Questions about FPGeneration

Discuss the technical details of an "open source" community-driven design of a polywell reactor.

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drmike
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Post by drmike »

I don't quite see how that can focus, but I don't have time to dig thru the math either. That is definitly a different take on the picture they draw, and it certainly be a balanced field that way. I'm used to octapoles in beam lines, but they are quite a different beast than this.
Interesting.

tombo
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Post by tombo »

They look like Bitter coils.
(said to be capable of 20T in another thread. not bad)
I think a Bitter coil kind of focuses the B field through its center hole.

The non-circular cross section conductors probably have lots of field lines intersecting the coils (bad).
Would that be the case in a Bitter coil too?

Nice way to reduce radiative heating and alpha blocking.

I would not try to weave them together.
I would make it more like those little copper tube examples that Dr Bussard showed late in the Google video. (I saw a name MP1? somewhere but can't remember.)
The Octopole version would have 6 vertexes with 4 edges each for an Eulerian path for the conductor. That works. The feed-lines could be run through the support strut and the feed-through shown in the top port.

Making a Bitter coil this way reminds me of origami.

The thickness in the radial direction would give good mechanical strength too.

This looks much like a device configuration that I have been playing with.
-Tom Boydston-
"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein

MSimon
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Post by MSimon »

Funny you should mention Euler.

Here is an interesting book:

http://www.georgehart.com/zomebook/zomebook.html

and a post I did that has a bearing on the subject (link also found in a thread I just opened in General):

http://powerandcontrol.blogspot.com/200 ... solar.html
Engineering is the art of making what you want from what you can get at a profit.

MSimon
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Post by MSimon »

The non-circular nature of a Bitter coil is only a problem very near the coil. Once you put a sheath around it (for containment of cooling fluids and for high voltage for the grid) the problem is very slight. Indrek did some simulations of copper wires in a quasi round and square configurations and at a short distance from the conductors in either configuration the field is circular. Of course more detailed studies would need to be done, but to a first approximation it is not a problem. The field conforms to the toroidal sheath.
Engineering is the art of making what you want from what you can get at a profit.

tombo
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Post by tombo »

The FPGeneration picture does not show a toroidal sheath.
It shows each of 3 coils as about 8” wide in the radial direction and 1” thick in the transverse direction and exposed to the plasma.
Wouldn’t that intersect quite a few of its own field lines?
The set of points close to their coils would form a thick closed sphere (roughly), so a sheath filling that volume would be cumbersome to say the least.

If they are running 20T maybe they are counting on very few electron/ions penetrating deeply enough into the field to get to a line that intersects the coil.
With the Polywell energy distribution the high energy tail will be smaller than that of a Gaussian distribution.
This should decrease the number lost to the solid surface, perhaps to a small enough fraction to be acceptable.

It seems to me that putting a toroidal sheath around a Bitter coil defeats the purpose.
You use up all that volume and intercept a lot more alphas. (8x in this case)
Consider the electron/ion that follows the (circular) (poloidal) field line just outside the toroidal sheath.
It will not intersect the sheath. Neither would it intersect the coil if the sheath were removed. So, what is the use of the sheath?

If you’re going to have that much volume inside the plasma why not use it all for windings?

Am I thinking clearly here correct or am I off target?
The energy distribution is narrower and lower in the tail than a Gaussian isn’t it?
The 20T assumption came from the Bitter coil discussion.
I assume they keep the cooling and all other functions inside the rectangular cross section shown. Else, I would have shown it.
Can they really get away with coils of that cross section (8"x1")? (Their coil path is another discussion.)
If they can get away with it can I?
That cross section has some nice advantages, but I don’t trust the rectangular cross section due to the experience with WB4 (and earlier).

Those Zome Works links are cute but I don’t see how the Fibonacci series connects.
My idea is simpler and more regular than the Euclidian solids shown there.
Well simpler in my mind. I need to run it past other folks.
Before you roll your eyes, it was inspired by a discussion by Dr Bussard near the end of the Google video.

I would like to show prints from my AutoCAD models for discussion when I can figure out how to insert a picture.
I hate trying to describe geometry with words; they are just not the right tools.
-Tom Boydston-
"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein

MSimon
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Post by MSimon »

Just put up a jpg link. I'll fix it if it doesn't work.

Simon
Engineering is the art of making what you want from what you can get at a profit.

MSimon
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Post by MSimon »

It seems to me that putting a toroidal sheath around a Bitter coil defeats the purpose.
You use up all that volume and intercept a lot more alphas. (8x in this case)
Consider the electron/ion that follows the (circular) (poloidal) field line just outside the toroidal sheath.
It will not intersect the sheath. Neither would it intersect the coil if the sheath were removed. So, what is the use of the sheath?
To prevent sharp points that would concentrate the electric field and cause plasma discharge. It also would serve as a channel for coolant.
If you’re going to have that much volume inside the plasma why not use it all for windings?
Good idea for uncooled coils. Not so hot for Bitter magnets as you have current density problems in any other than a square or rectangular form factor. You are laying up flat sheets.

I think the 20T is for superconductors. It may be possible with superconducting "wire" to fill the form. If ribbon is used you are back to Bitter type issues.

The Zome book I suggested in the article had a chapter on Euler.

I'd like to have some distinctive buildings associated with Fusion. Domes or something else. Zomes seem like a good compromise from an engineering standpoint. All pie in the sky for now.
Engineering is the art of making what you want from what you can get at a profit.

CharlesKramer
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Re: Questions about FPGeneration

Post by CharlesKramer »

kurt9 wrote:I stumbled upon a website (www.fpgeneration.com), which describes a mutli-pole ion source version of an IEC polywell. The guy, Alex Klein, has previously worked with Dr. Bussard. Can anyone here comment on Alex Klein's MIX approach to polywell fusion and how it compares with Dr. Bussard's approach? Any comments are appreciated.
Alex Klein update.

http://nextbigfuture.com/2011/05/fp-gen ... unded.html

[excerpt]

FP Generation was first formed in 2005 by two Columbia graduate students in the department of Applied Physics. In April of 2009, FPG raised $3 million in series A financing from two leading cleantech venture funds to demonstrate the viability of the MIX concept for net fusion power generation. After some initial theoretical, computational and design work, and a meeting of the technical advisory board in September 2009, FPG hired a team of physicists, engineers and technicians, and built a lab in Woburn, MA, 10 miles north of Boston.

As of April, 2011, FPGeneration is running out of funds to carry on the research. After two years of operations, our VCs have decided the technology is looking more like an extended research project than what they had signed up for initially. Unfortunately, in the absence of additional investment, this technology will be mothballed.

The MIX machine construction was completed by May 2010, but by the fall of that year it became clear that there were fundamental problems with the approach. In November, the team invented the MARBLE concept; this new device seems to solve the problems inherent in the MIX design. FPG built a prototype, which has been running since March 2011.

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