Characterization of tokamak edge turbulence by far-infrared laser scattering and Langmuir probes

The spectra, magnitude and spatial distribution of low-frequency (ω ≪ ω_ci) density fluctuation have been measured by two independent experimental methods in the edge plasma of the TEXT tokamak. Good agreement between far-infrared laser scattering and Langmuir probe measurements has been achieved and the strengths of each technique are evaluated. Langmuir probes are used to directly determine the particle flux induced by edge fluctuations (Γ ∝ ⟨ñ_×B⟩) and collective Thomson scattering permits an extension of these observations to the plasma interior. Results are presented for typical discharge conditions in a tokamak.