Towards ECWC Plasma Simulations With the SOLPS ‐ ITER Code

ABSTRACT Electron Cyclotron Wall Conditioning (ECWC) will be used in future devices such as ITER. These discharges feature non‐standard topologies of the magnetic field, as well as low temperatures and densities. The TOMATOR‐1D code is the only available tool at present to model ECWC plasmas. However, the model is 1‐D radial and cannot reproduce the 2‐D features of these discharges, e.g., the localised power deposition and the 2‐D poloidal magnetic field map. Moreover, it cannot provide deep insights on the achievable particle and energy fluxes on vessel walls. In this work, we set the first steps towards self‐consistent 2‐D modelling of ECWC plasmas with the Wide‐Grid version of the SOLPS‐ITER code, which now allows for simulations up to the vessel walls for arbitrary toroidally symmetric magnetic configurations. A new ECH power deposition scheme is implemented in SOLPS‐ITER, based on the one present in TOMATOR‐1D, and the two codes are then bench‐marked. Overall, a good agreement between the two codes is obtained for the quantities of interest, such as electron density and energy. The remaining 15% discrepancy is linked to differences identified between the two models that could not be overcome at present. The power deposition scheme is then extended to 2‐D and used to model a discharge in the TOMAS device. This work represents a first‐of‐a‐kind numerical simulation of realistic ECWC plasmas. The results obtained are then compared to available experimental data. SOLPS‐ITER reproduces both qualitatively and quantitatively the radial profile of the electron density, while the drift physics missing in the simulation leads to differences in the vertical profile. Finally, a prediction of wall fluxes is obtained, showing peaks on the low field side (LFS) as expected when a convective velocity is introduced to mimic the effect of the drift. This work poses solid basis for an accurate numerical modelling of ECWC plasmas and its validation against experimental data for larger devices such as TCV and ASDEX Upgrade.