Spheroidal Foci and POPS?

[alexjrgreen]

Frankly, all I see is a central blob - no surprise - and another blob that seems to be just outside the geometrical center of one of the coils. That doesn't make sense in either Rick's picture or mine. If it were my scientific reputation on the line, I would go to some lengths to rule out an artifact.

The second blob is reflected in the vacuum chamber viewport at 8 o'clock and again at 11 o'clock. So it's probably not an artefact.

[alexjrgreen]

At this condition, the electrons inside the
quasi-sphere “see“ small exit holes on the B cusp axes,
whose size is 1.5-2 times their gyro radius at that energy and
field strength.

If the electrons see a hole, I would expect them to fall out of it.

Like the electron jet in Figure 2 here Electric glow discharge.

That is what I claim to see in the WB7 photo, with the difference that the magrid is returning electrons to the wiffleball.

[Art Carlson]

Frankly, all I see is a central blob - no surprise - and another blob that seems to be just outside the geometrical center of one of the coils. That doesn't make sense in either Rick's picture or mine. If it were my scientific reputation on the line, I would go to some lengths to rule out an artifact.

The second blob is reflected in the vacuum chamber viewport at 8 o'clock and again at 11 o'clock. So it's probably not an artefact.

The reflection at 11 o'clock might make sense, although I couldn't say whether it is a reflection of the (much brighter) first blob or of the second one. What I can't figure out is the optics of the reflection at 8 o'clock. The source of light must be someplace completely different and probably lopsided, since there is no corresponding reflection at 2 o'clock.

[alexjrgreen]

What I can't figure out is the optics of the reflection at 8 o'clock. The source of light must be someplace completely different and probably lopsided, since there is no corresponding reflection at 2 o'clock.

The central axis is near the thin bright line. The corresponding reflections are near 12 o'clock and 3 o'clock, but they're quite faint because the angle is different.

[D Tibbets]

Frankly, all I see is a central blob - no surprise - and another blob that seems to be just outside the geometrical center of one of the coils. That doesn't make sense in either Rick's picture or mine. If it were my scientific reputation on the line, I would go to some lengths to rule out an artifact.

The second blob is reflected in the vacuum chamber viewport at 8 o'clock and again at 11 o'clock. So it's probably not an artefact.

Depends on your definition of artifact. I don't believe it is a photographic or reflection artifact. I believe it is an artifact in the sense that it is arcing, which is outside of the desired operational mode of the Polywell. There are too many neutrals and charged particles built up outside the magrid, allowing arcing, which is one of the critical conditions that Bussard said had to be avoided.
The picture is low resolution, highly compressed. Presumably, there are many more higher quality pictures aviable to EMC over a broad range of conditions. This picture, as A. Carlson says, tells nothing about what is going on within the Wiffleball (assuming there is such a thing and this picture represents it). It does show the border of the 'Wiffleball and the aprroximate shape of the cusps (at lest within the limits of the viewing angles). With the knowledge of the drive current and the B-field strength, some rough conclusions about how much the B-field is pushed back, and the gradient at the Wiffleball border (how fast the light drops off (at least if the picture was not overexposed in this area)) could be determined.
Some months ago, R. Nebel mentioned in another thread that earlier work had used photometry measurements to determine densities(?), and that they were suspect. He claimed that repeated tests on WB7 by another more reliable method was consistant with the earlier, less definitive tests.

Dan Tibbets

[D Tibbets]

"Thus, all of the individual physics issues and effects required
to make the concept work HAVE been proven by the
extensive experimental tests made since 1994 in the EMC2
R&D program. These include:
- The WB cusp trapping effect (explained further below;
WB-2,3,4,5), its physics and numerical rates.

"Further below" we find this:

When beta = unity is
achieved, it is possible to greatly increase trapped electron
density by modest increase in B field strength, for given
current drive. At this condition, the electrons inside the
quasi-sphere “see“ small exit holes on the B cusp axes,
whose size is 1.5-2 times their gyro radius at that energy and
field strength. ... Thus, this has been called Wiffle Ball (WB)
confinement ...

This is the only "numerical rate" I can find anywhere. His wording in the first quote suggests that this loss rate "HAS been proven by experimental tests." But the wording and context of the second quote sounds more like that is his model, which must still be compared to experiments. That is what I find frustrating (or worse) about Bussard. He is constantly suggesting things without stating them clearly. I tend to the interpretation that "1.5-2 times" comes from a model because from the descriptions of his apparatus, I don't believe he had the capability to actually measure the loss rate.

The first two links are more involved with the math, Forgive me for pointing this out as you have probably already perused them. The jargen is beyond me, do you feel these model (?) arguments are reasonable?
The lack of aviable data is certainly frustrating. Certainly Bussard kept his cards close to his chest, but remember that a large reason for that was the Navy embargo. It would have been nice if all the data had been dumped into the puplic domain once the contract expired, but Bussard's health and other concerns of EMC ^2 prevented that .

Dan Tibbets

[alexjrgreen]

The picture is low resolution, highly compressed.

OK. The photo can only take us so far...

It does, though, allow me to propose a model.

As depicted by Indrek, the (essentially cold) electrons are confined by the magnetic field of the six coils into a quasi spherical space with large holes opposite the centres of the coils and smaller holes at the corners (a wiffleball).

The electrons probably form a double well as discussed in Ryan Meyer's PhD thesis.

Electrons exit the large holes along the magnetic field lines in six jets, at very low radial velocity, are caught by the (relatively) positive charge on the magrid and recirculated back to the wiffleball.

Electrons exit the smaller holes in spikes (Indrek's depiction would suggest three legged Eiffel Towers) but are turned round by the mirror effect of the virtual coils at the corners and returned to the wiffleball.

The basic model therefore predicts no loss of electrons at all.

Over to Art...

[alexjrgreen]

This also shows very clearly why a permanent magnet can't be used.

On reflection, an axially magnetized toroidal permanent magnet like the ones Dan Tibbets has in his pressure cooker might be able to dodge a lot of the electron recirculation.

The hole in the middle would need to be just a little bit larger - something like this:

1" x 1/2" x 1/4" Rings

[Art Carlson]

The picture is low resolution, highly compressed.

OK. The photo can only take us so far...

It does, though, allow me to propose a model.

As depicted by Indrek, the (essentially cold) electrons are confined by the magnetic field of the six coils into a quasi spherical space with large holes opposite the centres of the coils and smaller holes at the corners (a wiffleball).

The electrons probably form a double well as discussed in Ryan Meyer's PhD thesis.

Electrons exit the large holes along the magnetic field lines in six jets, at very low radial velocity, are caught by the (relatively) positive charge on the magrid and recirculated back to the wiffleball.

Electrons exit the smaller holes in spikes (Indrek's depiction would suggest three legged Eiffel Towers) but are turned round by the mirror effect of the virtual coils at the corners and returned to the wiffleball.

The basic model therefore predicts no loss of electrons at all.

Over to Art...

Sorry. I have neither the time nor the inclination to go through the whole thing again. To give you a brief reminder: The loss fans will be quasi-neutral. Tell me about the energy losses via the ions.

[alexjrgreen]

Over to Art...

Sorry. I have neither the time nor the inclination to go through the whole thing again. To give you a brief reminder: The loss fans will be quasi-neutral. Tell me about the energy losses via the ions.

We haven't introduced any ions yet.

First we need a stable virtual grid...

[TallDave]

To give you a brief reminder: The loss fans will be quasi-neutral.

What would that look like in WB-7?

[alexjrgreen]

The loss fans will be quasi-neutral. Tell me about the energy losses via the ions.

Art,

You discussed this here and here.

The model I've just described is different from your assumptions in two important respects. Firstly, the electron sheets you describe are actually electron jets (tubes), and secondly, these jets extend out beyond the magrid so that ions beyond the magrid will be able to see them.

[D Tibbets]

Sorry. I have neither the time nor the inclination to go through the whole thing again. To give you a brief reminder: The loss fans will be quasi-neutral. Tell me about the energy losses via the ions.

Perhaps I'm confused (I say that a lot), do you mean the cusp losses when you mention loss fans?
I believe this would imply ambiploar cusp flows, which R. Nebel disputed. I don't understand all the details of why ions that do escape carry away only tolorable system energy, but it is a claim. I also do not understand how injected ions are introduced below the Wiffleball border unless there is some mechanism to bleed off some of thier initial radial potential energy. Neutral gass puffers seem more manigable in this regard as most of the neutrals would not ionize untill they reached the confined electrons. I think that the average ion can actually have a potential peak above the Wiffleball border where magnetic turning would limit their maximal excursion and the electrostatic effects would still be dminate. At the cusps the ions would climb higer because of no magnetic resistance, but that is ok up to some limit where the ions inertia overcomes the electrostatic field behind it and starts to 'see' enough of the electrons in the cusp. Of course once the magrid is reached, the ions zip away, though if the electrons in the cusp at some distance from the center can drag the ions along, in a ambipolar fasion (at that stage), then as the pair are exposed to the outside magrid charge, there would be an equal (?) and opposite effect- the electrons being attracted towards the grid (recirculating) would impead some of the ions outward acceleration due to the grid. I don't know how significant this would be at lessening the ions outward acceleration due to the magrid positive potential (minus the negative potential well still tugging on the ion, but it might mitigate some of the ion energy loss to the walls( at the cost of some drop in the potential well- so there are always compromises). This convoluted argument is mostly moot if there is an efficient direct energy converter that can capture the energy of the escaping fuel ions as well as the fusion ions (guessing 85% conversion eficiency as opposed to the default thermal capture efficiency of ~ 30%)

I believe the cusps are not ambipolar overall because of the excess electrons deep within the well that keep most of the ions below the cusp holes (out of the magnetic domain), This implies that a lot of the electrons at any given time are well below the Wiffleball border. The electrons in the cusps would 'pull' the ions outward less than the electrons near the center would 'tug' them back. Or, since the cusps are spaced on the outside of the main Wiffleball, Gauss's law would apply (at least partially) and ions would not see the cusp electrons' charge, unless they were upscattered well above the Wiffleball border in the cusp regions. While ions in this magnetic domain would have larger cusp excape holes compared to the electrons, I'm guessing that the numbers of ions reaching this height due to upscattering are rare enough that the realitive numbers compared to the electrons in this area more than compensates for the difference in realative cusp hole size.

Dan Tibbets

[Art Carlson]

The loss fans will be quasi-neutral. Tell me about the energy losses via the ions.

The model I've just described is different from your assumptions in two important respects. Firstly, the electron sheets you describe are actually electron jets (tubes), and secondly, these jets extend out beyond the magrid so that ions beyond the magrid will be able to see them.

You are welcome to fix that problem first, if you like. The losses through the line cusps should be about the same size as the losses through the point cusps. The beam escaping from the point cusps will also be quasineutral. Because the loss fans/beams extend beyond the magrid, the ions in them will be accelerated to the walls.

[alexjrgreen]

Because the loss fans/beams extend beyond the magrid, the ions in them will be accelerated to the walls.

The walls are almost as positive as the magrid. Why would the ions go there?