Modeling of erosion/deposition patterns observed during WEST high-fluence campaign

A deuterium high-fluence experimental campaign under changeless condition with attached plasma at the divertor strike lines was conducted in the WEST tokamak (spring 2023) to expose the ITER-grade actively-cooled divertor to ITER-relevant particle fluences by repeating the same plasma scenario of 70 s each on average, with a total cumulated plasma time of 10790 s. The goal of this work is to understand the erosion/deposition patterns observed on the divertor after the campaign by modeling the plasma conditions and the transport of tungsten. Impurities sources are monitored by visible spectroscopy, showing high content of boron and carbon all along the campaign especially on the high-field side where deposited layers are growing continuously. An analysis using visible spectroscopy (for WI 4009 Å radiance) and flush-mounted Langmuir probe measurements (to obtain n_e and T_e dependent local S/XB coefficients) gives estimates of the tungsten gross erosion flux up to 1.5 × 10¹⁹ part.m⁻².s⁻¹, leading to around 0.67 μm of net erosion near the outer strike point, assuming the high fluence campaign plasma time and 75 % prompt redeposition rates, while post-mortem analysis suggests higher values (around 7 μm of net erosion on the inner strike point) after both, foregoing and high-fluence campaign. To model those experimental observations, the first step is to simulate a plasma background with SOLEDGE3X-EIRENE, constrained by experimental measurements. Plasma backgrounds are simulated with proxy light impurity (O) with various concentrations (1 to 5 %) to match experimental conditions (particle flux and electron temperature at the edge). ERO2.0 simulates the transport of tungsten using the SOLEDGE3X-EIRENE plasma background and gives eroded and deposited tungsten flux on the wall. The final simulated erosion depth is barely the same for each oxygen concentrations and around 4 to 9 µm at both strike-points which is consistent with firsts estimates by post-mortem analysis. The far inner redeposition area is not recovered in the simulation and is subject to further work.