Spatial structure of the geodesic acoustic mode in the FT-2 tokamak by upper hybrid resonance Doppler backscattering

A new experimental technique is presented for the study of zonal flows in tokamak plasmas—upper hybrid resonance Doppler backscattering. The feasibility of the diagnostics is demonstrated allowing a complete characterization of the temporal and spatial behaviour of geodesic acoustic modes. The experimental results are obtained at the FT-2 tokamak.