Tiny bubbles, big fusion bang?

Tiny bubbles, big fusion bang?

By Charles Choi
UPI Science News
Published 3/5/2002 1:14 PM

Tiny bubbles that may trigger nuclear fusion -- the process powering the sun -- under easy "tabletop" conditions have ignited a controversy among scientists.

If the process can be reproduced in labs around the world, as many groups are feverishly trying to do, a new era in energy may dawn with clean, cheap nuclear power.

"We think it can be very, very great for humanity in general -- but we are not there yet," said lead researcher Rusi Taleyarkhan at Oak Ridge National Laboratory in Tennessee.

Taleyarkhan's team reports in Thursday's edition of Science that they have generated temperatures up to 10 million degrees Celsius -- as hot as the core of the sun -- by imploding bubbles only millimeters in diameter. The investigators also say they detected promising evidence of fusion, such as a type of radioactive hydrogen known as tritium and neutron emissions.

"We've gone through every possible care to make sure that what we have reported has been repeated in our laboratory," Taleyarkhan told United Press International. "We went through intense scrutiny from 10 to 12 referee groups from Science magazine before they accepted our findings for publication."

Fusion is when two atomic nuclei fuse together, a process that releases a million times more energy than any chemical reaction. Scientists have long tried to harness fusion as a power source because, unlike fission -- a nuclear reaction based on the breakup of atoms -- it leaves behind little radioactive waste and uses readily available raw materials.

However, fusion requires both extremely high pressures and temperatures, things up to now only generated artificially with powerful magnetic fields or high-energy lasers.

The researchers and their collaborators in New York and Russia believe the collapse of bubbles in acetone -- the kind of organic fluid found in paint thinner -- provides this key environment.

"The container is about the size of three coffee mugs," Taleyarkhan said, speaking from his home.

The acetone used in the experiment had all its normal hydrogens replaced with deuterium -- hydrogen atoms with one extra neutron. The researchers bombarded this "deuterated" acetone with high-pressure sound waves, inflating vapor bubbles inside that were smaller than the wavelengths of light -- only nanometers or billionths of a meter wide -- to hundreds of thousands of times their size.

The researchers say the catastrophic implosion of these bubbles fused deuterium atoms with each other to form tritium -- a kind of hydrogen with two extra neutrons -- even at 0 degrees Celsius. They also detected up to 1 million neutrons released per second while the bubbles collapsed, as well as the presence of tritium, a sign of deuterium-deuterium fusion.

These findings have been met with caution from most places, scorn from others.

"Pretty exciting stuff, huh? It might be, if the experiment had not been repeated by two experienced nuclear physicists ... (who) found no evidence ..." said Bob Park in a statement on the Web site of the American Physical Society. "Perhaps Science magazine covets the vast readership of Infinite Energy magazine."

While physicist Fred Becchetti of the University of Michigan in Ann Arbor said the jury was still out on the findings, the reviewers could find no obvious flaws in the work and 10 to 20 labs around the world could attempt the same experiment within weeks, confirming or disproving the results.

"Even under the very best of circumstances, people have to reproduce it again, and then we might start getting excited about it," Becchetti told UPI. "I'd like to reproduce it if I can."

Taleyarkhan remains cautiously optimistic. Immediate applications could range from medical diagnostics to food sterilization, he said. But Becchetti and others are skeptical over whether this kind of generator could produce the continuous power needed by cities instead of the pulses it seems to deliver now.

Becchetti added, however, "Never say never."

(Reported by Charles Choi in New York.)