Formation and Stability of Impurity "snakes" in Tokamak Plasmas
Authors: L. Delgado-Aparicio, et. al.
Abstract:
New observations of the formation and dynamics of long-lived impurity-induced helical "snake"
modes in tokamak plasmas have recently been carried-out on Alcator C-Mod. The snakes form
as an asymmetry in the impurity ion density that undergoes a seamless transition from a small
helically displaced density to a large crescent-shaped helical structure inside q < 1, with a regularly
sawtoothing core. The observations show that the conditions for the formation and persistence
of a snake cannot be explained by plasma pressure alone. Instead, many features arise naturally
from nonlinear interactions in a 3D MHD model that separately evolves the plasma density and
temperature.
__________________________________________________
Submitted to: Physical Review Letters (July 2013)
__________________________________________________
Download PPPL-4847 (pdf 274 KB 5 pp)
__________________________________________________