A note on asymmetry effects in x-mode reflectometry

摘要

In the presence of density gradients the propagation of electromagnetic waves in a magnetized plasma is modified with respect to the homogeneous case. The local dispersion relation depends on the sign of the angle of propagation and the polarity of the stationary magnetic field. The consequences for x-mode reflectometry are investigated with special emphasis on Doppler reflectometry. The results from full-wave 2D simulations are shown for the TJ-II stellarator and a small-scale laboratory experiment. Noticeable asymmetry effects are seen if the right-hand cut-off lies close to the upper-hybrid resonance.