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Desktop Cold Fusion Reconsidered
Armchair Anarchist writes "Nature.com reports on Rusi Taleyarkhan of Purdue University in West Lafayette, Indiana, who is once again claiming to have achieved ultrasound-induced fusion in deuterium-enriched acetone. Other experts are sceptical, but Taleyarkhan is keen to have other scientists check his results."
"Although the neutron count doubles at some points in the experiments, Putterman says that neutrons produced in random showers of cosmic rays, rather than fusion events, could be responsible. But Taleyarkhan points out that the neutron count was smaller in detectors further from the reaction chamber.
To prove that the neutrons are coming from fusion as bubbles burst, Putterman and Suslick suggest that the team closely monitor exactly when the neutrons appear. The current experiment simply counts up the number of neutrons detected over minutes, so correlations with bubble bursts cannot be seen."
They are NOT yet sure whether the neutrons come from bubbles or from cosmic rays.
So let's not start the usual jokes about using car stereos to power cars, sound waves harming swan ears, etc.
"Doing what i can, with what i have." ~ Burt Gummer
Unjustly dismissive. First off, even initially, Taleyarkhan rallied about as much support as he did opposition. Now, even much of his initial opposition considers his work valid. Sonofusion seems to be quite a real phenominon (albeit, currently six orders of magnitude from breakeven).
Here's a very interesting paper by him in Oct. 2005, in which they discuss many of the recent developments, including the potential for nonlinear scaling of efficiency and even the possibility of criticality. It's a very interesting read.
The *special* hell.
http://www.foresight.org/Conferences/MNT05/Abstrac ts/Donoabst.html
Even the lower temperature of only77 million degrees makes 15,000 degrees look positively arctic. Being able to do it in a container without magnetic containment in a vacuumUndue harshness given the state of the literature. It *has* been reproduced extensively, so those comments are completely incorrect; the main controversy is about the level of radiation emitted. Subsequent experiments in better conditions have reduced much of the criticism.
However, good comments on fusion's radiation. Even prized "pure" fusion reactions, such as B11+p, produce nasty radiation because you get some p-p fusion, you get some of the alpha particles (He4) as fusion reactants, even a tiny B12 or Dt impurity will dramatically increase the radiation levels, and all sorts of other problems.
The good thing about radiation from fusion reactors is that the fusing materials generally aren't "hot". The only problem is that irradiation of the reactor chamber itself can leave it radioactive; however, proper selection of construction materials can ensure that it has a short halflife, making reactor part disposal much less controversial.
The *special* hell.
So, no, there is no reason for your fatalistic attitude. *Will* it pan out? Who knows, but it is definitely worth investigation, just like the concept of fission criticality was early this century.
You mean last century?
-insert a witty something-
Perhaps if the energy released was in the form of heat instead of "light" then a chain reaction could occur.
Incorrect. First off, you get light even when there is no fusion; the light is simply blackbody radiation of very hot material that was heated by the coalescing of shocks from bubble collapse in a very small region. The *fusion* gives off most of its energy as high-energy neutrons.
It's six orders of magnitude from breakeven currently, but has a lot of potential to scale up, including potential for criticality. Will it actually pan out as a valid energy source? Who knows; it's still in its infancy.
The *special* hell.
I hope it was the exploding grapes in a microwave that got modded "Informative" and not the South Park reference. :D
The Chewbacca Defense
(That link is pretty damned cool, by the way.)
DATABASE WOW WOW
Oh damn, my nocluebie-o-meter just exploded!
"If this ever did achieve better than breakeven, it would make triggering a fusion bomb much easier. Currently fission is used to trigger a fusion bomb. This might make it easier, although I doubt it would be as compact."
Stupid. The imploding fusing bubble IS the fusion "bomb"! You might also have trouble with the fact that it occurs on the MICROSCOPIC scale and you need conditions equivalent to that on the cm to METER scale to set off a conventional fusion bomb. This has absoluelty no weapons applications whatsoever.
"Even if it doesn't reach breakeven, it still has weapons potential. This thing gives off neutrons. If it's portable, it could be set up someplace and used to spray neutron radiation in a city. At low levels of efficiency, it would just be a weapon of terror. At high levels, it's a dirty bomb."
OH NOES TEH TERRORISTS, AHHH!! Even if fusion yeild were scaled up by a million fold you would have to sit right on top of the damn thing for hours in order to get any kind of noticeable dose at all. Strapping a piece of explosives to a chunk of Cs-137 from some medical deviece to make a dirty bomb would be, oh jeez I don't know, about a billion times easier and more effective!?!
Why isn't there a "clueless -1" mod?
- "Hear that?! The percolations are imminent! Cease your ingress!"
Brennen (1995), Akhatov et al (2005), and Nigmatulin et al (2005) disagree with you. The shocks converge toward the center of the bubble cluster. Also, some of the central bubbles will coalesce into larger ones, thus creating more intense implosions on their own.
The *special* hell.
My mistake - seven orders (I was typing from memory). Taleyarkhan cites Lahey et al, 2005 for that number.
The *special* hell.
I don't know where Nature got the 15,000 degree number. I've seem reports of measurements of sonoluminescence temperatures of over 100,000 K (from the spectrum, and only a lower limit because the fluid wasn't transparent to high enough frequency light). For the fusion experiments different techniques were used and temperatures of over 100M K were targeted.
The case for fusion here is perhaps not solid yet, but if it is fusion, it's hot.
a,e,i,o,u and sometimes w and y (at be if of up cwm by)
As long as the fusion is happening within water, you'll deposit some energy inside the core. But let's say you've found a way to minimize that, and you've got a surrounding chamber that can go superhot. A few issues to contend with are
1) Heat flux. How do you ensure that the sono chamber stays cool while right next to a much hotter system?
2) Neutronics/materials. The wall(s) keeping the systems from mixing are going to see a whole lot of fast neutrons, which is a big problem. You have to pick a material that holds up well under fast neutron flux + heat.
These two issues are, ironically/unsurprisingly, two of the issues "conventional" magnetic fusion faces. In such a device, you've got vacuum pumps that run at cryogenic temperatures (1), and a so-called 'first wall' that sees a whole lotta neutrons over its operating lifetime (2). Needless to say, we don't have good solutions to these problems yet.
At least according to lenr-canr.org
which is the homepage for all research activities concerning
Low Energy Nuclear Reactions and Chemically Assisted Nuclear Reactions.
The original cold fusion experiments have been successfully replicated many times over.
There are hundreds scientists around the world working in the field
To quote the webpage:
"Cold fusion was never "debunked" and even the harshest critics until now have never suggested that it was fraudulent. The cold fusion effect was replicated at high signal to noise ratios by researchers at the Naval Air Warfare Center Weapons Division at China Lake, Shell, Amoco, SRI, Texas A&M, Los Alamos, Mitsubishi Res. Center, BARC Bombay, Tsinghua U. and over a hundred other world-class laboratories."
Couple ways around this.
The obvious answer is to pressurize the water. This will increase the boiling temperature, letting you run the reactor much hotter.
Alternately, if that is impractical, run multiple cells. Each cell may only be able to put off enough heat to produce a few volts, string enough of them together, and you can put out a lot of power. With proper design, increasing capacity would be relatively simple compared to a single large reactor. On the other hand, maintenance of potentially hundereds of minireactors could be a nightmare.
Sure. The first independent confirmation was by Yiban Xu and Adam Butt at Purdue in 2005. I could probably track down all of those who have confirmed his setup if you want; it's a relatively new field, so there shouldn't be too many papers.
The *special* hell.