Dynamic Simulation of the Electron Bernstein Wave Heating Under NBI Conditions in TJ-II Plasmas

In this work, we have calculated the expected properties of the Electron Bernstein Wave (EBW) heating using the O-X-B double mode conversion scenario in a plasma that evolves from Electron Cyclotron Resonance (ECR) to Neutral Beam Injection (NBI) heating in the TJ-II device. For this purpose, a transport simulation that reproduces the time evolution of a typical collapsing plasma heated by a combination of ECR and NBI power has been used. It is seen that the predicted EBW absorption depends strongly on the plasma characteristics, whose time evolution depends in turn on the heating properties. Therefore, the need of consistently computing the ray tracing and the plasma evolution is underlined. The fraction of the absorbed EBW heating power becomes very high as soon as the O mode cutoff layer appears. This guarantees the overlapping of both EBW and ECR heating, thus avoiding excessive plasma cooling when the wave cutoff is reached. The EBW power deposition profile evolves from off-axis to a much more centred shape that persists until the radiative collapse quenches the plasma. (c) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim