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Description
The Divertor Tokamak Test (DTT) facility, currently under design and construction at the ENEA Research Centre in Frascati (Italy), aims to assess alternative solutions to the heat and power exhaust challenge in future fusion reactors [1]. A key issue for its operation is plasma-wall interaction (PWI) [2], as material erosion can limit component lifetime while eroded impurities may migrate into the core plasma, causing dilution and radiative cooling. These effects must be carefully monitored and controlled across all DTT-envisioned scenarios, including negative triangularity (NT), which is a promising solution for achieving high confinement performances while working in a regime free from Edge Localised Modes (ELMs).
This work investigates tungsten divertor erosion and core plasma contamination in the DTT NT scenario using ERO2.0, a 3D Monte Carlo impurity transport code [3]. The deuterium background plasma is taken from SOLPS-ITER simulations, together with neon ion fluxes used for detachment control. Oxygen is added in ERO2.0 as a proxy for unseeded light impurities. Local simulations including the full 3D divertor geometry are also performed to identify optimal locations for PWI diagnostics, such as quartz crystal microbalances (QMBs). The results are compared with those obtained for the corresponding positive triangularity (PT) configuration.
In the absence of ELMs, Ne and O impurities dominate tungsten erosion. The influence of the ion incidence angle on the estimated erosion rate is assessed over the 0-70° range. The outer divertor leg operates under significantly hotter conditions than the inner leg, leading to a higher net erosion rate of approximately 0.2-0.4 nm/s near the strike point, substantially larger than in the corresponding PT case. Net deposition regions are observed in proximity to the erosion peak at both strike points. The sensitivity of erosion and migration estimates to the extrapolation of SOLPS-ITER plasma parameters from the computational grid to the material surface is also evaluated. From a migration perspective, the outer target is identified as the main contributor to core contamination, with the private flux region near the outer strike point being the most critical zone for tungsten influx due to weaker screening and relatively high local plasma parameters, in terms of ion flux and impact energy. Optimal QMB installation points in the dome-target gaps are assessed to ensure detectable W deposition.
[1] Romanelli F. et al., NF 64.11 (2024) 112015
[2] Roth J. et al., JNM 390–391 (2009) 1–9
[3] Romazanov J. et al., PS T170 (2017) 014018