EMC2 has published a polywell preprint on arXiv

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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D Tibbets
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Re: EMC2 has published a polywell preprint on arXiv

Postby D Tibbets » Mon Jun 30, 2014 4:04 am

The energy distribution curve is wrong in several ways.I have addressed this before. Assuming I am not to far off, any graph that shows the electron numbers and ion numbers (positive charges) must have the same area under the curve, within one part per million. Unless you drew a graph several meters wide with fine lines, you would not percieve any difference in the sum of numbers of each. Also, the energy distribution is critical. The average temperature of the ions and electrons is the same (within some small variance). The graph of the electron energy would peak near the edge and be minimal near the center. The opposite is true for the ions. That is why any comment about electron versus ion energy must have the average energy nearly equal, and must reference the radius from the center to be meaningful.

The magnetic fields the particles see are from two sources. The electromagnets create the field which dominates everywhere except very near the center at low Beta. But, at high Beta this electromagnetic field is pushed outward. There is a much larger volume where the electromagnets derived fields are essentially absent. The other magnetic field effects is due to individual fields of the charged particles as they move around each other. This complex dance is generally described as B field free. This is of course not true. But the important point is that all of these very many local interactions and global interactions between the charged particles can be seen at the very small scales, but at larger scales, the effects cancel each other out so that the gross behavior of the plasma is as if there was no magnetic field at all. Note that the electromagnet effect does not have to be zero within the Wiffleball border, it is just that the strength becomes so small that the resultant lorentz force turning has negligible effects on the charged particles behavior relative to local and global Coulomb forces.Those electrons that are scattered deeper into the electromagnetic field (upscattered) along with similarly upscattered ions (more energy than the electrostatic potential well confinement) do enter the magnetic field domain and more typical spiraling along magnetic lines and ExB diffusion collisions become significant. It is generally considered that this happens only a little for the ions over their lifetime. And for the electrons, while this occurs , it is a minor consideration. The patent application mentioned that electrons that become trapped in the Magrid B field and undergo subsequent ExB drift, only leads to about 1 % of the losses compared to the cusp escape losses. A very through modeling of the system would account for these different behaviors of select populations of charged particles. But, for first order, or general estimates, the portion of the Wiffleball confined plasma that is magnatized can be ignored.

Alphas, or any charged particle product of fusion will have KE greater than the electrostatic potential well. As such they are confined by the Wiffleball confinement just like the electrons. They see the same holes and have about the same chance of hitting the holes as the electrons.

[EDIT- Oops, according to Grad the cusp hole size is limited to the charged particle gyro radius at high Beta. So a high energy alpha would have a larger gyroradus at the same B field strength region, so the hole would be much larger than the electron hole. An electron may make over a hundred thousand passes before hitting a cusp hole, a fusion alpha may make only a thousand passes (Nebel's quote) before hitting it's corresponding larger cusp hole.]

They naturally leave the reaction volume. There is no need for extractors, diverters, etc like in a Tokamak. Provided the alpha particle gyroradius is less than the distance from the Wiffleball border to magrid surface distance, the dominate and natural way they leave is through a cusp. These preferred escape paths lends themselves to direct conversion arrays better than generally isotropic escape trajectories. It is still a complex problem, but much less than with random distributions. An important consideration is that the alphas hit the Magrid only infrequently,and as such they will not heat the Magrid surfaces much. Without direct conversion, they will hit the vacuum vessel walls or other structures and transfer their energy as heat. But these walls are at a greater radius from the center and as such have greater surface area, the thermal loads are less. With alphas exiting through cusps, the cones and sheets of alphas tend to concentrate in certain areas of the wall. This provides the problem and opertunity for localized thermal wall loading- heat (and inpact ceramics in these areas, more cooling pipes, etc. For the magrid the heating concerns comes mostly from neutrons if D-D, and Bremsstruhlung x-rays, especially for P-B11.

Dan Tibbets
Last edited by D Tibbets on Fri Jun 12, 2015 1:43 am, edited 2 times in total.
To error is human... and I'm very human.

D Tibbets
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Re: EMC2 has published a polywell preprint on arXiv

Postby D Tibbets » Mon Jun 30, 2014 4:33 am

My impression of the plasma guns are that a large current of probably electrons at several thousand volts is shot from the tungsten filament, and vaporizes several sheets of plastic, A fair to good (?) portion of the vaporized plastic is ionized,mostly as hydrogen ions and carbon ions, though possibly some more complex compounds and neutral gas may be present. Also mixed in is some tungston ions from the eroding cathode. It is much like a lightning bolt hitting a tree. The electron current is probably from a large capacitor bank.

Note that WB6 had plasma guns also :shock: . With the electron guns located at the corners, the adjacent magrid connecting nubs may have been the destination of much of the E-gun current. If my guestimates in another thread about electron injection efficiency in WB6 succeeding in injecting only a few amps out of ~ 45 Amps, the remainder had to go somewhere, If the input energy was reported as ~ 500 KW, then the rejected electrons had to hit a surface at the bottom of their potential well outside the magrid. That is just the nubs or the can surfaces through ExB diffusion.. I'm guessing it was primarily the nubs.

This implies that ~ 40 amps at ~ 12KV was hitting the nubs. That is about 450 to 480 KW. This would sputter stainless steel off the nubs and also cause outgasing of any gasses absorbed into the surface of the stainless steel nubs. This may appear as a feeble contributor compared to the plasma guns in 'mini-B'. But considering confinement times, much of the difference is made up. Confinement of ~ 2 milliseconds, compared to perhaps 0.02 milliseconds is a a 100 fold difference. This would result in a relative difference of ~ 45 MW vs ~ 700 MW. Then there is the relative hot electron injection rate relative to confinement time, again perhaps ~ 100 fold difference. Then volume differences, etc. makes for a complex comparison, but this illustrates that this generally undesired nub interference may have actually been contributing significantly to the plasma buildup in WB6.

If, and I repeat if, WB7 and subsequently WB8, had the e- guns placed on the face centered cusps as in 'mini-B', the nubs would not have had the exposure to these high powered e- gun electrons. This assumes that the rejected/ mirrored external electrons fired at the face centered cusps had a grounding surface such that the electrons could not loop around to an adjacent cusp- the corner cusps with their bridging nubs. These electrons that were rejected would be grounding at low voltage, thus low energy loss and low heating. This assumes that the magrids in WB7, and possibly WB8 were at high positive voltage. High voltage E-guns as in 'mini-B' changes things somewhat. And, if there was an absence of nubs in WB7.1? or WB 8 they would not have any nub derived plasma guns irregardless of where the E-guns were placed. In this case, everything else being equal, pushing to high Beta would be more difficult in these newer machines., at least till Dr Parks resorted to the hammer approach.

Dan Tibbets
To error is human... and I'm very human.

crowberry
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Re: EMC2 has published a polywell preprint on arXiv

Postby crowberry » Sat May 23, 2015 6:29 am

The EMC2 paper has been accepted for publication. From the EMC2 homepage:

An article documenting recent advances in wiffleball formation has been accepted for publication in Physical Review X. The article is scheduled to appear at PRX on June 17, pending post-production. An early draft is available via the arXiv e-print service.


This is the link to PRX homepage: http://journals.aps.org/prx/

mvanwink5
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Re: EMC2 has published a polywell preprint on arXiv

Postby mvanwink5 » Sat May 23, 2015 1:41 pm

If investors were waiting for publication there was 1 1/2 years (+) delay.
Near term, cheap, dark horse fusion hits the air waves, GF - TED, LM - Announcement. The race is on.

crowberry
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Re: EMC2 has published a polywell preprint on arXiv

Postby crowberry » Sat May 23, 2015 5:38 pm

Yes, it is a shame that it has taken so long. The paper is not so much for the investors, but for the advisors to the investors. Anyway the result is unfortunately that it most likely has delayed funding.

mvanwink5
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Re: EMC2 has published a polywell preprint on arXiv

Postby mvanwink5 » Sat May 23, 2015 6:10 pm

http://www.emc2fusion.org website has also been updated significantly (I had not noticed, hadn't even been looking as it has taken forever since the promise to update).

Take a look.
Near term, cheap, dark horse fusion hits the air waves, GF - TED, LM - Announcement. The race is on.

DeltaV
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Re: EMC2 has published a polywell preprint on arXiv

Postby DeltaV » Thu Jun 11, 2015 9:36 pm

Physical Review X paper available online for free:

High-Energy Electron Confinement in a Magnetic Cusp Configuration
Jaeyoung Park, Nicholas A. Krall, Paul E. Sieck, Dustin T. Offermann, Michael Skillicorn, Andrew Sanchez, Kevin Davis, Eric Alderson, and Giovanni Lapenta
Phys. Rev. X 5, 021024 – Published 11 June 2015
http://journals.aps.org/prx/abstract/10.1103/PhysRevX.5.021024

crowberry
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Re: EMC2 has published a polywell preprint on arXiv

Postby crowberry » Mon Jun 15, 2015 6:31 am

The published paper is modified a little bit compared to the preprint, but the essential content is the same. The published paper is more readable compared to the preprint. There are three added references:

12. K. N. Leung, N. Hershkowitz, and K. R. MacKenzie, Plasma confinement by localized cusps, Phys. Fluids 19, 1045 (1976).
22. J. U. Brackbill and D. W. Forslund, An implicit method for electromagnetic plasma simulation in two dimensions, J. Comput. Phys. 46, 271 (1982).
23. See Supplemental Material at http://link.aps.org/supplemental/10.110 ... X.5.021024 for movies of 3D simulation results as described in the Appendix.


The Leung paper http://dx.doi.org/10.1063/1.861575 is referenced already in this old EMC2 paper:
http://www.askmar.com/Fusion_files/EMC2%20Reports%20Reformatted/EMC2-0191-02%20Electron%20Leakage.pdf

Here is the abstract of the Leung paper:
Details of the confinement of primary ionizing electrons and plasma by multidipole fields are given. It is shown that primary electrons are very efficiently confined by the cusps, with leakage half‐widths given by the electron gyroradii. Plasma is confined much more weakly. Leakage half‐widths of helium, argon, and xenon plasmas are found to be twice the hydrid gyroradii. Plasma noise in the neighborhood of the hybrid frequency is observed in the cusp regions.

TallDave
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Re: EMC2 has published a polywell preprint on arXiv

Postby TallDave » Wed Jun 17, 2015 7:43 pm

Not that exciting, we already knew wiffleball confinement is a real thing, but nice to finally see this published.

It's interesting they talk about a reactor with 250MW input and 2GW output. That's a pretty hefty machine! I wonder what loss scaling assumptions went into that.
n*kBolt*Te = B**2/(2*mu0) and B^.25 loss scaling? Or not so much? Hopefully we'll know soon...

MSimon
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Re: EMC2 has published a polywell preprint on arXiv

Postby MSimon » Fri Jun 19, 2015 12:48 pm

DeltaV wrote:Physical Review X paper available online for free:

High-Energy Electron Confinement in a Magnetic Cusp Configuration
Jaeyoung Park, Nicholas A. Krall, Paul E. Sieck, Dustin T. Offermann, Michael Skillicorn, Andrew Sanchez, Kevin Davis, Eric Alderson, and Giovanni Lapenta
Phys. Rev. X 5, 021024 – Published 11 June 2015
http://journals.aps.org/prx/abstract/10.1103/PhysRevX.5.021024

Thanks!
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THE OPEN POLYWELL FUSION CONSORTIUM

Ivy Matt
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Re: EMC2 has published a polywell preprint on arXiv

Postby Ivy Matt » Sat Jun 20, 2015 3:31 am

TallDave wrote:Not that exciting, we already knew wiffleball confinement is a real thing, but nice to finally see this published.

It may not be the latest experimental results, but the importance of the paper is that it is in a peer-reviewed journal, and it is something EMC2 can point investors and other interested parties to.

Also, is it just me, or have we been hearing about beta a lot more frequently since the paper was first posted on arXiv?
Temperature, density, confinement time: pick any two.


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