Modeling of particle and energy transport in the edge plasma of Alcator C-Mod

In the present study recycling and transport in the edge plasma of Alcator C-Mod [I. H. Hutchinson et al;, Phys. Plasmas 1, 1511 (1994)] is modeled and analyzed with the multi-fluid code UEDGE [T. D. Rognlien et al;, J. Nucl. Mater. 196-198, 347 (1992)]. Matching the experimental plasma density profiles in the scrape-off layer (SOL) requires a spatially dependent effective anomalous diffusion coefficient D-perpendicular to growing rapidly towards the wall. The midplane pressure of neutral gas, P-mid, is a key parameter that reflects the magnitude of anomalous transport of plasma from the core. Recycling of plasma on the main chamber wall appears to be quite significant, especially in the case of high P(mid)similar to 0.3 mTorr when the main wall provides similar to 70% of recycling neutrals in the main chamber. In the upper SOL (well above the x point) draining of particles by the poloidal flow is weak and thus the particle balance is predominantly radial. For the radial heat transport it is found that energy flux carried by radial plasma convection and by charge-exchange (CX) neutrals is quite significant in SOL. In the high P-mid case, heat conduction by CX neutrals along with radial heat convection by plasma carries most of the power flux (similar to 75%) across the last closed flux surface. Even in the low P-mid case, heat conduction by CX neutrals dominates the radial heat flux far out in the SOL. (C) 1999 American Institute of Physics. [S1070-664X(99)02407-6].