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Successfull test of unique approach to fusion power

Published by under Energy,News categories on April 8, 2008

LDX fusion reactor photoAn MIT and Columbia University team has successfully tested a novel reactor that could chart a new path toward nuclear fusion, which could become a safe, reliable and nearly limitless source of energy. The Levitated Dipole Experiment, or LDX, uses a unique configuration where its main magnet is suspended, or levitated, by another magnet above.

LDX achieved fully levitated operation for the first time last November. A second test run was performed on March 21-22 of this year, in which it had an improved measurement capability and included experiments that clarified and illuminated the earlier results. These experiments demonstrate a substantial improvement in plasma confinement–significant progress toward the goal of producing a fusion reaction.

The LDX reactor consists of a supercooled, superconducting magnet about the size and shape of a large truck tire. When the reactor is in operation, this half-ton magnet is levitated inside a huge vacuum chamber, using another powerful magnet above the chamber to hold it aloft. This is the only superconducting magnet currently used in any U.S. fusion reactor.

The advantage of the levitating system is that it requires no internal supporting structure, which would interfere with the magnetic field lines surrounding the donut-shaped magnet, explains Jay Kesner of MIT’s Plasma Science and Fusion Center, joint director of LDX with Michael Mauel of Columbia. That allows the plasma inside the reactor to flow along those magnetic field lines without bumping into any obstacles that would disrupt it (and the fusion process).

The new approach to fusion being tested in the LDX is the first to use the simplest kind of magnet, a dipole; in a dipole field the plasma naturally gets condensed, which is inherently more stable.

Another potential advantage of the LDX approach is that it could use a more advanced fuel cycle, known as D-D, with only deuterium. Although it’s easier to get a self-sustaining reaction with D-T, tritium doesn’t exist naturally and must be manufactured, and the reaction produces energetic neutrons that damage the structure. The D-D approach would avoid these problems.

Besides providing data that might someday lead to a practical fusion reactor, the experimental device could provide important lessons about how planetary magnetic fields work, which is still poorly understood. So the experiment is of great interest to planetary physicists as well as to energy researchers.


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