改善閉じ込めと新古典効果

抄録

Matrix Inversion (MI) method is developed in order to estimate the neoclassical ion thermal diffusivity, χ_NC, correctly. In the MI method, effects of impurity on χ_NC are treated self-consistently and no approximation on the friction and the viscosity matrix elements is carried out. The comparison of χ_NC value between the MI method and the Chang-Hinton’s (CH) formula shows that the CH formula over-estimates χ_NC value twice as large as that of MI method for typical JT-60U plasmas. The different dependence of χ_NC on the inverse aspect ratio, ε, the effective charge number, Z_eff, and the normalized ion collisionality, ν_*i, between the MI method and the CH formula is presented. The radial electric field. E_r, is estimated from the momentum and the heat momentum balance equations parallel to the magnetic field. Profiles of E_r are compared between the two types of improved core confinement plasmas with internal transport barrier (ITB) in JT-60U, the “parabolic type ITB” and the “box type ITB”. In the box type ITB, the experimentally estimated thermal diffusivity. χ^exp, decreases in the core region. However, the E_r shear is not so strong. In the box type ITB, a strong E_r shear appears inside the ITB layer and the χ^exp value decreases drastically to the level of χ_NC. The E×B shearing rate becomes almost the same as the linear growth rate of the drift microinstability inside the ITB layer of the box type ITB.