Towards Integrated Target–SOL–Core Plasma Simulations for Fusion Devices with Liquid Metal Targets

Abstract

Self-healing liquid metal divertors (LMDs) based on the Capillary Porous Structure (CPS) concept are currently being considered among the possible solutions to the power exhaust problem in future fusion reactors. Indeed, the passive replenishment of the plasma-facing surface by capillary forces and the self-shielding of the target via vapor emission can potentially improve the divertor lifetime and its resilience to transient loads. On the other hand, the LMD target erosion can be significant due to evaporation and thermal sputtering, on top of physical sputtering, possibly leading to unacceptable core plasma dilution/power losses (for a low-Z/high-Z metal such as Li and Sn, respectively). For this reason, it is necessary to assess whether an LMD is compatible with an European DEMO (EU-DEMO) plasma scenario. This requires a self-consistent model of the impurity emission from the target, the plasma in both the scrape-off layer (SOL) and the core regions and the transport of impurities therein. In this paper, an an integrated modelling approach is proposed, which is based on SOLPS-ITER and includes its coupling with a target erosion model written in FreeFem++ and a core plasma model (ASTRA/STRAHL). An application of the coupled SOL-target model to simulate experiments performed in the Magnum-PSI linear plasma device with a CPS target filled with Li is also included to provide a first demonstration of the capabilities of the approach. Results are promising, being in good agreement (within a few degrees) with the measured target temperature distribution. In perspective, the modelling framework presented here will be applied to the EU-DEMO with an Sn divertor.

Deuterium retention in co-deposition with lithium in Magnum-PSI: experimental analysis and comparison with SOLPS-ITER

“…and T evap is the evaporation temperature in K. Although this is a simple approach and more involved descriptions of the evaporation process exists [46] the implementation in SOLPS-ITER is not straight-forward. However, there has been recent progress in coupling SOLPS-ITER with a Finite Element wall model [47] to improve the calculation of the evaporation flux.…”

“…Additionally, it is worth noticing that the Q cool calculated for the cases of 702 • C and 727 • C becomes negative, which indicates a non-physical situation as the amount of heat needed to evaporate the corresponding amount of lithium is much larger than the one reaching the target. This indicates the need of target models that self-consistently calculate the target temperature and thus the evaporation based on the heat reaching the target [47,51].…”