Posted on 01/10/2006 6:15:20 PM PST by PatrickHenry
Can the popping of tiny bubbles trigger nuclear fusion, a potential source of almost unlimited energy? This controversial idea is back on the table, because its main proponent has new results that, he claims, will silence critics. But others say that the latest experiment simply comes with its own set of problems.
The idea is simple enough. Blast a liquid with waves of ultrasound and tiny bubbles of gas are created, which release a burst of heat and light when they implode. The core of the bubble reaches 15,000° C, hot enough to wrench molecules apart. Physicists have even suggested that the intense conditions of this sonoluminescence could fuse atomic nuclei together, in the same process that keeps our Sun running.
Physicist Rusi Taleyarkhan of Purdue University in West Lafayette, Indiana, published the first evidence1 of this 'sonofusion' in 2002; he has been dogged by sceptics ever since.
The underlying physics behind the idea is valid, says Ken Suslick. An expert in sonoluminescence at the University of Illinois in Urbana-Champaign, Suslick tried and failed to replicate Taleyarkhan's first results. If the bubbles' collapse is sufficiently intense, it should indeed be able to crush atoms together. Taleyarkhan just hasn't done enough to prove it, says Suslick.
Needle in a haystack
Taleyarkhan's first experiments were conducted while he was based at Oak Ridge National Laboratory in Tennessee. His idea was to use liquid acetone in which hydrogen atoms had been replaced by their heavier brethren, deuterium. When deuterium nuclei fuse together, they emit a characteristic burst of neutrons. But critics pointed out that Taleyarkhan was using an external source of neutrons to 'seed' the bubbles, and that these were swamping his measurements of neutrons produced by the fusion reaction itself.
"This time round there are no external neutrons," he explains. Instead, his team loaded a mixture of deuterated acetone and benzene with a uranium salt. As the uranium undergoes radioactive decay it releases alpha particles, which can also seed bubble formation, says Taleyarkhan.
"In this experiment we use three independent neutron detectors and a gamma-ray detector," he adds. The results from the four instruments prove that fusion is happening inside his experiment, asserts Taleyarkhan.
Although uranium can release neutrons during fission reactions, Taleyarkhan rules them out because the neutrons he finds bear the energetic hallmark of having come from the fusion of two deuterium nuclei2.
Taleyarkhan's test reactor still puts out a lot less energy than it takes in, making it impractical for generating power. "We have a way to go before we break even," he admits. But in the meantime, he adds, it could be a cheap source of neutrons for analysing the structure of materials. The results are to be published in Physical Review Letters in a few weeks' time.
Unreliable sources
There is one big problem, however: the experiment doesn't always work, and the group is not sure why. Seth Putterman, a physicist at the University of California, Los Angeles, who has also tried to verify some of Taleyarkhan's experiments, notes that the paper does not reveal how many failed runs were required before the team saw a trace of fusion neutrons. "As a paper it doesn't convince me," says Putterman.
Putterman notes that the team did not continuously monitor background neutron levels. 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. "The key to improving the signal is timing," says Putterman.
Finding proof
Another obvious way to confirm that fusion is happening would be to look for tritium, a heavier isotope of hydrogen produced by fusion reactions. Tritium leaves a telltale signature of high-energy electrons when it decays and Taleyarkhan claimed to see this in similar previous experiments1,3. But in the current tests, tritium's signature is overwhelmed by ?-decay from the uranium, making it impossible to spot.
Given that Suslick and Putterman have both investigated Taleyarkhan's past claims, they think it odd that they were not consulted by the editors of Physical Review Letters about the paper. "There are other people who are very knowledgeable about this," comments Martin Blume, editor-in-chief of the American Physical Society.
Taleyarkhan says that Suslick and Putterman are welcome to visit his lab to see the results for themselves. Both are eager to go as soon as possible. "We look forward to seeing the experiment run," says Putterman.
[Footnotes are at the end of the original article.]
In order to be more popular they nowadays print many strange things both in Nature and in New Scientist. The latter wrote "Take a leap into hyperspace" http://www.newscientist.com/channel/fundamentals/mg18925331.200 with high crackpot index scores. It is sad that just a few days after the Physics year these things are published.
Yeah, Something about, how much Lucky/Fun/Profitable it was to work @ the plant, painting the watch dial for 5$ (L1920s/E1930s Great pay!) a day.
..."You tip the paint brush in your mouth."
Radium Paint....YIKES...the pic. were horrible/gross.
But, as despite the title, this isn't really "cold fusion." It's hot fusion in little collapsing bubbles.
Maybe I am missing the point here. A science article is going to be published in a supposedly reputable journal, it cannot be replicated, there is a selective peer review, it is hot fusion and not cold fusion as the title suggests, and this is not a problem? I guess my research experience and striving for integrity in publications does not apply in this field. (Not trying to be sarcastic. LOL!)
There is skepticism of Taleyarkhan's results, yes. People who have expressed same regarding earlier Taleyarkhan studies were disappointed at not being in the peer review process this time, yes.
OK, you are right.
The folks (young women, mostly) who painted the watch dials used fine foxhair brushes and, to 'sharpen' the brush tip, would lick it - similar to a seamstress licking the end of a thread before attempting to insert it through a needle's eye.
Over time that constant touching of the tongue with a radium-laden brush led to cancers of the tongue, mouth and jaw. This was the first indication that radiation exposure could cause cancer.
They probably ran out of money before they could get their hands on some tritium.
Damn! You beat me to it!
Yes, the girls/women that painted the dials had the bad habit of wetting the tip of thier paint brushes with their tongues to get that fine point to the bristles..
They ingested copious amounts of radium in the process..
Radium poisoning was the result.. The symptoms were very similar to advanced / accelerated aging.. ( or possibly blood poisoning.. They looked really bad.. tubercular..)
On another line about radium, I recall that after one of the plants had been torn down, and was being leveled, bulldozer operators refused to work the site.. ( This was North Carolina, South Carolina, not sure.. )
It seems that radium dust had mixed with the sandy soil of the site, sand that contained titanium..
The pressure of the bulldozers would create an electrical discharge, and the dozer operators would recieve severe shocks, sometimes experiencing small lightning bolts crackling in the air around them..
Occassionally, heavy impacts of the dozer blades would result in the soil exploding..
I have no idea where I read this story, I have searched for the source for years.. more than a decade.. without success..
But the story has stuck in my mind..
It may be an "urban legend", I don't know..
Some pretty scary stories about the end results to the affected sailors.
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