Impact of Generalized Sheath Boundary Conditions on Dynamics of Plasma Filaments at the Tokamak Edge

The impact of generalized sheath boundary conditions, taking into account the sheath perturbations driven by the Alfvén waves, on the propagation of plasma filaments at the tokamak edge is considered. A model describing the filament dynamics and containing new boundary conditions is developed. Estimates of the model control parameter—the sheath impedance—on the plasma transport are obtained. Simulations of the filament dynamics under the conditions characteristic of edge plasmas in NSTX and Alcator C‑Mod tokamaks are performed. It is shown that the sheath impedance leads to an increase in the mean values of the electrostatic potential and advection velocities of filaments, in agreement with experimental observations, requiring, at the same time, a more detailed description of the Alfvén wave reflection from the conducting surfaces of the installations.