Abstract
Waves in the ion cyclotron range of frequency (ICRF) are expected to play a central role in the heating of ITER plasmas during deuterium (D)–tritium (T) operation. These waves can also be used to drive current by direct electron damping of the fast wave, provided an appropriate antenna phasing is used. The corresponding current profile is peaked near the magnetic axis, and can have a beneficial effect on the discharge stability and performance. In this paper, two scenarios applicable during the activated phase of ITER operation are compared: second harmonic tritium heating and minority helium-3 heating, which differ in the addition of a small fraction of 3He ions (2%) in the DT mixture for the latter. The resulting change of the dominant ICRF heating scheme causes the discharge properties to differ appreciably. In this paper, a full-wave code is coupled to a Fokker–Planck solver and a current drive module to investigate in detail the effect of ICRF waves on the discharge. The impact of phasing on the scenario in terms of plasma heating and current drive efficiency is studied by simulating ICRF heating with various antenna toroidal spectra. It is found that despite a lower current drive efficiency, the addition of 3He in the discharge increases the single-pass absorption rate, the ion heating fraction, and makes the scenario essentially immune to details in the toroidal phasing and fast ion properties.
Published Version
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