Speaker
Description
EMC3-EIRENE modeling of detachment of 3D scenarios at DIII-D with resonant magnetic perturbations applied show that neon as a seeded impurity is able to semi-detach the ITER similar shape at comparatively lower separatrix impurity densities than seeded nitrogen. This impurity buildup is observed on the low-field side at the DIII-D shelf, leading to detachment of the far scrape-off layer (SOL), and remaining semi-attached at the strike line near the lower pumping gap on the floor. In the near SOL, there is neutral pressure buildup occurring for main ion species (D) densities with deep detachment observed for higher separatrix densities (5x1019 m-3), though not within the observed ELM suppression window. The simulations here are in support of an experimental campaign in which extrinsic impurities were used to study the impact on the SOL and exhaust of such species in ELM suppressed scenarios at DIII-D. In order to efficiently pump out these impurities, it is necessary to identify global transport dynamics for them as well as identifying safe operational limits for the wall components. The data collected during this campaign is used to denote differences in particle transport shown in these simulations and those collected with coherent imaging spectroscopy, charge exchange recombination, neutral pressure measurements and helium beam measurements. In addition, a coupled analysis to the ERO2.0 shows the effects of including helium in the simulations on plasma wall interactions, with He2+ being the main contributor to erosion (from other He charge states) on the divertor targets at DIII-D. This has been carried out with a new capability from EMC3-EIRENE, where charge state resolved fluxes can be directly mapped onto target surfaces to better account for the spatial distribution of the species in the 3D equilibria. A similar analysis is currently under investigation for other seeded impurities (i.e. neon, nitrogen), as the detached regimes achieved in the edge can significantly reduce the physical sputtering yield of carbon at the targets.
This work was funded by Department of Energy, Office of Fusion Energy Science, DE-SC0020284, DE-FC02-04ER54698, DE-AC52-07NA27344 and DE-AC02-09CH11466.