Tokamak edge plasma modeling using an improved onion-skin method.

摘要

Boundary (edge) plasma phenomena play a crucial role in the development of controlled thermonuclear fusion via magnetic confinement. In this work, the edge plasma are modeled by a coupled set of plasma/neutral transport equations; the neutral transport equations are solved by Monte-Carlo techniques (NIMBUS code), while the plasma transport equations are solved using an improved onion-skin method (OSM) based on the numerical techniques of computational fluid dynamics. The OSM approach, as defined in this thesis, consists of replacing the anomalous cross-field flux terms by (often simplified, always adjustable) cross-field source terms, and taking advantage of available diagnostic data (typically radial profiles of Gamma and Te from target Langmuir probes), of varying these cross-field sources in order to minimize the error between the solution and the diagnostic data. The OSM approach was shown capable of capturing the transition from attached to detached conditions in a tokamak divertor plasma, an important and timely aspect of present fusion research. The other applications presented in the thesis include a study of the sensitivity of modeling assumptions, a code-code comparison between the OSM and a standard 2D approach (represented by the EDGE2D code), and a code-experiment comparison with reciprocating probe data for Ohmic, L-mode and H-mode shots on the JET tokamak