It Is A Different Machine

[Art Carlson]

... The particles will "try" to move in the vXB direction as you say, but as soon as they start to move apart, the charge separation will produce an electric field in that direction. The particles will then experience an EXB drift in the (vXB)XB direction, i.e. in the direction of the initial motion v. The net effect is that both ions and electrons will more or less straight across the magnetic field. ...

Thank you for the clarification.
If the ions have MeVs of energy and the electrons have 10s to 100s of keV, won't they have enough to overcome the attraction?

Oh, and they would still be in the ~100keV MaGrid field too. How would that effect things?

There are too many possibilities to cover every case, although there is nothing about a high beam velocity that would negate the argument. I haven't understood exactly what you (all) think is happening (parameters of density, beam size and shape, temperature, velocities, ...), and there is a good chance I would disagree with some of it if I did. I just wanted to leave a warning that collective effects should not be neglected. Plasma Physics 101.

[KitemanSA]

I just wanted to leave a warning that collective effects should not be neglected. Plasma Physics 101.

And I am glad you are cuz I haven't reached the plasma physics minus 300 level yet!

[ravingdave]

The distintion is that your prior graphics had the ion deflecting round the minor diameter of the torus, along the field lines. Mine says the deflection will be into or out of the page, along the MAJOR circumference of the torus. Yours has it ending up orbiting the minor diameter. Mine has it drifting to the field edge (the wiffleball) then falling down the well.

So does anyone have a definitive answer for which is correct?

Edit (diameter to circumference, boy did I mess THAT one up!)

I'm sorry. I grabbed a couple of photos from the net just to illustrate the concept. As I had seen the magnetron example so many times, I thought it would be the most recognizable. No, it doesn't accurately illustrate what would happen in a polywell, but it gets the general idea across.

My whole point was, the idea of emitting ions from the casing of the MagGrid wouldn't work because the intense field would not allow ions to fall (in a straight line) towards the center. It would impart some degree of sideways (as opposed to radial) motion which would cause ions to orbit elliptically as opposed to fall straight through the center.

Sorry I wasn't more clear.



David

[KitemanSA]

I was kind of imagining each ion slowly drifting thru the intense magnetic field under both influences until it reached the wiffle ball, which I have been viewing as a magneto-pause due to the plasma pressure. At the WB, the electro-static well takes over and the ion falls. Anyway, that is what I have been imagining it. In what way am I wrong?

[ravingdave]

I was kind of imagining each ion slowly drifting thru the intense magnetic field under both influences until it reached the wiffle ball, which I have been viewing as a magneto-pause due to the plasma pressure. At the WB, the electro-static well takes over and the ion falls. Anyway, that is what I have been imagining it. In what way am I wrong?

Well, My understanding of how you would emit an ion goes something like this. You heat a sample until it reaches a vaporization point while it is electrically connected to a high positive potential. (Like the MagGrid which is what ? 100kv ? ) As a molecule breaks free from the mass, it's electrons are stripped off and absorbed by the remaining positive charge, at which point the positively charged ion is immediately repelled by the much stronger positive charge on the MagGrid, and it goes zipping away at a high velocity.

If this view is accurate, the ion doesn't do any drifting. It Immediately accelerates the instant it breaks free of the large mass. This would make it instantly responsive to any powerful magnetic field in the vicinity.


For that reason, I believe the ion would have to be injected at a point where the forces are balanced, such as the center of the torus. ( or a corner cusp )

Now I could be mistaken, and I usually don't make comments in the theory section because there are so many people here who really are experts (RNebel, Art Carlson, Dr. Mike, etc. ) and otherwise very knowledgeable ( MSimon, TallDave, Torluf, etc.) and so I usually just read what they've written, but things have been a little slow in the general area, so I figured i'd poke my two cents in over here for a change.

After all, poli-tics may be fun, but polyWell is what this site's all about !


I sure hope it works.


David

[93143]

There won't be a high positive charge on the inner side of the magrid. It should be basically neutral. Since the magrid cans are conductive, the charge will concentrate on the outer side.

EDIT: The above is wrong, for obvious reasons. See subsequent posts.

Ions in the magnetic field outside the wiffleball proper... seems like a very leaky/lossy arrangement to me.

[KitemanSA]

[/quote]

Well, My understanding of how you would emit an ion goes something like this. You heat a sample until it reaches a vaporization point while it is electrically connected to a high positive potential. (Like the MagGrid which is what ? 100kv ? )

So far, so good.

As a molecule breaks free from the mass, it's electrons are stripped off and absorbed by the remaining positive charge, at which point the positively charged ion is immediately repelled by the much stronger positive charge on the MagGrid, and it goes zipping away at a high velocity.

With you as far as you go. Then I have it that the act of zipping away from the MaGrid causes it to cross a VERY strong magnetic field wherein it tries to turn about on itself. As it comes back, the MaGrid slows it down, then re-accelerates it away wherein it turns around, is slowed down . . .This start-turn-stop start-turn-stop... is what I have been calling, for want of the educated term, drift. I also suspect that it isn't quite as clean as presented. None-the-less, eventually the ion runs out of magnetic field to turn it around and continues falling (perhaps with a residual radial velocity.

If this view is accurate, the ion doesn't do any drifting. It Immediately accelerates the instant it breaks free of the large mass. This would make it instantly responsive to any powerful magnetic field in the vicinity.

Concur, but see above.

For that reason, I believe the ion would have to be injected at a point where the forces are balanced, such as the center of the torus. ( or a corner cusp )

Sorry, non-sequitor. Just because it is responsive, why does that necessarily lead to needing to inject it at a cusp?

Now I could be mistaken, and I usually don't make comments in the theory section because there are so many people here who really are experts (RNebel, Art Carlson, Dr. Mike, etc. ) and otherwise very knowledgeable ( MSimon, TallDave, Torluf, etc.) and so I usually just read what they've written, but things have been a little slow in the general area, so I figured i'd poke my two cents in over here for a change.

After all, poli-tics may be fun, but polyWell is what this site's all about !

The brains you mention seem to pipe in when us neos set their teeth on edge with our guessing. That is why I am willing to make a bit of a fool of myself. It seems to be a prime path to REAL information!

SO: JOKE:
Q: What is the derivation of the word "politician"?
A: It is a combination of the Greek poly (many) and the French tete (head / face) so a politician is a beast with two or more faces.

Sounds about right, no?
Of course a beast with the moral fiber of two or more blood sucking insects (poly-ticks) is a good one too.

[ravingdave]

There won't be a high positive charge on the inner side of the magrid. It should be basically neutral. Since the magrid cans are conductive, the charge will concentrate on the outer side.

Ions in the magnetic field outside the wiffleball proper... seems like a very leaky/lossy arrangement to me.

You are refering to the "Faraday cage" effect? I may be mistaken about this, but I think this only applies when you don't have a highly negatively charged ball of electrons at the center of the cage.

The reason the Faraday cage works is because the electrical charges within the conducting material redistribute themselves so as to cancel the field's effects in the cage's interior.

When you have a highly negatively charged ball of Electrons in the Center of the Cage, you now have a Electric field differential between any point on the cage and the center.

I'm pretty sure that there WILL be a high positive charge on the inside of the MagGrid relative to the wiffleball.

One of you experts out there tell us which one of us is wrong.


David

[ravingdave]

For that reason, I believe the ion would have to be injected at a point where the forces are balanced, such as the center of the torus. ( or a corner cusp )

Sorry, non-sequitor. Just because it is responsive, why does that necessarily lead to needing to inject it at a cusp?

The reason i'm suggesting that it needs to be injected through the center of the torus or a cusp is to minimize lateral velocity. So that it falls "Straight" through the center, thereby maximizing the chance of a collision with another ion.







If it starts out with any residual non-radial velocity, it won't go through the center, it will "Orbit" the center elliptically.





In any case, that's how I see it. Experts ?

After all, poli-tics may be fun, but polyWell is what this site's all about !

The brains you mention seem to pipe in when us neos set their teeth on edge with our guessing. That is why I am willing to make a bit of a fool of myself. It seems to be a prime path to REAL information!

SO: JOKE:
Q: What is the derivation of the word "politician"?
A: It is a combination of the Greek poly (many) and the French tete (head / face) so a politician is a beast with two or more faces.

Sounds about right, no?
Of course a beast with the moral fiber of two or more blood sucking insects (poly-ticks) is a good one too.

A very apt description. Years ago I would have said it only applied to the opposition, but i've seen enough two-facedness from my side to conclude it is probably universal across the spectrum.



David

[KitemanSA]

If it starts out with any residual non-radial velocity, it won't go through the center, it will "Orbit" the center elliptically.

In any case, that's how I see it. Experts ?

It may start out with a bit of radial velocity, but annealing should take care of that pretty quick, no?

[93143]

When you have a highly negatively charged ball of Electrons in the Center of the Cage, you now have a Electric field differential between any point on the cage and the center.

I'm pretty sure that there WILL be a high positive charge on the inside of the MagGrid relative to the wiffleball.

One of you experts out there tell us which one of us is wrong.

Okay, I will.

I am. I reacted without thinking. Since the field has to be zero inside the magrid cans, obviously there have to be shielding charges on both sides... (Some expert. You'd never know my M.Sc. was in multiphase electrohydrodynamics...)

I still think having ions injected from there straight into the high-B region is asking for trouble...

[MSimon]

When you have a highly negatively charged ball of Electrons in the Center of the Cage, you now have a Electric field differential between any point on the cage and the center.

I'm pretty sure that there WILL be a high positive charge on the inside of the MagGrid relative to the wiffleball.

One of you experts out there tell us which one of us is wrong.

Okay, I will.

I am. I reacted without thinking. Since the field has to be zero inside the magrid cans, obviously there have to be shielding charges on both sides... (Some expert. You'd never know my M.Sc. was in multiphase electrohydrodynamics...)

I still think having ions injected from there straight into the high-B region is asking for trouble...

The fact that the field is non-uniform should affect what happens. High curvature near the coils low near the center.

Oh. Yeah. The field is non-uniform in a non-uniform way.

[ravingdave]

If it starts out with any residual non-radial velocity, it won't go through the center, it will "Orbit" the center elliptically.

In any case, that's how I see it. Experts ?

It may start out with a bit of radial velocity, but annealing should take care of that pretty quick, no?

That's what I hear from others, and I get the concept of annealing. I think i've read some criticism of the concept from Art, so it's not a foregone conclusion that there really is an annealing effect.

The annealing effect may not be robust enough if there is too much lateral motion of the ions. I don't know. We have to build more machines and do more experiments before this can be figured out for sure.


David

[93143]

The fact that the field is non-uniform should affect what happens. High curvature near the coils low near the center.

We haven't gotten that far yet. So long as there is ANY field, uniform or not, at the outer surface of the magrid (or any other conducting object), there will be a nonzero surface charge density there. This is because, barring eddy currents and other dynamic effects, the whole magrid is at the same electric potential (ie: zero field within the magrid structure), and the only way to produce a sudden discontinuity in the field like that is the interposition of a nonzero surface charge density.

Nonuniformity in the field over the surface of the magrid just alters the distribution of the shielding charge. Nonuniformity of the field away from the magrid has no (direct) effect whatsoever.

[ravingdave]

A worrying thought has occurred to me about alpha's streaming out of the cusps. Wouldn't they drag the electrons out with them thereby killing the wiffleball ?


I mean, if they are coming out in a stable beam or some such, then does this not create a sort of static pseudo virtual positive electrode all the way from the core to outside the MagGrid ?

Yeah, the alpha particles may be streaming individually, but collectively they are a large positive attracting force. Eventually, the electrons have to notice this and start moving towards this statically stable stream.

If i'm explaining this idea clearly enough, does anyone have an explanation as to why this won't happen ?

I remember Art Carlson talking about this exact effect with nothing more than just fuel ions, so if it is possible to pull electrons out of the wiffleball with fuel ions, wouldn't it also occur with Alpha particles ?


Just wondering.


David