The effects of the scattering by edge plasma density fluctuations on lower hybrid wave propagation

Scattering effects induced by edge density fluctuations on lower hybrid (LH) wave propagation are investigated. The scattering model used here is based on the work of Bonoli and Ott (1982 Phys. Fluids 25 361). It utilizes an electromagnetic wave kinetic equation solved by a Monte Carlo technique. This scattering model has been implemented in GENRAY, a ray-tracing code which explicitly simulates wave propagation, as well as collisionless and collisional damping processes, over the entire plasma discharge, including the scrape-off layer that extends from the separatrix to the vessel wall. A numerical analysis of the LH wave trajectories and the power deposition profile with and without scattering is presented for Alcator C-Mod discharges. Comparisons between the measured hard x-ray emission on Alcator C-Mod and simulations of the data obtained from the synthetic diagnostic included in the GENRAY/CQL3D package are shown, with and without the combination of scattering and collisional damping. Implications of these results on LH current drive are discussed.