MSimon wrote:Did you note that there were experimental results that supported the model? Not in detail though. More like "consistent with the model". In the early days this topic was beat to death. The conclusion was: no two beam instability in theory or practice. Of course that could have been wrong.
We await experimental verification either way.
No two-stream? I do not believe. As Mr. AlexK of FPGeneration also built Polywell like reactor and mentioned 2-stream and Wiebel here in this board. See the link above.
You wanted to say that instability in acceptable scales? Not causing disintegration of electron beams on separate clots?
This may correspond to true. Because of wide spread in velocities. But anyhow beta will not be equal to 1 and even close to 1. Once Dan has linked me an article from which if I understood correctly beta was equal to 0.14 (more than 6 times lower value).
And majority of my opponents from that beaten to death topic heard about two-stream instability first time.
That’s all that I’d like to say.
Roger wrote: All a Polywell needs is to 'introduce' electrons inside of the MCGrid, right?
Joe whats the big deal?
MaGrid, not MCGrid. No "Golden Arches" here!
I suspect L's description is a bit simplistic. All you have to do it introduce electrons "with a radial energy ~equal to the desired potential well depth" inside the MaGrid. However, he is still correct that no "beam" behavior is needed.
Robthebob wrote: I thought you had to drive the electrons through guns, because the electron losses are too fast, you need a gun to keep the well going. That was the Sydney people's paper was partially about.
IIRC, the USydney device was a cusp confinement machine, at least in their analyses, not a Wiffleball forming Polywell machine. I.e., it was a LOW beta machine!
Roger wrote: All a Polywell needs is to 'introduce' electrons inside of the MCGrid, right?
Joe whats the big deal?
MaGrid, not MCGrid. No "Golden Arches" here!
I suspect L's description is a bit simplistic. All you have to do it introduce electrons "with a radial energy ~equal to the desired potential well depth" inside the MaGrid. However, he is still correct that no "beam" behavior is needed.
I did purposely keep it "dummed down". I have learned with Joseph, primarily due to language barrier, to keep it simple. No offense intended to Joseph.
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)
the voltage differential between the electron source-MaGrid vice the voltage between the chamber wall-MaGrid?
Ok. Then you statement makes sense, but you used the term potential well differently than most do in reference to the Polywell (the well INSIDE the MaGrid) so it was a tad confusing.
D Tibbets wrote:Mattman, I don't know what efficiency in X ray reflection may be possible, but it is undesired any way. With ignition, and thermalized machines, feflecting x- rays might be desirable. But it is not wanted in a Polywell. The 'heat' in a Polywell or fusor comes from electrostatic acceleration. The waste heat from escaped electrons, ions, x-rays, or fusion ions or neutrons deposit their energies in structures (or direct conversion grids) and heat them up. Ignoring direct conversion, this heat produces electricity through a steam cycle. Not very efficient, but that is about the only way to harvest the heat.
In a Tokamak a portion of this heat is directly recycled in the machine- mosstly through thermalization of very hot/ energetic fusion ions. A Polywell is not an ignition machine, the hot fusion ions mostly escape the machine, and smack into walls or a conversion grid. Any x-rays produced in the Polywell deposite little of their energy in the plasma. They hit walls or penetrate into them. To harvest and recycle this energy, it has to be captured through a steam cycle or something like the direct 'onion skin converter' proposed by Eric Learner with the DPF. The DPF is a small machine, with possibly a beryllium anode that allows a large percentage of the x- rays to harvest the machine pro[per and enter a surrounding direct converter. With a different structure, and dynamics, I don't know if a Polywell could perform nearly as well in this X-ray direct conversion scheme.
Discussing clouds of ions in the center makes me wonder if you are taking too much of a static view. The electrons and ions are both moving all over the place. The important point is that their speeds change in this roughly spherical geometry depending on their radius from the center. The inverse relationship between the ions and electrons and the dynamic consequenses plays a hugh role in the Bremsstruhlung (hopefully spelled right this time) issue. Dwell time, local density changes, and even annealing plays a role. Especially if there is any convergence of the ions towards the center. This results in effective greater densities of ions in the center. This applies to electrons also. If the electrons were at high energies in these increased density areas, the Bremsstruhlung radiation is amplified. But since the electrons are low energy (low KE) in this region the Bremsstruhlung is much less. On the edge and in between the situation tends to reverse, but the ion density is now lesser in these regions. If there is no ion confluence (focus towards the center) or if the electron population is less radial/ more thermalized, this effect may be minimized. Thus the need for diluting the high Z Boron.
Also, referring to Fusors as operating at room temperature is extremely inaccurate. Ignoring the neutral background gas that may not be heated much, the actual fusing ions (or ion- neutral collisions) have very high center of mass KE/ temperatures. If the potential on the central cathode grid is ~ 10,000 volts, then the ions are accelerated to ~ 10,000 eV. This is equivalent to a temperature of ~ 110 million degrees C.
Dan,
I respect you. I will read this and think about it. Sorry it took so long to reply.
the voltage differential between the electron source-MaGrid vice the voltage between the chamber wall-MaGrid?
This definition both is not quite correct.
As potential distribution and consequently the depth of potential well analitically can be calculated with the help of Poisson's equation. And result will not be equal to potential difference of two metallic surfaces. http://en.wikipedia.org/wiki/Poisson's_equation
Poisson's equation Electrostatics
One of the cornerstones of electrostatics is the set-up and solving of problems that are described by the Poisson equation. Finding φ for some given f is an important practical problem, since this is the usual way to find the electric potential for a given charge distribution described by the density function.
And due to bolded part of the text Kiteman is wrong too when he says the it does not matter how electrons are distributed in reactor once the enter inside it.
Joseph Chikva wrote: And due to bolded part of the text Kiteman is wrong too when he says the it does not matter how electrons are distributed in reactor once the enter inside it.
If you are going to call someone wrong, at least have the decency to understand what he said.
"with a radial energy ~equal to the desired potential well depth" Where does that equate to "doesn't matter how electrons are distributed"? I DID mention that "BEAMS" are not necessary. But radial energy of ~well depth IS. Location around the sphere at the well edge doesn't matter but radial motion does.
KitemanSA wrote:Where does that equate to "doesn't matter how electrons are distributed"?
And what is it?
It is "with a radial energy ~equal to the desired potential well depth"
Joseph Chikva wrote:
KitemanSA wrote:Location around the sphere at the well edge doesn't matter...
Please define what is "Location around the sphere at the well edge".
What part do you not understand?
Joseph Chikva wrote:
Not density distribution?
Don't know, do you think it is? What I don't get is what you are trying to say. First you seem to say I said one thing, then you seem to say that I said the other. What are you talking about?
You started talking about beams but you seem to hav e gone off into never-never land.
KitemanSA wrote:You started talking about beams but you seem to hav e gone off into never-never land.
This time I started talking about potential well definition. And showed where you was wrong. As the depth of potentiall well is function of density distribution and so, location does matter.
That is all.
