Global drift wave map test particle simulations

Global drift wave map equations that allow the integration of particle orbi ts on long time scales are implemented to describe transport. Ensembles of test particles are tracked to simulate the low-confinement mode/reversed sh ear/enhanced reversed shear plasmas in the Tokamak Fusion Test Reactor (TFT R) tokamak and the Optimized Shear plasma in the Joint European Torus (JET) tokamak. The simulations incorporate a radial electric field, (E) over bar (r), obtained from a neoclassical calculation [Zhu , Phys. Plasmas 6, 2503 (1999)] and a model for drift wave fluctuations that takes into account cha nge in the mode structure due to (E) over bar(r) [Taylor , Plasma Phys. Con trolled Fusion 38, 1999 (1996)]. Steady state particle density profiles alo ng with two different measures of transport, the diffusion coefficient base d on a running time average of the particle displacement and that calculate d from the mean exit time, are obtained. For either weak or reversed magnet ic shear and highly sheared (E) over bar(r), particle transport barriers ar e observed to be established. In the presence of such a transport barrier, it is shown that there is, in general, a difference between the two measure s of transport. The difference is explained by a simple model of the transp ort barrier. (C) 2000 American Institute of Physics. [S1070-664X(00)00404-3 ].