Measurement of geodesic acoustic modes and the turbulent particle flux in the T-10 tokamak plasmas

Geodesic acoustic modes (GAMs) and the turbulent particle flux were studied in the T-10 tokamak in discharges with Ohmic (OH) and electron cyclotron heating (ECRH). The broadband oscillations of electric potential and density with frequencies up to 250 kHz were measured using a heavy ion beam probe (HIBP) in the plasma core. At the plasma edge, at a relative radius ρ > 0.8, the dominant GAM peak with a frequency of approximately 20 kHz and the noticeable peak of quasicoherent oscillations in the 40–100 kHz range were observed. Using a multislit energy analyzer, we estimate the poloidal electric field E_pol and the radial electrostatic turbulent particle flux, which is driven by drift in crossed E × B fields. The GAM peak was observed in the spectrum of potential oscillations, but it was practically absent in the spectrum of E_pol oscillations and in the frequency-resolved particle flux. However, the flux was observed in the broadband range. These results agree with the theoretical concept of GAM and our earlier measurements of symmetric poloidal structure of GAM potential perturbations. (paper)