Speaker
Description
Detailed 3D models of processes in materials subsurface and in plasma above the surface were recently developed and integrated into a single package, for the first time. This avoids uncertainties in predicting materials performance in fusion devices with complex geometries, magnetic, and electric fields. The upgraded ITMC-DYN+ package includes comprehensive sets of Monte Carlo and deterministic models to simulate a) collisional interactions in material and in plasma, b) particle motion in electromagnetic fields, c) thermal processes of diffusion and chemical reactions; d) D/T trapping in defects and intrinsic defects growth and evolution to other types. These models enable self-consistent analysis of time- and space- dependent changes in plasma facing materials (PFMs) and their effect on erosion/redeposition, potential plasma contamination, D/T retention and recycling, material properties degradation. The integrated models were benchmarked against experiments at DIII-D regarding material erosion/redeposition and D retention as well as against laboratory experiments on D retention and defects growth in tungsten-based materials.
We simulated the response of several PFMs during DIII-D discharges and calculated fluxes of generated impurities depending on plasma and material properties. Detailed simulations of tungsten-based alloys, proposed to strengthen W microstructure, and tungsten with deposited coating layers were performed to predict high Z material erosion, T co-deposition, and potential plasma contamination at various material surface conditions. Time-dependent, multi-species modeling showed the effects of interplay between preferential sputtering, local and extrinsic impurities deposition, and ExB drift on divertor material erosion, enrichment, and growth of mixed amorphous layers. Changes in material surface and in high-Z impurity source for current graphite walls at DIII-D and future metallic walls were critically assessed in this study. Our calculations for the conditions of graphite-free walls showed, e.g., that fast surface enrichment in W in compounds with low Z content results in near full suppression of W erosion and orders of magnitude reduction of low Z impurity from the divertor in comparison with a graphite wall environment where W erosion does not decrease with time. Our successful simulations of various experiments showed 1) the effects of surface contamination or enrichment in W on D diffusivity and retention, 2) changes in the surface microstructure induced by collisional interactions and by D supersaturation, 3) correlation between irradiation conditions and D retention in blisters and in dislocation networks. Ignoring such processes integration to predict performance of materials in complex PMI environment during steady state and transient operation may not yield correct results.