A broadband experimental study of Alfvén eigenmode (AE) damping and excitation examines both low-n and high-n AEs (0 < |n| < 9) with a single diagnostic. Direct measurements of the damping rate of stable AEs with the active MHD system, in conjunction with analytic and numerical calculation, indicate that AE stabilization in Alcator C-Mod is largely due to radiative damping. AEs are also regularly observed to become unstable during ICRF heating above 3 MW. The most unstable modes have moderate-n around n = −4, in agreement with the common scaling of kθρfast ≈ 1 at maximum excitation.
Active excitation and damping rate measurement of intermediate-n toroidal Alfvén eigenmodes in JET, C-Mod and MAST plasmas