Statistical characterization of fluctuation wave forms in the boundary region of fusion and nonfusion plasmas

The statistical properties of plasma fluctuations have been investigated in the plasma boundary region of fusion (tokamaks and stellarators) and nonfusion plasmas. Fluctuations in ion saturation current and floating potential have a near-Gaussian character in the proximity of the velocity shear layer (rsh). However, fluctuations deviate from a Gaussian distribution when moving inside of the plasma edge (r<rsh) or into the scrape-off layer region (r>rsh). Furthermore, fluctuations show sporadic pulses that are asymmetric in time. The present analysis shows a coupling of those pulses and the averaged flow in the shear layer region.