Alpha collector geometry idea...

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

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93143
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Alpha collector geometry idea...

Postby 93143 » Thu Jul 03, 2008 12:01 am


rcain
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Postby rcain » Sat Jul 05, 2008 1:16 am

you mean a bit like a sort of graduated anechoic chamber - an absorption filter if you will?

i was thinking of similar sorts of arrangements a while back to mitigate collisions with the grid coils - studying some of the models at http://www.falstad.com/mathphysics.html and seeing how charged particles behave around spikes, edges, corners, etc; wondering if they could be made useful rather than problematic.

are we on a similar wavelength?

93143
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Postby 93143 » Sat Jul 05, 2008 4:32 am


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Postby Jccarlton » Sat Jul 05, 2008 8:04 pm


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Postby MSimon » Sun Jul 06, 2008 3:16 pm


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Postby tombo » Fri Jul 11, 2008 5:27 am

93143 something like this?

Image
This is really quick and dirty just to have something to look at.
The first thing that jumps out at me is how rapidly the side electrodes diverge.
They would diverge more slowly in a dodecahedron.
The nasa paper from 1964 looks like a pretty good starting point.
http://ntrs.nasa.gov/search.jsp?R=21685 ... 4294967207
They were talking 10's of meters for this kind of deflection.
It would be good to see what follow up they have done in the succeeding 44 years.
If you would like me to tweak this sketch just ask.
-Tom Boydston-
"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein

93143
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Postby 93143 » Fri Jul 11, 2008 6:03 am


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Postby tombo » Fri Jul 11, 2008 6:21 am

-Tom Boydston-

"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein

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Postby dch24 » Fri Jul 11, 2008 6:30 am

tombo, that design sounds good to me. One question 93143 had was what the shape of the grids/plates for lateral deflection should be -- specifically, he did the thought experiment of lateral deflection using wedge-shaped plates, and noted that the high voltages would not allow a sharp edge on the inside of the profile.

Question for 93143: Assuming that an ellipsoid or anything beveled to a large enough radius, in the MaGrid shadow, does lateral deflection -- then would this have other problems I missed from the previous discussion of lateral deflection?

Question for tombo: How much deflection will the alphas see into the MaGrid shadow from alpha-alpha electrostatic forces, collisions, or other possible effects? I assume as their radial velocity drops the deviation into the shadow will be greater.

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Postby tombo » Sat Jul 12, 2008 9:16 pm

Actually I would prefer to bend the alpha paths the other way, making the shadowed volume larger and larger as we go away from the center.
The solution would take a 3D path integral of the alpha path grazing the Magrid.
The path would be determined by the maximum potential that could be placed on a deflector while keeping it within the shadow and would in turn determine the diameter and radial spacing of the next segment of deflector.
I’m imagining a series of positively charged rings or tubes with their thickness and spacing limited by the arc breakdown limits.

It might be a losing proposition because the deflection would need to grow more rapidly than the shadows diverge.
Also the alpha source is not going to be a point source but an extended source that in the worst case [for this optimization (but probably better for the Lawson criterion)] would come quite close to the Magrid leaving a very small shadow to start from.
Then the whole thing would need to be done again for the cube corners.
That math I'm sorry to say is beyond me. (Not without many weeks or months of review work just to get started.)
Although, I might be able to solve it piecewise kind of like a coarse integral.
And of course all this is preliminary to detailing out the energy separation floated above.

Oh, there is a problem with the spike. It can’t be negative can it? That will reduce the lateral field available.
Maybe a positive spike is right, but I was hoping to make the shadows into a growing wedge in which to locate the utilities. (You know: power, water, data etc.)

Yes, dch24 you are right Alpha – Alpha repulsion would expand the beam. With any luck that would be balanced by a Z-pinch effect. I would not expect significant lateral effects from collisions at those radial speeds. And, yes, I know it can’t have sharp edges. This picture was just a rough starting point for discussion.

Also, as Msimon pointed out the effects of the magnetic field would also need to be looked into.

As you can see I don’t have an answer here yet.
I’m still churning.
My next step here is to look up minimum radius for given high voltage objects at these pressures and verify the minimum spacing I’m using (25kv/cm from another thread) and I’m sure these are tied together.
But first I’m going to work on viewing Dr Mike’s model of my octahedron.

Uh-oh, I’ve been running off at the keyboard again. I hope I’m shedding more light than heat.
-Tom Boydston-

"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein

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Postby Aero » Sat Jul 12, 2008 10:29 pm

You can find the NASA paper on a link from here
I don't know how my first post got corrupted. I probably didn't do it right.
Aero

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Postby Aero » Sat Jul 12, 2008 11:19 pm

Aero

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Postby 93143 » Sun Jul 13, 2008 12:29 am


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Postby tombo » Sun Jul 13, 2008 5:05 am

-Tom Boydston-

"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein

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Postby Aero » Mon Jul 14, 2008 2:23 am

Aero


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