Build a Nuclear Fusion Reactor at Home

FridayBob writes "For those of you tired of waiting around for someone else to achieve the holy grail of physics, now's your chance to beat 'em all to it. All you need is some basic engineering skills, this site and the inspiration necessary to make your very own 'fusor' produce more energy than it consumes. Hopefully, you'll have more luck than its inventor, Philo T. Farnsworth, who first built it in the 1950's after inventing the television some 30 years earlier. If you run into problems you'll be able to count on a enthusiastic support group, as the contraption seems to have developed a cult following over the past few years. Okay, so I'm skeptical that this approach will ever really work, but at the very least it sounds like a really cool science project!"

Comments

But,,,

[unterderbrucke]

There was a kid who tried building a reactor once for his Boy Scout merit badge, and he got arrested for it. Do you want to risk that?

From their newbie page

[McCrapDeluxe]

But the most compelling promise of fusion is in the fuel itself: fusion is produced from an isotope of hydrogen called deuterium, which exists in the Earth's oceans in sufficient abundance to supply the planet's energy needs for hundreds of millions of years - until long after the Sun itself has flamed out.
The sun is supposed to burn out in 5 billion years, I believe.

CO2 isn't dirty either

[Spamalamadingdong]

but coal ash is. Currently, aside from the proton/boron-11 reaction (which yields 3 alpha particles) and deuterium-He3, I'm unaware of any fusion reaction which does not yield high-energy neutrons. The neutrons from deuterium-tritium fusion come out at 14.1 MeV, I don't recall the value for D-D fusion (which yields helium-3 and a neutron). High-energy neutrons create radioactive stuff by transmuting other nuclei.

The current state of fusion energy is pretty bad (way below a self-sustaining reaction) but this could still be used as a neutron source to drive a sub-critical fusion-fission reactor. Anyone who opposes fission power because of the spent-fuel issue wouldn't find this to be an improvement. (I would, because high-energy neutrons would be useful for transmuting fission products themselves, extracting their remnant energy and transforming them into stable isotopes. But I'm a geek and a technophile.)

Re:Inventor of television?

[rodgerd]

Baird was the first to demonstrate a working TV broadcast.

Re:Inventor of television?

[Jafafa Hots]

Zworykin or however its spelled stole his ideas from Farnsworth. Baird invented a mechanical TV system, which had very limited potential. Farnsworth invented electronic TV. He is the inventor of what everyone knows as TV, specifically he came up with the idea of scanning lines on a CRT to produce the image. The only practical way to have TV.

Dobutful ... I read through the patent

[Doctor K]

So I read through the patent and I've seen talks on electrostatic confinement fusion at plasma physics conferences (plasma physics is once again my day job).

I'm quite doubtful. My objection can be explained by looking at Figure 2 of the Hirsch and Meeks patent linked to through the fusor.net site.

You need accelerate the ions to high energy (or equivalently heat the ions to high temperatures) so that they will collide and fuse. If the energy is too low, electrostatic repulsion will prevent the nuclei from getting close enough to let the strong force do its work.

So what is my objection with Figure 2?

To confine a plasma with sufficient energy to have respectable amounts of fusion requires very high potentials (think many mega-volt DC potentials) to trap the ions if you are doing it electrostatically. If the potential barrier isn't high enough, the ions will escape the reactor without fusing---you dump all this energy into the ions and they just leave, taking your energy with them ...

For an electrostatic confinement system, you would need confining potentials comparable to the height of the nuclear electrostatic repulsion barrier (for the ions to fuse, they need to have energies higher than the nuclear electrostatic repulsion barrier but below the reactor electrostatic confinement barrier).

Figure 2 is the potential distribution for the reactor. The potentials are a couple _thousand_ times too small to have any chance of confining fusion capable ions. At no point in the patent was it explained (clearly ... legalese is not good science writing) why high energy ions would be trapped and fuse in such a modest potential well.

Kevin

P.S. Furthermore, a purely electrostatic confining potential is not allowed by Poisson's equation (the equation governing electrostatics), as is taught in any first year college physics class. The quick explanation is that Gauss's law implies the existance of a charge in the potential well. But if you are trying to make a trap to isolate a particle, that is exactly what you don't want in your well. For example, Penning traps use a combination of electrostatic confinement (confinement at the end-caps) and magnetic fields (radial confinement). However, I'll give them the benefit of the doubt as this appears to be relying on dynamic effects virtual cathode/anode effects. (Actually, much of the initial modeling of virtual cathodes was done by my thesis advisor in the 1960s.)