Model for Heat Pinch in Reversed Magnetic Shear Tokamak Plasmas

A simple model is proposed to explain the recent experiment in TFTR and the more recent one in JT-60U. In the model the significant reduction of effective thermal diffusivities of ions and electrons ( x_i^eff and x_e^eff) is attributed to the inward flows of drift wave energy, induced by the synergistic effects of the reversed magnetic shear and E X B velocity shear, where E is due to ion pressure gradient. Numerical results demonstrate the predictions of the present model, in particular, the numerical results for x_i^eff are in good agreement with experimental trents.