Questions Regarding Nuclear Fusion

jim hardy

i meant - hot fusion isn't making any electricity either. And, well, i wanted to not sound like a commercial for the site.
I didn't quite know how to take your statement about 'practical...tabletop fusion...' whether you were dismissing it or pointing that fact out.
i am aspergers positive so you have to be blunt with me.

Still it's a hobby site.
Not to disrespect hobbyists for after all they are responsible for most innovation.
They love what they are doing and will pour their souls into their avocation. Einstein, Wright Bros, Lindbergh and Steve Jobs all had day jobs..

Get your National Parks map.. It's almost halfway between West Yellowstone and Craters of the Moon.
Near Craters of the Moon is Arco Idaho and the expeimental breeder reactor that ran in 1950s. Another worthwhile visit.
A local eatery features the "Atomic Burger" in honor of Arco's being first civilian use of nuclear generated electricity.


Best of luck with your fusor.
Mine is just a daydream and some parts in a box.

Drakkith

I mean that a fusor will not be producing electricity in its current form. Either shielding the grids or removing them is required in order to reduce the losses incurred by the grid. You are correct in that magnetic confinement and inertial confinement have yet to produce power, however both of those have shown extensive work and improvement and could be said to be technically feasible. A standard fusor is not. Unless you just want a small device capable of producing neutrons.



I have no idea what your getting at. Where did you get any of this from us saying cold fusion isn't possible?


Nice! I'll have to remember to eat there one day. My fusor is some parts in my closet at the moment lol. Maybe one day...

jim hardy

i guess i'd lumped cold fusion hobbyists and fusor hobbyists together because they're both outside the mainstream research community......

as you observed they are quite different processes.

Direct collection of charge from a fusor could be that crazy breakthrough.


old jim

Drakkith

What do you mean? Breakthrough for what?

jim hardy

from your earlier post -

""The fusor has commercial uses as a neutron source, but unless some kind of crazy breakthrough comes along it will never provide anywhere close to breakeven power.""

the fused nuclei should be highly energetic, like mev,
if they could be collected as a small current at preposterously high voltage
the product V X I would be significant

i mention more in jest than any seriousness that a Tesla coil run backwards might be an approach.
But we're getting into Doc Brown and Flux Capacitor realm here, so i'll save my ramblings for a science fiction thread.

old jim

Drakkith

Well, the problem with a fusor is that many of the ions or electrons will collide with the grid and be lost. (In addition to causing it to deteriorate over time) It just isn't possible to hit breakeven with a standard grid in a fusor. That is why several other things are being tried, such as the polywell. The polywell is similar to a fusor, except that the grid is magnetically shielded so that the electrons are confined in the middle and any that leak out of the confinement are attracted to the positive voltage of the grid and re-enter instead of simply being lost. The magnets confine the electrons and keep them from impacting the grid. That to me is the kind of "breakthrough" that might make a fusor work. Even if it isn't called a fusor anymore.

Edit: It looks like you are proposing a power generation method known as Direct Conversion, where high velocity positive ions are slowed down and their energy is converted directly to electricity instead of being converted to heat and then to electricity.

cmb

That's one of the problems, but I'm not aware of any evidence that it is the most significant problem.

The ions form visible ion channels in the most energetically favourable regions of the e-field (between the grid wires). Those ion channels will undergo thermalisation (up and down scattering) and so some will be able to make it to the grounded shell, and collide with the shell where they generate secondary electrons, causing more ionisation at the ends of the beams, causing more ions in those particular ion channels. There is a self-generating nature to ions in the beam channels that miss the grids.

Ions formed elsewhere that do go on to strike the grid are short-lived and do not go on to generate further ions.

The main loss appears to be electrons - albeit from the grid wires. A fusor is a big 'discharge lamp' (then 'thermionic diode' once the grid heats up enough), and it is allowing (rather than blocking) electron current flow from the cathode to the grounded anode shell. It is a continuous current dump through a diode. This would appear to be the biggest source of energy loss.

Farnsworth's first designs (and subsequently Elmore-Tuck-Watson, design) worked off his observations of his electronic TV that electrons could be caused to multi-pact centrally. So the original fusor design was to generate a cloud of electrons which attracted the ions in. It didn't generate fusion. Nor did the ETW design (double potential well, no grid). Nor has Bussard's 'Polywell' yet reported any evidence of 'convergence' fusion*. Nor did LANL's Penning Trap fusion idea. Clearly, if you use electrons to pull in ions, it is like using a kid's toy crane to lift up a shipping container - it's not the shipping container that moves!!

*(the sum total of publically reported fusion in the Bussard Polywell is 3 clicks on a neutron detector - a thorough analysis of the origin of which has not been published)

The 'fusor' didn't start emitting neutrons until Hirsch came along and suggested using a physical grid to prove the convergence concept worked at all. And, actually, it doesn't anyway (!) because the fusions in a fusor actually come mainly from the fast ions colliding with the background neutral gases. The number of fast-fast ion collisions in a fusor is a tiny %.

So removal of the central grid of a fusor appears (to me, at least, though the 'intuitive' conclusion that the grid is 'the problem' seems very well entrenched now) does not appear to either a) be a route to avoiding all but a small %age of the losses, b) be possible anyway.