Analysis of damping rate measurements of toroidal Alfvén eigenmodes as a function of n: part II

Abstract

Complementing the database approach that has been presented in part I, this paper probes into individual plasma discharges and investigates the damping rate variations that are driven by the evolving plasma configurations. In addition to confirming the stabilizing effect of elongated plasma shapings on toroidal Alfvén eigenmodes, the significance of the span of the q profile is shown experimentally for the first time. It is found that, under conditions of transient current density profiles, the damping rate of medium-n modes has a dependence on the background plasma parameters that is distinctively different from that of low-n modes. The analysis of the correlation of the damping rate variations with the changes of the q profile shape and the alignment of the gaps of the shear Alfvén continuum leads to an assessment of the effect of the interaction of the modes with the Alfvén continuum as a function of n.