightly further in because of the inverse-square effect), and one at the centre. Perhaps this is related to the "multiple well" referenced in that Japanese paper I never bothered reading...?If the argument is now, also, that the electrons stay hanging around the edge and don't transit through the waffleball, then why would the ions at the edge head towards the centre when there is a locally higher negative charge at the edge? That seems to me to be just plain stretching the idea of 'space charge' far too far.