Sawtooth Control Mechanism in JET Using Off-Axis Toroidally Propagating ICRF Waves

The restricted range of the planned ICRH antennas in ITER is such that minority 3He is likely to be employed. Due to the negligible or reverse current drive contributions from minority 3He, it was thought that MHD control with toroidally propagating waves would not be viable. In contrast, the new explanation for the sawtooth control mechanism does not rely on net driven current, and was therefore predicted to function even with minority 3He. Consequently, minority 3He experiments in JET have been devised and carried out and interpreted with simulations in order to demonstrate the viability of sawtooth control using 3He minority in ITER, and to conclusively show that the previously assumed classical mechanism cannot explain ICRF sawtooth control experiments in JET.
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