Effects of LHCD on H-mode transition, pedestal and confinement on Alcator C-Mod*

Advanced scenario experiments on Alcator C-Mod seek to combine current profile control using lower hybrid current drive (LHCD) with the high confinement of H-mode plasmas. There is little prior experience with LHCD in H-modes at the high field (5.4 T) and density ($>$10$^{20}$ m$^{-3})$ typical of C-Mod, and ITER. We find good LH coupling in H-modes, though relatively low driven current is expected at the LH power available to date (up to 1.2 MW). An unexpected result was a reduction in density and increase in T$_{ped}$ in some LHCD experiments, indicative of an increase in edge particle transport. In other experiments aimed at exploring the ``hybrid'' scenario, LHCD was used to modify j(r) before H-modes, delaying sawteeth until well into the current flat top. The timing of ICRF and H-modes with respect to q$_{0}$=1 affected both L-H transition dynamics and the H-mode pedestal and confinement, producing transiently higher stored energy than in discharges without LHCD.