Study of GAMs and related turbulent particle flux with HIBP in the T-10 tokamak

The new findings in the behavior of geodesic acoustic modes (GAMs) and turbulent particle flux dynamics on the T-10 tokamak are presented. For the first time in T-10 the broadband oscillations (<250 kHz) of electric potential and density in Ohmic and ECRH regimes (B_t = 1.6...2.4 T, I_pl = 0.15...0.3 MA, n_e = (0.6...5)10¹⁹ m^-3) were measured by Heavy Ion Beam Probe (HIBP) in the core plasmas. At the periphery, at r/a > 0.8, the dominated GAM peak with frequency ∼ 14 kHz and noticeable peak of quasi-coherent oscillations in the frequency band 40...100 kHz were observed. The multichannel HIBP measurements were performed to measure poloidal electric field E_pol and to retrieve the electrostatic turbulent radial particle flux driven by Ex B drift. The preliminary experiment shows that in contrast to the power spectral density of plasma potentials, GAM peak was almost invisible in the E_pol power spectrum and on the frequency resolved turbulent particle flux. These results are consistent with the general concept of GAM as a high-frequency branch of zonal flows, having symmetric poloidal structure of potential perturbation, which were supported by earlier observation of poloidal mode number m=0 in T-10.