Like rapidly flowing gases and liquids, magnetically confined plasmas in tokamaks and related fusion devices exhibit a high degree of turbulence, which can generally destroy the optimal conditions for producing fusion energy. In a deeply encouraging new result, scientists have experimentally confirmed that turbulence can actually limit its own ability to wreak havoc.
Theoretical picture of self-generated turbulence flows in a tokamak cross section
Computer simulations of turbulence in the DIII-D tokamak agree with recent DIII-D experiments. Color contours illustrate the highly elongated structure of turbulence in the electron density
Researchers at the DIII-D tokamak at General Atomics have discovered that turbulence generates its own flows that act as a self-regulating mechanism. These flows, which are predicted theoretically and have been observed in computer simulations, create a "shearing" or tearing action that destroys turbulent eddies, as indicated by the figure. Such flows are like the large-scale zonal jets and patterns seen in the atmospheres of Jupiter and other large planets.
These turbulent flows have been clearly observed in recent experiments at DIII-D by using a special imaging system. The imaging measurements are obtained at a rate of one million frames per second and have a spatial resolution of about 1 cm. Observing and identifying these unique turbulence flows experimentally, and comparing their characteristics with theory, is helping to advance researchers understanding of this complex and crucial phenomena taking place in high temperature fusion plasmas.
David Harris | EurekAlert!
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