Interpretive modelling of boron transport in the boundary plasma of WEST experiments with the impurity powder dropper

Abstract

Boron (B) powder injection is a potential alternative to glow discharge boronization as a wall conditioning method for tokamaks. This technique is currently being studied in WEST experiments, during which B powder is injected by an Impurity Powder Dropper developed by PPPL. In order to interpret and analyse experimental trends, and to help develop future experiments, a modelling workflow using a boundary plasma simulation (SOLEDGE-EIRENE) and powder ablation simulation (Dust Injection Simulator) was developed and tested. The effect of adding a B neutral source to simulated deuterium + oxygen (D + O) plasmas was compared to experimental data from the WEST C5 campaign, where B powder was injected in a dedicated experiment. While the impact of B injection on radiated power ${P_{{\text{rad}}}}$ measurements at the upper divertor was similar, there were significant differences in measurements of ${P_{{\text{rad}}}}$ , outer strike point electron temperature $T_{\text{e}}^{{\text{OSP}}}$ and O-II line intensity at the lower divertor between experiment and simulation. This discrepancy suggests that those parameters were affected by phenomena not present in the simulations, with the most likely candidates being reduced D recycling and a reduced O sourcing from the divertor.

Keywords

• magnetic fusion
• plasma-wall interaction
• wall conditioning
• boundary plasma modelling
• impurity powder dropper
• WEST