reddit: We are nuclear fusion researchers, ask us anything

[KitemanSA]

Long text.
For your reference if fuel in fuel rod suffering neutron flux, so, that also suffers changes in his physical properties.
If you have good designer, he also considers solid fuel as an structural element.

This may explain Chernobyl. Any designer that considers fuel elements as structure needs to have his head examined.

Now, relying on a zirconium can to hold in fission products is also a tad silly. It tends to limit the duration of safe use of solid fuel elements. This is why I prefer Molten Salt Reactors.

But yet again you skittle about.
Reactor wall less of an issue with Fission JUMP fuel element.
No body claimed fusion reactor commercializable JUMP fission reactors commercial
PLEASE! Pick a subject and stick with it, if you can.

[Joseph Chikva]

Long text.
For your reference if fuel in fuel rod suffering neutron flux, so, that also suffers changes in his physical properties.
If you have good designer, he also considers solid fuel as an structural element.

This may explain Chernobyl. Any designer that considers fuel elements as structure needs to have his head examined.

Now, relying on a zirconium can to hold in fission products is also a tad silly. It tends to limit the duration of safe use of solid fuel elements. This is why I prefer Molten Salt Reactors.

But yet again you skittle about.
Reactor wall less of an issue with Fission JUMP fuel element.
No body claimed fusion reactor commercializable JUMP fission reactors commercial
PLEASE! Pick a subject and stick with it, if you can.

Kiteman here you are again conjecturing. As Chernobyl accident happened because technical director decided to test reactor on off-mode and made order to switch-off blocking systems. This is quite reliable design. As similar to Chernobyl reactors run successfully on all former USSR territory without significant accidents.
I have not much data on zirconium but only mentioned that in 70s zirconium was considered as one of candidates for first wall materials.
Pick a subject and stick with it yourself. Certainly if you can. As we had a talk about stability of plasma and real processes in Polywell and when you had not arguments you jumped on advantages of aneutronic fuel.
No doubt that aneutronic better than neutronic. But that fuel has one key disadvantage - on orders of magnitude lower cross-section. And, so, much difficult to realize positive energy balance. While I do not see any ability for Polywell of running with positive balance even on neutronic fuel.

[KitemanSA]

[/quote]

Kiteman here you are again conjecturing.

Actually, I was teasing.

As Chernobyl accident happened because technical director decided to test reactor on off-mode and made order to switch-off blocking systems. This is quite reliable design. As similar to Chernobyl reactors run successfully on all former USSR territory without significant accidents.

IIRC, and I may not, the Chernobyl design has a positive temperature coefficient which can make it tricky to control.

I have not much data on zirconium but only mentioned that in 70s zirconium was considered as one of candidates for first wall materials.
Pick a subject and stick with it yourself. Certainly if you can.

I try, but you keep skittling about.

As we had a talk about stability of plasma and real processes in Polywell and when you had not arguments you jumped on advantages of aneutronic fuel.

Cite please?

No doubt that aneutronic better than neutronic. But that fuel has one key disadvantage - on orders of magnitude lower cross-section.

Sorry, the peak cross section of p11B is only ~4 times smaller than the peak cross section of DT. And oh by the way, since Polywell is NOT a thermonuclear fusion device, it may be able to reach and sustain the energy required to reach that peak.

And, so, much difficult to realize positive energy balance. While I do not see any ability for Polywell of running with positive balance even on neutronic fuel.

Well, Joe, your being unable to see any ability for Polywell to work may just be due to your APPEARANT complete misunderstanding of it's theory.

But since you can't see any hope, well, then, I guess you'll be leaving this forum and no longer waste your time here.
Good bye, fare well. Don't let the door hit yer a$$ on the way out.

Psst, hey folks, what do you bet he doesn't leave? He says he can't see ANY way it can work. But I bet he remains just to spew his nastiness.

Yeah, I know, I've been kind of nasty to him recently. I've TRIED to be polite, but he makes it SO hard.

[Joseph Chikva]

Cross-section of pB11 at 100keV collision energy (center-of mass frame) 3E-4 barn, while DT at the same energy - 3.43 barn So, at this energy (which also is not so easy for realizing) pB's section more than 10000 times lower.
Yes, pB has a peak of 1.2 barn at somewhere 750keV but at what collision energy are you going to run? Do you know what kinetic energy should have bodies with differnet masses driving by the same voltage (potential well) for getting 750keV collision energy? What depth that well should have? 750keV or much deeper? If you do not know, B11 is 11 times heavier than p.
Yes, Mr. "does not matter what cross section has a fuel" certainly can say that I do not understand the theory.
But if this is so easy to run any reaction in Polywell, why WB6 produces only 1.5 mW of fusion power? I do not understand. Please, explain.

[D Tibbets]

Note that it does not matter much what layman think, except to challenge expert opinions with reasonable arguments (ie:pit one expert against another). This relates to the Rider vs Chacon perspectives. Rider does not believe that P-B11 fusion can be positive (Q>1). Chacon disagrees.

~ one milliwatt of fusion energy in WB6 is absolutely terrific, or absolutely dismal based on other factors. If the output is what is expected based on models of the Wiffleball, volume, and B field scaling, then the results are terrific. WB 7 has already (I presume) confirmed and better characterized the WB6 results
The next questions are if power and input costs scale as models predict and this is the purpose of WB8 testing. Rember that P-B11 fusion is a bonus. The real question is if D-D fusion can be made to work. Or the most basic question is if D-T fusion can be made to work at costs less than in Tokamaks.

It is not so much what voltage is needed to reach some desirable fusion cross section, but the cost of doing so. This relates to Bremsstruhlung losses, thermalization inefficiencies and containment issues. Bussard, etel have done their homework and these relationships are well described.
As for fusion cross section, no one claims that P-B11 or even D-D can match D-T cross sections at any given KE, the issue is can they do good enough when other considerations are factored in. Descriptions of a D-T burning Polywell and comparisons to a D-T burning Tokamak are not prevalent because optimistic predictions are that the comparison is worthless as the Polywell does not need to resort to this relatively easy burning but very problematic fuel.

Note that I have liitle understanding of the KE- or more specifically the velocity make up of a mixed fuel at a given voltage, but M. Simon has calculated this for the B-B11 resonance peak at ~ 75 KeV. He found that a potential well of ~ 50,000 Volts was needed. I assume this could be extrapolated to other COM KE, and it seems that a potential well depth of ~ 200,000 volts is adequate to obtain a useful fusion cross section for a more reasonable partially thermalized plasma, as this is a number used by Bussard. Compare this to perhaps 80,000 volt well depths for a working D-D Polywell, and perhaps ~ 30,000 Volts for a D-T Polywell. Because of thermalization issues, a Polywell is expected to reach these conditions easily compared to a Tokamak that is expected to reach average temperatures significantly lower. This is why D-T is the only possible fuel for Tokamaks. The input costs complicates the issues, but this is the basic difference between the thermalized approach and the Polywell approach. Even this distintion is complicated by DPF and FRC approaches. It is basically the temperature that can be obtained which determines the fuel of choice. Input costs then factor in when considering the energy profit.

Dan Tibbets

[Joseph Chikva]

Note that I have liitle understanding of the KE- or more specifically the velocity make up of a mixed fuel at a given voltage, but M. Simon has calculated this for the B-B11 resonance peak at ~ 75 KeV. He found that a potential well of ~ 50,000 Volts was needed.

Your little understanding can be easily improved.
Let's admit that we have a point negative charge at the center which creates potential distribution thus attracting ions from the edge.
At certain potential φ acceleration force acting on proton will be equal to F=eφ and for Boron F=5eφ
Acceleration for proton a=eφ/m and for Boron a=5eφ/11m
So, about 2 times lower acceleration in the same el-field.
dv=a*dt (a is not const)

So, proton and boron will have different momentums and moving from opposite directions and then colliding will not have static center-of-mass in laboratory frame (at the center where probability of collision should be maximum). In this case collision energy at center-of-mass frame is less than sum of kinetic energies of particles.

I do not know from where Mr. or Dr. Simon got peak of pB11 reaction at 75keV but I can see for example this article http://fds.oup.com/www.oup.co.uk/pdf/0-19-856264-0.pdf in which at 12 page Fig. 1.3 this peak is shown somewhere near 750keV.
Recall that sum of kinetic energies should be higher than this number if you want to get 1.2 barn cross section.
Let's admit 500keV for boron and little be less for proton. (I am lazy to calculate but sure that higher than this number)

The depth of potential well should be not less than 500keV in this case.
In opposite case all particles passing once the center will escape reactor.

[krenshala]

So, proton and boron will have different momentums and moving from opposite directions and then colliding will not have static center-of-mass in laboratory frame (at the center where probability of collision should be maximum). In this case collision energy at center-of-mass frame is less than sum of kinetic energies of particles

This would only be true if the reactions in a Polywell were not taking place in a spherical volume. Since the interactions take place in a spherical volume, the "moving in the opposite directions and then colliding" always means the collision happens at (or in close proximity to) the center of the device ... right where we want it to be.

[KitemanSA]

Let's admit 500keV for boron and little be less for proton. (I am lazy to calculate but sure that higher than this number)

The depth of potential well should be not less than 500keV in this case.
In opposite case all particles passing once the center will escape reactor.

Except that boron also has 5 charges. So 500keV is obtained with a well depth of 100kV. This is in the common range for IEC fusors.

My recollection is that the required MaGrid charge value was more like 150kV.

And M. Simon was talking about the resonance peak, not the general peak. There is a thin resonance peak at ~CoM KE ~120 keV by my chart. (At least I have always heard it called a resonance peak, anybody?)

And didn't I say he wouldn't leave?

[Joseph Chikva]

So, proton and boron will have different momentums and moving from opposite directions and then colliding will not have static center-of-mass in laboratory frame (at the center where probability of collision should be maximum). In this case collision energy at center-of-mass frame is less than sum of kinetic energies of particles

This would only be true if the reactions in a Polywell were not taking place in a spherical volume. Since the interactions take place in a spherical volume, the "moving in the opposite directions and then colliding" always means the collision happens at (or in close proximity to) the center of the device ... right where we want it to be.

For pair collision does not matter in which space two particles met each other. But I told about ideal for you radial motion of all particles. Actually this ideal picture will be too far from reality beacuse as I mentioned several posts ago particles suffer scatterings and not only center and there are not any forces in Polywell forcing particles to restore the direction.
There is an infinite set of straight lines not passing through the center. To be convinced this simply draw the circle and then draw several chords in it. And once scattered particle will decline from “right” radial direction.

[Joseph Chikva]

Let's admit 500keV for boron and little be less for proton. (I am lazy to calculate but sure that higher than this number)

The depth of potential well should be not less than 500keV in this case.
In opposite case all particles passing once the center will escape reactor.

Except that boron also has 5 charges. So 500keV is obtained with a well depth of 100kV. This is in the common range for IEC fusors.

My recollection is that the required MaGrid charge value was more like 150kV.

And M. Simon was talking about the resonance peak, not the general peak. There is a thin resonance peak at ~CoM KE ~120 keV by my chart. (At least I have always heard it called a resonance peak, anybody?)

And didn't I say he wouldn't leave?

Define please differnce between resonance and general peaks.
And why I should leave? Because your "noone said that all particles in Polywell pass throu center" not corresponds to true? First who repeted this nonces is Mr. kreshala. See post above.
Ok, I will calculate tomorrow and will show you with numbers that expected 500keV is low number.

[KitemanSA]

[/quote]

For pair collision does not matter in which space two particles met each other. But I told about ideal for you radial motion of all particles. Actually this ideal picture will be too far from reality beacuse as I mentioned several posts ago particles suffer scatterings and not only center and there are not any forces in Polywell forcing particles to restore the direction.

Actually, the hypothesis is that the ions anneal at the edge of the well and regain their dominantly radial motion.

There is an infinite set of straight lines not passing through the center. To be convinced this simply draw the circle and then draw several chords in it. And once scattered particle will decline from “right” radial direction.

Unless they anneal.
this was one of those "aw $#!t, oh good" moments in Dr. B's career. Someone (Todd?) published something that suggested what you keep saying. He is reported to have gotten VERY worried for a while until he convinced himself that the thermalization would tend to anneal; at least enough to allow the Polywell to get Q>>1.

Tom, you were there weren't you? Am I mis-remembering the story?

[Joseph Chikva]

Hogwash. Chaos generates chaos. How randomly moving particles can organize the ordered movement only with the help of collisions? Dr. Bussard gotten VERY worried. Tom, you were there weren't you?

[KitemanSA]

Define please differnce between resonance and general peaks.

Nope, cuz I can't, but I see them on all the CoM cross section plots. The curve slopes up, spikes, drops back, slopes up some more and then finally falls. The spike is the "resonance" peak and the top of the general slope is the general peak.

And why I should leave?

You said you did not believe there is ANY way that Polywell can work. If that is what you believe, why do you waste your time here? Any sane person with that opinion would leave. Does that suggest you are NOT sane?

Because your "noone said that all particles in Polywell pass throu center" not corresponds to true? First who repeted this nonces is Mr. kreshala. See post above.

You accused someone of stating that all lines thru a circle passed thru the center. That was a false statement. No one said that. Now you are saying that your statement was true because:

This would only be true if the reactions in a Polywell were not taking place in a spherical volume. Since the interactions take place in a spherical volume, the "moving in the opposite directions and then colliding" always means the collision happens at (or in close proximity to) the center of the device ... right where we want it to be.

Nowhere does he say that all lines thru a circle go thru the center. He does suggest that the dominant location for collisions of ions "moving in opposite directions" will be at or near the center. I can't speak for him, but I suspect he assumed that the discussion was about ions with sufficient CoM energy to fuse. Ions at the edge tend to be very slow and almost all their residual energy would be tangential. These conditions tend to "thermalize" the ions at a very low temperature and leave them ready to fall almost straight down the well. The "tangential velocity" which is also called "angular" will tend to anneal out of the system resulting in a dominant radial motion.

Ok, I will calculate tomorrow and will show you with numbers that expected 500keV is low number.

Could be. I've seen a plot where the abscissa was "light particle energy" and it had no resonance peak and the general peak was at ~500keV. Have fun.

[Joseph Chikva]

Kiteman, I see one maximum on a logarithmic axis closer to 1 MEV. And do not see any more. There are no there several humps. And let me to decide myself where to go and where to remain. And I need not belief in viability of Polywell as I see that definitely Polywell does not work and will not work. But this is difficult to explain to person who sees one hump but says “many”. Fusion may happen even if there is not head-head collision. But if you or any other say “spherical geometry and opposite motion” you mean only radial direction. If not considering very unlikely case of opposite motion according chord. And for your reference radial direction passes through center.
Regarding “annealing”: initially for me was very difficult to understand what this means. As every reading the NewEnergyTimes and Wikipedia here has his own terminology and his innovative vision on Laws of Nature. Via collisions, my friend, you can reach only uniformity of average velocities distribution. But not to convert random to coherent. My advise is to learn more from classic physics.
And to stop incorrect using of terms like “resonance peak” or “general peak”.

[JohnP]

And I need not belief in viability of Polywell as I see that definitely Polywell does not work and will not work.

The main thing to wait for is confirmation of scaling. Correct me if I'm wrong, but with the current dearth of information coming from EMC2, it's hard to tell if they've established scaling with WB8. Was there a date set as for release of information? Or are we stuck with educated guesses and tea-leaf reading for the forseeable future?