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Fusion fuels furore

IT HAD all the makings of a fun day out, for academics at least. U.S. government officials had summoned a handful of scientists from labs across the country to a confidential meeting in Arlington, Virginia. Not long into the meeting, a scientist — Rusi Taleyarkhan, of Purdue University in Indiana — showed a slide of his recent results. Immediately, the meeting descended into farce and fury. That was last June. Later this month, the research that triggered the furore will be published in a journal owned by the American Physical Society. Taleyarkhan's results suggest that his team succeeded in triggering nuclear fusion, , by doing little more than blasting a beaker of acetone with sound waves.

Attempts to harness the power of nuclear fusion, a potential source of limitless clean energy, have so far required vast, multibillion-dollar test reactors. In comparison, Taleyarkhan's fledgling reactor could be built with loose change, and is no bigger than a couple of coffee cups. Too good to be true? "It's difficult for me to say I believe it because it's so implausible,'' says Larry Crum, a physicist at the University of Washington.

The story of why Taleyarkhan's claim caused such a stir reveals much about the machinations of modern science. It is a tale of how the process of science, like any other business, is shaped by egos, rivalry and vested interests.

It all began in late 2001. At the time, Rusi Taleyarkhan was a researcher at the U.S. department of energy's Oak Ridge National Laboratory in Tennessee and one of a small group working on `sonofusion', an improbable but potentially groundbreaking new field of science.

The idea behind sonofusion is simple. If the conditions are right, blasting a jar of liquid with ultrasound can rip tiny holes in the liquid and slam them closed again, thousands of times a second. Get the bubbles to generate enough heat, and you might just be able to make atoms in the surrounding liquid fuse together; a simple way, in theory at least, of producing nuclear fusion. It sounds easy, but if it were, it would have been done decades ago. The showstopper is that the temperatures needed to generate fusion are mind bogglingly high, at least ten million degrees Celsius, the temperature at the heart of the Sun. Many scientists doubt that sonofusion will ever get as hot as that. The highest temperature produced this way, to be soon reported in the journal Physical Review Letters by Seth Putterman's group at the University of California, Los Angeles, is one million Celsius.

Taleyarkhan took a beaker of acetone and bombarded it with pulses of neutrons. The idea was that the neutrons would strike molecules in the acetone and create tiny bubbles, each around 10,000 times smaller than the width of a human hair. He then blasted the beaker with ultrasound, which stretched the tiny bubbles until they were a few millimetres across, before swiftly crushing them again.

The hydrogen atoms in the acetone were swapped for deuterium, a form of `heavy hydrogen'. With everything in place, Taleyarkhan flicked the on switch. Several months later, some of the country's experts on sonofusion were in for a shock. Each received a paper in the post from Science with a request to review it and send back their opinion.

The paper, by Taleyarkhan, described how his desktop experiment had produced nuclear fusion. ``It was very sloppy,'' says Ken Suslick, a physicist at the University of Illinois at Urbana-Champaign. The reviewers pointed out a series of what they regarded were serious flaws in the work.

One issue that caused concern was that Taleyarkhan's proof of fusion rested on having detected neutrons, which he claimed were produced by nuclear fusion reactions. But as Suslick points out, Taleyarkhan was blasting neutrons into the experiment. How did he know he wasn't detecting the neutrons he was pumping in? Taleyarkhan also claimed that his experiment produced tritium, another radioactive by-product of fusion reactions. The reviewers said Taleyarkhan's lab was probably contaminated with the stuff.

One referee thought the paper was so bad that he contacted Oak Ridge National Laboratory and urged it to hold an internal inquiry; if the paper was published it could put the institution's reputation at risk, he believed. Although no inquiry was ordered, another scientist at Oak Ridge, Mike Saltmarsh, and his colleague, Dan Shapira, set about trying to replicate it using more sensitive equipment. They couldn't get the same results.Undermining the work of those under the same roof, in the same field, is not done lightly in science. Having criticised the paper so heavily, Suslick and two other reviewers, Crum at the University of Washington and Seth Putterman at the University of California in Los Angeles, were in for another shock.

In March 2002, Science published the paper, defending the decision to publish in an accompanying editorial, which said the journal's mission was to bring interesting science to the public. Immediately the three drafted a letter of complaint and sent it to Don Kennedy, the editor of Science, who is based at Stanford University. When Kennedy refused to publish the letter, the scientists posted it on the Internet. It contained a damning criticism of Taleyarkhan's paper. To go public with their criticisms was an extraordinary move.

They also demanded to see the positive comments Science must have received that persuaded the journal to overrule them and publish the paper. Again, Science refused. By this point the scientific community had been cleaved into two uneven factions: those who thought Taleyarkhan might be on to something and those that thought he was at best a sloppy scientist. Taleyarkhan says now that it's nothing more than a case of sour grapes.

Despite rejecting the criticisms, Taleyarkhan set about repeating his experiment in the hope of getting good enough data. In June 2003, he took his results along to the government meeting in Arlington to share it with others. But he succeeded only in reigniting the controversy. Taleyarkhan's paper will appear in the journal Physical Review E, later this month. While many still refuse to accept Taleyarkhan's claims, Crum believes that it's time scientists at least accept he might be on to something. "Scientists are going to have to face the fact that this is now two papers published in major journals,'' he said. The only way to determine the truth in science is to have someone reproduce the effect you find. If it's really true, someone will find it. Nature doesn't cheat.'' — Guardian News Service

Ian Sample

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