A possibility of the strong anomalous absorption of the pump power in the X2-mode ECRH experiments

Abstract

The nonlinear stage of the low-threshold decay of a beam of the extraordinary waves which occurs in the vicinity of a local maximum of the hollow density profile and leads to the excitation of localized electron Bernstein (EB) wave and heavily damped ion Bernstein wave is analyzed. The transition of primary parametric decay instability to the saturation regime due to the presumably most important nonlinear mechanisms such as the pump wave depletion and the secondary decay of primary EB wave are considered in the case of a shallow potential well, in which only the fundamental-mode EB wave can be trapped. In this case characterized by the highest instability saturation level the problem is analyzed both analytically and numerically. The anomalous absorption of the pump power is estimated.