ELECTRIC POTENTIAL AND TURBULENCE IN OH AND ECRH LOW-DENSITY PLASMAS IN THE T-10 TOKAMAK

Geodesic Acoustic Modes (GAMs) and broadband (f <400 kHz) turbulence of the plasma electrostatic potential and electron density have been directly studied in OH and ECRH plasmas in the T-10 tokamak. Potential and density fluctuations measurements were carried out with Heavy Ion Beam Probe (HIBP) from the plasma core to the edge. Four different types of modes were observed in T-10 plasmas: GAM (fGAM=20-25 kHz) with higher frequency satellite (fsat=22-28 kHz), Stochastic Low-Frequency Modes (SLF) with fSLF=0-30 kHz, Low-Frequency Quasicoherent Modes (LFQC) with fLFQC=50150 kHz and High Frequency Quasi-Coherent modes (HFQC) with fHFQC=200-400 kHz). Both GAM and satellite have homogeneous radial distribution of the frequency and amplitude of electric potential fluctuations in OH and ECRH plasmas. Cross-correlation analysis supports modes identification, while bicoherence analysis have shown three-wave interaction for both GAM and satellite.

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