Self-Consistent Studies of Lower Hybrid Current Drive in ITER Relevant Regimes

Lower hybrid current drive (LHCD) is currently under consideration for off-axis current profile control in the ITER device. Upcoming LHCD experiments in the Alcator C-Mod tokamak will be performed in a wave physics regime close to that of ITER where B $\cong $ 5T, n$_{e }\cong $ 1 $\times $ 10$^{20 }$m$^{-3}$, and ($\omega _{pe }$/ $\omega _{ce})^{2 }\cong $ 1 and are therefore ideally suited to test physics issues related to off-axis current generation in a reactor regime. We have implemented the combined Fokker Planck -- ray tracing code (CQL3D-GENRAY) [1] at MIT and have used this code to carry out detailed studies of LH current drive for candidate target discharges in both ITER and C-Mod. The role of 2D velocity space effects in determining the driven current and radial power deposition profiles will be discussed as well as the efficacy of using ``compound'' LH grill spectra for controlling the location of power deposition. [1] R.W. Harvey and M.G. McCoy, Proc. of IAEA TCM on Advances in Simulation and Modeling of Thermonuclear Plasmas, Montreal, IAEA, Vienna (1993) p. 492.