Benchmark of the linear and non-linear RF rectified sheath boundary conditions implemented in the Petra-M FEM platform with the previous results obtained with the rfSOL code

The ICRF antenna and the plasma waves propagating in the SOL can drive several hundred-volt rectified sheath potentials at the plasma material interfaces. These potentials can cause erosion and sputtering of high Z-impurities, which may contaminate the core plasma leading to radiative collapse. For this reason, the implementation of the RF sheath boundary conditions (BC) in the RF solvers is a crucial step to improve ICRF modeling. Linear and non-linear RF sheath BCs have been recently implemented in the Petra-M FEM platform and a benchmark activity is presented in this work with the previous results obtained with the rfSOL code. We focus on the 2D cases with both 90-degree angle and oblique angle between the background magnetic field and the surface. Moreover, a comparison of the shaped wall on the RF sheath effects is also performed investigating the impact of the variation of the angle between the magnetic field and the surface. Finally, a comparison with the rfSOL code of a 2D circular tokamak cross-section with a limiter protrusion is also presented showing the role of the of the conversion from fast to slow waves on the sheaths. In all cases analyzed, an excellent agreement is found in the non-linear regimes between the two models.