High-n Ideal TAE Stability of ITER

The ideal MHD stability analysis of high-n (n is the toroidal mode number) Toroidal Alfvén Eigenmodes (TAE’s) is presented, using realistic and completely general ITER equilibria with shaped, up-down asymmetric, magnetic flux surfaces. An approach has been used, based on analytical-theoretical methods, which can give interesting results and allows us to analyze the conditions for enhanced TAE damping (although preventing us from computing the excitation thresholds). The frequency spectrum of TAE modes is found by solving the fully two dimensional problem using a two spatial-scale WKB formalism. The phase space integration is extended to a complete periodic orbit (at fixed frequency ω) in the (r,θk) phase-space (r is here a general flux coordinate and θk is the WKB eikonal entering in the expression of the radial envelope of the mode). The equilibria, analyzed here, are characterized by ideal TAE’s localized in the half outer part of the plasma column, where the α-particle drive is expected to be small and modes are likely affected by continuum damping.