Why people are so optimistical to Polywell?

[Joseph Chikva]

What kind of limitations Polywell's design has?
Such as space charge and its limitations, possibilities of instabilities' creation and development?
What are the results in experiments have been already done?

I tried to get this information in the web but could not.

[chrismb]

You are kidding us, right?

There are about 500 threads in each of the 'theory' and 'design' forums here, clawing over every scrap of info on polywell, and you can't find anything!?!?

Meanwhile, there is endless chin-wagging about what may or may not be the issues and status for past present and future WB projects in the 'news' forum.

Do some reading, buddy. What did your last slave die of?

[Joseph Chikva]

No kidding

Regarding results
Density x confinement duration like Lawson criterion or which other breakeven criteria is used for Polywell?

Regarding limitations
Space charge
I have read at FPGeneration's web-site the following:

One of the major obstacles that limits the fusion output in IEC devices is the result of repulsive electrostatic forces arising from the ions themselves.

Instabilities
Does electron beam injected to Polywell interact with background plasma being inside? Or no?

[Joseph Chikva]

Joke of my dead slave:

Electron Beam Plasma Instability

...This initial configuration is unstable to an electrostatic plasma wave which grows by tapping the free energy of the electron beam. At early times, the unstable waves grow exponentially...

The full text you can read here: http://www.netlib.org/utk/lsi/pcwLSI/text/node180.html

[CaptainBeowulf]

Joseph,

If you want insightful criticism of Polywell, search for all threads containing comments by Art Carlson on this site.

There are many other criticisms, but the discussions Art was involved in get to the heart of the physics, setting aside all the other engineering concerns.

I think people want to be optimistic about Polywell because a lot of them have gotten frustrated with Tokamak research - both its slow pace and the increasing expensive "megaproject" approach to it, which looks like it will never pan out into something commercially viable or compact enough to be useful on things like ships or spacecraft. There are also people like me who think that even if you fund one main line of research (Tokamaks), you should also fund other parallel approaches. After all, when they developed the atom bomb, they created both the "fat man" and "little boy" designs - parallel routes which both panned out in the end.

[Joseph Chikva]

Thank you very much.
I will read.

I only asked the question because see the conditions of creation of two-stream instability when electrons with non-zero arrange velocity (the beam) interacts with thermal electrons (zero arranged velocity).
I do not know on other types instabilities. But two-stream - without doubt.
And I do not see any way to solve this problem for Polywell design.

Regarding TOKAMAK and other projects I think the same as you.

[Nik]

When you consider that main-stream fusion designs have lurched from road-block to insurmountable obstacle for the last fifty years, with break-even always a decade or two away, the Polywell approach has come a long way, very quickly...

( Yes, yes, I even remember the 'figure of eight' Stellerator which was supposed to be two or, maybe, three iterations from over-unity... )

I want WB to come good because, in the near-term, (1) it breaks the global dependency on fossil fuels for baseline power and (2) it gives us the solar system as far as the Middle Oort...

[chrismb]

the Polywell approach has come a long way, very quickly...

Where is it? You know something we don't? Do you mean - it's had 30 years of funding and is still paying salaries?

[Joseph Chikva]

There may be because of my bad English. It seems that you haven't understood what I said.
I am asking only about the technical feasibility of Polywell.

And everybody knows about dependency of world economics on crude oil&gas. But we also can see that right now the Governments of top countries are not interested to overcome that.
Otherwise financing of different fusion programs would be more.

[D Tibbets]

If you are really interested read through the papers at this site:

http://www.askmar.com/Fusion.html


A good paper to start with may be:

http://www.askmar.com/Fusion_files/Some ... ations.pdf


Also, read through the back and forth between Dr R Nebel and Dr A Carlson.
It started on the Next Big Future, and transferred to this site.
Other threads have a lot of arguments, sometimes even useful arguments, but they are fragmented and will need persistence to work through.



Reading the 2008 patent application can also be enlightening:

http://prometheusfusionperfection.files ... tent08.pdf


Dan Tibbets

[Joseph Chikva]

Thank you.
I have already seen some papers including Dr. Bussard's paper you kindly noted me.

My questions are the following:
First:
Not in theory but results of experiments on WB-1.....WB-6?
Second:
Am I correct or no with declaration that Polywell obligatory will suffer 2-stream instability as electron beam interacts with background plasma?
Or may be this is not a problem for Polywell?

[93143]

There shouldn't be a "background plasma" as such; if ion guns are used (and in the latest machines they are), the electron population should be mostly from the electron injectors. Official word is (was?) that electrons don't thermalize before being lost... There will be two-stream effects, but it's not impossible that something like Landau damping could result in a stable pattern of standing Langmuir waves anchored at the wiffleball edge.

I hypothesized this a while back, after considering the fact (suggested to me by a conversation with Art Carlson) that the naive double-well model of wiffleball structure seems to produce a space charge distribution inconsistent with the operating voltage. I started to code a simulator to test my hypothesis with a simplified equation set, but unfortunately I got busy with other stuff and have not made much progress... also, I was considering it in a spherically-symmetric sense; 3D effects will mess it up somewhat...

...It's a complicated problem. At this point, probably the fastest way to find out if it works is to wait for EMC2's experiments to bear fruit. WB-8 apparently does what it was supposed to, which is a very hopeful sign...

[Joseph Chikva]

I know that it's a complicated problem.

Official word is (was?) that electrons don't thermalize before being lost...

And after being lost? Where are they going? Not into reaction zone?

And it's excellent if damping.
Because I heard about particles loosing with energies exceeding the potential well's depth. And thought that this is possible only thanks to instability’s growing and not damping.

One more question:
If there should not be the electrons scattered betweens ions (background plasma) how are you going to neutralize the space charge?
And what density of particles are you waiting for?

Thanks.

[KitemanSA]

And after being lost? Where are they going? Not into reaction zone?

No. IIUTC, electrons are "lost" to the MaGrid or the chamber wall.
As I understand it, the electrons that get downscattered make their way to the MaGrid via diffusion with a complete loss of energy while those that upscatter make their way back to the chamber wall with an almost complete recapture of energy.
Some have suggested that there may be a sphere of low temperature electrons outside the well but not yet having reached the MaGrid.
But none should be in the core area where the plasma is.
Please remember that there is a continuing inflow of max energy electrons, enough to heat most cooled electrons back to temp. That is part of the basic design.

[Joseph Chikva]

...the electrons that get downscattered make their way to the MaGrid via diffusion with a complete loss of energy.

Diffusion through what and where they (those diffunded electrons) are at the end?

Some have suggested that there may be a sphere of low temperature electrons outside the well but not yet having reached the MaGrid. But none should be in the core area where the plasma is.

So, do you declare that some electrons create a certain layer between the high energetic electrons and the core area where the plasma is?

Please remember that there is a continuing inflow of max energy electrons, enough to heat most cooled electrons back to temp. That is part of the basic design.

And also do you declare that some electrons heat another part of electrons? Via which mechanism? Colliding?