non-uniformly charged magrid?

[TallDave]

The charge is equal in every direction inside the sphere, or grid. As a charged particle gets closer to a wire or point charge on a hollow sphere. it experiences a greater attraction to that point. But, as this is happening the particle is passing increasing areas of the sphere/ wires- these surfaces are in the rear view mirror. They are increasingly further away, but there are a lot more of them. These competing forces exactly cancel out. That is why Gauss's law applies.

You can probably toss in Debye screening for some added fun, too -- i.e., does a particle near one edge really see all the cancelling forces from the rest of the grid, or is some proportion screened? I think we decided calculating that was tricky amidst currents.

What information do you have that indicates that WB8 has no physical connections between coils?

I'd sort of assumed that was the case from squinting at the design pic, though that's pretty speculative of course. I looked over Rick's comments recently and it doesn't look like he elaborated.

http://www.emc2fusion.org/

[KitemanSA]

What information do you have that indicates that WB8 has no physical connections between coils?

I'd sort of assumed that was the case from squinting at the design pic, though that's pretty speculative of course. I looked over Rick's comments recently and it doesn't look like he elaborated.

Ah, you had taken absence of evidence as evidence of absence. A common occurance. Dan, is it the same for you? I am asking, not to be contrary, but to try to understand WB8 better.

[TallDave]

Well... one might infer that they were trying to avoid using interconnects. But still speculative, and inference is always dangerous

[KitemanSA]

I inferred they were avoiding publishing potentially patentable IP.

[93143]

You can probably toss in Debye screening for some added fun, too -- i.e., does a particle near one edge really see all the cancelling forces from the rest of the grid, or is some proportion screened?

Debye screening isn't magic - it works on the same principle as Gauss' Law. And since Gauss' Law has decided in advance that there's no field inside a conducting spherical shell, at least none due to external charges or charges on the shell itself, there's nothing to indicate to the plasma that there are charges to be screened. So it won't screen them, and Gauss' Law will still prevent the shell from electrostatically affecting anything inside it.

Besides, the wiffleball acts as a point charge to anything between it and the magrid, to about the same order of approximation as the magrid constitutes a perfectly conducting spherical shell... in fact, this holds within the wiffleball too, with the part "below" the test particle being the point charge and the part "above" it having no effect at all (to first order) due to... drumroll please...

...Gauss' Law.

There's no gravity at the centre of the Earth, for the same reason.

[D Tibbets]

Well put and concise discription of Gauss Law.

But, of course there is gravity at the center of the Earth. There just is no Gravity. Picky, I know, but I believe capitalizing gravity refers to Earths gravity, while gravity itself is more universal. For instance, you would still experience the Sun's gravity at the center of the Earth. Mmm, ...of course so would the the rest of the Earth, so you would not notice any difference as the Earth is in freefall around the sun just as you are, but I believe this would represent a fundamental difference between gravity and electromagnetism.

Dan Tibbets

[happyjack27]

if the earth was hollow you would not experience gravity inside it. not gravity from the earth itself, at least. same applies to electromagnetism. you still feel _external_ charges from the inside of a hollow charged sphere, assuming, ofcourse, that the sphere is not conductive.

[D Tibbets]

What information do you have that indicates that WB8 has no physical connections between coils?

I'd sort of assumed that was the case from squinting at the design pic, though that's pretty speculative of course. I looked over Rick's comments recently and it doesn't look like he elaborated.

Ah, you had taken absence of evidence as evidence of absence. A common occurrence. Dan, is it the same for you? I am asking, not to be contrary, but to try to understand WB8 better.

Basically, my evidence, such as it is, is supposition based on Nebel's comments about the nub problems, hearsay from M. Simon (though what he said could be applied to nubs or separate standoffs), and the two pictures. One on EMC2's Website that shows the chamber which could accommodate separate assemblies being bolted on for each face, and the picture with Joel Rogers presentation, that shows this arrangement clearly. The question with J. Rogers illustration is if it is linked to EMC2 or is his own supposition.

http://www.plasma.ee.kansai-u.ac.jp/iec ... ogers2.pdf


Dan Tibbets

[KitemanSA]

Thank you for your response.

[93143]

you still feel _external_ charges from the inside of a hollow charged sphere, assuming, ofcourse, that the sphere is not conductive.

Exactly. Other gravitating bodies pull on matter at the exact centre of the Earth, because there is no adequate analogue to conductivity in a system of gravitating masses.

[TallDave]

Debye screening isn't magic - it works on the same principle as Gauss' Law. And since Gauss' Law has decided in advance that there's no field inside a conducting spherical shell, at least none due to external charges or charges on the shell itself, there's nothing to indicate to the plasma that there are charges to be screened. So it won't screen them, and Gauss' Law will still prevent the shell from electrostatically affecting anything inside it.

Ah, so such screening would only apply to charges on stuff within the Magrid, not on the Magrid itself (at least to the extent the Magrid is like a conducting sphere). That seems to makes sense, but then do you disagree with Dan's perspective of Gauss' Law being the result of charges on the sphere cancelling within the sphere? Presumably if they are cancelling at a given point in the sphere, they can also be screened from that point, but what you're saying sounds more like they just don't exist inside the sphere at all. Or is it just not possible to screen forces in such a way as to "reveal" the charges on the sphere to stuff inside?

Kite, I'm curious -- do you mean you think WB-8 does have nubs? Or are you just agnostic on the issue? Just wondered, I ask because I know you've thought about these things a lot.

[KitemanSA]

Kite, I'm curious -- do you mean you think WB-8 does have nubs? Or are you just agnostic on the issue? Just wondered, I ask because I know you've thought about these things a lot.

Agnostic, well, semi-so. I lean perhaps a TAD toward there being something in lieu of the WB6 nubs but not the wall mounts. And the only reason for this is that WB7.1 was supposed to investigate and resolve the nub issue and they SEEM to have stated that it was successful. I don't believe that WB7.1 could possibly have been made into a wall mounted unit. So if WB7.1 was successful, why would they need to wall mount WB8 with all its complexity? But that is just ignorance talking.

[93143]

Ah, so such screening would only apply to charges on stuff within the Magrid, not on the Magrid itself (at least to the extent the Magrid is like a conducting sphere). That seems to makes sense, but then do you disagree with Dan's perspective of Gauss' Law being the result of charges on the sphere cancelling within the sphere? Presumably if they are cancelling at a given point in the sphere, they can also be screened from that point, but what you're saying sounds more like they just don't exist inside the sphere at all. Or is it just not possible to screen forces in such a way as to "reveal" the charges on the sphere to stuff inside?

The charge carriers on a conducting shell will automatically distribute themselves so that there is no electric field anywhere inside the shell due either to the charge on it or any additional external charge concentrations. This is indeed a 'cancelling' effect; it arises from the fact that this is the minimum-energy distribution.

Thus the wiffleball plasma doesn't 'see' (electrostatically speaking) the magrid, or any other electrostatic influences external to the magrid (to first order, obviously). If there were no plasma, the electric potential inside the magrid would be flat.

Now, the plasma will have an effect on the charge distribution on the magrid, because the magrid charges can see the plasma charge. But the effect is symmetric and the upshot is the same.

Debye screening would apply to the charged wiffleball, if it were a thermal plasma - the potential drop would occur mostly within a debye length or three from the wiffleball edge, resulting in a rectangular well. But the kinetic energy of the injected electrons is what forms the well, and it is larger than the maximum electric potential energy difference in the plasma (rather than being much smaller than it), as well as having a highly nonthermal distribution, and thus a Polywell plasma as it is predicted to form breaks the assumptions underlying debye screening theory.

Notice what happened there - a thermal plasma can shield its own interior via debye screening, but it can't change what happens outside it - screening is a matter of charge cancellation via superposition, and if you have a spherically-symmetric plasma ball with a charge q, it really doesn't matter what it does internally; from the outside it's going to look like a point charge q.

Do you understand the Principle of Superposition?

[TallDave]

But the effect is symmetric and the upshot is the same

Ah, okay. I suspected that might explain it. Thanks for the explanation.

Do you understand the Principle of Superposition?

In principle, so to speak. The net response to some number of stimuli is the sum of the individual responses of those stimuli, or mathematically F(x1 + x2 + ...) = F(x1) + F(x2) + ...

Hmmm, I wonder what Joel did to calculate Debye length in his simulation and how that might have affected things...

[happyjack27]

Debye screening would apply to the charged wiffleball, if it were a thermal plasma - the potential drop would occur mostly within a debye length or three from the wiffleball edge, resulting in a rectangular well. But the kinetic energy of the injected electrons is what forms the well, and it is larger than the maximum electric potential energy difference in the plasma (rather than being much smaller than it), as well as having a highly nonthermal distribution, and thus a Polywell plasma as it is predicted to form breaks the assumptions underlying debye screening theory.

from my simulations, there are two regions of electron containment, one that covers most of the region inside the magrid, but stays just shy of it, and contains fairly thermalized electrons. it's looks like a "cloud", and does not have much visible variation in density from outside to inside.

the other region is a very small hollow spiky sphere of very cold electrons in the very center of the magrid. this area is MUCH denser than the thermalized electron cloud. and presumably these electrons are held in place by magnetic mirroring from multiple angles (from the multiple coils).

these electrons in the center, in the "wiffleball", again, are very COLD i.e. they have very little kinetic energy. and the wiffleball is not formed by kinetic energy, it is formed by a balance in pressure between, on the inside, mutual electrostatic repulsion of the electrons, and on the outside, the magnetic mirroring effect of the magnetic fields.

this hollow sphere in the very center is a conducting sphere of charge and thus by gauss's law any particles inside it will not "see" electromagnetic forces outside it. hence they only see their mutual electrostatic repulsion and slowly expand until they reach the wiffleball border, where they are either deflected by the mag field, or if the net pressure from mutual repulsion is great enough, leak out into the thermalized cloud of electrons that pervades most of the area inside the magrid.

i fear that some people mistake this outer cloud of electrons as the "wiffleball". if the electron density is too great for the magnetic field strength, the goey wiffleball center might simply pop like a wet ballon, leaving ONLY the cloud, save a small "soft" increase in density made of thermalized electrons where a rather discrete one made of cold electrons used to be. making for a much shallower potential well.