O-MODE AND X-MODE COUPLING EFFECTS IN TOROIDAL PLASMAS AT FUNDAMENTAL AND SECOND EC HARMONICS AND IMPLICATION FOR ITER

We present recent numerically well resolved ECRF 3D STELEC toroidal full wave code [1] modelling results for fundamental and second harmonics scenarios in several tokamaks and ITER. Improved numerical resolution for middle size tokamaks further solidly confirms previously discovered O- and X- modes strong coupling at fundamental harmonic leading to broadened power deposition profiles, in compare with ray tracing predictions, due to influence of Upper Hybrid Resonance (UHR). For the T-10/DIII-D tokamaks we consider O-mode outside launch cases with EC resonance in plasma with UHR usual "moon serp" surface and out off plasma EC resonance at High Field Side when UHR surface is in-plasma internally closed one with Electron Bernstein Waves (EBW) being excited inside of it due to mode conversion process. Combined self consistent dynamic O-mode, X-mode and EB waves structure is intriguing one and is shown. This out off plasma EC fundamental resonance scenario was discovered in WEGA stellarator [2]. In second harmonic scenarios we are concentrating on X-mode outside launch at sufficiently large plasma densities for JET, some times close (but lower) to this mode density cut off. Exact boundary problem EC wave solution again shows that simultaneously is exciting also the O-mode (with smaller amplitude), presumably due to reflection effects and wave depolarization at the wall.