Validity of the impurity entrainment assumption in the thermal stability analysis of multifaceted asymmetric radiation from the edge (MARFEs) in tokamak plasmas

Abstract

The assumption that impurity ion perturbations are entrained in phase and in fixed proportion with the main plasma ion perturbations is commonly made in analyses of radiative thermal instabilities in the edge of tokamak plasmas, leading to multifaceted asymmetric radiation from the edge (MARFE). An analysis in which the impurity ion perturbations are treated separately from the plasma ion perturbations demonstrates that this assumption does not alter the conclusion of the analysis regarding stability limits or edge density limits for the (m=0, k‖=0) mode, but that inclusion of a separate impurity ion perturbation in the analysis stabilizes the (m>0, k‖≠0) modes.