Hopes for a tabletop fusiondevice dimmed further Tuesday after scientists reacted to a Mondayannouncement, but the researcher who led the invention of the laboratory processremains convinced his experiments were viable and can be reproduced.

Rusi Taleyarkhan at the Oak RidgeNational Laboratory led a team that claimed to create nuclear fusion reactionsusing bubbles and sound. From the outset, Taleyarkhan cautiously noted that theresults needed to be duplicated by other researchers. A paper on the process isset to appear in the March 8 issue of the journal Science.

Prior to the planned publicrelease of the paper, however, another Oak Ridge group providedevidence that the results could not be duplicated.

Taleyarkhan's team had said they detected flashes of light,an isotope called tritium, and high-energy neutrons when they forced bubbles tocollapse under the pressure of intense sound waves in a process known assonoluminescence. The other Oak Ridge group said it detected no high-energyneutrons. Taleyarkhan's team responded Monday, saying the other group hadimproperly calibrated its detector.

Among scientists, replication ofresults is crucial in establishing the credibility of a claim.

Tuesday, Taleyarkhan told SPACE.com that he is still anxious tohelp other science teams try to reproduce the data, a stance he has maintainedfrom the beginning.

"If a system such as this isset up independently, along with the careful seeding and detection systems asdescribed in our paper, I am confident the results will be possible toconfirm," he said, adding that his team has "done this more than ahundred times already, dismantling the apparatus each day and starting afreshagain the next time for the past year-and-a-half."

Other researchers now questionwhether the device should ever have received so much attention.

"It's one of these thingswhere until you've got a reproducible experiment, it's not really worthspeculating much about it," said Mordecai-Mark Mac Low, a gas dynamicistin the department of astrophysics at the American Museum of Natural History inNew York. "I'm surprised Sciencechose to promote it, that is to give it the cover and pass around pressreleases about it."

Mac Low said that it is commonfor findings like this to be published, so that other researchers can work withthe data, but they are not typically ballyhooed much by the publication. Theweekly journal Science made theresults its cover story and circulated a press release to journalists,something they typically do with just one or two of the many stories in eachissue.

In a telephone interview, Mac Lowsaid that to explain their apparent measurements from the physical experiments,Taleyarkhan and his colleagues generated a computer simulation that included ashock wave pushed 10 times harder than in the actual experiment.

"They don't justify thatadequately," Mac Low said.

Nuclear fusion is a process thatreleases energy by building larger atoms from smaller ones. Its practicalapplication has long been sought as a way to provide safer, relativelyinexpensive power. Nuclear fission, a different sort of reaction, releasesenergy by splitting heavy atoms. It is the process behind nuclear power plantsand the atomic bomb.

The new tabletop fusion devicewas said to generate temperatures similar to the core of the Sun, where fusionis known to occur. Mac Low says such a result would also have generated X-raysand gamma rays, two things no one has ever been able to produce in anexperiment of this type.

Robert Park, a physicist whowrites for the American Physical Society, said in an online column thatTaleyarkhan's paper was accompanied by "unusual fanfare."

Fearing a repeat of a fiasco morethan a decade ago, in which a process called cold fusion was said to beaccomplished, some physicists who reviewed the paper for Science had advised against its publication. The review processlasted nearly a year.

Fred Becchetti of the University of Michigan had written a review of the Taleyarkhan paper, for Science, prior to Monday's announcement that the other Oak Ridge group could not reproduce the results. Tuesday, Becchetti said via e-mail that he remains open-minded but still guarded.

"As always, time will be theultimate judge," Becchetti said. "But I think there are severalgroups who can quickly try and duplicate the results."

Meanwhile, the Oak Ridge lab sitson two wildly disparate sets of findings and has taken a middle-of-the-roadattitude, providing this statement: "The preliminary measurements arepotentially very interesting, but it is premature to conclude that nuclearreactions have been achieved."

Lee Riedinger, Oak Ridge's deputydirector for science and technology, said,"The manuscript has been through external peer review, but thescientific record shows that tritium and neutron measurements at these levelsare difficult, and one must do further tests before firm conclusions can bedrawn."

If the apparatus is determined towork, it's unclear what it might lead to.

Its hard to know at this point what the ultimateimportance of this discovery will be," said Richard T. Lahey Jr., a RensselaerPolytechnic Institute researcher and co-author of the original paper.

Taleyarkhan said it would stillhave to be proven scalable in order to provide commercial power, a prospect hesaid is "unknown at the present."

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