Experimental evidence of the self-similarity and long-range correlations of the edge fluctuations in HT-6M tokamak

For a better understanding of long timescale transport dynamics, the rescal ed range analysis techniques, the autocorrelation function (ACF) and the pr obability distribution function (PDF) are used to investigate long-range de pendences in edge plasma fluctuations in an HT-GM tokamak. The results reve al the self-similar characters of the electrostatic fluctuations with self- similarity parameters (Hurst exponent) ranging from 0.64 to 0.79, taking in to consideration the (E) over right arrow (r) x (B) over right arrow rotati on-sheared effect. Fluctuation ACFs of both the ion saturation current and the floating potential, as well as PDF of the turbulence-induced particle f lux, have two distinct timescales. One corresponds to the decorrelation tim escale of local fluctuations (mus) and the other lasts to the order of the confinement time (ms). All these experimental results suggest that some of the mechanisms of the underlying turbulence are consistent with plasma tran sport as characterized by self-organized criticality (SOC).