Pocket-Sized Nuclear Fusion a Reality
LOS ANGELES, California, April 28, 2005 (ENS) - For the first time, scientists have created a nuclear fusion reaction on a desktop.
They did it simply, by heating a crystal, without the use of enormous particle accelerators and high temperature and pressure that have been conceived in the past as the way to reproduce and control the same energy that powers the Sun and stars.
Nuclear fusion has long been seen as the clean energy of the future if it could only be controlled. But this discovery will not solve the world's energy problems.
The inventors of the device emphasize that it cannot generate power because it does not support a self-sustaining thermonuclear reaction. They anticipate that their "simple palm-sized neutron generator" will be used to power small spacecraft, zap cancerous tumors, or peer into suspicious luggage.
A scientific team at the University of California-Los Angeles led by physicist Dr. Seth Putterman invented the toaster-sized device, detailed in Thursday's issue of the journal "Nature."
The team reports that gently heating a pyroelectric crystal of lithium tantalate from freezing to room temperature produces a powerful electric field.
This field is focused until it is strong enough to accelerate a beam of deuterium ions to about one percent of the speed of light. Deuterium is a stable isotope of hydrogen, meaning that it is not radioactive and has a very long life span.
When the accelerated beam of deuterium ions hits a target containing deuterium nuclei, they fuse to form helium-3, a combination of two protons and a neutron.
The process emits about 1,000 neutrons a second, and by allowing the crystal to heat up slowly, fusion can be sustained for as long as eight hours at over 400 times the background level, the scientists found.
This type of fusion is used today in commercially available instruments that determine the chemical composition of materials at a distance. Neutron beams are used at airports to see into checked and carry-on baggage, for secure area screening, and for minerals exploration and oil well logging.
But replacing these larger machines with a small crystal that generates a neutron stream is considered a breakthrough.
"Everyone will be talking about the fusion, but this crystal can also give off X-rays as it accelerates electrons," Putterman told "Nature." "This effectively creates a tiny radioactive source that can be turned on and off at will."
He said that such a radioactive source could one day be used "to target radiation at cancerous cells: a smaller version could be injected into the body and directed towards a tumor before being switched on." By contrast, today's radiation therapies kill healthy cells along with cancerous ones.
The other two members of the crystal fusion team are Brian Naranjo and Dr. James Gimzewski, UCLA professor of chemistry and executive member of the California Nanosystems Institute.
The 1989 claims of cold fusion were debunked by many scientists, including Putterman and Gimzewski. "Attempts to produce fusion in a room temperature solid-state setting, including 'cold' fusion and 'bubble' fusion, have met with deep scepticism," they write in the paper describing their device.
But Gimzewski says the cold fusion claims "stimulated creative experimentation that led to this crystal fusion technique.
"In 1989, like many scientists, the controversial cold-fusion claims made by Stanley Pons and Martin Fleischmann naturally stirred our interest," says Gimzewski. "This led us to playfully think of creating nuclear fusion by crashing a tip into a surface under electrochemical conditions."
"This seems now to be a ridiculous notion, but I had learned from working in STM that seemingly impossible and apparently ridiculous ideas sometimes do work. This was an example of what experimentation is all about."
The team is now trying to make the device smaller and increase the number of neutrons it generates.