Energy propagation and field structure of LH fast waves in the UCLA continuous current tokamak (CCT)

3D field maps of the lower hybrid fast waves have been measured in the UCLA CCT tokamak in both the current drive and test wave experiments. The waves was found to propagate at a relatively constant small angle (<20°) to the magnetic field lines. When launched from the edge, the plasma filters the antenna spectrum allowing only the component N//≊N⊥ to penetrate. The wave damping cannot be accounted for either by Landau or collisional damping. The measured N⊥/N//≊1 suggests mode scattering between the fast and slow modes. The low N// component however can be excited when launch directly at the center of the plasma using a small dipole antenna. Substantial asymmetry of the propagated wave pattern was observed in both the up‐down and in‐out directions.