Thursday, January 20, 2005

Sonofusion Researcher Winning Over Critics

In the January 22 issue, New Scientist published an article (subscription required) about sonofusion, or as its proponents now seem to prefer it be called, Acoustic Inertial Confinement Fusion (AICF). Widespread skepticism of Rusi Taleyarkhan's earlier claims seem to be melting in the face of his second paper, which used a much more methodical study of the reaction. In particular,
Instead of looking for fusion neutrons shortly after firing the initial burst, the group monitored their arrival continuously throughout the experiment. The results show that the initial burst used to seed the bubbles gradually dies down. Then, after a short time, a couple of peaks appear. These peaks, claims Taleyarkhan, are the bursts of neutrons generated in fusion reactions. "It's pretty solid evidence," says Michel Laberge, a physicist at General Fusion, a start-up in Vancouver, Canada, who also works on fusion research.

But the real beauty of the work is the control experiment that Taleyarkhan used to validate the results. He changed the timing of the initial neutron pulse, firing it when the pressure in the liquid was at its highest. Under high pressure, a bubble cannot form and so fusion cannot take place. Sure enough, the peaks that Taleyarkhan says are proof of fusion do not appear and so cannot be caused by neutrons from the initial burst. "It's very compelling data," says [UCLA researcher and Naranjo's thesis advisor Seth] Putterman.

While skeptics still abound, the new work is winning over many of his critics. DARPA plans on sponsoring a series of experiments with Taleyarkhan and some of his critics to end the debate one way or another. Things are looking up for him: another group at Purdue "led by Lefteri Tsoukalas has recreated the experiment" and will present his results in France in October.

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