Study of the linear conversion of lower hybrid waves in the FT-1 tokamak by the enhanced time-of-flight scattering technique

The propagation of lower hybrid (LH) waves in a tokamak plasma in the presence of an LH resonance surface is studied experimentally with the use of a specially elaborated technique based on the backscattering of the probing microwave radiation in the upper hybrid resonance region. The technique provides resolution in the wave vectors of the scattering density fluctuations. The conditions are determined under which the LH wave propagates in accordance with the predictions of linear theory and is converted into the short-wave-length ion Bernstein mode. The parameter range is found in which the predictions of linear theory fail to hold and the nonlinear effects come into play during LH wave conversion. The radial wavelengths of the LH and ion Bernstein waves are determined.