What are the latest findings in virutal cathode research?

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Scott Yannitell
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What are the latest findings in virutal cathode research?

Post by Scott Yannitell »

Hello,

Am I understanding correctly that a fusor cannot achieve net power because of the non transparency of the cathode grid? I read a long time ago that the polywell was concept that tried to capture electrons in a magnetic field in the center of the device to allow fuel ion species to flow into it. But I have not seen any news about it for some time. Last I heard electrons still got absorbed into the physical structure near the cusps.

There are a couple extra ways in which electrons can be made to fill a space. For instance: thermionic emission. I don't think thermionic emission could make for enough and a strong enough space charge to act as fuel bait so to say. What about flooding a ring shaped cavity that was coated in gold or platinium. When struck by an electron beam or uv laser, electrons could tear off of the surface providing a somewhat stronger space charge near it's surface. I suppose since any of these methods of generating space charge comes at too high of an energy cost, it would also fail to out compete a simple wire cage. What other ideas have you heard of getting electrons out of the way of a surface so that ions can be accelerated to them and not strike a material in the way? What about field emission of electrons? Of course all of these approaches would depend on a tube shaped fusor instead of a sphere. Perhaps that also is a reason it would not be beneficial.
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Liam David
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Re: What are the latest findings in virutal cathode research?

Post by Liam David »

The reasons a fusor can't achieve Q>1 don't really have anything to do with cathode transparency, per se. Of course, ions impacting the cathode and the resulting electron emission can (and do) significantly diminish efficiency by turning all that kinetic energy into heat. One could, however, envision a system where injected ions are recirculated through a low-pressure chamber for an arbitrarily long time (literally like the original fusor concepts). Ignoring any manufacturing precision-related effects that might aberrate perfectly-designed orbits (or any other non-fundamental issues), there are three fundamental limiting factors: space charge, molecular/ion/electron stopping power, and entropy.

Space charge: Deviates orbits and generally requires neutralization with electrons, which worsens the 2nd limiting factor. Ion densities without neutralization are too low to be useful for fusion.

Stopping power: In a system without negligible background gas (say, anything >1e-10 torr +- a few orders), the thick target yield equation, which takes into account the fusion cross-section and stopping power of the gas, gives a maximum Q of something like 1e-3. In a perfect vacuum with only beam-beam fusion and ignoring space charge, the stopping power of the ions+electrons on the ions limits your Q to not much more than 1e-3.

Entropy: There is some overlap with the previous point that I won't get into, but the basic idea is that there is a fundamental "force" working against you that arises from gradients in entropy within the particle phase space. Collisions will always attempt to thermalize a system, and preventing that in even the most ideal systems is very hard.


Regarding generating electrons, I haven't done the math but I think photoelectric emission from low-work function surfaces, as well as field emission enhanced by nanostructured surfaces, are among the most efficient. As for extracting them away from surfaces, you need either an electrode or space charge. Fundamentally, this is due to Gauss' law which states that electric field divergence requires local charge (div*E=rho).
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Richard Hull
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Re: What are the latest findings in virutal cathode research?

Post by Richard Hull »

Well done by Liam.

Suffice it to say, there is no path whatsoever that a purely electrostatic device will ever even approach "break even" or "ignition" No net fusion power to be found here. Tremendous energy loses are the norm. Often a billion to one net energy loss in the amateur device. Still, we do nuclear fusion.

There is little to recommend the big boy 25 billion dollar boondoggle of ITER either. Just like us, they keep doing the same thing over and over. The difference is they claim to be getting there, and they aren't! No one on earth has ever hit a net Q anywhere even slightly equal to 1.0. The recent announcement by NIF of a Q of 1.5 is a big lie, a nothing burger! The 3.5 megajoules of fusion energy from their laser blasted D-T pellet demanded that 300 megajoules of energy had to be sucked out of the local power utility for the laser's single 2.15 megajoule laser system! This "achievement" is about a 100 to one net loss! Somehow or other they try to convince us it is a big win for a few nanoseconds of fusion energy at, still, a net loss!

Fusion energy is as dead as a dodo bird for the future. Perhaps even for a very distant future.

Richard Hull
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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
Scott Yannitell
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Re: What are the latest findings in virutal cathode research?

Post by Scott Yannitell »

Thank You both for your answers. I do agree with Richard about the NIF announcement. The NIF's own website says that the driving energy is over 330 MJ I read from another source they even boosted the energy for the now famous shot result. Is there a sub forum on fusor.net for really weird ideas or is Fusor.net too grounded in reality to entertain some of the odd ideas I have come across for fusion of atomic nuclei? Maybe I poorly worded.. my request is that I am looking for a sub forum or thread to discuss solid state fusion ideas.
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Re: What are the latest findings in virutal cathode research?

Post by Frank Sanns »

Reasonable discussions can be posted in the Other Forms of Fusion area.


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Achiever's madness; when enough is still not enough. ---FS
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Putting My Data-Free Philosopher's Hat On Here...

Post by Paul_Schatzkin »

.
...based on all we know NOW...
Richard Hull wrote: Sat Jan 14, 2023 6:23 pm Fusion energy is as dead as a dodo bird for the future.
But, as stated elsewhere, what we don't know is... what we don't know.
Perhaps even for a very distant future.
Turn the telescope around... 200 years ago, who would have thought I'd be typing these words on a keyboard and they would show up on hundreds of screens scattered around the world?

200 years ago... who even knew what a keyboard was – let alone a screen!?

In other words, what we take for granted... was unknown... in the distant past.

No telling what will be discovered in the future – distant or otherwise.

--PS
Paul Schatzkin, aka "The Perfesser" – Founder and Host of Fusor.net
Author of The Boy Who Invented Television - http://farnovision.com/book.html
"Fusion is not 20 years in the future; it is 50 years in the past and we missed it."
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