Graphene and Carbyne inner grid

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Brandon_Davis
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Graphene and Carbyne inner grid

Post by Brandon_Davis »

I spent the past couple days reading up on this so as not to enter this forum sounding like a complete dolt, and one of the main things i came across was an inability to reach break-even due to the inner grid. the article i read https://fusor.net/newbie/files/Ligon-QED-IE.pdf said something about the inner grid blocking a small amount of the atoms, and "dooming it to operate at no more than 0.01% break-even." I think if you used Graphene for the inner grid, it should solve the problem seeing as it is only an atom thick. it is supposedly an extreme conductor, among other things. You can find out more about it here http://www.extremetech.com/tag/graphene another one i discovered is Carbyne, which is supposedly stronger than graphene. http://www.extremetech.com/extreme/1639 ... n-graphene Think these substances could solve the problem?
The difficult we do immediately, the impossible takes a little while longer.
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Richard Hull
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Re: Graphene and Carbyne inner grid

Post by Richard Hull »

Do it and report your results! Turn you idea into a reality and run with it.

Advice flows like wind over the deck, quick and smooth, but the actual doing flows like molasses in Anarctica at midnight.

Tom Ligon's paper, to which you refer, is dated and done prior to when any amateur fusion efforts with a fusor that was successful. His figure of the absolute limit of .01% of breakeven was way off base and had no real data to back it up. Real data in current reports among the best D-D fusors is actually .000000001 of break even.

The grid, in no significant, multiple order of magnitude manner, has any real role in boosting or reducing fusion in a simple D-D fusor! Grid effects related to fusion are totally blown out of proportion. It is a non-issue.

I'll warrant that regardless of assembly, geometry, material or applied voltage no living entity will ever exceed .000001 of breakeven in an amateur D-D fusor.

Dreams come all too easy, but then we all must wake up and smell the coffee.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Dan Tibbets
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Re: Graphene and Carbyne inner grid

Post by Dan Tibbets »

Several problems with a tiny diameter carbon wire. Fusors generally operate through the thermionic emmision of electrons from the wire. This is dependant on the temperature of the wire, a adiquate power supply (to keepup) and the surface area of the wire. A carbon (graphine wire that is only a few dozen nanometers thick will decrease the number of ions hitting it and thus improve the recirculation of the ions (everything else being equal). This will improve ion efficiency- perhaps Q, but not the power out put (the amount of fusion). Because of the much smaller electron emmisions, the concentration of ions will also be much smaller. In fact I suspect that there is a direct proportion of fusion power vs the electrode wire surface area, that multiplied by the ion recirculation factor. So I suspect that some modest gains in Q might be possible, but the ground that needs to be made up is so huge that it is hopeless.

A pratical concern is the durability of the graphine wire. Yes graphine is very tough, but you are talking about an extreamly thin wire that is bombarded by extreamly energetic wires. If a graphine wire can resist 10,000 degree C ions for a significant amount of time then that is equivalent to ion bombardments at one eV. The Fusor would operate at 10-200 thousand eV or the equivalent of ~ 100 million to 2 billion degrees C. Even a very tough wire will be quickly eroded. An analogy would be using a very energetic sand blaster against thick or thin metal surfaces The only thing that will lengthen the wire lifetime is thickness. If you could increase or maintain the electron emission in the thinner wire, you could maintain the power, but this is a tradeoff with accelerated electrode (any real electrode) erosion as a function of thickness.

This also ignores the electron losses. Even if the ions can be recirculated very well, the electrons still fly straight to the walls. To have any chance you have to have high recirculation of both ions and electrons, and in typical Fusors or the Elmore Tuck Watson versions the containment of electrons and ions tend to oppose each other. Through clever manipulation of both electrostatic and magnetic fields this opposing loss structure may be overcome(or at least this the claim). There have been efforts such as the Polywell and efforts (now abondened) by some MIT graduates. Lockheed Skunk Works may also have a machine similar to the Polywell. All of these efforts are multimillion dollar projects and they have an extremely long way to go. Such work can be done at smaller scales, but this is for science, and Q will remain very small fractions. An example would be the University of Sidney (I think?).

PS: The Polywell avoids the electrode erosion problem (along with transparency issues)by using a "virtual" electrode- Cathode. There is still a physical anode, but this is hopefully adequately shielded by magnetic fields (which in terms of transparency, is like a very thin wire, but the magnetic shielding presumably is much more efficient in this regard without the penalties...).

Dan Tibbets
Gonzalo Gonzalez
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Re: Graphene and Carbyne inner grid

Post by Gonzalo Gonzalez »

"Fusors generally operate through the thermionic emmision of electrons from the wire"

I have read the material here carefully, and I do not see where there is any thermionic emission of electrons in fusors. Unlike a polywell, where trapped electrons form a virtual anode, the fusor simply has a grid with a high voltage attracting the positive ions. I don't see any mention of flying electrons in basic fusor design. I also don't think the OP was talking about "carbon wires a few dozen nanometers thick", making a mesh, I am pretty sure he was referring to a graphene shell as the target grid itself (no wires). A Graphene shell should hold be able to hold a high negative potential without flinging off electrons; Any escape of electrons from the grid seem to me like a bad thing. I see what you are saying that, despite the tremendous current densities graphene is capable of, the absolute current a graphene grid could carry is small because the thickness is negligible; but if collisions with the grid are rare enough I don't see why there would be a significant current through that grid, requiring it to have a thickness. Likewise, while any grid heats up from collisions with the positive ions. the more "transparent" the grid is the less it would heat (the less "bombardment" it would take, as most ions would miss the grid). If there were some way to make a micro-perforated spherical graphene shell, that might be the ideal anode attracting ions while hardly getting hit or heated at all. A cylinder would be much easier to make, perhaps it could be perforated by laser for additional openness. Further, an atom-thick shell, being all surface, would radiate its heat extremely well. Thinking about actual grid temperatures of existing fusors, I am enlightened by Tom ligon's statement "Let's bury this "temperature" nonsense right now ... You may be amused to know the electrons hitting the screen of the typical television set are around 200 million degrees according to this scheme". The inner grid wires used in the fusor designs here are definitely not at anything like these temperatures, or they would vaporize.
Gonzalo Gonzalez
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Re: Graphene and Carbyne inner grid

Post by Gonzalo Gonzalez »

Reading more carefully I see now where the flying electrons occur in the machines that are later refinements of the original Farnsworth design, but those electrons are not being emitted by the inner grid but rather from the outer grid. Wonder whether the original Farnsworth design might work with the right inner grid.
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