Monte Carlo study of heat conductivity in stochastic boundaries: Application to the TEXTOR ergodic divertor

The heat balance equation is derived and solved for fusion edge plasma cond itions with (partially developed) ergodic magnetic-field structures. For th is purpose, a three-dimensional (3D) Monte Carlo code, "E3D," based upon th e "multiple local magnetic coordinate system approach" has been developed. Parameters typical for the Dynamic Ergodic Divertor (DED) of TEXTOR-94 (Tor us Experiment for the Technology Oriented Research) [K. H. Finken , Fusion Eng. Des. 37, 1 (1997)] are chosen in the applications. The plasma temperat ure fields and the profiles of the radial component of heat flux due to the classical parallel and anomalous perpendicular diffusion are calculated. B ecause of magnetic-field ergodization and diversion of field lines, paralle l conduction also can contribute to this radial flux. The results are compa red with theoretical predictions for two limiting cases: With the Rechester -Rosenbluth model of ergodization-induced transport and with a "laminar flo w model" proposed in the present paper. This latter model describes the eff ects of field line diversion. The diversion effect is shown to be dominant for TEXTOR-DED conditions. (C) 2001 American Institute of Physics.