Impurity Transport in Alcator C-Mod Plasmas

Impurity Transport in Alcator C-Mod Plasmas
Author: John E. Rice
Publisher:
Total Pages: 86
Release: 2005
Genre:
ISBN:

(cont.) These edge values of the transport coefficients during EDA H-mode are qualitatively similar to the neoclassical values. In ELM-free H-mode discharges, impurity accumulation occurs, dominated by large inward impurity convection in the pedestal region. A scaling of the impurity confinement time with H-factor reveals a very strong exponential dependence. In ITB discharges, there is significant impurity accumulation inside of the barrier foot, typically at r/a = 0.5. Steady state impurity density profiles in L-mode plasmas have a large up-down asymmetry near the last closed flux surface. The impurity density enhancement, in the direction opposite to the ion BxB drift, is consistent with modeling of neo-classical parallel impurity transport.