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 (IPD) developed by PPPL. In order to interpret and analyze experimental data, and to help develop future experiments, a modelling workflow using a boundary plasma simulation (SOLEDGE-EIRENE) and powder ablation simulation (Dust Injection Simulator, DIS) 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 measurements at the upper divertor was similar, there were significant differences in measurements of , outer strike point electron temperature 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.

Stability analysis of WEST L-mode discharges with improved confinement from boron powder injection

“…Even though the powder injection site is localized to the edge, there was significant density peaking from ρ ⩽ 0.8. This increase in core density was not attributed directly to the ionization of the B powder as simulations from SOLEDGE-EIRENE and DIS of WEST discharges with B powder injection indicated that the B atoms become fully ionized at ρ > 0.9 [29]. Therefore, the peaking of the core density was likely due to modified particle transport rather than a modified particle source.…”