Numerical Studies of poloidal field effects on ICRF mode conversion

In multi-ion species plasmas with a moderate minority fraction, the fast wave is partially mode converted to shorter wavelength modes at the ion-ion hybrid layer. In addition to Ion Bernstein Waves (IBW), mode conversion to Ion Cyclotron Waves (ICW) in the presence of a poloidal field has been predicted by Perkins [1] and confirmed experimentally on Alcator C-Mod [2]. In this work, we take a similar approach as in [1] and study the effect of the poloidal field on ICRF mode conversion in a one dimensional geometry. Solving the local dispersion relation numerically in the vicinity of the ion ion hybrid layer, we show dispersion curves for the fast wave and mode-converted Ion Cyclotron Wave in the cold plasma limit and with finite electron temperature. Due to the rapid upshift in k(parallel to), the Ion Cyclotron Wave can enter the acoustic domain omega/k parallel to nu(the) < 1 and propagate towards to the minority ion cyclotron layer, although it will strongly damp on electrons.