Characterization of Turbulence and Transport in Magnetic Confinement Devices

Abstract

Intermittency in the scrape-off layer (SOL) region of magnetically confine plasma and velocity intermittency of neutral flui are compared from the aspect of global and local multifractal properties. Density fluctuation in the MAST device are considered and contrasted to local velocity measurements of an air fl w into round free jet. Large deviation (multifractal) spectra are used to characterize global features revealing different energy cascade mechanisms in each of systems. A transformation invariant zero-crossing function is shown to be more reliable indicator of stable equilibrium states then the probability density function. In particular the zero-crossing function detects L-H transitions and recognizes ELMs as catastropohic events in the sense of stochastic catastrophy theory. The method may be of significan importance in the analysis and control of edge plasma turbulence.