Impact of enhanced far-SOL transport on first wall fluxes in ITER from full vessel edge-plasma simulations

Abstract

Estimates of plasma conditions in the far scrape-off layer (SOL) and of first wall (FW) fluxes in ITER are key input parameters to first wall erosion and impurity migration models, which are in turn involved in the assessment of FW panel lifetime and fuel retention studies. SOLEDGE3X up-to-the wall boundary plasma simulations are performed for ITER, based on an expected Pre-Fusion-Power-Operation (PFPO-1) scenario at P S O L = 20MW, including an impact study of enhanced far-SOL transport. This latter study concerns the possible formation of density shoulders, which are modelled here by applying an increase to the prescribed perpendicular particle and heat diffusivity coefficients maps in the far-SOL in the code, in order to flatten the density and temperature profiles there. Several kinds of such obtained “shoulders” are considered. A brief comparison with SOLPS-ITER is performed on the reference case with uniform coefficients, and shows good agreement. When far-SOL transport is increased, temperatures computed on the first wall rise to 20–30 eV for ions, and to 10–20 eV for electrons. It is also found that for first wall quantities of interest in the ITER machine, the assumed level of perpendicular transport in the far-SOL is the most relevant parameter, with the location at which transport is increased being much less important. • First wall fluxes and far scrape-off layer plasma backgrounds for low power 20MW ITER cases are simulated with SOLEDGE3X. • Enhanced far-SOL transport is studied to model the presence of density shoulders. • The most relevant parameter in this study for ITER is the perpendicular diffusion coefficients value in the far-SOL • Temperatures on the first wall can reach 20–30 eV for ions, and 10–20 eV for electrons. • In low power cases, even in the case of formation of density shoulders in the far-SOL, first wall power loads remains well within design limits.