Moss, W. C. et al. (1994) Hydrodynamic simulations of bubble collapse and picosecond sonoluminescence, Phys. Fluids 6, 2979–2985 Under extreme pressure and at temperatures of millions of degrees, such as at the center of the sun, deuterium atoms fuse in a reaction whose products include tritium–hydrogen’s radioactive heavy isotope–and neutrons. We applaud [Justin]’s determination to bring this project to a successful conclusion. It’s not unlike his dogged effort to make a cold plasma torch, or even his desktop radio telescope. If nothing else, [Justin Atkin] is persistent. How else do you explain a five-year quest to create sonoluminescence with simple tools?

The new signs of fusion in bubbles were so extraordinary that Lee L. Reidinger, the Oak Ridge lab’s deputy director for science and technology, commissioned two of the lab’s nuclear physicists, Dan Shapira and Michael J. Saltmarsh, to monitor the sonoluminescence setup using different detectors. They just don’t have the evidence,” says William C. Moss of Lawrence Livermore (Calif.) National Laboratory, one of several sonoluminescence specialists who have theorized that fusion in collapsing bubbles is feasible.

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Even if the experiments did yield fusion reactions, practical technology based on the phenomenon would be a long way off. However, many scientists have already pronounced the new findings dead wrong. Fusion is a problem best solved by the peoples of all nations working together, since the entire world will benefit from it." D. F. Gaitan, (1990) An experimental investigation of acoustic cavitation in gaseous liquids, Ph. D. thesis, Univ. of Mississippi; Gaitan, D. F. et al. (1992) Sonoluminescence and bubble dynamics for a single, stable, cavitation bubble, J. Acoust. Soc. Am. 91, 3166–3183. Barber, B. P. and Putterman, S. J. (1991) Observation of synchronous picosecond sonoluminescence, Nature 352, 318–320; The measured pulse width is less than 50ps.

So what exactly is sonoluminescence? The short answer is as the name suggests: a release of light caused by sound. In [Justin]’s case, he used an ultrasonic transducer to set up a standing wave at the resonant frequency of a flask of water. A drop of water is used to entrain a small air bubble, which is held in a stable position in the flask in much the same way as styrofoam beads are in an acoustic levitator. Turn off the lights and you’ll see that the bubble glows with a ghostly blue light. In the new work, Taleyarkhan and his collaborators used bursts of neutrons to fabricate clouds of short-lived, but extraordinarily large, sonoluminescence bubbles in acetone, the solvent in many nail-polish removers. In some tests, the researchers filled the flask with ordinary acetone, whose molecules each contain six hydrogen atoms. In other tests, they used deuterated acetone, in which deuterium atoms replace the hydrogen ones. On the other hand, scientists have produced tabletop fusion, for instance by zapping small clusters of atoms with high-powered lasers (SN: 3/27/99, p. 196: https://www.sciencenews.org/sn_arc99/3_27_99/fob1.htm). Moss, W. C. et al. (1997) Calculated pulse widths and spectra of a single sonoluminescing bubble, Science 276, 1398–1401. Other critics say that the most damning indictment of the new work is an unpublished follow-up experiment by a pair of nuclear physicists, also of the Oak Ridge lab.He is already thinking about his next project. “I was thinking that maybe I could make a hand-held laser cutter,” says Edwards. “So I’ve been looking into some really high-powered lasers.” That last part is critical. Gates said he's encouraged by fact that the W7-X project, and nuclear fusion research in general, is the result of close collaboration among scientists from around the world. However, sonoluminescence flashes typically occur at temperatures of thousands of degrees, not millions. “Such high temperatures are unlikely to occur” in the bubbles of the Oak Ridge setup, notes Lawrence A. Crum of the University of Washington in Seattle. The basis of the new energy source would be so-called sonoluminescence–a phenomenon in which bubbles of vapor in a liquid bombarded by sound waves rapidly implode, generating heat spikes and flashes of light in the bubbles (SN: 10/6/01, p. 213: Shrimps spew bubbles as hot as the sun). Taleyarkhan and several of his Oak Ridge colleagues collaborated on the research with scientists from Rensselaer Polytechnic Institute in Troy, N.Y., and the Russian Academy of Sciences in Ufa.