Posted on 03/05/2002 7:32:47 AM PST by blam
Desk-top fusion claim provokes controversy
11:47 05 March 02
NewScientist.com news service
Scientists think they have triggered nuclear fusion reactions - the holy grail of cheap and safe energy - simply by popping little bubbles in a cool liquid.
"If it is true, it is truly amazing - it could be a pivotal point in history," says Andrea Prosperetti, who studies bubbles at the Johns Hopkins University in Baltimore.
This neutron nucleated bubble is 6.5 mm long and is on the point of collapse (Photo: ORNL)
However, many scientists remain sceptical of the results reported by Rusi Taleyarkhan and his colleagues at Oak Ridge National Laboratory in Tennessee, including other researchers at ORNL who tried and failed to repeat the experiments.
The second ORNL team say they used a more sophisticated detection system. But team member Mike Saltmarsh says: "Our experiment saw no evidence for nuclear fusion. This does not prove that no nuclear fusion is going on - it's virtually impossible to prove a negative - but it does show that if it exists, it is at a very low level."
10 million degrees
Scientists have struggled for decades to harness the energy of controlled nuclear fusion, which is tipped to be safer, cleaner and more efficient than fission reactors.
This requires merging nuclei by overpowering the electrostatic repulsion between them. One way is to heat matter to around 10 million degrees, the temperature at which nuclear reactions take place in the heart of the Sun.
But that is easier said than done and, so far, no one has developed a fusion reactor that generates more energy than it uses up to drive the reactions.
One speculative alternative has been to use collapsing bubbles. Scientists have long known that passing sound waves through water can generate tiny bubbles. In the right conditions, these then emit light called sonoluminescence as they collapse and heat up to thousands of degrees. If they could get near the magic 10 million degrees, nuclear fusion might occur.
High-energy neutrons
Taleyarkhan's team say they may have done that. The team used a neutron beam to generate microscopic bubbles in acetone, in which the hydrogen atoms had been switched for deuterium, a heavy hydrogen isotope.
The team detected light and shock waves from the imploding bubbles, which coincided with emissions of high-energy neutrons. The neutrons had energies of 2.5 million electron volts - the expected energy for neutrons released as deuterium fuses to form helium. They also detected raised levels of tritium, another product of deuterium fusion.
But, though it is theoretically possible for collapsing bubbles to heat to astronomical temperatures, this only happens if they remain perfectly spherical as they implode. Instabilities tend to prevent this and a more realistic temperature may be 10,000 to 20,000 degrees, says Prosperetti.
And even if fusion did occur, there is no evidence that the process can generate more energy than it devours, or sustain itself without a power-hungry neutron source. However all the experts agree that they are keen to see the new experiment repeated again.
Journal reference: Science (vol 295, p 1868)
Here's a link to an article that mentions this:
I wouldn't think so after Pons & Fleishman.
Put Plato on the job; he's a sneaky little 'pus.
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