WASHINGTON -- A phenomenon that may be nuclear fusion was created in a laboratory bottle by researchers who zapped tiny dissolved bubbles with sound waves, which triggered a flash of light and a brief surge of superhigh temperatures.
Using a device described as the size of three stacked coffee cups, researchers at Oak Ridge National Laboratory and Rensselaer Polytechnic Institute say the phenomenon was like nuclear fusion in a bottle. Some scientists disputed the claim.
The study appears this week in the journal Science and was released for publication by the journal on Monday.
Researchers at Oak Ridge said the experiment, which they called "bubble fusion," created two signs of nuclear fusion: a burst of subatomic particles called neutrons and the production of tritium, an isotope of hydrogen.
In an unusual additional review, however, two other Oak Ridge researchers said the experiment's results were not accurate. This additional report was posted on the Internet by Science, along with a response by the original authors.
Harnessing nuclear fusion, the power that lights the sun, has long been a goal of researchers who view it as the ultimate energy source. Most researchers have concentrated on huge machines that mimic the sun by compressing hydrogen plasma and heating it to millions of degrees to force atoms to fuse. This reaction gives off heat and an isotope of helium, along with some subatomic particles.
In the experiment reported in Science, researchers used the simple equipment to create and analyze a brief flash and burst of heat that may be fusion.
R. P. Taleyarkhan of Oak Ridge, the first author of the study, said in Science that the experiment is true "tabletop physics," using an apparatus "the size of three coffee cups stacked on top of the other."
Richard Lahey Jr., a Rensselaer professor and a co-author of the study, said in a statement it was not clear whether the technique could be used as an energy source.
In the study, researchers used a beaker of a chemical called deuterated acetone. Normal acetone is a colorless, volatile liquid often used as a paint remover or chemical solvent. In deuterated acetone, the chemical's normal hydrogen atoms have been replaced with deuterium, a hydrogen isotope that is heavier than ordinary hydrogen and is capable of fusion reactions. When combined with oxygen, deuterium is sometimes called "heavy water."
The researchers introduced tiny bubbles, no bigger than the period at the end of a sentence, into the beaker. They then zapped the bubbles with sound waves. The bubbles rapidly expanded and then collapsed.
It's believed that the bubble collapse causes a momentary shock wave that creates high pressures, high temperatures and a flash of light, called sonoluminescence.
F.D. Becchetti, a physicist at the University of Michigan, said in Science that the study by Taleyarkhan needs to be confirmed by other researchers.
"If the results are confirmed, this new compact apparatus will be a unique tool for studying nuclear fusion reactions," said Becchetti. He said the experiments appear to have been carefully done and analyzed by reviewers.
"The results are credible until proven otherwise," said Becchetti.
In a repeat of the experiment, using slightly different equipment, D. Shapira and M.J. Saltmarsh of Oak Ridge claimed that the neutron emission they detected was too small to explain the tritium production reported by Taleyarkhan.
In a response, Taleyarkhan and his colleagues said Shapira and Saltmarsh misinterpreted their own results and that the level of neutron emission they detected was consistent with the original experiment.
The announcement of the Taleyarkhan tabletop fusion experiment is in sharp contrast to one that University of Utah researchers announced at a news conference in 1989. Unlike the Utah experiment, which was rejected by many other physicists, Taleyarkhan's experiment was reviewed by a committee of experts, selected by Science, before the study was accepted for publication.
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