tokamak-polywell hybrid fusor

[Jeff Mauldin]

This description gives a much better quick understanding of an idea I posted a while back which didn't seem to attract any attention. I was trying to describe, I think, this same idea in a message I posted in February of 2008.

viewtopic.php?t=584&postdays=0&postorder=asc&start=15

I thought this idea was (1) good because it would hopefully be easier to confine electrons in a torus than it is to confine positive ions and (2) bad because the virtual electrode would essentially be a line running around the center of the torus rather than a point in the center of a sphere. My thinking was that perhaps you could drastically reduce losses due to issues with electron confinement. Ion collisions resulting in fusion would presumably be much less common due to the non-spherical setup (the non-point virtual electrode). My hope was that electron retention and ion confinement in the whole thing would be so much better that you could let the ions oscillate for many cycles before ending up in a fusion collision. It did seem like you might get too many non-fusion collisions that would result in ions or electrons behaving in a manner detrimental to the desired behavior.

I thought about making a drawing to show what I was getting at, but the 'tokamak-polywell hybrid' word picture does a pretty good job. However, I didn't think of it as a tokamak at all, more of a torroidal polywell. A polywell with electron confinement inspired by the ion containment method used by tokamaks.

I thought about trying to do a drawing describing what I was thinking, but it seemed there seemed to be some thinking by commenters along the lines that other polywell geometries were being and had been discussed, and there wasn't any solid reason to think a non-spherical geometry would be better.

I certainly hadn't considered any things about what the behavior of the plasm inside such a device might look like

Naturally, since somebody else came up with this brilliant idea as well, we must be geniuses and it will obviously work.

[D Tibbets]

You can build IEC machines in a near spherical or cyclindrical geometery. A torus is essentially a cyclinder with the ends metting. But there is some curvature so the inside surface is different from the outside surface. How this would effect symetry issues is uncertain. Also, with a torus, any prefrence in charged particle motion would, I guess, result in a cascade effect untill almost all particles would be orbiting in the same direction. At that point the plasma would be magnitized. This would effect 'Wiffleball' considerations, and probably many other issues.

Even with all that , if only modest potential wells could be formed, I would think that ion crossfield diffusion losses could be improved. Also, density might be improved (see discussion about plasma pressure vs B field strength in the 2008 EMC2 patent application).

Add to that the Tri Alpha FRC effort. Apparently there is some electrostatic elements at work.

Certainly electrostatic elements have been added to various Mirror machines in efforts to improve efficiency. The Polywell seems to be the only example that seems to have managed the various trade offs in a net beneficial way.

There may be relatively unknown efforts to use non neutral plasmas in torus machines. If so it would take a dedicated search to ferret them out. It does seem an obvious option to try- " Hay , instead of using this neutral beam just to heat our plasma, lets add some excess electrons and see what happens!"

[EDIT] Some refrences that at least mention non neutral plasmas;

http://www.lawrence.edu/fast/stonekim/research.htm

http://ieeexplore.ieee.org/xpl/freeabs_ ... ber=697792

http://adsabs.harvard.edu/abs/2002AIPC..606..556T


Dan Tibbets

[Jeff Mauldin]

"...but due to the Lorentz force, the particles will tend to turn at right angles to the magnetic field, so some linear motion along the toroid length will tend to form and this will establish a direction which will cascade till most of the plasma has this behavior. It would be difficult and probably expensive to prevent this."

Is this true? My zero-order thinking is that unless ions started with some net motion in either direction around the torus, there is no way through collisions that they can develop net motion--if one goes one direction than the other involved in the collision goes another. It's possible that there might be a bias towards ions moving in one direction being the ones to hit the containment vessel and thus be eliminated, resulting in a bias towards one direction. You can't create energy from nothing, and you can't go from no (net) energy of motion in one particular direction to energy of motion in one particular direction. Would the energy to cause this somehow be extracted via interaction with the magnetic field? Or if you were converting mass to energy with fusion reactions would some of that energy go towards biasing the ion flow in one direction or the other?

[Jeff Mauldin]

...or maybe so. Momentum is conserved in a collsion, but not kinetic energy, right?

[93143]

Both are conserved in an elastic collision.

In an inelastic collision, momentum is conserved, and some energy is converted to other forms. For macroscopic collisions, you get heat, structural strain, acoustic energy, etc. In a plasma you get bremsstrahlung, nuclear excitation (in the case of totally plastic collisions, ie: fusion), and possibly other effects (I'm not a particle physicist). But if I'm not mistaken, non-fusion ion-ion Coulomb collisions tend to be basically elastic.

[D Tibbets]

"...but due to the Lorentz force, the particles will tend to turn at right angles to the magnetic field, so some linear motion along the toroid length will tend to form and this will establish a direction which will cascade till most of the plasma has this behavior. It would be difficult and probably expensive to prevent this."

Is this true? My zero-order thinking is that unless ions started with some net motion in either direction around the torus, there is no way through collisions that they can develop net motion--if one goes one direction than the other involved in the collision goes another. It's possible that there might be a bias towards ions moving in one direction being the ones to hit the containment vessel and thus be eliminated, resulting in a bias towards one direction. You can't create energy from nothing, and you can't go from no (net) energy of motion in one particular direction to energy of motion in one particular direction. Would the energy to cause this somehow be extracted via interaction with the magnetic field? Or if you were converting mass to energy with fusion reactions would some of that energy go towards biasing the ion flow in one direction or the other?

Of course it is true...
Actually, I'm basing my assumptions on my very limited understanding of chaos theory. Even in a almost totally random situation, an event will occur that favors some consequence, it then influences another event, and this cascades till a non random state dominates. It is much like tossing a coin, it might land exactly on an edge, but while balancing there it might be hit by one more molecule of air on one side. this is a very trivial event, but it sets in motion the cascade that leads to the coin falling onto one face.

Add to this the injection of the neutral beams that are used to fuel and heat the plasma in the torus. Unless it is absolutely perfectly radially aligned it will impart some initial angular momentum. The essentially limitless cylindrical shape of a Tokamak torus and the long confinement times gives plenty of opportunity and time for a dominate angular momentum to develop even if it is not wanted. Also, keep in mind that in a Tokamak the plasma is magnetized which means it will flow along the magnetic field lines created by external magnets and/or the magnetic field created by the dominate movement directions of the ions.

In a Polywell the story is different because of the near spherical geometry, and the confinement time that is at least ~ 10^4 times less. The increased density may change things some, but the potential well also probably changes things to a more radial dominance- that and edge annealing.
There may be some net angular momentum develop in a Polywell, but it has to be relatively tiny (?) otherwise the plasma would become magnetized, and I think this would eliminate the formation/ maintainance of a Wiffleball.

Dan Tibbets