Posted on 03/07/2002 8:34:09 PM PST by Phil V.
Table-top fusion
Here we go again
Mar 7th 2002
From The Economist print edition
Is the world about to witness a repetition of the cold-fusion fiasco?
AS PARENTS scare their children with stories of ghosts and ogres, so professors scare their students with stories of Pons and Fleischmann. In 1989 Stanley Pons and Martin Fleischmann, then researchers at Southampton University, in England, announced to an astonished world that they had performed nuclear fusion in apparatus built on a laboratory bench. For a few weeks people dreamed of limitless clean power. But other researchers failed to replicate their results and it was clear that a mistake had been made. Dr Pons and Dr Fleischmann were disgraced, and now labour in obscurity.
This week's Science includes a paper that makes similar, albeit more guarded, claims. The technique is different, but the apparatus still fits comfortably on a bench top. This time, the researchers do not state that they have seen fusion, but merely phenomena consistent with it. However, the subtext is clear: they think they have got there. Unfortunately, the ghost of hubris past will not let go of the subject. Another group of researchers has already claimed that it cannot replicate the trumpeted results.
Fusion involves colliding small atomic nuclei together to form larger ones, a process that releases energy. But, since atomic nuclei are positively charged, and like charges repel, it is a hard trick to pull off. It happens in the cores of stars, where high pressure squeezes nuclei close together, and high temperature means that they are travelling so fast that they overcome the repulsion. It can also be made to happen briefly on earth in huge machines that replicate stellar conditions.
These machines fuse nuclei of deuterium, a form of hydrogen that has a proton and a neutron in its nucleus, rather than the lone proton of normal hydrogen. When two deuterium nuclei fuse, they may form either tritium, a still heavier form of hydrogen that has a proton and two neutrons (a reaction that releases a proton), or a form of helium that has two protons and a neutron, thus releasing the surplus neutron. Deuterium is abundant, in effect forming an infinite potential fuel supply. But the machines are reckoned to be 50 years from commercialisation—and have been for most of the 50 years since people first started trying to build them.
A different, smaller-scale fusion technology could be a real boon. And the method described by Rusi Taleyarkhan, of Oak Ridge National Laboratory in Tennessee, and his colleagues looks plausible. Unlike Dr Pons and Dr Fleischmann, who used a technique derived from electrochemistry, Dr Taleyarkhan thinks he can generate the temperatures and pressures required by acoustic cavitation.
This involves sending powerful sound waves through a liquid. During the low-pressure trough of a wave, bubbles of vapour form in the liquid. During the high-pressure peak, these bubbles are squeezed into oblivion. The intense heating associated with this squeezing produces light—a phenomenon called sonoluminescence that has been known for a century. Many people have suspected that it could also be enough, combined with the high pressure involved, to promote fusion.
Dr Taleyarkhan and his colleagues picked acetone, whose molecules contain six hydrogen atoms, as the liquid. They ran the experiment with normal acetone, as a control, and with acetone that had been made with deuterium, rather than ordinary hydrogen. As they did so they looked for the release of neutrons of the energy associated with deuterium fusion. In the former case they found none. In the latter, they found significant numbers. They also analysed the acetone after the experiments, looking for further neutrons produced by the radioactive decay of tritium. These, too, were present in the experimental samples, and absent from the controls.
All of which would look pretty promising if Dan Shapira and Michael Saltmarsh, two of Dr Taleyarkhan's colleagues at Oak Ridge, had not written to Science a few days before publication saying that they had repeated the experiment with the same equipment, except that they used a different sort of neutron detector. They could, they said, find no sign of a neutron flux big enough to indicate anything approaching fusion.
Dr Taleyarkhan has replied that his critics did not understand their own results, which actually did show a flux of neutrons consistent with his own interpretation. The consequence is likely to be a big kerfuffle until yet further replications are carried out, ideally not at Oak Ridge, whose coffee room is now presumably at daggers-drawn. Watch this space.
The making of Guinness.
;)
Ya got a pool for swimming lessons?
Ya got Buddy's bitch to "adopt" him?
two blasts from the past, this a bit older:
Not Cold Fusion but: "Oak Ridge scientist exhausted, elated with response to research"
Knoxville News-Sentinel
Mar 7, 2002 | Frank Munger, News-Sentinel senior writer
Posted on 03/07/2002 1:31:06 AM PST by The Raven
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