December 04 2008 / by Garry Golden
Category: Energy Year: Beyond Rating: 7 Hot
MIT researchers are keeping hope alive in the long quest for fusion energy. Researchers have advanced our ability to harnesses one of the most complicated forms of energy science in the universe, but add a word of caution that real scalable reactors could still be 'decades away' as all eyes now focus on the ITER in France.
Fusion systems could generate enormous amounts of energy by tapping the same types of reactions found within stars. It has long been considered a 'holy grail' category within the energy sector because it produces no emissions or real waste, and its fuel sources are abundant.
MIT's Alcator C-Mod reactor has been in operation since 1993 and has the highest magnetic field and the highest plasma pressure of any fusion reactor in the world. It is also the largest fusion reactor operated by any university. [Image from MIT Fusion Movie]
Now MIT researchers believe they may have solved one of the most challenging problems how to propel the hot plasma (an electrically charged gas) around inside the donut-shaped reactor chamber so that the chamber doesn't lose its heat of millions of degrees to the cooler vessel walls.
"There's been a lot of progress," says physicist Earl Marmar, division head of the Alcator Project at the MIT Plasma Science and Fusion Center (PSFC). "We're learning a lot more about the details of how these things work."
The Power of Radio waves
Physicist Yijun Lin and principal research scientist John Rice now describe a very efficient method for using radio-frequency waves to push the plasma around inside the vessel, not only keeping it from losing heat to the walls but also preventing internal turbulence that can reduce the efficiency of fusion reactions.
"That's very important," Marmar says, because presently used techniques to push the plasma will not work in future, higher-power reactors such as the planned ITER (International Thermonuclear Experimental Reactor) now under construction in France, and so new methods must be found. "People have been trying to do this for decades."
France holds Key to Future of Fusion
Lin says that "some of these results are surprising to theorists," and as yet there is no satisfying theoretical foundation for why it works as it does. But the experimental results so far show that the method works, which could be crucial to the success of ITER and future power-generating fusion reactors. Lack of a controllable mechanism for propelling the plasma around the reactor "is potentially a showstopper," Rice says, and the ITER team is "very concerned about this."
Rice adds that "we've been looking for this effect for many years," trying different variations of fuel mixture, frequency of the radio waves, and other parameters. "Finally, the conditions were just right." Given that the ITER project, which will take 10 years to build, is already underway, "our results are just in time for this," Lin says. These results are being published in Physical Review Letters on Dec. 5. The work was sponsored by the US Department of Energy.