Modeling LH wave reduction through SOL blobs using synthetic turbulence data

Bodhi Biswas


Tuesday, November 19, 2019



PSFC Student Seminars

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.