Fusion Summary? [Archive] - Physics Forums

mheslep

May16-07, 06:19 PM

Is this homework? One can find articles on-line about each concept.
No, though my apologies for the overly broad post. I'm looking into some internal R&D work and trying to obtain a comparative high level view of the trade offs based purely on the soundness of the physics, independent of the $ and man hours invested to date, to the degree thats possible. Yes I'm well into the lit. on many of the approaches but then of course the issue in each area is that the researchers can be myopic about their particular approach: Tokamak'ers versus implosion, etc. Lidsky's "Trouble w/ Fusion" points some fingers.

Parameters to compare would be efficiency [(energy out)/(energy in)], confinement times, plasma density, reaction rate, . . .

Good observables but I think those metrics illustrate my points above:
1. They show for instance how magnetic confinement schemes completely dominate fusion discussion. Density is, what, 5-6 orders of magnitude different between implosion and mag confinement so thats not useful by itself. Confinement times (Larson), AFAICT, are not relevant to accelerator (driven) schemes like IEC or Rostoker's beam-beam beast (http://www.sciencemag.org/cgi/content/abstract/278/5342/1419?ck=nck)
2. $/time invested. If I want only soundness of idea and not $, do I look at Eout/Ein for 1970 Tokamaks or 1999 JET?

And what does one mean by IEC quickly thermalizes?
IEC is basically an accelerator like beam-beam system. I dont refer to the fusion products, but the reactants. That is, the is all reactant ions are accelerated by E fields to, say, 50KeV creating a completely non-maxwellian, mono energetic system. The ideal is they stay that way unto a fussion event, but it seems to be well established that for beam-beam systems that coulomb collisions dominate ~1000:1 and thus the reactants quickly thermalize - either escaping the system on the hot end or becoming unavailable for fusion on the cold end.

the p+B system is about as purely aneutronic as one can get, but it requires high temperatures with resulting high pressures, which is a major handicap for magnetic confinment. In the inertial confinment systems, it's those darn electrons which get in the way.
Ah, so lets get rid of (most) the electrons ;-) Non-neutral plasma work seems to be on the upswing.

Astronuc

May16-07, 08:06 PM

For IECs this might be of interest - http://fti.neep.wisc.edu/iec/ftisite1.htm

I don't believe non-neutral plasmas are necessarily practical from a stability perspective.

Inertial confinement has the problem of a cyrogenic fuel source (fuel pellet), the repeatability issue, and then net energy production vs input. Energy extraction is an issue - as well as a myriad of materials degradation issues.

Magnetic confinement has much the same problem along with the stabilty of magnetic confinement, and limiations on plasma density, which are a consequence on the limit on the magnetic field strength, which are a consequence of the limits on currents in the superconducting magnets.

Beam systems, including injected beams into magnetic confinement, have the drawback of beam energy efficiency and scattering of the beam by the plasma.

mheslep

May16-07, 09:53 PM

Thanks for your summary

For IECs this might be of interest - http://fti.neep.wisc.edu/iec/ftisite1.htm
Yes U. Wisc. seems to be IEC central HQ. The Rider[15] & Nevins [16] papers listed there (http://fti.neep.wisc.edu/iec/inertial_electrostatic_confineme.htm) in the overview section are most frequently cited stakes to heart of IEC, though I dont know that there is any experimental verification of the losses they claim.

I don't believe non-neutral plasmas are necessarily practical from a stability perspective.
Can you say more about that? I see that external mag confinement alone wouldn't work against the resulting space charge but why not w/ electric accelerators or a combination? Penning/Paul Traps? BTW a non-neutral conference:
http://sdphca.ucsd.edu/nnp2001/

Magnetic confinement has much the same problem along with the stability of magnetic confinement, and limitations on plasma density, which are a consequence on the limit on the magnetic field strength, which are a consequence of the limits on currents in the superconducting magnets.
This is an area where it appears to me that the basic idea is unsound. The external mag. field doesn't really confine anything, especially not heavy ions (Brillouin limit inversely related to mass). It only retards the inevitable random walk to escape the system. On the other hand an E field based recirculating accelerator or trap is actually confining the ion, theoretically forever.

Beam systems, including injected beams into magnetic confinement, have the drawback of beam energy efficiency and scattering of the beam by the plasma.
Yes, no question its going to scatter. The interesting question for me is (in a recirculating system) how fast does the scattering take place (loss power) relevant to the fusion power.

Astronuc

May17-07, 05:34 AM

The external mag. field doesn't really confine anything, especially not heavy ions Well, in a fusion plasma, one does not want heavy ions, which don't fuse and which cause much greater energy losses as a function of Z (nuclear charge and number electrons in neutral atom). Higher Z nuclei in plasmas lead to greater losses due to bremsstrahlung, recombination, electron-electron collisions (including ionization).

The external magnetic field does confine in Tokamak or other devices, but it is short term due to instabilities, which are exacerbated by non-uniformities in the plasma temperature distribution/ion/electron densities.

Non-neutral plasmas have the disadvantage of Coulomb repulsion in addition to temperature-related pressure. In theory, the dynamic (acceleration of the nuclei) in an IEC overcomes some of the pressure limitations, but by virtue of the continuity equation (rule, law) - what goes in, must come out, otherwise pressure will increase with matter accumulation, particularly in the number of particles does not change, i.e. if one does not get A + A = B, but rather A + A = B + B.

mheslep

May17-07, 11:50 AM

Well, in a fusion plasma, one does not want heavy ions, which don't fuse and which cause much greater energy losses as a function of Z (nuclear charge and number electrons in neutral atom). Higher Z nuclei in plasmas lead to greater losses due to bremsstrahlung, recombination, electron-electron collisions (including ionization).

I meant heavy D or T ions relative to the electron mass; the electron being much easier to confine as a result.

Non-neutral plasmas have the disadvantage of Coulomb repulsion in addition to temperature-related pressure. In theory, the dynamic (acceleration of the nuclei) in an IEC overcomes some of the pressure limitations, but by virtue of the continuity equation (rule, law) - what goes in, must come out, otherwise pressure will increase with matter accumulation, particularly in the number of particles does not change, i.e. if one does not get A + A = B, but rather A + A = B + B.
Granted a theoretical non-neutral IEC has Coulomb (and kinetic?) pressure to handle, but it has the advantage of having ~all the plasma mass being at reaction energy (at the bottom of the potential E well); vice a thermal, neutral Tokamak plasma where a) only the ions in the high energy tail of the Maxwellian distribution can practically fuse and most of the lower energy plasma mass is just along for the ride, and b) the electrons radiate significant Bremsstrahlung.

mheslep

RogerFox

Jun8-07, 06:16 PM

.

IEC - claims of mono energetic operation but analysis to date shows IEC quickly thermalizes and then realizes same problems as above.

etc.

Mark

Are you refering to wire grid IEC devices? I think so. Polywell IEC by Bussard over the last 11 yrs shows virtual cathode & potential well formation with no real electron losses, minimal to near zero maxwellian thermalization of ions. 100,000 times better output in relation to input than any previous Fusor type device.

Dr Bussards former assistant Tom Ligon, hangs here:
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=5367&start=916&posts=928

A schematic look at electron & ion flow in DR. Bussards WB6 IEC fusion reactor.
http://www.youtube.com/watch?v=jmp1cg3-WDY

http://www.emc2fusion.org

Google tech talk by Dr Bussard

http://video.google.com/videoplay?docid=1996321846673788606&q=bussard

mheslep

Jun10-07, 08:11 PM

...minimal to near zero maxwellian thermalization of ions...

I'm familiar with Bussard and the Polywell design, watched the video, read the papers, (including the ones from the early 90's by Krall), got the T-shirt. None of it documents measuring 'minimal to near zero ...'. What is your source for this claim? All of the physics I know of says that any beam - beam collision of ions will quickly thermalize.

RogerFox

Jun11-07, 01:44 AM

I'm familiar with Bussard and the Polywell design, watched the video, read the papers, (including the ones from the early 90's by Krall), got the T-shirt. None of it documents a claim of measuring 'minimal to near zero ...'. What is your source for this claim? All of the physics I know of says that any beam - beam collision of ions will quickly thermalize.

Since WB6 ran in late 2005, I am not aware of Krall or Rider writing about the topic. I don't understand citing 15 to 20 yr old papers to refute R&D done in late 2005.:rolleyes:
If Dr Bussards claim's are accurate.... does that suggest he solved the fuel ion thermalization? Would he have gotten increasing neutron counts if his fuel was thermalizing? Though Bussard does need to duplicate the results outside of the D.O.D. publishing embargo.

Bussard ran WB6 4 times, each time at increased drive conditions, each test yielded higher neutron counts. If Bussards WB6 results are duplicated, then Kral, Rider, etc might want to write anew.

Bussard touches on fuel thermaliztion in the google vid & Tom Ligon covers thermalization in response to Riders paper of 1995, here:
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=5367&start=901

If the ions would live sufficiently long and make enough passes without fusing, they would no doubt thermalize, or at least lose energy. This will also happen if the density is allowed to get too high. The key is achieving a density profile where high-energy collisions occur in the center at fusion energies, very low energy (and thermalized) collisions occur in the high-density ion turn-around zone near the magrid, and very few other collisions occur. A narrow range of optimal ion lifetime versus fusion density exists for any given size of machine and set of operating parameters (too high, thermalize, too low, too few fusions). Larger sizes are required for that optimal density to produce net power.

The thermalized turn-around zone is a key to killing two of Rider's objections. Rider believes A) the plasma will maxwellianize, and B) because it is maxwellian, some of the ions will upscatter in energy by collisions and so be able to exit the potential well complety. The outer collision zone does have maxwellian properties, but at very low energy levels, so it essentially removes the scatter in the energy of the fuel ions on every pass, essentially resetting the population to all near zero kinetic energy. Thus, thermalization keeps the machine from thermalizing.

Rider thinks the machine will have excessive bremsstrahlung losses. Bussard and Krall counter that the central region Rider thinks will cause bremsstrahlung due to mutual repulsion is actually a convergence zone for both electrons and ions. The electrons are making a virtual cathode that attracts ions, the ions make a virtual anode that attracts electrons, and the whole zone is never all that far from a neutral plasma. Control of virtual anode height controls the bremsstrahlung problem.

All of this says you need very good control of the ion population. WB6 and that puff gas system did not offer such control ... I suspect the system put in roughly the amount of gas needed, initially, but the amount continued to rise. Fusion occurred in the short period during which the right density profile existed. A successful machine will need to hold that condition.

It may be that it will occasionally be necessary to stop the reaction and clear the machine of junk gas, which may include fusion products in a power reactor.

Rider's final objection was dead-on right ... for HEPS, PXL-1, and WB-5. Cusp losses of electrons in a box machine are too high. They are irrelevant in a magrid machine. Electrons lost out the cusps come right back in.

mheslep

Jun11-07, 07:19 AM

Since WB6 ran in late 2005, I am not aware of Krall or Rider writing about the topic. I don't understand citing 15 to 20 yr old papers to refute R&D done in late 2005.:rolleyes:

No, that won't fly here on PF. I asked for a citation, and you talk 3rd hand about more 'R&D'.

Bussard ran WB6 4 times, each time at increased drive conditions, each test yielded higher neutron counts.
So you say. Citation please.

If Bussards WB6 results are duplicated, then Kral, Rider, etc might want to write anew.

Bussard touches on fuel thermaliztion in the google vid & Tom Ligon covers thermalization in response to Riders paper of 1995, here:
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=5367&start=901

Link from this forum to an enthusiast on another forum? No good here. Citation please.

[I]If the ions would live sufficiently long and make enough passes without fusing, they would no doubt thermalize, or at least lose energy. This will also happen if the density is allowed to get too high. The key is achieving a density profile where high-energy collisions occur in the center at fusion energies, very low energy (and thermalized) collisions occur in the high-density ion turn-around zone near the magrid, and very few other collisions occur. A narrow range of optimal ion lifetime versus fusion density exists for any given size of machine and set of operating parameters (too high, thermalize, too low, too few fusions). Larger sizes are required for that optimal density to produce net power.
I don't see any sense in this. The coulomb collision / fusion collision ratio does not change with density. This suggestion is akin to manipulating a light dimmer for effect: "If the light is too hot/drawing too much power Ill turn it down. And, if the light is too dim I'll just turn it up. There! Its bright and no heat."

The thermalized turn-around zone is a key to killing two of Rider's objections. Rider believes A) the plasma will maxwellianize, and B) because it is maxwellian, some of the ions will upscatter in energy by collisions and so be able to exit the potential well complety. The outer collision zone does have maxwellian properties,

No, you don't get to merely assert which area will be maxwellian and which will not.

Rider thinks the machine will have excessive bremsstrahlung losses. Bussard and Krall counter that the central region Rider thinks will cause bremsstrahlung due to mutual repulsion is actually a convergence zone for both electrons and ions.

Convergence zones? Bremsstrahlung power in a D-D or D-T plasma is proportional to the electron density and the electron energy, thats it. Its worse w/ the higher Z fuels.
P_{Br} [\textrm{Watt/m}^3] = \left[{n_e \over 7.69 \times 10^{18} \textrm{m}^{-3} }\right]^2 T_e[\textrm{eV}]^{1/2}

To reduce B. power then you either reduce the density or keep the electrons cold. Period. You don't get to waive this a way buy talking convergence zones.

Morbius

Jun11-07, 08:52 AM

To reduce B. power then you either reduce the density or keep the electrons cold. Period. You don't get to waive this a way buy talking convergence zones.
mheslep,

You got THAT right. Hot electrons are the "death knell" of ANY fusion plasma.

Even in HIGHLY convergent plasmas; like those found in ICF.

Once you couple strongly to the radiation field, which is what electrons do - then
you might as well just blow a hole in the side of your plasma - you have a BIG energy
sink.

Dr. Gregory Greenman
Physicist

mheslep

Jun11-07, 10:08 AM

,

...Hot electrons are the "death knell" of ANY fusion plasma.
Agreed for any neutral plasma thats optically thin to Bremsstrahlung. I'm interested in some non-neutral and degenerate plasma ideas for just this reason. For instance:

"Confinement Of Pure Ion Plasma In A Cylindrical Current Sheet"
http://www.osti.gov/bridge/servlets/purl/15113-w7GWk3/webviewable/15113.PDF

"Beyond the Brillouin limit with the Penning Fusion Experiment"
www.physics.udel.edu/~mitchell/journal_articles/bard97.pdf

"Aneutronic fusion in a degenerate plasma"
http://w3.pppl.gov/~fisch/fischpapers/2004/Son_PLA_04.pdf

RogerFox

Jun14-07, 01:20 AM

My apologies for my behavior, being a noobie with a cut & paste post.

mheslep,

Hot electrons are the "death knell" of ANY fusion plasma.

Dr. Gregory Greenman
Physicist

By hot electrons, do you mean when electron density is high as well as energy? Ala Bremsstrahlung ? (sp?)

Would electron energy at the center of the potential well (in a device such as WB6), be low energy but high density?

mheslep,

In the google video, From 55:09 to 55:17 RWB comments that they repeated the experiment 4 times. I know, crap as a cite, but it what it is.

EDIT:

http://stinet.dtic.mil/

EMC2-0891-04, and EMC2-1291-02

I was informed that these pertain to the HEPS device, a closed box design with large electron losses, from the DARPA days.

mheslep

Jun14-07, 12:59 PM

By hot electrons, do you mean when electron density is high as well as energy? Ala Bremsstrahlung ? (sp?)

I mean the temperature, or kinetic energy of the electron in eV. Typically Bremmsstrahlung becomes significant > 10KeV as per the above equation. There is X amount of radiation for each electron (on average), so more electrons = more radiation.

In the google video, From 55:09 to 55:17 RWB comments that they repeated the experiment 4 times. I know, crap as a cite, but it what it is.
Ok, what were the results each time? Ive only seen the figure of 3 neutrons quoted for one experiment.

RogerFox

Jun16-07, 06:05 PM

So,
if one were to take Bussard at face value, where electron density is high (center of potential well) those electrons are low speed. At least enough to avoid large Brem losses... ?

http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=ADA257895&Location=U2&doc=GetTRDoc.pdf

mheslep

Jun17-07, 04:01 PM

The electrons would be there w/ the high speed ions and collisions /w the ions will heat up the electrons.

I don't think the paper you list is the relevant reference. The earlier one addresses the howto for 'cold' electrons:
"Bremmstrahlung Radiation Losses in Polywell Systems", Bussard, '92
http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=A257646&Location=U2&doc=GetTRDoc.pdf

Ive been through it once and it warrants more time. At 1st look I've got two problems:
1. Everything up front seems to be standard plasma beam physics calculations: running the energy and particle density through the geometry of the system. To simplify the approach he initially disregards the ion collisions. Then finally on page 5 just before equation 11 he gets back to it:

...It is thus necessary to examine the ion/electron collisional energy exchange process in some detail.... Such energy exchange will, of course, occur in the core, mantle and edge regions...

He then proposes that, yes, the electrons will be heated in the core by the ions but that they will be cooled on the edge and that the two areas offset each other yielding a stable electron temperature. Ok, interesting idea. My 1st impression is that this is particle description of a heat transfer engine and as such its governed the thermodyamics (carnot cycle) and hence can't be very efficient. Thats a quick take - I don't really know. In any case this is a point of questionable physics and requires some detail description of why /how it can work. Bussard simply refers to 'Analysis of these processes shows the stable up scattered core energy...'. Come on. Addressing this point is the entire key to answering the question of radiation losses. This is the paper to show that and he says 'Analysis of these processes shows ...'? Furthermore this is problem number one to address in the lab starting back in '92; you don't even need to waste time w/ D or T fuels - just put any low Z ionized gas in there and measure your core electron temperature to verify this cold electron theory, or better yet measure the radiation level vs density if its high enough. Just answer this one question and Bussard et al will have much more serious attention. You don't need a 50 page paper, just a clearly documented note verifying cold electrons via test.

2. The ratio of fusion power to Bremm. power in equation 8 is shown to depend on density. Bremm. power and fusion power are directly dependent on density so that the two would cancel out in the ratio. So I'm not following this; I need another look. [EDIT, scratch this: I was confused by the density symbol ne in the paper and the hand written (dang these old papers ;-) nu e, two different things]

mheslep

RogerFox

Jun21-07, 04:42 PM

He then proposes that, yes, the electrons will be heated in the core by the ions but that they will be cooled on the edge and that the two areas offset each other yielding a stable electron temperature. Ok, interesting idea.
mheslep
An single ion is introduced into the device. The ion sees the potential well, shoots thru the well. Once past the well it slows (cooling?), turns, again seeing the well.

Ok, what were the results each time? Ive only seen the figure of 3 neutrons quoted for one experiment.

http://flux.aps.org/meetings/YR03/APR03/baps/abs/S3470011.html

Ions traveling slower than this, with energies below 200 keV, heat electrons ineffectively, implying that high ion and low electron temperatures can co-exist, drastically reducing bremsstrahlung and enhancing the prospects for net energy production.

Right, 3 neutrons at the detector. That may be the 12.5kV, mentioned by Tom Ligon here:

Looking at the data EMC2 produced, WB-6 ran at less magnetic field than any of the earlier models, and produced fusion as low as 5 kV, copious fusion at 12.5 kV. Fusors don't generally make easily-detectable fusion on DD that low. WB-6 is in a class by itself as IEC machines go.

http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=5367&start=16

Furthermore this is problem number one to address in the lab starting back in '92; you don't even need to waste time w/ D or T fuels - just put any low Z ionized gas in there and measure your core electron temperature to verify this cold electron theory, or better yet measure the radiation level vs density if its high enough. Just answer this one question and Bussard et al will have much more serious attention. mheslep

Yes, though a nice 50-100 page paper would be OK too, right?

RogerFox

Jun21-07, 06:01 PM

mheslep

Jun21-07, 07:05 PM

http://flux.aps.org/meetings/YR03/APR03/baps/abs/S3470011.html

Lerner is the Focus Fusion guy, selling T-shirts on his website. What does Lerner's talk have to do w/ the results of the WB6 tests?

mheslep

Jun21-07, 07:25 PM

http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=5367&start=16
From earlier, I thought we were done w/ posting links to other forums as evidence?

mheslep

Jun21-07, 07:32 PM

Edit: I was told table 2 shows Brem-losses as 1/32nd ?

Yep, for D-D, thats what it says, Pfb= ~ 32. AFAICT its so much hand waving to get to that point. Might just as well said losses were zero in Table 2.

mheslep

Jun21-07, 07:33 PM

Yes, though a nice 50-100 page paper would be OK too, right?
No, not if used as an excuse for not publishing anything ala "Much data to compile, daunting, we're working on it"

mheslep

Jun21-07, 07:49 PM

An single ion is introduced into the device. The ion sees the potential well, shoots thru the well. Once past the well it slows (cooling?), turns, again seeing the well.
Thats trading off kinetic energy for electrical potential energy, analogous to a mechanical pendulum in motion. There's little net energy loss for the ion. The idea mentioned above is about speed-up (heating) and slow-downs (cooling) ~ instantaneously due to collisions w/ other ions. Imagine again your single ion passing the well center at its maximum speed. Statistically, two undesirable things can happen upon if it collide. Crudely put: a) it gives up all its speed in a head-on or the like, and then its too slow to fuse and its stuck in the well, b) it gets 'rear ended' and speeds up so that it escapes the well and its energy is lost.

RogerFox

Jun22-07, 12:11 AM

Lerner is the Focus Fusion guy, selling T-shirts on his website. What does Lerner's talk have to do w/ the results of the WB6 tests?

I quoted a description of Lerners talk, in quote blocks, and provided a link. Which I thouht was reasonable behavior on the net. No?

mheslep

Jun22-07, 10:41 AM

I quoted a description of Lerners talk, in quote blocks, and provided a link. Which I thouht was reasonable behavior on the net. No?
Sure I suppose so. I'm just not sure how much credence to grant Lerner, and he doesn't have anything to do w/ Polywell/WB6.

RogerFox

Jun22-07, 03:25 PM

I'm just not sure how much credence to grant Lerner,

Granted. Some of what he has put on the web is rather strange.

and he doesn't have anything to do w/ Polywell/WB6.

Correct, but the program description might be considered germain in regard to Brem losses:

Ions traveling slower than this, with energies below 200 keV, heat electrons ineffectively, implying that high ion and low electron temperatures can co-exist, drastically reducing bremsstrahlung and enhancing the prospects for net energy production.

sunday

Jun23-07, 03:22 PM

Is Journal of Fusion Energy a peer-reviewed publication?

If yes, then could someone with plasma physics background tell me if this paper by Rostoker, Qerushi, and Binderbauer rebukes authoritatively Todd Ridder conclusions about the unfeasibility of p-B11 fusion?

http://forum.nasaspaceflight.com/forums/get-attachment.asp?attachmentid=25188

RogerFox

Jun23-07, 08:22 PM

Norman Roskoker recently got 5 mill up front total of 40 mill in VC, to develop p-B11 fusion, via TriAlpha Energy IIRC.

mheslep

Jun25-07, 01:09 PM

Is Journal of Fusion Energy a peer-reviewed publication?

Apparently not. It also publishes policy papers ala "Can Fusion and Fission Breeding Help Civilization Survive?"

I wasn't aware of this Rostoker publication. I hadn't seen anything from him since the Science article & responses in '98-99.

sunday

Jun25-07, 03:28 PM

Apparently not. It also publishes policy papers ala "Can Fusion and Fission Breeding Help Civilization Survive?"

I wasn't aware of this Rostoker publication. I hadn't seen anything from him since the Science article & responses in '98-99.

After posting I saw Journal of Fusion Energy published the infamous results on "less than warm fusion" by P&F. However, they say their standards for accepting papers have improved.

Can you follow the math? I'm only a dumb, lazy, EE, after all...

RogerFox

Jun25-07, 08:33 PM

2 of Bussard´s US Patents ( Nº 4826646 and 5160695 from 1989-1992) are cited in Monkhrost and Rostoker patent ( Nº 6852942 and others, years 2005-2007)

Bussard --> http://www.google.com/patents?vid=USPAT4826646
http://www.google.com/patents?vid=USPAT5160695

Rostoker --> http://www.google.com/patents?vid=USPAT6852942

mheslep

Jun26-07, 12:21 PM

Can you follow the math? I'm only a dumb, lazy, EE, after all...
Having a go. Looks like the key is rejection of Rider's particle energy distribution (equa. 3) which has the form:

f(v)=nK(e^{[-(v-v0)^2/v_{ts}^2]}+e^{[-(v+v0)^2/v_{ts}^2]})

where n density and K is some constant. They assert this doesn't apply to their reactor and suggest another distribution instead...
f_i(v)=(\frac{m_i}{2\pi T_i})^\frac{3}{2} n_i(r)e^{[-\frac{m_i}{2T_i}(v-V_i)^2]}
for which the time derivative of f(v) (aka the collision operator) goes to zero for 'like particles' and is small for ion-electron collisions. The recirculating power depends on the collision operator so if it is small so goes the recirc power.

sunday

Jun26-07, 12:29 PM

Having a go. Looks like the key is rejection of Rider's particle energy distribution (equa. 3) which has the form:
f(v)=nK
e^{[-(v-v0)^2/v_{ts}^2]}+e^{[-(v+v0)^2/v_{ts}^2]}

and asserts this other distribution instead...

<rostoker distro here soon...>

which the time derivative goes to zero for 'like particles'

Yep, and Rostoker dedicates a few harsh words to Ridder for apparently using that distribution only for the sake of finding a easy analytical solution, but I didn't see the reason Rostoker gives for using the other distribution.

May it be that Ridder used that distribution because "everybody knows" that all plasmas tend to adopt a Maxwell distribution, omitting the devices used to prevent that trend?

sunday

Jun26-07, 12:37 PM

(...
)They assert this doesn't apply to their reactor and suggest another distribution instead...
<rostoker distro here soon...>
for which the time derivative of f(v) (aka the collision operator) goes to zero for 'like particles' and is small for ion-electron collisions. The recirculating power depends on the collision operator so if it is small so goes the recirc power.

Bussard said that on the video, that collisions between ions and electrons have a very small probability. But I don't recall Bussard publishing "his" distribution.

Astronuc

Jun26-07, 05:31 PM

Is Journal of Fusion Energy a peer-reviewed publication? It is published by Springer, a reputable publishing house of scientific literature.

It does have an editorial board consisting of various academics. And the principal editor is Stephen O. Dean of Fusion Power Associates, Gaithersburg, MD, USA, which itself has member organizations consisting of universities, public and private research organizations and national labs.

Associate Editors

Igor Anisimov, Taras Shevchenko Kiev University, Ukraine; Niek Lopes Cardozo, FOM Institute for Plasma Physics Rijnhuizen, The Netherlands; Gennadi Dimov, Budker Institute of Nuclear Physics, Novosibirsk, Russia; Lev Golubchikov Kurchatov Institute, Moscow, Russia; Ryosuki Kodama, Institute of Laser Engineering, Osaka University, Japan; Yasuji Kozaki, Fusion and Advanced Technology Systems Division National Institute for Fusion Science (NIFS) National Institutes of Natural Sciences (NINS), Japan; Xing Zhong Li, Department of Physics, Tsinghua University, China; Masayuki Nagami, Department of Fusion Plasma Research, Naka Fusion Research Establishment, Japan; Francis Thio, Office of Fusion Energy Sciences, U.S. Department of Energy, MD, USA; Vladimir Voitsenya, Institute of Plasma Physics, Kharkov Institute of Physics and Technology, Ukraine; Simon Woodruff, University of Washington, WA, USA; M. Zakaullah, Plasma Physics Laboratory, Quaid-i-Azam University, Pakistan

How well they review various papers, I do not know.

Also the distribution function used by Rider is given as

f(v)=nK(e^{[-(v-v_0)^2/v_{ts}^2]}+e^{[-(v+v_0)^2/v_{ts}^2]}) in this case for v < v0.

I can't comment on the validity of claims without looking at other references, which I don't have.

Astronuc

Jun27-07, 04:46 PM

Thomas Dolan's textbook - Fusion Research, 1982

http://www.fusionnow.org/dolan.html

Excellent reference on fusion research.

cuddihy

Jul2-07, 02:24 PM

Thats trading off kinetic energy for electrical potential energy, analogous to a mechanical pendulum in motion. There's little net energy loss for the ion. The idea mentioned above is about speed-up (heating) and slow-downs (cooling) ~ instantaneously due to collisions w/ other ions. Imagine again your single ion passing the well center at its maximum speed. Statistically, two undesirable things can happen upon if it collide. Crudely put: a) it gives up all its speed in a head-on or the like, and then its too slow to fuse and its stuck in the well, b) it gets 'rear ended' and speeds up so that it escapes the well and its energy is lost.

If you don't accept the supposition that particle velocity distributions in an IEC device will be isotropic (the basic assumption of Rider's model), both (a) and (b) seem like silly concerns.

How do you get an isotropic ion velocity distribution in a potential well?

To see how silly (b) is, consider the potential well to be a gravity potential energy well, like one of those funnels you can drop marbles into. What are the odds that two marbles will collide, resulting in one of them being ejected from the funnel?

What about (a)? If a fuel ion loses sufficient energy, it will spend more time in the focus, and although it will be moving slower, it will be more likely to be hit by a faster moving ion.
This is a bigger concern, but here again Rostoker is right --there's no way to calculate this in the general sense. You would have to actually know the densities, energy distributions, and all effects combined. You can't calculate the general collision lifetime of a neutral spherical plasma ball and figure that's the same answer as for a specific device with an electrostatic gradient, different densities at different locations, and unspecified electron energies.

RogerFox

Jul2-07, 03:13 PM

To see how silly (b) is, consider the potential well to be a gravity potential energy well, like one of those funnels you can drop marbles into. What are the odds that two marbles will collide, resulting in one of them being ejected from the funnel?

Like ah.......a potential well that imparts enough energy to ions to escape the potential well...... is not a potential well.... no? Maybe .. ?:wink:

jambaugh

Jul2-07, 03:29 PM

In reply to the original post, I would mention some of the other problems with magnetic confinement fusion designs.

Specifically there are confinement stability issues (kink and pinch instabilities). Bussard notes in the Google talk that these are not present in the IEC designs since the magnetic fields are convex to the plasma.

With regard to the laser based inertial confinement fusion, as e.g. LANL's Shiva and Argus driven systems, there is no real hope of power generation at this time. For the most part these methods are useful for abstract research into fusion physics including weapons issues.

These electron thermalization issues not withstanding I think Bussard's program deserves much more study before being dismissed, especially relative to Tokomak's et al.

Given the economic feasibility for IEC design as a neutron source one would then imagine if any design might be scaled to power production levels this one would.

Much of the debate here sounds like a call for more research into Bussard's idea. Even if power generation is never achieved the research may yet yield fruitful applications in say using the design to "burn" (i.e. transmute) nuclear waste thereby improving things for fission power. And I'm inclined to hope that Bussard's design can achieve power generation.

mheslep

Jul2-07, 03:58 PM

If you don't accept the supposition that particle velocity distributions in an IEC device will be isotropic (the basic assumption of Rider's model), both (a) and (b) seem like silly concerns.
How do you get an isotropic ion velocity distribution in a potential well?
In a spherical IEC designs (fusors, Bussard Polywell) its given that ions approach the focus from all sides. I dont know about the Rostoker collider. In any case you'd have to enlighten me how a non-isotropic design, say only two collinear beams, doesn't suffer the same maxwellian fate.

To see how silly (b) is, consider the potential well to be a gravity potential energy well, like one of those funnels you can drop marbles into. What are the odds that two marbles will collide, resulting in one of them being ejected from the funnel?
Work the physics of your 'silly' analogy a little harder. Try bowl, not funnel. Take the friction away from the surface, make the marbles perfectly elastic and they will indeed bounce out, statistically. Your analogy as stated would have all the gas molecues in a container simply sink to the bottom.

What about (a)? If a fuel ion loses sufficient energy, it will spend more time in the focus, and although it will be moving slower, it will be more likely to be hit by a faster moving ion.
So? It gets hit but being slow it will likely not fuse. It just further randomizes the energy.

This is a bigger concern, but here again Rostoker is right --there's no way to calculate this in the general sense. You would have to actually know the densities, energy distributions, and all effects combined. You can't calculate the general collision lifetime of a neutral spherical plasma ball and figure that's the same answer as for a specific device with an electrostatic gradient, different densities at different locations, and unspecified electron energies.
Fusion by claim of the various designs only happens in the core or center 5% of the spherical devices, the only place by claim that density and ion energy is high enough for significant fusion. So one doesnt have to treat the entire device. Specifically, where do you see Rider mathematically wrong?

mheslep

Jul2-07, 04:15 PM

With regard to the laser based inertial confinement fusion, as e.g. LANL's Shiva and Argus driven systems, there is no real hope of power generation at this time. For the most part these methods are useful for abstract research into fusion physics including weapons issues.

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

These electron thermalization issues not withstanding I think Bussard's program deserves much more study before being dismissed, especially relative to Tokomak's et al.

Given the economic feasibility for IEC design as a neutron source one would then imagine if any design might be scaled to power production levels this one would.
Why, technically since this is PF, would you favor the Bussard approach over one of many others?(no Tokamaks, no lasers):
Tri-Alpha (http://http://www.topix.net/science/physics/2007/06/tri-alpha-energy-raises-40-million-in-venture-capital-for-nuclear-fusion)
Focus Fusion (http://www.google.com/url?sa=t&ct=res&cd=1&url=http%3A%2F%2Fwww.focusfusion.org%2F&ei=l2mJRvnjDaLSevX9zOQB&usg=AFQjCNFwzC6vYnbmxlQQ6BlJavkU4ndA6Q&sig2=4N3GRedtUCTyqQwYAQoIcA)
Sandia's Z-Pinch (http://www.sandia.gov/news/resources/releases/2007/rapid-fire-pulse.html)
do dah
do dah

RogerFox

Jul2-07, 05:27 PM

These electron thermalization issues not withstanding I think Bussard's program deserves much more study before being dismissed, especially relative to Tokomak's et al.

Agreed, ITER @ 13 billion vs WB7 @ 2 million.
IF WB7 validates WB6, but in a more open source/public manor, then a truncated dodec (WB8) is in order. If WB8 works, then scale up the size, maybe to 1 meter. Then do it again. As long as the previous device shows that the next step is worth it, keep building & testing.

Politics aside, Rider vs Bussard in the DOD, the DOD did fund IIRC 8 or 9 separate devices by Bussard. Funding contingent on the previous devices results of course.

If LN2 cooling is used then WB7 might be robust enough to run for some 10's of minutes. That would be interesting.

EDIT to add:

Us enthusiasts are making a recipe:

" preliminary specs for WB-7x of 4500 Gauss continuous at up to 75 KV drive with 25 Amps current. "

http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=5367&posts=1421#M158266

sunday

Jul2-07, 05:39 PM

Foger,

That is a serious accusation against Dr. Ridder. His supposed motives are orthogonal to the actual discussion-the question is if his maths are correct, or not.

Best regards.

JL Domingo

mheslep

Jul2-07, 06:05 PM

2nd that. Roger - If you can't provide evidence recommend you delete post #43 immediately.

mheslep

cuddihy

Jul2-07, 10:35 PM

In a spherical IEC designs (fusors, Bussard Polywell) its given that ions approach the focus from all sides. I dont know about the Rostoker collider.

I don't know about the Rostoker collider either.

First, Rider never disputes the possibility of an electrostatic potential well forming.

Isotropic velocity distribution in a plasma will always mean rapid Maxwellization. But particles approaching the focus from all sides =/= "isotropic velocity distribution" any more than a linear accelerator has an isotropic velocity distribution.
True enough, once you prove Maxwellianization will occur, isotropic velocity distribution will be an aspect of the resulting plasma. But starting with that assumption is rather circular.

Velocity components in any kind of electrostatic fusor will be overwelmingly radial, the closer to the focus the particle is. There's really no question that that cannot be termed "isotropic" without distorting the meaning of the term beyond recognition.

In any case you'd have to enlighten me how a non-isotropic design, say only two collinear beams, doesn't suffer the same maxwellian fate.

No electrostatically accelerated fusion macine will suffer this fate, unless the electric potential breaks down. Rider didn't touch that.

Work the physics of your 'silly' analogy a little harder. Try bowl, not funnel. Take the friction away from the surface, make the marbles perfectly elastic and they will indeed bounce out, statistically. Your analogy as stated would have all the gas molecues in a container simply sink to the bottom.

Ok, oversimplied the analogy. *Some* of the marbles will bounce out. *some* of them will also fuse.

So? It gets hit but being slow it will likely not fuse. It just further randomizes the energy.

Fusion by claim of the various designs only happens in the core or center 5% of the spherical devices, the only place by claim that density and ion energy is high enough for significant fusion. So one doesnt have to treat the entire device. Specifically, where do you see Rider mathematically wrong?

The same place as Rostoker, -- pretty much from the start. To begin with, he continually conflates ion temperature and velocity--once again, a useful concept in an isotropic Maxwell-Boltzmann distribution, questionable in an accelerator. That leads him to the assumption of the isotropic collision operator as noted by Rostoker referred to above.

His "maximally efficient system for maintaining a non-equilibrium distribution", the basis of his model, (page 69 if you're looking at his dissertation) is an unnecessary application of heat thermodynamics that leads to the search for "recirculating power," a nonsense concept for an accelerator. 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.

RogerFox

Jul2-07, 10:56 PM

RogerFox

Jul2-07, 11:43 PM

Ok, oversimplied the analogy. *Some* of the marbles will bounce out. *some* of them will also fuse.

As velocity increases, does the particle become inelastic...above a certain velocity... ?

I just started reading: Theory of Thermionic Vacuum Tubes by E. Leon Chaffee

Since WB6 was basically a vacume tube diode.....

sunday

Jul3-07, 02:58 AM

cuddihy

Jul3-07, 10:50 AM

LOL. I'll edit. But...

http://dspace.mit.edu/bitstream/1721.1/29869/1/31763419.pdf

Please read Riders acknowledgements, specifically look for the Office of Naval Research (ONR). Page 3 of the pdf. Looks like the ONR gave Rider a fellowship...

"the author is partially owned and operated by a graduate fellowship from the Office of Naval research"

..which is not exactly bought and paid for, so the edit.. but that is a poor choice of wording... don't ya think...

I think you're reading a little too much into his motives, here, Roger. Let's not forget Rostoker and Bussard were also each partially funded by the Office of Naval Research, albeit different parts of the office. What Bussard alleged about the politics is that his program was deliberately funded low to keep the budget below the threshold where DOE congressional staffers (not ONR) would see the program and request it killed. This isn't nefarious, just the way ricebowl budgeting works in our federal government.

What is a possibility about Rider's thesis, although there's no direct evidence to support it--in fact, Rider is pretty careful in his wording to hedge his results--(albeit in an arrogant way that suggests in the intro & conclusion summaries that he has successfully and self-eveidently ruled out all aneutronic fusion modes,)-- is that Rider bit off more than was reasonable to chew through for his subject thesis and dissertation, and once he realized it, facing a scholarship /funding window, he had to finish out with an overly simplistic, entirely analytical "general" model of aneutronic fusion machines.

It does take a high sense of self worth to assert that it is possible to create a universally applicable thermodynamic model of all possible fusion machines--Rider does this in a few paragraphs of part III of his dissertation. Although he doesn't claim so, this is the equivalent of fully creating and explaining the thermodynamic model of the carnot cycle, with all attendant ramifications, as an aside. If this were really a useful model or analysis, other plasma physicists would have picked up this model for use in their other fusion projects. Instead, it's only purpose has been, as Rostoker says, to discredit all forms of fusion not using D-T in a tokamok.

What would support this conclusion is the fact that, as you've stated, Rider went off in an completely different direction as soon as his defense was completed. Why go so far afield when you've invested so much time and effort? Why not fully flesh out the results of your analysis, unless, you think you've just created Beethoven's 9th, and nothing further can be done to make it better. Like I said, not exactly humble.

Anyway, this is just my opinion.

cuddihy

Jul3-07, 11:02 AM

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.

mheslep

Jul3-07, 11:20 AM

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

M. Simon

Jul3-07, 12:18 PM

Ha! Then please engage Morbius the subject:
http://www.physicsforums.com/showpost.php?p=1367374&postcount=42
http://www.physicsforums.com/showpost.php?p=1367512&postcount=44
http://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):
Tri-Alpha (http://http://www.topix.net/science/physics/2007/06/tri-alpha-energy-raises-40-million-in-venture-capital-for-nuclear-fusion)
Focus Fusion (http://www.google.com/url?sa=t&ct=res&cd=1&url=http%3A%2F%2Fwww.focusfusion.org%2F&ei=l2mJRvnjDaLSevX9zOQB&usg=AFQjCNFwzC6vYnbmxlQQ6BlJavkU4ndA6Q&sig2=4N3GRedtUCTyqQwYAQoIcA)
Sandia's Z-Pinch (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.

M. Simon

Jul3-07, 12:30 PM

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.

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

mheslep

Jul3-07, 01:03 PM

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?

mheslep

Jul3-07, 01:15 PM

sunday

Jul3-07, 02:23 PM

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 wich 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 lets 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?

mheslep

Jul3-07, 02:55 PM

Comments?
Forgive me: I don't really know what I'm talking about
He/She's right.

sunday

Jul3-07, 02:59 PM

He/She's right.

With the due respect, Why?

M. Simon

Jul3-07, 03:07 PM

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)?

RogerFox

Jul3-07, 03:14 PM

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 vacume 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 dont 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.

mheslep

Jul3-07, 03:21 PM

BTW how you coming on the vacuum tube book (Chafee)?
What happened to your posted link to that copyrighted book?

RogerFox

Jul3-07, 03:39 PM

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.

mheslep

Jul3-07, 04:02 PM

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:
"Can Inertial Electrostatic Confinement Work Beyond the Ion-Ion Collisional Time Scale? (http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PHPAEN000002000010003804000001&idtype=cvips&gifs=yes)", W.M Nevins Physics of Plasmas 2, 3804, 1995.

sunday

Jul3-07, 04:10 PM

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:
"Can Inertial Electrostatic Confinement Work Beyond the Ion-Ion Collisional Time Scale? (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...

RogerFox

Jul3-07, 04:39 PM

Sunday:

http://www.osti.gov/bridge/servlets/purl/41400-kmR97s/webviewable/41400.pdf

M. Simon

Jul3-07, 04:48 PM

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.

M. Simon

Jul3-07, 05:14 PM

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.

RogerFox

Jul3-07, 05:34 PM

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

RogerFox

Jul3-07, 05:43 PM

[I]

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 vacume 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. ..?

M. Simon

Jul3-07, 06:00 PM

IIRC it was Bussard who said that a polywell device such as WB6 is more akin to a vacume 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.

RogerFox

Jul3-07, 06:15 PM

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.

M. Simon

Jul3-07, 06:40 PM

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.

TallDave

Jul4-07, 12:46 AM

This might elucidate a bit.

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

Here's the back and forth between Rostoker and Rider (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?

M. Simon

Jul4-07, 05:45 AM

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 in to 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.

RogerFox

Jul4-07, 04:10 PM

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 ?

TallDave

Jul4-07, 06:02 PM

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.

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 ?

mheslep

Jul5-07, 09:57 AM

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 in#52 (http://www.physicsforums.com/showpost.php?p=1370035&postcount=52)

TallDave

Jul5-07, 01:34 PM

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 in#52 (http://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).

mheslep

Jul5-07, 04:48 PM

This might elucidate a bit.

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

Here's the back and forth between Rostoker and Rider (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.

TallDave

Jul5-07, 09:17 PM

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.

TallDave

Jul24-07, 09:30 PM

If this article is accurate, we'll get to find out for sure who's right.

http://www.nextenergynews.com/news1/nextnews7.24b.html

mheslep

Jul24-07, 09:48 PM

No 'Ca spokesman said', no sources at all, zip. I call BS.

TallDave

Jul25-07, 02:22 PM

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.

sanman

Jul25-07, 04:34 PM

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

RogerFox

Jul25-07, 11:28 PM

If this article is accurate, we'll get to find out for sure who's right.

http://www.nextenergynews.com/news1/nextnews7.24b.html

false alarm.

sanman

Jul26-07, 12:16 AM

TallDave

Jul26-07, 12:21 AM

false alarm.

We don't know for sure yet.

sanman

Jul26-07, 12:25 AM

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.

sanman

Jul26-07, 12:28 AM

http://www.ofes.fusion.doe.gov/more_html/2007BPM/BPM2007-Master-Wurden-final.pdf

Look at page 40 on that PDF

mheslep

Jul26-07, 01:38 PM

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.

mheslep

Jul26-07, 01:49 PM

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.

sanman

Jul26-07, 10:21 PM

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.

mheslep

Jul27-07, 01:07 PM

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.

Morbius

Jul27-07, 11:05 PM

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

sanman

Jul28-07, 11:19 AM

What if your electron dispersion for POPS could be maintained as some kind of travelling 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.

mheslep

Jul28-07, 06:37 PM

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.

mheslep

Jul28-07, 06:53 PM

What if ...
Electronic valve timing? Read up a little here and let me know if you think its analogous.
Chapter 20: Waves in Cold Plasmas: Two-Fluid Formalism (http://www.pma.caltech.edu/Courses/ph136/yr2004/0420.1.K.pdf)
Chapter 21: Kinetic Theory of Warm Plasmas (http://www.pma.caltech.edu/Courses/ph136/yr2004/0421.1.K.pdf)

sanman

Jul28-07, 08:18 PM

Electronic valve timing? Read up a little here and let me know if you think its analogous.
Chapter 20: Waves in Cold Plasmas: Two-Fluid Formalism (http://www.pma.caltech.edu/Courses/ph136/yr2004/0420.1.K.pdf)
Chapter 21: Kinetic Theory of Warm Plasmas (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.

TallDave

Apr23-08, 10:54 AM

mheslep

Apr23-08, 01:39 PM

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).Yes there's a picture of the latest device up on the EMC2 website w/ some joker locked inside it.
I have the Chacon paper:
Energy gain calculations in Penning fusion systems
using a bounce-averaged Fokker–Planck model

of which Nebel is not an author. Do have information or cite indicating Nebel supports the views in the Miley/Chacon paper?

TallDave

Apr23-08, 01:47 PM

Do have information or cite indicating Nebel supports the views in the Miley/Chacon paper?

Yes, Nebel has called the paper "the most complete treatise on" the issue (this is in the comments to the MSBNC blog entry mentioned above). He (Nebel) also mentioned at the TalkPolywell site that he discussed the matter with Chacon a couple weeks ago, and they consider the upscatter issue a "red herring" for Polywell.

His full comment, which you can find in the Theory Section of TalkPolywell under topic "worst case scattering and deeper wells":

I had a long talk with Luis Chacon about the ion scattering a few weeks back. We concluded that for the Polywell, these issues were a red herring. The reason is that the densities are so high in the Polywell that you really don't need the ion focussing to be all that good. If you are running a gridded system where particles are lost every 20 passes or so, then it is an issue. For the Polywell, the electron recirculation fraction appears to be ~ 1e5 so the effective energy loss from the electrons is small. Consequently, you don't need huge focussing to get the density high.

mheslep

Apr23-08, 04:06 PM

I see Chacon's paper cited a couple times; Chacon and Nebel are authors on all of them except the first, a 'how we computed it' paper partly on Chacon's work, and Knoll is also LLNL. I was hoping to see some independent comment.

Jacobian-free Newton–Krylov methods: a survey of approaches and applications - all 8 versions »
DA Knoll, DE Keyes - Journal of Computational Physics, 2004 - Elsevier
Jacobian-free Newton–Krylov (JFNK) methods are synergistic combinations of
Newton-type methods for superlinearly convergent solution of nonlinear equations
and Krylov subspace methods for solving the Newton correction equations. ...
Cited by 159 - Related Articles - Web Search

Experimental studies of electrostatic confinement on the intense neutron source-electron device - all 3 versions »
J Park, RA Nebel, WG Rellergert, MD Sekora - Physics of Plasmas, 2003 - link.aip.org
Theoretical works by Barnes and Nebel [RA Nebel and DC Barnes, Fusion Technol.
[bold 38], 28 (1998); DC Barnes and RA Nebel, Phys. Plasmas [bold 5], 2498
(1998)] have suggested that a tiny oscillating ion cloud may undergo a self- ...
Cited by 5 - Related Articles - Web Search - BL Direct

Periodically oscillating plasma sphere - all 4 versions »
J Park, RA Nebel, S Stange, SK Murali - Physics of Plasmas, 2005 - link.aip.org
The periodically oscillating plasma sphere, or POPS, is a novel fusion concept
first proposed by DC Barnes and RA Nebel [Fusion Technol. [bold 38], 28 (1998)].
POPS utilizes the self-similar collapse of an oscillating ion cloud in a ...
Cited by 3 - Related Articles - Web Search

Stability of thermal ions confined by rigid-rotor electron clouds in Penning fusion systems - all 2 versions »
L Chacón, DC Barnes - Physics of Plasmas, 2000 - link.aip.org
In the Penning fusion device, a spherical cloud of electrons, confined in a
Penning-type trap, creates the ion-confining electrostatic well. Calculations
performed with a bounce-averaged Fokker–Planck model have suggested that ...
Cited by 1 - Related Articles - Web Search - BL Direct

Two-dimensional electron-electron two-stream instability of an inertial electrostatic confinement … - all 5 versions »
A Marocchino, G Lapenta, EG Evstatiev, RA Nebel, J … - Physics of Plasmas, 2006 - link.aip.org
Theoretical works by Barnes and Nebel [DC Barnes and RA Nebel, Phys. Plasmas
[bold 5], 2498 (1998); RA Nebel and DC Barnes, Fusion Technol. [bold 38], 28
(1998)] have suggested that a tiny oscillating ion cloud (referred to as ...
Cited by 1 - Related Articles - Web Search - BL Direct

Equilibrium and low-frequency stability of a uniform density, collisionless, spherical Vlasov system - all 3 versions »
DC Barnes, L Chacón, JM Finn - Physics of Plasmas, 2002 - link.aip.org
Equilibrium and stability of a collisionless, spherical Vlasov system with
uniform density are considered. Such an electron system is useful for the
Periodically Oscillating Plasma Sphere (POPS) fusion system. In POPS the ...
Cited by 1 - Related Articles - Web Search - BL Direct

Space charge neutralization in inertial electrostatic confinement plasmas - all 4 versions »
EG Evstatiev, RA Nebel, L Chacón, J Park, G … - Physics of Plasmas, 2007 - link.aip.org
Inertial electrostatic confinement (IEC) schemes for fusion devices have been
studied both experimentally and theoretically for some 40 years. Purely
electrostatic systems and combinations of magnetic and electrostatic ..

TallDave

Apr23-08, 04:18 PM

The above-mentioned Park is also on the WB-7 team, btw.

I haven't seen much independent comment either. Might be more after WB-7 results are published, esp. if the larger 100MW demo reactor project gets picked up.

FWIW, Zubrin's "Energy Victory" has a chart showing a strong correlation between oil prices and fusion research funding, so that can't hurt the chances of a Polywell grant.

TallDave

May16-08, 10:24 AM

Sorry to bump again, but people might find this comment from Nebel interesting:

...let me suggest the following exercise. Let's assume that a Polywell reactor is in the wiffleball mode, namely that:

n*kBolt*Te = B**2/(2*mu0)

to make it simple, let's use mks units and assume B = 10 Tesla, mu0 =4.0e-7*pi, Te = 1.0e4 eV and kBolt = 1.6022e-19 Joules per eV. Calculate what n is and compare it to the ITER value at www iter org/a/index_nav_4.htm Tell me what you get.

...click on “read more” under the design section, then “main parameters” then on the “more” button. What you will find is that the average density of ITER is ~ 1.0e20/m**3. If you use the formula I sent you for the Polywell, you will get a density ~ 2.5e22/m**3. The upshot of this is that the Polywell has a power density that is ~ 62500 times bigger than ITER EVEN IF THERE IS NO ION CONVERGENCE! Thus, a Polywell should far outperform a Tokamak even with a constant density Maxwellian plasma. Even if Rider and Nevins were correct (which Chacon has pretty clearly shown they aren’t) this isn’t a show stopper. It has a lot more significance for Hirsch/Farnsworth machines that have low average densities than it does for the Polywell.

He says 62500, but I assume the 6 is a typo and he meant 2500.