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In JT-60, hot ion modes (T i (0) = 9-13 keV, H 0 beam into H + plasma) exhibiting peaked profiles of the ion temperature, T i (r), and the toroidal rotation velocity, V t (r) have been obtained with an effective safety factor q eff ~ 10. Experiments have been performed to study the characteristics of these peaked profiles in which q eff was scanned over the range 4.5 < q eff < 15. Peaking of the profiles of T i (r) and V t (r) occurs within a limited region. Moreover, the boundary of the region of improved performance is well characterized by the q = 1, 2 and 3 surfaces. The improvement in global confinement in JT-60 hot ion modes is attributed to the substantial increase in the volume of the enhanced confinement region within the q = 3 surface, in which region the peaked T i profile is generated
Koide et al. (1993) studied this question.