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This work is an analysis of an ion turbulence in a tokamak in the case where the thermal flux is fixed and the temperature profile is allowed to fluctuate. The system exhibits some features of self-organized critical systems. In particular, avalanches are observed. Also the frequency spectrum of the thermal flux exhibits a structure similar to the one of a sand pile automaton, including a 1/f behavior. However, the time average temperature profile is found to be supercritical, i.e. the temperature gradient stays above the critical value. Moreover, the heat diffusivity is lower for a turbulence calculated at fixed flux than at fixed temperature gradient, with the same time averaged temperature. This behaviour is attributed to a stabilizing effect of avalanches.

Additional information

Authors: GARBET X, CEA, CEN Cadarache, Saint-Paul-lez-Durance (FR);WALTZ R E, General Atomics, San Diego (US)
Bibliographic Reference: Report: EN (1998) 33pp.
Availability: Available from Association Euratom-CEA, CEN Cadarache, 13108 Saint-Paul-lez-Durance (FR)
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