An assessment of the first wall and limiter erosion during limiter discharge stages in DEMO

Abstract

The model elaborated on previously (Tokar 2018 Nucl. Fusion 58 016016) for the transport of neutral and charged plasma components in the DEMO scrape-off layer (SOL) with a divertor is reworked to describe limiter discharge phases. It provides radial profiles of the plasma density and temperatures of electrons and ions, averaged over flux surfaces, which are calculated self-consistently at the edge of the confined region and in the SOL, without prescribing any decay lengths at the last closed flux surface. It is assumed that on the limiter discharge phase in question the plasma will be in the L-mode of the energy confinement and the radial transport in the SOL is modeled with coefficients of the Bohm type. Computations give the plasma particle flows both to the limiters and to the first wall (FW). This allows us to assess the erosion rates by plasma ions of these reactor components. In the case of the FW physical sputtering with hot atoms generated in charge-exchange collisions of ions with neutral species, recycling from the wall and limiters is also taken into account.