Tuesday, November 19, 2019
Lower hybrid (LH) waves are an efficient means to drive off-axis current in a tokamak. Presently, both ray-tracing and full-wave simulations are unable to match experimental current drive (CD) profiles in Alcator C-Mod. The likely cause is scrape-off-layer (SOL) turbulence interactions that affect wave propagation. Synthetic SOL turbulence that account for intermittent blob-like structures is coupled to the ray-tracing/Fokker-Planck model GENRAY/CQL3D. In a slab geometry, refraction through blob-like turbulence is shown to result in increased wave scattering compared to previous models that assumed non-intermittent turbulence. This model is next used to study the effects of SOL refraction on power deposition and CD in an Alcator C-Mod geometry. Initial results show that the presence of SOL blobs lead to higher on-axis damping and smoother current profiles, which better match experiment.