Comparison of transient electron heat transport in LHD helical and JT-60U tokamak plasmas

Transient transport experiments are performed in plasmas with and without internal transport barriers (ITB) on LED and JT-60U. The dependence of chi e on the electron temperature, T-e, and on the electron temperature gradient, del T-e, is analysed with an empirical non-linear heat transport model. In plasmas without an ITB, two different types of non-linearity of the electron heat transport are observed from cold/heat pulse propagation: the X, depends on Te and del T-e in JT-60U, while the del T-e dependence is weak in LHD. Inside the ITB region, there is none or weak del T-e dependence both in LHD and JT-60U. Growth of the cold pulse driven by the negative T, dependence of X, is observed inside the ITB region (LHD) and near the boundary of the ITB region (JT-60U).