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Amateur Scientists Seek Fusion Reaction
ElvaWSJ writes "A small subculture of amateur physicists and science-fiction fans — fewer than 100 worldwide — are building working nuclear-fusion reactors at home. The designs are based on the work of Philo T. Farnsworth, an inventor of television, from the 1960s. Some of these hobbyists hope similar reactors can one day power the planet, but so far they consume more energy than they create."
Does anyone remember the "radioactive boyscout"?
David Hahn to make his own reactor (breeder, i think). He accumulated quantities of radium and tritium from smoke detectors and lantern mantles in a shed. The DOE had to lock down his parents whole house and yard to clean it up.
David Haun
No, this really works as advertised. It's a high school science faire level of complexity and cost (if you're willing to deal with stray neutrons). For practical reasons, it can't be made to produce more energy than it consumes, is all. The principles have been known since the 20s. Robert Bussard (of Bussard Ramjet fame) had patents on it.
But the stray neutrons (or other energetic particles, depending on the reaction) are the real problem with fusion as a power source. To quote TFA:
Fusion advocates say reactors would be relatively clean, generating virtually no air pollution and little long-lived radioactive waste. Today's nuclear power plants, in contrast, are fission-based, meaning they split atoms and create a highly radioactive waste that can take millennia to decompose.
The spent fuel from a fission reactor is just not that hard to deal with - park it in a contianment area as robust as the reactor itself for 5-10 years, and you're left with not-very-much not-very-radioactive waste that could be easily disposed of, if it weren't so valuable that we insist on keeping it instead.
It's the rest of the reactor that's the serious problem. Depending on the reactor design, quite a bit of the reactor structure can become radioactive over time.
Fusion is going to have the same problem. Even if you have a reactor vessel the size of a washing machine, you're going to need significant shielding, an energy transfer mechanism (water leading to a turbine or something), structural elements, etc. Surem the problem with spent fuel goes away, but the problem with speant reactors remains. Not something you'd want in everyone's basement.
Socialism: a lie told by totalitarians and believed by fools.
Are these the same yahoos that post videos of "perpetual" motion machines on Youtube?
No. Wikipedia is your friend.
Farnsworth - Hirsch - Meeks fusors are quite real and effective. They're easy to build even by hobbyists using readily obtainable parts. Commercial versions serve as controllable neutron sources. Fusion neutron output of up to a trillion per second has been reported and rates in the billions per second are easily obtainable. To date it is estimated that Farnsworth-Hirsch-Meeks fusors have produced far more total fusion neutrons than all other non-bomb fusion devices combined.
Downside is that they involve ions moving in a trajectory past a metal electrode, which they must pass without hitting many thousands of times on the average before they participate in a fusion reaction. Hitting the electrode loses the energy used to create the ion and attempt to confine it, dumping the energy as heat in the electrode. Getting the electrode to be sufficiently "transparent" to achieve breakeven seems to be a lost cause.
Bussard's family of Polywell fusion machine designs apparently started as an attempt to steer the ions around the inner electrode of a Farnsworth-Hirsch-Meeks machine using a magnetic field. But it has since developed into a different (though related) principle: Use the magnetic field from the self-shielding magnet/electrodes to confine electrons (which are much easier to handle), creating a high-density space charge in the center of the machine. Use the electrostatic field of the electrons to attract and confine the ions in this region at high density and temperature, resulting in fusion. The magnetic field still shields the inner structures and the field is convex toward the plasma, limiting the plasma instabilities the plague "conventional" fusion machines.
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" The designs are based on the work of Albert Michelson, co-proponent of luminiferous aether theory, from the 1890s."
It's worth reminding people that, whatever his original views of luminiferous aether, Michelson was one of the great experimentalists of the 19th century and his name is most firmly associated with the experiment that's widely credited with experimentaly destroying the credibility of aether theories.
(It's still possible to come up with aether theories even with the Michelson-Morley results (and the results of hundreds of other people who replicated and refined that result), but it's much more difficult, and the resulting theories end up rather hard to credit.) I assume that the original use of the word "proponent" was a typo).
http://www.geoffreylandis.com
Robert Bussard (of Bussard Ramjet fame) had patents on it.
The patents apply to a fancier version called the Polywell. Polywell attempts to cut losses to the point where net power is possible. As far as I know, no hobbyist has attempted that one yet. It's a much more expensive design that, depending on the fuel, would generate truly lethal doses of neutrons, and would need lots of shielding.
But the stray neutrons (or other energetic particles, depending on the reaction) are the real problem with fusion as a power source.
That actually depends on what your fuel source is. The common science fair level project uses hydrogen (not deuterium, even), and produces, IIRC, neutrons. There are other fuels possible, and some don't produce much of anything nasty. IIRC, Lithium 3 on one side and Lithium 4 on the other produces stable helium isotopes, and electricity, and absolutely nothing else.
There are still issues with fuel that misses other fuel striking internal components of the reaction chamber, which can produce some radioactivity, but getting to the self-sustaining point will also greatly reduce this sorts of unwanted collisions and ther resulting radioactive byproducts.
Actually, Bussard was trying to use a Boron-11 fuel matrix that doesn't release neutrons in the same fashion as Deuterium fusion does. One of the reasons for this is precisely to help cut down on the neutron flux coming from the reactor.
His design goal was to use it as a direct drop-in replacement for boilers at coal-fired power plants, using similar sorts of shielding and precautions as would be already in place for such a facility. Water in the boiler itself would offer what extra protection would be needed, and radiation levels for released radioactive products would be lower than would be typical for a coal plant as well.
FYI, coal plants release far more radioactive waste per kWh generated than the worst and most inefficient nuclear power plants... with perhaps the singlar exception of Chernobyl. Even that I'm not 100% certain of.
This said, you are correct that the fusion rate in a Polywell is something of a much greater concern if you actually got one going, and would be leathal if it used traditional fusion fuel targets.