ERO2.0 modelling of divertor marker erosion in ASDEX Upgrade L-mode experiments

Erosion of small marker surfaces in an experiment conducted at the ASDEX Upgrade tokamak was modelled using the ERO2.0 code. In the experiment 5 × 5 mm 2 and 1 × 1 mm 2 Au marker spots were exposed to a series of high-temperature L-mode plasmas in the low-field side strike point region to serve as proxies for measuring net and gross erosion of W, respectively. An ERO2.0 simulation setup was created for the experiment using background plasma produced using OSM and new angle-dependent reflection and sputtering data for Au generated with the SDTrimSP code. The simulated net erosion of the Au markers agreed closely with the measured values. The erosion of the Au markers was induced mainly by the light B, C and N impurities defined as fixed concentrations in the background plasma. The Au markers were found to undergo up to 15–20 times stronger net erosion in comparison to a uniform W surface. This was attributed to 3–4 times stronger gross erosion of Au in comparison to W and deposition of the eroded Au mostly outside of the markers. Consequently, the simulations suggest strongly compromised capability of Au to act as proxy markers for W in erosion studies due to the significantly higher gross erosion yield of Au and insufficient size of the 5 × 5 mm 2 markers for successful representation of net erosion, as eroded particles migrate along the plasma flow mostly outside the markers. • Erosion of Au marker surfaces in experiment conducted at AUG modelled using ERO2.0. • Simulated net erosion of Au markers agreed closely with measured values. • Erosion of Au markers was induced mainly by light B, C and N impurities. • Gross erosion of Au was 3–4 times higher in simulations in comparison to W. • Toroidal length of markers was found insufficient for net erosion studies.