Description
Tungsten (W) erosion from divertor targets remains a major source of high Z impurities in magnetic confinement fusion devices, where the resulting radiative power losses can constrain steady state operation. Conventional fluid and Monte Carlo (MC) simulations often employ simplified sheath prescriptions or fixed floating potential assumptions, which fail to capture the coupled kinetic processes governing particle–surface interactions.
In this work, we present an integrated modeling framework that couples the fluid edge plasma code Hermes-3 [1] with a kinetic treatment of the collisional, magnetic, and Debye sheaths using CLOVER and GYRAZE [2]. A dedicated MC particle-tracing module utilizes plasma parameters from the 1D fluid module to track ion trajectories through the kinetic sheath potential structures, calculating sputtering yields of W via the Eckstein formula.
The combined sheath model has been cross-compared with Particle In Cell (PIC) simulations [3], demonstrating robust agreement. Using this validated fluid–sheath workflow, we conducted a comparative assessment against standard approximations used in current fluid and impurity transport simulations. The results highlight the significant role of the magnetic presheath—often neglected in existing approaches—and provide a high fidelity reference for improving impurity source modeling in future large scale fusion simulations.
Acknowledgements: This work was partially funded by the FEAT SRTT, A*STAR.
[1] Dudson B, Kryjak M, Muhammed H, Hill P and Omotani J 2024 Hermes-3: Multi-component plasma simulations with BOUT++ Computer Physics Communications 296 108991
[2] Geraldini A, Ewart R J, Brunner S and Parra F I 2025 Characteristics of monotonic sheaths near a wall with grazing magnetic incidence
[3] Derouillat J, Beck A, Pérez F, Vinci T, Chiaramello M, Grassi A, Flé M, Bouchard G, Plotnikov I, Aunai N, Dargent J, Riconda C and Grech M 2018 Smilei : A collaborative, open-source, multi-purpose particle-in-cell code for plasma simulation Computer Physics Communications 222 351–73