Spectroscopic determination of kinetic parameters for frequency sweeping Alfvn eigenmodes

Lesur, M.*; Idomura, Yasuhiro   ; Shinohara, Koji; Garbet, X.*; JT-60 Team

We present a new method for analyzing fundamental kinetic plasma parameters, such as the linear drive and the external damping rate, based on experimental observations of chirping Alfvn eigenmodes. The method consists of fitting procedures of nonlinear chirping characteristics between the so-called Berk-Breizman model and the experiment, in a quasi-periodic chirping regime. This is the first method that does not require any internal diagnostics. The method is validated through comparisons of kinetic plasma parameters against former analyses of the Toroidicity induced Alfvn Eigenmode (TAE) on MAST. This approach is applied to the TAE on JT-60U, which yields an estimation of the kinetic parameters and suggests the existence of marginally unstable TAEs.