Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
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Frank Sanns
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Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by Frank Sanns »

It must be realized that losses in fusion attempts in gridded or gridless fusors are actually very similar.

In nature, charge wants to either separate or neutralize. Charge does not like to gather together and there are good fundementals to see that. Coulomb's law of F=K*q1*q2/r^2 makes sure of that. A micro amp of electrons flowing for one second will generate a restoring force of ~0.01N or ~0.002 pounds of force if separated by one meter. In a typical fusor of one quarter that size the forces are 16 times (inverse square law) higher.

For this reason, it is poor scientific judgement to think that charges will continue to accumulate. Significant charges do not stack up in a vacuous area of chamber. Electrons for example are going to hit the walls and neutralize or recirculate and recombine with ions and neutrals in the chamber. A fusor plasma is nearly all neutrals so even with a gridless or polywell design, electrons are going to lose their energy quickly to the walls or to neutrals/ions.

The other case for charges not stacking up is that if charge is stagnant then there is no power transfer and the forces will either tear the chamber apart (not likely) or they will disperse and neutralize (reality). If there is power transfer there is current and thus flow of electrons and ions and neutralization of charge.

These statements are true for gridded, gridless, and polywell fusors.

Frank Sanns
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by Chris Bradley »

Frank S. wrote:
> It must be realized that losses in fusion attempts in gridded or gridless fusors are actually very similar.
>
> These statements are true for gridded, gridless, and polywell fusors.


I am in general agreement, and will also add that the actual lossy processes are also pretty much the same for any *beam* type process. i.e. fusors and the like are recirculating systems, but the very first attempt to generate energy, Mark Oliphant back in 1934, was to drive just a straight deuteron beam into deuterium.

Now that idea may not have reached 'break-even' but 'dumb' recirculation processes like the fusor should be 'only' 4 or 5 orders of magnitude better (or so), so if a recirculation design has got half a chance, then at least we should see deuteron beams (i.e. anywhere where we've got fast deuterons and a neutral, or low-temp plasma, background) getting a good neutron rate out... but we don't. What we get is pretty lights! So recirculation might add a few orders of magnitude efficiency to a beam process, but we've got to find another 9 orders of magnitude!

For the reasons you give, Frank, I am therefore of the opinion that a pure electrostatic fusion-power method will not be practical. The magnetic [thermonuclear] methods are well in hand but seemingly elude a successful conclusion. As a result, I feel that the answer must lie in a combination of electrostatic and magnetic control (either, or possibly both, beam-type or thermal plasma).
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by DaveC »

I think we've been down this topical path, numerous times.... but, one never tires of the ruminating it inspires.

Frank - I think there may be some uinits problems in your example. A uA of current in a second would be a uC of charge - 10^-6 C ...

In Coulombs force equation,

F = (1/4pi e0 ) x (Q^2/r^2) ...

At i meter separation, the force F is 9E-9x1E-12/(1m^2) or about .009 N ,

if my calculator didn't fail me.

But your point stands, irrespective of the force magnitude... it is a Repulsive force.

The potential to bring ions into the prospective nuclear reaction range is a few 10's of kV.

U = 9E9x (1.6E-19)/(1E-12) a separation of 1 pico meter and potential in eV.

U = 1.4 kV


The fusion issue seems not to be one of having insufficient potential to get close, but of Q-M factors at these very small intranuclear distances. There is only a certain probability that the fusion process can happen.

If I'm not mistaken, this "intranuclear" process is within the "envelope" of what is called "collision cross section", . or the probability that a collision resulting in a particular scattering angle will occur between particles of a given energy U.

Collision cross section has a relatively understandable interpretation when we are considering atoms or molecules as hard spheres. As soon as we use real descriptions where the atom is a stew of oscillating charges and other entities, and molecules are two or more of this kind of atom attached to each other, and spinning, vibrating, and quivering randomly in space... what contstitutes a "collision" between these sorts of objects gets kind of vague. One can still use the tried and true definition based on what scatters, where.

When we go the extra mile, to ask what the likelihood of a "collision": like this yielding a rearrangement of the nuclear parts, it gets to be very complicated.

I don't understand this in any kind of detail. I suspect the true answer is inextricably connected to basic questions of subatomic particles and the "glue" that holds things together. It will be quite a while, I think before we have this picture.

So we deal at a simple and practical level: How many fusions are occurring per second at a particular energy of incoming particles. And of course, we usually only know the result, not even the number of attempted collisions, nor the real incoming energy distribution, only the maximum. So we are very, very information limited to date

There's clearly a lot more that could be used to quantify the present fusion processes at work in the D-D fusors or whatever configuration... if we only could figure a way to monitor better.

As I have expressed before on the Polywell or any kind of "well" concept, it is NOT obvious that merely by being contrained in some sort of energy well, a vast stew of whizing particles will have a better opportunity to fuse, than in some other way.

It reminds me of power transformers... the most efficient designs, (which at low frequency approach 98-99%),...are not resonant structures, but ones which minimize stored energy - lowest vars, highest power factor... to use EE talk.

So, it's curious to me, that we are trying to do the opposite with the fusor, in hopes it will yield higher collision "efficiency". I dunno ???

FWIW....

Dave Cooper
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by mheslep »

Frank S. wrote:
>...Electrons for example are going to hit the walls and neutralize or recirculate and recombine with ions and neutrals in the chamber. ...
Why don't you believe the Polywell's magnetic field design will contain the electrons? Also remember they only want to stack up enough charge balance to maintain a well depth of 100kV.
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by Frank Sanns »

Thanks Dave. Fixed the missing q. Conclusions still the same.

Frank
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by Frank Sanns »

As stated above, it will not CONTAIN electrons. During some very short time period (microsecond or less) after the HV is turned on, there will indeed be some charge separation. After that the scenario is as I described above. The flow of electrons will then be bound for transverse paths to the shell or more likely collisions with neutrals. Either way it is a total loss of input energy that is carried by the electrons.

Frank
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by Dustinit »

I dont totally agree with what you say Frank.
Theoretically most of what you say is correct but in reality

Ions which have alot of energy will not recombine with electrons
even if they are in a sea of electrons.

Electrons will not always hit the wall
if they see a larger accumulated positive space charge of ions, and a large space
charge of ions will try to neutralise itself by collecting electrons within its space charge
which is by definition Plasma. This does not exclusively mean recombination.
This environment cannot be separated into black and white but shades of grey.
Dustin
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by Frank Sanns »

And this is different from a conventional fusor how?

Frank
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by Carl Willis »

Hi Frank,

While what you note is correct about charged particles eventually getting lost or neutralized, it doesn't really compel the sweeping conclusion that they "won't accumulate in any fashion whatsoever" or "stack up in a vacuous area"--at least as far as impact on fusion efficiency is concerned.

Persistence of trapped energetic charged particles can be detected, measured, and optimized in fusor-like machines (the only specific example I know of is Park's and Nebel's experimental development of their "POPS" idea, but there have gotta be other examples out there). "Virtual electrodes" are an observed phenomenon of electrostatically-trapped particles, thought by fusioneers as early as Hirsch to be important to the central focusing and efficiency of fusors.

-Carl
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by Dustinit »

The loss mechanisms will be different,
Steady state losses may be equivalent but this is meaningless
if plasma densities and fusion events are an order of magnitude greater.
Ion path lengths can extend to kilometers in a magnetic field (as well as electrons)
This means residence time is greatly extended even if the steady state
losses are the same the density must be greater and also the oportunity for fusion.
What should be compared is perhaps Q.
You could liken it to a leaky dam of water, the two may leak the same amount
but I suspect there is alot more water behind one than the other.
Dustin.
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by tligon »

Frank,

I see a couple of misconceptions here. First, exactly what "walls" do you think the electrons will be lost to? The outer chamber walls? They are emitted at roughly wall potential, and you can easily set the emitters a few volts positive of that, in which case they won't be attracted to the walls at all. The walls are a cathode. Only the magrid is an anode. The magrid is magnetically insulated, so the electrons will have to make their way across that field in order to be lost to the magrid surface.

There are definitely mechanisms for that, but the question then becomes how long the electrons are prevented from doing so. Not forever, but neither is it instantaneous.

Second, there is no static "stacking up" of either charged species. The reason Dr. Bussard shifted the description of these machines from Inertial Electrostatic Fusion to Inertial Electrodynamic Fusion was, I'm sure, to dispel the misconception that you somehow shove the electrons in the middle of the machine and they just stay there. All the charged species are in vigorous motion. It is the continuous oscillation between kinetic and potential energy characteristic of moving thru the machine that creates the potential well, not electrons stuck in some static pudding. Don't neglect inertia!

It takes about 13 eV to knock the electron off a hydrogen atom. How will they recombine at 10 keV or more?

From what I can tell, the tests are done. I presume Physics knows what will work and what won't, even if we don't understand all the subtleties of Physics. Let's wait (patiently, trying not to pace a track into the carpet) for the reports. From what Dr. Nebel has said, the machine definitely does something. It worked well and repeatably, and they were "pleased with the results", but said they were "nuanced." So what is the point of sitting here declaring it will never work, when the tests are done?
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by Frank Sanns »

My appologies to you and to those working on Polywell concepts. It was improper of me to applied my understanding of the device and draw conclusions. I did see the results and I am pleased it is working out for all of you.

Frank
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by Frank Sanns »

My appologies to implying that charges can never be made to congregate. My intent was to show that they can not keep piling up as current contiues to flow on long time frames.

Frank
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by Carl Willis »

Hi Frank,

No apology in order.

I'd say that charge can keep piling up, as long as current is flowing--you just have to work progressively harder to maintain the net influx of charge into the control volume per Gauss' Law. Under the condition that you're only willing to do so much work per charge, then you reach an equilibrium where continuity can only be satisfied by having the inbound current equal the outbound current with no more charge being stored.

This is all just a rephrasing of basic tenets of electrostatics that you are knowledgeable in, but there is perhaps a wee bit of an over-generalization that can be read into the thing. Again, no apology required. I suspect my addition is mostly to the benefit of some of your readers, in the interest of clarity and utter correctness (pardon the apparent hubris).

-Carl
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Chris Bradley
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by Chris Bradley »

Tom Ligon wrote:
> It takes about 13 eV to knock the electron off a hydrogen atom. How will they recombine at 10 keV or more?

So you get a 10keV neutral out of it which then evades electric and magnetic fields resulting in the same losses as a fusor?! This isn't a thermal plasma we are talking about.

When it whams into something solid, it may embed or re-ionise or sputter, or some combination of these and other mechanisms.

Plus, in either the fusor or the Polywell, the ions are not always at 10keV. They reciprocate in their motion and will slow down as they change direction, increasing the likelihood of recombination/Coulomb-scattering/ionising/electron-sharing interactions with any particles. (all, but fusion!!!)

I also believe it is not possible to discount the electron flow into the magrid as being different to fusor losses (magnetic fields can never 'contain' but only 'guide' and electrons in the distribution 'tail' will cross through magnetic surfaces, as you have alluded to - a reduction is likely, but as per my other post a weak magnetic field could also be used for a similar purpose in the fusor). This loss should be enumerated wrt fusor before discounting a similarity in their mutual behaviours.

Also, discussing if charges 'accumulate' seems a bit disingenuous. Of course the charges themselves do not build up, but flow dynamically in and out of a region of space-charge and for both the fusor and Polywell will reach some point of continuity of local charge (in=out). I understood this as Frank's meaning. So what's the difference, fusor/polywell?
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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by Richard Hull »

I'm with Dave. Though these discussions are themselves circulatory and crop up over and over, they force thought anew and usually include newer members to our group on rather substantive though circular discussions. We often learn by listening to the thoughts of others which can sow the seeds of new ideas in ourselves.

I tend to view all of the above as illustrative of just how far we remain from a power ready answer in fusion. Nature has made matter proof against controlled ignition type fusion outside of the good offices of gravitational forces..... At least so far as we have seen. And yet, as we all know, fusion is truly easy to make happen. What a dichotomy.... a maddening dichotomy.

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Re: Talk, Polywell, Bussard, Neutron, Electron Losses with Gridless Fusor Design

Post by Chris Bradley »

Yes. Dave's points are well made. There is some useful expansion on Dave's points, I think:

Firstly, 'cross-sections', as I understand them, are not 'hard spheres' per se of course, but are actually experimental measurements then converted into 'hard sphere equivalents'! So, in that respect it's true that the literal 'meaning' is wrong, but this is fully accounted for when measuring off fusion/ionisation/electro-sharing, &c., reactions. (excepting Coulomb scattering which uses the physical notion of a sphere directly.)

Secondly, the issue of whether resonance, system energy and/or Q (as in quality factor) is of any concern to getting good fusion rates is an interesting thought. Specifically for fusion rates, however, there is a need to maintain a high 'energy' level, E, for the sum total of fast particle energies and to minimise their rate of energy loss, P (that is, the confinement time, E/P= tau) for the simple reason that fusion is probabilistic and so the higher the total number of particles 'whizzing around in the stew' at any one time the better. BUT at the same time this advantage of larger total energy, E, for FUSION gain must increment quicker that the disadvantages brought on for all the lossy processes with the consequential increase in P.

I don't think anyone's run a fusor to the point where tau begins to drop off, it certainly doesn't look like that, but Dave is right to keep open the idea that some other configuration of loss control at lower energy content may be an improvement.
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