Crazy Design Idea

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
winjim
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Crazy Design Idea

Post by winjim » Sat Sep 14, 2002 2:43 pm

Hi folks,

I would ultimately like to see fusors developed as power
sources. However, in the literature, the phrase 'grid losses'
keeps occurring as why this won't happen.

So I've been thinking about ways to get rid of the inner grid,
ala Bussard's Polywell patent. Since I'm months away from
being able to test these ideas, I thought I'd post them so
someone else could pursue them if so inclined.

The basic design is a fusor chamber made of two stainless
steel hemispheres, welded to flanges and bolted together to
form a complete sphere. For reference, the flanges would be
around the equator, the High Voltage feed through at the
North Pole and the vacuum connections at the South Pole.
Small ports for D2 introduction and a viewport would be place
on the surface appropriately.

Permanent magnets would be arranged on the exterior surface
so that their magnetic field penetrates through the stainless
steel into the fusor chamber. The arrangement of those
magnets would follow the Halbach Rotation Theorem. You
can look at:

http://http://www.matchrockets.com/ether/halbach.html

and

http://www-sldnt.slac.stanford.edu/nlc/ ... -067_2.pdf

for more information on Halbach arrays. Basically, the
permanent magnets are arranged so that a strong magnetic
flux appears on one side and little or none appears on the
other. In a circular arrangement, the flux can be made to
appear on the inside.

In the second link above, there is a particular arrangement
called a Quadrupole. This has 4 cusps where the field lines
come together and strong flux everywhere else. Imagine a
series of these Quadrupole Halbach arrays of varying
diameter stacked on top of each other so that each ring circles
the fusor chamber at a particular latitude. Proceeding from the
largest at the flange around the equator to the smallest around
each pole. This would create a magnetic field that would
have 4 'line cusps', to use Bussard's terminology, at 0,
90, 180 and 270 degrees longitude. Electrons would be
mostly confined by the magnetic field to the center of the
chamber, but leakage would occur at the line cusps.

To prevent this leakage, imagine an outer grid made of two
wire circles that are just smaller than the diameter of the
chamber, intersecting at right angles at the North and South
pole. Such a grid would be oriented so that the wire circles lie
in the cusps at 0, 90, 180 and 270 degrees longitude. If held
at a high negative voltage, these would set up an electric field
that would repel the electrons away from the magnetic cusps
and prevent leakage there. A third circle of wire could be
placed at the equator to cover the weakened field that would
occur there as a result of the flanges not allowing magnets to
be placed properly. The grid would also be the source of
emitted electrons.

If the free electrons were confined to the center of the
chamber, positive D2 ions would be attracted to them and
would collide in the center as in a standard fusor.

That's what I've been thinking about. Sorry for the length and
I had to write it hurridly since I'm losing my internet access for
a couple of weeks. I'd be glad to clear up anything that isn't
apparent and I'd love to hear everyone's thoughts on the
feasibility of this.

Thanks,
Jim

guest

Re: Crazy Design Idea

Post by guest » Sat Sep 14, 2002 5:29 pm

Not too crazy an idea..... That's why we are here.

I studied all the fusion techniques including the Polywell I settled for Dr Miley's Pulsed fusion work
simply because it suited my background and my budget.
We have plenty of ground to cover here in the fusion area.
Lots of work in very interesting areas ...... plenty for twice a hundred to do.
Unless someone is a multimillionare one has to cull his interests somewhat.
Pick a spot you like and pitch a tent so to speak.

The Halbach arrangement is a very good arrangement for magnetic deployment. Now the easy part is done and the fun really begins.....building it.
Budget the beast.
Create a place for it to happen.
Do ALL the preliminary plasma work to make sure it will Do what you think it will.
Build small test setup with just a few magnets first to see what's what.
If that works like you would like then build a medium rig recycling the first test into a bigger test to make sure scaling is working.
Then build the humongo rig.
Hey I started on my one horse fusor design about a year and a half ago.
Good Luck!
Happy Funding!

Fusion is fun!

Larry Leins
Fusion Tech

guest

Re: Crazy Design Idea

Post by guest » Tue Sep 17, 2002 12:11 am

What exactly is burssards patent number, I couldn't find his patent using a database search, so i want to find it directly. I know the basic jist, ie. using magnets to confine electrons to create a negative potential well etc. but i want to reference it. Thanks.

winjim
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Re: Crazy Design Idea

Post by winjim » Tue Sep 17, 2002 11:37 pm

Patent #4826646

grrr6
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Re: Crazy Design Idea

Post by grrr6 » Wed Sep 18, 2002 2:08 am

Thanks. It seems that you would need very powerful magnetic fields to confine the electrons with such energy(100 KeV - 1 MeV) also, how do you plan to insulate the grid from arcing to the housing? seems that it would have to be close to the edge of the housing, and at high voltage, so it would want to arc to the housing. Especially if you went with Bussards idea to use the housing for direct conversion of energy -> electricity. maybe if you coated the outside of the grid with a dialectric, leaving the inside to shoot electrons out, towards the center and the confining field. But it seems that even with this, the potential would still be high enough so that it would arc around from the inside to the housing. Although the electrons emitted would tend to limit the voltage on the grid right? Hehe, abuzz with ideas. All together sounds like a pretty darn good idea though.
Also, what happens to the magnetinc field in 3d? we know what happens at the equator, but when you move "north" does it have symmetry? could you make it have 6 cusps like sides of a cube or something?

guest

Re: Crazy Design Idea

Post by guest » Wed Sep 18, 2002 1:37 pm

The last patent tho good is not as good as
USPN # 5,160,695 dated 1992

What put me off this design was the fact that the
implementation included a superconducting shell to cart away the excess charges to make electricity.
My NASA buddies estimated this design to be in the nation enterprise catagory. ( over 5 million to test!! Yike!)

Larry Leins
Fusion Tech

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Richard Hull
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Re: Crazy Design Idea

Post by Richard Hull » Wed Sep 18, 2002 2:35 pm

Electrons, even 1mev jobs are easily moved about by magnetic fields of relatively little strength. Their mass is low and often, just a few hundred gauss in a small gap is all that is needed. I curly-Q 800kev betas in a 900 gauss field all the time as part of a beta steering demo.

Of course, such a field density is not easy to obtain in the middle of a large chamber with outside poles. This means a lot of magnetizing force or energy is needed to project a rather whimpy field. Magnetics is probably one of the worst forces in nature. Weak, and strictly the result of charges in motion, it has no inate existance of its own. A secondary, "also ran force", at best.

It's engineering implimentation is ultra expensive in structures of any size larger than 200 cubic inches (1/8th of a cubic foot). If control or variability of the field is required over 1000 gauss with gaps exceeding 10", you may be talking water cooled coils.

Magnetics engineering is virtually a black art.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

ChrisSmolinski
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Re: Crazy Design Idea

Post by ChrisSmolinski » Wed Sep 18, 2002 5:55 pm

Richard Hull wrote:
> It's engineering implimentation is ultra expensive in structures of any size larger than 200 cubic inches (1/8th of a cubic foot). If control or variability of the field is required over 1000 gauss with gaps exceeding 10", you may be talking water cooled coils.
>
> Magnetics engineering is virtually a black art.

Richard,

Do you know of any attempts to use magnetic fields to focus the isotropic radiation pattern of a beta source into something resembling a beam?

I've done some experiments using a rare earth magnet and a Pm147 (225 keV max) beta source, with a PIN diode detector, and was able to more than double the counting rate by careful placement of the magnet. Rotating the magnet 180 degrees (flipping poles) likewise dramatically decreased the counting rate. This wasn't a serious experiment, just some playing around to refute the ideas of a former colleage who said it couldn't be done ;-)

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Richard Hull
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Re: Crazy Design Idea

Post by Richard Hull » Wed Sep 18, 2002 7:23 pm

You can't steer all of the betas into a beam as you suggest.
The experiment you mention is exactly what I demo here. I have actually put this interesting demo on my video tape about radiation. "Radiation - What it is and how to measure it".

What is happening is that you are steering a larger fraction of variable energy betas into your detector. Many that were originally headed its way never hit it though. You will lose every single beta headed to your detector on a natural straight line path, but oddly you will force into the detector a large stream of widely variable energy particles over a much larger solid angle of emitted betas.

Seems odd, sounds odd, but it really happens. There is some critical position and orientation of a fixed energy PM where the range of beta energies will give the largest return to a fixed detector positioned nearby. (note* this only can be done with a true isotropic emitter in open air.) Place the source 2" back in a thick lead gun barrel of .5" bore and you now have the makings of a beta spectrometer.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

winjim
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Re: Crazy Design Idea

Post by winjim » Wed Sep 18, 2002 11:24 pm

I am certainly no magnetics engineer, but I think it might be
possible to generate a high enough mag. field inside the
chamber using permanent magnets in a Halbach configuration.
I believe that you can increase the field strength by increasing
the size of the magnets. Whether this is practical remains to
be seen and is one direction I intend to investigate by
simulation before I build anything.

Greg, I had exactly the same thought process you did. At
higher grid voltages, I thought about coating the side of the
grid closest to the chamber wall with ceramic and baking it on.
Don't know if that's possible or not though. For electrons to
arc around from the inside surface to the chamber wall, they
would have to cut through the strongest part of the magnetic
field and they might not be able to make it. Again, I don't
know.

The 3D mag field would be pretty symmetrical. For an 8"
sphere, imagine a Halbach ring ,around the equator, 8" in
diameter and 1" thick. Stacked on top of that would be
another ring 1" thick but slightly smaller diameter. A still
smaller ring would be on top of that one and so on until you
reach the pole. The reverse would be done below the
equator. The rings would all be oriented the same and so the
resulting cusps would be line cusps that ran from pole to pole.
The elements of the outer grid would be placed in these
cusps. That's the idea anyway. Aside from the cusps, the
mag field would be 0 close at the center of the chamber grow
stronger as you moved toward the wall in any direction.

Thanks,
Jim

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