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Applied Plasma Physics and Fusion Energy Seminar Series

Fall 2002

Tuesday, 3:30-4:30 PM in 479 EBU-II


November 19

Progress in Sustaining a Star on Earth: Improving the Magnetic Bottle (Tokamak) with "Plasma Surgery" and "Floating" the Plasma Away from the Walls

Steve Allen
Lawrence Livermore naational Laboratory

ABSTRACT:

The goal of Magnetic Fusion Energy is to sustain high temperature fusion reactions in a magnetic bottle. One design uses a doughnut-shaped device called the tokamak. Current tokamak research focuses on improving the confinement of the plasma by detailed shaping of the internal profiles (e.g. current, temperature) of the plasma with radio-frequency (RF) waves. Recent advances in diagnostic measurements of internal profiles, coupled with very-localized RF-driven current, has also enabled "plasma surgery" that stabilizes internal magneto-hydrodynamic instabilities, resulting in improved performance. However, even with effective magnetic confinement, there is localized exhaust heat from the core plasma which can damage the vessel walls and introduce impurities into the plasma. Recent advances have shown that a (visible and ultaviolet) radiating layer can effectively "float" the plasma away from the walls. This edge region is remarkably cold (a few eV) compared to the hot core plasma (several keV), and is a recombining plasma. Sophisticated numerical computer models are used to guide the experiments and develop an understanding of the basic physical processes. The US fusion program is currently developing a new "Burning Plasma" experimental plan with both national and international components; a progress report will be presented.

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