Scattering of lower-hybrid waves by density fluctuations

Lower-hybrid wave injection into tokamaks has been proposed for use in both bulk plasma heating and current drive schemes. However, experimental investigations show turbulent regions near the outside of tokamak plasmas that will scatter an initially collimated, monochromatic wave in both angle and frequency. Concern here is achieving a theoretical understanding of these processes to explain present results and predict the success of future experiments. In addition, the problem is of interest because of its relevance to other fields and basic physics. Results are related to typical tokamak plasma parameters showing that for most experiments, the majority of the incident energy is expected to reach the plasma center unless the tokamak plasma is unusually small and dense. However, the initial angular collimation may well be lost, reducing the probability of well defined resonance cones. Although the frequency broadening of the lower-hybrid waves will not significantly affect their propagation, it can be a few to many times the typical frequency of the turbulent density fluctuations - sufficient to account for measured spectral broadening in the Alcator tokamak