Google Polywell Fusion Counter

[Solo]

I agree that "beta=1" is ambiguous. I was thinking about your derivation in this thread where you assumed that the electron density times the electric field was the electric field energy density and set it equal to the magnetic field energy density. If the B-field and its energy density were higher than the plasma pressure, rho_e would be lower and the space charge shielding would be lower, so the machine would still have a decent well depth. (That was assuming only electrons in the cusp.)

You seem to have a fundamental misunderstanding, which Dr. Nebel has pointed out repeatedly, of the electron behavior outside the magrid. I have no understanding at all why you persist in thinking the electrons want to go to the walls of a machine with precisely one anode, the magrid. If you object to the emitter being at the same potential as the walls, so that the electrons can, unenthusiastically, go back to the walls, fine, we'll bias the cathode a hundred volts positive of the walls, and that will be that

Well, suppose that the central plasma has a potential equal to the ground because there is a sufficient supply of electrons. The plasma ions are hot, say 30keV. The electrons have 0 keV by assumption when the reach the central plasma. They are heated by the ions by colllision. Now their total energy is greater than the ground potential, so if they escape the cusp they will still have the kinetic energy corresponding to their central temperature left when they get to the wall, at ground potential again. They will hit the wall and be absorbed.

Or as you say, the emitter could be biased to ensure they impact the wall.

[alexjrgreen]

Or as you say, the emitter could be biased to ensure they impact the wall.

Or biased to ensure they don't impact the wall...

[Solo]

... in which case, on my reading, they will impact the emitter instead. But I also see that I misread Tom's statement.

The trouble with not allowing the electrons to impact the wall is that they have time to diffuse across the field and impact the magrid, which is a more serious energy loss (per electron) than being returned to ground with a few eV more than they started with. How the currents would compare is another story. The other problem with letting the electrons recirculate is that as they diffuse they broaden the plasma sheath and the cusps and this could lead to more ion loss.

[TallDave]

Solo,

I'm still confused as to why any significant number of electrons would climb the gradient from Magrid to wall. Are we thinking the field lines push them there?

[Aero]

Solo,

I'm still confused as to why any significant number of electrons would climb the gradient from Magrid to wall. Are we thinking the field lines push them there?

This thought troubles me also.

I was under the impression that some electrons drifted across the field lines directly from the Polywell to the Magrid, but mostly they spiraled around the field lines to the cusps where they escaped to recirculate. But after leaving the cusp region, they are still spiraling around the field lines, (with enough energy) climbing to the "top" and coming back into the Polywell via a different cusp. That only works if they leave the Polywell with enough energy to climb all the way out, and here is what troubles me.

Once electrons exit the cusp region (That is, they get further away from the center of the Polywell than the radius of the BFR), via the cusp, the positive Magrid is behind them, pulling them back. The electron with marginal energy either drifts across the (very dense) magnetic field near the cusp, destination Magrid, or spirals back into the Polywell via the same cusp that it exited. It seems to me that doing so will tend to "plug" the cusp. Until the original electron gets out of the way, more electrons will be blocked along that particular field line. The end result should be a build-up of negative charge in the cusp region. That would be good, wouldn't it? For blocking escaping electrons that is, not necessarily for containing ions.

[TallDave]

Aero,

Yes, I think that's the cold electron phenomenon Ligon has been alluding to. It's possible Bussard's "recirculation" was actually cusp-blocked oscillation.

My impression from Bussard was that the electron losses were either to cross-field diffusion or unshielded areas (e.g. the interconnects). In Valencia, he says he has an equation for this.

[KitemanSA]

Solo,

I'm still confused as to why any significant number of electrons would climb the gradient from Magrid to wall. Are we thinking the field lines push them there?

This thought troubles me also.

I was under the impression that some electrons drifted across the field lines directly from the Polywell to the Magrid,

??? What do you mean by "drifted... from the Polywell to the magrid? Are we talking Tom Ligon's theoretical cold electrons?

but mostly they spiraled around the field lines to the cusps where they escaped to recirculate. But after leaving the cusp region, they are still spiraling around the field lines, (with enough energy) climbing to the "top" and coming back into the Polywell via a different cusp. That only works if they leave the Polywell with enough energy to climb all the way out, and here is what troubles me.

There is no need to come in thru another cusp. Out, stop, back in is permissible. If it has too much energy, it doesn't stop before it hits the wall. I think that one of Art's points is that unless the vacuum chamber is HUGE, many of the field lines will intersect the wall. Thus they CAN'Tspiral out and AROUND.

Once electrons exit the cusp region (That is, they get further away from the center of the Polywell than the radius of the BFR), via the cusp, the positive Magrid is behind them, pulling them back. The electron with marginal energy either drifts across the (very dense) magnetic field near the cusp, destination Magrid, or spirals back into the Polywell via the same cusp that it exited.

OR, gets impacted by an electron with full or greater drive level energy and starts oscillating with renewed vigor.

DOES ANYONE KNOW IF THE ELECTRONS ANNEAL LIKE THE IONS?
Sorry for the shout, but I think it is a significant issue.

It seems to me that doing so will tend to "plug" the cusp. Until the original electron gets out of the way, more electrons will be blocked along that particular field line. The end result should be a build-up of negative charge in the cusp region. That would be good, wouldn't it? For blocking escaping electrons that is, not necessarily for containing ions.

I wonder what would happen if there were a solenoid tube from a "out" or a "funny"cusp to an "in". Hmm.

[Aero]

Re. the word, "drift." I think "diffuse" is the word I wanted.

[Art Carlson]

I'm still confused ...

Once electrons exit the cusp region (That is, they get further away from the center of the Polywell than the radius of the BFR), via the cusp, the positive Magrid is behind them, pulling them back. The electron with marginal energy either drifts across the (very dense) magnetic field near the cusp, destination Magrid, or spirals back into the Polywell via the same cusp that it exited. It seems to me that doing so will tend to "plug" the cusp. Until the original electron gets out of the way, more electrons will be blocked along that particular field line. The end result should be a build-up of negative charge in the cusp region. That would be good, wouldn't it? For blocking escaping electrons that is, not necessarily for containing ions.

I wish you guys would start thinking about both species at the same time. A potential that pushes electrons back will pull ions out. The electrons may tend to give the machine constipation, but the ions will work as an enema. My calculation shows that only very small potential differences can be maintained in the flux tube of a cusp.

[TallDave]

But again Art, there is a force selectively pushing electrons out of the plasma. If the cusp is small enough, that might be sufficient that no ions are pulled through.

[MSimon]

DOES ANYONE KNOW IF THE ELECTRONS ANNEAL LIKE THE IONS?

There is a vacuum tube built on the premise of electron annealing. It is called the klystron tube. Does it happen in Polywell? Good question.

[MSimon]

My calculation shows that only very small potential differences can be maintained in the flux tube of a cusp.

Which says the electric equipotential lines are bunching up some where.

That is the trouble with all this plasma stuff. It is like chasing your tail. Everything you do does something else.

[Aero]

Yesterday I posted this, in part.

Once electrons exit the cusp region (That is, they get further away from the center of the Polywell than the radius of the BFR), via the cusp, the positive Magrid is behind them, pulling them back. The electron with marginal energy either drifts across the (very dense) magnetic field near the cusp, destination Magrid, or spirals back into the Polywell via the same cusp that it exited. It seems to me that doing so will tend to "plug" the cusp. Until the original electron gets out of the way, more electrons will be blocked along that particular field line. The end result should be a build-up of negative charge in the cusp region. That would be good, wouldn't it? For blocking escaping electrons that is, not necessarily for containing ions.

I was thinking earlier about the consequences of electrons "plugging" the cusp. Where do they go? They don't climb out because they have already failed to do that. They may interfere with with themselves and oscillate in the radial direction but a dynamic plug is still a plug. They may diffuse across the field lines to the Magrid but they've already tried that, too. But we are sure there are electron losses, where do they go?

To the Magrid of course but I suspect they do not go quietly, so their should be evidence of their departure on the Magrid at the cusp. I was thinking of asking Dr. Nebel if their were burn marks or etchings on the Magrid near the throat of the cusp, but he posted this on another thread so I no longer think I need to ask. Of course, he didn't say where the hot spots were located in relation to the cusps.

I know that the confinement in the WB-7 is much, much better than ballistic. I also believe that the dominant energy flowthrough is in the electrons, not the ions. Glen Wurden (whom you probably know from LANL) has taken some fast framing pictures of the plasma, and the hot spots are on the coils, not the walls. While this isn't a proof, it's a pretty strong indicator.

viewtopic.php?p=16276#16276

[KitemanSA]

WARNING: WARNING: TOPIC RECLAMATION IN PROGRESS

Kiteman,

Polywell fusion without the quotes just returned 29,300 links from my computer! With quotes it was more like 4900. Just exactly how do you formulate your search? Or are we approaching a "Polywell fusion" singularity?

Wha??? Are you Googleing?
I have pretty generic preferences, search all languages, don't filter... and I am still getting 16,000 hits for Polywell fusion, no quotes. With quotes it goes to 4,440.

Ok, now this is just plain and truly weird!!
This PM at work, I got ~33000 when I tried Polywell fusion (no quotes). I thought "well this is strange" and checked my preferences and they were the same as here at home so I tried again and it was down to 15,700!! Now here at home it is at 31,3000. I have no idea what Google is doing!

[MSimon]

28,800 for polywell fusion

15,900 for Polywell Fusion