Empirical similarity of frequency spectra of the edge-plasma fluctuations in toroidal magnetic-confinement systems

Frequency spectra of fluctuations of the ion saturation current, floating p otential, and turbulent transport measured in the plasma edge of different fusion devices (tokamaks and stellarators) have been compared. All of the s pectra show the same behavior over the whole frequency range investigated, which supports universality of plasma turbulence or turbulent transport. Th e results obtained are an indication of edge-plasma turbulence evolving int o a critical state, independent of the size and plasma characteristics of t he device. [S0031 -9007(99)09024-9].