Carlson and Nebel

Discuss how polywell fusion works; share theoretical questions and answers.

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TallDave
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Post by TallDave »

Re: magnetized ions. Let me see if I understand Carlson's objection here.
Taking a magnetic field of 8 T and a (perpendicular) deuteron energy of 100 keV, I get a gyroradius of 8 mm. In a machine of radius 1.5 to 2 m, the ions will be highly magnetized. Is this now considered unimportant? What about Krall's calculation of the deflection of an ion falling in to the center?
http://en.wikipedia.org/wiki/Larmor_radius

So he's saying that given field strength of 8T and etc, the ions will spin around a gyroradius of 8 mm, breaking our pretty little double well and destroying ion focus?

I think he's missing that 1) the field strength falls off at the core, and 2) the electrons push back the field.

Does that sound right?

TallDave
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Post by TallDave »

Ah, more from Nebel:
Dr. Carlson:

The 8 mm gyroradius isn't a big deal since few of the ions will ever access that region of the device.In the middle the gyroradius is infinite which is where the ions spend their time.
The plasma is quasi-neutral (but not neutral) and the particle losses are ambipolar. MHD is not a good idea (just like it isn't for a Field Reversed Configuration) becasue there is a field null at r=0 and the wuiffle-ball effect (expansion of the plasma against the field) makes this low field region fill almos the entire plasma. Besides, the field line curvature is good everywhere so MHD stability isn't an issue.
I don't have the field magnitudes from the edge vs. the center of the coils at my fingertips, but the ratio of the field at the cusps in the corners vs. the cusps in the faces is about a factor of 2.
As for the midpoints on the faces of the cubes, since the adjacent conductors have currents in opposite directions they add between the conductors. Between the conductors should be the strongest fields in the entire system.

seedload
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Post by seedload »

TallDave wrote:Ah, more from Nebel:
Dr. Carlson:

...

As for the midpoints on the faces of the cubes, since the adjacent conductors have currents in opposite directions they add between the conductors. Between the conductors should be the strongest fields in the entire system.
...and it keeps striking me that that is a simple thing that Carlson is missing whenever he talks about zero field at the cusps. Does he think the fields are opposed and cancelling rather than in the same direction? That fact is so basic to the invention and would be such a peculiar oversite that I keep dismissing the notion that he doesn't understand it - assuming that he is talking about some other speculative zero field thingy that I don't understand because of my own lack of knowledge.

dch24
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Post by dch24 »

seedload wrote:...and it keeps striking me that that is a simple thing that Carlson is missing whenever he talks about zero field at the cusps. Does he think the fields are opposed and cancelling rather than in the same direction? That fact is so basic to the invention and would be such a peculiar oversite that I keep dismissing the notion that he doesn't understand it - assuming that he is talking about some other speculative zero field thingy that I don't understand because of my own lack of knowledge.
The magnetic field lines are parallel at the cusps. I think Dr. Carlson is talking about the electric field.

MSimon
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Post by MSimon »

seedload wrote:
TallDave wrote:Ah, more from Nebel:
Dr. Carlson:

...

As for the midpoints on the faces of the cubes, since the adjacent conductors have currents in opposite directions they add between the conductors. Between the conductors should be the strongest fields in the entire system.
...and it keeps striking me that that is a simple thing that Carlson is missing whenever he talks about zero field at the cusps. Does he think the fields are opposed and cancelling rather than in the same direction? That fact is so basic to the invention and would be such a peculiar oversite that I keep dismissing the notion that he doesn't understand it - assuming that he is talking about some other speculative zero field thingy that I don't understand because of my own lack of knowledge.
I think he means zero field in the direction of travel. i.e. the hole.

Which is how I discussed the matter until corrected.

Zero cross field (re: some particles in the system) would be a better way of describing it.
Engineering is the art of making what you want from what you can get at a profit.

charliem
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Post by charliem »

I wonder if anyone has ever tried to run a tokamak with a non neutral plasma. Keep interior walls at ground potential and compensate electron losses by injection from the exterior. A lot like a polywell.

At first sight looks like that could improve pure magnetic confinement.

hanelyp
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Post by hanelyp »

Running a tokomak in IEC mode (magnet confinement of electrons, electric confinement of ions) would be an interesting experiment. No cusps for electron leakage, but magnetic contours less favorable to stability.

seedload
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Post by seedload »

Carlson says,
Nebel's answers have not changed my mind, but they are interesting enough to keep me talking. I think, however, that viewforum.php?f=3 is a more appropriate and more convenient forum. Anyone who wants to follow this discussion should move over there.

charliem
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Post by charliem »

I think that having Carlson here would be great.

Nothing better to improve (or disprove) a discourse that a little opposition/competition to substantiate its points.
Last edited by charliem on Wed Jun 25, 2008 5:31 pm, edited 1 time in total.

tonybarry
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Post by tonybarry »

Nebel's answers have not changed my mind, but they are interesting enough to keep me talking. I think, however, that viewforum.php?f=3 is a more appropriate and more convenient forum. Anyone who wants to follow this discussion should move over there.
This is great. We can only improve our understanding.

Tony Barry[/img]

TallDave
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Post by TallDave »

I agree, having Carlson here would be great, and left a message on the MSNBC thread to that effect.

Munchausen
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Post by Munchausen »

By the way: Any comments on Indreks rather serious and seemingly wellfounded objections here:

http://tech.groups.yahoo.com/group/IEC_ ... ssage/1403

A comment not founded in any reasonings of technical nature is that dr. Nebel would certainly not speak publicly of scaling this technology into power generating reactors if the virtual cathode does not form in the WB-7.

Lest he has considered giving up his career in physics for selling T-shirts with the EMC2 logo.

JohnP
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Post by JohnP »

Munchausen wrote:By the way: Any comments on Indreks rather serious and seemingly wellfounded objections here:

http://tech.groups.yahoo.com/group/IEC_ ... ssage/1403

A comment not founded in any reasonings of technical nature is that dr. Nebel would certainly not speak publicly of scaling this technology into power generating reactors if the virtual cathode does not form in the WB-7.

Lest he has considered giving up his career in physics for selling T-shirts with the EMC2 logo.
I've read through this but not sure what the objections are. That the mag fields won't hold the electrons?

MSimon
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Post by MSimon »

JohnP wrote:
Munchausen wrote:By the way: Any comments on Indreks rather serious and seemingly wellfounded objections here:

http://tech.groups.yahoo.com/group/IEC_ ... ssage/1403

A comment not founded in any reasonings of technical nature is that dr. Nebel would certainly not speak publicly of scaling this technology into power generating reactors if the virtual cathode does not form in the WB-7.

Lest he has considered giving up his career in physics for selling T-shirts with the EMC2 logo.
I've read through this but not sure what the objections are. That the mag fields won't hold the electrons?
As far as I can tell the objection is that the well won't even form.

That was once my greatest objection. Until I read this:

http://wwwsoc.nii.ac.jp/aesj/division/f ... hikawa.pdf

I posted that url in reply to Indrek's objection. We shall see if that was the answer he was looking for.
Engineering is the art of making what you want from what you can get at a profit.

Indrek
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Post by Indrek »

My point there was not as much as that the well won't form at all but rather the _effective_ well depth for ions will be limited due to the coils having big holes in them (the other half of this mail is actually about an entirely different idea - you have to read the thread).

Going further have a look at this picture of the potential in a simulated polywell:

Image

This is from my (not that perfect) plasma simulation. In this picture the potential in the middle is quite low compared to the coils. But the recirculating electrons through the faces reduce the effective well depth - the ions will be able to escape through these holes.

The revelation I guess is that polywell can't work with recirculation alone - the effective well depth will be poor. The only salvation could be in the wiffleball.

But just in case I have to state here that my plasma simulation lacked important elements, was low resolution and I didn't manage to verify its correctness. So my results in this regard should be taken with caution.

- Indrek

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