Simple tetrahedra pyramid considered?

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JoeOh
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Simple tetrahedra pyramid considered?

Post by JoeOh »

Amidst my tinkering with the simple design of the Polywell, I am goofing around with the idea of a 3D triangle shaped version of the reactor. I am using the magnetic program ViziMag. The results seem to be better as far as a smaller magnetic "void" in the center of the simple pyramid.

Anyone else looked into this shape in greater detail?
I'd trade it all, for a little more :)

alexjrgreen
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Post by alexjrgreen »

Ars artis est celare artem.

KitemanSA
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Post by KitemanSA »

A tetrahedron will not work as a Polywell. A RECTIFIED tetrahedron (a.k.a., an OCTAhedron) will. A Polywell shape needs to have an even number of faces at each vertex. Tetrahedra only have three. Octahedra have 4.

Before anyone starts yelling that the cube only has three at each vertex, remember that the WB(x) series have all been (not so good) approximations of RECTIFIED cubes (a.k.a., cuboctahedra) which have 4 also.

One of the things Dr.B. wanted to do before going on to the 100MW demo unit was to improve the fidelity of that approximation (square planform magnets), and to use at least one higher order polyhedron (rectified dodecahedron).

TallDave
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Post by TallDave »

Did we ever rule out WB-8 being a dodec?

I guess there's no way to know the planform...

Art Carlson
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Post by Art Carlson »

KitemanSA wrote:One of the things Dr.B. wanted to do before going on to the 100MW demo unit was to improve the fidelity of that approximation (square planform magnets), and to use at least one higher order polyhedron (rectified dodecahedron).
Except that he also realized (eventually) that there are field nulls at the vertices of perfect polyhedra, going all the way to the center of the machine. Bad news. So he decided you have to have discreet coils and leave gaps between them.

JoeOh
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Post by JoeOh »

Yea Kiteman, A while after I posted this topic I began to think about the idea of vertex mirroring of coils and how it might upset the fields in an unexpected manner.

I guess the cube with circular coils is as simple as you can get. Plus It'd look better than a funky triangle. :)
I'd trade it all, for a little more :)

KitemanSA
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Post by KitemanSA »

Art Carlson wrote:
KitemanSA wrote:One of the things Dr.B. wanted to do before going on to the 100MW demo unit was to improve the fidelity of that approximation (square planform magnets), and to use at least one higher order polyhedron (rectified dodecahedron).
Except that he also realized (eventually) that there are field nulls at the vertices of perfect polyhedra, going all the way to the center of the machine. Bad news. So he decided you have to have discreet coils and leave gaps between them.
Yup, which he mentions in the Valencia paper (square planform with rounded corners). You can have gaps without having round coils. You can also have gaps without having DISCRETE coils. That is the genesis of the "X" cusp, a.k.a. the "holey X" cusp.

Spelling corrected based on "9"'s reference to the dictionary.
Last edited by KitemanSA on Wed Dec 16, 2009 5:44 pm, edited 1 time in total.

KitemanSA
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Post by KitemanSA »

JoeOh wrote:Yea Kiteman, A while after I posted this topic I began to think about the idea of vertex mirroring of coils and how it might upset the fields in an unexpected manner.

I guess the cube with circular coils is as simple as you can get. Plus It'd look better than a funky triangle. :)
Depends on what you consider "simple". It is possible to create plausible Polywell with only 4 circular magnets, though I am not sure how efficient it would be.

Art Carlson
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Post by Art Carlson »

KitemanSA wrote:
JoeOh wrote:Yea Kiteman, A while after I posted this topic I began to think about the idea of vertex mirroring of coils and how it might upset the fields in an unexpected manner.

I guess the cube with circular coils is as simple as you can get. Plus It'd look better than a funky triangle. :)
Depends on what you consider "simple". It is possible to create plausible Polywell with only 4 circular magnets, though I am not sure how efficient it would be.
I bid 2. Of course, that puts us back at the classic spindle cusp, but I never understood why more coils is supposed to be better. On the contrary, more coils only increase the number of point cusps and the lengths of the line cusps.

TDPerk
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Post by TDPerk »

"I never understood why more coils is supposed to be better. On the contrary, more coils only increase the number of point cusps and the lengths of the line cusps."

I understood that for the same energy input (at the cost of higher losses to pass throughs/supports) you had higher field strength, making the geometry of the cusp smaller in relation to the "electron gyro radius". A_cusp(effective) went down. Since the availability of the electrons to be outside the magrid to hit a pass through went down drastically as the cusp proportional geometry improved to be nearer the gyroradius, it was plausible that a dodecahedron would have a better confinement than a "cube".
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alexjrgreen
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Post by alexjrgreen »

Art Carlson wrote:I bid 2. Of course, that puts us back at the classic spindle cusp, but I never understood why more coils is supposed to be better. On the contrary, more coils only increase the number of point cusps and the lengths of the line cusps.
Perhaps kcdodd could check whether box corner reflection still works with only two coils.
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KitemanSA
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Post by KitemanSA »

Art Carlson wrote:
KitemanSA wrote: Depends on what you consider "simple". It is possible to create plausible Polywell with only 4 circular magnets, though I am not sure how efficient it would be.
I bid 2. Of course, that puts us back at the classic spindle cusp, but I never understood why more coils is supposed to be better. On the contrary, more coils only increase the number of point cusps and the lengths of the line cusps.
I fail to see how you can possibly get multiple PAIRS of fields around each vertex with only two circular coils. Four circular results in 4 real plus 4 virtual coils, 4 fields at each vertex. I can't envision the same with only two magnets.

As to more coils being better, maybe not if they are circular like the WB6/7/(8?). But if the coils more accurately follow the theoretical face shape, maybe they will be better. After all, the line-like cusps would effectively be eliminated. All the would be left would be point, and point-like X cusps.


KitemanSA
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Post by KitemanSA »

So your point is that the coils are separate, but lack discretion? :lol:

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