Correlation between low frequency turbulence and energy confinement in TFR

A close correlation between density fluctuations detected with the help of a coherent scattering experiment and the electron transport confinement time deduced from a zero-dimensional code valid at the centre of the discharge has been observed. This correlation suggests that turbulence is responsible for the confinement degradation observed in tokamak experiments. The correlation is similar in the Ohmic phases and the auxiliary heating phases, which suggests a continuity in this turbulent process. It is shown that the relative density fluctuation can vary much more than the density gradient length, in contradiction to the often quoted 'mixing length' relationship. (author)