Star in the Jar

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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. 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. 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.” Moss, W. C. et al. (1994) Hydrodynamic simulations of bubble collapse and picosecond sonoluminescence, Phys. Fluids 6, 2979–2985 In the current setup, creating sonoluminescence takes far more energy than the bubble collapse gives off, even if fusion is taking place, Taleyarkhan says.

This lays the groundwork for the exciting high-performance plasma operations expected in the near future," Gates said.

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What causes the glow? Good question. According to [Justin], we just don’t know for sure what causes it, although the leading theory is that cavitation of the bubble causes the trapped gas to compress and heat violently, turning into a brief bit of plasma. But there are problems with that theory, which is one of the reasons he wanted to show just how easy the process can be – now that he’s shaken out the bugs with five years of effort. It wasn’t easy getting the transducers attached and the driver circuit properly tuned, but with little more than a signal generator, an audio amp, and a spool of magnet wire, you too can make your own “star in a jar.” 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. Several detractors have compared the new Science report to the infamous “cold fusion” announcement made in 1989 (SN: 4/1/89, p. 196). Two electrochemists claimed then to have sparked fusion at room temperature by passing electric current through a bath of water in which ordinary hydrogen is replaced by deuterium, a heavier isotope. However, neither the original pair nor anyone else could reproduce those findings, which have since largely been discredited as a case study of mistaken science (SN: 6/22/91, p. 392).

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 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. 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. Bristling at comparisons to the cold-fusion drama, the Oak Ridge researchers say that their findings withstood extensive peer review before being published. The cold-fusion claim in 1989 was announced to reporters before being submitted for publication. 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.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. Fusion is a problem best solved by the peoples of all nations working together, since the entire world will benefit from it." His headmaster was concerned about safety. “There was the chance that I could be electrocuted by the high-voltage power supply ... and then probably the chance of the vacuum chamber imploding because of all the forces on it,” says Edwards, “but quite a minimal aspect to it was the radiation.” Using his younger sister’s fish tank filled with a water and boron solution: “The radiation wasn’t really an issue.” If nothing else, [Justin Atkin] is persistent. How else do you explain a five-year quest to create sonoluminescence with simple tools? 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).

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.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. When he was younger he’d trawl car boot sales and charity shops for uranium glass. “It’s just green glass, but if you put a UV light on it, it will glow bright alien green. And it’s sort of radioactive because it’s the uranium that gives it the colour,” explained Edwards. He saved up to buy a Geiger counter from the US. 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. 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. 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.