I-mode Plasmas with Combined ICRF Mode Conversion Flow Drive and Minority Heating on Alcator C-Mod

High performance I-mode plasmas have been obtained via ICRF mode conversion heating and flow drive, plus ICRF minority heating. The plasmas have reversed magnetic field (B$_{t0}\sim $5.1 T) and lower-single-null shape. External $^{3}$He is puffed to have n$_{He3}$/n$_{e}\sim $0.1 and the residual H level n$_{H}$/n$_{e}$ is about 0.05. We use 50 MHz RF power ($\le $2.5 MW) for D($^{3}$He) mode conversion flow drive and heating, and 80 MHz RF power ($\le $2.5 MW) for D(H) minority heating. The obtained I-mode plasmas have high T$_{e}$ ($\le $8 keV) and large rotation ($\le $100 km/s). The rotation profile has a large shear at r/a $\sim $ 0.9, which may help further enhance the plasma confinement. Because of the long slowdown time at high T$_{e}$ and relatively low density, a high energy H tail is generated. The tail also affects the sawtooth oscillation and produces large sawtooth crashes, which also trigger neoclassical tearing modes. The appearance of the NTMs often coincides with a slowdown of plasma rotation. The onset condition of these NTMs is at the low collisionality regime within the criterion established by studies on other tokamaks.