Register to reply

Fusion Summary?

by mheslep
Tags: fusion, summary
Share this thread:
mheslep
#91
Jul26-07, 01:38 PM
PF Gold
P: 3,081
Quote Quote by sanman View Post
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
#92
Jul26-07, 01:49 PM
PF Gold
P: 3,081
Quote Quote by sanman View Post
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
#93
Jul26-07, 10:21 PM
P: 656
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
#94
Jul27-07, 01:07 PM
PF Gold
P: 3,081
Quote Quote by sanman View Post
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
#95
Jul27-07, 11:05 PM
Sci Advisor
P: 1,152
Quote Quote by mheslep View Post
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
#96
Jul28-07, 11:19 AM
P: 656
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
#97
Jul28-07, 06:37 PM
PF Gold
P: 3,081
Quote Quote by Morbius View Post
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
#98
Jul28-07, 06:53 PM
PF Gold
P: 3,081
Quote Quote by sanman View Post
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
Chapter 21: Kinetic Theory of Warm Plasmas
sanman
#99
Jul28-07, 08:18 PM
P: 656
Quote Quote by mheslep View Post
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
Chapter 21: Kinetic Theory of Warm Plasmas
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
#100
Apr23-08, 10:54 AM
P: 31
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).
mheslep
#101
Apr23-08, 01:39 PM
PF Gold
P: 3,081
Quote Quote by TallDave View Post
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
#102
Apr23-08, 01:47 PM
P: 31
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
#103
Apr23-08, 04:06 PM
PF Gold
P: 3,081
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
#104
Apr23-08, 04:18 PM
P: 31
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
#105
May16-08, 10:24 AM
P: 31
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.
mheslep
#106
May16-08, 02:02 PM
PF Gold
P: 3,081
Quote Quote by TallDave View Post
Sorry to bump again, but people might find this comment from Nebel interesting:...
link? linky-link-link please? Or which paper?
TallDave
#107
May16-08, 03:48 PM
P: 31
Sorry, it doesn't let me post links :(

It was just a comment he made at Talk Polywell. Let's see if I can trick the anti-spam program:

www talk-polywell org/bb/viewtopic.php?t=468&postdays=0&postorder=asc&highlight=62500&start=30
Astronuc
#108
Jun18-08, 08:12 AM
Admin
Astronuc's Avatar
P: 21,827
Something that has been overlooked.

HSX is a modular coil stellarator optimized for quasi-helically symmetry located in the Electrical and Computer Engineering department at the University of Wisconsin. Plasma physics research goals include investigation of transport, turbulence, and confinement in a quasi-helically symmetric magnetic field.
http://www.hsx.wisc.edu/

http://www.hsx.wisc.edu/parameters.shtml

Coil Current (maximum): 13.4 kiloAmperes
Magnetic Field Strength (maximum): 1.37 Tesla
Power Density: 0.23 W/cubic centimeter (with Heating Power (ECRH): 100 kiloWatts)


Register to reply

Related Discussions
Introduction / Summary of Differentiation Mathematics Learning Materials 36
Summary of the key formula of QFT Quantum Physics 9
How does a brief summary look like? Introductory Physics Homework 2
Zero- Book Summary chp 0 Science & Math Textbooks 3
Basic summary Beyond the Standard Model 13