Alcator C-Mod experiments in support of the ITER baseline 15 MA scenario

Experiments on Alcator C-Mod from 2009?2012 have examined the rampup, flattop and rampdown phases of the proposed ITER 15?MA baseline scenario. Rampup studies show ICRF heating can significantly reduce the V-s requirement, and that an H-mode late in the ramp can reduce this further. ICRF modifications to li in L-mode are minimal, although the Te profile is peaked relative to ohmic in the plasma centre, and reduces the sawtooth onset times. Flattop plasmas targeting ITER baseline parameters have been sustained for 20?E or 8???13?CR, but only reach H98???0.6 at n/nGr?=?0.85, rising to 0.9 at n/nGr?=?0.65. Rampdown studies show H-modes can be routinely sustained with ICRF power injection, avoiding an OH coil over-current associated with the H?L transition. In addition, faster current rampdowns are preferred to avoid an over-current when an H?L transition ultimately does occur. In the H-mode rampdown the density is found to drop with Ip, preserving the n/nGr ratio, so long as ICRF power is injected.