The US Navy Publishes on Polywell.

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
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DrMatthew
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The US Navy Publishes on Polywell.

Post by DrMatthew »

Hello All,

The US Navy has published on the polywell. Below is their machine:

Image

You can read the paper here.
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Dave Xanatos
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Re: The US Navy Publishes on Polywell.

Post by Dave Xanatos »

Pretty direct validation of the concept. Thanks for this link & info.
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Chris Bradley
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Re: The US Navy Publishes on Polywell.

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I'd be interested in understanding how you arrive at your conclusion this is a 'validation of the concept'?

The 'concept' consists of;
1) confining electrons [now demonstrated]
2) confining ions because of the electric field caused by the electrons
3) causing acceleration of those ions due to electric fields
4) maintaining the electron confinement during the period of the acceleration of those ions
5) fusion between the accelerated ions
6) sufficient fusion energy produced to pay for all the energy inputs for steps 1 to 4.

Do you think they have also validated steps 2 to 6 with the contents of this paper? I'd like to know if I am missing something.
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Richard Hull
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Re: The US Navy Publishes on Polywell.

Post by Richard Hull »

Me thinks I detect a bit of leakage "rays" in the image supplied. Not perfect but a really cool image.

Chris is right on his part of the analysis.

Lots o' watts in shots, but no COP data. Sounds like they are falling into the hot fusion crowd's logic. State a ton o' them megawatts but on the time line show 'em microseconds. Too bad that at the electrical outlet, our flatscreens need to stay on for hours on end.

No hard data on neutron production (fusion) versus hard power input. No news is turly no news, but a pretty picture always impresses.

I am glad they finally published, however. This is something for the tax money.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: The US Navy Publishes on Polywell.

Post by Dave Xanatos »

Chris Bradley wrote:I'd be interested in understanding how you arrive at your conclusion this is a 'validation of the concept'?
You're missing nothing. I should have been more specific with regards to "concept", being, in my terminology, that concept refers to a fusor-like arrangement with a virtual cathode rather than a grid cathode. Grid cathodes will always be eaten, regardless of the materials or care in construction. For any future development *towards* a useful fusion system, it should be self-sustaining and not consume anything other than D, T or H (or Boron & protons)... it should certainly not need to be taken offline every week to have its guts replaced.

And also, "concept" also makes no reference to the horrific return on energy investment. Merely, as stated above, that a fusor-like system without a physical cathode should be possible. And I personally believe that the Polywell concept may provide a doorway to getting - if not to over-unity, then - at least closer to the point at which we may figure something out that will get us to over-unity. And I can't be put on the spot there because I freely admit I have nothing to back that up with - it's just a gut feeling :) But as an electronics engineer and hobbyist since I was literally four (that's 46 years under my belt playing with electrons) - my gut feelings have been right way more than not... at least in the field of electronics and other physical sciences I've played with.

I'm just convinced that we don't know some very critical things about what the fusion genie wants in order for it to dance for us on command with reckless abandon :) But I am equally convinced that we will figure it out. Things like fusors and polywells are helping a whole generation of curious kids - and adults - play with the genie a little. If the polywell turns out to be a better house for the genie, maybe it'll reward us with a tidbit! :)

If nothing else, the learning, the experience - that's where the gold is for me.

Dave

PS., also, the Navy's Conclusion: "This result validates the central premise of the Polywell fusion concept which uses high energy beam injected electrons to create an electrostatic potential well for ion acceleration and confinement." To me, that's good news. But who am I, anyway? :)
It would take decades of work, by thousands of scientists, in a particle accelerator powered by dump trucks of flaming grant money! - Professor Farnsworth/FUTURAMA
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Re: The US Navy Publishes on Polywell.

Post by Richard Hull »

I accept your concept of "proof of concept".

With no real numbers and net time ordered analysis of efficiency, power in versus power out, we can't know if this is a true advancement over the lowly fusor or not at this point. It has certainly proven the concept of its increased cost by many orders of magnitude over that of the fusor. With no analysis, it is quite possible it is many orders of magnitude worse at fusion than the fusor.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
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Re: The US Navy Publishes on Polywell.

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This paper reveals multiple challenges, but the purpose of this specific small machine was to prove the Wiffleball effect in undeniable terms. Apparently, despite Bussard's claims it proved difficult to obtain a Beta=1 condition/ Wiffleball in WB7 and WB8. There may be reasons for this discrepancy, but I will not bore you with my speculations.

The Wiffleball effect/ Beta=1 condition is an absolute essential for the Polywell concept to work. There is some wiggle room for other aspects but not for this one.

The bremsstruhlung x-ray radiation measurements can not be explained except by the Wiffleball effect, improving high energy electron confinement from a surprisingly low cusp confinement (I have excuses for this also) to about 40 times greater confinement with Beta = one. They also showed the magnetic field expulsion due to the diamagnetic effect of the plasma.

The problems with efficiently injecting electrons through the cusps has become more appreciated, along with several other aspects. But, as I said, the root question has been answered unequivocally.

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Re: The US Navy Publishes on Polywell.

Post by Bob Reite »

This experiment made no attempt to produce fusion that I can see, it just proves the confinement principle. But I'm glad to see that something has been published.
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Re: The US Navy Publishes on Polywell.

Post by Johannes westman »

The way I see it is that the only piece that is left is specifically the virtual cathode. If they cannot get that to work there is no point going further, since the device would be no different than the fusor.

Whether a virtual cathode will produce MORE occuring fusion than the fusor, now that is a different question. I guess we will just have to hope for success in the electron confinement department. Im still hopeful though.
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Re: The US Navy Publishes on Polywell.

Post by Dave Xanatos »

I'm staying hopeful as well, because I'm pretty sure that if we ever get energy from fusion, it'll have to be something without any physical structure in close proximity to the plasma. Look at how rapidly the best grids are degraded in a fusor. Add to that the fact that if we do actually continue using a "plasma ball", it's going to need to be many orders of magnitude more intense to produce useable energy. Unless we find a way to really improve our ion aim and drastically increase our fusion rates in very narrow confined microchannels.
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Re: The US Navy Publishes on Polywell.

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First off, congrats to these people for publishing and providing hard numbers for a real device relative to electron and ion (?) confinement. Also, while not in any way earth shaking relative to economical plasma confined fusion, achieving Beta = 1 or there about is a nice milestone for the Polywell device. Relative to any “cusp” confinement system, yes, achieving a Beta =1 is a big deal but such a plasma confinement configuration is a lost cause if, as I understand some current research on this particular topic, the Bremsstrahlung radiation loss issue isn’t somehow suppressed (while their electron "shielding well" may suppress some issues of Bremsstrahlung production, frankly, I do not see this effect stopping/reversing deuterium ions with no net energy cost/loss - for real fusion producing economic power, the number of required ions will be huge and creating a suppressing "electron well" would still appear far beyond what this Polywell has demonstrated.) Has this key problem ever been addressed by these people or other Polywell research or proven wrong/irrelevant?

When they state this in the conclusion –
“If the deep potential well can be formed and the scaling of the electron beam confinement is found to be favourable, as conjectured by Grad and others, it may be possible to construct a compact, low cost, high b fusion power reactor based on the Polywell concept.”

What!? This statement appears rather unsupported considering that their data does not address most energy issues for any such device. Besides, placing all responsibility for this statement on Grad and others for "proof" of this argument/conclusion, relative to their work this conclusion appears rather out of place. Second, they haven’t produced any neutrons at all much less produced any significant energy so the energy statement makes little sense. More critically, relative to anextremely energetic plasma, it does not appear to me that they have shown any results at all for a stable ion based plasma that is under going significant fusion producing energy - (i.e. any measurable energy) much less anything approaching a more realistic energy density of at least getting within four or five orders of magnitude of break-even (rather critical for this closing statement, wouldn't you think?) Finally, and I’d think most critically, what of energy loss by the ions that are forced by the Polywell field/confinement configuration to reverse and create the afore mentioned Bremsstrahlung radiation problem or are we somehow good on that?
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Re: The US Navy Publishes on Polywell.

Post by Dan Tibbets »

The purpose of this machine was primarily to overcome one barrier. That is the creation and very importantly the demonstration of the high Beta state. This seems to have been accomplished. Also demonstrated is densities of over 10^21 charged particles during the admittedly breif test runs. This density is adequate for useful fusion in moderate sized machines.Even full up, much stronger (magnetic field) machines have a target density of ~ 10^22 particles per cubic meter. This is ~ 100-1000 times greater than Tokamak projections which translates simply in machines with 100-1000 times less volume than a tokamak for the same fusion output. Actually Nebel gave a conservative estimate of a fusion output intensity ~ 60,000 greater than a tokamak. This is in a production working Polywell (the key work here is Working).

As mentioned in the paper, the virtual cathode/ potential well formation is not the issue. They seem to be satisfied with this. Remember this is only one machine and it is the smallest machine created only for a specific purpose. There does seem to be a question about the depth of the potential well and how much input energy is needed to achieve it. This in a pessimistic assessment might limit the machine to D-T fusion.

The bremsstruhlung issue is of course critical, but it applies mostly to advanced fuels like boron or helium 3. For deuterium or deuterium- tritium the issue is much less significant. Even Rider conceded that D-D might work. And at least those physicists working with the Polywell think Rider (and Nevens) got it wrong. Not their math but the assumptions and model that math was based on. The often mentioned counter argument comes partially from work by Chacon.

L. Chacón, G. H. Miley, D. C. Barnes and D. A. Knoll, "Energy gain calculations in Penning fusion systems using a bounce-averaged Fokker–Planck model" (Physics of Plasmas, Dec. 2000)


Why didn't they do fusion? Probably because they couldn't and even if they did get feeble D-D fusion it would be meaningless. Look at the details of this machine. They had a relatively feeble high energy electron gun, and the vast majority of the plasma came from an explosive injection of plastic by the two plasma guns. A powerful blast of electrons at perhaps ~ 1500 V and ~ 400 thousand amps, vaporized and ionized several thin layers of a plastic in only a few microseconds. Lots of hydrogen and carbon and even some tungsten was injected. It was an extremely dirty and diluted plasma from a fusion standpoint. What they wanted was a lot of ions and electrons. That a fair portion of the ions was high Z ions (multiply ionized) was a benefit as their primary demonstrative measurement was the bremsstruhlung output. They wanted to show the Wiffleball effect, and to do so within the constraints of budget and time they chose this smaller machine armed with cleverly designed diagnostics and a cheap shortcut to quickly filling the machine with enough density and energy to push out the magnetic field and create the high Beta, high confinement conditions that is THE ABSOLUTE REQUIREMENT for the machine to work. The explosive plasma guns is not necessarily the only way to accomplish this, but it was the easiest way that matched their budget and target.

The useful and profitable fusion question is based on the Triple product- confinement, temperature/ energy, and density.
This machine and paper addresses the confinement issue sucessfully. The other issues have been studied (successfully, or at least partially?) in the rest of their non reported body of work.

I will say though, that this machine achieved impressive densities, and demonstrated in these limited conditions that thermalization is not a rampant issue. How so? Well. the blast of plasma was at below 2000 Volts, and the x-ray filters stopped any bremsstruhlung or electron- wall x-ray emissions originating from this portion of the plasma electrons from reaching the detectors. Only the E-gun injected electrons at up to ~ 7,000 Volts contributed. If they thermalized with the extremely higher numbers of plasma gun charged particles (electrons ), the temperature would only have been changed a few volts, eg: 1500 eV to 1510 eV with only a small high energy thermal tail. I suspect this would have resulted in bremsstruhlung readings completely buried in the baseline noise. The measured signal implies that the high energy injected electrons maintained their "monoenergetic " distribution long enough for the measurements. How this extrapolates to other conditions is complex, but at least it does give a minimum baseline.

The measured bremsstruhlung was due to the density of the e-gun provided high energy electrons (that maintained their KE above the 2000 eV cutoff limit). First the e-guns were turned on, and an equilibrium was established based on the injection rate/ loss rate. This took a period of time (~ a few microseconds?). Once the plasma guns blasted in a high density lower energy plasma, this was added to the resident e-gun electrons. The high Beta/ Wiffleball condition was established about as fast as the plasma blast (~ 7 micro seconds). Once this condition was established, the confinement was improved ~ 40 times, so the input rate of high energy electrons was relatively higher than the loss rate. A new equilibrium was established, and this took a few micro seconds to occur. That is why there is a delay in the bremsstruhlung signal. The plasma injection was a pulse and once finished, the density and thus Beta would begin to drop due to losses from escape and radiative losses. So the duration of the Beta =1 (or near there) was limited, there was no makeup for the electron losses (and to a lesser degree the ion losses) so the confinement soon returned to the baseline. The e- gun high energy electrons was only a tiny portion of the total input represented, so they contributed trivially to the Wiffleball condition. What they very importantly did provide though, is the method for demonstrating the Wiffleball though their improved confinement- resultant increased equilibrium density (~40X?)- resultant increased bremmstruhlung output.

This is a good demonstration of how a good experimental physicist can do more with less.

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Re: The US Navy Publishes on Polywell.

Post by Dan Tibbets »

R. Hulls comment about the fuzziness of the plasma glow in the cusps is perhaps telling. I was dismayed by the seemingly huge spacing between the magnets. This had to harm cusp confinement. I know that the magnets have to have separation to limit ExB losses and keep these losses miner compared to the cusp losses. I was just amazed by the magnitude of the separation. I have wondered if this was based on the density and energy and B fields anticipated in the machine. WB6 had much smaller separations. The separation is and seems greater. It seems even greater because this is a smaller machine and the sizes of the magnets themselves are smaller, so the gaps are relatively larger.

The image of the machine at high Beta shows the cusp loss channels. It also shows that the glow also drops off gradually as you move from the mid line of the cusp. It is not a sharp demarcation as would be expected by the claimed sharp B field border on the Wiffleball edge. I suspect the fuzziness is thus a visual manifestation of the electron ExB drift going on. And since this visible glow is a result of recombination of free electrons with ions or neutral excitation/ relaxation processes it also shows that there are ions/ neutrals present. It doesn't say much about the relative loss rates. Id does though suggest that there were perhaps significant neutrals present, they are not contained and provide a convenient background for the electrons to interact with and create glow discharge.

I wonder about the efficiency of Plasma guns. They would certainly splatter and vaporize the vast majority of the plastic, but what percentage is ionized? Then there is the issue of recombination...

Again, a demonstration that this machine was far from ideal, but despite the inherent limitations, it got the job done. It was a bull in the china shop approach. A clever and trained bull, but still...

ExB drift or diffusion, for those interested, is an unavoidable loss through magnetic fields. It is based on an random walk process where a charged particle jumps across a magnetic field due to collisions with other similar charged particles. Diffusion is dependent on each jump, which is dependent on the gyro radius of the charged particle; and the density driven collision rate. This is one thing that drives tokamaks to such large sizes. The ion gyro radius is the limiting factor. In the Polywell, where only the electron gyro radius applies, has much slower ExB drift. This is one factor that allows Polywells to be smaller despite increased densities.

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Re: The US Navy Publishes on Polywell.

Post by Dan Tibbets »

Dr Parks gave a talk today at U. Cal Irving. And is giving a talk Monday at U Wisconsin Madison Monday 6/16. He is making the rounds. I hope more information is revealed.

http://www.physics.uci.edu/seminar/spec ... -high-beta

http://www.talk-polywell.org/bb/viewtop ... =10&t=5433

"Hey folks, got this email today from John Santarius. Dr. Park will be speaking at Univ. of Wisc. next week, and I will be in the audience :D . Any questions (scientific ones) you'd like me to ask?

"Colleagues,

Dr. Jaeyoung Park, President of EMC2, will give a talk on recent
cusp-confinement experiments in one of their Polywell devices. A
flyer is attached.

Date: Monday, June 16
Time: 2:30 PM
Location: 106 ERB"

Dan Tibbets
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