Star in the Jar

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Fusion is a problem best solved by the peoples of all nations working together, since the entire world will benefit from it." Moss, W. C. et al. (1997) Calculated pulse widths and spectra of a single sonoluminescing bubble, Science 276, 1398–1401. This lays the groundwork for the exciting high-performance plasma operations expected in the near future," Gates said.

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.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. 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. In the current setup, creating sonoluminescence takes far more energy than the bubble collapse gives off, even if fusion is taking place, Taleyarkhan says. 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.

If nothing else, [Justin Atkin] is persistent. How else do you explain a five-year quest to create sonoluminescence with simple tools?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. 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. 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. 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.”

However, he adds, mathematical models of the process suggest that much greater energy production may be possible. Of more immediate concern to him and his colleagues is the task of convincing other scientists that their evidence of fusion is sound. In terms of the big-picture goal, Gates said that nuclear fusion reactors, if properly developed and deployed, would provide the planet with safe, clean and virtually inexhaustible energy. 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.The fuel source is found in seawater in quantities sufficient to last tens of thousands of years," he said. "The waste product is helium, an inert gas. A viable fusion reactor would provide a secure, plentiful and environmentally benign energy resource to all nations." Hiller, R. et al. (1994) Effect of noble gas doping in single-bubble sonoluminescence, Science 266, 248–250. A group of scientists claims to have found evidence of nuclear fusion in a vase-size flask of liquid. The researchers say they created tiny bubbles that seemed to have collapsed with enough violence to force atomic nuclei to fuse. BUBBLE MAGIC. In a flask of acetone bombarded by sound waves, a cloud of bubbles (arrow) briefly swells to the size of a pea before collapsing. Courtesy of Oak Ridge Natl. Lab., Rensselaer Polytechnic Inst., Russian Acad. Sci. THE BIG SQUASH. A neutron pulse (arrow) combines with a sound signal (blue) in a flask of acetone to generate the conditions for a bubble (brown) to form, grow, and then implode with great force. After Taleyarkhan et al./Science Moss, W. C. et al. (1994) Hydrodynamic simulations of bubble collapse and picosecond sonoluminescence, Phys. Fluids 6, 2979–2985