Fullwave Simulations of Lower Hybrid Waves Coupled to 3D Fokker-Planck Solver: Comparison with Alcator C-Mod Experiment

Non-inductive lower hybrid current drive (LHCD) experiments have been carried out on the Alcator C-Mod tokamak and the hard x-ray (HXR) spectrum has been measured. An improved analysis technique of the experimental HXR data has been developed to more accurately evaluate the HXR flux for this type of discharge. We have simulated a similar LHCD discharge with the full wave code LHEAF (Lower Hybrid wavE Analysis based on FEM). This code, combined with the newly developed 3D Fokker-Planck (v_∥, v_⊥, r) and synthetic HXR diagnostic modules, to calculate the steady state electron distribution function in the plasma and the resulting HXR radiation spectrum. The simulated non-thermal x-ray proflle shave been found to be in good agreement with the measured experimental profile. In particular LHEAF simulations were able to reproduce the broad width of the measured HXR profile for a discharge with low n_∥, which has been a long standing issue for LHCD simulations on Alcator C-Mod.