Carlson and Nebel

Discuss how polywell fusion works; share theoretical questions and answers.

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scareduck
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Post by scareduck »

Not that I have a brain cell to squeeze between these two, but it seems to me this is a first-order problem.tonybarry is right, this should be double-checked independently. It also seems to me that neutrons out of the WB-6 should be pretty compelling evidence that ions aren't wandering aimlessly.

pstudier
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Post by pstudier »

scareduck wrote:It also seems to me that neutrons out of the WB-6 should be pretty compelling evidence that ions aren't wandering aimlessly.
A billion neutrons are not very impressive. From http://en.wikipedia.org/wiki/Polywell

Despite initial difficulties in spherical electron confinement, at the time of the 2005 research project's termination, Bussard had reported a neutron rate of 109 per second running D-D fusion reactions at only 12.5 kV (based on detection of three neutrons per test,[6] giving a wide confidence interval). He claimed that the fusion rate achieved by WB-6 is roughly 100,000 times greater than that Farnsworth managed to achieve at similar well depth and drive conditions.[7][8] Researchers at the University of Wisconsin-Madison have also claimed a neutron rate of up to 5x109 per second at voltages of 120 kV with a electrostatic fusor without magnetic fields.[9]

Commercial pulsed neutron generators can generate 3E10 neutrons/second, and a peak rate of 4E14 neutrons/second for 800 microseconds, although I believe this is D-T instead of D-D. See http://www.sciner.com/Neutron/index.htm
Fusion is easy, but break even is horrendous.

Tom Ligon
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Post by Tom Ligon »

At 10 keV?

scareduck
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Post by scareduck »

Tom Ligon wrote:At 10 keV?
Yes, exactly. The claim above is that it wouldn't work at all.

pstudier
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Post by pstudier »

Tom Ligon wrote:At 10 keV?
I don't have the specific voltage for that model, but the website says typically they are 80-180 Kev. They are simple accelerators with metal hydride targets, so it is much more likely that the accelerated hydrogen hits the metal rather than the hydrogen in the target. Of course, there is no confinement. The hydrogen atom hits the target and slows down real fast.

The power consumption is 500 watts. 3E10 neutrons/sec x 14Mev/neutron x 1.6E-13 watt-sec/Mev = 0.07 watts, or a total system heat out/energy in of 0.00014 if I didn't goof. How does this compare with the polywell? I don't know off hand what its input power was.
Fusion is easy, but break even is horrendous.

Tom Ligon
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Post by Tom Ligon »

I've run my own fusor at 10 kV and it doesn't do squat. It must be doing a little fusion, but I could never pick it out of the background, even with half-hour runs. It needs to get up to 18 kV before the signal is really clear. At that point I was calculating about 3000 DD fusions a second from the observed counts on two counters, a count every 1-2 seconds, with the counters maybe 30 cm from the center of the fusor.

More intriguing, although the counting statistic (1) was unusable, was the run they did at 5 keV well depth which apparently made d-d fusion (keep in mind there should be substantial opportunity for head-on collisions in the radial ion paths ... the star mode, if you will). If that machine had been able to run for a second at 130 kV, I'm not sure the team would have lived to write it up.

The fusion rate on WB6 for the power consumed would have been hideously bad. The fuel efficiency on the first internal combustion engine would have been pretty bad, too.

I'm personally content to see what the EMC2 team can report when peer review is done. What I do know is a number of people at LANL are looking at this, and they seem pretty darned hopeful considering their background. This program will get a fair look from competent people, and we'll see where it goes from there.

StevePoling
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vacuum tube lore vs numeric simulations

Post by StevePoling »

tonybarry wrote:With all due respect to Indrek, we must firstly establish the correctness of this model before making decisions based on it. Indrek's work relies wholly on numerical simulation and not on experimental results, therefore it is within the realm where people remote from the site may do useful checking.
I think we can posit the model is correct, while being incomplete. Every model is incomplete. The devil is in what gets left out of the model. I've heard of things like electron pressure squeezing magnetic field lines that I'll wager isn't shown.

Keep in mind that a generation of vacuum tube guys dreamed this up. They had some feel for the mob-dynamic of electrons flying about the inside of a radio or television tube. If the models explain all known vacuum tube phenomena, I think they'll be complete enough for this purpose.

scareduck
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Post by scareduck »

Tom's right. If Indrek's model were correct, we should expect a Polywell would require a much greater well depth in order to reach the same neutron count to overcome the likelihood of ion loss out of the well or aimless wandering within it (what Rider would probably call thermalization). The fact that it generates neutrons at roughly the same rate as the UW fusor at one tenth the well depth (error bands duly noted) is nevertheless pretty compelling.

Munchausen
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Post by Munchausen »

What does the picture on the EMC2 homepage prove in this respect? Isnt a certain well depth a necessary condition to obtain a plasma of that kind? What is the visible beam that stretches into the plasma? Some kind of diagnostics?

The man in charge of this spectacle claims they have achieved high power and have clearly not rejected the idea. That, if mr. Carlson cannot fire a little more convincing salvos at it, ought to be enough to justify some polywell daydreaming.

Whether more government money should be spent in this direction, is essentially up to the review committee to decide from the hard raw data presented.

Art Carlson
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Post by Art Carlson »

Munchausen wrote:The man in charge of this spectacle claims they have achieved high power and have clearly not rejected the idea. That, if mr. Carlson cannot fire a little more convincing salvos at it, ought to be enough to justify some polywell daydreaming.
Me? I've been holding back to give somebody a chance to answer my first salvo! But since that doesn't seem to be happening, maybe I should move on to the next set of problems. (See "Why is polywell supposed to be better than cusp confinement?" thread.)

TallDave
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Post by TallDave »

scareduck wrote:Tom's right. If Indrek's model were correct, we should expect a Polywell would require a much greater well depth in order to reach the same neutron count to overcome the likelihood of ion loss out of the well or aimless wandering within it (what Rider would probably call thermalization). The fact that it generates neutrons at roughly the same rate as the UW fusor at one tenth the well depth (error bands duly noted) is nevertheless pretty compelling.
Yes, it's very hard to see how that could happen otherwise.
I've been holding back to give somebody a chance to answer my first salvo! But since that doesn't seem to be happening
Hmmm, I thought that first question was pretty well addressed. Is there something specific you think was unanswered? I'm sure we'd be happy to try.

scareduck
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Post by scareduck »

Art Carlson wrote:Me? I've been holding back to give somebody a chance to answer my first salvo! But since that doesn't seem to be happening,
In this thread or that one?

tombo
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Post by tombo »

That 3D graph certainly is disappointing.
As is see it the distance from the coil to the coil centerpoint is similar to the distance from the coil to the device centerpoint.
I.e. the coil is only marginally closer to its own center than it is to the device center.
This clearly leads to a shallow well, so I am not surprised by this result.
I agree with 93143. Ws should have seen this coming. I guess we just assumed that Dr. Bussard et al had worked through this point. Maybe they have and we just have not caught up.
A dodecahedron with the same device diameter would have smaller coils.
This should help the well depth by making the coil center closer to the coil and so raising the saddle points without affecting (much) the field at the device center point.

Indrek,
How hard would it be to modify that model to show the dodecahedron?
(I’m thinking pretty tough as there are few features on the axes and the 1/48 symmetry computer resource saving strategy would have to be re-thought.)
(I know my cad model of the dodecahedron was a lot harder than the cubic one.)

Maybe this is why the emc2 folks went to a dodecahedron.
If that helps, then an icosahedron should be even better.
This effect could push us to even higher orders of polyhedrons.
(I still like my octahedron based series, although this shows why the higher order members of the family may be needed.)
-Tom Boydston-
"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein

Tom Ligon
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Post by Tom Ligon »

I think Dr. Bussard may have expected the dodec to be about 3x better than the truncube. It was not enough to make it necessary to tackle more and smaller magnets for the WB6 and 7 proof of concept models, but he wanted to build WB8 on that scale to see if it really helped, before going for larger scales. 3X sounds like a big improvement, but if it really gets 128X better for every doubling in radius, economics might favor a simpler but slightly bigger machine.

drmike
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Post by drmike »

I gotta take off for a camping trip, but when I get back I'll be able to plot a 3D picture of both the electric and magnetic fields from the raw MaGrid. It will be slightly different than what Indrek showed - with a zero field in the center and at the outside wall for E and zero field for B in the center and not quite zero at the outside wall. I think my outside wall is 3 times the coil radius, or distance from center of polywell to center of coil.

Art - the answer to the first salvo was homework: # Bussard, Robert W., King, Katherine E., "Electron Recirculation in Electrostatic Multicusp Systems: I-Confinement and Losses in Simple Power Law Wells," 1991, EMC2-0491-03

There are plenty of holes in there for you to shoot at!

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