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Levitated dipole : ウィキペディア英語版 | Levitated dipole
A levitated dipole is a nuclear fusion experiment using a superconducting torus which is magnetically levitated inside the reactor chamber. It is believed that such an apparatus could contain plasma more efficiently than other fusion reactor designs.〔 MIT News, David Chandler, MIT News Office, March 19, 2008. Accessed March 2008〕 The superconductor forms an axisymmetric magnetic field of a nature similar to Earth's or Jupiter's magnetospheres. The machine was run in a collaboration between MIT and Columbia University. The Levitated Dipole Experiment was funded by the US Department of Energy's Office of Fusion Energy, but funding for the LDX was ended in November 2011 to concentrate resources on Tokamak designs.〔(【引用サイトリンク】 url=http://www.fusenet.eu/node/216 )〕 == History == The Levitated Dipole is designed to be stable against "gentle" changes in the electric or magnetic field. This makes the Levitated Dipole unique when compared with other magnetically confinement machines. In those experiments, small fluctuations can cause significant energy loss. By contrast, in a dipolar magnetic field, fluctuations tend to compress the plasma, without energy loss. This compression effect was first noticed by Akira Hasegawa (of the Hasegawa-Mima equation) after participating in the Voyager 2 encounter with Uranus.〔Hasegawa, A., Comments on Plasma Physics and Controlled Fusion, 1987, vol. 1, p. 147.〕 Adapting this concept to a fusion experiment was first proposed by Dr. Jay Kesner (MIT) and Dr. Michael Mauel (Columbia) in the mid to late nineties.〔"Plasma Confinement in a Levitated Magnetic Dipole" MAGNETIC CONFINEMENT SYSTEMS〕 The pair assembled a team and raised money to build the machine. They achieved first plasma on Friday, August 13, 2004 at 12:53 PM. First plasma was done by (1) successfully levitating the dipole magnet and (2) RF heating the plasma.〔(【引用サイトリンク】 work=Levitated Dipole Experiment )〕 The LDX team has since successfully conducted several levitation tests, including a 40-minute suspension of the superconducting coil on February 9, 2007.〔(【引用サイトリンク】 work=Levitated Dipole Experiment )〕 Shortly after, the coil was damaged in a control test in February 2007 and replaced in May 2007.〔http://www.psfc.mit.edu/ldx/reports/status_0705.html〕 The replacement coil was inferior, a copper wound electromagnet, that was also water cooled. Scientific results, including the observation of an inward turbulent pinch, were reported in Nature Physics.
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