Alcator C-Mod Experiments in Support Of The ITER Baseline 15 MA Scenario
Authors: Charles E. Kessel, et. al.
Abstract:
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 center, and reduces the sawtooth onset times. Flattop
plasmas targeting ITER baseline parameters have been sustained for 20 τE or 8-13 τCR, 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.
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Submitted to: Nuclear Fusion (May 2013)
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Download PPPL-4934 (pdf 266 KB 26 pp)
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