Results are presented of the second harmonic heating experiments in the ion cyclotron range of frequencies (ICRF) on JT-60. Heating and confinement characteristics are investigated by using the hydrogen second harmonic (H-majority 2wjh) scheme and the hydrogen minority second harmonic (H-minority 2 ώ ch) scheme (nn/nHe « 0.1) in two toroidal phasing modes of antenna currents, in phase ((0, 0)) and out of phase ((π, 0)), at Pjc ^ 3 MW, ñj = (1.3-6.6) X 10 ” m‘^ and Ip = 1-2.4 MA. Efficient plasma heating has been demonstrated in both heating schemes. Intense non-Maxwellian ion tails are observed at low density. Sawtooth oscillations with an enhanced period in the electron temperature are found over a wide range of electron densities. The incremental energy confinement time, Te', for (tt, 0) phasing is larger than for (0, 0) phasing, irrespective of the heating scheme. In particular, H-minority 2wjh heating with (ir, 0) phasing shows excellent plasma heating with * 100-120 ms, which is larger than that of neutral beam injection (NBI) heating by a factor of about two. Different dependences of tÈ“ on Ip are obtained in the two heating schemes. The (0, 0) phasing data of ' in H-majority 20^» heating increase with Ip up to 1.9 MA, while the (tt, 0) phasing data in H-minority 2ü>ch heating are almost constant with Ip up to 2.4 MA. The global energy confinement shows an L-mode behaviour. The energy confinement time for H-minority 2uch heating at high density agrees well with the Shimomura-Odajima scaling.
ASJC Scopus subject areas
- Nuclear and High Energy Physics
- Condensed Matter Physics