Interpretive modeling of thermal transport in DIII-D boundary plasma

An interpretive 2D model for tokamak edge heat transport is developed and implemented in the framework of the boundary plasma transport code UEDGE [1], including radiation directly from experimental data and making certain simplifying assumptions for the transport (dropping convective, ohmic, and mechanical work terms that are usually small). In the tokamak scrape-off layer (SOL) and divertor, thermal transport is governed by the interplay of parallel and cross-field conduction and convection, and by radiative losses, and the predictive full-physics edge plasma transport codes (UEDGE, SOLPS etc.) include sophisticated models for the thermal transport physics; at the same time our interpretive model is simple enough to run fast and allows processing of a large number of shots and exploring trends in experimental data. Using IRTV data provides constraints on the interpretive model, thus allowing to infer the effective anomalous cross-field transport in the SOL and divertor regions. For a typical H-mode shot in DIII-D, the effective cross-field thermal diffusivity χ_⊥ in the edge is found from the interpretive model to be on the order of 1 m²/s, consistent with the values typically found for tokamak edge plasmas, and some interesting details of the χ_⊥ spatial profile are inferred. [1] Rognlien et al., Phys. Plasmas v.6, n.5, p.1851 (1999)