A finite-difference time-domain code is used to obtain the full-wave solution of the O–X mode conversion process for typical parameters of the TJ-II stellarator in a cylindrical geometry. This reduction of the complicated stellarator geometry to a cylindrical geometry is chosen since the conversion process occurs only over a limited radial plasma volume. In the calculations, Gaussian antenna beams are studied with the option of different beam waists in the poloidal and toroidal direction. Optimum conversion efficiency is found if the wavefront of the incident antenna beam is matched to the local curvature of the O–X conversion layer. Finally, the code is used to calculate the complete O–X–B conversion process into a Bernstein wave.
On the influence of 2D inhomogeneity on electromagnetic mode conversion near the cut-off surfaces in magnetized plasmas