Study of internal transport barriers by comparison of reversed shear and high- discharges in JT-60U

Reduction of electron thermal diffusivity was investigated by comparing the internal transport barrier (ITB) with that of high- discharges. In reversed shear discharges heated by neutral beams, reduction was significant when negative magnetic shear was strong. Radial location of ITB propagated outwards and then localized near the region of q-minimum for both the ion and the electron channels. Reduction in was also observed in the electron heating regime by ion cyclotron heating