The global confinement and the local transport properties of improved core
confinement plasmas in JT-60U were studied in connection with E-r shear for
mation. In the improved core confinement mode with internal transport barri
ers (ITBs), these are roughly classified into 'parabolic type' ITBs and 'bo
x type' ITBs. The parabolic type ITB has a reduced thermal diffusivity chi
in the core region; however, the E-r shear, dE(r)/dr, is not as strong. The
box type ITB has a very strong E-r shear at the thin ITB layer and chi dec
reases to the level of neoclassical transport there. The estimated ExB shea
ring rate, w(ExB), becomes almost the same as the linear growth rate of the
drift microinstability, gamma(L), at the ITB layer in the box type ITB. Ex
periments with hot ion mode plasmas during the repetitive L-H-L transition
showed that the thermal diffusivity clearly depends on the Er shear and the
strong E-r shear contributes to the reduced thermal diffusivity.