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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!"
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?
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.
There are several "inventors" of television. For example, Zworykin is yet another one. The one you talk about depends on your nationality, I suppose.
What a load of crap. Good luck. These reactors require more energy to run than they produce. And D2 (deuterium gas) isn't cheap either. As for the oceans having enough deuterium to let us outlast the sun... cods whallop. There's obviously a mis count there, or the numbers are fudged. Maybe if you produced such a small amout of energy that one could make it last longer that's possible, but the Sun contains more matter than the rest of the solar system combined. The Earth's oceans arent' even a drop in the bucket (pardon the experssion).
The energy gain, or lack there-of, is why there are no commercial fusion reactors, energy output doesn't off-set cost and energy input. -- It's not like fusion hasn't been achieved! It has. You may even want to check out the muon catalyzed fusion reactions that were being done right up until a year or so ago at TRIUMF in BC Canada, same problems there too... and that was the most promising in a long time.
Philo T. Farnsworth was the inventor of electronic television (using something to scan the picture on to the screen line by line). Everything before that was mechanical (involving a wheel with holes in it), including Bairds.
Not noteable, IMO a rubbish article.
Matter-antimatter reactions produce gamma rays and other high-energy radiation. In order to harness this energy, you need to convert it into electricity, which requires actually absorbing the radiation. But since gamma rays laugh at lead or gold shielding and blast right through, there's a wee problem.
In contrast, the device mentioned in the article produces alpha particles (when configured appropriately, using Boron fuel). Alpha particles, if they touch metals, suck off 2 electrons to become helium atoms. This produces a net charge, and voila - electricity. The use of alpha particles in this way (such as from radioactive decay of certain isotopes) is well-tested. Since the majority (perhaps 95%) of the energy produced would be in the form of alpha particles, this type of reactor has the potential to be extremely efficient.
Regrettably, I don't have the background to determine whether it's all a crock or not. It sounds plausible, but all the best ones do. I'll believe it when it's powering my computer, but I'd donate a dollar to see if it could be done.
High-speed Road Trip (18.000KPH)
Imagine all the little kiddies with their noses practically against the screen, getting dosed with ionizing radiation all the while. Or sitting in front of it, knees up, gonads up close and unshielded. One wonders if there would be identifiable effects from this... no time to check.
Scientists restrict study to entire physical universe; creationist
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.)
Scientists restrict study to entire physical universe; creationist
Get some real information on fusion:
European Community, Fusion Programme
U.S. Fusion Energy Sciences Program
International Thermonuclear Experimental Reactor or (ITER) site
a special Canadian ITER site
This page has a lot of links to different fusion sites around the world. These websites probably contain a lot more useful information than the slashdotted article.
By the way, my university happends to have a research center on plasma physics. It's not as easy as "some basic engineering skills, this site and the inspiration necessary to make your very own 'fusor' produce more energy than it consumes" =)
I read through some of the basic info on the page (before some of it got Slashdotted) and then started reading the forums. That's when I started finding the unfortunate schwag like this thread . The problem with all of these sorts of projects is that they tend to attract nutters who think they've rewritten the laws of physics in their garage from scratch using "maths" that they just can't divulge yet because they don't quite work. Ugh. Free energy weirdos and neuvo-quantum threory weirdos - two of a kind.
Things like this always make me wonder, if an area is so promising, why aren't there any academics out there getting funding to pursue it? I mean, I realize sometimes the academic ESTABLISHMENT can be closeminded, but if something has merit, there are usually a FEW academics who will go out on a limb and pursue it to the point that they demonstrate sufficiently interesting results to build a broader base of interest. I've never honestly heard of massive numbers of academics whole-hog ignoring truly promising areas out of some misguided conspiracy bullshit, and frankly it's quite hard to imagine, since the drive for personal fame and glory usually trumps the desire to avoid stepping on toes and to "toe the line".
It sounds like there is real work yet to be done to get these things close to breakeven, and it probably ain't gonna get done in some garage project, but hey, you never know.
Baird was the first to demonstrate a working TV broadcast.
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.
This space available.
energy.
The second law is about entropy. Do you know what entropy *is*? Entropy is the law that requires heat engines to consume fuel despite conservation of energy -- and the single most misunderstood law of physics. Parent poster was right.
KFG
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).
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... legalese is not good science writing) why high energy ions would be trapped and fuse in such a modest potential well.
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
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.)
The site recommends an article from tom ligon on Analog magazine, which talks about "the simplest fusion reactor". /.ed but over free bandwidth.
Since all you slashdot readers are kinda lazy here is the google cache for the article:
link
Its pretty nice, since the tripod page linked on the site is not
My english is sow-sow. Sowhat?
www.lenr-canr.org
(please see first) www.bovik.org/codeposition
www.bovik.org/codeposition/best.gif (confirmatory experiment you can do at home for less than the cost of building a Farnsworth fusor.)
Well ... mistaking the natural background neutron flux for fusion has been a recurring theme in exotic fusion research. (A recent example is the controversy over claims by Oak Ridge scientists that miniscule amounts of fusion were being produced by sonoluminescene.)
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I have no doubt that you can make a glowing ball of plasma with this technique. It wouldn't rock my world if there was an infinitesimal amount of fusion going on. But, I don't see any reason to believe this will be the next generation power source or could be developed into one.
This isn't an out of hand dismissal of the exotic techniques; I'm much more open to wacky ideas than many of my colleagues. And I don't have a whole lot of faith in mainstream techniques for fusion becoming viable power sources either (but that is another issue).
However, the mainstream techniques have calculated the requirements needed to make a viable fusion reactor. It is neatly summarized by the Lawson criteria. By looking at Lawson criteria, you can develop different strategies for designing a fusion reactor. The strategies amount to trade offs between plasma density, plasma temperature or duration of confinement. Laser and heavy-ion inertial confinement aim for high-density but short confinement time. Magnetic confinement uses a long confinement time but a low density. And so forth
I don't see anything here to indicate this is competitive with mainstreams techniques (which are themselves already lacking) and there are obvious problems with the physics in making the reactor more practical.
But I could be wrong.
Kevin
The Farnsworth Image Dissector sensed the whole image at once, turning it into a collimated beam of electrons. But then it deflected the collimated beam over a scanning aperture, only using a tiny portion of the beam at a time. This approach is very insensitive. The incoming light energy is divided by the number of pixels. Image dissectors thus only work with brighly lit scenes. Very brightly lit scenes. Even with a big lens, you needed bright sunlight. Early versions were hopeless, but by adding some photomultiplier stages, Farnsworth managed to increase the sensitivity a bit. But it was still lousy. Image dissectors are still used today for looking into furnaces, but not for much else.
Zworklin's Iconoscope, on the other hand, accumulated light over a whole frame time, and scanned it off a photosensitive plate with a scanning electron beam. Iconoscopes didn't have a photomultiplier stage, and they, too, produced a weak signal.
After much litigation, licensing, and years of work, RCA Labs finally produced the image orthicon, a complex and expensive tube that combined the photosensitive plate of the iconoscope with the photomultiplier stages of the image dissector. This, at last, produced a usable TV camera tube.
Strangely enough, I can't find any evidence that a Farnsworth-Hirsch-Bussard reactor has ever been built or tested.