- 14:51 27 April 2007
- NewScientist.com news service
- Tom Simonite
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A "spark plug" that should trigger nuclear fusion in a pellet of hydrogen every 10 seconds is being tested by Russian and US researchers.
The device fires an intense pulse of electricity – half a million amps and one hundred thousand volts. It has just completed preliminary testing at Sandia National Laboratories' "Z Machine" facility in New Mexico, US. Researchers hope the component could help narrow the gap between the fusion technique being used there and the one that currently leads the field. Some experts are sceptical about its chances, however.
Nuclear fusion harnesses the process that powers stars, generating power by binding atomic nuclear together. Unlike nuclear fission, which drives existing nuclear power stations, it offers hope of producing nuclear energy cleanly.
Sandia is developing a method called inertial confinement, to compress and heat small pellets of hydrogen isotopes. The processes forces the isotopes to fuse together, producing helium and releasing energy.
Although inertial confinement is popular in the US, an alternative technique, known magnetic confinement, has shown greater practical promise. This involves pushing hydrogen atoms together using magnetic fields and it is the basis for an experimental fusion reactor called ITER, an international project. Following several years of intense negotiations, ITER will be built in Caderache, France, in 2008.
Faster firing
Inertial confinement is less efficient partly because the fusion produced is relatively short-lived. Each time the reaction fizzles out, researchers have to wait hours while devices called Marx generators recharge. These components kick-start a fusion reaction and function like gigantic spark plugs.
But a new device called a linear transformer driver (LTD) could drive this kind of fusion for much longer. By firing every 10 seconds, engineers hope to boost fusion power output. Just a few of the components have been tested so far.
"This is the most significant advance in primary power generation in many decades," says Keith Matzen, director of Sandia's Pulsed Power Centre. Test firings show LTDs to be 50% more efficient than the method currently used at the Z Machine.
The LTDs were developed by researchers at the Institute of High Current Electronics in Tomsk, Russia, in collaboration with Sandia colleagues. Each "spark plug" is about the size of a shoebox and contains a switch coupled to several large capacitors. A circular ring of 20 such units, wired in parallel, can produce half a million amps and one hundred thousand volts. Linking several rings together increases the final voltage produced. Researchers estimate that about 60 rings should be enough to power a fusion reactor.
LTDs achieve better performance partly because they are simpler than Marx generators, which need extensive wiring and hundreds of thousands of gallons of insulating water and oil. Neither do LTDs generate the magnetic fields that slow the passage of current and reduce performance.
"Significant breakthrough"
"Fusion is an important future energy source, and this does seem to be a significant breakthrough in its field," says Duarte Borba, who works on the world's largest fusion reactor, the Joint European Torus in Culham, UK.
However, he adds that the magnetic confinement technique, which is used in JET and is the basis for ITER, is more advanced. "The basic technological pieces have already been built and are well tested – we just need to integrate them," he explains. "Simulations [of a finished reactor] may suggest big improvements from a new technique but until they are tried you can't be sure."
Results on LTD development will be presented at the IEEE International Pulsed Power and Symposium on Fusion Engineering conferences in Albuquerque in June 2007.
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