2D Polywell SIM

ladajo · Post by **ladajo** » Wed Dec 16, 2009 11:12 pm

And another popup I hadn't seen...

http://fti.neep.wisc.edu/static/TALKS/1 ... elroge.pdf

Edit: Corrected link...

alexjrgreen · Post by **alexjrgreen** » Wed Dec 16, 2009 11:20 pm

Also: PIC Simulation of Polywell

If Art is watching, perhaps he'd like to comment.

TallDave · Post by **TallDave** » Thu Dec 17, 2009 3:50 am

At steady state, the total electron count is about 2X the total ion count.
The densities of electrons and ions are equal inside the electrostatic potential well.
About the same number of electrons are trapped in cusps outside the central core as
there are inside the well, giving rise to the 2X overall difference in count.

Interesting.

Also:

Loss currents on tank walls:
Ions 0A, Electrons -30A

ladajo · Post by **ladajo** » Thu Dec 17, 2009 9:08 pm

I predicted before this will be Famulus's limiting factor once he puts his magrid in his chamber, the <oscillating> e-'s from the spikeyball (I will never get tired of calling it that) will need some space. I don't think his existing chamber is big enough.

Betruger · Post by **Betruger** » Thu Dec 17, 2009 9:12 pm

Didn't he sell the big chamber he intended to use for his polywell?

Giorgio · Post by **Giorgio** » Fri Dec 18, 2009 7:03 am

Yes, he did sell the big one he bought first as it was too much big for the vacuum pump he had.

Solo · Post by **Solo** » Fri Dec 18, 2009 4:02 pm

Here's the trouble with that simulation: if you notice, the electron density is about twice the ion density. That means the thing is nonneutral, and therefore the density is ridiculously low. This equilibrium can't be useful for fusion, nor can it reflect what's going on in Dr. Nebel's lab.

D Tibbets · Post by **D Tibbets** » Fri Dec 18, 2009 5:31 pm

Solo wrote:Here's the trouble with that simulation: if you notice, the electron density is about twice the ion density. That means the thing is nonneutral, and therefore the density is ridiculously low. This equilibrium can't be useful for fusion, nor can it reflect what's going on in Dr. Nebel's lab.

Twice the electrons overall, but near equal concentrations in the region where the ions dwell. I don't know if this was an assumption or if it fell out of his simulations but it makes sense. The ions are electrostatically contained by a similar number of electrons (greater by ~ 1ppm). But because of the cusp holes outside the area where the ions reside, the electrons are streaming out (and 9/10 streaming back in) and this population of electrons is ~ equal to those inside of the cusps. I believe this would represent qusineutrality inside the WB proper, but not in the cusps, thus the cusps are not ambipolar. I don't know whether this is an assumption or a derivation.

Assuming WB 7.1 had ion guns, I think the relative currents of the electron guns and the ion guns would tell the story (if such measurements were possible in the brief runs). I understand the limiting time factor in WB6 testing was due to the impercise gass puffers and subsequent arcing. With ion guns WB7.1 might have run at beta=1 for significantly longer times (a few milliseconds?).

Dan Tibbets

krenshala · Post by **krenshala** » Wed Dec 30, 2009 2:12 am

From a geometric view, having half the total electron population "divided" between 14 locations (the face and corner cusps) and the other half effectively concentrated in the center could also help explain why (more) ions are not lost through the cusps -- the well would be 14 times stronger negative potential than any individual cusp from the point of view of individual ions.

Robthebob · Post by **Robthebob** » Fri Jan 01, 2010 2:46 pm

why dont you guys ask Dr. Rogers. Try to see if you can get in contact with him, or is he part of Dr. Nebel's group?

MSimon · Post by **MSimon** » Fri Jan 01, 2010 6:50 pm

Robthebob wrote:why dont you guys ask Dr. Rogers. Try to see if you can get in contact with him, or is he part of Dr. Nebel's group?

Dr. Rogers is in contact with Dr. Nebel but is not constrained by him. He is very good re: answering questions if you contact him.

TallDave · Post by **TallDave** » Sun Jan 03, 2010 5:53 pm

Thanks Simon, I was already drafting something but wasn't sure we'd get a reply.