Temperature fluctuations and plasma edge turbulence in the Brazilian tokamak TBR

To investigate the tokamak turbulence, a set of Langmuir probes and a triple probe have been designed and used in the TBR [J. Fusion Energy 12, 529 (1993)] to measure average and fluctuating values of density, potential, and temperature of the plasma edge. The obtained results showed a significant influence of the temperature fluctuations in the transport parameters. Namely, taking into account this influence, the density and plasma potential power spectra were obtained, and the turbulence parameters reevaluated. Furthermore, the computed cross-power-spectra showed appreciable linear correlation, and the cross-bispectra showed a quadratic mode coupling between temperature fluctuations and other quantities. Significant bicoherence between these fluctuations was observed. Finally, for a fluctuation monitored at two probe points, no preferential direction for energy cascading was detected. (C) 1996 American Institute of Physics.