Resolve the H-mode fueling discrepancy between EMC3-EIRENE and MRPB

Resolve why the EMC3-EIRENE calculation predicts approximately a 21% reduction in confined-region fueling for the H-mode resonant-magnetic-perturbation discharge, whereas the multi-reservoir particle-balance model predicts approximately a 10% reduction in fueling efficiency, including by investigating the temperature-dependent rate coefficients in the steep-gradient H-mode pedestal region and the effects of transient ELMs.

Background

For the H-mode scenario, the detailed three-dimensional EMC3-EIRENE field-line analysis gives integrated confined-region fueling of 6.98×10206.98\times10^{20} ions/s without RMPs and 5.51×10205.51\times10^{20} ions/s with RMPs, corresponding to a 21% decrease. This is roughly twice the 10% decrease in fueling efficiency inferred from the multi-reservoir particle-balance model.

The paper identifies two possible sources of the discrepancy: EMC3-EIRENE is a steady-state model, whereas the experiment and the multi-reservoir model include transient ELM behavior, and the two approaches use different particle-source tracing and atomic and molecular rate data. Determining the contribution of these effects is necessary to establish whether the inferred RMP-induced fueling reduction is quantitatively reliable.

References

We suspect that this could be due to the fact that EMC3-EIRENE is a steady-state model while the experiment and MRPB both have transient ELM events as well as the full particle source tracing conducted with EIRENE with temperature and density dependent rates compared to the fixed atomic and molecular data used in the MRPB. A more detailed investigation and comparison of rate coefficients used and their temperature dependence in the steep gradient region of the H-mode pedestal could be conducted to resolve this.

— Determining neutral fueling response to RMPs in MAST using a multi-reservoir particle balance model and EMC3 EIRENE  (2608.19446 - Flesch et al., 19 Aug 2026) in Section 4.5, “Quantifying fueling for axisymmetric and RMP discharges”