Predictive and interpretative modelling of ASDEX-upgrade liquid metal divertor experiment

A liquid metal Capillary Porous System (CPS) test module filled with tin was studied in the ASDEX Upgrade (AUG) outer divertor. The CPS module was flush mounted as part of a target tile and exposed using the AUG divertor manipulator. In order to predict tin erosion from the designed module under typical AUG divertor loading conditions, the experiment was interpreted using the HeatLMD code. Preceding test exposures of the CPS in the high heat flux facility GLADIS were performed and interpreted by modelling to quantify the thermo-mechanical properties of the module. The results for the reference AUG discharge indicated a total of 2.6 × 1017 tin atoms (51 μg) would be eroded during the exposure, predominantly through temperature enhanced sputtering. The vapour cooling power was predicted to be negligible (5 kW/m2at the end of a 5 s exposure with heat flux from the plasma of 2 MW/m2). The module was expected to be compatible with plasma operation, with tin erosion too low for any significant effect on the plasma performance. However, interpretative modelling of the experimental discharge with the highest exposure time yielded significantly lower tin erosion than observed. To be attributed to tin radiation the experimentally observed increase in total radiative power (1.5 MW) would require 2 × 1018 tin atoms (peak calculated erosion rate) radiating in the core plasma. This would require every tin atom eroded, to reach the core, which is unlikely.