We modeled tungsten–carbon mixed surface evolution, sputtering erosion, and transport for the tungsten coated region of a small angle slot (SAS) divertor design for the DIII-D tokamak. This divertor concept aims to achieve a closed slot dissipative plasma to minimize heat load and surface erosion, and to study high-Z material performance. Our advanced simulations use coupled ITMC-DYN material mixing/response and 3D full kinetic REDEP/WBC erosion/redeposition code packages, with divertor plasma solution from the SOLPS-ITER package with 4 MW power input. The SAS design geometry and resulting in-slot plasma parameters cause significant differences in predicted sputter/transport from a conventional divertor. For 2% C/D incident plasma ratio, an equilibrium mixed C/W surface is attained at ∼30 s of discharge, from wall sputtered carbon transported to the 10 cm long tungsten divertor region. Tungsten remains exposed to the plasma, but the evolved surface composition varies with different C/D ratios. Tungsten is primarily sputtered from the mixed surface by impinging carbon ions in the +1 to +4 charge states, with some self-sputtering. Redeposition of sputtered tungsten to the divertor is significant, ∼80% along the higher plasma temperature attached plasma SAS entrance region, but this is less than the typically near-unity values for a conventional divertor. Plasma-incident carbon is highly backscattered (∼50%) from the mixed surface, with little redeposition (<10%); this helps maintain tungsten in the surface sputter zone. Carbon is mainly sputtered from the mixed surface by D+ ions, also with low redeposition (∼10%–30%). Finally, the modeling shows non-zero but low sputtered tungsten current from the divertor to the core plasma direction. These results appear favorable for effective testing of a tungsten-containing SAS divertor in DIII-D, and extrapolation of mixed-material evolution/response findings to the analogous low-Z/high-Z, Be/W, ITER plasma facing system.
我们模拟了DIII-D托卡马克小角槽（SAS）偏滤器设计中钨-碳混合表面演化、溅射侵蚀和输运过程。该偏滤器概念旨在通过封闭槽内耗散等离子体来最小化热负荷和表面侵蚀，并研究高Z材料性能。我们的先进模拟采用耦合的ITMC-DYN材料混合/响应和全三维动力学REDEP/WBC溅射/再沉积代码包，等离子体解来自SOLPS-ITER代码包，输入功率为4 MW。SAS设计的几何结构和由此产生的槽内等离子体参数导致预测的溅射/输运行为与常规偏滤器存在显著差异。在2% C/D入射等离子体比率下，约30秒放电后达到平衡的C/W混合表面，壁面溅射碳输运至10 cm长的钨偏滤器区域。钨仍暴露于等离子体，但表面成分随不同C/D比率而变化。钨主要通过入射碳离子（电荷态+1至+4）从混合表面溅射，并伴有少量自溅射。溅射钨在偏滤器区域的再沉积显著，在较高等离子体温度的附着型SAS入口区域约达80%，但低于常规偏滤器通常接近1的值。入射碳在混合表面高度反射（约50%），再沉积很少（<10%）；这有助于维持钨在表面溅射层中的存在。碳主要通过D+离子从混合表面溅射，再沉积率也较低（约10%–30%）。最后，模拟显示从偏滤器向芯部方向的溅射钨流非零但较低。这些结果似乎有利于在DIII-D中有效测试含钨SAS偏滤器，并将混合材料演化/响应结果外推至类似的低Z/高Z、Be/W ITER等离子体 facing 系统。