reddit: We are nuclear fusion researchers, ask us anything

[KitemanSA]

IF P-b11 can be done by Polywell, that makes Lunar He fueled Polywell's very interesting...

Why?

[Joseph Chikva]

Unless people like you prevent people who "don't know" from doing the research to find out, in which case you are your own self-fulfilling prophecy.

Hehe
Because I said that confined ions will thermalize plasma? But that's true

But are they confined long enough to be a problem? The statement was not that they were "confined", just that they would be unlikely to hit the MaGrid on their way out. How many transits to thermalize? How many transits to escape? Do you know? If not, you're just guessing too.

Or because despite you and others I said that two-stream instability should be investigated for Polywell? Dr. Nebel investigated and came to conclusion that only high themal electrons could prevent this type of instability.

Reference? Quote (in context)?

Or because I said that by increasing of plasma density electron-ion two straem instability also may be an issue for Polywell? That's true too.

It is also true that Aliens "may" invade tomorrow. Which is more likely?

Etc. etc. etc.

E.g.? E.g.? E.g.?

I see that you aren't able to argue.

Really? What have we been doing?

Because to ask questions doesn't mean to be the enemy. I am not enemy. On the contrary I help you to get rid of illusions.

First remove your own rose colored glasses?

Polywell is a convential magnetic trap extended to spherical geometry:
Conventional mag trap

And Polywell

First type of traps are usually thermaized by e.g. ion beams. As a rule significant part of those ions are confined. Why charged reaction products should not be confined in Polywell.
Two-stream instability will occur any time when beams are injected into background plasma. The matter is only in scale of those instabilities in different devices. The most dangerous are electron-electron, then ion-electron (ion-ion will not occur in Polywell). Increasing number density to the certain limit you would reach that electron-ion instability will gain destructive scale. And your goal is to increase the density when you talk about strong fields 7 or even 10 T.
Link on Dr. Nebel's article on investigation of possibility of 2-stream electron-electron instability is somewhere in this thread. You have read that and we discussed that when you told "no beams in Polywell". Recall "large angular momentums" that means "highly thermal electrons".
Also recall that initially ions will not have large angular momentums. And, so, electron-ion 2-stream instability at high densities is not likely but is inevitably.
Etc., etc., etc.

[KitemanSA]

Polywell is a convential magnetic trap extended to spherical geometry:
Conventional mag trap

And Polywell

Hmmmm. This may help explain some of your confusion. In your "mag trap" graphic, the currents in the two magnets are running the same way around so the north of one feeds into the south of the other. This is exactly opposite what the Polywell has. With the Polywell, all six magnets are pointed "in" so that north faces north (or vice versa).

As I understand it, this makes a huge difference.

[hanelyp]

Having the magnets arranged like the polywell makes a HUGE difference. The fields from opposite sides cancel in the center, leaving a magnetic well structure. Plasma in the well compresses the magnetic field against the coils, making a naturally stable system.

edit:
Found a video that illustrates the magnetic field in a polywell reasonably well.
http://www.youtube.com/watch?v=jmp1cg3-WDY

[D Tibbets]

Indeed. Mirror machines are of two types - the solenoid type where the magnetic poles face the same direction. The equatorial cusp is avoided, but the macro instabilities are unmanageable. The other variant is the opposing magnet mirror machine. This is what the Polywell starts from. There is an equatorial cusp(s)but macro instabilities are avoided. The problem is the leakage from the equatorial (line) cusp is large relative to the contained plasma volume. The Polywell modifies the line cusps so that, the leakage is much less per unit volume of contained plasma. Wiffleball formation extends this advantageous relationship even further, plus the advantageous increased densities that are possible.

Dan Tibbets

[Joseph Chikva]

As I understand it, this makes a huge difference.

Both confine charge particle moving at certain directions.
That's enough for seeing similarity. Regardless to which of those confinement schemes are more effective.

[ladajo]

Both confine charge particle moving at certain directions.

If I understand what you mean, no.

Polywell does not care about uniform direction of particles.

It cares about random oscillatory motion in a 4D volume.

[DeltaV]

Superconductor-like diamagnetic expulsion of the field lines by the electrons in the center is the key to formation of the "Wiffleball".

The bunched electrons effectively pull tight the "drawstrings" of the magnetic "bag".

[Joseph Chikva]

Both confine charge particle moving at certain directions.

If I understand what you mean, no.

Polywell does not care about uniform direction of particles.

It cares about random oscillatory motion in a 4D volume.

1. Where do you see “4D volume”?
2. "Does not care uniform direction of particles." does not mean that electrons and charged products of reaction do not have random directions. As they have. Recall "Large angular momentums" - the words of Dr. Nebel.
3. I understand the attempt of Polywell's developers to create such a magnetic field configuration, in which in the space occupied by plasma B is minimal. And plasma having diamagnetic properties should by this idea be retracted into this space. This means better confinement of randomly moving particles too. And better confinement of reaction products means faster thermalization. And this does not mean at all exclusion of two-stream instability.

[KitemanSA]

2. "Does not care uniform direction of particles." does not mean that electrons and charged products of reaction do not have random directions. As they have. Recall "Large angular momentums" - the words of Dr. Nebel.

Actually, you are yet again misquoting him. I find nowhere that he says there are "large" angular momenta. Also, there is the classic "linear vs spherical frame of reference issue here.

Nebels quote implies to me that there can be instability issues with SMALL angular momenta but go away when "large enough". "Large enough" angular momenta introduced to linear "beams" entering a Polywell and meeting at the center become "radial" as they spread out from the center. Radial, no longer "angular". And it seems that it doesn't take much spread of the radial electron flow to eliminate the instability. As long as they stay relatively radial, the "thermalization" will tend to be annealed, at the edge for the ions and in the center for the electrons.

Time will tell. Tick tock.

[Joseph Chikva]

Nebels quote implies to me that there can be instability issues with SMALL angular momenta but go away when "large enough".

You are arguing grammatically while me - physically. I little bit better than you aware with this type of instability. And it less interesting for me what you think how to interpret words of Dr. Nebels better.
And I only quote his article for ensure you that Polywell is a beam machine and stability of beams does matter.
"Small but large enough" is initially wrong statement as all scattered electrons in Polywell will be thermal. While ions initially will not be thermal. And at increased density electron-ions 2-stream would be significant challenge. At least this issue was not investigated yet.
When you will get some fusion events, you will get ions moving at random directions.

[ladajo]

Joseph,
Did you read any of the last round of spoon feed references I gave you?

1. Where do you see “4D volume”?

You don't???

[Joseph Chikva]

1. Where do you see “4D volume”?

You don't???

No. I am still living in 3D world. And spheric frame is 3D too. Good night.

[krenshala]

1. Where do you see “4D volume”?

You don't???

No. I am still living in 3D world. And spheric frame is 3D too. Good night.

It appears you are also ignoring time. The Polywell is NOT a static device, it is a dynamic device.

[Roger]

IF P-b11 can be done by Polywell, that makes Lunar He fueled Polywell's very interesting...

Why?

Consider it a question.