Fusion Will Never Work

[TheRadicalModerate]

However, I think Dittmar is not considering the fact that countries like Japan are already using the complete Plutonium fuel cycle in that they already have commercial FBRs.

Japan has a closed fuel cycle (i.e. they reprocess to produce MOX fuel assemblies) but their FBR program isn't really part of that cycle. There's only the one FBR at Monju. It'd be hard to call that "commercial".

[rcain]

climate control, population control and the coming UN Copenhagen summit:

http://www.larouchepac.com/node/12460

those in favour simply abstain.


it was on the tv news over here (UK) as an 'emerging' political debate, possible long term agreement. the (growing) contraview is that population control is a red herring to the issue, at least at this time. though perversely, drinking water and food are seen as real 'population control' issues.

(but i was more interested in the fision/energy debate that was kicking off).

to Aero below - quite so, hear hear! - my response was intended @::

If you have the political will you could have population control.

And it wouldn't harm the environment.

In America we favor the voluntary approach. You first.

Apologies for the digression

[Aero]

This is the news forum. Topic drift is frowned upon on this forum. Please focus on fusion or the lack there-of. Birth control is a topic suitable for the General forum.

[rcain]

However, I think Dittmar is not considering the fact that countries like Japan are already using the complete Plutonium fuel cycle in that they already have commercial FBRs.

Japan has a closed fuel cycle (i.e. they reprocess to produce MOX fuel assemblies) but their FBR program isn't really part of that cycle. There's only the one FBR at Monju. It'd be hard to call that "commercial".

Do we know what the Japanese have decided to roll-out over the next 10-30 years?

It seems to me, that if theres any process that needs 'perfecting', Japan leads the way.

[D Tibbets]

Other than IEC polywell, which concepts do not operate in thermodynamic equilibrium?

Any steady-state IEC polywell would also operate in thermodynamic equilibrium. The fusion products would immediately thermalize the plasma.

A pulsed system is probably the only one with a chance of working. Probably why the H-bomb worked so well. Actually, a fusion reactor that uses H-bombs would work. One helluva engineering project that would be.

You are (probably, or at least mostly) wrong.
According to Dr. Nebel in P-B11 fusion the high energy fusion ions- alphas, and presumably H3 and He3 ions produced from D-D fusion are traveling too fast to be contained by the potential well, so they leave the system through the cusps much faster than the fuel ions (by a factor of a thousand, a hundred thousand?) and leave with most, if not all of thier original energy (their mean free path is long enough that the ~ 1000 passes before escape will not result in many collisions)- ie they do not have any significant thermalizing effect within the magrid.

Dan Tibbets

[Shubedobedubopbopbedo]

You're assuming that collisions result in 100 percent transfer of energy. Most would not. What about collisions that are elastic and occur at an angle? I agree with Rider that the plasma would probably thermalize very quickly. Alpha particles for example are not like neutrinos, they don't just pass through 1000 lightyears of concrete without colliding with anything. If p-B11 ions collide, then alpha particles will collide too.

[TallDave]

I believe the answer is that the cross-section for alpha collisions is lower due to their high energy.

thread drift

http://www.abyssandapex.com/200710-wikihistory.html

[D Tibbets]

You're assuming that collisions result in 100 percent transfer of energy. Most would not. What about collisions that are elastic and occur at an angle? I agree with Rider that the plasma would probably thermalize very quickly. Alpha particles for example are not like neutrinos, they don't just pass through 1000 lightyears of concrete without colliding with anything. If p-B11 ions collide, then alpha particles will collide too.

Of course collisions would rarely transfer 100 percent energy transfer. The heavier fusion ions would tend to transfer a little less energy/ momentum to the lighter fuel ions (?) per collision. Also, due to confluence (central focus, central origen of most of the fusion ions) the scattering collisions would tend to be mostly radial- most of the collisions would occur near the center. This would tend to decrease the rate at which the fuel ions would pick up transverse motion. I suspect that the fuel ions would on average be upscattered in radial directions by the fusion ions. These in turn would tend to downscater with subsequent passes theough the center ( tend to rearend other fuel ions, averageing out the upscatering effect from the fusion ions. So, with my convoluted reasonong the fuel ions would pick up some energy from the fusion ions, but there may not be as much spread in the fuel ion radial speeds as you might see in a nonspherical , centrally focusing system. Also, keep in mind that any upscattered fuel ions that hit a cusp are more likely to escape that the mean energy fuel ion, so they leave the system faster, thereby impeading upscattering thermalization to a minor or moderate (?) extent. And, during their slightly shorter lifetimes, they may actually help impead the radial downscattering spread (major handwaving here). Also,keep in mind that transvers energy spread is impeaded by edge annealing (if you believe in it) I don't know if this edge annealing is susposed to have any effect on radial energy spread, though it may act somewhat like what I discribed above.
All this is ignoring TallDave's comment about the different ranges of speed also effecting the transfer of kinetic energy.

The basic determinate of the fuel ion thermalization with the fusion ions though is the infrequency of the collisions between the fuel ions and the fusion ions during the brief span of time that the fusin ions bounce around within the magnetic containment before they escape through a cusp. I'm too lazy to dig up the formula and calculate the mean free path for the fusion ions, but I'm assuming that expected collisions would be few enough, and those that do occur would be predominatly in the center, so the net effects on transverse and radial scatering are trivial, as implied by Dr. Nebels statement.

Dan Tibbets

[chrismb]

Of course collisions would rarely transfer 100 percent energy transfer.

Being pedantic (for which I am eminently qualified), actually it depends what frame of reference you're in. If you happen to be watching from the frame of the projectile particle after collision then you'd see 100% energy transfer. Kinetic energy is frame-dependent Ever seen a "Newton's cradle"?

The heavier fusion ions would tend to transfer a little less energy/ momentum to the lighter fuel ions (?) per collision.

Maximum transfer, in the lab frame, occurs between particles of the same mass. It is similar/dissimilar mass that is the key.

Also, due to confluence (central focus, central origen of most of the fusion ions) the scattering collisions would tend to be mostly radial- most of the collisions would occur near the center. This would tend to decrease the rate at which the fuel ions would pick up transverse motion.

Shoobybooby actually has a point here. As fast particles will, presumably, be emitting radially, they'll be following the same paths out as everything else. The notion that these wouldn't interact at 'non-central' radii is bizarre and is very wishful wishful thinking.

Also, keep in mind that any upscattered fuel ions that hit a cusp are more likely to escape that the mean energy fuel ion, so they leave the system faster, thereby impeading upscattering thermalization to a minor or moderate (?) extent. And, during their slightly shorter lifetimes, they may actually help impead the radial downscattering spread (major handwaving here).

You've lost me here, can't follow why you make this sequence of assumptions.

[alexjrgreen]

Also, keep in mind that any upscattered fuel ions that hit a cusp are more likely to escape that the mean energy fuel ion, so they leave the system faster, thereby impeading upscattering thermalization to a minor or moderate (?) extent. And, during their slightly shorter lifetimes, they may actually help impead the radial downscattering spread (major handwaving here).

You've lost me here, can't follow why you make this sequence of assumptions.

The upscattered ions leave through the central cusps and get frogmarched by the excess electrons past the magrid and back. They return with the "right" amount of energy.

[rcain]

http://www.askmar.com/Fusion_files/EMC2 ... %20Ion.pdf

- 'Core Collisional Ion Upscattering and Loss Time' - RW Bussard 1993

[alexjrgreen]

http://www.askmar.com/Fusion_files/EMC2 ... %20Ion.pdf

- 'Core Collisional Ion Upscattering and Loss Time' - RW Bussard 1993

That's a WB1/WB2 vintage paper. Before recirculation...

[D Tibbets]

......

Also, due to confluence (central focus, central origen of most of the fusion ions) the scattering collisions would tend to be mostly radial- most of the collisions would occur near the center. This would tend to decrease the rate at which the fuel ions would pick up transverse motion.

Shoobybooby actually has a point here. As fast particles will, presumably, be emitting radially, they'll be following the same paths out as everything else. The notion that these wouldn't interact at 'non-central' radii is bizarre and is very wishful wishful thinking.

....
during their short lifetimes, they may actually help impead the radial downscattering spread (major handwaving here).

You've lost me here, can't follow why you make this sequence of assumptions.

Depends on how you define the central region. Certainly not a point. Depending on the degree of confluence the dense core might be defined as a few percent of the total radius, of as much as 30-50% (?) of the radius. I believe that some degree of confluence is nessisary for practical fusion- Nebel said it did not need to be great. The mean free path would be shorter in this region so more collisions per cm traveled would occur. There would be some breakeven point where the shorter MFP in the core would overcome the greater distances the particles travel outside the core.


Concerning the second comment, I was hoping someone would explain my hand waving to me . At least in part, I was thinking that any down scattered fuel ions would not climb as high in the potential well so they would make up a higher relative proportion of the fuel ions in the core, so they would get in the way of the transiting fusion ions passing through the core more so then the average fuel ion. If these low energy fuel ions are rearended they will gain energy. If they are hit near headon by the fusion ions they mightl be knocked backwards at a speed closer to the average fuel ion speed (a lot of optomistic assumptions here).

Dan Tibbets

[D Tibbets]

Also, keep in mind that any upscattered fuel ions that hit a cusp are more likely to escape that the mean energy fuel ion, so they leave the system faster, thereby impeading upscattering thermalization to a minor or moderate (?) extent. And, during their slightly shorter lifetimes, they may actually help impead the radial downscattering spread (major handwaving here).

You've lost me here, can't follow why you make this sequence of assumptions.

The upscattered ions leave through the central cusps and get frogmarched by the excess electrons past the magrid and back. They return with the "right" amount of energy.

The positive ions, if they reach the magrid radius in a cusp will see the positive charge (minus the weaker potential well negative charge) and be accelerated to the vacuum vessel wall. They do not return- they act opposite to the recirculating electrons in thias region. Comments about Gauss's law/ Faraday cages may be confusing. It applies inside the magrid, but not outside.
I don't know how many local electrons will be in this area while they are being recirculated. But, based on some numbers- magnetic containment holds the electrons for ~1000-10,000 passes. Recirculation multiplies this by perhaps 10 to 100X. This implies that the vast majority of electrons at any given time are deep within the Wiffleball. If this density of electrons left behind cannot stop the ion before it reaches the magrid radius, the relatively few local electrons will not have much additional effect, certainly not enough to overcome the positive charge on the magrid.
Also, keep in mind that the cusp flows are not ambipolar according the R. Nebel- ie the more global conditions have enough influence to overcome any tendancy for local ions and electrons to pair up on a one for one basis.

Dan Tibbets

[D Tibbets]

http://www.askmar.com/Fusion_files/EMC2 ... %20Ion.pdf

- 'Core Collisional Ion Upscattering and Loss Time' - RW Bussard 1993

That's a WB1/WB2 vintage paper. Before recirculation...

I don't think recirculation of electrons would effect things within the magrid much. Recirculation is more of an issue for the energy cost of maintaining the required electron density within the magrid. Without recirculation you would just need to increase the current ( by a factor of 10-100X?) of the electron guns. This ignores some other issues like arcing.

Dan Tibbets