Density‑Decay Length Effects on RF Sheaths and Limiter Erosion in WEST ICRH antennas: Petra‑M and RFiMP Results

We examine how the SOL density profiles and electromagnetic conditions influence tungsten emission from WEST RF antenna limiters during ICRH. Petra‑M (3D finite‑element, frequency‑domain with nonlinear RF‑sheath BCs) provides parallel fields and rectified sheath potentials. For the plasma–material portion, the RFiMP workflow uses the hPIC2 particle‑in‑cell to calculate ion energy–angle distributions and the RustBCA code for sputtering yield coefficients. Using Child–Langmuir‑based sheath/erosion relations, and local plasma parameters, we compute the tungsten fluxes emitted by the RF limiters. This analytical estimate is compared with a higher‑fidelity result from the RFiMP outputs. Systematic scans over the SOL density decay length λn and antenna geometry show erosion‑flux hotspots aligned with regions between tiles/Faraday rods and along protruding edges, where sheath potentials peak and ion impact energies increase. RF‑only subtraction (total − thermal) exposes fine Faraday‑rod‑aligned spots on the inner faces with the largest erosion flux. Preliminary results indicate that shorter λn tends to reduce erosion, whereas longer λn broadens and intensifies it in higher‑density regions. These findings are compared with OES measurements at WEST and post‑campaign surface analyses.