Magnetics

Discuss how polywell fusion works; share theoretical questions and answers.

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Schneibster
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Magnetics

Post by Schneibster »

So, I know of this phenomenon from astrophysics called "magnetic reconnection." What happens is the Earth's magnetic field gets stretched and stressed by a solar storm, which creates an excitation in the solar wind. This excitation stretches and stresses the magnetic field, creating vortices which disconnect the magnetic lines of force downwind (that is, away from the Sun and toward interstellar space) for a time. However, this situation is not stable; when the excitation passes outward, then the magnetic lines reconnect, and it causes a whole bunch of magnetic vortices to spin off and create auroras, blow the electronics on satellites, and even blow up entire national power grids on Earth.

When I look at the geometry of the polywell I see conditions that seem to me could potentially create these sorts of effects. The thing I have to tell you is that these reconnection events sound very dramatic, but they are totally invisible to the human senses, and not all that easy to see even with delicate machine senses. Suppose you were in a room with strongly fluctuating magnetic fields like these, what would you expect to see? Absolutely nothing.

OTOH these events do have profound effects on charged particles, so blown coils and melted buss bars are probable consequences of these sorts of events.

I suggest that in order to make polywell fusion work these effects need to be clearly understood, and most likely eliminated from the generator environment.

Now, I may be teaching my grandma how to suck eggs. But the articles I read about this stuff really never quite seem to represent a realistic visualization of these phenomena. Certainly reconnection is not something I've heard anywhere around fusion. So I figured I'd ask.
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Schneibster
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Re: Magnetics

Post by Schneibster »

And another thought about magnetics, but along a different line: aren't magnetic fields the ideal way to extract energy from the reactor?
We need a directorate of science, and we need it to be voted on only by scientists. You don't get to vote on reality. Get over it. Elected officials that deny the findings of the Science Directorate are subject to immediate impeachment for incompetence.

D Tibbets
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Re: Magnetics

Post by D Tibbets »

Magnetic reconnection, instabilities, macro instabilities, pinches, etc. are all related to magnetic instabilities. Basically, when a stress is created the morphology of the plasma/ magnetic field interaction changes.
If this new morphology is more stable , the instability will grow, with each stage being more stable= ie: the potential enegy of the local interaction will decrease. This means that the reaction is exothermic, energy is released from the system and thus the reaction is progressive until an endpoint is reached- such as a pinch, it is a down hill process from a system energy standpoint.

In a Polywell, the argument is that the opposite is the case. Because the magnetic fieldsfrom the electromagnets are always convex towards the center or the contained non magnatized plasma, and perturbation that starts from various interactions actually increases the potential energy. The reaction requires the input of additional energy to progress. Because of this the tendancy is for the plasma - B field local disturbance to relax back to a lower energy state. This natural stability is nice as it apparently makes the control of the plasma much easier. In a Tokamak the unstable boundary conditions tend to go boom (litterally- not enough to destroy the robust machine, but enough to greatly shorten it's lifetime, and of course loose containment energy). Part of the current Tokemak efforts is to control these instabilities in real time with sophisticated interventions that are very complex.

I have read in two plasma physics texts describing this instability problem that occurs anywhere the border between the plasma and the B field is concave. In one text I did need to twist their perspective from plasma located outside of a field line to the general Polywell perspective of plasma inside a field line to clear up the description for me. You could talk about up scattered plasma that may penetrate further into the electromagnet B field beyond the Wiffleball border, and thus for this local plasma the field lines nearer the center are concave. But the saving grace is presumably that this plasma represents a tiny fraction of the total plasma, most of which is inside the Wiffleball and thus not exposed to B fields, except for the electrons at their turn around point where the electromagnet B field lines are convex towards the charged particles of interest.

The Tokamak and other magnatized plasmas have their own plasma induced gross magnetic field, in addition to the confining electromagnet B fields. I imagine this makes not only the border region susceptible to growing instabilities, but also deeper within the magnetized plasma. I'm not sure how much of a problem this plasma induced B field is from the perspective of instabilities, compared to the border conditions, but it is possibly another item of concern that the Polywell is supposedly immune to as the vast majority of the plasma is not magnatized.

The Polywell B field can be concave towards the center, but only at radii beyond the mid plane of the magnets. Here magnetic containment is already lost so it is essentially meaningless. Note though that when you look at the localized plasma (mostly electrons) in the cusps the B field lines are still convex towards the local plasma. I assume that electron recirculation is thus also mostly (?) immune to this instability.

A good analogy may be a drop of water. With a concave surface facing up, any water on the underside of the surface will collect towards one spot and form a drop which falls due to gravity. At any time as the drop forms the potential energy is reduced, it is an energy favorable condition for the drop formation to progress. If the surface is convex towards top, any water on the underside will tend to run away towards the edge, Ignoring the edges, the water will not form drops because it is energetically unfavorable. The edges can be viewed as the cusps. Thus cusp losses will greatly dominate over any instabilities. If you can control the cusp losses adequately, surface instabilities are of zero or minimal concern.

Dan Tibbets
To error is human... and I'm very human.

D Tibbets
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Re: Magnetics

Post by D Tibbets »

As for magnetic fields generating electricity, the current producing the magnetic field (fusion plasma stream) has to be alternating or pulsating. It is the changing magnetic field that transfers the energy. If you hook up the primary leads of a transformer to a DC source, the secondary leads will just sit there and look at you. The primary current has to be changing- magnetic field changing, which induces the current in the secondary.
Fusion schemes that pulsate rapidly would lend themselves to this conversion method. The Dense Plasma Focus, possibly a pulsating FRC system would work well with this conversion scheme. But the Polywell is envisioned as a steady state, constant current DC source. Transformers wont work. Here the kinetic energy of the particles need to be converted to useful electricity though deceleration grids , much like an CRT television tube in reverse. If the Polywell is pulsed, then transformers may be useful. In fact using some type of high voltage switching equipment down stream may be needed to convert the Polywell DC output into an alternating current so that step down transformers can be used. The alternative is to just let the highly energetic fusion ions (or neutrons) hit a surface and produce heat, and generate electricity through a steam cycle. But, there are several reasons why this is a poor alternative.

Dan Tibbets
To error is human... and I'm very human.

Schneibster
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Re: Magnetics

Post by Schneibster »

D Tibbets wrote:As for magnetic fields generating electricity, the current producing the magnetic field (fusion plasma stream) has to be alternating or pulsating.
Well, it has to be changing. From the POV of the E field at a fixed point, yes, it will alternate or pulse, as you prefer.
D Tibbets wrote:It is the changing magnetic field that transfers the energy. If you hook up the primary leads of a transformer to a DC source, the secondary leads will just sit there and look at you. The primary current has to be changing- magnetic field changing, which induces the current in the secondary.
:D Well actually I think that the Ćuk converter is the closest you can come to a true DC-DC transformer. As you increase the frequency the output voltage comes nearer and nearer to DC.

You're in my territory, now, EE.

The easiest way to think of it is that the E field moves electrons when it moves; to visualize it, think of lines of magnetic force, moving as the B field (which is associated with changes in the E field, which we already said is moving) changes, sweeping electrons along, if there is a conductive path for them.
D Tibbets wrote:Fusion schemes that pulsate rapidly would lend themselves to this conversion method. The Dense Plasma Focus, possibly a pulsating FRC system would work well with this conversion scheme.
Those guys with the plasma toroids, too. I got a link somewhere. They went quiet a while back.

Because of the nature of switching power converters, I have always expected that if pulsed fusion were what worked, then switchers would be the way the power would be converted to something usable instead of something that would blow out the headlights.
D Tibbets wrote:But the Polywell is envisioned as a steady state, constant current DC source. Transformers wont work. Here the kinetic energy of the particles need to be converted to useful electricity though deceleration grids , much like an CRT television tube in reverse. If the Polywell is pulsed, then transformers may be useful. In fact using some type of high voltage switching equipment down stream may be needed to convert the Polywell DC output into an alternating current so that step down transformers can be used. The alternative is to just let the highly energetic fusion ions (or neutrons) hit a surface and produce heat, and generate electricity through a steam cycle. But, there are several reasons why this is a poor alternative.

Dan Tibbets
I think you've misunderstood me: if a reconnection event happens in an "operating" polywell I expect melted copper. It's not a desirable thing, it's a problem to be avoided.

My second post doesn't really have anything to do with the first; the subject of the thread is "Magnetics" and I expect to ask a lot of different questions about the magnetics of the polywell. You have mashed them up together, but they weren't meant that way. They're two completely separate standalone ideas. And the first one is not about how to make the polywell better; it's about a thing that could make it not work at all if you don't watch out for it. The second is about a completely separate subject, how to extract power from it. I still suggest magnetics may hold the key; they can penetrate the structure where electric fields are stymied, and can also extract energy from charged accelerated particles.

Sorry perhaps I was unclear. It seems that way. Part of your response made sense.
We need a directorate of science, and we need it to be voted on only by scientists. You don't get to vote on reality. Get over it. Elected officials that deny the findings of the Science Directorate are subject to immediate impeachment for incompetence.

Schneibster
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Re: Magnetics

Post by Schneibster »

D Tibbets wrote:Magnetic reconnection, instabilities, macro instabilities, pinches, etc. are all related to magnetic instabilities. Basically, when a stress is created the morphology of the plasma/ magnetic field interaction changes.
If this new morphology is more stable , the instability will grow, with each stage being more stable= ie: the potential enegy of the local interaction will decrease. This means that the reaction is exothermic, energy is released from the system and thus the reaction is progressive until an endpoint is reached- such as a pinch, it is a down hill process from a system energy standpoint.
Yes, yes, yes, and all these are defects, where the polywell is concerned. That's what I was saying.

I read the rest of this and it's all based on that same misunderstanding.

I repeat, there is no external apparent change until one of these effects takes over, and then it burns your coil.

I notice you guys keep burning coils. Just sayin'.

Sorry to be abrupt, but I'm considerably more knowledgeable than you appear to think. Please don't treat me like an idiot; it's irritating.

For that matter I can't even get an answer to why the patent wasn't granted. So two great mysteries now surround the polywell.

I'm kidding but only barely. C'mon, man.
We need a directorate of science, and we need it to be voted on only by scientists. You don't get to vote on reality. Get over it. Elected officials that deny the findings of the Science Directorate are subject to immediate impeachment for incompetence.

Schneibster
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Re: Magnetics

Post by Schneibster »

Now back to reality, so you're saying you expect to extract power from the polywell by capturing/trapping/absorbing/whatever the ions, mostly alpha particles I presume, that escape through the corners?
We need a directorate of science, and we need it to be voted on only by scientists. You don't get to vote on reality. Get over it. Elected officials that deny the findings of the Science Directorate are subject to immediate impeachment for incompetence.

Stubby
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Re: Magnetics

Post by Stubby »

The best answer to why there is no patent is that it is not proven to work.
IE no net power.
IIRC the patent office wont touch a nuclear patent without net power production
Everything is bullshit unless proven otherwise. -A.C. Beddoe

hanelyp
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Re: Magnetics

Post by hanelyp »

If only patents if general were held to a similar standard of demonstrated operation...
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Schneibster
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Re: Magnetics

Post by Schneibster »

Stubby wrote:The best answer to why there is no patent is that it is not proven to work.
IE no net power.
IIRC the patent office wont touch a nuclear patent without net power production
Likely due to attempted LENR patents without production and perpetual motion machines and so forth.

Sure hope the 7th power scaling turns out to be right.
We need a directorate of science, and we need it to be voted on only by scientists. You don't get to vote on reality. Get over it. Elected officials that deny the findings of the Science Directorate are subject to immediate impeachment for incompetence.

GIThruster
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Re: Magnetics

Post by GIThruster »

Stubby wrote:The best answer to why there is no patent is that it is not proven to work.
This is a common misunderstanding. Whether something works or not is seldom the deciding factor whether to issue a patent. Some patent examiners will refuse a patent because they think it cannot work, but there are many thousands of US patents issued on supposed inventions that not only have never been tested, but in theory violate the simplest physics like conservation laws. this is why it is not useful to look for a patent when searching for emergent technology. The only utility in a patent is that one has control over whom gets research and commercial licenses so has a measure of control over development and future finance.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

D Tibbets
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Re: Magnetics

Post by D Tibbets »

There seems to be some narrow vision about the Fusion machines and the Polywell in particular. In machines that are susceptible to macro instabilities, such as Tokamaks, these pinches, etc are indeed very challenging to monitor and control. The point is that in the Polywell the geometry of the magnetic fields in relation to the plasma is inherently stable. Instabilities are non existent from a theoretical standpoint, though admittedly this would need to be confirmed experimentally and I don't know to what extent this was done. Macro instabilities can release a fair amount of stored energy (either hot plasma or through magnetic reconnection?) and can stress structures, at least with repeated exposure. The electromagnet burnout that destroyed a magnet in WB6 had nothing to do with magnetics directly*. It was a wearing away of the electrical wire insulation between the wires and the can surface with the high voltage of the magrid magnet cans. It was a simple short. There was ~ 12,000 volts differential here and only the transformer wire varnish insulation and presumably several sheets of mylar for insulation.

The electric field certainly responds/ is created by, etc by moving charged particles. But to induce a current in an adjacent wire through a magnetic coupled system the magnetic field has to change (collapse or expand) I'm am impressed by the intricacies of transformer design as it is not simple. There are many complexities such a historesis, etc. And certainly any transformer, wire or electronic component is going to have some capacitance and/ or inductance properties depending on the nature of the current, and certainly small capacitance at very high frequency can effectively filter a pulsating current or possibly even act as a blocking filter. All of this is in the realm of the electrical engineer, etc...

The principles of gross operation though is straight forward. If you wish to convert the KE of a particle you let it hit something and harvest the heat energy produced. With moving charged particles you can also harvest the energy more directly by decelerating the particles, which is what Polywell direct conversion is all about. It could work with constant DC current (charged particle flow) or variable. And with variable flow, transformer like effects can also be utilized, perhaps to the exclusion of electrostatic deceleration. The final choices are dependent on the ion/ electron flow characteristics and various engineering tradeoffs. Keep in mind that both electrons and ions are mobile charge carriers in this situation, it is not only the electrons- which are the only charge carriers in classic copper wire interpretations.

The goal of alphas for direct conversion, whether it is electrostatic or magnetic mediated, is simple. In the ideal proton - Boron11 reactor essentially all of the fusion energy is carried by the produced charged alpha particles, and thus all of the KE is susceptible to direct conversion at what ever efficiency you can manage (perhaps as high as 90%). The remaining KE ends up as heat which has to be removed, but it may not be worth the effort of transferring that heat to a massive and expensive steam plant. Not only is the conversion 2-3 times greater per unit of fusion energy, but the cost may also be smaller.
D-D or D-T fusion might also lend itself to direct conversion but as 50% or more of the fusion KE is bound to neutrons and neutrons are not effected by magnetic or electrostatic fields, they can only release their KE by hitting something directly- heat. The fusion charged particles that are created may or may not be as well behaved as the alphas from a P-B11 Polywell, they may have more variation in charged particle speeds, complicating the efficient direct conversion. Also, the percentage of the fusion energy that can be harvested directly is only ~50% at best, due to those pesky neutrons. Or not so pesky, if you are also needing to generate new tritiums.

In any commercial fusion reactor heat management will be high on the list of engineering challenges. The advantages of direct conversion of some or most of the energy may lessen the cooling concerns, may lessen or eliminate the need for a steam plant and turbines, and also greatly decrease the costs associated with those systems. Also, where Q is marginal, direct conversion schemes may be essential. In the DPF and perhaps in the FRC direct conversion of the plasma energy may be needed for profitable operation. Even the X-rays from Bremsstruhlung may need to be direct converted (as in the DPF, at least for burning P-B11 fuel).

* While the magnetic fields did not directly lead to the short in WB6, it was the variation on the fields (when the magnets were turned on and off for each test) that shifted the wires and is presumed to have worn away the insulation until insulation breakdown occurred and at 12,000 volts and with thousands of amps (or should I say Coulombs) stored in the capacitors, progressive failure and rapid heating quickly fried the electromagnet, at least locally. WB6 was a quick and cheap construction with little margin for error, that was built at the end of contract and money reserves in Bussard's final efforts to apply what he/ they had learned from previous experiments.


Dan Tibbets
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Schneibster
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Re: Magnetics

Post by Schneibster »

Thanks, Dan, fantastic. I'll probably have some questions when I've had time to digest this.
We need a directorate of science, and we need it to be voted on only by scientists. You don't get to vote on reality. Get over it. Elected officials that deny the findings of the Science Directorate are subject to immediate impeachment for incompetence.

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