Characteristic peaked profiles of ion temperature and toroidal rotation velocity in JT-60 hot ion modes

In JT-60, hot ion modes (Ti(0) = 9-13 keV, H0 beam into H+ plasma) exhibiting peaked profiles of the ion temperature, Ti(r), and the toroidal rotation velocity, Vt(r) have been obtained with an effective safety factor qeff ~ 10. Experiments have been performed to study the characteristics of these peaked profiles in which qeff was scanned over the range 4.5 < qeff < 15. Peaking of the profiles of Ti(r) and Vt(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 Ti profile is generated