Turbulent spectrum analysis in TFR tokamak plasmas

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Abstract
Low frequency turbulence in TFR has been studied over a wide range of parameters and under many experimental conditions and a modelling of the frequency spectrum is presented. The main results are as follows. In ohmic discharges the turbulent spectrum is peaked around Kx approximately 5 cm-1 (Kperpendicular to rho i approximately 0.6) and decreases monotonically for both larger and smaller values of Kx. The decrease for small Kx values is particularly severe. No single linear dispersion relation is possible but, rather, a large domain of phase velocities is covered by the most intense waves. During auxiliary ICRF heating experiments, there is an increase of the level of turbulence which is proportional to the square root of RF power. Finally a strong increase in the turbulence after minor and major disruptions is observed.