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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ladajo
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Re: EMC2 has published a polywell preprint on arXiv

Postby ladajo » Fri Jun 13, 2014 12:11 am

Nope, it does not.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

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

Postby D Tibbets » Fri Jun 13, 2014 5:08 am

I think this is the paper that is one of Dr Parks key references.

http://www.archive.org/stream/theoryofc ... 5/mode/2up

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

mattman
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Re: EMC2 has published a polywell preprint on arXiv

Postby mattman » Fri Jun 13, 2014 7:00 pm



Dan, I like this reference. Harold Grad was all about cusp confinement. I have read a hodge-podge of stuff on this, and I am attempting to organize it, into a list. Here is my rough list:


1. Cusp confinement loss rates (Dan's Reference)
2. Cusp confinement description: how the "Free-Boundary" idea, works (shown below)
3. Particle types around cusps (quoted below)

===========
Number 1

Dan,

This reference talks about cusp losses. It purposes an equation for the loss rate. It is a shame they could not get to measure that rate. A comparison against this theory paper would be REAL interesting.


============
Number 2


Both Dr. Grad and Dr. Tuck idealized a "Free-Boundary." In their words, they described it as (from page 179):


"We are interested in the containment and thermonuclear possibilities of a large family of stable magnetohydrodynamic free-boundary equilibrium configurations. The free boundary is a mathematical idealization in which there is a perfectly conducting plasma containing no magnetic field, separated at an interface (surface current) from a vacuum magnetic field. "

This is compared with a magnetized plasma. I am trying to draw both these ideas out. Feedback welcome. First, this is what a typical magnetized plasma would look like:

Image

Next, this is what happens when you form a "Free-Boundary". But, I am not sure which depiction is more accurate.

Image

Image


============
Number 3

Grad's simulated the types of particles that exsist around a cusp confinement. IDK how connected that is to the "free-boundary" concept they discussed above. This formed the basis of Joe Khachans paper. Here is my write up. To quote directly:



Biconic Cusps:

The biconic cusp idea was explored Dr. Harold Grad at NYU in the fifties and sixties. Biconic cusps are funny arrangements. They are fields generated when two electromagnet rings are placed close to one another. The fields looks like two water hoses facing each other – field lines spray out in all directions from the center. Between these magnets there is a null point. It is in the middle of the field. Particles passing through this point are scattered. It is easy to see how this is similar to the polywell, which is six rings facing one another. This is shown below.

Image

This geometry was first simulated in 1961 [8]. Simulations found that there were three types of particles: stable, erratic and a transition. The stable particles move very far away from the null point. This particle has a constant magnetic moment. When this particle reaches a dense field it is reflected. This is the same mechanism as in the mirror machines. The second particle type makes a full revolution very close to the middles. These are erratic. The third set is a transition, between these types. Fifty years later, Joe Khachan argued that these three types of electrons exist inside the polywell [7].

Image


pbelter
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Re: EMC2 has published a polywell preprint on arXiv

Postby pbelter » Fri Jun 13, 2014 8:18 pm

Alan Boyle has a new article on EMC2

http://www.nbcnews.com/science/science- ... ey-n130661

"Low-Cost Fusion Project Steps Out of the Shadows and Looks for Money"

EMC2 Fusion is planning a three-year, $30 million commercial research program to see if its unorthodox approach can provide a fast track to cheap nuclear fusion power

Roger
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Re: EMC2 has published a polywell preprint on arXiv

Postby Roger » Fri Jun 13, 2014 8:45 pm

mattman wrote:We have watched the polywell for many years, two questions have exist all that time:

1. Are the electrons in the center, non-thermal?

Electrons in the center form the potential well and by definition cant thermalize. Brem requires electrons to be dense and energetic, in the center we see dense and not energetic. There may an intermediate area, not the center and not the edge where electrons are both energetic and dense enough....

Since the Brem measurements on this device seemed to be in the ballpark of 25% and originating from the erosion of an electrode?, or other probe?, and EMC2 appeared to be fairly confident that this erosion was the sole cause of the Brem.... one might read between the lines that there is some indication that electron thermalization-brem wasn't a problem.
I like the p-B11 resonance peak at 50 KV acceleration. In2 years we'll know.

choff
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Re: EMC2 has published a polywell preprint on arXiv

Postby choff » Fri Jun 13, 2014 9:49 pm

One thing I picked up from the paper was this in regard to figure 6.

At B=0.6 kG, the x-ray result shows
changes in electron beam con nement property but the
signal is complex to interpret. In comparison, the x-ray
result clearly shows a well-de ned period of large increase
in electron beam con nement at B=2.7 kG. The excluded
magnetic
ux shows faster peaking and bigger diamag-
netic e ects at B=0.6 kG compared to B=2.7 kG. The
peak
ux exclusion for the B=0.6 kG case is equivalent
to 44% of the vacuum magnetic
ux, compared to 10%
for B=2.7 kG. The injected plasma density is compara-
ble initially, while the density decays rather rapidly for
B=0.6 kG.

Sorry about the formatting, but what I get is that they have a higher beta at lower magnetic field strength for the same amount of plasma, while still having comparable confinement. That could either mean diminishing returns for confinement with bigger magnets, or, there's a sweet spot for high beta conditions that only requires intermediately strong magnets. I think I heard the word relaxed in describing to the Skunkworks configuration somewhere. It would be hard to believe both projects never collaborated or exchanged notes, especially if they did find a sweet spot from experimenting with the knobs.
CHoff

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

Postby D Tibbets » Fri Jun 13, 2014 11:03 pm

Roger wrote:
mattman wrote:We have watched the polywell for many years, two questions have exist all that time:

1. Are the electrons in the center, non-thermal?

Electrons in the center form the potential well and by definition cant thermalize. Brem requires electrons to be dense and energetic, in the center we see dense and not energetic. There may an intermediate area, not the center and not the edge where electrons are both energetic and dense enough....

Since the Brem measurements on this device seemed to be in the ballpark of 25% and originating from the erosion of an electrode?, or other probe?, and EMC2 appeared to be fairly confident that this erosion was the sole cause of the Brem.... one might read between the lines that there is some indication that electron thermalization-brem wasn't a problem.


I'm not sure what you are reading into the data. I am not sure what the bremsstruhlung was as a percent of the input energy. I'm uncertain of the units on the y- axis of the graph. He did predict ~ 50 MW of bremsstruhlung in a D-T machine with an input energy of ~ 213 MW. In this machine there was some erosion of the tungsten electrode that delivered the electron (?) blast to the plastic sheets. I'm guessing resultant plasma was mostly the ionized plastic with some tungsten contamination. The amountof tungston eroded per shot is unknown. Was there 50 plasma shots, 200, 50,000? Considering that they would have to remove the plasma guns and reload them with new plastic membranes for each shot, a lot of shots would imply a huge amount of work, and vacuum pumping. The plasma from this gun was probably ~ 2 parts hydrogen for each 1 part of carbon and perhaps 0.001 parts tungsten. The carbon with an ionization state (Z) of up to 6 and the tunsten with up to 74, cause more bremsstruhlung radiation, but it is actually the electrons are the source of this radiation. This breaking radiation occurs as the electron whips around the relatively stationary ion. At the same electron energy. One unit of bremsstruhlung radiation would be produced from a close encounter with hydrogen, 36 with carbon and ~5000 for tungsten. Bremsstruhlung scales ( think) with electron temperature ^1.75 power, and interacting ion Z ^2. What the relative concentrations of these two ions were determines the final contribution. It is safe to say though that the vast majority of the bremsstruhlung came with electron enounters with these ions. The hydrohen ion contribution was much less. This was actually very useful for this machine. They wanted the most bremsstruglung they could get. For a fusing reactor though this would be intolerable, as the bremsstruhlung cooling and the input energy needed to overcome it is tremendous.

The potential well does not nessisarily require electrons in the center, they can cluster near the edge and provide the potential well provided they have enough energy. The potential well shape is dependent on central presence of electrons though. I understand this is a natural consequence of the ions traveling towards the center. The electrons get tugged along, but this tugging redirection of the electrons is limited to the velocity of the ions (I think), Because the electrons are lighter, at the same velocity they have much less energy- ~ 1/8th . The final electron energy at different radii is a complex mixture of initial electron energy and vectors, inter electron collisions, ion tugging, and space charge repulsion due to excess electrons. This is further modified by the shape of the interacting potential well, a complex problem also including things like debye length and plasma frequency. My understanding is that with the presence of ions the electron energies tend to fall as you approach the center. How much this changes is uncertain, but even small changes can make big differences in bremsstruhlung. Also important is the density of the ions at a given radius. If there is some confluence (central focus) of the ions, due to the near spherical geometry the density of ions will be greater, perhaps by as much as 100 fold relative to the ion density on the edge. You need these targets for the electrons to interact with to produce bremsstruhlung breaking radiation. Since at any given time most of the ions are towards the center, and the electrons have the lowest energy there, the bremsstruhlung output is less than if you assume a diffuse homogenous mixture of ions and electron energies. Because of the low Z, this latter case might be barely tolerable for D-D fusion, but not for P-B11 fusion. It is not just the electron energy and numbers at different radii, but the numbers of ions in that location as well.

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

classicpenny
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Re: EMC2 has published a polywell preprint on arXiv

Postby classicpenny » Fri Jun 13, 2014 11:38 pm

pbelter wrote, "Alan Boyle has a new article on EMC2: EMC2 Fusion is planning a three-year, $30 million commercial research program to see if its unorthodox approach can provide a fast track to cheap nuclear fusion power"

I have three multi-part questions:
1. Is the Navy still interested in the Polywell. If they are, why did they stop funding it?
2. If the Navy is still interested and the beta=1 wiffleball has been demonstrated, why isn't the US Department of Energy taking over and developing the full-scale Navy Nuclear Power System. It is their Congressionally Mandated job to do so. What is going on here?
3. Is it possible that Dr. Park is only asking for $30 million because he knows the VC people will never fund the full scale Polywell unless its a "sure thing"? And are we going to waste three more years "making sure?" I can see that that the potential rewards of a successful Polywell are BIG enough that in this case IT IS WORTH THE RISK to go for the full-scale machine at this point. Or am I missing some really important information here that both Dr. Bussard and Dr. Nebel also somehow missed?

I really want to know these things and I welcome any and all speculation - and if someone gets a chance to ask Dr. Park, all the better!

Bill Flint

Robthebob
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Re: EMC2 has published a polywell preprint on arXiv

Postby Robthebob » Sat Jun 14, 2014 12:04 am

1. Talk to ladajo

2. I'm gonna take a stab at it and say that because DoE is too invested with their current projects; I mean they didnt help when Bussard was looking for money, granted it's different back then, it was like, Bussard saying, "take my word for it." However, Park is saying, "look at the numbers."

I dont think DoE will help until after the demo is built and running; you cant argue anything when the gauge is reading positive. There are a couple people (some of them members of this forum) that has pieces of the story, I feel that at some point it may be useful to start writing down everything that has happened.
Throwing my life away for this whole Fusion mess.

paperburn1
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Re: EMC2 has published a polywell preprint on arXiv

Postby paperburn1 » Sat Jun 14, 2014 12:23 am

I can,t even get funding for a bigger ac unit for a network critical infrastructure. That much free money does not exist right now so 30 million.... not a chance.
I am not a nuclear physicist, but play one on the internet.

John Gallagher
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Re: EMC2 has published a polywell preprint on arXiv

Postby John Gallagher » Sat Jun 14, 2014 5:18 pm

The first wall problem for DT and the production of Tritium are known to be difficult engineering problems with fusion systems. I have often wondered how a large flux of high energy alphas would be handled in this geometry. Their interaction with the magnet housing and the coils themselves would make for an interesting thermal management problem. Also the alpha flux is not exactly a beam than can be decelerated as in a direct conversion device. I know that people have put a lot a effort and thought into this. I was wondering if anyone can tell me where to find information on these subjects.

hanelyp
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Re: EMC2 has published a polywell preprint on arXiv

Postby hanelyp » Sat Jun 14, 2014 6:55 pm

Alphas produced in a polywell would be mostly channeled through cusps in the magnetic field. From there it's through an electron recirculation grid, and across a potential gap to the direct conversion collector. The biggest obstruction I see in the path is the electron injectors.
The daylight is uncomfortably bright for eyes so long in the dark.

ladajo
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Re: EMC2 has published a polywell preprint on arXiv

Postby ladajo » Sat Jun 14, 2014 8:30 pm

Not all the cusps would need to have Electron injectors.
In fact, an emitting gun would act to some degree as a cusp "Alpha Plug" given the streaming of (e-) in, and the fact that other cusps with guns could provide an out.

Everyone seeks the path of least resistance right?
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)

What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

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

Postby D Tibbets » Sat Jun 14, 2014 10:07 pm

Alphas do not impinge on the magrid hardly at all, so thermal loading of the magnets by alpha particles is a non issue. According to Nebel, provided the B field is great enough relative to the machine radius, the alphas will be turned by the B field (gyroradius) and return towards the center. It will continue in this manner till it hits a cusp (after ~ 1000 passes according to Nebel, or what ever the Wiffleball trapping factor is). After escaping through a cusp it can transfer its energy by hitting the wall like other escaping charged particles or neutrons, or it could be decelerated with direct conversion. Admittedly direct conversion with the distributed cusps would be complicated. But, you do not need to capture all of the energy by direct conversion, even capturing 50% of the energy puts you ahead in the game from several perspectives.
ExB diffusion is trivial for the alphas. With KE in the MeV, the Coulomb collision cross section is very small (scales as 1/ KE^2)so there are only rare collisions to drive ExB drift/diffusion. This is also why alphas do not contribute much to plasma heating inside the machine. No ignition is possible or desired.

For the magrids the issue of external heating applies to neutrons if present in significant numbers (D-D and D-T fuel) and Bremsstruhlung radiation. Cyclotron radiation is relatively trivial. Also, fuel ions (or electrons) could heat the magnets through ExB drift, or by impacting exposed nubs if present. From the patent application it is mentioned that ExB losses will amount to ~ 1 % of the cusp losses. So, if your cusp losses are made up for with ~ 100MW of injection, the magnets might be heated by ~ 1 MW of ExB drift particles. Not trivial , but small compared to possible neutron exposure and Bremsstruhlung radiation heating.

Dan Tibbets
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 » Sat Jun 14, 2014 10:50 pm

mattman, the images are confusing me, especially the last two. If the B field is excluded there would be no noticable spiraling motions of the charged particles inside the Wiffleball border- which I take to be the transition zone. The drawing of a B field line inside this zone seems innapropriate. In the last image, the motion tracks seem to be curving, again this would not occur like this if the B field is excluded.

The transition zone is an interesting region. Ideally this transition zone would be a line, and thus any charged particle reaching it from the inside would immediately bounce back (billiard table analogy). With some thickness though complex partial orbits and multiple orbits may occur due to collisional effects. How many of these particles (promarily electrons get knocked deeper into the B field where their gyro orbits are complete without traveling inward enough to again encounter the border region the mirroring , spiraling motions seem appropriate. What percentage of the electrons are in this region as a percentage of the total is uncertain, but I would think it would be best if it is kept small. The ions are not involved with this border provided they are introduced below the peak of the electron induced electrostatic potential well. Those upscattered ions that do reach the border will also rebound back and only the most upscattered ions would enter the full magnetic domain. It is these upscattered ions and mostly electrons that proceed with ExB drift, and eventually hit the magnet unless they manage to escape a cusp.

It occurs to me though that with their greater gyroradius they are less likely to be trapped. Once turned the potential well may pull them back below the border region. I'm guessing that ExB losses for ions is small, even for those upscattered ions. Most ExB losses may be from electrons. And as claimed, that amounts to only about 1% of electron losses (before recirculation I believe). As such the electron current from the border is ~ 1% of the cusp current (eg: 100 MW through the cusps is accompanied by 1 MW to the magnets via ExB). The stable region is not really stable, though it may be convenient to consider it so for comparative purposes.

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


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