Pros and Cons of Fusion Power Generation

AI Thread Summary
The discussion focuses on the need for a comparative analysis of various fusion power generation approaches, including tokamaks, stellarators, and inertial electrostatic confinement (IEC). Key points include the challenges of neutron damage in magnetic confinement systems and the thermalization issues faced by IEC designs, which can hinder their efficiency. Participants emphasize the importance of comparing metrics such as energy efficiency, confinement times, and plasma density to evaluate the soundness of different fusion concepts. There is also debate about the practicality of non-neutral plasmas and the limitations of magnetic confinement due to instabilities and material degradation. Overall, the conversation highlights the complexities and trade-offs inherent in fusion research, calling for a more cohesive understanding of the physics involved.
  • #51
cuddihy said:
It's a self-licking ice cream cone of a model which presupposes its conclusions as initial conditions. You could use this model to prove a lightbulb doesn't work.

Let me just clarify, this was hyperbole. But this model could easily be used to prove that a Hirsch-Farnsworth fusor will not work, because the same thermodynamic conditions would apply as apply in a polywell. No part of this thermodynamic model is dependent on the power level, so it's not an aspect of the level fusors operate at either.

But the existence of fusors, the fact that they work exactly as theory says they should, belies the entire model.
 
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  • #52
cuddihy said:
No electrostatically accelerated fusion machine will suffer this fate, unless the electric potential breaks down. Rider didn't touch that.

Ok, I think I see where you are going with this now: The presence of the of the E field would somehow prevent energy distribution from becoming Maxwellian? I disagree. The E field can not reduce the entropy of the ions over time, it will only add a 'drift' bias on top of the Maxwellian distribution.
Why?
From Rider 3.77 in Fundamentals... the change in entropy over time due to the externally applied E-M field is
\frac{\partial{S}}{\partial{t}}=-\frac{Z_e}{m}\int{d^3vf( \textrm{ln} f + 3/2 )[(\nabla_v\cdot E)-\frac{v}{c}\cdot (\nabla_v \times B)]=0
where:
S is entropy
E, B are the externally applied fields.
Since \frac{v}{c}=\approx0 for ions in an IEC device and (\nabla_v\cdot E)=0 then then whole is ~ zero.
Or, per Rider, ".... is zero because the electric and magnetic fields do not depend of the velocities of the particles perceiving them (barring relativistic..)"

mheslep
 
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  • #53
It is all about gain.

mheslep said:
Ha! Then please engage Morbius the subject:
https://www.physicsforums.com/showpost.php?p=1367374&postcount=42
https://www.physicsforums.com/showpost.php?p=1367512&postcount=44
https://www.physicsforums.com/showpost.php?p=1367704&postcount=46


Why, technically since this is PF, would you favor the Bussard approach over one of many others?(no Tokamaks, no lasers):
http://http://www.topix.net/science/physics/2007/06/tri-alpha-energy-raises-40-million-in-venture-capital-for-nuclear-fusion"
http://www.google.com/url?sa=t&ct=r...QQ6BlJavkU4ndA6Q&sig2=4N3GRedtUCTyqQwYAQoIcA"
http://www.sandia.gov/news/resources/releases/2007/rapid-fire-pulse.html"
do dah
do dah

If you look at Rostoker's numbers you get drive energy requirements proportional to mass. Protons get 300 Kev. B11 gets 3.3 Mev.

In the Bussard reactor (I have calculated it myself) drive is proportional to electric charge. Protons get 200 Kev. B11 gets 1.0 Mev.

With a reaction that gives off 8.68 Mev that is quite a hefty trade off.

The Bussard reactor has more gain margin.
 
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  • #54
Maxwell was a demon

There is Maxwellianization at the center and at the edges. In the high density high energy region (center) energies scatter. In the high density low energy region (edge) it gets all redistributed at a lower energy so it re-peaks the distribution.

Or so the theory goes.

I'd like to build one and see if its true.


mheslep said:
Ok, I think I see where you are going with this now: The presence of the of the E field would somehow prevent energy distribution from becoming Maxwellian? I disagree. The E field can not reduce the entropy of the ions over time, it will only add a 'drift' bias on top of the Maxwellian distribution.
Why?
From Rider 3.77 in Fundamentals... the change in entropy over time due to the externally applied E-M field is
\frac{\partial{S}}{\partial{t}}=-\frac{Z_e}{m}\int{d^3vf(lnf+\frac{3}{2})[(\nabla_v\cdot E)-\frac{v}{c}\cdot (\nabla_v \times B)]=0
where:
S is entropy
E, B are the externally applied fields.
Since \frac{v}{c}=\approx0 for ions in an IEC device and (\nabla_v\cdot E)=0 then then whole is ~ zero.
Or, per Rider, ".... is zero because the electric and magnetic fields do not depend of the velocities of the particles perceiving them (barring relativistic..)"

mheslep
 
  • #55
M. Simon said:
If you look at Rostoker's numbers you get drive energy requirements proportional to mass. Protons get 300 Kev. B11 gets 3.3 Mev.

In the Bussard reactor (I have calculated it myself) drive is proportional to electric charge. Protons get 200 Kev. B11 gets 1.0 Mev.

With a reaction that gives off 8.68 Mev that is quite a hefty trade off.

The Bussard reactor has more gain margin.
What are you talking about? Pls don't hand-wave in this engineering forum - move over to general discussion. Which Rostoker numbers are proportional to mass? How are you defining gain in this context? Hefty trade-off?
 
  • #56
M. Simon said:
There is Maxwellianization at the center and at the edges. In the high density high energy region (center) energies scatter. In the high density low energy region (edge) it gets all redistributed at a lower energy so it re-peaks the distribution.

Or so the theory goes.

I'd like to build one and see if its true.
Please see
https://www.physicsforums.com/showthread.php?t=5374
 
  • #57
In the discussion about the Polywell topic in Wikipedia (http://en.wikipedia.org/wiki/Talk:Polywell), there is an interesting, if intuitive, approximation to velocity distribution in a polywell.

Regrettably, the author is unknown:

(...)
Regarding Maxwellianization, this is how i see it: the well establishes a relationship between the ions distance from the center and it's radial velocity. It's velocity perpendicular to it's radial velocity is essentially an angular velocity. So let's split this up into radial and angular velocities:

angular velocity: Assuming for a moment that the angular veocity for each ion is mantained (inertial), as the ion gets closer to the center the angular velocity's contribution to the kinetic energy decreases, such that when it's in the center it is exactly zero. (because a ball traveling in a circle of radius r at angular velocity 2pi is traveling with linear velocity 2pi*r.) So as ions approach the center, their angular velocity components become non-maxwellian, such that at the center they are all exactly the same: 0.

Now, dropping that assumption, the rule still applies, because it's a law of geometry (translation of coordinate systems). However, we add in maxwellianization of the angular velocity, which will make their angular velocities approach an average, with a normal distribution. That average, since as many will be going clockwise as counterclockwise, is zero. It is only a matter of what the standard deviation of the normal distribution is. Or, more precisely, how fast the standard deviation increases or decreases with respect to the distance from the center. (This is really a crude model, because they do not actually linear velocity perpendicular to their radial velocity as they go away from the center. their angular velocity decreases. the trajectory (in two dimensions) would look more like a polar rose or trefoil knot.) in any case, it seems to me that maxwellianization will tend to reduce the standard deviation of their angular velocities, leading to better focus.

radial velocity: Again, starting with the simpler non-maxwellian case: because of the radial electrostatic gradient, the radial velocity of an ion will be a function of its initial radial velocity and distance from the center. To simplify this, one can combine initial distance from center and radial velocity by finding the distance from the center in which the radial velocity is zero. Thus, if they all start from the same distance from the center at which the radial velocity is zero (disregarding that this is quasi-spherical rather than spherical), they will all have the same radial velocity at any given distance from the center.

Ideally, they all have zero radial velocity at the very outer edge of the sphere, thus giving them maximum kinetic energy at the center. this is what the polywell attempts to do by using microwaves to ionize the gas. according to mainstream scientific theory, the ionization rate will depend largely on how well matched the magnetic field strength at the point of ionization is to the frequency of the microwave radiation. Thus, since the magnetic field strength decreases as one goes towards the center, one can set the microwave frequency such that it ionizes the most at the very edge of the sphere.

So now let's take into account maxwellianization of the radial velocity component. And here is the key: potential energy does not maxwellianize. Sure, they will maxwellianize on the outside, all to the same low average velocity (and thus low standard deviation (i.e. "temperature"). But, since their initial distance from the center of the ions is all about the same (the very edge, where the gas is ionized), and their velocities (KE) are relatively low in comparison to their potential energy (the huge voltage gradient between the center and the outside), as they go toward the center they will be accelerated at the same rate, and thus their radial velocities relative to each other will stay the same. since maxwellianization is a function of velocities relative to each other, and not absolute velocities(throwing ice in space won't make it melt), maxwellianization will occur at the same rate, and their standard deviation ("temperature") will not increase as they go towards the center, even though their average KE gets much higher.

Now this doesn't take into account the fact that as ions are going towards the center, the same number of ions are going away from the center, at the same average radial velocity. So you have two sets of ions whose relative radial velocities are higher and higher as you approach the center. That is a possible source of additional maxwellianization. As I understand it, if they are flying past each other very fast, the ions going in opposite directions spend so little time at any distance from each other where inter-atomic forces would be significant that tehy don't really affect each other. So maxwellianization between inbound and outbound ions would occur at a higher rate as you get further from the center. - a maxwellianization that leads to zero average radial velocity. This causes the ions' "distance from the center at which their radial velocity is zero" to approach "far from the center" quicker than it approaches "close to the center". Leading towards the ideal condition mentioned earlier.

That's all very rough. Forgive me: I don't really know what I'm talking about. 69.131.30.74 00:59, 8 April 2007 (UTC)

Pity I haven't got the maths to model that intuition. My last battles with multidimensional differential operators were just before the fall of the Berlin Wall...

Comments?
 
  • #58
sunday said:
Comments?
Forgive me: I don't really know what I'm talking about
He/She's right.
 
  • #59
mheslep said:
He/She's right.

With the due respect, Why?
 
  • #60
mheslep said:
What are you talking about? Pls don't hand-wave in this engineering forum - move over to general discussion. Which Rostoker numbers are proportional to mass? How are you defining gain in this context? Hefty trade-off?

I take it you haven't read Rostoker 2004. Pity.

You can stop the hand waving now.

Gain = Energy out / drive energy.

Gain Bussard pB11 = 8.68Mev / 1.2 Mev
Gain Rostoker pB11 = 8.68 Mev / 3.6 Mev

This is the ultimate gain. Actual gain will be less.

BTW how you coming on the vacuum tube book (Chafee)?
 
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  • #61
cuddihy said:
Let's not forget Rostoker and Bussard were also each partially funded by the Office of Naval Research,...
this is just my opinion.

Right, both got ONR $$, I thought that was the point I was making...
AS far as the rest of your observations about Rider, very well said.
It is, at the very least a very strange story.

cuddihy, did you catch my bit on vacuum tubes circa 1933, and inelastic particles upthread? Since we are dealing with an ion accelerator.. are the ions going fast enough to become inelastic? If they are, they don't bounce...no?

if there is bounce we are talking about imparting spin... or exciting.. electrons changing orbits... no ?

I'm asking, because I'm not sure I have it right.
 
  • #62
M. Simon said:
BTW how you coming on the vacuum tube book (Chafee)?
What happened to your posted link to that copyrighted book?
 
  • #63
sunday said:
Yep, but one can always suppose that Ridder said that in tongue-in-cheek mode. I don't think a jest like that should be used to destroy the credibility of a scientist.

Nevertheless, Rider got a fellowship. If there was some gamesmanship, it was thru Rider's & the ONR's action and not mine. Rider took the money & ran away to work another field... no?

Forget the hyperbole, that I have introduced, forget it. Look at Riders actions.
 
  • #64
sunday said:
With the due respect, Why?
The argument is hard for me to parse. The part on angular momentum is just wrong about a basic conservation law.
So as ions approach the center, their angular velocity components become non-maxwellian, such that at the center they are all exactly the same: 0.

If a particle has somehow acquired some angular momentum (via a collision say) on the edge its not going become zero as falls down a radial potential gradient. The non zero angular mo means the particle will form some kind of orbit about the center, it will be defocused compared to a radially traveling particle, and in fact will never go through the center until/unless some other force other than the external qE force acts on it (another collision say). Its Phy mechanics 101.
And so on.

See Nevins for a good, mathematically modeled treatment:
"http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PHPAEN000002000010003804000001&idtype=cvips&gifs=yes" ", W.M Nevins Physics of Plasmas 2, 3804, 1995.
 
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  • #65
mheslep said:
The argument is hard for me to parse. The part on angular momentum is just wrong about a basic conservation law.


If a particle has somehow acquired some angular momentum (via a collision say) on the edge its not going become zero as falls down a radial potential gradient. The non zero angular mo means the particle will form some kind of orbit about the center, it will be defocused compared to a radially traveling particle, and in fact will never go through the center until/unless some other force other than the external qE force acts on it (another collision say). Its Phy mechanics 101.
And so on.

See Nevins for a good, mathematically modeled treatment:
"http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PHPAEN000002000010003804000001&idtype=cvips&gifs=yes" ", W.M Nevins Physics of Plasmas 2, 3804, 1995.

Yes, about radial velocities, I agree. But I find the part about radial velocities acceptable.

I have no access to the full text of the cited paper...
 
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  • #67
mheslep said:
What happened to your posted link to that copyrighted book?

The copyright has expired.

It is public domain. These things happen.

Despite that fact it appears that the link has been removed.

Pity. A lot to learn there.

Well if you look around you can find it.
 
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  • #68
I've found that most of the technical books published before about 1964 never had their copyrights renewed, so now are in the public domain. So I am endeavoring to digitize and post some selected books relating to the "vacuum tube age" of electronics here.

I have checked to the best of my ability to confirm that these works have expired copyrights and are now in the public domain. If you have information to the contrary, please contact me at:

For information about copyrights and copyright renewals, look here. Here's a nice, easy copyright renewal search tool.

Want to help? If you have any pre-1964 books relating to vacuum tube technology, radio, or electronics that you'd like to sacrifice, let me know. And when I say "sacrifice", I really do mean sacrifice - the way I do this is to cut the book loose from it's cover, then slice the pages away from the binding. This way I can send it through an automatic document feeder. I can scan a 400 page book in about one hour. I'll have to verify that the copyright is expired and has not been reviewed - I can do that before you send anything.


From:

http://www.pmillett.com/tecnical_books_online.htm

Which has lots more books on tubes.

I recommend it.
 
  • #69
John F. Santarius
University of Wisconsin
Injected electrons form a cloud throughout the interior of the sphere, resulting in a negative electrostatic potential well, as shown in Fig. 3. Ions are injected at low energy or created by neutral gas ionization at the outer edge of the electron cloud. These ions fall down the potential hill and converge on the origin of the sphere, giving a small, spherical core of high density (see Fig. 2). For a sufficiently deep potential well, steady-state fusion power can be generated in this core. Preliminary investigations of the Polywelltm concept have led to the conclusion that it can be a viable fusion reactor [2, 12-14],

2. R.W. Bussard, "Some Physics Considerations of Magnetic Inertial-Electrostatic Confinement: A New Concept for Spherical Converging-flow Fusion," Fusion Technology 19, 273 (1991).

12. N.A. Krall, "The Polywell: A Sperically Convergent Ion Focus Concept," Fusion Technology 22, 42 (1992).

13. M. Rosenberg and N.A. Krall, "The effect of collisions in maintaining a non-Maxwellian plasma distribution in a spherically convergent ion focus," Phys. Fluids B 4, 1788 (1992).14. S.K. Wong and N.A. Krall, "Potential well formation by injection of electrons with various energy distributions into a sphere or a slab," Physics of Fluids B 4, 4140 (1992).

although several questions remain [15, 16].

15. W.M. Nevins, "Can Inertial Electrostatic Confinement Work Beyond the Ion-Ion Collisional Time Scale?," Physics of Plasmas 2, 3804 (1995).

16. T.H. Rider, "A general critique of inertial-electrostatic confinement fusion systems," Physics of Plasmas 2, 1853 (1995).

http://fti.neep.wisc.edu/iec/inertial_electrostatic_confineme.htm

Santarius cites article pro & con, offering both sides for your consideration. From one of 2 (IIRC) University IEC programs in the US, (Urbana is the second, U of Wis has a working IEC reactor).

Dr. Kulcinski with IEC device

http://fti.neep.wisc.edu/iec/potential_uses.htm

Grahic: Likelihood of fusion
http://fti.neep.wisc.edu/iec/operat1.gif

Peer reviewed work from U of Wis. #10 looks good.

http://fti.neep.wisc.edu/iec/peer_reviewed.htm
 
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  • #70
M. Simon said:


Which has lots more books on tubes.


IIRC it was Bussard who said that a polywell device such as WB6 is more akin to a vacuum tube than a Tokamak, so would WB6 be a diode? Thats what I infered from the intro in Chaffee's book. WB6 is a Vacume tube diode. ..?
 
  • #71
RogerFox said:
IIRC it was Bussard who said that a polywell device such as WB6 is more akin to a vacuum tube than a Tokamak, so would WB6 be a diode? Thats what I infered from the intro in Chaffee's book. WB6 is a Vacume tube diode. ..?

Due to the electron beams in some ways it is like a beam power tube. Well formation is a beam power tube type phenomenon - a virtual suppressor grid. . The magnetic field makes it kind of like a magnetron diode. Add in grids on your electron guns an you really have a very strange tube.

Electron dominance is the key. Just as it is in most types of vacuum tubes.
 
  • #72
M. Simon said:
Due to the electron beams in some ways it is like a beam power tube. Well formation is a beam power tube type phenomenon - a virtual suppressor grid. . The magnetic field makes it kind of like a magnetron diode. Add in grids on your electron guns an you really have a very strange tube.

Electron dominance is the key. Just as it is in most types of vacuum tubes.

Then why do so many get hung up by talking the language of Tokamaks?
Rhetorical, I know, sorry.
 
  • #73
RogerFox said:
Then why do so many get hung up by talking the language of Tokamaks?
Rhetorical, I know, sorry.

Obsolete technology. People haven't studied it for decades. I haven't thought about it much for 20 years or so myself. Now I know more than I ever did.
 
  • #74
Hopefully this will help shed some light

This might elucidate a bit.

http://www.sciencemag.org/cgi/content/full/281/5375/307a

http://www.sciencemag.org/cgi/content/full/281/5375/307a" . Rostoker had the last word, which doesn't, of course, mean he was right.

Rostoker's argument seems to hinge on this (click link for equations, haven't been able to paste them):

Carlson employs a classical generic formula for the power density required to overcome the friction between proton and boron beams. This formula is inadequate for the Colliding Beam Fusion Reactor. The magnetic field is important, and it is distinguished by its absence in this formula. The complete formula can be derived by taking the appropriate moment of the Vlasov/Fokker-Planck equation.

Is there an error in his reasoning here?

mheslep, I believe this is what you referred to in #30.

They've just been given $40M to try to make a demo machine that will shock and amaze the world. Not sure what their timeline is, but based on what I remember reading, if we don't hear from them within a couple years then things probably aren't working out. Anyone have a better guesstimate?
 
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  • #75
Rostoker says: We have previously considered long, thin cylindrical shell models because they simplify many calculations.

Which says that their reactor model may be based on ease of calculation vs optimum design.

Rostoker says that his machine will require 3.6 Mev of power into get 8.68 Mev (per reaction) of power out at 580 Kev in the center of mass frame.

For Dr. Bussard's machine under similar conditions the drive energy is 1.2 Mev.
 
  • #76
TallDave said:
if we don't hear from them within a couple years then things probably aren't working out. Anyone have a better guesstimate?

Tri Alpha is not building a large device at first? Right? I mean they got 5 mill up front, right... so they are not talking about a ITER sized cathedral.

Yeah 2, 3 years tops. I'll bet Tri Alphs gets "Q" @ .65 or under for a buck, anyone else ?
 
  • #77
My recollection is that they are first building a smaller device, which is supposed be a good enough neutron source that it can be used for nuclear waste disposal.

RogerFox said:
Tri Alpha is not building a large device at first? Right? I mean they got 5 mill up front, right... so they are not talking about a ITER sized cathedral.

Yeah 2, 3 years tops. I'll bet Tri Alphs gets "Q" @ .65 or under for a buck, anyone else ?
 
  • #78
TallDave said:
Carlson employs a classical generic formula for the power density required to overcome the friction between proton and boron beams. This formula is inadequate for the Colliding Beam Fusion Reactor. The magnetic field is important, and it is distinguished by its absence in this formula. The complete formula can be derived by taking the appropriate moment of the Vlasov/Fokker-Planck equation.

Is there an error in his reasoning here?

mheslep, I believe this is what you referred to in #30.
Yes I think when he says with respect to thermalization "the magnetic field is important" he must be wrong, it is not important as I showed inhttps://www.physicsforums.com/showpost.php?p=1370035&postcount=52"
 
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  • #79
mheslep said:
Yes I think when he says with respect thermalization "the magnetic field is important" he must be wrong, it is not important as I showed inhttps://www.physicsforums.com/showpost.php?p=1370035&postcount=52"

Hmm, yes. I was hoping there was a specific flaw in Rostoker's derivation someone could point to. If the magnetic field can't reduce the entropy, it seems to me there ought to be some flaw we could point to in how they introduced it when they took the moment of the Vlasov/Fokker-Planck equation.

Obviously one of the two arguments must be using an inapplicable equation for the thermalization effects in an IEC device of the type described by Rostoker -- and similarly for Bussard's Polywell, to which Rider's thesis should apply as well (I asked Bussard if they might be publishing a detailed paper anytime soon, and he said probably not before the end of the year). It's hard to find much reference that would support either interpretation, but if it were easy we wouldn't be discussing it. Maybe we'll just have to wait and see if either IEC design actually works as the inventors claim.

I give them a 1 in 3 chance of being correct, and only that high because Bussard claims to have those n-counts and seems fairly credible (i.e. unlikely to have fabricated or misinterpreted them).
 
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  • #80
TallDave said:
This might elucidate a bit.

http://www.sciencemag.org/cgi/content/full/281/5375/307a

http://www.sciencemag.org/cgi/content/full/281/5375/307a" .

Well it was between Rostoker and Nevins/Carlson. Nevins w/ LLNL and Carlson at Max Planck. Rider is only cited. Nevins authored the "Can IEC work beyond..." paper in '95 so its to be expected he would publicly reply to the Rostoker-Monkhorst paper in Science 3 years later that basically ignored his well crafted objections to mono-energetic plasmas.
 
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  • #81
mheslep said:
Well it was between Rostoker and Nevins/Carlson. Nevins w/ LLNL and Carlson at Max Planck. Rider is only cited. Nevins authored the "Can IEC work beyond..." paper in '95 so its to be expected he would publicly reply to the Rostoker-Monkhorst paper in Science 3 years later that basically ignored his well crafted objections to mono-energetic plasmas.

Yes, silly of me. I get so used to seeing Rider's name in these discussions, I forgot it was Nevins who made the argument.
 
  • #83
No 'Ca spokesman said', no sources at all, zip. I call BS.
 
  • #84
mheslep said:
No 'Ca spokesman said', no sources at all, zip. I call BS.

Well, of course there are no sources. It's a leak, not a press release.

It might well be BS, or more likely, have some kernel of truth but not be entirely accurate (e.g., there is discussion of funding Polywell, but no decision yet).

Or it could be a total fabrication, for reasons unknown. Time will tell.
 
  • #85
I don't know if this has been posted here yet, but here is an interesting approach called the Periodically Oscillating Plasma Sphere:

http://www.lanl.gov/p/rh_pp_park.shtml

So basically it's inertial electrostatic confinement, but in the form of oscillating spheres akin to the sonofusion idea, only using electrostatics instead of sound.

http://fusor.net/board/download_thread.php?site=fusor&bn=fusor_theory&thread=1184299189
 
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  • #87
Does Dr Bussard's IEC fusion device have any reasonable chance of working? (ie. providing net energy output)

What about that POPS thing? I read something that said space charge neutralization in an oscillating plasma puts limits on the amount of compression of the plasma, whereas a steady state plasma has no such limits. So does that mean the POPS idea is a dead end?
 
  • #88
RogerFox said:
false alarm.

We don't know for sure yet.
 
  • #89
Does Dr Bussard's IEC fusion device have any reasonable chance of working? (ie. providing net energy output)

What about that POPS thing? I read something that said space charge neutralization in an oscillating plasma puts limits on the amount of compression of the plasma, whereas a steady state plasma has no such limits. So does that mean the POPS idea is a dead end?

http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PHPAEN000014000004042701000001&idtype=cvips&gifs=yes

A major issue for electron injected inertial electrostatic confinement (IEC) devices is space charge neutralization. A new formalism is developed that will allow this neutralization to occur for both oscillating and steady-state IEC plasmas. Results indicate that there are limits on the amount of compression that can be achieved by oscillating plasmas while simultaneously maintaining space charge neutralization and parabolic background potential. For steady-state plasmas, there are no such limits and space charge neutralization can be achieved even when the plasma becomes quasineutral.

To me, that sounds like POPS can't be made to work. It's nice that steady state plasmas have no charge neutralization problems, but they're not trying to achieve compression.
 
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  • #91
sanman said:
So basically it's inertial electrostatic confinement, but in the form of oscillating spheres akin to the sonofusion idea, only using electrostatics instead of sound.
Yes its IEC but no it has nothing in common, even in concept, w/ sonofusion.
 
  • #92
sanman said:
To me, that sounds like POPS can't be made to work.
No it means just what it says, there are limits to spherical approach as crafted.. Details in the paper, c.f., cylindrical approaches.
 
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  • #93
mhslep, are you saying that cylindrical might produce better results (ie. less constraint on achievable compression) than spherical?

What would that be called -- POPC?

They don't mention how much difficulty is posed by the constraint on space charge neutralization vs compression factor.

I wish someone could publish a "best neutron count achieved" or a "best energy input/output ratio" or whatever.

Because otherwise it's hard to get a sense of how serious an obstacle the space charge neutralization vs compression ratio problem is.
 
  • #94
sanman said:
mheslep, are you saying that cylindrical might produce better results (ie. less constraint on achievable compression) than spherical?
The paper makes clear that the difficulty in using electrons to neutralize the space charge in a spherical device is a geometrical one (angular momentum, etc). That particular issue would likely vanish w/ a cylindrical device as one would simply inject electrons along the central axis. The cylindrical design of course introduces other problems.
 
  • #95
mheslep said:
The paper makes clear that the difficulty in using electrons to neutralize the space charge in a spherical device is a geometrical one (angular momentum, etc). That particular issue would likely vanish w/ a cylindrical device as one would simply inject electrons along the central axis. The cylindrical design of course introduces other problems.
mheslep,

Yes - cylindrical fusion devices have been studied back in the '70s; which
ultimately culminated with the contruction of MFTF - Mirror Fusion Test Facility.

MFTF was a big cylindrical fusion device; the ends of which were sealed by
huge "yin-yang" magnets.

http://en.wikipedia.org/wiki/MFTF

The following shows a picture of one of the HUGE "yin-yang" magnets:

http://www.llnl.gov/pao/WYOP/Fusion_Energy.html

As the caption states, those magnets were the largest superconducting
system ever built. To get an idea of the size of the "yin-yang" magnets;
the red "sled" that moved the magnets rolled on big logs visible underneath
the sled.

Dr. Gregory Greenman
Physicist
 
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  • #96
What if your electron dispersion for POPS could be maintained as some kind of traveling wave that moved only as the plasma moved? Couldn't that charge dispersion then be considered as static/standing-wave in relation to the plasma, thereby affording the steady-state plasma interpretation that was mentioned as not having any compression limits?

Consider it analogous to electronic valve timing, or the new variable compression ratio technology for car engines.
 
  • #97
Morbius said:
mheslep,

Yes - cylindrical fusion devices have been studied back in the '70s; which
ultimately culminated with the construction of MFTF - Mirror Fusion Test Facility.

MFTF was a big cylindrical fusion device; the ends of which were sealed by
huge "yin-yang" magnets.
Thanks for the links. Yes I'm familiar and aware that the mirrors were in the end not satisfactory for sealing the cylinder, thus further advancing the torus. However, this is ~unrelated to my post above which discusses inertial electrostatic confinement, not magnetic confinement. Different physics, no thermal ignition with IEC.
 
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  • #98
sanman said:
What if ...
Electronic valve timing? Read up a little here and let me know if you think its analogous.
http://www.pma.caltech.edu/Courses/ph136/yr2004/0420.1.K.pdf
http://www.pma.caltech.edu/Courses/ph136/yr2004/0421.1.K.pdf
 
  • #99
mheslep said:
Electronic valve timing? Read up a little here and let me know if you think its analogous.
http://www.pma.caltech.edu/Courses/ph136/yr2004/0420.1.K.pdf
http://www.pma.caltech.edu/Courses/ph136/yr2004/0421.1.K.pdf

That talks about waves of the plasma.
I'm talking about having the injected electron charge dispersion move/change/rearrange as the plasma moves. The point was previously made that space charge neutralization by electron injection has limited effectiveness on an oscillating plasma as compared to a steady state plasma. So I'm saying that motion -- even oscillating motion -- is relative. Therefore electron injection could be dynamically modified while the plasma is moving/oscillating so that the electronic charge dispersion and the plasma seem static / steady-state relative to each other. Perhaps this might then alleviate the constraints on achievable compression ratio.

So my electronic timing analogy isn't so terribly out of place, imho.
 
  • #100
Bussard's Polywell fusion project was funded btw

Bussard passed away shortly after signing the Navy contract, and Nebel of the POPS paper has picked it up. They have the machine mostly built and are testing components. Nebel says they may have some results by May.

I was going to post links, but it won't let me. You can find the MSNBC mention of the project by Googling Nebel MSNBC.

There is still a lot of debate about whether bremsstrahlung losses will exceed fusion power, which can probably only be resolved by experiment. Nebel believes the ion upscattering is not a problem (see the Chacon reference in the Polywell wikipedia page).
 

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