Comparison of impurity and electron particle transport in JET discharges

A zone of reduced anomalous diffusivity for impurities in the central region of the discharge has been reported from several Tokamaks. In this paper the authors point out that this condition is not an occasional occurrence, but a very general feature. Indeed all JET cases analyzed, where the experimental conditions allow adequate sensitivity and space resolution for the measurement of the impurities diffusion coefficient, show unambiguously that this quantity is close to neoclassical levels within r=0.4a. Furthermore, from the analysis of the electron density profile in sawtooth-free phases of JET discharges with moderate electron temperature, the authors deduce that the electron particle diffusivity D p is also close to neoclassical in the same region. The values obtained for D p in that region during the early pre-sawtooth phases are the same as in Ohmic post-pellet phases.