A polywell inside a polywell
A polywell inside a polywell
Looking at some of the drawings on the internet it appears that the strong magnetic fields of the coils tend to get shoved out of the cavity by virtue of a magnetic pressure therein. If this pushing away of the field exacerbates cusp losses, why not have a larger polywell outside of the center polywell pushing that field back into the chamber? You could repeat this many times and end up with a kind of magnetic bottle / lens. Cool thing is, the second set of polywell donuts can have much beefier supports as it doesn't have to contend with electrons and ions flying into its supports.
Re: A polywell inside a polywell
My initial knee jerk is that you would need to look at field reversals and offest the coil axii for each layer. More layers means more drama for supports as well as exponential volume scaling for the chamber. It would get big fast. And chamber size dictacts a whole range of expensive engineering concerns, especially vacuum related.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)
Re: A polywell inside a polywell
It doesn't. It is what closes down the cusps and creates the wiffleball.ohiovr wrote:Looking at some of the drawings on the internet it appears that the strong magnetic fields of the coils tend to get shoved out of the cavity by virtue of a magnetic pressure therein. If this pushing away of the field exacerbates cusp losses, ...
Re: A polywell inside a polywell
For each point cusp think of a funnel. Fat end towards the core, skinny end towards the outside. Now imagine the plasma building pressure and expanding its ball outwards. As the ball expands, its arc cuts across a smaller sectional area of the cone. This is akin to the wiffleball. This same idea applies to line cusps. It is now a cross section of the cone that the cut is across.
The funnel cannot expand or move nearly as much due to the physical nature of the coils and the manifestation of the fields.
As you up the fields, the cone moves towards the center, as you weaken it, the cone (funnel) moves away from center.
Bottom line, stronger fields make more of a "spikey ball" (patent pending, trademark belonging to my son from a couple years back).
The funnel cannot expand or move nearly as much due to the physical nature of the coils and the manifestation of the fields.
As you up the fields, the cone moves towards the center, as you weaken it, the cone (funnel) moves away from center.
Bottom line, stronger fields make more of a "spikey ball" (patent pending, trademark belonging to my son from a couple years back).
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)
Re: A polywell inside a polywell
A use of the funnel analogy is good. The pool table versus the snooker table is a similar analogy. Basically, the hole which an electron can escape through is smaller relative to the total surface area of the sphere/ quasisphere.
Keep in mind that all of this applies as Beta=1 is approached from the low side. Past Beta=1 or Beta>1 things break down.
Additional layers might lead to an end magnification of the magnetic pressure but this would only be helpful if you cannot get desired magnetic field strengths with one magnet layer. Additional layers would also increase complexity, increase possibilities for ExB losses, edge instabilities, electron and ion injection complexity, etc.
Having said this, some local external electrostatic or magnetic fields may have specific advantages. But it is a very complex balancing act and easily can cause more harm than good. An example of this may be Loffle Bars, cusp plugging, etc.
At it's root, the Polywell is a set of simple ideas. Any modification adds complexity and confounds predictions. Some aditional complexity is needed to overcome some competing processes, but should be avoided if possible, else the path leads to tokamak like evolution.
Simple ideas?
1) electrons are confined by magnetic fields much better than ions (ExB issues)
2) manageable electron excess leads to highly efficient ion confinement and also serves as a means for ion acceleration and heating- a potential well.
3) Cusp losses can be minimized first through Polyhedral arrangements of magnets, then through high Beta operation (Wiffleball effect)
4) Magnetic field lines are always convex towards the plasma- edge instabilities are not a problem. Any additional magnetic field manipulation that changes this is harmful.
Some not so simple ideas derive from the sinple ones:
5) a potential well can lead to energy distributions that can modify thermalization processes, Bremsstruhlung processes, and ion pressure effects.
6) cusps make for convenient entry and exit windows. This has consequences for fusion ions (no ignition or fusion based self heating), up scattering can be selected against, electrons can be injected.
With recent revelations about potential well generation, and Wiffleball confinement the containment issues are mostly solved, the heating is well on the way to being solved. The injection of electrons into the machine without having counter productive effects on containment now seems the issue that may drive additional complexity with a balancing act of pluses and minuses. Additional efforts to improve containment is not an issue (I think). Why add further complexity if not needed and that always comes with their own can of worms.
The Lockheed system seems to have characteristics similar to Polywells. The difference is the linear arrange of magnets versus the pohyhedral. Both serve to decrease cusp losses (line cusps in particular). The Lockheed design adds additional complexity which may help overcome some of the deficiencies with the linear arrangement. It may also have some advantages, especially in what happens outside the magnets. Which has the best sum of characteristics is uncertain. Both may work, or not. I do suspect the Lockheed design may have advantages for direct conversion or for linear rocket thrust. If D-T fusion is anticipated, the Lockheed design may benefit from less magnet surface area to intercept neutrons. Many other considerations may apply. The Polywell is simpler though, so it could have the advantage in development, in terms of cost and time.
I personally like the Lockheed design as it follows some ideas and modeling I have done, but only in it's basic design. Once additional external magnets , and other additions that sound like some failed approaches in the past are added I become less optimistic.
Dan Tibbets
Keep in mind that all of this applies as Beta=1 is approached from the low side. Past Beta=1 or Beta>1 things break down.
Additional layers might lead to an end magnification of the magnetic pressure but this would only be helpful if you cannot get desired magnetic field strengths with one magnet layer. Additional layers would also increase complexity, increase possibilities for ExB losses, edge instabilities, electron and ion injection complexity, etc.
Having said this, some local external electrostatic or magnetic fields may have specific advantages. But it is a very complex balancing act and easily can cause more harm than good. An example of this may be Loffle Bars, cusp plugging, etc.
At it's root, the Polywell is a set of simple ideas. Any modification adds complexity and confounds predictions. Some aditional complexity is needed to overcome some competing processes, but should be avoided if possible, else the path leads to tokamak like evolution.
Simple ideas?
1) electrons are confined by magnetic fields much better than ions (ExB issues)
2) manageable electron excess leads to highly efficient ion confinement and also serves as a means for ion acceleration and heating- a potential well.
3) Cusp losses can be minimized first through Polyhedral arrangements of magnets, then through high Beta operation (Wiffleball effect)
4) Magnetic field lines are always convex towards the plasma- edge instabilities are not a problem. Any additional magnetic field manipulation that changes this is harmful.
Some not so simple ideas derive from the sinple ones:
5) a potential well can lead to energy distributions that can modify thermalization processes, Bremsstruhlung processes, and ion pressure effects.
6) cusps make for convenient entry and exit windows. This has consequences for fusion ions (no ignition or fusion based self heating), up scattering can be selected against, electrons can be injected.
With recent revelations about potential well generation, and Wiffleball confinement the containment issues are mostly solved, the heating is well on the way to being solved. The injection of electrons into the machine without having counter productive effects on containment now seems the issue that may drive additional complexity with a balancing act of pluses and minuses. Additional efforts to improve containment is not an issue (I think). Why add further complexity if not needed and that always comes with their own can of worms.
The Lockheed system seems to have characteristics similar to Polywells. The difference is the linear arrange of magnets versus the pohyhedral. Both serve to decrease cusp losses (line cusps in particular). The Lockheed design adds additional complexity which may help overcome some of the deficiencies with the linear arrangement. It may also have some advantages, especially in what happens outside the magnets. Which has the best sum of characteristics is uncertain. Both may work, or not. I do suspect the Lockheed design may have advantages for direct conversion or for linear rocket thrust. If D-T fusion is anticipated, the Lockheed design may benefit from less magnet surface area to intercept neutrons. Many other considerations may apply. The Polywell is simpler though, so it could have the advantage in development, in terms of cost and time.
I personally like the Lockheed design as it follows some ideas and modeling I have done, but only in it's basic design. Once additional external magnets , and other additions that sound like some failed approaches in the past are added I become less optimistic.
Dan Tibbets
To error is human... and I'm very human.