EMC2 news

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

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Tom Ligon
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Re: EMC2 news

Postby Tom Ligon » Thu Jan 21, 2016 10:29 pm

Dan, I think that's basically right. Dr. Bussard probably never achieved a proper high-beta wiffleball. He never had close to enough power and never had the electron injectors to get it in even if he had the power available. He thought he had achieved it on WB-2, but was letting the low energy plasma glow-balls mislead him.

One minor problem with the beta = 1 condition concept is that the magnetic field strength is not uniform. You pick some reasonable point at which you want to characterize the field strength of the machine and say something like, "We have 0.2 T on the axis of each coil in a plane with the coil, and so we say the field is 0.2 T." And then you calculate magnetic pressure from that value.

But the fields buck, and down in the center the magnetic field strength hits zero. So I think probably Dr. Bussard's machines might have hit beta = 1 over some small spiky region in the center, with very low plasma pressure working against near zero field. But that's not useful for the purposes of the machine. I suspect the, um, incident I had one day with PXL1 could have been powered by a small beta = 1 region near the center. The incident clearly involved plasma interacting with a collapsing magnetic field, producing a huge current reversal in the magnets that I managed to capture.

WB-Mini was said to reach about beta = 0.7. One day I'll sit down with Dr. Park and get the definition straight on that one as well. To do what it did, it had to push back the field, expanding that zero field region. So what I think happened (somebody straighten me out if I am wrong) is that the boundaries of that region were at beta = 1 for the magnetic pressure that deep in the machine, but just 70% of what the nominal magnetic field was out at the boundaries.

The lovely thing about this is, the containment is robust. The more you push the magnetic field back with plasma pressure, the stiffer the field gets. This is the wonderful property of Grad's Conjecture. Even if you hit what you are calling beta = 1, it does not mean you're teetering on the brink of instability ... push too hard and the machine pushes back.

D Tibbets
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Re: EMC2 news

Postby D Tibbets » Fri Jan 22, 2016 1:32 am

Tom Ligon (in his post above) has given me some food for thought.

Beta is just the ratio between the plasma pressure and the B field pressure. With the opposed magnets there has to be a point between them where the b field is zero. This may be an (almost?) infinity small region in the center. Even without a moving charged particle there may be some B field opposing force or pressure due to quantum mechanical effects- virtual particles, so the zero B field is greater than zero radius. Even with one moving real charged particle the B field is pushed out a little bit and this can be considered as a change in the Beta=1 condition to a greater radius. As plasma energy/ pressure (charged particles * KE) increases against a stable magnetic field, Beta =1 condition moves outward from the center. This is in some ways like a balloon inflating, but the dynamics of the magmetic field is different. The magnets themselves are not being pushed outward, provided they are anchored, but the gradient of the B field is being modified such that the B field free core expands outward. The B field strength beyond this free zone is not expanding or compressing. The gradient between the normal B field strength regions and the zero B field core is where the action is. This is a complex relationship and I'm not sure how to express it mathematically.
If you measure the B field at a radius of 1 relative to the B field at a radius of 50 (assume the magnets are at a radius of 100 units) the strengths at low Beta and high Beta would be unchanged provided the 50 radius was beyond the plasma- B field border. If the Beta=1 border was at 49 , then the gradient between zero strength B field and 'normal' B field would be the same as the low Beta field strength magnituded difference, but compressed into a distance of ~ 1/50th the original.

If you increase the plasma pressure, this border region moves further out and the border gradient becomes more pronounced. With consideration of the gyroradius of moving charged particles, this means the gyro orbit changes from a close to a circular orbit into one with increasing asymmetry- more elliptical or parabolic (I am still unsure which term is appropriate). The minor axis is small, but the major axis - towards the center of the machine, becomes greater. At some point as this gradient becomes greater relative to the KE of the charged particles of interest, a point will be reached where the particle will interact with other particles or reach the opposite side of the plasma space before the apex of the long axis of it's orbit is reached. The adiabetic behavior (if I am using the term correctly) is swamped by collisions. At this point Grad's conditions for particles rebounding off of the B field surface is met. This condition will occur at a B field gradient that is great enough. As such, the Beta=1 condition has to be pushed outward far enough that the local gradient at the border is sufficient for the 1/2 orbit- rebounding effect to manifest.

As measured to machine radius, this magic Beta= 1 radius must be some significant fraction of the total radius. This is somewhat of a moving target depending on B field and plasma components. There are two limiters on how much this radius can be. With an imaginary closed spherical magnetic containment the limit is the radius of the physical structure housing the magnets. In a real cusp machine, due to the outward contour of the cusps, this radius may be smaller.
With a cusp, the plasma/ B field border forms spikes and these spikes open up past the midplane radius of the magnets (assuming round magnet cans- other geometries may modify this somewhat). Pushing past this radius does not result in direct plasma impingement on the magnet cans, but it does lead to opening of the cusps with resultant greater plasma leakage. It becomes increasingly hard to maintain the plasma pressure, input costs go up rapidly. Also, the surfaces of the magnet cans will soon be reached so the limits are mutual.
I think Dr Parks mentioned that the High Beta border was at about 50% of the radius from the center to the machine radius. I don't know if he was referring to the radius to the can surface or the radius of the overall machine radius. The only parameter I know of is that the
B field measuring coxial cables that were placed 1-2 cm inside the magrid cans measured an ~ 40% drop off of the B field strength. I assume this means that the Beta one border was approaching this radius and that plasma hitting these cables was a hard limit against further Beta=1 expansion because losses would have quickly overwhelmed input.
If Beta= one is the target, it needs to be stipulated that this refers to the Beta =one condition at a radius near the narrowest portion of the cusps- at the radius of the midplane radius of the magrids. Due to the curvature of the cusps the radius away from the cusp- at the region equal distance between cusps, would be smaller - how much smaller is uncertain. This represents the maximum volume of plasma that can be contained with the best containment. In a real machine the volume/ radius could not be pushed past this in a sustainable manner because losses through the cusps and direct hits on the cans increases exponentially.

Considerations of electron versus ion gyroradii at the same KE and B field strength, ExB transport, thermal spread, recirculation, etc. all complicate this picture. Dr T. McGuire at Lockheed seems to think that these issues are workablee even without the ion confining potential well of the Polywell.

So, there are actually several considerations with high Beta. First, the border B field gradient has to be high enough for Grads conditions to be met. Secondly this condition is best at the maximum volume possible. Also, it helps if the density within this confined volume is as great as possible, thus stronger B fields. Relative losses is the ratio between this volume/ surface area versus the cusp hole sizes. Both are maximized/ minimized when Beta near one is realized at a radius near the midplane radius of the magrid in the cusp regions between the magnets. How close to this condition you have to get is uncertain. Is it 0.95, 0.8...? . Dr Parks reported an ~ 40 fold improvement in electron confinement with a Beta of ~ 0.7. Was this at the radius of the magrid, or the radius of the coaxial cables inside the magrid. Or was it at 50% of the radius of the machine. He mentioned ~50% (of what?) when asked how far out the plasma extended. I assume he meant the radius midway between the cusps, and I am uncertain what his reference radius was (overall machine radius, inner surface of magrids, coaxial cable radius, radius to corner cusps veres central face cusps, etc.).

I don't know if Mini B reached Grads criteria for essentially total adiabetic behavior, If my understanding is correct, his 0.7 Beta does not have to imply that Grads criteria was reached in a dominate fashion. He was still ~ 1000 fold below Grads theoretical confinement efficiency. Dr Parks effectively demonstrated marked improvement in cusp confinement at higher Beta, but he came nowhere close to Grads predictions of an ideal machine.


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

Tom Ligon
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Re: EMC2 news

Postby Tom Ligon » Fri Jan 22, 2016 4:54 am

Dan,

The visual model I'd like to build to demonstrate this to the curious public (especially for SF Convention dog and pony shows) would be a flat Lexan box containing some pipe sections that represent the magnets, arranged spaced out so they represent both the face and corner cusps, more or less.

Around these magnet casing anchors, I'd put pieces of sponge rubber cut to represent the approximate shape of the magnetic field lines. Layers of several different colors of several stiffnesses would be a very elegant visual representation.

In the center the easiest way to run the demo would be to have a balloon (and you're using a similar analogy). Inflating the balloon would push back the foam and show how the magnetic field would distort in response. You could visually see the air pressure (plasma pressure) equaling the foam pressure (magnetic pressure). I would expect the cusps to tighten up.

Of course, that's not quite how it works, because the balloon would not leak out the cusps, and in fact the proposed mechanism for the inflation is the development of a diamagnetic plasma that excludes the magnetic field. I think the better model might be the same foam, with an impermeable rubber outer layer, but leaky cusps. Injecting air in the middle at too low a flow would not inflate the system, it would leak out as fast as it came in. To inflate the system, you would need a very rapid injection of air, analogous to Park's very high power injection. If you can achieve that, you get the compression of the foam and hopefully a constriction of the leaks at the cusps.

It is not perfect. But do you think the analogy is useful?

Tom

ladajo
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Re: EMC2 news

Postby ladajo » Fri Jan 22, 2016 1:35 pm

Tom,
I like your idea, and with a little experimentation with various size o-rings as constrictors, and you should be able to find a flow balance that is representational.

The other way to do it would be to code up a 2D pnuematic/hydraulic SIM and show it on a screen.
What was the name of that software that let you do that? My son used to goof around with it all the time doing explosives sims. Have to look it up.
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)

paperburn1
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Re: EMC2 news

Postby paperburn1 » Sat Jan 23, 2016 9:09 am

Once more the red headed step child.
https://www.facebook.com/topic/Departme ... 1184082564

At leat they are looking at a safer fission reactor
I am not a nuclear physicist, but play one on the internet.

D Tibbets
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Re: EMC2 news

Postby D Tibbets » Mon Jan 25, 2016 7:44 pm

paperburn1 wrote:Once more the red headed step child.
https://www.facebook.com/topic/Departme ... 1184082564

At leat they are looking at a safer fission reactor


Methods to restrict the passive supercritical conditions in a fission reactor have been presented in the past. The one I am slightly familiar with is fuel rods that expand as they heat thus limiting the fission chain reaction. Even if the control rods stuck, the reactor would be limited.

This is not the most likely problem though. The big problem with fission reactors is that the fission products are highly radioactive and produce a lot of heat for extended periods of time even after the reactor is shut down- the fission chain reaction is stopped. From the Japanese reactor failures, I understand that the heat in a stable operating reactor is derived from 90% fission and 10 radioactive decay of the fission products. With fission stopped that is still 10% heat production. In a 1 GW thermal reactor, after shutdown there is still 100 MW of heat being produced. This decreases only gradually with a 90% decrease in about 7 hrs initially, with subsequent decreases scaling as about 10 fold decrease for every 7 fold increase in time. This is similar to atomic bomb fallout decay rates. So the thermal output in the above 1 GW thermal plant example would be 100 MW just after shutdown, 10 MW 7 hours later, 1 MW ~ 2 days later, 100 KW after ~ 2 weeks, etc. This continuing heat has to be removed or the core will continue to get hotter despite fission termination. As such, making a reactor safer is a two approach process. Stopping fission,which is easy with redundant methods, and maintaining cooling of the unavoidable radioactive heated core. It is this second problem that has caused most of the major accidents. Methods to add redundancy and reliability of the cooling options have been pushed, with obvious multiple failures. There are also methods proposed to make the core heating problem less through various means. You cannot stop the heating magnitude, but you can spread it out to a larger volume so that passive conduction and possibly passive convection will keep the temperature under control. I think the liquid salt reactors lend themselves to this approach. If coolent flow fails, the soup of radioactive products can be dumped into a larger container, perhaps with diluting liquid mass already in the reservoir. The thermal load is thus dilluted and there is greater surface area for cooling. Still, though, this is dependent on valves being opened. Passive valves like the blowout plugs on pressure cookers as a last resort are good, but still not foolproof.

Fusion reactors with their small fuel supplies inside the reactor at any given time are limited. The absence (or rather the very much less significant magnitude) of the radioactive product heating though is the major advantage. There is the potential though, for the energy stored in large and powerful superconducting magnets causing a mess.

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

mvanwink5
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Re: EMC2 news

Postby mvanwink5 » Mon Jan 25, 2016 8:30 pm

Except for the massive energy storage in the massive tokamak superconductor magnets.
Near term, cheap, dark horse fusion hits the air waves, GF - TED, LM - Announcement. The race is on.

D Tibbets
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Re: EMC2 news

Postby D Tibbets » Mon Jan 25, 2016 8:34 pm

[quote="Tom Ligon"]Dan,

The visual model I'd like to build to demonstrate this to the curious public (especially for SF Convention dog and pony shows) would be a flat Lexan box containing some pipe sections that represent the magnets, arranged spaced out so they represent both the face and corner cusps, more or less.

Around these magnet casing anchors, I'd put pieces of sponge rubber cut to represent the approximate shape of the magnetic field lines. Layers of several different colors of several stiffnesses would be a very elegant visual representation.

In the center the easiest way to run the demo would be to have a balloon (and you're using a similar analogy). Inflating the balloon would push back the foam and show how the magnetic field would distort in response. You could visually see the air pressure (plasma pressure) equaling the foam pressure (magnetic pressure). I would expect the cusps to tighten up.

Of course, that's not quite how it works, because the balloon would not leak out the cusps, and in fact the proposed mechanism for the inflation is the development of a diamagnetic plasma that excludes the magnetic field. I think the better model might be the same foam, with an impermeable rubber outer layer, but leaky cusps. Injecting air in the middle at too low a flow would not inflate the system, it would leak out as fast as it came in. To inflate the system, you would need a very rapid injection of air, analogous to Park's very high power injection. If you can achieve that, you get the compression of the foam and hopefully a constriction of the leaks at the cusps.

It is not perfect. But do you think the analogy is useful?

Tom[/quote

That would be an appealing demonstration. If the layers where very soft/ compressible to very stiff. Three layers might be soft foam rubber, exercise mat compressible layer, then tire rubber layer. Each layer would be nearly completely compressed before the next layer started . More layers would become increasingly challenging for finding appropriate layer material. With the inflating of the balloon the pushing out of the sequential layers is obvious, but more importantly the sequential compression of the softer layers would show the increasing pressure gradient/ B field gradient.

I'm not sure what the balloon would due to the B field/ foam layer contours. The foam may bulge into the 'cusps'. My understanding is that this does not occur with the B fields. The B field free radius increases, and the outer less steep portions of the cusps are flattened, but not pinched or bulged towards the midline axis of the cusps.

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

crowberry
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Re: EMC2 news

Postby crowberry » Thu Jan 28, 2016 7:32 am

Next Big Future has interviewed Jaeyoung Park. The interview is worth reading at http://nextbigfuture.com/2016/01/jaeyoung-park-confirms-publication-of.html.

crowberry
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Re: EMC2 news

Postby crowberry » Thu Jan 28, 2016 9:03 am

ladajo wrote:For those who didn't see this before;
Bob Hirsch covers the bases IRT ITER, he hits on everthing we have hit on here. Take it a step further, and apply the same thinking pattern to other projects.
The two top issues remain relevant: Plasma Stability, Materials.

http://issues.org/31-4/fusion-research-time-to-set-a-new-path/


Jaeyoung Park and Weston M. Stacey have both replied to the article by Robert Hirsch with their respective different views in Keeping fusion flexible at http://issues.org/32-1/forum-28/.

ladajo
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Re: EMC2 news

Postby ladajo » Thu Jan 28, 2016 1:26 pm

Why yes, yes they did... :)

Nice article by Brian Wang, even if I say so myself.
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)

Skipjack
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Re: EMC2 news

Postby Skipjack » Thu Jan 28, 2016 1:44 pm

Very cool article!

Tom Ligon
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Re: EMC2 news

Postby Tom Ligon » Thu Jan 28, 2016 4:29 pm

ITAR ... this will go down in history as a vile curse, like Niven's TANSTAAFL (There Ain't No Such Thing as a Free Lunch), and TANJ (There Ain't No Justice).

Years back at a conference space entrepreneurship, one space entrepreneur pointed to ITAR as the single biggest artificial hurdle facing free enterprise.

While I was at Rockwell Collins, we received corporate training on export restrictions. We were informed that all exports are either restricted by ITAR or EAR (Export Administration Regulations). EAR covers a world of "dual use" items that are not necessarily weapons but could conceivably be used for weapons. I suppose you could classify a baseball bat or a piece of dimension lumber that way, so, in essence, everything is dual use.

Further, we were told that even talking to a foreign national about technology was effectively an export of the technology. We were apprised to never talk to nobody, no-how, without a company lawyer present, who preferably did all the talking and managed to convey no information whatsoever.

Having been thus duly "COMSEC briefed", we were required to sign an oath of fealty to the Department of Commerce, on pain of imprisonment.

And evidently, poor Dr. Park went from one kind of gag order to another, while everybody wondered if he was covering something up.

Ivy Matt
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Re: EMC2 news

Postby Ivy Matt » Sat Jan 30, 2016 7:29 am

Alan Boyle has an article on Geekwire stating much the same thing as the NBF article:

http://www.geekwire.com/2016/emc2-reviv ... ar-fusion/
Temperature, density, confinement time: pick any two.

mvanwink5
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Re: EMC2 news

Postby mvanwink5 » Sat Jan 30, 2016 12:34 pm

'Either it works or it doesn't'

Not an optimistic statement. Either my lotto numbers are winners or they aren't or either the sun will come up or it won't, both statements fall into the same category but are vastly different.

Got the point EMC2? What kind of investor are you looking for?
Near term, cheap, dark horse fusion hits the air waves, GF - TED, LM - Announcement. The race is on.


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